Targeted temperature management at 33°C or 36℃ induces equivalent myocardial protection by inhibiting HMGB1 release in myocardial ischemia/reperfusion injury

NRIP1 is a downstream target of YY1 in promoting OGD/R-induced H9c2 cardiomyocyte injury and mitochondrial dysfunction

BACKGROUND AND OBJECTIVE

From a clinical standpoint, myocardial ischemia/reperfusion injury (MIRI) has always been an enormous challenge for the treatment of acute myocardial infarction (AMI). Molecular targeting therapy may help overcome this challenge. The present work aimed to elucidate the possible involvement of Yin-Yang 1 (YY1)/nuclear receptor-interacting protein 1 (NRIP1) and discover the molecular mechanism of MIRI.

METHODS

Herein, a cardiomyocyte ischemia/reperfusion (I/R) model was established via oxygen-glucose deprivation/re-oxygenation (OGD/R) damage in H9c2 cardiomyocytes. Reverse transcription-quantitative PCR and western blotting were conducted to measure the levels of YY1 and NRIP1 at the RNA and protein levels, respectively. H9c2 cell viability and apoptosis were assayed using the Cell Counting Kit-8, flow cytometry, and western blotting. In addition, superoxide dismutase, glutathione peroxidase, and malondialdehyde levels were analyzed as markers of oxidative stress. Additionally, mitochondrial membrane potential, which was measured via JC-1 staining, ATP content, Complex I activity, mitochondrial DNA copy number, and mitochondrial permeability transition pore (mPTP) opening rate were analyzed to evaluate mitochondrial activity. Moreover, luciferase reporter and chromatin immunoprecipitation assays experimentally validated the predicted affinity of YY1 with the NRIP1 promoter according to the HumanTFDB online tool.

RESULTS

YY1/NRIP1 were both highly expressed in OGD/R-injured H9c2 cardiomyocytes. Downregulation of NRIP1 improved cell viability, whereas it inhibited cell apoptosis and oxidative stress, and suppressed mitochondrial dysfunction in OGD/R-injured H9c2 cardiomyocytes. Importantly, it was verified that YY1 could bind to the NRIP1 promoter to positively regulate NRIP1 expression. The protective effects of NRIP1 knockdown against cardiomyocyte damage and mitochondrial dysfunction in OGD/R-injured H9c2 cardiomyocytes were partly abolished through overexpression of YY1.

CONCLUSION

NRIP1 emerged as a downstream target of YY1 in promoting OGD/R-induced H9c2 cardiomyocyte injury and mitochondrial dysfunction, providing novel ideas for targeted treatments to alleviate MIRI.

TARGETED TEMPERATURE MANAGEMENT AT 36°C IMPROVES SURVIVAL AND PROTECTS TISSUES BY MITIGATING THE DELETERIOUS INFLAMMATORY RESPONSE FOLLOWING HEMORRHAGIC SHOCK

ABSTRACT

Hemorrhagic shock (HS) is a life-threatening condition with high mortality rates despite current treatments. This study investigated whether targeted temperature management (TTM) could improve outcomes by modulating inflammation and protecting organs following HS. Using a rat model of HS, TTM was applied at 33°C and 36°C after fluid resuscitation. Surprisingly, TTM at 33°C increased mortality, while TTM at 36°C significantly improved survival rates. It also reduced histological damage in lung and kidney tissues, lowered serum lactate levels, and protected against apoptosis and excessive reactive oxygen species production. TTM at 36°C inhibited the release of high mobility group box 1 protein (HMGB1), a key mediator of inflammation, and decreased proinflammatory cytokine levels in the kidneys and lungs. Moreover, it influenced macrophage behavior, suppressing the harmful M1 phenotype while promoting the beneficial M2 polarization. Cytokine array analysis confirmed reduced levels of proinflammatory cytokines with TTM at 36°C. These results collectively highlight the potential of TTM at 36°C as a therapeutic approach to improve outcomes in HS. By addressing multiple aspects of injury and inflammation, including modulation of macrophage responses and cytokine profiles, TTM at 36°C offers promising implications for critical care management after HS, potentially reducing mortality and improving patient recovery.

Differences in Outcome of Patients with Cardiogenic Shock Associated with In-Hospital or Out-of-Hospital Cardiac Arrest

Cardiogenic Shock (CS) complicated by in-hospital (IHCA) or out-of-hospital cardiac arrest (OHCA) has a poor outcome. However, studies regarding the prognostic differences between IHCA and OHCA in CS are limited. In this prospective, observational study, consecutive patients with CS were included in a monocentric registry from June 2019 to May 2021. The prognostic impact of IHCA and OHCA on 30-day all-cause mortality was tested within the entire group and in the subgroups of patients with acute myocardial infarction (AMI) and coronary artery disease (CAD). Statistical analyses included univariable t-test, Spearman's correlation, Kaplan-Meier analyses, as well as uni- and multivariable Cox regression analyses. A total of 151 patients with CS and cardiac arrest were included. IHCA on ICU admission was associated with higher 30-day all-cause mortality compared to OHCA in univariable COX regression and Kaplan-Meier analyses. However, this association was solely driven by patients with AMI (77% vs. 63%; log rank p = 0.023), whereas IHCA was not associated with 30-day all-cause mortality in non-AMI patients (65% vs. 66%; log rank p = 0.780). This finding was confirmed in multivariable COX regression, in which IHCA was solely associated with higher 30-day all-cause mortality in patients with AMI (HR = 2.477; 95% CI 1.258-4.879; p = 0.009), whereas no significant association could be seen in the non-AMI group and in the subgroups of patients with and CAD. CS patients with IHCA showed significantly higher all-cause mortality at 30 days compared to patients with OHCA. This finding was primarily driven by a significant increase in all-cause mortality at 30 days in CS patients with AMI and IHCA, whereas no difference could be seen when differentiated by CAD.

HJ11 decoction restrains development of myocardial ischemia-reperfusion injury in rats by suppressing ACSL4-mediated ferroptosis

HJ11 is a novel traditional Chinese medicine developed from the appropriate addition and reduction of Si-Miao-Yong-An decoction, which has been commonly used to treat ischemia-reperfusion (I/R) injury in the clinical setting. However, the mechanism of action of HJ11 components remains unclear. Ferroptosis is a critical factor that promotes myocardial I/R injury, and the pathophysiological ferroptosis-mediated lipid peroxidation causes I/R injury. Therefore, this study explored whether HJ11 decoction ameliorates myocardial I/R injury by attenuating ACSL4-mediated ferroptosis. This study also explored the effect of ACSL4 expression on iron-dependent programmed cell death by preparing a rat model of myocardial I/R injury and oxygen glucose deprivation/reperfusion (OGD/R)-induced H9c2 cells. The results showed that HJ11 decoction improved cardiac function; attenuated I/R injury, apoptosis, oxidative stress, mitochondrial damage, and iron accumulation; and reduced infarct size in the myocardial I/R injury rat model. Additionally, HJ11 decoction suppressed the expression of ferroptosis-promoting proteins [Acyl-CoA synthetase long-chain family member 4 (ACSL4) and cyclooxygenase-2 (COX2)] but promoted the expression of ferroptosis-inhibiting proteins [ferritin heavy chain 1 (FTH1) and glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4)] in the myocardial tissues of the I/R injury rat model. Similar results were found with the OGD/R-induced H9c2 cells. Interestingly, ACSL4 knockdown attenuated iron accumulation, oxidative stress, and ferroptosis in the OGD/R-treated H9c2 cells. However, ACSL4 overexpression counteracted the inhibitory effect of the HJ11 decoction on OGD/R-triggered oxidative stress and ferroptosis in H9c2 cells. These findings suggest that HJ11 decoction restrained the development of myocardial I/R injury by regulating ACSL4-mediated ferroptosis. Thus, HJ11 decoction may be an effective medication to treat myocardial I/R injury.

Therapeutic hypothermia for stroke: Unique challenges at the bedside

Therapeutic hypothermia has shown promise as a means to improving neurological outcomes at several neurological conditions. At the clinical level, it has been shown to improve outcomes in comatose survivors of cardiac arrest and in neonatal hypoxic ischemic encephalopathy, but has yet to be convincingly demonstrated in stroke. While numerous preclinical studies have shown benefit in stroke models, translating this to the clinical level has proven challenging. Major obstacles include cooling patients with typical stroke who are awake and breathing spontaneously but often have significant comorbidities. Solutions around these problems include selective brain cooling and cooling to lesser depths or avoiding hyperthermia. This review will cover the mechanisms of protection by therapeutic hypothermia, as well as recent progress made in selective brain cooling and the neuroprotective effects of only slightly lowering brain temperature. Therapeutic hypothermia for stroke has been shown to be feasible, but has yet to be definitively proven effective. There is clearly much work to be undertaken in this area.

Recombinant Klotho Protein Ameliorates Myocardial Ischemia/Reperfusion Injury by Attenuating Sterile Inflammation

Currently, no effective therapy and potential target have been elucidated for preventing myocardial ischemia and reperfusion injury (I/R). We hypothesized that the administration of recombinant klotho (rKL) protein could attenuate the sterile inflammation in peri-infarct regions by inhibiting the extracellular release of high mobility group box-1 (HMGB1). This hypothesis was examined using a rat coronary artery ligation model. Rats were divided into sham, sham+ rKL, I/R, and I/R+ rKL groups (n = 5/group). Administration of rKL protein reduced infarct volume and attenuated extracellular release of HMGB1 from peri-infarct tissue after myocardial I/R injury. The administration of rKL protein inhibited the expression of pro-inflammatory cytokines in the peri-infarct regions and significantly attenuated apoptosis and production of intracellular reactive oxygen species by myocardial I/R injury. Klotho treatment significantly reduced the increase in the levels of circulating HMGB1 in blood at 4 h after myocardial ischemia. rKL regulated the levels of inflammation-related proteins. This is the first study to suggest that exogenous administration of rKL exerts myocardial protection effects after I/R injury and provides new mechanistic insights into rKL that can provide the theoretical basis for clinical application of new adjunctive modality for critical care of acute myocardial infarction.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses