Effects of intravenous cariporide on release of norepinephrine and myoglobin during myocardial ischemia/reperfusion in rabbits

MRP1-Dependent Extracellular Release of Glutathione Induces Cardiomyocyte Ferroptosis After Ischemia-Reperfusion

BACKGROUND

The membrane components of cardiomyocytes are rich in polyunsaturated fatty acids, which are easily oxidized. Thus, an efficient glutathione-based lipid redox system is essential for maintaining cellular functions. However, the relationship between disruption of the redox system during ischemia-reperfusion (IR), oxidized lipid production, and consequent cell death (ferroptosis) remains unclear. We investigated the mechanisms underlying the disruption of the glutathione-mediated reduction system related to ferroptosis during IR and developed intervention strategies to suppress ferroptosis.

METHODS

In vivo fluctuations of both intra- and extracellular metabolite levels during IR were explored via microdialysis and tissue metabolome analysis. Oxidized phosphatidylcholines were assessed using liquid chromatography high-resolution mass spectrometry. The areas at risk following IR were assessed using triphenyl-tetrazolium chloride/Evans blue stain.

RESULTS

Metabolomic analysis combined with microdialysis revealed a significant release of glutathione from the ischemic region into extracellular spaces during ischemia and after reperfusion. The release of glutathione into extracellular spaces and a concomitant decrease in intracellular glutathione concentrations were also observed during anoxia-reperfusion in an in vitro cardiomyocyte model. This extracellular glutathione release was prevented by chemical inhibition or genetic suppression of glutathione transporters, mainly MRP1 (multidrug resistance protein 1). Treatment with MRP1 inhibitor reduced the intracellular reactive oxygen species levels and lipid peroxidation, thereby inhibiting cell death. Subsequent in vivo evaluation of endogenously oxidized phospholipids following IR demonstrated the involvement of ferroptosis, as levels of multiple oxidized phosphatidylcholines were significantly elevated in the ischemic region 12 hours after reperfusion. Inhibition of the MRP1 transporter also alleviated intracellular glutathione depletion in vivo and significantly reduced the generation of oxidized phosphatidylcholines. Administration of MRP1 inhibitors significantly attenuated infarct size after IR injury.

CONCLUSIONS

Glutathione was released continuously during IR, primarily in an MRP1-dependent manner, and induced ferroptosis. Suppression of glutathione release attenuated ferroptosis and reduced myocardial infarct size following IR.

The Role of Cariporide in Protecting Saphenous Vein among Different Aldehyde Dehydrogenase Genotypes

OBJECTIVE

We aimed to study the effect of cariporide (CP) on protecting the saphenous vein and the role of acetaldehyde dehydrogenase 2 (ALDH2) in coronary artery bypass grafting (CABG).

BACKGROUND

The saphenous vein is the main graft material used in CABG. Recent studies suggested that CP is effective in protecting against various cardiovascular diseases.

METHODS

Segments of a surgically removed saphenous vein were used to examine the vascular response to CP. The ALDH2 genotype and expression of related proteins were assessed by Western blotting and immunohistochemistry.

RESULTS

Among the conditions tested, the University of Wisconsin solution with CP (4°C, 5 min) treatment showed the best protective effect on the saphenous vein. The incidence of major adverse cardiac events was higher in the ALDH2-GA (heterozygous mutant) genotype population after CABG.

CONCLUSION

CP plays a role in reducing the production of reactive oxygen species and apoptosis by ALDH2-mediated mitochondrial function improvement. The ALDH2 mutant genotype might be one of the risk factors for coronary atherosclerotic heart disease.

Mild Hypothermia Is Ineffective to Protect Against Myocardial Injury Induced by Chemical Anoxia or Forced Calcium Overload

Although hypothermia suppresses myocardial ischemia/reperfusion injury, whether it also protects the myocardium against cellular stresses such as chemical anoxia and calcium overload remains unknown. We examined the effect of mild hypothermia (33°C) on myocardial injury during ischemia/reperfusion, local administration of sodium cyanide (chemical anoxia), or local administration of maitotoxin (forced Ca overload) using cardiac microdialysis applied to the feline left ventricle. Baseline myoglobin levels (in ng/mL) were 237 ± 57 and 150 ± 46 under normothermia and hypothermia, respectively (mean ± SE, n = 6 probes each). Coronary artery occlusion increased the myoglobin level to 2600 ± 424 under normothermia, which was suppressed to 1160 ± 149 under hypothermia (P < 0.05). Reperfusion further increased the myoglobin level to 6790 ± 1550 under normothermia, which was also suppressed to 2060 ± 343 under hypothermia (P < 0.05). By contrast, hypothermia did not affect the cyanide-induced myoglobin release (930 ± 130 vs. 912 ± 62, n = 6 probes each) or the maitotoxin-induced myoglobin release (2070 ± 511 vs. 2110 ± 567, n = 6 probes each). In conclusion, mild hypothermia does not make the myocardium resistant to cellular stresses such as chemical anoxia and forced Ca overload.

Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure

The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials.

The immunotoxicity of aluminum trichloride on rat peritoneal macrophages via β2-adrenoceptors/cAMP pathway acted by norepinephrine

The previous research found that norepinephrine (NE) enhanced the immunotoxicity of aluminum trichloride (AlCl3) on rat peritoneal macrophages in vitro through activating the β2-adrenoceptors (β2-AR)/cAMP pathway. On that basis, the experiment in vivo was conducted in this experiment. Eighty Wistar rats were orally exposed to 0 (control group); 0.4 mg/mL (low-dose group); 0.8 mg/mL (mid-dose group) and 1.6 mg/mL (high-dose group) AlCl3 for 120 days, respectively. Aluminum (Al), NE, macrophage migration inhibitory factor (MIF) and tumor necrosis factor-α (TNF-α) contents in serum, cAMP content, β2-AR density, mRNA expressions of TNF-α, MIF and β2-AR in rat peritoneal macrophages were examined. These results showed that AlCl3 increased serum Al and NE contents, peritoneal macrophages cAMP content, the density and mRNA expression of the β2-AR, and decreased serum MIF and TNF-α contents, peritoneal macrophages mRNA expressions of MIF and TNF-α. Serum NE content was negatively correlated with serum TNF-α and MIF contents and peritoneal macrophages mRNA expressions of TNF-α and MIF, but positively correlated with cAMP content, density of β2-AR and mRNA expression of β2-AR of peritoneal macrophages. It indicated that AlCl3 suppresses peritoneal macrophages function of rats through β2-AR/cAMP pathway acted by NE.