Nitric oxide suppresses formation of malignant pleural effusion

In the present study, we were prompted to investigate the effect of NO signaling on the formation of malignant pleural effusion (MPE) and determined whether NO affects Th1/Th17 response in MPE. The development of MPE and survival of MPE mice were compared between wild-type and NOS2 ‒/‒ mice. The effect of NOS2 on vascular permeability of pleura and differentiation of Th1 and Th17 in MPE was also explored. Our current data show that production of NO is significantly enhanced in MPE as compared with peripheral circulation, and that nitric oxide synthase-2 (NOS2) deficiency increases pleural vascular permeability and thus promotes the development of MPE, and reduces the survival of mice bearing MPE. NOS2 deficiency inhibits Th1 cell differentiation and promotes Th17 cell differentiation. Our data provide the first evidence that NO inhibits MPE formation by inhibiting fluid extravasation into the pleural space and by promoting Th1 cell differentiation and suppressing Th17 cell differentiation. Overall, our results shed light on the mechanisms by which NO suppresses MPE formation, providing a promising therapeutic strategy in the management of MPE.