LncRNA H19-EZH2 interaction promotes liver fibrosis via reprogramming H3K27me3 profiles

Liver fibrosis is a wound-healing process characterized by excess formation of extracellular matrix (ECM) from activated hepatic stellate cells (HSCs). Previous studies show that both EZH2, an epigenetic regulator that catalyzes lysine 27 trimethylation on histone 3 (H3K27me3), and long non-coding RNA H19 are highly correlated with fibrogenesis. In the current study, we investigated the underlying mechanisms. Various models of liver fibrosis including Mdr2-/-, bile duct ligation (BDL) and CCl4 mice were adapted. We found that EZH2 was markedly upregulated and correlated with H19 and fibrotic markers expression in these models. Administration of EZH2 inhibitor 3-DZNeP caused significant protective effects in these models. Furthermore, treatment with 3-DZNeP or GSK126 significantly inhibited primary HSC activation and proliferation in TGF-β-treated HSCs and H19-overexpreesing LX2 cells in vivo. Using RNA-pull down assay combined with RNA immunoprecipitation, we demonstrated that H19 could directly bind to EZH2. Integrated analysis of RNA-sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) further revealed that H19 regulated the reprogramming of EZH2-mediated H3K27me3 profiles, which epigenetically promoted several pathways favoring HSCs activation and proliferation, including epithelial-mesenchymal transition and Wnt/β-catenin signaling. In conclusion, highly expressed H19 in chronic liver diseases promotes fibrogenesis by reprogramming EZH2-mediated epigenetic regulation of HSCs activation. Targeting the H19-EZH2 interaction may serve as a novel therapeutic approach for liver fibrosis.

Expression, purification, and biochemical characterization of the amino-terminal extracellular domain of the human calcium receptor

We purified the extracellular domain (ECD) of the human calcium receptor (hCaR) from the medium of HEK-293 cells stably transfected with a hCaR cDNA containing an isoleucine 599 nonsense mutation. A combination of lectin, anion exchange, and gel permeation chromatography yielded milligram quantities of >95% pure protein from 15 liters of starting culture medium. The purified ECD ran as an approximately 78-kDa protein on SDS-polyacrylamide gel electrophoresis and was found to be a disulfide-linked dimer. Its NH2-terminal sequence, carbohydrate content, and CD spectrum were defined. Tryptic proteolysis studies showed two major sites accessible to cleavage. These studies provide new insights into the structure of the hCaR ECD. Availability of purified ECD protein should permit further structural studies to help define the mechanism of Ca2+ activation of this G protein-coupled receptor.

Mutational analysis of the cysteines in the extracellular domain of the human Ca2+ receptor: effects on cell surface expression, dimerization and signal transduction

Mammalian calcium receptors (CaRs) share with the metabotropic glutamate receptors (mGluRs) the relative positions of 16 cysteine residues in the amino-terminal extracellular domain. To investigate the role of these cysteines, a series of mutants in the extracellular domain of the human CaR was prepared in which each of these 16 cysteine residues and three others not conserved in the mGluRs were replaced by serines. Wild-type and mutant CaR cDNAs were expressed in HEK-293 cells, and evaluated for expression and response to extracellular calcium. Mutation of three non-conserved cysteines and of two conserved cysteines produced proteins with near wild-type phenotype. In contrast, mutation of the other conserved cysteines gave proteins that showed drastic reduction in cell surface expression and/or failed to respond to calcium. We identified 14 cysteines essential for proper trafficking and function of the receptor, two of which may be involved in formation of a disulfide-linked dimer.

The carboxyl terminus of the human calcium receptor. Requirements for cell-surface expression and signal transduction

The G-protein-coupled calcium receptor plays a key role in extracellular calcium homeostasis. To examine the role of the membrane-spanning domains and the approximately 200-residue cytoplasmic carboxyl terminus of the calcium receptor in cell-surface expression and signal transduction, we transfected HEK-293 cells with a series of truncation and carboxyl-terminal missense mutants and analyzed expression by immunoblotting, glycosidase digestion, intact cell immunoassay, and extracellular calcium-stimulated phosphoinositide hydrolysis assay. Two truncation mutants terminating at residues 706 and 802 within the second and third intracellular loops, respectively, were not properly glycosylated, failed to reach the cell-surface, and showed no calcium response, indicating that mutant receptors with the full extracellular domain but only three or five transmembrane domains are improperly folded and/or processed. Truncation mutants terminating at residues 888 and 903 within the carboxyl terminus were equivalent to the wild type in all assays, whereas mutants truncated at residues 865 and 874 showed no response to calcium, despite only approximately 25% reduction in cell-surface expression. Mutants with a full-length carboxyl terminus but with residues between positions 874 and 888 replaced with alanines showed either no (Ala875, Ala876, and Ala879) or significantly reduced (Ala881-Ala883) calcium response at levels of cell-surface expression equivalent to those of the wild-type receptor. These results indicate that deletion of the majority of the carboxyl terminus is compatible with normal processing, cell-surface expression, and signal transduction of the receptor. The truncation and alanine substitution mutants identify a small region between residues 874 and 888 critical for normal signal transduction by the receptor.

A Ca(2+)-sensing receptor mutation causes hypoparathyroidism by increasing receptor sensitivity to Ca2+ and maximal signal transduction

Activating mutations of the Ca(2+)-sensing receptor (CaR) gene cause autosomal dominant hypoparathyroidism. Functional expression studies have been reported for several mutations, but have produced conflicting results. Thus, the mechanism by which these mutations activate the receptor is unclear. We describe here a new family with autosomal dominant hypoparathyroidism. The mother and three daughters experienced muscle spasms and/or seizures from early childhood. They were treated with oral calcium and vitamin D analogs, and all four patients developed hypercalciuria, nephrocalcinosis, and renal insufficiency. In this family, we identified a heterozygous missense mutation (F612S) involving the extracellular region of the CaR. The mutation cosegregated with disease. It was not present in 50 normal control individuals. We used site-directed mutagenesis to introduce this mutation into the CaR cDNA, and then expressed the mutant receptor in human embryonic kidney (HEK)-293 cells. In these cells, the accumulation of inositol phosphates was measured as a function of extracellular Ca2+ concentration. Compared with the wild-type receptor, the mutant receptor showed a left-shift in the concentration-response curve and an increase in the maximal response to high Ca2+ concentration. These effects did not appear to be mediated by changes in levels of receptor expression, as judged by ELISA, or by changes in receptor glycosylation, as judged by Western analysis. We conclude that this CaR mutation causes hypoparathyroidism by a dual increase in receptor sensitivity to extracellular Ca2+ and maximal signal transduction capacity.

Sporadic hypoparathyroidism caused by de Novo gain-of-function mutations of the Ca(2+)-sensing receptor

Activating mutations of the Ca(2+)-sensing receptor (CaR) gene have been identified in families with autosomal dominant hypoparathyroidism and in one patient with sporadic hypoparathyroidism. Here, we describe two additional patients with sporadic hypoparathyroidism. One patient presented with mild symptoms at age 18 yr; the other was severely symptomatic from infancy. A heterozygous missense mutation was identified in each patient. One mutation (L773R) involved the fifth transmembrane domain of the CaR, the other (N118K) affected the amino-terminal, extracellular domain. In both cases, the probands' parents lacked the mutation, indicating that the mutations arose de novo. In expression studies the mutations shifted the concentration-response curve to the left and increased maximal activity. We conclude that 1) sporadic hypoparathyroidism can be caused by de novo gain-of-function mutations of the CaR; 2) the phenotype can vary from mild to life-threatening hypocalcemia; 3) gain-of-function mutations can involve not only extracellular regions, as previously reported, but also transmembrane domains of the CaR; and 4) the mechanism of activation can involve both increased receptor sensitivity to Ca2+ and increased maximal signal transduction.

Posterior bow and vanishing line signs in diagnosis of burst fractures of the spine on plain radiographs

It is not uncommon to misdiagnose a burst fracture as a wedge compression fracture initially on plain film, resulting in a late progressive deformity and neurologic damage. The purpose of this study was to analyze the sensitivity, specificity and positive predictive value of plain radiographs in the diagnosis of thoracic and lumbar burst fractures using the posterior bow (PB) and vanishing line (VL) signs. Seven independent examiners, comprising three chief orthopedic residents, two radiologic third-year residents and two emergency attending physicians (orthopedists), randomly reviewed 26 sets of admission anteroposterior and lateral thoracolumbar spine radiographs taken in association with back injuries. They were asked to decide whether patients had a burst or a wedge compression fracture. All patients had computed tomography (CT) scans for diagnostic confirmation. The overall initial sensitivity using discriminant analysis in the diagnosis of burst fractures was 80%. This increased to 90% after the examiners were requested to use the PB and VL signs. The specificity decreased slightly from 75% to 71%, while the positive predictive value remained at 88%. Overdiagnosis of wedge compression fractures as burst fractures occurred, especially when the quality of the films was not ideal. We conclude that, with careful reading, the PB and VL signs help in identifying burst fractures on the initial plain film evaluation.

Effect of transmembrane Ca2+ gradient on the coupling of beta-adrenergic receptors and adenylyl cyclase

In order to investigate the effect of transmembrane Ca2+ gradient on Gs mediated coupling of beta-AR and adenylyl cyclase, beta-AR from duck erythrocytes and Gs and adenylyl cyclase from bovine brain cortices were co-reconstituted into asolectin liposomes with different transmembrane Ca2+ gradient. These proteoliposomes were proven to be impermeable to water-soluble substances. The results obtained indicate that a physiological transmembrane Ca2+ gradient (1000-fold) is essential for higher stimulation of adenylyl cyclase by hormone-activated beta-AR via coupling to Gs and can be further enhanced by the decrease of such Ca2+ gradient within certain range (100 fold) following Ca2+ influx into cells during signal transduction. Fluorescence polarization of DPH revealed that transmembrane Ca2+ gradient modulates adenylyl cyclase and its stimulation by hormones through mediating a change in lipid fluidity. Correspondent conformational changes of beta-AR were also detected from the fluorescence spectra and quenching of Acrylodan-labelled beta-AR in those proteoliposomes. It is suggested that a proper transmembrane Ca2+ gradient is essential for the optimal fluidity of the phospholipid bilayer in the proteoliposomes, which favors the formation of a suitable conformation of the reconstituted beta-AR and thus promotes the stimulation of adenylyl cyclase activities by hormone-activated beta-AR via Gs.

Two-level burst fractures: clinical evaluation and treatment options

Two-level burst fractures are rare. In a series of 180 surgically treated spinal fracture-dislocations, seven had such injuries, with an incidence of 3.9%. Four had fracture sites without contiguity: C4-T12 (one), L1-L4 (one), L2-L4 (one), and L2-L5 (one); and three with contiguity: T12-L1 (one), L1-L2 (one), and L2-L3 (one). L2 was the most frequently involved site, accounting for four in seven. Falling from height was the most common mechanism of injury, accounting for four in seven. Five in seven patients (71%) sustained multiple injuries. Chest traumas and extremity fractures were the ones most frequently associated. All of these patients had incomplete neurologic deficits at initial presentation. In the four discontiguous bursts, the neurologic levels corresponded to the cephalic ones. Six patients had follow-up periods of more than 2 years. Transpediculate systems were used in five, and at follow-up, two had screw breakages. In this series, the average neurologic recovery was 1.3 grades on the Frankel scale. In conclusion, it is mandatory to have a thorough organ system review when such patients are first seen. Then each fracture site would be judged seperately as either a stable or unstable burst preoperatively. Every effort should be made to treat any unstable segment via anterior, posterior, or combined approaches.

A follow-up study of porous-coated anatomic knee arthroplasty

Ninety-four patients (105 knees) having a porous-coated anatomic total knee arthroplasty were retrospectively studied. The mean follow-up period was 5.8 years. The diagnoses were osteoarthritis (90.5%) and rheumatoid arthritis (9.5%). There were 80 women and 14 men. The mean age at operation was 58.5 years. Clinical evaluation, using the Hospital for Special Surgery knee score along with radiography, was used to assess knee status before and after surgery. The postoperative mean axial alignment was 3 degrees varus compared with 11 degrees varus before surgery. Placement of the prosthetic components was acceptable, with the femoral component in 6.5 degrees of valgus and the tibial component in 1.9 degrees of varus and 1.1 degrees posterior inclination. Complications included eight aseptic loosenings, four patellar maltrackings, one patellar fracture, eight wound problems, and one extension contracture. Most of the patients' knee function improved after surgery. The initial, postoperative range of motion improved in patients receiving continuous passive motion (CPM) immediately after surgery (P = .03) compared to patients without CPM application; however, the long-term follow-up data show no significance (P = .06) whether CPM was used or not. Age, body weight, degree of arthritic change, and modes of fixation yielded no significant influence on the final outcome. The porous-coated anatomic total knee arthroplasty is a valuable alternative procedure in the advanced arthritic knee when the proper candidates are selected, accurate surgical technique is executed and a suitable fixation mode is chosen.

Effect of transmembrane Ca2+ gradient on Gs function

Gs and adenylate cyclase from bovine brain cortices were co-reconstituted into asolectin liposomes with or without 1000-fold transmembrane Ca2+ gradient. Obtained results showed that Gs activities of both binding GTP gamma S and stimulating adenylate cyclase were the highest in proteoliposomes, with a transmembrane Ca2+ gradient similar to the physiological situation and the lowest while the transmembrane Ca2+ gradient was in the inverse direction. Such a difference could be diminished following the dissipation of the transmembrane Ca2+ gradient by A23187. Time-resolved fluorescence anisotropy of diphenylhexatriene (DPH) has been used to compare the physical state of phospholipids among those proteoliposomes. It is suggested that a proper transmembrane Ca2+ gradient is essential for higher membrane fluidity, which may favor Gs function with higher GTP-binding activity and stimulation of adenylate cyclase.

Olecranon fractures treated with tension band wiring techniques--comparisons among three different configurations

Retrospective comparisons were conducted among 3 different configurations of tension band wiring techniques for adult olecranon fractures. The follow-up period was at least one year (average 26 months). All 3 configurations achieved high union rates with an average of 3.4 months to achieve union. However, the olecranon screw group or Kirschner wire group had a relatively higher satisfactory rate than the Rush pin group, even though there was no significance in statistics (P > 0.05). Complications were few, and implant migration occurred in the Rush pin or Kirschner wire group. The complications were not difficult to manage. The authors conclude that for olecranon fractures with a large fragment, olecranon screw or Kirschner wire can be chosen. For olecranon fractures with a small fragment, Kirschner wire should be utilized.