Methotrexate regulates ICAM-1 expression in recipients of rat cardiac allografts

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.

The changes in expression of ICAM-3, Ki-67, PCNA, and CD31 in psoriatic lesions before and after methotrexate treatment

Although the effectiveness of methotrexate (MTX) in the treatment of psoriasis is very well established, the mechanism of action is poorly understood. It was suggested that the therapeutic effect of MTX in psoriasis might be mediated by inhibition of adhesion molecule expression. The aim of our study was to investigate the different effects of MTX treatment on cell proliferation, inflammatory infiltrate, adhesion molecules, and angiogenesis in psoriasis, and to clarify the mechanism by which MTX exerts its therapeutic effects. Clinical response, the morpho-phenotypic changes, epidermal thickness, and mitosis count were analyzed and the expression of CD31 and ICAM-3, proliferative markers such as Ki-67, PCNA, were evaluated by immunohistochemical techniques in lesional psoriatic epidermis, before and after the treatment with MTX in ten patients. In posttreatment biopsies a decrease in the degree of epidermal hyperplasia and a significant reduction in the severity of the inflammatory infiltrate (P<0.05) were observed. In addition, CD31 and ICAM-3 expression was significantly decreased on dermal cellular infiltrate, (respectively; P<0.05, P<0.01). Ki67 and PCNA expression were suppressed concurrently in about 90% of cases (P<0.01). We suggest that MTX may have an inhibitory effect on an initial integral component of the pathways that lead to psoriasis. Immunopharmacologic intervention in adhesion event has the potential to improve psoriasis. Inhibition of revascularization may be another mechanism of action of MTX.

Methotrexate Prevents Renal Injury in Experimental Diabetic RatsviaAnti-Inflammatory Actions

Recent studies suggested the involvement of inflammatory processes in the pathogenesis of diabetic nephropathy. Methotrexate (MTX), a folic acid antagonist, is widely used for the treatment of inflammatory diseases. Recently, it has been shown that treatment with low-dose MTX reduces the cardiovascular mortality in patients with rheumatoid arthritis, suggesting that MTX has anti-atherosclerotic effects via its anti-inflammatory actions. This study was designed to determine the anti-inflammatory effects of this agent on diabetic nephropathy. Diabetes was induced in Sprague-Dawley rats with streptozotocin, and MTX (0.5 or 1.0 mg/kg) was administered once a week for 8 wk. Treatment with MTX reduced urinary albumin excretion, mesangial matrix expansion, macrophage infiltration, expression of TGF-beta and type IV collagen, and intercellular adhesion molecule-1 in glomeruli. MTX also reduced the high glucose-induced NF-kappaB activation in vitro and in vivo. The results indicate that intermittent administration of MTX prevented renal injuries without changes in blood glucose level and BP in experimental diabetic rats. The protective effects of MTX are suggested to be mediated by its anti-inflammatory actions through inhibition of NF-kappaB activation and consequent reduction of intercellular adhesion molecule-1 expression and macrophage infiltration. The results suggest that anti-inflammatory agents might be beneficial for the treatment of diabetic nephropathy.

The anti-inflammatory action of methotrexate is not mediated by lymphocyte apoptosis, but by the suppression of activation and adhesion molecules

Low-dose methotrexate (MTX) is an established and highly effective treatment for severe psoriasis and rheumatoid arthritis; however, its mechanism of action remains unclear. We investigated the effects of low-dose MTX on antigen-stimulated peripheral blood mononuclear cells and explored through which cellular pathways these effects are mediated. We show that MTX caused a dose-dependent suppression of T cell activation and adhesion molecule expression, and this was not due to lymphocyte apoptosis. The suppression of intercellular adhesion molecule (ICAM)-1 was adenosine and folate-dependent, while MTX suppression of the skin-homing cutaneous lymphocyte-associated antigen (CLA) was adenosine-independent. The effect of MTX on CLA, but not ICAM-1, required the constant presence of MTX in cultures. Thus, the suppression of T cell activation and T cell adhesion molecule expression, rather than apoptosis, mediated in part by adenosine or polyglutamated MTX or both, are important mechanisms in the anti-inflammatory action of MTX.

Combined donor leucocyte administration and immunosuppressive drug treatment for survival of rat heart allografts

BACKGROUND

Donor leucocytes (DL) play an important role in rat liver transplant tolerance and their postoperative administration can convert rejection to tolerance. They appear to induce early activation, altered patterns of infiltration and death of recipient alloreactive T cells. The ability of immunosuppressive drugs to combine with DL administration was examined in a rat heart transplant model.

METHODS

Immediately after PVG to DA heterotopic heart transplantation, 6 x 10(7) spleen DL were injected. Cyclosporine A (CsA), 1.5 mg/kg/day, or methotrexate (MTX), 0.1 or 0.2 mg/kg/day, were given from day (d) 0 to d4 (early) or from d3 to d7 (delayed). Castanospermine (CAST) was administered from d0 to d7 at 100 or 300 mg/kg/day. In a separate experiment, transplanted hearts and recipient spleens were collected from treatment groups for analysis of infiltrate and cytokine mRNA expression.

RESULTS

Delayed treatment with CsA or early treatment with MTX but not CAST combined with DL to result in prolonged graft survival. Recipients treated with DL and delayed CsA had a reduced level of intra-graft interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-4R mRNA expression and reduced infiltrate compared to DL alone. Early MTX plus DL led to almost complete inhibition of all markers of inflammation during treatment followed by a rapid increase after cessation. In combination with DL, CsA was more effective than MTX for induction of donor-specific tolerance at the dose and administration regimens tested.

CONCLUSIONS

Delayed CsA or early MTX combine with DL to prolong heart allograft survival. Early and extensive inhibition of rejection by MTX was less effective than delayed and partial inhibition of the response by CsA for induction of transplant tolerance.

Methotrexate inhibits proliferation and regulation of the expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 by cultured human umbilical vein endothelial cells

BACKGROUND

The mechanism by which a low dose of methotrexate (MTX) works to treat psoriasis is not clear. The overexpression of cell adhesion molecules on dermal vessels is important in the pathogenesis of psoriasis and is probably induced by upregulation of tumour necrosis factor (TNF)-alpha.

OBJECTIVES

To determine the effects of MTX at concentrations comparable with in vivo levels after the administration of low-dose MTX to human umbilical vein endothelial cells (HUVEC) on the growth and expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1).

METHODS

Cell proliferation assay, immunostaining, immunoblotting, cell enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction (RT-PCR) were performed to examine the effects of MTX on HUVEC.

RESULTS

MTX inhibited the proliferation of HUVEC at 10-7 mol L-1 and 10-6 mol L-1 without showing cytotoxic effects. It also inhibited TNF-alpha-induced ICAM-1 and VCAM-1 expression by HUVEC at 10-6 mol L-1. The inhibitory effect of MTX was more pronounced on ICAM-1 expression than on VCAM-1 expression. RT-PCR analysis revealed that TNF-alpha-induced ICAM-1 gene expression was strongly downregulated by MTX.

CONCLUSIONS

Low-dose MTX may act on psoriasis by suppressing the TNF-alpha-induced expression of ICAM-1 and VCAM-1 by vascular endothelial cells. Inhibition of neovascularization may be another mechanism of action of MTX.

The anti-inflammatory actions of methotrexate are critically dependent upon the production of reactive oxygen species

1 The mechanism of action by which methotrexate (MTX) exerts its anti-inflammatory and immunosuppressive effects remains unclear. The aim of this study is to investigate the hypothesis that MTX exerts these effects via the production of reactive oxygen species (ROS). 2 Addition of MTX (100 nM-10 micro M) to U937 monocytes induced a time and dose dependent increase in cytosolic peroxide [peroxide](cyt) from 6-16 h. MTX also caused corresponding monocyte growth arrest, which was inhibited (P<0.05) by pre-treatment with N-acetylcysteine (NAC; 10 mM) or glutathione (GSH; 10 mM). In contrast, MTX induction of [peroxide](cyt) in Jurkat T cells was more rapid (4 h; P<0.05), but was associated with significant apoptosis at 16 h at all doses tested (P<0.05) and was significantly inhibited by NAC or GSH (P<0.05). 3 MTX treatment of monocytes (10 nM-10 micro M) for 16 h significantly reduced total GSH levels (P<0.05) independently of dose (P>0.05). However, in T-cells, GSH levels were significantly elevated following 30 nM MTX treatment (P<0.05) but reduced by doses exceeding 1 micro M compared to controls (P<0.05). 4 MTX treatment significantly reduced monocyte adhesion to 5 h and 24 h LPS (1 micro g ml(-1)) activated human umbilical vein endothelial cells (HUVEC; P<0.05) but not to resting HUVEC. Pre-treatment with GSH prevented MTX-induced reduction in adhesion. 5 In conclusion, ROS generation by MTX is important for cytostasis in monocytes and cytotoxicity T-cells. Furthermore, MTX caused a reduction in monocyte adhesion to endothelial cells, where the mechanism of MTX action requires the production of ROS. Therefore its clinical efficacy can be attributed to multiple targets.