PIP2 and cholesterol interplay in inflammation and atherosclerosis

INTRODUCTION: Cholesterol accumulation in arterial macrophages leads to foam cell formation, Nlrp3 inflammasome activation, and IL-1b release. Phosphatidylinositol 4, 5-bisphosphate (PIP2) plays a role in the cholesterol efflux pathway and IL-1b release. The PIP2 phosphatase TMEM55b modulates cholesterol efflux but the mechanism of this effect is not clear. Miltefosine altered PIP2 localization and blunted Nlrp3 inflammasome in macrophages, but the mechanism of its anti-atherosclerotic properties is not clear. OBJECTIVES: To determine the effect of cellular PIP2 levels on ABCA1 mediated cholesterol efflux. To determine the mechanism by which Miltefosine reduces atherosclerosis in mice. METHODS AND RESULTS: The correlation between cellular PIP2 levels and ABCA1 mediated cholesterol efflux was determined. PIP2 levels were markedly increased in cholesterol-loaded cells vs. control macrophages (~ 22 % increase, N=3, mean±SD, *P=0.05). Expression of TMEM55b, a PIP2 phosphatase, in BHK cells resulted in ~ 70 % decrease in ABCA1 mediated cholesterol efflux (N=4, mean ± SD, P<0.0001). Miltefosine treated mice showed blunted in-vivo Nlrp3 inflammasome assembly and had significantly lowered IL-1b levels in peritoneal lavage (mean +SD; N=5, **p<0.001). Miltefosine-fed mice showed significantly higher reverse cholesterol transport to plasma, liver, and feces. The hyperlipidemic apoE-/- KO mice fed with Miltefosine (50 mg/kg/day) gained significantly less weight vs. controls and showed significantly decreased atherosclerotic lesions (≥50% smaller vs. controls; mean + SD, p<0.001 in females with N=10, and p<0.04 in males with N=12). Miltefosine altered gut microbiota in hyperlipidemic apoE-/- KO mice. CONCLUSION: PIP2 regulates ABCA1 mediated cellular cholesterol efflux. Miltefosine can dampen in-vivo Nlrp3 inflammasome assembly, increase reverse cholesterol transport, reduce high fat diet-induced weight gain, reduce atherosclerotic lesion area and alter gut microbiota. © FASEB.