Activating Transcription Factor Research Articles

Osthole induces accumulation of impaired autophagosome against pancreatic cancer cells

Pancreatic cancer (PC) is one of the most aggressive malignancies worldwide, and few effective therapeutics are available. Osthole (OST), a natural coumarin, has been proven to be a potential anticancer compound. In this study, we found that OST significantly inhibited PC growth both in vitro and in vivo. Notably, the anti-PC effect of OST is mediated by excessive autophagosome accumulation and consequent apoptosis in PC cells. Mechanistically, OST increased the number of autophagosomes via two pathways. First, OST induced autophagy initiation by suppressing the Akt/mTOR signaling pathway. Second, OST induced autophagic arrest by blocking autophagosome-lysosome fusion. Consistently, inhibition of autophagy initiation restored PC cell growth, whereas autophagic flux inhibitors exacerbated the antitumor effect of OST in PC cells, suggesting a cytotoxic role of OST-induced autophagosome accumulation. In addition, we found that OST upregulates the expression of activating transcription factor 3 (ATF3), resulting in inactivation of the Akt/mTOR signaling pathway and autophagy initiation in PC cells. ATF3 overexpression increased the activation of autophagy, and inhibition of ATF3 expression decreased autophagy. Taken together, our study provides new insights into the OST-induced growth inhibitory effect on PC cells, suggesting a promising potential therapeutic role of OST for PC treatment.

Nicotinamide riboside targets mitochondrial unfolded protein response to reduce alcohol-induced damage in Kupffer cells.

The pathogenesis of alcohol-related liver disease (ALD) is closely linked to mitochondrial dysfunction and impaired cellular energy metabolism. In this study, we explored how ethanol triggers inflammation, oxidative stress, and mitochondrial dysfunction in Kupffer cells, i.e.hepatic resident macrophages, primarily focusing on the mitochondrial unfolded protein response (UPRmt) using immortalized mouse Kupffer cells (ImKCs) and mouse primary KCs. The UPRmt is a cellular defense mechanism activated in response to the perturbation of mitochondrial proteostasis to maintain mitochondrial integrity and function by upregulating the expression of mitochondrial chaperones and proteases. We also determined whether nicotinamide riboside (NR), a NAD+ precursor, could mitigate ethanol-triggered cellular damage. When ImKCs were exposed to 80 mm ethanol for 72 h, they displayed inflammation, oxidative stress, and impaired mitochondrial function with decreased mitochondrial content and deformed mitochondrial crista structure. NR, however, counteracted the effects of ethanol. Furthermore, ethanol increased mRNA and protein levels of UPRmt genes, such as mitochondrial chaperones and proteases, which were attenuated by NR. Notably, the ethanol-induced shift in the entry of activating transcription factor 5 (ATF5), a putative transcriptional regulator of UPRmt, to the nucleus from the mitochondria was abolished by NR. The induction of UPRmt genes by ethanol was significantly repressed when Atf5 was knocked down, indicating the role of ATF5 in the induction of UPRmt genes in ImKCs exposed to ethanol. We also confirmed the induction of UPRmt gene expression in mouse and human livers exposed to alcohol. Our findings demonstrate the ability of NR to alleviate ethanol-induced oxidative stress, inflammation, and mitochondrial dysfunction, partly by modulating the ATF5-dependent UPRmt pathway in ImKCs, suggesting its potential for ALD therapy. © 2024 The Pathological Society of Great Britain and Ireland.

Advanced PROTAC and Quantitative Proteomics Strategy Reveals Bax Inhibitor-1 as a Critical Target of Icaritin in Burkitt Lymphoma

Understanding the molecular targets of natural products is crucial for elucidating their mechanisms of action, mitigating toxicity, and uncovering potential therapeutic pathways. Icaritin (ICT), a bioactive flavonoid, demonstrates significant anti-tumor activity but lacks defined molecular targets. This study employs an advanced strategy integrating proteolysis targeting chimera (PROTAC) technology with quantitative proteomics to identify ICT’s key targets. A library of 22 ICT-based PROTAC derivatives were synthesized, among which LJ-41 exhibited a superior IC50 of 5.52 μM against Burkitt lymphoma (CA-46) cells. Then, differential proteomic analysis identified Bax inhibitor-1 (BI-1) as a potential target. Target validation techniques, including cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS) assay, surface plasmon resonance (SPR) assay, and molecular docking, confirmed LJ-41’s high specificity for BI-1. Mechanistic investigations revealed that LJ-41 induces apoptosis through BI-1 degradation, triggering endoplasmic reticulum stress and activating inositol-requiring enzyme 1 α (IRE1α), activating transcription factor 6 (ATF6), and nuclear factor erythroid 2-related factor transcription factor heme oxygenase 1 (NRF2-HO-1) signaling pathways. This study establishes a refined methodological framework for natural product target discovery and highlights ICT-PROTAC derivatives’ potential for clinical application in Burkitt lymphoma treatment.

Engineering extracellular vesicles to transiently permeabilize the blood–brain barrier

BackgroundDrug delivery to the brain is challenging due to the restrict permeability of the blood brain barrier (BBB). Recent studies indicate that BBB permeability increases over time during physiological aging likely due to factors (including extracellular vesicles (EVs)) that exist in the bloodstream. Therefore, inspiration can be taken from aging to develop new strategies for the transient opening of the BBB for drug delivery to the brain.ResultsHere, we evaluated the impact of small EVs (sEVs) enriched with microRNAs (miRNAs) overexpressed during aging, with the capacity to interfere transiently with the BBB. Initially, we investigated whether the miRNAs were overexpressed in sEVs collected from plasma of aged individuals. Next, we evaluated the opening properties of the miRNA-enriched sEVs in a static or dynamic (under flow) human in vitro BBB model. Our results showed that miR-383-3p-enriched sEVs significantly increased BBB permeability in a reversible manner by decreasing the expression of claudin 5, an important tight junction protein of brain endothelial cells (BECs) of the BBB, mediated in part by the knockdown of activating transcription factor 4 (ATF4).ConclusionsOur findings suggest that engineered sEVs have potential as a strategy for the temporary BBB opening, making it easier for drugs to reach the brain when injected into the bloodstream.Graphical abstract

ATF3 deficiency promotes alveolar macrophage pyroptosis in sepsis-induced acute lung injury

BackgroundAcute lung injury (ALI) ranks among the leading reasons for death in septic patients. As an essential transcription factor associated with stress, activating transcription factor 3 (ATF3) participates in a variety of pathophysiological processes, including immunology and inflammation. However, the specific mechanism of ATF3 in pyroptosis of sepsis-induced ALI remains elusive. MethodsA mouse model of ALI was established by administering lipopolysaccharide (LPS) in vivo and LPS combined with adenosine triphosphate (ATP) in vitro to compare differences in ATF3 expression level. The role of ATF3 in pyroptosis was then assessed by knocking down ATF3 using small interfering RNA. The levels of interleukin-6 (IL-6), tumor necrosis factor-α, IL-1β, and IL-18 in mouse serum and cell culture supernatants were measured using enzyme-linked immunosorbent assay. Moreover, immunohistochemistry, immunofluorescence, Western blotting, co-immunoprecipitation, and quantitative reverse transcription polymerase chain reaction were employed for examining pyroptosis and pyroptotic pathways. ResultsBoth in vitro and in vivo ALI models were successfully established. LPS could activate the pyroptotic signaling pathway, and the expression level of ATF3 peaked 6h after LPS and ATP stimulation in vitro. ATF3 could interact with NLRP3 and potentially influence the assembly of the inflammasome. This mechanism could involve the inhibition of the classical pyroptotic pathway, including Caspase-1 and Gasdermin D transcription and cleavage, as well as the inhibition of the non-classical pyroptotic pathway, including transcription and cleavage of Caspase-11. ConclusionThe results indicated that inhibition of ATF3 could exacerbate sepsis-induced ALI by regulating pyroptotic pathways. The potential of targeting ATF3 as a future treatment strategy for ALI is noteworthy.

Grass Carp Reovirus (GCRV) infection activates the PERK-eIF2α pathway to promote the viral replication

Grass carp reovirus (GCRV) belongs to the genus Aquareovirus and is responsible for causing serious hemorrhagic disease in grass carp (Ctenopharyngodon idella), characterized by high mortality rates. Numerous animal viruses have been shown to activate endoplasmic reticulum stress (ERS). However, the potential for GCRV infection to induce ERS and its implications for viral infection remain unclear. In this study, we demonstrated that GCRV infection induces ERS, activates the protein kinase R-like ER kinase (PERK) pathway, and inhibits both the inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6) pathways within the unfolded protein response (UPR). Additionally, we modulated the levels of ERS and UPR pathways in CIK cells through drug treatment and small interfering RNAs (siRNAs). Our findings revealed that the onset of ERS accelerated GCRV infection, while the ATF6 and IRE1 pathways within the UPR negatively regulated GCRV infection. Conversely, the PERK pathway facilitated GCRV infection. Furthermore, we showed that GCRV infection induced oxidative stress, with the production of reactive oxygen species (ROS) being positively regulated by the PERK pathway and the downstream gene endoplasmic reticulum oxidoreductase-1α (ERO1α). Notably, ROS promoted GCRV infection. Collectively, our findings indicate that GCRV infection activates ERS, which in turn promotes viral infection through the PERK-ERO1α-ROS signaling pathway. Thus, the PERK pathway may serve as a novel antiviral target for the prevention of GCRV infection.

1α,25-hydroxyvitamin D3 alleviated rotavirus infection induced ferroptosis in IPEC-J2 cells by regulating the ATF3-SLC7A11-GPX4 axis

Rotavirus (RV) mainly infects mature intestinal epithelial cells and impairs intestinal absorption function, which leads to the death of infected cells and eventually fatal diarrhea. Ferroptosis is a novel regulatory cell death pattern, which can be caused by virus infection. 1α,25-hydroxyvitamin D3 (1,25D3) has an anti-RV infection effect and can regulate ferroptosis. However, whether RV infection can induce ferroptosis, and whether 1,25D3 can inhibit RV infection by regulating ferroptosis has not yet been studied. Present study shows that RV infection or erastin treatment induces IPEC-J2 cell death, which results in mitochondrial shrinkage, decreased mitochondrial membrane potential (MMP) and glutathione (GSH) content, increased MMP, intracellular Fe2+, reactive oxygen species (ROS), and malondialdehyde (MDA) contents. Meanwhile, ferrostatin-1 (Fer-1), liproxstatin-1 (Lip-1), and deferoxamine (DFO) treatment can effectively reverse the increase of intracellular Fe2+, ROS and MDA levels induced by RV infection. Moreover, RV infection increases activating transcription factor 3 (ATF3) mRNA and protein expressions, and inhibited SLC7A11 and glutathione peroxidase 4 (GPX4) expressions, which was partially alleviated by siATF3. 1,25D3 treatment significantly eliminates RV induced ferroptosis via ATF3-SLC7A11-GPX4 axis. Therefore, our results reveals that RV infection induces ferroptosis in IPEC-J2 cell and 1,25D3 alleviates RV induced ferroptosis by regulating the ATF3-SLC7A11-GPX4 axis.

Ceapin-A7 suppresses the protective effects of Octreotide in human and bovine lung endothelial cells.

Endothelial injury can be the cause and consequence of severe inflammation and injury. Synthetic somatostatin analogs - which suppress Growth Hormone - are FDA-approved drugs associated with anti-inflammatory activities. In the present study we suggest that the protective activities of Octreotide in human and bovine endothelial cells are mitigated by Ceapin-A7, which is an activating transcription factor 6 suppressor. To study endothelial function, we assessed protein expression levels of key cytoskeletal proteins, as well as paracellular permeability. To evaluate inflammation, we measured factors which promote vascular leak, as well as reactive oxygen species generation. Collectively, our study supports the involvement of activating transcription factor 6 in the protective effects of Octreotide in endothelial barrier function.

Self-Assembled Nanoparticles with Well-Defined Oligosaccharide Promote Osteogenesis by Regulating Golgi Stress Response.

Osteoporosis, a prevalent disease characterized by low bone density and increased fracture risk, poses significant health challenges for the elderly. Current treatments offer short-term benefits but are limited by long-term efficacy and adverse effects, highlighting the need for new strategies. Chondroitin sulfate polysaccharides (CS), a major component of the bone matrix, are crucial for bone and cartilage health. However, their role in osteoporosis is understudied due to the heterogeneity of natural CS. we found reduced CS levels in osteoporosis patients and developed CS4-NP, a self-assembled tetrasaccharide nanoparticle that mimics CS's structure. CS4-NP, which efficiently delivers the active CS4, significantly improves bone mass in ovariectomized osteoporosis models. It activates the Activating Transcription Factor 4-Cystathionine gamma-Lyase signaling axis in pre-osteoblasts, enhancing osteogenesis. our findings suggest that CS4-NP, an oligosaccharide-based nanomaterial, could address the limitations of current treatments and provide a viable strategy for osteoporosis.

Sinapic acid alleviates glutamate-induced excitotoxicity by inhibiting neuroinflammation and endoplasmic reticulum stress pathway in C6 glioma cells

Sinapic acid (SA) is a polyphenol compound derived from hydroxycinnamic acid found in various foods such as cereals and vegetables and has antioxidant, anti-inflammatory and neuroprotective properties. However, its effects on glutamate-induced excitotoxicity, which is important in neurodegenerative diseases, have not been fully elucidated. This study aimed to investigate the effect of SA on glutamate excitotoxicity and the possible role of proinflammatory cytokines and the endoplasmic reticulum (ER) stress pathway. In the study, C6 rat glioma cell line was used and the cells were divided into 4 groups: control, glutamate, SA and glutamate+SA. Cells were treated with 10 mM glutamate for 24 h to induce excitotoxicity. Additionally, SA was applied to cells at concentrations of 12.5 to 100 μM to examine its effects on glutamate excitotoxicity. XTT test was used for cell viability, and apoptotic cells were determined by immunofluorescence and flow cytometry methods. Proinflammatory cytokines (tumor necrosis factor-alpha, TNF-α and interleukin-beta, IL-1β), ER stress markers (glucose regulatory protein 78, GRP78; C/EBP homologous protein, CHOP and activating transcription factor-4, ATF-4) and caspase-3 was used to measure ELISA method. Findings indicated that SA (50 μM) significantly increased cell viability against glutamate-induced excitotoxicity (p < 0.05). Also, SA caused a significant decrease in TNF-α, IL-1β, GRP78, CHOP, ATF-4 and caspase-3 levels in glutamate-treated cells (p < 0.05). Flow cytometry and immunofluorescence staining results showed that SA reduced apoptosis in C6 glioma cells. In conclusion, our findings suggested that SA attenuated glutamate-induced excitotoxicity by preventing apoptosis through reducing proinflammatory cytokines and ER stress protein levels.

KPNB1-ATF4 induces BNIP3-dependent mitophagy to drive odontoblastic differentiation in dental pulp stem cells

BackgroundDifferentiating dental pulp stem cells (DPSCs) into odontoblasts is a critical process for tooth self-repair and dentine‒pulp engineering strategies in the clinic. However, the mechanism underlying the regulation of DPSC odontoblastic differentiation remains largely unknown. Here, we demonstrated that BCL-2 interacting protein 3 (BNIP3)-dependent mitophagy is associated with importin subunit beta-1 (KPNB1)-activating transcription factor 4 (ATF4), which promotes DPSC odontoblastic differentiation.MethodsThe key genes involved in DPSC odontogenic differentiation were identified via bioinformatics. Stable silencing or overexpression of BNIP3 was performed to investigate its impact on DPSC differentiation in vitro (n ≥ 3). To explore the role of BNIP3 in vivo, tooth root fragments loaded with the hydrogel-transfected DPSC complex were implanted into nude mice (n ≥ 6). Dual-luciferase reporter assays and chromatin immunoprecipitation (ChIP) polymerase chain reaction (PCR) were conducted to explore the binding site of ATF4 to the BNIP3 promoter (n ≥ 3). Mitochondrial function experiments were performed to investigate the impact of ATF4-BNIP3 on mitochondria (n ≥ 3). Immunoprecipitation (IP) mass spectrometry (MS) was used to investigate the interaction between ATF4 and its binding protein, KPNB1. Plasmids containing wild-type (WT)/mutant (MUT)-nuclear localization signal (NLS) forms of ATF4 were constructed to determine the specific amino acid residues recognized by KPNB1 and their effects on DPSC odontoblastic differentiation (n ≥ 3).ResultsCompared with those in the control group, the levels of autophagy and mitophagy, especially BNIP3-dependent mitophagy, were greater in the DPSC odontoblastic differentiation group (P < 0.05). Genetic silencing or overexpression of BNIP3 demonstrated that BNIP3 expression was positively correlated with the transition of DPSCs into odontoblasts both in vitro and in vivo (P < 0.05). ATF4 regulates the expression of BNIP3 by directly binding to approximately −1292 to −1279 bp and approximately −1185 to −1172 bp within the BNIP3 promoter region, which is associated with mitophagy and mitochondrial reactive oxygen species (mtROS) levels (P < 0.05). Moreover, ATF4 increased mitophagy, mitochondrial function, and cell differentiation potential via BNIP3 (P < 0.05). Mechanistically, KPNB1 is a novel interacting protein of ATF4 that specifically recognizes amino acids (aa) 280–299 within ATF4 to control its translocation into the nucleus and subsequent transcription and differentiation processes (P < 0.05).ConclusionsWe reported that the critical role of KPNB1/ATF4/BNIP3 axis-dependent mitophagy could provide new cues for the regeneration of the dental pulp‒dentin complex in DPSCs.Graphical

ATF3 regulates CDC42 transcription and influences cytoskeleton remodeling, thus inhibiting the proliferation, migration and invasion of malignant skin melanoma cells.

Cutaneous malignant melanoma (CMM) is one of the most aggressive and lethal types of skin cancer. Cytoskeletal remodeling is a key factor in the progression of CMM. Previous research has shown that activating transcription factor 3 (ATF3) inhibits metastasis in bladder cancer by regulating actin cytoskeleton remodeling through gelsolin. However, whether ATF3 plays a similar role in cytoskeletal remodeling in CMM cells remains unknown. Various gene and protein expression analyses were performed using techniques such as reverse transcription quantitative PCR, western blot, immunofluorescent staining, and immunohistochemical staining. CMM viability, migration, and invasion were examined through cell counting kit-8 and transwell assays. The interactions between cell division cycle 42 (CDC42) and ATF3 were investigated using chromatin immunoprecipitation and dual-luciferase reporter assays. CDC42 was upregulated in CMM tissues and cells. Cytoskeletal remodeling of CMM cells, as well as CMM cell proliferation, migration, and invasion, were inhibited by CDC42 or ATF3. ATF3 targeted the CDC42 promoter region to regulate its transcriptional activity. ATF3 suppresses cytoskeletal remodeling in CMM cells, thereby inhibiting CMM progression and metastasis through CDC42. This research may provide a foundation for using ATF3 as a therapeutic target for CMM.

ER-tethered stress sensor CREBH regulates mitochondrial unfolded protein response to maintain energy homeostasis

The Mitochondrial Unfolded Protein Response (UPRmt), a mitochondria-originated stress response to altered mitochondrial proteostasis, plays important roles in various pathophysiological processes. In this study, we revealed that the endoplasmic reticulum (ER)-tethered stress sensor CREBH regulates UPRmt to maintain mitochondrial homeostasis and function in the liver. CREBH is enriched in and required for hepatic Mitochondria-Associated Membrane (MAM) expansion induced by energy demands. Under a fasting challenge or during the circadian cycle, CREBH is activated to promote expression of the genes encoding the key enzymes, chaperones, and regulators of UPRmt in the liver. Activated CREBH, cooperating with peroxisome proliferator-activated receptor α (PPARα), activates expression of Activating Transcription Factor (ATF) 5 and ATF4, two major UPRmt transcriptional regulators, independent of the ER-originated UPR (UPRER) pathways. Hepatic CREBH deficiency leads to accumulation of mitochondrial unfolded proteins, decreased mitochondrial membrane potential, and elevated cellular redox state. Dysregulation of mitochondrial function caused by CREBH deficiency coincides with increased hepatic mitochondrial oxidative phosphorylation (OXPHOS) but decreased glycolysis. CREBH knockout mice display defects in fatty acid oxidation and increased reliance on carbohydrate oxidation for energy production. In summary, our studies uncover that hepatic UPRmt is activated through CREBH under physiological challenges, highlighting a molecular link between ER and mitochondria in maintaining mitochondrial proteostasis and energy homeostasis under stress conditions.

New insights into ER stress mediated by ATF6 and IRE1-XBP1 signals in yellow catfish under hypoxia

In aquaculture, fish are often exposed to the major stressor of hypoxia. However, the mechanism of hypoxia-induced stress remains unclear. The present study aimed to investigate the physiological and molecular responses of yellow catfish (Pelteobagrus fulvidraco) to hypoxia stress and to further elucidate its stress response mechanisms. Each fish (28.14 ± 0.75 g) in the hypoxia group was individually placed in a 1 L transparent plastic tank and transferred to a closed hypoxia environment, where the oxygen and carbon dioxide levels were adjusted to 2 % and 0.5 %, respectively. The results showed that hypoxia stress induced a stress response in yellow catfish, characterized by significant changes in lactate dehydrogenase (LD) and cortisol levels in plasma and liver, as well as increased apoptosis of brain cells and liver damage. Additionally, the HPA axis was activated, playing a crucial role in stress regulation during hypoxia exposure. And under hypoxia conditions, endoplasmic reticulum (ER) stress pathways were activated in yellow catfish liver, specifically showing significant upregulation of the activating transcription factor 6 (ATF6) and inositol-requiring enzyme 1 (IRE1)-X-box binding protein 1 (XBP1) signals, while the activated transcription factor 4 (ATF4) pathway remained inactive. The expression levels of atf6, ire1 and xbp1 genes, as well as ATF6, IRE1 and XBP1 proteins in the ATF6 and IRE1-XBP1 pathways, were significantly elevated. However, there was no significant differences in the expression levels of protein kinase R-like ER kinase (perk), eukaryotic translation initiation factor 2α (eif2α) and atf4 key genes, as well as PERK, EIF2α and ATF4 proteins in the PERK-ATF4 pathway. It is concluded for the first time that hypoxia significantly activates ER stress through the ATF6 and IRE1-XBP1 signaling pathways, but not the PERK-ATF4 pathway in yellow catfish. These findings not only provide new insights into the stress response mechanisms of fish but also offer the accurate molecular target of hypoxia-induced stress for aquaculture management.

Ivermectin inhibits the growth of ESCC by activating the ATF4-mediated endoplasmic reticulum stress-autophagy pathway.

Esophageal squamous cell carcinoma (ESCC) is one of the most common forms of malignancy worldwide. However, there is currently a lack of effective chemotherapeutic drugs for ESCC. Ivermectin is a broad-spectrum antiparasitic drug with notable antitumor activity. However, the cellular and molecular mechanisms by which ivermectin inhibits cancer growth remain unclear. In this study, we elucidate the role of ivermectin in ESCC suppression by activating the endoplasmic reticulum (ER) stress and autophagy pathways. In transcriptome analyses, we find that activating transcription factor 4 (ATF4) and DNA damage inducible transcript 3 (DDIT3) are involved in the activation of ER stress by ivermectin. Moreover, ivermectin treatment suppresses the growth of ESCC xenograft tumors in nude mice. Taken together, our results establish the antitumor molecular role of ivermectin in targeting the ER stress-autophagy pathway and suggest that ivermectin is a potential drug candidate for the treatment of ESCC.

Mutations in unfolded protein response regulator ATF6 cause hearing and vision loss syndrome.

Activating transcription factor 6 (Atf6) is a key regulator of the unfolded protein response (UPR) and is important for endoplasmic reticulum (ER) function and protein homeostasis in metazoan cells. Patients carrying loss-of-function ATF6 disease alleles develop the cone dysfunction disorder, achromatopsia. The impact of loss of ATF6 function on other cell types, organs, and diseases in people remains unclear. Here, we reported that progressive sensorineural hearing loss was a notable complaint in some patients carrying ATF6 disease alleles and that Atf6-/- mice also showed progressive auditory deficits affecting both genders. In mice with hearing deficits, we found disorganized stereocilia on hair cells and focal loss of outer hair cells. Transcriptomic analysis of Atf6-/- cochleae revealed marked induction of UPR, especially through the PERK arm. These findings identify ATF6 as an essential regulator of cochlear health and function. Furthermore, they supported that ATF6 inactivation in people causes progressive sensorineural hearing loss as part of a blindness-deafness genetic syndrome targeting hair cells and cone photoreceptors. Lastly, our genetic findings support ER stress as an important pathomechanism underlying cochlear damage and hearing loss with clinical implications for patient lifestyle modifications that minimize environmental/physiologic sources of ER stress to the ear.

Reactivation of senescence-associated endogenous retroviruses by ATF3 drives interferon signaling in aging.

Reactivation of endogenous retroviruses (ERVs) has been proposed to be involved in aging. However, the mechanism of reactivation and contribution to aging and age-associated diseases is largely unexplored. In this study, we identified a subclass of ERVs reactivated in senescent cells (termed senescence-associated ERVs (SA-ERVs)). These SA-ERVs can be bidirectional transcriptionally activated by activating transcription factor 3 (ATF3) to generate double-stranded RNAs (dsRNAs), which activate the RIG-I/MDA5-MAVS signaling pathway and trigger a type I interferon (IFN-I) response in senescent fibroblasts. Consistently, we found a concerted increased expression of ATF3 and SA-ERVs and enhanced IFN-I response in several tissues of healthy aged individuals and patients with Hutchinson-Gilford progeria syndrome. Moreover, we observed an accumulation of dsRNAs derived from SA-ERVs and higher levels of IFNβ in blood of aged individuals. Together, these results reveal a previously unknown mechanism for reactivation of SA-ERVs by ATF3 and illustrate SA-ERVs as an important component and hallmark of aging.

Fmo-4 promotes longevity and stress resistance via ER to mitochondria calcium regulation in C. elegans.

Flavin-containing monooxygenases (FMOs) are a conserved family of xenobiotic enzymes upregulated in multiple longevity interventions, including nematode and mouse models. Previous work supports that C. elegans fmo-2 promotes longevity, stress resistance, and healthspan by rewiring endogenous metabolism. However, there are five C. elegans FMOs and five mammalian FMOs, and it is not known whether promoting longevity and health benefits is a conserved role of this gene family. Here, we report that expression of C. elegans fmo-4 promotes lifespan extension and paraquat stress resistance downstream of both dietary restriction and inhibition of mTOR. We find that overexpression of fmo-4 in just the hypodermis is sufficient for these benefits, and that this expression significantly modifies the transcriptome. By analyzing changes in gene expression, we find that genes related to calcium signaling are significantly altered downstream of fmo-4 expression. Highlighting the importance of calcium homeostasis in this pathway, fmo-4 overexpressing animals are sensitive to thapsigargin, an ER stressor that inhibits calcium flux from the cytosol to the ER lumen. This calcium/fmo-4 interaction is solidified by data showing that modulating intracellular calcium with either small molecules or genetics can change expression of fmo-4 and/or interact with fmo-4 to affect lifespan and stress resistance. Further analysis supports a pathway where fmo-4 modulates calcium homeostasis downstream of activating transcription factor-6 (atf-6), whose knockdown induces and requires fmo-4 expression. Together, our data identify fmo-4 as a longevity-promoting gene whose actions interact with known longevity pathways and calcium homeostasis.

ATF3 mediates PM2.5-induced apoptosis and inflammation in ovarian granulosa cells.

Particulate matter 2.5 (PM2.5) pollution has emerged as a major global public health concern because of its adverse effects on human health. Our group has previously demonstrated that PM2.5 exposure can seriously impair ovarian function. However, the underlying mechanisms remain a mystery. This study verifies ovarian damage in mice, evidenced by inflammatory cell infiltration and follicular atresia, following 5 months of PM2.5 exposure via tracheal drip (35µg/m³ for low dose and 150µg/m³ for high dose). In addition, PM2.5 exposure inhibited the cell viability of human granulosa cells (KGN) and induced apoptosis at the concentrations of 50, 100, and 150µg/mL for 24h. The apoptosis of KGN cells induced by inflammation contributes to follicular atresia. Furthermore, we conducted RNA-sequencing analysis to identify the genes and pathways triggered by PM2.5 (100µg/mL) exposure, which decreases the KGN cell viability. We found a significant increase in Activating Transcription Factor 3 (ATF3). Further mechanistic studies reveal a strong association between PM2.5-induced apoptosis, inflammation, and ATF3 with its downstream oxidative stress signals. In summary, the ATF3 pathway serves a vital role in the ovarian injury caused by PM2.5 exposures.

Dengzhan Shengmai capsule ameliorates cognitive impairment via inhibiting ER stress in APP/PS1 mice

Ethnopharmacological relevanceAlzheimer's disease (AD) is a common type of neurodegenerative disease with the β-amyloid plaques (Aβ) deposition. Previously, Dengzhan Shengmai capsule (DZSM) has been shown to reduce the pathology associated with AD, but the underlying mechanism is unclear. Aim of studyThis study investigated the potential mechanisms of DZSM against AD. Materials and methodsThe six-month-old wild-type male mice and APP/PS1 double transgenic male mice were administered 0.9 % saline or DZSM for 8 weeks by gavage. Open field test, new object recognition test, and Morris Water maze test were used to assess spatial learning and memory. Aβ plaques in brains were visualized using ThT staining. Nissl staining, TUNEL staining, and Western blot analyses were used to detect the neuronal function and apoptosis level. The superoxide dismutase (SOD), glutathione peroxidase assay kit (GSH-Px), and malondialdehyde (MDA) kits were performed to assess oxidative stress levels. Then, immunofluorescence and Western blot analysis were applied to evaluate ER stress pathway protein levels. Finally, HT22 cells were treated by Aβ1-42 with or without DZSM medicated serum. Cell viability was assessed using the CCK-8 assay, and Western blot analysis was applied to evaluate ER stress pathway protein levels. ResultsOpen filed test, new object recognition test and Morris Water maze test showed that DZSM restored cognitive disorders in APP/PS1 mice. Immunohistochemistry and Thioflavin T staining results indicated that DZSM reduced Aβ plaques in the brain. Deeper and denser Nissl bodies were found in APP/PS1 mice after DZSM administration. Besides, APP/PS1 mice treated with DZSM showed a lower level of TUNEL and Bax/Bcl-2 ratio. DZSM improved the acetylcholine (ACh), choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity while reducing acetylcholinesterase (AChE) and malondialdehyde (MDA) activity. In addition, the levels of ER stress pathway containing Phospho-PKR-like ER kinase (P-PERK), phosphorylate eukaryotic initiation factor 2 (P-eIF2α), activating transcription factor 4 (ATF4), glutamine-rich protein 1 (QRICH1), phosphorylate inositol-requiring protein 1α (P-IRE1α), the spliced form of X-box binding protein 1 (XBP1s), activating transcription factor-6 (ATF6) and C/EBP homologous binding protein (CHOP) were decreased by DZSM. CCK-8 results indicated that DZSM medicated serum played cytoprotective effects on Aβ1-42-induced HT22 cells. Western blot results suggested DZSM possibly inhibited ER stress pathways in Aβ1-42-induced HT22 cells. ConclusionThe potential protective mechanism of DZSM on cognitive impairment in AD might be related to ER stress pathways.