Extracellular Adenosine Formation by Ecto-5'-Nucleotidase (CD73) Is No Essential Trigger for Early Phase Ischemic Preconditioning

Serum 5'-Nucleotidase as a Novel Predictor of Adverse Clinical Outcomes after Percutaneous Coronary Intervention in Patients with Coronary Artery Disease

Background

The correlation between 5 ' -Nucleotidase ( 5 ' -NT) and the clinical outcomes in coronary artery disease (CAD) patients following percutaneous coronary intervention (PCI) is not clear. This study aims to clarify this relationship.

Methods

The PRACTICE study enrolled 15,250 patients between December 2016 and October 2021. After filtering out those without 5 ' -NT data, a total of 6555 patients were analyzed with a median follow-up of 24 months. Based on the receiver operating characteristic (ROC) curve analysis, a 5 ' -NT level of 5.57 U/L was selected as the optimal cutoff value. All research samples were divided into high-value ( ≥ 5.57 U/L, n = 2346) and low-value groups ( < 5.57 U/L, n = 4209). Key clinical outcomes included all-cause death (ACD), cardiovascular death (CD), major adverse cardiovascular events (MACE), and major adverse cardiovascular and cerebrovascular events (MACCE). After separating patients into high and low value groups, multivariate Cox regression analysis was used to correct for potential confounding variables. Finally, risk ratios and their 95% confidence intervals (CIs) were calculated.

Results

During the follow-up period, 129 instances of ACD were recorded-49 cases (1.2%) in the low-value group and 80 cases (3.4%) in the high-value group. Similarly, 102 CDs occurred, including 42 low-value group cases (1.0%) and 60 high-value group cases (2.6%). A total of 363 MACE occurred, including 198 low-value group cases (4.7%) and 165 high-value group cases (7%). A total of 397 cases of MACCE occurred, including 227 low-value group cases (5.4%) and 170 high-value group cases (7.2%). As serum 5 ' -NT increased, the incidence of ACD, CD, MACE and MACCE increased. After multivariate Cox regression, high 5 ' -NT levels were linked with a 1.63-fold increase in ACD risk (hazard ratio [HR] = 2.630, 95% CI: [1.770-3.908], p < 0.001) when compared to low 5 ' -NT patients. Similarly, the risk of CD, MACE, and MACCE increased by 1.298-fold (HR = 2.298, 95% CI: [1.477-3.573], p < 0.001), 41% (HR = 1.410, 95% CI: [1.124-1.768], p = 0.003) and 30.5% (HR = 1.305, 95% CI: [1.049-1.623], p = 0.017), respectively.

Conclusions

high serum 5 ' -NT levels were independently correlated with adverse clinical outcomes in CAD patients following PCI, affirming its potential as a prognostic indicator.

The Role of Purinergic Signaling in Heart Transplantation

Heart transplantation remains the optimal treatment option for patients with end-stage heart disease. Growing evidence demonstrates that purinergic signals mediated by purine nucleotides and nucleosides play vital roles in heart transplantation, especially in the era of ischemia-reperfusion injury (IRI) and allograft rejection. Purinergic signaling consists of extracellular nucleotides and nucleosides, ecto-enzymes, and cell surface receptors; it participates in the regulation of many physiological and pathological processes. During transplantation, excess adenosine triphosphate (ATP) levels are released from damaged cells, and driver detrimental inflammatory responses largely via purinergic P2 receptors. Ecto-nucleosidases sequentially dephosphorylate extracellular ATP to ADP, AMP, and finally adenosine. Adenosine exerts a cardioprotective effect by its anti-inflammatory, antiplatelet, and vasodilation properties. This review focused on the role of purinergic signaling in IRI and rejection after heart transplantation, as well as the clinical applications and prospects of purinergic signaling.

CD73+ Mesenchymal Stem Cells Ameliorate Myocardial Infarction by Promoting Angiogenesis

With multipotent differentiation potential and paracrine capacity, mesenchymal stem cells (MSCs) have been widely applied in clinical practice for the treatment of ischemic heart disease. MSCs are a heterogeneous population and the specific population of MSCs may exhibit a selective ability for tissue repair. The aim of our research was to adapt the CD73⁺ subgroup of adipose derived MSCs (AD-MSCs) for the therapy of myocardial infarction (MI). In this research, AD-MSCs were isolated from adipose tissue surrounding the groin of mice and CD73⁺ AD-MSCs were sorted using flow cytometry. To investigate the therapeutic effects of CD73⁺ AD-MSCs, 1.2 × 10⁶ CD73⁺ AD-MSCs were transplanted into rat model of MI, and CD73^– AD-MSCs, normal AD-MSCs transplantation served as control. Our results revealed that CD73⁺ AD-MSCs played a more effective role in the acceleration function of cardiac recovery by promoting angiogenesis in a rat model of MI compared with mixed AD-MSCs and CD73^– AD-MSCs. Moreover, with the expression of CD73 in AD-MSCs, the secretion of VEGF, SDF-1α, and HGF factors could be promoted. It also shows differences between CD73⁺ and CD73^– AD-MSCs when the transcription profiles of these two subgroups were compared, especially in VEGF pathway. These findings raise an attractive outlook on CD73⁺ AD-MSCs as a dominant subgroup for treating MI-induced myocardial injury. CD73, a surface marker, can be used as a MSCs cell quality control for the recovery of MI by accelerating angiogenesis.

Mechanisms involved in adenosine pharmacological preconditioning-induced cardioprotection

Adenosine is a naturally occurring breakdown product of adenosine triphosphate and plays an important role in different physiological and pathological conditions. Adenosine also serves as an important trigger in ischemic and remote preconditioning and its release may impart cardioprotection. Exogenous administration of adenosine in the form of adenosine preconditioning may also protect heart from ischemia-reperfusion injury. Endogenous release of adenosine during ischemic/remote preconditioning or exogenous adenosine during pharmacological preconditioning activates adenosine receptors to activate plethora of mechanisms, which either independently or in association with one another may confer cardioprotection during ischemia-reperfusion injury. These mechanisms include activation of K_ATP channels, an increase in the levels of antioxidant enzymes, functional interaction with opioid receptors; increase in nitric oxide production; decrease in inflammation; activation of transient receptor potential vanilloid (TRPV) channels; activation of kinases such as protein kinase B (Akt), protein kinase C, tyrosine kinase, mitogen activated protein (MAP) kinases such as ERK 1/2, p38 MAP kinases and MAP kinase kinase (MEK 1) MMP. The present review discusses the role and mechanisms involved in adenosine preconditioning-induced cardioprotection.

Current knowledge on the role of P2Y receptors in cardioprotection against ischemia-reperfusion

During ischemia, numerous effective endogenous extracellular mediators have been identified, particularly, nucleosides such as adenosine as well as purinergic and pyrimidinergic nucleotides. They may play important regulatory roles within the cardiovascular system and notably as cardio-protectants. Indeed, the distribution of the P2Y receptors in mammalian heart includes several cellular constituents relevant for the pathophysiology of myocardial ischemia. Beside the well-known cardioprotective effect of adenosine, the additional protective role of P2Y receptors has emerged. However, interpretation of experimental results may be sometimes perplexing. This is due to the variability of: the experimental models, the endpoints criteria, the chemical structure of agonist and antagonist ligands and their concentrations, the sequences of drug administration with respect to the model used (before and/or during and/or after ischemia). The net effect may be in the opposite direction after a transient or a prolonged stimulation. Nevertheless, the overall reading of published data highlights the beneficial role of the P2Y_2/4 receptor stimulation, the useful and synergistic role of P2Y_6/11 receptor activation and even of the P2Y₁₁ receptor alone in cardioprotection. More, the P2Y₁₁ receptor could be involved in counter-regulation of profibrotic processes. Paradoxically, transient P2X₇ receptor stimulation could contribute to the net cardioprotective effect of ATP. Recently, experimental data have shown that blocking the P2Y₁₂ receptor after ischemia confers cardioprotection independently of platelet antiaggregatory effect. This suggests for P2Y receptors an important role in primary prevention and as a therapeutic target in myocardial protection during ischemia and reperfusion.