Recent Advances in the Pathogenesis and Drug Action in Periodic Paralyses and Related Channelopathies

The periodic paralysis (PP) are rare autosomal-dominant disorders associated to mutations in the skeletal muscle sodium, calcium, and potassium channel genes characterized by muscle fiber depolarization with un-excitability, episodes of weakness with variations in serum potassium concentrations. Recent advances in thyrotoxic PP and hypokalemic PP (hypoPP) confirm the involvement of the muscle potassium channels in the pathogenesis of the diseases and their role as target of action for drugs of therapeutic interest. The novelty in the gating pore currents theory help to explain the disease symptoms, and open the possibility to more specifically target the disease. It is now known that the fiber depolarization in the hypoPP is due to an unbalance between the novel identified depolarizing gating pore currents (Igp) carried by protons or Na+ ions flowing through aberrant alternative pathways of the mutant subunits and repolarizing inwardly rectifying potassium channel (Kir) currents which also includes the ATP-sensitive subtype. Abnormal activation of the Igp or deficiency in the Kir channels predispose to fiber depolarization. One pharmacological strategy is based on blocking the Igp without affecting normal channel gating. It remains safe and effective the proposal of targeting the KATP, Kir channels, or BK channels by drugs capable to specifically open at nanomolar concentrations the skeletal muscle subtypes with less side effects

Major channels involved in neuropsychiatric disorders and therapeutic perspectives

Voltage-gated ion channels are important mediators of physiological functions in the central nervous system. The cyclic activation of these channels influences neurotransmitter release, neuron excitability, gene transcription, and plasticity, providing distinct brain areas with unique physiological and pharmacological response. A growing body of data has implicated ion channels in the susceptibility or pathogenesis of psychiatric diseases. Indeed, population studies support the association of polymorphisms in calcium and potassium channels with the genetic risk for bipolar disorders (BPDs) or schizophrenia. Moreover, point mutations in calcium, sodium, and potassium channel genes have been identified in some childhood developmental disorders. Finally, antibodies against potassium channel complexes occur in a series of autoimmune psychiatric diseases. Here we report recent studies assessing the role of calcium, sodium, and potassium channels in BPD, schizophrenia, and autism spectrum disorders, and briefly summarize promising pharmacological strategies targeted on ion channels for the therapy of mental illness and related genetic tests

Acetazolamide opens the muscular K(Ca)2+ channel: A novel mechanism of action that may explain the therapeutic effect of the drug in hypokalemic periodic paralysis

Acetazolamide is a thiazide derivative clinically used in skeletal muscle disorders related to altered K+ homeostasis such as the periodic paralyses. The mechanism of action responsible for the therapeutic effects of the drug is still unknown, however. In the present work, we investigated the mechanism of action of acetazolamide in the K-deficient diet rat, an animal model of human hypokalemic periodic paralysis (hypoPP). The in vivo administration of 2.8- and 5.6-mg/kg-1/ day-1 concentrations of acetazolamide to K-deficient diet rats prevented paralysis and depolarization of the fibers induced by insulin. In the acetazolamide-treated animals, intense sarcolemma Ca2+-activated K+ channel (K(Ca)2+) activity was recorded. Acetazolamide also restored the serum K+ levels to control values. The concentrations of acetazolamide needed to enhance the K(Ca)2+ current by 50% in vitro were 6.17 and 4.01 x 10-6 M at -60 and +30 mV of membrane potentials, respectively. In normokalemic animals, the thiazide derivative enhanced the K(Ca)2+ current with similar efficacy. Our data demonstrate that the therapeutic effects of acetazolamide in the K-deficient diet rats and possibly in human hypokalemic periodic paralysis patients can be mediated by activation of the K(Ca)2+ channel

Laser-induced softening analysis of a hardened aluminum alloy by physical simulation

AbstractThe study focuses on the analysis of the softening effects of the work-hardened aluminum alloy sheets EN AW 5754 H32 1.5 mm thick, through the physical simulation of thermal cycles induced in the material by laser heat treatments (LHTs). A numerical-experimental approach was implemented to define the laser thermal cycles and to subsequently reproduce them on the GleebleTM 3180 physical simulator. The obtained softening was measured by microhardness and metallographic analysis tests. For the definition of laser thermal cycles, preliminary tests with a 2.5 kW CO2 laser source have been realized, and a three-dimensional transient finite element thermal models were developed and calibrated with the experimental results. The investigated laser heat treatment parameters explored thermal cycles with different shape, interaction time, and peak temperature. Physical simulation tests were performed using laser thermal cycles that showed the maximum softening of the aluminum alloy. A three-dimensional transient finite element thermoelectric model was developed to design the shape of the Gleeble specimens, which satisfy the heating and cooling rate required by laser thermal cycles. Results obtained show that it is possible to physically simulate the investigated laser thermal cycles, reducing the cross section of the shaped part of the specimen. Softening effects depend on the thermal cycle shape. Greater softening is observed by increasing the interaction time and the peak temperature, but beyond a peak temperature threshold value, negligible effects are detected

Molecular modeling of antibodies for the treatment of TNFα-related immunological diseases

Therapeutic monoclonal antibodies (mAbs) have high efficacy in treating TNF α-related immunological diseases. Other than neutralizing TNF α, these IgG1 antibodies exert Fc receptor-mediated effector functions such as the complement-dependent cytotoxicity (CDC) and antibody-dependent cell cytotoxicity (ADCC). The crystallizable fragment (Fc) of these IgG1 contains a single glycosylation site at Asn 297/300 that is essential for the CDC and ADCC. Glycosylated antibodies lacking core fucosylation showed an improved ADCC. However, no structural data are available concerning the ligand-binding interaction of these mAbs used in TNF α-related diseases and the role of the fucosylation. We therefore used comparative modeling for generating complete 3D mAb models that include the antigen-binding fragment (Fab) portions of infliximab, complexed with TNF α (4G3Y.pdb), the Fc region of the human IGHG1 fucosylated (3SGJ) and afucosylated (3SGK) complexed with the Fc receptor subtype Fcγ RIIIA, and the Fc region of a murine immunoglobulin (1IGT). After few thousand steps of energy minimization on the resulting 3D mAb models, minimized final models were used to quantify interactions occurring between Fcγ RIIIA and the fucosylated/afucosylated Fc fragments. While fucosylation does not affect Fab-TNF α interactions, we found that in the absence of fucosylation the Fc-mAb domain and Fcγ RIIIA are closer and new strong interactions are established between G129 of the receptor and S301 of the Chimera 2 Fc mAb; new polar interactions are also established between the Chimera 2 Fc residues Y299, N300, and S301 and the Fcγ RIIIA residues K128, G129, R130, and R155. These data help to explain the reduced ADCC observed in the fucosylated mAbs suggesting the specific AA residues involved in binding interactions

Convolutional Neural Network-Based Automatic Analysis of Chest Radiographs for the Detection of COVID-19 Pneumonia: A Prioritizing Tool in the Emergency Department, Phase I Study and Preliminary “Real Life” Results

The aim of our study is the development of an automatic tool for the prioritization of COVID-19 diagnostic workflow in the emergency department by analyzing chest X-rays (CXRs). The Convolutional Neural Network (CNN)-based method we propose has been tested retrospectively on a single-center set of 542 CXRs evaluated by experienced radiologists. The SARS-CoV-2 positive dataset (n = 234) consists of CXRs collected between March and April 2020, with the COVID-19 infection being confirmed by an RT-PCR test within 24 h. The SARS-CoV-2 negative dataset (n = 308) includes CXRs from 2019, therefore prior to the pandemic. For each image, the CNN computes COVID-19 risk indicators, identifying COVID-19 cases and prioritizing the urgent ones. After installing the software into the hospital RIS, a preliminary comparison between local daily COVID-19 cases and predicted risk indicators for 2918 CXRs in the same period was performed. Significant improvements were obtained for both prioritization and identification using the proposed method. Mean Average Precision (MAP) increased (p < 1.21 × 10(−21) from 43.79% with random sorting to 71.75% with our method. CNN sensitivity was 78.23%, higher than radiologists’ 61.1%; specificity was 64.20%. In the real-life setting, this method had a correlation of 0.873. The proposed CNN-based system effectively prioritizes CXRs according to COVID-19 risk in an experimental setting; preliminary real-life results revealed high concordance with local pandemic incidence

Zoledronic acid blocks overactive Kir6.1/SUR2-dependent KATP channels in skeletal muscle and osteoblasts in a murine model of Cantú syndrome

Cantú syndrome (CS) is caused by the gain of function mutations in th

Molecular determinants for the activating/blocking actions of the 2H-1,4-benzoxazine derivatives, a class of potassium channel modulators targeting the skeletal muscle KATP channels

The 2H-1,4-benzoxazine derivatives are modulators of the skeletal muscle ATP-sensitive-K+ channels (KATP), activating it in the presence of ATP but inhibiting it in the absence of nucleotide. To investigate the molecular determinants for the activating/blocking actions of these compounds, novel molecules with different alkyl or aryl-alkyl substitutes at position 2 of the 1,4-benzoxazine ring were prepared. The effects of the lengthening of the alkyl chain and of branched substitutes, as well as of the introduction of aliphatic/aromatic rings on the activity of the molecules, were investigated on the skeletal muscle KATP channels of the rat, in excised-patch experiments, in the presence or absence of internal ATP (10 -4 M). In the presence of ATP, the 2-n-hexyl analog was the most potent activator (DE50 = 1.08 × 10-10 M), whereas the 2-phenylethyl was not effective. The rank order of efficacy of the openers was 2-n-hexyl ≥2-cyclohexylmethyl &gt;2-isopropyl = 2-n-butyl = 2-phenyl ≥ 2-benzyl = 2-isobutyl analogs. In the absence of ATP, the 2-phenyl analog was the most potent inhibitor (IC50 = 2.5 × 10-11 M); the rank order of efficacy of the blockers was 2-phenyl ≥ 2-n-hexyl &gt; 2-n-butyl &gt; 2-cyclohexylmethyl, whereas the 2-phenylethyl, 2-benzyl, and 2-isobutyl 1,4-benzoxazine analogs were not effective; the 2-isopropyl analog activated the KATP channel even in the absence of nucleotide. Therefore, distinct molecular determinants for the activating or blocking actions for these compounds can be found. For example, the replacement of the linear with the branched alkyl substitutes at the position 2 of the 1,4-benzoxazine nucleus determines the molecular switch from blockers to openers. These compounds were 100-fold more potent and effective as openers than other KCO against the muscle KATP channels. Copyright © 2008 The American Society for Pharmacology and Experimental Therapeutics