Cyclic phosphatidic acid elicits neurotrophin-like actions in embryonic hippocampal neurons.

Cyclic phosphatidic acid (cPA; 1-acyl-sn-glycerol-2,3-cyclic phosphate) is an analog of the growth factor-like phospholipid mediator lysophosphatidic acid (LPA). As brain tissue is the richest source of cPA we tested its effects on hippocampal neurons from day 16/17 embryonic rat cultured in a serum-free medium. Nanomolar concentrations of cPA elicited a neurotrophic effect and promoted neurite outgrowth that exceeded that of 50 ng/mL nerve growth factor (NGF). Pertussis toxin, the LPA1/LPA3 receptor-selective antagonist dioctylglycerol pyrophosphate, the myristoylated inhibitory pseudosubstrate peptide of protein kinase A (PKI), Wortmannin and PD98059 abolished the neurite-promoting effect. cPA elicited a sustained activation of extracellular signal-related kinases (ERK) 1/2 and Akt. Clostridium difficile toxin B, an inhibitor of the Rho family of GTPases, reduced cPA-induced enhancement of neurite outgrowth. In B5P cells, a clonal cell line of PC12 cells overexpressing tyrosine kinase NGF receptor (TrkA), cPA elicited transphosphorylation of TrkA. cPA-elicited ERK activation was blocked by K252a and PKI. These results suggest that cPA mimics the effects of, and activates signaling pathways similar to, the neurotrophin NGF in cultured embryonic hippocampal neurons and B5P cells.