Mycophenolate mofetil inhibits rat and human mesangial cell proliferation by guanosine depletion

Background. Mycophenolate mofetil (MMF) is used for immunosuppression after renal transplantation because it reduces lymphocyte proliferation by inhib iting inosine monophosphate dehydrogenase (IMPDH) in lymphocytes and GTP bi osynthesis. In the present study we asked if therapeutic concentrations of MMF might interfere with mesangial cell(MC) proliferation which is involved in inflammatory proliferative glomerular diseases. Methods. Rat and human MCs were growth-arrested by withdrawal of fetal calf serum (FCS) and stimulated by addition of FCS, platelet-derived growth fac tor (PDGF) or lysophosphatidic acid (LPA). Different concentrations of MMF (0.019-10 mu M) were added concomitantly in the presence or absence of guan osine. MC proliferation was determined by [H-3]thymidine incorporation. Cel l viability was assessed by trypan blue exclusion. Apoptotic nuclei were st ained using the Hoechst dye H33258. Cytosolic free Ca2+ concentrations were determined with the fluorescent calcium chelator fura-2-AM. Results. MMF inhibited mitogen-induced rat MC proliferation with an IC50 of 0.45 +/- 0.13 mu M. Human MCs proved to be even more sensitive (IC50 0.19 +/- 0.06 mu M). Inhibition of MC proliferation was reversible and not accom panied by cellular necrosis or apoptosis. Addition of guanosine prevented t he antiproliferative effect of MMF, indicating that inhibition of IMPDH is responsible for decreased MC proliferation. Early signalling events of GTP- binding-protein-coupled receptors, such as changes in intracellular Ca2+ le vels were not affected by MMF. Conclusions. The results show that MMF has a concentration-dependent antipr oliferative effect on cultured MCs in the therapeutic range, which might be a rationale for the use of this drug in the treatment of mesangial prolife rative glomerulonephritis.