Lipidomic changes in a novel sepsis outcome-based analysis reveals potent pro-inflammatory and pro-resolving signaling lipids

The purpose of this study was to investigate changes in the lipidome of patients with sepsis to identify signaling lipids associated with poor outcomes that could be linked to future therapies. Adult patients with sepsis were enrolled within 24h of sepsis recognition. Patients meeting Sepsis-3 criteria were enrolled from the emergency department or intensive care unit and blood samples were obtained. Clinical data were collected and outcomes of rapid recovery, chronic critical illness (CCI), or early death were adjudicated by clinicians. Lipidomic analysis was performed on two platforms, the Sciex™ 5500 device to perform a lipidomic screen of 1450 lipid species and a targeted signaling lipid panel using liquid-chromatography tandem mass spectrometry. For the lipidomic screen, there were 274 patients with sepsis: 192 with rapid recovery, 47 with CCI, and 35 with early deaths. CCI and early death patients were grouped together for analysis. Fatty acid (FA) 12:0 was decreased in CCI/early death, whereas FA 17:0 and 20:1 were elevated in CCI/early death, compared to rapid recovery patients. For the signaling lipid panel analysis, there were 262 patients with sepsis: 189 with rapid recovery, 45 with CCI, and 28 with early death. Pro-inflammatory signaling lipids from ω-6 poly-unsaturated fatty acids (PUFAs), including 15-hydroxyeicosatetraenoic (HETE), 12-HETE, and 11-HETE (oxidation products of arachidonic acid [AA]) were elevated in CCI/early death patients compared to rapid recovery. The pro-resolving lipid mediator from ω-3 PUFAs, 14(S)-hydroxy docosahexaenoic acid (14S-HDHA), was also elevated in CCI/early death compared to rapid recovery. Signaling lipids of the AA pathway were elevated in poor-outcome patients with sepsis and may serve as targets for future therapies.

DHCR7 Expression Predicts Poor Outcomes and Mortality From Sepsis

This is a study of lipid metabolic gene expression patterns to discover precision medicine for sepsis.

OBJECTIVES

Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 d). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets.

DESIGN SETTING AND PARTICITPANTS

Secondary analysis of samples from prospectively enrolled sepsis patients (first 24 hr) and a zebrafish endotoxemia model for drug discovery. Patients were enrolled from the emergency department or ICU at an urban teaching hospital. Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing and reverse transcriptase polymerase chain reaction. A lipopolysaccharide zebrafish endotoxemia model was used for confirmation of human transcriptomic findings and drug discovery.

MAIN OUTCOMES AND MEASURES

The derivation cohort included 96 patients and controls (12 early death, 13 CCI, 51 rapid recovery, and 20 controls) and the validation cohort had 52 patients (6 early death, 8 CCI, and 38 rapid recovery).

RESULTS

The cholesterol metabolism gene 7-dehydrocholesterol reductase (DHCR7) was significantly up-regulated in both derivation and validation cohorts in poor outcome sepsis compared with rapid recovery patients and in 90-day nonsurvivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed up-regulation of dhcr7 and several of the same lipid genes up-regulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1, and ldlra) compared with controls. We then tested six lipid-based drugs in the zebrafish endotoxemia model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from lipopolysaccharide death in a model with 100% lethality.

CONCLUSIONS

DHCR7, an important cholesterol metabolism gene, was up-regulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Vutiglabridin Modulates Paraoxonase 1 and Ameliorates Diet-Induced Obesity in Hyperlipidemic Mice

Vutiglabridin is a clinical-stage synthetic small molecule that is being developed for the treatment of obesity and its target proteins have not been fully identified. Paraoxonase-1 (PON1) is an HDL-associated plasma enzyme that hydrolyzes diverse substrates including oxidized low-density lipoprotein (LDL). Furthermore, PON1 harbors anti-inflammatory and antioxidant capacities and has been implicated as a potential therapeutic target for treating various metabolic diseases. In this study, we performed a non-biased target deconvolution of vutiglabridin using Nematic Protein Organisation Technique (NPOT) and identified PON1 as an interacting protein. We examined this interaction in detail and demonstrate that vutiglabridin binds to PON1 with high affinity and protects PON1 against oxidative damage. Vutiglabridin treatment significantly increased plasma PON1 levels and enzyme activity but not PON1 mRNA in wild-type C57BL/6J mice, suggesting that vutiglabridin modulates PON1 post-transcriptionally. We further investigated the effects of vutiglabridin in obese and hyperlipidemic LDLR-/- mice and found that it significantly increases plasma PON1 levels, while decreasing body weight, total fat mass, and plasma cholesterol levels. Overall, our results demonstrate that PON1 is a direct, interacting target of vutiglabridin, and that the modulation of PON1 by vutiglabridin may provide benefits for the treatment of hyperlipidemia and obesity.

Role of Enterocyte Enpp2 and Autotaxin in Regulating Lipopolysaccharide Levels, Systemic Inflammation and Atherosclerosis

Conversion of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA) by autotaxin, a secreted phospholipase D, is a major pathway for producing LPA. We previously reported that feeding Ldlr^-/- mice standard mouse chow supplemented with unsaturated LPA or LPC qualitatively mimicked the dyslipidemia and atherosclerosis induced by feeding a Western diet (WD). Here we report that adding unsaturated LPA to standard mouse chow also increased the content of reactive oxygen species (ROS) and oxidized phospholipids (OxPL) in jejunum mucus. To determine the role of intestinal autotaxin, enterocyte specific Ldlr^-/-/Enpp2 knockout (iKO) mice were generated. In control mice, the WD increased enterocyte Enpp2 expression and raised autotaxin levels. Ex vivo, addition of OxPL to jejunum from Ldlr^-/- mice on a chow diet induced expression of Enpp2. In control mice, the WD raised OxPL levels in jejunum mucus, and decreased gene expression in enterocytes for a number of peptides and proteins that affect antimicrobial activity. On the WD, the control mice developed elevated levels of LPS in jejunum mucus and plasma, with increased dyslipidemia and increased atherosclerosis. All of these changes were reduced in the iKO mice. We conclude that the WD increases the formation of intestinal OxPL, which i) induce enterocyte Enpp2 and autotaxin resulting in higher enterocyte LPA levels; that ii) contribute to the formation of ROS that help to maintain the high OxPL levels; iii) decrease intestinal antimicrobial activity; and iv) raise plasma LPS levels that promote systemic inflammation and enhance atherosclerosis.

DHCR7 Expression Predicts Poor Outcomes and Mortality from Sepsis

Objective: Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 days). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets. Design: Secondary analysis of samples from prospectively enrolled sepsis patients and a zebrafish sepsis model for drug discovery. Setting: Emergency department or ICU at an urban teaching hospital. Patients: Sepsis patients presenting within 24 hours. Methods: Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing (RNA-seq) and reverse transcriptase polymerase chain reaction (RT-qPCR). A lipopolysaccharide (LPS) zebrafish sepsis model was used for confirmation of human transcriptomic findings and drug discovery. Measurements and Main Results: There were 96 samples in the derivation (76 sepsis, 20 controls) and 52 in the validation cohort (sepsis only). The cholesterol metabolism gene 7-Dehydrocholesterol Reductase ( DHCR7) was significantly upregulated in both derivation and validation cohorts in poor outcome sepsis compared to rapid recovery patients and in 90-day non-survivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed upregulation of dhcr7 and several of the same lipid genes upregulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1 , ldlra) compared to controls. We then tested six lipid-based drugs in the zebrafish sepsis model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from LPS death in a model with 100% lethality. Conclusions: DHCR7, an important cholesterol metabolism gene, was upregulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Abstract 3946: HDL associated Paraoxonase 1 reduces the ovarian tumorigenesis by enhancing the HDL function

Background: Membrane lipids/cholesterol determines the fluidity, clustering of receptors and other protein interactions that delineate signaling pathways for cell cycle/proliferation. Emerging evidences suggest that highly proliferative cancer cells show a high lipid and cholesterol avidity and are considered as hallmarks of cancer aggressiveness including ovarian cancer. Paraoxonase 1 (PON1) is a high density lipoprotein (HDL) associated enzyme with a plethora of functions. PON1 deficiency aggravates HDL inflammatory index, systemic inflammation, and results in lipid retention associated diseases including atherosclerosis and hepatic steatosis. Meta-analysis studies documented that PON1 polymorphisms are associated with various cancers including ovarian cancer and PON1 activity is negatively correlated with human ovarian tumor size, providing clinical association between PON1 and ovarian cancers. Yet, the role and mechanism of action of PON1 in ovarian cancer development has not been elucidated.

Hypothesis: We hypothesized that PON1 may inhibit the ovarian tumorigenesis by modulating HDL function.

Methods and Results: In this report, in patients with ovarian cancer, we observed that plasma PON1 levels are higher, but with lower activity compared to healthy control. Immunoprecipitation of plasma PON1, followed by ELISA against oxidized lipids suggest that PON1 is oxidatively modified, specifically by 4-HNE. In addition, PON1 activity is negatively correlated with HDL pro-inflammatory index. Using a xenograft mouse model, we demonstrate that overexpression of PON1 prevents the development of ovarian cancer. HDL from xenograft transgenic mice shows less pro-inflammatory properties with increased cholesterol efflux efficiency from ovarian cancer cells. Mechanistically, PON1 impairs VEGF signaling in ovarian cancer cells by increasing cholesterol (Mitogenic factor) efflux, resulting in reduced dimerization of vascular endothelial growth factor receptor 2 (VEGF-2R) and VEGF-2R phosphorylation (angiogenic inducer) as well as downstream signaling pathways, including Akt and ERK1/2 which in turn reduce the cell proliferation and angiogenesis. Furthermore, cholesterol and VEGF levels are significantly lowered in the tumor microenvironment in PON1 transgenic mice but there are no changes in the gene expressions that are associated with either cholesterol synthesis or its degradation pathways.

Conclusion: Taken together, we report for the first time that PON1 acts as a tumor suppressor of ovarian cancer by possibly reducing VEFG signaling and enhancing the HDL function, suggesting that activation of HDL associated PON1 might be a fruitful strategy to inhibit the ovarian tumor formation.

Citation Format: Asokan Devarajan, Victor Grijalva, Dawoud Sulaiman, Feng Su, Ellen O'Connor, Robin Farias-Eisner, Srinivasa Reddy. HDL associated Paraoxonase 1 reduces the ovarian tumorigenesis by enhancing the HDL function [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3946.

Abstract 3309: Cardioprotective paraoxonase 2 enhances the tumoricidal activity of natural killer cells in a paracrine manner

Background: Immune system can recognize the neoplastic cells and target them for destruction through tumoricidal process. Further, immune cell dysfunction leads to escape of cancer cells from immune recognition, lead to the initiation and progression of tumor formation. Clinical shreds of evidence suggest that the presence of intratumoral immune cells correlates with improved progression free and overall survival among patients with ovarian carcinoma and provide evidence of activation of antitumor mechanisms. Hence identification of drugs that target the cancer cells as well as activate the immune cells is a sound strategy for cancer therapy. Paraoxonase 2 (PON2) is a membrane-associated lactonase with lipid transport, anti-oxidant and phagocytosis/efferocytosis properties. PON2 deficiency aggravates systemic inflammation, and causes the metabolic associated diseases. Recently we have reported that overexpression of PON2 reduces the ovarian cells proliferation and tumor formation by reducing IGF-1 production and its signaling pathway. Further, using microarray based experiment, we have identified several pathways that modulate the immune cells function such as activation of Natural Killer (NK) cells, dendritic cell maturation, B cells activation, and communication between innate and an adaptive cells signaling pathway were regulated by PON2.

Hypothesis: PON2 enhances tumoricidal activity in a paracrine fashion.

Methods and Results: NK cells were isolated from control C57BL/6 and purity was assessed with flow cytometry using FITC anti mouse CD49B and results revealed that 95 % of NK cells population. NK cells treated with condition medium from ID8hPON2 (human PON2 overexpressed in mouse ovarian cancer cell line) show an increase in tumoricidal activity compared to condition medium from ID8EV. Neither ID8hPON2 nor ID8EV condition medium affects the viability of NK cells. Moreover, there is no difference in CD49B positive staining in the tumor microenvironment between ID8EV and ID8hPON2 cells receiving mice. Condition medium obtained from ID8hPON2 ID8EV group shows increases the interleukin 18 level and neutralizing antibody against IL18 fail to induce the tumoricidal activity indicating mechanistically PON2 enhances the tumoricidal activity via IL18 dependent manner. Furthermore, IL18 levels are increased in tumor micro environment. PON2 increase the IL18 through transactivation of c-Myc gene that are independent of mitochondrial function.

Conclusion: Taken together, our study for the first time showed that PON2 enhances the tumerocidal activity via paracrine manner by upregulating IL18 and PON2 could be used as conventional as well as immunotherapy for ovarian cancer.

Citation Format: Asokan Devarajan, Dawoud Sulaiman, Feng Su, Ekambaram Ganapathy, Robin Farias-Eisner, Srinivasa Reddy. Cardioprotective paraoxonase 2 enhances the tumoricidal activity of natural killer cells in a paracrine manner [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3309.

Abstract 1472: Paraoxonase 3 is a novel tumor suppressor protein in xenograft mouse model

Introduction: Dysfunction of mitochondrial respiratory chains or its associated machinery favors the aerobic glycolysis leading to upregulation of genes related to cell proliferation, metastasis, drug resistant and cancer cell stemness, i.e., the Warburg effect, which has a major role in the pathogenesis of tumor formation. Various studies have documented that perturbation of mitochondria leads to apoptosis suggesting that the precise spatiotemporal regulation of mitochondrial function is a critical regulator of both cell survival and death, whcih determine tumorigenesis. Paraoxonase 3 (PON3) is an intracellular protein localized to the mitochondrial associated membrane. PON3 binds coenzymes Q10 and regulates the respiratory complex activity and prevents the ubisemiquinone-mediated mitochondrial superoxide levels in response to stress conditions. PON3 deficiency leads to dysfunction of mitochondria, which along with an increase in mitochondrial oxidative stress causes systemic inflammation, atherosclerosis, obesity and gall stone formation. PON3 is upregulated in ovarian cancer tissues. However, it's expression in various stages of ovarian cancer and its role on cancer development have not been studied.

Hypothesis: PON3 expression may regulate the ovarian cancer development by enhancing the mitochondrial function.

Methods and Results: Using human ovarian carcinoma tissue array, we identified that PON3 expression was higher in both early and late stages of ovarian cancer when compared to normal tissue. Interestingly, we demonstrated that overexpression of PON3 prevented tumor formation in a mouse ovarian cancer xenograft model. Overexpression of PON3, (i) reduced the tumor angiogenesis marker, CD31 levels in the tumor microenvironment and (ii) inhibited ovarian cancer cell proliferation in both normoxic and hypoxic condition in vitro. Moreover, PON3 reduced VEGF levels (but not IGF-1 levels) under hypoxic conditions. Furthermore, mechanistically, overexpression of PON3 decreased the VEGF level by accelerating the proteasome-dependent protein degradation of hypoxia inducible factor-1 α (HIF-1α) under hypoxic conditions. Finally, we demonstrate that the inhibitory effect of PON3 on HIF-1α levels is, in part, mediated by mitochondrial function.

Conclusion: We report for the first time that PON3 functions as a tumor suppressor in ovarian cancer possibly by suppressing VEGF signaling via HIF-1α by enhancing the mitochondrial function suggesting that PON3 might be a successful strategy to inhibit the ovarian cancer development.

Citation Format: Asokan Devarajan, Feng Su, Dawoud Sulaiman, Dorothy Nguyen, Robin Farias-Eisner, Srinivasa T. Reddy. Paraoxonase 3 is a novel tumor suppressor protein in xenograft mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1472.

Abstract 885: The Role of Paraoxonase 2 (PON2) in Mitochondrial Membrane Phospholipid Composition and Lipid Peroxidation

Introduction: We have recently reported that PON2 plays a protective role against myocardial ischemia-reperfusion injury (IRI) by reducing oxidative stress and mitochondrial dysfunction, in the form of improved calcium retention capacity and integrity of the mitochondrial membrane potential. It is known that mitochondrial phospholipids (PL) play critical roles in mitochondrial homeostasis via maintenance of normal bioenergetics and membrane function. These PLs undergo oxidative stress during IRI resulting in an increase in lipid peroxidation, damage of the respiratory complexes and loss of mitochondrial membrane potential.

Hypothesis: PON2 protects cardiomyocytes against myocardial IRI by modulating the mitochondrial membrane phospholipid composition and lipid peroxidation.

Methods: Two methods were developed to measure 1) various oxidized lipid species (i.e. 5, 12, and 15 HETE, 9, 13 HODE, and 5-oxoETE) and inflammatory markers (lipid panel) and 2) a panel of phospholipid species (i.e. PC, PE, PS) (PLP) via mass spectrometry (ESI LC-MS/MS). Mitochondria were isolated from male C57BL6/J (WT) and PON2 deficient (PON2-def) mice. PLs were then extracted using a modified Bligh and Dyer method with the respective internal standards, and run on a SCIEX 5500 QTrap run in negative ion mode and controlled by Analyst 1.6.2 software. Data is expressed as mean±SEM. Student’s T-test is used for statistical analysis, with p<0.05 considered statistically significant.

Results: We determined that under baseline conditions, PON2-deficient mice have altered mitochondrial membrane PL composition and lipid peroxidation. We observe that PON2-def mitochondria have a significant decrease in various phosphatidylcholine species and an increase in phosphatidylethanolamine (42:9). In addition, there were variations in the composition of phosphatidylserine and phosphatidylinositol. The alteration of mitochondrial PL were accompanied by significant increases in various oxidized lipids including 9, 13-HODE, 14S, 17S-HDHA, 5, 15-HETE, and 5-oxoETE.

Conclusion: Our preliminary studies point to the important role that PON2 plays in modulating mitochondrial PL composition and lipid peroxidation, and warrant further investigation under myocardial IRI.

Apolipoprotein A-I mimetics mitigate intestinal inflammation in COX2-dependent inflammatory bowel disease model

Cyclooxygenase 2 (Cox2) total knockout and myeloid knockout (MKO) mice develop Crohn's-like intestinal inflammation when fed cholate-containing high fat diet (CCHF). We demonstrated that CCHF impaired intestinal barrier function and increased translocation of endotoxin, initiating TLR/MyD88-dependent inflammation in Cox2 KO but not WT mice. Cox2 MKO increased pro-inflammatory mediators in LPS-activated macrophages, and in the intestinal tissue and plasma upon CCHF challenge. Cox2 MKO also reduced inflammation resolving lipoxin A4 (LXA4) in intestinal tissue, while administration of an LXA4 analog rescued disease in Cox2 MKO mice fed CCHF. The apolipoprotein A-I (APOA1) mimetic 4F mitigated disease in both the Cox2 MKO/CCHF and piroxicam-accelerated Il10-/- models of inflammatory bowel disease (IBD) and reduced elevated levels of pro-inflammatory mediators in tissue and plasma. APOA1 mimetic Tg6F therapy was also effective in reducing intestinal inflammation in the Cox2 MKO/CCHF model. We further demonstrated that APOA1 mimetic peptides: i) inhibited LPS and oxidized 1-palmitoyl-2-arachidonoyl-sn-phosphatidylcholine (oxPAPC) dependent pro-inflammatory responses in human macrophages and intestinal epithelium; and ii) directly cleared pro-inflammatory lipids from mouse intestinal tissue and plasma. Our results support a causal role for pro-inflammatory and inflammation resolving lipids in IBD pathology and a translational potential for APOA1 mimetic peptides for the treatment of IBD.

Myeloid HO-1 modulates macrophage polarization and protects against ischemia-reperfusion injury

Macrophages polarize into heterogeneous proinflammatory M1 and antiinflammatory M2 subtypes. Heme oxygenase 1 (HO-1) protects against inflammatory processes such as ischemia-reperfusion injury (IRI), organ transplantation, and atherosclerosis. To test our hypothesis that HO-1 regulates macrophage polarization and protects against IRI, we generated myeloid-specific HO-1-knockout (mHO-1-KO) and -transgenic (mHO-1-Tg) mice, with deletion or overexpression of HO-1, in various macrophage populations. Bone marrow-derived macrophages (BMDMs) from mHO-1-KO mice, treated with M1-inducing LPS or M2-inducing IL-4, exhibited increased mRNA expression of M1 (CXCL10, IL-1β, MCP1) and decreased expression of M2 (Arg1 and CD163) markers as compared with controls, while BMDMs from mHO-1-Tg mice displayed the opposite. A similar pattern was observed in the hepatic M1/M2 expression profile in a mouse model of liver IRI. mHO-1-KO mice displayed increased hepatocellular damage, serum AST/ALT levels, Suzuki's histological score of liver IRI, and neutrophil and macrophage infiltration, while mHO-1-Tg mice exhibited the opposite. In human liver transplant biopsies, subjects with higher HO-1 levels showed lower expression of M1 markers together with decreased hepatocellular damage and improved outcomes. In conclusion, myeloid HO-1 expression modulates macrophage polarization, and protects against liver IRI, at least in part by favoring an M2 phenotype.

Treating the Intestine with Oral ApoA-I Mimetic Tg6F Reduces Tumor Burden in Mouse Models of Metastatic Lung Cancer

Having demonstrated that apolipoprotein A-I (apoA-I) mimetic peptides ameliorate cancer in mouse models, we sought to determine the mechanism for the anti-tumorigenic function of these peptides. CT-26 cells (colon cancer cells that implant and grow into tumors in the lungs) were injected into wild-type BALB/c mice. The day after injection, mice were either continued on chow or switched to chow containing 0.06% of a concentrate of transgenic tomatoes expressing the apoA-I mimetic peptide 6F (Tg6F). After four weeks, the number of lung tumors was significantly lower in Tg6F-fed mice. Gene expression array analyses of jejunum and lung identified Notch pathway genes significantly upregulated, whereas osteopontin (Spp1) was significantly downregulated by Tg6F in both jejunum and lung. In jejunum, Tg6F increased protein levels for Notch1, Notch2, Dll1, and Dll4. In lung, Tg6F increased protein levels for Notch1 and Dll4 and decreased Spp1. Tg6F reduced oxidized phospholipid levels (E06 immunoreactivity) and reduced 25-hydroxycholesterol (25-OHC) levels, which are known to inhibit Notch1 and induce Spp1, respectively. Notch pathway promotes anti-tumorigenic patrolling monocytes, while Spp1 facilitates pro-tumorigenic myeloid derived suppressor cells (MDSCs) formation. Tg6F-fed mice had higher numbers of patrolling monocytes in jejunum and in lung (p < 0.02), and lower plasma levels of Spp1 with reduced numbers of MDSCs in jejunum and in lung (p < 0.03). We conclude that Tg6F alters levels of specific oxidized lipids and 25-OHC to modulate Notch pathways and Spp1, which alter small intestine immune cells, leading to similar changes in lung that reduce tumor burden.

Transintestinal transport of the anti-inflammatory drug 4F and the modulation of transintestinal cholesterol efflux

The site and mechanism of action of the apoA-I mimetic peptide 4F are incompletely understood. Transintestinal cholesterol efflux (TICE) is a process involved in the clearance of excess cholesterol from the body. While TICE is responsible for at least 30% of the clearance of neutral sterols from the circulation into the intestinal lumen, few pharmacological agents have been identified that modulate this pathway. We show first that circulating 4F selectively targets the small intestine (SI) and that it is predominantly transported into the intestinal lumen. This transport of 4F into the SI lumen is transintestinal in nature, and it is modulated by TICE. We also show that circulating 4F increases reverse cholesterol transport from macrophages and cholesterol efflux from lipoproteins via the TICE pathway. We identify the cause of this modulation of TICE either as 4F being a cholesterol acceptor with respect to enterocytes, from which 4F enhances cholesterol efflux, or as 4F being an intestinal chaperone with respect to TICE. Our results assign a novel role for 4F as a modulator of the TICE pathway and suggest that the anti-inflammatory functions of 4F may be a partial consequence of the codependent intestinal transport of both 4F and cholesterol.

Effect of exposure to atmospheric ultrafine particles on production of free fatty acids and lipid metabolites in the mouse small intestine

BACKGROUND

Exposure to ambient ultrafine particulate matter (UFP) is a well-recognized risk factor for cardiovascular and respiratory diseases. However, little is known about the effects of air pollution on gastrointestinal disorders.

OBJECTIVE

We sought to assess whether exposure to ambient UFP (diameter < 180 nm) increased free fatty acids and lipid metabolites in the mouse small intestine.

METHODS

Ldlr-null mice were exposed to filtered air (FA) or UFP collected at an urban Los Angeles, California, site that was heavily affected by vehicular emissions; the exposure was carried out for 10 weeks in the presence or absence of D-4F, an apolipoprotein A-I mimetic peptide with antioxidant and anti-inflammation properties on a high-fat or normal chow diet.

RESULTS

Compared with FA, exposure to UFP significantly increased intestinal hydroxyeicosatetraenoic acids (HETEs), including 15-HETE, 12-HETE, 5-HETE, as well as hydroxyoctadecadienoic acids (HODEs), including 13-HODE and 9-HODE. Arachidonic acid (AA) and prostaglandin D2 (PGD2) as well as some of the lysophosphatidic acids (LPA) in the small intestine were also increased in response to UFP exposure. Administration of D-4F significantly reduced UFP-mediated increase in HETEs, HODEs, AA, PGD2, and LPA. Although exposure to UFP further led to shortened villus length accompanied by prominent macrophage and neutrophil infiltration into the intestinal villi, administration of D-4F mitigated macrophage infiltration.

CONCLUSIONS

Exposure to UFP promotes lipid metabolism, villus shortening, and inflammatory responses in mouse small intestine, whereas administration of D-4F attenuated these effects. Our findings provide a basis to further assess the mechanisms underlying UFP-mediated lipid metabolism in the digestive system with clinical relevance to gut homeostasis and diseases.