Combination of inhibitors for two glycolytic enzymes portrays high synergistic efficacy against Cryptosporidium parvum

Cryptosporidium is an intracellular protozoan parasite that causes serious enteric disease in humans and in a wide range of animals worldwide. Despite its high prevalence, no effective therapeutic drugs are available against life-threatening cryptosporidiosis in at-risk populations including malnourished children, immunocompromised patients, and neonatal calves. Thus, new efficacious drugs are urgently needed to treat all susceptible populations with cryptosporidiosis. Unlike other apicomplexans, Cryptosporidium parvum lacks the tricarboxylic acid cycle and the oxidative phosphorylation steps, making it solely dependent on glycolysis for metabolic energy production. We have previously reported that individual inhibitors of two unique glycolytic enzymes, the plant-like pyruvate kinase (CpPyK) and the bacterial-type lactate dehydrogenase (CpLDH), are effective against C. parvum, both in vitro and in vivo. Herein, we have derived combinations of CpPyK and CpLDH inhibitors with strong synergistic effects against the growth and survival of C. parvum, both in vitro and in an infection mouse model. In infected immunocompromised mice, compound combinations of NSC303244 + NSC158011 and NSC252172 + NSC158011 depicted enhanced efficacy against C. parvum reproduction and ameliorated intestinal lesions of cryptosporidiosis at doses fourfold lower than the total effective doses of individual compounds. Importantly, unlike individual compounds, NSC303244 + NSC158011 combination was effective in clearing the infection completely without relapse in immunocompromised mice. Collectively, our study has unveiled compound combinations that simultaneously block two essential catalytic steps for metabolic energy production in C. parvum to achieve improved efficacy against the parasite. These combinations are, therefore, lead compounds for the development of a new generation of efficacious anti-cryptosporidial drugs.

Lactate Dehydrogenase as a Potential Therapeutic Drug Target to Control Babesia bigemina

Babesia bigemina is a tick-borne apicomplexan hemoprotozoan responsible for bovine babesiosis. The current drugs used for bovine babesiosis treatment have several drawbacks, including toxicity, the lack of effectiveness to clear the parasite, and potential to develop resistance. Identifying compounds that target essential and unique parasite metabolic pathways is a rational approach toward finding alternative drug treatments. Based on the genome sequence and transcriptomics analysis, it can be inferred that anaerobic glycolysis is the dominant adenosine triphosphate (ATP) supply for Babesia, and lactate dehydrogenase (LDH) is one of the essential enzymes in this pathway. Furthermore, the Babesia LDH sequence is distinct from its bovine homologue and thus a potential chemotherapeutic target that would result in decreasing the ATP supply to the parasite but not to the host. Gossypol is a known efficient specific inhibitor of LDH in the sensu stricto B. bovis and the sensu lato B. microti, among other related parasites, but no such data are currently available in the sensu stricto B. bigemina parasites. Hereby, we show that the LDH amino acid sequence is highly conserved among sensu stricto but not in sensu lato Babesia spp. A predictive structural analysis of B. bigemina LDH showed the conservation of the key amino acids involved in the binding to gossypol compared to B. bovis. Gossypol has a significant (P < 0.0001) inhibitory effect on the in vitro growth of B. bigemina, with IC₅₀ of 43.97 mM after 72 h of treatment. The maximum IC (IC₉₈) was observed at 60 mM gossypol. However, a significant effect on the viability of cattle PBMC was observed when the cells were cultured with 60 mM (IC₉₈) gossypol compared with DMSO-exposed control cells. Interestingly, B. bigemina cultured at 3% oxygen expresses significantly higher levels of LDH and is more resistant to gossypol than the parasites maintained at ambient conditions containing ~20% oxygen. Altogether, the results suggest the potential of gossypol as an effective drug against B. bigemina infection, but the risk of host toxicity at therapeutic doses should be further evaluated in in vivo studies.

Protein arginine methyltransferase 3 promotes glycolysis and hepatocellular carcinoma growth by enhancing arginine methylation of lactate dehydrogenase A

BACKGROUND

Protein arginine methylation has emerged a pivotal role in cancer progression. However, the role of protein arginine methyltransferase 3 (PRMT3) in hepatocellular carcinoma (HCC) remains unknown.

METHODS

The expression pattern of PRMT3 in HCC was analysed using quantitative real-time-polymerase chain reaction (qRT-PCR), Western blotting and immunohistochemistry assays. Loss- and gain-of-function experiments were carried out to determine the oncogenic role of PRMT3 in HCC. Glucose consumption and lactate production assays, seahorse bioscience, mass spectrometry, co-immunoprecipitation, metabonomic analysis and site-specific mutation experiments were used to explore the underlying molecular mechanisms. Furthermore, a xenograft mouse model was established to investigate the effects of PRMT3 and its inhibitor, SGC707, treatment on tumour growth in vivo.

RESULTS

The expression of PRMT3 was significantly upregulated in HCC, with high expression of which correlated with poor prognosis. PRMT3 knockdown led to the decrease in proliferation, glycolysis of HCC cells and tumour growth, whilst its overexpression showed opposite results. The catalytic activity of PRMT3 was important in mediating these biological processes. Mechanistically, our data showed that PRMT3 interacted with and mediated asymmetric dimethylarginine (ADMA) modification of lactate dehydrogenase A (LDHA) at arginine 112 (R112). Compared with LDHA-wild-type (LDHA-WT) cells, LDHA-R112K-mutant-expressing HCC cells exhibited a decrease in lactate dehydrogenase (LDH) activity, HCC cell glycolysis and proliferation. Furthermore, the administration of SGC707, a selective inhibitor of PRMT3, disrupted the PRMT3-mediated LDHA methylation and abolished PRMT3-induced HCC glycolysis and tumour growth.

CONCLUSIONS

Our results suggested a novel oncogenic role of PRMT3 in HCC, and it could be a promising therapeutic target for HCC by linking post-translational modification and cancer metabolism.

Protective effect of Ssanghwa-tang fermented by Lactobacillus fermentum against carbon tetrachloride-induced acute hepatotoxicity in rats

Ssanghwa-tang (SHT) is a traditional herbal medicine formula that has been used for the development of physical strength, relief of pain, and the reduction of fatigue. In this study, we fermented SHT with Lactobacillus fermentum (L. fermentum), Lactobacillus gasseri (L.gasseri), or Lactobacillus casei (L.casei) to investigate the hepatoprotective effects of SHT and fermented SHT with Lactobacillus on carbon tetrachloride (CCl(4))-induced liver injury in rats. Rats were given CCl(4) (1 ml/kg, 50% CCl(4) in olive oil) intraperitoneally and either SHT or fermented SHTs (15 ml/kg) was administered 30 min before CCl(4). At 24 hr after CCl(4) injection, the levels of transaminases in the serum were markedly increased. These increases were significantly attenuated by either SHT + L. fermentum or SHT+ L.gasseri. However, SHT and SHT + L.casei showed slight suppression of the increase of transaminases. The liver histological changes were diminished by treatment with SHT + L. fermentum. Additionally, the potential hepatoprotective effect of fermented-SHTs correlated with the amount of unknown metabolite which is produced during fermentation process with L. fermentum, L.gasseri, or L.casei. Therefore, these results suggest that the hepatoprotective effect of SHT may be improved by fermentation with L. fermentum and the intestinal bacterial enzyme activities may likely play an important role in the pharmacological action of herbal medicines.

Mitochondrial regulation of caspase activation by cytochrome oxidase and tetramethylphenylenediamine via cytosolic cytochrome c redox state

Cytochrome c release from mitochondria induces caspase activation in cytosols; however, it is unclear whether the redox state of cytosolic cytochrome c can regulate caspase activation. By using cytosol isolated from mammalian cells, we find that oxidation of cytochrome c by added cytochrome oxidase stimulates caspase activation, whereas reduction of cytochrome c by added tetramethylphenylenediamine (TMPD) or yeast lactate dehydrogenase/cytochrome c reductase blocks caspase activation. Scrape-loading of cells with this reductase inhibited caspase activation induced by staurosporine. Similarly, incubating intact cells with ascorbate plus TMPD to reduce intracellular cytochrome c strongly inhibited staurosporine-induced cell death, apoptosis, and caspase activation but not cytochrome c release, indicating that cytochrome c redox state can regulate caspase activation. In homogenates from healthy cells cytochrome c was rapidly reduced, whereas in homogenates from apoptotic cells added cytochrome c was rapidly oxidized by some endogenous process. This oxidation was prevented if mitochondria were removed from the homogenate or if cytochrome oxidase was inhibited by azide. This suggests that permeabilization of the outer mitochondrial membrane during apoptosis functions not just to release cytochrome c but also to maintain it oxidized via cytochrome oxidase, thus maximizing caspase activation. However, this activation can be blocked by adding TMPD, which may have some therapeutic potential.

A methodology to study intracellular distribution of nanoparticles in brain endothelial cells

Cell internalisation and intracellular distribution of PEG-coated polyhexadecylcyanoacrylate (PEG-PHDCA) nanoparticles in rat brain endothelial cells (RBEC) have been investigated. A cell fractionation method has been developed based on the selective permeabilisation of RBEC plasma membrane by digitonin. By interacting with membrane cholesterol, digitonin creates pores allowing the release of soluble and diffusible species outside the cell. The selectivity of plasma membrane permeabilisation was controlled by using compartment markers such as lactate dehydrogenase (LDH) for cytoplasm and cathepsin B for lysosomes. An optimal digitonin concentration of 0.003% (w/v) has been identified to induce a pattern of membrane permeabilisation corresponding to the extraction of 72% LDH and less than 15% of Cathepsin B. Membrane permeabilisation at this digitonin concentration allows one to distinguish between the cell cytoplasm and its endo/lysosomal fraction. This methodology was applied to investigate the intracellular distribution of the nanoparticles after their incubation with the RBEC. The results showed that PEG-PHDCA nanoparticles were able to be internalised to a higher extent than PHDCA nanoparticles (after 20 min incubation). Additionally, these nanoparticles displayed different patterns of intracellular capture, depending on their specific surface composition: PEG-PHDCA nanoparticles were 48% in the plasma membrane, 24% in the cytoplasm, 20% in vesicular compartments and 8% associated with the fraction of the nucleus, the cytoskeleton and caveolae suggesting that PEG-PHDCA nanoparticle uptake by RBEC is specific and presumably due to endocytosis. Confocal microscopy studies confirmed the cellular uptake of PEG-PHDCA nanoparticles.

Viability assessment in sandwich-cultured rat hepatocytes after xenobiotic exposure

Troglitazone, bosentan and glibenclamide inhibit the bile salt export pump (Bsep) which transports taurocholate into bile. Sandwich-cultured rat hepatocytes maintain functional sodium taurocholate co-transporting polypeptide and Bsep transport proteins, and may be useful to study inhibition of transport by xenobiotics at concentrations below the lowest observable adverse effect level (LOAEL). The purpose of this study was to compare viability assessments determined with the neutral red, lactate dehydrogenase (LDH), alamar blue, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and propidium iodide assays in sandwich-cultured rat hepatocytes following exposure to xenobiotics known to inhibit Bsep, and to define the LOAEL for these xenobiotics in this system. The neutral red assay was not amenable to use in this model due to crystal formation on the collagen. Troglitazone decreased viability in every assay examined, with a LOAEL approximately 100 microM. Bosentan also decreased viability as measured by the LDH, MTT and propidium iodide assays, with a LOAEL approximately 200 microM; however, a significant decrease in viability was not observed with the alamar blue assay. Glibenclamide did not decrease viability with any assay at the xenobiotic concentrations examined in this study. Based on the results of this study, the LDH or propidium iodide assays would be the methods of choice to assess viability in sandwich-cultured rat hepatocytes after xenobiotic exposure.

The comparison of spontaneous LDH release activity from cultured PBMC with sera LDH activity in non-Hodgkin's lymphoma patients

Based on the fact that lactate dehydrogenase (LDH) enzyme is a very sensitive indicator of the cellular metabolic state, aerobic or anaerobic direction of glycolysis, activation status, and malignant transformation, in this study we compared values of the spontaneous LDH release from circulating PBMC with sera LDH activity in 53 different subtypes of non-Hodgkin's lymphoma (NHL) patients. Results shows that serum LDH was significantly (p < 0.05) elevated in comparison to the range values only in the advance clinical stage (III and IV) in all investigated subtypes of NHL according to The Working and REAL classification. On the other hand, the spontaneous LDH release from cultures PBMC is significantly (p < 0.01) elevated in early and advanced stage in all investigated forms of NHL in comparison to healthy controls. Based on consideration that an increase in spontaneous LDH release appears before elevated sera LDH activity, we conclude that determination of spontaneous LDH release by microassay from cultured cells together with other findings may help in the diagnosis of NHL patients, especially in patients with early stage of disease.

Cytotoxic effect and role of exogenous antioxidants in carpet dust mediated toxicity in rat hepatocytes in vitro

Carpet industries bear a great deal of economic and commercial significance in India. In order to safe guard the workers against the health hazards caused by dust in their occupational environment; it necessitates studying the biological importance of these dusts. The present study was designed to investigate the toxicity of carpet dust (knotted and tuffted) on isolated rat hepatocytes. The hepatocytes were isolated by collagenase perfusion method and cells were incubated with different concentration of carpet dust (100-5000 microg/10(6) cells) with various time (30-180 min) intervals. An exogenous antioxidant vitamin-E also used to find out the role of antioxidants and free radical production in carpet dust mediated toxicity. Cell viability by trypan blue exclusion and leakage of enzyme lactate dehydrogenase (LDH) were determined. Reduced glutathione (GSH), formation of thiobarbituric acid reactive substance (TBARS) were also measured. A significant decrease in the cell viability was observed after 60, 180 min upon incubation with tuffted carpet dust, while knotted carpet dust caused a significant decrease in the viability after 180 min. LDH leakage was parallel to the cell viability. Thiobarbituric acid reactive substance was significantly increased at 30 and 60 min with carpet dust treated hepatocytes. Dust at 1000 and 5000 microg dose level showed significantly increased formation of TBARS at 30 min incubation. However, when hepatocytes were co-incubated with carpet dust and Vit-E (10, 15 microM), a significant decrease in LDH release and TBARS production was observed while 15 microM Vit-E showed an enhanced protection than 10 microM Vit-E treated hepatocytes. The effect of carpet dust on cell viability, LDH leakage, TBARS production, GSH depletion was time and dose-dependent. Moreover, we observed that tuffted carpet dust causes greater effect than knotted one on the above mentioned parameters. Our studies also revealed that Vit-E in culture media diminishes the carpet dust mediated toxicity.

Recycling and utilization of metabolic wastes for energy production is an index of biochemical adaptation of fish under environmental pollution stress

The activity levels of lactate dehydrogenase and lactic acid were assessed in various tissues of the fish during exposure to lethal concentration of group-II Pyrethroids (deltamethrin, cypermethrin, fenvalerate and fluvalinate) for a period of 72 hours. The results showed steady increased levels in all the tissues (blood, muscle, brain and liver) with response pattern characteristic of their own. The increased LDH activity and lactic acid levels indicate the shifting of aerobic glycolysis to anaerobiosis and its further utilization for energy production during adaptation to toxic stress.

The use of respiratory enzymes as biomarkers of petroleum hydrocarbon exposure in Mytilus edulis planulatus

The effect of exposure to petroleum hydrocarbons via the water column and through contaminated sediment upon changes in respiratory enzymes in the common mussel (Mytilus edulis planulatus) was investigated. Mussels were exposed to three concentrations of the water-accommodated fraction (WAF) of Bass Strait crude oil, for 24, 48, and 96 h. In a second study mussels were exposed to three concentrations of crude oil-contaminated sediment for 2 weeks and 1, 2, 4 and 6 months. Activities of citrate synthase (CS) and lactate dehydrogenase (LDH) were measured in the gills. In mussels exposed to WAF, a significant decrease in CS activity was observed over time (P<0.05), whereas treatment did not cause a significant change in CS activity (P>0.05); neither treatment nor time had an effect on LDH activity. Exposure to contaminated sediment did not have a significant effect on CS activity, however, time had a significant effect on CS activity (P<0.05). Both time and treatment had an effect on LDH activity (P<0.05). Results demonstrated that changes in gill CS and LDH are not sensitive biomarkers of petroleum hydrocarbon exposure in M. edulis planulatus.

Hydrocarbon-induced changes to metabolic and detoxification enzymes of the Australian crimson-spotted rainbowfish (Melanotaenia fluviatilis)

The toxicity of petroleum hydrocarbons to marine aquatic organisms has been widely investigated; however, the effects on freshwater environments have largely been ignored. Selected biomarkers were measured in a freshwater species, the crimson-spotted rainbowfish (Melanotaenia fluviatilis). Fish were exposed to either a water-accommodated fraction (WAF) of crude oil or a dispersed crude oil water-accommodated fraction (DCWAF) for 3 days and were depurated for 14 days. Generally, biomarkers were altered following the short-term exposures but recovered after 14 days of depuration. Metabolic enzymes measured in gill tissue were citrate synthase and lactate dehydrogenase (LDH). As a result of WAF and DCWAF exposures, citrate synthase and LDH activities increased. Enzyme activities returned to control levels following depuration. Subsequent to the WAF exposure, hepatic ethoxyresorufin-O-deethylase (EROD) activity levels were higher than controls and they returned to control levels during depuration. For the DCWAF exposure, EROD was induced by a TPH (total petroleum hydrocarbons) concentration of 14.5 mg/L; however, after depuration the 14.5 mg/L TPH group had lower EROD activity than did controls. There were no changes in liver- to body-weight ratios or the histopathological organization of gill or liver tissues. As the majority of biomarkers returned to control levels after 14 days of depuration, rainbowfish were able to recover from short-term exposures to crude oil and dispersed crude oil.

Extensive protein carbonylation precedes acrolein-mediated cell death in mouse hepatocytes

Allyl alcohol hepatotoxicity is mediated by an alcohol dehydrogenase-derived biotranformation product, acrolein. This highly reactive alpha,beta-unsaturated aldehyde readily alkylates model proteins in vitro, forming, among other products, Michael addition adducts that possess a free carbonyl group. Whether such damage accompanies acrolein-mediated toxicity in cells is unknown. In this work we established that allyl alcohol toxicity in mouse hepatocytes involves extensive carbonylation of a wide range of proteins, and that the severity of such damage to a subset of 18-50 kDa proteins closely correlated with the degree of cell death. In addition to abolishing cytotoxicity and glutathione depletion, the alcohol dehydrogenase inhibitor 4-methyl pyrazole strongly attenuated protein carbonylation. Conversely, cyanamide, an aldehyde dehydrogenase inhibitor, enhanced cytotoxicity and protein carbonylation. Since protein carbonylation clearly preceded the loss of membrane integrity, it may be associated with the toxic process leading to cell death.

Restorative effects of zinc and selenium on cadmium-induced kidney oxidative damage in rats

OBJECTIVE

To investigate whether cadmium-induced oxidative stress in the kidney is influenced by zinc and selenium.

METHODS

Five groups of rats were maintained: (A) Cd (CdCl2, 400 micrograms.kg-1.day-1 intraperitoneal injection); (B) Cd + Zn (ZnCl2, 20 mg.kg-1.day-1 hypodermic injection); (C) Cd + Se (Na2SeO3, 350 micrograms.kg-1.day-1 via a stomach tube); (D) Cd + Zn + Se; (E) treated with physiological saline as a sham-handled control. The rats were given treatment for a period of 4 weeks. The activities of superoxide dismutase (SOD), glutathione peroxidase (GH-Px), catalase (CAT), and the level of malondialdehyde (MDA) in the kidney tissue were measured to assess the oxidative stress. Urinary lactate dehydrogenase (LDH) activity was used as an indicator of tubular cell damage caused by lipid peroxidation.

RESULTS

In group C and D, activities of SOD (110.5 +/- 5.2, 126.8 +/- 7.0; P < 0.05) and GSH-Px (85.7 +/- 4.9, 94.6 +/- 7.3; P < 0.05) were higher than those in group A (84.7 +/- 3.3; 56.9 +/- 3.8); and in group B, only the activity of GSH-Px (80.0 +/- 4.3, P < 0.01) increased in comparison with that in group A (56.9 +/- 3.8). Significant increase of MDA (P < 0.05) was seen in group B (31.1 +/- 4.7) and C (35.0 +/- 4.1) when compared with control values (17.2 +/- 1.8). No difference was found in the level of MDA between group D (18.9 +/- 2.6) and control. The activity of LDH in urine of control group (0.06 +/- 0.02) was lower than that of group A (0.46 +/- 0.19, P < 0.05), B (0.10 +/- 0.05, P < 0.05) and C (0.14 +/- 0.07, P < 0.05), and there was no significant change between control (0.06 +/- 0.02) and group D (0.08 +/- 0.02).

CONCLUSION

Zinc or selenium could partially alleviate the oxidative stress induced by cadmium in kidney, but administration cadmium in combination with zinc and selenium efficiently protects kidney from cadmium-induced oxidative damage.

[The role of hyperlactatedehydrogenasemia in induction of metabolic disorders in the body]

The effect of intravenous administration of lactate dehydrogenase (5000 E/kg) on some metabolic parameters was investigated. The hyperenzymemia was accompanied by changes of metabolite content (glutamate, 2-oxoglutarate, lactate, dihydroxyacetone phosphate) and enzyme activities (aldolase, lactate dehydrogenase, transaminase) in heart, liver and skeletal muscles. Intravenously administered tritiated lactate dehydrogenase was preferentially found in skeletal muscles, liver, kidneys and some other organs.

A mutation detected in DNA polymerase delta cDNA from Novikoff hepatoma cells correlates with abnormal catalytic properties of the enzyme

Tumor development is characterized by accumulation of mutations. Such mutations, if induced by carcinogens in DNA polymerase genes, would confer mutator properties on the DNA replication machinery, even at later stages of development. To investigate whether DNA polymerase delta can be mutated, we compared these enzymes from highly malignant Novikoff hepatoma cells and from regenerating normal rat liver. We sequenced the DNA polymerase delta cDNA from both sources and investigated the physico-chemical properties, inhibition characteristics, and copying fidelity of the purified enzymes. The cDNA sequences examined included the entire reading frame encoding the catalytic subunit (subunit I) of DNA polymerase delta. First-strand cDNAs were prepared from total RNA of both normal rat liver and Novikoff cells by reverse transcription, and the polymerase delta sequences were amplified by the polymerase chain reaction. cDNA (3325 bp) were sequenced. A single heterozygous mutation (CGG --> CAG) has been detected in nucleotide position 1948 (codon 648) of the polymerase delta gene from Novikoff cells, resulting in an Arg to Gln change. Position 648 lies just proximal to the conserved region VI, which is part of the "fingers" subdomain of alpha-like polymerases. This subdomain is involved in dNTP binding. Upon comparison of biochemical characteristics of partially purified DNA polymerase delta from both Novikoff cells and rat liver, the following properties of the enzyme from Novikoff cells were found to be altered: (i) K(50) values for nucleotide analogs (e.g. butylphenyl-dGTP) were lower, (ii) sensitivity to various antineoplastic drugs (e.g. doxorubicin, topotecan and distamycin) was enhanced, (iii) copying fidelity was decreased when primer templates containing O(6)-methylguanine were used, and (iv) the activity of DNA polymerase delta from Novikoff tumor cells was less stimulated by lactate dehydrogenase than the enzyme from normal cells. The altered biochemical characteristics of DNA polymerase delta from Novikoff cells suggest mutator properties. We conclude that the point mutation detected in the cDNA might be causally related to the observed changes in inhibition characteristics and copying fidelity.

Effects of selective and non-selective endothelin antagonists on ischemia-reperfusion damage in the isolated perfused murine liver

The objective of the present study was to clarify the differential effects of endothelinA (ETA) and ETB antagonism in the early phase of ischemia-reperfusion damage. Male Sprague Dawley rats were randomly divided into 4 groups: control (n = 10), bosentan (40 nM; n = 10), BQ-485 (20 nM; n = 10), and BQ-788 (50 nM; n = 10) to compare the effects of ETA or ETB or both ETA and ETB antagonists against the warm ischemia-reperfusion damage of murine livers. Isolated livers were perfused with oxygenated Krebs-Henseleit bicarbonate buffer solution and ET antagonists for 30 min before inducing warm ischemia (non-recirculating system). After 40 min without perfusate, measurements (portal pressure, O2 tensions of influent and effluent perfusate, liver enzymes, etc.) were taken up to 60 min after reperfusion. The BQ-788 group had significantly more liver damage than did the other groups, and more O2 consumption than did the bosentan group. BQ-485 and bosentan were more protective at some points after reperfusion. Antagonism of only the ETB receptors is detrimental, but antagonism of the ETA receptors appears to have a role in protecting the liver from warm ischemia-reperfusion damage in the early phase.

Modulation of DNA polymerases alpha, delta and epsilon by lactate dehydrogenase and 3-phosphoglycerate kinase

Literature documents that glycolytic enzymes (among them lactate dehydrogenase and 3-phosphoglycerate kinase) can reside in nuclei of mammalian cells and exert functions in DNA replication, transcription and DNA repair, in addition to their role as catalysts in the cytoplasm. Transfer of glycolytic enzymes to cell nuclei requires modification, for example phosphorylation. We studied the effects of phosphorylated lactate dehydrogenase and 3-phosphoglycerate kinase on (i) UV-induced DNA repair, using permeabilized human fibroblasts, and (ii) in vitro DNA synthesis catalyzed by purified DNA polymerases alpha, delta, and epsilon from proliferating rat liver. (i) Phosphorylated lactate dehydrogenase stimulated UV-induced DNA repair synthesis in normal fibroblasts in a dose-dependent manner; the unphosphorylated enzyme slightly inhibited. In repair-deficient xeroderma pigmentosum fibroblasts reparative synthesis was not enhanced whether lactate dehydrogenase was phosphorylated or not, indicating that reparative DNA synthesis must be possible in order to be stimulated. (ii) Activity of purified DNA polymerases alpha, delta, and epsilon was differentially stimulated or inhibited, according to the phosphorylation status of lactate dehydrogenase. DNA polymerases were also modulated by 3-phosphoglycerate kinase, depending on the primer-templates used which were gapped DNA (mimicking a repair mode of DNA synthesis) or single-stranded M13 DNA (representing the replicative mode of DNA synthesis). Since glycolytic enzymes in cell nuclei retain binding ability for their cofactors, cytoplasmic substrates and inhibitors, a regulatory linkage might exist between the energy state of a cell and its replicative and reparative functions.

Immune responses of chemically modified homologous LDH-C4 and their effect on fertility regulation in mice

PROBLEM

Lactate dehydrogenase-C4 (LDH-C4) is an iso-, allo- and auto-antigen of mammalian sperm. In spite of being cell specific, LDH-C4 does not induce infertility in females of homologous species after immunization. The present study examines the application of homologous LDH-C4 after chemical modifications in the immunological infertility of female mice.

METHODS

LDH-C4 from testes of LACA mice was chemically modified by interacting it with gossypol (gossy-LDH-C4) and glucosylation with lactose (Glu-LDH-C4) in vitro and evaluated for immune responses and induced immunological infertility in allogeneic Balb/c mice after inoculation through intrarectal route using A1(OH)3 as adjuvant.

RESULTS

Native LDH-C4, which elicited high antibody response after immunization with a primary (50 microgram) and three secondary doses (30 micrograms each) at an interval of 15 days each, did not reduce fertility significantly in mice. In contrast, study provides evidence that chemically modified LDH-C4 induces high infertility, since 85-100% of mice failed to conceive in two independent sets of experiments. Mice inoculated with modified LDH-C4 were associated with 2-3 fold anti-LDH-C4 antibody titre compared to antibody response elicited by native LDH-C4. Splenocytes from immunized non-pregnant mice were evaluated for polyclonal activation using Con A as mitogen. It was found that splenocytes primed with native LDH-C4 were significantly more stimulated than the non-immune control cultures. However cells primed with gossy-LDH-C4 were non-reactive to Con A and cells primed with glu-LDH-C4 were suppressed for ConA proliferation.

CONCLUSIONS

It is concluded that LDH-C4-gossypol adduct offers a potential application in the induction of infertility of homologous species in marked contrast to native LDH-C4. Application of A1(OH)3 as adjuvant in the induction of immune response through intra-rectal route has been suggested.

Pathways of hepatic oxalate synthesis and their regulation

Important features of hepatic oxalate synthesis remain uncertain despite its clinical significance. To clarify the terminal steps of the biosynthetic pathway and their modulation, we have examined oxalate and glyoxylate synthesis in vitro using isolated guinea pig peroxisomes and purified lactate dehydrogenase (LDH). Glycolate was rapidly oxidized to glyoxylate by isolated peroxisomes followed by a slower conversion of glyoxylate to oxalate. The glycolate oxidase (GO)-catalyzed conversion of glyoxylate to oxalate was strongly inhibited by physiological concentrations of glycolate and lactate. In contrast, the LDH-catalyzed conversion of glyoxylate to oxalate was only marginally affected by physiological concentrations of lactate and unaffected by physiological glycolate concentrations. This inhibition pattern suggests that LDH, not GO, catalyzes this conversion in vivo. Alanine inhibited oxalate synthesis by converting the bulk of the glyoxylate to glycine. On exposure to high alanine concentrations, however, inhibition was not complete and peroxisomes were able to convert sufficient glycolate to oxalate to account for daily endogenous oxalate production. NADH was a potent inhibitor of oxalate production by LDH by increasing glycolate formation from glyoxylate. Glycine was an ineffective source of glyoxylate, and an alkaline pH, a high-glycine concentration, and a prolonged incubation time were required to obtain a detectable synthesis. These results suggest that oxalate synthesis will be modulated by the metabolic state of the liver and resultant changes in NADH, lactate, and alanine levels.

A serum-free, pyruvate-free medium that supports neonatal neural/glial cultures

Tissue culture media with serum generally cause excessive astrocyte proliferation in neonatal brain cultures, and often fail to support neonatal neurons. Published serum-free media for brain cultures contain sodium pyruvate, which interferes with lactate dehydrogenase (LDH) assays for cell death. We wanted to use neonatal neural-glial cultures in LDH assays while avoiding astrocyte proliferation, so we developed a serum-free medium without sodium pyruvate. Our initial medium was based on that of Romijn et al. (J Neurosci Methods 23:75-83, 1988), testing selected additives. Cell survival in 8-10-day-old cultures was measured using 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). N-acetylcysteine, citrate, superoxide dismutase, ascorbate, supplemental amino acids, and high levels of transferrin improved survival. The optimized medium supported neonatal brain cells in reaggregates or in monolayers of 400 cells/mm2 for several weeks with large, healthy-appearing neurons and very little astrocyte proliferation. Neurons stained strongly for the neuronal marker class III beta-tubulin and the synapse marker synaptophysin. Electron microscopy of reaggregate cultures demonstrated abundant neurons with synapses in a dense neuropil. This medium will be useful for various in vitro applications, especially those using LDH assays or requiring the use of neonatal cells.

Bound substrate polypeptides can generally stabilize the tetradecameric structure of Cpn60 and induce its reassembly from monomers

We demonstrate that the previously observed stabilizing effect by the enzyme rhodanese of the oligomeric structure of Cpn60 is general and can be provided by six other proteins that can interact with Cpn60. All these substrate proteins, which include examples that are monomeric, as well as oligomeric polypeptides in their native states, were shown previously to be assisted in their refolding by the chaperonin. Strikingly, during the disassembly of Cpn60 in the presence of any of the substrate proteins, significant amounts of intermediates were detected. Furthermore, unfolded substrate proteins induce the reassembly of tetradecameric Cpn60 from monomers, and binding of each substrate protein stabilizes Cpn60 quaternary structure.

[The modelling of hyperfermentemia--a method for studying the mechanisms of the formation of metabolic disorders]

The model of hyperenzymia caused by injection of lactate dehydrogenase (5000 U/kg body weight) causes an increase of NADP.H-dependent oxidation in liver microsomes, without changing oxidative intensity in mitochondria, by such NAD.H-depended dehydrogenases as glutamate dehydrogenase and beta-hydroxybutyrate dehydrogenase. The aim of the interaction with exogenous lactate dehydrogenase in the glycolytic metabolone system, where increased carbohydrate disintegration in vivo is induced. There is a high detoxification processes associated with ammonia detoxification and urea production. The stability of membrane permeability is characterized by the absence of glutamate dehydrogenase and glucoso-6-phosphate dehydrogenase activity in blood plasma. It has been shown that the introduction of exogenic lactate dehydrogenase into the metabolism of experimental animals gives the possibility of using this enzyme as an enzymotherapeutic remedy.

Modulation of T cell functions by sperm-specific lactate dehydrogenase: fluorescence analysis of immune competent cells and local graft versus host reaction

Immune responses to a well-defined sperm-specific isogenic lactate dehydrogenase-C4 (LDH-C4) have been studied in C57Bl/Ks (H-2d) mice after immunization through intra-rectal route. Presence of anti-LDH-C4-antibodies in the sera of females immunized in presence or absence of adjuvant suggested that the immune system of mice becomes exposed to sperm antigens following intrarectal insemination. LDH-C4 primed lymphocytes from both males and females, when transferred in F1 hybrids, suppressed stimulation index of local graft versus host reaction. However, contrary to females, male counterparts which did not elicit measurable anti-LDH-C4-antibody titer, showed the presence of a higher proportion of Ly2+ and Ia+ fluorescence labelled cells in the spleen of LDH-C4 administered mice. Results suggest that males are more susceptible for immune suppression of T cell functions through generation of T suppressor cells. Sex differences in relation to immune deviation by intra-rectal administration of sperm-specific LDH-C4 in mice and their consequences in AIDS and AIDS-related complex diseases are described.

Stimulation of NADH oxidation by xanthine oxidase and polyvanadate in presence of some dehydrogenases and flavin compounds

The rates of NADH oxidation in presence of xanthine oxidase increase to a small and variable extent on addition of high concentrations of lactate dehydrogenase and other dehydrogenases. This heat stable activity is similar to polyvanadate-stimulation with respect to pH profile and SOD sensitivity. Isocitric dehydrogenase (NADP-specific) showed heat labile, SOD-sensitive polyvanadate-stimulated NADH oxidation activity. Polyvanadate-stimulated SOD-sensitive NADH oxidation was also found to occur with riboflavin, FMN and FAD in presence of a non-specific protein, BSA, suggesting that some flavoproteins may possess this activity.

Extracellular administration of lactate dehydrogenase and its effects on human plaque pH and acid anion concentrations

The effect of lactate dehydrogenase (LDH) on human plaque pH and acid anion concentrations in vivo was investigated. Rinsing with sucrose solutions supplemented with LDH (1 or 2 U/ml) gave rise to reduced pH fall, decreased cH area and an increase in the mean minimum pH when compared with rinsing with sucrose only (p less than 0.05). Mean acid anion estimations showed that plaque fluid concentrations of lactate, acetate and proprionate significantly decrease (p less than 0.05) following rinsing with sucrose containing LDH at both levels and decreases in succinate when 1 U/ml LDH was present, whereas formate concentrations were only significantly lower when 2 U/ml LDH was added to sucrose rinses. It is thought that the ability of LDH to produce an alteration in the acid end-products of plaque metabolism may provide some protection against dental caries.

An enzyme-assessed microplate-assay for neutrophil adherence. I. IgA-induced adherence of human PMNs

The binding of PMNs to extracellular matrix and cells is crucial to PMN host defense. Adherence mechanisms and the many families of molecules involved are major areas of study. We present here details of an enzyme-assessed microtiter plate assay for neutrophil adherence. This assay uses low numbers of cells (50,000/well) and permits analysis of several hundred wells in a short period of time, by using an ELISA reader. With this assay we observed 5- to 10-fold increases in the number of adherent human PMNs in response to nanogram amounts of LPS or as little as 5.0 micrograms/ml of aggregated IgA. Although fluoride blocked the LPS-induced adherence response, IgA-induced cell binding was largely unaffected.

Effects of lactate dehydrogenase on fissure caries in rats

The effect of supplementing the diet or drinking water with lactate dehydrogenase (LDH) on the formation of caries lesions in rats was investigated. Addition of LDH [20 and 5 mg/kg in the high-sucrose (65%) diet, 2 and 1 U/ml in the drinking water (LDH-specific activity 735 U/mg solid)] resulted in significant reductions (p less than 0.01) in the number and severity of caries lesions when the enzyme was administered to rats for 4 or 7 days, although no significant differences were found after 14 or 21 days. No differences were observed between effects of addition to water or diet. Fissure caries failed to develop when rats were fed a low sucrose diet (5%) containing LDH (20 mg/kg diet), whereas 50% of the animals in the control group developed lesions. The findings indicate that LDH may play an important role in delaying the onset of caries lesion formation in rats, and that the protection observed may be inversely related to the intensity of the cariogenic challenge.

Lactate dehydrogenase-induced conformational changes of F-actin in myosin-free ghost single fibres

The changes in conformation of F-actin induced by the binding of the glycolytic enzyme lactate dehydrogenase were studied in myosin-free single ghost muscle fibres. The formation of the lactate dehydrogenase-F-actin complex was accompanied by changes in the parameters of intrinsic (tryptophan) and extrinsic (rhodaminyl-phalloin) polarized fluorescence of ghost muscle fibre F-actin. Lactate dehydrogenase stimulated actin-activated Mg2+-ATPase of myosin subfragment 1 by 30%. F-actin of ghost fibres depressed lactate dehydrogenase activity to 20% of the initial values. It is suggested that the energy-providing mechanism is coupled with that of muscle contraction through conformational changes in F-actin.

Mechanism of action of (-)gossypol on ATP production in isolated hamster spermatids

The ATP content of round spermatids isolated from hamsters was decreased 90% after 18 h of incubation in the presence of 4 microM-(-)gossypol and 0.10% bovine serum albumin (BSA). The (+)-enantiomer had no effect under these incubation conditions. The Michaelis-Menten constant Km and the maximal initial velocity Vmax of cellular LDH-C4 were not significantly altered after 18 h of incubation of the spermatids with (-)gossypol. Furthermore, there was no effect of (-)gossypol on the production of 14CO2 from L-[U-14C]lactate. It is concluded that (-)gossypol does not inhibit ATP production in spermatids by an effect on the sperm-specific LDH-C4 enzyme or on the mitochondrial oxidation of pyruvate. Rather, (-)gossypol may have an effect on the coupling between electron transport and ATP synthesis in the mitochondria. This action of (-)gossypol may not involve the H+-conducting activity of gossypol, but could be produced through binding of (-)gossypol to specific mitochondrial proteins.

Pyruvate dehydrogenase activity in osmotically shocked rat brain mitochondria: stimulation by oxaloacetate

Pyruvate dehydrogenase complex activity (PDHC) measured by CO2 release isotopic assay has generally been much lower than activity measured by the spectrophotometric arylamine acetyltransferase assay (ArAT). Decarboxylation of [1-14C]pyruvate was measured in osmotically shocked rat brain cortical mitochondria. Activity is dependent on the concentration of the substrate pyruvate. Activity of 74.6 units +/- 12.3 SD (n = 22) was observed at 4 mM pyruvate (1 unit = 1 nmol pyruvate decarboxylated/min/mg protein). Activity was dependent on added NAD, CoA, and thiamine pyrophosphate, implying increased mitochondrial permeability after osmotic shock. Freeze/thaw with sonication of the mitochondrial preparation reduced PDHC activity to 11.5 units +/- 3.0 SD (n = 4). Oxaloacetate produced a marked stimulation of activity. The optimal assay contained 3 mM oxaloacetate, and without oxaloacetate activity fell to 15.4 units +/- 9.9 SD (n = 8). These studies highlight the importance of optimal substrate concentrations in the CO2 release isotopic PDHC method. Higher PDHC activity is found with intact mitochondria and thus activity values should be interpreted in the light of the presence or absence of intact mitochondria in individual preparations.

Lactate dehydrogenase in human cervical mucus: correlation with ovulation, influence of ovarian steroid hormones, and isozyme pattern

The glycolytic enzymes, lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase, and hexokinase in cervical mucus of 96 ovulatory women were serially measured daily during the menstrual cycle. Among all of the enzymes, the cyclic changes in LDH activity were the most significant, being high during the proliferative phase, gradually decreasing to the lowest level around ovulation, and then increasing markedly again. Estrogen inhibited cervical mucus LDH activity; progestrone accelerated it. Examination of the LDH isozyme pattern showed that H-LDH (H-subunit of LDH), being predominant throughout the cycle, apparently carries some responsibility for the cyclic change in LDH activity. In a comparison of LDH activity with the serum luteinizing hormone (LH) peak, the activity level nadir of LDH usually appeared between 1 day before and 1 day after the serum LH peak, pointing to the advantage of daily measurement of cervical mucus LDH activity for predicting the potential day of conception.

A method for enzymatic determination of citrate in serum and urine

A method for determination of citrate in serum and urine using citrate lyase is described. The influence of pH, zinc, magnesium, and calcium ions on the reaction velocity is studied. Citrate lyase activity is found rather insensitive to variations in pH round the pH-optimum at 8.2. Zinc ions activate the reactions. The optimal concentration of zinc ions in the reaction mixture is found to depend on the calcium concentration of samples. Perchloric acid is used for precipitation of proteins. The perchloric ion inhibits the reaction, and a procedure for removing perchlorate is given. Sensitivity of analysis is 0.005 mmo1/1 for serum and urine samples, respectively. No contamination of citrate lyase is found, and therefore addition of lactate dehydrogenase is considered unneccessary.

[Inhibition of exogenous lactate dehydrogenase in mammalian ova]

A technique of microinjection of exogenic commercial lactate dehydrogenase into the zygotes of rats has been elaborated. A selective inhibition of exogenous LDH-3, LDH-4 and LDH-5 was registered in the ova-recipients. Attempts to reproduce the selective inhibition of LDH-3, LDH-4 and LDH-5 by a microhomogenate made of zygotes were not successful. The identification of LDH from ovocytes and exogenic LDH was made according to their electrophoretic mobility relative to Bromphenol blue and LDH-1.

The interaction of reduced nicotinamide--adenine dinucleotide phosphate with reduced nicotinamide--adenine dinucleotide--ubiquinone reductase from bovine heart mitochondria

Reduction of the chromophores of mitochondrial NADH-ubiquinone reductase by NADPH reaches only 50% of the extent of reduction by NADH, monitored at 450 nm. This effect is due to autoxidation of an enzyme component at a higher rate than its reduction by NADPH.

Infertility in female rabbits immunized with lactate dehydrogenase X

Immunization of female rabbits with the sperm-specific lactate dehydrogenase (LDH-X) resulted in a highly significant reduction of pregnancies compared to nonimmunized controls. This is the first demonstration of immunosuppression of fertility by a crystalline protein shown to be strictly homogeneous by ultracentrifugation, polyacrylamide gel electrophoresis, immunodiffusion, and micro complement fixation.