leupeptins and Heart-Failure

The elevated expression of poly(ADP-ribose) polymerase-1 (PARP1) and increased PARP1 activity, namely, poly(ADP-ribosyl)ation (PARylation), have been observed in cardiac remodeling, leading to extreme energy consumption and myocardial damage. However, the mechanisms underlying the regulation of PARP1 require further study. WWP2, a HECT-type E3 ubiquitin ligase, is highly expressed in the heart, but its function there is largely unknown. Here, we clarified the role of WWP2 in the regulation of PARP1 and the impact of this regulatory process on cardiac remodeling. We determined that the knockout of WWP2 specifically in myocardium decreased the level of PARP1 ubiquitination and increased the effects of isoproterenol (ISO)-induced PARP1 and PARylation, in turn aggravating ISO-induced myocardial hypertrophy, heart failure, and myocardial fibrosis. Similar findings were obtained in a model of ISO-induced H9c2 cells with WWP2 knockdown, while the reexpression of WWP2 significantly increased PARP1 ubiquitination and decreased PAPR1 and PARylation levels. Mechanistically, coimmunoprecipitation results identified that WWP2 is a novel interacting protein of PARP1 and mainly interacts with its BRCT domain, thus mediating the degradation of PARP1 through the ubiquitin-proteasome system. In addition, lysine 418 (K418) and lysine 249 (K249) were shown to be of critical importance in regulating PARP1 ubiquitination and degradation by WWP2. These findings reveal a novel WWP2-PARP1 signal transduction pathway involved in controlling cardiac remodeling and may provide a basis for exploring new strategies for treating heart disorders related to cardiac remodeling.

Topics: Animals; Cardiomegaly; Fibrosis; Heart Failure; Humans; Isoproterenol; Leupeptins; Lysine; Male; Mice, Inbred C57BL; Mice, Transgenic; Models, Biological; Myocardium; Poly ADP Ribosylation; Poly(ADP-ribose) Polymerases; Proteasome Endopeptidase Complex; Protein Binding; Proteolysis; Ubiquitin; Ubiquitin-Protein Ligases; Ubiquitination; Ventricular Remodeling

Clusterin (CLU) is induced in many organs after tissue injury or remodeling. Recently, we show that CLU levels are increased in plasma and left ventricle (LV) after MI, however, the mechanisms involved are not yet elucidated. On the other hand, it has been shown that the activity of the protein degradation systems (PDS) is affected after MI with a decrease in ubiquitin proteasome system (UPS) and an increase in macroautophagy. The aim of this study was to decipher if the increased CLU levels after MI are in part due to the alteration of PDS activity. Rat neonate cardiomyocytes (NCM) were treated with different modulators of UPS and macroautophagy in order to decipher their role in CLU expression, secretion, and degradation. We observed that inhibition of UPS activity in NCM increased CLU mRNA levels, its intracellular protein levels (p-CLU and m-CLU) and its secreted form (s-CLU). Macroautophagy was also induced after MG132 treatment but is not active. The inhibition of macroautophagy induction in MG132-treated NCM increased CLU mRNA and m-CLU levels, but not s-CLU compared to NCM only treated by MG132. We also demonstrate that CLU can be degraded in NCM through proteasome and lysosome by a macroautophagy independent pathway. In another hand, CLU silencing in NCM has no effect either on macroautophagy or apoptosis induced by MG132. However, the overexpression of CLU secreted isoform in H9c2 cells, but not in NCM decreased apoptosis after MG132 treatment. Finally, we observed that increased CLU levels in hypertrophied NCM and in failing human hearts are associated with proteasome inhibition and macroautophagy alteration. All these data suggest that increased CLU expression and secretion after MI is, in part, due to a defect of UPS and macroautophagy activities in the heart and may have a protective effect by decreasing apoptosis induced by proteasome inhibition.

Topics: Animals; Apoptosis; Autophagy; Biopsy; Clusterin; Gene Silencing; Heart Failure; Humans; Hypertrophy; Leupeptins; Lysosomes; Myocardial Infarction; Myocardium; Myocytes, Cardiac; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteolysis; Rats; Ubiquitinated Proteins; Ubiquitination

The connexin 43 (Cx43) gap junction protein is important in the synchronization of contraction of cardiac myocytes. Abnormal expression of Cx43 contributes to ventricular arrhythmia, which is the major cause of sudden death in heart failure (HF). Cx43 is known to interact with zonula occludens (ZO)‑1, and the proteasome is involved in the regulation of Cx43 degradation. Although Cx43 is downregulated in heart failure, the underlying mechanisms remain to be elucidated. The present study aimed to investigate the effect of the MG132 proteasome inhibitor on the expression levels of Cx43, ZO‑1, 20S proteasome and ubiquitin in a rat model of HF, induced by adriamycin. MG132 reduced adriamycin‑induced injury in the failing heart. In addition, MG132 inhibited the expression of 20S proteasome and ubiquitin, accompanied by an upregulation in the expression of Cx43 and ZO‑1. These findings suggested that inhibition of the ubiquitin‑proteasome system upregulated the expression of Cx43. Therefore, the proteasome inhibitor may be used to prevent degradation of Cx43 in HF, and thus may prevent Cx43-mediated arrhythmia in HF.

Topics: Animals; Antibiotics, Antineoplastic; Cardiotonic Agents; Connexin 43; Doxorubicin; Drug Evaluation, Preclinical; Gene Expression Regulation; Heart Failure; Leupeptins; Male; Proteasome Inhibitors; Rats, Wistar; Up-Regulation; Ventricular Fibrillation; Zonula Occludens-1 Protein

Although the role of the ubiquitin-proteasome system (UPS) in cardiac hypertrophy induced by pressure overload has been consistently studied, the fundamental importance of the UPS in cardiac fibrosis has received much less attention. Our previous study found that proteasome inhibitor (MG132) treatment attenuated cardiac fibrosis and heart failure during the early and middle stages of pressure overload. However, the effects of this inhibitor on late-stage pressure overload hearts remain unclear and controversial. The present study was designed to investigate the effects and possible mechanisms of MG132 on cardiac fibrosis and dysfunction during the late stages of pressure overload. Male Sprague Dawley rats with abdominal aortic constriction (AAC) or a sham operation received an intraperitoneal injection of MG132 (0.1 mg kg⁻¹ day⁻¹) or vehicle for 16 weeks. Left ventricular (LV) function, collagen deposition and Ang II levels were evaluated at study termination. Ang II-stimulated adult rat cardiac fibroblasts were utilized to examine the effects of MG132 on collagen synthesis and the relationship between the renin-angiotensin-aldosterone system (RAAS) and the UPS. MG132 treatment attenuated ventricular dysfunction by suppressing cardiac fibrosis rather than inhibiting cardiac hypertrophy during the late-stages of pressure overload. We also found that Ang II activates UPS in the heart and MG132 attenuates Ang II-induced collagen synthesis via suppression of the NF-κB/TGF-β/Smad2 signaling pathways. Proteasome inhibition therefore could provide a new promising therapeutic strategy to prevent cardiac fibrosis and progression of heart failure even during the late-stages of pressure overload.

Topics: Angiotensin II; Animals; Cells, Cultured; Collagen; Disease Models, Animal; Down-Regulation; Fibrosis; Heart Failure; Heart Ventricles; Hypertension; Leupeptins; Male; Proteasome Inhibitors; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger; Severity of Illness Index; Signal Transduction; Transforming Growth Factor beta1; Ubiquitin; Ventricular Dysfunction, Left