Plasticité fonctionnelle du système nerveux périphérique : étude de l’effet de la photobiomodulation et du venin d’abeille après section-suture du nerf facial chez la souris adulte

Facial nerve injury in humans leads to major motor and sensory deficits. After this type of accident, damaged peripheral nerves can regenerate, but they often do so imperfectly, accompanied with severe consequences for the patient’s professional, social and family life. In France, 15,000 people are affected each year. Bell’s palsy accounts for 80% of these cases. It occurs suddenly, generally improving after a few weeks, but sometimes with sensory or motor sequelae. In 20% of cases, the origin is traumatic, vascular, post-surgical, or even cerebellopontine angle tumors, such as vestibular schwannoma. In this work, we investigate the potential effect of physical factors such as PBM and report for the first time the pharmacological effect of bee venom and its bioactive molecules on facial nerve regeneration after section-suture in mice. These studies were performed at two levels: behavioral and neuronal. The effect of PBM has been published in the literature. Infrared wavelength provides the cells with metabolic energy and adjusts their functioning in terms of cell and molecular biology. Within the cells, this energy activates cytochrome c in the mitochondria, leading to the production of adenosine triphosphate (ATP). BV has long been used in traditional medicine since the second century. It is based on the therapeutic effects of the bioactive molecules of bee venom, which have antioxidant, anti-inflammatory and immunomodulatory properties. There is evidence of its therapeutic efficacy through its biochemical pharmacological substances including enzymes like phospholipase A2 and peptides like melittin and apamin. The effects of the different molecules or enzymes contained in bee venom have been demonstrated in numerous pathologies, such as articular pathologies and demyelinating neurological pathologies (multiple sclerosis). Behavioral analyses were performed by videoscoring with a high-speed camera and using various devices to assess the recovery of whisker movement on the lesioned side from day 1 to day 30. We also assessed nasal deviation toward the intact side and the ability to close the ipsilateral eyelid completely from day 1 to day 38 and from day 1 to day 50, respectively. Morphologically, we assessed the re-establishment of facial motoneuron labeling with Fluorogold®, a fluorescent retrograde marker of axonal transport injected into the vibrissae, on D8, D12 and D28. We found that whisker movements recovery was significantly faster in treated than in control mice. A complete disappearance of nasal deviation was observed at 2 weeks in infrared and bee venom treated lesioned mice and at 5 weeks in controls. Finally, normal fluorogold labeling of the facial nuclei complex was restored 30 days after surgery in the treated animals (with PBM or bee venom), but no such restoration was ever observed in control animals. In conclusion, our data show that PBM/bee venom treatment at a distal site has a significant positive effect on facial nerve recovery. These findings pave the way for the clinical use of PBM in patients with nerve lesions. Also, this study opens a new line of research concerning bee venom and its possible effects on axonal regeneration.