Methotrexate induces intestinal mucositis and alters gut protein metabolism independently of reduced food intake

Abstract

One of the main secondary toxic side effects of antimitotic agents used to treat cancer patients is intestinal mucositis. This one is characterized by compromised digestive and absorptive functions, barrier integrity, and immune competence. At the same time, food intake is decreased, which may induce intestinal damages per se. The aim of the study was to characterize which alterations are specific to methotrexate, independently of the anorexic effect of the drug. Male Sprague-Dawley rats received subcutaneously saline solution as control group or 2.5 mg/kg of methotrexate during 3 days (D0-D2). Methotrexate-treated rats were compared with ad libitum and pair-fed controls. Histological examinations and specific markers of the immune and nonimmune gut barrier function were assessed at D4 or D7. Compared with ad libitum and pair-fed controls, methotrexate induced at D4 villus atrophy associated with epithelial necrosis. Mucosal protein synthesis rate and mucin contents of methotrexate treated rats were reduced. At the same time, cathepsin D proteolytic activity was increased compared with ad libitum and pair-fed controls, whereas calpain activity was increased when compared with the only pair-fed controls. These intestinal lesions were associated with various metabolic disturbances such as increased TNF-alpha level and inflammation score in the jejunum but also disturbances of amino acid concentrations in the duodenum and plasma. At D7, these alterations were partially or completely normalized. In addition to the consequences of a low food intake, methotrexate further impairs different biological processes leading to a dramatic loss of gut homeostasis. Targeted nutritional management of chemotherapy receiving patients should be set up to prevent or limit such alterations.

Enteral delivery of proteins stimulates protein synthesis in human duodenal mucosa in the fed state through a mammalian target of rapamycin–independent pathway

“…Proteasome activities were evaluated as previously described (3,28,29) by using spectrofluorimetry on a microtiter plate fluorometer (Mithras LB 940; Berthold Technologies) with fluorogenic proteasome substrates Suc-LLVY-MCA (PSIII; Calbiochem) for chymotrypsin-like activity, Boc-LSTR-MCA (Sigma Aldrich) for trypsin-like activity, and Z-LLE-MCA (Sigma Aldrich) for caspase-like or peptidyl-glutamyl peptidehydrolyzing activity in the presence or absence of proteasome inhibitor (10 mmol/L MG132; Sigma Aldrich). Thus, proteasome activity was calculated by using the difference between the activity measured in the absence of MG132 proteasome inhibitor and the activity measured in the presence of MG132 proteasome inhibitor.…”

“…In some pathophysiologic conditions, protein turnover is altered and may contribute to intestinal or systemic diseases. Gut protein metabolism can be affected by nutritional state (3)(4)(5) or nutritional interventions (1,4,(6)(7)(8). Amino acids, as constituents of proteins and signaling molecules, have been extensively tested in vitro and in vivo, but results have appeared to be model and condition dependent (9).…”

Mucositis and non-invasive markers of small intestinal function

“…It could also be argued that decreases in serum citrulline levels could indeed reflect the decreases in the patient's food intake, as reductions in and withdrawal from food is commonly observed in bone marrow transplant patients. 63 More recently, a study by Boukhettala et al 64 suggested that a reduction in food intake did not mimic citrulline levels observed in MTX-treated rats. However, this finding has yet to be confirmed in humans, or indeed, in cancer patients.…”

A Diet Containing Whey Protein, Glutamine, and TGFβ Modulates Gut Protein Metabolism During Chemotherapy-Induced Mucositis in Rats

“…In the placebo diet, whey proteins and TGFb-rich casein were replaced by TGFb-free casein and free glutamine by free alanine (Table 1). Mucositis was induced by three subcutaneous injections of 2.5 mg/kg MTX (Teva Pharma, Courbevoie, France) for 3 consecutive days (day 0, 1 and 2) as previously described [3,4]. Control rats received injections of saline (0.9%).…”

“…The pathophysiology of mucositis involves tissue lesions and secondary inflammatory response [2]. In rats, we recently reported that MTX treatment alters intestinal barrier function and protein metabolism [3] independent of the anorectic effect of MTX [4]. Indeed, MTX treatment was associated with a decrease of protein synthesis [4] and an increase of lysosomalmediated proteolysis in jejunal mucosa [3,4], which may contribute to the disruption of the gut barrier.…”