Myocardial Reactive Oxygen Species Research Articles

The contribution of SLC7A11-mediated ferroptosis to cardiac injury in iron overload cardiomyopathy: an in vitro study

Abstract Background Recent studies have indicated that iron overload can induce myocardial ferroptosis in iron overload cardiomyopathy (IOC), but the specific mechanisms, including the role of SLC7A11, remain unclear. Purpose By delving into the role of SLC7A11-mediated ferroptosis in IOC, this research endeavors to provide novel insights and therapeutic strategies for understanding and treating IOC. Methods To induce an in vitro model of IOC, wild-type rat cardiomyocytes (H9C2) were cultured in a ferric citrate (FAC) medium. Cardiomyocytes were exposed to various concentrations of iron overload (ranging from 0 mM to 2 mM) for durations of 4, 8, 12, and 24 hours. Cell viability at different FAC concentrations was assessed by the cell counting kit-8 (CCK8) assay and the level of the ferroptosis indicator malondialdehyde (MDA) was measured to determine the optimal concentration and duration of FAC treatment which was required to establish the IOC cell model. Next, ferroptosis indicators, including MDA, prostaglandin peroxide synthase 2 (PTGS2), and glutathione peroxidase 4 (GPX4), and the pivotal factor, SLC7A11 of IOC cardiomyocytes were evaluated. The protein and mRNA levels of SLC7A11 were assessed by molecular biology techniques. Additionally, the mitochondrial morphology of the IOC cardiomyocytes was meticulously examined by transmission electron microscopy (TEM). Flow cytometry was employed for detecting reactive oxygen species (ROS) levels. Furthermore, we elucidated the underlying mechanism of myocardial injury in IOC by overexpressing SLC7A11 and subsequently detecting changes in ferroptosis markers. Results CCK-8 results showed that the viability of cardiomyocytes exhibited dose-dependently with increasing FAC concentration (R2=0.5483, p<0.0001). Furthermore, the viability of cardiomyocytes remained relatively stable, with survival rates of approximately 50% and not decreasing below 50%. Additionally, the MDA content in IOC cardiomyocytes increased dose-dependently with the elevation of FAC concentration (R2=0.75, p<0.05), with a significant increase observed at 0.75mM. Expression levels of ferroptosis marker genes, GPX4 and PTGS2, both at the mRNA and protein levels, are indicative of diminished antioxidant capacity. Meanwhile, the level of myocardial MDA and ROS were markedly elevated, indicating underscoring increased oxidative stress within the IOC cardiomyocytes. Moreover, there was a downregulation in the expression of SLC7A11 mRNA and protein in IOC cardiomyocytes, suggesting a potential compensatory mechanism to counteract oxidative damage. TEM further elucidated cardiac mitochondrial injuries in IOC rats, including focal vacuolization, swelling, crest disruption, and even disappearance. Overexpression of SLC7A11 resulted in a significant augmentation of GPX4 and a reduction of PTGS2mRNA and protein expression levels. Conclusions Ferroptosis, mediated by SLC7A11, may represent a pivotal mechanism underlying myocardial injury in IOC.

Inhibition of Caspase-1-dependent pyroptosis alleviates myocardial ischemia/reperfusion injury during cardiopulmonary bypass (CPB) in type 2 diabetic rats

Cardiovascular complications pose a significant burden in type 2 diabetes mellitus (T2DM), driven by the intricate interplay of chronic hyperglycemia, insulin resistance, and lipid metabolism disturbances. Myocardial ischemia/reperfusion (MI/R) injury during cardiopulmonary bypass (CPB) exacerbates cardiac vulnerability. This study aims to probe the role of Caspase-1-dependent pyroptosis in global ischemia/reperfusion injury among T2DM rats undergoing CPB, elucidating the mechanisms underlying heightened myocardial injury in T2DM. This study established a rat model of T2DM and compared Mean arterial pressure (MAP), heart rate (HR), and hematocrit (Hct) between T2DM and normal rats. Myocardial cell morphology, infarction area, mitochondrial ROS and caspase-1 levels, NLRP3, pro-caspase-1, caspase-1 p10, GSDMD expressions, plasma CK-MB, cTnI, IL-1β, and IL-18 levels were assessed after reperfusion in both T2DM and normal rats. The role of Caspase-1-dependent pyroptosis in myocardial ischemia/reperfusion injury during CPB in T2DM rats was examined using the caspase-1 inhibitor VX-765 and the ROS scavenger NAC. T2DM rats demonstrated impaired glucose tolerance but stable hemodynamics during CPB, while showing heightened vulnerability to MI/R injury. This was marked by substantial lipid deposition, disrupted myocardial fibers, and intensified cellular apoptosis. The activation of caspase-1-mediated pyroptosis and increased reactive oxygen species (ROS) production further contributed to tissue damage and the ensuing inflammatory response. Notably, myocardial injury was mitigated by inhibiting caspase-1 through VX-765, which also attenuated the inflammatory cascade. Likewise, NAC treatment reduced oxidative stress and partially suppressed ROS-mediated caspase-1 activation, resulting in diminished myocardial injury. This study proved that Caspase-1-dependent pyroptosis significantly contributes to the inflammation and injury stemming from global MI/R in T2DM rats under CPB, which correlate with the surplus ROS generated by oxidative stress during reperfusion.

Beneficial Consequences of One-Month Oral Treatment with Cannabis Oil on Cardiac Hypertrophy and the Mitochondrial Pool in Spontaneously Hypertensive Rats.

Introduction: It has been demonstrated the dysregulation of the cardiac endocannabinoid system in cardiovascular diseases. Thus, the modulation of this system through the administration of phytocannabinoids present in medicinal cannabis oil (CO) emerges as a promising therapeutic approach. Furthermore, phytocannabinoids exhibit potent antioxidant properties, making them highly desirable in the treatment of cardiac pathologies, such as hypertension-induced cardiac hypertrophy (CH). Objective: To evaluate the effect of CO treatment on hypertrophy and mitochondrial status in spontaneously hypertensive rat (SHR) hearts. Methods: Three-month-old male SHR were randomly assigned to CO or olive oil (vehicle) oral treatment for 1 month. We evaluated cardiac mass and histology, mitochondrial dynamics, membrane potential, area and density, myocardial reactive oxygen species (ROS) production, superoxide dismutase (SOD), and citrate synthase (CS) activity and expression. Data are presented as mean ± SEM (n) and compared by t-test, or two-way ANOVA and Bonferroni post hoc test were used as appropriate. p < 0.05 was considered statistically significant. Results: CH was reduced by CO treatment, as indicated by the left ventricular weight/tibia length ratio, left ventricular mass index, myocyte cross-sectional area, and left ventricle collagen volume fraction. The ejection fraction was preserved in the CO-treated group despite the persistence of elevated systolic blood pressure and the reduction in CH. Mitochondrial membrane potential was improved and mitochondrial biogenesis, dynamics, area, and density were all increased by treatment. Moreover, the activity and expression of the CS were enhanced by treatment, whereas ROS production was decreased and the antioxidant activity of SOD increased by CO administration. Conclusion: Based on the mentioned results, we propose that 1-month oral treatment with CO is effective to reduce hypertrophy, improve the mitochondrial pool and increase the antioxidant capacity in SHR hearts.

Overexpression of MD1 ameliorates pathological myocardial remodeling in diabetic cardiomyopathy by TLR4/STAT3 signaling pathway

Diabetic cardiomyopathy (DCM) is characterized by oxidative damage and inflammatory responses. Myeloid differentiation protein 1 (MD1) exhibits antioxidant and anti-inflammatory properties. However, the specific role of MD1 in DCM has yet to be elucidated. This study aims to investigate the role of MD1 in DCM and to elucidate the underlying mechanisms. We utilized a gain-of-function approach to explore the involvement of MD1 in DCM. Diabetes was induced in MD1-transgenic (MD1-TG) mice and their wild-type (WT) counterparts via streptozotocin (STZ) injection. Additionally, a diabetes cell model was established using H9c2 cells exposed to high glucose levels. We conducted comprehensive evaluations, including pathological analyses, echocardiography, electrocardiography, and molecular assessments, to elucidate the underlying mechanisms of MD1 in DCM. Notably, MD1 expression was reduced in the hearts of STZ-induced diabetic mice. Overexpression of MD1 significantly improved cardiac function and markedly inhibited ventricular pathological hypertrophy and fibrosis in these mice. Furthermore, MD1 overexpression resulted in a substantial decrease in myocardial reactive oxygen species (ROS) accumulation, mitigating myocardial oxidative stress and reducing the levels of inflammation-related markers such as IL-1β, IL-6, and TNF-α. Mechanistically, MD1 overexpression inhibited the activation of the TLR4/STAT3 signaling pathway, as demonstrated in both in vivo and in vitro experiments. The overexpression of MD1 significantly impeded pathological cardiac remodeling and improved cardiac function in STZ-induced diabetic mice. This effect was primarily attributed to a reduction in ROS accumulation and mitigation of myocardial oxidative stress and inflammation, facilitated by the inhibition of the TLR4/STAT3 signaling pathway.

CircDiaph3 aggravates H/R-induced cardiomyocyte apoptosis and inflammation through miR-338-3p/SRSF1 axis

Acute myocardial infarction (AMI) is one of the most prevalent cardiovascular diseases, accounting for a high incidence rate and high mortality worldwide. Hypoxia/reoxygenation (H/R)-induced myocardial cell injury is the main cause of AMI. Several studies have shown that circular RNA contributes significantly to the pathogenesis of AMI. Here, we established an AMI mouse model to investigate the effect of circDiaph3 in cardiac function and explore the functional role of circDiaph3 in H/R-induced cardiomyocyte injury and its molecular mechanism. Bioinformatics tool and RT-qPCR techniques were applied to detect circDiaph3 expression in human patient samples, heart tissues of AMI mice, and H/R-induced H9C2 cells. CCK-8 was used to examine cell viability, while annexin-V/PI staining was used to assess cell apoptosis. Myocardial reactive oxygen species (ROS) levels were detected by immunofluorescence. Western blot was used to detect the protein expression of anti-apoptotic Bcl-2 while pro-apoptotic Bax and cleaved-Caspase-3. Furthermore, ELISA was used to detect inflammatory cytokines production. While bioinformatics tool and RNA pull-down assay were used to verify the interaction between circDiaph3 and miR-338-3p. We found that circDiaph3 expression was high in AMI patients and mice, as well as in H/R-treated H9C2 cells. CircDiaph3 silencing ameliorated apoptosis and inflammatory response of cardiomyocytes in vivo. Moreover, the knockdown of cirDiaph3 mitigated H/R-induced apoptosis and the release of inflammatory mediators like IL-1β, IL-6, and TNF-α in H9C2 cells. Mechanistically, circDiaph3 induced cell apoptosis and inflammatory responses in H/R-treated H9C2 cells by sponging miR-338-3p. Overexpressing miR-338-3p in H/R-treated cells prominently reversed circDiaph3-induced effects. Notably, miR-338-3p inhibited SRSF1 expression in H/R-treated H9C2 cells. While overexpressing SRSF1 abrogated miR-338-3p-mediated alleviation of apoptosis and inflammation after H/R treatment. To summarize, circDiaph3 aggravates H/R-induced cardiomyocyte apoptosis and inflammation through the miR-338-3p/SRSF1 axis. These findings suggest that the circDiaph3/miR-338-3pp/SRSF1 axis could be a potential therapeutic target for treating H/R-induced myocardial injury.

Myrtle Berries Seeds Prevent Dyslipidemia, Inflammation, and Excessive Cardiac Reactive Oxygen Species Production in Response to High-Fat Diet-Induced Obesity.

Anthocyanins are the major polyphenols in myrtle berries seeds aqueous extract (MBSAE). This study investigates the protective potentials of MBSAE against obesity lipotoxicity and inflammation induced by a high-fat diet (HFD). It also describes the underlying mechanisms involved in its protective effects, with special attention to myocardial reactive oxygen species (ROS) production. Male Wistar rats were fed HFD for 6 weeks to induce obesity. MBSAE (100 mg/kg, b.w., p.o.) was orally administered to HFD-fed rats. Anti-obesity effects were triggered by the inhibitory action of the MBSAE against the weights of the body, its relative heart and the total abdominal fat. Treatment with MBSAE also restored the lipid profile to baseline compared with the HFD rats and lowered also the white blood cells count, including neutrophils, lymphocytes, and basophils number as well as cytokines (tumor necrosis factor-α, interleukin [IL]-6, and IL-1β) levels in the rats serum, thus improving the tissue inflammatory status associated with obesity. Exposure of rats to HFD during 6 weeks induces a myocardial oxidative stress as assessed by deleterious effects on lipoperoxidation state, antioxidant enzyme (SOD, CAT, and GPx) activities as well as sulfhydryl groups and GSH rates. Of importance, our study shows also that HFD provokes a heart ROS (H2O2, OH•, and O2•-) overload. Of interest, all these oxidative heart disturbances were clearly ended by MBSAE treatment. Therefore, consumption of MBSAE as a natural extract may be a potential therapeutic strategy to treat obesity-associated diseases.

Effect and mechanisms of dexmedetomidine combined with macrophage migration inhibitory factor inhibition on the expression of inflammatory factors and AMPK in mice.

Reperfusion after acute myocardial infarction can cause ischemia/reperfusion (I/R) injury, which not only impedes restoration of the functions of tissues and organs but may also aggravate structural tissue and organ damage and dysfunction, worsening the patient's condition. Thus, the mechanisms that underpin myocardial I/R injury need to be better understood. We aimed to examine the effect of dexmedetomidine on macrophage migration inhibitory factor (MIF) in cardiomyocytes from mice with myocardial I/R injury and to explore the mechanistic role of adenosine 5'-monophosphate-activated protein kinase (AMPK) signaling in this process. Myocardial I/R injury was induced in mice. The expression of serum inflammatory factors, reactive oxygen species (ROS), adenosine triphosphate (ATP), and AMPK pathway-related proteins, as well as myocardial tissue structure and cell apoptosis rate, were compared between mice with I/R injury only; mice with I/R injury treated with dexmedetomidine, ISO-1 (MIF inhibitor), or both; and sham-operated mice. Dexmedetomidine reduced serum interleukin (IL)-6 and tumor necrosis factor-α concentrations and increased IL-10 concentration in mice with I/R injury. Moreover, dexmedetomidine reduced myocardial tissue ROS content and apoptosis rate and increased ATP content and MIF expression. MIF inhibition using ISO-1 reversed the protective effect of dexmedetomidine on myocardial I/R injury and reduced AMPK phosphorylation. Dexmedetomidine reduces the inflammatory response in mice with I/R injury and improves adverse symptoms, and its mechanism of action may be related to the MIF-AMPK pathway.

Bergenin alleviates myocardial ischemia‐reperfusion injury via SIRT1 signaling

Myocardial ischemia-reperfusion (MI/R) is a major risk factor for cardiovascular disease. At present, reducing oxidative stress and apoptosis is a crucial therapeutic strategy for ameliorating MI/R injury. However, there is a lack of drugs targeting oxidative stress and apoptosis for the clinical therapy of MI/R. Bergenin is a reportedly effective agent with antioxidative and antiapoptotic activity against acute injury. Nevertheless, the roles and potential mechanisms of bergenin against MI/R injury remain unknown. Here, we hypothesized that bergenin attenuated MI/R-induced apoptosis and reactive oxygen species (ROS) production via SIRT1. Mice were subjected to MI/R and treated with bergenin, after which the cardiac function, cardiomyocyte apoptosis, LDH release, and MDA content were evaluated. In vitro, myocardial injury model of H9c2 cells was induced by simulated ischemia/reperfusion (SI/R), apoptosis and oxidative stress was decreased after treated with bergenin. Bergenin significantly reduced myocardial apoptosis and ROS generation in vitro and improved cardiac function in vivo. Intriguingly, bergenin remarkably decreased apoptosis in cardiac tissue accompanied by SIRT1 upregulation following MI/R injury. Further studies showed that inhibiting SIRT1 blocked bergenin’s beneficial impact against apoptosis following SI/R injury through excessive oxidative stress and depression of the Bcl2 to Bax ratio. Collectively, these findings indicate that bergenin alleviates MI/R injury by ameliorating myocardial apoptosis and oxidative damage via the SIRT1 signaling pathway.

Mitochondrial antioxidant SkQ1 decreases inflammation following hemorrhagic shock by protecting myocardial mitochondria.

Background: Hemorrhagic shock (HS) is a type of hypovolemic shock characterized by hemodynamic instability, tissue hypoperfusion and cellular hypoxia. In pathophysiology, the gradual accumulation of reactive oxygen species (ROS) damages the mitochondria, leading to irreversible cell damage and the release of endogenous damage-associated molecular patterns (DAMPs) including mitochondrial DAMPs (MTDs), eventually triggering the inflammatory response. The novel mitochondria-targeted antioxidant SkQ1 (Visomitin) effectively eliminate excessive intracellular ROS and exhibits anti-inflammatory effects; however, the specific role of SkQ1 in HS has not yet been explicated. Methods and results: A 40% fixed-blood-loss HS rat model was established in this study. Transmission electron microscopy showed that after HS, the myocardial mitochondrial ultrastructure was damaged and the mtDNA release in circulation was increased and the differentially expressed genes were significantly enriched in mitochondrial and ROS-related pathways. Mitochondria-targeted antioxidant SkQ1 attenuated the increased ROS induced by HS in myocardial tissues and by oxygen-glucose deprivation (OGD) in cardiomyocytes. Ultrastructurally, SkQ1 protected the myocardial mitochondrial structure and reduced the release of the peripheral blood mtDNA after HS. RNA-seq transcriptome analysis showed that 56.5% of the inflammation-related genes, which altered after HS, could be significantly reversed after SkQ1 treatment. Moreover, ELISA indicated that SkQ1 significantly reversed the HS-induced increases in the TNF-α, IL-6, and MCP-1 protein levels in rat peripheral blood. Conclusion: HS causes damage to the rat myocardial mitochondrial structure, increases mtDNA release and ROS contents, activates the mitochondrial and ROS-related pathways, and induces systemic inflammatory response. The mitochondrial antioxidant SkQ1 can improve rat myocardial mitochondria ultrastructure, reduce mtDNA and ROS contents, and decrease inflammation by protecting myocardial mitochondria, thereby playing a novel protective role in HS.

The protective effects of procyanidin supplementation on PM2.5-induced acute cardiac injury in rats.

Numerous epidemiological and experimental studies have indicated that ambient fine particulate matter (PM2.5) exposure can lead to myocardial injury by inhibiting oxidative stress and apoptosis. The effects of procyanidin (PC) on PM2.5-induced cardiovascular diseases (CVDs) are still unknown. The purpose of this study was to explore the protective effect of PC supplementation on PM2.5-induced oxidative stress and cardiomyocyte apoptosis in rats. Rats were treated by gavage with three different PC concentrations (50, 100 and 200mg/kg) for 21days prior to exposure to 10mg/kg PM2.5 suspension liquid by intratracheal instillation every other day for three times. We determined myocardial reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the myocardium were measured. The expression levels of apoptosis-related proteins, including p-Akt/Akt, Bcl-2, caspase-3 and Bax, were determined. In addition, histopathological examination was used to evaluate cardiac injury. PM2.5 exposure noticeably elevated the contents of MDA and ROS and decreased the activities of GSH-Px and SOD. PM2.5 exposure inhibited Bcl-2 expression and up-regulated caspase-3 and Bax expression in the myocardium of rats. The anti-apoptosis-related index p-Akt/Akt was reduced. Moreover, pretreatment with PC could attenuate these PM2.5-induced changes. However, remarkable differences in the protective effect of different PC doses did not exist. The results indicated that PC supplementation could effectively attenuate the oxidative stress and apoptosis induced by PM2.5 in rat myocardial tissue.

NADPH Oxidase Mediates Oxidative Stress and Ventricular Remodeling through SIRT3/FOXO3a Pathway in Diabetic Mice.

Oxidative stress and mitochondrial dysfunction are important mechanisms of ventricular remodeling, predisposed to the development of diabetic cardiomyopathy (DCM) in type 2 diabetes mellitus. In this study, we have successfully established a model of type 2 diabetes using a high-fat diet (HFD) in combination with streptozotocin (STZ). The mice were divided into three groups of six at random: control, diabetes, and diabetes with apocynin and the H9c2 cell line was used as an in vitro model for investigation. We examined the molecular mechanisms of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation on mitochondrial dysfunction and ventricular remodeling in the diabetic mouse model. Hyperglycemia-induced oxidative stress led to a reduced expression of sirtuin 3 (SIRT3), thereby promoting forkhead box class O 3a (FOXO3a) acetylation in ventricular tissue and H9c2 cells. Reactive oxygen species (ROS) overproduction promoted ventricular structural modeling and conduction defects. These alterations were mitigated by inhibiting NADPH oxidase with the pharmaceutical drug apocynin (APO). Apocynin improved SIRT3 and Mn-SOD expression in H9c2 cells transfected with SIRT3 siRNA. In our diabetic mouse model, apocynin improved myocardial mitochondrial function and ROS overproduction through the recovery of the SIRT3/FOXO3a pathway, thereby reducing ventricular remodeling and the incidence of DCM.

GYY4137 ameliorates sepsis-induced cardiomyopathy via NLRP3 pathway

Sepsis-induced cardiomyopathy (SICM) has a poor prognosis, with no effective therapeutic strategy currently. This study aimed to explore the mechanism underlying SICM and investigate the protective role of the hydrogen sulfide (H2S) donor GYY4137. This study included patients with SICM and animal models of SICM with wild-type and Nlrp3−/− mice, which were treated with or without GYY4137. Echocardiography, ELISA, TUNEL staining, and immunofluorescence were used to investigate phenotypic alterations. Serum levels of H2S and cytokines were measured. Inflammatory cell infiltration in the myocardial tissue was identified using immunohistochemistry and immunofluorescence. RNA expression profiles were identified using RNA sequencing. The protective mechanism of GYY4137 was further validated in the crosstalk between macrophages and cardiomyocytes using immunoblotting, real-time polymerase chain reaction (RT-PCR), and immunofluorescence when conditional medium of macrophages boosted by LPS were co-cultured with cardiomyocytes. Patients and animal models of SICM presented with lower serum H2S levels and heart dysfunction. GYY4137 reduced macrophage infiltration in septic heart tissue. GO analysis suggested that GYY4137 was involved in the inflammatory process. GYY4137 inhibited NLRP3 inflammasome activity in macrophages, reduced the secretion of inflammatory factors, and decreased the production of reactive oxygen species (ROS) in cardiomyocytes, thus exerting protective effects against SICM. We further found that the protective effects of GYY4137 were absent in Nlrp3-knockout models. GYY4137 ameliorates myocardial injury in SICM via the NLRP3 pathway by inhibiting the inflammatory response and reducing the production of myocardial ROS.

LCZ696 ameliorates doxorubicin-induced cardiomyocyte toxicity in rats

Doxorubicin (DOX)-based chemotherapy induces cardiotoxicity, which is considered the main bottleneck for its clinical application. In this study, we investigated the potential benefit of LCZ696, an angiotensin receptor–neprilysin inhibitor against DOX-induced cardiotoxicity in rats and H9c2 cells and determined whether the mechanism underlying any such effects involves its antioxidant activity. Male Sprague–Dawley rats were randomly separated into four groups, each consisting of 15 rats (DOX (1.5 mg/kg/day intraperitoneally for 10 days followed by non-treatment for 8 days); DOX + valsartan (31 mg/kg/day by gavage from day 1 to day 18); DOX + LCZ696 (68 mg/kg/day by gavage from day 1 to day 18); and control (saline intraperitoneally for 10 days). DOX-induced elevation of cardiac troponin T levels on day 18 was significantly reduced by LCZ696, but not valsartan. The DOX-induced increase in myocardial reactive oxygen species (ROS) levels determined using dihydroethidium was significantly ameliorated by LCZ696, but not valsartan, and was accompanied by the suppression of DOX-induced increase in p47phox. LCZ696 recovered the DOX-induced decrease in phosphorylation of adenosine monophosphate-activated protein kinase and increased the ratio of Bax and Bcl-2. In H9c2 cardiomyocytes, LCZ696 reduced DOX-induced mitochondrial ROS generation and improved cell viability more than valsartan. Our findings indicated that LCZ696 ameliorated DOX-induced cardiotoxicity in rat hearts in vivo and in vitro, possibly by mediating a decrease in oxidative stress.

Honokiol Ameliorates Post-Myocardial Infarction Heart Failure Through Ucp3-Mediated Reactive Oxygen Species Inhibition.

Post-myocardial infarction heart failure (post-MI HF) is one of the leading global causes of death, and current prevention and treatment methods still cannot avoid the increasing incidence. Honokiol (HK) has previously been reported to improve myocardial ischemia/reperfusion injury and reverse myocardial hypertrophy by activating Sirt1 and Sirt3. We suspect that HK may also have a therapeutic effect on post-MI HF. In this study, we aimed to investigate the efficacy and mechanism of HK in the treatment of post-MI HF. We found that HK inhibited myocardial reactive oxygen species (ROS) production, reduced myocardial fibrosis, and improved cardiac function in mice after MI. HK also reduced the abnormality of mitochondrial membrane potential (MMP) and apoptosis of cardiomyocytes caused by peroxide in neonatal cardiomyocytes. RNAseq results revealed that HK restored the transcriptome changes to a certain extent and significantly enhanced the expression of mitochondrial inner membrane uncoupling protein isoform 3 (Ucp3), a protein that inhibits the production of mitochondrial ROS, protects cardiomyocytes, and relieves heart failure after myocardial infarction (MI). In cardiomyocytes with impaired Ucp3 expression, HK cannot protect against the damage caused by peroxide. More importantly, in Ucp3 knockout mice, HK did not change the increase in the ROS level and cardiac function damage after MI. Taken together, our results suggest that HK can increase the expression of the cardioprotective protein Ucp3 and maintain MMP, thereby inhibiting the production of ROS after MI and ameliorating heart failure.

Feasibility study of PET dynamic imaging of [18F]DHMT for quantification of reactive oxygen species in the myocardium of large animals

ObjectivesWe aimed to develop a dynamic imaging technique for a novel PET superoxide tracer, [18F]DHMT, to allow for absolute quantification of myocardial reactive oxygen species (ROS) production in a large animal model. MethodsSix beagle dogs underwent a single baseline dynamic [18F]DHMT PET study, whereas one animal underwent three serial dynamic studies over the course of chronic doxorubicin administration (1 mg·kg−1·week−1 for 15 weeks). During the scans, sequential arterial blood samples were obtained for plasma metabolite correction. The optimal compartment model and graphical analysis method were identified for kinetic modeling. Values for the left ventricular (LV) net influx rate, Ki, were reported for all the studies and compared with the LV standard uptake values (SUVs) and the LV-to-blood pool SUV ratios from the 60 to 90 minute static images. Parametric images were also generated. Results[18F]DHMT followed irreversible kinetics once oxidized within the myocardium in the presence of superoxide, as evidenced by the fitting generated by the irreversible two-tissue (2Ti) compartment model and the linearity of Patlak analysis. Myocardial Ki values showed a weak correlation with LV SUV (R2 = 0.27), but a strong correlation with LV-to-blood pool SUV ratio (R2 = 0.92). Generation of high-quality parametric images showed superior myocardial to blood contrast compared to static images. ConclusionsA dynamic PET imaging technique for [18F]DHMT was developed with full and simplified kinetic modeling for absolute quantification of myocardial superoxide production in a large animal model.

The Effect of Short-Term Intermittent Hypoxia Exposure on Mouse Myocardial Oxidative Stress and Cardiac Function

To investigate the effect of short-term intermittent hypoxia (IH) on the structure and function of mouse myocardium. Thirty male C57BL6/J mice were randomly assigned to two groups, a control (Con) group and an IH group exposed to hypoxic treatment at atmospheric pressure. The IH group received 10% oxygen pretreatment for 8 hours per day on 14 consecutive days, while the Con group was exposed to normoxia environment and all the other treatment the group received were identical to those given to the IH group, The body mass of the mice was monitored daily during the treatment. The exercise tolerance and the cardiac function of isolated heart were assessed at the end of IH exposure. Additionally, analysis was conducted regarding myocardial enzymology, histology, and other indicators relevant to oxidative stress, including protein carbonylation and lipid peroxidation. There was no significant difference in the exercise tolerance between the two groups. Nevertheless, IH mice showed enhanced cardiac function during isolated heart perfusion ( P<0.05). As compared to the control group, prominent alterations of myocardial structure were detected by transmission electron microscopy of the IH heart, accompanied by elevated creatine kinase-MB levels ( P<0.05). The levels of myocardial reactive oxygen species, protein carbonylation and lipid peroxidation were all significantly upregulated in the IH group as compared to the control group ( P<0.05). IH exposure induced myocardial oxidative stress damage and myofibrillar structural alteration in mice, but did not impair the exercise tolerance of the mice or the contractile function of the isolated heart.

Human Lysyl Oxidase Over-Expression Enhances Baseline Cardiac Oxidative Stress but Does Not Aggravate ROS Generation or Infarct Size Following Myocardial Ischemia-Reperfusion

Lysyl oxidase (LOX) is an enzyme critically involved in collagen maturation, whose activity releases H2O2 as a by-product. Previous studies demonstrated that LOX over-expression enhances reactive oxygen species (ROS) production and exacerbates cardiac remodeling induced by pressure overload. However, whether LOX influences acute myocardial infarction and post-infarct left ventricular remodeling and the contribution of LOX to myocardial oxidative stress following ischemia-reperfusion have not been analyzed. Isolated hearts from transgenic mice over-expressing human LOX in the heart (TgLOX) and wild-type (WT) littermates were subjected to global ischemia and reperfusion. Although under basal conditions LOX transgenesis is associated with higher cardiac superoxide levels than WT mice, no differences in ROS production were detected in ischemic hearts and a comparable acute ischemia-reperfusion injury was observed (infarct size: 56.24 ± 9.44 vs. 48.63 ± 2.99% of cardiac weight in WT and TgLOX, respectively). Further, similar changes in cardiac dimensions and function were observed in TgLOX and WT mice 28 days after myocardial infarction induced by transient left anterior descending (LAD) coronary artery occlusion, and no differences in scar area were detected (20.29 ± 3.10 vs. 21.83 ± 2.83% of left ventricle). Our data evidence that, although LOX transgenesis induces baseline myocardial oxidative stress, neither ROS production, infarct size, nor post-infarction cardiac remodeling were exacerbated following myocardial ischemia-reperfusion.

Effect of swimming training on the expression of PKC δ/p66Shc protein in mouse myocardium

Objective: To investigate the effects of different intensity of swimming training on p66Shc protein in mouse myocardium. Methods: Fifty Kunming mice were randomly divided into control group (Group C), weight-bearing swimming group (Group E), weight-bearing swimming + drug group (Group ER), non weight-bearing swimming group (Group P), non weight-bearing swimming + drug group (Group PR), with 10 mice in each group. Group C did not exercise. Groups E, ER, P, and PR received swimming training for 4 weeks. Groups E and ER performed weight-bearing swimming with a 3% body weight, and Group P and Group PR were swimming without weight-bearing, 60 min/d, 6 times/w. Mice in ER and PR groups were injected intraperitoneally with Rottlerin (0.3 mg/kg), a PKCδ inhibitor, before the last two exercises. Groups C, E, and P were injected with the same dose of normal saline. Samples were collected after training finished for 24 hours. The protein expressions of PKCδ, P-PKCδ, P66Shc, P-P66shc and NOX2 were detected by Western blot; PKCδ and P66Shc were detected by immunoprecipitation; malondialdehyde (MDA), reactive oxygen species (ROS) and superoxide dismutase (SOD) in myocardium and serum were analyzed by biochemistry. Results: Compared with Group C, the protein expressions of PKCδ, P-PKCδ, P66Shc, P-P66shc and NOX2 in Group E were increased significantly (P＜ 0.01), the serum and myocardial MDA levels, myocardial ROS were increased significantly (P＜0.05 or P＜0.01), and the myocardial SOD activity was decreased (P＜0.01), the PKCδ, P-PKCδ, P-P66shc and NOX2 in Group P were increased significantly (P＜0.05 or P＜0.01), and the myocardial SOD activity was enhanced (P＜0.05). Compared with Group E, the protein expressionS of PKCδ (P＜0.01), P-PKCδ (P＜0.01), P66Shc (P＜0.05), P-P66shc (P＜0.01), NOX2 (P＜0.05) in Group ER was decreased significantly, the protein expression of P66Shc in Group P was decreased significantly (P＜0.05), the myocardial MDA (P＜0.01) and ROS (P＜0.05) were decreased, and the activity of SOD was enhanced (P＜0.01). Compared with Group P, the protein expressions of PKCδ, P-PKCδ and P-P66shc in Group PR were decreased significantly (P＜0.01), while the expression of NOX2 was increased (P＜0.05). Conclusion: Both swimming training of two intensities promoted the increase of PKCδ protein and its phosphorylation in mouse cardiomyocytes. High-intensity swimming training could significantly enhance the expression and phosphorylation level of p66Shc protein, resulting in the production of ROS and the decrease of antioxidant enzyme activity. Low-intensity swimming training enhanced the phosphorylation of p66Shc, but did not promote its protein expression, resulting in the enhancement of myocardial antioxidant capacity and exercise adaptation.

LOX-1 Deletion Attenuates Myocardial Fibrosis in the Aged Mice, Particularly Those With Hypertension.

Background: Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a transmembrane glycoprotein that mediates uptake of oxidized low-density lipoprotein (ox-LDL) into cells. Previous studies had shown that LOX-1 deletion had a potential to inhibit cardiac fibrosis in mouse models of hypertension and myocardial infarction. Whether LOX-1 deletion also affects cardiac fibrosis associated with aging still remains unknown. The aim of this study was to investigate the effect of LOX-1 deletion on myocardial fibrosis in the aged mice.Methods: C57BL/6 mice and LOX-1 knockout (KO) mice with C57BL/6 background were studied to the age of 60 weeks. Both genotypes of aged mice were exposed to angiotensin II (Ang II) or saline for additional 4 weeks. The mice were then sacrificed, and myocardial fibrosis, reactive oxygen species (ROS) and expression of LOX-1, fibronectin, collagens, p22phox, and gp91phox were measured.Results: LOX-1 deletion markedly reduced Ang II-mediated rise of blood pressure in the aged mice (vs. saline-treated mice). LOX-1 deletion also limited fibrosis and decreased fibronectin and collagen-3 expression in the hearts of aged mice, but not the expression of collagen-1 and collagen-4. LOX-1 deletion also inhibited ROS production and p22phox expression. As the aged mice were exposed to Ang II for 4 weeks (resulting in hypertension), LOX-1 deletion more pronounced inhibiting myocardial fibrosis and ROS production, and decreasing expression of fibronectin, collagen-1, collagen-2, collagen-3, p22phox, and gp91phox.Conclusion: LOX-1 deletion limited fibrosis and ROS production in the hearts of aged mice. This effect was more pronounced in the aged mice with hypertension induced by Ang II infusion.

Dapagliflozin attenuates arrhythmic vulnerabilities by regulating connexin43 expression via the AMPK pathway in post-infarcted rat hearts

We have demonstrated that dapagliflozin, a sodium-glucose cotransporter (SGLT) 2 inhibitor, attenuates reactive oxygen species (ROS) production. Connexin43 playing a role in ventricular arrhythmia is sensitive to redox status. No data are available on the effects of dapagliflozin on arrhythmogenesis. This study was to determine whether dapagliflozin attenuated arrhythmias through modulating AMP-activated protein kinase (AMPK)/free radicals-induced connexin43 after myocardial infarction. After coronary ligation, normoglycemic male Wistar rats were randomized to either vehicle or dapagliflozin (0.1 mg/kg per day) for 4 weeks. Myocardial ROS levels were significantly increased (p < 0.05) and connexin43 levels were substantially decreased after myocardial infarction (p < 0.05). Dapagliflozin administration was associated with increased SGLT1, attenuated ROS and increased connexin43 levels in myocardium (all p < 0.05). During programmed electrical stimulation, arrhythmic severity was significantly improved in the dapagliflozin-treated infarcted rats than those in the vehicle-treated infarcted rats (p < 0.05). Dapagliflozin significantly increased AMPK phosphorylation compared to vehicle after infarction (p < 0.05). Inhibition of AMPK signaling by SBI-0206965 prevented increased SGLT1 and blocked the effects of dapagliflozin on attenuated ROS levels and increased connexin43 phosphorylation (all p < 0.05). SGLT1 inhibited by KGA-2727 showed attenuated ROS levels and increased connexin43 phosphorylation (both p < 0.05) although AMPK phosphorylation was not changed, implying SGLT1 activation was mediated by AMPK in dapagliflozin-treated hearts. Dapagliflozin-treated hearts had significantly increased connexin43 phosphorylation (p < 0.05), which was significantly decreased after adding 3-morpholinosydnonimine (p < 0.05). These data indicate that clinically-relevant dapagliflozin concentrations decreased free radicals content and increased connexin43 levels through AMPK-dependent and SGLT1-independent mechanisms, which attenuated ventricular arrhythmias in the normoglycemic infarcted rats.