Cadmium (Cd) is a well-recognized male reproductive toxicant that can cause testicular germ cell apoptosis. However, the underlying mechanism needs investigation. CG-1 mouse spermatogonia (spg) cells were treated with 20 μM cadmium chloride (CdCl2) for 24 h. Cell apoptosis was measured, and the expressions of key genes and protein biomarkers involved in endoplasmic reticulum (ER) stress were detected, respectively. Untargeted metabolomics was performed to identify different metabolites, and transcriptome analysis was conducted to screen differentially expressed genes (DEGs). Our results indicated that CdCl2 exposure caused cell apoptosis, and DEGs were involved in several apoptosis-related pathways. Moreover, CdCl2 exposure apparently increased the mRNA and protein expressions levels of both GRP78 and ATF6α, disrupting the expression of various metabolites, particularly amino acids. Conclusively, our study reveals the pathway of CdCl2 toxicity on mouse spg, providing a deep understanding of CdCl2-induced testicular toxicity.

Exosomes generated from mesenchymal stem cells (MSCs) are thought to be a unique therapeutic strategy for several autoimmune deficiency illnesses. The purpose of this study was to elucidate the protective effects of human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-Exo) on CD4+ T cells dysfunction during graft-versus-host disease (GVHD) and to identify the underlying processes involved. Here, we showed that hUCMSC-Exo treatment can effectively attenuate GVHD injury by alleviating redox metabolism disorders and inflammatory cytokine bursts in CD4+ T cells. Furthermore, hUCMSC-Exo ameliorate ER stress and ATF6/CHOP signaling-mediated apoptosis in CD4+ T cells and promote the development of CD4+IL-10+ T cells during GVHD. Moreover, downregulating miR-16-5p in hUCMSC-Exo impaired their ability to prevent CD4+ T cells apoptosis and weakened their ability to promote the differentiation of CD4+IL-10+ T cells. Collectively, the obtained data suggested that hUCMSC-Exo suppress ATF6/CHOP signaling-mediated ER stress and apoptosis in CD4+ T cells, enhance the differentiation of CD4+IL-10+ T cells, and reverse the imbalance of immune homeostasis in the GVHD process by transferring miR-16-5p. Our study provided further evidence that GVHD patients can benefit from hUCMSC-Exo-mediated therapy.

Intracerebral hemorrhage (ICH) comprises primary and secondary injuries, the latter of which induces increased inflammation and apoptosis and is more severe. Activating transcription factor 6 (ATF6) is a type-II transmembrane protein in the endoplasmic reticulum (ER). ATF6 target genes could improve ER homeostasis, which contributes to cryoprotection. Hence, we predict that ATF6 will have a protective effect on brain tissue after ICH.
The ICH rat model was generated through autologous blood injection into the right basal ganglia, the expression of ATF6 after ICH was determined by WB and IF. The expression of ATF6 was effectively controlled by means of intervention, and a series of measures was used to detect cell death, neuroinflammation, brain edema, blood-brain barrier and other indicators after ICH. Finally, the effects on long-term neural function of rats were measured by behavioral means.
ATF6 was significantly increased in the ICH-induced brain tissues. Further, ATF6 was found to modulate the expression of cystathionine γ-lyase (CTH) after ICH. Upregulation of ATF6 attenuated neuronal apoptosis and inflammation in ICH rats, along with mitigation of ICH-induced brain edema, blood-brain barrier deterioration, and cognitive behavior defects. Conversely, ATF6 genetic knockdown induced effects counter to those aforementioned.
This study thereby emphasizes the crucial role of ATF6 in secondary brain injury in response to ICH, indicating that ATF6 upregulation may potentially ameliorate ICH-induced secondary brain injury. Consequently, ATF6 could serve as a promising therapeutic target to alleviate clinical ICH-induced secondary brain injuries.

UNASSIGNED: ATF6-associated Achromatopsia (ACHM) is a rare autosomal recessive disorder characterized by reduction of visual acuity, photophobia, nystagmus, and poor color vision.
UNASSIGNED: Detailed ophthalmological examinations were performed in a Chinese patient with ACHM. Whole exome sequencing and Sanger sequencing were performed to detect the disease-causing gene in the patient.
UNASSIGNED: A 6-year-old girl presented photophobia, low vision and reduced color discrimination. Small yellow lesion in the macula of both eyes was observed. FAF demonstrated hypofluorescence in the macular fovea. OCT images revealed interruption of ellipsoid and interdigitation zone in the foveal area and a loss of the foveal pit. ERG showed relatively normal rod responses and unrecordable cone responses. Sequencing result identified a novel splicing variant c.354 + 6T>C in the ATF6 gene (NM_007348.4).
UNASSIGNED: We reported detailed clinical features and genetic analysis of a new Chinese ATF6-associated patient with ACHM.

Mammalian arenaviruses are rodent-borne zoonotic viruses, some of which can cause fatal hemorrhagic diseases in humans. The first discovered arenavirus, lymphocytic choriomeningitis virus (LCMV), has a worldwide distribution and can be fatal for transplant recipients. However, no FDA-approved drugs or vaccines are currently available. In this study, using a quantitative proteomic analysis, we identified a variety of host factors that could be needed for LCMV infection, among which we found that protein disulfide isomerase A4 (PDIA4), a downstream factor of endoplasmic reticulum stress (ERS), is important for LCMV infection. Biochemical analysis revealed that LCMV glycoprotein was the main viral component accounting for PDIA4 upregulation. The inhibition of ATF6-mediated ERS could prevent the upregulation of PDIA4 that was stimulated by LCMV infection. We further found that PDIA4 can affect the LCMV viral RNA synthesis processes and release. In summary, we conclude that PDIA4 could be a new target for antiviral drugs against LCMV.

Activating transcription factor 6 (ATF6) is critical for regulation of unfolded protein response (UPR), which is involved in the endoplasmic reticulum (ER) proteostasis maintenance and cellular redox regulation. In the present study, a ATF6 gene from the mud crab (designated as Sp-ATF6) has been cloned and identified. The open reading frame of Sp-ATF6 was 1917 bp, encoding a protein of 638 amino acids. The deduced amino acid sequences of Sp-ATF6 contained a typical basic leucine zipper (BZIP domain). Sp-ATF6 was widely expressed in all tested tissues, with the highest expression levels in the hemocytes and the lowest in the muscle. Subcellular localization showed that Sp-ATF6 was expressed in both nucleus and cytoplasm of S2 cells. The expression level of Sp-ATF6 was induced by hydrogen peroxide and V. parahaemolyticus challenge, indicating that the ATF6 pathway was activated in response to ER stress. In order to know more about the regulation mechanism of the Sp-ATF6, RNA interference experiment was investigated. Knocking down Sp-ATF6 in vivo can decrease the expression of antioxidant-related genes (CAT and SOD) and heat shock proteins (HSP90 and HSP70) after V. parahaemolyticus infection. All these results suggested that Sp-ATF6 played a crucial role in the defense against environmental stress and pathogen infection in crustaceans.

Diabetic cardiomyopathy (DCM) is a challenging diabetic complication that manifests as chronic inflammation. Yet, the mechanism underlying diabetes-associated myocardial injury is not fully understood. We investigated the pharmacological effects and mechanisms of linderalactone, a natural compound that can prevent diabetes-induced cardiomyopathy in mice. Diabetes was induced by a single dose of streptozotocin (120 mg/kg, i.p.). Diabetic mice were administrated with linderalactone (2.5 or 5 mg/kg) by gavage for five weeks. Harvested heart tissues were then subjected to RNA-sequencing analysis to explore the potential mechanism of linderalactone. Linderalactone prevented heart dysfunction by inhibiting myocardial hypertrophy, fibrosis, and inflammation, without altering blood glucose. RNA-sequencing indicated that linderalactone exerted its cardioprotective effects mainly by affecting the mitogen-activated protein kinase (MAPK)/ activating transcription factor 6 (ATF6) pathway. Linderalactone also suppressed endoplasmic reticulum (ER) stress mediated by the diabetes-activated MAPKs/ATF6 pathway, thereby reducing myocardial hypertrophy and inflammation in heart tissues and in cultured cardiomyocytes. Inhibition of MAPKs or a deficiency of ATF6 in cardiomyocytes mimicked the linderalactone-associated decreases in high glucose-induced hypertrophy and inflammation. Linderalactone showed beneficial effects in alleviating diabetic cardiomyopathy, in part by modulating the MAPK/ATF6 signaling pathway to mitigate myocardial hypertrophy and inflammation. Linderalactone may have clinical utility in the treatment for diabetes-associated cardiomyopathy.

UNASSIGNED: Ocular axial elongation is one of the features of myopia progression. Endoplasmic reticulum (ER) stress-associated scleral remodeling plays an important role in ocular axial elongation. Bisphenol A (BPA) is one of the most common environmental pollutants and is known to affect various human organs through ER stress. However, whether BPA exerts an effect on scleral remodeling remains unknown. The purpose of this study was to determine the effect of BPA on the development of myopia and scleral ER stress.
UNASSIGNED: BPA was administered by intraperitoneal injection. 4-PBA was administered as an endoplasmic reticulum stress inhibitor by eye drops. Refraction and axial length were measured by refractometer and SD-OCT system. Western blot was performed to detect the expression level of ER stress-related proteins.
UNASSIGNED: BPA-administered mice exhibit axial elongation and myopic refractive shift with endoplasmic reticulum stress in the sclera. BPA administration activated scleral PERK and ATF6 pathways, and 4-PBA eye drops attenuated ER stress response and suppressed myopia progression.
UNASSIGNED: BPA controlled axial elongation during myopia development in a mouse model by inducing scleral ER stress and activation of the PERK/ATF6 pathway. 4-PBA eye drops as ER stress inhibitor suppressed BPA-induced myopia development.

To address the molecular mechanisms underlying macrophage migration inhibitory factor (MIF) induced pulmonary artery smooth muscle cells (PASMCs) proliferation, migration and vascular remodeling in pulmonary hypertension (PH), primary cultured rat PASMCs and monocrotaline (MCT)-induced rats with PH were applied in the present study. The results showed that MIF increased signal transducer and activator of transcription 3 (STAT3) phosphorylation, and then stimulated activating transcription factor 6 (ATF6) activation, subsequently triggered autophagy activation, which further led to programmed cell death factor 4 (PDCD4) lysosomal degradation, and eventually promoted PASMCs proliferation/migration. In lung tissues of MCT rats, MIF protein expression was elevated, phosphorylation of STAT3 and activation of ATF6 were increased, activation of autophagy was evident, and reduction of PDCD4 was observed. Intervention with MIF inhibitor 4-Iodo-6-phenylpyrimidine (4-IPP), ATF6 blocker melatonin or autophagy inhibitor chloroquine, confirmed the in vitro interaction among MIF, STAT3, ATF6, autophagy and PDCD4 in MCT induced rats with PH. Targeting MIF/STAT3/ATF6/autophagy/PDCD4 axis effectively prevented the development of PH by suppressing PASMCs proliferation and vascular remodeling. In conclusions, we demonstrate that MIF activates the STAT3/ATF6/autophagy cascade and then degrades PDCD4 leading to PASMCs proliferation/migration and pulmonary vascular remodeling, suggesting that intervention this axis might have potential value in management of PH.

Activating transcription factor 6 (ATF6), one of the three sensor proteins in the endoplasmic reticulum (ER), is an important regulator of ER stress-induced apoptosis. ATF6 resides in the ER and, upon activation, is translocated to the Golgi apparatus, where it is cleaved by site-1 protease (S1P) to generate an amino-terminal cytoplasmic fragment. Although recent studies have made progress in elucidating the regulatory mechanisms of ATF6, its function during early porcine embryonic development under high-temperature (HT) stress remains unclear. In this study, zygotes were divided into four groups: control, HT, HT+ATF6 knockdown, and HT+PF (S1P inhibitor). Results showed that HT exposure induced ER stress, which increased ATF6 protein expression and led to a decrease in the blastocyst rate. Next, ATF6 expression was knocked down in HT embryos under microinjection of ATF6 double-stranded RNA (dsRNA). Results revealed that ATF6 knockdown (ATF6-KD) attenuated the increased expression of CHOP, an ER stress marker, and Ca 2+ release induced by HT. In addition, ATF6-KD alleviated homeostasis dysregulation among organelles caused by HT-induced ER stress, and further reduced Golgi apparatus and mitochondrial dysfunction in HT embryos. AIFM2 is an important downstream effector of ATF6. Results showed that ATF6-KD reduced the occurrence of AIFM2-mediated embryonic apoptosis at HT. Taken together, our findings suggest that ATF6 is a crucial mediator of apoptosis during early porcine embryonic development, resulting from HT-induced ER stress and disruption of organelle homeostasis.
激活转录因子 6 (activating transcription factor 6，ATF6) 是内质网中的三种传感器蛋白之一，是内质网应激诱导细胞凋亡的重要调节因子。 ATF6位于内质网中并在激活后转移到高尔基体，在那里它被 site-1-蛋白酶 (S1P) 切割以生成氨基末端胞质片段。 尽管最近的研究已在ATF6的调控机制方面取得了进展，但ATF6在高温(high temperature，HT) 情况下，对猪早期胚胎发育过程的影响还不清楚。在该研究中，胚胎被分为四组：对照组、HT组、HT+ATF6-KD组和 HT+PF（S1P抑制剂）组。结果表明，HT暴露诱导胚胎内质网应激，从而增加 ATF6 蛋白表达并导致囊胚率降低。由于显微注射ATF6 dsRNA，ATF6的表达水平在HT胚胎中被敲低，结果显示，ATF6-KD可以减弱由HT所导致的CHOP（内质网应激标记物）的表达增加以及Ca 2+的释放。 此外，ATF6-KD还减轻了HT诱导的ER应激所引起的细胞器稳态失衡，数据还显示ATF6-KD减少了HT胚胎中的高尔基体和线粒体功能障碍。AIFM2作为ATF6的重要下游蛋白，ATF6-KD减少了AIFM2介导的HT胚胎凋亡的发生。总之，这些结果表明 ATF6 是早期猪胚胎发育过程中，由 HT诱导的内质网应激和细胞器稳态失衡所引起细胞凋亡的重要介质。.