Naringenin complexed with hydroxypropyl-β-cyclodextrin improves the sciatic nerve regeneration through inhibition of p75NTR and JNK pathway

Peripheral nerve injuries are common conditions that often lead to dysfunctions. Although much knowledge exists on the several factors that mediate the complex biological process involved in peripheral nerve regeneration, there is a lack of effective treatments that ensure full functional recovery. Naringenin (NA) is the most abundant flavanone found in citrus fruits and it has promising neuroprotective, anti-inflammatory and antioxidant effects. This study aimed to enhance peripheral nerve regeneration using an inclusion complex containing NA and hydroxypropyl-beta-cyclodextrin (HP beta CD), named NA/HP beta CD. A mouse sciatic nerve crush model was used to evaluate the effects of NA/HP beta CD on nerve regeneration. Sensory and motor parameters, hyperalgesic behavior and the sciatic functional index (SFI), respectively, improved with NA treatment. Western blot analysis revealed that the levels of p75(NTR) ICD and p75(NTR) full length as well phospho-JNK/total JNK ratios were preserved by NA treatment. In addition, NA treatment was able to decrease levels of caspase 3. The concentrations of TNF-alpha and IL-1 beta were decreased in the lumbar spine, on the other hand there was an increase in IL-10. NA/HP beta CD presented a better overall morphological profile but it was not able to increase the number of myelinated fibers. Thus, NA was able to enhance nerve regeneration, and NA/HP beta CD decreased effective drug doses while maintaining the effect of the pure drug, demonstrating the advantage of using the complex over the pure compound.