Objective     To determine the protective effect of 6-formylindolo(3

2-b)carbazole (FICZ)

an endogenous ligand of aryl hydrocarbon receptor (AhR)

against lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS) in rats. Methods     Twenty-four adult SD rats were randomly divided into 4 groups (n=6 per group)

that is

control group

FICZ control group

LPS model group and FICZ treatment group. ARDS model was set up via intratracheal injection of LPS (3 mg/kg). The bronchoalveolar lavage fluid (BALF) and lung tissue were collected at 6 h after modeling. The injury of lung was characterized by wet/dry ratio and HE staining. The contents of inflammatory cytokines interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) as well as myeloperoxidase (MPO) in the lung tissue and/or BALF were determined by enzyme-linked immunosorbent assay (ELISA). AhR and NF-κB p65 expression in the lung tissue was detected by Western blotting. Results     Compared with LPS model group

FICZ treatment significantly ameliorated LPS-induced pulmonary edema and lung tissue injury

down-regulated the levels of TNF-α and IL-1β in both BALF and lung tissue

and decreased MPO content in lung tissue. In addition

FICZ could activate AhR and remarkably suppress the LPS-induced increment of nucleic NF-κB p65 in the necleus of lung tissue. Conclusion      FICZ exerts protective effects against LPS-induced lung injury in rat ARDS model via activating AhR and suppressing NF-κB p65 nuclear translocation.