Drug delivery system for poorly water-soluble compounds using lipocalin-type prostaglandin D synthase

Lipocalin-type prostaglandin D synthase (L-PGDS) is a member of the lipocalin superfamily and a secretory lipid-transporter protein, which binds a wide variety of hydrophobic small molecules. Here we show the feasibility of a novel drug delivery system (DDS), utilizing L-PGDS, for poorly water-soluble compounds such as diazepam (DZP), a major benzodiazepine anxiolytic drug, and 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX), an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist and anticonvulsant. Calorimetric experiments revealed for both compounds that each L-PGDS held three molecules with high binding affinities. By mass spectrometry, the 1:3 complex of L-PGDS and NBQX was observed. L-PGDS of 500μM increased the solubility of DZP and NBQX 7- and 2-fold, respectively, compared to PBS alone. To validate the potential of L-PGDS as a drug delivery vehicle in vivo, we have proved the prospective effects of these compounds via two separate delivery strategies. First, the oral administration of a DZP/L-PGDS complex in mice revealed an increased duration of pentobarbital-induced loss of righting reflex. Second, the intravenous treatment of ischemic gerbils with NBQX/L-PGDS complex showed a protective effect on delayed neuronal cell death at the hippocampal CA1 region. We propose that our novel DDS could facilitate pharmaceutical development and clinical usage of various water-insoluble compounds.

Possible roles of myostatin and PGC-1alpha in the increase of skeletal muscle and transformation of fiber type in cold-exposed chicks: expression of myostatin and PGC-1alpha in chicks exposed to cold

This study examined the hypothesis that myostatin and PGC-1alpha are involved in the increase in skeletal muscle mass and transformation of fiber type in cold-exposed chicks. One-week-old chicks were exposed to acute (24h) or long-term (8d) cold at 4 degrees C or kept warm at 30 degrees C. Acute cold exposure induced a significant increase in the skeletal muscle weight and the ratio of slow- to fast-fiber specific troponin I expression (sTnI/fTnI), accompanied by a significant decrease in lactate dehydrogenase activity. Expression of myostatin mRNA in the muscle was significantly lower in cold-exposed chicks than in the controls, whereas PGC-1alpha mRNA expression was significantly enhanced. These changes in the gene expression rapidly returned to the levels of the control chicks after the end of cold exposure, whereas the changes in fiber type and enzymatic activity were not resumed within 24h after removal of cold exposure. On the other hand, long-term exposure to cold resulted in a remarkable increase in skeletal muscle weight, accompanied by a significant increase in the ratio of sTnI/fTnI and the enzymatic activities of cytochrome oxidase and lactate dehydrogenase. However, the expression level of myostatin mRNA in cold-exposed chicks was not different from that in their age-matched control chicks and that of PGC-1alpha mRNA was significantly lower than in the controls. These results indicate that myostatin and PGC-1alpha expression in the skeletal muscle rapidly change in response to acute cold, suggesting the possibility that these two genes could be involved in the increase in muscle mass and transformation of fiber type, respectively, at the initial stage of adaptation in cold-exposed chicks.

Relationship between contents of lipocalin-type prostaglandin D synthase on the surface of infertility sperm and in seminal plasma

Lipocalin-type prostaglandin D synthase (L-PGDS) is localized in Leydig cells, sperm, and epithelial cells of the epididymis. The present study was to determine the correlation between content of this enzyme in seminal plasma and on the surface of sperm. We analyzed 90 semen samples. L-PGDS in seminal plasma was analyzed by an ELISA procedure. L-PGDS on sperm was analyzed by flow cytometry. The semen donors were categorized in three groups: normal, oligospermic, and azoospermic. According to results obtained, L-PGDS may have the ability to improve progressive motility of sperm, and L-PGDS in seminal plasma and on sperm surface may impact male fertility in the female reproductive tract.

Lipocalin-type and hematopoietic prostaglandin D synthases as a novel example of functional convergence

Prostaglandin (PG) D2 is a major PG produced in the central nervous system and is involved in the regulation of sleep and pain responses through DP receptors. It is also actively produced by mast cells, basophils, and Th2 cells, acting as an allergic mediator through DP and CRTH2 receptors. PGD2 is further dehydrated to produce PGJ2, delta12-PGJ2, and 15-deoxy-delta(12,14)-PGJ2, the last being a ligand for the nuclear receptor PPARgamma. PGD synthase (PGDS) catalyzes the isomerization of PGH2 to PGD2 in the presence of sulfhydryl compounds. Two distinct types of PGDS have been identified: one is the lipocalin-type PGDS (L-PGDS); and the other, the hematopoietic PGDS (H-PGDS). We isolated the human and mouse cDNAs and genes for L-PGDS and H-PGDS, determined their X-ray crystallographic structures, examined their tissue distribution profiles and cellular localization, and generated gene-knockout mice and human enzyme-overexpressing transgenic mice. L-PGDS and H-PGDS are quite different from each other, in terms of their amino acid sequence, tertiary structure, evolutional origin, chromosomal and cellular localization, tissue distribution, and also functional relevance. Therefore, L-PGDS and H-PGDS are considered to be a novel example of functional convergence.

Lipocalin type prostaglandin D-synthase: which role in male fertility?

Lipocalin type prostaglandin-D-synthase (L-PGDS), also called beta-trace, is an extracellular protein very abundant in compartments beyond blood-tissue barriers, such as the cerebrospinal fluid, the aqueous humor, the amniotic fluid and the seminal fluid. In the latter fluid the major function of L-PGDS does not seem to be the synthesis of prostaglandin D(2) (PGD(2)) from its precursor PGH(2), which is very unstable in aqueous solution. Instead, seminal L-PGDS, an important carrier of bile pigments, retinoids, thyroid hormones and essential fatty acids, would contribute to providing, beyond the blood-testis barrier, thyroid hormones and retinoids to the developing germ cells in the seminiferous tubules and the maturing spermatozoa in the epididymis.