Estrogen receptor alpha regulates matrix metalloproteinase-13 promoter activity primarily through the AP-1 transcriptional regulatory site

A regulatory mechanism of mouse kallikrein 1 gene expression by estrogen

Tissue kallikrein 1 (Klk1) is a serine protease that degrades several proteins including insulin-like growth factor binding protein-3 and extracellular matrix molecules. Klk1 mRNA expression in the mouse uterus was increased by estradiol-17β (E2). The present study aimed to clarify the regulatory mechanism for Klk1 expression by estrogen. The promoter analysis of the 5'-flanking region of Klk1 showed that the minimal promoter of Klk1 existed in the -136/+24 region, and the estrogen-responsive region in the -433/-136 region. Tamoxifen increased Klk1 mRNA expression and the promoter activity, suggesting the involvement of AP-1 sites. Site-directed mutagenesis for the putative AP-1 sites in the -433/-136 region showed that the two putative AP-1 sites were involved in the regulation of Klk1 expression. Binding of estrogen receptor α (ERα) to the -433/-136 region was revealed by Chip assay. These results indicated that ERα bound the two putative AP-1 sites and transactivated Klk1 in the mouse uterus.

Sex differences in musculoskeletal injury and disease risks across the lifespan: Are there unique subsets of females at higher risk than males for these conditions at distinct stages of the life cycle?

Sex differences have been reported for diseases of the musculoskeletal system (MSK) as well as the risk for injuries to tissues of the MSK system. For females, some of these occur prior to the onset of puberty, following the onset of puberty, and following the onset of menopause. Therefore, they can occur across the lifespan. While some conditions are related to immune dysfunction, others are associated with specific tissues of the MSK more directly. Based on this life spectrum of sex differences in both risk for injury and onset of diseases, a role for sex hormones in the initiation and progression of this risk is somewhat variable. Sex hormone receptor expression and functioning can also vary with life events such as the menstrual cycle in females, with different tissues being affected. Furthermore, some sex hormone receptors can affect gene expression independent of sex hormones and some transitional events such as puberty are accompanied by epigenetic alterations that can further lead to sex differences in MSK gene regulation. Some of the sex differences in injury risk and the post-menopausal disease risk may be "imprinted" in the genomes of females and males during development and sex hormones and their consequences only modulators of such risks later in life as the sex hormone milieu changes. The purpose of this review is to discuss some of the relevant conditions associated with sex differences in risks for loss of MSK tissue integrity across the lifespan, and further discuss several of the implications of their variable relationship with sex hormones, their receptors and life events.

Osteoarthritis as an Umbrella Term for Different Subsets of Humans Undergoing Joint Degeneration: The Need to Address the Differences to Develop Effective Conservative Treatments and Prevention Strategies

Osteoarthritis (OA) of joints such as the knee and hip are very prevalent, and the number of individuals affected is expected to continue to rise. Currently, conservative treatments after OA diagnosis consist of a series of increasingly invasive interventions as the degeneration and pain increase, leading very often to joint replacement surgery. Most interventions are focused on alleviating pain, and there are no interventions currently available that stop and reverse OA-associated joint damage. For many decades OA was considered a disease of cartilage, but it is now considered a disease of the whole multi-tissue joint. As pain is the usual presenting symptom, for most patients, it is not known when the disease process was initiated and what the basis was for the initiation. The exception is post-traumatic OA which results from an overt injury to the joint that elevates the risk for OA development. This scenario leads to very long wait lists for joint replacement surgery in many jurisdictions. One aspect of why progress has been so slow in addressing the needs of patients is that OA has been used as an umbrella term that does not recognize that joint degeneration may arise from a variety of mechanistic causes that likely need separate analysis to identify interventions unique to each subtype (post-traumatic, metabolic, post-menopausal, growth and maturation associated). A second aspect of the slow pace of progress is that the bulk of research in the area is focused on post-traumatic OA (PTOA) in preclinical models that likely are not clearly relevant to human OA. That is, only ~12% of human OA is due to PTOA, but the bulk of studies investigate PTOA in rodents. Thus, much of the research community is failing the patient population affected by OA. A third aspect is that conservative treatment platforms are not specific to each OA subset, nor are they integrated into a coherent fashion for most patients. This review will discuss the literature relevant to the issues mentioned above and propose some of the directions that will be required going forward to enhance the impact of the research enterprise to affect patient outcomes.

Mmp13 deletion in mesenchymal cells increases bone mass and may attenuate the cortical bone loss caused by estrogen deficiency

The protective effect of estrogens against cortical bone loss is mediated via direct actions on mesenchymal cells, but functional evidence for the mediators of these effects has only recently begun to emerge. We report that the matrix metalloproteinase 13 (MMP13) is the highest up-regulated gene in mesenchymal cells from mice lacking the estrogen receptor alpha (ERα). In sham-operated female mice with conditional Mmp13 deletion in Prrx1 expressing cells (Mmp13^ΔPrrx1), the femur and tibia length was lower as compared to control littermates (Mmp13f.^/f). Additionally, in the sham-operated female Mmp13^ΔPrrx1 mice cortical thickness and trabecular bone volume in the femur and tibia were higher and osteoclast number at the endocortical surfaces was lower, whereas bone formation rate was unaffected. Notably, the decrease of cortical thickness caused by ovariectomy (OVX) in the femur and tibia of Mmp13f.^/f mice was attenuated in the Mmp13^ΔPrrx1 mice; but the decrease of trabecular bone caused by OVX was not affected. These results reveal that mesenchymal cell-derived MMP13 may regulate osteoclast number and/or activity, bone resorption, and bone mass. And increased production of mesenchymal cell-derived factors may be important mediators of the adverse effect of estrogen deficiency on cortical, but not trabecular, bone.

Sex Differences in Biological Systems and the Conundrum of Menopause: Potential Commonalities in Post-Menopausal Disease Mechanisms

Sex-specific differences in biology and physiology likely start at the time of conception and progress and mature during the pre-puberty time frame and then during the transitions accompanying puberty. These sex differences are impacted by both genetics and epigenetic alterations during the maturation process, likely for the purpose of preparing for successful reproduction. For females, later in life (~45-50) they undergo another transition leading to a loss of ovarian hormone production at menopause. The reasons for menopause are not clear, but for a subset of females, menopause is accompanied by an increased risk of a number of diseases or conditions that impact a variety of tissues. Most research has mainly focused on the target cells in each of the affected tissues rather than pursue the alternative option that there may be commonalities in the development of these post-menopausal conditions in addition to influences on specific target cells. This review will address some of the potential commonalities presented by an integration of the literature regarding tissue-specific aspects of these post-menopausal conditions and data presented by space flight/microgravity (a condition not anticipated by evolution) that could implicate a loss of a regulatory function of the microvasculature in the risk attached to the affected tissues. Thus, the loss of the integration of the paracrine relationships between endothelial cells of the microvasculature of the tissues affected in the post-menopausal environment could contribute to the risk for post-menopausal diseases/conditions. The validation of this concept could lead to new approaches for interventions to treat post-menopausal conditions, as well as provide new understanding regarding sex-specific biological regulation.

Estrogen and bones after menopause: a reappraisal of data and future perspectives

Menopausal hormone therapy (MHT) is effective in preventing menopause-related bone loss and decreasing vertebral, non-vertebral and hip fracture risk. MHT contains estrogens that exert both antiosteoclastic and osteoanabolic effects. These effects are dose-dependent, as even ultra-low doses preserve or increase bone mineral density. The transdermal route of administration is effective on cancellous and cortical bone, although fracture data are still lacking. Hormone replacement therapy is the treatment of choice to preserve skeletal health in women with premature ovarian insufficiency and early menopause. MHT can be considered in women aged < 60 years or within 10 years since menopause as, in this population, benefits outweigh possible risks, such as breast cancer and cardiovascular events. Despite the ensuing bone loss after MHT discontinuation, a residual antifracture effect persists. However, in women at risk of fracture, subsequent antiosteoporotic therapy may be needed, either with an antiosteoclastic or osteoanabolic agent. In any case, longitudinal data from randomized controlled trials comparing different estrogen doses and routes of administration, as well as designating the optimal treatment strategy after MHT discontinuation, are needed to elucidate these issues further.

Sex-specific effects of LiCl treatment on preservation of renal function and extended life-span in murine models of SLE: perspective on insights into the potential basis for survivorship in NZB/W female mice

Considerable research effort has been invested in attempting to understand immune dysregulation leading to autoimmunity and target organ damage. In systemic lupus erythematosus (SLE), patients can develop a systemic disease with a number of organs involved. One of the major target organs is the kidney, but patients vary in the progression of the end-organ targeting of this organ. Some patients develop glomerulonephritis only, while others develop rapidly progressive end organ failure. In murine models of SLE, renal involvement can also occur. Studies performed over the past several years have indicated that treatment with LiCl of females, but not males of the NZB/W model, at an early age during the onset of disease, can prevent development of end-stage renal disease in a significant percentage of the animals. While on Li treatment, up to 80 % of the females can exhibit long-term survival with evidence of mild glomerulonephritis which does not progress to renal failure in spite of on-going autoimmunity. Stopping the treatment led to a reactivation of the disease and renal failure. Li treatment of other murine models of SLE was less effective and decreased survivorship in male BxSB mice, exhibited little effect on male MRL-lpr mice, and only modestly improved survivorship in female MRL-lpr mice. This perspective piece discusses the findings of several related studies which support the concept that protecting target organs such as the kidney, even in the face of continued immune insults and some inflammation, can lead to prolonged survival with retention of organ function. Some possible mechanisms for the effectiveness of Li treatment in this context are also discussed. However, the detailed mechanistic basis for the sex-specific effects of LiCl treatment particularly in the NZB/W model remains to be elucidated. Elucidating such details may provide important clues for development of effective treatment for patients with SLE, ~90 % of which are females.

Investigation of the effects of estrogen on skeletal gene expression during zebrafish larval head development

The development of craniofacial skeletal structures requires well-orchestrated tissue interactions controlled by distinct molecular signals. Disruptions in normal function of these molecular signals have been associated with a wide range of craniofacial malformations. A pathway mediated by estrogens is one of those molecular signals that plays role in formation of bone and cartilage including craniofacial skeletogenesis. Studies in zebrafish have shown that while higher concentrations of 17-β estradiol (E 2) cause severe craniofacial defects, treatment with lower concentrations result in subtle changes in head morphology characterized with shorter snouts and flatter faces. The molecular basis for these morphological changes, particularly the subtle skeletal effects mediated by lower E 2 concentrations, remains unexplored. In the present study we address these effects at a molecular level by quantitative expression analysis of sets of candidate genes in developing heads of zebrafish larvae treated with two different E 2 concentrations. To this end, we first validated three suitable reference genes, ppia2, rpl8 and tbp, to permit sensitive quantitative real-time PCR analysis. Next, we profiled the expression of 28 skeletogenesis-associated genes that potentially respond to estrogen signals and play role in craniofacial development. We found E 2 mediated differential expression of genes involved in extracellular matrix (ECM) remodelling, mmp2/9/13, sparc and timp2a, as well as components of skeletogenic pathways, bmp2a, erf, ptch1/2, rankl, rarab and sfrp1a. Furthermore, we identified a co-expressed network of genes, including cpn1, dnajc3, esr1, lman1, rrbp1a, ssr1 and tram1 with a stronger inductive response to a lower dose of E 2 during larval head development.

Effects of ultrasound on estradiol level, bone mineral density, bone biomechanics and matrix metalloproteinase-13 expression in ovariectomized rabbits

The aim of the present study was to observe the effect of ultrasound (US) on estradiol level, bone mineral density (BMD), bone biomechanics and matrix metalloproteinase-13 (MMP-13) expression in ovariectomized (OVX) rabbits. A total of 28 virgin New Zealand white rabbits were randomly assigned into the following groups: Control (control group), ovariectomy (OVX group), ovariectomy with ultrasound therapy (US group) and ovariectomy with estrogen replacement therapy group (ERT group). At 8 weeks after ovariectomy, the US group received ultrasound treatment while the ERT group were orally treated with conjugated estrogens, and the control and OVX groups remained untreated. The estradiol level, BMD and bone biomechanics, cartilage histology and the MMP-13 expression were analyzed after the intervention. The results indicate that the US treatment increased estradiol level, BMD and bone biomechanical function. Furthermore, the US treatment appeared to improve the recovery of cartilage morphology and decreased the expression of MMP-13 in OVX models. Furthermore, the results suggest that 10 days of US therapy was sufficient to prevent the reduction of estradiol, BMD and bone biomechanical function, to protect osteoarthritis cartilage structure, and to reduce MMP-13 transcription and expression in OVX rabbits. Therefore, US treatment may be a potential treatment for postmenopausal osteoarthritis and osteoporosis.

17β-Estradiol Ameliorates Tight Junction Disruption via Repression of MMP Transcription

The blood-brain barrier (BBB) or blood-spinal cord barrier (BSCB) formed by capillary endothelial cells provides a physical wall between the central nervous system (CNS) and circulating blood with highly selective permeability. BBB/BSCB disruption by activation of matrix metalloproteinases (MMPs) has been shown to result in further neurological damage after CNS injury. Recently it has been discovered that estrogen attenuates BBB/BSCB disruption in in vitro and in vivo models. However, the molecular mechanism underlying the estrogen-mediated attenuation of BBB/BSCB disruption has not been elucidated fully. In the present study, we found that 17β-estradiol (E2) suppresses nuclear factor-κB-dependent MMP-1b, MMP-2, MMP-3, MMP-9, MMP-10, and MMP-13 gene activation in microvessel endothelial bEnd.3 cells subjected to oxygen and glucose deprivation/reperfusion injury. E2 induced the recruitment of ERα and nuclear receptor corepressor to the nuclear factor-κB binding site on the MMPs' gene promoters. Consistently, ER antagonist ICI 182.780 showed opposite effects of E2. We further found that E2 attenuates tight junction disruption through the decreased degradation of tight junction proteins in bEnd.3 cells subjected to oxygen and glucose deprivation-reperfusion injury. In addition, E2 suppressed the up-regulation of MMP expression, leading to a decreased BSCB disruption in the injured spinal cord. In conclusion, we discovered the molecular mechanism underlying the protective role of estrogenin BBB/BSCB disruption using an in vitro and in vivo model. Our study suggests that estrogens may provide a potential therapeutic intervention for preserving BBB/BSCB integrity after CNS injury.

Estrogen receptor beta and truncated variants enhance the expression of transfected MMP-1 promoter constructs in response to specific mechanical loading

Background

Joint diseases such as osteoarthritis (OA) predominantly afflict post-menopausal women, suggesting a pertinent role for female hormones. Estrogen receptor beta (ER-β) has been detected in connective tissues of the knee joint suggesting that these tissues are responsive to the hormone estrogen. Matrix metalloproteinase-1 (MMP-1) activity contributes to cartilage degradation, a key factor leading to OA development in synovial joints. Two polymorphic forms of MMP-1 exist due to a deletion/insertion of the guanine residue in the promoter, and the 2G allelic variant of MMP-1 exhibits more activity than the 1G allele. Previous studies have demonstrated that the polymorphic forms of the human MMP-1 are influenced by the modulating effects of estrogen receptor isoforms. In addition to hormonal influences, physiological factors such as altered mechanical loading are also contributory features of OA. In the present study, the combined influence of biomechanical and hormonal variables on the activity of MMP-1 isoforms was evaluated. We hypothesized that the combined effects of ER-β and sheer stress will differentially activate the two allelic forms of MMP-1 in a hormone-independent manner.

Methods

HIG-82 synoviocytes were transiently transfected with 1G or 2G alleles (±) ER-β and subjected to either shear or equibiaxial stress. Next, 1G/2G promoter activity was measured to determine the combined influence of physiological stimuli. Truncated ER-β constructs were used to determine the importance of different domains of ER-β on 1G/2G activation.

Results

The 2G allele exhibited a constitutively higher activity than the 1G allele, which was further increased when the transfected cells were subject to shear stress, but not equibiaxial stress. Moreover, the combination of ER-β and shear stress further increased the activity levels of the 1G/2G allelic variants. Additionally, select AF-2 truncated ER-β variants led to increased activity levels for the 2G allele, indicating the AF-1 domain was likely involved in the response to mechanical stimulation.

Conclusions

These results suggest that the 1G/2G alleles of MMP-1 are influenced by specific mechanical stimuli like shear stress, as well as the ER-β receptor. These findings contribute to the potential allelic involvement in connective tissue diseases such as OA in females compared to males.

Effects of selective MMP-13 inhibition in squamous cell carcinoma depend on estrogen

Matrix metalloproteinases like MMP-13 cleave and remodel the extracellular matrix and thereby play a crucial role in tumor progression in vivo. Using a highly selective inhibitor to block MMP-13 protein activity, we demonstrate a striking inhibitory effect on invasive tumor growth and vascularization in murine skin squamous cell carcinoma (SCC). Therapy outcome critically depends on animal age in C57Bl/6 mice and was successful in old female but not in young female mice. Treatment success was recovered by ovariectomy in young and abolished by 17ß-estradiol supplementation in old mice, suggesting a hormone dependent inhibitor effect. Responsiveness of the tumorigenic keratinocytes BDVII and fibroblasts to 17ß-estradiol was confirmed in vitro, where MMP-13 inhibitor treatment led to a reduction of cell invasion and vascular endothelial growth factor (VEGF) release. This correlated well with a less invasive and vascularized tumor in treated mice in vivo. 17ß-estradiol supplementation also reduced invasion and VEGF release in vitro with no additional reduction on MMP-13 inhibitor treatment. This suggests that low 17ß-estradiol levels in old mice in vivo lead to enhanced MMP-13 levels and VEGF release, allowing a more effective inhibitor treatment compared to young mice. In our study, we present a strong link between lower estrogen levels in old female mice, an elevated MMP-13 level, which results in a more effective MMP-13 inhibitor treatment in fibroblasts and SCC cells in vitro and in vivo.

Menopausal hormone treatment cardiovascular disease: another look at an unresolved conundrum

Cardiovascular disease (CVD) is the most common cause of death in women. Before the Women's Health Initiative (WHI) hormone trials, evidence favored the concept that menopausal hormone treatment (MHT) protects against CVD. WHI studies failed to demonstrate CVD benefit, with worse net outcomes for MHT versus placebo in the population studied. We review evidence regarding the relationship between MHT and CVD with consideration of mechanisms and risk factors for atherogenesis and cardiac events, results of observational case-control and cohort studies, and outcomes of randomized trials. Estrogen effects on CVD risk factors favor delay or amelioration of atherosclerotic plaque development but may increase risk of acute events when at-risk plaque is present. Long-term observational studies have shown ∼40% reductions in risk of myocardial infarction and all-cause mortality. Analyses of data from randomized control trials other than the WHI show a ∼30% cardioprotective effect in recently menopausal women. Review of the literature as well as WHI data suggests that younger and/or more recently menopausal women may have a better risk-benefit ratio than older or remotely menopausal women and that CVD protection may only occur after >5 years; WHI women averaged 63 years of age (12 years postmenopausal) and few were studied for >6 years. Thus, a beneficial effect of long-term MHT on CVD and mortality is still an open question and is likely to remain controversial for the foreseeable future.

Estrogen increases the transcription of human α2-Heremans-Schmid-glycoprotein by an interplay of estrogen receptor α and activator protein-1

The expression of α2-Heremans-Schmid-glycoprotein (AHSG) was estrogen responsive in oophorectomized (OVX) osteopenic rats and HepG2 cells. Estrogen receptor α (ERα) interacted with the c-Jun/c-Fos heterodimer and indirectly associated with the -1488/-1482 activator protein-1 (AP-1) motif of the AHSG promoter. Estrogen increased c-Jun/c-Fos expression via the mitogen-activated protein kinase (MAPK) pathway.

INTRODUCTION

AHSG is a hepatic secretory protein implicated in the regulation of bone homeostasis. Serum AHSG in women has been reported to decrease after menopause and increase with estrogen therapy. The detailed regulatory mechanism of estrogen on AHSG is unclear.

METHODS

A postmenopausal osteoporosis model was generated in OVX rats. Skeletal parameters were determined by automatic biochemical analysis and dual X-ray absorptiometry. The expression of AHSG was evaluated by ELISA, real-time PCR, and Western blot. The 1.5-kb 5'-promoter region of AHSG was analyzed by serial truncation and luciferase assays. The putative -1488/-1482 AP-1 responsive element was identified by electrophoresis mobility shift assay (EMSA). Chromatin immunoprecipitation (ChIP), re-ChIP, and co-immunoprecipitation (Co-IP) were used to characterize the interaction of ERα and AP-1 at the -1488/-1482 AP-1 binding site. The MAPK pathway was evaluated using a specific inhibitor and active transfection.

RESULTS

The expression of AHSG was estrogen responsive in both OVX rats and estradiol (E2)/ERα-treated HepG2 cells. E2/ERα most prominently increased luciferase activity of a construct with a putative -1488/-1482 AP-1 binding element. ERα interacted with the c-Jun/c-Fos heterodimer and indirectly associated with the -1488/-1482 AP-1 motif of the AHSG promoter. c-Jun/c-Fos expression was increased via the MAPK pathway by E2/ERα.

CONCLUSION

Estrogen activated the transcription of AHSG through an indirect binding of ERα to the -1488/-1482 AP-1 binding element, with the c-Jun/c-Fos heterodimers.

Potential of Raloxifene in reversing osteoarthritis-like alterations in rat chondrocytes: an in vitro model study

The aim of this study was to investigate the effects of Raloxifene (Ral) on degeneration-related changes in osteoarthritis (OA)-like chondrocytes using two- and three-dimensional models. Five-azacytidine (Aza-C) was used to induce OA-like alterations in rat articular chondrocytes and the model was verified at molecular and macrolevels. Chondrocytes were treated with Ral (1, 5 and 10 mu M) for 10 days. Caspase-3 activity, gene expressions of aggrecan, collagen II, alkaline phosphatase (ALP), collagen X, matrix metalloproteinases (MMP-13, MMP-3 and MMP-2), and MMP-13, MMP-3 and MMP-2 protein expressions were studied in two-dimensional model. Matrix deposition and mechanical properties of agarose-chondrocyte discs were evaluated in three-dimensional model. One mu M Ral reduced expression of OA-related genes, decreased apoptosis, and MMP-13 and MMP-3 protein expressions. It also increased aggrecan and collagen II gene expressions relative to untreated OA-like chondrocytes. In three-dimensional model, 1 mu M Ral treatment resulted in increased collagen deposition and improved mechanical properties, although a significant increase for sGAG was not observed. In summation, 1 mu M Ral improved matrix-related activities, whereas dose increment reversed these effects except ALP gene expression and sGAG deposition. These results provide evidence that low-dose Ral has the potential to cease or reduce the matrix degeneration in OA.

Effects of electro-acupuncture on oestrogen levels, body weight, articular cartilage histology and MMP-13 expression in ovariectomised rabbits

BACKGROUND

Electro-acupuncture (EA) treatment has been shown to decrease pain and improve the function of ovariectomised (OVX) rats with osteoarthritis (OA); however, the underlying mechanisms remain unclear.

OBJECT

We used OVX rabbits to replicate natural human menopausal processes and to evaluate whether EA could be used to prevent and treat postmenopausal OA.

METHODS

The rabbits were randomly divided into four groups of eight: a normal control group (NC), an OVX group, an ERT group (oestrogen replacement therapy after OVX) and an EA group (EA therapy after OVX). After the interventions, all of the animals were killed. Serum oestrogen levels and body weight were measured. The transcription of matrix metalloproteinase-13 (MMP-13) mRNA was detected using reverse transcriptase-PCR. Modified Mankin scores were used for histological assessment. Expression of MMP-13 in cartilage was determined by immunohistochemistry.

RESULTS

Both the EA group and the ERT group had increased serum oestrogen levels (p=0.028, p=0.037 respectively), as well as decreased expression of MMP-13 (p=0.000, p=0.000, respectively), relative to the OVX group. The body weight of the EA group was lower than that of the OVX group and the NC group (p=0.007), as well as the ERT group (p=0.010).

CONCLUSIONS

EA could be a new method for preventing and treating postmenopausal OA by producing endogenous sex hormones that inhibit the expression of MMP-13 and cause weight loss with no side effects and a relatively low cost.

Estrogen activates matrix metalloproteinases-2 and -9 to increase beta amyloid degradation

Estrogen is known to affect different aspects of β-amyloid (Aβ) synthesis and degradation. The present work was undertaken to evaluate specifically whether matrix metalloproteinases (MMP) -2 and -9 are involved in Aβ degradation induced by estrogen and whether this is relevant to estrogen-induced neuroprotection. In SH-SY5Y human neuroblastoma cells, 10 nM 17β-estradiol (17β-E2) increases mRNA and intracellular protein expression of MMP-2 and -9, as well as the levels of the active forms of both enzymes released in the medium. Specificity of the effect is proved by prevention with the estrogen receptor (ER) antagonist ICI 182,780 (1 μM) and involvement of the ERα subtype is confirmed by the use of selective ERα or ERβ agonists (PPT, DPN) and antagonists (MPP, PHTPP). 17β-E2 significantly increases the degradation of Aβ, either transferred with the conditioned medium of H4-APPSw human neuroglioma cells, engineered to overproduce Aβ(1-40) and Aβ(1-42), or exogenously added as 2 μM Aβ(1-42). Both these effects are completely prevented by preexposure to the broad spectrum MMP inhibitor GM6001 (5 μM). Importantly, the 17β-E2-induced rescue of neuroblastoma cells challenged with 2 μM Aβ(1-42), an effect prevented by ICI 182,780 (1 μM), is mediated by MMPs, as it appears significantly reduced by GM6001 (5 μM) as well as by both MMP-2 (200 nM) and MMP-9 (200nM) selective inhibitors. In conclusion, the present study shows for the first time that MMP-2 and -9 give a main contribution to estrogen's neuroprotective effect.

Matrix metalloproteinase-1 expression can be upregulated through mitogen-activated protein kinase pathway under the influence of human epidermal growth factor receptor 2 synergized with estrogen receptor

In our previous work, Ets-1 upregulates human epidermal growth factor receptor 2 (HER2) induced matrix metalloproteinase 1 (MMP-1) expression. Based on the above knowledge and result, we hypothesized that estrogen receptor (ER) and its signaling pathway may affect MMP-1 expression under the influence of HER2. In addition, we investigated how the HER2 pathway cross-talk with the ER signaling pathway in genomic and nongenomic action of ER using reverse transcription-PCR, Western blot analysis, and ELISA assay. The results showed that ER-alpha expression increased MMP-1 expression under the presence of HER2. These upregulatory effects were mediated mainly by mitogen-activated protein kinase pathway and were reversed by downregulation of HER2 and/or ER. Activator protein DNA binding activity was involved in the MMP-1 expression. In summary, our results showed that ER can upregulate MMP-1 expression under the influence of HER2 in MCF-7 cells. In addition, this upregulatory effect was found to be mediated by mitogen-activated protein kinase pathway. MMP-1 might be an assigned target in interaction between ER and HER2.

Transcriptional activation of human MMP-13 gene expression by c-Maf in osteoarthritic chondrocyte

Matrix metalloproteinase (MMP)-13 has pivotal roles in the pathogenesis of Osteoarthritis (OA) and it is necessary to understand the regulatory mechanisms of MMP-13 expression. MMP-13 gene expression is regulated primarily at the transcriptional level. In this study, we investigated the role of c-maf in regulating MMP-13 transcription. Using transient transfection system with an c-maf construct, and MMP-13 promoter-luciferase constructs with specific mutations in transcription factor binding sites, we found that c-maf can significantly enhance MMP-13 promoter activity via the AP-1 site, By gene suppression with RNAi technology, we could show that c-maf downregulation leads to a reduced expression of MMP13. Chromatin immunoprecipitation assays reveal that c-maf binds to the MMP-13 gene promoter to a region of the MMP-13 promoter containing the AP-1 site. Taken together, these studies demonstrate a new level of transcriptional regulation of MMP-13 expression by the c-maf.

17beta-Estradiol inhibits matrix metalloproteinase-2 transcription via MAP kinase in fibroblasts

AIMS

Female sex and sex hormones contribute to cardiac remodelling. 17beta-estradiol (E2) is involved in the modulation of extracellular matrix composition and function. Here, we analysed the effect of E2 on matrix metalloproteinase (MMP)-2 gene expression and studied the underlying molecular mechanisms in rat cardiac fibroblasts and in a human fibroblast cell line.

METHODS AND RESULTS

In adult rat cardiac fibroblasts, E2 significantly decreased MMP-2 gene expression in an estrogen receptor (ER)-dependent manner. Transient transfection experiments of human MMP-2 (hMMP-2) promoter deletion constructs in a human fibroblast cell line revealed a regulatory region between -324 and -260 bp that is involved in E2/ERalpha-mediated repression of hMMP-2 gene transcription. Electrophoretic mobility shift assays (EMSA) and supershift analysis demonstrated the binding of transcription factor Elk-1 within this promoter region. Elk-1 was phosphorylated by E2 via the mitogen-activated protein kinase (MAPK) signalling pathway as shown by western blotting. Treatment of cells with the MAPK inhibitor PD98059 blocked the E2-dependent repression of hMMP-2 promoter activity as well as the endogenous MMP-2 mRNA levels in both human fibroblast cells and rat cardiac fibroblasts.

CONCLUSION

E2 inhibits MMP-2 expression via the ER and the MAPK pathway in rat cardiac fibroblasts and in a human fibroblast cell line. These mechanisms may contribute to sex-specific differences in fibrotic processes that are observed in human heart and other diseases.

Distinct roles for AF-1 and -2 of ER-alpha in regulation of MMP-13 promoter activity

Previous studies have indicated that ER-alpha can influence the activity of the MMP-13 promoter. ER-alpha activity is mediated by two separate transcriptional activation domains (AF-1 and AF-2). The present study focused on analyzing the roles of these domains on the activation of the MMP-13 promoter. Transfection of synoviocytes with an ER-alpha construct lacking the C-terminus AF-2 domain led to significant elevation in MMP-13 promoter activity compared to wild type ER-alpha. Progressive deletions in the N-terminal AF-1 domain led to significant losses in MMP-13 promoter activity. MMP-13 promoter mutagenesis indicated that an AP-1 regulatory site was essential for ER-alpha mutant activity. Thus, both AF-1 and AF-2 domains of ER-alpha are required for regulation of MMP-13 promoter activity. As ER variants and ER related proteins have been implicated in bone and joint disorders, these findings provide understanding of the possible role of ER variants in the development of such conditions.

Global analysis of nuclear receptor expression and dysregulation in human osteoarthritic articular cartilage: reduced LXR signaling contributes to catabolic metabolism typical of osteoarthritis

OBJECTIVE

Compare the expression and regulation of nuclear receptors (NRs) in osteoarthritic and normal human articular cartilage.

METHOD

The transcriptional levels of 48 NRs and additional related proteins were measured in mRNA from human articular cartilage from subjects with osteoarthritis (OA) and compared to samples from subjects without OA, using microarrays, individual quantitative reverse transcriptase polymerase chain reaction assays, and a custom human NR TaqMan Low Density Array (TLDA). The functional effect of liver X receptor (LXR) activity in cartilage was studied by measuring proteoglycan (PG) synthesis and degradation in articular cartilage explant cultures following treatment with the synthetic LXR agonist T0901317.

RESULTS

Thirty-one of 48 NRs analyzed by TLDA were found to be measurably expressed in human articular cartilage; 23 of these 31 NRs showed significantly altered expression in OA vs unaffected cartilage. Among these, LXRalpha and LXRbeta, and their heterodimeric partners retinoid X receptor (RXR)alpha and RXRbeta were all expressed at significantly lower levels in OA cartilage, as were LXR target genes ABCG1 and apolipoproteins D and E. Addition of LXR agonist to human OA articular chondrocytes and to cartilage explant cultures resulted in activation of LXR-mediated transcription and significant reduction of both basal and interleukin (IL)-1-mediated PG degradation.

CONCLUSIONS

Articular cartilage expresses a substantial number of NRs, and a large proportion of the expressed NRs are dysregulated in OA. In particular, LXR signaling in OA articular cartilage is impaired, and stimulation of LXR transcriptional activity can counteract the catabolic effects of IL-1. We conclude that LXR agonism may be a possible therapeutic option for OA.

Matrix metalloproteinase induction by relaxin causes cartilage matrix degradation in target synovial joints

Our long-term goal is to understand the mechanisms by which relaxin and estrogen potentially contribute to joint diseases, particularly those afflicting the fibrocartilaginous temporomandibular joint (TMJ). Previously, we showed that relaxin produces a dose-dependent induction of tissue-degrading enzymes of the matrix metalloproteinase (MMP) family, specifically MMP-1 (collagenase-1), MMP-3 (stromelysin-1), MMP-9 (92-kDa gelatinase), and MMP-13 (collagenase-3) in cell isolates and tissue explants from TMJ fibrocartilage. The induction of these MMPs is accompanied by loss of collagen and glycosaminoglycans (GAGs), which was blocked by a pan-MMP inhibitor. We also found the targeted in vivo loss of collagen and GAGs in TMJ discs of ovariectomized rabbits treated with beta-estradiol, relaxin, or both hormones together. Progesterone attenuated the induction of MMPs and matrix loss by relaxin and estrogen. The modulation of matrix composition in TMJ fibrocartilage by these hormones was similar to that observed in the pubic symphysis and differed from that of the knee meniscus. The two target tissues showing the greatest modulation of MMPs and matrix loss, namely, the TMJ disc and pubic symphysis, had similar expression profiles of the estrogen receptors alpha and beta, relaxin-1 receptor (RXFP1, LGR7), and insulin-like peptide 3 receptor (RXFP2, LGR8) and these profiles differed from those in cells from the knee meniscus. These findings suggest a novel model for targeted tissue turnover of cartilage of specific joints through hormone-mediated induction of select MMPs.

The amount and activity of active matrix metalloproteinase 13 is suppressed by estradiol and progesterone in human pelvic floor fibroblasts

As a key degrader of fibrillar collagens, matrix metalloproteinase 13 (MMP13), may contribute to the progression of pelvic organ prolapse. Here we aimed to define the regulation of MMP13 by estradiol and progesterone in the vaginal supportive tissues. Fibroblasts cultured from the arcus tendineous fasciae pelvis of three pre- and three postmenopausal women with prolapse were treated with 17-beta-estradiol (E2), progesterone (P4), E2 + P4, or E2 + ICI 182,780 (ICI). Collagenase inhibitor I (CI) and MG-132 were employed to investigate the mechanism of MMP13 degradation into inactive fragments (fragmentation) by hormones. The regulation of MMP13 in vivo was assessed by comparing tissues of ovariectomized (ovx) vs. sham-operated rats. Expression of MMP13 (proenzyme and active and fragment forms) was quantitated by Western immunoblotting, and MMP13 enzymatic activity was measured using a substrate degradation assay. The amount of cellular active MMP13 and MMP13 proteolytic activity decreased in the presence of hormones. The decrease was paralleled by increased proenzyme and fragment forms. MG-132, not CI, suppressed cellular MMP13 fragmentation. Active MMP13 increased in rats following ovx and was suppressed by E2 + P4 supplementation. Active MMP13 is suppressed in vivo and in vitro by estradiol and progesterone, suggesting a protective effect against vaginal supportive tissue deterioration.

ERalpha and AP-1 interact in vivo with a specific sequence of the F promoter of the human ERalpha gene in osteoblasts

Estrogen-responsive genes often have an estrogen response element (ERE) positioned next to activator protein-1 (AP-1) binding sites. Considering that the interaction between ERE and AP-1 elements has been described for the modulation of bone-specific genes, we investigated the 17-beta-estradiol responsiveness and the role of these cis-elements present in the F promoter of the human estrogen receptor alpha (ERalpha) gene. The F promoter, containing the sequence analyzed here, is one of the multiple promoters of the human ERalpha gene and is the only active promoter in bone tissue. Through electrophoretic mobility shift (EMSA), chromatin immunoprecipitation (ChIP), and re-ChIP assays, we investigated the binding of ERalpha and four members of the AP-1 family (c-Jun, c-fos, Fra-2, and ATF2) to a region located approximately 800 bp upstream of the transcriptional start site of exon F of the human ERalpha gene in SaOS-2 osteoblast-like cells. Reporter gene assay experiments in combination with DNA binding assays demonstrated that F promoter activity is under the control of upstream cis-acting elements which are recognized by specific combinations of ERalpha, c-Jun, c-fos, and ATF2 homo- and heterodimers. Moreover, ChIP and re-ChIP experiments showed that these nuclear factors bind the F promoter in vivo with a simultaneous occupancy stimulated by 17-beta-estradiol. Taken together, our findings support a model in which ERalpha/AP-1 complexes modulate F promoter activity under conditions of 17-beta-estradiol stimulation.

An update review of cellular mechanisms conferring the indirect and direct effects of estrogen on articular cartilage

OBJECTIVE

To review cellular mechanisms that have been proposed to mediate the indirect and direct effects of estrogen on articular cartilage, and to outline the remaining clinical questions that need to be clarified before utilizing the beneficial effects of estrogen for the prevention of osteoarthritis in early postmenopausal women.

DESIGN

Summary of original research papers and reviews listed in Pubmed (1980-2007).

RESULTS

Estrogen receptors have been identified in articular chondrocytes from various animals and humans. Molecular studies showed that estrogen can elicit genomic and rapid non-genomic effects on various cell types, including chondrocytes, and the latter effects are only inducible in females. In addition to direct effects, estrogen can also affect the homeostasis of articular cartilage by modulating the expression/production of different molecules such as various growth factors, inflammatory cytokines, matrix metalloproteinases, and reactive oxygen species. Moreover, in vivo observation argues for the notion that inhibition of subchondral bone turnover is also part of the mechanisms by which estrogen (and antiresorptive agents in general) can protect against joint degradation. Published studies undertaken at cellular, tissue, and in vivo levels illustrate that the effect of estrogen on cartilage may depend on the dose applied, the administration route, the time of initiation, and whether it is combined with a progestin.

CONCLUSIONS

The herein reviewed direct and indirect effects of estrogen on articular cartilage further corroborate the due consideration of estrogen therapy for maintaining not only bone but also cartilage health in postmenopausal women. Future studies in postmenopausal women are needed to clarify whether the efficacy of estrogen therapy can be further optimized by using other forms of estrogen, other progestins, or by initiating the therapy in the peri- or early postmenopausal period.

Polymorphisms in the promoter regions for human MMP-1 and MMP-13 lead to differential responses to the alpha and beta isoforms of estrogen receptor and their ligand in vitro

Estrogen receptors (ER) are present in connective tissues and therefore it is possible that the loss of estrogen after menopause influences the integrity of these tissues, contributing to development of degenerative conditions such as osteoporosis and osteoarthritis in a subset of women. Aberrant expression of matrix metalloproteinases (e.g. MMP-1 and MMP-13) has been implicated in the progression of these diseases. The present study investigated potential molecular mechanisms involved in the regulation of expression of MMP-1 and MMP-13 promoter variants by ER-alpha and ER-beta (+/-estrogen) in a transient transfection system. The results demonstrate that the activity of human MMP-1 and MMP-13 polymorphic variants is elevated in the presence of ER-alpha and ER-beta, and the single nucleotide polymorphisms present in the promoters of MMP-1 and MMP-13 variants leads to differential activities in response to the ER isoforms. Furthermore, the influence of 17-beta estradiol also varies depending upon whether the alpha or the beta isoform of ER is the modulator of these polymorphic variants. These findings support the conclusion that ER isoforms may be contributing to disease development and/or progression in genetically distinct subsets of women following menopause, and provide mechanistic insights into how such contributions are manifested.

Estrogen signaling through the transmembrane G protein-coupled receptor GPR30

Steroids play an important role in the regulation of normal physiology and the treatment of disease. Steroid receptors have classically been described as ligand-activated transcription factors mediating long-term genomic effects in hormonally regulated tissues. It is now clear that steroids also mediate rapid signaling events traditionally associated with growth factor receptors and G protein-coupled receptors. Although evidence suggests that the classical steroid receptors are capable of mediating many of these events, more recent discoveries reveal the existence of transmembrane receptors capable of responding to steroids with cellular activation. One such receptor, GPR30, is a member of the G protein-coupled receptor superfamily and mediates estrogen-dependent kinase activation as well as transcriptional responses. In this review, we provide an overview of the evidence for the cellular and physiological actions of GPR30 in estrogen-dependent processes and discuss the relationship of GPR30 with classical estrogen receptors.

Drug-induced arthritic and connective tissue disorders

OBJECTIVES

All pharmacologic agents have the potential for both benefit and toxicity. Among the more interesting and important adverse consequences of drug therapy are a range of joint and connective tissue complaints that may mimic or reproduce primary rheumatologic diseases. In this article, we review the literature on commonly used drugs reported to induce arthritis and/or connective tissue-based diseases. We assess the strength of the reported associations, discuss diagnostic features and treatment implications, and consider possible mechanisms for drug-induced genesis of rheumatic conditions.

METHODS

We reviewed the Medline database from 1987 to 2006 to identify drug-induced arthritic and connective-tissue disease syndromes, utilizing 48 search terms. A qualitative review was performed after the articles were abstracted and the relevant information was organized.

RESULTS

Three hundred fifty-seven articles of possible relevance were identified. Two hundred eleven publications were included in the final analysis (case series and reports, clinical trials, and reviews). Many drugs were identified as mimicking existing rheumatic conditions, including both well-established small molecules (eg, sulfasalazine) and recently introduced biologic agents (eg, antitumor necrosis factor agents). The most commonly reported drug-induced rheumatic conditions were lupus-like syndromes. Arthritis and vasculitis were also often reported.

CONCLUSIONS

Drug-induced rheumatic syndromes are manifold and offer the clinician an opportunity to define an illness that may remit with discontinuation of the offending agent. Early diagnosis and withdrawal of the drug may prevent unnecessary morbidity and disability.

Identification of target cells for the genomic effects of estrogens in bone

Estrogen has bone protective effects, but the exact mechanism behind these effects remains unclear. The aim of the present study was to identify the primary target cells in bone for the classical genomic effects of estrogens in vivo. For this purpose we have used reporter mice with a luciferase gene under the control of three estrogen-responsive elements (EREs), enabling detection of in vivo activation of gene transcription. Three-month-old ovariectomized mice were treated with a single dose (50 mug/kg) 17beta-estradiol (E2). Luciferase activity was analyzed in several tissues and in different bone marrow-derived lymphocyte enriched/depleted preparations using MacsMouse CD19 (for B lymphocytes) or CD90 (for T lymphocytes) MicroBeads (Miltenyi Biotec GmbH, Bergisch Gladbach, Germany). Histological characterization of cells with high luciferase content was performed using immunohistochemistry. Both cortical bone and bone marrow displayed a rapid (within 1 h) and pronounced E2-induced increase in luciferase activity. The luciferase activity in total bone marrow and in bone marrow depleted of lymphocytes was increased six to eight times more than in either B-lymphocyte or T-lymphocyte enriched cell fractions 4 h after the E2 injection, demonstrating that mature lymphocytes are not major direct targets for the genomic effect of estrogens in bone. Immunohistochemistry identified clear luciferase staining in hypertrophic growth plate chondrocytes, megakaryocytes, osteoblasts, and lining cells, whereas no staining was seen in proliferative chondrocyte. Although most of the osteocytes did not display any detectable luciferase staining, a subpopulation of osteocytes both in cortical and trabecular bone stained positive for luciferase. In conclusion, hypertrophic growth plate chondrocytes, megakaryocytes, osteoblasts, lining cells, and a subpopulation of osteocytes were identified to respond to estrogen via the classical ERE-mediated genomic pathway in bone. Furthermore, our findings indicate that possible direct estrogenic effects on the majority of osteocytes, not staining positive for luciferase, on proliferative chondrocytes and on mature lymphocytes are mediated by non-ERE actions.

Evidence that estrogen receptor beta enhances MMP-13 promoter activity in HIG-82 cells and that this enhancement can be influenced by ligands and involves specific promoter sites

Degradation of articular cartilage is characteristic of osteoarthritis, and matrix metalloproteinase-13 (MMP-13) has been implicated in this condition. Estrogen receptors (ERs) are present in connective tissues, indicating these tissues' potential responsiveness to estrogen. We based this study on the hypothesis that estrogen receptor beta (ERbeta) can modulate MMP-13 promoter activity. Transfection of cells with ERbeta constructs led to the induction of the endogenous MMP-13 gene, as evidenced by increased mRNA levels. The results also indicated that MMP-13 promoter construct activity in the HIG-82 cell line significantly increased when ERbeta was present, and that estrogen downregulated this response in a dose-dependent manner. ERbeta was shown to enhance MMP-13 expression somewhat more strongly than ERalpha, and the impact of a number of selective ER modulators (tamoxifen, raloxifene, and ICI 182,780) on ERbeta enhancement of promoter activity was found to be significantly less than that of estrogen. Furthermore, transcription regulatory sites in the MMP-13 promoter, specifically AP-1 and PEA-3, were shown to act in conjunction to mediate ERbeta effects. Thus, ERbeta likely influences MMP-13 promoter expression in normal and disease processes.

YB-1 binds to the MMP-13 promoter sequence and represses MMP-13 transactivation via the AP-1 site

Matrix metalloproteinases (MMPs) are key enzymes that implement degradation of the extracellular matrix during cellular invasion in development, tissue remodeling, and pathogenic disease states. MMP-13 has pivotal roles in the pathogenesis of invasive cancers and arthritis. Here we report the identification of Y-box binding protein-1 (YB-1) as a new repressor of MMP-13 transactivation. YB-1 binds in vitro in DNA affinity chromatography to the activator protein-1 (AP-1) DNA sequence within the MMP-13 promoter. Chromatin immunoprecipitation assays reveal that YB-1 binds in living cells to the MMP-13 gene promoter to a region of the MMP-13 promoter containing the AP-1 site. YB-1 represses tumor promoter-induced MMP-13 promoter transactivation at the AP-1 site. This is the first report demonstrating YB-1 binding in vitro and in living cells to a mammalian AP-1 target gene, and the first report of YB-1 regulation of the MMP-13 promoter.

Impact of age, systemic glucocorticoids, and progressive knee arthritis on specific mRNA levels in different areas of the rabbit cornea

PURPOSE

To determine the influence of factors such as age, osteoarthritis (OA), and glucocorticoid treatment on total RNA and mRNA regulation in the cornea and how these factors differ between prepupillary and peripheral areas of the cornea.

METHODS

Molecular analyses of corneal tissue were performed using rabbits of different age groups and skeletally mature animals that had undergone anterior cruciate ligament (ACL) transection, an established model of knee OA. Systemic glucocorticoids were administered to cohorts of the osteoarthritic and control animals to determine the influence of distal joint disease on the corneal response. Corneal tissue was analyzed for changes in mRNA levels for several relevant genes: collagen I, collagen III, collagen V, decorin core protein, cyclooxygenase-2 (COX-2), glucocorticoid receptor, and the housekeeping gene beta-actin.

RESULTS

The corneal tissue was found to have diminishing total RNA with age, which is consistent with previous studies in the literature. Interestingly, in skeletally mature animals, distal joint OA was found to affect corneal mRNA levels for several important structural and inflammatory genes (collagen I, decorin core protein, and COX-2) in a manner that progressed with OA progression. Although systemic glucocorticoid treatment did not alter mRNA levels in the normal cornea, it did counteract the changes observed early after OA induction (3 weeks) while having less of an effect in later, more established arthritis (6 weeks).

CONCLUSIONS

This study reveals that distal joint OA can affect mRNA levels for several structural and inflammatory genes of the cornea, changes that seem to be suppressed by systemic glucocorticoid treatment. These findings indicate that OA has associated systemic factors that influence corneal cell metabolism.

Genetic Involvement in Skin Wound Healing and Scarring in Domestic Pigs: Assessment of Molecular Expression Patterns in (Yorkshire × Red Duroc) × Yorkshire Backcross Animals

Yorkshire, red Duroc, and F1 (first-generation cross) pigs heal with normal, fibroproliferative/hypercontractile, and intermediate levels of scarring, respectively. The purpose of this study was to evaluate the healing phenotype of Yorkshire x F1 backcross animals, to address the molecular basis for genetic transmission of the red Duroc scarring phenotype. Macroscopically and histologically, full-thickness wounds on backcross animals followed the Yorkshire phenotype, with one exception; the backcross wounds exhibited contraction following re-epithelialization. The molecular expression patterns in the backcross animals generally correlated with the macroscopic and histologic findings. Compared to Yorkshire, red Duroc, and F1 wounds, the backcross wounds demonstrated a diminished initial inflammatory phase, followed by a prolonged expression of several relevant growth factors. Additionally, collagen expression was prolonged, expression of matrix metalloproteinases was increased, and alterations in tissue inhibitor of metalloproteinase expression were detected. Moreover, a subset of molecules still followed the red Duroc pattern of mRNA expression, a finding that allows for correlations between the scarring phenotype and the molecular expression patterns to be made in this model. The results indicate that a number of genes are likely involved in the red Duroc healing phenotype and that identification of the specific genes involved will require a more detailed genomic analysis.