Differential cytotoxic effects of mizoribine and its aglycone on human and murine cells and on normal and enzyme-deficient human cells

TCP1γ Subunit Is Indispensable for Growth and Infectivity of Leishmania donovani

T-complex protein-1 (TCP1) is a ubiquitous group II chaperonin and is known to fold various proteins, such as actin and tubulin. In Leishmania donovani, the γ subunit of TCP1 (LdTCP1γ) has been cloned and characterized. It forms a high-molecular-weight homo-oligomeric complex that performs ATP-dependent protein folding. In the present study, we evaluated the essentiality of the LdTCP1γ gene. Gene replacement studies indicated that LdTCP1γ is essential for parasite survival. The LdTCP1γ single-allele-replacement mutants exhibited slowed growth and decreased infectivity in mouse macrophages compared to the growth and infectivity of the wild-type parasites. Modulation of LdTCP1γ expression in promastigotes also modulated cell cycle progression. Suramin, an antitrypanosomal drug, not only inhibited the luciferase refolding activity of the recombinant LdTCP1γ (rLdTCP1γ) homo-oligomeric complex but also exhibited potential antileishmanial efficacy both in vitro and in vivo The interaction of suramin and LdTCP1γ was further validated by isothermal titration calorimetry. The study suggests LdTCP1γ as a potential drug target and also provides a framework for the development of a new class of drugs.

Mizoribine as sole immunosuppressive agent in islet xenotransplantation models: a candidate immunosuppressant causing no adverse effects on islets

Mizoribine (MZ) inhibits the differentiation and proliferation of helper T and B cells after antigen recognition by suppressing the purine biosynthesis pathway and nucleic acid synthesis. MZ has been used in kidney transplantation, but distinct data are unavailable for islet transplantation. The present study investigated the efficacy of MZ for islet xenotransplantation. Immunosuppressive effects of MZ were determined by mixed lymphocyte reaction (MLR) assay in vitro. Toxicities for Wistar rat islets were determined by adenosine triphosphate (ATP) contents of islets during 3-day culture and stimulation index in response to glucose after culture. Immunosuppressive effects in vivo were tested in a Wistar-to-B6 islet xenotransplantation model. MZ was administered continuously for 28 days subcutaneously or intramuscularly. MZ inhibited MLR response by approximately 50% at 0.1 μg/ml. ATP contents decreased with MZ >100 μg/ml, while stimulation index was maintained. Continuous infusion of MZ at 10 mg/kg maintained blood concentrations at 0.13-0.19 μg/ml, while intramuscular injection of MZ at 100 mg/kg/day (peak 520 μg/ml at 1 h postinjection) resulted in below measurable levels (<0.03 μg/ml) within 24 h. Graft survival was significantly prolonged following continuous infusion of 10 mg/kg/day compared to controls (31.0 ± 9.5 vs. 13.2 ± 5.2 days; p = 0.002). Furthermore, animals with intramuscular injection at doses of 3.2, 10, or 100 mg/kg/day showed significantly longer graft survival (20.0 ± 7.5, 22.0 ± 7.31, and 24.5 ± 8.1 days, respectively; p < 0.05 each). Histological examination showed significant suppression of lymphocyte infiltration by MZ administration. MZ showed immunosuppressive effects in an experimental islet xenotransplantation model without adverse effects on endocrine function of islet grafts.

Inhibitory effect of mizoribine on matrix metalloproteinase-1 production in synovial fibroblasts and THP-1 macrophages

To investigate the mechanism of antirheumatic action of mizoribine (MZR), we examined the expression of matrix metalloproteinase-1 (MMP-1) and MMP-3 utilizing THP-1 derived macrophage-like cells (THP-1 macrophages) and human synovial fibroblasts (SFs). The cells were respectively stimulated with lipopolysaccharide (LPS) and interleukin-1beta in the presence or absence of MZR in vitro. The concentrations of MMP-1 and MMP-3 in the supernatant were measured by enzyme-linked immunosorbent assay. The secretion of MMP-1 from SFs, as well as THP-1 macrophages, was inhibited by MZR in a dose-dependent manner. Furthermore, a quantitative real-time polymerase chain reaction revealed that MZR decreased the expression of MMP-1 messenger RNA. These findings may be an explanation for the clinical effect of MZR in patients with rheumatoid arthritis.

Proteome analysis for the identification of tumor-associated biomarkers in gastrointestinal cancer

Gastrointestinal cancers are usually diagnosed at advanced stages, making a curative treatment difficult. Biomarkers can help to overcome this problem by allowing earlier diagnosis, and thus better therapy. Proteomics tools are novel technologies to identify such biomarkers. This review summarizes advances in biomarker detection using two-dimensional gel electrophoresis (2D-PAGE), chromatography and mass spectrometry technologies. 2D-PAGE combined with mass spectrometry has led to the identification of several differentially expressed proteins in cancer tissue. However, for serum analysis, 2D-PAGE has severe limitations. For serum-based cancer diagnosis, surface-enhanced laser desorption-ionization time-of-flight (SELDI-TOF) mass spectrometry is a promising new technology. The potential of proteins identified with this technology as novel cancer biomarkers still needs to be confirmed in clinical trials.