OBJECTIVE: To investigate the role and mechanism of the cyclic guanosine monophosphate-adenosine monophosphate synthase/stimulator of interferon gene (cGAS/STING) pathway in oleic acid-induced acute lung injury (ALI) in mice. METHODS: Male wild-type C57BL/6J mice were randomly divided into five groups (each n = 10): normal control group, ALI model group, and 5, 50, 500 μg/kg inhibitor pretreatment groups. The ALI model was established by tail vein injection of oleic acid (7 mL/kg), while the normal control group received no intervention. The inhibitor pretreatment groups were intraperitoneally injected with the corresponding doses of cGAS inhibitor RU.521 respectively 1 hour before modeling. At 24 hours post-modeling, blood was collected, and mice were sacrificed. Lung tissue pathological changes were observed under light microscopy after hematoxylin-eosin (HE) staining, and pathological scores were assessed. Western blotting was used to detect the protein expressions of cGAS, STING, phosphorylated TANK-binding kinase 1 (p-TBK1), phosphorylated interferon regulatory factor 3 (p-IRF3), and phosphorylated nuclear factor-κB p65 (p-NF-κB p65) in lung tissue. Immunohistochemistry was performed to observe STING and p-NF-κB positive expressions in lung tissue. Serum interferon-β (IFN-β) levels were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Compared with the normal control group, the ALI model group exhibited significant focal alveolar thickening, intra-alveolar hemorrhage, pulmonary capillary congestion, and neutrophil infiltration in the pulmonary interstitium and alveoli, along with markedly increased pathological scores (10.33±0.58 vs. 1.33±0.58, P < 0.05). Protein expressions of cGAS, STING, p-TBK1, p-IRF3, and p-NF-κB p65 in lung tissue significantly increased [cGAS protein (cGAS/β-actin): 1.24±0.02 vs. 0.56±0.02, STING protein (STING/β-actin): 1.27±0.01 vs. 0.55±0.01, p-TBK1 protin (p-TBK1/β-actin): 1.34±0.03 vs. 0.22±0.01, p-IRF3 protein (p-IRF3/β-actin): 1.23±0.02 vs. 0.36±0.01, p-NF-κB p65 protein (p-NF-κB p65/β-actin): 1.30±0.02 vs. 0.53±0.02, all P < 0.05], positive expressions of STING and p-NF-κB in lung tissue were significantly elevated [STING (A value): 0.51±0.03 vs. 0.30±0.07, p-NF-κB (A value): 0.57±0.05 vs. 0.31±0.03, both P < 0.05], and serum IFN-β levels were also significantly higher (ng/L: 256.02±3.84 vs. 64.15±1.17, P < 0.05). The cGAS inhibitor pretreatment groups showed restored alveolar structural integrity, reduced inflammatory cell infiltration, and decreased hemorrhage area, along with dose-dependent lower pathological scores as well as the protein expressions of cGAS, STING, p-TBK1, p-IRF3 and p-NF-κB p65 in lung tissue, with significant differences between the 500 μg/kg inhibitor group and ALI model group [pathological score: 2.67±0.58 vs. 10.33±0.58, cGAS protein (cGAS/β-actin): 0.56±0.03 vs. 1.24±0.02, STING protein (STING/β-actin): 0.67±0.03 vs. 1.27±0.01, p-TBK1 protein (p-TBK1/β-actin): 0.28±0.01 vs. 1.34±0.03, p-IRF3 protein (p-IRF3/β-actin): 0.32±0.01 vs. 1.23±0.02, p-NF-κB p65 protein (p-NF-κB p65/β-actin): 0.63±0.01 vs. 1.30±0.02, all P < 0.05]. Compared with the ALI model group, positive expressions of STING and p-NF-κB in lung tissue were significantly reduced in the 500 μg/kg inhibitor group [STING (A value): 0.40±0.01 vs. 0.51±0.03, p-NF-κB (A value): 0.43±0.02 vs. 0.57±0.05, both P < 0.05], and serum IFN-β levels were also markedly reduced (ng/L: 150.03±6.19 vs. 256.02±3.84, P < 0.05). CONCLUSIONS The cGAS/STING pathway is activated in oleic acid-induced ALI, leading to exacerbated inflammatory responses and increased lung damage. RU.521 can inhibit cGAS, thereby down-regulating the expression of pathway proteins and cytokines, and providing protection to lung tissue.
Animals ; Acute Lung Injury/chemically induced* ; Male ; Nucleotidyltransferases/metabolism* ; Mice ; Signal Transduction ; Mice, Inbred C57BL ; Membrane Proteins/metabolism* ; Oleic Acid/adverse effects* ; Transcription Factor RelA/metabolism* ; Lung/pathology* ; Interferon Regulatory Factor-3/metabolism* ; Disease Models, Animal

The development of nonalcoholic fatty liver disease (NAFLD) is closely related to the fatty acid (FA) uptake. This study aimed to investigate the effect of Krüppel-like factor 9 (KLF9) on CD36 (typical fatty acid translocase), hepatocellular lipid metabolism as well as the development and progression of nonalcoholic fatty liver. High-fat diet-induced obese C57BL/6J mice and db/db mice were used to test the expression levels of Klf9 and Cd36 in the livers. The primary hepatocytes were isolated from C57BL/6J mice, treated with Ad-GFP, Ad-Klf9, Ad-shCtrl or Ad-shKlf9, and then incubated with oleic acid and palmitic acid for 24 h. Liver-specific knockout of Klf9 mice were established. The protein levels and relative mRNA levels were examined by Western blot and real-time PCR, respectively. Triglyceride content was determined by using an assay kit. Lipid content was determined by Oil Red O staining. The results showed that: (1) Klf9 expression levels were increased in the livers of high-fat diet-induced obese mice and db/db mice, compared to their respective control mice. (2) Adenovirus-mediated overexpression of Klf9 in primary hepatocytes increased Cd36 expression and cellular triglyceride contents. (3) In contrast, adenovirus-mediated knockdown of Klf9 expression in primary hepatocytes by Ad-shKlf9 decreased Cd36 expression and cellular triglyceride contents. (4) Finally, Klf9 deficiency decreased liver Cd36 expression and alleviated fatty liver phenotype of high-fat diet-induced obese mice. These results suggest that KLF9 can regulate hepatic lipid metabolism and development of NAFLD by promoting the expression of CD36.
Animals ; CD36 Antigens/metabolism* ; Diet, High-Fat ; Kruppel-Like Transcription Factors/metabolism* ; Lipid Metabolism ; Liver ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; Non-alcoholic Fatty Liver Disease/metabolism* ; Oleic Acid/metabolism*

To explore interleukin-6 (IL-6) production and characterize lipid accumulation in L02 hepatocytes induced by sodium oleate. L02 hepatocytes were incubated with 0, 37.5, 75, 150, 300, 600, or 1,200 μmol/L sodium oleate for 24 h, and the supernatant was collected to detect the concentration of IL-6. L02 hepatocytes were incubated with 300, 150, 75, or 0 μmol/L sodium oleate for 0-24 h. The supernatant was collected for detection of IL-6 and free fatty acids. L02 hepatocytes treated with 300 μmol/L sodium oleate for 0-24 h were stained with Oil Red O. With extended sodium oleate incubation time, IL-6 levels increased, and free fatty acids decreased. After 24 h incubation, IL-6 levels increased as sodium oleate increased from 37.5 to 300 μmol/L (
Dose-Response Relationship, Drug ; Hepatocytes/metabolism* ; Humans ; Interleukin-6/metabolism* ; Lipid Metabolism ; Oleic Acid/administration & dosage* ; Time Factors

Stearoyl-ACP Δ⁹ desaturase (SAD) catalyzes the synthesis of monounsaturated oleic acid or palmitoleic acid in plastids. SAD is the key enzyme to control the ratio of saturated fatty acids to unsaturated fatty acids in plant cells. In order to analyze the regulation mechanism of soybean oleic acid synthesis, soybean (Glycine max) GmSAD family members were genome-wide identified, and their conserved functional domains and physicochemical properties were also analyzed by bioinformatics tools. The spatiotemporal expression profile of each member of GmSADs was detected by qRT-PCR. The expression vectors of GmSAD5 were constructed. The enzyme activity and biological function of GmSAD5 were examined by Agrobacterium-mediated transient expression in Nicotiana tabacum leaves and genetic transformation of oleic acid-deficient yeast (Saccharomyces cerevisiae) mutant BY4389. Results show that the soybean genome contains five GmSAD family members, all encoding an enzyme protein with diiron center and two conservative histidine enrichment motifs (EENRHG and DEKRHE) specific to SAD enzymes. The active enzyme protein was predicted as a homodimer. Phylogenetic analysis indicated that five GmSADs were divided into two subgroups, which were closely related to AtSSI2 and AtSAD6, respectively. The expression profiles of GmSAD members were significantly different in soybean roots, stems, leaves, flowers, and seeds at different developmental stages. Among them, GmSAD5 expressed highly in the middle and late stages of developmental seeds, which coincided with the oil accumulation period. Transient expression of GmSAD5 in tobacco leaves increased the oleic acid and total oil content in leaf tissue by 5.56% and 2.73%, respectively, while stearic acid content was reduced by 2.46%. Functional complementation assay in defective yeast strain BY4389 demonstrated that overexpression of GmSAD5 was able to restore the synthesis of monounsaturated oleic acid, resulting in high oil accumulation. Taken together, soybean GmSAD5 has strong selectivity to stearic acid substrates and can efficiently catalyze the biosynthesis of monounsaturated oleic acid. It lays the foundation for the study of soybean seed oleic acid and total oil accumulation mechanism, providing an excellent target for genetic improvement of oil quality in soybean.
Fatty Acid Desaturases ; genetics ; metabolism ; Gene Expression Profiling ; Oleic Acid ; biosynthesis ; Phylogeny ; Plant Proteins ; genetics ; Seeds ; chemistry ; Soybeans ; classification ; enzymology ; genetics

The aim of the present study was to investigate the role of ferroptosis in acute lung injury (ALI) mouse model induced by oleic acid (OA). ALI was induced in the mice via the lateral tail vein injection of pure OA. The histopathological score of lung, lung wet-dry weight ratio and the protein content of bronchoalveolar lavage fluid (BALF) were used as the evaluation indexes of ALI. Iron concentration, glutathione (GSH) and malondialdehyde (MDA) contents in the lung tissues were measured using corresponding assay kits. The ultrastructure of pulmonary cells was observed by transmission electron microscope (TEM), and the expression level of prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA was detected by quantitative polymerase chain reaction (q-PCR). Protein expression levels of glutathione peroxidase 4 (GPX4), ferritin and transferrin receptor 1 (TfR1) in lung tissues were determined by Western blot. The results showed that histopathological scores of lung tissues, lung wet-dry weight ratio and protein in BALF in the OA group were higher than those of the control group. In the OA group, the mitochondria of pulmonary cells were shrunken, and the mitochondrial membrane was ruptured. The expression level of PTGS2 mRNA in the OA group was seven folds over that in the control group. Iron overload, GSH depletion and accumulation of MDA were observed in the OA group. Compared with the control group, the protein expression levels of GPX4 and ferritin in lung tissue were down-regulated in the OA group. These results suggest that ferroptosis plays a potential role in the pathogenesis of ALI in our mouse model, which may provide new insights for development of new drugs for ALI.
Acute Lung Injury ; chemically induced ; pathology ; Animals ; Apoptosis ; Bronchoalveolar Lavage Fluid ; chemistry ; Cyclooxygenase 2 ; metabolism ; Ferritins ; metabolism ; Glutathione ; analysis ; Glutathione Peroxidase ; metabolism ; Iron ; analysis ; Iron Overload ; physiopathology ; Lung ; cytology ; pathology ; Malondialdehyde ; analysis ; Mice ; Microscopy, Electron, Transmission ; Mitochondrial Membranes ; ultrastructure ; Oleic Acid

Acetic acid, as a main by-product generated in the pretreatment process of lignocellulose hydrolysis, significantly affects cell growth and lipid synthesis of oleaginous microorganisms. Therefore, we studied the tolerance of Rhodotorula glutinis to acetic acid and its lipid synthesis from substrate containing acetic acid. In the mixed sugar medium containing 6 g/L glucose and 44 g/L xylose, and supplemented with acetic acid, the cell growth was not:inhibited when the acetic acid concentration was below 10 g/L. Compared with the control, the biomass, lipid concentration and lipid content of R. glutinis increased 21.5%, 171% and 122% respectively when acetic acid concentration was 10 g/L. Furthermore, R. glutinis could accumulate lipid with acetate as the sole carbon source. Lipid concentration and lipid yield reached 3.20 g/L and 13% respectively with the initial acetic acid concentration of 25 g/L. The lipid composition was analyzed by gas chromatograph. The main composition of lipid produced with acetic acid was palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, including 40.9% saturated fatty acids and 59.1% unsaturated fatty acids. The lipid composition was similar to that of plant oil, indicating that lipid from oleaginous yeast R. glutinis had potential as the feedstock of biodiesel production. These results demonstrated that a certain concentration of acetic acid need not to be removed in the detoxification process when using lignocelluloses hydrolysate to produce microbial lipid by R. glutinis.
Acetic Acid ; Biofuels ; Biomass ; Culture Media ; Fatty Acids ; Hydrolysis ; Industrial Microbiology ; Lignin ; chemistry ; Linoleic Acid ; Lipids ; biosynthesis ; Oleic Acid ; Rhodotorula ; metabolism

The fruit of Pandanus tectorius (PTF) has a long history of use as a folk medicine to treat hyperlipidemia in Hainan province, South China. Our previous studies have shown that the n-butanol extract of PTF is rich in caffeoylquinic acids and has an adequate therapeutic effect on dyslipidemic animals induced by high-fat diet. In this work, seven caffeoylquinic acids isolated from PTF were screened for the lipid-lowering activity in HepG2 hepatoma cells. Oil-Red O staining, microscopy and intracellular triglyceride (TG) and total cholesterol (TC) quantification showed that 3-O-caffeoylquinic acid (3-CQA), 3, 5-di-O-caffeoylquinic acid (3,5-CQA), and 3,4,5-tri-O-caffeoylquinic acid (3,4,5-CQA) significantly inhibited lipid accumulation induced by oleic acid and decreased intracellular levels of TC and TG in a dose-dependent manner. These three caffeoylquinic acids showed no significant cytotoxicity at concentrations of 1 -50 μmol x L(-1) as determined by MTT assay. Realtime quantitative PCR revealed that 3-CQA and 3, 5-CQA significantly increased the expression of lipid oxidation-related genes PPARα, CPT-1 and ACOX1 while 3-CQA, 3, 5-CQA and 3,4,5-CQA decreased the expression of lipogenic genes SREBP-1c, SREBP-2, HMGR, ACC, FAS. Overall, 3-CQA, 3, 5-CQA and 3, 4, 5-CQA may be the principal hypolipidemic components in PTF which can decrease intracellular lipid accumulation through up-regulating the expression of lipid oxidative genes and down-regulating the expression of lipogenic genes.
Carcinoma, Hepatocellular ; metabolism ; China ; Cholesterol ; metabolism ; Gene Expression Regulation ; Hep G2 Cells ; Humans ; Lipid Metabolism ; Liver Neoplasms ; metabolism ; Oleic Acid ; Pandanaceae ; chemistry ; Quinic Acid ; analogs & derivatives ; chemistry ; Sterol Regulatory Element Binding Protein 1 ; Triglycerides ; metabolism

Recent data have revealed that inhibiting autophagy exacerbates lipid accumulation in hepatocytes and nitrite treatment reduces total triglyceride levels in the high-fat diet mice. Therefore, the present study aimed to determine the effects of nitrite on simple hepatic steatosis and the possible role of autophagy. Firstly, steatotic L-02 cells were induced by incubating L-02 cells with 1.2 mmol · L(-1) oleic acid (OA) for 24 h. Secondly, steatotic L-02 cells were treated with 0.2 mmol · L(-1) sodium nitrite (SN) plus 3-methyladenine (3-MA), or chloroquine (CQ) for 24 h, and then lipid accumulation was measured with oil red O staining and triglyceride quantification. The notable steatosis could be observed in L-02 cells following exposure to 1.2 mmol · L(-1) OA for 24 h. Treatment with 0.2 mmol · L(-1) sodium nitrite reduced lipid accumulation in steatotic L-02 cells. 3-MA weakened the ability of sodium nitrite to ameliorate hepatic steatosis. Additionally, the sodium nitrite increased number of LC3-II immunostaining puncta and LC3-II protein expression was confirmed by immunofluorescence or Western blot analysis, and the effects were enhanced by CQ treatment. The number of increased cytoplasm vacuoles and lysosomes increased was confirmed by phase contrast and fluorescence microscope respectively. The increased autolysosome was detected by electron microscopy, this phenomenon could be reversed by CQ treatment. These data demonstrated that sodium nitrite enhanced the autophagic flux and decomposition of triglycerides in steatotic L-02 cells.
Adenine ; analogs & derivatives ; Autophagy ; Blotting, Western ; Cells, Cultured ; Chloroquine ; Cytoplasm ; Fatty Liver ; Hepatocytes ; drug effects ; Humans ; Lipid Metabolism ; drug effects ; Microscopy, Fluorescence ; Microtubule-Associated Proteins ; metabolism ; Oleic Acid ; Sodium Nitrite ; pharmacology ; Triglycerides

The Escherichia coli fadR protein product, a paradigm/prototypical FadR regulator, positively regulates fabA and fabB, the two critical genes for unsaturated fatty acid (UFA) biosynthesis. However the scenario in the other Ɣ-proteobacteria, such as Shewanella with the marine origin, is unusual in that Rodionov and coworkers predicted that only fabA (not fabB) has a binding site for FadR protein. It raised the possibility of fad regulon contraction. Here we report that this is the case. Sequence alignment of the FadR homologs revealed that the N-terminal DNA-binding domain exhibited remarkable similarity, whereas the ligand-accepting motif at C-terminus is relatively-less conserved. The FadR homologue of S. oneidensis (referred to FadR_she) was over-expressed and purified to homogeneity. Integrative evidence obtained by FPLC (fast protein liquid chromatography) and chemical cross-linking analyses elucidated that FadR_she protein can dimerize in solution, whose identity was determined by MALDI-TOF-MS. In vitro data from electrophoretic mobility shift assays suggested that FadR_she is almost functionally-exchangeable/equivalent to E. coli FadR (FadR_ec) in the ability of binding the E. coli fabA (and fabB) promoters. In an agreement with that of E. coli fabA, S. oneidensis fabA promoter bound both FadR_she and FadR_ec, and was disassociated specifically with the FadR regulatory protein upon the addition of long-chain acyl-CoA thioesters. To monitor in vivo effect exerted by FadR on Shewanella fabA expression, the native promoter of S. oneidensis fabA was fused to a LacZ reporter gene to engineer a chromosome fabA-lacZ transcriptional fusion in E. coli. As anticipated, the removal of fadR gene gave about 2-fold decrement of Shewanella fabA expression by β-gal activity, which is almost identical to the inhibitory level by the addition of oleate. Therefore, we concluded that fabA is contracted to be the only one member of fad regulon in the context of fatty acid synthesis in the marine bacteria Shewanella genus.
Amino Acid Sequence ; Bacterial Proteins ; chemistry ; metabolism ; Base Sequence ; Binding Sites ; DNA, Bacterial ; metabolism ; Escherichia coli ; genetics ; metabolism ; Fatty Acid Synthase, Type II ; genetics ; metabolism ; Fatty Acids ; biosynthesis ; Gene Expression Regulation, Bacterial ; drug effects ; Molecular Sequence Data ; Oleic Acid ; pharmacology ; Protein Binding ; drug effects ; Regulon ; genetics ; Repressor Proteins ; chemistry ; metabolism ; Shewanella ; genetics ; metabolism

BACKGROUNDAcute lung injury (ALI) is a common syndrome associated with high morbidity and mortality in emergency medicine. Cell apoptosis plays a key role in the pathogenesis of ALI. Hydrogen sulfide (H(2)S) plays a protective role during acute lung injury. We designed this study to examine the role of H(2)S in the lung alveolar epithelial cell apoptosis in rats with ALI.

METHODSSixty-nine male Sprague Dawley rats were used. ALI was induced by intra-tail vein injection of oleic acid (OA). NaHS solution was injected intraperitonally 30 minutes before OA injection as the NaHS pretreatment group. Single sodium hydrosulfide pretreatment group and control group were designed. Index of quantitative assessment (IQA), wet/dry weight (W/D) ratio and the percentage of polymorphonuclear leukocyte (PMN) cells in the bronchoalveolar lavage fluid (BALF) were determined. H(2)S level in lung tissue was measured by a sensitive sulphur electrode. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and Fas protein was measured by immunohistochemical staining.

RESULTSThe level of endogenous H(2)S in lung tissue decreased with the development of ALI induced by OA injection. Apoptosis and Fas protein in alveolar epithelial cells increased in the ALI of rats but NaHS lessened apoptosis and Fas protein expression in alveolar epithelial cells of rats with ALI.

CONCLUSIONEndogenous H(2)S protects rats from oleic acid-induced ALI, probably by inhibiting cell apoptosis.

Acute Lung Injury ; chemically induced ; drug therapy ; metabolism ; Animals ; Apoptosis ; physiology ; Epithelial Cells ; drug effects ; Hydrogen Sulfide ; metabolism ; In Situ Nick-End Labeling ; Male ; Oleic Acid ; toxicity ; Rats ; Rats, Sprague-Dawley ; Sulfides ; pharmacology ; therapeutic use