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Fogarty MJ, Rana S, Mantilla CB, Sieck GC. Size-dependent differences in mitochondrial volume density in phrenic motor neurons. J Appl Physiol (1985) 2023; 134:1332-1340. [PMID: 37022966 PMCID: PMC10190832 DOI: 10.1152/japplphysiol.00021.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 04/07/2023] Open
Abstract
Neuromotor control of diaphragm muscle (DIAm) motor units is dependent on an orderly size-dependent recruitment of phrenic motor neurons (PhMNs). Slow (type S) and fast, fatigue resistant (type FR) DIAm motor units, which are frequently recruited to sustain ventilation, comprise smaller PhMNs that innervate type I and IIa DIAm fibers. More fatigable fast (type FF) motor units, which are infrequently recruited for higher force, expulsive behaviors, comprise larger PhMNs that innervate more type IIx/IIb DIAm fibers. We hypothesize that due to the more frequent activation and thus higher energy demand of type S and FR motor units, the mitochondrial volume density (MVD) of smaller PhMNs is greater compared with larger PhMNs. In eight adult (6 mo old) Fischer 344 rats, PhMNs were identified via intrapleural injection of Alexa488-conjugated cholera toxin B (CTB). Following retrograde CTB labeling, mitochondria in PhMNs were labeled by transdural infusion of MitoTracker Red. PhMNs and mitochondria were imaged using multichannel confocal microscopy using a ×60 oil objective. Following optical sectioning and three-dimensional (3-D) rendering, PhMNs and mitochondria were analyzed volumetrically using Nikon Elements software. Analysis of MVD in somal and dendritic compartments was stratified by PhMN somal surface area. Smaller PhMNs (likely S and FR units) had greater somal MVDs compared with larger PhMNs (likely FF units). By contrast, proximal dendrites or larger PhMNs had higher MVD compared with dendrites of smaller PhMNs. We conclude that more active smaller PhMNs have a higher mitochondrial volume density to support their higher energy demand in sustaining ventilation.NEW & NOTEWORTHY Type S and FR motor units, comprising smaller phrenic motor neurons (PhMNs) are regularly activated to perform indefatigable ventilatory requirements. By contrast, type FF motor units, comprising larger PhMNs, are infrequently activated to perform expulsive straining and airway defense maneuvers. This difference in activation history is mirrored in the mitochondrial volume density (MVD), with smaller PhMNs having higher MVD than larger PhMNs. In proximal dendrites, this trend was reversed, with larger PhMNs having higher MVD than smaller PhMNs, likely due to the maintenance requirements for the larger dendritic arbor of FF PhMNs.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Sabhya Rana
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
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Jaitovich A. Impaired regenerative capacity contributes to skeletal muscle dysfunction in chronic obstructive pulmonary disease. Am J Physiol Cell Physiol 2022; 323:C974-C989. [PMID: 35993519 PMCID: PMC9484993 DOI: 10.1152/ajpcell.00292.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 08/16/2022] [Accepted: 08/16/2022] [Indexed: 01/18/2023]
Abstract
Locomotor skeletal muscle dysfunction is a relevant comorbidity of chronic obstructive pulmonary disease (COPD) and is strongly associated with worse clinical outcomes including higher mortality. Over the last decades, a large body of literature helped characterize the process, defining the disruptive muscle phenotype caused by COPD that involves reduction in muscle mass, force-generation capacity, fatigue-tolerance, and regenerative potential following injury. A major limitation in the field has been the scarcity of well-calibrated animal models to conduct mechanistic research based on loss- and gain-of-function studies. This article provides an overall description of the process, the tools available to mechanistically investigate it, and the potential role of mitochondrially driven metabolic signals on the regulation muscle regeneration after injury in COPD. Finally, a description of future avenues to further expand on the area is proposed based on very recent evidence involving mitochondrial metabolic cues affecting myogenesis.
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Affiliation(s)
- Ariel Jaitovich
- Division of Pulmonary and Critical Care Medicine, Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
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Brown AD, Fogarty MJ, Davis LA, Dasgupta D, Mantilla CB, Sieck GC. Mitochondrial adaptations to inactivity in diaphragm muscle fibers. J Appl Physiol (1985) 2022; 133:191-204. [PMID: 35678745 PMCID: PMC9291409 DOI: 10.1152/japplphysiol.00090.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Type I and IIa diaphragm muscle (DIAm) fibers comprise slow and fast fatigue-resistant motor units that are recruited to accomplish breathing and thus have a high duty cycle. In contrast, type IIx/IIb fibers comprise more fatigable fast motor units that are infrequently recruited for airway protective and straining behaviors. We hypothesize that mitochondrial structure and function in type I and IIa DIAm fibers adapt in response to inactivity imposed by spinal cord hemisection at C2 (C2SH). At 14 days after C2SH, the effect of inactivity on mitochondrial structure and function was assessed in DIAm fibers. Mitochondria in DIAm fibers were labeled using MitoTracker Green (Thermo Fisher Scientific), imaged in three-dimensions (3-D) by fluorescence confocal microscopy, and images were analyzed for mitochondrial volume density (MVD) and complexity. DIAm homogenate from either side was assessed for PGC1α, Parkin, MFN2, and DRP1 using Western blot. In alternate serial sections of the same DIAm fibers, the maximum velocity of the succinate dehydrogenase reaction (SDHmax) was determined using a quantitative histochemical technique. In all groups and both sides of the DIAm, type I and IIa DIAm fibers exhibited higher MVD, with more filamentous mitochondria and had higher SDHmax normalized to both fiber volume and mitochondrial volume compared with type IIx/IIb Diam fibers. In the inactive right side of the DIAm, mitochondria became fragmented and MVD decreased in all fiber types compared with the intact side and sham controls, consistent with the observed reduction in PGC1α and increased Parkin and DRP1 expression. In the inactive side of the DIAm, the reduction in SDHmax was found only for type I and IIa fibers. These results show that there are intrinsic fiber-type-dependent differences in the structure and function of mitochondria in DIAm fibers. Following C2SH-induced inactivity, mitochondrial structure (MVD and fragmentation) and function (SDHmax) were altered, indicating that inactivity influences all DIAm fiber types, but inactivity disproportionately affected SDHmax in the more intrinsically active type I and IIa fibers.NEW & NOTEWORTHY Two weeks of diaphragm (DIAm) inactivity imposed by C2SH caused reduced mitochondrial volume density, mitochondrial fragmentation, and a concomitant reduction of SDHmax in type I and IIa DIAm fibers on the lesioned side. Type I and IIa DIAm fibers were far more sensitive to inactivation than type IIx/IIb fibers, which exhibited little pathology. Our results indicate that mitochondria in DIAm fibers are plastic in response to varying levels of activity.
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Mitochondrial morphology and function varies across diaphragm muscle fiber types. Respir Physiol Neurobiol 2022; 295:103780. [PMID: 34478909 PMCID: PMC8604766 DOI: 10.1016/j.resp.2021.103780] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 08/26/2021] [Accepted: 08/29/2021] [Indexed: 01/03/2023]
Abstract
In diaphragm muscle (DIAm), type I and IIa fibers are recruited to accomplish breathing, while type IIx/IIb fibers are recruited only during expulsive/straining behaviors. Thus, type I and IIa DIAm fibers are much more active (duty cycle of ∼40 %) than type IIx/IIb fibers (duty cycle of <1%), which we hypothesized underlies intrinsic differences in mitochondrial structure and function. MitoTracker Green labeled mitochondria were imaged in 3-D using confocal microscopy. Mitochondrial volume density (MVD, per muscle fiber volume) was higher, and mitochondria were more filamentous in type I and IIa DIAm compared to type IIx/IIb fibers. The maximum velocity of the succinate dehydrogenase reaction (SDHmax), measured using a quantitative histochemical technique was found to be higher in type I and IIa DIAm fibers compared to type IIx/IIb fibers with and without normalizing for MVD. These results are consistent with fiber type differences in the intrinsic structural and functional properties of DIAm fibers and closely match differences in energetic demands.
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Brown AD, Davis LA, Fogarty MJ, Sieck GC. Mitochondrial Fragmentation and Dysfunction in Type IIx/IIb Diaphragm Muscle Fibers in 24-Month Old Fischer 344 Rats. Front Physiol 2021; 12:727585. [PMID: 34650442 PMCID: PMC8505889 DOI: 10.3389/fphys.2021.727585] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 09/09/2021] [Indexed: 12/31/2022] Open
Abstract
Sarcopenia is characterized by muscle fiber atrophy and weakness, which may be associated with mitochondrial fragmentation and dysfunction. Mitochondrial remodeling and biogenesis in muscle fibers occurs in response to exercise and increased muscle activity. However, the adaptability mitochondria may decrease with age. The diaphragm muscle (DIAm) sustains breathing, via recruitment of fatigue-resistant type I and IIa fibers. More fatigable, type IIx/IIb DIAm fibers are infrequently recruited during airway protective and expulsive behaviors. DIAm sarcopenia is restricted to the atrophy of type IIx/IIb fibers, which impairs higher force airway protective and expulsive behaviors. The aerobic capacity to generate ATP within muscle fibers depends on the volume and intrinsic respiratory capacity of mitochondria. In the present study, mitochondria in type-identified DIAm fibers were labeled using MitoTracker Green and imaged in 3-D using confocal microscopy. Mitochondrial volume density was higher in type I and IIa DIAm fibers compared with type IIx/IIb fibers. Mitochondrial volume density did not change with age in type I and IIa fibers but was reduced in type IIx/IIb fibers in 24-month rats. Furthermore, mitochondria were more fragmented in type IIx/IIb compared with type I and IIa fibers, and worsened in 24-month rats. The maximum respiratory capacity of mitochondria in DIAm fibers was determined using a quantitative histochemical technique to measure the maximum velocity of the succinate dehydrogenase reaction (SDH max ). SDH max per fiber volume was higher in type I and IIa DIAm fibers and did not change with age. In contrast, SDH max per fiber volume decreased with age in type IIx/IIb DIAm fibers. There were two distinct clusters for SDH max per fiber volume and mitochondrial volume density, one comprising type I and IIa fibers and the second comprising type IIx/IIb fibers. The separation of these clusters increased with aging. There was also a clear relation between SDH max per mitochondrial volume and the extent of mitochondrial fragmentation. The results show that DIAm sarcopenia is restricted to type IIx/IIb DIAm fibers and related to reduced mitochondrial volume, mitochondrial fragmentation and reduced SDH max per fiber volume.
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Han YS, Delmotte P, Sieck GC. Effects of TNFα on Dynamic Cytosolic Ca 2 + and Force Responses to Muscarinic Stimulation in Airway Smooth Muscle. Front Physiol 2021; 12:730333. [PMID: 34393833 PMCID: PMC8363307 DOI: 10.3389/fphys.2021.730333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/09/2021] [Indexed: 11/30/2022] Open
Abstract
Previously, we reported that in airway smooth muscle (ASM), the cytosolic Ca2+ ([Ca2+]cyt) and force response induced by acetyl choline (ACh) are increased by exposure to the pro-inflammatory cytokine tumor necrosis factor α (TNFα). The increase in ASM force induced by TNFα was not associated with an increase in regulatory myosin light chain (rMLC20) phosphorylation but was associated with an increase in contractile protein (actin and myosin) concentration and an enhancement of Ca2+ dependent actin polymerization. The sensitivity of ASM force generation to elevated [Ca2+]cyt (Ca2+ sensitivity) is dynamic involving both the shorter-term canonical calmodulin-myosin light chain kinase (MLCK) signaling cascade that regulates rMLC20 phosphorylation and cross-bridge recruitment as well as the longer-term regulation of actin polymerization that regulates contractile unit recruitment and actin tethering to the cortical cytoskeleton. In this study, we simultaneously measured [Ca2+]cyt and force responses to ACh and explored the impact of 24-h TNFα on the dynamic relationship between [Ca2+]cyt and force responses. The temporal delay between the onset of [Ca2+]cyt and force responses was not affected by TNFα. Similarly, the rates of rise of [Ca2+]cyt and force responses were not affected by TNFα. The absence of an impact of TNFα on the short delay relationships between [Ca2+]cyt and force was consistent with the absence of an effect of [Ca2+]cyt and force on rMLC20 phosphorylation. However, the integral of the phase-loop plot of [Ca2+]cyt and force increased with TNFα, consistent with an impact on actin polymerization and, contractile unit recruitment and actin tethering to the cortical cytoskeleton.
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Affiliation(s)
- Young-Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Philippe Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
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Fitzgerald LF, Bartlett MF, Nagarajan R, Francisco EJ, Sup FC, Kent JA. Effects of old age and contraction mode on knee extensor muscle ATP flux and metabolic economy in vivo. J Physiol 2021; 599:3063-3080. [PMID: 33876434 DOI: 10.1113/jp281117] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 04/14/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We used 31-phosphorus magnetic resonance spectroscopy to quantify in vivo skeletal muscle metabolic economy (ME; mass-normalized torque or power produced per ATP consumed) during three 24 s maximal-effort contraction protocols: (1) sustained isometric (MVIC), (2) intermittent isokinetic (MVDCIsoK ), and (3) intermittent isotonic (MVDCIsoT ) in the knee extensor muscles of young and older adults. ME was not different between groups during the MVIC but was lower in older than young adults during both dynamic contraction protocols. These results are consistent with an increased energy cost of locomotion, but not postural support, with age. The effects of old age on ME were not due to age-related changes in muscle oxidative capacity or ATP flux. Specific power was lower in older than young adults, despite similar total ATP synthesis between groups. Together, this suggests a dissociation between cross-bridge activity and ATP utilization with age. ABSTRACT Muscle metabolic economy (ME; mass-normalized torque or power produced per ATP consumed) is similar in young and older adults during some isometric contractions, but less is known about potential age-related differences in ME during dynamic contractions. We hypothesized that age-related differences in ME would exist only during dynamic contractions, due to the increased energetic demand of dynamic versus isometric contractions. Ten young (Y; 27.5 ± 3.9 years, 6 men) and 10 older (O; 71 ± 5 years, 5 men) healthy adults performed three 24 s bouts of maximal contractions: (1) sustained isometric (MVIC), (2) isokinetic (120°·s-1 , MVDCIsoK ; 0.5 Hz), and (3) isotonic (load = 20% MVIC, MVDCIsoT ; 0.5 Hz). Phosphorus magnetic resonance spectroscopy of the vastus lateralis muscle was used to calculate ATP flux (mM ATP·s-1 ) through the creatine kinase reaction, glycolysis and oxidative phosphorylation. Quadriceps contractile volume (cm3 ) was measured by MRI. ME was calculated using the torque-time integral (MVIC) or power-time integral (MVDCIsoK and MVDCIsoT ), total ATP synthesis and contractile volume. As hypothesized, ME was not different between Y and O during the MVIC (0.12 ± 0.03 vs. 0.12 ± 0.02 Nm. s. cm-3 . mM ATP-1 , mean ± SD, respectively; P = 0.847). However, during both MVDCIsoK and MVDCIsoT , ME was lower in O than Y adults (MVDCIsoK : 0.011 ± 0.003 vs. 0.007 ± 0.002 J. cm-3 . mM ATP-1 ; P < 0.001; MVDCIsoT : 0.011 ± 0.002 vs. 0.008 ± 0.002; P = 0.037, respectively), despite similar muscle oxidative capacity, oxidative and total ATP flux in both groups. The lower specific power in older than young adults, despite similar total ATP synthesis between groups, suggests there is a dissociation between cross-bridge activity and ATP utilization with age.
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Affiliation(s)
- Liam F Fitzgerald
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Miles F Bartlett
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Rajakumar Nagarajan
- Human Magnetic Resonance Center, Institute for Applied Life Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Ericber Jimenez Francisco
- Mechatronics and Robotics Laboratory, Department of Mechanical & Industrial Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Frank C Sup
- Mechatronics and Robotics Laboratory, Department of Mechanical & Industrial Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Jane A Kent
- Muscle Physiology Laboratory, Department of Kinesiology, University of Massachusetts Amherst, Amherst, MA, 01003, USA
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Han YS, Delmotte PF, Arteaga GM, Sieck GC. Dynamic cytosolic Ca 2+ and force responses to muscarinic stimulation in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2021; 321:L91-L101. [PMID: 33908264 DOI: 10.1152/ajplung.00596.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
During agonist stimulation of airway smooth muscle (ASM), agonists such as ACh induce a transient increase in cytosolic Ca2+ concentration ([Ca2+]cyt), which leads to a contractile response [excitation-contraction (E-C) coupling]. Previously, the sensitivity of the contractile response of ASM to elevated [Ca2+]cyt (Ca2+ sensitivity) was assessed as the ratio of maximum force to maximum [Ca2+]cyt. However, this static assessment of Ca2+ sensitivity overlooks the dynamic nature of E-C coupling in ASM. In this study, we simultaneously measured [Ca2+]cyt and isometric force responses to three concentrations of ACh (1, 2.6, and 10 μM). Both maximum [Ca2+]cyt and maximum force responses were ACh concentration dependent, but force increased disproportionately, thereby increasing static Ca2+ sensitivity. The dynamic properties of E-C coupling were assessed in several ways. The temporal delay between the onset of ACh-induced [Ca2+]cyt and onset force responses was not affected by ACh concentration. The rates of rise of the ACh-induced [Ca2+]cyt and force responses increased with increasing ACh concentration. The integral of the phase-loop plot of [Ca2+]cyt and force from onset to steady state also increased with increasing ACh concentration, whereas the rate of relaxation remained unchanged. Although these results suggest an ACh concentration-dependent increase in the rate of cross-bridge recruitment and in the rate of rise of [Ca2+]cyt, the extent of regulatory myosin light-chain (rMLC20) phosphorylation was not dependent on ACh concentration. We conclude that the dynamic properties of [Ca2+]cyt and force responses in ASM are dependent on ACh concentration but reflect more than changes in the extent of rMLC20 phosphorylation.
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Affiliation(s)
- Young-Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Philippe F Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Grace M Arteaga
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Fogarty MJ, Rana S, Mantilla CB, Sieck GC. Quantifying mitochondrial volume density in phrenic motor neurons. J Neurosci Methods 2021; 353:109093. [PMID: 33549636 PMCID: PMC7990712 DOI: 10.1016/j.jneumeth.2021.109093] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/26/2021] [Accepted: 02/01/2021] [Indexed: 12/31/2022]
Abstract
BACKGROUND Previous assessments of mitochondrial volume density within motor neurons used electron microscopy (EM) to image mitochondria. However, adequate identification and sampling of motor neurons within a particular motor neuron pool is largely precluded using EM. Here, we present an alternative method for determining mitochondrial volume density in identified motor neurons within the phrenic motor neuron (PhMN) pool, with greatly increased sampling. NEW METHOD This novel method for assessing mitochondrial volume density in PhMNs uses a combination of intrapleural injection of Alexa 488-conjugated cholera toxin B (CTB) to retrogradely label PhMNs, followed by intrathecal application of MitoTracker Red to label mitochondria. This technique was validated by comparison to 3D EM determination of mitochondrial volume density as a "gold standard". RESULTS A mean mitochondrial volume density of ∼11 % was observed across PhMNs using the new MitoTracker Red method. This compared favourably with mitochondrial volume density (∼11 %) measurements using EM. COMPARISON WITH EXISTING METHOD The range, mean and variance of mitochondrial volume density estimates in PhMNs were not different between EM and fluorescent imaging techniques. CONCLUSIONS Fluorescent imaging may be used to estimate mitochondrial volume density in a large sample of motor neurons, with results similar to EM, although EM did distinguish finer mitochondrion morphology compared to MitoTracker fluorescence. Compared to EM methods, the assessment of a larger sample size and unambiguous identification of motor neurons belonging to a specific motor neuron pool represent major advantages over previous methods.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States; School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4067, Australia
| | - Sabhya Rana
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States
| | - Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States; Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55905, United States
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States.
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Inflammation-Induced Protein Unfolding in Airway Smooth Muscle Triggers a Homeostatic Response in Mitochondria. Int J Mol Sci 2020; 22:ijms22010363. [PMID: 33396378 PMCID: PMC7795579 DOI: 10.3390/ijms22010363] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/17/2020] [Accepted: 12/28/2020] [Indexed: 12/11/2022] Open
Abstract
The effects of airway inflammation on airway smooth muscle (ASM) are mediated by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα). In this review article, we will provide a unifying hypothesis for a homeostatic response to airway inflammation that mitigates oxidative stress and thereby provides resilience to ASM. Previous studies have shown that acute exposure to TNFα increases ASM force generation in response to muscarinic stimulation (hyper-reactivity) resulting in increased ATP consumption and increased tension cost. To meet this increased energetic demand, mitochondrial O2 consumption and oxidative phosphorylation increases but at the cost of increased reactive oxygen species (ROS) production (oxidative stress). TNFα-induced oxidative stress results in the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and mitochondria of ASM. In the ER, TNFα selectively phosphorylates inositol-requiring enzyme 1 alpha (pIRE1α) triggering downstream splicing of the transcription factor X-box binding protein 1 (XBP1s); thus, activating the pIRE1α/XBP1s ER stress pathway. Protein unfolding in mitochondria also triggers an unfolded protein response (mtUPR). In our conceptual framework, we hypothesize that activation of these pathways is homeostatically directed towards mitochondrial remodeling via an increase in peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) expression, which in turn triggers: (1) mitochondrial fragmentation (increased dynamin-related protein-1 (Drp1) and reduced mitofusin-2 (Mfn2) expression) and mitophagy (activation of the Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)/Parkin mitophagy pathway) to improve mitochondrial quality; (2) reduced Mfn2 also results in a disruption of mitochondrial tethering to the ER and reduced mitochondrial Ca2+ influx; and (3) mitochondrial biogenesis and increased mitochondrial volume density. The homeostatic remodeling of mitochondria results in more efficient O2 consumption and oxidative phosphorylation and reduced ROS formation by individual mitochondrion, while still meeting the increased ATP demand. Thus, the energetic load of hyper-reactivity is shared across the mitochondrial pool within ASM cells.
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Delmotte P, Han Y, Sieck GC. Cytoskeletal remodeling slows cross-bridge cycling and ATP hydrolysis rates in airway smooth muscle. Physiol Rep 2020; 8:e14561. [PMID: 32812390 PMCID: PMC7435030 DOI: 10.14814/phy2.14561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/03/2020] [Accepted: 08/05/2020] [Indexed: 12/14/2022] Open
Abstract
During isometric activation of airway smooth muscle (ASM), cross-bridge cycling and ATP hydrolysis rates decline across time even though isometric force is sustained. Thus, tension cost (i.e., ATP hydrolysis rate per unit of force during activation) decreases with time. The "latch-state" hypothesis attributes the dynamic change in cross-bridge cycling and ATP hydrolysis rates to changes in phosphorylation of the regulatory myosin light chain (rMLC20 ). However, we previously showed that in ASM, the extent of rMLC20 phosphorylation remains unchanged during sustained isometric force. As an alternative, we hypothesized that cytoskeletal remodeling within ASM cells results in increased internal loading of contractile proteins that slows cross-bridge cycling and ATP hydrolysis rates. To test this hypothesis, we simultaneously measured isometric force and ATP hydrolysis rate in permeabilized porcine ASM strips activated by Ca2+ (pCa 4.0). The extent of rMLC20 phosphorylation remained unchanged during isometric activation, even though ATP hydrolysis rate (tension cost) declined with time. The effect of cytoskeletal remodeling was assessed by inhibiting actin polymerization using Cytochalasin D (Cyto-D). In Cyto-D treated ASM, isometric force was reduced while ATP hydrolysis rate increased compared to untreated ASM strips. These results indicate that external transmission of force, cross-bridge cycling and ATP hydrolysis rates are affected by internal loading of contractile proteins.
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Affiliation(s)
- Philippe Delmotte
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMNUSA
| | - Young‐soo Han
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMNUSA
| | - Gary C. Sieck
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMNUSA
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Delmotte P, Sieck GC. Endoplasmic Reticulum Stress and Mitochondrial Function in Airway Smooth Muscle. Front Cell Dev Biol 2020; 7:374. [PMID: 32010691 PMCID: PMC6974519 DOI: 10.3389/fcell.2019.00374] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 12/16/2019] [Indexed: 12/16/2022] Open
Abstract
Inflammatory airway diseases such as asthma affect more than 300 million people world-wide. Inflammation triggers pathophysiology via such as tumor necrosis factor α (TNFα) and interleukins (e.g., IL-13). Hypercontraction of airway smooth muscle (ASM) and ASM cell proliferation are major contributors to the exaggerated airway narrowing that occurs during agonist stimulation. An emergent theme in this context is the role of inflammation-induced endoplasmic reticulum (ER) stress and altered mitochondrial function including an increase in the formation of reactive oxygen species (ROS). This may establish a vicious cycle as excess ROS generation leads to further ER stress. Yet, it is unclear whether inflammation-induced ROS is the major mechanism leading to ER stress or the consequence of ER stress. In various diseases, inflammation leads to an increase in mitochondrial fission (fragmentation), associated with reduced levels of mitochondrial fusion proteins, such as mitofusin 2 (Mfn2). Mitochondrial fragmentation may be a homeostatic response since it is generally coupled with mitochondrial biogenesis and mitochondrial volume density thereby reducing demand on individual mitochondrion. ER stress is triggered by the accumulation of unfolded proteins, which induces a homeostatic response to alter protein balance via effects on protein synthesis and degradation. In addition, the ER stress response promotes protein folding via increased expression of molecular chaperone proteins. Reduced Mfn2 and altered mitochondrial dynamics may not only be downstream to ER stress but also upstream such that a reduction in Mfn2 triggers further ER stress. In this review, we summarize the current understanding of the link between inflammation-induced ER stress and mitochondrial function and the role played in the pathophysiology of inflammatory airway diseases.
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Affiliation(s)
- Philippe Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
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Abstract
Breathing is achieved without thought despite being controlled by a complex neural network. The diaphragm is the predominant muscle responsible for force/pressure generation during breathing, but it is also involved in other non-ventilatory expulsive behaviors. This review considers alterations in diaphragm muscle fiber types and the neural control of the diaphragm across our lifespan and in various disease conditions.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
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14
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Vanden Hole C, Van Ginneken C, Prims S, Ayuso M, Van Cruchten S, Aerts P. Does intrauterine crowding affect the force generating capacity and muscle composition of the piglet front limb? PLoS One 2019; 14:e0223851. [PMID: 31600318 PMCID: PMC6786600 DOI: 10.1371/journal.pone.0223851] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 09/30/2019] [Indexed: 12/04/2022] Open
Abstract
In the pig, intrauterine competition (IUC) greatly affects postnatal traits, such as birth weight, but also locomotor capacities. In a previous study, our group discovered a lower motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets). In order to explain the force deficit causing this reduced motor performance, in a subsequent study, we investigated whether this deficit in L piglets was caused by a lower force generating capacity (FGC) of the extensors of the hind limb and/or a lower number of type II (fast-twitch) fibers in m. vastus lateralis. L piglets had a lower absolute FGC, but surprisingly, a higher relative FGC (to birth weight) in the hind limb, compared to N piglets. In addition, we found no differences in fiber composition of m. vastus lateralis. In the present study, we assessed whether this higher relative FGC is a common feature for front and hind limb locomotor muscles of L piglets. To that end, the physiological cross-sectional area of the main extensor muscles of the front limb was calculated from their volume and fiber length, in order to calculate both the absolute and the relative FGC. By immunohistochemical staining of m. triceps brachii caput longum, the percentage of type II (fast-contracting) fibers could be determined. Similar to the results of the hind limb, we found a smaller absolute FGC, but a larger relative FGC in the front limb of L piglets, compared to N piglets. In addition, m. triceps brachii caput longum did not have a different muscle fiber composition in L and N piglets. As such, we can conclude that IUC affects the locomotor muscles in the front and hind limb in a similar way and that the observed force deficit in L piglets cannot be explained by a different force generating capacity or a lower percentage of type II muscle fibers.
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Affiliation(s)
- Charlotte Vanden Hole
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Chris Van Ginneken
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Sara Prims
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Miriam Ayuso
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Steven Van Cruchten
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Peter Aerts
- Laboratory of Functional Morphology, Department of Biology, Faculty of Sciences, University of Antwerp, Wilrijk, Belgium
- Department of Movement and Sports Sciences, Faculty of Medicine and Health Sciences, University of Ghent, Ghent, Belgium
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15
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Sieck GC, Dogan M, Young‐Soo H, Osorio Valencia S, Delmotte P. Mechanisms underlying TNFα-induced enhancement of force generation in airway smooth muscle. Physiol Rep 2019; 7:e14220. [PMID: 31512410 PMCID: PMC6739507 DOI: 10.14814/phy2.14220] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/29/2019] [Accepted: 08/05/2019] [Indexed: 11/24/2022] Open
Abstract
Airway diseases such as asthma are triggered by inflammation and mediated by proinflammatory cytokines such as tumor necrosis factor alpha (TNFα). Our goal was to systematically examine the potential mechanisms underlying the effect of TNFα on airway smooth muscle (ASM) contractility. Porcine ASM strips were incubated for 24 h with and without TNFα. Exposure to TNFα increased maximum ASM force in response to acetylcholine (Ach), with an increase in ACh sensitivity (hyperreactivity), as reflected by a leftward shift in the dose-response curve (EC50 ). At the EC50 , the [Ca2+ ]cyt response to ACh was similar between TNFα and control ASM, while force increased; thus, Ca2+ sensitivity appeared to increase. Exposure to TNFα increased the basal level of regulatory myosin light chain (rMLC) phosphorylation in ASM; however, the ACh-dependent increase in rMLC phosphorylation was blunted by TNFα with no difference in the extent of rMLC phosphorylation at the EC50 ACh concentration. In TNFα-treated ASM, total actin and myosin heavy chain concentrations increased. TNFα exposure also enhanced the ACh-dependent polymerization of G- to F-actin. The results of this study confirm TNFα-induced hyperreactivity to ACh in porcine ASM. We conclude that the TNFα-induced increase in ASM force, cannot be attributed to an enhanced [Ca2+ ]cyt response or to an increase in rMLC phosphorylation. Instead, TNFα increases Ca2+ sensitivity of ASM force generation due to increased contractile protein content (greater number of contractile units) and enhanced cytoskeletal remodeling (actin polymerization) resulting in increased tethering of contractile elements to the cortical cytoskeleton and force translation to the extracellular matrix.
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Affiliation(s)
- Gary C. Sieck
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Murat Dogan
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Han Young‐Soo
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Sara Osorio Valencia
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
| | - Philippe Delmotte
- Department of Physiology and Biomedical EngineeringMayo ClinicRochesterMinnesota
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16
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Fogarty MJ, Sieck GC. Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals. Compr Physiol 2019; 9:715-766. [PMID: 30873594 PMCID: PMC7082849 DOI: 10.1002/cphy.c180012] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Symmorphosis is a concept of economy of biological design, whereby structural properties are matched to functional demands. According to symmorphosis, biological structures are never over designed to exceed functional demands. Based on this concept, the evolution of the diaphragm muscle (DIAm) in mammals is a tale of two structures, a membrane that separates and partitions the primitive coelomic cavity into separate abdominal and thoracic cavities and a muscle that serves as a pump to generate intra-abdominal (Pab ) and intrathoracic (Pth ) pressures. The DIAm partition evolved in reptiles from folds of the pleural and peritoneal membranes that was driven by the biological advantage of separating organs in the larger coelomic cavity into separate thoracic and abdominal cavities, especially with the evolution of aspiration breathing. The DIAm pump evolved from the advantage afforded by more effective generation of both a negative Pth for ventilation of the lungs and a positive Pab for venous return of blood to the heart and expulsive behaviors such as airway clearance, defecation, micturition, and child birth. © 2019 American Physiological Society. Compr Physiol 9:715-766, 2019.
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Affiliation(s)
- Matthew J Fogarty
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| | - Gary C Sieck
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
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17
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Vanden Hole C, Cleuren S, Van Ginneken C, Prims S, Ayuso M, Van Cruchten S, Aerts P. How does intrauterine crowding affect locomotor performance in newborn pigs? A study of force generating capacity and muscle composition of the hind limb. PLoS One 2018; 13:e0209233. [PMID: 30550550 PMCID: PMC6294349 DOI: 10.1371/journal.pone.0209233] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 11/30/2018] [Indexed: 11/19/2022] Open
Abstract
Intrauterine crowding (IUC) considerably influences postnatal traits in a polytocous species such as the pig. Previously, our group described how IUC affects locomotion during the piglet’s first days of life (until 96 h after birth). We noted a reduced motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets), indicating L piglets are unable to produce enough force. Our current study investigates whether this observed force deficit in L piglets is caused by a reduced force generating capacity in the muscles and/or a lower percentage of type II (fast-contracting) fibers. Volume and fiber length of the main extensor muscles of the hind limb were used to estimate the physiological cross-sectional area (PSCA) and hence calculate the maximal isometric force generating capacity (Fiso-max) of the hind limb. To check for developmental differences between the muscles of L and N piglets, Fiso-max was normalized to body weight (BW), thus yielding a dimensionless variable F’iso-max. To check for differences in muscle composition, m. vastus lateralis was stained immunohistochemically in order to determine the percentage of type II fibers through image analysis. Our results indicate that L piglets have a reduced absolute force generating capacity due to a lesser muscle mass, compared to N piglets. However, when normalized to BW L piglets actually show a larger force generating capacity, suggesting their muscles are more voluminous, given their body mass, than those of N piglets. However, no differences between L and N piglets were detected with regard to muscle composition of the m. vastus lateralis. Based on our data, we can say that neither normalized force generating capacity, nor muscle composition (of the m. vastus lateralis) can explain the observed force deficit in L piglets and as such the effect of IUC on locomotor performance.
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Affiliation(s)
- Charlotte Vanden Hole
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Silke Cleuren
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Chris Van Ginneken
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
- * E-mail:
| | - Sara Prims
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Miriam Ayuso
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Steven Van Cruchten
- Laboratory of Applied Veterinary Morphology, Department of Veterinary Sciences, Faculty of Biomedical, Pharmaceutical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Peter Aerts
- Laboratory of Functional Morphology, Department of Biology, Faculty of Sciences, University of Antwerp, Wilrijk, Belgium
- Department of Movement and Sports Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
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18
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Wang L, Geist J, Grogan A, Hu LYR, Kontrogianni-Konstantopoulos A. Thick Filament Protein Network, Functions, and Disease Association. Compr Physiol 2018; 8:631-709. [PMID: 29687901 PMCID: PMC6404781 DOI: 10.1002/cphy.c170023] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sarcomeres consist of highly ordered arrays of thick myosin and thin actin filaments along with accessory proteins. Thick filaments occupy the center of sarcomeres where they partially overlap with thin filaments. The sliding of thick filaments past thin filaments is a highly regulated process that occurs in an ATP-dependent manner driving muscle contraction. In addition to myosin that makes up the backbone of the thick filament, four other proteins which are intimately bound to the thick filament, myosin binding protein-C, titin, myomesin, and obscurin play important structural and regulatory roles. Consistent with this, mutations in the respective genes have been associated with idiopathic and congenital forms of skeletal and cardiac myopathies. In this review, we aim to summarize our current knowledge on the molecular structure, subcellular localization, interacting partners, function, modulation via posttranslational modifications, and disease involvement of these five major proteins that comprise the thick filament of striated muscle cells. © 2018 American Physiological Society. Compr Physiol 8:631-709, 2018.
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Affiliation(s)
- Li Wang
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Janelle Geist
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Alyssa Grogan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
| | - Li-Yen R. Hu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, Maryland, USA
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19
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Fogarty MJ, Mantilla CB, Sieck GC. Breathing: Motor Control of Diaphragm Muscle. Physiology (Bethesda) 2018; 33:113-126. [PMID: 29412056 PMCID: PMC5899234 DOI: 10.1152/physiol.00002.2018] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 01/05/2018] [Indexed: 12/12/2022] Open
Abstract
Breathing occurs without thought but is controlled by a complex neural network with a final output of phrenic motor neurons activating diaphragm muscle fibers (i.e., motor units). This review considers diaphragm motor unit organization and how they are controlled during breathing as well as during expulsive behaviors.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- School of Biomedical Sciences, The University of Queensland , Brisbane , Australia
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
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20
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Dogan M, Han YS, Delmotte P, Sieck GC. TNFα enhances force generation in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2017; 312:L994-L1002. [PMID: 28385814 PMCID: PMC5495949 DOI: 10.1152/ajplung.00550.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/15/2017] [Accepted: 04/03/2017] [Indexed: 11/22/2022] Open
Abstract
Airway inflammation is a hallmark of asthma, triggering airway smooth muscle (ASM) hyperreactivity and airway remodeling. TNFα increases both agonist-induced cytosolic Ca2+ concentration ([Ca2+]cyt) and force in ASM. The effects of TNFα on ASM force may also be due to an increase in Ca2+ sensitivity, cytoskeletal remodeling, and/or changes in contractile protein content. We hypothesized that 24 h of exposure to TNFα increases ASM force by changing actin and myosin heavy chain (MyHC) content and/or polymerization. Porcine ASM strips were permeabilized with 10% Triton X-100, and force was measured in response to increasing concentrations of Ca2+ (pCa 9.0 to 4.0) in control and TNFα-treated groups. Relative phosphorylation of the regulatory myosin light chain (p-MLC) and total actin, MLC, and MyHC concentrations were quantified at pCa 9.0, 6.1, and 4.0. Actin polymerization was quantified by the ratio of filamentous to globular actin at pCa 9.0 and 4.0. For determination of total cross-bridge formation, isometric ATP hydrolysis rate at pCa 4.0 was measured using an enzyme-coupled NADH-linked fluorometric technique. Exposure to TNFα significantly increased force across the range of Ca2+ activation but did not affect the intrinsic Ca2+ sensitivity of force generation. The TNFα-induced increase in ASM force was associated with an increase in total actin, MLC, and MyHC content, as well as an increase in actin polymerization and an increase in maximum isometric ATP hydrolysis rate. The results of this study support our hypothesis that TNFα increases force generation in ASM by increasing the number of contractile units (actin-myosin content) contributing to force generation.
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Affiliation(s)
- Murat Dogan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Young-Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Philippe Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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21
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Namuduri AV, Heras G, Mi J, Cacciani N, Hörnaeus K, Konzer A, Lind SB, Larsson L, Gastaldello S. A Proteomic Approach to Identify Alterations in the Small Ubiquitin-like Modifier (SUMO) Network during Controlled Mechanical Ventilation in Rat Diaphragm Muscle. Mol Cell Proteomics 2017; 16:1081-1097. [PMID: 28373296 DOI: 10.1074/mcp.m116.066159] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 04/03/2017] [Indexed: 12/17/2022] Open
Abstract
The small ubiquitin-like modifier (SUMO) is as a regulator of many cellular functions by reversible conjugation to a broad number of substrates. Under endogenous or exogenous perturbations, the SUMO network becomes a fine sensor of stress conditions by alterations in the expression level of SUMO enzymes and consequently changing the status of SUMOylated proteins. The diaphragm is the major inspiratory muscle, which is continuously active under physiological conditions, but its structure and function is severely affected when passively displaced for long extents during mechanical ventilation (MV). An iatrogenic condition called Ventilator-Induced Diaphragm Dysfunction (VIDD) is a major cause of failure to wean patients from ventilator support but the molecular mechanisms underlying this dysfunction are not fully understood. Using a unique experimental Intensive Care Unit (ICU) rat model allowing long-term MV, diaphragm muscles were collected in rats control and exposed to controlled MV (CMV) for durations varying between 1 and 10 days. Endogenous SUMOylated diaphragm proteins were identified by mass spectrometry and validated with in vitro SUMOylation systems. Contractile, calcium regulator and mitochondrial proteins were of specific interest due to their putative involvement in VIDD. Differences were observed in the abundance of SUMOylated proteins between glycolytic and oxidative muscle fibers in control animals and high levels of SUMOylated proteins were present in all fibers during CMV. Finally, previously reported VIDD biomarkers and therapeutic targets were also identified in our datasets which may play an important role in response to muscle weakness seen in ICU patients. Data are available via ProteomeXchange with identifier PXD006085. Username: reviewer26663@ebi.ac.uk, Password: rwcP5W0o.
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Affiliation(s)
- Arvind Venkat Namuduri
- From the ‡Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Gabriel Heras
- From the ‡Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Jia Mi
- §Department of Chemistry-BMC, Analytical Chemistry and Science for Lab Laboratory, Uppsala University, Box 599, Uppsala, SE-75124, Sweden.,¶Medicine and Pharmacy Research Center, Binzhou Medical University, Laishan District, No. 346, Guanhai Road, Yantai, Shandong Province, 264003 China
| | - Nicola Cacciani
- From the ‡Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Katarina Hörnaeus
- §Department of Chemistry-BMC, Analytical Chemistry and Science for Lab Laboratory, Uppsala University, Box 599, Uppsala, SE-75124, Sweden
| | - Anne Konzer
- §Department of Chemistry-BMC, Analytical Chemistry and Science for Lab Laboratory, Uppsala University, Box 599, Uppsala, SE-75124, Sweden
| | - Sara Bergström Lind
- §Department of Chemistry-BMC, Analytical Chemistry and Science for Lab Laboratory, Uppsala University, Box 599, Uppsala, SE-75124, Sweden
| | - Lars Larsson
- From the ‡Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, SE-17177, Sweden.,‖Department of Biobehavioral Health, The Pennsylvania State University, University Park, Pennsylvania 16801; and.,**Department of Clinical Neuroscience, Clinical Neurophysiology, Karolinska Institutet, Stockholm, SE-17177, Sweden
| | - Stefano Gastaldello
- From the ‡Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, SE-17177, Sweden;
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22
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Delmotte P, Sieck GC. Interaction between endoplasmic/sarcoplasmic reticulum stress (ER/SR stress), mitochondrial signaling and Ca(2+) regulation in airway smooth muscle (ASM). Can J Physiol Pharmacol 2014; 93:97-110. [PMID: 25506723 DOI: 10.1139/cjpp-2014-0361] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Airway inflammation is a key aspect of diseases such as asthma. Several inflammatory cytokines (e.g., TNFα and IL-13) increase cytosolic Ca(2+) ([Ca(2+)]cyt) responses to agonist stimulation and Ca(2+) sensitivity of force generation, thereby enhancing airway smooth muscle (ASM) contractility (hyper-reactive state). Inflammation also induces ASM proliferation and remodeling (synthetic state). In normal ASM, the transient elevation of [Ca(2+)]cyt induced by agonists leads to a transient increase in mitochondrial Ca(2+) ([Ca(2+)]mito) that may be important in matching ATP production with ATP consumption. In human ASM (hASM) exposed to TNFα and IL-13, the transient increase in [Ca(2+)]mito is blunted despite enhanced [Ca(2+)]cyt responses. We also found that TNFα and IL-13 induce reactive oxidant species (ROS) formation and endoplasmic/sarcoplasmic reticulum (ER/SR) stress (unfolded protein response) in hASM. ER/SR stress in hASM is associated with disruption of mitochondrial coupling with the ER/SR membrane, which relates to reduced mitofusin 2 (Mfn2) expression. Thus, in hASM it appears that TNFα and IL-13 result in ROS formation leading to ER/SR stress, reduced Mfn2 expression, disruption of mitochondrion-ER/SR coupling, decreased mitochondrial Ca(2+) buffering, mitochondrial fragmentation, and increased cell proliferation.
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Affiliation(s)
- Philippe Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 4-184 West Joseph SMH, 200 First Street SW, Rochester, MN 55905, USA
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23
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Maltais F, Decramer M, Casaburi R, Barreiro E, Burelle Y, Debigaré R, Dekhuijzen PNR, Franssen F, Gayan-Ramirez G, Gea J, Gosker HR, Gosselink R, Hayot M, Hussain SNA, Janssens W, Polkey MI, Roca J, Saey D, Schols AMWJ, Spruit MA, Steiner M, Taivassalo T, Troosters T, Vogiatzis I, Wagner PD. An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2014; 189:e15-62. [PMID: 24787074 DOI: 10.1164/rccm.201402-0373st] [Citation(s) in RCA: 683] [Impact Index Per Article: 68.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications. PURPOSE The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD. METHODS An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological approach was consistent with ATS standards. RESULTS We identified important advances in our understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD. Since the last update, landmark studies were published on the mechanisms of development of limb muscle dysfunction in COPD and on the treatment of this condition. We now have a better understanding of the clinical implications of limb muscle dysfunction. Although exercise training is the most potent intervention to address this condition, other therapies, such as neuromuscular electrical stimulation, are emerging. Assessment of limb muscle function can identify patients who are at increased risk of poor clinical outcomes, such as exercise intolerance and premature mortality. CONCLUSIONS Limb muscle dysfunction is a key systemic consequence of COPD. However, there are still important gaps in our knowledge about the mechanisms of development of this problem. Strategies for early detection and specific treatments for this condition are also needed.
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Abstract
Striated respiratory muscles are necessary for lung ventilation and to maintain the patency of the upper airway. The basic structural and functional properties of respiratory muscles are similar to those of other striated muscles (both skeletal and cardiac). The sarcomere is the fundamental organizational unit of striated muscles and sarcomeric proteins underlie the passive and active mechanical properties of muscle fibers. In this respect, the functional categorization of different fiber types provides a conceptual framework to understand the physiological properties of respiratory muscles. Within the sarcomere, the interaction between the thick and thin filaments at the level of cross-bridges provides the elementary unit of force generation and contraction. Key to an understanding of the unique functional differences across muscle fiber types are differences in cross-bridge recruitment and cycling that relate to the expression of different myosin heavy chain isoforms in the thick filament. The active mechanical properties of muscle fibers are characterized by the relationship between myoplasmic Ca2+ and cross-bridge recruitment, force generation and sarcomere length (also cross-bridge recruitment), external load and shortening velocity (cross-bridge cycling rate), and cross-bridge cycling rate and ATP consumption. Passive mechanical properties are also important reflecting viscoelastic elements within sarcomeres as well as the extracellular matrix. Conditions that affect respiratory muscle performance may have a range of underlying pathophysiological causes, but their manifestations will depend on their impact on these basic elemental structures.
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Affiliation(s)
- Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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25
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O'Connell RA, Carberry J, O'Halloran KD. Sternohyoid and diaphragm muscle form and function during postnatal development in the rat. Exp Physiol 2013; 98:1386-400. [PMID: 23709586 DOI: 10.1113/expphysiol.2013.073346] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Co-ordinated activity of the thoracic pump and pharyngeal dilator muscles is critical for maintaining airway calibre and respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in the airway dilator muscles. What is the main finding and its importance? Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a maturational shift in muscle myosin heavy chain phenotype. This maturation is accelerated in the sternohyoid muscle relative to the diaphragm and may have implications for the control of airway calibre in vivo. The striated muscles of breathing, including the thoracic pump and pharyngeal dilator muscles, play a critical role in maintaining respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in airway dilator muscles given that co-ordinated activity of both sets of muscles is needed for the maintenance of airway calibre and effective pulmonary ventilation. The form and function of sternohyoid and diaphragm muscles from Wistar rat pups [postnatal day (PD) 10, 20 and 30] was determined. Isometric contractile and endurance properties were examined in tissue baths containing Krebs solution at 35°C. Myosin heavy chain (MHC) isoform composition was determined using immunofluorescence. Muscle oxidative and glycolytic capacity was assessed by measuring the activities of succinate dehydrogenase and glycerol-3-phosphate dehydrogenase using semi-quantitative histochemistry. Sternohyoid and diaphragm peak isometric force and fatigue increased significantly with postnatal maturation. Developmental myosin disappeared by PD20, whereas MHC2B areal density increased significantly from PD10 to PD30, emerging earlier and to a much greater extent in the sternohyoid muscle. The numerical density of fibres expressing MHC2X and MHC2B increased significantly during development in the sternohyoid. Diaphragm succinate dehydrogenase activity and sternohyoid glycerol-3-phosphate dehydrogenase activity increased significantly with age. Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a postnatal shift in muscle MHC phenotype. The accelerated maturation of the sternohyoid muscle relative to the diaphragm may have implications for the control of airway calibre in vivo.
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Affiliation(s)
- R A O'Connell
- School of Medicine and Medical Science, University College Dublin, Dublin, Ireland.
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Greising SM, Gransee HM, Mantilla CB, Sieck GC. Systems biology of skeletal muscle: fiber type as an organizing principle. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2012; 4:457-73. [PMID: 22811254 DOI: 10.1002/wsbm.1184] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Skeletal muscle force generation and contraction are fundamental to countless aspects of human life. The complexity of skeletal muscle physiology is simplified by fiber type classification where differences are observed from neuromuscular transmission to release of intracellular Ca(2+) from the sarcoplasmic reticulum and the resulting recruitment and cycling of cross-bridges. This review uses fiber type classification as an organizing and simplifying principle to explore the complex interactions between the major proteins involved in muscle force generation and contraction.
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Affiliation(s)
- Sarah M Greising
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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Specific effects of endurance and sprint training on protein expression of calsequestrin and SERCA in mouse skeletal muscle. J Muscle Res Cell Motil 2012; 33:123-30. [PMID: 22466636 DOI: 10.1007/s10974-012-9290-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
Abstract
Calsequestrin (CSQ) is the main Ca²⁺ binding protein inside the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle. The present study demonstrates the specific effects of different training regimens on CSQ isoform 1 (CSQ1, the primary isoform) and SR Ca²⁺-ATPase (SERCA1, 2) expression in various skeletal muscles of mouse. CSQ1, SERCA1, and SERCA2 protein expression was determined with Western blot in m. soleus (SOL), m. extensor digitorum longus (EDL), m. gastrocnemius (GAS), m. rectus femoris (RF), and m. tibialis anterior (TA) muscles after completing a 6-week endurance or sprint training program. Endurance training induced decrease in CSQ1 concentration in SOL (p < 0.001) and in SERCA1 levels in GAS (p < 0.05), whereas increase in CSQ1 expression was detected in EDL (p < 0.01). After sprint training the concentration of CSQ1 increased in GAS (p < 0.01) and EDL (p < 0.01). Additionally, sprint exercise induced an increase in SERCA1 in GAS (p < 0.001) and a decline in TA (p < 0.05). SERCA2 was up-regulated with sprint training in GAS (p < 0.01). Myosin heavy chain (MHC) based fibre type composition altered differently depending on the muscle and the training regimen.These results indicate that (1) diverse training strategies used affect differently CSQ1 and SERCA1 concentrations in the skeletal muscle, (2) the regulation of CSQ1 and SERCA1 does not necessary follow the fast-slow definition despite the correlation between MHC isoforms, and (3) the changes in CSQ1 concentration occur prior to SERCA1 or SERCA2.
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Edwards A, Cao C, Pallone TL. Cellular mechanisms underlying nitric oxide-induced vasodilation of descending vasa recta. Am J Physiol Renal Physiol 2010; 300:F441-56. [PMID: 21084408 DOI: 10.1152/ajprenal.00499.2010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been observed that vasoactivity of explanted descending vasa recta (DVR) is modulated by intrinsic nitric oxide (NO) and superoxide (O(2)(-)) production (Cao C, Edwards A, Sendeski M, Lee-Kwon W, Cui L, Cai CY, Patzak A, Pallone TL. Am J Physiol Renal Physiol 299: F1056-F1064, 2010). To elucidate the cellular mechanisms by which NO, O(2)(-) and hydrogen peroxide (H(2)O(2)) modulate DVR pericyte cytosolic Ca(2+) concentration ([Ca](cyt)) and vasoactivity, we expanded our mathematical model of Ca(2+) signaling in pericytes. We incorporated simulations of the pathways that translate an increase in [Ca](cyt) to the activation of myosin light chain (MLC) kinase and cell contraction, as well as the kinetics of NO and reactive oxygen species formation and their effects on [Ca](cyt) and MLC phosphorylation. The model reproduced experimentally observed trends of DVR vasoactivity that accompany exposure to N(ω)-nitro-L-arginine methyl ester, 8-Br-cGMP, Tempol, and H(2)O(2). Our results suggest that under resting conditions, NO-induced activation of cGMP maintains low levels of [Ca](cyt) and MLC phosphorylation to minimize basal tone. This results from stimulation of Ca(2+) uptake from the cytosol into the SR via SERCA pumps, Ca(2+) efflux into the extracellular space via plasma membrane Ca(2+) pumps, and MLC phosphatase (MLCP) activity. We predict that basal concentrations of O(2)(-) and H(2)O(2) have negligible effects on Ca(2+) signaling and MLC phosphorylation. At concentrations above 1 nM, O(2)(-) is predicted to modulate [Ca(cyt)] and MCLP activity mostly by reducing NO bioavailability. The DVR vasoconstriction that is induced by high concentrations of H(2)O(2) can be explained by H(2)O(2)-mediated downregulation of MLCP and SERCA activity. We conclude that intrinsic generation of NO by the DVR wall may be sufficient to inhibit vasoconstriction by maintaining suppression of MLC phosphorylation.
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Affiliation(s)
- Aurélie Edwards
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, USA.
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Salvi N, Guellich A, Michelet P, Demoule A, Le Guen M, Renou L, Bonne G, Riou B, Langeron O, Coirault C. Upregulation of PPARbeta/delta is associated with structural and functional changes in the type I diabetes rat diaphragm. PLoS One 2010; 5:e11494. [PMID: 20628611 PMCID: PMC2900215 DOI: 10.1371/journal.pone.0011494] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 06/14/2010] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Diabetes mellitus is associated with alterations in peripheral striated muscles and cardiomyopathy. We examined diaphragmatic function and fiber composition and identified the role of peroxisome proliferator-activated receptors (PPAR alpha and beta/delta) as a factor involved in diaphragm muscle plasticity in response to type I diabetes. METHODOLOGY/PRINCIPAL FINDINGS Streptozotocin-treated rats were studied after 8 weeks and compared with their controls. Diaphragmatic strips were stimulated in vitro and mechanical and energetic variables were measured, cross bridge kinetics assessed, and the effects of fatigue and hypoxia evaluated. Morphometry, myosin heavy chain isoforms, PPAR alpha and beta/delta gene and protein expression were also assessed. Diabetes induced a decrease in maximum velocity of shortening (-14%, P<0.05) associated with a decrease in myosin ATPase activity (-49%, P<0.05), and an increase in force (+20%, P<0.05) associated with an increase in the number of cross bridges (+14%, P<0.05). These modifications were in agreement with a shift towards slow myosin heavy chain fibers and were associated with an upregulation of PPARbeta/delta (+314% increase in gene and +190% increase in protein expression, P<0.05). In addition, greater resistances to fatigue and hypoxia were observed in diabetic rats. CONCLUSIONS/SIGNIFICANCE Type I diabetes induced complex mechanical and energetic changes in the rat diaphragm and was associated with an up-regulation of PPARbeta/delta that could improve resistance to fatigue and hypoxia and favour the shift towards slow myosin heavy chain isoforms.
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Affiliation(s)
- Nadège Salvi
- UMRS INSERM 956, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Aziz Guellich
- UMRS INSERM 974, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Pierre Michelet
- UMRS INSERM 956, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Alexandre Demoule
- UMRS INSERM 974, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Pneumology, Groupe hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France
| | - Morgan Le Guen
- UMRS INSERM 956, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Anesthesiology and Critical Care, Groupe hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France
| | - Laure Renou
- UMR CNRS 7215, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Gisèle Bonne
- UMRS INSERM 974, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- UMR CNRS 7215, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Metabolic Biochemistry, Groupe hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France
| | - Bruno Riou
- UMRS INSERM 956, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Emergency Medicine and Surgery, Groupe hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France
- * E-mail:
| | - Olivier Langeron
- UMRS INSERM 956, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Anesthesiology and Critical Care, Groupe hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France
| | - Catherine Coirault
- UMRS INSERM 974, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- UMR CNRS 7215, Institut de Myologie, IFR14, Université Pierre et Marie Curie-Paris 6, Paris, France
- Department of Physiology, Hôpital de Bicêtre, APHP, Le Kremlin-Bicêtre, France
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Abstract
STUDY DESIGN Experimental laboratory study. OBJECTIVES The primary purpose was to investigate the independent effects of current amplitude, pulse duration, and current frequency on muscle fatigue during neuromuscular electrical stimulation (NMES). A second purpose was to determine if the ratio of the evoked torque to the activated area could explain muscle fatigue. BACKGROUND Parameters of NMES have been shown to differently affect the evoked torque and the activated area. The efficacy of NMES is limited by the rapid onset of muscle fatigue. METHODS AND MEASURES Seven healthy participants underwent 4 NMES protocols that were randomly applied to the knee extensor muscle group. The NMES protocols were as follows: standard protocol (Std), defined as 100-Hz, 450-micros pulses and amplitude set to evoke 75% of maximal voluntary isometric torque (MVIT); short pulse duration protocol (SP), defined as 100-Hz, 150-micros pulses and amplitude set to evoke 75% of MVIT; low-frequency protocol (LF), defined as 25-Hz, 450-micros pulses and amplitude set to evoke 75% of MVIT; and low-amplitude protocol (LA), defined as 100-Hz, 450-micros pulses and amplitude set to evoke 45% of MVIT. The peak torque was measured at the start and at the end of the 4 protocols, and percent fatigue was calculated. The outcomes of the 4 NMES protocols on the initial peak torque and activated cross-sectional area were recalculated from a companion study to measure torque per active area. RESULTS Decreasing frequency from 100 to 25 Hz decreased fatigue from 76% to 39%. Decreasing the amplitude and pulse duration resulted in no change of muscle fatigue. Torque per active area accounted for 57% of the variability in percent fatigue between Std and LF protocols. CONCLUSIONS Altering the amplitude of the current and pulse duration does not appear to influence the percent fatigue in NMES. Lowering the stimulation frequency results in less fatigue, by possibly reducing the evoked torque relative to the activated muscle area.
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Pollarine J, Moyer M, Van Lunteren E. Isotonic fatigue in laminin alpha2-deficient dy/dy dystrophic mouse diaphragm. Muscle Nerve 2008; 36:672-8. [PMID: 17661374 DOI: 10.1002/mus.20860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Laminin alpha2 deficiency causes approximately 50% of human congenital muscular dystrophies. Muscle in the corresponding dy/dy mouse model has reduced force but increased fatigue resistance during isometric contractions. To determine whether a similar pattern of alterations is present during isotonic contractions, dy/dy diaphragm was studied in vitro. During 20% load, dystrophic diaphragm had significantly reduced shortening, shortening velocity, work and power deficits, which persisted during the fatigue-inducing stimulation. In contrast, during 40% load, isotonic contractile performance of diseased muscle was impaired only mildly and only for some contractile parameters. At both loads, rate of isotonic fatigue when expressed relative to initial contractile values was similar for dystrophic and normal muscle, or in some instances slightly higher for dystrophic muscle. Therefore, fatigue resistance is considerably impaired during isotonic contractions relative to that reported previously for isometric contractions. This has important implications for increased susceptibility to respiratory failure in laminin alpha2-deficient muscular dystrophy.
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Affiliation(s)
- Jennifer Pollarine
- Department of Medicine, Case Western Reserve University, 10701 East Boulevard, Cleveland, Ohio 44106, USA.
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Sieck GC, Zhan WZ, Han YS, Prakash YS. Effect of denervation on ATP consumption rate of diaphragm muscle fibers. J Appl Physiol (1985) 2007; 103:858-66. [PMID: 17556500 DOI: 10.1152/japplphysiol.00988.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Denervation (DNV) of rat diaphragm muscle (DIAm) decreases myosin heavy chain (MHC) content in fibers expressing MHC(2X) isoform but not in fibers expressing MHC(slow) and MHC(2A). Since MHC is the site of ATP hydrolysis during muscle contraction, we hypothesized that ATP consumption rate during maximum isometric activation (ATP(iso)) is reduced following unilateral DIAm DNV and that this effect is most pronounced in fibers expressing MHC(2X). In single-type-identified, permeabilized DIAm fibers, ATP(iso) was measured using NADH-linked fluorometry. The maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) was determined using quantitative histochemistry. The effect of DNV on maximum unloaded shortening velocity (V(o)) and cross-bridge cycling rate [estimated from the rate constant for force redevelopment (k(TR)) following quick release and restretch] was also examined. Two weeks after DNV, ATP(iso) was significantly reduced in fibers expressing MHC(2X), but unaffected in fibers expressing MHC(slow) and MHC(2A). This effect of DNV on fibers expressing MHC(2X) persisted even after normalization for DNV-induced reduction in MHC content. With DNV, V(o) and k(TR) were slowed in fibers expressing MHC(2X), consistent with the effect on ATP(iso). The difference between V(max) ATPase and ATP(iso) reflects reserve capacity for ATP consumption, which was reduced across all fibers following DNV; however, this effect was most pronounced in fibers expressing MHC(2X). DNV-induced reductions in ATP(iso) and V(max) ATPase of fibers expressing MHC(2X) reflect the underlying decrease in MHC content, while reduction in ATP(iso) also reflects a slowing of cross-bridge cycling rate.
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Affiliation(s)
- Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic and Foundation, 200 First St. SW, Rochester, MN 55905, USA.
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Aravamudan B, Mantilla CB, Zhan WZ, Sieck GC. Denervation effects on myonuclear domain size of rat diaphragm fibers. J Appl Physiol (1985) 2006; 100:1617-22. [PMID: 16410375 DOI: 10.1152/japplphysiol.01277.2005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Denervation (DNV) of rat diaphragm muscle (DIAm) leads to selective atrophy of type IIx and IIb fibers, whereas the cross-sectional area of type I and IIa fibers remains unchanged or slightly hypertrophied. DIAm DNV also increases satellite cell mitotic activity and myonuclear apoptosis. Similar to other skeletal muscles, DIAm fibers are multinucleated, and each myonucleus regulates the gene products in a finite fiber volume, i.e., myonuclear domain (MND). MND size varies across DIAm fiber types in rank order, I < IIa < IIx < IIb [fiber type based on myosin heavy chain isoform expression]. We hypothesized that, after DNV, the total number of myonuclei per fiber does not change and, accordingly, that MND changes proportionately to the change in fiber size regardless of fiber type. Adult rats underwent unilateral (right side) DIAm DNV, and after 2 wk single fibers were dissected. Fiber cross-sectional area, myonuclear number, and MND were measured by confocal microscopy, and these values in DNV DIAm were compared with those obtained in controls. After DNV, type I fibers hypertrophied, type IIa fiber size was unchanged, and type IIx and IIb fibers atrophied compared with control. The total number of myonuclei per fiber was not affected by DNV. Accordingly, after DNV, type I fiber MND increased by 25%, whereas it decreased in type IIx and IIb fibers by 50 and 70%, respectively. These results suggest that MND is not maintained after DNV-induced DIAm fiber hypertrophy or atrophy. These results are interpreted with respect to consequent effects of DNV on myonuclear transcriptional activity and protein turnover.
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Affiliation(s)
- Bharathi Aravamudan
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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Orliaguet G, Riou B, Leguen M. [Postnatal maturation of the diaphragm muscle: ultrastructural and functional aspects]. ACTA ACUST UNITED AC 2004; 23:482-94. [PMID: 15158239 DOI: 10.1016/j.annfar.2003.12.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2003] [Accepted: 12/19/2003] [Indexed: 10/26/2022]
Abstract
OBJECTIVE In the diaphragm muscle, postnatal maturation is associated with major histological and biochemical modifications, as well as a progressive development of the sarcoplasmic reticulum (SR), which in turn are responsible for the progressive postnatal improvement in diaphragmatic contractility. However, the mechanisms by which postnatal maturation induces this improvement in diaphragmatic contractility remain poorly understood and controversial. The aim of this review is to analyze the data from the literature regarding the process involved in the postnatal improvement in diaphragmatic contractility. DATA SOURCES References obtained from Pubmed((R)) databank using keywords (diaphragm muscle, postnatal maturation, contractility, muscular fatigue, cross-bridge). DATA SYNTHESIS From a cytological point of view, the postnatal development of the diaphragm muscle is processed in two successive generations of fiber types, corresponding to the progressive adaptation of the diaphragm muscle to its physiological function. Indeed, the proportion in type I (slow, aerobic) and type IIB fibers (fast, anaerobic) progressively increases with postnatal maturation, while the proportion in type IIA fibers (fast, intermediate) progressively decreases. The histochemical classification of the type of fiber corresponds to the expression of the different isoforms of myosin heavy chains (MHC). Two types of MHC: MHC embryologic (MCH-emb) and MHC neonatal (MCH-neo), and one type of myosin light chains (MLC) are expressed in the foetal skeletal muscles, then are progressively eliminated during postnatal maturation. For many authors, this progressive transition from immature MHC (MCH-emb and neo) to adult MHC (by chronological order of appearance: MHC-2A, MHC-lente, MHC-2X, MHC-2B) could be responsible for the progressive improvement in postnatal diaphragmatic contractility. This transition could be modulated by external factors, mainly including neural and hormonal stimuli. For others, this transition in MHC expression do not play a major role, and other factors, including the postnatal maturation of the ryanodine receptor (RyR) or developmental changes in cross-bridges (CB) properties should play a central role. The most recent hypotheses proposed included the possibility of a postnatal transition in the expression of structural proteins, which are playing a major role in the maintenance of the stability of the sarcomer, and therefore in force generation.
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Affiliation(s)
- G Orliaguet
- Département d'anesthésie-réanimation chirurgicale, CHU Necker-Enfants-Malades, AP-HP, 7574 Paris cedex 15, France.
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Han YS, Geiger PC, Cody MJ, Macken RL, Sieck GC. ATP consumption rate per cross bridge depends on myosin heavy chain isoform. J Appl Physiol (1985) 2003; 94:2188-96. [PMID: 12588786 DOI: 10.1152/japplphysiol.00618.2002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we tested the hypothesis that intrinsic differences in ATP consumption rate per cross bridge exist across rat diaphragm muscle (Dia(m)) fibers expressing different myosin heavy chain (MHC) isoforms. During maximum Ca(2+) activation (pCa 4.0) of single, Triton X-permeabilized Dia(m) fibers, isometric ATP consumption rate was determined by using an NADH-linked fluorometric technique. The MHC concentration in single Dia(m) fibers was determined by densitometric analysis of SDS-PAGE gels and comparison to a standard curve of known MHC concentrations. Isometric ATP consumption rate varied across Dia(m) fibers expressing different MHC isoforms, being highest in fibers expressing MHC(2X) (1.14 +/- 0.08 nmol. mm(-3). s(-1)) and/or MHC(2B) (1.33 +/- 0.08 nmol. mm(-3). s(-1)), followed by fibers expressing MHC(2A) (0.77 +/- 0.11 nmol. mm(-3). s(-1)) and MHC(Slow) (0.46 +/- 0.03 nmol. mm(-3). s(-1)). These differences in ATP consumption rate also persisted when it was normalized for MHC concentration in single Dia(m) fibers. Normalized ATP consumption rate for MHC concentration varied across Dia(m) fibers expressing different MHC isoforms, being highest in fibers expressing MHC(2X) (2.02 +/- 0.19 s(-1)) and/or MHC(2B) (2.64 +/- 0.15 s(-1)), followed by fibers expressing MHC(2A) (1.57 +/- 0.16 s(-1)) and MHC(Slow) (0.77 +/- 0.05 s(-1)). On the basis of these results, we conclude that there are intrinsic differences in ATP consumption rate per cross bridge in Dia(m) fibers expressing MHC isoforms.
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Affiliation(s)
- Young-Soo Han
- Department of Anesthesiology, Mayo Medical School, Rochester, Minnesota 55905, USA
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Sieck GC, Prakash YS, Han YS, Fang YH, Geiger PC, Zhan WZ. Changes in actomyosin ATP consumption rate in rat diaphragm muscle fibers during postnatal development. J Appl Physiol (1985) 2003; 94:1896-902. [PMID: 12562672 DOI: 10.1152/japplphysiol.00617.2002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Early postnatal development of rat diaphragm muscle (Dia(m)) is marked by dramatic transitions in myosin heavy chain (MHC) isoform expression. We hypothesized that the transition from the neonatal isoform of MHC (MHC(Neo)) to adult fast MHC isoform expression in Dia(m) fibers is accompanied by an increase in both the maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) and the ATP consumption rate during maximum isometric activation (ATP(iso)). Rat Dia(m) fibers were evaluated at postnatal days 0, 14, and 28 and in adults (day 84). Across all ages, V(max) ATPase of fibers was significantly higher than ATP(iso). The reserve capacity for ATP consumption [1 - (ratio of ATP(iso) to V(max) ATP(ase))] was remarkably constant ( approximately 55-60%) across age groups, although at day 28 and in adults the reserve capacity for ATP consumption was slightly higher for fibers expressing MHC(Slow) compared with fast MHC isoforms. At day 28 and in adults, both V(max) ATPase and ATP(iso) were lower in fibers expressing MHC(Slow) followed in rank order by fibers expressing MHC(2A), MHC(2X), and MHC(2B). For fibers expressing MHC(Neo), V(max) ATPase, and ATP(iso) were comparable to values for adult fibers expressing MHC(Slow) but significantly lower than values for fibers expressing fast MHC isoforms. We conclude that postnatal transitions from MHC(Neo) to adult fast MHC isoform expression in Dia(m) fibers are associated with corresponding but disproportionate changes in V(max) ATPase and ATP(iso).
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Affiliation(s)
- Gary C Sieck
- Departments of Anesthesiology and Physiology and Biophysics, Mayo Medical School, Rochester, Minnesota 55905, USA.
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Mantilla CB, Sieck GC. Invited review: Mechanisms underlying motor unit plasticity in the respiratory system. J Appl Physiol (1985) 2003; 94:1230-41. [PMID: 12571144 DOI: 10.1152/japplphysiol.01120.2002] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neuromotor control of skeletal muscles, including respiratory muscles, is ultimately dependent on the function of the motor unit (comprising an individual motoneuron and the muscle fibers it innervates). Considerable diversity exists across diaphragm motor units, yet remarkable homogeneity is present (and maintained) within motor units. In recent years, the mechanisms underlying the development and adaptability of respiratory motor units have received great attention, leading to significant advances in our understanding of diaphragm motor unit plasticity. For example, following imposed inactivity of the diaphragm muscle, there are changes at phrenic motoneurons, neuromuscular junctions, and muscle fibers that tend to restore the ability of the diaphragm to sustain ventilation. The role of activity, neurotrophins, and other growth factors in modulating this adaptability is discussed.
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Affiliation(s)
- Carlos B Mantilla
- Department of Anesthesiology, Mayo Medical School, Rochester Minnesota 55905, USA
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Staib JL, Swoap SJ, Powers SK. Diaphragm contractile dysfunction in MyoD gene-inactivated mice. Am J Physiol Regul Integr Comp Physiol 2002; 283:R583-90. [PMID: 12184991 DOI: 10.1152/ajpregu.00080.2002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
MyoD is one of four myogenic regulatory factors found exclusively in skeletal muscle. In an effort to better understand the role that MyoD plays in determining muscle contractile properties, we examined the effects of MyoD deletion on both diaphragmatic contractile properties and myosin heavy chain (MHC) phenotype. Regions of the costal diaphragm from wild-type and MyoD knockout [MyoD (-/-)] adult male BALB/c mice (n = 8/group) were removed, and in vitro diaphragmatic contractile properties were measured. Diaphragmatic contractile measurements revealed that MyoD (-/-) animals exhibited a significant (P < 0.05) downward shift in the force-frequency relationship, a decrement in maximal specific tension (P(o); -33%), a decline in maximal shortening velocity (V(max); -37%), and concomitant decrease in peak power output (-47%). Determination of MHC isoforms in the diaphragm via gel electrophoresis revealed that MyoD elimination resulted in a fast-to-slow shift (P < 0.05) in the MHC phenotype toward MHC types IIA and IIX in MyoD (-/-) animals. These data indicate that MyoD deletion results in a decrease in diaphragmatic submaximal force generation and P(o), along with decrements in both V(max) and peak power output. Hence, MyoD plays an important role in determining diaphragmatic contractile properties.
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Affiliation(s)
- Jessica L Staib
- Department of Exercise and Sport Sciences, University of Florida, Gainesville, Florida 32611, USA
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Russ DW, Vandenborne K, Binder-Macleod SA. Factors in fatigue during intermittent electrical stimulation of human skeletal muscle. J Appl Physiol (1985) 2002; 93:469-78. [PMID: 12133852 DOI: 10.1152/japplphysiol.01010.2001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During an electrically elicited isometric contraction, the metabolic cost of attaining is greater than of maintaining force. Thus fatigue produced during such stimulation may not simply be a function of the force-time integral (FTI), as previously suggested. The goal of the present study was to evaluate fatigue produced in human medial gastrocnemius by intermittent, isometric electrical stimulation with trains of different frequencies (20, 40, or 80 Hz) and durations (300, 600, or 1,200 ms) that produced different peak forces and FTIs. Each subject (n = 10) participated in a total of six sessions. During each session, subjects received a pre- and postfatigue testing protocol and a different, 150-train fatiguing protocol. Each fatiguing protocol used only a single frequency and duration. The fatigue produced by the different protocols was correlated to the initial peak force of the fatiguing protocols (r2= 0.74-0.85) but not to the initial or total FTI. All of the protocols tested produced a proportionately greater impairment of force in response to low- vs. high-frequency stimulation (i.e., low-frequency fatigue). There was no effect of protocol on low-frequency fatigue, suggesting that all the protocols produced comparable levels of impairment in excitation-contraction coupling. These results suggest that, for brief stimulated contractions, peak force is a better predictor of fatigue than FTI, possibly because of the different metabolic demands of attaining and maintaining force.
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Affiliation(s)
- David W Russ
- Department of Exercise Science, University of Massachusetts, Amherst, Massachussetts 01003, USA
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Geiger PC, Cody MJ, Han YS, Hunter LW, Zhan WZ, Sieck GC. Effects of hypothyroidism on maximum specific force in rat diaphragm muscle fibers. J Appl Physiol (1985) 2002; 92:1506-14. [PMID: 11896017 DOI: 10.1152/japplphysiol.00095.2001] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that 1) hypothyroidism (Hyp) decreases myosin heavy chain (MHC) content per half-sarcomere in diaphragm muscle (Dia(m)) fibers, 2) Hyp decreases the maximum specific force (F(max)) of Dia(m) fibers because of the reduction in MHC content per half-sarcomere, and 3) Hyp affects MHC content per half-sarcomere and F(max) to a greater extent in fibers expressing MHC type 2X (MHC(2X)) and/or MHC type 2B (MHC(2B)). Studies were performed on single Triton X-permeabilized fibers activated at pCa 4.0. MHC content per half-sarcomere was determined by densitometric analysis of SDS-polyacrylamide gels and comparison with a standard curve of known MHC concentrations. After 3 wk of Hyp, MHC content per half-sarcomere was reduced in fibers expressing MHC(2X) and/or MHC(2B). On the basis of electron-microscopic analysis, this reduction in MHC content was also reflected by a decrease in myofibrillar volume density and thick filament density. Hyp decreased F(max) across all MHC isoforms; however, the greatest decrease occurred in fibers expressing fast MHC isoforms (approximately 40 vs. approximately 20% for fibers expressing slow MHC isoforms). When normalized for MHC content per half-sarcomere, force generated by Hyp fibers expressing MHC(2A) was reduced compared with control fibers, whereas force per half-sarcomere MHC content was higher for fibers expressing MHC(2X) and/or MHC(2B) in the Hyp Dia(m) than for controls. These results indicate that the effect of Hyp is more pronounced on fibers expressing MHC(2X) and/or MHC(2B) and that the reduction of F(max) with Hyp may be at least partially attributed to a decrease in MHC content per half-sarcomere but not to changes in force per cross bridge.
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Affiliation(s)
- Paige C Geiger
- Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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41
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Orliaguet G, Langeron O, Bouhemad B, Coriat P, LeCarpentier Y, Riou B. Effects of postnatal maturation on energetics and cross-bridge properties in rat diaphragm. J Appl Physiol (1985) 2002; 92:1074-82. [PMID: 11842042 DOI: 10.1152/japplphysiol.00613.2001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of maturation on cross-bridge (CB) properties were studied in rat diaphragm strips obtained at postnatal days 3, 10, and 17 and in adults (10-12 wk old). Calculations of muscle energetics and characteristics of CBs were determined from standard Huxley equations. Maturation did not change the curvature of the force-velocity relationship or the peak of mechanical efficiency. There was a significant increase in the total number of CBs per cross-sectional area (m) with aging but not in single CB force. The turnover rate of myosin ATPase increased, the duration of the CB cycle decreased, and the velocity of CBs decreased significantly only after the first week postpartum. There was a linear relationship between maximum total force and m (r = 0.969, P < 0.001), and between maximum unloaded shortening velocity and m (r = 0.728, P < 0.001). When this study in the rat and previous study in the hamster are compared, it appears that there are few species differences in the postnatal maturation process of the diaphragm.
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Affiliation(s)
- Gilles Orliaguet
- Department of Anesthesiology and Critical Care, Centre Hospitalo-Universitaire Necker-Enfants Malades, Assistance Publique-Hôpitaux de Paris, Université Paris V 75743 Paris Cedex 15, France.
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Russ DW, Elliott MA, Vandenborne K, Walter GA, Binder-Macleod SA. Metabolic costs of isometric force generation and maintenance of human skeletal muscle. Am J Physiol Endocrinol Metab 2002; 282:E448-57. [PMID: 11788378 DOI: 10.1152/ajpendo.00285.2001] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During isometric contractions, no true work is performed, so the force-time integral (FTI) is often used to approximate isometric work. However, the relationship between FTI and metabolic cost is not as linear. We tested the hypothesis that this nonlinearity was due to the cost of attaining a given force being greater than that of maintaining it. The ATP consumed per contraction in the human medial gastrocnemius muscle (n = 6) was determined by use of (31)P-NMR spectroscopy during eight different electrical stimulation protocols. Each protocol consisted of 8 trains of a single frequency (20 or 80 Hz) and duration (300, 600, 1,200, or 1,800 ms) performed under ischemic conditions. The cost of force generation was determined from the ATP turnover during the short-duration trains that did not attain a steady force level. Estimates of the cost of force maintenance at each frequency were determined by subtracting the ATP turnover during the shorter-duration trains from the turnover during the long-duration trains. The force generation phase of an isometric contraction was indeed more metabolically costly than the force maintenance phase during both 20- and 80-Hz stimulation. Thus the mean rate of ATP hydrolysis appeared to decline as contraction duration increased. Interestingly, the metabolic costs of maintaining force during 20-Hz and 80-Hz stimulation were comparable, although different levels of force were produced.
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Affiliation(s)
- David W Russ
- Department of Biomechanics and Movement Science, University of Delaware, Newark, Delaware 19716, USA
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Syme DA, Shadwick RE. Effects of longitudinal body position and swimming speed on mechanical power of deep red muscle from skipjack tuna (Katsuwonus pelamis). J Exp Biol 2002; 205:189-200. [PMID: 11821485 DOI: 10.1242/jeb.205.2.189] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
SUMMARY
The mechanical power output of deep, red muscle from skipjack tuna (Katsuwonus pelamis) was studied to investigate (i) whether this muscle generates maximum power during cruise swimming, (ii) how the differences in strain experienced by red muscle at different axial body locations affect its performance and (iii) how swimming speed affects muscle work and power output. Red muscle was isolated from approximately mid-way through the deep wedge that lies next to the backbone; anterior (0.44 fork lengths, ANT) and posterior (0.70 fork lengths, POST) samples were studied. Work and power were measured at 25°C using the work loop technique. Stimulus phases and durations and muscle strains (±5.5 % in ANT and ±8 % in POST locations) experienced during cruise swimming at different speeds were obtained from previous studies and used during work loop recordings. In addition, stimulus conditions that maximized work were determined. The stimulus durations and phases yielding maximum work decreased with increasing cycle frequency (analogous to tail-beat frequency), were the same at both axial locations and were almost identical to those used by the fish during swimming, indicating that the muscle produces near-maximal work under most conditions in swimming fish. While muscle in the posterior region undergoes larger strain and thus produces more mass-specific power than muscle in the anterior region, when the longitudinal distribution of red muscle mass is considered, the anterior muscles appear to contribute approximately 40 % more total power. Mechanical work per length cycle was maximal at a cycle frequency of 2–3 Hz, dropping to near zero at 15 Hz and by 20–50 % at 1 Hz. Mechanical power was maximal at a cycle frequency of 5 Hz, dropping to near zero at 15 Hz. These fish typically cruise with tail-beat frequencies of 2.8–5.2 Hz, frequencies at which power from cyclic contractions of deep red muscles was 75–100 % maximal. At any given frequency over this range, power using stimulation conditions recorded from swimming fish averaged 93.4±1.65 % at ANT locations and 88.6±2.08 % at POST locations (means ± s.e.m., N=3–6) of the maximum using optimized conditions. When cycle frequency was held constant (4 Hz) and strain amplitude was increased, work and power increased similarly in muscles from both sample sites; work and power increased 2.5-fold when strain was elevated from ±2 to ±5.5 %, but increased by only approximately 12 % when strain was raised further from ±5.5 to ±8 %. Taken together, these data suggest that red muscle fibres along the entire body are used in a similar fashion to produce near-maximal mechanical power for propulsion during normal cruise swimming. Modelling suggests that the tail-beat frequency at which power is maximal (5 Hz) is very close to that used at the predicted maximum aerobic swimming speed (5.8 Hz) in these fish.
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Affiliation(s)
- Douglas A Syme
- Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4.
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Machiels HA, van der Heijden HF, Heunks LM, Dekhuijzen PN. The effect of hypoxia on shortening contractions in rat diaphragm muscle. ACTA PHYSIOLOGICA SCANDINAVICA 2001; 173:313-21. [PMID: 11736693 DOI: 10.1046/j.1365-201x.2001.00895.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hypoxia is known to reduce isometric contractile properties of isolated rat diaphragm bundles. Its effect on isotonic contractile properties (i.e. force-velocity relationship and power output) has not been studied. We hypothesized that hypoxia reduces velocity of shortening and consequently power output of the unfatigued muscle, and shortens endurance time during isotonic contractions. Force-velocity relationship, power output, and fatigue resistance of rat diaphragm muscle bundles were measured during hypoxia (PO2: 6.6 +/- 0.2 kPa) and compared with hyperoxia (PO2: 91.8 +/- 0.7 kPa). Force was clamped from 1 to 100% of maximal tetanic force (Po). Fatigue during isotonic contractions was induced by repeated stimulation every 2 s at a clamp level of 33% of Po. Hypoxia did not affect isometric force generation compared with hyperoxia, nor contraction or relaxation time. In contrast, maximum shortening velocity decreased significantly (hypoxia: 4.2 +/- 0.3, hyperoxia: 6.0 +/- 0.2 Lo/s, P < 0.05). The force-velocity curve shifted downwards (P < 0.05). Hypoxia lowered power output at each load compared with hyperoxia (P < 0.05). The isotonic endurance time was shorter during hypoxia compared with hyperoxia (80 +/- 2 vs. 130 +/- 3 s, P < 0.05). These data show that hypoxia depresses isotonic contractile properties and power output, and reduces endurance time during repeated isotonic contractions.
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Affiliation(s)
- H A Machiels
- Department of Pulmonary Diseases, University Medical Centre Nijmegen, Nijmegen, The Netherlands
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Geiger PC, Cody MJ, Macken RL, Bayrd ME, Sieck GC. Effect of unilateral denervation on maximum specific force in rat diaphragm muscle fibers. J Appl Physiol (1985) 2001; 90:1196-204. [PMID: 11247914 DOI: 10.1152/jappl.2001.90.4.1196] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesize that 1) the effect of denervation (DNV) is more pronounced in fibers expressing fast myosin heavy chain (MHC) isoforms and 2) the effect of DNV on maximum specific force reflects a reduction in MHC content per half sarcomere or the number of cross bridges in parallel. Studies were performed on single Triton X-100-permeabilized fibers activated at a pCa (-log Ca2+ concentration) of 4.0. MHC content per half sarcomere was determined by densitometric analysis of SDS-PAGE gels and comparison to a standard curve of known MHC concentrations. After 2 of wk DNV, the maximum specific force of fibers expressing MHC2X was reduced by approximately 40% (MHC(2B) expression was absent), whereas the maximum specific force of fibers expressing MHC2A and MHC(slow) decreased by only approximately 20%. DNV also reduced the MHC content in fibers expressing MHC2X, with no effect on fibers expressing MHC2A and MHC(slow). When normalized for MHC content per half sarcomere, force generated by DNV fibers expressing MHC2X and MHC2A was decreased compared with control fibers. These results suggest the force per cross bridge is also affected by DNV.
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Affiliation(s)
- P C Geiger
- Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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Sieck GC, Regnier M. Invited Review: plasticity and energetic demands of contraction in skeletal and cardiac muscle. J Appl Physiol (1985) 2001; 90:1158-64. [PMID: 11181631 DOI: 10.1152/jappl.2001.90.3.1158] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Numerous studies have explored the energetic properties of skeletal and cardiac muscle fibers. In this mini-review, we specifically explore the interactions between actin and myosin during cross-bridge cycling and provide a conceptual framework for the chemomechanical transduction that drives muscle fiber energetic demands. Because the myosin heavy chain (MHC) is the site of ATP hydrolysis and actin binding, we focus on the mechanical and energetic properties of different MHC isoforms. Based on the conceptual framework that is provided, we discuss possible sites where muscle remodeling may impact the energetic demands of contraction in skeletal and cardiac muscle.
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Affiliation(s)
- G C Sieck
- Department of Anesthesiology, Mayo Medical School and Foundation, Rochester, Minnesota 55905, USA.
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47
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Han YS, Proctor DN, Geiger PC, Sieck GC. Reserve capacity for ATP consumption during isometric contraction in human skeletal muscle fibers. J Appl Physiol (1985) 2001; 90:657-64. [PMID: 11160066 DOI: 10.1152/jappl.2001.90.2.657] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) and ATP consumption rate during maximum isometric activation (ATP(iso)) were determined in human vastus lateralis (VL) muscle fibers expressing different myosin heavy chain (MHC) isoforms. We hypothesized that the reserve capacity for ATP consumption [1 -- (ratio of ATP(iso) to V(max) ATPase)] varies across VL muscle fibers expressing different MHC isoforms. Biopsies were obtained from 12 subjects (10 men and 2 women; age 21--66 yr). A quantitative histochemical procedure was used to measure V(max) ATPase. In permeabilized fibers, ATP(iso) was measured using an NADH-linked fluorometric procedure. The reserve capacity for ATP consumption was lower for fibers coexpressing MHC(2X) and MHC(2A) compared with fibers singularly expressing MHC(2A) and MHC(slow) (39 vs. 52 and 56%, respectively). Tension cost (ratio of ATP(iso) to generated force) also varied with fiber type, being highest in fibers coexpressing MHC(2X) and MHC(2A). We conclude that fiber-type differences in the reserve capacity for ATP consumption and tension cost reflect functional differences such as susceptibility to fatigue.
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Affiliation(s)
- Y S Han
- Department of Anesthesiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA
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Geiger PC, Cody MJ, Macken RL, Bayrd ME, Fang YH, Sieck GC. Mechanisms underlying increased force generation by rat diaphragm muscle fibers during development. J Appl Physiol (1985) 2001; 90:380-8. [PMID: 11133931 DOI: 10.1152/jappl.2001.90.1.380] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has been found that maximum specific force (F(max); force per cross-sectional area) of rat diaphragm muscle doubles from birth to 84 days (adult). We hypothesize that this developmental change in F(max) reflects an increase in myosin heavy chain (MHC) content per half-sarcomere (an estimate of the number of cross bridges in parallel) and/or a greater force per cross bridge in fibers expressing fast MHC isoforms compared with slow and neonatal MHC isoforms (MHC(slow) and MHC(neo), respectively). Single Triton 100-X-permeabilized fibers were activated at a pCa of 4.0. MHC isoform expression was determined by SDS-PAGE. MHC content per half-sarcomere was determined by densitometric analysis and comparison to a standard curve of known MHC concentrations. MHC content per half-sarcomere progressively increased during early postnatal development. When normalized for MHC content per half-sarcomere, fibers expressing MHC(slow) and coexpressing MHC(neo) produced less force than fibers expressing fast MHC isoforms. We conclude that lower force per cross bridge in fibers expressing MHC(slow) and MHC(neo) contributes to the lower F(max) seen in early postnatal development.
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Affiliation(s)
- P C Geiger
- Department of Physiology and Biophysics, Rochester, Minnesota 55905, USA
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Marchand E, Decramer M. Respiratory muscle function and drive in chronic obstructive pulmonary disease. Clin Chest Med 2000; 21:679-92. [PMID: 11194779 DOI: 10.1016/s0272-5231(05)70177-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Respiratory, and particularly inspiratory, muscle function is altered in COPD. Many of these alterations are secondary to a mechanical disadvantage related to hyperinflation. Other factors, including corticosteroid therapy and nutritional depletion, are also deleterious to muscle function. In addition, the load imposed on the respiratory muscles is increased in COPD. Combined with the altered respiratory muscle function, this increase induces important changes in respiratory muscle drive and recruitment. Moreover, the imbalance between respiratory muscle function and load is an important determinant of dyspnea and hypercapnia. Because much of the lung and airway derangements are irreversible in COPD, the respiratory muscles appear to be an attractive target for therapeutic interventions.
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Affiliation(s)
- E Marchand
- Respiratory Muscle Research Unit, Laboratory of Pneumology, Universitair Ziekenhuis Gasthuisberg, Katholieke Universiteit Leuven, Leuven, Belgium
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Sieck GC, Zhan WZ. Denervation alters myosin heavy chain expression and contractility of developing rat diaphragm muscle. J Appl Physiol (1985) 2000; 89:1106-13. [PMID: 10956357 DOI: 10.1152/jappl.2000.89.3.1106] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that unilateral denervation (DNV) of the rat diaphragm muscle (Dia(m)) in neonates at postnatal day 7 (D-7) alters normal transitions of myosin heavy chain (MHC) isoform expression and thereby affects postnatal changes in maximum specific force (P(o)) and maximum unloaded shortening velocity (V(o)). The relative expression of different MHC isoforms was analyzed electrophoretically. With DNV at D-7, expression of MHC(neo) in the Dia(m) persisted, and emergence of MHC(2X) and MHC(2B) was delayed. By D-21 and D-28, relative expression of MHC(2A) and MHC(2B) was reduced in DNV compared with control (CTL) animals. Expression of MHC(neo) also reappeared in adult Dia(m) by 2-3 wk after DNV, and relative expression of MHC(2B) was reduced. At each age, P(o) was reduced and V(o) was slowed by DNV, compared with CTL. In CTL Dia(m), postnatal changes in P(o) and V(o) were associated with an increase in fast MHC isoform expression. In DNV Dia(m), no such association existed. We conclude that, in the Dia(m), DNV induces alterations in both MHC isoform expression and contractile properties, which are not necessarily causally linked.
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Affiliation(s)
- G C Sieck
- Departments of Anesthesiology and Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
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