Role for phosphoinositidyl specific-phospholipase C-beta isoforms in inflammatory and angiogenic processes

Chemokines and lipids signal through G-protein coupled receptors (GPCR) and regulate a variety of physiological and pathophysiological processes. G-protein coupled receptors activate Phospholipase C-beta (PLC-β) isoforms leading to the generation of inositol (1,4,5) trisphosphate and diacylglycerol. To investigate a role PLC-β isoforms in regulating GPCR activities, two PLC-β isoforms, PLC-β2 and PLC-β3, were genetically altered in mice. The effect of genetic alteration in PLC-β isoforms was assayed in two in vivo models: (1) excisional wound healing and (2) Lewis Lung Carcinoma. Compared to wild type mice, mice lacking active PLC-β2 or PLC-β3 showed decreased monocytic infiltrate and delayed re-epithelialization during excisional wound healing. The wounds in these mice all resolved which showed PLC-β2 or PLC-β3 is not required for effective wound healing. In contrast, PLC-β2 and PLC-β3 mice bearing subcutaneous Lewis Lung Carcinoma tumors showed increased monocytic infiltrate. The tumors in the PLC-β deficient mice grew more slowly and had decreased angiogenesis. To determine a role for PLC-β isoforms in regulating endothelial cell functions, chemotaxis and in vitro angiogenic assays were used. Chemical inhibition and RNAi mediated knockdown of PLC-β blocked S1P induced endothelial cell chemotaxis in murine endothelial cell lines. Chemical inhibition of PLC-β also inhibited in vitro angiogenesis stimulated by S1P. The loss of endothelial cell chemotaxis to S1P was attributed to inhibition of Rac activation mediated by PLC because chemical inhibition of PLC reduced the amount of precipitated active Rac. Together these data showed the genetic alteration in PLC-β isoforms is not required for effective wound healing but is required for tumor associated angiogenesis mediated by S1P.