Glycine inhibits the LPS-induced increase in cytosolic Ca2+ concentration and TNFalpha production in cardiomyocytes by activating a glycine receptor.
OBJECTIVE
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-alpha (TNFalpha) 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 TNFalpha 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 microg/mL significantly stimulated TNFalpha production. GLY did not inhibit TNFalpha production induced by LPS at concentrations below 10 ng/mL but did significantly decrease TNFalpha release stimulated by 100 microg/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 alpha1 and beta subunit-immunoreactive spots were observed in cardiomyocytes, and GLY-evoked currents were blocked by strychnine.


CONCLUSIONS
Cardiomyocytes possess the glycine-gated chloride channel, through which GLY prevents the increase in [Ca2+]c and inhibits the TNFalpha production induced by LPS at high doses in neonatal rat cardiomyocytes.
Wang
Hua-dong
HD
Department of Pathophysiology, School of Medicine, Ji-nan University, Guangzhou 510632, China.
Lü
Xiu-xiu
XX
Lu
Da-xiang
DX
Qi
Ren-bin
RB
Wang
Yan-ping
YP
Fu
Yong-mei
YM
Wang
Li-wei
LW
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D005998:Glycine / Q000494:pharmacology*; D018684:Glycine Agents / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000009:adverse effects; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D011189:Potassium Chloride / Q000378:metabolism; D017680:Potassium Compounds / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018009:Receptors, Glycine / Q000819:agonists* / Q000378:metabolism*; D013331:Strychnine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D002316:Cardiotonic Agents; D018684:Glycine Agents; D008070:Lipopolysaccharides; D010710:Phosphates; D017680:Potassium Compounds; D018009:Receptors, Glycine; D014409:Tumor Necrosis Factor-alpha; D011189:Potassium Chloride; C013216:potassium phosphate; D013331:Strychnine; D007545:Isoproterenol; D002118:Calcium; D005998:Glycine