Effect of zinc-fingers and homeoboxes 2 in the dorsal root ganglion on peripheral nerve injury-induced pain hypersensitivity

Abstract

Objective To explore the roles of zinc-fingers and homeoboxes (ZHX) in the dorsal root ganglia (DRG) in peripheral nerve injury-induced pain hypersensitivity, and provide a new idea for molecular mechanism of neuropathic pain (NP). Methods (1) Twenty-four 8-week-old male C57BL6 mice were randomly divided into sham-operated group and chronic constriction injury (CCI) of the sciatic nerve model group (n=12). One d before modeling and 7 d after modeling, the changes of paw withdrawal frequency (PWF) to mechanical stimuli and paw withdrawal latency (PWL) to thermal stimulation were detected. Seven d after modeling, reverse transcription real-time quantitative PCR (RT-qPCR) was used to detect the ZHX1, ZHX2, and ZHX3 mRNA expressions, and Western blotting was employed to detect the ZHX2 protein expression. (2) Thirty-six 8-week-old male C57BL6 mice were randomly divided into equivalent dose solvent CCI group, nonsense negative control sequence [siNC] CCI group and ZHX2 siRNA CCI group, and equivalent dose solvent sham-operated group, siNC sham-operated group and ZHX2 siRNA sham-operated group (n=6); each treatment was given to the DRG. One d before drug injection and 7 d after drug injection, the changes of PWF to mechanical stimuli and PWL to thermal stimulation were detected; RT-qPCR was used to detect the ZHX2 mRNA expression. Results (1) Seven d after modeling, PWF was significantly increased and PWL was statistically shorten in the hind-paw of the ipsilateral side in the CCI group as compared with those in the sham-operated group (P<0.05); DRG ZHX2 mRNA expression in the CCI group increased for 1.71 times as compared with that in the sham-operated group, with significant difference (P<0.05); DRG ZHX2 protein expression in the CCI group increased for 2.15 times as compared with that in the sham-operated group, with significant difference (P<0.05). (2) As compared with the equivalent dose solvent sham-operated group, siNC sham-operated group and ZHX2 siRNA sham-operated group, equivalent dose solvent CCI group and siNC CCI group had significantly increased PWF and DRG ZHX2 mRNA expression, and statistically shorten PWL (P<0.05); and ZHX2 siRNA CCI group had significantly decreased PWF of the ipsilateral side and DRG ZHX2 mRNA expression, and statistically longer PWL of the ipsilateral side as compared with equivalent dose solvent CCI group and siNC CCI group (P<0.05). Conclusion Knockdown periphery nerve injury-induced DRG ZHX2 up-regulation attenuates pain hypersensitivity following periphery nerve injury, and ZHX2 may be a new potential target to treat NP. Key words: Dorsal root ganglia; Zinc-fingers and homeoboxes 2; Nerve injury; Neuropathic pain