Role of calcineurin in insulin-like growth factor-1-induced hypertrophy of cultured adult rat ventricular myocytes

The identification of hub-methylated differentially expressed genes in osteoarthritis patients is based on epigenomic and transcriptomic data

Introduction

Osteoarthritis (OA) refers to a commonly seen degenerative joint disorder and a major global public health burden. According to the existing literature, osteoarthritis is related to epigenetic changes, which are important for diagnosing and treating the disease early. Through early targeted treatment, costly treatments and poor prognosis caused by advanced osteoarthritis can be avoided.

Methods

This study combined gene differential expression analysis and weighted gene co-expression network analysis (WGCNA) of the transcriptome with epigenome microarray data to discover the hub gene of OA. We obtained 2 microarray datasets (GSE114007, GSE73626) in Gene Expression Omnibus (GEO). The R software was utilized for identifying differentially expressed genes (DEGs) and differentially methylated genes (DMGs). By using WGCNA to analyze the relationships between modules and phenotypes, it was discovered that the blue module (MEBlue) has the strongest phenotypic connection with OA (cor = 0.92, p = 4e-16). The hub genes for OA, also known as the hub methylated differentially expressed genes, were identified by matching the MEblue module to differentially methylated differentially expressed genes. Furthermore, this study used Gene set variation analysis (GSVA) to identify specific signal pathways associated with hub genes. qRT-PCR and western blotting assays were used to confirm the expression levels of the hub genes in OA patients and healthy controls.

Results

Three hub genes were discovered: HTRA1, P2RY6, and RCAN1. GSVA analysis showed that high HTRA1 expression was mainly enriched in epithelial-mesenchymal transition and apical junction; high expression of P2RY6 was mainly enriched in the peroxisome, coagulation, and epithelial-mesenchymal transition; and high expression of RCAN1 was mainly enriched in epithelial-mesenchymal-transition, TGF-β-signaling, and glycolysis. The results of the RT-qPCR and WB assay were consistent with the findings.

Discussion

The three genes tested may cause articular cartilage degeneration by inducing chondrocyte hypertrophy, regulating extracellular matrix accumulation, and improving macrophage pro-inflammatory response, resulting in the onset and progression of osteoarthritis. They can provide new ideas for targeted treatment of osteoarthritis.

Biology of the cardiac myocyte in heart disease

Cardiac hypertrophy is a major risk factor for heart failure, and it has been shown that this increase in size occurs at the level of the cardiac myocyte. Cardiac myocyte model systems have been developed to study this process. Here we focus on cell culture tools, including primary cells, immortalized cell lines, human stem cells, and their morphological and molecular responses to pathological stimuli. For each cell type, we discuss commonly used methods for inducing hypertrophy, markers of pathological hypertrophy, advantages for each model, and disadvantages to using a particular cell type over other in vitro model systems. Where applicable, we discuss how each system is used to model human disease and how these models may be applicable to current drug therapeutic strategies. Finally, we discuss the increasing use of biomaterials to mimic healthy and diseased hearts and how these matrices can contribute to in vitro model systems of cardiac cell biology.

Increased expression of NF-AT3 and NF-AT4 in the atria correlates with procollagen I carboxyl terminal peptide and TGF-β1 levels in serum of patients with atrial fibrillation

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. Unfortunately, the precise mechanisms and sensitive serum biomarkers of atrial remodeling in AF remain unclear. The aim of this study was to determine whether the expression of the transcription factors NF-AT3 and NF-AT4 correlate with atrial structural remodeling of atrial fibrillation and serum markers for collagen I and III synthesis.

Methods

Right and left atrial specimens were obtained from 90 patients undergoing valve replacement surgery. The patients were divided into sinus rhythm (n = 30), paroxysmal atrial fibrillation (n = 30), and persistent atrial fibrillation (n = 30) groups. NF-AT3, NF-AT4, and collagen I and III mRNA and protein expression in atria were measured. We also tested the levels of the carboxyl-terminal peptide from pro-collagen I, the N-terminal type I procollagen propeptides, the N-terminal type III procollagen propeptides, and TGF-β1 in serum using an enzyme immunosorbent assay.

Results

NF-AT3 and NF-AT4 mRNA and protein expression were increased in the AF groups, especially in the left atrium. NF-AT3 and NF-AT4 expression in the right atrium was increased in the persistent atrial fibrillation group compared the sinus rhythm group with similar valvular disease. In patients with AF, the expression levels of nuclear NF-AT3 and NF-AT4 correlated with those of collagens I and III in the atria and with PICP and TGF-β1 in blood.

Conclusions

These data support the hypothesis that nuclear NF-AT3 and NF-AT4 participates in atrial structural remodeling, and that PICP and TGF-β1 levels may be sensitive serum biomarkers to estimate atrial structural remodeling with atrial fibrillation.

Involvement of tissue transglutaminase in endothelin 1-induced hypertrophy in cultured neonatal rat cardiomyocytes

A potential link between tissue-type transglutaminase (tTG) and cardiac hypertrophy was suggested recently. However, whether tTG is implicated in hypertrophic agonist-induced cardiac hypertrophy is not yet known. The purpose of this study was to investigate the effects of tTG on cardiomyocyte hypertrophy induced by endothelin (ET) 1. Real-time quantitative RT-PCR and Western blot analysis demonstrated that ET-1 increased the expression of tTG mRNA and protein in cardiomyocytes by activating ET(A) receptors. ET-1 failed to cause increases in cell size and [(3)H]leucine uptake, sarcomere reorganization, and gene induction of the atrial natriuretic factor when cardiomyocytes were treated with monodansylcadaverine, a competitive inhibitor of tTG. Furthermore, the effects of ET-1 on multifunctional activities of tTG were determined by evaluating the incorporation of [(3)H]putrescine into N,N'-dimethylated casein and charcoal absorption, respectively. The results showed that ET-1 did not influence the basal transglutaminase activity of cardiomyocytes but significantly inhibited the 0.1-mmol/L Ca(2+)-stimulated transglutaminase activity. Otherwise, ET-1 elevated the activity of GTPase in a concentration- and time-dependent manner. In vivo, right ventricular hypertrophy induced by 2 weeks of chronic hypoxia was depressed by the tTG inhibitor cystamine (10 to 30 mg/kg, 2 times per day, IP) in a dose-dependent manner. Taken together, our data strongly supported the notion that tTG may act as a positive regulator of the hypertrophic program in response to ET-1. This is probably attributable to the signaling activity of tTG rather than transglutaminase activity.

Prevention of isoproterenol-induced cardiac hypertrophy by eugenol, an antioxidant

Recent reports on the involvement of calcineurin in cardiac hypertrophy and its susceptibility to free radicals, prompted us to examine possible beneficial effects of dietary antioxidants in this regard. In continuation of initialin vitro studies revealing eugenol to be a potent calcineurin inhibitor, we investigated its ability to reverse isoproterenol-induced cardiac hypertrophy in rats. Intraperitoneal administration of isoproterenol (1 mg/kg body wt/day for 10 days) induced cardiac hypertrophy with increased heart weight and enhanced apoptosis of myocytes concomitant with accumulation of reactive oxygen species, decreased glutathione contents, increased activities of calcineurin and protein kinase C in ventricular tissue. Administering eugenol for 3 days (1 mg/kg body wt/twice a day), followed by combined administration of isoproterenol and eugenol resulted in significant reversal of cardiac hypertrophy and restoration of above changes. These results suggest that eugenol, a natural antioxidant of dietary origin, may offer potential benefits in the management of cardiac hypertrophy.

Adenovirus-Mediated Overexpression of Diacylglycerol Kinase-ζ Inhibits Endothelin-1–Induced Cardiomyocyte Hypertrophy

Background— Diacylglycerol (DAG) is a lipid second messenger that transiently accumulates in cells stimulated by endothelin-1 (ET-1) and other Gαq protein-coupled receptor agonists. Diacylglycerol kinase (DGK) is thought to be an enzyme that controls the cellular levels of DAG by converting it to phosphatidic acid; however, the functional role of DGK has not been examined in cardiomyocytes. Because DGK inactivates DAG, a strong activator of protein kinase C (PKC), we hypothesized that DGK inhibited ET-1–induced activation of a DAG-PKC signaling cascade and subsequent cardiomyocyte hypertrophy.

Methods and Results— Real-time reverse transcription-polymerase chain reaction demonstrated a significant increase of DGK-ζ mRNA by ET-1 in cardiomyocytes. To determine the functional role of DGK-ζ, we overexpressed DGK-ζ in cardiomyocytes using a recombinant adenovirus encoding rat DGK-ζ (Ad-DGKζ). ET-1–induced translocation of PKC-ε was blocked by Ad-DGKζ ( P <0.01). Ad-DGKζ also inhibited ET-1–induced activation of extracellular signal-regulated kinase ( P <0.01). Luciferase reporter assay revealed that ET-1–mediated increase of activator protein-1 (AP1) DNA-binding activity was significantly inhibited by DGK-ζ ( P <0.01). In cardiomyocytes transfected with DGK-ζ, ET-1 failed to cause gene induction of atrial natriuretic factor, increases in [ 3 H]-leucine uptake, and increases in cardiomyocyte surface area.

Conclusions— We demonstrated for the first time that DGK-ζ blocked ET-1–induced activation of the PKC-ε–ERK-AP1 signaling pathway, atrial natriuretic factor gene induction, and resultant cardiomyocyte hypertrophy. DGK-ζ might act as a negative regulator of hypertrophic program in response to ET-1, possibly by controlling cellular DAG levels.

Disruption of growth hormone secretion alters Ca2+ current density and expression of Ca2+ channel and insulin-like growth factor genes in rat atria

The influence of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis on expression of low-voltage-activated (LVA) Ca2+ current in atrial tissue was investigated using spontaneous dwarf (SpDwf) rats, a mutant strain that lacks GH. Atrial myocytes from SpDwf rats express LVA and high-voltage-activated (HVA) Ca2+ currents and the Ca2+ channel alpha1-subunit genes CaV1.2, CaV2.3, CaV3.1, and CaV3.2. LVA current density decreases significantly beginning at, or shortly after, birth in normal animals; however, its density is maintained in SpDwf rats at 1 pA/pF for > or =12 wk after birth. The abundance of mRNAs encoding CaV2.3 and CaV3.2 declines with advancing age in normal atrial development, yet expression of CaV2.3 mRNA remains significantly elevated in older SpDwf animals. Quantitation of local transcript levels for mRNAs encoding IGF-I and IGF-I receptor (IGF-IR) also reveals significant differences in expression of these transcripts in atrial tissue of SpDwf animals compared with controls. In SpDwf rats, the abundance of IGF-IR mRNA remains elevated at many postnatal ages, whereas mRNA encoding IGF-I is maintained only in older animals. Physiological concentrations of IGF-I cause two- to threefold increases in LVA current density in primary cultures of atrial myocytes, and this effect is blocked by an antisense oligonucleotide targeting the IGF-IR. Thus disruption of GH production in SpDwf animals alters expression of atrial LVA Ca2+ channel and IGF genes as well as postnatal regulation of LVA Ca2+ current density, most likely acting through compensatory mechanisms via the local IGF-IR.

Improvement of ventricular arrhythmia by octreotide treatment in acromegalic cardiomyopathy

We report a case of acromegalic cardiomyopathy in a 46-year-old Japanese man with pituitary adenoma. Increased secretion of growth hormone and insulin-like growth factor I were detected. He had left ventricular hypertrophy, impaired cardiac function, and frequent ventricular premature complexes. After 2-month treatment with octreotide, a long-acting somatostatin analogue, levels of both hormones were decreased. At the same time, left ventricular hypertrophy (intraventricular septal thickness: 22.5 to 17.8 mm), cardiac function (ejection fraction: 38 to 50%), and frequency of ventricular premature complexes (17,249 to 2,882 beats a day) were improved. Transsphenoidal surgery was then safely performed. Treatment with octreotide is thought to have some effect on improvement of ventricular arrhythmia in acromegalic heart.

Involvement of calcineurin in transforming growth factor-beta-mediated regulation of extracellular matrix accumulation

Calcineurin is a calcium-dependent, serine/threonine phosphatase that functions as a signaling intermediate. In this study, we investigated the role of calcineurin in transforming growth factor-beta (TGF-beta)-mediated cellular effects and examined the signaling pathway involved in activation of calcineurin. Calcineurin is activated by TGF-beta in a time- and dose-dependent manner. Consistent with increased phosphatase activity, the calcineurin substrate, NFATc1, is dephosphorylated and transported to the nucleus. Inhibition of calcineurin prior to the addition of TGF-beta revealed that calcineurin is required for TGF-beta-mediated accumulation of extracellular matrix (ECM) proteins but not cell hypertrophy. Conversely, overexpression of constitutively active calcineurin was sufficient to induce ECM protein expression. The mechanism of calcineurin activation by TGF-beta was found to be induction of a low, sustained increase of intracellular calcium. Chelation of extracellular calcium blocked both TGF-beta-mediated calcium influx and calcineurin activity. Finally, calcium entry was found to be dependent upon generation of reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide. Accordingly, inhibition of ROS generation also blocked TGF-beta-mediated calcineurin phosphatase activity and decreased ECM accumulation. In conclusion, this study describes a new pathway for TGF-beta-mediated regulation of ECM via generation of ROS, calcium influx, and activation of calcineurin.

Dance band on the Titanic: biomechanical signaling in cardiac hypertrophy

Biomechanical signaling is a complex interaction of both intracellular and extracellular components. Both passive and active components are involved in the extracellular environment to signal through specific receptors to multiple signaling pathways. This review provides an overview of extracellular matrix, specific receptors, and signaling pathways for biomechanical stimulation in cardiac hypertrophy.

Circulating levels of insulin-like growth factor-1 and its binding proteins in patients with hypertrophic cardiomyopathy

Insulin-like growth factor-1 (IGF-1) is important in the hypertrophic response of the myocardium, so the present study was designed to elucidate whether the circulating levels of IGF-1 and its binding proteins (IGFBPs) are related to the disease condition of patients with hypertrophic cardiomyopathy (HCM), in particular the occurrence of congestive heart failure (CHF). The study group comprised 124 patients with HCM and 15 healthy control subjects. The HCM patients were subdivided into 3 groups: 39 with hypertrophic obstructive cardiomyopathy (HOCM), 67 with hypertrophic non-obstructive cardiomyopathy (HNCM), and 18 with HCM and a history of CHF (HF-HCM, n=18). Serum levels of IGF-1 and IGFBPs (IGFBP-1 and -3) were compared between groups. IGF-1 levels were significantly higher in patients with HOCM and HNCM, and lower in patients with HF-HCM than in control subjects (p<0.0001, p<0.005, and p<0.05, respectively). IGFBP-1 levels were significantly higher in patients with HF-HCM than in the other 3 groups (p<0.0001 for all). The findings suggest that circulating levels of IGF-1 and IGFBP-1 are related to the extent of myocardial injury in patients with HCM.

Comparison of nitric oxide production in response to carbachol between macrovascular and microvascular cardiac endothelial cells

Cardiac microvascular endothelial cells (EC) play an important role in the physiological regulation of coronary blood flow, but their function has not been rigorously examined, because suitable in vitro models have not been available. Cardiac macrovascular and microvascular EC were isolated and cultured from 14-16-week-old Sprague-Dawley rats to examine the pharmacological responses of carbachol-induced nitric oxide (NO) production using a Griess method. Carbachol-induced NO production was only detected in cardiac macrovascular EC, which suggests that endothelial production of NO differs between macrovascular and microvascular EC. Next, cardiac microvascular EC was treated with either vehicle, angiotensin-converting enzyme (ACE) inhibitor (captopril, 10 micromol/L) or angiotensin II type 1 (AT1) receptor antagonist (CV11974, 10 micromol/L) for 4 days. Carbachol-induced NO production was improved by captopril (136+/-45nmol, p<0.01 vs vehicle) and CV11974 (146+/-30nmol, p<0.01 vs vehicle). Angiotensin II concentration in the culture medium and protein expressions of endothelial nitric oxide synthase and AT1 receptor in the EC were similar among the 3 groups. Interestingly, the level of muscarinic subtype 3 (M3) receptor was significantly increased in the EC treated with captopril (214%, p<0.01) and CV11974 (296%, p<0.01). When cardiac microvascular EC were treated with neomycin (non-selective phospholipase C inhibitor), carbachol-induced NO production was also improved (146+/-35nmol, p<0.01, neomycin I mmol/L) together with increased expression of M3 receptor (p<0.01). These data suggest that the upregulation of the M3 receptor by captopril or CV11974 occurs via a phospholipase C-dependent pathway. Cardiac microvascular EC also produced NO constitutively, as did the macrovascular EC, but carbachol-induced NO production was decreased. The present data suggest that the upregulation of the M3 receptor by the ACE inhibitor and AT1 receptor antagonist is a new beneficial effect of these drugs on microvascular endothelial function.