Role of heat shock protein 22 in the protective effect of geranylgeranylacetone in response to oxidized-LDL

Abstract

Objective

The aim was to investigate the role and potential mechanism of geranylgeranylacetone (GGA) in the development of atherosclerosis, and to explore the role of heat shock protein 22 (HSP22) in mediating GGA effect.

Methods

Human coronary artery endothelial cell (HCAEC) was used for in vitro study. RNA interference was applied to suppress HSP22 in the cells. Cellular apoptosis and intracellular level of reactive oxygen species (ROS) were detected by flow cytometer, and proteins of HSP22, NF-κB, eNOS, and ICAM-1 were assessed by immunoblotting. HSP22^−/−//ApoE^−/−, and HSP22^+/+//ApoE^−/− mice were used to investigate the effect of GGA in the animal model of atherosclerosis. Atherosclerotic lesion of the mice aortas was evaluated by Oil Red O staining and H&E staining.

Results

GGA significantly inhibited HCAEC apoptosis in response to oxidized-LDL (ox-LDL), but stimulated HSP22 synthesis in the cells. Transfection of HSP22-siRNA in the cells resulted in complete blockage of the GGA effect on apoptosis. GGA also significantly inhibited ROS, NF-κB, and ICAM-1 in the cells transfected control siRNA, but not in the cells transfected with HSP22-siRNA. Atherosclerotic plaque in the aorta was significantly less in the wild type (WT) animals treated with GGA as stained either by Oil Red O or by H&E staining, but not in the HSP22-KO mice. GGA significantly inhibited expression of NF-κB and ICAM-1 in the WT mice, but not in the HSP22-KO mice.

Conclusion

GGA-induced HSP22, and inhibited ox-LDL-induced apoptosis as well as expression of NF-κB and ICAM-1 in the HCAECs. GGA also attenuated formation of atherosclerotic plaques in mice aorta. Suppression of HSP22 by siRNA resulted in blockage of the GGA inhibition on apoptosis or stimulation on NF-κB and ICAM-1. These findings suggested that GGA protects endothelial cells from injury in response to ox-LDL and block atherosclerotic development in mice aorta through induction of HSP22.

Keywords:

• geranylgeranylacetone (GGA)
• heat shock protein 22 (HSP22)
• endothelial cells
• inflammatory response
• atherosclerosis

Acknowledgment

This work was supported by research grant from the National Natural Science Foundation of China (No. 8166020210).

Availability of data and material

The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

This research was approved by the Ethics Committee of The Second Affiliated Hospital of Nanchang University. All methods were carried out in accordance with relevant guidelines and regulations. All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

Author contributions

Ren Gong and Yan-Qing Wu contributed to the conception and design of the study; Xi-Yong Li contributed to the acquisition of data; Huai-Jing Chen and Cong-Cong Xu performed the experiments; Hai-Yang Fang and Jian Xiang contributed to the analysis of data; Ren Gong wrote the manuscript. All authors reviewed and approved the final version of the manuscript. All authors contributed to the data analysis, drafting and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspect of the work. 

Disclosure

The authors declare that they have no competing interests in this work.

Supplementary materials

Figure S1 Representative image of HSP22 suppression by siRNA. HCAECs were transfected with HSP22-siRNA or non-specific siRNA as described in the Materials and methods section. Level of HSP22 was examined by immunoblotting as described in the Materials and methods section.

Figure S2 HSP22 expression in wild type and HSP22-knockout mice. (A) Representative image of HSP22 expression in wild type and HSP22-knockout mice. (B) Effect of GGA on HSP22 expression in wild type and HSP22-knockout mice.