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)

The signal transduction pathways initiated by Ca(2+)-mobilizing agonists, such as prostaglandin F(2alpha)(PGF(2alpha)) and carbachol (CCh), leading to activation of cytosolic phospholipase A(2)(cPLA(2)) and arachidonic acid (AA) release in a wide variety of tissues remain obscure. To further define the role of protein kinases in receptor mediated stimulation of cPLA(2)and consequently AA release we have investigated the role of mitogen-activated protein (MAP) kinases and protein kinase C (PKC) in PGF(2alpha)- and CCh-induced cPLA(2)phosphorylation and AA release in cat iris sphincter smooth muscle (CISM) cells. The cells were prelabeled with [(3)H]AA for 24 hr and incubated in the absence or presence of the agonist for 5-10 min as indicated. MAP kinases activities and cPLA(2)phosphorylation were determined in immunoprecipitates obtained by using anti-p38 MAP kinase and anti-cPLA(2)antibodies. We found that: (a) PGF(2alpha)and CCh increased p38 MAP kinase activity by 197 and 215%, respectively, and increased p42/p44 MAP kinase activity by 200 and 125%, respectively. (b) SB202190, a p38 MAP kinase specific inhibitor, inhibited PGF(2alpha)- and CCh-induced cPLA(2)phosphorylation by 92 and 85%, respectively, and AA release by 62 and 78%, respectively. (c) PD98059, a p42/p44 MAP kinase inhibitor, inhibited CCh-induced cPLA(2)phosphorylation by 70% and AA release by 71%, but had no effect on that of PGF(2alpha). (d) Inhibition of PKC activity by RO 31-8220 inhibited both PGF(2alpha)- and CCh-stimulation of p38 MAP kinase, p42/p44 MAP kinases and cPLA(2)phosphorylation. We conclude from these results that in CISM cells PGF(2alpha)-induced cPLA(2)phosphorylation and AA release is mediated through p38 MAP kinase, but not through p42/p44 MAP kinases, whereas that of CCh is mediated through both p38 MAP kinase and p42/p44 MAP kinases. These effects of PGF(2alpha)and CCh are regulated by the MAP kinases in a PKC-dependent manner. Studies aimed at elucidating the role of protein kinases in the coupling mechanism between the activation of PGF(2alpha)and muscarinic receptors, and the stimulation of cPLA(2)and AA release in the smooth muscles of the iris-ciliary body will provide important information about the role of protein kinases signaling pathways in smooth muscle function, as well as about the mechanism of the intraocular pressure-lowering effects of PGF(2alpha)and its analog, latanoprost, in glaucoma therapy.
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PMID:Effects of prostaglandin F(2alpha)and carbachol on MAP kinases, cytosolic phospholipase A(2)and arachidonic acid release in cat iris sphincter smooth muscle cells. 1131 Oct 50

A potential role for myosin light chain kinase (MLCK) in regulating intraocular pressure and outflow function has recently been reported in living monkey eye and rabbit eye. There is little information about the effects of the ocular hypotensive agents, prostaglandin F2alpha (PGF2alpha) and latanoprost on this signaling pathway in ocular tissues. The aim of this study was to determine the agonist activity of PGF2alpha, latanoprost and carbachol (CCh) on the MLCK pathway in isolated bovine iris sphincter and furthermore to investigate the existence of the FP receptor in this tissue. In the present studies on the MLCK pathway four signal transduction mechanism assays were employed, phosphoinositide (PI) turnover, p42/p44 MAP kinase phosphorylation and activation, MLC phosphorylation and contraction. In the studies on the existence of the FP receptor in the bovine iris sphincter, the pharmacology and expression of the FP receptor protein, using a polyclonal anti-FP-receptor antibody and Western blot analysis, were determined. The data obtained on the MLCK pathway showed that the three agonists stimulated the biochemical and pharmacological responses in a concentration and time-dependent manner and that the order of potency and efficacy is PGF2alpha>latanoprost>CCh. The EC50 values in the PI turnover, MAP kinase phosphorylation, MLC phosphorylation and contraction assays were for PGF2alpha: 9, 42, 200 and 140 nM, respectively, for latanoprost: 13, 59, 250 and 828 nM, respectively, and for CCh: 22, 200, 630 and 910 nM, respectively. Wortmannin, a selective inhibitor of MLCK, dose-dependently inhibited MLC phosphorylation and contraction induced by PGF2alpha, demonstrating a close relationship between activation of the MLCK pathway and contraction. The pharmacological studies showed that in the concentration range of 1 nM to 10 microM, the FP-receptor agonists caused concentration-response curves with the following order of potencies: 17-phenyl trinor PGF2alpha (bimatoprost acid)>PGF2alpha>cloprostenol>latanoprost>latanoprost acid>bimatoprost amide>>fluprostenol. Immunoblot analysis of the FP receptor demonstrated expression of the prostaglandin FP receptor protein in this smooth muscle. These results clearly indicate that the MLCK signaling pathway is involved in the FP-receptor function of the bovine iris sphincter and furthermore demonstrate that functional FP receptors exist and are expressed in this tissue.
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PMID:Effects of prostaglandin F2alpha, latanoprost and carbachol on phosphoinositide turnover, MAP kinases, myosin light chain phosphorylation and contraction and functional existence and expression of FP receptors in bovine iris sphincter. 1472 60

This study investigates the role of the MAP kinase pathway including c-jun, ATF-2 and JNK in glaucomatous eyes of rats and in optic nerve transection. Glaucoma was induced in one eye of 51 adult Wistar rats by laser treatment to the trabecular meshwork. Eighteen further rats underwent unilateral optic nerve transection. We studied the transcription factor c-jun, its activated form, phospho-c-jun, the transcription factor p-ATF-2, and the enzyme JNK by immunohistochemistry. The activation of p-c-jun was also investigated using western blot analysis. Treated and control eyes were compared in a masked way at multiple time points after injury. We found a statistically significant increase in immunolabelling for c-jun and phospho-c-jun in retinal ganglion cells (RGCs) from 1 day to 4 weeks after intraocular pressure (IOP) elevation. At 1 and 2 days after the laser treatment, a mean of 2.9+/-3.3 RGCsmm(-1) were positive for c-jun (n=12, p=0.005, t-test), increasing to a mean of 13.4+/-7.5 cells mm(-1) at 1 week (n=18, p=0.00005), and decreasing to 2.3+/-2.0 cells mm(-1) at 2 weeks (n=5, p=0.04) and 0.1+/-0.1 cells mm(-1) at 2 months. Few of the 47 control eyes had any labelling for c-jun or phospho-c-jun, while between 80 and 100% of elevated IOP eyes showed positivity during the first 2 weeks of experimental glaucoma. After optic nerve transection, c-jun and phospho-c-jun were also significantly activated at 1, 2 and 9 days (p<0.03, t-test). Western blot analysis demonstrated significantly increased phospho-c-jun amounts in both transected and glaucomatous eyes compared to control fellow eyes 1 week following treatment. JNK was not significantly activated in glaucoma or optic nerve transection. P-ATF-2 was not significantly activated in glaucoma, but was significantly increased 2 days after optic nerve transection. We conclude that the process leading to RGC death in experimental glaucoma and after optic nerve transection involves the activation of c-jun at the RGC layer. C-jun is activated more gradually in glaucoma then after optic nerve transection.
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PMID:The transcription factor c-jun is activated in retinal ganglion cells in experimental rat glaucoma. 1586 73

Glaucoma is the second leading cause of blindness in the world. Loss of vision in glaucomatous optic neuropathy is caused by the selective degeneration of retinal ganglion cells (RGCs). Ocular hypertension is a major risk factor in glaucoma, but visual field defects continue to progress in some patients despite the use of drugs that lower intraocular pressure. At present, there are no effective neuroprotective strategies for the treatment of this disease. The extracellular signal-regulated kinase (Erk) 1/2 pathway is an evolutionarily conserved mechanism used by several peptide factors to promote cell survival. Here we tested if selective activation of Erk1/2 protected RGCs in a rat model of experimental glaucoma. We used recombinant adeno-associated virus to transduce RGCs with genes encoding constitutively active or wild-type MEK1 (approved gene symbol MAP2K1), the upstream activator of Erk1/2. MEK1 gene transfer into RGCs markedly increased neuronal survival: 1366 +/- 70 RGCs/mm(2) (mean +/- SEM) were alive in the dorsal retina at 5 weeks after ocular hypertension surgery, a time when only 680 +/- 86 RGCs/mm(2) of these neurons remained in control eyes. We conclude that the Erk1/2 pathway plays a key role in the protection of RGCs from ocular hypertensive damage. This study identifies a novel gene therapy strategy in which selective activation of the Erk1/2 signaling pathway effectively slows cell death in glaucoma.
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PMID:Activation of the extracellular signal-regulated kinase 1/2 pathway by AAV gene transfer protects retinal ganglion cells in glaucoma. 1597 50

Prostaglandins (PGs) have been implicated in the regulation of intraocular pressure (IOP) by facilitating the remodeling of tissues involved in aqueous humor outflow. A contribution of cyclooxygenase-2 (COX-2)-dependent PGs to this process was emphasized by a recent study showing an impaired COX-2 expression in the nonpigmented ciliary epithelium (NPE) of patients with primary open-angle glaucoma. With the use of human NPE cells (ODM-2), the present study therefore investigated the effect of the antiglaucomatous drug latanoprost (PGF2alpha analog) on the expression of COX-2 and its association with the induction of matrix metalloproteinases (MMPs). In NPE cells, latanoprost led to a concentration- and time-dependent increase of COX-2 mRNA levels. Up-regulation of COX-2 expression was accompanied by phosphorylations of p38 mitogen-activated protein kinase (MAPK) and p42/44 MAPK and was abrogated by specific inhibitors of both pathways. PGE2 formation by latanoprost was abolished by the selective COX-2 inhibitor NS-398 and by the F-prostaglandin receptor antagonist AL-8810. Moreover, latanoprost led to a delayed up-regulation of MMP-1 mRNA, whereas the expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 remained unchanged. Latanoprost-induced MMP-1 mRNA and protein expression was abolished by NS-398 and by COX-2-silencing small-interfering RNA. In line with this finding, MMP-1 expression was also induced by PGE2, a major COX-2 product. As a whole, our results show that MMP-1 expression by latanoprost requires prior up-regulation of COX-2. Induction of COX-2- and subsequent MMP-1 expression in the NPE may represent a potential mechanism underlying the IOP-lowering and antiglaucomatous action of latanoprost.
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PMID:Latanoprost induces matrix metalloproteinase-1 expression in human nonpigmented ciliary epithelial cells through a cyclooxygenase-2-dependent mechanism. 1607 63

This study investigates whether the immediate early gene (IEG) products c-Fos and c-Jun are activated in vivo in monkeys with experimental glaucoma, and in vitro in cultured human ONH astrocytes exposed to hydrostatic pressure (HP). Three Rhesus monkeys with mild glaucomatous damage (mean intraocular pressure (IOP) 27 +/- 1.3 mm Hg approximately 42 weeks) and three with moderate glaucomatous damage (mean IOP 44 +/- 6.7% mm Hg approximately 11 weeks) were used for this study; the contralateral eye served as normal control (mean IOP 18.6 +/- 1.7 mm Hg). ONH tissues were stained with GFAP, DAPI, and c-Jun or c-Fos, and transcription factor positive and negative nuclei were counted to determine nuclear localization. Cultured human normal and glaucomatous ONH astrocytes exposed to elevated HP served as the in vitro model of elevated pressure. Activation and nuclear localization of c-Fos and c-Jun increased significantly in the monkeys with elevated IOP. These data correlated with axonal loss, reactive astrocytes, and remodeling of the optic disc. Cultured human ONH astrocytes showed increased nuclear localization of c-Fos and c-Jun under exposure to HP. Immunohistochemistry demonstrated that the upstream regulators of c-Fos and c-Jun, ERK-MAPK and MAPKp38 localized to the nuclei of ONH astrocytes in monkeys with experimental glaucoma. Taken together, these results demonstrate c-Fos and c-Jun activation in ONH astrocytes in vivo and in vitro, and that activation of both transcription factors is associated with ERK and MAPKp38 activation in experimental glaucoma, suggesting that activation of transcription factors may participate in the induction and maintenance of the reactive astrocyte phenotype in glaucomatous optic neuropathy.
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PMID:Long-term activation of c-Fos and c-Jun in optic nerve head astrocytes in experimental ocular hypertension in monkeys and after exposure to elevated pressure in vitro. 1608 Oct 55

To examine the expression of phosphorylated c-Jun N-terminal kinase (JNK) in cells in the retinal ganglion cell layer of glaucoma, intraocular pressure (IOP) of adult Wistar rats was elevated unilaterally by repeated trabecular argon laser photocoagulation 5 days after intracameral injection of India ink. Animals were euthanized after 3 days, and 1, 2, and 5 weeks of IOP elevation. Immunohistochemistry with specific antibodies against phosphorylated JNK was performed on retinas. Retrograde labeling using Fluorogold and fluorescence immunohistochemistry was performed on retinas 5 weeks after IOP elevation. TdT-mediated biotin-dUTP nick end labeling (TUNEL) was performed on the retinal sections to determine the rate of cell death. There was increased IOP (52.3%) from 3 days to 5 weeks after repeated trabecular laser photocoagulation. Mean number of TUNEL-positive cells in the retinal ganglion cell layer of eyes with experimental glaucoma was 0.43, 0.36, 0.57, and 0.19 per retinal section at 3 days, and 1, 2 and 5 weeks, respectively. No TUNEL-positive cells were noted in controls. In parallel to TUNEL, significantly increased numbers of phosphorylated JNK-labeled cells in the retinal ganglion cell layer were noted at 3 days (9.95 versus 4.15; P=0.005), 1 week (7.65 versus 4.00; P=0.006), 2 weeks (9.13 versus 4.48; P=0.032), and 5 weeks (8.06 versus 4.96; P=0.017) of IOP elevation when compared with contralateral control eyes. Fluorogold labeled RGCs were co-localized with increased phosphorylated JNK immunoreactivity. Some TUNEL-positive cells were phosphorylated JNK immuno-positive. Phosphorylation of JNK occurs in experimental glaucoma and may play a role in retinal ganglion cell death.
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PMID:Expression of phosphorylated c-Jun N-terminal protein kinase (JNK) in experimental glaucoma in rats. 1619 43

Prostaglandins (PGs) have been implicated in lowering intraocular pressure (IOP). A possible role of cyclooxygenase-2 (COX-2) in this process was emphasized by findings showing impaired COX-2 expression in the non-pigmented ciliary epithelium (NPE) of patients with primary open-angle glaucoma. The present study investigates the effect of the major COX-2 product, PGE(2), on the expression of its synthesizing enzyme in human NPE cells (ODM-2). PGE(2) led to an increase of COX-2 mRNA and protein expression, whereas the expression of COX-1 remained unchanged. Upregulation of COX-2 expression by PGE(2) was accompanied by time-dependent phosphorylations of p38 mitogen-activated protein kinase (MAPK) and p42/44 MAPK, and was abrogated by inhibitors of both pathways. Moreover, PGE(2)-induced COX-2 expression was suppressed by the intracellular calcium chelator, BAPTA/AM, and the protein kinase C inhibitor bisindolylmaleimide II, whereas the protein kinase A inhibitor H-89 was inactive in this respect. Induction of COX-2 expression was also elicited by butaprost (EP(2) receptor agonist) and 11-deoxy PGE(1) (EP(2)/EP(4) receptor agonist), but not by EP(1)/EP(3) receptor agonists (17-phenyl-omega-trinor PGE(2), sulprostone). Consistent with these findings, the EP(1)/EP(2) receptor antagonist, AH-6809, and the selective EP(4) receptor antagonist, ONO-AE3-208, significantly reduced PGE(2)-induced COX-2 expression. Collectively, our results demonstrate that PGE(2) at physiologically relevant concentrations induces COX-2 expression in human NPE cells via activation of EP(2)- and EP(4) receptors and phosphorylation of p38 and p42/44 MAPKs. Positive feedback regulation of COX-2 may contribute to the production of outflow-facilitating PGs and consequently to regulation of IOP.
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PMID:Prostaglandin E2 induces cyclooxygenase-2 expression in human non-pigmented ciliary epithelial cells through activation of p38 and p42/44 mitogen-activated protein kinases. 1625 48

Prostaglandins (PGs) and matrix metalloproteinases (MMP) have been implicated in lowering intraocular pressure (IOP) by facilitating aqueous humor outflow. A possible role of cyclooxygenase-2 (COX-2) in this process was emphasized by findings showing an impaired COX-2 expression in the nonpigmented ciliary epithelium (NPE) of patients with primary open-angle glaucoma. Using human NPE cells, the present study therefore investigated the effect of the IOP-lowering cannabinoid R(+)-methanandamide [R(+)-MA] on the expression of COX-2 and different MMPs and tissue inhibitors of MMPs (TIMPs). R(+)-MA led to a concentration- and time-dependent increase of COX-2 mRNA expression. R(+)-MA-induced COX-2 expression was accompanied by time-dependent phosphorylations of p38 mitogen-activated protein kinase (MAPK) and p42/44 MAPK and was abrogated by inhibitors of both pathways. Moreover, R(+)-MA increased the mRNA and protein expression of MMP-1, MMP-3, MMP-9, and TIMP-1 but not that of MMP-2 and TIMP-2. Inhibition of COX-2 activity with NS-398 [N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide] was associated with a virtually complete suppression of R(+)-MA-induced MMP-9 and TIMP-1 expression. Consistent with these data, MMP-9 and TIMP-1 expression was also induced by PGE2, a major COX-2 product. Two other COX-2-inducing cannabinoids, anandamide and Delta9-tetrahydrocannabinol, caused the same pattern of MMP and TIMP expression as R(+)-MA both in the absence and presence of NS-398. Altogether, cannabinoids induce the production of several outflow-facilitating mediators in the human NPE. Our results further imply an involvement of COX-2-dependent PGs in MMP-9 and TIMP-1 expression. In conclusion, stimulation of intraocular COX-2 and MMP expression may represent a potential mechanism contributing to the IOP-lowering action of different cannabinoids.
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PMID:R(+)-methanandamide and other cannabinoids induce the expression of cyclooxygenase-2 and matrix metalloproteinases in human nonpigmented ciliary epithelial cells. 1633 Apr 97

Astrocytes, the major glia in the nonmyelinated optic nerve head (ONH), connect via gap junctions built of connexin-43 (Cx43) to form a functional syncytium allowing communication and control of ionic and metabolic homeostasis of retinal ganglion cells (RGCs) axon. We examined gap junction intercellular communication (GJIC) by scrape loading assays in human ONH astrocytes exposed to hydrostatic (HP) or ambient pressure (CP) in vitro. Immunostaining, immunoprecipitation, and immunoblots were used to detect Cx43 distribution and phosphorylation in astrocytes exposed to HP with/without EGF receptor (EGFR) tyrosine kinase inhibitors AG1478 and AG82 and MAPK inhibitors U0126, PD98059, and SB203580. The data indicates that upon exposure to HP, astrocytes decrease GJIC and exhibit altered cellular localization and phosphorylation of Cx43. Inhibition of EGFR blocked the effects of HP on GJIC and HP-induced Cx43 tyrosine phosphorylation. Inhibitors of MAPK- ERK1/2 and -p38 caused partial closure of GJIC under CP and HP, which was maintained for 6 h. Inhibition of Big Mitogen-Activated Kinase 1/ERK5 (BMK1/ERK5) caused partial closure under CP and HP followed by full recovery after 6 h. Inhibition of MAPK did not affect the HP-induced increase in Cx43 serine 279/282 phosphorylation. We conclude that activation of the EGFR pathway in response to HP leads to decrease of GJIC via tyrosine phosphorylation of Cx43 in ONH astrocytes. In glaucoma under conditions of elevated intraocular pressure (IOP), astrocytes may lose GJIC altering the homeostasis of RGC axons, adopting the reactive phenotype, contributing to glaucomatous neuropathy.
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PMID:Pressure induces loss of gap junction communication and redistribution of connexin 43 in astrocytes. 1755 25


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