Cerebral and peripheral changes occurring in nitric oxide (NO) synthesis in a rat model of sleeping sickness: identification of brain iNOS expressing cells.
BACKGROUND
The implication of nitric oxide (NO) in the development of human African trypanosomiasis (HAT) using an animal model, was examined. The manner by which the trypanocidal activity of NO is impaired in the periphery and in the brain of rats infected with Trypanosoma brucei brucei (T. b. brucei) was analyzed through: (i) the changes occurring in NO concentration in both peripheral (blood) and cerebral compartments; (ii) the activity of nNOS and iNOS enzymes; (iii) identification of the brain cell types in which the NO-pathways are particularly active during the time-course of the infection.


RESULTS
NO concentration (direct measures by voltammetry) was determined in central (brain) and peripheral (blood) compartments in healthy and infected animals at various days post-infection: D5, D10, D16 and D22. Opposite changes were observed in the two compartments. NO production increased in the brain (hypothalamus) from D10 (+32%) to D16 (+71%), but decreased in the blood from D10 (-22%) to D16 (-46%) and D22 (-60%). In parallel with NO measures, cerebral iNOS activity increased and peaked significantly at D16 (up to +700%). However, nNOS activity did not vary. Immunohistochemical staining confirmed iNOS activation in several brain regions, particularly in the hypothalamus. In peritoneal macrophages, iNOS activity decreased from D10 (-83%) to D16 (-65%) and D22 (-74%) similarly to circulating NO.


CONCLUSIONS
The NO changes observed in our rat model were dependent on iNOS activity in both peripheral and central compartments. In the periphery, the NO production decrease may reflect an arginase-mediated synthesis of polyamines necessary to trypanosome growth. In the brain, the increased NO concentration may result from an enhanced activity of iNOS present in neurons and glial cells. It may be regarded as a marker of deleterious inflammatory reactions.
Amrouni
Donia
D
University of Lyon, Faculty of Medicine, EA 4170 Laboratory of Free Radicals, Energy Substrates and Cerebral Physiopathology, & Neurochem platform, Lyon, France.
Gautier-Sauvigné
Sabine
S
Meiller
Anne
A
Vincendeau
Philippe
P
Bouteille
Bernard
B
Buguet
Alain
A
Cespuglio
Raymond
R
D000818:Animals; D001253:Astrocytes / Q000201:enzymology; D001921:Brain / Q000378:metabolism* / Q000469:parasitology / Q000473:pathology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D055664:Electrochemical Techniques; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D006790:Host-Parasite Interactions; D006801:Humans; D007150:Immunohistochemistry; D017737:Macrophages, Peritoneal / Q000201:enzymology; D008297:Male; D017628:Microglia / Q000201:enzymology; D009474:Neurons / Q000201:enzymology; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000097:blood; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014346:Trypanosoma brucei brucei / Q000502:physiology; D014353:Trypanosomiasis, African / Q000201:enzymology / Q000378:metabolism* / Q000469:parasitology
D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II