Effects of systemic administration of ciliary neurotrophic factor on Bax and Bcl-2 proteins in the lumbar spinal cord of neonatal rats after sciatic nerve transection

Ciliary neurotrophic factor (CNTF) is a cytokine that plays a neuroprotective role in relation to axotomized motoneurons. We determined the effect of daily subcutaneous doses of CNTF (1.2 µg/g for 5 days; N = 13) or PBS (N = 13) on the levels of mRNA for Bcl-2 and Bax, as well as the expression and inter-association of Bcl-2 and Bax proteins, and the survival of motoneurons in the spinal cord lumbar enlargement of 2-day-old Wistar rats after sciatic nerve transection. Five days after transection, the effects were evaluated on histological and molecular levels using Nissl staining, immunoprecipitation, Western blot analysis, and reverse transcriptase-polymerase chain reaction. The motoneuron survival ratio, defined as the ratio between the number of motoneurons counted on the lesioned side vs those on the unlesioned side, was calculated. This ratio was 0.77 ± 0.02 for CNTF-treated rats vs 0.53 ± 0.02 for the PBS-treated controls (P < 0.001). Treatment with CNTF modified the level of mRNA, with the expression of Bax RNA decreasing 18 percent (with a consequent decrease in the level of Bax protein), while the expression of Bcl-2 RNA was increased 87 percent, although the level of Bcl-2 protein was unchanged. The amount of Bcl-2/Bax heterodimer increased 91 percent over that found in the PBS-treated controls. These data show, for the first time, that the neuroprotective effect of CNTF on neonatal rat axotomized motoneurons is associated with a reduction in free Bax, due to the inhibition of Bax expression, as well as increased Bcl-2/Bax heterodimerization. Thus, the neuroprotective action of the CNTF on axotomized motoneurons can be related to the inhibition of this apoptotic pathway.

Cntf: una citokina con potenciales efectos terapéuticos en patologías neurodegenerativas / Cntf: a cytokine with therapeutic potential for the treatment of neurodegenerative diseases

El factor neurotrófico ciliar (CNTF) es una citokina que tiene efectos tróficos sobre neuronas sensitivas y motoras, ya que modifica su expresión génica y afecta su supervivencia. Este trabajo es una revisión de los antecedentes de los efectos de la aplicación de CNTF en modelos animales de neuropatías degenerativas humanas,que han sugerido que esta citokina tiene potencialidades para convertirse en una herramienta para el tratamiento de pacientes con enfermedad de Huntington. También se describen los efectos de la aplicación experimental de CNTF a pacientes con esclerosis lateral amiotrófica. Entre las técnicas empleadas para aplicar CNTF en modelos animales se encuentran la implantación local de células modificadas genéticamente para secretar CNTF y el uso de vectores para insertar genes en neuronas. Estas técnicas de la biología molecular podrían emplearse como herramientas para el tratamiento preventivo de pacientes susceptibles de desarrollar una patología neurodegenerativa o para recuperar las funciones motoras y cognitivas en pacientes que hayan desarrollado la enfermedad.