Sesn2 gene ablation enhances susceptibility to gentamicin-induced hair cell death via modulation of AMPK/mTOR signaling

Abstract

The process of gentamicin-induced hair cell damage includes the activation of oxidative stress processes. Sestrins, as stress-responsive proteins, protect cells against oxidative stress. Sestrins, particularly Sestrin-2, suppress excessive reactive oxygen species (ROS) accumulation and inhibit mammalian target of rapamycin complex 1 (mTORC1). Thus, we addressed the role of Sestrin-2 in the regulation of sensory hair cell survival after gentamicin exposure. Here, we show that Sestrins were expressed in the inner ear tissues, and Sestrin-2 immunolocalized in sensory hair cells and spiral ganglion (SG). The expression of Sestrin-2 was unchanged, and later downregulated, in gentamicin-treated explants from wild-type mice in vitro. Compared with wild-type mice, Sestrin-2 knockout mice exhibited significantly greater hair cell loss in gentamicin-treated cochlear explants. Significant downregulation of phosphorylation of AMP-activated protein kinase alpha (AMPKα) and upregulation of the 70-kDa ribosomal protein S6 kinase (p70S6K) were measured in wild-type cochlear explants exposed to gentamicin compared with their untreated controls. Such regulatory effect was not observed between explants from untreated and gentamicin-treated knockout mice. The gentamicin effect on mTOR signaling was rapamycin-sensitive. Thus, our data provide evidence that Sestrin-2 plays an important role in the protection of hair cells against gentamicin, and the mTOR signaling pathway appears to be modulated by gentamicin during hair cell death.

Cigarette smoke exposure induces ROS-mediated autophagy by regulating sestrin, AMPK, and mTOR level in mice

“…After exposure to exacerbated stimuli, increased levels of SESN2 can activate AMPK, resulting in the negative regulation of mTOR [7,9,12]. In the present study, we also observed reduced SESN2 protein levels and AMPK phosphorylation and increased mTOR phosphorylation in the group exposed to CS for 45 days and supplemented with NAC.…”

“…In step III, we hypothesized that if CS increased ROS, leading to the augmentation of autophagy, the cessation of CS exposure would reduce the autophagic process. Therefore, we subjected the animals to 45 days of CS exposure and subsequent cessation at different times, (7,15,30, and 45 days). A significant reduction in DCF levels at 15, 30, and 45 days of cessation was observed as compared to CS exposure for 45 days group ( Figure 3A).…”

“…Effect of cigarette smoke (CS) cessation on ROS and autophagy markers in the lungs of mice after 45 days of CS exposure (n = 10 per group). Dichlorofluorescein (DCF) level (a), protein levels of SESN2 (b), AMPK phosphorylation (c), mTOR phosphorylation (d), ULK1 phosphorylation (e), ATG12 (f), LC3B (g), and representative western blot analysis of the evaluated proteins (h) in the control (non-exposed group), CS exposure for 45 days, and 45 days CS exposure followed by CS cessation for different days (7,15,30, and 45 days) groups. Data are expressed as the mean and standard error of the means (mean ± SEM) and analyzed statistically by one-way analysis of variance, followed by Tukey's HSD post hoc test (*p < 0.05 versus cont; # p < 0.05 versus 45 CS).…”

“…AMP-activated protein kinase (AMPK) is another strong candidate for influencing autophagy function and acts as an energy sensor to regulate cellular homeostasis [5]. AMPK induces autophagy in response to different cellular stresses, including oxidative stress [5][6][7][8]. Although the molecular mechanism underlying how ROS modulates AMPK has not been fully established, a role for the sestrin (SESN) family has been proposed [9].…”

CA1 pyramidal neuron gene expression mosaics in the Ts65Dn murine model of Down syndrome and Alzheimer's disease following maternal choline supplementation

“…Dyrk3 has also been shown to be involved with dendritic branching (Slepak, Salay, Lemmon, & Bixby, 2012), and in conjunction with Dyrk1a, promotes cell survival through phosphorylation of sirtuin 1 (Sirt1) (Guo, Williams, Schug, & Li, 2010), indicating dysregulation may negatively impact multiple signaling pathways, including the AMPK cascade. Sesn2 is a critical factor mediating reactive oxygen species formation, in part by inhibiting AMPK pathway member mTORC1 (Ebnoether, Ramseier, Cortada, Bodmer, & Levano-Huaman, 2017). Sesn2 is also induced by Ab exposure in vitro and upregulated in serum of AD patients (Chen, Chen, Wu, Huang, & Yang, 2014;Rai et al, 2016).…”