Effect of ischemic preconditioning and a Kv7 channel blocker on cardiac ischemia-reperfusion injury in rats

Potential Therapeutic Targets for Hypotension in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is marked by genetic mutations occurring in the DMD gene, which is widely expressed in the cardiovascular system. In addition to developing cardiomyopathy, patients with DMD have been reported to be susceptible to the development of symptomatic hypotension, although the mechanisms are unclear. Analysis of single-cell RNA sequencing data has identified potassium voltage-gated channel subfamily Q member 5 (KCNQ5) and possibly ryanodine receptor 2 (RyR2) as potential candidate hypotension genes whose expression is significantly upregulated in the vascular smooth muscle cells of DMD mutant mice. We hypothesize that heightened KCNQ5 and RyR2 expression contributes to decreased arterial blood pressure in patients with DMD. Exploring pharmacological approaches to inhibit the KCNQ5 and RyR2 channels holds promise in managing the systemic hypotension observed in individuals with DMD. This avenue of investigation presents new prospects for improving clinical outcomes for these patients.

Combined effects of methadone and quetiapine on respiratory rate, haemodynamic variables, and temperature in conscious rats

Fatal poisonings where both methadone and quetiapine are detected post-mortem occurs frequently in legal autopsy cases. It is unclear whether quetiapine increases the risk of fatal methadone poisoning or if it is merely detected due to widespread use. We hypothesized that methadone and quetiapine would have additive toxic effects on respiratory rate, blood pressure, and the QTc-interval. To investigate this hypothesis, we used telemetry implants for measurements of respiratory rate, haemodynamic variables, the velocity of blood pressure changes, temperature, and movement in conscious, freely moving male Wistar rats aged 12-13 weeks. The combined effects of three accumulative i.p. doses of methadone (2.5, 10, 15 mg/kg) and quetiapine (3, 10, 30 mg/kg) were compared to rats treated with the same doses of each drug alone, and a vehicle-treated group in a randomized investigator blinded study. No additive effects of quetiapine and methadone on respiratory rate, haemodynamic variables, or movement were observed. However, body temperature was significantly lower by approximately 1.5°C on average in the group treated with both methadone and quetiapine (15 + 30 mg/kg) compared to the other groups. This indicates a synergistic effect of quetiapine and methadone on thermoregulation, which may increase the risk of fatal poisoning. We suggest studying this finding further in human settings.

Slowly activating voltage-gated potassium current potentiation by ML277 is a novel cardioprotective intervention

Cardiovascular disease is thought to account for nearly a third of deaths worldwide, with ischemic heart disease, including acute coronary syndromes such as myocardial infarction, accounting for 1.7 million deaths per year. There is a clear need for interventions to impart cardioprotection against ischemia. Here, we show that the slowly activating voltage-gated potassium current (IKs) potentiator ML277 imparts cardioprotection against ischemia in cellular and whole-heart models by modulating the action potential duration. In three different metabolic inhibition and reperfusion models, an increased contractile recovery and cell survival was observed with ML277, indicative of protection. Finally, ML277 reduced infarct size in an ex vivo Langendorff coronary ligation model, including if only applied on reperfusion. In conclusion, potentiation of the IKs with ML277 imparted a cardioprotection that was equivalent to the protection reported previously by ischemic preconditioning. These data suggest that IKs potentiation may be therapeutically useful in acute coronary syndromes.

Migraine-Associated Mutation in the Na,K-ATPase Leads to Disturbances in Cardiac Metabolism and Reduced Cardiac Function

Background Mutations in ATP1A2 gene encoding the Na,K-ATPase α2 isoform are associated with familial hemiplegic migraine type 2. Migraine with aura is a known risk factor for heart disease. The Na,K-ATPase is important for cardiac function, but its role for heart disease remains unknown. We hypothesized that ATP1A2 is a susceptibility gene for heart disease and aimed to assess the underlying disease mechanism. Methods and Results Mice heterozygous for the familial hemiplegic migraine type 2-associated G301R mutation in the Atp1a2 gene (α2+/G301R mice) and matching wild-type controls were compared. Reduced expression of the Na,K-ATPase α2 isoform and increased expression of the α1 isoform were observed in hearts from α2+/G301R mice (Western blot). Left ventricular dilation and reduced ejection fraction were shown in hearts from 8-month-old α2+/G301R mice (cardiac magnetic resonance imaging), and this was associated with reduced nocturnal blood pressure (radiotelemetry). Cardiac function and blood pressure of 3-month-old α2+/G301R mice were similar to wild-type mice. Amplified Na,K-ATPase-dependent Src kinase/Ras/Erk1/2 (p44/42 mitogen-activated protein kinase) signaling was observed in hearts from 8-month-old α2+/G301R mice, and this was associated with mitochondrial uncoupling (respirometry), increased oxidative stress (malondialdehyde measurements), and a heart failure-associated metabolic shift (hyperpolarized magnetic resonance). Mitochondrial membrane potential (5,5´,6,6´-tetrachloro-1,1´,3,3´-tetraethylbenzimidazolocarbocyanine iodide dye assay) and mitochondrial ultrastructure (transmission electron microscopy) were similar between the groups. Proteomics of heart tissue further suggested amplified Src/Ras/Erk1/2 signaling and increased oxidative stress and provided the molecular basis for systolic dysfunction in 8-month-old α2+/G301R mice. Conclusions Our findings suggest that ATP1A2 mutation leads to disturbed cardiac metabolism and reduced cardiac function mediated via Na,K-ATPase-dependent reactive oxygen species signaling through the Src/Ras/Erk1/2 pathway.

ATP-Sensitive Potassium Channels Mediate the Cardioprotective Effect of Panax notoginseng Saponins against Myocardial Ischaemia-Reperfusion Injury and Inflammatory Reaction

Inflammatory response during myocardial ischemia reperfusion injury (MIRI) is essential for cardiac healing, while excessive inflammation extends the infarction and promotes adverse cardiac remodeling. Understanding the mechanism of these uncontrolled inflammatory processes has a significant impact during the MIRI therapy. Here, we found a critical role of ATP-sensitive potassium channels (K_ATP) in the inflammatory response of MIRI and its potential mechanism and explored the effects of Panax Notoginseng Saponins (PNS) during this possess. Rats underwent 40 min ischemia by occlusion of the left anterior descending (LAD) coronary artery and 60 min of reperfusion. PNS was treated at the corresponding time point before operation; 5-hydroxydecanoate (5-HD) and glybenclamide (Gly) (or Nicorandil (Nic)) were used as pharmacological blocker (or nonselective opener) of K_ATP. Cardiac function and pathomorphology were evaluated and a set of molecular signaling experiments was tested. K_ATP current density was measured by patch-clamp. Results revealed that in MIRI, PNS pretreatment restored cardiac function, reduced infarct size, and ameliorated inflammation through K_ATP. However, inhibiting K_ATP by 5-HD and Gly significantly reversed the effects, including NLRP3 inflammasome and inflammatory mediators IL-6, MPO, TNF-α, and MCP-1. Moreover, PNS inhibited the phosphorylation and nuclear translocation of NF-κB in I/R myocardium when the K_ATP was activated. Importantly, PNS promoted the expression of subunits and activation of K_ATP. The study uncovered K_ATP served as a new potential mechanism during PNS modulating MIRI-induced inflammation and promoting injured heart recovery. The manipulation of K_ATP could be a potential therapeutic approach for MIRI and other inflammatory diseases.

Impact of Administration Time and Kv7 Subchannels on the Cardioprotective Efficacy of Kv7 Channel Inhibition

Purpose

The mechanism of cardioprotection by Kv7.1-5 (KCNQ1-5) channels inhibition by XE991 is unclear. We examined the impact of administration time on the cardioprotective efficacy of XE991, the involvement of key pro-survival kinases, and the importance of the Kv7 subchannels.

Methods

Isolated perfused rat hearts were divided into five groups: 1) vehicle, 2) pre-, 3) post- or 4) pre- and post-ischemic administration of XE991 or 5) chromanol 293B (Kv7.1 inhibitor) followed by infarct size quantification. HL-1 cells undergoing simulated ischemia/reperfusion were exposed to either a) vehicle, b) pre-, c) per-, d) post-ischemic administration of XE991 or pre-, per- and post-ischemic administration of e) XE991, f) Chromanol 293B or g) HMR1556 (Kv7.1 inhibitor). HL-1 cell injury was evaluated by propidium iodide/Hoechst staining. Pro-survival kinase activation of Akt, Erk and STAT3 in XE991-mediated HL-1 cell protection was evaluated using phosphokinase inhibitors. Kv7 subtype expression was examined by RT-PCR and qPCR.

Results

XE991, but not Chromanol 293B, reduced infarct size and improved hemodynamic recovery in all isolated heart groups. XE991 protected HL-1 cells when administered during simulated ischemia. Minor activation of the survival kinases was observed in cells exposed to XE991 but pharmacological inhibition of kinase activation did not reduce XE991-mediated protection. Kv7 subchannels 1-5 were all present in rat hearts but predominately Kv7.1 and Kv7.4 were present in HL-1 cells and selective Kv7.1 did not reduce ischemia/reperfusion injury.

Conclusion

The cardioprotective efficacy of XE991 seems to depend on its presence during ischemia and early reperfusion and do not rely on RISK (p-Akt and p-Erk) and SAFE (p-STAT3) pathway activation. The protective effect of XE991 seems mainly mediated through the Kv7.4 subchannel.