Gap Junction Channel Modulates Pulmonary Vascular Permeability through Calcium in Acute Lung Injury: An Experimental Study

Abstract

Background: Increased pulmonary vascular permeability is a hallmark of acute lung injury (ALI). Gap junction channels (GJCs) connect adjacent cells and facilitate ion exchange. It remained unclear whether GJCs modulate pulmonary permeability in ALI through intracellular calcium. Objectives: This study aimed to verify if GJCs in pulmonary microvessel endothelial cells (PMVECs) modulate pulmonary vascular permeability in ALI via intracellular calcium. Methods: Firstly, an animal model of ALI was studied using connexin 40 (Cx40) inmunohistochemistry in the lung with Evans’ blue (EB) leakage. Then cultured PMVECs were divided into three groups: G_control, G_serum and G_blocker. Serum was obtained from animals with ALI following gunshot injury (injured serum). Initially, G_blocker was treated with the blocker of GJCs, and then G_serum and G_blocker were stimulated with the injured serum, respectively. GJCs, the permeability of cell monolayers and intracellular Ca²⁺ were assessed. Results: Cx40 time-dependently decreased, whereas EB leakage increased. Cx40 and EB leakage exhibited a strong inverse correlation (ρ = –0.934, p < 0.05). Injured serum decreased GJCs and expression of Cx40, whereas the blocker aggravated this effect. Similarly, when PMVEC monolayer was treated with injured serum, both permeability and intracellular Ca²⁺ increased. These effects were also aggravated with the blocker. Conclusions: Depression of GJCs of PMVECs increased pulmonary vascular permeability in ALI; this effect may be mediated by the overload of intracellular calcium.