PAC1 Agonist Maxadilan Reduces Atherosclerotic Lesions in Hypercholesterolemic ApoE-Deficient Mice

A possible involvement of immune- and vasoregulatory PACAP signaling at the PAC1 receptor in atherogenesis and plaque-associated vascular inflammation has been suggested. Therefore, we tested the PAC1 receptor agonist Maxadilan and the PAC1 selective antagonist M65 on plaque development and lumen stenosis in the ApoE^-/- atherosclerosis model for possible effects on atherogenesis. Adult male ApoE^-/- mice were fed a cholesterol-enriched diet (CED) or standard chow (SC) treated with Maxadilan, M65 or Sham. Effects of treatment on atherosclerotic plaques, lumen stenosis, apoptosis and pro-inflammatory signatures were analyzed in the brachiocephalic trunk (BT). The percentage of Maxadilan treated mice exhibiting plaques under SC and CED was lower than that of Sham or M65 treatment indicating opposite effects of Maxadilan and M65. Maxadilan application inhibited lumen stenosis in SC and CED mice compared to the Sham mice. In spite of increased cholesterol levels, lumen stenosis of Maxadilan-treated mice was similar under CED and SC. In contrast, M65 under SC or CED did not reveal a significant influence on lumen stenosis. Maxadilan significantly reduced the TNF-α-immunoreactive (TNF-α⁺) area in the plaques under CED, but not under SC. In contrast, the IL-1β⁺ area was reduced after Maxadilan treatment in SC mice but remained unchanged in CED mice compared to Sham mice. Maxadilan reduced caspase-3 immunoreactive (caspase-3⁺) in the tunica media under both, SC and CED without affecting lipid content in plaques. Despite persistent hypercholesterolemia, Maxadilan reduces lumen stenosis, apoptosis and TNF-α driven inflammation. Our data suggest that Maxadilan provides atheroprotection by acting downstream of hypercholesterolemia-induced vascular inflammation. This implicates the potential of PAC1-specific agonist drugs against atherosclerosis even beyond statins and PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors.