The role of transforming growth factor-ß2 in cigarette smoke-induced lung inflammation and injury.

ABSTRACT

AIMS: Transforming growth factor-ß2 (TGF-ß2) plays an important role in pleiotropic functions and has been reported to be involved in the pathogenesis of chronic obstructive lung disease. The role of TGF-ß2 in regulating cigarette smoke (CS)-induced lung inflammation and injury has not been investigated, and its underlying mechanism remains unclear. MAIN METHODS: Primary bronchial epithelial cells (PBECs) were treated with cigarette smoke extract (CSE), and the signaling pathway of TGF-ß2 regulating lung inflammation was investigated. Mice were exposed to CS and treated with TGF-ß2 i.p. or bovine whey protein extract containing TGF-ß2 p.o., and the role of TGF-ß2 in alleviating lung inflammation/injury was studied. KEY FINDINGS: In vitro, we demonstrated that TGF-ß2 attenuated CSE-induced IL-8 production from PBECs through the TGF-ß receptor I (TGF-ßRI), Smad3, and mitogen-activated protein kinase signaling pathways. Selective TGF-ßRI inhibitor (LY364947) and antagonist of Smad3 (SIS3) abolished the effect of TGF-ß2 on alleviating CSE-induced IL-8 production. In vivo, CS exposure for 4 weeks in mice increased the levels of total protein, inflammatory cell counts, and monocyte chemoattractant protein-1 in bronchoalveolar fluid and induced lung inflammation/injury, as revealed by immunohistochemistry. Administration of TGF-ß2 through intraperitoneal injection or oral feeding with bovine whey protein extract containing TGF-ß2 significantly reduced CS-induced lung inflammation and injury. SIGNIFICANCE: We concluded that TGF-ß2 reduced CSE-induced IL-8 production through the Smad3 signaling pathway in PBECs and alleviated lung inflammation/injury in CS-exposed mice. The anti-inflammatory effect of TGF-ß2 on CS-induced lung inflammation in humans deserves further clinical study.