Targeting TLR2 attenuates pulmonary inflammation and fibrosis by reversion of suppressive immune microenvironment.
Pulmonary fibrosis is a consequence of chronic lung injury and is associated with a high mortality. Despite the pathogenesis of pulmonary fibrosis remaining as an enigma, immune responses play a critical role in the deregulation of wound healing process after lung injury, which leads to fibrosis. Accumulating evidence argues the rationales for current treatments of pulmonary fibrosis using immunosuppressive agents such as corticosteroids. In this study, we report that bleomycin (BLM), a well-known fibrogenic agent functioning as a TLR2 agonist, induced the maturation of dendritic cells and release of cytokines. The BLM activation of TLR2 mediated a time-dependent alteration of immune responses in the lung. These responses resulted in an increase in the tissue-infiltrating proinflammatory cells and cytokines in the early period initially following BLM exposure and an increase in the tissue-infiltrating suppressive immune cells and factors during the later period following BLM exposure. TLR2 deficiency, however, reduced pulmonary inflammation, injury, and subsequently attenuated pulmonary fibrosis. Targeting TLR2 by a TLR2-neutralizing Ab not only markedly decreased animal death but also protected animals from the development of pulmonary fibrosis and reversed the established pulmonary fibrosis through regulating BLM-induced immunosuppressive microenvironments. Our studies suggest that TLR2 is a promising target for the development of therapeutic agents against pulmonary fibrosis and that eliminating immunosuppressive cells and factors via immunostimulants is a novel strategy for fibro-proliferative diseases. Moreover, combining BLM with an anti-TLR2 Ab or TLR2 antagonist for cancer therapy will improve the BLM therapeutic profile by enhancing anti-cancer efficacy and reducing systemic inflammation and pulmonary fibrosis.
Yang
Hong-Zhen
HZ
Molecular Immunology and Pharmacology Laboratory, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, 1 Xian Nong Tan St. Beijing 100050, People's Republic of China.
Cui
Bing
B
Liu
Han-Zhi
HZ
Chen
Zhi-Rong
ZR
Yan
Hui-Min
HM
Hua
Fang
F
Hu
Zhuo-Wei
ZW
D000818:Animals; D001761:Bleomycin / Q000009:adverse effects / Q000633:toxicity*; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002465:Cell Movement / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D004195:Disease Models, Animal; D007166:Immunosuppressive Agents / Q000009:adverse effects / Q000633:toxicity; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D007442:Intubation, Intratracheal; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000276:immunology* / Q000378:metabolism / Q000517:prevention & control*; D018417:Th1 Cells / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000172:deficiency* / Q000502:physiology
D007166:Immunosuppressive Agents; D018836:Inflammation Mediators; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D001761:Bleomycin