Effect of Benzo(a)pyrene on the Expression of miR-483-3p in Hepatocyte Primary Culture and Rat Liver.

Here, we suggested that the epigenetic mechanism of benzo(a)pyrene (BP) action might be based on the aryl hydrocarbon receptor (AhR)-mediated transcription of the target genes, including miRNAs, that have the dioxin response element (DRE) in their promoters. The effect of BP on the expression of the oncogenic miR-483-3p, its host gene IGF2, and target gene IGF1 in primary hepatocytes and in the liver of Wistar female rats was investigated. The activation of AhR was confirmed using selective AhR inhibitor CH-223191 and by evaluating expression of the target CYP1A1 gene. The lack of coordination between the expression of miR-483-3p and its host gene IGF2 was revealed, which may be due to the presence of the binding site for the estrogen receptor alpha (ERα), which is a negative expression regulator. Our results confirm the existence of the AhR-mediated pathway in the regulation of expression of miR-483-3p, IGF1, and IGF2 under BP exposure, which is of considerable interest for understanding the epigenetic mechanisms of the carcinogenic effect of BP.

Production and Analysis of Biological Properties of Recombinant Human Apolipoprotein A-I.

Production of recombinant human apolipoprotein A-I (apoA-I) in E. coli cells is described and its biological properties are compared with those of natural protein. Recombinant apoA-I was isolated as a chimeric polypeptide and then processed to a mature form apoA-I (rapo-I). We studied the ability of the resulting protein to penetrate into hepatocyte nuclei and regulate the rate of DNA biosynthesis in complex with estriol. Penetration of rapoA-I conjugated with FITC into hepatocyte nuclei was demonstrated. rapoA-I-estriol and apoA-I-estriol complexes induced similar increase in DNA biosynthesis rate in isolated hepatocytes, which confi rms functional similarity of the obtained recombinant mature protein (rapoA-I) and native human apoA-I.

Effect of apolipoprotein a-I complex with tetrahydrocortisone on protein biosynthesis and glucose absorption by rat hepatocytes.

We studied the effect of apolipoprotein A-I-tetrahydrocortisone complex on (14)C glucose absorption and lactate accumulation and on the rate of protein biosynthesis in isolated rat hepatocytes. The presence of apolipoprotein A-I-tetrahydrocortisone complex in the incubation medium increased absorption of labeled glucose by hepatocytes by 52%, while lactate content in the conditioning medium increased 4-fold. The rate of protein biosynthesis increased by 80% in comparison with control cells. It is hypothesized that the increase in protein biosynthesis rate in hepatocytes under the effect of apolipoprotein A-I-tetrahydrocortisone complex is due to stimulation of energy metabolism, specifically, of its glycolytic component.

[Effect of a complex of corticosteroids with apolipoprotein A-I on protein biosynthesis in cultured hepatocytes].

A complex of apolipoprotein A-I with steroid hormones containing reduced Δ4, 3-ketogroup in the A ring was shown to increase the rate of protein synthesis in the cultured rat hepatocytes. The biological activity of the hormones depends on the position of the oxygroup of the third carbonic atom and hydrogen at the fifth position of a carbonic atom. The cis-position is more preferable for the biological effect. The oxygroup at the third position of the A-ring may be replaced by the sulfo-group. The complex of dehydroepiandrosterone sulphate with apolipoprotein A-I increases the rate of protein biosynthesis in the cultured rat hepatocytes, which confirms the involvement of this hormone in the regulation of gene expression.

Effect of complexes of apolipoprotein A-I with tetrahydrocortisol and pregnenolone on protein biosynthesis in rat hepatocytes culture.

Complexes of apolipoprotein A-I with tetrahydrocortisol and pregnenolone exhibit high biological activity and increase the rate of protein biosynthesis in the culture of rat hepatocytes. An important role in this process is played by reduced delta44-3-keto group in the A-ring of steroid hormones. A complex of apolipoprotein A-I and pregnenolone modulated the rate of protein biosynthesis in liver cells. Hence, the observed changes are not organ-specific for this steroid. Our results suggest that this mechanism of regulation play an important role in intracellular regeneration and proliferation.

Interaction of apolipoproteins A-I and E in the regulation of DNA, RNA, and protein biosynthesis in cultured rat hepatocytes.

Experiments on hepatocyte culture showed that apolipoprotein A-I-tetrahydrocortisol complex increases the rate of DNA, RNA, and protein biosynthesis measured by radioactive label incorporation. Apolipoprotein E acted as competitor of the apolipoprotein A-I-tetrahydrocortisol complex and abolished biological activity of the latter. We hypothesize that this mechanism of regulation plays an important role in processes of intracellular regeneration and proliferation.