Immunohistochemical and histopathological studies of effects of methotrexate on the pancreas of albino rats and the role of folic acid supplementation

ABSTRACT

Methotrexate is an antimetabolite that is widely used for rheumatoid arthritis, psoriasis, autoimmune and inflammatory diseases. Even with the newer biological agents, methotrexate continues to serve as a reference point. However, its long-term clinical use is restricted due to its severe side effects and toxicity. A severe side effect of methotrexate may cause decrease or disruption of cancer chemotherapy. Therefore a better understanding of its histopathological mechanism is necessary to develop adapted curative strategies. Folic acid is a water-soluble B vitamin that is implicated in the synthesis of purines and pyrimidines, the essential precursors of DNA. The aim of this study is to investigate the toxic effect of methotrexate on the pancreas of adult female albino rats. It should be noted that there are relatively few studies that have addressed folic acid supplementation with the use of methotrexate on tissue which show a very active metabolic process such as pancreas. Therefore, the efficacy of folic acid against rnethotrexate induced exocrine and endocrine pancreatic cell injury was assessed. Rats were divided into four groups consisting of 10 rats in each group. Group 1, control group; group 2; the folic acid receiving group, group 3, the methotrexate-injected group and group 4, the methotrexate and the folic acid for 4 week. Tissues were removed while the rats were under ether anesthesia. Pancreatic tissues were processed for histological examination and stained routinely with Haematoxylin and Eosin for observing general morphological changes. Sections of the pancreas were stained with Masson's trichrome to demonstrate the collagen fibres. Histochemical PAS stain was also performed for glycogen detection. In addition, immunohistochemical investigation of different groups was carried out. So, pancreatic tissues from different groups were studied using a monoclonal antibody to insulin. In the current study, microscopic examination of control group stained with H and E showed normal architecture of pancreas. No pathologic changes in the pancreatic islets and surrounding acini were detected in the folic acid group [group 2], In contrast, the methotrexate-treated group showed that, acinar cell dissociation, marked vacuolation and congestion. There are broadly multiple cytoplasmic vacuoles of variable sizes in the exocrine pancreatic acinar cells. Moreover, Methotrexate induced damaging effects on pancreatic islets in rats as detected by immunohistochemistry While administration of folic acid and methotrexate, the combination group [group 4] displayed regression of acinar cell and pancreatic islets toxicity. The present investigation proved that methotrexate should be used with caution for fear of pancreatitis. The methotrexate long-term therapy requires maintaining a slight balance between benefits and risks. It was concluded that folic acid might be beneficial in preventing methotrexate induced pancreatic injury. Therefore, folic acid supplementation may be a promise as a therapy policy for every patient who receives methotrexate. Further investigation should be carried out to identify the precise mechanism underlying the protective effects of folic acid as well as the clinical interference to reduce methotrexate induced damage in pancreatic tissue