SiO2 stimulates macrophage stress to induce the transformation of lung fibroblasts into myofibroblasts and its relationship with the sphingomyelin metabolic pathway.

Silicosis is a serious occupational disease with the highest incidence in China. However, its pathogenesis has not been fully elucidated. Studies have shown that the sphingomyelin signaling pathway may play an important role in different fibrotic diseases but its role in silicosis-mediated fibrosis is still unclear. In this study, the supernatant of human peripheral blood mononuclear cell line (THP-1)-derived macrophages exposed to silica (SiO2 ) was used to stimulate the transformation of human embryonic lung fibroblast cell line (HFL-1) into myofibroblasts, and the intervention effect of recombinant human acid ceramidase (rAC) was observed. The results showed that SiO2 stimulated the production of reactive oxygen species and malondialdehyde in the supernatant of THP-1-derived macrophages and increased the secretion of TGF-ß1, TNF-α, and IL-8. In addition, we found that the expression levels of α-SMA, FN, Col I, and Col III in HFL-1 cells increased. Meanwhile, the activities of ASMase and ACase and the expression levels of Cer, Sph, and S1P were increased. Intervention by rAC can suppress these changes to different degrees. In conclusion, the present study shows that SiO2 dust poisoning may stimulate HFL-1 cell differentiation into myofibroblasts by inducing oxidative stress in THP-1-derived macrophages, thereby promoting the secretion of a variety of inflammatory factors and activating the sphingolipid signaling pathway in HFL-1 cells. Exogenous rAC can effectively interfere with the stimulation of HFL-1 cells by silica in vitro.

Enhancement of LC3-associated efferocytosis for the alleviation of intestinal inflammation.

LC3-associated phagocytosis (LAP) is an instrumental machinery for the clearance of extracellular particles including apoptotic cells for the alleviation of inflammation. While pharmacological approaches to modulate LAP for inflammation regulation have been poorly explored, in our study we identified a novel compound, columbamine (COL), which can trigger LAP and enhance efferocytosis in an animal model of colitis to attenuate inflammation. We found that COL directly binds to and biasedly activates FPR2 (formyl peptide receptor 2) to promote efferocytosis and alleviate colitis. Biochemically, COL induces an interaction between RAC1 and the PIK3C3/VPS34-RUBCN/RUBICON complex, stimulating LC3-associated efferocytosis. These findings provide a novel interpretation of the potential roles of LAP in regulating inflammatory bowel disease (IBD), reveal the relationship between G protein-coupled receptors (GPCRs) and LAP, and highlight the role of RAC1 in regulating the PIK3C3/VPS34-RUBCN complex in LAP.

Synthetic Biomimetic Liposomes Harness Efferocytosis Machinery for Highly Efficient Macrophages-Targeted Drug Delivery to Alleviate Inflammation.

Macrophages play pivotal roles in the regulation of inflammatory responses and tissue repair, making them a prime target for inflammation alleviation. However, the accurate and efficient macrophages targeting is still a challenging task. Motivated by the efficient and specific removal of apoptotic cells by macrophages efferocytosis, a novel biomimetic liposomal system called Effero-RLP (Efferocytosis-mediated Red blood cell hybrid Liposomes) is developed which incorporates the membrane of apoptotic red blood cells (RBCs) with liposomes for the purpose of highly efficient macrophages targeting. Rosiglitazone (ROSI), a PPARγ agonist known to attenuate macrophage inflammatory responses, is encapsulated into Effero-RLP as model drug to regulate macrophage functions in DSS-induced colitis mouse model. Intriguingly, the Effero-RLP exhibits selective and efficient uptake by macrophages, which is significantly inhibited by the efferocytosis blocker Annexin V. In animal models, the Effero-RLP demonstrates rapid recognition by macrophages, leading to enhanced accumulation at inflammatory sites. Furthermore, ROSI-loaded Effero-RLP effectively alleviates inflammation and protects colon tissue from injury in the colitis mouse model, which is abolished by deletion of macrophages from mice model. In conclusion, the study highlights the potential of macrophage targeting using efferocytosis biomimetic liposomes. The development of Effero-RLP presents novel and promising strategies for alleviating inflammation.

Targeting macrophage autophagy for inflammation resolution and tissue repair in inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic, non-specific, recurrent inflammatory disease, majorly affecting the gastrointestinal tract. Due to its unclear pathogenesis, the current therapeutic strategy for IBD is focused on symptoms alleviation. Autophagy is a lysosome-mediated catabolic process for maintaining cellular homeostasis. Genome-wide association studies and subsequent functional studies have highlighted the critical role of autophagy in IBD via a number of mechanisms, including modulating macrophage function. Macrophages are the gatekeepers of intestinal immune homeostasis, especially involved in regulating inflammation remission and tissue repair. Interestingly, many autophagic proteins and IBD-related genes have been revealed to regulate macrophage function, suggesting that macrophage autophagy is a potentially important process implicated in IBD regulation. Here, we have summarized current understanding of macrophage autophagy function in pathogen and apoptotic cell clearance, inflammation remission and tissue repair regulation in IBD, and discuss how this knowledge can be used as a strategy for IBD treatment.

Enhancement of efferocytosis through biased FPR2 signaling attenuates intestinal inflammation.

Efficient clearance of dying cells (efferocytosis) is an evolutionarily conserved process for tissue homeostasis. Genetic enhancement of efferocytosis exhibits therapeutic potential for inflammation resolution and tissue repair. However, pharmacological approaches to enhance efferocytosis remain sparse due to a lack of targets for modulation. Here, we report the identification of columbamine (COL) which enhances macrophage-mediated efferocytosis and attenuates intestinal inflammation in a murine colitis model. COL enhances efferocytosis by promoting LC3-associated phagocytosis (LAP), a non-canonical form of autophagy. Transcriptome analysis and pharmacological characterization revealed that COL is a biased agonist that occupies a part of the ligand binding pocket of formyl peptide receptor 2 (FPR2), a G-protein coupled receptor involved in inflammation regulation. Genetic ablation of the Fpr2 gene or treatment with an FPR2 antagonist abolishes COL-induced efferocytosis, anti-colitis activity and LAP. Taken together, our study identifies FPR2 as a potential target for modulating LC3-associated efferocytosis to alleviate intestinal inflammation and highlights the therapeutic value of COL, a natural and biased agonist of FPR2, in the treatment of inflammatory bowel disease.

Ferulic Acid in Animal Models of Alzheimer's Disease: A Systematic Review of Preclinical Studies.

Alzheimer's disease (AD) is a neurodegenerative disease with a high incidence in the elderly. Many preclinical studies show that a natural product, ferulic acid (FA), displays neuroprotective effects in AD models. This review aims to systematically review and meta-analyze published pre-clinical researches about the effects, mechanism, and clinical prospects of FA in the treatment of AD. According to the pre-determined search strategy and inclusion criteria, a total of 344 animals in 12 papers were included in the meta-analysis. We used the fixed effects model to analyze data and I2 and p values to indicate heterogeneity. Results show that FA treatment can effectively improve rodents' spatial memory ability in MWM and Y maze experiments (I2 ≥ 70, p < 0.005), and reduce the deposition of Aß in the brains of various model animals (I2 ≥ 50, p < 0.005). The potential mechanisms include anti-amyloidogenesis, anti-inflammation, anti-oxidation, mitochondrial protection, and inhibition of apoptosis. In conclusion, we systematically review and meta-analyze the literature reporting the effects of FA treatment on AD rodent models and solidify the benefits of FA in reducing Aß deposition and improving memory in preclinical experiments. We also point out the limitations in the current research design and provide a strategy for the production research of FA in the future.

Pharmacological insights into autophagy modulation in autoimmune diseases.

As a cellular bulk degradation and survival mechanism, autophagy is implicated in diverse biological processes. Genome-wide association studies have revealed the link between autophagy gene polymorphisms and susceptibility of autoimmune diseases including systemic lupus erythematosus (SLE) and inflammatory bowel disease (IBD), indicating that autophagy dysregulation may be involved in the development of autoimmune diseases. A series of autophagy modulators have displayed protective effects on autoimmune disease models, highlighting the emerging role of autophagy modulators in treating autoimmune diseases. This review explores the roles of autophagy in the autoimmune diseases, with emphasis on four major autoimmune diseases [SLE, rheumatoid arthritis (RA), IBD, and experimental autoimmune encephalomyelitis (EAE)]. More importantly, the therapeutic potentials of small molecular autophagy modulators (including autophagy inducers and inhibitors) on autoimmune diseases are comprehensively analyzed.

PI3KC3 complex subunit NRBF2 is required for apoptotic cell clearance to restrict intestinal inflammation.

NRBF2, a regulatory subunit of the ATG14-BECN1/Beclin 1-PIK3C3/VPS34 complex, positively regulates macroautophagy/autophagy. In this study, we report that NRBF2 is required for the clearance of apoptotic cells and alleviation of inflammation during colitis in mice. NRBF2-deficient mice displayed much more severe colitis symptoms after the administration of ulcerative colitis inducer, dextran sulfate sodium salt (DSS), accompanied by prominent intestinal inflammation and apoptotic cell accumulation. Interestingly, we found that nrbf2-/- mice and macrophages displayed impaired apoptotic cell clearance capability, while adoptive transfer of nrbf2+/+ macrophages to nrbf2-/- mice alleviated DSS-induced colitis lesions. Mechanistically, NRBF2 is required for the generation of the active form of RAB7 to promote the fusion between phagosomes containing engulfed apoptotic cells and lysosomes via interacting with the MON1-CCZ1 complex and regulating the guanine nucleotide exchange factor (GEF) activity of the complex. Evidence from clinical samples further reveals the physiological role of NRBF2 in maintaining intestinal homeostasis. In biopsies of UC patient colon, we observed upregulated NRBF2 in the colon macrophages and the engulfment of apoptotic cells by NRBF2-positive cells, suggesting a potential protective role for NRBF2 in UC. To confirm the relationship between apoptotic cell clearance and IBD development, we compared TUNEL-stained cell counts in the UC with UC severity (Mayo Score) and observed a strong correlation between the two indexes, indicating that apoptotic cell population in colon tissue correlates with UC severity. The findings of our study reveal a novel role for NRBF2 in regulating apoptotic cell clearance to restrict intestinal inflammation.Abbreviation: ANOVA: analysis of variance; ATG14: autophagy related 14; ATG16L1: autophagy related 16-like 1 (S. cerevisiae); BMDM: bone marrow-derived macrophage; BSA: bovine serum albumin; CD: Crohn disease; CD68: CD68 molecule; CFP: cyan fluorescent protein; CMFDA: 5-chloromethylfluorescein diacetate; Co-IP, co-immunoprecipitation; CPR: C-reactive protein; Cy7: cyanine 7 maleimide; DAB: diaminobezidine 3; DAI: disease activity indexes; DAPI: 4'6-diamidino-2-phenylindole; DMEM: dulbecco's modified eagle's medium; DMSO: dimethyl sulfoxide; DOC: sodium deoxycholate; DSS: dextran sulfate sodium; EDTA: ethylenediaminetetraacetic acid; EGTA: ethylenebis (oxyethylenenitrilo) tetraacetic acid; FBS: fetal bovine serum; FITC: fluorescein isothiocyanate; FRET: Förster resonance energy transfer; GDP: guanine dinucleotide phosphate; GEF: guanine nucleotide exchange factor; GFP: green fluorescent protein; GTP: guanine trinucleotide phosphate; GWAS: genome-wide association studies; HEK293: human embryonic kidney 293 cells; HRP: horseradish peroxidase; IBD: inflammatory bowel disease; IgG: immunoglobin G; IL1B/IL-1ß: interleukin 1 beta; IL6: interleukin 6; IRGM: immunity related GTPase M; ITGAM/CD11b: integrin subunit alpha M; KO: knockout; LRRK2: leucine rich repeat kinase 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MPO: myeloperoxidase; NaCl: sodium chloride; NEU: neutrophil; NOD2: nucleotide binding oligomerization domain containing 2; NP40: nonidet-P40; NRBF2: nuclear receptor binding factor 2; PBS: phosphate buffer saline; PCR: polymerase chain reaction; PE: P-phycoerythrin; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3P: phosphatidylinositol-3-phosphate; PTPRC/CD45: protein tyrosine phosphatase receptor type C; SDS-PAGE: sodium dodecylsulphate-polyacrylamide gel electrophoresis; TBST: tris-buffered saline Tween-20; Tris-HCl: trihydroxymethyl aminomethane hydrochloride; TUNEL: TdT-mediated dUTP nick-end labeling; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; WB: western blotting; WT: wild type; YFP: yellow fluorescent protein.

Corrigendum: The Role of S1P and the Related Signaling Pathway in the Development of Tissue Fibrosis.

[This corrects the article DOI: 10.3389/fphar.2018.01504.].

The Role of S1P and the Related Signaling Pathway in the Development of Tissue Fibrosis.

Tissue fibrosis, including pulmonary fibrosis, hepatic fibrosis, and cardiac fibrosis, is an important stage in the development of many diseases. It can lead to structural damage and dysfunction and even severe carcinogenesis or death. There is currently no effective method for the treatment of fibrosis. At present, the molecular mechanism of tissue fibrosis has not yet been fully elucidated, but many studies have demonstrated that it is involved in conveying the complex messages between fibroblasts and various cytokines. Sphingosine 1-phosphate (S1P) is a naturally bioactive sphingolipid. S1P and the related signaling pathways are important intracellular metabolic pathways involved in many life activities, including cell proliferation, differentiation, apoptosis, and cellular signal transduction. Increasing evidence suggests that S1P and its signaling pathways play an important role in the development of tissue fibrosis; however, the mechanisms of these effects have not yet been fully elucidated, and even the role of S1P and its signaling pathways are still controversial. This article focuses on the role of S1P and the related signaling pathways in the development of fibrosis of lung, liver, heart, and other tissues, with emphasis on the application of inhibitors of some of molecules in the pathway in clinical treatment of fibrosis diseases.