Project description:Long wavelength Ultraviolet (UVA-1) radiation causes oxidative stress that leads to the formation of noxious substances within the skin. As a defensive mechanism skin cells produce detoxifying enzymes and antioxidants when they detect modified molecules. We have recently shown that UVA-1 irradiation oxidizes the abundant membrane phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC), which then induced the synthesis of the stress response protein heme oxygenase 1 (HO-1) in dermal fibroblasts. Here we examined the effects of UVA-1 and (UV-) oxidized phospholipids on the global gene expression in human dermal fibroblasts. We identified a cluster of genes that were co-induced by UVA-1-oxidized PAPC and UVA-1 radiation. The cluster included HO-1, glutamate-cysteine ligase modifier subunit (GCLM), aldo-keto reductases-1-C1 and -C2 (AKR1C1, AKR1C2), and interleukin 8 (IL8). These genes are members of the cellular stress response system termed âantioxidant responseâ or âPhase II detoxificationâ. Accordingly, the regulatory regions of all these genes contain binding sites for NF-E2-related factor 2 (Nrf2), a major regulator of the antioxidant response. Both UVA-1 irradiation and treatment with oxidized lipids led to increased nuclear accumulation of Nrf2. Silencing expression of Nrf2 using siRNA or using cells and tissue from Nrf2-deficient mice, we show that the induction of the co-regulated genes was suppressed. Expression of other canonical UVA-1-induced genes, including cyclooxygenase 2 (Cox2) and interleukin 6 (IL6) was unaltered in the absence of Nrf2. Together, our data show that UVA-1-mediated lipid oxidation induces induction of antioxidant response genes, which is dependent on the redox-regulated transcription factor Nrf2. To activate Nrf2 is a major strategy for novel antioxidant drugs, the skin photo-adaptation (SPA) inducers. Our finding that specific uv-oxidized lipids act similar sheds a new (ultraviolet) light on the usually detrimental âimageâ of UV generated lipid mediators. Experiment Overall Design: we profiled global mRNA expression levels in human dermal fibroblasts that had been treated with either UVA-1 or oxidized lipids. To investigate the effect of oxidized phospholipids on gene regulation, we used two preparations, which differed in their degree of oxidation; the minimally oxidized UV-PAPC resulting from UVA-1 irradiation of PAPC, and air-oxidized PAPC (OxPAPC), which represents the full spectrum of oxidation products (Gruber 07) (Reis et al., 2005). We irradiated dermal fibroblasts with UVA-1 (40J/cmÂ²) or treated them with UV-PAPC, OxPAPC or native PAPC (100Âµg/ml each). We analyzed global gene expression four hours after stimulation with gene arrays (Affymetrix U133A Plus 2.0 Gene Chips).

Project description:Long wavelength Ultraviolet (UVA-1) radiation causes oxidative stress that leads to the formation of noxious substances within the skin. As a defensive mechanism skin cells produce detoxifying enzymes and antioxidants when they detect modified molecules. We have recently shown that UVA-1 irradiation oxidizes the abundant membrane phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC), which then induced the synthesis of the stress response protein heme oxygenase 1 (HO-1) in dermal fibroblasts. Here we examined the effects of UVA-1 and (UV-) oxidized phospholipids on the global gene expression in human dermal fibroblasts. We identified a cluster of genes that were co-induced by UVA-1-oxidized PAPC and UVA-1 radiation. The cluster included HO-1, glutamate-cysteine ligase modifier subunit (GCLM), aldo-keto reductases-1-C1 and -C2 (AKR1C1, AKR1C2), and interleukin 8 (IL8). These genes are members of the cellular stress response system termed “antioxidant response” or “Phase II detoxification”. Accordingly, the regulatory regions of all these genes contain binding sites for NF-E2-related factor 2 (Nrf2), a major regulator of the antioxidant response. Both UVA-1 irradiation and treatment with oxidized lipids led to increased nuclear accumulation of Nrf2. Silencing expression of Nrf2 using siRNA or using cells and tissue from Nrf2-deficient mice, we show that the induction of the co-regulated genes was suppressed. Expression of other canonical UVA-1-induced genes, including cyclooxygenase 2 (Cox2) and interleukin 6 (IL6) was unaltered in the absence of Nrf2. Together, our data show that UVA-1-mediated lipid oxidation induces induction of antioxidant response genes, which is dependent on the redox-regulated transcription factor Nrf2. To activate Nrf2 is a major strategy for novel antioxidant drugs, the skin photo-adaptation (SPA) inducers. Our finding that specific uv-oxidized lipids act similar sheds a new (ultraviolet) light on the usually detrimental “image” of UV generated lipid mediators.

Project description:Oxidized phospholipids are thought to promote atherogenesis by stimulating endothelial cells (ECs) to produce inflammatory cytokines, such as IL-8. In studies with mouse models, we previously demonstrated that genetic variation in inflammatory responses of endothelial cells to oxidized lipids contributes importantly to atherosclerosis susceptibility. We now show that similar variations occur in cultured aortic ECs derived from multiple heart transplant donors. These variations were stably maintained between passages and, thus, reflect either genetic or epigenetic regulatory differences. Expression array analysis of aortic EC cultures derived from 12 individuals revealed that >1,000 genes were regulated by oxidized phospholipids. We have used the observed variations in the sampled population to construct a gene coexpression network comprised of 15 modules of highly connected genes. We show that several identified modules are significantly enriched in genes for known pathways and confirm a module enriched for unfolded protein response (UPR) genes using siRNA and the UPR inducer tunicamycin. On the basis of the constructed network, we predicted that a gene of unknown function (MGC4504) present in the UPR module is a target for UPR transcriptional activator ATF4. Our data also indicate that IL-8 is present in the UPR module and is regulated, in part, by the UPR. We validate these by using siRNA. In conclusion, we show that interindividual variability can be used to group genes into pathways and predict gene-gene regulatory relationships, thus identifying targets potentially involved in susceptibility to common diseases such as atherosclerosis. Twelve individual HAEC lines were treated in duplicate (in 35-mm dishes) for 4 h in media containing PAPC (40 μg/ml) or oxidized PAPC (OxPAPC) at 20 ug/ml or 40 μg/ml. Cytoplasmic RNA was isolated by using an RNAeasy kit (Qiagen) and analyzed on an Agilent 2100 Bioanalyzer (Agilent, Palo Alto, CA) to assess RNA integrity. Double-stranded cDNAs were synthesized from total RNA by using the cDNA Synthesis System (Invitrogen, Carlsbad, CA). Biotin-labeled cRNA was generated and used to probe Affymetrix (Santa Clara, CA) Human Genome U133 Plus 2.0 arrays according to the manufacturer’s recommendations (Affymetrix). The Microarray Suite 5.0 software (Affymetrix) was used to analyze image data and make the absolute call for each measurement. The array data were normalized with the median invariant method (31).

Project description:Objective：Phospholipase D1 (PLD1), a phosphatidylcholine-hydrolyzing enzyme, has been found to be involved in cellular lipid metabolism. However, how PLD1 involves in hepatocyte lipid metabolism and thus affects non-alcoholic fatty liver diseases (NAFLD) has not been explicitly explored. Method: NAFLD is induced in hepatocyte-specific Pld1 knockout (Pld1(H)-KO) mice or control (Pld1-Flox) mice with a high fat diet (HFD) for 20 weeks. Plasma glucose and lipid levels, liver lipid and function parameters and inflammation- and fibrogenesis-related gene expression levels were studied. Changes in lipid composition of liver were detected by lipidomic analyses. Changes in gene expression profile were detected by mRNA sequencing. In vitro, alpha mouse liver 12 (AML12) cells were incubated with sodium palmitate (SP) to explore the mechanisms of PLD1 on development of NAFLD. The protein levels of PLD1 and CD36 were detected in the liver tissues of NAFLD patients. Finally, the therapeutic effect of NAFLD by inhibiting PLD with 5-Fluoro-2-indolyl deschlorohalopemide (FIPI) was examined. Results: PLD1 expression levels were increased in the liver tissues of NAFLD patients and the hepatocytes of HFD-induced mice. Compared with Pld1-Flox mice, Pld1(H)-KO mice exhibited lower plasma glucose and lipids levels, and decreased lipid accumulation, inflammation and fibrosis related gene expression levels in the liver tissues after HFD feeding. Inhibition of hepatocyte PLD1 significantly altered lipid composition, especially phosphatidic acids (PA) and lyso-PAs (LPA) levels in the liver tissues after NAFLD. Transcriptomic analysis showed that hepatocyte specific deficiency of PLD1 mainly decreased CD36 expression levels in the NAFLD liver tissues, which was confirmed at the protein and gene expression levels. In vitro, inhibition of PLD1 markedly decreased CD36 expression and lipid accumulation in SP treated AML12 cells. Furthermore, PA, the downstream product catalyzed by PLD1, increased the expression levels of CD36 and lipid accumulation in vitro, which was reversed by PPARγ antagonist. These suggested that PPARγ played an important role in transcriptional regulation of CD36 expression after PA stimulation. Finally, PLD inhibitor FIPI had significant therapeutic effect on HFD-induced NAFLD. Conclusion: Hepatocyte-specific deficiency of PLD1 ameliorates lipid accumulation and NAFLD development by inhibiting PPARγ/CD36 pathway conducted by PA.

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Oxidized Lipids and CD36-Mediated Lipid Peroxidation in CD8 T Cells Suppress Anti-Tumor Immune Responses

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