c Constant cross talk between Candida albicans yeast cells and their human host determines the outcome of fungal colonization and, eventually, the progress of infectious disease (candidiasis). An effective weapon used by C. albicans to cope with the host defense system is the release of 10 distinct secreted aspartic proteases (SAPs). Here, we validate a hypothesis that neutrophils and epithelial cells use the antimicrobial peptide LL-37 to inactivate C. albicans at sites of candidal infection and that C. albicans uses SAPs to effectively degrade LL-37. LL-37 is cleaved into multiple products by SAP1 to -4, SAP8, and SAP9, and this proteolytic processing is correlated with the gradual decrease in the antifungal activity of LL-37. Moreover, a major intermediate of LL-37 cleavage-the LL-25 peptide-is antifungal but devoid of the immunomodulatory properties of LL-37. In contrast to LL-37, LL-25 did not affect the generation of reactive oxygen species by neutrophils upon treatment with phorbol esters. Stimulating neutrophils with LL-25 (rather than LL-37) significantly decreased calcium flux and interleukin-8 production, resulting in lower chemotactic activity of the peptide against neutrophils, which may decrease the recruitment of neutrophils to infection foci. LL-25 also lost the function of LL-37 as an inhibitor of neutrophil apoptosis, thereby reducing the life span of these defense cells. This study indicates that C. albicans can effectively use aspartic proteases to destroy the antimicrobial and immunomodulatory properties of LL-37, thus enabling the pathogen to survive and propagate.A s a polymorphic opportunistic fungal pathogen, Candida albicans colonizes distinct niches in the human body such as the oral and vaginal cavities and the gut. In healthy individuals, C. albicans is controlled by the host immune system, epithelial barriers, and coexisting commensal microorganisms (1). However, under certain circumstances, C. albicans causes relatively easily curable superficial infections, as well as life-threatening deepseated and disseminated candidiases (2). The transition of C. albicans from a commensal to a pathogen depends mostly on the status of the host's immune system; therefore, the major risk factors for candidiasis include immunosuppressive therapy, indwelling vascular catheters, neutropenia, and prolonged treatment with broad-spectrum antibiotics (3). The pathogenic potential of C. albicans is determined by several factors, including molecules that mediate adhesion to and invasion of host cells, secreted hydrolases, polymorphisms, biofilm formation, and adaptation to stressful environmental conditions within the host organism (4).Neutrophils, which constitute the first line of host defense against microbial pathogens, are recruited to the infection site, where they rapidly respond with diverse antimicrobial mechanisms that demonstrate both intra-and extracellular processes such as phagocytosis and the degranulation and formation of neutrophil extracellular traps (NETs) (5). All of these processes inv...

The increased incidence of severe disseminated infections caused by the opportunistic yeast-like fungi Candida spp. highlights the urgent need for research into the major virulence factors of these pathogens-extracellular aspartic proteinases of the candidapepsin and yapsin families. Classically, these enzymes were considered to be generally destructive factors that damage host tissues and provide nutrients for pathogen propagation. However, in recent decades, novel and more specific functions have been suggested for extracellular candidal proteinases. These include contributions to cell wall maintenance and remodeling, the formation of polymicrobial biofilms, adhesion to external protective barriers of the host, the deregulation of host proteolytic cascades (such as the complement system, blood coagulation and the kallikrein-kinin system), a dysregulated host proteinase-inhibitor balance, the inactivation of host antimicrobial peptides, evasion of immune responses and the induction of inflammatory mediator release from host cells. Only a few of these activities recognized in Candida albicans candidapepsins have been also confirmed in other Candida species, and characterization of Candida glabrata yapsins remains limited.

BackgroundCandida albicans yeast produces 10 distinct secreted aspartic proteases (Saps), which are some of the most important virulence factors of this pathogenic fungus. One of the suggested roles of Saps is their deregulating effect on various proteolytic cascades that constitute the major homeostatic systems in human hosts, including blood coagulation, fibrinolysis, and kallikrein-kinin systems. This study compared the characteristics of the action of all 10 Saps on human kininogens, which results in generating proinflammatory bradykinin-related peptides (kinins).ResultsRecombinant forms of Saps, heterologously overexpressed in Pichia pastoris were applied. Except for Sap7 and Sap10, all Saps effectively cleaved the kininogens, with the highest hydrolytic activity toward the low-molecular-mass form (LK). Sap1–6 and 8 produced a biologically active kinin—Met-Lys-bradykinin—and Sap3 was exceptional in terms of the kinin-releasing yield (>60% LK at pH 5.0 after 24 hours). Des-Arg1-bradykinin was released from LK by Sap9 at a comparably high yield, but this peptide was assumed to be biologically inactive because it was unable to interact with cellular B2-type kinin receptors. However, the collaborative actions of Sap9 and Sap1, −2, −4–6, and −8 on LK rerouted kininogen cleavage toward the high-yield release of the biologically active Met-Lys-bradykinin.ConclusionsOur present results, together with the available data on the expression of individual SAP genes in candidal infection models, suggest a biological potential of Saps to produce kinins at the infection foci. The kinin release during candidiasis can involve predominant and complementary contributions of two different Sap3- and Sap9-dependent mechanisms.

In this review we present the current knowledge of factors that can influence the yield and regulation of vitamin B1, B2, B3 and B9 biosynthesis in plants which can be important for human nutrition. A summary of modern methods applied for vitamin analysis in biological materials is also provided. Contributions of selected vitamins to the homeostasis of the human organism, as well as their relations to the progress or prevention of some important diseases such as cancer, cardiovascular diseases, diabetes and Alzheimer's disease are discussed in the light of recent investigations. Better understanding of the mechanisms of vitamin uptake by human tissues and possible metabolic or genetic backgrounds of vitamin deficiencies can open new perspectives on the medical strategies and biotechnological processes of food fortification.

Microorganisms that create mixed-species biofilms in the human oral cavity include, among others, the opportunistic fungus Candida albicans and the key bacterial pathogen in periodontitis, Porphyromonas gingivalis. Both species use arsenals of virulence factors to invade the host organism and evade its immune system including peptidylarginine deiminase that citrullinates microbial and host proteins, altering their function. We assessed the effects of this modification on the interactions between the C. albicans cell surface and human plasminogen and kininogen, key components of plasma proteolytic cascades related to the maintenance of hemostasis and innate immunity. Mass spectrometry was used to identify protein citrullination, and microplate tests to quantify the binding of modified plasminogen and kininogen to C. albicans cells. Competitive radioreceptor assays tested the affinity of citrullinated kinins to their specific cellular receptors. The citrullination of surface-exposed fungal proteins reduced the level of unmodified plasminogen binding but did not affect unmodified kininogen binding. However, the modification of human proteins did not disrupt their adsorption to the unmodified fungal cells. In contrast, the citrullination of kinins exerted a significant impact on their interactions with cellular receptors reducing their affinity and thus affecting the role of kinin peptides in the development of inflammation.