No abstract

BackgroundAnthracyclines-induced cardiotoxicity has become one of the major restrictions of their clinical applications. Klotho showed cardioprotective effects. This study aimed to investigate the effects and possible mechanisms of klotho on doxorubicin (DOX)-induced cardiotoxicity.Material/MethodsRats and isolated myocytes were exposed to DOX and treated with exogenous klotho. Specific inhibitors and siRNAs silencing MAPKs were also used to treat the animals and/or myocytes. An invasive hemodynamic method was used to determine cardiac functions. Intracellular ROS generation was evaluated by DHE staining. Western blotting was used to determine the phosphorylation levels of JNK, ERK, and p38 MAPKs in plasma extracts and Nrf2 in nuclear extracts. Nuclear translocation of Nrf2 in myocytes was evaluated by immunohistochemistry. Cell apoptosis was evaluated by TUNEL assay and flow cytometry.ResultsKlotho treatment improved DOX-induced cardiac dysfunction in rats. The DOX-induced ROS accumulation and cardiac apoptosis were attenuated by klotho. Impaired phosphorylations of MAPKs, Nrf2 translocation and expression levels of HO1 and Prx1 were also attenuated by klotho treatment. However, the anti-oxidant and anti-apoptotic effects of klotho on DOX-exposed myocardium and myocytes were impaired by both specific inhibitors and siRNAs against MAPKs. Moreover, the recovery effects of klotho on phosphorylations of MAPKs, Nrf2 translocation and expression levels of HO1 and Prx1 were also impaired by specific inhibitors and siRNAs against MAPKs.ConclusionsBy recovering the activation of MAPKs signaling, klotho improved cardiac function loss which was triggered by DOX-induced ROS mediated cardiac apoptosis.

Objective. The objective of this study was to investigate the involved mechanisms of advanced glycation end product- (AGE-) exacerbated atherosclerosis (AS). Methods. Toll-like receptor 4 (TLR4) inhibitor was administrated to type 2 diabetes mellitus (T2DM) AS rats. Atherosclerotic plaque, M1 macrophage infiltration, and VSMCs phenotypes were evaluated. AGE-exposed primary macrophages were treated with specific siRNAs knocking down receptor for AGEs (RAGE) and TLR4. Phenotypes of M1 macrophage and VSMCs were identified by fluorescent stains. Contact and noncontact coculture models were established. VSMCs and macrophages were cocultured in these models. ELISA was used to detect inflammatory cytokine concentrations. Relative mRNA expression levels were determined by real-time PCR. Relative protein expression and phosphorylation levels were evaluated by Western blots assays. Results. TLR4 inhibitor treatment significantly reduced arterial stenosis, infiltration of M1 polarized macrophages, and contractile-to-synthetic phenotype conversion of VSMCs in DM AS animals. RAGE and TLR4 silencing dramatically reduced AGE-induced macrophage M1 polarization, inflammatory cytokine secretion, and RAGE/TLR4/forkhead box protein C2 (FOXC2)/signaling which inhibited delta-like ligand 4 (Dll4) expression in macrophages. AGE-treated macrophages induced VSMC phenotypic conversion via activating Notch pathway in a contact coculture model rather than a noncontact model. The VSMC phenotypic conversion induction capability of macrophages was attenuated by RAGE and TLR4 silencing. Conclusions. AGEs induced activation of RAGE/TLR4/FOXC2 signaling, which featured macrophage with Dll4 high expression during M1 polarization. These macrophages promoted contractile-synthetic phenotypic conversion of VSMCs through the Dll4/Notch pathway after direct cell-to-cell contacts.

No abstract