17ß-Estradiol-induced interaction of estrogen receptor α and human atrial essential myosin light chain modulates cardiac contractile function.

Chronic increased workload of the human heart causes ventricular hypertrophy, re-expression of the atrial essential myosin light chain (hALC-1), and improved contractile function. Although hALC-1 is an important positive inotropic regulator of the human heart, little is known about its regulation. Therefore, we investigated the role of the sex hormone 17ß-estradiol (E2) on hALC-1 gene expression, the underlying molecular mechanisms, and the impact of this regulatory process on cardiac contractile function. We showed that E2 attenuated hALC-1 expression in human atrial tissues of both sexes and in human ventricular AC16 cells. E2 induced the nuclear translocation of estrogen receptor alpha (ERα) and hALC-1 in AC16 cells, where they cooperatively regulate the transcriptional activity of hALC-1 gene promoter. E2-activated ERα required the estrogen response element (ERE) motif within the hALC-1 gene promoter to reduce its transcriptional activity (vehicle: 15.55 ± 4.80 vs. E2: 6.51 ± 3.69; ~2 fold). This inhibitory effect was potentiated in the presence of hALC-1 (vehicle: 11.13 ± 3.66 vs. E2: 2.18 ± 1.10; ~5 fold), and thus, hALC-1 acts as a co-repressor of ERα-mediated transcription. Yeast two-hybrid screening of a human heart cDNA library revealed that ERα interacts physically with hALC-1 in the presence of E2. This interaction was confirmed by Co-Immunoprecipitation and immunofluorescence in human atrium. As a further novel effect, we showed that chronic E2-treatment of adult mouse cardiomyocytes overexpressing hALC-1 resulted in reduced cell-shortening amplitude and twitching kinetics of these cells independent of Ca2+ activation levels. Together, our data showed that the expression of hALC-1 gene is, at least partly, regulated by E2/ERα, while hALC-1 acts as a co-repressor. The inotropic effect of hALC-1 overexpression in cardiomyocytes can be significantly repressed by E2.

Surface-modified loaded human red blood cells for targeting and delivery of drugs.

Red blood cells (RBCs) are natural carriers which can be used for targeted drug delivery. Conditions during loading and surface modification are essential for carrier-RBC preparation for specifically targeted drug delivery. Therefore, human RBCs were loaded with albumin and magnetic nanoparticles (NPs) by different hypotonic haemolysis procedures and compared based on loading efficiency and membrane damage. Samples were analysed by flow cytometry and confocal microscopy. The optimized loading procedure resulted in 90% albumin-loaded carrier-RBCs with <4% Annexin V binding and 263 pg iron per RBC after loading with iron oxide NPs. Albumin-loaded RBCs were subsequently surface conjugated with insulin and IgG via biotin-streptavidin. Insulin-conjugated carrier-RBCs were observed to attach and to be internalized by cultured endothelial cells. Uptake was not observed for carrier-RBCs non-specifically modified with IgG. Attachment of other peptides with high specificity will open novel opportunities for targeting various cells, tissues and for crossing biological barriers.