Estrogen and progesterone receptors in murine models of systemic lupus erythematosus.

Estrogens are believed to play a role in the etiology of both human and murine systemic lupus erythematosus (lupus; SLE), presumably through the agency of their cellular receptor proteins. There is now considerable interest in the molecular mechanism of action of estrogens in immune tissues, particularly with regard to autoimmune disorders, which are generally more prevalent in women. In this laboratory, an attempt is being made to characterize estrogen receptors in murine models of SLE and to try and relate this to estrogen receptor function in vivo. The initial aim was to compare binding properties of estrogen receptors in brain, reproductive and immune tissues of BALB/c and MRL/MP-lpr/lpr mice. The latter strain spontaneously develops an autoimmune disease resembling human systemic lupus erythematosus (lupus; SLE). It is hypothesized that estradiol, through its receptors, mediates the progression of murine SLE, and that in autoimmune disease, the estrogen receptor is functionally and/or structurally changed. Initial studies suggest that there are differences in estrogen receptors between BALB/c mice, which do not get autoimmune disease, and two strains that do, MRL/MP-lpr/lpr and NZB/W mice. In MRL mice, these differences may be reflected in impaired priming of the progesterone receptor.

Impaired estrogen priming of progesterone receptors in uterus of MRL/MP-lpr/lpr mice, a model of systemic lupus erythematosus (SLE).

Estrogens exacerbate the autoimmune disease SLE and progesterone is immunoprotective. Estrogens increase synthesis of progesterone receptors (PR) and it is hypothesized that this physiological balance may be impaired in SLE. To test this, cytosolic PR were measured in hypothalamus, thymus and uterus from 6-week-old female ovariectomized BALB/c and MRL/MP-lpr/lpr mice 48 h after s.c. injection of estradiol benzoate (3.2 microg/0.1 ml; OB) in peanut oil or 0.1 ml peanut oil alone. PR were measured using [(3)H]ORG 2058, which does not bind to corticosteroid-binding globulin (CBG), and bound and free ligand were separated using minicolumns of Sephadex LH20 at 0 degrees C. PR were measured in cytosols from hypothalamus and uterus of oil-treated BALB/c mice, but were undetectable in thymus, whereas receptors were measurable in all three tissues of MRL mice. There was a significantly greater priming effect of OB on PR in uterus of BALB/c mice, but not in hypothalamus, and PR became detectable in thymus cytosols from BALB/c mice. Also, the apparent affinity of the binding reaction between [(3)H]ORG 2058 and PR was significantly higher than those measured in other tissues in hypothalamic cytosols of both strains. These results suggest that there is an impairment of estrogen priming of progesterone receptors in uterus and perhaps thymus of MRL mice.

Strain differences in binding properties of estrogen receptors in immature and adult BALB/c and MRL/MP-lpr/lpr mice, a model of systemic lupus erythematosus.

The aim was to compare binding properties of estrogen receptors in brain, reproductive and immune tissues of immature and adult female BALB/c mice, and in the same tissues of MRL/MP-lpr/lpr mice. The latter strain spontaneously develops an autoimmune disease resembling human systemic lupus erythematosus (lupus; SLE). It is hypothesized that estradiol, through its receptors, mediates the progression of murine SLE. High-speed cytosols were prepared from hypothalamus, spleen, thymus and uterus of both strains, and incubated with the synthetic estrogen (3)H-moxestrol (NEN). Scatchard plots were derived from binding isotherms obtained after in vitro incubation. In addition, cervical lymph nodes from MRL mice could be used, but were too small in BALB/c mice. There was a significant increase in the affinity of the binding reaction i.e. a decrease in the apparent molar dissociation constant (Kd), in immune tissues and uterus with maturation in MRL but not BALB/c mice, whose tissues had, overall, a lower affinity for (3)H-moxestrol. Receptor concentrations were significantly higher in spleen and cervical lymph nodes of adult compared with immature MRL mice, but the opposite pattern was observed in BALB/c mouse spleen on maturation. These properties of estrogen receptors in MRL mice may underlie estrogen-mediated exacerbation of murine SLE.

Insulin lispro versus regular insulin in children with type 1 diabetes on twice daily insulin.

OBJECTIVE: The aim of this study was to compare the clinical efficacy and safety of insulin lispro with regular insulin in 5- to 10-yr-old prepubertal children on twice daily insulin. RESEARCH DESIGN AND METHODS: Thirty-five children (16 M, 19 F) completed an open-label randomised crossover study, with each child receiving insulin lispro for 3 months and regular insulin for 3 months in addition to their intermediate-acting insulin. Families were instructed to give regular insulin 30 min before meals and insulin lispro immediately before meals. Glycaemic control was monitored by eight-point blood glucose profiles and six weekly hemoglobin A1cs (HbA1cs) and the frequency and severity of hypoglycaemia was documented. RESULTS: The endpoint HbA1c after 3 months on insulin lispro (8.33%, SD+/-0.89) was not significantly different to that on regular insulin (8.14%, SD+/-0.77). No significant differences were found in blood glucose levels before or after meals, 2-h postprandial glucose excursions or in blood glucose levels before bed between the treatments. However, blood glucose levels at 3 am were significantly lower on regular insulin than on insulin lispro (mean difference -2.35 mmol/L (95%CI: -3.98, -0.72, p=0.01). There was no significant difference in the frequency of hypoglycaemic episodes between the groups. CONCLUSIONS: The main advantage of insulin lispro in children on twice daily insulin was found to be its greater convenience, this being achieved without a deterioration in glycaemic control. The higher 3 am blood glucose levels in those on insulin lispro could translate to reduced nocturnal hypoglycaemia in some individuals.

Evidence for sexual dimorphism of estrogen receptors in hypothalamus and thymus of neonatal and immature Wistar rats.

It is hypothesized that the rat thymus is sexually differentiated. To begin testing this, we used the 5-day-old rat, whose hypothalamus is sexually differentiated during this period. Cytosolic estrogen receptors (ER) were measured in cytosols prepared from the brain, thymus and uterus of Wistar rats at 5, 18 and 30 days post-partum. ER concentrations were significantly higher in hypothalamus in cytosols of female 5-day-old rats, and this difference had disappeared by day 18. The pattern in thymus was identical to that observed in hypothalamus, suggesting the presence in the thymus of the aromatase system that converts androgen to estrogen, and that estrogen-mediated sexual differentiation of thymus might be proceeding at 5 days. Unlike the case for hypothalamus, no experimental model exists at present for testing functional sexual differentiation in thymus. Therefore we tested the effects of aromatase inhibitors on estrogen receptor activity in thymus well after the five-day period, and before atrophy of the thymus has commenced. Male and female rats were implanted at 15 days of age with SILASTIC implants containing 5 mg of estradiol or with 25 mg of the aromatase inhibitor 4-hydroxyandrostenedione (4-OHA) and cytosolic ER prepared at 30 days and activity measured. Administration of estradiol resulted in failure to detect available receptor, suggesting that the binding components measured were ER. After 4-OHA administration, ER concentrations were significantly increased in cytosols from male but not female hypothalamus and thymus. There is therefore a basis for exploring further the hypothesis that rat thymus is sexually differentiated.