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Background: Cardiac fibrosis is the hallmark of all forms of chronic heart disease. Activation and proliferation of cardiac fibroblasts are the prime mediators of cardiac fibrosis. Existing studies show that ROS and inflammatory cytokines produced during fibrosis not only signal proliferative stimuli but also contribute to DNA damage. Therefore, as a prerequisite to maintain sustained proliferation in fibroblasts, activation of distinct DNA repair mechanism is essential., Result: In this study, we report that TET3, a DNA demethylating enzyme, which has been shown to be reduced in cardiac fibrosis and to exert antifibrotic effects does so not only through its demethylating activity but also through maintaining genomic integrity by facilitating error-free homologous recombination (HR) repair of DNA damage. Using both in vitro and in vivo models of cardiac fibrosis as well as data from human heart tissue, we demonstrate that the loss of TET3 in cardiac fibroblasts leads to spontaneous DNA damage and in the presence of TGF-β to a shift from HR to the fast but more error-prone non-homologous end joining repair pathway. This shift contributes to increased fibroblast proliferation in a fibrotic environment. In vitro experiments showed TET3's recruitment to H2O2-induced DNA double-strand breaks (DSBs) in mouse cardiac fibroblasts, promoting HR repair. Overexpressing TET3 counteracted TGF-β-induced fibroblast proliferation and restored HR repair efficiency. Extending these findings to human cardiac fibrosis, we confirmed TET3 expression loss in fibrotic hearts and identified a negative correlation between TET3 levels, fibrosis markers, and DNA repair pathway alteration., Conclusion: Collectively, our findings demonstrate TET3's pivotal role in modulating DDR and fibroblast proliferation in cardiac fibrosis and further highlight TET3 as a potential therapeutic target., (© 2024. The Author(s).)

Neural cell adhesion molecule (NCAM) and fibroblast growth factor receptor 1 (FGFR1) cross-talk have been involved in epithelial-to-mesenchymal transition (EMT) process during carcinogenesis. Since EMT also contributes to maladaptive repair and parenchymal damage during renal fibrosis, we became encouraged to explore the role of NCAM/FGFR1 signaling as initiating or driving forces of EMT program in cultured human proximal tubular epithelial cells (TECs). TECs stimulated with TGF-β1 (10ng/mL) was used as an established in vitro EMT model. TGF-β1 downstream effectors were detected in vitro, as well as in 50 biopsies of different human kidney diseases to explore their in vivo correlation. NCAM/FGFR1 signaling and its modulation by FGFR1 inhibitor PD173074 (100nM) were analyzed by light microscopy, immunolabeling, qRT-PCR and scratch assays. Morphological changes associated with EMT appeared 48h after TGF-ß1 treatment and was clearly apparent after 72 hours, followed by loss of CDH1 (encoding E-Cadherin) and transcriptional induction of SNAI1 (SNAIL), SNAI2 (SLUG), TWIST1, MMP2, MMP9, CDH2 (N-Cadherin), ITGA5 (integrin-α5), ITGB1 (integrin-β1), ACTA2 (α-SMA) and S100A4 (FSP1). Moreover, at the early stage of EMT program (24 hours upon TGF-β1 exposure), transcriptional induction of several NCAM isoforms along with FGFR1 was observed, implicating a mechanistic link between NCAM/FGFR1 signaling and induction of EMT. These assumptions were further supported by the inhibition of the EMT program after specific blocking of FGFR1 signaling by PD173074. Finally, there was evidence for an in vivo TGF-β1 pathway activation in diseased human kidneys and correlation with impaired renal excretory functions. Collectively, NCAM/FGFR1 signaling appears to be involved in the initial phase of TGF-ß1 initiated EMT which can be effectively suppressed by application of FGFR inhibitor. [ABSTRACT FROM AUTHOR]

Progression of chronic kidney disease associated with progressive fibrosis and impaired tubular epithelial regeneration is still an unmet biomedical challenge because, once chronic lesions have manifested, no effective therapies are available as of yet for clinical use. Prompted by various studies across multiple organs demonstrating that preconditioning regimens to induce endogenous regenerative mechanisms protect various organs from later incurring acute injuries, we here aimed to gain insights into the molecular mechanisms underlying successful protection and to explore whether such pathways could be utilized to inhibit progression of chronic organ injury. We identified a protective mechanism controlled by the transcription factor ARNT that effectively inhibits progression of chronic kidney injury by transcriptional induction of ALK3, the principal mediator of antifibrotic and proregenerative bone morphogenetic protein-signaling (BMP-signaling) responses. We further report that ARNT expression itself is controlled by the FKBP12/YY1 transcriptional repressor complex and that disruption of such FKBP12/YY1 complexes by picomolar FK506 at subimmunosuppressive doses increases ARNT expression, subsequently leading to homodimeric ARNT-induced ALK3 transcription. Direct targeting of FKBP12/YY1 with in vivo morpholino approaches or small molecule inhibitors, including GPI-1046, was equally effective for inducing ARNT expression, with subsequent activation of ALK3-dependent canonical BMP-signaling responses and attenuated chronic organ failure in models of chronic kidney disease, and also cardiac and liver injuries. In summary, we report an organ-protective mechanism that can be pharmacologically modulated by immunophilin ligands FK506 and GPI-1046 or therapeutically targeted by in vivo morpholino approaches. [ABSTRACT FROM AUTHOR]