[LPS and PMA induced PKC-alpha and PKC-epsilon activation and translocation in murine peritoneal macrophages]

Abstract

Suppressor macrophages induced by the continuous invasion of tumor cells and parasites, which can acquire an ability in vitro to kill or inhibit tumor cells and inhibit the activity of T, B lymphocytes and NK cells, have been indicated. We have developed a procedure previously to modulate the suppressor macrophages by bacterial lipopolysaccharide (LPS). The modulated macrophages remained and even enhanced the ability to inhibit tumor growth and to up-regulate or enhance the activities of T, B lymphocytes and NK cells in vitro. However, the mechanisms of macrophage modulation by LPS are unknown. This investigation was designed to analyze the regulation of PKC activity and to characterize the isoforms of PKC during macrophage modulation by using Western blot and endogenous substrate phosphorylation (PKC-DESP). In rest cells, PKC-beta was found to be the most abundant isoform in macrophages; and PKC-alpha, beta was found predominantly in the cytosol. Using PMA as a positive control, we found that the immuno-modulator agent--LPS triggered the physical translocation from the cytosol onto the membrane of PKC-alpha and PKC-epsilon, but PKC-beta (beta I or beta II) was difficult to detect. The analysis of PKC-DESP showed a pattern with a time course similar to that observed with Western blot. We observed that LPS and PMA increase the level of phosphorylation of 55 kDa and 74 kDa proteins with a corresponding decrease in the cytosolic proteins. It suggests that the translocation of PKC-alpha and PKC-epsilon, may be important events involving in the PKC-pathway by LPS-mediated modulation in suppressor macrophages.