Injury elicited increase in spinal cord neurosteroid content analysed by gas chromatography mass spectrometry.

LABOMBARDA F; PIANOS A; LIERE P; EYCHENNE B; GONZALEZ, S; CAMBOURG A; DE NICOLA; SCHUMACHER M; GUENNOUN, R

Marrakech, Marruecos

Congreso; 2 eme Colloque Mediteranien de Neurosciences.; 2006

Progesterone (PROG) exerts protective effects throughout the nervous system after injury. In addiction, some steroids, which have been named “neurosteroids”, can be synthesized de novo from cholesterol in brain, spinal cord (SC) and in peripheral nerves. The objective of this work was to study the effects of spinal cord injury (SCI), combined with castration and adrenalectomy, and of PROG treatment on steroids levels and styeroidogenic enzyme expression in the adult male rat SC. SCI was performed by transecting the SC totally at thoracic level T10. Steroids levels were measured by chromatography / mass spectrometry in SC and plasma. In the SC of intact rats, significant levels of pregnenolone (PREG), PROG, 5a-dihydroprogesterone, 3a,5a-tetrahydroprogesterone were detected. The levels of these steroids increased in SC 72h after transection without significant increase in plasma. After combined adrenalectomy and gonadectomy, significant levels of PREG and PROG remained in SC, suggesting their local de novo synthesis. In SC of adrenalectomized and gonadectomized rats, there was an increase of PREG 24h SC transaction, followed at 72h by a concomitant increase in its direct metabolite, PROG. These obstervation are consistent with an increase in PREG synthesis and in its local convertion to PROG after SCI. Results form Real Time PCR showed no significant changes in P5450scc and 3b-HSD mRNA levels after SCI, suggesting that the observed increase in PREG and PROG did not involve an increase in the expression of enzymes involved in their synthesis. PROG treatment after SCI, resulted in a very large increase in PROG, 5a-dihydroprogesterone, 3a,5a-tetrahydroprogesterone,  in both plasma and SC. The ratio of reduced metabolites to PROG was 65-times higher in SC than in plasma, suggesting that they likely originated from local synthesis in SC. This study demonstrated that SC has the capacity to synthesize PREG, PROG 5a-dihydroprogesterone and 3a,5a-tetrahydroprogesterone and that the levels of these neurosteroids increased after SCI. Our results strongly suggest an important role for locally synthesis neurosteoids in the response of the SC to injury.