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MAPK Inhibition (mapk + inhibition)
Selected AbstractsToll-like receptor and tumour necrosis factor dependent endotoxin-induced acute lung injuryINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 6 2007Dieudonnée Togbe Summary Recent studies on endotoxin/lipopolysaccharide (LPS)-induced acute inflammatory response in the lung are reviewed. The acute airway inflammatory response to inhaled endotoxin is mediated through Toll-like receptor 4 (TLR4) and CD14 signalling as mice deficient for TLR4 or CD14 are unresponsive to endotoxin. Acute bronchoconstriction, tumour necrosis factor (TNF), interleukin (IL)-12 and keratinocyte-derived chemokine (KC) production, protein leak and neutrophil recruitment in the lung are abrogated in mice deficient for the adaptor molecules myeloid differentiation factor 88 (MyD88) and Toll/Interleukin-1 receptor (TIR)-domain-containing adaptor protein (TIRAP), but independent of TIR-domain-containing adaptor-inducing interferon-beta (TRIF). In particular, LPS-induced TNF is required for bronchoconstriction, but dispensable for inflammatory cell recruitment. Lipopolysaccharide induces activation of the p38 mitogen-activated protein kinase (MAPK). Inhibition of pulmonary MAPK activity abrogates LPS-induced TNF production, bronchoconstriction, neutrophil recruitment into the lungs and broncho-alveolar space. In conclusion, TLR4-mediated, bronchoconstriction and acute inflammatory lung pathology to inhaled endotoxin are dependent on TLR4/CD14/MD2 expression using the adapter proteins TIRAP and MyD88, while TRIF, IL-1R1 or IL-18R signalling pathways are dispensable. Further downstream in this axis of signalling, TNF blockade reduces only acute bronchoconstriction, while MAPK inhibition abrogates completely endotoxin-induced inflammation. [source] Differentiation-dependent association of phosphorylated extracellular signal-regulated kinase with the chromatin of osteoblast-related genesJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2010Yan Li Abstract The ERK/MAP kinase pathway is an important regulator of gene expression and differentiation in postmitotic cells. To understand how this pathway controls gene expression in bone, we examined the subnuclear localization of P-ERK in differentiating osteoblasts. Induction of differentiation was accompanied by increased ERK phosphorylation and expression of osteoblast-related genes, including osteocalcin (Bglap2) and bone sialoprotein (Ibsp). Confocal immunofluorescence microscopy revealed that P-ERK colocalized with the RUNX2 transcription factor in the nuclei of differentiating cells. Interestingly, a portion of this nuclear P-ERK was directly bound to the proximal promoter regions of Bglap2 and Ibsp. Furthermore, the level of P-ERK binding to chromatin increased with differentiation, whereas RUNX2 binding remained relatively constant. The P-ERK-chromatin interaction was seen only in RUNX2-positive cells, required intact RUNX2-selective enhancer sequences, and was blocked with MAPK inhibition. These studies show for the first time that RUNX2 specifically targets P-ERK to the chromatin of osteoblast-related genes, where it may phosphorylate multiple substrates, including RUNX2, resulting in altered chromatin structure and gene expression. © 2010 American Society for Bone and Mineral Research [source] Constitutive activation of the mitogen-activated protein kinase pathway impairs vitamin D signaling in human prostate epithelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2010Zhentao Zhang We studied the effect of prolonged activation of mitogen-activated protein kinase (MAPK) signaling on 1,25 dihydroxyvitamin D (1,25(OH)2D3) action in the immortalized human prostate epithelial cell line RWPE1 and its Ki-Ras transformed clone RWPE2. 1,25(OH)2D3 -treatment caused growth arrest and induced gene expression in both cell lines but the response was blunted in RWPE2 cells. Vitamin D receptor (VDR) levels were lower in RWPE2 cells but VDR over-expression did not increase vitamin-D-mediated gene transcription in either cell line. In contrast, MAPK inhibition restored normal vitamin D transcriptional responses in RWPE2 cells and MAPK activation with constitutively active MEK1R4F reduced vitamin-D-regulated transcription in RWPE1 cells. 1,25(OH)2D3 -mediated transcription depends upon the VDR and its heterodimeric partner the retinoid X receptor (RXR) so we studied whether changes in the VDR,RXR transcription complex occur in response to MAPK activation. Mutation of putative phosphorylation sites in the activation function 1 (AF-1) domain (S32A, T82A) of RXR, restored 1,25(OH)2D3 -mediated transactivation in RWPE2 cells. Mammalian two-hybrid and co-immunoprecipitation assays revealed a vitamin-D-independent interaction between steroid receptor co-activator-1 (SRC-1) and RXR, that was reduced by MAPK activation and was restored in RWPE2 cells by mutating S32 and T82 in the RXR, AF-1 domain. Our data show that a common contributor to cancer development, prolonged activation of MAPK signaling, impairs 1,25(OH)2D3 -mediated transcription in prostate epithelial cells. This is due in part to the phosphorylation of critical amino acids in the RXR, AF-1 domain and impaired co-activator recruitment. J. Cell. Physiol. 224: 433,442, 2010. © 2010 Wiley-Liss, Inc. [source] Role of atypical protein kinase C isozymes and NF-,B in IL-1,-induced expression of cyclooxygenase-2 in human myometrial smooth muscle cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2007Sara V. Duggan Increased myometrial expression of cyclooxygenase-2 (Cox-2) at term results from elevated local levels of inflammatory cytokines, and its inhibition provides a potential route for intervention in human pre-term labor. We have identified a role for atypical protein kinase C (PKC) isozymes in IL-1,-induced Cox-2 expression in human myometrial smooth muscle cells (HMSMC). The PKC inhibitor GF109203X (10 µM) inhibited IL-1,-induced Cox-2 protein and RNA expression, which were also reduced by MAPK and nuclear factor ,B (NF-,B) inhibitors. GF109203X did not affect MAPK activities, and neither did it replicate the effect of p38 MAPK inhibition on Cox-2 mRNA stability, suggesting that PKC operates through an independent mechanism. The effect of GF109203X remained intact after depletion of conventional and novel PKC isozymes by phorbol ester pre-treatment. In contrast LY379196 (10 µM), which at micromolar concentrations inhibits all but atypical PKCs, did not affect Cox-2 expression. A peptide corresponding to the pseudosubstrate sequence of atypical PKCs blocked Cox-2 protein expression, whereas the sequence from conventional PKCs was ineffective. GF109203X did not affect NF-,B binding to nuclear proteins, but strongly reduced NF-,B-dependent transcription in luciferase reporter assays. Our findings indicate that IL-1,-induced Cox-2 expression in HMSMC in culture requires p38-MAPK-mediated mRNA stabilization and an independent activation of Cox-2 transcription which is dependent on the action of atypical PKCs, probably through direct stimulation of the transactivating activity of NF-,B. J. Cell. Physiol. 210: 637,643, 2007. © 2006 Wiley-Liss, Inc. [source] Helicobacter pylori and mitogen-activated protein kinases regulate the cell cycle, proliferation and apoptosis in gastric epithelial cellsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 7pt2 2008Song-Ze Ding Abstract Background and Aims:,Helicobacter pylori infection activates mitogen-activated protein kinases (MAPK) and modulates cell proliferation and apoptosis. However, the relationship between H. pylori infection and MAPK signaling in controlling cell proliferation and apoptosis is not clear, nor has the role of MAPK on the gastric epithelial cell cycle and proliferation been established. Therefore, we investigated the effects of H. pylori infection and MAPK inhibition on these processes. Methods:, Gastric epithelial cell lines (AGS and MKN45) were infected with H. pylori and/or treated with MAPK inhibitors. Cell cycle and apoptosis were measured by flow cytometry. Cell cycle proteins and proliferation were monitored by western blot and cell count, respectively. Results:, Infection with H. pylori resulted in dose-dependent MAPK activation, cell cycle arrest, reduced proliferation and increased apoptosis. The effect of H. pylori and MAPK at various cell cycle checkpoints was noted: MEK1/2 and p38 inhibition increased H. pylori -induced cell cycle G1 arrest, while JNK inhibition reduced G1 arrest. MEK1/2 inhibition increased p21, p27 and cyclin E and JNK inhibition additionally increased cyclin D1 expression. Both inhibitors decreased cell proliferation. All inhibitors enhanced apoptosis after H. pylori infection. We also detected MAPK cross-talk in AGS cells: p38 and JNK inhibitors increased ERK activation. The p38 inhibitor increased JNK and the MEK1/2 inhibitor decreased JNK activation only during H. pylori infection. Conclusions:, These results suggest H. pylori and MAPK differentially regulate the cell cycle, proliferation and apoptosis in gastric epithelial cells. The imbalance between H. pylori infection and MAPK activation likely contributes to the H. pylori -induced pathogenesis. [source] Minocycline exerts inhibitory effects on multiple mitogen-activated protein kinases and I,B, degradation in a stimulus-specific manner in microgliaJOURNAL OF NEUROCHEMISTRY, Issue 2 2006Maria Nikodemova Abstract CNS inflammation mediated by microglial activation can result in neuronal and glial cell death in a variety of neurodegenerative and demyelinating diseases. Minocycline, a second-generation tetracycline, has profound anti-inflammatory properties in the CNS mediated, in part, by inhibition of microglia. MAPK and nuclear factor-,B (NF-,B) activation are hallmarks of activated microglia and they are critical for the expression of many inflammatory mediators. In the present study, we investigated minocycline effects on activation of p38, c-Jun-N-terminal activated protein kinase (JNK) 1/2 and extracellular signal regulated kinase (ERK) 1/2 MAPKs and inhibitor , of NF-,B (I,B,) degradation in BV-2 and primary microglial cells. Our results demonstrate that minocycline has the ability to inhibit all MAPKs but these effects strongly depend on the stimulus used for MAPK activation. Minocycline significantly decreased activation of all lipopolysaccharide-stimulated MAPKs but it was without effect on MAPKs activated by H2O2. Minocycline inhibited JNK1/2 and ERK1/2 but not p38 when stimulated by 2,,3,- O -(4-benzoylbenzoyl)-adenosine 5,-triphosphate, indicating that minocycline affects only certain upstream signaling target(s) that are stimulus-specific. Our data also suggest that protein kinase C (PKC) inhibition may be partially involved in the minocycline mechanism of MAPK inhibition. In addition, minocycline attenuated lipopolysaccharide-stimulated degradation of I,B, implying a possible inhibitory role on NF-,B transcriptional activity. [source] p38 MAPK inhibition modulates rabbit nucleus pulposus cell response to IL-1,JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 7 2008Rebecca K. Studer Abstract Analysis of disc gene expression implicated IL-1 in the development of intervertebral disc degeneration (IDD) in a rabbit stab model. The purpose of these studies is to determine the role of p38 Mitogen Activated Protein Kinase (p38 MAPK) signaling in nucleus pulposus cell response to IL-1, and to compare rabbit nucleus pulposus (rNP) cell responses to IL-1 activation with those in a stab model of disc degeneration. NP cells maintained in alginate bead culture were exposed to IL-1, with or without p38 MAPK inhibition. RNA was isolated for reverse transcription polymerase chain reaction (RT-PCR) analysis of gene expression, conditioned media analyzed for accumulation of nitric oxide (NO) and prostaglandin E-2 (PGE-2), and proteoglycan synthesis measured after 10 days. IL-1 upregulation of mRNA for cycloxygenase-2 (COX-2), matrix metalloproteinase-3 (MMP-3), IL-1, and IL-6, was blunted by p38 inhibition while downregulation of matrix proteins (collagen I, collagen II, aggrecan) and insulin-like-growth-factor I (IFG-1) was also reversed. mRNA for tissue inhibitor of matrixmetalloproteinase-1 (TIMP-1) was modestly increased by IL-1, while those for Transforming Growth Factor-, (TGF-,) SOX-9, and versican remained unchanged. Blocking p38 MAPK reduced IL-1 induced NO and PGE-2 accumulation and partially restored proteoglycan synthesis. p38 MAPK inhibition in control cells increased mRNA for matrix proteins (aggrecan, collagen II, versican, collagen I) and anabolic factors (IGF-1, TGF, and SOX-9) from 50% to 120%, decreased basal PGE-2 accumulation, but had no effect on message for TIMP-1, MMP-3, or COX-2. Inhibition of p38 MAPK in cytokine-activated disc cells blunts gene expression and production of factors associated with inflammation, pain, and disc matrix catabolism while reversing IL-1 downregulation of matrix protein gene expression and proteoglycan synthesis. The results support the hypothesis that IL-1 could be responsible for many of the mRNA changes seen in rabbit NP in the stab model of disc degeneration, and uphold the concept that development of molecular techniques to block p38 MAPK could provide a therapeutic approach to slow the course of intervertebral disc degeneration. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:991,998, 2008 [source] cAMP blocks MAPK activation and sclerotial development via Rap-1 in a PKA-independent manner in Sclerotinia sclerotiorumMOLECULAR MICROBIOLOGY, Issue 1 2005Changbin Chen Summary Sclerotinia sclerotiorum is a filamentous ascomycete phytopathogen able to infect an extremely wide range of cultivated plants. Our previous studies have shown that increases in cAMP levels result in the impairment of the development of the sclerotium, a highly differentiated structure important in the disease cycle of this fungus. cAMP also inhibits the activation of a S. sclerotiorum mitogen-activated protein kinase (MAPK), which we have previously shown to be required for sclerotial maturation; thus cAMP-mediated sclerotial inhibition is modulated through MAPK. However, the mechanism(s) by which cAMP inhibits MAPK remains unclear. Here we demonstrate that a protein kinase A (PKA)-independent signalling pathway probably mediates MAPK inhibition by cAMP. Expression of a dominant negative form of Ras, an upstream activator of the MAPK pathway, also inhibited sclerotial development and MAPK activation, suggesting that a conserved Ras/MAPK pathway is required for sclerotial development. Evidence from bacterial toxins that specifically inhibit the activity of small GTPases, suggested that Rap-1 or Ras is involved in cAMP action. The Rap-1 inhibitor, GGTI-298, restored MAPK activation in the presence of cAMP, further suggesting that Rap-1 is responsible for cAMP-dependent MAPK inhibition. Importantly, inhibition of Rap-1 is able to restore sclerotial development blocked by cAMP. Our results suggest a novel mechanism involving the requirement of Ras/MAPK pathway for sclerotial development that is negatively regulated by a PKA-independent cAMP signalling pathway. Cross-talk between these two pathways is mediated by Rap-1. [source] Efficacy, pharmacodynamics, and safety of VX-702, a novel p38 MAPK inhibitor, in rheumatoid arthritis: Results of two randomized, double-blind, placebo-controlled clinical studies,ARTHRITIS & RHEUMATISM, Issue 5 2009Nemanja Damjanov Objective To assess the efficacy and safety of VX-702, a p38 MAPK inhibitor, in patients with active, moderate-to-severe rheumatoid arthritis (RA). Methods Two 12-week, double-blind, placebo-controlled studies of VX-702 were conducted in patients with active, moderate-to-severe RA. In the VeRA study, 313 patients received placebo or 2 daily doses of VX-702. In Study 304, 117 patients received placebo, daily VX-702, or twice weekly VX-702 in addition to concomitant methotrexate (MTX). Study end points included the proportion of patients meeting the American College of Rheumatology 20% improvement criteria (an ACR20 response), ACR50 and ACR70 responses, changes in the serum levels of biomarkers of inflammation, and safety assessments. Results The numerically superior ACR20 response rates among patients receiving VX-702 compared with those receiving placebo in both studies did not reach pairwise statistical significance at the highest doses in either study. At week 12 in the VeRA study, ACR20 response rates were 40%, 36%, and 28% among patients receiving 10 mg of VX-702, 5 mg of VX-702, and placebo, respectively. In Study 304, the response rates were 40%, 44%, and 22% for patients receiving 10 mg VX-702 daily plus MTX, 10 mg VX-702 twice weekly plus MTX, and placebo, respectively. Reductions in the levels of C-reactive protein, soluble tumor necrosis factor receptor p55, and serum amyloid A were observed as early as week 1 in both studies, but these levels rapidly returned to baseline values by week 4. The overall frequency of adverse events was similar between the VX-702 and placebo groups. In the VeRA study, serious infections were more frequent in the VX-702 groups compared with the placebo group (2.4% versus 0%) but not in Study 304 (2.6% versus 4.9%). Conclusion The modest clinical efficacy plus the transient suppression of biomarkers of inflammation observed in this study suggest that p38 MAPK inhibition may not provide meaningful, sustained suppression of the chronic inflammation seen in RA. [source] Adalimumab therapy rapidly inhibits p38 mitogen-activated protein kinase activity in lesional psoriatic skin preceding clinical improvementBRITISH JOURNAL OF DERMATOLOGY, Issue 6 2010L. Soegaard-Madsen Summary Background, The pathogenesis of psoriasis and the mechanisms of action of antitumour necrosis factor (TNF)-, therapies are incompletely understood. Objectives, To investigate the early molecular effects of adalimumab in psoriatic skin. Methods, Biopsies taken from patients with psoriasis were examined before and after the onset of adalimumab therapy. TNF-, protein level and mRNA expression were measured by enzyme-linked immunosorbent assay and quantitative reverse transcription,polymerase chain reaction, respectively. The activities of p38 mitogen-activated protein kinase (MAPK) and extracellular regulated kinase 1 and 2 (ERK1/2) as well as the downstream kinases MAPK-activated protein kinase 2 (MK2) and mitogen- and stress-activated protein kinase 1 and 2 (MSK1/2) were measured by Western blot analyses. Results, We demonstrated that clinical and histological improvements were detected from day 14. The increased activity of p38 MAPK in lesional psoriatic skin was significantly inhibited by adalimumab already at day 4. The activities of ERK1/2, MSK1/2 and MK2 were reduced at the end of study (day 84) when the level of TNF-, in lesional psoriatic skin reached the nonlesional level, and the Psoriasis Area and Severity Index score was reduced. Conclusions, The rapid inhibition of p38 MAPK by adalimumab in lesional psoriatic skin preceded clinical and histological improvements, demonstrating an association between TNF-, neutralization and p38 MAPK inhibition. Thus, inhibition of p38 MAPK may be a novel mechanism by which adalimumab mediates its antipsoriatic effect. [source] Apoptosis signal-regulating kinase 1-mediated sustained p38 mitogen-activated protein kinase activation regulates mycoplasmal lipoprotein- and staphylococcal peptidoglycan-triggered Toll-like receptor 2 signalling pathwaysCELLULAR MICROBIOLOGY, Issue 9 2005Takeshi Into Summary Toll-like receptor (TLR) 2 functions as a sensor for detecting various microbial components conserved in bacteria or fungi in innate immunity. TLR2 induces several signalling pathways linking to activation of the transcriptional factors NF-,B and AP-1 as well as induction of cell death. In human embryonic kidney 293 cells expressed human TLR2, mycoplasmal lipoproteins (MLP) or staphylococcal peptidoglycans (PGN) induced sustained phosphorylation of p38 mitogen-activated protein kinase (MAPK), accompanied by generation of reactive oxygen species. This observation encouraged us to examine roles of apoptosis signal-regulating kinase 1 (ASK1) in TLR2 signalling, because ASK1 is an upstream activator of p38 MAPK during exposure to oxidative stress and other stressful stimuli. A kinase-inactive mutant of ASK1 greatly impaired the sustained phosphorylation of p38 MAPK induced by MLP or PGN. This mutant also attenuated MLP- or PGN-induced transcriptional activities of NF-,B and AP-1 via inhibition of p38 MAPK activation. MLP- or PGN-induced cell death reactions, including DNA fragmentation and caspase-3/7 activation, were also downregulated by the ASK1 mutant via p38 MAPK inhibition. Furthermore, TLR2 signalling had a potential to phosphorylate and dephosphorylate ASK1 at Ser83 residue. Thus, MLP and PGN have capabilities to induce ASK1-dependent signalling pathways which regulate p38 MAPK activation through TLR2, leading to activation of NF-,B and AP-1 as well as induction of cell death. [source] | |||||||||||||