Effects of endothelin-1 antagonist BQ610 on hypoxia-induced injury and [Ca2+]i changes in cultured neonatal rat cardiomyocytes

Shexiang Tongxin Dropping Pill () Protects against Na2S2O4-Induced Hypoxia-Reoxygenation Injury in H9c2 Cells

OBJECTIVES

To investigate the protective effects of Shexiang Tongxin Dropping Pill (, STP) on Na₂S₂O₄-induced hypoxia-reoxygenation injury in cardiomyoblast H9c2 cells.

METHODS

The cell viability and levels of mRNA and protein expression in H9c2 cells were determined following Na₂S₂O₄-induced hypoxia using Hoechst staining, annexin V/propidium iodide (PI) flow cytometry, real-time polymerase chain reaction and Western blot analysis.

RESULTS

STP pretreatment significantly increased the viability and inhibited aberrant morphological changes in H9c2 cardiomyoblast cells induced by Na₂S₂O₄ treatment (P<0.05). In addition, STP pretreatment attenuated Na₂S₂O₄-induced hypoxic damage, down-regulated the expression of pro-apoptotic Bax, and up-regulated the expression of anti-apoptotic Bcl-2 in H9c2 cells (P<0.05).

CONCLUSIONS

STP was strongly cardioprotective in hypoxia-reoxygenation injury by preventing hypoxic damage and inhibiting cellular apoptosis. These results further support the use of STP as an effective drug for the treatment of ischemic heart disease.

Antagonism of endothelin-1 inhibits hypoxia-induced apoptosis in cardiomyocytes

Apoptosis is well documented to be a common feature of many pathological processes of the heart. Exogenous endothelin-1 (ET-1) has been shown to be proapoptotic or antiapoptotic, depending on ET-1 concentration, cell type, and the ratio of ETA/ETB receptor subtypes. The role of endogenous ET-1 in cardiomyocyte apoptosis, however, is not clarified. This study observed the effects of the ETA-receptor antagonists BQ610 and BQ123 and the ETB-receptor antagonist BQ788 on hypoxia-induced apoptosis in primary cultured neonatal rat cardiomyocytes. Hypoxic apoptosis was induced by incubating cardiomyocytes in serum-free medium under 3% O2 and 5% CO2 for 24 h and evaluated by TUNEL analysis and flow cytometry. TUNEL analysis showed that the apoptotic cardiomyocytes constituted 24.2% +/- 2.2% of the total cells under hypoxic conditions. Treatment with BQ610 (5 micromol/L) significantly reduced the apoptosis rate to 13.2% +/- 3.7% (data from 4 independent experiments, p < 0.01 vs. hypoxia). Flow cytometry showed that the percentage of apoptotic cells positively stained with annexin V and propidium iodide was 42.76% +/- 4.44% (n = 12) in cultures subjected to hypoxia. BQ123 at 0.04, 0.2, and 1.0 micromol/L dose-dependently reduced the apoptosis rate to 34.00% +/- 10.35% (n = 6, p < 0.05), 30.38% +/- 8.28% (n = 6, p < 0.01), and 22.89% +/- 4.19% (n = 6, p < 0.01), respectively. In contrast, BQ788 did not affect hypoxic apoptosis. These findings suggested that endogenous ET-1 contributed to hypoxia-induced apoptosis in cultured cardiomyocytes, which was mediated by ETA receptors, but not by ETB receptors.

Salusins protect neonatal rat cardiomyocytes from serum deprivation-induced cell death through upregulation of GRP78

Salusin-alpha and salusin-beta are newly identified bioactive peptides with hemodynamic and mitogenic activities. Recent studies have shown that salusins improve calcium uptake and protein synthesis in neonatal rat cardiomyocytes, suggesting that salusins may be regulatory factors for myocardial growth and hypertrophy. In this study, we investigated whether salusins improve the survival of cardiomyocytes after serum deprivation. Cultured neonatal cardiomyocytes were treated with or without salusins (salusin-alpha or salusin-beta) at a concentration range of 10 to 10 mol/L for 24 h under serum deprivation conditions. Cardiomyocytes viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazonium bromide assay. Cell death or apoptosis rate was identified by flow cytometry analysis. Compared to serum deprivation-only groups, cardiomyocyte viability was significantly increased in salusin-alpha or salusin-beta groups. Cell death rate was decreased after administration of 10 mol/L salusin-alpha or salusin-beta. Salusin-beta was able to decrease the apoptotic rate. Salusins also increased the expression of cardiomyocyte glucose-regulated protein 78 (GRP78) as estimated by Western blot. Furthermore, antisense oligodeoxynucleotide specifically against GRP78 attenuated or abrogated antiapoptosis or survival effects of salusin-beta. These findings suggest that salusin-alpha and salusin-beta may be a potential survival factor against serum deprivation-induced myocardial cell death and that this cardioprotective effect may involve an upregulation of GRP78 expression in cardiomyocytes.