Suppression of phosphorylated MAPK and caspase 3 by carbon dioxide.

Although CO2 is produced during the oxidation of different substrates in all types of cells, the role of this gas in the regulation of cellular function is not clearly understood. Since changes in several signal transduction as well as apoptotic, anti-apoptotic, and other proteins are known to modify cellular function, we investigated if some of these proteins are altered upon incubating the rat hind leg skeletal muscle in a medium enriched with CO2 (1000-1200 ppm) for 30 min. CO2 was observed to depress phosphorylated levels of ERK1 (P44) and ERK2 (P42) without affecting the unphosphorylated content of these MAPK proteins. On the other hand, no change in p38 MAPK protein was found but the content of its degradation product 30 kDa proteins (both phosphorylated and unphosphorylated) was decreased. No alterations in the content of other signaling proteins (PKA and Akt), inflammatory molecule (TNF-α), and vascular endothelial growth factor (VEGF) were seen upon exposure of the muscle to CO2. The content for apoptotic and anti-apoptotic proteins (Bad and Bcl2), except for a decrease in caspase 3, were also not affected by CO2. These results indicate that CO2 may serve as a gasotransmitter to regulate cellular function by depressing MAPK and caspase 3 activities.