Regulation of Protein Kinase C (PKC) zeta expression in experimental ocular inflammation in Lewis rats

Abstract

Abstract: : Purpose: To analyze PKCzeta expression during ocular inflammation and after treatment with IL–13, a cytokine with potent anti–inflammatory properties, or tamoxifen, an estrogen receptor modulator. Methods: We studied PKCzeta expression during endotoxin–induced uveitis (EIU) in rats treated with intravitreal injection of IL–13 simultaneously with LPS injection, and during S–Ag–induced experimental autoimmune uveoretinitis (EAU) in rats treated with tamoxifen encapsulated in biodegradable nanoparticles (NP–TAM) administered intravenously 13 days after S–Ag immunization. Eyes were taken from EIU and EAU rats at different time intervals after LPS or S–Ag injection. In addition, draining lymph node cells from EAU rats were taken 16 days after S–Ag immunization and stimulated in vitro with S–Ag and Concanavalin–A (Con–A). Immunohistochemistry and western blotting were performed on ocular tissues and lymph node using antibodies specific for PKCzeta, NF–kappa–B, Bcl–2, Bax, glia (GFAP) and inflammatory cells (ED1, OX62, CD4). Results: Constitutive expression of PKCzeta was detected in normal ocular tissues, but expression increased at the onset of ocular inflammation during EIU and EAU. The inflammatory stress induced the translocation of PKCzeta from the cytosol to the membrane and the nucleus of retinal and inflammatory cells. Interestingly, the treatment with IL–13 restored normal expression of PKCzeta in ocular tissues. Draining lymph node cells from EAU rats stimulated in vitro with S–Ag and Con–A showed stronger S–Ag–specific activation of PKCzeta in CD4+ and ED1+ cells and weaker activation in OX–62+ dendritic cells. Treatment with NP–TAM decreased PKCzeta expression in CD4+ and ED1+ cells. A decrease in NF–kappa–B expression and an increase in Bcl–2 were observed in lymph node cells by western blotting. Conclusions: We have shown previously that IL–13 and NP–TAM inhibit EIU and EAU, respectively, in association with inhibition of intraocular inflammatory cytokines. Here we demonstrate that the effects of these treatments may stem from regulatory effects of PKCzeta on NF–kappa–B, Bcl–2 and Bax expression in ocular tissues and in inflammatory cells. The understanding of specific pathways that regulate cytokine release and damage to neural cells within the eye may indicate new targets for treatment of ocular inflammation.

Keywords: uveitis–clinical/animal model • inflammation • immunomodulation/immunoregulation