TGF-beta 1-induced epithelial-to-mesenchymal transition and therapeutic intervention in diabetic nephropathy

Background/Aims: Epithelial-to-mesenchymal cell transformation (EMT) is the trans-differentiation of tubular epithelial cells into myofibroblasts, an event underlying progressive chronic kidney disease in diabetes, resulting in fibrosis. Mainly reported in proximal regions of the kidney, EMT is now recognized as a key contributor to the loss of renal function throughout the nephron in diabetic nephropathy (DN). Concomitant upregulation of TGF-beta in diabetes makes this pro-fibrotic cytokine an obvious candidate in the development of these fibrotic complications. This article reviews recent findings clarifying our understanding of the role of TGF-beta and associated sub-cellular proteins in EMT. Methods: To understand the pathology of EMT and the role of TGF-beta, we reviewed the literature using PubMed for English language articles that contained key words related to EMT, TGF-beta and DN. Results: EMT and phenotypic plasticity of epithelial cells throughout the nephron involves cytoskeletal reorganization and de novo acquisition of classic mesenchymal markers. Concurrent downregulation of epithelial adhesion molecules results in a loss of function and decreased cell coupling, contributing to a loss of epithelial integrity. TGF-beta 1 is pivotal in mediating these phenotypic changes. Conclusion: TGF-beta-induced EMT is a key contributor to fibrotic scar formation as seen in DN, and novel routes for future therapeutic intervention are discussed

Communication through an extra dimension

If our visible universe is considered a trapped shell in a five-dimensional hyper-universe, all matter in it may be connected by superluminal signals traveling through the fifth dimension. Events in the shell are still causal, however, the propagation of signals proceeds at different velocities depending on the fifth coordinate.Comment: Latex format, 12 pages. References modifie

SGK1 in the kidney: disrupted sodium transport in diabetes and beyond

Renal complications of diabetes can be severe; however, the mechanisms that underlie the development and progression of diabetic nephropathy are poorly understood. Recent evidence suggests that the serum and glucocorticoid induced kinase-1 (SGK1) may be key to this process. SGK1 expression and function are increased in models of diabetes and polymorphisms of the SGK1 gene are associated with type 2 diabetes mellitus. A key regulator of sodium transport within the renal epithelium of the distal nephron, SGK1 was originally isolated as a glucocorticoid-sensitive gene that regulated the epithelial sodium channel (ENaC; known also as the sodium channel, nonvoltage-gated 1, SCNN1). It is now apparent that SGK1 modulates sodium re-absorption by a number of sodium transporters/channels throughout the length of the nephron including; the Na+/H+ exchange isoform 3 (NHE3), the Na+Cl- co-transporter (NCC) and the Na+/K+-ATPase. In addition, SGK1 is regulated by a diverse range of factors including; insulin, glucose, intracellular calcium, transforming growth factor-beta1, flow rate and osmolality. This brief review examines the evidence supporting an involvement of SGK1 in diabetic nephropathy and discusses how dysregulated sodium transport may account for the development of secondary hypertension associated with the condition. Furthermore, the article examines how aberrant SGK1 expression and activity may be responsible for the cellular changes seen in the damaged nephron

Functional expression of TRPV4 channels in human collecting duct cells: implications for secondary hypertension in diabetic nephropathy

Background. The Vanilloid subfamily of transient receptor potential (TRPV) ion channels has been widely implicated in detecting osmotic and mechanical stress. In the current study, we examine the functional expression of TRPV4 channels in cell volume regulation in cells of the human collecting duct. Methods. Western blot analysis, siRNA knockdown, and microfluorimetry were used to assess the expression and function of TRPV4 in mediating Ca2+-dependent mechanical stimulation within a novel system of the human collecting duct (HCD). Results. Native and siRNA knockdown of TRPV4 protein expression was confirmed by western blot analysis. Touch was used as a cell-directed surrogate for osmotic stress. Mechanical stimulation of HCD cells evoked a transient increase in [Ca2+]i that was dependent upon thapsigargin-sensitive store release and Ca2+ influx. At 48 hrs, high glucose and mannitol (25 mM) reduced TRPV4 expression by 54% and 24%, respectively. Similar treatment doubled SGK1 expression. Touch-evoked changes were negated following TRPV4 knockdown. Conclusion. Our data confirm expression of Ca2+-dependent TRPV4 channels in HCD cells and suggest that a loss of expression in response to high glucose attenuates the ability of the collecting duct to exhibit regulatory volume decreases, an effect that may contribute to the pathology of fluid and electrolyte imbalance as observed in diabetic nephropathy

Visfatin reduces gap junction mediated cell-to-cell communication in proximal tubule-derived epithelial cells

Background/Aims: In the current study we examined if the adipocytokine, visfatin, alters connexin-mediated intercellular communication in proximal tubule-derived epithelial cells. Methods: The effects of visfatin (10-200ng/mL) on cell viability and cytotoxicity in HK2-cells were assessed by MTT, crystal violet and lactate dehydrogenase assays. Western blot analysis was used to confirm expression of Cx26, Cx40 and Cx43. The effect of visfatin (10-200ng/mL) on TGF-β1 secretion was confirmed by ELISA, and the effects of both TGF-β1 (2-10ng/mL) and visfatin (10-200ng/mL) on connexin expression were assessed by western blot. Functional intercellular communication was determined using transfer of Lucifer Yellow and paired-whole cell patch clamp electrophysiology. Results: In low glucose (5mM), visfatin (10-200ng/mL) did not affect membrane integrity, cytotoxicity or cell viability at 48hrs, but did evoke a concentration-dependent reduction in Cx26 and Cx43 expression. The expression of Cx40 was unaffected. At 48hrs, visfatin (10-200ng/mL) increased the secretion of TGF-β1 and the visfatin-evoked changes in connexin expression were mimicked by exogenous application of the pro-fibrotic cytokine (2-10ng/ml). Visfatin reduced dye transfer between coupled cells and decreased functional conductance, with levels falling by 63% as compared to control. Although input resistance was increased following visfatin treatment by 166%, the change was not significant as compared to control. The effects of visfatin on Cx-expression and cell-coupling were blocked in the presence of a TGF-β1 specific neutralizing antibody. Conclusions: The adipocytokine visfatin selectively evoked a non-toxic reduction in connexin expression in HK2-cells. The loss in gap-junction associated proteins was mirrored by a loss in functional conductance between coupled cells. Visfatin increased TGF-β secretion and the pattern of change for connexins expression was mimicked by exogenous application of TGF-β1. The effect of visfatin on Cx-expression and dye transfer were negated in the presence of a TGF-β1 neutralising antibody. These data suggest that visfatin reduces connexin-mediated intercellular communication in proximal tubule-derived epithelial cells via a TGF-β dependent pathway. © 2013 S. Karger AG, Base

Lorentz-invariant Bohmian mechanics

A derivation of the Bohm model, and some general comments about it, are given. A modification of the model which is formally local and Lorentz-invariant is introduced, and its properties studied for a simple experiment

Calcium-sensing receptor activation increases cell-cell adhesion and ß-cell function

Background/Aims: The extracellular calcium-sensing receptor (CaR) is expressed in pancreatic β-cells where it is thought to facilitate cell-to-cell communication and augment insulin secretion. However, it is unknown how CaR activation improves β-cell function. Methods: Immunocytochemistry and western blotting confirmed the expression of CaR in MIN6 β-cell line. The calcimimetic R568 (1µM) was used to increase the affinity of the CaR and specifically activate the receptor at a physiologically appropriate extracellular calcium concentration. Incorporation of 5-bromo-2’-deoxyuridine (BrdU) was used to measure cell proliferation, whilst changes in non-nutrient-evoked cytosolic calcium were assessed using fura-2-microfluorimetry. AFM-single-cell-force spectroscopy related CaR-evoked changes in epithelial (E)-cadherin expression to improved functional tethering between coupled cells. Results: Activation of the CaR over 48hr doubled the expression of E-cadherin (206±41%) and increased L-type voltage-dependent calcium channel expression by 70% compared to control. These changes produced a 30% increase in cell-cell tethering and elevated the basal-to-peak amplitude of ATP (50µM) and tolbutamide (100µM)-evoked changes in cytosolic calcium. Activation of the receptor also increased PD98059 (1-100µM) and SU1498 (1-100µM)-dependent β-cell proliferation. Conclusion: Our data suggest that activation of the CaR increases E-cadherin mediated functional tethering between β-cells and increases expression of L-type VDCC and secretagogue-evoked changes in [Ca2+]i. These findings could explain how local changes in calcium, co-released with insulin, activate the CaR on neighbouring cells to help ensure efficient and appropriate secretory function

The Differential Contributions of Auditory-verbal and Visuospatial Working Memory on Decoding Skills in Children Who Are Poor Decoders

This study investigated the differential contribution of auditory-verbal and visuospatial working memory (WM) on decoding skills in second- and fifth-grade children identified with poor decoding. Thirty-two second-grade students and 22 fifth-grade students completed measures that assessed simple and complex auditory-verbal and visuospatial memory, phonological awareness, orthographic knowledge, listening comprehension and verbal and nonverbal intelligence. Bivariate correlations revealed that complex auditory-verbal WM was moderately and significantly correlated to word attack at second grade. The simple auditory-verbal WM measure was moderately and significantly correlated to word identification in fifth grade. The complex visuospatial WM measures were not correlated to word identification or word attack for second-grade students. However, for fifth-grade participants, there was a negative correlation between a complex visuospatial WM measure and word attack and a positive correlation between orthographic knowledge and word identification. Different types of WM measures predicted word identification and word attack ability in second and fifth graders. We wondered whether the processes involved in visuospatial memory (the visuospatial sketchpad) or auditory-verbal memory (the phonological loop), acting alone, would predict decoding skills. They did not. Similarly, the cognitive control abilities related to executive functions (measured by our complex memory tasks), acting alone, did not predict decoding at either grade. The optimal prediction models for each grade involved various combinations of storage, cognitive control, and retrieval processes. Second graders appeared to rely more on the processes involved in auditory-verbal WM when identifying words, while fifth-grade students relied on the visuospatial domains to identify words. For second-grade students, both complex visuospatial and auditory-verbal WM predicted word attack ability, but by fifth grade, only the visual domains predicted word attack. This study has implications for training instruction in reading. It was not the individual contributions of auditory-verbal or visuospatial WM that best predicted reading ability in second and fifth grade decoders, but rather, a combination of factors. Training WM in isolation of other skills does not increase reading ability. In fact, for young students, too much WM storage can interfere with learning to decode

Do macroscopic properties dictate microscopic probabilities?

Aharonov and Reznik have recently (in quant-ph/0110093) argued that the form of the probabilistic predictions of quantum theory can be seen to follow from properties of macroscopic systems. An error in their argument is identified.Comment: LaTeX, 6 pages, no figure

Acute Liver Dysfunction Criteria in Critically Ill Children: The PODIUM Consensus Conference

CONTEXT Develop evidence-based criteria for individual organ dysfunction. OBJECTIVES Evaluate current evidence and develop contemporary consensus criteria for acute liver dysfunction with associated outcomes in critically ill children. DATA SOURCES Electronic searches of PubMed and Embase conducted from January 1992 to January 2020, used medical subject heading terms and text words to characterize acute liver dysfunction and outcomes. STUDY SELECTION Studies evaluating critically ill children with acute liver dysfunction, assessed screening tools, and outcomes were included. Studies evaluating adults, infants ≤36 weeks gestational age, or animals or were reviews/commentaries, case series with sample size ≤10, or non-English language studies were excluded. DATA EXTRACTION Data were abstracted from each eligible study into a data extraction form along with risk of bias assessment by a task force member. RESULTS The systematic review supports criteria for acute liver dysfunction, in the absence of known chronic liver disease, as having onset of symptoms <8 weeks, combined with biochemical evidence of acute liver injury, and liver-based coagulopathy, with hepatic encephalopathy required for an international normalized ratio between 1.5 and 2.0. LIMITATIONS Unable to assess acute-on-chronic liver dysfunction, subjective nature of hepatic encephalopathy, relevant articles missed by reviewers. CONCLUSIONS Proposed criteria identify an infant, child, or adolescent who has reached a clinical threshold where any of the 3 outcomes (alive with native liver, death, or liver transplant) are possible and should prompt an urgent liaison with a recognized pediatric liver transplant center if liver failure is the principal driver of multiple organ dysfunction