Differential expression of Gs in a murine model of homocysteinemic heart failure

Abstract

High plasma homocysteine levels are a known risk factor in heart failure and sudden cardiac death. The G proteins, G_s (stimulatory) and G_i (inhibitory), are involved in calcium regulation; overexpression has pathological consequences. The aims of this study were to examine the differential expression of G_s G protein and G_i in the hearts of hyperhomocysteinemic (Hhcy) mice, and to determine if homocysteine (Hcy) acts as an agonist in cell culture to mediate the change in G protein isoforms. To create Hhcy, heterozygous cystathionine-β-synthase (CBS) knockout (KO) mice were used. Mice were sacrificed, hearts were excised, cardiac tissue homogenates were prepared, and Western blots were performed. The results suggested that G_s G protein was downregulated in cardiac tissue of heterozygous CBS KO mice to 46% that of control hearts. However, the intracellular G_i G protein content remained the same in heterozygous CBS KO mice. Transformed cardiomyocyte HL-1 cells were treated with varying concentrations of homocysteine. The results suggested no detectable differential G_s and G_i expression. This suggested that Hcy did not act as an agonist in vitro to alter G protein content, but that Hcy produced some other in vivo effects to incur these results.