Sandra J Petty1,2,3,4,5, Carol J Milligan2, Marian Todaro1, Kay L Richards2, Pamuditha K Kularathna6, Charles N Pagel6, Chris R French1,3,5, Elisa L Hill-Yardin7, Terence J O'Brien1,3,5, John D Wark5,8, Eleanor J Mackie6, Steven Petrou2. 1. The Department of Medicine, Melbourne Brain Centre at The Royal Melbourne Hospital, The University of Melbourne, Parkville, Victoria, Australia. 2. The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia. 3. Department of Neurology, The Royal Melbourne Hospital, Parkville, Victoria, Australia. 4. Academic Centre, Ormond College, Parkville, Victoria, Australia. 5. Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Parkville, Victoria, Australia. 6. Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, Australia. 7. Department of Physiology, University of Melbourne, Parkville, Victoria, Australia. 8. Bone and Mineral Medicine, The Royal Melbourne Hospital, Parkville, Victoria, Australia.
Abstract
OBJECTIVE: Fracture risk is a serious comorbidity in epilepsy and may relate to the use of antiepileptic drugs (AEDs). Many AEDs inhibit ion channel function, and the expression of these channels in osteoblasts raises the question of whether altered bone signaling increases bone fragility. We aimed to confirm the expression of voltage-gated sodium (NaV ) channels in mouse osteoblasts, and to investigate the action of carbamazepine and phenytoin on NaV channels. METHODS: Immunocytochemistry was performed on primary calvarial osteoblasts extracted from neonatal C57BL/6J mice and additional RNA sequencing (RNASeq) was included to confirm expression of NaV . Whole-cell patch-clamp recordings were made to identify the native currents expressed and to assess the actions of carbamazepine (50 μm) or phenytoin (50 μm). RESULTS: NaV expression was demonstrated with immunocytochemistry, RNA sequencing, and functionally, with demonstration of robust tetrodotoxin-sensitive and voltage-activated inward currents. Application of carbamazepine or phenytoin resulted in significant inhibition of current amplitude for carbamazepine (31.6 ± 5.9%, n = 9; p < 0.001), and for phenytoin (35.5 ± 6.9%, n = 7; p < 0.001). SIGNIFICANCE: Mouse osteoblasts express NaV , and native NaV currents are blocked by carbamazepine and phenytoin, supporting our hypothesis that AEDs can directly influence osteoblast function and potentially affect bone strength. Wiley Periodicals, Inc.
OBJECTIVE:Fracture risk is a serious comorbidity in epilepsy and may relate to the use of antiepileptic drugs (AEDs). Many AEDs inhibit ion channel function, and the expression of these channels in osteoblasts raises the question of whether altered bone signaling increases bone fragility. We aimed to confirm the expression of voltage-gated sodium (NaV ) channels in mouse osteoblasts, and to investigate the action of carbamazepine and phenytoin on NaV channels. METHODS: Immunocytochemistry was performed on primary calvarial osteoblasts extracted from neonatal C57BL/6J mice and additional RNA sequencing (RNASeq) was included to confirm expression of NaV . Whole-cell patch-clamp recordings were made to identify the native currents expressed and to assess the actions of carbamazepine (50 μm) or phenytoin (50 μm). RESULTS:NaV expression was demonstrated with immunocytochemistry, RNA sequencing, and functionally, with demonstration of robust tetrodotoxin-sensitive and voltage-activated inward currents. Application of carbamazepine or phenytoin resulted in significant inhibition of current amplitude for carbamazepine (31.6 ± 5.9%, n = 9; p < 0.001), and for phenytoin (35.5 ± 6.9%, n = 7; p < 0.001). SIGNIFICANCE: Mouse osteoblasts express NaV , and native NaV currents are blocked by carbamazepine and phenytoin, supporting our hypothesis that AEDs can directly influence osteoblast function and potentially affect bone strength. Wiley Periodicals, Inc.
Authors: Brandon A Coates; Jennifer A McKenzie; Evan G Buettmann; Xiaochen Liu; Paul M Gontarz; Bo Zhang; Matthew J Silva Journal: Bone Date: 2019-07-29 Impact factor: 4.398