Protective effect of beta-glucan against oxidative organ injury in a rat model of sepsis

Tezosentan attenuates organ injury and mesenteric blood flow decrease in endotoxemia and cecal ligation and puncture

BACKGROUND

Decreased mesenteric blood flow and multiple organ injury due to free radicals are the consequences of septic shock. Since the blockade of endothelin receptors was reported to exert beneficial effects, we investigated the effects of tezosentan, a novel dual endothelin receptor antagonist, in two different experimental models of septic shock induced either by the injection of Escherichia coli endotoxin (ETX, 20 mg/kg, i.p.) or by cecal ligation and puncture (CLP).

STUDY DESIGN

Swiss albino mice received tezosentan (10 mg/kg, i.p.) or its solvent saline (0.9% NaCl, w/v) twice at 2 and 22 h after ETX or CLP. At 24 h, the animals were anesthetized and the mesenteric blood flow was monitored for 15 min by using perivascular ultrasonic Doppler flowmeter. Then the animals were exsanguinated, and spleen, liver, and kidneys were isolated accordingly for histopathological examination. Thiobarbituric acid reacting substances and glutathione and myeloperoxides activities were also determined in the liver.

RESULTS

In both ETX and CLP models, there was a decrease in mesenteric blood flow which was blocked by tezosentan. Similarly, tezosentan significantly attenuated the histopathological injury inflicted by both models. Although the glutathione levels were decreased and thiobarbituric acid reacting substances and myeloperoxidase activity were increased by ETX and CLP, tezosentan has failed to block these alterations in a consistent manner. However, a significant interaction between CLP and tezosentan with regard to myeloperoxidase activity and glutathione should be taken as partial evidence to explain the underlying mechanism of protection offered by tezosentan against liver injury.

CONCLUSIONS

Therefore, we concluded that tezosentan, by working via mechanisms mostly other than the blockade of free radical induced damage, is a useful treatment option for combating the deleterious effects of septic shock such as mesenteric ischemia as well as liver, spleen, and kidney injury.

Oral and systemic administration of beta-glucan protects against lipopolysaccharide-induced shock and organ injury in rats

beta-Glucans are glucose polymers with a variety of stimulatory effects on the immune system. The objective of this study was to determine the effect of prophylactic oral administration of soluble Saccharomyces cerevisiae-derived beta-1,3/1,6-glucan (SBG) on the outcome of experimental endotoxaemia and shock-associated organ injury. Male Wistar rats were pretreated with SBG orally (SBGpo, 20 mg/kg/day) for 14 days, subcutaneously (SBGsc, 2 mg/kg/day) for 3 days, or vehicle (placebo). Rats were anaesthetized and subjected to endotoxaemia by intravenous infusion of Escherichia coli lipopolysaccharide (LPS) (6 mg/kg) or saline infusion (sham). We observed significant levels of plasma beta-glucan in the SBGpo group (P<0 x 5), although the SBGsc group had levels approximately 40-fold higher despite a 10-fold lower dose. SBG prophylaxis caused enhanced blood pressure recovery following LPS-induced blood pressure collapse. Oral treatment with SBG attenuated the LPS-induced rise in plasma creatinine levels (P<0 x 05), indicating protection against renal injury. SBG also attenuated the plasma levels of aspartate aminotransferase and alanine aminotransferase (SBGpo, P<0 x 01; SBGsc, P<0 x 01), indicating protection against LPS-induced hepatic injury. A moderate increase in baseline interleukin (IL)-1beta levels was observed in the SBGsc group (P< 0 x 05). In the LPS-challenged rats, plasma levels of proinflammatory cytokines was moderately reduced in both SBG-treated groups compared to placebo. SBG treatment, particularly oral administration, had a striking effect on the haemodynamics of LPS-treated rats, although only a minute fraction of the orally administered beta-glucan translocated to the circulation. Enhanced organ perfusion may thus be responsible for the attenuated levels of indicators of kidney and liver injury seen in SBG-treated rats.

BETA-GLUCAN ATTENUATES INFLAMMATORY CYTOKINE RELEASE AND PREVENTS ACUTE LUNG INJURY IN AN EXPERIMENTAL MODEL OF SEPSIS

Sepsis is one of the most important risk factors in acute respiratory distress syndrome (ARDS). beta-Glucan is a potent reticuloendothelial modulating agent, the immunobiological activity of which is mediated in part by an increase in the number and function of macrophages. In this study, we investigated the putative protective role of beta-glucan against sepsis-induced lung injury. Sepsis was induced by cecal ligation and puncture (CLP) in Wistar rats. The control group received saline, and the treatment groups received beta-glucan or beta-glucan + beta-1,3-D-glucanase. Five hours thereafter, plasma tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta, and IL-6 levels were determined. Presence of lung injury was determined via lung tissue myeloperoxidase (MPO) activity, intercellular adhesion molecule (ICAM) 1 levels, and histopathological examination at 18 h after CLP. In a separate set of experiments, survival was monitored for 7 days after CLP. beta-Glucan treatment led to a significant increase in survival rate (63% in glucan-treated rats vs 38% in saline-treated rats). Administration of the beta-glucan inhibitor abrogated beta-glucan's survival benefit (50%). After CLP, plasma TNF-alpha, IL-1beta, and IL-6 concentrations were increased in control animals. When beta-glucan was administered, it completely blocked the elevation of TNF-alpha, IL-1beta, and IL-6. Administration of beta-1,3-D-glucanase suppressed glucan-induced decrease in cytokines. Animals treated with beta-glucan showed a significant reduction in lung injury score, a marked decrease in ICAM-1 expression, and a significant decrease in MPO levels. In contrast, beta-1,3-D-glucanase caused a significantly increased MPO and ICAM-1 levels in the lung. These data reveal that beta-glucan treatment improved the course of CLP-induced peritonitis and attenuated the lung injury. Administration of beta-glucanase inhibited the beta-glucan activity and resulted in enhanced lung injury.

Effects of ß-glucan fromAureobasidium pullulans on acute inflammation in mice

The effects of beta-glucan isolated from Aureobasidium pullulans were observed on acute xylene-induced inflammation. beta-glucan at a dose of 62.5, 125 or 250 mg/kg were administered once orally to xylene-treated mice (0.03 mL of xylene was applied on the anterior surface of the right ear to induce inflammation), and the body weight change, ear weight, histological profiles and histomorphometrical analyses of ear were conducted upon sacrifice. The xylene was topically applied 30 min after dosing with beta-glucan. The results were compared to those of diclofenac, indomethacin and dexamethasone (15 mg/kg injected once intraperitoneally). All animals were sacrificed 2 h after xylene application. Xylene application resulted in marked increases in induced ear weights compared to that of intact control ear; hence, the differences between intact and induced ear were also significantly increased. The histological characteristics of acute inflammation, such as severe vasodilation, edematous changes of skin and infiltration of inflammatory cells, were detected in xylene-treated control ears with marked increase in the thickness of the ear tissues. However, these xylene-induced acute inflammatory changes were significantly and dose-dependently decreased by beta-glucan treatment. We conclude that beta-glucan from A. pullulans has a somewhat favorable effect in the reduction of the acute inflammatory responses induced by xylene application in mice.

β-Glucan protects against chronic nicotine-induced oxidative damage in rat kidney and bladder

In this study, we investigated the protective effect of β-glucan against nicotine induced oxidative damage in urinary bladder and kidney tissues. Wistar albino rats were injected i.p. with nicotine hydrogen bitartarate (0.6mg/kg daily for 21 days) or saline. β-Glucan (50mg/kg, p.o.) was administered alone or with nicotine injections for 21 days. After decapitation, the urinary bladder and kidney tissues were taken for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, and myeloperoxidase (MPO) activity. Tissue samples were also examined histologically. In serum samples MDA, GSH, BUN, creatinine, TNF-α levels and LDH activity were analyzed. Chronic nicotine administration caused a significant decrease in GSH levels and increases in MDA levels and MPO activity in kidney and bladder tissues, suggesting oxidative organ damage, which was also histologically verified. Furthermore, β-glucan restored the reduced GSH levels, while it significantly decreased MDA levels and MPO activity. Renal function tests, LDH and TNF-α levels, which were increased significantly due to nicotine administration, were decreased with β-glucan treatment. The present data suggest that β-glucan supplementation effectively counteracts the chronic nicotine toxicity and attenuates oxidative damage of bladder and kidney tissues possibly by its antioxidant effects.

Carboxymethyl β-glucan Binds to Corneal Epithelial Cells and Increases Cell Adhesion to Laminin and Resistance to Oxidative Stress

PURPOSE

Polysaccharides are frequently used as viscoelastic agents to improve pharmacokinetics of ophthalmic preparations. Recently, polysaccharides from yeast cell walls such as beta-glucans have emerged as bioactive molecules endowed with immunomodulatory and cytoprotective properties. In this study, we investigated the effects of carboxymethyl beta-glucan (CMG), a water-soluble derivative of yeast beta-glucan, on cultured rabbit corneal epithelial cells.

METHODS

We developed a fluorescein-labeled CMG to visualize its binding to corneal cells by means of digital microscopy and image deconvolution. The effects of CMG on adhesion and survival of corneal epithelial cells exposed to noxious stimuli were also studied.

RESULTS

CMG binds defined regions scattered throughout the body of corneal cells, suggesting binding specificity. Tridimensional reconstruction of fluorescence shows that binding is localized mainly at the plasma and nuclear membranes. Interestingly, CMG binding is highly represented at the level of focal adhesion of cells spreading onto laminin. Accordingly, CMG promotes adhesion of corneal epithelial cells to laminin without affecting their proliferation rate. CMG also protects cells from oxidative stress-dependent cell death, being ineffective in preventing ultraviolet B cytotoxicity.

CONCLUSIONS

Data show that CMG dynamically binds to corneal epithelial cells, promoting cell adhesion and resistance to oxidative stress.

Liu-Shen-Wan, a traditional Chinese medicine, improves survival in sepsis induced by cecal ligation and puncture via reducing TNF-α levels, MDA content and enhancing macrophage phagocytosis

Sepsis in humans is a difficult condition to treat and is often associated with a high mortality rate. Here, we investigated putative protective effects of Liu-Shen-Wan (LSW), a well-known Chinese formula used in treating infectious diseases, against polymicrobial sepsis induced by cecal ligation and puncture (CLP). The oral administration of LSW, at the first dose of 60 mg/kg and then 30 mg/kg every 12 h, significantly improved the survival of CLP mice during a 4-day observation period. The effects of LSW on the inflammatory response (circulating tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) levels and malondialdehyde (MDA) content-an index of lipid peroxidation), infectious degree (peritoneal bacteria counts), and innate immunity function (leukocyte counts, macrophage phagocytosis and neutrophil respiratory burst) were further examined in rats. We demonstrated that treatment of LSW significantly decreased elevated levels of circulating TNF-alpha at 4 h and further reduced plasma MDA levels at 24 h after CLP, at first doses of 15 and 30 mg/kg and then 7.5 and 15 mg/kg every 12 h. Moreover, LSW markedly enhanced clearance of intraperitoneal bacteria associated with the increasing count of peritoneal leukocytes and enhancing phagocytic activity of macrophages partly impaired at 24 h after CLP. In contrast, LSW lightly reduced IL-1 levels at 4 h and failed to improve deactivated respiratory burst activity of neutrophils at 24 h after CLP. Thus, LSW exerts protective effects against sepsis induced by CLP, mainly by reducing plasma TNF-alpha and MDA levels and enhancing peritoneal macrophage phagocytosis, suggesting that it is a potential agent in the prevention and treatment of sepsis.

Acetaminophen-induced toxicity is prevented by β-d-glucan treatment in mice

The protective effect of beta-glucan against oxidative injury caused by acetaminophen was studied in mice liver. BALB-c mice (25-30 g) were pre-treated with beta-d-glucan (50 mg/kg, p.o.) for 10 days and on the 11th day they received an overdose of acetaminophen (900 mg/kg, i.p.). Four hours after the acetaminophen injection, mice were decapitated and their blood was taken to determine serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and tumor necrosis factor-alpha (TNF-alpha) levels. Tissue samples of the liver were taken for histological examination or for the determination of levels of malondialdehyde, an end product of lipid peroxidation; glutathione (GSH), a key antioxidant; and myeloperoxidase activity, an index of tissue neutrophil infiltration. The formation of reactive oxygen species in hepatic tissue samples was monitored by using the chemiluminescence technique with luminol and lucigenin probes. Acetaminophen caused a significant decrease in the GSH level of the tissue, which was accompanied with significant increases in the hepatic luminol and lucigenin chemiluminescence values, malondialdehyde level, MPO activity and collagen content. Similarly, serum ALT, AST levels, as well as LDH and TNF-alpha, were elevated in the acetaminophen-treated group when compared with the control group. On the other hand, beta-d-glucan treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by acetaminophen. In conclusion, these results suggest that beta-d-glucan exerts cytoprotective effects against oxidative injury through its antioxidant properties and may be of therapeutic use in preventing acetaminophen toxicity.

Prolonged reduction of leukocyte membrane-associated Dectin-1 levels following beta-glucan administration

Dectin-1 is the primary pattern recognition receptor for fungal glucans. Dectin-1 mediates the internalization and biological response to glucans. We examined the effect of i.v. or i.p. glucan phosphate (GP) administration on Dectin-1 membrane expression in murine peripheral blood leukocytes, splenocytes, bone marrow, and peritoneal cells from 3 h to 10 days after injection. Circulating leukocytes were also examined for uptake and internalization of glucans from the blood. Fluorescent-labeled GP was taken up from the systemic circulation by circulating peripheral leukocytes, splenocytes, and peritoneal cells. Following internalization, glucan colocalized with Dectin-1 in an intracellular vesicle. A single parenteral injection of GP resulted in a significant reduction (approximately 33-85%) in peripheral leukocyte membrane-associated Dectin-1 positivity that lasted for up to 7 days. The loss of leukocyte membrane-associated Dectin-1 after GP administration was primarily due to decreased levels of Dectin-1 on neutrophil and monocyte membranes with no significant changes in the percentage of neutrophils or monocytes circulating in the blood. Administration of control carbohydrate polymers, i.e., mannan or pullulan, which are not ligands for Dectin-1, did not decrease Dectin-1 leukocyte positivity, indicating that the effect on Dectin-1 is specific to glucans. In fact, mannan administration increased leukocyte Dectin-1 positivity, thus demonstrating a differential effect on leukocyte Dectin-1, compared with GP. We conclude that systemic administration of GP has a specific and prolonged effect on loss of leukocyte membrane Dectin-1 positivity. These data may have important implications for developing dosing regimens for immunomodulatory carbohydrates.

β-glucan ameliorates methotrexate-induced oxidative organ injury via its antioxidant and immunomodulatory effects

Methotrexate is an antifolate that is widely used in the treatment of rheumatic disorders and malignant tumors. The efficacy of methotrexate is often limited by severe side effects and toxic sequelae, where oxidative stress is noticeable. In the present study, the possible protective effect of beta-glucan in methotrexate-induced toxicity was investigated. Following a single dose of methotrexate injection (20 mg/kg), either saline or beta-glucan (50 mg/kg; orally) was administered for 5 days. After decapitation of the rats, trunk blood was obtained and the ileum, liver and kidney were removed to measure tissue malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content, as well as histological examination. Methotrexate caused a significant decrease in GSH levels, while MDA levels, MPO activity and collagen content were increased in all the tissues (P<0.05-0.001). On the other hand, administration of beta-glucan following methotrexate abolished the depletion of GSH and inhibited the increases in MDA, MPO activity and collagen content, while the histological analysis revealed that beta-glucan attenuated the tissue damage. Stimulation index, an indicator of oxidative burst in the neutrophils, was decreased by methotrexate (P<0.001), while beta-glucan abolished this effect. Furthermore, increased leukocyte apoptosis and cell death in methotrexate-treated animals were inhibited by beta-glucan (P<0.05). Thus, the findings of the present study suggest that beta-glucan, through its antioxidant and immunoregulatory effects, may be of therapeutic value in alleviating the leukocyte apoptosis, oxidative tissue injury and thereby the intestinal and hepatorenal side effects of methotrexate treatment.

Effect of melatonin on healing of colonic anastomosis in a rat model of peritonitis

BACKGROUND

The aim of this study is to determine the effect of melatonin on intestinal anastomosis in the presence of peritonitis.

MATERIAL AND METHODS

32 Wistar albino rats were randomized into four groups (n = 8): A (sham), B (control), C (melatonin 5 mg/kg), and D (melatonin 10 mg/kg). In group A, only cecal dissection was carried out. In the other groups, cecal ligation and puncture (CLP) followed cecal dissection in order to induce bacterial peritonitis. 24 h after the previous operation, cecal resection and ileocolic anastomosis were performed in the rats of all groups. In group C (5 mg/kg) and group D (10 mg/kg), melatonin was injected for 5 consecutive days starting after CLP. At the 48th hour of the CLP procedure, blood was drawn via the tail vein for tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) analysis, and on the 4th day of the experiment relaparotomy was carried out for bursting pressure (BP) measurements. The intestinal tissue containing the anastomotic line was then snap-frozen in liquid nitrogen and stored at -80 degrees C for determination of tissue levels of malondialdehyde (MDA) and glutathione (GSH).

RESULTS

The tissue MDA level, blood TNF-alpha and IL-6 levels of group B were significantly higher than in the other groups, whereas the BP results and GSH levels of group B were found to be significantly lower than in the other groups. The results of groups C and D are statistically different from those of group B. When we compared the results of groups C and D, we found significantly higher results in terms of BP and GSH levels in group D and also significantly lower results in terms of MDA, blood TNF-alpha and IL-6 levels in group D.

CONCLUSION

The findings of this experiment suggest that melatonin has a dose-independent positive effect on wound healing of colonic anastomosis.

β-glucan protects against burn-induced oxidative organ damage in rats

Thermal injury may lead to systemic inflammatory response, and multiple organ failure. Generation of reactive oxygen radicals and lipid peroxidation play important roles in burn-induced remote organ injury. In the present study, we investigated the putative protective effect of local or systemic beta-glucan treatment on burn-induced remote organ injury. Wistar albino rats were exposed to 90 degrees C bath for 10 s to induce thermal trauma. beta-glucan (3.75 mg/rat locally or 50 mg/kg orally) or saline was administered immediately after the trauma and were repeated twice daily in 48 h groups. Rats were decapitated either 6 or 48 h after burn injury and the skin, lung, liver, ileum and kidney tissues were taken for the measurement of malondialdehyde (MDA)--an index of lipid peroxidation--and glutathione (GSH)--a key antioxidant--levels. Neutrophil infiltration was evaluated by the measurement of tissue myeloperoxidase (MPO) activity, while the tumor necrosis factor-alpha (TNF-alpha) levels were measured in serum samples. Skin tissues were also examined microscopically. Severe skin scald injury (30% of total body surface area) caused significant decreases in GSH levels of the liver and intestinal tissues (p<0.01-<0.001), while MDA levels were significantly (p<0.01-p<0.001) increased at post-burn 6 and 48 h. Both local and systemic beta-glucan treatments significantly reversed (p<0.01-p<0.001) the elevations in MDA levels, while reduced GSH levels were reversed back to control levels (p<0.01-p<0.001); and the raised MPO levels were significantly decreased (p<0.05-p<0.001). The results indicate that both systemic and local administration of beta-glucan were effective against burn-induced oxidative tissue damage in the rat. beta-glucans, besides their immunomodulatory effects, have additional antioxidant properties. Therefore, beta-glucans merit consideration as therapeutic agents in the treatment of burn injuries.