Downregulation of electroacupuncture at ST36 on TNF-α in rats with ulcerative colitis

摘要

AIM: To investigate the regulatory effect of electroacupuncture (EA) at Zusanli (ST36) on tumor necrosis factor-alpha (TNF-) in rats with ulcerative colitis (UC), and further elucidate the therapeutic mechanism of EA on UC. METHODS: Thirty-two male Sprague-Dawley (SD) rats were randomly divided into four groups (n=8): normal control group, UC control group, UC+ST36 group and UC+non-acupoint group. A solution containing ethanol and 2,4,6-trinitrobenzenesulfonic acid (TNBS) was instilled into the distal colon in the rat (at a dose of 100 mg/kg) to set up UC rat model. Rats in wakefulness state of UC+ST36 group were stimulated at ST36 by EA once a day, while those of UC+non-acupoint group were done at 0.5 cm beside ST36. After 10 d treatment, all rats were sacrificed simultaneously. Colon musocal inflammation and damage were assessed by measuring colon mass, morphologic damage score, colonic myeloperoxidase enzyme (MPO) activity, serum TNF-α and colonic TNF-α mRNA level. Morphologic damage score was examined under stereomicroscope. Colonic MPO activity was measured by spectrophotometer method. Serum TNF-α concentration was determined by radioimmunoassay (RIA). Colonic TNF-α mRNA expression level was analyzed by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Ratio of colonic mass/body mass (m_C/m_B) and activity of colonic MPO (μkat/g tissue) markedly increased (8.5+-2.6 vs 2.5+-0.4; 145+-25 vs 24+-8, P<0.01 vs normal control group). Compared with normal control rats, serum TNF-α and colonic TNF-α mRNA level in UC control group were increased 2.5 fold (2 278+-170 vs 894+-248, P<0.01) and 4.3 fold (0.98+-0.11 vs 0.23+-0.11, P<0.01) respectively. After EA at ST36, m_C/m_B and MPO activity were reduced significantly (5.3+-2.0 vs 8.5+-2.6; 104+-36 vs 145+-25, P<0.01, 0.05) compared with those of UC control group. Serum TNF-α and colonic TNF-α mRNA level were inhibited by EA stimulation at ST36 (P<0.01). The inhibitory rate was 16 % and 44 % respectively. Morphologic damage score was also increased markedly in rat with UC (P<0.01), whereas it was decreased by EA at ST36 (P<0.05). There was no significant difference between UC control group and UC+EA at non-acupoint (P>0.05). Furthermore, these parameters were highly correlated with each other (P<0.01). CONCLUSION: Serum TNF-α concentration and colonic TNF-α mRNA expression level are increased significantly in UC rats in correlation with the severity of disease. It indicates that TNF-α is closely involved in the immune abnormalities and inflammatory responses in UC. EA at ST36 has therapeutic effect on UC by downregulating serum TNF-α and colonic TNF-α mRNA expression. High levels of TNF-α and its corresponding mRNA expression seem to be implicated in the pathogenesis of UC.