Isogenic strain construction and gene mapping in Candida albicans.

Lipid nanoparticles (SLN, NLC) in cosmetic and pharmaceutical dermal products.

LL-37, the only human member of the cathelicidin family of antimicrobial peptides.

Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. AMPs are gene-encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially, which exhibit broad spectrum antimicrobial activity. AMPs have been the subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important breakthrough and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and the additional functions of AMPs.

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Antimicrobial peptides: key components of the innate immune system

Antimicrobial peptides, which have been isolated from many bacteria, fungi, plants, invertebrates and vertebrates, are an important component of the natural defenses of most living organisms. The isolated peptides are very heterogeneous in length, sequence and structure, but most of them are small, cationic and amphipathic. These peptides exhibit broad-spectrum activity against Gram-positive and Gram-negative bacteria, yeasts, fungi and enveloped viruses. A wide variety of human proteins and peptides also have antimicrobial activity and play important roles in innate immunity. In this review we discuss three important groups of human antimicrobial peptides. The defensins are cationic non-glycosylated peptides containing six cysteine residues that form three intramolecular disulfide bridges, resulting in a triple-stranded beta-sheet structure. In humans, two classes of defensins can be found: alpha-defensins and beta-defensins. The defensin-related HE2 isoforms will also be discussed. The second group is the family of histatins, which are small, cationic, histidine-rich peptides present in human saliva. Histatins adopt a random coil conformation in aqueous solvents and form alpha-helices in non-aqueous solvents. The third group comprises only one antimicrobial peptide, the cathelicidin LL-37. This peptide is derived proteolytically from the C-terminal end of the human CAP18 protein. Just like the histatins, it adopts a largely random coil conformation in a hydrophilic environment, and forms an alpha-helical structure in a hydrophobic environment.

Human antimicrobial peptides: defensins, cathelicidins and histatins.

Cytotoxicity of submicron emulsions and solid lipid nanoparticles for dermal application

The yeast transcriptional response to murine Bax expression was compared with the changes induced by H2O2 treatment via microarray technology Although most of the Bax-responsive genes were also triggered by H2O2 treatment, OYE3, ICY2, MLS1 and BTN2 were validated to have a Bax-specific transcriptional response not shared with the oxidative stress trigger In knockout experiments, only deletion of OYE3, coding for yeast Old yellow enzyme, attenuated the rate of Bax-induced growth arrest, cell death and NADPH decrease Lipid peroxidation was completely absent in ΔOYE3 expressing Bax However, the absence of OYE3 sensitized yeast cells to H2O2-induced cell death, and increased the rate of NADPH decrease and lipid peroxidation Our results clearly indicate that OYE3 interferes with Bax- and H2O2-induced lipid peroxidation and cell death in Saccharomyces cerevisiae

Old yellow enzyme interferes with Bax-induced NADPH loss and lipid peroxidation in yeast.

In past decades the gold standard for topical burn treatment was the use of silver sulfadiazine. Due to toxicity caused by the silver, the cream base itself, or a combination of both negatively influencing the wound healing process, the healthcare industry searched for alternatives. In recent years, various dressings containing silver have become available to wound professionals. Although these have been reported to be a significant improvement, the dressings still show residual cytotoxicity. Given the ongoing debate about whether and how these dressings influence cell survival, this article endeavours to clarify some of the mystique surrounding the subject. Various commercially available silver-type dressings were analysed in vitro and attention was paid to the cell death stage induced by these dressings on different cell lines. The results show that within 2 hours, for all dressings tested, cells undergo cell death and further analysis suggests that the death stage induced is dependent on the cell line and type of dressing investigated. Further, the antimicrobial activity of all dressings was analysed. The silver dressings tested have potent antimicrobial activity. Our results showed, however, that silver dressings induce rapid cell death of cells involved in wound healing. We therefore recommend the use of silver dressings only on critically contaminated wounds rather than use on a de facto basis.

Differential cell death programmes induced by silver dressings in vitro

Bax is a pro-apoptotic member of the Bcl-2 family of proteins involved in the regulation of genetically programmed cell death in mammalian cells. It has been shown that heterologous expression of Bax in several yeast species, such as Saccharomyces cerevisiae, Schizosaccharomyces pombe and Pichia pastoris, also induces cell death. In this study we investigated the effects of Bax expression in the pathogenic yeast Candida albicans. Cell death inducing expression of Bax required a synthetic BAX gene that was codon-optimized for expression in Candida albicans. Expression of this BAX gene resulted in growth inhibition and cell death. By fusing Bax with the yeast enhanced green fluorescent protein of Aequoria victoria, the cell death-inducing effect of Bax was increased due to reduced proteolytic degradation of Bax. Using this fusion protein we showed that, upon expression in C. albicans, Bax co-localizes with the mitochondria. Furthermore, we showed for the first time that expression of Bax in yeast causes the mitochondria, which are normally distributed throughout the cell, to cluster in the perinuclear region.

Kris De Smet

Papers

Human antimicrobial peptides: defensins, cathelicidins and histatins.

Cytotoxicity of submicron emulsions and solid lipid nanoparticles for dermal application

Old yellow enzyme interferes with Bax-induced NADPH loss and lipid peroxidation in yeast.

Differential cell death programmes induced by silver dressings in vitro

Bax-induced cell death in Candida albicans.