Objective: To investigate the regulatory effect of electroacupuncture (EA) at Zusanli (ST36) on tumor necrosis factor-alpha (TNF-alpha) 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-alpha and colonic TNF-alpha mRNA level. Morphologic damage score was examined under stereomicroscope. Colonic MPO activity was measured by spectrophotometer method. Serum TNF-alpha concentration was determined by radioimmunoassay (RIA). Colonic TNF-alpha 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 (microkat/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-alpha and colonic TNF-alpha 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-alpha and colonic TNF-alpha 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).

Conclusions: Serum TNF-alpha concentration and colonic TNF-alpha mRNA expression level are increased significantly in UC rats in correlation with the severity of disease. It indicates that TNF-alpha is closely involved in the immune abnormalities and inflammatory responses in UC. EA at ST36 has therapeutic effect on UC by downregulating serum TNF-alpha and colonic TNF-alpha mRNA expression. High levels of TNF-alpha and its corresponding mRNA expression seem to be implicated in the pathogenesis of UC.