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

Ozone-mediated cerebral protection: Unraveling the mechanism through ferroptosis and the NRF2/SLC7A11/GPX4 signaling pathway

BACKGROUND

The pathogenesis of brain ischemic/reperfusion (I/R) insult is characterized by neuronal loss due to excessive oxidative stress responses. Ferroptosis, a form of oxidative cell death, can be triggered when the balance between antioxidants and pro-oxidants in cells is disrupted. Ozone, a natural bioactive molecule with antioxidant/anti-apoptotic and pro-autophagic properties, has been shown to enhance the antioxidant system's capacity and ameliorate oxidative stress. However, its role in neuronal ferroptosis remains unclear. Therefore, we investigated the functions and possible mechanisms of ozone in cerebral I/R-induced ferroptotic neuronal death.

METHODS

A cerebral ischemia-reperfusion injury model was induced in Sprague-Dawley (SD) rats pre-treated with ozone. Intraperitoneal administration of the NRF2 inhibitor ML385, the SLC7A11 inhibitor Erastin, and the GPX4 inhibitor RSL3 was performed one hour prior to model establishment.

RESULTS

Our results showed that ozone preconditioning mitigated neuronal damage caused by cerebral I/R, reduced the severity of neurological deficits, lowered cerebral infarct volume in middle cerebral artery occlusion (MCAO) rats, and decreased the volume of cerebral infarcts. Transmission electron microscopy, immunofluorescence, and Western blotting indicated ferroptosis following MCAO-induced brain damage. MCAO resulted in morphological damage to neuronal mitochondria, increased lipid peroxidation accumulation, and elevated malondialdehyde (MDA) production. Furthermore, MCAO decreased levels of FTH1 and GPX4 (negative regulators of ferroptosis) and increased ACSL4 levels (a positive regulator of ferroptosis). Ozone preconditioning demonstrated a neuroprotective effect by increasing NRF2 nuclear translocation and the expression of SLC7A11 and GPX4. Treatment with ML385, Erastin, and RSL3 significantly reversed ozone preconditioning's protective effect on neuronal ferroptosis.

CONCLUSION

Our findings demonstrated that ozone treatment attenuates ferroptosis in a cerebral ischemia/reperfusion injury rat model via the NRF2/SLC7A11/GPX4 pathway, providing a theoretical basis for ozone's potential use as a therapy to prevent ischemic stroke.

Ozone pretreatment alleviates ischemiareperfusion injury-induced myocardial ferroptosis by activating the Nrf2/Slc7a11/Gpx4 axis

Myocardial ischemiareperfusion injury (MIRI) is defined as the additional damage that occurs during the process of restoring blood flow to the heart tissue after ischemia-induced damage. Ozone is a powerful oxidizer, but low concentrations of ozone can protect various organs from oxidative stress. Some studies have demonstrated a link between ozone and myocardioprotection, but the mechanism remains unclear. To establish an in vivo animal model of ischemiareperfusion injury (I/R), this study utilized C57 mice, while an in vitro model of hypoxia-reoxygenation (H/R) injury was developed using H9c2 cardiomyocytes to simulate ischemiareperfusion injury. Ozone pretreatment was used in in vitro and in vivo experiments. Through this research, we found that ozone therapy can reduce myocardial injury, and further studies found that ozone regulates the expression levels of these ferroptosis-related proteins and transcription factors in the H/R model, which were screened by bioinformatics. In particular, nuclear translocation of Nrf2 was enhanced by pretreatment with ozone, inhibited ferroptosis and ameliorated oxidative stress by initiating the expression of Slc7a11 and Gpx4. Significantly, Nrf2 gene silencing reverses the protective effects of ozone in the H/R model. In summary, our results suggest that ozone protects the myocardium from I/R damage through the Nrf2/Slc7a11/Gpx4 signaling pathway, highlighting the potential of ozone as a new coronary artery disease therapy.

L-ascorbic acid could ameliorate the damage of myocardial microvascular endothelial cell caused by hypoxia-reoxygenation via targeting HMGB1

In this study, we intend to explore the potential function of l-ascorbic acid in hypoxia-reoxygenation (H/R)-induced damage of CMECs and its related molecular mechanism. With different concentrations of l-ascorbic acid treatment, the proliferation, migration, inflammation and autophagy of cardiac microvascular endothelial cells (CMECs) were determined by several biological experiments. Si-HMGB1 transfection was used to reduce HMGB1 expression and to detect the function of HMGB1 in H/R-induced damage of CMECs. Under H/R condition, the proliferation and migration abilities of CMECs were reduced, and the inflammation and autophagy of CMECs were increased. Whereas, after l-ascorbic acid treatment, the reduction in the proliferation and migration of CMECs, as well as the increase in the inflammation and autophagy of CMECs induced by H/R were reversely altered. HMGB1 was confirmed as a specific target of l-ascorbic acid, and si-HMGB1 treatment strengthened the beneficial effect of l-ascorbic acid on H/R-induced damage of CMECs, followed by further reduction in the proliferation and migration abilities of CMECs, as well as the increase in the inflammation and autophagy of CMECs. Few studies have reported the function of l-ascorbic acid in myocardial ischemia on CMECs, but our experimental data showed that l-ascorbic acid treatment could ameliorate the H/R-induced damage of CMECs by regulating HMGB1 expression.

Asiaticoside attenuates oxygen-glucose deprivation/reoxygenation-caused injury of cardiomyocytes by inhibiting autophagy

Asiaticoside is a natural triterpene compound derived from Centella asiatica, possessing confirmed cardioprotective property. However, the roles of asiaticoside in regulating oxygen-glucose deprivation/reoxygenation (OGD/R)-caused cardiomyocyte dysfunction remain largely obscure. Human cardiomyocyte AC16 cells were stimulated with OGD/R to mimic myocardial ischemia/reperfusion injury and treated with asiaticoside. Cytotoxicity was investigated by CCK-8 assay and lactate dehydrogenase (LDH) release analysis. Autophagy- and Wnt/β-catenin signaling-related protein levels were measured via western blotting. Asiaticoside (0-20 μM) did not induce cardiomyocyte cytotoxicity. Asiaticoside (20 μM) mitigated OGD/R-induced autophagy, cytotoxicity, oxidative stress, and myocardial injury. Rapamycin, an autophagy inductor, reversed the influences of asiaticoside on autophagy, cytotoxicity, oxidative stress, and myocardial injury, whereas 3-methyadanine, an autophagy inhibitor, played an opposite effect. Asiaticoside (20 μM) attenuated OGD/R-induced Wnt/β-catenin signaling inactivation, which was reversed after transfection with si-β-catenin. Transfection with si-β-catenin attenuated the influences of asiaticoside on autophagy, cytotoxicity, oxidative stress, and myocardial injury. In conclusion, asiaticoside protected against OGD/R-induced cardiomyocyte cytotoxicity, oxidative stress, and myocardial injury via blunting autophagy through activating the Wnt/β-catenin signaling, indicating the therapeutic potential of asiaticoside in myocardial ischemia/reperfusion injury.

Activation of Delta-Opioid Receptor Protects ARPE19 Cells against Oxygen-Glucose Deprivation/Reoxygenation-Induced Necroptosis and Apoptosis by Inhibiting the Release of TNF-α

PURPOSE

Retinal ischemia-reperfusion injury (RIRI) is the basis of the pathology that leads to many retinal diseases and induces necroptosis and apoptosis. Tumor necrosis factor-α (TNF-α) is critically involved in necroptosis and apoptosis. Delta-opioid receptor (DOR) activation inhibits TNF-α release in our previous studies, it might prevent necroptosis and apoptosis by inhibiting the release of TNF-α. However, the role of TNF-α and DOR in necroptosis and apoptosis of retinal pigment epithelial (RPE) cells remains largely unknown. Here, we explored the mechanisms of TNF-α and DOR in necroptosis and apoptosis using an oxygen-glucose deprivation/reoxygenation (OGD/R) model of adult retinal pigment epithelial cell line-19 (ARPE19) cells.

MATERIALS AND METHODS

ARPE19 cells were exposed to OGD/R conditions to mimic RIRI in vitro. Cell viability was quantified using the Cell Counting Kit-8 (CCK-8) assay. Morphological changes were observed by inverted microscopy. TNF-α protein levels in cell lysates were measured by enzyme-linked immunosorbent assay (ELISA). The DOR agonist TAN-67 and antagonist naltrindole (NTI) were used to pretreat cells for 1 or 2 hours before OGD24/R36 administration. Calcein acetoxymethylester/propidium iodide (Calcein-AM/PI) and Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining were used to detect necroptotic and apoptotic ARPE19 cells, respectively. The protein expression of DOR, p-RIP1 (RIP1), p-RIP3 (RIP3), p-MLKL (MLKL), and cleaved Caspase3 (Caspase3) was measured by western blotting.

RESULTS

OGD severely damaged ARPE19 cells. Prolonged reoxygenation significantly increased TNF-α level and decreased DOR expression in ARPE19 cells. Pretreatment with the DOR agonist TAN-67 (10 µM) significantly improved ARPE19 cell viability after OGD24/R36 by reducing the number of necroptotic and apoptotic cells. Furthermore, DOR activation significantly inhibited TNF-α release and suppressed the expression of proteins related to necroptosis and apoptosis, including p-RIP1, p-RIP3, p-MLKL, and cleaved Caspase3, after OGD24/R36. This effect was reversed by the DOR antagonist NTI.

CONCLUSION

These results strongly suggest that DOR activation inhibits necroptosis and apoptosis by decreasing TNF-α release, leading to the prevention of OGD/R-induced injury in ARPE19 cells. This study provides an innovative idea for clinical treatment strategies for retinal damage and vision loss due to RIRI.