J Nutr Health.  2019 Apr;52(2):176-184. 10.4163/jnh.2019.52.2.176.

Emodin exerts protective effect against palmitic acid-induced endoplasmic reticulum stress in HepG2 cells

• Thomas SS
• Park S
• Cha YS
• Kim KA

• KMID: 2444941
• DOI: http://doi.org/10.4163/jnh.2019.52.2.176

Abstract

PURPOSE
Protein overloading in the endoplasmic reticulum (ER) leads to endoplasmic reticulum stress, which exacerbates various disease conditions. Emodin, an anthraquinone compound, is known to have several health benefits. The effect of emodin against palmitic acid (PA) - induced ER stress in HepG2 cells was investigated.
METHODS
HepG2 cells were treated with varying concentrations of palmitic acid to determine the working concentration that induced ER stress. ER stress associated genes such as ATF4, XBP1s, CHOP and GRP78 were checked using RT- PCR. In addition, the expression levels of unfolded protein response (UPR) associated proteins such as IRE1α, eIF2α and CHOP were checked using immunoblotting to confirm the induction of ER stress. The effect of emodin on ER stress was analyzed by treating HepG2 cells with 750 µM palmitic acid and varying concentrations of emodin, then analyzing the expression of UPR associated genes.
RESULTS
It was evident from the mRNA and protein expression results that palmitic acid significantly increased the expression of UPR associated genes and thereby induced ER stress. Subsequent treatment with emodin reduced the mRNA expression of ATF4, GRP78, and XBP1s. Furthermore, the protein levels of p-IRE1α, p-elF2α and CHOP were also reduced by the treatment of emodin. Analysis of sirtuin mRNA expression showed that emodin increased the levels of SIRT4 and SIRT7, indicating a possible role in decreasing the expression of UPR-related genes.
CONCLUSION
Altogether, the results suggest that emodin could exert a protective effect against fatty acid-induced ER stress and could be an agent for the management of various ER stress related diseases.

Keyword

emodin; palmitic acid; endoplasmic reticulum stress; sirtuins

MeSH Terms

Emodin*
Endoplasmic Reticulum Stress*
Endoplasmic Reticulum*
Hep G2 Cells*
Immunoblotting
Insurance Benefits
Palmitic Acid
Polymerase Chain Reaction
RNA, Messenger
Sirtuins
Unfolded Protein Response
Emodin
Palmitic Acid
RNA, Messenger
Sirtuins

Figure

• 

  Fig. 1 (A) Effect of PA alone, (B) Effect of emodin alone on cell viability of HepG2 cells. Values are expressed as mean ± SD. Values with different letters indicate significance between groups by ANOVA with Duncan's multiple range test at p < 0.05. CON, control; BSA, bovine serum albumin; PA, palmitic acid

• 

  Fig. 2 ER stress related genes on treatment with different concentrations of PA in HepG2 cells (A) mRNA expression and (B) protein expression and fold change. Values are expressed as mean ± SD. Values with different letters indicate significance between groups by ANOVA with Duncan's multiple range test at p < 0.05. PA, palmitic acid; CON, control; BSA, bovine serum albumin

• 

  Fig. 3 Effect of emodin on PA induced ER stress marker genes in HepG2 cells (A) mRNA expression and (B) protein expression and fold change. Values are expressed as mean ± SD. Values with different letters indicate significance between groups by ANOVA with Duncan's multiple range test at p < 0.05. PA: palmitic acid, CON, control; BSA, bovine serum albumin; E0, 0 µM; E1, 1 µM; E2, 2 µM; E4, 4 µM of emodin

• 

  Fig. 4 Effect of emodin on PA induced ER stress marker genes in HepG2 cells. Values are expressed as mean ± SD. Values with different letters indicate significance between groups by ANOVA with Duncan's multiple range test at p < 0.05. PA, palmitic acid; E0, 0 µM; E1, 1 µM; E2, 2 µM; E4, 4 µM of emodin

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