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Ma Y.,Sun Yat Sen University | Chen Y.,Sun Yat Sen University | Yang Y.,Sun Yat Sen University | Chen B.,Peoples Hospital of Guizhou Province | And 5 more authors.
Biochemical Pharmacology | Year: 2013

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. © 2012 Elsevier Inc.

Ma Y.,Sun Yat Sen University | Chen B.,Peoples Hospital of Guizhou Province | Liu D.,Sun Yat Sen University | Yang Y.,Sun Yat Sen University | And 4 more authors.
Biochemical Pharmacology | Year: 2011

Although MG132, a proteasome inhibitor, is suggested to impede secondary cardiac remodeling after hypertension, the mechanism and optimal duration of treatment remain unknown. This study was designed to investigate the effects and possible mechanism of MG132 on hypertension-induced cardiac remodeling. Male Sprague-Dawley rats subjected to abdominal aortic constriction (AAC) or sham operation received an intraperitoneal injection of MG132 (0.1 mg kg-1 day-1) or vehicle over a 2- or 8-week period. In the end, left ventricular (LV) function was evaluated with echocardiography and pressure tracing. Collagen deposition within the LV myocardium was assessed with Masson's trichrome staining. Ubiquitin-proteasome system (UPS), NF-κB, I-κB, TGFβ1 and Smad2 within the LV tissue were evaluated. In addition, angiotensin II within both plasma and LV tissue was also examined. Compared with the sham groups, the vehicle-treated AAC group exhibited a higher angiotensin II level, LV/body weight ratio, septal and posterior wall thicknesses, and a markedly reduced cardiac function (P < 0.05). Treatment with MG132 for 8 weeks attenuated these cardiac remodeling parameters and improved cardiac function (P < 0.01). 2- and 8-week hypertension led to activation of UPS, which was followed by activation of NF-κB and increased expression of TGFβ1 and Smad2 (P < 0.01). MG132 significantly inhibited NF-κB activity and down-regulate the levels of TGFβ1 and Smad2 expression by 2 and still at 8 weeks (P < 0.01). Short- and long-term treatment with MG132 significantly attenuated hypertension-induced cardiac remodeling and dysfunction, which may be mediated by the NF-κB/TGFβ1 signaling pathway. © 2011 Elsevier Inc. All rights reserved.

Li Y.,Peoples Hospital of Guizhou Province | Du X.,Huazhong University of Science and Technology
The Journal of Membrane Biology | Year: 2014

Swelling-activated chloride currents (ICl.swell) play an important role in cardiac electrophysiology and arrhythmogenesis. However, the regulation of these currents has not been clarified to date. In this research, we focused on the function of phenylephrine, an α1-adrenoceptor agonist, in the regulation of ICl.swell in human atrial myocytes. We recorded ICl.swell evoked by a hypotonic bath solution with the whole-cell patch-clamp technique. We found that ICl.swell increased over time, and it was difficult to achieve absolute steady state. Phenylephrine potentiated ICl.swell from -1.00 ± 0.51 pA/pF at -90 mV and 2.58 ± 1.17 pA/pF at +40 mV to -1.46 ± 0.70 and 3.84 ± 1.67 pA/pF, respectively (P < 0.05, n = 6), and the upward trend in ICl.swell was slowed after washout. This effect was concentration-dependent, and the α1-adrenoceptor antagonist prazosin shifted the dose-effect curve rightward. Addition of prazosin or the protein kinase C (PKC) inhibitor bisindolylmaleimide (BIM) attenuated the effect of phenylephrine. The PKC activator phorbol 12,13-dibutyrate (PDBu) activated ICl.swell from -1.69 ± 1.67 pA/pF at -90 mV and 5.58 ± 6.36 pA/pF at +40 mV to -2.41 ± 1.95 pA/pF and 7.05 ± 6.99 pA/pF, respectively (P < 0.01 at -90 mV and P < 0.05 at +40 mV; n = 6). In conclusion, the α1-adrenoceptor agonist phenylephrine augmented ICl.swell, a result that differs from previous reports in other animal species. The effect was attenuated by BIM and mimicked by PDBu, which indicates that phenylephrine might modulate ICl,swell in a PKC-dependent manner. © 2014 Springer Science+Business Media New York.

Huang B.-T.,Southern Medical University | Zeng Q.-C.,Guangdong Medical College | Yu J.,University of Colorado at Denver | Liu X.-L.,Southern Medical University | And 2 more authors.
Medical Oncology | Year: 2012

The purpose of the study was to compare the antitumor efficacy and safety profile of high-dose homoharringtonine as induction and post-induction therapy compared to either standard-dose homoharringtonine or daunorubicin in elderly patients with newly diagnosed acute myeloid leukemia. A total of 254 patients, age range 60-77 years received induction and post-induction therapy containing daunorubicin, standard-dose homoharringtonine, or high-dose homoharringtonine. After one course of induction therapy, the overall complete remission rate was similar between treatment arms (58.7%, P =.92). Among 161 patients with acute myeloid leukemia (non-M5 subtype), estimated median overall survival was 39, 29, and 37 months, respectively, in the daunorubicin, standarddose homoharringtonine, and high-dose homoharringtonine treatment groups (P =.53). In the 93 patients with acute myeloid leukemia-M5 subtype, there was a significant difference in estimated median overall survival: 24, 24, and 52 months, respectively, in the daunorubicin, standarddose homoharringtonine, and high-dose homoharringtonine treatment groups (P =.003). There was no significant difference in drug-related adverse events between treatment arms. High-dose homoharringtonine does not clearly increase the complete remission rate of elderly patients with acute myeloid leukemia. However, in the subset of elderly patients with acute monocytic leukemia, high-dose homoharringtonine as a first-line regimen prolonged overall survival with minimal toxicity. © 2011 Springer Science+Business Media, LLC.

Chen B.L.,Peoples Hospital of Guizhou Province
Nan fang yi ke da xue xue bao = Journal of Southern Medical University | Year: 2010

To investigate the effects of AICAR on the activity of transcription factor FOXO1 and expression of ubiquitin ligase MuRF1 in rat cardiomyocytes, and explore the possible role of AMP-activated protein kinase (AMPK) in proteolysis pathways. In vitro cultured neonatal rat cardiac myocytes were treated with AICAR, and Western blotting was used to detect the phosphorylation of FOXO1 and expression of MuRF1 in the cells. AICAR activated AMPK in rat cardiac myocytes. Activated AMPK significantly inhibited the phosphorylation of FOXO1 and increased MuRF1 protein expression. AMPK may regulate proteolysis by activating FOXO1 transcription factor and up-regulating MuRF1 expression.

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