3 research outputs found
The Role of ABCG2 in the Pathogenesis of Primary Hyperuricemia and GoutâAn Update
Urate homeostasis in humans is a complex and highly heritable process that involves i.e., metabolic urate biosynthesis, renal urate reabsorption, as well as renal and extrarenal urate excretion. Importantly, disturbances in urate excretion are a common cause of hyperuricemia and gout. The majority of urate is eliminated by glomerular filtration in the kidney followed by an, as yet, not fully elucidated interplay of multiple transporters involved in the reabsorption or excretion of urate in the succeeding segments of the nephron. In this context, genome-wide association studies and subsequent functional analyses have identified the ATP-binding cassette (ABC) transporter ABCG2 as an important urate transporter and have highlighted the role of single nucleotide polymorphisms (SNPs) in the pathogenesis of reduced cellular urate efflux, hyperuricemia, and early-onset gout. Recent publications also suggest that ABCG2 is particularly involved in intestinal urate elimination and thus may represent an interesting new target for pharmacotherapeutic intervention in hyperuricemia and gout. In this review, we specifically address the involvement of ABCG2 in renal and extrarenal urate elimination. In addition, we will shed light on newly identified polymorphisms in ABCG2 associated with early-onset gout
Active RhoA Exerts an Inhibitory Effect on the Homeostasis and Angiogenic Capacity of Human Endothelial Cells
Background The small GTPase RhoA (Ras homolog gene family, member A) regulates a variety of cellular processes, including cell motility, proliferation, survival, and permeability. In addition, there are reports indicating that RhoAâROCK (rho associated coiledâcoil containing protein kinase) activation is essential for VEGF (vascular endothelial growth factor)âmediated angiogenesis, whereas other work suggests VEGFâantagonistic effects of the RhoAâROCK axis. Methods and Results To elucidate this issue, we examined human umbilical vein endothelial cells and human coronary artery endothelial cells after stable overexpression (lentiviral transduction) of constitutively active (G14V/Q63L), dominantânegative (T19N), or wildâtype RhoA using a series of in vitro angiogenesis assays (proliferation, migration, tube formation, angiogenic sprouting, endothelial cell viability) and a human umbilical vein endothelial cells xenograft assay in immuneâincompetent NOD scid gamma mice in vivo. Here, we report that expression of active and wildâtype RhoA but not dominantânegative RhoA significantly inhibited endothelial cell proliferation, migration, tube formation, and angiogenic sprouting in vitro. Moreover, active RhoA increased endothelial cell death in vitro and decreased human umbilical vein endothelial cellârelated angiogenesis in vivo. Inhibition of RhoA by C3 transferase antagonized the inhibitory effects of RhoA and strongly enhanced VEGFâinduced angiogenic sprouting in controlâtreated cells. In contrast, inhibition of RhoA effectors ROCK1/2 and LIMK1/2 (LIM domain kinase 1/2) did not significantly affect RhoAârelated effects, but increased angiogenic sprouting and migration of controlâtreated cells. In agreement with these data, VEGF did not activate RhoA in human umbilical vein endothelial cells as measured by a Förster resonance energy transferâbased biosensor. Furthermore, global transcriptome and subsequent bioinformatic gene ontology enrichment analyses revealed that constitutively active RhoA induced a differentially expressed gene pattern that was enriched for gene ontology biological process terms associated with mitotic nuclear division, cell proliferation, cell motility, and cell adhesion, which included a significant decrease in VEGFRâ2 (vascular endothelial growth factor receptor 2) and NOS3 (nitric oxide synthase 3) expression. Conclusions Our data demonstrate that increased RhoA activity has the potential to trigger endothelial dysfunction and antiangiogenic effects independently of its wellâcharacterized downstream effectors ROCK and LIMK
Amyloid-Beta Induced Changes in Vesicular Transport of BDNF in Hippocampal Neurons
The neurotrophin brain derived neurotrophic factor (BDNF) is an important growth factor in the CNS. Deficits in transport of this secretory protein could underlie neurodegenerative diseases. Investigation of disease-related changes in BDNF transport might provide insights into the cellular mechanism underlying, for example, Alzheimerâs disease (AD). To analyze the role of BDNF transport in AD, live cell imaging of fluorescently labeled BDNF was performed in hippocampal neurons of different AD model systems. BDNF and APP colocalized with low incidence in vesicular structures. Anterograde as well as retrograde transport of BDNF vesicles was reduced and these effects were mediated by factors released from hippocampal neurons into the extracellular medium. Transport of BDNF was altered at a very early time point after onset of human APP expression or after acute amyloid-beta(1-42) treatment, while the activity-dependent release of BDNF remained unaffected. Taken together, extracellular cleavage products of APP induced rapid changes in anterograde and retrograde transport of BDNF-containing vesicles while release of BDNF was unaffected by transgenic expression of mutated APP. These early transport deficits might lead to permanently impaired brain functions in the adult brain