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

<p>Abstract</p> <p>Background</p> <p>Cerebral 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.</p> <p>Methods</p> <p>C57Bl/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.</p> <p>Results</p> <p>PbA-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.</p> <p>Conclusions</p> <p>These 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.</p

Monoclonal auto-antibodies and sera of autoimmune patients react with Plasmodium falciparum and inhibit its in vitro growth

The relationship between autoimmunity and malaria is not well understood. To determine whether autoimmune responses have a protective role during malaria, we studied the pattern of reactivity to plasmodial antigens of sera from 93 patients with 14 different autoimmune diseases (AID) who were not previously exposed to malaria. Sera from patients with 13 different AID reacted against Plasmodium falciparum by indirect fluorescent antibody test with frequencies varying from 33-100%. In addition, sera from 37 AID patients were tested for reactivity against Plasmodium yoelii 17XNL and the asexual blood stage forms of three different P. falciparum strains. In general, the frequency of reactive sera was higher against young trophozoites than schizonts (p < 0.05 for 2 strains), indicating that the antigenic determinants targeted by the tested AID sera might be more highly expressed by the former stage. The ability of monoclonal auto-antibodies (auto-Ab) to inhibit P. falciparum growth in vitro was also tested. Thirteen of the 18 monoclonal auto-Ab tested (72%), but none of the control monoclonal antibodies, inhibited parasite growth, in some cases by greater than 40%. We conclude that autoimmune responses mediated by auto-Ab may present anti-plasmodial activity

Efficacy of different nitric oxide-based strategies in preventing experimental cerebral malaria by Plasmodium berghei ANKA

Submitted by Sandra Infurna ([email protected]) on 2017-04-18T15:35:29Z No. of bitstreams: 1 leonardo2_carvalho_etal_IOC_2012.pdf: 999955 bytes, checksum: c33bcd75b4b7eab314cad46f4da7ddb3 (MD5)Approved for entry into archive by Sandra Infurna ([email protected]) on 2017-04-18T15:42:36Z (GMT) No. of bitstreams: 1 leonardo2_carvalho_etal_IOC_2012.pdf: 999955 bytes, checksum: c33bcd75b4b7eab314cad46f4da7ddb3 (MD5)Made available in DSpace on 2017-04-18T15:42:36Z (GMT). No. of bitstreams: 1 leonardo2_carvalho_etal_IOC_2012.pdf: 999955 bytes, checksum: c33bcd75b4b7eab314cad46f4da7ddb3 (MD5) Previous issue date: 2012La Jolla Bioengineering Institute. Center for Malaria Research. San Diego, CA, USA / Universidade Federal do Rio de Janeiro. Laboratório de Inflamação e Imunidade. Rio de Janeiro, RJ, Brasil.La Jolla Bioengineering Institute. Center for Malaria Research. San Diego, CA, USA / Fundação Oswaldo Cruz. Instituto de Pesquisa Clínica Evandro Chagas. Serviço de Parasitologia. Rio de Janeiro, RJ, Brasil.La Jolla Bioengineering Institute. Center for Malaria Research. San Diego, CA, USA.La Jolla Bioengineering Institute. Center for Malaria Research. San Diego, CA, USA / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Pesquisa em Malária. Rio de Janeiro, RJ, Brasil.Background: Low nitric oxide (NO) bioavailability plays a role in the pathogenesis of human as well as of experimental cerebral malaria (ECM) caused by Plasmodium berghei ANKA (PbA). ECM is partially prevented by administration of the NOdonor dipropylenetriamine NONOate (DPTA-NO) at high concentration (1 mg/mouse), which also induces major side effects such as a sharp drop in blood pressure. We asked whether alternative strategies to improve NO bioavailability with minor side effects would also be effective in preventing ECM. Methodology/Principal Findings: Mice were infected with PbA and prophylactically treated twice a day with bolus injections of L-arginine, Nv-hydroxy-nor-Arginine (nor-NOHA), tetrahydrobiopterin (BH4), separately or combined, sodium nitrite, sildenafil or sildenafil plus DPTA-NO starting on day 0 of infection. L-arginine and BH4 supplementation, with or without arginase inhibition by nor-NOHA, increased plasma nitrite levels but failed to protect against ECM development. Accordingly, prophylactic treatment with continuous delivery of L-arginine using osmotic pumps also did not improve survival. Similar outcomes were observed with sodium nitrite sildenafil (aimed at inhibiting hosphodiesterase-5) or with DPTA-NO. However, sildenafil (0.1 mg/mouse) in combination with a lower dose (0.1 mg/mouse) of DPTA-NO decreased ECM incidence (8267.4% mortality in the saline group and 38610.6% in the treated group; p,0.05). The combined prophylactic therapy did not aggravate anemia, had delayed effects in systolic, diastolic and mean arterial blood pressure and induced lower effects in pulse pressure when compared to DPTA-NO 1 mg/mouse. Conclusions/Significance: These data show that sildenafil lowers the amount of NO-donor needed to prevent ECM, resulting also in lesser side effects. Prophylactic L-arginine when given in bolus or continuous delivery and bolus BH4 supplementation, with or without arginase inhibition, were able to increase NO bioavailability in PbA-infected mice but failed to decrease ECM incidence in the doses and protocol used

PDE-5 inhibition with sildenafil or sodium nitrite (NaNO₂) supplementation did not prevent ECM.

<p>Cumulative survival (A), course of parasitemia (B), rectal temperature (C), and motor behavior score (D) of PbA-infected mice prophylactic treated with saline (n = 28), NaNO₂ (n = 13), and sildenafil at 0.1 (n = 19), 0.01 (n = 12) or 0.001(n = 5) mg/mouse. Rectal temperature and motor behavior score were measured on day 6 of infection. There were no significant differences in the parameters analyzed (p>0.05 for all comparisons).</p

L-arginine and/or tetrahydro-L-Biopterin (BH4) supplementation combined or not with arginase inhibition did not prevent ECM.

<p>Cumulative survival (A), course of parasitemia (B), rectal temperature (C), and motor behavior score (D) of PbA-infected mice treated with bolus injections of saline (n = 22), L-arginine 4 mg/mouse (n = 9), the arginase inhibitor Nω-hydroxy-nor-Arginine (nor-NOHA) 250 µg/mouse (n = 15), BH4 1 mg/mouse (n = 9), nor-NOHA+L-arginine (n = 16), and nor-NOHA+L-arginine+BH4 (n = 9). Rectal temperature and motor behavior score were measured on day 6 of infection. Exhaled NO (E) from selected groups was measured 1 hour after the morning treatment on day 5 of infection (n≥5 per group). Plasma nitrite (F) from selected groups treated with bolus injections. Cumulative survival (<b>G</b>) and plasma nitrite (<b>H</b>) of PbA-infected mice prophylactic treated with continuous L-arginine or saline supplementation using implanted osmotic pumps (n = 10 per group). Plasma nitrite (F, H) was measured on samples collected prior to the morning dosing on day 6 of infection (n≥5 per group). *p<0.05, **p<0.01, ***p<0.001, arrows indicate the presence of a linear trend.</p

PDE-5 inhibition with sildenafil decreases the amount of dipropylenetriamine NONOate (DPTA-NO) necessary to prevent ECM.

<p>Cumulative survival (A), course of parasitemia (B), rectal temperature (C), and motor behavior score (D) of PbA-infected mice treated with saline (n = 29), DPTA-NO (1, 0.1 or 0.01 mg/mouse, n = 10 per group), DPTA-NO+sildenafil (0.1 mg/mouse of each drug, n = 18), and sildenafil (0.1 mg/mouse, n = 19). Plasma nitrite (E) and hematocrit (F) from selected groups were measured on samples collected prior to the morning dosing on day 6 of infection (n≥5 per group). *p<0.05, **p<0.01, ***p<0.001, arrows indicate the presence of a linear trend.</p