Protein Kinase Cζ (PKCζ) Regulates Ocular Inflammation and Apoptosis in Endotoxin-Induced Uveitis (EIU) : Signaling Molecules Involved in EIU Resolution by PKCζ Inhibitor and Interleukin-13

We show that inhibitory effect of interleukin-13 on endotoxin-induced uveitis in the Lewis rat is dependent on signaling activity of protein kinase Cζ (PKCζ). To understand the effect of interleukin-13 or PKCζ inhibitor treatment, the activation status of rat bone marrow-derived macrophages was studied in vitro. At 6 hours, lipopolysaccharide-stimulated macrophages produced tumor necrosis factor-α (TNF-α) with nuclear factor κB (NF-κB)/p65 expression. Treatment led to absence of NF-κB/p65 expression and low levels of TNF-α, suggesting accelerated inactivation of macrophages. At 24 hours after lipopolysaccharide stimulation, nuclear NF-κB/p65 decreased and nuclear NF-κB/p50 increased, associated with nuclear BCL-3 and a low level of TNF-α, indicating onset of spontaneous resolution. Treatment limited PKCζ cleavage, with expression of nuclear NF-κB/p50 and BCL-3 and low nuclear NF-κB/p65 promoting macrophage survival, as evidenced by Bcl-2 expression. At 24 hours, intraocular treatment decreased membranous expression of PKCζ by ocular cells, reduced vascular leakage with low nitric-oxide synthase-2 expression in vascular endothelial cells, and limited inflammatory cell infiltration with decreased intraocular TNF-α, interleukin-6, and nitric-oxide synthase-2 mRNA. Importantly, treatment decreased nuclear NF-κB/p65, increased transforming growth factor-β2, and reduced caspase 3 expression in infiltrating macrophages, implying a change of their phenotype within ocular microenvironment. Treatment accelerated endotoxin-induced uveitis resolution through premature apoptosis of neutrophils related to high expression of toll-like receptor 4 and caspase 3.