Toluene diisocyanate exposure and autotaxin-lysophosphatidic acid signalling

Toluene diisocyanate (TDI) is a reactive chemical used in manufacturing plastics. TDI exposure adversely affects workers' health, causing occupational asthma, but individuals differ in susceptibility. We recently suggested a role for signalling mediated by the enzyme autotaxin (ATX) and its product, lysophosphatidic acid (LPA), in TDI toxicity. Here we genotyped 118 TDI-exposed workers for six single-nucleotide polymorphisms (SNPs) in genes encoding proteins implicated in ATX-LPA signalling: purinergic receptor P2X7 (P2RX7), CC motif chemokine ligand 2 (CCL2), interleukin 1β (IL1B), and caveolin 1 (CAV1). Two P2RX7 SNPs (rs208294 and rs2230911) significantly modified the associations between a biomarker of TDI exposure (urinary 2,4-toluene diamine) and plasma LPA; two IL1B SNPs (rs16944 and rs1143634) did not. CAV1 rs3807989 modified the associations, but the effect was not statistically significant (p = 0.05-0.09). In vitro, TDI-exposed bronchial epithelial cells (16HBE14o-) rapidly released ATX and IL-1β. P2X7 inhibitors attenuated both responses, but confocal microscopy showed non-overlapping localizations of ATX and IL-1β, and down-regulation of CAV1 inhibited the ATX response but not the IL-1β response. This study indicates that P2X7 is pivotal for TDI-induced ATX-LPA signalling, which was modified by genetic variation in P2RX7. Furthermore, our data suggest that the TDI-induced ATX and IL-1β responses occur independently.