AT1 Receptor Modulator Attenuates the Hypercholesterolemia-Induced Impairment of the Myocardial Ischemic Post-Conditioning Benefits

Gasotransmitters and noble gases in cardioprotection: unraveling molecular pathways for future therapeutic strategies

Despite recent progress, ischemic heart disease poses a persistent global challenge, driving significant morbidity and mortality. The pursuit of therapeutic solutions has led to the emergence of strategies such as ischemic preconditioning, postconditioning, and remote conditioning to shield the heart from myocardial ischemia/reperfusion injury (MIRI). These ischemic conditioning approaches, applied before, after, or at a distance from the affected organ, inspire future therapeutic strategies, including pharmacological conditioning. Gasotransmitters, comprising nitric oxide, hydrogen sulfide, sulfur dioxide, and carbon monoxide, play pivotal roles in physiological and pathological processes, exhibiting shared features such as smooth muscle relaxation, antiapoptotic effects, and anti-inflammatory properties. Despite potential risks at high concentrations, physiological levels of gasotransmitters induce vasorelaxation and promote cardioprotective effects. Noble gases, notably argon, helium, and xenon, exhibit organ-protective properties by reducing cell death, minimizing infarct size, and enhancing functional recovery in post-ischemic organs. The protective role of noble gases appears to hinge on their modulation of molecular pathways governing cell survival, leading to both pro- and antiapoptotic effects. Among noble gases, helium and xenon emerge as particularly promising in the field of cardioprotection. This overview synthesizes our current understanding of the roles played by gasotransmitters and noble gases in the context of MIRI and cardioprotection. In addition, we underscore potential future developments involving the utilization of noble gases and gasotransmitter donor molecules in advancing cardioprotective strategies.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Benazepril hydrochloride protects against doxorubicin cardiotoxicity by regulating the PI3K/Akt pathway

Doxorubicin (DOX) stimulates the generation of reactive oxygen species, thereby impairing mitochondrial functions. Angiotensin-converting enzyme inhibitors (ACEIs) have been identified to exhibit protective effects on cardiovascular diseases. The present study aimed to test the hypothesis that an ACEI benazepril hydrochloride (HCl) may protect against DOX-induced cardiotoxicity. The DOX injury model was established using rat embryonic cardiac myoblast cells (H9c2 cell line) treated with DOX in vitro. H9c2 cells were treated with benazepril-HCl, DOX or a mixture of DOX and benazepril-HCl to measure the activities of myocardial enzymes including lactate dehydrogenase (LDH), superoxide dismutase, catalase and glutathione peroxidase, in addition to the concentration of malondialdehyde in the culture medium. Cells without any treatment were used as a control. DOX treatment increased the levels of activity of myocardial enzymes in H9c2 cells compared with those in the untreated control cells. Additionally, co-treatment with benazepril-HCl significantly reduced the levels of apoptosis occurring due to DOX-mediated cellular damage. The mechanistic experiment revealed that pretreatment with benazepril-HCl counteracted the DOX-induced oxidative stress and suppressed the activation of apoptosis via the PI3K/Akt signaling pathway. By contrast, an Akt inhibitor (MK2206) inhibited the protective effects of benazepril-HCl against DOX-induced H9c2 cell injury, as revealed by increased LDH release in H9c2 cells. These results suggested that benazepril-HCl may potentially be administered as an adjuvant for DOX in long-term clinical use.

Renin angiotensin system blockage by losartan neutralize hypercholesterolemia-induced inflammatory and oxidative injuries

Objectives: This study explores the protective role of losartan (LT) against oxidative and inflammatory damages in different physiological systems including heart, liver, and kidney tissue in hypercholesterolemic rats.

Methods: After induction of hypercholesterolemia by high cholesterol diet for 6 weeks, LT was administered for 4 weeks. In serum, the levels of lipoproteins, aminotransferases, creatine kinases, urea, apoptosis, and inflammatory markers were measured. In cardiac, hepatic, and renal tissues, lipid peroxidation product and GSH as well as antioxidant enzymatic activities were assayed. Finally, histopathological assessment evaluated the structural damage in cardiac, hepatic, and renal tissues.

Results: Serum markers of cardiac, hepatic, and renal toxicities including creatine kinases, aminotransferases, and urea were attenuated by LT in hypercholesterolemic animals. Moreover, LT markedly corrected the elevated levels of lipoproteins, apoptosis, and inflammatory biomarkers. Hypercholesterolemia-induced lipid peroxidation, low GSH levels, and diminished activities of antioxidant enzymes were prominently improved in LT treated animals. Histopathological alterations by hypercholesterolemia in heart, liver, and kidney tissues were ameliorated by LT.

Conclusion: This study confirmed the pathological enrollment of renin–angiotensin system in hypercholesterolemia-associated metabolic alterations. LT had a significant cardiac, hepatic, and renal protective role against these impairments through down-regulation of oxidative damage, inflammation and necrosis.

Angiotensin II Type 1 Receptor Blocker, Fimasartan, Reduces Vascular Smooth Muscle Cell Senescence by Inhibiting the CYR61 Signaling Pathway

BACKGROUND AND OBJECTIVES

Angiotensin II (Ang II) has been suggested to accelerate vascular senescence, however the molecular mechanism(s) remain unknown.

METHODS

We cultured human coronary artery smooth muscle cells (hCSMCs) and treated Ang II and/or fimasartan. Or we transfected adenoviral vectors expressing CYR61 (Ad-CYR61) or antisense CYR61 (Ad-As-CYR61). Cellular senescence was evaluated senescence-associated β-galactosidase (SA-β-gal) assay. The molecular mechanisms were investigated real-time PCR and western blots.

RESULTS

SA-β-gal-positive cells significantly increased in Ang II-treated hCSMCs (5.77±1.43-fold compared with the control). The effect of Ang II was significantly attenuated by pretreatment with the Ang II type 1 receptor blocker, fimasartan (2.00±0.92-fold). The expression of both p53 and p16 senescence regulators was significantly increased by Ang II (p53: 1.39±0.17, p16: 1.19±0.10-fold vs. the control), and inhibited by fimasartan. Cysteine-rich angiogenic protein 61 (CYR61) was rapidly induced by Ang II. Compared with the control, Ad-CYR61-transfected hCSMCs showed significantly increased SA-β-gal-positive cells (3.47±0.65-fold). Upon transfecting Ad-AS-CYR61, Ang II-induced senescence (3.74±0.23-fold) was significantly decreased (1.77±0.60-fold). p53 expression by Ang II was significantly attenuated by Ad-AS-CYR61, whereas p16 expression was not regulated. Ang II activated ERK1/2 and p38 MAPK, which was significantly blocked by fimasartan. ERK and p38 inhibition both regulated Ang II-induced CYR61 expression. However, p53 expression was only regulated by ERK1/2, whereas p16 expression was only attenuated by p38 MAPK.

CONCLUSIONS

Ang II induced vascular senescence by the ERK/p38 MAPK-CYR61 pathway and ARB, fimasartan, protected against Ang II-induced vascular senescence.

Gastrodin attenuates microglia activation through renin-angiotensin system and Sirtuin3 pathway

Microglia activation and its mediated production of proinflammatory mediators play important roles in different neurodegenerative diseases; hence, modulation of microglia activation has been considered a potential therapeutic strategy to ameliorate neurodegeneration. This study was aimed to determine whether Gastrodin, a common herbal agent known to possess neuroprotective property, can attenuate production of proinflammatory mediators in activated microglia through the renin-angiotensin system (RAS) and Sirtuin3 (SIRT3). Expression of various members of the RAS including ACE, AT₁, AT_2, and SIRT3 in activated microglia was assessed by immunofluorescence and Western blot in hypoxic-ischemia brain damage (HIBD) in postnatal rats, and in BV-2 microglia in vitro challenged with lipopolysaccharide (LPS) with or without Gastrodin treatment. Expression of NOX-2, a subunit of NADPH oxidase, and proinflammatory mediators including iNOS and TNF-α, was also evaluated. The present results showed that expression of ACE, AT₁, NOX-2, iNOS and TNF-α was markedly increased in activated microglia in the corpus callosum of HIBD rats, and in LPS stimulated BV-2 microglia. Remarkably, the expression was markedly attenuated following Gastrodin treatment. Conversely, Gastrodin enhanced AT₂ and SIRT3 protein expression. In BV-2 microglia treated with Azilsartan, a specific inhibitor of AT₁ (AT₁I group), NOX-2 expression was decreased whereas that of SIRT3 in LPS + AT₁I and LPS + Gastrodin group was increased when compared with the controls. In LPS + AT₁I + Gastrodin group, SIRT3 expression was further augmented. More importantly, Gastrodin effectively reduced caspase 3 protein expression level in the HIBD rats coupled with a significant decrease in caspase 3 positive cells. We conclude that Gastrodin can exert its protective effects against the hypoxic-ischemia brain damage in the present experimental HIBD model. It is suggested that this is mainly through suppression of expression of RAS (except for AT₂ and SIRT3) and proinflammatory mediators e.g. TNF-α in activated microglia.

Remote Ischemic Conditioning by Effluent Collected from a Novel Isolated Hindlimb Model Reduces Infarct Size in an Isolated Heart Model

Background and Objectives

Experimental protocols for remote ischemic conditioning (RIC) utilize models in which a tourniquet is placed around the hindlimb or effluent is collected from an isolated heart. In analyzing the humoral factors that act as signal transducers in these models, sampled blood can be influenced by systemic responses, while the effluent from an isolated heart might differ from that of the hindlimb. Thus, we designed a new isolated hindlimb model for RIC and tested whether the effluent from this model could affect ischemia/reperfusion (IR) injury and if the reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways are involved in RIC.

Materials and Methods

After positioning needles into the right iliac artery and vein of rats, Krebs-Henseleit buffer was perfused using a Langendorff apparatus, and effluent was collected. The RIC protocol consisted of 3 cycles of IR for 5 minutes. In the RIC effluent group, collected effluent was perfused in an isolated heart for 10 minutes before initiating IR injury.

Results

Compared with the control group, the infarct area in the RIC effluent group was significantly smaller (31.2%±3.8% vs. 20.6%±1.8%, p<0.050), while phosphorylation of signal transducer and activation of transcription-3 (STAT-3) was significantly increased. However, there was a trend of increased phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in this group.

Conclusion

This is the first study to investigate the effect of effluent from a new isolated hindlimb model after RIC on IR injury in an isolated heart model. The RIC effluent was effective in reducing the IR injury, and the cardioprotective effect was associated with activation of the SAFE pathway.