The Sodium-Glucose Cotransporter-2 Inhibitor Canagliflozin Alleviates Endothelial Dysfunction Following In Vitro Vascular Ischemia/Reperfusion Injury in Rats

In a rat model of bypass DuraGraft ameliorates endothelial dysfunction of arterial grafts

Coronary artery bypass surgery can result in endothelial dysfunction due to ischemia/reperfusion (IR) injury. Previous studies have demonstrated that DuraGraft helps maintain endothelial integrity of saphenous vein grafts during ischemic conditions. In this study, we investigated the potential of DuraGraft to mitigate endothelial dysfunction in arterial grafts after IR injury using an aortic transplantation model. Lewis rats (n = 7-9/group) were divided in three groups. Aortic arches from the control group were prepared and rings were immediately placed in organ baths, while the aortic arches of IR and IR + DuraGraft rats were preserved in saline or DuraGraft, respectively, for 1 h before being transplanted heterotopically. After 1 h after reperfusion, the grafts were explanted, rings were prepared, and mounted in organ baths. Our results demonstrated that the maximum endothelium-dependent vasorelaxation to acetylcholine was significantly impaired in the IR group compared to the control group, but DuraGraft improved it (control: 89 ± 2%; IR: 24 ± 1%; IR + DuraGraft: 48 ± 1%, p < 0.05). Immunohistochemical analysis revealed decreased intercellular adhesion molecule-1, 4-hydroxy-2-nonenal, caspase-3 and caspase-8 expression, while endothelial cell adhesion molecule-1 immunoreactivity was increased in the IR + DuraGraft grafts compared to the IR-group. DuraGraft mitigates endothelial dysfunction following IR injury in a rat bypass model. Its protective effect may be attributed, at least in part, to its ability to reduce the inflammatory response, oxidative stress, and apoptosis.

Protective Mechanisms of SGLTi in Ischemic Heart Disease

Ischemic heart disease (IHD) is a common clinical cardiovascular disease with high morbidity and mortality. Sodium glucose cotransporter protein inhibitor (SGLTi) is a novel hypoglycemic drug. To date, both clinical trials and animal experiments have shown that SGLTi play a protective role in IHD, including myocardial infarction (MI) and ischemia/reperfusion (I/R). The protective effects may be involved in mechanisms of energy metabolic conversion, anti-inflammation, anti-fibrosis, ionic homeostasis improvement, immune cell development, angiogenesis and functional regulation, gut microbiota regulation, and epicardial lipids. Thus, this review summarizes the above mechanisms and aims to provide theoretical evidence for therapeutic strategies for IHD.

Empagliflozin reduces endoplasmic reticulum stress associated TXNIP/NLRP3 activation in tunicamycin-stimulated aortic endothelial cells

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have proven to be of therapeutic significance for cardiovascular diseases beyond the treatment of type 2 diabetes. Recent studies have demonstrated the beneficial effects of SGLT2i on endothelial cell (EC) dysfunction, but the underlying cellular mechanisms remain to be clarified. In this study, we sought to understand the effect of empagliflozin (EMPA; Jardiance®) on cell homeostasis and endoplasmic reticulum (ER) stress signaling. ER stress was induced by tunicamycin (Tm) in human abdominal aortic ECs treated with EMPA over 24 h. Tm-induced ER stress caused increases in the protein expression of thioredoxin interacting protein (TXNIP), NLR-family pyrin domain-containing protein 3 (NLRP3), C/EBP homologous protein (CHOP), and in the ratio of phospho-eIF2α/eIF2α. EMPA (50-100 µM) resulted in a dampened downstream activation of ER stress as seen by the reduced expression of CHOP and TXNIP/NLRP3 in a dose-dependent manner. Nuclear factor erythroid 2-related factor 2 (nrf2) translocation was also attenuated in EMPA-treated ECs. These results suggest that EMPA improves redox signaling under ER stress which in turn attenuates the activation of TXNIP/NLRP3.

Effects of hypoxia versus ischaemia on vascular functions of isolated rat thoracic aorta: revisiting the in vitro vascular ischaemia/reperfusion model

Introduction

The in vitro rat vascular ischaemia and reperfusion model is used to evaluate the molecular and functional effects of potential agents against ischaemia and reperfusion injury of autologous graft veins. However, there is no consensus on whether hypoxia, rather than ischaemia, is sufficient to induce vascular dysfunction.

Aim

To compare the effects of hypoxia and ischaemia, with or without reperfusion, on the vascular functions of isolated thoracic aortic rings of rats.

Material and methods

Thoracic aortas of 12 male Sprague-Dawley rats (350-500 g, 18-24 months old) were isolated and divided into rings that were randomly allocated to control, ischaemia, hypoxia, ischaemia-reperfusion, and hypoxia-reperfusion groups. Aortic rings other than those of the control group were stored at 4°C for 24 h in saline. For ischaemia, saline was gassed with nitrogen. After 24 h, aortic rings in the ischaemia-reperfusion and hypoxia-reperfusion groups were incubated with 200 μM sodium hypochlorite for 30 min. Vascular and endothelial functions were tested in an organ bath set-up.

Results

Vascular response to potassium chloride (80 mM) decreased in all experimental groups compared to the control group (p = 0.007), but phenylephrine-induced contraction (10-5 M) increased only in the ischaemia-reperfusion group (p < 0.0001). Acetylcholine (10-11-10-5 M)-induced endothelium-dependent vasorelaxations were impaired in all groups - particularly in the ischaemia-reperfusion group (p = 0.0011). Sodium nitroprusside (10-12-10-7 M)-induced endothelium-independent vasorelaxations were similar across all groups (p = 0.1258).

Conclusions

Ischaemia followed by reperfusion should be implanted to achieve maximum endothelial and contractile dysfunction in vitro, and to replicate ischaemia and reperfusion injury of autologous graft veins.

Preservation solution Custodiol containing human alpha-1-antitrypsin improves graft recovery after prolonged cold ischemic storage in a rat model of heart transplantation

Introduction

The shortage of available donor hearts and the risk of ischemia/reperfusion injury restrict heart transplantation (HTX). Alpha-1-antitrypsin (AAT), a well-characterized inhibitor of neutrophil serine protease, is used in augmentation therapy to treat emphysema due to severe AAT deficiency. Evidence demonstrates its additional anti-inflammatory and tissue-protective effects. We hypothesized that adding human AAT in a preservation solution reduces graft dysfunction in a rat model of HTX following extended cold ischemic storage.

Methods

The hearts from isogenic Lewis donor rats were explanted, stored for either 1h or 5h in cold Custodiol supplemented with either vehicle (1h ischemia, n=7 or 5h ischemia, n=7 groups) or 1 mg/ml AAT (1h ischemia+AAT, n=7 or 5h ischemia+AAT, n=9 groups) before heterotopic HTX. Left-ventricular (LV) graft function was evaluated in vivo 1.5h after HTX. Immunohistochemical detection of myeloperoxydase (MPO) was performed in myocardial tissue and expression of 88 gene quantified with PCR was analyzed both statistical and with machine-learning methods.

Results

After HTX, LV systolic function (dP/dt_max 1h ischemia+AAT 4197 ± 256 vs 1h ischemia 3123 ± 110; 5h ischemia+AAT 2858 ± 154 vs 5h ischemia 1843 ± 104mmHg/s, p<0.05) and diastolic function (dP/dt_min 5h ischemia+AAT 1516 ± 68 vs 5h ischemia 1095 ± 67mmHg/s, p<0.05) at an intraventricular volume of 90µl were improved in the AAT groups compared with the corresponding vehicle groups. In addition, the rate pressure product (1h ischemia+AAT 53 ± 4 vs 1h ischemia 26 ± 1; 5h ischemia+AAT 37 ± 3 vs 5h ischemia 21 ± 1mmHg*beats/min at an intraventricular volume of 90µl; p<0.05) was increased in the AAT groups compared with the corresponding vehicle groups. Moreover, the 5h ischemia+AAT hearts exhibited a significant reduction in MPO-positive cell infiltration in comparison to the 5h ischemia group. Our computational analysis shows that ischemia+AAT network displays higher homogeneity, more positive and fewer negative gene correlations than the ischemia+placebo network.

Discussion

We provided experimental evidence that AAT protects cardiac grafts from prolonged cold ischemia during HTX in rats.

Canagliflozin attenuates thioacetamide-induced liver injury through modulation of HMGB1/RAGE/TLR4 signaling pathways

Thioacetamide (TAA), a classic liver toxic compound, is used to establish experimental models of liver injury via induction of inflammation and oxidative stress. The current study was employed to explore the effects of canagliflozin (CANA), a sodium glucose cotransporter 2 (SGLT-2) inhibitor and antidiabetic agent, on TAA-induced acute liver injury.

METHODS

A rat model of acute hepatic injury was established using single intraperitoneal injection of TAA (500 mg/kg) and rats received CANA (10 and 30 mg/kg, orally) once daily for 10 days prior to TAA challenge. Liver function, oxidative stress, and inflammatory parameters were measured in serum and hepatic tissues of rats.

RESULTS

Elevated levels of liver enzymes, hepatic malondialdehyde (MDA), and serum lactate dehydrogenase (LDH) were significantly attenuated by CANA. CANA also increased hepatic superoxide dismutase (SOD) and glutathione (GSH). Hepatic levels of high-mobility group box 1 (HMGB1), toll like receptor4 (TLR4), receptor for advanced glycation end products (RAGE), and pro-inflammatory cytokines (IL-6, and IL-1β) were normalized with CANA. Additionally, Hepatic expression of p-JNK/p-p38 MAPK was significantly attenuated by CANA compared to TAA-treated rats. CANA also decreased hepatic immunoexpression of NF-κB and TNF-α and attenuated hepatic histopathological alterations via reduction of inflammation and necrosis scores and collagen deposition. Moreover, mRNA expression levels of TNF-α and IL-6 were reduced upon CANA treatment.

CONCLUSION

CANA attenuates TAA-prompted acute liver damage, via suppressing HMGB1/RAGE/TLR4 signaling, regulation of oxidative stress and inflammation pathways.

Sodium-Glucose Cotransporter 2 Inhibitor Canagliflozin Antagonizes Salt-Sensitive Hypertension Through Modifying Transient Receptor Potential Channels 3 Mediated Vascular Calcium Handling

Background Salt-sensitive hypertension is highly prevalent and associated with cardiorenal damage. Large clinical trials have demonstrated that SGLT2 (sodium-glucose cotransporter 2) inhibitors exert hypotensive effect and cardiorenal protective benefits in patients with hypertension with and without diabetes. However, the underlying mechanism remains elusive. Methods and Results Dahl salt-sensitive rats and salt-insensitive controls were fed with 8% high-salt diet and some of them were treated with canagliflozin. The blood pressure, urinary sodium excretion, and vascular function were detected. Transient receptor potential channel 3 (TRPC3) knockout mice were used to explain the mechanism. Canagliflozin treatment significantly reduced high-salt-induced hypertension and this effect was not totally dependent on urinary sodium excretion in salt-sensitive hypertensive rats. Assay of vascular function and proteomics showed that canagliflozin significantly inhibited vascular cytoplasmic calcium increase and vasoconstriction in response to high-salt diet. High salt intake increased vascular expression of TRPC3 in salt-sensitive rats, which could be alleviated by canagliflozin treatment. Overexpression of TRPC3 mimicked salt-induced vascular cytosolic calcium increase in vitro and knockout of TRPC3 erased the antihypertensive effect of canagliflozin. Mechanistically, high-salt-induced activation of NCX1 (sodium-calcium exchanger 1) reverse mode increased cytoplasmic calcium level and vasoconstriction, which required TRPC3, and this process could be blocked by canagliflozin. Conclusions We define a previously unrecognized role of TRPC3/NCX1 mediated vascular calcium dysfunction in the development of high-salt-induced hypertension, which can be improved by canagliflozin treatment. This pathway is potentially a novel therapeutic target to antagonize salt-sensitive hypertension.

Pleiotropic effects of SGLT2 inhibitors and heart failure outcomes

Heart failure (HF) represents a major public health concern with increasing prevalence among aging populations, with multifactorial pathophysiology including inflammation, oxidative stress, endothelial dysfunction, and fibrosis, among others. Lately, the use of sodium-glucose cotransporter-2 (SGLT2) inhibitors, originally destined for the treatment of type 2 diabetes mellitus, have revolutionized the treatment of HF. In this review article, we provide the milestones and the latest mechanistic evidence of SGLT2 inhibition in HF. Owing to the results of experimental studies, several pleiotropic effects of SGLT2 inhibitors have been proposed, including the restoration of autophagy which may be significant in the reversal of the aforementioned HF pathophysiology according to a latest hypotheses. Additional mechanisms consist of the regulation of inflammatory, oxidative, and fibrotic pathways, together with the improvement of endothelial function and reduction of epicardial adipose tissue. Other than their role as antidiabetic agents, a reduction in heart failure hospitalizations has been noted following their use in clinical trials, irrespective of DM status and degree of systolic dysfunction. Upcoming randomized trials are expected to additional clinical and mechanistic evidence regarding the diverse effects of SGLT2 inhibition across the spectrum of heart failure.

Nitrotyrosine, Nitrated Lipoproteins, and Cardiovascular Dysfunction in Patients with Type 2 Diabetes: What Do We Know and What Remains to Be Explained?

Diabetes mellitus (DM) is a strong risk factor for the development of cardiovascular diseases (CVDs), which are the most important cause of morbidity and mortality in the population of patients living with DM. DM is associated with lipid metabolism disorders characterized by a decrease in the high-density lipoprotein blood concentration, an increase in the triglyceride blood concentration, and the presence of modified lipoproteins not routinely measured in clinical practice. Nitrated lipoproteins are produced by the nitration of the tyrosyl residues of apolipoproteins by myeloperoxidase. There is some evidence from the research conducted showing that nitrated lipoproteins may play a role in the development of cardiovascular dysfunction, but this issue requires further investigation. It was found that the nitration of HDL particles was associated with a decrease in caspase-3 and paraoxonase-1 activity, as well as a decrease in the activity of cholesterol transport via ABCA1, which reduces the protective effect of HDL particles on the cardiovascular system. Less information has been collected about the role of nitrated LDL particles. Thus far, much more information has been obtained on the relationship of nitrotyrosine expression with the presence of cardiovascular risk factors and the development of cardiovascular dysfunction. The purpose of this paper is to provide an extensive review of the literature and to present the most important information on the current state of knowledge on the association between nitrotyrosine and nitrated lipoproteins with dysfunction of the cardiovascular system, especially in patients living with DM. Moreover, directions for future research in this area were discussed.

Scutellarin Reduces Cerebral Ischemia Reperfusion Injury Involving in Vascular Endothelium Protection and PKG Signal

Flavonoid glycoside scutellarin (SCU) has been widely applied in the treatment of cerebral ischemic diseases in China. In this article, we conducted research on the working mechanisms of SCU in hypoxia reoxygenation (HR) injury of isolated cerebral basilar artery (BA) and erebral ischemia reperfusion (CIR) injury in rat models. In isolated rat BA rings, HR causes endothelial dysfunction (ED) and acetylcholine (ACh) induces endothelium-dependent vasodilation. The myography result showed that SCU (100 µM) was able to significantly improve the endothelium-dependent vasodilation induced by Ach. However, SCU did not affect the ACh-induced relaxation in normal BA. Further studies suggested that SCU (10-1000 µM) dose-dependently induced relaxation in isolated BA rings which were significantly blocked by the cGMP dependent protein kinase (PKG) inhibitor Rp-8-Br-cGMPs (PKGI-rp, 4 µM). Pre-incubation with SCU (500 µM) reversed the impairment of endothelium-dependent vasodilation induced by HR, but the reversing effect was blocked if PKGI-rp (4 µM) was added. The brain slice staining test in rats' model of middle cerebral artery occlusion (MCAO) induced CIR proved that the administration of SCU (45, 90 mg/kg, iv) significantly reduced the area of cerebral infarction. The Western blot assay result showed that SCU (45 mg/kg, iv) increased brain PKG activity and PKG protein level after CIR surgery. In conclusion, our findings suggested that SCU possesses the ability of protecting brain cells against CIR injury through vascular endothelium protection and PKG signal.

Graft Preservation Solution DuraGraft® Alleviates Vascular Dysfunction Following In Vitro Ischemia/Reperfusion Injury in Rats

Vascular ischemia/reperfusion injury (IRI) in patients undergoing coronary artery bypass grafting can result in graft failure and the need for repeat revascularization procedures. DuraGraft^® has been shown to protect structure and function in saphenous vein grafts against IRI. We compared the effect of DuraGraft^® to saline solution on arterial grafts submitted to IRI. Rat thoracic aortic rings were harvested and immediately mounted in organ bath chambers (control, n = 7 rats) or underwent cold ischemic preservation either in saline (IR, n = 9 rats) or DuraGraft^® (IR+Dura, n = 9 rats). Vascular function was measured ex vivo and immunohistochemistry was performed. Impaired maximum vasorelaxation (R_max) to ACh in the IR-group compared to controls was ameliorated by DuraGraft^®, indicating an improvement in endothelial function (R_max to ACh (%): IR + Dura 73 ± 2 vs. IR 48 ± 3, p < 0.05). Additionally, decreased aortic ring sensitivity to ACh (pD₂-value: -log 50% maximum response) seen after IR in the saline group was increased by DuraGraft^® (pD₂ to ACh: IR+Dura 7.1 ± 0.1 vs. IR 6.3 ± 0.2, p < 0.05). Impaired maximum contractile response to phenylephrine and high potassium chloride concentrations in the IR group compared to controls was significantly improved by DuraGraft^®. DuraGraft^® alleviates vascular dysfunction following IRI by reducing nitro-oxidative stress and the expression of ICAM-1, without leukocytes engagement.

Protection of multiple ischemic organs by controlled reperfusion

Reperfusion injury (RI) is a harmful complication that takes place during recanalization treatment of ischemic organs. Currently, there are no efficacious treatments for protecting the organs against RI. Therefore, it is necessary to discover new strategies to prevent RI. As a novel intervention technique, controlled reperfusion has promising effects on protecting multiple organs from RI, and it is done by adjusting physical parameters of blood flow or chemical compositions of the reperfusion liquid. In this brief review, the status of various controlled reperfusion methods is presented, as well as their application in the protection of ischemic organs.

Cardiovascular Benefits from Gliflozins: Effects on Endothelial Function

Type 2 diabetes mellitus (T2DM) is a known independent risk factor for atherosclerotic cardiovascular disease (CVD) and solid epidemiological evidence points to heart failure (HF) as one of the most common complications of diabetes. For this reason, it is imperative to consider the prevention of CV outcomes as an effective goal for the management of diabetic patients, as important as lowering blood glucose. Endothelial dysfunction (ED) is an early event of atherosclerosis involving adhesion molecules, chemokines, and leucocytes to enhance low-density lipoprotein oxidation, platelet activation, and vascular smooth muscle cell proliferation and migration. This abnormal vascular phenotype represents an important risk factor for the genesis of any complication of diabetes, contributing to the pathogenesis of not only macrovascular disease but also microvascular damage. Gliflozins are a novel class of anti-hyperglycemic agents used for the treatment of Type 2 diabetes mellitus (T2DM) that selectively inhibit the sodium glucose transporter 2 (SGLT2) in the kidneys and have provoked large interest in scientific community due to their cardiovascular beneficial effects, whose underlying pathophysiology is still not fully understood. This review aimed to analyze the cardiovascular protective mechanisms of SGLT2 inhibition in patients T2DM and their impact on endothelial function.