Catestatin reverses the hypertrophic effects of norepinephrine in H9c2 cardiac myoblasts by modulating the adrenergic signaling.

Catestatin (CST) is a catecholamine release-inhibitory peptide secreted from the adrenergic neurons and the adrenal glands. It regulates the cardiovascular functions and it is associated with cardiovascular diseases. Though its mechanisms of actions are not known, there are evidences of cross-talk between the adrenergic and CST signaling. We hypothesized that CST moderates the adrenergic overdrive and studied its effects on norepinephrine-mediated hypertrophic responses in H9c2 cardiac myoblasts. CST alone regulated the expression of a number of fetal genes that are induced during hypertrophy. When cells were pre-treated CST, it blunted the modulation of those genes by norepinephrine. Norepinephrine (2 µM) treatment also increased cell size and enhanced the level of Troponin T in the sarcomere. These effects were attenuated by the treatment with CST. CST attenuated the immediate generation of ROS and the increase in glutathione peroxidase activity induced by norepinephrine treatment. Expression of fosB and AP-1 promoter-reporter constructs was used as the endpoint readout for the interaction between the CST and adrenergic signals at the gene level. It showed that CST largely attenuates the stimulatory effects of norepinephrine and other mitogenic signals through the modulation of the gene regulatory modules in a characteristic manner. Depending upon the dose, the signaling by CST appears to be disparate, and at 10-25 nM doses, it primarily moderated the signaling by the β1/2-adrenoceptors. This study, for the first time, provides insights into the modulation of adrenergic signaling in the heart by CST.