BAICALEIN RELIEVES BRAIN INJURY VIA INHIBITING FERROPTOSIS AND ENDOPLASMIC RETICULUM STRESS IN A RAT MODEL OF CARDIAC ARREST

Ruthenium red alleviates post-resuscitation myocardial dysfunction by upregulating mitophagy through inhibition of USP33 in a cardiac arrest rat model

Cardiac arrest (CA) remains a leading cause of death, with suboptimal survival rates despite efforts involving cardiopulmonary resuscitation and advanced life-support technology. Post-resuscitation myocardial dysfunction (PRMD) is an important determinant of patient outcomes. Myocardial ischemia/reperfusion injury underlies this dysfunction. Previous reports have shown that ruthenium red (RR) has a protective effect against cardiac ischemia-reperfusion injury; however, its precise mechanism of action in PRMD remains unclear. This study investigated the effects of RR on PRMD and analyzed its underlying mechanisms. Ventricular fibrillation was induced in rats, which were then subjected to cardiopulmonary resuscitation to establish an experimental CA model. At the onset of return of spontaneous circulation, RR (2.5 mg/kg) was administered intraperitoneally. Our study showed that RR improved myocardial function and reduced the production of oxidative stress markers such as malondialdehyde (MDA), glutathione peroxidase (GSSG), and reactive oxygen species (ROS) production. RR also helped maintain mitochondrial structure and increased ATP and GTP levels. Additionally, RR effectively attenuated myocardial apoptosis. Furthermore, we observed downregulation of proteins closely related to mitophagy, including ubiquitin-specific protease 33 (USP33) and P62, whereas LC3B (microtubule-associated protein light chain 3B) was upregulated. The upregulation of mitophagy may play a critical role in reducing myocardial injury. These results demonstrate that RR may attenuate PRMD by promoting mitophagy through the inhibition of USP33. These effects are likely mediated through diverse mechanisms, including antioxidant activity, apoptosis suppression, and preservation of mitochondrial integrity and energy metabolism. Consequently, RR has emerged as a promising therapeutic approach for addressing post-resuscitation myocardial dysfunction.

COMBINATION OF HYPEROXYGENATION AND TARGETED TEMPERATURE MANAGEMENT IMPROVES FUNCTIONAL OUTCOMES OF POST CARDIAC ARREST SYNDROME IRRESPECTIVE OF CAUSES OF ARREST IN RATS

ABSTRACT

Background: The high mortality rates of patients who are resuscitated from cardiac arrest (CA) are attributed to post cardiac arrest syndrome (PCAS). This study evaluated the effect of hyperoxygenation and targeted temperature management (TTM) on PCAS in rats with different causes of CA. Methods and Results: One hundred sixty-eight Sprague-Dawley rats were equally divided into asphyxial and dysrhythmic groups. Animals were further randomized into four subgroups immediately after resuscitation: normoxia-normothermia (NO-NT), ventilated with 21% oxygen under normothermia; hyperoxia-normothermia (HO-NT), ventilated with 100% oxygen for 3 hours under normothermia; normoxia-hypothermia (NO-HT), ventilated with 21% oxygen for 3 hours under hypothermia; and hyperoxia-hypothermia (HO-HT), ventilated with 100% oxygen for 3 hours under hypothermia. Post resuscitation cardiac dysfunction, neurological recovery, and pathological analysis were assessed. For asphyxial CA, HO-NT and HO-HT (68.8% and 75.0%) had significantly higher survival than NO-NT and NO-HT (31.3% and 31.3%). For dysrhythmic CA, NO-HT and HO-HT (81.3% and 87.5%) had significantly higher survival than NO-NT and HO-NT (44.0% and 50.0%). When all of the rats were considered, the survival rate was much higher in HO-HT (81.3%). Compared with NO-NT (57.7% ± 14.9% and 40.3% ± 7.8%), the collagen volume fraction and the proportion of fluoro-jade B-positive area in HO-HT (14.0% ± 5.7% and 28.0% ± 13.3%) were significantly reduced. Conclusion: The beneficial effects of hyperoxygenation and TTM are dependent on the cause of arrest: hyperoxygenation benefits asphyxial, whereas TTM benefits dysrhythmic CA. The combination of hyperoxygenation and TTM could effectively improve the functional outcome of PCAS regardless of the cause of CA.

Levosimendan and Dobutamin Attenuate LPS-Induced Inflammation in Microglia by Inhibiting the NF-κB Pathway and NLRP3 Inflammasome Activation via Nrf2/HO-1 Signalling

Hypovolemic shock is a circulatory failure, due to a loss in the effective circulating blood volume, that causes tissue hypoperfusion and hypoxia. This condition stimulates reactive oxygen species (ROS) and pro-inflammatory cytokine production in different organs and also in the central nervous system (CNS). Levosimendan, a cardioprotective inodilator, and dobutamine, a β1-adrenergic agonist, are commonly used for the treatment of hypovolemic shock, thanks to their anti-inflammatory and antioxidant effects. For this reason, we aimed at investigating levosimendan and dobutamine's neuroprotective effects in an "in vitro" model of lipopolysaccharide (LPS)-induced neuroinflammation. Human microglial cells (HMC3) were challenged with LPS (0.1 µg/mL) to induce an inflammatory phenotype and then treated with levosimendan (10 µM) or dobutamine (50 µM) for 24 h. Levosimendan and dobutamine significantly reduced the ROS levels and markedly increased Nrf2 and HO-1 protein expression in LPS-challenged cells. Levosimendan and dobutamine also decreased p-NF-κB expression and turned off the NLRP3 inflammasome together with its downstream signals, caspase-1 and IL-1β. Moreover, a reduction in TNF-α and IL-6 expression and an increase in IL-10 levels in LPS-stimulated HMC3 cells was observed following treatment. In conclusion, levosimendan and dobutamine attenuated LPS-induced neuroinflammation through NF-κB pathway inhibition and NLRP3 inflammasome activation via Nrf2/HO-1 signalling, suggesting that these drugs could represent a promising therapeutic approach for the treatment of neuroinflammation consequent to hypovolemic shock.

REMIMAZOLAM IMPROVES THE MARKERS OF POSTRESUSCITATION CEREBRAL INJURY IN A SWINE MODEL OF CARDIAC ARREST

ABSTRACT

Introduction: Previous studies have manifested that those sedatives acting on γ-aminobutyric acid A (GABAa) receptor could produce effective brain protection against regional and global ischemic stimulation. The present study was designed to investigate the effect of a novel GABAa receptor agonist, remimazolam postconditioning (RP) on cerebral outcome after global ischemic stimulation induced by cardiac arrest and resuscitation in swine. Methods: A total of 24 swine were used in this study, in which the animals were randomly divided into the following three groups: sham group (n = 6), cardiopulmonary resuscitation (CPR) group (n = 9), and CPR + RP group (n = 9). The experimental model was established by the procedure of 10 min of cardiac arrest and 5 min of CPR. Those resuscitated swine in the CPR + RP group received an intravenous infusion of 2.5 mg/kg of remimazolam within 60 min. Postresuscitation cerebral injury biomarkers and neurological function were evaluated for a total of 24 h. At 24 h after resuscitation, brain cortex was harvested to evaluate the severity of pathologic damage, including tissue inflammation, oxidative stress, apoptosis, and necroptosis. Results: Baseline characteristics and CPR outcomes were not significantly different between the CPR and CPR + RP groups. After resuscitation, significantly greater cerebral injury and neurological dysfunction were observed in the CPR and CPR + RP groups than in the sham group. However, remimazolam postconditioning significantly alleviated cerebral injury and improved neurological dysfunction after resuscitation when compared with the CPR group. At 24 h after resuscitation, tissue inflammation, oxidative stress, and cell apoptosis and necroptosis were significantly increased in the CPR and CPR + RP groups when compared with the sham group. Nevertheless, the severity of pathologic damage mentioned previously were significantly milder in those swine treated with the remimazolam when compared with the CPR group. Conclusions: In a swine model of cardiac arrest and resuscitation, the remimazolam administered after resuscitation significantly improved the markers of postresuscitation cerebral injury and therefore protected the brain against global ischemic stimulation.

A New Perspective in the Treatment of Ischemic Stroke: Ferroptosis

Ischemic stroke is a common neurological disease. Currently, there are no Food and Drug Administration-approved drugs that can maximize the improvement in ischemic stroke-induced nerve damage. Hence, treating ischemic stroke remains a clinical challenge. Ferroptosis has been increasingly studied in recent years, and it is closely related to the pathophysiological process of ischemic stroke. Iron overload, reactive oxygen species accumulation, lipid peroxidation, and glutamate accumulation associated with ferroptosis are all present in ischemic stroke. This article focuses on describing the relationship between ferroptosis and ischemic stroke and summarizes the relevant substances that ameliorate ischemic stroke-induced neurological damage by inhibiting ferroptosis. Finally, the problems in the treatment of ischemic stroke targeting ferroptosis are discussed, hoping to provide a new direction for its treatment.

Baicalein ameliorates polymyxin B-induced acute renal injury by inhibiting ferroptosis via regulation of SIRT1/p53 acetylation

The polypeptide antibiotic Polymyxin B (PMB) can cause acute kidney injury (AKI), we found that ferroptosis is one of the main mechanisms of renal injury caused by PMB. It was reported that baicalein can inhibit ferroptosis. Therefore, in this study we examined whether baicalein could attenuate PMB-induced renal injury by inhibiting ferroptosis. We confirmed that baicalein could reduce PMB-induced renal injury in vivo and in vitro studies. In the in vitro study, baicalein significantly increased the survival rate of human HK2 tubular epithelial cells. The results of HE staining and electron microscopy in mice also showed that baicalein reduced PMB-induced renal injury, and significantly decreased the levels of BUN and Scr. By detecting ferroptosis-related indicators, we found that pre-incubation of baicalein in HK2 cells down-regulated Fe2+ level, lipid peroxidation, MDA and HO-1 which had been increased by PMB. Furthermore, baicalein up-regulated the levels of SCL7A11, GPX4 and GSH that were decreased by PMB. Moreover, intraperitoneal injection of baicalein in the animal model down-regulated kidney iron level, PTGS2 and 4HNE, and increased the GSH level, which suggested that baicalein could inhibit PMB-induced ferroptosis. Finally, by detecting changes in levels of p53 and p53 K382 acetylation, baicalein was observed to decrease elevated p53 K382 acetylation after PMB treatment, further confirming that baicalein inhibits ferroptosis by reducing p53 K382 acetylation via upregulation of SIRT1 expression. In conclusion, these results suggest that baicalein decreases p53 acetylation level by elevating SIRT1, which can then inhibit PMB-induced ferroptosis and ultimately attenuates AKI.