Hugo Cejas

IL-17RA Signaling Reduces Inflammation and Mortality during Trypanosoma cruzi Infection by Recruiting Suppressive IL-10-Producing Neutrophils

Members of the IL-17 cytokine family play an important role in protection against pathogens through the induction of different effector mechanisms. We determined that IL-17A, IL-17E and IL-17F are produced during the acute phase of T. cruzi infection. Using IL-17RA knockout (KO) mice, we demonstrate that IL-17RA, the common receptor subunit for many IL-17 family members, is required for host resistance during T. cruzi infection. Furthermore, infected IL-17RA KO mice that lack of response to several IL-17 cytokines showed amplified inflammatory responses with exuberant IFN-γ and TNF production that promoted hepatic damage and mortality. Absence of IL-17RA during T. cruzi infection resulted in reduced CXCL1 and CXCL2 expression in spleen and liver and limited neutrophil recruitment. T. cruzi-stimulated neutrophils secreted IL-10 and showed an IL-10-dependent suppressive phenotype in vitro inhibiting T-cell proliferation and IFN-γ production. Specific depletion of Ly-6G+ neutrophils in vivo during T. cruzi infection raised parasitemia and serum IFN-γ concentration and resulted in increased liver pathology in WT mice and overwhelming wasting disease in IL-17RA KO mice. Adoptively transferred neutrophils were unable to migrate to tissues and to restore resistant phenotype in infected IL-17RA KO mice but migrated to spleen and liver of infected WT mice and downregulated IFN-γ production and increased survival in an IL-10 dependent manner. Our results underscore the role of IL-17RA in the modulation of IFN-γ-mediated inflammatory responses during infections and uncover a previously unrecognized regulatory mechanism that involves the IL-17RA-mediated recruitment of suppressive IL-10-producing neutrophils.

Impaired Activity of Phagocytic Cells in Candida albicans Infection after Exposure to Chronic Varied Stress

Objective: Candidiasis is a prototypic opportunistic fungal disease that may follow severe modulations of the immune system of the host. The purpose of this study was to evaluate which innate immune mechanisms involved in the protection against fungal invasion are impaired under stress conditions. Methods: Wistar rats were infected intraperitoneally with Candida albicans and immediately exposed to chronic varied stress (CVS) over 10 days (CVS; Ca-S); the fungal burden (CFU), histopathological lesion and ACTH levels were evaluated. Additionally, functional assessment of peritoneal cells (PC) included the phagocytic and anticandidacidal activities and the production of H2O2 and NO. Results: In the only infected animals (Ca), C. albicans colonization stimulated an efficient inflammatory response, while in Ca-S rats poor tissue reactions were associated with increased CFU in livers and kidneys (p < 0.05, Ca vs. Ca-S). Whereas the phagocytic process was not modified, the candidacidal activity of PC was significantly decreased after the application of CVS (p < 0.001, Ca vs. Ca-S). The H2O2 production by macrophages and neutrophils was downregulated by the infection, and while at early intervals these cells possessed a residual oxidative capacity, by day 10, the production of this metabolite was blocked. Spontaneous NO production by macrophages was significantly increased in both Ca and Ca-S animals (p < 0.001), but in stressed rats, this reactive nitrogen intermediate was noticeably downregulated (p < 0.05, Ca vs. Ca-S). The hyperactivity of hypothalamus-pituitary-adrenal axis after exposure to stress was confirmed by an increase in baseline plasma ACTH levels. Conclusion: These results show that during infection with C. albicans, the exposure to CVS contributes to the spread of the fungus and downregulates critical functions of phagocytic cells involved in the control of this opportunistic pathogen.

Cytokines involved in the immunosuppressor period in experimental fasciolosis in rats

The aim of this study was to evaluate the kinetics of the cytokines interferon-gamma, interleukin-2, interleukin-10 and interleukin-4 produced by spleen mononuclear cells stimulated by Con A during an experimental infection in rats with Fasciola hepatica. The proliferative response to Con A of Spm cells from rats infected with F. hepatica was significantly decreased on day 7 post-infection (P<0.006) and simultaneously an increase of interferon-gamma, interleukin-10 and interleukin-4 production along with a decrease of interleukin-2 by spleen mononuclear cells were observed. Interleukin-4 and interleukin-10 were involved in ablating cellular proliferation in vitro, as the addition of neutralising antibodies to either cytokine reversed the proliferative block. The addition of exogenous recombinant interleukin-2 also restored the proliferative response by spleen mononuclear cells obtained 7 days after infection from infected rats. At the same time, we found an increase in interleukin-10 production by peritoneal cells (in close contact with the flukes) and decreased nitric oxide levels. In addition, histological studies on the liver on day 7 after infection showed the presence of parasite inside migratory tunnels in the parenchyma, and polymorphonuclear leukocytes, predominantly eosinophils, around the parasite. The transient suppression in proliferative response mediated by cytokines interleukin-4 and interleukin-10 in the spleen, and diminution of nitric oxide production in the peritoneum could be mechanisms to evade the protective immune response during the first stages of liver penetration by the parasite.

Male Rodent Genital Tract Infection With Chlamydia Muridarum: Persistence in the Prostate Gland That Triggers Self-Immune Reactions in Genetically Susceptible Hosts

PURPOSE We investigated Chlamydia trachomatis infection and its pathogenic consequences in the male rodent genital tract. MATERIALS AND METHODS Male rats were inoculated in the meatal urethra with Chlamydia muridarum. We sought bacterial DNA at early and late times after inoculation in different parts of the male genital tract. Histological alterations and the immune response against prostate antigens were analyzed. RESULTS Male rats showed ascending infection with wide dissemination of bacteria in the genital tract at an early time point after inoculation. At later stages bacteria persisted only in some parts of the genital tract and in the prostate gland. C. muridarum was also detected in semen in a high proportion of rats irrespective of an acute or chronic stage of infection. Histological alterations that accompanied C. muridarum were especially observed in the prostate and mainly composed of CD3+ cell infiltration. Positive humoral and cellular responses against prostate antigens were noted in a considerable number of infected rats. NOD mice, an autoimmune, prostatitis prone strain, showed a similar pattern with C. muridarum in the prostate of 100% of infected mice, which was again accompanied by mononuclear cell infiltration and antibodies against prostate antigens at early and late times after inoculation. CONCLUSIONS Results reveal that C. muridarum infects the male rodent genitourinary tract with special persistence in the prostate gland, where it causes chronic inflammation that in turn may act as a trigger factor for self-immune reactions in susceptible hosts.

BAFF Mediates Splenic B Cell Response and Antibody Production in Experimental Chagas Disease

Background B cells and antibodies are involved not only in controlling the spread of blood circulating Trypanosoma cruzi, but also in the autoreactive manifestations observed in Chagas disease. Acute infection results in polyclonal B cell activation associated with hypergammaglobulinemia, delayed specific humoral immunity and high levels of non-parasite specific antibodies. Since TNF superfamily B lymphocyte Stimulator (BAFF) mediates polyclonal B cell response in vitro triggered by T. cruzi antigens, and BAFF-Tg mice show similar signs to T. cruzi infected mice, we hypothesized that BAFF can mediate polyclonal B cell response in experimental Chagas disease. Methodology/Principal Findings BAFF is produced early and persists throughout the infection. To analyze BAFF role in experimental Chagas disease, Balb/c infected mice were injected with BR3:Fc, a soluble receptor of BAFF, to block BAFF activity. By BAFF blockade we observed that this cytokine mediates the mature B cell response and the production of non-parasite specific IgM and IgG. BAFF also influences the development of antinuclear IgG and parasite-specific IgM response, not affecting T. cruzi-specific IgG and parasitemia. Interestingly, BAFF inhibition favors the parasitism in heart. Conclusions/Significance Our results demonstrate, for the first time, an active role for BAFF in shaping the mature B cell repertoire in a parasite infection.

Lack of TNFRI signaling enhances annexin A1 biological activity in intestinal inflammation.

We evaluated whether the lack of TNF-α signaling increases mucosal levels of annexin A1 (AnxA1); the hypothesis stems from previous findings showing that TNF-α neutralization in Crohns disease patients up-regulates systemic AnxA1 expression. Biopsies from healthy volunteers and patients under anti-TNF-α therapy with remittent ulcerative colitis (UC) showed higher AnxA1 expression than those with active disease. We also evaluated dextran sulfate sodium (DSS)-acute colitis in TNF-α receptor 1 KO (TNFR1-/-) strain with impaired TNF-α signaling and C57BL/6 (WT) mice. Although both strains developed colitis, TNFR1-/- mice showed early clinical recovery, lower myeloperoxidase (MPO) activity and milder histopathological alterations. Colonic epithelium from control and DSS-treated TNFR1-/- mice showed intense AnxA1 expression and AnxA1+ CD4+ and CD8+ T cells were more frequent in TNFR1-/- animals, suggesting an extra supply of AnxA1. The pan antagonist of AnxA1 receptors exacerbated the colitis outcome in TNFR1-/- mice, supporting the pivotal role of AnxA1 in the early recovery. Our findings demonstrate that the TNF-α signaling reduction favors the expression and biological activity of AnxA1 in inflamed intestinal mucosa.

Immune neuroendocrine interactions during a fungal infection in immunocompetent or immunosuppressed hosts.

The yeast Candida albicans belongs to the microflora of healthy individuals, although it can infect a variety of tissues ensuing changes in the host’s immune status. To evaluate the effect of neuroendocrine input on the early immune response during the fungal infection, we use a 3-day paradigm of chronic varied stress in Wistar rats infected with C. albicans. We find that stress mediators contribute to the spread of the fungus and downregulate critical functions of phagocytic cells at the infection site. Phenotypic and functional alterations of effector cells account for the decreased resistance to candidiasis and condition the development of the adaptive response. Stressed hosts exhibit a higher fungal burden in kidneys and livers associated with hyphal forms. The hepatic inflammatory reaction is compromised with severe steatosis, increment of functional enzymes, marked lipid peroxidation and hepatocyte apoptosis. Moreover, infection-related sickness symptoms are significantly increased by exposure to stress with anorexia, weight loss, lack of leptin and depletion of glycogen depots. Food deprivation exacerbates the liver injury. Stress mediators perturb the complex immune and metabolic program that operates early during fungal spread and promotes severe tissue damage.

Immune-metabolic balance in stressed rats during Candida albicans infection.

We evaluated the host metabolic response to chronic varied stress during infection with the fungus Candida albicans. We used four groups of female Wistar rats: normal uninfected and unstressed, stressed, C. albicans infected and infected, and stressed. Infected rats reacted with rapid metabolic adjustments, evident as anorexia and body weight loss, partly mediated by glucocorticoids and TNF-α. Higher circulating levels of IL-6 and glucose (p < 0.05) revealed the progress and catabolic effect of the inflammatory response. Infected and stressed rats instead showed anorexia associated with infection and weight loss as the result of reduced food intake. This group exhibited a prompt reduction in circulating leptin on day 3 (p < 0.05), reduction in glucose levels and depletion of hepatic glycogen depots. We also evaluated the contribution of TNF-α, glucocorticoids, and food deprivation to liver damage. Lipid peroxidation in liver detected in the infected and infected-stressed groups was exacerbated by the glucocorticoid receptor antagonist RU 486, suggesting the modulatory activity of glucocorticoids, while hepatic fat accumulation and glycogen depletion decreased with anti-TNF-α treatment. Food deprivation exacerbated liver injury while the response to stress contributed to greater fungal colonization. Our findings emphasize the impact of metabolic alterations on tissue damage when the host immune activity is modulated by stress mediators.

Oxalate induces breast cancer

BackgroundMicrocalcifications can be the early and only presenting sign of breast cancer. One shared characteristic of breast cancer is the appearance of mammographic mammary microcalcifications that can routinely be used to detect breast cancer in its initial stages, which is of key importance due to the possibility that early detection allows the application of more conservative therapies for a better patient outcome. The mechanism by which mammary microcalcifications are formed is still largely unknown but breast cancers presenting microcalcifications are more often associated with a poorer prognosis.MethodsWe combined Capillary Electrochromatography, histology, and gene expression (qRT-PCR) to analyze patient-matched normal breast tissue vs. breast tumor. Potential carcinogenicity of oxalate was tested by its inoculation into mice. All data were subjected to statistical analysis.ResultsTo study the biological significance of oxalates within the breast tumor microenvironment, we measured oxalate concentration in both human breast tumor tissues and adjoining non-pathological breast tissues. We found that all tested breast tumor tissues contain a higher concentration of oxalates than their counterpart non-pathological breast tissue. Moreover, it was established that oxalate induces proliferation of breast cells and stimulates the expression of a pro-tumorigenic gene c-fos. Furthermore, oxalate generates highly malignant and undifferentiated tumors when it was injected into the mammary fatpad in female mice, but not when injected into their back, indicating that oxalate does not induce cancer formation in all types of tissues. Moreover, neither human kidney-epithelial cells nor mouse fibroblast cells proliferate when are treated with oxalate.ConclusionsWe found that the chronic exposure of breast epithelial cells to oxalate promotes the transformation of breast cells from normal to tumor cells, inducing the expression of a proto-oncogen as c-fos and proliferation in breast cancer cells. Furthermore, oxalate has a carcinogenic effect when injected into the mammary fatpad in mice, generating highly malignant and undifferentiated tumors with the characteristics of fibrosarcomas of the breast. As oxalates seem to promote these differences, it is expected that a significant reduction in the incidence of breast cancer tumors could be reached if it were possible to control oxalate production or its carcinogenic activity.

Intestinal mononuclear cells primed by systemic IL-12 display long-term ability to aggravate colitis in mice

To address whether the burst of systemic interleukin‐12 (IL‐12) influences intestinal inflammation elicited by luminal stimuli, we induced IL‐12 release by cDNA injection in C57BL/6 mice and simultaneously started dextran sulphate sodium administration. The sequence of the inflammatory response triggered by IL‐12 release was characterized by assessing myeloperoxidase activity and histological damage in colon samples on days 1, 3, 5 and 7 after colitis induction. To evaluate the persistence of IL‐12 priming, colitis was induced in mice 7 or 60 days after cDNA injection. Under IL‐12 influence, the development of acute colitis presented a faster and selective infiltration of inflammatory mononuclear cells in the lamina propria. Recruitment was driven by systemic cytokines rather than luminal antigens. Interestingly, when colitis was triggered 7 or 60 days after the cytokine storm, cells maintained the ability to worsen clinical signs of intestinal inflammation. Together, a systemic IL‐12 burst effectively primed intestinal cells that became more prone to develop inflammatory responses. Activation was long‐lasting because intestinal cells maintained their inflammatory potential and their ability to aggravate colitis.