Relative bioavailability of oral low dose methotrexate. A comparison of 2 different formulations

Methotrexate and Triptolide regulate Notch signaling pathway by targeting the Nedd4-Numb axis

Methotrexate (MTX) is used to treat rheumatoid arthritis, acute leukemia, and psoriasis. MTX can cause certain side effects, such as myelosuppression, while the exact mechanism of myelosuppression caused by MTX is unknown. Notch signaling pathway has been considered to be essential to regulate hematopoietic stem cell (HSC) regeneration and homeostasis, thus contributing to bone marrow hematopoiesis. However, whether MTX affects Notch signaling remains unexplored. Here, our study provides evidence that MTX strongly suppresses the Notch signaling pathway. We found that MTX inhibited the interaction between Nedd4 with Numb, thus restricting K48-linked polyubiquitination of Numb and stabilizing Numb proteins. This in turn inhibited the Notch signaling pathway by reducing Notch1 protein levels. Interestingly, we found that a monomeric drug, Triptolide, is capable of alleviating the inhibitory effect of MTX on Notch signaling pathway. This study promotes our understanding of MTX-mediated regulation of Notch signaling and could provide ideas to alleviate MTX-induced myelosuppression.

Treatment of rheumatoid arthritis

PURPOSE

Current and investigational treatments of rheumatoid arthritis (RA) are described.

SUMMARY

The current therapies used to treat RA include nonsteroidal antiinflammatory drugs (NSAIDs), used for the management of pain and inflammation; disease-modifying antirheumatic drugs (DMARDs), used as first-line therapy for all newly diagnosed cases of RA; and biological-response modifiers, targeted agents that selectively inhibit specific molecules of the immune system. Glucocorticoids and other antirheumatic drugs are also used to treat RA. DMARDs include methotrexate, hydroxychloroquine, sulfasalazine, and leflunomide. NSAIDs and glucocorticoids are effective in controlling the pain, inflammation, and stiffness related to RA. Unlike NSAIDs, they slow clinical and radiographic progression of RA. The biological-response modifiers include infliximab, etanercept, and adalimumab (inhibitors of tumor necrosis factor [TNF]-alpha); anakinra, a recombinant inhibitor of interleukin-1; abatacept, the first costimulation blocker; and rituximab, a chimeric anti-CD20 monoclonal antibody. Investigational therapies for RA include anti-interleukin-6-receptor monoclonal antibodies, new TNF-alpha inhibitors (including one for oral administration), and antibodies against proteins critical for B-cell function and survival. Data accumulated in the past decade favor early aggressive therapy for patients suspected of having RA, including early referral to a rheumatologist, new diagnostic techniques, and aggressive therapy with DMARDs, glucocorticoids, and biological agents. The benefits of this approach have been demonstrated in clinical trials.

CONCLUSION

Pharmacologic treatments of RA include NSAIDs, glucocorticoids, DMARDs, and biological agents. With an improved understanding of the pathophysiology of RA and the evidence from various clinical trials with the agents, early aggressive therapy with a combination of drugs or biological agents may be warranted for the effective treatment of RA.

Low-dose methotrexate: a mainstay in the treatment of rheumatoid arthritis

Methotrexate administered weekly in low doses is a mainstay in the therapy of rheumatoid arthritis. Although originally developed as a folate antagonist for the treatment of cancer, its mechanism of action in the therapy of rheumatoid arthritis remains less clear. Several mechanisms have been proposed including inhibition of T cell proliferation via its effects on purine and pyrimidine metabolism, inhibition of transmethylation reactions required for the prevention of T cell cytotoxicity, interference with glutathione metabolism leading to alterations in recruitment of monocytes and other cells to the inflamed joint, and promotion of the release of the endogenous anti-inflammatory mediator adenosine. These mechanisms of action and the role of methotrexate in the suppression of rheumatoid arthritis are reviewed.

Total and free methotrexate pharmacokinetics in rheumatoid arthritis patients

The pharmacokinetics of total and free methotrexate (MTX) were investigated in 50 patients with rheumatoid arthritis. Each patient received 10 mg MTX intramuscularly. The free and total plasma concentrations of MTX were measured over a 36-h period after drug administration by using the Abbott TDx fluorescence polarization immunoassay. Plasma concentrations of MTX were described by a biexponential function. The mean terminal elimination half-lives of total and free MTX were 9.4 and 8.4 h, respectively, and the corresponding mean residence times, 8.5 and 9.2 h. No difference in these parameters was found by comparing total and free MTX. Total plasma clearance of the free fraction averaged 215 ml/min. The statistical comparison of the variations with time of the ratio of free to total MTX during the 36 h after the dose showed that the free fraction was significantly increased for 8 h after drug administration (p < 0.001). To describe these variations, the changes of the free MTX concentrations (unbound) were related to the changes of the total MTX concentrations by using the Hill equation. Mean plasma protein binding ranged from 20 to 57% for these patients.

Serum immunoreactive erythropoietin in children with acute leukaemia at various stages of disease--and the effects of treatment

Most children with leukaemia are anaemic at diagnosis and at various times during treatment. Serum erythropoietin (EPO) was estimated in 27 children with acute leukaemia (n = 26) or lymphoma (n = 1) at diagnosis (n = 16), in relation to treatment with high-dose methotrexate (MTX, n = 11) or cytosine arabinoside (Ara-C, n = 8), and during oral maintenance therapy (n = 10). At diagnosis, in children with anaemia serum EPO was increased, and was inversely related to haemoglobin (Hb). After treatment with high-dose MTX, in some children serum EPO increased where Hb was unchanged or increased. After treatment with high-dose Ara-C, Hb declined, and serum EPO increased markedly in everyone. During oral maintenance therapy without significant anaemia, serum EPO was slightly increased in some children. In conclusion, children with leukaemia respond to anaemia with increased serum EPO concentration, but in relation to treatment with high-dose MTX and Ara-C, additional mechanisms may influence the EPO concentration.