Botulinum toxin A dampened inflammatory response in BV-2 microglial cells.

Our previous studies have demonstrated the analgesic effects of botulinum toxin type A (BoNT/A) in a pre-clinical model of rheumatoid arthritis of the temporomandibular joint, where we proposed that BoNT/A decreases the neurogenic milieu after reaching the subnucleus caudalis. However, it is unknown whether BoNT/A directly regulates microglial cell activity. Therefore, the present study investigates the effects of BoNT/A on a microglial murine cell lineage (BV-2) in different inflammatory conditions. Cellular viability and proliferation were carried out with different concentrations of BoNT/A (ranging from 0.3125 to 20 U/mL) for 24 h. Cells were primed with carrageenan (300 μg/mL) or Lipopolysaccharides (LPS) (20 ng/mL). The gene expression of IL-1β, IL-6, IL-18, TNF-α, Ikkβ, p65, Iba1 were quantified using PCR-RT. The supernatant was used to determine IL-1β, IL-6, and TNF-α levels. For all data, the significance level was set at 5%. Overall, data analysis revealed that BoNT/A 1.25 U/mL exhibited the greatest effect cell viability and proliferation. In addition, genes associated with inflammatory response in both stimuli (carrageenan and LPS) were downregulated in the presence of BoNT/A. Lastly, BoNT/A mitigates the protein levels of IL-1β and TNF-α in a time and dose-dependent manner. In conclusion, our results revealed that BoNT/A directly modulates the microglial cells' activities in an inflammatory context, opening new perspectives for using BoNT/A, considering its potential immunomodulatory effect.