Response to ‘Reply to Gohar on “Lungs, methotrexate and psoriasis”, a comment on “Fatal, incidental, idiopathic pulmonary fibrosis in a patient receiving long‐term low‐dose methotrexate for psoriasis”’

Molecular mechanisms underlying methotrexate-induced intestinal injury and protective strategies

Methotrexate (MTX) is a folic acid reductase inhibitor that manages various malignancies as well as immune-mediated inflammatory chronic diseases. Despite being frequently prescribed, MTX's severe multiple toxicities can occasionally limit its therapeutic potential. Intestinal toxicity is a severe adverse effect associated with the administration of MTX, and patients are significantly burdened by MTX-provoked intestinal mucositis. However, the mechanism of such intestinal toxicity is not entirely understood, mechanistic studies demonstrated oxidative stress and inflammatory reactions as key factors that lead to the development of MTX-induced intestinal injury. Besides, MTX causes intestinal cells to express pro-inflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), which activate nuclear factor-kappa B (NF-κB). This is followed by the activation of the Janus kinase/signal transducer and activator of the transcription3 (JAK/STAT3) signaling pathway. Moreover, because of its dual anti-inflammatory and antioxidative properties, nuclear factor erythroid-2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) has been considered a critical signaling pathway that counteracts oxidative stress in MTX-induced intestinal injury. Several agents have potential protective effects in counteracting MTX-provoked intestinal injury such as omega-3 polyunsaturated fatty acids, taurine, umbelliferone, vinpocetine, perindopril, rutin, hesperidin, lycopene, quercetin, apocynin, lactobacillus, berberine, zinc, and nifuroxazide. This review aims to summarize the potential redox molecular mechanisms of MTX-induced intestinal injury and how they can be alleviated. In conclusion, studying these molecular pathways might open the way for early alleviation of the intestinal damage and the development of various agent plans to attenuate MTX-mediated intestinal injury.

Ultrasensitive therapeutic drug monitoring of methotrexate by a structure-switching aptamer with cascade primer exchange reaction

As a folate antagonist, methotrexate (MTX) has been widely used in clinics with good effects on various tumors and inflammatory diseases. While the optimum dosage and total body clearance of MTX usually varies between individuals and even low-dose MTX has side effects, high-dose MTX may cause life-threatening side effects. Therefore, a convenient and simple method toward MTX sensing is highly demanded. Herein, we report a highly sensitive and selective method for therapeutic drug monitoring (TMD) of MTX by integrating a highly specific MTX-dependent structure-switching aptamer with a primer exchange reaction-based signal amplification technique. The detection limit is down to 1.7 nM with a linear range from 0.01 to 1 μM in buffer. More importantly, the sensing strategy can effectively detect MTX in a complex bio-environment with a linear response range from 0.05 to 2 μM and a LOD of 12.4 nM in 10% FBS and a range of 0.2 to 5 μM with a LOD of 63.73 nM in 10% whole blood. Considering the high sensitivity and selectivity and good performance in blood, the method reported herein paves a new avenue for the effective determination of MTX in clinics.

Selection of a Structure-Switching Aptamer for the Specific Methotrexate Detection

Methotrexate (MTX), a folate antagonist drug, has been widely used for treating various cancers. Since high-dose MTX treatment can cause unwanted serious side effects, tracking the blood concentration of MTX is essential for safe medication. However, available methods are often complex, time-consuming, and expensive. In this study, a highly selective DNA aptamer was selected for recognizing MTX based on a capture-systematic evolution of ligands by an exponential enrichment (C-SELEX) approach. Taking advantage of our selected MTX aptamer, we further unveil a novel structure-switching fluorescent sensor for the specific and rapid monitoring of MTX with good analytical performances (i.e., a linear detection range of 0.1-2 μM with a low detection limit (LOD) of 0.03 μM in buffer and a linear detection range of 0.5-10 μM with an LOD of 0.18 μM in 50% serum). Compared with conventional methods, this assay has great potential for detecting the blood concentration of MTX in clinical use. By coupling with other sensory techniques, our presented aptamer will potentially inspire the development of various sensors toward the monitoring of MTX.