Endothelial cell biomechanical adaptation to altered connexin 43 expression under fluid shear stress.

We examined how pharmacological modulation of connexin 43 (Cx43; also known as GJA1) regulates endothelial biomechanics under static conditions and laminar fluid shear stress (FSS). Cx43 activity was either inhibited with 2',5'-dihydroxychalcone (chalcone) or enhanced with retinoic acid (RA), and biomechanical responses were quantified by measuring tractions, intercellular stress, and cell velocity. Low-dose chalcone increased tractions and intercellular stresses under both static and FSS conditions, whereas high-dose chalcone attenuated these stresses. In contrast, low-dose RA reduced tractions and intercellular stresses under static conditions but enhanced them under FSS, while high-dose RA consistently suppressed mechanical stresses. Chalcone treatment caused dose-dependent reductions in F-actin stress fibers and a reduction in gap junction intercellular communication (GJIC). RA treatment preserved actin organization and increased GJIC up to a threshold concentration, beyond which GJIC declined. Together, these findings demonstrate that Cx43 may regulate endothelial biomechanics in a dose-dependent and flow-dependent manner, supporting a role for gap junctions in endothelial mechanoadaptation to fluid shear stress.