ER stress contributes to autophagy induction by adiponectin in macrophages: Implication in cell survival and suppression of inflammatory response

ADPN Regulates Oxidative Stress-Induced Follicular Atresia in Geese by Modulating Granulosa Cell Apoptosis and Autophagy

Geese are susceptible to oxidative stress during reproduction, which can lead to follicular atresia and impact egg production. Follicular atresia is directly triggered by the apoptosis and autophagy of granulosa cells (GCs). Adiponectin (ADPN), which is secreted by adipose tissue, has good antioxidant and anti-apoptotic capacity, but its role in regulating the apoptosis of GCs in geese is unclear. To investigate this, this study examined the levels of oxidative stress, apoptosis, and autophagy in follicular tissues and GCs using RT-qPCR, Western blotting, immunofluorescence, flow cytometry, transcriptomics and other methods. Atretic follicles exhibited high levels of oxidative stress and apoptosis, and autophagic flux was obstructed. Stimulating GCs with H2O2 produced results similar to those of atretic follicles. The effects of ADPN overexpression and knockdown on oxidative stress, apoptosis and autophagy in GCs were investigated. ADPN was found to modulate autophagy and reduced oxidative stress and apoptosis in GCs, in addition to protecting them from H2O2-induced damage. These results may provide a reasonable reference for improving egg-laying performance of geese.

Sestrin2 can alleviate endoplasmic reticulum stress to improve traumatic brain injury by activating AMPK/mTORC1 signaling pathway

Traumatic brain injury (TBI), as a serious central nervous system disease, can result in severe neurological dysfunction or even disability and death of patients. The early and effective intervention of secondary brain injury can improve the prognosis of TBI. Endoplasmic reticulum (ER) stress is one of the main reasons to recover TBI. ER stress inhibition may be beneficial in treating TBI. Sestrin2 is a crucial regulator of ER stress, and its activation can significantly improve TBI. In this paper, we analyze the biological function of sestrin2, the latest findings on ER stress, and the relationship between ER stress and TBI. We elucidate the relationship of sestrin2 inhibiting ER stress via activating the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin complex 1 (MTORC1) signaling. Finally, we elaborate on the possible role of sestrin2 in TBI and explain how its activation potentially improves TBI.

Status of Research on Sestrin2 and Prospects for its Application in Therapeutic Strategies Targeting Myocardial Aging

Cardiac aging is accompanied by changes in the heart at the cellular and molecular levels, leading to alterations in cardiac structure and function. Given today's increasingly aging population, the decline in cardiac function caused by cardiac aging has a significant impact on quality of life. Antiaging therapies to slow the aging process and attenuate changes in cardiac structure and function have become an important research topic. Treatment with drugs, including metformin, spermidine, rapamycin, resveratrol, astaxanthin, Huolisu oral liquid, and sulforaphane, has been demonstrated be effective in delaying cardiac aging by stimulating autophagy, delaying ventricular remodeling, and reducing oxidative stress and the inflammatory response. Furthermore, caloric restriction has been shown to play an important role in delaying aging of the heart. Many studies in cardiac aging and cardiac aging-related models have demonstrated that Sestrin2 has antioxidant and anti-inflammatory effects, stimulates autophagy, delays aging, regulates mitochondrial function, and inhibits myocardial remodeling by regulation of relevant signaling pathways. Therefore, Sestrin2 is likely to become an important target for antimyocardial aging therapy.

Identifying autophagy-related genes as potential targets for immunotherapy in tuberculosis

PURPOSE

Identifying of host-directed targets and molecular markers of immune response for tuberculosis (TB) immunotherapy is urgent and meaningful. Previous studies have demonstrated an important role of autophagy in the course and pathophysiology of TB and is associated with the efficacy of TB treatment. However, its role in TB immunotherapy is still incomplete.

METHODS

The effect of autophagy on intracellular bacteria load was examined in sulforaphane (SFN)-treated THP-1 cells. The immune infiltration was assessed based on public databases. Functional enrichment analysis revealed the pathways involved. LASSO Cox regression analysis was employed to identify hub genes. Moreover, machine learning analysis was used to obtain important targets of TB immunotherapy. Finally, the relationship between hub genes and immune infiltration was assessed, as well as the relevance of chemokines.

RESULTS

We found that SFN reduced intracellular bacteria load by enhancing autophagy in THP-1 cells. Thirty-two autophagy-related genes (ARGs) were identified, three types of immune cells (macrophages, neutrophils, and DC cells) were significantly enriched in TB patients, and 6 hub genes (RAB5A, SQSTM1, MYC, MAPK8, MAPK3, and FOXO1) were closely related to TB immune infiltration. The 32 ARGs were mainly involved in autophagy, apoptosis, and tuberculosis pathways. FOXO1, SQSTM1, and RAB5A were identified as important target genes according to the ranking of variable importance, with FOXO1 being a potential autophagy-related target of TB immunotherapy.

CONCLUSION

This study highlights the association between autophagy-related genes and immune infiltration in TB. Three key genes, especially FOXO1, regulated by SFN, will provide new insights into diagnostic and immunotherapy strategies for clinical tuberculosis.

Sestrin2: multifaceted functions, molecular basis, and its implications in liver diseases

Sestrin2 (SESN2), a highly conserved stress-responsive protein, can be triggered by various noxious stimuli, such as hypoxia, DNA damage, oxidative stress, endoplasmic reticulum (ER) stress, and inflammation. Multiple transcription factors regulate SESN2 expression, including hypoxia-inducible factor 1 (HIF-1), p53, nuclear factor E2-related factor 2 (Nrf2), activating transcription factor 4 (ATF4), ATF6, etc. Upon induction, SESN2 generally leads to activation of adenosine monophosphate-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin complex 1 (mTORC1). To maintain cellular homeostasis, SESN2 and its downstream molecules directly scavenge reactive oxygen species or indirectly influence the expression patterns of key genes associated with redox, macroautophagy, mitophagy, ER stress, apoptosis, protein synthesis, and inflammation. In liver diseases including acute liver injury, fatty liver diseases, hepatic fibrosis, and hepatocellular carcinoma (HCC), SESN2 is abnormally expressed and correlated with disease progression. In NAFLD, SESN2 helps with postponing disease progression through balancing glycolipid metabolism and macroautophagy (lipophagy), and rectifying oxidative damage and ER stress. During hepatic fibrosis, SESN2 represses HSCs activation and intrahepatic inflammation, hindering the occurrence and progress of fibrogenesis. However, the role of SESN2 in HCC is controversial due to its paradoxical pro-autophagic and anti-apoptotic effects. In conclusion, this review summarizes the biological functions of SESN2 in hypoxia, genotoxic stress, oxidative stress, ER stress, and inflammation, and specifically emphasizes the pathophysiological significance of SESN2 in liver diseases, aiming to providing a comprehensive understanding for SESN2 as a potential therapeutic target in liver diseases.

Rhinacanthin-C but Not -D Extracted from Rhinacanthus nasutus (L.) Kurz Offers Neuroprotection via ERK, CHOP, and LC3B Pathways

Neurodegenerative diseases present an increasing problem as the world's population ages; thus, the discovery of new drugs that prevent diseases such as Alzheimer's, and Parkinson's diseases are vital. In this study, Rhinacanthin-C and -D were isolated from Rhinacanthus nasustus, using ethyl acetate, followed by chromatography to isolate Rhinacanthin-C and -D. Both compounds were confirmed using NMR and ultra-performance-LCMS. Using glutamate toxicity in HT-22 cells, we measured cell viability and apoptosis, ROS build-up, and investigated signaling pathways. We show that Rhinacanthin-C and 2-hydroxy-1,4-naphthoquinone have neuroprotective effects against glutamate-induced apoptosis in HT-22 cells. Furthermore, we see that Rhinacanthin-C resulted in autophagy inhibition and increased ER stress. In contrast, low concentrations of Rhinacanthin-C and 2-hydroxy-1,4-naphthoquinone prevented ER stress and CHOP expression. All concentrations of Rhinacanthin-C prevented ROS production and ERK1/2 phosphorylation. We conclude that, while autophagy is present in HT-22 cells subjected to glutamate toxicity, its inhibition is not necessary for cryoprotection.

Platelet-rich plasma improves lipopolysaccharide-induced inflammatory response by upgrading autophagy

Objectives

Platelet-rich plasma (PRP) plays an important role at all stages of wound healing, including the inflammatory stage. Macrophage autophagy has been found to influence the inflammatory response process. However, it is unclear whether PRP can affect inflammatory responses via macrophage autophagy. In the present study, we explored the effect of PRP on inflammatory responses and researched the underlying mechanism.

Methods

RAW 264.7 macrophages were treated with PRP and/or lipopolysaccharide (LPS). The effects of PRP on the expression of inflammatory factors were determined by ELISA and qRT-PCR. Macrophage autophagosomes were also assessed by TEM and immunofluorescence. Autophagy and NLRP3-related proteins were investigated using Western blot analysis.

Results

PRP reduced the levels of inflammatory factors and increased autophagy in RAW 264.7 cells. Pretreatment with 3-MA, which is an autophagy inhibitor, abolished the impact of PRP on the inflammatory response. Moreover, PRP induced macrophage autophagy by activating the NLRP3 inflammasome.

Conclusions

These results show that PRP can attenuate LPS-induced inflammatory responses by enhancing autophagy via NLRP3. These study also provides a new perspective on the molecular mechanism of PRP therapy in wound healing.

Sestrin2 induction contributes to anti-inflammatory responses and cell survival by globular adiponectin in macrophages

Adiponectin, an adipose tissue-derived hormone, exhibits a modulatory effect on cell death/survival and possesses potent anti-inflammatory properties. However, the underlying molecular mechanisms remain elusive. Sestrin2, a stress-inducible metabolic protein, has shown cytoprotective and inflammation-modulatory effects under stressful conditions. In this study, we examined the role of sestrin2 signaling in the modulation of cell survival and inflammatory responses by globular adiponectin (gAcrp) in macrophages. We observed that gAcrp induced a significant increase in sestrin2 expression in both RAW 264.7 murine macrophages and primary murine macrophages. Notably, gAcrp treatment markedly increased expression of hypoxia inducible factor-1 α (HIF-1α) and gene silencing of HIF-1α blocked sestrin2 induction by gAcrp. In addition, pretreatment with a pharmacological inhibitor of ERK or PI3K abrogated both sestrin2 and HIF-1α expression by gAcrp, indicating that ERK/PI3K-mediated HIF-1α signaling pathway plays a critical role in sestrin2 induction by gAcrp. Furthermore, sestrin2 induction is implicated in autophagy activation, and knockdown of sestrin2 prevented enhanced cell viability by gAcrp. Moreover, gene silencing of sestrin2 caused restoration of gAcrp-induced expression of anti-inflammatory genes in a gene-selective manner. Taken together, these results indicate that sestrin2 induction critically contributes to cell survival and anti-inflammatory responses by gAcrp in macrophages.

Endoplasmic Reticulum Quality Control in Immune Cells

The endoplasmic reticulum quality control (ERQC) system, including endoplasmic reticulum-associated degradation (ERAD), the unfolded protein response (UPR), and autophagy, presides over cellular protein secretion and maintains proteostasis in mammalian cells. As part of the immune system, a variety of proteins are synthesized and assembled correctly for the development, activation, and differentiation of immune cells, such as dendritic cells (DCs), macrophages, myeloid-derived-suppressor cells (MDSCs), B lymphocytes, T lymphocytes, and natural killer (NK) cells. In this review, we emphasize the role of the ERQC in these immune cells, and also discuss how the imbalance of ER homeostasis affects the immune response, thereby suggesting new therapeutic targets for immunotherapy.

Endoplasmic reticulum stress and unfolded protein response in cardiovascular diseases

Cardiovascular diseases (CVDs), such as ischaemic heart disease, cardiomyopathy, atherosclerosis, hypertension, stroke and heart failure, are among the leading causes of morbidity and mortality worldwide. Although specific CVDs and the associated cardiometabolic abnormalities have distinct pathophysiological and clinical manifestations, they often share common traits, including disruption of proteostasis resulting in accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER). ER proteostasis is governed by the unfolded protein response (UPR), a signalling pathway that adjusts the protein-folding capacity of the cell to sustain the cell's secretory function. When the adaptive UPR fails to preserve ER homeostasis, a maladaptive or terminal UPR is engaged, leading to the disruption of ER integrity and to apoptosis. ER stress functions as a double-edged sword, with long-term ER stress resulting in cellular defects causing disturbed cardiovascular function. In this Review, we discuss the distinct roles of the UPR and ER stress response as both causes and consequences of CVD. We also summarize the latest advances in our understanding of the importance of the UPR and ER stress in the pathogenesis of CVD and discuss potential therapeutic strategies aimed at restoring ER proteostasis in CVDs.

ROS-Dependent ER Stress and Autophagy Mediate the Anti-Tumor Effects of Tributyltin (IV) Ferulate in Colon Cancer Cells

Organotin compounds represent potential cancer therapeutics due to their pro-apoptotic action. We recently synthesized the novel organotin ferulic acid derivative tributyltin (IV) ferulate (TBT-F) and demonstrated that it displays anti-tumor properties in colon cancer cells related with autophagic cell death. The purpose of the present study was to elucidate the mechanism of TBT-F action in colon cancer cells. We specifically show that TBT-F-dependent autophagy is determined by a rapid generation of reactive oxygen species (ROS) and correlated with endoplasmic reticulum (ER) stress. TBT-F evoked nuclear factor erythroid-2 related factor 2 (Nrf2)-mediated antioxidant response and Nrf2 silencing by RNA interference markedly increased the anti-tumor efficacy of the compound. Moreover, as a consequence of ROS production, TBT-F increased the levels of glucose regulated protein 78 (Grp78) and C/EBP homologous protein (CHOP), two ER stress markers. Interestingly, Grp78 silencing produced significant decreasing effects on the levels of the autophagic proteins p62 and LC3-II, while only p62 decreased in CHOP-silenced cells. Taken together, these results indicate that ROS-dependent ER stress and autophagy play a major role in the TBT-F action mechanism in colon cancer cells and open a new perspective to consider the compound as a potential candidate for colon cancer treatment.

IRE1α-JNK pathway-mediated autophagy promotes cell survival in response to endoplasmic reticulum stress during the initial phase of hepatic steatosis

AIMS

It has been widely reported that autophagy and inositol-requiring enzyme-1α (IRE1α)-c-Jun N-terminal kinase (JNK) pathway was involved in cell survival under endoplasmic reticulum (ER) stress, but their specific roles in hepatic steatosis remain unclear. This study aimed to determine the interaction between autophagy and IRE1α-JNK pathway on cell survival in response to ER stress during the initial phase of hepatic steatosis.

METHODS

Hepatic steatosis was induced in HepG2 cells by supplementing oleic acid (OA). Lipid accumulation was evaluated by BODIPY493/503 staining. ER stress and IRE1α-JNK signaling were investigated by western blot. Autophagy was monitored by western blot, GFP-LC3 plasmid and immunofluorescence staining, while apoptosis was determined by western blotting, Annexin-V-FITC/PI staining and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.

KEY FINDINGS

Aggravated lipid accumulation was found under increased ER stress during the initial phase of hepatic steatosis. Meanwhile, an increase of autophagy and no alteration of apoptosis were observed under increased ER stress. Interestingly, autophagy was induced by ER stress, while autophagy suppression led to an increase of apoptosis in response to ER stress Moreover, further study showed that IRE1α-JNK pathway was activated after ER stress and consequently induced autophagy, which promoted cell survival in the initial phase of hepatic steatosis.

SIGNIFICANCE

We conclude that IRE1α-JNK pathway was activated during ER stress in the initial phase of hepatic steatosis and promoted cell survival by enhancing autophagy. Targeting IRE1α-JNK-autophagy signaling may provide new insight into preventive strategies for hepatic steatosis.