Physiopathological studies in septic rats and the use of fructose 1,6-bisphosphate as cellular protection

1, 6-dilauroyl-D-fructofuranose ameliorates lipopolysaccharide-induced septic acute kidney injury via inhibiting caspase 1 mediated pyroptosis formation in rat

BACKGROUND

Sepsis is a systemic inflammatory state associated with acute kidney injury (AKI) and high mortality. However, sepsis-induced AKI cannot be effectively prevented or treated using current antimicrobial therapies and supportive measures. We explored the therapeutic effect of newly developed fructose esters on sepsis-induced AKI (S-AKI).

METHODS

We used the surface plasmon resonance technique and ultrasensitive chemiluminescence analyzer to characterize the lipopolysaccharide (LPS)/endotoxin binding activity and antioxidant capability of fructose esters. We assessed the extent of fructose ester gastrointestinal digestion using rat intestinal acetone powder. We examined the therapeutic effect of fructose esters on LPS-induced S-AKI by evaluating the blood and renal reactive oxygen species (ROS) amounts, caspase 1 mediated pyroptosis, inflammation, microcirculation, and renal dysfunction.

RESULTS

Our data showed that the fructose esters are not easily hydrolyzed by the rat intestinal acetone powder, suggesting their high stability in the gastrointestinal tract. 1,6-dilauroyl-D-fructofuranose (FDL) dose-dependently scavenged H2O2 and displayed a higher binding affinity to LPS compared to sialic acid and fructose did. LPS significantly enhanced caspase 1 mediated pyroptosis and increased leukocyte infiltration, blood and renal ROS amount, and blood urea nitrogen (BUN) and creatinine level, whereas FDL significantly depressed these LPS-enhanced parameters. In addition, the increased plasma inflammatory cytokines levels using LPS could be reduced by intravenous fructose ester FDL treatment.

CONCLUSION

Our data suggest that FDL, with its antioxidant activity against H2O2, can neutralize LPS toxicity using a high binding affinity, and attenuate S-AKI by inhibiting caspase 1 mediated pyroptosis, thereby ameliorating renal oxidative stress and dysfunction.

Fish Oil - Omega-3 Exerts Protective Effect in Oxidative Stress and Liver Dysfunctions Resulting from Experimental Sepsis

Background

Sepsis is a severe global health problem, with high morbidity and mortality. In sepsis, one of the main affected organs is the liver. Hepatic alterations characterize a negative prognostic. Omega-3 fatty acids (ω3), eicosapentaenoic acid, and docosahexaenoic acid, are part of the main families of polyunsaturated fatty acids. ω3 has been used in studies as sepsis treatment and as a treatment for non-alcoholic liver disease.

Aim

We aimed to evaluate the effects of treatment with fish oil (FO) rich in ω3 on liver changes and damage resulting from experimental sepsis.

Methodology

A model of severe sepsis in Wistar rats was used. Oxidative stress in the liver tissue was evaluated by means of tests of thiobarbituric acid reactive substances, 2,7-dihydrodichlorofluorescein diacetate , catalase, and glutathione peroxidase, in the serum TBARS, DCF, thiols and, to assess liver dysfunction, alanine aminotransferase and aspartate aminotransferase. Hepatic tissue damage was evaluated using H&E histology.

Results

In assessments of oxidative stress in liver tissue, a protective effect was observed in the tests of TBARS, DCF, CAT, and GPx, when compared the sepsis versus sepsis+ω3 groups. Regarding the oxidative stress in serum, a protective effect of treatment with ω3 was observed in the TBARS, DCF, and thiols assays, in the comparison between the sepsis and sepsis+ω3 groups. ω3 had also a beneficial effect on biochemical parameters in serum in the analysis of ALT, creatinine, urea, and lactate, observed in the comparison between the sepsis and sepsis+ω3 groups.

Conclusion

The results suggest ω3 as a liver protector during sepsis with an antioxidant effect, alleviating injuries and dysfunctions.

Octyl gallate decrease lymphocyte activation and regulates neutrophil extracellular traps release

BACKGROUND

Inflammation is a complex mechanism with an objective to destroy and eliminate the invading microorganisms. During acute inflammation, the neutrophils are the major cells involved in this process and, although they defend the organism, must die to not generate damage. The two major mechanisms that drive neutrophils to death are: apoptosis and a novel mechanism recently discovered denominated NETosis. This process is a "suicidal mechanism", in which the cells release "neutrophil extracellular traps" (NETs) during the inflammatory response. Octyl gallate (OG) is one of the gallic acid derivates, with several protective effects, such as antioxidant and anti-inflammatory in cancer models. Thus, this study aimed to investigate the action of OG on the proliferation of lymphocytes, neutrophils activation, and its effectiveness in an experimental sepsis model.

METHODS

Lymphocytes and neutrophils were obtained from healthy donors. Cell viability, apoptosis, NETs release and antioxidant capacity of OG were observed. In addition, survival was evaluated in an experimental model of sepsis in C57BL/6 mice.

RESULTS

Our study demonstrated, for the first time, that the OG can act as an inhibitor of reactive oxygen species (ROS) release, NETs formation in primary human neutrophils and, modulates the lipopolysaccharide (LPS) effect in neutrophil apoptosis. The OG also inhibited peripheral blood mononuclear cells (PBMCs) proliferation in vitro. Despite the positive results, we did not observe an increase in the survival of septic animals.

CONCLUSIONS

The pharmacological potential of OG, modulating activation of neutrophils and lymphocytes, suggests the use as an adjuvant therapeutic strategy in inflammatory diseases.

Sepsis-Associated Encephalopathy: from Pathophysiology to Progress in Experimental Studies

Sepsis is an organ dysfunction caused by an uncontrolled inflammatory response from the host to an infection. Sepsis is the main cause of morbidity and mortality in intensive care units (ICU) worldwide. One of the first organs to suffer from injuries resulting from sepsis is the brain. The central nervous system (CNS) is particularly vulnerable to damage, mediated by inflammatory and oxidative processes, which can cause the sepsis-associated encephalopathy (SAE), being reported in up to 70% of septic patients. This review aims to bring a summary of the main pathophysiological changes and dysfunctions in SAE, and the main focuses of current experimental studies for new treatments and therapies. The pathophysiology of SAE is complex and multifactorial, combining intertwined processes, and is promoted by countless alterations and dysfunctions resulting from sepsis, such as inflammation, neuroinflammation, oxidative stress, reduced brain metabolism, and injuries to the integrity of the blood-brain barrier (BBB). The treatment is limited once its cause is not completely understood. The patient's sedation is far to provide an adequate treatment to this complex condition. Studies and experimental advances are important for a better understanding of its pathophysiology and for the development of new treatments, medicines, and therapies for the treatment of SAE and to reduce its effects during and after sepsis.

Fructose-1,6-Bisphosphate Prevents Bleomycin-Induced Pulmonary Fibrosis in Mice and Inhibits the Proliferation of Lung Fibroblasts

Pulmonary fibrosis is a specific form of interstitial pneumonia. In addition to the idiopathic cause, it may be caused by drugs such as bleomycin (BLM)-used in the treatment of tumors. Fructose-1,6-bisphosphate (FBP) is a high-energy endogenous glycolytic compound that has antifibrotic, anti-inflammatory, and immunomodulatory effects. The aim of this study was to investigate the effects of FBP on both BLM-induced pulmonary fibrosis in mice and in a human embryonic lung fibroblast (MRC-5) culture system. C57BL/6 mice were divided into four groups: control, FBP, BLM, and BLM plus FBP. A single dose of bleomycin (7.5 U/kg) was administered intratracheally, and survival, body weight, Ashcroft score, and histological analysis were evaluated. Pulmonary function and bronchoalveolar lavage fluid (BALF) were also evaluated after a single dose of bleomycin (1.2 U/kg-intratracheally). Treatment with FBP (500 mg/kg) was given on day 0 intraperitoneally. Fibroblasts (MRC-5 cells) were used to access the effect of FBP in vitro. In vivo, FBP increased the survival rate and reduced body weight loss (BLM vs. BLM plus FBP-p < 0.05). FBP also prevented BLM-induced loss of pulmonary function and decreased BALF inflammatory cells, level of fibrosis, and superficial collagen density (p < 0.05). In vitro, FBP (0.62 and 1.25 mM) had inhibitory activity on MRC-5 cells and was able to induce senescence in fibroblasts. These results showed that FBP has the potential of reducing the toxic effects of BLM and may provide supportive therapy for conventional methods used for the treatment of cancer.

Fructose-1,6-bisphosphate preserves glucose metabolism integrity and reduces reactive oxygen species in the brain during experimental sepsis

Sepsis is one of the main causes of hospitalization and mortality in Intensive Care Units. One of the first manifestations of sepsis is encephalopathy, reported in up to 70% of patients, being associated with higher mortality and morbidity. The factors that cause sepsis-associated encephalopathy (SAE) are still not well known, and may be multifactorial, as perfusion changes, neuroinflammation, oxidative stress and glycolytic metabolism alterations. Fructose-1,6-bisphosphate (FBP), a metabolite of the glycolytic route, has been reported as neuroprotective agent. The present study used an experimental sepsis model in C57BL/6 mice. We used in vivo brain imaging to evaluate glycolytic metabolism through microPET scans and the radiopharmaceutical ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Brain images were obtained before and 12 h after the induction of sepsis in animals with and without FBP treatment. We also evaluated the treatment effects in the brain oxidative stress by measuring the production of reactive oxygen species (ROS), the activity of catalase (CAT) and glutathione peroxidase (GPx), and the levels of fluorescent marker 2'7'-dichlorofluorescein diacetate (DCF). There was a significant decrease in brain glucose metabolism due to experimental sepsis. A significant protective effect of FBP treatment was observed in the cerebral metabolic outcomes. FBP also modulated the production of ROS, evidenced by reduced CAT activity and lower levels of DCF. Our results suggest that FBP may be a possible candidate in the treatment of SAE.

Mesenchymal stem cells decrease lung inflammation during sepsis, acting through inhibition of the MAPK pathway

Background

Sepsis is a severe medical condition that ranks among the top 10 causes of death worldwide and which has permanently high incidence rates. Mesenchymal stem cells (MSCs) have been found to be potent modulators of immune responses. More importantly, there is evidence that MSCs have a beneficial effect on preclinical models of polymicrobial sepsis. However, the changes caused by the MSCs in the effector cells of the host immune system remain unclear.

Methods

A mouse model of sepsis (male C57BL/6 mice) with three experimental groups was used for experiments in vivo: a control group, an untreated septic group, and a septic group treated with MSCs. In vitro experiments were performed using a cell line of pulmonary macrophages (RAW 264.7) co-cultured with MSCs and stimulated with lipopolysaccharide (LPS).

Results

In vivo we demonstrated that treatment with MSCs was able to reduce the expression of cyclooxygenase-2 (COX-2) and nuclear factor kappa B (NF-κB), and thereby decrease the production of inflammatory cytokines. In vitro experiments using a co-culture of macrophages with MSCs showed a decrease in COX-2 and NF-κB, and showed that this reduction was directly related to the ability of MSCs to inhibit phosphorylation of ERK, RSK, and p38, enzymes that belong to the family of mitogen-activated protein kinases (MAPKs).

Conclusions

This study demonstrated that MSCs are able to inhibit the MAPK pathway activation, modulating the inflammatory response during sepsis. This understanding that MSCs can remodel the response of host cells and improve the course of sepsis is essential for developing new treatments for this pathology.

Mesenchymal stem cells cannot affect mRNA expression of toll-like receptors in different tissues during sepsis

OBJECTIVE AND DESIGN

Experimental animal models and human clinical studies support a crucial role for TLRs in infectious diseases. The aim of this study was to test the ability of MSCs, which have immunomodulatory effects, of altering the mRNA expression of toll-like receptors during a experimental model of sepsis in different tissues.

MATERIALS AND METHODS

Three experimental groups (male C57BL/6 mice) were formed for the test: control group, untreated septic group and septic group treated with MSCs (1 × 10⁶ cells/animal). Lungs, cortex, kidney, liver and colon tissue were dissected after 12 h of sepsis induction and TLR2/3/4/9 mRNA were evaluated by RT-qPCR.

RESULTS

We observed a decrease of TLR2 and 9 mRNA expression in the liver of the sepsis group, while TLR3 was decreased in the lung and liver. No change was found between the sepsis group and the sepsis + MSC group.

CONCLUSIONS

In this model of experimental sepsis the MSCs were unable to modify the mRNA expression of the different toll-like receptors evaluated.

Mesenchymal stem cells decrease splenocytes apoptosis in a sepsis experimental model

OBJECTIVE AND DESIGN

Mesenchymal stem cells (MSCs) are potent modulators of immune responses. Sepsis is the association of a systemic inflammatory response with an infection. The aim of this study was to test the ability of MSCs derived from adipose tissue, which have immunomodulatory effects, and to inhibit the septic process in an experimental model of mice.

METHODS

Three experimental groups (male C57BL/6 mice) were formed for the test: control group, untreated septic group and septic group treated with MSCs (1 × 10(6) cells/animal).

RESULTS

In the control group, there were no deaths; in the untreated septic group, the mortality rate was 100 % within 26 h; in the septic group treated with MSCs, the mortality rate reached 40 % within 26 h. The group treated with MSCs was able to reduce the markers of tissue damage in the liver and pancreas. The treated group had a reduction of inflammatory markers. Furthermore, the MSCs-treated group was able to inhibit the increase of apoptosis in splenocytes observed in the untreated septic group.

CONCLUSIONS

Our data showed that MSCs ameliorated the immune response with decrease of inflammatory cytokines and increase anti-inflammatory IL-10; moreover, inhibited splenocytes apoptosis and, consequently, inhibited tissue damage during sepsis.

Fructose-1,6-bisphosphate reduces the mortality in Candida albicans bloodstream infection and prevents the septic-induced platelet decrease

Due to the fact that an increased number of patients have experienced bloodstream infections caused by Candida species and the high mortality of this infection, there is a need for a strategy to reduce this scenery. One possible strategy is the use of new drugs, such as fructose-1,6-bisphosphate (FBP), which is a high-energy glycolytic metabolite and has shown to have therapeutic effects in several pathological conditions such as ischemia, shock, toxic injuries, and bacterial sepsis. The aim of this manuscript was to determine the role of FBP in experimental Candida albicans bloodstream infection. We used mice that were divided into three experimental groups: sham (not induced), bloodstream infection (induced with intratracheal instillation of C. albicans) and FBP (bloodstream infection plus FBP 500 mg/kg i.p.). Blood was taken for assessment of complete hematological profile and cytokine assay (IL-6 and MCP-1). Results of the study demonstrated that mortality decreased significantly in groups that received FBP. All cytokine and hematological indexes of FBP group were similar to bloodstream infection group with exception of platelets count. FBP significantly prevented the decrease in platelets. Taken together, our results demonstrate that FBP prevented the mortality in C. albicans bloodstream infection.

Effect of N-acetylcysteine and fructose-1,6-bisphosphate in the treatment of experimental sepsis

Sepsis is a syndrome caused by uncontrolled systemic inflammatory response of the individual, which represents a serious epidemiological problem worldwide. The aim of this study was to investigate the effect of N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP) in the treatment of experimental sepsis. We used rats that were divided into five experimental groups: normal control (not induced), septic control (induced using a capsule with non sterile fecal content and Escherichia coli), treated with FBP (500 mg/kg i.p.), treated with NAC (150 mg/kg i.p.), and treated with the combination of FBP with NAC. In the group treated with NAC, 16.68% of the mice survived, the FBP reduced the mortality of mice during the acute stage of the disease and increased the animals' survival time in 33.34%, and the combination of drugs had no effect. Our results show that NAC prevented the mortality of animals after septic induction. These data confirm the validity of the use of NAC in the treatment of sepsis. Our data also show that the synergistic action with FBP does not improve the picture.

Bench-to-bedside review: sepsis - from the redox point of view

The pathogenesis of sepsis and its progression to multiple organ dysfunction syndrome and septic shock have been the subject of investigations for nearly half a century. Controversies still exist with regard to understanding the molecular pathophysiology of sepsis in relation to the complex roles played by reactive oxygen species, nitric oxide, complements and cytokines. In the present review we categorise the key turning points in sepsis development and outline the most probable sequence of events leading to cellular dysfunction and organ failure under septic conditions. We have applied an integrative approach in order to fuse current state-of-the-art knowledge about redox processes involving hydrogen peroxide, nitric oxide, superoxide, peroxynitrite and hydroxyl radical, which lead to mitochondrial respiratory dysfunction. Finally, from this point of view, the potential of redox therapy targeting sepsis is discussed.

Lipopolysaccharide (LPS) induction of nitric oxide synthase-2 and cyclooxygenase-2 is impaired in fructose overloaded rats

AIMS

Fructose (F) overload in rats induces metabolic dysfunctions that resemble the human metabolic syndrome. In this paper, we aimed to investigate the response of F overload rats to lipopolysaccharide (LPS) challenge in terms of nitric oxide (NO) production and prostanoids (PR) release.

MAIN METHODS

NO blood steady-state concentration was monitored through the detection of nitrosyl-hemoglobin complexes (NO-Hb) by electronic spin resonance. Production of 6-keto PGF(1)α, PGE(2), PGF(2)α and TXB(2) was measured in aorta and mesenteric beds by HPLC. Western blot analysis was used to examine the changes in the expression levels of NOS-2 and COX-2 in aorta.

KEY FINDINGS

Our results showed that increases in NO circulating steady-state concentration and PR production by aorta and mesenteric beds 6h after LPS administration were significantly attenuated in F overload rats with respect to control animals. Oxidative stress parameters were equally affected in the presence or absence of the F treatment. Aorta protein levels of NOS-2 and COX-2, two enzymes inducible by LPS, were significantly lower in F overload rats with respect to control rats at the end of the treatment (-39% and -61% for NOS-2 and COX-2 respectively).

SIGNIFICANCE

These results suggest that the metabolic alterations established by 15 weeks of F overload should affect the response to LPS challenge due to an attenuation in the induction of NOS-2 and COX-2. This effect would be one of the components contributing to abnormalities in the course of the inflammatory response in other conditions associated to insulin resistance, such as diabetes.

Fructose-1,6-bisphosphate inhibits in vitro and ex vivo platelet aggregation induced by ADP and ameliorates coagulation alterations in experimental sepsis in rats

Sepsis is a systemic response to an infection that leads to a generalized inflammatory reaction. There is an intimate relationship between procoagulant and proinflammatory activities, and coagulation abnormalities are common in septic patients. Pharmaceutical studies have focused to the development of substances that act on coagulation abnormalities and on the link between coagulation and inflammation. Fructose-1,6-bisphosphate (FBP) is a high-energy glycolitic metabolite that in the past two decades has been shown therapeutic effects in great number of pathological situations, including sepsis. The aims of this study were to assess the effects of FBP on platelet aggregation in vitro and ex vivo in healthy and septic rats and evaluate the use of FBP as a treatment for thrombocytopenia and coagulation abnormalities in abdominal sepsis in rat. FBP inhibited platelet aggregation (P < 0.001) in vitro in healthy rats from the smallest dose tested, 2.5 mM, in a dose-dependent manner. The mean effective dose calculated was 10.6 mM. The highest dose tested, 40 mM, completely inhibited platelet aggregation (P < 0.001) induced by ADP. Platelet aggregation in plasma from septic rats was inhibited only with higher doses of FBP, starting from 20 mM (P < 0.001). The calculated mean effective dose was 19.3 mM. Ex vivo platelet aggregation in septic rats was significantly lower (P < 0.05) than healthy rats and the treatment with FBP, at the dose of 2 g/kg, diminished the platelet aggregation at the extension of 27% (P < 0.001), suggesting that FBP is a potent platelet aggregation inhibitor in vivo. Moreover, treatment with FBP 2 g/kg prevented thrombocytopenia (P < 0.001), prolongation of prothrombin and partial thromboplastin time (P < 0.001), but not fibrinogen, in septic rats. The most important findings in this study are that FBP is a potent platelet aggregation inhibitor, in vitro and ex vivo. It presents protective effects on coagulation abnormalities, which can represent a treatment against DIC. The mechanisms for these effects remain under investigation.

Fructose 1,6-bisphosphate reduced TNF-alpha-induced apoptosis in galactosamine sensitized rat hepatocytes through activation of nitric oxide and cGMP production

Fructose 1,6-P2 (F1,6BP) protects rat liver against experimental hepatitis induced by galactosamine (GalN) by means of two parallel effects: prevention of inflammation, and reduction of hepatocyte sensitization to tumour necrosis factor-alpha (TNF-alpha). In a previous paper we reported the underlying mechanism involved in the prevention of inflammation. In the present study, we examined the intracellular mechanisms involved in the F1,6BP inhibition of the apoptosis induced by TNF-alpha in parenchyma cells of GalN-sensitized rat liver. We hypothesized that the increased nitric oxide (NO) production in livers of F1,6BP-treated rats mediates the antiapoptotic effect. This hypothesis was evaluated in cultured primary rat hepatocytes challenged by GalN plus tumour necrosis factor-alpha (GalN+TNF-alpha), to reproduce in vitro the injury associated with experimental hepatitis. Our results show a reduction in apoptosis concomitant with an increase in NO production and with a reduction in oxidative stress. In such conditions, guanylyl cyclase is activated and the increase in cGMP reduces the TNF-alpha-induced apoptosis in hepatocytes. These results provide new insights in the protective mechanism activated by F1,6BP and confirm its interest as a hepatoprotective agent.

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.

Influence of fructose-1,6-diphosphate on endotoxin-induced lung injuries in sheep

BACKGROUND

Fructose-1,6-diphosphate (FDP) is reported to have a salutary effect in endotoxin shock and sepsis. This investigation describes the effect of FDP on pulmonary and systemic hemodynamics, lung lymph protein clearance, and leukocyte count in sheep infused with Escherichia coli endotoxin.

MATERIALS AND METHODS

Anesthetized sheep (n = 18), some of which underwent thoracotomy to cannulate lymphatic nodes, were used in this study. After stabilization, all sheep received E. coli endotoxin, 5 microg/kg i.v. infusion over 30 min. Concomitant with the endotoxin infusion, half of the animals were randomly selected to receive an i.v. bolus of FDP (10%), 50 mg/kg, followed by a continuous infusion of 5 mg.kg(-1).min(-1) for 4 h; the rest were treated in the same manner with glucose (10%) in 0.9% NaCl.

RESULTS

Pulmonary artery pressure (PAP) and resistance in the glucose group increased from 20.8 +/- 1.6 to 36.7 +/- 3.2 mmHg (P < 0.007) and from 531 +/- 114 to 1137 +/- 80 dyn.s(-1).cm(-5), respectively (P < 0.005). Despite an increase during endotoxin infusion, these parameters in the FDP group returned to control values. There were no differences in left ventricular pressures, cardiac output, heart rate, and arterial oxygen tension between the groups. In the glucose group, lymph protein clearance was higher (P < 0.01) and blood leukocyte count was lower (P < 0.02). The wet/dry lung weight ratio (g/g) for the glucose group was 5.57 +/- 0.04 and for the FDP-treated group 4.76 +/- 0.06 (P < 0.0005).

CONCLUSION

FDP treatment attenuated significantly the characteristic pulmonary hypertension, lung lymph protein clearance, and pulmonary vascular leakage seen in sheep infused with endotoxin.

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.

Vascular endothelial growth factor is increased during the first 48 hours of human septic shock and correlates with vascular permeability

Meningococcal septic shock is an important cause of morbidity and mortality in children and young adults worldwide and is the prototypical gram-negative septic shock. One of the key factors in the development of shock is increased microvascular permeability. Vascular endothelial growth factor (VEGF) is a central factor in angiogenesis and is an important mediator of vascular permeability. Thirteen patients with meningococcal infection (eight presenting with shock) were investigated in the early phase of invasive meningococcal disease. Cytokines, complement activation, and VEGF plasma concentrations were measured during the first 48 h on the pediatric intensive care unit. Increased cytokine concentrations and activation of the complement system were observed. VEGF plasma concentrations were increased (median 193 pg/mL, range 71-1082) and were highest in the presence of shock (208 pg/mL, 169-1082) compared with patients presenting without shock (92 pg/mL range 71-299). VEGF concentration at admission correlated with the severity of disease (pediatric risk of mortality score, R=0.90 [Spearman], P=0.0001) and the amount of fluids administered within the first 24 h (R=0.90, P<0.0001). In all patients, a decrease in VEGF was associated with a decrease in fluid intake during t=24 to 48 h. The results suggest that apart from correlation with IL-1 beta, -10, -12, and complement activation, microvascular permeability in sepsis is also closely linked to the plasma concentration of VEGF. The role of VEGF in sepsis-associated increased microvascular permeability needs further exploration and may represent a new therapeutic target.

Fructose-1,6 diphosphate as a protective agent for experimental ischemic acute renal failure

Cold ischemia time is a risk factor for the development of acute renal failure in the immediate post-transplant period. In this study, we aimed to determine if intravenous fructose-1,6-diphosphate (FDP), given before nephrectomy, attenuates renal cell injury in a cold ischemia model. Male adult Wistar rats were subjected to infusion of either FDP 350 mg/kg (group F, n=6), an equal volume of 0.9% NaCl (group S, n=6), an equal volume/osmolality of mannitol (group M, n=6) or no infusion (group C, n=7). Kidneys were then perfused in situ with Collins solution and nephrectomy was performed. Other kidney slices were stored in Collins solution at 4 degrees C. Adenosine triphosphate (ATP) levels and lactate dehydrogenase (LDH) release were examined at 0, 24, 48 and 72 h. Other slices, obtained after 50 min immersion in Collins solution at 37 degrees C, were frozen for characterization of cytoskeletal preservation using phalloidin-FITC staining. Apical fluorescence intensity of proximal tubule cells, indicative of the F-actin concentration, was measured in a fluorescence microscope interfaced with computer image analysis system. Adenosine triphosphate levels, after up to 72 h of tissue incubation, were higher (P<0.05) in the FDP group when compared to other groups. In addition, LDH release was smaller (P<0.0001) in the FDP group. The F-actin concentration of proximal tubule cells cells was greater in the FDP group (P<0.0001). Results indicate that FDP is a useful tool to increase tissue viability in a rat kidney subjected to cold ischemia, by maintaining ATP cell content, decreasing LDH release and preventing microfilament disruption of proximal tubule cells.

Anti-inflammatory effects of fructose-1,6-bisphosphate on carrageenan-induced pleurisy in rat

In the present study, we evaluated the effect of fructose-1,6-bisphosphate (FBP), a high energy intermediate metabolite of glycolysis, in an acute model of lung injury. Injection of carrageenan into the pleural cavity of rats elicited an acute inflammation response characterized by a fluid accumulation in the pleural cavity which contained a large number of polymorphonuclear neutrophils. FBP (500mg/kg) attenuated the inflammation parameters: exudate volume, total leukocytes and the number of polymorphonuclear leukocytes, but the protein concentration in the exudate was not significantly affected by treatment with FBP. The precise site and mechanism of the anti-inflammatory effect was not addressed, considering the diverse pharmacological actions of FBP. This drug has anti-inflammatory actions suggesting that it may represent a novel strategy for the modulation of inflammatory response.

Protective effect of Fructose-1,6-Bisphosphate in the cold storage solution for liver preservation in rat hepatic transplantation

Fructose-1,6-bisphosphate (FBP) has been reported to have a protective effect on liver injury following ischemic/reperfusion periods. FBP maintains ATP levels and thereby cellular energy metabolism, which is important to the liver during cold preservation. In the present study, we evaluated the effects of FBP on the composition of storage solutions for cold liver preservation. Adult male Wistar rats were randomly divided into three experimental groups. Hepatic perfusion and preservation were performed with UW, UW plus 10 mmol/L FBP (UWM), and FBP 10 mmol/L (FBPS) alone solutions. Biochemical measurements of AST, ALT, and TBARS were performed on samples of the cold storage solution at 0, 12, 18, and 24 hours preservation. FBPS and UW solutions showed similar preservation grades during 18 hours. Addition of 10 mmol/L of FBP to UW solution induced liver injury and a poor preservation grade. FBP appears to protect the liver from injury caused by free radicals when the preservation time is less than 18 hours. Therefore, FBP may exert a protective effect for the preservation of livers during cold storage, and could represent an important component of new cold storage solutions.

Vessel injury and capillary leak

OBJECTIVE

To understand the mechanism of pathologic capillary leak in the critically ill patient.

DESIGN

Review of normal and altered physiology of the microvasculature. Review of recent literature describing pathogenesis, mediators, and interventions influencing capillary leak and microvascular repair.

SETTING

In vitro and in vivo studies, the latter including animal and human subjects.

MEASUREMENTS AND MAIN RESULTS

Capillary leak with resultant edema develops in the critical care setting on the basis of perturbations in Starling's equation, primarily as a result of increased capillary permeability to larger molecules. This process is most likely fueled by inflammatory mediators or mechanical stress. Attempts to prevent or treat this process remain largely unsuccessful; resuscitation is more often symptomatic than therapeutic. Models of microvascular repair focus on discrete injury and may not be applicable to the recovery of capillary damage secondary to a systemic leak

CONCLUSIONS

Our understanding of capillary leak syndrome remains fragmented and weighted toward specific mediators contributing to the leak. The implications of extensive edema and the mechanism by which it resolves continue to be the subject of speculation rather than study.

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.