Nox2 mediates high fat high sucrose diet-induced nitric oxide dysfunction and inflammation in aortic smooth muscle cells

Abstract

Diet-induced obesity and metabolic syndrome are important contributors to cardiovascular diseases. The decreased nitric oxide (NO) bioactivity in endothelium and the impaired response of smooth muscle cell (SMC) to NO significantly contribute to vascular pathologies, including atherosclerosis and arterial restenosis after angioplasty. Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) is an important mediator of NO function in both endothelial cells and SMCs, and its irreversible oxidation impair its stimulation by NO. We used C57BL/6J mice fed a high fat, high sucrose diet (HFHSD) to study the role of SMC SERCA in diet-induced obesity and metabolic syndrome. We found that HFHSD upregulated Nox2 based NADPH oxidase, induced inflammation, increased irreversible SERCA oxidation, and suppressed the response of aortic SERCA to NO. Cultured aortic SMCs from mice fed HFHSD showed increased reactive oxygen species production, Nox2 upregulation, irreversible SERCA oxidation, inflammation, and a decreased ability of NO to inhibit SMC migration. Overexpression of wild type SERCA2b or downregulation of Nox2 restored NO-mediated inhibition of migration in SMCs isolated from HFHSD-fed mice. In addition, tumor necrosis factor alpha (TNFα) increased Nox2 which induced SERCA oxidation and inflammation. Taken together, Nox2 induced by HFHSD plays significant roles in controlling SMC responses to NO and TNFα-mediated inflammation, which may contribute to the development of cardiovascular diseases in diet-induced obesity and metabolic syndrome.

Vascular Smooth Muscle Sirtuin-1 Protects Against Diet-Induced Aortic Stiffness

“…Aortic wall stiffening was associated with increased inflammation, as measured by cytokines TNFα, MCP-1, MIP1α, decreased nitric oxide (NO) bioavailability, and increased extracellular matrix cross-linking in the aortic wall 16 . We further demonstrated that, in the setting of dietary obesity, TNFα-induced activation of the oxidant-generating enzyme NADPH oxidase, Nox2, is a major determinant of inflammation associated with functional impairment of aortic smooth muscle cells 17 . VSM cell functional alterations have recently emerged has important determinants of vascular stiffening, contributing ∼ 50% to aortic stiffness 18-20 .…”

“…Our previous work showed a link between HFHS-feeding, arterial stiffness and the production of oxidants in the aortas of obese mice, leading to inflammation and functional impairment in VSM cells, associated with increases in TNFα 16, 17 . Therefore, we assessed whether the amelioration of arterial stiffness by SirT1 activators and genetic overexpression of SirT1 were mediated by anti-inflammatory and anti-oxidant effects.…”

“…As we previously reported that, in our model of obesity, VSM Nox2 is a major source of oxidants in the aorta 17 , we first assessed whether the anti-oxidant effects of SirT1 on the aortic wall were mediated by downregulation of Nox2. We found no significant changes in Nox2 expression in VSM of aortic sections of HFHS-fed SMTG (n=6), compared with HFHS-fed controls (Supplemental Figure S4).…”

“…We previously demonstrated that arterial stiffness develops within two months in mice fed HFHS 16 and that, at the molecular level, obesity-induced vascular remodeling and stiffening are associated with impaired NO bioavailability and TNFα-induced inflammatory responses in VSM, leading to functional impairment of VSM cells 17 and increased extracellular matrix remodeling 16 . VSM cell functional alterations, such as increases in VSM cell contractility and stiffness 18-20 , and extracellular matrix remodeling 35 are major contributors to aortic wall stiffening.…”

“…Aortic smooth muscle cells were isolated by enzymatic dissociation, as we previously described 17, 23 .…”