Wenguang Feng

Estrogen Modulates Inflammatory Mediator Expression and Neutrophil Chemotaxis in Injured Arteries

Background—We have previously shown that estrogen (17&bgr;-estradiol; E2) inhibits neointima formation and migration of leukocytes, particularly neutrophils, into rat carotid arteries after acute endoluminal injury. This study tested the hypothesis that E2 inhibits expression of adhesion molecules, chemokines, and proinflammatory cytokines in rat carotid arteries in the early hours after balloon injury, thus attenuating the stimulus for leukocyte entry and negatively modulating the injury response. Methods and Results—Ovariectomized (OVX) rats were randomly assigned to treatment with E2 or vehicle (V) and subjected to balloon injury of the right carotid artery. After 2, 6, and 24 hours, rats were euthanized, and both carotid arteries were processed for real-time reverse transcription–polymerase chain reaction (2 and 24 hours), ELISA (6 hours), or neutrophil chemotaxis assay (24 hours). Expression of mRNA for adhesion molecules (P-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1), chemoattractants (cytokine-induced neutrophil chemoattractant [CINC]-2&bgr; and monocyte chemoattractant protein [MCP]-1), and proinflammatory cytokines (interleukin [IL]-1 and IL-6) was markedly increased (2 to 5000 times) in injured arteries of OVX+V rats at 2 hours and was reduced by 24 hours. E2 significantly attenuated expression of the proinflammatory mediators (by 60% to 80%) at 2 hours. ELISA confirmed injury-induced upregulation of neutrophil and monocyte/macrophage chemoattractants (CINC-2&agr;, MCP-1) in OVX+V arteries and E2-induced inhibition of CINC-2&agr; expression. E2 significantly (by 65%) inhibited neutrophil chemotactic activity of arterial homogenates. Conclusions—E2 attenuates the early vascular injury response, at least in part, by negatively modulating proinflammatory mediator expression and the resultant chemotactic activity of injured vessels for neutrophils.

Hormone Replacement Therapy and Inflammation. Interactions in Cardiovascular Disease

Inflammation plays a central role in the pathogenesis of many forms of vascular disease, including atherosclerosis. Atherogenesis begins with endothelial damage, and the damaged endothelium expresses adhesion molecules, chemokines, and proinflammatory cytokines that direct atherosclerotic plaque formation and spill into the circulation as biomarkers of atherosclerotic disease risk. Menopausal hormone therapy, including a variety of estrogen preparations with or without a progestin, has negative modulatory effects on most of these soluble inflammatory markers, including E-selectin, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha, inconsistent effects on interleukin-6, and stimulatory effects on transforming growth factor-beta, a vasoprotective cytokine. In contrast, C-reactive protein, a circulating proinflammatory cytokine produced in both liver and atherosclerotic arteries, increases in response to oral conjugated estrogens but not to transdermal estrogen. Although C-reactive protein is clearly linked to increased cardiovascular disease risk in women, the hormone-induced rise in this biomarker is not associated with increased risk and may be related to a first-pass effect of C-reactive protein production in the liver after oral estrogen absorption. Many important questions about the effects of ovarian hormones on vascular inflammation and the pathogenesis of vascular disease cannot be answered in human subjects. Insights from fundamental mechanistic studies in animal models are needed to delineate the cellular/molecular events that determine whether these hormones protect or injure blood vessels.

Increased protein O-GlcNAc modification inhibits inflammatory and neointimal responses to acute endoluminal arterial injury

Inflammation plays a major role in vascular disease. We have shown that leukocyte infiltration and inflammatory mediator expression contribute to vascular remodeling after endoluminal injury. This study tested whether increasing protein O-linked-N-acetylglucosamine (O-GlcNAc) levels with glucosamine (GlcN) and O-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino-N-phenylcarbamate (PUGNAc) inhibits acute inflammatory and neointimal responses to endoluminal arterial injury. Ovariectomized rats were treated with a single injection of GlcN (0.3 mg/g ip), PUGNAc (7 nmol/g ip) or vehicle (V) 2 h before balloon injury of the right carotid artery. O-GlcNAc-modified protein levels decreased markedly in injured arteries of V-treated rats at 30 min, 2 h, and 24 h after injury but returned to control (contralateral uninjured) levels after 14 days. Both GlcN and PUGNAc increased O-GlcNAc-modified protein levels in injured arteries compared with V controls at 30 min postinjury; the GlcN-mediated increase persisted at 24 h but was not evident at 14 days. Proinflammatory mediator expression increased markedly after injury and was reduced significantly (30-50%) by GlcN and PUGNAc. GlcN and PUGNAc also inhibited infiltration of neutrophils and monocytes in injured arteries. Chronic (14 days) treatment with GlcN reduced neointima formation in injured arteries by 50% compared with V controls. Acute GlcN and PUGNAc treatment increases O-GlcNAc-modified protein levels and inhibits acute inflammatory responses in balloon-injured rat carotid arteries; 14 day GlcN treatment inhibits neointima formation in these vessels. Augmenting O-GlcNAc modification of proteins in the vasculature may represent a novel anti-inflammatory and vasoprotective mechanism.

O -GlcNAc Modification of NFκB p65 Inhibits TNF-α-Induced Inflammatory Mediator Expression in Rat Aortic Smooth Muscle Cells

Background We have shown that glucosamine (GlcN) or O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc) treatment augments O-linked-N-acetylglucosamine (O-GlcNAc) protein modification and attenuates inflammatory mediator expression, leukocyte infiltration and neointima formation in balloon injured rat carotid arteries and have identified the arterial smooth muscle cell (SMC) as the target cell in the injury response. NFκB signaling has been shown to mediate the expression of inflammatory genes and neointima formation in injured arteries. Phosphorylation of the p65 subunit of NFκB is required for the transcriptional activation of NFκB. This study tested the hypothesis that GlcN or PUGNAc treatment protects vascular SMCs against tumor necrosis factor (TNF)-α induced inflammatory stress by enhancing O-GlcNAcylation and inhibiting TNF-α induced phosphorylation of NFκB p65, thus inhibiting NFκB signaling. Methodology/Principal Findings Quiescent rat aortic SMCs were pretreated with GlcN (5 mM), PUGNAc (10−4 M) or vehicle and then stimulated with TNF-α (10 ng/ml). Both treatments inhibited TNF-α-induced expression of chemokines [cytokine-induced neutrophil chemoattractant (CINC)-2β and monocyte chemotactic protein (MCP)-1] and adhesion molecules [vascular cell adhesion molecule (VCAM)-1 and P-Selectin]. Both treatments inhibited TNF-α induced NFκB p65 activation and promoter activity, increased NFκB p65 O-GlcNAcylation and inhibited NFκB p65 phosphorylation at Serine 536, thus promoting IκBα binding to NFκB p65. Conclusions There is a reciprocal relationship between O-GlcNAcylation and phosphorylation of NFκB p65, such that increased NFκB p65 O-GlcNAc modification inhibits TNF-α-Induced expression of inflammatory mediators through inhibition of NFκB p65 signaling. These findings provide a mechanistic basis for our previous observations that GlcN and PUGNAc treatments inhibit inflammation and remodeling induced by acute endoluminal arterial injury.

Aging leads to increased levels of protein O-linked N-acetylglucosamine in heart, aorta, brain and skeletal muscle in Brown-Norway rats

Changes in the levels of O-linked N-acetyl-glucosamine (O-GlcNAc) on nucleocytoplasmic protein have been associated with a number of age-related diseases such as Alzheimer’s and diabetes; however, there is relatively little information regarding the impact of age on tissue O-GlcNAc levels. Therefore, the goal of this study was to determine whether senescence was associated with alterations in O-GlcNAc in heart, aorta, brain and skeletal muscle and if so whether there were also changes in the expression of enzymes critical in regulating O-GlcNAc levels, namely, O-GlcNAc transferase (OGT), O-GlcNAcase and glutamine:fructose-6-phosphate amidotransferase (GFAT). Tissues were harvested from 5- and 24-month old Brown-Norway rats; UDP-GlcNAc, a precursor of O-GlcNAc was assessed by HPLC, O-GlcNAc and OGT levels were assessed by immunoblot analysis and GFAT1/2, OGT, O-GlcNAcase mRNA levels were determined by RT-PCR. In the 24-month old animals serum insulin and triglyceride levels were significantly increased compared to the 5-month old group; however, glucose levels were unchanged. Protein O-GlcNAc levels were significantly increased with age (30–107%) in all tissues examined; however, paradoxically the expression of OGT, which catalyzes O-GlcNAc formation, was decreased by ∼30% in the heart, aorta and brain. In the heart increased O-GlcNAc was associated with increased UDP-GlcNAc levels and elevated GFAT mRNA while in other tissues we found no difference in UDP-GlcNAc or GFAT mRNA levels. These results demonstrate that senescence is associated with increased O-GlcNAc levels in multiple tissues and support the notion that dysregulation of pathways leading to O-GlcNAc formation may play an important role in the development of age-related diseases.

Aged rats lose vasoprotective and anti-inflammatory actions of estrogen in injured arteries.

Objective: 17&bgr;-Estradiol (E2) negatively modulates neointima formation, leukocyte infiltration, and proinflammatory mediator expression after vascular injury in young (10-wk-old) ovariectomized (OVX) rats. Trials of E2 in elderly postmenopausal women have not confirmed a vasoprotective effect. This study tested the hypothesis that responsiveness to E2 is lost in injured arteries of aged (12-mo-old) OVX rats. Design: E2- or vehicle-treated OVX rats underwent balloon injury of the carotid artery and were killed after 2 weeks for morphometric examination of arteries, after 24 hours for assessment of leukocyte infiltration, and after 2 hours for quantification of proinflammatory mediator mRNA expression. Results: Neointima formation was significantly reduced in aged compared with young vehicle-treated rats. E2 treatment had directionally opposite effects on intima/media ratios in aged (+75%) and young (−40%) rats. Injury induced increases in infiltrating total leukocytes, neutrophils, monocytes/macrophages, and expression of proinflammatory mediators in arteries of aged rats; E2 had no effect on these inflammatory responses to injury. Estrogen receptor &agr; and &bgr; protein expression were similar in carotid arteries of young and aged rats on immunofluorescence testing. Conclusions: Aged OVX rats lose the vasoprotective and anti-inflammatory responses to exogenous E2 seen in younger animals. These results may be relevant to the lack of vasoprotection observed in outcome trials of estrogen therapy in postmenopausal women.

Nicotine worsens the severity of nephropathy in diabetic mice: implications for the progression of kidney disease in smokers.

Epidemiological studies have established the role of cigarette smoking as a risk factor in the progression of chronic kidney disease, including diabetic nephropathy. We have previously reported that nicotine promotes mesangial cell proliferation and hypertrophy via activation of nonneuronal nicotinic acetylcholine receptors and that nicotine worsens renal injury in a model of acute glomerulonephritis (Jaimes E, Tian RX, Raij L. Am J Physiol Heart Circ Physiol 292: H76-H82, 2007; Jaimes EA, Tian RX, Joshi M, Raij L. Am J Nephrol 29: 319-326, 2009). These studies were designed to test the hypothesis that nicotine worsens renal injury in db/db mice, a well-established model of diabetic nephropathy, and that reactive oxygen species play an important as mediators of these effects. For these studies, nicotine (100 μg/ml) was administered in the drinking water to control and db/db mice for 10 wk. Blood pressure was measured by the tail-cuff method, and urine was collected for proteinuria. At death, kidneys were collected for histology and molecular biology. The administration of nicotine did not result in significant changes in blood pressure or blood glucose and resulted in cotinine levels similar to those found in the plasma of smokers. In diabetic mice, the administration of nicotine significantly increased urinary protein excretion (1-fold), glomerular hypertrophy, and mesangial area (∼20%). These changes were accompanied by significant increases in NADPH oxidase 4 (∼30%) and increased nitrotyrosine and Akt expression. In vitro, we determined that nicotine has additive effects to high glucose on reactive oxygen species generation and Akt phosphorylation in human mesangial cells. These findings unveil novel mechanisms that may result in the development of novel strategies in the treatment and prevention of diabetic nephropathy in smokers.

Estrogen modulates NFκB signaling by enhancing IκBα levels and blocking p65 binding at the promoters of inflammatory genes via estrogen receptor-β.

Background NFκB signaling is critical for expression of genes involved in the vascular injury response. We have shown that estrogen (17β-estradiol, E2) inhibits expression of these genes in an estrogen receptor (ER)-dependent manner in injured rat carotid arteries and in tumor necrosis factor (TNF)-α treated rat aortic smooth muscle cells (RASMCs). This study tested whether E2 inhibits NFκB signaling in RASMCs and defined the mechanisms. Methodology/Principal Findings TNF-α treated RASMCs demonstrated rapid degradation of IκBα (10–30 min), followed by dramatic increases in IκBα mRNA and protein synthesis (40–60 min). E2 enhanced TNF-α induced IκBα synthesis without affecting IκBα degradation. Chromatin immunoprecipitation (ChIP) assays revealed that E2 pretreatment both enhanced TNF-α induced binding of NFκB p65 to the IκBα promoter and suppressed TNF-α induced binding of NFκB p65 to and reduced the levels of acetylated histone 3 at promoters of monocyte chemotactic protein (MCP)-1 and cytokine-induced neutrophil chemoattractant (CINC)-2β genes. ChIP analyses also demonstrated that ERβ can be recruited to the promoters of MCP-1 and CINC-2β during co-treatment with TNF-α and E2. Conclusions These data demonstrate that E2 inhibits inflammation in RASMCs by two distinct mechanisms: promoting new synthesis of IκBα, thus accelerating a negative feedback loop in NFκB signaling, and directly inhibiting binding of NFκB to the promoters of inflammatory genes. This first demonstration of multifaceted modulation of NFκB signaling by E2 may represent a novel mechanism by which E2 protects the vasculature against inflammatory injury.

Estrogen Treatment Abrogates Neointima Formation in Human C-Reactive Protein Transgenic Mice

Objective—Previously we established that the vascular injury response was attenuated in ovariectomized wild-type rodents treated with 17&bgr;-estradiol (E2). We also showed that the response to acute vascular injury in transgenic mice expressing human C-reactive protein (CRPtg) is exaggerated compared with their nontransgenic (NTG) counterparts. Herein we tested the hypothesis that E2 modulates vascular injury in the CRPtg mouse. Methods and Results—Intact (INT) or ovariectomized (OVX) CRPtg and NTG, treated with E2 or vehicle, had their right common carotid artery ligated. Resultant neointima formation was exaggerated in CRPtg compared with NTG, whether INT or OVX, but was prevented in both genotypes by E2. Expression of human CRP protein (immunohistochemical analysis) and mRNA (laser microdissection followed by real-time quantitative RT-PCR) was detected in the neointima of OVX CRPtg and was greatly diminished by E2 treatment. CRP was not detected in uninjured arteries or in the media of injured arteries, and blood CRP level was consistently low. Conclusions—The exaggerated response to vascular injury in CRPtg is associated with increased neointimal expression of human CRP. E2 reduces both neointima formation and neointimal expression of human CRP, suggesting that E2 is vasoprotective.

Nicotine exposure and the progression of chronic kidney disease: role of the α7-nicotinic acetylcholine receptor

Clinical studies have established the role of cigarette smoking as a risk factor in the progression of chronic kidney disease (CKD). We have shown that nicotine promotes mesangial cell proliferation and hypertrophy via nonneuronal nicotinic acetylcholine receptors (nAChRs). The α7-nAChR is one of the most important subunits of the nAChRs. These studies were designed to test the hypothesis that nicotine worsens renal injury in rats with 5/6 nephrectomy (5/6Nx) and that the α7-nAChR subunit is required for these effects. We studied five different groups: Sham, 5/6Nx, 5/6Nx + nicotine (Nic; 100 μg/ml dry wt), 5/6Nx + Nic + α7-nAChR blocker methyllicaconitine (MLA; 3 mg·kg(-1)·day(-1) sq), and Sham + Nic. Blood pressure was measured by the tail-cuff method, and urine was collected for proteinuria. After 12 wk, the rats were euthanized and kidneys were collected. We observed expression of the α7-nAChR in the proximal and distal tubules. The administration of nicotine induced a small increase in blood pressure and resulted in cotinine levels similar to those found in the plasma of smokers. In 5/6Nx rats, the administration of nicotine significantly increased urinary protein excretion (onefold), worsened the glomerular injury score and increased fibronectin (∼ 50%), NADPH oxidase 4 (NOX4; ∼100%), and transforming growth factor-β expression (∼200%). The administration of nicotine to sham rats increased total proteinuria but not albuminuria, suggesting direct effects on tubular protein reabsorption. These effects were prevented by MLA, demonstrating a critical role for the α7-nAChR as a mediator of the effects of nicotine in the progression of CKD.