Biochemical and Electrophysiological Modification of Amyloid Transthyretin on Cardiomyocytes.
Transthyretin (TTR) amyloidoses are familial or sporadic degenerative conditions that often feature heavy cardiac involvement. Presently, no effective pharmacological therapy for TTR amyloidoses is available, mostly due to a substantial lack of knowledge about both the molecular mechanisms of TTR aggregation in tissue and the ensuing functional and viability modifications that occur in aggregate-exposed cells. TTR amyloidoses are of particular interest regarding the relation between functional and viability impairment in aggregate-exposed excitable cells such as peripheral neurons and cardiomyocytes. In particular, the latter cells provide an opportunity to investigate in parallel the electrophysiological and biochemical modifications that take place when the cells are exposed for various lengths of time to variously aggregated wild-type TTR, a condition that characterizes senile systemic amyloidosis. In this study, we investigated biochemical and electrophysiological modifications in cardiomyocytes exposed to amyloid oligomers or fibrils of wild-type TTR or to its T4-stabilized form, which resists tetramer disassembly, misfolding, and aggregation. Amyloid TTR cytotoxicity results in mitochondrial potential modification, oxidative stress, deregulation of cytoplasmic Ca2+levels, and Ca2+cycling. The altered intracellular Ca2+cycling causes a prolongation of the action potential, as determined by whole-cell recordings of action potentials on isolated mouse ventricular myocytes, which may contribute to the development of cellular arrhythmias and conduction alterations often seen in patients with TTR amyloidosis. Our data add information about the biochemical, functional, and viability alterations that occur in cardiomyocytes exposed to aggregated TTR, and provide clues as to the molecular and physiological basis of heart dysfunction in sporadic senile systemic amyloidosis and familial amyloid cardiomyopathy forms of TTR amyloidoses.
Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy; Center of Molecular Medicine, University of Florence, Florence, Italy.
Laura
L
Sartiani
Department of Biomedical, Experimental and Clinical Sciences "Mario Serio,", University of Florence, Florence, Italy; Research Centre on the Molecular Basis of Neurodegeneration, University of Florence, Florence, Italy. Electronic address: monica.bucciantini@unifi.it.
Monica
M
Bucciantini
Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy; Center of Molecular Medicine, University of Florence, Florence, Italy.
Valentina
V
Spinelli
Department of Biomedical, Experimental and Clinical Sciences "Mario Serio,", University of Florence, Florence, Italy.
Manuela
M
Leri
Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy.
Antonino
A
Natalello
Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
Daniele
D
Nosi
Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy.
Silvia
S
Maria Doglia
Department of Physics, University of Genoa, Genoa, Italy.
Annalisa
A
Relini
Department of Physics, University of Genoa, Genoa, Italy.
Amanda
A
Penco
Department of Molecular Medicine, Institute of Biochemistry, University of Pavia, Pavia, Italy.
Sofia
S
Giorgetti
Department of Health Science, University of Florence, Florence, Italy.
Elisabetta
E
Gerace
Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy.
Guido
G
Mannaioni
Department of Molecular Medicine, Institute of Biochemistry, University of Pavia, Pavia, Italy; Wolfson Drug Discovery Unit, Centre for Amyloidosis and Acute Phase Proteins, Division of Medicine, University College London, London, United Kingdom.
Vittorio
V
Bellotti
Department of Biomedical, Experimental and Clinical Sciences "Mario Serio,", University of Florence, Florence, Italy.
Stefania
S
Rigacci
Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy; Center of Molecular Medicine, University of Florence, Florence, Italy; Research Centre on the Molecular Basis of Neurodegeneration, University of Florence, Florence, Italy.
Elisabetta
E
Cerbai
Department of Biomedical, Experimental and Clinical Sciences "Mario Serio,", University of Florence, Florence, Italy; Research Centre on the Molecular Basis of Neurodegeneration, University of Florence, Florence, Italy.
Massimo
M
Stefani
D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D055724:Electrophysiological Phenomena; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011228:Prealbumin / Q000737:chemistry* / Q000378:metabolism*; D066329:Protein Aggregates
D000682:Amyloid; D011228:Prealbumin; D066329:Protein Aggregates; D002118:Calcium