Screening Natural Products for Effects on Nerve Growth Factor (NGF) Stimulated Neuritogenesis and Neuritic Outgrowth

Neuritic outgrowth is a fundamental process in the differentiation of neurons. The neurites, upon sprouting from the cell body of a neurone, give rise to both axons and dendrites. Studies on the mechanism of neuritogenesis have been significantly important in understanding the brain cell biology and function, and are playing an increasing role in pathology and medicine of neurodegenerative diseases. PC12 cells, a line derived from a rat pheochromocytoma, respond to NGF by switching from an immature chromaffin-cell-like phenotype to a sympathetic-neuron-like one, complete with the outgrowth of long branching neuritis. This cell line is useful in bioassays for investigation of potential drugs for neurodegenerative diseases. PC12 and Neuroscreen-1 (NS-1, Cellnomics®) (a PC12 sub-clone optimized for NGF stimulated neuritic outgrowth) were compared for NGF stimulated neuritic outgrowth.

Figure 1: Stimulation of neuritic outgrowth in NS-1 cells by NGF (A) Control (B)1.25 (C) 2.5 (D) 5.00 (E)10.0 (F) 50ng/ml.

The NS-1 cells were markedly more sensitive to NGF stimulation than PC-12 cells and showed a dose-dependent neuritogenesis (Figure 1). The neuritic outgrowth was quantified by analysis of digital cell images for average number neuritic nodes/cell and average length of the neurites. Suboptimal concentrations of NGF (0.625 and 1.25ng/mL) were used to investigate the effect of several natural products on neurtic outgrowth. Harmine was found to potentiate NGF-stimulated neuritic outgrowth in NS-1 cells. Harmine is a potent inhibitor of Monoamine Oxidase (MAO)-A. Also, harmine and related compounds have shown potential anti-Parkinson's activity. The agents, which stimulate neuritogenesis may have potential to be developed as treatments for neurodegenerative diseases.