PKCη as a promising therapeutic target for TNFa-induced inflammatory disorders in chronic cutaneous wounds

Abstract

Protein kinase C? (PKC?) is a member of the atypical protein kinase C family. Its roles in macrophages or skin-resident keratinocytes have not been fully evaluated. In this study, we provide evidence that PKC? mediates lipopolysaccharide (LPS)-induced tumor necrosis factor a (TNFa) gene expression in the mouse macrophage cell line, RAW264.7. TNFa has been proven to be one of the main culprits of chronic wounds and impaired acute wounds, which are characterized by excessive inflammation, enhanced proteolysis and reduced matrix deposition. Among the multiple effects of TNFa on keratinocytes, the induction of chemokines which are indispensable factors involved in the massive infiltration of various inflammatory cells into skin lesions serves as a crucial mechanism. In the present study, we found that PKC? inhibitor or its specific siRNA inhibited the TNFa-induced upregulation in the levels of the chemokines, interleukin (IL)-8, monocyte chemotactic protein-1 (MCP-1) and intercellular cell adhesion molecule-1 (ICAM-1) in HaCaT keratinocytes. Moreover, under a disrupted inflammatory environment, activated keratinocytes can synthesize large amounts of matrix metalloproteinases (MMP), which has a negative effect on tissue remodeling. We discovered that TNFa promoted the expression of MMP9 in a PKC?-dependent manner. Further experiments revealed that nuclear factor-?B (NF-?B) was a key downstream molecule of PKC?. In addition, as shown in vitro, PKC? was not involved in the TNFa-induced decrease in HaCaT cell migration and proliferation. In vivo experiments demonstrated that TNFa-induced wound closure impairment and inflammatory disorders were significantly attenuated in the PKC? inhibitor group. On the whole, our findings suggest that PKC? is a crucial regulator in LPS- or TNFa-induced inflammatory responses in RAW264.7 cells and HaCaT keratinocytes, and that PKC?/ NF-?B signaling may be a potential target for interventional therapy for TNFa-induced skin inflammatory injury.