Connexin43 modulates neutrophil recruitment to the lung

Abstract

Transmigration of neutrophils through the microvascular endothelium is a cardinal event of acute inflammation. It has been suggested that gap junctions made of connexin43 (Cx43) may serve as a conducting pathway to spread inflammatory signals within the lung capillary network. To determine whether Cx43 contributes to neutrophil transmigration in vivo, the number of transmigrated neutrophils was monitored in lungs of Cx43 mouse models subjected to inflammation by intratracheal instillations of Pseudomonas aeruginosa lipopolysaccharide (LPS). Cx43 was detected in inflamed lungs independently of neutrophil recruitment, whereas Cx43 up-regulation was not detected in mice genetically protected from inflammation. Mice heterozygous for the Cx43 gene (gja1) showed a 56% (P < 0.01) reduction in airway neutrophil count. In contrast, increased (P < 0.05) neutrophil recruitment in response to LPS was observed in a mouse model expressing a mutant Cx43 with enhanced channel conductivity. In vitro adhesion assays showed that reduced conductivity of Cx43 channels with 43Gap26, a Cx43 blocking peptide, decreased adhesion of neutrophils to endothelial cells. Finally, we found that instillation of 43Gap26 in inflamed lungs reduced neutrophil transmigration by 65% (P < 0.05). These results indicate that inflammatory mediators up-regulate alveolar Cx43 to promote neutrophil recruitment to the airspace. Cx43 may therefore represent a pharmacological target in lung diseases characterized by excessive neutrophil recruitment to the airways.

Neutrophil Intercellular Communication in Acute Lung Injury. Emerging Roles of Microparticles and Gap Junctions

“…Cytoplasmic dye transfer experiments and compatible electron microscopy ( Figure 2) have also suggested possible endothelial GJIC with recruited neutrophils (23,26). Surprisingly, inflammatory insults generally attenuate GJIC (26,53), despite an increase in the connexin content of cells in the distal lung (18,54). This discordance may arise from the inflammatory internalization of endothelial connexin 43 (50).…”

“…The loss of endothelial connexin 43 was associated with an attenuation of leukocyte adhesion in the cremasteric microcirculation (55). Concordantly, proinflammatory effects of pulmonary connexin 43 were observed, although these findings were thought to reflect endothelial-endothelial GJIC (54). Conversely, an in vitro study using human umbilical vein endothelial cells reported that gap junction blockade augmented neutrophil transmigration (26).…”

Prostaglandin E2 Regulation of Cystic Fibrosis Transmembrane Conductance Regulator Activity and Airway Surface Liquid Volume Requires Gap Junctional Communication

“…In support of this idea, we found that the inhibition of GJIC by well-known GJBs, including the 43 Gap26 mimetic peptide for Cx43, fully prevented the activation of CFTR current. 43 Gap26 is an analogue to part of the amino-acid sequence of the first extracellular loop of Cx43, and is known to inhibit Cx43-mediated cell-to-cell communication by preventing docking gap junction channels in airway cells (24,33,34). Finally, the inhibition of GJIC resulted in ASL volume collapse in the presence of PGE 2 , not only in Calu-3 cells but also in primary cultures of well-polarized HAECs grown at the air-liquid interface.…”

Reciprocal Regulation between Proinflammatory Cytokine-induced Inducible NO Synthase (iNOS) and Connexin43 in Bladder Smooth Muscle Cells

“…On the one hand, they participate in the regulation of almost every step of the inflammatory response, including antigen presentation, chemokine and cytokine production, inflammatory cell migration, adhesion, and activation (12)(13)(14)(15)(16)(17). On the other hand, the proinflammatory mediators LPS, TNF␣, and NO have been identified as potent regulators of GJs in a variety of cell types (14, 18 -23).…”