Stress-induced cardiac insufficiency relating to abnormal leptin and FKBP12.6 is ameliorated by CPU0213, an endothelin receptor antagonist, which is not affected by the CYP3A suppressing effect of erythromycin

Erdosteine salvages cardiac necrosis: Novel effect through modulation of MAPK and Nrf-2/HO-1 pathway

Isoproterenol (ISO) induced oxidative stress and inflammation is involved in the pathogenesis of myocardial necrosis. To optimize the effect of erdosteine against myocardial necrosis, male albino Wistar rats were divided into eight groups (n = 6), that is, normal, ISO-control, erdosteine pretreatment with ISO. Rats were administered erdosteine orally for 28 days. Two doses of ISO (85 mg/kg), s.c. were given to ISO-C and erdosteine treatment groups on the 27th and 28th day. On the 29th day, hemodynamic parameters were recorded and the heart was excised for further parameters. In ISO-C rats, significantly increased levels of inflammatory markers, pro-oxidants, and structural damage were observed as compared with normal group. Furthermore, immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling revealed an increased expression of apoptotic proteins. Erdosteine at 80 mg/kg reversed the deleterious effects of ISO and normalized myocardium. Erdosteine showed anti-inflammatory, antiapoptotic, and antioxidant activities through inhibition of MAPK and Nrf-2/HO-1 pathways. To conclude, erdosteine was found protective in ISO-induced myocardial necrosis through MAPK and Nrf-2/HO-1 pathway.

CPUY11018, an azimilide derivative, ameliorates isoproterenol-induced cardiac insufficiency through relieving dysfunctional mitochondria and endoplasmic reticulum

Objectives

Deterioration of cardiac performance under stress may be partly mediated by dysfunctional mitochondria and endoplasmic reticulum (ER) that is likely related to an activation of NADPH oxidase (NOX) and an increase in pro-inflammatory factors. We investigated if a new compound CPUY11018 (CPUY) derived from Azimilide could ameliorate the stress impaired cardiac performance.

Methods

Forty-eight male Sprague Dawley rats were randomly divided into six groups and were injected with isoproterenol (ISO, 1 ml/kg, s.c.) for 10 days. Cardiac myocytes and fibroblasts from neonate rats were incubated with ISO. CPUY was employed and compared with apocynin (APO) – an inhibitor of NOX.

Key findings

In ISO-treated group, the compromised haemodynamics and cardiac remodelling were significant with dysfunctional mitochondria indicated by decreased MnSOD and mitochondrial membrane potential, and an enhanced reactive oxygen species genesis. Downregulation of FKBP12.6, CASQ2 and SERCA2a was also remarkable in vivo and in vitro implying an abnormal ER. Upregulated Nox4, p22phox and p47phox were significant, associated with upregulation of Src, IκBβ and NFκB, and downregulation of pAMPK/AMPK and Cx40 in vivo and in vitro. These abnormalities were relieved by CPUY and APO.

Conclusions

CPUY is potential in managing cardiac insufficiency through normalizing mitochondria and ER in the affected heart.

Exogenous hydrogen sulfide alleviates high glucose-induced cardiotoxicity via inhibition of leptin signaling in H9c2 cells

Hydrogen sulfide (H₂S) protects cardiomyoblasts against high glucose (HG)-induced injury by inhibiting the activation of p38 mitogen-activated protein kinase (MAPK). This study aims to determine whether the leptin-p38 MAPK pathway is involved in HG-induced injury and whether exogenous H2S prevents the HG-induced insult through inhibition of the leptin-p38 MAPK pathway in H9c2 cells. H9c2 cells were treated with 35 mM glucose (HG) for 24 h to establish a HG-induced cardiomyocyte injury model. Cell viability; mitochondrial membrane potential (ΔΨ m); apoptosis; reactive oxygen species (ROS) level; and leptin, leptin receptor, and p38 MAPK expression level were measured by the methods indicated. The results showed pretreatment of H9c2 cells with NaHS before exposure to HG led to an increase in cell viability, decrease in apoptotic cells, ROS generation, and a loss of ΔΨ m. Exposure of H9c2 cells to 35 mM glucose for 24 h significantly upregulated the expression levels of leptin and leptin receptors. The increased expression levels of leptin and leptin receptors were markedly attenuated by pretreatment with 400 μM NaHS. In addition, the HG-induced increase in phosphorylated (p) p38 MAPK expression was ameliorated by pretreatment with 50 ng/ml leptin antagonist. In conclusion, the present study has demonstrated for the first time that the leptin-p38 MAPK pathway contributes to the HG-induced injury in H9c2 cells and that exogenous H₂S protects H9c2 cells against HG-induced injury at least in part by inhibiting the activation of leptin-p38 MAPK pathway.

AQP4 KO exacerbating renal dysfunction is mediated by endoplasmic reticulum stress and p66Shc and is attenuated by apocynin and endothelin antagonist CPU0213

Aquaporin 4 (AQP4) is essential in normal kidney. We hypothesized that AQP4 knockout (KO) may exacerbate pro-inflammatory factors in the stress induced renal insufficiency. Mechanisms underlying are likely due to activating renal oxidative stress adaptor p66Shc and endoplasmic reticulum (ER) stress that could be mediated by endothelin (ET)-NADPH oxidase (NOX) pathway. AQP4 KO and wild type (WT) mice were randomly divided into 4 groups: control, isoproterenol (1mg/kg, s.c., 5d), and interventions in the last 3 days with either apocynin (NADPH oxidase inhibitor, 100mg/kg, p.o.) or CPU0213 (a dual endothelin receptor antagonist 200mg/kg, p.o.). In addition, HK2 cells were cultured in 4 groups: control, isoproterenol (10(-6)M), intervened with apocynin (10(-6)M) or CPU0213 (10(-6)M). In AQP4 KO mice elevated creatinine levels were further increased by isoproterenol compared to AQP4 KO alone. In RT-PCR, western blot and immunohistochemical assay p66Shc and PERK were significantly increased in the kidney of AQP4 KO mice, associated with pro-inflammatory factors CX40, CX43, MMP-9 and ETA compared to the WT mice. Expression of AQP4 was escalated in isoproterenol incubated HK2 cells, and the enhanced protein of PERK and p-PERK/PERK, and p66shc in vivo and in vitro were significantly attenuated by either apocynin or CPU0213. In conclusion, AQP4 KO deteriorates renal dysfunction due to exacerbating ER stress and p66Shc in the kidney. Either endothelin antagonism or NADPH oxidase blockade partly relieves renal dysfunction through suppressing abnormal biomarkers by APQ4 KO and isoproterenol in the kidney.

Sildenafil and FDP-Sr attenuate diabetic cardiomyopathy by suppressing abnormal expression of myocardial CASQ2, FKBP12.6, and SERCA2a in rats

AIM

To study whether calcium-modulating proteins CASQ2, FKBP12.6 and SERCA2a participate in diabetic cardiomyopathy, and whether the beneficial actions of testosterone, sildenafil or fructose diphosphate Sr (FDP-Sr) in the treatment of diabetic cardiomyopathy result from suppressing these molecules.

METHODS

Fifty male Sprague-Dawley (SD) rats were divided into five groups. Except for the normal group (non-diabetic), the other four groups were injected with streptozotocin (STZ, 60 mg/kg, ip) to induce diabetes. Four weeks after STZ injection, the four groups received sildenafil (12 mg·kg(-1)·d(-1), ig, for 4 week), FDP-Sr (200 mg/kg, ig, for 4 week), testosterone propionate (4 mg·kg(-1)·d(-1), sc, for 4 week), or no treatment, respectively.

RESULTS

In the diabetic rats, blood glucose, free fatty acids, triglycerides, total cholesterol, and low-density lipoprotein cholesterol (LDL-C) were significantly increased, while high-density lipoprotein cholesterol (HDL-C) was significantly reduced, as compared to the non-diabetic rats. Cardiac dysfunction and myocardial hypertrophy of the diabetic rats were associated with increased mRNA and protein expression of iNOS, OBRb, and PKCɛ, while expression of CASQ2, SERCA2a, and FKBP12.6 was significantly down-regulated. Sildenafil and FDP-Sr, but not testosterone, significantly attenuated the biomarker abnormalities, without changing the metabolic abnormalities.

CONCLUSION

CASQ2, FKBP12.6 and SERCA2a were down-regulated in diabetic cardiomyopathy. Sildenafil and FDP-Sr, but not testosterone, attenuated the cardiac dysfunction in diabetic cardiomyopathy, without changing the metabolic abnormalities, which may results from inhibiting oxidative and inflammatory cytokines and improving calcium homeostasis.

Isoproterenol-induced FKBP12.6/12 downregulation is modulated by ETA and ETB receptors and reversed by argirhein, a derivative of rhein

AIM

To investigate which endothelin receptors mediated isoproterenol (ISO)-induced downregulation of FKBP12.6/12 in cardiomyocytes and study whether argirhein, a novel compound containing rhein and L-arginine that has anti-inflammatory activity, could reverse the downregulation of FKBP12.6/12 induced by ISO.

METHODS

Neonatal rat cardiomyocytes were incubated with ISO to downregulate FKBP12.6/12. Then the cells were treated with a selective ET(A) blocker (PD156707) and a ET(B) blocker (IRL1038), a dual ET(A)/ET(B) antagonist (CPU0213), and argirhein, respectively. FKBP12.6/12 expression was assayed by RT-PCR, Western blot, and immunocytochemistry.

RESULTS

The expression of FKBP12.6 mRNA was reduced by 37.7% (P<0.01) and 28.9% (P<0.05) relative to the control by ISO 1 and 0.1 μmol/L, respectively, but no response to ISO 0.01 μmol/L was observed in vitro. FKBP12.6/12 protein expression was reduced by 47.2% (P<0.01) and 37.8% (P<0.05) by ISO 1 and 0.1 μmol/L, respectively. This decrease was reversed significantly by PD156707, or IRL1038, and CPU0213. CPU0213 was more potent than either PD156707 or IRL-1038. Argirhein 10 μmol/L blunted the downregulation of FKBP12.6/12 by ISO, as demonstrated by the rising mRNA and protein levels and by the fluorescent density of the ISO-incubated cardiomyocytes.

CONCLUSION

In cardiomyocytes, the ISO induced downregulation of FKBP12.6/12 is modulated by both ET(A) and ET(B). A new compound, argirein, reversed the down-regulation of FKBP12.6/12 expression in myocardial cells stimulated with ISO.

Isoflurane preconditioning increases endothelial cell tolerance to in-vitro simulated ischaemia

OBJECTIVES

Isoflurane preconditioning has been shown to protect endothelial cells against lipopolysaccharide and cytokine induced injury. This study was designed to determine whether isoflurane preconditioning increased endothelial cell tolerance to ischaemia.

METHODS

Bovine pulmonary arterial endothelial cells were exposed or not exposed to various concentrations of isoflurane for 1 h. After a 30-min isoflurane-free period, cells were subjected to oxygen-glucose deprivation (OGD) for 3 h and reoxygenation for 1 h. Lactate dehydrogenase release from cells was used to measure cell injury. In some experiments, various protein kinase C (PKC) inhibitors and ATP-sensitive potassium channel (K(ATP) channel) inhibitors were present from 30 min before isoflurane treatment to the end of isoflurane treatment.

KEY FINDINGS

Isoflurane preconditioning dose-dependently decreased the OGD induced lactate dehydrogenase release. This protection was inhibited by 2 µM chelerythrine, a general PKC inhibitor, or 10 µM Gö6976, an inhibitor for the conventional PKCs. This protection was also inhibited by 0.3 µM glybenclamide, a general K(ATP) channel inhibitor, and 500 µM 5-hydroxydecanoate, a mitochondrial K(ATP) channel blocker. In addition, pretreatment with 100 µM diazoxide, a K(ATP) channel activator, for 1 h also reduced OGD induced endothelial cell injury. This diazoxide induced protection was inhibited by chelerythrine.

CONCLUSIONS

The results suggest that isoflurane preconditioning induces endothelial protection against in-vitro simulated ischemia. This protection may be mediated at least in part by conventional PKCs and mitochondrial K(ATP) channels. The results also indicate that PKCs may be downstream of K(ATP) channels in causing endothelial protection.

Isoproterenol disperses distribution of NADPH oxidase, MMP-9, and pPKCepsilon in the heart, which are mitigated by endothelin receptor antagonist CPU0213

AIM

Spatial dispersion of bioactive substances in the myocardium could serve as pathological basis for arrhythmogenesis and cardiac impairment by beta-adrenoceptor stimulation. We hypothesized that dispersed NADPH oxidase, protein kinase Cepsilon (PKCepsilon), early response gene (ERG), and matrix metalloproteinase 9(MMP-9) across the heart by isoproterenol (ISO) medication might be mediated by the endothelin (ET) - ROS pathway. We aimed to verify if ISO induced spatially heterogeneous distribution of pPKCepsilon, NAPDH oxidase, MMP-9 and ERG could be mitigated by either an ET receptor antagonist CPU0213 or iNOS inhibitor aminoguanidine.

METHODS

Rats were treated with ISO (1 mg/kg sc) for 10 days, and drug interventions (mg/kg) either CPU0213 (30 sc) or aminoguanidine (100 ip) were administered on days 8-10. Expression of NADPH oxidase, MMP-9, ERG, and PKCepsilon in the left and right ventricle (LV, RV) and septum (S) were measured separately.

RESULTS

Ventricular hypertrophy was found in the LV, S, and RV, in association with dispersed QTc and oxidative stress in ISO-treated rats. mRNA and protein expression of MMP-9, PKCepsilon, NADPH oxidase and ERG in the LV, S, and RV were obviously dispersed, with augmented expression mainly in the LV and S. Dispersed parameters were re-harmonized by either CPU0213, or aminoguanidine.

CONCLUSION

We found at the first time that ISO-induced dispersed distribution of pPKCepsilon, NADPH oxidase, MMP-9, and ERG in the LV, S, and RV of the heart, which were suppressed by either CPU0213 or aminoguanidine. It indicates that the ET-ROS pathway plays a role in the dispersed distribution of bioactive substances following sustained beta-receptor stimulation.