Dexmedetomidine Preconditioning Protects Cardiomyocytes Against Hypoxia/Reoxygenation-Induced Necroptosis by Inhibiting HMGB1-Mediated Inflammation

Necroptosis: a significant and promising target for intervention of cardiovascular disease

Due to changes in dietary structures, population aging, and the exacerbation of metabolic risk factors, the incidence of cardiovascular disease continues to rise annually, posing a significant health burden worldwide. Cell death plays a crucial role in the onset and progression of cardiovascular diseases. As a regulated endpoint encountered by cells under adverse stress conditions, the execution of necroptosis is regulated by classicalpathways, the calmodulin-dependent protein kinases (CaMK) pathway, and mitochondria-dependent pathways, and implicated in various cardiovascular diseases, including atherosclerosis, myocardial infarction, myocardial ischemia-reperfusion injury (IRI), heart failure, diabetic cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomyopathy, chemotherapy drug-induced cardiomyopathy, and abdominal aortic aneurysm (AAA). To further investigate potential therapeutic targets for cardiovascular diseases, we also analyzed the main molecules and their inhibitors involved in necroptosis in an effort to uncover insights for treatment.

Dexmedetomidine Inhibits Ferroptosis to Alleviate Hypoxia/Reoxygenation-Induced Cardiomyocyte Injury by Regulating the HDAC2/FPN Pathway

PURPOSE

Myocardial ischemia/reperfusion injury (MIRI) is closely associated with ferroptosis. Dexmedetomidine (Dex) has good therapeutic effects on MIRI. This study investigates whether dexmedetomidine (Dex) regulates ferroptosis during MIRI by affecting ferroportin1 (FPN) levels and elucidates the underlying mechanisms.

METHODS

A murine MIRI model was established using male C57BL/6 J mice subjected to 30 min of left anterior descending coronary artery ligation followed by 48 h of reperfusion. In vitro, cardiomyocyte hypoxia/reoxygenation (H/R) models were created with 16 h of hypoxia and 8 h of reoxygenation. Triphenyltetrazolium chloride (TTC) staining was employed to determine infarct size. The pathological changes in myocardial tissues were assessed using hematoxylin-eosin (HE) staining. Lipid reactive oxygen species (ROS) level was detected using BODIPY™ 581/591 C11, and ferrous iron (Fe2+) and malondialdehyde (MDA) levels were measured using the kits. Cardiomyocyte viability was examined using cell counting kit-8 (CCK8) assay. The histone H3 lysine 27 acetylation (H3K27Ac) level in the FPN promoter region was determined using DNA pulldown assay. Chromatin immunoprecipitation (ChIP) assay was used to investigate the relationship between histone deacetylase 2 (HDAC2) and FPN promoter.

RESULTS

Dex alleviated ferroptosis in cardiomyocytes by upregulating FPN levels, which mitigated H/R-induced oxidative damage. FPN knockdown abolished the protective effects of Dex, confirming its dependence on FPN expression. Additionally, HDAC2 knockdown alleviated I/R-induced myocardial injury and ferroptosis in mice. Moreover, H/R-induced HDAC2 upregulation transcriptionally inhibited FPN expression by reducing the H3K27Ac level in the FPN promoter region, but Dex therapy restored this impact via inhibition of HDAC2. As expected, HDAC2 overexpression partially reversed the inhibitory effect of Dex on H/R-mediated cardiomyocyte ferroptosis.

CONCLUSION

Dex alleviated H/R-mediated cardiomyocyte ferroptosis through regulating the HDAC2/FPN axis. Our findings lend theoretical support to the use of Dex in MIRI therapy.

Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine

PURPOSE

Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury.

RESULTS AND CONCLUSION

Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Dexmedetomidine promotes necroptosis by upregulating PARP1 in non-small cell lung cancer

The score and prognostic value of necroptosis were analyzed in the TCGA and GSE120622 datasets. Necroptosis has the highest correlation with the immune microenvironment, and the high score in NSCLC correlates with poor prognosis. Differentially expressed genes between non-small cell lung cancer (NSCLC) and controls in both datasets were identified and subjected to construct co-expression networks, respectively. Black and blue modules were selected because of high correction with necroptosis. The intersected two module genes were mainly involved in immune and inflammatory response, cell cycle process and DNA replication. Nine marker genes of necroptosis were identified in these modules and considered as candidate genes. Based on candidate genes, we identified two clusters utilizing concordance clustering, additionally dividing NSCLC samples into high- and low-risk groups. There were significant differences in overall survival between two clusters and between high- and low-risk groups. Furthermore, PARP1 was found among the candidate genes to be the target gene of dexmedetomidine acting on necroptosis. Molecular experimental results found that PARP1 was highly expressed in the dexmedetomidine treated NSCLC compared with the NSCLC. Candidate genes associated with necroptosis may provide a powerful prognostic tool for precision oncology. Dexmedetomidine may target PARP1 to promote necroptosis and then affect NSCLC.

16α-OHE1 alleviates hypoxia-induced inflammation and myocardial damage via the activation of β2-Adrenergic receptor

OBJECTIVE

Myocardial injuries resulting from hypoxia are a significant concern, and this study aimed to explore potential protective strategies against such damage. Specifically, we sought to investigate the cardioprotective effects of 16α-hydroxyestrone (16α-OHE1).

METHODS

Male Sprague‒Dawley (SD) rats were subjected to hypoxic conditions simulating high-altitude exposure at 6000 m in a low-pressure chamber for 7 days. Before and during hypoxic exposure, estradiol (E2) and various doses of 16α-OHE1 were administered for 14 days. Heart weight/body weight (HW/BW), myocardial structure, Myocardial injury indicators and inflammatory infiltration in rats were measured. H9C2 cells cultured under 5% O2 conditions received E2 and varying doses of 16α-OHE1; Cell viability, apoptosis, inflammatory infiltration, and Myocardial injury indicators were determined. Expression levels of β2AR were determined in rat hearts and H9C2 cells. The β2AR inhibitor, ICI 118,551, was employed to investigate β2AR's role in 16α-OHE1's cardioprotective effects.

RESULTS

Hypoxia led to substantial myocardial damage, evident in increased heart HW, CK-MB, cTnT, ANP, BNP, structural myocardial changes, inflammatory infiltration, and apoptosis. Pre-treatment with E2 and 16α-OHE1 significantly mitigated these adverse changes. Importantly, the protective effects of E2 and 16α-OHE1 were associated with the upregulation of β2AR expression in both rat hearts and H9C2 cells. However, inhibition of β2AR by ICI 118,551 in H9C2 cells nullified the protective effect of 16α-OHE1 on myocardium.

CONCLUSION

Our findings suggest that 16α-OHE1 can effectively reduce hypoxia-induced myocardial injury in rats through β2ARs, indicating a promising avenue for cardioprotection.

Dexmedetomidine attenuates lipopolysaccharide-induced renal cell fibrotic phenotypic changes by inhibiting necroinflammation via activating α2-adrenoceptor: A combined randomised animal and in vitro study

BACKGROUND

Acute kidney injury (AKI) was reported to be one of the initiators of chronic kidney disease (CKD) development. Necroinflammation may contribute to the progression from AKI to CKD. Dexmedetomidine (Dex), a highly selective α2-adrenoreceptor (AR) agonist, has cytoprotective and "anti-" inflammation effects. This study was designed to investigate the anti-fibrotic properties of Dex in sepsis models.

METHODS

C57BL/6 mice were randomly treated with an i.p. injection of lipopolysaccharides (LPS) (10 mg/kg) alone, LPS with Dex (25 μg/kg), or LPS, Dex and Atipamezole (Atip, an α2-adrenoreceptor antagonist) (500 μg/kg) (n=5/group). Human proximal tubular epithelial cells (HK2) were also cultured and then exposed to LPS (1 μg/ml) alone, LPS and Dex (1 μM), transforming growth factor-beta 1 (TGF-β1) (5 ng/ml) alone, TGF-β1 and Dex, with or without Atip (100 μM) in culture media. Epithelial-mesenchymal transition (EMT), cell necrosis, necroptosis and pyroptosis, and c-Jun N-terminal kinase (JNK) phosphorylation were then determined.

RESULTS

Dex treatment significantly alleviated LPS-induced AKI, myofibroblast activation, NLRP3 inflammasome activation, and necroptosis in mice. Atip counteracted its protective effects. Dex attenuated LPS or TGF-β1 induced EMT and also prevented necrosis, necroptosis, and pyroptosis in response to LPS stimulation in the HK2 cells. The anti-EMT effects of Dex were associated with JNK phosphorylation.

CONCLUSIONS

Dex reduced EMT following LPS stimulation whilst simultaneously inhibiting pyroptosis and necroptosis via α2-AR activation in the renal tubular cells. The "anti-fibrotic" and cytoprotective properties and its clinical use of Dex need to be further studied.

Regulated cell death in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R) injury most commonly occurs in coronary artery disease when prompt reperfusion is used to salvage the ischemic myocardium. Cardiomyocyte death is a significant component of myocardial I/R injury and its mechanism was previously thought to be limited to apoptosis and necrosis. With the discovery of novel types of cell death, ferroptosis, necroptosis, and pyroptosis have been shown to be involved in myocardial I/R. These new forms of regulated cell death cause cardiomyocyte loss and exacerbate I/R injury by affecting reactive oxygen species (ROS) generation, calcium stress, and inflammatory cascades, subsequently mediating adverse remodeling, cardiac dysfunction, and heart failure. Herein, we review the roles of ferroptosis, necroptosis, and pyroptosis in myocardial I/R and discuss their contribution to pathology.

Pharmaceutical Therapies for Necroptosis in Myocardial Ischemia-Reperfusion Injury

Cardiovascular disease morbidity/mortality are increasing due to an aging population and the rising prevalence of diabetes and obesity. Therefore, innovative cardioprotective measures are required to reduce cardiovascular disease morbidity/mortality. The role of necroptosis in myocardial ischemia-reperfusion injury (MI-RI) is beyond doubt, but the molecular mechanisms of necroptosis remain incompletely elucidated. Growing evidence suggests that MI-RI frequently results from the superposition of multiple pathways, with autophagy, ferroptosis, and CypD-mediated mitochondrial damage, and necroptosis all contributing to MI-RI. Receptor-interacting protein kinases (RIPK1 and RIPK3) as well as mixed lineage kinase domain-like pseudokinase (MLKL) activation is accompanied by the activation of other signaling pathways, such as Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), NF-κB, and JNK-Bnip3. These pathways participate in the pathological process of MI-RI. Recent studies have shown that inhibitors of necroptosis can reduce myocardial inflammation, infarct size, and restore cardiac function. In this review, we will summarize the molecular mechanisms of necroptosis, the links between necroptosis and other pathways, and current breakthroughs in pharmaceutical therapies for necroptosis.

Natural emodin reduces myocardial ischemia/reperfusion injury by modulating the RUNX1/miR‑142‑3p/DRD2 pathway and attenuating inflammation

Acute myocardial infarction is one of the leading causes of death worldwide. Although timely reperfusion could attenuate myocardial ischemia injury and reduce mortality, it causes severe secondary injury to the myocardium known as myocardial ischemia/reperfusion injury (MIRI) with unmet clinical needs. Emodin has a protective effect on MIRI in rodents. However, the precise mechanism underlying its pharmacological effect remains poorly understood. Accordingly, the present study used mRNA and microRNA (miRNA) sequencing based on MIRI mouse models to determine the mechanism involved. Emodin was found to prevent MIRI and attenuate the inflammation of myocardium in the MIRI model. In addition, by using an interdisciplinary approach, the present study uncovered that emodin suppressed the runt-related transcription factor 1 (RUNX1), which is a transcription factor of miR-142-3p, in either MIRI or the hypoxia/reoxygenation injury model. Furthermore, miR-142-3p can negatively regulate dopamine receptor D2 (DRD2), which acted as an anti-inflammatory factor to suppress NF-κB-dependent inflammation and prevent MIRI. These results were demonstrated by both cellular hypoxia/reoxygenation and mouse MIRI models. Overall, the present study provided an unrevealed molecular mechanism for emodin function. Emodin could inhibit NF-κB-triggered inflammation in MIRI by regulating the RUNX1/miR-142-3p/DRD2 pathway. Therefore, the RUNX1/miR-142-3p/DRD2 pathway presented a novel target for MIRI treatment, and the application of emodin in clinical practice may improve the treatment of MIRI.

[New aspects of perioperative organ protection]

BACKGROUND

Acutely occurring organ damage significantly contributes to morbidity and mortality in the perioperative context.

OBJECTIVE

This article highlights new clinical perspectives on how perioperative organ damage can be prevented and ameliorated by influencing the high mobility group box 1 protein (HMGB1) signaling.

MATERIAL AND METHODS

A MEDLINE search was performed in the fields of clinical and basic research. The presentation of basic mechanisms of perioperative organ damage and the discussion of the importance of HMGB1 in prevention and treatment by pharmaceutical and nonpharmaceutical interventions are the focus of the review.

RESULTS

The HMGB1 is a central element in the pathogenesis of septic and aseptic inflammation-induced organ damage. Remote ischemic preconditioning (RIPC) and dexmedetomidine are highly effective approaches to mitigate or prevent organ damage.

CONCLUSION

The RIPC and dexmedetomidine offer protective properties in ischemia-reperfusion injury as well as in inflammation-related organ damage, which are mediated by HMGB1, among others. This effectively protects the kidneys, heart, lungs, liver and brain. The application of these concepts should be considered in routine clinical practice.

Dexmedetomidine prevents cardiomyocytes from hypoxia/reoxygenation injury via modulating tetmethylcytosine dioxygenase 1-mediated DNA demethylation of Sirtuin1

Myocardial hypoxia/reoxygenation (H/R) injury is a common pathological change in patients with acute myocardial infarction undergoing reperfusion therapy. Dexmedetomidine (DEX) has been found to substantially improve ischemia-mediated cell damage. Here, we focus on probing the role and mechanism of DEX in ameliorating myocardial H/R injury. Oxygen–glucose deprivation and reoxygenation (OGD/R) were applied to construct the H/R injury model in human myocardial cell lines. After different concentrations of DEX’s treatment, cell counting kit-8 (CCK-8) assay and BrdU assay were employed to test cell viability. The profiles of apoptosis-related proteins Bcl2, Bax, Bad and Caspase3, 8, 9 were determined by Western blot (WB). The expression of inflammatory factors interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α) was checked by reverse transcription-polymerase chain reaction (RT-PCR). By conducting WB, we examined the expression of NF-κB, Sirt1, Tet methylcytosine dioxygenase 1 (TET1) and DNA methylation-related proteins (DNA methyltransferase 1, DNMT1; DNA methyltransferase 3 alpha, DNMT3A; and DNA methyltransferase 3 beta, DNMT3B). Our data showed that OGD/R stimulation distinctly hampered the viability and elevated apoptosis and inflammatory factor expression in cardiomyocytes. DEX treatment notably impeded myocardial apoptosis and inflammation and enhanced cardiomyocyte viability. OGD/R enhanced total DNA methylation levels in cardiomyocytes, while DEX curbed DNA methylation. In terms of mechanism, inhibiting TET1 or Sirtuin1 (Sirt1) curbed the DEX-mediated myocardial protection. TET1 strengthened demethylation of the Sirt1 promoter and up-regulated Sirt1. DEX up-regulates Sirt1 by accelerating TET1 and mediating demethylation of the Sirt1 promoter and improves H/R-mediated myocardial injury.

T1AM Attenuates the Hypoxia/Reoxygenation-Induced Necroptosis of H9C2 Cardiomyocytes via RIPK1/RIPK3 Pathway

Purpose

To investigate the detailed mechanism of 3-iodothyronamine (T1AM) in cell apoptosis and programmed necrosis of hypoxia/reoxygenation- (H/R-) induced H9C2 injury.

Materials and Methods

Cardiomyocyte H9C2 cells were cultured in vitro for the establishment of cardiomyocyte H/R models. Cells were randomly divided into four groups: the control group, H/R group, T1AM pretreatment group, T1AM pretreatment and H/R (6 μm T1AM+H/R) group. The degree of myocardial injury was determined by the detection of the cardiomyocyte inhibition rate by CCK8 and the detection of lactic dehydrogenase (LDH) activity. Cell apoptosis was assessed through TUNEL assay and flow cytometry analysis. The protein level and mRNA level of RIPK1, RIPK3, and CAMKII were detected by western blotting and qRT-PCR.

Results

Compared with the control group, the cell inhibition rate was dramatically elevated in the H/R group. LDH release of cardiomyocytes was significantly increased. Protein and mRNA expressions of RIPK1, RIPK3, and CAMKII were significantly enhanced. Compared with the H/R group, the cell inhibition rate, LDH release, cardiomyocyte necroptosis rate, and protein and mRNA levels of RIPK1, RIPK3, and CAMKII of the T1AM+H/R group were significantly decreased.

Conclusion

Pretreatment with T1AM could alleviate cardiomyocytes' H/R injury and inhibit necroptosis of cardiomyocytes, which might exert a protective function upon activation of the RIPK1/RIPK3 pathway.

Receptor Interacting Protein Kinases 1/3: The Potential Therapeutic Target for Cardiovascular Inflammatory Diseases

The receptor interacting protein kinases 1/3 (RIPK1/3) have emerged as the key mediators in cell death pathways and inflammatory signaling, whose ubiquitination, phosphorylation, and inhibition could regulate the necroptosis and apoptosis effectually. Recently, more and more studies show great interest in the mechanisms and the regulator of RIPK1/3-mediated inflammatory response and in the physiopathogenesis of cardiovascular diseases. The crosstalk of autophagy and necroptosis in cardiomyocyte death is a nonnegligible conversation of cell death. We elaborated on RIPK1/3-mediated necroptosis, pathways involved, the latest regulatory molecules and therapeutic targets in terms of ischemia reperfusion, myocardial remodeling, myocarditis, atherosclerosis, abdominal aortic aneurysm, and cardiovascular transplantation, etc.

Inhibition of lncRNA NEAT1 protects endothelial cells against hypoxia/reoxygenation‑induced NLRP3 inflammasome activation by targeting the miR‑204/BRCC3 axis

Cardiovascular ischemia/reperfusion (I/R) injury is primarily caused by oxygen recovery after prolonged hypoxia. Previous studies found that the long non coding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1) was involved in cardiovascular pathology, and that NOD-like receptor protein 3 (NLRP3) inflammasome activation-dependent pyroptosis played a key role in cardiovascular I/R injury. The present study aimed to explore the molecular mechanism of I/R pathogenesis in order to provide novel insights for potential future therapies. Cell viability and lactate dehydrogenase enzyme activity assays were used to detect cell injury after human umbilical vein endothelial cells (HUVECs) were subjected to hypoxia/reoxygenation (H/R). The expression of the NEAT1/microRNA (miR)-204/BRCA1/BRCA2-containing complex subunit 3 (BRCC3) axis was examined by reverse transcription-quantitative PCR, and the associations among genes were confirmed by luciferase reporter assays. Western blotting and ELISA were used to measure the level of NLRP3 inflammasome activation-dependent pyroptosis. The results demonstrated that NEAT1, BRCC3 expression and NLRP3 inflammasome activation-dependent pyroptosis were significantly increased in H/R-injured HUVECs, whereas silencing BRCC3 or NEAT1 attenuated H/R-induced injury and pyroptosis. NEAT1 positively regulated BRCC3 expression via competitively binding with miR-204. Moreover, NEAT1 overexpression counteracted miR-204 mimic-induced injury, BRCC3 expression and NLRP3 inflammasome activation-dependent pyroptosis. Taken together, these findings demonstrated that inhibition of lncRNA NEAT1 protects HUVECs against H/R-induced NLRP3 inflammasome activation by targeting the miR-204/BRCC3 axis.

Astragalin Protects against Spinal Cord Ischemia Reperfusion Injury through Attenuating Oxidative Stress-Induced Necroptosis

Spinal cord ischemia/reperfusion (SCI/R) injury is a devastating complication usually occurring after thoracoabdominal aortic surgery. However, it remains unsatisfactory for its intervention by using pharmacological strategies. Oxidative stress is a main pharmacological process involved in SCI/R, which will elicit downstream programmed cell death such as the novel defined necroptosis. Astragalin is a bioactive natural flavonoid with a wide spectrum of pharmacological activities. Herein, we firstly evaluated the effect of astragalin to oxidative stress as well as the possible downstream necroptosis after SCI/R in mice. Our results demonstrated that astragalin improves the ethological score and histopathological deterioration of SCI/R mice. Astragalin mitigates oxidative stress and ameliorates inflammation after SCI/R. Astragalin blocks necroptosis induced by SCI/R. That is, the amelioration of astragalin to the motoneuron injury and histopathological changes. Indicators of oxidative stress, inflammation, and necroptosis after SCI/R were significantly blocked. Summarily, we firstly illustrated the protection of astragalin against SCI/R through its blockage to the necroptosis at downstream of oxidative stress.

Dexmedetomidine preconditioning mitigates myocardial ischemia/reperfusion injury via inhibition of mast cell degranulation

The degranulation of cardiac mast cells is associated with occurrence and development of myocardial ischemia/reperfusion (I/R) injury. Dexmedetomidine has a cardioprotective effect from I/R injury. The purpose of this study was to investigate whether dexmedetomidine preconditioning induced cardioprotection is related to suppression of degranulation of cardiac mast cell. Both in vivo and in vitro experimental results revealed that hemodynamic disorder, arrhythmia, infarct size, histopathological score, and mast cell degranulation were dramatically increased in I/R injury groups compared with non-I/R groups, and mastocyte secretagogue compound 48/80 aggravated these damages, but it can be improved by dexmedetomidine preconditioning. Similarly, compound 48/80 increased levels of cardiac troponin I (cTnI) and tryptase, cardiomyocytes apoptosis, and expression of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), and nuclear factor-kappa B p65 (NF-κB p65) in cardiac tissues induced by I/R injury, but it can be partially decreased by dexmedetomidine pretreatment. Compound 48/80 inhibited proliferation of H9C2(2-1) and RBL-2H3, exacerbated apoptosis of H9C2(2-1), and elevated levels of cTnI and tryptase, while both of which were abolished by dexmedetomidine pretreatment. Our data suggest that dexmedetomidine preconditioning alleviates the degranulation of mast cells and the apoptosis of cardiomyocytes caused by I/R injury, and inhibits the activation of inflammatory related factors HMGB1, TLR4, and NF-κB p65.

Role of HMGB1 in TNF-α Combined with Z-VAD-fmk-Induced L929 Cells Necroptosis

The present study established a necroptosis model in vitro and investigated the role of HMGB1 in cell necroptosis. A combination of tumor necrosis factor-α and z-VAD-fmk was used to induce necroptosis in L929 cells with necroptosis inhibitor necrostatin-1 applied as an intervention. Flow cytometry and transmission electron microscopy (TEM) were used to measure cell necroptosis. Western blotting assay was applied to detect the expression of receptor-interacting serine/threonine-protein kinase 3 (RIPK3), mixed lineage kinase domain-like pseudokinase (MLKL) and HMGB1. Co-immunoprecipitation (Co-IP) assay was used to confirm the interaction between HMGB1 and RIPK3. Our study demonstrated that HMGB1 migrated from the nucleus to the cytoplasm at the onset of necroptosis and was subsequently released passively to the extracellular matrix. Further experiments determined that the binding of HMGB1 with RIPK3 in the cytoplasm was loose during necroptosis. By contrast, when necroptosis was inhibited, the interaction in the cytoplasm was tight suggesting that this association between HMGB1 and RIPK3 might affect its occurrence. In conclusion, the transfer of HMGB1 from nucleus to cytoplasm, and its interaction with RIPK3 might be potentially involved in necroptosis.

Ozone induces tolerance against cardiomyocytes oxygen-glucose deprivation/reperfusion through inhibition of autophagy pathway

Previous studies have reported that excess activation of autophagy in cardiomyocytes is associated with an increase in myocardial oxygen-glucose deprivation/reperfusion (OGD/R) injury. Ozone therapy affords significant cardio-protection against myocardial OGD/R injury. The present study was designed to determine whether ozone-induced tolerance to myocardial OGD/R injury was mediated by inhibiting autophagy. Subsequently, the rat cardio myoblast H9C2 cell line was used in the present study. A model of H9C2 cells under OGD/R was established. The cells were incubated with different concentrations of ozone (10-60 µg/ml) during reperfusion. Furthermore, to investigate the role of autophagy in OGD/R-induced injury, the autophagy inducer and inhibitor were applied. Cell viability was detected by Cell Counting kit-8 assay. Cell apoptosis was evaluated by flow cytometry. Oxidative stress was examined by superoxide dismutase, lactate dehydrogenase and malondialdehyde levels. The expressions of apoptosis regulator B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (BAX), cleaved caspase-3, markers of autophagy microtuble-associated protein 1 light chain 3 (LC3), autophagy-related protein 5 (Atg5) and Beclin-1 were measured by western blot analysis. As a result, OGD/R notably decreased cell viability and induced apoptosis in H9C2 cells, while ozone (10-40 µg/ml) reversed the noxious effects of OGD/R on H9C2 cells, and 20 µg/ml ozone was the most effective. Ozone inhibited the decrease in the ratio of Bcl-2/BAX and the expression of cleaved caspase-3, and inhibited the increase in the ratio of LC3-II/LC3-I and the expression of Atg5 and Beclin-1 elicited by OGD/R, as well as dose-dependently preventing OGD/R-induced oxidative stress. Furthermore, rapamycin markedly reversed the effects of ozone (20 µg/ml) on OGD/R-induced expression of autophagy marker proteins and 3-methyladenine further improved the effect of ozone. Taken together, the results of the present study provided a credible mechanism by which ozone treatment at low concentrations could protect the myocardium from OGD/R-induced injury by inhibiting autophagy.

Mitochondria and Pharmacologic Cardiac Conditioning-At the Heart of Ischemic Injury

Pharmacologic cardiac conditioning increases the intrinsic resistance against ischemia and reperfusion (I/R) injury. The cardiac conditioning response is mediated via complex signaling networks. These networks have been an intriguing research field for decades, largely advancing our knowledge on cardiac signaling beyond the conditioning response. The centerpieces of this system are the mitochondria, a dynamic organelle, almost acting as a cell within the cell. Mitochondria comprise a plethora of functions at the crossroads of cell death or survival. These include the maintenance of aerobic ATP production and redox signaling, closely entwined with mitochondrial calcium handling and mitochondrial permeability transition. Moreover, mitochondria host pathways of programmed cell death impact the inflammatory response and contain their own mechanisms of fusion and fission (division). These act as quality control mechanisms in cellular ageing, release of pro-apoptotic factors and mitophagy. Furthermore, recently identified mechanisms of mitochondrial regeneration can increase the capacity for oxidative phosphorylation, decrease oxidative stress and might help to beneficially impact myocardial remodeling, as well as invigorate the heart against subsequent ischemic insults. The current review highlights different pathways and unresolved questions surrounding mitochondria in myocardial I/R injury and pharmacological cardiac conditioning.

The role of RIPK3-regulated cell death pathways and necroptosis in the pathogenesis of cardiac ischaemia-reperfusion injury

Despite advancements in management of acute myocardial infarction, this disease remains one of the leading causes of death. Timely reestablishment of epicardial coronary blood flow is the cornerstone of therapy; however, substantial amount of damage can occur as a consequence of cardiac ischaemia/reperfusion (I/R) injury. It has been previously proposed that the pathway leading to major cell death, apoptosis, is responsible for cardiac I/R injury. Nevertheless, there is compelling evidence to suggest that necroptosis, a programmed necrosis, contributes remarkably to both myocardial injury and microcirculatory dysfunction following cardiac I/R injury. Receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like pseudokinase (MLKL) are shown as the major mediators of necroptosis. In addition to the traditional perception that RIPK1/RIPK3/MLKL-dependent plasma membrane rupture is fundamental to this process, several RIPK3-related pathways such as endoplasmic reticulum stress and mitochondrial fragmentation have also been implicated in cardiac I/R injury. In this review, reports from both in vitro and in vivo studies regarding the roles of necroptosis and RIPK3-regulated necrosis in cardiac I/R injury have been collectively summarized and discussed. Furthermore, reports on potential interventions targeting these processes to attenuate cardiac I/R insults to the heart have been presented in this review. Future investigations adding to the knowledge obtained from these previous studies are needed in the pursuit of discovering the most effective pharmacological agent to improve cardiac I/R outcomes.

A Critical Appraisal of the Effects of Anesthetics on Immune-system Modulation in Critically Ill Patients With COVID-19

Purpose

The aim of the present article was to briefly summarize current knowledge about the immunomodulatory effects of general anesthetics and the possible clinical effects of this immunomodulation in patients with COVID-19.

Methods

The PubMed, Scopus, and Google Scholar databases were comprehensively searched for relevant studies.

Findings

The novel coronavirus causes a wide spectrum of clinical manifestations, with a large absolute number of patients experiencing severe pneumonia and rapid progression to acute respiratory distress syndrome and multiple organ failure. In these patients, the equilibrium of the inflammatory response is a major determinant of survival. The impact of anesthetics on immune-system modulation may vary and includes both pro-inflammatory and anti-inflammatory effects.

Implications

Inhibition of the development of severe inflammation and/or the enhancement of inflammation resolution by anesthetics may limit organ damage and improve outcomes in patients with COVID-19.

Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial damage is a critical contributor to cardiac ischemia/reperfusion (I/R) injury. Mitochondrial quality control (MQC) mechanisms, a series of adaptive responses that preserve mitochondrial structure and function, ensure cardiomyocyte survival and cardiac function after I/R injury. MQC includes mitochondrial fission, mitochondrial fusion, mitophagy and mitochondria-dependent cell death. The interplay among these responses is linked to pathological changes such as redox imbalance, calcium overload, energy metabolism disorder, signal transduction arrest, the mitochondrial unfolded protein response and endoplasmic reticulum stress. Excessive mitochondrial fission is an early marker of mitochondrial damage and cardiomyocyte death. Reduced mitochondrial fusion has been observed in stressed cardiomyocytes and correlates with mitochondrial dysfunction and cardiac depression. Mitophagy allows autophagosomes to selectively degrade poorly structured mitochondria, thus maintaining mitochondrial network fitness. Nevertheless, abnormal mitophagy is maladaptive and has been linked to cell death. Although mitochondria serve as the fuel source of the heart by continuously producing adenosine triphosphate, they also stimulate cardiomyocyte death by inducing apoptosis or necroptosis in the reperfused myocardium. Therefore, defects in MQC may determine the fate of cardiomyocytes. In this review, we summarize the regulatory mechanisms and pathological effects of MQC in myocardial I/R injury, highlighting potential targets for the clinical management of reperfusion.

Inhibition of cathepsin S attenuates myocardial ischemia/reperfusion injury by suppressing inflammation and apoptosis

Myocardial ischemia/reperfusion (I/R) injury leads to high mortality and morbidity due to the incomplete understanding of the underlying mechanism and the consequent lack of effective therapy. The present study revealed and validated key candidate genes in relation to inflammation and apoptosis pathways underlying myocardial I/R injury. Cathepsin S was identified as the top hub protein based on the protein-protein interaction analysis, and, thus, its role during myocardial I/R injury was further investigated. Myocardial I/R in mice resulted in significantly increased levels of myocardial injury biomarkers (cardiac troponin I, lactic dehydrogenase, and creatinine kinase-MB) and inflammatory cytokines (interleukin-1β [IL-1β], IL-6, and tumor necrosis factor-α), elevated apoptosis rate, and upregulated protein expression of cleaved caspase-8, cleaved caspase-3, and cleaved poly ADP-ribose polymerase. These abovementioned changes were blocked by two different selective cathepsin S inhibitors, LY3000328 or MIV-247. Moreover, Kaplan-Meier survival plot showed that cathepsin S inhibition improved 21-day survival rate following myocardial I/R injury. This study demonstrated that the inhibition of cathepsin S alleviated myocardial I/R-induced injury by suppressing inflammation and apoptosis, which may be used in clinical applications of cardioprotection.

Prognostic value of plasma HMGB1 in ischemic stroke patients with cerebral ischemia-reperfusion injury after intravenous thrombolysis

BACKGROUND

To investigate the value of plasma high mobility group box protein 1 (HMGB1) in evaluating the prognosis of cerebral ischemia-reperfusion injury (CIRI) in ischemic stroke patients.

METHODS

132 ischemic stroke patients were recruited. Before and after thrombolytic therapy at 2 h, 6 h, 12 h, 24 h, and 36 h, the Glasgow Coma Scale (GCS) and National Institutes of Health Stroke Scale (NIHSS) were recorded. The Modified Rankin scale (mRS) was used to assess the prognosis at 3 months.

RESULTS

The NIHSS score, GCS score and plasma HMGB1 level peaked at 6 h after thrombolytic therapy, and plasma HMGB1 level was positively correlated with infarct volume and NIHSS score, and negatively correlated with GCS score. Plasma HMGB1 level at 6 h had the highest value in identifying patients with poor unfavorable functional outcome after 3 months, with a sensitivity of 86.8% and a specificity of 74.0%. Logistic regression results showed that plasma HMGB1 had a strong association with unfavorable functional outcome [odds ratio (OR) =1.621, P<0.001]. After adjusting for infarct volume and NIHSS score did not attenuate the association (OR=1.381, P=0.005). Finally, we found that plasma HMGB1 at 6 h had the highest value in identifying patients with non-survival after 3 months (χ²=28.655, P<0.001). Logistic regression results showed that plasma HMGB1 had a strong association with non-survival (OR=2.315, P<0.001). After adjusting for infarct volume and NIHSS score did not attenuate the association (OR=2.013, P<0.001).

CONCLUSION

Plasma HMGB1 exerts a good predictive value for CIRI in ischemic stroke patients, and its increased expression is correlated with worse prognosis.

Comparison of Cardioprotective Effects of Propofol versus Sevoflurane in Pediatric Living Donor Liver Transplantation

Background

Our study compared the myocardiac protective effect of propofol vs. sevoflurane in pediatric patients receiving living donor liver transplantation (LDLT) surgery.

Material/Methods

We randomly and equally divided 120 children who underwent LDLT into a sevoflurane group and a propofol group. Preoperative, intraoperative, and postoperative data were collected and compared between the 2 groups. The concentrations of cTnI, CK-MB, IL-6, TNF-α, and HMGB1 at 5 min after induction (T0), 30 min in the anhepatic period (T1), and 3 h after reperfusion (T2), and at the end of surgery (T3) were measured.

Results

There was no statistically significant difference in the characteristics of children in the 2 groups. Compared with T0, the levels of IL-6 and TNF-α at T1, T2, and T3 were higher, while the HMGB1 at T2 and T3 were higher (P<0.05). A similar trend for IL-6, TNF-α, and HMGB1 at different time points in the 2 groups was observed. Compared with T0, the cTnI and CK-MB at T2 and T3 were significantly higher (P<0.05), but there was no significant difference at different time points in the 2 groups. For the adverse events, there was no significant difference between the 2 groups.

Conclusions

Our study shows that the cardioprotective effect in pediatric patients undergoing living donor liver transplantation is similar with propofol and sevoflurane anesthesia.

Dexmedetomidine pretreatment protects the heart against apoptosis in ischemia/reperfusion injury in diabetic rats by activating PI3K/Akt signaling in vivo and in vitro

Dexmedetomidine (DEX) exerts cardioprotection against ischemia/reperfusion injury. However, the precise mechanisms underlying this cardioprotective effect in diabetic rats are still not fully understood. The aim of the present study was to investigate the cardioprotective mechanism of DEX pretreatment on myocardial ischemia/reperfusion (I/R) injury in diabetic rats. A total of 25 streptozotocin-induced diabetic rats were equally randomized into five groups: i) Sham, ii) DEX (100 μg/kg); iii) myocardial I/R; iv) myocardial I/R+DEX (10 μg/kg); and v) myocardial I/R+DEX (100 μg/kg) groups. Primary cardiomyocytes were cultured in DEX for 1 h, and then oxygen and glucose deprivation (OGD)/R for 36 h. These results showed that pretreatment with DEX significantly decreased the I/R-induced size of the myocardial infarction, structural damage, morphological changes and apoptosis in myocardial cells, as well as levels of creatinine kinase, malondialdehyde and cardiac troponin I, and increased the I/R-induced superoxide dismutase activity in vivo and in vitro. Furthermore, immunohistochemical staining and western blot analysis revealed that DEX pretreatment significantly increased the I/R-induced expression levels of B-cell lymphoma 2 (Bcl-2), phosphorylated phosphoinositide 3-kinase (pPI3K) and pAkt, and significantly decreased those of pBcl-2 associated agonist of cell death, Bcl-2-associated X protein and cleaved caspase 3 in vivo and in vitro. In addition, all of these cardioprotective effects of DEX were reversed by yohimbine and LY294002 pretreatment. These results suggested that DEX pretreatment may activate the PI3K/Akt signaling pathway in an α₂ adrenoceptor-dependent manner. DEX pretreatment may exert cardioprotective effects against myocardial ischemia/reperfusion injury in diabetic rats through the I/R-induced inhibition of cell apoptosis by activating the PI3K/Akt signaling pathway.

The Effects of Dexmedetomidine in a Rat Model of Sepsis-Induced Lung Injury are Mediated Through the Adenosine Monophosphate-Activated Protein Kinase (AMPK)/Silent Information Regulator 1 (SIRT1) Pathway

BACKGROUND This study aimed to investigate the effects of dexmedetomidine in a rat model of sepsis-induced lung injury and the role of the adenosine monophosphate-activated protein kinase (AMPK) gene and silent information regulator 1 (SIRT1) gene signaling pathway. MATERIAL AND METHODS Sixty 28-week-old healthy male Sprague-Dawley rats were randomly divided into three groups, the sham group, the model group, and the dexmedetomidine-treated group. The rat model of sepsis-induced lung injury was developed by surgical cecal ligation and puncture. Lung tissues examined histologically in the three study groups. Cell apoptosis was measured using the TUNEL assay, and the expression of inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1ß (IL-1ß), and IL-10 were measured in rat lung tissue by enzyme-linked immunosorbent assay (ELISA). Apoptosis-associated proteins and AMPK/SIRT1 pathway-associated protein expression levels were detected using Western blot. RESULTS Dexmedetomidine significantly increased the survival rate and reduced the body temperature of rats in the model group with sepsis-induced lung injury, reduced lung injury, significantly reduced apoptosis in lung tissues, and reduced the expression levels of TNF-alpha, and IL-1ß, and increased the levels of IL-10. Dexmedetomidine significantly reduced the expression of caspase-3 in the rat lung tissue (P<0.01), and significantly increased the expression of Bcl-2/Bax and the phosphorylation levels of AMPK, SIRT1, nuclear factor-kappaB (NF-kappaB), and forkhead box class O 3a (FOXO3a). CONCLUSIONS In a rat model of sepsis-induced lung injury, dexmedetomidine reduced lung damage by activating the AMPK/SIRT1 signaling pathway and reduced the expression of inflammatory cytokines and cell apoptosis.

Dexmedetomidine alleviates insulin resistance in hepatocytes by reducing endoplasmic reticulum stress

PURPOSE

Dexmedetomidine (DEX) stabilizes intraoperative blood glucose levels and reduces insulin resistance (IR), a common perioperative complication. However, the molecular mechanisms underlying these effects remain unclear. Since endoplasmic reticulum stress (ERS) is a mechanism of IR, this study sought to examine whether DEX can effectively alleviate IR by reducing ERS.

METHODS

HepG2 and LO2 cells were treated with different concentrations of insulin. The glucose content assay and Cell Counting Kit-8 (CCK-8) were then employed to determine the optimal insulin concentration capable of inducing IR without affecting cell viability. Insulin-resistant hepatocytes were cultured with different concentrations of DEX for 24 h, and the glucose concentration in the supernatant was measured. ERS was assessed by qPCR and western blotting. The latter was also used to quantify the expression of phosphorylated protein kinase B (p-AKT), phosphoenolpyruvate carboxykinase (PEPCK), and glucose 6 phosphatase (G6Pase), which are key proteins involved in the action of insulin.

RESULTS

After 48-h of culturing with 10 μg/mL insulin, glucose consumption in hepatocytes was found to be reduced. IR hepatocytes cultured with 10, 100, or 1000 ng/ml DEX for 24 h showed a concentration-dependent increase in glucose consumption. Elevated mRNA and protein levels of ERS markers binding immunoglobulin protein (BIP) and ER protein 29 (ERp29), were reversed by DEX treatment. Moreover, reduced p-AKT and increased PEPCK and G6Pase protein levels in IR hepatocytes were also restored following DEX treatment.

CONCLUSION

DEX may alleviate IR in hepatocytes by reducing ERS serving to restore insulin action via the IRS-1/PI3K/AKT pathway.

Salvianolic acid B protects against myocardial ischaemia-reperfusion injury in rats via inhibiting high mobility group box 1 protein expression through the PI3K/Akt signalling pathway

Salvianolic acid B (Sal B) has a significant protective effect on myocardial ischaemia-reperfusion (I/R) injury. Therefore, the aims of this study were to determine the effects of Sal B on myocardial ischaemic-reperfusion (I/R) injury in rats and to explore whether its underlying mechanism of cardioprotection occurs through activating the expression of the phosphoinositide 3-kinase/protein, kinase B (PI3K/Akt) and inhibiting the expression of high mobility group protein 1 (HMGB1). Ninety Sprague-Dawley rats were randomized into five groups: group 1 (sham-operated), group 2 (myocardial I/R), group 3 (low dose of Sal B+I/R), group 4 (high dose of Sal B+I/R), and group 5 (high dose of Sal B+I/R+LY294002, which is a specific PI3k inhibitor). All I/R rats received 30 min myocardial ischaemia followed by 24-h reperfusion. Cardiac function, infarct size, myocardial injury marker levels, inflammatory response and cardiomyocyte apoptosis as well as Bcl-2, Bax, P-Akt, HMGB1 and TLR4 expression were measured. In the current study, Sal B significantly ameliorated myocardial I/R injury in a dose-dependent manner, ameliorated cardiac function, reduced myocardial infarction size, decreased myocardial injury marker expression, decreased inflammatory responses, reduced apoptosis, activated PI3K/Akt expression and inhibited HMGB1 expression. However, all effects of Sal B were significantly reversed by LY294002. Overall, the present study indicated that Sal B attenuated myocardial I/R injury by activating PI3K/Akt and inhibiting the release of HMGB1 in rats.

Current translational potential and underlying molecular mechanisms of necroptosis

Cell death has a fundamental impact on the evolution of degenerative disorders, autoimmune processes, inflammatory diseases, tumor formation and immune surveillance. Over the past couple of decades extensive studies have uncovered novel cell death pathways, which are independent of apoptosis. Among these is necroptosis, a tightly regulated, inflammatory form of cell death. Necroptosis contribute to the pathogenesis of many diseases and in this review, we will focus exclusively on necroptosis in humans. Necroptosis is considered a backup mechanism of apoptosis, but the in vivo appearance of necroptosis indicates that both caspase-mediated and caspase-independent mechanisms control necroptosis. Necroptosis is regulated on multiple levels, from the transcription, to the stability and posttranslational modifications of the necrosome components, to the availability of molecular interaction partners and the localization of receptor-interacting serine/threonine-protein kinase 1 (RIPK1), receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL). Accordingly, we classified the role of more than seventy molecules in necroptotic signaling based on consistent in vitro or in vivo evidence to understand the molecular background of necroptosis and to find opportunities where regulating the intensity and the modality of cell death could be exploited in clinical interventions. Necroptosis specific inhibitors are under development, but >20 drugs, already used in the treatment of various diseases, have the potential to regulate necroptosis. By listing necroptosis-modulated human diseases and cataloging the currently available drug-repertoire to modify necroptosis intensity, we hope to kick-start approaches with immediate translational potential. We also indicate where necroptosis regulating capacity should be considered in the current applications of these drugs.

Johnny on the Spot-Chronic Inflammation Is Driven by HMGB1

Although much has been made of the role of HMGB1 acting as an acute damage associated molecular pattern (DAMP) molecule, prompting the response to tissue damage or injury, it is also released at sites of chronic inflammation including sites of infection, autoimmunity, and cancer. As such, the biology is distinguished from homeostasis and acute inflammation by the recruitment and persistence of myeloid derived suppressor cells, T regulatory cells, fibrosis and/or exuberant angiogenesis depending on the antecedents and the other individual inflammatory partners that HMGB1 binds and focuses, including IL-1β, CXCL12/SDF1, LPS, DNA, RNA, and sRAGE. High levels of HMGB1 released into the extracellular milieu and its persistence in the microenvironment can contribute to the pathogenesis of many if not all autoimmune disorders and is a key factor that drives inflammation further and worsens symptoms. HMGB1 is also pivotal in the maintenance of chronic inflammation and a “wound healing” type of immune response that ultimately contributes to the onset of carcinogenesis and tumor progression. Exosomes carrying HMGB1 and other instructive molecules are released and shape the response of various cells in the chronic inflammatory environment. Understanding the defining roles of REDOX, DAMPs and PAMPs, and the host response in chronic inflammation requires an alternative means for positing HMGB1's central role in limiting and focusing inflammation, distinguishing chronic from acute inflammation.