Matrix metalloproteinase-2 stimulates collagen-I expression through phosphorylation of focal adhesion kinase in rat cardiac fibroblasts

Mog1 deficiency promotes cardiac contractile dysfunction and isoproterenol-induced arrhythmias associated with cardiac fibrosis and Cx43 remodeling

Our earlier studies identified MOG1 as a Nav1.5-binding protein that promotes Nav1.5 intracellular trafficking to plasma membranes. Genetic studies have identified MOG1 variants responsible for cardiac arrhythmias. However, the physiological functions of MOG1 in vivo remain incompletely characterized. In this study, we generated Mog1 knockout (Mog1^-/-) mice. Mog1^-/- mice did not develop spontaneous arrhythmias at the baseline, but exhibited a prolongation of QRS duration. Mog1^-/- mice treated with isoproterenol (ISO), but not with flecainide, exhibited an increased risk of arrhythmias and even sudden death. Mog1^-/- mice had normal cardiac morphology, however, LV systolic dysfunction was identified and associated with an increase in ventricular fibrosis. Whole-cell patch-clamping and Western blotting analysis clearly demonstrated the normal cardiac expression and function of Nav1.5 in Mog1^-/- mice. Further RNA-seq and iTRAQ analysis identified critical pathways and genes, including extracellular matrix (Mmp2), gap junction (Gja1), and mitochondrial components that were dysregulated in Mog1^-/- mice. RT-qPCR, Western blotting, and immunofluorescence assays revealed reduced cardiac expression of Gja1 in Mog1^-/- mice. Dye transfer assays confirmed impairment of gap-junction function; Cx43 gap-junction enhancer ZP123 decreased arrhythmia inducibility in ISO-treated Mog1^-/- mice. Transmission electron microscopy analysis revealed abnormal sarcomere ultrastructure and altered mitochondrial morphology in Mog1^-/- mice. Mitochondrial dynamics was found to be disturbed, and associated with a trend toward increased mitochondrial fusion in Mog1^-/- mice. Meanwhile, the level of ATP supply was increased in the hearts of Mog1^-/- mice. These results indicate that MOG1 plays an important role in cardiac electrophysiology and cardiac contractile function.

Spironolactone alleviates myocardial fibrosis via inhibition of Ets‑1 in mice with experimental autoimmune myocarditis

Spironolactone improves cardiac structure, function and prognosis in patients with heart failure and delays the progression of cardiac fibrosis. However, the exact underlying mechanism of this process remains to be elucidated. The present study therefore aimed to explore the protective effect and underlying mechanism of the aldosterone receptor antagonist, spironolactone, on myocardial fibrosis in mice with experimental autoimmune myocarditis (EAM). The EAM model was induced in BALB/c mice via immunization with murine cardiac α-myosin heavy chain sequence polypeptides. The cardiac function of the mice was assessed using echocardiography and the levels of inflammatory cytokines were quantified using ELISA. E26 transformation-specific sequence-1 (Ets-1) expression was knocked down using lentivirus-mediated small interference RNA. Total collagen deposition was assessed using Masson's trichrome and Ets-1, TGF-β1, Smad2/3, collagen I and III protein expression levels were detected using immunohistochemistry and western blotting. MMP-2 and MMP-9 mRNA expression levels and activity was determined using reverse transcription-quantitative PCR and gelatin zymography, respectively. The results of the present study demonstrated that spironolactone significantly improved myocardium hypertrophy, diastolic cardiac function and decreased myocardial inflammation and collagen deposition induced by EAM. Spironolactone treatment significantly inhibited Ets-1 and smad2/3 phosphorylation. In addition, inhibition of Ets-1 reduced the expression and activity of MMP-2 and MMP-9 and decreased cardiac fibrosis in EAM mice. The results indicated that the improvement of myocardial fibrosis by spironolactone may be associated with the TGF-β1/Smad-2/3/Ets-1 signaling pathway in EAM mice.

Inhibition of focal adhesion turnover prevents osteoblastic differentiation through β‐catenin mediated transduction of pro‐osteogenic substrate

The mechanism by which substrate surface characteristics are transduced by osteoblastic cells and their progenitors is not fully known. Data from previous studies by our group suggest the involvement of β‐catenin in the mechanism by which substrate surface characteristics are transduced. This focal adhesion and β‐catenin mediated mechanism functions through the liberation of β‐catenin from focal adhesion complexes in response to pro‐osteogenic substrate (POS) characteristics. After liberation, β‐catenin translocates and facilitates upregulation of genes associated with osteogenesis. It is not known whether the observed correlation between focal adhesion turnover and β‐catenin translocation directly results from focal adhesion turnover. In this study we inhibited focal adhesion turnover using a focal adhesion kinase inhibitor PF‐573228. We found that inhibition of focal adhesion turnover resulted in an abrogation of the more rapid translocation and increased transcriptional activity of β‐catenin induced by POS. In addition, inhibition of focal adhesion turnover mitigated the increase in osteoblastic differentiation induced by a POS as measured by alkaline phosphatase enzymatic activity and osteogenic gene and protein expression. Together, these data, coupled with previous findings, suggest that the observed β‐catenin translocation is a result of focal adhesion turnover, providing evidence for a focal adhesion initiated, β‐catenin mediated mechanism of substrate surface signal transduction.

The effect of nutraceuticals on multiple signaling pathways in cardiac fibrosis injury and repair

Cardiac fibrosis is one of the most common pathological conditions caused by different heart diseases, including myocardial infarction and diabetic cardiomyopathy. Cardiovascular disease is one of the major causes of mortality worldwide. Cardiac fibrosis is caused by different processes, including inflammatory reactions and oxidative stress. The process of fibrosis begins by changing the balance between production and destruction of extracellular matrix components and stimulating the proliferation and differentiation of cardiac fibroblasts. Many studies have focused on finding drugs with less adverse effects for the treatment of cardiovascular disease. Some studies show that nutraceuticals are effective in preventing and treating diseases, including cardiovascular disease, and that they can reduce the risk. However, big clinical studies to prove the therapeutic properties of all these substances and their adverse effects are lacking so far. Therefore, in this review, we tried to summarize the knowledge on pathways and mechanisms of several nutraceuticals which have shown their usefulness in the prevention of cardiac fibrosis.

Decreased Collagen Type I is Associated with Increased Metalloproteinase-2 Activity and Protein Expression of Leptin in the Myocardium of Obese Rats

Fundamento

A obesidade é um fator de risco para complicações médicas, incluindo o sistema cardiovascular. Há informações limitadas sobre o colágeno no coração obeso. Nosso estudo anterior demonstrou uma redução dos níveis proteicos de colágeno miocárdico tipo I em ratos obesos alimentados com uma dieta com alto teor de gordura durante 34 semanas. No entanto, os mecanismos responsáveis pelos níveis baixos não estão completamente elucidados.

Objetivo

O objetivo deste estudo foi testar a hipótese de que a redução do colágeno tipo I está associada ao aumento da atividade da metaloproteinase-2 (MMP-2), a qual está ligada à elevação de leptina no miocárdio de ratos obesos.

Métodos

Ratos Wistar machos com 30 dias de idade foram randomizados em dois grupos: controle (dieta padrão) e obeso (dieta com alto teor de gordura), e alimentados durante 34 semanas. Foram avaliados as características gerais dos animais e os perfis metabólicos e endócrinos. Foram avaliados as expressões proteicas miocárdicas de colágeno tipo I, leptina e inibidores teciduais de metaloproteinases (TIMP), bem como a atividade da MMP-2. O teste de correlação de Pearson foi aplicado para determinar as associações entre variáveis. O nível de significância foi de 5%.

Resultados

Os animais obesos apresentaram índice de adiposidade mais elevado em comparação ao controle. Foram observadas comorbidades como intolerância à glicose, hiperinsulinemia, resistência à insulina, hiperleptinemia e hipertensão nos ratos obesos. A obesidade reduziu o colágeno tipo I, TIMP-1 e TIMP-2, e aumentou a leptina e a MMP-2 no miocárdio. Houve uma correlação negativa entre o colágeno tipo I e a MMP-2 e uma correlação positiva entre a leptina e a MMP-2.

Conclusão

Foi confirmada a hipótese de que a redução do colágeno tipo I está associada ao aumento da atividade da MMP-2 e da expressão de leptina no miocárdio de ratos obesos. (Arq Bras Cardiol. 2020; 115(1):61-70)

Ski drives an acute increase in MMP-9 gene expression and release in primary cardiac myofibroblasts

Many etiologies of heart disease are characterized by expansion and remodeling of the cardiac extracellular matrix (ECM or matrix) which results in cardiac fibrosis. Cardiac fibrosis is mediated in cardiac fibroblasts by TGF‐β₁/R‐Smad2/3 signaling. Matrix component proteins are synthesized by activated resident cardiac fibroblasts known as myofibroblasts (MFB). These events are causal to heart failure with diastolic dysfunction and reduced cardiac filling. We have shown that exogenous Ski, a TGF‐β₁/Smad repressor, localizes in the cellular nucleus and deactivates cardiac myofibroblasts. This deactivation is associated with reduction of myofibroblast marker protein expression in vitro, including alpha smooth muscle actin (α‐SMA) and extracellular domain‐A (ED‐A) fibronectin. We hypothesize that Ski also acutely regulates MMP expression in cardiac MFB. While acute Ski overexpression in cardiac MFB in vitro was not associated with any change in intracellular MMP‐9 protein expression versus LacZ‐treated controls,exogenous Ski caused elevated MMP‐9 mRNA expression and increased MMP‐9 protein secretion versus controls. Zymographic analysis revealed increased MMP‐9‐specific gelatinase activity in myofibroblasts overexpressing Ski versus controls. Moreover, Ski expression was attended by reduced paxillin and focal adhesion kinase phosphorylation (FAK ‐ Tyr 397) versus controls. As myofibroblasts are hypersecretory and less motile relative to fibroblasts, Ski's reduction of paxillin and FAK expression may reflect the relative deactivation of myofibroblasts. Thus, in addition to its known antifibrotic effects, Ski overexpression elevates expression and extracellular secretion/release of MMP‐9 and thus may facilitate internal cytoskeletal remodeling as well as extracellular ECM components. Further, as acute TGF‐β₁ treatment of primary cardiac MFB is known to cause rapid translocation of Ski to the nucleus, our data support an autoregulatory role for Ski in mediating cardiac ECM accumulation.

Effects of milrinone on inflammatory response-related gene expressions in cultured rat cardiomyocytes

Congestive heart failure (CHF) is defined as a cardiac dysfunction leading to low cardiac output and inadequate tissue perfusion. Intravenous positive inotropes are used to increase myocardial contractility in hospitalized patients with advanced heart failure. Milrinone is a phosphodiesterase Ⅲ inhibitor and used most commonly for inotropic effect. The well-known PROMISE study investigated the effects of milrinone on mortality in patients with severe CHF, and concluded that long-term therapy with milrinone increased morbidity and mortality among patients with advanced CHF. Previous studies have suggested that phosphodiesterase inhibitors can have potential effects on inflammatory pathways. Hence, we hypothesized that milrinone may alter inflammatory gene expressions in cardiomyocytes, thus leading to adverse clinical outcomes. We used rat cardiomyocyte cell line H9C2 and studied the impact of exposing cardiomyocytes to milrinone (10 μmol/L) for 24 hours on inflammatory gene expressions. RNA extracted from cultured cardiomyocytes was used for whole rat genome gene expression assay (41,000 genes). The following changes in inflammatory response-related gene expressions were discovered. Genes with increased expressions included: THBS2 (+9.98), MMP2 (+3.47), DDIT3 (+2.39), and ADORA3 (+3.5). Genes with decreased expressions were: SPP1 (-5.28) and CD14 (-2.05). We found that the above mentioned gene expression changes seem to indicate that milrinone may hinder the inflammatory process which may potentially lead to adverse clinical outcomes. However, further in vivo and clinical investigations will be needed to illustrate the clinical relevance of these gene expression changes induced by milrinone.

Antifibrotic cardioprotection of berberine via downregulating myocardial IGF-1 receptor-regulated MMP-2/MMP-9 expression in diabetic rats

Diabetic cardiac fibrosis increases ventricular stiffness and facilitates the occurrence of diastolic dysfunction. Our previous studies have shown that berberine, a natural alkaloid, attenuates cardiac ischemia-reperfusion injury in diabetic rats. The aim of present study was to investigate the effects of long-term berberine treatment on cardiac remodeling in diabetic rats and the underlying mechanisms. Diabetic rats induced by low-dose streptozotocin injection combined with 8 wk of high-fat diet displayed significant cardiac matrix collagen deposition and dysfunction, whereas berberine administration (200 mg·kg^-1·day^-1, gavage 4 wk) significantly ameliorated cardiac fibrosis and dysfunction and reduced cardiac IGF-1 receptor (IGF-1R) expression in diabetic rats. Interestingly, IGF-1R expression was upregulated in cardiac fibroblasts isolated from diabetic hearts or cultured in high-glucose conditions (30 mM). High glucose treatment or IGF-1R overexpression increased matrix metalloproteinase (MMP)-2/MMP-9 expression, α-smooth muscle actin (α-SMA), and collagen type I expression in cardiac fibroblasts. In contrast, berberine treatment significantly inhibited IGF-1R expression and exerted an antifibrotic effect in high glucose-cultured cardiac fibroblasts, as manifested by decreased MMP-2/MMP-9, α-SMA, and collagen type I expression, whereas IGF-1R siRNA plus berberine treatment did not further enhance this antifibrotic effect compared with berberine treatment alone. Taken together, long-term berberine treatment ameliorates cardiac fibrosis and dysfunction by downregulating IGF-1R expression in cardiac fibroblasts and subsequently reducing MMP-2/MMP-9, α-SMA, and collagen type I expression in diabetic hearts. The findings suggest the therapeutic potential of berberine for diabetic cardiomyopathy associated with cardiac fibrosis. NEW & NOTEWORTHY Berberine downregulated IGF-1 receptor expression and matrix metalloproteinase-2/matrix metalloproteinase-9 levels in cardiac fibroblasts and thus inhibited fibroblast differentiation and collagen overproduction in diabetic hearts, suggesting a novel mechanism for antifibrotic cardioprotection of berberine in type 2 diabetes.

Regulation of miR-29b and miR-30c by vitamin D receptor activators contributes to attenuate uraemia-induced cardiac fibrosis

Background

Uraemic cardiomyopathy, a process mainly associated with increased myocardial fibrosis, is the leading cause of death in chronic kidney disease patients and can be prevented by vitamin D receptor activators (VDRAs). Since some microRNAs (miRNAs) have emerged as regulators of the fibrotic process, we aimed to analyse the role of specific miRNAs in VDRA prevention of myocardial fibrosis as well as their potential use as biomarkers.

Methods

Wistar rats were nephrectomized and treated intraperitoneally with equivalent doses of two VDRAs: calcitriol and paricalcitol. Biochemical parameters, cardiac fibrosis, miRNA (miR-29b, miR-30c and miR-133b) levels in the heart and serum and expression of their target genes collagen I (COL1A1), matrix metalloproteinase 2 (MMP-2) and connective tissue growth factor (CTGF) in the heart were evaluated.

Results

Both VDRAs attenuated cardiac fibrosis, achieving a statistically significant difference in the paricalcitol-treated group. Increases in RNA and protein levels of COL1A1, MMP-2 and CTGF and reduced expression of miR-29b and miR-30c, known regulators of these pro-fibrotic genes, were observed in the heart of chronic renal failure (CRF) rats and were attenuated by both VDRAs. In serum, significant increases in miR-29b, miR-30c and miR-133b levels were observed in CRF rats, which were prevented by VDRA use. Moreover, vitamin D response elements were identified in the three miRNA promoters.

Conclusions

VDRAs, particularly paricalcitol, attenuated cardiac fibrosis acting on COL1A1, MMP-2 and CTGF expression, partly through regulation of miR-29b and miR-30c. These miRNAs and miR-133b could be useful serum biomarkers for cardiac fibrosis and also potential new therapeutic targets.

Irisin inhibits high glucose-induced endothelial-to-mesenchymal transition and exerts a dose-dependent bidirectional effect on diabetic cardiomyopathy

Emerging evidence indicates that irisin provides beneficial effects in diabetes. However, whether irisin influences the development of diabetic cardiomyopathy (DCM) remains unclear. Therefore, we investigated the potential role and mechanism of action of irisin in diabetes‐induced myocardial dysfunction in mice. Type 1 diabetes was induced in mice by injecting streptozotocin, and the diabetic mice were administered recombinant r‐irisin (low or high dose: 0.5 or 1.5 μg/g body weight/day, I.P.) or PBS for 16 weeks. Irisin treatment did not alter blood glucose levels in the diabetic mice. However, the results of echocardiographical and histopathological assays indicated that low‐dose irisin treatment alleviated cardiac fibrosis and left ventricular function in the diabetic mice, whereas high‐dose irisin failed to mitigate the ventricular function impairment and increased collagen deposition. The potential mechanism underlying the effect of low‐dose irisin involved irisin‐mediated inhibition of high glucose‐induced endothelial‐to‐mesenchymal transition (EndMT); conversely, high‐dose irisin treatment enhanced high glucose‐induced MMP expression by stimulating MAPK (p38 and ERK) signalling and cardiac fibroblast proliferation and migration. Low‐dose irisin alleviated DCM development by inhibiting high glucose‐induced EndMT. By contrast, high‐dose irisin disrupted normal MMP expression and induced cardiac fibroblast proliferation and migration, which results in excess collagen deposition. Thus, irisin can inhibit high glucose‐induced EndMT and exert a dose‐dependent bidirectional effect on DCM.

Canstatin stimulates migration of rat cardiac fibroblasts via secretion of matrix metalloproteinase-2

Type IV collagen, a nonfibrillar type, is ubiquitously expressed in the basement membrane around cardiomyocytes. Canstatin, a cleaved product of α2 chain of type IV collagen, is an antiangiogenic factor. Because it has not been clarified whether canstatin exerts other biological activities in heart, we investigated the effects of canstatin on adult rat cardiac fibroblasts. Cell migration was determined by Boyden chamber assay. Western blotting was performed to detect secretion of matrix metalloproteinase-2 (MMP-2) and MMP-9 and phosphorylation of extracellular signal-regulated kinase (ERK). Localization of MMP-2 was detected by immunofluorescence staining. Canstatin (250 ng/ml) significantly increased migration, secretion, and activity of MMP-2 but not MMP-9. CTTHWGFTLC peptide, an MMP inhibitor and small interfering RNA (siRNA) against MMP-2 suppressed the canstatin-induced (250 ng/ml, 24 h) migration. Canstatin (250 ng/ml, 30 min) significantly increased phosphorylation of ERK. PD98059, a MEK inhibitor, significantly suppressed the canstatin-induced (250 ng/ml, 24 h) migration but not secretion of MMP-2. An increase in MMP-2 expression was observed in cytoplasm of the canstatin-treated (250 ng/ml) cardiac fibroblasts (within 30 min). Canstatin induced actin stress fiber formation, which was inhibited by Y-27632, a Rho-associated kinase inhibitor. Y-27632 also suppressed the canstatin-induced (250 ng/ml, 24 h) MMP-2 secretion. Canstatin (250 ng/ml, 30 min) failed to induce ERK phosphorylation in MMP-2 siRNA-treated cardiac fibroblasts. In conclusion, this study revealed a novel function of canstatin for inducing cell migration of adult rat cardiac fibroblasts at least in part by ERK phosphorylation through MMP-2 secretion, possibly via actin cytoskeletal change.

Prohibitin overexpression improves myocardial function in diabetic cardiomyopathy

Prohibitin (PHB) is a highly conserved protein implicated in various cellular functions including proliferation, apoptosis, tumor suppression, transcription, and mitochondrial protein folding. However, its function in diabetic cardiomyopathy (DCM) is still unclear. In vivo, type 2 diabetic rat model was induced by using a high-fat diet and low-dose streptozotocin. Overexpression of the PHB protein in the model rats was achieved by injecting lentivirus carrying PHB cDNA via the jugular vein. Characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. Rats with DCM showed severe insulin resistance, left ventricular dysfunction, fibrosis and apoptosis. PHB overexpression ameliorated the disease. Cardiofibroblasts (CFs) and H9c2 cardiomyoblasts were used in vitro to investigate the mechanism of PHB in altered function. In CFs treated with HG, PHB overexpression decreased expression of collagen, matrix metalloproteinase activity, and proliferation. In H9c2 cardiomyoblasts, PHB overexpression inhibited apoptosis induced by HG. Furthermore, the increased phosphorylation of extracellular signal–regulated kinase (ERK) 1/2 was significantly decreased and the inhibited phosphorylation of Akt was restored in DCM. Therefore, PHB may be a new therapeutic target for human DCM.

Estrogen receptor beta signals to inhibition of cardiac fibrosis

Cardiac fibrosis evolves from the cardiac hypertrophic state. In this respect, estrogen and estrogen receptor beta (ERβ) inhibit the effects of cardiac hypertrophic peptides that also stimulate fibrosis. Here we determine details of the anti-fibrotic functions of ERβ. In acutely isolated rat cardiac fibroblasts. E2 or a specific ERβ agonist (βLGND2) blocked angiotensin II (AngII) signaling to fibrosis. This resulted from ERβ activating protein kinase A and AMP kinase, inhibiting both AngII de-phosphorylation of RhoA and the resulting stimulation of Rho kinase. Inhibition of Rho kinase from ERβ signaling resulted in marked decrease of TGFβ expression, connective tissue growth factor production and function, matrix metalloproteinases 2 and 9 expression and activity, and the conversion of fibroblasts to myofibroblasts. Production of collagens I and III were also significantly decreased. Several important aspects were corroborated in-vivo from βLGND2-treated mice that underwent AngII-induced cardiac hypertrophy. Thus, ERβ in cardiac fibroblasts prevents key aspects of cardiac fibrosis development.

Inhibition of Pin1 alleviates myocardial fibrosis and dysfunction in STZ-induced diabetic mice

Therapeutic management of diabetic myocardial fibrosis remains an unsolved clinical problem. Pin1, a peptidyl-prolyl isomerase, impacts diverse cellular processes and plays a pivotal role in regulating cardiac pathophysiology. Here we investigate the potential mechanism of action of Pin1 and its role in diabetes-induced myocardial fibrosis and dysfunction in mice. Cardiac Pin1, transforming growth factor β1 (TGF-β1), α-smooth muscle actin (α-SMA) and extracellular matrix deposits (collagen I and III) are found to be increased in diabetic mice, which are effectively prevented by Pin1 inhibition by juglone. Pin1 inhibition alleviates cardiac fibrosis and dysfunction. In vitro, high glucose increases Pin1 expression with an accompanying increase in phospho-Akt (Ser 473), p-Smad2, p-Smad3, TGF-β1, and α-SMA in cardiac fibroblasts (CFs). These increases are effectively prevented by the inhibition of Pin1 by juglone. Furthermore, Pin1 inhibition inhibits HG-induced CF proliferation and migration. Our results indicate that Pin1 inhibition attenuates cardiac extracellular matrix deposition by regulating the phosphorylation of Akt, TGF-β1/Smads, MMP activities, and α-SMA expression in diabetic mice.

Alpha1a-Adrenoceptor Genetic Variant Triggers Vascular Smooth Muscle Cell Hyperproliferation and Agonist Induced Hypertrophy via EGFR Transactivation Pathway

α_1a Adrenergic receptors (α_1aARs) are the predominant AR subtype in human vascular smooth muscle cells (SMCs). α_1aARs in resistance vessels are crucial in the control of blood pressure, yet the impact of naturally occurring human α_1aAR genetic variants in cardiovascular disorders remains poorly understood. To this end, we present novel findings demonstrating that 3D cultures of vascular SMCs expressing human α_1aAR-247R (247R) genetic variant demonstrate significantly increased SMC contractility compared with cells expressing the α_1aAR-WT (WT) receptor. Stable expression of 247R genetic variant also triggers MMP/EGFR-transactivation dependent serum- and agonist-independent (constitutive) hyperproliferation and agonist-dependent hypertrophy of SMCs. Agonist stimulation reduces contractility Using pathway-specific inhibitors we determined that the observed hyperproliferation of 247R-expressing cells is triggered via β-arrestin1/Src/MMP-2/EGFR/ERK-dependent mechanism. MMP-2-specific siRNA inhibited 247R-triggered hyperproliferation indicating MMP-2 involvement in 247R-triggered hyperproliferation in SMCs. β-arrestin1-specific shRNA also inhibited 247R-triggered hyperproliferation but did not affect hypertrophy in 247R-expressing SMCs, indicating that agonist-dependent hypertrophy is independent of β-arrestin1. Our data reveal that in different cardiovascular cells the same human receptor genetic variant can activate alternative modulators of the same signaling pathway. Thus, our findings in SMCs demonstrate that depending on the type of cells expressing the same receptor (or receptor variant), different target-specific inhibitors could be used to modulate aberrant hyperproliferative or hypertrophic pathways in order to restore normal phenotype.

Sp1 Mediates a Therapeutic Role of MiR-7a/b in Angiotensin II-Induced Cardiac Fibrosis via Mechanism Involving the TGF-β and MAPKs Pathways in Cardiac Fibroblasts

MicroRNA-7a/b (miR-7a/b) protects cardiac myocytes from apoptosis during ischemia/reperfusion injury; however, its role in angiotensin II (ANG II)-stimulated cardiac fibroblasts (CFs) remains unknown. Therefore, the present study investigated the anti-fibrotic mechanism of miR-7a/b in ANG II-treated CFs. ANG II stimulated the expression of specific protein 1 (Sp1) and collagen I in a dose- and time-dependent manner, and the overexpression of miR-7a/b significantly down-regulated the expression of Sp1 and collagen I stimulated by ANG II (100 nM) for 24 h. miR-7a/b overexpression effectively inhibited MMP-2 expression/activity and MMP-9 expression, as well as CF proliferation and migration. In addition, miR-7a/b also repressed the activation of TGF-β, ERK, JNK and p38 by ANG II. The inhibition of Sp1 binding activity by mithramycin prevented collagen I overproduction; however, miR-7a/b down-regulation reversed this effect. Further studies revealed that Sp1 also mediated miR-7a/b-regulated MMP expression and CF migration, as well as TGF-β and ERK activation. In conclusion, miR-7a/b has an anti-fibrotic role in ANG II-treated CFs that is mediated by Sp1 mechanism involving the TGF-β and MAPKs pathways.

The Nuclear Factor kappaB Inhibitor Pyrrolidine Dithiocarbamate Prevents Cardiac Remodelling and Matrix Metalloproteinase-2 Up-Regulation in Renovascular Hypertension

Imbalanced matrix metalloproteinase (MMP) activity is involved in hypertensive cardiac hypertrophy. Pharmacological inhibition of nuclear factor kappaB (NF-кB) with pyrrolidine dithiocarbamate (PDTC) can prevent MMP up-regulation. We suggested that treatment with PDTC could prevent 2-kidney, 1-clip (2K1C) hypertension-induced left ventricular remodelling. Sham-operated controls or 2K1C rats with hypertension received either vehicle or PDTC (100 mg/kg/day) by gavage for 8 weeks. Systolic blood pressure was monitored every week. Histological assessment of left ventricles was carried out with haematoxylin/eosin sections, and fibrosis was quantified in picrosirius red-stained sections. Oxidative stress was evaluated in heart samples with the dihydroethidium probe. Cardiac MMP activity was determined by in situ zymography, and cardiac MMP-2 was assessed by immunofluorescence. 2K1C surgery significantly increased systolic blood pressure in the 2K1C vehicle. PDTC exerted antihypertensive effects after 2 weeks of treatment. Histology revealed increased left ventricular and septum wall thickness associated with augmented myocyte diameter in hypertensive rats, which were reversed by treatment with PDTC. Hypertensive rats developed pronounced cardiac fibrosis with increased interstitial collagen area, increased cardiac reactive oxygen species levels, gelatinase activity and MMP-2 expression. PDTC treatment decreased these alterations. These findings show that PDTC modulates myocardial MMP-2 expression and ameliorates cardiac remodelling in renovascular hypertension. These results suggest that interfering with MMP expression at transcriptional level may be an interesting strategy in the therapy of organ damage associated with hypertension.

Stromal matrix metalloproteinase 2 regulates collagen expression and promotes the outgrowth of experimental metastases

Breast cancer survival rates decrease from 99% for patients with local disease to 25% for those with distant metastases. Matrix metalloproteinases (MMPs), including MMP2, are associated with metastatic progression. We found that loss of host MMP2 reduces the proliferation of experimental metastases in the lungs and identified fibroblasts in tumour-bearing lungs as the major source of MMP2. In vitro, spheroidal mammary tumour growth was increased by co-culture with control fibroblasts isolated from tumour-bearing lungs, but not when fibroblasts with stable Mmp2 knockdown were used. This result prompted us to assess whether MMP2 was responsible for a tumour-proliferative, activated fibroblast phenotype. To test this, we evaluated: (a) fibroblasts from wild-type tumour-bearing lungs, with or without shRNA-mediated MMP2 knockdown; and (b) normal, quiescent fibroblasts isolated from either WT or Mmp2(-/-) mice. Quantitative PCR revealed that Mmp2 knockdown attenuated expression of two markers of activation (α-smooth muscle actin and vimentin), but there was minimal expression in quiescent WT or Mmp2(-/-) fibroblasts, as expected. Placing quiescent fibroblasts under activating conditions led to increases in activation-associated transcripts in WT but not Mmp2(-/-) fibroblasts. Additionally, Mmp2 knockdown fibroblasts showed significantly decreased expression of the matrix transcripts collagen I, collagen IV and fibronectin. Addition of active TGFβ was sufficient to rescue the MMP2-dependent collagen I and IV expression, while MMP2-induced collagen expression was blocked by the addition of TGFβ1-neutralizing antibody. Gene expression data in stromal cells of human breast cancers reveal that MMP2 expression is also positively correlated with activation and matrix transcripts. Thus, we present a model whereby MMP2 production in tumour fibroblasts is important for TGFβ1 activity and subsequent activation of fibroblasts to a matrix-producing, proliferation-supportive phenotype. Overall, our results reveal a previously undefined role for MMP2 in metastatic outgrowth mediated by fibroblasts, and extend the mechanisms by which MMPs contribute to tumour progression.

Inhibition of high-mobility group box 1 improves myocardial fibrosis and dysfunction in diabetic cardiomyopathy

BACKGROUND

High-mobility group box 1 (HMGB1) is an important mediator of the inflammatory response. Its expression is increased in diabetic cardiomyopathy (DCM), but its role is unclear. We investigated the potential role and mechanism of HMGB1 in diabetes-induced myocardial fibrosis and dysfunction in mice.

METHODS

In vivo, type 1 diabetes was induced by streptozotocin (STZ) in mice. HMGB1 expression was knocked down by lentivirus-mediated short-hairpin RNA (shRNA). Cardiac function was assessed by echocardiography. Total collagen deposition was assessed by Masson's trichrome and Picrosirius red staining. HMGB1, collagen I and III, and transforming growth factor β1 (TGF-β1) expression was quantified by immunostaining and western bolt analysis. In vitro, isolated neonatal cardiac fibroblasts were treated with high glucose (HG) or recombinant HMGB1 (rHMGB1). Pharmacologic (neutralizing anti-HMGB1 antibody) or genetic (shRNA-HMGB1) inhibition of HMGB1 was used to investigate the role of HMGB1 in HG-induced functional changes of cardiac fibroblasts.

RESULTS

In vivo, HMGB1 was diffusely expressed in the myocardium of diabetic mice. HMGB1 silencing ameliorated left ventricular dysfunction and remodeling and decreased collagen deposition in diabetic mice. In vitro, HG induced HMGB1 translocation and secretion in both viable cardiomyocytes and fibroblasts. Administration of rHMGB1 dose-dependently increased the expression of collagens I and III and TGF-β1 in cardiac fibroblasts. HMGB1 inhibition reduced HG-induced collagen production, matrix metalloproteinase (MMP) activities, proliferation, and activated mitogen-activated protein kinase signaling in cardiac fibroblasts.

CONCLUSIONS

HMGB1 inhibition could alleviate cardiac fibrosis and remodeling in diabetic cardiomyopathy. Inhibition of HMGB1 might have therapeutic potential in the treatment of the disease.

Role of caveolin-1 in atrial fibrillation as an anti-fibrotic signaling molecule in human atrial fibroblasts

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the general population; yet, the precise mechanisms resulting in AF are not fully understood. Caveolin-1 (Cav-1), the principal structural component of caveolae organelles in cardiac fibroblasts, is involved in several cardiovascular conditions; however, the study on its function in atrium, in particular, in AF, is still lacking. This report examines the hypothesis that Cav-1 confers an anti-AF effect by mediating atrial structural remodeling through its anti-fibrotic action. We evaluated the expression of Cav-1, transforming growth factor-β1 (TGF-β1), and fibrosis in atrial specimens of 13 patients with AF and 10 subjects with sinus rhythm, and found that the expression of Cav-1 was significantly downregulated, whereas TGF-β1 level, collagens I/III contents and atrial fibrosis were markedly increased, in AF. Western blot analysis demonstrated that treatment of human atrial fibroblasts (HAFs) with TGF-β1 resulted in a concentration- and time-dependent repression of Cav-1. Downregulation of Cav-1 with siRNA increased the TGF-β1-induced activation of Smad signal pathway and collagens production in HAFs. Furthermore, incubation of HAFs with the peptides derived from Cav-1 to achieve Cav-1 gain-of-function abolished the TGF-β1-induced production of collagens I/III and decreases of MMP-2/-9 expression. Therefore it was concluded that Cav-1 is an important anti-AF signaling mediator by conferring its anti-fibrotic effects in atrium.

N-terminal truncated intracellular matrix metalloproteinase-2 induces cardiomyocyte hypertrophy, inflammation and systolic heart failure

Matrix metalloproteinase-2 (MMP-2) is increasingly recognized as a major contributor to progressive cardiac injury within the setting of ischemia-reperfusion injury and ischemic ventricular remodeling. A common feature of these conditions is an increase in oxidative stress, a process that engages multiple pro-inflammatory and innate immunity cascades. We recently reported on the identification and characterization of an intracellular isoform of MMP-2 generated by oxidative stress-mediated activation of an alternative promoter located within the first intron of the MMP-2 gene. Transcription from this site generates an N-terminal truncated 65 kDa isoform of MMP-2 (NTT-MMP-2) that lacks the secretory sequence and the inhibitory prodomain region. The NTT-MMP-2 isoform is intracellular, enzymatically active and localizes in part to mitochondria. Expression of the NTT-MMP-2 isoform triggers Nuclear Factor of Activated T-cell (NFAT) and NF-κB signaling with the expression of a highly defined innate immunity transcriptome, including Interleukin-6, MCP-1, IRF-7 and pro-apoptotic transcripts. To determine the functional significance of the NTT-MMP-2 isoform in vivo we generated cardiac-specific NTT-MMP-2 transgenic mice. These mice developed progressive cardiomyocyte and ventricular hypertrophy associated with systolic heart failure. Further, there was evidence for cardiomyocyte apoptosis and myocardial infiltration with mononuclear cells. The NTT-MMP-2 transgenic hearts also demonstrated more severe injury following ex vivo ischemia-reperfusion injury. We conclude that a novel intracellular MMP-2 isoform induced by oxidant stress directly contributes, in the absence of superimposed injury, to cardiomyocyte hypertrophy. inflammation, systolic heart failure and enhanced susceptibility to ischemia-reperfusion injury.

The role of focal adhesion complexes in fibroblast mechanotransduction during scar formation

Historically, great efforts have been made to elucidate the biochemical pathways that direct the complex process of wound healing; however only recently has there been recognition of the importance that mechanical signals play in the process of tissue repair and scar formation. The body's physiologic response to injury involves a dynamic interplay between mechanical forces and biochemical cues which directs a cascade of signals leading ultimately to the formation of fibrotic scar. Fibroblasts are a highly mechanosensitive cell type and are also largely responsible for the generation of the fibrotic matrix during scar formation and are thus a critical player in the process of mechanotransduction during tissue repair. Mechanotransduction is initiated at the interface between the cell membrane and the extracellular matrix where mechanical signals are first translated into a biochemical response. Focal adhesions are dynamic multi-protein complexes through which the extracellular matrix links to the intracellular cytoskeleton. These focal adhesion complexes play an integral role in the propagation of this initial mechanical cue into an extensive network of biochemical signals leading to widespread downstream effects including the influx of inflammatory cells, stimulation of angiogenesis, keratinocyte migration, fibroblast proliferation and collagen synthesis. Increasing evidence has demonstrated the importance of the biomechanical milieu in healing wounds and suggests that an integrated approach to the discovery of targets to decrease scar formation may prove more clinically efficacious than previous purely biochemical strategies.

Preliminary Exploration on Anti-Fibrosis Effect of Kaempferol in Mice with Schistosoma Japonicum Infection

This study is to explore the effectiveness and mechanism of kaempferol on treatment of hepatic fibrosis induced by schistosoma egg. Thirty-six healthy male balb/c mice were randomly divided into 6 groups, including negative group, positive group, and 4 different dosages of kaempferol treatment groups. Each mouse was infected with 20 schistosoma Cercariae japonicum, except the ones in the negative group. Four weeks later, every infected mouse was administrated with 500mg/kg/day praziquantel for 2 days, and all kaempferol groups were followed by a 4-week administration of kaempferol with 5, 10, 15 and 20mg/kg/day respectively, while both control groups were administrated with normal saline. AH the mice were sacrificed on the 59th day after infection. The liver tissues were taken for Masson staining to detect collagen and real-time quantitative PCR to detect the mRNA expression of IL-13, collagen 1 and MMP-2. As a result, Masson stain showed that the optical density of the interested region in the positive group was significantly higher than that in the negative group (P<0.01), and the optical density in all kaempferol groups was significantly lower than that in the positive group (P<0.05 or P<0.01). Real-time PCR showed that the mRNA expression of IL-13 in the positive group was significantly higher than that in the negative group (P<0.01), and the expression of IL-13 in the 20mg/kg and 15mg/kg kaempferol groups was significantly lower than that in the positive group, respectively (P<0.05). The mRNA expression of collagen 1 in the positive group was significantly higher than that in the negative group (P<0.01), and mRNA expression of collagen 1 in the 20mg/kg kaempferol group was significantly lower than that in the positive group (P<0.05). There were no significant differences between the positive and negative groups on mRNA expression of MMP-2. The mRNA expression of MMP-2 in all kaempferol groups was significantly higher than that in the positive group (P<0.05 or P<0.01). In conclusion, kaempferol can ameliorate schistosoma egg-induced hepatic fibrosis via regulating the IL-13 signal pathway. Kaempferol is very likely to be an IL-13 targeted anti-fibrosis medicine.