Cell death induced by NLRP3-palmitate axis impairs pulmonary damage tolerance and aggravates immunopathology during obesity-tuberculosis comorbidity.

A low-grade and persistent inflammation, which is the hallmark of obesity, requires the participation of NLRP3 and cell death. During Mycobacterium tuberculosis infection, NLRP3 signaling is important for bacterial killing by macrophages in vitro but was shown to be dispensable for host protection in vivo. We hypothesized that during obesity-tuberculosis (TB) comorbidity, NLRP3 signaling might play a detrimental role by inducing excessive inflammation. We employed a model of high-fat-diet-induced obesity, followed by M. tuberculosis infection in C57BL/6 mice. Obese mice presented increased susceptibility to infection and pulmonary immunopathology compared to lean mice. Using treatment with NLRP3 antagonist and Nlrp3-/- mice, we showed that NLRP3 signaling promoted cell death, with no effect in bacterial loads. The levels of palmitate were higher in the lungs of obese infected mice compared to lean counterparts, and we observed that this lipid increased M. tuberculosis-induced macrophage death in vitro, which was dependent on NLRP3 and caspase-1. At the chronic phase, although lungs of obese Nlrp3-/- mice showed an indication of granuloma formation compared to obese wild-type mice, there was no difference in the bacterial load. Our findings indicate that NLRP3 may be a potential target for host-directed therapy to reduce initial and severe inflammation-mediated disease and to treat comorbidity-associated TB. © 2022 The Pathological Society of Great Britain and Ireland.

Interleukin 17A acts synergistically with interferon γ to promote protection against Leishmania infantum infection.

Interleukin 17 (IL-17) is an inflammatory cytokine that plays a protective role against intracellular parasites. The role of IL-17 during Leishmania infection remains controversial and poorly defined. We evaluated whether IL-17 participates in the host immune response to Leishmania infantum. IL-17A is present in sera from patients with visceral leishmaniasis and decreases after successful treatment. In C57BL/6 infected mice, higher production of IL-17A coincided with the peak of parasitism. Il17ra(-/-) mice were more susceptible to infection and also exhibited reduced inflammatory infiltration and interferon γ (IFN-γ)-expressing CD4+ T-cell frequencies than wild-type mice. The frequencies of FoxP3+ CD4+ T cells and interleukin 10 (IL-10)-expressing CD4+ T cells were increased in Il17ra(-/-) mice. We also demonstrated that IL-17A acts synergistically with IFN-γ to potentiate NO production and leishmanicidal activity in infected macrophages. Therefore, our results indicate that L. infantum induces IL-17A production, which promotes the control of parasite replication by strengthening T-helper type 1 responses and NO production and prevents regulatory T-cell and IL-10-expressing T-cell expansion.

Dual effect of Lutzomyia longipalpis saliva on Leishmania braziliensis infection is mediated by distinct saliva-induced cellular recruitment into BALB/c mice ear.

BACKGROUND: Leishmania parasites are transmitted to their vertebrate hosts by infected Phlebotomine sand flies during the blood meal of the flies. Sand fly saliva is known to enhance Leishmania spp. infection, while pre-exposure to saliva protects mice against parasitic infections. In this study, we investigated the initial inflammatory leucocyte composition induced by one or three inocula of salivary gland extract (SGE) from Lutzomyia longipalpis in the presence or absence of Leishmania braziliensis. RESULTS: We demonstrated that inoculating SGE once (SGE-1X) or three times (SGE-3X), which represented a co-inoculation or a pre-exposure to saliva, respectively, resulted in different cellular infiltrate profiles. Whereas SGE-1X led to the recruitment of all leucocytes subtypes including CD4(+) T cells, CD4(+)CD25(+) T cells, dendritic cells, macrophages and neutrophils, the immune cell profile in the SGE-3X group differed dramatically, as CD4(+) T cells, CD4(+)CD25(+) T cells, dendritic cells, macrophages and neutrophils were decreased and CD8(+) T cells were increased. The SGE-1X group did not show differences in the ear lesion size; however, the SGE-1X group harbored a higher number of parasites. On the other hand, the SGE-3X group demonstrated a protective effect against parasitic disease, as the parasite burden was lower even in the earlier stages of the infection, a period in which the SGE-1X group presented with larger and more severe lesions. These effects were also reflected in the cytokine profiles of both groups. Whereas the SGE-1X group presented with a substantial increase in IL-10 production, the SGE-3X group showed an increase in IFN-γ production in the draining lymph nodes. Analysis of the inflammatory cell populations present within the ear lesions, the SGE-1X group showed an increase in CD4(+)FOXP3(+) cells, whereas the CD4(+)FOXP3(+) population was reduced in the SGE-3X group. Moreover, CD4(+) T cells and CD8(+) T cells producing IFN-γ were highly detected in the ears of the SGE-3X mice prior to infection. In addition, upon treatment of SGE-3X mice with anti-IFN-γ monoclonal antibody, we observed a decrease in the protective effect of SGE-3X against L. braziliensis infection. CONCLUSIONS: These results indicate that different inocula of Lutzomyia longipalpis salivary gland extract can markedly modify the cellular immune response, which is reflected in the pattern of susceptibility or resistance to Leishmania braziliensis infection.

Artepillin C Reduces Allergic Airway Inflammation by Induction of Monocytic Myeloid-Derived Suppressor Cells.

Propolis is a natural product produced by bees that is primarily used in complementary and alternative medicine and has anti-inflammatory, antibacterial, antiviral, and antitumoral biological properties. Some studies have reported the beneficial effects of propolis in models of allergic asthma. In a previous study, our group showed that green propolis treatment reduced airway inflammation and mucus secretion in an ovalbumin (OVA)-induced asthma model and resulted in increased regulatory T cells (Treg) and polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) frequencies in the lungs, two leukocyte populations that have immunosuppressive functions. In this study, we evaluated the anti-inflammatory effects of artepillin C (ArtC), the major compound of green propolis, in the context of allergic airway inflammation. Our results show that ArtC induces in vitro differentiation of Treg cells and monocytic MDSC (M-MDSC). Furthermore, in an OVA-induced asthma model, ArtC treatment reduced pulmonary inflammation, eosinophil influx to the airways, mucus and IL-5 secretion along with increased frequency of M-MDSC, but not Treg cells, in the lungs. Using an adoptive transfer model, we confirmed that the effect of ArtC in the reduction in airway inflammation was dependent on M-MDSC. Altogether, our data show that ArtC exhibits an anti-inflammatory effect and might be an adjuvant therapy for allergic asthma.

T1/ST2 deficient mice display protection against Leishmania infantum experimental infection.

T1/ST2 is a surface marker selectively expressed on type 2 helper (TH2) effector cells. As Leishmania infection in susceptible BALB/c mice have ascribed to a polarized TH2 response, this study aim to investigate the T1/ST2 (the receptor for IL-33), as a typical TH2 marker in the postulation that a shift towards a beneficial TH1 response would occur in the absence of ST2. For this, ST2 knockout (ST2-/-) and WT BALB/c mice were experimentally infected in the retro-orbital sinus with L. infantum. We showed that ST2-/- animals displayed better control of parasite burden in both spleen and liver tissues at different time points of chronic phases, and reduced spleenomegaly and hepatomegaly compared with the wild-type (WT) mice. This was associated with increased in the IFN-γ levels and expression by CD4+ and CD8+ lymphocytes. The inflammatory response encompasses transaminases (AST and ALT) releases and NO productions were remarkably lower in ST2-/- mice compared with WT. These data suggest that, ST2-/-) exert protection against L. infantum infection and probably shift the immune response toward TH1 induction.

Antileishmanial activity of ruthenium(II)tetraammine nitrosyl complexes.

The complexes trans-[Ru(NO)(NH(3))(4)L](X)(3) (X = BF(4)(-), PF(6)(-) or Cl(-) and L = N-heterocyclic ligands, P(OEt)(3), SO(3)(-2)), and [Ru(NO)Hedta)] were shown to exhibit IC(50pro) in the range of 36 (L = imN) to 5000 microM (L = imC). The inhibitory effects of trans-[Ru(NO)(NH(3))(4)imN](BF(4))(3) and of the Angeli's salt on the growth of the intramacrophage amastigote form studied were found to be similar while the trans-[Ru(NH(3))(4)imN(H(2)O)](2+) complex was found not to exhibit any substantial antiamastigote effect. The trans-[Ru(NO)(NH(3))(4)imN](BF(4))(3) compound, administered (500 nmol kg(-1) day(-1)) in BALB/c mice infected with Leishmania major, was found to exhibit a 98% inhibition on the parasite growth. Furthermore, this complex proved to be at least 66 times more efficient than glucantime in in vivo experiments.

Effect of interleukin-10 on the Paracoccidioides brasiliensis killing by gamma-interferon activated human neutrophils.

Paracoccidioidomycosis, a deep mycosis endemic in Latin America, is a chronic granulomatous disease caused by the fungus Paracoccidioides brasiliensis. Phagocytic cells play a critical role against this fungus, and several studies have shown the effects of activator and suppressive cytokines on macrophage and monocyte functions. However, studies on polymorphonuclear neutrophils (PMNs), that are the first cells recruited to the infection sites, are scarcer. Thus, the objective of this paper was to assess whether interleukin-10 (IL-10), a potent anti-inflammatory cytokine, is able to block the activity of IFN-gamma-activated human PMNs upon P. brasiliensis intracellular killing, in vitro. The results showed that IFN-gamma-activated PMNs have an effective fungicidal activity against the fungus. This activity was associated with the release of high levels of H(2)O(2), the metabolite involved in phagocytic cells antifungal activities. However, the concomitant incubation of these cells with IFN-gamma and IL-10 significantly blocked IFN-gamma activation. As a consequence, PMNs killing activity and H(2)O(2) release were inhibited. Together, our results show the importance of PMNs exposure to activator or suppressor cytokines in the early stages of paracoccidioidomycosis infection.