Author's reply
Dear Dr Madias, thank you for your comments on my review [1]. As you question, desensitization ofβ1-AR [2] alone may not explain apical akinesis, because β1-AR is not essential for myocardial contraction in physiological conditions. Therefore, combination of desensitization of β1-AR and upregulation of the β2-AR may be necessary to explain akinesis in super physiological condition. Causal relationship is another challenging issue. As you pointed out, desensitization of β1- or β2-AR may be aftermath rather than cause of myocardial dysfunction. Results from our previous study using serial endomyocardial biopsy specimens showing that GRK-2 and β-arrestin2 on the cell membrane were markedly reduced in the recovery phase from acute phase may support our hypothesis [2]. Thank you again for your interest and valuable comments.
References
- 1.Okura H. Update of takotsubo syndrome in the era of COVID-19. J Cardiol. 2020 [Elsevier: Please update] [Google Scholar]
- 2.Nakano T, Onoue K, Nakada Y, Nakagawa H, Kumazawa T, Ueda T, et al. Alteration of beta-adrenoceptor signaling in left ventricle of acute phase takotsubo syndrome: a human study. Sci Rep. 2018;8:12731. doi: 10.1038/s41598-018-31034-z. [DOI] [PMC free article] [PubMed] [Google Scholar]