Question:

CT-1 is a cardioprotective cytokine which acts through LIF receptor β/glycoprotein 130 (gp130)-coupled signaling pathways. In the present study the effects of CT-1 on the differentiation of cardiac cells from mouse embryonic stem (ES) cells was investigated.

Results:

Our data show that CT-1 as well gp130 expression was transiently increased during cardiomyogenesis of ES cells. Treatment of differentiating ES cells with CT-1 dose-dependent stimulated cardiomyogenesis, increased the cardiac transcription factors MEF2c and Nkx-2.5, the cardiac structural proteins α-actinin, MLC2a, MYH7, MLC1a and MLC2v as well as HCN4 which is prominently expressed in the pace maker region of the mammalian heart. Furthermore cultivation of ES cells under hypoxic (1% oxygen) conditions significantly increased CT-1 expression. In isolated cells CT-1 elicited a transient calcium response which was abolished in presence of the intracellular calcium chelator BAPTA, AM. Exogenous treatment with CT-1 as well as hypoxia treatment resulted in intracellular CT-1 translocation into the cell nucleus within 2-4 h. The stimulation of cardiomyogenesis by CT-1 as well as nuclear translocation of CT-1 under normoxic and hypoxic conditions was abolished in the presence of BAPTA, AM, the nitric oxide (NO)-synthase inhibitor L-NAME and the free radical scavenger N-(2-mercaptopropionyl)-glycine (NMPG).

Conclusions:

It is concluded that nuclear translocation of CT-1 is central to CT-1-mediated cardiomyogenesis and involves intracellular calcium, NO and reactive oxygen species in CT-1 regulated signal transduction pathways.