Effective relief of neuropathic pain by adeno-associated virus-mediated expression of a small hairpin RNA against GTP cyclohydrolase 1.
BACKGROUND
Recent studies show that transcriptional activation of GTP cyclohydrolase I (GCH1) in dorsal root ganglia (DRG) is significantly involved in the development and persistency of pain symptoms. We thus hypothesize that neuropathic pain may be attenuated by down-regulation of GCH1 expression, and propose a gene silencing system for this purpose.


RESULTS
To interrupt GCH1 synthesis, we designed a bidirectional recombinant adeno-associated virus encoding both a small hairpin RNA against GCH1 and a GFP reporter gene (rAAV-shGCH1). After rAAV-shGCH1 was introduced into the sciatic nerve prior to or following pain-inducing surgery, therapeutic efficacy and the underlying mechanisms were subsequently validated in animal models. The GFP expression data indicates that rAAV effectively delivered transgenes to DRG. Subsequently reduced GCH1 expression was evident from immunohistochemistry and western-blotting analysis. Along with the down-regulation of GCH1, the von Frey test correspondingly indicated a sharp decline in pain symptoms upon both pre- and post-treatment with rAAV-shGCH1. Interestingly, GCH1 down-regulation additionally led to decreased microglial activation in the dorsal horn, implying an association between pain attenuation and reduced inflammation.


CONCLUSIONS
Therefore, the data suggests that GCH1 levels can be reduced by introducing rAAV-shGCH1, leading to pain relief. Based on the results, we propose that GCH1 modulation may be developed as a clinically applicable gene therapy strategy to treat neuropathic pain.
Kim
Sung Jin
SJ
Departments of Microbiology, University of Ulsan College of Medicine, Seoul, Korea. sktjdwls@hanmail.net
Lee
Won Il
WI
Lee
Yoon Sun
YS
Kim
Dong Hou
DH
Chang
Jin Woo
JW
Kim
Seong Who
SW
Lee
Heuiran
H
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D000229:Dependovirus / Q000235:genetics*; D006136:GTP Cyclohydrolase / Q000235:genetics* / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D009437:Neuralgia / Q000628:therapy*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D051381:Rats
D034741:RNA, Small Interfering; D006136:GTP Cyclohydrolase