Effects of TGF‐α gene knockout on epithelial cell kinetics and repair of methotrexate‐induced damage in mouse small intestine

Abstract

While previous studies have indicated that exogenous TGF-alpha stimulates epithelial growth, maintenance, and repair of the gut, roles of endogenous TGF-alpha are less well-defined particularly in the small bowel. The current study examined effects of TGF-alpha knockout on adult small intestinal epithelial cell proliferation, migration, apoptosis, and damage/repair response after methotrexate treatment. Compared to normal mice, TGF-alpha gene knockout did not affect crypt cell production, mitosis position, migration, and apoptosis in non-injured intestine. RT-PCR gene expression analysis revealed presence of four out of six TGF-alpha related EGF family ligands in the normal intestine, suggesting a possible functional redundancy of the EGF family in maintenance of the intestine. Although TGF-alpha gene knockout did not significantly impair the overall mucosal repair in methotrexate-induced acute damage in the small intestine, it resulted in a higher apoptotic response in the early hours following methotrexate challenge, and a delayed and reduced crypt cell proliferation during repair. Consistently, after methotrexate challenge, intestinal TGF-alpha mRNA was found to be markedly upregulated in the early hours and during repair in the wild type, and there were similar profiles in the increased expression of all other ligands (except EGF) between the wild type and knockout intestines. Therefore, despite a possible functional redundancy among the EGF family ligands in the normal small intestine, TGF-alpha may play a role in modulating the early apoptotic events and in enhancing the subsequent reparative proliferative response in the methotrexate-damaged intestine.

Effect of Oral Glutamine on Enterocyte Turnover during Methotrexate-Induced Mucositis in Rats

“…Growing evidence suggests that cell apoptosis plays a crucial role in this process. Our data showed that programmed cell death is one of the pathways leading to mucosal damage as well as to marked mucosal atrophy observed in half of the animals following MTX administration, and is consistent with data reported by other investigators [18, 19]. Both decreased cell proliferation and increased cell apoptosis suggest a decreased enterocyte turnover, which might explain mucosal hypoplasia after MTX treatment.…”

Steamed root of Rehmannia glutinosa Libosch (Plantaginaceae) alleviates methotrexate-induced intestinal mucositis in rats

“…2a and b). This result confirms that MTX has toxic effects on rapidly proliferating crypt epithelial cells (Pinkerton and Milla 1984;Xian et al, 1999;2000;2002;Xian, 2003).…”

“…Up to now the widely accepted hypothesis on the pathobiology of mucositis includes five phases of mucositis development and resolution: initiation, primary damage response, signal amplification, ulceration and healing (Al-Dasooqi et al, 2013;Crohns et al, 2009;Gilliam and St. Clair, 2011;Il'yasova et al, 2009;Sonis, 2009). Both DNA and non-DNA damages exert on epithelial and submucosal cells following chemotherapy, which cause intricate sequential biological events, such as generation of reactive oxygen species (ROS), transcription factor activation, pro-inflammatory cytokine expression/accumulation, nitrosative stress, cell apoptosis, reduction in epithelial cell proliferation, changes in growth factor expression, proteolysis, bacterial colonization, and activation of enteric immune and nervous systems (Al-Dasooqi et al, 2013;Kolli et al, 2008;Logan et al, 2007;2009;Qutob et al, 2013;Sonis, 2009;Xian et al, 1999Xian et al, , 2000Xian et al, , 2002Xian, 2003;Zhan et al, 2014). Great efforts have been applied to evaluate/ develop interventions that prevent or reduce the toxic effects of chemotherapy, such as intensive oral hygiene care and usage of antiseptics, antimicrobial and anti-inflammatory agents, cytokines, growth factors, antioxidants, immune modulators and homeopathic agents (McCulloch et al, 2014;Nadhanan et al, 2013;Qutob et al, 2013;Rodríguez-Caballero et al, 2012).…”

Folinic acid attenuates methotrexate chemotherapy‐induced damages on bone growth mechanisms and pools of bone marrow stromal cells

“…Ninety minutes prior to sacrifice, rats were i.p. injected with 5 0 -bromo-2 0 -deoxyuridine (BrdU) (Sigma, NSW, Australia) at 50 mg/kg for cell proliferation study (Xian et al, 2002. Both hind limbs were dissected.…”