Biomedical subjects

J-F Arnal

Publications and source records attributed to J-F Arnal.

4 recordsLinked to original sources

PubMed2006

IRES-dependent regulation of FGF-2 mRNA translation in pathophysiological conditions in the mouse.

The mRNA coding for FGF-2 (fibroblast growth factor 2), a major angiogenic factor, is translated by an IRES (internal ribosome entry site)-dependent mechanism. We have studied the role of the IRES in the regulation of FGF-2 expression in vivo, under pathophysiological conditions, by creating transgenic mice lines expressing bioluminescent bicistronic transgenes. Analysis of FGF-2 IRES activity indicates strong tissue specificity in adult brain and testis, suggesting a role of the IRES in the activation of FGF-2 expression in testis maturation and brain function. We have explored translational control of FGF-2 mRNA under diabetic hyperglycaemic conditions, as FGF-2 is implied in diabetes-related vascular complications. FGF-2 IRES is specifically activated in the aorta wall in streptozotocin-induced diabetic mice, in correlation with increased expression of endogenous FGF-2. Thus, under hyperglycaemic conditions, where cap-dependent translation is blocked, IRES activation participates in FGF-2 overexpression, which is one of the keys of diabetes-linked atherosclerosis aggravation. IRES activation under such pathophysiological conditions may involve ITAFs (IRES trans-acting factors), such as p53 or hnRNP AI (heterogeneous nuclear ribonucleoprotein AI), recently identified as inhibitory or activatory ITAFs respectively for FGF-2 IRES.

Animals↗

PubMed2005

Nasal nitric oxide, the guardian of paranasal sinuses, is paradoxically increased by high doses of intravenous glucocorticoids.

BACKGROUND: High concentrations of nitric oxide (NO) originating from a type-2 nitric oxide synthase (NOS2) located within the paranasal sinuses are measured in nasal air in man. NO is believed to play a central role in nonspecific defense of paranasal sinuses. Glucocorticoids (GCs), a therapeutic often used for a wide range of diseases, is known to strongly downregulate NOS2. AIMS OF THE STUDY: To investigate the effect of very high intravenous doses of GCs on nasal NO in man. METHODS: Nasal NO was measured in 15 patients without any history of allergy or chronic airway disorder who were treated for 3 days with a daily dose of 1000 mg methylprednisolone for an exacerbation of multiple sclerosis. Nasal NO was also measured in 30 matched control subjects. RESULTS: In control subjects, the maximal value of nasal NO [mean (SE)] was 233 (8) part per billion (ppb), and did not differ from patients with multiple sclerosis [maximum value: 219 (13) ppb; left nostril: 214 (12) ppb; right nostril: 215 (12) ppb]. After GCs treatment, nasal NO increased in patients [maximum value: 250 (13) ppb (P < 0.0001); left nostril: 249 (12) ppb (P < 0.0001); right nostril: 244 (13) ppb (P < 0.0001)]. CONCLUSIONS: We conclude that GCs do not decrease but even increase nasal NO.

Adult↗

PubMed2004

Estrogens and atherosclerosis.

Numerous epidemiological as well as experimental studies have suggested that estradiol (E2) prevents atherosclerosis development. However two controlled prospective and randomized studies in women using hormone replacement therapy (HRT) did not confirm this beneficial effect. We then decided to use mouse models of atherosclerosis to define the possible mechanisms involved and the reasons for the discrepancy. We have shown that, although serum cholesterol decreases, this influence on lipid metabolism is negligible. Surprisingly, E2 induces an inflammatory-immune response towards a T helper cell (Th1) profile with increasing interferon-gamma production that could destabilize atheromatous plaques, and could account for the increase in the frequency of cardiovascular events in women undergoing HRT. At the level of the endothelium, E2 induces an increase in nitric oxide (NO) biodisponibility, but this phenomenon does not concern the development of fatty streaks. Nevertheless, the atheroprotective effect is apparently mediated at the level of the endothelium by a mechanism that has still to be characterized in molecular terms. These new acquisitions constitute a basis for new pharmacological developments allowing the prevention of deleterious effects and preserving the beneficial ones.

Animals↗

PubMed2002

Estradiol alters nitric oxide production in the mouse aorta through the alpha-, but not beta-, estrogen receptor.

Although estradiol (E(2)) has been recognized to exert several vasculoprotective effects in several species, its effects in mouse vasomotion are unknown, and consequently, so is the estrogen receptor subtype mediating these effects. We investigated the effect of E(2) (80 microg/kg/day for 15 days) on NO production in the thoracic aorta of ovariectomized C57Bl/6 mice compared with those given placebo. E(2) increased basal NO production. In contrast, the relaxation in response to ATP, to the calcium ionophore A23187, and to sodium nitroprusside was unaltered by E(2), whereas acetylcholine-elicited relaxation was decreased. The abundance of NO synthase I, II, and III immunoreactive proteins (using Western blot) in thoracic aorta homogenates was unchanged by E(2). To determine the estrogen receptor (ER) subtype involved in these effects, transgenic mice in which either the ERalpha or ERbeta has been disrupted were ovariectomized and treated, or not, with E(2). Basal NO production was increased and the sensitivity to acetylcholine decreased in ERbeta knockout mice in response to E(2), whereas this effect was abolished in ERalpha knockout mice. Finally, these effects of E(2) on vasomotion required long-term and/or in vivo exposure, as short-term incubation of aortic rings with 10 nmol/L E(2) in the isolated organ chamber did not elicit any vasoactive effects. In conclusion, this study demonstrates that ERalpha, but not ERbeta, mediates the beneficial effect of E(2) on basal NO production.

Adenosine Triphosphate↗