Endothelin receptor antagonist CPU0213 and vitamin E reverse downregulation of FKBP12.6 and SERCA2a: a role of hyperphosphorylation of PKCepsilon

Exogenous hydrogen sulphide ameliorates diabetic cardiomyopathy in rats by reversing disordered calcium-handling system in sarcoplasmic reticulum

OBJECTIVES

Hydrogen sulphide (H2 S) has been found to be involved in cardiovascular diseases, but the exact mechanism has not been clarified. The purpose of this study was to investigate whether sodium hydrogen sulphide (NaHS), the donor of H2 S, can improve diabetic cardiomyopathy by reversing disordered calcium-handling system in sarcoplasmic reticulum (SR).

METHODS

Sprague Dawley rats were injected with streptozotocin (STZ, 60 mg/kg, i.p.) to build diabetic model. Treatment groups included: aminoguanidine group (AG, 100 mg/kg, p.o.) and NaHS group (5 mg/kg per day, s.c.).

KEY FINDINGS

Cardiac dysfunction and myocardial hypertrophy were found in diabetic model (DM) group, along with increased ROS levels and upregulated mRNA and protein expressions of NADPH p22(phox) , endothelin A receptor (ETA ) and protein kinase Cε (PKCε). Expressions of calcium-handling proteins in SR including FK506-binding proteins (FKBP12.6), sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) and calsequestrin 2 (CASQ2) were downregulated in DM group, accompanied by elevated concentration of diastolic free calcium in high glucose-incubated cardiomyocytes, indicating of calcium leak. After treated by NaHS, these abnormalities were attenuated significantly.

CONCLUSIONS

Exogenous H2 S played a protective role in diabetic cardiomyopathy by inhibiting abnormal calcium-handling system in SR and ET-NADPH oxidase-PKCε pathway.

Argirein alleviates stress-induced and diabetic hypogonadism in rats via normalizing testis endothelin receptor A and connexin 43

AIM

Argirein (rhein-arginine) is a derivative of rhein isolated from Chinese rhubarb (Rheum Officinale Baill.) that exhibits antioxidant and anti-inflammatory activities. In the present study we investigated the effects of argirein on stress-induced (hypergonadotrophic) and diabetic (hypogonadotrophic) hypogonadism in male rats.

METHODS

Stress-induced and diabetic hypogonadism was induced in male rats via injection of isoproterenol (ISO) or streptozotocin (STZ). ISO-injected rats were treated with argirein (30 mg·kg(-1)·d(-1), po) or testosterone replacement (0.5 mg·kg(-1)·d(-1), sc) for 5 days, and STZ-injected rats were treated with argirein (40-120 mg·kg(-1)·d(-1), po) or aminoguanidine (100 mg·kg(-1)·d(-1), po) for 4 weeks. After the rats were euthanized, blood samples and testes were collected. Serum hormone levels were measured, and the expression of endothelin receptor A (ETA), connexin 43 (Cx43) and other proteins in testes was detected. For in vitro experiments, testis homogenate was prepared from normal male rats, and incubated with ISO (1 μmol/L) or high glucose (27 mmol/L).

RESULTS

ISO injection induced hyper-gonadotrophic hypogonadism characterized by low testosterone and high FSH and LH levels in the serum, whereas STZ injection induced hypogonadotrophic hypogonadism as evidenced by low testosterone and low FSH and LH levels in the serum. In the testes of ISO- and STZ-injected rats, the expression of ETA, MMP-9, NADPH oxidase and pPKCε was significantly increased, and the expression of Cx43 was decreased. Administration of argirein attenuated both the abnormal serum hormone levels and the testis changes in ISO- and STZ-injected rats, and aminoguanidine produced similar actions in STZ-injected rats; testosterone replacement reversed the abnormal serum hormone levels, but did not affect the testis changes in ISO-injected rats. Argirein (0.3-3 μmol/L) exerted similar effects in testis homogenate incubated with ISO or high glucose in vitro.

CONCLUSION

Two types of hypogonadism of male rats exhibit increased expression of ETA and depressed expression of Cx43 in testes, despite different patterns of serum FSH and LH. Argirein alleviates the two types of male hypogonadism via normalizing ETA and Cx43 in testes.

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.

Depressed calcium-handling proteins due to endoplasmic reticulum stress and apoptosis in the diabetic heart are attenuated by argirein

Diabetic cardiomyopathy (DC) is a unique disease frequently complicated to diabetes mellitus, manifesting endoplasmic reticulum (ER) stress and depressed calcium-handling proteins. We hypothesized that the abnormal FKBP12.6, SERCA2a, and CASQ2 are consequent to ER stress and apoptosis that are likely due to an entity of inflammation. These abnormalities may be attributed to reactive oxygen species genesis from activated NADPH oxidase which could respond to argirein (AR) through its anti-inflammatory activity. Sprague Dawley rats were randomly divided into six groups. Except the normal group, rats were injected with streptozotocin (STZ; 60 mg/kg, i.p.) once. During weeks 5 to 8 following STZ injection, rats were treated (in milligrams per kilogram per day, i.g.) with aminoguanidine (AMG, 100; an inducible nitric oxide synthase and AGEs inhibitor) or three doses of AR (50, 100, and 200). FKBP12.6, SERCA2a, and CASQ2 and ER stress chaperones Bip and PERK and apoptotic molecules were monitored in vivo and in vitro. Impaired cardiac performance and downregulated FKBP12.6, SERCA2a, and CASQ2 were significant in DC in vivo, and abnormal calcium-handling proteins were also found in high-glucose-incubated myocytes in vitro. ER stress manifested by upregulated Bip and PERK was predominant in association with DNA ladder and upregulated Bax and downregulated BCL-2 in vivo and in vitro. AR is effective to attenuate these abnormalities compared to AMG. Diabetic myocardium has inflammatory entity expressed as ER stress contributing to downregulated calcium-handling proteins. AR has potential in managing DC through attenuating depressed calcium-handling proteins, activated ER stress, and apoptosis in the myocardium.

Raisanberine protected pulmonary arterial rings and cardiac myocytes of rats against hypoxia injury by suppressing NADPH oxidase and calcium influx

AIM

To investigate the protection of pulmonary arterial rings and cardiac myocytes of rats by raisanberine (RS), a derivative of berberine, against hypoxia injury and to elucidate the action mechanisms.

METHODS

Adult SD rats were exposed to intermittent hypoxia for 17 d or 28 d. The pulmonary arterial rings were isolated and vascular activity was measured using a transducer and computer-aided system. The difference in the tension produced by phenylephrine in the presence and absence of L-nitroarginine (10 μmol/L) was referred to as the NO bioavailability; the maximum release of NO was assessed by the ratio of the maximal dilatation caused by ACh to those caused by sodium nitroprusside. After the lungs were fixed, the internal and the external diameters of the pulmonary arterioles were measured using a graphic analysis system. Cultured cardiac myocytes from neonatal rats were exposed to H(2)O(2) (10 μmol/L) to mimic hypoxia injury. ROS generation and [Ca(2+)](i) level in the myocytes were measured using DHE and Fluo-3 fluorescence, respectively.

RESULTS

Oral administration of RS (80 mg/kg), the NADPH oxidase inhibitor apocynin (APO, 80 mg/kg) or Ca(2+) channel blocker nifedipine (Nif, 10 mg/kg,) significantly alleviated the abnormal increase in the vasoconstriction force and endothelium-related vasodilatation induced by the intermittent hypoxia. The intermittent hypoxia markedly decreased the NO bioavailability and maximal NO release from pulmonary arterial rings, which were reversed by APO or RS administration. However, RS administration did not affect the NO bioavailability and maximal NO release from pulmonary arterial rings of normal rats. RS, Nif or APO administration significantly attenuated the pulmonary arteriole remodeling. Treatment of cultured cardiac myocytes with RS (10 μmol/L) suppressed the ROS generation and [Ca(2+)](i) increase induced by H(2)O(2), which were comparable to those caused by APO (10 μmol/L) or Nif (0.1 μmol/L).

CONCLUSION

Raisanberine relieved hypoxic/oxidant insults to the pulmonary artery and cardiac myocytes of rats by suppressing activated NADPH oxidase and increased calcium influx.

Comparison of sildenafil with strontium fructose diphosphate in improving erectile dysfunction against upregulated cavernosal NADPH oxidase, protein kinase Cε, and endothelin system in diabetic rats

Objectives

Phosphodiesterase type 5 inhibitors are potent in relieving erectile dysfunction (ED), however, they are less satisfactory in diabetic patients, probably due to the pro-inflammatory biomarkers caused by diabetes. Therefore, it was interesting to compare the effects of sildenafil with strontium fructose 1,6-diphosphate (FDP-Sr) on cavernosal vascular activity and expressions of pro-inflammatory biomarkers in diabetic rats.

Methods

Male Sprague-Dawley rats were injected with streptozocin (60 mg/kg, i.p.) to develop diabetes. The animals were diabetic for eight weeks with sildenafil (12 mg/kg per day) or FDP-Sr (200 mg/kg per day) being administered for the last four of those eight weeks.

Key findings

Sildenafil was more effective in relieving reduced vascular dilatation (relevant to ED), but less in attenuating over-expressions of NADPH oxidase p22, p47 and p67 subunits, and ETA/BR (endothelin receptor type A and type B) in the diabetic cavernosum. In contrast, FDP-Sr was less effective in improving ED, but more effective in normalizing the abnormal NADPH oxidase and ETA/BR.

Conclusions

The activated NADPH oxidase and upregulated ETAR and ETBR due to diabetic lesions played a minor or moderate role in ED. By offering extra ATP, FPD-Sr suppressed these abnormalities, however, sildenafil did not. A combined therapy of sildenafil with FDP-Sr may be more effective in relieving ED in diabetic patients through normalizing pro-inflammatory cytokines and improving the nitric oxide/cGMP pathway in the cavernosum.

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.

Role of endothelin receptor A and NADPH oxidase in vascular abnormalities

Vascular dilatation is critically impaired in many diseases and is encountered by an upregulated endothelin receptor A (ETA) in the vasculature in association with a decline in nitric oxide bioavailability. Diabetic vasculopathy is characterized as a compromised vascular dilatation, implicated in many diabetic complications. It appears to be activated ETA and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase in the vasculature. Glucose-lowering agents do not always blunt these changes, as these changes may be progressive leading to the end stage of renal disease. The vascular insults by hypertension, hyperglycemia and aging may share the changes with diabetic vascular beds. Endothelin receptor antagonist CPU0213 and ingredients from plant origins such as CPU86017, p-benzyl-tetra-hydro-berberine are effective in attenuating vascular abnormality by normalizing changes of biomarkers in the vascular wall. The early sign of subclinical atherosclerosis presented as an intima media thickness in the carotid may indicate endothelium dysfunction. The reduced ABI (ankle brachial index) has been taken to predict patients at risk for cardiovascular and cerebrovascular events, and an increased risk of mortality from all causes and cardiovascular disease. An application of agents which suppress the activated ET-NADPH oxidase in the vascular wall is beneficial to attenuate vascular abnormalities. It is worth testing the activity of these agents further for the potential in relieving abnormal vascular activity, reducing the risk of morbidity and mortality in patients at risk.

CPU86017, a berberine derivative, attenuates cardiac failure through normalizing calcium leakage and downregulated phospholamban and exerting antioxidant activity

AIM

To investigate whether CPU86017, a berberine derivative, attenuates heart failure by blocking calcium influx and exerting its antioxidant activity.

METHODS

Myocardial infarction was induced in male Sprague-Dawley rats for 17 d followed by isoproterenol (ISO) (5 mg/kg, sc) treatment for 5 d to reduce cardiac function. The rats were divided into 5 groups: sham operation, myocardial infarction (MI), MI plus ISO, and co-treated (in mg/kg, po) with either propranolol (PRO, 10) or CPU86017 (80). Hemodynamic measurements were conducted, and measurements of the redox system, calcium handling proteins and endothelin (ET) system in vivo were done. Furthermore, calcium flux studies and PLB immunocytochemistry were conducted in vitro.

RESULTS

Compared to sham operation, HF was evident following MI and further worsened by ISO treatment. This occurred in parallel with downregulated mRNA and protein production of SERCA2a, PLB, and FKBP12.6, and was associated with upregulation of preproET-1, endothelin converting enzyme, and PKA mRNA production in the myocardium in vivo. Calcium leakage was induced by ISO treatment of isolated beating myocytes in vitro. These changes were attenuated by treatment with either PRO or CPU86017. PLB fluorescence in myocytes was downregulated by ISO treatment, and was relieved significantly by treatment with antioxidant aminoguanidine, ascorbic acid or CPU86017 in vitro.

CONCLUSION

HF, calcium leakage, downregulated PLB, FKBP12.6, SERCA2a production, and upregulated PKA were caused by ISO treatment, and were abolished by CPU86017 treatment. The beneficial effects of CPU86017 are attributable to its antioxidant and calcium influx blocking effects.

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

Objectives

Cardiac injury induced by isoprenaline produces stress. This stress can be mediated by the activated endothelin and leptin pathway; thus, the endothelin receptor antagonist CPU0213 may reverse these changes. CPU0213 is metabolized mainly by cytochrome P450 (CYP)3A, thus, erythromycin, an inhibitor of CYP3A, could affect its effects by raising its plasma levels.

Methods

Forty rats were divided into five groups. Group 1 rats were normal. Group 2 rats were administered isoprenaline (1 mg/kg, s.c.) for 10 days. Groups 3, 4 and 5 were administered isoprenaline, but group 3 was given erythromycin (100 mg/kg, p.o.) alone on days six to ten, group 4 was given CPU0213 20 mg/kg (s.c.) on days six to ten, whilst group 5 received erythromycin plus CPU0213 on days six to ten. Measurements were conducted to observe changes in the haemodynamics, cardiac weight index, serum lactate dehydrogenase and creatine kinase levels, and expression of endothelin receptor A (ETa), leptin and its OBRb receptor.

Key findings

In isoprenaline-treated rats, cardiac hypertrophy and dysfunction were found. This was associated with upregulated myocardial leptin protein and OBRb receptor mRNA. Immunohistochemical assay of ETa was upregulated, accompanied with downregulation of FKBP12.6 (calstabin 2) in isoprenaline-treated rats. These effects were significantly reversed by CPU0213. HPLC assay presented an increased plasma level of CPU0213 by erythromycin, but no change in its effects.

Conclusions

CPU0213 improved isoprenaline-induced cardiomyopathy by modulating ETa, leptin and FKBP12.6. However, erythromycin increased plasma levels but did not change its effects.

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.