Abstract 225: Lack Of Map Kinase Phosphatase-5 In Macrophages Protects Ldlr-null Mice Against Atherogenesis

Objective: Mitogen-activated protein kinases (MAPKs), including JNK, ERK, and p38 MAPK, are critical in regulating the expression of various pro-inflammatory and anti-inflammatory cytokines and chemokines. Previous work has suggested that the absence of MAP Kinase Phosphatase-5 (MKP-5) inhibits oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cell formation without influencing the MAKP activation. The current study is to determine the role of macrophage MKP-5 in the pathogenesis of atherosclerosis and underlying mechanisms. Approach and Results: Nine-week-old male congenic MKP-5 deficient (MKP-5 -/- ) and C57Bl/6J control (WT) mice on an LDL receptor knock-out (LDLR -/- ) background were fed with a high-fat diet containing 1.25% cholesterol (HFD) for 14 weeks. Global deficiency of MKP-5 attenuated atherosclerotic plaque formation without altering the lipid profile in vivo. To further elucidate the macrophage-specific effect of MKP-5 in atherogenesis, Lethally irradiated LDLR -/- mice were transplanted with WT or MKP-5 -/- bone marrow and subjected to high-fat feeding. Mice transplanted with MKP-5 -/- bone marrow developed smaller atherosclerotic lesions accompanied by decreased lipid deposition and macrophage content compared to WT. Lack of MKP-5 in macrophages reduced plasma levels of interleukin-1α (IL-1α) and IL-7, elevated anti-inflammatory cytokines IL-1 receptor antagonist (IL-1rn), and IL-4. Mechanistically, lack of MKP-5 in macrophages inhibited ox-LDL-induced foam cell formation through enhanced cholesterol efflux mediated by increased expression of ATP-binding cassette transporters ABCA1 and ABCG1. Conclusions: These data suggest that the myeloid MKP-5 deficiency reduces atherosclerosis progression and foam cell formation by ameliorating cholesterol efflux and inhibiting inflammation.