Regulation Of Endothelial Homeostasis Research Articles

Abstract P278: Coronary Microvascular Dysfunction Is Associated With Augumented Autophagy-lysosomal Signaling In Mice With Hypercholesterolemic Diet

Accumulating evidence indicates coronary microvascular dysfunction (CMD) contributes to myocardial ischemia with or without epicardial coronary atherosclerosis. However, it remains unknown which molecular pathway is associated with compromised coronary microvascular function preceding the development of myocardial ischemic injury. Recent studies suggest that autophagy-lysosomal signaling pathway is involved in the regulation of endothelial homeostasis under various metabolic stresses such as hypercholesterolemia. In this study, the early effects of hypercholesterolemia on the function and integrity of coronary microcirculation were studied in mice and the expressions of various molecular markers of autophagy-lysosome pathway were also determined in the coronary circulation. Mice were fed a hypercholesterolemic paigen diet (PD) for 8 weeks and coronary microvascular function was determined by measuring coronary flow reserve (CFR) under baseline and hyperemic conditions. The effects of PD on cardiac function or remodeling were also assessed by echocardiograph or immunohistochemistry studies. In PD-fed hypercholesterolemic mice, hyperemia-induced increase in CFR was significantly abrogated compared to that in normal chow diet-fed (ND) control mice (PD: 1.583±0.4193 vs. ND: 3.087±0.586) (n=7-8). The diet-induced hypercholesterolemia did not lead to cardiac dysfunction (EF%, PD: 59.870±7.549 vs ND: 64.040±9.088) or hypertrophic remodeling (LV mass (mg), PD: 92.240±14.410 vs ND: 96.030±25.07). PD increased mild cardiac inflammation and fibrosis but did not resulted in rarefaction in the myocardium. In small coronary arterial wall, PD induced endothelial inflammasome activation and inflammation, which was accompanied by upregulation of autophagy and lysosome signaling pathway. In conclusion, hypercholesterolemic diet induces CMD without alterations in cardiac function or remodeling. These alterations in coronary microvascular function represent the early effects of diet-induced hypercholesterolemia, which may be ameliorated with activation of autophagy and lysosome signaling pathways.

Abstract P275: Deletion Of Endothelial Leptin Receptor Elevates Blood Pressure And Impairs Endothelial-dependent Relaxation Via Upregulation Of Endothelial Glycolytic Enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3)

The adipokine leptin plays a crucial role in blood pressure (BP) regulation notably by exerting pressor effects centrally via sympatho-activation and depressor effects via direct activation of its receptor (LepR) peripherally resulting in nitric oxide (NO)-mediated vasodilation. However, the predominant effects and cell type responsible for leptin-mediated NO production is not clearly understood. Herein, we examined the effect of selective deletion of LepR in endothelial cells (LepR EC-/- , KO) on BP and vascular function. BP recording via radiotelemetry in male KO and WT (LepR EC+/+ ) mice revealed significant increases in diastolic and mean arterial pressure in KO mice (DBP, WT: 90.2±2.1 vs. KO: 100.1±3.6; MAP, WT: 105.7±2.1 vs. KO: 113.7±2.6 mmHg, n=5, p<0.05). There was no difference in Systolic blood pressure or heart rate between KO and WT. Leptin infusion (0.9mg/kg/day,7 days) elicits a significant increase in BP of WT but not KO mice (DBP, WT: 89.2± 2.6 vs WT+Leptin 95.7±3.3; MAP, WT: 104 ±2.8 vs WT+Leptin: 110 ±2.7, n=5, p<0.05). We quantified sympathetic contribution to BP elevation by measuring BP response to glanglionic blockade (Hexamethonium). At baseline, KO mice exhibited a lower BP response than WT supporting a reduced neurogenic control of BP regulation in KO mice. Vascular contribution to high BP was investigated using wire myography in thoracic aorta. LepR deficiency impaired endothelial-dependent relaxation (EDR) to acetylcholine (n=7, p<0.05). L-NAME completely abolished EDR in KO and WT indicating that EC LepR deficiency reduced NO bioavailability. Recent evidence presents PFKFB3-mediated EC glycolysis as a new regulator of endothelial homeostasis. We found that aortic EC from KO exhibited increased PFKFB3 mRNA expression (p=0.065) and PFKFB3 inhibition restored EDR in KO. Remarkably, overexpression of PFKFB3 increased EC glycolysis in vitro and impaired EDR in WT aortic rings ex vivo . Collectively, our data suggest that impaired endothelial leptin receptor signaling induces a PFKFB3-dependent hyper-glycolytic phenotype resulting in NO deficiency and endothelial dysfunction that predisposes to higher BP regardless the reduced sympatho-activation which might prevent the increase in BP induced by exogenous leptin.

ETS-Related Gene Expression in Healthy Femoral Arteries With Focal Calcifications.

Bone development-related genes are enriched in healthy femoral arteries, which are more prone to calcification, as documented by the predominance of fibrocalcific plaques at the femoral location. We undertook a prospective histological study on the presence of calcifications in normal femoral arteries collected from donors. Since endothelial-to-mesenchymal transition (EndMT) participates in vascular remodeling, immunohistochemical (IHC) and molecular markers of EndMT and chondro-osteogenic differentiation were assessed. Transmission electron microscopy (TEM) was used to describe calcification at its inception. Two hundred and fourteen femoral arteries were enrolled. The mean age of the donors was 39.9 ± 12.9 years; male gender prevailed (M: 128). Histology showed a normal architecture; calcifications were found in 52 (24.3%) cases, without correlations with cardiovascular risk factors. Calcifications were seen on or just beneath the inner elastic lamina (IEL). At IHC, SLUG was increasingly expressed in the wall of focally calcified femoral arteries (FCFA). ETS-related gene (ERG), SLUG, CD44, and SOX-9 were positive in calcifications. RT-PCR showed increased levels of BPM-2, RUNX-2, alkaline phosphatase, and osteocalcin osteogenic transcripts and increased expression of the chondrogenic marker, SOX-9, in FCFA. TEM documented osteoblast-like cells adjacent to the IEL, releasing calcifying vesicles from the cell membrane. The vesicles were embedded in a proteoglycan-rich matrix and were entrapped in IEL fenestrations. In this study, ERG- and CD44-positive cell populations were found in the context of increased SLUG expression, thus supporting the participation of EndMT in FCFA; the increased transcript expression of osteochondrogenic markers, particularly SOX-9, reinforced the view that EndMT, osteochondrogenesis, and neoangiogenesis interact in the process of arterial calcification. Given its role as a transcription factor in the regulation of endothelial homeostasis, arterial ERG expression can be a clue of endothelial dysregulation and changes in IEL organization which can ultimately hinder calcifying vesicle diffusion through the IEL fenestrae. These results may have a broader implication for understanding arterial calcification within a disease context.

Endothelial Foxp1 Suppresses Atherosclerosis via Modulation of Nlrp3 Inflammasome Activation

Endothelial dysfunction results in sustained and chronic vascular inflammation, which is central to atherosclerotic diseases. However, transcriptional regulation of vascular endothelial inflammation has not been well clarified. This study aims to explore Foxp (forkhead box P) transcription factor 1 in regulation of endothelial homeostasis, atherogenesis, and its mechanisms. To assess the importance of Foxp1 in atherosclerosis, Foxp1 expression was analyzed in human coronary artery and mouse artery, and we observed significant downregulation of Foxp1 in atherosclerotic and atherosusceptible endothelium. Endothelial-specific Foxp1 knockout mice (Foxp1ECKO) were bred onto ApoeKO mice to generate endothelial Foxp1-deletion hyperlipidemic model Foxp1ECKO;ApoeKO, which displayed significant increases in atherosclerotic lesion formation in aortas and aortic roots with enhanced monocyte adhesion, migration, and infiltration into the vascular wall and formation of inflammatory lipid-laden macrophages. In contrast, endothelial-specific Foxp1 overexpression mice Foxp1ECTg;ApoeKO exhibited reduced atherosclerotic lesion formation with less monocyte infiltration. Foxp1 was further identified as a gatekeeper of vessel inflammation by direct regulation of endothelial inflammasome components, including Nlrp3 (NLR [nucleotide-binding and leucine-rich repeat immune receptors] family pyrin domain containing 3), caspase-1, and IL (interleukin)-1β. Moreover, endothelial Foxp1 was found to be regulated by Klf2 (Kruppel-like factor 2). Oscillatory shear stress downregulated Foxp1 expression via repressing Klf2 expression in endothelium, and, therefore, promoted endothelial inflammasome activation, leading to atherosclerotic lesion formation. Simvastatin upregulated the reduced expression of Klf2 and Foxp1 in atherosusceptible vascular endothelium and alleviated vascular inflammation contributing to its inhibitory effect in atherosclerosis. These data are the first in vivo experimental validation of an atheroprotective role of endothelial Klf2 and Foxp1, which reveals a Klf2-Foxp1 transcriptional network in endothelial cells as a novel regulator of endothelial inflammasome activation for atherogenesis, therefore, provides opportunities for therapeutic intervention of atherosclerotic diseases and uncovers a novel atheroprotective mechanism for simvastatin.

Astragaloside IV and cycloastragenol are equally effective in inhibition of endoplasmic reticulum stress-associated TXNIP/NLRP3 inflammasome activation in the endothelium

Ethnopharmacological relevanceAstragaloside IV and cycloastragenol are present together in Astragalus membranaceus Moench (Fabaceae) and this study aims to simultaneously investigate their regulation of endothelial homeostasis in the setting of endoplasmic reticulum stress (ER stress). Material and methodsWe stimulated endothelial cells with palmitate (PA 100μM) to evoked ROS-associated ER stress and observed the effects of astragaloside IV and cycloastragenol on thioredoxin-interacting protein (TXNIP) expression, NLRP3 inflammasome activation and mitochondrion-dependent apoptosis. ResultsAstragaloside IV and cycloastragenol inhibited ROS generation and attenuated ER stress inducer IRE1α phosphorylation, indicating the inhibition of ROS-associated ER stress. In response to ER stress, TXNIP expression increased, accompanied with NLRP3 induction and increased IL-1β and IL-6 production, but these alternations were reversed by treatment with astragaloside IV and cycloastragenol, demonstrating the inhibitory effects of astragaloside IV and cycloastragenol on TXNIP/NLRP3 inflammasome activation. Inflammasome activation led to mitochondrial cell death in endothelial cells, whereas astragaloside IV and cycloastragenol restored the loss of the mitochondrial membrane potential with inhibition of caspase-3 activity, and thereby protected cells from ER stress-induced apoptosis. Astragaloside IV and cycloastragenol enhanced AMPK phosphorylation and AMPK inhibitor compound C diminished their beneficial effects, indicative of the potential role of AMPK in their regulation. ConclusionsAstragaloside IV and cycloastragenol suppressed ROS-associated ER stress and then inhibited TXNIP/NLRP3 inflammasome activation with regulation of AMPK activity, and thereby ameliorated endothelial dysfunction by inhibiting inflammation and reducing cell apoptosis. Simultaneous investigations further showed that astragaloside IV and cycloastragenol were equally effective in regulation of endothelial homeostasis.

Mangiferin inhibits endoplasmic reticulum stress-associated thioredoxin-interacting protein/NLRP3 inflammasome activation with regulation of AMPK in endothelial cells

BackgroundEndothelial dysfunction is tightly associated with cardiovascular complications in diabetic patients. This study aims to investigate the effects of mangiferin on the regulation of endothelial homeostasis under endoplasmic reticulum stress (ER stress) conditions. ResultsHigh glucose (25mmol/L) exposure induced ER stress and promoted ROS production in endothelial cells. Mangiferin effectively inhibited ER stress-associated oxidative stress by attenuating IRE1α phosphorylation and reducing ROS production. In response to ER stress, thioredoxin-interacting protein (TXNIP) expression increased, followed by NLRP3 inflammasome activation and increased IL-1β secretion. Mangiferin treatment attenuated the expressions of TXNIP and NLRP3 and reduced IL-1β and IL-6 production, demonstrating its inhibitory effects on TXNIP/NLRP3 inflammasome activation. NLRP3 inflammasome activation is responsible for mitochondrial cell death. Mangiferin restored the loss of the mitochondrial membrane potential (Δψm) and inhibited caspase-3 activity, and thereby protected cells from high glucose-induced apoptosis. Moreover, mangiferin inhibited ET-1 secretion and restored the loss of NO production when cells were exposed to high glucose. Mangiferin enhanced AMPK phosphorylation and AMPK inhibitor compound C diminished its beneficial effects, indicating the potential role of AMPK in its action. ConclusionOur work showed the beneficial effects of mangiferin on the improvement of endothelial homeostasis and elucidated the molecular pathway through which mangiferin ameliorated endothelial dysfunction by inhibition of ER stress-associated TXNIP/NLRP3 inflammasome activation in endothelial cells. SignificanceThese findings demonstrated the beneficial effects of mangiferin on the regulation of endothelial homeostasis and indicated its potential application in the management of diabetic cardiovascular complications.

Angiopoietin-1 is associated with cerebral vasospasm and delayed cerebral ischemia in subarachnoid hemorrhage

BackgroundAngiopoietin-1 (Ang-1) and -2 (Ang-2) are keyplayers in the regulation of endothelial homeostasis and vascular proliferation. Angiopoietins may play an important role in the pathophysiology of cerebral vasospasm (CVS). Ang-1 and Ang-2 have not been investigated in this regard so far.Methods20 patients with subarachnoid hemorrhage (SAH) and 20 healthy controls (HC) were included in this prospective study. Blood samples were collected from days 1 to 7 and every other day thereafter. Ang-1 and Ang-2 were measured in serum samples using commercially available enzyme-linked immunosorbent assay. Transcranial Doppler sonography was performed to monitor the occurrence of cerebral vasospasm.ResultsSAH patients showed a significant drop of Ang-1 levels on day 2 and 3 post SAH compared to baseline and HC. Patients, who developed Doppler sonographic CVS, showed significantly lower levels of Ang-1 with a sustained decrease in contrast to patients without Doppler sonographic CVS, whose Ang-1 levels recovered in the later course of the disease. In patients developing cerebral ischemia attributable to vasospasm significantly lower Ang-1 levels have already been observed on the day of admission. Differences of Ang-2 between SAH patients and HC or patients with and without Doppler sonographic CVS were not statistically significant.ConclusionsAng-1, but not Ang-2, is significantly altered in patients suffering from SAH and especially in those experiencing CVS and cerebral ischemia. The loss of vascular integrity, regulated by Ang-1, might be in part responsible for the development of cerebral vasospasm and subsequent cerebral ischemia.