Botulinum toxin type A inhibits microglia pyroptosis by suppressing Cblb-mediated degradation of Pdlim1 to attenuate neuropathic pain.

[BACKGROUND] Microglia pyroptosis, a newly identified form of inflammatory cell death, is involved in the development of neuropathic pain (NP). Botulinum toxin type A (BTX-A) has been shown to be effective in relieving NP, but the mechanisms involved have not been clarified.

[METHODS] A mice model of NP was established with chronic constriction injury (CCI) method. The expression levels of key molecules and the extent of microglia pyroptosis were assessed using RT-qPCR, western blot, ELISA and immunofluorescence. Moreover, lipopolysaccharide (LPS) was used in vitro to induce pyroptosis of microglia to explore the potential molecular mechanisms of BTX-A.

[RESULT] In a mice model of NP, BTX-A administration increased the pain threshold and decreased the Cblb protein expression level, consistent with the results of in vitro experiments. Functional experiments and mouse models were respectively used to evaluate the severity of microglia pyroptosis. The results showed that BTX-A inhibited microglia pyroptosis through Cblb protein. Subsequently, mass spectrometry (MS) analysis and immunoprecipitation were conducted to identify proteins interacting with Cblb. The results identified Pdlim1 was a potential interacting partner of Cblb, which regulats the ubiquitination of Pdlim1. Mechanically, Cblb binds to the PDZ and LIM domains of Pdlim1 and then targets Pdlim1 at K244 for ubiquitination and proteasome-mediated degradation. Pdlim1 knockdown lentiviral plasmid was constructed and stable Pdlim1 knockdown microglial cell lines were established for rescue experiments. The results demonstrated that BTX-A suppresses microglia pyroptosis via Pdlim1/NF-κB signaling axis. Finally, intrathecal injection of adeno-associated virus overexpressing Cblb was used in rescue experiments. The results confirmed that BTX-A attenuates neuropathic pain via the Cblb/Pdlim1/NF-kB signaling axis.

[CONCLUSIONS] This study demonstrates that BTX-A suppresses the activity of Cblb, thereby reducing Pdlim1 protein degradation, inhibiting the NF-kB pathway, and ultimately mitigating microglia pyroptosis. Our findings suggest that Cblb could serve as a novel therapeutic target for BTX-A in the treatment of NP.