Nephroprotective effects of Aralia taibaiensis in a high-fat diet-streptozotocin rat model of diabetic nephropathy.

Diabetic nephropathy (DN) has emerged as the foremost cause of end-stage renal disease (ESRD) globally. Endoplasmic reticulum (ER) stress plays a critical role in DN progression. Triterpenoid saponin from Aralia taibaiensis (sAT) has been reported to possess anti-diabetic and anti-oxidant effects. The aim of this study was to examine the influence of sAT on DN treatment and elucidate potential underlying mechanisms. A high-fat diet (HFD) and Streptozotocin (STZ) were employed to induce DN in male Sprague Dawley (SD) rats which were subsequently treated with varying concentrations of sAT for 8 weeks. Our findings reveal that different doses of sAT significantly mitigated hyperglycemia, reduced urinary albumin excretion, and decreased plasma creatinine and blood urea nitrogen levels in DN rats. Moreover, sAT administration improved body weight, alleviated renal fibrosis and histopathological changes in the diabetic kidneys. Notably, sAT treatment partially restored increased Bax expression and decreased Bcl-2 expression. Additionally, sAT inhibited ER stress-related proteins, including GRP78, p-PERK, ATF4 and CHOP in kidneys of DN rats. These results suggest that sAT ameliorated experimental diabetic nephropathy, at least in part, through ER stress pathway. These findings provide a scientific basis for the potential development of sAT as a therapeutic agent for DN treatment.

Overcoming Cancer Persister Cells by Stabilizing the ATF4 Promoter G-quadruplex.

Persister cells (PS) selected for anticancer therapy have been recognized as a significant contributor to the development of treatment-resistant malignancies. It is found that imposing glutamine restriction induces the generation of PS, which paradoxically bestows heightened resistance to glutamine restriction treatment by activating the integrated stress response and initiating the general control nonderepressible 2-activating transcription factor 4-alanine, serine, cysteine-preferring transporter 2 (GCN2-ATF4-ASCT2) axis. Central to this phenomenon is the stress-induced ATF4 translational reprogramming. Unfortunately, directly targeting ATF4 protein has proven to be a formidable challenge because of its flat surface. Nonetheless, a G-quadruplex structure located within the promoter region of ATF4 (ATF4-G4) is uncovered and resolved, which functions as a transcriptional regulator and can be targeted by small molecules. The investigation identifies the natural compound coptisine (COP) as a potent binder that interacts with and stabilizes ATF4-G4. For the first time, the high-resolution structure of the COP-ATF4-G4 complex is determined. The formation of this stable complex disrupts the interaction between transcription factor AP-2 alpha (TFAP2A) and ATF4-G4, resulting in a substantial reduction in intracellular ATF4 levels and the eventual death of cancer cells. These seminal findings underscore the potential of targeting the ATF4-G4 structure to yield significant therapeutic advantages within the realm of persister cancer cells induced by glutamine-restricted therapy.

ATF4-mediated different mode of interaction between autophagy and mTOR determines cell fate dependent on the level of ER stress induced by Cr(VI).

Hexavalent chromium [Cr(VI)] exists widely in occupational environments. The mechanistic target of rapamycin (mTOR) has been well-documented to regulate autophagy negatively. However, we found that low concentration of Cr(VI) (0.2 µM) elevated both mTOR and autophagy and promote cell survival. Conversely, high concentration of Cr(VI) (6 µM) caused cell death by inhibiting mTOR and subsequently inducing autophagy. Tunicamycin (Tm), as an Endoplasmic reticulum (ER) stress activator was used to induce mild ER stress at 0.1 µg/ml and it activated both autophagy and mTOR, which also caused cell migration in a similar manner to that observed with low concentration of Cr(VI). Severe ER stress caused by Tm (2 µg/ml) decreased mTOR, increased autophagy and then inhibited cell migration, which was the same as 6 µM Cr(VI) treatment, although Cr(VI) in high concentration inhibited ER stress. Activating transcription factor 4 (ATF4), a downstream target of ER stress, only increased under mild ER stress but decreased under severe ER stress and 6 µM Cr(VI) treatment. Chromatin immunoprecipitation (ChIP) experiment indicated that ATF4 could bind to the promoter of ATG4B and AKT1. To sum up, our data revealed that mild ER stress induced by low concentration of Cr(VI) could enhance transcriptional regulation of ATG4B and AKT1 by ATF4, which induced both autophagy and mTOR to promote cell viability.

Polystyrene microplastics trigger testosterone decline via GPX1.

As an emerging environmental endocrine disruptor, polystyrene microplastics (PS-MPs) are considered to have the anti-androgenic feature and impair male reproductive function. To explore the adverse effects of PS-MPs on testosterone synthesis and male reproduction and further elucidate underlying mechanisms, BALB/c mice and Leydig cells were employed in the present work. The results indicated that 50 µm PS-MPs accumulated in mouse testes and were internalized into the cytoplasm. This not only damaged the testicular histomorphology and ultrastructure, but also reduced the viability of Leydig cells and the serum level of GnRH, FSH, LH, and testosterone. After PS-MPs exposure, the ubiquitination degradation and miR-425-3p-targeted modulation synergistically contributed to the suppression of GPX1, which induced oxidative stress and subsequently activated the PERK-EIF2α-ATF4-CHOP pathway of endoplasmic reticulum (ER) stress. The transcription factor CHOP positively regulated the expression of SRD5A2 by directly binding to its promoter region, thereby accelerating testosterone metabolism and ultimately lowing testosterone levels. Besides, PS-MPs compromised testosterone homeostasis via interfering with the hypothalamic-pituitary-testis (HPT) axis. Taken together, PS-MPs possess an anti-androgenic characteristic and exert male reproductive damage effects. The antioxidant enzyme GPX1 plays a crucial role in the PS-MPs-mediated testosterone decline.

Induction of the PERK-eIF2α-ATF4 Pathway in M1 Macrophages under Endoplasmic Reticulum Stress.

Translation inhibition can activate two cell death pathways. The first pathway is activated by translational aberrations, the second by endoplasmic reticulum (ER) stress. In this work, the effect of ribosome-inactivating protein type II (RIP-II) viscumin on M1 macrophages derived from the THP-1 cell line was investigated. The number of modified ribosomes was evaluated by real-time PCR. Transcriptome analysis revealed that viscumin induces the ER stress activated by the PERK sensor.

Nitidine chloride inhibits mTORC1 signaling through ATF4-mediated Sestrin2 induction and targets IGF2R for lysosomal degradation.

AIMS: Nitidine chloride (NC), a natural phytochemical alkaloid derived from Zanthoxylum nitidum (Roxb.) DC, exhibits multiple bioactivities, including antitumor, anti-inflammatory, and other therapeutic effects. However, the primary targets of NC and the mechanism of action (MOA) have not been explicitly defined. METHODS: We explored the effects of NC on mTORC1 signaling by immunoblotting and fluorescence microscopy in wild-type and gene knockout cell lines generated by the CRISPR/Cas9 gene editing technique. We identified IGF2R as a direct target of NC via the drug affinity-responsive target stability (DARTS) method. We investigated the antitumor effects of NC using a mouse melanoma B16 tumor xenograft model. KEY FINDINGS: NC inhibits mTORC1 activity by targeting amino acid-sensing signaling through activating transcription factor 4 (ATF4)-mediated Sestrin2 induction. NC directly binds to IGF2R and promotes its lysosomal degradation. Moreover, NC displayed potent cytotoxicity against various cancer cells and inhibited B16 tumor xenografts. SIGNIFICANCE: NC inhibits mTORC1 signaling through nutrient sensing and directly targets IGF2R for lysosomal degradation, providing mechanistic insights into the MOA of NC.

Tetrahydrocurcumin Attenuates Polymyxin B Sulfate-Induced HK-2 Cells Apoptosis by Inhibiting Endoplasmic Reticulum Stress-Mediated PERK/eIF2α/ATF4/CHOP Signaling Pathway Axis.

The clinical application of polymyxin B (PMB) is limited by its nephrotoxic effects, making the reduction of PMB-induced nephrotoxicity has become a pressing concern for clinicians. Tetrahydrocurcumin (THC), known for its beneficial characteristics in biological functions, presents an attractive option for intervention therapy to mitigate PMB-induced nephrotoxicity. However, the underlying mechanism of how THC mitigates PMB-induced nephrotoxicity is still poorly understood. Here, we first evaluated the potential of THC intervention therapy to mitigate PMB-induced nephrotoxicity in an in vitro model of PMB-induced cell injury. Moreover, we demonstrated that THC effectively protected HK-2 cells from PMB-induced apoptosis by using cell counting kit-8 and flow cytometry assay. THC could also suppress PMB-induced endoplasmic reticulum (ER) stress via PERK/eIF2α/ATF4/CHOP pathway. In addition, using PERK inhibitor GSK2606414 to inhibit ER stress also alleviated PMB-induced apoptosis. Taken together, these findings provide novel insights that THC possesses the ability to alleviate PMB-induced nephrotoxicity by inhibiting the ER stress-mediated PERK/eIF2α/ATF4/CHOP axis, which sheds light on the benefits of THC as an intervention strategy to reduce PMB-induced nephrotoxicity, thus providing a potential avenue for improved clinical outcomes in patients receiving PMB treatment.

Feasibility exploration of GSH in the treatment of acute hepatic encephalopathy from the aspects of pharmacokinetics, pharmacodynamics, and mechanism.

Our previous study highlighted the therapeutic potential of glutathione (GSH), an intracellular thiol tripeptide ubiquitous in mammalian tissues, in mitigating hepatic and cerebral damage. Building on this premise, we posited the hypothesis that GSH could be a promising candidate for treating acute hepatic encephalopathy (AHE). To verify this conjecture, we systematically investigated the feasibility of GSH as a therapeutic agent for AHE through comprehensive pharmacokinetic, pharmacodynamic, and mechanistic studies using a thioacetamide-induced AHE rat model. Our pharmacodynamic data demonstrated that oral GSH could significantly improve behavioral scores and reduce hepatic damage of AHE rats by regulating intrahepatic ALT, AST, inflammatory factors, and homeostasis of amino acids. Additionally, oral GSH demonstrated neuroprotective effects by alleviating the accumulation of intracerebral glutamine, down-regulating glutamine synthetase, and reducing taurine exposure. Pharmacokinetic studies suggested that AHE modeling led to significant decrease in hepatic and cerebral exposure of GSH and cysteine. However, oral GSH greatly enhanced the intrahepatic and intracortical GSH and CYS in AHE rats. Given the pivotal roles of CYS and GSH in maintaining redox homeostasis, we investigated the interplay between oxidative stress and pathogenesis/treatment of AHE. Our data revealed that GSH administration significantly relieved oxidative stress levels caused by AHE modeling via down-regulating the expression of NADPH oxidase 4 (NOX4) and NF-κB P65. Importantly, our findings further suggested that GSH administration significantly regulated the excessive endoplasmic reticulum (ER) stress caused by AHE modeling through the iNOS/ATF4/Ddit3 pathway. In summary, our study uncovered that exogenous GSH could stabilize intracerebral GSH and CYS levels to act on brain oxidative and ER stress, which have great significance for revealing the therapeutic effect of GSH on AHE and promoting its further development and clinical application.

Niacin, an innovative protein kinase-C-dependent endoplasmic reticulum stress reticence in murine Parkinson's disease.

AIMS: Niacin (NIA) supplementation showed effectiveness against Parkinson's disease (PD) in clinical trials. The depletion of NAD and endoplasmic reticulum stress response (ERSR) are implicated in the pathogenesis of PD, but the potential role for NAD precursors on ERSR is not yet established. This study was undertaken to decipher NIA molecular mechanisms against PD-accompanied ERSR, especially in relation to PKC. METHODS: Alternate-day-low-dose-21 day-subcutaneous exposure to rotenone (ROT) in rats induced PD. Following the 5th ROT injection, rats received daily doses of either NIA alone or preceded by the PKC inhibitor tamoxifen (TAM). Extent of disease progression was assessed by behavioral, striatal biochemical and striatal/nigral histopathological/immunohistochemical analysis. KEY FINDINGS: Via activating PKC/LKB1/AMPK stream, NIA post-treatment attenuated the ERSR reflected by the decline in ATF4, ATF6 and XBP1s to downregulate the apoptotic markers, CHOP/GADD153, p-JNK and active caspase-3. Such amendments congregated in motor activity/coordination improvements in open field and rotarod tasks, enhanced grid test latency and reduced overall PD scores, while boosting nigral/striatal tyrosine hydroxylase immunoreactivity and increasing intact neurons (Nissl stain) in both SNpc and striatum that showed less neurodegeneration (H&E stain). To different extents, TAM reverted all the NIA-related actions to prove PKC as a fulcrum in conveying the drug neurotherapeutic potential. SIGNIFICANCE: PKC activation is a pioneer mechanism in the drug ERSR inhibitory anti-apoptotic modality to clarify NIA promising clinical and potent preclinical anti-PD efficacy. This kinase can be tagged as a druggable target for future add-on treatments that can assist dopaminergic neuronal aptitude against this devastating neurodegenerative disease.

Beta-adrenergic stimulation promotes an endoplasmic reticulum stress-dependent inflammatory program in salivary gland epithelial cells.

The effect of beta-adrenergic stimulation on human labial minor salivary gland epithelial cells (LMSGEC) on IL-6 production, and its dependency to endoplasmic reticulum (ER) stress were investigated. Primary LMSGEC from Sjögren's syndrome (SS) patients and controls in culture were stimulated with epinephrine and IL-6 expression was evaluated by qPCR and ELISA. The expression of ß-ARs in cultured LMSGEC was tested by qPCR, while adrenoceptors and cAMP levels were examined in LMSGs by immunofluorescence. ER evaluation was performed by Transmission electron microscopy (TEM) and ER stress by Western blot. Adrenergic induced IL-6 production by cultured LMSGEC was evaluated after alleviation of the ER stress by applying Tauroursodeoxycholic acid (TUDCA) and silencing of PKR-like ER kinase (PERK) and activating transcription factor 4 (ATF4) RNAs. Expression of IL-6 by LMSGEC was upregulated after ß-adrenergic stimulation, while the silencing of adrenoreceptors downregulated IL-6. The amelioration of ER stress, as well as the silencing of PERK/ATF4, prevented epinephrine-induced upregulation of IL-6. Adrenergic stimulation led to higher and sustained IL-6 levels secreted by LMSGEC of SS patients compared to controls. Adrenergic signaling was endogenously enhanced in LMSGEC of SS patients (expression of ß-ARs in situ, intracellular cAMP in cultured LMSGEC). In parallel, SS-LMSGEC expressed dilated ER (TEM) and higher levels of GRP78/BiP. PERK/ATF4 pathway of the ER stress emerged a considerable mediator of adrenergic stimulation for IL-6 production by the LMSGEC. An enhanced endogenous adrenergic activation and a stressed ER observed in SS-LMSGEC may contribute to a sustained IL-6 production by these cells after adrenergic stimulation.

Prenatal Inflammatory Exposure Predisposes Offspring to Chronic Kidney Diseases Via the Activation of the eIF2α-ATF4 Pathway.

It has recently become more recognized that renal diseases in adults can originate from adverse intrauterine (maternal) environmental exposures. Previously, we found that prenatal lipopolysaccharide (LPS) exposure can result in chronic renal inflammation, which leads to renal damage in older offspring rats. To test whether prenatal inflammatory exposure predisposes offspring to renal damage, a mouse model of oral adenine consumption-induced chronic kidney disease (CKD) was applied to offspring from prenatal LPS-treated mothers (offspring-pLPS) and age-matched control offspring of prenatal saline-treated mothers (offspring-pSaline). We found that offspring-pLPS mice presented with more severe renal collagen deposition and renal dysfunction after 4 weeks of adenine consumption than sex- and treatment-matched offspring-pSaline controls. To illustrate the underlying molecular mechanism, we subjected offspring-pLPS and offspring-pSaline kidneys to genome-wide transcriptomic analysis. Bioinformatic analysis of the sequencing data, together with further experimental confirmation, revealed a strong activation of the PERK-eIF2α-ATF4-mediated unfolded protein response (UPR) in offspring-pLPS kidneys, which likely contributed to the CKD predisposition seen in offspring-pLPS mice. More importantly, the specific eIF2α-ATF4 signaling inhibitor ISIRB was able to prevent adenine-induced CKD in the offspring-pLPS mice. Our findings suggest that the eIF2α-ATF4-mediated UPR, but not PERK, is likely the major disease-causing pathway in prenatal inflammatory exposure-induced CKD predisposition. Our study also suggests that targeting this signaling pathway is a potentially promising approach for CKD treatment.

ATF4 inhibits tumor development and mediates p-GCN2/ASNS upregulation in colon cancer.

Colon cancer (CC) is a highly malignant tumor with a high incidence and poor prognosis. This study aimed to explore the function and molecular mechanisms of activating transcription factor 4 (ATF4) in CC. The expression levels of ATF4, GCN2, and ASNS in CC tissues were measured using immunohistochemistry (IHC) and reverse transcription quantitative PCR (RT-qPCR). Cell counting kit-8 (CCK-8), clone formation, transwell, and flow cytometry assays were conducted to assess cell viability, clonogenicity, migration, invasion, cell cycle, and apoptosis, respectively, in the ATF4 knockdown and overexpression SW480 cell lines. The effect of ATF4 on the expression of GCN2 and ASNS was detected using RT-qPCR, Chip-qPCR, and western blotting. ATF4, GCN2, and ASNS were expressed at low levels in CC tissues, and all had a significant negative correlation with tumor diameter. ATF4 knockdown promoted cell proliferation, invasion, and S-phase cell cycle and inhibited apoptosis in SW480 cells. In contrast, ATF4 overexpression had the opposite effect. Furthermore, ATF4 overexpression enhanced ATF4 binding to the ASNS promoter region. ATF4 knockdown significantly inhibited the expression of p-GCN2 and ASNS, whereas ATF4 overexpression significantly upregulated their expression. ATF4 inhibited CC cell viability, clone formation ability, migration, and invasion and promoted apoptosis, possibly by regulating the expression of p-GCN2 and ASNS. Our study provides a novel potential therapeutic target for the treatment of CC.

Crosstalk between ferroptosis and necroptosis in cerebral ischemia/reperfusion injury and Naotaifang formula exerts neuroprotective effect via HSP90-GCN2-ATF4 pathway.

BACKGROUND: Cerebral ischemia/reperfusion injury (CIRI) is a sequence of pathophysiological processes after blood recanalization in the patients with ischemic stroke, and has become the hinder for the rehabilitation. Naotaifang formula (NTF) has exhibited the clinical effectiveness for this disease. However, its action effects and molecular mechanisms against CIRI are not fully elucidated. PURPOSE: The research was to clarify the crosstalk between ferroptosis and necroptosis in CIRI, and uncover the mechanism underlying the neuroprotection of NTF. METHODS: This study established MCAO/R rat models with various reperfusion times. Western blot, transmission electron microscope, laser speckle imaging, immunofluorescence, immunohistochemistry and pathological staining were conducted to detect and analyze the obtained results. Subsequently, various NTF doses were used to intervene in MCAO/R rats, and biology experiments, such as western blot, Evans blue, immunofluorescence and immunohistochemistry, were used to analyze the efficacy of NTF doses. The effect of NTF was further clarified through in vitro experiments. Eventually, HT22 cells that suffered OGD/R were subjected to pre-treatment with plasmids overexpressing HSP90, MLKL, and GPX4 to indicate the interaction among ferroptosis and necroptosis. RESULTS: There was a gradual increase in the Zea Longa score and cerebral infarction volume following CIRI with prolonged reperfusion. Furthermore, the expression of factors associated with pro-ferroptosis and pro-necroptosis was upregulated in the cortex and hippocampus. NTF alleviated ferroptosis and necroptosis in a dose-dependent manner, downregulated HSP90 levels, reduced blood-brain barrier permeability, and thus protected nerve cells from CIRI. The results in vitro research aligned with those of the in vivo research. HSP90 and MLKL overexpression promoted necroptosis and ferroptosis while activating the GCN2-ATF4 pathway. GPX4 overexpression had no effect on necroptosis or the associated signaling pathway. The administration of NTF alone, as well as its combination with the overexpression of HSP90, MLKL, or GPX4 plasmids, decreased the expression levels of factors associated with pro-ferroptosis and pro-necroptosis and reduced the protein levels of the HSP90-GCN2-ATF4 pathway. Moreover, the regulatory effects of the NTF alone group on GSH, ferrous iron, and GCN2 were more significant compared with those of the HSP90 overexpression combination group. CONCLUSION: Ferroptosis and necroptosis were gradually aggravated following CIRI with prolonged reperfusion. MLKL overexpression may promote ferroptosis and necroptosis, while GPX4 overexpression may have little effect on necroptosis. HSP90 overexpression accelerated both forms of cell death via the HSP90-GCN2-ATF4 pathway. NTF alleviated ferroptosis and necroptosis to attenuate CIRI by regulating the HSP90-GCN2-ATF4 pathway. Our research provided evidence for the potential of drug development by targeting HSP90, MLKL, and GPX4 to protect against ischemic stroke.

Polystyrene Nanoplastics Induce Lipid Metabolism Disorder by Activating the PERK-ATF4 Signaling Pathway in Mice.

In recent years, the study of microplastics (MPs) and nanoplastics (NPs) and their effects on human health has gained significant attention. The impacts of NPs on lipid metabolism and the specific mechanisms involved remain poorly understood. To address this, we utilized high-throughput sequencing and molecular biology techniques to investigate how endoplasmic reticulum (ER) stress might affect hepatic lipid metabolism in the presence of polystyrene nanoplastics (PS-NPs). Our findings suggest that PS-NPs activate the PERK-ATF4 signaling pathway, which in turn upregulates the expression of genes related to lipid synthesis via the ATF4-PPARγ/SREBP-1 pathway. This activation leads to an abnormal accumulation of lipid droplets in the liver. 4-PBA, a known ER stress inhibitor, was found to mitigate the PS-NPs-induced lipid metabolism disorder. These results demonstrate the hepatotoxic effects of PS-NPs and clarify the mechanisms of abnormal lipid metabolism induced by PS-NPs.

Molecular characterization of the ER stress-inducible factor CRELD2.

Previously, we found by constructing various luciferase reporters that a well-conserved ATF6-binding element in the CRELD2 promoter is activated by transient ATF6 overexpression. In this study, we established ATF6-deficient and ATF4-deficient cell lines to analyze CRELD2 mRNA and protein expression together with that of other ER stress-inducible factors. Our results showed that ATF6 deficiency markedly suppressed tunicamycin (Tm)-induced expression of unglycosylated CRELD2. This reduction reflected a decrease in the CRELD2 transcription level. On the other hand, a putative ATF4-binding site in the mouse CRELD2 promoter did not respond to Tm stimulation, but ATF4 loss resulted in reductions in CRELD2 mRNA and protein expression, accompanied by a decrease in Tm-induced ATF6 expression. In contrast, transient suppression of GADD34, an ATF4 downstream factor, suppressed Tm-induced CRELD2 protein expression without a decrease in ATF6 protein expression. Furthermore, we investigated the association of CRELD2 with a well-known ERAD substrate, namely, an α1-antitripsin truncation mutant, NHK, by generating various CRELD2 and NHK constructs. Coimmunoprecipitation of these proteins was observed only when the cysteine in the CXXC motif on the N-terminal side of CRELD2 was replaced with alanine, and the interaction between the two was found to be disulfide bond-independent. Taken together, these findings indicate that CRELD2 expression is regulated by multiple factors via transcriptional and posttranscriptional mechanisms. In addition, the N-terminal structure of CRELD2, including the CXXC motif, was suggested to play a role in the association of the target proteins. In the future, the identification and characterization of factors interacting with CRELD2 will be useful for understanding protein homeostasis under various ER stress conditions.

Downregulation of TRIB3 enhances the sensitivity of lung cancer cells to amino acid deprivation by suppressing AKT activation.

Tribbles pseudokinase 3 (TRIB3), a member of the mammalian Tribbles family, is implicated in multiple biological processes. This study aimed to investigate the biological functions of TRIB3 in lung cancer and its effect on amino acid-deprived lung cancer cells. TRIB3 mRNA expression was elevated in lung cancer tissues and cell lines compared to normal lung tissues and cells. TRIB3 knockdown markedly reduced the viability and proliferation of H1299 lung cancer cells. Deprivation of amino acids, particularly arginine, glutamine, lysine, or methionine, strongly increased TRIB3 expression via ATF4 activation in H1299 lung cancer cells. Knockdown of TRIB3 led to transcriptional downregulation of ATF4 and reduced AKT activation induced by amino acid deprivation, ultimately increasing the sensitivity of H1299 lung cancer cells to amino acid deprivation. Additionally, TRIB3 knockdown enhanced the sensitivity of H1299 cells to V-9302, a competitive antagonist of transmembrane glutamine flux. These results suggest that TRIB3 is a pro-survival regulator of cell viability in amino acid-deficient tumor microenvironments and a promising therapeutic target for lung cancer treatment.

Plant-derived bioactive compounds and their novel role in central nervous system disorder treatment via ATF4 targeting: A systematic literature review.

Central nervous system (CNS) disorders exhibit exceedingly intricate pathogenic mechanisms. Pragmatic and effective solutions remain elusive, significantly compromising human life and health. Activating transcription factor 4 (ATF4) participates in the regulation of multiple pathophysiological processes, including CNS disorders. Considering the widespread involvement of ATF4 in the pathological process of CNS disorders, the targeted regulation of ATF4 by plant-derived bioactive compounds (PDBCs) may become a viable strategy for the treatment of CNS disorders. However, the regulatory relationship between PDBCs and ATF4 remains incompletely understood. Here, we aimed to comprehensively review the studies on PDBCs targeting ATF4 to ameliorate CNS disorders, thereby offering novel directions and insights for the treatment of CNS disorders. A computerized search was conducted on PubMed, Embase, Web of Science, and Google Scholar databases to identify preclinical experiments related to PDBCs targeting ATF4 for the treatment of CNS disorders. The search timeframe was from the inception of the databases to December 2023. Two assessors conducted searches using the keywords "ATF4," "Central Nervous System," "Neurological," "Alzheimer's disease," "Parkinson's Disease," "Stroke," "Spinal Cord Injury," "Glioblastoma," "Traumatic Brain Injury," and "Spinal Cord Injury." Overall, 31 studies were included, encompassing assessments of 27 PDBCs. Combining results from in vivo and in vitro studies, we observed that these PDBCs, via ATF4 modulation, prevent the deposition of amyloid-like fibers such as Aß, tau, and α-synuclein. They regulate ERS, reduce the release of inflammatory factors, restore mitochondrial membrane integrity to prevent oxidative stress, regulate synaptic plasticity, modulate autophagy, and engage anti-apoptotic mechanisms. Consequently, they exert neuroprotective effects in CNS disorders. Numerous PDBCs targeting ATF4 have shown potential in facilitating the restoration of CNS functionality, thereby presenting expansive prospects for the treatment of such disorders. However, future endeavors necessitate high-quality, large-scale, and comprehensive preclinical and clinical studies to further validate this therapeutic potential.

Triclosan administration to humanized UDP-glucuronosyltransferase 1 neonatal mice induces UGT1A1 through a dependence on PPARα and ATF4.

Triclosan (TCS) is an antimicrobial toxicant found in a myriad of consumer products and has been detected in human tissues, including breastmilk. We have evaluated the impact of lactational TCS on UDP-glucuronosyltransferase 1A1 (UGT1A1) expression and bilirubin metabolism in humanized UGT1 (hUGT1) neonatal mice. In hUGT1 mice, expression of the hepatic UGT1A1 gene is developmentally delayed resulting in elevated total serum bilirubin (TSB) levels. We found that newborn hUGT1 mice breastfed or orally treated with TCS presented lower TSB levels along with induction of hepatic UGT1A1. Lactational and oral treatment by gavage with TCS leads to the activation of hepatic nuclear receptors constitutive androstane receptor (CAR), peroxisome proliferator-activated receptor alpha (PPARα), and stress sensor, activating transcription factor 4 (ATF4). When CAR-deficient hUGT1 mice (hUGT1/Car-/-) were treated with TCS, TSB levels were reduced with a robust induction of hepatic UGT1A1, leaving us to conclude that CAR is not tied to UGT1A1 induction. Alternatively, when PPARα-deficient hUGT1 mice (hUGT1/Pparα-/-) were treated with TCS, hepatic UGT1A1 was not induced. Additionally, we had previously demonstrated that TCS is a potent inducer of ATF4, a transcriptional factor linked to the integrated stress response. When ATF4 was deleted in liver of hUGT1 mice (hUGT1/Atf4ΔHep) and these mice treated with TCS, we observed superinduction of hepatic UGT1A1. Oxidative stress genes in livers of hUGT1/Atf4ΔHep treated with TCS were increased, suggesting that ATF4 protects liver from excessive oxidative stress. The increase oxidative stress may be associated with superinduction of UGT1A1. The expression of ATF4 in neonatal hUGT1 hepatic tissue may play a role in the developmental repression of UGT1A1.

Neuroreceptor Inhibition by Clozapine Triggers Mitohormesis and Metabolic Reprogramming in Human Blood Cells.

The antipsychotic drug clozapine demonstrates superior efficacy in treatment-resistant schizophrenia, but its intracellular mode of action is not completely understood. Here, we analysed the effects of clozapine (2.5-20 µM) on metabolic fluxes, cell respiration, and intracellular ATP in human HL60 cells. Some results were confirmed in leukocytes of clozapine-treated patients. Neuroreceptor inhibition under clozapine reduced Akt activation with decreased glucose uptake, thereby inducing ER stress and the unfolded protein response (UPR). Metabolic profiling by liquid-chromatography/mass-spectrometry revealed downregulation of glycolysis and the pentose phosphate pathway, thereby saving glucose to keep the electron transport chain working. Mitochondrial respiration was dampened by upregulation of the F0F1-ATPase inhibitory factor 1 (IF1) leading to 30-40% lower oxygen consumption in HL60 cells. Blocking IF1 expression by cotreatment with epigallocatechin-3-gallate (EGCG) increased apoptosis of HL60 cells. Upregulation of the mitochondrial citrate carrier shifted excess citrate to the cytosol for use in lipogenesis and for storage as triacylglycerol in lipid droplets (LDs). Accordingly, clozapine-treated HL60 cells and leukocytes from clozapine-treated patients contain more LDs than untreated cells. Since mitochondrial disturbances are described in the pathophysiology of schizophrenia, clozapine-induced mitohormesis is an excellent way to escape energy deficits and improve cell survival.

Phenylbutyric acid inhibits hypoxia-induced trophoblast apoptosis and autophagy in preeclampsia via the PERK/ATF-4/CHOP pathway.

Preeclampsia (PE) is a common pregnancy complication with a high mortality rate. Abnormally activated endoplasmic reticulum stress (ERS) is believed to be responsible for the destruction of key placental cells-trophoblasts. Phenylbutyric acid (4-PBA), an ERS inhibitor, is involved in regulating the development of ERS-related diseases. At present, how 4-PBA affects trophoblasts and its mechanisms is still unclear. In this study, PE cell models were established by stimulating HTR-8/SVneo cells with hypoxia. To verify the underlying mechanisms of 4-PBA on PE, CCT020312, an activator of PERK, was also used. The results showed that 4-PBA restored hypoxia-induced trophoblast viability, inhibited HIF-1α protein expression, inflammation, and PERK/ATF-4/CHOP pathway. Hoechst 33342 staining and flow cytometry results confirmed that 4-PBA decreased hypoxia-induced apoptosis in trophoblasts. The results of the JC-1 analysis and apoptosis initiation enzyme activity assay also demonstrated that 4-PBA inhibited apoptosis related to the mitochondrial pathway. Furthermore, by detecting autophagy in trophoblasts, an increased number of autophagic vesicles, damaged mitochondria, enhanced dansylcadaverine fluorescence, enhanced levels of autophagy proteins Beclin-1, LC3II, and decreased p62 were seen in hypoxia-stimulated cells. These changes were reversed by 4-PBA. Furthermore, it was observed that CCT020312 reversed the effects of 4-PBA on the viability, apoptosis, and autophagosome number of hypoxia-induced trophoblasts. In summary, 4-PBA reduces autophagy and apoptosis via the PERK/ATF-4/CHOP pathway and mitochondrial pathway, thereby restoring the viability of hypoxic trophoblasts. These findings provide a solid evidence base for the use of 4-PBA in PE treatment and guide a new direction for improving the outcomes of patients with PE.