Tetramethylpyrazine reverses high-glucose induced hypoxic effects by negatively regulating HIF-1\u03b1 induced BNIP3 expression to ameliorate H9c2 cardiomyoblast apoptosis

Shih-Ping Liu,Chang-Hai Tsai,Fuu-Jen Tsai,Qiaowen Li,Yuan-Man Hsu,Chih-Hsin Tang,Jing-Gung Chung,Shulin Wang,Jai-Sing Yang,Marthandam Asokan Shibu,Chih-Yang Huang

doi:10.1186/s12986-020-0432-x

Abstract

BackgroundDiabetic patients are highly vulnerable to hypoxic injury, which is associated with hypoxia induced BNIP3 expression that subsequently activate apoptosis. Our previous research show that Tetramethylpyrazine (TMP), a food flavoring agent, represses the hypoxia induced BNIP3 expression attenuate myocardial apoptosis. In this study, we evaluate the effect of TMP to provide protection against hypoxia aggravated high-glucose associated cellular apoptosis.MethodsThe cytoprotective effect of TMP against high glucose induced cellular damages was determined on embryo derived H9c2 cardiomyoblast cells that were subjected to 5% hypoxia for 24 h and subjected to different duration of 33 mM high glucose challenge. Further, the involvement of HIF-1α and BNIP3 in cellular damage and the mechanism of protection of TMP were determined by overexpression and silencing HIF-1α and BNIP3 protein expression.ResultsThe results show that hypoxic effects on cell viability aggravates with high glucose challenge and this augmentative effect is mediated through BNIP3 in H9c2 cardiomyoblast cells. However, TMP administration effectively reversed the augmented HIF-1α levels and BNIP3 elevation. TMP improved the survival of H9c2 cells and effectively suppressed apoptosis in H9c2 cells. Further comparison on the effects of TMP on H9c2 cells challenged with high glucose and those challenged with hypoxia show that TMP precisely regulated the hypoxic intensified apoptotic effects in high-glucose condition.ConclusionThe results clearly show that flavoring agent-TMP attenuates cytotoxicity amplified by hypoxia challenge in high glucose condition by destabilizing HIF-1α.

Highlights

Diabetic patients are highly vulnerable to hypoxic injury, which is associated with hypoxia induced Bcl-2 adenovirus E1B nineteen-kilodalton interacting protein 3 (BNIP3) expression that subsequently activate apoptosis
The results show that the synergistic effect of hypoxia and high glucose stress elevated the apoptotic cell death (Fig. 2a) which correlation with BNIP3 levels (Fig. 2b)
TMP inhibits cellular apoptosis triggered by high glucose stress under hypoxia and downregulates BNIP3 levels To investigate the effect of TMP on H9c2 cells under synergistic hypoxia and high glucose stress 5 μM, 10 μM and 20 μM of TMP was treated to the cells cultured in high glucose media under hypoxia

Summary

Introduction

Diabetic patients are highly vulnerable to hypoxic injury, which is associated with hypoxia induced BNIP3 expression that subsequently activate apoptosis. Our previous research show that Tetramethylpyrazine (TMP), a food flavoring agent, represses the hypoxia induced BNIP3 expression attenuate myocardial apoptosis. We evaluate the effect of TMP to provide protection against hypoxia aggravated high-glucose associated cellular apoptosis. Numerous studies have revealed hyperglycemia as an independent risk factor that can directly inflict cardiac damage, thereby contributing to diabetic cardiomyopathy [3]. Initial responses of cardiac cells to hyperglycemic condition include abnormal metabolism, abnormal fetal gene expression and defects in cellular organelles [4]. Diabetes is an independent risk factor for CVD, evidences show that hyperglycemia, contributes to myocardial damage following ischemic events [6] Cardiomyocyte death follows as a consequence to these abnormalities and forms a reason for subsequent collagen accumulation and reduced contractile function [5].

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