Involvement of NADPH oxidase and iNOS in rodent pulmonary cytokine responses to urban air and mineral particles

We have investigated the potential of two complex mineral particles ( feldspar and mylonite), quartz ( Min- U- Sil), and suspended particulate matter ( SRM- 1648) ( SPM) from urban air to induce inflammatory cytokine responses in primary rat alveolar type 2 cells and alveolar macrophages, and the involvement of cellular formation of free radicals in these responses. All particle types induced an increased release of interleukin ( IL)- 6 and macrophage inflammatory protein ( MIP)- 2 from type 2 cells. Diphenyleneiodonium chloride ( DPI), a selective inhibitor of NADPH- oxidase, reduced the IL- 6 and MIP- 2 responses to quartz, SPM and mylonite. N( 3-[ Aminomethyl] benzyl) acetamidine ( 1400W), a selective inhibitor of inducible nitric oxide synthase ( iNOS), significantly reduced the Il- 6 response to SPM and feldspar in the type 2 cells. The macrophages displayed significantly increased TNF-alpha and MIP- 2 release upon exposure to quartz or SPM. Here, DPI significantly reduced the tumor necrosis factor ( TNF)-alpha and MIP- 2 responses to quartz, and the MIP- 2 response to SPM. Nosignificant effect of 1400Wwas detected in the alveolar macrophages. The role of particle- induced cellular generation of free radicals in lung cytokine responses was further elucidated in mice that lacked either NADPH- oxidase or iNOS as well as in wild- type ( wt) mice. All particles were able to elicit increased cytokine levels in the bronchoalveolar lavage ( BAL) fluid of the mice, although the levels depended on particle type. The NADPH- oxidase knockout ( KO) mice demonstrated a significantly lower IL- 6 and MIP- 2 responses to SPM compared to their respective wt mice. The iNOS KO mice displayed significantly reduced IL- 6, TNF-alpha, and MIP- 2 responses to SPM. The overall results indicate the involvement of cellular free- radical formation in the pulmonary cytokine responses to particles of varying composition.