Plasma and rectal adenosine in inflammatory bowel disease: effect of methotrexate

Current, experimental, and future treatments in inflammatory bowel disease: a clinical review

Inflammatory bowel diseases (IBDs) may result from dysregulated mucosal immune responses directed toward the resident intestinal microbiota. This review describes the hallmark immunobiology of Crohn's disease and ulcerative colitis as well as therapeutic targets and mechanisms of action for current, experimental, and future treatments in IBD. Conventional therapies include 5-aminosalicylic acid, glucocorticosteroids, thiopurines, and methotrexate. Since 1997, monoclonal antibodies have gained widespread use. These consist of antibodies directed against pro-inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-12, and IL-23, or anti-homing antibodies directed against α4β7 integrin. Emerging oral therapies include modulators of intracellular signal transduction such as Janus kinase inhibitors. Vitamin D may help to regulate innate and adaptive immune responses. Modulation of the intestinal microbiota, using live microorganisms (probiotics), substrates for the colonic microbiota (prebiotics), or fecal microbiota transplantation (FMT), is in development. Dietary supplements are in widespread use, but providing evidence for their benefit is challenging. Stem cell treatment and nervous stimulation are promising future treatments.

Time to clinical response and remission for therapeutics in inflammatory bowel diseases: What should the clinician expect, what should patients be told?

An awareness of the expected time for therapies to induce symptomatic improvement and remission is necessary for determining the timing of follow-up, disease (re)assessment, and the duration to persist with therapies, yet this is seldom reported as an outcome in clinical trials. In this review, we explore the time to clinical response and remission of current therapies for inflammatory bowel disease (IBD) as well as medication, patient and disease related factors that may influence the time to clinical response. It appears that the time to therapeutic response varies depending on the indication for therapy (Crohn's disease or ulcerative colitis). Agents with the most rapid time to clinical response included corticosteroids, calcineurin inhibitors, exclusive enteral nutrition, aminosalicylates and anti-tumor necrosis factor therapy which will work in most patients within the first 2 mo. Vedolizumab, methotrexate and thiopurines had a longer time to clinical response and can take several months to achieve maximal efficacy. Factors affecting the time to clinical response of therapies included use of concomitant therapy, disease duration, smoking status, disease phenotype and advanced age. There appears to be marked variation in time to clinical response for therapies used in IBD which is further influenced by disease and patient related factors. Understanding the expected time to therapeutic response is integral to inform further decision making, maintain a patient-centered approach and ensure treatment is given an appropriate timeframe to achieve maximal benefit prior to cessation.

Mechanism of action of methotrexate in rheumatoid arthritis, and the search for biomarkers

The treatment and outcomes of patients with rheumatoid arthritis (RA) have been transformed over the past two decades. Low disease activity and remission are now frequently achieved, and this success is largely the result of the evolution of treatment paradigms and the introduction of new therapeutic agents. Despite the rapid pace of change, the most commonly used drug in RA remains methotrexate, which is considered the anchor drug for this condition. In this Review, we describe the known pharmacokinetic properties and putative mechanisms of action of methotrexate. Consideration of the pharmacodynamic perspective could inform the development of biomarkers of responsiveness to methotrexate, enabling therapy to be targeted to specific groups of patients. Such biomarkers could revolutionize the management of RA.

Methotrexate for induction of remission in ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory bowel disease. Corticosteroids and 5-aminosalicylates are the most commonly used therapies. However, many patients require immunosuppressive therapy for steroid-refractory and steroid-dependent disease. Methotrexate is a medication that is effective for treating a variety of inflammatory diseases, including Crohn's disease. This review was performed to determine the effectiveness of methotrexate treatment in UC patients. This review is an update of a previously published Cochrane review.

OBJECTIVES

To assess the efficacy and safety of methotrexate for induction of remission in patients with UC.

SEARCH METHODS

MEDLINE, EMBASE, CENTRAL and the Cochrane IBD/FBD group specialized trials register were searched from from inception to June 26, 2014. Study references and review papers were also searched for additional trials. Abstracts from major gastroenterological meetings were searched to identify research published in abstract form only.

SELECTION CRITERIA

Randomized controlled trials comparing methotrexate with placebo or an active comparator in patients with active ulcerative colitis were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed studies for eligibility, extracted data and assessed study quality using the Cochrane risk of bias tool. The primary outcome measure was the proportion of patients who achieved clinical remission and withdrawal from steroids as defined by the studies and expressed as a percentage of the total number of patients randomized (intention-to-treat analysis). We calculated the risk ratio (RR) and corresponding 95% confidence intervals (95% CI) for dichotomous outcomes. The overall quality of the evidence supporting the primary outcome was assessed using the GRADE criteria.

MAIN RESULTS

Two studies (n = 101 patients) were included in the review. One study (n = 67) compared oral methotrexate 12.5 mg/week) to placebo. The other study (n = 34) compared oral methotrexate (15 mg/week) to 6-mercaptopurine (1.5 mg/kg/day) and 5-aminosalicylic acid (3 g/day). The placebo-controlled study was judged to be at low risk of bias. The other study was judged to be at high risk of bias due to an open-label design. There was no statistically significant difference in clinical remission rates between methotrexate and placebo patients. Forty-seven per cent (14/30) of methotrexate patients achieved clinical remission and complete withdrawal from steroids during the study period compared to 49% (18/37) of placebo patients (RR 0.96, 95% CI 0.58 to 1.59. A GRADE analysis indicated that the overall quality of the evidence supporting this outcome was low due to very sparse data (32 events). There were no statistically significant differences in the proportion of patients who achieved clinical remission and withdrawal from steroids in the study comparing oral methotrexate to 6-mercaptopurine and 5-aminosalicylic acid. At 30 weeks, 58% (7/12) of methotrexate patients achieved clinical remission and withdrawal from steroids compared to 79% (11/14) of 6-mercaptopurine patients (RR 0.74, 95% CI 0.43 to 1.29) and 25% of 5-aminosalicylic acid patients (RR 2.33, 95% CI 0.64 to 8.49). GRADE analyses indicated that the overall quality of the evidence was very low due to very sparse data (18 and 9 events respectively) and and high risk of bias. In the placebo-controlled trial two patients (7%) were withdrawn from the methotrexate group due to adverse events (leucopenia, migraine) compared to one patient (3%) who had a rash in the placebo group (RR 2.47, 95% CI 0.23 to 25.91). Adverse events experienced by methotrexate patients in the active comparator study included nausea and dyspepsia, mild alopecia, mild increase in aspartate aminotransferase levels, peritoneal abscess, hypoalbuminemia, severe rash and atypical pneumonia.

AUTHORS' CONCLUSIONS

Although methotrexate was well-tolerated, the studies showed no benefit for methotrexate over placebo or active comparators. The results for efficacy outcomes between methotrexate and placebo, methotrexate and 6-mercaptopurine and methotrexate and 5-aminosalicylic acid were uncertain. Whether a higher dose or parenteral administration would be effective for induction therapy is unknown. At present there is no evidence supporting the use of methotrexate for induction of remission in active ulcerative colitis. A trial in which larger numbers of patients receive a higher dose of oral methotrexate should be considered. Currently there are two large ongoing placebo-controlled trials (METEOR and MERIT-UC) assessing the efficacy and safety of intramuscular or subcutaneous methotrexate in patients with active UC which may help resolve the evidence supporting the use of methotrexate as therapy for active of ulcerative colitis.

Interkingdom adenosine signal reduces Pseudomonas aeruginosa pathogenicity

Pseudomonas aeruginosa is becoming recognized as an important pathogen in the gastrointestinal (GI) tract. Here we demonstrate that adenosine, derived from hydrolysis of ATP from the eucaryotic host, is a potent interkingdom signal in the GI tract for this pathogen. The addition of adenosine nearly abolished P. aeruginosa biofilm formation and abolished swarming by preventing production of rhamnolipids. Since the adenosine metabolite inosine did not affect biofilm formation and since a mutant unable to metabolize adenosine behaved like the wild-type strain, adenosine metabolism is not required to reduce pathogenicity. Adenosine also reduces production of the virulence factors pyocyanin, elastase, extracellular polysaccharide, siderophores and the Pseudomonas quinolone signal which led to reduced virulence with Caenorhabditis elegans. To provide insights into how adenosine reduces the virulence of P. aeruginosa, a whole-transcriptome analysis was conducted which revealed that adenosine addition represses genes similar to an iron-replete condition; however, adenosine did not directly bind Fur. Therefore, adenosine decreases P. aeruginosa pathogenicity as an interkingdom signal by causing genes related to iron acquisition to be repressed.

Revisiting the immunomodulators tacrolimus, methotrexate, and mycophenolate mofetil: their mechanisms of action and role in the treatment of IBD

Inflammatory bowel diseases (IBDs) are thought to result from unopposed immune responses to normal gut flora in a genetically susceptible host. A variety of immunomodulating therapies are applied for the treatment of patients with IBDs. The first-line treatment for IBDs consists of 5-aminosalicylate and/or budesonide. However, these first-line therapies are often not suitable for continuous treatment or do not suffice for the treatment of severe IBD. Recently, efforts have been made to generate novel selective drugs that are more effective and have fewer side effects. Despite promising results, most of these novel drugs are still in a developmental stage and unavailable for clinical application. Yet, another class of established immunomodulators exists that is successful in the treatment of inflammatory bowel diseases. While waiting for emerging novel therapies, the use of these more established drugs should be considered. Furthermore, one of the advantages of using established immunomodulators is the well-documented knowledge on the long-term side effects and on the mechanisms of action. In this review, the authors discuss 3 well-known immunomodulators that are being applied with increased frequency for the treatment of IBD: tacrolimus, methotrexate, and mycophenolate mofetil. These agents have been used for many years as treatment modalities for immunosuppression after organ transplantation, for the treatment of cancer, and for immunomodulation in several other immune-mediated diseases. First, this review discusses the potential targets for immunomodulating therapies in IBDs. Second, the immunomodulating mechanisms and effects of the 3 immunomodulators are discussed in relationship to these treatment targets.

Methotrexate modulates the kinetics of adenosine in humans in vivo

BACKGROUND

Animal studies suggest that the anti-inflammatory effect of methotrexate (MTX) is mediated by increased adenosine concentrations.

OBJECTIVE

To assess the effect of MTX on the vasodilator effects of adenosine and the nucleoside uptake inhibitor, dipyridamole, in humans in vivo as a marker for changes in adenosine kinetics.

METHODS

Ten patients with active arthritis were treated with MTX (15 mg/week). Measurements were performed before and after 12 weeks of treatment. At these time points, the activity of adenosine deaminase was measured in isolated lymphocytes, and forearm blood flow (FBF) was determined by venous occlusion plethysmography during administration of adenosine and dipyridamole into the brachial artery.

RESULTS

The Vmax of adenosine deaminase in lymphocytes was reduced by MTX treatment (p<0.05). MTX significantly enhanced vasodilator response to adenosine (0.5 and 1.5 microg/min/dl of forearm tissue; mean (SE) FBF ratio increased from 1.2 (0.2) to 1.4 (0.2) and 2.2 (0.2) ml/dl/min, respectively, before and from 1.3 (0.1) to 1.8 (0.2) and 3.2 (0.5) ml/dl/min during MTX treatment; p<0.05). Also, dipyridamole-induced vasodilatation (30 and 100 microg/min/dl) was enhanced by MTX (FBF ratio increased from 1.2 (0.2) to 1.5 (0.3) and 1.8 (0.2), respectively, before and from 1.3 (0.1) to 1.8 (0.2) and 2.4 (0.4) during MTX treatment; p<0.05).

CONCLUSIONS

MTX treatment inhibits deamination of adenosine and potentiates adenosine-induced vasodilatation. Also dipyridamole-induced vasodilatation is enhanced by MTX treatment, suggesting an increased extracellular formation of adenosine. These effects on the adenosine kinetics in humans may contribute to the therapeutic efficacy of MTX.

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.

Review article: monitoring of immunomodulators in inflammatory bowel disease

The armamentarium of medications for the treatment of inflammatory bowel disease is growing and becoming more complicated to use. Immunomodulators are a class of medications that have found a niche for the treatment of Crohn's disease and ulcerative colitis. Because of the mounting supporting evidence for efficacy, the most commonly-used immunomodulators are azathioprine, mercaptopurine, methotrexate and ciclosporin. These medications are being used more often due to their steroid-sparing and potentially surgery-sparing effects. Immunomodulators are also known for a significant side-effect profile and require careful monitoring. This review provides the latest information for clinicians on efficacy, side-effects, dosing and monitoring of these medications for treatment of inflammatory bowel disease.

Experience with the use of low-dose methotrexate for inflammatory bowel disease

BACKGROUND

Thiopurine drugs (azathioprine and 6-mercaptopurine) are well established in the treatment of patients with inflammatory bowel disease. However, some patients are intolerant or resistant to thiopurine drugs and their management remains a challenge. Several studies have suggested methotrexate is effective for the induction and maintenance of remission in Crohn's disease.

OBJECTIVE

This study was conducted because the overall data on clinical efficacy of methotrexate in inflammatory bowel disease remain limited and there are no data regarding fistulating Crohn's disease or concomitant use of methotrexate with thiopurine drugs in inflammatory bowel disease.

METHODS

This study was a retrospective review of medical notes. Clinical response was defined as sustained withdrawal of oral steroids or fistula improvement. New episodes of steroid therapy, infliximab or surgery during the first 6 months were considered as failure to achieve clinical response.

RESULTS

Seventy-two patients were studied (66 Crohn's disease and six ulcerative colitis). The mean dose of methotrexate used was 18.2 mg/week. Clinical response was achieved in 22 of 54 patients (40.7%) who completed 6 months of methotrexate treatment. For patients with Crohn's disease, fistula improvement was achieved in eight of 18 (44.4%) patients compared with 11 of 30 (36.7%) receiving methotrexate for steroid withdrawal. Clinical response was achieved in six of 15 patients (40%) treated with methotrexate and azathioprine at the same time compared with 16 of 39 patients (41%) treated with methotrexate alone.

CONCLUSIONS

Methotrexate is reasonably effective in clinical practice as a steroid sparing agent in inflammatory bowel disease. The efficacy in fistulating Crohn's disease justifies its use as an immunomodulator in these patients. Combined azathioprine and methotrexate treatment appears to offer no advantage over methotrexate alone.

Clinical pharmacology of inflammatory bowel disease therapies

Knowledge about the clinical pharmacology of medical therapy of inflammatory bowel disease has incrementally advanced. Small studies with mesalamine have suggested that intestinal mucosal concentrations of mesalamine may predict clinical response to mesalamine therapy. Increased expression of glucocorticoid receptor beta and increased expression of the multidrug resistance drug pump P-glycoprotein 170 have been proposed as markers of drug resistance to glucocorticoids. A baseline determination of thiopurine methyltransferase phenotype or genotype may predict early leukopenia in patients treated with azathioprine or 6- mercaptopurine. Serial measurement of erythrocyte 6-thioguanine nucleotides may be useful in tailoring the dose of these medications. A loading dose of intravenous azathioprine does not accelerate the time to response in patients with steroid-treated Crohn's disease; however, standard azathioprine may work more quickly than previously reported. Methotrexate, 15 to 25 mg/wk, is effective for the treatment of Crohn's disease (active or in remission), and there is no significant difference in the erythrocyte concentrations of methotrexate polyglutamate in patients with inflammatory bowel disease receiving 15 mg, compared with 25 mg, subcutaneously on a weekly basis.

Biochemistry of cyclooxygenase (COX)-2 inhibitors and molecular pathology of COX-2 in neoplasia

Several types of human tumors overexpress cyclooxygenase (COX) -2 but not COX-1, and gene knockout transfection experiments demonstrate a central role of COX-2 in experimental tumorigenesis. COX-2 produces prostaglandins that inhibit apoptosis and stimulate angiogenesis and invasiveness. Selective COX-2 inhibitors reduce prostaglandin synthesis, restore apoptosis, and inhibit cancer cell proliferation. In animal studies they limit carcinogen-induced tumorigenesis. In contrast, aspirin-like nonselective NSAIDs such as sulindac and indomethacin inhibit not only the enzymatic action of the highly inducible, proinflammatory COX-2 but the constitutively expressed, cytoprotective COX-1 as well. Consequently, nonselective NSAIDs can cause platelet dysfunction, gastrointestinal ulceration, and kidney damage. For that reason, selective inhibition of COX-2 to treat neoplastic proliferation is preferable to nonselective inhibition. Selective COX-2 inhibitors, such as meloxicam, celecoxib (SC-58635), and rofecoxib (MK-0966), are NSAIDs that have been modified chemically to preferentially inhibit COX-2 but not COX-1. For instance, meloxicam inhibits the growth of cultured colon cancer cells (HCA-7 and Moser-S) that express COX-2 but has no effect on HCT-116 tumor cells that do not express COX-2. NS-398 induces apoptosis in COX-2 expressing LNCaP prostate cancer cells and, surprisingly, in colon cancer S/KS cells that does not express COX-2. This effect may due to induction of apoptosis through uncoupling of oxidative phosphorylation and down-regulation of Bcl-2, as has been demonstrated for some nonselective NSAIDs, for instance, flurbiprofen. COX-2 mRNA and COX-2 protein is constitutively expressed in the kidney, brain, spinal cord, and ductus deferens, and in the uterus during implantation. In addition, COX-2 is constitutively and dominantly expressed in the pancreatic islet cells. These findings might somewhat limit the use of presently available selective COX-2 inhibitors in cancer prevention but will probably not deter their successful application for the treatment of human cancers.