SPTLC3 Is Essential for Complex I Activity and Contributes to Ischemic Cardiomyopathy.

BACKGROUND: Dysregulated metabolism of bioactive sphingolipids, including ceramides and sphingosine-1-phosphate, has been implicated in cardiovascular disease, although the specific species, disease contexts, and cellular roles are not completely understood. Sphingolipids are produced by the serine palmitoyltransferase enzyme, canonically composed of 2 subunits, SPTLC1 (serine palmitoyltransferase long chain base subunit 1) and SPTLC2 (serine palmitoyltransferase long chain base subunit 2). Noncanonical sphingolipids are produced by a more recently described subunit, SPTLC3 (serine palmitoyltransferase long chain base subunit 3). METHODS: The noncanonical (d16) and canonical (d18) sphingolipidome profiles in cardiac tissues of patients with end-stage ischemic cardiomyopathy and in mice with ischemic cardiomyopathy were analyzed by targeted lipidomics. Regulation of SPTLC3 by HIF1α under ischemic conditions was determined with chromatin immunoprecipitation. Transcriptomics, lipidomics, metabolomics, echocardiography, mitochondrial electron transport chain, mitochondrial membrane fluidity, and mitochondrial membrane potential were assessed in the cSPTLC3KO transgenic mice we generated. Furthermore, morphological and functional studies were performed on cSPTLC3KO mice subjected to permanent nonreperfused myocardial infarction. RESULTS: Herein, we report that SPTLC3 is induced in both human and mouse models of ischemic cardiomyopathy and leads to production of atypical sphingolipids bearing 16-carbon sphingoid bases, resulting in broad changes in cell sphingolipid composition. This induction is in part attributable to transcriptional regulation by HIF1α under ischemic conditions. Furthermore, cardiomyocyte-specific depletion of SPTLC3 in mice attenuates oxidative stress, fibrosis, and hypertrophy in chronic ischemia, and mice demonstrate improved cardiac function and increased survival along with increased ketone and glucose substrate metabolism utilization. Depletion of SPTLC3 mechanistically alters the membrane environment and subunit composition of mitochondrial complex I of the electron transport chain, decreasing its activity. CONCLUSIONS: Our findings suggest a novel essential role for SPTLC3 in electron transport chain function and a contribution to ischemic injury by regulating complex I activity.

Targeting tumor-derived NLRP3 reduces melanoma progression by limiting MDSCs expansion.

Interleukin-1ß (IL-1ß)-mediated inflammation suppresses antitumor immunity, leading to the generation of a tumor-permissive environment, tumor growth, and progression. Here, we demonstrate that nucleotide-binding domain, leucine-rich containing family, pyrin domain-containing-3 (NLRP3) inflammasome activation in melanoma is linked to IL-1ß production, inflammation, and immunosuppression. Analysis of cancer genome datasets (TCGA and GTEx) revealed greater NLRP3 and IL-1ß expression in cutaneous melanoma samples (n = 469) compared to normal skin (n = 324), with a highly significant correlation between NLRP3 and IL-1ß (P < 0.0001). We show the formation of the NLRP3 inflammasome in biopsies of metastatic melanoma using fluorescent resonance energy transfer analysis for NLRP3 and apoptosis-associated speck-like protein containing a CARD. In vivo, tumor-associated NLRP3/IL-1 signaling induced expansion of myeloid-derived suppressor cells (MDSCs), leading to reduced natural killer and CD8+ T cell activity concomitant with an increased presence of regulatory T (Treg) cells in the primary tumors. Either genetic or pharmacological inhibition of tumor-derived NLRP3 by dapansutrile (OLT1177) was sufficient to reduce MDSCs expansion and to enhance antitumor immunity, resulting in reduced tumor growth. Additionally, we observed that the combination of NLRP3 inhibition and anti-PD-1 treatment significantly increased the antitumor efficacy of the monotherapy by limiting MDSC-mediated T cell suppression and tumor progression. These data show that NLRP3 activation in melanoma cells is a protumor mechanism, which induces MDSCs expansion and immune evasion. We conclude that inhibition of NLRP3 can augment the efficacy of anti-PD-1 therapy.

The interleukin-1 receptor type I promotes the development of aging-associated cardiomyopathy in mice.

BACKGROUND: Aging is associated with metabolic and structural changes causing heart failure with preserved ejection fraction (HFpEF). Interleukin-1 (IL-1) is a pro-inflammatory cytokine involved in aging-related inflammation. OBJECTIVE: We sought to determine whether IL-1 mediates aging-related changes in the heart, as seen in HFpEF. METHODS: We studied age-matched young (4-month-old), middle-aged (14-month-old), and old (23-month-old) wild-type (WT) C57BL/6J and IL-1 receptor type I deficient (IL1RI-KO) male mice. Echocardiography was used to evaluate left ventricular (LV) dimensions and systolic/diastolic function, and a pressure transducer was used to measure the LV end-diastolic pressure. Picrosirius red stain was used to assess for myocardial interstitial fibrosis (MIF) at pathology. RESULTS: WT and IL-1RIKO mice showed a normal cardiac phenotype at young age, without any differences between the two groups. With aging, the WT mice developed LV concentric hypertrophy (as measured by a significant increase in LV mass [+42%, P < 0.01] and relative wall thickness [+34%, P < 0.01]), whereas the aging IL-1RI-KO mice did not. With aging, the WT mice also developed diastolic dysfunction (as measured by a significant increase in isovolumetric relaxation time [+148%, P < 0.01] and a significantly higher LV end-diastolic pressure [+174%, P < 0.01]), whereas the aging IL1RI-KO did not. Aged WT mice showed a significant increase in MIF (+124%, P < 0.01) at cardiac pathology, whereas the aging IL-1RI-KO did not. CONCLUSIONS: Genetically-modified mice lacking the IL-1RI receptor, not responsive to IL-1, are protected from aging-related LV hypertrophy, fibrosis, and diastolic dysfunction. These data support a central role of IL-1 in the pathophysiology of aging-related HFpEF.

Inflammasome formation in the lungs of patients with fatal COVID-19.

OBJECTIVE: The orf8b protein of the coronavirus SARS-CoV, analogous to SARS-CoV-2, triggers the NLRP3 inflammasome in macrophages in vitro. Deregulated inflammasome-mediated release of interleukin-1 family cytokines is important in hyper-inflammatory syndromes, like happens in SARS-CoV-2-mediated cytokine release syndrome. We propose that an intense inflammasome formation characterizes the lungs of patients with fatal COVID-19 disease due to pneumonia and acute respiratory distress syndrome (ARDS). METHODS: Samples from four patients with confirmed COVID-19 pneumonia who had been hospitalized at the Hospital of the University of Trieste (Italy) and died of ARDS and four lung samples from a historical repository from subjects who had died of cardiopulmonary arrest and had not been placed on mechanical ventilation and without evidence of pulmonary infection at postmortem examination were collected. Pathology samples had been fixed in formalin 10% at time of collection and subsequently embedded in paraffin. We conducted staining for ASC (Apoptosis-associated Speck-like protein containing a Caspase recruitment domain), NLRP3 (NACHT, LRR, and PYD domains-containing protein 3), and cleaved caspase-1. RESULTS: Intense expression of the inflammasome was detected, mainly in leukocytes, within the lungs of all patients with fatal COVID-19 in the areas of lung injury. The number of ASC inflammasome specks per high power fields was significantly higher in the lungs of patients with fatal COVID-19 as compared with the lungs of control subjects (52 ± 22 vs 6 ± 3, P = 0.0064). CONCLUSIONS: These findings identify the presence of NLRP3 inflammasome aggregates in the lungs of fatal COVID-19 pneumonia thus providing the potential molecular link between viral infection and cytokine release syndrome.

NLRP3 Inflammasome in Acute Myocardial Infarction.

Acute myocardial infarction (AMI) is associated with the induction of a sterile inflammatory response that leads to further injury. The NACHT, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a macromolecular structure responsible for the inflammatory response to injury or infection. NLRP3 can sense intracellular danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is primed and triggered by locally released damage-associated molecular patterns and amplifies the inflammatory response and cell death through caspase-1 activation. Here, we examine the scientific evidence supporting a role for NLRP3 in AMI and the available strategies to inhibit the effects of the inflammasome. Our focus is on the beneficial effects seen in experimental models of AMI in preclinical animal models and the initial results of clinical trials.

Inflammasome, pyroptosis, and cytokines in myocardial ischemia-reperfusion injury.

Myocardial ischemia-reperfusion injury induces a sterile inflammatory response, leading to further injury that contributes to the final infarct size. Locally released danger-associated molecular patterns lead to priming and triggering of the NOD-like receptor protein 3 inflammasome and amplification of the inflammatory response and cell death by activation of caspase-1. We review strategies inhibiting priming, triggering, or caspase-1 activity or blockade of the inflammasome-related cytokines interleukin-1ß and interleukin-18, focusing on the beneficial effects in experimental models of acute myocardial infarction in animals and the initial results of clinical translational research trials.

An Orally Available NLRP3 Inflammasome Inhibitor Prevents Western Diet-Induced Cardiac Dysfunction in Mice.

BACKGROUND: A diet rich in saturated fat and sugars (Western diet, WD) induces myocardial expression of the NLRP3 inflammasome and dysfunction in mice. We therefore hypothesized that a diet enriched with an orally available NLRP3 inflammasome inhibitor could prevent WD-induced cardiac dysfunction in mice. METHODS: Ten-week-old CD-1 male mice were fed WD or standard diet (SD) for 8 weeks. The compound 16673-34-0, an orally active NLRP3 inhibitor, was added to the diet at a concentration of 100 mg/Kg. The plasmatic levels of the NLRP3 inflammasome inhibitor were measured. Food intake, body weight, and glucose tolerance were assessed. Cardiac systolic and diastolic functions were measured by Doppler echocardiography at baseline, 4 weeks, and 8 weeks. RESULTS: WD induced a significant increase in body weight (+14%, P = 0.02), impaired glucose tolerance (+34%, P = 0.03), and a significant increase in isovolumetric relaxation time (+129%, P = 0.03) and reduction in left ventricular ejection fraction (-10%, P = 0.03), as compared to standard chow diet (SD). The treatment with NLRP3 inhibitor in the diet prevented cardiac systolic and diastolic dysfunction (P < 0.05 for left ventricular ejection fraction, isovolumetric relaxation time, and myocardial performance index in WD with drug vs. WD without drug), without significant changes in heart rate and metabolic parameters. CONCLUSIONS: An orally available NLRP3 inhibitor prevented WD-induced cardiac dysfunction in obese mice.

A Preclinical Translational Study of the Cardioprotective Effects of Plasma-Derived Alpha-1 Anti-trypsin in Acute Myocardial Infarction.

BACKGROUND: The area of myocardial infarction continues to expand for hours after reperfusion. The injured but viable myocardium may be salvaged if the signals leading to cell death are interrupted. Activation of the caspase-1 inflammasome in the heart shortly after ischemia-reperfusion contributes to the final infarct size. Plasma-derived α-1 anti-trypsin (AAT) has shown to inhibit inflammasome formation in vitro and in vivo. To explore the potential translational clinical value of AAT as a therapeutic, we conducted a series of preclinical experiments designed to simulate clinically relevant scenarios. METHODS: Adult male CD1 mice were used. The left anterior descending coronary artery was ligated for 30 or 75 minutes followed by reperfusion, to explore different severity of ischemic injury. Plasma-derived AAT (Prolastin C) was administered intraperitoneally after reperfusion, without pretreatment, exploring 3 different doses (60, 120, and 180 mg/kg). In a subgroup of mice, we administered Prolastin C with a delay of 30 minutes after reperfusion to simulate the clinical context of delayed administration, and we also used a model of permanent coronary artery ligation without reperfusion. Finally, we tested whether a single dose at reperfusion was sufficient to maintain a benefit in the longer term (7 days). Infarct size was measured by 3 different and independent methodologies: pathology, plasma levels of troponin I, and wall motion abnormalities at echocardiography. RESULTS: Prolastin C given at reperfusion after 30 minutes of ischemia provided a powerful reduction in infarct size (>50% reduction in all methodology used, all P < 0.01) without a clear dose-dependent response. Prolongation of ischemia to 75 minutes nor a delay in treatment by 30 minutes after reperfusion had any negative impact on Prolastin C effects. A single dose given at reperfusion was as effective as multiple daily doses. When given to the mouse without reperfusion, Prolastin C failed to reduce infarct size. CONCLUSIONS: Plasma-derived AAT (Prolastin C) given as an adjunct to reperfusion powerfully limits the final infarct size across a wide range of experiments in the mouse reproducing clinically relevant scenarios, such as variable duration of ischemia, delay in administration in the drug, and a large therapeutic index.

Reduction of Myocardial Ischemia-Reperfusion Injury by Inhibiting Interleukin-1 Alpha.

BACKGROUND: Interleukin-1α (IL-1α) released by dying cells is an alarmin that activates the innate immunity. We hypothesized that after myocardial ischemia-reperfusion (I/R) injury, IL-1α amplifies the myocardial damage by activating the inflammasome and caspase-1. METHODS: Adult male CD1 mice were used. The left anterior descending coronary artery was ligated for 30 minutes, after 24 hours of reperfusion. An IL-1α blocking antibody (15 µg/kg intraperitoneally) or matching vehicle was given after reperfusion. A subgroup of mice underwent sham surgery. We assessed the effects of IL-1α blockade on caspase-1 activity, infarct size, cardiac troponin I serum levels, and left ventricular fractional shortening, 24 hours after I/R. RESULTS: I/R led to inflammasome formation, and IL-1α blockade significantly reduced inflammasome formation, reflected by a >50% reduction in caspase-1 activity versus vehicle (P = 0.03). IL-1α blockade also reduced the infarct size (-52% infarct expressed as percentage of area at risk, and -79% for cardiac troponin I serum levels, P < 0.001 vs. vehicle) and preserved the left ventricular fractional shortening (31 ± 3% vs. 25 ± 2%, P < 0.001 vs. vehicle). CONCLUSION: IL-1α blockade after I/R reduces the inflammasome activation, decreases the infarct size, and preserves the left ventricular function. IL-1α blockade may therefore represent a novel therapeutic strategy to reduce I/R injury.

Recombinant Human Alpha-1 Antitrypsin-Fc Fusion Protein Reduces Mouse Myocardial Inflammatory Injury After Ischemia-Reperfusion Independent of Elastase Inhibition.

BACKGROUND: Alpha-1-antitrypsin (AAT) is an abundant plasma protein with neutrophil elastase-inhibiting activity, and AAT is available as a plasma-derived therapeutic (pAAT). In experimental myocardial infarction, pAAT reduced acute inflammatory injury because of ischemia-reperfusion. The aim of the present study was to assess the properties of a recombinant protein composed of human AAT fused to the human immunoglobulin (Ig) G1 Fc fragment (rhAAT-Fc) in experimental myocardial infarction. METHODS: Ten-week-old CD1 male mice underwent transient occlusion (30 minutes) of the left anterior coronary artery. rhAAT-Fc (2 mg/kg) or pAAT (60 mg/kg) were administered upon reperfusion. We used human plasma-derived Ig (2 mg/kg) or a matching volume of NaCl 0.9% as control solutions. After 24 hours, infarct size and caspase-1 activity were quantified. The left ventricular ejection fraction (LVEF) was measured by echocardiography at 24 hours and 7 days. A variant of rhAAT-Fc lacking elastase inhibition activity, rhAAT-Fc, was also tested. RESULTS: The rhAAT-Fc induced a significant reduction in infarct size (P < 0.01 vs. all controls, P > 0.05 vs. pAAT). Caspase-1 activity was reduced to the same degree with rhAAT-Fc and pAAT (-70%; P < 0.05; P > 0.05 rhAAT-Fc vs. pAAT). The effects on infarct size after a single administration were reflected by preservation of LVEF at 24 hours and 7 days (all P < 0.05). rhAAT-Fc without elastase inhibiting activity, rhAAT-Fc, conferred comparable effects on infarct size, caspase-1 activity, and LVEF (P > 0.2 vs. rhAAT-Fc). CONCLUSIONS: The pAAT and recombinant human AAT-Fc reduce the acute myocardial inflammatory injury after ischemia-reperfusion in the mouse leading to preservation of viable myocardium and systolic function, independent on the effects on neutrophil elastase.

Role of Interleukin-1 in Radiation-Induced Cardiomyopathy.

Thoracic X-ray therapy (XRT), used in cancer treatment, is associated with increased risk of heart failure. XRT-mediated injury to the heart induces an inflammatory response leading to cardiomyopathy. The aim of this study was to determine the role of interleukin (IL)-1 in response to XRT injury to the heart and on the cardiomyopathy development in the mouse. Female mice with genetic deletion of the IL-1 receptor type I (IL-1R1 knockout mice [IL-1R1 KO]) and treatment with recombinant human IL-1 receptor antagonist anakinra, 10 mg/kg twice daily for 7 d, were used as independent approaches to determine the role of IL-1. Wild-type (wt) or IL-1R1 KO mice were treated with a single session of XRT (20 or 14 gray [Gy]). Echocardiography (before and after isoproterenol challenge) and left ventricular (LV) catheterization were performed to evaluate changes in LV dimensions and function. Masson's trichrome was used to assess myocardial fibrosis and pericardial thickening. After 20 Gy, the contractile reserve was impaired in wt mice at d 3, and the LV ejection fraction (EF) was reduced after 4 months when compared with sham-XRT. IL-1R1 KO mice had preserved contractile reserve at 3 d and 4 months and LVEF at 4 months after XRT. Anakinra treatment for 1 d before and 7 d after XRT prevented the impairment in contractile reserve. A significant increase in LV end-diastolic pressure, associated with increased myocardial interstitial fibrosis and pericardial thickening, was observed in wt mice, as well as in IL-1R1 KO-or anakinra-treated mice. In conclusion, induction of IL-1 by XRT mediates the development of some, such as the contractile impairment, but not all aspects of the XRT-induced cardiomyopathy, such as myocardial fibrosis or pericardial thickening.

NLRP3-mediated inflammation in cardio-oncology: sterile yet harmful.

Despite significant advances and the continuous development of novel, effective therapies to treat a variety of malignancies, cancer therapy-induced cardiotoxicity has been identified as a prominent cause of morbidity and mortality, closely competing with secondary malignancies. This unfortunate limitation has prompted the inception of the field of cardio-oncology with its purpose to provide the necessary knowledge and key information on mechanisms that support the use of the most efficacious cancer therapy with minimal or no interruption while paying close attention to preventing cardiovascular related morbidity and mortality. Several mechanisms that contribute to cancer therapy-induced cardiotoxicity have been proposed and studied. These mainly involve mitochondrial dysfunction and reactive oxygen species-induced oxidative stress, lysosomal damage, impaired autophagy, cell senescence, DNA damage, and sterile inflammation with the formation and activation of the NLRP3 inflammasome. In this review, we focus on describing the principal mechanisms for different classes of cancer therapies that lead to cardiotoxicity involving the NLRP3 inflammasome. We also summarize current evidence of cardio-protection with inflammasome inhibitors in the context of heart disease in general, and further highlight the potential application of this evidence for clinical translation in at risk patients for the purpose of preventing cancer therapy associated cardiovascular morbidity and mortality.

Priorities in Cardio-Oncology Basic and Translational Science: GCOS 2023 Symposium Proceedings: JACC: CardioOncology State-of-the-Art Review.

Despite improvements in cancer survival, cancer therapy-related cardiovascular toxicity has risen to become a prominent clinical challenge. This has led to the growth of the burgeoning field of cardio-oncology, which aims to advance the cardiovascular health of cancer patients and survivors, through actionable and translatable science. In these Global Cardio-Oncology Symposium 2023 scientific symposium proceedings, we present a focused review on the mechanisms that contribute to common cardiovascular toxicities discussed at this meeting, the ongoing international collaborative efforts to improve patient outcomes, and the bidirectional challenges of translating basic research to clinical care. We acknowledge that there are many additional therapies that are of significance but were not topics of discussion at this symposium. We hope that through this symposium-based review we can highlight the knowledge gaps and clinical priorities to inform the design of future studies that aim to prevent and mitigate cardiovascular disease in cancer patients and survivors.

Cardiac complications of cancer therapies.

The quest of defeating cancer and improving prognosis in survivors has generated remarkable strides forward in research and have advanced the development of new antineoplastic therapies. These achievements, combined with rapid screening and early detection, have considerably extended the life expectancy of patients surviving multiple types of malignancies. Consequently, chemotherapy-related toxicity in several organ systems, especially the cardiovascular system, has surfaced as one of the leading causes of morbidity and mortality among cancer survivors. Recent evidence classifies chemotherapy-induced cardiotoxicity as the second-leading cause of morbidity and mortality, closely comparing with secondary cancer malignancies. While a certain degree of cardiotoxicity has been reported to accompany most chemotherapies, including anthracyclines, anti-metabolites, and alkylating agents, even the latest targeted cancer therapies such as immune checkpoint inhibitors and tyrosine kinase inhibitors have been associated with acute and chronic cardiac sequelae. In this chapter, we focus on describing the principal mechanism(s) for each class of chemotherapeutic agents that lead to cardiotoxicity and the innovative translational research approaches that are currently being explored to prevent or treat cancer therapy-induced cardiotoxicity and related cardiac complications.

Cardiac Gene Therapy With Relaxin Receptor 1 Overexpression Protects Against Acute Myocardial Infarction.

Relaxin is a pleiotropic hormone shown to confer cardioprotection in several preclinical models of cardiac ischemia-reperfusion injury. In the present study, the effects of up-regulating relaxin family peptide receptor 1 (RXFP1) via adeno-associated virus serotype 9 (AAV9) vectors were investigated in a mouse model of myocardial infarction. AAV9-RXFP1 vectors were generated and injected in adult male CD1 mice. Up-regulation of Rxfp1 was confirmed via quantitative polymerase chain reaction, and overexpressing animals showed increased sensitivity to relaxin-induced ventricular inotropic response. Overexpressing animals also demonstrated reduced infarct size and preserved cardiac function 24 hours after ischemia-reperfusion. Up-regulation of RXFP1 via AAV9 vectors has potential therapeutic utility in preventing adverse remodeling after myocardial infarction.

Chronic treatment with serelaxin mitigates adverse remodeling in a murine model of ischemic heart failure and modulates bioactive sphingolipid signaling.

Relaxin is a pleiotropic hormone demonstrated to confer cardioprotection in animal models of myocardial infarction and ischemic heart failure by modulating inflammation, fibrosis and arrhythmogenesis. Several of these pathways in the ischemic myocardium are intricately tied with the downstream signaling of bioactive sphingolipids, which play an active role during post-infarction remodeling. In this current study, we examined the effects of relaxin on sphingosine 1-phosphate (S1P), and the potential benefits of relaxin treatment on cardiac health in a rodent model of ischemic heart failure. Acute (30 min) and sub-acute (24 h) treatment of primary cardiomyocytes with serelaxin (recombinant human relaxin-2) increased the cardiomyocyte content of S1P. In the rodent model, treatment with relaxin for 28 days following myocardial ischemia by way of permanent left coronary artery occlusion improved survival and cardiac function, reduced fibrosis and apoptosis, and mitigated the expression of several pro-inflammatory and pro-fibrotic markers. The expression of beclin-1 (autophagy marker) was also reduced. The expression of S1P was significantly higher in cardiac tissue and plasma samples extracted from serelaxin-treated mice at day 28. In conclusion, our studies show a significant protection from relaxin in ischemic heart disease, and demonstrate the association between relaxin signaling and S1P generation.

An update on the pathophysiology of acute and recurrent pericarditis.

INTRODUCTION: Pericarditis is an inflammatory disease of the pericardium. Progress has been done in recent years in the understanding of its pathophysiology. In particular, preclinical and clinical studies have contributed to increasing our knowledge on the role of interleukin (IL)-1 and NLRP3 (NACHT, leucine-rich repeat, and pyrin domain-containing protein 3) inflammasome. EVIDENCE ACQUISITION: Information for this study has been retrieved in original articles, reviews, systematic reviews, and meta-analyses identified through PubMed using the following search terms (or combination of terms): "pericarditis," "acute pericarditis," "recurrent pericarditis," "idiopathic recurrent acute pericarditis," "autoimmunity," "autoinflammation," "outcomes." Only articles published in English were included. Additional papers identified from the reference list of the retrieved articles were also considered. EVIDENCE SYNTHESIS: Based on current evidence, pericarditis should be considered as an inflammatory reaction to various stimuli, including chemical/physical, infectious, or ischemic ones, with a viral infection being a common etiology. Interaction of pathogens or irritants with toll-like receptor (TLRs) and stimulation of IL-1 receptor by IL-1α and IL-1ß leads to an increased transcription of proinflammatory genes, including those needed for NLRP3 inflammasome assembly. This pathway is confirmed indirectly by the beneficial effect of colchicine (an indirect NLRP3 inflammasome inhibitor) and IL-1 blockers in patients with recurrent pericarditis. More recently, a direct evidence of the NLRP3 inflammasome within the inflamed pericardium has been provided as well. It may, however, occur that self-antigens on the surface of mesothelial cells or microbial peptides may stimulate autoreactive T cells along with B cells producing antiheart antibodies, although less evidence is available on this. CONCLUSIONS: Some uncertainties still remain about the role of neutrophils, neutrophil extracellular traps (NETs), and pericardial interstitial cells in recurrent and constrictive pericarditis. Unraveling these aspects might have a direct impact on the development of novel targeted therapies, especially considering the increasing number of drugs targeting NETs.

Mitigation of Radiation-Induced Lung and Heart Injuries in Mice by Oral Sepiapterin after Irradiation.

After radiation exposure, endothelium-dependent vasorelaxation is impaired due to impaired nitric oxide production. Endothelial dysfunction is characterized by uncoupled endothelial nitric oxide synthase activity, oxidation of the reduced cofactor tetrahydrobiopterin to dihydrobiopterin as one well recognized mechanism. Oral treatment with sepiapterin, a tetrahydrobiopterin precursor, decreased infiltrating inflammatory cells and cytokine levels in mice with colitis. We therefore tested whether a synthetic sepiapterin, PTC923, might mitigate radiation-induced cardiac and pulmonary injuries. C57L/J wild-type 6-8-week-old mice of both sexes received 5 Gy total-body irradiation (TBI), followed by a top-up dose of 6.5 Gy to the thorax (total thoracic dose of 11.5 Gy). Starting from 24 h postirradiation, mice were treated once daily with 1 mg/kg PTC923 for six days by oral gavage. Assessment of lung injury by breathing rate was measured every other week and echocardiography to assess heart function was performed at different time points (8, 30, 60, 90 and 180 days). Plasma proteins (fibrinogen, neutrophil elastase, C-reactive protein, and IL-6) were assessed as well. TBI induced a reduction in cardiac contractile reserve and an impairment in diastolic function restored by daily oral PTC923. Postirradiation lung injury was significantly delayed by PTC923. TBI mice treated with PTC923 experienced a longer survival compared to nonirradiated mice (71% vs. 40% of mice alive after 180 days). PTC923-treated mice showed a reduction in inflammatory mediators, especially IL-6 and IL-1b. In conclusion, these findings support the proposal that PTC923 is a potential mitigator of cardiac and lung injury caused by TBI.

Refining murine heterotopic heart transplantation: A model to study ischemia and reperfusion injury in donation after circulatory death hearts.

Heart transplantation is a lifesaving procedure, which is limited by the availability of donor hearts. Using hearts from donors after circulatory death, which have sustained global ischemia, requires thorough studies on reliable and reproducible models that developing researchers may not have mastered. By combining the most recent literature and our recommendations based on observations and trials and errors, the methods here detail a sound in vivo heterotopic heart transplantation model for rats in which protective interventions on the ischemic heart can be studied, and thus allowing the scientific community to advance organ preservation research. Knowledge gathered from reproducible animal models allow for successful translation to clinical studies.

The Role of NLRP3 Inflammasome in Pericarditis: Potential for Therapeutic Approaches.

Human samples of patients with chronic pericarditis and appropriate control subjects were stained for the inflammasome components. A mouse model of pericarditis was developed through the intrapericardial injection of zymosan A. Different inflammasome blockers were tested in the mouse model. Patients with pericarditis presented an intensification of the inflammasome activation compared with control subjects. The experimental model showed the pathological features of pericarditis. Among inflammasome blockers, NLRP3 inflammasome inhibitor, anakinra, and interleukin-1 trap were found to significantly improve pericardial alterations. Colchicine partially improved the pericardial inflammation. An intense activation of the inflammasome in pericarditis was demonstrated both in humans and in mice.