Bradykinin preconditioning improves the profile of cell survival proteins and limits apoptosis after cardioplegic arrest

A comprehensive review on current understanding of bradykinin in COVID-19 and inflammatory diseases

Bradykinin, a member of the kallikrein–kinin system (KKS), is a potent, short-lived vasoactive peptide that acts as a vasodilator and an inflammatory mediator in a number of signaling mechanisms. Bradykinin induced signaling is mediated through kinin B1 (BDKRB1) and B2 (BDKRB2) transmembrane receptors coupled with different subunits of G proteins (G_αi/G_α0, G_αq and G_β1γ2). The bradykinin-mediated signaling mechanism activates excessive pro-inflammatory cytokines, including IL-6, IL-1β, IL-8 and IL-2. Upregulation of these cytokines has implications in a wide range of clinical conditions such as inflammation leading to fibrosis, cardiovascular diseases, and most recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In SARS-CoV-2 infection, bradykinin is found to be at raised levels and is reported to trigger a diverse array of symptoms. All of this brings bradykinin to the core point as a molecule of immense therapeutic value. Our understanding of its involvement in various pathways has expanded with time. Therefore, there is a need to look at the overall picture that emerges from the developments made by deciphering the bradykinin mediated signaling mechanisms involved in the pathological conditions. It will help devise strategies for developing better treatment modalities in the implicated diseases. This review summarizes the current state of knowledge on bradykinin mediated signaling in the diverse conditions described above, with a marked emphasis on the therapeutic potential of targeting the bradykinin receptor.

Why is endothelial resilience key to maintain cardiac health?

Myocardial injury as induced by myocardial infarction results in tissue ischemia, which critically incepts cardiomyocyte death. Endothelial cells play a crucial role in restoring oxygen and nutrient supply to the heart. Latest advances in single-cell multi-omics, together with genetic lineage tracing, reveal a transcriptional and phenotypical adaptation to the injured microenvironment, which includes alterations in metabolic, mesenchymal, hematopoietic and pro-inflammatory signatures. The extent of transition in mesenchymal or hematopoietic cell lineages is still debated, but it is clear that several of the adaptive phenotypical changes are transient and endothelial cells revert back to a naïve cell state after resolution of injury responses. This resilience of endothelial cells to acute stress responses is important for preventing chronic dysfunction. Here, we summarize how endothelial cells adjust to injury and how this dynamic response contributes to repair and regeneration. We will highlight intrinsic and microenvironmental factors that contribute to endothelial cell resilience and may be targetable to maintain a functionally active, healthy microcirculation.

Autocrine Bradykinin Release Promotes Ischemic Preconditioning-Induced Cytoprotection in Bovine Aortic Endothelial Cells

The aims of this study were to assess whether ischemic preconditioning (PC) induces bradykinin (Bk) synthesis in bovine aortic endothelial cells (bAECs) and, if so, to explore the molecular mechanisms by which this peptide provides cytoprotection against hypoxia. PC was induced by exposing bAECs to three cycles of 15 min of hypoxia followed by 15 min of reoxygenation. Bk synthesis peaked in correspondence to the early and late phases of PC (10⁻¹² M and 10⁻¹¹ M, respectively) and was abolished by a selective tissue kallikrein inhibitor, aprotinin. Stimulation with exogenous Bk at concentrations of 10⁻¹² M and 10⁻¹¹ M reduced the cell death induced by 12 h of hypoxia by 50%. Pretreatment with HOE−140, a Bk receptor 2 (BKR2) inhibitor, in bAECs exposed to 12 h of hypoxia, abrogated the cytoprotective effect of early and late PC, whereas des-Arg-HOE-140, a Bk receptor 1 (BKR1) inhibitor, affected only the late PC. In addition, we found that PC evoked endocytosis and the recycling of BKR2 during both the early and late phases, and that inhibition of these pathways affected PC-mediated cytoprotection. Finally, we evaluated the activation of PKA and Akt in the presence or absence of BKR2 inhibitor. HOE-140 abrogated PKA and Akt activation during both early and late PC. Consistently, BKR2 inhibition abolished cross-talk between PKA and Akt in PC. In bAECs, Bk-synthesis evoked by PC mediates the protection against both apoptotic and necrotic hypoxia-induced cell death in an autocrine manner, by both BKR2- and BKR1-dependent mechanisms.

Microvascular dysfunction in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass

PURPOSE OF REVIEW

The purpose of the current review is to describe the changes of microvascular function in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass (CPB) and cardiac surgery.

RECENT FINDINGS

Cardiac surgery, especially that involving cardioplegia and CPB, is associated with significant changes in vascular reactivity of coronary/peripheral microcirculation, vascular permeability, gene/protein expression, and programmed cell death, as well as with increased morbidity and mortality after surgical procedures. In particular, these changes are more profound in patients with poorly controlled diabetes.

SUMMARY

Because alterations in vasomotor regulation are critical aspects of mortality and morbidity of cardioplegia/CPB, a better understanding of diabetic regulation of microvascular function may lead to improved postoperative outcomes of patients with diabetes after cardioplegia/CPB and cardiac surgery.

Bradykinin preconditioning improves therapeutic potential of human endothelial progenitor cells in infarcted myocardium

Objectives

Stem cell preconditioning (PC) is a powerful approach in reducing cell death after transplantation. We hypothesized that PC human endothelial progenitor cells (hEPCs) with bradykinin (BK) enhance cell survival, inhibit apoptosis and repair the infarcted myocardium.

Methods

The hEPCs were preconditioned with or without BK. The hEPCs apoptosis induced by hypoxia along with serum deprivation was determined by annexin V-fluorescein isothiocyanate/ propidium iodide staining. Cleaved caspase-3, Akt and eNOS expressions were determined by Western blots. Caspase-3 activity and vascular endothelial growth factor (VEGF) levels were assessed in hEPCs. For invivo studies, the survival and cardiomyocytes apoptosis of transplanted hEPCs were assessed using 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindodi- carbocyanine,4-chlorobenzenesul-fonate salt labeled hEPCs and TUNEL staining. Infarct size and cardiac function were measured at 10 days after transplantation, and the survival of transplanted hEPCs were visualized using near-infrared optical imaging.

Results

Invitro data showed a marked suppression in cell apoptosis following BK PC. The PC reduced caspase-3 activation, increased the Akt, eNOS phosphorylation and VEGF levels. Invivo data in preconditioned group showed a robust cell anti-apoptosis, reduction in infarct size, and significant improvement in cardiac function. The effects of BK PC were abrogated by the B2 receptor antagonist HOE140, the Akt and eNOS antagonists LY294002 and L-NAME, respectively.

Conclusions

The activation of B2 receptor-dependent PI3K/Akt/eNOS pathway by BK PC promotes VEGF secretion, hEPC survival and inhibits apoptosis, thereby improving cardiac function invivo. The BK PC hEPC transplantation for stem cell-based therapies is a novel approach that has potential for clinical used.

Altered apoptosis-related signaling after cardioplegic arrest in patients with uncontrolled type 2 diabetes mellitus

BACKGROUND

We investigated the effects of cardioplegic arrest and reperfusion (CP/Rep) on myocardial apoptosis and key apoptotic mediators, such as apoptosis-inducing factor, caspase 3, caspase 8, caspase 9, poly(adenosine diphosphate-ribose) polymerase, B-cell lymphoma 2 (Bcl-2) family proteins, and protein kinase C (PKC), in uncontrolled type 2 diabetic, controlled type 2 diabetic, and nondiabetic patients.

METHODS AND RESULTS

Right atrial tissue was harvested pre- and post-CP/Rep from uncontrolled type 2 diabetic patients (hemoglobin A1c=9.6 ± 0.25), controlled type 2 diabetic patients (hemoglobin A1c=6.5 ± 0.15), and nondiabetic patients (hemoglobin A1c=5.4 ± 0.12) undergoing coronary artery bypass grafting (n=8/group). Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining was used for the identification of apoptotic cells. Total and modified apoptosis-inducing factor, Bcl-2 family proteins, phospho-PKC-α, phospho-PKC-β1, and poly(adenosine diphosphate-ribose) polymerase were quantified by immunoblotting or immunohistochemistry. At baseline, the number of apoptotic cells and expression of total apoptosis-inducing factor, Bcl-2, Bak, and Bax in the pre-CP/Rep atrial tissue from uncontrolled type 2 diabetic patients were significantly increased compared with those of nondiabetic or controlled type 2 diabetic patients (P<0.05). After CP/Rep, the amount of apoptotic cells, apoptosis-inducing factor, phospho-Bad, phospho-PKC-α, phospho-PKC-β1, and cleaved poly(adenosine diphosphate-ribose) polymerase in post-CP/Rep atrial tissue were increased in all 3 groups compared with pre-CP/Rep. These increases after CP/Rep were more pronounced in the uncontrolled type 2 diabetic group. In addition, there were significant increases in the expression of cleaved caspase 8 and caspase 9 in the basal and post-CP/Rep atrium of uncontrolled type 2 diabetic group compared with nondiabetic or controlled type 2 diabetic group.

CONCLUSIONS

Uncontrolled diabetes mellitus is associated with increases in myocardial apoptosis and expression of key apoptosis mediators at baseline and in the setting of CP/Rep.

Related transcriptional enhancer factor 1 increases endothelial-dependent microvascular relaxation and proliferation

OBJECTIVE

Related transcriptional enhancer factor 1 (RTEF-1) is a key transcriptional regulator in endothelial function. In this study, we investigated a possible role for RTEF-1 in the regulation of microvascular relaxation and the underlying mechanism involved. Activation of fibroblast growth factor receptor 1 (FGFR1) by FGFs increases vasodilation, although transcriptional control of the molecular mechanisms underlying FGFR1 is still unclear.

MATERIALS AND METHODS

We demonstrated that RTEF-1 stimulated FGFR1 expression at the transcriptional level, specifically an area including Sp1 elements, as evidenced by promoter assays. Additionally, RTEF-1 increased FGFR1 mRNA and protein expression in vitro and in VE-cadherin-promoted RTEF-1 (VE-Cad/RTEF-1) transgenic mice, whereas RTEF-1 siRNA blocked the upregulation of FGFR1 expression. Furthermore, increased endothelial-dependent microvessel relaxation was observed in the coronary arteries of VE-Cad/RTEF-1 mice, and increased proliferation was observed in RTEF-1-overexpressing cells, both of which correlated to increased FGF/FGFR1 signaling and endothelial nitric oxide synthase (eNOS) upregulation. Our results indicate that RTEF-1 acts as a transcriptional stimulator of FGFR1 and is involved in FGF pathways by increasing microvessel dilatation via eNOS.

CONCLUSIONS

These findings suggest that RTEF-1 plays an important role in FGFR1- stimulated vasodilatation. Understanding the effect of RTEF-1 in microvessel relaxation may provide beneficial knowledge in improving treatments in regards to ischemic vascular disorders.

Polymerized placenta hemoglobin attenuates ischemia/reperfusion injury and restores the nitroso-redox balance in isolated rat heart

Ischemia/reperfusion (I/R) injury mainly caused by oxidative stress plays a major role in cardiac damage. The extent of the I/R injury is also an important factor that determines the function of a transplanted heart. This study first examined whether hemoglobin-based oxygen carriers (HBOCs) could protect isolated rat heart from I/R injury and then elucidated the underlying mechanism. Using the Langendorff model, isolated Sprague-Dawley rat hearts were arrested and stored at 4 degrees C for 8 h and then reperfused for 2 h. Compared with St. Thomas' solution (STS) and rat self blood in STS, polymerized placenta hemoglobin (PolyPHb) in STS greatly improved heart contraction and decreased infarction size. The extent of myocardial apoptosis was also significantly decreased, which was related to reduced iNOS-derived nitric oxide production, increased protein ratio of Bcl-2/Bax, and reduced caspase-3 activity and cleavage level. Furthermore, PolyPHb in STS did not increase malondialdehyde, peroxynitrite, or mitochondrial hydrogen peroxide formation, but greatly elevated superoxide dismutase activity and preserved mitochondrial ATP synthesis, which served to maintain redox homeostasis in I/R heart. In conclusion, our results demonstrate that HBOCs protected isolated heart from I/R injury and this protection was associated with attenuation of NO-mediated myocardial apoptosis and restoration of the nitroso-redox balance.

Modulation by bradykinin and nitric oxide of angiotensin II-induced apoptosis in a vascular smooth muscle cell phenotype

There is evidence for a clinical benefit of ACE inhibitors or AT1 antagonists in cardiovascular diseases with deleterious smooth muscle cells (SMC) apoptosis. We have previously shown that angiotensin II (Ang II) induces a phenotype-dependent SMC apoptosis. We asked whether bradykinin (BK) and nitric oxide (NO) could modulate Ang II-induced SMC apoptosis. BK alone did not induce significant apoptosis in either spindle (Sp-SMC) or epithelioid (Ep-SMC) SMC phenotypes cultured in serum reduction, but phenotype-dependently, reduced cell proliferation. Pretreatment with BK partly impaired Ang II-induced reduction of Ep-SMC culture viability and partly prevented apoptotic features. Pretreatment with sodium nitroprusside completely prevented all Ang II-induced deleterious effects in Ep-SMC, i. e. reduction of culture viability, Annexin V binding, nuclear condensation and cell fragmentation. These findings indicate that the BK-NO system may phenotype-dependently modulate SMC survival and in particular may oppose, mostly by NO, Ang II-induction of apoptosis in the Ep-SMC phenotype.

Nitric oxide homeostasis as a target for drug additives to cardioplegia

The vascular endothelium of the coronary arteries has been identified as the important organ that locally regulates coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and vasoactive peptides. NO is constitutively produced in endothelial cells by endothelial nitric oxide synthase (eNOS). NO derived from this enzyme exerts important biological functions including vasodilatation, scavenging of superoxide and inhibition of platelet aggregation. Routine cardiac surgery or cardiologic interventions lead to a serious temporary or persistent disturbance in NO homeostasis. The clinical consequences are "endothelial dysfunction", leading to "myocardial dysfunction": no- or low-reflow phenomenon and temporary reduction of myocardial pump function. Uncoupling of eNOS (one electron transfer to molecular oxygen, the second substrate of eNOS) during ischemia-reperfusion due to diminished availability of L-arginine and/or tetrahydrobiopterin is even discussed as one major source of superoxide formation. Therefore maintenance of normal NO homeostasis seems to be an important factor protecting from ischemia/reperfusion (I/R) injury. Both, the clinical situations of cardioplegic arrest as well as hypothermic cardioplegic storage are followed by reperfusion. However, the presently used cardioplegic solutions to arrest and/or store the heart, thereby reducing myocardial oxygen consumption and metabolism, are designed to preserve myocytes mainly and not endothelial cells. This review will focus on possible drug additives to cardioplegia, which may help to maintain normal NO homeostasis after I/R.