Linking inflammation and coagulation: novel drug targets to treat organ ischemia

The potential role of ischaemia-reperfusion injury in chronic, relapsing diseases such as rheumatoid arthritis, Long COVID, and ME/CFS: evidence, mechanisms, and therapeutic implications

Ischaemia–reperfusion (I–R) injury, initiated via bursts of reactive oxygen species produced during the reoxygenation phase following hypoxia, is well known in a variety of acute circumstances. We argue here that I–R injury also underpins elements of the pathology of a variety of chronic, inflammatory diseases, including rheumatoid arthritis, ME/CFS and, our chief focus and most proximally, Long COVID. Ischaemia may be initiated via fibrin amyloid microclot blockage of capillaries, for instance as exercise is started; reperfusion is a necessary corollary when it finishes. We rehearse the mechanistic evidence for these occurrences here, in terms of their manifestation as oxidative stress, hyperinflammation, mast cell activation, the production of marker metabolites and related activities. Such microclot-based phenomena can explain both the breathlessness/fatigue and the post-exertional malaise that may be observed in these conditions, as well as many other observables. The recognition of these processes implies, mechanistically, that therapeutic benefit is potentially to be had from antioxidants, from anti-inflammatories, from iron chelators, and via suitable, safe fibrinolytics, and/or anti-clotting agents. We review the considerable existing evidence that is consistent with this, and with the biochemical mechanisms involved.

Levels of Fibrin Degradation Products at Admission With Acute Ischemic Stroke Correlate With the NIH Stroke Scale Score 1 h After Intravenous Thrombolysis

Background: Fibrin degradation products (FDPs) are fragments released by the plasmin-mediated degradation of fibrinogen or fibrin. Whether plasma levels of these fragments can predict the thrombolytic effect of recombinant tissue plasminogen activator (r-tPA) remains unknown.

Methods: We performed a hospital-based study of patients with acute ischemic stroke (AIS) to explore the relationship between FDP levels at admission and the NIH Stroke Scale (NIHSS) score 1 h after thrombolysis treatment. In this retrospective, single-center study, the data of all patients with AIS who received r-tPA treatment at Beijing Tiantan Hospital from January 2019 to October 2020 were collected and analyzed. Demographic and clinical data, including laboratory examinations, were also analyzed.

Results: A total of 339 patients with AIS were included in this study. Of these, 151 showed favorable effects of r-tPA, and 188 showed unsatisfactory effects at 1 h after thrombolysis. Overall, we found an inverse relationship between the FDPs levels at admission and the NIHSS score. A significant difference was observed when using the interquartile range of the FDPs levels (1.31 μg/mL) as a cutoff value (P = 0.003, odds ratio [OR] = 1.95, 95% confidence interval [CI]: 1.26–3.01), even after adjusting for confounding factors (P = 0.003, OR = 2.23, 95% CI: 1.31–3.77). In addition, significant associations were observed in the tertile (T3) and quartile (Q3, Q4) FDP levels when compared with T1 or Q1. A nomogram was also employed to create a model to predict an unsatisfactory effect of r-tPA. We found that FDP levels, white blood cell count, age, D-dimer level, and body mass index could influence the thrombolytic effect of r-tPA.

Conclusion: In conclusion, the present study demonstrated that the levels of FDPs at admission can be used as a prognostic factor to predict the curative effect of r-tPA.

Impact of Circuit Size on Coagulation and Hemolysis Complications in Pediatric Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) circuit volume, patient size, and blood flow may influence coagulation and hemolysis complications. We performed a single-center retrospective analysis of ECMO patients over a 6.5 year period. In 299 ECMO runs, 13% required coagulation-associated circuit changes. Respiratory ECMO was associated with coagulation-associated circuit changes [odds ratio (O/R) 2.8, p < 0.05] and developed severe (plasma-free hemoglobin [pfHb] > 100 mg/dl) hemolysis (O/R 2.3, p < 0.05). Severe hemolysis and component changes were associated with hospital mortality (O/R 2.3 and 2.5, respectively, p < 0.05). The activated partial thromboplastin time (aPTT) to residence time (RT) ratio (aPTT/RT) was used as a surrogate for coagulation risk. We found that aPTT/RT > 2.5 more than doubled time to circuit change (3-8 days, p < 0.05), but aPTT/RT > 3 increased bleeding risks and hospital mortality (O/R 1.8; p < 0.1). Hemolysis was associated with patient weight and circuit to patient volume ratio (CPVR) (p < 0.05), but not pump type. Hemolysis slightly increased with transfusion (p = 0.08), and transfusion requirements increased for CPVR >50% (p < 0.1).Our data suggest that pediatric respiratory ECMO patients are more likely to develop coagulation and hemolysis complications, which are associated with increased mortality. This may result from higher inflammatory processes, which affect coagulation and red cell fragility. Minimizing circuit volume, inflammation, and red cell stress may help to reduce these two complications and their associated mortality.

Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA): update and insights into current practices and future directions for research and implementation

Background

In this review, we assess the state of Resuscitative Endovascular Occlusion of the Aorta (REBOA) today with respect to out-of-hospital (OOH) vs. inhospital (H) use in blunt and penetrating trauma, as well as discuss areas of promising research that may be key in further advancement of REBOA applications.

Methods

To analyze the trends in REBOA use, we conducted a review of the literature and identified articles with human or animal data that fit the respective inclusion and exclusion criteria. In separate tables, we compiled data extracted from selected articles in categories including injury type, zone and duration of REBOA, setting in which REBOA was performed, sample size, age, sex and outcome. Based on these tables as well as more detailed review of some key cases of REBOA usage, we assessed the current state of REBOA as well as coagulation and histological disturbances associated with its usage. All statistical tests were 2-sided using an alpha=0.05 for significance. Analysis was done using SAS 9.5 (Cary, NC). Tests for significance was done with a t-test for continuous data and a Chi Square Test for categorical data.

Results

In a total of 44 cases performed outside of a hospital in both military and civilian settings, the overall survival was found to be 88.6%, significantly higher than the 50.4% survival calculated from 1,807 cases of REBOA performed within a hospital (p<.0001). We observe from human data a propensity to use Zone I in penetrating trauma and Zone III in blunt injuries. We observe lower final metabolic markers in animal studies with shorter REBOA time and longer follow-up times.

Conclusions

Further research related to human use of REBOA must be focused on earlier initiation of REBOA after injury which may depend on development of rapid vascular access devices and techniques more so than on any new improvements in REBOA. Future animal studies should provide detailed multisystem organ assessment to accurately define organ injury and metabolic burden associated with REBOA application. Overall, animal studies must involve realistic models of injury with severe clinical scenarios approximating human trauma and exsanguination, especially with long-term follow-up after injury.

Macrophages in xenotransplantation

Xenotransplantation refers to organ transplantation across species. Immune rejection of xenografts is stronger and faster than that of allografts because of significant molecular differences between species. Recent studies have revealed the involvement of macrophages in xenograft and allograft rejections. Macrophages have been shown to play a critical role in inflammation, coagulation, and phagocytosis in xenograft rejection. This review presents a recent understanding of the role of macrophages in xenograft rejection and possible strategies to control macrophage-mediated xenograft rejection.

Extrapolating novel techniques utilised in solid organ transplantation to the microsurgical and vascularised composite allograft arena

Ischemia reperfusion injury (IRI) is characterised initially by restriction of oxygenated blood flow to an organ bed, resulting in tissue hypoxia and ischaemic injury, followed by further 'reperfusion' injury upon restoration of perfusion, with an influx of oxygen, inflammatory cells and generation of free radicals. The culmination is a complex interplay between cellular and biochemical processes involved in inflammation and coagulation, exhibited as the 'no re-flow' phenomenon. Under ideal circumstances, autologous free tissue transfer is performed with short ischemic times. However, there are certain clinical scenarios where the ischaemic period can be prolonged due to technical and non-technical factors. IRI is inevitable and can be possibly more pronounced in such cases. In these cases, there may be a role for plastic surgeons to adopt some of the anti-ischaemia reperfusion injury (IRI) practices used in solid organ transplantation (SOT). Knowledge of the current trends in SOT IRI reduction should be discussed by plastic surgeons to assess whether certain facets can be extrapolated into the plastic and reconstructive armamentarium. These can be applicable to more challenging microsurgical cases, including composite free tissue transfer. Three important aspects are discussed further in this editorial: (1) cold flushing, (2) machine perfusion and pharmacological manipulation. Ongoing research will need to study the impact these potential interventions will have on the acute complications but also in which subset of patients they would be most beneficial. This area is novel and exciting but cautious implementation is advised with careful scrutiny of future data.

To What Extent Are the Terminal Stages of Sepsis, Septic Shock, Systemic Inflammatory Response Syndrome, and Multiple Organ Dysfunction Syndrome Actually Driven by a Prion/Amyloid Form of Fibrin?

A well-established development of increasing disease severity leads from sepsis through systemic inflammatory response syndrome, septic shock, multiple organ dysfunction syndrome, and cellular and organismal death. Less commonly discussed are the equally well-established coagulopathies that accompany this. We argue that a lipopolysaccharide-initiated (often disseminated intravascular) coagulation is accompanied by a proteolysis of fibrinogen such that formed fibrin is both inflammatory and resistant to fibrinolysis. In particular, we argue that the form of fibrin generated is amyloid in nature because much of its normal α-helical content is transformed to β-sheets, as occurs with other proteins in established amyloidogenic and prion diseases. We hypothesize that these processes of amyloidogenic clotting and the attendant coagulopathies play a role in the passage along the aforementioned pathways to organismal death, and that their inhibition would be of significant therapeutic value, a claim for which there is considerable emerging evidence.

Links between coagulation, inflammation, regeneration, and fibrosis in kidney pathology

Acute kidney injury (AKI) involves nephron injury leading to irreversible nephron loss, ie, chronic kidney disease (CKD). Both AKI and CKD are associated with distinct histological patterns of tissue injury, but kidney atrophy in CKD involves tissue remodeling with interstitial inflammation and scarring. No doubt, nephron atrophy, inflammation, fibrosis, and renal dysfunction are associated with each other, but their hierarchical relationships remain speculative. To better understand the pathophysiology, we provide an overview of the fundamental danger response programs that assure host survival upon traumatic injury from as early as the first multicellular organisms, ie, bleeding control by coagulation, infection control by inflammation, epithelial barrier restoration by re-epithelialization, and tissue stabilization by mesenchymal repair. Although these processes assure survival in the majority of the populations, their dysregulation causes kidney disease in a minority. We discuss how, in genetically heterogeneous population, genetic variants shift balances and modulate danger responses toward kidney disease. We further discuss how classic kidney disease entities develop from an insufficient or overshooting activation of these danger response programs. Finally, we discuss molecular pathways linking, for example, inflammation and regeneration or inflammation and fibrosis. Understanding the causative and hierarchical relationships and the molecular links between the danger response programs should help to identify molecular targets to modulate kidney injury and to improve outcomes for kidney disease patients.

Noncardiac Challenges in the Cardiac ICU: Feeding, Growth and Gastrointestinal Complications, Anticoagulation, and Analgesia

Outcomes following cardiac intensive care unit (CICU) admission are influenced by many factors including initial cardiac diagnosis, surgical complexity, and burden of critical illness. Additionally, the presence of noncardiac issues may have a significant impact on outcomes and the patient experience during and following an intensive care unit stay. This review focuses on three common noncardiac areas which impact outcomes and patient experience in and beyond the CICU: feeding and growth, pain and analgesia, and anticoagulation. Growth failure and feeding dysfunction are commonly encountered in infants requiring cardiac surgery and have been associated with worse surgical and developmental outcomes. Recent studies most notably in the single ventricle population have demonstrated improved weight gain and outcomes when feeding protocols are implemented. Children undergoing cardiac surgery may experience both acute and chronic pain. Emerging research is investigating the impact of sedatives and analgesics on neurodevelopmental outcomes and quality of life. Improved pain scores and standardized management of pain and withdrawal may improve the patient experience and outcomes. Effective anticoagulation is a critical component of perioperative care but may be complicated by inflammation, multiorgan dysfunction, and patient factors. Advances in monitoring of anticoagulation and emerging therapies are reviewed.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Strategies to optimize kidney recovery and preservation in transplantation: specific aspects in pediatric transplantation

In renal transplantation, live donor kidney grafts are associated with optimum success rates due to the shorter period of ischemia during the surgical procedure. The current shortage of donor organs for adult patients has caused a shift towards deceased donors, often with co-morbidity factors, whose organs are more sensitive to ischemia-reperfusion injury, which is unavoidable during transplantation. Donor management is pivotal to kidney graft survival through the control of the ischemia-reperfusion sequence, which is known to stimulate numerous deleterious or regenerative pathways. Although the key role of endothelial cells has been established, the complexity of the injury, associated with stimulation of different cell signaling pathways, such as unfolded protein response and cell death, prevents the definition of a unique therapeutic target. Preclinical transplant models in large animals are necessary to establish relationships and kinetics and have already contributed to the improvement of organ preservation. Therapeutic strategies using mesenchymal stem cells to induce allograft tolerance are promising advances in the treatment of the pediatric recipient in terms of reducing/withdrawing immunosuppressive therapy. In this review we focus on the different donor management strategies in kidney graft conditioning and on graft preservation consequences by highlighting the role of endothelial cells. We also propose strategies for preventing ischemia-reperfusion, such as cell therapy.

Nontoxic polyphosphate inhibitors reduce thrombosis while sparing hemostasis

Polyphosphate (polyP) is secreted by activated platelets and has been shown to contribute to thrombosis, suggesting that it could be a novel antithrombotic target. Previously reported polyP inhibitors based on polycationic substances, such as polyethylenimine, polyamidoamine dendrimers, and polymyxin B, although they attenuate thrombosis, all have significant toxicity in vivo, likely due to the presence of multiple primary amines responsible for their polyP binding ability. In this study, we examined a novel class of nontoxic polycationic compounds initially designed as universal heparin reversal agents (UHRAs) to determine their ability to block polyP procoagulant activity and also to determine their utility as antithrombotic treatments. Several UHRA compounds strongly inhibited polyP procoagulant activity in vitro, and 4 were selected for further examination in mouse models of thrombosis and hemostasis. Compounds UHRA-9 and UHRA-10 significantly reduced arterial thrombosis in mice. In mouse tail bleeding tests, administration of UHRA-9 or UHRA-10 was associated with significantly less bleeding compared with therapeutically equivalent doses of heparin. Thus, these compounds offer a new platform for developing novel antithrombotic agents that target procoagulant anionic polymers such as polyP with reduced toxicity and bleeding side effects.

Effectiveness of laser Doppler perfusion monitoring in the assessment of microvascular function in patients undergoing on-pump coronary artery bypass grafting

OBJECTIVES

To evaluate the effectiveness of single-point laser Doppler perfusion monitoring (LDPM) in the assessment of microvascular reactivity in the skin during cardiopulmonary bypass (CPB).

DESIGN

Cross-sectional observational study.

SETTING

Government-affiliated teaching hospital.

PARTICIPANTS

Twenty male patients aged 60 ± 2 years who underwent coronary artery bypass grafting under CPB.

INTERVENTIONS

The authors assessed the endothelium-dependent vasodilation of the skin microcirculation at the forehead and forearm using LDPM coupled with thermal hyperemia. This measurement was performed before and after the induction of anesthesia, during and after CPB, and 24 h after the end of the surgical procedure.

RESULTS

The basal values of microvascular flow before the induction of anesthesia were significantly higher in the skin of the forehead compared with that of the forearm. There were no significant alterations in microvascular reactivity throughout the recording periods for both recording sites, as assessed by the vasodilation range expressed as cutaneous vascular conductance (arbitrary perfusion units/mean arterial pressure).

CONCLUSIONS

Using LDPM, the authors showed that the microcirculatory bed of the skin of the forehead, which is readily accessible during cardiac surgery, is a suitable model for the study of microvascular reactivity and tissue perfusion in cardiovascular surgical procedures using CPB. This technique could, thus, be suitable for evaluating the effects of drugs or technical procedures on tissue perfusion during cardiac surgery under cardiopulmonary bypass.

Efficacy of low molecular weight heparin in patients with acute exacerbation of chronic obstructive pulmonary disease receiving ventilatory support

INTRODUCTION

Severe and acute exacerbation of chronic obstructive pulmonary disease (COPD) is associated with a high mortality. Since COPD is an airway inflammatory disease, and heparin has shown anti-inflammatory effects in previous studies, we evaluated the clinical effect of low molecular weight heparin (LMWH; nadroparin) in COPD patients admitted into the hospital due to acute exacerbations.

METHODS

Sixty-six patients admitted to the intensive care unit (ICU) were randomly divided into control group (n = 33) and LMWH group (n = 33). The control group received conventional treatment, including oxygen therapy (non-invasive or conventional mechanical ventilation), anti-infection, atomization expectorant, spasmolysis, anti-asthmatics, and nutritional support. The LMWH group received the same treatment plus LMWH for 1 week. The levels of plasma C-reactive protein, interleukin-6, and fibrinogen were measured. The main outcomes were duration of mechanical ventilation, length of ICU stay, and hospital stay.

RESULTS

There were no significant differences between the groups with respect to demographics, severity of illness, and gas exchange variables. The levels of plasma C-reactive protein, interleukin-6, and fibrinogen were significantly decreased in the LMWH group. LMWH significantly reduced the mean duration of mechanical ventilation (6.6 days vs. 3.8 days; p < 0.01), the length of ICU stay (8.5 days vs. 5.6 days; p < 0.01) and hospital stay (14.3 days vs. 11.3 days; p < 0.01).

CONCLUSIONS

The addition of LMWH to standard therapy benefits COPD patients with acute exacerbation.

Platelet aggregation measurement for assessment of hemostasis failure mechanisms in patients with gastroduodenal ulcer bleeding

Background

The purpose of this study was to identify factors associated with the risk of unsustainable hemostasis in patients with gastric and duodenal ulcer bleeding by in vitro assessment of platelet reactivity using artificial neural networks.

Methods

Patients with gastroduodenal ulcers complicated by bleeding were studied. Platelet aggregation was measured using aggregometry with adenosine diphosphate 5 μM, epinephrine 2.5 μM, 5-hydroxytryptophan 10 μM, collagen 1 μM, and thrombin 0.06 NIH Unit/mL as agonists. Multiple logistic regression was used to evaluate the independent relationship between demographic, clinical, endoscopic, and laboratory data and in vitro assessment of platelet reactivity and local parameters of hemostasis in patients with ulcer bleeding.

Results

Analysis of platelet aggregation in patients with gastroduodenal ulcer bleeding allowed the variability of platelet response to different agonists used in effective concentration which induces 50% platelet aggregation (EC₅₀) to be established. The relationship between platelet aggregation and the spatial-temporal characteristics of ulcers complicated by bleeding was demonstrated. Adrenoreactivity of platelets was associated with time elapsed since the start of ulcer bleeding and degree of hemorrhage. The lowest platelet response to collagen and thrombin was detected in patients with active bleeding (P < 0.001) and unsustainable recent bleeding (P < 0.01). Decreased adenosine diphosphate-induced platelet aggregation in patients with ulcer bleeding was correlated with the platelet response to thrombin (r = 0.714, P < 0.001) and collagen (r = 0.584, P < 0.01).

Conclusion

Estimation of platelet reactivity in vitro indicates the key mechanisms of failure of hemostasis in patients with ulcer bleeding. In addition to gender, an important determinant of unsustainable hemostasis was a decreased platelet response to thrombin and adenosine diphosphate.

The beneficial effects of a direct thrombin inhibitor, dabigatran etexilate, on the development and stability of atherosclerotic lesions in apolipoprotein E-deficient mice : dabigatran etexilate and atherosclerosis

PURPOSE

Dabigatran etexilate (DE) constitutes a novel, direct thrombin inhibitor. Regarding the association of thrombin with atherogenesis, we assessed the effects of DE on the development and stability of atherosclerotic lesions in apolipoprotein-E deficient (ApoE-/-) mice.

MATERIALS-METHODS

Fifty male ApoE-/- mice were randomized to receive western-type diet either supplemented with DE 7.5 mg DE/g chow) (DE-group, n = 25) or matching placebo as control (CO-group, n = 25) for 12 weeks. After this period, all mice underwent carotid artery injury with ferric chloride and the time to thrombotic total occlusion (TTO) was measured. Then, mice were euthanatized and each aortic arch was analyzed for the mean plaque area, the content of macrophages, elastin, collagen, nuclear factor kappaB (NFκB), vascular cell adhesion molecule-1 (VCAM-1), matrix metalloproteinase-9 (MMP-9) and its inhibitor (TIMP-1).

RESULTS

DE-group showed significantly longer TTO compared to CO-group (8.9 ± 2.3 min vs 3.5 ± 1.1 min, p < 0.001) and the mean plaque area was smaller in DE-group than CO-group (441.00 ± 160.01 × 10(3) μm(2) vs 132.12 ± 32.17 × 10(3) μm(2), p < 0.001). Atherosclerotic lesions derived from DE-treated mice showed increased collagen (p = 0.043) and elastin (p = 0.031) content, thicker fibrous caps (p < 0.001) and reduced number of internal elastic lamina ruptures per mm of arterial girth (p < 0.001) when compared to CO-group. Notably, DE treatment seemed to promote plaque stability possibly by reducing concentrations of NFκB, VCAM-1, macrophages and MMP-9 and increasing TIMP-1 within atherosclerotic lesions (p < 0.05).

CONCLUSIONS

DE attenuates arterial thrombosis, reduces lesion size and may promote plaque stability in ApoE-/- mice. The plaque-stabilizing effects of chronic thrombin inhibition might be the result of the favorable modification of inflammatory mechanisms.

Adora2b signaling on bone marrow derived cells dampens myocardial ischemia-reperfusion injury

BACKGROUND

Cardiac ischemia-reperfusion (I-R) injury represents a major cause of cardiac tissue injury. Adenosine signaling dampens inflammation during cardiac I-R. The authors investigated the role of the adenosine A2b-receptor (Adora2b) on inflammatory cells during cardiac I-R.

METHODS

To study Adora2b signaling on inflammatory cells, the authors transplanted wild-type (WT) bone marrow (BM) into Adora2b(-/-) mice or Adora2b(-/-) BM into WT mice. To study the role of polymorphonuclear leukocytes (PMNs), neutrophil-depleted WT mice were treated with an Adora2b agonist. After treatments, mice were exposed to 60 min of myocardial ischemia and 120 min of reperfusion. Infarct sizes and troponin I concentrations were determined by triphenyltetrazolium chloride staining and enzyme-linked immunosorbent assay, respectively.

RESULTS

Transplantation of WT BM into Adora2b(-/-) mice decreased infarct sizes by 19 ± 4% and troponin I by 87.5 ± 25.3 ng/ml (mean ± SD, n = 6). Transplantation of Adora2b(-/-) BM into WT mice increased infarct sizes by 20 ± 3% and troponin I concentrations by 69.7 ± 17.9 ng/ml (mean ± SD, n = 6). Studies on the reperfused myocardium revealed PMNs as the dominant cell type. PMN depletion or Adora2b agonist treatment reduced infarct sizes by 30 ± 11% or 26 ± 13% (mean ± SD, n = 4); however, the combination of both did not produce additional cardioprotection. Cytokine profiling showed significantly higher cardiac tumor necrosis factor α concentrations in Adora2b(-/-) compared with WT mice (39.3 ± 5.3 vs. 7.5 ± 1.0 pg/mg protein, mean ± SD, n = 4). Pharmacologic studies on human-activated PMNs revealed an Adora2b-dependent tumor necrosis factor α release.

CONCLUSION

Adora2b signaling on BM-derived cells such as PMNs represents an endogenous cardioprotective mechanism during cardiac I-R. The authors' findings suggest that Adora2b agonist treatment during cardiac I-R reduces tumor necrosis factor α release of PMNs, thereby dampening tissue injury.