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

Myocardial interaction of apixaban after experimental acute volume overload

Objective

Acute volume overload (AVO) induces early ischemia-like changes in intramyocardial arteries. We investigated whether the Factor Xa (FXa) inhibitor apixaban interacts with the myocardium early after AVO.

Methods

Fifty-five syngeneic Fisher rats underwent surgical abdominal aortocaval fistula to induce AVO. Among them, 17 rats were treated with apixaban (10 mg/kg/day). The myocardial outcome was studied using histological analysis and by measuring atrial natriuretic peptide (ANP) and matrix metalloprotease 9 (MMP9) gene expression.

Results

After 3 days, the total number of intramyocardial arteries was significantly increased in the AVO+apixaban (AVO+A) group compared with that in the AVO group (12.0  ±  1.2 and 10.2 ± 1.5, point score units, respectively). In the AVO+A group, there were significantly more edematous nuclei in myocardial arteries in the right and left ventricle compared with that in the AVO group. ANP and MMP9 expression levels continued to increase significantly in the AVO+A group compared with those in the AVO group.

Conclusion

Apixaban interacts with intramyocardial arteries in the left and right ventricles after AVO and ANP and MMP9 expression levels increased. Thus, the myocardial effect of Factor Xa inhibition needs to be monitored after AVO.

Regenerative cross talk between cardiac cells and macrophages

Aside from the first week postnatal, murine heart regeneration is restricted and responses to damage follow classic fibrotic remodeling. Recent transcriptomic analyses have suggested that significant cross talk with the sterile immune response could maintain a more embryonic-like signaling network that promotes acute, transient responses. However, with age, this response-likely mediated by neonatal yolk sac macrophages-then transitions to classical macrophage-mediated, cardiac fibroblast (CF)-based remodeling of the extracellular matrix (ECM) after myocardial infarction (MI). The molecular mechanisms that govern the change with age and drive fibrosis via inflammation are poorly understood. Using multiple ribonucleic acid sequencing (RNA-Seq) datasets, we attempt to resolve the relative contributions of CFs and macrophages in the bulk-healing response of regenerative (postnatal day 1) and nonregenerative hearts (postnatal day 8+). We performed an analysis of bulk RNA-Seq datasets from myocardium and cardiac fibroblasts as well as a single-cell RNA-Seq dataset from cardiac macrophages. MI-specific pathway differences revealed that nonregenerative hearts generated more ECM and had larger matricellular responses correlating with inflammation, produced greater chemotactic gradients to recruit macrophages, and expressed receptors for danger-associated molecular patterns at higher levels than neonates. These changes could result in elevated stress-response pathways compared with neonates, converging at NF-κB and activator protein-1 (AP-1) signaling. Profibrotic gene programs, which greatly diverge on day 3 post MI, lay the foundation for chronic fibrosis, and thus postnatal hearts older than 7 days typically exhibit significantly less regeneration. Our analyses suggest that the macrophage ontogenetic shift in the heart postnatally could result in detrimental stress signaling that suppresses regeneration.NEW & NOTEWORTHY Immediately postnatal mammalian hearts are able to regenerate after infarction, but the cells, pathways, and molecules that regulate this behavior are unclear. By comparing RNA-Seq datasets from regenerative mouse hearts and older, nonregenerative hearts, we are able to identify biological processes that are hallmarks of regeneration. We find that sterile inflammatory processes are upregulated in nonregenerative hearts, initiating profibrotic gene programs 3 days after myocardial infarction that can cause myocardial disease.

In vitro differentiation of W8B2+ human cardiac stem cells: gene expression of ionic channels and spontaneous calcium activity

Background

Human cardiac stem cells expressing the W8B2 marker (W8B2⁺ CSCs) were recently identified and proposed as a new model of multipotent CSCs capable of differentiating into smooth muscle cells, endothelial cells and immature myocytes. Nevertheless, no characterization of ion channel or calcium activity during the differentiation of these stem cells has been reported.

Methods

The objectives of this study were thus to analyze (using the TaqMan Low-Density Array technique) the gene profile of W8B2⁺ CSCs pertaining to the regulation of ion channels, transporters and other players involved in the calcium homeostasis of these cells. We also analyzed spontaneous calcium activity (via the GCaMP calcium probe) during the in vitro differentiation of W8B2⁺ CSCs into cardiac myocytes.

Results

Our results show an entirely different electrophysiological genomic profile between W8B2⁺ CSCs before and after differentiation. Some specific nodal genes, such as Tbx3, HCN, ICaT, L, KV, and NCX, are overexpressed after this differentiation. In addition, we reveal spontaneous calcium activity or a calcium clock whose kinetics change during the differentiation process. A pharmacological study carried out on differentiated W8B2⁺ CSCs showed that the NCX exchanger and IP3 stores play a fundamental role in the generation of these calcium oscillations.

Conclusions

Taken together, the present results provide important information on ion channel expression and intrinsic calcium dynamics during the differentiation process of stem cells expressing the W8B2 marker.

Atrial natriuretic peptide inhibits epithelial-mesenchymal transition (EMT) of bronchial epithelial cells through cGMP/PKG signaling by targeting Smad3 in a murine model of allergic asthma

Background: Atrial natriuretic peptide (ANP) inhibits TGF-β1-induced epithelial-mesenchymal transition (EMT) in human airway cells. We aim to explore the role and mechanism of ANP on EMT of bronchial epithelial cells from murine model of allergic asthma in vitro. Methods: Murine model of allergic asthma was established with BALB/c mice using ovalbumin (OVA). Bronchial epithelial cells were isolated from OVA-exposed mice, and then were cocultured with TGF-β1, ANP, natriuretic peptide receptor A antagonist, cGMP analog, cGMP inhibitor or/and protein kinase G (PKG) inhibitor, respectively. We assessed expressions of E-Cadherin, α-SMA, cGMP, Smad3 and p-Smad3 in the murine cells before and after Smad3 silence. Results: Compared with bronchial epithelial cells from controls and OVA-exposed mice without additional stimulation, the mRNA and protein expressions of E-Cadherin were decreased but α-SMA expressions were increased in cells with TGF-β1 stimulation from OVA-exposed mice in vitro. That could be reversed by ANP. The effect of ANP could be mimicked by the cGMP analog, which could be reversed by cGMP or PKG inhibitor. Moreover, the phosphorylated Smad3 expression was consistent with that of α-SMA. When Smad3 was silenced, Smad3 was mostly expressed in cytoplasm. In contrast, it is mostly expressed in nucleus of non-silenced cells during EMT. Conclusions: In a murine model of allergic asthma, ANP could inhibit TGF-β1-induced EMT of bronchial epithelial cells through cGMP/PKG signaling, targeting TGF-β1/Smad3 via attenuating phosphorylation of Smad3 in vitro, which may provide potential of ANP in treating allergic asthma with airway remodeling.

Protective Effect of RA on Myocardial Infarction-Induced Cardiac Fibrosis via AT1R/p38 MAPK Pathway Signaling and Modulation of the ACE2/ACE Ratio

Rosmarinic acid (α-o-caffeoyl-3,4-dihydroxyphenyllactic acid, RA) is a major active constituent of Rosmarinus officinalis Linn. (rosemary) having significant anti-inflammatory, anti-apoptotic, and antioxidant effects. However, the cardioprotection of RA is still not understood. The present study was designed, for the first time, to investigate the cardioprotection of RA on myocardial infarction (MI)-induced cardiac fibrosis and to clarify the possible mechanisms. MI was induced in adult rats by left anterior descending coronary artery ligation, and animals were then administered RA (50, 100, or 200 mg/kg) by gavage. Compared with the model group, RA treatment ameliorated changes in the left ventricular systolic pressure (LVSP), +dp/dtmax, and -dp/dtmax after 4 weeks. This was associated with attenuation of infarct size, collagen volume fraction (CVF), expression of collagen I, collagen III, alpha smooth muscle actin (α-SMA), and hydroxyproline (Hyp) concentrations. RA treatment was also associated with decreased angiotensin-converting enzyme (ACE) expression and increased ACE2 expression, as well as decreased expression of angiotensin type 1 receptor (AT1R) and phospho-p38 mitogen-activated protein kinase (p38 MAPK). Thus, RA can protect against cardiac dysfunction and fibrosis following MI, likely due to decreasing ACE expression and increasing ACE2 expression via the AT1R/p38 MAPK pathway.

The potential role of atrial natriuretic peptide in the effects of Angiotensin-(1-7) in a chronic atrial tachycardia canine model

Objective:

The objective of this article is to investigate the possible role of atrial natriuretic peptide (ANP) in Angiotensin-(1–7) (Ang-(1–7)) signaling pathway on atrial electrical and structural remodeling in a chronic rapid atrial pacing canine model.

Methods:

Twenty-four dogs were randomly assigned to four groups: a sham group, paced control group, a paced + Ang-(1–7) group and a paced + Ang-(1–7) + A-71915 group. Atrial rapid pacing (ARP) at 600 bpm was maintained for 14 days except in the animals from the sham group. During the pacing, Ang-(1–7) (6 μg•kg-1•h-1) or Ang-(1–7) (6 μg•kg-1•h-1) + A-71915 (ANP receptor antagonist, 0.30 μg•kg-1•h-1) were given intravenously, respectively. After pacing, it was measured that electrophysiological parameters including atrial effective refractory periods (ERPs), inducibility and duration of atrial fibrillation (AF), I_CaL and I_Na changed, where I_CaL refers to voltage-dependent L-type Ca²⁺ current and I_Na refers to cardiac sodium current. Then, the fibrosis and the expression of Cav1.2, I_Nav1.5α subunit, TGF-β₁ and ANP in atria were assessed.

Results:

After ARP, compared with the sham group, the atrial ERPs at six sites in each dog were shortened with the increasing in inducibility and duration of AF in the paced control group. The density of I_CaL, I_Na and the expression of Cav1.2, I_Nav1.5α subunit mRNA were decreased. Atrial tissue from the paced dogs showed significant interstitial fibrosis. The expression of TGF-β₁ and ANP in mRNA and protein levels were increased. Compared with the paced control group, the shortening of atrial ERPs, and the increasing of inducibility and duration of AF induced by ARP were alleviated by Ang-(1–7) treatment (p < 0.05). The density of I_CaL and I_Na and the expression of Cav1.2 and I_Nav1.5α subunit mRNA were slightly decreased. Atrial tissue showed less interstitial fibrosis after Ang-(1–7) treatment. The increasing of ANP expression was improved by Ang-(1–7), while the increasing of TGF-β₁ expression was alleviated by Ang-(1–7) (p < 0.05). A-71915 treatment blocked the beneficial effects of Ang-(1–7) on the aforementioned electrophysiological parameters and atrial fibrosis. And A-71915 treatment blocked Ang-(1–7), improving the expression of TGF-β₁.

Conclusion:

Ang-(1–7) prevented atrial structural and electrical remodeling induced by ARP. Furthermore, Ang-(1–7) promoted ANP secretion, and ANP played a crucial role in the cardiac protection of the former.