Paclitaxel-induced cytoskeletal and focal adhesion reorganisation alters connexin43 and α-smooth muscle actin in cardiac cells

Paclitaxel, a microtubule-stabilising anticancer drug, exhibits cardiotoxicity; however, the impact of microtubule stabilisation on cytoskeletal and focal adhesion proteins and their consequences on key proteins in cardiac cells remains inconclusive. A 10-100 nmol of paclitaxel treatment for 24 h stabilised microtubules in H9c2 cells and rat cardiac fibroblasts. In H9c2 cells, a significant increase in the mean fluorescence intensity of bundled microtubules and a decrease in microtubule spreading area were observed. Actin was reorganised into more parallelly aligned stress filaments, with vinculin at the actin filament ends significantly decreased, and appeared localised at the centre in all treated groups. In cardiac fibroblasts, the changes in mean fluorescent intensity of bundled microtubules and spreading area were evident only at higher paclitaxel concentrations. Actin stress fibres were disrupted to punctate actin, peripherally localised vinculin appeared filamentous or punctate, and dose-dependent changes were observed in actin and vinculin. The results indicate that the rearrangements in cytoskeletal and focal adhesion proteins were specific in each cell type. Further, proteins specific to H9c2 and cardiac fibroblasts were probed. Connexin 43 (Cx43) in H9c2 cells showed altered localisation with a significant decrease in mean intensity, number, and plaque size at the periphery or apposition membranes, indicating compromised cell-cell communications. Additionally, in cardiac fibroblasts, the cage-like network of vimentin and the prominent α-SMA stress fibres were disrupted into smaller aggregates. Disrupted α-SMA stress fibres increased with paclitaxel concentration. Collectively, these changes reduced cell migration in cardiac fibroblasts, which may affect the repair and remodelling process following cardiac injury.