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Pathways Critical (pathway + critical)

Distribution by Scientific Domains

Life Sciences	71%
Medical Sciences	28%

Selected Abstracts

Secretion of matrix metalloproteinase-9 by the proinflammatory cytokine, IL-1,: a role for the dual signalling pathways, Akt and Erk

GENES TO CELLS, Issue 6 2003
A. R. M. Ruhul Amin
Background: Matrix metalloproteinases including MMP-9 mediate matrix destruction during chronic inflammatory diseases such as arthritis and atherosclerosis. MMP-9 up-regulation by inflammatory cytokines involve interactions between several transcription factors including activator protein-1 and NF,B. The upstream regulatory pathways are less well understood. Results: To search for the mechanism of tissue destruction in the process of inflammatory disorders, we investigated the signalling pathway critical for the activation of MMP-9 expression and secretion by IL-1,. Treatment of Balb 3T3 cells with IL-1, activated MMP-9 transcription and subsequent secretion in a time- and dose-dependent manner. Concomitantly, IL-1, treatment of cells activated phosphorylation of Akt, Erk and p38. Treatment of cells with either LY294002, a PI3K inhibitor, or expression of a dominant negative form of Akt drastically suppressed the IL-1,-dependent secretion of MMP-9. Pretreatment of cells with a MEK1 inhibitor, U0126, also strongly inhibited IL-1,-dependent secretion of MMP-9. In contrast, pre-treatment with a specific p38 kinase inhibitor, SB203580, had no effect on IL-1,-dependent secretion of MMP-9. In addition, cells expressing constitutively active form of Akt or MEK1 showed no clear activation of MMP-9 secretion, whereas these cells responded well to IL-1, treatment. However, co-transfection of cells with both active Akt and MEK1 was sufficient to induce MMP-9 secretion without stimulation with IL-1,. Conclusion: Taken together, our results suggest that IL-1, stimulation of cells activates MMP-9 secretion by the activation of the dual signalling pathways, the PI3K-Akt and MEK1-Erk and constitutive activation of these pathways were sufficient to induce MMP-9 secretion. [source]

An MLCK-dependent window in late G1 controls S phase entry of proliferating rodent hepatocytes via ERK-p70S6K pathway,

HEPATOLOGY, Issue 1 2006
Anne Bessard
We show that MLCK (myosin light chain kinase) plays a key role in cell cycle progression of hepatocytes: either chemical inhibitor ML7 or RNA interference led to blockade of cyclin D1 expression and DNA replication, providing evidence that MLCK regulated S phase entry. Conversely, inhibition of RhoK by specific inhibitor Y27632 or RhoK dominant-negative vector did not influence progression in late G1 and S phase entry. Inhibition of either MLCK or RhoK did not block ERK1/2 phosphorylation, whereas MLCK regulated ERK2-dependent p70S6K activation. In addition, DNA synthesis was reduced in hepatocytes treated with p70S6K siRNA, demonstrating the key role played by the kinase in S phase entry. Interestingly, after the G1/S transition, DNA replication in S phase was no longer dependent on MLCK activity. We strengthened this result by ex vivo experiments and evidenced an MLCK-dependent window in late G1 phase of regenerating liver after two-thirds partial hepatectomy. In conclusion, our results underline an MLCK-dependent restriction point in G1/S transition, occurring downstream of ERK2 through the regulation of p70S6K activation, and highlighting a new signaling pathway critical for hepatocyte proliferation. (HEPATOLOGY 2006;44:152,163.) [source]

Screening method to identify inhibitors of siderophore biosynthesis in the opportunistic fungal pathogen, Aspergillus fumigatus

LETTERS IN APPLIED MICROBIOLOGY, Issue 1 2009
L.J. Pinto
Abstract Aims:,Aspergillus fumigatus is the most common cause of airborne mould infections in immunocompromised patients worldwide. Our aim was to develop a method to identify agents that inhibit siderophore biosynthesis because this pathway is unique to the fungus and is essential for virulence. Methods and Results:, A high-throughput two-step screening assay was developed using 96-well plates in which fungal growth and siderophore production is assessed spectrophotometrically. If a compound inhibits growth only in iron-limited medium (screen 1), its effect on siderophore production is then determined (screen 2). The proof of concept was demonstrated using a known antifungal agent, amphotericin B, and a strain of A. fumigatus deficient in siderophore production. Conclusions:, The two-stage screening method clearly identified growth defects in A. fumigatus related specifically to siderophore biosynthesis. Significance and Impact of the Study:, The increasing incidence of life-threatening fungal infections has produced an urgent need for novel antifungal agents. The method described in this report will facilitate the identification of novel antifungal compounds that inhibit a pathway critical for A. fumigatus virulence and have a reduced probability of affecting host metabolism. [source]

Integrative genomic analyses of neurofibromatosis tumours identify SOX9 as a biomarker and survival gene

EMBO MOLECULAR MEDICINE, Issue 4 2009
Shyra J. Miller
Abstract Understanding the biological pathways critical for common neurofibromatosis type 1 (NF1) peripheral nerve tumours is essential, as there is a lack of tumour biomarkers, prognostic factors and therapeutics. We used gene expression profiling to define transcriptional changes between primary normal Schwann cells (n,=,10), NF1-derived primary benign neurofibroma Schwann cells (NFSCs) (n,=,22), malignant peripheral nerve sheath tumour (MPNST) cell lines (n,=,13), benign neurofibromas (NF) (n,=,26) and MPNST (n,=,6). Dermal and plexiform NFs were indistinguishable. A prominent theme in the analysis was aberrant differentiation. NFs repressed gene programs normally active in Schwann cell precursors and immature Schwann cells. MPNST signatures strongly differed; genes up-regulated in sarcomas were significantly enriched for genes activated in neural crest cells. We validated the differential expression of 82 genes including the neural crest transcription factor SOX9 and SOX9 predicted targets. SOX9 immunoreactivity was robust in NF and MPSNT tissue sections and targeting SOX9 , strongly expressed in NF1-related tumours , caused MPNST cell death. SOX9 is a biomarker of NF and MPNST, and possibly a therapeutic target in NF1. [source]

Aqueous exposure to 4-nonylphenol and 17,-estradiol increases stress sensitivity and disrupts ion regulatory ability of juvenile Atlantic salmon

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2007
Darren T. Lerner
Abstract Population declines of wild Atlantic salmon have been attributed to an array of anthropogenic disturbances, including dams, commercial and recreational fishing, habitat loss, and pollution. Environmental contaminants in particular, can act as environmental stressors on fish, typically causing disruption of ion homeostasis due to their close association with the aquatic environment. To examine the effects of the xenoestrogen 4-nonylphenol (NP) or 17,-estradiol (E2) on stress sensitivity and ion regulation, we exposed juvenile Atlantic salmon continuously for 21 d to either 10 or 100 ,g/L NP (NP-L or NP-H), 2 ,g/L E2 (positive control), or vehicle control during the parr-smolt transformation in April. After treatment, fish were sampled in freshwater (FW), transferred to 30, seawater (SW) for 24 h, or subjected to a handling stress. Estradiol and NP-H increased plasma vitellogenin in males and females, and E2 increased gonadosomatic index only in males. In FW, E2 reduced sodium potassium,activated adenosine triphosphatase activity as well as plasma levels of growth hormone, insulin-like growth factor I, and triiodothyronine. Both E2 and NP-H reduced plasma sodium in FW and increased plasma chloride in SW. Plasma Cortisol levels pre- and poststressor were significantly elevated by all treatments relative to controls, but only E2 increased plasma glucose before and after the stressor. These results indicate that exposure of anadromous salmonids to environmental estrogens heightens sensitivity to external stressors, impairs ion regulation in both FW and SW, and disrupts endocrine pathways critical for smolt development. [source]

Predictive toxicogenomics approaches reveal underlying molecular mechanisms of nongenotoxic carcinogenicity

MOLECULAR CARCINOGENESIS, Issue 12 2006
Alex Y. Nie
Toxicogenomics technology defines toxicity gene expression signatures for early predictions and hypotheses generation for mechanistic studies, which are important approaches for evaluating toxicity of drug candidate compounds. A large gene expression database built using cDNA microarrays and liver samples treated with over one hundred paradigm compounds was mined to determine gene expression signatures for nongenotoxic carcinogens (NGTCs). Data were obtained from male rats treated for 24 h. Training/testing sets of 24 NGTCs and 28 noncarcinogens were used to select genes. A semiexhaustive, nonredundant gene selection algorithm yielded six genes (nuclear transport factor 2, NUTF2; progesterone receptor membrane component 1, Pgrmc1; liver uridine diphosphate glucuronyltransferase, phenobarbital-inducible form, UDPGTr2; metallothionein 1A, MT1A; suppressor of lin-12 homolog, Sel1h; and methionine adenosyltransferase 1, alpha, Mat1a), which identified NGTCs with 88.5% prediction accuracy estimated by cross-validation. This six genes signature set also predicted NGTCs with 84% accuracy when samples were hybridized to commercially available CodeLink oligo-based microarrays. To unveil molecular mechanisms of nongenotoxic carcinogenesis, 125 differentially expressed genes (P,<,0.01) were selected by Student's t -test. These genes appear biologically relevant, of 71 well-annotated genes from these 125 genes, 62 were overrepresented in five biochemical pathway networks (most linked to cancer), and all of these networks were linked by one gene, c - myc. Gene expression profiling at early time points accurately predicts NGTC potential of compounds, and the same data can be mined effectively for other toxicity signatures. Predictive genes confirm prior work and suggest pathways critical for early stages of carcinogenesis. © 2006 Wiley-Liss, Inc. [source]

Breaking symmetry: a clinical overview of left-right patterning

CLINICAL GENETICS, Issue 6 2004
K Maclean
It is increasingly recognized that mutations in genes and pathways critical for left-right (L-R) patterning are involved in common isolated congenital malformations such as congenital heart disease, biliary tract anomalies, renal polycystic disease, and malrotation of the intestine, indicating that disorders of L-R development are far more common than a 1 in 10,000 incidence of heterotaxia might suggest. Understanding L-R patterning disorders requires knowledge of molecular biology, embryology, pediatrics, and internal medicine and is relevant to day-to-day clinical genetics practice. We have reviewed data from mammalian (human and mouse) L-R patterning disorders to provide a clinically oriented perspective that might afford the clinician or researcher additional insights into this diagnostically challenging area. [source]