Selected contribution: estrogen receptor-alpha gene transfer inhibits proliferation and NF-kappaB activation in VSM cells from female rats

The role of sex steroid hormones in the pathophysiology and treatment of sarcopenia

Sex steroids influence the maintenance and growth of muscles. Decline in androgens, estrogens and progesterone by aging leads to the loss of muscular function and mass, sarcopenia. These steroid hormones can interact with different signaling pathways through their receptors. To date, sex steroid hormone receptors and their exact roles are not completely defined in skeletal and smooth muscles. Although numerous studies focused on the effects of sex steroid hormones on different types of cells, still many unexplained molecular mechanisms in both skeletal and smooth muscle cells remain to be investigated. In this paper, many different molecular mechanisms that are activated or inhibited by sex steroids and those that influence the growth, proliferation, and differentiation of skeletal and smooth muscle cells are reviewed. Also, the similarities of cellular and molecular pathways of androgens, estrogens and progesterone in both skeletal and smooth muscle cells are highlighted. The reviewed signaling pathways and participating molecules can be targeted in the future development of novel therapeutics.

17β estradiol regulates adhesion molecule expression in mesangial cells during glomerulonephritis

We showed previously that 17β estradiol (E2) led to improved survival in nephrotoxic serum induced nephritis (NTN) in male mice. In this study we determined whether E2 regulates vascular cell adhesion molecule (VCAM)-1, an adhesion molecule that is upregulated in kidney during autoimmune nephritis, in mesangial cells (MC). We show that E2 inhibited VCAM-1 up-regulation in kidneys in vivo during NTN, and in MCs upon TNFα stimulation. VCAM-1 up-regulation in MCs was controlled by the transcription factor NFκB. E2 inhibited RNA polymerase II recruitment to the VCAM-1 promoter, but not p65 recruitment. Interestingly E2 inhibited TNFα stimulated interaction between poly (ADP-ribose) polymerase-1 (PARP-1) and p65. As PARP-1 is required for VCAM-1 upregulation in MCs, our data suggest that E2 may inhibit pre-initiation complex formation at VCAM-1 promoter by inhibiting PARP-1 recruitment to p65. We propose that E2 plays an important role in regulating renal inflammation locally.

Efficacy of female rat models in translational cardiovascular aging research

Cardiovascular disease is the leading cause of death in women in the United States. Aging is a primary risk factor for the development of cardiovascular disease as well as cardiovascular-related morbidity and mortality. Aging is a universal process that all humans undergo; however, research in aging is limited by cost and time constraints. Therefore, most research in aging has been done in primates and rodents; however it is unknown how well the effects of aging in rat models translate into humans. To compound the complication of aging gender has also been indicated as a risk factor for various cardiovascular diseases. This review addresses the systemic pathophysiology of the cardiovascular system associated with aging and gender for aging research with regard to the applicability of rat derived data for translational application to human aging.

Raloxifene suppresses experimental autoimmune encephalomyelitis and NF-κB-dependent CCL20 expression in reactive astrocytes

Recent clinical data have led to the consideration of sexual steroids as new potential therapeutic tools for multiple sclerosis. Selective estrogen receptor modulators can exhibit neuroprotective effects like estrogen, with fewer systemic estrogen side effects than estrogen, offering a more promising therapeutic modality for multiple sclerosis. The important role of astrocytes in a proinflammatory effect mediated by CCL20 signaling on inflammatory cells has been documented. Their potential contribution to selective estrogen receptor modulator-mediated protection is still unknown. Using a mouse model of chronic neuroinflammation, we report that raloxifene, a selective estrogen receptor modulator, alleviated experimental autoimmune encephalomyelitis–an animal model of multiple sclerosis–and decreased astrocytic production of CCL20. Enzyme-linked immunosorbent assay, immunohistochemistry imaging and transwell migration assays revealed that reactive astrocytes express CCL20, which promotes Th17 cell migration. In cultured rodent astrocytes, raloxifene inhibited IL-1β-induced CCL20 expression and chemotaxis ability for Th17 migration, whereas the estrogen receptor antagonist ICI 182,780 blocked this effect. Western blotting further indicated that raloxifene suppresses IL-1β-induced NF-κB activation (phosphorylation of p65) and translocation but does not affect phosphorylation of IκB. In conclusion, these data demonstrate that raloxifene provides robust neuroprotection against experimental autoimmune encephalomyelitis, partially via an inhibitory action on CCL20 expression and NF-κB pathways in reactive astrocytes. Our results contribute to a better understanding of the critical roles of raloxifene in treating experimental autoimmune encephalomyelitis and uncover reactive astrocytes as a new target for the inhibitory action of estrogen receptors on chemokine CCL20 expression.

Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats

Fever, an important component of the host's defense response to immune challenge, is absent or attenuated in rats near the term of pregnancy. The present experiments were carried out to determine the role of endogenous glucocorticoids in mediating the altered core temperature (Tc) response to exogenous pyrogen (i.e., Escherichia coli LPS). For the experiments, metyrapone-a glucocorticoid synthesis inhibitor-was administered to near-term pregnant rats prior to an EC(100) dose of E. coli LPS. Administration of LPS following vehicle elicited a significant corticosterone response and resulted in a decrease in Tc (i.e., hypothermia). Prior administration of metyrapone, however, which abolished the corticosterone response and altered the pyrogenic/cryogenic cytokine response to LPS, eliminated hypothermia and restored the febrile response. Our results provide evidence that endogenous glucocorticoids play a role in mediating the altered febrile response to immune stimuli observed in rats near the term of pregnancy.

Sex differences in the coronary vasodilation induced by 17 β-oestradiol in the isolated perfused heart from spontaneously hypertensive rats

AIM

The relaxation induced by oestrogen in the coronary vascular bed from normotensive rats has been well described. However, almost nothing is known about this action in spontaneously hypertensive rats (SHR). We investigated the effect of 17 β-oestradiol (E(2) ) in coronary arteries from SHR as well as the contribution of the endothelium and the vascular smooth muscle to this action.

METHODS

Coronary arteries from male and female rats were used. Mean arterial pressure (MAP) and baseline coronary perfusion pressure (CPP) were determined. The effects of 10 μm E(2) were assessed by in bolus administration before and after endothelium denudation (0.25 μm sodium deoxycholate) or perfusion with 100 μm N(ω)-nitro-L-arginine methyl ester (L-NAME), 2.8 μm indomethacin, 0.75 μm clotrimazole, 100 μm L-NAME after endothelium denudation (0.25 μm sodium deoxycholate), 100 μm L-NAME plus 2.8 μm indomethacin, 0.75 μm clotrimazole plus 2.8 μm indomethacin and 4 mm tetraethylammonium (TEA).

RESULTS

  MAP was higher in the male group, while CPP was higher in the female group (P<0.05). There were no differences in E(2)-induced relaxation between females and males (-17±1.6 vs. -17±2% respectively). Only in the female group the E(2) response was significantly attenuated after endothelium removal or perfusion with clotrimazole. The response to E(2) was reduced in both groups with L-NAME, L-NAME plus indomethacin, L-NAME after endothelium removal or TEA.

CONCLUSIONS

Nitric oxide, endothelium-derived hyperpolarizing factor and potassium channels may have the most important role to E(2) response in the female group, whereas nitric oxide and potassium channels may have the most important role in the male group.

Estrogen and mechanisms of vascular protection

Estrogen has antiinflammatory and vasoprotective effects when administered to young women or experimental animals that appear to be converted to proinflammatory and vasotoxic effects in older subjects, particularly those that have been hormone free for long periods. Clinical studies have raised many important questions about the vascular effects of estrogen that cannot easily be answered in human subjects. Here we review cellular/molecular mechanisms by which estrogen modulates injury-induced inflammation, growth factor expression, and oxidative stress in arteries and isolated vascular smooth muscle cells, with emphasis on the role of estrogen receptors and the nuclear factor-kappaB (NFkappaB) signaling pathway, as well as evidence that these protective mechanisms are lost in aging subjects.

DNA-binding ability of NF-kappaB is affected differently by ERalpha and ERbeta and its activation results in inhibition of estrogen responsiveness

Estrogenic effects involve interactions between estrogen receptors (ERs), response elements, and nuclear proteins. It is hypothesized that interaction between ER and NF-kappa B may affect the regulation of responsive genes. Electrophoretic mobility shift assay (EMSA) was performed to assess if the interaction of ERs and NF- kappaB affect their respective DNA-binding activities, and alkaline phosphatase assay was done to evaluate estrogenic activity. EMSA revealed that ERs inhibit DNA-binding of p50 and p65, whereas p50 did not impair ER alpha binding. Stimulation with estradiol inhibited DNA binding of NF-kappaB in ERalpha-transfected endometrial stromal cells (ESCs). Moreover, activation of NF-kappaB significantly decreased estrogen responsiveness of Ishikawa cells and ERalpha-transfected ESC. Our results suggest that ERs downregulate NF-kappaB-dependent gene activation by directly preventing DNA binding. However, NF-kappaB-mediated inhibition of ER-dependent gene activation may be carried out indirectly rather than through a direct inhibition of ER-DNA binding. These findings offer new insight into the specific role of ERalpha and could eventually help in developing therapeutics for endometriosis.

Dysregulation of CREB binding protein triggers thrombin-induced proliferation of vascular smooth muscle cells

Thrombin is a potent mitogen for vascular smooth muscle cells (VSMCs). CBP has been regarded as a potential therapeutic target on the basis of its ability to affect cell growth. Therefore we hypothesized that CBP mediates thrombin-induced proliferation of VSMCs. We constructed recombinant adenoviral vector that expresses four short hairpin RNA (shRNA) targeting rat CBP mRNA (CBP-shRNA/Ad). VSMCs were infected with CBP-shRNA/Ad and treated with thrombin. CBP level were analyzed by quantitative real-time PCR and Western blot. To evaluate VSMC proliferation, the cell cycle and DNA synthesis were analyzed by flow cytometry and (3)H-thymidine incorporation, respectively. CBP-shRNA/Ad infection inhibited thrombin-induced CBP expression in a dose-dependent manner concomitant with a decrease in the percentage of cells in the S phase and in DNA synthesis. These findings suggest that CBP plays a pivotal role in the S phase progression of VSMCs.

Inhibition of vascular inflammation by dehydroepiandrosterone sulfate in human aortic endothelial cells: roles of PPARalpha and NF-kappaB

Dehydroepiandrosterone sulfate (DHEAS) is a hormone produced by the adrenal gland and is a precursor for both androgens and estrogens. Atherosclerosis is a well characterized inflammatory disease, but little is known about the role of DHEAS in vascular inflammation. We hypothesize that DHEAS can reduce inflammation in vascular endothelial cells and the mechanism involves the peroxisome proliferator-activated receptor alpha (PPARalpha), thereby inhibiting transcription factors involved in endothelial cell inflammation. To test our hypothesis, aortic endothelial cells were pretreated for 48 h with DHEAS, then with TNF-alpha. TNF-alpha-induced upregulation of the expression of inflammatory genes interleukin (IL)-8 and intracellular adhesion molecule (ICAM)-1 was attenuated by incubation with DHEAS. DHEAS inhibited the TNF-alpha-induced surface expression of vascular cell adhesion molecule (VCAM)-1. This effect was abolished by the addition of MK866, a PPARalpha inhibitor, indicating that PPARalpha is involved in the mechanism of this inhibition. The addition of the aromatase inhibitor letrozole had no effect on the inhibition of TNF-alpha-induced VCAM-1 expression by DHEAS. Treatment of endothelial cells with DHEAS dramatically inhibited the TNF-alpha-induced activation of NF-kappaB, an inflammatory transcription factor, and increased protein levels of the NF-kappaB inhibitor, IkappaB-alpha. These results signify the ability of DHEAS to directly inhibit the inflammatory process and show a potential direct effect of DHEAS on vascular inflammation that has implications for the development of atherosclerotic cardiovascular disease.

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.

Sex differences in bronchiolar epithelium response after the inhalation of lead acetate (Pb)

In order to identify if there were sex differences in lead (Pb) lung concentrations and in bronchiolar response after its inhalation, a mice inhalation model was conducted. Sixty CD-1 adult mice from each sex inhaled separately, lead acetate 0.1 M for 1 h, thrice weekly during 15 days. Animals were evaluated for Pb-lung concentrations by atomic absorption spectrometry and for morphological evaluation by scanning electron microscopy (SEM). Higher Pb-lung concentrations were determined in females, however, more cell damage was found in males, finding that correlated with an increased loss of the nonciliated bronchiolar cells (NCBC) more sloughing and necrosis. Differences in particle clearance, oxidative stress handling, cytokines pathway activation and cytochrome P450 enzymes activity, all influenced by sex hormones, might be a possible explanation for our findings. The relevance of further studies in this field is stressed, as well as its relation to the different development expected for each sex in disease evolution, possible complications and treatment response.

Transcription factor cross-talk: the estrogen receptor and NF-kappaB

The NF-kappaB family of transcription factors regulates many genes that are essential primarily for the development, maintenance and function of the innate and adaptive immune systems. Thus, aberrant activity of the nuclear factor NF-kappaB has a role in many pathological conditions with inflammatory and autoimmune components. Estrogen receptors (ERs) are transcription factors that mediate the biological responses to the sex hormone estrogen and are essential for reproduction and for functions of the cardiovascular, skeletal and nervous systems. Recent studies have demonstrated molecular cross-talk between these families of transcription factors in which the ER mediates inhibition of NF-kappaB activity at several levels. Such cross-talk between these important regulators of the endocrine and immune systems might be exploited for the treatment of cancer and inflammatory and autoimmune diseases.

Divergent effects of estrogen and nicotine on Rho-kinase expression in human coronary vascular smooth muscle cells

Recent studies have demonstrated that up-regulated Rho-kinase plays an important role in the pathogenesis of coronary arteriosclerosis and vasospasm. We have shown that inflammatory stimuli, such as angiotensin II and interleukin-1beta, up-regulate Rho-kinase expression and activity in human coronary vascular smooth muscle cells, for which intracellular signal transduction mediated by protein kinase C and NF-kappaB is involved. Here, we show that estrogen down-regulates while nicotine up-regulates Rho-kinase and that nicotine counteracts the inhibitory effect of estrogen on angiotensin II-induced Rho-kinase expression. Furthermore, we demonstrated that the intracellular signal transduction of the inhibitory effect of estrogen is mediated by an estrogen receptor. These results demonstrate that inflammatory stimuli up-regulate Rho-kinase, for which estrogen (mediated by an estrogen receptor) and nicotine exert divergent inhibitory and stimulatory effects on the Rho-kinase expression, respectively, and may explain in part why the incidence of arteriosclerotic and vasospastic disorders is increased in postmenopausal women and smokers.

Characterization of a human REL-estrogen receptor fusion protein with a reverse conditional transforming activity in chicken spleen cells

Overexpression of the human REL transcription factor can malignantly transform chicken spleen cells in vitro. In this report, we have created and characterized a cDNA encoding a chimeric protein (RELDelta424-490-ER) in which sequences of a highly transforming REL mutant (RELDelta424-490) are fused to the ligand-binding domain of the human estrogen receptor (ER). Surprisingly, RELDelta424-490-ER is constitutively nuclear in A293 cells, and RELDelta424-490-ER activates transcription in the absence, but not in the presence, of estrogen in kappaB-site reporter gene assays. Furthermore, RELDelta424-490-ER transforms chicken spleen cells in the absence of estrogen, but the addition of estrogen blocks the ability of RELDelta424-490-ER-transformed cells to form colonies in soft agar, even though estrogen induces increased nuclear translocation of RELDelta424-490-ER in these cells. ERalpha can also inhibit REL-dependent transactivation in trans in an estrogen-dependent manner, and ERalpha can interact with REL in vitro. Thus, the RELDelta424-490-ER fusion protein shows an unusual, reverse hormone regulation, in that its most prominent biological activities (transformation and transactivation) are inhibited by estrogen, probably due to an estrogen-induced interaction between the ER sequences and sequences in the Rel homology domain. Nevertheless, these results indicate that the continual activity of REL is required to sustain the transformed state of chicken spleen cells in culture, suggesting that direct and specific inhibitors of REL may have therapeutic efficacy in certain human lymphoid cancers.

Genotoxic differences by sex in nasal epithelium and blood leukocytes in subjects residing in a highly polluted area

We describe differences by sex in genotoxic damage found in a population of medical students exposed to a highly oxidative atmosphere, compared with a control group, measured by the single-cell gel electrophoresis assay and histological changes in nasal epithelium smears. Cells were obtained from the nasal epithelium and blood leukocytes. Higher DNA damage in nasal cells and leukocytes was found in males compared to females and control subjects. The percentage of squamous metaplastic changes in the nasal epithelium was also higher in males compared with females and controls. The co-mutation of normal nasal epithelium by squamous cells might modify its protective function in the nose, increasing the risk of damage to the lower respiratory tract. Although, as medical students, males and females were exposed to the same environment and activity patterns, male genotoxicity damage was higher in control and exposed subjects. More research should be done in order to identify direct or indirect sexual hormone intervention.

Neuroimmune response to endogenous and exogenous pyrogens is differently modulated by sex steroids

The objective of this study was to explore whether and how ovarian hormones interact with the febrile response to pyrogens. Estrogen and progesterone treatment of ovariectomized rats was associated with a reduction in lipopolysaccharide (LPS)-induced fever, compared with ovariectomized controls. LPS-fever reduction was accompanied by reduced levels of the inducible cyclooxygenase-2 (COX-2) protein expression in the hypothalamus as well as reduced plasma levels of IL-1beta. The amount of LPS-induced IL-6 in the plasma was not affected by ovarian hormone replacement. In contrast, hypothalamic COX-2 expression in response to intraperitoneal injection of IL-1beta was potentiated by the ovarian hormone replacement. IL-1beta induced a moderate increase in plasma levels of IL-6 that was suppressed by ovarian hormone replacement. These data suggest that ovarian hormone replacement attenuated the proinflammatory response to LPS by suppressing the LPS-induced IL-1beta production and COX-2 expression in the hypothalamus. The markedly different action of ovarian hormones on IL-1beta and LPS effects suggests that this sex hormone modulation of the immune response is a function of the nature of infection and provides further evidence that LPS actions are different from those of IL-1beta.