The Gap Junction Protein Connexin 43 Half-channel Effects And Mechanisms In The Regulation Of Proliferation Of H9c2 Cells

Connexin 43, known to be the main protein building blocks of gap junctions and hemichannels in mammalian heart, plays an important role in cardiocytes proliferation. Gap junctional intercellular communication (GJIC) has been suggested to be necessary for cellular proliferation and differentiation. However, the effect of connexin 43 hemichannel on cardiocytes proliferation and the mechanism remains unclear. This paper works on the role of Cx43 hemichannel in H9c2 cells proliferation and the mechanisms involved in.Wnt signaling is an important modulator of Cx43, and local accumulation of cx43 transcript expression was observed in the limb mesenchyme of transgenic mice ectopically expressing wntl. In cardiomyocytes, Wnt pathway has been considered to be involved in regulation of proliferation. Our previous report also confirmed that the expression of Cx43 in Wnt-3a+-H9c2 cells was increased. We examined the activity of hemichannel in Wnt-3a+-H9c2 cells by EthBr up take, and found increased fluorescence which indicated enhanced hemichannel activity. Glycyrrhetinic acid (GA), an aglycone saponin extracted from licorice root, which is known to be essential for its anti-inflammatory and anti-ulcerous activities, has been widely used as a potent inhibitor of GJIC. This study also confirmed that 18β-GA inhibited the hemichannel activity of H9c2 and Wnt-3a+-H9c2 cells. Then we used Wnt-3a transfected cells to increase hemichannel activity and 18β-GA to block hemichannels and studied their effects on cell proliferation.and the results showed that inhibited hemichannel activity increased cell proliferation rates.Intracellular ATP has emerged as energy source and phosphate donor in enzymatic processes. Recently, Cx43 hemichannels have been observed to have a role in several physiological and pathological process including volume regulation, efflux of NAD+ and ATP. It is likely that hemichannels serve as one pathway for release of these small substances present intracellular. Extracellular ATP may activate specific membrane receptors, the P2 purinergic receptor family, and be involved in various cell processes such as regulation of cardiovascular functions. ATP are found to be essential in the generation of neuron during embryonic development. ATP increases DNA synthesis in retinal cultures prepared from chicken embryos with no more than 7 or 8 days in vivo. The retinal pigment epithelium (RPE) releases ATP through connexin 43 hemichannels to control proliferation of neuronal precursor cells. Ca2+ signaling induced by cADPR generated from NAD+ released through Cx43 hemichannels increase proliferation in 3T3 fibroblasts via shorten its S phase. ATP, which has been known as the diffusible messenger in cell signaling pathways in multiple cell types, is characterized to induce elevation of intracellular astrocytic [Ca2+]. To investigate the mechanism involved in the effect of hemichannel on cell proliferation, intracellular [Ca2+] and ATP in H9c2 and Wnt-3a+-H9c2 cells treated with 18β-GA was examind. The results indicated that the change of intracellular ATP released and [Ca2+] were signals by which the hemichannel regulated proliferation in H9c2 cells, but they were not modulated in parallel.In conclusion, the change of ATP and [Ca2+] mediated by Cx43 hemichannel was involved in modulation of H9c2 cell proliferation.