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LN Fleisher, MC McGahan, JB Ferrell; Involvement of PKC in IL-1ß-Induced MMP-9 Release from Pigmented Ciliary Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3245.
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Purpose: MMPs are thought to play important roles in corneal wound healing, glaucoma, uveitis, and proliferative vitreoretinopathy. Despite the potential benefits of a comprehensive understanding of the intracellular mechanisms controlling MMP-9 production and release, the pathways regulating these processes in ocular tissues such as the ciliary body are essentially unknown. We have shown that IL-1ß stimulates release of MMP-9 from rabbit pigmented ciliary epithelial cells (PE) through a pathway(s) requiring activation of NFΚB and PKC. The purpose of the present investigation was to determine whether PKC is part of, or separate from the signaling pathway linking IL-1ß-induced NFΚB activation to stimulation of MMP-9 release. Methods: Confluent, nontransformed first-passage rabbit PE were incubated for 24 h in serum-free medium containing IL-1ß (500 U/ml), the PKC activator, PMA (0.1 µM) or both agents, with or without the NFΚB inhibitors, BAY 11-7085 or MG-132. MMP-9 release (ng/ml) was measured by ELISA. Results are expressed as mean ± SEM. Results: Coincubation of PE with IL-1ß + PMA synergistically stimulated MMP-9 release (IL-1ß = 4.97 ± 0.89, PMA= 8.23 ± 0.63, IL-1ß + PMA = 39.8 ± 4.2). IL-1ß- or PMA-induced MMP-9 release was reduced by BAY 11-7085 or MG-132. However, PMA-induced MMP-9 release was more sensitive to each inhibitor and was reduced to a greater extent. Only the highest dose (10 µM) of BAY 11-7085 or MG-132 inhibited IL-1ß-induced MMP-9 release (46% reduction for each inhibitor). In contrast, 1 and 10 µM BAY 11-7085 or MG-132 reduced PMA-induced MMP-9 release by 65% and 75% (BAY 11-7085) and 79% and 94% (MG-132). Conclusion: NFΚB activation is required if stimulation of MMP-9 release is to proceed through a PKC-dependent pathway. Furthermore, the synergistic stimulation of MMP-9 release by IL-1ß + PMA suggests that the pathways turned on by IL-1ß or PKC activation converge on a common mediator, most likely NFΚB. Both IL-1ß- and PMA-induced MMP-9 release were reduced by two different NFΚB inhibitors. However, these inhibitors differed considerably in terms of the extent to which MMP-9 release was reduced, since IL-1ß-induced MMP-9 release was inhibited less effectively. We have previously reported that IL-1ß-induced stimulation of MMP-9 release was only partially reduced by PKC inhibition. Taken together, these results suggest that IL-1ß also induces MMP-9 release through a pathway not requiring PKC activation. It is well documented that IL-1ß activates NFΚB through an NFΚB-inducing kinase/IΚB kinase pathway. This may be the PKC-independent pathway operative in rabbit PE cells.
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