1
|
Cizauskas HE, Burnham HV, Panni A, Peña A, Alvarez-Arce A, Davis MT, Araujo KN, Delligatti CE, Edassery S, Kirk JA, Arora R, Barefield DY. Proteolytic degradation of atrial sarcomere proteins underlies contractile defects in atrial fibrillation. Am J Physiol Heart Circ Physiol 2024; 327:H460-H472. [PMID: 38940916 PMCID: PMC11442024 DOI: 10.1152/ajpheart.00148.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 05/24/2024] [Accepted: 06/07/2024] [Indexed: 06/29/2024]
Abstract
Atrial fibrillation (AFib) is the most common cardiac rhythm disturbance, often treated via electrical cardioversion. Following rhythm restoration, a period of depressed mechanical function known as atrial stunning occurs, suggesting that defects in contractility occur in AFib and are revealed upon restoration of rhythm. This project aims to define the contractile remodeling that occurs in AFib. To assess contractile function, we used a canine atrial tachypacing model of induced AFib. Mass spectrometry analysis showed dysregulation of contractile proteins in samples from AFib compared with sinus rhythm atria. Atrial cardiomyocytes show reduced force of contraction, decreased resting tension, and increased calcium sensitivity in skinned single cardiomyocyte studies. These alterations correlated with degradation of myofilament proteins including myosin heavy chain altering force of contraction, titin altering resting tension, and troponin I altering calcium sensitivity. We measured degradation of other myofilament proteins, including cardiac myosin binding protein C and actinin, that show degradation products in the AFib samples that are absent in the sinus rhythm atria. Many of the degradation products appeared as discrete cleavage products that are generated by calpain proteolysis. We assessed calpain activity and found it to be significantly increased. These results provide an understanding of the contractile remodeling that occurs in AFib and provide insight into the molecular explanation for atrial stunning and the increased risk of atrial thrombus and stroke in AFib.NEW & NOTEWORTHY Atrial fibrillation is the most common cardiac rhythm disorder, and remodeling during atrial fibrillation is highly variable between patients. This study has defined the biophysical changes in contractility that occur in atrial fibrillation along with identifying potential molecular mechanisms that may drive this remodeling. This includes proteolysis of several myofilament proteins including titin, troponin I, myosin heavy chain, myosin binding protein C, and actinin, which is consistent with the observed contractile deficits.
Collapse
Affiliation(s)
- Hannah E Cizauskas
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Hope V Burnham
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Azaria Panni
- Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Alexandra Peña
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Alejandro Alvarez-Arce
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - M Therese Davis
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Kelly N Araujo
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Christine E Delligatti
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Seby Edassery
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Jonathan A Kirk
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| | - Rishi Arora
- Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - David Y Barefield
- Department of Cell and Molecular Physiology, Loyola University Chicago, Chicago, Illinois, United States
| |
Collapse
|
2
|
Kell DB, Lip GYH, Pretorius E. Fibrinaloid Microclots and Atrial Fibrillation. Biomedicines 2024; 12:891. [PMID: 38672245 PMCID: PMC11048249 DOI: 10.3390/biomedicines12040891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 03/27/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
Atrial fibrillation (AF) is a comorbidity of a variety of other chronic, inflammatory diseases for which fibrinaloid microclots are a known accompaniment (and in some cases, a cause, with a mechanistic basis). Clots are, of course, a well-known consequence of atrial fibrillation. We here ask the question whether the fibrinaloid microclots seen in plasma or serum may in fact also be a cause of (or contributor to) the development of AF. We consider known 'risk factors' for AF, and in particular, exogenous stimuli such as infection and air pollution by particulates, both of which are known to cause AF. The external accompaniments of both bacterial (lipopolysaccharide and lipoteichoic acids) and viral (SARS-CoV-2 spike protein) infections are known to stimulate fibrinaloid microclots when added in vitro, and fibrinaloid microclots, as with other amyloid proteins, can be cytotoxic, both by inducing hypoxia/reperfusion and by other means. Strokes and thromboembolisms are also common consequences of AF. Consequently, taking a systems approach, we review the considerable evidence in detail, which leads us to suggest that it is likely that microclots may well have an aetiological role in the development of AF. This has significant mechanistic and therapeutic implications.
Collapse
Affiliation(s)
- Douglas B. Kell
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool L69 7ZB, UK
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Søltofts Plads, Building 220, 2800 Kongens Lyngby, Denmark
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Private Bag X1 Matieland, Stellenbosch 7602, South Africa
| | - Gregory Y. H. Lip
- Liverpool Centre for Cardiovascular Science at University of Liverpool, Liverpool John Moores University and Liverpool Heart and Chest Hospital, Liverpool L7 8TX, UK;
- Danish Center for Health Services Research, Department of Clinical Medicine, Aalborg University, 9220 Aalborg, Denmark
| | - Etheresia Pretorius
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool L69 7ZB, UK
- Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Private Bag X1 Matieland, Stellenbosch 7602, South Africa
| |
Collapse
|
3
|
Cizauskas HE, Burnham HV, Panni A, Pena A, Alvarez-Arce A, Davis MT, Araujo KN, Delligatti C, Edassery S, Kirk JA, Arora R, Barefield DY. Proteolytic degradation of atrial sarcomere proteins underlies contractile defects in atrial fibrillation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.05.565691. [PMID: 37961455 PMCID: PMC10635151 DOI: 10.1101/2023.11.05.565691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Aims Atrial fibrillation (AFib) is the most common cardiac rhythm disturbance. Treatment of AFib involves restoration of the atrial electrical rhythm. Following rhythm restoration, a period of depressed mechanical function known as atrial stunning occurs that involves decreased blood flow velocity and reduced atrial contractility. This suggests that defects in contractility occur in AFib and are revealed upon restoration of rhythm. The aim of this project is to define the contractile remodeling that occurs in AFib. Methods and Results To assess contractile function, we used a canine atrial tachypacing model of induced AFib. Mass spectrometry analysis showed dysregulation of contractile proteins in samples from AFib compared to sinus rhythm atria. Atrial cardiomyocytes showed reduced force of contraction in skinned single cardiomyocyte calcium-force studies. There were no significant differences in myosin heavy chain isoform expression. Resting tension is decreased in the AFib samples correlating with reduced full-length titin in the sarcomere. We measured degradation of other myofilament proteins including cMyBP-C, actinin, and cTnI, showing significant degradation in the AFib samples compared to sinus rhythm atria. Many of the protein degradation products appeared as discrete cleavage products that are generated by calpain proteolysis. We assessed calpain activity and found it to be significantly increased. Skinned cardiomyocytes from AFib atria showed decreased troponin I phosphorylation, consistent with the increased calcium sensitivity that was found within these cardiomyocytes. Conclusions With these results it can be concluded that AFib causes alterations in contraction that can be explained by both molecular changes occurring in myofilament proteins and overall myofilament protein degradation. These results provide an understanding of the contractile remodeling that occurs in AFib and provides insight into the molecular explanation for atrial stunning and the increased risk of atrial thrombus and stroke in AFib.
Collapse
|
4
|
Nedios S, Deneke T. Anticoagulation after cardioversion of atrial fibrillation: What if we could stop earlier than 4 weeks? Int J Cardiol 2022; 352:61-62. [PMID: 35143873 DOI: 10.1016/j.ijcard.2022.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 02/04/2022] [Indexed: 11/18/2022]
Affiliation(s)
- Sotirios Nedios
- Department of Electrophysiology, Heart Center, University of Leipzig, Germany; Department of Cardiology, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University Medical Center, the Netherlands.
| | - Thomas Deneke
- Heart Center Bad Neustadt, Rhoen-Clinic Campus Bad Neustadt, Germany
| |
Collapse
|