Na+/Ca2+ exchanger activity modulates connective tissue growth factor mRNA expression in transforming growth factor beta1- and Des-Arg10-kallidin-stimulated myofibroblasts

Kinin B1 receptor blockade attenuates hepatic fibrosis and portal hypertension in chronic liver diseases in mice

BACKGROUND AND AIMS

Kinin B1 receptors (B1Rs) are implicated in the pathogenesis of fibrosis. This study examined the anti-fibrotic effects of B1R blockade with BI 113823 in two established mouse models of hepatic fibrosis induced by intraperitoneal carbon tetrachloride (CCl₄) injection or bile duct ligation (BDL). The mechanisms underlying the protection afforded by B1R inhibition were examined using human peripheral blood cells and LX2 human hepatic stellate cells (HSCs).

METHODS

Fibrotic liver diseases were induced in mice by intraperitoneal carbon tetrachloride (CCl₄) injection for 6 weeks, and by bile duct ligation (BDL) for 3 weeks, respectively. Mice received daily treatment of vehicle or BI 113823 (B1R antagonist) from onset of the experiment until the end of the study.

RESULTS

B1Rs were strongly induced in fibrotic mouse liver. BI 113823 significantly attenuated liver fibrosis and portal hypertension (PH), and improved survival in both CCl₄ and BDL mice. BI 113823 significantly reduced the expression of fibrotic proteins α-SMA, collagens 1, 3, 4, and profibrotic growth factors PDGF, TGFβ, CTGF, VEGF, proliferating cell nuclear antigen; and reduced hepatic Akt phosphorylation in CCl₄- and BDL-induced liver fibrosis. BI 113823 also reduced expression of Cytokines IL-1, IL-6; chemokines MCP-1, MCP-3 and infiltration of inflammatory cells; and inhibited human monocyte and neutrophil activation, transmigration, TNF-α & MPO production in vitro. BI 113823 inhibited TGF-β and B1R agonist-stimulated human-HSC activation, contraction, proliferation, migration and fibrosis protein expression, and inhibited activation of PI3K/Akt signalling pathway.

CONCLUSIONS

B1Rs merits consideration as a novel therapeutic target for chronic liver fibrosis and PH.

An overview of kinin mediated events in cancer progression and therapeutic applications

Kinins are bioactive peptides generated in the inflammatory milieu of the tissue microenvironment, which is involved in cancer progression and inflammatory response. Kinins signals through activation of two G-protein coupled receptors; inducible Bradykinin Receptor B1 (B1R) and constitutive receptor B2 (B2R). Activation of kinin receptors and its cross-talk with receptor tyrosine kinases activates multiple signaling pathways, including ERK/MAPK, PI3K, PKC, and p38 pathways regulating cancer hallmarks. Perturbations of the kinin-mediated events are implicated in various aspects of cancer invasion, matrix remodeling, and metastasis. In the tumor microenvironment, kinins initiate fibroblast activation, mesenchymal stem cell interactions, and recruitment of immune cells. Albeit the precise nature of kinin function in the metastasis and tumor microenvironment are not completely clear yet, several kinin receptor antagonists show anti-metastatic potential. Here, we showcase an overview of the complex biology of kinins and their role in cancer pathogenesis and therapeutic aspects.

Persistent DNA strand breaks induce a CAF-like phenotype in normal fibroblasts

Cancer-associated fibroblasts (CAFs) are an emerging target for cancer therapy as they promote tumour growth and metastatic potential. However, CAF targeting is complicated by the lack of knowledge-based strategies aiming to selectively eliminate these cells. There is a growing body of evidence suggesting that a pro-inflammatory microenvironment (e.g. ROS and cytokines) promotes CAF formation during tumorigenesis, although the exact mechanisms involved remain unclear. In this study, we reveal that a prolonged pro-inflammatory stimulation causes a de facto deficiency in base excision repair, generating unrepaired DNA strand breaks and thereby triggering an ATF4-dependent reprogramming of normal fibroblasts into CAF-like cells. Based on the phenotype of in vitro-generated CAFs, we demonstrate that midostaurin, a clinically relevant compound, selectively eliminates CAF-like cells deficient in base excision repair and prevents their stimulatory role in cancer cell growth and migration.

A critical appraisal of the role of intracellular Ca2+-signaling pathways in Kawasaki disease

Kawasaki disease is a multi-systemic vasculitis that generally occurs in children and that can lead to coronary artery lesions. Recent studies showed that Kawasaki disease has an important genetic component. In this review, we discuss the single-nucleotide polymorphisms in the genes encoding proteins with a role in intracellular Ca²⁺ signaling: inositol 1,4,5-trisphosphate 3-kinase C, caspase-3, the store-operated Ca²⁺-entry channel ORAI1, the type-3 inositol 1,4,5-trisphosphate receptor, the Na⁺/Ca²⁺ exchanger 1, and phospholipase Cß4 and Cß1. An increase of the free cytosolic Ca²⁺ concentration is proposed to be a major factor in susceptibility to Kawasaki disease and disease outcome, but only for polymorphisms in the genes encoding the inositol 1,4,5-trisphosphate 3-kinase C and the Na⁺/Ca²⁺ exchanger 1, the free cytosolic Ca²⁺ concentration was actually measured and shown to be increased. Excessive cytosolic Ca²⁺ signaling can result in hyperactive calcineurin in T cells with an overstimulated nuclear factor of activated T cells pathway, in hypersecretion of interleukin-1ß and tumor necrosis factor-α by monocytes/macrophages, in increased urotensin-2 signaling, and in an overactivation of vascular endothelial cells.

Genetic Variation in the SLC8A1 Calcium Signaling Pathway Is Associated With Susceptibility to Kawasaki Disease and Coronary Artery Abnormalities

Background—

Kawasaki disease (KD) is an acute pediatric vasculitis in which host genetics influence both susceptibility to KD and the formation of coronary artery aneurysms. Variants discovered by genome-wide association studies and linkage studies only partially explain the influence of genetics on KD susceptibility.

Methods and Results—

To search for additional functional genetic variation, we performed pathway and gene stability analysis on a genome-wide association study data set. Pathway analysis using European genome-wide association study data identified 100 significantly associated pathways ( P <5×10 − 4 ). Gene stability selection identified 116 single nucleotide polymorphisms in 26 genes that were responsible for driving the pathway associations, and gene ontology analysis demonstrated enrichment for calcium transport ( P =1.05×10 − 4 ). Three single nucleotide polymorphisms in solute carrier family 8, member 1 ( SLC8A1 ), a sodium/calcium exchanger encoding NCX1, were validated in an independent Japanese genome-wide association study data set (meta-analysis P =0.0001). Patients homozygous for the A (risk) allele of rs13017968 had higher rates of coronary artery abnormalities ( P =0.029). NCX1, the protein encoded by SLC8A1 , was expressed in spindle-shaped and inflammatory cells in the aneurysm wall. Increased intracellular calcium mobilization was observed in B cell lines from healthy controls carrying the risk allele.

Conclusions—

Pathway-based association analysis followed by gene stability selection proved to be a valuable tool for identifying risk alleles in a rare disease with complex genetics. The role of SLC8A1 polymorphisms in altering calcium flux in cells that mediate coronary artery damage in KD suggests that this pathway may be a therapeutic target and supports the study of calcineurin inhibitors in acute KD.

Na+/Ca2+ exchangers regulate the migration and proliferation of human gastric myofibroblasts

Gastrointestinal myofibroblasts are contractile, electrically nonexcitable, transitional cells that play a role in extracellular matrix production, in ulcer healing, and in pathophysiological conditions they contribute to chronic inflammation and tumor development. Na+/Ca2+ exchangers (NCX) are known to have a crucial role in Ca2+ homeostasis of contractile cells, however, no information is available concerning the role of NCX in the proliferation and migration of gastrointestinal myofibroblasts. In this study, our aim was to investigate the role of NCX in the Ca2+ homeostasis, migration, and proliferation of human gastrointestinal myofibroblasts, focusing on human gastric myofibroblasts (HGMs). We used microfluorometric measurements to investigate the intracellular Ca2+ and Na+ concentrations, PCR analysis and immunostaining to show the presence of the NCX, patch clamp for measuring NCX activity, and proliferation and migration assays to investigate the functional role of the exchanger. We showed that 53.0±8.1% of the HGMs present Ca2+ oscillations, which depend on extracellular Ca2+ and Na+, and can be inhibited by NCX inhibitors. NCX1, NCX2, and NCX3 were expressed at both mRNA and protein levels in HGMs, and they contribute to the intracellular Ca2+ and Na+ homeostasis as well, regardless of the oscillatory activity. NCX inhibitors significantly blocked the basal and insulin-like growth factor II-stimulated migration and proliferation rates of HGMs. In conclusion, we showed that NCX plays a pivotal role in regulating the Ca2+ homeostasis, migration, and proliferation of HGMs. The inhibition of NCX activity may be a potential therapeutic target in hyperproliferative gastric diseases.

Roles of transient receptor potential canonical (TRPC) channels and reverse-mode Na+/Ca2+ exchanger on cell proliferation in human cardiac fibroblasts: effects of transforming growth factor β1

Expression of transient receptor potential canonical channels (TRPC) and the effects of transforming growth factor-β1 (TGF-β1) on Ca2+ signals and fibroblast proliferation were investigated in human cardiac fibroblasts. The conventional and quantitative real-time RT-PCR, western blot, immunocytochemical analysis, and intracellular Ca2+ concentration [Ca2+]i measurement were applied. Cell proliferation and cell cycle progression were assessed using MTT assays and fluorescence activated cell sorting. Human cardiac fibroblasts have the expression of TRPC1,3,4,6 mRNA and proteins. 1-oleoyl-2-acetyl-sn-glycerol (OAG) and thapsigargin induced extracellular Ca(2+)-mediated [Ca2+]i rise. siRNA for knock down of TRPC6 reduced OAG-induced Ca2+ entry. Hyperforin as well as angiotensin II (Ang II) induced Ca2+ entry. KB-R7943, a reverse-mode Na+/Ca2+ exchanger (NCX) inhibitor, and/or replacement of Na+ with NMDG+ inhibited thapsigargin-, OAG- and Ang II-induced Ca2+ entry. Treatment with TGF-β1 increased thapsigargin-, OAG- and Ang II-induced Ca2+ entry with an enhancement of TRPC1,6 protein expression, suppressed by KB-R7943. TGF-β1 and AngII promoted cell cycle progression from G0/G1 to S/G2/M and cell proliferation. A decrease of the extracellular Ca2+ and KB-R7943 suppressed it. Human cardiac fibroblasts contain several TRPC-mediated Ca2+ influx pathways, which activate the reverse-mode NCX. TGF-β1 enhances the Ca2+ influx pathways requiring Ca2+ signals for its effect on fibroblast proliferation.

Ca(2+) /calmodulin- dependent protein kinase II mediates transforming growth factor-β-induced hepatic stellate cells proliferation but not in collagen α1(I) production

AIM

  Hepatic stellate cells (HSC) are the major players in hepatic fibrosis. As a most potent mitogen, transforming growth factor-β (TGF-β) strongly activates HSC and increases intracellular Ca(2+) concentration. Here, we assessed the potential role of Ca(2+) /calmodulin-dependent protein kinase II (CaMKII), a main downstream effector of the Ca(2+) signal in liver fibrogenesis cascade.

METHODS

  A human immortal HSC cell line, LX-2, and primary rat hepatic stellate cells were used in current study. CaMKII blockage and Akt inhibition were performed by KN-93/CaMKIIα siRNA and LY294002, respectively. HSC proliferation was detected by 5-bromodeoxyuridine incorporation assay. Real-time polymerase chain reaction, western blot and enzyme-linked immunosorbent assay were used to measure mRNA, cellular protein and protein in medium, respectively. Procollagen α1(I) expression was detected by immunocytochemistry. The role of CaMKII on TGF-β/Smad-induced collagen α1(I) expression was determined by (CAGA)(12) -MLP luciferase activity assay.

RESULTS

  TGF-β dramatically increased CaMKII mRNA, and total and phosphorylated CaMKII expression. KN-93 and CaMKIIα siRNA suppressed TGF-β-mediated HSC proliferation. CaMKII interruption blocked TGF-β-elicited Akt activation. LY294002 arrested HSC proliferation and collagen α1(I) production but had no effect on CaMKII. Furthermore, CaMKII led to increased p21 and p27 expression. KN-93 and CaMKIIα siRNA inhibited TGF-β-induced and basal collagen α1(I) production but had no effect on the activity of (CAGA)(12) -MLP luciferase in response to TGF-β stimulation.

CONCLUSION

  CaMKII is a pivotal signal in TGF-β-induced fibrogenic cascades by means of stimulating HSC proliferation, and involved in a basal collagen production. Therefore, CaMKII will be a potentially effective target in the development of therapeutic intervention strategies to attenuate hepatic fibrosis.

Changes in the myocardial interstitium and contribution to the progression of heart failure

The myocardial interstitium is highly organized and orchestrated, whereby small disruptions in composition, spatial relationships, or content lead to altered myocardial systolic and/or diastolic performance. These changes in extracellular matrix structure and function are important in the progression to heart failure in pressure overload hypertrophy, dilated cardiomyopathy, and ischemic heart disease. The myocardial interstitium is not a passive entity, but rather a complex and dynamic microenvironment that represents an important structural and signaling system within the myocardium.

Pulmonary fibrosis: a possible diabetic complication

Diabetic complications affect many organs in diabetic patients. Emerging evidence indicates that diabetes can increase the risk of pulmonary dysfunction. Early epidemiological studies from different populations on whether diabetes was an independent risk for pulmonary dysfunction were inconclusive. Recent epidemiological studies and systematic reviews clearly indicate that diabetes is an independent risk factor for pulmonary dysfunction. Given that pulmonary fibrosis is an important predictor of mortality in people with this chronic disease, whether diabetes directly causes pulmonary fibrosis is an important unresolved clinical question. This review combines recent epidemiological data with findings from basic research to indicate that diabetes induces pulmonary fibrosis. We then discuss the possible underlying mechanisms for the histological and biochemical pathology. At the end of this review, we emphasize that diabetic pulmonary fibrosis as a potential diabetic complication warrants more attention.

Involvement of Na+/Ca2+ exchanger in migration and contraction of rat cultured tendon fibroblasts

In response to injury and inflammation of tendons, tendon fibroblasts are activated, migrate to the wound, and eventually induce contraction of the extracellular matrices to repair the tissue. Under such conditions, Ca(2+) signalling is involved in motility and contractility of tendon fibroblasts. Using cultured tendon fibroblasts isolated from rat Achilles tendons, we investigated functional expression of Na(+)/Ca(2+) exchangers (NCX). The fluorometric study showed that the intracellular Ca(2+) concentration ([Ca(2+)](i)) was increased by reducing extracellular Na(+) concentration ([Na(+)](o)) in tendon fibroblasts. Selective NCX inhibitors, KB-R7943 and SEA0400, both attenuated [Na(+)](o)-dependent [Ca(2+)](i) elevation and the resting [Ca(2+)](i) in tendon fibroblasts. RT-PCR, Western blots and sequence analyses revealed that NCX1.3 and NCX1.7 were expressed in cultured tendon fibroblasts. NCX2 mRNA was undetected. NCX3 expression was negligibly low. Immunofluorescence microscopy indicated that NCX1 protein localized in the plasma membrane especially at the microspikes of tendon fibroblasts. In the wound-healing scratch assay, the cells migrated toward the space created by a scratch and almost completely filled the space within 48 h. This phenomenon was significantly suppressed by KB-R7943 and SEA0400. Furthermore, the NCX inhibitors abrogated the tendon fibroblast-mediated collagen-matrix contractions. Two types of siRNAs for NCX1 also suppressed the migration and contraction of tendon fibroblasts. We conclude that NCX is expressed and mediates Ca(2+) influx in cultured tendon fibroblasts. Since the pharmacological inhibitors and siRNA for NCX1 suppressed motility and contractility of tendon fibroblasts, NCX may play an important role in the function of tendon fibroblasts in the wound healing.

Aldosterone-and-salt-induced cardiac fibrosis is independent from angiotensin II type 1a receptor signaling in mice

Aldosterone infusion with high salt treatment induces cardiac fibrosis in rats. Aldosterone enhanced angiotensin II (Ang II) has been shown to induce proliferation and increase the expression of Ang II receptor mRNA and Ang II binding in vitro. To investigate the role of Ang II type 1a receptor (AT1aR) in aldosterone-and-salt (Ald-NaCl)-induced cardiac fibrosis, we subcutaneously infused aldosterone (0.15 microg/h) and 1% NaCl (Ald-NaCl) into AT1aR knockout mice (AT1aR-KO) or wild type mice (Wt). To examine the role of NaCl on cardiac fibrosis, we gave some of the aldosterone-treated AT1aR-KO tap water (Ald-H2O). Ald-NaCl treatment increased systolic blood pressure and induced cardiac hypertrophy in both strains, whereas there were no such changes in the mice without aldosterone. Severe cardiac fibrosis was seen in Ald-NaCl-treated AT1aR-KO and not in Ald-NaCl-treated Wt. In contrast, Ald-NaCl-treated Wt with co-administration of an active metabolite of olmesartan, the AT1aR antagonist (10 mg/kg/day) did not show cardiac fibrosis. Na+/H+ exchanger, and Na+-K+ ATPase alpha2 subunit mRNA were decreased in AT1aR-KO. Na+/Ca2) exchanger mRNA was lower in AT1aR-KO than Wt and was decreased by Ald-NaCl in both strains. Phosphorylation of epidermal growth factor receptor and extracellular signal-regulated kinase was increased by Ald-NaCl treatment in AT1aR-KO. Connective tissue growth factor (CTGF) and osteopontin mRNA were increased and accumulation of CTGF proteins was seen in the hearts of Ald-NaCl-treated AT1aR-KO. Ald-H2O-treated AT1aR-KO did not show any cardiac fibrosis. These results suggest that Ald-NaCl-induced cardiac fibrosis required both aldosterone and salt. Because cardiac fibrosis was exaggerated in Ald-NaCl-treated AT1aR-KO but was not seen in Wt treated with Ald-NaCl and olmesartan, AT1aR may not play a primary role in progression of cardiac fibrosis by Ald-NaCl, and gene disruption of AT1aR may have some implications in this model.

The participation of the Na+-Ca2+ exchanger in primary cardiac myofibroblast migration, contraction, and proliferation

Cardiac ventricular myofibroblast motility, proliferation, and contraction contribute to post-myocardial infarct wound healing, infarct scar formation, and remodeling of the ventricle remote to the site of infarction. The Na+-Ca2+ exchanger (NCX1) is involved in altered calcium handling in cardiac myocytes during cardiac remodeling associated with heart failure, however, its role in cardiac myofibroblast cell function is unexplored. In this study we investigated the involvement of NCX1 as well as the role of non-selective-cation channels (NSCC) in cardiac myofibroblast cell function in vitro. Immunofluorescence and Western blots revealed that P1 cells upregulate alpha-smooth muscle actin (alphaSMA) and embryonic smooth muscle myosin heavy chain (SMemb) expression. NCX1 mRNA and proteins as well as Ca(v)1.2a protein are also expressed in P1 myofibroblasts. Myofibroblast motility in the presence of 50 ng/ml PDGF-BB was blocked with AG1296. Myofibroblast motility, contraction, and proliferation were sensitive to KB-R7943, a specific NCX1 reverse-mode inhibitor. In contrast, only proliferation and contraction, but not motility were sensitive to nifedipine, while gadolinium (NSCC blocker) was only associated with decreased motility. ML-7 treatment was associated with inhibition of the chemotactic response and contraction. Thus cardiac myofibroblast chemotaxis, contraction, and proliferation were sensitive to different pharmacologic treatments suggesting that regulation of transplasmalemmal calcium movements may be important in growth factor receptor-mediated processes. NCX1 may represent an important moiety in suppression of myofibroblast functions.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Connective tissue growth factor: a role in airway remodelling in asthma?

1. Severe persistent asthma is accompanied by structural changes in the airway, referred to as remodelling. The mechanisms driving airway remodelling are poorly understood. 2. Transforming growth factor (TGF)-beta is increased in the airways of patients with asthma. Many of the effects of TGF-beta are mediated by connective tissue growth factor (CTGF). 3. Overexpression of CTGF is linked to many fibrotic diseases, but its exact role in airway remodelling is unknown. 4. Connective tissue growth factor mediates cell adhesion, migration, proliferation, survival, extracellular matrix synthesis and has a role in angiogenesis. 5. Current asthma therapies do not inhibit CTGF induction. 6. Understanding the mechanisms underlying the role of CTGF in airway remodelling may lead to new therapeutic strategies for asthma.

Preservation and expansion of the primate keratocyte phenotype by downregulating TGF-beta signaling in a low-calcium, serum-free medium

PURPOSE

To demonstrate whether the original keratocyte phenotype is maintained with proliferative activity by suppressing TGF-beta signaling in rhesus monkey keratocytes expanded in a serum-free and low-[Ca2+] medium.

METHODS

Rhesus monkey keratocytes were isolated from central corneal buttons by collagenase digestion for 16 hours, seeded on plastic in Dulbecco's modified Eagle's medium (DMEM) containing insulin-transferrin-sodium selenite (ITS) supplement (DMEM/ITS) or 10% fetal bovine serum (DMEM/10% FBS), or in a defined keratinocyte serum-free medium (KSFM). After confluence, cells in KSFM were continuously subcultured at a 1-to-3 split. Cellular proliferation was analyzed by immunostaining for Ki67 and the MTT assay. The cellular phenotype was determined by immunostaining for aldehyde dehydrogenase (ALDH), keratocan, and CD34 and by the expression of keratocan promoter-driven enhanced cyan fluorescent protein (ECFP). The stability of the keratocyte phenotype was examined by switching KSFM to DMEM/ITS and DMEM/10% FBS. TGF-beta signaling was monitored by measuring the promoter activity of TGF-beta1, -beta2, and -beta RII after transient adenoviral transfection, and cytolocalization of Smad2 and Smad4.

RESULTS

In KSFM, monkey keratocytes proliferated while maintaining the expression of keratocan, CD34, and ALDH proteins and keratocan promoter-driven ECFP for at least 15 passages. The nuclear accumulation of Smad2 and Smad4 and the promoter activities of TGF-beta1 and -beta RII were significantly downregulated in KSFM compared with DMEM/10% FBS. In KSFM, an increase of [Ca2+] to 1.8 mM and addition of 10% FBS synergistically downregulated the keratocan promoter activity, facilitated Smad2 and Smad4 nuclear translocation, and upregulated TGF-beta1 and -beta RII promoter activities.

CONCLUSIONS

The normal monkey keratocyte phenotype can be maintained in a low-calcium, serum-free medium by downregulating Smad-mediated TGF-beta signaling.