Candida albicans Modulates Murine and Human Beta Defensin-1 during Vaginitis.

Vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis (RVVC) are two forms of a disease caused by Candida spp. ß-defensin (BD) is one of the most important families of antimicrobial peptides in the female genital tract and includes molecules that exert essential local functions as antimicrobial and PMN chemoattractant peptides. However, the information on their role during murine and human VVC and RVVC is limited. Thus, we analyzed the behavior and contribution of BD1 to the local response in a VVC mice model and the local cytokine profile and human BD1 and BD3 expression in cervicovaginal lavage from patients with VVC and RVVC. We demonstrated that, in patients with RVVC BD1, mRNA and protein expression were severely diminished and that the aspartate proteinase and lipase secreted by C. albicans are involved in that decrease. This study provides novel information about the pathogenesis of VVC and describes a highly efficient C. albicans escape strategy for perpetuating the infection; these results may contribute to the development of new or combined treatment approaches.

Oxidative and nitrosative stress responses during macrophage-Candida albicans biofilm interaction.

Candida albicans is an important source of device-associated infection because of its capacity for biofilm formation. This yeast has the ability to form biofilms which favors the persistence of the infection. Furthermore, the innate immune response has a critical role in the control of these infections and macrophages (Mø) are vital to this process. An important fungicidal mechanism employed by Mø involves the generation of toxic reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI). The interaction between biofilms and these immune cells, and the contribution of oxidative and nitrosative stress, that is determinant to the course of the infection, remains elusive. The aim of this study was to investigate this interaction. To this purpose, two models of Mø-biofilms contact, early (model 1) and mature (model 2) biofilms, were used; and the production of ROS, RNI and the oxidative stress response (OSR) were evaluated. We found that the presence of Mø decreased the biofilm formation at an early stage and increased the production of ROS and RNI, with activation of ORS (enzymatic and nonenzymatic). On the other hand, the interaction between mature biofilms and Mø resulted in an increasing biofilm formation, with low levels of RNI and ROS production and decrease of OSR. Dynamic interactions between Mø and fungal biofilms were also clearly evident from images obtained by confocal scanning laser microscopy. The prooxidant-antioxidant balance was different depending of C. albicans biofilms stages and likely acts as a signal over their formation in presence of Mø. These results may contribute to a better understanding of the immune-pathogenesis of C. albicans biofilm infections.

Protective phenotypes of club cells and alveolar macrophages are favored as part of endotoxin-mediated prevention of asthma.

Atopic asthma is a chronic allergic disease that involves T-helper type 2 (Th2)-inflammation and airway remodeling. Bronchiolar club cells (CC) and alveolar macrophages (AM) are sentinel cells of airway barrier against inhaled injuries, where allergy induces mucous metaplasia of CC and the alternative activation of AM, which compromise host defense mechanisms and amplify Th2-inflammation. As there is evidence that high levels of environmental endotoxin modulates asthma, the goal of this study was to evaluate if the activation of local host defenses by Lipopolysaccharide (LPS) previous to allergy development can contribute to preserving CC and AM protective phenotypes. Endotoxin stimulus before allergen exposition reduced hallmarks of allergic inflammation including eosinophil influx, Interleukin-4 and airway hyperreactivity, while the T-helper type 1 related cytokines IL-12 and Interferon-γ were enhanced. This response was accompanied by the preservation of the normal CC phenotype and the anti-allergic proteins Club Cell Secretory Protein (CCSP) and Surfactant-D, thereby leading to lower levels of CC metaplasia and preventing the increase of the pro-Th2 cytokine Thymic stromal lymphopoietin. In addition, classically activated alveolar macrophages expressing nitric oxide were promoted over the alternatively activated ones that expressed arginase-1. We verified that LPS induced a long-term overexpression of CCSP and the innate immune markers Toll-like receptor 4, and Tumor Necrosis Factor-α, changes that were preserved in spite of the allergen challenge. These results demonstrate that LPS pre-exposition modifies the local bronchioalveolar microenvironment by inducing natural anti-allergic mechanisms while reducing local factors that drive Th2 type responses, thus modulating allergic inflammation.

Oxidative and nitrosative stress in Staphylococcus aureus biofilm.

Diverse chemical and physical agents can alter cellular functions associated with oxidative metabolism, thus stimulating the production of reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI) in planktonic bacterial physiology. However, more research is necessary to determine the precise role of cellular stress in biofilm. The present study was designed to address the issues of Staphylococcus aureus biofilm formation with respect to the generation of oxidative and nitrosative stress. We studied three pathogenic S. aureus clinical strains and an ATCC strain exposed to a different range of culture conditions (time, temperature, pH, reduction and atmospheric conditions) using quantitative methods of biofilm detection. We observed that cellular stress could be produced inside biofilms, thereby affecting their growth, resulting in an increase of ROS and RNI production, and a decrease of the extracellular matrix under unfavorable conditions. These radical oxidizers could then accumulate in an extracellular medium and thus affect the matrix. These results contribute to a better understanding of the processes that enable adherent biofilms to grow on inert surfaces and lead to an improved knowledge of ROS and RNI regulation, which may help to clarify the relevance of biofilm formation in medical devices.

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-alpha. 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-alpha, 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-alpha 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.

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.

El hígado como órgano inmunológico / The liver and immune organ

La prevalencia de enfermedades hepáticas a nivel mundial registra cifras alarmantes. Solo la infección por malaria afecta a 500 millones de personas por año a nivel mundial. Enfermedades de etiología viral como hepatitis B y C, contribuyen al aumento de la casuística y por su caracter de patologías de tipo crónico evolucionan a formas severas como la fibrosis o los procesos neoplásicos. La relevancia del hígado como órgano central en la maquinaria metabólica del organismo y como clave partícipe de la respuesta inflamatoria sistémica, indican la necesidad de preservar sus capacidades funcionales.

Cytokines and the immune-neuroendocrine network: What did we learn from infection and autoimmunity?

The initial view of the neuroendocrine-immune communication as the brake of immune activation is changing. Recent evidence suggests that the optimization of the body's overall response to infection could be actually the role of the immune-endocrine network. In gradually more complex organisms, the multiplicity of host-pathogen interfaces forced the development of efficient and protective responses. Molecules such as cytokines and Toll-like receptors (TLRs) are distributed both in the periphery and in the brain to participate in a coordinated adaptive function. When sustained release of inflammatory mediators occurs, as in autoimmune diseases, undesirable pathological consequences become evident with different manifestations and outcomes. Clearly, organisms are not well adapted to that disregulated condition yet, suggesting that additional partners within neuroendocrine-immune interactions might emerge from the evolutionary road.

Neurocandidiasis, definiendo las interacciones patógeno/huésped en este particular sitio del organismo / Neurocandidiasis, defending host/pathogen intereactions in this particular site of the body

La colonización del sistema Nervioso Central por Candida Alnicans u otras especies de este género es un hecho no poco frecuente y de elevado riesgo para el huésped. La morbi-mortalidad asociada a esta presentación de la micosis y la ausencia de terapias exitosas comprometen aún más los alcances de esta patología. Otros factores que contribuyen a otorgar mayor complejidad a este escenario son las particularidades inherentes a este patógeno oportunista y las características del nicho biológico colonizado. En el presente artículo revisamos aspectos importantes del agente etiológico, sus características más destacadas y las estrategias de agresión/invasión involucradas durante su interacción con el huésped. Las peculiaridades de este sitio considerado de ¶Inmunoprivilegio÷, los mediadores y células que contribuyen a otorgarle tal estatus y su implicancia en la evolución y severidad del proceso también son considerados. El creciente desafío de su diagnóstico, la promoción de alternativas terapéuticas y el desarrollo de nuevas estrategias constituyen un verdadero desafío que convoca a investigadores de distancias disciplinas a comprometer esfuerzos.(AU)

Neurocandidiasis, definiendo las interacciones patógeno/huésped en este particular sitio del organismo / Neurocandidiasis, defending host/pathogen intereactions in this particular site of the body

La colonización del sistema Nervioso Central por Candida Alnicans u otras especies de este género es un hecho no poco frecuente y de elevado riesgo para el huésped. La morbi-mortalidad asociada a esta presentación de la micosis y la ausencia de terapias exitosas comprometen aún más los alcances de esta patología. Otros factores que contribuyen a otorgar mayor complejidad a este escenario son las particularidades inherentes a este patógeno oportunista y las características del nicho biológico colonizado. En el presente artículo revisamos aspectos importantes del agente etiológico, sus características más destacadas y las estrategias de agresión/invasión involucradas durante su interacción con el huésped. Las peculiaridades de este sitio considerado de “Inmunoprivilegio”, los mediadores y células que contribuyen a otorgarle tal estatus y su implicancia en la evolución y severidad del proceso también son considerados. El creciente desafío de su diagnóstico, la promoción de alternativas terapéuticas y el desarrollo de nuevas estrategias constituyen un verdadero desafío que convoca a investigadores de distancias disciplinas a comprometer esfuerzos.

Hepatocellular apoptosis during Candida albicans colonization: involvement of TNF-alpha and infiltrating Fas-L positive lymphocytes.

The liver constitutes the first barrier in the control of hematogenous dissemination of Candida albicans of intestinal origin. In rats infected with C. albicans, this organ limits the growth of the yeast and mounts an efficient inflammatory reaction. However, in rats infected and exposed to chronic varied stress, the hepatic inflammatory reaction is compromised and the outcoming of the infection is more severe. Although in both groups the fungal burden is associated with hepatotoxicity, steatosis, increment of hepatic enzymes and lipid peroxidation, stress-related differences are clearly evident. Herein, we evaluated in infected and infected-stressed hosts the involvement of apoptosis and pro-apoptotic signals in the hepatic injury during the acute step of C. albicans infection. We studied in situ apoptosis by 4',6-diamidino-2-phenylindole dihydrochloride and terminal deoxynucleotidyl transferase dUTP nick-end labeling reactions, the levels of local tumor necrosis factor (TNF)-alpha mRNA by reverse transcription-PCR and the Fas/Fas-L expression by immunohistochemistry and western blot. We also purified intrahepatic lymphocytes (IHLs) to evaluate the dynamic of recruitment following the infection and to characterize the in vivo and in vitro interaction of C. albicans with this subset evaluating the kinetic of Fas-L and Toll-like receptor-2 (TLR-2) expression. This work shows, for the first time, the occurrence of in situ apoptosis of hepatocytes as well as the kinetic of IHL recruitment early during the C. albicans infection. Moreover, our results demonstrate the ability of the fungus to up-regulate the Fas-L and TLR-2 expression in this subset. In the scenario of early liver injury, the recruited IHLs and the modulated expression of TNF-alpha, Fas-L and TLR-2 molecules could act coordinately in delivering death signals.

Opposite effects of galectin-1 on alternative metabolic pathways of L-arginine in resident, inflammatory, and activated macrophages.

Recent evidence has implicated galectins and their carbohydrate ligands as master regulators of the inflammatory response. Galectin-1, a member of this family, has shown specific anti-inflammatory and immunoregulatory effects. To gain insight into the potential mechanisms involved in these effects, we investigated the effects of galectin-1 in L-arginine metabolism of peritoneal rat macrophages. Pretreatment of macrophages with galectin-1 resulted in a dose- and time-dependent inhibition of lipopolysaccharide-induced nitric oxide (NO) production, accompanied by a decrease in inducible nitric oxide synthase (iNOS) expression (the classic pathway of L-arginine). On the other hand, galectin-1 favored the balance toward activation of L-arginase, the alternative metabolic pathway of L-arginine. Inhibition of NO production was not the result of increased macrophage apoptosis because addition of this beta-galactoside-binding protein to macrophages under the same experimental conditions did not affect the apoptotic threshold of these cells. To understand how endogenous galectin-1 is regulated in macrophages under inflammatory stress, we finally explored the ultrastructural distribution, expression, and secretion of galectin-1 in resident, inflammatory, and activated macrophages. This study provides an alternative cellular mechanism based on the modulation of L-arginine metabolism to understand the molecular basis of the anti-inflammatory properties displayed by this carbohydrate-binding protein.

Aspectos básicos de la neuroendocrinoinmunología (NEI) / Basic aspects of the neuroendocrinoimmunology

En este artículo se discuten los aspectos básicos de la interacción entre los sistemas neuroendócrino e inmune. Existen dos vías principales de comunicación ente el cerebro y el sistema inmune: el sistema nervioso autónomo y la rama neuroendócrina a través de los productos que libera la pituitaria. La pincipal influencia del cerebro sobre la función inmune es ejercida a través del eje hipotálamo-pituitaria adrenal (HPA). Ciertos neurotransmisores, neuropéptidos y neurohormonas afectan la función inmune tanto in vivo como in vitro. Además, las células inmunes expresan en sua membranas receptores para esas moléculas. Una característica de esta comunicación es su bidireccionalidad ya que las citoquinas que se producen y liberan durante la respuesta inmune pueden a su vez, afectar al eje HPA. En este contexto, describimos parte de nuestro trabajo experimental desarrolado en ratas infectadas com Candida albicans y expuestas a un esquema de estrés crónico y variado. (AU)

Aspectos básicos de la neuroendocrinoinmunología (NEI) / Basic aspects of the neuroendocrinoimmunology

En este artículo se discuten los aspectos básicos de la interacción entre los sistemas neuroendócrino e inmune. Existen dos vías principales de comunicación ente el cerebro y el sistema inmune: el sistema nervioso autónomo y la rama neuroendócrina a través de los productos que libera la pituitaria. La pincipal influencia del cerebro sobre la función inmune es ejercida a través del eje hipotálamo-pituitaria adrenal (HPA). Ciertos neurotransmisores, neuropéptidos y neurohormonas afectan la función inmune tanto in vivo como in vitro. Además, las células inmunes expresan en sua membranas receptores para esas moléculas. Una característica de esta comunicación es su bidireccionalidad ya que las citoquinas que se producen y liberan durante la respuesta inmune pueden a su vez, afectar al eje HPA. En este contexto, describimos parte de nuestro trabajo experimental desarrolado en ratas infectadas com Candida albicans y expuestas a un esquema de estrés crónico y variado.