Paracoccidioides brasiliensis infection increases regulatory T cell counts in female C57BL/6 mice infected via two distinct routes.

Studies that show an overview of the peripheral immune response in a model of Paracoccidioides brasiliensis (Pb) infection in females are scarce in the literature. We sought to characterize the innate and adaptive immune responses in female C57BL/6 mice infected with Pb through two distinct routes of administration, intranasal and intravenous. In addition to the lung, P. brasiliensis yeast cells were observed in liver and brain tissues of females infected intravenously. To our knowledge, our study is the first to prove the presence of this pathogenic fungus in the cerebral cortex of female mice. During the initial stages of infection, augmented expression of both MHCII and CD86 was observed on the surface of CD11c+ pulmonary antigen-presenting cells (APCs) in intranasally and intravenously infected females. However, CD40 expression was downregulated in these cells. Concomitantly with increasing serum IL-10 levels, we noted that splenic dendritic cells (DCs) from both intravenously- and intranasally-infected female mice had acquired an immature phenotype. Further, increased T regulatory cell counts were observed in female mice infected via both routes, along with an increase in the infiltration of IL-10-producing CD8+ T cells into the lungs. Moreover, we noted that P. brasiliensis infection resulted in enhanced IL-10 production - by CD11c+ APCs in the lung tissue - and induction of Th17 polarization. Taken together, our results suggest that P. brasiliensis could modulates the immune response in female mice by influencing the balance between regulatory T cells (Tregs) and Th17 polarization.

Sildenafil ameliorates EAE by decreasing apoptosis in the spinal cord of C57BL/6 mice.

Apoptosis is one form of cell death that is intimately related to health and pathological conditions. In most neuroinflammatory and/or neurodegenerative diseases, apoptosis is associated with disease development and pathology and inhibition of this process leads to considerable amelioration. It is becoming evident that apoptosis also participates in the pathogenesis of Multiple Sclerosis (MS) and its animal model, Experimental Autoimmune Encephalomyelitis (EAE). Drugs such as Sildenafil, a Phosphodiesterase type 5 Inhibitor (PDE5I), have proven to be neuroprotective in MS models. However, it is not known whether Sildenafil is able to modulate cell death, specifically apoptosis, in EAE mice. Therefore, the aim of this study was to determine the effects of Sildenafil on extrinsic and intrinsic apoptosis pathways in the spinal cord of C57BL/6 mice with EAE. TUNEL analysis showed that EAE mice had elevated number of TUNEL+ cells and that treatment with Sildenafil led to reduced number of dying cells, indicating that Sildenafil was able to inhibit cell death. We observed that both extrinsic and intrinsic pathways of apoptosis were governing the dynamics of EAE progression. We showed that in EAE mice there were increased levels of extrinsic (Caspase-8, -3, TNF-α, FADD) and intrinsic (Caspase-9, Bax and Cytochrome C) apoptosis markers. Bcl-2, an anti-apoptotic protein, was downregulated in EAE mice. We also demonstrated that EAE mice had increased levels of non-caspase mediators of cell survival/cell death (p-IκBα and p-MAPK-p38). Besides, EAE mice presented augmented demyelination. Nevertheless, this is the first research to demonstrate that Sildenafil, when administered concomitant to disease induction, modulated the expression of pro- and anti-apoptotic proteins of the extrinsic and intrinsic pathways, as well as diminished the expression of non-caspase mediators and promoted remyelination in the spinal cord, indicating neuroprotective effects. Thus, the present study demonstrated that Sildenafil inhibits apoptosis by two distinct, although interconnected, mechanisms: directly by modulating caspase expression (through extrinsic and intrinsic pathways) and indirectly by modulating the expression of molecules involved in cell death and/or cell survival.