KO Mice (ko + mouse)

Distribution by Scientific Domains
Distribution within Medical Sciences

Selected Abstracts

Loss of steroidogenic factor 1 alters cellular topography in the mouse ventromedial nucleus of the hypothalamus

Aline M. Davis
Abstract Knockout (KO) mice lacking the orphan nuclear receptor steroidogenic factor 1 (SF-1) exhibit marked structural abnormalities of the ventromedial nucleus of the hypothalamus (VMH). In this study, we sought to determine the molecular mechanisms underlying the VMH abnormalities. To trace SF-1-expressing neurons, we used a SF-1/enhanced green fluorescent protein (eGFP) transgene. Although the total numbers of eGFP-positive cells in wild-type (WT) and SF-1 KO mice were indistinguishable, cells that normally localize precisely within the VMH were scattered more diffusely in adjacent regions in SF-1 KO mice. This abnormal distribution is likely due to the loss of SF-1 expression in VMH neurons rather than secondary effects of deficient steroidogenesis, as redistribution also was seen in mice with a CNS-specific KO of SF-1. Thus, the absence of SF-1 alters the distribution of cells that normally form the VMH within the mediobasal hypothalamus. Consistent with this model, the hypothalamic expression patterns of the transcription factors islet-1 and nkx2.1 also were displaced in SF-1 KO mice. Independent of gene expression, birthdate analyses further suggested that cells with earlier birthdates were affected more severely by the loss of SF-1 than were later born cells. We conclude that the absence of SF-1 causes major changes in cellular arrangement within and around the developing VMH that result from altered cell migration. 2004 Wiley Periodicals, Inc. J Neurobiol 60: 424,436, 2004 [source]

Endothelially Derived Nitric Oxide Affects the Severity of Early Acetaminophen-induced Hepatic Injury in Mice

Steven D. Salhanick MD
Abstract Objectives: The precise mechanism of hepatocellular toxicity following acetaminophen (APAP) poisoning remains unclear. Nitric oxide is implicated in APAP toxicity as an inflammatory signaling molecule and as a precursor to the free radical peroxynitrate. The effects of inducible nitric oxide synthase (iNOS)-derived NO in APAP toxicity are known; however, the role of endothelial nitric oxide synthase (eNOS)-derived NO is unknown. The authors sought to evaluate the effect of eNOS-derived NO during APAP toxicity. Methods: C57BL6/J mice deficient in eNOS (eNOS KO) or iNOS (iNOS KO) and wild-type mice (WT) were treated with 300 mg/kg APAP. Alanine aminotransferase levels and plasma nitrate and nitrite levels were measured. Hypoxia inducible factor (HIF)-1, and Glucose Transporter 1 (Glut-1) levels were determined by Western blot. Results: Alanine aminotransferase levels were significantly elevated in all treated animals. Alanine aminotransferase levels were significantly lower in eNOS KO and iNOS KO than in treated WT animals. Plasma nitrate/nitrite levels were significantly higher in WT animals than in iNOS KO and eNOS KO animals. HIF-1, expression was increased in WT mice and decreased in iNOS KO mice. Glut-1 is a downstream, indirect marker of HIF function. Glut-1 expression was increased in WT and eNOS KO mice. Conclusions: Deficiency of either iNOS or eNOS results in decreased NO production and is associated with reduced hepatocellular injury following APAP poisoning. HIF-1, and Glut-1 levels are increased following APAP poisoning, implying that HIF-1, is functional during the pathogenic response to APAP poisoning. [source]

MAPK3 deficiency drives autoimmunity via DC arming

Ivo Bendix
Abstract DC are professional APC that instruct T cells during the inflammatory course of EAE. We have previously shown that MAPK3 (Erk1) is important for the induction of T-cell anergy. Our goal was to determine the influence of MAPK3 on the capacity of DC to arm T-cell responses in autoimmunity. We report that DC from Mapk3,/, mice have a significantly higher membrane expression of CD86 and MHC-II and , when loaded with the myelin oligodendrocyte glycoprotein , show a superior capacity to prime nave T cells towards an inflammatory phenotype than Mapk3+/+ DC. Nonetheless and as previously described, Mapk3,/, mice were only slightly but not significantly more susceptible to myelin oligodendrocyte glycoprotein-induced EAE than WT littermate mice. However, Mapk3+/+ mice engrafted with Mapk3,/, BM (KO,WT) developed a severe form of EAE, in direct contrast to WT,KO mice, which were even less sick than control WT,WT mice. An infiltration of DC and accumulation of Th17 cells was also observed in the CNS of KO,WT mice. Therefore, triggering of MAPK3 in the periphery might be a therapeutic option for the treatment of neuroinflammation since absence of this kinase in the immune system leads to severe EAE. [source]

A CIITA-independent pathway that promotes expression of endogenous rather than exogenous peptides in immune-privileged sites

Abstract A CIITA-independent pathway of MHC class II expression has been found in the eye and the brain, both immune-privileged sites. Although corneal endothelial cells were unable to express MHC class,II in response to IFN-, alone, these cells readily expressed MHC class,II molecules via a CIITA-independent pathway when triggered by simultaneous exposure to IFN-, and TNF-,. CIITA-independent expression of MHCclass,II molecules enabled corneal endothelial cells to present cytosolic, but not endosomal, ovalbumin (OVA) to OVA-primed T,cells. To determine whether CIITA-independentexpression of MHC class,II is relevant in vivo, minor,H-only-incompatible corneal allografts prepared from CIITA knockout (KO) mice, MHC class,II KO mice or wild-type donors were placed ineyes of normal mice. Cornea allografts from wild-type and CIITA KO mice suffered similar rejection fates, whereas far fewer class,II-deficient corneas were rejected. In addition, MHC class,II-bearing macrophages were observed in cuprizone-induced inflammatory and demyelinating brain lesions of CIITA KO mice. We conclude that class,II expression via the CIITA-independent pathway enhances the vulnerability to rejection of corneal grafts expressing minor antigens. The potential relevance of CIITA-independent MHC class,II expression at immune-privileged sites is discussed in relation to tolerance to strong autoantigens. [source]

Role of peroxynitrite in methamphetamine-induced dopaminergic neurotoxicity and sensitization in mice

Syed F. Ali
Methamphetamine (METH)-induced dopaminergic neurotoxicity is thought to be associated with the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Recently, we have reported that copper/zinc(CuZn)-superoxide dismutase transgenic mice are resistant to METH-induced neurotoxicity. In the present study, we examined the role of the neuronal nitric oxide synthase (nNOS), susceptibility of nNOS knockout (KO) mice and sensitization to psychostimulants after neurotoxic doses of METH. Male SwissWebster mice were treated with or without 7-nitroindazole (7-NI) along with METH (5 mg/kg,ip,q 3h 3) and were sacrificed 72 h after the last METH injection. Dopamine (DA) and dopamine transporter (DAT) binding sites were determined in striatum from saline and METH-treated animals. 7-NI completely protected against the depletion of DA, and DAT in striatum. In follow-up experiments nNOS KO mice along with appropriate control (C57BL/6N, SV129 and B6JSV129) mice were treated with METH (5 mg/kg,ip, q 3h 3) and were sacrificed 72 h after dosing. This schedule of METH administrations resulted in only 10,20% decrease in tissue content of DA and no apparent change in the number of DAT binding sites in nNOS KO mice. However, this regime of METH resulted in a significant decrease in the content of DA as well as DAT binding sites in the wild-type animals. Pre-exposure to single or multiple doses of METH resulted in a marked locomotion sensitization in response to METH. However, the nNOS KO mice show no sensitization in response to METH after single or multiple injections of METH. Therefore, these studies strongly suggest the role of peroxynitrite, nNOS and DA system in METH-induced neurotoxicity and behavioral sensitization. [source]

Mu opioid receptor modulation of somatodendritic dopamine overflow: GABAergic and glutamatergic mechanisms

V. I. Chefer
Abstract Mu opioid receptor (MOR) regulation of somatodendritic dopamine neurotransmission in the ventral tegmental area (VTA) was investigated using conventional microdialysis in freely moving rats and mice. Reverse dialysis of the MOR agonist DAMGO (50 and 100 ,m) into the VTA of rats produced a concentration-dependent increase in dialysate dopamine concentrations. Basal dopamine overflow in the VTA was unaltered in mice lacking the MOR gene. However, basal ,-aminobutyric acid (GABA) overflow in these animals was significantly increased, whereas glutamate overflow was decreased. Intra-VTA perfusion of DAMGO into wild-type (WT) mice increased dopamine overflow. GABA concentrations were decreased, whereas glutamate concentrations in the VTA were unaltered. Consistent with the loss of MOR, no effect of DAMGO was observed in MOR knockout (KO) mice. These data provide the first direct demonstration of tonically active MOR systems in the VTA that regulate basal glutamatergic and GABAergic neurotransmission in this region. We hypothesize that increased GABAergic neurotransmission following constitutive deletion of MOR is due to the elimination of a tonic inhibitory influence of MOR on GABAergic neurons in the VTA, whereas decreased glutamatergic neurotransmission in MOR KO mice is a consequence of intensified GABA tone on glutamatergic neurons and/or terminals. As a consequence, somatodendritic dopamine release is unaltered. Furthermore, MOR KO mice do not exhibit the positive correlation between basal dopamine levels and the glutamate/GABA ratio observed in WT mice. Together, our findings indicate a critical role of VTA MOR in maintaining an intricate balance between excitatory and inhibitory inputs to dopaminergic neurons. [source]

The maintenance of specific aspects of neuronal function and behavior is dependent on programmed cell death of adult-generated neurons in the dentate gyrus

Woon Ryoung Kim
Abstract A considerable number of new neurons are generated daily in the dentate gyrus (DG) of the adult hippocampus, but only a subset of these survive, as many adult-generated neurons undergo programmed cell death (PCD). However, the significance of PCD in the adult brain for the functionality of DG circuits is not known. Here, we examined the electrophysiological and behavioral characteristics of Bax -knockout (Bax -KO) mice in which PCD of post-mitotic neurons is prevented. The continuous increase in DG cell numbers in Bax -KO mice resulted in the readjustment of afferent and efferent synaptic connections, represented by age-dependent reductions in the dendritic arborization of DG neurons and in the synaptic contact ratio of mossy fibers with CA3 dendritic spines. These neuroanatomical changes were associated with reductions in synaptic transmission and reduced performance in a contextual fear memory task in 6-month-old Bax -KO mice. These results suggest that the elimination of excess DG neurons via Bax -dependent PCD in the adult brain is required for the normal organization and function of the hippocampus. [source]

Impact of S100B on local field potential patterns in anesthetized and kainic acid-induced seizure conditions in vivo

Seiichi Sakatani
Abstract S100B is a calcium-binding protein predominantly expressed in astrocytes. Previous studies using gene-manipulated animals have suggested that the protein has a role in synaptic plasticity and learning. In order to assess the physiological roles of the protein in active neural circuitry, we recorded spontaneous neural activities from various layers of the neocortex and hippocampus in urethane-anesthetized S100B knockout (KO) and wildtype (WT) control mice. Typical local field oscillation patterns including the slow (0.5,2 Hz) oscillations in the neocortex, theta (3,8 Hz) and sharp wave-associated ripple (120,180 Hz) oscillations in the hippocampus were observed in both genotypes. Comparisons of the frequency, power and peak amplitude have shown that these oscillatory patterns were virtually indistinguishable between WT and KO. When seizure was induced by intraperitoneal injection of kainic acid, a difference between WT and KO appeared in the CA1 radiatum local field potential pattern, where seizure events were characterized by prominent appearance of hyper-synchronous gamma band (30,80 Hz) activity. Although both genotypes developed seizures within 40 min, the gamma amplitude was significantly smaller during the development of seizures in KO mice. Our results suggest that deficiency of S100B does not have a profound impact on spontaneous neural activity in normal conditions. However, when neural activity was sufficiently raised, activation of S100B-related pathways may take effect, resulting in modulation of neural activities. [source]

Paradoxical effects of prodynorphin gene deletion on basal and cocaine-evoked dopaminergic neurotransmission in the nucleus accumbens

V. I. Chefer
Abstract Quantitative and conventional microdialysis were used to investigate the effects of constitutive deletion of the prodynorphin gene on basal dopamine (DA) dynamics in the nucleus accumbens (NAc) and the responsiveness of DA neurons to an acute cocaine challenge. Saline- and cocaine-evoked locomotor activity were also assessed. Quantitative microdialysis revealed that basal extracellular DA levels were decreased, while the DA extraction fraction, an indirect measure of DA uptake, was unchanged in dynorphin (DYN) knockout (KO) mice. The ability of cocaine to increase NAc DA levels was reduced in KO. Similarly, cocaine-evoked locomotor activity was decreased in KO. The selective kappa opioid receptor agonist U-69593 decreased NAc dialysate DA levels in wildtype mice and this effect was enhanced in KO. Administration of the selective kappa opioid receptor (KOPr) antagonist nor-binaltorphimine to KO mice attenuated the decrease in cocaine-induced DA levels. However, it was ineffective in altering the decreased locomotor response to cocaine. These studies demonstrate that constitutive deletion of prodynorphin is associated with a reduction of extracellular NAc DA levels and a decreased responsiveness to acute cocaine. Data regarding the effects of U-69593 and nor-binaltorphimine in KO suggest that the kappa opioid receptor is up-regulated as a consequence of prodynorphin gene deletion and that this adaptation underlies the decrease in basal DA dynamics and cocaine-evoked DA levels observed in DYN KO mice. These findings suggest that the phenotype of DYN KO mice is not solely due to loss of endogenous opioid peptide but also reflects developmental compensations that occur at the level of the opioid receptor. [source]

Tonic regulation of satiety by 5-HT1B receptors in the mouse: converging evidence from behavioural and c- fos immunoreactivity studies?

Michelle D. Lee
Abstract Activation of 5-HT1B receptors is thought to play an important role in the inhibitory influence of serotonin on feeding behaviour and body weight in mammals. Earlier studies have shown that 5-HT1B -knockout (KO) mice eat more and are heavier than wild-type (WT) controls and that the selective 5-HT1B receptor agonist CP-94,253 reduces food intake in food-deprived mice. Here we characterize the behavioural effects of both CP-94,253 and the selective 5-HT1B receptor antagonist SB224289 on feeding and other behaviours within the behavioural satiety sequence, and also report a c- fos mapping study using CP-94,253. CP-94,253 produced a dose-dependent suppression of food intake with a profile consistent with a selective effect on feeding behaviour. These effects were absent or reduced in 5-HT1B -KO mice and in WT mice pretreated with SB224289. SB224289 administered alone enhanced food intake consistent with impaired satiation; a similar effect was apparent in 5-HT1B -KO mice compared to WT. CP-94,253 induced c- fos in a range of structures previously implicated in the expression of feeding behaviour. These results suggest that the activation of 5-HT1B receptors is an important component of endogenous satiation mechanisms in the mouse. [source]

5-HT1B receptor knockout mice show a compensatory reduction in 5-HT2C receptor function

Peter G. Clifton
Abstract Although null mutant (,knockout') mice have provided valuable animal models to complement traditional approaches to psychopharmacology, such animals may also show complex adaptations to the induced mutation. Here we demonstrate that serotonin1B (5-HT1B) receptor knockout (KO) mice show adaptations in serotonin2C (5-HT2C) receptor-mediated functions. They show smaller reductions in food intake and locomotor activity in response to administration of 5-HT2C receptor agonists that are not accounted for by altered drug disposition. These effects are not mimicked by pretreatment of wildtype (WT) mice with a 5-HT1B receptor antagonist showing that they result from a longer term adaptation to the loss of 5-HT1B receptor function and not from a short-term interaction between 5-HT1B - and 5-HT2C -mediated functions. In addition, we show that 5-HT1B receptor KO mice have a lowered hypothalamic c-fos response to the administration of 5-HT2C receptor agonists. These results demonstrate that compensatory adaptations to the constitutive loss of 5-HT1B receptors may be an important determinant of the altered response of 5-HT1B KO mice to a variety of pharmacological challenges. [source]

Altered presynaptic function in monoaminergic neurons of monoamine oxidase-A knockout mice

Catarina . Owesson
Abstract Monoamine oxidase-A knockout (MAO-A KO) mice have elevated brain serotonin (5-HT) and noradrenaline (NA) levels, and one would therefore anticipate increased monoamine release and compensatory changes in other aspects of presynaptic monoamine function. In this study we used voltammetry in brain slices from the locus coeruleus (LC), dorsal raphe (DRN) and striatum (CPu) in 7-week-old MAO-A KO and C3H control mice to measure stimulated monoamine efflux and its control by amine transporters and autoreceptors. In LC, peak NA efflux on stimulation (99 pulses, 100 Hz) was higher in MAO-A KO than C3H mice (938 58 nm cf. 511 42 nm; P < 0.001). The NA uptake half time (t) was longer in MAO-A KO than in C3H mice (6.0 0.9 s cf. 1.9 0.3 s; P < 0.001) and the selective NA reuptake inhibitor desipramine (50 nm) had a smaller effect in MAO-A KO mice. NA transporter binding was significantly lower in the LC of MAO-A KO mice compared to C3H controls (P < 0.01) but not in the DRN. The ,2 agonist dexmedetomidine (10 nm) decreased stimulated NA efflux more in C3H than in MAO-A KO mice (73.3% cf. 29.6% inhibition, P < 0.001). In DRN, peak 5-HT efflux on stimulation (99 pulses, 100 Hz) was greater (P < 0.01) in MAO-A KO (262 44 nm) than C3H mice (157 16 nm). Moreover, 5-HT uptake t was longer (P < 0.05) in MAO-A KO than in C3H mice (8.8 1.1 s cf. 4.9 0.6 s, P < 0.05) and the effect of citalopram (75 nm) was attenuated in MAO-A KOs. Serotonin transporter binding was also lower in both the DRN and LC of MAO-A KO mice. The 5-HT1A agonist 8-OH-DPAT (1 m) decreased 5-HT efflux more in C3H than in MAO-A KO mice (38.3% inhibition cf. 21.6%, P < 0.001). In contrast, there were no significant differences between MAO-A KO and C3H mice in CPu dopamine efflux and uptake and the effect of the D2/3 agonist quinpirole was similar in the two strains. In summary, MAO-A KO mice show major dysregulation of monoaminergic presynaptic mechanisms such as autoreceptor control and transporter kinetics. [source]

Male and female Fmr1 knockout mice on C57 albino background exhibit spatial learning and memory impairments

K. B. Baker
Impaired spatial learning is a prominent deficit in fragile X syndrome (FXS). Previous studies using the Fmr1 knockout (KO) mouse model of FXS have not consistently reported a deficit in spatial learning. Fmr1 KO mice bred onto an albino C57BL/6J- Tyrc-Brd background showed significant deficits in several primary measures of performance during place navigation and probe trials in the Morris water maze. Fmr1 KO mice were also impaired during a serial reversal version of the water maze task. We examined fear conditioning as an additional cognitive screen. Knockout mice exhibited contextual memory deficits when trained with unsignaled shocks; however, deficits were not found in a separate group of KO mice trained with signaled shocks. No potentially confounding genotypic differences in locomotor activity were observed. A decreased anxiety-like profile was apparent in the open field, as others have noted, and also in the platform test. Also as previously reported, startle reactivity to loud auditory stimuli was decreased, prepulse inhibition and social interaction increased in KO mice. Female Fmr1 KO mice were tested along with male KO mice in all assays, except for social interaction. The female and male KO exhibited very similar impairments indicating that sex does not generally drive the behavioral symptoms of the disorder. Our results suggest that procedural factors, such as the use of albino mice, may help to reliably detect spatial learning and memory impairments in both sexes of Fmr1 KO mice, making it more useful for understanding FXS and a platform for evaluating potential therapeutics. [source]

Serotonin 5-HT2C receptors regulate anxiety-like behavior

L. K. Heisler
Central serotonin (5-hydroxytryptamine, 5-HT) systems have been implicated in the pathophysiology and treatment of anxiety disorders, which are among the world's most prevalent psychiatric conditions. Here, we report that the 5-HT2C receptor (5-HT2CR) subtype is critically involved in regulating behaviors characteristic of anxiety using male 5-HT2CR knockout (KO) mice. Specific neural substrates underlying the 5-HT2CR KO anxiolytic phenotype were investigated, and we report that 5-HT2CR KO mice display a selective blunting of extended amygdala corticotropin-releasing hormone neuronal activation in response to anxiety stimuli. These findings illustrate a mechanism through which 5-HT2CRs affect anxiety-related behavior and provide insight into the neural circuitry mediating the complex psychological process of anxiety. [source]

Behavioral and neurochemical phenotyping of Homer1 mutant mice: possible relevance to schizophrenia

K. K. Szumlinski
Homer proteins are involved in the functional assembly of postsynaptic density proteins at glutamatergic synapses and are implicated in learning, memory and drug addiction. Here, we report that Homer1 -knockout (Homer1 -KO) mice exhibit behavioral and neurochemical abnormalities that are consistent with the animal models of schizophrenia. Relative to wild-type mice, Homer1 -KO mice exhibited deficits in radial arm maze performance, impaired prepulse inhibition, enhanced ,behavioral despair', increased anxiety in a novel objects test, enhanced reactivity to novel environments, decreased instrumental responding for sucrose and enhanced MK-801- and methamphetamine-stimulated motor behavior. No-net-flux in vivo microdialysis revealed a decrease in extracellular glutamate content in the nucleus accumbens and an increase in the prefrontal cortex. Moreover, in Homer1 -KO mice, cocaine did not stimulate a rise in frontal cortex extracellular glutamate levels, suggesting hypofrontality. These behavioral and neurochemical data derived from Homer1 mutant mice are consistent with the recent association of schizophrenia with a single-nucleotide polymorphism in the Homer1 gene and suggest that the regulation of extracellular levels of glutamate within limbo-corticostriatal structures by Homer1 gene products may be involved in the pathogenesis of this neuropsychiatric disorder. [source]

Oxytocin and estrogen receptor , and , knockout mice provide discriminably different odor cues in behavioral assays

M. Kavaliers
Social behavior involves both the recognition and production of social cues. Mice with selective deletion (knockout) of either the gene for oxytocin (OT) or genes for the estrogen receptor (ER) -, or -, display impaired social recognition. In this study we demonstrate that these gene knockout mice also provide discriminably different social stimuli in behavioral assays. In an odor choice test, which is a measure of social interest and discrimination, outbred female Swiss-Webster mice discriminated the urine odors of male knockouts (KO: OTKO, ,ERKO, ,ERKO) from the odors of their wildtype littermates (WT: OTWT, ,ERWT, ,ERWT). Females showed marked initial choices of the urine odors of OTWT and ,ERWT males over those of OTKO and ,ERKO males, and ,ERKO males over ,ERWT males. The odors of OTKO and ,ERKO males also induced aversive, analgesic responses, with the odors of WTs having no significant effects. Odors of both the ,ERWT and ,ERKO males induced aversive, analgesic responses, with the odors of the WT inducing significantly greater analgesia. The odors of restraint stressed WT and KO males also elicited analgesia with, again, females displaying significantly greater responses to the odors of stressed OTKO and ,ERKO males than their WTs, and significantly lower analgesia to the odors of stressed ,ERKO than ,ERWT males. These findings show that the KO mice are discriminated from their WTs on the basis of odor and that the various KOs differ in the relative attractiveness/aversiveness of their odors. Therefore, in behavioral assays one causal route by which gene inactivation alters the social behavior of knockout mice may be mediated through the partners' modified responses to their odors. [source]

Enhanced Connexin 43 immunoreactivity in penumbral areas in the human brain following ischemia

GLIA, Issue 5 2006
Taizen Nakase
Abstract Astrocytes support neurons not only physically but also chemically by secreting neurotrophic factors and energy substrates. Moreover, astrocytes establish a glial network and communicate through gap junctions in the brain. Connexin 43 (Cx43) is one of major component proteins in astrocytic gap junctions. Heterozygote Cx43 KO mice and astrocyte specific Cx43 KO mice exhibited amplified brain damage after ischemic insults, suggesting a neuroprotective role for astrocytic gap junctions. However, some reports mentioned unfavorable effects of gap junctions in neuronal support. Therefore, the role of astrocytic gap junctions under ischemic condition remains controversial. Since these studies have been performed using animal models, we investigated the Cx43 expression in human brain after stroke. Brain slice sections were prepared from pathological samples in our hospital. Embolic stroke brains sectioned because of the stroke were considered as acute ischemic models. Multiple infarction brains sectioned because of pneumonia or cancer were considered as chronic models. We observed the levels of Cx43 in both lesioned and intact areas, and compared them with acute and chronic models. As the results, astrocytes were strongly activated in penumbral lesions both of acute and chronic ischemic models. The Cx43 immunoreactivity was significantly amplified in the penumbra of chronic model compared to that of the acute model. Neurons were well preserved in chronic model compared to acute model. These findings suggested that the brain may generate neuronal protection by increasing the levels of Cx43 and amplifying the astrocytic gap junctional intercellular communication under hypoxic condition. 2006 Wiley-Liss, Inc. [source]

S -adenosylmethionine regulates dual-specificity mitogen-activated protein kinase phosphatase expression in mouse and human hepatocytes,

HEPATOLOGY, Issue 6 2010
Maria Lauda Tomasi
Increased mitogen-activated protein kinase (MAPK) activity correlates with a more malignant hepatocellular carcinoma (HCC) phenotype. There is a reciprocal regulation between p44/42 MAPK (extracellular signal-regulated kinase [ERK]1/2) and the dual-specificity MAPK phosphatase MKP-1/DUSP1. ERK phosphorylates DUSP1, facilitating its proteasomal degradation, whereas DUSP1 inhibits ERK activity. Methionine adenosyltransferase 1a (Mat1a) knockout (KO) mice express hepatic S -adenosylmethionine (SAM) deficiency and increased ERK activity and develop HCC. The aim of this study was to examine whether DUSP1 expression is regulated by SAM and if so, elucidate the molecular mechanisms. Studies were conducted using Mat1a KO mice livers, cultured mouse and human hepatocytes, and 20S and 26S proteasomes. DUSP1 messenger RNA (mRNA) and protein levels were reduced markedly in livers of Mat1a KO mice and in cultured mouse and human hepatocytes with protein falling to lower levels than mRNA. SAM treatment protected against the fall in DUSP1 mRNA and protein levels in mouse and human hepatocytes. SAM increased DUSP1 transcription, p53 binding to DUSP1 promoter, and stability of its mRNA and protein. Proteasomal chymotrypsin-like and caspase-like activities were increased in Mat1a KO livers and cultured hepatocytes, which was blocked by SAM treatment. SAM inhibited chymotrypsin-like and caspase-like activities by 40% and 70%, respectively, in 20S proteasomes and caused rapid degradation of some of the 26S proteasomal subunits, which was blocked by the proteasome inhibitor MG132. SAM treatment in Mat1a KO mice for 7 days raised SAM, DUSP1, mRNA and protein levels and lowered proteosomal and ERK activities. Conclusion: DUSP1 mRNA and protein levels are lower in Mat1a KO livers and fall rapidly in cultured hepatocytes. SAM treatment increases DUSP1 expression through multiple mechanisms, and this may suppress ERK activity and malignant degeneration. HEPATOLOGY 2010 [source]

Stat4 and Stat6 signaling in hepatic ischemia/reperfusion injury in mice: HO-1 dependence of Stat4 disruption-mediated cytoprotection

HEPATOLOGY, Issue 2 2003
Xiu-Da Shen
Ischemia/reperfusion (I/R) injury remains an important problem in clinical organ transplantation. There is growing evidence that T lymphocytes, and activated CD4+ T cells in particular, play a key role in hepatic I/R injury. This study analyzes the role of signal transducer and activator of transcription 4 (Stat4) and Stat6 signaling in liver I/R injury. Using a partial lobar warm ischemia model, groups of wild-type (WT), T cell,deficient, Stat4-/Stat6-deficient knockout (KO) mice were assessed for the extent/severity of I/R injury. Ninety minutes of warm ischemia followed by 6 hours of reperfusion induced a fulminant liver failure in WT and Stat6 KO mice, as assessed by hepatocellular damage (serum alanine aminotransferase [sALT] levels), neutrophil accumulation (myeloperoxidase [MPO] activity) and histology (Suzuki scores). In contrast, T cell deficiency (nu/nu mice) or disruption of Stat4 signaling (Stat4 KO mice) reduced I/R insult. Unlike adoptive transfer of WT or Stat6-deficient T cells, infusion of Stat4-deficient T cells failed to restore hepatic I/R injury and prevented tumor necrosis factor , (TNF-,) production in nu/nu mice. Diminished TNF-,/Th1-type cytokine messenger RNA (mRNA)/protein elaborations patterns, along with overexpression of heme oxygenase-1 (HO-1),accompanied hepatic cytoprotection in Stat4 KO recipients. In contrast, HO-1 depression restored hepatic injury in otherwise I/R resistant Stat4 KOs. In conclusion, Stat4 signaling is required for, whereas Stat4 disruption protects against, warm hepatic I/R injury in mice. The cytoprotection rendered by Stat4 disruption remains HO-1,dependent. [source]

CD14 contributes to pulmonary inflammation and mortality during murine tuberculosis

IMMUNOLOGY, Issue 2 2008
Catharina W. Wieland
Summary Toll-like receptors play an essential role in the innate recognition of micro-organisms by the host. CD14 is one of the extracellular adaptor proteins required for recognition of Gram-negative bacteria and possibly also Mycobacterium tuberculosis. Therefore, we intranasally infected wild-type (WT) and CD14 knock-out (KO) mice with virulent M. tuberculosis H37Rv. We found no differences in bacterial load in the main target organ lung up to 32 weeks after infection. From 20 weeks onward 57% of WT mice succumbed, whereas all CD14 KO mice survived. The improved outcome of CD14 KO mice was accompanied by reduced pulmonary inflammation; lung cell counts and percentage of inflamed lung tissue were reduced in CD14 WT mice. These data suggest that during chronic infection CD14 KO mice are protected from lethality caused by lung tuberculosis because of a reduction of the inflammatory response. [source]

LPS-Induced Inhibition of Osteogenesis Is TNF-, Dependent in a Murine Tooth Extraction Model,,

Nobuyoshi Tomomatsu
Abstract TNF-, is a major etiologic factor of inflammatory bone diseases such as periodontitis and rheumatoid arthritis. In addition, patients with metabolic diseases such as chronic heart disease and diabetes have significantly increased plasma levels of TNF-,. Several lines of evidence show inhibition of osteoblastogenesis by TNF-, in vitro. Therefore, bone formation and osteogenesis in these patients might be inhibited because of TNF-,. However, little is known about the inhibitory role of TNF-, in bone formation/osteogenesis in vivo. The purpose of this study was to investigate the role of TNF-, in osteogenesis using a murine tooth extraction model. Lipopolysaccharide (LPS) was injected subcutaneously into the calvariae of either wildtype (WT) or TNF-,,deficient (KO) mice. The left incisor was extracted 4 days after LPS injection. The measuring area was established as the tooth socket under the mesial root of the first molar. A significant increase in serum TNF-, levels after LPS injection was observed in WT mice. The BMD of the tooth socket was significantly decreased by LPS injection 21 days after extraction in WT but not in KO mice. Histomorphometric analysis showed a significant decrease in the mineral apposition rate after LPS injection, which appeared at an early stage in WT but not in KO mice. Injection of a peptide that blocked the TNF-, signaling pathway by preventing transmission of the NF-,B signal recovered the inhibition of osteogenesis observed after LPS injection. In conclusion, TNF-, might play a major role in LPS-induced inhibition of osteogenesis under inflammatory conditions. [source]

Targeted Deletion of the Sclerostin Gene in Mice Results in Increased Bone Formation and Bone Strength,,

Xiaodong Li
Abstract Introduction: Sclerosteosis is a rare high bone mass genetic disorder in humans caused by inactivating mutations in SOST, the gene encoding sclerostin. Based on these data, sclerostin has emerged as a key negative regulator of bone mass. We generated SOST knockout (KO) mice to gain a more detailed understanding of the effects of sclerostin deficiency on bone. Materials and Methods: Gene targeting was used to inactivate SOST and generate a line of SOST KO mice. Radiography, densitometry, ,CT, histomorphometry, and mechanical testing were used to characterize the impact of sclerostin deficiency on bone in male and female mice. Comparisons were made between same sex KO and wildtype (WT) mice. Results: The results for male and female SOST KO mice were similar, with differences only in the magnitude of some effects. SOST KO mice had increased radiodensity throughout the skeleton, with general skeletal morphology being normal in appearance. DXA analysis of lumbar vertebrae and whole leg showed that there was a significant increase in BMD (>50%) at both sites. ,CT analysis of femur showed that bone volume was significantly increased in both the trabecular and cortical compartments. Histomorphometry of trabecular bone revealed a significant increase in osteoblast surface and no significant change in osteoclast surface in SOST KO mice. The bone formation rate in SOST KO mice was significantly increased for trabecular bone (>9-fold) at the distal femur, as well as for the endocortical and periosteal surfaces of the femur midshaft. Mechanical testing of lumbar vertebrae and femur showed that bone strength was significantly increased at both sites in SOST KO mice. Conclusions:SOST KO mice have a high bone mass phenotype characterized by marked increases in BMD, bone volume, bone formation, and bone strength. These results show that sclerostin is a key negative regulator of a powerful, evolutionarily conserved bone formation pathway that acts on both trabecular and cortical bone. [source]

Intestinal Calcium Transporter Genes Are Upregulated by Estrogens and the Reproductive Cycle Through Vitamin D Receptor-Independent Mechanisms,

SJ Van Cromphaut
Abstract 1,,25(OH)2 -vitamin D strongly regulates the expression of the epithelial calcium channel CaT1. CaT1 expression is reduced in ERKO, mice and induced by estrogen treatment, pregnancy, or lactation in VDR WT and KO mice. Estrogens and vitamin D are thus independent potent regulators of the expression of this calcium influx mechanism, which is involved in active intestinal calcium absorption. Introduction: Active duodenal calcium absorption consists of three major steps: calcium influx into, transfer through, and extrusion out of the enterocyte. These steps are carried out by the calcium transport protein 1 (CaT1), calbindin-D9K, and the plasma membrane calcium ATPase (PMCA1b), respectively. We investigated whether estrogens or hormonal changes during the female reproductive cycle influence the expression of these genes, and if so, whether these effects are vitamin D-vitamin D receptor (VDR) dependent. Materials and Methods: We evaluated duodenal expression patterns in estrogen receptor (ER), and -, knockout (KO) mice, as well as in ovariectomized, estrogen-treated, pregnant, and lactating VDR wild-type (WT) and VDR KO mice. Results: Expression of calcium transporter genes was not altered in ERKO, mice. CaT1 mRNA expression was reduced by 55% in ERKO, mice, while the two other calcium transporter genes were not affected. Ovariectomy caused no change in duodenal expression pattern of VDR WT and KO mice, whereas treatment with a pharmacologic dose of estrogens induced CaT1 mRNA expression in VDR WT (4-fold) and KO (8-fold) mice. Pregnancy enhanced CaT1 expression equally in VDR WT and KO mice (12-fold). Calbindin-D9K and PMCA1b expression increased to a lesser extent and solely in pregnant VDR WT animals. In lactating VDR WT and KO mice, CaT1 mRNA expression increased 13 times, which was associated with a smaller increase in calbindin-D9K protein content and PMCA1b mRNA expression. Conclusions: Estrogens or hormonal changes during pregnancy or lactation have distinct, vitamin D-independent effects at the genomic level on active duodenal calcium absorption mechanisms, mainly through a major upregulation of the calcium influx channel CaT1. The estrogen effects seem to be mediated solely by ER,. [source]

Regulation of lipopolysaccharide-induced inflammatory response and endotoxemia by ,-arrestins,

Katie J. Porter
,-Arrestins are scaffolding proteins implicated as negative regulators of TLR4 signaling in macrophages and fibroblasts. Unexpectedly, we found that ,-arrestin-1 (,-arr-1) and -2 knockout (KO) mice are protected from TLR4-mediated endotoxic shock and lethality. To identify the potential mechanisms involved, we examined the plasma levels of inflammatory cytokines/chemokines in the wild-type (WT) and ,-arr-1 and -2 KO mice after lipopolysaccharide (LPS, a TLR4 ligand) injection. Consistent with lethality, LPS-induced inflammatory cytokine levels in the plasma were markedly decreased in both ,-arr-1 and -2 KO, compared to WT mice. To further explore the cellular mechanisms, we obtained splenocytes (separated into CD11b+ and CD11b, populations) from WT, ,-arr-1, and -2 KO mice and examined the effect of LPS on cytokine production. Similar to the in vivo observations, LPS-induced inflammatory cytokines were significantly blocked in both splenocyte populations from the ,-arr-2 KO compared to the WT mice. This effect in the ,-arr-1 KO mice, however, was restricted to the CD11b, splenocytes. Our studies further indicate that regulation of cytokine production by ,-arrestins is likely independent of MAPK and I,B,-NF,B pathways. Our results, however, suggest that LPS-induced chromatin modification is dependent on ,-arrestin levels and may be the underlying mechanistic basis for regulation of cytokine levels by ,-arrestins in vivo. Taken together, these results indicate that ,-arr-1 and -2 mediate LPS-induced cytokine secretion in a cell-type specific manner and that both ,-arrestins have overlapping but non-redundant roles in regulating inflammatory cytokine production and endotoxic shock in mice. J. Cell. Physiol. 225: 406,416, 2010. 2010 Wiley-Liss, Inc. [source]

Effects of myostatin deletion in aging mice

AGING CELL, Issue 5 2009
Michael R. Morissette
Summary Inhibitors of myostatin, a negative regulator of skeletal muscle mass, are being developed to mitigate aging-related muscle loss. Knock-out (KO) mouse studies suggest myostatin also affects adiposity, glucose handling and cardiac growth. However, the cardiac consequences of inhibiting myostatin remain unclear. Myostatin inhibition can potentiate cardiac growth in specific settings (Morissette et al., 2006), a concern because of cardiac hypertrophy is associated with adverse clinical outcomes. Therefore, we examined the systemic and cardiac effects of myostatin deletion in aged mice (27,30 months old). Heart mass increased comparably in both wild-type (WT) and KO mice. Aged KO mice maintained twice as much quadriceps mass as aged WT; however, both groups lost the same percentage (36%) of adult muscle mass. Dual-energy X-ray absorptiometry revealed increased bone density, mineral content, and area in aged KO vs. aged WT mice. Serum insulin and glucose levels were lower in KO mice. Echocardiography showed preserved cardiac function with better fractional shortening (58.1% vs. 49.4%, P = 0.002) and smaller left ventricular diastolic diameters (3.41 vs. 2.71, P = 0.012) in KO vs. WT mice. Phospholamban phosphorylation was increased 3.3-fold in KO hearts (P < 0.05), without changes in total phospholamban, sarco(endo)plasmic reticulum calcium ATPase 2a or calsequestrin. Aged KO hearts showed less fibrosis by Masson's Trichrome staining. Thus, myostatin deletion does not affect aging-related increases in cardiac mass and appears beneficial for bone density, insulin sensitivity and heart function in senescent mice. These results suggest that clinical interventions designed to inhibit skeletal muscle mass loss with aging could have beneficial effects on other organ systems as well. [source]

GAT-1 regulates both tonic and phasic GABAA receptor-mediated inhibition in the cerebral cortex

Luca Bragina
Abstract ,-Aminobutyric acid 1 (GAT-1) is the most copiously expressed GABA transporter; we studied its role in phasic and tonic inhibition in the neocortex using GAT-1 knockout (KO) mice. Immunoblotting and immunocytochemical studies showed that GAT-2 and GAT-3 levels in KOs were unchanged and that GAT-3 was not redistributed in KOs. Moreover, the expression of GAD65/67 was increased, whereas that of GABA or VGAT was unchanged. Microdialysis studies showed that in KOs spontaneous extracellular release of GABA and glutamate was comparable in WT and KO mice, whereas KCl-evoked output of GABA, but not of glutamate, was significantly increased in KOs. Recordings from layer II/III pyramids revealed a significant increase in GABAAR-mediated tonic conductance in KO mice. The frequency, amplitude and kinetics of spontaneous inhibitory post-synaptic currents (IPSCs) were unchanged, whereas the decay time of evoked IPSCs was significantly prolonged in KO mice. In KO mice, high frequency stimulation of GABAergic terminals induced large GABAAR-mediated inward currents associated with a reduction in amplitude and decay time of IPSCs evoked immediately after the train. The recovery process was slower in KO than in WT mice. These studies show that in the cerebral cortex of GAT-1 KO mice GAT-3 is not redistributed and GADs are adaptively changed and indicate that GAT-1 has a prominent role in both tonic and phasic GABAAR-mediated inhibition, in particular during sustained neuronal activity. [source]

Transthyretin enhances nerve regeneration

Carolina E. Fleming
Abstract Mutations in transthyretin (TTR) are associated with familial amyloid polyneuropathy, a neurodegenerative disorder characterized by TTR deposition in the PNS. The aim of this study was to unravel whether TTR has a role in nerve physiology that could account for its preferential accumulation in the PNS, when mutated. The sensorimotor performance of wild-type and TTR knockout (KO) littermate mice was compared and showed impairment in mice lacking TTR. Given the possibility that, upon regeneration, the consequences arising from TTR absence might be exacerbated, nerve crush was performed in both strains. TTR KO mice presented delayed functional recovery resulting from decreased number of myelinated and unmyelinated fibers. Moreover, in transgenic mice in a TTR KO background, expressing human TTR in neurons, this phenotype was rescued, reinforcing that TTR enhances nerve regeneration. In vitro assays showed that neurite outgrowth and extension were decreased in the absence of TTR, probably underlying the decreased number of regenerating axons in TTR KO mice. Our findings demonstrate that TTR participates in nerve physiology and that it enhances nerve regeneration. Moreover, the assignment of a TTR function in nerve biology and repair, may explain its preferential deposition, when mutated, in the PNS of familial amyloid polyneuropathy patients. [source]

Workshop 5: NAAG and NAALADase: Functional Properties in the Central and Peripheral Nervous System

D. Bacich
Glutamate carboxypeptidase II (GCPII, also known as N-acetylated-alpha-linked acidic dipeptidase or NAALADase) knockout (KO) mice were generated by inserting a GCPII targeting cassette containing a PGK-Neo resistance marker and stop codons in exons 1 and 2, and removal of exons 1 and 2 intron/exon boundary sequence. Embryonic stem cells were injected into C57BL6 blastocysts, and chimeric offspring born. Germline transmission was confirmed by mating the chimeras to generate heterozygous KO mice. Crossing heterozygous mice generated F2 generation mice homozygous for the null mutant, as confirmed by loss of GCPII protein. NAAG hydrolyzing activity was minimal (0.07 pmol/mg/min) in KO tissue, with normal levels (4.82 pmol/mg/min) in wild types and intermediate levels (1.73 pmol/mg/min) in heterozygotes. Preliminary neuropathy experiments showed KO mice are less affected by nerve-crush and recover faster from the damage-induced neuropathy, as indicated by EMG recording and nerve morphology. Similarly, GCPII KO mice subjected to high dose vitamin B6 displayed less severe neuropathy than wild types, as indicated by reduced sensory nerve conduction velocity and morphological deficits. Also, in a transient middle cerebral artery occlusion model, GCPII KO mice were significantly more resistant to the effects of cerebral ischemia than their wildtype littermates. Findings support GCPII involvement in stroke and in mediating chronic neuropathic conditions and suggest GCPII inhibitors may be useful in treatment of brain ischemia as well as peripheral neuropathies. [source]

Tibolone Rapidly Attenuates the GABAB Response in Hypothalamic Neurones

J. Qiu
Tibolone is primarily used for the treatment of climacteric symptoms. Tibolone is rapidly converted into three major metabolites: 3,- and 3,-hydroxy (OH)-tibolone, which have oestrogenic effects, and the ,4-isomer (,4-tibolone), which has progestogenic and androgenic effects. Because tibolone is effective in treating climacteric symptoms, the effects on the brain may be explained by the oestrogenic activity of tibolone. Using whole-cell patch clamp recording, we found previously that 17,-oestradiol (E2) rapidly altered ,-aminobutyric acid (GABA) neurotransmission in hypothalamic neurones through a membrane oestrogen receptor (mER). E2 reduced the potency of the GABAB receptor agonist baclofen to activate G-protein-coupled, inwardly rectifying K+ (GIRK) channels in hypothalamic neurones. Therefore, we hypothesised that tibolone may have some rapid effects through the mER and sought to elucidate the signalling pathway of tibolone's action using selective inhibitors and whole cell recording in ovariectomised female guinea pigs and mice. A sub-population of neurones was identified post hoc as pro-opiomelanocortin (POMC) neurones by immunocytochemical staining. Similar to E2, we have found that tibolone and its active metabolite 3,OH-tibolone rapidly reduced the potency of the GABAB receptor agonist baclofen to activate GIRK channels in POMC neurones. The effects were blocked by the ER antagonist ICI 182 780. Other metabolites of tibolone (3,OH-tibolone and ,4-tibolone) had no effect. Furthermore, tibolone (and 3,OH-tibolone) was fully efficacious in ER, knockout (KO) and ER,KO mice to attenuate GABAB responses. The effects of tibolone were blocked by phospholipase C inhibitor U73122. However, in contrast to E2, the effects of tibolone were not blocked by protein kinase C inhibitors or protein kinase A inhibitors. It appears that tibolone (and 3,OH-tibolone) activates phospholipase C leading to phosphatidylinositol bisphosphate metabolism and direct alteration of GIRK channel function. Therefore, tibolone may enhance synaptic efficacy through the Gq signalling pathways of mER in brain circuits that are critical for maintaining homeostatic functions. [source]

Double Oestrogen Receptor , and , Knockout Mice Reveal Differences in Neural Oestrogen-Mediated Progestin Receptor Induction and Female Sexual Behaviour

A. E. Kudwa
Abstract To test the hypothesis that oestrogen receptor , (ER,) and ER, act together to mediate the actions of oestrogen in the ventromedial hypothalamus (VMH), we used mice with single or double knockout mutations of the ER, and ER, genes. Ovariectomized mice were implanted with 17,-oestradiol and killed 5 days later. Oestradiol treatment promoted progestin receptor (PR)-immunoreactivity (-ir) in the VMH of all genotypes, but was maximal in brains of wild-type and ER,KO females. Analysis of specific VMH subregions revealed that PR-ir induction was limited to the caudal VMH in ER,KO and ER,,KO mice. In the rostral VMH, oestradiol only induced PR-ir in wild-type and ER,KO mice, and the number of PR-ir neurones in this region was greater in ER,KO than wild-type females. Next, we tested the ability of a dopamine agonist and progesterone to facilitate sexual behaviour in females lacking functional ER,, ER,, or both receptors. Ovariectomized mice were implanted with oestradiol, and tested for sexual behaviour three times after administration of the dopamine agonist, apomorphine, followed by two tests concurrent with progesterone treatment and a final test with just apomorphine treatment. ER,KO and ER,,KO females failed to display lordosis under any testing conditions, while ER,KO females exhibited lordosis behaviour equal to that of wild-type females. Our data show that a subpopulation of PR-ir neurones is induced by oestradiol in the caudal VMH of female mice lacking both ER, and ER, genes. We hypothesize that this action of oestradiol is either mediated by a novel ER or by the mutant portion of the AF2 subregion of the ER, gene present in ER,KO brain. However, despite the presence of PR in VMH, females lacking a functional ER, gene do not display sexual behaviour, via either ligand-dependent or -independent activation. [source]