Maria Alice da Cruz Höfling

Acute blood-brain barrier permeabilization in rats after systemic Phoneutria nigriventer venom

A highly controlled transport of substances at the interface between blood and brain characterizes the blood-brain barrier (BBB), fundamental for maintenance of the homeostasis of the cerebral milieu. In this study, we investigated the time course (15 min, 1, 2, and 5 h) of BBB opening induced by intravenous (i.v.) injection of Phoneutria nigriventer spider venom (PNV) using quantitative and morphological approaches on cerebellum and hippocampus vessels for assessment of BBB permeability. The results showed vasogenic edema and tracer extravasation faster and severalfold higher in hippocampus than in cerebellum. Reactive astrocytes with swollen perivascular end-feet processes were found only in cerebellum. An immediate and total degradation of laminin in capillaries occurred resulting in the disappearance of the basement membrane. In medium-sized vessels, this effect was less prominent. The changes were transient, with cerebellum in general presenting a faster recovery. However, at 5 h laminin was overexpressed, principally in hippocampus. The rapid and abrupt shift of laminin expression in capillaries (at 15 min) coincided with the immediate and severe signs of intoxication shown by the animals, but not with the peak of leakage of vessels and vasogenic edema, which occurred later (1-2 h). The findings suggest a complex regulatory mechanism, since the extension of BBB impairment caused by PNV depends on the region of the SNC, and on the vessels types. It is suggested that the components of the BBB (gliovascular unit) have a critical role in these differences. P. nigriventer venom can be a useful tool to explore the mechanisms of BBB.

Aspectos da espermatogênese de tucunaré, Cichla ocellaris Schneider, 1801 (TELEOSTEI, CICHLIDAE).

Sequential cytological events οf Cichla ocellaris spermatogenesis were studied with electron microscopy from the est spermatocyte to the nature spermatozoa. Five stages of sermatid maturation were described.

Dendritic cells treated with crude Plasmodium berghei extracts acquire immune-modulatory properties and suppress the development of autoimmune neuroinflammation.

Dendritic cells (DCs) are professional antigen‐presenting cells specifically targeted during Plasmodium infection. Upon infection, DCs show impaired antigen presentation and T‐cell activation abilities. In this study, we aimed to evaluate whether cellular extracts obtained from Plasmodium berghei‐infected erythrocytes (PbX) modulate DCs phenotypically and functionally and the potential therapeutic usage of PbX‐modulated DCs in the control of experimental autoimmune encephalomyelitis (EAE, the mouse model for human multiple sclerosis). We found that PbX‐treated DCs have impaired maturation and stimulated the generation of regulatory T cells when cultured with naive T lymphocytes in vitro. When adoptively transferred to C57BL/6 mice the EAE severity was reduced. Disease amelioration correlated with a diminished infiltration of cytokine‐producing T cells in the central nervous system as well as the suppression of encephalitogenic T cells. Our study shows that extracts obtained from P. berghei‐infected erythrocytes modulate DCs towards an immunosuppressive phenotype. In addition, the adoptive transfer of PbX‐modulated DCs was able to ameliorate EAE development through the suppression of specific cellular immune responses towards neuro‐antigens. To our knowledge, this is the first study to present evidence that DCs treated with P. berghei extracts are able to control autoimmune neuroinflammation.

Exacerbation of Autoimmune Neuro-Inflammation in Mice Cured from Blood-Stage Plasmodium berghei Infection

The thymus plays an important role shaping the T cell repertoire in the periphery, partly, through the elimination of inflammatory auto-reactive cells. It has been shown that, during Plasmodium berghei infection, the thymus is rendered atrophic by the premature egress of CD4+CD8+ double-positive (DP) T cells to the periphery. To investigate whether autoimmune diseases are affected after Plasmodium berghei NK65 infection, we immunized C57BL/6 mice, which was previously infected with P.berghei NK65 and treated with chloroquine (CQ), with MOG35–55 peptide and the clinical course of Experimental Autoimmune Encephalomyelitis (EAE) was evaluated. Our results showed that NK65+CQ+EAE mice developed a more severe disease than control EAE mice. The same pattern of disease severity was observed in MOG35–55-immunized mice after adoptive transfer of P.berghei-elicited splenic DP-T cells. The higher frequency of IL-17+- and IFN-γ+-producing DP lymphocytes in the Central Nervous System of these mice suggests that immature lymphocytes contribute to disease worsening. To our knowledge, this is the first study to integrate the possible relationship between malaria and multiple sclerosis through the contribution of the thymus. Notwithstanding, further studies must be conducted to assert the relevance of malaria-induced thymic atrophy in the susceptibility and clinical course of other inflammatory autoimmune diseases.

Violacein Treatment Modulates Acute and Chronic Inflammation through the Suppression of Cytokine Production and Induction of Regulatory T Cells

Inflammation is a necessary process to control infection. However, exacerbated inflammation, acute or chronic, promotes deleterious effects in the organism. Violacein (viola), a quorum sensing metabolite from the Gram-negative bacterium Chromobacterium violaceum, has been shown to protect mice from malaria and to have beneficial effects on tumors. However, it is not known whether this drug possesses anti-inflammatory activity. In this study, we investigated whether viola administration is able to reduce acute and chronic autoimmune inflammation. For that purpose, C57BL/6 mice were intraperitoneally injected with 1 μg of LPS and were treated with viola (3.5mg/kg) via i.p. at the same time-point. Three hours later, the levels of inflammatory cytokines in the sera and phenotypical characterization of leukocytes were determined. Mice treated with viola presented a significant reduction in the production of inflammatory cytokines compared with untreated mice. Interestingly, although viola is a compound derived from bacteria, it did not induce inflammation upon administration to naïve mice. To test whether viola would protect mice from an autoimmune inflammation, Experimental Autoimmune Encephalomyelitis (EAE)-inflicted mice were given viola i.p. at disease onset, at the 10th day from immunization. Viola-treated mice developed mild EAE disease in contrast with placebo-treated mice. The frequencies of dendritic cells and macrophages were unaltered in EAE mice treated with viola. However, the sole administration of viola augmented the levels of splenic regulatory T cells (CD4+Foxp3+). We also found that adoptive transfer of viola-elicited regulatory T cells significantly reduced EAE. Our study shows, for the first time, that violacein is able to modulate acute and chronic inflammation. Amelioration relied in suppression of cytokine production (in acute inflammation) and stimulation of regulatory T cells (in chronic inflammation). New studies must be conducted in order to assess the possible use of viola in therapeutic approaches in human autoimmune diseases.