RESUMO
TGF-ß-centered epithelial-mesenchymal transition (EMT) is a key process involved in radiation-induced pulmonary injury (RIPI) and pulmonary fibrosis. PIEZO1, a mechanosensitive calcium channel, is expressed in myeloid cell and has been found to play an important role in bleomycin-induced pulmonary fibrosis. Whether PIEZO1 is related with radiation-induced EMT remains elusive. Herein, we found that PIEZO1 is functional in rat primary type II epithelial cells and RLE-6TN cells. After irradiation, PIEZO1 expression was increased in rat lung alveolar type II epithelial cells and RLE-6TN cell line, which was accompanied with EMT changes evidenced by increased TGF-ß1, N-cadherin, Vimentin, Fibronectin, and α-SMA expression and decreased E-cadherin expression. Addition of exogenous TGF-ß1 further enhanced these phenomena in vitro. Knockdown of PIEZO1 partly reverses radiation-induced EMT in vitro. Mechanistically, we found that activation of PIEZO1 could upregulate TGF-ß1 expression and promote EMT through Ca2+/HIF-1α signaling. Knockdown of HIF-1α partly reverses enhanced TGF-ß1 expression caused by radiation. Meanwhile, the expression of PIEZO1 was up-regulated after TGF-ß1 co-culture, and the mechanism could be traced to the inhibition of transcription factor C/EBPß expression by TGF-ß1. Irradiation also caused a decrease in C/EBPß expression in RLE-6TN cells. Dual luciferase reporter assay and chromatin immunoprecipitation assay (ChIP) confirmed that C/EBPß represses PIEZO1 expression by binding to the PIEZO1 promoter. Furthermore, overexpression of C/EBPß by using the synonymous mutation to C/EBPß siRNA could reverse siRNA-induced upregulation of PIEZO1. In summary, our research suggests a critical role of PIEZO1 signaling in radiation-induced EMT by forming positive feedback with TGF-ß1.
RESUMO
Pulmonary endothelial cell dysfunction plays an important role in ionizing radiation (IR)-induced lung injury. Whether pulmonary endothelial cell ferroptosis occurs after IR and what are the underlying mechanisms remain elusive. Here, we demonstrate that 15-Gy IR induced ferroptosis characterized by lethal accumulation of reactive oxygen species (ROS), lipid peroxidation, mitochondria shrinkage, and decreased glutathione peroxidase 4 (GPX4) and SLC7A11 expression in pulmonary endothelial cells. The phenomena could be mimicked by Yoda1, a specific activator of mechanosensitive calcium channel PIEZO1. PIEZO1 protein expression was upregulated by IR in vivo and in vitro. The increased PIEZO1 expression after IR was accompanied with increased calcium influx and increased calpain activity. The effects of radiation on lung endothelial cell ferroptosis was partly reversed by inhibition of PIEZO1 activity using the selective inhibitor GsMTx4 or inhibition of downstreaming Ca2+/calpain signaling using PD151746. Both IR and activation of PIEZO1 led to increased degradation of VE-cadherin, while PD151746 blocked these effects. VE-cadherin knockdown by specific siRNA causes ferroptosis-like phenomena with increased ROS and lipid peroxidation in the lung endothelial cells. Overexpression of VE-cadherin partly recused the ferroptosis caused by IR or PIEZO1 activation as supported by decreased ROS production, lipid peroxidation and mitochondria shrinkage compared to IR or PIEZO1 activation alone. In summary, our study reveals a previously unrecognized role of PIEZO1 in modulating ferroptosis, providing a new target for future mitigation of radiation-induced lung injury.
RESUMO
OBJECTIVE: Recent evidence suggests that the effects of mesenchymal progenitor cell transplantation into the infarcted myocardium might be mediated by local paracrine angiogenesis. We compared the effects of mesenchymal progenitor cell transplantation versus those of a primarily angiogenic cell, the endothelial progenitor cell, in a rat model of myocardial infarction. METHODS: Twenty-one days after left anterior descending artery ligation, rats were injected in their infarcted anterior myocardium with 1 x 10(6) mesenchymal progenitor cells, 1 x 10(6) endothelial progenitor cells, 5 x 10(5) mesenchymal progenitor cells plus 5 x 10(5) endothelial progenitor cells, or phosphate-buffered saline (n = 6-8 per group). Echocardiography was performed before injection and 4 weeks later, after which rats were killed and immunohistochemical analyses performed. RESULTS: Connexin43 density was greater in cell-treated groups compared with that seen in the phosphate-buffered saline group (by 91.6% +/- 15.2%, P < .001), with no observed difference between cell-treated groups (P > or = .3). Endothelial progenitor cell treatment increased arteriolar density within the infarct border zone (by 297%, 205%, and 101% vs phosphate-buffered saline, mesenchymal progenitor cell, and mesenchymal progenitor cell/endothelial progenitor cell treatment, respectively; P < .01). Postoperative left ventricular ejection fraction (endothelial progenitor cell: 68.3% +/- 9.8% vs mesenchymal progenitor cell/endothelial progenitor cell: 55.0% +/- 11.1%, mesenchymal progenitor cell: 53.0% +/- 6.0%, and phosphate-buffered saline: 49.6% +/- 9.5%) and fractional shortening (endothelial progenitor cell: 32.4% +/- 5.1% vs mesenchymal progenitor cell: 22.5% +/- 5.4% and phosphate-buffered saline: 21.3% +/- 5.3%) were greater in endothelial progenitor cell-treated rats versus those receiving other treatments (all P < .05). Only endothelial progenitor cells prevented further contractile deterioration compared with baseline values (P = .8), whereas other groups had continued loss of function after treatment. CONCLUSION: Compared with the use of mesenchymal progenitor cells, cell transplantation with endothelial progenitor cells after myocardial infarction resulted in better neovascularization and contractility. This suggests that angiogenesis is an important mechanism in attenuating the progression of left ventricular dysfunction after myocardial infarction.