TRPM7 regulates angiotensin II-induced sinoatrial node fibrosis in sick sinus syndrome rats by mediating Smad signaling

Abstract

Sinoatrial node fibrosis is involved in the pathogenesis of sinus sick syndrome (SSS). Transient receptor potential (TRP) subfamily M member 7 (TRPM7) is implicated in cardiac fibrosis. However, the mechanisms underlying the regulation of sinoatrial node (SAN) fibrosis in SSS by TRPM7 remain unknown. The aim of this study was to investigate the role of angiotensin II (Ang II)/TRPM7/Smad pathway in the SAN fibrosis in rats with SSS. The rat SSS model was established with sodium hydroxide pinpoint pressing permeation. Forty-eight rats were randomly divided into six groups: normal control (ctrl), sham operation (sham), postoperative 1-, 2-, 3-, and 4-week SSS, respectively. The tissue explant culture method was used to culture cardiac fibroblasts (CFs) from rat SAN tissues. TRPM7 siRNA or encoding plasmids were used to knock down or overexpress TRPM7. Collagen (Col) distribution in SAN and atria was assessed using PASM–Masson staining. Ang II, Col I, and Col III levels in serum and tissues or in CFs were determined by ELISA. TRPM7, smad2 and p-smad2 levels were evaluated by real-time PCR, and/or western blot and immunohistochemistry. SAN and atria in rats of the SSS groups had more fibers and higher levels of Ang II, Col I and III than the sham rats. Similar findings were obtained for TRPM7 and pSmad2 expression. In vitro, Ang II promoted CFs collagen synthesis in a dose-dependent manner, and potentiated TRPM7 and p-Smad2 expression. TRPM7 depletion inhibited Ang II-induced p-Smad2 expression and collagen synthesis in CFs, whereas increased TRPM7 expression did the opposite. SAN fibrosis is regulated by the Ang II/TRPM7/Smad pathway in SSS, indicating that TRPM7 is a potential target for SAN fibrosis therapy in SSS.

Development of a Rat Model of Sick Sinus Syndrome Using Pinpoint Press Permeation

“…Our findings are similar to those reported previously [11]. In SSSB rats with stable heart rates, there was a time-dependent increase in collagen as determined by Masson staining.…”

“…Surface electrocardiogram was continuously monitored using a BL-420F data acquisition and analysis system. To confirm establishment of the rat SSS model, a custom-made device was used as previously described [11]. A provision of respiratory support to experimental animals was ensured using tracheostomy with a small ventilator (Figure 1 I).…”

“…As previously described [11, 12], heart tissue samples were embedded in paraffin and sectioned (4 μ m) before immunohistochemical analysis. After dewaxing and debenzolization, rabbit anti-HCN4 antibody (ab66501; Abcam, USA) was added to the sections at a dilution of 1:200 at 4°C overnight, followed by washing with tris buffered saline (TBS) at room temperature, with subsequent addition of anti-rabbit horseradish peroxidase (Beijing Zhongshan Golden Bridge Biotechnology Co.) at 37°C for 2 h. Finally, the sections were counterstained with hematoxylin, dehydrated, and mounted using neutral gum.…”

Ca2+ Signaling in Cardiac Fibroblasts and Fibrosis-Associated Heart Diseases

“…A role of TRPM7 in mediating the fibrogenesis cascade has also been observed in rat cardiac fibroblasts [193][194][195][196]. Moreover, TRPM7 is also suggested to be involved in fibrogenesis in rat sinus nodes [192], and in fibrosis induced by isoproterenol and oxidative stress [195]. Thus, it seems that TRPM7 may serve as a potential target for fibrosis-associated heart diseases.…”

TRPM7 ameliorates the blue light-induced apoptosis of RPE cells involving PKC/ERK

“…TRPM7 is a member of the Transient Receptor Potential (TRP) channel superfamily, which is widely expressed in mammalian heart, liver, lung, kidney, and retina [12,13]. TRPM7 is a bifunctional protein with a dual structure of ion channels and protein kinases.…”