The Lysophosphatidic Acid Type 2 Receptor Is Required for Protection Against Radiation-Induced Intestinal Injury.

Background & Aims: We recently identified lysophosphatidic acid (LPA) as a potent antiapoptotic agent for the intestinal epithelium. The objective of the present study was to evaluate the effect of octadecenyl thiophosphate (OTP), a novel rationally designed, metabolically stabilized LPA mimic, on radiation-induced apoptosis of intestinal epithelial cells in vitro and in vivo. Methods: The receptors and signaling pathways activated by OTP were examined in IEC-6 and RH7777 cell lines and wild-type and LPA₁ and LPA₂ knockout mice exposed to different apoptotic stimuli. Results: OTP was more efficacious than LPA in reducing gamma irradiation–, camptothecin-, or tumor necrosis factor α/cycloheximide–induced apoptosis and caspase-3-8, and caspase-9 activity in the IEC-6 cell line. In RH7777 cells lacking LPA receptors, OTP selectively protected LPA₂ but not LPA₁ and LPA₃ transfectants. In C57BL/6 and LPA₁ knockout mice exposed to 15 Gy gamma irradiation, orally applied OTP reduced the number of apoptotic bodies and activated caspase-3–positive cells but was ineffective in LPA₂ knockout mice. OTP, with higher efficacy than LPA, enhanced intestinal crypt survival in C57BL/6 mice but was without any effect in LPA₂ knockout mice. Intraperitoneally administered OTP reduced death caused by lethal dose (LD)_{100 /30} radiation by 50%. Conclusions: Our data indicate that OTP is a highly effective antiapoptotic agent that engages similar prosurvival pathways to LPA through the LPA₂ receptor subtype. [Copyright &y& Elsevier]