G-protein coupled estrogen receptor-mediated non-genomic facilitatory effect of estrogen on cooling-induced reduction of skin blood flow in mice.

An enhanced vasoconstrictor activity of cutaneous arteries participates in the reduction of skin blood flow induced by cooling stimulation. Raynaud's phenomenon, which is characterized by intense cooling-induced constriction of cutaneous arteries, is more common in women during the period from menarche to menopause. We thus investigated the effect of 17ß-estradiol (E2) on cooling-induced reduction of plantar skin blood flow (PSBF) in mouse in vivo. Ovariectomized female ddY mice, anaesthetized with pentobarbital, were treated with tetrodotoxin for eliminating the sympathetic nerve tone and artificially ventilated. The PSBF was measured by laser Doppler flowmetry. Cooling air temperature around the foot from 25 to 20, 15, or 10°C decreased the PSBF in a temperature-dependent manner, which was suppressed by the specific α2C-adrenoceptor antagonist MK-912. When E2 was intravenously administered as a bolus followed by a constant infusion for 10min just before the cooling stimulation, the cooling-induced reduction of PSBF was facilitated by E2 in a dose-dependent manner. The facilitatory effect of E2 was not induced after the treatment with MK-912. Similar facilitatory effect was induced by an intravenous application of G-1, an agonist of G protein-coupled estrogen receptor (GPER, also termed GPR30). Moreover, the facilitatory effect of E2 was abolished by the GPER antagonist G15. These results suggest that acute administration of E2 leads to the facilitation of cooling-induced, α2C-adrenoceptor-mediated reduction of skin blood flow via the activation of the non-genomic estrogen receptor GPER.

Occurrence of cytotoxic 9-oxononanoyl secosterol aldehydes in human low-density lipoprotein.

The reaction products of three major cholesteryl esters, cholesteryl palmitate (C16:0-CE), cholesteryl oleate (C18:1-CE), and cholesteryl linoleate (C18:2-CE), present in human low-density lipoprotein (LDL) treated with ozone were isolated and characterized. In vitro ozonization of C16:0-CE was found to form the palmitoyl ester of secosterol-A (3ß-hydroxy-5-oxo-5,6-secocholestan-6-al) and its aldolization product secosterol-B (3ß-hydroxy-5ß-hydroxy-B-norcholestane-6ß-carboxaldehyde). On the other hand, when C18:1-CE and C18:2-CE were oxidized by ozone, the aldehyde 9-oxononanoyl cholesterol (9-ONC) was formed as a primary product, which was then further oxidized to form 9-oxononanoyl secosterol-A (9-ON-secoA) and 9-oxononanoyl secosterol-B (9-ON-secoB). The compounds 9-ON-secoA and -B, but not 9-ONC, were found to exhibit strong cytotoxicity against human leukemia HL-60 cells. An LC-ESI-MS/MS method was developed for the detection of these cholesteryl ester ozonolysis products by derivatizing them with dansyl hydrazine. Using this method, we found for the first time that low concentrations of 9-ON-secoA and -B, but not palmitoyl secosterols, were present in human LDL. These novel oxidized cholesterol esters, 9-ON-secoA and -B, probably play important roles in the pathogenesis of several inflammatory disorders such as cancer, diabetes, atherosclerosis, and neurodegenerative diseases.

Identification of nobiletin, a polymethoxyflavonoid, as an enhancer of adiponectin secretion.

Adiponectin, an adipocyte-derived protein with insulin-sensitizing, anti-diabetic and anti-atherogenic activities, is known to be induced during adipocyte differentiation. Nobiletin, a citrus polymethoxy flavonoid, was found to induce the differentiation of ST-13 preadipocytes into mature adipocytes and enhance the production of adiponectin protein at a concentration of 10 microM.