Discovery of a Novel Series of Homo sapiens Caseinolytic Protease P Agonists for Colorectal Adenocarcinoma Treatment via ATF3-Dependent Integrated Stress Response.

Homo sapiens caseinolytic protease P (HsClpP) activation is a promising strategy for colon cancer treatment. In this study, CCG1423 was identified as a selective activator of HsClpP. After optimization, NCA029 emerged as the most potent compound, with an EC50 of 0.2 µM against HsClpP. Molecular dynamics revealed that the affinity of NCA029 for the YYW aromatic network is crucial for its selectivity toward HsClpP. Furthermore, NCA029 displayed favorable pharmacokinetics and safety profiles and significantly inhibited tumor growth in HCT116 xenografts, resulting in 83.6% tumor inhibition. Mechanistically, NCA029 targeted HsClpP, inducing mitochondrial dysfunction and activating the ATF3-dependent integrated stress response, ultimately causing cell death in colorectal adenocarcinoma. These findings highlight NCA029 as an effective HsClpP activator with potential for colon cancer therapy.

Transcription Factor ATF3 Mediating SOCS3 Expression Aggravates Renal Ischemia-Reperfusion Injury by Activating Mitophagy.

INTRODUCTION: Suppressor of cytokine signaling 3 (SOCS3) is highly expressed in mice with renal ischemia/reperfusion (RI/R) injury and has the potential to regulate mitophagy. On this basis, this study further investigates the possible mechanism via which SOCS3 affects RI/R by regulating mitophagy. METHOD: After establishing a RI/R injury mouse model and a hypoxia/reoxygenation (H/R) cell model, the effects of silenced SOCS3 on injury and mitophagy in the above models were analyzed by ELISA, quantitative real-time polymerase chain reaction, Western blot, pathological sections, CCK-8 assay, flow cytometry, and JC-1 assay. Mechanistic studies were carried out with the help of database analysis and binding validation experiments (chromatin immunoprecipitation, dual-luciferase reporter assay, and co-immunoprecipitation). After the binding target was identified, the regulatory relationship between the target gene and SOCS3 was verified by rescue experiments. RESULT: The large increase in blood urea nitrogen (BUN) and creatinine (Cr) levels verified the success of the RI/R model. SOCS3 expression was up-regulated in RI/R mice. Silenced SOCS3 alleviated kidney damage and mitochondrial abnormalities in RI/R mice and inhibited mitophagy at the molecular level. Likewise, silenced SOCS3 alleviated H/R-induced cell damage and mitophagy. Finally, activating transcription factor 3 (ATF3) was determined to bind to the promoter of SOCS3, which interacted with insulin-like growth factor 1 receptor (IGF1R). Rescue experiments confirmed the effect of ATF3 on SOCS3 expression and the underlying regulatory mechanism. CONCLUSION: ATF3 mediates SOCS3 expression to promote the activation of mitophagy, thereby aggravating renal ischemia-reperfusion injury.

Docosahexaenoic Acid (DHA) Reduces LPS-Induced Inflammatory Response Via ATF3 Transcription Factor and Stimulates Src/Syk Signaling-Dependent Phagocytosis in Microglia.

BACKGROUND/AIMS: Microglial cells play a crucial role in the development of neuroinflammation in response to harmful stimuli, such as infection, ischemia or injury. Their chronic activation, however, is associated with a progression of neurodegenerative diseases. Therefore, looking for potential factors limiting microglial activation, the effect of docosahexaenoic acid (DHA) on the inflammatory response and TREM2-dependent phagocytic activity in microglia was investigated. METHODS: In LPS-induced primary microglia preincubated with DHA, or without preincubation the expression of ATF3 and TREM2 genes and TREM2, Syk, Akt proteins were determined by RT-PCR and WB, respectively. Cell viability was assayed by MTT and cytokine and chemokine expression was determined by the Proteome Profiler assay. Moreover, the phagocytic activity of microglia was assayed using immunofluorescence. RESULTS: We found that DHA significantly increased the expression of ATF3 , and decreased the levels of CINC-1, CINC-2αß, CINC-3 chemokines, IL-1α and IL-1ß cytokines, and ICAM-1 adhesion protein. Additionally, preincubation of microglia with DHA resulted in increased Src/Syk kinases activation associated with increased phagocytic microglia activity. CONCLUSION: These findings indicate that DHA efficiently inhibits ATF3-dependent release of proinflammatory mediators and enhances phagocytic activity of microglia. The study provides a new mechanism of DHA action in reactive microglia, which may help limit neuronal damage caused by the pro-inflammatory milieu in the brain.

ATF3 regulates SPHK1 in cardiomyocyte injury via endoplasmic reticulum stress.

AIM: Endoplasmic reticulum (ER) stress is common in different human pathologies, including cardiac diseases. Sphingosine kinase-1 (SPHK1) represents an important player in cardiac growth and function. Nevertheless, its function in cardiomyocyte ER stress remains vague. This study sought to evaluate the mechanism through which SPHK1 might influence ER stress during myocardial infarction (MI). METHODS: MI-related GEO data sets were queried to screen differentially expressed genes. Murine HL-1 cells exposed to oxygen-glucose deprivation (OGD) and mice with MI were induced, followed by gene expression manipulation using short hairpin RNAs and overexpression vectors. The activating transcription factor 3 (ATF3) and SPHK1 expression was examined in cells and tissues. Cell counting kit-8, TUNEL, DHE, HE, and Masson's staining were conducted in vitro and in vivo. The inflammatory factor concentrations in mouse serum were measured using ELISA. Finally, the transcriptional regulation of SPHK1 by ATF3 was validated. RESULTS: ATF3 and SPHK1 were upregulated in vivo and in vitro. ATF3 downregulation reduced the SPHK1 transcription. ATF3 and SPHK1 downregulation increased the viability of OGD-treated HL-1 cells and decreased apoptosis, oxidative stress, and ER stress. ATF3 and SPHK1 downregulation narrowed the infarction area and attenuated myocardial fibrosis in mice, along with reduced inflammation in the serum and ER stress in the myocardium. In contrast, SPHK1 reduced the protective effect of ATF3 downregulation in vitro and in vivo. CONCLUSIONS: ATF3 downregulation reduced SPHK1 expression to attenuate cardiomyocyte injury in MI.

MicroRNA-22-3p in human umbilical cord mesenchymal stem cell-secreted exosomes inhibits granulosa cell apoptosis by targeting KLF6 and ATF4-ATF3-CHOP pathway in POF mice.

BACKGROUND: Human umbilical cord mesenchymal stem cells (hUCMSCs)-derived exosomes carrying microRNAs (miRNAs) have promising therapeutic potential in various disorders, including premature ovarian failure (POF). Previous evidence has revealed the low plasma level of miR-22-3p in POF patients. Nevertheless, exosomal miR-22-3p specific functions underlying POF progression are unclarified. METHODS: A cisplatin induced POF mouse model and in vitro murine ovarian granulosa cell (mOGC) model were established. Exosomes derived from miR-22-3p-overexpressed hUCMSCs (Exos-miR-22-3p) were isolated. CCK-8 assay and flow cytometry were utilized for measuring mOGC cell viability and apoptosis. RT-qPCR and western blotting were utilized for determining RNA and protein levels. The binding ability between exosomal miR-22-3p and Kruppel-like factor 6 (KLF6) was verified using luciferase reporter assay. Hematoxylin-eosin staining, ELISA, and TUNEL staining were performed for examining the alteration of ovarian function in POF mice. RESULTS: Exos-miR-22-3p enhanced mOGC viability and attenuated mOGC apoptosis under cisplatin treatment. miR-22-3p targeted KLF6 in mOGCs. Overexpressing KLF6 reversed the above effects of Exos-miR-22-3p. Exos-miR-22-3p ameliorated cisplatin-triggered ovarian injury in POF mice. Exos-miR-22-3p repressed ATF4-ATF3-CHOP pathway in POF mice and cisplatin-treated mOGCs. CONCLUSION: Exosomal miR-22-3p from hUCMSCs alleviates OGC apoptosis and improves ovarian function in POF mouse models by targeting KLF6 and ATF4-ATF3-CHOP pathway.

[Overexpression of ATF3 inhibits the differentiation of goat intramuscular preadipocytes].

The aim of this study was to investigate the effect of activating transcription factor 3 (ATF3) on the differentiation of intramuscular preadipocytes in goat, and to elucidate its possible action pathway at the molecular level. In this study, the recombinant plasmid of goat pEGFP-N1-ATF3 was constructed, and the intramuscular preadipocytes were transfected with liposomes. The relative expression levels of adipocyte differentiation marker genes were detected by quantitative real-time PCR (qRT-PCR). After transfection of goat intramuscular preadipocytes with the goat pEGFP-N1-ATF3 overexpression vector, it was found that the accumulation of lipid droplets was inhibited, and the adipocyte differentiation markers PPARγ, C/EBPα and SREBP1 were extremely significantly down-regulated (P < 0.01), while C/EBPß and AP2 were significantly down-regulated (P < 0.05). The ATF3 binding sites were predicted to exist in the promoter regions of PPARγ, C/EBPα and AP2 by the ALGGEN PROMO program. The overexpression of goat ATF3 inhibits the accumulation of lipid droplets in intramuscular preadipocytes, and this effect may be achieved by down-regulating PPARγ, C/EBPα and AP2. These results may facilitate elucidation of the regulatory mechanism of ATF3 in regulating the differentiation of goat intramuscular preadipocytes.

Activating transcription factor 3 mediates apoptotic functions through a p53-independent pathway in human papillomavirus 18 infected HeLa cells.

Activating transcription factor 3 (ATF3) is the first p53 stability regulator that interferes with the ubiquitination of p53. However, the E6 oncoprotein of high-risk human papillomaviruses (HPVs) binds to and induces proteasome-dependent degradation of the host p53 protein. Herein, we investigate the effects of ATF3 overexpression on cell cycle progression and apoptosis in HPV-18-infected HeLa cells, and further examine whether ATF3 could alter the apoptosis level of HeLa cells through the inhibition of E6-mediated p53 degradation. Cytological function of HeLa cells prior and subsequent to the overexpression of ATF3 was assessed using cell cycle and annexin V/PI flow cytometry analysis. Western blotting assays revealed no significant effect of ATF3 on the levels of p53 and E6 in HeLa cells. However, annexin V staining demonstrated increases in apoptosis. ATF3 acts as a tumor suppressor factor in HPV18-related cervical cancer which mediates apoptotic functions through a p53-independent pathway.

Nickel oxide nanoparticles induce apoptosis and ferroptosis in airway epithelial cells via ATF3.

Exposure to nickel oxide nanoparticles (NiONPs), which have been widely produced and applied in industry, leads to adverse pulmonary and systemic effects. The aim of this study is to investigate the involvement of apoptosis and ferroptosis in NiONPs-induced acute lung injury (ALI). Intratracheal instillation of NiONPs into mice elevated the levels of pro-inflammatory cytokines, neutrophils, and proteins in the bronchoalveolar lavage fluid, and triggered apoptosis and ferroptosis in the lung tissues. Consistently, NiONPs-induced apoptosis and ferroptosis were observed in in vitro experiments using human lung epithelial cells. Activating transcription factor 3 (ATF3), a stress-inducible transcription factor, was upregulated by NiONPs exposure in both murine lung tissues and human lung epithelial cells. Moreover, human lung epithelial cells with ATF3 deficiency exhibited a lower level of apoptosis and ferroptosis when exposed to NiONPs. Collectively, our findings demonstrated that ATF3 was responsive to NiONPs exposure, and promoted NiONPs-induced apoptosis and ferroptosis in lung epithelial cells, indicating that ATF3 is a potential biomarker and therapeutic target for NiONPs-associated ALI.

Transcriptional factor ATF3 protects against colitis by regulating follicular helper T cells in Peyer's patches.

Disruption of mucosal immunity plays a critical role in the pathogenesis of inflammatory bowel disease, yet its mechanism remains not fully elucidated. Here, we found that activating transcription factor 3 (ATF3) protects against colitis by regulating follicular helper T (TFH) cells in the gut. The expression of ATF3 in CD4+ T cells was negatively correlated with the severity of ulcerative colitis in clinical patients. Mice with ATF3 deficiency in CD4+ T cells (CD4creAtf3fl/fl ) were much more susceptible to dextran sulfate sodium-induced colitis. The frequencies of TFH cells, not other T cell subsets, were dramatically decreased in Peyer's patches from CD4creAtf3fl/fl mice compared with Atf3fl/fl littermate controls. The defective TFH cells significantly diminished germinal center formation and IgA production in the gut. Importantly, adoptive transfer of TFH or IgA+ B cells caused significant remission of colitis in CD4creAtf3fl/fl mice, indicating the TFH-IgA axis mediated the effect of ATF3 on gut homeostasis. Mechanistically, B cell lymphoma 6 was identified as a direct transcriptional target of ATF3 in CD4+ T cells. In summary, we demonstrated ATF3 as a regulator of TFH cells in the gut, which may represent a potential immunotherapeutic target in colitis.