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Arachidonic acid inhibits retinoic acid‐induced neuritogenesis of human neuroblastoma SH‐SY5Y cells

Polyisoprenylated proteins regulate intracellular processes such as cell growth, differentiation, oncogenic transformation and actin cytoskeletal organization. Recent discoveries show that polyunsaturated fatty acids (PUFAs) may be involved in neurodegenerative diseases. PUFAs such as arachidonic (AA), and eicosapentaenoic acids (EPA) induce apoptosis in cultured cells. This effect has recently been shown to correlate with the inhibition of polyisoprenylated methylated protein methyl esterase (PMPMEase). We propose that abnormally high levels of PUFAs may be deleterious to neuronal cells. Enzyme kinetics analysis with PMPMEase revealed a 2‐fold decrease in KM from 16.2 ± 1.34 to 8.60 ± 1.20 and 7.84 ± 1.02 μM in the presence of 10 μM AA or EPA, respectively. A relatively severe degenerative effect of AA on SH‐SY5Y cells was observed in the absence of 10% FBS (EC50 of 6.2 μM). AA (2 – 10 μM) caused concentration and time‐dependent inhibition of neuritogenesis in retinoic acid (RA)‐differentiated SH‐SY5Y cells. Significant decreases in the percentage of neurite‐bearing cells and neurite lengths were observed after 24 h with 10 μM AA. These results suggest that excessive PMPMEase inhibition may extend beyond controlling cell viability to the degeneration of vulnerable cells such as neurons.