Cyclic
phosphatidic acid (cPA) is a naturally occurring
phospholipid mediator with a unique cyclic
phosphate ring at the sn-2 and sn-3 positions of its
glycerol backbone. We have previously shown that cPA significantly suppresses
ischemia-induced delayed neuronal death and the accumulation of
glial fibrillary acidic protein in the CA1 region of the rat hippocampus. These results indicated that the systemic administration of cPA can protect hippocampal neurons against
ischemia-induced delayed neuronal cell death. In the current study, we investigated the effects of cPA on neuronal cell death caused by
hypoxia in vitro and the molecular mechanisms underlying these effects. We used
cobalt chloride (
CoCl(2)) to expose cells to hypoxic conditions in vitro. Treating mouse
neuroblastoma (Neuro2A) cells with
CoCl(2) induced nuclear
DNA condensation and
phosphatidylserine exposure. However, adding cPA led to the suppression of CoCl(2)-induced apoptosis in a cPA dose-dependent manner and attenuated the increase in the Bax/Bcl-2 ratio caused by
CoCl(2). Quantitative PCR analysis showed that Neuro2A cells strongly express the LPA(1), LPA(2), and LPA(6), which are
G-protein coupled receptors that can be activated by cPA. To date, LPA(1) and LPA(2) have been reported to exhibit antiapoptotic activity. Therefore, to assess the roles of LPA(1) and LPA(2) on cPA-induced neuroprotective functions,
Ki16425, a selective LPA(1) and LPA(3) antagonist, was adopted to know the LPA(1) function and
siRNA was used to knockdown the expression of LPA(2). On the basis of our results, we propose that cPA-induced protection of Neuro2A cells from CoCl(2)-induced
hypoxia damage is mediated via LPA(2).