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Cathepsin A contributes to left ventricular remodeling by degrading the antioxidant enzyme extracellular superoxide dismutase

ABSTRACT: In the heart, the serine carboxypeptidase cathepsin A (CatA) is distributed between lysosomes and the extracellular matrix (ECM). CatA-mediated degradation of extracellular peptides may contribute to ECM-remodeling and left ventricular (LV) dysfunction. This study aimed to evaluate the effects of CatA overexpression on LV remodeling. A proteomic analysis of the secretome of adult mouse cardiac fibroblasts upon digestion by CatA identified the extracellular antioxidant enzyme superoxide dismutase (EC-SOD) as a novel substrate of CatA (5-fold decreased abundance; p=0.0001). In vitro, cardiomyocytes and cardiac fibroblasts expressed and secreted CatA protein. EC-SOD protein was expressed and secreted only by cardiac fibroblasts. Cardiomyocyte-specific over-expression of CatA and increased activity in the LV of transgenic mice (CatA-TG) reduced EC-SOD protein levels by 43% (p<0.001). Loss of EC-SOD-mediated anti-oxidative protection resulted in accumulation of superoxide radicals (WT: 4.54±1.2 vs. CatA-TG: 8.62±2.3µmol/mg tissue/min; p=0.0012), increased inflammation, myocyte hypertrophy (WT: 19.8±1.0 vs. CatA-TG: 21.9±1.8µm; p=0.024), cellular apoptosis, and elevated mRNA expression of hypertrophy-related and pro-fibrotic marker genes, without effecting intracellular detoxifying proteins. In CatA-TG mice LV interstitial fibrosis formation was enhanced by 19% (p=0.028) and type I/type III collagen ratio was shifted towards higher abundance of collagen I fibers (p=0.026). Cardiac remodeling in CatA-TG was accompanied by increased LV weight/body weight and LV enddiastolic volume (WT: 50.8±5.8 vs. CatA-TG: 61.9±6.2 µl; p=0.018). Thus, in the heart CatA-mediated reduction of EC-SOD protein contributes to increased oxidative stress, myocyte hypertrophy, ECM remodeling and inflammation. This implicates CatA as a potential therapeutic target to prevent ventricular remodeling.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Cell Culture, Fibroblast Of Cardiac Tissue

SUBMITTER: Xiaoke Yin

LAB HEAD: Manuel Mayr

PROVIDER: PXD019895 | Pride | 2020-07-10

REPOSITORIES: Pride

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Project description:Background: Galectin-3 is upregulated in heart disease, and its inhibition has been reported to confer benefits on cardiac remodeling and dysfunction. It remains unknown whether galectin-3 plays a biological role in a setting of dilated cardiomyopathy (DCM). We determined galectin-3 expression in transgenic (TG) mice with cardiac-restricted overexpression of mammalian sterile 20-like kinase 1 (Mst1-TG), and studied the effects of pharmacological and genetic inhibition of galectin-3 on the DCM phenotype. Methods and results: The DCM phenotype of male Mst1-TG mice was assessed at 2, 3 and 6 months of age. Galectin-3 deletion in Mst1-TG mice was achieved by cross-breeding Mst1-TG with galectin-3 knockout (KO) mice to produce genotypes of non-TG (nTG), KO, Mst1-TG, and Mst1-TG mice with partial or complete deletion of the galectin-3 gene. Pharmacological inhibition of galectin-3 was tested by treating Mst1-TG mice with modified citrus pectin for 4 months. Changes in the DCM phenotype were assessed by serial echocardiography, ECG recording and biochemical assays. Mst1-TG mice exhibited upregulated levels of cardiac galectin-3 expression by 40~50-fold, atrial dilatation, reduced left ventricular (LV) ejection fraction, increased LV volume at systole and diastole, atrial conduction delay, severe cardiac fibrosis, and upregulated fibrosis-related genes. Galectin-3 gene deletion in Mst1-TG mice attenuates increased LV volume at systole and diastole, atrial conduction delay and cardiac fibrogenesis. Treatment with modified citrus pectin in Mst1-TG mice did not confer benefit on the DCM phenotype, possibly due to the very high expression of galectin-3. Conclusion: Galectin-3 expression is markedly increased in Mst1-TG hearts exhibiting DCM. Galectin-3 gene deletion effectively suppressed cardiac fibrotic signaling and LV dilatation, and was associated with better function. Thus, suppression of galectin-3 expression may represent a potential therapeutic approach in DCM. The development of new galectin-3 inhibitors are warranted.

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Cathepsin A contributes to left ventricular remodeling by degrading the antioxidant enzyme extracellular superoxide dismutase

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