Sestrin2 in hypoxia and hypoxia-related diseases

Acute Lung Injury and the NLRP3 Inflammasome

Acute lung injury (ALI) manifests through harm to the capillary endothelium and alveolar epithelial cells, arising from a multitude of factors, leading to scattered interstitial alterations, pulmonary edema, and subsequent acute hypoxic respiratory insufficiency. Acute lung injury (ALI), along with its more serious counterpart, acute respiratory distress syndrome (ARDS), carry a fatality rate that hovers around 30-40%. Its principal pathological characteristic lies in the unchecked inflammatory reaction. Currently, the main strategies for treating ALI are alleviation of inflammation and prevention of respiratory failure. Concerning the etiology of ALI, NLRP3 Inflammasome is essential to the body's innate immune response. The composition of this inflammasome complex includes NLRP3, the pyroptosis mediator ASC, and pro-caspase-1. Recent research has reported that the inflammatory response centered on NLRP3 inflammasomes plays a key part in inflammation in ALI, and may hence be a prospective candidate for therapeutic intervention. In the review, we present an overview of the ailment characteristics of acute lung injury along with the constitution and operation of the NLRP3 inflammasome within this framework. We also explore therapeutic strategies targeting the NLRP3 inflammasome to combat acute lung injury.

Sestrin2 Protects Human Lens Epithelial Cells (HLECs) Against Apoptosis in Cataracts Formation: Interaction Between Endoplasmic Reticulum (ER) Stress and Oxidative Stress (OS) is Involved

PURPOSE

To explore the correlation of endoplasmic reticulum stress (ERS) and oxidative stress (OS), and the protective effect of Sestrin2 (SESN2) on human lens epithelial cells (HLECs).

METHODS

Tunicamycin (TM) was used to induce ERS in HLECs. 4-Phenylbutyric acid (4-PBA) was used to inhibit ERS. Eupatilin applied to HLECs as SESN2 agonist. SESN2 expression was knocked down via si-RNA in HLECs. The morphological changes of HLECs were observed by microscope. ER-tracker to evaluate ERS, ROS production assay to measure ROS, flow cytometry to calculate cell apoptosis rate. Immunofluorescence to observe Nrf2 translocation, and effects of TM or EUP on SESN2. Western blot and qPCR were used to evaluate the expression of GRP78, PERK, ATF4, CHOP, Nrf2, and SESN2 expression in HLECs with different treatment groups.

RESULTS

ERS can elevate the expression of ROS and Nrf2 to induce OS. Upregulation of SESN2 was observed in ERS-mediate OS. Overexpression of SESN2 can reduce the overexpression of ERS-related protein GRP78, PERK, ATF4, proapoptotic protein CHOP, OS-related protein Nrf2, as well as ROS, and alleviate ERS injury at the same time. Whereas knockdown of SESN2 can upregulate the expression of GRP78, PERK, ATF4, CHOP, Nrf2, ROS, and deteriorate ERS damage.

CONCLUSIONS

ERS can induce OS, they form a vicious cycle to induce apoptosis in HLECs, which may contribute to cataract formation. SESN2 could protect HLECs against the apoptosis by regulating the vicious cycle between ERS and OS.

Sestrin2 ameliorates diabetic retinopathy by regulating autophagy and ferroptosis

Diabetic retinopathy (DR) is a serious microvascular complication of diabetes. The aim of this study was to explore the effect of Sestrin2 on DR through the regulation of autophagy and ferroptosis levels and its mechanism. In vitro and in vivo DR models were established by high glucose (HG) and streptozotocin (STZ) induction of ARPE-19 human retinal pigment epithelial cells and C57BL/6 mice, respectively. In this study, we demonstrated that after HG treatment, the activity of ARPE-19 cells was decreased, the apoptosis rate was increased, endoplasmic reticulum (ER) stress was activated, autophagy levels were decreased, and ferroptosis levels were increased. Overexpression of Sestrin2 enhanced cell viability, reduced apoptosis and ferroptosis, and enhanced autophagy. However, the effect of overexpression of Sestrin2 was attenuated after the addition of the STAT3 phosphorylation activator Colivelin TFA (C-TFA), the mTOR pathway activator MHY1485 or the autophagy inhibitor 3-methyladenine (3-MA). In addition, the effect of Sestrin2 knockdown on cells was opposite to the effect of overexpression of Sestrin2, while the effect of Sestrin2 knockdown was attenuated after treatment with the ER stress inhibitor 4-phenylbutyric acid (4-PBA). Animal experiments also confirmed the results of cell experiments and attenuated the effects of overexpression of Sestrin2 after injection of the ferroptosis activators erastin or 3-MA. Our study revealed that Sestrin2 inhibits ferroptosis by inhibiting STAT3 phosphorylation and ER stress and promoting autophagy levels, thereby alleviating DR.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo

Dynamic variations in the concentration and abnormal distribution of endogenous biomarkers are strongly associated with multiple physiological and pathological states. Therefore, it is crucial to design imaging systems capable of real-time detection of dynamic changes in biomarkers for the accurate diagnosis and effective treatment of diseases. Recently, ratiometric imaging has emerged as a widely used technique for sensing and imaging of biomarkers due to its advantage of circumventing the limitations inherent to conventional intensity-dependent signal readout methods while also providing built-in self-calibration for signal correction. Here, the recent progress of ratiometric probes and their applications in sensing and imaging of biomarkers are outlined. Ratiometric probes are classified according to their imaging mechanisms, and ratiometric photoacoustic imaging, ratiometric optical imaging including photoluminescence imaging and self-luminescence imaging, ratiometric magnetic resonance imaging, and dual-modal ratiometric imaging are discussed. The applications of ratiometric probes in the sensing and imaging of biomarkers such as pH, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), gas molecules, enzymes, metal ions, and hypoxia are discussed in detail. Additionally, this Review presents an overview of challenges faced in this field along with future research directions.

Sestrin2 Regulates Endoplasmic Reticulum Stress-Dependent Ferroptosis to Engage Pulmonary Fibrosis by Nuclear Factor Erythroid 2-Related Factor 2/Activating Transcription Factor 4 (NRF2/ATF4)

Pulmonary fibrosis (PF) can lead to chronic inflammation, the destruction of alveoli and irreversible lung damage. Sestrin2 is a highly protective stress-inducible protein that is involved in the cell response to various stress factors and the regulation of homeostasis and has a certain protective effect against PF. In this study, TGF-β1 was used to establish a PF cell model. Bleomycin was used to induce PF in mice, and the expression levels of related proteins were detected by western blotting. The levels of the inflammatory cytokine, TNF-α, IL-6, and IL-1β were detected by enzyme-linked immunosorbent assays. Immunoprecipitation was used to verify the interaction between ATF4 and NRF2 and between Sestrin2 and NRF2 to explore the specific mechanism by which Sestrin2 affects PF. The results showed that Sestrin2 inhibited fibroblast-to-myofibroblast transition (FMT), improved inflammation, promoted cell proliferation, and alleviated PF. Activating transcription factor 4/nuclear factor erythroid 2-related factor 2 (NRF2/ATF4) signaling pathway activation could alleviate endoplasmic reticulum stress, inhibit ferroptosis and FMT, and reduce reactive oxygen species levels, thereby alleviating PF. Overexpression of ATF4 and the addition of a ferroptosis inducer reversed Sestrin2-mediated alleviation of PF. In conclusion, Sestrin2 alleviates PF and endoplasmic reticulum stress-dependent ferroptosis through the NRF2/ATF4 pathway.

Sestrin2 in diabetes and diabetic complications

Diabetes is a global health problem which is accompanied with multi-systemic complications. It is of great significance to elucidate the pathogenesis and to identify novel therapies of diabetes and diabetic complications. Sestrin2, a stress-inducible protein, is primarily involved in cellular responses to various stresses. It plays critical roles in regulating a series of cellular events, such as oxidative stress, mitochondrial function and endoplasmic reticulum stress. Researches investigating the correlations between Sestrin2, diabetes and diabetic complications are increasing in recent years. This review incorporates recent findings, demonstrates the diverse functions and regulating mechanisms of Sestrin2, and discusses the potential roles of Sestrin2 in the pathogenesis of diabetes and diabetic complications, hoping to highlight a promising therapeutic direction.

Serum Sestrin2 Emerges as a Prognostic Biomarker of Human Aneurysmal Subarachnoid Hemorrhage: A Prospective Observational Cohort Single-Center Study

Background

Sestrin2 functions as a neuroprotective factor. Herein, serum sestrin2 was investigated with respect to its associations with severity, delayed cerebral ischemia (DCI) and prognosis of aneurysmal subarachnoid hemorrhage (aSAH).

Methods

In this prospective, observational, cohort, single-center study, serum sestrin2 levels were measured at entry into the study in 45 healthy controls and at admission in 135 aSAH patients. Also, they were gauged in other time points (namely, at days 1, 2, 3, 5 and 7) among 45 patients. Unfavorable prognosis was defined as extended Glasgow Outcome Scale (GOSE) scores of 1-4 at six months after aSAH.

Results

Serum sestrin2 levels were immediately raised at admission in patients, increased thereafter, peaked at day 2, declined afterwards till day 7, and were significantly higher than those in controls (all P<0.001). Serum sestrin2 levels had independent correlation with Hunt-Hess scores (beta, 1.715; 95% confidence interval (CI), 0.595-2.835; P=0.003) and modified Fisher scores (beta, 2.505; 95% CI, 1.102-3.907; P=0.001). Alternatively, serum sestrin2 levels, which were independently correlated with 6-month GOSE scores (beta, -0.050; 95% CI, -0.099-0.001; P=0.044), were independently associated with DCI (odds ratio, 1.079; 95% CI, 1.008-1.156; P=0.029) and unfavorable prognosis (odds ratio, 1.093; 95% CI, 1.020-1.172; P=0.012). DCI and prognosis prediction models, which were composed of serum sestrin2, Hunt-Hess scores and modified Fisher scores, were comparatively stable and clinically beneficial under calibration curve and decision curve. Prognosis prediction model showed significantly higher area under receiver operating characteristic curve than serum sestrin2, Hunt-Hess scores and modified Fisher scores alone (all P<0.05).

Conclusion

A significant enhancement of serum sestrin2 levels after aSAH is independently related to severity, DCI and poor prognosis following aSAH. The models incorporating serum sestrin2 perform well in predicting the DCI and prognosis of aSAH patients. Presumably, determination of serum sestrin2 may be of clinical significance in aSAH.

An update on the molecular mechanism and pharmacological interventions for Ischemia-reperfusion injury by regulating AMPK/mTOR signaling pathway in autophagy

AMP-activated protein kinase (5'-adenosine monophosphate-activated protein kinase, AMPK)/mammalian target of rapamycin (mTOR) is an important signaling pathway maintaining normal cell function and homeostasis in vivo. The AMPK/mTOR pathway regulates cellular proliferation, autophagy, and apoptosis. Ischemia-reperfusion injury (IRI) is secondary damage that frequently occurs clinically in various disease processes and treatments, and the exacerbated injury during tissue reperfusion increases disease-associated morbidity and mortality. IRI arises from multiple complex pathological mechanisms, among which cell autophagy is a focus of recent research and a new therapeutic target. The activation of AMPK/mTOR signaling in IRI can modulate cellular metabolism and regulate cell proliferation and immune cell differentiation by adjusting gene transcription and protein synthesis. Thus, the AMPK/mTOR signaling pathway has been intensively investigated in studies focused on IRI prevention and treatment. In recent years, AMPK/mTOR pathway-mediated autophagy has been found to play a crucial role in IRI treatment. This article aims to elaborate the action mechanisms of AMPK/mTOR signaling pathway activation in IRI and summarize the progress of AMPK/mTOR-mediated autophagy research in the field of IRI therapy.

Sestrin2 suppresses ferroptosis to alleviate septic intestinal inflammation and barrier dysfunction

OBJECTIVE

Alterations in intestinal function play a crucial role in the pathogenesis of sepsis, and the repair of the intestinal barrier is a potential strategy for the treatment of sepsis. Sestrin2 (SESN2), a highly conserved stress-responsive protein, can be induced in response to stress.

AIM

This paper aimed to explore the role and mechanism of SESN2 in septic intestinal dysfunction. Methods: Blood samples were collected from patients with septic intestinal dysfunction, and Caco-2 cells were subjected to lipopolysaccharide (LPS) to construct in vitro models. The expression level of SESN2 was determined in the blood samples and cells. The impacts of SESN2 overexpression on cell inflammation, oxidative stress, barrier integrity, and MAPK/Nrf2 signaling were evaluated. To determine the mediated role of MAPK signaling and ferroptosis, AMPK inhibitor (Compound C) and ferroptosis inducer (erastin) were separately used to treat cells, and the influences on the above aspects in cells were assessed.

RESULTS

The expression level of SESN2 was down-regulated in patients with septic intestinal dysfunction and LPS-induced cells. SESN2 overexpression was found to suppress cell inflammation and oxidative stress, maintain barrier integrity and activate AMPK/Nrf2 signaling. Following the AMPK signaling was inhibited or the ferroptosis was triggered, the effects of SESN2 overexpression on the cells were both reversed.

CONCLUSION

Reduced SESN2 contributed to inflammatory response and barrier dysfunction in septic intestinal dysfunction by promoting ferroptosis via activating the AMPK/Nrf2 signaling pathway.

Matrix metalloproteinase-9 and substance-P as predictors for early-stage diagnosis of acute mountain sickness

INTRODUCTION

Although acute mountain sickness (AMS) can be a life-threatening condition, early diagnosis is difficult due to vague and non-specific symptoms. The aim of this study is to investigate biochemical markers that can detect high-altitude diseases in advance. Eight different biomarkers (BNP, HIF-1α, NGAL, MMP-3, MMP-9, SESN2, substance P (SP), and U-II) were studied, and their relationship with AMS was investigated.

METHODS

Of the 84 mountaineers who participated in the mountaineering training organized by the Turkish Mountaineering Federation in the Rize Kaçkar Mountains in 2018, 52 volunteered to participate in the study. Twelve hours after the participants reached an altitude of 2200 m (exposed to moderate hypoxia), their vital parameters were measured, and blood samples were taken for biochemistry tests. Vital signs and Lake Louise (LL) AMS scores were recorded every 24 h during the following 72 h. The participants were divided into two groups according to their LL scores: those with AMS and those without (AMS+ and AMS -), and the vital parameters and biomarker levels of both groups were compared and evaluated.

RESULTS

Of the volunteers participating in the study, 35 (67.3%) were male and 17 (32.7%) were female, although there was no gender difference in terms of susceptibility to AMS. Among the investigated markers in the AMS + group, MMP-9 and SP were statistically significantly higher (p = 0.037 and p = 0.038, respectively). There were no statistical differences between AMS- and AMS+ groups with regard to heart rate, oxygen saturation, and systolic and diastolic blood pressure values (p = 0.507, p = 0.929, p = 0.955, p = 0.572, respectively).

CONCLUSION

There were significant differences between the AMS- and AMS+ groups in terms of MMP-9 and SP. However, differences in physical indexes between the groups were not statistically significant. This could provide objective indexes for scanning and screening individuals susceptible to AMS in the early stages of rapid ascending.