Methotrexate modulates tight junctions through NF-κB, MEK, and JNK pathways.

Area of Science:

• Gastroenterology
• Oncology
• Molecular Biology

Background:

• Chemotherapy frequently causes intestinal mucositis, a condition linked to increased intestinal permeability.
• The precise mechanisms regulating tight junction (TJ) proteins during chemotherapy-induced intestinal damage are not fully understood.

Purpose of the Study:

• To investigate the regulation of three key TJ proteins—claudin-1, occludin, and zonula occludens-1—in the context of anticancer treatment.
• To elucidate the molecular pathways involved in chemotherapy-induced alterations of intestinal barrier function.

Main Methods:

• Methotrexate (MTX) was administered to Sprague-Dawley rats and Caco-2 cell monolayers to induce intestinal mucositis.
• Western blot and microscopy were used to assess TJ protein expression and distribution.
• Transepithelial electrical resistance and fluorescein isothiocyanate-dextran flux assays evaluated paracellular permeability in vitro. Cytokine production and signaling pathways were also analyzed.

Main Results:

• MTX treatment altered TJ protein distribution and reduced claudin-1 and occludin expression in rats during acute mucositis, with recovery observed later.
• In Caco-2 cells, MTX increased paracellular permeability, associated with altered occludin and zonula occludens-1 expression and distribution.
• These MTX-induced changes were linked to increased proinflammatory cytokine production and were preventable by inhibiting MEK1/2, JNK, and NF-κB pathways.

Conclusions:

• MTX treatment increases intestinal permeability through alterations in TJ protein expression and distribution.
• The observed effects are potentially mediated by MAPK and NF-κB signaling pathways.
• Targeting these pathways presents a promising strategy to reduce the gastrointestinal side effects of chemotherapy.