Cholesterol synthesis in cultured human peripheral lymphocytes. Influence of LDL, HDL, cholesterol/phosphatidylcholine liposomes and complete serum

Vitellogenin 1 is essential for fish reproduction by transporting DHA-containing phosphatidylcholine from liver to ovary

Vitellogenins (Vtgs) are essential for female reproduction in oviparous animals, yet the exact roles and mechanisms remain unknown. In the present study, we knocked out vtg1, which is the most abundant Vtg in zebrafish, Danio rerio via the CRISPR/Cas 9 technology. We aimed to identify the roles of Vtg1 and related mechanisms in reproduction and development. We found that, the Vtg1-deficient female zebrafish reduced gonadosomatic index, egg production, yolk granules and mature follicles in ovary compared to the wide type (WT). Moreover, the Vtg1-deficient zebrafish diminished hatching rates, cumulative survival rate, swimming capacity and food intake, but increased malformation rate, and delayed swim bladder development during embryo and early-larval phases. The Vtg1-deficiency in female broodstock inhibited docosahexaenoic acid-enriched phosphatidylcholine (DHA-PC) transportation from liver to ovary, which lowered DHA-PC content in ovary and offspring during larval stage. However, the Vtg1-deficient zebrafish increased gradually the total DHA-PC content via exogeneous food intake, and the differences in swimming capacity and food intake returned to normal as they matured. Furthermore, supplementing Vtg1-deficient zebrafish with dietary PC and DHA partly ameliorated the impaired female reproductive capacity and larval development during early phases. This study indicates that, DHA and PC carried by Vtg1 are crucial for female fecundity, and affect embryo and larval development through maternal-nutrition effects. This is the first study elucidating the nutrient and physiological functions of Vtg1 and the underlying biochemical mechanisms in fish reproduction and development.

The role of lipoproteins in the transport and uptake of cyclosporine and dihydro-tacrolimus into HepG2 and JURKAT cell lines

OBJECTIVES

We wish to examine the role of lipoproteins in the transport and cellular uptake of cyclosporine (CsA) and tacrolimus.

DESIGN AND METHODS

The distribution of tritiated CsA and tacrolimus among lipoproteins was determined in normo- and hypertriglyceridemic sera. The uptake of these two drugs into HepG2 and JURKAT cell lines was assessed in the presence of various concentrations of low density lipoproteins. (LDL).

RESULTS

Our data showed that about 60% of these drugs were transported by high density lipoprotein in normolipidemic sera, while about 50-60% were carried by very low density lipoprotein in hypertriglyceridemic sera. Almost 80% of CsA and 70% of tacrolimus entered HepG2 and JURKAT cells within the first hour of incubation in lipoprotein free media. However, the uptake was decreased (CsA by 60% and tacrolimus by 40%) in the presence of LDL.

CONCLUSIONS

Lipoproteins play a major role in the transport of CsA and tacrolimus, but not in their cellular uptake.

Lipoprotein interactions with T cells: an update

The role of plasma lipoproteins in atherogenesis is well recognized but the physiological relevance of their immunoregulatory properties is still questioned. Here Karine Traill and colleagues outline the recent advances that have been made towards unravelling the mechanisms of immunoregulation by lipoproteins in vitro and consider whether any of these mechanisms are operative in vivo. In particular they address the possible detrimental effects of high serum lipoprotein levels on immune function and the question of whether hyperlipidemia (or hypercholesterolemia) should be considered a risk factor for diminished immunity, for example in old age.

The role of lipoproteins in EBV early antigen induction in Raji cells

Synthesis of the Epstein-Barr virus (EBV) associated early antigen (EA) can be induced by a variety of agents in Raji cells, a latently EBV-infected Burkitt lymphoma line. We investigated the role of lipoproteins in this EA induction system. Cell growth was not affected by lipoprotein-deficiency, but EA induction by most combinations of the inducers TPA (tetradecanoyl-phorbol-acetate), IdU (iododeoxyuridine), n-BA (n-butyric acid), anti-IgM and EA inducing factor (EIF), was greatly reduced. Only the inducer combination TPA/n-BA was completely independent of the presence of lipoproteins, indicating a different induction pathway. Removing the lipid moieties of the culturing serum did not result in reduced EA induction. Thus, the lowered EA inducibility in lipoprotein-deficiency is due to the absence of the protein moiety (apolipoprotein). Addition of HDL or VLDL partially reconstituted the original EA inducibility, whereas LDL had no effect. Lipoproteins were particularly important during the first 4 hours of induction, the phase where inducers may act on cell membrane structures (e.g., receptors). But lipoproteins were also required throughout the incubation period, even in a late and inducer independent phase.

Relationships between lymphocyte cholesterol homeostasis and LDL-cholesterol

The homeostasis of cholesterol was studied in lymphocytes freshly isolated from the blood and cultured with or without low-density lipoprotein (LDL). The content of cholesterol decreased in the lymphocytes cultured without LDL, whereas LDL substituted for cellular cholesterol losses, in spite of almost suppressed LDL-receptor and lymphocyte cholesterol synthesis. Free cholesterol was taken up from LDL mainly via cholesterol exchange and, in contrast to esterified cellular cholesterol, rapidly excreted into the medium. In vitro stimulation of lymphocyte cholesterol synthesis was correlated to the ratio of esterified to free LDL-cholesterol in the blood from which the lymphocytes had been isolated. This result probably reflects the different rates of influx and efflux of esterified or free cholesterol between plasma lipoproteins and lymphocytes. These effects should be taken into account if LDL-cholesterol is determined in plasma for the evaluation of an individual's atherosclerotic risk.