Sevoflurane prevents vulnerable plaque disruption in apolipoprotein E-knockout mice by increasing collagen deposition and inhibiting inflammation

Background: Sevoflurane may reduce the occurrence of major adverse cardiovascular events (MACCEs) in surgical patients, although the mechanisms are poorly understood. We hypothesised that sevoflurane stabilises atherosclerotic plaques by inhibiting inflammation and enhancing prolyl-4-hydroxylase alpha 1 (P4H alpha 1), the rate-limiting subunit for the P4H enzyme essential for collagen synthesis. Methods: We established a vulnerable arterial plaque model in apolipoprotein E-knockout mice (ApoE(-/-)) fed a high-fat diet that underwent daily restraint/noise stress, with/without a single prior exposure to sevoflurane for 6 h (1-3%; n=30 per group). In vitro, smooth muscle cells (SMCs) were incubated with tumour necrosis factor-alpha in the presence/absence of sevoflurane. Immunohistochemistry, immunoblots, and mRNA concentrations were used to quantify the effect of sevoflurane on plaque formation, expression of inflammatory cytokines, P4H alpha 1, and collagen subtypes in atherosclerotic plaques or isolated SMCs. Results: In ApoE(-/-) mice, inhalation of sevoflurane 1-3% for 6 h reduced the aortic plaque size by 8-29% in a dose-dependent manner, compared with control mice that underwent restraint stress alone (P<0.05); this was associated with reduced macrophage infiltration and lower lipid concentrations in plaques. Sevoflurane reduced gene transcription and protein expression levels of pro-inflammatory cytokines (>= 69-75%; P<0.05) and matrix metalloproteinases (>= 39-65%; P<0.05) at both gene transcription and protein levels, compared with controls. Sevoflurane dose dependently increased Types I and III collagen deposition through enhanced protein expression of P4Ha1, both in vivo and in vitro (0.7-3.3-fold change; P<0.05). Conclusions: Sevoflurane dose dependently promotes plaque stabilisation and decreases the incidence of plaque disruption in ApoE(-/-) mice by increasing collagen deposition and inhibiting inflammation. These mechanisms may contribute to sevoflurane reducing MACCE.