Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tubedown-1 (tbdn-1) is a mammalian homologue of the N-terminal acetyltransferase subunit NAT1 of Saccharomyces cerevisiae and copurifies with an acetyltransferase activity. Tbdn-1 expression in endothelial cells becomes downregulated during the formation of capillary-like structures in vitro and is regulated in vivo in a manner which suggests a functional role in dampening blood vessel development. Here we show that tbdn-1 is expressed highly in the vitreal vascular network (tunica vasculosa lentis and vasa hyaloidea propria) during the pruning and remodeling phases of this transient structure. The vitreal blood vessels of mice harboring a targeted inactivation of TGF-beta2 fail to remodel and abnormally accumulate, a phenomenon reminiscent of the ocular pathology resembling persistent fetal vasculature (PFV) in humans. Since suppression of normal tbdn-1 expression has been previously observed in retinal vessel proliferation, we analyzed vitreal vascular changes and tbdn-1 expression in TGF-beta2(-/-) eyes. The nuclei of vitreal vessel endothelial cells in TGF-beta2(-/-) eyes express proliferating cell nuclear antigen (PCNA) and exhibit increased levels of active (P42/44)mitogen-activated protein kinase (phospho-(P42/44)MAPK), characteristics consistent with proliferative endothelial cells. In contrast to normal vitreal vessels, collagen IV expression exhibited a disorganized pattern in the TGF-beta2(-/-) vitreal vessels, suggesting vessel disorganization and possibly a breakdown of vessel basal laminae. Moreover, vitreal vessels of TGF-beta2(-/-) mice lack expression of pericyte markers (CD13, alpha smooth muscle actin) and show ultrastructural changes consistent with pericyte degeneration. The accumulating vitreal blood vessels of TGF-beta2(-/-) mice, while maintaining expression of the endothelial marker von Willebrand Factor, show a significant decrease in the expression of tbdn-1. We addressed the functional role of tbdn-1 in the regulation of vitreal blood vessels using an in vitro model of choroid-retina capillary outgrowth. Clones of the RF/6A fetal choroid-retina endothelial cell line showing suppression of tbdn-1 levels after overexpression of an antisense TBDN-1 cDNA display a significant increase in the formation of capillary-like structures in vitro compared with controls. These findings suggest that tbdn-1 inhibits capillary-like formation in vitro and may serve to dampen vitreal blood vessel formation preceding the regression of the vitreal vasculature during development. Our results also suggest that tbdn-1 may participate with TGF-beta2 in regulating normal development of the vitreal vasculature.
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PMID:Tubedown-1 in remodeling of the developing vitreal vasculature in vivo and regulation of capillary outgrowth in vitro. 1221 25

The aim of this study was to evaluate the effect of cariporide, a selective Na(+)/H(+) exchange inhibitor, on isolated and cultured hepatic stellate cells (HSCs) and in 2 in vivo models of rat liver fibrosis. Platelet-derived growth factor (PDGF)-induced HSC proliferation, evaluated by measuring the percentage of bromodeoxyuridine-positive cells, was significantly inhibited by cariporide, with a maximal effect at 10 micromol/L. Incubation with cariporide did not inhibit PDGF-induced extracellular-regulated kinase 1/2 (ERK1/2), Akt (a downstream component of the phosphatidylinositol [PI]-3 kinase pathway), and protein kinase C (PKC) activation but reduced PDGF-induced activation of the Na(+)/H(+) exchanger, with a maximal effect at 10 micromol/L. Rats treated with dimethylnitrosamine (DMN; 10 mg/kg) for 1 and 5 weeks received a diet with or without 6 ppm cariporide. Treatment with cariporide reduced the degree of liver injury, as determined by alanine aminotransferase (ALT) values, also when administered after the induction of hepatic damage. This was associated with reduced HSC activation and proliferation and reduced collagen deposition, as determined by morphometric evaluation of alpha-smooth muscle actin (SMA)/proliferating cell nuclear antigen-positive cells and percentage of Sirius red-positive parenchyma, respectively. Moreover, cariporide was also able to reduce alpha(1)I procollagen messenger RNA (mRNA) expression. Similar effects were observed in bile duct-ligated (BDL) rats. In conclusion, selective inhibition of the Na(+)/H(+) exchanger by cariporide may represent an effective therapeutic strategy in the treatment of hepatic fibrosis.
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PMID:Selective Na+/H+ exchange inhibition by cariporide reduces liver fibrosis in the rat. 1254 Jul 75

The myocardium responds to chronic pressure or volume overload by activation and proliferation of cardiac fibroblasts and their differentiation into myofibroblasts. Because alpha-smooth muscle actin (SMA) expression is the classical marker for myofibroblast differentiation, we examined force-induced SMA expression and regulation by specific MAPK pathways. Rat cardiac fibroblasts were separated from myocytes and smooth muscle cells, cultured, and phenotyped by using the presence of SMA, vimentin, and ED-A fibronectin and the absence of desmin as myofibroblast markers. Static tensile forces (0.65 pN/microm2) were applied to fibroblasts via collagen-coated magnetite beads. In neonatal cardiac fibroblasts cultured for 1 day, immunostaining and Western and Northern blotting showed very low basal levels of SMA. After the application of force, there were 1.5- to 2-fold increases of SMA protein and mRNA within 4 h. Force-induced SMA expression was dependent on ERK phosphorylation and on intact actin filaments. In contrast to cells cultured for 1 day, cells grown for 3 days on rigid substrates showed prominent stress fibers and high basal levels of SMA, which were reduced by 32% within 4 h after force application. ERK was not activated by force, but p38 phosphorylation was required for force-induced inhibition of SMA expression. These results indicate that mechanical force-induced regulation of SMA content is dependent on myofibroblast differentiation and by selective activation of MAPKs.
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PMID:Mechanical force regulation of myofibroblast differentiation in cardiac fibroblasts. 1284 14

Angiotensin II (AngII) plays an important role in renal damage by acting on hemodynamics, cell-growth, proliferation, and fibrosis, mainly by effects on the AngII type 1 (AT(1)) receptor. The AT(1) receptor activates several intracellular signaling molecules such as mitogen-activated protein kinases extracellular signal-regulated kinase (ERK) and p38, but their role in AngII-mediated renal damage is not well characterized. We therefore investigated whether pharmacologic blockade of ERK and p38 could prevent renal damage in high-renin homozygous transgenic rats (Ren2), with the effects of an AT(1) receptor antagonist (AT(1)-RA) as a reference. Seven-week-old homozygous Ren2 rats were treated with low-dose AT(1)-RA candesartan, ERK inhibitor tyrphostin, or p38 inhibitor SB239063 for 4 weeks. Untreated Ren2 and SD rats served as controls. Blood pressure was measured at 7 and 11 weeks. At 11 weeks, plasma renin activity (PRA) and serum aldosterone were determined, and the animals were killed. Kidney sections were scored for glomerular and interstitial smooth muscle actin and glomerular desmin expression as early markers for renal damage. Mesangial matrix expansion was determined as a marker for structural damage. PRA and aldosterone levels were elevated in untreated Ren2 rats in comparison to SD controls. AT(1)-RA further increased PRA but decreased aldosterone. All parameters of renal damage were elevated in untreated Ren2 rats. Blood pressure was not elevated at week 7 in Ren2 and not affected by either treatment. Mild signs of hypertensive damage were found in untreated Ren2 rats. All interventions significantly diminished damage to glomerular epithelium and interstitium. In addition, AT(1) receptor and p38 blockade reduced mesangial matrix expansion. In homozygous Ren2 rats, renal damage was ameliorated by a nonhypotensive dose of an AT(1)-RA and, similarly, by blockade of ERK or p38. This suggests that ERK and p38 are involved in AngII-mediated renal damage.
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PMID:Specific MAP-kinase blockade protects against renal damage in homozygous TGR(mRen2)27 rats. 1469 Dec 94

The mitogen-activated protein kinase p38 is activated by mechanical force, but the cellular elements that mediate force-induced p38 phosphorylation are not defined. As alpha-smooth muscle actin (SMA) is an actin isoform associated with force generation in fibroblasts, we asked if SMA participates in the activation of p38 by force. Tensile forces (0.65 pn/mum(2)) generated by magnetic fields were applied to collagen-coated magnetite beads bound to Rat-2 cells. Immunoblotting showed that p38alpha was the predominant p38 isoform. Analysis of bead-associated proteins demonstrated that SMA enrichment of collagen receptor complexes required the alpha2beta1 integrin. SMA was present almost entirely as filaments. Swinholide depolymerized SMA filaments and blocked force-induced p38 phosphorylation and force-induced increases of SMA. Knockdown of SMA (70% reduction) using RNA interference did not affect beta-actin but inhibited force-induced p38 phosphorylation by 50%. Inhibition of Rho kinase blocked SMA filament assembly, force-induced increases of SMA, and force-induced p38 activation. Force application increased SMA content and enhanced the association of phosphorylated p38 with SMA filaments. Blockade of p38 phosphorylation by SB203586 abrogated force-induced increases of SMA. In cells transfected with SMA promoter-beta-galactosidase fusion constructs, co-transfection with constitutively active p38 or MKK6 increased SMA promoter activity by 2.5-3-fold. Dominant negative p38 blocked force-induced activation of the SMA promoter. In SMA negative cells, there was no force-induced p38 phosphorylation. We conclude that force-induced p38 phosphorylation is dependent on an SMA filament-dependent pathway that uses a feed-forward amplification loop to synergize force-induced SMA expression with p38 activation.
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PMID:Smooth muscle actin determines mechanical force-induced p38 activation. 1559 Oct 55

Ochratoxin A (OTA) is a mycotoxin involved in the development of chronic nephropathies and a known carcinogen. As we have shown previously, OTA activates mitogen-activated protein kinases [extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-jun amino-terminal kinase (JNK), and extracellular-regulated protein kinase 38 (p38)] in proximal tubular cells (opossum kidney and normal rat kidney epithelial). ERK1/2, JNK, or p38 are thought to mediate opposite action on apoptosis, fibrosis, and inflammation. As we have already shown, OTA activates the latter processes. Here, we investigated the effect of OTA in the absence or presence of the ERK1/2 inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4bis(2-aminophenylthio)-butadiene] to test whether OTA then will exert increased toxicity. In the presence of ERK1/2 inhibition, OTA decreased cell number and protein to a significantly larger extent compared with OTA alone. The same was true for epithelial tightness, apoptosis (caspase-3 activity), and necrosis (lactate dehydrogenase release). Furthermore, simultaneous inhibition of ERK1/2 amplified the effect of OTA on markers of inflammation (nuclear factor of the kappa-enhancer in B cells activity), fibrosis (collagen secretion), and epithelial mesenchymal transition (alpha smooth muscle actin). OTA induces phenomena typical for chronic interstitial nephropathy and activates ERK1/2, JNK, and p38 in proximal tubular cells. Inhibition of ERK1/2 aggravates the effects of OTA or even induces toxicity at normally nontoxic concentrations. This is highly likely due to activation of JNK and p38. Our data indicate a new mechanistic explanation for the toxic actions induced by OTA, and they are notable with respect to a possible coexposition of the kidney to OTA and naturally occurring ERK1/2 inhibitors. Finally, our data give rise to an attractive hypothesis on the coincidence of increased OTA exposition and urinary tract tumors in humans.
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PMID:Proximal tubular toxicity of ochratoxin A is amplified by simultaneous inhibition of the extracellular signal-regulated kinases 1/2. 1562 19

Ochratoxin A (OTA) is a nephrotoxic and cancerogenic mycotoxin. There is epidemiological evidence that OTA exposition leads to cortical interstitial nephropathies in humans. However, virtually no data are available investigating the effect of OTA on renal cortical cells with respect to induction of nephropathy. Thus, we investigated whether OTA is able to induce changes of cellular properties potentially leading to interstitial nephropathy, using proximal tubular cell lines (OK, NRK-52E). OTA decreased cell number and cell protein time and dose dependently. Accordingly we investigated the effect of 100 nM or 1000 nM OTA. The decline of cell number after OTA exposure is due to necrosis and apoptosis, as measured by LDH release or DNA ladder formation and caspase-3 activation, respectively. OTA incubation of proximal tubular cells also resulted in a loss of epithelial tightness as determined by diffusion of FITC labeled inulin. Inflammation, fibrosis and epithelial-to-mesenchymal transition are described in chronic interstitial renal disease. Therefore, we also investigated the effect of OTA on NFkappaB activity, collagen secretion and generation of alpha smooth muscle actin. OTA alone was sufficient to induce the latter parameters in proximal tubular cells. Finally, OTA is a nephrotoxcic substance and elevated activity of mitogen activated protein kinases (MAPK) is described in nephropathies. As we investigated the effect of OTA on activity of ERK, JNK and p38 by ELISA, we found that OTA activates the MAPK measured dose dependently. In summary, OTA induced phenomena typical for chronic interstitial nephropathy, like loss of cells and epithelial tightness, necrosis and apoptosis as well as markers of inflammation, fibrosis and epithelial-to-mesenchymal transition in proximal tubular cells. Thus, we could show for the first time that OTA is able to induce key parameters of nephropathy in proximal tubular cells in culture. Moreover OTA interacts with MAPK and thus may exert its specific toxic actions.
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PMID:The nephrotoxin ochratoxin A induces key parameters of chronic interstitial nephropathy in renal proximal tubular cells. 1566 23

Myofibroblasts characterized by alpha smooth muscle actin(alpha-SMA) expression play a key role in pulmonary fibrosis. Transforming growth factor-beta1 (TGF-beta1) is likely to be involved in the emergence of myofibroblasts, but the intracellular signal pathways for this process have not been well determined. The aim of the present study was to investigate the role of mitogen-activated protein kinase (MAPK)/activator protein-1 (AP-1) signaling pathways in TGF-beta1-induced alpha-SMA expression in human fetal lung fibroblasts (HLF-02). We found that TGF-beta1 treatment activated p38 kinase and extracellular signal-regulated kinase (Erk) in HLF-02 cells. The induction of alpha-SMA by TGF-beta1 was suppressed by p38 kinase inhibitor (SB203580) and Erk inhibitor (PD98059). AP-1 inhibitor curcumin also inhibited TGF-beta1-induced alpha-SMA expression. In addition, dominant negative mutant c-Jun (TAM67) downregulated TGF-beta1-induced AP-1 transactivation and alpha-SMA expression. In additional, PD98059 but not SB203580 inhibited the AP-1 DNA binding activity induced by TGF-beta1. Based on these findings, we conclude that p38 kinase, Erk, and AP-1 are responsible for the alpha-SMA expression induced by TGF-beta1 in human fetal lung fibroblasts. Erk is involved in inducing alpha-SMA expression via AP-1 activation.
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PMID:Role of extracellular signal-regulated kinase, p38 kinase, and activator protein-1 in transforming growth factor-beta1-induced alpha smooth muscle actin expression in human fetal lung fibroblasts in vitro. 1659 50

Fibroblast growth factor receptor (FGFR) activation by basic fibroblast growth factor (FGF-2) serves to naturally repress the myofibroblast activation of valvular interstitial cells (VICs). Co-receptors for FGF-2, the heparan sulfate proteoglycans (HSPGs), are key participants in the formation of active FGF-2 signaling complexes. Bioactive environments regulating the myofibroblast phenotype were created by utilizing heparin glycosaminoglycan as a competitive inhibitor of HSPGs. First, soluble heparin was delivered to compete with cell-surface HSPG for the binding of FGF-2. Exogenous soluble heparin prevented serum-dependent activation of the classic mitogen-activated protein kinase (MAPK) and induced myofibroblast alpha smooth muscle actin (alphaSMA) expression and collagen production. Next, heparin-functionalized hydrogel cell substrates were polymerized from vinyl-modified precursors and rendered adhesive through incorporation of RGDS peptide. Culture of VICs on heparin-modified gels induced alphaSMA expression and inhibited MAPK activity compared to control gel substrates lacking heparin. Additionally, heparin-functionalized gels continued to induce alphaSMA expression in serum-free culture conditions, suggesting that bioactivity was independent of exogenous soluble mediators. Biomaterial scaffolds targeting cell surface growth factor receptors are a promising new direction for regulating cell functions in tissue-engineering applications.
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PMID:Material-based regulation of the myofibroblast phenotype. 1747 22

It has been well appreciated that aldosterone (Aldo) plays a direct profibrotic role in the kidney but the underlying mechanism is unclear. We examined the role of Aldo in epithelial-mesenchymal transition (EMT) both in vitro and in vivo. Exposure of human renal proximal tubular cells to Aldo for 48 h dose dependently induced EMT as evidenced by conversion to the spindle-like morphology, loss of E-cadherin, and de novo expression of alpha-smooth muscle actin (SMA); the effect was noticeable at 50 nM and maximal at 100 nM. The EMT was completely blocked by the selective mineralocorticoid receptor (MR) antagonist eplerenone. Aldo time dependently increased intracellular reactive oxygen species (ROS) production that was detectable at 15 min and peaked (2.3-fold) at 60 min, as assessed by 2',7'-dichlorofluorescin diacetate fluorescence. Aldo-induced oxidative stress and EMT were both abolished by the mitochondrial respiratory chain complex I inhibitor rotenone, but not the NADPH oxidase inhibitor apocynin. Aldo induced phosphorylation of ERK1/2 that was completely blocked by rotenone. Male 129-C57/BL6 mice were treated with deoxycorticosterone acetate (DOCA) salt (subcutaneous implantation of 50 mg of DOCA pellet plus 1% NaCl as drinking fluid) for 3 wk and animals were treated with vehicle or rotenone (600 ppm in diet) for the last week. DOCA salt induced a 2.5-fold increase in alpha-SMA and a 30% reduction of E-cadherin, as assessed by real-time RT-PCR, that were both restricted to renal epithelial cells, as determined by immunohistochemistry. In contrast, DOCA salt-induced changes in alpha-SMA and E-cadherin were completely blocked by treatment with rotenone. These observations suggest that Aldo induces EMT via MR-mediated, mitochondrial-originated, ROS-dependent ERK1/2 activation in renal tubular epithelial cells.
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PMID:Aldosterone induces epithelial-mesenchymal transition via ROS of mitochondrial origin. 1759 22


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