Candida glabrata binds to glycosylated and lectinic receptors on the coronary endothelial luminal membrane and inhibits flow sense and cardiac responses to agonists

Inflammatory mechanisms and intervention strategies for sepsis-induced myocardial dysfunction

Sepsis-induced myocardial dysfunction (SIMD) is the leading cause of death in patients with sepsis in the intensive care units. The main manifestations of SIMD are systolic and diastolic dysfunctions of the myocardium. Despite our initial understanding of the SIMD over the past three decades, the incidence and mortality of SIMD remain high. This may be attributed to the large degree of heterogeneity among the initiating factors, disease processes, and host states involved in SIMD. Previously, organ dysfunction caused by sepsis was thought to be an impairment brought about by an excessive inflammatory response. However, many recent studies have shown that SIMD is a consequence of a combination of factors shaped by the inflammatory responses between the pathogen and the host. In this article, we review the mechanisms of the inflammatory responses and potential novel therapeutic strategies in SIMD.

O-Linked Glycans of Candida albicans Interact with Specific GPCRs in the Coronary Endothelium and Inhibit the Cardiac Response to Agonists

Candida albicans is an opportunistic fungal pathogen that may cause invasive infections in immunocompromised patients, disseminating through the bloodstream to other organs. In the heart, the initial step prior to invasion is the adhesion of the fungus to endothelial cells. Being the fungal cell wall's outermost structure and the first to come in contact with host cells, it greatly modulates the interplay that later will derive in the colonization of the host tissue. In this work, we studied the functional contribution of N-linked and O-linked mannans of the cell wall of C. albicans to the interaction with the coronary endothelium. An isolated rat heart model was used to assess cardiac parameters related to vascular and inotropic effects in response to phenylephrine (Phe), acetylcholine (aCh) and angiotensin II (Ang II) when treatments consisting of: (1) live and heat-killed (HK) C. albicans wild-type yeasts; (2) live C. albicans pmr1Δ yeasts (displaying shorter N-linked and O-linked mannans); (3) live C. albicans without N-linked and O-linked mannans; and (4) isolated N-linked and O-linked mannans were administered to the heart. Our results showed that C. albicans WT alters heart coronary perfusion pressure (vascular effect) and left ventricular pressure (inotropic effect) parameters in response to Phe and Ang II but not aCh, and these effects can be reversed by mannose. Similar results were observed when isolated cell walls, live C. albicans without N-linked mannans or isolated O-linked mannans were perfused into the heart. In contrast, C. albicans HK, C. albicans pmr1Δ, C. albicans without O-linked mannans or isolated N-linked mannans were not able to alter the CPP and LVP in response to the same agonists. Taken together, our data suggest that C. albicans interaction occurs with specific receptors on coronary endothelium and that O-linked mannan contributes to a greater extent to this interaction. Further studies are necessary to elucidate why specific receptors preferentially interact with this fungal cell wall structure.

Host-pathogen interaction in Candida glabrata infection: current knowledge and implications for antifungal therapy

INTRODUCTION

The opportunistic fungal pathogen Candida glabrata poses a clinical challenge in the successful treatment of invasive Candida infections, owing to its low inherent susceptibility toward azole antifungals and the recent acquisition of coresistance toward azole and echinocandin drugs. Compared to other prevalent Candida bloodstream pathogens, C. glabrata neither exhibits secreted proteolytic activity nor invokes a strong immune response in a variety of host cells and is less virulent. It also does not form true hyphae, and the success of C. glabrata, therefore, as a prevalent human fungal pathogen, appears to be built upon a distinct set of virulence attributes.

AREAS COVERED

The focus of this review is to outline, in brief, the interaction of C. glabrata with the host, deduced from the knowledge gained from different in vitro, ex vivo, and in vivo model systems. In addition, we briefly discuss the current antifungals, antifungal resistance mechanisms, and the development of new antifungal therapies, along with the available information on the host response.

EXPERT OPINION

A detailed understanding of stresses, selection pressures and differential immune responses in the presence and absence of antifungals that C. glabrata encounters in varied niches of the host, is required to design effective antifungal therapy.

Candida glabrata: A Lot More Than Meets the Eye

Candida glabrata is an opportunistic human fungal pathogen that causes superficial mucosal and life-threatening bloodstream infections in individuals with a compromised immune system. Evolutionarily, it is closer to the non-pathogenic yeast Saccharomyces cerevisiae than to the most prevalent Candida bloodstream pathogen, C. albicans. C. glabrata is a haploid budding yeast that predominantly reproduces clonally. In this review, we summarize interactions of C. glabrata with the host immune, epithelial and endothelial cells, and the ingenious strategies it deploys to acquire iron and phosphate from the external environment. We outline various attributes including cell surface-associated adhesins and aspartyl proteases, biofilm formation and stress response mechanisms, that contribute to the virulence of C. glabrata. We further discuss how, C. glabrata, despite lacking morphological switching and secreted proteolytic activity, is able to disarm macrophage, dampen the host inflammatory immune response and replicate intracellularly.

Candida glabrata's Genome Plasticity Confers a Unique Pattern of Expressed Cell Wall Proteins

Candida glabrata is the second most common cause of candidemia, and its ability to adhere to different host cell types, to microorganisms, and to medical devices are important virulence factors. Here, we consider three characteristics that confer extraordinary advantages to C. glabrata within the host. (1) C. glabrata has a large number of genes encoding for adhesins most of which are localized at subtelomeric regions. The number and sequence of these genes varies substantially depending on the strain, indicating that C. glabrata can tolerate high genomic plasticity; (2) The largest family of CWPs (cell wall proteins) is the EPA (epithelial adhesin) family of adhesins. Epa1 is the major adhesin and mediates adherence to epithelial, endothelial and immune cells. Several layers of regulation like subtelomeric silencing, cis-acting regulatory regions, activators, nutritional signaling, and stress conditions tightly regulate the expression of many adhesin-encoding genes in C. glabrata, while many others are not expressed. Importantly, there is a connection between acquired resistance to xenobiotics and increased adherence; (3) Other subfamilies of adhesins mediate adherence to Candida albicans, allowing C. glabrata to efficiently invade the oral epithelium and form robust biofilms. It is noteworthy that every C. glabrata strain analyzed presents a unique pattern of CWPs at the cell surface.