Cytokine and growth factor regulation of macrophage scavenger receptor expression and function

Regulation of macrophage scavenger receptor (MSR) activity may be an important determinant of the extent of atherogenesis and the efficacy of host defense. The effect of M-CSF on this pathway was studied using a recently developed monoclonal antibody to murine MSR. M-CSF markedly and selectively increased MSR synthesis in murine macrophages (Mφ); post-translationally the receptor appeared more stable and shifted to a predominantly surface distribution. Functionally M-CSF enhanced modified lipoprotein uptake and increased divalent cation-independent adhesion in vitro. These results suggest a plausible mechanism whereby M-CSF production in the atheromatous plaque micro-environment could promote the recruitment and retention of mononuclear phagocytes and subsequent foam cell formation. In addition, the Th1 cytokine (γ-interferon) and Th2 cytokine (interleukin-4) had differential effects on MSR glycosylation in vitro suggesting a further possible regulatory role by these lymphokines on macrophage MSR function.