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The present study sought to investigate the association between silent information regulator 1 (SIRT1) and autophagy during systemic inflammatory response syndrome following burn injury. The experimental burn model in mice and macrophages were established. SIRT1 mRNA expression was quantified by quantitative real-time PCR. The protein levels of SIRT1 and the conversion of light chain 3 (LC3)-I to LC3-II were determined by western blot analysis. The formation of autophagosomes was assessed by green fluorescence protein-tagged LC3 fluorescence. The contents of inflammatory cytokines interleukin (IL)-1, IL-6, IL-10 and IL-18 were measured by ELISA. SIRT1 was highly expressed in burned tissues and RAW264.7 cells treated with serum obtained from mice with burn injuries. Moreover, SIRT1 overexpression augmented, whereas sirtinol, an inhibitor of SIRT1, attenuated burn injury-induced increasing number of autophagosomes and expression levels of LC3-II/LC3-I in RAW264.7 cells. Besides, sirtinol effectively prevented SIRT1-induced pro-inflammation during burn injury. Furthermore, autophagy inhibition by 3-methyladenine significantly attenuated SIRT1 overexpression-mediated pro-inflammatory cytokine production. SIRT1 abolished burn injury-induced inflammatory response by inducing autophagy., Competing Interests: Competing interests: None declared., (© American Federation for Medical Research 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Sepsis is a complex inflammatory disorder in which high mortality is associated with an excessive inflammatory response. Inhibitor of growth 4 (ING4), which is a cofactor of histone acetyltransferase and histone deacetylase complexes, could negatively regulate this inflammation. However, the exact molecular signaling pathway regulated by ING4 remains uncertain. As a pivotal histone deacetylase, Sirtuin1 (SIRT1), which is widely accepted to be an anti-inflammatory molecule, has not been found to be linked to ING4. This study investigated how ING4 is involved in the regulation of inflammation by constructing lipopolysaccharide (LPS)-induced macrophage and mouse sepsis models. Our results revealed that ING4 expression decreased, whereas the levels of proinflammatory cytokines increased in LPS-stimulated cultured primary macrophages and RAW 264.7 cells. ING4 transfection was confirmed to alleviate the LPS-induced upregulation of proinflammatory cytokine expression both in vitro and in vivo. In addition, ING4-overexpressing mice were hyposensitive to an LPS challenge and displayed reduced organ injury. Furthermore, immunoprecipitation indicated a direct interaction between ING4 and the SIRT1 protein. Moreover, ING4 could block nuclear factor-kappa B (NF-κB) P65 nuclear translocation and restrict P65 acetylation at lysine 310 induced by LPS treatment. These results are the first to clarify that the anti-inflammatory role of ING4 is associated with SIRT1, through which ING4 inhibits NF-κB signaling activation. Our studies provide a novel signaling axis involving ING4/SIRT1/NF-κB in LPS-induced sepsis., (© 2020 The Authors. Immunology & Cell Biology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Systemic inflammatory response syndrome (SIRS) is associated with excessive inflammatory response, however, the pathophysiology of inflammation is poorly understood. The retinoid-related orphan receptor α (RORα) is a key inflammatory regulator, but the mechanisms underlying its role remain unclear. The aim of this study was to investigate how RORα was involved in the regulation of inflammatory response. Here we put forward a hypothesis that RORα might negatively regulate inflammatory response by controlling silent information regulator Sirtuin 1 (SIRT1) expression. Stimulation of macrophages in vitro with LPS and LPS administration in vivo were used to explore the function of RORα and the relationship between RORα and SIRT1. We found that the level of RORα was suppressed in macrophages stimulated with LPS and overexpression or knockdown of RORα by transfection with lentivirus or siRNAs significantly decreased or increased, respectively, the pro-inflammatory cytokines IL-1β, TNF, IL-6 and MCP-1. Importantly, overexpression of RORα suppressed inflammation and alleviated LPS-induced organ injury in vivo. Further study showed that RORα could regulate SIRT1 expression and, consequently, affect deacetyation and nuclear translocation of nuclear factor-kappa B (NF-κB) subunit p65. Moreover, the activation of SIRT1 by its specific agonist, SR1720, could reduce the expression of proinflammatory cytokines in RORα knockdown macrophages stimulated with LPS. In conclusion, we demonstrated that RORα could alleviate LPS-induced inflammation and organ injury both in vivo and in vitro by blocking NF-κB p65 nuclear translocation and restricting acetylation of NF-κB p65 at lysine 310 via the regulation of SIRT1 expression. Targeting RORα might be a promising therapeutic strategy to regulate inflammatory disorders., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Trauma or burn injuries that affect the deep dermis often produce a hypertrophic scar, which limits patients' joint movement and generates an aesthetic problem. Inflammation is believed to be one of the main pathogenic mechanisms. We found that IL-17 was increased in scar tissues from patients with hypertrophic scar compared with normal skin. Recombinant mouse IL-17 was subcutaneously injected into mice that underwent full-thickness excision surgery to investigate the role of IL-17 in scar formation. Mice stimulated with IL-17 showed aggravated fibrogenesis, delayed wound healing, and increased inflammation. In addition, macrophage infiltration was also increased. According to the results of the Transwell assay, IL-17 promoted macrophage infiltration through an indirect mechanism. After depleting macrophages with clodronate liposomes, the effect of IL-17 disappeared. Levels of monocyte chemotactic protein (MCP) 1, MCP2, and MCP3 (together referred to as MCPs) were increased by IL-17 stimulation. Bindarit (an inhibitor of MCPs) was used to verify the role of MCPs. In addition, the Ly6C-low macrophages were responsible for wound fibrogenesis in mice. In this study, we detected the increased levels of IL-17 for the first time and revealed that IL-17 induced the infiltration of a specific subtype of macrophages to aggravate fibrosis through an MCP-dependent mechanism. Thus, our results provide a better understanding of scar formation and new strategies for scar prevention., (Copyright © 2018 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Molecular mechanisms for macrophage immune responses modulated by SIRT1 during sepsis remain unclear. Here, we show that SIRT1 expression is down-regulated in macrophages from mouse sepsis model or LPS stimulation. SIRT1 expression in macrophages correlates with low levels of a long noncoding RNA (lncRNA)-NONMMUT003701 [named as lncRNA-CCL2]. SIRT1 inhibits lncRNA-CCL2 expression via sustaining a repressive chromatin state in the lncRNA-CCL2 locus. The inflammation cytokines expression is downregulated by knockdown of lncRNA-CCL2. Such inhibition can be reversed partly by decreased SIRT1 activity. Thus, this work uncovers previously unidentified mechanisms in which SIRT1 associates with lncRNA and lncRNA regulates macrophage inflammatory response., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The type III histone deacetylase SIRT1 has recently emerged as a critical immune regulator by suppressing T-cell immunity and macrophage activation during inflammation, but its mechanism in regulating inflammatory response in macrophages remains unclear. Here we show that the expression of SIRT1 in macrophage cells decreased following the release of inflammation cytokines when the cells were stimulated with LPS. IRF8, an important regulator in monocyte differentiation and macrophage polarization, showed the opposite trend, with SIRT1 expression levels increasing after the cells treated with LPS. Co-immunoprecipitation and immunofluorescence experiments showed that SIRT1 could not only interact with IRF8, but also deacetylate it. LPS treatment had no effect on the expression of IRF8 in macrophage cells in which sirt1 was specifically deleted. Our results show that IRF8 may be the target of histone deacetylase SIRT1 to regulate the inflammation in the macrophage cells.

The present study sought to investigate the association between silent information regulator 1 (SIRT1) and autophagy during systemic inflammatory response syndrome following burn injury. The experimental burn model in mice and macrophages were established. SIRT1 mRNA expression was quantified by quantitative real-time PCR. The protein levels of SIRT1 and the conversion of light chain 3 (LC3)-I to LC3-II were determined by western blot analysis. The formation of autophagosomes was assessed by green fluorescence protein-tagged LC3 fluorescence. The contents of inflammatory cytokines interleukin (IL)-1, IL-6, IL-10 and IL-18 were measured by ELISA. SIRT1 was highly expressed in burned tissues and RAW264.7 cells treated with serum obtained from mice with burn injuries. Moreover, SIRT1 overexpression augmented, whereas sirtinol, an inhibitor of SIRT1, attenuated burn injury-induced increasing number of autophagosomes and expression levels of LC3-II/LC3-I in RAW264.7 cells. Besides, sirtinol effectively prevented SIRT1-induced pro-inflammation during burn injury. Furthermore, autophagy inhibition by 3-methyladenine significantly attenuated SIRT1 overexpression-mediated pro-inflammatory cytokine production. SIRT1 abolished burn injury-induced inflammatory response by inducing autophagy. [ABSTRACT FROM AUTHOR]

Background/Aims: Inflammation is an essential component of innate immunity against pathogens, but is tightly regulated, such as by Krüppel-like factor 4 (Klf4), to prevent injury. Klf4 also regulates macrophage polarization, although the mechanisms underlying both functions are poorly understood. The aim of this study was to investigate whether and how Klf4 prevents unregulated inflammation. Methods: The bone marrow-derived macrophages and RAW264.7 cell line were used. Quantitative real-time PCR was used to determine inflammatory cytokines (IL-1β, TNF-α, IL-6 and MCP-1), Klf4 and MCPIP1 transcript levels. Extraction of nuclear and cytoplasmic proteins and Immunoblotting were used to determine Klf4, MCPIP1, relative kinases from NF-κB pathway and K63-linked polyubiquitins expression in nucleus and cytoplasm separately. Dual luciferase reporter assay was used to analyze whether Klf4 mediate MCPIP1 transcription. Immunoprecipitation was used to determine the protein interaction among Klf4, MCPIP1, TRAF6 and K63-linked polyubiquitins. Secretion of IL-1β and TNF-α into sera in mice was measured by Enzyme-linked immunosorbent assay. Results: We found that exposure to lipopolysaccharides suppresses Klf4 expression, even as it induces release of pro-inflammatory cytokines. Strikingly, Klf4 overexpression significantly lowered cytokine secretion and NF-κB signaling in the cytoplasm following exposure to lipopolysaccharide, even though Klf4 was exclusively nuclear. The cytoplasmic effects are likely mediated by MCP-1 induced protein 1 (MCPIP1), a deubiquitinase and a key modulator of inflammation that accumulates both in the nucleus and cytoplasm in response to Klf4. Indeed, binding between MCPIP1 and K63 polyubiquitins is attenuated in macrophages overexpressing Klf4, suggesting that MCPIP1 is an intermediator induced by Klf4 in the nucleus to remove K63 polyubiquitins from TRAF6 in the cytoplasm, and thereby impede NF-κB and inflammatory signaling. Importantly, Klf4 overexpression in mice alleviated sepsis symptoms following exposure to lipopolysaccharides. Conclusion: The data highlight Klf4 as an essential MCPIP1-dependent modulator of innate immunity that protects against excessive and self-destructive inflammation. [ABSTRACT FROM AUTHOR]

Abstract MicroRNA-146a is a well-studied microRNA participating in immune and inflammatory diseases, but its role in sepsis has not been investigated. Here in our study, we found increased level of microRNA-146a in macrophage stimulated by lipopolysaccharide. In addition, the mRNA level of Notch1 was also increased. Up-regulation of microRNA-146a by miR-146a-mimic alleviated inflammatory responses of macrophage, for the levels of IL-1β, IL-6 and CCL-2 were decreased, and the activation of NF-κB signaling was inhibited. The histological examination showed that microRNA-146a protected against organ damage in mice with lipopolysaccharide injection, and the level of inflammatory factors, Cr, BUN, AST and ALT in serum were all decreased, reflecting the alleviated inflammation and recovered organ function. Then predicting databases were used and Notch1 was predicted as one of the potential targets of microRNA-146a. Knockout of Notch1 in macrophage showed reduced secretion of inflammatory factors and attenuated activation of NF-κB signaling in response to lipopolysaccharide. Specifically knockout of Notch1 in macrophage protected mice from LPS induced organ damage and dysfunction. Therefore, we prove that miR-146a acts as an inhibitor of inflammation by targeting Notch1 in macrophage, therefore protects mice from organ damage in sepsis. Highlights • LPS increased miR-146a in macrophage. • miR-146a decreased inflammatory response of macrophage and protected against organ damage induced by LPS. • miR-146a directly targeted Notch1 to anti-inflammation. [ABSTRACT FROM AUTHOR]