Objectives: Nicotine has been identified to promote atherosclerosis. But the mechanism of nicotine induced atherogenesis has not been well elucidated. This study focus on the role of mast cell in nicotine induced atherogenesis and plaque instability.
Methods: Peritoneal administration of 100mM disodium cromoglicate (DSCG) was introduced to inhibit mast cell degranulation. 45 ApoE deficient mice were divided into 3 groups: high-fat diet, high-fat diet + nicotine, and high-fat diet + nicotine + DSCG. After 12 weeks of treatments, atherosclerotic lesion size of the aortas were quantified. Toluidine blue and tryptase staining identified mast cell count and activation at the lesion. Immuno-staining were used to evaluate the inflammatory filtration, smooth muscle cell proliferation and collagen content in the lesion. In vitro , bone marrow-derived mast cells (BMMCs) were harvested and treated with PBS as a negative control, compound 48/80 as a positive control,100μg/ml nicotine, nicotine with 100mM DSCG pretreatment and nicotine with 10μg/ml mecamylamine pretreatment. At 0.5hr,1hr and 2hrs, supernatants were harvested to analyze the mast cell degranulation. Futhermore, conditioned medium were also used to induce the macrophage migration and foam cell formation.
Results: Nicotine increases plaque size, and macrophage infiltration, decreases smooth muscle collagen content along with the increases in mast cells count and activation ratio at the lesion, which could be inhibited by DSCG.Nicotine induced mast cell degranulation at 2 hours comparing to PBS (43.60% vs 2.3%) , which could be inhibited by mast cell stablizer DSCG (23.7%) and nAChR blocker mecamylamine (20.35%). Macrophage migration ability in the compound 48/80 and nicotine conditional medium group were significantly higher comparing to PBS, DSCG and mecamylamine group. Foam cell formation ratio in the compound 48/80 and nicotine conditional group were significantly higher comparing to PBS, DSCG and mecamylamine group.
Conclusions: Nicotine induces mast cell degranulation through nAChR and then increases macrophages function, which leads to plaque instability. Administration of mast cell stabilizer showed potential of preventing nicotine induced atherogenesis.