BLT1, the primary functional receptor of
Leukotriene B4 (
LTB4), is involved in tissue
inflammation by mediating leukocyte recruitment, and recently LTB4-dependent
inflammation was reported to promote lung
tumor growth. Exposure to
diesel exhaust particle (
DEP), the major component of
particulate matter 2.5 (PM2.5), can elicit
lung inflammation, which may increase the risk of
lung cancer. However, it remains unknown about the critical factors mediating
DEP-induced
lung inflammation and the subsequent effect on
tumor metastasis. In this study, we found that
DEP exposure led to acute
lung inflammation, characterized by abundant infiltration of neutrophils and elevated lung levels in
LTB4, as well as several pro-inflammatory
cytokines and
chemokines, including IL-1β,
IL-6, TNF-α, CXCL1/2. Furthermore,
DEP exposure promoted lung
metastasis of 3LL and 4T1 cells. BLT1 blockade by its specific antagonist
U75302 significantly inhibited neutrophilic
lung inflammation following
DEP exposure. Importantly, BLT1 blockade before the onset of
inflammation significantly reduced
DEP-enhanced lung
metastasis, which was associated with greatly decreased infiltrating neutrophils in lungs. Interestingly, BLT1 blockade after the occurrence of lung
metastases had no effect on the magnitude of lung
metastasis, suggesting that inhibition of BLT1-mediated
lung inflammation was insufficient to suppress established metastatic
tumor. Administration of BLT2 inhibitor
LY255283 fails to inhibit
DEP-induced
lung inflammation and
tumor metastasis. Collectively, our results demonstrate that
DEP exposure causes BLT1-mediated lung neutrophilic
inflammation, which is critical for
tumor lung
metastasis, and suggest that interruption of the LTB4-BLT1 axis could be useful for preventing PM2.5-induced
inflammation and subsequent susceptible to lung
metastasis.