Background: Sex is an important modifier of the development of cardiovascular disease; women consistently display less hypertrophy, fewer changes in pathologic gene expression, and less cardiac dysfunction compared to men exposed to the same pathological stimuli. The signaling pathways responsible for these sexual dimorphisms, especially within the cardiomyocyte, are not well understood.
Objective: To investigate sexual dimorphisms in activation of signaling pathways and expression of genes related to cardiomyocyte contractility in response to a pathological stimulus in isolated adult rat ventricular myocytes (ARVMs).
Methods: ARVMs from both sexes were isolated using a Langendorff perfusion apparatus and treated with the β-adrenergic agonist isoproterenol (ISO) or vehicle (saline) for 24 hours. Activated signaling molecules were detected by performing a phospho-kinase antibody array (R&D Systems) in ARVMs isolated from two rats of each sex treated with ISO or vehicle. Total RNA was isolated from these cells, and real-time PCR was used to determine expression levels of calcium handling genes, including Cav1.2 and sodium calcium exchanger (NCX1).
Results: A distinct profile of activated signaling molecules was observed between male and female ARVMs in response to ISO. Female ARVMs displayed activation of kinases such as Akt, ERK1/2, p38α, GSK3α/β and MSK1/2. Male ARVMs were characterized by an activation of signaling molecules such as PLCγ1, RSK1/2/3 and c-Jun. ARVMs of both sexes displayed activation of signaling molecules such as eNOS, STAT3 and mTOR. Because the activated signaling molecules identified with the array can modulate expression of calcium handling genes, expression of these genes was analyzed. In response to ISO treatment, female ARVMs displayed an increase in NCX1 expression normalized to vehicle (1.63 ± 0.079) as well as Cav1.2 expression (1.48 ± 0.072). However, these increases were not observed in male cells.
Conclusions: Cardiomyocytes isolated from rats of different sexes display distinct responses to the pathological stimulus ISO. Understanding the mechanisms responsible for these sexual dimorphisms can lead to the development of more effective treatment options for both men and women with cardiovascular disease.