Hyperoxia is still broadly used in clinical practice in order to assure organ oxygenation in
critically ill patients, albeit known toxic effects. In this present study, we hypothesize that
lysophosphatidic acid (LPA) mediates NKT cell activation in a mouse model of hyperoxic
lung injury. In vitro, pulmonary NKT cells were exposed to
hyperoxia for 72 h, and the induction of the ectonucleotide
pyrophosphatase/
phosphodiesterase 2 (ENPP-2) was examined and production of
lysophosphatidic acid (LPA) was measured. In vivo, animals were exposed to 100 %
oxygen for 72 h and lungs and serum were harvested. Pulmonary NKT cells were then incubated with the LPA antagonist
Brp-LPA. Animals received
BrP-LPA prior to
oxygen exposure. Autotaxin (ATX, ENPP-2) was significantly up-regulated on pulmonary NKT cells after
hyperoxia (p < 0.01) in vitro. LPA levels were increased in supernatants of
hyperoxia-exposed pulmonary NKT cells. LPA levels were significantly reduced by incubating NKT cells with LPA-BrP during
oxygen exposure (p < 0,05) in vitro.
Hyperoxia-exposed animals showed significantly increased serum levels of LPA (p ≤ 0,05) as well as increased pulmonary NKT cell numbers in vivo.
BrP-LPA injection significantly improved survival as well as significantly decreased
lung injury and lowered pulmonary NKT cell numbers. We conclude that NKT cell-induced hyperoxic
lung injury is mediated by pro-inflammatory LPA generation, at least in part, secondary to ENPP-2 up-regulation on pulmonary NKT cells. Being a potent LPA antagonist,
BrP-LPA prevents
hyperoxia-induced
lung injury in vitro and in vivo.