Effects of dimethyl sulphoxide on the synthesis of plasma proteins in the human hepatoma HepG2. Induction of an acute-phase-like reaction.
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ABSTRACT:
SUBMITTER: Iwasa F
PROVIDER: S-EPMC1149393 | biostudies-other | 1988 Aug
REPOSITORIES: biostudies-other
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Project description:The effects of acute-phase inducers and dimethyl sulphoxide (Me2SO) on delta-aminolaevulinate (ALA) synthase in HepG2 cells were examined. Treatment of cells with Me2SO resulted in a significant increase in ALA synthase activity. Interleukin-6 increased ALA synthase activity only slightly, but it substantially potentiated the induction of ALA synthase by Me2SO. These data suggest that ALA synthase activity in liver is altered during acute-phase reactions.
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Project description:Exposure of cultured human hepatoma cells (Hep G2) to medium containing 2% (v/v) dimethyl sulphoxide resulted in an approximate doubling in the activity of delta-aminolaevulinate dehydratase, an increase in the haem content and a decreased growth rate; induced enzyme activity was decrease by 50% after treatment with alpha-amanitin. The findings are strikingly similar to those seen in murine Friend-virus-transformed erythroleukaemia cells.
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Project description:Acute phase reaction (APR) is a systemic inflammation triggered by several conditions associated with lipid profile alterations. We evaluated whether APR also associates with changes in cholesterol synthesis and absorption, HDL structure, composition, and cholesterol efflux capacity (CEC). We analyzed 59 subjects with APR related to infections, oncologic causes, or autoimmune diseases and 39 controls. We detected no difference in markers of cholesterol synthesis and absorption. Conversely, a significant reduction of LpA-I- and LpAI:AII-containing HDL (-28% and -44.8%, respectively) and of medium-sized HDL (-10.5%) occurred in APR. Total HDL CEC was impaired in APR subjects (-18%). Evaluating specific CEC pathways, we found significant reductions in CEC by aqueous diffusion and by the transporters scavenger receptor B-I and ABCG1 (-25.5, -41.1 and -30.4%, respectively). ABCA1-mediated CEC was not affected. Analyses adjusted for age and gender provided similar results. In addition, correcting for HDL-cholesterol (HDL-C) levels, the differences in aqueous diffusion total and ABCG1-CEC remained significant. APR subjects displayed higher levels of HDL serum amyloid A (+20-folds; P = 0.003). In conclusion, APR does not associate with cholesterol synthesis and absorption changes but with alterations of HDL composition and a marked impairment of HDL CEC, partly independent of HDL-C serum level reduction.
| S-EPMC5625127 | biostudies-literature
Project description:Acute-phase protein (APPs) serum levels have been studied in many human diseases, and their components contribute to host defense during the evolution of infectious diseases by acting as part of the innate immune system. Based on the importance of establishing new experimental models, the present investigation evaluated the modulation of APPs following inflammatory stimulus by the inoculation of Aeromonas hydrophila in tilapias. Fish were sampled 6 and 24 hours post-infection. Tilapias presented increase of positive APPs such as ceruloplasmin, haptoglobin, alpha-2-macroglobulin and complement C3, as well as decrease of negative APPs such as albumin and transferrin. The protein response of tilapias during the course of bacterial infection showed correlation with the kinetics of cellular accumulation in the inflamed focus with significant increase of granulocytes, thrombocytes, lymphocytes and macrophages. However, granulocytes were the predominant cells, associated with increment in the reactive oxygen species (ROS) production. Showing responses similar to those observed in humans, the modulation of APPs and the kinetics of cellular accumulation in the exudate demonstrate the feasibility of this alternative experimental model for advances and studies to understand changes in pathophysiological mechanisms of acute inflammatory reaction due to bacterial infection.
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Project description:Erythropoietin (Epo)-producing hepatoma cells (HepG2) reveal, in addition to the cytochromes of the respiratory chain, a photometrically measurable haem signal with absorbance maxima at 559 nm and 427 nm, suggesting the presence of a b-type cytochrome. This activity exhibited a low midpoint potential, CO-binding spectra and reduction which was insensitive to both cyanide and antimycin. This haem possessed a 22 kDa subunit and might be part of an electron transfer chain similar to the NADPH oxidase, since the NADPH oxidase cytosolic activating factor (p47) could be identified by Western blot analysis. H2O2, which was detected inside the cells by confocal microscopy, might therefore be produced by the suggested electron transfer chain. This cyanide- and antimycin-insensitive but hypoxia-sensitive cytochrome b would be an attractive candidate for controlled Epo production in response to pO2.
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Project description:delta-Aminolaevulinate (ALA) synthase, the rate-limiting enzyme in haem biosynthesis in the normal liver, was examined in human HepG2 hepatoma cells. Haemin, up to 100 microM, had no effect on ALA synthase activity in vitro; it did, however, exhibit a dose-dependent inhibitory action when added to cells growing in culture (half-maximal inhibition at 1 microM). The half-life of ALA synthase activity after haemin treatment was 2 h, which was similar to that found after treatment with cycloheximide. Cells treated with actinomycin D showed a longer half-life of the enzyme activity, i.e. 4 h, compared with haemin or cycloheximide treatment. Treatment of cells with succinylacetone markedly inhibited the activity of ALA dehydratase and 59Fe incorporation into haem, but in increased ALA synthase activity. Both the haemin-induced repression and the succinylacetone-mediated de-repression of ALA synthase activity were reversible within 4 h after replacing the medium with fresh medium without the chemical. In addition to succinylacetone, dimethyl sulphoxide and 3-methylcholanthrene induced the enzyme. Induction of ALA synthase by these chemicals was also suppressed by treatment of cells with haemin. These findings indicate that the level of ALA synthase in HepG2 cells is maintained by both synthesis and degradation of the enzyme, and that the synthesis of the enzyme is regulated by the concentration of regulatory free haem in the cell.
| S-EPMC1133345 | biostudies-other
Project description:Expression of late embryogenesis abundant (LEA) proteins is highly correlated with desiccation tolerance in anhydrobiotic animals, selected land plants, and bacteria. Genes encoding two LEA proteins, one localized to the cytoplasm/nucleus (AfrLEA2) and one targeted to mitochondria (AfrLEA3m), were stably transfected into human HepG2 cells. A trehalose transporter was used for intracellular loading of this disaccharide. Cells were rapidly and uniformly desiccated to low water content (<0.12 g H(2)O/g dry weight) with a recently developed spin-drying technique. Immediately on rehydration, control cells without LEA proteins or trehalose exhibited 0% membrane integrity, compared with 98% in cells loaded with trehalose and expressing AfrLEA2 or AfrLEA3m; surprisingly, AfrLEA3m without trehalose conferred 94% protection. Cell proliferation across 7 d showed an 18-fold increase for cells dried with AfrLEA3m and trehalose, compared with 27-fold for nondried controls. LEA proteins dramatically enhance desiccation tolerance in mammalian cells and offer the opportunity for engineering biostability in the dried state.
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Project description:Background and purposeStem cell transplantation therapy is a promising option for treatment of severe ischaemic heart disease. Dimethyl sulphoxide (DMSO) differentiates P19CL6 embryonic carcinoma cells into cardiomyocyte-like cells, but with low differentiation capacity. To improve the degree of this differentiation, we have assessed several derivatives of the differentiation-inducing factor-1 (DIF-1), originally found in the cellular slime mould Dictyostelium discoideum, on P19CL6 cells.Experimental approachP19CL6 cells were cultured with each derivative and 1% DMSO for up to 16 days. Differentiation was assessed by measuring the number of beating and non-beating aggregates, and the expression of genes relevant to cardiac tissue. The mechanism of action was investigated using a T-type Ca(2+) channel blocker.Key resultsOf all the DIF-1 derivatives tested only Br-DIF-1 showed any effects on cardiomyocyte differentiation. In the presence of 1% DMSO, Br-DIF-1 (0.3-3 µM) significantly and dose-dependently increased the number of spontaneously beating aggregates compared with 1% DMSO alone, by day 16. Expression of mRNA for T-type calcium channels was significantly increased by Br-DIF-1 + 1% DMSO compared with 1% DMSO alone. Mibefradil (a T-type Ca(2+) channel blocker; 100 nM) and a small interfering RNA for the T-type Ca(2+) channel both significantly decreased the beating rate of aggregates induced by Br-DIF-1 + 1% DMSO.Conclusions and implicationsBr-DIF-1 accelerated the differentiation, induced by 1% DMSO, of P19CL6 cells into spontaneously beating cardiomyocyte-like cells, partly by enhancing the expression of the T-type Ca(2+) channel gene.
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Project description:Serum amyloid A (SAA) proteins SAA1 and SAA2 are prominent acute-phase reactants which circulate in association with the high-density-lipoprotein (HDL) fraction of plasma. Plasma levels of SAA1 and SAA2 increase dramatically, by as much as 1000-fold, within 24 h of tissue injury and then rapidly decrease with cessation of the inflammatory stimulus, suggesting that SAA clearance and/or catabolism is important to the re-establishment of homoeostasis. In this context, aberrant SAA catabolism has long been considered a potential factor in the pathogenesis of reactive amyloidosis. To initiate studies aimed at understanding the differential regulation of SAA metabolism, we have produced 35S-labelled murine SAA1 and SAA2 in Escherichia coli, bound them individually to HDL, and then compared the plasma-clearance characteristics of SAA1 and SAA2 under normal and acute-phase conditions. When bound to normal HDL, SAA2 [half-life (t1/2) = 30 min] was cleared significantly faster than SAA1 (t1/2 = 75 min). Clearance of SAA1 and SAA2 was significantly slower when each was bound to acute-phase HDL as opposed to normal HDL, when clearance rates were determined in acute-phase mice versus normal mice, and when normal HDL was remodelled to contain both recombinant isotypes rather than just one of the isotypes. Thus it appears that an increased amount of SAA on HDL, or possibly the combined presence of both isotypes on HDL, is associated with a prolongation in the plasma half-life of SAA.
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