Muscle contraction accelerates IL-6 mRNA expression in the rat masseter muscle.
OBJECTIVE
This study was conducted to determine if interleukin-6 (IL-6) and interleukin-1beta (IL-1beta) mRNA expression increase in response to muscle contraction caused by repetitive electrical stimulation of the rat masseter muscle.


METHODS
Male Wistar rats weighing 140-160 g were divided randomly into the following three groups: electrical stimulation (ES) group (n=21), carrageenan injection (CI) group (n=24), and ES under dantrolene sodium (muscle relaxant) injection (ESDI) group (n=7). ES or CI was done to the left masseter; and mock ES or mock CI to the right. Muscle tissues on both sides were sampled for total RNA isolation. Real-time RT-PCR was performed, with the cyclophilin A (CypA) mRNA level in each sample as an internal control. Mean relative IL-6 (il-6/cypA) and IL-1beta (il-1beta/cypA) mRNA levels were compared between the experimental and mock-treated sides within each group.


RESULTS
Mean IL-6/CypA levels in the ES- or CI-treated muscle significantly increased, without any significant incremental change observed in either mock-treated muscle. Interestingly, the increase in the il-6/cypA level caused by the ES was suppressed by the injection of dantrolene sodium in the ESDI group. Furthermore, the mean il-1beta/cypA level in the CI-treated masseter also significantly increased without any significant incremental change observed in the mock-treated muscle. However, there was no significant difference in the mean il-1beta/cypA levels in the masseter between the ES- and the mock-treated sides.


CONCLUSIONS
These results show that IL-6 mRNA expression in the rat masseter muscle was accelerated by the CI or by repetitive muscle contraction induced by ES. Since the mRNA level of IL-1beta, a well-known proinflammatory cytokine, was not altered by the contraction, the accelerated IL-6 mRNA expression elicited by the muscle contraction does not seem to be related to local inflammation.
Ono
Tsuyoshi
T
Department of Oral and Maxillofacial Rehabilitation, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8525, Japan.
Maekawa
Kenji
K
Watanabe
Shogo
S
Oka
Hisao
H
Kuboki
Takuo
T
D000818:Animals; D002351:Carrageenan / Q000494:pharmacology; D021984:Cyclophilin A / Q000032:analysis / Q000235:genetics; D003620:Dantrolene / Q000494:pharmacology; D004558:Electric Stimulation; D018836:Inflammation Mediators / Q000494:pharmacology; D053583:Interleukin-1beta / Q000032:analysis / Q000235:genetics; D015850:Interleukin-6 / Q000032:analysis* / Q000235:genetics; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000276:immunology*; D009119:Muscle Contraction / Q000187:drug effects / Q000276:immunology*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
D018836:Inflammation Mediators; D053583:Interleukin-1beta; D015850:Interleukin-6; D009125:Muscle Relaxants, Central; D012333:RNA, Messenger; D002351:Carrageenan; D021984:Cyclophilin A; D003620:Dantrolene