The impact of chronic estrogen deprivation on immunologic parameters in the ovariectomized rhesus monkey (Macaca mulatta) model of menopause

Sex differences in neuroimmunoendocrine communication. Involvement on longevity

Endocrine, nervous, and immune systems work coordinately to maintain the global homeostasis of the organism. They show sex differences in their functions that, in turn, contribute to sex differences beyond reproductive function. Females display a better control of the energetic metabolism and improved neuroprotection and have more antioxidant defenses and a better inflammatory status than males, which is associated with a more robust immune response than that of males. These differences are present from the early stages of life, being more relevant in adulthood and influencing the aging trajectory in each sex and may contribute to the different life lifespan between sexes.

Effects of natural aging and gender on pro-inflammatory markers

The term inflammaging is now widely used to designate the inflammatory process of natural aging. During this process, cytokine balance is altered, presumably due to the loss of homeostasis, thus contributing to a greater predisposition to disease and exacerbation of chronic diseases. The aim of the study was to analyze the relationship between pro-inflammatory markers and age in the natural aging process of healthy individuals. One hundred and ten subjects were divided into 5 groups according to age (22 subjects/group). Interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) were quantified using the ELISA method. High-sensitivity C-reactive protein (hsCRP) was analyzed by turbidimetry according to laboratory procedures. The main findings of this study were: a positive correlation between hsCRP and IL-6 as a function of age (110 subjects); women showed stronger correlations; the 51-60 age group had the highest values for hsCRP and IL-6; women presented higher values for hsCRP in the 51-60 age group and higher values for IL-6 in the 61-70 age group; and men showed higher values in the 51-60 age group for hsCRP and IL-6. In conclusion, the natural aging process increased IL-6 and hsCRP levels, which is consistent with the inflammaging theory; however, women presented stronger correlations compared to men (IL-6 and hsCRP) and the 51-60 age range seems to be a key point for these increases. These findings are important because they indicate that early preventive measures may minimize the increase in these inflammatory markers in natural human aging.

Exploring immunomodulation by endocrine changes in Lady Windermere syndrome

Lung disease due to nontuberculous mycobacteria (NTM) occurs with disproportionate frequency in postmenopausal women with a unique phenotype and without clinically apparent predisposing factors. Dubbed 'Lady Windermere syndrome', the phenotype includes low body mass index (BMI), tall stature and higher than normal prevalence of scoliosis, pectus excavatum and mitral valve prolapse. Although the pathomechanism for susceptibility to NTM lung disease in these patients remains uncertain, it is likely to be multi-factorial. A role for the immunomodulatory consequences of oestrogen deficiency and altered adipokine production has been postulated. Altered levels of adipokines and dehydroepiandrosterone have been demonstrated in patients with NTM lung disease. Case reports of NTM lung disease in patients with hypopituitarism support the possibility that altered endocrine function influences disease susceptibility. This paper catalogues the evidence for immunomodulatory consequences of predicted endocrine changes in Lady Windermere syndrome, with emphasis on the immune response to NTM. Collectively, the data warrant further exploration of an endocrine link to disease susceptibility in Lady Windermere syndrome.

17β-Estradiol induces proliferation of endometrial NK cells (CD56+) in postmenopausal women

OBJECTIVE

The aim of this report was to evaluate the impact of hormone replacement therapy (HRT) on lymphocytic infiltration of the endometrium in postmenopausal women.

METHOD

This study included 58 Japanese patients who had undergone hysterectomy at the University Hospital of Occupational and Environmental Health, Japan. Before surgery, nine patients had received 17β-estradiol (E2), 0.72 mg transdermally for 2-8 weeks (E2 group); 16 patients had received an Estra-1,3,5(10)-triene-3,16α, 17β-triol (E3) vaginal tablet 0.5 mg per month five times (E3 group); and 19 patients had received 17β-estradiol, 0.62 mg, and norethindrone acetate (P), 2.70 mg for 3-16 weeks (E2 + P group). Fourteen patients received no HRT (control group). We examined uterine tissue specimens immunohistochemically for CD45+, CD3+, CD4+, CD8+, CD20+, CD56+, and Ki67 antigen-positive cells.

RESULTS

The numbers of CD56 + cells were significantly increased in the E2 group compared with all other groups (E2 vs. E3: 7.0 vs. 0.75, p = 0.017; E2 vs. E2 + P: 7.0 vs. 0.58, p = 0.009; E2 vs.

CONTROL

7.0 vs. 0.43, p = 0.010). The numbers of CD3+ cells were significantly increased in the E2 group compared with the control group (149.3 vs. 42.6, p = 0.008).

CONCLUSION

17β-Estradiol induced the proliferation of endometrial uterine natural killer cells (CD56+) in postmenopausal women.

Effects of Bu-Shen-Ning-Xin Decoction on immune cells of the spleen and bone marrow in ovariectomized mice

Osteoimmunology is a new discipline that focuses on the interaction between the bones and the immune system. Immune cells play an important role in bone metabolism. The aim of this study was to illustrate the effect of Bu-Shen-Ning-Xin Decoction (BSNXD) on lymphocytes in the spleen and bone marrow to explore the potential role on the bone. C57BL/6 mice were divided into four groups: sham, ovariectomized (OVX), OVX+BSNXD, and OVX+ estrogen. The sham and OVX groups were treated with saline, the OVX+BSNXD group was treated with BSNXD, and the OVX+ estrogen group was treated with estrogen. After mice were sacrificed, the spleens and bones were collected, and the lymphocytes in the spleen and bone marrow were analyzed. We found that BSNXD lessened the extent of the increase of CD4⁺ and bone marrow. In contrast, these numbers were both increased in the OVX group. BSNXD had no influence on the percentage of γδ T cells. However, it increased the proportion of NK cells in the spleen and bone marrow. BSNXD lessened the extent of the increase of monocytes by ovariectomy. In vitro experiment, we found Tregs can decrease osteoclastogenesis when co-cultured with osteoclast precursor cells. This study suggests that BSNXD changes the immune environment and immune cells have a role in bone metabolism in OVX mice.

Age-related differences in cardiac ischemia-reperfusion injury: effects of estrogen deficiency

Despite conflicting evidence for the efficacy of hormone replacement therapy in cardioprotection of postmenopausal women, numerous studies have demonstrated reductions in ischemia/reperfusion (I/R) injury following chronic or acute exogenous estradiol (E2) administration in adult male and female, gonad-intact and gonadectomized animals. It has become clear that ovariectomized adult animals may not accurately represent the combined effects of age and E2 deficiency on reductions in ischemic tolerance seen in the postmenopausal female. E2 is known to regulate the transcription of several cardioprotective genes. Acute, non-genomic E2 signaling can also activate many of the same signaling pathways recruited in cardioprotection. Alterations in cardioprotective gene expression or cardioprotective signal transduction are therefore likely to result within the context of aging and E2 deficiency and may help explain the reduced ischemic tolerance and loss of cardioprotection in the senescent female heart. Quantification of the mitochondrial proteome as it adapts to advancing age and E2 deficiency may also represent a key experimental approach to uncover proteins associated with disruptions in cardiac signaling contributing to age-associated declines in ischemic tolerance. These alterations have important ramifications for understanding the increased morbidity and mortality due to ischemic cardiovascular disease seen in postmenopausal females. Functional perturbations that occur in mitochondrial respiration and Ca(2+) sensitivity with age-associated E2 deficiency may also allow for the identification of alternative therapeutic targets for reducing I/R injury and treatment of the leading cause of death in postmenopausal women.

Quantitative proteomic analysis reveals novel mitochondrial targets of estrogen deficiency in the aged female rat heart

The incidence of myocardial infarction rises sharply at menopause, implicating a potential role for estrogen (E(2)) loss in age-related increases in ischemic injury. We aimed to identify quantitative changes to the cardiac mitochondrial proteome of aging females, based on the hypothesis that E(2) deficiency exacerbates age-dependent disruptions in mitochondrial proteins. Mitochondria isolated from left ventricles of adult (6 mo) and aged (24 mo) F344 ovary-intact or ovariectomized (OVX) rats were labeled with 8plex isobaric tags for relative and absolute quantification (iTRAQ; n = 5-6/group). Groups studied were adult, adult OVX, aged, and aged OVX. In vivo coronary artery ligation and in vitro mitochondrial respiration studies were also performed in a subset of rats. We identified 965 proteins across groups and significant directional changes in 67 proteins of aged and/or aged OVX; 32 proteins were unique to aged OVX. Notably, only six proteins were similarly altered in adult OVX (voltage-dependent ion channel 1, adenine nucleotide translocator 1, cytochrome c oxidase subunits VIIc and VIc, catalase, and myosin binding protein C). Proteins affected by aging were primarily related to cellular metabolism, oxidative stress, and cell death. The largest change occurred in monoamine oxidase-A (MAO-A), a source of oxidative stress. While acute MAO-A inhibition induced mild uncoupling in aged mitochondria, reductions in infarct size were not observed. Age-dependent alterations in mitochondrial signaling indicate a highly selective myocardial response to E(2) deficiency. The combined proteomic and functional approaches described here offer possibility of new protein targets for experimentation and therapeutic intervention in the aged female population.

Accelerated immune senescence and reduced response to vaccination in ovariectomized female rhesus macaques

Aging is associated with a general dysregulation in immune function, commonly referred to as "immune senescence". Several studies have shown that female sex steroids can modulate the immune response. However, the impact of menopause-associated loss of estrogen and progestins on immune senescence remains poorly understood. To help answer this question, we examined the effect of ovariectomy on T-cell homeostasis and function in adult and aged female rhesus macaques. Our data show that in adult female rhesus macaques, ovariectomy increased the frequency of naïve CD4 T cells. In contrast, ovariectomized (ovx) aged female rhesus macaques had increased frequency of terminally differentiated CD4 effector memory T cells and inflammatory cytokine-secreting memory T cells. Moreover, ovariectomy reduced the immune response (T-cell cytokine and IgG production) following vaccination with modified vaccinia ankara in both adult and aged female rhesus macaques compared to ovary-intact age-matched controls. Interestingly, hormone therapy (estradiol alone or in conjunction with progesterone) partially improved the T-cell response to vaccination in aged ovariectomized female rhesus macaques. These data suggest that the loss of ovarian steroids, notably estradiol and progesterone, may contribute to reduced immune function in post-menopausal women and that hormone therapy may improve immune response to vaccination in this growing segment of the population.

The role of the brain in female reproductive aging

In middle-aged women, follicular depletion is a critical factor mediating the menopausal transition; however, all levels of the hypothalamic-pituitary-gonadal (HPG) axis contribute to the age-related decline in reproductive function. To help elucidate the complex interactions between the ovary and brain during middle-age that lead to the onset of the menopause, we utilize animal models which share striking similarities in reproductive physiology. Our results show that during middle-age, prior to any overt irregularities in estrous cyclicity, the ability of 17beta-estradiol (E(2)) to modulate the cascade of neurochemical events required for preovulatory gonadotropin-releasing hormone (GnRH) release and a luteinizing hormone (LH) surge is diminished. Middle-aged female rats experience a delay in and an attenuation of LH release in response to E(2). Additionally, although we do not observe a decrease in GnRH neuron number until a very advanced age, E(2)-mediated GnRH neuronal activation declines during the earliest stages of age-related reproductive decline. Numerous hypothalamic neuropeptides and neurochemical stimulatory inputs (i.e., glutamate, norepinephrine (NE), and vasoactive intestinal peptide (VIP)) that drive the E(2)-mediated GnRH/LH surge appear to dampen with age or lack the precise temporal coordination required for a specific pattern of GnRH secretion, while inhibitory signals such as gamma-aminobutyric acid (GABA) and opioid peptides remain unchanged or elevated during the afternoon of proestrus. These changes, occurring at the level of the hypothalamus, lead to irregular estrous cycles and, ultimately, the cessation of reproductive function. Taken together, our studies indicate that the hypothalamus is an important contributor to age-related female reproductive decline.

Role of aging versus the loss of estrogens in the reduction in vascular function in female rats

Although aging is known to lead to increased vascular stiffness, the role of estrogens in the prevention of age-related changes in the vasculature remains to be elucidated. To address this, we measured vascular function in the thoracic aorta in adult and old ovariectomized (ovx) rats with and without immediate 17beta-estradiol (E2) replacement. In addition, aortic mRNA and protein were analyzed for proteins known to be involved in vasorelaxation. Aging in combination with the loss of estrogens led to decreased vasorelaxation in response to acetylcholine and sodium nitroprusside, indicating either smooth muscle dysfunction and/or increased fibrosis. Loss of estrogens led to increased vascular tension in response to phenylephrine, which could be partially restored by E2 replacement. Levels of endothelial nitric oxide synthase and inducible nitric oxide synthase did not differ among the groups, nor did total nitrite plus nitrate levels. Old ovx exhibited decreased expression of both the alpha and beta-subunits of soluble guanylyl cyclase (sGC) and had impaired nitric oxide signaling in the vascular smooth muscle. Immediate E2 replacement in the aged ovx prevented both the impairment in vasorelaxation, and the decreased sGC receptor expression and abnormal sGC signaling within the vascular smooth muscle.

Timing of estrogen replacement influences atherosclerosis progression and plaque leukocyte populations in ApoE-/- mice

Studies of the effects of estrogen replacement therapy on coronary heart disease risk have produced conflicting results. We hypothesize that this may be explained by differences in the length of estrogen deficiency prior to initiation of treatment and associated variation in plaque inflammation or stage of progression. The goal of this study was to determine whether estrogen administered after a period of deficiency affects plaque progression and leukocyte populations. Ovariectomized ApoE-/- mice were treated as follows: group 1: continuous estrogen for 90 days (E+/+); group 2: placebo for 45 days followed by estrogen for 45 days (E-/+); group 3: estrogen for 45 days followed by placebo for 45 days (E+/-); and group 4: placebo for 90 days (E-/-). Serum lipoprotein concentrations, plaque size and inflammatory cell (macrophage, CD3+, CD4+, CD8+, dendritic cell, and NK cell) densities were quantified. Plaque size was smaller in groups receiving early estrogen therapy. CD3+ and total inflammatory cell densities were lower in late estrogen therapy groups. The CD8 to dendritic cell ratio was significantly lower in the E-/+ group only. These results suggest that a period of estrogen deficiency followed by reintroduction alters the immunologic environment of atherosclerotic lesions as well as plaque progression.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Improvement of immune cell functions in aged mice treated for five weeks with soybean isoflavones

Aging is associated with an impaired immune system as well as with a decline of several hormones, such as estrogens. Dietary phytoestrogens have been proposed as an alternative to hormone replacement therapy. The beneficial action of soybean compounds is probably due to isoflavones, whose role as immunomodulators has been investigated with increasing interest. The aim of the present work was to study whether a 5-week administration of a diet enriched in soybean isoflavones and green tea could influence the immune function of mice that were sham-operated or ovariectomized. Natural killer activity (NK) and lymphoproliferation in response to the mitogens concanavaline A (Con A) and lipopolysaccharide (LPS), were studied in peritoneal leukocytes. Both treatments with soybean or green tea plus soybean were highly effective in improving these immune parameters with respect to control groups. Since the immune system is a marker of health and a predictor of longevity, an adequate treatment with isoflavones could be useful in slowing down the effects of the aging process through an improvement in the two relevant immune functions studied.

Progestin-based contraceptive suppresses cellular immune responses in SHIV-infected rhesus macaques

Nine rhesus macaques in groups of three received a single dose of the injectable progestin-based contraceptive Depo-Provera 5 weeks prior to challenge intravaginally with varying doses of a mixture of the pathogenic CXCR4 (X4)-SHIV(SF33A) and CCR5 (R5)-SHIV(SF162P3) isolates. As controls, seven Depo-naive animals were inoculated once with a high-dose of the mixed inoculum. Irrespective of inoculum dose, acute viremia was higher in the Depo-treated than in the Depo-naive animals. Further, genetic complexity of the replicating virus was greater and replication of the X4 virus was favored in dually infected animals treated with Depo-Provera. Analysis of cellular immune responses revealed slower response rates in virus-specific IFN-gamma production to SIV Gag in the Depo-treated macaques. The immunosuppressive effect of Depo-Provera on mounting an antiviral cellular immune response may account for the increase viral burden and diversity, and the predominance of X4 virus replication in SHIV infected macaques that were administered the progestin-based contraceptive.

Effects of 17beta-estradiol on the expression of IL-6, IL-11 and NF-kappaB in human MG-63 osteoblast-like cell line

In order to characterize the effects of 17beta-estradiol (17beta-E2) on the expression of IL-6, IL-11 and NF-kappaB in the human MG-63 osteoblast-like cell line, the expression of IL-6 was detected by RT-PCR, Northern blot and Western blot. The expression of IL-11 was determined by RT-PCR, and NF-kappaB by Western blot. The results showed that 17beta-E2 down-regulated the expression of IL-6 mRNA and protein, IL-11 mRNA and NF-kappaB protein in MG-63 cells. It was suggested that the expression of NF-kappaB, IL-6 and IL-11 in MG-63 cells could be suppressed by 17beta-E2, and this might lend support to estrogen replacement therapy in postmenopausal women.

Estrogenic regulation of tissue factor and tissue factor pathway inhibitor in platelets

Oral estrogen treatment increases thrombotic risk. Tissue factor (TF), tissue factor pathway inhibitor (TFPI), and platelet interaction with leukocytes are important determinants of thrombogenesis. Therefore, the present study was designed to define and compare platelet TF and TFPI mRNA and adhesion protein expression in platelets derived from animals treated with different types of oral estrogens. Ovariectomized pigs were treated with 17beta-estradiol (2 mg/day), conjugated equine estrogen (CEE; 0.625 mg/day), or raloxifene (60 mg/day) for 4 wk. Compared with intact animals, ovariectomy and treatment differentially affected populations of leukocytes: neutrophils decreased whereas lymphocytes increased significantly 4 wk after ovariectomy and with 17beta-estradiol and CEE treatments; eosinophils increased only with 17beta-estradiol treatment. Content of TF protein increased in platelets from 17beta-estradiol- and raloxifene-treated pigs, whereas TF mRNA was detected only in platelets from 17beta-estradiol- and CEE treated pigs. TFPI mRNA increased in platelets after ovariectomy and estrogen treatment. Only a trace of TFPI protein was detected, but a higher-molecular-mass protein was observed in all treatment groups. Expression of CD40 and CD40 ligand increased with ovariectomy and decreased with 17beta-estradiol and CEE treatments more than with raloxifene. The ratio of activated to basal P-selectin expression decreased with ovariectomy and increased with raloxifene treatments. These results suggest that estrogenic formulations may affect individual thrombotic risk by different mechanisms that regulate TF and platelet-leukocytic interactions. These studies provide the rationale for evaluation of interactions among platelets and TF and TFPI expression on thrombin generation during estrogen treatment in humans.

Changes with ageing in several leukocyte functions of male and female rats

The impairment of the immune system with aging, or 'immunosenescence', appears to contribute to the increased morbidity and mortality of aged subjects. T cell functions and Natural Killer activity seem to be the immune responses most affected by ageing. Since the immune system works more efficiently in females than in males, we have studied the changes of several immune functions with age in rats of both sexes. In addition, we have investigated if ovariectomy, a model of menopause in rats, produces a loss of this gender-related advantage. In the present work, the changes with age (2, 6, 12, 14, 18, 22 and 24 months old) in lymphocyte chemotaxis, T lymphoproliferative response to the mitogen ConA, IL-2 release and Natural Killer activity of cells from axillary nodes and spleen of male and female rats as well as of females ovariectomized at 12 months of age have been studied. An age-related decrease was found in all investigated functions, with a slightly different evolution depending on the immune organ and gender considered. In general, the data obtained show that a certain degree of immunosenescence takes place with age in rats, with males being less immunocompetent than intact age-matched females, but showing an immune response similar to that of ovariectomized animals.

Immune effects of surgical menopause and estrogen replacement therapy in peri-menopausal women

The complex relationship between sex hormones and immune function suggests that sex hormone deficiency and estrogen replacement therapy (ERT) in post-menopausal women may have pleiotropic effects on immune function. For this reason, we aimed to investigate short-term effects of surgical menopause and ERT on immunity profile in peri-menopausal women. Seventeen healthy peri-menopausal women who were to undergo total abdominal hysterectomy and bilateral salpingo-oopherectomy (TAH + BSO) for uterine myoma were enrolled into this study. Three blood samples were collected from each patient: 1-day prior to surgery, 30 days after the operation (before ERT) and 30 days after transdermal ERT. The percentages of peripheral blood lymphocyte subpopulations, serum interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) concentrations were determined by flow-cytometry and ELISA, respectively. Following TAH + BSO, the percentage of CD8+ cells was increased ( P < 0.001 ) while the percentage of CD19+ cells, serum IL-4, and IFN-gamma concentration and the ratio of CD4+ to CD8+ cells were decreased ( P < 0.001, P < 0.001, P < 0.002, and P < 0.05 respectively). After ERT, this trend reversed and a decrease in the CD8+ cells ( P < 0.001 ), increase in the CD19+ cells percentages ( P < 0.02 ) and increase in serum IFN-gamma concentration ( P < 0.002 ) were observed. Although an increasing trend in the CD4+ to CD8+ ratio occurred by ERT, this was not significant. However, the decrease in the serum IL-4 concentration after TAH + BSO was not reversed by ERT. Hormone deficiency in post-menopausal women may cause an impaired immune response, and ERT can restore this phenomenon. Estrogen seems to have an important role in the regulation of immune function.

Menopausal increases in pulsatile gonadotropin-releasing hormone release in a nonhuman primate (Macaca mulatta)

Reproductive function in all vertebrates is controlled by the circhoral release of the neuropeptide, GnRH, into the portal capillary system leading to the anterior pituitary. Despite its primary role in sexual maturation and the maintenance of adult reproductive function, changes in the concentrations and pattern of GnRH release have not yet been reported in any primate species during the menopausal transition and postmenopause. Such knowledge is essential for ascertaining both the mechanisms for, and consequences of, the menopausal process. Here we used a push-pull perfusion method to measure and compare the parameters of pulsatile GnRH release in adult rhesus monkeys at 8.4 +/- 1.5 yr (young adult females, early follicular phase, n = 6) and 28.8 +/- 0.3 yr (aged females, n = 4, of which two monkeys were in the menopausal transition, and two were postmenopausal). Our results demonstrate that: 1) GnRH release is pulsatile in both young and aged monkeys; 2) mean concentrations of GnRH increase during reproductive aging; and 3) GnRH pulse frequency does not differ between aged monkeys and young monkeys in the early follicular phase. We conclude that not only do GnRH neurons have the continued capacity to release GnRH in a pulsatile manner but also they can do so with enhanced GnRH levels in aged primates. To our knowledge, this is the first direct demonstration of elevated pulsatile GnRH concentrations in a primate species during reproductive senescence, a result that may have implications for menopausal symptoms.

Immunomodulatory effects of estrogen and progesterone replacement in a nonhuman primate model

A novel postmenopausal nonhuman primate model consisting of healthy young and old ovariectomized rhesus macaques was used to assess the short-term immunomodulatory effects of transdermally administered estrogen and progesterone. Specifically, we determined estrogen- and progesterone-induced changes in absolute numbers of circulating lymphocytes (B lymphocytes, CD4+ lymphocytes, and CD8+ lymphocytes) as well as lymphocytes expressing the activation markers CD25 and CD69. In addition, we assessed B and T lymphocyte activity, i.e, immunoglobulin (Ig) and interferon-gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMCs). In general, treatment with estrogen or progesterone resulted in decreased lymphocyte numbers and in down-modulation of activation markers. In addition, hormone replacement resulted in a decreasing trend for PBMC IFN-gamma production, whereas PBMC Ig production was minimally affected. Hormone treatment seemed to influence young and old animals differently, with the young animals appearing more susceptible to its immune system-related effects. These results indicate that, in our animal model exogenously administered hormones may dynamically interact with the immune system, resulting in in vivo modulation of lymphocyte numbers and activity.

Changes in proinflammatory cytokine activity after menopause

There is now a large body of evidence suggesting that the decline in ovarian function with menopause is associated with spontaneous increases in proinflammatory cytokines. The cytokines that have obtained the most attention are IL-1, IL-6, and TNF-alpha. The exact mechanisms by which estrogen interferes with cytokine activity are still incompletely known but may potentially include interactions of the ER with other transcription factors, modulation of nitric oxide activity, antioxidative effects, plasma membrane actions, and changes in immune cell function. Experimental and clinical studies strongly support a link between the increased state of proinflammatory cytokine activity and postmenopausal bone loss. Preliminary evidence suggests that these changes also might be relevant to vascular homeostasis and the development of atherosclerosis. Better knowledge of the mechanisms and the time course of these interactions may open new avenues for the prevention and treatment of some of the most prevalent and important disorders in postmenopausal women.

Postmenopausal oestrogen replacement therapy and atherosclerosis: can current compounds provide cardiovascular protection?

The natural oestrogen, 17 beta-oestradiol, has been implicated in protection from atherosclerosis, a chronic systemic vascular disease with an inflammatory component accounting for the majority of morbidity and mortality in Western countries. Despite the protective effects of 17 beta-oestradiol in premenopausal women and experimental evidence demonstrating inhibitory effects of oestrogen on atherosclerosis progression, it is currently unclear whether hormone replacement therapy can affect cardiovascular morbidity and mortality in postmenopausal women. The recent advances in understanding the mechanisms of oestrogen action demonstrated roles for different oestrogen receptors and oestrogen metabolites in the pathogenesis of vascular injury and endothelial cell dysfunction. However, their respective role in the process of atherogenesis remains yet to be elucidated. Moreover, the availability of novel drugs with tissue- and/or receptor-specific actions will help to understand the role of oestrogen in cardiovascular diseases. Several ongoing large-scale clinical trials using opposed or unopposed replacement therapy with natural or synthetic oestrogens, or selective oestrogen receptor modulators (SERMs) will resolve the question whether the drugs currently available have therapeutic potential to interfere with the progression of atherosclerosis and its complications.