Hypoxia plus Glucose Deprivation Increases NF-κB Activation and Downstream Pro-Inflammatory Enzyme Levels in Human Brain Vascular Smooth Muscle Cells

Vascular inflammation is a key component for cerebrovascular disease and ischemic injury is suggested to be a significant contributor, resulting in either myocardial ischemia or stroke. A strong inflammatory response is characterized by the release of inflammatory cytokines, thus producing and/or activating pro-inflammatory proteins in the cell. Our previous studies have demonstrated that hypoxia plus glucose deprivation (HGD), an in vitro model of ischemia, increases the proinflammatory mediator, cyclooxygenase-2 levels (COX-2), in vascular tissues. Nuclear factor kappa B (NF-κB) activation is an upstream transcription factor of COX-2 and had been suggested to be involved in “sterile” inflammation in experimental stroke models. Mechanisms underlying the development and progression of inflammation in the cerebrovasculature following ischemic injury in human tissue has not been addressed. Thus, the purpose of this study was to examine the impact of HGD on NF-κB expression and activation in human brain vascular smooth muscle cells (HBVSMC). In addition, we assessed pro-inflammatory mediator levels of downstream NF-κB transcription products, COX-2 and iNOS, and level of its upstream receptor, TLR4. Primary HBVSMC at passage 7 were treated with normoxia (room air) or HGD (1% O2). Following exposure to HGD (3h), cells were isolated, homogenized, and total protein content determined. Lysates, either whole cell or nuclear and cytosolic fractions, were prepped for western blot and analysis. Anti-α-smooth muscle actin was used to verify HBVSMC origin and -actin was used as a loading control. NF-κBp65, phosphorylated NF-κBp65, COX-2, and TLR4 protein levels were all measured post HGD. NF-κBp65 total protein was expressed in HBVSMC and a trend for an increase in levels following HGD was observed. Indirect activation of pNF-kBp65 was assessed via nuclear fractionation studies and was increased following HGD. Lamin AC was used to verify nuclear fractionation. Additional findings suggested that HBVSMC expressed TLR4 however, total protein levels of TLR4 were not altered by HGD. COX-2 and iNOS protein levels were also increased following HGD. In conclusion, these studies indicate that HGD alters proinflammatory enzyme levels, potentially by altering NF-κBp65 activation in human vascular smooth muscle cells. Funding Support: University of Arizona Sarver Heart Center and University of Arizona Valley Research Project Grant VRP P1 (RG).