Epigallocatechin-3-gallate has dual, independent effects on the cardiac sarcoplasmic reticulum/endoplasmic reticulum Ca2+ ATPase

Abstract

We determined the effects of epigallocatechin-3-gallate (EGCG) and epicatechin (EC), on pump turnover and Ca2+ transport by the cardiac form of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA). Fluorescence spectroscopy was used to directly measure SERCA ATPase activity and to measure Ca2+ uptake into cardiac sarcoplasmic reticulum (SR) vesicles and microsomes derived from human embryonic kidney (HEK) cells expressing human cardiac SERCA2a. We found that EGCG reduces the maximum velocity of Ca2+ uptake into cardiac SR vesicles and increases the Ca2+-sensitivity of uptake in a concentration-dependent manner. EC is less potent than EGCG in increasing the Ca2+-sensitivity of uptake and does not affect maximum uptake velocity. The EGCG-dependent reduction in Ca2+ uptake velocity is well correlated with direct inhibition of SERCA. The effect of EGCG on the Ca2+-sensitivity of Ca2+ uptake into cardiac SR vesicles is affected by the phosphorylation status of phospholamban (PLB). When cardiac SERCA2a is expressed in HEK cells without PLB, EGCG reduces the maximum velocity of Ca2+ uptake but does not affect the Ca2+-sensitivity of uptake into microsomes derived from these cells indicating that the effect of EGCG on Ca2+-sensitivity requires the presence of PLB. Our results show that EGCG has dual effects on SERCA function in cardiac SR vesicles: it directly affects SERCA by reducing maximum uptake velocity; it increases the Ca2+-sensitivity of Ca2+ uptake in a manner that appears to depend on the interaction between SERCA and PLB.

Coordinated Regulation of Murine Cardiomyocyte Contractility by Nanomolar (−)-Epigallocatechin-3-Gallate, the Major Green Tea Catechin

“…This finding is consistent with another independent report, demonstrating that no significant effect on SERCA2 activity was observed with EGCG at a concentration Ͻ4.8 M (Kargacin et al, 2011). Ca 2ϩ influx via L-type Ca 2ϩ channels triggers Ca 2ϩ release from the SR (Nä bauer et al, 1989).…”

Long-Term Oral Administration of Theaphenon-E Improves Cardiomyocyte Mechanics and Calcium Dynamics by Affecting Phospholamban Phosphorylation and ATP Production

“…Dephosphorylated PLB interacts with SERCA2 and inhibits the pumping activity, whereas phosphorylation of PLB relieves the inhibitory effects resulting in increased calcium re-uptake into the SR and enhanced contractility [46], as we actually observed. On the other hand, our observations are consistent with data published by Kargacin et al [7] who demonstrated that EGCG increases SR Ca 2+ uptake by altering the transmembrane interaction between SERCA2 and PLB, which in turn depends on the phosphorylation status of the latter. It is well known that the cardiac excitation-contraction coupling is highly dependent on Ca 2+ transient, that is handled through an array of ion channels, antiporters and pumps that are finally regulated, at post-translational level, by phosphorylation.…”

“…Mechanistic studies have demonstrated that tea polyphenols may influence many aspects of cardiovascular function by their interaction with a list of intracellular target sites, such as several ion channels and ion exchangers (Na ), intracellular Ca 2+ storage, and sarcomeric Troponin protein [7,13,15]. Another study reported that EGCG acute administration in cardiomyocytes, isolated from a transgenic mice model of hypertrophic cardiomyopathy, ameliorated sarcomere shortening and lowered relaxation time by decreasing the thin myofilament Ca 2+ sensitivity [10].…”

“…Although previous data strongly suggest that tea extracts can have benefits on cardiac function by targeting different proteins and intracellular molecular pathways, most studies refer to the effects of acute exposure to catechins and have been performed on cell lines, perfused rat hearts or isolated cardiomyocytes, subcellular cardiomyocyte organelles or in-silico models [6,7,[15][16][17][18][19]. Short/long term effects of catechin treatment on heart function and ventricular remodelling have been also evaluated in experimental models of heart diseases or aged-related ventricular dysfunction [9,13].…”

Epigallocatechin-3-Gallate Accelerates Relaxation and Ca2+ Transient Decay and Desensitizes Myofilaments in Healthy and Mybpc3-Targeted Knock-in Cardiomyopathic Mice

“…We therefore assume that at this concentration EGCg does not increase sarcoplasmic reticulum (SR) Ca 2+ load. Data from canine SR vesicles and HEK293 cell microsomes show that EGCg concentrations > 4.8 μM directly inhibit SR calcium ATPase (Kargacin et al, 2011). Additionally, Feng et al reported no effect on SERCA in rabbit cardiac and skeletal SR membranes with 1–2 μM EGCg (Feng et al, 2012; Najafi et al, 2015).…”