SARS-CoV-2 binding to ACE2 triggers pericyte-mediated angiotensin-evoked cerebral capillary constriction

The SARS-CoV-2 receptor, ACE2, is found on pericytes, contractile cells enwrapping capillaries that regulate brain, heart and kidney blood flow. ACE2 converts vasoconstricting angiotensin II into vasodilating angiotensin-(1-7). In brain slices from hamster, which has an ACE2 sequence similar to human ACE2, angiotensin II alone evoked only a small capillary constriction, but evoked a large pericyte-mediated capillary constriction generated by AT1 receptors in the presence of the SARS-CoV-2 receptor binding domain (RBD). The effect of the RBD was mimicked by blocking ACE2. A mutated non-binding RBD did not potentiate constriction. A similar RBD-potentiated capillary constriction occurred in human cortical slices. This constriction reflects an RBD-induced decrease in the conversion of angiotensin II to angiotensin-(1-7). The clinically-used drug losartan inhibited the RBD-potentiated constriction. Thus AT1 receptor blockers could be protective in SARS-CoV-2 infection by reducing pericyte-mediated blood flow reductions in the brain, and perhaps the heart and kidney.

Metabolic Syndrome Alters the Cargo of Mitochondria-Related microRNAs in Swine Mesenchymal Stem Cell-Derived Extracellular Vesicles, Impairing Their Capacity to Repair the Stenotic Kidney

Background. Coexisting metabolic syndrome (MetS) and renal artery stenosis (RAS) are linked to poor renal outcomes. Mesenchymal stem/stromal cell- (MSC-) derived extracellular vesicles (EVs) from lean animals show superior ability to repair the experimental MetS+RAS kidney compared to EVs from MetS pig MSCs. We hypothesized that MetS leads to selective packaging in porcine EVs of microRNAs capable of targeting mitochondrial genes, interfering with their capacity to repair the MetS+RAS kidney. Methods. Five groups of pigs ( n = 7 each) were studied after 16 weeks of diet-induced MetS and RAS (MetS+RAS) and MetS+RAS 4 weeks after a single intrarenal delivery of EVs harvested from allogeneic adipose tissue-derived MSCs isolated from Lean or MetS pigs, and Lean or MetS sham controls. Single-kidney blood flow (RBF) and glomerular filtration rate (GFR) were assessed in vivo with multidetector CT, whereas EV microRNA cargo, renal tubular mitochondrial structure and bioenergetics, and renal injury pathways were assessed ex vivo. Results. microRNA sequencing revealed 19 dysregulated microRNAs capable of targeting several mitochondrial genes in MetS-EVs versus Lean-EVs. Lean- and MetS-EVs were detected in the stenotic kidney 4 weeks after administration. However, only MetS-EVs failed to improve renal mitochondrial density, structure, and function or attenuate oxidative stress, tubular injury, and fibrosis. Furthermore, Lean-EVs but not MetS-EVs restored RBF and GFR in MetS+RAS. Conclusion. MetS alters the cargo of mitochondria-related microRNAs in swine MSC-derived EVs, which might impair their capacity to repair the poststenotic kidney in MetS+RAS. These observations may contribute to develop approaches to improve the efficacy of MSC-EVs for patients with MetS.

Abstract 278: A Novel Resuscitative Agent, Centhaquine (Lyfaquin®), has the Potential to Treat Acute Kidney Injury Following Hemorrhagic Shock

Introduction: Centhaquine (CQ) is being developed as a first-in-class resuscitative agent to treat hemorrhagic shock. Its safety, tolerability and efficacy have been demonstrated through pre-clinical studies and phase I, II and III clinical trials (NCT02408731, NCT04056065 and NCT04045327). Shock is often complicated with acute kidney injury (AKI). Hypothesis: CQ will increase renal blood flow (RBF) and attenuate hypoxia related damage after hemorrhagic shock. We investigated whether CQ improves RBF and provides protection after hemorrhagic shock. Methods: Rats were anesthetized, and carotid artery, femoral artery and femoral vein were catheterized. Renal arteries were clamped, hemorrhage was induced and mean arterial pressure (MAP) was maintained between 35-40 mmHg for 30 min. After 20 min of hemorrhage, renal arteries were de-clamped and hemorrhage continued for 10 more min. Resuscitation was performed with either normal saline (NS) or CQ (0.02 mg/kg) infusion for 10 min. MAP, heart rate and RBF were monitored for 120 min after which rats were sacrificed, kidneys were collected and analyzed with western blots and immunofluorescence. Results: Resuscitation with CQ produced a significant improvement in RBF (at 30 min 257.03±21.2 vs 199.81±42.32, p=0.002 sustained till 120 min 211.76±27.47 vs 148.24±42.39, p=0.002 of infusion) compared to NS. A non-significant increase in MAP was observed in CQ compared to NS. Western blots showed significantly higher expression HIF1-A (1.13±0.19 vs 0.86±0.16) and lower expression of early kidney damage marker, NGAL (0.35±0.16 vs 0.82±0.31) in CQ vs NS. Immunofluorescence showed significantly higher expression of HIF1-A and lower expression of Bax in cortex (HIF1-A 11.19±0.31 vs 8.43±0.39, p=0.03689, Bax 18.09±0.47 vs 24.80±2.01, p=0.0010) of CQ than NS and similar change was observed in medulla. Expression of PHD3 and Cytochrome C was higher in the cortex (PHD3 5.38±0.38 vs 4.05±0.12, p=0.0348, Cytochrome C 24.95±0.65 vs 29.24±1.87, p=0.01429) of CQ than NS. HIF1-B expression was similar in CQ and NS groups. Conclusions: CQ (Lyfaquin®) is a frontline resuscitative agent with a potential to treat hemorrhagic shock related AKI by improving kidney blood flow and decreasing hypoxia related tissue damage.

Chlorogenic acid alleviates sepsis-induced endothelial barrier dysfunction and the underlying mechanism

Background Chlorogenic acid (CGA) has been shown to improve inflammatory cytokines in patients with ulcerative colitis. Vascular endothelial barrier dysfunction is closely related to sepsis. We hypothesize that CGA plays an important role in treating sepsis by protecting the mesenteric endothelial barrier. Methods Severe sepsis was established by cecal ligation and puncture (CLP) in SD rats. Immediately after the induction of sepsis, CGA (20 mg/kg) was administered intravenously, and the effects of CGA on mesenteric vascular leakage, hemodynamics, liver and kidney blood flow, and the ultrastructure of the mesenteric endothelial cells were determined. The transendothelial electrical resistance and the Transwell permeability assays were used for observing endothelial barrier function in vascular endothelial cells (VECs). ZO-1 and VE-cadherin expression were observed by immunohistochemistry and western blotting. Results FITC-BSA leakage from mesenteric micro-vessels was significantly increased after septic shock, which was significantly improved by CGA. Liver and kidney blood flow were increased by 41.2% and 38.4%, respectively, after CGA administration compared with the septic shock group. Hemodynamic status was significantly decreased after septic shock, and significantly improved by CGA. The 72-h survival rate of septic shock rats in the CGA group (50%) was significantly higher than the septic shock group (6.25%). CGA improved the tight junction opening after septic shock and also significantly up-regulated the expression of ZO-1 and VE-cadherin. CGA also protected endothelial hyperpermeability against lipopolysaccharide-stimulated VEC injury by increasing the expression of ZO-1 and VE-cadherin in vitro. Conclusion CGA was beneficial for endothelial barrier function in rats with septic shock, which is the major contribution to CGA with respecting to improving hemodynamic status and organ perfusion. The underlying mechanism involved CGA up-regulation of ZO-1 and VE-cadherin.