Functional interplay between bradykinin receptors and transient receptor potential vanilloid-1 in lipopolysaccharide-induced acute lung injury in mice

In this study, we investigated the functional interplay between bradykinin receptors and the transient receptor potential vanilloid-1 (TRPV1) channel in a mouse model of acute lung injury (ALI) induced by lipopolysaccharide (LPS). Lung and bronchoalveolar lavages were collected at 6 and 24 h after the induction of ALI and evaluated for changes in body weight, inflammatory marker levels, lung injury, and TRPV1 expression. Pretreatments with a TRPV1 antagonist (capsazepine) or B₁ and B₂ receptor antagonists, i.e., DALBK and HOE 140, respectively, were evaluated in this ALI mouse model. The histological score revealed higher levels of lung injury in mice treated with LPS (5 and 10 mg/kg), assessed at both 6 and 24 h, compared to the vehicle-treated group. A loss of body weight was observed within 24 h of ALI induction. Furthermore, collagen deposition, pulmonary oedema, leukocyte influx, and increased cytokine levels were also observed following LPS administration. Pretreatment with capsazepine, DALBK, or HOE 140 not only reversed all inflammatory parameters but also prevented the increased expression of TRPV1 observed in the lungs of mice subjected LPS-induced ALI. Our data suggest that, following LPS-induced ALI, bradykinin activates both B₁ and B₂ receptors associated with the subsequent activation of TRPV1. These findings suggest that bradykinin can activate both B₁ and B₂ receptors, which may contribute functionally to TRPV1 upregulation and activation during LPS-induced ALI. This novel pathway appears to sustain inflammation, offering a new therapeutic target for ALI and ARDS.