Lack of resolution sensor drives age-related cardiometabolic and cardiorenal defects and impedes inflammation-resolution in heart failure

RvD1 and LXA4 inhibitory effects on cardiac voltage-gated potassium channels

The resolution of inflammation is modulated by specialized pro-resolving lipid mediators (SPMs), which can be modified in some cardiovascular diseases. Among these SPMs, RvD1 and LXA4 prevent atrial fibrillation (AF) remodeling and cardiac hypertrophy, respectively in animal models. However, little is known about their electrophysiological effects on cardiac voltage-gated (VG) ion channels. We used the patch-clamp technique in heterologous systems and cardiomyocytes to assess the acute effects of RvD1, and LXA4, on VG potassium currents. In silico simulations were used to predict the effect of current modulation on the atrial and ventricular action potentials (AP). RvD1 (5 nM) reduced IKs (channel KV7.1/KCNE1) in COS-7 cells and guinea-pig cardiomyocytes by 50.3 ± 7.3 % and 29.9 ± 5.4 % at + 40 mV, respectively, without modifying its voltage dependence. RvD1 was more potent than LXA4. In heterologous systems, RvD1 was also tested on IKur (channel KV1.5), Ito (channel KV4.3/KChIP2), IKr (channel KV11.1), and IK1 (channel Kir2.1) with the largest inhibitory effect on IKs and IKr. In in silico simulations RvD1 prolonged repolarization significantly in both atrial and ventricular myocytes. All these results provide a comprehensive evaluation of RvD1 and LXA4 on cardiac human potassium channels, at pathophysiologically relevant concentrations, being RvD1 more potent than LXA4. The predicted effects on the AP suggest that, along with their antiinflammatory action, RvD1 may reverse AF-induced electrical remodeling in the atria by their modulation of K+ currents. The same action might instead contribute to ventricular functional remodeling; however, direct evidence for this is missing.

Formyl-peptide receptor type 2 activation mitigates heart and lung damage in inflammatory arthritis

Rheumatoid arthritis (RA) is associated with heart and lung dysfunction. Current therapies fail to attenuate such complications. Here, we identify formyl-peptide receptor type 2 (FPR2) as a therapeutic target to treat heart and lung dysfunction associated with inflammatory arthritis. Arthritic mice on high levels of dietary homocysteine develop cardiac diastolic dysfunction and reduced lung compliance, mirroring two comorbidities in RA. Therapeutic administration of a small molecule FPR2 agonist (BMS986235) to hyper-homocysteine arthritic mice prevented diastolic dysfunction (monitored by echocardiography) and restored lung compliance. These tissue-specific effects were secondary to reduced neutrophil infiltration, modulation of fibroblast activation and phenotype (in the heart) and attenuation of monocyte and macrophage numbers (in the lung). A dual FPR1/2 agonist (compound 43) failed to prevent the reduction in lung compliance of arthritic mice and promoted the accumulation of inflammatory monocytes and pro-fibrotic macrophages in lung parenchyma. This cellular response lies downstream of FPR1-mediated potentiation of CCL2-dependent monocyte chemotaxis and activation. This finding supports the therapeutic development of selective FPR2 agonists to mitigate two impactful comorbidities associated with inflammatory arthritides.

Exploring receptors for pro-resolving and non-pro-resolving mediators as therapeutic targets for sarcopenia

Sarcopenia is defined by a reduction in both muscle strength and mass. Sarcopenia may be an inevitable component of the aging process, but it may also be accelerated by comorbidities and metabolic derangements. The underlying mechanisms contributing to these pathological changes remain poorly understood. We propose that chronic inflammation-mediated networks and metabolic defects that exacerbate muscle dysfunction are critical factors in sarcopenia and related diseases. Consequently, utilizing specialized pro-resolving mediators (SPMs) that function through specific G-protein coupled receptors (GPCRs) may offer effective therapeutic options for these disorders. However, challenges such as a limited understanding of SPM/receptor signaling pathways, rapid inactivation of SPMs, and the complexities of SPM synthesis impede their practical application. In this context, stable small-molecule SPM mimetics and receptor agonists present promising alternatives. Moreover, the aged adipose-skeletal axis may contribute to this process. Activating non-SPM GPCRs on adipocytes, immune cells, and muscle cells under conditions of systemic, chronic, low-grade inflammation (SCLGI) could help alleviate inflammation and metabolic dysfunction. Recent preclinical studies indicate that both SPM GPCRs and non-SPM GPCRs can mitigate symptoms of aging-related diseases such as obesity and diabetes, which are driven by chronic inflammation and metabolic disturbances. These findings suggest that targeting these receptors could provide a novel strategy for addressing various chronic inflammatory conditions, including sarcopenia.

Failure to resolve inflammation contributes to juvenile onset cardiac damage in a mouse model of Duchenne Muscular Dystrophy

Absence of dystrophin protein causes cardiac dysfunction in patients with Duchenne muscular dystrophy (DMD). Unlike boys with DMD, the common mouse model of DMD (B10-mdx) does not manifest cardiac deficits until late adulthood. This has limited our understanding of the mechanism and therapeutic approaches to target the pediatric onset of cardiac pathology in DMD. Here we show that the mdx mouse model on the DBA/2J genetic background (D2-mdx) displays juvenile-onset cardiac degeneration. Molecular and histological analysis revealed that cardiac damage in this model is linked to increased leukocyte chemotactic signaling and an inability to resolve inflammation. These deficiencies result in chronic inflammation and fibrotic conversion of the extracellular matrix (ECM) in the juvenile D2-mdx heart. To address these pathologies, we tested the utility of pro-resolution therapy to clear chronic cardiac inflammation. Use of an N-formyl peptide receptor (FPR) agonist helped physiologically resolve inflammation and mitigate the downstream events that lead to fibrotic degeneration of cardiomyocytes, preventing juvenile onset cardiac muscle loss. These results establish the utility of D2-mdx model to study events associated with pediatric-onset cardiac damage and demonstrates pro-resolution therapy as an alternate to anti-inflammatory therapy for treating cardiac degenerative pathology responsible for cardiomyopathy in DMD patients.

Inflammation and resolution in obesity

Inflammation is an essential physiological defence mechanism, but prolonged or excessive inflammation can cause disease. Indeed, unresolved systemic and adipose tissue inflammation drives obesity-related cardiovascular disease and type 2 diabetes mellitus. Drugs targeting pro-inflammatory cytokine pathways or inflammasome activation have been approved for clinical use for the past two decades. However, potentially serious adverse effects, such as drug-induced weight gain and increased susceptibility to infections, prevented their wider clinical implementation. Furthermore, these drugs do not modulate the resolution phase of inflammation. This phase is an active process orchestrated by specialized pro-resolving mediators, such as lipoxins, and other endogenous resolution mechanisms. Pro-resolving mediators mitigate inflammation and development of obesity-related disease, for instance, alleviating insulin resistance and atherosclerosis in experimental disease models, so mechanisms to modulate their activity are, therefore, of great therapeutic interest. Here, we review current clinical attempts to either target pro-inflammatory mediators (IL-1β, NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome, tumour necrosis factor (TNF) and IL-6) or utilize endogenous resolution pathways to reduce obesity-related inflammation and improve cardiometabolic outcomes. A remaining challenge in the field is to establish more precise biomarkers that can differentiate between acute and chronic inflammation and to assess the functionality of individual leukocyte populations. Such advancements would improve the monitoring of drug effects and support personalized treatment strategies that battle obesity-related inflammation and cardiometabolic disease.

ANXA1-FPR2 axis mitigates the susceptibility to atrial fibrillation in obesity via rescuing AMPK activity in response to lipid overload

Atrial fibrillation (AF) is the most prevalent arrhythmia in clinical practice, and obesity serves as a significant risk factor for its development. The underlying mechanisms of obesity-related AF remain intricate and have yet to be fully elucidated. We have identified FPR2 as a potential hub gene involved in obesity-related AF through comprehensive analysis of four transcriptome datasets from AF patients and one transcriptome dataset from obese individuals, and its expression is up-regulated in both AF and obese individuals. Interestingly, ANXA1, the endogenous ligand of FPR2, was found to exhibit differential expression with AF and obesity. Specifically, it was observed to be down-regulated in AF patients but up-regulated in obese individuals. The susceptibility to AF in obese mice induced by high-fat diet (HFD) was increased following with the FPR2 blocker Boc-2.The administration of exogenous ANXA1 active peptide chain Ac2-26 can mitigate the susceptibility to AF in obese mice by attenuating atrial fibrosis, lipid deposition, oxidative stress injury, and myocardial cell apoptosis. However, this protective effect against AF susceptibility is reversed by AAV9-shAMPK-mediated AMPK specific knockdown in the myocardium. The vitro experiments demonstrated that silencing ANXA1 exacerbated lipid deposition, oxidative stress injury, and apoptosis induced by palmitic acid (PA) in cardiomyocytes. Additionally, Ac2-26 effectively mitigated myocardial lipid deposition, oxidative stress injury, and apoptosis induced by PA. These effects were impeded by FPR2 inhibitors Boc-2 and WRW4. The main mechanism involves the activation of AMPK by ANXA1 through FPR2 in order to enhance fatty acid oxidation in cardiomyocytes, thereby ultimately leading to a reduction in lipid accumulation and associated lipotoxicity. Our findings demonstrate that the ANXA1-FPR2 axis plays a protective role in obesity-associated AF by alleviating metabolic stress in the atria of obese mice, thereby emphasizing its potential as a promising therapeutic target for AF.

Lipoxin A4 improves cardiac remodeling and function in diabetes-associated cardiac dysfunction

BACKGROUND

Diabetic heart disease may eventually lead to heart failure, a leading cause of mortality in diabetic individuals. The lack of effective treatments for diabetes-induced heart failure may result from a failure to address the underlying pathological processes, including chronic, low-grade inflammation. Previous studies have reported that lipoxin A4 (LXA4), known to promote resolution of inflammation, attenuates diabetes-induced atherosclerosis, but its impact on diabetic hearts has not been sought. Thus, we aimed to determine whether LXA4 therapeutic treatment attenuates diabetes-induced cardiac pathology.

METHODS

Six-week-old male apolipoprotein E-deficient (ApoE-/-) mice were followed for 16 weeks after injection of streptozotocin (STZ, 55 mg/kg/day, i.p. for 5 days) to induce type-1 diabetes (T1DM). Treatment with LXA4 (5 μg/kg, i.p.) or vehicle (0.02% ethanol, i.p.) was administered twice weekly for the final 6 weeks. One week before endpoint, echocardiography was performed within a subset of mice from each group. At the end of the study, mice were euthanized with sodium pentobarbital (100 mg/kg i.p.) and hearts were collected for ex vivo analysis, including histological assessment, gene expression profiling by real-time PCR and protein level measurement by western blot.

RESULTS

As expected diabetic mice showed a significant elevation in plasma glycated hemoglobin (HbA1c) and glucose levels, along with reduced body weight. Vehicle-treated diabetic mice exhibited increased cardiac inflammation, macrophage content, and an elevated ratio of M1-like to M2-like macrophage markers. In addition, myocardial fibrosis, cardiomyocytes apoptosis and hypertrophy (at the genetic level) were evident, with echocardiography revealing early signs of left ventricular (LV) diastolic dysfunction. Treatment with LXA4 ameliorated diabetes-induced cardiac inflammation, pro-inflammatory macrophage polarization and cardiac remodeling (especially myocardial fibrosis and cardiomyocytes apoptosis), with ultimate improvement in cardiac function. Of note, this improvement was independent of glucose control.

CONCLUSIONS

These findings demonstrated that LXA4 treatment attenuated the extent of cardiac inflammation in diabetic hearts, resulting in limited cardiac remodeling and improved LV diastolic function. This supports further exploration of LXA4-based therapy for the management of diabetic heart disease. The recent development of stable LXA4 mimetics holds potential as a novel strategy to treat cardiac dysfunction in diabetes, paving the way for innovative and more effective therapeutic strategies.

Specialized pro-resolving mediators in vascular inflammation and atherosclerotic cardiovascular disease

Timely resolution of the acute inflammatory response (or inflammation resolution) is an active, highly coordinated process that is essential to optimal health. Inflammation resolution is regulated by specific endogenous signalling molecules that function as 'stop signals' to terminate the inflammatory response when it is no longer needed; to actively promote healing, regeneration and tissue repair; and to limit pain. Specialized pro-resolving mediators are a superfamily of signalling molecules that initiate anti-inflammatory and pro-resolving actions. Without an effective and timely resolution response, inflammation can become chronic, a pathological state that is associated with many widely occurring human diseases, including atherosclerotic cardiovascular disease. Uncovering the mechanisms of inflammation resolution failure in cardiovascular diseases and identifying useful biomarkers for non-resolving inflammation are unmet needs. In this Review, we discuss the accumulating evidence that supports the role of non-resolving inflammation in atherosclerosis and the use of specialized pro-resolving mediators as therapeutic tools for the treatment of atherosclerotic cardiovascular disease. We highlight open questions about therapeutic strategies and mechanisms of disease to provide a framework for future studies on the prevention and treatment of atherosclerosis.

Resolvin E1 improves efferocytosis and rescues severe aplastic anemia in mice

Severe aplastic anemia (SAA) is a rare, fatal disease characterized by severe cytopenias and loss of hematopoietic stem cells (HSCs). Immune-mediated destruction and inflammation are known drivers of SAA, however, the underlying mechanisms driving persistent inflammation are unknown. Current treatments for SAA rely on immunosuppressive therapies or HSC transplantation, however, these treatments are not always effective. Using an established mouse model of SAA, we observed a significant increase in apoptotic cells within the bone marrow (BM) and impaired efferocytosis in SAA mice, relative to radiation controls. Single-cell transcriptomic analysis revealed heterogeneity among BM monocytes and unique populations emerged during SAA characterized by increased inflammatory signatures and significantly increased expression of Sirpa and Cd47. CD47, a "don't eat me" signal, was increased on both live and apoptotic BM cells, concurrent with markedly increased expression of signal regulatory protein alpha (SIRPα) on monocytes. Functionally, SIRPα blockade improved cell clearance and reduced accumulation of CD47-positive apoptotic cells. Lipidomic analysis revealed a reduction in the precursors of specialized pro-resolving lipid mediators (SPMs) and increased prostaglandins in the BM during SAA, indicative of impaired inflammation resolution. Specifically, 18-HEPE, a precursor of E-series resolvins, was significantly reduced in SAA-induced mice relative to radiation controls. Treatment of SAA mice with Resolvin E1 (RvE1) improved efferocytic function, BM cellularity, platelet output, and survival. Our data suggest that impaired efferocytosis and inflammation resolution contributes to SAA progression and demonstrate that SPMs, such as RvE1, offer new and/or complementary treatments for SAA that do not rely on immune suppression.

Extrinsic and intrinsic modulators of inflammation-resolution signaling in heart failure

Chronic and uncleared inflammation is the root cause of various cardiovascular diseases. Fundamentally, acute inflammation is supportive when overlapping with safe clearance of inflammation termed resolution; however, if the lifestyle-directed extrinsic factors such as diet, sleep, exercise, or physical activity are misaligned, that results in unresolved inflammation. Although genetics play a critical role in cardiovascular health, four extrinsic risk factors-unhealthy processed diet, sleep disruption or fragmentation, sedentary lifestyle, thereby, subsequent stress-have been identified as heterogeneous and polygenic triggers of heart failure (HF), which can result in several complications with indications of chronic inflammation. Extrinsic risk factors directly impact endogenous intrinsic factors, such as using fatty acids by immune-responsive enzymes [lipoxygenases (LOXs)/cyclooxygenases (COXs)/cytochromes-P450 (CYP450)] to form resolution mediators that activate specific resolution receptors. Thus, the balance of extrinsic factors such as diet, sleep, and physical activity feed-forward the coordination of intrinsic factors such as fatty acids-enzymes-bioactive lipid receptors that modulates the immune defense, metabolic health, inflammation-resolution signaling, and cardiac health. Future research on lifestyle- and aging-associated molecular patterns is warranted in the context of intrinsic and extrinsic factors, immune fitness, inflammation-resolution signaling, and cardiac health.

Unleashing the power of formyl peptide receptor 2 in cardiovascular disease

N-formyl peptide receptors (FPRs) are seven-transmembrane, G protein-coupled receptors with a wide distribution in immune and non-immune cells, recognizing N-formyl peptides from bacterial and mitochondrial origin and several endogenous signals. Three FPRs have been identified in humans: FPR1, FPR2, and FPR3. Most FPR ligands can activate a pro-inflammatory response, while a limited group of FPR agonists can elicit anti-inflammatory and homeostatic responses. Annexin A1 (AnxA1), a glucocorticoid-induced protein, its N-terminal peptide Ac2-26, and lipoxin A4 (LXA4), a lipoxygenase-derived eicosanoid mediator, exert significant immunomodulatory effects by interacting with FPR2 and/or FPR1. The ability of FPRs to recognize both ligands with pro-inflammatory or inflammation-resolving properties places them in a crucial position in the balance between activation against harmful events and maintaince of tissue integrity. A new field of investigation focused on the role of FPRs in the setting of heart injury. FPRs are expressed on cardiac macrophages, which are the predominant immune cells in the myocardium and play a key role in heart diseases. Several endogenous (AnxA1, LXA4) and synthetic compounds (compound 43, BMS-986235) reduced infarct size and promoted the resolution of inflammation via the activation of FPR2 on cardiac macrophages. Further studies should evaluate FPR2 role in other cardiovascular disorders.

Resolvin E1 improves efferocytosis and rescues severe aplastic anemia in mice

Current treatments for severe aplastic anemia (SAA) rely on hematopoietic stem cell (HSC) transplantation and immunosuppressive therapies, however these treatments are not always effective. While immune-mediated destruction and inflammation are known drivers of SAA, the underlying mechanisms that lead to persistent inflammation are unknown. Using an established mouse model of SAA, we observed a significant increase in apoptotic cells within the bone marrow (BM) and demonstrate impaired efferocytosis in SAA mice, as compared to radiation controls. Single-cell transcriptomic analysis revealed heterogeneity among BM monocytes and unique populations emerged during SAA characterized by increased inflammatory signatures and significantly increased expression of Sirpa and Cd47. CD47, a "don't eat me" signal, was increased on both live and apoptotic BM cells, concurrent with markedly increased expression of signal regulatory protein alpha (SIRPα) on monocytes. Functionally, SIRPα blockade improved cell clearance and reduced accumulation of CD47-positive apoptotic cells. Lipidomic analysis revealed a reduction in the precursors of specialized pro-resolving lipid mediators (SPMs) and increased prostaglandins in the BM during SAA, indicative of impaired inflammation resolution. Specifically, 18-HEPE, a precursor of E-series resolvins, was significantly reduced in SAA-induced mice relative to radiation controls. Treatment of SAA mice with Resolvin E1 (RvE1) improved efferocytic function, BM cellularity, platelet output, and survival. Our data suggest that impaired efferocytosis and inflammation resolution contributes to SAA progression and demonstrate that SPMs, such as RvE1, offer new and/or complementary treatments for SAA that do not rely on immune suppression.

Metabolic landscape in cardiac aging: insights into molecular biology and therapeutic implications

Cardiac aging is evident by a reduction in function which subsequently contributes to heart failure. The metabolic microenvironment has been identified as a hallmark of malignancy, but recent studies have shed light on its role in cardiovascular diseases (CVDs). Various metabolic pathways in cardiomyocytes and noncardiomyocytes determine cellular senescence in the aging heart. Metabolic alteration is a common process throughout cardiac degeneration. Importantly, the involvement of cellular senescence in cardiac injuries, including heart failure and myocardial ischemia and infarction, has been reported. However, metabolic complexity among human aging hearts hinders the development of strategies that targets metabolic susceptibility. Advances over the past decade have linked cellular senescence and function with their metabolic reprogramming pathway in cardiac aging, including autophagy, oxidative stress, epigenetic modifications, chronic inflammation, and myocyte systolic phenotype regulation. In addition, metabolic status is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and chronic inflammation. However, further elucidation of the metabolism involvement in cardiac degeneration is still needed. Thus, deciphering the mechanisms underlying how metabolic reprogramming impacts cardiac aging is thought to contribute to the novel interventions to protect or even restore cardiac function in aging hearts. Here, we summarize emerging concepts about metabolic landscapes of cardiac aging, with specific focuses on why metabolic profile alters during cardiac degeneration and how we could utilize the current knowledge to improve the management of cardiac aging.

Modified Signaling of Membrane Formyl Peptide Receptors in NADPH-Oxidase Regulation in Obesity-Resistant Mice

The signaling of membrane receptors is modified in obesity characterized by low-grade inflammation. The obesity-resistant state of organisms is poorly understood. We analyzed the generation of reactive oxygen species (ROS) initiated though membrane formyl peptide receptors (Fpr1, Fpr2) in bone-marrow granulocytes of obesity-resistant mice (ORM). A chemiluminescence assay was used to assess NADPH-oxidase-related intensity of ROS generation. ORM were chosen from animals that received high-fat diets and had metric body parameters as controls (standard diet). High spontaneous ROS production was observed in ORM cells. The EC50 for responses to bacterial or mitochondrial peptide N-formyl-MLF was higher in ORM with and without inflammation vs. the same control groups, indicating an insignificant role of high-affinity Fpr1. Increased responses to synthetic peptide WKYMVM (Fpr2 agonist) were observed in controls with acute inflammation, but they were similar in other groups. Fpr2 was possibly partially inactivated in ORM owing to the inflammatory state. Weakened Fpr1 and Fpr2 signaling via MAPKs was revealed in ORM using specific inhibitors for p38, ERK1/2, and JNK. P38 signaling via Fpr2 was lower in ORM with inflammation. Thus, a high-fat diet modified FPRs' role and suppressed MAPK signaling in NADPH-oxidase regulation in ORM. This result can be useful to understand the immunological features of obesity resistance.

Cellular mechanisms underlying the impairment of macrophage efferocytosis

The phagocytosis and clearance of dying cells by macrophages, a process termed efferocytosis, is essential for both maintaining homeostasis and promoting tissue repair after infection or sterile injury. If not removed in a timely manner, uncleared cells can undergo secondary necrosis, and necrotic cells lose membrane integrity, release toxic intracellular components, and potentially induce inflammation or autoimmune diseases. Efferocytosis also initiates the repair process by producing a wide range of pro-reparative factors. Accumulating evidence has revealed that macrophage efferocytosis defects are involved in the development and progression of a variety of inflammatory and autoimmune diseases. The underlying mechanisms of efferocytosis impairment are complex, disease-dependent, and incompletely understood. In this review, we will first summarize the current knowledge about the normal signaling and metabolic processes of macrophage efferocytosis and its importance in maintaining tissue homeostasis and repair. We then will focus on analyzing the molecular and cellular mechanisms underlying efferocytotic abnormality (impairment) in disease or injury conditions. Next, we will discuss the potential molecular targets for enhanced efferocytosis in animal models of disease. To provide a balanced view, we will also discuss some deleterious effects of efferocytosis.

Fpr2 exacerbates Streptococcus suis-induced streptococcal toxic shock-like syndrome via attenuation of neutrophil recruitment

The life-threatening disease streptococcal toxic shock-like syndrome (STSLS), caused by the bacterial pathogen Streptococcus suis (S. suis). Proinflammatory markers, bacterial load, granulocyte recruitment, and neutrophil extracellular traps (NETs) levels were monitored in wild-type (WT) and Fpr2^-/- mice suffering from STSLS. LXA4 and AnxA1, anti-inflammatory mediators related to Fpr2, were used to identity a potential role of the Fpr2 in STSLS development. We also elucidated the function of Fpr2 at different infection sites by comparing the STSLS model with the S. suis-meningitis model. Compared with the WT mice, Fpr2^-/- mice exhibited a reduced inflammatory response and bacterial load, and increased neutrophil recruitment. Pretreatment with AnxA1 or LXA4 impaired leukocyte recruitment and increased both bacterial load and inflammatory reactions in WT but not Fpr2^-/- mice experiencing STSLS. These results indicated that Fpr2 impairs neutrophil recruitment during STSLS, and this impairment is enhanced by AnxA1 or LXA4. By comparing the functions of Fpr2 in different S. suis infection models, inflammation and NETs was found to hinder bacterial clearance in S. suis meningitis, and conversely accelerate bacterial clearance in STSLS. Therefore, interference with neutrophil recruitment could potentially be harnessed to develop new treatments for this infectious disease.

Deletion of macrophage Gpr101 disrupts their phenotype and function dysregulating host immune responses in sterile and infectious inflammation

We recently found that the G protein coupled receptor GPR101 mediates the phagocyte-directed pro-resolving activities of RvD5_{n-3 DPA} (n-3 docosapentaenoic acid-derived Resolvin D5). Herein, we investigated the endogenous role of this pro-resolving receptor in modulating macrophage biology using a novel mouse line where the expression of Gpr101 was conditionally deleted in macrophages (Mac^Gpr101KO). Peritoneal macrophages obtained from naïve Mac^Gpr101KO mice displayed a marked shift in the expression of phenotypic and activation markers, including the Interleukin (IL)-10 and IL-23 receptors. Loss of Gpr101 on macrophages was also associated with a significant disruption in their cellular metabolism and a decreased ability to migrate towards the chemoattractant Mcp-1. The alterations in macrophage phenotype observed in Gpr101 deficient macrophages were maintained following inflammatory challenge. This was linked with an increased inflammatory response in the Gpr101 deficient animals and a reduced ability of phagocytes, including macrophages, to clear bacteria. Loss of Gpr101 on macrophages disrupted host pro-resolving responses to zymosan challenge with Mac^Gpr101KO mice exhibiting significantly higher neutrophil numbers and a delay in the resolution interval when compared with control mice. These observations were linked with a marked dysregulation in peritoneal lipid mediator concentrations in Gpr101 deficient mice, with a downregulation of pro-resolving mediators including MaR2_{n-3 DPA}, Resolvin (Rv) D3 and RvE3. Together these findings identify Gpr101 as a novel regulator of both macrophage phenotype and function, modulating key biological activities in both limiting the propagation of inflammation and expediting its resolution.

The cardiac wound healing response to myocardial infarction

Myocardial infarction (MI) is defined as evidence of myocardial necrosis consistent with prolonged ischemia. In response to MI, the myocardium undergoes a series of wound healing events that initiate inflammation and shift to anti-inflammation before transitioning to tissue repair that culminates in scar formation to replace the region of the necrotic myocardium. The overall response to MI is determined by two major steps, the first of which is the secretion of proteases by infiltrating leukocytes to breakdown extracellular matrix (ECM) components, a necessary step to remove necrotic cardiomyocytes. The second step is the generation of new ECM that comprises the scar; and this step is governed by the cardiac fibroblasts as the major source of new ECM synthesis. The leukocyte component resides in the middle of the two-step process, contributing to both sides as the leukocytes transition from pro-inflammatory to anti-inflammatory and reparative cell phenotypes. The balance between the two steps determines the final quantity and quality of scar formed, which in turn contributes to chronic outcomes following MI, including the progression to heart failure. This review will summarize our current knowledge regarding the cardiac wound healing response to MI, primarily focused on experimental models of MI in mice. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Immune System Diseases > Molecular and Cellular Physiology.

Aspirin modulates production of pro-inflammatory and pro-resolving mediators in endothelial cells

Endothelial cells synthesize biochemical signals to coordinate a response to insults, resolve inflammation and restore barrier integrity. Vascular cells release a variety of vasoactive bioactive lipid metabolites during the inflammatory response and produce pro-resolving mediators (e.g., Lipoxin A4, LXA4) in cooperation with leukocytes and platelets to bring a halt to inflammation. Aspirin, used in a variety of cardiovascular and pro-thrombotic disorders (e.g., atherosclerosis, angina, preeclampsia), potently inhibits proinflammatory eicosanoid formation. Moreover, aspirin stimulates the synthesis of pro-resolving lipid mediators (SPM), so-called Aspirin-Triggered Lipoxins (ATL). We demonstrate that cytokines stimulated a time- and dose-dependent increase in PGI2 (6-ketoPGF1α) and PGE2 formation that is blocked by aspirin. Eicosanoid production was caused by cytokine-induced expression of cyclooxygenase-2 (COX-2). We also detected increased production of pro-resolving LXA4 in cytokine-stimulated endothelial cells. The R-enantiomer of LXA4, 15-epi-LXA4, was enhanced by aspirin, but only in the presence of cytokine challenge, indicating dependence on COX-2 expression. In contrast to previous reports, we detected arachidonate 5-lipoxygenase (ALOX5) mRNA expression and its cognate protein (5-lipoxygenase, 5-LOX), suggesting that endothelial cells possess the enzymatic machinery necessary to synthesize both pro-inflammatory and pro-resolving lipid mediators independent of added leukocytes or platelets. Finally, we observed that, endothelial cells produced LTB4 in the absence of leukocytes. These results indicate that endothelial cells produce both pro-inflammatory and pro-resolving lipid mediators in the absence of other cell types and aspirin exerts pleiotropic actions influencing both COX and LOX pathways.

Formyl peptide receptor 2 as a potential therapeutic target for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a global health burden whose existing treatment is largely dependent on anti-inflammatory agents. Despite showing some therapeutic actions, their clinical efficacy and adverse events are unacceptable. Resolution as an active and orchestrated phase of inflammation involves improper inflammatory response with three key triggers, specialized pro-resolving mediators (SPMs), neutrophils and phagocyte efferocytosis. The formyl peptide receptor 2 (FPR2/ALX) is a human G protein-coupled receptor capable of binding SPMs and participates in the resolution process. This receptor has been implicated in several inflammatory diseases and its association with mouse model of IBD was established in some resolution-related studies. Here, we give an overview of three reported FPR2/ALX agonists highlighting their respective roles in pro-resolving strategies.

Formylpeptide receptor 2: Nomenclature, structure, signalling and translational perspectives: IUPHAR review 35

We discuss the fascinating pharmacology of formylpeptide receptor 2 (FPR2; often referred to as FPR2/ALX since it binds lipoxin A₄ ). Initially identified as a low-affinity 'relative' of FPR1, FPR2 presents complex and diverse biology. For instance, it is activated by several classes of agonists (from peptides to proteins and lipid mediators) and displays diverse expression patterns on myeloid cells as well as epithelial cells and endothelial cells, to name a few. Over the last decade, the pharmacology of FPR2 has progressed from being considered a weak chemotactic receptor to a master-regulator of the resolution of inflammation, the second phase of the acute inflammatory response. We propose that exploitation of the biology of FPR2 offers innovative ways to rectify chronic inflammatory states and represents a viable avenue to develop novel therapies. Recent elucidation of FPR2 structure will facilitate development of the anti-inflammatory and pro-resolving drugs of next decade.

Drugging the efferocytosis process: concepts and opportunities

The daily removal of billions of apoptotic cells in the human body via the process of efferocytosis is essential for homeostasis. To allow for this continuous efferocytosis, rapid phenotypic changes occur in the phagocytes enabling them to engulf and digest the apoptotic cargo. In addition, efferocytosis is actively anti-inflammatory and promotes resolution. Owing to its ubiquitous nature and the sheer volume of cell turnover, efferocytosis is a point of vulnerability. Aberrations in efferocytosis are associated with numerous inflammatory pathologies, including atherosclerosis, cancer and infections. The recent exciting discoveries defining the molecular machinery involved in efferocytosis have opened many avenues for therapeutic intervention, with several agents now in clinical trials.

New Horizons in the Treatment of Age-Associated Obesity, Sarcopenia and Osteoporosis

The rapid increase in both the lifespan and proportion of older adults in developed countries is accompanied by the dramatic growth of age-associated chronic diseases, including obesity, sarcopenia, and osteoporosis. Hence, prevention and treatment of age-associated chronic diseases has become increasingly urgent. The key to achieving this goal is a better understanding of the mechanisms underlying their pathophysiology, some aspects of which, despite extensive investigation, are still not fully understood. Aging, obesity, sarcopenia, and osteoporosis are characterized by the creation of a systemic, chronic, low-grade inflammation (SCLGI). The common mechanisms that govern the development of these chronic conditions include a failed resolution of inflammation. Physiologically, the process of inflammation resolution is provided mainly by specialized pro-resolving mediators (SPMs) acting via cognate G protein-coupled receptors (GPCRs). Noteworthy, SPM levels and the expression of their receptors are significantly reduced in aging and the associated chronic disorders. In preclinical studies, supplementation of SPMs or their stable, small-molecule SPM mimetics and receptor agonists reveals clear beneficial effects in inflammation-related obesity and sarcopenic and osteoporotic conditions, suggesting a translational potential. Age-associated chronic disorders are also characterized by gut dysbiosis and the accumulation of senescent cells in the adipose tissue, skeletal muscle, and bones. Based on these findings, we propose SCLGI resolution as a novel strategy for the prevention/treatment of age-associated obesity, sarcopenia, and osteoporosis. Our approach entails the enhancement of inflammation resolution by SPM mimetics and receptor agonists in concert with probiotics/prebiotics and compounds that eliminate senescent cells and their pro-inflammatory activity.

Metabolic transformation of fat in obesity determines the inflammation resolving capacity of splenocardiac and cardiorenal networks in heart failure

All fats are not created equal, and despite the extensive literature, the effect of fat intake is the most debated question in obesity, cardiovascular, and cardiorenal research. Cellular and molecular mechanisms underlying cardiac dysfunction and consequent heart failure in the setting of obesity are not well understood. Our understanding of how fats are metabolically transformed after nonreperfused myocardial infarction (MI), in particular, is incomplete. Here, using male C57BL/6J mice (2 mo old), we determined the role of omega-6 fatty acids, provided as safflower oil (SO) for 12 wk, followed by supplementation with docosahexaenoic acid (DHA; n-3 fatty acids) for 8 wk before MI. With SO feeding, inflammation resolution was impaired. Specialized proresolving mediators (SPMs) increased in DHA-fed mice to reverse the effects of SO, whereas prostaglandins and thromboxane B2 were reduced in the spleen and amplified multiple resolving mechanisms in heart and kidney post-MI. DHA amplified the number of resolving macrophages and cardiac reparative pathways of the splenocardiac and cardiorenal networks in acute heart failure, with higher Treg cells in chronic heart failure and marked expression of Foxp3+ in the myocardium. Our findings indicate that surplus ingestion of SO intensified systemic, baseline, nonresolving inflammation, and DHA intake dominates splenocardiac resolving phase with the biosynthesis of SPMs and controlled cardiorenal inflammation in heart failure survivor mice.NEW & NOTEWORTHY Chronic and surplus dietary intake of safflower oil (SO) increased plasma creatinine dysregulated post-MI splenocardiac inflammation coincides with the dysfunctional cardiorenal network. In contrast, docosahexaenoic acid (DHA) increases post-MI survival in chronic heart failure. DHA transforms into specialized proresolving mediators (SPMs) and limited proinflammatory prostaglandins and thromboxanes following myocardial infarction (MI). DHA promotes Ly6Clow resolving macrophages and T regulatory cells (Foxp3+) in a splenocardiac manner post-MI.

Inflammation and resolution signaling in cardiac repair and heart failure

Unresolved inflammation is a key mediator of advanced heart failure. Especially, damage, pathogen, and lifestyle-associated molecular patterns are the major factors in initiating baseline inflammatory diseases, particularly in cardiac pathology. After a significant cardiac injury like a heart attack, splenic and circulating leukocytes begin a highly optimized sequence of immune cell recruitment (neutrophils and monocytes) to coordinate effective tissue repair. An injured cardiac tissue repair and homeostasis are dependent on clearance of cellular debris where the recruited leukocytes transition from a pro-inflammatory to a reparative program through resolution process. After a cardiac injury, macrophages play a decisive role in cardiac repair through the biosynthesis of endogenous lipid mediators that ensure a timely tissue repair while avoiding chronic inflammation and impaired cardiac repair. However, dysregulation of resolution of inflammation processes due to cardiometabolic defects (obesity, hypertension, and diabetes), aging, or co-medication(s) lead to impaired cardiac repair. Hence, the presented review demonstrates the fundamental role of leukocytes, in particular macrophages orchestrate the inflammation and resolution biology, focusing on the biosynthesis of specialized lipid mediators in cardiac repair and heart failure. This work was supported by research funds from National Institutes of Health (AT006704, HL132989, and HL144788) to G.V.H. The authors acknowledges the use of Servier Medical Art image bank and Biorender that is used to create schematic Figures 1–3.

Targeting the Metabolic-Inflammatory Circuit in Heart Failure With Preserved Ejection Fraction

PURPOSE OF REVIEW

Heart failure with preserved ejection fraction (HFpEF) is a leading cause of morbidity and mortality. The current mechanistic paradigm supports a comorbidity-driven systemic proinflammatory state that evokes microvascular and myocardial dysfunction. Crucially, diabetes and obesity are frequently prevalent in HFpEF patients; as such, we review the involvement of a metabolic-inflammatory circuit in disease pathogenesis.

RECENT FINDINGS

Experimental models of diastolic dysfunction and genuine models of HFpEF have facilitated discovery of underlying drivers of HFpEF, where metabolic derangement and systemic inflammation appear to be central components of disease pathophysiology. Despite a shared phenotype among these models, molecular signatures differ depending on type and combination of comorbidities present. Inflammation, oxidative stress, hypertension, and metabolic derangements have been positioned as therapeutic targets to suppress the metabolic-inflammatory circuit in HFpEF. However, the stratification of unique patient phenogroups within the collective HFpEF subgroup argues for specific interventions for distinct phenogroups.

Specialized Proresolving Lipid Mediators: A Potential Therapeutic Target for Atherosclerosis

Cardiovascular disease (CVD) is a global public health issue due to its high morbidity, mortality, and economic impact. The implementation of innovative therapeutic alternatives for CVD is urgently required. Specialized proresolving lipid mediators (SPMs) are bioactive compounds derived from ω-3 and ω-6 fatty acids, integrated into four families: Lipoxins, Resolvins, Protectins, and Maresins. SPMs have generated interest in recent years due to their ability to promote the resolution of inflammation associated with the pathogeneses of numerous illnesses, particularly CVD. Several preclinical studies in animal models have evidenced their ability to decrease the progression of atherosclerosis, intimal hyperplasia, and reperfusion injury via diverse mechanisms. Large-scale clinical trials are required to determine the effects of SPMs in humans. This review integrates the currently available knowledge of the therapeutic impact of SPMs in CVD from preclinical and clinical studies, along with the implicated molecular pathways. In vitro results have been promising, and as such, SPMs could soon represent a new therapeutic alternative for CVD.

The utilisation of resolvins in medicine and tissue engineering

Recent advances in the field of regenerative medicine and biomaterial science have highlighted the importance of controlling immune cell phenotypes at the biomaterial interface. These studies have clearly indicated that a rapid resolution of the inflammatory process, mediated by a switch in the macrophage population towards a reparative phenotype, is essential for tissue regeneration to occur. While various biomaterial surfaces have been developed in order to impart immunomodulatory properties to the resulting constructs, an alternative strategy involving the use of reparative biological cues, known as resolvins, is emerging in regenerative medicine. This review reports on the mechanisms via which resolvins participate in the resolution of inflammation and describes their current utilisation in pre-clinical and clinical settings, along with their effectiveness when combined with biomaterial constructs in tissue engineering applications. STATEMENT OF SIGNIFICANCE: The resolution of the inflammatory process is necessary for achieving tissue healing and regeneration. Resolvins are lipid mediators and play a key role in the resolution of the inflammatory response and can be used in as biological cues to promote tissue regeneration. This review describes the various biological inflammatory mechanisms and pathways involving resolvins and how their action results in a pro-healing response. The use of these molecules in the clinical setting is then summarised for various applications along with their limitations. Lastly, the review focuses on the emergence resolvins in tissue engineering products including the use of a more stable form which holds greater prospect for regenerative purposes.

Utility of the Specialized Pro-Resolving Mediators as Diagnostic and Prognostic Biomarkers in Disease

A precision medicine approach is widely acknowledged to yield more effective therapeutic strategies in the treatment of patients with chronic inflammatory conditions than the prescriptive paradigm currently utilized in the management and treatment of these patients. This is because such an approach will take into consideration relevant factors including the likelihood that a patient will respond to given therapeutics based on their disease phenotype. Unfortunately, the application of this precision medicine paradigm in the daily treatment of patients has been greatly hampered by the lack of robust biomarkers, in particular biomarkers for determining early treatment responsiveness. Lipid mediators are central in the regulation of host immune responses during both the initiation and resolution of inflammation. Amongst lipid mediators, the specialized pro-resolving mediators (SPM) govern immune cells to promote the resolution of inflammation. These autacoids are produced via the stereoselective conversion of essential fatty acids to yield molecules that are dynamically regulated during inflammation and exert potent immunoregulatory activities. Furthermore, there is an increasing appreciation for the role that these mediators play in conveying the biological actions of several anti-inflammatory therapeutics, including statins and aspirin. Identification and quantitation of these mediators has traditionally been achieved using hyphenated mass spectrometric techniques, primarily liquid-chromatography tandem mass spectrometry. Recent advances in the field of chromatography and mass spectrometry have increased both the robustness and the sensitivity of this approach and its potential deployment for routine clinical diagnostics. In the present review, we explore the evidence supporting a role for specific SPM as potential biomarkers for patient stratification in distinct disease settings together with methodologies employed in the identification and quantitation of these autacoids.

PCOS: A Chronic Disease That Fails to Produce Adequately Specialized Pro-Resolving Lipid Mediators (SPMs)

Introduction: Polycystic ovary syndrome (PCOS) is an endocrinological disorder that affects 5–15% of women of their reproductive age and is a frequent cause of infertility. Major symptoms include hyperandrogenism, ovulatory dysfunction, and often obesity and/or insulin resistance. PCOS also represents a state of chronic low-grade inflammation that is closely interlinked with the metabolic features. “Classical” pro-inflammatory lipid mediators such as prostaglandins (PG), leukotrienes (LT), or thromboxanes (TX) are derived from arachidonic acid (AA) and are crucial for the initial response. Resolution processes are driven by four families of so-called specialized pro-resolving mediators (SPMs): resolvins, maresins, lipoxins, and protectins. The study aimed to establish lipid mediator profiles of PCOS patients compared to healthy women to identify differences in their resolutive and pro-inflammatory lipid parameters. Material and Methods: Fifteen female patients (18–45 years) were diagnosed with PCOS according to Rotterdam criteria, and five healthy women, as a comparator group, were recruited for the study. The main outcome measures were: pro-inflammatory lipid mediators (PG, LT, TX) and their precursor AA, SPMs (resolvins, maresins, protectins, lipoxins), their precursors EPA, DHA, DPA, and their active biosynthesis pathway intermediates (18-HEPE, 17-HDHA, 14-HDHA). Results: The level of pro-inflammatory parameters in serum was significantly higher in PCOS-affected women. The ratio (sum of pro-inflammatory molecules)/(sum of SPMs plus hydroxylated intermediates) reflecting the inflammatory state was significantly lower in the group of healthy women. Conclusion: There is a strong pro-inflammatory state in PCOS patients. Further research will clarify whether supplementation with SPMs or their precursors may improve this state.

Dysfunction of resolution receptor triggers cardiomyopathy of obesity and signs of non-resolving inflammation in heart failure

Heart failure with preserved ejection fraction (HFpEF) has been an emerging type of cardiac disease since the pseudo-left ventricle function is preserved; therefore, challenges in finding the target and treatment. Damage and pathogen-associated molecular patterns (DAMPs and PAMPs) are widely investigated in acute and chronic inflammation in heart failure; however, lifestyle-associated molecular patterns (LAMPs: diet, sleep, exercise), particularly in obesity, remains of interest due to the enormous increase of HFpEF patients. In this review, we covered obesity-related cardiomyopathy, LAMPs, and resolution receptor dysfunction in the context of heart failure with preserved ejection fraction.

Neutrophils in chronic inflammatory diseases

Chronic inflammation is a component of many disease conditions that affect a large group of individuals worldwide. Chronic inflammation is characterized by persistent, low-grade inflammation and is increased in the aging population. Neutrophils are normally the first responders to acute inflammation and contribute to the resolution of inflammation. However, in chronic inflammation, the role of neutrophils is less well understood and has been described as either beneficial or detrimental, causing tissue damage and enhancing the immune response. Emerging evidence suggests that neutrophils are important players in several chronic diseases, such as atherosclerosis, diabetes mellitus, nonalcoholic fatty liver disease and autoimmune disorders. This review will highlight the interaction of neutrophils with other cells in the context of chronic inflammation, the contribution of neutrophils to selected chronic inflammatory diseases, and possible future therapeutic strategies.

Formyl peptide receptor 2 and heart disease

Formyl peptide receptor type 2 (FPR2) regulates the initiation and resolution phases of the inflammatory response. In the setting of heart injury and disease, dysregulated inflammation can potentiate maladaptive healing and pathological remodeling of the heart leading to cardiac dysfunction and failure. The potential to regulate and resolve adverse inflammation is postulated to improve outcome in the setting of heart disease. This review covers emerging concepts on the role of FPR2 in heart disease and strategies to activate pro-resolution processes to limit disease progression. We summarize key preclinical studies that support use of FPR2 agonists in heart disease. Finally, we briefly discuss the status of FPR2 agonists under evaluation in the clinic.

Heart Failure Syndrome With Preserved Ejection Fraction Is a Metabolic Cluster of Non-resolving Inflammation in Obesity

Heart failure with preserved ejection fraction (HFpEF) is an emerging disease with signs of nonresolving inflammation, endothelial dysfunction, and multiorgan defects. Moreover, based on the clinical signs and symptoms and the rise of the obesity epidemic, the number of patients developing HFpEF is increasing. From recent molecular and cellular studies, it becomes evident that HFpEF is not a single and homogenous disease but a cluster of heterogeneous pathophysiology with aging at the base of the pyramid. Obesity superimposed on aging drives the number of inflammatory pathways that intersect with metabolic dysfunction and suboptimal inflammation. Here, we compiled information on obesity-directed macrophage dysfunction that coincide with metabolic defects. Obesity-associated proinflammatory stimuli facilitates heart and interorgan inflammation in HFpEF. Furthermore, diversified mechanisms that drive heart failure urge the need of studying pervasive and unresolved inflammation in animal models to understand HFpEF. A broad and system-based approach will help to study major translational aspects of HFpEF, since no single animal model recapitulates all signs of differential HFpEF stages in the clinical setting. Here, we covered experimental models that target HFpEF and emphasized the advances observed with formyl peptide 2 (FPR2) receptor, a prime sensor that is important in inflammation-resolution signaling. Dysfunction of FPR2 led to the development of spontaneous obesity, impaired macrophage function, and triggered kidney fibrosis, providing evidence of multiorgan defects in HFpEF in an obesogenic aging experimental model.

Inositol hexaphosphate modulates the behavior of macrophages through alteration of gene expression involved in pathways of pro- and anti-inflammatory responses, and resolution of inflammation pathways

Inositol hexaphosphate (IP6) is a dietary compound commonly obtained from corn, rice, etc. Although we may consume significant amount of IP6 daily, it is unclear whether this diet will impact macrophages' fate and function. Therefore, we characterized the underlying relationship between IP6 and macrophage polarization in this study. We specifically examined the signature gene expression profiles associated with pro- and anti-inflammatory responses, and resolution of inflammation pathways in macrophages under the influence of IP6. Interestingly, our data suggested that IP6 polarizes bone marrow-derived macrophages (BMDM) into an M2a-like subtype. Our results also demonstrated that IP6 reduces lipopolysaccharide-induced apoptosis and pro-inflammatory responses in macrophages. In contrast, the expression levels of genes related to anti-inflammatory responses and resolution of inflammation pathways are upregulated. Our findings collectively demonstrated that IP6 has profound modulation effects on macrophages, which warrant further research on the therapeutic benefits of IP6 for inflammatory diseases.

Metabolipidomic profiling reveals an age-related deficiency of skeletal muscle pro-resolving mediators that contributes to maladaptive tissue remodeling

Specialized pro-resolving mediators actively limit inflammation and support tissue regeneration, but their role in age-related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography-tandem mass spectrometry and tested whether treatment with the pro-resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro-resolving mediators 8-oxo-RvD1, resolvin E3, and maresin 1, as well as many anti-inflammatory cytochrome P450-derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro-inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E₂ ) and 12-lipoxygenase (e.g., 12-hydroxy-eicosatetraenoic acid), but aged mice produced fewer markers of pro-resolving mediators including the lipoxins (15-hydroxy-eicosatetraenoic acid), D-resolvins/protectins (17-hydroxy-docosahexaenoic acid), E-resolvins (18-hydroxy-eicosapentaenoic acid), and maresins (14-hydroxy-docosahexaenoic acid). Similar absences of downstream pro-resolving mediators including lipoxin A₄ , resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro-resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non-steroidal anti-inflammatory drugs.

Changes in brown adipose tissue lipid mediator signatures with aging, obesity, and DHA supplementation in female mice

Brown adipose tissue (BAT) dysfunction in aging and obesity has been related to chronic unresolved inflammation, which could be mediated by an impaired production of specialized proresolving lipid mediators (SPMs), such as Lipoxins-LXs, Resolvins-Rvs, Protectins-PDs, and Maresins-MaRs. Our aim was to characterize the changes in BAT SPMs signatures and their association with BAT dysfunction during aging, especially under obesogenic conditions, and their modulation by a docosahexaenoic acid (DHA)-rich diet. Lipidomic, functional, and molecular studies were performed in BAT of 2- and 18-month-old lean (CT) female mice and in 18-month-old diet-induced obese (DIO) mice fed with a high-fat diet (HFD), or a DHA-enriched HFD. Aging downregulated Prdm16 and UCP1 levels, especially in DIO mice, while DHA partially restored them. Arachidonic acid (AA)-derived LXs and DHA-derived MaRs and PDs were the most abundant SPMs in BAT of young CT mice. Interestingly, the sum of LXs and of PDs were significantly lower in aged DIO mice compared to young CT mice. Some of the SPMs most significantly reduced in obese-aged mice included LXB4 , MaR2, 4S,14S-diHDHA, 10S,17S-diHDHA (a.k.a. PDX), and RvD6. In contrast, DHA increased DHA-derived SPMs, without modifying LXs. However, MicroPET studies showed that DHA was not able to counteract the impaired cold exposure response in BAT of obese-aged mice. Our data suggest that a defective SPMs production could underlie the decrease of BAT activity observed in obese-aged mice, and highlight the relevance to further characterize the physiological role and therapeutic potential of specific SPMs on BAT development and function.

Lipoxin A4 activates ALX/FPR2 to attenuate inflammation in Aspergillus fumigatus keratitis

PURPOSE

To explore the anti-inflammatory effect of lipoxin A4 (LXA4) in Aspergillus fumigatus (A. fumigatus) keratitis and the underlying mechanisms.

METHODS

In A. fumigatus keratitis mouse models, enzyme-linked immunosorbent assay (ELISA) was used to detect the level of LXA4. Clinical scores were utilized to evaluate fungal keratitis (FK) severity. Fungal load was assessed by plate count. Immunofluorescence staining, HE staining and myeloperoxidase (MPO) assays were carried out to evaluate the neutrophil infiltration and activity. In A. fumigatus infected mouse corneas and inactivated A. fumigatus-stimulated RAW264.7 cells, quantitative real time polymerase chain reaction (qRT-PCR) and ELISA were applied to assess the expression of pro-inflammatory mediators and anti-inflammatory factors.Reactive oxygen species (ROS) was determined by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining in RAW264.7 cells.

RESULTS

LXA4 level was significantly increased in mice with A. fumigatus keratitis. In an A. fumigatus keratitis mouse model, LXA4 treatment alleviated FK severity, reduced fungal load and repressed neutrophil infiltration and activity. Additionally, LXA4 inhibited the expression of pro-inflammatory mediators including IL-1β, TNF-α, IL-6, cyclooxygenase-2 (COX-2), TLR-2, TLR-4, Dectin-1 and iNOS, and promoted the expression of anti-inflammatory factors IL-10 and Arg-1. In RAW264.7 cells, LXA4 receptor/formyl peptide receptor 2 (ALX/FPR2) blockade reversed the anti-inflammatory effect of LXA4. LXA4 suppressed inactivated A. fumigatus induced elevated ROS production in RAW264.7 cells, which was abrogated by ALX/FPR2 antagonist Boc-2.

CONCLUSION

LXA4 ameliorated inflammatory response by suppressing neutrophil infiltration, downregulating the expression of pro-inflammatory mediators and ROS production through ALX/FPR2 receptor in A. fumigatus keratitis.

Lipoxin A4 Restores Septic Renal Function via Blocking Crosstalk Between Inflammation and Premature Senescence

Acute kidney injury (AKI) occurs in half of patients with septic shock, resulting in unacceptably high mortality. However, effective preventive treatments are still lacking. We hypothesized that pretreatment with lipoxin A4 (LXA4), known to promote inflammation resolution, may attenuate septic AKI via blocking crosstalk between inflammation and cellular senescence. In this study, rats developed AKI following cecal ligation and puncture (CLP), as evidenced by a dynamic increase in serum creatinine, blood urea nitrogen, urinary kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, and pathological injury, accompanied by increased levels of inflammation (IL-6, TNF-α, and HMGB1) and tubular cell senescence. While, on the one hand, inhibition of senescence with rapamycin restored renal function and attenuated septic inflammatory response, on the other hand, LXA4 administration inhibited renal inflammation and tubular epithelial cell senescence after CLP. Ultimately, pretreatment with LXA4 significantly restored renal function and increased the survival rate of rats after CLP. Furthermore, LXA4 inhibited NF-κB-mediated inflammatory response and the p53/p21 senescence pathway in vivo and in vitro. However, the effect was reversed by PPAR-γ siRNA and antagonist. These results indicated that LXA4 exerted its renoprotective effects by blocking the crosstalk between inflammation and premature senescence in a PPAR-γ-dependent manner. Our findings also suggested that premature senescence plays a critical role in septic AKI and that inhibition of the crosstalk between inflammation and premature senescence may represent a new and major mechanism through which LXA4 attenuates septic AKI.

Lipoxygenase inhibitor ML351 dysregulated an innate inflammatory response leading to impaired cardiac repair in acute heart failure

The presistent increase of 12/15 lipoxygenase enzyme activity is correlated with uncontrolled inflammation, leading to organ dysfunction. ML351, a potent 12/15 lipoxygenase (12/15LOX) inhibitor, was reported to reduce infarct size and inflammation in a murine ischemic stroke model. In the presented work, we have applied three complementary experimental approaches, in-vitro, ex-vivo, and in-vivo, to determine whether pharmacological inhibition of 12/15LOX could dampen the inflammatory response in adult mice after Kdo2-Lipid A (KLA) as an endotoxin stimulator or post myocardial infarction (MI). Male C57BL/6 (8-12 weeks) mice were subjected to permanent coronary ligation thereby inducing acute heart failure (MI-d1 and MI-d5) for in-vivo studies. 12/15LOX antagonist ML351 (50 mg/kg) was subcutaneously injected 2 h post-MI, while MI-controls received saline. For ex-vivo experiments, ML351 (25 mg/kg) was injected as bolus after 5 min of inflammatory stimulus (KLA 1 μg/g) injection. Peritoneal macrophages (PMɸ) were harvested after 4 h post KLA. For in-vitro studies, PMɸ were treated with KLA (100 ng/mL), ML351 (10 µM), or KLA + ML351 for 4 h, and inflammatory response was evaluated. In-vivo, 5LOX expression was reduced after ML351 administration, inducing a compensatory increase of 12LOX that sensitized PMɸ toward a proinflammatory state. This was marked by higher inflammatory cytokines and dysregulation of the splenocardiac axis post-MI. ML351 treatment increased CD11b⁺ and Ly6C^high populations in spleen and Ly6G⁺ population in heart, with a decrease in F4/80⁺ macrophage population at MI-d1. In-vitro results indicated that ML351 suppressed initiation of inflammation while ex-vivo results suggested ML351 overactivated inflammation consequently delaying the resolution process. Collectively, in-vitro, ex-vivo, and in-vivo results indicated that pharmacological blockade of lipoxygenases using ML351 impaired initiation of inflammation thereby dysregulated acute immune response in cardiac repair.

Cardiac Dysfunction in Rheumatoid Arthritis: The Role of Inflammation

Rheumatoid arthritis is a chronic, systemic inflammatory disease that carries an increased risk of mortality due to cardiovascular disease. The link between inflammation and atherosclerotic disease is clear; however, recent evidence suggests that inflammation may also play a role in the development of nonischemic heart disease in rheumatoid arthritis (RA) patients. We consider here the link between inflammation and cardiovascular disease in the RA community with a focus on heart failure with preserved ejection fraction. The effect of current anti-inflammatory therapeutics, used to treat RA patients, on cardiovascular disease are discussed as well as whether targeting resolution of inflammation might offer an alternative strategy for tempering inflammation and subsequent inflammation-driven comorbidities in RA.

Cells of the Immune System in Cardiac Remodeling: Main Players in Resolution of Inflammation and Repair After Myocardial Infarction

The burden of heart failure (HF), developing after myocardial infarction MI, still represents a major issue in clinical practice. Failure of appropriate resolution of inflammation during post-myocardial injury is associated with unsuccessful left ventricular remodeling and underlies HF pathogenesis. Cells of the immune system have been shown to mediate both protective and damaging effects in heart remodeling. This ambiguity of the role of the immune system and inconsistent results of the recent clinical trials question the benefits of anti-inflammatory therapies during acute MI. The present review will summarize knowledge of the roles that different cells of the immune system play in the process of post-infarct cardiac healing. Data on the phenotype, active molecules and functions of the immune cells, based on the results of both experimental and clinical studies, will be provided. For some cellular subsets, such as macrophages, neutrophils, dendritic cells and lymphocytes, an anti-inflammatory activity has been attributed to the specific subpopulations. Activity of other cells, such as eosinophils, mast cells, natural killer (NK) cells and NKT cells has been shown to be highly dependent of the signals created by micro-environment. Also, new approaches for classification of cellular phenotypes based on the single-cell RNA sequencing allow better understanding of the phenotype of the cells involved in resolution of inflammation. Possible perspectives of immune-mediated therapy for AMI patients are discussed in the conclusion. We also outline unresolved questions that need to be solved in order to implement the current knowledge on the role of the immune cells in post-MI tissue repair into practice.

Regulation of Inflammation and Oxidative Stress by Formyl Peptide Receptors in Cardiovascular Disease Progression

G protein-coupled receptors (GPCRs) are the most important regulators of cardiac function and are commonly targeted for medical therapeutics. Formyl-Peptide Receptors (FPRs) are members of the GPCR superfamily and play an emerging role in cardiovascular pathologies. FPRs can modulate oxidative stress through nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) production whose dysregulation has been observed in different cardiovascular diseases. Therefore, many studies are focused on identifying molecular mechanisms of the regulation of ROS production. FPR1, FPR2 and FPR3 belong to the FPRs family and their stimulation triggers phosphorylation of intracellular signaling molecules and nonsignaling proteins that are required for NADPH oxidase activation. Some FPR agonists trigger inflammatory processes, while other ligands activate proresolving or anti-inflammatory pathways, depending on the nature of the ligands. In general, bacterial and mitochondrial formylated peptides activate a proinflammatory cell response through FPR1, while Annexin A1 and Lipoxin A4 are anti-inflammatory FPR2 ligands. FPR2 can also trigger a proinflammatory pathway and the switch between FPR2-mediated pro- and anti-inflammatory cell responses depends on conformational changes of the receptor upon ligand binding. Here we describe the detrimental or beneficial effects of the main FPR agonists and their potential role as new therapeutic and diagnostic targets in the progression of cardiovascular diseases.

Deciphering key genes in cardio-renal syndrome using network analysis

Cardio-renal syndrome (CRS) is a rapidly recognized clinical entity which refers to the inextricably connection between heart and renal impairment, whereby abnormality to one organ directly promotes deterioration of the other one. Biological markers help to gain insight into the pathological processes for early diagnosis with higher accuracy of CRS using known clinical findings. Therefore, it is of interest to identify target genes in associated pathways implicated linked to CRS. Hence, 119 CRS genes were extracted from the literature to construct the PPIN network. We used the MCODE tool to generate modules from network so as to select the top 10 modules from 23 available modules. The modules were further analyzed to identify 12 essential genes in the network. These biomarkers are potential emerging tools for understanding the pathophysiologic mechanisms for the early diagnosis of CRS. Ontological analysis shows that they are rich in MF protease binding and endo-peptidase inhibitor activity. Thus, this data help increase our knowledge on CRS to improve clinical management of the disease.

Role of polyunsaturated fatty acids in ischemic stroke - A perspective of specialized pro-resolving mediators

Polyunsaturated fatty acids (PUFAs) have been proposed as beneficial for cardiovascular health. However, results from both epidemiological studies and clinical trials have been inconsistent, whereas most of the animal studies showed promising benefits of PUFAs in the prevention and treatment of ischemic stroke. In recent years, it has become clear that PUFAs are metabolized into various types of bioactive derivatives, including the specialized pro-resolving mediators (SPMs). SPMs exert multiple biofunctions, such as to limit excessive inflammatory responses, regulate lipid metabolism and immune cell functions, decrease production of pro-inflammatory factors, increase anti-inflammatory mediators, as well as to promote tissue repair and homeostasis. Inflammation has been recognised as a key contributor to the pathophysiology of acute ischemic stroke. Owing to their potent pro-resolving actions, SPMs are potential for development of novel anti-stroke therapy. In this review, we will summarize current knowledge of epidemiological studies, basic research and clinical trials concerning PUFAs in stroke prevention and treatment, with special attention to SPMs as the unsung heroes behind PUFAs.

Race-based and sex-based differences in bioactive lipid mediators after myocardial infarction

AIMS

Leucocyte-directed specialized pro-resolving mediators (SPMs) are essential for cardiac repair, and their biosynthesis coincides with the expression of pro-inflammatory mediators; however, the precise quantitation during an acute myocardial infarction (MI) event is poorly understood in race-specific and sex-specific manner. Coronary heart disease is the leading cause of death and disability in the USA. Although the prevalence of coronary heart disease is similar between Black and White patients, cardiovascular events (including MI), rehospitalization, and mortality are disproportionately higher in Black patients. Therefore, understanding differences in inflammation and resolution can enable the development of predictive, personalized, and precise treatment and attenuate sex/racial disparities. Thus, herein, we assess differences in bioactive lipids and SPMs, between Black and White patients experiencing an acute MI.

METHODS AND RESULTS

From the PRiME-GGAT cohort, we collected plasma after MI within 24-48 h from 22 Black (15 male and 7 female) and 31 White (23 male and 8 female) subjects for a comparative race-based and sex-based analyses. MI was confirmed using a biochemical measurement of plasma troponin and ST elevation. Plasma levels of three essential polyunsaturated fatty acids [arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA)] and a set of 40 bioactive lipid mediators with major emphasis on SPMs were quantified by liquid chromatography-mass spectrometry. AA and DHA were higher in White male and female patients, and EPA was noted higher only in White male patients compared with White female and Black male and female patients. Lipoxygenase-mediated AA-derived 12-hydroxyeicosatetraenoic acid (29-63%) and 15-hydroxyeicosatetraenoic acid (3-9%) and DHA-derived 17-hydroxydocosahexaenoic acid (3-22%) and 14-hydroxydocosahexaenoic acid (7-10%) were major bioactive lipid mediators in plasma. The SPM signature resolvin E1 was significantly lower in Black patients compared with White male and female patients, whereas protectin D1 was lower in White male patients compared with White female and Black male and female patients.

CONCLUSION

Our comparative analyses of fatty acids and respective cyclooxygenase-derived and lipoxygenase-derived SPM signatures capture the heterogeneity of disease pathology and elucidate potential mechanisms underlying sex-based and race-based differences following MI.

Specialized pro-resolving lipid mediators in cardiovascular disease, diagnosis, and therapy

Persistent inflammation is the key aggravator in many cardiovascular diseases, including atherosclerosis, aneurysm, injury/reperfusion, thrombosis, and neointimal hyperplasia following surgical or percutaneous interventions. Resolution is an active process orchestrated by specialized pro-resolving lipid mediators (SPMs) which tamp down acute inflammatory signals, promote healing and facilitate a return to homeostasis. SPMs are endogenously derived from poly-unsaturated fatty acids, and their biologic activity is mediated via specific G-protein coupled receptor binding. The potency of SPM in regulating the inflammatory response has encouraged investigation into their therapeutic and diagnostic use in cardiovascular pathologies. Herein we describe the translational groundwork which has established the synthesis and interactions of SPM in cardiovascular and hematologic cells, the therapeutic effects of SPM in animal models of cardiovascular disease, and some early technologies that harness and attempt to optimize SPM delivery and "resolution pharmacology". Further studies are required to precisely determine the mechanisms of resolution in the cardiovascular system and to determine the clinical settings in which SPM can be utilized to optimize patient outcomes.

Deficit of resolution receptor magnifies inflammatory leukocyte directed cardiorenal and endothelial dysfunction with signs of cardiomyopathy of obesity

Chronic unresolved inflammation is the primary determinant of cardiovascular disease. Precise mechanisms that define the genesis of unresolved inflammation in heart failure with preserved ejection fraction (HFpEF) are of interest due to the obesity epidemic. To examine the obesity phenotype and its direct/indirect consequences, multiple approaches were employed using the lipoxin receptor (abbreviated as ALX) dysfunction mouse model. Indirect calorimetry analyses revealed that the deletion of ALX dysregulated energy metabolism driving toward age-related obesity. Heart function data suggest that obesity-prone ALX deficient mice had impaired myocardium strain. Comprehensive measurement of chemokines, extracellular matrix, and arrhythmogenic arrays confirmed the dysregulation of multiple ion channels gene expression with amplified inflammatory chemokines and cytokines response at the age of 4 months compared with WT counterparts. Quantitative analyses of leukocytes demonstrated an increase of proinflammatory Ly6C^hi CCR2⁺ macrophages in the spleen and heart at a steady-state resulting in an inflamed splenocardiac axis. Signs of subtle inflammation were marked with cardiorenal, endothelial defects with decreased CD31 and eNOS and an increased iNOS and COX2 expression. Thus, ALX receptor deficiency serves as an experimental model that defines multiple cellular and molecular mechanisms in HFpEF that could be a target for the development of HFpEF therapy in cardiovascular medicine.