Mycophenolate mofetil combined with a cyclooxygenase-2 inhibitor ameliorates murine lupus nephritis

Background. Approaches to the treatment of lupus nephritis include immunosuppressants associated with anti-inflammatory drugs, mainly steroids, which, however, cause major side effects. Mycophenolate mofetil (MMF) has been described as being less toxic than conventional immunosuppressants, and it was effective in preventing progressive nephritis in lupus mice. Our study evaluated the therapeutic effect of MMF in NZB/W F1 hybrid mice with established disease. We also examined the combination of MMF with a selective cyclooxygenase-2 (COX-2) inhibitor, DFU, based on previous findings of excessive renal production of COX-2-derived thromboxane A₂ (TXA₂) in lupus nephritis. Methods. Four groups of NZB/W mice (N = 30 each group), starting at five months of age, were given daily by gavage the following: vehicle, MMF 60 mg/kg, DFU 3 mg/kg, or MMF + DFU. Fifteen mice for each group were used for the survival studies, and the remaining mice were sacrificed at nine months. Results. MMF or DFU alone partially delayed the onset of proteinuria compared with vehicle. Combined therapy was significantly (P <0.05) more effective than single drugs. Animal survival was partially ameliorated by MMF and significantly improved by the drug combination in comparison with the vehicle (P = 0.005) and DFU alone (P <0.03). At nine months, serum blood urea nitrogen (BUN) levels were lower in all of the treated groups than in the vehicle group. Renal damage was also limited, but to a greater extent in mice given the combined therapy. In untreated mice, renal COX-2 mRNA expression was up-regulated, and generation of TXB₂, the stable breakdown product of TXA₂, increased. DFU prevented the abnormal renal TXB₂ production, confirming the COX-2 origin of this eicosanoid, whereas renal 6-keto-PGF_1α and prostaglandin E₂ (PGE₂) were not affected substantially. Conclusions. These results offer a strong case for exploring the possibility that in humans MMF combined with COX-2 inhibitors has a role in the treatment options for lupus nephritis. This combined drug therapy may be at least as effective as steroids but without the obvious nephrotoxicity of the latter.