Showing papers by "Brian R. Wamhoff published in 2012"

Tonicity-independent regulation of the osmosensitive transcription factor TonEBP (NFAT5)

Abstract: Tonicity-responsive enhancer binding protein (TonEBP/nuclear factor of activated T-cells 5 [NFAT5]) is a Rel homology transcription factor classically known for its osmosensitive role in regulating cellular homeostasis during states of hypo- and hypertonic stress A recently growing body of research indicates that TonEBP is not solely regulated by tonicity, but that it can be stimulated by various tonicity-independent mechanisms in both hypertonic and isotonic tissues Physiological and pathophysiological stimuli such as cytokines, growth factors, receptor and integrin activation, contractile agonists, ions, and reactive oxygen species have been implicated in the positive regulation of TonEBP expression and activity in diverse cell types These new data demonstrate that tonicity-independent stimulation of TonEBP is critical for tissue-specific functions like enhanced cell survival, migration, proliferation, vascular remodeling, carcinoma invasion, and angiogenesis Continuing research will provide a better understanding as to how these and other alternative TonEBP stimuli regulate gene expression in both health and disease

NFAT5 expression in bone marrow-derived cells enhances atherosclerosis and drives macrophage migration.

Abstract: Objective: We have previously shown that the transcription factor, nuclear factor of activated T-cells 5 (NFAT5), regulates vascular smooth muscle cell phenotypic modulation, but the role of NFAT5 in atherosclerosis is unknown. Our main objective was to determine if NFAT5 expression in bone marrow (BM)-derived cells altered atherosclerotic development and macrophage function. Methods and Results: NFAT5+/-ApoE-/- mice were generated for in vivo atherosclerosis studies. Following high fat diet feeding, en face analysis of the thoracic aorta established that genome-wide NFAT5 haploinsufficiency reduced atherosclerotic lesion formation by 73%. BM transplant studies revealed that transplantation of NFAT5+/-ApoE-/- marrow into NFAT5+/+ApoE-/- mice resulted in a similar 86% reduction in lesion formation. In vitro functional analysis of BM-derived macrophages demonstrated that NFAT5 is required for macrophage migration, which is a key event in the propagation of atherosclerosis. Conclusion: We have identified NFAT5 in BM-derived cells as a positive regulator of atherosclerotic lesion formation and macrophage function in the vasculature.

Intravascular ultrasound detection and delivery of molecularly targeted microbubbles for gene delivery

Abstract: We are investigating the combination of microbubble-based targeted drug delivery and intravascular ultrasound (IVUS) imaging as a potential therapy to reduce incidence of restenosis following stent placement in atherosclerotic coronary arteries. The goal of these studies was to determine whether IVUS could be used to detect targeted microbubbles and enhance drug/gene delivery through targeting. Quiescent vascular smooth muscle cells (SMCs) were stimulated with cytokine IL-1β to induce the inflammatory cell surface marker vascular cell adhesion molecule 1 (VCAM-1). Molecular-targeted (VCAM-1 Ab or IgG control Ab), fluorescent-labeled microbubbles were conjugated with plasmid DNA expressing green fluorescent protein (GFP, pMax-GFP) and exposed to the inflamed SMCs under flow to measure adhesion compared with control microbubbles. Gene delivery was performed using a modified IVUS catheter to generate 1.5-MHz ultrasound at 200 kPa. Detection of adherent microbubbles to inflamed SMCs in culture and flow chambers was measured using an IVUS catheter and scanner. VCAM-1-targeted microbubbles enhanced adhesion to inflamed SMCs 100-fold over nontargeted microbubbles. Compared with noninflamed SMCs, VCAM-1-targeted microbubbles exhibited a 7.9-fold increase in adhesion to IL-1β-treated cells. Targeted microbubbles resulted in a 5.5-fold increase in plasmid DNA transfection over nontargeted microbubbles in conjunction with a focused 2.54-cm (1-in) diameter 1-MHz transducer and also enhanced transfection by the modified IVUS transducer at 1.5 MHz. Targeted microbubbles (at a density of 3 × 104 microbubbles/mm2) increased IVUS image intensity 13.2 dB over non-microbubble-coated surfaces. Rupture of microbubbles from the modified IVUS transducer resulted in a 53% reduction in image intensity. Taken together, these results indicate that IVUS may be used to detect targeted microbubbles to inflamed vasculature and subsequently deliver a gene/drug locally.

Organotypic systems in drug metabolism and toxicity: challenges and opportunities.

Abstract: Introduction: The frequent failure of high-throughput screening cell-based tools to accurately predict in vivo responses, coupled with limitations of animal models in predicting human safety or drug efficacy, impairs the de-risking process for biotechnology/pharmaceutical companies as they make important decisions to enter human clinical trials. Organotypic systems strive to fill the gap between these screening and in vivo studies and provide a solution. Areas covered: The authors examine the various approaches to recreate physiological response on the bench and trace the evolution of organotypic systems, while discussing intrinsic challenges and opportunities that lie ahead. Furthermore, they cite literature that is the foundation of several biotechnology research companies addressing this issue and discuss major government-funded initiatives to aid the development of these systems in an effort to fill this existing gap. Expert opinion: Decisions from translational systems that bridge basic drug efficacy...

Multifunction intravascular ultrasound for microbubble based drug delivery

Abstract: A compact, single element, mechanically rotated intravascular ultrasound (IVUS) transducer for microbubble-based drug delivery and imaging has been designed and fabricated. This device provides displacement, delivery, and imaging capabilities to enable microbubble-based delivery of a therapeutic drug and delivery verification. The IVUS transducer was designed and fabricated to operate at a center frequency of 7 MHz. Acoustic radiation radiation force displacement of microbubbles, fluorophore delivery using microbubbles in vitro and imaging capabilities were demonstrated. Finally, a fluorescent model drug was delivered under physiological flow conditions to an ex vivo porcine artery using the prototype IVUS.