부산대학교 도서관

Kalirin is a 270-kDa scaffolding protein comprising 2 GTP exchange factors (GEFs). KALRN has been associated with human atherosclerosis (athero) in multiple genetic studies, and carotid injury produced more neointimal hyperplasia in WT than in Kalrn mice. Therefore, we tested the hypothesis that Kalirin aggravates atherosclerosis (athero). Surprisingly, on Western diet Kalrn/Apoe mice developed 2.0±0.5-fold more aortic athero (en face, p<0.001) and 2.0±0.02-fold more brachiocephalic athero lesion area (p<0.005) than congenic Apoe mice, even though blood pressures and serum cholesterols were equivalent. This anti-atherogenic activity of Kalirin resided, in part, in macrophages (Mϕs): LysM-Cre/Kalrn/Apoe mice evinced 1.3 ±0.2-fold more aortic athero than Kalrn/Apoe mice (p<0.01). To test Kalirin effects on Mϕ activity, we used ≥3 independently isolated, matched Kalrn and WT bone marrow-derived Mϕ lines for each experiment. We tested RhoGEF activity by G-LISA: in response to LPS, Kalrn Mϕs produced 23% less Rac1/2/3 activation and 25% more RhoA activation than WT Mϕs (p<0.01 each); thus, Kalirin appears to activate Rac and inhibit RhoA in Mϕs. Isolated by negative selection with magnetic beads (84±4% purity), Kalrn monocytes migrated 29% less than WT in response to MCP-1 (p<0.05), but equivalently to CSF-1 (Neuroprobe membranes). Because Kalirin promotes secretion of neuropeptides in the CNS, we tested whether it affects Mϕ cytokine secretion. In response to LPS, Kalrn Mϕs secreted 39±6% less of the anti-inflammatory cytokine IL-10 than WT Mϕs (1.8±0.2 vs 2.5±0.3 μg/ml/mg protein, p<0.05), but equivalent levels of the pro-inflammatory cytokine IL-6 (2.9±0.3 vs 3.0±0.5 μg/ml/mg protein). To determine whether Kalirin inhibits iNOS activity in Mϕs as it does in heterologous systems (by preventing iNOS dimerization), we induced Mϕ iNOS expression with interferon-γ and LPS. While Kalrn and WT Mϕs expressed equivalent levels of iNOS (by immunoblot), Kalrn Mϕs produced 38±10% more NO· than WT Mϕs (assessed as nitrite in the medium). We conclude that Kalirin attenuates athero in part through Mϕ-specific mechanisms that include augmentation of IL-10 secretion and inhibition of iNOS activity.