Differentiation of pharmacotherapy with Fasudil and Riluzole in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Although there was progress in understanding the aetiopathogenesis of ALS in recent years, clinical researchers still have only one established pharmaceutical for treatment of ALS in human which is Riluzole and prolongs survival merely for a few months. Thus, the quest for more effective neuroprotective drugs is an object of current research. In several models of neurodegeneration, the neuroprotective effect of rho kinase (ROCK) inhibition was demonstrated. In previous trials in the SOD1G93A mouse model it has been shown that the ROCK inhibitor Fasudil prolongs overall survival, enhances survival of motor neurons and improves motor function in the rotarod performance test. Here, a Fasudil dosage of 30 mg/kg BW was superior to the dosage of 100mg/kg BW. The aim of the current study was to examine therapeutic effects of a low-dose therapy with Fasudil 10 mg/kg BW. The study contains as well a behavioral and clinical testing phase including the evaluation of survival and a cross-sectional part with intermediate histologic and pathologic investigations. We employed four treatment groups for SOD1G93A mice: low-dose Fasudil (10 mg/kg BW), Fasudil (30 mg/kg BW), Riluzole (30 mg/kg BW) and the combination of low-dose Fasudil (10 mg/kg BW) with Riluzole (30 mg/kg BW) and added two control conditions with healthy wildtype-group and an untreated control-group. The assessments included overall survival, clinical development based on bodyweight and a clinical score. Furthermore, motor function was investigated by the rotarod performance test and by the video-based gait analysis system CatWalk XT. The cognitive performance was tested by using the novel object recognition test. The improvement of motor coordination in the rotarod performance test by Fasudil 30 mg/kg BW could be confirmed. In this group, the video-based gait analysis system CatWalk XT showed improvement in general motor capability. Moreover, paralysis, functional use, agility and strength of the hind limbs were improved. The low-dose treatment with Fasudil 10 mg/kg BW enabled mice to obtain strength and agility of hind and front limbs comparable to the healthy wild-type group. The combinational treatment of low-dose Fasudil and Riluzole showed promising but no significant better effects. Here, there was no significant improvement on surviving lower motor neurons in the histologic evaluation on day of life 120. Muscular atrophy of the gastrocnemius muscle was completely prevented through the treatment with low dosed Fasudil and equally through Riluzole. In conclusion, this study demonstrates an improvement in motor performance for the low-dose treatment with Fasudil in the SOD1G93A mouse model. Thereby, the therapeutic potential of ROCK inhibition in ALS was confirmed. Combinational treatment with Riluzole did not show any positive additive effects. The exact molecular interactions of Fasudil and Riluzole should be further investigated to better design future treatments with these two substances.2018-12-1