Cardioprotective Effects of Serca2a Overexpression Against Ischemiareperfusion- induced Injuries in Rats

An updated review of YAP: A promising therapeutic target against cardiac aging?

The transcriptional co-activator Yes-associated protein (YAP) functions as a downstream effector of the Hippo signaling pathway and plays a crucial role in cardiomyocyte survival. In its non-phosphorylated activated state, YAP binds to transcription factors, activating the transcription of downstream target genes. It also regulates cell proliferation and survival by selectively binding to enhancers and activating target genes. However, the upregulation of the Hippo pathway in human heart failure inhibits cardiac regeneration and disrupts astrogenesis, thus preventing the nuclear translocation of YAP. Existing literature indicates that the Hippo/YAP axis contributes to inflammation and fibrosis, potentially playing a role in the development of cardiac, vascular and renal injuries. Moreover, it is a key mediator of myofibroblast differentiation and fibrosis in the infarcted heart. Given these insights, can we harness YAP's regenerative potential in a targeted manner? In this review, we provide a detailed discussion of the Hippo signaling pathway and consolidate concepts for the development and intervention of cardiac anti-aging drugs to leverage YAP signaling as a pivotal target.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury

BACKGROUND

Sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) is a key protein that maintains myocardial Ca 2+ homeostasis. The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation (small ubiquitin-like modifier) process after ischemia/reperfusion injury (I/RI) in vitro and in vivo .

METHODS

Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout (KO) and wild-type mice with I/RI were compared. SUMO-relevant protein expression and localization were detected by quantitative real-time PCR (RT-qPCR), Western blotting, and immunofluorescence in vitro and in vivo . Serca2a-SUMOylation, infarct size, and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes, were detected by immunoprecipitation, triphenyltetrazolium chloride (TTC)-Evans blue staining, and echocardiography respectively.

RESULTS

The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO + I/RI groups. Senp1 and Senp2 messenger ribose nucleic acid (mRNA) and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI. However, the highest levels in HL-1 cells were recorded at 12 h. Senp2 expression increased in the cytoplasm, unlike that of Senp1. Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline, reduced the infarction area, and improved cardiac function, while inhibition of Senp1 protein could not restore the above indicators.

CONCLUSION

I/RI activated Senp1 and Senp2 protein expression, which promoted Serca2a-deSUMOylation, while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

SERCA2a ameliorates cardiomyocyte T-tubule remodeling via the calpain/JPH2 pathway to improve cardiac function in myocardial ischemia/reperfusion mice

Transverse-tubules (T-tubules) play pivotal roles in Ca²⁺-induced, Ca²⁺ release and excitation–contraction coupling in cardiomyocytes. The purpose of this study was to uncover mechanisms where sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA2a) improved cardiac function through T-tubule regulation during myocardial ischemia/reperfusion (I/R). SERCA2a protein expression, cytoplasmic [Ca²⁺]_i, calpain activity, junctophilin-2 (JPH2) protein expression and intracellular localization, cardiomyocyte T-tubules, contractility and calcium transients in single cardiomyocytes and in vivo cardiac functions were all examined after SERCA2a knockout and overexpression, and Calpain inhibitor PD150606 (PD) pretreatment, following myocardial I/R. This comprehensive approach was adopted to clarify SERCA2a mechanisms in improving cardiac function in mice. Calpain was activated during myocardial I/R, and led to the proteolytic cleavage of JPH2. This altered the T-tubule network, the contraction function/calcium transients in cardiomyocytes and in vivo cardiac functions. During myocardial I/R, PD pretreatment upregulated JPH2 expression and restored it to its intracellular location, repaired the T-tubule network, and contraction function/calcium transients of cardiomyocytes and cardiac functions in vivo. SERCA2a suppressed calpain activity via [Ca²⁺]_i, and ameliorated these key indices. Our results suggest that SERCA2a ameliorates cardiomyocyte T-tubule remodeling via the calpain/JPH2 pathway, thereby improving cardiac function in myocardial I/R mice.

Luteolin modulates SERCA2a via Sp1 upregulation to attenuate myocardial ischemia/reperfusion injury in mice

The sarco/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) is responsible for calcium transport during excitation-contraction coupling and is essential for maintaining myocardial systolic/diastolic function and intracellular Ca2+ levels. Therefore, it is important to investigate mechanisms whereby luteolin modulates SERCA2a expression to attenuate myocardial ischemia/reperfusion injury. C57BL/6j mice were randomly divided into eight groups. The expression and activity of SERCA2a was measured to assess interactions between the SERCA2a promoter and the Sp1 transcription factor, and the regulatory effects of luteolin. We used serum LDH release, serum cardiac troponin I level, hemodynamic data, myocardial infarction size and apoptosis-related indices to measure SERCA2a cardio-protective effects of luteolin pretreatment. Sp1 binding to SERCA2a promoter under ischemia/reperfusion conditions in the presence or absence of luteolin was analyzed by chromatin immunoprecipitation. Our experimental results indicated that during myocardial ischemia/reperfusion injury, luteolin pretreatment upregulated the expression levels of SERCA2a and Sp1. Sp1 overexpression enhanced the expression of SERCA2a at the transcriptional level. Luteolin pretreatment reversed the expression of SERCA2a through the increased expression of Sp1. Moreover, we demonstrated that luteolin pretreatment appeared to exert myocardial protective effects by upregulating the transcriptional activity of SERCA2a, via Sp1. In conclusion, during myocardial ischemia/reperfusion, Sp1 appeared to downregulate the expression of SERCA2a. Luteolin pretreatment was shown to improve SERCA2a expression via the upregulation of Sp1 to attenuate myocardial ischemia/reperfusion injury.

Adenoviral βARKct Cardiac Gene Transfer Ameliorates Postresuscitation Myocardial Injury in a Porcine Model of Cardiac Arrest

OBJECTIVE

The aim of the study was to determine whether the inhibition of the G-protein-coupled receptor kinase 2 by adenoviral βARKct cardiac gene transfer can ameliorate postresuscitation myocardial injury in pigs with cardiac arrest (CA) and explore the mechanism of myocardial protection.

METHODS

Male landrace domestic pigs were randomized into the sham group (anesthetized and instrumented, but ventricular fibrillation was not induced) (n = 4), control group (ventricular fibrillation 8 min, n = 8), and βARKct group (ventricular fibrillation 8 min, n = 8). Hemodynamic parameters were monitored continuously. Blood samples were collected at baseline, 30 min, 2 h, 4 h, and 6 h after the return of spontaneous circulation (ROSC). Left ventricular ejection fraction was assessed by echocardiography at baseline and 6 h after ROSC. These animals were euthanized, and the cardiac tissue was removed for analysis at 6 h after ROSC.

RESULTS

Compared with those in the sham group, left ventricular +dp/dtmax, -dp/dtmax, cardiac output (CO), and ejection fraction (EF) in the control group and the βARKct group were significantly decreased at 6 h after the restoration of spontaneous circulation. However, the βARKct treatment produced better left ventricular +dp/dtmax, -dp/dtmax, CO, and EF after ROSC. The βARKct treatment also produced lower serum cardiac troponin I, CK-MB, and lactate after ROSC. Furthermore, the adenoviral βARKct gene transfer significantly increased β1 adrenergic receptors, SERCA2a, RyR2 levels, and decreased GRK2 levels compared to control.

CONCLUSIONS

The inhibition of GRK2 by adenoviral βARKct cardiac gene transfer can ameliorate postresuscitation myocardial injury through beneficial effects on restoring the sarcoplasmic reticulum Ca-handling proteins expression and upregulating the β1-adrenergic receptor level after cardiac arrest.

Novel Molecular Targets Participating in Myocardial Ischemia-Reperfusion Injury and Cardioprotection

Worldwide morbidity and mortality from acute myocardial infarction (AMI) and related heart failure remain high. While effective early reperfusion of the criminal coronary artery after a confirmed AMI is the typical treatment at present, collateral myocardial ischemia-reperfusion injury (MIRI) and pertinent cardioprotection are still challenging to address and have inadequately understood mechanisms. Therefore, unveiling the related novel molecular targets and networks participating in triggering and resisting the pathobiology of MIRI is a promising and valuable frontier. The present study specifically focuses on the recent MIRI advances that are supported by sophisticated bio-methodology in order to bring the poorly understood interrelationship among pro- and anti-MIRI participant molecules up to date, as well as to identify findings that may facilitate the further investigation of novel targets.

Effects of Tiaozhi Granule on Regulation of Autophagy Levels in HUVECs

Sera from the rats with Tiaozhi granule treatment were collected. Human umbilical vein endothelial cells (HUVECs) were incubated with different dosage of sera with Tiaozhi granule for 48 hours. Rapamycin or angiotensin II was applied to activate autophagy in HUVECs with or without different dosages of sera of Tiaozhi granule. The mRNA expressions of Atg5, Atg7, Beclin-1, and mammal target of rapamycin (mTOR) were detected by real-time PCR. Autophagic flux markers (protein expression of LC3, Beclin-1, and p62) were examined by western blot analyses. The number of autophagosomes was visualized by immunofluorescence analysis with LC3-II labelling. Results showed that Tiaozhi granule sera increase cell autophagic levels by increase of mRNA of Atg5, Atg7, Beclin-1, and mTOR and increase of autophagic flux and also number of autophagosomes. However, in response to rapamycin or Ang II stimulation, activated autophagic levels were alleviated by Tiaozhi granule sera by reduction of mRNA of Atg5, Atg7, Beclin-1, mTOR, autophagic flux, and also number of autophagosomes. Our present data demonstrate that Tiaozhi granule plays a dual role in response to different cell conditions, which is to increase cell autophagy under physiological condition and to suppress cell excessive autophagy under pathological condition.