Objective:

2

To investigate whether ginsenoside-Rb1 (Gs-Rb1) improves the CoCl

2

-induced autophagy of cardiomyocytes via upregulation of adenosine 5'-monophosphate-activated protein kinase (AMPK) pathway.

Methods:

2

Ventricles from 1- to 3-day-old Wistar rats were sequentially digested

separated and incubated in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum for 3 days followed by synchronization. Neonatal rat cardiomyocytes were randomly divided into 7 groups: control group (normal level oxygen)

hypoxia group (500 μmol/L CoCl

2

)

Gs-Rb1 group (200 μmol/L Gs-Rb1 + 500 μmol/L CoCl2)

Ara A group (500 μmol/L Ara A + 500 μmol/L CoCl

2

)

Ara A+ Gs-Rb1 group (500 μmol/L Ara A + 200 μmol/L Gs-Rb1 + 500 μmol/L CoCl

2

)

AICAR group [1 mmol/L 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) + 500 μmol/L CoCl

2

]

and AICAR+Gs-Rb1 group (1 mmol/L AICAR + 200 μmol/L Gs-Rb1 + 500 μmol/L CoCl

2

). Cells were treated for 12 h and cell viability was determined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and cardiac troponin I (cTnI) levels were detected by enzyme-linked immunosorbent assay (ELISA). AMPK activity was assessed by 2'

7'-dichlorofluorescein diacetate (DCFH-DA) ELISA assay. The protein expressions of Atg4B

Atg5

Atg6

Atg7

microtubule-associated protein 1A/1B-light chain 3 (LC3)

P62

and active-cathepsin B were measured by Western blot.

Results:

2

Gs-Rb1 significantly improved the cell viability of hypoxia cardiomyocytes (

P

<

0.01). However

the viability of hypoxia-treated cardiomyocytes was significantly inhibited by Ara A (

P

<

0.01). Gs-Rb1 increased the AMPK activity of hypoxia-treated cardiomyocytes. The AMPK activity of hypoxia-treated cadiomyocytes was inhibited by Ara A (

P

<

0.01) and was not affected by AICAR (

P

=0.983). Gs-Rb1 up-regulated Atg4B

Atg5

Beclin-1

Atg7

LC3B Ⅱ

the LC3BⅡ/Ⅰ ratio and cathepsin B activity of hypoxia cardiomyocytes (

P

<

0.05)

each of these protein levels was significantly enhanced by Ara A (all

P

<

0.01)

but was not affected by AICAR (all

P

>

0.05). Gs-Rb1 significantly down-regulated P62 levels of hypoxic cardiomyocytes (

P

<

0.05). The P62 levels of hypoxic cardiomyocytes were inhibited by Ara A (

P

<

0.05) and were not affected by AICAR (

P

=0.871).

Conclusion:

2

Gs-Rb1 may improve the viability of hypoxia cardiomyocytes by ameliorating cell autophagy via the upregulation of AMPK pathway.