Design,structural and functional characterization of a Temporin-1b analog active against Gram-negative bacteria

Background

Temporins are small antimicrobial peptides secreted by the Rana temporaria showing mainly activity against Gram-positive bacteria. However, different members of the temporin family, such as Temporin B, act in synergy also against Gram-negative bacteria. With the aim to develop a peptide with a wide spectrum of antimicrobial activity we designed and analyzed a series of Temporin B analogs.

Methods

Peptides were initially obtained by Ala scanning on Temporin B sequence; antimicrobial activity tests allowed to identify the TB_G6A sequence, which was further optimized by increasing the peptide positive charge (TB_KKG6A). Interactions of this active peptide with the LPS of E. coli were investigated by CD, fluorescence and NMR.

Results

TB_KKG6A is active against Gram-positive and Gram-negative bacteria at low concentrations. The peptide strongly interacts with the LPS of Gram-negative bacteria and folds upon interaction into a kinked helix.

Conclusion

Our results show that it is possible to widen the activity spectrum of an antimicrobial peptide by subtle changes of the primary structure. TB_KKG6A, having a simple composition, a broad spectrum of antimicrobial activity and a very low hemolytic activity, is a promising candidate for the design of novel antimicrobial peptides.

General significance

The activity of antimicrobial peptides is strongly related to the ability of the peptide to interact and break the bacterial membrane. Our studies on TB_KKG6A indicate that efficient interactions with LPS can be achieved when the peptide is not perfectly amphipathic, since this feature seems to help the toroidal pore formation process.     

Auranofin Is Highly Efficacious against Toxoplasma gondii In Vitro and in an In Vivo Experimental Model of Acute Toxoplasmosis

Background

The mainstay of toxoplasmosis treatment targets the folate biosynthetic pathways and has not changed for the last 50 years. The activity of these chemotherapeutic agents is restricted to one lifecycle stage of Toxoplasma gondii, they have significant toxicity, and the impending threat of emerging resistance to these agents makes the discovery of new therapies a priority. We now demonstrate that auranofin, an orally administered gold containing compound that was FDA approved for treatment of rheumatoid arthritis, has activity against Toxoplasma gondii in vitro (IC₅₀ = 0.28 µM) and in vivo (1 mg/kg).

Methods/Principal Findings

Replication within human foreskin fibroblasts of RH tachyzoites was inhibited by auranofin. At 0.4 µM, auranofin inhibited replication, as measured by percent infected fibroblasts at 24 hrs, (10.94% vs. 24.66% of controls; p = 0.0003) with no effect on parasite invasion (16.95% vs. 12.91% p = 0.4331). After 18 hrs, 62% of extracellular parasites treated with auranofin were non-viable compared to control using an ATP viability assay (p = 0.0003). In vivo, a previously standardized chicken embryo model of acute toxoplasmosis was used. Fourteen day old chicken embryos were injected through the chorioallantoic vein with 1×10⁴ tachyzoites of the virulent RH strain. The treatment group received one dose of auranofin at the time of inoculation (1 mg/kg estimated body weight). On day 5, auranofin-treated chicken embryos were 100% protected against death (p = 0.0002) and had a significantly reduced parasite load as determined by histopathology, immunohistochemistry and by the number of parasites quantified by real-time PCR.

Conclusions

These results reveal in vitro and in vivo activity of auranofin against T. gondii, suggesting that it may be an effective alternative treatment for toxoplasmosis.     

The next‐generation BET inhibitor,PLX51107, delays melanoma growth in a CD8‐mediated manner

Epigenetic agents such as bromodomain and extra‐terminal region inhibitors (BETi) slow tumor growth via tumor intrinsic alterations; however, their effects on antitumor immunity remain unclear. A recent advance is the development of next‐generation BETi that are potent and display a favorable half‐life. Here, we tested the BETi, PLX51107, for immune‐based effects on tumor growth in BRAF V600E melanoma syngeneic models. PLX51107 delayed melanoma tumor growth and increased activated, proliferating, and functional CD8+ T cells in tumors leading to CD8+ T‐cell‐mediated tumor growth delay. PLX51107 decreased Cox2 expression, increased dendritic cells, and lowered PD‐L1, FasL, and IDO‐1 expression in the tumor microenvironment. Importantly, PLX51107 delayed the growth of tumors that progressed on anti‐PD‐1 therapy; a response associated with decreased Cox2 levels, decreased PD‐L1 expression on non‐immune cells, and increased intratumoral CD8+ T cells. Thus, next‐generation BETi represent a potential first‐line and secondary treatment strategy for metastatic melanoma by eliciting effects, at least in part, on antitumor CD8+ T cells.     

Experimental antibacterial therapy with puroindolines,lactoferrin and lysozyme in Listeria monocytogenes-infected mice

Puroindoline A and puroindoline B from plant seeds, bovine lactoferrin and chicken eggs lysozyme are antimicrobial proteins of innate immune system that lyse invading organisms. We investigate their potential antibacterial activity against Listeria monocytogenes in a mouse model. Bacteria were isolated from various organs for 7 days after challenge. Livers displayed consistently higher bacterial count (up to 10⁷ cfu/g) than spleens, kidneys and brains. The efficacy of the AMPs was therefore established by measuring the infection level (cfu number) of these organs. Puroindoline A and puroindoline B (5 mg/mouse), lactoferrin and lysozyme (1.25 mg/mouse), intravenously injected individually, inhibited bacterial growth completely. Puroindoline A, puroindoline B and lactoferrin were effective when administered 24 h before infection; lysozyme was effective at the time of infection or 5 days after. Their combined use resulted in the enhancement of individual antibacterial activities. Complete inhibition of bacterial growth was observed using concurrently 0.059 mg/mouse of puroindoline A and 0.019 mg/mouse of puroindoline B, lactoferrin and lysozyme. Individual antimicrobial proteins reduced significantly the expression level of pro-inflammatory cytokines (IL-6, IL-8, INF-γ and TNF-α), acute phase proteins (C-reactive protein and fibrinogen) and the T lymphocyte antigens CD4, CD8a, CD8b and CD25. These results suggest their potential use for the control of L. monocytogenes infections.     

CDK inhibitors (p16/p19/p21) induce senescence and autophagy in cancer-associated fibroblasts, “fueling” tumor growth via paracrine interactions,without an increase in neo-angiogenesis

Here, we investigated the compartment-specific role of cell cycle arrest and senescence in breast cancer tumor growth. For this purpose, we generated a number of hTERT-immortalized senescent fibroblast cell lines overexpressing CDK inhibitors, such as p16(INK4A), p19(ARF) or p21(WAF1/CIP1). Interestingly, all these senescent fibroblast cell lines showed evidence of increased susceptibility toward the induction of autophagy (either at baseline or after starvation), as well as significant mitochondrial dysfunction. Most importantly, these senescent fibroblasts also dramatically promoted tumor growth (up to ~2-fold), without any comparable increases in tumor angiogenesis. Conversely, we generated human breast cancer cells (MDA-MB-231 cells) overexpressing CDK inhibitors, namely p16(INK4A) or p21(WAF1/CIP1). Senescent MDA-MB-231 cells also showed increased expression of markers of cell cycle arrest and autophagy, including β-galactosidase, as predicted. Senescent MDA-MB-231 cells had retarded tumor growth, with up to a near 2-fold reduction in tumor volume. Thus, the effects of CDK inhibitors are compartment-specific and are related to their metabolic effects, which results in the induction of autophagy and mitochondrial dysfunction. Finally, induction of cell cycle arrest with specific inhibitors (PD0332991) or cellular stressors [hydrogen peroxide (H₂O₂) or starvation] indicated that the onset of autophagy and senescence are inextricably linked biological processes. The compartment-specific induction of senescence (and hence autophagy) may be a new therapeutic target that could be exploited for the successful treatment of human breast cancer patients.     

A novel synthetic peptide from a tomato defensin exhibits antibacterial activities against Helicobacter pylori

Defensins are a class of cysteine‐rich proteins, which exert broad spectrum antimicrobial activity. In this work, we used a bioinformatic approach to identify putative defensins in the tomato genome. Fifteen proteins had a mature peptide that includes the well‐conserved tetradisulfide array. We selected a representative member of the tomato defensin family; we chemically synthesized its γ‐motif and tested its antimicrobial activity. Here, we demonstrate that the synthetic peptide exhibits potent antibacterial activity against Gram‐positive bacteria, such as Staphylococcus aureus A170, Staphylococcus epidermidis, and Listeria monocytogenes, and Gram‐negative bacteria, including Salmonella enterica serovar Paratyphi, Escherichia coli, and Helicobacter pylori. In addition, the synthetic peptide shows minimal (<5%) hemolytic activity and absence of cytotoxic effects against THP‐1 cells. Finally, SolyC exerts an anti‐inflammatory activity in vitro, as it downregulates the level of the proinflammatory cytokines TNF‐α and IFN‐γ. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Selection of bacteriophage-resistant mutants of Streptococcus thermophilus

Phage-resistant mutants have been isolated from Streptococcus thermophilus. Selection was carried out using anti-phage antibodies or Hoechst 33258-labelled phages. Two mutants out of eight tested displayed reduced acidifying capacity. Selection of the bacteria that extruded more rapidly the fluorochrome 5-6-carboxyfluorescein diacetate (CFDA) restored the acidifying capacity of these two mutants to the level of the parental strains. Mutants displaying phage resistance and good acidifying capacity were obtained in 4-5 days. New phages that are able to overcome the protection mechanisms of the existing bacteria arise continually in the dairy environment. The procedures described here permit to replace promptly the starter culture susceptible to newly emerged phages with a resistant one.     

Monoallelic expression of mouse <Emphasis Type="Italic">Cd4</Emphasis> gene

A 7-bp deletion in the Cd4 gene, present in the strain MOLF/Ei of Mus musculus molossinus and absent in laboratory mouse strains (Mus musculus musculus), provided the means to distinguish the parental origin of the Cd4 alleles expressed in single cells of F₁ (AKR × MOLF/Ei) and F₁ (Balb/C × MOLF/Ei) hybrids. Single-cell RT-PCR showed that the individual CD4⁺ lymphocyte expresses either the maternal or the paternal Cd4 allele, never both. In situ hybridization proved that Cd4 alleles replicate asynchronously, as expected in the case of genes expressed monoallelically.     

A multicenter,randomized, placebo controlled,multiple-dose,safety and pharmacokinetic study of AIT-082 (Neotrofin) in mild Alzheimer's disease patients

A phase 1, randomized, double-blind, placebo-controlled, dose escalation study of the purine derivative, AIT-082 (Neotrofin, NeoTherapeutics) was conducted in mild Alzheimer's disease (AD) patients to evaluate multiple-dose safety, tolerability, and pharmacokinetics. Possible short-term effects of AIT-082 on cognition and memory were preliminarily investigated. AIT-082 is currently being developed as a potential treatment for Alzheimer's disease and other neurological disorders. Pre-clinical studies indicate that AIT-082 has memory enhancing properties, stimulates neuritogenesis and the production of neurotrophic factors. Patients received an oral dose of AIT-082 or placebo daily for one week. Thirty-six AD patients were divided into three dose cohorts; each dose cohort consisted of twelve patients with 8 patients randomized to AIT-082 and 4 to placebo. The 3 doses of AIT-082 evaluated in this study were 100 mg/day, 500 mg/day, and 2,000 mg/day. There were no serious adverse events at any dose and the drug was well tolerated without significant side effects. AIT-082 was orally and rapidly absorbed, resulting in peak serum concentrations within 2 hours with an elimination half-life of approximately 20 hours. Higher doses resulted in corresponding increases in peak concentrations and areas under the curve (AUC). There was an approximate 2-fold accumulation in AIT-082 with daily dosing (as reflected by the AUC) at steady state. There were no significant differences by treatment arm on the clinical or neuropsychological evaluations. AIT-082 was rapidly absorbed by the oral route with a half-life suitable for dosing once or twice daily. No problems with tolerability or safety were found. AIT-082 appears suitable for testing in larger clinical trials for the treatment of AD and other neurologic disorders.     

Acidic fibroblast growth factor inhibits osteoblast differentiation in vitro: Altered expression of collagenase,cell growth-related,and mineralization-associated genes

Fibroblast growth factors (FGF) are osteoblast mitogens, but their effects on bone formation are not clearly understood. Most in vitro studies examining the effects of FGFs on osteoblasts have been performed only during the initial proliferative stage of osteoblast culture. In these studies, we examined the consequential effect of acidic FGF in cultures of rat fetal diploid osteoblasts that undergo a developmental differentiation program producing a mineralized bone-like matrix. During the initial growth period (days 1–10), addition of acidic FGF (100 μg/ml) to actively proliferating cells increased (P < 0.05) ³H-thymidine uptake (2,515 ± 137, mean ± SEM vs. 5,884 ± 818 cpm/10⁴ cells). During the second stage of maturation (days 10–15), osteoblasts form multilayered nodules of cells and accumulate matrix, followed by mineralization (stage 3, days 16–29). Addition of acidic FGF to the osteoblast cultures from days 7 to 15 completely blocked nodule formation. Furthermore, addition of acidic FGF after nodule formation (days 14–29) inhibited matrix mineralization, which was associated with a marked increase in collagenase gene expression, and resulted in a progressive change in the morphology of the nodules, with only a few remnants of nonmineralized nodules present by day 29. Histochemical and biochemical analyses revealed a decrease in alkaline phosphatase and mineral content, confirming the acidic FGF-induced inhibition of nodule and matrix formation. To identify mechanisms contributing to these changes, we examined expression of cell growth and bone phenotypic markers. Addition of acidic FGF during the proliferative phase (days 7–8) enhanced histone H4, osteopontin, type 1 collagen, and TGF-β mRNA levels, which are coupled to proliferating osteoblasts, and blocked the normal developmental increase in alkaline phosphatase and osteocalcin gene expression and calcium accumulation. Addition of acidic FGF to the cultures during matrix maturation (days 14–15) reactivated H4, osteopontin, type I collagen, and TGF-β gene expression, and decreased alkaline phosphatase and osteocalcin gene expression. In an in vivo experiment, rats were treated with up to 60 μg/kg/day acidic FGF intravenously for 30 days. Proliferation of osteoblasts and deposition of bone occurred in the marrow space of the diaphysis of the femur in a dose-related fashion. The metaphyseal areas were unaffected by treatment. In conclusion, our data suggest that acidic FGF is a potent mitogen for early stage osteoblasts which leads to modifications in the formation of the extracellular matrix; increases in TGF-β and collagenase are functionally implicated in abrogating competency for nodule formation. Persistence of proliferation prevented expression of alkaline phosphatase and osteocalcin, also contributing to the block in the progression of the osteoblast developmental sequence. © 1996 Wiley-Liss, Inc.