Myriaporone 3/4 structure--activity relationship studies define a pharmacophore targeting eukaryotic protein synthesis

Myriaporones are naturally occurring compounds which structurally resemble the southern hemisphere of the tedanolide family of macrolide antitumor agents. Despite the fact that myriaporone 3/4 represents only a portion of tedanolide, it nonetheless retains much of its biological activity. We show here that like tedanolide, myriaporone 3/4 inhibits protein synthesis and proliferation of mammalian cells with low nanomolar potencies but displays no prokaryotic growth inhibitory effect. Moreover, myriaporone 3/4 displays a very rapid, reversible and p21-independent activity to block S phase progression in mammalian cells. Structure-activity relationship studies revealed that the C18-C19 epoxide and the C14 hydroxymethyl group (tedanolide numbering) of myriaporone 3/4 are required for cell cycle inhibition. These constitute previously unidentified and/or novel pharmacophores for myriaporone 3/4. Our results show that the important biological activities associated with the structurally complex tedanolides are present and can be harnessed in the chemically much simpler myriaporones. This greatly increases the value of the latter as investigative tools for biochemical research as well as for development of potential therapeutics.     

Aging, disability, and frailty: implications for universal design

Throughout the world all populations are seeing burgeoning numbers of "elders", defined as persons aged 65 year and older. In many countries, including Japan, the United States, Norway, Sweden and the United Kingdom, those aged over 65 are at or approaching 15% of the population. As their numbers have increased, so have their health care expenses, leading to extensive research on the health, well being, and life expectancy of these increasingly older elders. Today this group is further sub-divided: the young-old ages 65-74, the old-old ages 75-84, and the oldest-old ages 85+, for both health care and research purposes. However broad variation still characterizes even these groupings. Rates of frailty and disability increase with increasing age among these elders. For example, inabilities to complete at least one activity of daily living increased from about 5-7% at ages 65-69 years to about 28-36% at ages 85+ in 1987. Death rates continue to decline at all ages past 50 years and rates of disability seem to be doing the same. For the foreseeable future, we may expect increasing numbers of older, frail elders than in previous decades. Thus, people are not only living longer, they generally are healthier at advanced ages than were previous cohorts, thus "old age" disabilities of the 20th century will be put off to even older ages during the 21st century. As yet there is no clear way to assess senescent changes in humans, although activities of daily living, allostatic load, and frailty indices have all been suggested. One future need is greater development and use of universal and accessible design in all aspects of the built environment.     

The marine sponge metabolite mycothiazole: A novel prototype mitochondrial complex I inhibitor

A natural product chemistry-based approach was applied to discover small-molecule inhibitors of hypoxia-inducible factor-1 (HIF-1). A Petrosaspongia mycofijiensis marine sponge extract yielded mycothiazole (1), a solid tumor selective compound with no known mechanism for its cell line-dependent cytotoxic activity. Compound 1 inhibited hypoxic HIF-1 signaling in tumor cells (IC₅₀ 1 nM) that correlated with the suppression of hypoxia-stimulated tumor angiogenesis in vitro. However, 1 exhibited pronounced neurotoxicity in vitro. Mechanistic studies revealed that 1 selectively suppresses mitochondrial respiration at complex I (NADH-ubiquinone oxidoreductase). Unlike rotenone, MPP⁺, annonaceous acetogenins, piericidin A, and other complex I inhibitors, mycothiazole is a mixed polyketide/peptide-derived compound with a central thiazole moiety. The exquisite potency and structural novelty of 1 suggest that it may serve as a valuable molecular probe for mitochondrial biology and HIF-mediated hypoxic signaling.     

Assessing the trypanocidal potential of natural and semi-synthetic diketopiperazines from two deep water marine-derived fungi

Human African trypanosomiasis (HAT, commonly known as African sleeping sickness) is categorized as a neglected disease, as it afflicts >50,000 people annually in sub-saharan Africa, and there are few formal programs in the world focused on drug discovery approaches for this disease. In this study, we examined the crude extracts of two fungal strains (Aspergillus fumigatus and Nectria inventa) isolated from deep water sediment which provided >99% growth inhibition at 1 μg/mL of Trypanosoma brucei, the causative parasite of HAT. A collection of fifteen natural products was supplemented with six semi-synthetic derivatives and one commercially available compound. Twelve of the compounds, each containing a diketopiperazine core, showed excellent activity against T. brucei (IC₅₀ = 0.002–40 μM), with selectivity over mammalian cells as great as 20-fold. The trypanocidal diketopiperazines were also tested against two cysteine protease targets Rhodesain and TbCatB, where five compounds showed inhibition activity at concentrations less than 20 μM. A preliminary activity pattern is described and analyzed.     

Serotonergic modulation of male-like pseudocopulatory behavior in the parthenogenetic whiptail lizard, Cnemidophorus uniparens

Hormone-neurotransmitter interactions form an important link through which hormones influence a variety of behavioral processes. Typically, sexual behavior is dimorphic with males mounting receptive females. In the all-female lizard species Cnemidophorus uniparens, individuals display both male-like pseudocopulation and female-like receptivity. These respective behavioral states are correlated with high circulating concentrations of progesterone following ovulation and of estrogen preceding it. In sexual species, serotonin is involved in male-typical mounting, and, as reported here, in male-like pseudosexual behavior in this unisexual species. In the first study, C. uniparens were ovariectomized and treated systemically with exogenous androgen, a hormonal regimen that results in individuals displaying only male-like pseudosexual behavior. An increase in serotonin levels in the preoptic area coupled with the suppression of male-like pseudocopulation was observed in androgen-treated lizards injected with 5-hydroxytryptophan (the precursor of serotonin) and clorgyline (a monoamine oxidase inhibitor) compared to vehicle-treated controls. Our second experiment involved ovariectomizing lizards and either injecting them with estradiol or implanting them with either an empty (Blank) or a progesterone- or testosterone-containing Silastic capsule. Treatment with para-chlorophenylalanine (an inhibitor of tryptophan hydroxylase) facilitated male-like pseudosexual behavior depending on the circulating hormonal milieu and decreased serotonin levels in the preoptic area. Our data suggest that serotonin is inhibitory to male-like pseudosexual behavior in C. uniparens but more importantly that the hormonal environment modulates the serotonin system at the level of the preoptic area, with the serotonergic system then establishing behavioral thresholds that allow for this behavior to be "gated".     

Unraveling the Numerous Biosynthetic Products of the Marine Sediment-Derived Fungus, Aspergillus insulicola

A new tripeptide, pre-sclerotiotide F (3), was isolated from a marine sediment-derived fungus, Aspergillus insulicola, along with five known compounds, one of which was new at the time of isolation, scerotiotide F (4). The absolute configuration elucidation of the new compound was determined using a combination of NMR, HR-ESI-MS, and optical rotation analyses. Cytotoxicities were measured in vitro against selected cancer cells. The effects of pre-sclerotiotide F (3) and sclerotiotide F (4) on LPS-induced NF-κB and iNOS expression were also measured.     

Morphological Changes in the Midgut of Aedes aegypti L. (Diptera: Culicidae) Larvae Following Exposure to an Annona coriacea (Magnoliales: Annonaceae) Extract

Bioinsecticides are important in the control of disease vectors, but data regarding their physiological effects on target insects are incomplete. This study describes morphological changes that occur in the midgut of third instar Aedes aegypti L. (Diptera: Culicidae) following treatment with a methanolic extract of Annona coriacea (Magnoliales: Annonaceae). Dissected midguts were subdivided into anterior and posterior regions and analyzed by light and scanning electron microscopy. Insects exposed to the extract displayed intense, destructive cytoplasmic vacuolization in columnar and regenerative midgut cells. The apical surfaces of columnar cells exhibited cytoplasmic protrusions oriented toward the lumen, suggesting that these cells could be involved in apocrine secretory processes and/or apoptosis. We report that A. coriacea extracts induced morphological alterations in the midgut of A. aegypti midgut larvae, supporting the use of plant extracts for control of the dengue vector.