Gene Expression of the Na⁺–Ca²⁺ Exchanger, SERCA2a and Calsequestrin after Myocardial Ischemia in the Neonatal Rabbit Heart

Abstract

Background: Neonatal hearts are less susceptible to developing myocardial dysfunction after hypoxia and/or ischemia than adult hearts. Differences in intracellular calcium homeostasis may be responsible for reduced calcium overload of the immature myocardium leading to the observed protection against ischemia. Objective: To assess differences in baseline and post-ischemic gene expression of calcium handling proteins after ischemia in neonatal and adult rabbit hearts. Methods: We used isolated antegrade perfused rabbit hearts (age 2 days, 28 days, n = 32), which were exposed to ischemia and hypothermia simulating myocardial stunning comparable to neonatal asphyxia. Gene and protein expression of the sodium–calcium exchanger (NCX), the sarco-endoplasmatic reticulum Ca²⁺-ATPase 2a (SERCA) and calsequestrin (CSQ) were measured using quantitative real-time PCR and Western blotting. Results: After ischemia and reperfusion in neonatal and adult hearts, a significant decrease in myocardial performance was recorded. At the mRNA level, significant differences in the baseline expression of NCX, SERCA and CSQ between neonatal and adult hearts were observed. In neonatal post-ischemic hearts, NCX and CSQ expression were significantly higher at the mRNA level than in controls. In contrast, SERCA expression remained unchanged in neonatal hearts and decreased in adult hearts compared to the non-ischemic controls. Conclusion: These findings suggest that changes in gene expression of calcium handling proteins may be involved in the different susceptibility of neonatal compared to adult hearts to developing myocardial dysfunction after ischemia.

Modulation of expression of Na+/Ca2+ exchanger in heart of rat and mouse under stress

“…An increase in the intracellular Na + concentration has been shown to correlate with Ca 2+ overload. Enhanced gene expression of this transport system was observed also in the adult failing hearts (Hampton et al 2000) and in ischaemic neonatal hearts (Seehase et al 2006). Experimental evidence supports the proposal that Na + /H + exchange is primarily responsible for Na + influx during hypoxia/ ischaemia.…”

“…In this work, we observed an increase in the NCX1 mRNA levels in both left ventricle and isolated cardiomyocytes from the left ventricle. Enhanced gene expression of this transport system was observed also in the adult failing hearts (Hampton et al 2000) and in ischaemic neonatal hearts (Seehase et al 2006). Increased gene expression of the NCX preserves intracellular calcium homeostasis under conditions of ischaemic and hypoxic stress, thereby attenuating contractile dysfunction.…”

Growth Hormone Secretagogues Protect Mouse Cardiomyocytes from in vitro Ischemia/Reperfusion Injury through Regulation of Intracellular Calcium

“…The basal level of [Ca 2+ ] i was increased in ischemic cells with or without GHS treatment. The basal level of [Ca 2+ ] i would reflect the activity of both SERCA2a and RyR2s [35]. Following the recovery of SERCA2a activity by GHS treatment (FIG.…”

β-Adrenergic Inhibition Prevents Action Potential and Calcium Handling Changes during Regional Myocardial Ischemia

“…The half-life of many Ca 2+ handling proteins is quite long (e.g., up to 2–3 days for SERCA, 9+ h for PLB) (Andersson et al, 2009 ; Teng et al, 2015 ), suggesting that significant changes in protein expression are unlikely within 15 min of ischemia. Indeed, previous studies in the adult rabbit heart indicated that SERCA mRNA levels were decreased following 60 min ischemia, but protein expression remained unchanged (Seehase et al, 2006 ).…”