Microbial-induced Redox Imbalance in the Neonatal Lung Is Ameliorated by Live Biotherapeutics

Bronchopulmonary dysplasia (BPD) is a common lung disease of premature infants. Hyperoxia exposure and microbial dysbiosis are contributors to BPD development. However, the mechanisms linking pulmonary microbial dysbiosis to worsening lung injury are unknown. Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that regulates oxidative stress responses and modulates hyperoxia-induced lung injury. We hypothesized that airway dysbiosis would attenuate Nrf2-dependent antioxidant function, resulting in a more severe phenotype of BPD. Here, we show that preterm infants with a Gammaproteobacteria-predominant dysbiosis have increased endotoxin in tracheal aspirates, and mice monocolonized with the representative Gammaproteobacteria Escherichia coli show increased tissue damage compared with germ-free (GF) control mice. Furthermore, we show Nrf2-deficient mice have worse lung structure and function after exposure to hyperoxia when the airway microbiome is augmented with E. coli. To confirm the disease-initiating potential of airway dysbiosis, we developed a novel humanized mouse model by colonizing GF mice with tracheal aspirates from human infants with or without severe BPD, producing gnotobiotic mice with BPD-associated and non-BPD-associated lung microbiomes. After hyperoxia exposure, BPD-associated mice demonstrated a more severe BPD phenotype and increased expression of Nrf2-regulated genes, compared with GF and non-BPD-associated mice. Furthermore, augmenting Nrf2-mediated antioxidant activity by supporting colonization with Lactobacillus species improved dysbiotic-augmented lung injury. Our results demonstrate that a lack of protective pulmonary microbiome signature attenuates an Nrf2-mediated antioxidant response, which is augmented by a respiratory probiotic blend. We anticipate antioxidant pathways will be major targets of future microbiome-based therapeutics for respiratory disease.

Nicotine, smoking, podocytes, and diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage kidney disease. Besides glycemic and blood pressure control, environmental factors such as cigarette smoking (CS) adversely affect the progression of DN. The effects of CS on DN progression have been attributed to combustion-generated molecules without consideration to the role of nicotine (NIC), responsible for the addictive properties of both CS and electronic cigarettes (ECs). Podocytes are essential to preserve the structure and function of the glomerular filtration barrier, and strong evidence indicates that early podocyte loss promotes DN progression. We performed experiments in human podocytes and in a mouse model of diabetes that develops nephropathy resembling human DN. We determined that NIC binding to podocytes in concentrations achieved with CS and ECs activated NADPH oxidase, which sets in motion a dysfunctional molecular network integrated by cyclooxygenase 2, known to induce podocyte injury; downregulation of AMP-activated protein kinase, important for maintaining cellular energy stores and antioxidation; and upregulation of CD36, which increased lipid uptake and promoted apoptosis. In diabetic mice, NIC increased proteinuria, a recognized marker of chronic kidney disease progression, accompanied by reduced glomerular podocyte synaptopodin, a crucial stabilizer of the podocyte cytoskeleton, and increased fibronectin expression. This novel study critically implicates NIC itself as a contributor to DN progression in CS and EC users.NEW & NOTEWORTHY In this study, we demonstrate that nicotine increases the production of reactive oxygen species, increases cyclooxygenase-2 expression, and upregulates Cd36 while inducing downregulation of AMP-activated protein kinase. In vivo nicotine increases proteinuria and fibronectin expression in diabetic mice. This study demonstrates that effects of nicotine on podocytes are responsible, at least in part, for the deleterious effects of smoking in the progression of chronic kidney disease, including diabetic nephropathy.

MicroRNA 219-5p inhibits alveolarization by reducing platelet derived growth factor receptor-alpha

BACKGROUND

MicroRNA (miR) are small conserved RNA that regulate gene expression post-transcription. Previous genome-wide analysis studies in preterm infants indicate that pathways of miR 219-5p are important in infants with Bronchopulmonary Dysplasia (BPD).

METHODS

Here we report a prospective cohort study of extremely preterm neonates wherein infants diagnosed with severe BPD expressed increased airway miR-219-5p and decreased platelet derived growth factor receptor alpha (PDGFR-α), a target of mir-219-5p and a key regulator of alveolarization, compared to post-conception age-matched term infants.

RESULTS

miR-219-5p was highly expressed in the pulmonary epithelial lining in lungs of infants with BPD by in situ hybridization of human infant lungs. In both in vitro and in vivo (mouse) models of BPD, miR-219-5p was increased on exposure to hyperoxia compared with the normoxia control, with a complementary decrease of PDGFR-α. To further confirm the target relationship between miR-219 and PDGFR-α, pulmonary epithelial cells (MLE12) and lung primary fibroblasts were treated with a mimic of miR-219-5p and a locked nucleic acid (LNA) based inhibitor of miR-219-5p. In comparison with the control group, the level of miR-219 increased significantly after miR-219 mimic treatment, while the level of PDGFR-α declined markedly. LNA exposure increased PDGFR-α. Moreover, in BPD mouse model, over-expression of miR-219-5p inhibited alveolar development, indicated by larger alveolar spaces accompanied by reduced septation.

CONCLUSIONS

Taken together, our results demonstrate that increased miR-219-5p contributes to the pathogenesis of BPD by targeting and reducing PDGFR-α. The use of specific miRNA antagonists may be a therapeutic strategy for preventing the development of BPD.

The closed eye harbours a unique microbiome in dry eye disease

Dry eye affects millions of individuals. In experimental models, dry eye disease is associated with T helper cell 17-mediated inflammation of the ocular surface that may cause persistent damage to the corneal epithelium. However, the initiating and perpetuating factors associated with chronic inflammation of the ocular surface remain unclear. The ocular microbiota alters ocular surface inflammation and may influence dry eye disease development and progression. Here, we collected serial samples of tears on awakening from sleep, closed eye tears, during a randomized clinical trial of a non-pharmaceutical dry eye therapy and used 16S rRNA metabarcoding to characterize the microbiome. We show the closed dry eye microbiome is distinct from the healthy closed eye microbiome, and that the microbiome remains distinct despite daily saline eye wash upon awakening. The ocular microbiome was described only recently, and this report implicates a distinct microbiome in ocular disease development. Our findings suggest an interplay between microbial commensals and inflammation on the ocular surface. This information may inform future studies of the pathophysiological mechanisms of dry eye disease.

COX-2-derived prostaglandins as mediators of the deleterious effects of nicotine in chronic kidney disease

Tobacco smoking has been identified as a risk factor in the progression of chronic kidney disease (CKD). In previous studies, we showed that nicotine induces cyclooxygenase (COX)-2 expression in vivo and in vitro and that the administration of nicotine in vivo worsens the severity of renal injury in a model of subtotal renal ablation. In the present study, we tested the role of COX-2-derived prostaglandins on the deleterious effects of nicotine in CKD. Sham and 5/6 nephrectomy (5/6Nx) rats received tap water or nicotine (100 μg/mL) in the drinking water for 12 wk. Additional groups also systemically received the COX-2 inhibitor NS-398 (1.5 mg·kg^-1·day^-1 via osmotic minipump). The administration of nicotine worsened renal injury and proteinuria in 5/6Nx rats and increased proteinuria in sham rats. 5/6Nx rats had increased cortical production of the prostaglandins PGE₂, PGI₂, PGD₂, and PGF_2α and of thromboxane A₂. In these rats, nicotine reduced the production of all prostaglandins examined except thromboxane A₂. Treatment with the COX-2 inhibitor NS-398 resulted in complete inhibition of all prostaglandins studied and ameliorated renal injury and proteinuria in 5/6Nx rats on nicotine but not in 5/6 Nx rats on tap water. Nicotine also reduced the expression of megalin in all groups examined, and this was partially prevented by COX-2 inhibition. In the present study, we showed that in CKD, nicotine worsens renal injury at least in part by producing an imbalance in the production of prostaglandins. This imbalance in the production of prostaglandins likely plays a role in the deleterious effects of smoking on the progression of CKD.

Activated PMN Exosomes: Pathogenic Entities Causing Matrix Destruction and Disease in the Lung

Here, we describe a novel pathogenic entity, the activated PMN (polymorphonuclear leukocyte, i.e., neutrophil)-derived exosome. These CD63⁺/CD66b⁺ nanovesicles acquire surface-bound neutrophil elastase (NE) during PMN degranulation, NE being oriented in a configuration resistant to α1-antitrypsin (α1AT). These exosomes bind and degrade extracellular matrix (ECM) via the integrin Mac-1 and NE, respectively, causing the hallmarks of chronic obstructive pulmonary disease (COPD). Due to both ECM targeting and α1AT resistance, exosomal NE is far more potent than free NE. Importantly, such PMN-derived exosomes exist in clinical specimens from subjects with COPD but not healthy controls and are capable of transferring a COPD-like phenotype from humans to mice in an NE-driven manner. Similar findings were observed for another neutrophil-driven disease of ECM remodeling (bronchopulmonary dysplasia [BPD]). These findings reveal an unappreciated role for exosomes in the pathogenesis of disorders of ECM homeostasis such as COPD and BPD, providing a critical mechanism for proteolytic damage.

Effects of hyperoxia on alveolar and pulmonary vascular development in germ-free mice

Airway microbial dysbiosis is associated with subsequent bronchopulmonary dysplasia (BPD) development in very preterm infants. However, the relationship of airway microbiome in normal pulmonary development has not been defined. To better understand the role of the airway microbiome, we compared normal and abnormal alveolar and pulmonary vascular development in mice with or without a microbiome. We hypothesized that the lungs of germ-free (GF) mice would have an exaggerated phenotypic response to hyperoxia compared with non-germ-free (NGF) mice. With the use of a novel gnotobiotic hyperoxia chamber, GF and NGF mice were exposed to either normoxia or hyperoxia. Alveolar morphometry, pulmonary mechanics, echocardiograms, inflammatory markers, and measures of pulmonary hypertension were studied. GF and NGF mice in normoxia showed no difference, whereas GF mice in hyperoxia showed protected lung structure and mechanics and decreased markers of inflammation compared with NGF mice. We speculate that an increase in abundance of pathogenic bacteria in NGF mice may play a role in BPD pathogenesis by regulating the proinflammatory signaling and neutrophilic inflammation in lungs. Manipulation of the airway microbiome may be a potential therapeutic intervention in BPD and other lung diseases.

Mitochondrial DNA variation modulates alveolar development in newborn mice exposed to hyperoxia

Hyperoxia-induced oxidant stress contributes to the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants. Mitochondrial functional differences due to mitochondrial DNA (mtDNA) variations are important modifiers of oxidant stress responses. The objective of this study was to determine whether mtDNA variation independently modifies lung development and mechanical dysfunction in newborn mice exposed to hyperoxia. Newborn C57BL6 wild type (C57ⁿ/C57^mt, C57WT) and C3H/HeN wild type (C3Hⁿ/C3H^mt, C3HWT) mice and novel Mitochondrial-nuclear eXchange (MNX) strains with nuclear DNA (nDNA) from their parent strain and mtDNA from the other-C57MNX (C57ⁿ/C3H^mt) and C3HMNX (C3Hⁿ/C57^mt)-were exposed to 21% or 85% O₂ from birth to postnatal day 14 (P14). Lung mechanics and histopathology were examined on P15. Neonatal mouse lung fibroblast (NMLF) bioenergetics and mitochondrial superoxide (O₂^-) generation were measured. Pulmonary resistance and mitochondrial O₂^- generation were increased while alveolarization, compliance, and NMLF basal and maximal oxygen consumption rate were decreased in hyperoxia-exposed C57WT mice (C57ⁿ/C57^mt) versus C57MNX mice (C57ⁿ/C3H^mt) and in hyperoxia-exposed C3HMNX mice (C3Hⁿ/C57^mt) versus C3HWT (C3Hⁿ/C3H^mt) mice. Our study suggests that neonatal C57 mtDNA-carrying strains have increased hyperoxia-induced hypoalveolarization, pulmonary mechanical dysfunction, and mitochondrial bioenergetic and redox dysfunction versus C3H mtDNA strains. Therefore, mtDNA haplogroup variation-induced differences in mitochondrial function could modify neonatal alveolar development and BPD susceptibility.

Heterozygous Pkhd1C642* mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney

Heterozygosity for human polycystic kidney and hepatic disease 1 ( PKHD1) mutations was recently associated with cystic liver disease and radiographic findings resembling medullary sponge kidney (MSK). However, the relevance of these associations has been tempered by a lack of cystic liver or renal disease in heterozygous mice carrying Pkhd1 gene trap or exon deletions. To determine whether heterozygosity for a smaller Pkhd1 defect can trigger cystic renal disease in mice, we generated and characterized mice with the predicted truncating Pkhd1^C642* mutation in a region corresponding to the middle of exon 20 cluster of five truncating human mutations (between PKHD1^G617fs and PKHD1^G644*). Mouse heterozygotes or homozygotes for the Pkhd1^C642* mutation did not have noticeable liver or renal abnormalities on magnetic resonance images during their first weeks of life. However, when aged to ~1.5 yr, the Pkhd1^C642* heterozygotes developed prominent cystic liver changes; tissue analyses revealed biliary cysts and increased number of bile ducts without signs of congenital hepatic fibrosis-like portal field inflammation and fibrosis that was seen in Pkhd1^C642* homozygotes. Interestingly, aged female Pkhd1^C642* heterozygotes, as well as homozygotes, developed radiographic changes resembling MSK. However, these changes correspond to proximal tubule ectasia, not an MSK-associated collecting duct ectasia. In summary, by demonstrating that cystic liver and kidney abnormalities are triggered by heterozygosity for the Pkhd1^C642* mutation, we provide important validation for relevant human association studies. Together, these investigations indicate that PKHD1 mutation heterozygosity (predicted frequency 1 in 70 individuals) is an important underlying cause of cystic liver disorders and MSK-like manifestations in a human population.

Exosomal microRNA predicts and protects against severe bronchopulmonary dysplasia in extremely premature infants

Premature infants are at high risk for developing bronchopulmonary dysplasia (BPD), characterized by chronic inflammation and inhibition of lung development, which we have recently identified as being modulated by microRNAs (miRNAs) and alterations in the airway microbiome. Exosomes and exosomal miRNAs may regulate cell differentiation and tissue and organ development. We discovered that tracheal aspirates from infants with severe BPD had increased numbers of, but smaller, exosomes compared with term controls. Similarly, bronchoalveolar lavage fluid from hyperoxia-exposed mice (an animal model of BPD) and supernatants from hyperoxia-exposed human bronchial epithelial cells (in vitro model of BPD) had increased exosomes compared with air controls. Next, in a prospective cohort study of tracheal aspirates obtained at birth from extremely preterm infants, utilizing independent discovery and validation cohorts, we identified unbiased exosomal miRNA signatures predictive of severe BPD. The strongest signal of reduced miR-876-3p in BPD-susceptible compared with BPD-resistant infants was confirmed in the animal model and in vitro models of BPD. In addition, based on our recent discovery of increased Proteobacteria in the airway microbiome being associated with BPD, we developed potentially novel in vivo and in vitro models for BPD combining Proteobacterial LPS and hyperoxia exposure. Addition of LPS led to a larger reduction in exosomal miR 876-3p in both hyperoxia and normoxia compared with hyperoxia alone, thus indicating a potential mechanism by which alterations in microbiota can suppress miR 876-3p. Gain of function of miR 876-3p improved the alveolar architecture in the in vivo BPD model, demonstrating a causal link between miR 876-3p and BPD. In summary, we provide evidence for the strong predictive biomarker potential of miR 876-3p in severe BPD. We also provide insights on the pathogenesis of neonatal lung disease, as modulated by hyperoxia and microbial product-induced changes in exosomal miRNA 876-3p, which could be targeted for future therapeutic development.

The Airway Microbiome at Birth

Alterations of pulmonary microbiome have been recognized in multiple respiratory disorders. It is critically important to ascertain if an airway microbiome exists at birth and if so, whether it is associated with subsequent lung disease. We found an established diverse and similar airway microbiome at birth in both preterm and term infants, which was more diverse and different from that of older preterm infants with established chronic lung disease (bronchopulmonary dysplasia). Consistent temporal dysbiotic changes in the airway microbiome were seen from birth to the development of bronchopulmonary dysplasia in extremely preterm infants. Genus Lactobacillus was decreased at birth in infants with chorioamnionitis and in preterm infants who subsequently went on to develop lung disease. Our results, taken together with previous literature indicating a placental and amniotic fluid microbiome, suggest fetal acquisition of an airway microbiome. We speculate that the early airway microbiome may prime the developing pulmonary immune system, and dysbiosis in its development may set the stage for subsequent lung disease.

Transcription factor avian erythroblastosis virus E26 oncogen homolog-1 is a novel mediator of renal injury in salt-sensitive hypertension

Transcription factor E26 transformation-specific sequence-1 (ETS-1) is a transcription factor that regulates the expression of a variety of genes, including growth factors, chemokines, and adhesion molecules. We recently demonstrated that angiotensin II increases the glomerular expression of ETS-1 and that blockade of ETS-1 ameliorates the profibrotic and proinflammatory effects of angiotensin II. The Dahl salt-sensitive rat is a paradigm of salt-sensitive hypertension associated with local activation of the renin-angiotensin system. In these studies, we determined whether: (1) salt-sensitive hypertension is associated with renal expression of ETS-1 and (2) ETS-1 participates in the development of end-organ injury in salt-sensitive hypertension. Dahl salt-sensitive rats were fed a normal-salt diet (0.5% NaCl diet) or a high-salt diet (4% NaCl) for 4 weeks. Separate groups on high-salt diet received an ETS-1 dominant-negative peptide (10 mg/kg/d), an inactive ETS-1 mutant peptide (10 mg/kg/d), the angiotensin II type 1 receptor blocker candesartan (10 mg/kg/d), or the combination high-salt diet/dominant-negative peptide/angiotensin II type 1 receptor blocker for 4 weeks. High-salt diet rats had a significant increase in the glomerular expression of the phosphorylated ETS-1 that was prevented by angiotensin II type 1 receptor blocker. ETS-1 blockade reduced proteinuria, glomerular injury score, fibronectin expression, urinary transforming growth factor-β excretion, and macrophage infiltration. Angiotensin II type 1 receptor blocker reduced proteinuria, glomerular injury score, and macrophage infiltration, whereas concomitant ETS-1 blockade and angiotensin II type 1 receptor blocker had additive effects and reduced interstitial fibrosis. Our studies demonstrated that salt-sensitive hypertension results in increased glomerular expression of phosphorylated ETS-1 and suggested that ETS-1 plays an important role in the pathogenesis of end-organ injury in salt-sensitive hypertension.

Diet modulation is an effective complementary agent in preventing and treating breast cancer lung metastasis

A significant percentage of breast cancer victims will suffer from metastases indicating that new approaches to preventing breast cancer metastasis are thus needed. Dietary stearate (ST) and chemotherapy have been shown to reduce breast cancer metastasis. We tested the complementary use of dietary ST with a taxol-based chemotherapy which work through separate mechanisms to reduce breast cancer metastasis. We therefore carried out a prevention study in which diets were initiated prior to human MDA-MB-435 cancer cells being injected into the host and a treatment study in which diets were combined with paclitaxel (PTX). Using an orthotopic athymic nude mouse model and three diets [corn oil (CO) control diet, low fat (LF) or ST] the prevention study demonstrated that the ST diet decreased the incidence of lung metastasis by 50 % compared to both the LF and CO diets. The ST diet also reduced the number and size of metastatic lung nodules compared to the LF diet. Results of the treatment study indicated that both the CO and ST diets decreased the number of mice with lung metastasis compared to the LF diet. Both CO and ST also decreased the number of lung metastases per mouse compared to the LF diet however only the ST diet cohort was significant. Histomorphometric analysis of the lung tumor tissue indicated that the ST diet plus PTX decreased angiogenesis compared to the LF diet plus PTX. In conclusion these results support combining diet with chemotherapy in both treatment and prevention settings.

Abstract 475: The Transcription Factor ETS-1: A Critical Mediator of Renal Injury in Salt Sensitive Hypertension

The transcription factor ETS-1 regulates the expression of several growth factors, chemokines and cytokines. We have recently shown that ETS-1 is a mediator of the pro-inflammatory and pro-fibrotic effects of Angiotensin II in the kidney (HTN ’12). Herein, we tested the hypothesis that the renal expression of ETS-1 is increased in the Dahl salt-sensitive (DS) rat, a paradigm of salt-sensitive hypertension in humans, and that ETS-1 mediates renal injury in this model of hypertension. DS rats (n=6 per group) were fed a normal salt diet (0.5% NaCl, NS) or a high salt diet (4% NaCl, HS) for 4 weeks. Four additional groups (n=6 per group) on HS diet received: ETS-1 dominant negative peptide (HS/DN, 10mg/kg/day) to block ETS-1, a control ETS-1 mutant peptide (HS/MU, 10mg /kg/day), the AT1 receptor blocker Candesartan (HS/ARB 10 mg/kg/day) or a combination of DN and ARB (HS/DN/ARB). HS rats had a ~ 3 fold increase in the cortical expression of ETS-1 as assessed by western blot (WB). Treatment with DN, MU, ARB or DN/ARB resulted in small and non-significant reductions in BP as compared to HS. (Table). Compared with LS, HS rats had increased proteinuria (Bio-Rad), higher glomerular injury score (GIS), increased fibronectin expression (WB) and urinary TGF-β (ELISA) that were improved by DN but not by MU (table). ARB reduced proteinuria and GIS (table). Treatment with DN/ARB resulted in further improvements in renal injury as compared to DN and ARB (table).

In conclusion we have demonstrated that hypertensive DS rats have increased cortical expression of ETS-1 and that blockade of ETS-1 improves renal injury in this model of hypertension.

Role of the transcription factor erythroblastosis virus E26 oncogen homolog-1 (ETS-1) as mediator of the renal proinflammatory and profibrotic effects of angiotensin II

Angiotensin II (Ang II) plays a major role in the pathogenesis of end-organ injury in hypertension via its diverse hemodynamic and nonhemodynamic effects. Erythroblastosis virus E26 oncogen homolog-1 (ETS-1) is an important transcription factor recently recognized as an important mediator of cell proliferation, inflammation, and fibrosis. In the present studies, we tested the hypothesis that ETS-1 is a common mediator of the renal proinflammatory and profibrotic effects of Ang II. C57BL6 mice (n=6 per group) were infused with vehicle (control), Ang II (1.4 mg/kg per day), Ang II and an ETS-1 dominant-negative peptide (10 mg/kg per day), or Ang II and an ETS-1 mutant peptide (10 mg/kg per day) via osmotic minipump for 2 or 4 weeks. The infusion of Ang II resulted in significant increases in blood pressure and left ventricular hypertrophy, which were not modified by ETS-1 blockade. The administration of ETS-1 dominant-negative peptide significantly attenuated Ang II-induced renal injury as assessed by urinary protein excretion, mesangial matrix expansion, and cell proliferation. Furthermore, ETS-1 dominant-negative peptide but not ETS-1 mutant peptide significantly reduced Ang II-mediated upregulation of transforming growth factor-β, connective tissue growth factor, and α-smooth muscle actin. In addition, ETS-1 blockade reduced several proinflammatory effects of Ang II, including macrophage infiltration, nitrotyrosine expression, and NOX4 mRNA expression. Our studies suggest that ETS-1 is a common mediator of the proinflammatory and profibrotic effects of Ang II-induced hypertensive renal damage and may result in the development of novel strategies in the treatment and prevention of end-organ injury in hypertension.

Abstract 483: The Signaling Pathways of Nicotine-induced ERK1/2 Phosphorylation in Rat Mesangial Cells

Tobacco smoking is associated with accelerated progression of chronic kidney disease of different etiologies including diabetes and hypertension. However, the mechanisms involved are not well understood. We have previously reported that nicotine, a biologically active compound present in high concentrations in tobacco, induces cell proliferation and fibronectin production in mesangial cells which are prevented by ERK1/2 inhibition (AJP’05). In these studies we determined whether rat mesangial cells (MC) express nicotine receptors and characterized the signaling pathways that lead to ERK1/2 phosphorylation in response to nicotine. MC were grown in DMEM with 15% FBS in the presence of 0.4 mg/ml G418 and starved for 24 hours in DMEM without FBS before treatment. We first demonstrated that MC are endowed with several nicotinic Ach receptor (nAChR) subunits including α2-7 and β1-4 as assessed by western blot. Treatment of rat MC with nicotine at 10 -7 M caused a time-dependent ERK1/2 phosphorylation which peaked after 10 min of stimulation( N=3). Several protein kinase inhibitors were then used to identify the upstream kinases that mediate nicotine-induced ERK1/2 phosphorylation. The calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93 (10 -7 M) decreased the ERK1/2 phosphorylation level by ∼57% (0.41 of 0.95) as compared to nicotine. The PKC inhibitor Go6983 at 10 -9 M, the PKA inhibitor H89 (10 -8 M) and the EGFR inhibitor AG 1478 (10 -7 M) also inhibited ERK1/2 phosphorylation by 60% (0.38 of 0.95), 48% (0.63 of 1.20) and 68% (0.40 of 1.23) respectively as compared to nicotine. Given the role of the nicotine receptors as agonist-regulated Ca 2+ channels, we determined the effects of Ca 2+ channel blockade on nicotine induced ERK1/2 phosphorylation. Treatment of MC with the calcium channel Verapamil (10 -9 M) resulted in 33% (0.49 of 0.73) inhibition of ERK1/2 phosphorylation as compared to nicotine. In summary, we have determined in these studies that rat MC are endowed with several nAChR subunits and that ERK1/2 phosphorylation in response to nicotine requires CaMK II, PKA, PKC and EGFR. In addition, we have demonstrated that these effects require Ca 2+ consistent with the role of the nAChR as agonist-regulated Ca 2+ channels in MC.

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.

The transcription factor ETS-1 regulates angiotensin II-stimulated fibronectin production in mesangial cells

Angiotensin II (ANG II) produced as result of activation of the renin-angiotensin system (RAS) plays a critical role in the pathogenesis of chronic kidney disease via its hemodynamic effects on the renal microcirculation as well as by its nonhemodynamic actions including the production of extracellular matrix proteins such as fibronectin, a multifunctional extracellular matrix protein that plays a major role in cell adhesion and migration as well as in the development of glomerulosclerosis. ETS-1 is an important transcription factor essential for normal kidney development and glomerular integrity. We previously showed that ANG II increases ETS-1 expression and is required for fibronectin production in mesangial cells. In these studies, we determined that ANG II induces phosphorylation of ETS-1 via activation of the type 1 ANG II receptor and that Erk1/2 and Akt/PKB phosphorylation are required for these effects. In addition, we characterized the role of ETS-1 on the transcriptional activation of fibronectin production in mesangial cells. We determined that ETS-1 directly activates the fibronectin promoter and by utilizing gel shift assays and chromatin immunoprecipitation assays identified two different ETS-1 binding sites that promote the transcriptional activation of fibronectin in response to ANG II. In addition, we identified the essential role of CREB and its coactivator p300 on the transcriptional activation of fibronectin by ETS-1. These studies unveil novel mechanisms involved in RAS-induced production of the extracellular matrix protein fibronectin in mesangial cells and establish the role of the transcription factor ETS-1 as a direct mediator of these effects.