The effects of fructose diphosphate on routine coagulation tests in vitro

To evaluate the effects of fructose diphosphate (FDP) on routine coagulation tests in vitro, we added FDP into the mixed normal plasma to obtain the final concentration of 0, 1, 2, 3, 4, 5, 6, 10, 15, 20, 25, 30 and 35 mg/mL of drug. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen (FBG) and thrombin time (TT) of samples were analyzed with blood coagulation analyzers from four different manufacturers(Sysmex, Stago, SEKISUI and Werfen) and their corresponding reagents, respectively. Before the experiment, we also observed whether there were significant differences in coagulation test results of different lots of reagents produced by each manufacturer. At the same time as the four routine clotting tests, the Sysmex blood coagulation analyzer and its proprietary analysis software were used to detect the change of maximum platelet aggregation rate in platelet-rich plasma after adding FDP (0, 1, 2, 3, 4, 5 and 6 mg/mL). The results of PT, aPTT and TT showed a FDP (0-35 mg/mL) concentration-dependent increase and a FBG concentration-dependent decrease. The degree of change (increase or decrease) varied depending on the assay system, with PT and aPTT being more affected by the Sysmex blood coagulation testing instrument reagent system and less affected by CEKISUI, TT less affected by CEKISUI and more affected by Stago, and FBG less affected by Stago and more affected by Sysmex. The results of PT, aPTT and TT were statistically positively correlated with their FDP concentrations, while FBG was negatively correlated. The correlation coefficients between FDP and the coagulation testing systems of Sysmex, Stago, Werfen and SEKISUI were 0.975, 0.988, 0.967, 0.986 for PT, and 0.993, 0.989, 0.990 and 0.962 for aPTT, 0.994, 0.960, 0.977 and 0.982 for TT, - 0.990, - 0.983, - 0.989 and - 0.954 for FBG, respectively. Different concentrations of FDP (0, 1, 2, 3, 4, 5 and 6 mg/mL) had different effects on the maximum aggregation rate of platelet induced by the agonists of adenosine diphosphate (ADP, 5 µmol/L), arachidonic acid (Ara, 1 mmol/L), collagen (Col, 2.5 µg/mL) and epinephrine (Epi,10 µmol/L), but the overall downward trend was consistent, that is, with the increase of FDP concentration, the platelet aggregation rate decreased significantly. Our experimental study demonstrated a possible effect of FDP on the assays of coagulation and Platelet aggregation, which may arise because the drug interferes with the coagulation and platelet aggregation detection system, or it may affect our in vivo coagulation system and Platelet aggregation function, the real mechanism of which remains to be further verified and studied.

Phosphofructokinases A and B from Mycobacterium tuberculosis Display Different Catalytic Properties and Allosteric Regulation

Tuberculosis (TB) remains one of the major health concerns worldwide. Mycobacterium tuberculosis (Mtb), the causative agent of TB, can flexibly change its metabolic processes during different life stages. Regulation of key metabolic enzyme activities by intracellular conditions, allosteric inhibition or feedback control can effectively contribute to Mtb survival under different conditions. Phosphofructokinase (Pfk) is one of the key enzymes regulating glycolysis. Mtb encodes two Pfk isoenzymes, Pfk A/Rv3010c and Pfk B/Rv2029c, which are differently expressed upon transition to the hypoxia-induced non-replicating state of the bacteria. While pfkB gene and protein expression are upregulated under hypoxic conditions, Pfk A levels decrease. Here, we present biochemical characterization of both Pfk isoenzymes, revealing that Pfk A and Pfk B display different kinetic properties. Although the glycolytic activity of Pfk A is higher than that of Pfk B, it is markedly inhibited by an excess of both substrates (fructose-6-phosphate and ATP), reaction products (fructose-1,6-bisphosphate and ADP) and common metabolic allosteric regulators. In contrast, synthesis of fructose-1,6-bisphosphatase catalyzed by Pfk B is not regulated by higher levels of substrates, and metabolites. Importantly, we found that only Pfk B can catalyze the reverse gluconeogenic reaction. Pfk B thus can support glycolysis under conditions inhibiting Pfk A function.

Inhibition of Recombinant Aldose-6-Phosphate Reductase from Peach Leaves by Hexose-Phosphates, Inorganic Phosphate and Oxidants

Glucitol, also known as sorbitol, is a major photosynthetic product in plants from the Rosaceae family. This sugar alcohol is synthesized from glucose-6-phosphate by the combined activities of aldose-6-phosphate reductase (Ald6PRase) and glucitol-6-phosphatase. In this work we show the purification and characterization of recombinant Ald6PRase from peach leaves. The recombinant enzyme was inhibited by glucose-1-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate and orthophosphate. Oxidizing agents irreversibly inhibited the enzyme and produced protein precipitation. Enzyme thiolation with oxidized glutathione protected the enzyme from insolubilization caused by diamide, while incubation with NADP+ (one of the substrates) completely prevented enzyme precipitation. Our results suggest that Ald6PRase is finely regulated to control carbon partitioning in peach leaves.

Fructose-1,6-bisphosphate ameliorates lipopolysaccharide-induced dysfunction of blood-brain barrier

Fructose-1,6-bisphosphate (FBP), a glycolytic intermediate, has neuroprotective effects in various brain injury models. However, its effects on blood-brain barrier (BBB) are largely unknown. In this study, we investigated the effects of FBP on lipopolysaccharide (LPS)-induced BBB dysfunction in in vitro BBB model comprising co-culture of mouse brain endothelial cell line, bEnd.3 and mouse primary astrocyte and explored its action mechanism therein involved. LPS induced the impairment of endothelial permeability and transendothelial electrical resistance (TEER). The functional changes were confirmed by alterations in immunostaining for junctional proteins occludin, ZO-1 and VE-cadherin, such as the loss of cortical staining pattern and appearance of intercellular gaps in endothelial cells. Co-administration of FBP alleviated the deleterious effects of LPS on BBB permeability and TEER in a dose dependent manner. And also FBP inhibited the LPS-induced changes in the distribution of endothelial junctional proteins, resulting in the better preservation of monolayer integrity. FBP suppressed the production of reactive oxygen species (ROS) but did not affect cyclooxygenase-2 expression and prostaglandin E₂ production in endothelial cells stimulated with LPS. Taken together, these data suggest that FBP could ameliorate LPS-induced BBB dysfunction through the maintenance of junctional integrity, which might be mediated by downregulation of ROS production.

Nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase is phosphorylated in wheat endosperm at serine-404 by an SNF1-related protein kinase allosterically inhibited by ribose-5-phosphate

Nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase (np-Ga3PDHase) is a cytosolic unconventional glycolytic enzyme of plant cells regulated by phosphorylation in heterotrophic tissues. After interaction with 14-3-3 proteins, the phosphorylated enzyme becomes less active and more sensitive to regulation by adenylates and inorganic pyrophosphate. Here, we acknowledge that in wheat (Triticum aestivum), np-Ga3PDHase is specifically phosphorylated by the SnRK (SNF1-related) protein kinase family. Interestingly, only the kinase present in heterotrophic tissues (endosperm and shoots, but not in leaves) was found active. The specific SnRK partially purified from endosperm exhibited a requirement for Mg(2+) or Mn(2+) (being Ca(2+) independent), having a molecular mass of approximately 200 kD. The kinase also phosphorylated standard peptides SAMS, AMARA, and SP46, as well as endogenous sucrose synthase, results suggesting that it could be a member of the SnRK1 subfamily. Concurrently, the partially purified wheat SnRK was recognized by antibodies raised against a peptide conserved between SnRK1s from sorghum (Sorghum bicolor) and maize (Zea mays) developing seeds. The wheat kinase was allosterically inhibited by ribose-5-phosphate and, to a lesser extent, by fructose-1,6-bisphosphate and 3-phosphoglycerate, while glucose-6-phosphate (the main effector of spinach [Spinacia oleracea] leaves, SnRK1) and trehalose-6-phosphate produced little or no effect. Results support a distinctive allosteric regulation of SnRK1 present in photosynthetic or heterotrophic plant tissues. After in silico analysis, we constructed two np-Ga3PDHase mutants, S404A and S447A, identifying serine-404 as the target of phosphorylation. Results suggest that both np-Ga3PDHase and the specific kinase could be under control, critically affecting the metabolic scenario involving carbohydrates and reducing power partition and storage in heterotrophic plant cells.

Posttranslational modification of 6-phosphofructo-1-kinase as an important feature of cancer metabolism

Background

Human cancers consume larger amounts of glucose compared to normal tissues with most being converted and excreted as lactate despite abundant oxygen availability (Warburg effect). The underlying higher rate of glycolysis is therefore at the root of tumor formation and growth. Normal control of glycolytic allosteric enzymes appears impaired in tumors; however, the phenomenon has not been fully resolved.

Methodology/Principal Findings

In the present paper, we show evidence that the native 85-kDa 6-phosphofructo-1-kinase (PFK1), a key regulatory enzyme of glycolysis that is normally under the control of feedback inhibition, undergoes posttranslational modification. After proteolytic cleavage of the C-terminal portion of the enzyme, an active, shorter 47-kDa fragment was formed that was insensitive to citrate and ATP inhibition. In tumorigenic cell lines, only the short fragments but not the native 85-kDa PFK1 were detected by immunoblotting. Similar fragments were detected also in a tumor tissue that developed in mice after the subcutaneous infection with tumorigenic B16-F10 cells. Based on limited proteolytic digestion of the rabbit muscle PFK-M, an active citrate inhibition-resistant shorter form was obtained, indicating that a single posttranslational modification step was possible. The exact molecular masses of the active shorter PFK1 fragments were determined by inserting the truncated genes constructed from human muscle PFK1 cDNA into a pfk null E. coli strain. Two E. coli transformants encoding for the modified PFK1s of 45,551 Da and 47,835 Da grew in glucose medium. The insertion of modified truncated human pfkM genes also stimulated glucose consumption and lactate excretion in stable transfectants of non-tumorigenic human HEK cell, suggesting the important role of shorter PFK1 fragments in enhancing glycolytic flux.

Conclusions/Significance

Posttranslational modification of PFK1 enzyme might be the pivotal factor of deregulated glycolytic flux in tumors that in combination with altered signaling mechanisms essentially supports fast proliferation of cancer cells.

[Role of HO/CO in IL-beta induced pancreatic islets apoptosis and the effect of fructose-1, 6-disphosphate]

AIM

To investigate the protective role of HO/CO systems in IL-1beta induced islest apoptosis and to explore the mechanisms of the protective effect of fructose-1, 6-disphosphate (FDP).

METHODS

The pancreases of the rats were removed to collect islets cells. The cells were incubated with IL-1beta with/or FDP. Cell activity, insulin secretion, HO-1 activity, CO content and apoptotic percentage were detected.

RESULTS

HO-1 activity and CO content of the normal control group were low. IL-1beta induced a significant decrease of cell activity and insulin release, flow cytometry analysis showed that apoptotic percentage of islet cells remarkably increased following the addition of IL-1beta, FDP obviously improved the islets cellular activity damaged by IL-1beta, and basic amount of insulin secretion and stimulated by high glucose were improved (P < 0.01). Content of CO and activity of HO-1 were higher in the IL-1beta group than the normal control group (P < 0.05), and there were significant differences between the FDP groups and IL-1beta group. FDP decreased cell apoptotic percentage. Activities of HO-1 and content of CO were higher than that in the IL-1beta group (P < 0.01).

CONCLUSION

FDP can attenuate the IL-1beta induced apoptosis of cultured beta cells, the mechanism of which may be improved HO-1 activity and CO content.

Fructose-1,6-diphosphate attenuates acute lung injury induced by lipopolysaccharide in mice

Fructose-1,6-diphosphate (FDP), a high-energy glycolytic pathway intermediate, is reported to have a salutary effect in endotoxic shock and sepsis, but its underlying mechanism of action in inflammation is incompletely understood. In this study, our aim was to examine the function of FDP on acute lung injury (ALI) induced by lipopolysaccharide (LPS). We found that in vitro pretreatment with FDP remarkably repressed the production of TNF-alpha and IL-6 in murine alveolar macrophages MH-S exposed to LPS. In the mouse model of LPS-induced inflammatory lung injury, intravenous precondition of a single 400 mg/kg dose of FDP resulted in a significant reduction in LPS-mediated extravasation of Evans blue dye albumin, bronchoalveolar lavage leucocyte content, and lung tissue myeloperoxidase activity (reflecting phagocyte infiltration). Furthermore, histopathologic examination indicated that alveolitis with inflammatory cells infiltration and alveolar hemorrhage in the alveolar space was less severe in the FDP-treated mice than in the mice treated by LPS alone at 24 h. Additionally, pretreatment with FDP markedly decreased the transcription of TNF-alpha, IL-6 and inducible NO synthase (iNOS), and suppressed the nuclear translocation of NF-kappaB in lung tissues in response to LPS challenge. These results thus suggested that FDP plays an anti-inflammatory role in LPS-mediated acute lung injury, possibly through abrogation of NF-kappaB activation.

Strontium fructose 1,6-diphosphate rescues adenine-induced male hypogonadism and upregulates the testicular endothelin-1 system

1. Male hypogonadism is a major problem that starts to affect middle-aged men and has adversely effects on human sexual life. The aim of the present study was to investigate the effect of strontium fructose 1,6-diphosphate (FDP-Sr) on male hypogonadism in rats. 2. The pharmacological model of testis dysfunction was created by administration of adenine (200 mg/kg per day, i.g.) for 30 days. Three doses of FDP-Srs (200, 100 and 50 mg/kg per day, i.g.) were administered in parallel with adenine. Finally, mating behaviour index (the mounting latency and the number of mounting events), the total number of spermatozoa and sperm motility, related enzyme function and gene regulation and the mRNA levels of steroidogenic acute regulatory protein (StAR), cytochrome P450 side-chain cleavage enzyme (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), prepro-endothelin (ET)-1, endothelin-converting enzyme (ECE) and endothelin receptor A (ET(A)) were analysed. 3. The results showed that adenine significantly prolonged the mounting latency and decreased the number of mounting events, markedly reduced the total number of spermatozoa, slowed sperm motility and decreased testicular enzyme activity in the testes. At the mRNA level, adenine significantly downregulated serum testosterone, StAR, P450sc and 3beta-HSD. In parallel, adenine also targeted the ET-1 system, significantly downregulating mRNA levels of prepro-ET-1, ECE and ET(A). Administration of FDP-Sr dose-dependently reversed these effects. 4. In conclusion, adenine-induced testis dysfunction appears to be manifested as loss of sexual function in association with decreased spermatogenesis and reduced mRNA levels of steroidogenesis and the testicular ET-1 system. These abnormalities were significantly restored by FDP-Sr in a dose-dependent manner. These data indicate the possibility of using FDP-Sr to treat male hypogonadism.

Effects of fructose-1,6-diphosphate on endo- and myocardial purine metabolism during coronary artery bypass grafting surgery

AIM

During ischemia, the glycolytic pathway is up-regulated to anaerobically produce adenosine triphosphate (ATP). However, this is short-lived, due to negative feedback on phosphofructokinase from accumulating lactate. Since fructose-1,6-diphosphate (FDP) enters glycolysis distal to this inhibitory site, exogenously administered FDP may yield ATP-independent lactate accumulation and thus ameliorate ischemic injury. The aim of this prospective randomized study was to investigate whether the improved myocardial preservation by FDP could be attributed to improved intermediary metabolism in patients who underwent coronary artery bypass grafting surgery (CABG).

METHODS

Thirty-eight patients scheduled for elective CABG were studied. During operation, aortic and coronary sinus blood were collected at different timepoints and analysed by chromatography. Ten patients received 250 mg/kg FDP and 10 received 5% dextrose (control) as intravenous pretreatment prior to cardiopulmonary bypass. In the second stage, 9 patients received 2.5 mM (1.4 g/L) FDP and 9 patients 5% dextrose with the cardioplegic solution. Myocardial metabolism was quantified by measuring nucleotide catabolites including inosine and hypoxanthine.

RESULTS

The release of inosine-hypoxantine was increased in both the FDP and the control groups; however, compared to baseline, inosine-hypoxantine levels were significantly elevated at 0, 1, 5 and 10 minutes following reperfusion in the control group. This was in contrast to the earlier recovery to baseline levels (after 5 minutes following reperfusion) in the FDP group.

CONCLUSION

These data suggest that FDP may contribute to myocardial cytoprotection during cardiopulmonary bypass. Moreover, myocardial nucleotide metabolite levels showed no evidence for a protective effect of FDP on nucleotide degradation between the treated and the control groups.

Fructose 1,6-Diphosphate Alleviates UV-Induced Oxidative Skin Damage in Hairless Mice

Reactive oxygen species (ROS) are involved in the deleterious effects of UV light on skin. The antioxidant defense system is considered to be crucial for protecting skin from ROS. Recently, we showed that fructose 1,6-diphosphate (FDP), a glycolytic metabolite, reduced oxidative stress in UVB-irradiated keratinocytes. This study set out to determine whether topically applied FDP could exert protective effects against UV-induced skin damage in hairless mice. An in vitro skin permeation study using Franz-type diffusion cells showed that the amount of [14C]-FDP that diffused through the skin increased in a time-dependent manner, and about 3.5% of the applied FDP penetrated the skin after 24 h. Topical application of FDP (1%) preserved the endogenous antioxidant capacity of skin such as catalase and glutathione, which were significantly reduced after UVB irradiation without FDP. FDP also reversed the loss of catalase protein and prevented the accumulation of carbonylated proteins induced by UVB irradiation. These results provide evidence that topically administered FDP could penetrate into the skin and attenuate UVB-induced oxidative skin damage in hairless mice.

The effects of fructose-1,6-bisphosphate and dexamethasone on acute inflammation and T-cell proliferation

OBJECTIVE AND DESIGN

Chronic glucocorticoid treatment is associated with pharmacological resistance. We investigated the auxiliary effects of fructose-1,6-bisphosphate (FBP) on dexamethasone (DEX)-related modulation of inflammation and T-cell proliferation.

METHODS

Acute inflammation (pleurisy) was induced by injection of carrageenan into the pleural cavity of rats that were treated in vivo with DEX s. c. and FBP i. p. Peripheral blood mononuclear cells were isolated and T-cell sensitivity to FBP and DEX was evaluated in vitro.

RESULTS

FBP and DEX reduced the exudate volume, protein concentration and neutrophils in the pleural cavity. However no synergistic effects were observed when these compounds were tested simultaneously. In contrast, both compounds dose-dependently and synergistically suppressed T-cell proliferation.

CONCLUSION

These data suggest that FBP may be beneficial as auxiliary drug for the treatment of patients with acquired glucocorticoid resistance.

Effect of normothermic perfusion using fructose-1,6-bisphosphate for maintenance of liver function during in situ extended hepatectomy by the total hepatic vascular exclusion technique

BACKGROUND

Recently, hepatic surgery has made remarkable progress, and it is important to use appropriate liver perfusion. We evaluated the effect of normothermic liver perfusion with the addition of fructose-1, 6-bisphosphate (FBP) and oxygenation to maintain liver parenchymal, non-parenchymal, and Kupffer cell function.

MATERIALS AND METHODS

The rats were divided into five groups according to the perfusate and continuous perfusion was performed: Control group = 4 degrees C lactate Ringer with 10% glucose (LRG) solution; normothermic group = 25 degrees C LRG solution; normothermic oxygenated group = 25 degrees C oxygenated LRG solution; normothermic FBP group = 25 degrees C LRG solution with addition of 10 mmol/L FBP; normothermic oxygenated FBP group = 25 degrees C oxygenated LRG solution with addition of 10 mmol/L FBP. Parameters under evaluation were oxygen consumption, liver energy level (adenosine triphosphate, total adenine nucleotide), glutathione, lipid peroxide, hyaluronic acid uptake ratio, apoptosis, and histomorphology. Moreover, we studied the effect of FBP and normothermia on Kupffer cells activation in vitro.

RESULTS

Liver energy level was lower in the normothermic group than the control group. But, it was improved by oxidation or addition of FBP, and it was satisfactorily maintained up to 120 min in the group with normothermic oxygenated FBP. Hyaluronic acid uptake was maintained highly at all times as measured in normothermic oxygenated FBP group. The uptake of lipopolysaccharide was significantly higher as a result of adding FBP, compared with that in the control group and the normothermic group. Moreover, the apoptotic index in the liver was decreased in normothermic FBP group compared to control group.

CONCLUSIONS

The normothermic liver perfusion under additional FBP and oxygenation protects both parenchymal and non-parenchymal cells from reperfusion injury.

Fructose-1,6-bisphosphate enhances hypothermic preservation of cardiac myocytes

BACKGROUND

Previous studies from our project found that fructose-1,6-bisphosphate (FBP) enhanced the functional recovery of animal hearts after hypothermic preservation, and that rat cardiac myocytes take up FBP at 3 degrees C. In this study we tested the effects of FBP, as well as other compounds related to glycolysis and pyruvate oxidation, on the hypothermic preservation of myocytes.

METHODS

Isolated myocytes were incubated in ischemic suspensions at 3 degrees C, and aliquots examined over 72 hours for retention of rod-shaped morphology. In some experiments adenine nucleotide levels were measured by high-performance liquid chromatography (HPLC).

RESULTS

FBP at 1 to 10 mmol/liter markedly reduced the death rate (65% reduction at 5 mmol/liter). Glucose at 2 to 10 mmol/liter was less beneficial (20% reduction). Insulin increased the death rate by about 25% when present alone, and it did not enhance the beneficial effects of FBP or glucose. Dichloroacetate (DCA), which stimulates pyruvate dehydrogenase, had little effect at 0.5 to 10 mmol/liter. Glucose and DCA did not increase the beneficial effects of FBP. After 6 to 24 hours of hypothermia, FBP- and glucose-treated cells had 25% to 50% higher ATP levels and 10% to 20% higher ATP:ADP ratios than untreated cells. Effects of FBP on preservation of morphology were much greater than effects on ATP levels.

CONCLUSIONS

The results suggest that the effects of FBP and glucose were through glycolytic ATP production rather than through sugar oxidation via pyruvate dehydrogenase. The divergence in effects on preservation and effects on ATP suggests a role for a sub-cellular compartment of ATP in preservation.

Fructose 1,6-bisphosphate prevented endotoxemia, macrophage activation, and liver injury induced by D-galactosamine in rats

OBJECTIVE

Fructose 1,6-bisphosphate (F1,6BP) protects organs against a wide range of challenges involving inflammation. We hypothesized that the primary action of F1,6BP is to prevent macrophage activation and cytokine release. Our aim was to determine the tissue and cellular targets for this bisphosphorylated sugar and to provide new insights into its mechanisms of action.

DESIGN

Prospective, controlled laboratory study.

SETTING

Animal resource facilities and research laboratory.

SUBJECTS

Male Sprague-Dawley rats (200-250 g body weight).

INTERVENTIONS

The protective action of F1,6BP was analyzed in galactosamine (GalN)-induced hepatitis in rats. The in vivo effects of F1,6BP were evaluated by changes in transaminase activities, blood endotoxins, and tumor necrosis factor (TNF)-alpha production in GalN-challenged rats. The targets of F1,6BP to reduce macrophage response to lipopolysaccharide (LPS) were determined by correlation between changes in TNF-alpha production and K+ fluxes through cell membrane in primary cultures of Kupffer cells.

MEASUREMENTS AND MAIN RESULTS

The in vivo results indicate that F1,6BP treatment prevented GalN-induced injury in liver parenchymal cells. This protection was mainly associated with a reduction of the inflammatory response. F1,6BP prevention of GalN-induced endotoxemia correlated with preclusion of mast cell degranulation and histamine release that preceded the increased plasma endotoxins and liver production of TNF-alpha. In addition, F1,6BP treatment decreased sensitivity to LPS, which reduced the GalN-induced increase in TNF-alpha. The in vitro results show that F1,6BP inhibited Kupffer cell response and reduced TNF-alpha production by preventing LPS-induced K+ channel activation.

CONCLUSIONS

The role of exogenous F1,6BP as a K+ channel modulator underlies its antihistaminic and anti-inflammatory action and increases its interest as a protective compound.

Fructose-1,6-diphosphate suppresses T-lymphocyte proliferation, promotes apoptosis and inhibits interleukins-1, 6, beta-actin mRNAs, and transcription factors expression

The overall objective of this study was to determine the role fructose 1,6-diphosphate (FDP), a naturally occurring glycolytic intermediate, plays in activated T-lymphocytes. The hypothesis is twofold. First, we propose that FDP inhibits T cell proliferation to a greater extent than fructose-1-phosphate (F1P), fructose-6-phosphate (F6P) and mannose-6-phosphate (M6P); second, we argue that FDP suppresses immune activation by inhibiting inflammatory cytokine expression, inhibiting expression of key transcription factors, and by inducing apoptosis in immune cells. Rat spleen cells were incubated with concanavalin A (ConA) and increasing concentrations of FDP. Proliferation was determined by tritiated thymidine uptake. FDP inhibited splenocyte proliferation in a dose-related manner while F1P, F6P, M6P demonstrated inhibition only at high concentrations (5000 microg/ml). RNA was harvested from FDP and ConA-treated cells and IL-1 and IL-6 gene expression was analyzed by RT-PCR. IL-1 and IL-6 mRNA expression was completely inhibited at 500-5000 microg/ml FDP. Apoptosis in FDP-treated lymphocytes was determined by DNA fragmentation and flow cytometry. Propidium iodide (PI) staining demonstrated a 39% rate of apoptosis in splenocytes treated with ConA and 5000 microg/ml FDP. Extensive DNA fragmentation was present at 250-5000 microg/ml FDP, and maximal inhibition occurred at 5 microg/ml. F1P, F6P and M6P showed maximal inhibition only at 5000 microg/ml. Nuclear extracts from FDP-treated splenocytes were analyzed by electrophoretic mobility shift assay. ConA activation of NF-kappaB and AP-1 was dramatically inhibited by FDP. Interestingly, beta-actin showed extensive inhibition with FDP and ConA, thus suggesting new possibilities of its being used as a therapeutic modality in arterial injury where the beta-actin, an important cytoskeleton element, plays a very important role. These data indicate that FDP may be a useful immunosuppressive agent. In conclusion, FDP is not only an immunosuppressant but also an anti-inflammatory agent.

Effect of intracellular delivery of energy metabolites on intracellular Ca2+ in mouse islets of Langerhans

Regulation of glucose-induced oscillations in intracellular Ca2+ concentration ([Ca2+]i) was investigated by using a novel technique, electroporation from an electrolyte-filled capillary, to deliver energy metabolites to the intracellular compartment of mouse islets. Intracellular application of ATP resulted in a nifedipine-sensitive increase in [Ca2+]i, consistent with a KATP-channel dependent mechanism of Ca2+ influx. [Ca2+]i in islets exposed to 10 mM glucose oscillated with a period of approximately 3 min, often superimposed with faster oscillations. Electroporation of ATP blocked all types of oscillations and elevated [Ca2+]i while delivery of ADP had no effect on oscillations. Intracellular delivery of glucose-6-phosphate or fructose-1,6-bisphosphate tended to transform slow oscillations to fast oscillations. These results demonstrate that modulation of ATP concentrations and glycolytic flux are important in development of slow oscillations.

Evaluation of fructose 1,6 diphosphate for salvage of ischemic gracilis flaps in rats

Fructose 1, 6 diphosphate (FDP), a metabolic intermediate, provides an alternative mechanism to circumvent the rate-limiting step in the Kreb's cycle. This agent has been observed to prevent the effects of ischemia on heart tissue and kidney function and the effects of endotoxic shock. It has been shown conclusively to minimize the adverse effects of ischemia-reperfusion injury in experimental pedicled skin flaps in animals. The present study was done to evaluate the effect of intra-arterial administration of FDP on salvage of ischemic microvascular transfer of gracilis muscle flaps in rats, with the premise that it might prolong the ischemia time of muscle flaps at room temperature, thus increasing chances of flap survival. Irrigation with FDP did not change the quantitative survival of the flaps, but there was qualitative improvement on histologic evaluation and DNA analysis. Decreased inflammatory damage and DNA fragmentation were seen at the 2.5-hr period. Histologic staining for mitochondrial oxygenation in gracilis muscle also showed increased uptake in the FDP-treated group vs. control at the 2.5-hr ischemia period. Further experiments with different modes of FDP administration should be carried out to identify more effective means of amelioration of flap ischemia.

Unique kinetic mechanism of Plasmodium falciparum adenylosuccinate synthetase

Adenylosuccinate synthetase (AdSS) catalyses the Mg(2+) dependent formation of adenylosuccinate from IMP and aspartate, the reaction being driven by the hydrolysis of GTP to GDP. All characterized AdSS thus far exhibit a random kinetic mechanism. We present here kinetic evidence that unlike all other AdSS, Plasmodium falciparum AdSS (PfAdSS) has ordered substrate binding. Inhibition studies show that binding of GTP requires IMP binding while aspartate binds to the enzyme-IMP-GTP complex. A structural basis for this difference in mechanism is presented. Kinetically, PfAdSS is closer to the mouse acidic isozyme rather than to the mouse basic isozyme. The mouse acidic isozyme is thought to play a role in the purine nucleotide biosynthetic pathway. Regulation of PfAdSS in vivo can therefore, be expected to be similar to the mouse acidic isozyme, in agreement with the role of PfAdSS as the only pathway for the synthesis of adenine nucleotides in the parasite. However, PfAdSS differs from both the mammalian homologs in that fructose-1,6-bisphosphate, a potent inhibitor of the mammalian enzyme, is an activator of PfAdSS. The differences highlighted here are promising in terms of species-specific drug design, targeting this essential enzyme in the parasite.

Neuroprotection by fructose-1,6-bisphosphate involves ROS alterations via p38 MAPK/ERK

Fructose-1,6-bisphosphate (FBP) is a glucose metabolism intermediate that shows a neuroprotective action in animal models of ischemia and other injuries. The intracellular mechanism of FBP on neuroprotection has not been previously defined. Here, we examined whether FBP has a neuroprotective effect against excitotoxicity, and whether it affects the production of reactive oxygen species (ROS), which are involved in the MAPK pathway in cortical neurons. FBP prevented neuronal death in a dose-dependent manner following 24 h of treatment with the excitotoxin, NMDA. After 8 h of NMDA treatment, we observed FBP-induced inhibition of the production of intracellular ROS, and at the earlier time FBP suppressed NMDA-induced p-p38 and p-ERK expression. In addition, MAPK inhibitors reduced NMDA-induced excitotoxicity and also ROS production. Taken together, our results suggest that the neuroprotective effects of FBP could be explained by down-regulation of free radical production through the p38MAPK/ERK pathway.

The effect of fructose-1, 6-diphosphate and HTK solution on protecting primary cardiac muscle cells of rat with cold preservation

In this study we tried to investigate the effect of fructose-1,6-diphosphate and HTK solution on protecting primary cardiac muscle cells of rat with cold preservation. The primary cardiac muscle cells of rat were cultured in vitro with four preservation solutions respectively: 0.9% sodium chloride solution (group A), FDP (group B), HTK solution (group C) and a mixture of FDP and HTK solution (group D). The cells were preserved for 6, 8 and 10 h at 0-4 degrees C. The values of AST and LDH-L and the Na+-K+ ATPase activity in cardiac muscle cells were detected, and the survival rate of cardiac muscle cells was detected with trypan blue staining. The values of AST and LDH-L in group C and group D were remarkable lower those in group A and group B (P<0.001), while the Na+-K+ ATPase activity and the survival rate of cells in group C and group D were much higher than those in group A and group B (P<0.001). The values of AST and LDH-L after 6 hours in group D decreased much more than those in group C (P<0.01), while the Na+-K4 ATPase activity and the survival rate of cells in group D improved more than those in group C (P<0. 01). Both of the HTK solution and the mixture of HTK and FDP solution have an evident effect on protecting the primary cardiac muscle cells of rat in vitro with cold preservation, Compared with the HTK solution, the mixture solution has a better short-term protective effect.

Neuroprotective effect of D-fructose-1,6-bisphosphate against beta-amyloid induced neurotoxicity in rat hippocampal organotypic slice culture: involvement of PLC and MEK/ERK signaling pathways

D-fructose-1,6-bisphosphate (FBP) is an endogenous intermediate of glycolytic pathway which has potent neuroprotective effect against various neurotoxic insults. This study examined whether FBP could antagonize the neurotoxicity induced by amyloid beta-peptide (Abeta) in rat hippocampal organotypic slice cultures, and the possible mechanism was also explored. Treatment with FBP (concentration ranges from 1.7 mM to 10 mM) significantly decreased the cell death in hippocampal slices in the presence of Abeta at 24h, 48 h and 72 h, and this neuroprotective effect of FBP against Abeta was not in a dose-dependent manner, FBP 3.5 mM has better neuroprotective effect than that of other FBP concentration groups. Treatment with FBP slightly but significantly increases the ATP levels in hippocampal slices in the presence of Abeta. However, the increment of ATP levels was similar among various FBP concentration groups. Neuroprotective effect of FBP 3.5 mM against Abeta induced neurotoxicity in hippocampal slices was attenuated by addition of phospholipase C (PLC) inhibitor, U73122, mitogen activated extracellular signal protein kinase (MEK) inhibitor, U0126, or extracellular signal activated protein kinase (ERK) inhibitor, PD98059 at 24 h, 48 h and 72 h. However, co-treatment with these three kinds of inhibitors did not change the FBP's effect on ATP levels. Our results suggested FBP has neuroprotective effect against Abeta induced neurotoxicity in hippocampal slice cultures, and FBP plays role not only as an alternative energy source, but also a modulator of PLC and MEK/ERK pathways to regulate the cellular response and survival.

Effect of fructose-1,6-bisphosphate in the cold storage solution after 12 and 36 hours of rat liver preservation

Fructose-1,6-bisphosphate (FBP) has been reported to have a protective effect on liver injury following ischemic/reperfusion periods because it maintains ATP levels during cold preservation. In the present study, we evaluated the effects of addition of FBP to storage solutions for cold liver preservation during 12 or 36 hours. Adult male Wistar rats were randomly divided into three experimental groups. The hepatic perfusion and preservation were performed with these solutions: UW; UW plus 10 mmol/L FBP; and FBP 10 mmol/L (FBPS) alone. The biochemical measurements of AST and ALT were performed on samples of the cold storage solution after 12- or 36-hour preservation. UW and FBPS solutions showed similar preservation grades at 12 hours. Addition of 10 mmol/L of FBP to UW solution induced liver injury and a poor preservation grade during 12 or 36 hours. UW solution was better than FBPS after 36 hours preservation. UW solution continues to offer a superior performance for liver preservation during long times; however, FBPS may be an alternative for short cold preservation times.

Cloning and expression of theClostridium thermocellumL-lactate dehydrogenase gene inEscherichia coliand enzyme characterization

The structural gene for L-lactate dehydrogenase (LDH) (EC.1.1.1.27) from Clostridium thermocellum 27405 was cloned in Escherichia coli by screening the Lambda Zap II phage library of C. thermocellum genomic DNA. In one positive clone, an open reading frame of 948 base pairs corresponded to C. thermocellum ldh gene encoding for the predicted 315-residue protein. The ldh gene was successfully expressed in E. coli FMJ39 (ldh mutant) under the lac promoter. The recombinant enzyme was partially purified from E. coli cell extracts and its kinetic properties were determined. Clostridium thermocellum LDH was shown to catalyze a highly reversible reaction and to be an allosteric enzyme that is activated by fructose-1,6-diphosphate (FDP). For pyruvate, partially purified LDH had Kmand Vmaxvalues of 7.3 mmol/L and 87 µmol/min, respectively, and in the presence of FDP, a 24-fold decrease in Kmand a 5.7-fold increase in Vmaxwere recorded. The enzyme exhibited no marked catalytic activity for lactate in the absence of FDP, whereas Kmand Vmaxvalues were 59.5 mmol/L and 52 µmol/min, respectively, in its presence. The enzyme did not lose activity when incubated at 65 °C for 5 min.Key words: L-lactate dehydrogenase purification, thermophilic bacteria.

[The effect of esafosfina on cerebral circulation in intact and ischemized rat brain]

The physiological metabolite esafosfina (fructose 1,6-diphosphate) influences the cerebral circulation of intact male rats. Injected intravenously in a dose of 250 mg/kg, esafosfina improved both the blood supply to brain and the local blood flow in the parietal region. Under the conditions of global transient cerebral ischemia, the cerebrovascular effect of the drug tends to increase. Esafosfina produced dissimilar changes in the arterial blood level, which could be explained by various basic status of the test animals. The pronounced cerebrovascular activity of esafosfina plays a key role in its neuroprotector effect.

Energy failure in astrocytes increases the vulnerability of neurons to spreading depression

A neuroprotective role of astrocytes has been hypothesized, but the mechanism is debated and in vivo evidence is limited. To test this hypothesis, a sublethal stressor (spreading depression) and fluorocitrate (FC), a selective inhibitor of the astrocytic Krebs cycle, were used in urethane-anaesthetized adult rats. Neuronal damage was assessed 24 h after treatment with silver stain and immunoreactivity for a 72-kDa heat-shock protein. ATP levels and mitochondrial aconitase activity, a marker indicating exposure to reactive oxygen species, were measured after 4 and 24 h. Spreading depression alone did not affect ATP levels, mitochondrial aconitase activity, or induce neuronal injury in the cortex. Local or intraventricular injection of FC significantly decreased ATP levels and mitochondrial aconitase activity, but did not produce neuronal damage. In animals receiving injections of FC and then spreading depression, there was evidence of significant neuronal stress and damage. Isocitrate, which bypasses the metabolic inhibition produced by FC, prevented all of the changes seen after the combination of FC and spreading depression. One-hour pretreatment with dimethyl sulfoxide (a scavenger of hydroxyl radicals), deferoxamine (an iron chelator) or fructose-1,6-bisphosphate also blocked inactivation of mitochondrial aconitase, ATP depletion and the neuronal damage induced by FC and spreading depression. These experiments demonstrate that inhibition of the metabolism of astrocytes, with a decrease in ATP levels, will increase the susceptibility of neurons to the stress induced by spreading depression. The neuroprotective effects of dimethyl sulfoxide, deferoxamine and fructose-1,6-bisphosphate suggest that oxidative stress contributes to the neurotoxicity in this situation.

Protective effects of exogenous fructose-1,6-biphosphate during small bowel transplantation in rats

BACKGROUND

We assessed the effect of adding exogenous fructose-1,6-biphosphate (F16BP) to the preservation solution (University of Wisconsin storage solution) used during an experimental procedure of small bowel transplantation in rats.

METHODS

We studied levels of the nucleotides hypoxanthine/xanthine and adenosine in tissue after cold ischemia, as well as histologic changes and associated deleterious processes such as bacterial translocation produced by the reperfusion associated with the transplantation.

RESULTS

The groups of rats treated with F16BP showed the lowest levels of hypoxanthine/xanthine and uric acid, the highest levels of adenosine, and the lowest levels of histologic damage and lactate dehydrogenase release to the bloodstream. Consumption of intestinal hypoxanthine during reperfusion was lowest in the groups treated with F16BP, as was the incidence of bacterial translocation.

CONCLUSIONS

This study shows a protective effect of exogenous F16BP added to University of Wisconsin solution during experimental intestinal transplantation in rats. This protective effect, reflected by decreased intestinal damage and bacterial translocation, was related to a decrease in adenosine triphosphate depletion during cold ischemia before intestinal transplantation, and to the reduced availability of xanthine oxidase substrates for free radical generation during reperfusion.

A potential role for fructose-2,6-bisphosphate in the stimulation of hepatic glucokinase gene expression

The effects of fructose-2,6-bisphosphate (F-2,6-P(2)) on hepatic glucokinase (GK) and glucose-6-phosphatase (G-6-Pase) gene expression were investigated in streptozotocin-treated mice, which exhibited undetectable levels of insulin. Hepatic F-2,6-P(2) levels were manipulated by adenovirus-mediated overexpression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. Streptozotocin treatment alone or with infusion of control adenovirus leads to a dramatic decrease in hepatic F-2,6-P(2) content compared with normal nondiabetic mice. This is accompanied by a 14-fold decrease in GK and a 3-fold increase in G-6-Pase protein levels, consistent with a diabetic phenotype. Streptozotocin-treated mice that were infused with adenovirus-overexpressing an engineered 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase with high kinase activity and little bisphosphatase activity showed high levels of hepatic F-2,6-P(2). Surprisingly, these mice had a 13-fold increase in GK protein and a 2-fold decrease in G-6-Pase protein compared with diabetic controls. The restoration of GK is associated with increases in the phosphorylation of Akt upon increasing hepatic F-2,6-P(2) content. Moreover, the changes in levels of F-2,6-P(2) and Akt phosphorylation revealed a pattern similar to that of streptozotocin mice treated with insulin, indicating that increasing hepatic content of F-2,6-P(2) mimics the action of insulin. Because G-6-Pase gene expression was down-regulated only after the restoration of euglycemia, the effect of F-2,6-P(2) was indirect. Also, the lowering of blood glucose by high F-2,6-P(2) was associated with an increase in hepatic nuclear factor 1-alpha protein, a transcription factor involved in G-6-Pase gene expression. In conclusion, F-2,6-P(2) can stimulate hepatic GK gene expression in an insulin-independent manner and can secondarily affect G-6-Pase gene expression by lowering the level of plasma glucose.

Inhibition of fructose-1,6-bisphosphatase by a new class of allosteric effectors

A highly constrained pseudo-tetrapeptide (OC252-324) further defines a new allosteric binding site located near the center of fructose-1,6-bisphosphatase. In a crystal structure, pairs of inhibitory molecules bind to opposite faces of the enzyme tetramer. Each ligand molecule is in contact with three of four subunits of the tetramer, hydrogen bonding with the side chain of Asp187 and the backbone carbonyl of residue 71, and electrostatically interacting with the backbone carbonyl of residue 51. The ligated complex adopts a quaternary structure between the canonical R- and T-states of fructose-1,6-bisphosphatase, and yet a dynamic loop essential for catalysis (residues 52-72) is in a conformation identical to that of the T-state enzyme. Inhibition by the pseudo-tetrapeptide is cooperative (Hill coefficient of 2), synergistic with both AMP and fructose 2,6-bisphosphate, noncompetitive with respect to Mg2+, and uncompetitive with respect to fructose 1,6-bisphosphate. The ligand dramatically lowers the concentration at which substrate inhibition dominates the kinetics of fructose-1,6-bisphosphatase. Elevated substrate concentrations employed in kinetic screens may have facilitated the discovery of this uncompetitive inhibitor. Moreover, the inhibitor could mimic an unknown natural effector of fructose-1,6-bisphosphatase, as it interacts strongly with a conserved residue of undetermined functional significance.

Effects of n-3 fatty acid, fructose-1, 6-diphosphate and glutamine on mucosal cell proliferation and apoptosis of small bowel graft after transplantation in rats

AIM: To evaluate the effects of n-3 fatty acids (n-3FA), fructose-1, 6-diphosphate (FDP) and glutamine (GLN) on mucosal cell proliferation and apoptosis of small bowel graft.

METHODS: One hundred and ninety-six inbred strain Wistar rats were grouped as donors and recipients, and underwent heterotopic small bowel transplantation (SBT). n-3FA, FDP and GLN were administered via gastric tube as well as venous infusion for 10 d before and after surgery, respectively. The proliferation and apoptosis of mucosal cells were analyzed with flow cytometry and in situ cell death detection kits.

RESULTS: Apparent apoptosis and minor proliferation of mucosal cells of small bowel graft after transplantation were observed. A higher mucosal cell proliferative index and lower apoptotic index were found in all small bowel grafts after supplying with n-3FA, FDP and GLN.

CONCLUSION: Nutritional support with n-3FA, FDP and GLN promotes mucosal cell proliferation significantly, and prevents mucosal cell from undergoing apoptosis with different degrees. These regulatory effects on the apoptosis alter the structure and absorption function of transplanted small bowel favorably.

Regulation and mutational analysis of the HPr kinase/phosphorylase from Bacillus subtilis

In most Gram-positive bacteria, catabolite repression is mediated by a bifunctional enzyme, the HPr kinase/phosphorylase (HprK/P). It has recently been shown that HprK/P could catalyze the phosphorylation of the protein HPr by using pyrophosphate (PP(i)) as a phosphate donor instead of ATP. Here we showed that, as for ATP, PP(i) binds to the enzyme with strong positive cooperativity. However, in contrast to ATP, PP(i) binding does not modify the fluorescence properties of the unique Trp residue of Bacillus subtilis HprK/P. In addition, to understand how two conserved motifs, namely, the P-loop and the specific signature of this family, participate in the three enzymatic activities of HprK/Ps (ATP-kinase, PP(i)-kinase, and phosphorylase), several site-directed mutants were generated. Whereas the three activities are mediated by the P-loop which is directly involved in the binding of ATP, PP(i), or Pi, the signature motif seems to be involved preferentially in the dephosphorylation reaction. On the basis of these results, we propose a model in which the binding of the allosteric activator FBP induces a conformational change of a central loop located above the active site of HprK/P, thereby allowing the ATP binding. However, this conformational change is not required for the binding of PP(i).

Identification of a nerve ending-enriched 29-kDa protein, labeled with [3-32P]1,3-bisphosphoglycerate, as monophosphoglycerate mutase: inhibition by fructose-2,6-bisphosphate via enhancement of dephosphorylation

Glucose metabolism is of vital importance in normal brain function. Evidence indicates that glycolysis, in addition to production of ATP, plays an important role in maintaining normal synaptic function. In an effort to understand the potential involvement of a glycolytic intermediate(s) in synaptic function, we have prepared [3-32P]1,3-bisphosphoglycerate and [32P]3-phosphoglycerate and sought their interaction with a specific nerve-ending protein. We have found that a 29-kDa protein is the major component labeled with either [3-32P]1,3-bisphosphoglycerate or [32P]3-phosphoglycerate. The protein was identified as monophosphoglycerate mutase (PGAM). This labeling was remarkably high in the brain and synaptosomal cytosol fraction, consistent with the importance of glycolysis in synaptic function. Of interest, fructose-2,6-bisphosphate (Fru-2,6-P2) inhibited PGAM phosphorylation and enzyme activity. Moreover, Fru-2,6-P2 potently stimulated release of [32P]phosphate from the 32P-labeled PGAM (EC50 = 1 microM), suggesting that apparent reduction of PGAM phosphorylation and enzyme activity by Fru-2,6-P2 may be due to stimulation of dephosphorylation of PGAM. The significance of these findings is discussed.

Characterization of myoglobin toxicity in renal cortical slices from Fischer 344 rats

Rhabdomyolysis is associated with acute renal failure. The following study first characterized myoglobin in vitro toxicity using renal cortical slices isolated from male Fischer 344 rats. This model provided interaction between various cells within the nephron and provides myoglobin access predominantly through the basolateral membrane. Second, this study examined the effect of deferoxamine (DFX) and glutathione on myoglobin toxicity to determine the role of radicals and iron. Renal cortical slices were incubated for 30-120 min with 0, 4, 10 or 12 mg/ml myoglobin. Myoglobin was pretreated with 4 mM ascorbic acid prior to addition to the slices to ensure that myoglobin was in its reduced state. In other experiments tissues were pretreated for 15 min with 0.1 mM of the iron chelator DFX or 30 min with 1 mM glutathione prior to co-incubation with myoglobin. Finally, slices were pretreated with 1 mM glutathione for 30 min, rinsed and incubated only with myoglobin. Early event changes occurred within a 60 min exposure and included a decline in pyruvate-stimulated gluconeogenesis, increased lipid peroxidation levels and decreased glutathione levels. Loss of ATP levels and increased lactate dehydrogenase (LDH) release required a 120 min exposure to myoglobin. DFX reduced myoglobin induced effects on LDH leakage but had no effect on gluconeogenesis suggesting that myoglobin toxicity had an iron dependent (LDH) and independent (gluconeogenesis) pathway. Pretreatment with glutathione provided complete protection and was mediated by intracellular events.

Using fructose-1,6-diphosphate during hypothermic rabbit-heart preservation: a high-energy phosphate study

BACKGROUND

In this study, we evaluated the effects of fructose-1,6-diphosphate (FDP) on high-energy phosphate metabolism during 18-hour hypothermic rabbit-heart preservation.

METHODS

Under general anesthesia and artificial ventilation, hearts from 42 adult New Zealand white rabbits were harvested, flushed, and preserved in St. Thomas solution at 4(o)C for 18 hours. In the study group (n = 15), FDP (5 mmol/liter) was added to the St. Thomas solution, whereas in the control group (n = 17), fructose (5 mmol/liter) was added. Another 10 hearts did not undergo hypothermic storage, but were used as the normal group for high-energy phosphate concentration comparison.

RESULTS

After 18 hours of hypothermic preservation, myocardial high-energy phosphate content decreased in both preservation groups. In the study group, left ventricular adenosine triphosphate (ATP) content was 33% of that in the normal hearts, but in the control group, ATP decreased to 14% of normal. Adenosine diphosphate (ADP) content, energy charge, and ATP-to-ADP ratio showed similar decreases. The high-energy phosphate profile (content in the atria and ventricles and the ratio of ATP to ADP to AMP) was maintained in the study group but not in the control group. High-energy phosphate metabolites such as inosine monophosphate (IMP), inosine, and hypoxanthine increased in both preservation groups, but the increase was more prominent in the control group.

CONCLUSION

Adding FDP to St. Thomas solution attenuated the depletion of high-energy phosphate concentration in the preserved hearts. This difference was especially prominent in the left and right ventricles. The protective effect of FDP during hypothermic heart preservation deserves further study.

Effects of sodium magnesium fructose diphosphate on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome

AIM

To study the effects of sodium magnesium fructose diphosphate (SMFD) on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome, so as to explore the protective mechanisms of SMFD on cerebral ischemia.

METHODS

The synaptosomes from normal rat brain were prepared by phase partition and cultured with oxygen-glucose deprivation to establish ischemic synaptosome model. The intrasynaptosomal free calcium concentration and nitric oxide synthase activity were detected separately after the synaptosomes were co-incubated with SMFD (1.3 mmol.L-1) or fructose-1, 6-diphosphate (FDP, 4.0 mmol.L-1) for 60 min.

RESULTS

SMFD decreased the free calcium concentration and reduced the activity of nitric oxide synthase (NOS) of ischemic synaptosomes. Its effects were more powerful than those of FDP.

CONCLUSION

SMFD may protect neurons from ischemic injury by preventing intracellular Ca2+ overload and inhibiting the activity of nitric oxide synthase.

Effects of fructose-1,6-bisphosphate on morphological and functional neuronal integrity in rat hippocampal slices during energy deprivation

D-fructose-1,6-bisphosphate, a high energy glycolytic intermediate, attenuates ischemic damage in a variety of tissues, including brain. To determine whether D-fructose-1,6-bisphosphate serves as an alternate energy substrate in the CNS, rat hippocampal slices were treated with D-fructose-1,6-bisphosphate during glucose deprivation. Unlike pyruvate, an endproduct of glycolysis, 10 mM D-fructose-1,6-bisphosphate did not preserve synaptic transmission or morphological integrity of CA1 pyramidal neurons during glucose deprivation. Moreover, during glucose deprivation, 10-mM D-fructose-1,6-bisphosphate failed to maintain adenosine triphosphate levels in slices. D-fructose-1,6-bisphosphate, however, attenuated acute neuronal degeneration produced by 200 microM iodoacetate, an inhibitor of glycolysis downstream of D-fructose-1,6-bisphosphate. Because (5S, 10R)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine, an antagonist of N-methyl-D-aspartate receptors, exhibited similar protection against iodoacetate damage, we examined whether (5S, 10R)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine and D-fructose-1,6-bisphosphate share a common neuroprotective mechanism. Indeed, D-fructose-1,6-bisphosphate diminished N-methyl-D-aspartate receptor-mediated synaptic responses and partially attenuated neuronal degeneration induced by 100-microM N-methyl-D-aspartate. Taken together, these results indicate that D-fructose-1,6-bisphosphate is unlikely to serve as an energy substrate in the hippocampus, and that neuroprotective effects of D-fructose-1,6-bisphosphate are mediated by mechanisms other than anaerobic energy supply.

Characterization of myoglobin toxicity in renal cortical slices from Fischer 344 rats

Rhabdomyolysis is associated with acute renal failure. The following study first characterized myoglobin in vitro toxicity using renal cortical slices isolated from male Fischer 344 rats. This model provided interaction between various cells within the nephron and provides myoglobin access predominantly through the basolateral membrane. Second, this study examined the effect of deferoxamine (DFX) and glutathione on myoglobin toxicity to determine the role of radicals and iron. Renal cortical slices were incubated for 30-120 min with 0, 4, 10 or 12 mg/ml myoglobin. Myoglobin was pretreated with 4 mM ascorbic acid prior to addition to the slices to ensure that myoglobin was in its reduced state. In other experiments tissues were pretreated for 15 min with 0.1 mM of the iron chelator DFX or 30 min with 1 mM glutathione prior to co-incubation with myoglobin. Finally, slices were pretreated with 1 mM glutathione for 30 min, rinsed and incubated only with myoglobin. Early event changes occurred within a 60 min exposure and included a decline in pyruvate-stimulated gluconeogenesis, increased lipid peroxidation levels and decreased glutathione levels. Loss of ATP levels and increased lactate dehydrogenase (LDH) release required a 120 min exposure to myoglobin. DFX reduced myoglobin induced effects on LDH leakage but had no effect on gluconeogenesis suggesting that myoglobin toxicity had an iron dependent (LDH) and independent (gluconeogenesis) pathway. Pretreatment with glutathione provided complete protection and was mediated by intracellular events.

Regulation of the central glycolytic genes in Bacillus subtilis: binding of the repressor CggR to its single DNA target sequence is modulated by fructose-1,6-bisphosphate

Glycolysis is one of the best and widely conserved general metabolic pathways. Bacillus subtilis enzymes catalysing the central part of glycolysis, gathering the steps of interconversion of the triose phosphates from dihydroxyacetone-phosphate to phosphoenolpyruvate, are encoded by five genes, gapA, pgk, tpi, pgm and eno. They are transcribed in a hexacistronic operon together with cggR, the first cistron, encoding the repressor of this gapA operon. Using deletion analysis, we have localized the CggR operator between the promoter and the first gene of the operon. CggR was purified and used in gel mobility shift assays and DNase I footprinting experiments to delimit its target sequence. Site-directed mutagenesis and in vivo tests demonstrated that it consists of two direct-repeats (CGGGACN6TGTCN4CGGGACN6TG TC). Sequence analysis and transcriptome comparison of a wild-type and a cggR mutant strain strongly suggested that CggR regulates only the gapA operon. The presence of glycolytic carbon sources induces expression of the gapA operon. Genetic experiments allowed us to identify the metabolic steps required for the formation of the CggR effector. In vitro experiments with the suggested candidates allowed us to demonstrate that fructose-1,6-biphosphate (FBP) acts as an inhibitor of CggR DNA-binding activity (10 mM for full inhibition). FBP is thus the major signal for both CcpA-dependent catabolite repression (or activation) and activation of the central glycolytic genes. Genomic sequence comparisons suggest that these results can apply to numerous low-G+C, Gram-positive bacterial species.

Fructose-1,6-bisphosphate for improved outcome after hypothermic circulatory arrest in pigs

OBJECTIVE

Fructose-1,6-bisphosphate is a high-energy intermediate in the anaerobic metabolism. It enhances glycolysis, preserves cellular adenosine triphosphate, and prevents the increase of intracellular calcium during ischemia. The potential neuroprotective effect of fructose-1,6-bisphosphate during hypothermic circulatory arrest was evaluated in a surviving porcine model.

METHODS

Twenty-four pigs were randomly assigned to receive two intravenous infusions of either fructose-1,6-bisphosphate (500 mg/kg) or saline solution. The first infusion was given immediately before a 75-minute period of hypothermic circulatory arrest and the second was given immediately after hypothermic circulatory arrest.

RESULTS

The 7-day survivals were 83.3% in the fructose-1,6-bisphosphate group and 41.7% in the control group (P =.09). The treated animals had significantly better postoperative behavioral scores. The administration of fructose-1,6-bisphosphate was associated with higher venous phosphate and sodium levels, lower venous ionized calcium levels, higher blood osmolarity, and a better fluid balance. Intracranial pressure and venous creatine kinase isoenzyme MB were significantly lower in the fructose-1,6-bisphosphate group during rewarming (P =.01 and P =.001, respectively). Among the treated animals, brain glucose, pyruvate and lactate levels tended to be higher, brain glycerol levels tended to be lower, and the histopathologic score of the brain was significantly lower (P =.04).

CONCLUSIONS

Intravenous administration of fructose-1,6-bisphosphate at 500 mg/kg before and after hypothermic circulatory arrest in a surviving porcine model was associated with better survival, behavioral outcome, and histopathologic score. The observed lower blood creatine kinase isoenzyme MB and brain glycerol levels and the higher brain glucose, pyruvate, and lactate levels in the fructose-1,6-bisphosphate group suggest that this drug has supportive effects on myocardial and brain metabolisms.

Fructose-1,6-biphosphate prevents excitotoxic neuronal cell death in the neonatal mouse brain

The excitotoxic cascade may represent an important pathway leading to brain damage and cerebral palsy. Brain lesions induced in newborn mice by ibotenate (acting on N-methyl-D-aspartate receptors) and by S-bromowillardiine (acting on alpha-3-amino-hydroxy-5-methyl-4-isoxazole propionic acid and kainate receptors) mimic some aspects of white matter cysts and transcortical necrosis observed in human perinatal brain damage. Fructose 1,6-biphosphate (FBP) is a high-energy glycolytic pathway intermediate which, in therapeutic doses, is non-toxic and neuroprotective in hypoxic-ischemic models of brain injury. Mechanisms of action include modulation of intracellular calcium through phospholipase C (PLC) activation. The goal of this study was to determine the neuroprotective effects of FBP in a mouse model of neonatal excitotoxic brain injury. Mice that received intraperitoneal FBP had a significant reduction in size of ibotenate-induced (80% reduction) or S-bromowillardiine-induced (40% reduction) cortical plate lesions when compared with control animals. Studies of fragmented DNA and cleaved caspase 3 confirmed the survival promoting effects of FBP. FBP had no detectable effect on excitotoxic white matter lesions. The effects of FBP were antagonized by co-administration of PLC, protein kinase C or mitogen-associated protein kinase inhibitors but not by protein kinase A inhibitor. A moderate, transient cooling of pups immediately after the insult extended the therapeutic window for FBP, as FBP administered 24 h after ibotenate was still significantly neuroprotective in these pups. This data extends the neuroprotective profile of FBP in neonatal brain injury and identifies gray matter lesions involving N-methyl-D-aspartate receptors as a major target for this promising drug.

Immunomodulatory effect of fructose-1,6-bisphosphate on T-lymphocytes

Sepsis remains an important and life-threatening problem, and is the most common cause of death in the intensive care unit. One promising therapeutic candidate for protection against injury in sepsis is fructose-1,6-bisphosphate (FBP), a high-energy glycolytic pathway intermediate. The objective of the study was to establish a role for FBP on the immune system, especially in lymphocyte proliferation. Peripheral blood mononuclear cells (PBMCs) were isolated from the blood of healthy humans by gradient centrifugation. T-lymphocytes were stimulated for 96 h with phytohemagglutinin (PHA) and varying concentration of FBP. Fructose-1,6-bisphosphate at concentrations between 1.2 and 10 mM decreased proliferation of T-lymphocytes and reduced the viability only at concentrations 5.0 and 10 mM. The levels of soluble IL-2 receptor were reduced at FBP concentrations between 1.2 and 10 mM. In conclusion, this study demonstrates that FBP has important effect on immunomodulatory and this result can be correlated with the protection against injury in sepsis.

Fructose-1,6-bisphosphate preserves intracellular glutathione and protects cortical neurons against oxidative stress

Fructose-1,6-bisphosphate (FBP), an endogenous intermediate of glycolysis, protects the brain against ischemia-reperfusion injury. The mechanisms of FBP protection after cerebral ischemia are not well understood. The current study was undertaken to determine whether FBP protects primary neurons against hypoxia and oxidative stress by preserving reduced glutathione (GSH). Cultures of pure cortical neurons were subjected to oxygen deprivation, a donor of nitric oxide and superoxide radicals (3-morpholinosydnonimine), an inhibitor of glutathione synthesis (L-buthionine-sulfoximine) or glutathione reductase (1,3-bis(2-chloroethyl)-1-nitrosourea) in the presence or absence of FBP (3.5 mM). Neuronal viability was determined using an 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. FBP protected neurons against hypoxia-reoxygenation and oxidative stress under conditions of compromised GSH metabolism. The efficacy of FBP depended on duration of hypoxia and was associated with higher intracellular GSH concentration, an effect partly mediated via increased glutathione reductase activity.

Fructose-1,6-biphosphate and nucleoside pool modifications prevent neutrophil accumulation in the reperfused intestine

Fructose-1,6-biphosphate (F16BP) attenuates ischemia/reperfusion (I/R) injury by inhibiting microvascular leukocyte adhesion or reducing neutrophil-derived oxygen free-radical production, but the causes of this action, the mechanisms in vivo, and the possible implication of nucleoside pool modifications are still controversial issues. We explored whether F16BP's inhibition of free-radical production and neutrophil recruitment is a result of its effect on adenosine (Ado) accumulation during intestinal I/R injury. The effects of F16BP administration were tested on the nucleotide/nucleoside metabolism at the end of the ischemic period and on microvascular neutrophil recruitment and free-radical production after reperfusion in vivo, in the presence or absence of Ado deaminase (ADA). Infusion of F16BP markedly increased endogenous Ado, decreased xanthine accumulation during the ischemic period, and inhibited neutrophil recruitment and subsequent neutrophil free-radical generation during reperfusion. Administration of ADA reversed these processes. The results provide strong evidence that F16BP prevents neutrophil accumulation and neutrophil free-radical generation during intestinal I/R by a key mechanism that modifies the nucleoside pool, leading to an endogenous accumulation of Ado and to a reduction of xanthine during ischemia.

Activation of the neuroprotective ERK signaling pathway by fructose-1,6-bisphosphate during hypoxia involves intracellular Ca2+ and phospholipase C

The mechanism of the neuroprotective action of the glycolytic pathway intermediate fructose-1,6-bisphosphate (FBP) may involve activation of a phospholipase-C (PLC) dependent MAP kinase signaling pathway. In this study, we determined whether FBP's capacity to decrease delayed cell death in hippocampal slice cultures is dependent on PLC signaling or activation of the intracellular Ca(2+)-MEK/ERK neuroprotective signaling cascade. FBP (3.5 mM) reduced delayed death from oxygen/glucose deprivation in CA1, CA3 and dentate neurons in slice cultures. The phospholipase-C inhibitor U73122 and the MEK1/2 inhibitor U0126 prevented this protection. In hippocampal and cortical neurons, FBP increased phospho-ERK1/2 (p42/44) immunostaining during hypoxic, but not normoxic conditions. Increased phospho-ERK immunostaining was dependent on PLC and also on MEK 1/2, an upstream regulator of ERK. Further, we found that FBP enhancement of phospho-ERK immunostaining depended on [Ca(2+)](i): PLC inhibition and the IP(3) receptor blocker xestospongin C prevented FBP from increasing [Ca(2+)](i) and increasing phospho-ERK levels. However, while FBP-induced increases in [Ca(2+)](i) were blocked by xestospongin and a PLC inhibitor, [Ca(2+)](i) increases induced by the neuroprotective growth factor BDNF were not prevented. We conclude that during hypoxia FBP initiates a series of neuroprotective signals which include PLC activation, small increases in [Ca(2+)](i), and increased activity of the MEK/ERK signaling pathway.

Glucose metabolites inhibit protein phosphatases and directly promote insulin exocytosis in pancreatic beta-cells

In human type 2 diabetes mellitus, loss of glucose-sensitive insulin secretion is an early pathogenetic event. Glucose is the cardinal physiological stimulator of insulin secretion from the pancreatic beta-cell, but the mechanisms involved in glucose sensing are not fully understood. Specific ser/thr protein phosphatase (PPase) inactivation by okadaic acid promotes Ca(2+) entry and insulin exocytosis in the beta-cell. We now show that glycolytic and Krebs cycle intermediates, whose concentrations increase upon glucose stimulation, not only dose dependently inhibit ser/thr PPase enzymatic activities, but also directly promote insulin exocytosis from permeabilized beta-cells. Thus, fructose-1,6-bisphosphate, phosphoenolpyruvate, 3-phosphoglycerate, citrate, and oxaloacetate inhibit PPases and significantly enhance insulin exocytosis, nonadditive to that of okadaic acid, at micromolar Ca2+ concentrations. In contrast, the effect of GTP is potentiated by okadaic acid, suggesting that the action of GTP does not require PPase inactivation. We conclude that specific glucose metabolites and GTP inhibit beta-cell PPase activities and directly stimulate Ca2+-independent insulin exocytosis. The glucose metabolites, but not GTP, seem to require PPase inactivation for their stimulatory effect on exocytosis. Thus, an increase in phosphorylation state, through inhibition of protein dephosphorylation by metabolic intermediates, may be a novel regulatory mechanism linking glucose sensing to insulin exocytosis in the beta-cell.

Fructose-1,6-diphosphate attenuates prostaglandin E2 production and cyclo-oxygenase-2 expression in UVB-irradiated HaCaT keratinocytes

1. Fructose-1,6-diphosphate (FDP), a glycolytic metabolite, is reported to ameliorate inflammation and inhibit the nitric oxide production in murine macrophages stimulated with endotoxin. It is also reported that FDP has cytoprotective effects against hypoxia or ischaemia/reperfusion injury in brain and heart. However, underlying mechanisms of its various biological activities are not completely understood. 2. In this study, we examined the effects of FDP on UVB-induced prostaglandin production in HaCaT keratinocytes. 3. Ultraviolet B (UVB, 280-320 nm) irradiation (30 mJ cm(-2)) increased prostaglandin E(2)(PGE(2)) production, which was significantly decreased by FDP in a concentration dependent manner. NS-398, a cyclo-oxygenase-2 (COX-2) selective inhibitor completely inhibited UVB-induced PGE(2) production showing that COX-2 activity is responsible for the increase in PGE(2) production under our experimental conditions. 4. UVB irradiation increased total COX activity and COX-2 mRNA in HaCaT keratinocytes, which were significantly blocked by FDP in a concentration dependent manner. 5. N-acetylcysteine (NAC) significantly attenuated UVB-induced PGE(2) production, COX activity and COX-2 mRNA expression indicating oxidative components might contribute to these events. 6. FDP reduced UVB-induced increase in cellular reactive oxygen species (ROS) level although it did not show direct radical scavenging effect in the experiment using 1,1-diphenyl-2picrylhydrazil (DPPH). FDP preserved the cellular antioxidant capacity including catalase activity and GSH content after irradiation. 7. Our data obtained hitherto suggest that FDP may have a protective role in UVB-injured keratinocyte by attenuating PGE(2) production and COX-2 expression, which are possibly through blocking intracellular ROS accumulation.

Fructose-1,6-Bisphosphate inhibits excess activation of Kupffer cell function induced by endotoxin

The effect and mechanism of action of fructose-1,6-bisphosphate (FBP) on Kupffer cell activation were studied in vitro. Kupffer cell was activated by isolation procedure alone from the hepatic tissue. In cultured rat Kupffer cells stimulated by endotoxin, treatment with 5-20 mM FBP not only preserved phagocytic activity, but also inhibited secretion of cytokines (tumor necrosis factor-a and interleukin-1beta) and production of nitric oxide (NOx). Moreover, treatment with 10 mM FBP suppressed the elevation in the intracellular Ca2+ concentration on Kupffer cells stimulated by phorbol 12-myristate 13-acetate, which suggested that this effect may be one of the agents that limit the activation of Kupffer cells. The administration of FBP was effective in the prevention of endotoxin-induced hepatopathy, and we suggest that this may have useful clinical applications.

Storage solution containing fructose-1,6-bisphosphate inhibits the excess activation of Kupffer cells in cold liver preservation

BACKGROUND

In liver transplantation, the activation of Kupffer cells at the time of cold preservation and reperfusion is considered to play an important role. In the present study, the usefulness of cold storage solution containing fructose-1,6-bisphosphate (FBP) was compared with University of Wisconsin (UW) solution in the function of Kupffer cells.

METHODS

Kupffer cells were separated from rat liver stored at 4 degrees C in each storage solution. Four kinds of storage solutions were used: UW, simplified UW without FBP (0-FBP), and solutions with 10 or 20 mM FBP (10-FBP, 20-FBP). Lipopolysaccharide (LPS) labeled by fluorescein was loaded after 12 or 24 hr of cold preservation in each solution. The rates of cells uptaking LPS as phagocytic ability were measured using flow cytometry. Tumor necrosis factor-alpha, cytokine-induced neutrophil chemoattractant, and nitric oxide (NO) were measured in the supernatant.

RESULTS

Tumor necrosis factor-alpha values in the 20-FBP group were significantly lower than those in the UW group. Cytokine-induced neutrophil chemoattractant values at 60 min after loading LPS were significantly lower in the 20-FBP group than in the UW group. NO values at 24 hr after loading LPS were significantly lower in the 20-FBP group compared with the UW group. The 20-FBP group was highest in the rates of cells uptaking LPS after 24-hr cold preservation.

CONCLUSIONS

The storage solution containing FBP controlled the secretion of cytokines and NO from Kupffer cells and maintained phagocytic ability. This solution was considered to be more useful than UW solution for Kupffer cell protection.