I. William Browder

Glucans exhibit weak antioxidant activity, but stimulate macrophage free radical activity

Polymeric carbohydrates have been reported to modulate inflammatory responses in vitro and in vivo. Previous reports suggest that certain carbohydrate polymers, such as (1-->3)-beta-D-glucans, may possess free radical scavenging activity. If glucans are free radical scavengers then it might explain, in part, the ability of these ligands to modulate inflammatory responses. The present study examined the free radical scavenging activity of a variety of carbohydrate polymers and the effect of the polymers on free radical levels in a murine macrophage cell line. All of the carbohydrates exhibited concentration dependent antioxidant effects (EC(50) range = 807 to 43 microg/ml). However, the antioxidant activity for the carbohydrates was modest in comparison with PDTC (EC(50) = 0.13 microg/ml) and the carbohydrate concentration required for antioxidant activity was high (x EC(50) = 283 microg/ml). The antioxidant ability of the polymers was greater (p < .05) than their monosaccharide constituents, i.e., dextrose EC(50) = 807 vs. glucan sulfate EC(50) = 43 microg/ml. Coincubation of glucans with murine J774a.1 cells increased free radical levels when compared to controls. Therefore, the weak free radical scavenging activity of glucan polymers cannot explain their modulatory effect on inflammatory responses in tissue culture and/or disease models of inflammation.

A method for the solubilization of a (1->3)-β-D-glucan isolated from Saccharomyces cerevisiae

This report describes a method for the solubilization of a micro-particulate beta-D-glucan. Insoluble glucan is dissolved in methyl sulfoxide and urea (8M) and partially phosphorylated at 100 degrees. The resulting water-soluble product is called glucan phosphate. The conversion rate is 70%, and the preparation is endotoxin free as determined by the Limulus lysate procedure. Glucan phosphate is composed of 34.66% C, 6.29% H, 42.83% O, and 2.23% P and has a repeating-unit empirical formula of (C6H10O5)7.PO3H2, indicating a phosphate group substitution on every seventh glucose subunit. Molecular-weight averages, polydispersity, and intrinsic viscosity were determined by aqueous high-performance size-exclusion chromatography (s.e.c.) with on-line, multi-angle laser light scattering (m.a.l.l.s.) photometry and differential viscometry (d.v.). Two polymer peaks were resolved. Peak 1 (Mw = 3.57 x 10(6) daltons), represents approximately 2% of the total polymers, while peak 2 (Mw = 1.10 x 10(5) daltons) comprises approximately 98% of polymers. 13C- and 31P-n.m.r. spectroscopy confirmed the beta-1,3 interchain linkage and the presence of a phosphate group. In solution, glucan phosphate polymers self-associate in a triple-helical arrangement. The ability to prepare a immunologically active, non-toxic, water-soluble beta-D-glucan preparation will greatly enhance the clinical utility of this class of compounds.

Protection against Myocardial Ischemia/Reperfusion Injury in TLR4-Deficient Mice Is Mediated through a Phosphoinositide 3-Kinase-Dependent Mechanism

TLRs play a critical role in the induction of innate and adaptive immunity. However, TLRs have also been reported to mediate the pathophysiology of organ damage following ischemia/reperfusion (I/R) injury. We have reported that TLR4−/− mice show decreased myocardial injury following I/R; however, the protective mechanisms have not been elucidated. We examined the role of the PI3K/Akt signaling pathway in TLR4−/− cardioprotection following I/R injury. TLR4−/− and age-matched wild-type (WT) mice were subjected to myocardial ischemia for 45 min, followed by reperfusion for 4 h. Pharmacologic inhibitors of PI3K (wortmannin or LY294002) were administered 1 h before myocardial I/R. Myocardial infarct size/area at risk was reduced by 51.2% in TLR4−/− vs WT mice. Cardiac myocyte apoptosis was also increased in WT vs TLR4−/− mice following I/R. Pharmacologic blockade of PI3K abrogated myocardial protection in TLR4−/− mice following I/R. Specifically, heart infarct size/area at risk was increased by 98% in wortmannin and 101% in LY294002-treated TLR4−/− mice, when compared with control TLR4−/− mice. These data indicate that protection against myocardial I/R injury in TLR4−/− mice is mediated through a PI3K/Akt-dependent mechanism. The mechanisms by which PI3K/Akt are increased in the TLR4−/− myocardium may involve increased phosphorylation/inactivation of myocardial phosphatase and tensin homolog deleted on chromosome 10 as well as increased phosphorylation/inactivation of myocardial glycogen synthase kinase-3β. These data implicate innate immune signaling pathways in the pathology of acute myocardial I/R injury. These data also suggest that modulation of TLR4/PI3K/Akt-dependent signaling pathways may be a viable strategy for reducing myocardial I/R injury.

Modulation of tissue Toll-like receptor 2 and 4 during the early phases of polymicrobial sepsis correlates with mortality.

OBJECTIVE To determine whether there was a correlation between induction of polymicrobial sepsis, modulation of tissue Toll-like receptor (TLR) gene, and protein expression and survival outcome. DESIGN Prospective, randomized animal study. SETTING University medical school research laboratory. SUBJECTS Age- and weight-matched ICR/HSD mice. INTERVENTIONS Sepsis was induced by cecal ligation and puncture (CLP). No-surgery and sham (laparotomy)-operated mice were controls. We also examined tissue TLR2 and TLR4 messenger RNA and TLR4 protein levels in mice treated with an immunomodulator that increases survival in polymicrobial sepsis. In the immunomodulator study, mice were treated with glucan phosphate (50 mg/kg, intraperitoneally) 1 hr before CLP. No-surgery, sham surgery, glucan + no-surgery, sham surgery + glucan, and CLP groups were employed as controls. MEASUREMENTS AND MAIN RESULTS Total RNA was isolated from liver, lung, and spleen at 0, 1, 3, 6, 8, and 24 hrs after CLP. TLR gene expression was assessed by reverse transcription-polymerase chain reaction. Tissue TLR4 protein levels were evaluated at 24 hrs by Western blot and immunohistochemistry. CLP sepsis increased (p <.05) liver and lung TLR2 and TLR4 gene expression compared with controls. TLR4 protein concentrations also were increased. Increased TLR2/4 gene and TLR4 protein expression correlated with mortality. Immunoprophylaxis with glucan phosphate increased (p <.001) long-term survival (20% vs. 70%) but inhibited (p <.05) CLP-induced increases in tissue TLR2 and TLR4 messenger RNA expression as well as TLR4 protein expression. CONCLUSIONS Early increases in TLR2/4 gene and TLR4 protein expression correlated with mortality, whereas blunting TLR gene and protein expression correlated with improved long-term survival. This suggests that early up-regulation of tissue TLR2/4 may play a role in the proinflammatory response and pathophysiology of polymicrobial sepsis.

Preconditioning with a TLR2 specific ligand increases resistance to cerebral ischemia/reperfusion injury

The brains resistance to ischemic injury can be transiently augmented by prior exposure to a sub-lethal stress stimulus, i.e. preconditioning. It has been reported that Toll-like receptors (TLRs) are involved in the preconditioning-induced protective effect against ischemic brain injury. In this study, we investigated the effect of preconditioning with a TLR2 specific ligand, Pam3CSK4, on focal cerebral ischemia/reperfusion (I/R) injury in mice. Pam3CSK4 was administered systemically 24 h before the mice were subjected to focal cerebral ischemia (1 h) followed by reperfusion. Cerebral infarct size was determined, blood brain barrier (BBB) permeability was evaluated, and expression of tight-junction proteins were examined after focal cerebral I/R. Results showed that pre-treatment with Pam3CSK significantly reduced brain infarct size (1.9+/-0.5% vs 9.4+/-2.2%) compared with the untreated I/R group. Pam3CSK4 pre-treatment also significantly reduced acute mortality (4.3% vs 24.2%), preserved neurological function (8.22+/-0.64 vs 3.91+/-0.57), and attenuated brain edema (84.61+/-0.08% vs 85.29+/-0.09%) after cerebral I/R. In addition, Pam3CSK4 pre-treatment preserved BBB function as evidenced by decreased leakage of serum albumin (0.528+/-0.026 vs 0.771+/-0.059) and Evans Blue (9.23+/-0.72 microg/mg vs 12.56+/-0.65 microg/mg) into brain tissue. Pam3CSK4 pre-treatment also attenuated the loss of the tight junction protein occludin in response to brain I/R injury. These results suggest that TLR2 is a new target of ischemic preconditioning in the brain and preconditioning with a TLR2 specific ligand will protect the brain from I/R injury.

Normal Human Fibroblasts Express Pattern Recognition Receptors for Fungal (1→3)-β-d-Glucans

ABSTRACT Fungal cell wall glucans nonspecifically stimulate various aspects of innate immunity. Glucans are thought to mediate their effects via interaction with membrane receptors on macrophages, neutrophils, and NK cells. There have been no reports of glucan receptors on nonimmune cells. We investigated the binding of a water-soluble glucan in primary cultures of normal human dermal fibroblasts (NHDF). Membranes from NHDF exhibited saturable binding with an apparent dissociation constant (KD) of 8.9 ± 1.9 μg of protein per ml and a maximum binding of 100 ± 8 resonance units. Competition studies demonstrated the presence of at least two glucan binding sites on NHDF. Glucan phosphate competed for all binding sites, with a KD of 5.6 μM (95% confidence interval [CI], 3.0 to 11 μM), while laminarin competed for 69% ± 6% of binding sites, with a KD of 3.7 μM (95% CI, 1.9 to 7.3 μM). Glucan (1 μg/ml) stimulated fibroblast NF-κB nuclear binding activity and interleukin 6 (IL-6) gene expression in a time-dependent manner. NF-κB was activated at 4, 8, and 12 h, while IL-6 mRNA levels were increased by 48% at 8 h. This is the first report of pattern recognition receptors for glucan on human fibroblasts and the first demonstration of glucan binding sites on cells other than leukocytes. It also provides the first evidence that glucans can directly modulate the functional activity of NHDF. These results provide new insights into the mechanisms by which the host recognizes and responds to fungal (1→3)-β-d-glucans and suggests that the response to glucans may not be confined to cells of the immune system.

Development, physicochemical characterization and preclinical efficacy evaluation of a water soluble glucan sulfate derived from Saccharomyces cerevisiae

This report describes the development, characterization and preclinical efficacy evaluation of water soluble glucan sulfate. Glucan sulfate was derived from insoluble beta-1,3-D-glucan isolated from Saccharomyces cerevisiae. The proposed repeating unit empirical formula of glucan sulfate is [(C6H10O5)5.3H2SO4]n. Two polymer peaks were resolved by aqueous high-performance size exclusion chromatography (HPSEC) with on-line multi-angle laser light scattering (MALLS) photometry and differential viscometry. Peak 1 (MW = 1219697 Da) represents approximately 1% of the total polymers, while peak 2 (MW = 8884 Da) accounts for approximately 99% of polymers. 13C-NMR spectroscopy suggests that glucan sulfate polymer strands may be partially cross-linked. Glucan sulfate (250 mg/kg, i.v.) increased (P less than 0.01) macrophage vascular clearance of 131I-reticuloendothelial emulsion by 42% (P less than 0.01) and in vitro bone marrow proliferation by 46% (P less than 0.05). Glucan sulfate (250 mg/kg, i.v.) increased (P less than 0.05) median survival time of C57B1/6J mice with syngeneic melanoma B16 or sarcoma M5076. In addition, glucan sulfate immunoprophylaxis increased resistance of mice to challenge with Escherichia coli, Candida albicans or Mouse Hepatitis Virus strain A-59. We concluded that: (1) insoluble beta-1,3-D-glucan can be converted to a water soluble sulfated form; (2) glucan sulfate activates macrophages and stimulates bone marrow; (3) glucan sulfate exerts antitumor therapeutic activity, and (4) glucan sulfate immunoprophylaxis will modify the course of experimental infectious disease.

Enhancement of interleukin-1 and interleukin-2 production by soluble glucan

Soluble glucan, a beta-1,3-linked polyglucose, is a biologic response modifier effective in the therapy of experimental neoplasia, infectious diseases and immunosuppression. Interleukin-1 (IL-1) and interleukin-2 (IL-2) are endogenous immunomodulators which are essential for effective immune responsiveness. In view of its broad spectrum of immunobiological activity, the ability of glucan to enhance the production of IL-1 and IL-2 was evaluated. Splenic IL-1 and IL-2 secretion as well as plasma IL-1 and IL-2 levels were determined in Sprague-Dawley rats receiving glucan (100 mg/kg, i.p.) at intervals ranging from 12 days to 1 h prior to collection of splenocytes and plasma. Glucan (100 mg/kg) was also injected either s.c., i.p. or i.v. on days -4, -3 and -2 prior to harvesting splenocytes on day 0. Splenic macrophage IL-1 production was initially elevated 12 h following glucan injection and was maintained for a 5 day period. IL-2 secretion by splenic lymphocytes was enhanced 6 h post-glucan and remained elevated for an additional 9 days. Plasma IL-1 activity was elevated 12 h post-injection, while IL-2 activity in plasma was enhanced at 1 h post-glucan. Peak IL-1 and IL-2 activity in plasma occurred 9 and 12 days, respectively, following glucan administration. With regard to route of administration, IV glucan was most effective in inducing lymphokine production. This study demonstrates that: (1) glucan will enhance IL-1 and IL-2 production and (2) elevations in lymphokine production can be maintained up to 12 days post-glucan.

Pre-clinical safety evaluation of soluble glucan

Soluble glucan, a beta-1,3-linked glucopyranose biological response modifier, is effective in the therapy of experimental neoplasia, infectious diseases and immune suppression. Currently, soluble glucan is undergoing phase I clinical trials. The present study describes the pre-clinical safety evaluation of soluble glucan in mice, rats, guinea pigs and rabbits. ICR/HSD mice and Harlan Sprague-Dawley rats received a single i.v. injection of soluble glucan in doses ranging from 40 to 1000 mg/kg. Soluble glucan administration did not induce mortality, appearance or behavioral changes in mice or rats. In subsequent studies, mice and guinea pigs were injected i.p. with glucan (250 mg/kg) for 7 consecutive days. ICR/HSD mice gained weight at the same rate as the saline-treated controls. In contrast, guinea pigs receiving i.p. injections of soluble glucan showed a significant (P less than 0.05) 10-13% decrease in weight gain over the 7 day period. No other toxicologic, behavioral or appearance changes were noted. To examine chronic toxicity, soluble glucan was administered twice weekly for a period of 30 or 60 days to ICR/HSD mice in the dose of 40, 200 or 1000 mg/kg. No deaths were observed in any group. Chronic glucan administration did not alter body weight, liver, lung or kidney weight. However, a significant splenomegaly was observed in both the 30 and 60 day study. Histopathologic examination showed no tissue alterations at 40 or 200 mg/kg. However, at 1000 mg/kg a mononuclear infiltrate was observed in the liver. Pyrogenicity testing, employing New Zealand white rabbits, revealed that parenteral glucan administration (5 mg/kg) did not significantly alter body temperature. These data indicate that the systemic administration of soluble glucan, over a wide dose range, does not induce mortality or significant toxicity, an important consideration in preparing soluble glucan for parenteral administration to human populations.

Benefits of pulmonary artery catheter and transesophageal eehocardiographic monitoring in laparoscopic cholecystectomy patients with cardiac disease

BACKGROUND Because the abdominal insufflation and desufflation associated with laparoscopic procedures may adversely effect a compromised myocardium, patients with significant cardiopulmonary disease should be closely monitored during these procedures. The utility of intraoperative pulmonary artery catheter (PAC) and transesophageal echocardiography (TEE) monitoring was studied in 10 patients with moderate to severe cardiopulmonary disease to identify patients at greatest risk for cardiovascular complications during laparoscopic cholecystectomy. METHODS Ten patients were enrolled in this prospective study; 7 had suffered a previous myocardial infarction, 6 had undergone coronary artery bypass grafting, and 9 had disease classified as Goldmans class II or greater. The heart was monitored by TEE throughout the laparoscopic cholecystectomy by using real-time, two-dimensional mode to study the wall thickness and motion. Several PAC measurements were taken directly: cardiac output, systemic vascular resistance, pulmonary artery wedge pressure, and central venous pressure. Heart rate and blood pressure were also obtained at corresponding intervals. Cardiac index, stroke volume, and left and right ventricular stroke work were then calculated. RESULTS TEE demonstrated no significant changes in ventricular wall motion throughout laparoscopy. In patients who had postoperative cardiovascular complications, significant changes in cardiac index, left ventricular stroke work, and stroke volume were seen after pneumoperitoneum release. Compared to that of patients who did not develop complications, the cardiac index in those with complications dropped 42% (3.10 +/- 0.72 versus 1.80 +/- 0.10 L/min per m2, respectively; P < 0.01); left ventricular stroke work dropped 64% (139.00 +/- 11.36 versus 50.38 +/- 10.55 g x min/beat, respectively; P < 0.01); and stroke volume dropped 51% (86.90 +/- 12.68 versus 42.50 +/- 5.08 mL/beat, respectively; P < 0.01). CONCLUSIONS PCA monitoring in patients with compromised cardiac function is useful in identifying patients who may not tolerate hemodynamic changes after pneumoperitoneum release. Normalization of hemodynamic changes secondary to abdominal insufflation and desufflation in patients with compromised hearts may not occur in patients with compromised hearts may not occur for hours postoperatively. Abnormal hemodynamic changes occur within the first hour after desufflation in patients who later develop cardiovascular complications, which are heralded by significant drops in left ventricular stroke work, cardiac index, and stroke volume. TEE did not prove to be useful for intraoperative monitoring.