Seed Bank Changes with Time-Since-Fire In Florida Rosemary Scrub

The soil seed bank plays a central role in the regeneration of obligate seeding species in fire-prone habitats. We evaluated how seed density and species composition changed with time-since-fire in the Florida, USA, rosemary scrub community. Because fire affects habitat availability and plant demographic variation, we predicted that soil seed density would be low in recently burned and long-unburned stands and high at intermediate time-since-fire. Seed bank soil samples were collected from a chronosequence of time-since-fire composited from two trials conducted in 1992-1993 and 2008-2009: two sites each of 3, 6, 10, and 24 years post-fire, and 3 long-unburned (similar to 67 years) sites. The seedling emergence method was used to determine species composition of the seed bank. Across all time-since-fire age classes, herbaceous species dominated the seed bank, while long-lived subshrubs and shrubs were present in low densities. Seed banks from sites three years post-fire were distinct from the other sites. When species were sorted as functional groups, seed density was related with time-since-fire for subshrubs and ruderal herbs, but not for scrub herbs and graminoids. Subshrubs and ruderal herbs had highest seed densities in recently burned stands. Seed densities of Florida rosemary (Ceratiola ericoides Michx.) (the major obligate seeding shrub in this community) were associated with time-since-fire and showed highest densities at recently burned and long-unburned sites. The seed banks of two scrub herb species, paper nailwort (Paronychia chartacea Fernald) and nodding pinweed (Lechea cernua Small), were associated with time-since-fire. They reached peaks in density in the first ten years post-fire, corresponding with similar changes in their aboveground abundances with time-since-fire. Soil seed densities of several species and functional groups were associated with time-since-fire, but timing of peak seed density varied depending on species\u27 life span and age of reproductive maturity

Developing drugs targeting transition metal homeostasis

Metal dyshomeostasis is involved in the pathogenesis and progression of diseases including cancer and neurodegenerative diseases. Metal chelators and ionophores are well known modulators of transition metal homeostasis, and a number of these molecules are in clinical trials. Metal-binding compounds are not the only drugs capable of targeting transition metal homeostasis. This review presents recent highlights in the development of chelators and ionophores for the treatment of cancer and neurodegenerative disease. Moreover, we discuss the development of small molecules that alter copper and iron homeostasis by inhibiting metal transport proteins. Finally, we consider the emergence of metal regulatory factor 1 as a drug target in diseases where it mediates zinc-induced signalling cascades leading to pathogenesis

Selenium Metabolism in Cancer Cells: The Combined Application of XAS and XFM Techniques to the Problem of Selenium Speciation in Biological Systems

Determining the speciation of selenium in vivo is crucial to understanding the biological activity of this essential element, which is a popular dietary supplement due to its anti-cancer properties. Hyphenated techniques that combine separation and detection methods are traditionally and effectively used in selenium speciation analysis, but require extensive sample preparation that may affect speciation. Synchrotron-based X-ray absorption and fluorescence techniques offer an alternative approach to selenium speciation analysis that requires minimal sample preparation. We present a brief summary of some key HPLC-ICP-MS and ESI-MS/MS studies of the speciation of selenium in cells and rat tissues. We review the results of a top-down approach to selenium speciation in human lung cancer cells that aims to link the speciation and distribution of selenium to its biological activity using a combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM). The results of this approach highlight the distinct fates of selenomethionine, methylselenocysteine and selenite in terms of their speciation and distribution within cells: organic selenium metabolites were widely distributed throughout the cells, whereas inorganic selenium metabolites were compartmentalized and associated with copper. New data from the XFM mapping of electrophoretically-separated cell lysates show the distribution of selenium in the proteins of selenomethionine-treated cells. Future applications of this top-down approach are discussed

Inhibition of Copper Transport Induces Apoptosis in Triple-Negative Breast Cancer Cells and Suppresses Tumor Angiogenesis

Treatment of advanced breast cancer remains challenging. Copper and some of the copper-dependent proteins are emerging therapeutic targets because they are essential for cell proliferation and survival, and have been shown to stimulate angiogenesis and metastasis. Here, we show that DCAC50, a recently developed small-molecule inhibitor of the intracellular copper chaperones, ATOX1 and CCS, reduces cell proliferation and elevates oxidative stress, triggering apoptosis in a panel of triple-negative breast cancer (TNBC) cells. Inhibition of ATOX1 activity with DCAC50 disrupts copper homeostasis, leading to increased copper levels, altered spatial copper redistribution, and accumulation of ATP7B to the cellular perinuclear region. The extent and impact of this disruption to copper homeostasis vary across cell lines and correlate with cellular baseline copper and glutathione levels. Ultimately, treatment with DCAC50 attenuates tumor growth and suppresses angiogenesis in a xenograft mouse model, and prevents endothelial cell network formation in vitro Co-treatment with paclitaxel and DCAC50 enhances cytotoxicity in TNBC and results in favorable dose reduction of both drugs. These data demonstrate that inhibition of intracellular copper transport targets tumor cells and the tumor microenvironment, and is a promising approach to treat breast cancer

Cellular Fates of Manganese(II) Pentaazamacrocyclic Superoxide Dismutase (SOD) Mimetics: Fluorescently Labeled MnSOD Mimetics, X-ray Absorption Spectroscopy, and X-ray Fluorescence Microscopy Studies

Manganese(II) pentaazamacrocyclic complexes (MnPAMs) can act as small-molecule mimics of manganese superoxide dismutase (MnSOD) with potential therapeutic application in conditions linked to oxidative stress. Previously, the in vitro mechanism of action has been determined, their activity has been demonstrated in cells, and some representatives of this class of MnSOD mimetics have entered clinical trials. However, MnPAM uptake, distribution, and metabolism in cells are largely unknown. Therefore, we have used X-ray fluorescence microscopy (XFM) and X-ray absorption spectroscopy (XAS) to study the cellular fate of a number of MnPAMs. We have also synthesized and characterized fluorescently labeled (pyrene and rhodamine) manganese(II) pyane [manganese(II) trans-2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),14,16-triene] derivatives and investigated their utility for cellular imaging of MnPAMs. Their SOD activity was determined via a direct stopped-flow technique. XFM experiments show that treatment with amine-based manganese(II) pyane type pentaazamacrocycles leads to a 10-100-fold increase in the overall cellular manganese levels compared to the physiological levels of manganese in control cells. In treated cells in general, manganese was distributed throughout the cell body, with a couple of notable exceptions. The lipophilicity of the MnPAMs, examined by partitioning in octanol-buffer system, was a good predictor of the relative cellular manganese levels. Analysis of the XAS data of treated cells revealed that some fraction of amine-based MnPAMs taken up by the cells remained intact, with the rest transformed into SOD-active manganese(II) phosphate. Higher phosphate binding constants, determined from the effect of the phosphate concentration on in vitro SOD activity, were associated with more extensive metabolism of the amine-based MnPAMs to manganese(II) phosphate. In contrast, the imine-based manganese(II) pydiene complex that is prone to hydrolysis was entirely decomposed after uptake and free manganese(II) was oxidized to a manganese(III) oxide type species, in cytosolic compartments, possibly mitochondria. Complex stability constants (determined for some of the MnPAMs) are less indicative of the cellular fate of the complexes than the corresponding phosphate binding constants

X-ray fluorescence imaging of single human cancer cells reveals that the N-heterocyclic ligands of iodinated analogues of ruthenium anticancer drugs remain coordinated after cellular uptake

Analogues of KP1019 containing iodinated indazole ligands were prepared to investigate the biological fate of the Ru-N-heterocycle bond in this class of anticancer agents. The new complexes, 5-iodoindazolium trans-tetrachloridobis(5-iodoindazole)ruthen(III)ate (1) and 5-iodoindazolium trans-tetrachlorido(dimethyl sulfoxide)(5-iodoindazole)ruthen(III)ate (3), were characterized by elemental analysis, mass spectrometry and UV-vis spectrophotometry. Tetramethylammonium salts of these complexes (2 and 4) were synthesized and characterized in a similar manner. Half-maximum inhibitory concentrations of 2 and 4 with regard to A549 cells at 24 h were determined on the basis of the dose-response curves derived from real-time cell adhesion impedance measurements and were shown to be in the same range as those determined for KP1019 and NAMI-A using the same method. X-ray fluorescence imaging of single cultured A549 cells treated with 2 or 4 showed that, in both cases, the distribution of ruthenium and iodine was identical, indicating that the Ru-N bonds in the anionic complexes remained intact after incubation in culture medium and subsequent cellular uptake and processing.Sumy Antony, Jade B. Aitken, Stefan Vogt, Barry Lai, Tracey Brown, Leone Spiccia, Hugh H. Harri