Exercise reduces inflammation and cell proliferation in rat colon carcinogenesis.
OBJECTIVE
There is evidence that the risk of colon cancer is reduced by appropriate levels of physical exercise. Nevertheless, the mechanisms involved in this protective effect of exercise remain largely unknown. Inflammation is emerging as a unifying link between a range of environment exposures and neoplastic risk. The carcinogen dimethyl-hydrazine (DMH) induces an increase in epithelial cell proliferation and in the expression of the inflammation-related enzyme cyclooxigenase-2 (COX-2) in the colon of rats. Our aim was to verify whether these events could be attenuated by exercise.


METHODS
Four groups of eight Wistar rats were used in the experiment. The groups G1 and G3 were sedentary (controls), and the groups G2 and G4 were submitted to 8 wk of swimming training, 5 d.wk. The groups G3 and G4 were given subcutaneous injections of DMH immediately after the exercise protocols. Fifteen days after the neoplasic induction, the rats were sacrificed and the colon was processed for histological examination and immunohistochemistry staining of proliferating cell nuclear antigen (PCNA) and COX-2.


RESULTS
We found a significant increase in the PCNA-labeling index in both DMH-treated groups of rats. However, this increase was significantly attenuated in the training group G4 (P < 0.01). Similar results were observed in relation to the COX-2 expression.


CONCLUSIONS
From our findings, we conclude that exercise training exerts remarkable antiproliferative and antiinflammatory effects in the rat colonic mucosa, suggesting that this may be an important mechanism to explain how exercise protects against colonic cancer.
Demarzo
Marcelo Marcos Piva
MM
Department of Pathology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto-São Paulo, Brazil.
Martins
Lisandra Vanessa
LV
Fernandes
Cleverson Rodrigues
CR
Herrero
Fábio Augusto
FA
Perez
Sérgio Eduardo de Andrade
SE
Turatti
Aline
A
Garcia
Sérgio Britto
SB
D000818:Animals; D049109:Cell Proliferation / Q000528:radiation effects*; D003110:Colonic Neoplasms / Q000503:physiopathology*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000187:drug effects; D004127:Dimethylhydrazines; D007249:Inflammation / Q000503:physiopathology* / Q000517:prevention & control; D015850:Interleukin-6 / Q000096:biosynthesis; D007413:Intestinal Mucosa / Q000502:physiology / Q000503:physiopathology*; D008297:Male; D010805:Physical Conditioning, Animal; D051381:Rats; D017208:Rats, Wistar; D012307:Risk Factors
D004127:Dimethylhydrazines; D015850:Interleukin-6; D051546:Cyclooxygenase 2