Proresolving lipid mediators and liver disease

Mechanisms of immunity in acutely decompensated cirrhosis and acute-on-chronic liver failure

The identification of systemic inflammation (SI) as a central player in the orchestration of acute-on-chronic liver failure (ACLF) has opened new avenues for the understanding of the pathophysiological mechanisms underlying this disease condition. ACLF, which develops in patients with acute decompensation of cirrhosis, is characterized by single or multiple organ failure and high risk of short-term (28-day) mortality. Its poor outcome is closely associated with the severity of the systemic inflammatory response. In this review, we describe the key features of SI in patients with acutely decompensated cirrhosis and ACLF, including the presence of a high blood white cell count and increased levels of inflammatory mediators in systemic circulation. We also discuss the main triggers (i.e. pathogen- and damage-associated molecular patterns), the cell effectors (i.e. neutrophils, monocytes and lymphocytes), the humoral mediators (acute phase proteins, cytokines, chemokines, growth factors and bioactive lipid mediators) and the factors that influence the systemic inflammatory response that drive organ failure and mortality in ACLF. The role of immunological exhaustion and/or immunoparalysis in the context of exacerbated inflammatory responses that predispose ACLF patients to secondary infections and re-escalation of end-organ dysfunction and mortality are also reviewed. Finally, several new potential immunogenic therapeutic targets are debated.

Relationship between Compound α-Ketoacid and Microinflammation in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) refers to the presence of structural or functional abnormalities in the kidneys that affect health, lasting for more than 3 months. CKD is not only the direct cause of global incidence rate and mortality, but also an important risk factor for cardiovascular disease. Persistent microinflammatory state has been recognized as an important component of CKD, which can lead to renal fibrosis and loss of renal function, and plays a crucial role in the pathophysiology and progression of the disease. Simultaneously, compound α-Ketoacid can bind nitrogen-containing metabolites in the blood and accelerate their excretion from the body, thereby reducing the level of metabolic waste, alleviating gastrointestinal reactions in patients, and reducing the inflammatory response and oxidative stress state of the body. Compound α-Ketoacid contains amino acids required by CKD patients. In this review, we explore the relationship between compound α-Ketoacid and microinflammation in patients with CKD. The review indicated that compound α-Ketoacid can improve the microinflammatory state in CKD patients by improving the nutritional status of CKD patients, improving patient's acid-base balance disorder, regulating oxidative stress, improving gut microbiota, and regulating abnormal lipid metabolism.

Anti-inflammatory strategies for hepatic encephalopathy: preclinical studies

Hepatic encephalopathy (HE) is a potentially reversible neuropsychiatric syndrome. Often, HE causes cognitive and motor dysfunctions due to an acute or chronic insufficiency of the liver or a shunting between the hepatic portal vein and systemic vasculature. Liver damage induces peripheral changes, such as in the metabolism and peripheral inflammatory responses that trigger exacerbated neuroinflammation. In experimental models, anti-inflammatory strategies have demonstrated neuroprotective effects, leading to a reduction in HE-related cognitive and motor impairments. In this scenario, a growing body of evidence has shown that peripheral and central nervous system inflammation are promising preclinical targets. In this review, we performed an overview of FDA-approved drugs and natural compounds which are used in the treatment of other neurological and nonneurological diseases that have played a neuroprotective role in experimental HE, at least in part, through anti-inflammatory mechanisms. Despite the exciting results from animal models, the available data should be critically interpreted, highlighting the importance of translating the findings for clinical essays.

Resolution Pharmacology: Focus on Pro-Resolving Annexin A1 and Lipid Mediators for Therapeutic Innovation in Inflammation

Chronic diseases that affect our society are made more complex by comorbidities and are poorly managed by the current pharmacology. While all present inflammatory etiopathogeneses, there is an unmet need for better clinical management of these diseases and their multiple symptoms. We discuss here an innovative approach based on the biology of the resolution of inflammation. Studying endogenous pro-resolving peptide and lipid mediators, how they are formed, and which target they interact with, can offer innovative options through augmenting the expression or function of pro-resolving pathways or mimicking their actions with novel targeted molecules. In all cases, resolution offers innovation for the treatment of the primary cause of a given disease and/or for the management of its comorbidities, ultimately improving patient quality of life. By implementing resolution pharmacology, we harness the whole physiology of inflammation, with the potential to bring a marked change in the management of inflammatory conditions.

Effects of statins on specialized pro-resolving mediators: An additional pathway leading to resolution of inflammation

Statins are a class of cholesterol-lowering drugs that inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Anti-inflammatory and antioxidant properties, as well as improvement of endothelial function and plaque stabilization have also been proposed as parts of the pleiotropic effects of statins. Specialized pro-resolving mediators (SPMs) are endogenous lipid-derived molecules originating from ω-6 and ω-3 polyunsaturated fatty acids, such as arachidonic, docosahexaenoic and eicosapentaenoic acid that trigger and modulate the resolution of inflammation. Impaired SPM biosynthesis can lead to excessive or chronic inflammation and is implicated in the pathogenesis of several diseases. Exogenous administration of SPMs, including lipoxin, maresin, protectin, have been shown to improve both bacterial and viral infections, mainly in preclinical models, thus minimizing inflammation. Statin-triggered-SPM production in several in vitro and in vivo models may represent another anti-inflammatory pathway involving these drugs. This commentary discusses scientific publications on the effects of statins on SPMs and the resolution of inflammation process.

Lipids in Liver Failure Syndromes: A Focus on Eicosanoids, Specialized Pro-Resolving Lipid Mediators and Lysophospholipids

Lipids are organic compounds insoluble in water with a variety of metabolic and non-metabolic functions. They not only represent an efficient energy substrate but can also act as key inflammatory and anti-inflammatory molecules as part of a network of soluble mediators at the interface of metabolism and the immune system. The role of endogenous bioactive lipid mediators has been demonstrated in several inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, cancer). The liver is unique in providing balanced immunotolerance to the exposure of bacterial components from the gut transiting through the portal vein and the lymphatic system. This balance is abruptly deranged in liver failure syndromes such as acute liver failure and acute-on-chronic liver failure. In these syndromes, researchers have recently focused on bioactive lipid mediators by global metabonomic profiling and uncovered the pivotal role of these mediators in the immune dysfunction observed in liver failure syndromes explaining the high occurrence of sepsis and subsequent organ failure. Among endogenous bioactive lipids, the mechanistic actions of three classes (eicosanoids, pro-resolving lipid mediators and lysophospholipids) in the pathophysiological modulation of liver failure syndromes will be the topic of this narrative review. Furthermore, the therapeutic potential of lipid-immune pathways will be described.

Reduced Plasma Extracellular Vesicle CD5L Content in Patients With Acute-On-Chronic Liver Failure: Interplay With Specialized Pro-Resolving Lipid Mediators

Acute-on chronic liver failure (ACLF) is a syndrome that develops in patients with acutely decompensated cirrhosis (AD). It is characterized by a systemic hyperinflammatory state, leading to multiple organ failure. Our objective was to analyze macrophage anti-inflammatory protein CD5L in plasma extracellular vesicles (EVs) and assess its as yet unknown relationship with lipid mediators in ACLF. With this aim, EVs were purified by size exclusion chromatography from the plasma of healthy subjects (HS) (n=6) and patients with compensated cirrhosis (CC) (n=6), AD (n=11) and ACLF (n=11), which were defined as positive for CD9, CD5L and CD63 and their size, number, morphology and lipid mediator content were characterized by NTA, EM, and LC-MS/MS, respectively. Additionally, plasma CD5L was quantified by ELISA in 10 HS, 20 CC and 149 AD patients (69 ACLF). Moreover, macrophage CD5L expression and the biosynthesis of specialized lipid mediators (SPMs) were characterized in vitro in primary cells. Our results indicate that circulating EVs were significantly suppressed in cirrhosis, regardless of severity, and showed considerable alterations in CD5L and lipid mediator content as the disease progressed. In AD, levels of EV CD5L correlated best with those of the SPM RvE1. Analysis of total plasma supported these data and showed that, in ACLF, low CD5L levels were associated with circulatory (p<0.001), brain (p<0.008) and respiratory (p<0.05) failure (Mann-Whitney test). Functional studies in macrophages indicated a positive feedback loop between CD5L and RvE1 biosynthesis. In summary, we have determined a significant alteration of circulating EV contents in ACLF, with a loss of anti-inflammatory and pro-resolving molecules involved in the control of acute inflammation in this condition.

Resolvin E1-ChemR23 Axis Regulates the Hepatic Metabolic and Inflammatory Transcriptional Landscape in Obesity at the Whole Genome and Exon Level

Resolvin E1 (RvE1) is an immunoresolvent that is synthesized from eicosapentaenoic acid and can bind the receptor ERV1/ChemR23. We previously showed activation of the RvE1-ChemR23 axis improves hyperglycemia and hyperinsulinemia of obese mice; however, it remains unclear how RvE1 controls glucose homeostasis. Here we investigated hepatic metabolic and inflammatory transcriptional targets of the RvE1-ChemR23 axis using lean and obese wild type (WT) and ChemR23 knockout (KO) mice. We conducted an in-depth transcriptional study by preforming whole gene-level and exon-level analyses, which provide insight into alternative splicing variants and miRNA regulation. Compared to controls, WT and KO obese mice in the absence of RvE1 displayed similar gene-level profiles, which entailed dysregulated pathways related to glucose homeostasis. Notably, obese WT mice relative to lean controls showed a robust decrease in pathways related to the biosynthesis of unsaturated fatty acids. At the exon-level, obese ChemR23 KOs compared to obese WT mice displayed changes in pathways related to hepatic lipid transport, cholesterol metabolism, and immunological functions such as complement cascades and platelet activation. Importantly, upon RvE1 administration to WT obese mice, we discovered upregulated genes in pathways relating to insulin sensitivity and downregulated genes related to regulators of TGF-β signaling. This transcriptional profile was generally not recapitulated with obese ChemR23 KO mice administered RvE1. Collectively, gene and exon-level analyses suggest RvE1 controls the hepatic transcriptional profile related to glucose homeostasis, insulin sensitivity, and inflammation in a manner that is largely dependent on ChemR23. These studies will drive future mechanistic experiments on the RvE1-ChemR23 axis.