Ac-SDKP inhibits transforming growth factor-beta1-induced differentiation of human cardiac fibroblasts into myofibroblasts

Ac-SDKP attenuates ER stress-stimulated collagen production in cardiac fibroblasts by inhibiting CHOP-mediated NF-κB expression

Inflammation and cardiac fibrosis are prevalent pathophysiologic conditions associated with hypertension, cardiac remodeling, and heart failure. Endoplasmic reticulum (ER) stress triggers the cells to activate unfolded protein responses (UPRs) and upregulate the ER stress chaperon, enzymes, and downstream transcription factors to restore normal ER function. The mechanisms that link ER stress-induced UPRs upregulation and NF-κB activation that results in cardiac inflammation and collagen production remain elusive. N-Acetyl-Ser-Asp-Lys-Pro (Ac-SDKP), a natural tetrapeptide that negatively regulates inflammation and fibrosis, has been reported. Whether it can inhibit ER stress-induced collagen production in cardiac fibroblasts remains unclear. Thus, we hypothesized that Ac-SDKP attenuates ER stress-stimulated collagen production in cardiac fibroblasts by inhibiting CHOP-mediated NF-κB expression. We aimed to study whether Ac-SDKP inhibits tunicamycin (TM)-induced ER stress signaling, NF-κB signaling, the release of inflammatory cytokine interleukin-6, and collagen production in human cardiac fibroblasts (HCFs). HCFs were pre-treated with Ac-SDKP (10 nM) and then stimulated with TM (0.25 μg/mL). We found that Ac-SDKP inhibits TM-induced collagen production by attenuating ER stress-induced UPRs upregulation and CHOP/NF-κB transcriptional signaling pathways. CHOP deletion by specific shRNA maintains the inhibitory effect of Ac-SDKP on NF-κB and type-1 collagen (Col-1) expression at both protein and mRNA levels. Attenuating ER stress-induced UPR sensor signaling by Ac-SDKP seems a promising therapeutic strategy to combat detrimental cardiac inflammation and fibrosis.

Prepared for special issue on thymosins Thymosin β4 and the anti-fibrotic switch

Wound healing involves a rapid response to the injury by circulating cells, followed by inflammation with an influx of inflammatory cells that release various factors. Soon after, cellular proliferation begins to replace the damaged cells and extracellular matrix, and then tissue remodeling restores normal tissue function. Various factors can lead to pathological wound healing when excessive and irreversible connective tissue/extracellular matrix deposition occurs, resulting in fibrosis. The process is initiated when immune cells, such as macrophages, release soluble factors that stimulate fibroblasts. TGFβ is the most well-characterized macrophage derived pro-fibrotic mediator. Other soluble mediators of fibrosis include connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), and interleukin 10 (IL-10). Thymosin β4 (Tβ4) has shown therapeutic benefit in preventing fibrosis/scarring in various animal models of fibrosis/scarring. The mechanism of action of Tβ4 appears related, in part, to a reduction in the inflammatory response, including a reduction in macrophage infiltration, decreased levels of TGFβ and IL-10, and reduced CTGF activation, resulting in both prevention of fibroblast conversion to myofibroblasts and production of normally aligned collagen fibers. The amino N-terminal end of Tβ4, SDKP (serine-aspartate-lysine-proline), appears to contain the majority of anti-fibrotic activity and has shown excellent efficacy in many animal models of fibrosis, including liver, lung, heart, and kidney fibrosis. Ac-SDKP not only prevents fibrosis but can reverse fibrosis. Unanswered questions and future directions will be presented with regard to therapeutic uses alone and in combination with already approved drugs for fibrosis.

The Role of Tβ4-POP-Ac-SDKP Axis in Organ Fibrosis

Fibrosis is a pathological process in which parenchymal cells are necrotic and excess extracellular matrix (ECM) is accumulated due to dysregulation of tissue injury repair. Thymosin β4 (Tβ4) is a 43 amino acid multifunctional polypeptide that is involved in wound healing. Prolyl oligopeptidase (POP) is the main enzyme that hydrolyzes Tβ4 to produce its derivative N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) which is found to play a role in the regulation of fibrosis. Accumulating evidence suggests that the Tβ4-POP-Ac-SDKP axis widely exists in various tissues and organs including the liver, kidney, heart, and lung, and participates in the process of fibrogenesis. Herein, we aim to elucidate the role of Tβ4-POP-Ac-SDKP axis in hepatic fibrosis, renal fibrosis, cardiac fibrosis, and pulmonary fibrosis, as well as the underlying mechanisms. Based on this, we attempted to provide novel therapeutic strategies for the regulation of tissue damage repair and anti-fibrosis therapy. The Tβ4-POP-Ac-SDKP axis exerts protective effects against organ fibrosis. It is promising that appropriate dosing regimens that rely on this axis could serve as a new therapeutic strategy for alleviating organ fibrosis in the early and late stages.

Using different geometries to modulate the cardiac fibroblast phenotype and the biomechanical properties of engineered connective tissues

Tissue engineering with human cardiac fibroblasts (CF) allows identifying novel mechanisms and anti-fibrotic drugs in the context of cardiac fibrosis. However, substantial knowledge on the influences of the used materials and tissue geometries on tissue properties and cell phenotypes is necessary to be able to choose an appropriate model for a specific research question. As there is a clear lack of information on how CF react to the mold architecture in engineered connective tissues (ECT), we first compared the effect of two mold geometries and materials with different hardnesses on the biomechanical properties of ECT. We could show that ECT, which formed around two distant poles (non-uniform model) were less stiff and more strain-resistant than ECT, which formed around a central rod (uniform model), independent of the materials used for poles and rods. Next, we investigated the cell state and could demonstrate that in the uniform versus non-uniform model, the embedded cells have a higher cell cycle activity and display a more pronounced myofibroblast phenotype. Differential gene expression analysis revealed that uniform ECT displayed a fibrosis-associated gene signature similar to the diseased heart. Furthermore, we were able to identify important relationships between cell and tissue characteristics, as well as between biomechanical tissue parameters by implementing cells from normal heart and end-stage heart failure explants from patients with ischemic or dilated cardiomyopathy. Finally, we show that the application of pro- and anti-fibrotic factors in the non-uniform and uniform model, respectively, is not sufficient to mimic the effect of the other geometry. Taken together, we demonstrate that modifying the mold geometry in tissue engineering with CF offers the possibility to compare different cellular phenotypes and biomechanical tissue properties.

RAS inhibition in resident fibroblast biology

Angiotensin II (Ang II) is a primary mediator of profibrotic signaling in the heart and more specifically, the cardiac fibroblast. Ang II-mediated cardiomyocyte hypertrophy in combination with cardiac fibroblast proliferation, activation, and extracellular matrix production compromise cardiac function and increase mortality in humans. Profibrotic actions of Ang II are mediated by increasing production of fibrogenic mediators (e.g. transforming growth factor beta, scleraxis, osteopontin, and periostin), recruitment of immune cells, and via increased reactive oxygen species generation. Drugs that inhibit Ang II production or action, collectively referred to as renin angiotensin system (RAS) inhibitors, are first line therapeutics for heart failure. Moreover, transient RAS inhibition has been found to persistently alter hypertensive cardiac fibroblast responses to injury providing a useful tool to identify novel therapeutic targets. This review summarizes the profibrotic actions of Ang II and the known impact of RAS inhibition on cardiac fibroblast phenotype and cardiac remodeling.

A long-acting isomer of Ac-SDKP attenuates pulmonary fibrosis through SRPK1-mediated PI3K/AKT and Smad2 pathway inhibition

Idiopathic pulmonary fibrosis (IPF) is a progressive, life-threatening lung disease with a poor prognosis. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a critical negative regulator of fibrosis development. However, it's extremely short half-life greatly limits its applications. Previously, we reported an Ac-SDKP analog peptide in which Asp and Lys residues were replaced with D-amino acids (Ac-SD_D K_D P). Ac-SD_D K_D P exhibits better resistance to angiotensin-1-converting enzyme (ACE)-mediated degradation and a longer half-life than Ac-SDKP in rat and human sera. The objective of this study was to explore the potential application of Ac-SD_D K_D P for the treatment of IPF and to clarify the underlying mechanisms. We found that Ac-SD_D K_D P exerted similar antifibrotic effects as Ac-SDKP on human fetal lung fibroblast-1 (HFL-1) proliferation, α-smooth muscle actin (α-SMA), collagen I and collagen III expression, and Smad-2 phosphorylation in vitro. In vivo, Ac-SD_D K_D P exhibited significantly greater protective effects against bleomycin-induced pulmonary fibrosis than Ac-SDKP in mice. α-SMA, CD45, collagen I and collagen III expression, and Smad-2 phosphorylation were significantly decreased in the lungs of Ac-SD_D K_D P-treated but not Ac-SDKP-treated mice. Furthermore, a pull-down experiment was used to screen for molecules that interact with Ac-SDKP. Co-immunoprecipitation (Co-IP) and computer-based molecular docking experiments demonstrated an interaction between Ac-SDKP or Ac-SD_D K_D P (Ac-SDKP/Ac-SD_D K_D P) and serine/arginine-rich protein-specific kinase 1 (SRPK1) that caused inhibition SRPK1-mediated phosphatidylinositol-3 kinase/ serine/threonine kinase (PIK3/AKT) signaling pathway activation and Smad2 phosphorylation and thereby attenuated lung fibrosis. Our data suggest that long-acting Ac-SD_D K_D P may potentially be an effective drug for the treatment of pulmonary fibrosis. The interacting molecule and antifibrotic mechanism of Ac-SDKP/Ac-SD_D K_D P were also identified, providing an experimental and theoretical foundation for the clinical application of the drug.

N-acetyl-seryl-aspartyl-lysyl-proline is a valuable endogenous antifibrotic peptide for kidney fibrosis in diabetes: An update and translational aspects

N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous peptide that has been confirmed to show excellent organ-protective effects. Even though originally discovered as a modulator of hemotopoietic stem cells, during the recent two decades, AcSDKP has been recognized as valuable antifibrotic peptide. The antifibrotic mechanism of AcSDKP is not yet clear; we have established that AcSDKP could target endothelial-mesenchymal transition program through the induction of the endothelial fibroblast growth factor receptor signaling pathway. Also, recent reports suggested the clinical significance of AcSDKP. The aim of this review was to update recent advances of the mechanistic action of AcSDKP and discuss translational research aspects.

The Expression of BNP, ET-1, and TGF-β1 in Myocardium of Rats with Ventricular Arrhythmias

Ventricular arrhythmia (VA) is a major component of sudden cardiac death (SCD). To investigate the expression of brain natriuretic peptide (BNP), endothelin-1 (ET-1), and transforming growth factor-beta 1 (TGF-β1) during VA, we established a rat model of VA induced by BaCl₂ solution through a microinjector pump. PD142893 (ET-1 receptor blocker) and SB431542 (TGF-β1 receptor type I blocker) were used to explore the effect of ET-1 and TGF-β1 on BNP expression in the myocardium after VA. BNP, ET-1, and TGF-β1 in rat myocardium were assayed by western blot and immunohistochemical staining for proteins, and real-time quantitative polymerase chain reaction for mRNAs. We found increased expression of BNP and ET-1 in rat myocardium that was associated with the duration of VA. However, TGF-β1 protein expression remained unchanged. Such early increases in BNP and ET-1 may be attributed to fatal arrhythmias associated with SCD, suggesting these may be novel biomarkers of this disease. After intraperitoneal injection of PD142893 and SB431542, respectively, BNP was downregulated in the myocardium of the left ventricle; however, this was abrogated by co-application of the two inhibitors. These results suggested that both ET-1 and TGF-β1, by specifically binding to their receptors, might be involved in the myocardial synthesis of BNP during VA in vivo.

N-acetyl-seryl-aspartyl-lysyl-proline treatment protects heart against excessive myocardial injury and heart failure in mice

Myocardial infarction (MI) in mice results in cardiac rupture at 4-7 days after MI, whereas cardiac fibrosis and dysfunction occur later. N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) has anti-inflammatory, anti-fibrotic, and pro-angiogenic properties. We hypothesized that Ac-SDKP reduces cardiac rupture and adverse cardiac remodeling, and improves function by promoting angiogenesis and inhibiting detrimental reactive fibrosis and inflammation after MI. C57BL/6J mice were subjected to MI and treated with Ac-SDKP (1.6 mg/kg per day) for 1 or 5 weeks. We analyzed (1) intercellular adhesion molecule-1 (ICAM-1) expression; (2) inflammatory cell infiltration and angiogenesis; (3) gelatinolytic activity; (4) incidence of cardiac rupture; (5) p53, the endoplasmic reticulum stress marker CCAAT/enhancer binding protein homology protein (CHOP), and cardiomyocyte apoptosis; (6) sarcoplasmic reticulum Ca2+ ATPase (SERCA2) expression; (7) interstitial collagen fraction and capillary density; and (8) cardiac remodeling and function. Acutely, Ac-SDKP reduced cardiac rupture, decreased ICAM-1 expression and the number of infiltrating macrophages, decreased gelatinolytic activity, p53 expression, and myocyte apoptosis, but increased capillary density in the infarction border. Chronically, Ac-SDKP improved cardiac structures and function, reduced CHOP expression and interstitial collagen fraction, and preserved myocardium SERCA2 expression. Thus, Ac-SDKP decreased cardiac rupture, ameliorated adverse cardiac remodeling, and improved cardiac function after MI, likely through preserved SERCA2 expression and inhibition of endoplasmic reticulum stress.

Tβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin β4 (Tβ4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for Tβ4 and (or) its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by 2 successive enzymes, meprin α and prolyl oligopeptidase. We also discussed the possible mechanisms involved in the Tβ4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, Tβ4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, Tβ4 and Ac-SDKP have antifibrotic and anti-inflammatory properties in the arteries, heart, lungs, and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of Tβ4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular, and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.

d-amino acid modification protects N-Acetyl-seryl-aspartyl-lysyl-proline from physiological hydroxylation and increases its antifibrotic effects on hepatic fibrosis

N-Acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a critical negative regulator of fibrosis development in the liver. However, its extremely short half-life in vivo greatly compromises its potential applications. Here, we report an Ac-SDKP analog peptide with d-amino acid replacement (Ac-SD_D K_D P). The stability of Ac-SD_D K_D P and its prevention of liver fibrosis were investigated in vitro and in vivo. The stabilities of Ac-SDKP and Ac-SD_D K_D P exposed to angiotensin-1-converting enzyme (ACE) and their half-lives in rats and human sera were determined by high-performance liquid chromatography. The inhibitory effects of Ac-SDKP and Ac-SD_D K_D P on the proliferation and activation of hepatic stellate cells (HSC-T6) were evaluated using the Cell Counting Kit-8, Western blotting, reverse transcription quantitative polymerase chain reaction, and immunofluorescence assays. Finally, the protective effects of Ac-SDKP and Ac-SD_D K_D P on carbon tetrachloride (CCl₄ )-induced liver fibrosis in rats were compared. d-Amino acid replacement significantly enhanced the stability of the peptide to ACE and prolonged the half-life of Ac-SDKP in rats and human sera. The Ac-SDKP-mediated inhibition of HSC-T6 cell proliferation was well preserved, and Ac-SD_D K_D P exerted inhibitory effects comparable to Ac-SDKP on α-smooth muscle actin (α-SMA), collagen I and III expression, and phosphorylated-Smad-2 expression. After intraperitoneal (i.p.) administration, Ac-SD_D K_D P exhibited significantly greater protection than Ac-SDKP against CCl₄ -induced liver fibrosis in rats. The serum alanine aminotransferase, aspartate aminotransferase, albumin, and total protein levels of the Ac-SD_D K_D P-treated rats were significantly lower than those of the Ac-SDKP-treated rats. α-SMA, CD45, and collagen I and III expression, as well as Smad-2 phosphorylation were significantly attenuated in the livers of the Ac-SD_D K_D P-treated rats compared to those of the Ac-SDKP-treated rats. Furthermore, we showed that the Ac-SD_D K_D P concentration in the rat liver increased to a physiological level of 60 min after i.p. administration, although i.p. administration of Ac-SDKP failed to enhance the peptide concentration in the rat liver. Our findings indicate that d-amino acid replacement is a simple and effective method to enhance the stability of Ac-SDKP. Ac-SD_D K_D P represents potential application of Ac-SDKP in fibrosis treatment and provides a new potential treatment strategy for liver fibrosis. © 2019 IUBMB Life, 71(9):1302-1312, 2019.

Renal release of N-acetyl-seryl-aspartyl-lysyl-proline is part of an antifibrotic peptidergic system in the kidney

The antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is released from thymosin-β4 (Tβ4) by the meprin-α and prolyl oligopeptidase (POP) enzymes and is hydrolyzed by angiotensin-converting enzyme (ACE). Ac-SDKP is present in urine; however, it is not clear whether de novo tubular release occurs or if glomerular filtration is the main source. We hypothesized that Ac-SDKP is released into the lumen of the nephrons and that it exerts an antifibrotic effect. We determined the presence of Tβ4, meprin-α, and POP in the kidneys of Sprague-Dawley rats. The stop-flow technique was used to evaluate Ac-SDKP formation in different nephron segments. Finally, we decreased Ac-SDKP formation by inhibiting the POP enzyme and evaluated the long-term effect in renal fibrosis. The Tβ4 precursor and the releasing enzymes meprin-α and POP were expressed in the kidneys. POP enzyme activity was almost double that in the renal medulla compared with the renal cortex. With the use of the stop-flow technique, we detected the highest Ac-SDKP concentrations in the distal nephron. The infusion of a POP inhibitor into the kidney decreased the amount of Ac-SDKP in distal nephron segments and in the proximal nephron to a minor extent. An ACE inhibitor increased the Ac-SDKP content in all nephron segments, but the increase was highest in the distal portion. The chronic infusion of a POP inhibitor increased kidney medullary fibrosis, which was prevented by Ac-SDKP. We conclude that Ac-SDKP is released by the nephron and is part of an important antifibrotic system in the kidney.

Inhibitory effect of tranilast on the myofibroblast differentiation of rat mesenchymal stem cells induced by transforming growth factor‑β1 in vitro

Mesenchymal stem cell (MSC) transplantation is able to attenuate organ fibrosis; however, increasing evidence has indicated that MSCs may be an important cell source of myofibroblasts, which are vital pathogenic cells in fibrotic diseases. The results of the present study revealed that co‑culturing with exogenous transforming growth factor (TGF)‑β1 can induce the transdifferentiation of cultured rat MSCs into myofibroblasts in vitro. Treatment of the MSCs with tranilast [N‑(3',4'‑dimethoxycinnamoyl)‑anthranilic acid] attenuated this fibrotic process. Immunocytochemical staining, western blot analysis, reverse transcription‑quantitative polymerase chain reaction analysis and cell viability assays were performed in order to evaluate the molecular mechanisms underlying the effects of tranilast on TGF‑β1‑mediated MSC‑to‑myofibroblast activation. The results demonstrated that TGF‑β1 upregulated the expression of α‑smooth muscle actin (α‑SMA) and collagen type I, and increased the phosphorylation of mothers against decapentaplegic homolog 3 (Smad3) and extracellular signal‑regulated kinase 1/2 (ERK1/2) in the rat MSCs; by contrast, tranilast pretreatment downregulated their expression. Furthermore, the proliferation of MSCs induced by TGF‑β1 was decreased by pretreatment with tranilast. In conclusion, the results of the present study demonstrated that tranilast treatment markedly suppressed the TGF‑β1‑induced differentiation of cultured rat MSCs into myofibroblasts, potentially by inhibiting the Smad3 and ERK1/2 signaling pathways. Therefore, this may be a potential antifibrotic therapeutic strategy, serving as an adjuvant treatment following transplantation of MSCs.

Influence of the interaction between Ac‑SDKP and Ang II on the pathogenesis and development of silicotic fibrosis

N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural tetrapeptide that is released from thymosin β4 by prolyl oligopeptides. It is hydrolyzed by the key enzyme of the renin-angiotensin system, angiotensin-converting enzyme (ACE). The aim of the present study was to investigate the alterations in Ac-SDKP and the ACE/angiotensin II (Ang II)/angiotensin II type 1 (AT1) receptor axis and its impact on the pathogenesis and development of silicotic fibrosis. For in vivo studies, a HOPE MED 8050 exposure control apparatus was used to establish different stages of silicosis in a rat model treated with Ac-SDKP. For in vitro studies, cultured primary lung fibroblasts were induced to differentiate into myofibroblasts by Ang II, and were pretreated with Ac-SDKP and valsartan. The results of the present study revealed that, during silicosis development, ACE/Ang II/AT1 expression in local lung tissues increased, whereas that of Ac-SDKP decreased. Ac-SDKP and the ACE/AT1/Ang II axis were inversely altered in the development of silicotic fibrosis. Ac-SDKP treatment had an anti-fibrotic effect in vivo. Compared with the silicosis group, the expression of α-smooth muscle actin (α-SMA), Collagen (Col) I, Fibronectin (Fn) and AT1 were significantly downregulated, whereas matrix metalloproteinase-1 (MMP-1) expression and the MMP-1/tissue inhibitor of metalloproteinases-1 (TIMP-1) ratio was increased in the Ac-SDKP treatment group. In vitro, pre-treatment with Ac-SDKP or valsartan attenuated the expression of α-SMA, Col I, Fn and AT1 in Ang II-induced fibroblasts. In addition, MMP-1 expression and the MMP-1/TIMP-1 ratio were significantly higher in Ac-SDKP and valsartan pre-treatment groups compared with the Ang II group. In conclusion, the results of the present study suggest that an imbalance between Ac-SDKP and ACE/Ang II/AT1 molecules promotes the development of silicosis and that Ac-SDKP protects against silicotic fibrosis by inhibiting Ang II-induced myofibroblast differentiation and extracellular matrix production.

Human cardiac fibroblasts adaptive responses to controlled combined mechanical strain and oxygen changes in vitro

Upon cardiac pathological conditions such as ischemia, microenvironmental changes instruct a series of cellular responses that trigger cardiac fibroblasts-mediated tissue adaptation and inflammation. A comprehensive model of how early environmental changes may induce cardiac fibroblasts (CF) pathological responses is far from being elucidated, partly due to the lack of approaches involving complex and simultaneous environmental stimulation. Here, we provide a first analysis of human primary CF behavior by means of a multi-stimulus microdevice for combined application of cyclic mechanical strain and controlled oxygen tension. Our findings elucidate differential human CFs responses to different combinations of the above stimuli. Individual stimuli cause proliferative effects (PHH3⁺ mitotic cells, YAP translocation, PDGF secretion) or increase collagen presence. Interestingly, only the combination of hypoxia and a simulated loss of contractility (2% strain) is able to additionally induce increased CF release of inflammatory and pro-fibrotic cytokines and matrix metalloproteinases.

DOI:http://dx.doi.org/10.7554/eLife.22847.001

When the supply of oxygen to the heart is reduced, its cells start to die within hours, the heart muscle becomes less able to contract, and the area becomes inflamed. This inflammation is accompanied by an influx of immune cells. It also activates other cells known as cardiac fibroblasts that help to break down the framework of molecules that supported the damaged heart tissue and replace it with a scar. This response is part of the normal repair process, but it can lead to the formation of scar tissue in non-damaged areas of the heart. Excess scar tissue makes the heart muscle less able to contract and increases the affected individual’s chance of dying.

Understanding how this repair process works is an important step in developing strategies to minimise the damage caused by coronary artery disease or heart attacks. However, existing laboratory models are only partly able to recreate the conditions seen in real heart tissue. To properly understand the response at the level of living cells, a more complete model is needed.

Ugolini et al. now report improvements to a small device, referred to as a lab-on-chip, that can subject cells to mechanical strain. The improvements mean the device could also recreate other conditions seen early on in damaged heart tissue, specifically the reduced supply of oxygen. Replicating combinations of mechanical changes and oxygen supplies meant that the impact of these conditions on human cardiac fibroblasts could be directly observed in the laboratory for the first time. Ugolini et al. found that a lack of contraction and low oxygen levels triggered the cardiac fibroblasts to produce inflammatory molecules and molecules associated with the formation of scar tissue. This resembles the response seen in living hearts.

The next step is to improve the lab-on-chip device further by adding other cell types, including heart muscle cells and immune cells. A more complete model may aid future research into how our hearts operate in both health and disease.

DOI:http://dx.doi.org/10.7554/eLife.22847.002

Acetylated α-Tubulin Regulated by N-Acetyl-Seryl-Aspartyl-Lysyl-Proline(Ac-SDKP) Exerts the Anti-fibrotic Effect in Rat Lung Fibrosis Induced by Silica

Silicosis is the most serious occupational disease in China. The objective of this study was to screen various proteins related to mechanisms of the pathogenesis of silicosis underlying the anti-fibrotic effect of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) using proteomic profile analysis. We also aimed to explore a potential mechanism of acetylated α-tubulin (α-Ac-Tub) regulation by Ac-SDKP. Two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) were used to assess the different protein expression profiles between control and silicosis rats treated with or without Ac-SDKP. Twenty-nine proteins were identified to be potentially involved in the progression of silicosis and the anti-fibrotic effect of Ac-SDKP. Our current study finds that 1) the lost expression of Ac-Tub-α may be a new mechanism in rat silicosis; 2) treatment of silicotic rats with N-acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) inhibits myofibroblast differentiation and collagen deposition accompanied by stabilizing the expression of α-Ac-Tub in vivo and in vitro, which is related with deacetylase family member 6 (HDAC6) and α-tubulin acetyl transferase (α-TAT1). Our data suggest that α-Ac-Tub regulation by Ac-SDKP may potentially be a new anti-fibrosis mechanism.

Effect of Antifibrotic MicroRNAs Crosstalk on the Action of N-acetyl-seryl-aspartyl-lysyl-proline in Diabetes-related Kidney Fibrosis

N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous antifibrotic peptide. We found that suppression of AcSDKP and induction of dipeptidyl peptidase-4 (DPP-4), which is associated with insufficient levels of antifibrotic microRNA (miR)s in kidneys, were imperative to understand the mechanisms of fibrosis in the diabetic kidneys. Analyzing streptozotocin (STZ)-induced diabetic mouse strains, diabetic CD-1 mice with fibrotic kidneys could be differentiated from less-fibrotic diabetic 129Sv mice by suppressing AcSDKP and antifibrotic miRs (miR-29s and miR-let-7s), as well as by the prominent induction of DPP-4 protein expression/activity and endothelial to mesenchymal transition. In diabetic CD-1 mice, these alterations were all reversed by AcSDKP treatment. Transfection studies in culture endothelial cells demonstrated crosstalk regulation of miR-29s and miR-let-7s against mesenchymal activation program; such bidirectional regulation could play an essential role in maintaining the antifibrotic program of AcSDKP. Finally, we observed that AcSDKP suppression in fibrotic mice was associated with induction of both interferon-γ and transforming growth factor-β signaling, crucial molecular pathways that disrupt antifibrotic miRs crosstalk. The present study provides insight into the physiologically relevant antifibrotic actions of AcSDKP via antifibrotic miRs; restoring such antifibrotic programs could demonstrate potential utility in combating kidney fibrosis in diabetes.

Cardioprotection by Thymosin Beta 4

Treatment with thymosin beta 4 (Tβ4) reduces infarct volume and preserves cardiac function in preclinical models of cardiac ischemic injury. These effects stem in part from decreased infarct size, but additional benefits are likely due to specific antifibrotic and proangiogenic activities. Injected or transgenic Tβ4 increase blood vessel growth in large and small animal models, consistent with Tβ4 converting hibernating myocardium to an actively contractile state following ischemia. Tβ4 and its degradation products have antifibrotic effects in in vitro assays and in animal models of fibrosis not related to cardiac injury. This large number of pleiotropic effects results from Tβ4's many interactions with cellular signaling pathways, particularly indirect regulation of cellular motility and movement via the SRF-MRTF-G-actin transcriptional pathway. Variation in effects and effect sizes in animal models may potentially be due to variable distribution of Tβ4. Preclinical studies of PK/PD relationships and a reliable pharmacodynamic biomarker would facilitate clinical development of Tβ4.

TGF-β1/FGF-2 signaling mediates the 15-HETE-induced differentiation of adventitial fibroblasts into myofibroblasts

Background

Pulmonary adventitial fibroblasts (PAFs) are activated under stress stimuli leading to their differentiation into myofibroblasts, which is involved in vessel remodeling. 15-HETE is known as an important factor in vessel remodeling under hypoxia; however, the role of 15-HETE in PAF phenotypic alteration is not clear.

Results

The effect of 15-HETE on PAF phenotypic alterations was investigated in the present study. PAFs were treated with 15-HETE (0.5 μM) for 24 h, and the myofibroblast marker α-smooth muscle actin (α-SMA) was analyzed. The 15-HETE induced α-SMA expression and cell morphology. 15-HETE upregulated FGF-2 levels in PAFs, and knockdown FGF-2 by siRNAs blocked the enhanced α-SMA expression induced by 15-HETE. p38 kinase was activated, and blocked depressed 15-HETE-induced FGF-2 expression. The downstream of p38 pathway, Egr-1 activation, was also raised by 15-HETE treatment, and silenced Egr-1 suppressed the 15-HETE-induced upregulation of FGF-2. TGF-β1 was upregulated with FGF-2 treatment, and α-SMA expression induced by FGF-2 was inhibited after the cell was transferred with TGF-β1 siRNA. Meanwhile, FGF-2 increased α-SMA expression and improved proliferation, which was associated with p27^kip1 and cyclin E variation.

Conclusions

The above results suggest that p38/Egr-1 pathway-mediated FGF-2 is involved in 15-HETE-induced differentiation of PAFs into myofibroblasts and cell proliferation.

Vascular endothelial growth factor-D mediates fibrogenic response in myofibroblasts

Vascular endothelial growth factor (VEGF)-D is a crucial mediator of angiogenesis. Following myocardial infarction (MI), cardiac VEGF-D and VEGF receptor (VEGFR)-3 are significantly upregulated. In addition to endothelial cells, myofibroblasts at the site of MI highly express VEGFR-3, implicating the involvement of VEGF-D in cardiac fibrogenesis that promotes repair and remodeling. The aim of the current study was to further explore the critical role of VEGF-D in fibrogenic response in myofibroblasts. Myofibroblast proliferation, migration, collagen synthesis, and degradation were investigated in cultured cardiac myofibroblasts subjected to VEGF-D with/without VEGFR antagonist or ERK inhibitor. Vehicle-treated cells served as controls. Myofibroblast proliferation and migration were detected by BrdU assay and Boyden Chamber method, respectively. Expression of type I collagen, metalloproteinase (MMP)-2/-9, tissue inhibitor of MMP (TIMP)-1/-2, and ERK phosphorylation were evaluated by Western blot analyses. Our results revealed that compared to controls, (1) VEGF-D significantly increased myofibroblast proliferation and migration; (2) VEGF-D significantly upregulated type I collagen synthesis in a dose- and time-dependent manner; (3) VEGFR antagonist abolished VEGF-D-induced myofibroblast proliferation and type I collagen release; (4) VEGF-D stimulated MMP-2/-9 and TIMP-1/-2 synthesis; (5) VEGF-D activated ERK phosphorylation; and (6) ERK inhibitor abolished VEGF-D-induced myofibroblast proliferation and type I collagen synthesis. Our in vitro studies have demonstrated that VEGF-D serves as a crucial profibrogenic mediator by stimulating myofibroblast growth, migration and collagen synthesis. Further studies are underway to determine the role of VEGF-D in fibrous tissue formation during cardiac repair following MI.

Persistent phenotypic shift in cardiac fibroblasts: impact of transient renin angiotensin system inhibition

Fibrotic cardiac remodeling ultimately leads to heart failure - a debilitating and costly condition. Select antihypertensive agents have been effective in reducing or slowing the development of cardiac fibrosis. Moreover, some experimental studies have shown that the reduction in fibrosis induced by these agents persists long after stopping treatment. What has not been as well investigated is whether this transient treatment results in a protection against future fibrotic cardiac remodeling. In the present review, previously published studies are re-examined to assess whether the relative percent increase in collagen deposition over an off-treatment period is attenuated, relative to control, following transient antihypertensive treatment in young or adult rats. Present findings suggest that transient inhibition of the renin angiotensin system (RAS) not only produces a sustained reduction in cardiac fibrosis, but also results in a degree of protection against future collagen deposition. In addition, prior transient RAS inhibition appears to alter the cardiac fibroblast phenotype such that these cells show a muted response to myocardial injury - namely reduced proliferation, chemokine release, and collagen deposition. This review puts forth several potential mechanisms underlying this long-term cardiac protection that is afforded by transient RAS inhibition. Specifically, fibroblast phenotypic change, cardiac fibroblast apoptosis, sustained suppression of the RAS, persistent reduction in left ventricular hypertrophy, and persistent reduction in arterial pressure are each discussed. Identifying the mechanisms ultimately responsible for this change in cardiac fibroblast response to injury, hypertension, and aging may reveal novel targets for therapy.

Erythropoietin Decreases the Occurrence of Myocardial Fibrosis by Inhibiting the NADPH-ERK-NF-x03BA;B Pathway

OBJECTIVES

The aim of this study was to investigate the protective role of erythropoietin (EPO) against myocardial fibrosis (MF).

METHODS

Pressure-overloaded rats were established by abdominal aortic constriction, the rats were randomly divided in a double-blind manner into 3 groups (n = 12 for each group): sham-operated rats (sham), operated rats receiving physiological saline (vehicle) and operated rats receiving 4,000 U/kg rhEPO (EPO group). The vehicle and drugs were administered to rats by intraperitoneal injection. In addition, cultured adult rat cardiac fibroblasts (CFs) were utilized to investigate the role of EPO in CF proliferation and collagen secretion.

RESULTS

After 4 weeks, besides an increase in blood pressure, myocardial hypertrophy, collagen deposition in the myocardium and decreased cardiac function were observed in the pressure-overloaded rats. The expression of NADPH oxidase (Nox2 and Nox4) and inflammatory cytokines (CD45, F4/80 and MCP-1) was also significantly increased. All these alterations were prevented by EPO. TGF-β promoted CF proliferation, collagen secretion, ROS production and Nox2/Nox4 expression, which was inhibited by EPO. In addition, the TGF-β-induced increase of ERK1/2 phosphorylation and NF-x03BA;B expression were attenuated by EPO.

CONCLUSION

EPO inhibited rat MF induced by pressure overload and improved myocardial function by decreasing CF proliferation and differentiation via inhibition of the NADPH-ERK-NF-x03BA;B pathway.

Structural basis of Ac-SDKP hydrolysis by Angiotensin-I converting enzyme

Angiotensin-I converting enzyme (ACE) is a zinc dipeptidylcarboxypeptidase with two active domains and plays a key role in the regulation of blood pressure and electrolyte homeostasis, making it the principal target in the treatment of cardiovascular disease. More recently, the tetrapetide N-acetyl-Ser–Asp–Lys–Pro (Ac-SDKP) has emerged as a potent antifibrotic agent and negative regulator of haematopoietic stem cell differentiation which is processed exclusively by ACE. Here we provide a detailed biochemical and structural basis for the domain preference of Ac-SDKP. The high resolution crystal structures of N-domain ACE in complex with the dipeptide products of Ac-SDKP cleavage were obtained and offered a template to model the mechanism of substrate recognition of the enzyme. A comprehensive kinetic study of Ac-SDKP and domain co-operation was performed and indicated domain interactions affecting processing of the tetrapeptide substrate. Our results further illustrate the molecular basis for N-domain selectivity and should help design novel ACE inhibitors and Ac-SDKP analogues that could be used in the treatment of fibrosis disorders.

Effects of thymosin β4 and its N-terminal fragment Ac-SDKP on TGF-β-treated human lung fibroblasts and in the mouse model of bleomycin-induced lung fibrosis

Thymosin β4 (Tβ4) and its amino-terminal fragment comprising N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) have been reported to act as anti-inflammatory and anti-fibrotic agents in vitro and in vivo. In recent papers, we have shown that Tβ4 exerts a widely protective role in mice treated with bleomycin, and in particular, we have demonstrated its inhibitory effects on both inflammation and early fibrosis.

OBJECTIVES

In this study, the putative anti-proliferative and anti-fibrogenic effects of Tβ4 and Ac-SDKP were evaluated in vitro. In addition, the effects of Tβ4 up to 21 days were evaluated in the bleomycin mouse model of lung fibrosis.

METHODS

We utilized both control and TGF-β-stimulated primary human lung fibroblasts isolated from both idiopathic pulmonary fibrosis (IPF) and control tissues. The in vivo effects of Tβ4 were assessed in CD1 mice treated with bleomycin.

RESULTS

In the in vitro experiments, we observed significant anti-proliferative effects of Ac-SDKP in IPF fibroblasts. In those cells, Ac-SDKP significantly inhibited TGF-β-induced α-SMA and collagen expression, hallmarks of fibroblast differentiation into myofibroblasts triggered by TGF-β. In vivo, despite its previously described protective role in mice treated with bleomycin at 7 days, Tβ4 failed to prevent fibrosis induced by the drug at 14 and 21 days.

CONCLUSION

We conclude that, compared to Tβ4, Ac-SDKP may have greater potential as an anti-fibrotic agent in the lung. Further in vivo experiments are warranted.

Sodium tanshinone IIA sulfonate attenuates the transforming growth factor-β1-induced differentiation of atrial fibroblasts into myofibroblasts in vitro

The differentiation of atrial fibroblasts into myofibroblasts is a critical event in atrial fibrosis. One of the most important factors in atrial fibroblast differentiation is transforming growth factor-β1 (TGF-β1). Accumulating evidence indicates that sodium tanshinone IIA sulfonate (STS) possesses antifibrotic properties. In this study, we therefore investigated whether STS attenuates the TGF-β1‑induced differentiation of atrial fibroblasts. TGF-β1 enhanced collagen production, collagen synthesis and the expression of collagen type I and III, as shown by hydroxyproline assay, collagen synthesis assay and western blot analysis, respectively. In addition, as shown by immunohistochemistry and western blot analysis, TGF-β1 enhanced the expression of α-smooth muscle actin (α-SMA), which is the hallmark of myofibroblast differentiation. These responses were attenuated by treatment with STS. In addition, STS suppressed the TGF-β1‑induced expression of phosphorylated (p)Smad/pSmad3 expression and nuclear translocation. Furthermore, STS suppressed extracellular signal-regulated kinase (ERK) phosphorylation. In conclusion, the current study demonstrates that STS exerts antifibrotic effects by modulating atrial fibroblast differentiation through ERK phosphorylation and the Smad pathway.

Large-scaled metabolic profiling of human dermal fibroblasts derived from pseudoxanthoma elasticum patients and healthy controls

Mutations in the ABC transporter ABCC6 were recently identified as cause of Pseudoxanthoma elasticum (PXE), a rare genetic disorder characterized by progressive mineralization of elastic fibers. We used an untargeted metabolic approach to identify biochemical differences between human dermal fibroblasts from healthy controls and PXE patients in an attempt to find a link between ABCC6 deficiency, cellular metabolic alterations and disease pathogenesis. 358 compounds were identified by mass spectrometry covering lipids, amino acids, peptides, carbohydrates, nucleotides, vitamins and cofactors, xenobiotics and energy metabolites. We found substantial differences in glycerophospholipid composition, leucine dipeptides, and polypeptides as well as alterations in pantothenate and guanine metabolism to be significantly associated with PXE pathogenesis. These findings can be linked to extracellular matrix remodeling and increased oxidative stress, which reflect characteristic hallmarks of PXE. Our study could facilitate a better understanding of biochemical pathways involved in soft tissue mineralization.

The biological significance of angiotensin-converting enzyme inhibition to combat kidney fibrosis

Both angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker have been recognized as renin-angiotensin system (RAS) inhibitors. These two RAS inhibitors are rarely recognized as drugs with distinct pharmacological effects in the clinic or most clinical trials. Some preclinical basic research and clinical trials indicate that ACE-I might display superior organ-protective effects, especially anti-fibrotic effects. Such anti-fibrotic effects of ACE-I could be associated with an endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). In this review, we focused on the anti-fibrotic effects of RAS inhibition and the endogenous anti-fibrotic peptide AcSDKP.

N-acetyl-seryl-aspartyl-lysyl-proline: a valuable endogenous anti-fibrotic peptide for combating kidney fibrosis in diabetes

Fibroproliferative diseases are responsible for 45% of deaths in the developed world. Curing organ fibrosis is essential for fibroproliferative diseases. Diabetic nephropathy is a common fibroproliferative disease of the kidney and is associated with multiorgan dysfunction. However, therapy to combat diabetic nephropathy has not yet been established. In this review, we discuss the novel therapeutic possibilities for kidney fibrosis in diabetes focusing on the endogenous anti-fibrotic peptide, N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), which is the substrate for angiotensin-converting enzyme and exhibits meaningful anti-fibrotic effects in various experimental models of fibrotic disease.

N-acetyl-seryl-aspartyl-lysyl-proline reduces cardiac collagen cross-linking and inflammation in angiotensin II-induced hypertensive rats

We have reported previously that Ac-SDKP (N-acetyl-seryl-aspartyl-lysyl-proline) reduces fibrosis and inflammation (in macrophages and mast cells). However, it is not known whether Ac-SDKP decreases collagen cross-linking and lymphocyte infiltration; lymphocytes modulate both collagen cross-linking and ECM (extracellular matrix) formation in hypertension. Thus we hypothesized that (i) in AngII (angiotensin II)-induced hypertension, Ac-SDKP prevents increases in cross-linked and total collagen by down-regulating LOX (lysyl oxidase), the enzyme responsible for cross-linking, and (ii) these effects are associated with decreased pro-fibrotic cytokine TGFβ (transforming growth factor β) and the pro-inflammatory transcription factor NF-κB (nuclear factor κB) and CD4+/CD8+ lymphocyte infiltration. We induced hypertension in rats by infusing AngII either alone or combined with Ac-SDKP for 3 weeks. Whereas Ac-SDKP failed to lower BP (blood pressure) or LV (left ventricular) hypertrophy, it did prevent AngII-induced increases in (i) cross-linked and total collagen, (ii) LOX mRNA expression and LOXL1 (LOX-like 1) protein, (iii) TGFβ expression, (iv) nuclear translocation of NF-κB, (v) CD4+/CD8+ lymphocyte infiltration, and (vi) CD68+ macrophages infiltration. In addition, we found a positive correlation between CD4+ infiltration and LOXL1 expression. In conclusion, the effect of Ac-SDKP on collagen cross-linking and total collagen may be due to reduced TGFβ1, LOXL1, and lymphocyte and macrophage infiltration, and its effect on inflammation could be due to lower NF-κB.

Antifibrotic effect of N-acetyl-seryl-aspartyl-lysyl-proline on bile duct ligation induced liver fibrosis in rats

AIM: To investigate the preventive effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on bile duct ligation (BDL)-induced liver fibrosis in rats.

METHODS: Liver fibrosis in rats was induced by BDL and AcSDKP was infused subcutaneously for 2 wk via a osmotic minipump (Alzet 2ML4) immediately after BDL operation. After scarifying, serum and liver specimens were collected. Hematoxylin and eosin staining, Sirius red staining, enzyme linked immunosorbent assay, Western blot or real-time polymerase chain reaction were used to determinate liver functions, histological alterations, collagen deposition, mRNA expression of markers for fibroblasts, transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-7 (BMP-7).

RESULTS: When compared to model rats, chronic exogenous AcSDKP infusion suppressed profibrogenic TGF-β1 signaling, α-smooth muscle actin positivity (α-SMA), fibroblast specific protein-1 (FSP-1) staining and collagen gene expression. Col I, Col III, matrix metalloproteinase-2, tissue inhibitors of metalloproteinase-1 and tissue inhibitors of metalloproteinase-2 mRNA expressions were all significantly downregulated by AcSDKP infusion (2.02 ± 1.10 vs 14.16 ± 6.50, 2.02 ± 0.45 vs 10.00 ± 3.35, 2.91 ± 0.30 vs 7.83 ± 1.10, 4.64 ± 1.25 vs 18.52 ± 7.61, 0.46 ± 0.16 vs 0.34 ± 0.12, respectively, P < 0.05). Chronic exogenous AcSDKP infusion attenuated BDL-induced liver injury, inflammation and fibrosis. BDL caused a remarkable increase in alanine transaminase, aspartate transaminase, total bilirubin, and prothrombin time, all of which were reduced by AcSDKP infusion. Mast cells, collagen accumulation, α-SMA, TGF-β1, FSP-1 and BMP-7 increased. The histological appearance of liver specimens was also improved.

CONCLUSION: Infusion of exogenous AcSDKP attenuated BDL-induced fibrosis in the rat liver. Preservation of AcSDKP may be a useful therapeutic approach in the management of liver fibrosis.

N-Acetyl-seryl-aspartyl-lysyl-proline inhibits ET-1-induced collagen production by preserving Src homology 2-containing protein tyrosine phosphatase-2 activity in cardiac fibroblasts

N-Acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) inhibits endothelin-1 (ET-1)-induced activation of p44/42 mitogen-activated protein kinase (p44/42 MAPK) and collagen production in cultured rat cardiac fibroblasts (RCFs). However, we do not know whether its inhibitory effect on p44/42 MAPK is due to the altered activity of protein tyrosine phosphatases (PTPs), which in turn downregulate the p44/42 MAPK signaling pathway. The activity of Src homology 2-containing protein tyrosine phosphatase-2 (SHP-2) is downregulated by ET-1 in RCFs; thus, we hypothesized that Ac-SDKP inhibits ET-1-stimulated collagen production in part by preserving SHP-2 activity and thereby inhibiting p44/42 MAPK phosphorylation. When we stimulated RCFs with ET-1 in the presence or absence of Ac-SDKP, we found that (a) PTP activity was reduced by ET-1 and (b) this effect was counteracted by Ac-SDKP in a dose-dependent fashion. Next, we extracted SHP-2 from RCF lysates by immunoprecipitation and determined that (a) ET-1 inhibited SHP-2 by 40 % and (b) this effect was prevented by Ac-SDKP. However, Ac-SDKP failed to inhibit ET-1-induced p44/42 MAPK phosphorylation in RCFs treated with SHP-2 short hairpin RNA (shRNA); in contrast, in cells transfected with control shRNA, Ac-SDKP's inhibitory effect on ET-1-induced p44/42 MAPK activation remained intact. Moreover, the inhibitory effect of Ac-SDKP on ET-1-stimulated collagen production was blunted in cells treated with the SHP-1/2 inhibitor NSC-87877. Thus, we concluded that the inhibitory effect of Ac-SDKP on ET-1-stimulated collagen production by RCFs is mediated in part by preserving SHP-2 activity and thereby preventing p44/42 MAPK activation. Ac-SDKP or its analogs could represent a new therapeutic tool to treat fibrotic diseases in the cardiovascular system.

Elevation of the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline: a blood pressure-independent beneficial effect of angiotensin I-converting enzyme inhibitors

Blockade of the renin-angiotensin system (RAS) is well recognized as an essential therapy in hypertensive, heart, and kidney diseases. There are several classes of drugs that block the RAS; these drugs are known to exhibit antifibrotic action. An analysis of the molecular mechanisms of action for these drugs can reveal potential differences in their antifibrotic roles. In this review, we discuss the antifibrotic action of RAS blockade with an emphasis on the potential importance of angiotensin I-converting enzyme (ACE) inhibition associated with the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP).

Intrapericardial procedures for cardiac regeneration by stem cells: need for minimal invasive access (AttachLifter) to the normal pericardial cavity

In view of the only modest functional and anatomical improvements achieved by bone marrow-derived cell transplantation in patients with heart disease, the question was addressed whether the intracoronary, transcoronary-venous, and intramyocardial delivery routes are adequate. It is hypothesized that an intrapericardial delivery of stem cells or activators of resident cardiac stem cells increases therapeutic benefits. From such an intrapericardial depot, cells or modulating factors, such as thymosin β4 or Ac-SDKP, are expected to reach the myocardium with sustained kinetics. Novel tools which provide access to the pericardial space even in the absence of pericardial effusion are, therefore, described. When the pericardium becomes attached to the suction head (monitored by an increase in negative pressure), the pericardium is lifted from the epicardium ("AttachLifter"). The opening of the suction head ("Attacher") is narrowed by flexible clamps which grab the tissue and improve the vacuum seal in the case of uneven tissue. A ridge, i.e.,"needle guidance", on the suction head excludes injury to the epicardium, whereby the pericardium is punctured by a needle which resides outside the suction head. A fiberscope can be used to inspect the pericardium prior to puncture. Based on these procedures, the role of the pericardial space and the presence of pericardial effusion in cardiac regeneration can be assessed.

Protein NMR in biomedical research

Nuclear magnetic resonance (NMR) spectroscopy is a versatile biophysical technique with wide applicability in drug discovery research, particularly for the detection and characterization of molecular interactions. This review highlights in a comprehensive manner the aspects of biomolecular NMR which are most beneficial for pharmaceutical research and presents them as contributions to the different stages of a drug discovery program: target selection, assay development, lead generation and lead optimization. Emphasis is put on the concept of the particular NMR application, rather than on technical details, and on recent examples. Finally, an appendix of frequently asked questions is given.