Therapeutic effect of Lipoxin A4 in malaria-induced acute lung injury.

Acute lung injury (ALI) models are characterized by neutrophil accumulation, tissue damage, alteration of the alveolar capillary membrane, and physiological dysfunction. Lipoxin A4  (LXA4 ) is an anti-inflammatory eicosanoid that was demonstrated to attenuate lipopolysaccharide-induced ALI. Experimental models of severe malaria can be associated with lung injury. However, to date, a putative effect of LXA4  on malaria (M)-induced ALI has not been addressed. In this study, we evaluated whether LXA4 exerts an effect on M-ALI. Male C57BL/6 mice were randomly assigned to the following five groups: noninfected; saline-treated Plasmodium berghei-infected; LXA4 -pretreated P. berghei-infected (LXA4  administered 1 h before infection and daily, from days 0 to 5 postinfection), LXA4 - and LXA4 receptor antagonist BOC-2-pretreated P. berghei-infected; and LXA4 -posttreated P. berghei-infected (LXA4  administered from days 3 to 5 postinfection). By day 6, pretreatment or posttreatment with LXA4  ameliorate lung mechanic dysfunction reduced alveolar collapse, thickening and interstitial edema; impaired neutrophil accumulation in the pulmonary tissue and blood; and reduced the systemic production of CXCL1. Additionally, in vitro treatment with LXA4 prevented neutrophils from migrating toward plasma collected from P. berghei-infected mice. LXA4  also impaired neutrophil cytoskeleton remodeling by inhibiting F-actin polarization. Ex vivo analysis showed that neutrophils from pretreated and posttreated mice were unable to migrate. In conclusion, we demonstrated that LXA4  exerted therapeutic effects in malaria-induced ALI by inhibiting lung dysfunction, tissue injury, and neutrophil accumulation in lung as well as in peripheral blood. Furthermore, LXA4 impaired the migratory ability of P. berghei-infected mice neutrophils.

Endothelial-Leukocyte Interaction in Severe Malaria: Beyond the Brain.

Malaria is the most important parasitic disease worldwide, accounting for 1 million deaths each year. Severe malaria is a systemic illness characterized by dysfunction of brain tissue and of one or more peripheral organs as lungs and kidney. The most severe and most studied form of malaria is associated with cerebral complications due to capillary congestion and the adhesion of infected erythrocytes, platelets, and leukocytes to brain vasculature. Thus, leukocyte rolling and adhesion in the brain vascular bed during severe malaria is singular and distinct from other models of inflammation. The leukocyte/endothelium interaction and neutrophil accumulation are also observed in the lungs. However, lung interactions differ from brain interactions, likely due to differences in the blood-brain barrier and blood-air barrier tight junction composition of the brain and lung endothelium. Here, we review the importance of endothelial dysfunction and the mechanism of leukocyte/endothelium interaction during severe malaria. Furthermore, we hypothesize a possible use of adjunctive therapies to antimalarial drugs that target the interaction between the leukocytes and the endothelium.

Mesenchymal stromal cell therapy attenuated lung and kidney injury but not brain damage in experimental cerebral malaria.

INTRODUCTION: Malaria is the most relevant parasitic disease worldwide, and still accounts for 1 million deaths each year. Since current antimalarial drugs are unable to prevent death in severe cases, new therapeutic strategies have been developed. Mesenchymal stromal cells (MSC) confer host resistance against malaria; however, thus far, no study has evaluated the therapeutic effects of MSC therapy on brain and distal organ damage in experimental cerebral malaria. METHODS: Forty C57BL/6 mice were injected intraperitoneally with 5 × 10(6) Plasmodium berghei-infected erythrocytes or saline. After 24 h, mice received saline or bone marrow (BM)-derived MSC (1x10(5)) intravenously and were housed individually in metabolic cages. After 4 days, lung and kidney morphofunction; cerebrum, spleen, and liver histology; and markers associated with inflammation, fibrogenesis, and epithelial and endothelial cell damage in lung tissue were analyzed. RESULTS: In P. berghei-infected mice, BM-MSCs: 1) reduced parasitemia and mortality; 2) increased phagocytic neutrophil content in brain, even though BM-MSCs did not affect the inflammatory process; 3) decreased malaria pigment detection in spleen, liver, and kidney; 4) reduced hepatocyte derangement, with an increased number of Kupffer cells; 5) decreased kidney damage, without effecting significant changes in serum creatinine levels or urinary flow; and 6) reduced neutrophil infiltration, interstitial edema, number of myofibroblasts within interstitial tissue, and collagen deposition in lungs, resulting in decreased lung static elastance. These morphological and functional changes were not associated with changes in levels of tumor necrosis factor-α, keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8), or interferon-γ, which remained increased and similar to those of P. berghei animals treated with saline. BM-MSCs increased hepatocyte growth factor but decreased VEGF in the P. berghei group. CONCLUSIONS: BM-MSC treatment increased survival and reduced parasitemia and malaria pigment accumulation in spleen, liver, kidney, and lung, but not in brain. The two main organs associated with worse prognosis in malaria, lung and kidney, sustained less histological damage after BM-MSC therapy, with a more pronounced improvement in lung function.

Lipoxin A4 attenuates endothelial dysfunction during experimental cerebral malaria.

A breakdown of the brain-blood barrier (BBB) due to endothelial dysfunction is a primary feature of cerebral malaria (CM). Lipoxins (LX) are specialized pro-resolving mediators that attenuate endothelial dysfunction in different vascular beds. It has already been shown that LXA4 prolonged Plasmodium berghei-infected mice survival by a mechanism that depends on inhibiting IL-12 production and CD8(+)IFN-γ(+) T cells in brain tissue; however, the effects of this treatment on endothelial dysfunction induced during experimental cerebral malaria (ECM) remains to be elucidated. Herein, we investigate the role of LXA4 on endothelial dysfunction during ECM. The treatment of P. berghei-infected mice with LXA4 prevented BBB breakdown and ameliorated behavioral symptoms but did not modulate TNF-α production. In addition, microcirculation analysis showed that treatment with LXA4 significantly increased functional capillary density in brains of P. berghei-infected C57BL/6 mice. Furthermore, histological analyses of brain sections demonstrated that exogenous LXA4 reduced capillary congestion that was accompanied by reduced ICAM-1 expression in the brain tissue. In agreement, LXA4 treatment of endothelial cells stimulated by Plasmodium berghei (Pb)- or Plasmodium falciparum (Pf)-parasitized red blood cells (RBCs) inhibited ICAM-1 expression. Additionally, LXA4 treatment restored the expression of HO-1 that is reduced during ECM. As well, LXA4 treatment inhibits PbRBC and PfRBC adhesion to endothelial cells that was reversed by the use of an HO-1 inhibitor (ZnPPIX). Our results demonstrate for the first time that LXA4 ameliorates endothelial dysfunction during ECM by modulating ICAM-1 and HO-1 expression in brain tissue.

Anti-inflammatory effects of methyl ursolate obtained from a chemically derived crude extract of apple peels: potential use in rheumatoid arthritis.

Ursolic acid (UA), a pentacyclic triterpene acid found in apple peels (Malus domestica, Borkh, Rosaceae), has a large spectrum of pharmacological effects. However, the vegetal matrix usually produces highly viscous and poorly soluble extracts that hamper the isolation of this compound. To overcome this problem, the crude EtOH-AcOEt extract of commercial apple peels was exhaustively treated with diazomethane, after which methyl ursolate (MU) was purified by column chromatography and characterized spectrometrically. The anti-inflammatory effects of UA and MU (50 mg/kg) were analyzed by zymosan-induced paw edema, pleurisy and in an experimental arthritis model. After 4 h of treatment with UA and MU, paw edema was reduced by 46 and 44 %, respectively. Both UA and MU inhibited protein extravasation into the thoracic cavity; tibio-femoral edema by 40 and 48 %, respectively; and leukocyte influx into the synovial cavity after 6 h by 52 and 73 %, respectively. Additionally, both UA and MU decreased the levels of mediators related to synovial inflammation, such as KC/CXCL-1 levels by 95 and 90 %, TNF-α levels by 76 and 71 %, and IL-1ß levels by 57 and 53 %, respectively. Both the compounds were equally effective when assayed in different inflammatory models, including experimental arthritis. Hence, MU may be considered to be a useful anti-inflammatory derivative to overcome the inherent poor solubility of UA for formulating pharmaceutical products.

Early and late acute lung injury and their association with distal organ damage in murine malaria.

Severe malaria is characterised by cerebral oedema, acute lung injury (ALI) and multiple organ dysfunctions, however, the mechanisms of lung and distal organ damage need to be better clarified. Ninety-six C57BL/6 mice were injected intraperitoneally with 5×10(6)Plasmodium berghei ANKA-infected erythrocytes or saline. At day 1, Plasmodium berghei infected mice presented greater number of areas with alveolar collapse, neutrophil infiltration and interstitial oedema associated with lung mechanics impairment, which was more severe at day 1 than day 5. Lung tumour necrosis factor-α and chemokine (C-X-C motif) ligand 1 levels were higher at day 5 compared to day 1. Lung damage occurred in parallel with distal organ injury at day 1; nevertheless, lung inflammation and the presence of malarial pigment in distal organs were more evident at day 5. In conclusion, ALI develops prior to the onset of cerebral malaria symptoms. Later during the course of infection, the established systemic inflammatory response increases distal organ damage.