• Cheng-Yuan Lai, Ming-Chun Hsieh, Yu-Cheng Ho, An-Sheng Lee, Hsueh-Hsiao Wang, Jen-Kun Cheng, Yat-Pang Chau, and Hsien-Yu Peng.
• From the Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan (C.-Y.L.); Department of Medicine, Mackay Medical College, New Taipei, Taiwan (C.-Y.L., M.-C.H., Y.-C.H., A.-S.L., H.-H.W., J.-K.C., Y.-P.C., H.-Y.P.); Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan (M.-C.H.); and Department of Anesthesiology, Mackay Memorial Hospital, Taipei, Taiwan (J.-K.C.).
• Anesthesiology. 2017 Jun 1; 126 (6): 1077-1095.

BackgroundGrowth arrest and DNA-damage-inducible protein 45β reactivates methylation-silenced neural plasticity-associated genes through DNA demethylation. However, growth arrest and DNA-damage-inducible protein 45β-dependent demethylation contributes to neuropathic allodynia-associated spinal plasticity remains unclear.MethodsAdult male Sprague-Dawley rats (654 out of 659) received a spinal nerve ligation or a sham operation with or without intrathecal application of one of the following: growth arrest and DNA-damage-inducible protein 45β messenger RNA-targeted small interfering RNA, lentiviral vector expressing growth arrest and DNA-damage-inducible protein 45β, Ro 25-6981 (an NR2B-bearing N-methyl-D-aspartate receptor antagonist), or KN-93 (a calmodulin-dependent protein kinase II antagonist) were used for behavioral measurements, Western blotting, immunofluorescence, dot blots, detection of unmodified cytosine enrichment at cytosine-phosphate-guanine site, chromatin immunoprecipitation quantitative polymerase chain reaction analysis, and slice recordings.ResultsNerve ligation-enhanced growth arrest and DNA-damage-inducible protein 45β expression (n = 6) in ipsilateral dorsal horn neurons accompanied with behavioral allodynia (n = 7). Focal knockdown of growth arrest and DNA-damage-inducible protein 45β expression attenuated ligation-induced allodynia (n = 7) by reducing the binding of growth arrest and DNA-damage-inducible protein 45β to the voltage-dependent T-type calcium channel 3.2 subunit promoter (n = 6) that decreased expression of and current mediated by the voltage-dependent T-type calcium channel 3.2 subunit (both n = 6). In addition, NR2B-bearing N-methyl-D-aspartate receptors and calmodulin-dependent protein kinase II act in an upstream cascade to increase growth arrest and DNA-damage-inducible protein 45β expression, hence enhancing demethylation at the voltage-dependent T-type calcium channel 3.2 subunit promoter and up-regulating voltage-dependent T-type calcium channel 3.2 subunit expression. Intrathecal administration of Ro 25-6981, KN-93, or a growth arrest and DNA-damage-inducible protein 45β-targeting small interfering RNA (n = 6) reversed the ligation-induced enrichment of unmodified cytosine at the voltage-dependent T-type calcium channel 3.2 subunit promoter by increasing the associated 5-formylcytosine and 5-carboxylcytosine levels.ConclusionsBy converting 5-formylcytosine or 5-carboxylcytosine to unmodified cytosine, the NR2B-bearing N-methyl-D-aspartate receptor, calmodulin-dependent protein kinase II, or growth arrest and DNA-damage-inducible protein 45β pathway facilitates voltage-dependent T-type calcium channel 3.2 subunit gene demethylation to mediate neuropathic allodynia.

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