Effect of catecholestrogen administration during adriamycin-induced cardiomyopathy in ovariectomized rat

The therapeutical beneficial effect of estrogen-derived metabolites or catecholestrogens is controversial. These molecules are produced during estrogen therapy based on 17-β-estradiol treatment. The metabolization of 17-β-estradiol is carried out in brain, kidney or liver, and triggers different products such as 2- and 4- hydroxyestradiol (2OH and 4OH). These products have shown antioxidant properties against oxidative stress (OS) in several experimental models. Different noxious side effects related to those metabolites have also been observed upon estrogen therapy. In this sense, catecholestrogens seem to be implicated in tumoral and mutagenic process after long treatment with estrogens substitutive therapy.

In our study, we have verified that 2OH and 4OH have antioxidant and cardioprotective effects against adriamycin (AD)-induced cardiomyopathy in ovariectomized (OVX) rats. Catecholestrogens diminished the lipid peroxides and carbonyl protein (CO) content, and different enzymes related to cell injury (creatinine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase) in cardiac tissue from OVX-, AD-, and OVX+AD-treated rats. All these changes were correlated to a recovery on reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in heart tissue.

The present study showed that 2OH and 4OH reduced all the parameters related to OS, antioxidant depletion and cardiac injury in OVX rats treated or not with AD.     

Effects of 17β-estradiol and antioxidant administration on oxidative stress and insulin resistance in ovariectomized rats

The prevalence of insulin resistance syndrome increases during menopause with the overproduction of reactive oxygen species and impairment of the free radical scavenger function. Therefore, we investigated the effects of 17β-estradiol (E(2)) and vitamin E, as an antioxidant, on lipid peroxidation and antioxidant levels in the brain cortex and liver of ovariectomized rats as well as on insulin resistance in those rats. Forty female Sprague-Dawley rats, 3?months of age and weighing 231.5?± 9.4 g, were divided into 4 groups: sham, ovariectomized (OVX), OVX treated with E(2) (40 μg/kg subcutaneously), and OVX treated with E(2) and vitamin E (100?mg/kg intraperitoneally). The 4 groups received the appropriate treatment every day for 8?weeks. Levels of glutathione, glutathione peroxidase, superoxide dismutase , catalase, and malondialdehyde in the brain cortex and liver of ovariectomized rats were measured. Also, fasting plasma insulin, glucose, and homeostatis model assessment of insulin resistance (HOMA-IR) were determined. Malondialdehyde increased and antioxidants (glutathione, glutathione peroxidase, catalase, superoxide dismutase) decreased in the brain cortex and liver of OVX rats. Also, fasting glucose, insulin, and HOMA-IR increased in OVX rats. E(2) and E(2) plus vitamin E decreased malondialdehyde and increased antioxidants in the brain cortex and liver of OVX rats. Moreover, they decreased fasting glucose, insulin, and HOMA-IR in ovariectomized rats. This study demonstrates that E(2) and E(2) plus vitamin E supplementation to OVX rats may improve insulin resistance, strengthen the antioxidant system, and reduce lipid peroxidation.     

17β-Estradiol and Vitamin E Modulates Oxidative Stress-Induced Kidney Toxicity in Diabetic Ovariectomized Rat

The aim of this study was to investigate the effects of vitamin E (alpha-tocopherol) and 17β-estradiol (E(2)) supplementation on malondialdehyde (MDA), glutathione (GSH), vitamin A, beta carotene, selenium-dependent glutathione peroxidase (GSH-Px), zinc-dependent superoxide dismutase (SOD), and copper/zinc-dependent catalase (CAT) values in the kidney of ovariectomized (OVX) diabetic rats. Forty-two female rats were randomly divided into seven equal groups as follows: group I, control; group II, OVX; group III, OVX+E(2); group IV, OVX+E(2)+alpha-tocopherol; group V, OVX+diabetic; group VI, OVX+diabetic+E(2); and group VII, OVX+diabetic+E(2)+alpha-tocopherol. E(2) (40?μg?kg(-1)/day) and alpha-tocopherol (100?μg?kg(-1)/day) were given. Bilateral ovariectomy was performed in all groups except group I. After 4?weeks, antioxidant and MDA levels in the kidney for all groups were analyzed. GSH-Px, CAT, SOD, GSH levels, vitamin A, and beta carotene levels were decreased in OVX group compared to those in the control group but MDA level was elevated via ovariectomy. However, E(2) and E(2)+alpha-tocopherol supplementations in OVX group was associated with an increase in the GSH-Px, GSH, CAT and Zn-SOD values, vitamin A, and beta carotene levels but a decrease in MDA levels in kidney. The MDA levels in the kidney of diabetic OVX rats were found higher than those in the control and OVX groups. However, GSH, GSH-Px, CAT, SOD, vitamin A, and beta carotene levels in kidney were lower in OVX diabetic rats. On the other hand, E(2) and E(2)+alpha-tocopherol supplementations to OVX diabetic rats have caused an increase in GSH-Px, CAT and SOD, GSH, vitamin A, and beta carotene levels but a decrease in MDA levels. In conclusion, the E(2) and E(2)+alpha-tocopherol supplementations to diabetic OVX and OVX rats may strengthen the antioxidant defense system by reducing lipid peroxidation, and therefore they may play a role in preventing renal disorders.     

The possible role of estrogen and selective estrogen receptor modulators in a rat model of Parkinson's disease

AimThe aim of the present study was to assess and compare the effect of 17β-estradiol and two different selective estrogen receptor modulators (SERMs), tamoxifen and raloxifene, as well as a selective estrogen receptor alpha agonist, propyl-pyrazole-triol (PPT) and a selective estrogen receptor beta agonist, diarylpropionitrile (DPN), on behavioral and biochemical alterations in 6-hydroxydopamine (6-OHDA)-induced nigral dopaminergic cell death in rats.Main methods80 female Wister rats were used. Animals were divided into eight equal groups: Group I; Sham operated, Group II; subjected to ovariectomy (OVX), Group III; OVX rats received striatal injection of 6-OHDA, Groups IV–VIII; OVX rats received striatal injection of 6-OHDA and were injected daily with 17β-estradiol, tamoxifen, raloxifene, PPT and DPN respectively for 5 days before 6-OHDA and continued for further 2 weeks.Key findingsResults showed that striatal injection of 6-OHDA produced significant behavioral alteration suggestive of PD, together with significant decrease in striatal dopamine, homovanillic acid (HVA) and 3,4-dihydroxyphenyl acetic acid (DOPAC) concentrations. 6-OHDA-induced nigral dopaminergic cell death was characterized by oxidative stress, evidenced by significant decrease in striatal glutathione peroxidase activity, as well as apoptosis, evidenced by significant increase in nigral caspase-3 activity. Treatment with 17β-estradiol, raloxifene, PPT, but neither tamoxifen nor DPN, resulted in significant amelioration of the behavioral and biochemical alterations induced by 6-OHDA.SignificanceThese findings suggest that estrogen and some SERMs having estrogenic agonist activity in the brain, like raloxifene, might exert beneficial effect in PD.     

Retroperitoneal white adipose tissue mitochondrial function and adiponectin expression in response to ovariectomy and 17β-estradiol replacement

Sexual dimorphism has been previously found both in mitochondrial biogenesis and function and in adiponectin expression of retroperitoneal WAT. However, little is known about the E2 effects on WAT mitochondrial function. Accordingly, the aim of this study was to examine in greater depth the role of estrogens in sexual dimorphism. This was accomplished by studying the effects of ovariectomy and E2 replacement on retroperitoneal WAT mitochondrial function. Fourteen-week-old female and ovariectomized (OVX) female Wistar rats were used in this study. The ovariectomy was performed at 5 weeks of age and at 10 weeks of age OVX rats were divided into two experimental groups: OVX, and OVX treated with 17β-estradiol (E2) (OVX+E2). Subcutaneous injections of E2 (10 μg/kg/48 h) were administered to the OVX+E2 rats for 4 weeks previous to the sacrifice whereas OVX rats were treated only with the vehicle. Levels of the main markers for mitochondrial biogenesis and function and those representatives of the antioxidant defense system and insulin sensitivity were determined. Additionally, the mRNA levels of the α and β estrogen receptors and of some adipocyte differentiation markers were studied. Our results indicate that retroperitoneal WAT was able to adapt itself to ovariectomy without any changes in mitochondrial function markers or for the adiponectin levels. However, E2 supplementation led to an unexpected decrease in: TFAM protein levels, in LPL, PPARγ and adiponectin gene expression and in the systemic HMW adiponectin levels. This decrease is probably due to the down-regulation of the ERα mRNA expression to avoid an over-stimulation by E2.     

Endothelial Relaxation Mechanisms and Oxidative Stress Are Restored by Atorvastatin Therapy in Ovariectomized Rats

The studies on hormone replacement therapy (HRT) in females with estrogen deficiency are not conclusive. Thus, non-estrogen therapies, such as atorvastatin (ATO), could be new strategies to substitute or complement HRT. This study evaluated the effects of ATO on mesenteric vascular bed (MVB) function from ovariectomized (OVX) female rats. Female rats were divided into control SHAM, OVX, and OVX treated with 17β-estradiol (EST) or ATO groups. The MVB reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine staining, and the expression of target proteins by western blot. The reduction in acetylcholine-induced relaxation in OVX rats was restored by ATO or EST treatment. The endothelium-dependent nitric oxide (NO) component was reduced in OVX rats, whereas the endothelium-derived hyperpolarizing factor (EDHF) component or prostanoids were not altered in the MVBs. Endothelial dysfunction in OVX rats was associated with oxidative stress, an up-regulation of iNOS and NADPH oxidase expression and a down-regulation of eNOS expression. Treatment with ATO or EST improved the NO component of the relaxation and normalized oxidative stress and the expression of those signaling pathways enzymes. Thus, the protective effect of ATO on endothelial dysfunction caused by estrogen deficiency highlights a significant therapeutic benefit for statins independent of its effects on cholesterol, thus providing evidence that non-estrogen therapy could be used for cardiovascular benefit in an estrogen-deficient state, such as menopause.     

Brain Endogenous Estrogen Levels Determine Responses to Estrogen Replacement Therapy via Regulation of BACE1 and NEP in Female Alzheimer’s Transgenic Mice

Estrogens have been found to improve memory and reduce risk of dementia, although conflicting results such as failure of estrogen replacement therapy for treatment of Alzheimer's disease (AD) also has been reported. Only recently, our published human brain studies showed a depletion of brain estrogen in women with AD, while other studies have demonstrated cognitive impairment believed to be caused by inhibition of endogenous estrogen synthesis in females. To investigate whether the shortage of brain estrogen alters the sensitivity of response to estrogen replacement therapy, we have used genetic and surgical animal models to examine the response of estrogen treatment in AD neuropathology. Our studies have shown that early treatment with 17β-estradiol (E2) or genistein could reduce brain amyloid levels by increasing Aβ clearance in both APP23 mice with genetic deficiency of aromatase (APP/Ar^+/?), in which the brains contain nondetectable levels of estrogen, and in APP23 mice with an ovariectomy (APP/OVX), in which the brains still contain certain levels of estrogen. However, only APP/Ar^+/? mice showed a great reduction in brain amyloid plaque formation after E2 or genistein treatment along with downregulation of β-secretase (BACE1) mRNA and protein expression. Our results suggest that early and long-term usage of E2 and/or genistein may prevent AD pathologies in a dependent manner on endogenous brain estrogen levels in aged females.     

Free Radicals Appear to Affect Survival of Hepatocytes at 4°C

1) Rat hepatocytes, stored in a simple salts medium for 24 h at 4°C, retain more than 80% of their capacity to synthesize glucose from lactate.

2) The combination of NH₄Cl with oleate is cytotoxic during storage and during subsequent incubation of hepatocytes from 48 h starved rats, but not to hepatocytes from fed rats.

3) Protection against cytotoxicity is afforded by albumin and by a number of other compounds, notably polyols and glycerol.

4) These compounds appear to exert their effects by scavenging free radicals and, in the case of polyols and glycerol, by supplying reducing equivalents to maintain the redox state of the cell in the face of increased flux through glutathione peroxidase.     

雌激素在大鼠杏仁核与纹状体多巴胺代谢中作用的差异

为探讨雌激素对大鼠杏仁核（amygdala,Amy）与纹状体（striatum,Str）多巴胺（dopamine,DA）代谢的作用,本实验采用离体电化学检测技术--高效液相色谱法（high performance liquid chromatography,HPLC）测定正常雌鼠及经雌激素处理的去卵巢（ovariectomy,OVX）雌鼠Amy和Sr的DA及其代谢产物的组织含量。实验结果显示,OVX雌鼠经雌激素处理后,可引起Amy的DA及其代谢产物含量减少,而Str的DA及其代谢产物含量不受其影响。OVX雌鼠Amy的DA更新率低于正常及雌激素处理的OVX鼠,Amy组织的DA含量约是Str组织的1/6,而更新率是Str的2倍左右。以上结果提示,雌性大鼠血清雄激素浓度可影响其Amy组织的DA代谢及组织含量,而Str的DA组织含量不因雌激素浓度的改变而变化。     

Thiols can either enhance or suppress DNA damage induction by catecholestrogens

The estrogen metabolites catecholestrogens (or hydroxyestrogens) are involved in carcinogenesis and the development of resistance to methotrexate. This induction of drug resistance correlates with the relative efficiency of catecholestrogens in the generation of reactive oxygen species (ROS) and the induction of DNA strand breaks. Although antioxidants can neutralize ROS, the generation of these reactive species by catecholestrogens can be enhanced by electron donors like NADH. Therefore, this study was undertaken to determine the ability of different thiol agents (GSH, NAC, DTT, DHLA) to either inhibit or enhance the level of DNA damage induced by the H(2)O(2) generating system 4-hydroxyestradiol/Cu(II). Our results show that GSH, DTT, and DHLA inhibited the induction of the 4-hydroxyestradiol/Cu(II)-mediated DNA damage, with GSH showing the best potential. In contrast, the GSH precursor NAC at low concentrations was able to enhance the level of oxidative damage, as observed with NADH. NAC can reduce Cu(II) to Cu(I) producing the radical NAC&z.rad;, which can generate the superoxide anion. However, the importance of this pathway appears to be relatively minor since the addition of NAC to the 4-hydroxyestradiol/Cu(II) system generates about 15 times more DNA strand breaks than NAC and Cu(II) alone. We suggest that NAC can perpetuate the redox cycle between the quinone and the semiquinone forms of the catecholestrogens, thereby enhancing the production of ROS. In conclusion, this study demonstrates the crucial importance of the choice of antioxidant as potential therapy against the negative biological effects of estrogens.     

Long-term melatonin or 17beta-estradiol supplementation alleviates oxidative stress in ovariectomized adult rats

Melatonin is an endogenously generated potent antioxidant. Our previous results indicated that melatonin improved learning and memory deficits in the transgenic mouse model of Alzheimer's disease (AD) and ovariectomized (OVX) rats by improving cholinergic nerve system dysfunction, preventing apoptosis. In this study we aim to investigate the antioxidative effects of melatonin or estradiol in the brains of ovariectomized rats. OVX Sprague-Dawley rats received daily injections of melatonin (5, 10, or 20 mg/kg), 17beta-estradiol (80 microg/kg), or sesame oil for 16 weeks. We found an increase in brain mitochondrial thiobarbituric acid-reactive substances (TBARS) levels, a decrease in mitochondrial glutathione (GSH) content as well as mitochondrial superoxide dismutase (SOD) activity and upregulation of the apoptotic-related factors, such as Bax, Caspase-3, and Prostate apoptosis response-4 (Par-4) in the frontal cortex of OVX rats. In addition to oxidative stress, OVX also caused decreased activities of mitochondrial respiration complex I and complex IV, which implicated mitochondrial dysfunction. Melatonin or 17beta-estradiol antagonized the detrimental effects induced by OVX. Furthermore, immunohistochemistry results revealed that the abnormal upregulation of the apoptotic related factor such as Bax, Caspase-3, and (Par-4) greatly reduced expression after melatonin or 17beta-estradiol supplement action. These findings demonstrate the important effects of melatonin or 17beta-estradiol on postmenopausal neuropathy and support the potential application of melatonin in the treatment of dementia in postmenopausal women. Early, long-term melatonin application is a promising strategy which could potentially be applied in a clinical setting.     

Long-term D-galactose injection combined with ovariectomy serves as a new rodent model for Alzheimer's disease

Estrogen deprivation and oxidative stress have been well established as two main factors closely related to the pathological development of Alzheimer's disease (AD). The aim of the present study is to investigate whether these two components act synergistically to accelerate the pathophysiological course of AD. To do this, we examined the effect of long-term intraperitoneal administration of D-galactose (D-gal) into ovariectomized (OVX) rats. Six weeks later, the OVX and d-gal-injected rats exhibited a higher degree of cognitive and memory impairment. This was accompanied by cholinergic neuronal loss in the forebrain and synaptic degeneration in the hippocampus and cerebral cortex which was not observed in intact controls, animals receiving injections of d-gal alone, untreated OVX animals or OVX animals receiving both D-gal and 17-beta estradiol. The typical histopathological alterations associated with AD, including intracellular deposition of amyloid beta peptide and the appearance of intracellular neurofibrillary tangles and nuclear granulovacuolar bodies, were observed in the hippocampus of OVX and D-gal-injected rats but not in other control groups. These results strongly suggest that estrogen deprivation and oxidative stress behave synergistically to enhance the development and progression of AD. Long-term OVX combined with D-gal injection serves as an ideal AD rodent model capable of mimicking pathological, neurochemical and behavioral alterations in AD.     

A comparative study of the effect of 17β-estradiol and estriol on peripheral pain behavior in rats

Although estradiol has been reported to influence pain sensitivity, the role of estriol (an estradiol metabolite and another widely used female sex hormone) remains unclear. In this study, pain behavior tests, whole-cell patch clamp recording and Western blotting were used to determine whether estriol plays a role in pain signal transduction and transmission. Either systemic or local administration of 17β-estradiol produced a significant rise of mechanical pain threshold, while estriol lacked this effect in normal and ovariectomized (OVX) rats following estriol replacement. Local administration of 17β-estradiol or estriol significantly decreased ATP-induced spontaneous hind-paw withdrawal duration (PWD), which was blocked by an estrogen receptor antagonist, ICI 182, 780. However, systemic application of estriol in normal or OVX rats lacked this similar effect. In cultured dorsal root ganglion neurons, estriol attenuated α,β-methylene ATP-induced transient currents which were blocked by ICI 182, 780. In complete Freund's adjuvant treated (CFA) rats, systemic application of 17β-estradiol or estriol decreased the mechanical pain threshold significantly, but did not change the inflammatory process. Similar effects were observed after estriol replacement in OVX rats. The expression of c-fos in lumbosacral spinal cord dorsal horn (SCDH) was increased significantly by administration of 17β-estradiol but not estriol, and not by estriol replacement in OVX rats. These results suggest that 17β-estradiol but not estriol plays an anti-hyperalgesic role in physiological pain. However, both peripheral 17β-estradiol and estriol play anti-hyperalgesic roles in ATP-induced inflammatory pain. Systemic application of estriol as well as 17β-estradiol plays hyperalgesic roles in CFA-induced chronic pain.     

Evaluation of the Preventive Effect of Isoflavone Extract on Bone Loss in Ovariectomized Rats

To examine a potential role for soybean phytoestrogens in postmenopausal bone loss, twenty-four 12-week-old Sprague-Dawley rats were divided randomly into 4 groups and given controlled diets for 16 weeks. The treatment groups were as followed: sham operated, ovariectomized (OVX) control, OVX + isoflavone extract (6.25 g/kg), and OVX + 17β-estradiol (4 mg/kg). OVX treatments reduced femoral and fourth lumbar vertebral bone density and mineral content (p<0.01), decreased uterine weight (p<0.01), accelerated body weight increases (p<0.05), and increased the activities (p<0.01) of both serum alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP). Supplementation with isoflavone prevented the losses of bone density and mineral content caused by OVX (p<0.01). Although both isoflavone and 17β-estradiol exhibited similar bone-sparing ability on the OVX-induced bone loss, the effect of isoflavone was not the same as that of 17β-estradiol on the serum ALP and TRAP, body weight increase, and uterine weight change. We concluded that dietary supplementation with soybean isoflavone can prevent postmenopausal bone loss via a different mechanism of estrogen in OVX rats.     

Protective effect of estrogens against oxidative damage to heart and skeletal muscle in vivo and in vitro

Estrogen has been shown to protect skeletal muscle from damage and to exert antioxidant properties. The purpose of the present study was to investigate the antioxidant and protective properties of estrogens in rodent cardiac and skeletal muscle and H9c2 cells. Female Sprague-Dawley rats were separated into three groups, ovariectomized (OVX), ovariectomized with estrogen replacement (OVX + E2), and intact control (SHAM), and were assessed at two time periods, 4 and 8 weeks. Rodents hearts were analyzed for basal and iron-stimulated lipid peroxidation in the absence and presence of beta-estradiol (betaE2) by measuring thiobarbituric acid reactive species (TBARS). Isolated soleus (SOL) and extensor digitorum longus (EDL) were analyzed for creatine kinase (CK) efflux. Using H9c2 cells, the in vitro effects of betaE2 and its isomer alpha-estradiol were investigated under glucose-free/hypoxic conditions. TBARS assay was also performed on the H9c2 in the presence or absence of betaE2. The results indicate that OVX rodent hearts are more susceptible to lipid peroxidation than OVX + E2 hearts. OVX soleus showed higher cumulative efflux of CK than OVX + E2. Furthermore, H9c2 survival during oxidative stress was enhanced when estrogen was present, and both OVX hearts at 4 weeks and H9c2 cells particularly were protected from oxidative damage by estrogens. We conclude that estrogen protects both skeletal and cardiac muscle from damage, and its antioxidant activity can contribute to this protection.     

Effect of soybean oil on atherogenic metabolic risks associated with estrogen deficiency in ovariectomized rats

The aim of the present study was to investigate the cardiac biomarker changes in experimental bilateral ovariectomized (OVX) rats in addition to evaluating the role of soybean oil-supplemented diet to attenuate these alterations. Female rats were divided into four groups and treated for 2 months as follows: groups 1 and 2 fed with standard diet with or without 15% soybean oil. Groups 3 and 4 were bilateral OVX and received the standard diet with or without 15% soybean oil. The results revealed that rats subjected to ovariectomy exhibited an inhibition in estrogen and high-density lipoprotein cholesterol levels and marked increase of lipid profile, low-density lipoprotein cholesterol, and VLDL-C accompanied with a marked elevation in atherogenic index, cardiac enzyme activity, tumor necrosis factor-α, and C-reactive protein. Signs of cardiovascular injury which included an increase in cardiac thiobarbituric acid-reactive substances were concomitantly noticed with a reduction in the reduced glutathione, total antioxidant capacity, and superoxide dismutase. However, supplementation of soybean oil resulted in the restoration of the changed lipid profile and improved cardiac biomarkers near to normal values as well as improved inflammatory and antioxidant status. It was concluded that consumption of soybean oil may have a role in retarding atherosclerosis and risk of cardiovascular disorders associated with estrogen deficiency in ovariectomy status.     

Ovariectomy increases neuronal amyloid-beta binding alcohol dehydrogenase level in the mouse hippocampus

Ovarian hormone decline after menopause may influence cognitive performance and increase the risk for Alzheimer's disease (AD) in women. Amyloid-β peptide (Aβ) has been proposed to be the primary cause of AD. In this study, we examined whether ovariectomy (OVX) could affect the levels of cofactors Aβ-binding alcohol dehydrogenase (ABAD) and receptor for advanced glycation endproducts (RAGE), which have been reported to potentiate Aβ-mediated neuronal perturbation, in mouse hippocampus, correlating with estrogen and Aβ levels. Female ICR mice were randomly divided into ovariectomized or sham-operated groups, and biochemical analyses were carried out at 5 weeks after the operation. OVX for 5 weeks significantly decreased hippocampal 17β-estradiol level, while it tended to reduce the hormone level in serum, compared with the sham-operated control. In contrast, OVX did not affect hippocampal Aβ_1-40 level, although it significantly increased serum Aβ_1-40 level. Furthermore, we demonstrated that OVX increased hippocampal ABAD level in neurons, but not astrocytes, while it did not affect RAGE level. These findings suggest that the expression of neuronal ABAD depends on estrogen level in the hippocampus and the increase in serum Aβ and hippocampal ABAD induced by ovarian hormone decline may be associated with pre-stage of memory deficit in postmenopausal women and Aβ-mediated AD pathology.     

Postnatal gender-dependent maturation of cellular cysteine uptake

Background. In view of the functional capacity of glutathione synthesis in premature infants, and because the availability of cysteine is one the rate limiting steps in glutathione synthesis, we hypothesized that the low glutathione levels in premature infants may be due to immaturity of the active cellular uptake of cysteine.

Objective. To document in cells from newborn infants the effect of maturity and gender on cysteine uptake and consequently on glutathione levels.

Methods. Incorporation of L-[35S] cysteine was measured in leukocytes from cord blood and from tracheal aspirates (TAC) of newborn infants of varying (gestational as well as postnatal) ages and gender. Cysteine uptake was correlated with glutathione in TAC.

Results. The maturity of newborn girls positively influences cysteine uptake, which is responsible for 78% of the variation in their glutathione content. However, in newborn boys, gestational and postnatal ages did not influence the cysteine uptake.

Discussion. Cysteine uptake appears to be the limiting step explaining the reported gender-related differences in glutathione as well as the low levels of this central antioxidant found in premature infants. The immature cysteine uptake found in cells from premature infants raises questions about the bioavailability of this conditionally essential amino acid in regimens of parenteral nutrition for human neonates.     

Catecholestrogens are MCF-7 cell estrogen receptor agonists

Catecholestrogens are important metabolites of estradiol and estrone in the human. Considerable interest has focused on the catecholestrogens 2-hydroxy- and 4-hydroxyestradiol since they bind to the estrogen receptor with an affinity in the range of estradiol. Using the MCF-7 cell line, we analysed the capacity of purified catecholestrogens to transform the estrogen receptor into its high affinity nuclear binding form and to effect receptor-dependent processes such as proliferation and expression of the progesterone receptor (PR). Incubations with 2-hydroxy- and 4-hydroxyestradiol at 10⁻⁸ M for 1 h resulted in tight nuclear binding of the estrogen receptor. During treatment of the cells with catecholestrogens we obtained a marked increase in proliferation rate of 36 and 76% for 2-hydroxy- and 4-hydroxyestradiol, respectively, relative to the inductive effect of estradiol (100%). The PR level, was slightly increased by treatment with 2-hydroxyestradiol (10%), whereas treatment with 4-hydroxyestradiol increased the PR level at 28%, compared to estradiol (100%). Form these results we conclude that the 2- and 4-hydroxylated derivatives of estradiol are active hormones and are able to initiate estrogen receptor mediated processes in MCF-7 cells.     

The effect of 17β-estradiol treatment on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin

We performed the dosing experiment to establish whether estrogen administration has any beneficial effects on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin. Thirty-five Wistar rats, 28 weeks of age, received ovariectomies (OVX) or sham operations and were divided into five groups. Group I was the sham group, Groups 2–5 were ovariectomized. Group 2 was the OVX-control, Group 3 treated with thyroxin 30 μg/kg/day (T4), Group 4, 17β-estradiol 0.3 mg/kg/week (E2), and Group 5, the combination of T4 and E2. The duration of the experiment was 12 weeks. At the end of the experiment, serum chemistries were measured. Bone minerals in the femur were determined with single photon absorptiometry and bone turnover was assessed histomorphometrically. Alkaline-phosphatase increased in Group 3 (OVX-T4), but it reduced in Groups 4 (OVX-E2) and 5 (OVX-T4 + E2). Bone minerals decreased in Groups 2 (OVX) and 3. In Group 4, it was preserved at the same level as in Group 1. Group 5 showed a significant increase of bone mass compared with Group 1. Eroded surface and osteoid surface increased in Groups 2 and 3 and they were reduced in Groups 4 and 5. Bone volume and mineral apposition rate were at a maximum in Group 5. This study demonstrated that 17β-estradiol was capable of preventing the bone mass decrease by regulating the turnover in ovariectomized rats taking a mild dose of thyroxin. Osteoblast function appeared to be stimulated in combination with 17β-estradiol and thyroxin.