| 1. |
|
|
| 2. |
|
|
| 3. |
- Aspenström-Fagerlund, Bitte, et al.
(författare)
-
Fatty acids increase paracellular absorption of aluminium across Caco-2 cell monolayers
- 2009
-
Ingår i: Chemico-Biological Interactions. - : Elsevier BV. - 0009-2797 .- 1872-7786. ; 181:2, s. 272-278
-
Tidskriftsartikel (refereegranskat)abstract
- Passive paracellular absorption, regulated by tight junctions (TJs), is the main route for absorption of poorly absorbed hydrophilic substances. Surface active substances, such as fatty acids, may enhance absorption of these substances by affecting the integrity of TJ and increasing the permeability. It has been suggested that aluminium (Al) absorption occurs mainly by the paracellular route. Herein, we investigated if physiologically relevant exposures of fully differentiated Caco-2 cell monolayers to oleic acid and docosahexaenoic acid (DHA), which are fatty acids common in food, increase absorption of Al and the paracellular marker mannitol. In an Al toxicity test, mannitol and Al absorption through Caco-2 cell monolayers were similarly modulated by Al concentrations between 1 and 30mM, suggesting that absorption of the two compounds occurred via the same pathways. Exposure of Caco-2 cell monolayers to non-toxic concentrations of Al (2mM) and (14)C-mannitol in fatty acid emulsions (15 and 30mM oleic acid, 5 and 10mM DHA) caused a decreased transepithelial electrical resistance (TEER). Concomitantly, fractional absorption of Al and mannitol, expressed as percentage of apical Al and mannitol retrieved at the basolateral side, increased with increasing dose of fatty acids. Transmission electron microscopy was applied to assess the effect of oleic acid on the morphology of TJ. It was shown that oleic acid caused a less structured morphology of TJ in Caco-2 cell monolayers. Taken together our findings indicate that fatty acids common in food increase the paracellular intestinal absorption of Al. These findings may influence future risk assessment of human Al exposure.
|
|
| 4. |
- Carlquist, Magnus, et al.
(författare)
-
Flavonoids as inhibitors of human carbonyl reductase 1
- 2008
-
Ingår i: Chemico-Biological Interactions. - : Elsevier BV. - 1872-7786 .- 0009-2797. ; 174:2, s. 98-108
-
Tidskriftsartikel (refereegranskat)abstract
- Human carbonyl reductase 1 (CBR1), that is one of the enzymes responsible for the reduced efficiency of treatments by the antineoplastic agents anthracyclines, was functionally expressed in Saccharomyces cerevisiae. CBR1 was purified and kinetically characterised using daunorubicin as substrate. CBR1-catalysed reduction of daunorubicin followed an apparent Michaelis-Menten kinetics with K-M = 85.2 +/- 26.7 mu M and V-max =3490 +/- 220 mu mol/(min g protein). The type of inhibition for the flavonoid compound rutin was determined by studying initial reaction rates in the presence of rutin. The inhibition kinetics was found to follow an apparent mixed inhibition with K-ic = 1.8 +/- 1.2 mu M and K-iu = 2.8 +/- 1.6 mu M. IC50-values were also determined for a set of flavonoids in order to identify essential structure for inhibition activity. Computational docking experiments of the four best inhibitors to the catalytic site of CBR1 showed that the flavonoid skeleton structure was the binding part of the molecule. The presence of a sugar moiety in I and 2, or a sugar mimicking part in 9. directed the orientation of the flavonoid so that the sugars were pointing outwards, giving rise to a stabilising effect to the binding. Finally, additional binding epitopes that interacted with various parts of the flavonoid ligand were identified and could potentially be targeted for further improvement of inhibition activity. These included; hydrogen-binding sites surrounding Ser139 and Cys226, Met234 and Tyr193 or Trp229; aromatic-aromatic interaction with Tyr193, Trp229 or NADPH; van der Waals interactions with IIe140. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Hultberg, Malin, et al.
(författare)
-
Oxidative stress decreases extracellular homocysteine concentration in human hepatoma (HepG2) cell cultures
- 2007
-
Ingår i: Chemico-Biological Interactions. - : Elsevier BV. - 1872-7786 .- 0009-2797. ; 165:1, s. 54-58
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Mild hyperhomocysteinemia is associated with premature vascular disease. The mechanism behind the vascular injuries is, however, still unknown. Homocysteine may be catabolized in the trans sulfuration pathway to cysteine. Cystathionine beta-synthase, which catalyses the first step in the transsulfuration pathway is redox-sensitive. We have therefore investigated total extracellular homocysteine turnover in the presence of oxidative stress in human cell lines. Methods: The turnover of total extracellular homocysteine in HeLa and hepatoma cell cultures has been investigated in the presence of hydrogen peroxide. Furthermore, the effect of hydrogen peroxide on the removal of high amounts of exogenously added homocysteine was also studied. Results: Total extracellular homocysteine concentration in hepatoma cell cultures decreased in the presence of hydrogen peroxide, whereas the extracellular homocysteine concentration in HeLa cell cultures was not influenced. There was no significant change of intracellular homocysteine in any type of cell cultures. Furthermore, the presence of hydrogen peroxide did not increase the removal of exogenously added homocysteine. Conclusion: The presence of hydrogen peroxide probably increases the activity of the transsulfuration pathway in hepatoma cell cultures, which increases the intracellular use of homocysteine and lowers its extracellular release. Consequently this mechanism might tend to lower total plasma homocysteine concentration in oxidative stress. (c) 2006 Elsevier Ireland Ltd. All rights reserved.
|
|
| 9. |
|
|
| 10. |
- Hultberg, Malin, et al.
(författare)
-
Traces of copper ions deplete glutathione in human hepatoma cell cultures with low cysteine content
- 2007
-
Ingår i: Chemico-Biological Interactions. - : Elsevier BV. - 1872-7786 .- 0009-2797. ; 167:1, s. 56-62
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Cell death induced by intracellutar glutathione depletion has been reported to be dependent on the presence of trace amounts of extracellular copper ions. Since little is known about the relationship between glutathione depletion and copper homeostasis, we have in the present study further investigated the role of low amounts of copper ions in glutathione depletion. Methods: Glutathione turnover was investigated in HeLa and hepatoma cell cultures with normal and low cysteine content in the presence of copper ions (1 and 10 mu mol/L) and two other glutathione-stimulating agents (lipoic acid and mercury ions). Results: Copper ions (10 mu mol/L) caused relatively small increases in total amount of glutathione (the sum of the intracellular and the extracellular amount of glutathione) in HeLa and hepatoma cell cultures with normal cysteine levels (420 nmol/mL) compared to control cell cultures, whereas lipoic acid and mercury ions strongly increased total glutathione in both types of cell cultures. Lower amount of total glutathione was observed in cell cultures with a lower cysteine levels (84 nmol/mL), which is similar to that in human plasma. A strongly decreased total amount of glutathione in the presence of copper ions was observed in hepatoma cell cultures with lower cysteine levels, whereas the other agents showed effects similar to those described for cell cultures with normal cysteine levels. Conclusion: Glutathione synthesis in hepatoma cell cultures is probably more sensitive to a low cysteine level than HeLa cell cultures, and the presence of copper ions further decreases the availability of cysteine probably by increasing the disultide binding to cysteine residues in extracellular proteins, which causes a further decrease of total glutathione. (c) 2007 Elsevier Ireland Ltd. All rights reserved.
|
|
