Predominant Role of Nuclear Versus Membrane Estrogen Receptor α in Arterial Protection: Implications for Estrogen Receptor α Modulation in Cardiovascular Prevention/Safety

BACKGROUND: Although estrogen receptor α (ERα) acts primarily as a transcription factor, it can also elicit membrane-initiated steroid signaling. Pharmacological tools and transgenic mouse models previously highlighted the key role of ERα membrane-initiated steroid signaling in 2 actions of estrogens in the endothelium: increase in NO production and acceleration of reendothelialization. METHODS AND RESULTS: Using mice with ERα mutated at cysteine 451 (ERaC451A), recognized as the key palmitoylation site required for ERα plasma membrane location, and mice with disruption of nuclear actions because of inactivation of activation function 2 (ERaAF20 = ERaAF2°), we sought to fully characterize the respective roles of nuclear membrane-initiated steroid signaling in the arterial protection conferred by ERα. ERaC451A mice were fully responsive to estrogens to prevent atheroma and angiotensin II-induced hypertension as well as to allow flow-mediated arteriolar remodeling. By contrast, ERαAF20 mice were unresponsive to estrogens for these beneficial vascular effects. Accordingly, selective activation of nuclear ERα with estetrol was able to prevent hypertension and to restore flow-mediated arteriolar remodeling. CONCLUSIONS: Altogether, these results reveal an unexpected prominent role of nuclear ERα in the vasculoprotective action of estrogens with major implications in medicine, particularly for selective nuclear ERα agonist, such as estetrol, which is currently under development as a new oral contraceptive and for hormone replacement therapy in menopausal women

Covalent cross-linking of liver collagen by pyridinoline increases in the course of experimental alveolar echinococcosis

We report that covalent cross-linking of collagen molecules by pyridinoline increases significantly in liver in a murine model of alveolar echinococcosis. The highest amount of pyridinoline per collagen molecule (up to 3.5 fold the control values) is found in liver parasitic lesions. It is also increased, but to a far lesser extent, at distance from the fibrotic areas, in macroscopically normal zones of the liver, suggesting that the increase in mature collagen cross-linking occurring in the fibrogenesis due to Echinococcus multilocularis infection involves the whole liver. The comparison of these data with those we have obtained in another parasitic disease, murine schistosomiasis leading to a milder liver fibrosis, largely reversible following chemotherapy, supports a relationship between the liver pyridinoline level and the severity of liver fibrosis. Pyridinoline could be a tissular marker of chronic liver fibrosis in parasitic diseases

Lysyl Oxidase cDNA of Myofibroblast from Mouse Fibrotic Liver

International audienceIn order to study the regulation of lysyl oxydase (LO) in fibrosis, mRNAs were extracted from an enriched population of myofibroblasts (MF) isolated from liver of schistosomiasis infected mouse. Four mRNAs (5.5kb, 4.5kb, 2.4kb and 2.0kb) hybridizing with a LO cDNA probe were transcribed in fibrotic liver, but only the two largest mRNAs were found in MF. A cDNA library was constructed, allowing the cloning of twenty four cDNAs. The largest clone of 4689bp should correspond to the 5.5kb mRNA. Its sequence was essentially similar to the NIH-3T3 fibroblasts LO-ras recision gene (rrg4) cDNA, with the same exon/intron structure, but with some differences at the sites of initiation of transcription which were shown to occur mainly at -392 and -358 nucleotides before the putative start of translation. These two main sites of initiation did not explain the origin of the 4.5kb and 5.5kb mRNAs, and as no spliced variants were found among the 24 clones, some regulation should also involve the 3'end region.In order to study the regulation of lysyl oxydase (LO) in fibrosis, mRNAs were extracted from an enriched population of myofibroblasts (MF) isolated from liver of schistosomiasis infected mouse. Four mRNAs (5.5kb, 4.5kb, 2.4kb and 2.0kb) hybridizing with a LO cDNA probe were transcribed in fibrotic liver, but only the two largest mRNAs were found in MF. A cDNA library was constructed, allowing the cloning of twenty four cDNAs. The largest clone of 4689bp should correspond to the 5.5kb mRNA. Its sequence was essentially similar to the NIH-3T3 fibroblasts LO-ras recision gene (rrg4) cDNA, with the same exon/intron structure, but with some differences at the sites of initiation of transcription which were shown to occur mainly at -392 and -358 nucleotides before the putative start of translation. These two main sites of initiation did not explain the origin of the 4.5kb and 5.5kb mRNAs, and as no spliced variants were found among the 24 clones, some regulation should also involve the 3'end region