Impact of neuropathic pain on the gene expression and activity of cytochrome P450side-chain-cleavage in sensory neural networks.

Development of efficient therapy against chronic and stubborn pains requires fundamental identification of adequate cellular and molecular targets. This study combined cellular, molecular and biochemical approaches to investigate the gene expression and enzymatic activity of cytochrome P450side-chain-cleavage (P450scc) in spinal neural networks under normal and neuropathic pain states. P450scc is the key onset enzyme for steroidogenesis in endocrine glands and for neurosteroid biosynthesis in nerve cells. The P450scc gene was over-expressed in spinal and supra-spinal networks during neuropathic pain provoked by sciatic nerve ligature. Plasticity was observed in P450scc cellular distribution in pain circuits and its activity also increased inducing in vivo, hyper-secretion of pregnenolone and allopregnanolone which strongly stimulates type A receptors for g-aminobutyric acid, a pivotal neurotransmitter involved in pain modulation. These results, by establishing a direct link between neuropathic pain and neuroactive steroid formation in the nervous system, open new perspectives for chronic-pain modulation by endogenous neurosteroids.