High-density lipoprotein, mitochondrial dysfunction and cell survival mechanisms

Sphingosine 1-phosphate protective effect on human proximal tubule cells submitted to an in vitro ischemia model: the role of JAK2/STAT3

Acute kidney injury is a serious public health problem worldwide, being ischemia and reperfusion (I/R) the main lesion-aggravating factor that contributes to the evolution towards chronic kidney disease. Nonetheless, intervention approaches currently available are just considered palliative options. In order to offer an alternative treatment, it is important to understand key factors involved in the development of the disease including the rescue of the affected cells and/or the release of paracrine factors that are crucial for tissue repair. Bioactive lipids such as sphingosine 1-phosphate (S1P) have significant effects on the modulation of signaling pathways involved in tissue regeneration, such as cell survival, proliferation, differentiation, and migration. The main objective of this work was to explore the protective effect of S1P using human kidney proximal tubule cells submitted to a mimetic I/R lesion, via ATP depletion. We observed that the S1P pre-treatment increases cell survival by 50% and preserves the cell proliferation capacity of injured cells. We showed the presence of different bioactive lipids notably related to tissue repair but, more importantly, we noted that the pre-treatment with S1P attenuated the ischemia-induced effects in response to the injury, resulting in higher endogenous S1P production. All receptors but S1PR3 are present in these cells and the protective and proliferative effect of S1P/S1P receptors axis occur, at least in part, through the activation of the SAFE pathway. To our knowledge, this is the first time that S1PR4 and S1PR5 are referred in these cells and also the first indication of JAK2/STAT3 pathway involvement in S1P-mediated protection in an I/R renal model.

High-Density Lipoproteins at the Interface between the NLRP3 Inflammasome and Myocardial Infarction

Despite significant therapeutic advancements, morbidity and mortality following myocardial infarction (MI) remain unacceptably high. This clinical challenge is primarily attributed to two significant factors: delayed reperfusion and the myocardial injury resulting from coronary reperfusion. Following reperfusion, there is a rapid intracellular pH shift, disruption of ionic balance, heightened oxidative stress, increased activity of proteolytic enzymes, initiation of inflammatory responses, and activation of several cell death pathways, encompassing apoptosis, necroptosis, and pyroptosis. The inflammatory cell death or pyroptosis encompasses the activation of the intracellular multiprotein complex known as the NLRP3 inflammasome. High-density lipoproteins (HDL) are endogenous particles whose components can either promote or mitigate the activation of the NLRP3 inflammasome. In this comprehensive review, we explore the role of inflammasome activation in the context of MI and provide a detailed analysis of how HDL can modulate this process.

The role of high-density lipoprotein cholesterol, apolipoprotein A and paraoxonase-1 in the pathophysiology of neuroprogressive disorders

Lowered high-density lipoprotein (HDL) cholesterol has been reported in major depressive disorder, bipolar disorder, first episode of psychosis, and schizophrenia. HDL, its major apolipoprotein component, ApoA1, and the antioxidant enzyme paraoxonase (PON)1 (which is normally bound to ApoA1) all have anti-atherogenic, antioxidant, anti-inflammatory, and immunomodulatory roles, which are discussed in this paper. The paper details the pathways mediating the anti-inflammatory effects of HDL, ApoA1 and PON1 and describes the mechanisms leading to compromised HDL and PON1 levels and function in an environment of chronic inflammation. The molecular mechanisms by which changes in HDL, ApoA1 and PON1 might contribute to the pathophysiology of the neuroprogressive disorders are explained. Moreover, the anti-inflammatory actions of ApoM-mediated sphingosine 1-phosphate (S1P) signalling are reviewed as well as the deleterious effects of chronic inflammation and oxidative stress on ApoM/S1P signalling. Finally, therapeutic interventions specifically aimed at improving the levels and function of HDL and PON1 while reducing levels of inflammation and oxidative stress are considered. These include the so-called Mediterranean diet, extra virgin olive oil, polyphenols, flavonoids, isoflavones, pomegranate juice, melatonin and the Mediterranean diet combined with the ketogenic diet.

An Addition of U0126 Protecting Heart Grafts From Prolonged Cold Ischemia-Reperfusion Injury in Heart Transplantation: A New Preservation Strategy

BACKGROUND

Ischemia-reperfusion injury (IRI) is the major cause of primary graft dysfunction in organ transplantation. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in cell physiological and pathological processes including IRI. This study aims to investigate whether inhibition of ERK signaling with U0126 can prevent prolonged cold IRI in heart transplantation.

METHODS

Rat cardiac cell line H9c2 cells were treated with U0126 before exposure to hypothermic hypoxia/reoxygenation (H/R) conditions. The effect of U0126 on H9c2 cells in response to H/R stress was determined by measuring cell death, reactive oxygen species production, mitochondrial membrane potential, and ERK signaling activation. Mouse syngeneic heterotopic heart transplantation was conducted, where a donor heart was preserved in the University of Wisconsin (UW) solution supplemented with U0126 for 24 hours at 4°C before transplantation. Heart graft function, histopathologic changes, apoptosis, and fibrosis were measured to assess IRI.

RESULTS

Phosphorylated ERK was increased in both in vitro H/R-injured H9c2 cells and in vivo heart grafts with IRI. Pretreatment with U0126 inhibited ERK phosphorylation and prevented H9c2 cells from cell death, reactive oxygen species generation, and mitochondrial membrane potential loss in response to H/R. Preservation of donor hearts with U0126-supplemented solution improved graft function and reduced IRI by reductions in cell apoptosis/death, neutrophil infiltration, and fibrosis of the graft.

CONCLUSIONS

Addition of U0126 to UW solution reduces ERK signal activation and attenuates prolonged cold IRI in a heart transplantation model. ERK inhibition with U0126 may be a useful strategy to minimize IRI in organ transplantation.

Inactivated pseudomonas aeruginosa protects against myocardial ischemia reperfusion injury via Nrf2 and HO-1

The current study investigated the protective effects of inactivated pseudomonas aeruginosa (IPA) on myocardial ischemia reperfusion injury (MIR/I) and the mechanisms governing this interaction. Left anterior descending coronary artery ligation was performed on rats for 30 min and reperfusion was performed for a subsequent 2 h. Rat hearts were obtained and the myocardial infarction area was determined using nitroblue tetrazolium. Myocardial cell apoptosis was determined using flow cytometry. Malondialdehyde (MDA) content, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity and catalase (CAT) activities were assayed using the corresponding kits. Additionally, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were assayed using western blot and immunofluorescence analysis. When compared with the model group, the results of IPA treatment revealed improved heart function, reduced myocardial infarction area and reduced endothelial cell apoptosis, which led to decreased LDH and MDA levels, and increased SOD and CAT levels in serum, and decreased LDH and MDA levels and increased SOD and CAT in myocardial tissues. Moreover, increased Nrf2 and HO-1 expression levels in the myocardial tissues were also observed at all concentrations of IPA. It was concluded that IPA pretreatment ameliorated MIR/I and reduced endothelial apoptosis and oxidative stress via the Nrf2/HO-1 pathway.

Downregulation of miR-3568 Protects Against Ischemia/Reperfusion-Induced Cardiac Dysfunction in Rats and Apoptosis in H9C2 Cardiomyocytes Through Targeting TRIM62

microRNA-3568 (miR-3568) has been reported to be associated with atherosclerosis. Only few data describe the expression and underlying mechanism of miR-3568 in regulating cardiac ischemia-reperfusion (I/R) injury such as apoptosis. In this study, we therefore sought to investigate the potential function of miR-3568 in simulated I/R-induced apoptosis in H9C2 cardiomyocytes and related signaling pathways involved. Flow cytometry was performed to examine the cell apoptosis. The expression of miR-3568, Survivin, Bcl-2, ERK, JNK, p38, AKT, and STAT3 was measured by western blot and quantitative real-time PCR. The correlation between TRIM62 and p-STAT3 was measured by co-immunoprecipitation and ubiquitination. We found that miR-3568 expression in simulated I/R-induced H9C2 cardiomyocytes was increased in a time-dependent manner. miR-3568 mimic transfection in H9C2 cardiomyocytes significantly enhanced cell apoptosis, decreased the expression of Bcl-2 and Survivin, and activated STAT3 signaling, which were reversed by miR-3568 inhibitor. The direct interaction between miR-3568 and the 3'-untranslated region (UTR) of TRIM62 mRNA was confirmed by dual-luciferase reporter assay. TRIM62 overexpression or AG490, a selective inhibitor of JAK2/STAT3 significantly, significantly inhibited I/R and miR-3568 mimic induced cell apoptosis and STAT3 activation. TRIM62 was found to interact with and induce ubiquitination of p-STAT3. The facilitating role of miR-3568 in I/R injury was also observed in our in vivo rat models. In conclusion, our study suggests that miR-3568 promotes simulated I/R-induced apoptosis in H9C2 cardiomyocytes through targeting TRIM62.

HDL therapy today: from atherosclerosis, to stent compatibility to heart failure

Epidemiologically, high-density lipoprotein (HDL) cholesterol levels have been inversely associated to cardiovascular (CV) events, although a Mendelian Randomisation Study had failed to establish a clear causal role. Numerous atheroprotective mechanisms have been attributed to HDL, the main being the ability to promote cholesterol efflux from arterial walls; anti-inflammatory effects related to HDL ligands such as S1P (sphingosine-1-phosphate), resolvins and others have been recently identified. Experimental studies and early clinical investigations have indicated the potential of HDL to slow progression or induce regression of atherosclerosis. More recently, the availability of different HDL formulations, with different phospholipid moieties, has allowed to test other indications for HDL therapy. Positive reports have come from studies on coronary stent biocompatibility, where the use of HDL from different sources reduced arterial cell proliferation and thrombogenicity. The observation that low HDL-C levels may be associated with an enhanced risk of heart failure (HF) has also suggested that HDL therapy may be applied to this condition. HDL infusions or apoA-I gene transfer were able to reverse heart abnormalities, reduce diastolic resistance and improve cardiac metabolism. HDL therapy may be effective not only in atherosclerosis, but also in other conditions, of relevant impact on human health.Key messagesHigh-density lipoproteins have as a major activity that of removing excess cholesterol from tissues (particularly arteries).Knowledge on the activity of high-density lipoproteins on health have however significantly widened.HDL-therapy may help to improve stent biocompatibility and to reduce peripheral arterial resistance in heart failure.

Apolipoprotein A-I improves hepatic autophagy through the AMPK pathway

Dysfunction in lipid metabolism may result in a decrease in hepatic autophagy, which contributes to the pathogenesis of non-alcoholic steatohepatitis. ATP-binding cassette transporter A1 transports free cholesterol and phospholipids to apolipoprotein A-I (apoA-I) to form nascent high-density lipoprotein particles. Results from previous studies showed that the overexpression of apoA-I significantly reduced levels of hepatic lipids and endoplasmic reticulum stress by modifying lipid transport. Here, we investigated the effects of apoA-I overexpression on hepatic autophagy in cultured hepatocytes and mice. The overexpression of apoA-I in HepG2 cells resulted in an increase in the levels of autophagy as well as the phosphorylation of AMP-activated protein kinase α (AMPKα) and ULK1 and a decrease in the phosphorylation of mammalian target of rapamycin (mTOR). An AMPK inhibitor and siRNA eliminated this apoA-I effect. Consistently, apoA-I transgenic mice showed increased autophagy and AMPKα phosphorylation. These results suggest that apoA-I overexpression alleviates steatohepatitis by increasing hepatic autophagy through the AMPK-mTOR-ULK1 pathway.

Sphingosine-1-phosphate attenuates hypoxia/reoxygenation-induced cardiomyocyte injury via a mitochondrial pathway

Our previous study showed that Sphingosine-1-phosphate (S1P) could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury via the JAK-STAT pathway and maintain normal myocardial mitochondria integrity in vivo. However, it is not known yet whether S1P can relieve mitochondrial dysfunction via the mitochondrial apoptotic pathway and its detailed mechanism remains to be investigated. The aim of this study was to demonstrate the mitochondrial protective effects of S1P in a cardiomyocyte H/R injury model. In the present study, we established a H/R model in H9c2 cells. Cell viability was determined by the MTT assay, and apoptosis was evaluated by annexin V-FITC/PI staining. Mitochondrial calcium ion concentration, mitochondrial membrane potential (ΔΨm), opening of the mitochondrial permeability transition pore (mPTP), and release of cytochrome C were detected by laser confocal microscopy. The results showed that S1P inhibited the decrease in cell viability induced by H/R injury and reduced apoptosis. Confocal microscopy showed that S1P prevented loss of ΔΨm, relieved mitochondrial calcium overload, and inhibited opening of the mPTP and release of cytochrome C. The STAT3 inhibitor STATTIC can reverse the antiapoptotic effects of S1P and block the effect of S1P on mitochondria. Taken together, our results indicate that S1P protects cardiomyocytes against H/R injury by relieving mitochondrial dysfunction via the STAT3 pathway.

USP49 inhibits ischemia-reperfusion-induced cell viability suppression and apoptosis in human AC16 cardiomyocytes through DUSP1-JNK1/2 signaling

Dual-specificity protein phosphatases (DUSP) also known as mitogen-activated protein kinase (MAPK) phosphatases (MKPs) can dephosphorylate MAPKs, including extracellular signal-regulated kinase, c-Jun N-terminal kinase (JNK), and p38. DUSP1-mediated JNK dephosphorylation has been found to play an antiapoptotic role against cardiac ischemia-reperfusion (I/R) injury. However, the regulation of DUSP1-JNK pathway remains unclear. In the current study, ubiquitin-specific peptidase 49 (USP49) expression in human AC16 cardiomyocytes following I/R injury was measured by real-time polymerase chain reaction and western blot analysis. Cell viability, apoptosis, the Bax, Bcl-2, and DUSP1 expression, and the activity of MAPKs in AC16 cardiomyocytes following indicated treatment was measured by CCK-8, flow cytometry, and western blot analysis. The direct interaction between USP49 and DUSP1 was measured by coimmunoprecipitation and ubiquitination analysis. The effect of USP49 on apoptosis and JNK activity in rat cardiomyocytes following I/R injury was also measured by TUNEL and western blot analysis. Here, we found that USP49 expression was time-dependently increased in AC16 cardiomyocytes following I/R. I/R-induced cell apoptosis and JNK1/2 activation both in in vivo and in vitro reversed by USP49 overexpression in AC16 cardiomyocytes. Inhibiting JNK1/2 activation significantly inhibited USP49 knockdown-induced the cell viability inhibition, apoptosis and the JNK1/2 activation in AC16 cardiomyocytes. Moreover, USP49 positively regulated DUSP1 expression through deubiquitinating DUSP1. Overall, our findings establish USP49 as a novel regulator of DUSP1-JNK1/2 signaling pathway with a protective role in cardiac I/R injury.

Melatonin and cardioprotection against ischaemia/reperfusion injury: What's new? A review

Melatonin is a pleiotropic hormone with several functions. It binds to specific receptors and to a number of cytosolic proteins, activating a vast array of signalling pathways. Its potential to protect the heart against ischaemia/reperfusion damage has attracted much attention, particularly in view of its possible clinical applications. This review will focus mainly on the possible signalling pathways involved in melatonin-induced cardioprotection. In particular, the role of the melatonin receptors and events downstream of receptor activation, for example, the reperfusion injury salvage kinase (RISK), survivor activating factor enhancement (SAFE) and Notch pathways, the sirtuins, nuclear factor E2-related factor 2 (Nrf2) and translocases in the outer membrane (TOM70) will be discussed. Particular attention is given to the role of the mitochondrion in melatonin-induced cardioprotection. In addition, a brief overview will be given regarding the status quo of the clinical application of melatonin in humans.

Therapeutic efficacy of cyclosporin A against spinal cord injury in rats with hyperglycemia

The present study aimed to explore the therapeutic effects of cyclosporin A (CsA) on spinal cord injury (SCI) in rats with hyperglycemia and to identify a novel potential method to treat SCI in the presence of hyperglycemia. Female Sprague‑Dawley (SD) rats were randomly allocated into four groups: Sham, SCI, SCI+hyperglycemia and SCI+hyperglycemia+CsA groups. Streptozotocin‑induced hyperglycemic SD rats and a weight‑drop contusion SCI model were established. The Basso, Beattie, Bresnahan scale and inclined plane test were used to evaluate the neurological function of the rats. Flow cytometric assay was performed to detect the apoptotic rates of cells in the spinal cord. ELISA and western blot analysis were performed to determine the levels of interleukin (IL)‑10, tumor necrosis factor (TNF)‑α, cyclophilin‑D (Cyp‑D) and apoptosis‑inducing factor (AIF). The results demonstrated that CsA significantly improved the neurological function of the SCI rats with hyperglycemia. CsA markedly reduced the number of apoptotic cells exaggerated by hyperglycemia in the spinal cord of the SCI rats. CsA significantly decreased the expression levels of IL‑10, TNF‑α, Cyp‑D and AIF in the spinal cord of the SCI rats. Overall, the present study revealed a significant role of CsA in the treatment of SCI in the presence of hyperglycemia by inhibiting the apoptosis of spinal cord cells.