Exogenous nitric oxide decreases brain vascular inflammation, leakage and venular resistance during Plasmodium berghei ANKA infection in mice

Abstract

BackgroundCerebral malaria (CM) is a lethal complication of Plasmodium falciparum infections. In the Plasmodium berghei ANKA (PbA) murine model, CM is associated with marked brain inflammation, increased expression of endothelial cell adhesion molecules and leukocyte and platelet accumulation in brain vessels, causing vascular occlusion and decreased blood flow, damaging the endothelium and leading to blood-brain barrier breakdown, leakage and hemorrhages. Exogenous nitric oxide (NO) administration largely prevents the syndrome. Here we evaluated whether the mechanism of action of NO in preventing murine CM is related to its anti-inflammatory properties and to protection of the endothelium.MethodsC57Bl/6 mice infected with PbA were treated twice a day with saline or dipropylenetriamineNONOate (DPTA-NO). Endothelial cell adhesion molecule (ICAM-1, VCAM, E- and P-selectin) expression in brain tissue on day 6 of infection was assessed in both groups by western blot. For intravital microscopy studies, DPTA-NO-treated and saline-treated mice with a previously implanted closed cranial window were injected with albumin-FITC, anti-CD45-TxR and anti-CD41-FITC antibodies on day 6 of infection for quantification of albumin leakage, leukocyte and platelet adherence in pial vessels.ResultsPbA-infected mice treated with the NO-donor DPTA-NO showed decreased expression of ICAM-1 and P-selectin, but not VCAM-1, in the brain, compared to saline-treated mice. DPTA-NO treatment also decreased the number of adherent leukocytes and platelets in pial vessels, particularly in venules 30-50 μm in diameter, decreased inflammatory vascular resistance and prevented the occurrence of arteriolar and venular albumin leakage observed in saline-treated PbA-infected mice, as assessed by intravital microscopy.ConclusionsThese results indicate that the protective effect of exogenous NO on murine CM is associated with decreased brain vascular expression of inflammatory markers resulting in attenuated endothelial junction damage and facilitating blood flow.

Transdermal Glyceryl Trinitrate as an Effective Adjunctive Treatment with Artemether for Late-Stage Experimental Cerebral Malaria

“…Similarly to human severe malaria, low NO bioavailability has been linked to the genesis of ECM (9,22,23). We have shown that exogenous NO administration in the form of NO donors such as dipropylenetriamine NONOate (DPTA-NO) and S-nitrosoglutathione (GSNO) decreases ECM incidence, as well as cerebral edema, leukocyte accumulation, and hemorrhages (22,24,25). Similar findings were obtained with inhaled NO (26).…”

“…Indeed, iNOS and eNOS upregulation has been shown to be triggered by an increase in oxidative stress under conditions of low NO bioavailability (47), similar to the conditions observed in ECM (37). Therefore, providing exogenous NO during PbA infection may prevent the very causes of iNOS and eNOS upregulation, decreasing inflammation and ameliorating endothelial function in ECM (22,24,25). Glyceryl trinitrate had a more uniform effect in preventing iNOS than eNOS upregulation, resulting in more variable expression of the latter.…”

“…We have previously shown that NO donors such as DPTA-NO and GSNO partially prevent ECM development and decrease vascular pathology, improving pial blood flow and attenuating vasoconstriction, inflammation, and hemorrhages (24,25,33). Glyceryl trinitrate showed similar effects and, as a drug for potential use in the clinical setting, it has a number of advantages over DPTA-NO and GSNO: (i) clinical data on glyceryl trinitrate are abundant, with a long history of efficacy and safety; (ii) several formulations are available, including transdermal patches that allow continuous delivery of sustained levels for prolonged periods of time; (iii) available formulations are stable for long periods at room temperature; and (iv) glyceryl trinitrate is inexpensive and easily accessible.…”

Nitric Oxide / Cyclic Nucleotide Regulation of Globin Genes in Erythropoiesis

“…The protecting effects of exogenous NO on murine cerebral malaria are associated with decreased brain vascular expression of inflammatory markers, ICAM-1 and P-selectin, resulting in attenuated endothelial damage and facilitating blood flow (Zanini et al, 2011). Previous reports demonstrated reduced NO levels in severe malaria related to impaired production of NO, reduced mononuclear cell iNOS expression and NOS substrate arginine (Anstey et al, 1996;Lopansri et al, 2003).…”

Pathophysiological Mechanisms in Gaseous Therapies for Severe Malaria

“…NO decreases the expression of endothelium activation markers and reduces the expression of adhesion molecules, such as ICAM-1 and P-selectin, resulting in decreased vascular permeability (61) and leukocyte and platelet adhesion (62).…”