Endoplasmic reticulum stress, cell death and tumor: Association between endoplasmic reticulum stress and the apoptosis pathway in tumors (Review)

Regulatory effects of Trichinella spiralis serpin-type serine protease inhibitor on endoplasmic reticulum stress and oxidative stress in host intestinal epithelial cells

Endoplasmic reticulum stress (ERS) and oxidative stress (OS) are adaptive responses of the body to stressor stimulation. Although it has been verified that Trichinella spiralis (T. spiralis) can induce ERS and OS in the host, their association is still unclear. Therefore, this study explored whether T. spiralis-secreted serpin-type serine protease inhibitor (TsAdSPI) is involved in regulating the relationship between ERS and OS in the host intestine. In this study, mice jejunum and porcine small intestinal epithelial cells (IECs) were detected using qPCR, western blotting, immunohistochemistry (IHC), immunofluorescence (IF), and detection kits. The results showed that ERS- and OS-related indexes changed significantly after TsAdSPI stimulation, and Bip was located in IECs, indicating that TsAdSPI could induce ERS and OS in IECs. After the use of an ERS inhibitor, OS-related indexes were inhibited, suggesting that TsAdSPI-induced OS depends on ERS. When the three ERS signalling pathways, ATF6, IRE1, and PERK, were sequentially suppressed, OS was only regulated by the PERK pathway, and the PERK-eif2α-CHOP-ERO1α axis played a key role. Similarly, the expression of ERS-related indexes and the level of intracellular Ca2+ were inhibited after adding the OS inhibitor, and the expression of ERS-related indexes decreased significantly after inhibiting calcium transfer. This finding indicated that TsAdSPI-induced OS could affect ERS by promoting Ca2+ efflux from the endoplasmic reticulum. The detection of the ERS and OS sequences revealed that OS occurred before ERS. Finally, changes in apoptosis-related indexes were detected, and the results indicated that TsAdSPI-induced ERS and OS could regulate IEC apoptosis. In conclusion, TsAdSPI induced OS after entering IECs, OS promoted ERS by enhancing Ca2+ efflux, and ERS subsequently strengthened OS by activating the PERK-eif2α-CHOP-ERO1α axis. ERS and OS induced by TsAdSPI synergistically promoted IEC apoptosis. This study provides a foundation for exploring the invasion mechanism of T. spiralis and the pathogenesis of host intestinal dysfunction after invasion.

Newsights of endoplasmic reticulum in hypoxia

The endoplasmic reticulum (ER) is important to cells because of its essential functions, including synthesizing three major nutrients and ion transport. When cellular homeostasis is disrupted, ER quality control (ERQC) system is activated effectively to remove misfolded and unfolded proteins through ER-phagy, ER-related degradation (ERAD), and molecular chaperones. When unfolded protein response (UPR) and ER stress are activated, the cell may be suffering a huge blow, and the most probable consequence is apoptosis. The membrane contact points between the ER and sub-organelles contribute to communication between the organelles. The decrease in oxygen concentration affects the morphology and structure of the ER, thereby affecting its function and further disrupting the stable state of cells, leading to the occurrence of disease. In this study, we describe the functions of ER-, ERQC-, and ER-related membrane contact points and their changes under hypoxia, which will help us further understand ER and treat ER-related diseases.

An ultrasound-activated nanoplatform remodels tumor microenvironment through diverse cell death induction for improved immunotherapy

Although nanomaterial-based nanomedicine provides many powerful tools to treat cancer, most focus on the "immunosilent" apoptosis process. In contrast, ferroptosis and immunogenic cell death, two non-apoptotic forms of programmed cell death (PCD), have been shown to enhance or alter the activity of the immune system. Therefore, there is a need to design and develop nanoplatforms that can induce multiple modes of cell death other than apoptosis to stimulate antitumor immunity and remodel the immunosuppressive tumor microenvironment for cancer therapy. In this study, a new type of multifunctional nanocomposite mainly consisting of HMME, Fe3+ and Tannic acid, denoted HFT NPs, was designed and synthesized to induce multiple modes of cell death and prime the tumor microenvironment (TME). The HFT NPs consolidate two functions into one nano-system: HMME as a sonosensitizer for the generation of reactive oxygen species (ROS) 1O2 upon ultrasound irradiation, and Fe3+ as a GSH scavenger for the induction of ferroptosis and the production of ROS ·OH through inorganic catalytic reactions. The administration of HFT NPs and subsequent ultrasound treatment caused cell death through the consumption of GSH, the generation of ROS, ultimately inducing apoptosis, ferroptosis, and immunogenic cell death (ICD). More importantly, the combination of HFT NPs and ultrasound irradiation could reshape the TME and recruit more T cell infiltration, and its combination with immune checkpoint blockade anti-PD-1 antibody could eradicate tumors with low immunogenicity and a cold TME. This new nano-system integrates sonodynamic and chemodynamic properties to achieve outstanding therapeutic outcomes when combined with immunotherapy. Collectively, this study demonstrates that it is possible to potentiate cancer immunotherapy through the rational and innovative design of relatively simple materials.

Protein homeostasis maintained by HOOK1 levels promotes the tumorigenic and stemness properties of ovarian cancer cells through reticulum stress and autophagy

BACKGROUND

Ovarian cancer has a high mortality rate mainly due to its resistance to currently used therapies. This resistance has been associated with the presence of cancer stem cells (CSCs), interactions with the microenvironment, and intratumoral heterogeneity. Therefore, the search for new therapeutic targets, particularly those targeting CSCs, is important for improving patient prognosis. HOOK1 has been found to be transcriptionally altered in a substantial percentage of ovarian tumors, but its role in tumor initiation and development is still not fully understood.

METHODS

The downregulation of HOOK1 was performed in ovarian cancer cell lines using CRISPR/Cas9 technology, followed by growth in vitro and in vivo assays. Subsequently, migration (Boyden chamber), cell death (Western-Blot and flow cytometry) and stemness properties (clonal heterogeneity analysis, tumorspheres assay and flow cytometry) of the downregulated cell lines were analysed. To gain insights into the specific mechanisms of action of HOOK1 in ovarian cancer, a proteomic analysis was performed, followed by Western-blot and cytotoxicity assays to confirm the results found within the mass spectrometry. Immunofluorescence staining, Western-blotting and flow cytometry were also employed to finish uncovering the role of HOOK1 in ovarian cancer.

RESULTS

In this study, we observed that reducing the levels of HOOK1 in ovarian cancer cells reduced in vitro growth and migration and prevented tumor formation in vivo. Furthermore, HOOK1 reduction led to a decrease in stem-like capabilities in these cells, which, however, did not seem related to the expression of genes traditionally associated with this phenotype. A proteome study, along with other analysis, showed that the downregulation of HOOK1 also induced an increase in endoplasmic reticulum stress levels in these cells. Finally, the decrease in stem-like properties observed in cells with downregulated HOOK1 could be explained by an increase in cell death in the CSC population within the culture due to endoplasmic reticulum stress by the unfolded protein response.

CONCLUSION

HOOK1 contributes to maintaining the tumorigenic and stemness properties of ovarian cancer cells by preserving protein homeostasis and could be considered an alternative therapeutic target, especially in combination with inducers of endoplasmic reticulum or proteotoxic stress such as proteasome inhibitors.

Unraveling the path to osteoarthritis management: targeting chondrocyte apoptosis for therapeutic intervention

Osteoarthritis (OA) is a chronic disease affecting joints and further causing disabilities. This disease affects around 240 million people worldwide. It is a multifactorial disease, and its etiology is difficult to determine. Although numerous therapeutic strategies are available, the therapies are aimed at reducing pain and improving patients' quality of life. Hence, there is an urgent need to develop disease-modifying drugs (DMOAD) that can reverse or halt OA progression. Apoptosis is a cell removal process that is important in maintaining homeostatic mechanisms in the development and sustaining cell population. The apoptosis of chondrocytes is believed to play an important role in OA progression due to poor chondrocytes self-repair abilities to maintain the extracellular matrix (ECM). Hence, targeting chondrocyte apoptosis can be one of the potential therapeutic strategies in OA management. There are various mediators and targets available to inhibit apoptosis such as autophagy, endoplasmic reticulum (ER) stress, oxidative stress, and inflammation. As such, this review highlights the importance and potential targets that can be aimed to reduce chondrocyte apoptosis.

Targeting LxCxE cleft pocket of retinoblastoma protein in M2 macrophages inhibits ovarian cancer progression

Ovarian cancer remains a major health threat with limited treatment options available. It is characterized by immunosuppressive tumor microenvironment (TME) maintained by tumor- associated macrophages (TAMs) hindering anti-tumor responses and immunotherapy efficacy. Here we show that targeting retinoblastoma protein (Rb) by disruption of its LxCxE cleft pocket, causes cell death in TAMs by induction of ER stress, p53 and mitochondria-related cell death pathways. A reduction of pro-tumor Rb high M2-type macrophages from TME in vivo enhanced T cell infiltration and inhibited cancer progression. We demonstrate an increased Rb expression in TAMs in women with ovarian cancer is associated with poorer prognosis. Ex vivo, we show analogous cell death induction by therapeutic Rb targeting in TAMs in post-surgery ascites from ovarian cancer patients. Overall, our data elucidates therapeutic targeting of the Rb LxCxE cleft pocket as a novel promising approach for ovarian cancer treatment through depletion of TAMs and re-shaping TME immune landscape.

Statement of significance

Currently, targeting immunosuppressive myeloid cells in ovarian cancer microenvironment is the first priority need to enable successful immunotherapy, but no effective solutions are clinically available. We show that targeting LxCxE cleft pocket of Retinoblastoma protein unexpectedly induces preferential cell death in M2 tumor-associated macrophages. Depletion of immunosuppressive M2 tumor-associated macrophages reshapes tumor microenvironment, enhances anti-tumor T cell responses, and inhibits ovarian cancer. Thus, we identify a novel paradoxical function of Retinoblastoma protein in regulating macrophage viability as well as a promising target to enhance immunotherapy efficacy in ovarian cancer.

A new insight into Cd exposure-induced hemocyte reduction in Lymantria dispar larvae: Involvement of the ROS-ATF6-ER stress-apoptosis pathway

Hemocytes are important targets for heavy metal-induced immunotoxicity in insects. This study aimed to investigate the mechanism by which cadmium (Cd) exposure affects the hemocyte count in Lymantria dispar larvae. The results showed that the number of larval hemocytes was significantly decreased under Cd exposure, accompanied by a significant increase in the apoptosis rate and the expression of Caspase-3. The endoplasmic reticulum (ER) of hemocytes in the Cd-treated group showed irregular swelling. Expression levels of ER stress indicator genes (CHOP, Bip1, Bip2, Bip3, and Bip4) were significantly higher in the Cd-treated group. Among the three pathways that potentially mediate ER stress, only the key genes in the ATF6 pathway (ATF6, S1P-1, S1P-2, and WFS1) exhibited differential responses to Cd exposure. Cd exposure significantly increased the levels of reactive oxygen species (ROS) and the expression of oxidative stress-related genes (CNCC, P38, and ATF2) in hemocytes. Studies using inhibitors confirmed that apoptosis mediated the decrease in hemocyte count, ER stress mediated apoptosis, ATF6 pathway mediated ER stress, and ROS or oxidative stress mediated ER stress through the activation of the ATF6 pathway. Taken together, the ROS-ATF6-ER stress-apoptosis pathway is responsible for the reduction in the hemocyte count of Cd-treated L. dispar larvae.

Borax affects cellular viability by inducing ER stress in hepatocellular carcinoma cells by targeting SLC12A5

Hepatocellular carcinoma (HCC) presents a persistent challenge to conventional therapeutic approaches. SLC12A5 is implicated in an oncogenic capacity and facilitates the progression of cancer. The objective of this investigation is to scrutinize the inhibitory effects of borax on endoplasmic reticulum (ER)-stress and apoptosis mediated by SLC12A5 in HepG2 cells. Initially, we evaluated the cytotoxic impact of borax on both HL-7702 and HepG2 cell lines. Subsequently, the effects of borax on cellular morphology and the cell cycle of these lines were examined. Following this, we explored the impact of borax treatment on the mRNA and protein expression levels of SLC12A5, C/EBP homologous protein (CHOP), glucose-regulated protein-78 (GRP78), activating transcription factor-6 (ATF6), caspase-3 (CASP3), and cytochrome c (CYC) in these cellular populations. The determined IC50 value of borax for HL-7702 cells was 40.8 mM, whereas for HepG2 cells, this value was 22.6 mM. The concentrations of IC50 (22.6 mM) and IC75 (45.7 mM) of borax in HepG2 cells did not manifest morphological aberrations in HL-7702 cells. Conversely, these concentrations in HepG2 cells induced observable morphological and nuclear abnormalities, resulting in cell cycle arrest in the G1/G0 phase. Additionally, the levels of SLC12A5, ATF6, CHOP, GRP78, CASP3, and CYC were elevated in HepG2 cells in comparison to HL-7702 cells. Moreover, SLC12A5 levels decreased following borax treatment in HepG2 cells, whereas ATF6, CHOP, GRP78, CASP3, and CYC levels exhibited a significant increase. In conclusion, our data highlight the potential therapeutic effects of borax through the regulation of ER stress in HCC by targeting SLC12A5.

Melatonin inhibits tongue squamous cell carcinoma: Interplay of ER stress-induced apoptosis and autophagy with cell migration

Tongue squamous cell carcinoma (TSCC) occupies a high proportion of oral squamous cell carcinoma. TSCC features high lymph node metastasis rates and chemotherapy resistance with a poor prognosis. Therefore, an effective therapy strategy is needed to improve patient prognosis. Melatonin (MT) is a natural indole compound shown to have anti-tumor effects in several cancers. This study focused on the role and mechanism of MT in TSCC cells. The results of the study suggest that MT could inhibit cell proliferation in CRL-1623 cells. Western blot analysis showed the down-regulate of cyclin B1 and the up-regulate P21 protein by MT. MT was also shown to down-regulate the expression of Zeb1, Wnt5A/B, and β-catenin protein and up-regulate E-cadherin to inhibit the migration of CRL-1623 cells. MT also promoted the expression of ATF4, ATF6, Bip, BAP31 and CHOP in CRL-1623 cells leading to endoplasmic reticulum stress, and induced autophagy and apoptosis in CRL-1623 cells. Western blots showed that MT could promote the expression of Bax, LC3, and Beclin1 proteins and inhibit the expression of p62. We screened differentially expressed long non-coding RNAs (lncRNAs) in MT-treated cells and found that the expression of MALAT1 and H19 decreased. Moreover, MT inhibited tumor growth in nude mice inoculated with CRL-1623 cells. These results suggest that MT could induce autophagy, promote apoptosis, and provide a potential natural compound for the treatment of TSCC.

Impact of Obesity-Related Endoplasmic Reticulum Stress on Cancer and Associated Molecular Targets

Obesity, characterized by excessive body fat, is closely linked to endoplasmic reticulum (ER) stress, leading to insulin resistance and type 2 diabetes. Inflammatory pathways like c-Jun N-terminal kinase (JNK) worsen insulin resistance, impacting insulin signaling. Moreover, ER stress plays a substantial role in cancer, influencing tumor cell survival and growth by releasing factors like vascular endothelial growth factor (VEGF). The unfolded protein response (UPR) is pivotal in this process, offering both pro-survival and apoptotic pathways. This review offers an extensive exploration of the sophisticated connection between ER stress provoked by obesity and its role in both the onset and advancement of cancer. It delves into the intricate interplay between oncogenic signaling and the pathways associated with ER stress in individuals who are obese. Furthermore, this review sheds light on potential therapeutic strategies aimed at managing ER stress induced by obesity, with a focus on addressing cancer initiation and progression. The potential to alleviate ER stress through therapeutic interventions, which may encompass the use of small molecules, FDA-approved medications, and gene therapy, holds great promise. A more in-depth examination of pathways such as UPR, ER-associated protein degradation (ERAD), autophagy, and epigenetic regulation has the potential to uncover innovative therapeutic approaches and the identification of predictive biomarkers.

PIKFYVE inhibitors trigger interleukin-24-dependent cell death of autophagy-dependent melanoma

Inhibitors specifically targeting the 1-phosphatidylinositol 3-phosphate 5-kinase (PIKFYVE) disrupt lysosome homeostasis, thereby selectively terminating autophagy-dependent human cancer cells in vivo as well as in vitro without harming the viability of nonmalignant cells. To elucidate the mechanism by which PIKFYVE inhibition induces cell death, autophagy-dependent melanoma cells were compared with normal foreskin fibroblasts. RNA sequence profiling suggested that PIKFYVE inhibitors upregulated an endoplasmic reticulum (ER) stress response involving interleukin-24 (IL24; also known as MDA7) selectively in melanoma cells. Subsequent biochemical and genetic analyses confirmed these results and extended them to tumor xenografts in which tumor formation and expansion were inhibited. IL24 expression was upregulated by the DDIT3/CHOP/CEBPz transcription factor, a component of the PERK-dependent ER-stress response. Ectopic expression of IL24-induced cell death in melanoma cells, but not in foreskin fibroblasts, whereas ablation of the IL24 gene in melanoma cells prevented death. IL24 upregulation was triggered specifically by PIKFYVE inhibition. Thus, unlike thapsigargin and tunicamycin, which induce ER-stress indiscriminately, PIKFYVE inhibitors selectively terminated PIKFYVE-sensitive melanoma by inducing IL24-dependent ER-stress. Moreover, induction of cell death by a PIKFYVE inhibitor together with ectopic expression of IL24 protein was cumulative, thereby confirming the therapeutic potential of PIKFYVE inhibitors in the treatment of melanoma.

Activin A induces apoptosis of human lung adenocarcinoma A549 cells through endoplasmic reticulum stress pathway

Activin A, a member of the transforming growth factor‑β (TGF‑β) superfamily, has been implicated in the tumorigenesis and progression of various cancers. However, it remains unclear whether activin A induces apoptosis in human lung adenocarcinoma cells through the endoplasmic reticulum (ER) stress pathway. In the present study, BrdU, flow cytometry and western blotting were used to examine cell proliferation, apoptosis and protein expression, respectively. The present study revealed that activin A inhibited human lung adenocarcinoma A549 cell proliferation, induced apoptosis, and upregulated the protein levels of C/EBP homologous protein (CHOP), growth arrest and DNA damage‑inducible protein 34 (GADD34), cleaved‑caspase‑3 and caspase‑12. Furthermore, the administration of activin A did not alter the levels of suppressor of mothers against decapentaplegic 3 (Smad3) or phosphorylated (p)‑Smad3 proteins, whereas, it significantly elevated the levels of ActRIIA and p‑extracellular signal regulated kinase proteins 1 and 2 (ERK1/2) proteins in A549 cells. The apoptotic effects of activin A on A549 cells were attenuated by the ERK inhibitor FR180204, which also downregulated CHOP and caspase‑12 protein levels. Additionally, activin A increased intracellular calcium flux in A549 cells, and the calcium ion chelator BAPTA acetoxymethyl ester (BAPTA‑AM) inhibited activin A‑induced A549 cell apoptosis, whereas the calcium agonist ionomycin significantly increased apoptosis of A549 cells induced by activin A. These findings indicated that the activation of the ER stress pathway resulting in apoptosis of A549 cells triggered by activin A is facilitated by the ActRIIA‑ERK1/2 signaling and calcium signaling. The present findings suggest that the agonists of ERK and calcium signaling exhibit promising clinical therapeutic potential for the induction of apoptosis in lung adenocarcinoma.

The Role of Regulatory Cell Death in Vitiligo

Vitiligo is one of the common chronic autoimmune skin diseases in clinic, which is characterized by localized or generalized depigmentation and seriously affects the physical and mental health of patients. At present, the pathogenesis of vitiligo is not clear; mainly, heredity, autoimmunity, oxidative stress, melanocyte (MC) self-destruction, and the destruction, death, or dysfunction of MCs caused by various reasons are always the core of vitiligo. Regulatory cell death (RCD) is an active and orderly death mode of cells regulated by genes, which widely exists in various life activities, plays a pivotal role in maintaining the homeostasis of the organism, and is closely related to the occurrence and development of many diseases. With the deepening of the research and understanding of RCD, people gradually found that there are many different forms of RCD in the lesions and perilesional skin of vitiligo patients, such as apoptosis, autophagy, pyroptosis, ferroptosis, and so on. Different cell death modes have different mechanisms in vitiligo, and different RCDs can interact and regulate each other. In this article, the mechanism related to RCD in the pathogenesis of vitiligo is reviewed, which provides new ideas for exploring the pathogenesis and targeted treatment of vitiligo.

Trends in Anti-Tumor Effects of Pseudomonas aeruginosa Mannose-Sensitive-Hemagglutinin (PA-MSHA): An Overview of Positive and Negative Effects

Cancer is a leading cause of death worldwide, for which finding the optimal therapy remains an ongoing challenge. Drug resistance, toxic side effects, and a lack of specificity pose significant difficulties in traditional cancer treatments, leading to suboptimal clinical outcomes and high mortality rates among cancer patients. The need for alternative therapies is crucial, especially for those resistant to conventional methods like chemotherapy and radiotherapy or for patients where surgery is not possible. Over the past decade, a novel approach known as bacteria-mediated cancer therapy has emerged, offering potential solutions to the limitations of conventional treatments. An increasing number of in vitro and in vivo studies suggest that the subtype of highly virulent Pseudomonas aeruginosa bacterium called Pseudomonas aeruginosa mannose-sensitive-hemagglutinin (PA-MSHA) can successfully inhibit the progression of various cancer types, such as breast, lung, and bladder cancer, as well as hepatocellular carcinoma. PA-MSHA inhibits the growth and proliferation of tumor cells and induces their apoptosis. Proposed mechanisms of action include cell-cycle arrest and activation of pro-apoptotic pathways regulated by caspase-9 and caspase-3. Moreover, clinical studies have shown that PA-MSHA improved the effectiveness of chemotherapy and promoted the activation of the immune response in cancer patients without causing severe side effects. Reported adverse reactions were fever, skin irritation, and pain, attributed to the overactivation of the immune response. This review aims to summarize the current knowledge obtained from in vitro, in vivo, and clinical studies available at PubMed, Google Scholar, and ClinicalTrials.gov regarding the use of PA-MSHA in cancer treatment in order to further elucidate its pharmacological and toxicological properties.

The Dual Role of Sulforaphane-Induced Cellular Stress-A Systems Biological Study

The endoplasmic reticulum (ER) plays a crucial role in cellular homeostasis. When ER stress is generated, an autophagic self-digestive process is activated to promote cell survival; however, cell death is induced in the case of excessive levels of ER stress. The aim of the present study was to investigate the effect of a natural compound called sulforaphane (SFN) upon ER stress. Our goal was to investigate how SFN-dependent autophagy activation affects different stages of ER stress induction. We approached our scientific analysis from a systems biological perspective using both theoretical and molecular biological techniques. We found that SFN induced the various cell-death mechanisms in a concentration- and time-dependent manner. The short SFN treatment at low concentrations promoted autophagy, whereas the longer treatment at higher concentrations activated cell death. We proved that SFN activated autophagy in a mTORC1-dependent manner and that the presence of ULK1 was required for its function. A low concentration of SFN pre- or co-treatment combined with short and long ER stress was able to promote cell survival via autophagy induction in each treatment, suggesting the potential medical importance of SFN in ER stress-related diseases.

Bioinformatics-driven discovery of silica nanoparticles induces apoptosis and renal damage via the unfolded protein response in NRK-52E cells and rat kidney

Silica nanoparticles (SiNPs) are nanomaterials with widespread applications in drug delivery and disease diagnosis. Despite their utility, SiNPs can cause chronic kidney disease, hindering their clinical translation. The molecular mechanisms underlying SiNP-induced renal toxicity are complex and require further investigation. To address this challenge, we employed bioinformatics tools to predict the potential mechanisms underlying renal damage caused by SiNPs. We identified 1627 upregulated differentially expressed genes (DEGs) and 1334 downregulated DEGs. Functional enrichment analysis and protein-protein interaction network revealed that SiNP-induced renal damage is associated with apoptosis. Subsequently, we verified that SiNPs induced apoptosis in an in vitro model of NRK-52E cells via the unfolded protein response (UPR) in a dose-dependent manner. Furthermore, in an in vivo rat model, high-dose SiNP administration via tracheal drip caused hyalinization of the renal tubules, renal interstitial lymphocytic infiltration, and collagen fiber accumulation. Concurrently, we observed an increase in UPR-related protein levels at the onset of renal damage. Thus, our study confirmed that SiNPs induce apoptosis and renal damage through the UPR, adding to the theoretical understanding of SiNP-related kidney damage and offering a potential target for preventing and treating kidney injuries in SiNP clinical applications.

Paeoniflorin Induces ER Stress-Mediated Apoptotic Cell Death by Generating Nox4-Derived ROS under Radiation in Gastric Cancer

Gastric cancer is one of the most prevalent cancer types worldwide, and its resistance to cancer therapies, such as chemotherapy and radiotherapy, has made treating it a major challenge. Paeoniflorin (PF) is one potential pharmacological treatment derived from paeony root. However, in cancer, the molecular mechanisms and biological functions of PF are still unclear. In the present study, we found that PF exerts anti-tumor effects in vivo and in vitro and induces apoptotic cell death through ER stress, calcium (Ca2+), and reactive oxygen species (ROS) release in gastric cancer cells. However, ROS inhibition by DPI and NAC blocks cell death and the PERK signaling pathway via the reduction of Nox4. Moreover, PF triggers a synergistic inhibitory effect of the epithelial-mesenchymal transition (EMT) process under radiation exposure in radiation-resistant gastric cancer cells. These findings indicate that PF-induced Ca2+ and ROS release overcomes radioresistance via ER stress and induces cell death under radiation in gastric cancer cells. Therefore, PF, in combination with radiation, may be a powerful strategy for gastric cancer therapy.

Pan-Inhibition of Protein Disulfide Isomerase Caused Cell Death through Disrupting Cellular Proteostasis in Pancreatic Ductal Adenocarcinoma Cells

The protein disulfide isomerase (PDI) family is a group of thioredoxin endoplasmic reticulum (ER)-resident enzymes and molecular chaperones that play crucial roles in the correct folding of proteins. PDIs are upregulated in multiple cancer types and are considered a novel target for cancer therapy. In this study, we found that a potent pan-PDI inhibitor, E64FC26, significantly decreased the proliferation of pancreatic ductal adenocarcinoma (PDAC) cells. As expected, E64FC26 treatment increased ER stress and the unfolded protein response (UPR), as evidenced by upregulation of glucose-regulated protein, 78-kDa (GRP78), phosphorylated (p)-PKR-like ER kinase (PERK), and p-eukaryotic initiation factor 2α (eIF2α). Persistent ER stress was found to lead to apoptosis, ferroptosis, and autophagy, all of which are dependent on lysosomal functions. First, there was little cleaved caspase-3 in E64FC26-treated cells according to Western blotting, but a higher dose of E64FC26 was needed to induce caspase activity. Then, E64FC26-induced cell death could be reversed by adding the iron chelator, deferoxamine, and the reactive oxygen species scavengers, ferrostatin-1 and N-acetylcysteine. Furthermore, the autophagosome-specific marker, light chain 3B (LC3B)-II, increased, but the autolysosome marker, sequestosome 1 (SQSTM1)/p62, was not degraded in E64FC26-treated cells. Using the FUW mCherry-LC3 plasmid and acridine orange staining, we also discovered a lower number of acidic vesicles, such as autolysosomes and mature lysosomes, in E64FC26-treated cells. Finally, E64FC26 treatment increased the cathepsin L precursor (pre-CTSL) but decreased mature CTSL expression according to Western blotting, indicating a defective lysosome. These results suggested that the PDI inhibitor, E64FC26, might initially impede proper folding of proteins, and then induce ER stress and disrupt proteostasis, subsequently leading to lysosomal defects. Due to defective lysosomes, the extents of apoptosis and ferroptosis were limited, and fusion with autophagosomes was blocked in E64FC26-treated cells. Blockade of autolysosomal formation further led to the autophagic cell death of PDAC cells.

Apoptosis mechanisms induced by 15d-PMJ2 in HCT116 colon cancer cells: insights into CHOP10/TRB3/Akt signaling

Agents that stimulate the endoplasmic reticulum (ER) stress pathway are being exploited pharmacologically to induce cancer cell death. Cytotoxic ER stress is typically regulated by the transcription factor, C/EBP homologous protein 10 (CHOP10). Products of CHOP10 transcription include the pro-apoptotic proteins: ER oxidoreductase 1α (ERO1α), death receptor-5 (DR5), and tribbles-related protein 3 (TRB3). Our previous findings showed cell death induced by 15-deoxy- Δ12,14 prostamide J2 (15d-PMJ2) occurred in an ER stress-dependent manner. However, the pathway by which 15d-PMJ2 regulates ER stress-mediated death downstream of CHOP10 has not been identified. Our results demonstrate 5 µM 15d-PMJ2 increased CHOP10 expression and apoptosis in HCT116 colon cancer cells. In cells treated with pharmacological inhibitors of ER stress, 15d-PMJ2-induced apoptosis was reliant upon the ER stress pathway. To investigate the role of CHOP10 and its transcriptional products in apoptosis, genetic deletion of CHOP10 (CHOP10-KO) was performed using the CRISPR/Cas9 system. The apoptotic action of 15d-PMJ2 was blunted in cells lacking CHOP10 expression. The deletion of CHOP10 reduced the expression of DR5, ERO1α, and TRB3 although only the expression of TRB3 was significantly reduced. Therefore, we overexpressed TRB3 in CHOP10-KO cells and observed that the activation of Akt was inhibited and 15d-PMJ2-induced apoptosis was restored. Thus, a mechanism of apoptosis elicited by 15d-PMJ2 includes the stimulation of CHOP10/TRB3/Akt inhibition. Given the important role these signaling molecules play in cancer cell fate, 15d-PMJ2 may be an effective inducer of apoptosis in cancer cells.

PPP1R3A inhibits osteogenesis and negatively regulates intracellular calcium levels in calcific tendinopathy

Calcific tendinopathy (CT) is defined by the progressive accumulation of calcium crystals in tendonic regions that results in severe pain in patients. The etiology of CT is not fully elucidated. In this study, we elucidate the role of PPP1R3A in CT. A significant decrease in PPP1R3A expression was observed in CT patient tissues, which was further confirmed in tissues from a CT-induced rat model. Overexpression of PPP1R3A ex vivo reduced the expression of osteo/chondrogenic markers OCN and Sox9, improved tendon tissue architecture, and reduced intracellular Ca2+ levels. Overexpression of SERCA2 and knockdown of Piezo1 decreased expression of osteo/chondrogenic markers and intracellular calcium in PPP1R3A-knockdown tendon cells. Lastly, PPP1R3A expression was regulated at the posttranscriptional level by binding of HuR. Collectively, the present study indicates that PPP1R3A plays an important role in regulating calcium homeostasis in tendon cells via Piezo1/SERCA2, rendering it a promising target for therapeutic interventions of CT.

Immunological effects of the PE/PPE family proteins of Mycobacterium tuberculosis and related vaccines

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (Mtb), and its incidence and mortality are increasing. The BCG vaccine was developed in the early 20th century. As the most widely administered vaccine in the world, approximately 100 million newborns are vaccinated with BCG every year, which has saved tens of millions of lives. However, due to differences in region and race, the average protective rate of BCG in preventing tuberculosis in children is still not high in some areas. Moreover, because the immune memory induced by BCG will weaken with the increase of age, it is slightly inferior in preventing adult tuberculosis, and BCG revaccination cannot reduce the incidence of tuberculosis again. Research on the mechanism of Mtb and the development of new vaccines against TB are the main strategies for preventing and treating TB. In recent years, Pro-Glu motif-containing (PE) and Pro-Pro-Glu motif-containing (PPE) family proteins have been found to have an increasingly important role in the pathogenesis and chronic protracted infection observed in TB. The development and clinical trials of vaccines based on Mtb antigens are in progress. Herein, we review the immunological effects of PE/PPE proteins and the development of common PE/PPE vaccines.

Activation of cDCs and iNKT cells contributes to triptolide-induced hepatotoxicity via STING signaling pathway and endoplasmic reticulum stress

Triptolide (TP) exhibits therapeutic potential against multiple diseases. However, its application in clinics is limited by TP-induced hepatoxicity. TP can activate invariant natural killer T (iNKT) cells in the liver, shifting Th1 cytokine bias to Th2 cytokine bias. The damaging role of iNKT cells in TP-induced hepatoxicity has been established, and iNKT cell deficiency can mitigate hepatotoxicity. However, the activation of iNKT cells in vitro by TP requires the presence of antigen-presenting cells. Therefore, we hypothesized that TP could induce dendritic cells (DCs) to activate iNKT cells, thereby leading to hepatotoxicity. The hepatic conventional DCs (cDCs) exhibited immunogenic activities after TP administration, upregulating the expression of CD1d, co-stimulatory molecules, and IL-12. Neutralization with IL-12p40 antibody extenuated TP-induced hepatotoxicity and reduced iNKT cell activation, suggesting that IL-12 could cause liver injury by activating iNKT cells. TP triggered the activation and upregulation of STING signaling pathway and increased endoplasmic reticulum (ER) stress. Downregulation of STING reduced cDC immunogenicity, inhibiting the activation of iNKT cells and hepatic damage. These indicated the regulatory effects of STING pathway on cDCs and iNKT cells, and the important roles it plays in hepatoxicity. ER stress inhibitor, 4-phenylbutyrate (4-PBA), also suppressed iNKT cell activation and liver injury, which might be regulated by the STING signaling pathway. Our results demonstrated the possible mechanisms underlying TP-induced hepatoxicity, where the activation of cDCs and iNKT cells was stimulated by upregulated STING signaling and increased ER stress as a result of TP administration.

Immunogenic landscape and risk score prediction based on unfolded protein response (UPR)-related molecular subtypes in hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the most common type of cancer and causes a significant number of cancer-related deaths worldwide. The molecular mechanisms underlying the development of HCC are complex, and the heterogeneity of HCC has led to a lack of effective prognostic indicators and drug targets for clinical treatment of HCC. Previous studies have indicated that the unfolded protein response (UPR), a fundamental pathway for maintaining endoplasmic reticulum homeostasis, is involved in the formation of malignant characteristics such as tumor cell invasiveness and treatment resistance. The aims of our study are to identify new prognostic indicators and provide drug treatment targets for HCC in clinical treatment based on UPR-related genes (URGs).

Methods

Gene expression profiles and clinical information were downloaded from the TCGA, ICGC and GEO databases. Consensus cluster analysis was performed to classify the molecular subtypes of URGs in HCC patients. Univariate Cox regression and machine learning LASSO algorithm were used to establish a risk prognosis model. Kaplan-Meier and ROC analyses were used to evaluate the clinical prognosis of URGs. TIMER and XCell algorithms were applied to analyze the relationships between URGs and immune cell infiltration. Real time-PCR was performed to analyze the effect of sorafenib on the expression levels of four URGs.

Results

Most URGs were upregulated in HCC samples. According to the expression pattern of URGs, HCC patients were divided into two independent clusters. Cluster 1 had a higher expression level, worse prognosis, and higher expression of immunosuppressive factors than cluster 2. Patients in cluster 1 were more prone to immune escape during immunotherapy, and were more sensitive to chemotherapeutic drugs. Four key UPR genes (ATF4, GOSR2, PDIA6 and SRPRB) were established in the prognostic model and HCC patients with high risk score had a worse clinical prognosis. Additionally, patients with high expression of four URGs are more sensitive to sorafenib. Moreover, ATF4 was upregulated, while GOSR2, PDIA6 and SRPRB were downregulated in sorafenib-treated HCC cells.

Conclusion

The UPR-related prognostic signature containing four URGs exhibits high potential application value and performs well in the evaluation of effects of chemotherapy/immunotherapy and clinical prognosis.

Forsythiaside A alleviates Lipopolysacchrride-induced acute liver Injury through inhibiting endoplasmic reticulum stress and NLRP3 inflammasome activation

The liver is the primary site of inflammation caused by bacterial endotoxins in sepsis, and septic acute liver injury (SALI) is usually associated with poor outcomes in sepsis. Forsythiaside A (FTA), an active constituent of Forsythia suspensa, has been reported to have anti-inflammatory properties, antioxidant properties, and protective properties against neuroinflammation, sepsis, and edema.Therefore, the purpose of the present study was to examine FTA's potential effects on lipopolysaccharide (LPS)-induced SALI in mice.Our results indicated that pretreatment with FTA significantly attenuated aspartate aminotransferase (AST) and aminoleucine transferase (ALT) levels in plasma, ameliorated histopathological damage, inhibited hepatocyte apoptosis, diminished the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 in the liver from mice exposed to LPS. Furthermore, our data showed that the administration of LPS resulted in robust endoplasmic reticulum (ER) stress response, as evidenced by GRP78 upregulation, p-PERK activation, elF2α phosphorylation, and ATF4 and CHOP overexpression in the liver. This, in turn, led to nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome activation, including the cleavage of caspase-1, secretion of IL-1β, and pyroptotic cell death in the liver specimens. Importantly, the ER stress response induced by the LPS challenge was blocked by FTA administration. Correspondingly, NLRP3 inflammasome activation was significantly ameliorated by the pretreatment with FTA. Thus, we demonstrated that FTA pretreatment could protect mice from LPS-induced SALI, and its protective effects were possibly mediated by inhibiting ER stress response and subsequent NLRP3 inflammasome activation.

Nanotherapy based on magneto-mechanochemical modulation of tumor redox state

Magnetic nanoparticles (MNs) are typically used as contrast agents for magnetic resonance imaging or as drug carriers with a remotely controlled delivery to the tumor. However, they can also potentiate the action of anticancer drugs under the influence of applied constant magnetic (CMFs) and electromagnetic fields (EMFs). This review demonstrates the role of magneto-mechanochemical effects produced by MNs alone and loaded with anticancer agents (MNCs) in response to CMFs and EMFs for modulation of tumor redox state. The combined treatment is suggested to act by two mechanisms: spin-dependent electron transport propagates free radical chain reactions, while magnetomechanical interactions cause conformational changes in drug molecules loaded onto MNs and generate reactive oxygen species (ROS). By adjusting the parameters of CMFs and EMFs during the magneto-mechanochemical synthesis and subsequent treatment, it is possible to modulate ROS production and switch redox signaling involved in ERK1/2 and NF-κB pathways from initiation of tumor growth to inhibition. Observations of tumor volume in different animal models and treatment combinations reported a 6%-70% reduction as compared with conventional drugs. Despite these results, there is a general lack of research in magnetic nanotheranostics that link redox changes across multiple levels of organization in the tumor-bearing host. Further multidisciplinary studies with more focus on the relationship between the electron transport processes in biomolecules and their effects on the tumor-host interaction should accelerate the clinical translation of magnetic nanotheranostics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Interrelation between Programmed Cell Death and Immunogenic Cell Death: Take Antitumor Nanodrug as an Example

Programmed cell death (PCD, mainly including apoptosis, necrosis, ferroptosis, pyroptosis, and autophagy) and immunogenic cell death (ICD), as important cell death mechanisms, are widely reported in cancer therapy, and understanding the relationship between the two is significant for clinical tumor treatments. Considering that vast nanodrugs are developed to induce tumor PCD and ICD simultaneously, in this review, the interrelationship between PCD and ICD is described using nanomedicines as examples. First, an overview of PCD patterns and focus on the morphological differences and interconnections among them are provided. Then the interrelationship between apoptosis and ICD in terms of endoplasmic reticulum stress is described by introducing various cancer treatments and the recent developments of nanomedicines with inducible immunogenicity. Next, the crosstalk between non-apoptotic (including necrosis, ferroptosis, pyroptosis, and autophagy) signaling pathways and ICD is introduced and their relationship through various nanomedicines as examples is further illustrated. Finally, the relationship between PCD and ICD and its application prospects in the development of new ICD nanomaterials are summarized. This review is believed to deepen the understanding of the relationship between PCD and ICD, extend the biomedical applications of various nanodrugs, and promote the progress of clinical tumor therapy.

Construction of a multifunctional peptide nanoplatform for nitric oxide release and monitoring and its application in tumor-bearing mice

As a "star molecule", nitric oxide (NO) either promotes or inhibits many physiological processes depending on its concentration. The in situ generation and monitoring of therapeutic gas molecules has been a problem that many researchers have been working to address due to the stochastic nature of gas molecule movement. There are still relatively few studies using short peptides as NO storage systems, and there are still challenges in monitoring NO release in situ with real-time imaging over long periods of time. In this work, a morphologically transformable NO release, diagnosis and treatment integrated multifunctional nanoplatform was fabricated. A new NO-activated probe (DPBTD) with emission in the first near infrared (NIR-I) region was encapsulated into the hydrophobic domains of Ac-KLVFFAL-NH₂ peptide derivatives as a biosensor for NO release. Peptide scaffolds were endowed with the capacity of controlled NO release by the introduction of NO donor (organic nitrates). Interestingly, morphology of the nanoplatform could be transformed from one-dimensional (1D) nanowires to two-dimensional (2D) nanosheets via nanorods transition state under tip sonication, which was allowed for better cell uptake. Eventually, this nanocarrier was used for stimuli-responsive NO release, real-time imaging and treatment in tumor tissues of 4T1 tumor-bearing mice. This strategy expands the application potential of peptide-based nanomaterials and provides ideas for monitoring the progress of gas-mediated cancer therapy.

GRAMD4 regulates PEDV-induced cell apoptosis inhibiting virus replication via the endoplasmic reticulum stress pathway

Porcine epidemic diarrhea (PED) caused by the porcine epidemic diarrhea virus (PEDV) has caused huge losses in the swine industry worldwide. Glucosyltransferase Rab-like GTPase activator and myotubularin domain containing 4 (GRAMD4) is a proapoptotic protein, which replaced p53 inducing mitochondrial apoptosis. However, the relationship between GRAMD4 and PEDV has not been reported. Here, we aimed to investigate the potential role of GRAMD4 during PEDV infection. In this study, we used co-immunoprecipitation (co-IP) and mass spectrometry to identify GRAMD4 interaction with PEDV non-structural protein 6 (NSP6). Immunoprecipitation and laser confocal microscopy were utilized to demonstrate that GRAMD4 interacts with NSP6. NSP6 reduces GRAMD4 production through PERK and IRE1 pathway-mediated apoptosis. We demonstrated that overexpression of GRAMD4 effectively impaired the replication of PEDV, whereas knockdown of GRAMD4 facilitated the replication of PEDV. Overexpression of GRAMD4 increased GRP78, phosphorylated PERK (p-PERK), phosphorylated IRE1(p-IRE1) levels, promoted CHOP, phosphorylated JNK (p-JNK), Bax expression, caspase 9 and caspase 3 cleavage, and inhibited Bcl-2 production. Knockdown of GRAMD4 has the opposite effect. Finally, deletion of the GRAM domain of GRAMD4 cannot cause endoplasmic reticulum stress (ER stress)-mediated apoptosis and inhibit virus replication. In conclusion, these studies revealed the mechanism by which GRAMD4 was associated with ER stress and apoptosis regulating PEDV replication. NSP6 acted as a potential down-regulator of GRAMD4 and promoted the degradation of GRAMD4. GRAMD4 played a role in facilitating apoptosis and restricting virus replication, and the GRAM domain was required. These findings provided a reference for host-PEDV interactions and offered the possibility for PEDV decontamination and prevention.

Novel Indole-Chalcone Derivative-Ligated Platinum(IV) Prodrugs Attenuate Cisplatin Resistance in Lung Cancer through ROS/ER Stress and Mitochondrial Dysfunction

Developing multifunctional platinum(IV) prodrugs via integrating bioactive pharmacophores into one entity is an attractive strategy to ameliorate the defects of platinum(II) drugs. Herein, a series of indole-chalcone derivative-ligated platinum(IV) complexes were synthesized and evaluated for their anticancer activities. Among them, optimal complex 17a exerted superior activity compared to that of cisplatin (CDDP) against the tested cells but showed lower cytotoxicity toward human normal lung cells. Detailed mechanisms demonstrated that 17a significantly enhanced intracellular accumulation, induced DNA damage, and inhibited migration in A549/CDDP cells. Furthermore, 17a efficiently disturbed the tubulin-microtubule system, initiated reactive oxygen species (ROS)-mediated endoplasmic reticulum stress, and activated a mitochondrion-dependent apoptosis signaling pathway. Besides, 17a was superior to free drugs or their combination in inhibiting cancer growth in A549/CDDP xenografts without inducing obvious side effects. The physical mixture of 16a and CDDP was almost identical to 17a but showed apparent systematic side effects. In summary, our studies may provide an efficient treatment regimen for CDDP resistance.

Fluorescent probes for ferroptosis bioimaging: advances, challenges, and prospects

Ferroptosis is a form of regulatory cell death distinct from caspase-dependent apoptosis and plays an important role in life entities. Since ferroptosis involves a variety of complex regulatory factors, the levels of certain biological species and microenvironments would change during this process. Thus, the investigation of the level fluctuation of key target analytes during ferroptosis is of great significance for disease treatment and drug design. Toward this aim, multiple organic fluorescent probes with simple preparation and non-destructive detection have been developed, and research over the past decade has uncovered a vast array of homeostasis and other physiological characteristics of ferroptosis. However, this significant and cutting-edge topic has not yet been reviewed. In this work, we aim to highlight the latest breakthrough results of fluorescent probes for monitoring various bio-related molecules and microenvironments during ferroptosis at the cellular, tissue and in vivo levels. Accordingly, this tutorial review has been organized according to the target molecules identified by the probes including ionic species, reactive sulfur species, reactive oxygen species, biomacromolecules, microenvironment, and others. In addition to providing new insights into the findings of each fluorescent probe in ferroptosis studies, we also discuss the defects and limitations of the probes developed, and highlight the potential challenges and further prospects in this domain. We anticipate that this review will convey profound implications for designing powerful fluorescent probes to decrypt changes in key molecules and microenvironments during ferroptosis.

Endoplasmic Reticulum Stress in Renal Cell Carcinoma

The endoplasmic reticulum is an organelle exerting crucial functions in protein production, metabolism homeostasis and cell signaling. Endoplasmic reticulum stress occurs when cells are damaged and the capacity of this organelle to perform its normal functions is reduced. Subsequently, specific signaling cascades, together forming the so-called unfolded protein response, are activated and deeply impact cell fate. In normal renal cells, these molecular pathways strive to either resolve cell injury or activate cell death, depending on the extent of cell damage. Therefore, the activation of the endoplasmic reticulum stress pathway was suggested as an interesting therapeutic strategy for pathologies such as cancer. However, renal cancer cells are known to hijack these stress mechanisms and exploit them to their advantage in order to promote their survival through rewiring of their metabolism, activation of oxidative stress responses, autophagy, inhibition of apoptosis and senescence. Recent data strongly suggest that a certain threshold of endoplasmic reticulum stress activation needs to be attained in cancer cells in order to shift endoplasmic reticulum stress responses from a pro-survival to a pro-apoptotic outcome. Several endoplasmic reticulum stress pharmacological modulators of interest for therapeutic purposes are already available, but only a handful were tested in the case of renal carcinoma, and their effects in an in vivo setting remain poorly known. This review discusses the relevance of endoplasmic reticulum stress activation or suppression in renal cancer cell progression and the therapeutic potential of targeting this cellular process for this cancer.

Recent Advances in Cancer Therapeutic Copper-Based Nanomaterials for Antitumor Therapy

Copper serves as a vital microelement which is widely present in the biosystem, functioning as multi-enzyme active site, including oxidative stress, lipid oxidation and energy metabolism, where oxidation and reduction characteristics are both beneficial and lethal to cells. Since tumor tissue has a higher demand for copper and is more susceptible to copper homeostasis, copper may modulate cancer cell survival through reactive oxygen species (ROS) excessive accumulation, proteasome inhibition and anti-angiogenesis. Therefore, intracellular copper has attracted great interest that multifunctional copper-based nanomaterials can be exploited in cancer diagnostics and antitumor therapy. Therefore, this review explains the potential mechanisms of copper-associated cell death and investigates the effectiveness of multifunctional copper-based biomaterials in the field of antitumor therapy.

Only one carbon difference determines the pro-apoptotic activity of α-tocopheryl esters

α-Tocopheryl succinate (TS), a redox-silent succinyl ester of natural α-Tocopherol, has emerged as a novel anti-cancer agent. However, the underlying mechanism is unclear. We found that the terminal dicarboxylic moiety of tocopheryl esters contributes to apoptosis induction and thus cytotoxicity. To further examine this relationship, we compared the pro-apoptotic activity of TS, which has four carbon atoms in the terminal dicarboxylic moiety, to that of a newly synthesized, tocopheryl glutarate (Tglu), which has five. Cytotoxicity assays in vitro confirmed that TS stimulated apoptosis, while Tglu was non-cytotoxic. In investigating biological mechanisms leading to these opposing effects, we found that TS caused an elevation of intracellular superoxide, but Tglu did not. TS increased intracellular Ca²⁺ in cultured cells, suggesting induction of endoplasmic reticulum (ER) stress; however, Tglu did not affect Ca²⁺ homeostasis. 1,4,5-trisphosphate (IP₃ ) receptor antagonist 2-Aminoethyl diphenylborinate (2-APB) decreased TS-induced intracellular Ca²⁺ , restored mitochondrial activity and cell viability in TS-treated cells, establishing the ER-mitochondria relationship in apoptosis induction. Moreover, real-time PCR, immunostaining and Western blotting assays revealed that TS downregulated glucose-regulated protein 78 (GRP78), which maintains ER homeostasis and promotes cell survival. Conversely, Tglu upregulates GRP78. Taken together, our results suggest a model in which TS-mediated superoxide production and GRP78 inhibition induce ER stress, which elevates intracellular Ca²⁺ and depolarizes mitochondria, leading to apoptosis. Because Tglu does not affect superoxide generation and increases GRP78 expression, it inhibits ER stress and is thereby non-cytotoxic. Our research provides insight into the structure-activity relationship of tocopheryl esters regarding the induction of apoptosis.

SLC12A5 promotes hepatocellular carcinoma growth and ferroptosis resistance by inducing ER stress and cystine transport changes

BACKGROUND

Hepatocellular carcinoma (HCC) has a poor prognosis and new effective treatments are needed. SLC12A5 plays important roles in multiple complex pathological states and is overexpressed in a variety of malignancies. However, the effects of SLC12A5 in HCC have not been determined.

METHODS

SLC12A5 expression was assessed by immunostaining and western blotting. A cell viability assay was used to detect cell proliferation. Flow cytometry was used to evaluate the intracellular calcium concentration and cell cycle. Ferroptosis was detected by transmission electron microscopy, lipid peroxidation, and glutathione assays. Subcutaneous tumor formation experiments were used to validate the tumorigenic effect of SLC12A5 in vivo. RNA-seq was used to evaluate the molecular mechanisms underlying the effects of SLC12A5. The therapeutic efficacy of targeting SLC12A5 was assessed in a patient-derived xenograft (PDX) model.

RESULTS

High SLC12A5 expression was strongly associated with a poor clinical prognosis and promoted HCC growth. Mechanistically, SLC12A5 promoted ER stress to enhance calcium release and upregulated PNCK expression levels. Concomitantly, PNCK was significantly activated by calcium ions released from the ER. PNCK activated and induced the phosphorylation of PI3K/AKT/mTOR pathway components. Furthermore, SLC12A5 inhibited ferroptosis in HCC by upregulating the expression of xCT, a cystine transporter.

CONCLUSION

High SLC12A5 levels were correlated with a poor prognosis, promoted tumorigenesis, and inhibited ferroptosis in HCC. These findings suggested that SLC12A5 is a therapeutic target and provide insight into the link between ER stress and ferroptosis in HCC.

Organelle-Specific Mechanisms in Crosstalk between Apoptosis and Ferroptosis

Apoptosis has been extensively studied, whereas ferroptosis is a newly discovered form of regulated cell death that involves iron-dependent accumulations of lipid hydroperoxides. While these two cell death mechanisms were initially believed to be mutually exclusive, recent studies have revealed cellular contexts requiring a balanced interaction between them. Numerous subcellular sites and signaling molecules within these sites are involved in both processes, either as modules or switches that allow cells to choose on how to proceed. The close relationships between apoptosis and ferroptosis, as well as the possibility of switching from one to the other, are described in this review. To understand the crosstalk between apoptosis and ferroptosis, various organelle-specific mechanisms must be analyzed and compared. The ability to switch apoptosis to ferroptosis by targeting cellular organelles has a great potential in cancer therapy.

Effect of Flammulina velutipes polysaccharides on endoplasmic reticulum stress-mediated apoptosis by activating PLC-IP3 pathway in HepG2 cells

Flammulina velutipes polysaccharides (FVP) have been proven to induce apoptosis in HepG2 cells. It is well known that endoplasmic reticulum stress (ERS) is involved in apoptosis. However, ERS mediates FVP-induced apoptosis in HepG2 cells remains unclear. In our study, the results indicated that FVP caused ERS in HepG2 cells. They showed that FVP were water-soluble polysaccharides with the weight average molecular weight of 1972 kDa, which were mainly composed of mannose, gluconic acid, glucose, galactose, xylose and fructose in a molar ratio of 6.6 : 1.3 : 79.9 : 7.4 : 3.4 : 1.5. After FVP treatment, the expression levels of genes and proteins related to ERS were upregulated. The inhibition of ERS by 4-phenylbutyric acid (4-PBA) pretreatment could significantly reduce the role of FVP in inducing apoptosis. We further found the results of immunofluorescence and flow cytometry showing that Ca²⁺ in the ERS leaked out, and the intracellular Ca²⁺ concentration increased after FVP treatment. The pretreatment with the phospholipase C (PLC) inhibitor U73122 proved that FVP caused excessive intracellular Ca²⁺ concentration by activating the phospholipase C-inositol-1,4,5-triphosphate (PLC-IP3) pathway, resulting in ERS, and ultimately leading to apoptosis. In summary, our results indicated that FVP induced ERS-mediated apoptosis by activating PLC-IP3 pathway in HepG2 cells. PRACTICAL APPLICATION: This work may suggest that FVP could be used as an adjuvant therapy to anticancer drugs, providing new application prospects and possibilities.

Cyt-C Mediated Mitochondrial Pathway Plays an Important Role in Oocyte Apoptosis in Ricefield Eel (Monopterus albus)

Apoptosis plays a key role in the effective removal of excessive and defective germ cells, which is essential for sequential hermaphroditism and sex change in vertebrates. The ricefield eel, Monopterus albus is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. Previous studies have demonstrated that apoptosis is involved in sex change in M. albus. However, the apoptotic signaling pathway is unclear. In the current study, we explored the underlying mechanism of apoptosis during gonadal development and focused on the role of the mitochondrial apoptosis signaling pathway in sex change in M. albus. Flow cytometry was performed to detect apoptosis in gonads at five sexual stages and ovary tissues exposed to hydrogen peroxide (H2O2) in vitro. Then the expression patterns of key genes and proteins in the mitochondrial pathway, death receptor pathway and endoplasmic reticulum (ER) pathway were examined. The results showed that the apoptosis rate was significantly increased in the early intersexual stage and then decreased with the natural sex change from female to male. Quantitative real-time PCR revealed that bax, tnfr1, and calpain were mainly expressed in the five stages. ELISA demonstrated that the relative content of cytochrome-c (cyt-c) in the mitochondrial pathway was significantly higher than that of caspase8 and caspase12, with a peak in the early intersexual stage, while the levels of caspase8 and caspase12 peaked in the late intersexual stage. Interestingly, the Pearson’s coefficient between cyt-c and the apoptosis rate was 0.705, which suggests that these factors are closely related during the gonadal development of M. albus. Furthermore, the cyt-c signal was found to be increased in the intersexual stage by immunohistochemistry. After incubation with H2O2, the mRNA expression of mitochondrial pathway molecules such as bax, apaf-1, and caspase3 increased in ovary tissues. In conclusion, the present results suggest that the mitochondrial apoptotic pathway may play a more important role than the other apoptotic pathways in sex change in M. albus.

Subcellular delivery of lipid nanoparticles to endoplasmic reticulum and mitochondria

Primarily responsible for the biogenesis and metabolism of biomolecules, endoplasmic reticulum (ER) and mitochondria are gradually becoming the targets of therapeutic modulation, whose physiological activities and pathological manifestations determine the functional capacity and even the survival of cells. Drug delivery systems with specific physicochemical properties (passive targeting), or modified by small molecular compounds, polypeptides, and biomembranes demonstrating tropism for ER and mitochondria (active targeting) are able to reduce the nonselective accumulation of drugs, enhancing efficacy while reducing side effects. Lipid nanoparticles feature high biocompatibility, diverse cargo loading, and flexible structure modification, which are frequently used for subcellular organelle-targeted delivery of therapeutics. However, there is still a lack of systematic understanding of lipid nanoparticle-based ER and mitochondria targeting. Herein, we review the pathological significance of drug selectively delivered to the ER and mitochondria. We also summarize the molecular basis and application prospects of lipid nanoparticle-based ER and mitochondria targeting strategies, which may provide guidance for the prevention and treatment of associated diseases and disorders. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Pitavastatin protects against neomycin-induced ototoxicity through inhibition of endoplasmic reticulum stress

Irreversible injury to inner ear hair cells induced by aminoglycoside antibiotics contributes to the formation of sensorineural hearing loss. Pitavastatin (PTV), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has been reported to exert neuroprotective effects. However, its role in aminoglycoside-induced hearing loss remains unknown. The objectives of this study were to investigate the beneficial effects, as well as the mechanism of action of PTV against neomycin-induced ototoxicity. We found that PTV remarkably reduced hair cell loss in mouse cochlear explants and promoted auditory HEI-OC1 cells survival after neomycin stimulation. We also observed that the auditory brainstem response threshold that was increased by neomycin was significantly reduced by pretreatment with PTV in mice. Furthermore, neomycin-induced endoplasmic reticulum stress in hair cells was attenuated by PTV treatment through inhibition of PERK/eIF2α/ATF4 signaling. Additionally, we found that PTV suppressed the RhoA/ROCK/JNK signal pathway, which was activated by neomycin stimulation in HEI-OC1 cells. Collectively, our results showed that PTV might serve as a promising therapeutic agent against aminoglycoside-induced ototoxicity.

Transcriptome analysis endoplasmic reticulum-stress response in Litopenaeus vannamei hemocytes

Numerous studies have proved that endoplasmic reticulum (ER)-stress is an important cause of aquatic animal diseases. Therefore, for effectively preventing and controlling aquatic animal diseases, a systematic and in-depth understanding of the environmental stress response in aquatic animals is necessary. In present study, the influence of ER-stress in Litopenaeus vannamei was investigated using Illumina HiSeq based RNA-Seq. Comparing to the cDNA library of hemocytes treated with DMSO in L. vannamei, 286 unigenes were significantly upregulated and 473 unigenes were significantly down-regulated in the Thapsigargin treated group. KEGG analysis indicated that the differentially expressed genes (DEGs) are mainly related to ER-stress, immune as well as metabolism. Besides the classical ER-stress response pathways, the regulation of cell cycle and DNA replication are also important measures of ER-stress response. It has been suggested that the influence of ER-stress on immune genes might be an important factor in environmental stress inducing shrimp disease. Our investigation exhibited that immune-related DEG Prophenoloxidase activating enzyme 2 (LvPPAE2) roled in anti-pathogen immunity of shrimp. This study provides a solid foundation for uncovering the environmental adaptation response and especially its relationship with L. vannamei immune system.

Revealing the Effects of Endoplasmic Reticulum Stress on Ferroptosis by Two-Channel Real-Time Imaging of pH and Viscosity

Endoplasmic reticulum (ER) is sensitive to changes in the intracellular environment such as pH and viscosity, and slight changes may trigger stress response. Besides, different from apoptosis and necrosis, ferroptosis is the result of lipid peroxidation accumulation. There is evidence that ferroptosis is closely related to endoplasmic reticulum stress (ERS). However, the possible changes in the pH and viscosity of the ER during the ferroptosis process have not yet been studied. Therefore, we used a new type of ER-targeted dual-excitation fluorescent probe (DSPI-3) to investigate the possible changes of pH and viscosity of ER during the ferroptosis. The novel probe DSPI-3 exhibited a highly sensitive and selective response to pH and viscosity. During the bioimaging process, it was found that the ER acidified and viscosity increased during the ferroptosis process induced by erastin, while the cells treated with ferrostatin-1 did not alter significantly. In addition, when dithiothreitol (DTT) and erastin stimulated the cells at the same time, we discovered that ER was acidified considerably at short notice, but the pH was slightly increased in the later stage. Besides, the change of the viscosity enhanced slowly with the passage of time, and there was a noteworthy decline in the later stage, demonstrating that the DTT-induced ERS accelerated the process of ferroptosis. We hope that this unique fluorescent probe can provide an effective method for studying the relationship between ERS and ferroptosis.

Targeting c-Myc Unbalances UPR towards Cell Death and Impairs DDR in Lymphoma and Multiple Myeloma Cells

Multiple myeloma (MM) and primary effusion lymphoma (PEL) are aggressive hematological cancers, for which the search for new and more effective therapies is needed. Both cancers overexpress c-Myc and are highly dependent on this proto-oncogene for their survival. Although c-Myc inhibition has been shown to reduce PEL and MM survival, the underlying mechanisms leading to such an effect are not completely clarified. In this study, by pharmacologic inhibition and silencing, we show that c-Myc stands at the cross-road between UPR and DDR. Indeed, it plays a key role in maintaining the pro-survival function of UPR, through the IRE1α/XBP1 axis, and sustains the expression level of DDR molecules such as RAD51 and BRCA1 in MM and PEL cells. Moreover, we found that c-Myc establishes an interplay with the IRE1α/XBP1 axis whose inhibition downregulated c-Myc, skewed UPR towards cell death and enhanced DNA damage. In conclusion, this study unveils new insights into the molecular mechanisms leading to the cytotoxic effects of c-Myc inhibition and reinforces the idea that its targeting may be a promising therapeutic approach against MM and PEL that, although different cancers, share some similarities, including c-Myc overexpression, constitutive ER stress and poor response to current chemotherapies.

Nobiletin as an inducer of programmed cell death in cancer: a review

Cancer resistance to therapy is a big issue in cancer therapy. Tumours may develop some mechanisms to reduce the induction of cell death, thus stimulating tumour growth. Cancer cells may show a low expression and activity of tumour suppressor genes and a low response to anti-tumour immunity. These mutations can increase the resistance of cancer cells to programmed cell death mechanisms such as apoptosis, ferroptosis, pyroptosis, autophagic cell death, and some others. The upregulation of some mediators and transcription factors such as Akt, nuclear factor of κB, signal transducer and activator of transcription 3, Bcl-2, and others can inhibit cell death in cancer cells. Using adjuvants to induce the killing of cancer cells is an interesting strategy in cancer therapy. Nobiletin (NOB) is a herbal-derived agent with fascinating anti-cancer properties. It has been shown to induce the generation of endogenous ROS by cancer cells, leading to damage to critical macromolecules and finally cell death. NOB may induce the activity of p53 and pro-apoptosis mediators, and also inhibit the expression and nuclear translocation of anti-apoptosis mediators. In addition, NOB may induce cancer cell killing by modulating other mechanisms that are involved in programmed cell death mechanisms. This review aims to discuss the cellular and molecular mechanisms of the programmed cell death in cancer by NOB via modulating different types of cell death in cancer.

Dynamic Visualization of Endoplasmic Reticulum Stress in Living Cells via a Two-Stage Cascade Recognition Process

The endoplasmic reticulum (ER) is crucial for the regulation of multiple cellular processes, such as cellular responses to stress and protein synthesis, folding, and posttranslational modification. Nevertheless, monitoring ER physiological activity remains challenging due to the lack of powerful detection methods. Herein, we built a two-stage cascade recognition process to achieve dynamic visualization of ER stress in living cells based on a fluorescent carbon dot (CD) probe, which is synthesized by a facile one-pot hydrothermal method without additional modification. The fluorescent CD probe enables two-stage cascade ER recognition by first accumulating in the ER as the positively charged and lipophilic surface of the CD probe allows its fast crossing of multiple membrane barriers. Next, the CD probe can specifically anchor on the ER membrane via recognition between boronic acids and o-dihydroxy groups of mannose in the ER lumen. The two-stage cascade recognition process significantly increases the ER affinity of the CD probe, thus allowing the following evaluation of ER stress by tracking autophagy-induced mannose transfer from the ER to the cytoplasm. Thus, the boronic acid-functionalized cationic CD probe represents an attractive tool for targeted ER imaging and dynamic tracking of ER stress in living cells.

Shikonin induced Apoptosis Mediated by Endoplasmic Reticulum Stress in Colorectal Cancer Cells

Shikonin is a naphthoquinone pigment isolated from the root of Lithospermum erythrorhizon, which has displayed potent anti-tumor properties. However, the effects of shikonin in colorectal cancer cells have not been yet fully investigated. In this study, we demonstrated that shikonin significantly inhibited the activity of colorectal cancer cells in a time- and dose-dependent manner. The flow cytometry and western blot results indicated that shikonin induced cell apoptosis by down-regulating BCL-2 and activating caspase-3/9 and the cleavage of PARP. The expression of BiP and the PERK/elF2α/ATF4/CHOP and IRE1α /JNK signaling pathways were upregulated after shikonin treatment. The pre-treatment with N-acetyl cysteine significantly reduced the cytotoxicity of shikonin. Taken together, shikonin could inhibit proliferation of the colorectal cancer cell through the activation of ROS mediated-ER stress. The in vivo results showed that shikonin effectively inhibited tumor growth in the HCT-116 and HCT-15 xenograft models. In conclusion, shikonin inhibited the proliferation of colorectal cancer cells in vitro and in vivo and warrants future investigation.