Project description:Involvement of the Toll-like receptor 4 (TLR4) in maladaptive cardiac remodeling and heart failure (HF) upon pressure overload has been studied extensively, but less is known about the role of TLR2. Interplay and redundancy of TLR4 with TLR2 have been reported in other organs but were not investigated during cardiac dysfunction. We explored whether TLR2 deficiency leads to less adverse cardiac remodeling upon chronic pressure overload and whether TLR2 and TLR4 additively contribute to this. We subjected 35 male C57BL/6J mice (wildtype (WT) or TLR2 knockout (KO)) to sham or transverse aortic constriction (TAC) surgery. After 12 weeks, echocardiography and electrocardiography were performed, and hearts were extracted for molecular and histological analysis. TLR2 deficiency (n = 14) was confirmed in all KO mice by PCR and resulted in less hypertrophy (heart weight to tibia length ratio (HW/TL), smaller cross-sectional cardiomyocyte area and decreased brain natriuretic peptide (BNP) mRNA expression, p < 0.05), increased contractility (QRS and QTc, p < 0.05), and less inflammation (e.g., interleukins 6 and 1β, p < 0.05) after TAC compared to WT animals (n = 11). Even though TLR2 KO TAC animals presented with lower levels of ventricular TLR4 mRNA than WT TAC animals (13.2 ± 0.8 vs. 16.6 ± 0.7 mg/mm, p < 0.01), TLR4 mRNA expression was increased in animals with the largest ventricular mass, highest hypertrophy, and lowest ejection fraction, leading to two distinct groups of TLR2 KO TAC animals with variations in cardiac remodeling. This variation, however, was not seen in WT TAC animals even though heart weight/tibia length correlated with expression of TLR4 in these animals (r = 0.078, p = 0.005). Our data suggest that TLR2 deficiency ameliorates adverse cardiac remodeling and that ventricular TLR2 and TLR4 additively contribute to adverse cardiac remodeling during chronic pressure overload. Therefore, both TLRs may be therapeutic targets to prevent or interfere in the underlying molecular processes.

Project description:Aims: Cardiac fibroblasts (CFs) play a crucial role in cardiac remodelling, which is a common cause of heart failure (HF). However, the molecular mechanisms underlying the fibroblast-to-myofibroblast transition remain largely unknown. Foxm1 is well known in various cardiopulmonary pathologies. However, Foxm1-driven CF activation in the progression of cardiac remodelling to HF remains to be investigated. Methods: Changes in Foxm1 expression were assessed in samples from patients with HF and mice with transverse aortic constriction (TAC)-induced cardiac remodelling. Pharmacologic antagonist FDI-6 was used to explore the effects of Foxm1 inhibition on post-TAC outcomes. Tcf21-Cre and PostnMCM were used to evaluate Foxm1 loss- and gain-of-function in CFs and myofibroblasts, respectively. Cardiac function and remodelling were examined by echocardiography and histological analysis. Foxm1 downstream target genes were identified by mass spectrometry (MS) and transcriptomic analysis. Post-translational regulation was evaluated by in vitro chromatin immunoprecipitation, co-immunoprecipitation, and ubiquitination assays. Pharmacological inhibition of Usp10 or knockout of p38γ in vivo verified the signalling pathway by which Foxm1 regulated cardiac remodelling. Results: Foxm1 was upregulated in human HF samples as well as in the mouse cardiac remodelling model. CFs were the primary cell type responsible for Foxm1 upregulation. Foxm1 pharmacological inhibition or genetic knockout in CFs or myofibroblasts significantly attenuated TAC-induced cardiac remodelling and HF. Conversely, conditional overexpression of Foxm1 in CFs or myofibroblasts resulted in more severe pathological cardiac remodelling and dysfunction. Combined RNA-sequencing and MS analysis revealed that Foxm1 promoted Usp10 expression by binding to its promoter. Usp10 interacted with p38γ, resulting in p38γ deubiquitination and thus inﬂuencing the downstream p38 mitogen-activated protein kinase (MAPK) signalling pathway. Pharmacological inhibition of Usp10 or genetic knockout of p38γ ameliorated the exacerbated TAC-induced cardiac remodelling in mice with myofibroblast-specific Foxm1 overexpression. Conclusion: Our findings reveal an essential role of Foxm1 in CF activation during cardiac remodelling. These results suggest that targeting the Foxm1/Usp10/p38γ MAPK axis may represent a new potential therapeutic strategy against pathological cardiac remodelling and HF.

Dataset Information

Complement 5a Receptor deficiency does not influence adverse cardiac remodeling after pressure-overload in mice.

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Complement 5a Receptor deficiency does not influence adverse cardiac remodeling after pressure-overload in mice.

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