PACAP deficiency aggravates atherosclerosis in ApoE deficient mice

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) plays an important role in cytoprotection, inflammation and cardiovascular regulation. Thus, we studied the involvement of PACAP in atherogenesis. Differentiated human THP-1 macrophages (MΦ) were stimulated with oxidized low-density lipoproteins (oxLDL) and the influence of PACAP38 treatment on lipid content and TNF release was determined. To test the effect of PACAP deficiency (PACAP^?/?) on the development of atherosclerosis under standard chow (SC) or cholesterol-enriched diet (CED) in vivo, PACAP^?/? mice were crossbred with ApoE^?/? to generate PACAP^?/?/ApoE^?/? mice. Blood cholesterol and triglyceride levels were quantified. Lumen stenosis in the brachiocephalic trunk, cellularity and amounts of pro-inflammatory as well as autophagy-, apoptosis- and necroptosis-relevant proteins were analysed in atherosclerotic plaques by quantitative immunohistochemistry. In vitro, PACAP38 inhibited oxLDL-induced intracellular lipid storage as well as TNF release in MФ. In vivo, after SC, but not under CED, PACAP^?/?/ApoE^?/? mice showed an increased lumen stenosis compared to ApoE^?/? mice. In atherosclerotic plaques of PACAP^?/?/ApoE^?/? mice, the immunoreactive areas of TNF⁺, IL-1β⁺, autophagic, apoptotic and necroptotic cells were increased. In contrast, the overall cell density was decreased compared to ApoE^?/? under SC, while no differences were seen under CED. Similar plasma cholesterol levels were observed in PACAP^?/?/ApoE^?/? and ApoE^?/? mice under the respective feeding regime. Thus, PACAP^?/-/ApoE^?/? mice represent a novel mouse model of accelerated atherosclerosis where CED is not required. Our data indicate that PACAP acts as an endogenous atheroprotective neuropeptide. Thus, stable PACAP agonists may have potential as anti-atherosclerotic therapeutics. The specific PACAP receptor(s) mediating atheroprotection remain(s) to be identified.