The NLRP3 inflammasome contributes to host protection during Sporothrix schenckii infection.

Sporotrichosis is a mycosis caused by fungi from the Sporothrix schenckii species complex, whose prototypical member is Sporothrix schenckii sensu stricto. Pattern recognition receptors (PRRs) recognize and respond to pathogen-associated molecular patterns (PAMPs) and shape the following adaptive immune response. A family of PRRs most frequently associated with fungal recognition is the nucleotide-binding oligomerization domain-like receptor (NLR). After PAMP recognition, NLR family pyrin domain-containing 3 (NLRP3) binds to apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1 to form the NLRP3 inflammasome. When activated, this complex promotes the maturation of the pro-inflammatory cytokines interleukin-1ß (IL-1ß) and IL-18 and cell death through pyroptosis. In this study, we aimed to evaluate the importance of the NLRP3 inflammasome in the outcome of S. schenckii infection using the following three different knockout (KO) mice: NLRP3-/- , ASC-/- and caspase-1-/- . All KO mice were more susceptible to infection than the wild-type, suggesting that NLRP3-triggered responses contribute to host protection during S. schenckii infection. Furthermore, the NLRP3 inflammasome appeared to be critical for the ex vivo release of IL-1ß, IL-18 and IL-17 but not interferon-γ. Additionally, a role for the inflammasome in shaping the adaptive immune response was suggested by the lower frequencies of type 17 helper T (Th17) cells and Th1/Th17 but not Th1 cells in S. schenckii-infected KO mice. Overall, our results indicate that the NLRP3 inflammasome links the innate recognition of S. schenckii to the adaptive immune response, so contributing to protection against this infection.

Hydrophobicity and antioxidant activity acting together for the beneficial health properties of nordihydroguaiaretic acid.

Nordihydroguaiaretic acid (NDGA) and rosmarinic acid (RA), phenolic compounds found in various plants and functional foods, have known antioxidant and anti-inflammatory properties. In the present study, we comparatively investigated the importance of hydrophobicity and oxidisability of NDGA and RA, regarding their antioxidant and pharmacological activities. Using a panel of cell-free antioxidant protocols, including electrochemical measurements, we demonstrated that the anti-radical capacities of RA and NDGA were similar. However, the relative capacity of NDGA as an inhibitor of NADPH oxidase (ex vivo assays) was significantly higher compared to RA. The inhibitory effect on NADPH oxidase was not related to simple scavengers of superoxide anions, as confirmed by oxygen consumption by the activated neutrophils. The higher hydrophobicity of NDGA was also a determinant for the higher efficacy of NDGA regarding the inhibition of the release of hypochlorous acid by PMA-activated neutrophil and cytokine (TNF-α and IL-10) production by Staphylococcus aureus-stimulated peripheral blood mononuclear cells. In conclusion, although there have been extensive studies about the pharmacological properties of NDGA, our study showed, for the first time, the importance not only of its antioxidant activity, but also its hydrophobicity as a crucial factor for pharmacological action.

Caffeic Acid phenethyl ester: consequences of its hydrophobicity in the oxidative functions and cytokine release by leukocytes.

Numerous anti-inflammatory properties have been attributed to caffeic acid phenethyl ester (CAPE), an active component of propolis. NADPH oxidases are multienzymatic complexes involved in many inflammatory diseases. Here, we studied the importance of the CAPE hydrophobicity on cell-free antioxidant capacity, inhibition of the NADPH oxidase and hypochlorous acid production, and release of TNF-α and IL-10 by activated leukocytes. The comparison was made with the related, but less hydrophobic, caffeic and chlorogenic acids. Cell-free studies such as superoxide anion scavenging assay, triene degradation, and anodic peak potential (E pa) measurements showed that the alterations in the hydrophobicity did not provoke significant changes in the oxidation potential and antiradical potency of the tested compounds. However, only CAPE was able to inhibit the production of superoxide anion by activated leukocytes. The inhibition of the NADPH oxidase resulted in the blockage of production of hypochlorous acid. Similarly, CAPE was the more effective inhibitor of the release of TNF-α and IL-10 by Staphylococcus aureus stimulated cells. In conclusion, the presence of the catechol moiety and the higher hydrophobicity were essential for the biological effects. Considering the involvement of NADPH oxidases in the genesis and progression of inflammatory diseases, CAPE should be considered as a promising anti-inflammatory drug.

Influence of FcγRIIIb polymorphism on its ability to cooperate with FcγRIIa and CR3 in mediating the oxidative burst of human neutrophils.

Considering that human neutrophil FcγRIIa and FcγRIIIb receptors interact synergistically with CR3 in triggering neutrophil functional responses, allelic polymorphisms in these receptors might influence such interactions. We assessed whether FcγRIIIb polymorphisms affect FcγR/CR cooperation in mediating the neutrophil oxidative burst (OB), in particular the FcγRIIIb/CR3 cooperation that occurs via lectin-saccharide-like interactions. The OB of human neutrophil antigen (HNA)-1a-, HNA-1b-, and HNA-1a/-1b-neutrophils stimulated with immune complexes, opsonized or not with serum complement, was measured by the luminol-enhanced chemiluminescence assay. Compared with HNA-1a-neutrophils, HNA-1b-neutrophils exhibited reduced FcγR-stimulated OB, but increased FcγR/CR-stimulated OB. It suggests that (i) FcγR and CR cooperate more effectively in HNA-1b-neutrophils, and (ii) the HNA-1b allotype influences the FcγRIIIb cooperation with FcγRIIa, but not with CR3. HNA-1a- and HNA-1b-neutrophils exhibited similar OB responses elicited via CR3 alone or via FcγR/CR-independent pathways. In addition, the level of FcγRIIIb, FcγRIIa, and CR3 expression did not differ significantly among the neutrophil groups studied. Together, these results demonstrate that the HNA-1b allotype influences the functional cooperation between FcγRIIIb and FcγRIIa, and suggest that the difference in the glycosylation pattern between HNA-1a and HNA-1b does not affect the FcγRIIIb cooperation with CR3.