Deep Dermal Injection As a Model of <em>Candida albicans</em> Skin Infection for Histological Analyses

The skin is an extremely extended organ of the body and, due to this large surface, it is continuously exposed to microorganisms. Skin damage can easily ...

University of Milano-Bicocca

Model organisms and in particular the budding yeast Saccharomyces cerevisiae have been instrumental in advancing our understanding of cell cycle progression. The asymmetric division of the budding yeast and the tight coupling between cell growth and division have challenged the theoretical understanding of the cell size structure of growing yeast populations. Past efforts have centered on modeling the steady-state theoretical age distribution for asymmetric division from which a cell size distribution can be derived assuming dispersion of cell size within each age class. Different developments, especially in the field of flow cytometry, allowed the determination of a number of cellular properties and their joint distributions for the entire population and the different subpopulations as well. A new rigorous framework for modeling directly the dynamics of size distributions of structured yeast populations has been proposed, which readily extends to modeling of more complex conditions, such as transient growth. Literature on the structure of growing yeast populations and modeling of cell cycle progression is reviewed.

Analysis and modeling of growing budding yeast populations at the single cell level.

Brown band disease (BrB), a virulent coral disease characterized by a dense concentration of ciliates ingesting coral tissue, is responsible for ongoing coral losses on Indo-Pacific reefs. Although several efforts have been made to identify the microbial communities associated with BrB and study the disease ecology, less attention has been given to the effect of ciliate presence on coral physiology. Levels of the mitochondrial heat shock protein 60-kDa (Hsp60, a biomarker indicative of cellular stress) were analyzed in apparently healthy coral polyps located at different distances along the advancing front of infection in Acropora muricata colonies affected by BrB in a Maldivian reef. Different Hsp60 levels were found in different parts of the same colony. Starting from a basal protein level in the healthy control colonies, a down-regulation of Hsp60 expression was detected near the ciliate band, indicating that the Hsp60 defense activity was probably already compromised due to the rapid progression rate of the BrB ciliate on the diseased branches and/or to the etiology of the disease. Moving away from the band, the Hsp60 levels gradually returned to a state comparable to that found in the control, showing that cellular damage was confined to areas near the infection. In conclusion, we propose the analysis of Hsp60 modulation as a useful tool for examining physiological variations that are not detected at the morphological level in corals subjected to epizootic diseases, while providing new insights into the immune response of corals. 

Modulation of Hsp60 in response to coral brown band disease.

Nicotinamide (NAM), a form of vitamin B, is a byproduct and noncompetitive inhibitor of the deacetylation reaction catalyzed by Sirtuins. These represent a family of evolutionarily conserved NAD-dependent deacetylases that are well-known critical regulators of metabolism and aging and whose founding member is Sir2 of Saccharomyces cerevisiae. Here, we investigated the effects of NAM supplementation in the context of yeast chronological aging, the established model for studying aging of postmitotic quiescent mammalian cells. Our data show that NAM supplementation at the diauxic shift results in a phenocopy of chronologically aging sir2Δ cells. In fact, NAM-supplemented cells display the same chronological lifespan extension both in expired medium and extreme Calorie Restriction. Furthermore, NAM allows the cells to push their metabolism toward the same outcomes of sir2Δ cells by elevating the level of the acetylated Pck1. Both these cells have the same metabolic changes that concern not only anabolic pathways such as an increased gluconeogenesis but also respiratory activity in terms both of respiratory rate and state of respiration. In particular, they have a higher respiratory reserve capacity and a lower non-phosphorylating respiration that in concert with a low burden of superoxide anions can affect positively chronological aging.

Nicotinamide supplementation phenocopies SIR2 inactivation by modulating carbon metabolism and respiration during yeast chronological aging.

Black band disease (BBD) is a widespread coral pathology caused by a microbial consortium dominated by cyanobacteria, which is significantly contributing to the loss of coral cover and diversity worldwide. Since the effects of the BBD pathogens on the physiology and cellular stress response of coral polyps appear almost unknown, the expression of some molecular biomarkers, such as Hsp70, Hsp60, HO-1, and MnSOD, was analyzed in the apparently healthy tissues of Goniopora columna located at different distances from the infection and during two disease development stages. All the biomarkers displayed different levels of expression between healthy and diseased colonies. In the healthy corals, low basal levels were found stable over time in different parts of the same colony. On the contrary, in the diseased colonies, a strong up-regulation of all the biomarkers was observed in all the tissues surrounding the infection, which suffered an oxidative stress probably generated by the alternation, at the progression front of the disease, of conditions of oxygen supersaturation and hypoxia/anoxia, and by the production of the cyanotoxin microcystin by the BBD cyanobacteria. Furthermore, in the infected colonies, the expression of all the biomarkers appeared significantly affected by the development stage of the disease. In conclusion, our approach may constitute a useful diagnostic tool, since the cellular stress response of corals is activated before the pathogens colonize the tissues, and expands the current knowledge of the mechanisms controlling the host responses to infection in corals.

The cellular stress response of the scleractinian coral Goniopora columna during the progression of the black band disease.

Resveratrol (RSV) is a naturally occurring polyphenolic compound endowed with interesting biological properties/functions amongst which are its activity as an antioxidant and as Sirtuin activating compound towards SIRT1 in mammals. Sirtuins comprise a family of NAD-dependent protein deacetylases that are involved in many physiological and pathological processes including aging and age-related diseases. These enzymes are conserved across species and SIRT1 is the closest mammalian orthologue of Sir2 of Saccharomyces cerevisiae. In the field of aging researches, it is well known that Sir2 is a positive regulator of replicative lifespan and, in this context, the RSV effects have been already examined. Here, we analyzed RSV effects during chronological aging, in which Sir2 acts as a negative regulator of chronological lifespan (CLS). Chronological aging refers to quiescent cells in stationary phase; these cells display a survival-based metabolism characterized by an increase in oxidative stress. We found that RSV supplementation at the onset of chronological aging, namely at the diauxic shift, increases oxidative stress and significantly reduces CLS. CLS reduction is dependent on Sir2 presence both in expired medium and in extreme Calorie Restriction. In addition, all data point to an enhancement of Sir2 activity, in particular Sir2-mediated deacetylation of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase (Pck1). This leads to a reduction in the amount of the acetylated active form of Pck1, whose enzymatic activity is essential for gluconeogenesis and CLS extension.

During yeast chronological aging resveratrol supplementation results in a short-lived phenotype Sir2-dependent.

Nuclear factor of activated T cells (NFAT) is activated in innate immune cells downstream of pattern recognition receptors, but little is known about NFAT's functions in innate immunity compared with adaptive immunity. We show that early activation of NFAT balances the two major phases of the innate response to  skin infections: the protective containment (abscess) and the elimination (expulsion) phases. During the early containment phase, transforming growth factor- (TGF-) induces the deposit of collagen around newly recruited polymorphonuclear cells to prevent microbial spreading. During the elimination phase, interferon- (IFN-) blocks differentiation of fibroblasts into myofibroblasts by antagonizing TGF- signaling. IFN- also induces the formation of plasmin that, in turn, promotes abscess capsule digestion and skin ulceration for microbial discharge. NFAT controls innate IFN-γ production and microbial expulsion. This cross-talk between the innate immune and the fibrinolytic systems also occurs during infection with  and is a protective response to minimize tissue damage and optimize pathogen elimination.

Marina Vai

Department of Biotechnology and Biosciences

University of Milano-Bicocca

Deep Dermal Injection As a Model of Candida albicans Skin Infection for Histological Analyses

Marina Vai

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Biotechnology and Biosciences

University of Milano-Bicocca

Deep Dermal Injection As a Model of Candida albicans Skin Infection for Histological Analyses

Department of Biotechnology and Biosciences