Synthetic sulfonolipids deduced from sulfonoquinovosyl diacylglycerols of sea urchin reduces hepatic ischemia-reperfusion injury in rats.

BACKGROUND: In hepatic surgery and liver transplantation, ischemia-reperfusion (I/R) is an unavoidable process, and protection against hepatic I/R injury is a major unresolved problem. In this study, we investigated whether 3-O-(6-deoxy-6-sulfono-beta-D-glucopyranosyl)-1,2-di-O-acylglycerol bound to saturated C18 fatty acids (beta-SQAG9), which was derived from sea urchin intestines, could reduce this injury. This agent was recently reported to have immunosuppressive effects in allogeneic rat skin grafts. MATERIALS & METHODS: Male Lewis rats were divided into two experimental groups. Group 1 rats were injected with SQAG9 (50 mg/kg) into the penile vein 15 minutes before the induction of ischemia and into the portal vein just reperfusion. The same amounts of normal saline were injected into rats in the control group (group 2). Each experimental groups included six rats. Seventy percent hepatic ischemia (20 minutes) was induced by occluding the blood vessels and bile duct with a vascular clamp. For examination of hepatic function, serum levels of aspartate aminotransferase, (AST) alanine transaminase (ALT), and lactic dehydrogenase (LDH) were measured. In addition, histological examination was also assessed. RESULTS: Three hours after reperfusion, the mean plasma concentration of AST, ALT, LDH in group 1 was suppressed compared with group 2. Six hours after reperfusion, the hepatic damage in group 1 was mild in comparison with that in group 2. CONCLUSIONS: Our data demonstrated that SQAG-9 reduced the warm hepatic I/R injury.

Specific interaction between an oligosaccharide on the tumor cell surface and the novel antitumor agents, sulfoquinovosylacylglycerols.

Some sulfoquinovosylacylglycerols (SQAG) have been shown to be potent DNA polymerase inhibitors, and to have strong antitumor activity in vivo. In this study, we investigated the mode of action of SQAG with regard to the interaction with the tumor cell surface. Of the SQAG used, the monoacyl forms (SQMG) with C18-, C18:1- or C16-fatty acids (SQMG-alphaC18, -alphaC18:1 or -alphaC16) effectively inhibited cell proliferation of a human adenocarcinoma cell line, DLD-1, but SQMG-alphaC14 and the diacyl forms (SQDG) did not. Analysis of the interaction of SQMG-alphaC18 and -alphaC18:1 on three oligosaccharides of cell surface, sLe(A), Le(X), and SM3, by flow cytometry demonstrated that the most effective interaction was observed on sLe(A). DLD-1 cells bound to SQMG-alphaC18:1-coated plates, and this binding was inhibited by monoclonal antibody against sLe(A) or SM3. However, these cells did not bind to SQMG-alphaC14-coated plates. Moreover the cytotoxic effects of SQMG-alphaC18, -alphaC18:1 on DLD-1 cells was inhibited by monoclonal antibodies against sLe(A) or SM3. Our results suggested that the interaction of SQMGs and sLe(A) plays an important role in suppression of the DLD-1 cell proliferation.

Galactosyldiacylglycerol, a mammalian DNA polymerase alpha-specific inhibitor from a sea alga, Petalonia bingbamiae.

The glycolipid galactosyldiacylglycerol (GDG), containing C16:0 and C18:1 fatty acids, was isolated from the sea alga Petalonia bingbamiae as a potent inhibitor of the activities of mammalian DNA polymerase alpha (pol. alpha). GDG, however, had no effect on pol. alpha from a fish or a higher plant. The inhibition of pol. alpha by GDG was dose-dependent with an IC50 value of 54 microM. The compound did not influence the activities of other replicative DNA polymerases such as mammalian pol. delta, or repair-related enzymes such as mammalian pol. beta. GDG also did not influence the activities of prokaryotic DNA polymerases such as the Klenow fragment of DNA polymerase I, T4 DNA polymerase, Taq DNA polymerase, DNA polymerases from the higher plant, cauliflower, or DNA metabolic enzymes such as calf thymus terminal deoxynucleotidyl transferase, human immunodeficiency virus type 1 reverse transcriptase and deoxyribonuclease 1. Kinetic analysis of the compound showed that pol. alpha was non-competitively inhibited with respect to both the DNA template and the nucleotide substrate. In this study, we demonstrated the structure-function relationship in the selective inhibition of pol. alpha by the glycolipid group.

Synthesis of sulfoquinovosylacylglycerols, inhibitors of eukaryotic DNA polymerase alpha and beta.

Sulfoquinovosyldiacylglycerols (SQDGs) and sulfoquinovosylmonoacylglycerols (SQMGs), bearing diverse fatty acids, were synthesized from D-glucose, and were examined for enzymatic inhibitions of DNA polymerase alpha and beta. These results indicated that the carbon numbers of the fatty acids were highly related to the activities, at least in vitro, of eukaryotic DNA polymerase inhibition.

Structure-activity relationship of a novel group of mammalian DNA polymerase inhibitors, synthetic sulfoquinovosylacylglycerols.

We reported previously that sulfolipids in the sulfoquinovosylacylglycerol class from a fern and an alga are potent inhibitors of DNA polymerase alpha and beta and potent anti-neoplastic agents. In developing a procedure for chemical synthesis of sulfolipids, we synthesized many derivatives and stereoisomers of sulfoquinovosylmonoacylglycerol (SQMG) / sulfoquinovosyldiacylglycerol (SQDG). Some of these molecules were stronger inhibitors than the SQMG / SQDG originally reported as natural compounds. In this study, we examined the structure-inhibitory function relationship of synthetic SQMG / SQDG and its relationship to cytotoxic activity. The inhibitory effect is probably mainly dependent on the fatty acid effect, which we reported previously, although each of the SQMG / SQDG was a much stronger inhibitor than the fatty acid alone that was present in the SQMG / SQDG. The inhibitory effect could be influenced by the chain size of fatty acids in the SQMG / SQDG. The sulfate moiety in the quinovose was also important for the inhibition. Lineweaver-Burk plots of SQMG / SQDG indicated that DNA polymerase alpha was non-competitively inhibited, but the SQMG / SQDG were effective as antagonists of both template-primer DNA-binding and nucleotide substrate-binding of DNA polymerase beta. The SQMG had an cytotoxic effect, but the SQDG tested did not. The SQDG might not be able to penetrate into cells. Based on these results, we discuss the molecular action of SQMG / SQDG and propose drug design strategies for developing new anti-neoplastic agents.

Studies on a novel DNA polymerase inhibitor group, synthetic sulfoquinovosylacylglycerols: inhibitory action on cell proliferation.

Some chemically synthesized sulfoquinovosylmonoacylglycerols (SQMG)-sulfoquinovosyldiacylglycerols (SQDG) have been reported to selectively and strongly inhibit the activities of mammalian DNA polymerases alpha and beta in vitro. In this study, using human cancer cell lines, we investigated the effects of SQMG-SQDG on the DNA polymerase in the cells. In the presence of n-decane, the IC(50) values on cell growth were approximately 1-5 microM for SQMG and about 0.3-1 microM for SQDG. The values were almost the same as the in vitro enzyme inhibitory levels. The cell lines were arrested in early S-phase by SQMG-SQDG at the concentrations of 0.1-4.7 microM in a manner dependent on incubation time, suggesting that SQMG-SQDG blocked the primary step of DNA replication by inhibiting DNA polymerase, possibly alpha-type. We also demonstrated the localization of SQMG in the cell using the fluorescent SQMG analog, SQMGalpha-NBDD, which was synthesized in our laboratory. SQMGalpha-NBDD was localized in the nucleus and on the nuclear surface, but the binding site seemed not to be the DNA/chromatin, suggesting that the SQMG-SQDG might interact with molecules located close to the DNA/chromatin and on the nuclear surface. These results suggested a correlation between the in vitro biochemical action of the SQMG-SQDGs and their intracellular mode of action.