PDIA1 acts as master organizer of NOX1/NOX4 balance and phenotype response in vascular smooth muscle

Changes in vascular smooth muscle cell (VSMC) phenotype underlie disease pathophysiology and are strongly regulated by NOX NADPH oxidases, with NOX1 favoring synthetic proliferative phenotype and NOX4 supporting differentiation. Growth factor-triggered NOX1 expression/activity strictly depends on the chaperone oxidoreductase protein disulfide isomerase-A1 (PDIA1). Intracellular PDIA1 is required for VSMC migration and cytoskeleton organization, while extracellular PDIA1 fine-tunes cytoskeletal mechanoadaptation and vascular remodeling. We hypothesized that PDIA1 orchestrates NOX1/NOX4 balance and VSMC phenotype. Using an inducible PDIA1 overexpression model in VSMC, we showed that early PDIA1 overexpression (for 24-48 h) increased NOX1 expression, hydrogen peroxide steady-state levels and spontaneous VSMC migration distances. Sustained PDIA1 overexpression for 72 h and 96 h supported high NOX1 levels while also increasing NOX4 expression and, remarkably, switched VSMC phenotype to differentiation. Differentiation was preceded by increased nuclear myocardin and serum response factor-response element activation, with no change in cell viability. Both NOX1 and hydrogen peroxide were necessary for later PDIA1-induced VSMC differentiation. In primary VSMC, PDIA1 knockdown decreased nuclear myocardin and increased the proliferating cell nuclear antigen expression. Newly-developed PDIA1-overexpressing mice (TgPDIA1) exhibited normal general and cardiovascular baseline phenotypes. However, in TgPDIA1 carotids, NOX1 was decreased while NOX4 and calponin expressions were enhanced, indicating overdifferentiation vs. normal carotids. Moreover, in a rabbit overdistension injury model during late vascular repair, PDIA1 silencing impaired VSMC redifferentiation and NOX1/NOX4 balance. Our results suggest a model in which PDIA1 acts as an upstream organizer of NOX1/NOX4 balance and related VSMC phenotype, accounting for baseline differentiation setpoint.