Suppression of NF-κB reduces myocardial no-reflow

Pathophysiology of Red Blood Cell Trapping in Ischemic Acute Kidney Injury

Red blood cell (RBC) trapping describes the accumulation of RBCs in the microvasculature of the kidney outer medulla that occurs following ischemic acute kidney injury (AKI). Despite its prominence in human kidneys following AKI, as well as evidence from experimental models demonstrating that the severity of RBC trapping is directly correlated with renal recovery, to date, RBC trapping has not been a primary focus in understanding the pathogenesis of ischemic kidney injury. New evidence from rodent models suggests that RBC trapping is responsible for much of the tubular injury occurring in the initial hours after kidney reperfusion from ischemia. This early injury appears to result from RBC cytotoxicity and closely reflects the injury profile observed in human kidneys, including sloughing of the medullary tubules and the formation of heme casts in the distal tubules. In this review, we discuss what is currently known about RBC trapping. We conclude that RBC trapping is likely avoidable. The primary causes of RBC trapping are thought to include rheologic alterations, blood coagulation, tubular cell swelling, and increased vascular permeability; however, new data indicate that a mismatch in blood flow between the cortex and medulla where medullary perfusion is maintained during cortical ischemia is also likely critical. The mechanism(s) by which RBC trapping contributes to renal functional decline require more investigation. We propose a renewed focus on the mechanisms mediating RBC trapping, and RBC trapping-associated injury is likely to provide important knowledge for improving AKI outcomes. © 2024 American Physiological Society. Compr Physiol 14:5325-5343, 2024.

Interleukin-36 is vasculoprotective in both sexes despite sex-specific changes in the coronary microcirculation response to IR injury

Aims

Risks and outcomes of myocardial infarction (MI) are different between men and women and some studies have demonstrated that the latter have a higher risk of mortality. Whilst there are many reasons for this, it may also partially be linked to stronger innate and adaptive immune responses mounted by females compared to males. However, little is known about how sex impacts the coronary microvessels, the site where inflammatory processes take place, after an MI. Intravital and laser speckle microscopy was used to image coronary microvessels and ventricular perfusion in vivo in response to myocardial ischaemia-reperfusion (IR) injury in male and female mice. Interleukin-36 (IL-36) is the latest addition to the IL-1 superfamily of pro-inflammatory cytokines and has recently been shown to mediate inflammation in a number of non-cardiovascular diseases. Its role in mediating potential sex-related microcirculatiory pertubations in the heart are unknown. Therefore, the vasculoprotective efficacy of an IL-36 receptor antagonist (IL-36Ra) was also investigated.

Methods and results

Immunostaining and flow cytometry demonstrated higher expression of IL-36 and its receptor in female hearts, an observation confirmed in human samples. Intravital imaging of the anaesthetised mouse beating heart identified significantly greater neutrophil recruitment in female hearts, but a greater burden of thrombotic disease in male hearts. Male mice had reduced functional capillary density and were unable to restore perfusion to baseline values as effectively as females. However, female mice had significantly larger infarcts. Interestingly, IL-36Ra decreased inflammation, improved perfusion, and reduced infarct size in both sexes despite increasing platelet presence in male hearts. Mechanistically, this was explained by IL-36Ra attenuating endothelial oxidative damage and VCAM-1 expression. Importantly, IL-36Ra administration during ischaemia was critical for vasculoprotection to be realised.

Conclusion

This novel study identified notable sex-related differences in the coronary microcirculatory response to myocardial IR injury which may explain why some studies have noted poorer outcomes in women after MI. Whilst contemporary MI treatment focuses on anti-platelet strategies, the heightened presence of neutrophils in female IR injured coronary microvessels necessitates the development of an effective anti-inflammatory approach for treating female patients. We also emphasise the importance of early intervention during the ischaemic period in order to maximise therapeutic effectiveness.

Lipopolysaccharide Pretreatment Prevents Medullary Vascular Congestion following Renal Ischemia by Limiting Early Reperfusion of the Medullary Circulation

BACKGROUND

Vascular congestion of the renal medulla-trapped red blood cells in the medullary microvasculature-is a hallmark finding at autopsy in patients with ischemic acute tubular necrosis. Despite this, the pathogenesis of vascular congestion is not well defined.

METHODS

In this study, to investigate the pathogenesis of vascular congestion and its role in promoting renal injury, we assessed renal vascular congestion and tubular injury after ischemia reperfusion in rats pretreated with low-dose LPS or saline (control). We used laser Doppler flowmetry to determine whether pretreatment with low-dose LPS prevented vascular congestion by altering renal hemodynamics during reperfusion.

RESULTS

We found that vascular congestion originated during the ischemic period in the renal venous circulation. In control animals, the return of blood flow was followed by the development of congestion in the capillary plexus of the outer medulla and severe tubular injury early in reperfusion. Laser Doppler flowmetry indicated that blood flow returned rapidly to the medulla, several minutes before recovery of full cortical perfusion. In contrast, LPS pretreatment prevented both the formation of medullary congestion and its associated tubular injury. Laser Doppler flowmetry in LPS-pretreated rats suggested that limiting early reperfusion of the medulla facilitated this protective effect, because it allowed cortical perfusion to recover and clear congestion from the large cortical veins, which also drain the medulla.

CONCLUSIONS

Blockage of the renal venous vessels and a mismatch in the timing of cortical and medullary reperfusion results in congestion of the outer medulla's capillary plexus and promotes early tubular injury after renal ischemia. These findings indicate that hemodynamics during reperfusion contribute to the renal medulla's susceptibility to ischemic injury.

Targeting IL-36 improves age-related coronary microcirculatory dysfunction and attenuates myocardial ischaemia-reperfusion injury in mice

Following myocardial infarction (MI), elderly patients have a poorer prognosis than younger patients, which may be linked to increased coronary microvessel susceptibility to injury. Interleukin-36 (IL-36), a newly discovered proinflammatory member of the IL-1 superfamily, may mediate this injury, but its role in the injured heart is currently not known. We first demonstrated the presence of IL-36(α/β) and its receptor (IL-36R) in ischemia/reperfusion-injured (IR-injured) mouse hearts and, interestingly, noted that expression of both increased with aging. An intravital model for imaging the adult and aged IR-injured beating heart in real time in vivo was used to demonstrate heightened basal and injury-induced neutrophil recruitment, and poorer blood flow, in the aged coronary microcirculation when compared with adult hearts. An IL-36R antagonist (IL-36Ra) decreased neutrophil recruitment, improved blood flow, and reduced infarct size in both adult and aged mice. This may be mechanistically explained by attenuated endothelial oxidative damage and VCAM-1 expression in IL-36Ra–treated mice. Our findings of an enhanced age-related coronary microcirculatory dysfunction in reperfused hearts may explain the poorer outcomes in elderly patients following MI. Since targeting the IL-36/IL-36R pathway was vasculoprotective in aged hearts, it may potentially be a therapy for treating MI in the elderly population.

Inhibition of miR-218-5p reduces myocardial ischemia-reperfusion injury in a Sprague-Dawley rat model by reducing oxidative stress and inflammation through MEF2C/NF-κB pathway

Following myocardial ischemia, myocardial reperfusion injury causes oxidative stress (OS) and inflammation, leading to myocardial cell apoptosis and necrosis. Recently, emerging studies have shown that microRNAs (miRNAs) contribute to the pathophysiology associated with myocardial ischemia-reperfusion (I/R). In this study, we conducted both in-vitro and in-vivo experiments to explore the role of miR-218-5p in ischemia-reperfusion (I/R)- or oxygen and glucose deprivation/reperfusion (OGD/R)-mediated cardiomyocyte injury. A total 44 Sprague-Dawley (SD) rats were used, and randomly divided into four groups, control group (n = 11), miR-218-5p-in group (n = 11), I/R group (n = 11), I/R + miR-218-5p-in group (n = 11). Our data showed that miR-218-5p was overexpressed in H9C2 cardiomyocytes under OGD/R treatment. miR-218-5p inhibition reduced the lactate dehydrogenase (LDH) activity and the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD), as well as the expression of tumor necrosis factor alpha (TNF-α), interleukin (IL-1β), and IL-6. Oppositely, miR-218-5p overexpression aggravated OGD/R-mediated damage on H9C2 cells, whereas nuclear factor kappa B (NF-κB) pathway inhibition or myocyte enhancer factor 2C (MEF2C) upregulation reversed miR-218-5p mimics-mediated effects. Bioinformatics analysis predicted that miR-218-5p targeted and dampened its expression, which was testified by the dual-luciferase reporter assay and RNA pull-down assay. In vivo, inhibiting miR-218-5p declined LDH activities and ROS, MDA and SOD levels in rat myocardial tissues under I/R injury, alleviated myocardial fibrosis and inflammatory reactions, and reduced myocardial infarction area. Overall, inhibition of miR-218-5p choked oxidative stress and inflammation in myocardial I/R injury via targeting MEF2C/NF-κB axis, thus relieving the disease progression.

Inflammation during Percutaneous Coronary Intervention-Prognostic Value, Mechanisms and Therapeutic Targets

Periprocedural myocardial injury and myocardial infarction (MI) are not infrequent complications of percutaneous coronary intervention (PCI) and are associated with greater short- and long-term mortality. There is an abundance of preclinical and observational data demonstrating that high levels of pre-, intra- and post-procedural inflammation are associated with a higher incidence of periprocedural myonecrosis as well as future ischaemic events, heart failure hospitalisations and cardiac-related mortality. Beyond inflammation associated with the underlying coronary pathology, PCI itself elicits an acute inflammatory response. PCI-induced inflammation is driven by a combination of direct endothelial damage, liberation of intra-plaque proinflammatory debris and reperfusion injury. Therefore, anti-inflammatory medications, such as colchicine, may provide a novel means of improving PCI outcomes in both the short- and long-term. This review summarises periprocedural MI epidemiology and pathophysiology, evaluates the prognostic value of pre-, intra- and post-procedural inflammation, dissects the mechanisms involved in the acute inflammatory response to PCI and discusses the potential for periprocedural anti-inflammatory treatment.

The protective effect of piperine against isoproterenol-induced inflammation in experimental models of myocardial toxicity

Myocardial infarction (MI) eventually exacerbates inflammatory response due to the release of inflammatory and pro-inflammatory factors. The aim of this study is to explore the protective efficacy of piperine supplementation against the inflammatory response in isoproterenol (ISO)-induced MI. Masson Trichome staining was executed to determine myocardial tissue architecture. Immunohistochemistry was performed for IL-6, TNF-α. RT-PCR studies were performed to ascertain the gene expression of IL-6, TNF-α, iNOS, eNOS, MMP-2, MMP-9, and collagen-III. Western blotting was performed to determine expression of HIF-1α, VEGF, Nrf-2, NF-ƙB, Cox-2, p-38, phospho-p38, ERK-1/2, phospho-ERK-1/2, and collagen-I. HIF-1α, VEGF, and iNOS expression were significantly upregulated with concomitant decline in eNOS expression in the heart myocardial tissue of rats received ISO alone whereas piperine pretreatment prevented these changes in ISO administered rats. Current results revealed ROS-mediated activation of MAPKs, namely, p-p38, p-ERK1/2 in the heart tissue of ISO administered group. Piperine pretreatment significantly prevented these changes in ISO treated group. NF-κB is involved in the modulation of gene expressions responsible for tissue repair. ISO-induced NF-κB-p65 expression was significantly reduced in the group pretreated with piperine and mitigated extent of myocardial inflammation. A significant increase in cardiac fibrosis upon ISO treatment was reported due to the increased hydroxyproline content, MMP-2 & 9 and upregulation of collagen-I protein compared to control group. All these cardiac hypertrophy markers were decreased in 'piperine pretreated ISO administered group' compared to group received ISO injection. Current findings concluded that piperine as a nutritional intervention could prevent inflammation of myocardium in ISO-induced MI.

Pathophysiology and diagnosis of coronary microvascular dysfunction in ST-elevation myocardial infarction

Early mechanical reperfusion of the epicardial coronary artery by primary percutaneous coronary intervention (PCI) is the guideline-recommended treatment for ST-elevation myocardial infarction (STEMI). Successful restoration of epicardial coronary blood flow can be achieved in over 95% of PCI procedures. However, despite angiographically complete epicardial coronary artery patency, in about half of the patients perfusion to the distal coronary microvasculature is not fully restored, which is associated with increased morbidity and mortality. The exact pathophysiological mechanism of post-ischaemic coronary microvascular dysfunction (CMD) is still debated. Therefore, the current review discusses invasive and non-invasive techniques for the diagnosis and quantification of CMD in STEMI in the clinical setting as well as results from experimental in vitro and in vivo models focusing on ischaemic-, reperfusion-, and inflammatory damage to the coronary microvascular endothelial cells. Finally, we discuss future opportunities to prevent or treat CMD in STEMI patients.

Pyrrolidine Dithiocarbamate Attenuates Cardiocyte Apoptosis and Ameliorates Heart Failure Following Coronary Microembolization in Rats

Background

Nuclear factor-kB is highly activated in cardiovascular disorders. However, few articles have targeted at the role of nuclear factor-kB inhibitor in heart failure.

Aims

To evaluate the effects of nuclear factor-kB inhibitor pyrrolidine dithiocarbamate on cardiocyte apoptosis and cardiac function in a rat heart failure model.

Study Design

Animal experiment.

Methods

A stable and reproducible rat heart failure model (n=64) was prepared by injecting homologous microthrombotic particles into the left ventricle of Sprague–Dawley rats while obstructing the ascending aorta to produce coronary microembolization. Rats with heart failure were randomized into untreated (HFu) and pyrrolidine dithiocarbamate-treated (HFp) groups; the latter received an intraperitoneal injection of pyrrolidine dithiocarbamate (100 mg/kg/day) 1 h prior to surgery as well as on postoperative days 1-7. The sham group comprised 32 Sprague–Dawley rats. Eight rats from each group were sacrificed on days 1, 3, 7, and 14 postoperatively. Masson’s trichrome staining was used to determine the micro-fibrotic area to indicate the severity of myocardial loss. Terminal transferase uridine triphosphate nick end labeling staining was used to detect apoptotic cardiomyocytes. Echocardiography and hemodynamics were performed to evaluate left ventricular function.

Results

Rats with heart failure exhibited pathological changes evidenced by patchy myocardial fibrosis, remarkably elevated severity of myocardial loss, and persistently reduced left ventricular function. At the end of the study, compared with the HFu group, myocardial infarct size was reduced by 28% (p=0.001), cardiocyte apoptosis was suppressed (7.17%±1.47% vs 2.83%±0.75%, p<0.001), cardiac function parameters such as left ventricular ejection fraction (80%±4% vs 61%±6%), left ventricular + dP/dt max (4828±289 vs 2918±76 mmHg.s−1), left ventricular - dP/dt max (4398±269 vs 2481±365 mmHg.s−1), and left ventricular systolic pressure (126±13 vs 100±10 mmHg) were significantly increased, and left ventricular end-diastolic pressure was reduced (18±2 vs 13±1 mmHg) (p<0.001, for all) in the HFu group.

Conclusion

Our rat model can adequately mimic heart failure via coronary vessel embolization. Moreover, pyrrolidine dithiocarbamate treatment can reduce cardiocyte apoptosis and improve cardiac function, which may be beneficial for patients with heart failure secondary to myocardial infarction.

Myocardial reperfusion injury and oxidative stress: Therapeutic opportunities

Acute myocardial infarction (AMI) is the leading cause of death worldwide. Its associated mortality, morbidity and complications have significantly decreased with the development of interventional cardiology and percutaneous coronary angioplasty (PCA) treatment, which quickly and effectively restore the blood flow to the area previously subjected to ischemia. Paradoxically, the restoration of blood flow to the ischemic zone leads to a massive production of reactive oxygen species (ROS) which generate rapid and severe damage to biomolecules, generating a phenomenon called myocardial reperfusion injury (MRI). In the clinical setting, MRI is associated with multiple complications such as lethal reperfusion, no-reflow, myocardial stunning, and reperfusion arrhythmias. Despite significant advances in the understanding of the mechanisms accounting for the myocardial ischemia reperfusion injury, it remains an unsolved problem. Although promising results have been obtained in experimental studies (mainly in animal models), these benefits have not been translated into clinical settings. Thus, clinical trials have failed to find benefits from any therapy to prevent MRI. There is major evidence with respect to the contribution of oxidative stress to MRI in cardiovascular diseases. The lack of consistency between basic studies and clinical trials is not solely based on the diversity inherent in epidemiology but is also a result of the methodological weaknesses of some studies. It is quite possible that pharmacological issues, such as doses, active ingredients, bioavailability, routes of administration, co-therapies, startup time of the drug intervention, and its continuity may also have some responsibility for the lack of consistency between different studies. Furthermore, the administration of high ascorbate doses prior to reperfusion appears to be a safe and rational therapy against the development of oxidative damage associated with myocardial reperfusion. In addition, the association with N-acetylcysteine (a glutathione donor) and deferoxamine (an iron chelator) could improve the antioxidant cardioprotection by ascorbate, making it even more effective in preventing myocardial reperfusion damage associated with PCA following AMI.

Associations of CXCL16, miR‑146a and miR‑146b in atherosclerotic apolipoprotein E‑knockout mice

Atherosclerosis is the primary cause of cardiovascular and cerebrovascular diseases. Recent studies have revealed that C‑X‑C motif chemokine ligand 16 (CXCL16), microRNA (miR)‑146a and miR‑146b may have important roles in atherosclerotic diseases. However, the associations of CXCL16, miR‑146a and miR‑146b in atherosclerotic diseases in vivo remain unclear. Previous studies have demonstrated that miR‑146a and miR‑146b may negatively regulate the toll like receptor (TLR4)/nuclear factor (NF)‑κB signaling pathway to repress the inflammatory response. The present study investigated the associations of CXCL16, miR‑146a and miR‑146b in atherosclerotic apolipoprotein E (ApoE)‑/‑ mice in vivo. The expression levels of CXCL16, TLR4/NF‑κB signaling pathway, miR‑146a and miR‑146b in the control and atherosclerotic ApoE‑/‑ mice were investigated via reverse transcription‑quantitative polymerase chain reaction and western blot analysis. The present study demonstrated that the expression of CXCL16 was significantly upregulated in atherosclerotic ApoE‑/‑ mice compared with control ApoE‑/‑ mice. The expression levels of TRL4, interleukin‑1 receptor‑associated kinase 1, tumor necrosis factor receptor associated factor 6, NF‑κB, tumor necrosis factor‑α and interleukin‑1β were also significantly upregulated in atherosclerotic ApoE‑/‑ mice compared with control mice. However, the present study revealed that the expression levels of miR‑146a and miR‑146b were significantly downregulated in atherosclerotic ApoE‑/‑ mice compared with control ApoE‑/‑ mice. Overall, the results of the present study suggested that CXCL16 may regulate the TRL4/NF‑κB/CXCL16 signaling pathway, and that miR‑146a and miR‑146b may negatively regulate CXCL16 via this pathway in atherosclerosis in vivo.

Prognostic Association of Circulating Neutrophil Count with No-Reflow in Patients with ST-Segment Elevation Myocardial Infarction following Successful Primary Percutaneous Intervention

Objective

The aim of the present study was to investigate the predictive value of neutrophil count for no-reflow in patients with ST-segment elevation myocardial infarction (STEMI) who underwent successful primary percutaneous intervention (PCI).

Methods

We conducted a retrospective study of 361 patients diagnosed with acute STEMI between 2011 and 2015. All patients underwent successful PCI within 12 h from the onset of symptoms. Angiographic no-reflow was diagnosed based on a post-PCI thrombolysis in myocardial infarction flow grade ≤ 2 without mechanical obstruction. According to a neutrophil count cut-off determined by receiver operating characteristic curve analysis, patients were divided into two groups: group A (neutrophil count < 9.14 × 10⁹/L) and group B (neutrophil count ≥ 9.14 × 10⁹/L).

Results

Compared to patients in the normal reflow group, patients with no-reflow had higher neutrophil counts (P < 0.05). The incidence rate of no-reflow in group A (18, 9.3%) was significantly lower than that in group B (38). Multivariate logistic regression analysis revealed that a neutrophil count ≥ 9.14 × 10⁹/L was independently predictive for no-reflow (odds ratio = 4.474, 95% confidence interval: 1.610–12.433, P = 0.004) after adjusting for potential confounders.

Conclusions

A circulating neutrophil count ≥ 9.14 × 10⁹/L is independently associated with no-reflow in patients with acute STEMI following primary PCI.

Simulated ischemia/reperfusion-induced p65-Beclin 1-dependent autophagic cell death in human umbilical vein endothelial cells

Myocardial ischemia/reperfusion (I/R) injury detrimentally alters the prognosis of patients undergoing revascularization after acute myocardial infarction. Our previous study demonstrated that NF-κB-induced autophagy plays a detrimental role in cardiac I/R injury using a rabbit myocardial I/R model. In this study, we sought to explore the specific mechanism of this autophagy-mediated cell damage in an in vitro simulated ischemia/reperfusion (sI/R) model using human umbilical vein endothelial cells. Our current study demonstrates that simulated I/R induces autophagy in a p65-Beclin 1-dependent manner, which can be suppressed with the inhibition of NF-κB. Furthermore, rapamycin which promotes autophagy, exacerbates sI/R-induced cell death. While 3-methyladenine rescues cell damage. Our data thus suggest that I/R promotes NF-κB p65 activity mediated Beclin 1-mediated autophagic flux, thereby exacerbating myocardial injury.

Paeonol Protects Rat Heart by Improving Regional Blood Perfusion during No-Reflow

No-reflow phenomenon, defined as inadequate perfusion of myocardium without evident artery obstruction, occurs at a high incidence after coronary revascularization. The mechanisms underlying no-reflow is only partially understood. It is commonly caused by the swelling of endothelial cells, neutrophil accumulation, and vasoconstriction, which are all related to acute inflammation. Persistent no-reflow can lead to hospitalization and mortality. However, an effective preventive intervention has not yet been established. We have previously found that paeonol, an active extraction from the root of Paeonia suffruticosa, can benefit the heart function by inhibiting tissue damage after ischemia, reducing inflammation, and inducing vasodilatation. To further investigate the potential cardioprotective action of paeonol on no-reflow, healthy male Wistar rats were randomly divided into four groups: sham, ischemia-reperfusion (I/R) injury (left anterior descending coronary artery was ligated for 4 h followed by reperfusion for 8 h), and I/R injury pretreated with paeonol at two different doses. Real-time myocardial contrast echocardiography was used to monitor regional blood perfusion and cardiac functions. Our data indicated that paeonol treatment significantly reduces myocardial infarct area and no-reflow area (n = 8; p < 0.05). Regional myocardial perfusion (A·β) and cardiac functions such as ejection fraction, stroke volume, and fractional shortening were elevated by paeonol (n = 8; p < 0.05). Paeonol also lowered the serum levels of lactate dehydrogenase, creatine kinase, cardiac troponin T, and C-reactive protein, as indices of myocardial injury. Paeonol exerts beneficial effects on attenuating I/R-associated no-reflow injuries, and may be considered as a potential preventive treatment for cardiac diseases or post-coronary revascularization in which no-reflow often occurs.

N-myc downstream-regulated gene 4, up-regulated by tumor necrosis factor-α and nuclear factor kappa B, aggravates cardiac ischemia/reperfusion injury by inhibiting reperfusion injury salvage kinase pathway

N-myc downstream-regulated gene 4 (NDRG4) is expressed weakly in heart and has been reported to modulate cardiac development and QT interval duration, but the role of NDRG4 in myocardial ischemia/reperfusion (I/R) injury remains unknown. In the present study, we analyzed the expression as well as potential function of cardiac NDRG4 and investigated how NDRG4 expression is regulated by inflammation. We found that NDRG4 was weakly expressed in cardiomyocytes and that its expression increased significantly both in I/R injured heart and in hypoxia-reoxygenation (H/R) injured neonatal rat ventricular myocytes (NRVMs). The increased NDRG4 expression aggravated myocardial I/R injury by inhibiting the activation of the reperfusion injury salvage kinase (RISK) pathway. Forced over-expression of NDRG4 inhibited RISK activation and exacerbated injury not only in I/R injured heart, but also in H/R treated NRVMs, whereas short hairpin RNA (shRNA)-mediated knock-down of NDRG4 enhanced RISK activation and attenuated injury. Upon injury, myocardial NDRG4 expression was induced by tumor necrosis factor-α (TNF-α) through nuclear factor kappa B (NF-κB), and we found that pre-treatment with inhibitors of either TNF-α or NF-κB blocked NDRG4 expression as well as I/R injury in vivo and H/R injury in vitro. Our study indicates that up-regulation of NDRG4 aggravates myocardial I/R injury by inhibiting activation of the RISK pathway, thereby identifying NDRG4 as a potential therapeutic target in I/R injury.

Tumor necrosis factor-α and its role as a mediator in myocardial infarction: A brief review

Tumor necrosis factor-α (TNF-α) contributes to myocardial infarction (MI) injury. Polymorphism of TNF-α gene promoter region and secretion and release of TNF-α and its transformation by a series of signaling pathways are all changed at different points of pathophysiological process in MI. Researches also investigated TNF-α antagonists and their potential therapeutic role in the setting of MI and heart failure at both molecular and clinical level. This article briefly reviews TNF-α and its mechanism as a mediator in MI.

Reactive oxygen species contribute to simulated ischemia/reperfusion-induced autophagic cell death in human umbilical vein endothelial cells

Background

Autophagy is important for cells to degrade protein aggregates and organelles. Our preliminary study suggests that ischemia/reperfusion in rabbit hearts promoted autophagic myocardial injury, resulting in no-reflow phenomenon. In this study, we sought to further understand the mechanism and outcome of the upregulation of autophagy in ischemia/reperfusion.

Material/Methods

We employed a simulated ischemia/reperfusion (sI/R) model in human umbilical vein endothelial cells (HUVECs) in vitro, in the presence or absence of antioxidants.

Results

Our study confirms that sI/R induces autophagy in HUVECs as measured by increased expression of Beclin 1 and microtubule-associated protein 1 light chain 3 (LC3), electron microscopic analysis, and special biofluorescent staining with monodansylcadaverine. This sI/R-induced autophagy was also accompanied by increased levels of p65 protein expression and cell death. In addition, we detected the accumulation of reactive oxygen species (ROS) after sI/R. Moreover, with the application of ROS scavengers that block the release of ROS, we were able to demonstrate that inhibition of autophagy increases cell survival.

Conclusions

The study suggests that ROS accumulation is involved in the sI/R-induced autophagic cell death in HUVECs.

Investigating the protective role of death receptor 3 (DR3) in renal injury using an organ culture model

Death receptor 3 (DR3; also designated as Wsl-1, Apo3, LARD, TRAMP, TNFRSF25, and TR3) is a member of the tumor necrosis factor (TNF) receptor superfamily that has emerged as a major regulator of inflammation and autoimmune diseases. DR3 contains a homologous intracellular region called the death domain (DD) that can bind adaptor proteins, which also contain a DD, initiating cellular responses such as caspase activation and apoptotic cell death. However, in other circumstances DR3 can initiate induction of transcription genes and gene products that can prevent cell death from occurring. Our laboratory has reported an inducible expression of DR3 in human and mouse tubular epithelial cells in renal injury, but its function in these setting still remains unclear. To directly manipulate and evaluate the role of DR3 in vivo, I have used an in vitro organ culture (OC) model, which I have developed in our laboratory. In this chapter, I will describe in detail the OC model used to study the role of DR3 in renal injury and discuss its advantages and limitations. In my hands, the OC model has proven to be an efficient tool for studying human cell heterogeneity, basal and regulated receptor expression, signalling pathways, and various biological responses not readily achievable in traditional cell culture models. Various assays can be carried out on organ cultures including histology, biochemistry, cell biology, and molecular biology, which will not be described in detail in this chapter.

CXCL16 in kidney and cardiovascular injury

CXC chemokine ligand 16 (CXCL16) is a CXC soluble chemokine, an adhesion molecule and a cell surface scavenger receptor. CXCL16 regulates inflammation, tissue injury and fibrosis. Parenchymal renal cells, vascular wall cells, leukocytes and platelets express and/or release CXCL16 under the regulation of inflammatory mediators. CXCL16 expression is increased in experimental and human nephropathies. Targeting CXCL16 protected from experimental glomerular injury or interstitial fibrosis. Conflicting results were reported for experimental cardiovascular injury. High circulating CXCL16 levels are associated to human kidney and cardiovascular disease and urinary CXCL16 may increase in kidney injury. In conclusion, mounting evidence suggests a role of CXCL16 in kidney and cardiovascular disease. However, a better understanding is still required before exploring CXCL16 targeting in the clinic.

The selective 5-LOX inhibitor 11-keto-β-boswellic acid protects against myocardial ischemia reperfusion injury in rats: involvement of redox and inflammatory cascades

Myocardial ischemia induces 5-lipoxygenase (LOX) translocation and leukotriene production in the heart. Leukotrienes increase inflammatory responses aggravating, thereby, ischemia-reperfusion (I/R) injury. This study aimed to investigate whether the selective 5-LOX inhibitor 11-keto-β-boswellic acid (11-keto BA), in three different dose levels, exert a protective effect on myocardial I/R injury in an in vivo rat heart model. Sixty male Wister rats were used in this study and divided into five equal groups (n=12): GP1, sham-operated receiving normal saline; Gp 2, rats were subjected to 45 min left anterior descending coronary artery ligation followed by 4 h reperfusion to serve as I/R group. Gps 3-5 received 11-keto BA in doses 250, 500, 1,000 mg/kg, respectively, via an oral gavage for 7 days then were exposed to I/R. I/R injury induced a significant elevation in myeloperoxidase activity and gene expression of intracellular adhesion molecules, cyclooxygenase-2, 5-lipooxygenasae, nuclear factor kappa-beta, tumor necrosis factor alpha, nuclear factor (erythroid-derived 2)-like 2, and hemeoxygenease-1 consequently with reduction in glutathione peroxidase in heart tissues. Furthermore, immunohistochemical examination of the heart tissues showed positive immuostaining for both 3-nitrotyrosine and caspase-3 with DNA-ladder formation in all diseased rats. 11-keto BA in three dose levels exerted dose dependent cardioprotective effect manifested by dose-dependent reduction in serum lactate dehydrogenase and infract size through mechanisms related to enhancement of antioxidant capacity and prevention of inflammatory cascades.

NF-κB-mediated induction of autophagy in cardiac ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury severely attenuates the benefit of revascularization after acute myocardial infarction, in which transcription factor NF-κB plays an important role. Recently, there is increasing evidence to suggest that autophagy is involved in this process. We sought to define the role of NF-κB in the induction of autophagy during cardiac I/R injury. The left circumflex coronary arteries of New Zealand white rabbits were ligated for 1.5h, followed by reperfusion for 1h to induce I/R injury. Production of reactive oxygen species (ROS) was detected in myocardial injury area following I/R injury. Furthermore, the results indicated that the cardiac area at risk (AAR) for ischemia has the most abundant expression of Beclin 1 in parallel to p65 expression after cardiac I/R injury. Inhibition of NF-κB significantly attenuated Beclin 1 expression and autophagy in the AAR, which was associated with a marked reduction in the extent of the AAR. Our data thus suggests that I/R injury promotes NF-κB activity, in response to ROS, to aggravate myocardial injury through the activation of Beclin 1-mediated autophagy.

The role of NF-κB signaling in the maintenance of pluripotency of human induced pluripotent stem cells

NF-κB signaling plays an essential role in maintaining the undifferentiated state of embryonic stem (ES) cells. However, opposing roles of NF-κB have been reported in mouse and human ES cells, and the role of NF-κB in human induced pluripotent stem (iPS) cells has not yet been clarified. Here, we report the role of NF-κB signaling in maintaining the undifferentiated state of human iPS cells. Compared with differentiated cells, undifferentiated human iPS cells showed an augmentation of NF-κB activity. During differentiation induced by the removal of feeder cells and FGF2, we observed a reduction in NF-κB activity, the expression of the undifferentiation markers Oct3/4 and Nanog, and the up-regulation of the differentiated markers WT-1 and Pax-2. The specific knockdown of NF-κB signaling using p65 siRNA also reduced the expression of Oct3/4 and Nanog and up-regulated WT-1 and Pax-2 but did not change the ES-like colony formation. Our results show that the augmentation of NF-κB signaling maintains the undifferentiated state of human iPS and suggest the importance of this signaling pathway in maintenance of human iPS cells.

No-Reflow Phenomenon

No-reflow is responsible for 40% of the primary percutaneous coronary intervention without complete myocardial reperfusion despite successful reopening of the infarct-related artery. This review describes the main pathophysiological mechanisms of no-reflow, its clinical manifestation, including the strong association with increased in-hospital mortality, malignant arrhythmias, and cardiac failure as well as the diagnostic methods. The latter ranges from simple angiographic thrombolysis in myocardial infarction grade score to more complex angiographic indexes, imaging techniques such as myocardial contrast echo or cardiac magnetic resonance, and surrogate clinical end points such as ST-segment resolution. This review also summarizes the strategies of prevention and treatment of no-reflow, considering the most recent studies results regarding medical therapy and devices.