Neurodegeneration and increased production of nitrotyrosine, nitric oxide synthase, IFN-gamma and S100beta protein in the spinal cord of IL-12p40-deficient mice infected with Trypanosoma cruzi.
OBJECTIVE
Chagas' disease is caused by Trypanosoma cruzi and occurs in most Latin American countries. The protozoan may colonize the central nervous system (CNS) of immune-compromised human hosts, thus causing neuronal disorders. Systemic control of the intracellular forms of the parasite greatly depends on the establishment of a TH1 response and subsequent nitric oxide (NO) release. At the CNS, it is known that low concentrations of NO promote neuronal survival and growth, while high concentrations exert toxic effects and neuron death. Accounting for NO production by astrocytes is the glia-derived factor S100beta, which is overproduced in some neurodegenerative diseases. In the current work, we studied the expression of NO, interferon (IFN)-gamma and S100beta in the spinal cord tissue of IL-12p40KO mice infected with T. cruzi, a model of neurodegenerative process.


METHODS
IL-12p40KO and wild-type (WT) female mice infected with T. cruzi Sylvio X10/4 (10(5) trypomastigotes, intraperitoneally) were euthanized when IL-12p40KO individuals presented limb paralysis. Spinal cord sections were submitted to immunohistochemical procedures for localization of neurofilament, laminin, nitrotyrosine, NO synthases (NOS), IFN-gamma and S100beta. The total number of neurons was estimated by stereological analysis and the area and intensity of immunoreactivities were assessed by microdensitometric/morphometric image analysis.


RESULTS
No lesion was found in the spinal cord sections of WT mice, while morphological disarrangements, many inflammatory foci, enlarged vessels, amastigote nests and dying neurons were seen at various levels of IL-12p40KO spinal cord. Compared to WT mice, IL-12p40KO mice presented a decrement on total number of neurons (46.4%, p < 0.05) and showed increased values of immunoreactive area for nitrotyrosine (239%, p < 0.01) and NOS (544%, p < 0.001). Moreover, the intensity of nitrotyrosine (16%, p < 0.01), NOS (38%, p < 0.05) and S100beta (21%, p < 0.001) immunoreactivities were also augmented. No IFN-gamma-labeled cells were seen in WT spinal cord tissue, contrary to IL-12p40KO tissue that displayed inflammatory infiltrating cells and also some parenchymal cells positively labeled.


CONCLUSIONS
We suggest that overproduction of NO may account for neuronal death at the spinal cord of T. cruzi-infected IL-12p40KO mice and that IFN-gamma and S100beta may contribute to NOS activation in the absence of IL-12.
Bombeiro
André Luis
AL
Department of Immunology, Biomedical Sciences Institute, University of São Paulo, São Paulo, Brazil. andrelb@icb.usp.br
D'Império Lima
Maria Regina
MR
Chadi
Gerson
G
Alvarez
José Maria
JM
D000818:Animals; D002478:Cells, Cultured; D014355:Chagas Disease / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D005260:Female; D006790:Host-Parasite Interactions; D007113:Immunity, Innate / Q000276:immunology; D018836:Inflammation Mediators / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D053762:Interleukin-12 Subunit p40 / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009187:Myelitis / Q000378:metabolism* / Q000469:parasitology / Q000503:physiopathology; D009410:Nerve Degeneration / Q000378:metabolism* / Q000469:parasitology / Q000503:physiopathology; D009414:Nerve Growth Factors / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000469:parasitology / Q000473:pathology; D009569:Nitric Oxide / Q000096:biosynthesis*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D010264:Paraplegia / Q000378:metabolism / Q000469:parasitology / Q000503:physiopathology; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism* / Q000469:parasitology / Q000503:physiopathology; D014349:Trypanosoma cruzi / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D018836:Inflammation Mediators; D053762:Interleukin-12 Subunit p40; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D007371:Interferon-gamma; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse