Weak estrogenic activity of phenol red in the culture medium: its role in the study of the regulation of prolactin release in vitro

Gender and the Sex Hormone Estradiol Affect Multiple Sclerosis Risk Gene Expression in Epstein-Barr Virus-Infected B Cells

Multiple Sclerosis (MS) is a complex immune-mediated disease of the central nervous system. Treatment is based on immunomodulation, including specifically targeting B cells. B cells are the main host for the Epstein-Barr Virus (EBV), which has been described as necessary for MS development. Over 200 genetic loci have been identified as increasing susceptibility to MS. Many MS risk genes have altered expression in EBV infected B cells, dependent on the risk genotype, and are themselves regulated by the EBV transcription factor EBNA2. Females are 2-3 times more likely to develop MS than males. We investigated if MS risk loci might mediate the gender imbalance in MS. From a large public dataset, we identified gender-specific associations with EBV traits, and MS risk SNP/gene pairs with gender differences in their associations with gene expression. Some of these genes also showed gender differences in correlation of gene expression level with Estrogen Receptor 2. To test if estrogens may drive these gender specific differences, we cultured EBV infected B cells (lymphoblastoid cell lines, LCLs), in medium depleted of serum to remove the effects of sex hormones as well as the estrogenic effect of phenol red, and then supplemented with estrogen (100 nM estradiol). Estradiol treatment altered MS risk gene expression, LCL proliferation rate, EBV DNA copy number and EBNA2 expression in a sex-dependent manner. Together, these data indicate that there are estrogen-mediated gender-specific differences in MS risk gene expression and EBV functions. This may in turn contribute to gender differences in host response to EBV and to MS susceptibility.

Estrogen Plays a Crucial Role in Rab9-Dependent Mitochondrial Autophagy, Delaying Arterial Senescence

Background

The risk of cardiovascular disease is known to increase after menopause. Mitochondria, which undergo quality control via mitochondrial autophagy, play a crucial role in the regulation of cellular senescence. The aim of this study was to investigate whether the effect of estrogen‐mediated protection from senescence on arteries is attributed to the induction of mitochondrial autophagy.

Methods and Results

We used human umbilical vein cells, vascular smooth muscle cells, and 12‐week‐old female C57BL/6 mice. The administration of 17β‐estradiol (E2) to cells inhibited cellular senescence and mitochondrial dysfunction. Furthermore, E2 increased mitochondrial autophagy, maintaining mitochondrial function, and retarding cellular senescence. Of note, E2 did not modulate LC3 (light chain 3), and ATG7 (autophagy related 7) deficiency did not suppress mitochondrial autophagy in E2‐treated cells. Conversely, E2 increased the colocalization of Rab9 with LAMP2 (lysosomal‐associated membrane protein 2) signals. The E2‐mediated effects on mitochondrial autophagy were abolished by the knockdown of either Ulk1 or Rab9. These results suggest that E2‐mediated mitochondrial autophagy is associated with Rab9‐dependent alternative autophagy. E2 upregulated SIRT1 (sirtuin 1) and activated LKB1 (liver kinase B1), AMPK (adenosine monophosphate‐activated protein kinase), and Ulk1, indicating that the effect of E2 on the induction of Rab9‐dependent alternative autophagy is mediated by the SIRT1/LKB1/AMPK/Ulk1 pathway. Compared with the sham‐operated mice, ovariectomized mice showed reduced mitochondrial autophagy and accelerated mitochondrial dysfunction and arterial senescence; these detrimental alterations were successfully rescued by the administration of E2.

Conclusions

We showed that E2‐induced mitochondrial autophagy plays a crucial role in the delay of vascular senescence. The Rab9‐dependent alternative autophagy is behind E2‐induced mitochondrial autophagy.

Divergent effects of 17-β-estradiol on human vascular smooth muscle and endothelial cell function diminishes TNF-α-induced neointima formation

Coronary heart disease (CHD) is a condition characterized by increased levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α). TNF-α can induce vascular endothelial cell (EC) and smooth muscle cell (SMC) dysfunction, central events in development of neointimal lesions. The reduced incidence of CHD in young women is believed to be due to the protective effects of estradiol (E2). We therefore investigated the effects of TNF-α on human neointima formation and SMC/EC functions and any modulatory effects of E2. Saphenous vein (SV) segments were cultured in the presence of TNF-α (10 ng/ml), E2 (2.5 nM) or both in combination. Neointimal thickening was augmented by incubation with TNF-α, an effect that was abolished by co-culture with E2. TNF-α increased SV-SMC proliferation in a concentration-dependent manner that was optimal at 10 ng/ml (1.5-fold increase), and abolished by E2 at all concentrations studied (1-50 nM). Surprisingly, E2 itself at low concentrations (1 and 5 nM) stimulated SV-SMC proliferation to a level comparable to that of TNF-α alone. SV-EC migration was significantly impaired by TNF-α (42% of control), and co-culture with E2 partially restored the ability of SV-EC to migrate and repair the wound. In contrast, TNF-α increased SV-SMC migration by 1.7-fold, an effect that was completely reversed by co-incubation with E2. Finally, TNF-α potently induced ICAM-1 and VCAM-1 expression in both SV-EC and SV-SMC. However there was no modulation by E2 in either cell-type. In conclusion, TNF-α induced SV neointima formation, increased SMC proliferation and migration, impaired SV-EC migration and increased expression of adhesion molecules. E2 exerted distinct cell-type and function-specific modulation, the mechanisms underlying which are worthy of further detailed study.

cAMP increases Ca2+-dependent exocytosis through both PKA and Epac2 in mouse melanotrophs from pituitary tissue slices

Cyclic AMP regulates Ca(2+)-dependent exocytosis through a classical protein kinase A (PKA)-dependent and an alternative cAMP-guanine nucleotide exchange factor (GEF)/Epac-dependent pathway in many secretory cells. Although increased cAMP is believed to double secretory output in isolated pituitary cells, the direct target(s) for cAMP action and a detailed and high-time resolved analysis of the effect of intracellular cAMP levels on the secretory activity in melanotrophs are still lacking. We investigated the effect of 200 microM cAMP on the kinetics of secretory vesicle depletion in mouse melanotrophs from fresh pituitary tissue slices. The whole-cell patch-clamp technique was used to depolarize melanotrophs and increase the cytosolic Ca(2+) concentration ([Ca(2+)](i)). Exogenous cAMP elicited an about twofold increase in cumulative membrane capacitance change and approximately 34% increase of high-voltage activated Ca(2+) channel amplitude. cAMP-dependent mechanisms did not affect [Ca(2+)](i), since the application of forskolin failed to change [Ca(2+)](i) in melanotrophs, a phenomenon readily observed in anterior lobe. Depolarization-induced secretion resulted in two distinct kinetic components: a linear and a threshold component, both stimulated by cAMP. The linear component (ATP-independent) probably represented the exocytosis of the release-ready vesicles, whereas the threshold component was assigned to the exocytosis of secretory vesicles that required ATP-dependent reaction(s) and > 800 nM [Ca(2+)](i). The linear component was modulated by 8-pCPT-2Me-cAMP (Epac agonist), while either H-89 (PKA inhibitor) or Rp-cAMPS (the competitive antagonist of cAMP binding to PKA) completely prevented the action of cAMP on the threshold component. In line with this, 6-Phe-cAMP, (PKA agonist), increased the threshold component. From our study, we suggest that the stimulation of cAMP production by application of oestrogen, as found in pregnant mice, increases the efficacy of the hormonal output through both PKA and cAMP-GEFII/Epac2-dependent mechanisms.

Voltage-activated Ca(2+) channels and their role in the endocrine function of the pituitary gland in newborn and adult mice

We have prepared fresh pituitary gland slices from adult and, for the first time, from newborn mice to assess modulation of secretory activity via voltage-activated Ca(2+) channels (VACCs). Currents through VACCs and membrane capacitance have been measured with the whole-cell patch-clamp technique. Melanotrophs in newborns were significantly larger than in adults. In both newborn and adult melanotrophs activation of VACCs triggered exocytosis. All pharmacologically isolated VACC types contributed equally to the secretory activity. However, the relative proportion of VACCs differed between newborns and adults. In newborn cells L-type channels dominated and, in addition, an exclusive expression of a toxin-resistant R-type-like current was found. The expression of L-type VACCs was up-regulated by the increased oestrogen levels observed in females, and was even more emphasized in the cells of pregnant females and oestrogen-treated adult male mice. We suggest a general mechanism modulating endocrine secretion in the presence of oestrogen and particularly higher sensitivity to treatments with L-type channel blockers during high oestrogen physiological states.

Altered steroidogenesis in whole-ovary and adrenal culture in cycling rats

Cultures of minced, whole-ovary (whole-ovary culture) were used to determine if three selected chemicals altered steroidogenic profiles. First, phenolsulfonthalein (PST), when used in culture medium, was tested for its influence on in vitro steroidogenesis. Next, aminoglutethimide (AGTP; 0 or 150 mg/kg once) and di(2-ethylhexyl)phthalate (DEHP; 0 or 1500 mg/kg/day for 10 days) were administered in vivo to young adult cycling rats, and the ovaries and adrenals were removed and cultured for 1 h. Ovarian steroidogenic profiles of progesterone (P), testosterone (T), and estradiol (E) release into the medium were measured using radioimmunoassay techniques. PST in medium significantly decreased ovarian P production and altered T and E production so that the T/E ratio was significantly altered. Therefore, PST was excluded in the later studies. DEHP altered steroid profiles so that proestrus appeared to be delayed. AGTP decreased P and E production significantly, and T production was increased slightly in proestrus ovaries. These AGTP alterations in T and E resulted in a highly significant increase in the T/E ratio. Adrenals from the DEHP and AGTP experiments were also cultured for 1 h, and P was assayed in the medium. AGTP, but not DEHP, significantly increased the production of P in adrenals. Whole-ovary culture is recommended as an in vitro test for chemicals suspected of interfering with steroidogenesis in vivo. This test model should be placed strategically between in vivo studies of reproductive toxicity and complex in vitro mechanistic studies.

Phenol red: an inhibitor of thyroglobulin iodination in cultured porcine thyroid cells

Phenol red, commonly used as a pH indicator in tissue culture media, is known to possess estrogenic properties. We investigated the effect of phenol red on the process of thyroglobulin iodination which occurs only at the apical surface of porcine thyroid cells when cultured in porous bottom chambers. When phenol red was added simultaneously to both compartments (apical and basolateral), separated by the polarized monolayer, thyroglobulin iodination was inhibited by about 86% without any effect on thyroglobulin secretion and apical iodine concentration. When phenol red was added separately to either the apical or basal media, inhibition was 68% and 43%, respectively. A large amount of phenol red which was introduced into the basal medium crossed through the monolayer. Thus, inhibition was dependent upon the concentration of phenol red present in the apical compartment. A maximal inhibition was observed from 30 microM apical concentration. Phenol red acts as a substrate for thyroperoxidase in the iodination reaction.

Estrogen-like effects of 7,12-dimethylbenz(a)anthracene on the female rat hypothalamo-pituitary axis

We have recently demonstrated that 7,12-dimethylbenz(a)anthracene (DMBA), a potent inducer of mammary tumors in rodents, can in vitro decrease the number of membrane dopamine D2 receptors and stimulate prolactin (PRL) release, by direct estrogen-like actions on anterior pituitary. In the present study, we tested the ability of DMBA to mimic the in vivo estradiol (17 beta E2) effects on pituitary D2 receptors and on PRL as well as LH release. We have found that DMBA, like 17 beta E2, when injected to ovariectomized rats, induced a decrease in the number of anterior pituitary D2 receptors, a release of PRL and exerted a biphasic (acute negative and longer term positive) action on LH secretion. We thus examined the ability of DMBA to interact with 17 beta E2 receptors in the hypothalamo-pituitary axis: DMBA binds to the pituitary cytosolic estrogen receptors with an affinity 0.001% that of 17 beta E2. Finally [3H]DMBA binds to hypothalamus-containing brain sections. This binding was displaced partially by RU 2858 a pure estrogen agonist and totally by tamoxifen, a purported estrogen antagonist. No competition for [3H]DMBA binding was observed with an androgen (RU 1881) or a glucocorticoid (RU 26988) agonist. From these data, it may be concluded that DMBA can act as a partial estrogen in pituitary and hypothalamic tissues.

Cycle-related LHRH responsiveness of superfused pituitary cells in a Phenol red free medium

Anterior pituitary cell cultures are frequently used in studying the control of gonadotropin secretion. Historically, many (if not most) of these studies have been performed in the presence of Phenol red as a pH indicator. Phenol red preparations, because of their potential estrogenic activity, may have influenced the results of previous studies defining the relative luteinizing hormone releasing hormone responsiveness of rat anterior pituitary-cells derived from various stages of the estrous cycle. We therefore felt it of interest to investigate this possibility by repeating our previous cycle-related superfusion studies [(1988) Life Sci. 42, 61-72] in the absence of these Phenol red preparations. Comparisons of data obtained in the presence or absence of Phenol red revealed cells derived from late proestrous (19.00) and cultured in the absence of Phenol red continued to evidence the highest LH responsiveness. However, diestrous 1 08.00 cells cultured in the absence of Phenol red were lower in responsiveness than previously observed in the presence of the substance and the responsiveness of proestrous 08.00 and 15.00 in the presence was lower in comparison to the same stages in the absence of Phenol red. The results suggest that Phenol red preparations are capable of modulating LHRH responsiveness in superfusion and that the effect is more pronounced at certain cycle stages than at others.

Weak estrogenic activity of phenol red in the pituitary gonadotroph: re-evaluation of estrogen and antiestrogen effects

Phenol Red (Phr) which is widely used as a pH indicator in cell culture media has recently been described to possess estrogenic activity in different cell types. In the present study we investigated if the dye shows such activity on LH secretion of cultivated rat pituitary cells and controlled the established effects of estradiol (E2) and keoxifene (K) in this model in the absence of Phenol Red. 24 h treatment of pituitary cell cultures with Phr led to enhancement of GnRH-stimulated LH secretion whereas 4 h treatment reduced LH secretion. When the cells received E2 instead of Phr for the indicated incubation periods we observed nearly identical results i.e. a short-term inhibitory and a long-term stimulatory effect on LH secretion. 24 h treatment of pituitary cell cultures with increasing concentrations of Phr led to a stimulatory effect on GnRH-stimulated LH secretion an effect that occurred at 10 microM got maximal at 100 microM and was lost at higher concentrations resulting in a bell-shaped dose-response curve. The inhibitory action of Phr was present at concentrations greater than or equal to 10 microM. Both effects could be blocked by the antiestrogen K indicating their specificity. K has recently been described to induce an antigonadotrophic effect in this model. Although high concentrations of the antiestrogen were still able to inhibit LH secretion this effect was not present at lower concentrations when Phr-free culture medium was used in the experiments. Thus Phr showed weak estrogenic activity in the gonadotroph. The established actions of E2 and K on LH secretion were qualitatively reproducible when Phr was excluded from the culture medium.

The effect of clozapine on prolactin secretion at the level of the lactotroph

Clozapine is an antipsychotic drug which is unusual in that it has no dopamine receptor-blocking activity. Previous studies gave conflicting results whether administration of clozapine induces hyperprolactinemia. In the present study it was shown that a wide concentration range of clozapine does not interfere with dopamine-mediated inhibition of prolactin (PRL) secretion by normal cultured rat pituitary cells. This in contrast to other neuroleptics, like haloperidol and trifluoperazine. Clozapine does also not antagonize norepinephrine-mediated inhibition of PRL secretion. Clozapine exerts at micromolar concentrations a direct inhibitory action on PRL release by cultured normal rat pituitary cells. In cultured rat pituitary tumor cells, these high concentrations of clozapine directly inhibit PRL release as well as the DNA content of the cells, suggesting a direct antimitotic action. In this model clozapine was about 5-10 times less potent than trifluperazine. Clozapine and trifluoperazine exert an additive inhibitory action both on PRL release and on the DNA content of the pituitary tumor cells. It is concluded that clozapine does not interfere at the pituitary level with dopamine-mediated inhibition of PRL release. At micromolar concentrations clozapine may act on lactotrophs as a calmodulin-inhibitor. These observations suggest that the transient PRL-releasing effects which have been observed in both animal and human studies after clozapine administration are mediated via supra-pituitary actions of the drug.

Phenol red mimics biological actions of estradiol: enhancement of osteoblast proliferation in vitro and of type I collagen gene expression in bone and uterus of rats in vivo

Since osteoblasts are direct targets for estradiol in vitro, and Phenol Red has been reported to bear estrogen-like bioactivity, we investigated whether the pH indicator also mimicked the biological effects of estradiol on bone cells in vitro. We then asked whether estrogenic effects of Phenol Red could be observed in vivo, firstly on the uterus, and if so, whether Phenol Red could also effect bone in vivo. The proliferation of calvarial osteoblasts was stimulated by commercially available preparations of Phenol Red in a dose-dependent manner at 1.5-50 microM. This effect was not abolished in the presence of an antibody against insulin-like growth factor I. In addition, Phenol Red increased alpha 1 (I) collagen mRNA levels of osteoblasts in vitro. 17 beta-estradiol (1.5 micrograms) or Phenol Red (10 mg) administration to immature female rats (45-50 g) resulted in a weight gain of the uterus, and alpha 1(I) procollagen transcripts were more abundant in RNA prepared from uterus of drug-treated rats than observed in the control rats. Similarly, higher procollagen mRNA steady-state levels were observed in RNA prepared from parietal bones of Phenol Red or estradiol-treated rats compared to RNA from control rats. The data extend previous findings in vitro by demonstrating that Phenol Red also exerts estrogen-like effects in vivo. Moreover, we show that Phenol Red stimulates bone cells and, therefore, is likely to interfere at least in experiments designed to investigate estrogen effects on osteoblasts.

Differential responses of pituitary kallikrein and prolactin to tamoxifen and chlorotrianisene

Glandular kallikrein, a trypsin-like serine protease, and prolactin (PRL) are both estrogen-induced proteins in rat anterior pituitary lactotrophs. The estrogen agonist and antagonist effects of tamoxifen (TAM, a triphenylethylene antiestrogen) and chlorotrianisene (TACE, a triphenylethylene estrogen) on anterior pituitary glandular kallikrein and PRL were examined to see if TAM and TACE differentially affect these estrogen response of lactotrophs after in vivo dosing of rats. TAM and TACE acted as partial agonists on PRL and uterine weight induction. In contrast, on glandular kallikrein induction TAM acted as a pure estrogen antagonist and TACE acted as an almost pure antagonist. The results document that both TAM and TACE exhibit protein-specific estrogen agonist and antagonist efficacies in lactotrophs, with the estrogen induction of glandular kallikrein being particularly sensitive to antagonism by TAM in vivo. The marked antiestrogen character of TACE was surprising since TACE has been classified and clinically used as an estrogen.