Norepinephrine and ANG II stimulate secretion of TGF-beta by neonatal rat cardiac fibroblasts in vitro

Innervation of the developing kidney in vivo and in vitro

Within the adult kidney, renal neurites can be observed alongside the arteries where they play a role in regulating blood flow. However, their role and localization during development has so far not been described in detail. In other tissues, such as the skin of developing limb buds, neurons play an important role during arterial differentiation. Here, we aim to investigate whether renal nerves could potentially carry out a similar role during arterial development in the mouse kidney. In order to do so, we used whole-mount immunofluorescence staining to identify whether the timing of neuronal innervation correlates with the recruitment of arterial smooth muscle cells. Our results show that neurites innervate the kidney between day 13.5 and 14.5 of development, arriving after the recruitment of smooth muscle actin-positive cells to the renal arteries.

Stem cell‐derived extracellular vesicles reduce the expression of molecules involved in cardiac hypertrophy—In a model of human-induced pluripotent stem cell-derived cardiomyocytes

Cardiac pathological hypertrophy is the major risk factor that usually progresses to heart failure. We hypothesized that extracellular vesicles (EVs), known to act as important mediators in regulating physiological and pathological functions, could have the potential to reduce the cardiac hypertrophy and the ensuing cardiovascular diseases. Herein, the effects of mesenchymal stem cell-derived extracellular vesicles (EV-MSCs) on cardiac hypertrophy were investigated. EVs were isolated from the secretome of human adipose tissue-derived stem cells (EV-ADSCs) or bone marrow-derived stem cells (EV-BMMSCs). Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were stimulated with AngII and TGF-β1, in absence or presence of EVs. The results showed that exposure of hiPSC-CMs to AngII and TGF-β1 generated in vitro model of hypertrophic cardiomyocytes characterized by increases in surface area, reactive oxygen species production, protein expression of cardiac-specific biomarkers atrial natriuretic factor, migration inhibitory factor, cTnI, COL1A1, Cx43, α-SMA and signalling molecules SMAD2 and NF-kBp50. The presence of EV-ADSCs or EV-BMMSCs in the hiPSC-CM culture along with hypertrophic stimuli reduced the protein expressions of hypertrophic specific markers (ANF, MIF, cTnI, COL1A1) and the gene expressions of IL-6 molecule involved in inflammatory process associated with cardiac hypertrophy and transcription factors SMAD2, SMAD3, cJUN, cFOS with role in cardiomyocyte hypertrophic response induced by AngII and TGF-β1. The EV-ADSCs were more effective in reducing the protein expressions of hypertrophic and inflammatory markers, while EV-BMMSCs in reducing the gene expressions of transcription factors. Notably, neither EV-ADSCs nor EV-BMMSCs induced significant changes in cardiac biomarkers Cx43, α-SMA and fibronectin. These different effects of stem cell-derived EVs could be attributed to their miRNA content: some miRNAs (miR-126-3p, miR-222-3p, miR-30e-5p, miR-181b-5p, miR-124-3p, miR-155-5p, miR-210-3p hsa-miR-221-3p) were expressed in both types of EVs and others only in EV-ADSCs (miR-181a-5p, miR-185-5p, miR-21-5p) or in EV-BMMSCs (miR-143-3p, miR-146a-5p, miR-93-5p), some of these attenuating the cardiac hypertrophy while others enhance it. In conclusion, in hiPSC-CMs the stem cell-derived EVs through their cargo reduced the expression of hypertrophic specific markers and molecules involved in inflammatory process associated with cardiac hypertrophy. The data suggest the EV potential to act as therapeutic mediators to reduce cardiac hypertrophy and possibly the subsequent cardiovascular events.

Intercellular model predicts mechanisms of inflammation-fibrosis coupling after myocardial infarction

After myocardial infarction (MI), cardiac cells work together to regulate wound healing of the infarct. The pathological response to MI yields cardiac remodelling comprising inflammatory and fibrosis phases, and the interplay of cellular dynamics that underlies these phases has not been elucidated. This study developed a computational model to identify cytokine and cellular dynamics post-MI to predict mechanisms driving post-MI inflammation, resolution of inflammation, and scar formation. Additionally, this study evaluated the interdependence between inflammation and fibrosis. Our model bypassed limitations of in vivo approaches in achieving cellular specificity and performing specific perturbations such as global knockouts of chemical factors. The model predicted that inflammation is a graded response to initial infarct size that is amplified by a positive feedback loop between neutrophils and interleukin 1β (IL-1β). Resolution of inflammation was driven by degradation of IL-1β, matrix metalloproteinase 9, and transforming growth factor β (TGF-β), as well as apoptosis of neutrophils. Inflammation regulated TGFβ secretion directly through immune cell recruitment and indirectly through upregulation of macrophage phagocytosis. Lastly, we found that mature collagen deposition was an ultrasensitive switch in response to inflammation, which was amplified primarily by cardiac fibroblast proliferation. These findings describe the relationship between inflammation and fibrosis and highlight how the two responses work together post-MI. This model revealed that post-MI inflammation and fibrosis are dynamically coupled, which provides rationale for designing novel anti-inflammatory, pro-resolving or anti-fibrotic therapies that may improve the response to MI. KEY POINTS: Inflammation and matrix remodelling are two processes involved in wound healing after a heart attack. Cardiac cells work together to facilitate these processes; this is done by secreting cytokines that then regulate the cells themselves or other cells surrounding them. This study developed a computational model of the dynamics of cardiac cells and cytokines to predict mechanisms through which inflammation and matrix remodelling is regulated. We show the roles of various cytokines and signalling motifs in driving inflammation, resolution of inflammation and fibrosis. The novel concept of inflammation-fibrosis coupling, based on the model prediction that inflammation and fibrosis are dynamically coupled, provides rationale for future studies and for designing therapeutics to improve the response after a heart attack.

A Catecholaldehyde Metabolite of Norepinephrine Induces Myofibroblast Activation and Toxicity via the Receptor for Advanced Glycation Endproducts: Mitigating Role of l-Carnosine

Monoamine oxidase (MAO) is rapidly gaining appreciation for its pathophysiologic role in cardiac injury and failure. Oxidative deamination of norepinephrine by MAO generates H₂O₂ and the catecholaldehyde 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), the latter of which is a highly potent and reactive electrophile that has been linked to cardiotoxicity. However, many questions remain as to whether catecholaldehydes regulate basic physiological processes in the myocardium and the pathways involved. Here, we examined the role of MAO-derived oxidative metabolites in mediating the activation of cardiac fibroblasts in response to norepinephrine. In neonatal murine cardiac fibroblasts, norepinephrine increased reactive oxygen species (ROS), accumulation of catechol-modified protein adducts, expression and secretion of collagens I/III, and other markers of profibrotic activation including STAT3 phosphorylation. These effects were attenuated with MAO inhibitors, the aldehyde-scavenging dipeptide l-carnosine, and FPS-ZM1, an antagonist for the receptor for advanced glycation endproducts (RAGE). Interestingly, treatment of cardiac fibroblasts with a low dose (1 μM) of DOPEGAL-modified albumin phenocopied many of the effects of norepinephrine and also induced an increase in RAGE expression. Higher doses (>10 μM) of DOPEGAL-modified albumin were determined to be toxic to cardiac fibroblasts in a RAGE-dependent manner, which was mitigated by l-carnosine. Collectively, these findings suggest that norepinephrine may influence extracellular matrix remodeling via an adrenergic-independent redox pathway in cardiac fibroblasts involving the MAO-mediated generation of ROS, catecholaldehydes, and RAGE. Furthermore, since elevations in the catecholaminergic tone and oxidative stress in heart disease are linked with cardiac fibrosis, this study illustrates novel drug targets that could potentially mitigate this serious disorder.

Cardiac fibrosis: Myofibroblast-mediated pathological regulation and drug delivery strategies

Cardiac fibrosis remains an unresolved problem in heart diseases. After initial injury, cardiac fibroblasts (CFs) are activated and subsequently differentiate into myofibroblasts (myoFbs) that are major mediator cells in the pathological remodeling. MyoFbs exhibit proliferative and secretive characteristics, and contribute to extracellular matrix (ECM) turnover, collagen deposition. The persistent functions of myoFbs lead to fibrotic scars and cardiac dysfunction. The anti-fibrotic treatment is hindered by the elusive mechanism of fibrosis and lack of specific targets on myoFbs. In this review, we will outline the progress of cardiac fibrosis and its contributions to the heart failure. We will also shed light on the role of myoFbs in the regulation of adverse remodeling. The communication between myoFbs and other cells that are involved in the heart injury and repair respectively will be reviewed in detail. Then, recently developed therapeutic strategies to treat fibrosis will be summarized such as i) chimeric antigen receptor T cell (CAR-T) therapy with an optimal target on myoFbs, ii) direct reprogramming from stem cells to quiescent CFs, iii) "off-target" small molecular drugs. The application of nano/micro technology will be discussed as well, which is involved in the construction of cell-based biomimic platforms and "pleiotropic" drug delivery systems.

Substrate Stiffness and Stretch Regulate Profibrotic Mechanosignaling in Pulmonary Arterial Adventitial Fibroblasts

Pulmonary arterial adventitial fibroblasts (PAAFs) are important regulators of fibrotic vascular remodeling during the progression of pulmonary arterial hypertension (PAH), a disease that currently has no effective anti-fibrotic treatments. We conducted in-vitro experiments in PAAFs cultured on hydrogels attached to custom-made equibiaxial stretchers at 10% stretch and substrate stiffnesses representing the mechanical conditions of mild and severe stages of PAH. The expression of collagens α(1)I and α(1)III and elastin messenger RNAs (Col1a1, Col3a1, Eln) were upregulated by increased stretch and substrate stiffness, while lysyl oxidase-like 1 and α-smooth muscle actin messenger RNAs (Loxl1, Acta2) were only significantly upregulated when the cells were grown on matrices with an elevated stiffness representative of mild PAH but not on a stiffness representative of severe PAH. Fibronectin messenger RNA (Fn1) levels were significantly induced by increased substrate stiffness and transiently upregulated by stretch at 4 h, but was not significantly altered by stretch at 24 h. We modified our published computational network model of the signaling pathways that regulate profibrotic gene expression in PAAFs to allow for differential regulation of mechanically-sensitive nodes by stretch and stiffness. When the model was modified so that stiffness activated integrin β3, the Macrophage Stimulating 1 or 2 (MST1\2) kinases, angiotensin II (Ang II), transforming growth factor-β (TGF-β), and syndecan-4, and stretch-regulated integrin β3, MST1\2, Ang II, and the transient receptor potential (TRP) channel, the model correctly predicted the upregulation of all six genes by increased stiffness and the observed responses to stretch in five out of six genes, although it could not replicate the non-monotonic effects of stiffness on Loxl1 and Acta2 expression. Blocking Ang II Receptor Type 1 (AT1R) with losartan in-vitro uncovered an interaction between the effects of stretch and stiffness and angiotensin-independent activation of Fn1 expression by stretch in PAAFs grown on 3-kPa matrices. This novel combination of in-vitro and in-silico models of PAAF profibrotic cell signaling in response to altered mechanical conditions may help identify regulators of vascular adventitial remodeling due to changes in stretch and matrix stiffness that occur during the progression of PAH in-vivo.

Immune regulation of cardiac fibrosis post myocardial infarction

Pathological changes resulting from myocardial infarction (MI) include extracellular matrix alterations of the left ventricle, which can lead to cardiac stiffness and impair systolic and diastolic function. The signals released from necrotic tissue initiate the immune cascade, triggering an extensive inflammatory response followed by reparative fibrosis of the infarct area. Immune cells such as neutrophils, monocytes, macrophages, mast cells, T-cells, and dendritic cells play distinct roles in orchestrating this complex pathological condition, and regulate the balance between pro-fibrotic and anti-fibrotic responses. This review discusses how molecular signals between fibroblasts and immune cells mutually regulate fibrosis post-MI, and outlines the emerging pharmacological targets and therapies for modulating inflammation and cardiac fibrosis associated with MI.

Noradrenaline modulates CD4+ T cell priming in rat experimental autoimmune encephalomyelitis: a role for the α1-adrenoceptor

Pharmacological blockade of α₁-adrenoceptor is shown to influence development of experimental autoimmune encephalomyelitis (EAE), an IL-17-producing CD4+TCR+ (Th17) cell-mediated disease mimicking multiple sclerosis. Considering significance of CD4+ cell priming for the clinical outcome of EAE, the study examined α₁-adrenoceptor-mediated influence of catecholamines, particularly those derived from draining lymph node (dLN) cells (as catecholamine supply from nerve fibers decreases with the initiation of autoimmune diseases) for CD4+ cell priming. The results confirmed diminishing effect of immunization on nerve fiber-derived noradrenaline supply and showed that antigen presenting and CD4+ cells synthesize catecholamines, while antigen presenting cells and only CD4+CD25+Foxp3+ regulatory T cells (Tregs) express α₁-adrenoceptor. The analysis of influence of α₁-adrenoceptor antagonist prazosin on the myelin basic protein (MBP)-stimulated CD4+ lymphocytes in dLN cell culture showed their diminished proliferation in the presence of prazosin. This was consistent with prazosin enhancing effect on Treg frequency and their Foxp3 expression in these cultures. The latter was associated with upregulation of TGF-β expression. Additionally, prazosin decreased antigen presenting cell activation and affected their cytokine profile by diminishing the frequency of cells that produce Th17 polarizing cytokines (IL-1β and IL-23) and increasing that of IL-10-producing cells. Consistently, the frequency of all IL-17A+ cells and those co-expressing GM-CSF within CD4+ lymphocytes was decreased in prazosin-supplemented MBP-stimulated dLN cell cultures. Collectively, the results indicated that dLN cell-derived catecholamines may influence EAE development by modulating interactions between distinct subtypes of CD4+ T cells and antigen presenting cells through α₁-adrenoceptor and consequently CD4+ T cell priming.

A high-fat diet rich in corn oil induces cardiac fibrosis in rats by activating JAK2/STAT3 and subsequent activation of ANG II/TGF-1β/Smad3 pathway: The role of ROS and IL-6 trans-signaling

This study compared the effect of low-fat diet (LFD) and high-fat diet rich in corn oil (HFD-CO) on left ventricular (LV) fibrosis in rats and examined their effect of angiotensin II (ANG II), JAK/STAT, and TGF-1β/smad3 pathways. As compared to LFD which didn't affect any of the measured parameters, HFD-CO-induced type 2 diabetes phenotype and increased LV collagen synthesis. Mechanistically, it increased LV levels of ROS, ANG II, ACE, IL-6, s-IL-6Rα, TGF-β1, Smad-3, and activities of JAK1/2 and STAT1/3. AG490, a JAK2 inhibitor, partially ameliorated these effect while Losartan, an AT1 inhibitor completely abolished collagen synthesis. However, with both treatments, levels of ANG II, IL-6, and s-IL-6Rα, and activity of JAK1/STAT3 remained high, all of which were normalized by co-administration of NAC or IL-6 neutralizing antibody. In conclusion: HFD-CO enhances LV collage synthesis by activation of JAK1/STAT3/ANG II/TGF-1β/smad3 pathway. PRACTICAL APPLICATIONS: We report that chronic consumption of a high-fat diet rich in corn oil (HFD-CO) induces diabetes mellitus phenotype 2 associated with left ventricular (LV) cardiac fibrosis in rats. The findings of this study show that HFD-CO, and through the increasing generation of ROS and IL-6 levels and shedding, could activate LV JAK1/2-STAT1/3  and  renin-angiotensin system (RAS) signaling pathways, thus creating a positive feedback between the two which ultimately leads to activation of TGF-1β/Smad3 fibrotic pathway. Herein, we also report a beneficial effect of the antioxidant, NAC, or IL-6 neutralizing antibody in preventing such adverse effects of such HFD-CO. However, this presents a warning message to the current sudden increase in idiopathic cardiac disorders, especially with the big shift in our diets toward n-6 PUFA.

TGF-β1 (Transforming Growth Factor-β1) Plays a Pivotal Role in Cardiac Myofibroblast Arrhythmogenicity

BACKGROUND

TGF-β₁ (transforming growth factor-β₁) importantly contributes to cardiac fibrosis by controlling differentiation, migration, and collagen secretion of cardiac myofibroblasts. It is still elusive, however, to which extent TGF-β₁ alters the electrophysiological phenotype of myofibroblasts and cardiomyocytes and whether it affects proarrhythmic myofibroblast-cardiomyocyte crosstalk observed in vitro.

METHODS AND RESULTS

Patch-clamp recordings of cultured neonatal rat ventricular myofibroblasts revealed that TGF-β₁, applied for 24 to 48 hours at clinically relevant concentrations (≤2.5 ng/mL), causes substantial membrane depolarization concomitant with a several-fold increase of transmembrane currents. Transcriptome analysis revealed TGF-β₁-dependent changes in 29 of 63 ion channel/pump/connexin transcripts, indicating a pleiotropic effect on the electrical phenotype of myofibroblasts. Whereas not affecting cardiomyocyte membrane potentials and cardiomyocyte-cardiomyocyte gap junctional coupling, TGF-β₁ depolarized cardiomyocytes coupled to myofibroblasts by ≈20 mV and increased gap junctional coupling between myofibroblasts and cardiomyocytes >5-fold as reflected by elevated connexin 43 and consortin transcripts. TGF-β₁-dependent cardiomyocyte depolarization resulted from electrotonic crosstalk with myofibroblasts as demonstrated by immediate normalization of cardiomyocyte electrophysiology after targeted disruption of coupled myofibroblasts and by cessation of ectopic activity of cardiomyocytes coupled to myofibroblasts during pharmacological gap junctional uncoupling. In cardiac fibrosis models exhibiting slow conduction and ectopic activity, block of TGF-β₁ signaling completely abolished both arrhythmogenic conditions.

CONCLUSIONS

TGF-β₁ profoundly alters the electrophysiological phenotype of cardiac myofibroblasts. Apart from possibly contributing to the control of cell function in general, the changes proved to be pivotal for proarrhythmic myofibroblast-cardiomyocyte crosstalk in vitro, which suggests that TGF-β₁ may play a potentially important role in arrhythmogenesis of the fibrotic heart.

Propranolol Attenuates Surgical Stress-Induced Elevation of the Regulatory T Cell Response in Patients Undergoing Radical Mastectomy

Surgical stress and inflammatory response induce the release of catecholamines and PGs, which may be key factors in facilitating cancer recurrence through immunosuppression. Animal studies have suggested the efficacy of perioperative blockades of catecholamines and PGs in reducing immunosuppression. In this study, to our knowledge, we present the first report of the effects of perioperative propranolol and/or parecoxib on peripheral regulatory T cells (Tregs) in breast cancer patients. Patients were randomly assigned to control, propranolol, parecoxib, and propranolol plus parecoxib groups. We demonstrated that levels of circulating epinephrine, norepinephrine, and PGE2increased in response to surgery. Meanwhile, peripheral FOXP3 mRNA level and Treg frequencies were elevated on postoperative day 7. Propranolol administration, rather than parecoxib, attenuated such elevation of Tregs, indicating the critical roles for catecholamines in surgery-induced promotion of Tregs. Besides, propranolol plus parecoxib treatment demonstrated no additive or synergistic effects. Furthermore, a study of Treg activity on CD4(+)T cell responses to specific tumor Ags was performed in the control and propranolol groups. Propranolol abrogated the increased Treg activity and accompanying suppression of CD4(+)T cell responses after surgery. Finally, we conducted ex vivo experiments on the effects of varying concentrations of epinephrine and/or propranolol on Treg proliferation over PBMCs from breast cancer patients, to provide further direct evidence strengthening our clinical observations. Epinephrine markedly promoted Treg proliferation, whereas propranolol prevented such enhancement effect. In conclusion, our study highlights beneficial roles for propranolol in inhibiting Treg responses in vivo and in vitro, and demonstrates that propranolol could alleviate surgical stress-induced elevation of Tregs in breast cancer patients.

Signaling mechanism underlying the promotion of keratinocyte migration by angiotensin II

Re-epithelialization begins early during skin wound healing and is regulated by various growth factors and cytokines. Angiotensin II promotes the migration of keratinocytes and thereby contributes to wound healing. We investigated the mechanism by which angiotensin II stimulates human keratinocyte migration. Angiotensin II-induced keratinocyte migration was inhibited by an angiotensin II type 1 receptor (AT1R) antagonist (candesartan) or an angiotensin II type 2 receptor (AT2R) antagonist (PD123319) as well as by depletion of AT1R or AT2R. A biased agonist for AT1R, [Sar(1),Ile(4),Ile(8)]angiotensin II, induced cell migration, whereas depletion of β-arrestin2 inhibited angiotensin II-induced migration. Angiotensin II-induced migration was blocked by neutralizing antibodies to transforming growth factor-β (TGF-β) as well as by the TGF-β receptor inhibitor SB431542. The amount of TGF-β1 was increased in the culture medium of angiotensin II-treated cells, and this effect was inhibited by candesartan or PD123319. Both angiotensin II- and TGF-β-induced cell migration were inhibited by neutralizing antibodies to the epidermal growth factor (EGF) receptor but not by those to EGF receptor ligands. Angiotensin II-induced phosphorylation of the EGF receptor, and this effect was inhibited by candesartan, PD123319, SB431542, or depletion of β-arrestin2, but not by neutralizing antibodies to heparin-binding EGF-like growth factor. Our results indicate that β-arrestin-dependent signaling downstream of AT1R as well as AT2R signaling are necessary for angiotensin II-induced keratinocyte migration, and that such signaling promotes generation of the active form of TGF-β, consequent activation of the TGF-β receptor, and transactivation of the EGF receptor by the TGF-β receptor.

Cardiac intercellular communication: are myocytes and fibroblasts fair-weather friends?

The cardiac fibroblast (CF) has historically been thought of as a quiescent cell of the heart, passively maintaining the extracellular environment for the cardiomyocytes (CM), the functional cardiac cell type. The increasingly appreciated role of the CF, however, extends well beyond matrix production, governing many aspects of cardiac function including cardiac electrophysiology and contractility. Importantly, its contributions to cardiac pathophysiology and pathologic remodeling have created a shift in the field's focus from the CM to the CF as a therapeutic target in the treatment of cardiac diseases. In response to cardiac injury, the CF undergoes a pathologic phenotypic transition into a myofibroblast, characterized by contractile smooth muscle proteins and upregulation of collagens, matrix proteins, and adhesion molecules. Further, the myofibroblast upregulates expression and secretion of a variety of pro-inflammatory, profibrotic mediators, including cytokines, chemokines, and growth factors. These mediators act in both an autocrine fashion to further activate CFs, as well as in a paracrine manner on both CMs and circulating inflammatory cells to induce myocyte dysfunction and chronic inflammation, respectively. Together, cell-specific cytokine-induced effects exacerbate pathologic remodeling and progression to HF. A better understanding of this dynamic intercellular communication will lead to novel targets for the attenuation of cardiac remodeling. Current strategies aimed at targeting cytokines have been largely unsuccessful in clinical trials, lending insights into ways that such intercellular cross talk can be more effectively attenuated. This review will summarize the current knowledge regarding CF functions in the heart and will discuss the regulation and signaling behind CF-mediated cytokine production and function. We will then highlight clinical trials that have exploited cytokine cross talk in the treatment of heart failure and provide novel strategies currently under investigation that may more effectively target pathologic CF-CM communication for the treatment of cardiac disease. This review explores novel mechanisms to directly attenuate heart failure progression through inhibition of signaling downstream of pro-inflammatory cytokines that are elevated after cardiac injury.

Sympathetic inhibition of IL-6, IFN-γ, and KC/CXCL1 and sympathetic stimulation of TGF-β in spleen of early arthritic mice

OBJECTIVES

The connection between sympathetic nerve fibers and immune cells in the spleen is known. In the context of arthritis, the functional meaning of the neuroimmune contact remains unclear. From immunization until disease outbreak, the sympathetic nervous system (SNS) has a proinflammatory influence which is converted into an anti-inflammatory influence after disease outbreak. This study investigated the influence of neuronally released neurotransmitters on IFN-γ, KC (CXCL1), IL-6, and TGF-β in spleen of mice shortly after outbreak of collagen type II-induced arthritis.

METHODS

Spleens were removed when animals reached an arthritis score of 3 on a scale of 1-16 (approx. on day 32) in order to generate 0.35 mm-thick spleen slices. Spleen slices were transferred to superfusion microchambers in order to electrically induce release of sympathetic neurotransmitters. By means of this technique, the effect of physiologically released neurotransmitters was investigated on secretion of IFN-γ, KC, IL-6, and TGF-β.

RESULTS

High amounts of IFN-γ, KC, IL-6, and TGF-β were released from superfused spleen, and electrical stimulation markedly inhibited IFN-γ, KC, and IL-6 release but pronouncedly stimulated TGF-β. The adrenergic influence via β-adrenoceptors stimulated release of IL-6 and, particularly, TGF-β. However, catecholamines inhibit release of IL-6 via α1-adrenergic pathways but without any effect on TGF-β. The co-transmitter adenosine stimulated IL-6 release via A1-adenosine receptors but no influence was recognized on TGF-β.

CONCLUSION

At disease outbreak, electrically released endogenous neurotransmitters of the SNS inhibit IFN-γ, KC, and IL-6 but β-adrenergically stimulate TGF-β. This creates an anti-inflammatory milieu that might be responsible for the observed dual influence of the SNS on arthritis.

Effects of AT1- and beta-adrenergic receptor antagonists on TGF-beta1-induced fibrosis in transgenic mice

BACKGROUND

Transforming growth factor-beta1 (TGF-beta1) is involved in interstitial remodelling promoting collagen synthesis and suppressing collagen degradation by inhibition of collagenases. TGF-beta1 mediates angiotensin II-dependent effects and modulates beta1-adrenergic signalling. To study the effect of neuroendocrine antagonism on TGF-beta-induced hypertrophic and fibrotic phenotype, we treated TGF-beta1 (Cys223,225Ser) transgenic mice (TGF-beta1-TG) with either the beta1-receptor blocker metoprolol (MET), the angiotensin II type I (AT1)-receptor antagonist telmisartan (TEL) or an antibody blocking TGF-beta1 signalling (TGFbeta1-sR-Ab).

MATERIAL AND METHODS

Transforming growth factor-beta1-TG mice (8 weeks) overexpressing TGF-beta1 were treated with either TEL (10 mg kg(-1)), MET (350 mg kg(-1)) or a soluble TGF-beta1 receptor antibody (1 mg kg(-1)) for 6 weeks. Morphological analyses of interstitium and cardiomyocytes were related to expression of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) by immunoblotting and zymography.

RESULTS

In TGF-beta1-TG mice, myocardial interstitial total collagen content was fourfold elevated compared to that of controls (P < 0.05) and was lowered under the treatment with TEL (P < 0.05). Protein expression of TIMP-1 and -4 was increased in TGF-beta1-TG but inhibited by TEL (TIMP-1 and TIMP-4) and MET (TIMP-1), while collagenase activity was decreased in TGF-beta1-TG and normalized by treatment with TEL (MMP-1 and MMP-13) and MET (MMP-1) (P < 0.05). Morphometric measurements of cardiomyocyte diameter and area demonstrated similar antihypertrophic effects for all treatment groups.

CONCLUSION

The AT1-antagonist TEL reduced myocardial hypertrophy and interstitial fibrosis in TGF-beta1-TG mice by normalizing MMP/TIMP ratio. beta1-Adrenergic inhibition by MET as well as TGF-beta1 antagonism induced antihypertrophic rather than antifibrotic effects. Inhibition of both renin-angiotensin system and beta1-adrenergic system may exert different but synergistic effects to reduce myocardial remodelling.

The sympathetic nervous system modulates CD4(+)FoxP3(+) regulatory T cells via a TGF-beta-dependent mechanism

CD4(+)FoxP3(+) Tregs are essential mediators of the peripheral immune response to self-antigens. Accordingly, the homeostatic regulation of Treg activity and number would impact on the immune response to both self- and non-self antigens. Because the sympathetic nervous system (SNS) interacts chemically and physically with the central and peripheral immune system and exerts a direct influence on antigen-presenting cells and effector lymphocytes, we have investigated the effect of chemical ablation of the SNS on the number and function of peripheral Treg. Removal of murine peripheral sympathetic innervation by 6-hydroxydopamine induced an increase in splenic and lymph node CD4(+)FoxP3(+) Tregs by a TGF-beta-dependent mechanism. Further, this increase in Tregs coincides with an inhibition of the induction of experimental autoimmune encephalomyelitis. Our results demonstrate that the SNS is an important contributor to the maintenance of peripheral Treg and TGF-beta acts as a bridge between the immune system and the nervous system. Neurological events mediated by the SNS, such as a stress response, may affect the number of T cells that regulate an immune response. Additionally, targeting Tregs via the SNS may be a novel approach to the prevention or treatment of autoimmune diseases.

Surgical denervation of ocular sympathetic afferents decreases local transforming growth factor-beta and abolishes immune privilege

Mounting evidence points to a role for the sympathetic nervous system in suppressing inflammation. This role might be of specific relevance for immune privilege in the eye, where, sporadically, patients with denervated sympathetic fibers develop chronic inflammation. The present study used mice to investigate whether the robust innervation of intraocular structures by the sympathetic system plays a role in maintaining ocular immune privilege. We first performed surgical removal of the superior cervical ganglion, which supplies sympathetic fibers to the eye, and studied the immune response generated against soluble antigens or allogeneic tumor cells injected into the ocular anterior chamber under these conditions. Our results show that in the absence of functional sympathetic fibers, the eye loses its ability to prevent either the immune rejection of intraocular allogeneic tumor cells or the suppression of delayed type hypersensitivity responses against soluble antigens injected in the anterior chamber. This loss of immune privilege is accompanied by a decrease in the concentration of transforming growth factor-beta in the aqueous humor. These results suggest that immune privilege is lost in the absence of a functional sympathetic innervation of the eye, allowing intraocular immune responses to become exaggerated. We conclude that ocular sympathetic nerves are critical for the generation and maintenance of immune privilege in the eye through the facilitation of local transforming growth factor-beta production.

Role of Angiotensin II Receptor Subtypes in Conjunctival Wound Healing

PURPOSE

To investigate the role of angiotensin II (Ang II) receptor subtypes in subconjunctival injury.

METHODS

A wound-healing model was developed by subconjunctival blunt dissection in male wild-type, AT1a receptor-deficient (AT1aKO) and AT2 receptor-deficient (AT2KO) mice. Collagen deposition and cell infiltration were evaluated histologically. Expression of collagen, matrix metalloproteinase (MMP), and tissue inhibitor of metalloproteinase-1 (TIMP-1) were determined by real-time PCR.

RESULTS

Subconjunctival injury increased the infiltration of inflammatory cells, collagen deposition in the subconjunctival space, and the expression of collagen type I and type III, TIMP-1 and MMP2. In AT1aKO mice, collagen deposition, cell infiltration, and expression of collagen and TIMP-1 were inhibited, but MMP2 expression was enhanced. In contrast, in AT2KO mice, the increase in collagen deposition, cell infiltration, and expression of collagen and TIMP-1 were further enhanced.

CONCLUSIONS

These results indicate that AT1a and AT2 receptor stimulation may in addition to other mechanisms be antagonistically involved in the wound-healing process after subconjunctival injury.

Cardiac fibroblasts: at the heart of myocardial remodeling

Cardiac fibroblasts are the most prevalent cell type in the heart and play a key role in regulating normal myocardial function and in the adverse myocardial remodeling that occurs with hypertension, myocardial infarction and heart failure. Many of the functional effects of cardiac fibroblasts are mediated through differentiation to a myofibroblast phenotype that expresses contractile proteins and exhibits increased migratory, proliferative and secretory properties. Cardiac myofibroblasts respond to proinflammatory cytokines (e.g. TNFalpha, IL-1, IL-6, TGF-beta), vasoactive peptides (e.g. angiotensin II, endothelin-1, natriuretic peptides) and hormones (e.g. noradrenaline), the levels of which are increased in the remodeling heart. Their function is also modulated by mechanical stretch and changes in oxygen availability (e.g. ischaemia-reperfusion). Myofibroblast responses to such stimuli include changes in cell proliferation, cell migration, extracellular matrix metabolism and secretion of various bioactive molecules including cytokines, vasoactive peptides and growth factors. Several classes of commonly prescribed therapeutic agents for cardiovascular disease also exert pleiotropic effects on cardiac fibroblasts that may explain some of their beneficial outcomes on the remodeling heart. These include drugs for reducing hypertension (ACE inhibitors, angiotensin receptor blockers, beta-blockers), cholesterol levels (statins, fibrates) and insulin resistance (thiazolidinediones). In this review, we provide insight into the properties of cardiac fibroblasts that underscores their importance in the remodeling heart, including their origin, electrophysiological properties, role in matrix metabolism, functional responses to environmental stimuli and ability to secrete bioactive molecules. We also review the evidence suggesting that certain cardiovascular drugs can reduce myocardial remodeling specifically via modulatory effects on cardiac fibroblasts.

Cardiac hypertrophy induced by sustained β-adrenoreceptor activation: pathophysiological aspects

Cardiac hypertrophy is promoted by adrenergic over-activation and represents an independent risk factor for cardiovascular morbidity and mortality. The basic knowledge about mechanisms by which sustained adrenergic activation promotes myocardial growth, as well as understanding how structural changes in hypertrophied myocardium could affect myocardial function has been acquired from studies using an animal model of chronic systemic beta-adrenoreceptor agonist administration. Sustained beta-adrenoreceptor activation was shown to enhance the synthesis of myocardial proteins, an effect mediated via stimulation of myocardial growth factors, up-regulation of nuclear proto-oncogenes, induction of cardiac oxidative stress, as well as activation of mitogen-activated protein kinases and phosphatidylinositol 3-kinase. Sustained beta-adrenoreceptor activation contributes to impaired cardiac autonomic regulation as evidenced by blunted parasympathetically-mediated cardiovascular reflexes as well as abnormal storage of myocardial catecholamines. Catecholamine-induced cardiac hypertrophy is associated with reduced contractile responses to adrenergic agonists, an effect attributed to downregulation of myocardial beta-adrenoreceptors, uncoupling of beta-adrenoreceptors and adenylate cyclase, as well as modifications of downstream cAMP-mediated signaling. In compensated cardiac hypertrophy, these changes are associated with preserved or even enhanced basal ventricular systolic function due to increased sarcoplasmic reticulum Ca(2+) content and Ca(2+)-induced sarcoplasmic reticulum Ca(2+) release. The increased availability of Ca(2+) to maintain cardiomyocyte contraction is attributed to prolongation of the action potential due to inhibition of the transient outward potassium current as well as stimulation of the reverse mode of the Na(+)-Ca(2+) exchange. Further progression of cardiac hypertrophy towards heart failure is due to abnormalities in Ca(2+) handling, necrotic myocardial injury, and increased myocardial stiffness due to interstitial fibrosis.

Inhibition of PPAR-α activity in mice with cardiac-restricted expression of tumor necrosis factor: potential role of TGF-β/Smad3

A shift in energy substrate utilization from fatty acids to glucose has been reported in failing hearts, resulting in improved oxygen efficiency yet perhaps also contributing to a state of energy deficiency. Peroxisome proliferator-activated receptor (PPAR)-α, the principal transcriptional regulator of cardiac fatty acid β-oxidation (FAO) genes, is downregulated in heart failure, and this may contribute to reduced fatty acid utilization. Cardiomyopathic states are also accompanied by elevated levels of circulating cytokines, such as tumor necrosis factor (TNF), as well as increased local production of cytokines and profibrotic factors, such as transforming growth factor (TGF)-β. However, whether these molecular pathways directly modulate cardiac energy metabolism and PPAR-α activity is not known. Therefore, FAO capacity and FAO gene expression were determined in mice with cardiac-restricted overexpression of TNF (MHCsTNF3). MHCsTNF3 hearts had significantly lower FAO capacity and decreased expression of PPAR-α and FAO target genes compared with control hearts. Surprisingly, TNF had little effect on PPAR-α activity and FAO rates in cultured ventricular myocytes, suggesting that TNF acts indirectly on myocyte FAO in vivo. We found that TGF-β expression was upregulated in MHCsTNF3 hearts and that treatment of cultured myocytes with TGF-β significantly suppressed FAO rates and directly impaired PPAR-α activity, a result reproduced by Smad3 overexpression. This work demonstrates that TGF-β signaling pathways directly suppress PPAR-α activity and reduce FAO in cardiac myocytes, perhaps in response to locally elevated TNF. Although speculative, TGF-β-driven repair mechanisms may also include the additional benefit of limiting FAO in injured myocardium.

Altered expression of angiotensin II receptor subtypes and transforming growth factor-beta in the heart of nitrofen-induced diaphragmatic hernia in rats

The renin-angitensin system (RAS) plays an important role as a growth factor in cardiac development. Angiotensin converting enzyme is involved in converting angiotensin I to angiotensin II (Ag-II). The effects of Ag-II are mediated by two primary receptors, type 1 (AT1) and type 2 (AT2). Ag-II stimulates transforming growth factor-beta1(TGF-beta1) and acts as a potent stimulant of myocyte growth and fetal contractile protein gene transcription. The aim of this study was to determine the expression of Ag-II receptor subtypes and TGF-beta1 in the hypoplastic heart of nitrofen-induced congenital diaphragmatic hernia (CDH). CDH was induced in pregnant rats following administration of 100 mg nitrofen on day 9.5. The fetuses were divided into three groups: normal controls (n=16), nitrofen-treated without CDH (n=16), and nitrofen-induced CDH (n=16). Reverse transcriptase-polymerase chain reaction was performed to evaluate mRNA expression of AT1, AT2, and TGF-beta1. Levels of mRNA were expressed as a ratio of the band density divided by that of beta-actin. AT1 and AT2 mRNA expressions were significantly decreased in CDH heart compared with controls (0.43+/-0.33 vs. 1.0+/-0.48 and 0.62+/-0.23 vs. 1.4+/-0.43, respectively). TGF-beta1 mRNA expressions were also significantly decreased in CDH heart compared with controls (0.38+/-0.17 vs. 0.72+/-0.26). No significant difference was found between the hearts of controls and nitrofen-treated rats without CDH. The decreased expression of AT1, AT2, and TGF-beta1 mRNA in the hypoplastic heart suggests that the downregulation of RAS may be involved in the pathogenesis of cardiac hypoplasia in nitrofen-induced CDH.

Mechanisms of blood pressure variability-induced cardiac hypertrophy and dysfunction in mice with impaired baroreflex

Enhanced blood pressure variability contributes to left ventricular hypertrophy and end-organ damage, even in the absence of hypertension. We hypothesized that the greater number of high-blood pressure episodes associated with enhanced blood pressure variability causes cardiac hypertrophy and dysfunction by activation of mechanosensitive and autocrine pathways. Normotensive mice were subjected to sinoaortic baroreceptor denervation (SAD) or sham surgery. Twelve weeks later, blood pressure variability was doubled in SAD compared with sham-operated mice. Blood pressure did not differ. Cardiac hypertrophy was reflected in greater heart/body weight ratios, larger myocyte cross-sectional areas, and greater left ventricular collagen deposition. Furthermore, left ventricular atrial and brain natriuretic peptide mRNA expression was greater in SAD than in sham-operated mice. SAD had higher left ventricular end-diastolic pressures and lower myocardial contractility indexes, indicating cardiac dysfunction. Cardiac protein content of phosphorylated p125 focal adhesion kinase (p125 FAK) and phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) was greater in SAD than in sham-operated mice, indicating activation of mechanosensitive pathways of cardiac hypertrophy. Furthermore, enhanced cardiac renin and transforming growth factor-β1 (TGFbeta1) protein content indicates activation of autocrine pathways of cardiac hypertrophy. Adrenal tyrosine hydroxylase protein content and the number of renin-positive glomeruli were not different, suggesting that sympathetic activation and the systemic renin-angiotensin system did not contribute to cardiac hypertrophy. In conclusion, more frequent blood pressure rises in subjects with high blood pressure variability activate mechanosensitive and autocrine pathways leading to cardiac hypertrophy and dysfunction even in the absence of hypertension.

Sympathetic nervous system regulation of liver repair

This chapter reviews recent evidence that the sympathetic nervous system (SNS) regulates liver repair by modulating the phenotypes of hepatic stellate cells (HSCs), the liver's principal fibrogenic cells, and hepatic epithelial progenitors, i.e., oval cells. SNS nerve fibers touch HSCs and these cells express adrenoceptors, suggesting that HSCs may be targets for SNS neurotransmitters. HSCs also contain catecholamine biosynthetic enzymes, release norepinephrine (NE), and are growth-inhibited by adrenoceptor antagonists. In addition, HSCs from mice with reduced levels of NE grow poorly in culture and exhibit inhibited activation during liver injury. Finally, growth and injury-related fibrogenic responses are rescued by adrenoceptor agonists. Thus, certain SNS inhibitors (SNSIs) protect experimental animals from cirrhosis. Conversely, SNSIs enhance the hepatic accumulation of oval cells (OCs) in injured livers. This response is associated with improved liver injury. Because SNSIs do not affect the expression of cytokines, growth factors, or growth factor receptors that are known to regulate OCs, and OCs express adrenoceptors, it is conceivable that catecholamines influence OCs by direct interaction with OC adrenoceptors. Given evidence that the SNS regulates the viability and activation of HSCs and OCs differentially, SNSIs may be novel therapies to improve the repair of damaged livers.

Angiotensin converting enzyme inhibition for cardiac hypertrophy in patients with end-stage renal disease: what is the evidence?

Dialysis patients show a high prevalence of cardiovascular complications among which left ventricular hypertrophy is one of the most frequent and is independently predictive of mortality. A recent study indicates that partial regression of left ventricular hypertrophy improves mortality and reduces cardiovascular events in end-stage renal disease (ESRD) patients, suggesting the importance of targeting therapeutic strategies to reduce cardiac hypertrophy and improve the outcome in these patients. The pathogenesis of left ventricular hypertrophy in ESRD patients is multifactorial and includes hypertension, activation of the renin-angiotensin system, increased sympathetic activity, chronic volume overload, chronic anaemia and hyperparathyroidism. In this paper, we review the available experimental and clinical evidence showing the important contribution of the renin-angiotensin system as well as its interaction with the sympathetic nervous system in the pathogenesis of left ventricular hypertrophy in ESRD patients. Furthermore, we summarize the results of currently available clinical studies that examined the effects of angiotensin-converting enzyme inhibition or angiotensin receptor antagonism on left ventricular hypertrophy in ESRD patients, and review evidences that support the use of angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists in the ESRD population.

Norepinephrine-induced changes in cardiac transforming growth factor-beta isoform expression pattern of female and male rats

Transforming growth factor-beta (TGF-beta) is a ubiquitous growth-regulating protein with an essential role in tissue repair and formation of extracellular matrix (ECM). To better understand the role of different isoforms of TGF-beta in the cardiac remodeling process induced by norepinephrine (NE), the expression of TGF-beta1, TGF-beta2, and TGF-beta3 was studied and compared with the expression of collagen. NE (0.1 mg/kg. h) was intravenously infused in female and male Sprague-Dawley rats for several time periods, and freshly obtained ventricular myocardium after 1 day was dissociated into myocyte and nonmyocyte fractions. Prazosin (0.1 mg/kg x h) and metoprolol (1 mg/kg. h) were used to block alpha- and beta-adrenoceptors, respectively. After NE infusion, the three isoforms of TGF-beta were differentially induced as far as the magnitude and the time course is concerned. The increased expression of TGF-beta2 started earlier with a maximum after 12 hours and was more pronounced (10-fold elevation) than that of the other two isoforms, with a clear specificity for the left ventricle in female hearts. This specificity was also seen in male rats with 16-fold elevation of TGF-beta2 after 1 day of NE-stimulation. The increase of TGF-beta2 was significant only in the myocyte fraction obtained from female as well as from male hearts. The expression of the mRNA of all TGF-beta isoforms of collagen type I and type III, and of the matrix metalloproteinase (MMP)-2 and its inhibitor TIMP-2 was reduced predominantly by alpha-adrenoceptor blockade with prazosin. The increase in TGF-beta isoforms correlated with that of the mRNA expression of collagens, MMP-2 and TIMP-2.

Blockade of β1- and desensitization of β2-adrenoceptors reduce isoprenaline-induced cardiac fibrosis

The aim of the present study was to analyse the role of beta(1)- and beta(2)-adrenoceptors in the catecholamine-induced myocardial remodeling, especially the interstitial fibrosis. Wistar rats were subjected to a 2-week chronic isoprenaline administration (30 microg/kg/h). Rats received a concomitant treatment with the selective beta(1)-adrenoceptor antagonist, bisoprolol (50 mg/kg/day p.o.) or were chronically pretreated with the selective beta(2)-adrenoceptor agonist salbutamol (40 microg/kg/h) for 1 week to induce beta(2)-adrenoceptor desensitization. The pretreatment with salbutamol induced a 59% down-regulation of left ventricular beta(2)-adrenoceptors compared to control. The extent of the isoprenaline-induced left ventricular fibrosis was significantly reduced in both the bisoprolol and salbutamol groups compared with the control isoprenaline-treated group especially in the apical region (1.7+/-0.6% and 1.4+/-0.3% versus 6.0+/-1.3%, respectively, P<0.005). beta(1)-adrenoceptor blockade and beta(2)-adrenoceptors down-regulation provided similar protection against isoprenaline-induced cardiac interstitial fibrosis suggesting that both beta-adrenoceptors are involved in such cardiac remodeling process.

Angiotensin-converting enzyme inhibition but not beta-adrenergic blockade limits transforming growth factor-beta overexpression in acute normotensive anti-thy1 glomerulonephritis

OBJECTIVE

Recent experimental studies in chronic kidney disease have suggested that sympathicolytic drugs, similar to angiotensin II antagonism, limit renal fibrosis independent of blood pressure control. Using the model of acute and normotensive anti-thy1 glomerulonephritis, we analysed the action of beta-adrenergic blockade (as compared with angiotensin-converting enzyme inhibition) on renal overexpression of the profibrotic cytokine transforming growth factor (TGF)-beta.

METHODS

One day after induction of anti-thy1 glomerulonephritis, rats were given increasing doses of the beta-blockers metoprolol or nebivolol (0.1-fold, one-fold, 10-fold and 20-fold of the known blood pressure dose) until day 6 and the 20-fold dose until day 12. Additional animals were treated with a high dose of the angiotensin-converting enzyme inhibitor enalapril. At the end of each experiment, blood pressure and heart rate were recorded, glomerular matrix expansion was scored histologically, and protein expression of TGF-beta(1), fibronectin and plasminogen activator inhibitor-1 was determined in the supernatant of cultured glomeruli.

RESULTS

Metoprolol and nebivolol reduced heart rate in a dose-dependent manner. Blood pressure was normal in untreated animals and not significantly affected by either treatment. Compared with untreated nephritic rats, TGF-beta(1) overexpression was not significantly changed by metoprolol or nebivolol in any dose or treatment period. In contrast, TGF-beta(1) levels were significantly reduced by enalapril both 6 and 12 days after disease induction (-52 and -63%, respectively). The changes in glomerular matrix score, fibronectin and plasminogen activator inhibitor-1 production closely followed expression of TGF-beta(1).

CONCLUSIONS

In a model of acute and normotensive glomerular fibrosis, beta-adrenergic antagonism does not reduce TGF-beta overexpression, suggesting that its pressure-independent antifibrotic action may be limited to chronic renal diseases. The beneficial effect of angiotensin II inhibition even on acute matrix expansion may be a relevant mechanism as to the explanation of its superiority in treating fibrotic renal diseases.

Differential response of cardiac fibroblasts from young adult and senescent rats to ANG II

The intracardiac ANG II-forming pathway is activated in the senescent myocardium, raising the possibility of enhanced ANG II effects on cardiac fibroblasts. This study established an in vitro model of cultured cardiac fibroblasts from aged rats to examine if the response of these cells to ANG II is modified in the aged heart. Levels of mRNA encoding renin, angiotensinogen, and the AT(1) receptor subtype in cardiac fibroblasts from young adult and senescent rats were quantified by RT-PCR, net collagen production by a hydroxyproline-based assay, and transforming growth factor (TGF)-beta levels using a commercial kit. In cardiac fibroblasts from young adult rats, ANG II significantly enhanced AT(1) mRNA levels, net collagen production, and TGF-beta production. In fibroblasts from the aged myocardium, ANG II downregulated AT(1) mRNA expression, had a less pronounced effect on net collagen production, and had no effect on TGF-beta production. Such age-related modification of the response of cardiac fibroblasts to ANG II may counteract the effects of augmented intracardiac ANG II production in the senescent heart, limiting fibrogenesis.

The beta 2-adrenergic agonist salbutamol potentiates oral induction of tolerance, suppressing adjuvant arthritis and antigen-specific immunity

Therapeutic protocols for treating autoimmune diseases by feeding autoantigens during the disease process have not been very successful to date. In vitro it has been shown that beta-adrenergic agonists inhibit pro-inflammatory cytokine production and up-regulate anti-inflammatory cytokine production. We hypothesized that the protective effect of oral administration of Ag would be enhanced by oral coadministration of the beta(2)-adrenergic agonist salbutamol. Here we demonstrate that oral administration of salbutamol in combination with the Ag mycobacterial 65-kDa heat shock protein increased the efficacy of disease-suppressive tolerance induction in rat adjuvant arthritis. To study the mechanism of salbutamol in more detail, we also tested oral administration of salbutamol in an OVA tolerance model in BALB/c mice. Oral coadministration of OVA/salbutamol after immunization with OVA efficiently suppressed both cellular and humoral responses to OVA. Coadministration of salbutamol was associated with an immediate increase in IL-10, TGF-beta, and IL-1R antagonist in the intestine. The tolerizing effect of salbutamol/OVA was maintained for at least 12 wk. At this time point IFN-gamma production in Ag-stimulated splenocytes was increased in the OVA/salbutamol-treated animals. In conclusion, salbutamol can be of great clinical benefit for the treatment of autoimmune diseases by promoting oral tolerance induction.

Alterations of beta-adrenergic signaling and cardiac hypertrophy in transgenic mice overexpressing TGF-beta(1)

Transforming growth factor-beta(1) (TGF-beta(1)) promotes or inhibits cell proliferation and induces fibrotic processes and extracellular matrix production in numerous cell types. Several cardiac diseases are associated with an increased expression of TGF-beta(1) mRNA, particularly during the transition from stable cardiac hypertrophy to heart failure. In vitro studies suggest a link between TGF-beta(1) signaling and the beta-adrenergic system. However, the in vivo effects of this growth factor on myocardial tissue have been poorly identified. In transgenic mice overexpressing TGF-beta(1) (TGF-beta), we investigated the in vivo effects on cardiac morphology, beta-adrenergic signaling, and contractile function. When compared with nontransgenic controls (NTG), TGF-beta mice revealed significant cardiac hypertrophy (heart weight, 164 +/- 7 vs. 130 +/- 3 mg, P < 0.01; heart weight-to-body weight ratio, 6.8 +/- 0.3 vs. 5.1 +/- 0.1 mg/g, P < 0.01), accompanied by interstitial fibrosis. These morphological changes correlated with an increased expression of hypertrophy-associated proteins such as atrial natriuretic factor (ANF). Furthermore, overexpression of TGF-beta(1) led to alterations of beta-adrenergic signaling as myocardial beta-adrenoceptor density increased from 7.3 +/- 0.3 to 11.2 +/- 1.1 fmol/mg protein (P < 0.05), whereas the expression of beta-adrenoceptor kinase-1 and inhibitory G proteins decreased by 56 +/- 9.7% and 58 +/- 7.6%, respectively (P < 0.05). As a consequence of altered beta-adrenergic signaling, hearts from TGF-beta showed enhanced contractile responsiveness to isoproterenol stimulation. In conclusion, we conclude that TGF-beta(1) induces cardiac hypertrophy and enhanced beta-adrenergic signaling in vivo. The morphological alterations are either induced by direct effects of TGF-beta(1) or may at least in part result from increased beta-adrenergic signaling, which may contribute to excessive catecholamine stimulation during the transition from compensated hypertrophy to heart failure.

AT1 receptor blockade reduces cardiac calcineurin activity in hypertensive rats

The possible role of calcineurin in the attenuation of cardiac hypertrophy and fibrosis by blockade of the angiotensin II type 1 (AT1) receptor was investigated in Dahl salt-sensitive (DS) rats. The effect of the calcineurin inhibitor FK506 was also studied. DS rats progressively developed severe hypertension when fed a diet containing 8% NaCl from 7 weeks of age. In addition, marked cardiac hypertrophy and fibrosis were apparent and the activity of calcineurin and its mRNA expression in the myocardium was increased in these animals at 12 weeks in comparison with age-matched Dahl salt-resistant rats. The abundance of angiotensin-converting enzyme (ACE) and transforming growth factor (TGF)-beta1 mRNAs was also increased in the hearts of DS rats at 12 weeks. Treatment of DS rats with a non-antihypertensive dose of the selective AT1 receptor blocker candesartan (1 mg/kg per day) or FK506 (0.1 mg/kg per day) from 7 to 12 weeks attenuated both calcineurin activity and its mRNA expression in the heart, as well as the development of cardiac hypertrophy and fibrosis, without affecting cardiac function. Treatment with candesartan, but not FK506, prevented the upregulation of ACE and TGF-beta1 gene expression. Both candesartan and FK506 prevented the load-induced induction of fetal-type cardiac genes. These results demonstrate that AT1 receptor blockade attenuates the development of cardiac hypertrophy and fibrosis as well as the activation of calcineurin, without an antihypertensive effect, in rats with salt-sensitive hypertension. Calcineurin may be downstream from TGF-beta1 in AT1 receptor-mediated angiotensin II signaling in vivo.

The regulation of human vascular smooth muscle extracellular matrix protein production by alpha- and beta-adrenoceptor stimulation

OBJECTIVE

The sympathetic nervous system (SNS) is commonly activated in hypertension; however, the role of SNS activation in the pathogenesis of cardiovascular structural changes remains poorly defined. In particular, the effect of adrenergic stimulation on extracellular matrix (ECM) protein production by human cardiovascular cells is unknown. The present study thus investigated the direct effect of adrenergic stimulation on ECM protein production by cultured human vascular smooth muscle (VSM) cells.

METHODS AND RESULTS

Exposing human VSM cells to norepinephrine increased collagen protein production by 42%, P < 0.01, when compared to control (unstimulated) cells. This effect was mediated by the alpha1-adrenoceptor, since it was inhibited by the selective alpha1-adrenoceptor antagonist; prazosin (2 micromol/l) and reproduced by the selective alpha1-adrenoceptor agonist; phenylephrine (10 micromol/l). In contrast, beta-adrenoceptor stimulation - isoprenaline (1 micromol/l) or norepinephrine (10 micromol/l) + prazosin (2 micromol/l) - inhibited collagen production by 12%, P < 0.01. This inhibitory effect was mediated via the beta1-adrenoceptor, since it was blocked by atenolol (beta1-adrenoceptor antagonist) but not butoxamine (beta2-adrenoceptor antagonist). Fibronectin, another ECM protein, was similarly regulated by alpha- and beta-adrenoceptor stimulation. Transforming growth factor beta1 (TGFbeta1) mRNA expression by human VSM cells was also significantly influenced by adrenergic stimulation, being increased by phenylephrine (alpha-agonist) and inhibited by isoprenaline (beta-agonist).

CONCLUSIONS

These results uniquely demonstrate the capacity for adrenergic stimulation to directly modulate TGFbeta1 expression and ECM protein synthesis by the human cardiovascular system.

Stimulation of collagen production by transforming growth factor-beta1 during differentiation of cardiac fibroblasts to myofibroblasts

The aim of the present study was to elucidate how transforming growth factor-beta(1) (TGF-beta(1)) can stimulate collagen deposition in cardiac tissue by interstitial cells via stimulation of fibroblasts, via myofibroblasts, or via differentiation of fibroblasts to myofibroblasts. The dose- and time-dependent stimulation of collagen production and of expression of alpha-smooth muscle actin (alpha-SMA), a marker of myofibroblasts, was studied in cultures of second-passage adult rat cardiac fibroblasts. The TGF-beta(1)-stimulated collagen production is positively correlated (r=0.68, P<0.001) with the appearance of alpha-SMA. Only at high concentrations (40 to 600 pmol/L) and after a long time (24 to 48 hours) of incubation, TGF-beta(1) increases the collagen production and stimulates the differentiation of fibroblasts to myofibroblasts. The maximal stimulation of the collagen production (2-fold, P<0.001) observed after incubation of cultures of fibroblasts with 600 pmol/L TGF-beta(1) for 48 hours is accompanied by a maximal stimulation of alpha-SMA expression (3.5-fold, P<0.001), when cultures consist mainly of myofibroblasts. The stimulation of collagen production cannot be reversed either after additional incubation of TGF-beta(1)-stimulated second-passage cultures for 2 days or in their offspring in the next third passage after incubation for 7 days without TGF-beta(1). The increased collagen production in these third-passage cultures cannot be further stimulated by TGF-beta(1). Our data suggest that TGF-beta(1)-stimulated collagen production in cultures of adult rat cardiac ventricular fibroblasts cannot be explained by a direct stimulation of the collagen production either in fibroblasts or in myofibroblasts. Instead, TGF-beta(1) induces the differentiation of fibroblasts to myofibroblasts, which have a higher activity for collagen production than fibroblasts.

Angiotensin II-induced stimulation of collagen secretion and production in cardiac fibroblasts is mediated via angiotensin II subtype 1 receptors

The possible contributions of the angiotensin receptor subtypes 1 (AT1) and 2 (AT2) to angiotensin II (Ang II)-induced changes in collagen secretion and production were studied using the specific angiotensin AT1- and AT2-receptor antagonists telmisartan and P-186, respectively. Cardiac fibroblasts (from normal male adult rats) from passage 2 were cultured to confluency and incubated in the presence of 10(-10) to 10(-6) M Ang II in serum-free Dulbecco's MEM medium for 24 hours. Collagen production and secretion were assayed by'H-Proline incorporation; non-collagen production and secretion were also calculated. Ang II dose-dependently increased collagen secretion and production in rat adult cardiac fibroblasts in culture. Non-collagen secretion and production were also concentration-dependently increased by Ang II. Addition of 100 nmol/l Ang II increased (p<0.01) collagen secretion and production bv 75+/-6 (SEM)% and 113+/-23%, respectively, and non-collagen secretion and production by 65+/-6% and 57+/-16%, respectively. Pretreatment of cardiac fibroblasts with telmisartan completely blocked the Ang II-induced increase in collagen secretion (p<0.001) and production(p<0.05) and in non-collagen secretion (p<0.01) and production (p<0.01). P-186 had no effect on the Ang II-induced increase in collagen secretion and production. Addition of telmisartan and P-186 did not affect collagen secretion and production in basal cardiac fibroblasts. Our data demonstrate that the effects of Ang II on collagen secretion and production in adult rat cardiac fibroblasts in culture are AT1-receptor mediated, since they were abolished by the specific AT1-receptor antagonist, telmisartan, but not by the specific AT2-receptor antagonist, P-186.

Endogenous cyclic AMP-adenosine pathway regulates cardiac fibroblast growth

Our previous studies show that cardiac fibroblasts express the extracellular "cAMP-adenosine pathway," that is, the generation of adenosine from extracelluar cAMP. The goal of this study was to assess whether activation of the cAMP-adenosine pathway by stimulation of endogenous cAMP synthesis regulates cardiac fibroblast growth. Cardiac fibroblasts in 3D cultures were used as the model system. Treatment of cardiac fibroblasts with forskolin, isoproterenol, or norepinephrine increased cAMP production and extracellular levels of adenosine, and these effects were prevented by inhibition of adenylyl cyclase (2',5'-dideoxyadenosine). Treatment with forskolin, isoproterenol, or norepinephrine for 24 hours inhibited DNA synthesis ((3)H-thymidine incorporation), and this effect was enhanced by combined inhibition of adenosine deaminase (erythro-9-[2-hydroxy-3-nonyl] adenine) plus adenosine kinase (iodotubercidin). Inhibition of adenylyl cyclase or adenosine receptors (1,3-dipropyl-8-p-sulfophenylxanthine or KF17837) prevented the effects of forskolin, isoproterenol, and norepinephrine on DNA synthesis. Forskolin also inhibited protein synthesis ((3)H-leucine incorporation) and cell proliferation, and these effects were blocked by adenosine receptor antagonism. Treatment of cardiac fibroblasts with norepinephrine for >48 hours but not <48 hours increased DNA synthesis, protein synthesis, and cell number. However, blockade of adenylyl cyclase or antagonism of adenosine receptors caused norepinephrine to induce proliferation in <48 hours. Our findings indicate that the endogenous cAMP-adenosine pathway regulates cardiac fibroblast growth.

Transforming growth factor-beta(1) induces angiotensin-converting enzyme synthesis in rat cardiac fibroblasts during their differentiation to myofibroblasts

OBJECTIVES

Appearance of angiotensin-converting enzyme (ACE) in fibrotic tissue can be the result of the action either of one particular growth factor or of cross-talk between multiple factors. Transforming growth factor-beta1 (TGF-beta(1)) is an effective inducor of the differentiation of cultured fibroblasts to myofibroblasts, which are heterogeneous cells with different phenotypes. The present study investigated whether TGF-beta(1) is able to induce, in vitro, the differentiation of cultured fibroblasts to myofibroblasts with a phenotype containing ACE.

DESIGN

Adult rat cardiac ventricular fibroblasts were obtained from hearts perfused with collagenase. Cells from second passage were always used. Rat cardiac ventricular fibroblasts were incubated with TGF-beta(1) (10 ng/ml) for seven days. Cell characterisation was performed using light microscopy and indirect immunostaining. Presence of vimentin, desmin, factor VIII, alpha-smooth muscle actin, and ACE was checked with both immunostaining and Western blotting. ACE activity was measured fluorometrically with hippuryl-histidyl-leucine as substrate. Synthesis of DNA was measured as (3)H-thymidine incorporation.

RESULTS

Fibroblasts contained two types of activity of hip-his-leu degradation, namely a lisinopril-dependent activity (ACE activity) and a lisinopril-independent activity ('ACE-like' activity) which is performed by peptidase(s) other than ACE. The ACE activity constituted approximately 30% of the total activity. TGF-beta(1) induced an increase in both ACE activity and ACE protein (detected by immunoblotting) by 4.5 +/- 0.9- and 6.9 +/- 2.0-fold, respectively (p<0.05). This induction of ACE was accompanied by a profound modification of the fibroblasts phenotype, which consisted of a change in cell morphology, an enlargement of cell volume and an increase in cell protein content. TGF-beta(1) profoundly inhibited (3)H-thymidine incorporation and the number of cells in growing cultures. The induction of alpha-smooth muscle actin by TGF-beta(1) (6.8 +/- 2.8-fold increase, p<0.05) simultaneously with these modifications in cell morphology and proliferation indicates the appearance of myofibroblasts. These myofibroblasts did not contain desmin.

CONCLUSION

TGF-beta(1) is able to induce the appearance of ACE in cultures of adult rat cardiac ventricular fibroblasts. The appearance of the enzyme is accompanied by the differentiation of fibroblasts to myofibroblasts.

Interleukin-6 family of cytokines mediate angiotensin II-induced cardiac hypertrophy in rodent cardiomyocytes

This study was designed to investigate whether angiotensin II induces the interleukin (IL)-6 family of cytokines in cardiac fibroblasts and, if so, whether these cytokines can augment cardiac hypertrophy. Angiotensin II increased IL-6, leukemia inhibitory factor (LIF) and cardiotrophin-1 mRNA by 6.5-, 10.2-, and 2.0-fold, respectively, but did not affect IL-11, ciliary neurotrophic factor, or oncostatin M in cardiac fibroblasts. Enzyme-linked immunosorbent assay revealed that angiotensin II-stimulated conditioned medium from cardiac fibroblasts contained 9.3 ng/ml IL-6 at 24 h, which was 24-fold higher than the control. It phosphorylated gp130 and STAT3 in cardiomyocytes, which was reduced with RX435 (anti-gp130 blocking antibody). It increased [(3)H]phenylalanine uptake and cell area by 44% and 86% in cardiomyocytes compared with mock medium. RX435 suppressed these increases by 26% and 38%, while TAK044 (endothelin-A/B-R blocker) suppressed them by 52% and 52%, respectively. Antisense oligonucleotides against LIF and cardiotrophin-1 blocked their up-regulation, and attenuated the conditioned medium-induced increase in [(3)H]phenylalanine uptake by 21% and 13%, respectively. The combination of antisense oligonucleotides to LIF and cardiotrophin-1 decreased their uptake by 33%. These results indicated that angiotensin II induced IL-6, LIF, and cardiotrophin-1 in cardiac fibroblasts, and that these cytokines, particularly LIF and cardiotrophin-1, activated gp130-linked signaling and contributed to angiotensin II-induced cardiomyocyte hypertrophy.

Rapid effects of stretched myocardial and vascular cells on gene expression of neonatal rat cardiomyocytes with emphasis on autocrine and paracrine mechanisms

Passive stretch of the heart has a direct effect on cardiomyocytes and other cell types including cardiac fibroblasts, endothelial cells, and vascular smooth muscle cells (VSMCs). Cardiomyocytes are targets for the action of peptide growth factors found in myocardium, suggesting an autocrine or paracrine model of the hypertrophic process. In this study we examined stretch-dependent cellular communication between cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. Stationary cardiomyocytes were incubated with stretch-conditioned medium (CM0-CM60) derived from stretched (for 0-60 min) cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. The expression levels of protooncogenes (as c-fos, c-jun, and fra-1) were measured, and as an indication of a hypertrophic response the expression of atrial natriuretic peptide (ANP) was measured. Stationary cardiomyocytes that have been incubated for 30 min with CM from stretched (for 0-60 min) cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs showed distinct gene expression patterns that were time-dependent and cell-type specific. In stationary cardiomyocytes, CM derived from stretched cardiomyocytes caused decreased c-fos and fra-1 expression by 37 and 20%, respectively (CM30), elevated c-jun expression by 20% (CM45-CM60), and increased ANP expression by 106% (CM45). CM derived from stretched cardiac fibroblasts caused increased c-fos expression by 41% (CM60), no significant changes in c-jun expression, and increased fra-1 and ANP expression by 39 and 20%, respectively (CM45). CM derived from stretched VSMCs induced an initial decrease in c-fos expression followed by an increase of 13% (CM45) and induced increased c-jun, fra-1, and ANP expression by 39, 24, and 22%, respectively. CM15-CM60 derived from stretched endothelial cells caused decreased c-fos, c-jun and fra-1 expression by 20, 25, and 25%, respectively, and increased ANP expression by 18%. Our data indicate that gene expression of cardiomyocytes in stretched myocardium is regulated by mediators released by cardiomyocytes, cardiac fibroblasts, endothelial cells, and VSMCs. This observation emphasizes the involvement of nonmyocyte cells in the early stages of cardiomyocyte hypertrophy caused by cardiac stretch.

Cyclic stretch induces the release of growth promoting factors from cultured neonatal cardiomyocytes and cardiac fibroblasts

Growth factors and hormones may play an autocrine/paracrine role in mechanical stress-induced cardiac hypertrophy. Using an in vitro model of mechanical stress, i.e. stretch of cardiomyocytes and cardiac fibroblasts, we tested the involvement of growth factors and hormones in this process. We found that conditioned medium (CM) derived from 4 h cyclicly (1 Hz) stretched cardiomyocytes increased the rate of protein synthesis in static cardiomyocytes by 8 +/- 3%. Moreover, CM derived from 2 h stretched fibroblasts increased the rate of protein synthesis in static fibroblasts as well as in static cardiomyocytes by 8 +/- 2 and 6 +/- 2%, respectively. Analysis of CM using size-exclusion HPLC showed that cardiomyocytes and fibroblasts released at least three factors with MW < or = 10 kD, their quantities being time-dependently increased by stretch. Subsequent analyses using immunoassays revealed that cardiomyocytes released atrial natriuretic peptide (ANP) and transforming growth factor-beta1 (TGFbeta1) being increased by 45 +/- 17 and 21 +/- 4% upon 4 h of stretch, respectively. Fibroblasts released TGFbeta1 and very low quantity of endothelin-1 (ET-1). The release of TGFbeta1 was significantly increased by 18 +/- 4% after 24 h of stretch in fibroblasts. Both cell types released no detectable amount of angiotensin II (Ang II). In conclusion, upon cyclic stretch cardiomyocytes and fibroblasts secrete growth factors and hormones which induce growth responses in cardiomyocytes and fibroblasts in an autocrine/paracrine way. TGFbeta secreted by cardiomyocytes and fibroblasts, and ANP secreted by cardiomyocytes are likely candidates. We found no evidence for the involvement of Ang II and ET-1 in autocrine/paracrine mechanisms between cardiac cell types.

Carbohydrate availability affects ammonemia during exercise after beta 2-adrenergic blockade

PURPOSE

Beta-adrenergic blockade increases blood ammonia concentration during exercise. The purpose of this study was to assess the role of decreased carbohydrate availability in this process.

METHODS

Wistar rats (N = 47) were injected intravenously with a selective beta 2-adrenoceptor blocker (ICI 118,551), placebo, or beta 2-blocker + glucose 1 h before a treadmill exercise test. Blood samples were taken to measure the concentration of ammonia, glucose, lactic acid, free fatty acids (FFA), glycerol, branched-chain amino acids (BCAA), and muscle samples for determination of glycogen content.

RESULTS

Beta 2-adrenergic blockade shortened running time to exhaustion (23 +/- 4.3 min compared to 44 +/- 5.2 min with placebo), increased blood ammonia levels (146.7 +/- 16.21 micromol x L(-1) compared to 47.5 +/- 0.92 micromol x L(-1) with placebo) and prevented exercise-induced glycogen breakdown in soleus and gastrocnemius muscles. Pre-exercise supplementation of glucose during beta 2-blockade restored exercise-induced glycogen breakdown and reduced blood ammonia concentration during exercise (66.5 +/- 5.65 mmol x L(-1)) but did not improve exercise capacity (26 +/- 3.2 min) when compared with beta2-blockade alone.

CONCLUSION

The results suggest that the enhanced rise in blood ammonia concentration during exercise after beta-blockade is caused by impaired carbohydrate availability.

Angiotensin II and alpha(v)beta(3) integrin expression in rat neonatal cardiac fibroblasts

We recently demonstrated that alpha(v)beta(3) integrins are involved in the mechanisms of angiotensin II (Ang II)-induced DNA synthesis and collagen gel contractions in rat cardiac fibroblasts (CFBs), cellular mechanisms that are relevant for cardiac remodeling. The aim of the present study was to elucidate the effect of Ang II and other growth factors on the regulation of the alpha(v)beta(3) integrins in fibroblasts from neonatal rat hearts. The alpha(v)beta(3) integrin receptor expression was significantly increased (P<0.05) at the mRNA level after treatment with Ang II, transforming growth factor-beta(1) (TGF-beta(1)), and platelet-derived growth factor (PDGF) for 8 and 16 hours. The surface expression of the alpha(v) and beta(3) integrin subunits was elevated after 32 and 48 hours (P<0.05) as determined with flow cytometry. To investigate fibroblast motility, we performed chemotaxis experiments with transwell chambers. Ang II was chemotactic for CFBs, as tested with checkerboard experiments. The chemotactic effect was concentration dependent and was completely blocked by Ang II type 1 receptor blockers but not by Ang II type 2 receptor blocker PD 123319. Ang II- and PDGF-BB-mediated chemotaxis could be significantly inhibited by RGD peptides and the blocking antibodies against alpha(v)beta(3) integrin (both P<0.01). Adhesion of CFBs to vitronectin was partially inhibited by an antibody to alpha(v)beta(3) integrin but was mainly mediated by an alpha(v)beta(5) integrin. Relevant in vivo expression of alpha(v)beta(3) integrin by CFBs was confirmed with in situ hybridization with probes for alpha(v) and beta(3) mRNA in rat hearts. The present study demonstrates that the expression of alpha(v)beta(3) integrin is augmented by Ang II, PDGF, and TGF-beta(1) in neonatal CFBs. Furthermore, this integrin is involved in the chemotaxis, motility, and adhesion of CFBs. The present findings support the current concept that integrins participate in the control of fibroblast behavior during cardiac remodeling mechanisms.

The myocardial matrix and the development and progression of ventricular remodeling

Our conceptual framework of chronic heart failure is based upon the neurohormonal model. In this construct, neurohormonal systems that provide short-term homeostasis remain activated after a myocardial injury, producing progressive ventricular dysfunction and worsening heart failure. However, this model fails to explain several important clinical phenomena, that can be explained by an expanded model of heart failure that focuses on myocardial matrix events as the triggers for disease progression. This model embraces the neurohormonal model and integrates the roles of the immune system and the myocardial fibroblast within the matrix to more fully describe the initiation and progression of the disease.

Changes in gene expression with iron loading and chelation in cardiac myocytes and non-myocytic fibroblasts

Iron overload is associated with long-term cardiac iron accumulation and tissue changes such as fibrosis. To determine short-term iron-dependent changes in expression of genes associated with iron homeostasis and fibrosis we measured mRNA on Northern blots prepared from cultured rat neonatal cardiomyocytes and non-myocytes (fibroblasts) as a function of iron loading and chelation. Transferrin receptor mRNA was reduced in myocytes exposed to various concentrations of iron for 3 days and this decline was associated with a 63% decline in iron-response element (IRE) binding of iron regulatory protein-1, indicating that myocytes utilize IRE-dependent mechanisms to modulate gene expression. In myocytes iron caused a dose-dependent decline in mRNAs coding for transforming growth factor- beta(1)(TGF- beta(1)), biglycan, and collagen type I while plasminogen activator inhibitor-1 mRNA was unaffected by iron loading and decorin mRNA doubled. Total TGF- beta bioactivity was also decreased by iron loading. Thus, the effects of iron loading on genes related to cardiac fibrosis are gene-specific. Addition of deferoxamine for 1 day did not have any significant effect on any of these genes. Parallel changes in gene expression were exhibited by non-myocytes (fibroblasts), where chelation also decreased TGF- beta(1)mRNA and activity, and mRNA for collagen type I and biglycan, and collagen synthesis. In addition to these changes in transcripts associated with matrix formation the mRNA of the metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase was unaffected by iron loading but doubled in both cell types upon treatment with deferoxamine. These findings suggest that in both cardiac myocytes and non-myocyte fibroblasts gene expression is coupled to intracellular iron pools by gene-specific and IRE-dependent and idependent mechanisms. This linkage may influence matrix deposition, a significant component of cardiac injury.

Angiotensin converting enzyme in human synovium: increased stromal [(125)I]351A binding in rheumatoid arthritis

OBJECTIVE

To determine whether tissue angiotensin converting enzyme (ACE) is increased in synovia from patients with rheumatoid arthritis, osteoarthritis or chondromalacia patellae.

METHODS

Sections of synovia from patients with rheumatoid arthritis (n = 7), osteoarthritis (n = 7) or chondromalacia patellae (n = 6) were tested for immunoreactivity for ACE, and for binding of the ACE inhibitor [(125)I]351A. The amount of ACE was measured with computer assisted image analysis as the proportion of synovial section area occupied by ACE-immunoreactive cells, and the density of [(125)I]351A binding.

RESULTS

[(125)I]351A binding sites had characteristics of ACE and colocalised with ACE-like immunoreactivity to microvascular endothelium and fibroblast-like stromal cells in inflamed and non-inflamed human synovium. Stromal [(125)I]351A binding densities (B(eq)) and the fraction of synovial section area occupied by ACE-immunoreactivity (fractional area) were higher in synovia from patients with rheumatoid arthritis (B(eq) 28 amol/mm(2), fractional area 0.21) than from those with osteoarthritis (B(eq) 9 amol/mm(2), fractional area 0.10) or chondromalacia patellae (B(eq) 9 amol/mm(2), fractional area 0.09)(p < 0.05). Density of [(125)I]351A binding to stroma was similar to that to blood vessels in rheumatoid arthritis, but less dense than vascular binding in chondromalacia patellae and osteoarthritis. Increases in [(125)I]351A binding densities were attributable to increases in the numbers of binding sites, and were consistent with an increase in the density of ACE bearing stromal cells.

CONCLUSION

ACE is upregulated in synovial stroma in rheumatoid arthritis. Increased tissue ACE may result in increased local generation of the vasoconstrictor and mitogenic peptide angiotensin II and thereby potentiate synovial hypoxia and proliferation in rheumatoid arthritis.

Mechanism of cardiac fibrosis by angiotensin. New insight revealed by genetic engineering

Accumulating data show that excess of angiotensin II (Ang II) is involved in cardiac fibrosis. Many experimental studies suggested that Ang II induces cardiac fibrosis not by its blood pressure-raising action, but rather by a direct action on the heart. However, it has been difficult to distinguish the local and systemic actions in vivo. Recent genetic technology sheds new light on this problem. This review focuses on the recent advances and newly arising issues regarding the mechanism of Ang II-induced cardiac fibrosis.

Communication between myocytes and fibroblasts in cardiac remodeling in angiotensin chimeric mice

To characterize the mode of action of angiotensin II (Ang II) in cardiac remodeling, we generated chimeric mice that are made of both homozygous Ang II receptor type 1A gene (Agtr1a) null mutant cells and Agtr1a intact cells expressing the lacZ gene (ROSA26). Both Agtr1a null and intact myocytes and interstitial cells independently form areas that are randomly distributed throughout the heart. The distribution of ROSA26 cardiomyocytes overlaps completely with that of Ang II binding, indicating that the majority of Ang II receptors reside on cardiomyocytes. When Ang II (1 ng/g body weight/min) was infused for 2 weeks, mice developed mild to moderate hypertension. The proliferating cardiac fibroblasts identified by bromodeoxyuridine staining were present predominantly in the areas surrounded by Agtr1a intact cardiomyocytes. When control chimeric mice made of wild-type cells and ROSA26 cells (i.e., both carrying intact Agtr1a) were infused with Ang II, fibroblast proliferation was found equally in these cardiomyocyte types. When compared with Agtr1a null mutant chimeras, the control chimeras had more extensive cardiac fibrosis, most prominently in perivascular regions. Therefore, in response to Ang II, cardiac fibroblasts proliferate through both the local and systemic action of Ang II. Importantly, the former is determined by the Ang II receptor of neighboring cardiomyocytes, indicating that a communication between myocytes and fibroblasts plays an important role during Ang II-dependent cardiac remodeling.