Dominant hydrophobic interactions with ß-glucan in nanoarchitectonics with mixed Langmuir monolayers of cholesterol/dipalmitoyl phosphatidyl choline.

The polysaccharide ß-glucan, found in the cell wall of cereals such as wheat, oats, and barley, is believed to lower the concentration of bad cholesterol in humans, but the molecular-level mechanisms responsible for such an action are unknown. In this study, we use Langmuir monolayers of cholesterol and dipalmitoyl phosphatidyl choline (DPPC) as cell membrane models that are made to interact with ß-glucan. Neat cholesterol and mixed cholesterol/DPPC monolayers were expanded upon incorporating ß-glucan from the aqueous subphase. This incorporation was found to induce ordering in mixed monolayers and dehydration of the carbonyl group at higher cholesterol concentrations. These effects are attributed to hydrophobic interactions as identified with polarization-modulated infrared reflection-absorption spectroscopy. They correlate well with the hypothesis that cholesterol levels can be lowered by the formation of soluble fibers with ß-glucan through hydrophobic interactions, blocking cholesterol absorption by the organism.

Experimental evidence for the mode of action based on electrostatic and hydrophobic forces to explain interaction between chitosans and phospholipid Langmuir monolayers.

The interaction between chitosans and Langmuir monolayers mimicking cell membranes has been explained with an empirical scheme based on electrostatic and hydrophobic forces, but so far this has been tested only for dimyristoyl phosphatidic acid (DMPA). In this paper, we show that the mode of action in such a scheme is also valid for dipalmitoyl phosphatidyl choline (DPPC) and dipalmitoyl phosphatidyl glycerol (DPPG), whose monolayers were expanded and their compressibility modulus decreased by interacting with chitosans. In general, the effects were stronger for the negatively charged DPPG in comparison to DPPC, and for the low molecular weight chitosan (LMWChi) which was better able to penetrate into the hydrophobic chains than the high molecular weight chitosan (Chi). Penetration into the hydrophobic chains was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum frequency generation (SFG) spectroscopy. A slight reduction in conformational order of the lipid chains induced by the chitosans was quantitatively estimated by measuring the ratio between the intensities of the methyl (r(+)) and methylene (d(+)) peaks in the SFG spectra for DPPG. The ratio decreased from 35.6 for the closely packed DPPG monolayer to 7.0 and 6.6 for monolayers containing Chi and LMWChi, respectively. Since in both cases there was a significant phospholipid monolayer expansion, the incorporation of chitosans led to chitosan-rich and lipid-rich condensed domains, which mantained conformational order for their hydrophobic tails. The stronger effects from LMWChi are ascribed to an easier access to the hydrophobic tails, as corroborated by measuring aggregation in solution with dynamic light scattering, where the hydrodynamic radius for LMWChi was close to half of that for Chi. Taken together, the results presented here confirm that the same mode of action applies to different phospholipids that are important constituents of mammalian (DPPC) and bacterial (DPPG) cell membranes.

Semifluorinated thiols in Langmuir monolayers - a study by nonlinear and linear vibrational spectroscopies.

A series of semifluorinated thiols of the general formula CmF2m+1CnH2nSH (abbr. FmHnSH) have been synthesized and characterized in Langmuir monolayers with surface pressure-area isotherms, complemented with polarization-modulated reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation (SFG) techniques. A comparative analysis was performed for compounds having the same length of fluorinated segment (F10) and variable length of the hydrogenated part (H6, H10, H12), and having identical hydrogenated segment (H12) connected to a fluorinated moiety of different lengths (F6, F8, F10). For the sake of comparison, an alkanethiol (H18SH) was also examined, and F10H10COOH and F10H10OH molecules were used for helping the assignment of SFG spectra of CH stretches. SFG was applied to investigate the hydrocarbon chain and the terminal CF3 group, while PM-IRRAS was used to probe CF2 groups. The number of gauche defects in the hydrocarbon chain increased with the increasing length of the molecule, either by elongation of the hydrogenated or perfluorinated part. SFG measurements recorded at three polarization combinations (ppp, ssp, sps) enabled us to estimate the tilt angle of the terminal CF3 group in semifluorinated thiol molecules as ranging from 35° to 45°, which is consistent with nearly vertical fluorinated segments. Upon increasing the surface pressure, the fluorinated segment gets slightly more upright, but the hydrocarbon chain tilt increases while keeping the same average number of gauche defects. The extent of disorder in the hydrogenated segment may be controlled by varying the size of the fluorinated segment, and this could be exploited for designing functionalized surfaces with insertion of other molecules in the defect region.

Understanding the biocide action of poly(hexamethylene biguanide) using Langmuir monolayers of dipalmitoyl phosphatidylglycerol.

The disinfectant activity of poly(hexamethylene biguanide) (PHMB) has been explored in industrial applications, in agriculture and in food manipulation, but this biocide action is not completely understood. It is believed to arise from electrostatic interactions between the polyhexanide group and phosphatidylglycerol, which is the main phospholipid on the bacterial membrane. In this study, we investigated the molecular-level interactions between PHMB and dipalmitoyl phosphatidylglycerol (DPPG) in Langmuir monolayers that served as cell membrane models. PHMB at a concentration of 2×10(-4) g L(-1) in a Theorell-Stenhagen at pH 3.0 and in a phosphate at pH 7.4 was used as a subphase to prepare the DPPG monolayers. Surface pressure-area isotherms showed that PHMB adsorbs and penetrates into the DPPG monolayers, expanding them and increasing their elasticity under both conditions examined. Results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) indicated that PHMB induces disorder in the DPPG chains and dehydrates their C=O groups, especially for the physiological medium. Overall, these findings point to hydrophobic interactions and dehydration being as relevant as electrostatic interactions to explain changes in membrane fluidity and permeability, believed to be responsible for the biocide action of PHMB.

Chitosan does not inhibit enzymatic action of human pancreatic lipase in Langmuir monolayers of 1,2-didecanoyl-glycerol (DDG).

In this study, we tested the hypothesis according to which chitosan reduces lipid digestion by blocking the access of lipases to ingested fat. Because lipase action takes place mostly at interfaces, we produced Langmuir films of 1,2-didecanoyl-glycerol (DDG), which is the substrate for human pancreatic lipase (HPL). The experimental assays were carried out in acidic medium, at pH 3.0, to ensure that chitosan is completely soluble. Chitosan was found to affect strongly the surface activity of HPL that forms a Gibbs monolayer at the air/water interface, but did not inhibit the enzymatic action of HPL toward the DDG monolayer. The latter was observed using two surface-specific spectroscopic techniques, namely polarization-modulated infrared reflection-absorption and sum-frequency generation (SFG). The extension of DDG hydrolysis calculated using SFG spectroscopy was 33% in the absence of chitosan, and ranged from 29 to 50% in the presence of chitosan at concentrations of 0.20 g L(-1) and 0.30 g L(-1), respectively. Therefore, fat "protection" by chitosan is unlikely to be an important factor in fat reduction.

Interaction of O-acylated chitosans with biomembrane models: probing the effects from hydrophobic interactions and hydrogen bonding.

One of the major challenges in establishing the mechanisms responsible for the chitosan action in biomedical applications lies in the determination of the molecular-level interactions with the cell membrane. In this study, we probed hydrophobic interactions and H-bonding in experiments with O,O'-diacetylchitosan (DACT) and O,O'-dipropionylchitosan (DPPCT) incorporated into monolayers of distinct phospholipids, the zwitterionic dipalmitoyl phosphatidyl choline (DPPC), and the negatively charged dipalmitoyl phosphatidyl glycerol (DPPG) and dimyristoyl phosphatidic acid (DMPA). The importance of hydrophobic interactions was confirmed with the larger effects observed for DACT and DPPCT than for parent chitosan (Chi), particularly for the more hydrophobic DPPCT. Such larger effects were noted in surface pressure isotherms and elasticity of the monolayers. Since H-bonding is hampered for the chitosan derivatives, which have part of their hydroxyl groups shielded by O-acylation, these effects indicate that H-bonding does not play an important role in the chitosan-membrane interactions. Using polarization-modulated infrared reflection absorption (PM-IRRAS) spectroscopy, we found that the chitosan derivatives were incorporated into the hydrophobic chain of the phospholipids, even at high surface pressures comparable to those in a real cell membrane. Taken together, these results indicate that the chitosan derivatives containing hydrophobic moieties would probably be more efficient than parent chitosan as antimicrobial agents, where interaction with the cell membrane is crucial.

Low molecular-weight chitosans are stronger biomembrane model perturbants.

The influence from the chitosan molecular weight on its interaction with cell membrane models has been studied. A low molecular weight chitosan (LMWChi) adsorbed from the subphase expanded the surface pressure-area and surface potential-area isotherms of dimyristoyl phosphatidic acid (DMPA) monolayers and decreased the compressional modulus. The expansion in the monolayers and the decrease in the compressional modulus were larger for LMWChi than for a high molecular weight chitosan (Chi). The polymeric nature is still essential for the interaction though, which was demonstrated by measuring negligible changes in the mechanical properties of the DMPA monolayer when the subphase contained glucosamine and acetyl-glucosamine. The results were rationalized in a model through which chitosan interacted with the membrane via electrostatic and hydrophobic interactions, with the smaller chains of LMWChi having less steric hindrance to be accommodated in the membrane. In summary, the activity based on membrane interactions depends on the distribution of molar mass, with lower molecular weight chitosan more likely to have stronger effects.

Properties of 7ND-CCL2 are modulated upon fusion to Fc.

7ND, a truncated version of the chemokine MCP-1/CCL2 lacking amino acids 2-8, is a potent antagonist of CCR2. In contrast to CCL2, 7ND is an obligate monomer. Similar to other chemokines, the in vivo half-life of 7ND is very short and its use as an antagonist in disease models is thus limited. We therefore constructed a 7ND-Fc fusion protein to extend the half-life of 7ND and overcome its limitations as a potential therapeutic antagonist. When we tested the properties of the fusion molecule in vitro, we found to our surprise that 7ND-Fc, in contrast to 7ND, produced a distinct, albeit small, chemotactic response in THP-1 cells, and a robust chemotactic response in L1.2 cells stably transfected with CCR2. To test whether this unexpected observation might be due to the bivalency of 7ND-Fc stemming from the dimeric nature of Fc fusions, we produced a heterodimeric Fc fusion which displays only one 7ND moiety, using a technology called strand exchange of engineered CH3 domains (SEED). The monovalent construct had properties equivalent to the parent 7ND. Furthermore, partial agonist activity appears to depend on receptor density as well as the signaling pathway examined. However, we were able to show that 7ND-Fc, but not 7ND alone, has antagonistic activity in experimental autoimmune encephalomyelitis, a murine model of multiple sclerosis.

Experimental infection with Schistosoma mansoni in CCR5-deficient mice is associated with increased disease severity, as CCR5 plays a role in controlling granulomatous inflammation.

The plasma level of the chemokine CCL3 is elevated in patients with chronic severe schistosomiasis mansoni. We have previously shown that CCL3(-/-) mice with experimental infection showed diminished pathology and worm burden compared to those of wild-type (WT) mice. To elucidate further the role of CC chemokines during schistosomiasis mansoni infection, we evaluated the course of infection in C57BL/6J mice deficient in CCR5, one of the receptors for CCL3. The CCR5 deficiency proved to be remarkably deleterious to the host, since mortality rates reached 70% at 14 weeks postinfection in CCR5(-/-) mice and 19% in WT mice. The increased lethality was not associated with an increased parasite burden, since similar numbers of eggs and adult worms were found in mice from both groups. Liver granulomas of chronically infected CCR5(-/-) mice were larger and showed greater numbers of cells and collagen deposition than liver granulomas from WT mice. This was associated with higher levels of production of intereleukin-5 (IL-5), IL-13, CCL3, and CCL5 in infected CCR5(-/-) mice than in infected WT mice. Moreover, at 8 weeks after infection, just before changes in pathology and mortality, the numbers of FoxP3-positive cells were lower in liver granulomas of CCR5(-/-) mice than in WT mice. In conclusion, the CCR5 deletion is deleterious to mice infected with Schistosoma mansoni, and this is associated with enhanced fibrosis and granulomatous inflammation.

Phosphoinositide 3-kinase γ plays a critical role in bleomycin-induced pulmonary inflammation and fibrosis in mice.

PI3Kγ is central in signaling diverse arrays of cellular functions and inflammation. Pulmonary fibrosis is associated with pulmonary inflammation, angiogenesis, and deposition of collagen and is modeled by instillation of bleomycin. The role of PI3Kγ in mediating bleomycin-induced pulmonary inflammation and fibrosis in mice and potential mechanisms involved was investigated here. WT or PI3Kγ KO mice were instilled with bleomycin and leukocyte subtype influx, cytokine and chemokine levels, and angiogenesis and tissue fibrosis evaluated. The activation of lung-derived leukocytes and fibroblasts was evaluated in vitro. The relevance of PI3Kγ for endothelial cell function was evaluated in HUVECs. PI3Kγ KO mice had greater survival and weight recovery and less fibrosis than WT mice after bleomycin instillation. This was associated with decreased production of TGF-ß(1) and CCL2 and increased production of IFN-γ and IL-10. There was reduced expression of collagen, fibronectin, α-SMA, and von Willebrand factor and decreased numbers and activation of leukocytes and phosphorylation of AKT and IκB-α. PI3Kγ KO mice had a reduced number and area of blood vessels in the lungs. In vitro, treatment of human endothelial cells with the PI3Kγ inhibitor AS605240 decreased proliferation, migration, and formation of capillary-like structures. AS605240 also decreased production of collagen by murine lung-derived fibroblasts. PI3Kγ deficiency confers protection against bleomycin-induced pulmonary injury, angiogenesis, and fibrosis through the modulation of leukocyte, fibroblast, and endothelial cell functions. Inhibitors of PI3Kγ may be beneficial for the treatment of pulmonary fibrosis.

Role of CCL3/MIP-1alpha and CCL5/RANTES during acute Trypanosoma cruzi infection in rats.

Chagas' disease is caused by Trypanosoma cruzi infection and is characterized by chronic fibrogenic inflammation and heart dysfunction. Chemokines are produced during infection and drive tissue inflammation. In rats, acute infection is characterized by intense myocarditis and regression of inflammation after control of parasitism. We investigated the role of CCL3 and CCL5 during infection by using DNA vaccination encoding for each chemokine separately or simultaneously. MetRANTES treatment was used to evaluate the role of CCR1 and CCR5, the receptors for CCL3 and CCL5. Vaccination with CCL3 or CCL5 increased heart parasitism and decreased local IFN-gamma production, but did not influence intensity of inflammation. Simultaneous treatment with both plasmids or treatment with MetRANTES enhanced cardiac inflammation, fibrosis and parasitism. In conclusion, chemokines CCL3 and CCL5 are relevant, but not essential, for control of T. cruzi infection in rats. On the other hand, combined blockade of these chemokines or their receptors enhanced tissue inflammation and fibrosis, clearly contrasting with available data in murine models of T. cruzi infection. These data reinforce the important role of chemokines during T. cruzi infection but suggest that caution must be taken when expanding the therapeutic modulation of the chemokine system in mice to the human infection.

The flavonoid dioclein reduces the production of pro-inflammatory mediators in vitro by inhibiting PDE4 activity and scavenging reactive oxygen species.

Reactive oxygen species, cytokines and chemokines produced at inflammatory sites are pivotal events in the progression of many diseases. Flavonoids are well-known for their antioxidant and anti-inflammatory activities. Here, we investigated the effects of the flavonoid dioclein on the production of mediators of inflammation in vitro and possible underlying mechanisms. Murine macrophages were pretreated with dioclein, rolipram, a PDE4 (cyclic nucleotide phosphosdiesterase type 4) inhibitor, or butylated hydroxytoluene (BHT), an antioxidant, and then activated with LPS or LPS/IFN-gamma. The concentration of TNF-alpha, IL-6, CXCL1/KC, CCL2/JE, and nitric oxide (NO) was determined on culture supernatants. To evaluate potential mechanisms of action, dioclein was tested for inhibition of PDE4 activity and for antioxidant properties by chemiluminescence assays. Dioclein was efficient in reducing the production of cytokines, chemokines and NO in a concentration-dependent manner (from 5 to 50muM). Dioclein was more effective than BHT and rolipram, while having similar inhibitory effects to the combination of BHT plus rolipram. Dioclein inhibited PDE4 activity with an approximate IC(50) of 16.8+/-1.4muM and strongly reduced the concentration of reactive oxygen species in cell and cell-free systems, being more effective than the standard antioxidant BHT. The flavonoid dioclein possesses significant antioxidant and PDE4 inhibitory activity, showing that the substance may have substantial advantages over mechanisms of action already described for many flavonoids. Such effects account for the anti-inflammatory effects of dioclein, mainly by reducing the concentration of mediators of inflammation, such as cytokines, chemokines and reactive oxygen species by macrophages.

Essential role of platelet-activating factor receptor in the pathogenesis of Dengue virus infection.

Severe dengue infection in humans causes a disease characterized by thrombocytopenia, increased levels of cytokines, increased vascular permeability, hemorrhage, and shock. Treatment is supportive. Activation of platelet-activating factor (PAF) receptor (PAFR) on endothelial cells and leukocytes induces increase in vascular permeability, hypotension, and production of cytokines. We hypothesized that activation of PAFR could account for the major systemic manifestations of dengue infection. Inoculation of adult mice with an adapted strain of Dengue virus caused a systemic disease, with several features of the infection in humans. In PAFR(-/-) mice, there was decreased thrombocytopenia, hemoconcentration, decreased systemic levels of cytokines, and delay of lethality, when compared with WT infected mice. Treatment with UK-74,505, an orally active PAFR antagonist, prevented the above-mentioned manifestations, as well as hypotension and increased vascular permeability, and decreased lethality, even when started 5 days after virus inoculation. Similar results were obtained with a distinct PAFR antagonist, PCA-4246. Despite decreased disease manifestation, viral loads were similar (PAFR(-/-)) or lower (PAFR antagonist) than in WT mice. Thus, activation of PAFR plays a major role in the pathogenesis of experimental dengue infection, and its blockade prevents more severe disease manifestation after infection with no increase in systemic viral titers, suggesting that there is no interference in the ability of the murine host to deal with the infection. PAFR antagonists are disease-modifying agents in experimental dengue infection.

Role of the chemokines CCL3/MIP-1 alpha and CCL5/RANTES in sponge-induced inflammatory angiogenesis in mice.

OBJECTIVE: We examined the potential contribution of CCL3 and CCL5 to inflammatory angiogenesis in mice. METHODS: Polyester-polyurethane sponges were implanted in mice and blood vessel counting and hemoglobin, myeloperoxidase and N-acetylglucosaminidase measurements used as indexes for vascularization, neutrophil and macrophage accumulation, respectively. RESULTS: CCL3 and CCL5 were expressed throughout the observation period. Exogenous CCL3 enhanced angiogenesis in WT, but angiogenesis proceeded normally in CCL3(-/-) mice, suggesting that endogenous CCL3 is not critical for sponge-induced angiogenesis in mice. CCL5 expression was detected at day 1, but levels significantly increased thereafter. Exogenous CCL5 reduced angiogenesis in WT mice possible via CCR5 as CCL5 was without an effect in CCR5(-/-) mice. Treatment of WT with the CCR1/CCR5 antagonist, Met-RANTES, prevented neutrophil and macrophage accumulation, but enhanced sponge vascularization. CONCLUSION: Thus, endogenous CCL3 appears not to play a role in driving sponge-induced inflammatory angiogenesis in mice. The effects of CCL5 were anti-angiogenic and appeared to be mediated via activation of CCR5.

Role of the chemokine receptor CXCR2 in bleomycin-induced pulmonary inflammation and fibrosis.

Pulmonary fibrosis is characterized by chronic inflammation and excessive collagen deposition. Neutrophils are thought to be involved in the pathogenesis of lung fibrosis. We hypothesized that CXCR2-mediated neutrophil recruitment is essential for the cascade of events leading to bleomycin-induced pulmonary fibrosis. CXCL1/KC was detected as early as 6 hours after bleomycin instillation and returned to basal levels after Day 8. Neutrophils were detected in bronchoalveolar lavage and interstitium from 12 hours and peaked at Day 8 after instillation. Treatment with the CXCR2 receptor antagonist, DF2162, reduced airway neutrophil transmigration but led to an increase of neutrophils in lung parenchyma. There was a significant reduction in IL-13, IL-10, CCL5/RANTES, and active transforming growth factor (TGF)-beta(1) levels, but not on IFN-gamma and total TGF-beta(1,) and enhanced granulocyte macrophage-colony-stimulating factor production in DF2162-treated animals. Notably, treatment with the CXCR2 antagonist led to an improvement of the lung pathology and reduced collagen deposition. Using a therapeutic schedule, DF2162 administered from Days 8 to 16 after bleomycin reduced pulmonary fibrosis and levels of active TGF-beta(1) and IL-13. DF2162 treatment reduced bleomycin-induced expression of von Willebrand Factor, a marker of angiogenesis, in the lung. In vitro, DF2162 reduced the angiogenic activity of IL-8 on human umbilical vein endothelial cells. In conclusion, we show that CXCR2 plays an important role in mediating fibrosis after bleomycin instillation. The compound blocks angiogenesis and the production of pro-angiogenic cytokines, and decreases IL-8-induced endothelial cell activation. An effect on neutrophils does not appear to account for the major effects of the blockade of CXCR2 in the system.

The role of chemokines in controlling granulomatous inflammation in Schistosoma mansoni infection.

Chemokines are a superfamily of low-molecular-weight cytokines that were initially described for their chemoattractant activity. It is now clear chemokines have several other activities that modulate immune processes. Chemokines appear to play a role in the pathogenesis of several inflammatory diseases. The role of chemokines and their receptors in mediating granulomatous inflammation induced by Schistosoma mansoni egg antigens presented in particulate manner have been studied in detail. Much less is known of the role of chemokines in mediating inflammation during the course of S. mansoni infection. Our studies in mice suggest a relevant role for the chemokine CCL3 and the receptor CCR5 in the pathogenesis of experimental S. mansoni infection. Absence of CCL3 is associated with decrease in granuloma size, fibrosis and parasite load. In humans, levels of CCL3 in plasma associate with disease severity and may be useful for diagnostic purposes. In contrast, absence of CCR5 is associated with enhanced lethality, granuloma size and fibrosis. It is suggested that the balance of chemokine production and chemokine receptor activation are important determinants of the fate of infection in experimental animals and humans.

The role of macrophage migration inhibitory factor in the cascade of events leading to reperfusion-induced inflammatory injury and lethality.

Ischemia and reperfusion (I/R) injury is associated with a systemic inflammatory response, characterized by intense tumor necrosis factor (TNF)-alpha production and TNF-alpha-dependent tissue injury. Macrophage migration inhibitory factor (MIF) is a potent proinflammatory cytokine that may induce TNF-alpha release and play an important role in innate immune and inflammatory responses. The aim of this work was to assess whether MIF was involved the inflammatory cascade and injury that follows intestinal I/R. To this end, wild-type (WT) and MIF-deficient (MIF(-/-)) mice underwent 60 minutes of ischemia followed by 60 minutes of reperfusion, after which they were culled for the assessment of inflammatory parameters. I/R was accompanied by an increase in circulating levels of MIF and an increase of vascular permeability, hemorrhage, and production of TNF-alpha in the intestine and lungs. The latter parameters were markedly suppressed in reperfused MIF(-/-) mice, and this was associated with decreased lethality (80% in WT versus 20% in MIF(-/-) mice). Interestingly, the reperfusion-associated neutrophil accumulation in the intestine and lungs was similar in WT and MIF(-/-) mice. Leukocytes isolated from lungs of MIF(-/-) mice were less activated, as assessed by their response to zymosan in a luminol-enhanced chemiluminescence assay. In conclusion, our results suggest that MIF plays an important role in the cascade of events leading to TNF-alpha production and reperfusion-induced tissue injury and lethality in mice.

ST2, an IL-1R family member, attenuates inflammation and lethality after intestinal ischemia and reperfusion.

Ischemia reperfusion injury is characterized by local and systemic inflammation leading to considerable mortality. Previously, we have reported that soluble T1/ST2 (sST2), a member of the IL-1 receptor gene family, inhibits LPS-induced macrophage proinflammatory cytokine production. Here, we report the therapeutic effect of sST2-Fc in a murine model of intestinal ischemia reperfusion-induced injury. Administration of sST2-Fc fusion protein i.v., 10 min before reperfusion, reduced the production of TNF-alpha dose-dependently in the intestine and in the lungs. The sST2-Fc treatment with the highest dose (100 mug) resulted in inhibited vascular permeability, neutrophilia, and hemorrhage in the intestine and the lungs compared with controls treated with normal IgG. This was associated with down-regulated tissue levels of proinflammatory cytokines, markedly reduced serum TNF-alpha levels, and increased survival of mice from the sST2-Fc-treated group after ischemia and reperfusion injury. The beneficial effect of sST2-Fc treatment was associated with elevated IL-10 production in intestine and lung. sST2-Fc was not able to prevent the inflammatory response associated with intestinal ischemia and reperfusion in IL-10-deficient mice, suggesting that sST2 exerts its anti-inflammatory effect in a IL-10-dependent manner. These results also demonstrate that sST2-Fc may provide a novel, complementary approach in treating ischemic reperfusion injury.

The role of chemokines in Schistosoma mansoni infection: insights from human disease and murine models

Chemokines are a superfamily of low-molecular-weight cytokines that were initially described for their chemoattractant activity. It is now clear chemokines have several other activities that modulate immune processes. More than 50 chemokines ligands and at least 19 receptors have been described to date. Depending on the number of N-terminal cysteine residues, chemokines are grouped in the subfamilies CXC, CC, C or CX3C. A growing body of evidence suggests a role for chemokines in the pathogenesis of several inflammatory diseases. Our studies involving mice and humans infected with Schistosoma mansoni suggest an important role of the chemokine CCL3 and its receptors (CCR1 and CCR5) in the pathogenesis of severe schistosomiasis. We suggest that the differential activation of CCR1 or CCR5 during the course of schistosomiasis may dictate the outcome of the disease.

A DNA vaccine encoding CCL4/MIP-1beta enhances myocarditis in experimental Trypanosoma cruzi infection in rats.

Chagas' disease, caused by Trypanosoma cruzi, is a major cause of cardiovascular disease in Latin America. Exacerbated inflammation disproportional to parasite load characterizes chronic myocardial lesions in chagasic patients. Chemokines and their receptors are expected to account for the renewed inflammatory processes after the inoculation of the parasite, but their potential unique functions are far from being clear. Herein, we evaluated the effect of a DNA vaccine encoding CCL4/MIP-1beta, a CC-chemokine, in T. cruzi-elicited myocarditis in rats. Holtzman rats were given intramuscularly cardiotoxin and the CCL4/MIP-1beta DNA-containing plasmid (100microg) was delivered in this muscular site four times. Fourteen days after last immunization, animals were inoculated with a myotropical CL-Brener T. cruzi clone. Peak of parasitism was observed at day 15 after infection, preceding the peak of myocardial inflammation at day 20. Myocarditis was still intense at day 30, but the inflammatory infiltrates showed a more focal distribution. The expression of CCL2/MCP-1 and CCL4/MIP-1beta correlated closely with the kinetics of myocardial inflammation. The CCL4/MIP-1beta DNA vaccine induced an increase of the levels of the anti-CCL4/MIP-1beta observed in T. cruzi-infected animals. This was associated with an exacerbation of myocardial inflammation and fibrosis, although alterations in parasitemia and myocardial parasitism were not observed. Our data suggest that CCL4/MIP-1beta plays a role in preventing excessive inflammation and pathology rather than in controlling parasite replication.