Effect of pyrroloquinoline quinone on neuropathic pain following chronic constriction injury of the sciatic nerve in rats.

Pyrroloquinoline quinone PQQ is a naturally occurring redox cofactor that acts as an essential nutrient, antioxidant, and redox modulator. PQQ has been demonstrated to oxidize the redox modulatory site of N-methyl-d-aspartic acid (NMDA) receptors. Such agents are known to be neuroprotective in experimental stroke models. However, there is not report about the therapeutic effect of PQQ on neuropathic pain. We tested the effects of oral administration of PQQ on neuropathic pain of rats with chronic constriction injury (CCI) of the sciatic nerve. The repeated oral administration of PQQ (20 and 40mg/kg, once a day for 4 weeks, from day 1 after the injury) attenuated both thermal and mechanical hyperalgesia, and also attenuated the muscle atrophy. The anti-hyperalgesic activity of PQQ was associated with a significant reduction of pro-inflammatory mediators such as tumor necrosis factor alpha (TNF-α) and lipid peroxide malondialdehyde (MDA) levels. In the present investigation, PQQ is shown to have analgesic effect which was found in the first time, probably through reducing the release of pro-inflammatory mediator and inhibiting oxidative stress.