Project description:Obesity-associated insulin resistance is characterized by a state of chronic, low-grade inflammation that is associated with the accumulation of M1 proinflammatory macrophages in adipose tissue. Although different evidence explains the mechanisms linking the expansion of adipose tissue and adipose tissue macrophage (ATM) polarization, in the current study we investigated the concept of lipid-induced toxicity as the pathogenic link that could explain the trigger of this response. We addressed this question using isolated ATMs and adipocytes from genetic and diet-induced murine models of obesity. Through transcriptomic and lipidomic analysis, we created a model integrating transcript and lipid species networks simultaneously occurring in adipocytes and ATMs and their reversibility by thiazolidinedione treatment. We show that polarization of ATMs is associated with lipid accumulation and the consequent formation of foam cell–like cells in adipose tissue. Our study reveals that early stages of adipose tissue expansion are characterized by M2-polarized ATMs and that progressive lipid accumulation within ATMs heralds the M1 polarization, a macrophage phenotype associated with severe obesity and insulin resistance. Furthermore, rosiglitazone treatment, which promotes redistribution of lipids toward adipocytes and extends the M2 ATM polarization state, prevents the lipid alterations associated with M1 ATM polarization. Our data indicate that the M1 ATM polarization in obesity might be a macrophage-specific manifestation of a more general lipotoxic pathogenic mechanism. This indicates that strategies to optimize fat deposition and repartitioning toward adipocytes might improve insulin sensitivity by preventing ATM lipotoxicity and M1 polarization. 15 samples; 2 genotypes and 2 time points
Project description:We report the differential gene expression between ECM1- sufficient and -deficient peritoneal macrophage. Inflammatory bowel disease (IBD) comprises chronic relapsing disorders of the gastrointestinal tract characterized pathologically by intestinal inflammation and epithelial injury. Here, we uncover a new function of extracellular matrix protein 1 (ECM1) in promoting the pathogenesis of human and mouse IBD. ECM1 was highly expressed in macrophages, particularly tissue-infiltrated macrophages under inflammatory conditions, and ECM1 expression was significantly induced during IBD progression. The macrophage-specific knockout of ECM1 resulted in increased arginase 1 (ARG1) expression and impaired polarization into the M1 macrophage phenotype following LPS treatment.RNA-sequencing data indicated an alternative metabolic process and a higher arginine metabolic level in ECM1-deficient macrophages compared with ECM1-sufficient macrophages. A mechanistic study showed that ECM1 can negatively regulate M1 macrophage polarization through the GM-CSF/STAT5 signalling pathway. Pathological changes in mice with dextran sodium sulphate-induced IBD were alleviated by the specific knockout of the ECM1 gene in macrophages. Taken together, our findings show that ECM1 has an important function in promoting M1 macrophage polarization, which is critical for controlling inflammation and tissue repair in the intestine.
Project description:Background: Macrophages are a heterogeneous cell population which in response to the cytokine milieu polarize in either classically activated macrophages (M1) or alternatively activated macrophages (M2). This plasticity makes macrophages essential in regulating inflammation, immune response and tissue remodeling and a novel therapeutic target in inflammatory diseases such as atherosclerosis. The aim of the study was to describe the transcriptomic profiles of differently polarized human macrophages to generate new hypotheses on the biological function of the different macrophage subtypes. Methods and Results: M1 polarization was obtained by IFN-γ and LPS, M2a by IL-4, whereas IL-10 induced a “deactivated” state (M2c). Transcription profile of M1, M2a and M2c macrophages was performed at 6, 12 and 24h after polarization with Whole Human Genome Agilent Microarray technique. Gene Ontology (GO) classification revealed that M1 showed a significant up-regulation whereas M2a a down-regulation of GO terms involved in immunity and inflammation compared to resting macrophage (RM). Unexpectedly, canonical and non-canonical Wnt genes and gene groups, promoting inflammation and tissue remodeling, were up-regulated in M2a compared to RM. Key results were confirmed by real time-PCR. Conclusion: Results from gene expression profile confirmed the specific properties of differentially polarized macrophages. However, the enhanced expression of canonical and non-canonical Wnt pathways in M2a suggests a possible dual role for alternative activation in the modulation of low-grade inflammation. Four-condition experiment, RM, M1, M2a, M2c. Three point of time course, three replicates for each condition. Dual color experiment, reference sample: human leucocytes
Project description:TNF-mediated macrophage polarization is important for inflammatory disease pathogenesis, but mechanisms that regulate polarization are not well understood. Transcriptomic and epigenomic analysis of the TNF response in primary human macrophages revealed late phase activation of SREBP2, the master regulator of cholesterol biosynthesis genes. TNF stimulation extended the genomic profile of SREBP2 occupancy to include binding to and activation of inflammatory and interferon response genes independently of its functions in sterol metabolism. Genetic ablation of SREBP function shifted the balance of macrophage polarization from M1 to an M2-like reparative phenotype in peritonitis and skin wound healing models. Genetic ablation of SREBP activity in myeloid cells or topical pharmacological inhibition of SREBP improved skin wound healing under homeostatic and chronic inflammatory conditions. Our results identify a new function and mechanism of action for SREBP2 in augmenting TNF-induced M1 macrophage polarization and inflammation, and open therapeutic avenues for promoting wound repair.
Project description:TNF-mediated macrophage polarization is important for inflammatory disease pathogenesis, but mechanisms that regulate polarization are not well understood. Transcriptomic and epigenomic analysis of the TNF response in primary human macrophages revealed late phase activation of SREBP2, the master regulator of cholesterol biosynthesis genes. TNF stimulation extended the genomic profile of SREBP2 occupancy to include binding to and activation of inflammatory and interferon response genes independently of its functions in sterol metabolism. Genetic ablation of SREBP function shifted the balance of macrophage polarization from M1 to an M2-like reparative phenotype in peritonitis and skin wound healing models. Genetic ablation of SREBP activity in myeloid cells or topical pharmacological inhibition of SREBP improved skin wound healing under homeostatic and chronic inflammatory conditions. Our results identify a new function and mechanism of action for SREBP2 in augmenting TNF-induced M1 macrophage polarization and inflammation, and open therapeutic avenues for promoting wound repair.
Project description:TNF-mediated macrophage polarization is important for inflammatory disease pathogenesis, but mechanisms that regulate polarization are not well understood. Transcriptomic and epigenomic analysis of the TNF response in primary human macrophages revealed late phase activation of SREBP2, the master regulator of cholesterol biosynthesis genes. TNF stimulation extended the genomic profile of SREBP2 occupancy to include binding to and activation of inflammatory and interferon response genes independently of its functions in sterol metabolism. Genetic ablation of SREBP function shifted the balance of macrophage polarization from M1 to an M2-like reparative phenotype in peritonitis and skin wound healing models. Genetic ablation of SREBP activity in myeloid cells or topical pharmacological inhibition of SREBP improved skin wound healing under homeostatic and chronic inflammatory conditions. Our results identify a new function and mechanism of action for SREBP2 in augmenting TNF-induced M1 macrophage polarization and inflammation, and open therapeutic avenues for promoting wound repair.
Project description:TNF-mediated macrophage polarization is important for inflammatory disease pathogenesis, but mechanisms that regulate polarization are not well understood. Transcriptomic and epigenomic analysis of the TNF response in primary human macrophages revealed late phase activation of SREBP2, the master regulator of cholesterol biosynthesis genes. TNF stimulation extended the genomic profile of SREBP2 occupancy to include binding to and activation of inflammatory and interferon response genes independently of its functions in sterol metabolism. Genetic ablation of SREBP function shifted the balance of macrophage polarization from M1 to an M2-like reparative phenotype in peritonitis and skin wound healing models. Genetic ablation of SREBP activity in myeloid cells or topical pharmacological inhibition of SREBP improved skin wound healing under homeostatic and chronic inflammatory conditions. Our results identify a new function and mechanism of action for SREBP2 in augmenting TNF-induced M1 macrophage polarization and inflammation, and open therapeutic avenues for promoting wound repair.
Project description:Macrophage polarization followed by acute myocardial infarction (MI) is essential for the regulation of inflammation and scar formation. Tripartite motif-containing protein 21 (TRIM21), a member of E3 ubiquitin ligases, is a crucial mediator in the process of inflammation and heart failure. However, the potential roles of TRIM21 in modulating post-MI inflammation and macrophage polarization remain elusive. We detected that the levels of TRIM21 were significantly reduced in macrophages of WT mice after MI. In contrast, MI was ameliorated in TRIM21 knockout (TRIM21-/-) mice with improved cardiac remodeling, characterized by a marked decrease in mortality, increased wall thickness, and improved cardiac function in comparison with wild-type (WT) MI mice. Importantly, TRIM21 deficiency decreased the post-MI apoptosis and DNA damage in the hearts of mice, and the accumulation of M1 phenotype macrophages in infarcted hearts significantly decreased in TRIM21-/- mice compared with WT controls. Mechanistically, depletion of TRIM21 orchestrated the process of M1 macrophage polarization via a PI3K/Akt signaling pathway. Overall, these data reveal that TRIM21 drives the inflammatory response and cardiac remodeling after MI via stimulating M1 macrophage polarization through a PI3K/Akt signaling pathway.
Project description:Obesity-associated insulin resistance is characterized by a state of chronic, low-grade inflammation that is associated with the accumulation of M1 proinflammatory macrophages in adipose tissue. Although different evidence explains the mechanisms linking the expansion of adipose tissue and adipose tissue macrophage (ATM) polarization, in the current study we investigated the concept of lipid-induced toxicity as the pathogenic link that could explain the trigger of this response. We addressed this question using isolated ATMs and adipocytes from genetic and diet-induced murine models of obesity. Through transcriptomic and lipidomic analysis, we created a model integrating transcript and lipid species networks simultaneously occurring in adipocytes and ATMs and their reversibility by thiazolidinedione treatment. We show that polarization of ATMs is associated with lipid accumulation and the consequent formation of foam cell–like cells in adipose tissue. Our study reveals that early stages of adipose tissue expansion are characterized by M2-polarized ATMs and that progressive lipid accumulation within ATMs heralds the M1 polarization, a macrophage phenotype associated with severe obesity and insulin resistance. Furthermore, rosiglitazone treatment, which promotes redistribution of lipids toward adipocytes and extends the M2 ATM polarization state, prevents the lipid alterations associated with M1 ATM polarization. Our data indicate that the M1 ATM polarization in obesity might be a macrophage-specific manifestation of a more general lipotoxic pathogenic mechanism. This indicates that strategies to optimize fat deposition and repartitioning toward adipocytes might improve insulin sensitivity by preventing ATM lipotoxicity and M1 polarization.