Size control of arsenic trioxide nanocrystals grown in nanowells.

This paper describes a new strategy to generate nanocrystalline drugs through the precipitation of drug molecules in attoliter nanowells. We controlled the size of arsenic trioxide (ATO) nanocrystals by simply changing the concentration of ATO solution in the nanowells; particles with sizes ranging from 55 to 175 nm were formed. This approach only requires the drugs to be soluble in a solvent and thus can be broadly applicable to produce other drugs in nanocrystalline form.

A copper hyperaccumulation phenotype correlates with pathogenesis in Cryptococcus neoformans.

Cryptococcus neoformans is a major human pathogen and a cause of meningoencephalitis in immunocompromised patients. Many factors contribute to the extraordinary survivability and pathogenicity of this fungus in humans, including copper homeostasis pathways. Previous work has shown that deletion of the copper-dependent regulator Cuf1 results in decreased virulence and dissemination in brain infection, suggesting that copper acquisition is important to the persistence of this pathogen. Here, we show that the minimal copper quota of C. neoformans is maintained at a high level even when grown under conditions of stringent copper limitation. Intriguingly, when this fungal pathogen is grown in standard and copper-enriched media, it sequesters even higher levels of this essential metal, achieving levels that are far higher than non-pathogenic S. cerevisiae. The hypothesis that copper acquisition plays an essential role in virulence is further corroborated by the findings that a hypovirulent CUF1-deletant strain of C. neoformans retrieved from infected mice contains almost a 6-fold lower concentration of intracellular copper than the pathogenic wild-type strain. The concentration difference arises in part from larger-sized cuf1Δ cell. Under in vitro growth conditions, the size of the cuf1Δ cells is normal and the hypertrophy phenotype is readily induced in vitro under conditions of copper starvation. Taken together, these data suggest that acquisition of extraordinary levels of copper is an important factor in the survivability of the pathogen in the copper-deplete environment of infection, and effective copper concentration may play an important role in the pathogenesis of C. neoformans.

Nano-encapsulation of arsenic trioxide enhances efficacy against murine lymphoma model while minimizing its impact on ovarian reserve in vitro and in vivo.

Advances in cancer therapy have increased the rate of survival of young cancer patients; however, female lymphoma patients frequently face a temporary or permanent loss of fertility when treated with traditional cytotoxic agents. The potential loss of fertility is an important concern that can influence treatment decisions for many premenopausal cancer patients. The negative effect of chemotherapeutic agents and treatment protocols to patients' fertility-referred to as fertotoxicity-are thus an increasingly important cancer survivorship issue. We have developed a novel nanoscale formulation of arsenic trioxide, a potent drug for treatment of hematological malignancies, and demonstrate that it has significantly better activity in a murine lymphoma model than the free drug. In parallel, we have developed a novel in vitro assay of ovarian follicle function that predicts in vivo ovarian toxicity of therapeutic agents. Our results reveal that the nanotherapeutic agent is not only more active against lymphoma, but is fertoprotective, i.e., it is much less deleterious to ovarian function than the parent drug. Thus, our in vitro assay allows rapid evaluation of both established and experimental anticancer drugs on ovarian reserve and can inform the selection of efficacious and fertility-sparing treatment regimens for reproductive-age women diagnosed with cancer.

Accumulation of cadmium in insulin-producing ß cells.

Evidence suggests that chronic low level cadmium exposure impairs the function of insulin-producing ß cells and may be associated with type-2 diabetes mellitus. Herein, we describe the cadmium content in primary human islets and define the uptake kinetics and effects of environmentally relevant cadmium concentrations in cultured ß cells. The average cadmium content in islets from 10 non-diabetic human subjects was 29 ± 7 nmol/g protein (range 7 to 72 nmol/g protein). Exposure of the ß-cell line MIN6 to CdCl 2 concentrations between 0.1 and 1.0 µmol/L resulted in a dose- and time-dependent uptake of cadmium over 72 h. This uptake resulted in an induction of metallthionein expression, likely enhancing cellular cadmium accumulation. Furthermore, cadmium accumulation resulted in an inhibition of glucose stimulated insulin secretion in MIN6 cells and primary mouse islets. Our results indicate that this impairment in ß-cell function is not due to an increase in cell death or due to an increase in oxidative stress. We conclude that mouse ß cells accumulate cadmium in a dose- and time-dependent manner over a prolonged time course at environmentally relevant concentrations. This uptake leads to a functional impairment of ß-cell function without significant alterations in cell viability, expression of genes important for ß-cell function or increase in oxidative stress.

Acute cytokine-mediated downregulation of the zinc transporter ZnT8 alters pancreatic beta-cell function.

Genetic studies suggest that Zn transporters such as ZnT8 play a role in insulin secretion by pancreatic beta-cells; however, little is known about the dynamic roles of Zn trafficking pathways on beta-cell physiology. To test the acute effects of the inflammatory cytokines interleukin 1 beta (IL1 beta) and tumor necrosis factor alpha (TNFalpha) on Zn homeostasis, the mRNA expression profile of Zn transporters of the ZnT and ZIP families was examined. Exposure of MIN6 cells or primary murine islets to IL1 beta or TNFalpha altered the mRNA expression profile of Zn transporters; most notable was decreased ZnT8 mRNA levels. siRNA-mediated gene knockdown was used to examine the effects of decreased ZnT8 expression in primary dispersed murine islet cells from C57/BL6 mice and MIN6 cells. ZnT8 knockdown in these murine islets led to reduced glucose stimulated insulin secretion without altering the total cellular insulin content or cell viability at normal or supraphysiological Zn concentrations. The labile Zn content determined by flow cytometry after loading with the Zn-specific sensor FluoZin-3 AM was decreased in MIN6 cells following ZnT8 knockdown or IL1 beta treatment. These results suggest that an acute decrease in ZnT8 levels impairs beta-cell function and Zn homeostasis, and may contribute to inflammatory cytokine-induced alterations in beta-cell function.

A novel nanoparticulate formulation of arsenic trioxide with enhanced therapeutic efficacy in a murine model of breast cancer.

PURPOSE: The clinical success of arsenic trioxide (As(2)O(3)) in hematologic malignancies has not been replicated in solid tumors due to poor pharmacokinetics and dose-limiting toxicity. We have developed a novel nanoparticulate formulation of As(2)O(3) encapsulated in liposomal vesicles or "nanobins" [(NB(Ni,As)] to overcome these hurdles. We postulated that nanobin encapsulation of As(2)O(3) would improve its therapeutic index against clinically aggressive solid tumors, such as triple-negative breast carcinomas. EXPERIMENTAL DESIGN: The cytotoxicity of NB(Ni,As), the empty nanobin, and free As(2)O(3) was evaluated against a panel of human breast cancer cell lines. The plasma pharmacokinetics of NB(Ni,As) and free As(2)O(3) were compared in rats to measure drug exposure. In addition, the antitumor activity of these agents was evaluated in an orthotopic model of human triple-negative breast cancer. RESULTS: The NB(Ni,As) agent was much less cytotoxic in vitro than free As(2)O(3) against a panel of human breast cancer cell lines. In contrast, NB(Ni,As) dramatically potentiated the therapeutic efficacy of As(2)O(3) in vivo in an orthotopic model of triple-negative breast cancer. Reduced plasma clearance, enhanced tumor uptake, and induction of tumor cell apoptosis were observed for NB(Ni,As). CONCLUSIONS: Nanobin encapsulation of As(2)O(3) improves the pharmacokinetics and antitumor efficacy of this cytotoxic agent in vivo. Our findings demonstrate the therapeutic potential of this nanoscale agent and provide a foundation for future clinical studies in breast cancer and other solid tumors.