Abstract
Aim:
Previous studies have demonstrated that glycine (GLY) markedly reduces lipopolysaccharide (LPS)-induced myocardial injury. However, the mechanism of this effect is still unclear. The present study investigated the effect of GLY on cytosolic calcium concentration ([Ca2+]c) and tumor necrosis factor-α (TNFα) production in cardiomyocytes exposed to LPS, as well as whether the glycine-gated chloride channel is involved in this process.
Methods:
Neonatal rat cardiomyocytes were isolated, and the [Ca2+]c and TNFα levels were determined by using Fura-2 and a Quantikine enzyme-linked immunosorbent assay, respectively. The distribution of the GLY receptor and GLY-induced currents in cardiomyocytes were also investigated using immunocytochemistry and the whole-cell patch-clamp technique, respectively.
Results:
LPS at concentrations ranging from 10 ng/mL to 100 μg/mL significantly stimulated TNFα production. GLY did not inhibit TNFα production induced by LPS at concentrations below 10 ng/mL but did significantly decrease TNFα release stimulated by 100 μg/mL LPS and prevented an LPS-induced increase in [Ca2+]c, which was reversed by strychnine, a glycine receptor antagonist. GLY did not block the isoproterenol-induced increase in [Ca2+]c, but did prevent the potassium chloride-induced increase in [Ca2+]c in cardiomyocytes. Strychnine reversed the inhibition of the KCl–stimulated elevation in [Ca2+]c by GLY. In chloride-free buffer, GLY had no effect on the dipotassium hydrogen phosphate-induced increase in [Ca2+]c. Furthermore, GLY receptor α1 and β subunit-immunoreactive spots were observed in cardiomyocytes, and GLY-evoked currents were blocked by strychnine.
Conclusion:
Cardiomyocytes possess the glycine-gated chloride channel, through which GLY prevents the increase in [Ca2+]c and inhibits the TNFα production induced by LPS at high doses in neonatal rat cardiomyocytes.
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Acknowledgements
This project was supported by grants from the National Natural Science Foundation of China (No 30470718) and the Guangdong Natural Science Foundation (No 04105844).
The authors are grateful to Prof Li-xin CHEN, Dr Lin-yan ZHU, and Mr Lin-jie YANG in the school of medicine, Ji-nan University, for the electrophysiological experiments.
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Wang, Hd., Lü, Xx., Lu, Dx. et al. Glycine inhibits the LPS-induced increase in cytosolic Ca2+ concentration and TNFα production in cardiomyocytes by activating a glycine receptor. Acta Pharmacol Sin 30, 1107–1114 (2009). https://doi.org/10.1038/aps.2009.106
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DOI: https://doi.org/10.1038/aps.2009.106
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