Suppression of atrial natriuretic peptide/natriuretic peptide receptor-A-mediated signaling upregulates angiotensin-II-induced collagen synthesis in adult cardiac fibroblasts

Triiodo-L-thyronine (T3) downregulates Npr1 gene (coding for natriuretic peptide receptor-A) transcription in H9c2 cells: involvement of β-AR-ROS signaling

INTRODUCTION

Natriuretic peptide receptor-A (NPR-A) signaling system is considered as an intrinsic productive mechanism of the heart that opposes abnormal cardiac remodeling and hypertrophic growth. NPR-A is coded by Npr1 gene, and its expression is downregulated in the hypertrophied heart.

AIM

We sought to examine the levels of Npr1 gene transcription in triiodo-L-thyronine (T3) treated hypertrophied cardiomyocyte (H9c2) cells, in vitro, and also the involvement of β-adrenergic receptor (β-AR) - Reactive oxygen species (ROS) signaling system in the down-regulation of Npr1 transcription also studied.

MAIN METHODS

Anti-hypertrophic Npr1 gene transcription was monitored in control and T3-treated (dose and time dependent) H9c2 cells, using a real time PCR method. Further, cell size, intracellular cGMP, ROS, hypertrophy markers (ANP, BNP, α-sk, α-MHC and β-MHC), β-AR, and protein kinase cGMP-dependent 1 (PKG-I) genes expression were also determined. The intracellular cGMP and ROS levels were determined by ELISA and DCF dye method, respectively. In addition, to neutralize T3 mediated ROS generation, H9c2 cells were treated with T3 in the presence and absence of antioxidants [curcumin (CU) or N-acetyl-L-cysteine (NAC)].

RESULTS

A dose dependent (10 pM, 100 pM, 1 nM and 10 nM) and time dependent (12 h, 24 h and 48 h) down-regulation of Npr1 gene transcription (20, 39, 60, and 74% respectively; 18, 55, and 85%, respectively) were observed in T3-treated H9c2 cells as compared with control cells. Immunofluorescence analysis also revealed that a marked down regulation of NPR- A protein in T3-treated cells as compared with control cells. Further, a parallel downregulation of cGMP and PKG-I (2.4 fold) were noticed in the T3-treated cells. In contrast, a time dependent increased expression of β-AR (60, 72, and 80% respectively) and ROS (26, 48, and 74%, respectively) levels were noticed in T3-treated H9c2 cells as compared with control cells. Interestingly, antioxidants, CU or NAC co-treated T3 cells displayed a significant reduction in ROS (69 and 81%, respectively) generation and to increased Npr1 gene transcription (81 and 88%, respectively) as compared with T3 alone treated cells.

CONCLUSION

Our result suggest that down regulation of Npr1 gene transcription is critically involved in T3- induced hypertrophic growth in H9c2 cells, and identifies the cross-talk between T3-β-AR-ROS and NPR-A signaling.

Cfa-circ002203 was upregulated in rapidly paced atria of dogs and involved in the mechanisms of atrial fibrosis

BACKGROUND AND AIMS

The role of circular RNAs (circRNAs) in the pathophysiology of cardiovascular disease is gradually being elucidated; however, their roles in atrial fibrillation (AF)-related fibrosis are largely unknown. This study aimed to characterize the different circRNA profiles in the rapid-pacing atria of dogs and explore the mechanisms involved in atrial fibrosis.

METHODS

A rapid right atrial-pacing model was established using electrical stimulation from a pacemaker. After 14 days, atrial tissue was collected for circRNA sequencing analysis. In vitro fibrosis was established by stimulating canine atrial fibroblasts with angiotensin II (Ang II). The fibroblasts were transfected with siRNA and overexpressing plasmids to explore the effects of cfa-circ002203 on fibroblast proliferation, migration, differentiation, and the expression of fibrosis-related proteins.

RESULTS

In total, 146 differentially expressed circRNAs were screened, of which 106 were upregulated and 40 were downregulated. qRT-PCR analysis showed that cfa-circ002203 was upregulated in both in vivo and in vitro fibroblast fibrosis models. The upregulation of cfa-circ002203 enhanced proliferation and migration while weakening the apoptosis of fibroblasts. Western blotting showed that cfa-circ002203 overexpression increased the protein expression levels of fibrosis-related indicators (Col I, Col III, MMP2, MMP9, and α-SMA) and decreased the protein expression levels of pro-apoptotic factors (Bax and Caspase 3) in Ang II-induced fibroblast fibrosis.

CONCLUSION

Cfa-circ002203 might serve as an active promoter of the proliferation, migration, and fibrosis of atrial fibroblasts and is involved in AF-induced fibroblast fibrosis.

Molecular Signaling Mechanisms and Function of Natriuretic Peptide Receptor-A in the Pathophysiology of Cardiovascular Homeostasis

The discovery of atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP) and their cognate receptors has greatly increased our knowledge of the control of hypertension and cardiovascular homeostasis. ANP and BNP are potent endogenous hypotensive hormones that elicit natriuretic, diuretic, vasorelaxant, antihypertrophic, antiproliferative, and antiinflammatory effects, largely directed toward the reduction of blood pressure (BP) and cardiovascular diseases (CVDs). The principal receptor involved in the regulatory actions of ANP and BNP is guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA), which produces the intracellular second messenger cGMP. Cellular, biochemical, molecular, genetic, and clinical studies have facilitated understanding of the functional roles of natriuretic peptides (NPs), as well as the functions of their receptors, and signaling mechanisms in CVDs. Transgenic and gene-targeting (gene-knockout and gene-duplication) strategies have produced genetically altered novel mouse models and have advanced our knowledge of the importance of NPs and their receptors at physiological and pathophysiological levels in both normal and disease states. The current review describes the past and recent research on the cellular, molecular, genetic mechanisms and functional roles of the ANP-BNP/NPRA system in the physiology and pathophysiology of cardiovascular homeostasis as well as clinical and diagnostic markers of cardiac disorders and heart failure. However, the therapeutic potentials of NPs and their receptors for the diagnosis and treatment of cardiovascular diseases, including hypertension, heart failure, and stroke have just begun to be expanded. More in-depth investigations are needed in this field to extend the therapeutic use of NPs and their receptors to treat and prevent CVDs.

Silencing Survivin: a Key Therapeutic Strategy for Cardiac Hypertrophy

Cardiac hypertrophy, in its aspects of localized thickening of the interventricular septum and concentric increase of the left ventricle, constitutes a risk factor of heart failure. Myocardial hypertrophy, in the presence of different degree of myocardial fibrosis, is paralleled by significant molecular, cellular, and histological changes inducing alteration of cardiac extracellular matrix composition as well as sarcomeres and cytoskeleton remodeling. Previous studies indicate osteopontin (OPN) and more recently survivin (SURV) overexpression as the hallmarks of heart failure although SURV function in the heart is not completely clarified. In this study, we investigated the involvement of SURV in intracellular signaling of hypertrophic cardiomyocytes and the impact of its transcriptional silencing, laying the foundation for novel target gene therapy in cardiac hypertrophy. Oligonucleotide-based molecules, like theranostic optical nanosensors (molecular beacons) and siRNAs, targeting SURV and OPN mRNAs, were developed. Their diagnostic and therapeutic potential was evaluated in vitro in hypertrophic FGF23-induced human cardiomyocytes and in vivo in transverse aortic constriction hypertrophic mouse model. Engineered erythrocyte was used as shuttle to selectively target and transfer siRNA molecules into unhealthy cardiac cells in vivo. The results highlight how the SURV knockdown could negatively influence the expression of genes involved in myocardial fibrosis in vitro and restores structural, functional, and morphometric features in vivo. Together, these data suggested that SURV is a key factor in inducing cardiomyocytes hypertrophy, and its shutdown is crucial in slowing disease progression as well as reversing cardiac hypertrophy. In the perspective, targeted delivery of siRNAs through engineered erythrocytes can represent a promising therapeutic strategy to treat cardiac hypertrophy. Theranostic SURV molecular beacon (MB-SURV), transfected into FGF23-induced hypertrophic human cardiomyocytes, significantly dampened SURV overexpression. SURV down-regulation determines the tuning down of MMP9, TIMP1 and TIMP4 extracellular matrix remodeling factors while induces the overexpression of the cardioprotective MCAD factor, which counterbalance the absence of pro-survival and anti-apoptotic SURV activity to protect cardiomyocytes from death. In transverse aortic constriction (TAC) mouse model, the SURV silencing restores the LV mass levels to values not different from the sham group and counteracts the progressive decline of EF, maintaining its values always higher with respect to TAC group. These data demonstrate the central role of SURV in the cardiac reverse remodeling and its therapeutic potential to reverse cardiac hypertrophy.

Targeting cardiac fibrosis in heart failure with preserved ejection fraction: mirage or miracle?

Cardiac fibrosis is central to the pathology of heart failure, particularly heart failure with preserved ejection fraction (HFpEF). Irrespective of the underlying profibrotic condition (e.g. ageing, diabetes, hypertension), maladaptive cardiac fibrosis is defined by the transformation of resident fibroblasts to matrix-secreting myofibroblasts. Numerous profibrotic factors have been identified at the molecular level (e.g. TGFβ, IL11, AngII), which activate gene expression programs for myofibroblast activation. A number of existing HF therapies indirectly target fibrotic pathways; however, despite multiple clinical trials in HFpEF, a specific clinically effective antifibrotic therapy remains elusive. Therapeutic inhibition of TGFβ, the master-regulator of fibrosis, has unfortunately proven toxic and ineffective in clinical trials to date, and new approaches are needed. In this review, we discuss the pathophysiology and clinical implications of interstitial fibrosis in HFpEF. We provide an overview of trials targeting fibrosis in HFpEF to date and discuss the promise of potential new therapeutic approaches and targets in the context of underlying molecular mechanisms.

The Role of Natriuretic Peptides in the Regulation of Cardiac Tolerance to Ischemia/Reperfusion and Postinfarction Heart Remodeling

In the past 10 years, mortality from acute myocardial infarction has not decreased despite the widespread introduction of percutaneous coronary intervention. The reason for this situation is the absence in clinical practice of drugs capable of preventing reperfusion injury of the heart with high efficiency. In this regard, noteworthy natriuretic peptides (NPs) which have the infarct-limiting effect, prevent reperfusion cardiac injury, prevent adverse post-infarction remodeling of the heart. Atrial natriuretic peptide does not have the infarct-reducing effect in rats with alloxan-induced diabetes mellitus. NPs have the anti-apoptotic and anti-inflammatory effects. There is indirect evidence that NPs inhibit pyroptosis and autophagy. Published data indicate that NPs inhibit reactive oxygen species production in cardiomyocytes, aorta, heart, kidney and the endothelial cells. NPs can suppress aldosterone, angiotensin II, endothelin-1 synthesize and secretion. NPs inhibit the effects aldosterone, angiotensin II on the post-receptor level through intracellular signaling events. NPs activate guanylyl cyclase, protein kinase G and protein kinase A, and reduce phosphodiesterase 3 activity. NO-synthase and soluble guanylyl cyclase are involved in the cardioprotective effect of NPs. The cardioprotective effect of natriuretic peptides is mediated via activation of kinases (AMPK, PKC, PI3 K, ERK1/2, p70s6 k, Akt) and inhibition of glycogen synthase kinase 3β. The cardioprotective effect of NPs is mediated via sarcolemmal K_ATP channel and mitochondrial K_ATP channel opening. The cardioprotective effect of brain natriuretic peptide is mediated via MPT pore closing. The anti-fibrotic effect of NPs may be mediated through inhibition TGF-β1 expression. Natriuretic peptides can inhibit NF-κB activity and activate GATA. Hemeoxygenase-1 and peroxisome proliferator-activated receptor γ may be involved in the infarct-reducing effect of NPs. NPs exhibit the infarct-limiting effect in patients with acute myocardial infarction. NPs prevent post-infarction remodeling of the heart. To finally resolve the question of the feasibility of using NPs in AMI, a multicenter, randomized, blind, placebo-controlled study is needed to assess the effect of NPs on the mortality of patients after AMI.

Genetic Ablation and Guanylyl Cyclase/Natriuretic Peptide Receptor-A: Impact on the Pathophysiology of Cardiovascular Dysfunction

Mice bearing targeted gene mutations that affect the functions of natriuretic peptides (NPs) and natriuretic peptide receptors (NPRs) have contributed important information on the pathogenesis of hypertension, kidney disease, and cardiovascular dysfunction. Studies of mice having both complete gene disruption and tissue-specific gene ablation have contributed to our understanding of hypertension and cardiovascular disorders. These phenomena are consistent with an oligogenic inheritance in which interactions among a few alleles may account for genetic susceptibility to hypertension, renal insufficiency, and congestive heart failure. In addition to gene knockouts conferring increased risks of hypertension, kidney disorders, and cardiovascular dysfunction, studies of gene duplications have identified mutations that protect against high blood pressure and cardiovascular events, thus generating the notion that certain alleles can confer resistance to hypertension and heart disease. This review focuses on the intriguing phenotypes of Npr1 gene disruption and gene duplication in mice, with emphasis on hypertension and cardiovascular events using mouse models carrying Npr1 gene knockout and/or gene duplication. It also describes how Npr1 gene targeting in mice has contributed to our knowledge of the roles of NPs and NPRs in dose-dependently regulating hypertension and cardiovascular events.

Valporic acid enhances the Atrial Natriuretic Peptide (ANP) mediated anti-hypertrophic activity by modulating the Npr1 gene transcription in H9c2 cells in vitro

The present study was aimed to determine whether stimulating Npr1 gene activity using Valporic acid (VA), a small short chain fatty acid molecule can enhance ANP mediated anti-hypertrophic activity in isoproterenol (ISO) - treated H9c2 cells in vitro. H9c2 cells were treated with ISO (10^-5 M) and co-treated with VA (10^-5 M) in the presence and absence of ANP (10^-8M), for 48h. ATRA (10^-5 M) was used as a positive inducer of Npr1 gene transcription. The mRNA expression of Npr1 and PKG-I genes, proto-oncogenes (c-fos, c-jun and c-myc) and hypertrophic markers (ANP, BNP, α-sk and β-MyHC), genes were determined by quantitative PCR (qPCR). The protein profiling of NPR-A, PKG-I and cGMP were evaluated by Western blot, immunofluorescence and ELISA respectively. A marked reduction in the level of expression of Npr1 (3- fold) and PKG-I (2.5-fold) genes and increased expression of proto-oncogenes (p< 0.001, respectively) and hypertrophic marker genes (p<0.001, respectively) were noticed in the ISO-treated H9c2 cells as compared with control cells. In contrast, the VA treated cells showed maximal Npr1 gene expression (3.5-fold) as compared with ATRA treated cells (2 fold), which is well correlated with the intracellular cGMP levels (80% vs 60%) and reduced (2.5-fold) HDAC -1&-2 mRNA expression. Furthermore, VA or ATRA treatment effectively reversed the ISO-induced altered expression of Npr1 and PKG-I genes, proto-oncogenes, and hypertrophic markers genes. Interestingly, the results of the present study suggest that ANP mediated anti-hypertrophic activity was enhanced with either VA (p<0.001) or ATRA (p<0.01) co-treatment. Together, we conclude that VA in combination with ANP can be a novel therapeutical approach for the treatment and management of left ventricular cardiac hypertrophy.

Suppression of Npr1, not Npr2 gene function induces hypertrophic growth in H9c2 cells in vitro

Npr1 gene (coding for NPR-A) and Npr2 gene (coding for NPR-B) are identified as intrinsic anti-hypertrophic genes that opposes abnormal cardiac remodeling. However, the functional role of Npr1 and Npr2 genes during cardiac hypertrophic growth is not well understood. Hence, the present investigation was aimed to study the effect of Npr1 and Npr2 gene silencing, respectively on β-AR activation induced cardiac hypertrophic growth in H9c2 cells in vitro. The control, Npr1, and Npr2 gene suppressed H9c2 cells, respectively were treated with ISO (10^-5 M) for 48 h. The mRNA and protein expression profile of NPR-A, NPR-B, PKG-I and cGMP were analyzed by qPCR, Western blotting, ELISA, and immunofluorescence methods, respectively. A marked increase in cell size (30.10 ± 0.51 μm vs 61.83 ± 0.43 μm, 2-fold) accompanied by elevated hypertrophic marker genes (α-sk and β-MHC 3-fold, respectively) expression was observed in Npr1 gene suppressed H9c2 cells as compared with control cells. In contrast, the Npr2 gene suppression in H9c2 cells neither altered the cell size nor the level of hypertrophic marker genes expression. Upon exposure to Isoproterenol, the Npr1 suppressed H9c2 cells exhibited further increase in cell size (1.5 fold), whereas, no significant increase in cell size or marker genes expression was noticed in Npr2 suppressed cells. Moreover, the intracellular cGMP level was down-regulated by 2-fold in Npr1 suppressed cells, while, no significant change was observed in Npr2 suppressed cells. Together, these results suggest that Npr1, not Npr2 gene function is positively associated with the initiation of cardiac fetal gene program and development of cardiac hypertrophic growth.

Differential expression and regulation of anti-hypertrophic genes Npr1 and Npr2 during β-adrenergic receptor activation-induced hypertrophic growth in rats

We sought to determine the effect of chronic activation of β-adrenergic receptor (β-AR) on the left ventricular (LV) expression profile of Npr1 and Npr2 (coding for NPR-A and NPR-B, respectively) genes, and the functional activity of these receptors in adult Wistar rat hearts. The Npr1 gene expression was markedly reduced (3.5-fold), while the Npr2 gene expression was up regulated (4-fold) in Isoproterenol (ISO)-treated heart as compared with controls. A gradual reduction in NPR-A protein (3-fold), cGMP levels (75%) and a steady increased expression of NPR-B protein (4-fold), were noticed in ISO hearts. Further, in-vitro membranes assay shows that NPR-A dependent guanylyl cyclase (GC) activity was down-regulated (2-fold), whereas NPR-B dependent GC activity was increased (5-fold) in ISO treated hearts. Atenolol treatment normalized the altered expression of Npr1 and Npr2 genes. In conclusion, the chronic β-AR activation differentially regulates Npr1 and Npr2 genes in the heart. Npr1 down regulation is positively associated with the development of left ventricular hypertrophy (LVH) in ISO rats.

The dipeptidyl peptidase inhibitor linagliptin and the angiotensin II receptor blocker telmisartan show renal benefit by different pathways in rats with 5/6 nephrectomy

Dipeptidyl peptidase (DPP)-4 inhibitors delay chronic kidney disease (CKD) progression in experimental diabetic nephropathy in a glucose-independent manner. Here we compared the effects of the DPP-4 inhibitor linagliptin versus telmisartan in preventing CKD progression in non-diabetic rats with 5/6 nephrectomy. Animals were allocated to 1 of 4 groups: sham operated plus placebo; 5/6 nephrectomy plus placebo; 5/6 nephrectomy plus linagliptin; and 5/6 nephrectomy plus telmisartan. Interstitial fibrosis was significantly decreased by 48% with linagliptin but a non-significant 24% with telmisartan versus placebo. The urine albumin-to-creatinine ratio was significantly decreased by 66% with linagliptin and 92% with telmisartan versus placebo. Blood pressure was significantly lowered by telmisartan, but it was not affected by linagliptin. As shown by mass spectrometry, the number of altered peptide signals for linagliptin in plasma was 552 and 320 in the kidney. For telmisartan, there were 108 peptide changes in plasma and 363 in the kidney versus placebo. Linagliptin up-regulated peptides derived from collagen type I, apolipoprotein C1, and heterogeneous nuclear ribonucleoproteins A2/B1, a potential downstream target of atrial natriuretic peptide, whereas telmisartan up-regulated angiotensin II. A second study was conducted to confirm these findings in 5/6 nephrectomy wild-type and genetically deficient DPP-4 rats treated with linagliptin or placebo. Linagliptin therapy in wild-type rats was as effective as DPP-4 genetic deficiency in terms of albuminuria reduction. Thus, linagliptin showed comparable efficacy to telmisartan in preventing CKD progression in non-diabetic rats with 5/6 nephrectomy. However, the underlying pathways seem to be different.

A new Agkistrodon halys venom-purified protein C activator prevents myocardial fibrosis in diabetic rats

Aim

To assess the effects of protein C activator (PCA) from Agkistrodon halys snake venom on cardiac fibrosis in streptozotocin (STZ) induced diabetic rat model, and investigate the mechanisms of its action.

Methods

PCA was identified by one-dimensional reversed phase liquid chromatography – mass spectrometry/mass spectrometry. Male Sprague-Dawley rats (120-140 g) were randomly assigned to negative control (NC) and diabetic group. Diabetes was induced by STZ in high-fat diet fed rats. Diabetic group was subdivided into three groups: diabetic group (DM), diabetic group treated with PCA (0.5, 2, and 8 mg/kg), and diabetic group treated with metformin (5 mg/kg, positive control). NC and DM groups received the same volume of distilled water. Left ventricular mass index (LVWI) and collagen volume fraction were measured by hematoxylin and eosin and Masson staining. Transforming growth factor beta-1 (TGF-β1) and interleukin 1 beta (IL-1β) levels were determined by enzyme-linked immunosorbent assay.

Results

The diabetic rat model was successfully established by STZ induction and high-fat diet. Glucose level, LVWI, TGF-β1 and IL-1β level, and collagen volume fraction were significantly reduced in diabetic rats treated by PCA in a dose-dependent manner (P < 0.050), especially in the high dose (8 mg/kg) group (P < 0.010), compared to diabetes group. The high dose PCA had the same effect as metformin positive control in reducing the level of fasting blood glucose. PCA decreased the expression of MMP-2 and reduced that of TIMP-2.

Conclusion

Our results indicate that PCA has anti-fibrotic effects and that it may be used to treat myocardial fibrosis.

Recombinant human brain natriuretic peptide attenuates trauma-/haemorrhagic shock-induced acute lung injury through inhibiting oxidative stress and the NF-κB-dependent inflammatory/MMP-9 pathway

Acute lung injury (ALI) is one of the most serious complications in traumatic patients and is an important part of multiple organ dysfunction syndrome (MODS). Recombinant human brain natriuretic peptide (rhBNP) is a peptide with a wide range of biological activity. In this study, we investigated local changes in oxidative stress and the NF-κB-dependent matrix metalloproteinase-9 (MMP-9) pathway in rats with trauma/haemorrhagic shock (TH/S)-induced ALI and evaluated the effects of pretreatment with rhBNP. Forty-eight rats were randomly divided into four groups: sham operation group, model group, low-dosage rhBNP group and high-dosage rhBNP group (n = 12 for each group). Oxidative stress and MPO activity were measured by ELISA kits. MMP-9 activity was detected by zymography analysis. NF-κB activity was determined using Western blot assay. With rhBNP pretreatment, TH/S-induced protein leakage, increased MPO activity, lipid peroxidation and metalloproteinase (MMP)-9 activity were inhibited. Activation of antioxidative enzymes was reversed. The phosphorylation of NF-κB and the degradation of its inhibitor IκB were suppressed. The results suggested that the protection mechanism of rhBNP is possibly mediated through upregulation of anti-oxidative enzymes and inhibition of NF-κB activation. More studies are needed to further evaluate whether rhBNP is a suitable candidate as an effective inhaling drug to reduce the incidence of TH/S-induced ALI.

Improving vagal activity ameliorates cardiac fibrosis induced by angiotensin II: in vivo and in vitro

Cardiac remodeling is characterized by overactivity of the renin–angiotensin system (RAS) and withdrawal of vagal activity. We hypothesized that improving vagal activity could attenuate cardiac fibrosis induced by angiotensin II (Ang II) in vivo and in vitro. Rats were subjected to abdominal aorta constriction (AAC) with or without pyridostigmine (PYR) (31 mg/kg/d). After 8 weeks, PYR significantly decreased Ang II level, AT1 protein expression, and collagen deposition in cardiac tissue and improved heart rate variability, baroreflex sensitivity and cardiac function, which were abolished by atropine. In vitro, treatment of cardiac fibroblasts (CFs) with Ang II (10⁻⁷ M) increased cell proliferation, migration, transformation, and secretory properties, which were significantly diminished by acetylcholine (ACh, 10⁻⁶ M). Subsequently, Ang II significantly increased collagen type I expression as well as metalloproteinase (MMP)-2 expression and activity. Transforming growth factor (TGF)-β1 expression and Smad3 phosphorylation presented a similar trend. Notably, the knockdown of the acetylcholine M₂ receptor by siRNA could abolish ACh anti-fibrotic action. These data implicated cholinesterase inhibitor can increase vagal activity and reduce local Ang II level, and ACh inhibit Ang II pro-fibrotic effects. Our findings suggested that the parasympathetic nervous system can serve as a promising target for cardiac remodeling treatment.

Effects of Atrial Natriuretic Peptide on Rat Ventricular Fibroblasts During Differentiation Into Myofibroblasts

Atrial natriuretic peptide antifibrotic properties are mainly described in cardiac myocytes or in induced cardiac myofibroblasts (Angiotensin II or TGF-β induced differentiation). In the present work, we investigate the effects of ANP/NPRA/cGMP system in modulating rat cardiac fibroblasts function. Cardiac fibroblasts were isolated from adult Wistar male rats and cultured in the presence of serum in order to induce fibroblasts differentiation. Cultures were then treated with ANP (1 µM), 8-Br-cGMP (100 µM) or IBMX (100 µM), a non-specific phosphodiesterases inhibitor. ANP significantly decreased proliferation rate and collagen secretion. Its effect was mimicked by the cGMP analog, while combining ANP with 8-Br-cGMP did not lead to additional effects. Moreover intracellular cGMP levels were elevated when cells were incubated with ANP confirming that ANP intracellular pathway is mediated by cGMP. Additionally, immunoblotting and immunofluorescence were used to confirm the presence of guanylyl cyclase specific natriuretic peptide receptors A and B. Finally we scanned specific cGMP dependent PDEs via RT-qPCR, and noticed that inhibiting all PDEs led to an important decrease in proliferation rate. Effect of ANP became more prominent after 10 culture days, confirming the importance of ANP in fibroblasts to myofibroblasts differentiation. Uncovering cellular aspects of ANP/NPRA/cGMP signaling system provided more elements to help understand cardiac fibrotic process.

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.

Renal C3 complement component: feed forward to diabetic kidney disease

BACKGROUND

Diabetic nephropathy is the main cause of end-stage renal disease and has reached epidemic proportions.

METHODS

Comprehensive genomic profiling (RNAseq) was employed in the ZS (F1 hybrids of Zucker and spontaneously hypertensive heart failure) model of diabetic nephropathy. Controls were lean littermates.

RESULTS

Diabetic nephropathy in obese, diabetic ZS was accelerated by a single episode of renal ischemia (DI). This rapid renal decline was accompanied by the activation of the renal complement system in DI, and to a lesser extent in sham-operated diabetic rats (DS). In DI there were significant increases in renal mRNA encoding C3, C4, C5, C6, C8, and C9 over sham-operated lean normal controls (LS). Moreover, mRNAs encoding the receptors for the anaphylatoxins C3a and C5a were also significantly increased in DI compared to LS. The classic complement pathway was activated in diabetic kidneys with significant increases of C1qa, C1qb, and C1qc mRNAs in DI over LS. In addition, critical regulators of complement activation were significantly attenuated in DI and DS. These included mRNAs encoding CD55, decay accelerating factor, and CD59, which inhibit the membrane attack complex. C3, C4, and C9 proteins were demonstrated in renal tubules and glomeruli. The complement RNAseq data were incorporated into a gene network showing interactions among C3-generating renal tubular cells and other immune competent migratory cells.

CONCLUSIONS

We conclude that local activation of the complement system mediates renal injury in diabetic nephropathy.

Impaired sinoatrial node function and increased susceptibility to atrial fibrillation in mice lacking natriuretic peptide receptor C

Natriuretic peptides (NPs) are critical regulators of the cardiovascular system that are currently viewed as possible therapeutic targets for the treatment of heart disease. Recent work demonstrates potent NP effects on cardiac electrophysiology, including in the sinoatrial node (SAN) and atria. NPs elicit their effects via three NP receptors (NPR-A, NPR-B and NPR-C). Among these receptors, NPR-C is poorly understood. Accordingly, the goal of this study was to determine the effects of NPR-C ablation on cardiac structure and arrhythmogenesis. Cardiac structure and function were assessed in wild-type (NPR-C(+/+)) and NPR-C knockout (NPR-C(-/-)) mice using echocardiography, intracardiac programmed stimulation, patch clamping, high-resolution optical mapping, quantitative polymerase chain reaction and histology. These studies demonstrate that NPR-C(-/-) mice display SAN dysfunction, as indicated by a prolongation (30%) of corrected SAN recovery time, as well as an increased susceptibility to atrial fibrillation (6% in NPR-C(+/+) vs. 47% in NPR-C(-/-)). There were no differences in SAN or atrial action potential morphology in NPR-C(-/-) mice; however, increased atrial arrhythmogenesis in NPR-C(-/-) mice was associated with reductions in SAN (20%) and atrial (15%) conduction velocity, as well as increases in expression and deposition of collagen in the atrial myocardium. No differences were seen in ventricular arrhythmogenesis or fibrosis in NPR-C(-/-) mice. This study demonstrates that loss of NPR-C results in SAN dysfunction and increased susceptibility to atrial arrhythmias in association with structural remodelling and fibrosis in the atrial myocardium. These findings indicate a critical protective role for NPR-C in the heart.

Protective activity of gallic acid against glyoxal -induced renal fibrosis in experimental rats

This study was designed to evaluate the protective activity of gallic acid (GA) against glyoxal (GO) an advanced glycation intermediate-induced renal fibrosis in experimental rats. Glyoxal (i.p) at a dose of 15 mg/Kg body weight/day for 4 weeks induces renal fibrosis. GA was administered orally (100 mg/Kg body weight/day) along with GO for 4 weeks. The anti-fibrotic activity of GA was analyzed by measuring the collagen synthesis and deposition in renal tissues using mRNA expression analysis and Masson trichrome staining (MTS), respectively. The nephroprotective potential of GA was assessed by quantifying the markers of kidney damage such as serum blood-urea-nitrogen (BUN), creatinine (CR) and alkaline phosphatase (AP). Moreover, basement membrane damage in renal tissues was analysed by periodic acid Schiff’s (PAS) staining. GA co-treatment markedly suppressed the GO-induced elevation in mRNA expression of collagenIand III, MMP-2, MMP-9 and NOX (p < 0.05, respectively) genes as compared with GO alone infused rats. In addition, GA co-treatment significantly attenuated the GO -induced elevation in serum markers such as BUN, CR and AP levels (p < 0.05, respectively). Furthermore, GA co-treatment restored back the decreased renal super oxide dismutase (SOD) activity (p < 0.05) thereby assuage the reactive oxygen species (ROS) generation, and maintained the normal architecture of glomerulus. The present study clearly indicates that GO -induces renal fibrosis by enhancing GO/receptor of advanced glycation end product (RAGE) induced ROS generation and GA effectively counteracted GO-induced renal fibrosis by its ROS quenching and anti-glycation activity.

Safflower yellow inhibits angiotensin II-induced adventitial fibroblast proliferation and migration

Safflower yellow (SY) has been widely used in Chinese medicine for the treatment of ischemic cardiocerebrovascular disease. Recent studies have indicated that SY has a reverse effect on vascular remodeling (VR). However, its detailed mechanisms require further study to provide more scientific evidence for the clinical treatment of VR. This study aims to investigate the effects of SY on angiotensin II (Ang II)-induced cell proliferation, migration, apoptosis, and extracellular matrix in rat aortic adventitial fibroblasts (AFs). The proliferation and migration rates of AFs treated with Ang II for 24 h were higher than those of untreated AFs; and increases in the expression of p-ERK1/2, AP-1, collagen I, and collagen III were observed. Treatment with SY significantly downregulated cell proliferation, migration, and the expression of p-ERK1/2, AP-1, collagen I, and collagen III. We also found that the cell percentage of apoptosis of AFs treated with Ang II for 24 h was lower than those of untreated AFs. After treatment with SY, the percentage of apoptosis was increased. SY exhibits anti-proliferative, anti-migratory, and pro-apoptotic activities in rat aortic AFs, perhaps through the Ang II/ERK/AP-1 signaling pathway. The present findings may provide new clues regarding the potential function of SY to treat or prevent VR.

Atrial natriuretic peptide (ANP) inhibits DMBA/croton oil induced skin tumor growth by modulating NF-κB, MMPs, and infiltrating mast cells in swiss albino mice

Cardiac hormone atrial natriuretic peptide (ANP) and its receptor, natriuretic peptide receptor-A (NPR-A) are implicated as a vital regulator of cancer cell growth and tumor progression. However, the underlying mechanism by which ANP opposes the cancer growth in in-vivo remains unknown. Herein, we investigated the anti-cancer activity of ANP on 7, 12-dimethyl benzanthracence (DMBA)/Croton oil- induced two-step skin carcinogenic mouse model. Skin tumor incidence and tumor volume were recorded during the experimental period of 16 weeks. ANP (1 μg/kg body weight/alternate days for 4 weeks) was injected subcutaneously from the 13th week of DMBA/Croton oil induction. ANP treatment markedly inhibited the skin tumor growth (P<0.001). A significant reduction in the level of NF-κB activation (P<0.001), infiltrating mast cell count (P<0.01) and MMP-2/-9 (P<0.001, respectively) were noticed in the ANP treated mice skin tissue. Further, ANP treatment revert back the altered levels of serum LDH-4, C-reactive protein (CRP), and enzymatic antioxidants (SOD and CAT activities) to near normal level. Taken together, the results of this study suggest that ANP opposes the skin carcinogenesis by suppressing the inflammatory response and MMPs.