Effect of rottlerin, a PKC-δ inhibitor, on TLR-4-dependent activation of murine microglia

In microglia, Toll-like receptors have been shown to recognize pathogen-associated molecular patterns and initiate innate immune responses upon interaction with infectious agents. The effect of rottlerin, a PKC-δ specific inhibitor, on TLR-4-mediated signaling was investigated in murine microglia stimulated with lipopolysaccharide and taxol. Pretreatment of microglia cells with rottlerin decreased LPS- and taxol-induced nitric oxide production in a concentration-dependent manner (IC50 = 99.1 ± 1.5 nM). Through MTT and FACS analysis, we found that the inhibition effect of rottlerin was not due to microglial cell death. Rottlerin pretreatment also attenuated LPS-induced phosphorylation of IκB-α, nuclear translocation of NF-κB, and expression of type II nitric oxide synthase. In addition, microglial phagocytosis in response to TLR-4 activation was diminished in which rottlerin was pretreated. Together, these data raise the possibility that certain PKC-δ specific inhibitors can modulate TLR-4-derived signaling and inflammatory target gene expression, and can alter susceptibility to microbial infection and chronic inflammatory diseases in central nervous system.