Anti-infectious and anti-inflammatory effects of peptide fragments sequentially derived from the antimicrobial peptide centrocin 1 isolated from the green sea urchin, Strongylocentrotus droebachiensis

Bacterial resistance against antibiotic treatment has become a major threat to public health. Antimicrobial peptides (AMPs) have emerged as promising alternative agents for treatment of infectious diseases. This study characterizes novel synthetic peptides sequentially derived from the AMP centrocin 1, isolated from the green sea urchin, for their applicability as anti-infective agents.The microbicidal effect of centrocin 1 heavy chain (CEN1 HC-Br), its debrominated analogue (CEN1 HC), the C-terminal truncated variants of both peptides, i.e. CEN1 HC-Br (1--20) and CEN1 HC (1--20), as well as the cysteine to serine substituted equivalent CEN1 HC (Ser) was evaluated using minimal microbicidal concentration assay. The anti-inflammatory properties were assessed by measuring the inhibition of secretion of pro-inflammatory cytokines. All the peptides tested exhibited marked microbicidal and anti-inflammatory properties. No difference in efficacy was seen comparing CEN1 HC-Br and CEN1 HC, while the brominated variant had higher cytotoxicity. C-terminal truncation of both peptides reduced salt-tolerability of the microbicidal effect as well as anti-inflammatory actions. Also, serine substitution of cysteine residue decreased the microbicidal effect. Thus, from the peptide variants tested, CEN1 HC showed the best efficacy and safety profile. Further, CEN1 HC significantly reduced bacterial counts in two different animal models of infected wounds, while Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance against this peptide under continued selection pressure. In summary, CEN1 HC appears a promising new antimicrobial agent, and clinical studies are warranted to evaluate the applicability of this AMP for local treatment of infections in man

Opposite transcriptional regulation in skeletal muscle of AMP-activated protein kinase gamma3 R225Q transgenic versus knock-out mice

AMP-activated protein kinase (AMPK) is an evolutionarily conserved heterotrimer important for metabolic sensing in all eukaryotes. The muscle-specific isoform of the regulatory gamma-subunit of the kinase, AMPK gamma3, has an important role in glucose uptake, glycogen synthesis, and fat oxidation in white skeletal muscle, as previously demonstrated by physiological characterization of AMPK gamma3 mutant (R225Q) transgenic (TgPrkag3(225Q)) and gamma3 knock-out (Prkag3(-/-)) mice. We determined AMPK gamma3-dependent regulation of gene expression by analyzing global transcription profiles in glycolytic skeletal muscle from gamma3 mutant transgenic and knock-out mice using oligonucleotide microarray technology. Evidence is provided for coordinated and reciprocal regulation of multiple key components in glucose and fat metabolism, as well as skeletal muscle ergogenics in TgPrkag3(225Q) and Prkag3(-/-) mice. The differential gene expression profile was consistent with the physiological differences between the models, providing a molecular mechanism for the observed phenotype. The striking pattern of opposing transcriptional changes between TgPrkag3(225Q) and Prkag3(-/-) mice identifies differentially expressed targets being truly regulated by AMPK and is consistent with the view that R225Q is an activating mutation, in terms of its downstream effects. Additionally, we identified a wide array of novel targets and regulatory pathways for AMPK in skeletal muscle

Antimicrobial peptides : An emerging category of therapeutic agents

Antimicrobial peptides (AMPs), also known as host defense peptides, are short and generally positively charged peptides found in a wide variety of life forms from microorganisms to humans. Most AMPs have the ability to kill microbial pathogens directly, whereas others act indirectly by modulating the host defense systems. Against a background of rapidly increasing resistance development to conventional antibiotics all over the world, efforts to bring AMPs into clinical use are accelerating. Several AMPs are currently being evaluated in clinical trials as novel anti-infectives, but also as new pharmacological agents to modulate the immune response, promote wound healing, and prevent post-surgical adhesions. In this review, we provide an overview of the biological role, classification, and mode of action of AMPs, discuss the opportunities and challenges to develop these peptides for clinical applications, and review the innovative formulation strategies for application of AMPs.Published 27 December</p

PXL01 in sodium hyaluronate results in increased PRG4 expression: a potential mechanism for anti-adhesion

Purpose: To investigate the anti-adhesive mechanisms of PXL01 in sodium hyaluronate (HA) by using the rabbit lactoferrin peptide, rabPXL01 in HA, in a rabbit model of healing tendons and tendon sheaths. The mechanism of action for PXL01 in HA is interesting since a recent clinical study of the human lactoferrin peptide PXL01 in HA administered around repaired tendons in the hand showed improved digit mobility. Materials and methods: On days 1, 3, and 6 after tendon injury and surgical repair, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to assess mRNA expression levels for genes encoding the mucinous glycoprotein PRG4 (also called lubricin) and a subset of matrix proteins, cytokines, and growth factors involved in flexor tendon repair. RabPXL01 in HA was administered locally around the repaired tendons, and mRNA expression was compared with untreated repaired tendons and tendon sheaths. Results: We observed, at all time points, increased expression of PRG4 mRNA in tendons treated with rabPXL01 in HA, but not in tendon sheaths. In addition, treatment with rabPXL01 in HA led to repression of the mRNA levels for the pro-inflammatory mediators interleukin (IL)-1β, IL-6, and IL-8 in tendon sheaths. Conclusions: RabPXL01 in HA increased lubricin mRNA production while diminishing mRNA levels of inflammatory mediators, which in turn reduced the gliding resistance and inhibited the adhesion formation after flexor tendon repair

Regulation of metabolism and inflammation in liver and skeletal muscle

Type 2 diabetes (T2D) is a complex metabolic disorder characterised by hyperinsulinaemia, hyperglycaemia and dyslipidaemia. Obesity is the major risk factor for development of insulin resistance, a main predictor of T2D. Recent evidence indicates that nutrient excess and obesity lead to chronic low-grade inflammation in metabolic tissues, which further promotes insulin resistance. AMP-activated protein kinase (AMPK), a central regulator of energy homeostasis, increases insulin sensitivity in liver and skeletal muscle and lowers the plasma glucose level, thus reverting the major metabolic disturbances in T2D. Serine/threonine protein kinase 25 (STK25) was found to be differentially expressed in skeletal muscle, comparing AMPKγ3 (Prkag3-/-) knockout mice to wild-type littermates, indicating a potential role for STK25 in regulation of energy homeostasis in skeletal muscle. In Paper I, genes regulating the circadian rhythm (Cry2, Nr1d1 and Bhlhb2) were shown to be differentially expressed in skeletal muscle from wild-type mice treated with the AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), while they remained unaltered in AMPKγ3 knockout mice. Furthermore, the respiratory exchange ratio (RER) was elevated during the dark period of observation in wild-type mice reflecting a diurnal shift in substrate utilisation from lipid oxidation at daytime to carbohydrate utilisation during nighttime. However, no day/night shift in the RER profile was observed in Prkag3-/- littermates. Thus, this study suggests that APMK, as a central energy sensor, could be one important node linking energy metabolism to the circadian clock function. In Papers II and III, the AMPK agonists, AICAR and metformin, are shown to markedly decrease the expression of IL-6-induced serum amyloid A (SAA) cluster genes, haptoglobin and suppressor of cytokine signalling 3 (SOCS3) in the human hepatocyte cell line HepG2. By repressing AMPK activity with small interfering (si)RNA the inhibitory effect of AMPK on SAA expression by both AICAR and metformin was reversed (Paper II), indicating that the effect of the agonists is mediated by AMPK activation. Further, we show that AMPK interferes with IL-6 signalling by decreasing IL-6-induced phosphorylation of Janus kinase 1 (JAK1), src homology 2 domain containing protein tyrosine phosphatase 2 (SHP2) and signal transducer and activator of transcription 3 (STAT3) in HepG2 cells (Papers II and III). In addition, pharmacological activation of AMPK was shown to repress IL-6-induced inflammation in vivo by suppression of STAT3 activity in mouse liver (Paper III). This suggests that AMPK is an important intracellular link between metabolic and inflammatory pathways in liver. In Paper IV we show that partial reduction of STK25 by siRNA increases uncoupling protein 3 (UCP3), glucose transporter 1 (GLUT1), GLUT4 and hexokinase 2 (HK2) in the rodent myoblast cell line L6, both at mRNA and protein level. Correspondingly, the rates of palmitate oxidation and insulin-stimulated glucose uptake were elevated after partial depletion of STK25. In conclusion, our studies suggest a role of STK25 as a negative regulator of glucose and lipid metabolism in skeletal muscle. Impaired glucose uptake and fatty acid metabolism by skeletal muscle is a hallmark of insulin resistance, and therefore, STK25 could be an important new mediator to be evaluated for therapeutic intervention in T2D and related complications