Sex differences in distribution of cannabinoid receptors (CB1 and CB2), S100A6 and CacyBP/SIP in human ageing hearts

BACKGROUND: Women live about 4 years longer due to lower prevalence of cardiovascular complication with ageing. However, the mechanisms involved in the preservation of heart functionality in women have not been fully elucidated. The endocannabinoid system fulfils a significant role in the regulation of cardiovascular system functioning. Cannabinoids, acting through specific receptors (CB1 and CB2), influence on blood pressure, heart rate and myocardial contractility. The function of cardiac muscle cells is strictly dependent on calcium ions. Calcium homeostasis in cardiomyocytes is subjected to complex regulation via calcium-binding proteins. Among them, increasing attention has been paid to the recently discovered S100A6 and CacyBP/SIP. In order to better understand sex differences in the regulation of cardiomyocyte function during ageing, we undertook the present research aimed at immunohistochemical identification and comparative evaluation of cannabinoid receptors, S100A6 and CacyBP/SIP, in the myocardium of ageing men and women. METHODS: The study was conducted on the hearts of 12 men and 10 women (organ donors) without a history of cardiovascular disease. The subjects were divided into two age groups: subjects older than 50 years and subjects under 50 years old. Paraffin heart sections were processed by immunohistochemistry for detection of cannabinoids receptors, S100A6 and CacyBP/SIP. In the heart samples from each study, participant’s expression of genes coding for CB1, CB2, S100A6 and CacyBP/SIP using real-time PCR method was measured. RESULTS: CB1 and CB2 immunoreactivity in the cytoplasm of cardiomyocytes in the heart of subjects over 50 was weaker than in younger individuals. In the heart of younger men, CB1-immunoreactivity was weaker and CB2-immunoreaction was stronger compared to women. In the hearts of older men, the CB1-immunostaining was more intense and CB2-immunoreactivity was weaker than in women. Immunodetection of CB1 shoved the presence of receptor in the intercalated discs, but only in the hearts of individuals over the 50 years old. In the hearts of older individuals, stronger immunolabelling was observed for S100A6 and CacyBP/SIP. Male hearts had greater S100A6-immunoreactivity (both age groups) but less CacyBP/SIP immunostaining (individuals over 50 years) compared to the age-matched women. The expression of genes coding CB1, CB2, S100A6 and CacyBP/SIP in the human heart was sex and age-dependent. Observed changes between men and women as well as between subject under and over 50 years were consistent with immunohistochemically stated changes in peptide content. CONCLUSION: Together, the data presented here indicate a close interaction between ageing and sex on the distribution and levels of cannabinoid receptors (CB1, CB2), S100A6 and CacyBP/SIP in the human heart.