Macrophages are central cells both in the immune response and in iron homeostasis. Iron is both essential and potentially toxic. Therefore, iron acquisition, transport, storage, and release are tightly regulated, by several important proteins. Cytosolic ferritin is an iron storage protein composed of 24 subunits of either the L-or the H-type chains. H-ferritin differs from L-ferritin in the capacity to oxidize fe 2+ to fe 3+ . In this work, we investigated the role played by H-ferritin in the macrophages' ability to respond to immune stimuli and to deal with exogenously added iron. We used mice with a conditional deletion of the H-ferritin gene in the myeloid lineage to obtain bone marrow-derived macrophages. These macrophages had normal viability and gene expression under basal culture conditions. However, when treated with interferon-gamma and lipopolysaccharide they had a lower activation of Nitric Oxide Synthase 2. Furthermore, H-ferritin-deficient macrophages had a higher sensitivity to ironinduced toxicity. This sensitivity was associated with a lower intracellular iron accumulation but a higher production of reactive oxygen species. These data indicate that H-ferritin modulates macrophage response to immune stimuli and that it plays an essential role in protection against iron-induced oxidative stress and cell death.Since macrophages and iron metabolism are tightly connected and H-ferritin is crucial for iron storage inside the cells, we hypothesized that H-ferritin has a key role in macrophages viability, development, activation, and iron handling. To test this hypothesis, we used mice with a conditional deletion of the H-ferritin gene (Fth1) in the myeloid lineage, generated from the H-ferritin-loxP mice created by Lukas Kuhn and collaborators 17 . We obtained bone marrow-derived macrophages (BMDM) from these mice and found that although in vitro macrophage differentiation proceeded normally, H-ferritin-deficient BMDM had subtle alterations in their response to immune stimulation and a marked increase in susceptibility to oxidative stress and cell death induced by exogenously added iron. Scientific RepoRtS |(2020) 10:3061 | https://doi.

Hepcidin is a small cysteine rich peptide that regulates the sole known cellular iron exporter, ferroportin, effectively controlling iron metabolism. Contrary to humans, where a single hepcidin exists, many fish have two functionally distinct hepcidin types, despite having a single ferroportin gene. This raises the question of whether ferroportin is similarly regulated by the iron regulator Hamp1 and the antimicrobial Hamp2. In sea bass (Dicentrarchus labrax), iron overload prompted a downregulation of ferroportin, associated with an upregulation of hamp1, whereas an opposite response was observed during anemia, with no changes in hamp2 in either situation. During infection, ferroportin expression decreased, indicating iron withholding to avoid microbial proliferation. In vivo administration of Hamp1 but not Hamp2 synthetic peptides caused significant reduction in ferroportin expression, indicating that in teleost fish with two hepcidin types, ferroportin activity is mediated through the iron-regulator Hamp1, and not through the dedicated antimicrobial Hamp2. Additionally, in vitro treatment of mouse macrophages with fish Hamp1 but not Hamp2 caused a decrease in ferroportin levels. These results raise questions on the evolution of hepcidin and ferroportin functional partnership and open new possibilities for the pharmaceutical use of selected fish Hamp2 hepcidins during infections, with no impact on iron homeostasis.

The structure and membrane interactions of three antimicrobial peptides from the lactoferrin family were investigated through different techniques. Circular dichroism shows that the peptides adopt a secondary structure in the presence of DMPC/DMPG, and DSC reveals that they all interact with these membranes, albeit differently, whereas only LFchimera has an effect in pure zwitterionic membranes of DMPC. DSC further shows that membrane action is weakest for LFcin17-30, increases for LFampin265-284 and is largest for LFchimera. These differences are clearly reflected in a different structure upon interaction, as revealed by SAX. This technique shows that LFcin17-30 only induces membrane segregation (two lamellar phases are apparent upon cooling from fluid phase), whereas LFampin265-284 induces micellization of the membrane with structure compatible to a micellar cubic phase of space group Pm3n, and LFchimera leads to membrane destruction through the formation of two cubic phases, Pn3m and Im3m. These structural results show a remarkable parallel with the ones obtained previously by freeze fracture microscopy of the effect of these peptides against Candida albicans.

No abstract

dMycobacterium avium causes respiratory disease in susceptible individuals, as well as disseminated infections in immunocompromised hosts, being an important cause of morbidity and mortality among these populations. Current therapies consist of a combination of antibiotics taken for at least 6 months, with no more than 60% overall clinical success. Furthermore, mycobacterial antibiotic resistance is increasing worldwide, urging the need to develop novel classes of antimicrobial drugs. One potential and interesting alternative strategy is the use of antimicrobial peptides (AMP). These are present in almost all living organisms as part of their immune system, acting as a first barrier against invading pathogens. In this context, we investigated the effect of several lactoferrin-derived AMP against M. avium. Short peptide sequences from both human and bovine lactoferricins, namely, hLFcin1-11 and LFcin17-30, as well as variants obtained by specific amino acid substitutions, were evaluated. All tested peptides significantly inhibited the axenic growth of M. avium, the bovine peptides being more active than the human. Arginine residues were found to be crucial for the display of antimycobacterial activity, whereas the all-D-amino-acid analogue of the bovine sequence displayed the highest mycobactericidal activity. These findings reveal the promising potential of lactoferricins against mycobacteria, thus opening the way for further research on their development and use as a new weapon against mycobacterial infections.

No abstract

Despite the common usage of the term, researchers and practitioners have not been able properly to explain what team spirit is and what benefits and drawbacks it might bring to teams. Several definitions have been proposed, but not in a consistent manner. Using a qualitative approach, we worked with one football team to shed light on how individuals experience and characterize team spirit. Our results suggest that team spirit is built around four paradoxes: these are a paradox of selfless egoism; a paradox of results; a paradox of conflict, and a paradox of relationships. Essentially, team spirit can be viewed as an inter-subjectively shared facility with which individual members of a team can balance opposing tensions in a consistent way, managing to maintain a healthy synthesis between individual and collective needs and expectations, preventing the team from dominating the individuals, as well as specific individuals from capturing the team.

An understanding of the mechanism of action of antimicrobial peptides is fundamental to the development of new and more active antibiotics. In the present work, we use a wide range of techniques (SANS, SAXD, DSC, ITC, CD, and confocal and electron microscopy) in order to fully characterize the interaction of a cecropin A-melittin hybrid antimicrobial peptide, CA(1-7)M(2-9), of known antimicrobial activity, with a bacterial model membrane of POPE/POPG in an effort to unravel its mechanism of action. We found that CA(1-7)M(2-9) disrupts the vesicles, inducing membrane condensation and forming an onionlike structure of multilamellar stacks, held together by the intercalated peptides. SANS and SAXD revealed changes induced by the peptide in the lipid bilayer thickness and the bilayer stiffening in a tightly packed liquid-crystalline lamellar phase. The analysis of the observed abrupt changes in the repeat distance upon the phase transition to the gel state suggests the formation of an L phase. To the extent of our knowledge, this is the first time that the L phase is identified as part of the mechanism of action of antimicrobial peptides. The energetics of interaction depends on temperature, and ITC results indicate that CA(1-7)M(2-9) interacts with the outer leaflet. This further supports the idea of a surface interaction that leads to membrane condensation and not to pore formation. As a result, we propose that this peptide exerts its antimicrobial action against bacteria through extensive membrane disruption that leads to cell death.