Protective effect of novel pyridoindole derivatives on ischemia/reperfusion injury of the isolated rat heart

Metabolic Syndrome in Hypertriglyceridemic Rats: Effects of Antioxidants

Long-lasting disturbances in lipid and glucose metabolism present in metabolic syndrome (MetS) lead to serious cardiovascular diseases. The study was aimed to evaluate the effect of natural antioxidant vitamin E (VitE, 100 mg/kg/day, p.o.) on basal biochemical and physiological parameters characterizing MetS and on the changed function of the heart. Furthermore, the possible potentiation of VitE effect by synthetic pyridoindole antioxidant SMe1EC2 (SMe, 15 mg/kg/day, p.o.) was also tested. MetS was induced in hereditary hypertriglyceridemic rats (HTG) by the 5 weeks administration of high-fat fructose diet (HFFD: 1 % cholesterol, 7.5 % pork lard, 10 % fructose). The heart function was tested using Langendorff preparation under constant pressure. The functional parameters of isolated heart, dysrhythmias and evoked fibrillations were evaluated in conditions of ischemia-reperfusion. The HFFD increased body weight gain and serum levels of total cholesterol, low-density lipoproteins and blood glucose. The HFFD significantly increased heart flow and force of contraction, compared to standard diet (SD). During the reperfusion, the HFFD caused the increase of the ventricular premature beats number at the expense of decreasing the duration of serious dysrhythmias (ventricular tachycardias and fibrillations). The addition of VitE, SMe or their combination to the HFFD decreased body weight gain, depressed blood pressure, improved particular biochemical parameters. The combination of VitE and SMe suppressed the occurrence of serious dysrhythmias. Our data indicate that the HFFD-related disturbances led to alterations within pathophysiology in HTG rats. The results showed that a combination of antioxidants might have the potential to amend disorders accompanying MetS.

Integrin-Linked Kinase Activation Prevents Ventricular Arrhythmias Induced by Ischemia/Reperfusion Via Inhibition of Connexin 43 Remodeling

Ischemia reperfusion (I/R)-induced arrhythmia is a serious complication in patients with cardiac infarction. Remodeling of connexin (Cx) 43, manifested as phosphorylation, contributes significantly to arrhythmogenesis. Integrin-linked kinase (ILK) attenuated ventricular remodeling and improved cardiac function in rats after myocardial infarction. We hypothesized that ILK, through Cx43 phosphorylation, would be protective against I/R-induced ventricular arrhythmias. Our study showed that I/R-induced ventricular arrhythmias were attenuated by an ILK agonist LPTP and worsened by the ILK inhibitor Cpd22. I/R disrupted Cx43 distribution, but it was partially normalized in the presence of LPTP. Compared with I/R, the phosphorylation of Akt was increased significantly after pretreatment with LPTP. The increase in phosphorylated Akt was physiologically significant because, in the presence of the Akt inhibitor MK2206, the protective effects of LPTP were blocked. This indicated that ILK activation prevented I/R-induced-ventricular arrhythmia, an effect potentially related to inhibition of Cx43 remodeling via Akt activation.

Role of Oxidative Stress in Reperfusion following Myocardial Ischemia and Its Treatments

Myocardial ischemia is a disease with high morbidity and mortality, for which reperfusion is currently the standard intervention. However, the reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MI/RI). Oxidative stress is one of the most important pathological mechanisms in reperfusion injury, which causes apoptosis, autophagy, inflammation, and some other damage in cardiomyocytes through multiple pathways, thus causing irreversible cardiomyocyte damage and cardiac dysfunction. This article reviews the pathological mechanisms of oxidative stress involved in reperfusion injury and the interventions for different pathways and targets, so as to form systematic treatments for oxidative stress-induced myocardial reperfusion injury and make up for the lack of monotherapy.

Protective effect of inhibiting TRPM7 expression on hypoxia post-treatment H9C2 cardiomyocytes

BACKGROUND

Transient receptor potential channel 7 (TRPM7) plays an important role in maintaining intracellular ion concentration and osmotic pressure.

OBJECTIVE

The purpose of this study was to investigate the role and mechanism of inhibiting the expression of TRPM7 in the treatment of distal myocardial ischemia.

METHODS

H9C2 cells were treated with hypoxia post-treatment and reperfusion, respectively, detect the expression of HIF-1α and TRPM7, the concentration of Ca2+ and the degree of apoptosis in the H9C2 cells. The relevant miRNAs targeting TRPM7 were searched, the TRPM7 interference vectors were constructed, and the interference of different interference vectors on TRPM7 in H9C2 cells was detected.

RESULTS

The results showed that hypoxia post-treatment treatment would lead to increased expression of miR-22-3p which directly targeting TRPM7, decreased expression of TRPM7, increased expression of HIF-α and increased intracellular Ca2+ concentration. While reperfusion can increase the expression of HIF-1α and TRPM7 in H9C2 cells and increase the degree of apoptosis.

CONCLUSION

Knockdown of TRPM7 can significantly reduce reperfusion injury in H9C2 cells, reduce the degree of apoptosis, and the TRPM7 interference vector can inhibit the expression of TRPM7 and have a certain protective effect on the reperfusion injury of H9C2 cells.

A pyridoindole antioxidant SMe1EC2 regulates contractility, relaxation ability, cation channel activity, and protein-carbonyl modifications in the aorta of young and old rats with or without diabetes mellitus

We studied the effects of treatment with SMe1EC, a hexahydropyridoindole antioxidant, on vascular reactivity, endothelial function, and oxidonitrosative stress level of thoracic aorta in young and old rats with or without diabetes mellitus. The rats were grouped as young control (YC 3 months old), old control (OC 15 months old), young diabetic (YD), old diabetic (OD), young control treated (YCT), old control treated (OCT), young diabetic treated (YDT), and old diabetic treated (ODT). Diabetes was induced by streptozotocin injection and subsequently SMe1EC2 (10 mg/kg/day, p.o.) was administered to YCT, OCT, YDT, and ODT rats for 5 months. In young and old rats, diabetes resulted in hypertension, weight loss, hyperglycemia, and hypertriglyceridemia, which were partially prevented by SMe1EC2. SMe1EC2 also inhibited the diabetes-induced increase in aorta levels of AGEs (advanced glycosylation end-protein adducts), 4-HNE (4-hydroxy-nonenal-histidine), 3-NT (3-nitrotyrosine), and RAGEs (receptors for AGEs). The contractions of the aorta rings to phenylephrine (Phe) and KCL did not significantly change, but acetylcholine (ACh) and salbutamol relaxations were reduced in OC compared to YC rats. Diabetes induction increased Phe contractions in YC and OC rats, KCL contractions in YC rats, and did not cause further inhibition in already inhibited ACh and salbutamol relaxations in OC rats. We have achieved the lowest levels of ACh relaxation in YD rats compared to other groups. SMe1EC2 did not change the response of aorta to ACh, salbutamol and Phe in YC rats, and ameliorated ACh relaxations in OC and YD but not in OD rats. In YDT and ODT rats, increased Phe and KCL contractions, high blood pressure, and impaired salbutamol relaxations were amended by SMe1EC2. Phe contractions observed in YD and OD rats as well as KCl contractions observed in OC rats were the lowest levels when the rats were treated with SMe1EC2. When the bath solution was shifted to cyclopiazonic acid (CYP) or CYP plus Ca²⁺-free medium, the contraction induced by a single dose of Phe (3 × 10^-6 M) was more inhibited in YD and OD than in YC but not in OC rats. In SMe1EC2-treated rats, neither the presence of CFM nor CFM plus CYP exhibited a significant change in response of aorta to a single dose of Phe. These findings suggest that α1-adrenergic receptor signaling is activated in both age groups of diabetic rats, diabetes activates K⁺-depolarization and calcium mobilization via Ca_V especially in the aorta of young rats, and sensitizes the aorta of old rats to the regulating effect of SMe1EC2. ACh relaxations were inhibited in YC rats, increased in OC rats and unchanged in YD and OD rats when aortic rings pretreated with TEA, an inhibitor of calcium-activated K⁺ channels (K_Ca), or 4-aminopyridine (4-AP), an inhibitor of voltage-sensitive K⁺ channels (K_V). ACh relaxations were inhibited in YCT, OCT, and YDT rats in the presence of 4-AP or TEA. In ODT rats, 4-AP did not change ACh relaxation but TEA inhibited. These findings suggest that the contribution of K_v and K_Ca to ACh relaxation is likely upregulated by SMe1EC2 when the relaxations were inhibited by aging or diabetes. We conclude that SMe1EC2 might be a promising agent for aging and diabetes related vascular disorders.

Monotherapy of experimental metabolic syndrome: II. Study of cardiovascular effects

Metabolic syndrome belongs to the most important risk factors of cardiovascular diseases. The aim of this study was to investigate changes in cardiovascular system induced by high cholesterol and high fat diet (HCHF) in HTG rats and their influence by a pyridoindole antioxidant - SMe1EC2 (S). The effects of S were compared with those of atorvastatin (A). Male HTG rats were fed HCHF (1% cholesterol + 7.5% lard) for 4 weeks. S and A were administered p.o., 50 mg/kg b.w. Following experimental groups were used: Wistar rats (W), hypertriglyceridemic rats (HTG), HTG rats fed HCHF (CHOL), HTG+S (S-HTG), CHOL+S (S-CHOL), and CHOL+A (A-CHOL). Values of blood pressure (BP) and selected ECG parameters were monitored in conscious animals, functions of the isolated heart and aorta were analyzed ex vivo. At the end of the experiment, systolic (sBP) and diastolic (dBP) blood pressure was increased in HTG and CHOL. S and A decreased BP in all treated groups. Accordingly with BP changes, the aortic endothelial function of CHOL was damaged. Both S and A administration ameliorated the endothelium-dependent relaxation to values of W. PQ and QTc intervals were prolonged in CHOL, while the treatment with S or A improved ECG findings. Prodysrhythmogenic threshold was decreased significantly in CHOL and both treatments returned it to the control values. In conclusion, HCHF increased BP, impaired endothelial relaxation of the aorta and potentiated susceptibility of myocardium to dysrhythmias. The effect of S on the changes induced by HCHF diet was more pronounced than that of A.

Effect of a novel stobadine derivative on isolated rat arteries

The antioxidant and reactive-oxygen-species-scavenging activity of stobadine has been demonstrated in previous studies. Recently, chemical modification of this leading structure led to the synthesis of other pyridoindole derivatives with significantly increased intrinsic antioxidant efficacy. Further structural modifications of stobadine provided the opportunity to increase bioavailability and attenuate unwanted side effects, such as α-adrenolytic activity. The aim of the work was to evaluate the direct effect of a novel pyridoindole, SMe1EC2, on the vascular wall ex vivo. The vasomotor effect of SMe1EC2 (1×10^–8–1×10^–4 mol/l) was measured on isolated and pressurized rat cerebral and coronary arterioles using video-microscopy. The effect of SMe1EC2 (1×10^–6 and 1×10^–5 mol/l) on high potassium-, phenylephrine- or serotonin-induced contraction or acetylcholine-induced relaxation was also determined in aortic rings. We found that SMe1EC2 (1×10^–8–1×10^–4 mol/l) elicited significant dilatations in both cerebral and coronary arterioles (max dilatation: 25±8% and 18±5% respectively). Yet, SMe1EC2 (1×10^–6 and 1×10^–5 mol/l) did not influence the tone of aortic rings nor did it affect high potassium-, phenylephrine- or serotonin -induced contractions and acetylcholine-induced relaxation. Thus SMe1EC2 was able to dilate resistance arteries but did not affect aortic contractility. It is likely that SMe1EC2 does not possess α1-adrenolytic and anti-serotoninergic activity in the vascular wall.

Granulocyte colony-stimulating factor improves early remodeling in isoproterenol-induced cardiac injury in rats

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) has been used in some animal models and humans with well-established cardiovascular diseases. However, its effects in the initial stage of progressive non-ischemic heart failure are unknown.

METHODS

Wistar rats (260-300 g) were divided into three groups: control (without any intervention), ISO (150 mg/kg isoproterenol hydrochloride sc, once a day for two consecutive days), and ISO-GCSF (50 μg/kg/d G-CSF for 7 days beginning 24 h after the last administration of ISO). Echocardiography was performed at baseline and after 30 days of follow-up. Subsequently, animals were anesthetized for hemodynamic analysis. The left ventricle was removed for analysis of interstitial collagen deposition and cardiomyocyte hypertrophy.

RESULTS

Isoproterenol led to left ventricular dilation (control, 7.7 ± 0.14 mm; ISO, 8.7 ± 0.16 mm; ISO-GCSF 7.8 ± 0.09 mm; p < 0.05), myocardial fibrosis (control, 2.0 ± 0.18%; ISO, 9.1 ± 0.81%; ISO-GCSF 5.9 ± 0.58%; p < 0.05) and cardiomyocyte hypertrophy (control, 303 ± 10 μm(2); ISO, 356 ± 18 μm(2); ISO-GCSF 338 ± 11 μm(2); p < 0.05). However, G-CSF partially prevented collagen deposition and left ventricular enlargement, with a slight effect on hypertrophy. Characterizing a compensated stage of disease, hemodynamic analysis did not change.

CONCLUSION

G-CSF administered for 7 days was effective in preventing the onset of ventricular remodeling induced by high-dose isoproterenol with decreased collagen deposition and chamber preservation.