Glycine-nitronyl nitroxide conjugate protects human umbilical vein endothelial cells against hypoxia/reoxygenation injury via multiple mechanisms and ameliorates hind limb ischemia/reperfusion injury in rats

HuMSC-EVs Protect Endothelial Cells Against Hypoxia/Reoxygenation Injury by Inhibiting the Pannexin 1/p38-MAPK Pathway

Vascular endothelial cell dysfunction plays an important role in myocardial ischemia-reperfusion (I/R) injury, and pannexin 1 (Panx1), an ATP-permeable channel, is closely associated with the pathophysiological processes of I/R injury. The purpose of this study was to investigate the protective effects of human umbilical cord mesenchymal stromal cell-derived extracellular vesicles (HuMSC-EVs) and the underlying mechanism in a model of I/R injury. For the cellular model of I/R injury, human umbilical vein endothelial cells (HuVECs) were exposed to hypoxia/reoxygenation (H/R) conditions. The model cells were then treated with HuMSC-EVs, and the effects on cell survival and specific signaling activities were observed. The results showed that after H/R exposure, Panx1 expression and other markers of cellular damage were increased in HuVECs. However, treatment with HuMSC-EVs inhibited the H/R-induced increase in Panx1 expression and improved HuVEC survival. Mechanistically, HuMSC-EVs were found to inhibit the p38 mitogen-activated protein kinase (MAPK)-dependent apoptosis pathway, as evidenced by increased Bcl2 expression and reductions in p38 MAPK phosphorylation, Bax expression, and cleaved-caspase 3 expression. Together our data suggest that HuMSC-EVs alleviate H/R-induced apoptosis among HuVECs by inhibiting activity of the Panx1/p38-MAPK-dependent apoptosis pathway.

Pro-angiogenic Terbium Hydroxide Nanorods Improve Critical Limb Ischemia in Part by Amelioration of Ischemia-Induced Endothelial Injury

Critical limb ischemia (CLI) refers to a severe condition resulting from gradual obstruction in the supply of blood, oxygen, and nutrients to the limbs. The most promising clinical solution to CLI is therapeutic angiogenesis. This study explored the potency of pro-angiogenic terbium hydroxide nanorods (THNR) for treatment of CLI, with a major focus on their impact on ischemia-induced maladaptive alterations in endothelial cells as well as on vascularization in ischemic limbs. This study demonstrated that, in hypoxia-exposed endothelial cells, THNR improve survival and promote proliferation, migration, restoration of nitric oxide production, and regulation of vascular permeability. Based on molecular studies, these attributes of THNR can be traced to the stimulation of PI3K/AKT/eNOS signaling pathways. Besides, Wnt/GSK-3β/β-catenin signaling pathways may also play a role in the therapeutic actions of THNR. Furthermore, in the murine model of CLI, THNR administration can integrally re-establish blood perfusion with concomitant reduction of muscle damage and inflammation. Additionally, improvement of locomotor activities and motor coordination in ischemic limbs in THNR treated mice is also evident. Overall, the study demonstrates that THNR have the potential to be developed as an efficacious and cost-effective alternative clinical therapy for CLI, using a nanomedicine approach.

Molecular Insight into Acute Limb Ischemia

Acute limb ischemia (ALI) is defined as a sudden reduction in blood flow to a limb, resulting in cessation of blood flow and, therefore, cessation of the delivery of nutrients and oxygen to the tissues of the lower limb. Despite optimal treatment to restore blood flow to ischemic tissues, some patients may suffer from ischemia/reperfusion (I/R) syndrome, the most severe complication after a revascularization procedure used to restore blood flow. There are multiple molecular and cellular factors that are involved in each phase of ALI. This review focuses firstly on molecular and cellular factors of arterial thrombosis, highlighting the role of atherosclerotic plaques, smooth muscle cells (SMCs), and cytokine which may alter key components of the extracellular matrix (ECM). Then, molecular and cellular factors of arterial embolism will be discussed, highlighting the importance of thrombi composition. Molecular and cellular factors of ischemia/reperfusion syndrome are analyzed in depth, highlighting several important mechanisms related to tissue damage, such as inflammation, apoptosis, autophagy, necrosis, and necroptosis. Furthermore, local and general complications of ALI are discussed in the context of molecular alterations. Ultimately, the role of novel biomarkers and targeted therapies is discussed.

Mechanisms and Interventions on Acute Lower Limb Ischemia/Reperfusion Injury: A Review and Insights from Cell to Clinical Investigations

AIM

This review aims to highlight mechanistic insights on skeletal muscle ischemia/reperfusion injury (IRI), a potentially life-threatening complication after acute lower limb ischemia. Lower limb IRI produces a wide spectrum of manifestations, ranging from local skeletal muscle necrosis to multi-organ failure. There is increasing evidence from both in vitro and in vivo reports to demonstrate several promising interventions that have successfully reduced IRI in skeletal muscle ischemic models. However, clinical studies to confirm their benefits are still lacking.

METHOD

We conducted a comprehensive search of English literature listed in the PubMed database (All related published articles shown in PubMed until September 2020 have been included in this review), using the following keywords: acute limb ischemia, acute arterial occlusion, compartment syndrome, ischemic reperfusion injury, revascularization and hypoxic reoxygenation.

RESULT

58 articles pertinent to acute limb ischemia models were identified. The underlying mechanisms associated with IRI in skeletal muscle are due to excessive mitochondrial production of reactive oxygen species (ROS), cellular apoptosis and activation of inflammatory cascades. Several therapeutic interventions including both pharmacological and non-pharmacological treatments have been investigated and some showed promising results. These interventions include antioxidation, anti-inflammation, anti-hypertension, controlled-reperfusion and ischemic preconditioning. Further clinical studies are needed to warrant their use in a clinical setting for lower limb IRI treatment.

CONCLUSION

This review comprehensively summarizes the mechanisms underlying IRI in lower limb ischemia. The reports currently available regarding the potential therapeutic interventions against lower limb IRI from in vitro, in vivo and clinical studies are presented and discussed. These findings may provide mechanistic insights for devising the strategies to improve the clinical outcomes in IRI patients in the near future. Further clinical studies are needed to warrant their use in a clinical setting for lower limb IRI treatment.

Design, synthesis and biological evaluation of novel nitric oxide donors with antioxidative activity

Reactive oxygen species (ROS) are the primary cause of organic nitrate drug tolerance and endothelial dysfunction. In order to scavenge the ROS and maintain the therapeutic effect of nitrates, we designed and synthesized ten new types of dual-acting nitrate molecules by combining NIT-type nitroxides and 5-ISMN. These included two types of novel epimeric nitroxide-nitrate conjugates (15(S) and 15(R)), which had pharmacophore connections. We also synthesized 8 NIT radicals without 5-ISMN in order to compare the activities of these novel nitric oxide donors. Several dual-acting nitroxide-based nitrate conjugates showed the ability to release NO and cause anti-oxidant effects in human umbilical vein endothelial cells. Among these conjugates, 15(S) showed the most prominent pro-vasodilative effect. In angiotensin II infusion-induced hypertensive mice, 15(S) treatment for 4 weeks decreased both the systolic and diastolic blood pressures and ameliorated the vascular endothelial and smooth muscle functions of isolated thoracic aortas. In addition, the vascular structure of the mice was restored and their vascular oxidative stress was decreased. The results suggest that these novel nitric oxide donors can be used as potential drugs in the treatment of vascular diseases. Therefore, the strategy of using a combination of antioxidants and NO-donors can be a promising way to develop novel organic nitrate drugs for future use in combating disease.

Protective Role of Sulodexide on Renal Injury Induced by Limb Ischemia-Reperfusion

Background

Though widely known as a potent antithrombin agent with protective effects on the kidney and other remote organs, it is currently ambiguous when it comes to sulodexide's function on ischemia-reperfusion (I/R) injury. With this research, we pursued to further explore how sulodexide exerts its influence on limb I/R injury, in which deleterious effects on the kidney were what we primarily focused on.

Methods

We randomized twenty-four C57BL/6 male rats into three groups, namely, sham operation group (control group), I/R group, and sulodexide pretreatment group. Hematoxylin and eosin staining was applied for discovery of renal histological changes. Serum creatinine (Cr) and serum urea nitrogen (BUN) were measured. Apoptotic parameters were detected by the TdT-mediated dUTP Nick-End Labeling method. To what extent and levels that antiapoptotic and proapoptotic proteins were expressed could be sensitively revealed by immunohistochemistry assay. Lipid peroxidation product propylene glycol and inflammatory factors were examined by enzyme-linked immunosorbent assay. Additionally, an extracorporeal hypoxia-reoxygenation (H/R) model of human renal proximal tubule epithelial HK2 cells was established. Our targets lay in cell proliferation and apoptosis, and we used western blotting to reflect apoptosis-related gene expression.

Results

The levels of serum BUN, Cr, and inflammatory factors in sulodexide-intervened rats manifested significant reduction when compared with the I/R group. Also, sulodexide could protect the kidney from histological changes and could effectively inhibit intraparenchymal apoptosis. Furthermore, adding 2 μl/mL or 5 μl/mL of sulodexide to H/R model cells in vitro gave rise to significant restoration of the degenerative proliferation capacity of the HK2 cells following H/R injury and late cellular apoptosis experienced dramatic reduction versus the H/R group. When treated with 5 μl/mL of sulodexide at a dose of 10 mg/kg, the levels of the antiapoptotic proteins were increased, while the proapoptotic proteins showed opposite trends. Notable escalation on antiapoptotic protein expression level, in contrast with the opposite trends exhibited in proapoptotic proteins, was observed with 5 μl/mL sulodexide pretreatment with the dosage being 10 mg/kg.

Conclusion

Sulodexide can protect against kidney damage caused by I/R injury of the lower limbs by enhancing cell proliferation, inhibiting apoptosis, reducing inflammatory reactions, and scavenging oxygen free radicals.

Protective effect of nitronyl nitroxide against hypoxia-induced damage in PC12 cells

Hypoxia induces cellular oxidative stress that is associated with neurodegenerative diseases. HPN (4'-hydroxyl-2-substituted phenyl nitronyl nitroxide), a stable nitronyl nitroxide, has excellent free radical scavenging properties. The purpose of this study was to investigate the protective effects of HPN on hypoxia-induced damage in PC12 cells. It was shown that HPN significantly attenuated hypoxia-induced loss of cell viability, release of lactate dehydrogenase (LDH), and morphological changes in PC12 cells. Moreover, hypoxic PC12 cells had increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), and expression of HIF-1α and VEGF, but had reduced levels of superoxide dismutase (SOD) and catalase (CAT), and HPN reversed these changes. HPN also inhibited hypoxia-induced cell apoptosis via suppressing the expression of Bax, cytochrome c, and caspase-3, and inducing the expression of Bcl-2. These results indicate that the protective effects of HPN on hypoxia-induced damage in PC12 cells is associated with the suppression of hypoxia-induced oxidative stress and cell apoptosis. HPN could be a promising candidate for the development of a novel neuroprotective agent.

Liraglutide Increases VEGF Expression via CNPY2-PERK Pathway Induced by Hypoxia/Reoxygenation Injury

Liraglutide (Lir) is a glucagon-like peptide-1 receptor agonist that lowers blood sugar and reduces myocardial infarct size by improving endothelial cell function. However, its mechanism has not yet been clarified. Unfolded protein response (UPR) plays an important role in the pathogenesis of myocardial ischemia-reperfusion injury. It determines the survival of cells. Endoplasmic reticulum position protein homologue 2 (CNPY2) is a novel initiator of UPR that also participates in angiogenesis. To this extent, the current study further explored whether Lir regulates angiogenesis through CNPY2. In our article, a hypoxia/reoxygenation (H/R) injury model of human umbilical vein endothelial cells (HUVECs) was established and the effect of Lir on HUVECs was first evaluated by the Cell Counting Kit-8. Endothelial tube formation was used to analyze the ability of Lir to induce angiogenesis. Subsequently, the effect of Lir on the concentrations of hypoxia-inducible factor 1α (HIF1α), vascular endothelial growth factor (VEGF), and CNPY2 was detected by enzyme-linked immunosorbent assay. To assess whether Lir regulates angiogenesis through the CNPY2-initiated UPR pathway, the expression of UPR-related pathway proteins (CNPY2, GRP78, PERK, and ATF4) and angiogenic proteins (HIF1α and VEGF) was detected by reverse transcription-polymerase chain reaction and Western blot. The results confirmed that Lir significantly increased the expression of HIF1α and VEGF as well as the expression of CNPY2-PERK pathway proteins in HUVECs after H/R injury. To further validate the experimental results, we introduced the PERK inhibitor GSK2606414. GSK2606414 was able to significantly decrease both the mRNA and protein expression of ATF4, HIF1α, and VEGF in vascular endothelial cells after H/R injury. The effect of Lir was also inhibited using GSK2606414. Therefore, our study suggested that the CNPY2-PERK pathway was involved in the mechanism of VEGF expression after H/R injury in HUVECs. Lir increased the expression of VEGF through the CNPY2-PERK pathway, which may promote endothelial cell angiogenesis and protect HUVEC from H/R damage.

Protective effects of two novel nitronyl nitroxide radicals on heart failure induced by hypobaric hypoxia

AIMS

Hypobaric hypoxia (HH), linked to oxidative stress, impairs cardiac function. We synthesized a novel nitronyl nitroxide radical, an HPN derivative (HEPN) and investigated the protective effects of HEPN and HPN against HH-induced heart injury in mice and the underlying mechanisms of action.

MAIN METHODS

Mice were administered with HPN (200 mg/kg) or HEPN (200 mg/kg) 30 min before exposed to HH. The cardiac function was measured. Serum AST, CK, LDH and cTnI were estimated. Heart tissue oxidase activity, SOD, CAT, GSH-Px, ROS and MDA were estimated. ATP content, Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase activity was measured. The expression of HIF-1, VEGF, Nrf2, HO-1, Bax, Bcl-2, Caspase-3 was estimated.

KEY FINDINGS

Results showed that pretreatment with HEPN or HPN led to a dramatic decrease in the activity of biochemical markers AST, CK, LDH and cTnI in murine serum. They increased the activity of SOD, CAT and GSH-Px and reduced the level of ROS and MDA in the hearts of mice. HEPN and HPN could increase the expression of Nrf2 and OH-1. They could maintain the ATPase activity. The Bax and Caspase-3 expression as well as the ratio of Bax/Bcl-2 were significantly downregulated and the Bcl-2 expression was upregulated by HPN or HEPN compared to the HH group. They may attenuate the HH-induced oxidant stress via free radical scavenging activity.

SIGNIFICANCE

The present study showed that the nitronyl nitroxide radical HEPN and HPN may be potential therapeutic agents for treatment of HH-induced cardiac dysfunction.

Hypoxia-Protective Azaphilone Adducts from Peyronellaea glomerata

Peyronellones A and B (1 and 2), a pair of rare tetracyclic caged adducts of azaphilone with pyruvic acid, along with four new analogues (3-6), were isolated from solid cultures of the endophytic fungus Peyronellaea glomerata. Their structures were elucidated through spectroscopic analysis, and their absolute configurations were unambiguously determined by a combination of single-crystal X-ray crystallography, Rh₂(OCOCF₃)₄-induced ECD experiments, ECD calculations, and modified Mosher methods. Compound 2 (5 μM) was found to have a significant hypoxia-protective effect that improved the survival rate of hypoxia/reoxygenation-treated human umbilical vein endothelial cells from 35% to 70%, which was equal to the potency of the positive control, verapamil. Flow cytometry analysis suggested 2 could inhibit H/R-induced late-stage apoptosis of this cell line.