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Alimentary tract (AT) mucositis is a serious problem complicating cancer treatment, however, its pathobiology remains incompletely understood. Nuclear factor-κB (NF-κB) and pro-inflammatory cytokines are considered to have important roles in its development. This has been previously demonstrated in different sites of the AT following administration of irinotecan in an animal model using the Dark Agouti rat. The aim of the present study was to determine whether the changes that occur in the AT are affected by the type of mucotoxic drug. Female DA rats were given a single dose of either methotrexate (1.5 mg/kg intramuscularly) or 5-fluorouracil (150 mg/kg intraperitoneally). Rats were killed at 30, 60, 90 min, 2, 6, 12, 24, 48 and 72 h. Control rats received no treatment. Samples of oral mucosa, jejunum and colon were collected. Haematoxylin and eosin stained sections were examined with respect to histological evidence of damage and standard immunohistochemical techniques were used to demonstrate tissue expression of NF-κB, TNF, IL-1β and IL-6. Both MTX and 5-FU administration caused histological evidence of tissue damage in the AT as well as changes in tissue expression of NF-κB and specific pro-inflammatory cytokines. This study, however, demonstrated that there were differences in the timing of histological changes as well as the timing and intensity of pro-inflammatory cytokine tissue expression caused by the different drugs. The results from this study suggest that there are differences in the mucositis pathobiology caused by different drugs. This may have important ramifications for the management of mucositis particularly with respect to the development of treatment regimens for mucositis. Further investigations are required to determine the exact pathways that lead to damage caused by the different drugs. [ABSTRACT FROM AUTHOR]

The pathobiology of alimentary tract (AT) mucositis is complex and there is limited information about the events which lead to the mucosal damage that occurs during cancer treatment. Various transcription factors and proinflammatory cytokines are thought to play important roles in pathogenesis of mucositis. The aim of this study was to determine the expression of nuclear factor-κB (NF-κB), tumor necrosis factor (TNF) and interleukins-1β (IL-1β) and -6 (IL-6) in the AT following the administration of the chemotherapeutic agent irinotecan. Eighty-one female dark Agouti rats were assigned to either control or experimental groups according to a specific time point. Following administration of irinotecan, rats were monitored for the development of diarrhoea. The rats were killed at times ranging from 30 min to 72 h after administration of irinotecan. Oral mucosa, jejunum and colon were collected and standard immunohistochemical techniques were used to identify NF-κB, TNF, IL-1β and IL-6 within the tissues. Sections were also stained with haematoxylin and eosin for histological examination. Irinotecan caused mild to moderate diarrhoea in a proportion of the rats that received the drug. Altered histological features of all tissues from rats administered irinotecan were observed which included epithelial atrophy in the oral mucosa, reduction of villus height and crypt length in the jejunum and a reduction in crypt length in the colon. Tissue staining for NF-κB, TNF and IL-1β and IL-6 peaked at between 2 and 12 h in the tissues examined. This is the first study to demonstrate histological and immunohistochemical evidence of changes occurring concurrently in different sites of the AT following chemotherapy. The results of the study provide further evidence for the role of NF-κB and associated pro-inflammatory cytokines in the pathobiology of AT mucositis. The presence of these factors in tissues from different sites of the AT also suggests that there may be a common pathway along the entire AT causing mucositis following irinotecan administration. [ABSTRACT FROM AUTHOR]