The synthetic antimicrobial peptide LTX21 induces inflammatory responses in a human whole blood model and a murine peritoneum model.

The global spread of antimicrobial resistance and the increasing number of immune-compromised patients are major challenges in modern medicine. Targeting bacterial virulence or the human host immune system to increase host defence are important strategies in the search for novel antimicrobial drugs. We investigated the inflammatory response of the synthetic short antimicrobial peptide LTX21 in two model systems: a human whole blood ex vivo model and a murine in vivo peritoneum model - both reflecting early innate immune response. In the whole blood model, LTX21 increased the secretion of a range of different cytokines, decreased the level of tumour necrosis factor (TNF) and activated the complement system. In a haemolysis assay, we found 2.5% haemolysis at a LTX21 concentration of 500 mg/L. In the murine model, increased influx of white blood cells (WBCs) and polymorphonuclear neutrophils (PMNs) in the murine peritoneal cavity was observed after treatment with LTX21. In addition, LTX21 increased monocyte chemoattractant protein-1 (MCP-1). In conclusion, LTX21 affected the inflammatory response; the increase in cytokine secretion, complement activation and WBC influx indicates an activated inflammatory response. The present results indicate the impact of LTX21 on the host-pathogen interplay. Whether this will also affect the course of infection has to be investigated.

Ultrapure Wood Nanocellulose-Assessments of Coagulation and Initial Inflammation Potential.

Using a lepirudin-based human whole blood model, we evaluated the initial inflammatory and coagulation responses of dense and porous ultrapure (<50 endotoxin units/grams) cellulose nanofibrils (CNF), of carboxylated grade. The CNF was compared to the wound dressing AquaCel because it is a potential wound-healing material. The porous CNF aerogels induced the strongest coagulation potential measured as prothrombin factor 1.2 (PTF1.2). AquaCel induced the strongest complement response by terminal complement complex (TCC) and surface C3c. All materials activated leukocytes CD11b, while the levels of only 3 of 27 cytokines were significantly changed, limited to (i) an elevation of the monocyte chemoattractant protein-1 (MCP-1/CCL) by the CNF aerogel, (ii) a reduction of eosinophil chemotactic proteins (eotaxin/CCL11) by the CNF aerogel, and (iii) a reduction of platelet-derived growth factor BB (PDGF-BB) by all CNF materials. In conclusion, the CNF materials and AquaCel differently activate coagulation, complement, and cytokines, improving the selection possibilities in various treatment situations of wound healing.

Loxosceles venom Sphingomyelinase D activates human blood leukocytes: Role of the complement system.

Envenomation by Loxosceles spiders can result in severe systemic and local reactions, which are mainly triggered by Sphingomyelinase D (SMase D), a toxic component of Loxosceles venom. SMase D induces a systemic inflammatory condition similar to the reaction observed during an endotoxic shock. Considering the potent pro-inflammatory potential of Loxosceles venom and the SMase D, in this study we have used the whole human blood model to study the endotoxic-like shock triggered by SMase D. Recombinant purified SMase D from L. intermedia venom, similarly to LPS, induced activation of blood leukocytes, as observed by the increase in the expression of CD11b and TLR4, production of reactive oxygen and nitrogen species (superoxide anion and peroxynitrite) and release of TNF-α. Complement consumption in the plasma was also detected, and complement inhibition by compstatin decreased the SMase D and LPS-induced leukocyte activation, as demonstrated by a reduction in the expression of CD11b and TLR4 and superoxide anion production. Similar results were found for the L. intermedia venom, except for the production of TNF-α. These findings indicate that SMase D present in Loxosceles venom is able to activate leukocytes in a partially complement-dependent manner, which can contribute to the systemic inflammation that follows envenomation by this spider. Thus, future therapeutic management of systemic Loxosceles envenomation could include the use of complement inhibitors as adjunct therapy.