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Figueroa L, Kraeva N, Manno C, Toro S, Ríos E, Riazi S. Abnormal calcium signalling and the caffeine-halothane contracture test. Br J Anaesth 2019; 122:32-41. [PMID: 30579404 PMCID: PMC6334558 DOI: 10.1016/j.bja.2018.08.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/16/2018] [Accepted: 08/06/2018] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The variable clinical presentation of malignant hyperthermia (MH), a disorder of calcium signalling, hinders its diagnosis and management. Diagnosis relies on the caffeine-halothane contracture test, measuring contraction forces upon exposure of muscle to caffeine or halothane (FC and FH, respectively). Patients with above-threshold FC or FH are diagnosed as MH susceptible. Many patients test positive to halothane only (termed 'HH'). Our objective was to determine the characteristics of these HH patients, including their clinical symptoms and features of cytosolic Ca2+ signalling related to excitation-contraction coupling in myotubes. METHODS After institutional ethics committee approval, recruited patients undergoing contracture testing at Toronto's MH centre were assigned to three groups: HH, doubly positive (HS), and negative patients (HN). A clinical index was assembled from musculoskeletal symptoms and signs. An analogous calcium index summarised four measures in cultured myotubes: resting [Ca2+]cytosol, frequency of spontaneous cytosolic Ca2+ events, Ca2+ waves, and cell-wide Ca2+ spikes after electrical stimulation. RESULTS The highest values of both indexes were found in the HH group; the differences in calcium index between HH and the other groups were statistically significant. The principal component analysis confirmed the unique cell-level features of the HH group, and identified elevated resting [Ca2+]cytosol and spontaneous event frequency as the defining HH characteristics. CONCLUSIONS These findings suggest that HH pathogenesis stems from excess Ca2+ leak through sarcoplasmic reticulum channels. This identifies HH as a separate diagnostic group and opens their condition to treatment based on understanding of pathophysiological mechanisms.
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Affiliation(s)
- L Figueroa
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - N Kraeva
- Malignant Hyperthermia Investigation Unit of the University Health Network, Toronto, ON, Canada; Department of Anaesthesia & Pain Management, Toronto General Hospital, University of Toronto, Toronto, ON, Canada
| | - C Manno
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - S Toro
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - E Ríos
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.
| | - S Riazi
- Malignant Hyperthermia Investigation Unit of the University Health Network, Toronto, ON, Canada; Department of Anaesthesia & Pain Management, Toronto General Hospital, University of Toronto, Toronto, ON, Canada
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Todd JJ, Razaqyar MS, Witherspoon JW, Lawal TA, Mankodi A, Chrismer IC, Allen C, Meyer MD, Kuo A, Shelton MS, Amburgey K, Niyazov D, Fequiere P, Bönnemann CG, Dowling JJ, Meilleur KG. Novel Variants in Individuals with RYR1-Related Congenital Myopathies: Genetic, Laboratory, and Clinical Findings. Front Neurol 2018; 9:118. [PMID: 29556213 PMCID: PMC5845096 DOI: 10.3389/fneur.2018.00118] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 02/19/2018] [Indexed: 12/23/2022] Open
Abstract
The ryanodine receptor 1-related congenital myopathies (RYR1-RM) comprise a spectrum of slow, rare neuromuscular diseases. Affected individuals present with a mild-to-severe symptomatology ranging from proximal muscle weakness, hypotonia and joint contractures to scoliosis, ophthalmoplegia, and respiratory involvement. Although there is currently no FDA-approved treatment for RYR1-RM, our group recently conducted the first clinical trial in this patient population (NCT02362425). This study aimed to characterize novel RYR1 variants with regard to genetic, laboratory, muscle magnetic resonance imaging (MRI), and clinical findings. Genetic and histopathology reports were obtained from participant's medical records. Alamut Visual Software was used to determine if participant's variants had been previously reported and to assess predicted pathogenicity. Physical exams, pulmonary function tests, T1-weighted muscle MRI scans, and blood measures were completed during the abovementioned clinical trial. Six novel variants (two de novo, three dominant, and one recessive) were identified in individuals with RYR1-RM. Consistent with established RYR1-RM histopathology, cores were observed in all biopsies, except Case 6 who exhibited fiber-type disproportion. Muscle atrophy and impaired mobility with Trendelenburg gait were the most common clinical symptoms and were identified in all cases. Muscle MRI revealed substantial inter-individual variation in fatty infiltration corroborating the heterogeneity of the disease. Two individuals with dominant RYR1 variants exhibited respiratory insufficiency: a clinical symptom more commonly associated with recessive RYR1-RM cases. This study demonstrates that a genetics-led approach is suitable for the diagnosis of suspected RYR1-RM which can be corroborated through histopathology, muscle MRI and clinical examination.
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Affiliation(s)
- Joshua J Todd
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Muslima S Razaqyar
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Jessica W Witherspoon
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Tokunbor A Lawal
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Ami Mankodi
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke--NINDS (NIH), Bethesda, MD, United States
| | - Irene C Chrismer
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Carolyn Allen
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Mary D Meyer
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Anna Kuo
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Monique S Shelton
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
| | - Kim Amburgey
- Division of Neurology, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Dmitriy Niyazov
- Department of Pediatrics, Ochsner Medical Center, New Orleans, LA, United States
| | - Pierre Fequiere
- Division of Neurology, Children's of Alabama, Birmingham, AL, United States
| | - Carsten G Bönnemann
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke--NINDS (NIH), Bethesda, MD, United States
| | - James J Dowling
- Department of Paediatrics, Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, Hospital for Sick Children, Toronto, ON, Canada
| | - Katherine G Meilleur
- Neuromuscular Symptoms Unit, National Institute of Nursing Research (NIH), Bethesda, MD, United States
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A chemical chaperone improves muscle function in mice with a RyR1 mutation. Nat Commun 2017; 8:14659. [PMID: 28337975 PMCID: PMC5376670 DOI: 10.1038/ncomms14659] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 01/20/2017] [Indexed: 12/28/2022] Open
Abstract
Mutations in the RYR1 gene cause severe myopathies. Mice with an I4895T mutation in the type 1 ryanodine receptor/Ca2+ release channel (RyR1) display muscle weakness and atrophy, but the underlying mechanisms are unclear. Here we show that the I4895T mutation in RyR1 decreases the amplitude of the sarcoplasmic reticulum (SR) Ca2+ transient, resting cytosolic Ca2+ levels, muscle triadin content and calsequestrin (CSQ) localization to the junctional SR, and increases endoplasmic reticulum (ER) stress/unfolded protein response (UPR) and mitochondrial ROS production. Treatment of mice carrying the I4895T mutation with a chemical chaperone, sodium 4-phenylbutyrate (4PBA), reduces ER stress/UPR and improves muscle function, but does not restore SR Ca2+ transients in I4895T fibres to wild type levels, suggesting that decreased SR Ca2+ release is not the major driver of the myopathy. These findings suggest that 4PBA, an FDA-approved drug, has potential as a therapeutic intervention for RyR1 myopathies that are associated with ER stress. Mutations in the RyR1 channel cause core myopathies. Here the authors show that ER stress and the unfolded protein response underlie the pathology caused by a common RyR1 channel mutation, and show that treatment with a chemical chaperone restores muscle function in mice.
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