Autophagy inhibitor 3-methyladenine alleviates overload-exercise-induced cardiac injury in rats

Abstract

Overload-exercise (OE) causes myocardial injury through inducing autophagy and apoptosis. In this study we examined whether an autophagy inhibitor 3-methyladenine (3-MA) could alleviate OE-induced cardiac injury. Rats were injected with 3-MA (15 mg/kg, iv) or saline before subjected to various intensities of OE, including no swim (control), 2 h swim (mild-intensity exercise, MIE), 2 h swim with 2.5% body weight overload (moderate OE; MOE), 5% overload (intensive OE; IOE) or 2.5% overload until exhausted (exhaustive OE; EOE). After OE, the hearts were harvested for morphological and biochemiacal analysis. The cardiac morphology, autophagosomes and apoptosis were examined with H&E staining, transmission electron microscopy and TUNEL analysis, respectively. Autophagy-related proteins to (LC3-II/I and Beclin-1) and apoptosis-related proteins (Bcl-2/Bax) were assessed using Western blotting. Our results showed that compared with the control, MIE did not change the morphological structures of the heart tissues that exhibited intact myocardial fibers and neatly arranged cardiomyocytes. However, IOE resulted in irregular arrangement of cardiomyocytes and significantly increased width of cardiomyocytes, whereas EOE caused more swollen and even disrupted cardiomyocytes. In parallel with the increased OE intensity (MOE, IOE, EOE), cardiomyocyte autophagy and apoptosis became more and more prominent, evidenced by the increasing number of autophagosomes and expression levels of LC3-II/I and Beclin-1 as well as the increasing apoptotic cells and decreasing Bcl-2/Bax ratio. 3-MA administration significantly attenuated OE-induced morphological changes of cardiomyocytes as well as all the autophagy- and apoptosis-related abnormalities in MOE, IOE and EOE rats. Thus, the autophagy inhibitor 3-MA could alleviate OE-induced heart injury in rats.

Blockage of AMPK-ULK1 Pathway Mediated Autophagy Promotes Cell Apoptosis to Increase Doxorubicin Sensitivity in Breast Cancer (BC) Cells: An in vitro Study

“…Speci cally, the DS-BC and CR-BC cells were subjected to high-dose Dox stimulation, and we found that Dox stimulation speci cally increased LC3B-II/I ratio, decreased p62 expression levels and facilitated autophagosomes formation in DR-BC cells, instead of DS-BC cells, suggesting that autophagy was activated in DR-BC cells under Dox pressure. Given the fact that autophagy protected cells from death [13,14], we next explored whether autophagy was pivotal for regulating Dox-resistance in BC cells by utilizing its inhibitor 3-methyladenine (3-MA) [23]. As expected, the results showed that 3-MA inhibited autophagy in DR-BC cells treated with Dox.…”

Blockage of AMPK-ULK1 pathway mediated autophagy promotes cell apoptosis to increase doxorubicin sensitivity in breast cancer (BC) cells: an in vitro study

“…Speci cally, the DS-BC and CR-BC cells were subjected to high-dose Dox stimulation, and we found that Dox stimulation speci cally increased LC3B-II/I ratio, decreased p62 expression levels and facilitated autophagosomes formation in DR-BC cells, instead of DS-BC cells, suggesting that autophagy was activated in DR-BC cells under Dox pressure. Given the fact that autophagy protected cells from death [13,14], we next explored whether autophagy was pivotal for regulating Dox-resistance in BC cells by utilizing its inhibitor 3methyladenine (3-MA) [23]. As expected, the results showed that 3-MA inhibited autophagy in DR-BC cells treated with Dox.…”

“…Nevertheless, the detailed mechanisms are still not fully understood. To solve this issue, the inhibitor for autophagy, 3-methyladenine (3-MA) [23], was used in this study, and we validated that 3-MA aggravated the inhibiting effects of Dox on cell proliferation in Dox-resistant BC (DR-BC) cells, which rendered the possibility that autophagy might play a protective role to enhance Dox-resistance under high-dose Dox stimulation in BC cells. AMP-activated protein kinase (AMPK)-Unc-51-like kinase 1 (ULK1) signaling cascade was crucial for autophagy initiation [24][25][26], and activation of AMPK-ULK1 pathway triggered protective autophagy to promote cell survival under environmental stress, such as oxidative stress [27] and cigarette smoke exposure [28].…”

Moderate, but Not Excessive, Training Attenuates Autophagy Machinery in Metabolic Tissues

“…Li et al [ 35 ] verified that an acute exhaustive exercise session suppressed autophagy, which was linked to ischemia-hypoxia injury in rat myocardium. In contrast, exhaustive overload-exercise-induced autophagy was related to disrupted cardiomyocytes [ 36 ]. According to Sciarretta and coworkers [ 37 ], the functional implications of the induction or suppression of the autophagy pathway in the heart under different experimental conditions must be further investigated.…”