Stearoyl lysophosphatidylcholine prevents lipopolysaccharide-induced extracellular release of high mobility group box-1 through AMP-activated protein kinase activation

Comparative analysis of lysophospholipid metabolism profiles and clinical characteristics in patients with high vs. low C-reactive protein levels in acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND

The precise role of lysophospholipids (LysoPLs) in the pathogenesis of acute exacerbations of Chronic Obstructive Pulmonary Disease (AECOPD) remains unclear. In this study, we sought to elucidate the differences in serum LysoPL metabolite profiles and their correlation with clinical features between patients with low versus high CRP levels.

METHODS

A total of 58 patients with AECOPD were enrolled in the study. Patients were classified into two groups: low CRP group (CRP < 20 mg/L, n = 34) and high CRP group (CRP ≥ 20 mg/L, n = 24). Clinical data were collected, and the LysoPL metabolite profiles were analyzed using Liquid Chromatography-Mass Spectrometry (LC-MS) and identified by matching with the LipidBlast library.

RESULTS

Nineteen differential LysoPLs were initially identified through Student's t-test (p < 0.05 and VIP > 1). Subsequently, four LysoPLs, LPC(16:0), LPE(18:2), LPC(22:0), and LPC(24:0), were identified by FDR adjustment (adjusted p < 0.05). These four lysoPLs had a significant negative correlation with CRP. Integrative analysis revealed that LPC (16:0) and LPC (22:0) correlated with less hypercapnic respiratory failure and ICU admission.

CONCLUSION

AECOPD patients with high CRP levels demonstrated a distinctive LysoPL metabolism profile, with LPC (16:0), LPE(18:2), LPC(22:0), and LPC(24:0) being the most significantly altered lipid molecules. These alterations were associated with poorer clinical outcomes.

The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

Reputable evidence from multiple studies suggests that excessive and uncontrolled inflammation plays an indispensable role in mediating, amplifying, and protracting acute lung injury (ALI). Traditionally, immunity and energy metabolism are regarded as separate functions regulated by distinct mechanisms, but recently, more and more evidence show that immunity and energy metabolism exhibit a strong interaction which has given rise to an emerging field of immunometabolism. Mammalian lungs are organs with active fatty acid metabolism, however, during ALI, inflammation and oxidative stress lead to a series metabolic reprogramming such as impaired fatty acid oxidation, increased expression of proteins involved in fatty acid uptake and transport, enhanced synthesis of fatty acids, and accumulation of lipid droplets. In addition, obesity represents a significant risk factor for ALI/ARDS. Thus, we have further elucidated the mechanisms of obesity exacerbating ALI from the perspective of fatty acid metabolism. To sum up, this paper presents a systematical review of the relationship between extensive fatty acid metabolic pathways and acute lung injury and summarizes recent advances in understanding the involvement of fatty acid metabolism-related pathways in ALI. We hold an optimistic believe that targeting fatty acid metabolism pathway is a promising lung protection strategy, but the specific regulatory mechanisms are way too complex, necessitating further extensive and in-depth investigations in future studies.

Myristoyl lysophosphatidylcholine is a biomarker and potential therapeutic target for community-acquired pneumonia

There is no gold standard for evaluating the severity of community-acquired pneumonia (CAP), and it is still based on a score. This study aimed to use the metabolomics method to find promised biomarkers in assessing disease severity and potential therapeutic targets for CAP. The result found that the metabolites in the plasma samples of CAP patients had significantly different between the acute phase and the remission phase, especially lysophosphatidylcholine (LPCs) in glycerophospholipids, whose levels are negatively linked to the severity of the disease. Subsequently, the two key metabolites of myristoyl lysophosphatidylcholine (LPC 14:0) and LPC 16:1 were screened. We analyzed the predictive performance of the two metabolites using Spearman-related analysis and ROC curves, and LPC14:0 showed more satisfactory diagnostic performance than LPC16:1. Then we explored the protective role and mechanism of LPC 14:0 in animal and cell models. The results showed that LPC 14:0 could inhibit the LPS-induced secretion of IL-1β, IL-6, and TNF-α, lower the ROS and MDA levels, and decreased the depletion of SOD and GSH, thereby reducing lung tissue and cell damage, such as down-regulating the protein level in BALF, lung W/D ratio, MPO activity, and apoptosis. We found that LPC 14:0 inhibited LPS-induced inflammatory response and oxidative stress, and the above protection was achieved by inhibiting LPS-induced activation of the NLRP3 inflammasome. LPC 14:0 may serve as a novel biomarker for predicting the severity of CAP. In addition, our exploration of the role of LPC 14:0 in animal and cellular models has reinforced its promise as a therapeutic target to improve the clinical efficacy for CAP.

Lysophosphatidylcholine induces adenosine release from macrophages via TRPM7-mediated mitochondrial activation

Even though macrophages have the potential to harm tissues through excessive release of inflammatory mediators, they play protective roles to maintain tissue integrity. In this study, we hypothesized that lysophosphatidylcholine (LPC), via G2A and A2B receptors, puts brakes on macrophages by the induction of adenosine release which could contribute to termination of inflammation. Mechanistically, LPC-induced PGE2 production followed by the activation of cAMP/protein kinase A (PKA) pathway which results in the activation of LKB1/AMPK signaling pathway leading to increasing Mg2+ influx concomitantly with an increase in mitochondrial membrane potential (MMP, Δψm) and ATP production. Then, ATP is converted to adenosine intracellularly followed by efflux via ENT1. In a parallel pathway, LPC-induced elevation of cytosolic calcium was essential for adenosine release, and Ca2+/calmodulin signaling cooperated with PKA to regulate ENT1 permeation to adenosine. Pharmacological blockade of TRPM7 and antisense treatment suppressed LPC-induced adenosine release and magnesium influx in bone marrow-derived macrophages (BMDMs). Moreover, LPC suppressed LPS-induced phosphorylation of connexin-43, which may counteract TLR4-mediated inflammatory response. Intriguingly, we found LPC increased netrin-1 production from BMDMs. Netrin-1 induces anti-inflammatory signaling via A2B receptor. In the presence of adenosine deaminase which removes adenosine in the medium, the chemotaxis of macrophages toward LPC was significantly increased. Hypoxia and metabolic acidosis are usually developed in a variety of inflammatory situations such as sepsis. We found LPC augmented hypoxia- or acidosis-induced adenosine release from BMDMs. These results provide evidence of LPC-induced brake-like action on macrophages by adenosine release via cellular magnesium signaling.

Differential Characteristics of HMGB2 Versus HMGB1 and their Perspectives in Ovary and Prostate Cancer

We have summarized common and differential functions of HMGB1 and HMGB2 proteins with reference to pathological processes, with a special focus on cancer. Currently, several "omic" approaches help us compare the relative expression of these 2 proteins in healthy and cancerous human specimens, as well as in a wide range of cancer-derived cell lines, or in fetal versus adult cells. Molecules that interfere with HMGB1 functions, though through different mechanisms, have been extensively tested as therapeutic agents in animal models in recent years, and their effects are summarized. The review concludes with a discussion on the perspectives of HMGB molecules as targets in prostate and ovarian cancers.

An Updated Review of Pro- and Anti-Inflammatory Properties of Plasma Lysophosphatidylcholines in the Vascular System

Lysophosphatidylcholines are a group of bioactive lipids heavily investigated in the context of inflammation and atherosclerosis development. While present in plasma during physiological conditions, their concentration can drastically increase in certain inflammatory states. Lysophosphatidylcholines are widely regarded as potent pro-inflammatory and deleterious mediators, but an increasing number of more recent studies show multiple beneficial properties under various pathological conditions. Many of the discrepancies in the published studies are due to the investigation of different species or mixtures of lysophatidylcholines and the use of supra-physiological concentrations in the absence of serum or other carrier proteins. Furthermore, interpretation of the results is complicated by the rapid metabolism of lysophosphatidylcholine (LPC) in cells and tissues to pro-inflammatory lysophosphatidic acid. Interestingly, most of the recent studies, in contrast to older studies, found lower LPC plasma levels associated with unfavorable disease outcomes. Being the most abundant lysophospholipid in plasma, it is of utmost importance to understand its physiological functions and shed light on the discordant literature connected to its research. LPCs should be recognized as important homeostatic mediators involved in all stages of vascular inflammation. In this review, we want to point out potential pro- and anti-inflammatory activities of lysophospholipids in the vascular system and highlight recent discoveries about the effect of lysophosphatidylcholines on immune cells at the endothelial vascular interface. We will also look at their potential clinical application as biomarkers.

Effects of gastrodin against carbon tetrachloride induced kidney inflammation and fibrosis in mice associated with the AMPK/Nrf2/HMGB1 pathway

Gastrodin (GAS), the main phenolic glycoside extracted from Gastrodia elata Blume, exhibits potential renoprotective properties.

Fucoxanthin prevents lipopolysaccharide-induced depressive-like behavior in mice via AMPK- NF-κB pathway

Fucoxanthin (FX), a natural carotenoid abundant in edible brown seaweeds, has been shown the great anti-oxidant, anti-inflammatory and anti-diabetic effects in vivo and in vitro. The present study was designed to investigate the effects of FX on lipopolysaccharide (LPS)-induced behavioral defects in mice. In depressive behavior tests, the increased immobility time of forced swimming test and tail suspension test by LPS treatment in mice, which were significantly reversed by FX treatment (200 mg/kg, i.g.). In anxiety behavior tests, LPS injection was neither influence the anxiety-related parameters in marble burying test nor that in elevated plus maze test. Interestingly, anxiolytic effects were observed in single FX treated control and LPS-induced mice groups. FX treatment also reversed LPS-induced body weight loss and food intake decreases. Biochemical analysis indicated that FX inhibited LPS-induced overexpression of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), as well as iNOS and COX-2 in the hippocampus, frontal cortex and hypothalamus, via the modulation of AMPK-NF-κB signaling pathway.

Stearoyl lysophosphatidylcholine inhibits LPS-induced extracellular release of HMGB1 through the G2A/calcium/CaMKKβ/AMPK pathway

Stearoyl lysophosphatidylcholine (sLPC) has protective effects against several lethal sepsis models, even after induction of sepsis, which is associated with sLPC-mediated inhibition of high mobility group box 1 (HMGB1) release. This study investigated the mechanism by which sLPC inhibits lipopolysaccharide (LPS)-induced extracellular secretion of HMGB1 after the onset of sepsis. sLPC increased AMPK phosphorylation and the binding of AMPK to calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ), one of the upstream signals of AMPK. Inhibition of CaMKKβ activity decreased sLPC-mediated inhibition of HMGB1 release, and sLPC increased the concentration of intracellular calcium. Blocking of the macrophage G protein-coupled receptor G2A (G2A) suppressed AMPK phosphorylation, suppressed increases in the intracellular levels of calcium, and prevented the inhibition of HMGB1 release by sLPC. In particular, when macrophages were incubated with sLPC even after LPS treatment, sLPC increased the phosphorylation of AMPK and the binding of CaMKKβ and AMPK, and suppressed the secretion of HMGB1. In addition, sLPC administered 1 h before or 4 h after establishment of sepsis significantly diminished circulating HMGB1 levels in mice. sLPC inhibited LPS-induced extracellular release of HMGB1 through the activation of the G2A/calcium/CaMKKβ/AMPK pathway. These findings suggest that sLPC may be a potential anti-inflammatory agent for acute inflammatory conditions such as sepsis.

Ginsenoside Rb1 increases macrophage phagocytosis through p38 mitogen-activated protein kinase/Akt pathway

Background

Ginsenoside Rb1, a triterpene saponin, is derived from the Panax ginseng root and has potent antiinflammatory activity. In this study, we determined if Rb1 can increase macrophage phagocytosis and elucidated the underlying mechanisms.

Methods

To measure macrophage phagocytosis, mouse peritoneal macrophages or RAW 264.7 cells were cultured with fluorescein isothiocyanate–conjugated Escherichia coli, and the phagocytic index was determined by flow cytometry. Western blot analyses were performed.

Results

Ginsenoside Rb1 increased macrophage phagocytosis and phosphorylation of p38 mitogen-activated protein kinase (MAPK), but inhibition of p38 MAPK activity with SB203580 decreased the phagocytic ability of macrophages. Rb1 also increased Akt phosphorylation, which was suppressed by LY294002, a phosphoinositide 3-kinase inhibitor. Rb1-induced Akt phosphorylation was inhibited by SB203580, (5Z)-7-oxozeaenol, and small-interfering RNA (siRNA)–mediated knockdown of p38α MAPK in macrophages. However, Rb1-induced p38 MAPK phosphorylation was not blocked by LY294002 or siRNA-mediated knockdown of Akt. The inhibition of Akt activation with siRNA or LY294002 also inhibited the Rb1-induced increase in phagocytosis. Rb1 increased macrophage phagocytosis of IgG-opsonized beads but not unopsonized beads. The phosphorylation of p21 activated kinase 1/2 and actin polymerization induced by IgG-opsonized beads and Rb1 were inhibited by SB203580 and LY294002. Intraperitoneal injection of Rb1 increased phosphorylation of p38 MAPK and Akt and the phagocytosis of bacteria in bronchoalveolar cells.

Conclusion

These results suggest that ginsenoside Rb1 enhances the phagocytic capacity of macrophages for bacteria via activation of the p38/Akt pathway. Rb1 may be a useful pharmacological adjuvant for the treatment of bacterial infections in clinically relevant conditions.

Alda-1 Protects Against Acrolein-Induced Acute Lung Injury and Endothelial Barrier Dysfunction

Inhalation of acrolein, a highly reactive aldehyde, causes lung edema. The underlying mechanism is poorly understood and there is no effective treatment. In this study, we demonstrated that acrolein not only dose-dependently induced lung edema but also promoted LPS-induced acute lung injury. Importantly, acrolein-induced lung injury was prevented and rescued by Alda-1, an activator of mitochondrial aldehyde dehydrogenase 2. Acrolein also dose-dependently increased monolayer permeability, disrupted adherens junctions and focal adhesion complexes, and caused intercellular gap formation in primary cultured lung microvascular endothelial cells (LMVECs). These effects were attenuated by Alda-1 and the antioxidant N-acetylcysteine, but not by the NADPH inhibitor apocynin. Furthermore, acrolein inhibited AMP-activated protein kinase (AMPK) and increased mitochondrial reactive oxygen species levels in LMVECs-effects that were associated with impaired mitochondrial respiration. AMPK total protein levels were also reduced in lung tissue of mice and LMVECs exposed to acrolein. Activation of AMPK with 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside blunted an acrolein-induced increase in endothelial monolayer permeability, but not mitochondrial oxidative stress or inhibition of mitochondrial respiration. Our results suggest that acrolein-induced mitochondrial dysfunction may not contribute to endothelial barrier dysfunction. We speculate that detoxification of acrolein by Alda-1 and activation of AMPK may be novel approaches to prevent and treat acrolein-associated acute lung injury, which may occur after smoke inhalation.

Advanced glycation end-products produced systemically and by macrophages: A common contributor to inflammation and degenerative diseases

Advanced glycation end products (AGEs) and their receptor have been implicated in the progressions of many intractable diseases, such as diabetes and atherosclerosis, and are also critical for pathologic changes in chronic degenerative diseases, such as Alzheimer's disease, Parkinson's disease, and alcoholic brain damage. Recently activated macrophages were found to be a source of AGEs, and the most abundant form of AGEs, AGE-albumin excreted by macrophages has been implicated in these diseases and to act through common pathways. AGEs inhibition has been shown to prevent the pathogenesis of AGEs-related diseases in human, and therapeutic advances have resulted in several agents that prevent their adverse effects. Recently, anti-inflammatory molecules that inhibit AGEs have been shown to be good candidates for ameliorating diabetic complications as well as degenerative diseases. This review was undertaken to present, discuss, and clarify current understanding regarding AGEs formation in association with macrophages, different diseases, therapeutic and diagnostic strategy and links with RAGE inhibition.

Vitexin alleviates lipopolysaccharide‑induced islet cell injury by inhibiting HMGB1 release

Diabetes mellitus (DM) is a chronic metabolic disease, where the predominant pathogenesis is pancreatic β‑cells dysfunction or injury. It has been well established that inflammation leads to a gradual exhaustion of pancreatic β‑cell function with decreased β‑cell mass likely resulting from pancreatic β‑cells apoptosis or death. Vitexin, a major bioactive flavonoid compound in plants has numerous pharmacological properties, including antioxidant, anti‑inflammatory and antimyeloperoxidase. Whether vitexin can protect pancreatic β‑cells against lipopolysaccharide (LPS)‑induced pro‑inflammatory cytokine production and apoptosis has received little attention. The present study investigated the potential effects of vitexin on LPS‑induced pancreatic β‑cell injury and apoptosis. It was revealed that apoptosis and damage induced by LPS in islet tissue of rats and INS‑1 cells was significantly decreased in response to vitexin treatment. In addition, pretreatment with vitexin decreased the levels of the pro‑inflammatory cytokines tumor necrosis factor‑α and high mobility group box 1 (HMGB1) in LPS‑induced rats. Further experiments demonstrated that vitexin pretreatment suppressed the activation of P38 mitogen‑activated protein kinase signaling pathways in LPS‑induced INS‑1 cells. In conclusion, the results indicated that vitexin prevented LPS‑induced islet tissue damage in rats, and INS‑1 cells injury and apoptosis by inhibiting HMGB1 release. Therefore, the present study provided clear evidence indicating that vitexin may be a viable therapeutic strategy for the treatment of DM.

Naringin Decreases TNF-α and HMGB1 Release from LPS-Stimulated Macrophages and Improves Survival in a CLP-Induced Sepsis Mice

Naringin, a flavanone glycoside extracted from various plants, has a wide range of pharmacological effects. In the present study, we investigated naringin’s mechanism of action and its inhibitory effect on lipopolysaccharide-induced tumor necrosis factor-alpha and high-mobility group box 1 expression in macrophages, and on death in a cecal ligation and puncture induced mouse model of sepsis. Naringin increased heme oxygenase 1 expression in peritoneal macrophage cells through the activation of adenosine monophosphate-activated protein kinase, p38, and NF-E2-related factor 2. Inhibition of heme oxygenase 1 abrogated the naringin’s inhibitory effect on high-mobility group box 1 expression and NF-kB activation in lipopolysaccharide-stimulated macrophages. Moreover, mice pretreated with naringin (200 mg/kg) exhibited decreased sepsis-induced mortality and lung injury, and alleviated lung pathological changes. However, the naringin’s protective effects on sepsis-induced lung injury were eliminated by zinc protoporphyrin, a heme oxygenase 1 competitive inhibitor. These results revealed the mechanism underlying naringin’s protective effect in inflammation and may be beneficial for the treatment of sepsis.