SIRT6 protects retinal ganglion cells against hydrogen peroxide-induced apoptosis and oxidative stress by promoting Nrf2/ARE signaling via inhibition of Bach1
Graphical abstract
Introduction
Oxidative stress-induced death of retinal ganglion cells (RGCs) is a major pathomechanism of multiple retinal degenerative diseases, such as glaucoma [1]. Glaucoma is characterized by excessive RGC death, which leads to irreversible vision loss [2]. Under pathologic conditions, reactive oxygen species (ROS) are generated at high levels causing DNA damage, lipid peroxidation, and calcium overload, which eventually result in RGC death and apoptosis [3]. However, the precise molecular mechanism underlying oxidative stress-induced damage of RGCs remains largely unknown. Therefore, it is essential to identify new regulators involved in oxidative stress-induced damage of RGCs, which may aid the development of promising targeted therapies for retinal degenerative diseases.
Mammalian sirtuins, the homologues of the yeast silent information regulator 2, are a group of NAD+-dependent histone deacetylases consisting of seven members (SIRT1-SIRT7) [4]. Among these sirtuins, SIRT6 has attracted particular interest due to its importance in various physiological and pathological processes [5]. SIRT6 is mainly a nuclear protein that preferentially deacetylates histone H3 lysine 9 and lysine 56 and regulates the transcriptional activities of multiple transcription factors, including p53, nuclear factor-κB and hypoxia inducible factor-1α [[5], [6], [7]]. Therefore, SIRT6 is a multifunctional protein involved in diverse cellular processes, including cell proliferation, apoptosis, the cell cycle, and differentiation [8]. Notably, the dysregulation of SIRT6 has been implicated in various diseases, including cancer, neurological disorders, and cardiovascular diseases [[9], [10], [11]]. Therefore, SIRT6 has emerged as a promising therapeutic target for treating related diseases.
Nuclear factor erythroid 2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that regulates cellular defenses against oxidative stress [12]. Under the stimuli of oxidative stress, Nrf2 translocates to the nucleus from the cytoplasm and binds to antioxidant response element (ARE) to activate the production of antioxidants [13]. However, targeting between Nrf2 and ARE sequences is negatively regulated by BTB and CNC homology 1 (Bach1), because Bach1 competitively binds to ARE-like sequences [14]. Therefore, Bach1 functions as an inhibitor of Nrf2/ARE signaling. Nrf2/ARE has been suggested as a therapeutic target for overcoming oxidative stress-induced damage in various diseases [[15], [16], [17]]. Interestingly, Nrf2/ARE signaling is involved in ocular neurodegenerative diseases through regulation of oxidative stress-induced damage of RGCs [18]. Therefore, a better understanding of the regulatory mechanism of Nrf2/ARE signaling in oxidative stress-induced damage of RGCs will aid the development of novel strategies for RGC protection.
SIRT6 has been reported to confer a cytoprotective effect against oxidative stress-induced cellular damage of various cell types [11,[19], [20], [21]]. However, whether SIRT6 is involved in oxidative stress-induced damage of RGCs remains unclear. In the present study, we aimed to investigate the potential role and regulatory mechanism of SIRT6 in hydrogen peroxide (H2O2)-induced oxidative damage of RGCs in vitro.
Section snippets
Cell culture
Primary RGCs were isolated from rat retinal cells according to a previously described method [22]. In brief, retinas isolated from neonatal SD rats were digested by papain and collagenase in Eagle's balanced salt solution for 30 min at 37 °C. Then, the retinas were triturated sequentially by a narrow-bore Pasteur pipette. Therefore, the yielded single cells were collected after centrifugation and resuspended in phosphate-buffered saline (PBS) containing 0.1% bovine serum albumin (BSA). Cells
SIRT6 expression is decreased in H2O2-treated RGCs
To explore the potential role of SIRT6 in regulating oxidative damage in RGCs, we treated RGCs with H2O2 to establish oxidative damage and then detected the change in expression of SIRT6 in response to oxidative stress. Our results showed reduced SIRT6 expression in RGCs after H2O2 treatment (Fig. 1A and B), indicating that SIRT6 may play a critical role in regulating oxidative damage in RGCs.
SIRT6 overexpression reduces H2O2-induced apoptosis and ROS production in RGCs
To investigate whether SIRT6 exerts a protective effect against H2O2-induced oxidative damage, we
Discussion
In this study, we reported an important role of SIRT6 in regulating oxidative stress-induced damage of RGCs. Our results showed that SIRT6 overexpression repressed apoptosis and ROS production in RGCs induced by H2O2 treatment. We elucidated that the molecular mechanism underlying the SIRT6-mediated protective effect is associated with its promotional effect on activation of Nrf2/ARE signaling via inhibition of Bach1 (Fig. 6F). Our study suggests that SIRT6 may serve as a potential target for
Conflicts of interest
The authors declare that they have no conflict of interest.
References (46)
- et al.
Trichostatin A inhibits deacetylation of histone H3 and p53 by SIRT6
Arch. Biochem. Biophys.
(2018) - et al.
Sirtuin 6 protects the brain from cerebral ischemia/reperfusion injury through NRF2 activation
Neuroscience
(2017) - et al.
Nrf2-Keap1 defines a physiologically important stress response mechanism
Trends Mol. Med.
(2004) - et al.
Sirtuin 6 protects the heart from hypoxic damage
Exp. Cell Res.
(2015) - et al.
SIRT6 suppresses cancer stem-like capacity in tumors with PI3K activation independently of its deacetylase activity
Cell Rep.
(2017) - et al.
Overexpressed SIRT6 attenuates cisplatin-induced acute kidney injury by inhibiting ERK1/2 signaling
Kidney Int.
(2018) - et al.
SIRT6 protects against hepatic ischemia/reperfusion injury by inhibiting apoptosis and autophagy related cell death
Free Radic. Biol. Med.
(2018) - et al.
SIRT6 links histone H3 lysine 9 deacetylation to NF-kappaB-dependent gene expression and organismal life span
Cell
(2009) - et al.
Oxidative stress in neurodegenerative diseases
Mol. Neurobiol.
(2016) - et al.
Retinal ganglion cell death in experimental glaucoma and after axotomy occurs by apoptosis
Invest. Ophthalmol. Vis. Sci.
(1995)
Retinal diseases associated with oxidative stress and the effects of a free radical scavenger (Edaravone)
Oxid. Med. Cell Longev.
Sirtuins as regulators of metabolism and healthspan
Nat. Rev. Mol. Cell Biol.
SIRT6, a protein with many faces
Biogerontology
Evolutionarily conserved and nonconserved cellular localizations and functions of human SIRT proteins
Mol. Biol. Cell
Sirtuin 6: a review of biological effects and potential therapeutic properties
Mol. Biosyst.
The complex role of SIRT6 in carcinogenesis
Carcinogenesis
SIRT6 protects cardiomyocytes against ischemia/reperfusion injury by augmenting FoxO3alpha-dependent antioxidant defense mechanisms
Basic Res. Cardiol.
Molecular mechanism of nrf2 activation by oxidative stress
Antioxid. Redox Signal
Heme regulates the dynamic exchange of Bach1 and NF-E2-related factors in the Maf transcription factor network
Proc. Natl. Acad. Sci. U. S. A.
Nrf2 defends the lung from oxidative stress
Antioxid. Redox Signal
Nrf2: a potential molecular target for cancer chemoprevention by natural compounds
Antioxid. Redox Signal
Small molecule modulators of Keap1-Nrf2-ARE pathway as potential preventive and therapeutic agents
Med. Res. Rev.
The Nrf2 signaling in retinal ganglion cells under oxidative stress in ocular neurodegenerative diseases
Int. J. Biol. Sci.
Cited by (36)
Antioxidative effects of ghrelin on human trabecular meshwork cells
2024, Journal Francais d'OphtalmologieSirtuins as novel pharmacological targets in podocyte injury and related glomerular diseases
2022, Biomedicine and PharmacotherapyCitation Excerpt :SIRT3 knockout exacerbated SOD2 acetylation in Ang II-infused mice [130]. SIRT6 can activate the Nrf2/antioxidant responsive element (ARE) signaling pathway against oxidative stress in cells [131]. Positive feedback between SIRT1, SIRT6, and the Nrf2/ARE signaling pathway has been reported in podocytes [88,127].
Remifentanil alleviates hypoxic-ischemic brain damage-induced cognitive impairment via BACH1
2022, Neuroscience LettersInhibiting BTB domain and CNC homolog 1 (Bach1) as an alternative to increase Nrf2 activation in chronic diseases
2022, Biochimica et Biophysica Acta - General SubjectsCitation Excerpt :Hence, in Sirt6- knockout mice, nonalcoholic steatohepatitis is worsened compared with the wild type [78]. In retinal ganglion cells treated with hydrogen peroxide (H2O2), SIRT6 overexpression has been reported to promote nuclear accumulation of Nrf2 and increase the antioxidant response element activity by suppressing Bach1 [79]. FBXO22, a subunit of the SCF E3 ligase F-box receptor, plays an essential role in cancer development and is also a regulator of senescence induction via ubiquitylation of p53 for degradation [80].
Restoring the oxidative balance in age-related diseases – An approach in glaucoma
2022, Ageing Research Reviews