Circadian Profiles in the Embryonic Chick Heart: L-Type Voltage-Gated Calcium Channels and Signaling Pathways

Abstract

Circadian clocks exist in the heart tissue and modulate multiple physiological events, from cardiac metabolism to contractile function and expression of circadian oscillator and metabolic-related genes. Ample evidence has demonstrated that there are endogenous circadian oscillators in adult mammalian cardiomyocytes. However, mammalian embryos cannot be entrained independently to light-dark (LD) cycles in vivo without any maternal influence, but circadian genes are well expressed and able to oscillate in embryonic stages. The authors took advantage of using chick embryos that are independent of maternal influences to investigate whether embryonic hearts could be entrained under LD cycles in ovo. The authors found circadian regulation of L-type voltage-gated calcium channels (L-VGCCs), the ion channels responsible for the production of cardiac muscle contraction in embryonic chick hearts. The mRNA levels and protein expression of VGCCα1C and VGCCα1D are under circadian control, and the average L-VGCC current density is significantly larger when cardiomyocytes are recorded during the night than day. The phosphorylation states of several kinases involved in insulin signaling and cardiac metabolism, including extracellular signal-regulated kinase (Erk), stress-activated protein kinase (p38), protein kinase B (Akt), and glycogen synthase kinase-3β (GSK-3β), are also under circadian control. Both Erk and p38 have been implicated in regulating cardiac contractility and in the development of various pathological states, such as cardiac hypertrophy and heart failure. Even though both Erk and phosphoinositide 3-kinase (PI3K)-Akt signaling pathways participate in complex cellular processes regarding physiological or pathological states of cardiomyocytes, the circadian oscillators in the heart regulate these pathways independently, and both pathways contribute to the circadian regulation of L-VGCCs.

Peptide Lv augments L-type voltage-gated calcium channels through vascular endothelial growth factor receptor 2 (VEGFR2) signaling

“…All chicken embryos were maintained at 39°C ± 0.5°C. Chicken hearts were harvested at embryonic day 12 (E12) and ventricular cardiomyocytes were dissociated and cultured on poly-d-lysine/collagen double-coated dishes (for biochemical and molecular biological assays) or coverslips (for electrophysiological recordings) as described previously [18]. The culture medium contained Dulbecco’s modified Eagle’s medium (DMEM; Biowhittaker, Walkersville, MD, USA), 5% fetal bovine serum (FBS, Hyclone, Logan, UT, USA), 10% heat-inactivated horse serum (Biowhittaker), 2 mM GlutaMAX (Gibco/Invitrogen, Carlsbad, CA, USA), 50 U/mL penicillin (Sigma, St. Louis, MO, USA), 50 μg/mL streptomycin (Sigma), and 5 μg/mL retinol (Sigma).…”

Cardiac-Specific Mutation of Clock Alters the Quantitative Measurements of Physical Activities without Changing Behavioral Circadian Rhythms

“…Nonetheless, circadian changes in the heart from gene expression to metabolism to contractile function are intrinsic and independent of autonomic inputs (Bray et al, 2008; Durgan et al, 2005; Durgan et al, 2006; Young and Bray, 2007). We previously showed that at the cellular level, the L-type voltage-gated calcium channels (L-VGCCs) and phosphorylation states of several signaling molecules, such as extracellular signal–regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)–protein kinase B (AKT), are under circadian control in chick cardiomyocytes (Ko et al, 2010). However, we obtained heart tissue and cardiomyocytes from entrained whole chicken embryos, making it difficult to dissect the significance of peripheral cardiac oscillators on daily rhythms independent of the master clock.…”

Consequences of Circadian and Sleep Disturbances for the Cardiovascular System

“…159 Also, L-type calcium channel current densities increase during the active period which is consistent with the nocturnal elevation in murine heart rate. 155,157 Moreover, circadian variations in potassium channel interacting protein-2 (KChIP2) affect potassium channel opening in a manner that is consistent with changes in action potential duration and circadian variations in heart rate. In vivo, the kruppel-like factor 15 (circadian output gene) knockout mice display increased susceptibility to ventricular arrhythmias, and reduced expression of potassium channel interacting protein 2.…”