Expression Of Endoplasmic Reticulum Research Articles

Proteome profiling of cutaneous leishmaniasis lesions due to dermotropic Leishmania donovani in Sri Lanka

BackgroundCharacterization of the host response in cutaneous leishmaniasis (CL) through proteome profiling has gained limited insights into leishmaniasis research compared to that of the parasite. The primary objective of this study was to comprehensively analyze the proteomic profile of the skin lesions tissues in patients with CL, by mass spectrometry, and subsequent validation of these findings through immunohistochemical methods.MethodsEight lesion specimens from leishmaniasis-confirmed patients and eight control skin biopsies were processed for proteomic profiling by mass spectrometry. Formalin-fixed paraffin-embedded lesion specimens from thirty patients and six control skin specimens were used for Immunohistochemistry (IHC) staining. Statistical analyses were carried out using SPSS software. The chi-square test was used to assess the association between the degree of staining for each marker and the clinical and pathological features.ResultsSixty-seven proteins exhibited significant differential expression between tissues of CL lesions and healthy controls (p < 0.01), representing numerous enriched biological processes within the lesion tissue, as evident by both the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Reactome databases. Among these, the integrated endoplasmic reticulum stress response (IERSR) emerges as a pathway characterized by the up-regulated proteins in CL tissues compared to healthy skin. Expression of endoplasmic reticulum (ER) stress sensors, inositol-requiring enzyme-1 (IRE1), protein kinase RNA-like ER kinase (PERK) and activating transcription factor 6 (ATF6) in lesion tissue was validated by immunohistochemistry.ConclusionsIn conclusion, proteomic profiling of skin lesions carried out as a discovery phase study revealed a multitude of probable immunological and pathological mechanisms operating in patients with CL in Sri Lanka, which needs to be further elaborated using more in-depth and targeted investigations. Further research exploring the intricate interplay between ER stress and CL pathophysiology may offer promising avenues for the development of novel diagnostic tools and therapeutic strategies in combating this disease.

Cell division cyclin 25C knockdown inhibits hepatocellular carcinoma development by inducing endoplasmic reticulum stress.

Cell division cyclin 25C (CDC25C) is a protein that plays a critical role in the cell cycle, specifically in the transition from the G2 phase to the M phase. Recent research has shown that CDC25C could be a potential therapeutic target for cancers, particularly for hepatocellular carcinoma (HCC). However, the specific regulatory mechanisms underlying the role of CDC25C in HCC tumorigenesis and development remain incompletely understood. To explore the impact of CDC25C on cell proliferation and apoptosis, as well as its regulatory mechanisms in HCC development. Hepa1-6 and B16 cells were transduced with a lentiviral vector containing shRNA interference sequences (LV-CDC25C shRNA) to knock down CDC25C. Subsequently, a xenograft mouse model was established by subcutaneously injecting transduced Hepa1-6 cells into C57BL/6 mice to assess the effects of CDC25C knockdown on HCC development in vivo. Cell proliferation and migration were evaluated using a Cell Counting Kit-8 cell proliferation assays and wound healing assays, respectively. The expression of endoplasmic reticulum (ER) stress-related molecules (glucose-regulated protein 78, X-box binding protein-1, and C/EBP homologous protein) was measured in both cells and subcutaneous xenografts using quantitative real-time PCR (qRT-PCR) and western blotting. Additionally, apoptosis was investigated using flow cytometry, qRT-PCR, and western blotting. CDC25C was stably suppressed in Hepa1-6 and B16 cells through LV-CDC25C shRNA transduction. A xenograft model with CDC25C knockdown was successfully established and that downregulation of CDC25C expression significantly inhibited HCC growth in mice. CDC25C knockdown not only inhibited cell proliferation and migration but also significantly increased the ER stress response, ultimately promoting ER stress-induced apoptosis in HCC cells. The regulatory mechanism of CDC25C in HCC development may involve the activation of ER stress and the ER stress-induced apoptosis signaling pathway.

Endoplasmic reticulum stress response in immune cells contributes to experimental autoimmune encephalomyelitis pathogenesis in rats

We examined the role of endoplasmic reticulum (ER) stress and the ensuing unfolded protein response (UPR) in the development of the central nervous system (CNS)-directed immune response in the rat model of experimental autoimmune encephalomyelitis (EAE). The induction of EAE with syngeneic spinal cord homogenate in complete Freund's adjuvant (CFA) caused a time-dependent increase in the expression of ER stress/UPR markers glucose-regulated protein 78 (GRP78), X-box-binding protein 1 (XBP1), C/EBP homologous protein (CHOP), and phosphorylated eukaryotic initiation factor 2α (eIF2α) in the draining lymph nodes of both EAE-susceptible Dark Agouti (DA) and EAE-resistant Albino Oxford (AO) rats. However, the increase in ER stress markers was more pronounced in AO rats. CFA alone also induced ER stress, but the effect was weaker and less sustained compared to full immunization. The ultrastructural analysis of DA lymph node tissue by electron microscopy revealed ER dilatation in lymphocytes, macrophages, and plasma cells, while immunoblot analysis of CD3-sorted lymph node cells demonstrated the increase in ER stress/UPR markers in both CD3+ (T cell) and CD3− (non-T) cell compartments. A positive correlation was observed between the levels of ER stress/UPR markers in the CNS-infiltrated mononuclear cells and the clinical activity of the disease. Finally, the reduction of EAE clinical signs by ER stress inhibitor ursodeoxycholic acid was associated with the decrease in the expression of mRNA encoding pro-inflammatory cytokines TNF and IL-1β, and encephalitogenic T cell cytokines IFN-γ and IL-17. Collectively, our data indicate that ER stress response in immune cells might be an important pathogenetic factor and a valid therapeutic target in the inflammatory damage of the CNS.

Norcantharidin inhibits the malignant progression of cervical cancer by inducing endoplasmic reticulum stress.

The antitumor effect of norcantharidin (NCTD) has been widely reported. However, whether NCTD can inhibit cervical cancer remains unknown. In the present study, it was shown that NCTD inhibited the viability of cervical cancer cells and caused cell cycle arrest in a concentration‑dependent manner. Further analysis revealed that the NCTD‑induced reduction in cell viability could be reversed by the inhibitor of apoptosis z‑VAD‑FMK and by the inhibitor of endoplasmic reticulum (ER) stress, 4‑phenylbutyric acid (4‑PBA). Additionally, NCTD led to the accumulation of reactive oxygen species as well as a decrease in the mitochondrial membrane potential in cervical cancer cells, whereas 4‑PBA pre‑treatment attenuated these alterations. In addition, NCTD increased the expression of the apoptosis‑related proteins Bip, activating transcription factor (ATF) 4 and C/EBP homologous protein in a concentration‑dependent manner. Moreover, NCTD significantly increased the expression of the ER stress‑related signaling molecules protein kinase R‑like ER kinase, inositol‑requiring enzyme 1 and ATF6, but 4‑PBA abolished these effects. Invivo experiments showed that NCTD significantly inhibited the growth of subcutaneous tumors in mice. Additionally, the expression of ER stress‑related molecules and apoptosis‑related proteins increased significantly after NCTD treatment. In conclusion, NCTD induces apoptosis by activating ER stress and ultimately curtails the progression of cervical cancer.

Protective Effects of Inulin on Stress-Recurrent Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the digestive tract and is closely associated with the homeostasis of the gut microbiota. Inulin, as a natural prebiotic, displays anti-inflammatory activity and maintains equilibrium of the intestinal microbiota. In this study, our research aimed to explore the potential of inulin in enhancing intestinal immunity and reducing inflammation in stress-recurrent IBD. In this study, a co-culture intestinal epithelium model and a stress-recurrent IBD mouse model was used to examine the protective effects of inulin. It was observed that inulin digesta significantly reduced pro-inflammatory cytokine expression (CXCL8/IL8 and TNFA) and increased MUC2 expression in intestinal epithelial cells. In vivo, our findings showed that Inulin intake significantly prevented IBD symptoms. This was substantiated by a decrease in serum inflammatory markers (IL-6, CALP) and a downregulation of inflammatory cytokine (Il6) in colon samples. Additionally, inulin intake led to an increase in short-chain fatty acids (SCFAs) in cecal contents and a reduction in the expression of endoplasmic reticulum (ER) stress markers (CHOP, BiP). Our results highlight that inulin can improve stress-recurrent IBD symptoms by modulating microbiota composition, reducing inflammation, and alleviating ER stress. These findings suggested the therapeutic potential of inulin as a dietary intervention for ameliorating stress-recurrent IBD.

Licochalcone A induces endoplasmic reticulum stress-mediated apoptosis of endometrial cancer cells via upregulation of GRP78 expression.

Licochalcone A (LicA), a natural compound extracted from licorice root, has been shown to exert a variety of anticancer activities. Whether LicA has such effects on endometrial cancer (EMC) is unclear. This study aims to investigate the antitumor effects of LicA on EMC. Our results show that LicA significantly reduced the viability and induced apoptosis of EMC cells and EMC-7 cells from EMC patients. LicA was also found to induce endoplasmic reticulum (ER) stress, leading to increased expression of ER-related proteins (GRP78/PERK/IRE1α/CHOP) in EMC cell lines. Suppression of GRP78 expression in human EMC cells treated with LicA significantly attenuated the effects of LicA, resulting in reduced ER-stress mediated cell apoptosis and decreased expression of ER- and apoptosis-related proteins. Our findings demonstrate that LicA induces apoptosis in EMC cells through the GRP78-mediated ER-stress pathway, emphasizing the potential of LicA as an anticancer therapy for EMC.

Protein tyrosine phosphatase 1B contributes to neuropathic pain by aggravating NF-κB and glial cells activation-mediated neuroinflammation via promoting endoplasmic reticulum stress.

Neuropathic pain is a prevalent and highly debilitating condition that impacts millions of individuals globally. Neuroinflammation is considered a key factor in the development of neuropathic pain. Accumulating evidence suggests that protein tyrosine phosphatase 1B (PTP1B) plays a crucial role in regulating neuroinflammation. Nevertheless, the specific involvement of PTP1B in neuropathic pain remains largely unknown. This study aims to examine the impact of PTP1B on neuropathic pain and unravel the underlying molecular mechanisms implicated. In the current study, we evaluated the paw withdrawal threshold (PWT) of male rats following spared nerve injury (SNI) to assess the presence of neuropathic pain. To elucidate the underlying mechanisms, western blotting, immunofluorescence, and electron microscopy techniques were employed. Our results showed that SNI significantly elevated PTP1B levels, which was accompanied by an increase in the expression of endoplasmic reticulum (ER) stress markers (BIP, p-PERK, p-IRE1α, and ATF6) and phosphorylated NF-κB in the spinal dorsal horn. SNI-induced mechanical allodynia was impaired by the treatment of intrathecal injection of PTP1B siRNA or PTP1B-IN-1, a specific inhibitor of PTP1B. Moreover, the intrathecal administration of PTP1B-IN-1 effectively suppressed the expression of ER stress markers (BIP, p-PERK/p-eIF2α, p-IRE1α, and ATF6), leading to the inhibition of NF-κB, microglia, and astrocytes activation, as well as a decrease in pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β. However, these effects were reversed by intrathecal administration of tunicamycin (Tm, an inducer of ER stress). Additionally, intrathecal administration of Tm in healthy rats resulted in the development of mechanical allodynia and the activation of NF-κB-mediated neuroinflammatory signaling. The upregulation of PTP1B induced by SNI facilitates the activation of NF-κB and glial cells via ER stress in the spinal dorsal horn. This, in turn, leads to an increase in the production of pro-inflammatory cytokines, thereby contributing to the development and maintenance of neuropathic pain. Therefore, targeting PTP1B could be a promising therapeutic strategy for the treatment of neuropathic pain.

Abstract C018: Spatial profiling of tumor associated cells expressing endoplasmic reticulum stress proteins predicts poor outcomes in pancreatic cancer patients

Abstract The crosstalk between pancreatic cancer (PC) cells and cells of the tumor microenvironment (TME), such as immune cells and cancer associated fibroblasts (CAFs), has important implications for tumor progression. It is evident that the expression of endoplasmic reticulum (ER) stress proteins (e.g., BiP or CHOP) in tumor cells has survival implications for patients. For example, high BiP expression in tumor cells is correlated with poor survival in PC patients. However, the effect of these proteins in TME cells is currently unknown. We have employed quantitative multiplex immunofluorescence on a tumor microarray cohort of 259 treatment naive pancreatic cancer patient samples and 41 normal pancreas samples. We investigated the impact of expression of ER stress proteins BiP or CHOP in CAFS (α-SMA+), immune cells (CD45+), endothelial cells (CD31+) and tumor cells (PanCK+). HALO AI (Indica Labs) was used to conduct cell/tissue classifications and spatial proximity analysis. Notably, the proportion of CAFs and endothelial cells expressing BiP or CHOP was significantly (p&amp;lt;0.01-0.0001) increased in tumor sections compared to non-tumor sections. When considering the tumor sections, increased BiP expression in CAFs and endothelial cells was found to be correlated with vascular invasion (p=0.0388 and p=0.0318 respectively). Interestingly, there was also a positive correlation between the percent of total CAFs and the percent of BiP positive cells (p=0.0037, r=0.293) or CHOP positive cells (p=0.0001, r=0.235), suggesting that ER stress could be associated with activation of CAFs. Spatial analysis was next utilized to explore the distribution of cells expressing BiP or CHOP within the TME. Remarkably, when examining the average distance in a 500 μm radius, our findings showed that immune cells expressing BiP or CHOP were located significantly (p&amp;lt;0.0001) closer to tumor cells compared to non-expressing immune cells. Interestingly, increased distance of CHOP expressing immune cells to tumor cells was negatively correlated (p=0.037, r=-0.137) with tumor size. We next examined these cells within a 20 μm radius of tumor cells, as it represents a physiologically feasible distance for direct cell-cell contact. Increased numbers of CHOP CD45 cells within the 20 μm radius was correlated with poorer overall survival (p=0.0062) and event free survival (p=0.046). Similarly, in CAFS, BiP expressing cells were found on average closer to tumor cells (p&amp;lt;0.0001), although this was not associated with patient survival. The observed correlation between elevated ER stress in TME cells with adverse patient outcomes indicates the importance of BiP or CHOP as potential therapeutic targets. Furthermore, the spatial analysis results provide insights into the organization of TME cells, shedding light on the significance of ER stress in the TME. These findings contribute to our understanding of the complex interplay between ER stress, tumor biology, and patient outcomes in PC. Citation Format: Georgia M. Porter, Murray Norris, Minoti Apte, Angelica Merlot. Spatial profiling of tumor associated cells expressing endoplasmic reticulum stress proteins predicts poor outcomes in pancreatic cancer patients [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C018.

Glycyrrhizin alleviates radiation-induced lung injury by regulating the NLRP3 inflammasome through endoplasmic reticulum stress.

Radiation pneumonitis (RP) is the major adverse response of radiation therapy for thoracic malignant tumors, and there is a lack of effective interventions. The aim of this study was to investigate the radioprotective effect of Glycyrrhizin (GL) on RP and its potential mechanism. The body weight and lung weight of mice were monitored. HE staining was used to observe lung injury, and the expression of endoplasmic reticulum (ER) stress biomarkers and the activation of NLRP3 inflammasome were determined by Western blotting and immunohistochemistry. Flow cytometry was performed to check MLE-12 apoptosis. ER stress activator, Tunicamycin (Tuni), was used to verify the potential mechanism of GL. A systemic pharmacology explored the potential targets and pathways of GL. In this study, the lungs of irradiated mice showed significant pneumonic changes. In vivo and in vitro assay, NLRP3 inflammasome was significantly activated, the expression of ER stress biomarkers was elevated, flow cytometry confirms increased apoptosis in irradiated MLE-12 cells. GL inhibits the activation of NLRP3 inflammasome and ER stress pathways. Furthermore, systemic pharmacology revealed that the radioprotective effect of GL may be related to the MAPK signaling pathway. In the present study, the results indicated that GL may regulate NLRP3 inflammasome through ER stress, thus exerting irradiation-protective effects on RP, and the ER stress pathway may be a potential target for RP treatment.

NOTCH1-mutated chronic lymphocytic leukemia displays high endoplasmic reticulum stress response with druggable potential.

Constitutive activation of NOTCH1-wild-type (NT1-WT) signaling is associated with poor outcomes in chronic lymphocytic leukemia (CLL), and NOTCH1 mutation (c.7541_7542delCT), which potentiates NOTCH1 signaling, worsens the prognosis. However, the specific mechanisms of NOTCH1 deregulation are still poorly understood. Accumulative evidence mentioned endoplasmic reticulum (ER) stress/unfolded protein response (UPR) as a key targetable pathway in CLL. In this study, we investigated the impact of NOTCH1 deregulation on CLL cell response to ER stress induction, with the aim of identifying new therapeutic opportunities for CLL. We performed a bioinformatics analysis of NOTCH1-mutated (NT1-M) and NT1-WT CLL to identify differentially expressed genes (DEGs) using the rank product test. Quantitative real-time polymerase chain reaction (qPCR), Western blotting, cytosolic Ca2+, and annexin V/propidium iodide (PI) assay were used to detect curcumin ER stress induction effects. A median-effect equation was used for drug combination tests. The experimental mouse model Eμ-TCL1 was used to evaluate the impact of ER stress exacerbation by curcumin treatment on the progression of leukemic cells and NOTCH1 signaling. Bioinformatics analysis revealed gene enrichment of the components of the ER stress/UPR pathway in NT1-M compared to those in NT1-WT CLL. Ectopic expression of NOTCH1 mutation upregulated the levels of ER stress response markers in the PGA1 CLL cell line. Primary NT1-M CLL was more sensitive to curcumin as documented by a significant perturbation in Ca2+ homeostasis and higher expression of ER stress/UPR markers compared to NT1-WT cells. It was also accompanied by a significantly higher apoptotic response mediated by C/EBP homologous protein (CHOP) expression, caspase 4 cleavage, and downregulation of NOTCH1 signaling in NT1-M CLL cells. Curcumin potentiated the apoptotic effect of venetoclax in NT1-M CLL cells. In Eμ-TCL1 leukemic mice, the administration of curcumin activated ER stress in splenic B cells ex vivo and significantly reduced the percentage of CD19+/CD5+ cells infiltrating the spleen, liver, and bone marrow (BM). These cellular effects were associated with reduced NOTCH1 activity in leukemic cells and resulted in prolonged survival of curcumin-treated mice. Overall, our results indicate that ER stress induction in NT1-M CLL might represent a new therapeutic opportunity for these high-risk CLL patients and improve the therapeutic effect of drugs currently used in CLL.

Positive Allosteric Modulator of SERCA Pump NDC-1173 Exerts Beneficial Effects in Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is an irreversible neurodegenerative disease that affects millions of people worldwide. AD does not have a cure and most drug development efforts in the AD field have been focused on targeting the amyloid pathway based on the "amyloid cascade hypothesis". However, in addition to the amyloid pathway, substantial evidence also points to dysregulated neuronal calcium (Ca2+) signaling as one of the key pathogenic events in AD, and it has been proposed that pharmacological agents that stabilize neuronal Ca2+ signaling may act as disease-modifying agents in AD. In previous studies, we demonstrated that positive allosteric regulators (PAMs) of the Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) pump might act as such Ca2+ stabilizing agents. In the present study, we report the development of a novel SERCA PAM agent, compound NDC-1173. To test the effectiveness of this compound, we performed behavioral studies with the APP/PS1 transgenic AD mouse model. We also evaluated effects of this compound on expression of endoplasmic reticulum (ER) stress genes in the hippocampus of APP/PS1 mice. The results of this study support the hypothesis that the SERCA pump is a potential novel therapeutic drug target and that NDC-1173 is a promising lead molecule for developing disease-modifying agents in AD.

Tl(I) and Tl(III) induce reticulum stress in MDCK cells

The effects of the exposure of proliferating MDCK cells to thallium [Tl(I) or Tl(III)] on cell viability and proliferation were investigated. Although Tl stopped cell proliferation, the viability was > 95%. After 3 h, two autophagy markers (SQSTM-1 expression and LC3β localization) were altered, and at 48 h increased expression of SQSTM-1 (60%) and beclin-1 (50–100%) were found. At 24 h, the expression of endoplasmic reticulum (ER) stress markers ATF-6 and IRE-1 were increased in 100% and 150%, respectively, accompanied by XBP-1 splicing and nuclear translocation. At 48 h, major ultrastructure abnormalities were found, including ER enlargement and cytoplasmic vacuolation which was not prevented by protein synthesis inhibition. Increased PHB (85% and 40% for Tl(I) and Tl(III), respectively) and decreased β-tubulin (45%) expression were found which may be related to the promotion of paraptosis. In summary, Tl(I) and Tl(III) promoted ER stress and probably paraptosis in MDCK cells, impairing their proliferation.

Architecture and dynamics of a desmosome-endoplasmic reticulum complex.

The endoplasmic reticulum (ER) forms a dynamic network that contacts other cellular membranes to regulate stress responses, calcium signalling and lipid transfer. Here, using high-resolution volume electron microscopy, we find that the ER forms a previously unknown association with keratin intermediate filaments and desmosomal cell-cell junctions. Peripheral ER assembles into mirror image-like arrangements at desmosomes and exhibits nanometre proximity to keratin filaments and the desmosome cytoplasmic plaque. ER tubules exhibit stable associations with desmosomes, and perturbation of desmosomes or keratin filaments alters ER organization, mobility and expression of ER stress transcripts. These findings indicate that desmosomes and the keratin cytoskeleton regulate the distribution, function and dynamics of the ER network. Overall, this study reveals a previously unknown subcellular architecture defined by the structural integration of ER tubules with an epithelial intercellular junction.

Endoplasmic reticulum stress in the adipose tissue and monocyte chemoattractant protein-1 are involved in tacrolimus-induced diabetes mellitus.

Tacrolimus is an independent risk factor for new-onset diabetes after transplantation (NODAT). This study aimed to identify the mechanisms underlying tacrolimus-induced NODAT. About 80 kidney-transplant patients receiving tacrolimus were divided into NODAT and non-NODAT groups after 1 year. Binary logistic regression was used to identify risk factors for NODAT. Insulin resistance indices were estimated using the homeostasis model assessment. The blood levels of 13 adipocytokines were measured 1 week after transplantation. A tacrolimus-induced diabetes mouse model was used to reveal the underlying mechanisms. The cumulative NODAT incidence was 12.7% at 1 year (median, 6 months; range, 3-12 months). Tacrolimus trough levels ≥10 ng/mL during the first 3 months (odds ratio: 2.54, p = .012) were related to NODAT. Insulin resistance indices were higher in NODAT patients than in non-NODAT patients at 3, 6, and 12 months. Monocyte chemoattractant protein (MCP)-1 was overexpressed in blood in NODAT patients. In the animal experiments, postprandial blood glucose and insulin levels, insulin pathway protein levels in adipose tissue, MCP-1 expression in blood and adipose tissue, and number of macrophages in adipose tissue were markedly higher in tacrolimus-treated mice than in control mice, and these increases were dose-dependent. The expression of endoplasmic reticulum (ER) stress proteins in adipose tissue was increased in a tacrolimus dose-dependent manner. In conclusion, tacrolimus-induced insulin resistance. Tacrolimus trough levels ≥10 ng/mL during the first 3 postoperative months were an independent risk factor for NODAT. ER stress and MCP-1 underlie tacrolimus-induced diabetes.

Asthmatic lung fibroblasts promote type 2 immune responses via endoplasmic reticulum stress response dependent thymic stromal lymphopoietin secretion.

Lung fibroblasts contribute to asthma pathology partly through modulation of the immune environment in the airway. Tumor necrosis factor-α (TNFα) expression is upregulated in asthmatic lungs. How asthmatic lung fibroblasts respond to TNFα stimulation and subsequently regulate immune responses is not well understood. Endoplasmic reticulum (ER) stress and unfolded protein responses (UPR) play important roles in asthma, but their functional roles are still under investigation. In this study, we investigated TNFα-induced cytokine production in primary lung fibroblasts from asthmatic vs. non-asthmatic human subjects, and downstream effects on type 2 immune responses. TNFα significantly upregulated IL-6, IL-8, C-C motif chemokine ligand 5 (CCL5), and thymic stromal lymphopoietin (TSLP) mRNA expression and protein secretion by lung fibroblasts. Asthmatic lung fibroblasts secreted higher levels of TSLP which promoted IL-33-induced IL-5 and IL-13 production by peripheral blood mononuclear cells. TNFα exposure enhanced expression of ER stress/UPR pathways in both asthmatic and non-asthmatic lung fibroblasts, especially inositol-requiring protein 1α in asthmatics. ER stress/UPR inhibitors decreased IL-6, CCL5, and TSLP protein secretion by asthmatic lung fibroblasts. Our data suggest that TNFα and lung fibroblasts form an important axis in asthmatic lungs to promote asthmatic inflammation that can be attenuated by inhibiting ER stress/UPR pathway.

A FAM46C-Dependent Molecular Circuit Modulates Antibody Synthesis and Proliferation in Plasma Cell Dyscrasias

Plasma cells (PCs) are the terminal effectors of B lymphocyte differentiation in charge of antibody production. Such intensive task requires rapid endoplasmic reticulum (ER) expansion and the concerted induction of the machinery affording ER import, folding, and trafficking along the secretory route. Moreover, the by-products of massive immunoglobulin (Ig) production cause a peculiar dependence of PCs on protein degradative pathways with a crucial clinical consequence: theextraordinary success of proteasome inhibitors against multiple myeloma (MM) and systemic light chain amyloidosis (AL). Notably, an essential player in the proteomic reshaping occurring during PC differentiation is the non-canonical poly(A)polymerase FAM46C/TENT5C. Upon B cell activation, FAM46C is induced to polyadenylate and stabilize mRNAs encoding Igs and ER-targeted proteins, thus promoting humoral immune responses (Mroczek et al., 2017; Bilska et al., 2020). Interestingly, FAM46C locus on chromosome 1p12 is mutated or deleted in up to 20% MM patients (Chapman et al., 2011; Boyd et al., 2011, Barbieri et al., 2016), suggesting that MM cells are subject to a selective pressure to restrict FAM46C expression and activity, to ultimately curb Ig synthesis and secretion in favor of cell survival and tumor growth. Accordingly, exogenous re-expression of FAM46C in mutated MM cells raised the secretory capacity beyond sustainability, resulting in intracellular ATP reduction, ROS accumulation and increased apoptotic susceptibility (Fucci et al., 2020). Our research aims to discover the precise molecular circuits, centered on FAM46C, regulating PC secretory capacity in efficient coordination with degradative pathways, to discover unprecedented vulnerabilities of PCs and new therapeutic opportunities against PC dyscrasias. To clarify the molecular mechanisms underlying the effects of FAM46C on Ig secretion we combined cutting-edge protein biochemistry, imaging and unbiased proteomic assays and adopted in vitro and in vivo models of MM and AL. In these models, we disclosed that FAM46C concertedly promotes the expression of ER and Golgi proteins, potently expanding the secretory apparatus and light chain (LC) secretion. To assess the impact of FAM46C on PC proliferation and disease progression in vivo, we silenced or overexpressed FAM46C in AMLC-2 cells that bear a hemizygous loss in 1p12 region (Arendt et al., 2008). Following intravenous injection into Rag2-/- IL2rg-/- mice, we found remarkably reduced tumor growth and longer survival in recipients of FAM46C-overexpressing cells, despite higher initial circulating LC levels, as compared to other groups. Moreover, we observed intermediate disease progression in mice receiving mock-transduced ALMC-2 cells, attesting to dose-dependent impact of FAM46C. The in vivo association of higher secretory activity with drastically decreased PC proliferation reveals that FAM46C uncouples monoclonal component levels from disease burden. Finally, among FAM46C-modulated proteins, we found SRP components and RNA methyltransferases involved in ribosome assembly and tRNA processing. The data unveil a new role played by FAM46C in PCs, in addition to its mRNA stabilizing activity, indicating the existence of a previously unrecognized integrated network coordinating ribosome biogenesis, protein translation, and ER expansion, potentially crucial to harmonize intensive protein secretion with cellular homeostasis. Altogether, our studies disclose an unexpected molecular circuit orchestrating Ig synthesis and secretion, and regulating PC proliferation and survival that may be exploited to design new therapeutic strategies aimed to reduce pathogenic LC production, to eliminate MM and AL cells, and to improve the efficacy of current therapeutic regimens.

Inhibition of USP1 activates ER stress through Ubi-protein aggregation to induce autophagy and apoptosis in HCC

The deubiquitinating enzyme USP1 (ubiquitin-specific protease 1) plays a role in the progression of various tumors, emerging as a potential therapeutic target. This study aimed to determine the role of USP1 as a therapeutic target in hepatocellular carcinoma (HCC). We detected USP1 expression in the tumor and adjacent tissues of patients with HCC using immunohistochemical staining. We evaluated the effect of the USP1 inhibitor ML-323 on HCC cell proliferation and cell cycle using a CCK-8 cell-counting kit and plate cloning assays, and propidium iodide, respectively. Apoptosis was detected by annexin V-FITC/Propidium Iodide (PI) staining and caspase 3 (casp3) activity. Transmission electron microscopy and LC3B immunofluorescence were used to detect autophagy. Western blotting was used to detect the accumulation of ubiquitinated proteins, the expression of endoplasmic reticulum (ER) stress-related proteins, and the AMPK-ULK1/ATG13 signaling pathway. We demonstrated that ML-323 inhibits the growth of HCC cells and induces G1 phase cell cycle arrest by regulating cyclin expression. ML-323 treatment resulted in the accumulation of ubiquitinated proteins, induced ER stress, and triggered Noxa-dependent apoptosis, which was regulated by the Activating Transcription Factor 4(ATF4). Moreover, active ER stress induces protective autophagy by increasing AMPK phosphorylation; therefore, we inhibited ER stress using 4-Phenylbutyric acid (4-PBA), which resulted in ER stress reduction, apoptosis, and autophagy in ML-323-treated HCC cells. In addition, blocking autophagy using the AMPK inhibitor compound C (CC), chloroquine (CQ), or bafilomycin A1 (BafA1) enhanced the cytotoxic effect of ML-323. Our findings revealed that targeting USP1 may be a potential strategy for the treatment of HCC.

Mechanisms of Cd-Induced Cytotoxicity in Normal Human Skin Keratinocytes: Implication for Human Health.

Cadmium (Cd) is one of the toxic heavy metals found widely in the environment. Skin is an important target organ of Cd exposure. However, the adverse effects of Cd on human skin are still not well known. In this study, normal human skin keratinocytes (HaCaT cells) were studied for changes in cell viability, morphology, DNA damage, cycle, apoptosis, and the expression of endoplasmic reticulum (ER) stress-related genes (XBP-1, BiP, ATF-4, and CHOP) after exposure to Cd for 24 h. We found that Cd decreased cell viability in a concentration-dependent manner, with a median lethal concentration (LC50) of 11 µM. DNA damage induction was evidenced by upregulation of the level of γ-H2AX. Furthermore, Cd induced G0/G1 phase cell cycle arrest and apoptosis in a dose-dependent manner and upregulated the mRNA levels of ER stress biomarker genes (XBP-1, BiP, ATF4, and CHOP). Taken together, our results showed that Cd induced cytotoxicity and DNA damage in HaCaT cells, eventually resulting in cell cycle arrest in the G0/G1 phase and apoptosis. In addition, ER stress may be involved in Cd-induced HaCaT apoptosis. Our data imply the importance of reducing Cd pollution in the environment to reduce its adverse impacts on human skin.

Endoplasmic reticulum stress triggered autophagy and regulated the phenotype transformation of rheumatoid arthritis synovial fibroblasts via the IRE1/JNK pathway.

BackgroundPrevious studies have indicated that endoplasmic reticulum (ER) stress may actively promote the pathogenesis of rheumatoid arthritis (RA) by evoking autophagy. However, the underlying mechanism remains largely unknown. This study aimed to explore the mechanism of the ER stress-autophagy pathway in regulating the phenotype transformation of rheumatoid arthritis synovial fibroblasts (RASFs).MethodsSynovial tissue was obtained from RA and osteoarthritis (OA) patients during joint replacement surgery. ER stress/autophagy signature markers were examined in synovial tissue by real-time quantitative polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry. Phenotype transformation of RASFs, including increased cell proliferation and invasion capability, was measured by CCK-8 assay and transwell invasion assay. Signaling pathways were further investigated and inositol requiring enzyme 1 (IRE1) was down-regulated in RASFs by transfecting specific short hairpin RNA-ERN1 (shRNA-ERN1) carried by lentiviral vectors.ResultsThe expression of ER stress/autophagy pathway-associated proteins, including GRP78, IRE1, protein kinase R-like endoplasmic reticulum kinase (PERK), and LC3, was significantly increased in RA synovium compared with OA synovium. After stimulation with tumor necrosis factor alpha (TNF-α) in vitro, the proliferation and invasion ability of RASFs were upregulated, while this phenomenon could be inhibited by 4-PBA (ER stress inhibitor) or 3-MA (autophagy inhibitor). The expression of IRE1 and p-JNK in particular, occurred in an obviously time-dependent manner after stimulation with TNF-α. Moreover, the proliferation and invasion of RASFs were inhibited after transfection with sh-RNA-ERN1 to downregulate IRE1 expression.ConclusionsER stress triggered autophagy via the IRE1/JNK pathway to regulate the phenotype transformation of RASFs, indicating an important role of the ER stress-autophagy pathway in the pathological process of synovitis in RA.

Mitochondrial ROS in Slc4a11 KO Corneal Endothelial Cells Lead to ER Stress.

Recent studies from Slc4a11 −/− mice have identified glutamine-induced mitochondrial dysfunction as a significant contributor toward oxidative stress, impaired lysosomal function, aberrant autophagy, and cell death in this Congenital Hereditary Endothelial Dystrophy (CHED) model. Because lysosomes are derived from endoplasmic reticulum (ER)—Golgi, we asked whether ER function is affected by mitochondrial ROS in Slc4a11 KO corneal endothelial cells. In mouse Slc4a11 −/− corneal endothelial tissue, we observed the presence of dilated ER and elevated expression of ER stress markers BIP and CHOP. Slc4a11 KO mouse corneal endothelial cells incubated with glutamine showed increased aggresome formation, BIP and GADD153, as well as reduced ER Ca2+ release as compared to WT. Induction of mitoROS by ETC inhibition also led to ER stress in WT cells. Treatment with the mitochondrial ROS quencher MitoQ, restored ER Ca2+ release and relieved ER stress markers in Slc4a11 KO cells in vitro. Systemic MitoQ also reduced BIP expression in Slc4a11 KO endothelium. We conclude that mitochondrial ROS can induce ER stress in corneal endothelial cells.