OBJECTIVE

To investigate whether honokiol (HNK) acted as an analgesic in connection with inhibiting the voltage-gated proton channel (Hv1).

METHODS

The model of gouty arthritis was induced by injecting monosodium urate (MSU) crystals into the hind ankle joint of mice. HNK was given by intragastric administration. Ankle swelling degree and mechanical allodynia were evaluated using ankle joint circumference measurement and von Frey filaments, respectively. Hv1 current, tail current, and action potential in dorsal root ganglion (DRG) neurons were recorded with patch-clamp techniques.

RESULTS

HNK (10, 20, 40 mg/kg) alleviated inflammatory response and mechanical allodynia in a dose-dependent manner. In normal DRG neurons, 50 µM Zn or 2-GBI significantly inhibited the Hv1 current and the current density of Hv1 increased with increasing pH gradient. The amplitude of Hv1 current significantly increased on the 3rd after MSU treatment, and HNK dose-dependently reversed the upregulation of Hv1 current. Compared with MSU group, 40 mg/kg HNK shifted the activation curve to the direction of more positive voltage and increased reversal potential to the normal level. In addition, 40 mg/kg HNK reversed the down-regulation of tail current deactivation time constant (τ) but did not alter the neuronal excitability of DRG neurons in gouty mice.

CONCLUSION

HNK may be a potential analgesic by inhibiting Hv1 current.