Lithothamnion muelleri controls inflammatory responses, target organ injury and lethality associated with graft-versus-host disease in mice.

Lithothamnion muelleri (Hapalidiaceae) is a marine red alga, which is a member of a group of algae with anti-inflammatory, antitumor, and immunomodulatory properties. The present study evaluated the effects of treatment with Lithothamnion muelleri extract (LM) in a model of acute graft-versus-host disease (GVHD), using a model of adoptive splenocyte transfer from C57BL/6 donors into B6D2F1 recipient mice. Mice treated with LM showed reduced clinical signs of disease and mortality when compared with untreated mice. LM-treated mice had reduced tissue injury, less bacterial translocation, and decreased levels of proinflammatory cytokines and chemokines (interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-C motif) ligand 3 (CCL3) and chemokine (C-C motif) ligand 5 (CCL5)). The polysaccharide-rich fraction derived from LM could inhibit leukocyte rolling and adhesion in intestinal venules, as assessed by intravital microscopy. LM treatment did not impair the beneficial effects of graft-versus-leukaemia (GVL). Altogether, our studies suggest that treatment with Lithothamnion muelleri has a potential therapeutic application in GVHD treatment.

Treatment with Apocynin Limits the Development of Acute Graft-versus-Host Disease in Mice.

Graft-versus-host disease (GVHD) is the most serious complication limiting the clinical utility of allogeneic hematopoietic stem cell transplantation (HSCT), in which lymphocytes of donors (graft) are activated in response to the host antigen. This disease is associated with increased inflammatory response through the release of inflammatory mediators such as cytokines, chemokines, and reactive oxygen species (ROS). In this study, we have evaluated the role of ROS in GVHD pathogenesis by treatment of recipient mice with apocynin (apo), an inhibitor of intracellular translocation of cytosolic components of NADPH oxidase complex. The pharmacological blockade of NADPH oxidase resulted in prolonged survival and reduced GVHD clinical score. This reduction in GVHD was associated with reduced levels of ROS and TBARS in target organs of GVHD in apocynin-treated mice at the onset of the mortality phase. These results correlated with reduced intestinal and liver injuries and decreased levels of proinflammatory cytokines and chemokines. Mechanistically, pharmacological blockade of the NADPH oxidase was associated with inhibition of recruitment and accumulation of leukocytes in the target organs. Additionally, the chimerism remained unaffected after treatment with apocynin. Our study demonstrates that ROS plays an important role in mediating GVHD, suggesting that strategies aimed at blocking ROS production may be useful as an adjuvant therapy in patients subjected to bone marrow transplantation.

Nanocomposite treatment reduces disease and lethality in a murine model of acute graft-versus-host disease and preserves anti-tumor effects.

Graft versus host disease (GVHD) is an immunological disorder triggered by bone marrow transplantation that affects several organs, including the gastrointestinal tract and liver. Fullerenes and their soluble forms, fullerols, are nanocomposites with a closed symmetrical structure with anti-inflammatory and anti-oxidant properties. The present study evaluated the effects of treatment with the fullerol (C60(OH)18-20) in the development and pathogenesis of GVHD in a murine model. Mice with experimental GVHD that were treated with the fullerol showed reduced clinical signs of disease and mortality compared with untreated mice. Treatment with the fullerol decreased the hepatic damage associated with reduced hepatic levels of reactive oxygen species, pro-inflammatory cytokines and chemokines (IFN-γ TNF-α, CCL2, CCL3 and CCL5) and reduced leukocyte accumulation. The amelioration of GVHD after treatment with the fullerol was also associated with reduced intestinal lesions and consequent bacterial translocation to the blood, liver and peritoneal cavity. Moreover, the fullerol treatment alleviated the GVHD while preserving effects of the graft against a leukemia cell line (GFP+P815). In summary, the fullerol was effective in reducing the GVHD inflammatory response in mice and may suggest novel ways to treat this disease.

Treadmill exercise induces neutrophil recruitment into muscle tissue in a reactive oxygen species-dependent manner. An intravital microscopy study.

Intense exercise is a physiological stress capable of inducing the interaction of neutrophils with muscle endothelial cells and their transmigration into tissue. Mechanisms driving this physiological inflammatory response are not known. Here, we investigate whether production of reactive oxygen species is relevant for neutrophil interaction with endothelial cells and recruitment into the quadriceps muscle in mice subjected to the treadmill fatiguing exercise protocol. Mice exercised until fatigue by running for 56.3±6.8 min on an electric treadmill. Skeletal muscle was evaluated by intravital microscopy at different time points after exercise, and then removed to assess local oxidative stress and histopathological analysis. We observed an increase in plasma lactate and creatine kinase (CK) concentrations after exercise. The numbers of monocytes, neutrophils, and lymphocytes in blood increased 12 and 24 hours after the exercise. Numbers of rolling and adherent leukocytes increased 3, 6, 12, and 24 hours post-exercise, as assessed by intravital microscopy. Using LysM-eGFP mice and confocal intravital microscopy technology, we show that the number of transmigrating neutrophils increased 12 hours post-exercise. Mutant gp91phox-/- (non-functional NADPH oxidase) mice and mice treated with apocynin showed diminished neutrophil recruitment. SOD treatment promoted further adhesion and transmigration of leukocytes 12 hours after the exercise. These findings confirm our hypothesis that treadmill exercise increases the recruitment of leukocytes to the postcapillary venules, and NADPH oxidase-induced ROS plays an important role in this process.

Platelet-activating factor receptor plays a role in the pathogenesis of graft-versus-host disease by regulating leukocyte recruitment, tissue injury, and lethality.

PAF is a potent lipid mediator involved in several manifestations of acute inflammation, including leukocyte influx, leukocyte interaction with endothelium, and production of inflammatory cytokines. The present study evaluated the relevance of PAFR for the pathogenesis of acute GVHD using a model of adoptive transfer of splenocytes from WT or PAFR(-/-) C57BL/6J to B6D2F1 mice. Mice, which received PAFR(-/-) splenocytes or treatment with the PAFR antagonist, showed reduced clinical signs of disease and no mortality. In GVHD mice receiving PAFR(-/-) splenocytes, there was deceased bacterial translocation and tissue injury. Furthermore, production of proinflammatory cytokines and chemokines (TNF-α, IFN-γ, CCL2, CCL3, and CCL5) and accumulation of CD8(+) cells in intestine and liver were reduced in mice transplanted with the PAFR(-/-) splenocyte. Mechanistically, an absence or pharmacological blockade of PAFR was associated with decreased rolling and adhesion of leukocytes to the mesenteric microcirculation, as assessed by intravital microscopy. Despite decreased GVHD, there was maintained GVL activity when PAFR(-/-) leukocytes were transferred into WT mice. In conclusion, PAFR on donor leukocytes plays a critical role in GVHD by mediating leukocyte influx and cytokine production in target tissues. PAFR antagonist may potentially be useful in the treatment of GVHD in bone marrow-transplanted patients.

PI3Kγ controls leukocyte recruitment, tissue injury, and lethality in a model of graft-versus-host disease in mice.

PI(3)Kγ is thought to mediate leukocyte migration to injured tissues and may be important in the pathogenesis of various T-lymphocyte-dependent pathologies, including autoimmune and inflammatory diseases. The present study evaluated the relevance of PI(3)Kγ in donor cells for the pathogenesis of acute GVHD using a model of adoptive transfer of splenocytes from WT or PI(3)Kγ(-/-) C57BL/6J mice to B6D2F1 mice, and mice that received PI(3)Kγ(-/-) cells showed reduced clinical signs of disease, bacterial translocation, tissue injury, and lethality rates. This was associated with reduced production of proinflammatory cytokines and chemokines (TNF-α, IFN-γ, CCL2, CCL3, and CCL5) and reduced infiltration of CD8(+), CD4(+), and CD11c(+) cells in the small intestine. Mechanistically, in addition to decreasing production of proinflammatory mediators, absence or pharmacological blockade of PI(3)Kγ was associated with decreased rolling and adhesion of leukocytes to the mesenteric microcirculation, as assessed by intravital microscopy. Despite decreased GVHD, there was maintained GVL activity when PI(3)Kγ(-/-) leukocytes were transferred into WT mice. In conclusion, PI(3)Kγ plays a critical role in GVHD by mediating leukocyte influx and activation in tissues. PI(3)Kγ inhibitors may be useful in the treatment of GVHD in patients undergoing BMT.