Effect of Protein Kinase C delta (PKC-δ) Inhibition on the Transcriptome of Normal and Systemic Sclerosis Human Dermal Fibroblasts In Vitro

Previous studies demonstrated that protein kinase C-delta (PKC-delta) inhibition with the selective inhibitor, rottlerin, resulted in potent downregulation of type I collagen expression and production in normal human dermal fibroblasts and abrogated the exaggerated type I collagen production and expression in fibroblasts cultured from affected skin from patients with the fibrosing disorder systemic sclerosis (SSc). To elucidate the mechanisms involved in the ability of PKC-delta to regulate collagen production in fibroblasts, we examined the effects of PKC-delta inhibition on the transcriptome of normal and SSc human dermal fibroblasts. Normal and SSc human dermal fibroblasts were incubated with rottlerin (5 mu M), and their gene expression was analyzed by microarrays. Pathway analysis and gene ontology analysis of differentially expressed genes in each comparison were performed. Identification of significantly overrepresented transcriptional regulatory elements (TREs) was performed using the Promoter Analysis and Interaction Network Toolset (PAINT) program. PKC-delta activity was also inhibited using RNA interference (siRNA) and by treating fibroblasts with a specific PKC-delta inhibitory cell permeable peptide. Differential gene expression of 20 genes was confirmed using real time PCR. PKC-delta inhibition caused a profound change in the transcriptome of normal and SSc human dermal fibroblasts in vitro. Pathway and gene ontology analysis identified multiple cellular and organismal pathways affected by PKC-delta inhibition. Furthermore, both pathway and PAINT analyses indicated that the transcription factor NFkB played an important role in the transcriptome changes induced by PKC-delta inhibition. Multiple genes involved in the degradation of the extracellular matrix components were significantly reduced in SSc fibroblasts and their expression was increased by PKC-delta inhibition. These results indicate that isoform-specific inhibition of PKC-delta profibrotic effects may represent a novel therapeutic approach for SSc and other fibrotic diseases.