A TRPC6-dependent pathway for myofibroblast transdifferentiation and wound healing in vivo

Cardiac myofibroblast engulfment of dead cells facilitates recovery after myocardial infarction

Myocardial infarction (MI) results in the generation of dead cells in the infarcted area. These cells are swiftly removed by phagocytes to minimize inflammation and limit expansion of the damaged area. However, the types of cells and molecules responsible for the engulfment of dead cells in the infarcted area remain largely unknown. In this study, we demonstrated that cardiac myofibroblasts, which execute tissue fibrosis by producing extracellular matrix proteins, efficiently engulf dead cells. Furthermore, we identified a population of cardiac myofibroblasts that appears in the heart after MI in humans and mice. We found that these cardiac myofibroblasts secrete milk fat globule-epidermal growth factor 8 (MFG-E8), which promotes apoptotic engulfment, and determined that serum response factor is important for MFG-E8 production in myofibroblasts. Following MFG-E8-mediated engulfment of apoptotic cells, myofibroblasts acquired antiinflammatory properties. MFG-E8 deficiency in mice led to the accumulation of unengulfed dead cells after MI, resulting in exacerbated inflammatory responses and a substantial decrease in survival. Moreover, MFG-E8 administration into infarcted hearts restored cardiac function and morphology. MFG-E8-producing myofibroblasts mainly originated from resident cardiac fibroblasts and cells that underwent endothelial-mesenchymal transition in the heart. Together, our results reveal previously unrecognized roles of myofibroblasts in regulating apoptotic engulfment and a fundamental importance of these cells in recovery from MI.

ADP-Induced Ca2+ Signaling and Proliferation of Rat Ventricular Myofibroblasts Depend on Phospholipase C-Linked TRP Channels Activation Within Lipid Rafts

Nucleotides released during heart injury affect myocardium electrophysiology and remodeling through P2 purinoceptors activation in cardiac myofibroblasts. ATP and UTP endorse [Ca²⁺ ]_i accumulation and growth of DDR-2/α-SMA-expressing myofibroblasts from adult rat ventricles via P2Y₄ and P2Y₂ receptors activation, respectively. Ventricular myofibroblasts also express ADP-sensitive P2Y₁ , P2Y₁₂ , and P2Y₁₃ receptors as demonstrated by immunofluorescence confocal microscopy and western blot analysis, but little information exists on ADP effects in these cells. ADP (0.003-3 mM) and its stable analogue, ADPßS (100 μM), caused fast [Ca²⁺ ]_i transients originated from thapsigargin-sensitive internal stores, which partially declined to a plateau sustained by capacitative Ca²⁺ entry through transient receptor potential (TRP) channels inhibited by 2-APB (50 μM) and flufenamic acid (100 μM). Hydrophobic interactions between G_q/11 -coupled P2Y purinoceptors and TRP channels were suggested by prevention of the ADP-induced [Ca²⁺ ]_i plateau following PIP₂ depletion with LiCl (10 mM) and cholesterol removal from lipid rafts with methyl-ß-cyclodextrin (2 mM). ADP [Ca²⁺ ]_i transients were insensitive to P2Y₁ , P2Y₁₂ , and P2Y₁₃ receptor antagonists, MRS2179 (10μM), AR-C66096 (0.1 μM), and MRS2211 (10μM), respectively, but were attenuated by suramin and reactive blue-2 (100 μM) which also blocked P2Y₄ receptors activation by UTP. Cardiac myofibroblasts growth and type I collagen production were favored upon activation of MRS2179-sensitive P2Y₁ receptors with ADP or ADPßS (30 μM). In conclusion, ADP exerts a dual role on ventricular myofibroblasts: [Ca²⁺ ]_i transients are mediated by fast-desensitizing P2Y₄ receptors, whereas the pro-fibrotic effect of ADP involves the P2Y₁ receptor activation. Data also show that ADP-induced capacitative Ca²⁺ influx depends on phospholipase C-linked TRP channels opening in lipid raft microdomains. J. Cell. Physiol. 232: 1511-1526, 2017. © 2016 Wiley Periodicals, Inc.

Aristoyunnolin H attenuates extracellular matrix secretion in cardiac fibroblasts by inhibiting calcium influx

Aristoyunnolin H is a novel aristophyllene sesquiterpenoid isolated from the traditional Chinese medicine Aristolochia yunnanensis Franch. The present research was designed to explore the anti-fibrotic effects of aristoyunnolin H in adult rat cardiac fibroblasts (CFs) stimulated with angiotensin II (Ang II). Western blot analysis data showed that aristoyunnolin H reduced the upregulation of fibronectin (FN), connective tissue growth factor and collagen I(Col I) production induced by Ang II in CFs. By studying the dynamic intracellular changes of Ca²⁺, we further found that while aristoyunnolin H relieved the calcium influx, it has no effect on intracellular calcium store release. Meanwhile, aristoyunnolin H also inhibited the Ang II-stimulated phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II. In conclusion, aristoyunnolin H may attenuate extracellular matrix secretion in vitro by inhibiting Ang II-induced calcium signaling.

Altered physiological functions and ion currents in atrial fibroblasts from patients with chronic atrial fibrillation

The contribution of human atrial fibroblasts to cardiac physiology and pathophysiology is poorly understood. Fibroblasts may contribute to arrhythmogenesis through fibrosis, or by directly altering electrical activity in cardiomyocytes. The objective of our study was to uncover phenotypic differences between cells from patients in sinus rhythm (SR) and chronic atrial fibrillation (AF), with special emphasis on electrophysiological properties. We isolated fibroblasts from human right atrial tissue for patch-clamp experiments, proliferation, migration, and differentiation assays, and gene expression profiling. In culture, proliferation and migration of AF fibroblasts were strongly impaired but differentiation into myofibroblasts was increased. This was associated with a higher number of AF fibroblasts expressing functional Nav1.5 channels. Strikingly Na(+) currents were considerably larger in AF cells. Blocking Na(+) channels in culture with tetrodotoxin did not affect proliferation, migration, or differentiation in neither SR nor AF cells. While freshly isolated fibroblasts showed mostly weak rectifier currents, fibroblasts in culture developed outward rectifier K(+) currents of similar amplitude between the SR and AF groups. Adding the K(+) channel blockers tetraethylammonium and 4-aminopyridin in culture reduced current amplitude and inhibited proliferation in the SR group only. Analysis of gene expression revealed significant differences between SR and AF in genes encoding for ion channels, collagen, growth factors, connexins, and cadherins. In conclusion, this study shows that under AF conditions atrial fibroblasts undergo phenotypic changes that are revealed in culture. Future experiments should be performed in situ to understand the nature of those changes and whether they affect cardiac electrical activity.

Myofibroblasts and inflammatory cells as players of cardiac fibrosis

On myocardial infarction, many cells are injured or died owing to arterial occlusion. Intracellular molecules released from injured or dead cells initiate inflammatory responses that play important roles in cardiac remodeling including fibrosis. Fibrosis is an excess accumulation of extracellular collagen. Currently, drugs used to treat cardiac fibrosis are not commercially available. Myofibroblasts are responsible for the production and secretion of collagen. Infiltrating inflammatory cells interact with fibroblasts or other cells and promote myofibroblast formation. Inflammatory cells also modulate the activities of myofibroblasts. Regulation of collagen production is critical for modulating the progression of fibrosis. Hence, the manipulation of activities of inflammatory cells and myofibroblasts will provide promising therapeutic targets for treatment of cardiac fibrosis.

Tadalafil Treatment Delays the Onset of Cardiomyopathy in Dystrophin-Deficient Hearts

Background

Cardiomyopathy is a leading cause of mortality among Duchenne muscular dystrophy patients and lacks effective therapies. Phosphodiesterase type 5 is implicated in dystrophic pathology, and the phosphodiesterase type 5 inhibitor tadalafil has recently been studied in a clinical trial for Duchenne muscular dystrophy.

Methods and Results

Tadalafil was evaluated for the prevention of cardiomyopathy in the mdx mouse and golden retriever muscular dystrophy dog models of Duchenne muscular dystrophy. Tadalafil blunted the adrenergic response in mdx hearts during a 30‐minute dobutamine challenge, which coincided with cardioprotective signaling, reduced induction of μ‐calpain levels, and decreased sarcomeric protein proteolysis. Dogs with golden retriever muscular dystrophy began daily tadalafil treatment prior to detectable cardiomyopathy and demonstrated preserved cardiac function, as assessed by echocardiography and magnetic resonance imaging at ages 18, 21, and 25 months. Tadalafil treatment improved golden retriever muscular dystrophy histopathological features, decreased levels of the cation channel TRPC6, increased total threonine phosphorylation status of TRPC6, decreased m‐calpain levels and indicators of calpain target proteolysis, and elevated levels of utrophin. In addition, we showed that Duchenne muscular dystrophy patient myocardium exhibited increased TRPC6, m‐calpain, and calpain cleavage products compared with control human myocardium.

Conclusions

Prophylactic use of tadalafil delays the onset of dystrophic cardiomyopathy, which is likely attributed to modulation of TRPC6 levels and permeability and inhibition of protease content and activity. Consequently, phosphodiesterase type 5 inhibition is a candidate therapy for slowing the development of cardiomyopathy in Duchenne muscular dystrophy patients.

Molecular networks underlying myofibroblast fate and fibrosis

Fibrotic remodeling is a hallmark of most forms of cardiovascular disease and a strong prognostic indicator of the advancement towards heart failure. Myofibroblasts, which are a heterogeneous cell-type specialized for extracellular matrix (ECM) secretion and tissue contraction, are the primary effectors of the heart's fibrotic response. This review is focused on defining myofibroblast physiology, its progenitor cell populations, and the core signaling network that orchestrates myofibroblast differentiation as a way of understanding the basic determinants of fibrotic disease in the heart and other tissues.

Activin A stimulates the proliferation and differentiation of cardiac fibroblasts via the ERK1/2 and p38-MAPK pathways

Activin A is a key regulator of cardiac fibrosis. However, little is known about the mechanisms by which it contributes to cardiac fibrosis. Our study explored the effects of activin A on proliferation and differentiation of adult rat cardiac fibroblasts (CFs) via the activin A receptor, activin receptor-like kinase 4 (ALK4). CF proliferation was measured by CCK8 and EdU assays, while differentiation, fibrosis and signaling were measured by western blot analysis of α-smooth muscle actin, collagen type I, phosphorylated extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (p38-MAPK) expression. Activin A levels were measured by ELISA and western blot analysis. We demonstrated that CFs express activin A and its expression was significantly enhanced by angiotensin II (Ang II), but follistatin (activin A inhibitor) significantly reversed Ang II-induced activin A upregulation, CF proliferation, differentiation, collagen type I expression as well as ERK1/2 and p38-MAPK pathways activation. Conversely, recombinant activin A largely increased these parameters in both the presence and absence of Ang II. Interestingly, p38-MAPK (SB203580) and ALK4 (SB431542) inhibitors significantly reduced all activin A-mediated responses; however, an ERK1/2 inhibitor (PD98059) could only significantly reduce CF proliferation and collagen type I expression but not differentiation. Importantly, the most significant effects were observed in the presence vs. absence of Ang II. Thus, activin A promotes basal and Ang II-induced CF proliferation and differentiation via ALK4, and the effects are partly mediated through the ERK1/2 and p38-MAPK pathways. These data suggest that activin A is a potential therapeutic target for cardiac fibrosis.

Cardiac Mechano-Gated Ion Channels and Arrhythmias

Mechanical forces will have been omnipresent since the origin of life, and living organisms have evolved mechanisms to sense, interpret, and respond to mechanical stimuli. The cardiovascular system in general, and the heart in particular, is exposed to constantly changing mechanical signals, including stretch, compression, bending, and shear. The heart adjusts its performance to the mechanical environment, modifying electrical, mechanical, metabolic, and structural properties over a range of time scales. Many of the underlying regulatory processes are encoded intracardially and are, thus, maintained even in heart transplant recipients. Although mechanosensitivity of heart rhythm has been described in the medical literature for over a century, its molecular mechanisms are incompletely understood. Thanks to modern biophysical and molecular technologies, the roles of mechanical forces in cardiac biology are being explored in more detail, and detailed mechanisms of mechanotransduction have started to emerge. Mechano-gated ion channels are cardiac mechanoreceptors. They give rise to mechano-electric feedback, thought to contribute to normal function, disease development, and, potentially, therapeutic interventions. In this review, we focus on acute mechanical effects on cardiac electrophysiology, explore molecular candidates underlying observed responses, and discuss their pharmaceutical regulation. From this, we identify open research questions and highlight emerging technologies that may help in addressing them.

Old dog, new tricks: novel cardiac targets and stress regulation by protein kinase G

The second messenger cyclic guanosine 3'5' monophosphate (cGMP) and its downstream effector protein kinase G (PKG) have been discovered more than 40 years ago. In vessels, PKG1 induces smooth muscle relaxation in response to nitric oxide signalling and thus lowers systemic and pulmonary blood pressure. In platelets, PKG1 stimulation by cGMP inhibits activation and aggregation, and in experimental models of heart failure (HF), PKG1 activation by inhibiting cGMP degradation is protective. The net effect of the above-mentioned signalling is cardiovascular protection. Yet, while modulation of cGMP-PKG has entered clinical practice for treating pulmonary hypertension or erectile dysfunction, translation of promising studies in experimental HF to clinical success has failed thus far. With the advent of new technologies, novel mechanisms of PKG regulation, including mechanosensing, redox regulation, protein quality control, and cGMP degradation, have been discovered. These novel, non-canonical roles of PKG1 may help understand why clinical translation has disappointed thus far. Addressing them appears to be a requisite for future, successful translation of experimental studies to the clinical arena.

Regeneration of pancreatic insulin-producing cells by in situ adaptive cell conversion

The impaired ability to produce or respond to insulin, a hormone synthetized by the pancreatic β-cells, leads to diabetes. There is an excruciating need of finding new approaches to protect or restore these cells once they are lost. Replacement and ex vivo directed reprogramming methods have an undeniable therapeutic potential, yet they exhibit crucial flaws. The in vivo conversion of adult cells to functional insulin-producing cells is a promising alternative for regenerative treatments in diabetes. The stunning natural transdifferentiation potential of the adult endocrine pancreas was recently uncovered. Modulating molecular targets involved in β-cell fate maintenance or in general differentiation mechanisms can further potentiate this intrinsic cell plasticity, which leads to insulin production reconstitution.

TRPA1 is functionally co-expressed with TRPV1 in cardiac muscle: Co-localization at z-discs, costameres and intercalated discs

Transient receptor potential channels of the ankyrin subtype-1 (TRPA1) and vanilloid subtype-1 (TRPV1) are structurally related, non-selective cation channels that show a high permeability to calcium. Previous studies indicate that TRP channels play a prominent role in the regulation of cardiovascular dynamics and homeostasis, but also contribute to the pathophysiology of many diseases and disorders within the cardiovascular system. However, no studies to date have identified the functional expression and/or intracellular localization of TRPA1 in primary adult mouse ventricular cardiomyocytes (CMs). Although TRPV1 has been implicated in the regulation of cardiac function, there is a paucity of information regarding functional expression and localization of TRPV1 in adult CMs. Our current studies demonstrate that TRPA1 and TRPV1 ion channels are co-expressed at the protein level in CMs and both channels are expressed throughout the endocardium, myocardium and epicardium. Moreover, immunocytochemical localization demonstrates that both channels predominantly colocalize at the Z-discs, costameres and intercalated discs. Furthermore, specific TRPA1 and TRPV1 agonists elicit dose-dependent, transient rises in intracellular free calcium concentration ([Ca²⁺]_i) that are abolished in CMs obtained from TRPA1^−/− and TRPV1^−/− mice. Similarly, we observed a dose-dependent attenuation of the TRPA1 and TRPV1 agonist-induced increase in [Ca²⁺]_i when WT CMs were pretreated with increasing concentrations of selective TRPA1 or TRPV1 channel antagonists. In summary, these findings demonstrate functional expression and the precise ultrastructural localization of TRPA1 and TRPV1 ion channels in freshly isolated mouse CMs. Crosstalk between TRPA1 and TRPV1 may be important in mediating cellular signaling events in cardiac muscle.

Cardiac Fibrosis: The Fibroblast Awakens

Myocardial fibrosis is a significant global health problem associated with nearly all forms of heart disease. Cardiac fibroblasts comprise an essential cell type in the heart that is responsible for the homeostasis of the extracellular matrix; however, upon injury, these cells transform to a myofibroblast phenotype and contribute to cardiac fibrosis. This remodeling involves pathological changes that include chamber dilation, cardiomyocyte hypertrophy and apoptosis, and ultimately leads to the progression to heart failure. Despite the critical importance of fibrosis in cardiovascular disease, our limited understanding of the cardiac fibroblast impedes the development of potential therapies that effectively target this cell type and its pathological contribution to disease progression. This review summarizes current knowledge regarding the origins and roles of fibroblasts, mediators and signaling pathways known to influence fibroblast function after myocardial injury, as well as novel therapeutic strategies under investigation to attenuate cardiac fibrosis.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Transcriptional control of cardiac fibroblast plasticity

Cardiac fibroblasts help maintain the normal architecture of the healthy heart and are responsible for scar formation and the healing response to pathological insults. Various genetic, biomechanical, or humoral factors stimulate fibroblasts to become contractile smooth muscle-like cells called myofibroblasts that secrete large amounts of extracellular matrix. Unfortunately, unchecked myofibroblast activation in heart disease leads to pathological fibrosis, which is a major risk factor for the development of cardiac arrhythmias and heart failure. A better understanding of the molecular mechanisms that control fibroblast plasticity and myofibroblast activation is essential to develop novel strategies to specifically target pathological cardiac fibrosis without disrupting the adaptive healing response. This review highlights the major transcriptional mediators of fibroblast origin and function in development and disease. The contribution of the fetal epicardial gene program will be discussed in the context of fibroblast origin in development and following injury, primarily focusing on Tcf21 and C/EBP. We will also highlight the major transcriptional regulatory axes that control fibroblast plasticity in the adult heart, including transforming growth factor β (TGFβ)/Smad signaling, the Rho/myocardin-related transcription factor (MRTF)/serum response factor (SRF) axis, and Calcineurin/transient receptor potential channel (TRP)/nuclear factor of activated T-Cell (NFAT) signaling. Finally, we will discuss recent strategies to divert the fibroblast transcriptional program in an effort to promote cardiomyocyte regeneration. This article is a part of a Special Issue entitled "Fibrosis and Myocardial Remodeling".

The Living Scar--Cardiac Fibroblasts and the Injured Heart

Cardiac scars, often dubbed 'dead tissue', are very much alive, with heterocellular activity contributing to the maintenance of structural and mechanical integrity following heart injury. To form a scar, non-myocytes such as fibroblasts are recruited from intra- and extra-cardiac sources. Fibroblasts perform important autocrine and paracrine signaling functions. They also establish mechanical and, as is increasingly evident, electrical junctions with other cells. While fibroblasts were previously thought to act simply as electrical insulators, they may be electrically connected among themselves and, under some circumstances, to other cells including cardiomyocytes. A better understanding of these biophysical interactions will help to target scar structure and function, and will facilitate the development of novel therapies aimed at modifying scar properties for patient benefit.

The Role of Cell Plasticity in Tissue Repair: Adaptive Cellular Reprogramming

It is becoming clear that a radical change of cell identity of differentiated cells in vivo, triggered by injury or other adversity, provides an essential route to recovery for many different mammalian tissues. This process, which we term adaptive cellular reprogramming, promotes regeneration in one of two ways: by providing a transient class of repair cells or by directly replacing cells lost during tissue damage. Controlling adaptive changes in cell fate in vivo in order to promote the body's own cell therapy, particularly by pharmacology rather than genetics, is likely to become an increasingly active area of future work.

Second Messenger-Operated Calcium Entry Through TRPC6

Canonical transient receptor potential 6 (TRPC6) proteins assemble into heteromultimeric structures forming non-selective cation channels. In addition, many TRPC6-interacting proteins have been identified like some enzymes, channels, pumps, cytoskeleton-associated proteins, immunophilins, or cholesterol-binding proteins, indicating that TRPC6 are engaged into macromolecular complexes. Depending on the cell type and the experimental conditions used, TRPC6 activity has been reported to be controlled by diverse modalities. For instance, the second messenger diacylglycerol, store-depletion, the plant extract hyperforin or H2O2 have all been shown to trigger the opening of TRPC6 channels. A well-characterized consequence of TRPC6 activation is the elevation of the cytosolic concentration of Ca(2+). This latter response can reflect the entry of Ca(2+) through open TRPC6 channels but it can also be due to the Na(+)/Ca(2+) exchanger (operating in its reverse mode) or voltage-gated Ca(2+) channels (recruited in response to a TRPC6-mediated depolarization). Although TRPC6 controls a diverse array of biological functions in many tissues and cell types, its pathophysiological functions are far from being fully understood. This chapter covers some key features of TRPC6, with a special emphasis on their biological significance in kidney and blood cells.

MBNL1-mediated regulation of differentiation RNAs promotes myofibroblast transformation and the fibrotic response

The differentiation of fibroblasts into myofibroblasts mediates tissue wound healing and fibrotic remodelling, although the molecular programme underlying this process remains poorly understood. Here we perform a genome-wide screen for genes that control myofibroblast transformation, and identify the RNA-binding protein muscleblind-like1 (MBNL1). MBNL1 overexpression promotes transformation of fibroblasts into myofibroblasts, whereas loss of Mbnl1 abrogates transformation and impairs the fibrotic phase of wound healing in mouse models of myocardial infarction and dermal injury. Mechanistically, MBNL1 directly binds to and regulates a network of differentiation-specific and cytoskeletal/matrix-assembly transcripts to promote myofibroblast differentiation. One of these transcripts is the nodal transcriptional regulator serum response factor (SRF), whereas another is calcineurin Aβ. CRISPR-Cas9-mediated gene-editing of the MBNL1-binding site within the Srf 3′UTR impairs myofibroblast differentiation, whereas in vivo deletion of Srf in fibroblasts impairs wound healing and fibrosis. These data establish a new RNA-dependent paradigm for myofibroblast formation through MBNL1.

Fibroblast-to-myofibroblast differentiation is crucial for wound healing and regeneration. Davis et al. describe a new regulatory mechanism underlying myofibroblast differentiation via the RNA-binding protein MBNL1, which promotes the maturation of certain mRNA transcripts that are integral nodes in fibroblast differentiation.

Low intensity 635 nm diode laser irradiation inhibits fibroblast-myofibroblast transition reducing TRPC1 channel expression/activity: New perspectives for tissue fibrosis treatment

BACKGROUND AND OBJECTIVE

Low-level laser therapy (LLLT) or photobiomodulation therapy is emerging as a promising new therapeutic option for fibrosis in different damaged and/or diseased organs. However, the anti-fibrotic potential of this treatment needs to be elucidated and the cellular and molecular targets of the laser clarified. Here, we investigated the effects of a low intensity 635 ± 5 nm diode laser irradiation on fibroblast-myofibroblast transition, a key event in the onset of fibrosis, and elucidated some of the underlying molecular mechanisms.

MATERIALS AND METHODS

NIH/3T3 fibroblasts were cultured in a low serum medium in the presence of transforming growth factor (TGF)-β1 and irradiated with a 635 ± 5 nm diode laser (continuous wave, 89 mW, 0.3 J/cm(2) ). Fibroblast-myofibroblast differentiation was assayed by morphological, biochemical, and electrophysiological approaches. Expression of matrix metalloproteinase (MMP)-2 and MMP-9 and of Tissue inhibitor of MMPs, namely TIMP-1 and TIMP-2, after laser exposure was also evaluated by confocal immunofluorescence analyses. Moreover, the effect of the diode laser on transient receptor potential canonical channel (TRPC) 1/stretch-activated channel (SAC) expression and activity and on TGF-β1/Smad3 signaling was investigated.

RESULTS

Diode laser treatment inhibited TGF-β1-induced fibroblast-myofibroblast transition as judged by reduction of stress fibers formation, α-smooth muscle actin (sma) and type-1 collagen expression and by changes in electrophysiological properties such as resting membrane potential, cell capacitance and inwardly rectifying K(+) currents. In addition, the irradiation up-regulated the expression of MMP-2 and MMP-9 and downregulated that of TIMP-1 and TIMP-2 in TGF-β1-treated cells. This laser effect was shown to involve TRPC1/SAC channel functionality. Finally, diode laser stimulation and TRPC1 functionality negatively affected fibroblast-myofibroblast transition by interfering with TGF-β1 signaling, namely reducing the expression of Smad3, the TGF-β1 downstream signaling molecule.

CONCLUSION

Low intensity irradiation with 635 ± 5 nm diode laser inhibited TGF-β1/Smad3-mediated fibroblast-myofibroblast transition and this effect involved the modulation of TRPC1 ion channels. These data contribute to support the potential anti-fibrotic effect of LLLT and may offer further informations for considering this therapy as a promising therapeutic tool for the treatment of tissue fibrosis.

Function and Therapeutic Potential of Noncoding RNAs in Cardiac Fibrosis

Cardiac fibrosis as a result of excessive extracellular matrix deposition leads to stiffening of the heart, which can eventually lead to heart failure. An important event in cardiac fibrosis is the transformation of fibroblasts into myofibroblasts, which secrete large amounts of extracellular matrix proteins. Although the function of protein-coding genes in myofibroblast activation and fibrosis have been a topic of investigation for a long time, it has become clear that noncoding RNAs also play key roles in cardiac fibrosis. This review discusses the involvement of microRNAs and long noncoding RNAs in cardiac fibrosis and summarizes the issues related to translating these findings into real-life therapies.

Transmembrane proteoglycans control stretch-activated channels to set cytosolic calcium levels

Syndecans regulate members of the transient receptor potential family to control cytosolic calcium levels with impact on cell adhesion, junction formation, and neuronal guidance.

Transmembrane heparan sulfate proteoglycans regulate multiple aspects of cell behavior, but the molecular basis of their signaling is unresolved. The major family of transmembrane proteoglycans is the syndecans, present in virtually all nucleated cells, but with mostly unknown functions. Here, we show that syndecans regulate transient receptor potential canonical (TRPCs) channels to control cytosolic calcium equilibria and consequent cell behavior. In fibroblasts, ligand interactions with heparan sulfate of syndecan-4 recruit cytoplasmic protein kinase C to target serine714 of TRPC7 with subsequent control of the cytoskeleton and the myofibroblast phenotype. In epidermal keratinocytes a syndecan–TRPC4 complex controls adhesion, adherens junction composition, and early differentiation in vivo and in vitro. In Caenorhabditis elegans, the TRPC orthologues TRP-1 and -2 genetically complement the loss of syndecan by suppressing neuronal guidance and locomotory defects related to increases in neuronal calcium levels. The widespread and conserved syndecan–TRPC axis therefore fine tunes cytoskeletal organization and cell behavior.

TRPC6 is the endothelial calcium channel that regulates leukocyte transendothelial migration during the inflammatory response

Weber et al. identify TRPC6 as the calcium channel mediating the transient increase in endothelial cytosolic free calcium concentration required for transendothelial migration of leukocytes during the inflammatory response.

Leukocyte transendothelial migration (TEM) is a tightly regulated, multistep process that is critical to the inflammatory response. A transient increase in endothelial cytosolic free calcium ion concentration (↑[Ca²⁺]_i) is required for TEM. However, the mechanism by which endothelial ↑[Ca²⁺]_i regulates TEM and the channels mediating this ↑[Ca²⁺]_i are unknown. Buffering ↑[Ca²⁺]_i in endothelial cells does not affect leukocyte adhesion or locomotion but selectively blocks TEM, suggesting a role for ↑[Ca²⁺]_i specifically for this step. Transient receptor potential canonical 6 (TRPC6), a Ca²⁺ channel expressed in endothelial cells, colocalizes with platelet/endothelial cell adhesion molecule-1 (PECAM) to surround leukocytes during TEM and clusters when endothelial PECAM is engaged. Expression of dominant-negative TRPC6 or shRNA knockdown in endothelial cells arrests neutrophils apically over the junction, similar to when PECAM is blocked. Selectively activating endothelial TRPC6 rescues TEM during an ongoing PECAM blockade, indicating that TRPC6 functions downstream of PECAM. Furthermore, endothelial TRPC6 is required for trafficking of lateral border recycling compartment membrane, which facilitates TEM. Finally, mice lacking TRPC6 in the nonmyeloid compartment (i.e., endothelium) exhibit a profound defect in neutrophil TEM with no effect on leukocyte trafficking. Our findings identify endothelial TRPC6 as the calcium channel mediating the ↑[Ca²⁺]_i required for TEM at a step downstream of PECAM homophilic interactions.

Pathophysiology of Myocardial Infarction

Myocardial infarction is defined as sudden ischemic death of myocardial tissue. In the clinical context, myocardial infarction is usually due to thrombotic occlusion of a coronary vessel caused by rupture of a vulnerable plaque. Ischemia induces profound metabolic and ionic perturbations in the affected myocardium and causes rapid depression of systolic function. Prolonged myocardial ischemia activates a "wavefront" of cardiomyocyte death that extends from the subendocardium to the subepicardium. Mitochondrial alterations are prominently involved in apoptosis and necrosis of cardiomyocytes in the infarcted heart. The adult mammalian heart has negligible regenerative capacity, thus the infarcted myocardium heals through formation of a scar. Infarct healing is dependent on an inflammatory cascade, triggered by alarmins released by dying cells. Clearance of dead cells and matrix debris by infiltrating phagocytes activates anti-inflammatory pathways leading to suppression of cytokine and chemokine signaling. Activation of the renin-angiotensin-aldosterone system and release of transforming growth factor-β induce conversion of fibroblasts into myofibroblasts, promoting deposition of extracellular matrix proteins. Infarct healing is intertwined with geometric remodeling of the chamber, characterized by dilation, hypertrophy of viable segments, and progressive dysfunction. This review manuscript describes the molecular signals and cellular effectors implicated in injury, repair, and remodeling of the infarcted heart, the mechanistic basis of the most common complications associated with myocardial infarction, and the pathophysiologic effects of established treatment strategies. Moreover, we discuss the implications of pathophysiological insights in design and implementation of new promising therapeutic approaches for patients with myocardial infarction.

From GTP and G proteins to TRPC channels: a personal account

By serendipity and good fortune, as a postdoctoral fellow in 1967, I landed at the right place at the right time, as I was allowed to investigate the mechanism by which hormones activate the enzyme adenylyl cyclase (then adenyl cyclase) in Martin Rodbell's Laboratory at the NIH in Bethesda, Maryland. The work uncovered first, the existence of receptors separate from the enzyme and then, the existence of transduction mechanisms requiring guanosine-5'-triphosphate (GTP) and Mg(2+). With my laboratory colleagues first and postdoctoral fellows after leaving NIH, I participated in the development of the field "signal transduction by G proteins," uncovered by molecular cloning several G-protein-coupled receptors (GPCRs) and became interested in both the molecular makeup of voltage-gated Ca channels and Ca2+ homeostasis downstream of activation of phospholipase C (PLC) by the Gq/11 signaling pathway. We were able to confirm the hypothesis that there would be mammalian homologues of the Drosophila "transient receptor potential" channel and discovered the existence of six of the seven mammalian genes, now called transient receptor potential canonical (TRPC) channels. In the present article, I summarize from a bird's eye view of what I feel were key findings along this path, not only from my laboratory but also from many others, that allowed for the present knowledge of cell signaling involving G proteins to evolve. Towards the end, I summarize roles of TRPC channels in health and disease.

Evidence of a Role for Fibroblast Transient Receptor Potential Canonical 3 Ca2+ Channel in Renal Fibrosis

Transient receptor potential canonical (TRPC) Ca(2+)-permeant channels, especially TRPC3, are increasingly implicated in cardiorenal diseases. We studied the possible role of fibroblast TRPC3 in the development of renal fibrosis. In vitro, a macromolecular complex formed by TRPC1/TRPC3/TRPC6 existed in isolated cultured rat renal fibroblasts. However, specific blockade of TRPC3 with the pharmacologic inhibitor pyr3 was sufficient to inhibit both angiotensin II- and 1-oleoyl-2-acetyl-sn-glycerol-induced Ca(2+) entry in these cells, which was detected by fura-2 Ca(2+) imaging. TRPC3 blockade or Ca(2+) removal inhibited fibroblast proliferation and myofibroblast differentiation by suppressing the phosphorylation of extracellular signal-regulated kinase (ERK1/2). In addition, pyr3 inhibited fibrosis and inflammation-associated markers in a noncytotoxic manner. Furthermore, TRPC3 knockdown by siRNA confirmed these pharmacologic findings. In adult male Wistar rats or wild-type mice subjected to unilateral ureteral obstruction, TRPC3 expression increased in the fibroblasts of obstructed kidneys and was associated with increased Ca(2+) entry, ERK1/2 phosphorylation, and fibroblast proliferation. Both TRPC3 blockade in rats and TRPC3 knockout in mice inhibited ERK1/2 phosphorylation and fibroblast activation as well as myofibroblast differentiation and extracellular matrix remodeling in obstructed kidneys, thus ameliorating tubulointerstitial damage and renal fibrosis. In conclusion, TRPC3 channels are present in renal fibroblasts and control fibroblast proliferation, differentiation, and activation through Ca(2+)-mediated ERK signaling. TRPC3 channels might constitute important therapeutic targets for improving renal remodeling in kidney disease.

Role of TRPV1 in the Differentiation of Mouse Embryonic Stem Cells into Cardiomyocytes

Cytosolic Ca²⁺ ([Ca²⁺]_i) is an important signal that regulates cardiomyocyte differentiation during cardiogenesis. TRPV1 is a Ca²⁺-permeable channel that is expressed in cardiomyocytes. In the present study, we utilized mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) as a model to investigate the functional role of TRPV1 in cardiomyocyte differentiation. Induction of embryonic stem cells into cardiomyocytes was achieved using embryoid body (EB)-based differentiation method. Quantitative PCRs showed an increased TRPV1 expression during the differentiation process. In [Ca²⁺]_i measurement study, application of TRPV1 agonists, capsaicin and camphor, elicited a [Ca²⁺]_i rise in mESC-CMs, the effect of which was abolished by TRPV1-shRNA. In functional study, treatment of EBs with TRPV1 antagonists (capsazepine and SB366791) and TRPV1-shRNA reduced the size of the EBs and decreased the percentage of spontaneously beating EBs. TRPV1 antagonists and TRPV1-shRNA also suppressed the expression of cardiomyocyte marker genes, including cardiac actin, c-TnT, c-TnI, and α-MHC. Taken together, this study demonstrated an important functional role of TRPV1 channels in the differentiation of mESCs into cardiomyocytes.

Sirt7 Contributes to Myocardial Tissue Repair by Maintaining Transforming Growth Factor-β Signaling Pathway

BACKGROUND

Sirt7, 1 of the 7 members of the mammalian sirtuin family, promotes oncogenic transformation. Tumor growth and metastasis require fibrotic and angiogenic responses. Here, we investigated the role of Sirt7 in cardiovascular tissue repair process.

METHODS AND RESULTS

In wild-type mice, Sirt7 expression increased in response to acute cardiovascular injury, including myocardial infarction and hind-limb ischemia, particularly at the active wound healing site. Compared with wild-type mice, homozygous Sirt7-deficient (Sirt7(-/-)) mice showed susceptibility to cardiac rupture after myocardial infarction, delayed blood flow recovery after hind-limb ischemia, and impaired wound healing after skin injury. Histological analysis showed reduced fibrosis, fibroblast differentiation, and inflammatory cell infiltration in the border zone of infarction in Sirt7(-/-) mice. In vitro, Sirt7(-/-) mouse-derived or Sirt7 siRNA-treated cardiac fibroblasts showed reduced transforming growth factor-β signal activation and low expression levels of fibrosis-related genes compared with wild-type mice-derived or control siRNA-treated cells. These changes were accompanied by reduction in transforming growth factor receptor I protein. Loss of Sirt7 activated autophagy in cardiac fibroblasts. Transforming growth factor-β receptor I downregulation induced by loss of Sirt7 was blocked by autophagy inhibitor, and interaction of Sirt7 with protein interacting with protein kinase-Cα was involved in this process.

CONCLUSION

Sirt7 maintains transforming growth factor receptor I by modulating autophagy and is involved in the tissue repair process.

A background Ca2+ entry pathway mediated by TRPC1/TRPC4 is critical for development of pathological cardiac remodelling

AIMS

Pathological cardiac hypertrophy is a major predictor for the development of cardiac diseases. It is associated with chronic neurohumoral stimulation and with altered cardiac Ca(2+) signalling in cardiomyocytes. TRPC proteins form agonist-induced cation channels, but their functional role for Ca(2+) homeostasis in cardiomyocytes during fast cytosolic Ca(2+) cycling and neurohumoral stimulation leading to hypertrophy is unknown.

METHODS AND RESULTS

In a systematic analysis of multiple knockout mice using fluorescence imaging of electrically paced adult ventricular cardiomyocytes and Mn(2+)-quench microfluorimetry, we identified a background Ca(2+) entry (BGCE) pathway that critically depends on TRPC1/C4 proteins but not others such as TRPC3/C6. Reduction of BGCE in TRPC1/C4-deficient cardiomyocytes lowers diastolic and systolic Ca(2+) concentrations both, under basal conditions and under neurohumoral stimulation without affecting cardiac contractility measured in isolated hearts and in vivo. Neurohumoral-induced cardiac hypertrophy as well as the expression of foetal genes (ANP, BNP) and genes regulated by Ca(2+)-dependent signalling (RCAN1-4, myomaxin) was reduced in TRPC1/C4 knockout (DKO), but not in TRPC1- or TRPC4-single knockout mice. Pressure overload-induced hypertrophy and interstitial fibrosis were both ameliorated in TRPC1/C4-DKO mice, whereas they did not show alterations in other cardiovascular parameters contributing to systemic neurohumoral-induced hypertrophy such as renin secretion and blood pressure.

CONCLUSIONS

The constitutively active TRPC1/C4-dependent BGCE fine-tunes Ca(2+) cycling in beating adult cardiomyocytes. TRPC1/C4-gene inactivation protects against development of maladaptive cardiac remodelling without altering cardiac or extracardiac functions contributing to this pathogenesis.

Phosphodiesterase 9A controls nitric-oxide-independent cGMP and hypertrophic heart disease

Cyclic guanosine monophosphate (cGMP) is a second messenger molecule that transduces nitric-oxide- and natriuretic-peptide-coupled signalling, stimulating phosphorylation changes by protein kinase G. Enhancing cGMP synthesis or blocking its degradation by phosphodiesterase type 5A (PDE5A) protects against cardiovascular disease. However, cGMP stimulation alone is limited by counter-adaptions including PDE upregulation. Furthermore, although PDE5A regulates nitric-oxide-generated cGMP, nitric oxide signalling is often depressed by heart disease. PDEs controlling natriuretic-peptide-coupled cGMP remain uncertain. Here we show that cGMP-selective PDE9A (refs 7, 8) is expressed in the mammalian heart, including humans, and is upregulated by hypertrophy and cardiac failure. PDE9A regulates natriuretic-peptide- rather than nitric-oxide-stimulated cGMP in heart myocytes and muscle, and its genetic or selective pharmacological inhibition protects against pathological responses to neurohormones, and sustained pressure-overload stress. PDE9A inhibition reverses pre-established heart disease independent of nitric oxide synthase (NOS) activity, whereas PDE5A inhibition requires active NOS. Transcription factor activation and phosphoproteome analyses of myocytes with each PDE selectively inhibited reveals substantial differential targeting, with phosphorylation changes from PDE5A inhibition being more sensitive to NOS activation. Thus, unlike PDE5A, PDE9A can regulate cGMP signalling independent of the nitric oxide pathway, and its role in stress-induced heart disease suggests potential as a therapeutic target.

Increased TRPM6 expression in atrial fibrillation patients contribute to atrial fibrosis

BACKGROUND

Transient receptor potential (TRP) family plays important roles in cardiovascular system. We investigated the relationship between transient receptor potential channel subfamily M6 (TRPM6) and atrial fibrosis in rheumatic heart disease patients with atrial fibrillation (AF).

METHODS

The right atrial tissue samples were obtained from 64 patients with rheumatic heart diseases who underwent heart valve replacement surgery, and composed of 34 sinus rhythm (SR) patients and 30 AF patients. Hematoxylin and Eosin (HE) staining was used to observe cross-sectional area (CSA) of myocardial cell. Masson staining and measurement of connective tissue growth factor (CTGF), transforming growth factor beta 1 (TGF-β 1), and collagen type I/III (Collagen I/III) were performed to determine atrial fibrosis. The mRNA and protein levels of TRPM6 were detected by real-time quantitative polymerase chain reaction (RT-PCR) and western blotting, respectively.

RESULTS

Marked increases were observed in CSA of myocardial cell and myocardial collagen volume fraction in AF group compared with the SR group (all P<0.05). The mRNA levels of myocardial fibrosis markers (CTGF, TGF-beta 1, Collagen I/III) in AF group increased significantly compared to the SR group (all P<0.05). TRPM6 mRNA and protein levels in AF group were elevated markedly in comparison with SR group (P<0.01).

CONCLUSION

These findings revealed that increased TRPM6 mRNA and protein levels may contribute to atrial fibrosis, and suggested that TRPM6 might be involved in AF development by promoting fibrogenesis.

Intestinal myofibroblast TRPC6 channel may contribute to stenotic fibrosis in Crohn's disease

BACKGROUND

Intestinal fibrosis is a frequent complication of Crohn's disease (CD) and often leads to detrimental stricture formation. Myofibroblasts play active roles in mediating fibrotic changes in various tissues. We investigated whether transient receptor potential channels in intestinal myofibroblasts are involved in CD-associated intestinal fibrosis.

METHODS

An intestinal myofibroblast cell line (InMyoFibs) was stimulated with transforming growth factor-β1 (TGF-β1) to model excessive fibrosis. Biopsy samples from nonstenotic or stenotic intestinal regions from patients with CD were used for quantitative comparisons of transient receptor potential channel and fibrosis-associated factor expression levels.

RESULTS

TGF-β1 treatment transformed spindle-shaped InMyoFibs into filament-shaped cells with enhanced α-actin stress fiber formation, transient receptor potential canonical (TRPC) 4 and TRPC6 messenger RNA and protein expression, and basal- and agonist-induced Ca influxes. TGF-β1 also enhanced the formation of TRPC6/smooth muscle α-actin, TRPC6/N-cadherin, and TRPC4/N-cadherin coimmunoprecipitates. Inhibition of TRPC6 in InMyoFibs by RNA interference or dominant-negative mutations suppressed TGF-β1-induced Ca influxes, stress fiber formation, and smooth muscle α-actin expression, but increased COL1A1, interleukin (IL)-10, and IL-11 expression, as well as Smad-2, ERK, and p38-MAPK phosphorylation. Similar increases in phosphorylation levels were observed with TRPC and calcineurin inhibitors. In stenotic areas in patients with CD, TRPC6, ACTA2 (smooth muscle α-actin), CDH2 (N-cadherin), COL1A1, IL-10, and IL-11 were significantly increased.

CONCLUSIONS

These results suggest that augmented Ca influxes due to TRPC6 upregulation facilitate stress fiber formation and strengthen cell-cell interactions by negatively regulating the synthesis of antifibrotic factors in TGF-β1-treated myofibroblasts. Similar changes observed in stenotic areas of patients with CD suggest the therapeutic significance of targeting TRPC6.

TRP channels in skin: from physiological implications to clinical significances

TRP channels are expressed in various cells in skin. As an organ system to border the host and environment, many nonneuronal cells, including epidermal keratinocytes and melanocytes, express several TRP channels functionally distinct from sensory processing. TRPV1 and TRPV3 in keratinocytes of the epidermis and hair apparatus inhibit proliferation, induce terminal differentiation, induce apoptosis, and promote inflammation. Activation of TRPV4, 6, and TRPA1 promotes regeneration of the severed skin barriers. TRPA1 also enhances responses in contact hypersensitivity. TRPCs in keratinocytes regulate epidermal differentiation. In human diseases with pertubered epidermal differentiation, the expression of TRPCs are altered. TRPMs, which contribute to melanin production in melanocytes, serve as significant prognosis markers in patients with metastatic melanoma. In summary, not only act in sensory processing, TRP channels also contribute to epidermal differentiation, proliferation, barrier integration, skin regeneration, and immune responses. In diseases with aberrant TRP channels, TRP channels might be good therapeutic targets.

Role of TRP channels in the cardiovascular system

The transient receptor potential (TRP) superfamily consists of a large number of nonselective cation channels with variable degree of Ca(2+)-permeability. The 28 mammalian TRP channel proteins can be grouped into six subfamilies: canonical, vanilloid, melastatin, ankyrin, polycystic, and mucolipin TRPs. The majority of these TRP channels are expressed in different cell types including both excitable and nonexcitable cells of the cardiovascular system. Unlike voltage-gated ion channels, TRP channels do not have a typical voltage sensor, but instead can sense a variety of other stimuli including pressure, shear stress, mechanical stretch, oxidative stress, lipid environment alterations, hypertrophic signals, and inflammation products. By integrating multiple stimuli and transducing their activity to downstream cellular signal pathways via Ca(2+) entry and/or membrane depolarization, TRP channels play an essential role in regulating fundamental cell functions such as contraction, relaxation, proliferation, differentiation, and cell death. With the use of targeted deletion and transgenic mouse models, recent studies have revealed that TRP channels are involved in numerous cellular functions and play an important role in the pathophysiology of many diseases in the cardiovascular system. Moreover, several TRP channels are involved in inherited diseases of the cardiovascular system. This review presents an overview of current knowledge concerning the physiological functions of TRP channels in the cardiovascular system and their contributions to cardiovascular diseases. Ultimately, TRP channels may become potential therapeutic targets for cardiovascular diseases.

TRP channels in the skin

Emerging evidence suggests that transient receptor potential (TRP) ion channels not only act as 'polymodal cellular sensors' on sensory neurons but are also functionally expressed by a multitude of non-neuronal cell types. This is especially true in the skin, one of the largest organs of the body, where they appear to be critically involved in regulating various cutaneous functions both under physiological and pathophysiological conditions. In this review, we focus on introducing the roles of several cutaneous TRP channels in the regulation of the skin barrier, skin cell proliferation and differentiation, and immune functions. Moreover, we also describe the putative involvement of several TRP channels in the development of certain skin diseases and identify future TRP channel-targeted therapeutic opportunities.

TRPV4 mediates myofibroblast differentiation and pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disorder with no effective medical treatments available. The generation of myofibroblasts, which are critical for fibrogenesis, requires both a mechanical signal and activated TGF-β; however, it is not clear how fibroblasts sense and transmit the mechanical signal(s) that promote differentiation into myofibroblasts. As transient receptor potential vanilloid 4 (TRPV4) channels are activated in response to changes in plasma membrane stretch/matrix stiffness, we investigated whether TRPV4 contributes to generation of myofibroblasts and/or experimental lung fibrosis. We determined that TRPV4 activity is upregulated in lung fibroblasts derived from patients with IPF. Moreover, TRPV4-deficient mice were protected from fibrosis. Furthermore, genetic ablation or pharmacological inhibition of TRPV4 function abrogated myofibroblast differentiation, which was restored by TRPV4 reintroduction. TRPV4 channel activity was elevated when cells were plated on matrices of increasing stiffness or on fibrotic lung tissue, and matrix stiffness-dependent myofibroblast differentiation was reduced in response to TRVP4 inhibition. TRPV4 activity modulated TGF-β1-dependent actions in a SMAD-independent manner, enhanced actomyosin remodeling, and increased nuclear translocation of the α-SMA transcription coactivator (MRTF-A). Together, these data indicate that TRPV4 activity mediates pulmonary fibrogenesis and suggest that manipulation of TRPV4 channel activity has potential as a therapeutic approach for fibrotic diseases.

Effects of methylglyoxal on human cardiac fibroblast: roles of transient receptor potential ankyrin 1 (TRPA1) channels

Cardiac fibroblasts contribute to the pathogenesis of cardiac remodeling. Methylglyoxal (MG) is an endogenous carbonyl compound produced under hyperglycemic conditions, which may play a role in the development of pathophysiological conditions including diabetic cardiomyopathy. However, the mechanism by which this occurs and the molecular targets of MG are unclear. We investigated the effects of MG on Ca(2+) signals, its underlying mechanism, and cell cycle progression/cell differentiation in human cardiac fibroblasts. The conventional and quantitative real-time RT-PCR, Western blot, immunocytochemical analysis, and intracellular Ca(2+) concentration [Ca(2+)]i measurement were applied. Cell cycle progression was assessed using the fluorescence activated cell sorting. MG induced Ca(2+) entry concentration dependently. Ruthenium red (RR), a general cation channel blocker, and HC030031, a selective transient receptor potential ankyrin 1 (TRPA1) antagonist, inhibited MG-induced Ca(2+) entry. Treatment with aminoguanidine, a MG scavenger, also inhibited it. Allyl isothiocyanate, a selective TRPA1 agonist, increased Ca(2+) entry. The use of small interfering RNA to knock down TRPA1 reduced the MG-induced Ca(2+) entry as well as TRPA1 mRNA expression. The quantitative real-time RT-PCR analysis showed the prominent existence of TRPA1 mRNA. Expression of TRPA1 protein was confirmed by Western blotting and immunocytochemical analyses. MG promoted cell cycle progression from G0/G1 to S/G2/M, which was suppressed by HC030031 or RR. MG also enhanced α-smooth muscle actin expression. The present results suggest that methylglyoxal activates TRPA1 and promotes cell cycle progression and differentiation in human cardiac fibroblasts. MG might participate the development of pathophysiological conditions including diabetic cardiomyopathy via activation of TRPA1.