Indole-3-Acetamido-Polyamines as Antimicrobial Agents and Antibiotic Adjuvants.

The widespread incidence of antimicrobial resistance necessitates the discovery of new classes of antimicrobials as well as adjuvant molecules that can restore the action of ineffective antibiotics. Herein, we report the synthesis of a new class of indole-3-acetamido-polyamine conjugates that were evaluated for antimicrobial activities against a panel of bacteria and two fungi, and for the ability to enhance the action of doxycycline against Pseudomonas aeruginosa and erythromycin against Escherichia coli. Compounds 14b, 15b, 17c, 18a, 18b, 18d, 19b, 19e, 20c and 20d exhibited strong growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans, with minimum inhibitory concentrations (MIC) typically less than 0.2 µM. Four analogues, including a 5-bromo 15c and three 5-methoxyls 16d-f, also exhibited intrinsic activity towards E. coli. Antibiotic kill curve analysis of 15c identified it to be a bactericide. While only one derivative was found to (weakly) enhance the action of erythromycin against E. coli, three examples, including 15c, were found to be strong enhancers of the antibiotic action of doxycycline against P. aeruginosa. Collectively, these results highlight the promising potential of α,ω-disubstituted indole-3-acetamido polyamine conjugates as antimicrobials and antibiotic adjuvants.

Acacia senegal Budmunchiamines as a Potential Adjuvant for Rejuvenating Phenicol Activities towards Escherichia coli-Resistant Strains.

The continuous emergence of bacterial resistance alters the activities of different antibiotic families and requires appropriate strategies to solve therapeutic impasses. Medicinal plants are an attractive source for researching alternative and original therapeutic molecules. In this study, the fractionation of natural extracts from A. senegal and the determination of antibacterial activities are associated with molecular networking and tandem mass spectrometry (MS/MS) data used to characterize active molecule(s). The activities of the combinations, which included various fractions plus an antibiotic, were investigated using the "chessboard" test. Bio-guided fractionation allowed the authors to obtain individually active or synergistic fractions with chloramphenicol activity. An LC-MS/MS analysis of the fraction of interest and molecular array reorganization showed that most identified compounds are Budmunchiamines (macrocyclic alkaloids). This study describes an interesting source of bioactive secondary metabolites structurally related to Budmunchiamines that are able to rejuvenate a significant chloramphenicol activity in strains that produce an AcrB efflux pump. They will pave the way for researching new active molecules for restoring the activity of antibiotics that are substrates of efflux pumps in enterobacterial-resistant strains.

New Polyaminoisoprenyl Antibiotics Enhancers against Two Multidrug-Resistant Gram-Negative Bacteria from Enterobacter and Salmonella Species.

A series consisting of new polyaminoisoprenyl derivatives were prepared in moderate to good chemical yields varying from 32 to 64% according to two synthetic pathways: (1) using a titanium-reductive amination reaction affording a 50/50 mixture of cis and trans isomers and (2) a direct nucleophilic substitution leading to a stereoselective synthesis of the compounds of interest. These compounds were then successfully evaluated for their in vitro antibiotic enhancer properties against resistant Gram-negative bacteria of four antibiotics belonging to four different families. The mechanism of action against Enterobacter aerogenes of one of the most efficient of these chemosensitizing agents was precisely evaluated by using fluorescent dyes to measure outer-membrane permeability and to determine membrane depolarization. The weak cytotoxicity encountered led us to perform an in vivo experiment dealing with the treatment of mice infected with Salmonella typhimurium and affording preliminary promising results in terms of tolerance and efficiency of the polyaminoisoprenyl derivative 5r/doxycycline combination.

Characterization of a new aerosol antibiotic/adjuvant combination for the treatment of P. aeruginosa lung infections.

The lack of novel classes of antibiotics as well as the constant increase of multidrug resistant bacteria are leaving the clinicians disarmed to treat bacterial infections, especially those caused by Gram-negative pathogens. Among all the investigated solutions, the design of adjuvants able to enhance antibiotics activities appears to be one of the most promising. In this context, a polyamino-isoprenyl derivative has been recently identified to be able to potentiate, at a very low concentration the activity of doxycycline against P. aeruginosa bacterial strains by increasing its intracellular concentration. On the other hand, since aerosol therapy allows a rapid drug administration and targets the respiratory system by avoiding the first pass effect and minimizing undesirable systemic effects, we have developed the first adjuvant/antibiotic combination in an aerosolized form and demonstrated the feasibility of such an approach. Thus, combination aerosol droplets have been demonstrated in sizes suitable for inhalation (3.4 and 4.4 µm mass median aerodynamic diameter and 54 and 60% of the aerodynamic particle size distribution less than 5 µm, as measured for the adjuvant NV716 and doxycycline, respectively and with properties (stoichiometric 1:1 ratio of NV716 salt to drug) that would support further development as an inhaled dosage form. Taken together, our results suggest that these molecules could be successfully delivered at the requested concentration in the lungs and then able to decrease drug consumption as well as increase treatment efficacy.

Three-component synthesis of chromeno ß-lactam hybrids for inflammation and cancer screening.

Highly diastereoselective synthesis of chromeno ß-lactam hybrids was achieved by an efficient one-pot three-component reaction. With this procedure, the desired ß-lactam products were obtained in good yields and with exclusive cis stereoselection, by combining a variety of benzaldehydes, malononitrile, and either 5,5-dimethylcyclohexane-1,3-dione or 4-hydroxycoumarin in the presence of 1,4-diazabicyclo [2.2.2]octane under reflux conditions. These adducts were structurally characterized on the basis of IR, 1D and 2D NMR spectra, X-ray analysis, H-H COSY and H-C HSQC two-dimensional NMR experiments, and elemental analysis. Each of the synthesized compounds was screened for anti-inflammatory and anticancer activities. ß-Lactams 5b and 8b showed a 53.4 and 19.8 anti-inflammatory ratio, respectively, and 5b appeared more active than the well-known dexamethasone corticosteroid used for the treatment of rheumatoid and skin inflammation. ß-Lactams 5a, 5b, 5e, 5f, 5g, 8c, 8j and 8p also showed good antitumor activity against the SW1116 (colon cancer) cell line without notable cytotoxicity towards the HepG2 control cell line.

LMO4 is required to maintain hypothalamic insulin signaling.

Insulin action at the hypothalamus controls glucose homeostasis by suppressing hepatic glucose production and promoting glucose uptake by muscle. However, the mechanisms that control central insulin signaling have not been fully elucidated. Previously, we showed that LMO4 is highly expressed in hypothalamic nuclei that regulate glucose homeostasis. Here, we determined how loss of LMO4 in the hypothalamus would affect central insulin signaling and glucose homeostasis. In transgenic mice that have LMO4 in ablated in glutamatergic neurons, we found that insulin signaling is impaired in the hypothalamus as well as in peripheral tissues (liver and skeletal muscle). Impaired glucose homeostasis was associated with a markedly elevation in hypothalamic protein tyrosine phosphatase 1B (PTP1B) activity. PTP1B is a key phosphatase that terminates insulin signaling by dephosphorylating its receptor and downstream signaling molecules. Importantly, we found that administration of a selective PTP1B inhibitor Trodusquemine to the hypothalamus restored central insulin signaling and improved the response of peripheral tissues to insulin in these LMO4-deficient mice. Thus, our study reveals an essential requirement for LMO4 to modulate central insulin signaling.

The LIM domain only 4 protein is a metabolic responsive inhibitor of protein tyrosine phosphatase 1B that controls hypothalamic leptin signaling.

Protein tyrosine phosphatase 1B (PTP1B) counteracts leptin signaling and is a therapeutic target for obesity and diabetes. Here we found that LIM domain only 4 (LMO4) inhibits PTP1B activity by increasing the oxidized inactive form of PTP1B. Mice with neuronal ablation of LMO4 have elevated PTP1B activity and impaired hypothalamic leptin signaling, and a PTP1B inhibitor normalized PTP1B activity and restored leptin control of circulating insulin levels. LMO4 is palmitoylated at its C-terminal cysteine, and deletion of this residue prevented palmitoylation and retention of LMO4 at the endoplasmic reticulum and abolished its inhibitory effect on PTP1B. Importantly, LMO4 palmitoylation is sensitive to metabolic stress; mice challenged with a brief high-fat diet or acute intracerebroventricular infusion of saturated fatty acid had less palmitoylated LMO4, less oxidized PTP1B, and increased PTP1B activity in the hypothalamus. Thus, unleashed PTP1B activity attributable to loss of LMO4 palmitoylation may account for rapid loss of central leptin signaling after acute exposure to saturated fat.

Isolation and characterization of a new steroid derivative as a powerful antioxidant from Cleome arabica in screening the in vitro antioxidant capacity of 18 Algerian medicinal plants.

Hydromethanolic extracts from 18 Algerian medicinal plants were screened for their phenolic contents and radical scavenging activities. The phenolic extract of Cleome arabica (Capparaceae) was found to be the most active one. Purification of this extract by semi-preparative high performance liquid chromatography led to the isolation and identification of new steroid derivative. The structure of the active principle is proposed as (17-(4-hydroxy-1,5-dimethylhexyl)-2,3,7-(acetyloxy) gona-1,3,5(10)-trien-15-ol). Compared to six other standard antioxidants which were ascorbic acid, α-tocopherol, Trolox, (+) catechin, p-coumaric acid and gallic acid, the isolated compound was found to be significantly more active in the radical scavenging assay using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Similar results were obtained in the hemolysis assay. The antioxidant capacities of the methanolic extract of C. arabica and its principle compound indicate that this plant may be an important source of chemopreventive and chemotherapeutic natural products activity.