Characterization of the in vitro, ex vivo, and in vivo Efficacy of the Antimicrobial Peptide DPK-060 Used for Topical Treatment.

Antimicrobial peptides, also known as host defense peptides, have recently emerged as a promising new category of therapeutic agents for the treatment of infectious diseases. This study evaluated the preclinical in vitro, ex vivo, and in vivo antimicrobial activity, as well as the potential to cause skin irritation, of human kininogen-derived antimicrobial peptide DPK-060 in different formulations designed for topical delivery. We found that DPK-060 formulated in acetate buffer or poloxamer gel caused a marked reduction of bacterial counts of Staphylococcus aureus in vitro (minimum microbicidal concentration <5 µg/ml). We also found that DPK-060 in poloxamer gel significantly suppressed microbial survival in an ex vivo wound infection model using pig skin and in an in vivo mouse model of surgical site infection (≥99 or ≥94% reduction in bacterial counts was achieved with 1% DPK-060 at 4 h post-treatment, respectively). Encapsulation of DPK-060 in different types of lipid nanocapsules or cubosomes did not improve the bactericidal potential of the peptide under the applied test conditions. No reduction in cell viability was observed in response to administration of DPK-060 in any of the formulations tested. In conclusion, the present study confirms that DPK-060 has the potential to be an effective and safe drug candidate for the topical treatment of microbial infections; however, adsorption of the peptide to nanocarriers failed to show any additional benefits.

The novel antimicrobial peptide PXL150 in the local treatment of skin and soft tissue infections.

Dramatic increase in bacterial resistance towards conventional antibiotics emphasises the importance to identify novel, more potent antimicrobial therapies. Antimicrobial peptides (AMPs) have emerged as a promising new group to be evaluated in therapeutic intervention of infectious diseases. Here we describe a novel AMP, PXL150, which demonstrates in vitro a broad spectrum microbicidal action against both Gram-positive and Gram-negative bacteria, including resistant strains. The potent microbicidal activity and broad antibacterial spectrum of PXL150 were not associated with any hemolytic activity. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance towards PXL150 during continued selection pressure. PXL150 caused a rapid depolarisation of cytoplasmic membrane of S. aureus, and dissipating membrane potential is likely one mechanism for PXL150 to kill its target bacteria. Studies in human cell lines indicated that PXL150 has anti-inflammatory properties, which might be of additional benefit. PXL150 demonstrated pronounced anti-infectious effect in an in vivo model of full thickness wounds infected with MRSA in rats and in an ex vivo model of pig skin infected with S. aureus. Subcutaneous or topical application of the peptide in rats did not lead to any adverse reactions. In conclusion, PXL150 may constitute a new therapeutic alternative for local treatment of infections, and further studies are warranted to evaluate the applicability of this AMP in clinical settings.

House dust mite allergen activates human eosinophils via formyl peptide receptor and formyl peptide receptor-like 1.

The objective was to evaluate which receptors house dust mite (HDM) and birch pollen extracts engage to activate human eosinophils. Chemotaxis and degranulation were studied in eosinophils pretreated with pertussis toxin and other antagonists of G protein-coupled receptors, e.g. the formyl peptide receptor (FPR), CC chemokine receptor 3 (CCR3) and leukotriene receptor B4 (LTB(4)R). Inhibition of the FPR as well as desensitization of the receptor rendered eosinophils anergic to activation by the allergens. Blockade of CCR3 or LTB(4)R did not affect eosinophilic reactivity. It was determined by PCR that human eosinophils express the FPR family members FPR and FPR-like 1 (FPRL1). HDM, unlike birch pollen, evoked calcium fluxes in HL-60 cells transfected with FPR or FPRL1. Although both allergens gave rise to calcium transients in neutrophils, which also express FPR and FPRL1, only the HDM response was decreased by the FPR antagonist. Moreover, neutrophils migrated toward HDM but not to birch pollen. Eosinophils pretreated with inhibitors of MAPK p38, ERK1/2 or protein kinase C exhibited diminished responsiveness to the aeroallergens. This study indicates that FPR and FPRL1 mediate the activation of eosinophils by HDM, whereas birch pollen employs other pathways shared with FPR to activate human eosinophils.