Boldine Attenuates Mechanical Allodynia and Mitigates Transcriptomic Changes in a Mouse Model of Chronic Constriction Injury

Background/Objectives: Neuropathic pain is a complex chronic disorder affecting roughly 7–10% of the population. Current neuropathic pain treatments fail to provide adequate relief in at least ~40% of patients and are usually accompanied by side effects that are sometimes severe. In this study, we investigated the effect of boldine, a natural occurring alkaloid, in attenuating peripheral nerve injury-induced neuropathic pain symptoms and transcriptomic changes. Methods: Male C57BL6 mice underwent chronic constriction injury (CCI) to the sciatic nerve. Customized diet containing boldine or control diet was administered immediately after surgery. Mechanical pain responses were measured by Von Frey filament test. Spontaneous pain-like weight bearing behavior was assessed using the dynamic weight bearing system. L3–L5 spinal cords were collected 15 days after injury and subjected to quantitative PCR and bulk RNA sequencing. Results: CCI led to ipsilateral hypersensitivity of mechanical pain responses and weight-bearing deficits including reduced rearing duration, ipsilateral/contralateral weight support ratio, and ipsilateral hind paw posed duration. Boldine treatment substantially attenuated CCI-induced mechanical allodynia but not the weight bearing deficits. Gene expression analysis showed that boldine inhibited CCI-induced upregulation of inflammatory mediators in the spinal cord. RNA sequencing analysis revealed several pain-related canonical pathways and upstream factors after CCI, and boldine treatment markedly reversed these CCI-induced transcriptomic changes. Conclusions: Early oral administration of boldine attenuated CCI-induced mechanical allodynia and was associated with reduced inflammatory gene expression and reversal of multiple injury-related transcriptomic changes in the spinal cord. These preliminary preclinical findings support further investigation of boldine and do not establish therapeutic efficacy in established neuropathic pain.