Arsenic alters vascular smooth muscle cell focal adhesion complexes leading to activation of FAK-src mediated pathways.

Chronic exposure to arsenic has been linked to tumorigenesis, cardiovascular disease, hypertension, atherosclerosis, and peripheral vascular disease; however, the molecular mechanisms underlying its pathological effects remain elusive. In this study, we investigated arsenic-induced alteration of focal adhesion protein complexes in normal, primary vascular smooth muscle cells. We demonstrate that exposure to environmentally relevant concentrations of arsenic (50 ppb As(3+)) can alter focal adhesion protein co-association leading to activation of downstream pathways. Co-associated proteins were identified and quantitated via co-immunoprecipitation, SDS-PAGE, and Western blot analysis followed by scanning densitometry. Activation of MAPK pathways in total cell lysates was evaluated using phosphor-specific antibodies. In our model, arsenic treatment caused a sustained increase in FAK-src association and activation, and induced the formation of unique signaling complexes (beginning after 3-hour As(3+) exposure and continuing throughout the 12-hour time course studied). The effects of these alterations were manifested as chronic stimulation of downstream PAK, ERK and JNK pathways. Past studies have demonstrated that these pathways are involved in cellular survival, growth, proliferation, and migration in VSMCs.

Liposomes form nanotubules and long range networks in the presence of electric field.

Liposomes are lipid bilayer-bound micron scale structures critical to therapeutic treatments, biophysical studies, cosmetics, food, constrained volume experiments, and gene transfer. Applying an electric field to separate mixtures of liposomes played a role in their discovery and is still presently used for a variety of processes. Our group has found agreement between models of electric field-induced transport and capillary electrophoresis measurements where the liposomes are described as slightly elongated with the charged lipids migrating to form a local dipole. Here we show much more diverse structures that cannot be accounted for in these models. A variety of morphologies emerge, from individual liposomes being stretched into nanotubules several microns in length to long-range organized assemblies of liposomes over tens of microns. Based in this result, existing theories for electromigration of soft particles need to be re-addressed. Also, the formation of nanoscale lipid tubules suggests that unique structures for bionanoengineering can be fabricated. Much higher intrinsic fields than those applied here are observed in biology that suggests mechanical electrostatic interaction may play role in shape and function of individual biological membranes and networks of membrane-bound structures.

Increased hexokinase II expression in the renal glomerulus of mice in response to arsenic.

Epidemiological studies link arsenic exposure to increased risks of cancers of the skin, kidney, lung, bladder and liver. Additionally, a variety of non-cancerous conditions such as diabetes mellitus, hypertension, and cardiovascular disease have been associated with chronic ingestion of low levels of arsenic. However, the biological and molecular mechanisms by which arsenic exerts its effects remain elusive. Here we report increased renal hexokinase II (HKII) expression in response to arsenic exposure both in vivo and in vitro. In our model, HKII was up-regulated in the renal glomeruli of mice exposed to low levels of arsenic (10 ppb or 50 ppb) via their drinking water for up to 21 days. Additionally, a similar effect was observed in cultured renal mesangial cells exposed to arsenic. This correlation between our in vivo and in vitro data provides further evidence for a direct link between altered renal HKII expression and arsenic exposure. Thus, our data suggest that alterations in renal HKII expression may be involved in arsenic-induced pathological conditions involving the kidney. More importantly, these results were obtained using environmentally relevant arsenic concentrations.

Electrophoretic and dielectrophoretic field gradient technique for separating bioparticles.

We describe a new device for separation of complex biological particles and structures exploiting many physical properties of the biolytes. The device adds a new longitudinal gradient feature to insulator dielectrophoresis, extending the technique to separation of complex mixtures in a single channel. The production of stronger local field gradients along a global gradient allows particles to enter, initially transported through the channel by electrophoresis and electroosmosis, and to be isolated according to their characteristic physical properties, including charge, polarizability, deformability, surface charge mobility, dielectric features, and local capacitance. In this work, the separation mechanism is described in terms of the relevant electromechanical principles, and proof-of-principle is demonstrated using various bacteria cells as model systems. The results demonstrate the selectivity of the technique and suggest that it may form the foundation for a versatile and useful tool for separating mixtures of complex biological particles and structures.

Effects of deformability, uneven surface charge distributions, and multipole moments on biocolloid electrophoretic migration.

Liposomes have been widely used as cellular and bioparticle mimics due to their lipid bilayer structure and relative ease of production and manipulation. Such biocolloids are frequently characterized by capillary electrophoresis (CE), which promises a wealth of information about such properties as surface charge, composition, and rigidity. The applicability of this information is somewhat limited, however, since it is interpreted with colloidal theories that do not account for the unique properties of biocolloids. In this work, the effects of deformability, mobile surface charges, intrinsic polarizability, and uneven surface charge distributions are incorporated into colloidal theories in order to better model the electrophoretic behaviors of liposomes.

Examination of the electrophoretic behavior of liposomes.

The electromigration of liposomes is a complex process resulting in many unexpected behaviors that are difficult to address with existing theories. In this study, the electrophoretic behaviors of liposome populations under various conditions were examined through the use of capillary electrophoresis and the results compared to classical electrokinetic, colloid, and spheroid theories. To elucidate the possible effects of applied field strength, bilayer rigidity, and surface charge on these behaviors, the electrophoretic mobilities of liposome populations were monitored while varying the applied potential, ionic strength of the medium, and the surface charge and cholesterol content of the liposomes. On the basis of comparisons made to the theoretical predictions, our results suggest that liposomal deformation and field-induced polarization may occur during electrophoresis and these mechanisms help to describe many of the observed behaviors.