Brequinar sodium, mycophenolic acid, and cyclosporin A inhibit different stages of IL-4- or IL-13-induced human IgG4 and IgE production in vitro

Mycophenolate mofetil attenuates pulmonary arterial hypertension in rats

Pulmonary arterial hypertension (PAH) is characterized by abnormal proliferation of smooth muscle cells (SMCs), leading to occlusion of pulmonary arterioles, right ventricular (RV) hypertrophy, and death. We investigated whether mycophenolate mofetil (MMF), a potent immunosuppresssant, prevents the development of monocrotaline (MCT)-induced PAH in rats. MMF effectively decreased RV systolic pressure and RV hypertrophy, and reduced the medial thickness of pulmonary arteries. MMF significantly inhibited the number of proliferating cell nuclear antigen (PCNA)-positive cells, infiltration of macrophages, and expression of P-selectin and interleukin-6 on the endothelium of pulmonary arteries. The infiltration of T cells and mast cells was not affected by MMF. In vitro experiments revealed that mycophenolic acid (MPA), an active metabolite of MMF, dose-dependently inhibited proliferation of human pulmonary arterial SMCs. MMF attenuated the development of PAH through its anti-inflammatory and anti-proliferative properties. These findings provide new insight into the potential role of immunosuppressants in the treatment of PAH.

Mycophenolate mofetil prevents the development of experimental autoimmune myocarditis

Experimental autoimmune myocarditis (EAM) is characterized by the appearance of multinucleated giant cells. EAM leads to severe myocardial damage and is a useful model of human giant cell myocarditis. We investigated whether mycophenolate mofetil (MMF), which is a potent immunosuppressant, prevents the development of myocarditis in a rat EAM model, and focused on the role of osteopontin (OPN) in the pathogenesis of this disorder. Adult Lewis rats were immunized with porcine cardiac myosin to establish EAM. The early MMF treatment completely prevented the development of EAM, and the late MMF treatment was also effective even against established EAM. Echocardiogram demonstrated that left ventricular function was also improved by the treatment with MMF. Real-time RT-PCR analysis showed that both early and late MMF treatments significantly inhibited myocarditis-induced OPN mRNA expression in the heart. Immunohistochemistry revealed that OPN expression was prominent in the myocardium on day 14, whereas expression was observed in the infiltrated macrophages on day 21. Mycophenolic acid (MPA) did inhibit agonist-induced OPN expression in cultured cardiomyocytes. These results show the therapeutic potential of MMF for autoimmune myocarditis and provide new insights into the pathogenesis of this disease.

Switch from cyclosporine A to mycophenolate mofetil in nephrotic children

Nephrotoxicity is a well-known adverse effect of cyclosporine A (CyA) treatment in children with steroid-dependent (SD) and steroid-resistant (SR) nephrotic syndrome (NS). We analyzed nine children (age: 3.3-15.7 years, two girls) with SD or SR NS who experienced a significant decrease in their GFR under CyA treatment as measured by inulin clearance (C(IN)). Mycophenolate mofetil (MMF) was introduced progressively until doses of 1 g/1.73 m(2) twice daily were reached. CyA treatment was stopped after introduction of MMF and oral steroids were reduced if possible. After a median follow up of 261 days, no adverse effects of MMF such as diarrhea or hematological anomalies occurred in our patients. After switching from CyA to MMF, those children with SD NS remained in remission without proteinuria and those with SR NS did not show any significant changes in their residual proteinuria. The serum protein level did not change significantly in any of the children analyzed. GFR increased from a mean of 76.9+/-4.8 to 119.9+/-5.9 mL/1.73 m(2) per min (P<0.001). Oral steroid treatment could be reduced from a median [range] prednisone dose of 0.85 [0.26-2.94] mg/kg/d pre-MMF to 0.29 [0-1.1] mg/kg per day (P=0.026), and blood pressure decreased moderately after CyA withdrawal, but the difference did not reach statistical significance. We conclude that a switch from CyA to MMF seems to be safe for children with SDNS and SRNS in terms of side effects as well as disease control, at least in the short term. Interruption of CyA treatment lead to rapid amelioration of kidney function in these children, often associated with steroid sparing, which may lead to additional benefit for growth velocity, blood pressure and physical appearance.

Mycophenolate mofetil in lupus glomerulonephritis

The optimal treatment of severe lupus nephritis is unclear. Regimens consisting of steroid and cyclophosphamide (CYC) appear to be most effective. However, up to 15% of patients are refractory to CYC treatment, and 30% to 50% of patients still develop end-stage renal disease. Moreover, infection and gonadal toxicity are major concerns of CYC use in patients of the reproductive age. More effective, but less toxic, regimens are needed. Mycophenolate mofetil (MMF) is a new immunosuppressive agent that selectively inhibits activated lymphocytes and renal mesangial cells. Experience with MMF in solid-organ transplantation has shown the safety of this drug and its superiority over azathioprine (AZA) in the prevention of acute graft rejection. Data from experimental models of immune-mediated glomerulonephritis, particularly lupus nephritis, have shown that MMF ameliorates autoimmune phenomena, retards renal damage, and improves outcome. Although the use of MMF in lupus nephritis is still in its preliminary stage, uncontrolled experience has confirmed its efficacy in patients with serious disease recalcitrant to conventional cytotoxic agents. Controlled studies, albeit small and lacking statistical power, have shown that MMF is as effective as CYC in the induction of renal remission in the short term. With the current dosage used in systemic lupus erythematosus, MMF appears to be well tolerated, with no serious toxicities reported. Significantly less ovarian toxicity compared with CYC is particularly attractive for the consideration of MMF in lupus nephritis. However, the lack of long-term efficacy data and comparative studies with standard CYC regimens is the major deterrent for the first-line use of MMF in high-risk patients at this juncture.

Mycophenolate mofetil treatment for primary glomerular diseases

BACKGROUND

Treatment of primary glomerular diseases may be unsuccessful or have potential toxicities. Therefore, we evaluated the use of mycophenolate mofetil (MMF) for empirical treatment of primary glomerulopathies.

METHODS

Forty-six patients with biopsy-proven primary glomerulopathies received MMF for > or =3 months as adjunctive or primary treatment. Median (range) 24-hour urine protein to creatinine ratio (Up/c) and serum creatinine at the start and end of MMF therapy were compared using the Wilcoxon signed-ranks test.

RESULTS

Overall, the median Up/c decreased from 4.7 (range <0.1, 20.3) to 1.1 (<0.1, 14.3; P < 0.001) at the end of MMF treatment with no significant change in median serum creatinine 1.3 (0.6 to 6.1) to 1.2 (0.5 to 6.5) mg/dL. Median serum albumin increased from 3.4 (1.4, 4.6) to 4.1 (1.7, 48) g/dL (P < 0.001) and the median serum cholesterol decreased from 270 (148, 795) to 220 (140, 309) mg/dL (P < 0.001) post-treatment. For those with minimal change disease, a complete steroid withdrawal was accomplished in 5/6 steroid dependent patients. Focal segmental glomerulosclerosis (FSGS) patients had a median Up/c that decreased from 2.7 (0.1, 20.3) to 0.8 (<0.1, 8.2; P = 0.001) in 18 patients. In membranous nephropathy (MN) patients, the median Up/c decreased from 7.3 (0.1, 18.5) to 1.5 (<0.1, 14.3) (P = 0.001) in 17 patients. No significant change in median serum creatinine was detected in FSGS or MN patient groups during treatment.

CONCLUSIONS

Empirical MMF therapy in the majority of patients with primary glomerulopathies was well tolerated and achieved the goals of steroid withdrawal, improvement of nephrotic syndrome, and stabilization of renal function.

Mycophenolate mofetil and its mechanisms of action

Mycophenolate mofetil (MMF, CellCept(R)) is a prodrug of mycophenolic acid (MPA), an inhibitor of inosine monophosphate dehydrogenase (IMPDH). This is the rate-limiting enzyme in de novo synthesis of guanosine nucleotides. T- and B-lymphocytes are more dependent on this pathway than other cell types are. Moreover, MPA is a fivefold more potent inhibitor of the type II isoform of IMPDH, which is expressed in activated lymphocytes, than of the type I isoform of IMPDH, which is expressed in most cell types. MPA has therefore a more potent cytostatic effect on lymphocytes than on other cell types. This is the principal mechanism by which MPA exerts immunosuppressive effects. Three other mechanisms may also contribute to the efficacy of MPA in preventing allograft rejection and other applications. First, MPA can induce apoptosis of activated T-lymphocytes, which may eliminate clones of cells responding to antigenic stimulation. Second, by depleting guanosine nucleotides, MPA suppresses glycosylation and the expression of some adhesion molecules, thereby decreasing the recruitment of lymphocytes and monocytes into sites of inflammation and graft rejection. Third, by depleting guanosine nucleotides MPA also depletes tetrahydrobiopterin, a co-factor for the inducible form of nitric oxide synthase (iNOS). MPA therefore suppresses the production by iNOS of NO, and consequent tissue damage mediated by peroxynitrite. CellCept(R) suppresses T-lymphocytic responses to allogeneic cells and other antigens. The drug also suppresses primary, but not secondary, antibody responses. The efficacy of regimes including CellCept(R) in preventing allograft rejection, and in the treatment of rejection, is now firmly established. CellCept(R) is also efficacious in several experimental animal models of chronic rejection, and it is hoped that the drug will have the same effect in humans.

Administration of mycophenolate mofetil in a murine model of acute graft-versus-host disease after bone marrow transplantation

BACKGROUND

Graft-versus-host disease (GVHD) remains the most significant obstacle to the use of allogeneic bone marrow transplantation as a treatment for leukemia and other hematological malignancies. Because current GVHD treatment regimens such as cyclosporine and methotrexate are only partially effective, there is a need for new immunosuppressive drugs for the treatment of this condition.

METHODS

A recently developed immunosuppressive drug, mycophenolate mofetil (MM), was tested in a fully mismatched (C57BL/6 donors to BALB/c recipients) murine model of acute GVHD after bone marrow transplantation.

RESULTS

A dose regimen of 30 mg/kg/day given by oral gavage and begun at 1 day before transplant had no positive effect on survival and was found to retard the rate of marrow engraftment as measured by absolute blood neutrophil counts. In all subsequent experiments, treatment was begun on day 5 after transplant. Three different doses (30, 60, and 90 mg/kg/day) were tested, but no significant improvement in mean survival time (MST) was observed for the first two doses (P=0.412 and 0.100, respectively). The highest dose (90 mg/kg/day) reduced MST (P=0.059), and no further dose increases were attempted. MM in combination with cyclosporine also failed to improve MST compared with animals treated with cyclosporine alone or controls.

CONCLUSIONS

These results suggest that MM given orally is not effective in this murine model of GVHD and may not have a role in the treatment and prevention of acute GVHD arising from bone marrow transplantation in the clinical setting.

Potentiation of in vitro synthesis of human IgE by cyclosporin A (CsA)

In this study, we investigated the modulatory effects of CsA on in vitro synthesis of IgE, IgG1 and IgG4 by human peripheral blood mononuclear cells (PBMC). In contrast to its known immunosuppressive effect, we have demonstrated that a low dose of CsA (10(-7) M, 120 ng/ml) potentiated IgE production by up to 40-fold (i.e. from 33 +/- 4.5 to 1346 +/- 290 ng/ml). This potentiation was specific for IgE since no such effect was demonstrable with IgG1 and IgG4. Potentiation of IgE synthesis by CsA in the PBMC cultures was partly due to CsA acting on T cells, as demonstrated by the addition of CsA-treated T cells to T cell-depleted cultures. However, potentiation was also demonstrable in a T cell-depleted, anti-CD40-stimulated culture (four-fold increase from 400 +/- 48 to 1606 +/- 127 ng/ml). Our data therefore suggest that there are at least two mechanisms for CsA-induced potentiation of IgE synthesis, one T cell-dependent and the other T cell-independent. The clinical implications of these findings are discussed with regard to the use of CsA in the treatment of Th2-mediated diseases.