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Elevation in circulating levels of oxidized low-density lipoprotein (oxLDL) and vascular inflammation are significant risk factors for the pathogenesis of vascular diseases, such as atherosclerosis and stroke. OxLDL, via the lectin-like oxLDL receptor 1 (LOX-1), has been shown to increase inflammation and oxidative stress resulting in augmented and/or attenuated vasoreactivity responses ex vivo. However, the precise mechanistic contribution of oxLDL mediated by LOX-1 on inflammatory and oxidative stress mediators as well as vasoreactivity remains to be elucidated. We hypothesized that oxLDL via the LOX-1 receptor would increase inflammation in the vasculature which in part will contribute to altered vasoreactivity. Thoracic aortic rings (1mm) were isolated from 7-mo C57BL/6J intact male mice where endothelium intact or denuded rings were mounted in a wire myography chamber and preincubated (2h) with +/-oxLDL (50μg/dL). Cumulative force (mN) concentration-response curves to phenylephrine (PE) were generated in the continued presence of oxLDL and from these curves the EC50 was determined and used to contract rings to assess acetylcholine (ACh) dependent responses. BI-0115 (10μM; selective LOX-1 inhibitor) was used to determine LOX-1 receptor dependence. Utilizing in vitro experiments, male human aortic and brain vascular smooth cells (HAoVSMCs and HBVSMCs) were conditioned with oxLDL (12h; 50 and 25μg/dL) and then treated with BI-0115 for 6h in the continued presence of +/-oxLDL. Vascular pro-inflammatory markers, COX-2 and IL-1β, were assessed using qRT-PCR. In endothelial intact aortic rings, we observed that oxLDL increased PE-contraction and these responses were LOX-1 and endothelial dependent. Additionally, we observed that oxLDL attenuated ACh-relaxation in endothelial intact rings a LOX-1 dependent manner. Together these data suggest that oxLDL via LOX-1 elicits endothelial dysregulation which could in part contribute to augmented contractility. We next examined the role of oxLDL on VSM-derived inflammatory mediators which could be in part underlying the observed enhanced aortic ring contractile response. In HAoVSMC we observed a decrease in COX-2 mRNA following exposure to BI-0115 with low dose oxLDL. Moreover, in the HBVSMCs, we observed that oxLDL alone increased mRNA levels of COX-2 and IL-1β in a dose and LOX-1 dependent manner. Together these data suggest that oxLDL/LOX-1 increases VSM-derived inflammation and endothelial dysregulation which together contribute to increased contractility. We further conclude that LOX-1 inhibition and the resulting attenuation of VSM inflammatory mediators and altered endothelial/VSM vasoreactivity, suggests that LOX-1 may be a viable target for maintaining vessel homeostasis in cardiovascular diseases. University of Arizona Valley Research Partnership Grant VRP37 P2 (RJG), American Heart Association 19AIREA34480018 (RJG). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Endothelial integrity is critical in mitigating a vicious cascade of secondary injuries following acute ischemic stroke (AIS). Matrix metalloproteinase-9 (MMP-9), a contributor to endothelial integrity loss, is elevated during stroke and is associated with worsened stroke outcome. We investigated the FDA approved selective sphingosine-1-phosphate receptor 1 (S1PR1) ligand, ozanimod, on the regulation/activity of MMP-9 as well as endothelial barrier components (PECAM-1, claudin-5, and ZO-1) in human brain microvascular endothelial cells (HBMECs) following hypoxia plus glucose deprivation (HGD). We previously reported that S1PR1 activation improves HBMEC integrity; however, specific mechanisms underlying S1PR1 involvement in barrier integrity have not been clearly elucidated. We hypothesized that ozanimod would attenuate an HGD-induced increase in MMP-9 activity which would concomitantly attenuate the loss of integral barrier components. Male HBMECs were treated with ozanimod (0.5nM) or vehicle and exposed to 3h normoxia (21% O2) or HGD (1% O2). Immunoblotting, zymography, qRT-PCR, and immunocytochemical labeling techniques assessed processes related to MMP-9 and barrier markers. We observed that HGD acutely increased MMP-9 activity and reduced claudin-5 and PECAM-1 levels, and ozanimod attenuated these responses. In situ analysis via PROSPER, suggested that attenuation of MMP-9 activity may be a primary factor in maintaining these integral barrier proteins. We also observed that HGD increased intracellular mechanisms associated with augmented MMP-9 activation, however ozanimod had no effect on these targeted factors. Thus, we conclude that ozanimod has the potential to attenuate HGD mediated decreases in HBMEC integrity in part by decreasing MMP-9 activity as well as preserving barrier properties.Graphical Abstract

Severe traumatic brain injury results in cognitive dysfunction in part due to vascular perturbations. In contrast, the long-term vasculo-cognitive pathophysiology of mild TBI (mTBI) remains unknown. We evaluated mTBI effects on chronic cognitive and cerebrovascular function and assessed their interrelationships. Sprague-Dawley rats received midline fluid percussion injury (N=20) or sham (N=21). Cognitive function was assessed (3- and 6-month novel object recognition (NOR), novel object location (NOL) and temporal order object recognition (TOR)). 6-month cerebral blood flow (CBF) and blood volume (CBV) using contrast MRI and ex vivo pial artery endothelial and smooth muscle-dependent function were measured. mTBI rats showed impaired NOR, with similar (non-significant) trends in NOL/TOR. Regional CBF and CBV were similar in sham and mTBI. NOR correlated with CBF in lateral hippocampus, medial hippocampus and primary somatosensory barrel cortex while inversely correlating with arterial smooth muscle-dependent dilation. 6-month baseline endothelial and smooth muscle-dependent arterial function were similar among mTBI and sham, but post-angiotensin II stimulation, mTBI showed no change in smooth muscle-dependent dilation from baseline response, unlike the reduction in sham. mTBI led to chronic cognitive dysfunction and altered angiotensin II-stimulated smooth muscle-dependent vasoreactivity, a paradigm that could advance understanding of the long-term sequelae of human mild TBI.

A basic tenet of biology is that body temperature (Tb) has a marked effect on oxygen uptake of resting animals. For most animals, the temperature coefficient (Q10) is >> 2.5; e.g., resting oxygen uptake changes about 11% per degree C change in Tb. An important consequence of this dependence is that hyperthermia could be deleterious for hypoxic animals, particularly for oxygen sensitive organs, e.g., heart and brain. Conversely, a moderate degree of hypothermia could be beneficial during hypoxia. This concept is not new. Forced hypothermia is sometimes used in surgical procedures, particularly for heart and brain surgery. However, in many situations where hypothermia might have benefits, e.g., pediatric intensive care, it is not permitted. This is due in part to dogma and in part to the real and potential disadvantages of hypothermia, even in severely hypoxic animals. Among these in ventricular fibrillation. This is apparently preventable if blood pH is allowed to rise following the "Buffalo Curve." Another important disadvantage, were it to occur, is elevation of oxygen demand due to a thermogenic responses. However, at least in some species, the thermogenic response is blunted during hypoxia; e.g., in young rats. Furthermore, even if a thermogenic response occurs, this takes place primarily in muscles (shivering) and brown fat (non-shivering) and not in the O2-sensitive organs, heart and brain. A third disadvantage, for prolonged hypothermia, might be impairment of the immune response, a serious problem if hypoxia is combined with infection. This paper will review four aspects of behavioral fever and hypothermia: the occurrence among animals, the mechanisms and mediators that might trigger behavioral responses, and the functional significance.