Anion transporters based on small molecules have received attention as therapeutic agents because of their potential to disrupt cellular ion homeostasis. However, a direct correlation between a change in cellular chloride anion concentration and cytotoxicity has not been established for synthetic ion carriers. Here we show that two pyridine diamide-strapped calix[4]pyrroles induce coupled chloride anion and sodium cation transport in both liposomal models and cells, and promote cell death by increasing intracellular chloride and sodium ion concentrations. Removing either ion from the extracellular media or blocking natural sodium channels with amiloride prevents this effect. Cell experiments show that the ion transporters induce the sodium chloride influx, which leads to an increased concentration of reactive oxygen species, release of cytochrome c from the mitochondria and apoptosis via caspase activation. However, they do not activate the caspase-independent apoptotic pathway associated with the apoptosis-inducing factor. Ion transporters, therefore, represent an attractive approach for regulating cellular processes that are normally controlled tightly by homeostasis.

Exposure to mercury causes severe damage to various tissues and organs in humans. Concern over mercury toxicity has encouraged the development of efficient, sensitive, and selective methods for the in vivo detection of mercury. Although a variety of chemosensors have been exploited for this purpose, no in vivo monitoring systems have been described to date. In this report, we describe an irreversible rhodamine chemosensor-based, real-time monitoring system to detect mercury ions in living cells and, in particular, vertebrate organisms. The chemosensor responds rapidly, irreversibly, and stoichiometrically to mercury ions in aqueous media at room temperature. The results of experiments with mammalian cells and zebrafish show that the mercury chemosensor is cell and organism permeable and that it responds selectively to mercury ions over other metal ions. In addition, real-time monitoring of mercury-ion uptake by cells and zebrafish using this chemosensor shows that saturation of mercury-ion uptake occurs within 20-30 min in cells and organisms. Finally, accumulation of mercury ions in zebrafish tissue and organs is readily detected by using this rhodamine-based chemosensor.

A fluorescent probe based on fluorescein displays an excellent selectivity and sensitivity for thiols and its application for bioimaging is described.

Fluorescent probes have been used extensively to monitor biomolecules and biologically relevant species in vitro and in vivo. A new trend in this area that has been stimulated by the desire to obtain more detailed information about the biological effects of analytes is the change from live cell to whole animal fluorescent imaging. Zebrafish has received great attention for live vertebrate imaging due to several noticeable advantages. In this tutorial review, recent advances in live zebrafish imaging using fluorescent probes, such as fluorescent proteins, synthetic fluorescent dyes and quantum dots, are highlighted.

A fluorescein-based fluorescent probe displays fluorescence enhancement for palladium species in the typical oxidation states of 0, +2 and +4 and is applied to monitor accumulated palladium in living organisms.

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cell-surface anion channel that permeates chloride and bicarbonate ions. The most frequent mutation of CFTR that causes cystic fibrosis is the deletion of phenylalanine at position 508 (ΔF508), which leads to defects in protein folding and cellular trafficking to the plasma membrane. The lack of the cell-surface CFTR results in a reduction in the lifespan due to chronic lung infection with progressive deterioration of lung function. Hsc70 plays a crucial role in degradation of mutant CFTR by the ubiquitin-proteasome system. To date, various Hsc70 inhibitors and transcription regulators have been tested to determine whether they correct the defective activity of mutant CFTR. However, they exhibited limited or questionable effects on restoring the chloride channel activity in cystic fibrosis cells. Herein, we show that a small molecule apoptozole (Az) has high cellular potency to promote membrane trafficking of mutant CFTR and its chloride channel activity in cystic fibrosis cells. Results from affinity chromatography and ATPase activity assay indicate that Az inhibits the ATPase activity of Hsc70 by binding to its ATPase domain. In addition, a ligand-directed protein labeling and molecular modeling studies also suggest the binding of Az to an ATPase domain, in particular, an ATP-binding pocket. It is proposed that Az suppresses ubiquitination of ΔF508-CFTR maybe by blocking interaction of the mutant with Hsc70 and CHIP, and, as a consequence, it enhances membrane trafficking of the mutant.

The heat shock protein HSP70 plays antiapoptotic and oncogenic roles, and thus its inhibition has been recognized as a potential avenue for anticancer therapy. Here we describe the small molecule, apoptozole (Az), which inhibits the ATPase activity of HSP70 by binding to its ATPase domain and, as a result, induces an array of apoptotic phenotypes in cancer cells. Affinity chromatography provides evidence that Az binds HSP70 but not other types of heat shock proteins including HSP40, HSP60, and HSP90. We also demonstrate that Az induces cancer cell death via caspase-dependent apoptosis by disrupting the interaction of HSP70 with APAF-1. Animal studies indicate that Az treatment retards tumor growth in a xenograft mouse model without affecting mouse viability. These studies suggest that Az will aid the development of new cancer therapies and serve as a chemical probe to gain a better understanding of the diverse functions of HSP70.

A highly sensitive fluorescent turn-on probe specific for methylmercury species as well as inorganic mercury ions has been developed on the basis of mercury ion-promoted hydrolysis of a fluorescein-derived aryl vinyl ether.