Browsing by Subject "JNK Mitogen-Activated Protein Kinases / metabolism"
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Item A feed-forward regulation of endothelin receptors by c-Jun in human non-pigmented ciliary epithelial cells and retinal ganglion cells(PLOS, 2017-09-22) Wang, Junming; Ma, Hai-Ying; Krishnamoorthy, Raghu R.; Yorio, Thomas; He, Shaoqingc-Jun, c-Jun N-terminal kinase(JNK) and endothelin B (ETB) receptor have been shown to contribute to the pathogenesis of glaucoma. Previously, we reported that an increase of c-Jun and CCAAT/enhancer binding protein beta (C/EBPbeta) immunohistostaining is associated with upregulation of the ETB receptor within the ganglion cell layer of rats with elevated intraocular pressure (IOP). In addition, both transcription factors regulate the expression of the ETB receptor in human non-pigmented ciliary epithelial cells (HNPE). The current study addressed the mechanisms by which ET-1 produced upregulation of ET receptors in primary rat retinal ganglion cells (RGCs) and HNPE cells. Treatment of ET-1 and ET-3 increased the immunocytochemical staining of c-Jun and C/EBPbeta in primary rat RGCs and co-localization of both transcription factors was observed. A marked increase in DNA binding activity of AP-1 and C/EBPbeta as well as elevated protein levels of c-Jun and c-Jun-N-terminal kinase (JNK) were detected following ET-1 treatment in HNPE cells. Overexpression of ETA or ETB receptor promoted the upregulation of c-Jun and also elevated its promoter activity. In addition, upregulation of C/EBPbeta augmented DNA binding and mRNA expression of c-Jun, and furthermore, the interaction of c-Jun and C/EBPbeta was confirmed using co-immunoprecipitation. Apoptosis of HNPE cells was identified following ET-1 treatment, and overexpression of the ETA or ETB receptor produced enhanced apoptosis. ET-1 mediated upregulation of c-Jun and C/EBPbeta and their interaction may represent a novel mechanism contributing to the regulation of endothelin receptor expression. Reciprocally, c-Jun was also found to regulate the ET receptors and C/EBPbeta appeared to play a regulatory role in promoting expression of c-Jun. Taken together, the data suggests that ET-1 triggers the upregulation of c-Jun through both ETA and ETB receptors, and conversely c-Jun also upregulates endothelin receptor expression, thereby generating a positive feed-forward loop of endothelin receptor activation and expression. This feed-forward regulation may contribute to RGC death and astrocyte proliferation following ET-1 treatment.Item In vitro and in vivo neuroprotective effects of cJun N-terminal kinase inhibitors on retinal ganglion cells(BioMed Central Ltd., 2016-04-21) Kim, Byung-Jin; Silverman, Sean M.; Liu, Yang; Wordinger, Robert J.; Pang, Iok-Hou; Clark, Abbot F.BACKGROUND: The c-Jun N-terminal kinase (JNK) signaling pathway plays an important role in neuronal pathophysiology. Using JNK inhibitors, we examined involvement of the JNK pathway in cultured rat retinal ganglion cell (RGC) death and in mouse retinal ischemia/reperfusion (I/R) injury of the visual axis. The in vitro effects of JNK inhibitors were evaluated in cultured adult rat retinal cells enriched in RGCs. Retinal I/R was induced in C57BL/6J mice through elevation of intraocular pressure to 120 mmHg for 60 min followed by reperfusion. SP600125 was administered intraperitoneally once daily for 28 days. Phosphorylation of JNK and c-Jun in the retina was examined by immunoblotting and immunohistochemistry. The thickness of retinal layers and cell numbers in the ganglion cell layer (GCL) were examined using H&E stained retinal cross sections and spectral domain optical coherence tomography (SD-OCT). Retinal function was measured by scotopic flash electroretinography (ERG). Volumetric measurement of the superior colliculus (SC) as well as VGLUT2 and PSD95 expression were studied. RESULTS: JNK inhibitors SP600125 and TAT-JNK-III, dose-dependently and significantly (p < 0.05) protected against glutamate excitotoxicity and trophic factor withdrawal induced RGC death in culture. In the I/R model, phosphorylation of JNK (pJNK) in the retina was significantly (p < 0.05) increased after injury. I/R injury significantly (p < 0.05) decreased the thickness of retinal layers, including the whole retina, inner plexiform layer, and inner nuclear layer and cell numbers in the GCL. Administration of SP600125 for 28 days protected against all these degenerative morphological changes (p < 0.05). In addition, SP600125 significantly (p < 0.05) protected against I/R-induced reduction in scotopic ERG b-wave amplitude at 3, 7, 14, 21 and 28 days after injury. SP600125 also protected against the I/R-induced losses in volume and levels of synaptic markers in the SC. Moreover, the protective effects of SP600125 in the retina and SC were also detected even with only 7 days (Days 1-7 after I/R) of SP600125 treatment. CONCLUSIONS: Our results demonstrate the important role the JNK pathway plays in retinal degeneration in both in vitro and in vivo models and suggest that JNK inhibitors may be a useful therapeutic strategy for neuroprotection of RGCs in the retina.Item TGFbeta2 Induces the Formation of Cross-Linked Actin Networks (CLANs) in Human Trabecular Meshwork Cells Through the Smad and Non-Smad Dependent Pathways(ARVO Journals, 2017-02) Montecchi-Palmer, Michela; Bermudez, Jaclyn Y.; Webber, Hannah C.; Patel, Gaurang C.; Clark, Abbot F.; Mao, WeimingPurpose: Increased intraocular pressure results from increased aqueous humor (AH) outflow resistance at the trabecular meshwork (TM) due to pathologic changes including the formation of cross-linked actin networks (CLANs). Transforming growth factor beta2 (TGFbeta2) is elevated in the AH and TM of primary open angle glaucoma (POAG) patients and induces POAG-associated TM changes, including CLANs. We determined the role of individual TGFbeta2 signaling pathways in CLAN formation. Methods: Cultured nonglaucomatous human TM (NTM) cells were treated with control or TGFbeta2, with or without the inhibitors of TGFbeta receptor, Smad3, c-Jun N-terminal kinases (JNK), extracellular signal regulated kinase (ERK), P38, or Rho-associated protein kinase (ROCK). NTM cells were cotreated with TGFbeta2 plus inhibitors for 10 days or pretreated with TGFbeta2 for 10 days followed by 1-hour inhibitor treatment. NTM cells were immunostained with phalloidin-Alexa-488 and 4',6-diamidino-2-phenylindole (DAPI). Data were analyzed using 1-way ANOVA and Dunnett's post hoc test. Results: TGFbeta2 significantly induced CLAN formation (n = 6 to 12, P < 0.05), which was completely inhibited by TGFbeta receptor, Smad3, and ERK inhibitors, as well as completely or partially inhibited by JNK, P38, and ROCK inhibitors, depending on cell strains. One-hour exposure to ROCK inhibitor completely resolved formed CLANs (P < 0.05), whereas TGFbeta receptor, Smad3 inhibitor, and ERK inhibitors resulted in partial or complete resolution. The JNK and P38 inhibitors showed partial or no resolution. Among these inhibitors, the ROCK inhibitor was the most disruptive to the actin stress fibers, whereas ERK inhibition showed the least disruption. Conclusions: TGFbeta2-induced CLANs in NTM cells were prevented and resolved using various pathway inhibitors. Apart from CLAN inhibition, some of these inhibitors also had different effects on actin stress fibers.