Changes in Cx43 and NaV1.5 expression precede the occurrence of substantial fibrosis in calcineurin-induced murine cardiac hypertrophy.
In mice, the calcium-dependent phosphatase calcineurin A (CnA) induces a transcriptional pathway leading to pathological cardiac hypertrophy. Interestingly, induction of CnA has been frequently noticed in human hypertrophic and failing hearts. Independently, the arrhythmia vulnerability of such hearts has been regularly associated with remodeling of parameters determining electrical conduction (expression level of connexin43 (Cx43) and NaV1.5, connective tissue architecture), for which the precise molecular basis and sequence of events is still unknown. Recently, we observed reduced Cx43 and NaV1.5 expression in 4-week old mouse hearts, overexpressing a constitutively active form of CnA (MHC-CnA model), but the order of events is still unknown. Therefore, three key parameters of conduction (Cx43, NaV1.5 and connective tissue expression) were characterized in MHC-CnA ventricles versus wild-type (WT) during postnatal development on a weekly basis. At postnatal week 1, CnA overexpression induced cardiac hypertrophy in MHC-CnA. Moreover, protein and RNA levels of both Cx43 and NaV1.5 were reduced by at least 50% as compared to WT. Cx43 immunoreactive signal was reduced at week 2 in MHC-CnA. At postnatal week 3, Cx43 was less phosphorylated and RNA level of Cx43 normalized to WT values, although the protein level was still reduced. Additionally, MHC-CnA hearts displayed substantial fibrosis relative to WT, which was accompanied by increased RNA levels for genes previously associated with fibrosis such as Col1a1, Col1a2, Col3a1, Tgfb1, Ctgf, Timp1 and microRNA miR-21. In MHC-CnA, reduction in Cx43 and NaV1.5 expression thus coincided with overexpression of CnA and hypertrophy development and preceded significant presence of fibrosis. At postnatal week 4 the alterations in conductional parameters observed in the MHC-CnA model lead to abnormal conduction and arrhythmias, similar to those observed in cardiac remodeling in heart failure patients. The MHC-CnA model, therefore, provides for a unique model to resolve the molecular origin of conductional remodeling in detail.
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Magda S C
MS
Fontes
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Antonia J A
AJ
Raaijmakers
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Tessa
T
van Doorn
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Bart
B
Kok
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Sylvia
S
Nieuwenhuis
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Roel
R
van der Nagel
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Marc A
MA
Vos
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Teun P
TP
de Boer
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Harold V M
HV
van Rijen
Division of Heart & Lungs, Department of Medical Physiology, University Medical Center Utrecht, Utrecht, The Netherlands.
Marti F A
MF
Bierhuizen
D000818:Animals; D000831:Animals, Newborn; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism*; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D024022:Fibrillar Collagens / Q000235:genetics / Q000378:metabolism; D005355:Fibrosis; D015870:Gene Expression; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism
C526318:CCN2 protein, mouse; D018031:Connexin 43; D024022:Fibrillar Collagens; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568321:Scn5a protein, mouse; C508961:Tgfb1 protein, mouse; C560825:Timp1 protein, mouse; D019715:Tissue Inhibitor of Metalloproteinase-1; D053773:Transforming Growth Factor beta1; D055513:Connective Tissue Growth Factor; D019703:Calcineurin