LONG-TERM INCUBATION OF LOW CONCENTRATION OF ARACHIDONIC ACID PROMOTES THE DIFFERENTIATION OF PC-12 CELLS TOWARD CHOLINERGIC-LIKE NEURON IN THE PRESENCE OF NGF

Objectives: We determined whether low concentration of AA will influence the differentiation of PC-12 cells toward either dopaminergic-like neuron or cholinergic–like neurons.

Methods: 1)PC12 cell culture 2)NGF-induced differentiation of PC12 cell 3)Immunoblotting assay 4)Immunocytochemical assay 5)Choline transferase activity assay.

Results: Addition of low concentration of AA, 1 uM or 5 uM, significantly increased the proportion of potential differentiated cells but partly inhibited the neurite outgrowth. However, AA did not have any significant effect on both parameters of differentiation in the absence of NGF. AA the co-addition of low concentration of AA. This effect of AA could not be affected by the addition of NDGA, aspirin, miconazole and protein kinase C inhibitor, H7, in the cultured medium. Immunocytochemical study showed that NGF could facilitate the expression of ChAT and tyrosine hydroxylase on both un-differentiated and differentiated cells, shown by an increased number of cells possess relatively higher density of TH or ChAT. Co-incubation of AA with NGF could further increase the expression of ChAT by increasing the proportion of differentiated cells possess higher density of ChAT. However, it did not affect of the expression of TH. This result indicated that low concentration of AA could promote PC12 cells to differentiate toward cholinergic-like neurons, and such effect of AA is likely not mediated by AA metabolites or by an activation of protein kinase C.

Conclusion: Long-term exposure to low concentration of arachidonic acid might pormote the differentation of PC12 cell toward cholinergic neuron by a mechanism other than the known metabolite pathways of arachidonic acid.