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It was shown previously that a metabolite of acetaminophen (APAP), N-acetyl-p-benzoquinone imine (NAPQI), is a potent vasodilator, which could underlie the hypotension observed when APAP is administered intravenously. However, it is unknown whether APAP metabolism to NAPQI is possible in the vasculature. In this study, we examine the hypothesis that APAP is metabolized by cytochrome P450 enzymes within the endothelium, which may be accelerated in critically ill patients by the presence of elevated myeloperoxidase (MPO). Exposure of human coronary artery endothelial cells (HCAECs) to APAP resulted in the formation of protein-bound APAP adducts. Proteomic analysis of HCAECs exposed to APAP showed upregulation of CYP20A1, together with proteins involved in the pentose phosphate pathway and maintaining redox homeostasis. Proteomic analyses of mesenteric arteries from rats administered intravenous APAP are consistent with a key role of the vascular wall in APAP metabolism, with similar proteomic pathway changes identified in HCAECs. These changes occurred over a short timeframe and were not seen in the corresponding proteomic analyses of liver tissue. Intracellular thiols were depleted in HCAECs upon APAP treatment, which was partially attenuated by ketoconazole, consistent with the involvement of cytochrome P450 enzymes in the metabolism of APAP to a thiol-reactive metabolite such as NAPQI. Evidence was also obtained for the metabolism of APAP to a thiol-reactive intermediate by MPO in the absence of chloride ions, consistent with NAPQI formation. Taken together, these data provide a putative mechanism to explain the presentation of hypotension in critically ill patients following IV APAP administration.

Inadequate adaption to mechanical forces, including blood pressure, contributes to development of arterial aneurysms. Recent studies have pointed to a mechanoprotective role of YAP and TAZ in vascular smooth muscle cells (SMCs). Here, we identified reduced expression of YAP1 in human aortic aneurysms. Vascular SMC–specific knockouts (KOs) of YAP/TAZ were thus generated using the integrin α8–Cre (Itga8-Cre) mouse model (i8-YT-KO). i8-YT-KO mice spontaneously developed aneurysms in the abdominal aorta within 2 weeks of KO induction and in smaller arteries at later times. The vascular specificity of Itga8-Cre circumvented gastrointestinal effects. Aortic aneurysms were characterized by elastin disarray, SMC apoptosis, and accumulation of proteoglycans and immune cell populations. RNA sequencing, proteomics, and myography demonstrated decreased contractile differentiation of SMCs and impaired vascular contractility. This associated with partial loss of myocardin expression, reduced blood pressure, and edema. Mediators in the inflammatory cGAS/STING pathway were increased. A sizeable increase in SOX9, along with several direct target genes, including aggrecan (Acan), contributed to proteoglycan accumulation. This was the earliest detectable change, occurring 3 days after KO induction and before the proinflammatory transition. In conclusion, Itga8-Cre deletion of YAP and TAZ represents a rapid and spontaneous aneurysm model that recapitulates features of human abdominal aortic aneurysms.