The effect of adenosine on proliferation of human endothelial cells was investigated by adding adenosine to the medium of cultures derived from human umbilical veins. Cell counts on cultures grown in 10 microM adenosine for 4-7 days were 41-53% greater than counts from control cultures. In contrast, 10 microM adenosine had no effect on growth of a human fibroblast cell strain (IMR-90). Neither inosine nor 2',5'-dideoxyadenosine influenced endothelial cell growth at concentrations of 0.1 or 10 microM. Addition of adenosine deaminase abolished the proliferative effect of added adenosine and inhibited proliferation by 16% in control cultures, suggesting that endogenous adenosine may enhance proliferation in culture. The adenosine receptor antagonist, 8-phenyltheophylline, at 0.1 and 1.0 microM blocked the enhanced proliferation caused by 10 microM adenosine. Addition of 10 microM adenosine enhanced DNA synthesis in endothelial cell cultures as indicated by an increased incorporation of [3H]thymidine into acid-insoluble cell material. The results indicate that addition of physiological concentrations of adenosine to human umbilical vein endothelial cell cultures stimulates proliferation, possibly via a surface receptor, and suggest that adenosine may be a factor for human endothelial cell growth and possibly angiogenesis.

Background: Glucocorticoid is widely used as an anti-inflammatory drug in various diseases however excess of it often causes cardiovascular complications. The present study was undertaken to understand the molecular mechanism of glucocorticoid-induced cardiac dysfunction. Methods: Rats were treated daily with synthetic glucocorticoid, dexamethasone with or without mifepristone or losartan up to 15 days. Hemodynamic parameters were measured by PV-loop method using Millar’s instrument. Cardiac remodelling, fibrosis and oxidative stress were monitored after 15 days. Results: The systolic blood pressure was increased whereas the heart beat and cardiac output (n=6) were decreased by dexamethasone. Dexamethasone caused increase in the heart weight to body weight ratio (P<0.001, n=20), increased level of mRNA of atrial natriuretic peptide and an increased deposition of collagens in the extracellular matrix of the left ventricle which were inhibited by both mifepristone and losartan. The rate of oxygen consumption was decreased in association with increased levels of hypoxia inducible factor 1α, lipid peroxidation (P<0.01, n=3) and superoxide dismutase activity (P<0.01, n=3) in dexamethasone treated rat heart. All these changes were reversed by mifepristone and losartan. Conclusions: The excess of glucocorticoid induces cardiac remodelling and pathophysiolgical changes of the myocardium via angiotensin II signalling pathway.

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This study elucidates the role of metabolic remodeling in cardiac dysfunction induced by hyperthyroidism. Cardiac hypertrophy, structural remodeling, and expression of the genes associated with fatty acid metabolism were examined in rats treated with triiodothyronine (T 3 ) alone (8 mg/100 g body weight (BW), i.p.) for 15 days or along with a peroxisome proliferator-activated receptor alpha agonist bezafibrate (Bzf; 30 mg/100 g BW, oral) and were found to improve in the Bzf co-treated condition. Ultrastructure of mitochondria was damaged in T 3 -treated rat heart, which was prevented by Bzf co-administration. Hyperthyroidism-induced oxidative stress, reduction in cytochrome c oxidase activity, and myocardial ATP concentration were also significantly checked by Bzf. Heart function studied at different time points during the course of T 3 treatment shows an initial improvement and then a gradual but progressive decline with time, which is prevented by Bzf co-treatment. In summary, the results demonstrate that hyperthyroidism inflicts structural and functional damage to mitochondria, leading to energy depletion and cardiac dysfunction.

BackgroundAnnexins are calcium dependent phospholipid binding proteins that are expressed in a wide variety of tissues and implicated in various extra- and intracellular processes. In myocardial tissue, annexins A2, A5 and A6 are particularly abundant, of which the expression levels of annexin A6 has been found to be maximal. Conflicting reports from transgenic mice overexpressing annexin A6 or null mice lacking annexin A6 showed imbalances in intracellular calcium turnover and disturbed cardiac contractility. However, few studies have focussed on the signalling module of annexin A6 in the heart either in normal or in pathological state.ResultsTo identify the putative binding partners of annexin A6 in the heart, ventricular extracts were subjected to glutathione S-transferase (GST)- annexin A6 pull down assay and the GST- annexin A6 bound proteins were identified by mass spectrometry. The pull down fractions of ventricular extracts with GST-full length annexin A6 as well as GST-C terminus deleted annexin A6 when immunoblotted with anti sarcomeric alpha (α)-actinin antibody showed the presence of α-actinin in the immunoblot which was absent when GST-N terminus deleted annexin A6 was used for pull down. Overexpression of green fluorescent protein (GFP) tagged full length annexin A6 showed z-line like appearance in cardiomyocytes whereas GFP-N termimus deleted annexin A6 was mostly localized to the nucleus. Overexpression of GFP-C terminus deleted annexin A6 in cardiomyocytes showed aggregate like appearance in the cytoplasm. Double immunofluorescent staining of cardiomyocytes with anti annexin A6 and anti sarcomeric α-actinin antibodies showed perfect co-localization of these two proteins with annexin A6 appearing like a component of sarcomere. Transient knockdown of annexin A6 in cardiomyocytes by shRNA significantly enhances the contractile functions but does not affect the z-band architecture, as revealed by α-actinin immunostaining in shRNA treated cells.ConclusionsIn overall, the present study demonstrated for the first time that annexin A6 physically interacts with sarcomeric α-actinin and alters contractility of cardiomyocytes suggesting that it might play important role in excitation and contraction process.