ABSTRACT
Owing to their excellent antimicrobial activities with a relatively low cost of production, lipopeptides are being intensively investigated as potential alternatives to popular antimicrobials. However, a critical obstacle for their application is a relatively high toxicity, hence a lot of attention has been paid to designing new molecules with optimal properties. In this study we synthesized the following lipopeptides: C16-KK-NH2, C16-KεK-NH2, C16-KKK-NH2, C16-KRK-NH2, C16-RR-NH2, C16-RRR-NH2, (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2. Their antimicrobial activity against representative strains of Gram-positive bacteria, Gram-negative bacteria and fungi has been confirmed. The compounds have been evaluated with regard to the safety of their application in dermatology. The cytotoxicity was determined in HaCaT keratinocytes using MTT assay, whereas Strat M membranes placed in Franz diffusion cells were used to assess their ability to skin permeation. The compounds containing one hexadecanoic acid chain turned out to be very toxic towards human keratinocytes, while lipopeptides containing two fatty acid chains (decanoic and dodecanoic) demonstrated much lower cytotoxicity. For the most promising lipopeptide, (C10)2-KKKK-NH2, the measured IC50 on HaCaT keratinocytes was few times higher as compared to MICs obtained for the tested bacteria. Both groups of lipopeptides did not permeate the model membranes and therefore lack of permeation through human skin could be expected. The results of this work encourage further research on the potential application of lipopeptides with two fatty acids as novel antimicrobials.
Subject(s)
Anti-Bacterial Agents/chemistry , Antifungal Agents/chemistry , Arginine/analogs & derivatives , Arginine/chemistry , Lipopeptides/chemistry , Lysine/analogs & derivatives , Lysine/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/toxicity , Antifungal Agents/pharmacology , Antifungal Agents/toxicity , Arginine/pharmacology , Arginine/toxicity , Cell Line , Cell Survival/drug effects , Drug Design , Fungi/drug effects , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Humans , Keratinocytes/cytology , Keratinocytes/drug effects , Lipopeptides/pharmacology , Lipopeptides/toxicity , Lysine/pharmacology , Lysine/toxicity , Permeability , Structure-Activity RelationshipABSTRACT
The human body expresses over 100 host defense peptides and proteins (antimicrobial peptides, AMPs). The compounds are produced by tissues and mucosal surfaces, e.g. skin, the digestive and urinary tract, the ocular surface and neutrophils, and are believed to play a crucial role in defense from microbial infection. They are considered to protect the human body against microbial infections due to their antimicrobial and immunomodulatory activities. As well as having strong antimicrobial activity towards a broad spectrum of microorganisms, AMPs have been found to interact with neutrophils, monocytes and T-cells and promote the production of cytokines. They also neutralize the action of lipopolysaccharide (LPS) and play a crucial role in wound healing processes. In response to the microbial stimuli the AMPs are released in order to fight the infection, however there are several microorganisms evading the human immune system by downregulation of AMPs. Decreased or elevated expression of AMPs is associated also with several non-infectious diseases. Despite numerous studies conducted in the field of AMPs over the last few decades, their exact role in physiological and pathological processes remains to be explained. In this paper, we review the most significant human AMPs and their potential roles in maintaining human homeostasis as well as in pathological processes.
