Inosine 5'-monophosphate dehydrogenase (IMPDH) is a key enzyme of de novo GMP biosynthesis. The expression and activity of IMPDH can be affected by diseases and physiological process. It is the drug target for anticancer, antiviral, antimicrobial and immunosuppressive therapeutics. Not only catalytic action but the other biological functions of IMPDH also play an important role in diseases. The basic functions, mechanism of catalysis, classification of inhibitors, biological functions and the latest advances to IMPDH will be illustrated in this review. It is expected to be helpful to the discovery of new inhibitors and biological functions of IMPDH.
Animals ; Binding Sites ; Catalysis ; Drug Design ; Drug Discovery ; Enzyme Inhibitors ; classification ; pharmacology ; Humans ; IMP Dehydrogenase ; antagonists & inhibitors ; genetics ; metabolism ; Inosine Monophosphate ; metabolism ; Molecular Structure ; NAD ; metabolism ; Polymorphism, Genetic

A series of phthalazine ketone compounds were synthesized and the structures were confirmed by H NMR and HR-MS spectrum. All target compounds were obtained through 7 steps, including selective reduction, nitration, bromination, ring enlargement, reduction, Knoevenagel and acylated reaction. The compounds were evaluated for their immunosuppressive effects of T-cell proliferation and inhibitory activity of IMPDH type II in vitro, as well as their structure-activity relationship were assessed. Several compounds exhibited strong immunosuppressive properties, especially compounds 7f and 7h, with IC50 values of 0.093 micromol x L(-1) and 0.14 micromol x L(-1) respectively, which were superior to mycophenolic acid. The information obtained from the studies may be useful for further research on the immunosuppressive agents.
Animals ; Cell Proliferation ; drug effects ; Female ; IMP Dehydrogenase ; metabolism ; Immunosuppressive Agents ; chemical synthesis ; chemistry ; pharmacology ; Inhibitory Concentration 50 ; Mice ; Mice, Inbred BALB C ; Phthalazines ; chemical synthesis ; chemistry ; pharmacology ; Spleen ; cytology ; Structure-Activity Relationship ; T-Lymphocytes ; drug effects

PURPOSE: Mizoribine (MZR), an inhibitor of Inosine monophosphate (IMP) dehydrogenase which depletes cellular GTP, is clinically used as an immunosuppressive drug. This study was designed to evaluate the mechanism by which MZR exerts the cytotoxic effect on Jurkat T cells. METHODS: Jurkat T cell is a human T lymphocytic cell line. It was obtained from the Korean Type Culture Collection. Cell viability was measured by the MTT assay and flow cytometry. Caspase activity assay, Western blotting, 2-D PAGE, and mitochondrial membrane potential were detected using biochemical analysis. Morphologic finding was observed by Hoechst staining. RESULTS: The data demonstrated that the treatment of MZR decreased cell viability in a dose- and time-dependent manner. MZR-induced cell death was confirmed as apoptosis, which was characterized by chromatin condensation and H2AX phosphorylation. MZR increased the catalytic activity of caspase-3 protease, -8 protease and -9 proteases. The activation of caspase-3 protease was further confirmed by the degradation of polymerase (PARP), a substrate of caspase-3 protease by MZR in Jurkat T cells. Furthermore, MZR induced the changes of the mitochondrial transmembrane potential (MTP) and the cytosolic release of cytochrome c from the mitochondria. In addition, MZR induced the decrease of Bcl-X(L) expression whereas the increase of Bcl-X(S), Bak and Bim expression. Guanosine markedly inhibited cell viability and apoptosis through consistent suppression of the activity of caspase-8 protease, an upstream caspase among the caspase family, H2AX phosphorylation and PARP cleavage in MZR-treated cells. Also, I have screened the expression profile of proteins in the Jurkat T cells by using two-dimensional (2-D) gel electrophoresis. Among 300 spots resolved in the 2-D gels, the comparison of the control versus apoptotic cells revealed that the signal intensity of 10 spots was decreased and 5 spots was increased. CONCLUSION: The results suggest that MZR functions as an inhibitor of IMP dehydrogenase in apoptosis of Jurkat T cells via activation of intrinsic caspase cascades as well as mitochondrial dysfunction.
Apoptosis* ; Blotting, Western ; Caspase 3 ; Caspase 8 ; Cell Death ; Cell Line ; Cell Survival ; Chromatin ; Cytochromes c ; Cytosol ; Electrophoresis ; Flow Cytometry ; Gels ; Guanosine ; Guanosine Triphosphate ; Humans ; IMP Dehydrogenase ; Inosine Monophosphate ; Membrane Potential, Mitochondrial ; Membrane Potentials ; Mitochondria ; Oxidoreductases ; Peptide Hydrolases ; Phosphorylation ; T-Lymphocytes*

PURPOSE: Mizoribine (MZR), an inhibitor of Inosine monophosphate (IMP) dehydrogenase which depletes cellular GTP, is clinically used as an immunosuppressive drug. This study was designed to evaluate the mechanism by which MZR exerts the cytotoxic effect on Jurkat T cells. METHODS: Jurkat T cell is a human T lymphocytic cell line. It was obtained from the Korean Type Culture Collection. Cell viability was measured by the MTT assay and flow cytometry. Caspase activity assay, Western blotting, 2-D PAGE, and mitochondrial membrane potential were detected using biochemical analysis. Morphologic finding was observed by Hoechst staining. RESULTS: The data demonstrated that the treatment of MZR decreased cell viability in a dose- and time-dependent manner. MZR-induced cell death was confirmed as apoptosis, which was characterized by chromatin condensation and H2AX phosphorylation. MZR increased the catalytic activity of caspase-3 protease, -8 protease and -9 proteases. The activation of caspase-3 protease was further confirmed by the degradation of polymerase (PARP), a substrate of caspase-3 protease by MZR in Jurkat T cells. Furthermore, MZR induced the changes of the mitochondrial transmembrane potential (MTP) and the cytosolic release of cytochrome c from the mitochondria. In addition, MZR induced the decrease of Bcl-X(L) expression whereas the increase of Bcl-X(S), Bak and Bim expression. Guanosine markedly inhibited cell viability and apoptosis through consistent suppression of the activity of caspase-8 protease, an upstream caspase among the caspase family, H2AX phosphorylation and PARP cleavage in MZR-treated cells. Also, I have screened the expression profile of proteins in the Jurkat T cells by using two-dimensional (2-D) gel electrophoresis. Among 300 spots resolved in the 2-D gels, the comparison of the control versus apoptotic cells revealed that the signal intensity of 10 spots was decreased and 5 spots was increased. CONCLUSION: The results suggest that MZR functions as an inhibitor of IMP dehydrogenase in apoptosis of Jurkat T cells via activation of intrinsic caspase cascades as well as mitochondrial dysfunction.
Apoptosis* ; Blotting, Western ; Caspase 3 ; Caspase 8 ; Cell Death ; Cell Line ; Cell Survival ; Chromatin ; Cytochromes c ; Cytosol ; Electrophoresis ; Flow Cytometry ; Gels ; Guanosine ; Guanosine Triphosphate ; Humans ; IMP Dehydrogenase ; Inosine Monophosphate ; Membrane Potential, Mitochondrial ; Membrane Potentials ; Mitochondria ; Oxidoreductases ; Peptide Hydrolases ; Phosphorylation ; T-Lymphocytes*