Objectives: Chemically induced mucosal inflammation in animal models is a suitable tool for studying factors in the pathogenesis of inflammatory bowel disease. The aim of this study was to determine whether absence of histamine has an effect on the development of experimental colitis.
Methods: Histamine-deficient, histidine decarboxylase (HDC) knockout Balb/c mice and genetically identical control animals with intact HDC were studied. Colitis was induced by the administration of 2% dextran sodium sulphate in drinking water. Mice were killed after 5 days and disease activity assessed by clinical, histologic, and immunohistologic parameters. Bacterial components of stool were examined.
Results: Clinical disease activity was higher in the mice with intact HDC (disease activity index, 2.21) than in the histamine-deficient knock-out mice (1.88). Histologic findings were similar in the two groups. On day 5, the inflammation score of the HDC sufficient group was 5.25 (±1.055) and the crypt score was 5.00 (±1.128). The scores in the HDC knock-out group were 4.667 (± 0.707) and 4.667 (± 0.86), respectively. There was a significant difference in the number of interleukin (IL-10)–producing lymphocytes in colon mucosa. Large numbers of IL-10–positive lymphocytes were observed in wild type mice both those with DSS induced colitis and untreated controls. Only sporadic IL-10 positivity was found in histamine-deficient mice. Significant differences were found in the composition of the fecal bacterial flora between the two groups.
Conclusion: The reduced number of IL-10–positive lymphocytes in the intestinal mucosa of histamine-deficient, histidine decarboxylase knockout mice and the altered fecal bacterial flora in these animals suggest that histamine may play a role in the pathophysiology of inflammation in the colon of normal animals by upregulating local IL-10 production and stimulating a local shift to Th2 response.
*Peéterfy S. Hospital, Department of Gastroenterology; †St. Janos Hospital, Department of Pathology; ‡Uzsoki Hospital, Department of Pathology; §Semmelweis University, Department of Genetics, Cell- and Immunobiology, Budapest; ||Johan Béla National Center of Epidemiology; ¶Semmelweis University, I. Department of Pediatrics; #Semmelweis University, II. Department of Internal Medicine; **Molecular Immunology Research Group, Hungarian Academy of Sciences-Semmelwies University, Budapest, Hungary
Received June 17, 2003; accepted January 12, 2004.
Supported by grants ETT159, 300/2000, OTKA 031887, and OM 00346/2001.
Address correspondence and reprint requests to Andras Falus, PhD, DSc, Professor, Department of Genetics, Cell- and Immunobiology, Budapest, Semmelweis University, 1089 Budapest, Nagyvárad tér 4, Hungary (e-mail: email@example.com).