Overexpression of sarcoendoplasmic reticulum calcium ATPase 2a promotes cardiac sympathetic neurotransmission via abnormal endoplasmic reticulum and mitochondria Ca2+ regulation

Journal article

Reduced cardiomyocyte excitation-contraction coupling and downregulation of the sarco-endoplasmic reticulum calcium ATPase 2a (SERCA2a) is associated with heart failure. This has led to viral transgene upregulation of SERCA2a in cardiomyocytes as a treatment. We hypothesized that SERCA2a gene therapy expressed under a similar promiscuous cytomegalovirus promoter could also affect the cardiac sympathetic neural axis and promote sympatho-excitation. Stellate neurons were isolated from 90-120g male, Sprague Dawley (SD), Wistar Kyoto (WKY), and spontaneously hypertensive rats (SHR). Neurons were infected with Ad-mCherry or Ad-mCherry-hATP2Aa (SERCA2a). Intracellular Ca2+ changes were measured using Fura-2AM in response to KCl, caffeine, thapsigargin and FCCP to mobilize intracellular Ca2+ stores. The effect of SERCA2a on neurotransmitter release was measured using 3H-norepinephrine overflow from 340-360g SD rat atria in response to right stellate ganglia stimulation. Upregulation of SERCA2a resulted in greater neurotransmitter release in response to stellate stimulation compared to control (Empty: 98.7±20.5cpm, n=7. SERCA: 186.5±28.41cpm, n=8. *P<0.05). In isolated SD rat stellate neurons SERCA2a overexpression facilitated greater depolarisation induced Ca2+ transients (Empty: 0.64±0.03au, n=57. SERCA: 0.75±0.03au, n=68. *P<0.05), along with increased endoplasmic reticulum and mitochondria Ca2+ load. Similar results were observed in WKY and age matched SHRs despite no further increase in ER load being observed in the SHR (SHR. Empty: 0.16±0.04au, n=18. SERCA: 0.17±0.02au, n=25). In conclusion, SERCA2a upregulation in cardiac sympathetic neurons resulted in increased neurotransmission and increased Ca2+ loading into intracellular stores. Whether the increased Ca2+ transient and neurotransmission following SERCA2A overexpression contributes to enhanced sympathoexcitation in heart failure patients remains to be determined.

Authors: Shanks, J; Herring, N; Johnson, E; Liu, K; Li, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Heart Association
• Journal: Hypertension
• Volume: 69
• Issue: 4
• Pages: 625-632
• Publication date: 2017-01-01
• Acceptance date: 2017-01-19
• DOI: 10.1161/HYPERTENSIONAHA.116.08507
• EISSN: 1524-4563
• ISSN: 0194-911X
• Keywords: spontaneously hypertensive rat; sympathetic nervous system; SERCA calcium ATPase; stellate ganglia; hypertension