Gap junction protein connexin43 exacerbates lung vascular permeability

Area of Science:

• Cell Biology
• Pulmonary Medicine
• Vascular Physiology

Background:

• Increased vascular permeability in the lungs leads to pulmonary edema, worsening outcomes in Acute Respiratory Distress Syndrome (ARDS) and sepsis.
• While tight and adherens junctions are known regulators of endothelial barrier function, the role of gap junctions and connexins in pulmonary vascular permeability remains understudied.
• Connexins are implicated in modulating inflammatory signaling in various cell types, suggesting a potential role in pulmonary endothelial cells.

Purpose of the Study:

• To investigate the hypothesis that connexins regulate pulmonary endothelial permeability.
• To explore the relationship between connexin expression, intercellular communication, and the permeability response to inflammatory stimuli in human pulmonary endothelial cells.

Main Methods:

• Cultured human pulmonary endothelial cells were treated with inflammatory stimuli (thrombin, lipopolysaccharide, cyclic stretch).
• Connexin43 (Cx43) mRNA and protein levels were assessed.
• Intercellular communication was measured using Lucifer yellow transfer.
• Transendothelial electrical resistance (TER) was monitored.
• Cx43 expression was reduced using siRNA, and the effect of carbenoxolone (a connexin inhibitor) was evaluated.
• Myosin light chain phosphorylation was assessed.

Main Results:

• Inflammatory stimuli (thrombin, LPS, stretch) increased Cx43 mRNA and protein levels.
• Thrombin and LPS enhanced intercellular communication.
• Thrombin-induced decrease in TER was attenuated by carbenoxolone and Cx43 knockdown.
• Cx43 knockdown and carbenoxolone also abrogated thrombin-induced myosin light chain phosphorylation.
• These findings indicate Cx43 amplifies inflammatory responses increasing lung vascular permeability.

Conclusions:

• Increased expression of connexin43 (Cx43) and enhanced intercellular communication contribute to elevated lung vascular permeability during inflammation.
• Connexins, particularly Cx43, play a significant role in regulating pulmonary endothelial barrier function.
• Targeting Cx43 or connexin function may represent a therapeutic strategy for managing inflammatory lung diseases like ARDS.