Intracerebral Injection of Heme Induces Lipid Peroxidation, Neuroinflammation, and Sensorimotor Deficits.

Background and Purpose: Heme is a red blood cell component released in the brain parenchyma following intracerebral hemorrhage. However, the study of the pathophysiological mechanisms triggered by heme in the brain is hampered by the lack of well-established in vivo models of intracerebral heme injection. This study aims to optimize and characterize a protocol of intrastriatal heme injection in mice, with a focus on the induction of lipid peroxidation, neuroinflammation and, ultimately, sensorimotor deficits. We also evaluated the involvement of NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3), an inflammasome sensor, in the behavior deficits induced by heme in this model. Methods: Mice were injected with heme in the striatum for the evaluation of neuroinflammation and brain damage through histological and biochemical techniques. Immunoblot was used to evaluate the expression of proteins involved in heme/iron metabolism and antioxidant responses and the activation of the MAPK (mitogen-activated protein kinase) signaling pathway. For the assessment of neurological function, we followed-up heme-injected mice for 2 weeks using the rotarod, elevated body swing, and cylinder tests. Mice injected with the vehicle (sham), or autologous blood were used as controls. Results: Heme induced lipid peroxidation and inflammation in the brain. Moreover, heme increased the expression of HO-1 (heme oxygenase-1), ferritin, p62, and superoxide dismutase 2, and activated the MAPK signaling pathway promoting pro-IL (interleukin)-1ß production and its cleavage to the active form. Heme-injected mice exhibited signs of brain damage and reactive astrogliosis around the injection site. Behavior deficits were observed after heme or autologous blood injection in comparison to sham-operated controls. In addition, behavior deficits and IL-1ß production were reduced in Nlrp3 knockout mice in comparison to wild-type mice. Conclusions: Our results show that intracerebral heme injection induces neuroinflammation, and neurological deficits, in an NLRP3-dependent manner, suggesting that this is a feasible model to evaluate the role of heme in neurological disorders.

Lack of galectin-3 speeds Wallerian degeneration by altering TLR and pro-inflammatory cytokine expressions in injured sciatic nerve.

Wallerian degeneration (WD) comprises a series of events that includes activation of non-neuronal cells and recruitment of immune cells, creating an inflammatory milieu that leads to extensive nerve fragmentation and subsequent clearance of the myelin debris, both of which are necessary prerequisites for effective nerve regeneration. Previously, we documented accelerated axon regeneration in animals lacking galectin-3 (Gal-3), a molecule associated with myelin clearance. To clarify the mechanisms underlying this enhanced regeneration, we focus here on the early steps of WD following sciatic nerve crush in Gal-3(-/-) mice. Using an in vivo model of nerve degeneration, we observed that removal of myelin debris is more efficient in Gal-3(-/-) than in wild-type (WT) mice; we next used an in vitro phagocytosis assay to document that the phagocytic potential of macrophages and Schwann cells was enhanced in the Gal-3(-/-) mice. Moreover, both RNA and protein levels for the pro-inflammatory cytokines IL-1ß and TNF-α, as well as for Toll-like receptor (TLR)-2 and -4, show robust increases in injured nerves from Gal-3(-/-) mice compared to those from WT mice. Collectively, these data indicate that the lack of Gal-3 results in an augmented inflammatory profile that involves the TLR-cytokine pathway, and increases the phagocytic capacity of Schwann cells and macrophages, which ultimately contributes to speeding the course of WD.

Oral immunization with Lactococcus lactis secreting attenuated recombinant staphylococcal enterotoxin B induces a protective immune response in a murine model.

BACKGROUND: Staphylococcus aureus is unrestrictedly found in humans and in animal species that maintain thermal homeostasis. Inadequate cleaning of processing equipment or inappropriate handling can contaminate processed food and cause severe food poisoning. Staphylococcal enterotoxin B (SEB), a potent superantigenic exotoxin, is produced by 50% of clinical isolates of S. aureus and is associated with massive food poisoning and with the induction of toxic shock syndrome. RESULTS: A gene sequence encoding a recombinant SEB (rSEB), devoid of superantigenic activity, was successfully cloned and expressed in a cytoplasmic or a secreted form in the food-grade lactic acid bacterium Lactococcus lactis. The recombinant protein detected in the cytoplasm or in the culture medium exhibited the expected molecular mass and was recognized by a SEB-polyclonal antibody. Oral immunization with the recombinant L. lactis strains induced a protective immune response in a murine model of S. aureus infection. Immunized mice survived intraperitoneal challenge with an S. aureus SEB-producer strain. Counts of S. aureus in the spleen of rSEB-immunized mice were significantly reduced. The rSEB-immunized mice showed significant titers of anti-SEB IgA and IgG in stools and serum, respectively. Both recombinant L. lactis strains were able to elicit cellular or systemic immune responses in mice, with no significant difference if rSEB was produced in its cytoplasmic or secreted form. However, recombinant L. lactis expressing the cytoplasmic rSEB increased the survival rate of the challenged mice by 43%. CONCLUSIONS: These findings show the vaccine efficacy of L. lactis carrying an attenuated SEB, in a murine model, following lethal S. aureus challenge.

Infection of Endothelial Cells by Dengue Virus Induces ROS Production by Different Sources Affecting Virus Replication, Cellular Activation, Death and Vascular Permeability.

Exacerbated inflammatory response and altered vascular function are hallmarks of dengue disease. Reactive oxygen species (ROS) production has been associated to endothelial barrier disturbance and microvascular alteration in distinct pathological conditions. Increased ROS has been reported in in vitro models of dengue virus (DENV) infection, but its impact for endothelial cell physiology had not been fully investigated. Our group had previously demonstrated that infection of human brain microvascular endothelial cells (HBMEC) with DENV results in the activation of RNA sensors and production of proinflammatory cytokines, which culminate in cell death and endothelial permeability. Here, we evaluated the role of mitochondrial function and NADPH oxidase (NOX) activation for ROS generation in HBMEC infected by DENV and investigated whether altered cellular physiology could be a consequence of virus-induced oxidative stress. DENV-infected HBMECs showed a decrease in the maximal respiratory capacity and altered membrane potential, indicating functional mitochondrial alteration, what might be related to mtROS production. Indeed, mtROS was detected at later time points after infection. Specific inhibition of mtROS diminished virus replication, cell death, and endothelial permeability, but did not affect cytokine production. On the other hand, inhibition of NOX-associated ROS production decreased virus replication and cell death, as well as the secretion of inflammatory cytokines, including IL-6, IL-8, and CCL5. These results demonstrated that DENV replication in endothelial cells induces ROS production by different pathways, which impacts biological functions that might be relevant for dengue pathogenesis. Those data also indicate oxidative stress events as relevant therapeutical targets to avoid vascular permeability, inflammation, and neuroinvasion during DENV infection.

Arginase 1 is a marker of protection against illness in contacts of leprosy patients.

Leprosy household contacts are generally more prone to develop the disease compared to the general population. Previous studies have demonstrated that genes related to the alternative activation (M2) profile in macrophages are associated with the increased bacillary load in multibacillary leprosy patients (MB), and that contacts of MB patients have a higher risk of contracting the disease. In addition, positive serological responses to PGL-1 or LID-1 are associated with a higher risk of disease. We performed a 5-year follow-up of contacts of leprosy patients and evaluated the pattern of gene and protein expression in cells from contacts that developed leprosy during this period. Leprosy household contacts had decreased soluble CD163 and heme oxygenase 1 (HO-1) serum levels when compared with healthy donors and leprosy patients. In contrast, arginase 1 activities were higher in contacts when compared with both healthy donors and leprosy patients. Of the contacts, 33 developed leprosy during the follow-up. Gene expression analysis revealed reduced ARG1 expression in these contacts when compared with contacts that did not develop disease. Arginase activity was a good predictive marker of protection in contacts (sensitivity: 90.0%, specificity: 96.77%) and the association with serology for anti-PGL-1 and anti-LID-1 increased the sensitivity to 100%. Altogether, the data presented here demonstrate a positive role of arginase against leprosy and suggest that the evaluation of arginase activity should be incorporated into leprosy control programs in order to aid in the decision of which contacts should receive chemoprophylaxis.

Plasma and memory antibody responses to Gamma SARS-CoV-2 provide limited cross-protection to other variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to be a global problem in part because of the emergence of variants of concern that evade neutralization by antibodies elicited by prior infection or vaccination. Here we report on human neutralizing antibody and memory responses to the Gamma variant in a cohort of hospitalized individuals. Plasma from infected individuals potently neutralized viruses pseudotyped with Gamma SARS-CoV-2 spike protein, but neutralizing activity against Wuhan-Hu-1-1, Beta, Delta, or Omicron was significantly lower. Monoclonal antibodies from memory B cells also neutralized Gamma and Beta pseudoviruses more effectively than Wuhan-Hu-1. 69% and 34% of Gamma-neutralizing antibodies failed to neutralize Delta or Wuhan-Hu-1. Although Class 1 and 2 antibodies dominate the response to Wuhan-Hu-1 or Beta, 54% of antibodies elicited by Gamma infection recognized Class 3 epitopes. The results have implications for variant-specific vaccines and infections, suggesting that exposure to variants generally provides more limited protection to other variants.

c-MAF-dependent perivascular macrophages regulate diet-induced metabolic syndrome.

Macrophages are an essential part of tissue development and physiology. Perivascular macrophages have been described in tissues and appear to play a role in development and disease processes, although it remains unclear what the key features of these cells are. Here, we identify a subpopulation of perivascular macrophages in several organs, characterized by their dependence on the transcription factor c-MAF and displaying nonconventional macrophage markers including LYVE1, folate receptor 2, and CD38. Conditional deletion of c-MAF in macrophage lineages caused ablation of perivascular macrophages in the brain and altered muscularis macrophages program in the intestine. In the white adipose tissue (WAT), c-MAF­deficient perivascular macrophages displayed an altered gene expression profile, which was linked to an increased vascular branching. Upon feeding high-fat diet (HFD), mice with c-MAF­deficient macrophages showed improved metabolic parameters compared with wild-type mice, including less weight gain, greater glucose tolerance, and reduced inflammatory cell profile in WAT. These results define c-MAF as a central regulator of the perivascular macrophage transcriptional program in vivo and reveal an important role for this tissue-resident macrophage population in the regulation of metabolic syndrome.

Chloroquine inhibits pro-inflammatory effects of heme on macrophages and invivo.

BACKGROUND: Chloroquine has been used successfully to treat Malaria, including by chloroquine-resistant Plasmodium sp., indicating that it has effects on disease itself. Since heme has inflammatory effects and contributes to the pathogenesis of hemolytic diseases, we hypothesize that the anti-inflammatory effect of chloroquine is partially due to its inhibitory effect on heme-induced macrophage activation and on inflammatory tissue damage. METHODS: Bone marrow derived macrophages (BMDMs) were incubated with chloroquine before stimulation with heme, in different conditions, to evaluate cytokines secretion, ROS production, mitogen activated protein kinases (MAPK) or spleen tyrosine kinase (Syk) activation, alone or combined with LPS. The effects of chloroquine upon heme inflammation were also evaluated in vivo, through simultaneous i.p. injection of LPS and heme, intratracheal instillation of Poly-IC followed by heme injection, and in a rhabdomyolysis model. RESULTS: Chloroquine inhibited TNF secretion, mitochondrial ROS production, MAPK, and Syk activation induced by heme. Inhibition of TNF production could be mimicked by zinc ionophore quercetin, but not by primaquine, a chloroquine analog with low affinity for heme. IL-6 and IL-1ß secretions induced by heme in the presence of PRRs agonists were inhibited by chloroquine, but not by calcium chelator BAPTA or inhibitor of endosomal acidification concamycin B. Chloroquine also protected mice from heme inflammatory effects in vivo, inhibiting lethal synergism with PRR agonists, lung pathology caused by heme injection after intratracheal instillation of Poly-IC, and delaying death after rhabdomyolisis. CONCLUSION: Our data indicate that chloroquine might be used as a supportive therapy to control heme-induced deleterious inflammation in different hemolytic diseases.

The extracellular release of Schistosoma mansoni HMGB1 nuclear protein is mediated by acetylation.

Schistosoma mansoni HMGB1 (SmHMGB1) was revealed to be a substrate for the parasite histone acetyltransferases SmGCN5 and SmCBP1. We found that full-length SmHMGB1, as well as its HMG-box B (but not HMG-box A) were acetylated in vitro by SmGCN5 and SmCBP1. However, SmCBP1 was able to acetylate both substrates more efficiently than SmGCN5. Interestingly, the removal of the C-terminal acidic tail of SmHMGB1 (SmHMGB1DeltaC) resulted in increased acetylation of the protein. We showed by mammalian cell transfection assays that SmHMGB1 and SmHMGB1DeltaC were transported from the nucleus to the cytoplasm after sodium butyrate (NaB) treatment. Importantly, after NaB treatment, SmHMGB1 was also present outside the cell. Together, our data suggest that acetylation of SmHMGB1 plays a role in cellular trafficking, culminating with its secretion to the extracellular milieu. The possible role of SmHMGB1 acetylation in the pathogenesis of schistosomiasis is discussed.

Mayaro Virus Replication Restriction and Induction of Muscular Inflammation in Mice Are Dependent on Age, Type-I Interferon Response, and Adaptive Immunity.

Mayaro virus (MAYV) is an emergent arbovirus first described in forest regions of the American continent, with recent and increasing notification of urban area circulation. Similar to Chikungunya (CHIKV) and other arthritogenic Alphavirus, MAYV-induced disease shows a high prevalence of persistent arthralgia, and myalgia. Despite this, knowledge regarding pathogenesis and characteristics of host immune response of MAYV infections are still limited. Here, using different ages of wild-type (WT), adult Type I Interferon receptor deficient (IFNAR-/-), and adult recombination activation gene-1 deficient (RAG-/-) mice, we have investigated the dependence of age, innate and adaptive immunity for the control of MAYV replication, tissue damage, and inflammation in mice. We have found that MAYV induces clinical signal and replicates in young WT mice, which gain the ability to restrict MAYV replication with aging. In addition, we observed that mice age and type I interferon response are related to restriction of MAYV infection and muscular inflammation in mice. Moreover, MAYV continues to replicate persistently in RAG-/- mice, being detected at blood and tissues 40 days post infection, indicating that adaptive immunity is essential to MAYV clearance. Despite chronic replication, infected adult RAG-/- mice did not develop an apparent signal of muscle damage in early and late infection. On the other hand, MAYV infection in young WT and adult IFNAR-/- mice triggers an increase in the expression of pro-inflammatory mediators, such as TNF, IL-6, KC, IL-1ß, MCP-1, and RANTES, in muscle tissue, and decreases TGF-ß expression, that were not significantly modulated in adult WT and RAG-/- mice. Taken together, our data demonstrated that age, innate and adaptive immunity are important to restrict MAYV replication and that adaptive immunity is also involved in MAYV-induced tissue damage. These results contribute to the comprehension of MAYV pathogenesis, and describe translational mice models for further studies of MAYV infection, vaccine tests, and therapeutic strategies against this virus.

Indoleamine 2,3-dioxygenase and iron are required for Mycobacterium leprae survival.

Our previous study has demonstrated that IL-10 may modulate both indoleamine 2,3-dioxygenase (IDO) and CD163 expression in lepromatous leprosy (LL) cells, favoring Mycobacterium leprae persistence through induction of regulatory pathways and iron storage. Here, we observed that in LL lesion cells there is an increase in the expression of proteins involved in iron metabolism such as hemoglobin (Hb), haptoglobin, heme oxygenase 1 and transferrin receptor 1 (TfR1) when compared to tuberculoid leprosy (BT) cells. We also found increased iron deposits and diminished expression of the iron exporter ferroportin 1 in LL lesion cells. Hemin, but not FeSO4 stimulation, was able to enhance M. leprae viability by a mechanism that involves IDO. Analysis of cell phenotype in lesions demonstrated a predominance of M2 markers in LL when compared with BT lesion cells. A positive correlation between CD163 and PPARG with the bacillary index (BI) was observed. In contrast, TNF, STAT1 and CSF2 presented a negative correlation with the BI. In summary, this study demonstrates that iron may regulate IDO expression by a mechanism that involves IL-10, which may contribute for the predominance of M2-like phenotype in LL lesions that favors the phagocytosis and maintenance of M. leprae in host cells.

Macrophage migration inhibitory factor drives neutrophil accumulation by facilitating IL-1ß production in a murine model of acute gout.

This study evaluated the role of macrophage migration inhibitory factor in inflammation caused by monosodium urate crystals. The concentration of macrophage migration inhibitory factor was increased in synovial fluid of patients with acute gout, and there was a positive correlation between intra-articular macrophage migration inhibitory factor and IL-1ß concentrations. In mice, the injection of monosodium urate crystals into the knee joint increased the levels of macrophage migration inhibitory factor in macrophages and in inflamed tissue. The injection of recombinant macrophage migration inhibitory factor into the joint of mice reproduced the inflammatory response observed in acute gout, including histologic changes, the recruitment of neutrophils, and increased levels of IL-1ß and CXCL1. Importantly, the accumulation of neutrophils and the amount IL-1ß in the joints were reduced in macrophage migration inhibitory factor-deficient mice when injected with monosodium urate crystals. We observed a similar effect when we blocked macrophage migration inhibitory factor with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid or anti-macrophage migration inhibitory factor. In addition, the blockade of IL-1R and CXCR2 reduced recombinant macrophage migration inhibitory factor-induced neutrophil recruitment. Mechanistically, recombinant macrophage migration inhibitory factor is important for the synthesis of il1ß mRNA in vivo and in isolated macrophages. Altogether, macrophage migration inhibitory factor promotes neutrophil accumulation and is important for IL-1ß production, which are 2 crucial events contributing to the pathogenesis of acute gout.

Design, synthesis, and evaluation of hydroxamic acid derivatives as promising agents for the management of Chagas disease.

Today, there are approximately 8 million cases of Chagas disease in the southern cone of South America alone, and about 100 million people are living with the risk of becoming infected. The present pharmacotherapy is sometimes ineffective and has serious side effects. Here, we report a series of 4,5-dihydroisoxazoles incorporating hydroxamate moieties, which act as effective inhibitors of the carbonic anhydrase (CA) from Trypanosoma cruzi (TcCA). One compound (5g) was evaluated in detail and shows promising features as an antitrypanosomal agent. Excellent values for the inhibition of growth for all three developmental forms of the parasite were observed at low concentrations of 5g (IC50 values from 7.0 to <1 µM). The compound has a selectivity index (SI) of 6.7 and no cytotoxicity to macrophage cells. Preliminary in vivo data showed that 5g reduces bloodstream parasites and that all treated mice survived; it was also more effective than the standard drug benznidazole.