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Liang N, Hennebelle M, Gaul S, Johnson CD, Zhang Z, Kirpich IA, McClain CJ, Feldstein AE, Ramsden CE, Taha AY. Feeding mice a diet high in oxidized linoleic acid metabolites does not alter liver oxylipin concentrations. Prostaglandins Leukot Essent Fatty Acids 2021; 172:102316. [PMID: 34403987 PMCID: PMC9157566 DOI: 10.1016/j.plefa.2021.102316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 06/11/2021] [Accepted: 06/17/2021] [Indexed: 11/19/2022]
Abstract
The oxidation of dietary linoleic acid (LA) produces oxidized LA metabolites (OXLAMs) known to regulate multiple signaling pathways in vivo. Recently, we reported that feeding OXLAMs to mice resulted in liver inflammation and apoptosis. However, it is not known whether this is due to a direct effect of OXLAMs accumulating in the liver, or to their degradation into bioactive shorter chain molecules (e.g. aldehydes) that can provoke inflammation and related cascades. To address this question, mice were fed a low or high LA diet low in OXLAMs, or a low LA diet supplemented with OXLAMs from heated corn oil (high OXLAM diet). Unesterified oxidized fatty acids (i.e. oxylipins), including OXLAMs, were measured in liver after 8 weeks of dietary intervention using ultra-high pressure liquid chromatography coupled to tandem mass-spectrometry. The high OXLAM diet did not alter liver oxylipin concentrations compared to the low LA diet low in OXLAMs. Significant increases in several omega-6 derived oxylipins and reductions in omega-3 derived oxylipins were observed in the high LA dietary group compared to the low LA group. Our findings suggest that dietary OXLAMs do not accumulate in liver, and likely exert pro-inflammatory and pro-apoptotic effects via downstream secondary metabolites.
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Kaufmann B, Reca A, Kim AD, Feldstein AE. Novel Mechanisms for Resolution of Liver Inflammation: Therapeutic Implications. Semin Liver Dis 2021; 41:150-162. [PMID: 34107544 DOI: 10.1055/s-0041-1723031] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Traditional concepts have classically viewed resolution of inflammation as a passive process yet insight into the pathways by which inflammation is resolved has challenged this idea. Resolution has been revealed as a highly dynamic and active event that is essential to counteract the dysregulated inflammatory response that drives diverse disease states. Abrogation of the hepatic inflammatory response through the stimulation of proresolving mechanisms represents a new paradigm in the setting of chronic inflammatory-driven liver diseases. Elucidation of the role of different cells of the innate and adaptive immune system has highlighted the interplay between them as an important orchestrator of liver repair. A finely tuned interaction between neutrophils and macrophages has risen as revolutionary mechanism that drives the restoration of hepatic function and architecture. Specialized proresolving mediators have also been shown to act as stop signals of the inflammatory response and promote resolution as well as tissue regeneration. In this review, we discuss the discovery and understanding of the mechanisms by which inflammation is resolved and highlight novel proresolving pathways that represent promising therapeutic strategies.
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Daemen S, Gainullina A, Kalugotla G, He L, Chan MM, Beals JW, Liss KH, Klein S, Feldstein AE, Finck BN, Artyomov MN, Schilling JD. Dynamic Shifts in the Composition of Resident and Recruited Macrophages Influence Tissue Remodeling in NASH. Cell Rep 2021; 34:108626. [PMID: 33440159 PMCID: PMC7877246 DOI: 10.1016/j.celrep.2020.108626] [Citation(s) in RCA: 158] [Impact Index Per Article: 52.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 10/22/2020] [Accepted: 12/18/2020] [Indexed: 02/07/2023] Open
Abstract
Macrophage-mediated inflammation is critical in the pathogenesis of non-alcoholic steatohepatitis (NASH). Here, we describe that, with high-fat, high-sucrose-diet feeding, mature TIM4pos Kupffer cells (KCs) decrease in number, while monocyte-derived Tim4neg macrophages accumulate. In concert, monocyte-derived infiltrating macrophages enter the liver and consist of a transitional subset that expresses Cx3cr1/Ccr2 and a second subset characterized by expression of Trem2, Cd63, Cd9, and Gpmnb; markers ascribed to lipid-associated macrophages (LAMs). The Cx3cr1/Ccr2-expressing macrophages, referred to as C-LAMs, localize to macrophage aggregates and hepatic crown-like structures (hCLSs) in the steatotic liver. In C-motif chemokine receptor 2 (Ccr2)-deficient mice, C-LAMs fail to appear in the liver, and this prevents hCLS formation, reduces LAM numbers, and increases liver fibrosis. Taken together, our data reveal dynamic changes in liver macrophage subsets during the pathogenesis of NASH and link these shifts to pathologic tissue remodeling.
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Gaul S, Leszczynska A, Alegre F, Kaufmann B, Johnson CD, Adams LA, Wree A, Damm G, Seehofer D, Calvente CJ, Povero D, Kisseleva T, Eguchi A, McGeough MD, Hoffman HM, Pelegrin P, Laufs U, Feldstein AE. Hepatocyte pyroptosis and release of inflammasome particles induce stellate cell activation and liver fibrosis. J Hepatol 2021; 74:156-167. [PMID: 32763266 PMCID: PMC7749849 DOI: 10.1016/j.jhep.2020.07.041] [Citation(s) in RCA: 282] [Impact Index Per Article: 94.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 07/13/2020] [Accepted: 07/28/2020] [Indexed: 12/19/2022]
Abstract
BACKGROUND & AIMS Increased hepatocyte death contributes to the pathology of acute and chronic liver diseases. However, the role of hepatocyte pyroptosis and extracellular inflammasome release in liver disease is unknown. METHODS We used primary mouse and human hepatocytes, hepatocyte-specific leucine 351 to proline Nlrp3KICreA mice, and GsdmdKO mice to investigate pyroptotic cell death in hepatocytes and its impact on liver inflammation and damage. Extracellular NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes were isolated from mutant NLRP3-YFP HEK cells and internalisation was studied in LX2 and primary human hepatic stellate cells. We also examined a cohort of 154 adult patients with biopsy-proven non-alcoholic fatty liver disease (Sir Charles Gairdner Hospital, Nedlands, Western Australia). RESULTS We demonstrated that primary mouse and human hepatocytes can undergo pyroptosis upon NLRP3 inflammasome activation with subsequent release of NLRP3 inflammasome proteins that amplify and perpetuate inflammasome-driven fibrogenesis. Pyroptosis was inhibited by blocking caspase-1 and gasdermin D activation. The activated form of caspase-1 was detected in the livers and in serum from patients with non-alcoholic steatohepatitis and correlated with disease severity. Nlrp3KICreA mice showed spontaneous liver fibrosis under normal chow diet, and increased sensitivity to liver damage and inflammation after treatment with low dose lipopolysaccharide. Mechanistically, hepatic stellate cells engulfed extracellular NLRP3 inflammasome particles leading to increased IL-1β secretion and α-smooth muscle actin expression. This effect was abrogated when cells were pre-treated with the endocytosis inhibitor cytochalasin B. CONCLUSIONS These results identify hepatocyte pyroptosis and release of inflammasome components as a novel mechanism to propagate liver injury and liver fibrosis development. LAY SUMMARY Our findings identify a novel mechanism of inflammation in the liver. Experiments in cell cultures, mice, and human samples show that a specific form of cell death, called pyroptosis, leads to the release of complex inflammatory particles, the NLRP3 inflammasome, from inside hepatocytes into the extracellular space. From there they are taken up by other cells and thereby mediate inflammatory and pro-fibrogenic stress signals. The discovery of this mechanism may lead to novel treatments for chronic liver diseases in the future.
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Chu AL, Schilling JD, King KR, Feldstein AE. The Power of Single-Cell Analysis for the Study of Liver Pathobiology. Hepatology 2021; 73:437-448. [PMID: 32740968 PMCID: PMC7854989 DOI: 10.1002/hep.31485] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/19/2020] [Accepted: 07/03/2020] [Indexed: 12/29/2022]
Abstract
Single cell transcriptomics has emerged as a powerful lens through which to study the molecular diversity of complex tissues such as the liver, during health and disease, both in animal models and in humans. The earliest gene expression methods measured bulk tissue RNA, but the results were often confusing because they derived from the combined transcriptomes of many different cell types in unknown proportions. To better delineate cell-type-specific expression, investigators developed cell isolation, purification, and sorting protocols, yet still, the RNA derived from ensembles of cells obscured recognition of cellular heterogeneity. Profiling transcriptomes at the single-cell level has opened the door to analyses that were not possible in the past. In this review, we discuss the evolution of single cell transcriptomics and how it has been applied for the study of liver physiology and pathobiology to date.
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Kaufmann B, Reca A, Wang B, Friess H, Feldstein AE, Hartmann D. Mechanisms of nonalcoholic fatty liver disease and implications for surgery. Langenbecks Arch Surg 2020; 406:1-17. [PMID: 32833053 PMCID: PMC7870612 DOI: 10.1007/s00423-020-01965-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 08/09/2020] [Indexed: 02/08/2023]
Abstract
Background Nonalcoholic fatty liver disease (NAFLD) has become the most common form of chronic liver disease in both adults and children worldwide. Understanding the pathogenic mechanisms behind NAFLD provides the basis for identifying risk factors, such as metabolic syndrome, pancreatoduodenectomy, and host genetics, that lead to the onset and progression of the disease. The progression from steatosis to more severe forms, such as steatohepatitis, fibrosis, and cirrhosis, leads to an increased number of liver and non-liver complications. Purpose NAFLD-associated end-stage liver disease (ESLD) and hepatocellular carcinoma (HCC) often require surgery as the only curative treatment. In particular, the presence of NAFLD together with the coexisting metabolic comorbidities that usually occur in these patients requires careful preoperative diagnosis and peri-/postoperative management. Bariatric surgery, liver resection, and liver transplantation (LT) have shown favorable results for weight loss, HCC, and ESLD in patients with NAFLD. The LT demand and the increasing spread of NAFLD in the donor pool reinforce the already existing lack of donor organs. Conclusion In this review, we will discuss the diverse mechanisms underlying NAFLD, its implications for surgery, and the challenges for patient management.
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Knorr J, Wree A, Tacke F, Feldstein AE. The NLRP3 Inflammasome in Alcoholic and Nonalcoholic Steatohepatitis. Semin Liver Dis 2020; 40:298-306. [PMID: 32526788 DOI: 10.1055/s-0040-1708540] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Nonalcoholic steatohepatitis (NASH) and alcoholic hepatitis (ASH) are advanced forms of fatty liver diseases that are associated with a high morbidity and mortality worldwide. Patients with ASH or NASH are more susceptible to the progression of fibrosis and cirrhosis up to the development of hepatocellular carcinoma. Currently, there are limited medical therapies available. Accompanied by the asymptomatic disease progression, the demand for liver transplants is high. This review provides an overview about the growing evidence for a central role of NLR family pyrin domain containing 3 (NLRP3) inflammasome, a multiprotein complex that acts as a central driver of inflammation via activation of caspase 1, maturation and release of pro-inflammatory cytokines including interleukin-1β, and trigger of inflammatory pyroptotic cell death in both NASH and ASH. We also discuss potential therapeutic approaches targeting NLRP3 inflammasome and related upstream and downstream pathways to develop prognostic biomarkers and medical treatments for both liver diseases.
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Van Name MA, Savoye M, Chick JM, Galuppo BT, Feldstein AE, Pierpont B, Johnson C, Shabanova V, Ekong U, Valentino PL, Kim G, Caprio S, Santoro N. A Low ω-6 to ω-3 PUFA Ratio (n-6:n-3 PUFA) Diet to Treat Fatty Liver Disease in Obese Youth. J Nutr 2020; 150:2314-2321. [PMID: 32652034 PMCID: PMC7467848 DOI: 10.1093/jn/nxaa183] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 02/28/2020] [Accepted: 06/08/2020] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Recent literature suggests that the Western diet's imbalance between high ω-6 (n-6) and low ω-3 (n-3) PUFA intake contributes to fatty liver disease in obese youth. OBJECTIVES We tested whether 12 wk of a low n-6:n-3 PUFA ratio (4:1) normocaloric diet mitigates fatty liver and whether the patatin-like containing domain phospholipase 3 (PNPLA3) rs738409 variant affects the response. METHODS In a single-arm unblinded study, obese youth 9-19 y of age with nonalcoholic fatty liver disease were treated with a normocaloric low n-6:n-3 PUFA ratio diet for 12 wk. The primary outcome was change in hepatic fat fraction (HFF%), measured by abdominal MRI. Metabolic parameters included alanine aminotransferase (ALT), lipids, measures of insulin sensitivity, and plasma oxidized linoleic acid metabolites (OXLAMs). Outcomes were also analyzed by PNPLA3 rs738409 genotype. Wilcoxon's signed rank test, the Mann-Whitney U test, and covariance pattern modeling were used. RESULTS Twenty obese adolescents (median age: 13.3 y; IQR: 10.5-16.4 y) were enrolled and 17 completed the study. After 12 wk of dietary intervention, HFF% decreased by 25.8% (P = 0.009) despite stable weight. We observed a 34.4% reduction in ALT (P = 0.001), 21.9% reduction in triglycerides (P = 0.046), 3.28% reduction in LDL cholesterol (P = 0.071), and a 26.3% improvement in whole body insulin sensitivity (P = 0.032). The OXLAMs 9-hydroxy-octadecandienoic acid (9-HODE) (P = 0.011), 13-HODE (P = 0.007), and 9-oxo-octadecadienoic acid (9-oxoODE) (P = 0.024) decreased after 12 wk. HFF% declined in both the not-at-risk (CC/CG) and at-risk (GG) PNPLA3 rs738409 genotype groups, with significant (P = 0.016) HFF% reduction in the GG group. Changes in 9-HODE (P = 0.023), 9-oxoODE (P = 0.009), and 13-oxoODE (P = 0.003) differed between the 2 genotype groups over time. CONCLUSIONS These data suggest that, independently of weight loss, a low n-6:n-3 PUFA diet ameliorates the metabolic phenotype of adolescents with fatty liver disease and that response to this diet is modulated by the PNPLA3 rs738409 genotype.This trial was registered at clinicaltrials.gov as NCT01556113.
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Povero D, Yamashita H, Ren W, Subramanian MG, Myers RP, Eguchi A, Simonetto DA, Goodman ZD, Harrison SA, Sanyal AJ, Bosch J, Feldstein AE. Characterization and Proteome of Circulating Extracellular Vesicles as Potential Biomarkers for NASH. Hepatol Commun 2020; 4:1263-1278. [PMID: 32923831 PMCID: PMC7471415 DOI: 10.1002/hep4.1556] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/17/2020] [Accepted: 05/11/2020] [Indexed: 12/25/2022] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is currently one of most common forms of chronic liver disease globally. NAFLD represents a wide spectrum of liver involvement from nonprogressive isolated steatosis to nonalcoholic steatohepatitis (NASH), characterized by liver necroinflammation and fibrosis and currently one of the top causes of end‐stage liver disease and hepatocellular carcinoma. At present, there is a lack of effective treatments, and a central barrier to the development of therapies is the requirement for an invasive liver biopsy for diagnosis of NASH. Discovery of reliable, noninvasive biomarkers are urgently needed. In this study, we tested whether circulating extracellular vesicles (EVs), cell‐derived small membrane‐surrounded structures with a rich cargo of bioactive molecules, may serve as reliable noninvasive “liquid biopsies” for NASH diagnosis and assessment of disease severity. Total circulating EVs and hepatocyte‐derived EVs were isolated by differential centrifugation and size‐exclusion chromatography from serum samples of healthy individuals, patients with precirrhotic NASH, and patients with cirrhotic NASH. EVs were further characterized by flow cytometry, electron microscopy, western blotting, and dynamic light scattering assays before performing a proteomics analysis. Our findings suggest that levels of total and hepatocyte‐derived EVs correlate with NASH clinical characteristics and disease severity. Additionally, using proteomics data, we developed understandable, powerful, and unique EV‐based proteomic signatures for potential diagnosis of advanced NASH. Conclusion: Our study shows that the quantity and protein constituents of circulating EVs provide strong evidence for EV protein–based liquid biopsies for NAFLD/NASH diagnosis.
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Eguchi A, Yan R, Pan SQ, Wu R, Kim J, Chen Y, Ansong C, Smith RD, Tempaku M, Ohno-Machado L, Takei Y, Feldstein AE, Tsukamoto H. Comprehensive characterization of hepatocyte-derived extracellular vesicles identifies direct miRNA-based regulation of hepatic stellate cells and DAMP-based hepatic macrophage IL-1β and IL-17 upregulation in alcoholic hepatitis mice. J Mol Med (Berl) 2020; 98:1021-1034. [PMID: 32556367 DOI: 10.1007/s00109-020-01926-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/11/2020] [Accepted: 05/14/2020] [Indexed: 02/07/2023]
Abstract
Extracellular vesicles (EVs) have been growingly recognized as biomarkers and mediators of alcoholic liver disease (ALD) in human and mice. Here we characterized hepatocyte-derived EVs (HC-EVs) and their cargo for their biological functions in a novel murine model that closely resembles liver pathology observed in patients with alcoholic hepatitis (AH), the most severe spectrum of ALD. The numbers of circulating EVs and HC-EVs were significantly increased by 10-fold in AH mice compared with control mice. The miRNA (miR)-seq analysis detected 20 upregulated and 4 downregulated miRNAs (P < 0.001-0.05) in AH-HC-EVs. Treatment of murine primary hepatic stellate cells (HSCs) with AH-HC-EVs induced α-SMA (P < 0.05) and Col1a1 (P < 0.001). Smad7 and Nr1d2 genes, which were downregulated in HSCs from the AH mice, were predicted targets of 20 miRs upregulated in AH-HC-EVs. Among them were miR-27a and miR-181 which upon transfection in HSCs, indeed repressed Nr1d2, the quiescent HSC marker. AH-HC-EVs were also enriched with organelle proteins and mitochondrial DNA (10-fold, P < 0.05) and upregulated IL-1β and IL-17 production by hepatic macrophages (HMs) from AH mice in a TLR9-dependent manner. These results demonstrate HC-EV release is intensified in AH and suggest that AH-HC-EVs orchestrate liver fibrogenesis by directly targeting the quiescent HSC transcripts via a unique set of miRNAs and by amplifying HSC activation via DAMP-based induction of profibrogenic IL-1β and IL-17 by HMs. KEY MESSAGES: • Circulating EVs and HC-EVs were increased in AH mice compared with control mice • AH-HC-EVs were enriched in miRNAs, organelle proteins, and mitochondrial DNA • AH-HC-EVs increased cytokine production by AH-HMs in a TLR9-dependent manner.
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Eguchi A, Fukuda S, Kuratsune H, Nojima J, Nakatomi Y, Watanabe Y, Feldstein AE. Identification of actin network proteins, talin-1 and filamin-A, in circulating extracellular vesicles as blood biomarkers for human myalgic encephalomyelitis/chronic fatigue syndrome. Brain Behav Immun 2020; 84:106-114. [PMID: 31759091 PMCID: PMC7010541 DOI: 10.1016/j.bbi.2019.11.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/24/2019] [Accepted: 11/18/2019] [Indexed: 01/14/2023] Open
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a serious, debilitating disorder with a wide spectrum of symptoms, including pain, depression, and neurocognitive deterioration. Over 17 million people around the world have ME/CFS, predominantly women with peak onset at 30-50 years. Given the wide spectrum of symptoms and unclear etiology, specific biomarkers for diagnosis and stratification of ME/CFS are lacking. Here we show that actin network proteins in circulating extracellular vesicles (EVs) offer specific non-invasive biomarkers for ME/CFS. We found that circulating EVs were significantly increased in ME/CFS patients correlating to C-reactive protein, as well as biological antioxidant potential. Area under the receiver operating characteristic curve for circulating EVs was 0.80, allowing correct diagnosis in 90-94% of ME/CFS cases. From two independent proteomic analyses using circulating EVs from ME/CFS, healthy controls, idiopathic chronic fatigue, and depression, proteins identified from ME/CFS patients are involved in focal adhesion, actin skeletal regulation, PI3K-Akt signaling pathway, and Epstein-Barr virus infection. In particular, talin-1, filamin-A, and 14-3-3 family proteins were the most abundant proteins, representing highly specific ME/CFS biomarkers. Our results identified circulating EV number and EV-specific proteins as novel biomarkers for diagnosing ME/CFS, providing important information on the pathogenic mechanisms of ME/CFS.
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Schuster-Gaul S, Geisler LJ, McGeough MD, Johnson CD, Zagorska A, Li L, Wree A, Barry V, Mikaelian I, Jih LJ, Papouchado BG, Budas G, Hoffman HM, Feldstein AE. ASK1 inhibition reduces cell death and hepatic fibrosis in an Nlrp3 mutant liver injury model. JCI Insight 2020; 5:123294. [PMID: 31996485 PMCID: PMC7098717 DOI: 10.1172/jci.insight.123294] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 12/18/2019] [Indexed: 12/14/2022] Open
Abstract
Hepatic inflammasome activation is considered a major contributor to liver fibrosis in NASH. Apoptosis signal-regulating kinase 1 (ASK1) is an apical mitogen-activated protein kinase that activates hepatic JNK and p38 to promote apoptosis, inflammation, and fibrosis. The aim of the current study was to investigate whether pharmacologic inhibition of ASK1 could attenuate hepatic fibrosis driven by inflammasome activation using gain-of-function NOD-like receptor protein 3 (Nlrp3) mutant mice. Tamoxifen-inducible Nlrp3 knock-in (Nlrp3A350V/+CreT-KI) mice and WT mice were administered either control chow diet or diet containing the selective ASK1 inhibitor GS-444217 for 6 weeks. Livers of Nlrp3-KI mice had increased inflammation, cell death, and fibrosis and increased phosphorylation of ASK1, p38, and c-Jun. GS-444217 reduced ASK1 pathway activation, liver cell death, and liver fibrosis. ASK1 inhibition resulted in a significant downregulation of genes involved in collagen production and extracellular matrix deposition, as well as in a reduced hepatic TNF-α expression. ASK1 inhibition also directly reduced LPS-induced gene expression of Collagen 1A1 (Col1a1) in hepatic stellate cells isolated from Nlrp3-KI mice. In conclusion, ASK1 inhibition reduced liver cell death and fibrosis downstream of inflammatory signaling induced by NLRP3. These data provide mechanistic insight into the antifibrotic mechanisms of ASK1 inhibition.
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Alkhouri N, Kohli R, Feldstein AE. Designing Clinical Trials in Pediatric Nonalcoholic Steatohepatitis: Tips for Patient Selection and Appropriate Endpoints. Hepatol Commun 2019; 3:1563-1570. [PMID: 31832567 PMCID: PMC6887671 DOI: 10.1002/hep4.1449] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 10/20/2019] [Indexed: 12/17/2022] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is common in children and may progress to nonalcoholic steatohepatitis (NASH), advanced fibrosis, and even cirrhosis in childhood or early adulthood, indicating the need for pharmacologic treatment in this age group. Multiple trials are evaluating different therapeutic targets for NASH with fibrosis in adults, and the U.S. Food and Drug Administration has recently provided clear guidance to the pharmaceutical industry on developing drugs for the treatment of noncirrhotic NASH with liver fibrosis. Pediatric NAFLD has several unique aspects that distinguish it from the adult disease in terms of histology, our understanding of the natural history, and the utility of noninvasive tests. These differences have the potential to impact the design of clinical trials to test different drugs in the pediatric population. The aim of this article is to provide a review of common misconceptions regarding pediatric NAFLD and key differences from adult NAFLD. We have provided our recommendations on the design of early proof-of-concept and late phase 2 trials based on lessons learned from previous clinical trials. We believe that clinical drug development for children with NAFLD should happen in parallel with ongoing adult trials.
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Calvente CJ, Tameda M, Johnson CD, del Pilar H, Lin YC, Adronikou N, De Mollerat Du Jeu X, Llorente C, Boyer J, Feldstein AE. Neutrophils contribute to spontaneous resolution of liver inflammation and fibrosis via microRNA-223. J Clin Invest 2019; 129:4091-4109. [PMID: 31295147 PMCID: PMC6763256 DOI: 10.1172/jci122258] [Citation(s) in RCA: 162] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/03/2019] [Indexed: 02/06/2023] Open
Abstract
Persistent, unresolved inflammation in the liver represents a key trigger for hepatic injury and fibrosis in various liver diseases and is controlled by classically activated pro-inflammatory macrophages, while restorative macrophages of the liver are capable of reversing inflammation once the injury trigger ceases. Here we have identified a novel role for neutrophils as key contributors to resolving the inflammatory response in the liver. Using two models of liver inflammatory resolution, we found that mice undergoing neutrophil depletion during the resolution phase exhibited unresolved hepatic inflammation, activation of the fibrogenic machinery and early fibrosis. These findings were associated with an impairment of the phenotypic switch of pro-inflammatory macrophages into a restorative stage after removal of the cause of injury and an increased NLRP3 / miR-223 ratio. Mice with a deletion of the granulocyte specific miR-223 gene showed a similarly impaired resolution profile that could be reversed by restoring miR-223 levels using a miR-223 3p mimic or infusing neutrophils from wildtype animals. Collectively, our findings reveal a novel role for neutrophils in the liver as resolving effector cells that induce pro-inflammatory macrophages into a restorative phenotype, potentially via miR-223.
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Wree A, Holtmann TM, Inzaugarat ME, Feldstein AE. Novel Drivers of the Inflammatory Response in Liver Injury and Fibrosis. Semin Liver Dis 2019; 39:275-282. [PMID: 31100758 DOI: 10.1055/s-0039-1685515] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hepatocyte demise as well as signals released by stressed hepatocytes have been now recognized as important triggers of liver inflammation. While traditional concepts classically viewed hepatocyte cell death to occur by either a nonlytic, noninflammatory form (apoptosis), or lytic, proinflammatory nonregulated cell death (necrosis), recent studies have provided evidence for additional mechanisms that can contribute to both acute and chronic liver damage. Two novel forms of cell death, pyroptosis and necroptosis, are of particular importance as they are highly regulated and intrinsically proinflammatory. Additionally, stressed hepatocytes may also release signals to attract and activate monocytes into proinflammatory macrophages. In this review, the authors discuss recent developments supporting the role of novel triggers of liver inflammation in various forms of liver injury and their potential translational implications.
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Povero D, Pinatel EM, Leszczynska A, Goyal NP, Nishio T, Kim J, Kneiber D, de Araujo Horcel L, Eguchi A, Ordonez PM, Kisseleva T, Feldstein AE. Human induced pluripotent stem cell-derived extracellular vesicles reduce hepatic stellate cell activation and liver fibrosis. JCI Insight 2019; 5:125652. [PMID: 31184999 DOI: 10.1172/jci.insight.125652] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Progression of fibrosis and the development of cirrhosis are responsible for the liver related morbidity and mortality associated with chronic liver diseases. There is currently a great unmet need for effective anti-fibrotic strategies. Stem cells play a central role in wound healing responses to restore liver homeostasis following injury. Here we tested the hypothesis that extracellular vesicles (EVs) isolated from induced pluripotent stem cells (iPSC) modulate hepatic stellate cell (HSCs) activation and may have anti-fibrotic effects. Human iPSCs were generated by reprogramming primary skin fibroblasts. EVs were isolated by differential centrifugation, quantified by flow cytometry (FACS) and characterized by dynamic light scattering (DLS) and electron microscopy (TEM). Primary human HSCs were activated with TGFβ (10 ng/mL) and exposed to iPSC-EVs. Efficacy of iPSC-EVs was tested on HSC in vitro and in two murine models of liver injury (CCl4 and bile duct ligation). Characterization of iPSC-derived EVs by flow cytometry identified a large population of EVs released by iPSC, primarily with a diameter of 300 nm and that could be visualized by TEM as round, cup-shaped objects. Fluorescent tracing assays detected iPSC-EVs in HSC cytosol after a short incubation and EV uptake by HSCs resulted in both decrease of pro-fibrogenic markers αSMA, CollagenIα1, Fibronectin and TIMP-1 and HSC pro-fibrogenic responses such as chemotaxis and proliferation. Genomics analyses of iPSC-EV miRNA cargo revealed 22 highly expressed miRNAs, among which miR-92a-3p resulted the most abundant. Transcriptome analysis identified 60 genes down-modulated and 235 up-regulated in TGF-β-primed HSC in presence or absence of iPSC-EVs. Intravenous injection of iPSC-EVs in CCl4 and bile duct ligation-induced liver fibrosis resulted in anti-fibrotic effects at protein and gene levels. Results of this study identify iPSC-EVs as a novel anti-fibrotic approach that may reduce or reverse liver fibrosis in patients with chronic liver disease.
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Eguchi A, Kostallari E, Feldstein AE, Shah VH. Extracellular vesicles, the liquid biopsy of the future. J Hepatol 2019; 70:1292-1294. [PMID: 30982591 PMCID: PMC7094760 DOI: 10.1016/j.jhep.2019.01.030] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 01/07/2019] [Accepted: 01/30/2019] [Indexed: 01/08/2023]
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Newfield RS, Graves CL, Newbury RO, Schwimmer JB, Proudfoot JA, Say DS, Feldstein AE. Non-alcoholic fatty liver disease in pediatric type 2 diabetes: Metabolic and histologic characteristics in 38 subjects. Pediatr Diabetes 2019; 20:41-47. [PMID: 30467936 DOI: 10.1111/pedi.12798] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 11/10/2018] [Accepted: 11/15/2018] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Obesity and type 2 diabetes (T2D) is risk factors for non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). In children with T2D and liver biopsies, we investigated correlations between NAFLD/NASH and transaminase activity, A1c, lipids, and histologic changes in repeat biopsies. METHODS Liver histology of children with T2D was evaluated using the NASH CRN scoring system and NAFLD Activity Score (NAS). We included results ≤6 months from biopsy and A1c nearest biopsy. RESULTS Thirty-eight subjects (21 females, 17 males, 63.2% Hispanic, 15.8% Caucasian) had T2D diagnosed at 13.4 ± 2.7 years, 78.9% using metformin and 50% on insulin. Histological diagnosis of NAFLD occurred at mean age 14.3 ± 2.3 years, notable for NASH in 61%. Steatosis grade was higher in children with NASH than those without (mean 2.6 ± 0.7 vs 2.1 ± 0.5 (P < 0.001). Stage 3 fibrosis was noted only in subjects with NASH (26%). ALT was higher in NASH vs those without (112 ± 56 vs 85 ± 112, P = 0.016). NAS correlated with A1c (r = 0.51, P < 0.01) and triglycerides (r = 0.5, P < 0.01), and inversely with high-density lipoprotein (HDL) (r = -0.42, P = 0.04). Males had lower HDL and higher triglycerides (P < 0.04). In eight subjects with repeat biopsies, NAS was equal (37.5%) or improved (62.5%), and steatosis decreased (68.1% to 32.8%, P = 0.027). CONCLUSIONS In children with T2D and NAFLD, NASH is common. Having advanced fibrosis in 26% of NASH cases at this age is concerning. Better control of lipids, weight, and diabetes may help avoid worsening in NAS.
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Inzaugarat ME, Johnson CD, Holtmann TM, McGeough MD, Trautwein C, Papouchado BG, Schwabe R, Hoffman HM, Wree A, Feldstein AE. NLR Family Pyrin Domain-Containing 3 Inflammasome Activation in Hepatic Stellate Cells Induces Liver Fibrosis in Mice. Hepatology 2019; 69:845-859. [PMID: 30180270 PMCID: PMC6351190 DOI: 10.1002/hep.30252] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 08/14/2018] [Indexed: 12/25/2022]
Abstract
The NLR family pyrin domain-containing 3 (NLRP3) inflammasome plays an important role in liver fibrosis (LF) development. However, the mechanisms involved in NLRP3-induced fibrosis are unclear. Our aim was to test the hypothesis that the NLRP3 inflammasome in hepatic stellate cells (HSCs) can directly regulate their activation and contribute to LF. Primary HSCs isolated from wild-type (WT), Nlrp3-/- , or Nlrp3L351PneoR knock-in crossed to inducible (estrogen receptor Cre-CreT) mice were incubated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP), or 4OH-tamoxifen, respectively. HSC-specific Nlrp3L351P knock-in mice were generated by crossing transgenic mice expressing lecithin retinol acyltransferase (Lrat)-driven Cre and maintained on standard rodent chow for 6 months. Mice were then sacrificed; liver tissue and serum were harvested. Nlrp3 inflammasome activation along with HSC phenotype and fibrosis were assessed by RT-PCR, western blotting, fluorescence-activated cell sorting (FACS), enzyme-linked immunosorbent assay, immunofluorescence (IF), and immunohistochemistry (IHC). Stimulated WT HSCs displayed increased levels of NLRP3 inflammasome-induced reactive oxygen species (ROS) production and cathepsin B activity, accompanied by an up-regulation of mRNA and protein levels of fibrotic makers, an effect abrogated in Nlrp3-/- HSCs. Nlrp3L351P CreT HSCs also showed elevated mRNA and protein expression of fibrotic markers 24 hours after inflammasome activation induced with 4-hydroxytamoxifen (4OHT). Protein and mRNA expression levels of fibrotic markers were also found to be increased in isolated HSCs and whole liver tissue from Nlrp3L351P Lrat Cre mice compared to WT. Liver sections from 24-week-old NlrpL351P Lrat Cre mice showed fibrotic changes with increased alpha smooth muscle actin (αSMA) and desmin-positive cells and collagen deposition, independent of inflammatory infiltrates; these changes were also observed after LPS challenge in 8-week-old NlrpL351P Lrat Cre mice. Conclusion: Our results highlight a direct role for the NLRP3 inflammasome in the activation of HSCs directly triggering LF.
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Tricò D, Di Sessa A, Caprio S, Chalasani N, Liu W, Liang T, Graf J, Herzog RI, Johnson CD, Umano GR, Feldstein AE, Santoro N. Oxidized Derivatives of Linoleic Acid in Pediatric Metabolic Syndrome: Is Their Pathogenic Role Modulated by the Genetic Background and the Gut Microbiota? Antioxid Redox Signal 2019; 30:241-250. [PMID: 28279074 PMCID: PMC6277079 DOI: 10.1089/ars.2017.7049] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 12/28/2022]
Abstract
We tested whether oxidized linoleic acid metabolites (OXLAM) are associated with pediatric metabolic syndrome (MetS) and a proatherogenic lipoprotein profile in 122 obese adolescents. Furthermore, we examined whether genetic and metagenomic factors can modulate plasma OXLAM concentrations by genotyping the fatty acid desaturase 1/2 (FADS) gene and by characterizing the gut microbiota. Subjects with MetS (n = 50) showed higher concentrations of 9- and 13-oxo-octadecadienoic acid (9- and 13-oxo-ODE) than subjects without MetS (n = 72). Both metabolites were associated with an adverse lipoprotein profile that was characterized by elevated very small-dense low-density lipoprotein (p < 0.005) and large very low-density lipoprotein particles (p = 0.01). Plasma 9- and 13-oxo-ODE were higher in subjects carrying the haplotype AA of the FADS gene cluster (p = 0.030 and p = 0.048, respectively). Furthermore, the reduced gut bacterial load was associated with higher 9-oxo-ODE concentrations (p = 0.035). This is the first study showing that high plasma OXLAM concentrations are associated with MetS and suggesting that the leading factors for high plasma concentrations of OXLAM might be the genetic background and the composition of the gut microbiota. In conclusion, high concentrations of 9- and 13-oxo-ODE, which may be the result of a genetic predisposition and a reduced gut bacterial load, are associated with MetS and with a proatherogenic lipoprotein profile in obese adolescents.
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Banales JM, Feldstein AE, Sänger H, Lukacs-Kornek V, Szabo G, Kornek M. Extracellular Vesicles in Liver Diseases: Meeting Report from the International Liver Congress 2018. Hepatol Commun 2019; 3:305-315. [PMID: 30766966 PMCID: PMC6357829 DOI: 10.1002/hep4.1300] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/12/2018] [Indexed: 02/06/2023] Open
Abstract
Extracellular vesicles (EVs) are small and heterogeneous membrane‐bound structures released by cells and found in all biological fluids. They are effective intercellular communicators, acting on a number of close and/or distant target cells. EV cargo may reflect the cell of origin as well as the specific stress that induces their formation and release. They transport a variety of bioactive molecules, including messenger RNA, noncoding RNAs, proteins, lipids, and metabolites, that can be transferred among cells, regulating various cell responses. Alteration in the concentration and composition of EVs in biological fluids is a typical hallmark of pathologies in different liver diseases. Circulating EVs can serve as biomarkers or as messengers following uptake by other cells. This review is a meeting report from the International Liver Congress 2018 (European Association for the Study of the Liver) celebrated in Paris (Symposium: Extracellular vesicles and signal transmission) that discusses the role of EVs in several liver diseases, highlighting their potential value as disease biomarkers and therapeutic opportunities.
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Mann J, Reeves HL, Feldstein AE. Liquid biopsy for liver diseases. Gut 2018; 67:2204-2212. [PMID: 30177542 DOI: 10.1136/gutjnl-2017-315846] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/24/2018] [Accepted: 07/25/2018] [Indexed: 12/12/2022]
Abstract
With the growing number of novel therapeutic approaches for liver diseases, significant research efforts have been devoted to the development of liquid biopsy tools for precision medicine. This can be defined as non-invasive reliable biomarkers that can supplement and eventually replace the invasive liver biopsy for diagnosis, disease stratification and monitoring of response to therapeutic interventions. Similarly, detection of liver cancer at an earlier stage of the disease, potentially susceptible to curative resection, can be critical to improve patient survival. Circulating extracellular vesicles, nucleic acids (DNA and RNA) and tumour cells have emerged as attractive liquid biopsy candidates because they fulfil many of the key characteristics of an ideal biomarker. In this review, we summarise the currently available information regarding these promising and potential transformative tools, as well as the issues still needed to be addressed for adopting various liquid biopsy approaches into clinical practice. These studies may pave the way to the development of a new generation of reliable, mechanism-based disease biomarkers.
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Maricic I, Marrero I, Eguchi A, Nakamura R, Johnson CD, Dasgupta S, Hernandez CD, Nguyen PS, Swafford AD, Knight R, Feldstein AE, Loomba R, Kumar V. Differential Activation of Hepatic Invariant NKT Cell Subsets Plays a Key Role in Progression of Nonalcoholic Steatohepatitis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2018; 201:3017-3035. [PMID: 30322964 PMCID: PMC6219905 DOI: 10.4049/jimmunol.1800614] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 09/07/2018] [Indexed: 02/07/2023]
Abstract
Innate immune mechanisms play an important role in inflammatory chronic liver diseases. In this study, we investigated the role of type I or invariant NKT (iNKT) cell subsets in the progression of nonalcoholic steatohepatitis (NASH). We used α-galactosylceramide/CD1d tetramers and clonotypic mAb together with intracytoplasmic cytokine staining to analyze iNKT cells in choline-deficient l-amino acid-defined (CDAA)-induced murine NASH model and in human PBMCs, respectively. Cytokine secretion of hepatic iNKT cells in CDAA-fed C57BL/6 mice altered from predominantly IL-17+ to IFN-γ+ and IL-4+ during NASH progression along with the downmodulation of TCR and NK1.1 expression. Importantly, steatosis, steatohepatitis, and fibrosis were dependent upon the presence of iNKT cells. Hepatic stellate cell activation and infiltration of neutrophils, Kupffer cells, and CD8+ T cells as well as expression of key proinflammatory and fibrogenic genes were significantly blunted in Jα18-/- mice and in C57BL/6 mice treated with an iNKT-inhibitory RAR-γ agonist. Gut microbial diversity was significantly impacted in Jα18-/- and in CDAA diet-fed mice. An increased frequency of CXCR3+IFN-γ+T-bet+ and IL-17A+ iNKT cells was found in PBMC from NASH patients in comparison with nonalcoholic fatty liver patients or healthy controls. Consistent with their in vivo activation, iNKT cells from NASH patients remained hyporesponsive to ex-vivo stimulation with α-galactosylceramide. Accumulation of plasmacytoid dendritic cells in both mice and NASH patients suggest their role in activation of iNKT cells. In summary, our findings indicate that the differential activation of iNKT cells play a key role in mediating diet-induced hepatic steatosis and fibrosis in mice and its potential involvement in NASH progression in humans.
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Alkhouri N, Johnson C, Adams L, Kitajima S, Tsuruno C, Colpitts TL, Hatcho K, Lawitz E, Lopez R, Feldstein AE. Correction: Serum Wisteria floribunda agglutinin-positive Mac-2-binding protein levels predict the presence of fibrotic nonalcoholic steatohepatitis (NASH) and NASH cirrhosis. PLoS One 2018; 13:e0205541. [PMID: 30286196 PMCID: PMC6171937 DOI: 10.1371/journal.pone.0205541] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Ramsden CE, Hennebelle M, Schuster S, Keyes GS, Johnson CD, Kirpich IA, Dahlen JE, Horowitz MS, Zamora D, Feldstein AE, McClain CJ, Muhlhausler BS, Makrides M, Gibson RA, Taha AY. Effects of diets enriched in linoleic acid and its peroxidation products on brain fatty acids, oxylipins, and aldehydes in mice. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1206-1213. [PMID: 30053599 PMCID: PMC6180905 DOI: 10.1016/j.bbalip.2018.07.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 07/12/2018] [Accepted: 07/21/2018] [Indexed: 02/08/2023]
Abstract
BACKGROUND Linoleic acid (LA) is abundant in modern industrialized diets. Oxidized LA metabolites (OXLAMs) and reactive aldehydes, such as 4-hydroxy-2-nonenal (4-HNE), are present in heated vegetable oils and can be endogenously synthesized following consumption of dietary LA. OXLAMs have been implicated in cerebellar degeneration in chicks; 4-HNE is linked to neurodegenerative conditions in mammals. It unknown whether increasing dietary LA or OXLAMs alters the levels of oxidized fatty acids (oxylipins), precursor fatty acids, or 4-HNE in mammalian brain. OBJECTIVES To determine the effects of increases in dietary OXLAMs and dietary LA, on levels of fatty acids, oxylipins, and 4-HNE in mouse brain tissues. METHODS Mice (n = 8 per group) were fed one of three controlled diets for 8 weeks: (1) a low LA diet, (2) a high LA diet, or (3) the low LA diet with added OXLAMs. Brain fatty acids, oxylipins, and 4-HNE were quantified in mouse cerebellum and cerebral cortex by gas chromatography-flame ionization detection, liquid chromatography-tandem mass spectrometry, and immunoblot, respectively. RESULTS Increasing dietary LA significantly increased omega-6 fatty acids, decreased omega-3 fatty acids, and increased OXLAMs in brain. Dietary OXLAMs had minimal effect on oxidized lipids but did decrease both omega-6 and omega-3 fatty acids. Neither dietary LA nor OXLAMs altered 4-HNE levels. CONCLUSION Brain fatty acids are modulated by both dietary LA and OXLAMs, while brain OXLAMs are regulated by endogenous synthesis from LA, rather than incorporation of preformed OXLAMs.
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