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Hashitani H, Takeya M, van Helden DF. Commonality and heterogeneity of pacemaker mechanisms in the male reproductive organs. J Physiol 2024. [PMID: 38607187 DOI: 10.1113/jp284756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 03/26/2024] [Indexed: 04/13/2024] Open
Abstract
During emission, the first phase of ejaculation, smooth muscle in organs of the male reproductive tract (MRT) vigorously contract upon sympathetic nerve excitation to expel semen consisting of sperm and seminal plasma. During inter-ejaculation phases, the epididymis, seminal vesicles and prostate undergo spontaneous phasic contractions (SPCs), this transporting and maintaining the quality of sperm and seminal plasma. Recent studies have revealed platelet-derived growth factor receptor α-expressing (PDGFRα+) subepithelial interstitial cells in seminal vesicles subserve the role of pacemaker cells that electrically drive SPCs in this organ. PDGFRα+ smooth muscle cells in the epididymis also appear to function as pacemaker cells implicating PDGFRα as a potential signature molecule in MRT pacemaking. The dominant mechanism driving pacemaking in these organs is the cytosolic Ca2+ oscillator. This operates through entrainment of the release-refill cycle of Ca2+ stores, the released Ca2+ ions opening Ca2+-activated chloride channels, including in some cases ANO1 (TMEM16A), with the resultant pacemaker potential activating L-type voltage-dependent Ca2+ channels in the smooth muscle causing contraction (viz. SPCs). A second pacemaker mechanism, namely the membrane oscillator also has a role in specific cases. Further investigations into the commonality and heterogeneity of MRT pacemakers will open an avenue for understanding the pathogenesis of male infertility associated with deterioration of seminal plasma.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Mitsue Takeya
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, Kurume, Japan
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, Faculty of Health, Medicine and Wellbeing & Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia
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Walweel K, Beard N, van Helden DF, Laver DR. Dantrolene inhibition of ryanodine channels (RyR2) in artificial lipid bilayers depends on FKBP12.6. J Gen Physiol 2023; 155:e202213277. [PMID: 37279522 PMCID: PMC10244881 DOI: 10.1085/jgp.202213277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 03/18/2023] [Accepted: 05/22/2023] [Indexed: 06/08/2023] Open
Abstract
Dantrolene is a neutral hydantoin that is clinically used as a skeletal muscle relaxant to prevent overactivation of the skeletal muscle calcium release channel (RyR1) in response to volatile anesthetics. Dantrolene has aroused considerable recent interest as a lead compound for stabilizing calcium release due to overactive cardiac calcium release channels (RyR2) in heart failure. Previously, we found that dantrolene produces up to a 45% inhibition RyR2 with an IC50 of 160 nM, and that this inhibition requires the physiological association between RyR2 and CaM. In this study, we tested the hypothesis that dantrolene inhibition of RyR2 in the presence of CaM is modulated by RyR2 phosphorylation at S2808 and S2814. Phosphorylation was altered by incubations with either exogenous phosphatase (PP1) or kinases; PKA to phosphorylate S2808 or endogenous CaMKII to phosphorylate S2814. We found that PKA caused selective dissociation of FKBP12.6 from the RyR2 complex and a loss of dantrolene inhibition. Rapamycin-induced FKBP12.6 dissociation from RyR2 also resulted in the loss of dantrolene inhibition. Subsequent incubations of RyR2 with exogenous FKBP12.6 reinstated dantrolene inhibition. These findings indicate that the inhibitory action of dantrolene on RyR2 depends on RyR2 association with FKBP12.6 in addition to CaM as previously found.
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Affiliation(s)
- Kafa Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, Australia
| | - Nicole Beard
- Faculty of Science and Technology, University of Canberra, Bruce, Australia
| | - Dirk F. van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, Australia
| | - Derek R. Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, Australia
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Tamanna S, Morosin SK, Delforce SJ, van Helden DF, Lumbers ER, Pringle KG. Renin-angiotensin system (RAS) enzymes and placental trophoblast syncytialisation. Mol Cell Endocrinol 2022; 547:111609. [PMID: 35202745 DOI: 10.1016/j.mce.2022.111609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 02/14/2022] [Accepted: 02/18/2022] [Indexed: 10/19/2022]
Abstract
Placental renin-angiotensin system (RAS) components; prorenin, angiotensinogen, and angiotensin (Ang) II type 1 receptor (AT1R) are upregulated during syncytialisation. This study examined whether angiotensin-converting enzyme (ACE), ACE2 and neprilysin (NEP) are also altered during syncytialisation. Two in vitro models of syncytialisation were used: forskolin-treated BeWo cells and spontaneously syncytialising primary human trophoblast cells. Term placentae and primary trophoblasts had the highest levels of ACE, ACE2 and NEP mRNA. In primary trophoblasts, ACE mRNA levels significantly increased with syncytialisation, ACE2 and NEP mRNA levels decreased. ACE, ACE2 and NEP protein levels and ACE2 activity did not change. Syncytialisation of primary trophoblasts decreased soluble (s)ACE and sNEP but not sACE2 levels. In primary trophoblasts, the balance between the enzymes controlling the two opposing pathways of the RAS was maintained. These findings were unable to be reproduced in BeWo cells. Future studies exploring placental levels of these enzymes in pregnancies complicated by placental insufficiency are warranted.
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Affiliation(s)
- Sonia Tamanna
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia; Pregnancy and Reproduction Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia; Department of Biochemistry and Molecular Biology, University of Dhaka, Dhaka, Bangladesh
| | - Saije K Morosin
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia; Pregnancy and Reproduction Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia
| | - Sarah J Delforce
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia; Pregnancy and Reproduction Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia
| | - Eugenie R Lumbers
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia; Pregnancy and Reproduction Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia
| | - Kirsty G Pringle
- School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle, Newcastle, NSW, Australia; Pregnancy and Reproduction Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia; Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.
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van Helden DF. Insights into permeability control of the fenestrated endothelium of the jejunal microvasculature. Pflugers Arch 2022; 474:485-486. [PMID: 35243520 DOI: 10.1007/s00424-022-02680-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 10/18/2022]
Affiliation(s)
- Dirk F van Helden
- Faculty of Health & Medicine and Hunter Medical Research Institute, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, NSW, 2308, Australia.
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Tamanna S, Clifton VL, Rae K, van Helden DF, Lumbers ER, Pringle KG. Corrigendum: Angiotensin Converting Enzyme 2 (ACE2) in Pregnancy: Preeclampsia and Small for Gestational Age. Front Physiol 2021; 12:692761. [PMID: 34093245 PMCID: PMC8173707 DOI: 10.3389/fphys.2021.692761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 04/16/2021] [Indexed: 11/24/2022] Open
Affiliation(s)
- Sonia Tamanna
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
| | - Vicki L Clifton
- School of Medicine, Robinson Research Institute, University of Adelaide, Adelaide, SA, Australia.,Mater Medical Research Institute and Translational Research Institute, University of Queensland, Brisbane, QLD, Australia
| | - Kym Rae
- Mater Medical Research Institute and Translational Research Institute, University of Queensland, Brisbane, QLD, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia
| | - Eugenie R Lumbers
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
| | - Kirsty G Pringle
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
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Ferdoushi A, Griffin N, Marsland M, Xu X, Faulkner S, Gao F, Liu H, King SJ, Denham JW, van Helden DF, Jobling P, Jiang CC, Hondermarck H. Tumor innervation and clinical outcome in pancreatic cancer. Sci Rep 2021; 11:7390. [PMID: 33795769 PMCID: PMC8017010 DOI: 10.1038/s41598-021-86831-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 03/09/2021] [Indexed: 02/06/2023] Open
Abstract
Pancreatic cancer is a highly aggressive malignancy characterized by poor survival, recurrence after surgery and resistance to therapy. Nerves infiltrate the microenvironment of pancreatic cancers and contribute to tumor progression, however the clinicopathological significance of tumor innervation is unclear. In this study, the presence of nerves and their cross-sectional size were quantified by immunohistochemistry for the neuronal markers S-100, PGP9.5 and GAP-43 in a series of 99 pancreatic cancer cases versus 71 normal adjacent pancreatic tissues. A trend was observed between the presence of nerves in the tumor microenvironment of pancreatic cancer and worse overall patient survival (HR = 1.8, 95% CI 0.77-4.28, p = 0.08). The size of nerves, as measured by cross-sectional area, were significantly higher in pancreatic cancer than in the normal adjacent tissue (p = 0.002) and larger nerves were directly associated with worse patient survival (HR = 0.41, 95% CI 0.19-0.87, p = 0.04). In conclusion, this study suggests that the presence and size of nerves within the pancreatic cancer microenvironment are associated with tumor aggressiveness.
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Affiliation(s)
- Aysha Ferdoushi
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
- Department of Biotechnology and Genetic Engineering, Mawlana Bhashani Science and Technology University, Tangail, 1902, Bangladesh
| | - Nathan Griffin
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Mark Marsland
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Xiaoyue Xu
- School of Population Health, Faculty of Medicine, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Sam Faulkner
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Fangfang Gao
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Hui Liu
- Department of Biochemistry and Molecular Biology, School of Laboratory Medicine, Bengbu Medical College, Bengbu, 233030, People's Republic of China
| | - Simon J King
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - James W Denham
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
- School of Medicine and Public Health, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Phillip Jobling
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
| | - Chen Chen Jiang
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia
- School of Medicine and Public Health, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Hubert Hondermarck
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, 2308, Australia.
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, 2305, Australia.
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7
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Pineda S, Nikolova-Krstevski V, Leimena C, Atkinson AJ, Altekoester AK, Cox CD, Jacoby A, Huttner IG, Ju YK, Soka M, Ohanian M, Trivedi G, Kalvakuri S, Birker K, Johnson R, Molenaar P, Kuchar D, Allen DG, van Helden DF, Harvey RP, Hill AP, Bodmer R, Vogler G, Dobrzynski H, Ocorr K, Fatkin D. Conserved Role of the Large Conductance Calcium-Activated Potassium Channel, K Ca1.1, in Sinus Node Function and Arrhythmia Risk. Circ Genom Precis Med 2021; 14:e003144. [PMID: 33629867 DOI: 10.1161/circgen.120.003144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND KCNMA1 encodes the α-subunit of the large-conductance Ca2+-activated K+ channel, KCa1.1, and lies within a linkage interval for atrial fibrillation (AF). Insights into the cardiac functions of KCa1.1 are limited, and KCNMA1 has not been investigated as an AF candidate gene. METHODS The KCNMA1 gene was sequenced in 118 patients with familial AF. The role of KCa1.1 in normal cardiac structure and function was evaluated in humans, mice, zebrafish, and fly. A novel KCNMA1 variant was functionally characterized. RESULTS A complex KCNMA1 variant was identified in 1 kindred with AF. To evaluate potential disease mechanisms, we first evaluated the distribution of KCa1.1 in normal hearts using immunostaining and immunogold electron microscopy. KCa1.1 was seen throughout the atria and ventricles in humans and mice, with strong expression in the sinus node. In an ex vivo murine sinoatrial node preparation, addition of the KCa1.1 antagonist, paxilline, blunted the increase in beating rate induced by adrenergic receptor stimulation. Knockdown of the KCa1.1 ortholog, kcnma1b, in zebrafish embryos resulted in sinus bradycardia with dilatation and reduced contraction of the atrium and ventricle. Genetic inactivation of the Drosophila KCa1.1 ortholog, slo, systemically or in adult stages, also slowed the heartbeat and produced fibrillatory cardiac contractions. Electrophysiological characterization of slo-deficient flies revealed bursts of action potentials, reflecting increased events of fibrillatory arrhythmias. Flies with cardiac-specific overexpression of the human KCNMA1 mutant also showed increased heart period and bursts of action potentials, similar to the KCa1.1 loss-of-function models. CONCLUSIONS Our data point to a highly conserved role of KCa1.1 in sinus node function in humans, mice, zebrafish, and fly and suggest that KCa1.1 loss of function may predispose to AF.
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Affiliation(s)
- Santiago Pineda
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Vesna Nikolova-Krstevski
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.)
| | - Christiana Leimena
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Andrew J Atkinson
- Institute of Cardiovascular Sciences, University of Manchester, United Kingdom (A.J.A., H.D.)
| | - Ann-Kristin Altekoester
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Charles D Cox
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Arie Jacoby
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Inken G Huttner
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.)
| | - Yue-Kun Ju
- Bosch Institute, University of Sydney, Camperdown (Y.-K.J., D.G.A.)
| | - Magdalena Soka
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Monique Ohanian
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Gunjan Trivedi
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.)
| | - Sreehari Kalvakuri
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Katja Birker
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Renee Johnson
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.)
| | - Peter Molenaar
- Faculty of Health, Queensland University of Technology (P.M.).,School of Medicine, University of Queensland, Prince Charles Hospital, Brisbane, Queensland, Australia (P.M.)
| | - Dennis Kuchar
- Cardiology Department, St Vincent's Hospital, Darlinghurst (D.K., D.F.)
| | - David G Allen
- Bosch Institute, University of Sydney, Camperdown (Y.-K.J., D.G.A.)
| | - Dirk F van Helden
- University of Newcastle and Hunter Medical Research Institute, NSW, Australia (D.F.v.H.)
| | - Richard P Harvey
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.)
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.)
| | - Rolf Bodmer
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Georg Vogler
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Halina Dobrzynski
- Institute of Cardiovascular Sciences, University of Manchester, United Kingdom (A.J.A., H.D.).,Jagiellonian University Medical College, Cracow, Poland (H.D.)
| | - Karen Ocorr
- Development, Aging & Regeneration Program, Sanford-Burnham Prebys Medical Discovery Institute, La Jolla, CA (S.P., S.K., K.B., R.B., G.V., K.O.)
| | - Diane Fatkin
- Victor Chang Cardiac Research Institute, Darlinghurst (V.N.-K., C.L., A.-K.A., C.D.C., A.J., I.G.H., M.S., M.O., G.T., R.J., R.P.H., A.P.H., D.F.).,Faculty of Medicine, UNSW Sydney, Kensington (V.N.-K., I.G.H., R.J., R.P.H., A.P.H., D.F.).,Cardiology Department, St Vincent's Hospital, Darlinghurst (D.K., D.F.)
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Tamanna S, Clifton VL, Rae K, van Helden DF, Lumbers ER, Pringle KG. Angiotensin Converting Enzyme 2 (ACE2) in Pregnancy: Preeclampsia and Small for Gestational Age. Front Physiol 2020; 11:590787. [PMID: 33101066 PMCID: PMC7554608 DOI: 10.3389/fphys.2020.590787] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 09/09/2020] [Indexed: 01/14/2023] Open
Abstract
Introduction An imbalance in angiotensin (Ang) peptides could contribute to the pathophysiology of preeclampsia (PE) and poor fetal growth. Methods We measured maternal plasma levels of Ang peptides and converting enzymes in non-pregnant women (n = 10), in normal pregnant women (n = 59), women delivering small for gestational age babies (SGA, n = 25) across gestation (13–36 weeks) and in women with PE (n = 14) in their third trimester. Results Plasma ACE, ACE2, and Ang-(1-7) levels, and ACE2 activity were significantly higher in normal pregnant women compared with non-pregnant women; neprilysin (NEP) levels were not changed. In SGA pregnancies, ACE and ACE2 levels were higher in early-mid pregnancy compared with normal pregnant women. In women with PE, plasma ACE, ACE2, NEP, and Ang-(1-7) levels and ACE2 activity were lower than levels in normal pregnant women. Conclusion The higher plasma ACE2 levels and activity in pregnancy could be driving the higher Ang-(1-7) levels. The early gestation increases in ACE and ACE2 levels in SGA pregnancies highlights the possibility that these enzymes could be used as potential early biomarkers of poor fetal growth. In women with PE, the reduced ACE2 and NEP levels at term, could be contributing to the reduction in Ang-(1-7) levels. These findings suggest that dysfunctional relationships between two key enzymes in the circulating RAS are involved in the pathogenesis of PE and SGA. Since soluble ACE2 can prevent binding of the novel coronavirus, SARS-CoV-2, to membrane bound ACE2, the interplay between ACE2 and the coronavirus and its impact in pregnancy requires further investigation.
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Affiliation(s)
- Sonia Tamanna
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
| | - Vicki L Clifton
- Robinson Research Institute, School of Medicine, University of Adelaide, Adelaide, SA, Australia.,Mater Medical Research Institute and Translational Research Institute, University of Queensland, Brisbane, QLD, Australia
| | - Kym Rae
- Mater Medical Research Institute and Translational Research Institute, University of Queensland, Brisbane, QLD, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia
| | - Eugenie R Lumbers
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
| | - Kirsty G Pringle
- Priority Research Centre for Reproductive Sciences, University of Newcastle, Newcastle, NSW, Australia.,School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.,Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia
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9
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Ferdoushi A, Li X, Griffin N, Faulkner S, Jamaluddin MFB, Gao F, Jiang CC, van Helden DF, Tanwar PS, Jobling P, Hondermarck H. Schwann Cell Stimulation of Pancreatic Cancer Cells: A Proteomic Analysis. Front Oncol 2020; 10:1601. [PMID: 32984024 PMCID: PMC7477957 DOI: 10.3389/fonc.2020.01601] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 07/23/2020] [Indexed: 12/12/2022] Open
Abstract
Schwann cells (SCs), the glial component of peripheral nerves, have been identified as promoters of pancreatic cancer (PC) progression, but the molecular mechanisms are unclear. In the present study, we aimed to identify proteins released by SCs that could stimulate PC growth and invasion. Proteomic analysis of human primary SC secretome was performed using liquid chromatography–tandem mass spectrometry, and a total of 13,796 unique peptides corresponding to 1,470 individual proteins were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment were conducted using the Database for Annotation, Visualization, and Integrated Discovery. Metabolic and cell–cell adhesion pathways showed the highest levels of enrichment, a finding in line with the supportive role of SCs in peripheral nerves. We identified seven SC-secreted proteins that were validated by western blot. The involvement of these SC-secreted proteins was further demonstrated by using blocking antibodies. PC cell proliferation and invasion induced by SC-conditioned media were decreased using blocking antibodies against the matrix metalloproteinase-2, cathepsin D, plasminogen activator inhibitor-1, and galectin-1. Blocking antibodies against the proteoglycan biglycan, galectin-3 binding protein, and tissue inhibitor of metalloproteinases-2 decreased only the proliferation but not the invasion of PC cells. Together, this study delineates the secretome of human SCs and identifies proteins that can stimulate PC cell growth and invasion and therefore constitute potential therapeutic targets.
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Affiliation(s)
- Aysha Ferdoushi
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia.,Department of Biotechnology and Genetic Engineering, Mawlana Bhashani Science and Technology University, Tangail, Bangladesh
| | - Xiang Li
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Nathan Griffin
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Sam Faulkner
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - M Fairuz B Jamaluddin
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Fangfang Gao
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Chen Chen Jiang
- Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia.,School of Medicine and Public Health, The University of Newcastle, Callaghan, NSW, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Pradeep S Tanwar
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Phillip Jobling
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
| | - Hubert Hondermarck
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute, University of Newcastle, New Lambton, NSW, Australia
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10
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Helden DFV, Dosen PJ, O'Leary MA, Isbister GK. Two pathways for venom toxin entry consequent to injection of an Australian elapid snake venom. Sci Rep 2019; 9:8595. [PMID: 31197231 PMCID: PMC6565734 DOI: 10.1038/s41598-019-45022-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 05/23/2019] [Indexed: 11/09/2022] Open
Abstract
Here we test and refute the hypothesis that venom toxins from an Australian elapid, the Eastern Brown snake (Pseudonaja textilis, PTx), solely require lymphatic transport to enter the circulation. Studies were made using anaesthetised non-recovery rats in which a marker dye (India ink) or highly potent PTx venom was injected into the hind paw. The studies required a means of inhibiting lymphatic function, as achieved by cooling of the test hind limb to low temperatures (~3 °C). Maintained entry of a non-lethal dose (0.15 mg/kg) and respiratory arrest consequent to injection of a lethal dose (1 mg/kg) of PTx venom at these low temperatures indicate that venom including toxin components enter the circulation directly via the vascular system, a process facilitated by, but not dependent on, lymphatic transport. Notably, the venom had a direct effect on vascular permeability markedly increasing this to allow extravasation of plasma albumin (MWt ~60 kDa).
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Affiliation(s)
- Dirk F van Helden
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia.
| | - Peter J Dosen
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia
| | - Margaret A O'Leary
- Clinical Toxicology Research Group, University of Newcastle, Callaghan, New South Wales, Australia
| | - Geoffrey K Isbister
- Clinical Toxicology Research Group, University of Newcastle, Callaghan, New South Wales, Australia
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11
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Walweel K, Gomez-Hurtado N, Oo YW, Beard NA, Dos Remedios C, Johnson CN, Chazin WJ, van Helden DF, Knollmann BC, Laver DR. Calmodulin Mutants Linked to Catecholaminergic Polymorphic Ventricular Tachycardia Fail to Inhibit Human RyR2 Channels. J Am Coll Cardiol 2019; 70:115-117. [PMID: 28662798 DOI: 10.1016/j.jacc.2017.04.055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 04/11/2017] [Accepted: 04/26/2017] [Indexed: 10/19/2022]
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12
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Walweel K, Gomez-Hurtado N, Rebbeck RT, Oo YW, Beard NA, Molenaar P, Dos Remedios C, van Helden DF, Cornea RL, Knollmann BC, Laver DR. Calmodulin inhibition of human RyR2 channels requires phosphorylation of RyR2-S2808 or RyR2-S2814. J Mol Cell Cardiol 2019; 130:96-106. [PMID: 30928430 DOI: 10.1016/j.yjmcc.2019.03.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 02/19/2019] [Accepted: 03/25/2019] [Indexed: 01/08/2023]
Abstract
Calmodulin (CaM) is a Ca-binding protein that binds to, and can directly inhibit cardiac ryanodine receptor calcium release channels (RyR2). Animal studies have shown that RyR2 hyperphosphorylation reduces CaM binding to RyR2 in failing hearts, but data are lacking on how CaM regulates human RyR2 and how this regulation is affected by RyR2 phosphorylation. Physiological concentrations of CaM (100 nM) inhibited the diastolic activity of RyR2 isolated from failing human hearts by ~50% but had no effect on RyR2 from healthy human hearts. Using FRET between donor-FKBP12.6 and acceptor-CaM bound to RyR2, we determined that CaM binds to RyR2 from healthy human heart with a Kd = 121 ± 14 nM. Ex-vivo phosphorylation/dephosphorylation experiments suggested that the divergent CaM regulation of healthy and failing human RyR2 was caused by differences in RyR2 phosphorylation by protein kinase A and Ca-CaM-dependent kinase II. Ca2+-spark measurements in murine cardiomyocytes harbouring RyR2 phosphomimetic or phosphoablated mutants at S2814 and S2808 suggest that phosphorylation of residues corresponding to either human RyR2-S2808 or S2814 is both necessary and sufficient for RyR2 regulation by CaM. Our results challenge the current concept that CaM universally functions as a canonical inhibitor of RyR2 across species. Rather, CaM's biological action on human RyR2 appears to be more nuanced, with inhibitory activity only on phosphorylated RyR2 channels, which occurs during exercise or in patients with heart failure.
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Affiliation(s)
- Kafa Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
| | - Nieves Gomez-Hurtado
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Robyn T Rebbeck
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA.
| | - Ye Wint Oo
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW 2308, Australia
| | - Nicole A Beard
- Faculty of Science and Technology, University of Canberra, Bruce, ACT 2617, Australia.
| | - Peter Molenaar
- School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia; Northside Clinical School of Medicine, University of Queensland, Cardio-vascular Molecular & Therapeutics Translational Research Group, The Prince Charles Hospital, Chermside, QLD 4032. Australia.
| | - Cris Dos Remedios
- Bosch Institute, Discipline of Anatomy, University of Sydney, Sydney, New South Wales 2006, Australia.
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
| | - Razvan L Cornea
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA.
| | - Björn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, NSW 2308, Australia.
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13
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Dora KA, van Helden DF. Endothelial tubes: another window into lymphatic function. J Physiol 2017; 595:7267-7268. [PMID: 29063612 DOI: 10.1113/jp275323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Kim A Dora
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
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14
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Carreiro JN, Magnani M, Jobling P, van Helden DF, Nalivaiko E, Braga VA. Resveratrol restores uterine contractions during hypoxia by blockade of ATP-sensitive potassium channels. J Funct Foods 2017. [DOI: 10.1016/j.jff.2017.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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15
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van Helden DF, Kamiya A, Kelsey S, Laver DR, Jobling P, Mitsui R, Hashitani H. Nerve-induced responses of mouse vaginal smooth muscle. Pflugers Arch 2017; 469:1373-1385. [DOI: 10.1007/s00424-017-1995-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 03/30/2017] [Accepted: 05/10/2017] [Indexed: 12/23/2022]
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16
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Zhang HM, van Helden DF, McCurdy DW, Offler CE, Patrick JW. Plasma Membrane Ca2+-Permeable Channels are Differentially Regulated by Ethylene and Hydrogen Peroxide to Generate Persistent Plumes of Elevated Cytosolic Ca2+ During Transfer Cell Trans-Differentiation. Plant Cell Physiol 2015; 56:1711-20. [PMID: 26139237 DOI: 10.1093/pcp/pcv100] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/25/2015] [Indexed: 05/24/2023]
Abstract
The enhanced transport capability of transfer cells (TCs) arises from their ingrowth wall architecture comprised of a uniform wall on which wall ingrowths are deposited. The wall ingrowth papillae provide scaffolds to amplify plasma membranes that are enriched in nutrient transporters. Using Vicia faba cotyledons, whose adaxial epidermal cells spontaneously and rapidly (hours) undergo a synchronous TC trans-differentiation upon transfer to culture, has led to the discovery of a cascade of inductive signals orchestrating deposition of ingrowth wall papillae. Auxin-induced ethylene biosynthesis initiates the cascade. This in turn drives a burst in extracellular H2O2 production that triggers uniform wall deposition. Thereafter, a persistent and elevated cytosolic Ca(2+) concentration, resulting from Ca(2+) influx through plasma membrane Ca(2+)-permeable channels, generates a Ca(2+) signal that directs formation of wall ingrowth papillae to specific loci. We now report how these Ca(2+)-permeable channels are regulated using the proportionate responses in cytosolic Ca(2+) concentration as a proxy measure of their transport activity. Culturing cotyledons on various combinations of pharmacological agents allowed the regulatory influence of each upstream signal on Ca(2+) channel activity to be evaluated. The findings demonstrated that Ca(2+)-permeable channel activity was insensitive to auxin, but up-regulated by ethylene through two independent routes. In one route ethylene acts directly on Ca(2+)-permeable channel activity at the transcriptional and post-translational levels, through an ethylene receptor-dependent pathway. The other route is mediated by an ethylene-induced production of extracellular H2O2 which then acts translationally and post-translationally to up-regulate Ca(2+)-permeable channel activity. A model describing the differential regulation of Ca(2+)-permeable channel activity is presented.
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Affiliation(s)
- Hui-ming Zhang
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan, NSW, 2308 Australia
| | - David W McCurdy
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia
| | - Christina E Offler
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia
| | - John W Patrick
- School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, 2308 Australia
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17
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Affiliation(s)
- Dirk F van Helden
- Cardiovascular and Neuroscience Research Network, School of Biomedical Sciences and Pharmacy, Faculty of Health & Medicine and Hunter Medical Research Institute, University of Newcastle, NSW 2308, Australia
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18
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Walweel K, Li J, Molenaar P, Imtiaz MS, Quail A, dos Remedios CG, Beard NA, Dulhunty AF, van Helden DF, Laver DR. Differences in the regulation of RyR2 from human, sheep, and rat by Ca²⁺ and Mg²⁺ in the cytoplasm and in the lumen of the sarcoplasmic reticulum. ACTA ACUST UNITED AC 2015; 144:263-71. [PMID: 25156119 PMCID: PMC4144672 DOI: 10.1085/jgp.201311157] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiac ryanodine receptors (RyR2) from humans, rats, and sheep show differential sensitivity to calcium and magnesium, with regulation of human RyR2 resembling that of sheep more than that of rat. Regulation of the cardiac ryanodine receptor (RyR2) by intracellular Ca2+ and Mg2+ plays a key role in determining cardiac contraction and rhythmicity, but their role in regulating the human RyR2 remains poorly defined. The Ca2+- and Mg2+-dependent regulation of human RyR2 was recorded in artificial lipid bilayers in the presence of 2 mM ATP and compared with that in two commonly used animal models for RyR2 function (rat and sheep). Human RyR2 displayed cytoplasmic Ca2+ activation (Ka = 4 µM) and inhibition by cytoplasmic Mg2+ (Ki = 10 µM at 100 nM Ca2+) that was similar to RyR2 from rat and sheep obtained under the same experimental conditions. However, in the presence of 0.1 mM Ca2+, RyR2s from human were 3.5-fold less sensitive to cytoplasmic Mg2+ inhibition than those from sheep and rat. The Ka values for luminal Ca2+ activation were similar in the three species (35 µM for human, 12 µM for sheep, and 10 µM for rat). From the relationship between open probability and luminal [Ca2+], the peak open probability for the human RyR2 was approximately the same as that for sheep, and both were ∼10-fold greater than that for rat RyR2. Human RyR2 also showed the same sensitivity to luminal Mg2+ as that from sheep, whereas rat RyR2 was 10-fold more sensitive. In all species, modulation of RyR2 gating by luminal Ca2+ and Mg2+ only occurred when cytoplasmic [Ca2+] was <3 µM. The activation response of RyR2 to luminal and cytoplasmic Ca2+ was strongly dependent on the Mg2+ concentration. Addition of physiological levels (1 mM) of Mg2+ raised the Ka for cytoplasmic Ca2+ to 30 µM (human and sheep) or 90 µM (rat) and raised the Ka for luminal Ca2+ to ∼1 mM in all species. This is the first report of the regulation by Ca2+ and Mg2+ of native RyR2 receptor activity from healthy human hearts.
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Affiliation(s)
- Kafa Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
| | - Jiao Li
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
| | - Peter Molenaar
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland 4001, Australia School of Medicine, University of Queensland, Brisbane, Queensland 4006, Australia Critical Care Research Group, The Prince Charles Hospital Foundation, Chermside, Queensland 4032, Australia
| | - Mohammad S Imtiaz
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
| | - Anthony Quail
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
| | - Cris G dos Remedios
- Bosch Institute, Discipline of Anatomy, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Nicole A Beard
- Faculty of Education, Science, Technology, and Mathematics, University of Canberra, Canberra, Australian Capital Territory 2601, Australia
| | - Angela F Dulhunty
- The John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2600, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales 2308, Australia
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19
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Beard DJ, McLeod DD, Logan CL, Murtha LA, Imtiaz MS, van Helden DF, Spratt NJ. Intracranial pressure elevation reduces flow through collateral vessels and the penetrating arterioles they supply. A possible explanation for 'collateral failure' and infarct expansion after ischemic stroke. J Cereb Blood Flow Metab 2015; 35:861-72. [PMID: 25669909 PMCID: PMC4420869 DOI: 10.1038/jcbfm.2015.2] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 12/22/2014] [Accepted: 12/27/2014] [Indexed: 01/09/2023]
Abstract
Recent human imaging studies indicate that reduced blood flow through pial collateral vessels ('collateral failure') is associated with late infarct expansion despite stable arterial occlusion. The cause for 'collateral failure' is unknown. We recently showed that intracranial pressure (ICP) rises dramatically but transiently 24 hours after even minor experimental stroke. We hypothesized that ICP elevation would reduce collateral blood flow. First, we investigated the regulation of flow through collateral vessels and the penetrating arterioles arising from them during stroke reperfusion. Wistar rats were subjected to intraluminal middle cerebral artery (MCA) occlusion (MCAo). Individual pial collateral and associated penetrating arteriole blood flow was quantified using fluorescent microspheres. Baseline bidirectional flow changed to MCA-directed flow and increased by >450% immediately after MCAo. Collateral diameter changed minimally. Second, we determined the effect of ICP elevation on collateral and watershed penetrating arteriole flow. Intracranial pressure was artificially raised in stepwise increments during MCAo. The ICP increase was strongly correlated with collateral and penetrating arteriole flow reductions. Changes in collateral flow post-stroke appear to be primarily driven by the pressure drop across the collateral vessel, not vessel diameter. The ICP elevation reduces cerebral perfusion pressure and collateral flow, and is the possible explanation for 'collateral failure' in stroke-in-progression.
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Affiliation(s)
- Daniel J Beard
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Damian D McLeod
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Caitlin L Logan
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Lucy A Murtha
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Mohammad S Imtiaz
- 1] School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia [2] Computational Cardiology Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia
| | - Neil J Spratt
- 1] School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia [2] Department of Neurology, John Hunter Hospital, Hunter New England Local Health District, New Lambton Heights, New South Wales, Australia
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20
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Oo YW, Gomez-Hurtado N, Walweel K, van Helden DF, Imtiaz MS, Knollmann BC, Laver DR. Essential Role of Calmodulin in RyR Inhibition by Dantrolene. Mol Pharmacol 2015; 88:57-63. [PMID: 25920678 DOI: 10.1124/mol.115.097691] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Accepted: 04/28/2015] [Indexed: 12/17/2022] Open
Abstract
Dantrolene is the first line therapy of malignant hyperthermia. Animal studies suggest that dantrolene also protects against heart failure and arrhythmias caused by spontaneous Ca(2+) release. Although dantrolene inhibits Ca(2+) release from the sarcoplasmic reticulum of skeletal and cardiac muscle preparations, its mechanism of action has remained controversial, because dantrolene does not inhibit single ryanodine receptor (RyR) Ca(2+) release channels in lipid bilayers. Here we test the hypothesis that calmodulin (CaM), a physiologic RyR binding partner that is lost during incorporation into lipid bilayers, is required for dantrolene inhibition of RyR channels. In single channel recordings (100 nM cytoplasmic [Ca(2+)] + 2 mM ATP), dantrolene caused inhibition of RyR1 (rabbit skeletal muscle) and RyR2 (sheep) with a maximal inhibition of Po (Emax) to 52 ± 4% of control only after adding physiologic [CaM] = 100 nM. Dantrolene inhibited RyR2 with an IC50 of 0.16 ± 0.03 µM. Mutant N98S-CaM facilitated dantrolene inhibition with an IC50 = 5.9 ± 0.3 nM. In mouse cardiomyocytes, dantrolene had no effect on cardiac Ca(2+) release in the absence of CaM, but reduced Ca(2+) wave frequency (IC50 = 0.42 ± 0.18 µM, Emax = 47 ± 4%) and amplitude (IC50 = 0.19 ± 0.04 µM, Emax = 66 ± 4%) in the presence of 100 nM CaM. We conclude that CaM is essential for dantrolene inhibition of RyR1 and RyR2. Its absence explains why dantrolene inhibition of single RyR channels has not been previously observed.
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Affiliation(s)
- Ye Win Oo
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Nieves Gomez-Hurtado
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Kafa Walweel
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Mohammad S Imtiaz
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Bjorn C Knollmann
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle and Hunter Medical Research Institute, Callaghan, New South Wales, Australia (Y.W.O., K.W., D.F.H., M.S.I., D.R.L.); and Division of Clinical Pharmacology, School of Medicine, Vanderbilt University, Nashville, Tennessee (N.G.-H., B.C.K.)
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21
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Nikolaev YA, Dosen PJ, Laver DR, van Helden DF, Hamill OP. Single mechanically-gated cation channel currents can trigger action potentials in neocortical and hippocampal pyramidal neurons. Brain Res 2015; 1608:1-13. [PMID: 25765154 DOI: 10.1016/j.brainres.2015.02.051] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 02/26/2015] [Indexed: 02/04/2023]
Abstract
The mammalian brain is a mechanosensitive organ that responds to different mechanical forces ranging from intrinsic forces implicated in brain morphogenesis to extrinsic forces that can cause concussion and traumatic brain injury. However, little is known of the mechanosensors that transduce these forces. In this study we use cell-attached patch recording to measure single mechanically-gated (MG) channel currents and their affects on spike activity in identified neurons in neonatal mouse brain slices. We demonstrate that both neocortical and hippocampal pyramidal neurons express stretch-activated MG cation channels that are activated by suctions of ~25mm Hg, have a single channel conductance for inward current of 50-70pS and show weak selectivity for alkali metal cations (i.e., Na(+)<K(+)<Cs(+)). Significantly, single MG channel currents activated on the soma trigger spiking/action potentials in both neocortical and hippocampal pyramidal neurons. Not all neuron types studied here expressed MG channel currents. In particular, locus coeruleus and cerebellar Purkinje neurons showed no detectable MG channel activity. Moreover their robust rhythmic spike activity was resistant to mechanical modulation. Our observation that a single MG channel current can trigger spiking predicates the need for reassessment of the long held view that the impulse output of central neurons depends only upon their intrinsic voltage-gated channels and/or their integrated synaptic input.
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Affiliation(s)
- Yury A Nikolaev
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia; Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia
| | - Peter J Dosen
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia
| | - Owen P Hamill
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, New South Wales 2308, Australia; Department of Neuroscience and Cell Biology, UTMB, Galveston, TX 77555, USA.
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Zhang HM, Imtiaz MS, Laver DR, McCurdy DW, Offler CE, van Helden DF, Patrick JW. Polarized and persistent Ca²⁺ plumes define loci for formation of wall ingrowth papillae in transfer cells. J Exp Bot 2015; 66:1179-90. [PMID: 25504137 PMCID: PMC4339585 DOI: 10.1093/jxb/eru460] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Transfer cell morphology is characterized by a polarized ingrowth wall comprising a uniform wall upon which wall ingrowth papillae develop at right angles into the cytoplasm. The hypothesis that positional information directing construction of wall ingrowth papillae is mediated by Ca(2+) signals generated by spatiotemporal alterations in cytosolic Ca(2+) ([Ca(2+)]cyt) of cells trans-differentiating to a transfer cell morphology was tested. This hypothesis was examined using Vicia faba cotyledons. On transferring cotyledons to culture, their adaxial epidermal cells synchronously trans-differentiate to epidermal transfer cells. A polarized and persistent Ca(2+) signal, generated during epidermal cell trans-differentiation, was found to co-localize with the site of ingrowth wall formation. Dampening Ca(2+) signal intensity, by withdrawing extracellular Ca(2+) or blocking Ca(2+) channel activity, inhibited formation of wall ingrowth papillae. Maintenance of Ca(2+) signal polarity and persistence depended upon a rapid turnover (minutes) of cytosolic Ca(2+) by co-operative functioning of plasma membrane Ca(2+)-permeable channels and Ca(2+)-ATPases. Viewed paradermally, and proximal to the cytosol-plasma membrane interface, the Ca(2+) signal was organized into discrete patches that aligned spatially with clusters of Ca(2+)-permeable channels. Mathematical modelling demonstrated that these patches of cytosolic Ca(2+) were consistent with inward-directed plumes of elevated [Ca(2+)]cyt. Plume formation depended upon an alternating distribution of Ca(2+)-permeable channels and Ca(2+)-ATPase clusters. On further inward diffusion, the Ca(2+) plumes coalesced into a uniform Ca(2+) signal. Blocking or dispersing the Ca(2+) plumes inhibited deposition of wall ingrowth papillae, while uniform wall formation remained unaltered. A working model envisages that cytosolic Ca(2+) plumes define the loci at which wall ingrowth papillae are deposited.
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Affiliation(s)
- Hui-Ming Zhang
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Mohammad S Imtiaz
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Derek R Laver
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
| | - David W McCurdy
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Christina E Offler
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Dirk F van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
| | - John W Patrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
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Gravina FS, van Helden DF, Kerr KP, de Oliveira RB, Jobling P. Phasic contractions of the mouse vagina and cervix at different phases of the estrus cycle and during late pregnancy. PLoS One 2014; 9:e111307. [PMID: 25337931 PMCID: PMC4206458 DOI: 10.1371/journal.pone.0111307] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 09/30/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND/AIMS The pacemaker mechanisms activating phasic contractions of vaginal and cervical smooth muscle remain poorly understood. Here, we investigate properties of pacemaking in vaginal and cervical tissues by determining whether: 1) functional pacemaking is dependent on the phase of the estrus cycle or pregnancy; 2) pacemaking involves Ca2+ release from sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) -dependent intracellular Ca2+ stores; and 3) c-Kit and/or vimentin immunoreactive ICs have a role in pacemaking. METHODOLOGY/PRINCIPAL FINDINGS Vaginal and cervical contractions were measured in vitro, as was the distribution of c-Kit and vimentin positive interstitial cells (ICs). Cervical smooth muscle was spontaneously active in estrus and metestrus but quiescent during proestrus and diestrus. Vaginal smooth muscle was normally quiescent but exhibited phasic contractions in the presence of oxytocin or the K+ channel blocker tetraethylammonium (TEA) chloride. Spontaneous contractions in the cervix and TEA-induced phasic contractions in the vagina persisted in the presence of cyclopiazonic acid (CPA), a blocker of the SERCA that refills intracellular SR Ca2+ stores, but were inhibited in low Ca2+ solution or in the presence of nifedipine, an inhibitor of L-type Ca2+channels. ICs were found in small numbers in the mouse cervix but not in the vagina. CONCLUSIONS/SIGNIFICANCE Cervical smooth muscle strips taken from mice in estrus, metestrus or late pregnancy were generally spontaneously active. Vaginal smooth muscle strips were normally quiescent but could be induced to exhibit phasic contractions independent on phase of the estrus cycle or late pregnancy. Spontaneous cervical or TEA-induced vaginal phasic contractions were not mediated by ICs or intracellular Ca2+ stores. Given that vaginal smooth muscle is normally quiescent then it is likely that increases in hormones such as oxytocin, as might occur through sexual stimulation, enhance the effectiveness of such pacemaking until phasic contractile activity emerges.
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Affiliation(s)
- Fernanda S. Gravina
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Dirk F. van Helden
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Karen P. Kerr
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Ramatis B. de Oliveira
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Phillip Jobling
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
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van Helden DF, Thomas PA, Dosen PJ, Imtiaz MS, Laver DR, Isbister GK. Pharmacological approaches that slow lymphatic flow as a snakebite first aid. PLoS Negl Trop Dis 2014; 8:e2722. [PMID: 24587472 PMCID: PMC3937289 DOI: 10.1371/journal.pntd.0002722] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 01/17/2014] [Indexed: 11/18/2022] Open
Abstract
Background This study examines the use of topical pharmacological agents as a snakebite first aid where slowing venom reaching the circulation prevents systemic toxicity. It is based on the fact that toxin molecules in most snake venoms are large molecules and generally first enter and traverse the lymphatic system before accessing the circulation. It follows on from a previous study where it was shown that topical application of a nitric oxide donor slowed lymph flow to a similar extent in humans and rats as well as increased the time to respiratory arrest for subcutaneous injection of an elapid venom (Pseudonaja textilis, Ptx; Eastern brown snake) into the hind feet of anaesthetized rats. Methodology/Principal Findings The effects of topical application of the L-type Ca2+ channel antagonist nifedipine and the local anesthetic lignocaine in inhibiting lymph flow and protecting against envenomation was examined in an anaesthetized rat model. The agents significantly increased dye-measured lymph transit times by 500% and 390% compared to controls and increased the time to respiratory arrest to foot injection of a lethal dose of Ptx venom by 60% and 40% respectively. The study also examined the effect of Ptx venom dose over the lethal range of 0.4 to 1.5 mg/kg finding a negative linear relationship between increase in venom dose and time to respiratory arrest. Conclusions/Significance The findings suggest that a range of agents that inhibit lymphatic flow could potentially be used as an adjunct treatment to pressure bandaging with immobilization (PBI) in snakebite first aid. This is important given that PBI (a snakebite first aid recommended by the Australian National Health and Medical research Council) is often incorrectly applied. The use of a local anesthetic would have the added advantage of reducing pain. Snakebite remains a major problem worldwide causing death or serious illness in many tens of thousands of victims annually. An approach to reduce the burden of envenoming is to provide optimum first aid procedures. We have previously shown that topical application of a nitric oxide (NO) donor slowed lymph flow to similar extent in humans and rats as well as increased the time to respiratory arrest by ∼50% for subcutaneous injection of eastern brown snake venom into the hind feet of anaesthetized rats. The present study examines the use of several other topical pharmacological agents that aim to slow venom toxins reaching the circulation through the lymphatic system. The study found that the agents examined were similarly effective to that previously found for the NO donor. The fact that one of these is a commonly used topical local anesthetic may be an ideal adjunct first aid, as it provides first aid while reducing pain.
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Affiliation(s)
- Dirk F. van Helden
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia
- Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia
- * E-mail:
| | - Paul A. Thomas
- School of Medicine, University of Queensland, Brisbane, Queensland, Australia
- Department of Nuclear Medicine, Royal Brisbane and Women's Hospital, Herston, Queensland, Australia
| | - Peter J. Dosen
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia
| | - Mohammad S. Imtiaz
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia
| | - Derek R. Laver
- School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, New South Wales, Australia
| | - Geoffrey K. Isbister
- School of Medicine and Public Health, University of Newcastle, Callaghan, New South Wales, Australia
- Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle, Waratah, New South Wales, Australia
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de Oliveira RB, Gravina FS, Lim R, Brichta AM, Callister RJ, van Helden DF. Developmental changes in pacemaker currents in mouse locus coeruleus neurons. Brain Res 2011; 1425:27-36. [PMID: 22018689 DOI: 10.1016/j.brainres.2011.09.053] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 09/16/2011] [Accepted: 09/23/2011] [Indexed: 10/17/2022]
Abstract
The present study compares the electrophysiological properties and the primary pacemaker currents that flow during the interspike interval in locus coeruleus (LC) neurons from infant (P7-12 days) and young adult (8-12 weeks) mice. The magnitude of the primary pacemaker currents, which consist of an excitatory TTX-sensitive Na(+) current and an inhibitory voltage-dependent K(+) current, increased in parallel during development. We found no evidence for the involvement of hyperpolarization-activated (I(H)) or Ca(2+) currents in pacemaking in infant or adult LC neurons. The incidence of TTX-resistant spikes, observed during current clamp recordings, was greater in adult neurons. Neurons from adult animals also showed an increase in voltage fluctuations, during the interspike interval, as revealed in the presence of the K(+) channel blocker, 4-AP (1mM). In summary, our results suggest that mouse LC neurons undergo changes in basic electrophysiological properties during development that influence pacemaking and hence spontaneous firing in LC neurons.
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Affiliation(s)
- Ramatis B de Oliveira
- School of Biomedical Sciences and Pharmacy, University of Newcastle, University Drive, NSW 2308, Australia.
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Laver DR, van Helden DF. Three independent mechanisms contribute to tetracaine inhibition of cardiac calcium release channels. J Mol Cell Cardiol 2011; 51:357-69. [DOI: 10.1016/j.yjmcc.2011.05.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 04/26/2011] [Accepted: 05/11/2011] [Indexed: 11/27/2022]
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Imtiaz MS, von der Weid PY, Laver DR, van Helden DF. SR Ca2+ store refill—a key factor in cardiac pacemaking. J Mol Cell Cardiol 2010; 49:412-26. [DOI: 10.1016/j.yjmcc.2010.03.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 01/01/2023]
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Abstract
1. Mechanisms underlying the generation and propagation of gastrointestinal slow wave depolarizations have long been controversial. The present review aims to collate present knowledge on this subject with specific reference to slow waves in gastric smooth muscle. 2. At present, there is strong agreement that interstitial cells of Cajal (ICC) are the pacemaker cells that generate slow waves. What has been less clear is the relative role of primary types of ICC, including the network in the myenteric plexus (ICC-MY) and the intramuscular network (ICC-IM). It is concluded that both ICC-MY and ICC-IM are likely to serve a major role in slow wave generation and propagation. 3. There has been long-standing controversy as to how slow waves 'propagate' circumferentially and down the gastrointestinal tract. Two mechanisms have been proposed, one being action potential (AP)-like conduction and the other phase wave-based 'propagation' resulting from an interaction of coupled oscillators. Studies made on single bundle gastric strips indicate that both mechanisms apply with relative dominance depending on conditions; the phase wave mechanism is dominant under circumstances of rhythmically generating slow waves and the AP-like propagation is dominant when the system is perturbed. 4. The phase wave mechanism (termed Ca(2+) phase wave) uses cyclical Ca(2+) release as the oscillator, with coupling between oscillators mediated by several factors, including: (i) store-induced depolarization; (ii) resultant electrical current flow/depolarization through the pacemaker cell network; and (iii) depolarization-induced increase in excitability of downstream Ca(2+) stores. An analogy is provided by pendulums in an array coupled together by a network of springs. These, when randomly activated, entrain to swing at the same frequency but with a relative delay along the row giving the impression of a propagating wave. 5. The AP-like mechanism (termed voltage-accelerated Ca(2+) wave) propagates sequentially like a conducting AP. However, it is different in that it depends on regenerative store Ca(2+) release and resultant depolarization rather than regenerative activation of voltage-dependent channels in the cell membrane. 6. The applicability of these mechanisms to describing propagation in large intact gastrointestinal tissues, where voltage-dependent Ca(2+) entry is also likely to be functional, is discussed.
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Affiliation(s)
- Dirk F van Helden
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, Callaghan, New South Wales, Australia.
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Abstract
Entrained oscillations in Ca(2+) underlie many biological pacemaking phenomena. In this article, we review a long-range signaling mechanism in smooth muscle that results in global outcomes of local interactions. Our results are derived from studies of the following: (a) slow-wave depolarizations that underlie rhythmic contractions of gastric smooth muscle; and (b) membrane depolarizations that drive rhythmic contractions of lymphatic smooth muscle. The main feature of this signaling mechanism is a coupled oscillator-based synchronization of Ca(2+) oscillations across cells that drives membrane potential changes and causes coordinated contractions. The key elements of this mechanism are as follows: (a) the Ca(2+) release-refill cycle of endoplasmic reticulum Ca(2+) stores; (b) Ca(2+)-dependent modulation of membrane currents; (c) voltage-dependent modulation of Ca(2+) store release; and (d) cell-cell coupling through gap junctions or other mechanisms. In this mechanism, Ca(2+) stores alter the frequency of adjacent stores through voltage-dependent modulation of store release. This electrochemical coupling is many orders of magnitude stronger than the coupling through diffusion of Ca(2+) or inositol 1,4,5-trisphosphate, and thus provides an effective means of long-range signaling.
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Affiliation(s)
- Mohammad S Imtiaz
- Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada.
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von der Weid PY, Rahman M, Imtiaz MS, van Helden DF. Spontaneous transient depolarizations in lymphatic vessels of the guinea pig mesentery: pharmacology and implication for spontaneous contractility. Am J Physiol Heart Circ Physiol 2008; 295:H1989-2000. [PMID: 18790842 DOI: 10.1152/ajpheart.00007.2008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Guinea pig mesenteric lymphatic vessels exhibit rhythmic constrictions induced by action potential (AP)-like spikes and initiated by entrainment of spontaneous transient depolarizations (STDs). To characterize STDs and the signaling mechanisms responsible for their occurrence, we used intracellular microelectrodes, Ca2+ imaging, and pharmacological agents. In our investigation of the role of intracellular Ca2+ released from Ca2+ stores, we observed that intracellular Ca2+ transients accompanied some STDs, although there were many exceptions where Ca2+ transients occurred without accompanying STDs. STD frequency and amplitude were markedly affected by activators/inhibitors of inositol 1,4,5-trisphosphate receptors (IP3Rs) but not by treatments known to alter Ca2+ release via ryanodine receptors. A role for Ca2+-activated Cl(-) (Cl(Ca)) channels was indicated, as STDs were dependent on the Cl(-) but not Na+ concentration of the superfusing solution and were inhibited by the Cl(Ca) channel blockers niflumic acid (NFA), anthracene 9-carboxylic acid, and 5-nitro-2-(3-phenylpropylamino)benzoic acid but not by the volume-regulated Cl(-) blocker DIDS. Increases in STD frequency and amplitude induced by agonist stimulation were also inhibited by NFA. Nifedipine, the hyperpolarization-activated inward current blocker ZD-7288, and the nonselective cation/store-operated channel blockers SKF-96365, Gd3+, and Ni2+ had no or marginal effects on STD activity. However, nifedipine, 2-aminoethoxydiphenyl borate, NFA, SKF-96365, Gd3+, and Ni2+ altered the occurrence of spontaneous APs. Our findings support a role for Ca2+ release through IP3Rs and a resultant opening of Cl(Ca) channels in STD generation and confirm the importance of these events in the initiation of lymphatic spontaneous APs and subsequent contractions. The abolition of spontaneous APs by blockers of other excitatory ion channels suggests a contribution of these conductances to lymphatic pacemaking.
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Affiliation(s)
- Pierre-Yves von der Weid
- Inflammation Research Network, Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB, Canada T2N 4N1.
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Imtiaz MS, Zhao J, Hosaka K, von der Weid PY, Crowe M, van Helden DF. Pacemaking through Ca2+ stores interacting as coupled oscillators via membrane depolarization. Biophys J 2007; 92:3843-61. [PMID: 17351003 PMCID: PMC1869001 DOI: 10.1529/biophysj.106.095687] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
This study presents an investigation of pacemaker mechanisms underlying lymphatic vasomotion. We tested the hypothesis that active inositol 1,4,5-trisphosphate receptor (IP(3)R)-operated Ca(2+) stores interact as coupled oscillators to produce near-synchronous Ca(2+) release events and associated pacemaker potentials, this driving action potentials and constrictions of lymphatic smooth muscle. Application of endothelin 1 (ET-1), an agonist known to enhance synthesis of IP(3), to quiescent lymphatic smooth muscle syncytia first enhanced spontaneous Ca(2+) transients and/or intracellular Ca(2+) waves. Larger near-synchronous Ca(2+) transients then occurred leading to global synchronous Ca(2+) transients associated with action potentials and resultant vasomotion. In contrast, blockade of L-type Ca(2+) channels with nifedipine prevented ET-1 from inducing near-synchronous Ca(2+) transients and resultant action potentials, leaving only asynchronous Ca(2+) transients and local Ca(2+) waves. These data were well simulated by a model of lymphatic smooth muscle with: 1), oscillatory Ca(2+) release from IP(3)R-operated Ca(2+) stores, which causes depolarization; 2), L-type Ca(2+) channels; and 3), gap junctions between cells. Stimulation of the stores caused global pacemaker activity through coupled oscillator-based entrainment of the stores. Membrane potential changes and positive feedback by L-type Ca(2+) channels to produce more store activity were fundamental to this process providing long-range electrochemical coupling between the Ca(2+) store oscillators. We conclude that lymphatic pacemaking is mediated by coupled oscillator-based interactions between active Ca(2+) stores. These are weakly coupled by inter- and intracellular diffusion of store activators and strongly coupled by membrane potential. Ca(2+) store-based pacemaking is predicted for cellular systems where: 1), oscillatory Ca(2+) release induces depolarization; 2), membrane depolarization provides positive feedback to induce further store Ca(2+) release; and 3), cells are interconnected. These conditions are met in a surprisingly large number of cellular systems including gastrointestinal, lymphatic, urethral, and vascular tissues, and in heart pacemaker cells.
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Affiliation(s)
- Mohammad S Imtiaz
- Neuroscience Group, School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Newcastle, Australia.
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van Helden DF, Hosaka K, Imtiaz MS. Rhythmicity in the microcirculation. Clin Hemorheol Microcirc 2006; 34:59-66. [PMID: 16543618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Many blood and lymphatic vessels undergo spontaneous rhythmical constrictions. Such activity is an intrinsic property of the smooth muscle in the walls of these vessels and is induced or enhanced by a wide range of activators including pressure-induced distension and sympathetic neurotransmitters in both blood vessels and lymphatic vessels. This review considers present understanding of vasomotion.
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Affiliation(s)
- Dirk F van Helden
- School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan, NSW, Australia.
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Hosaka K, Rayner SE, von der Weid PY, Zhao J, Imtiaz MS, van Helden DF. Calcitonin gene-related peptide activates different signaling pathways in mesenteric lymphatics of guinea pigs. Am J Physiol Heart Circ Physiol 2005; 290:H813-22. [PMID: 16172164 DOI: 10.1152/ajpheart.00543.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of calcitonin gene-related peptide (CGRP) on constriction frequency, smooth muscle membrane potential (V(m)), and endothelial V(m) of guinea pig mesenteric lymphatics were examined in vitro. CGRP (1-100 nM) caused an endothelium-dependent decrease in the constriction frequency of perfused lymphatic vessels. The endothelium-dependent CGRP response was abolished by the CGRP-1 receptor antagonist CGRP-(8-37) (1 microM) and pertussis toxin (100 ng/ml). This action of CGRP was also blocked by the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine (L-NNA; 10 microM), an action that was reversed by the addition of L-arginine (100 microM). cGMP, adenylate cyclase, cAMP-dependent protein kinase (PKA), and ATP-sensitive K+ (K+(ATP)) channels were all implicated in the endothelium-dependent CGRP response because it was abolished by methylene blue (20 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 microM), dideoxyadenosine (10 microM), N-[2-(p-bromociannamylamino)-ethyl]-5-isoquinolinesulfonamide-dichloride (H89; 1 microM) and glibenclamide (10 microM). CGRP (100 nM), unlike acetylcholine, did not alter endothelial intracellular Ca2+ concentration or V(m). CGRP (100 nM) hyperpolarized the smooth muscle V(m), an effect inhibited by L-NNA, H89, or glibenclamide. CGRP (500 nM) also caused a decrease in constriction frequency. However, this was no longer blocked by CGRP-(8-37). CGRP (500 nM) also caused smooth muscle hyperpolarization, an action that was now not blocked by L-NNA (100 microM). It was most likely mediated by the activation of the cAMP/PKA pathway and the opening of K+(ATP) channels because it was abolished by H89 or glibenclamide. We conclude that CGRP, at low to moderate concentrations (i.e., 1-100 nM), decreases lymphatic constriction frequency primarily by the stimulation of CGRP-1 receptors coupled to pertussis toxin-sensitive G proteins and the release of NO from the endothelium or enhancement of the actions of endogenous NO. At high concentrations (i.e., 500 nM), CGRP also directly activates the smooth muscle independent of NO. Both mechanisms of activation ultimately cause the PKA-mediated opening of K+(ATP) channels and resultant hyperpolarization.
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Affiliation(s)
- Kayoko Hosaka
- School of Biomedical Sciences, Faculty of Health, Univ. of Newcastle, Callaghan, NSW 2308, Australia
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Abstract
Slow waves are rhythmic depolarizations that underlie mechanical activity of many smooth muscles. Slow waves result through rhythmic Ca(2+) release from intracellular Ca(2+) stores through inositol 1,4,5-trisphosphate (IP(3)) sensitive receptors and Ca(2+)-induced Ca(2+) release. Ca(2+) oscillations are transformed into membrane depolarizations by generation of a Ca(2+)-activated inward current. Importantly, the store Ca(2+) oscillations that underlie slow waves are entrained across many cells over large distances. It has been shown that IP(3) receptor-mediated Ca(2+) release is enhanced by membrane depolarization. Previous studies have implicated diffusion of Ca(2+) or the second messenger IP(3) across gap junctions in synchronization of Ca(2+) oscillations. In this study, a novel mechanism of Ca(2+) store entrainment through depolarization-induced IP(3) receptor-mediated Ca(2+) release is investigated. This mechanism is significantly different from chemical coupling-based mechanisms, as membrane potential has a coupling effect over distances several orders of magnitude greater than either diffusion of Ca(2+) or IP(3) through gap junctions. It is shown that electrical coupling acting through voltage-dependent modulation of store Ca(2+) release is able to synchronize oscillations of cells even when cells are widely separated and have different intrinsic frequencies of oscillation.
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Affiliation(s)
- Mohammad S Imtiaz
- The Neuroscience Group, School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan NSW 2308, Australia.
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Abstract
In vitro experiments were performed to investigate the actions of endothelin-1 (ET-1) on vasomotion and vasospasm in guinea-pig mesenteric lymphatics. ET-1 modulated lymphatic vasomotion independent of the endothelium, with lower concentrations (<or=10 nm) increasing lymphatic vasomotion and higher concentrations (>or=100 nm) causing vasospasm. ET-1-induced increases in vasomotion were accompanied by an increase in tonic [Ca2+]i. These actions were inhibited by the ETA receptor antagonist BQ-123 (1 microm), the phospholipase C (PLC) inhibitor U73122 (5 microm), removal of extracellular Ca2+, chelation of intracellular Ca2+ with BAPTA/AM (10 microm), the store Ca2+-ATPase inhibitor thapsigargin (1 microm), caffeine (10 mm) and the inositol 1,4,5-trisphosphate (IP3) receptor blocker heparin and 2-APB (30 microm). In contrast, the ETB receptor antagonist BQ-788 (1 microm), ryanodine (1 & 20 microm), pertussis toxin (PTx) or Cs+ had no significant actions on vasomotion or the magnitude of increase in tonic [Ca2+]i. ET-1-induced vasospasm was accompanied by a transient increase in smooth muscle [Ca2+]i followed by a sustained plateau, an action that was abolished by removal of extracellular Ca2+, but only marginally inhibited by nifedipine (1 microm). Caffeine (10 mm), SKF 96165 (30 microm) or U73122 (5 microm) together with nifedipine (1 microm) abolished ET-1-induced vasospasm and increase in [Ca2+]i. These results indicate that ET-1 increases lymphatic vasomotion by acting on smooth muscle ETA receptors and activation of G-protein-PLC-IP3 cascade, which is known to cause pacemaker Ca2+ release and resultant pacemaker potentials. High concentrations of ET-1 cause a failure in Ca2+ homeostasis causing vasospasm, triggered by excessive Ca2+ influx primarily through store-operated channels (SOCs) with l-Ca2+ voltage-operated channels (VOCs) also contributing, but to a much lesser extent.
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Affiliation(s)
- Jun Zhao
- The Neuroscience Group, Discipline of Human Physiology, The School of Biomedical Sciences, Faculty of Medicine and Health Sciences, The University of Newcastle, Room MS 405, Callaghan, NSW 2308, Australia
| | - Dirk F van Helden
- The Neuroscience Group, Discipline of Human Physiology, The School of Biomedical Sciences, Faculty of Medicine and Health Sciences, The University of Newcastle, Room MS 405, Callaghan, NSW 2308, Australia
- Author for correspondence:
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36
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Abstract
Ca2+ imaging and multiple microelectrode recording procedures were used to investigate a slow wave-like electrical rhythmicity in single bundle strips from the circular muscle layer of the guinea-pig gastric pylorus. The 'slow waves' (SWs) consisted of a pacemaker and regenerative component, with both potentials composed of more elementary events variously termed spontaneous transient depolarizations (STDs) or unitary potentials. STDs and SW pacemaker and regenerative potentials exhibited associated local and distributed Ca2+ transients, respectively. Ca2+ transients were often larger in cellular regions that exhibited higher basal Ca2+ indicator-associated fluorescence, typical of regions likely to contain intramuscular interstitial cells of Cajal (ICCIM). The emergence of rhythmicity arose through entrainment of STDs resulting in pacemaker Ca2+ transients and potentials, events that exhibited considerable spatial synchronicity. Application of ACh to strips exhibiting weak rhythmicity caused marked enhancement of SW synchronicity. SWs and underlying Ca2+ increases exhibited very high 'apparent conduction velocities' ('CVs') orders of magnitude greater than for sequentially conducting Ca2+ waves. Central interruption of either intercellular connectivity or inositol 1,4,5-trisphosphate receptor (IP3R)-mediated store Ca2+ release in strips caused SWs at the two ends to run independently of each other, consistent with a coupled oscillator-based mechanism. Central inhibition of stores required much wider regions of blockade than inhibition of connectivity indicating that stores were voltage-coupled. Simulations, made using a conventional store array model but now including depolarization coupled to IP3R-mediated Ca2+ release, predicted the experimental findings. The linkage between membrane voltage and Ca2+ release provides a means for stores to interact as strongly coupled oscillators, resulting in the emergence of Ca2+ phase waves and associated pacemaker potentials. This distributed pacemaker triggers regenerative Ca2+ release and resultant SWs.
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Affiliation(s)
- Dirk F van Helden
- The Neuroscience Group, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Newcastle, NSW 2308, Australia.
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37
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Abstract
A qualitative mathematical model is presented that examines membrane potential feedback on synthesis of inositol 1,4,5-trisphosphate (IP(3)), and its role in generation and modulation of slow waves. Previous experimental studies indicate that slow waves show voltage dependence, and this is likely to result through membrane potential modulation of IP(3). It is proposed that the observed response of the tissue to current pulse, pulse train, and maintained current injection can be explained by changes in IP(3), modulated through a voltage-IP(3) feedback loop. Differences underlying the tissue responses to current injections of opposite polarities are shown to be due to the sequence of events following such currents. Results from this model are consistent with experimental findings and provide further understanding of these experimental observations. Specifically, we find that membrane potential can induce, abolish, and modulate slow wave frequency by altering the excitability of the tissue through the voltage-IP(3) feedback loop.
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Affiliation(s)
- Mohammad S Imtiaz
- The Neuroscience Group, The Faculty of Medicine & Health Sciences, The University of Newcastle, NSW 2308, Australia
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38
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Zhao J, van Helden DF. ATP-induced endothelium-independent enhancement of lymphatic vasomotion in guinea-pig mesentery involves P2X and P2Y receptors. Br J Pharmacol 2002; 137:477-87. [PMID: 12359629 PMCID: PMC1573521 DOI: 10.1038/sj.bjp.0704899] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The present study has investigated mechanisms underlying ATP-induced endothelium-independent enhancement of vasomotion in guinea-pig mesenteric lymphatic vessels. 2. Lymphatic vasomotion, vessel tone and smooth muscle [Ca(2+)](i) showed similar ATP concentration-response curves. 3. ATP, at 0.1 mM, caused a biphasic increase in tonic [Ca(2+)](i) and superimposed vasomotion-associated Ca(2+) transients. All ATP-induced [Ca(2+)](i) changes were abolished by incubating the smooth muscle with suramin (0.1 mM). 4. alpha,beta-MeATP (0.1 mM) and UTP (0.1 mM) caused similar changes in [Ca(2+)](i) but the responses to these agonists were smaller than to ATP. 5. The actions of alpha,beta-MeATP (0.1 mM) were inhibited by suramin (0.1 mM) and PPADS (30 micro M) but not by reactive blue 2 (30 micro M). 6. In the presence of alpha,beta-MeATP (0.1 mM), the increases in tonic [Ca(2+)](i) and vasomotion-associated Ca(2+) transients induced by ATP (0.1 mM) were inhibited by U73122 (5 micro M), CPA (20 micro M) and heparin, whereas U73343 (5 micro M) and pre-treatment with PTx (100 ng ml(-1)) had no significant effects. 7. Depletion of the intracellular stores with CPA (20 micro M) caused an increase in [Ca(2+)](i), which was not blocked by desensitization of P(2X) receptors with alpha,beta-MeATP. 8. The data indicate that ATP, at relatively high concentrations increases lymphatic smooth muscle [Ca(2+)](i) and vasomotion through activation of P(2X1) and P(2Y2) purinoceptors present on lymphatic smooth muscle. The increase in [Ca(2+)](i) is likely to result from Ca(2+) release from inositol-1,4,5-trisphosphate-sensitive stores as well as Ca(2+) influx through store-operated channels and P(2X)-gated channels.
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Affiliation(s)
- Jun Zhao
- The Neuroscience Group, School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Dirk F van Helden
- The Neuroscience Group, School of Biomedical Sciences, Faculty of Health, The University of Newcastle, Callaghan, NSW, 2308, Australia
- Author for correspondence:
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