Upregulation of cystathionine-β-synthetase expression contributes to inflammatory pain in rat temporomandibular joint.
BACKGROUND
Hydrogen sulfide (H2S), an endogenous gaseotransmitter/modulator, is becoming appreciated that it may be involved in a wide variety of processes including inflammation and nociception. However, the role for H2S in nociceptive processing in trigeminal ganglion (TG) neuron remains unknown. The aim of this study was designed to investigate whether endogenous H2S synthesizing enzyme cystathionine-β-synthetase (CBS) plays a role in inflammatory pain in temporomandibular joint (TMJ).


METHODS
TMJ inflammatory pain was induced by injection of complete Freund's adjuvant (CFA) into TMJ of adult male rats. Von Frey filaments were used to examine pain behavioral responses in rats following injection of CFA or normal saline (NS). Whole cell patch clamp recordings were employed on acutely isolated TG neurons from rats 2 days after CFA injection. Western blot analysis was carried out to measure protein expression in TGs.


RESULTS
Injection of CFA into TMJ produced a time dependent hyperalgesia as evidenced by reduced escape threshold in rats responding to VFF stimulation. The reduced escape threshold was partially reversed by injection of O-(Carboxymethyl) hydroxylamine hemihydrochloride (AOAA), an inhibitor for CBS, in a dose-dependent manner. CFA injection led to a marked upregulation of CBS expression when compared with age-matched controls. CFA injection enhanced neuronal excitability as evidenced by depolarization of resting membrane potentials, reduction in rheobase, and an increase in number of action potentials evoked by 2 and 3 times rheobase current stimulation and by a ramp current stimulation of TG neurons innervating the TMJ area. CFA injection also led to a reduction of IK but not IA current density of TG neurons. Application of AOAA in TMJ area reduced the production of H2S in TGs and reversed the enhanced neural hyperexcitability and increased the IK currents of TG neurons.


CONCLUSIONS
These data together with our previous report indicate that endogenous H2S generating enzyme CBS plays an important role in TMJ inflammation, which is likely mediated by inhibition of IK currents, thus identifying a specific molecular mechanism underlying pain and sensitization in TMJ inflammation.
Xiuhua
X
Miao
Xiaowen
X
Meng
Geping
G
Wu
Zhong
Z
Ju
Hong-Hong
HH
Zhang
Shufen
S
Hu
The Affiliated Zhangjiagang Hospital of Soochow University, Zhangjiagang 215600, P,R, China. guangyinxu@suda.edu.cn.
Guang-Yin
GY
Xu
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003541:Cystathionine beta-Synthase / Q000037:antagonists & inhibitors / Q000235:genetics*; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005620:Freund's Adjuvant / Q000008:administration & dosage; D006862:Hydrogen Sulfide / Q000378:metabolism; D006930:Hyperalgesia / Q000150:complications / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D007249:Inflammation / Q000150:complications / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D007267:Injections; D008297:Male; D010146:Pain / Q000150:complications / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013704:Temporomandibular Joint / Q000201:enzymology* / Q000294:innervation / Q000473:pathology / Q000503:physiopathology; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation / Q000235:genetics*
D004791:Enzyme Inhibitors; D024642:Potassium Channels, Voltage-Gated; D005620:Freund's Adjuvant; D003541:Cystathionine beta-Synthase; D006862:Hydrogen Sulfide