Alternations of cardiac IK1 and Ito from FKBP12.6 transgenic mouse heart and potential impact of cardiac hypertrophy

Dynamics expression of DmFKBP12/Calstabin during embryonic early development of Drosophila melanogaster

Background

Calcium signaling are conserved from invertebrates to vertebrates and plays critical roles in many molecular mechanisms of embryogenesis and postnatal development. As a critical component of the signaling pathway, the RyR medicated calcium-induced calcium release signaling system, has been well studied along with their regulator FK506-binding protein 12 (FKBP12/Calstabin). Lack of FKBP12 is known to result in lethal cardiac dysfunction in mouse. However, precisely how FKBP12 is regulated and effects calcium signaling in Drosophila melanogaster remains largely unknown.

Results

In this study, we identified both temporal and localization changes in expression of DmFKBP12, a translational and transcriptional regulator of Drosophila RyR (DmRyR) and FKBP12, through embryonic development. DmFKBP12 is first expressed at the syncytial blastoderm stage and undergoes increased expression during the cellular blastoderm and early gastrulation stages. At late gastrulation, DmFKBP12 expression begins to decline until it reaches homeostasis, which it then maintains throughout the rest of development. Throughout these described changes in expression, DmFKBP12 mRNA remain stable, which indicates that protein dynamics are attributed to regulation at the mRNA to protein translation level. In addition to temporal changes in expression, dynamic expression profiles during Drosophila development also revealed DmFKBP12 localization. Although DmFKBP12 is distributed evenly between the anterior to posterior poles of the blastoderm egg, the protein is expressed more strongly in the cortex of the early Drosophila gastrula with the highest concentration found in the basement membrane of the cellular blastoderm. Fertilized egg, through the profile as under-membrane cortex distribution concentering onto basement at cellular blastoderm, to the profile as three-gem layer localization in primitive neuronal and digestion architecture of early Drosophila gastrula. By late gastrulation, DmFKBP12 is no longer identified in the yolk or lumen of duct structures and has relocated to the future brain (suboesophageal and supraesophageal ganglions), ventral nervous system, and muscular system. Throughout these changes in distribution, in situ DmFKBP12 mRNA monitoring detected equal distribution of DmFKBP12 mRNA, once again indicating that regulation of DmFKBP12 occurs at the translational level in Drosophila development.

Conclusion

As a critical regulator of the DmRyR-FKBP complex, DmFKBP12 expression in Drosophila fluctuates temporally and geographically with the formation of organ systems. These finding indicate that DmFKBP12 and RyR associated calcium signaling plays an essential role in the successful development of Drosophila melanogaster. Further study on the differences between mammalian RyR-FKBP12 and Drosophila DmRyR-FKBP12 can be exploited to develop safe pesticides.

Electronic supplementary material

The online version of this article (10.1186/s13578-019-0270-6) contains supplementary material, which is available to authorized users.

Resveratrol Ameliorates Cardiac Hypertrophy by Down-regulation of miR-155 Through Activation of Breast Cancer Type 1 Susceptibility Protein

BACKGROUND

The polyphenol resveratrol (Rev) has been reported to exhibit cardioprotective effects, such as inhibition of TAC (transverse aortic constriction) or isoprenaline (ISO)-induced hypertrophy. MicroRNA-155 (miR-155) was found to be decreased in hypertrophic myocardium, which could be further reduced by pretreatment of Rev. The study was designed to investigate the molecular effects of miR-155 on cardiac hypertrophy, focusing on the role of breast cancer type 1 susceptibility protein (BRCA1).

METHODS AND RESULTS

We demonstrated that Rev alleviated severity of hypertrophic myocardium in a mice model of cardiac hypertrophy by TAC treatment. Down-regulation of miR-155 was observed in pressure overload- or ISO-induced hypertrophic cardiomyoctyes. Interestingly, administration of Rev substantially attenuated miR-155 level in cardiomyocytes. In agreement with its miR-155 reducing effect, Rev relieved cardiac hypertrophy and restored cardiac function by activation of BRCA1 in cardiomyoctyes. Our results further revealed that forkhead box O3a (FoxO3a) was a miR-155 target in the heart. And miR-155 directly repressed FoxO3a, whose expression was mitigated in miR-155 agomir and mimic treatment in vivo and in vitro.

CONCLUSIONS

We conclude that BRCA1 inactivation can increase expression of miR-155, contributing to cardiac hypertrophy. And Rev produces their beneficial effects partially by down-regulating miR-155 expression, which might be a novel strategy for treatment of cardiac hypertrophy.

Na+-induced Ca2+ influx through reverse mode of Na+-Ca2+ exchanger in mouse ventricular cardiomyocyte

Background

Dobutamine is commonly used for clinical management of heart failure and its pharmacological effects have long been investigated as inotropics via β–receptor activation. However, there is no electrophysiological evidence if dobutamine contributes inotropic action due at least partially to the reverse mode of Na⁺-Ca²⁺ exchanger (NCX) activation.

Methods

Action potential (AP), voltage-gated Na⁺ (I_Na), Ca²⁺ (I_Ca), and K⁺ (I_to and I_K1) currents were observed using whole-cell patch technique before and after dobutamine in ventricular cardiomyocytes isolated from adult mouse hearts. Another sets of observation were also performed with Kb-r7943 or in the solution without [Ca²⁺]_o.

Results

Dobutamine (0.1–1.0 μM) significantly enhanced the AP depolarization with prolongation of AP duration (APD) in a concentration-dependent fashion. The density of I_Nawas also increased concentration-dependently without alternation of voltage-dependent steady-status of activation and inactivation, reactivation as well. Whereas, the activities for I_Ca, I_to, and I_K1 were not changed by dobutamine. Intriguingly, the dobutamine-mediated changes in AP repolarization were abolished by 3 μM Kb-r7943 pretreatment or by simply removing [Ca²⁺]_o without affecting accelerated depolarization. Additionally, the ratio of APD₅₀/APD₉₀ was not significantly altered in the presence of dobutamine, implying that effective refractory period was remain unchanged.

Conclusion

This novel finding provides evidence that dobutamine upregulates of voltage-gated Na⁺ channel function and Na⁺ influx-induced activation of the reverse mode of NCX, suggesting that dobutamine may not only accelerate ventricular contraction via fast depolarization but also cause Ca²⁺ influx, which contributes its positive inotropic effect synergistically with β-receptor activation without increasing the arrhythmogenetic risk.