Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

Role of C/EBP Homologous Protein (CHOP) and Nupr1 Interaction in Endoplasmic Reticulum Stress-Induced Apoptosis of Lens Epithelial Cells

Our study mainly analyzed the mechanism of C/EBP homologous protein (CHOP) and its interacting protein Nupr1 on endoplasmic reticulum stress (ERS) induced lens epithelial cells (LEC) apoptosis. Cell proliferation was detected by CCK-8. Apoptosis was detected by flow cytometry and TUNEL. Nupr1 expression was detected by RT-qPCR. The expressions of CHOP, Nupr1, apoptosis-related protein, and ERS-related protein were detected by Western blot. DCFH-DA probe was used to detect cell ROS. The SOD, GSH-PX, and MDA contents were detected by the kit. Co-IP was used to detect the interaction between CHOP and Nupr1. The morphology of the lens was detected by HE staining. The result shows that Tunicamycin (TU) can induce endoplasmic reticulum stress and apoptosis in LEC in a concentration-dependent manner. TU induction leads to the occurrence of CHOP nuclear translocation. Overexpression of CHOP can further enhance the inhibitory effect of TU on LEC proliferation and the promotion of apoptosis, while knockdown of CHOP has the opposite effect. CHOP and Nupr1 are interacting proteins, and knockdown of Nupr1 or addition of Nupr1 inhibitor ZZW-115 can reverse the effects of TU and overexpression of CHOP, respectively. It has been observed in animal experiments that treatment with oe-CHOP can further aggravate the pathological lesions of the rat lens, while ZZW-115 can reverse the effect of oe-CHOP to a certain extent and improve the lesions of the rat lens. Overall, CHOP interacts with Nupr1 to regulate apoptosis caused by ERS and mediate cataract progression in rats, and this study provides a new potential therapeutic target for the treatment of cataract.

Intricate subcellular journey of nanoparticles to the enigmatic domains of endoplasmic reticulum

It is evident that site-specific systemic drug delivery can reduce side effects, systemic toxicity, and minimal dosage requirements predominantly by delivering drugs to particular pathological sites, cells, and even subcellular structures. The endoplasmic reticulum (ER) and associated cell organelles play a vital role in several essential cellular functions and activities, such as the synthesis of lipids, steroids, membrane-associated proteins along with intracellular transport, signaling of Ca2+, and specific response to stress. Therefore, the dysfunction of ER is correlated with numerous diseases where cancer, neurodegenerative disorders, diabetes mellitus, hepatic disorder, etc., are very common. To achieve satisfactory therapeutic results in certain diseases, it is essential to engineer delivery systems that can effectively enter the cells and target ER. Nanoparticles are highly biocompatible, contain a variety of cargos or payloads, and can be modified in a pliable manner to achieve therapeutic effectiveness at the subcellular level when delivered to specific organelles. Passive targeting drug delivery vehicles, or active targeting drug delivery systems, reduce the nonselective accumulation of drugs while reducing side effects by modifying them with small molecular compounds, antibodies, polypeptides, or isolated bio-membranes. The targeting of ER and closely associated organelles in cells using nanoparticles, however, is still unsymmetrically understood. Therefore, here we summarized the pathophysiological prospect of ER stress, involvement of ER and mitochondrial response, disease related to ER dysfunctions, essential therapeutics, and nanoenabled modulation of their delivery to optimize therapy.

Structural and functional insight into thiazolidinone derivatives as novel candidates for anticancer drug design: in vitro biological and in-silico strategies

The compounds 2a-2h containing a thiazolidinone pharmacophore were synthesized via hetrerocylization of thiosemicarbazones with dimethyl acetylenedicarboxylate. The hybrid molecules were evaluated for anticancer activity against the human cell lines MCF-7, T47D (human breast adenocarcinoma) and HeLa (cervical cancer). Compounds 2c showed effective cytotoxicity on MCF-7 and HeLa (GI₅₀ 6.40 ± 0.10 μM/mL and GI₅₀10.30 ± 1.09 μM/mL), and compound 2d also showed effective cytotoxicity against MCF-7 and HeLa cell lines i.e., (GI₅₀ 16.60 ± 0.21 μM/mL and GI₅₀ 15.02 ± 0.14 μM/mL). These findings were comparable to cisplatin (azane;dichloroplatinum) the standard drug (GI₅₀ 13.20 ± μM/mL and 15.10 μM/mL respectively) and consequently nominated for determination of the mode of cell death. The results revealed the cytotoxic effects of 2c and 2d by induction of apoptosis in MCF-7 and HeLa cell lines. Moreover the results were further supported by the Molecular Docking which predicts the binding interactions of the best anticancer ligands with Ribonucleotide reductase (RNR), which is essential enzyme required for de-novo synthesis of DNA precursors. Molecular dynamic simulations were also performed to determine the stability of protein-ligand complex under different simulated conditions. In addition, the computational studies including DFTs, ADMET properties suggested these compounds can act as lead molecules, for the synthesis of novel drug candidates for the treatment of specific cancer and its associated malignancies.

Upregulation of Glutaminyl Cyclase Contributes to ERS-Induced Apoptosis in PC12 Cells

Glutaminyl cyclase (QC) is responsible for converting the N-terminal glutaminyl and glutamyl of the proteins into pyroglutamate (pE) through cyclization. It has been confirmed that QC catalyzes the formation of neurotoxic pE-modified Aβ in the brain of AD patients. But the effects of upregulated QC in diverse diseases have not been much clear until recently. Here, RNA sequencing was applied to identify differentially expressed genes (DEGs) in PC12 cells with QC overexpressing or knockdown. A total of 697 DEGs were identified in QC overexpressing cells while only 77 in QC knockdown cells. Multiple bioinformatic approaches revealed that the DEGs in QC overexpressing group were enriched in endoplasmic reticulum stress (ERS) related signaling pathways. The gene expression patterns of 23 DEGs were confirmed by RT-qPCR, in which the genes related to ERS showed the highest consistency. We also revealed the protein levels of GRP78, PERK, CHOP, and PARP-1, and caspase family was significantly upregulated by overexpressing QC. Moreover, overexpressing QC significantly increased apoptosis of PC12 cells in a time dependent manner. However, no significant alteration was observed in QC knockdown cells. Therefore, our study indicated that upregulated QC could induce ERS and apoptosis, which consequently trigger diseases by catalyzing the generation of pE-modified mediators.

Comparative Transcriptomics and Proteomics of Cancer Cell Lines Cultivated by Physiological and Commercial Media

Aiming to reduce the gap between in vitro and in vivo environment, a complex culture medium, Plasmax, was introduced recently, which includes nutrients and metabolites with concentrations normally found in human plasma. Herein, to study the influence of this medium on cellular behaviors, we utilized Plasmax to cultivate two cancer cell lines, including one breast cancer cell line, MDA-MB-231BR, and one brain cancer cell line, CRL-1620. Cancer cells were harvested and prepared for transcriptomics and proteomics analyses to assess the discrepancies caused by the different nutritional environments of Plasmax and two commercial media: DMEM, and EMEM. Total RNAs of cells were extracted using mammalian total RNA extract kits and analyzed by next-generation RNA sequencing; proteomics analyses were performed using LC-MS/MS. Gene oncology and pathway analysis were employed to study the affected functions. The cellular invasion and cell death were inhibited in MDA-MB-231BR cell line when cultured in Plasmax compared to DMEM and EMEM, whereas the invasion, migration and protein synthesis of CRL-1620 cell line were activated in Plasmax in relative to both commercial media. The expression changes of some proteins were more significant compared to their corresponding transcripts, indicating that Plasmax has more influence upon regulatory processes of proteins after translation. This work provides complementary information to the original study of Plasmax, aiming to facilitate the selection of appropriate media for in vitro cancer cell studies.

Inositol-Requiring Kinase 1 Regulates Apoptosis via Inducing Endoplasmic Reticulum Stress in Colitis Epithelial Cells

BACKGROUND

Endoplasmic reticulum stress (ERS) has been studied as critical factor during occurrence and development of ulcerative colitis (UC). However, the role of ERS in inflamed UC remains unclear.

AIMS

The purpose of this study was to analyze the role of inositol-requiring kinase 1 (IRE-1), a major regulator of ER, in regulating ERS and cell viability.

METHODS

In UC mucosa tissue, IRE-1, BiP, XBP-1s, CHOP caspase-12 and GADD34 mRNA were assayed by qRT-PCR. Then, human normal colon epithelial cell line (NCM-460) and colon fibroblast cell line (CCD-33Co) were cultured, and downregulated or upregulated IRE-1 expression. ERS was induced with 100 ng/mL of Interleukin 6 (IL-6). CCK8 assay was performed to analyze cell proliferation. Flow cytometry analysis was conducted to detect the apoptosis. Western blot assay was used to examine ERS markers.

RESULTS

IRE-1, BiP, XBP-1s, caspase-12 and CHOP mRNA were highly expressed in UC mucosa tissue, and the expression of GADD34 mRNA significantly decreased. These results show that ERS-induced unfolded protein response was enhanced in UC mucosa tissue. In cells, silencing the expression of IRE-1 could suppress cell proliferation and promote apoptosis through activating unfolded protein response, while the over-expression of IRE-1 had the opposite effect. IL-6 could induce ERS and cells apoptosis. Furthermore, we demonstrated that shRNA IRE-1 could enhance the inhibition of IL-6 on cells viability.

CONCLUSIONS

Inhibition of IRE-1 enhanced unfolded protein response and cells apoptosis and IL-6-induced ERS and suggested that IRE-1 might be a potential target of UC.

MicroRNA-150 affects endoplasmic reticulum stress via MALAT1-miR-150 axis-mediated NF-κB pathway in LPS-challenged HUVECs and septic mice

AIMS

Sepsis is a systemic inflammatory complication, which is the common cause of death in critical patients. This study aimed to evaluate the potential regulatory mechanisms of miR-150 in lipopolysaccharide (LPS)-challenged HUVECs and cecal ligation and puncture (CLP)-induced septic mice.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs) were challenged with LPS. Pulmonary arterial endothelial cells (PAECs) were isolated from CLP-induced septic mice. The mRNA and protein levels of target molecules were detected by RT-qPCR and Western blotting. Apoptosis of HUVECs was determined by Annexin V/PI staining on a flow cytometry. The interaction between miR-150 and MALAT1 was assessed by luciferase reporter assay, RIP and RNA pull-down assay.

KEY FINDINGS

MiR-150 was downregulated in LPS-induced HUVECs. MiR-150 mimics restrained LPS-induced inflammatory response by reducing TNF-α and IL-6 levels, but increasing IL-10 level. Moreover, miR-150 mimics downregulated endoplasmic reticulum (ER) stress-related proteins, GRP78 and CHOP levels in LPS-exposed HUVECs. Additionally, LPS-induced apoptosis was suppressed by miR-150 mimics via decreasing cleaved caspase-3 and Bax levels, while enhancing Bcl-2 level. Mechanistically, MALAT1 could competitively bind to miR-150. LPS-induced apoptosis, ER stress and inflammation were promoted by MALAT1 overexpression, but reversed by siMALAT1. Furthermore, miR-150 inhibitor strengthened LPS-induced apoptosis, ER stress and inflammation, which could be attenuated by siMALAT1 via regulating NF-κB pathway. Finally, agomiR-150 repressed ER stress and inflammatory response in PAECs isolated from septic mice via decreasing MALAT1 level.

SIGNIFICANCE

Our findings suggest that miR-150 affects sepsis-induced endothelial injury by regulating ER stress and inflammation via MALAT1-mediated NF-κB pathway.

Endoplasmic Reticulum Stress Increases Multidrug-resistance Protein 2 Expression and Mitigates Acute Liver Injury

BACKGROUND

Multidrug-resistance protein (MRP) 2 is a key membrane transporter that is expressed on hepatocytes and regulated by nuclear factor kappa B (NF-κB). Interestingly, endoplasmic reticulum (ER) stress is closely associated with liver injury and the activation of NF-κB signaling.

OBJECTIVE

Here, we investigated the impact of ER stress on MRP2 expression and the functional involvement of MRP2 in acute liver injury.

METHODS

ER stress, MRP2 expression, and hepatocyte injury were analyzed in a carbon tetrachloride (CCl4)-induced mouse model of acute liver injury and in a thapsigargin (TG)-induced model of ER stress.

RESULTS

CCl4 and TG induced significant ER stress, MRP2 protein expression and NF- κB activation in mice and LO2 cells (P < 0.05). Pretreatment with ER stress inhibitor 4- phenyl butyric acid (PBA) significantly mitigated CCl4 and TG-induced ER stress and MRP2 protein expression (P < 0.05). Moreover, pretreatment with pyrrolidine dithiocarbamic acid (PDTC; NF-κB inhibitor) significantly inhibited CCl4-induced NF-κB activation and reduced MRP2 protein expression (1±0.097 vs. 0.623±0.054; P < 0.05). Furthermore, hepatic downregulation of MRP2 expression significantly increased CCl4- induced ER stress, apoptosis, and liver injury.

CONCLUSION

ER stress enhances intrahepatic MRP2 protein expression by activating NF-κB. This increase in MRP2 expression mitigates ER stress and acute liver injury.

ROR2 induces cell apoptosis via activating IRE1α/JNK/CHOP pathway in high-grade serous ovarian carcinoma in vitro and in vivo

Background

Epithelial ovarian cancer (EOC) is the most lethal cancer in female genital tumors. New disease markers and novel therapeutic strategies are urgent to identify considering the current status of treatment. Receptor tyrosine kinases family plays critical roles in embryo development and disease progression. However, ambivalent research conclusions of ROR2 make its role in tumor confused and the underlying mechanism is far from being understood. In this study, we sought to clarify the effects of ROR2 on high-grade serous ovarian carcinoma (HGSOC) cells and reveal the mechanism.

Methods

Immunohistochemistry assay and western-blot assay were used to detect proteins expression. ROR2 overexpression adenovirus and Lentivirus were used to create ROR2 overexpression model in vitro and in vivo, respectively. MTT assay, colony formation assay and transwell assay were used to measure the proliferation, invasion and migration ability of cancer cells. Flow cytometry assay was used to detect cell apoptosis rate. Whole transcriptome analysis was used to explore the differentially expressed genes between ROR2 overexpression group and negative control group. SiRNA targeted IRE1α was used to knockdown IRE1α. Kira6 was used to inhibit phosphorylation of IRE1α.

Results

Expression of ROR2 was significantly lower in HGSOC tissues compared to normal fallopian tube epithelium or ovarian surface epithelium tissues. In HGSOC cohort, patients with advanced stages or positive lymph nodes were prone to express lower ROR2. Overexpression of ROR2 could repress the proliferation of HGSOC cells and induce cell apoptosis. RNA sequencing analysis indicated that ROR2 overexpression could induce unfold protein response. The results were also confirmed by upregulation of BIP and phosphorylated IRE1α. Furthermore, pro-death factors like CHOP, phosphorylated JNK and phosphorylated c-Jun were also upregulated. IRE1α knockdown or Kira6 treatment could reverse the apoptosis induced by ROR2 overexpression. Finally, tumor xenograft experiment showed ROR2 overexpression could significantly repress the growth rate and volume of transplanted tumors.

Conclusions

Taken together, ROR2 downregulation was associated with HGSOC development and progression. ROR2 overexpression could repress cell proliferation and induce cell apoptosis in HGSOC cells. And the underlying mechanism might be the activation of IRE1α/JNK/CHOP pathway induced by ROR2.

Crocin Improves Cognitive Behavior in Rats with Alzheimer's Disease by Regulating Endoplasmic Reticulum Stress and Apoptosis

AIM

To investigate the effect of crocin on the learning and memory acquisition of AD rats and its underlying mechanisms.

METHODS

A total of 48 healthy male SD rats were randomly divided into control group, AD model group, resveratrol group, and crocin group, with 12 rats per group. AD model was established by injecting Aβ 25-35 to the lateral ventricle of rats, and thereafter the rats were administrated with resveratrol (40 mg/kg), crocin (40 mg/kg), or PBS daily for 14 days. Y-maze test and sucrose preference test were used to detect the learning and memory acquisition of rats. Neuronal apoptosis was detected by TUNEL staining and Western blot for apoptosis-related proteins Bax, Bcl-2, and Caspase-3. Immunofluorescence staining and Western blot tests were used to detect the expression of glucose regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) in hippocampal CA1 region (Hippo) and prefrontal cortical neurons (PFC).

RESULTS

The learning and memory abilities of AD rats were significantly decreased, which was significantly rescued by resveratrol and crocin. The apoptotic cell number of Hippo and PFC neurons in AD model group was significantly higher than that in control group (P<0.01), while resveratrol and crocin significantly decreased the apoptotic cell number in AD group (P<0.01). Compared with the control group, the expression of Bcl2 in PFC and hippo of AD model group was significantly decreased (P<0.01), while those of Bax, Caspase3, GRP78, and CHOP were significantly increased (P<0.01). Resveratrol and crocin could significantly reverse the expression of these proteins in AD rats (P<0.05).

CONCLUSION

Crocin can improve the learning and memory ability of AD rats possibly by reducing endoplasmic reticulum stress and neuronal apoptosis.

Safranal induces DNA double-strand breakage and ER-stress-mediated cell death in hepatocellular carcinoma cells

Poor prognoses remain the most challenging aspect of hepatocellular carcinoma (HCC) therapy. Consequently, alternative therapeutics are essential to control HCC. This study investigated the anticancer effects of safranal against HCC using in vitro, in silico, and network analyses. Cell cycle and immunoblot analyses of key regulators of cell cycle, DNA damage repair and apoptosis demonstrated unique safranal-mediated cell cycle arrest at G2/M phase at 6 and 12 h, and at S-phase at 24 h, and a pronounced effect on DNA damage machinery. Safranal also showed pro-apoptotic effect through activation of both intrinsic and extrinsic initiator caspases; indicating ER stress-mediated apoptosis. Gene set enrichment analysis provided consistent findings where UPR is among the top terms of up-regulated genes in response to safranal treatment. Thus, proteins involved in ER stress were regulated through safranal treatment to induce UPR in HepG2 cells.

The antioxidant transcription factor Nrf2 modulates the stress response and phenotype of malignant as well as premalignant pancreatic ductal epithelial cells by inducing expression of the ATF3 splicing variant ΔZip2

Pancreatic ductal adenocarcinoma (PDAC) exhibits one of the worst survival rates of all cancers. While death rates show declining trends in the majority of cancers, PDAC registers rising rates. Based on the recently described crosstalk between TGF-β1 and Nrf2 in the PDAC development, the involvement of ATF3 and its splice variant ΔZip2 in TGF-β1- and Nrf2-driven pancreatic tumorigenesis was investigated. As demonstrated here, PDAC (Panc1, T3M4) cells or premalignant H6c7 pancreatic ductal epithelial cells differentially express ΔZip2- and ATF3, relating to stronger Nrf2 activity seen in Panc1 cells and TGF-ß1 activity in T3M4 or H6c7 cells, respectively. Treatment with the electrophile/oxidative stress inducer tBHQ or the cytostatic drug gemcitabine strongly elevated ΔZip2 expression in a Nrf2-dependent fashion. The differential expression of ATF3 and ΔZip2 in response to Nrf2 and TGF-ß1 relates to differential ATF3-gene promoter usage, giving rise of distinct splice variants. Nrf2-dependent ΔZip2 expression confers resistance against gemcitabine-induced apoptosis, only partially relating to interference with ATF3 and its proapoptotic activity, e.g., through CHOP-expression. In fact, ΔZip2 autonomously activates expression of cIAP anti-apoptotic proteins. Moreover, ΔZip2 favors and ATF3 suppresses growth and clonal expansion of PDAC cells, again partially independent of each other. Using a Panc1 tumor xenograft model in SCID-beige mice, the opposite activities of ATF3 and ΔZip2 on tumor-growth and chemoresistance were verified in vivo. Immunohistochemical analyses confirmed ΔZip2 and Nrf2 coexpression in cancerous and PanIN structures of human PDAC and chronic pancreatitis tissues, respectively, which to some extent was reciprocal to ATF3 expression. It is concluded that depending on selective ATF3-gene promoter usage by Nrf2, the ΔZip2 expression is induced in response to electrophile/oxidative (here through tBHQ) and xenobiotic (here through gemcitabine) stress, providing apoptosis protection and growth advantages to pancreatic ductal epithelial cells. This condition may substantially add to pancreatic carcinogenesis driven by chronic inflammation.

Roles of endoplasmic reticulum stress and autophagy on H2O2‑induced oxidative stress injury in HepG2 cells

Endoplasmic reticulum stress (ERS) can be induced by a variety of physiological and pathological factors including oxidative stress, which triggers the unfolded protein response to deal with ERS. Autophagy has been hypothesized to be a means for tumor cells to increase cell survival under conditions of hypoxia, metabolic stress and even chemotherapy. Although they may function independently from each other, there are also interactions between responses to oxidative stress injury induced by pathologic and pharmacological factors. The aim of the present study was to investigate the effects of ERS and autophagy on H2O2‑induced oxidative stress injury in human HepG2 hepatoblastoma cells. It was demonstrated that exposure of HepG2 cells to H2O2 decreased cell viability and increased reactive oxygen species (ROS) levels in a dosage‑dependent manner. In addition, apoptosis and autophagy rates were elevated and reduced following cell exposure to H2O2 + the ERS inducer Tunicamycin (TM), and to H2O2 + the ERS inhibitor Salubrinal (SAL), compared with the cells treated with H2O2 alone, respectively. Further studies revealed that TM enhanced the expression of ERS‑related genes including glucose‑regulated protein‑78/binding immunoglobulin protein, inositol‑requiring kinase‑I and activating transcription factor 6 and C/EBP‑homologous protein 10, which were attenuated by SAL compared with cells exposed to H2O2 alone. The data from the present study also demonstrated that LC3II/LC3‑I and p62, members of autophagy‑related genes, were increased and decreased in cells treated with H2O2 + TM compared with cells treated with H2O2, respectively, indicating that autophagy was stimulated by ERS. Furthermore, a reduction in the levels of pro caspase‑3 and pro caspase‑9, and elevation level of caspase‑12 were observed in cells exposed to H2O2 + TM compared with cells treated with H2O2, respectively, suggesting apoptosis induced by H2O2 was enhanced by ERS or autophagy triggered by H2O2. The above results suggest that the ERS inducer may be a potential target for pharmacological intervention targeted to ERS or autophagy to enhance oxidative stress injury of tumor cells induced by antitumor drugs.

Secreted GRP78 activates EGFR-SRC-STAT3 signaling and confers the resistance to sorafeinib in HCC cells

Acquired resistance is a common phenomenon for HCC patients who undergone sorafenib treatment, however the mechanism by which acquired resistance develops remains elusive. In this study, we found that GRP78 could be detected in the serum samples of HCC patients and the conditional medium of multiple HCC cell lines, suggesting that GRP78 is secreted by HCC cells. Further studies showed that secreted GRP78 facilitated the proliferation and inhibited the apoptosis induced by sorafenib both in HCC cell lines and in tumor xenografts. We further found that secreted GRP78 could interact physically with EGFR, therefore activates EGFR signaling pathway. knockdown of EGFR decreased secreted GRP78 induced phosphorylation of SRC and STAT3. By contrast, overexpression of EGFR further enhanced the phosphorylation of SRC and STAT3 induced by secreted GRP78, suggesting the critical role of EGFR in secreted GRP78 conferred resistance to sorafeinib. Moreover, inhibition of SRC by PP2 antagonized the resistance to sorafenib and inhibited the activation of STAT3 conferred by secreted GRP78. Taken together, our results showed that secreted GRP78 could interact with EGFR, activate EGFR-SRC-STAT3 signaling, conferring the resistance to sorafenib.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

Synthesis and in vitro evaluation of zerumbone pendant derivatives: potent candidates for anti-diabetic and anti-proliferative activities

A series of zerumbone pendant derivatives were synthesized and evaluated for their α-glucosidase, α-amylase and glycation inhibition activities.

Endoplasmic Reticulum Is Involved in Myocardial Injury in a Miniature Swine Model of Coronary Artery Stenosis Exposed to Acceleration-Associated Stress

This study aimed to investigate the effects of myocardial injury in a minimally-invasive miniature swine model with different levels of coronary artery stenosis (CAS) and exposed to maximal tolerated +Gz. Proximal left anterior descending branch was ligated in 20 swine. Five swine underwent a sham operation. A trapezoid acceleration curve was used for +Gz stress. Pathological changes of myocardial tissue were detected by H&E staining. Apoptotic cardiomyocytes were detected by TUNEL. GRP78 and CHOP were investigated by immunohistochemistry and western blot. CAS models were successful in 18 animals.Compared with the sham-operated group (+8.00±0.71 Gz), the maximal tolerated +Gz values of the moderate stenosis (+6.00±0.89 Gz, P<0.05) and severe stenosis groups (+5.20±0.84 Gz, P<0.05) were decreased.Compared with sham animals (12.16±1.25%), after exposure to maximum +Gz, apoptotic cells of the moderate (43.53±8.42%, P<0.05) and severe stenosis group (60.50±9.35%, P<0.05) were increased, MDA content was increased (1.89 and 4.91 folds, respectively, P<0.05), and SOD activity was reduced (-13.66% and -21.71%, respectively). After exposure to maximum +Gz, GRP78 protein expression was low in the sham-operated (0.29±0.05) and mild stenosis groups (0.35±0.04), while expression was high in the moderate (0.72±0.04, P<0.05) and severe stenosis groups (0.65±0.07, P<0.05). CHOP protein expression was not observed in the sham-operated group, while expression was high in the moderate and severe stenosis groups. These results indicated that Under maximum exposure to +Gz stress, different levels of CAS led to different levels of myocardial injury. Endoplasmic reticulum response is involved in the apoptosis of cardiomyocytes after +Gz stress.

Endoplasmic reticulum stress is involved in the response of human laryngeal carcinoma cells to Carboplatin but is absent in Carboplatin-resistant cells

The major obstacle of successful tumor treatment with carboplatin (CBP) is the development of drug resistance. In the present study, we found that following treatment with CBP the amount of platinum which enters the human laryngeal carcinoma (HEp2)-derived CBP-resistant (7T) cells is reduced relative to the parental HEp2. As a consequence, the formation of reactive oxidative species (ROS) is reduced, the induction of endoplasmic reticulum (ER) stress is diminished, the amount of inter- and intrastrand cross-links is lower, and the induction of apoptosis is depressed. In HEp2 cells, ROS scavenger tempol, inhibitor of ER stress salubrinal, as well as gene silencing of ER stress marker CCAAT/enhancer-binding protein (CHOP) increases their survival and renders them as resistant to CBP as 7T cell subline but did not influence the survival of 7T cells. Our results suggest that in HEp2 cells CBP-induced ROS is a stimulus for ER stress. To the contrary, despite the ability of CBP to induce formation of ROS and activate ER stress in 7T cells, the cell death mechanism in 7T cells is independent of ROS induction and activation of ER stress. The novel signaling pathway of CBP-driven toxicity that was found in the HEp2 cell line, i.e. increased ROS formation and induction of ER stress, may be predictive for therapeutic response of epithelial cancer cells to CBP-based therapy.

BRSK2 is regulated by ER stress in protein level and involved in ER stress-induced apoptosis

The accumulation of unfolded protein in lumen of the endoplasmic reticulum (ER) triggers a cell stress response called ER stress, which induces the transcriptional up-regulation of a number of proteins, including molecular chaperones and folding enzymes, the global inhibition of protein synthesis, and the activation of apoptotic pathways. The molecular mechanism underlying the apoptotic response has remained largely elusive. AMP activated protein kinase (AMPK) has been implicated in ER stress-induced apoptosis through its role in attenuating ER stress. BRSK2 (brain selective kinase 2, also known as SAD-A) is a serine/threonine kinase of the AMPK family. Here, we demonstrate that the BRSK2 protein levels are significantly down-regulated in response to ER stress in PANC-1 and HeLa cells. Furthermore, we also observed that ER stress induces endogenous BRSK2 to localize to the ER. Importantly, knockdown of endogenous BRSK2 expression enhances ER stress-mediated apoptosis in cells while over express BRSK2 in wild type or kinase-dead type both reduce the apoptosis. BRSK2 knockdown increases the transcription of CHOP and the levels of cleaved caspase-3 in cells in response to ER stress while over expression of BRSK2 decrease CHOP mRNA and levels of cleaved caspase-3. Taken together, our findings demonstrate ER stress may reduce BRSK2 protein and change BRSK2 subcellular localization, which in turn alleviate ER stress-induced apoptosis.

Synthesis of chalcones with anticancer activities

Several chalcones were synthesized and their in vitro cytotoxicity against various human cell lines, including human breast adenocarcinoma cell line MCF-7, human lung adenocarcinoma cell line A549, human prostate cancer cell line PC3, human adenocarcinoma cell line HT-29 (colorectal cancer) and human normal liver cell line WRL-68 was evaluated. Most of the compounds being active cytotoxic agents, four of them with minimal IC₅₀ values were chosen and studied in detail with MCF-7 cells. The compounds 1, 5, 23, and 25 were capable in eliciting apoptosis in MCF-7 cells as shown by multiparameter cytotoxicity assay and caspase-3/7, -8, and -9 activities (p < 0.05). The ROS level showed 1.3-fold increase (p < 0.05) at the low concentrations used and thus it was concluded that the compounds increased the ROS level eventually leading to apoptosis in MCF-7 cells through intrinsic as well as extrinsic pathways.

The African swine fever virus DP71L protein recruits the protein phosphatase 1 catalytic subunit to dephosphorylate eIF2alpha and inhibits CHOP induction but is dispensable for these activities during virus infection

The African swine fever virus (ASFV) DP71L protein is present in all isolates as either a short form of 70 to 72 amino acids or a long form of about 184 amino acids, and both of these share sequence similarity to the C-terminal domain of the herpes simplex virus ICP34.5 protein and cellular protein GADD34. In the present study we expressed DP71L in different mammalian cells and demonstrated that DP71L causes dephosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α) in resting cells and during chemical-induced endoplasmic reticulum stress and acts to enhance expression of cotransfected reporter genes. We showed that DP71L binds to all the three isoforms (α, β, and γ) of the protein phosphatase 1 catalytic subunit (PP1c) and acts by recruiting PP1c to eIF2α. We also showed that DP71L inhibits the induction of ATF4 and its downstream target, CHOP. We investigated the eIF2α phosphorylation status and induction of CHOP in porcine macrophages infected by two ASFV field isolates, Malawi Lil20/1 and Benin 97/1, and two DP71L deletion mutants, MalawiΔNL and E70ΔNL. Our results showed that deletion of the DP71L gene did not cause an increase in the level of eIF2α phosphorylation or induction of CHOP, indicating that DP71L is not the only factor required by the virus to control the phosphorylation level of eIF2α during infection. We therefore hypothesize that ASFV has other mechanisms to prevent the eIF2α phosphorylation and the subsequent protein synthesis inhibition.