Conformational properties of serum albumin binding sites in rats with different behaviour in the open field test

A fluorescent reporter detects details of aromatic ligand interference in drug-binding sites of human serum albumin

Human serum albumin (HSA) transports many ligands including small aromatic molecules: metabolites, drugs etc. Phenylbutazone is an anti-inflammatory drug, which binds to the drug-binding site I of HSA. Its interaction with this site has been studied using a fluorescent dye, CAPIDAN, whose fluorescence in serum originates from HSA and is sensitive to the changes in HSA site I in some diseases. Its fluorescence in HSA solutions is strongly suppressed by phenylbutazone. This phenomenon seems to be a basic sign of a simple drug-dye competition. However, a more detailed study of the time-resolved fluorescence decay of CAPIDAN has shown that phenylbutazone lowers fluorescence without changing the total amount of bound dye. In brief, the HSA-bound dye forms three populations due to three types of environment at the binding sites. The first two populations probably have a rather strong Coulomb interaction with the positive charge of residues Arginine 218 or Arginine 222 in site I and are responsible for approximately 90% of the total fluorescence. Phenylbutazone blocks this interaction and therefore lowers this fluorescence. At the same time the binding of the third population increases considerably in the presence of phenylbutazone, and, as a result, the actual number of bound dye molecules remains almost unchanged despite the ligand competition. So, time resolved fluorescence of the reporter allows to observe details of interactions and interference of aromatic ligands in drug binding site I of HSA both in isolated HSA and in serum.

Dizocilpine and cycloheximide prevent inhibition of c-Fos gene expression by delta sleep-inducing peptide in the paraventricular nucleus of the hypothalamus in rats with different resistance to emotional stress

The effects of the non-competitive NMDA-receptor blocker MK-801 (dizocilpine) and the protein synthesis inhibitor cycloheximide on the delta sleep-inducing peptide (DSIP) inhibition of c-Fos immediate early gene expression were studied in the parvocellular subdivision of the hypothalamic paraventricular nucleus (pPVN) of male Wistar rats with either high or low resistance to emotional stress, predicted from differences in their open-field behaviour. The experiments show that intraperitoneal (i.p.) DSIP injection (60 nmol/kg) decreased the number of Fos-immunoreactive (Fos-IR) cells in the pPVN, activated by immobilization. The NMDA-receptor antagonist dizocilpine (MK-801) (90 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats predisposed to emotional stress. The protein synthesis inhibitor cycloheximide (210 nmol i.c.v.) prevented the inhibition of c-Fos expression by DSIP in the pPVN of rats that were resistant to emotional stress. The experiments indicate that the DSIP effect on c-Fos gene expression might be mediated by NMDA-receptors. DSIP may induce production of some protein transcription factors, transmitting a signal from membrane NMDA-receptors to the nucleus.

A potential role for free fatty acids in the pathogenesis of preeclampsia

OBJECTIVE

Pregnant women with the vascular complication of preeclampsia show altered lipid metabolism characterized by elevated circulating triglycerides and nonesterified free fatty acids. We have compared the effect of maternal plasma from women with and without preeclampsia on cultured vascular endothelial cells and determined whether these plasma-induced changes were reproduced with free fatty acid solutions of palmitic, oleic and linoleic acid, representative of circulating levels reported in preeclampsia.

METHODS

Lipid accumulation was quantified by oil-red O staining, apoptosis by terminal dUTP nick-end labelling (TUNEL) and the measurement of mitochondrial redox capacity, and membrane potential recorded using MTT reduction and JC-1 accumulation for human umbilical vein endothelial cells (HUVECs) exposed to plasma and free fatty acids.

RESULTS

Lipid droplet accumulation was significantly increased in cultured HUVECs conditioned with maternal plasma from pregnancies with preeclampsia compared with normal uncomplicated controls. This increase was replicated following exposure to free fatty acids at the combined concentrations defined in preeclampsia. Plasma from these women also caused a significant decrease in mitochondrial dehydrogenase activity, a marked reduction in mitochondrial membrane potential and an increase in apoptosis compared with normal pregnancy. Again these effects were reproduced using free fatty acids in combination at the levels previously associated with preeclampsia.

CONCLUSION

These findings support the concept of a circulating pathogenic factor for preeclampsia and highlight the possibility that this factor is not a single compound but perhaps the combined elevation of the free fatty acids palmitic, oleic and linoleic acid in the maternal circulation.

Creation of new physicochemical methods for blood analysis on the base of fluorescent probes

This review deals with the development of new methods for studies of blood cells and plasma, based on the use of special dye molecules, the so-called fluorescent probes. These probes can also be used for clinical diagnosis. Probes and new methods on the basis of these probes were created for measurements of plasma and serum lipoproteins, serum albumin binding centers, blood leukocyte intracellular lipoproteins, allergens.