Original articleActivation of Nrf2 by Ginsenoside Rh3 protects retinal pigment epithelium cells and retinal ganglion cells from UV
Graphical abstract
Introduction
Long-term or excessive Ultra-violet (UV) radiation shall induce cytotoxicity to resident retinal pigment epithelium (RPE) cells (RPEs) and retinal ganglion cells (RGCs) [1], [2], which is one important cause of retinal degeneration [3], [4], [5]. Existing evidences have demonstrated that UV radiation will induce profound reactive oxygen species (ROS) production and oxidative stress, along with lipid peroxidation, calcium overload and DNA damages, which eventually will lead to death and apoptosis of RPEs and RGCs [1], [2], [6], [7], [8], [9], [10]. On the other hand, our group and others have shown that ROS scavenging could efficiently protect retinal cells from UV damages [1], [2], [6], [7], [8], [9], [10].
Ginseng, a well-known traditional herbal medicine, has been widely-utilized in ancient China [11], [12]. The ginseng's pharmacological properties are mainly attributed by the active component ginsenosides [11], [12]. Ginsenosides might exert different functions in different types of cells [11], [12]. Ginsenoside Rg5 is the main active component of heat-processed ginseng, which has displayed anti-cancer, anti-inflammatory, and ROS-scavenging activities [13], [14], [15], [16]. Ginsenoside Rh3 (“Rh3”) is a bacterial metabolite of Ginsenoside Rg5 [17], [18]. Existing evidences have investigated the potential cytoprotective and anti-inflammatory function of Rh3 [17], [18]. Its potential activity on UV-induced retinal cell damages has not been studied thus far.
Nuclear-factor-E2-related factor 2 (Nrf2) signaling is arguably one of the most important anti-oxidant axis [19], [20], [21]. As a transcription fact, Nrf2 binds to the antioxidant responsive element (ARE), which is essential for the transcription and expression of multiple key anti-oxidative enzymes [19], [20], [21], including heme oxygenase-1 (HO1), NAD(P)H quinone oxidoreductase 1 (NQO1) and γ-glutamyl cysteine ligase catalytic subunit (GCLC) [19]. Activation of Nrf2 could lead to a profound anti-oxidant response, and protects cells from oxidative stresses [19], [20], [21]. Nrf2's activity is tightly controlled by its suppresser protein Keap1, the latter is an adaptor of a Cul3-ubiquitin ligase complex, which dictates cytosol Nrf2 ubiquitination and proteasomal degradation [19], [20], [21]. Activated Nrf2 disassociates with Keap1 in cytoplasm, causing it accumulation and nuclear translocation [19], [20], [21].
Our studies and others have shown that activation of Nrf2 is a fine strategy to protect retinal cells from UV radiation and oxidative stress [8], [22], [23], [24]. For example, we showed that Salvianolic acid A protected RPEs from hydrogen peroxide (H2O2) via activating Nrf2-HO1 signaling [22]. Similarly, activation of Akt-Nrf2 signaling axis by 3H-1,2-dithiole-3-thione (D3T) also exerted cytoprotection in RPEs against UV [8]. A novel Akt activator, SC79-mediated RPE protection against UV also required Akt-Nrf2 signaling [23]. Our recent study found that microRNA-141 (miRNA-141)-mediated silence of Keap1 activated Nrf2 signaling and protected RPEs and RGCs from UV [24]. In the present study, we show that Rh3 inhibits UV-induced oxidative damages in retinal cells via activating Nrf2 signaling.
Section snippets
Reagents, chemicals and antibodies
The analytical standard ginsenoside Rh3 (“Rh3″, CAS no. 105558–26-7) [18], [25], [26], with the formula [3β, 12β,20Z)− 12-Hydroxydammara-20(22),24-dien-3-yl-β-D-glucopyranoside or C36H60O7 (MW: 604.86), was purchased from MCE China (HY-N0606, Shanghai, China). Quality control of Rh3 by HPLC (> 99%) was performed via the supplier. The following antibodies, HO-1 (#70081, 28kD), NQO1 (#3187, 29kD), Nrf2 (#12721, 98kD), Keap1 (#8047, 60kD), α-Tubulin (#2125, 52kD) and Lamin B1 (#13435, 55kD), were
Ginsenoside Rh3 protects human RPEs and RGCs from UV radiation
Here, we studied the potential effect of Ginsenoside Rh3 (“Rh3″) on UV-treated retinal cells. ARPE-19 is a well-established human RPE cell line [8], [23], [36]. In line with our previous findings [8], [23], UV irradiation (UVB/A2, 30 mJ/cm2) in APRE-19 cells (“RPEs”) resulted in significant cell viability reduction (MTT OD decrease, Fig. 1A) and cell death (Trypan blue ratio increase, Fig. 1B). Notably, UV-induced cytotoxicity in RPEs was attenuated with pre-treatment (30 min before UV) of Rh3 (
Discussion
The transcription factor Nrf2 plays a vital role in ARE-mediated expression of phase II detoxifying and antioxidant enzymes, as well as in the prevention of cell damages caused by oxidative stress [38]. In the current study, we provided evidences to support that Rh3 could be an efficient Nrf2 activator in retinal cells. in both human RPEs and RGCs, pretreatment with Rh3 inhibited UV-induced ROS production and following apoptotic/non-apoptotic cell death. Rh3 treatment in human retinal cells
Conclusion
In summary, Rh3 protected RPEs and RGCs from UV radiation through activation of Nrf2 signaling. Expression of miR-141 could be the key mechanism of Rh3-induced Nrf2 activation and retinal cell protection. The in vivo studies demonstrated that Rh3 intravitreal injection protected mouse retinas from UV. Nrf2 activation and miR-141 upregulation were also noticed in Rh3-treated mouse retinas. Our results imply that Rh3 might have therapeutic value for UV or oxidative stress-associated retinal
Acknowledgements
This work was generously supported by the grants from the National Natural Science Foundation of China (Grant No. 81371055, 81570859, 81670878, 81302195, 31371139, 81571282, 81771457 and 81700859), grants from the Medical Science and Technology Development Project Fund of Nanjing (YKK16271, YKK14193, YKK15241, YKK16269, YKK16270), Grants from Natural Science Foundation of Jiangsu Province (BK2016022104, BK20171065, BK20170060).
Competing interests
The authors declare that they have no competing interests.
Author contributions
All authors carried out the experiments, participated in the design of the study and performed the statistical analysis, participated in its design and coordination and helped to draft the manuscript.
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2022, Trends in NeurosciencesTargeting Keap1 by miR-626 protects retinal pigment epithelium cells from oxidative injury by activating Nrf2 signaling
2019, Free Radical Biology and MedicineCitation Excerpt :We reported that Salvianolic acid A can offer RPE cytoprotection against H2O2 through activation of the Nrf2-HO1 cascade [8]. Recently, we found that ginsenoside Rh3 (GRh3) activated Nrf2 cascades to protect RPE cells and retinal ganglion cells (RGCs) from UVR [18]. A potential strategy to activate Nrf2 signaling is to inhibit/silence its suppressor protein Keap1 [21–23].
Targeting cullin 3 by miR-601 activates Nrf2 signaling to protect retinal pigment epithelium cells from hydrogen peroxide
2019, Biochemical and Biophysical Research CommunicationsCitation Excerpt :For instance, Salvianolic acid A activated Nrf2 cascade to protect RPE cells from oxidative stress [8]. Similarly, other agents, including Ginsenoside Rh3 [9], 3H-1,2-dithiole-3-thione (D3T) [10] and SC79 (a novel Akt activator [11]), can offer RPE cytoprotection against various oxidative stimuli via activation of Nrf2 signaling. Under the resting conditions, Nrf2 localizes in cytosol and directly associates with Kelch-like ECH-associated protein 1 (Keap1)-cullin 3 (Cul3)-E3 ligase complex, the latter is responsible for Nrf2 degradation by ubiquitination [12,13].
Ginsenosides: the need to move forward from bench to clinical trials
2019, Journal of Ginseng ResearchCitation Excerpt :Ginsenosides are generally metabolized by the bacteria in the human intestine to deglycosylated forms, which could be easily absorbed in the bloodstream and act as a bioactive ingredient [52]. Ginsenoside Rh3 (G-Rh3) is a bacterial metabolite of ginsenoside Rg5 (G-Rg5) [53], and treatment of human retinal cells with G-Rh3 induced the nuclear factor (erythroid-derived 2)-2 activation [54]. Moreover, G-Rh3 was reported to protect against memory deficits in mice by suppressing acetylcholinesterase activity as well as by inducing hippocampal brain-derived neurotrophic factor expression and cyclic adenosine monophosphate (cAMP) response element–binding protein activation [55].
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Co-first authors.