Evaluation of distinct modes of oxidative secondary injury generated in heat-treated cells of Escherichia coli with solid/liquid and complex/semi-synthetic media sets

AIMS

To characterize and evaluate oxidative secondary injury generated in heat-treated Escherichia coli cells during recovery cultivation either on agar or in a broth of a semi-synthetic enriched M9 (EM9) medium and a complex Luria broth (LB) medium with different types of antioxidants.

METHODS AND RESULTS

E. coli cells grown in the EM9 and LB broth were heated at 50^o C in a buffer (pH7.0). Heated cells were recovered on the same kind of agar medium as that used for growth, with or without different antioxidants. Although these antioxidants mostly protected the cells from oxidative secondary injury on the recovery media, sodium thiosulfate and sodium pyruvate were most protective on EM9 and LB agars, respectively. Determination of viability using the most probable number and growth delay analysis methods showed significant reductions in the protective effects of antioxidants in the EM9 and LB media.

CONCLUSION

Oxidative secondary injury generated in heated E. coli cells was found to be qualitatively and quantitatively diverse under cellular and environmental conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results suggest that different modes of oxidation should be considered in viability determination and injured cell enumeration of heat-treated cells.

OASIS/CREB3L1 is a factor that responds to nuclear envelope stress

The nuclear envelope (NE) safeguards the genome and is pivotal for regulating genome activity as the structural scaffold of higher-order chromatin organization. NE had been thought as the stable during the interphase of cell cycle. However, recent studies have revealed that the NE can be damaged by various stresses such as mechanical stress and cellular senescence. These types of stresses are called NE stress. It has been proposed that NE stress is closely related to cellular dysfunctions such as genome instability and cell death. Here, we found that an endoplasmic reticulum (ER)-resident transmembrane transcription factor, OASIS, accumulates at damaged NE. Notably, the major components of nuclear lamina, Lamin proteins were depleted at the NE where OASIS accumulates. We previously demonstrated that OASIS is cleaved at the membrane domain in response to ER stress. In contrast, OASIS accumulates as the full-length form to damaged NE in response to NE stress. The accumulation to damaged NE is specific for OASIS among OASIS family members. Intriguingly, OASIS colocalizes with the components of linker of nucleoskeleton and cytoskeleton complexes, SUN2 and Nesprin-2 at the damaged NE. OASIS partially colocalizes with BAF, LEM domain proteins, and a component of ESCRT III, which are involved in the repair of ruptured NE. Furthermore, OASIS suppresses DNA damage induced by NE stress and restores nuclear deformation under NE stress conditions. Our findings reveal a novel NE stress response pathway mediated by OASIS.

Gene-edited human stem cell-derived β cells from a patient with monogenic diabetes reverse preexisting diabetes in mice

Differentiation of insulin-producing pancreatic β cells from induced pluripotent stem cells (iPSCs) derived from patients with diabetes promises to provide autologous cells for diabetes cell replacement therapy. However, current approaches produce patient iPSC-derived β (SC-β) cells with poor function in vitro and in vivo. Here, we used CRISPR-Cas9 to correct a diabetes-causing pathogenic variant in Wolfram syndrome 1 (WFS1) in iPSCs derived from a patient with Wolfram syndrome (WS). After differentiation to β cells with our recent six-stage differentiation strategy, corrected WS SC-β cells performed robust dynamic insulin secretion in vitro in response to glucose and reversed preexisting streptozocin-induced diabetes after transplantation into mice. Single-cell transcriptomics showed that corrected SC-β cells displayed increased insulin and decreased expression of genes associated with endoplasmic reticulum stress. CRISPR-Cas9 correction of a diabetes-inducing gene variant thus allows for robust differentiation of autologous SC-β cells that can reverse severe diabetes in an animal model.

Toxic effects of endoplasmic reticulum stress transducer BBF2H7-derived small peptide fragments on neuronal cells

Aggregation, fibril formation, and deposition of amyloid β (Aβ) protein are believed to be the central pathogeneses of Alzheimer's disease (AD). Numerous studies have shown that fibril formation is promoted by preformed seeds at the beginning of the aggregation process. Therefore, aggregated molecules that promote fibrillization of Aβ protein as seeds could affect the pathology. We recently found that approximately 40 amino acid hydrophobic peptides, BBF2H7-derived small peptide (BSP) fragments, are generated via intramembranous cleavage under endoplasmic reticulum (ER) stress conditions. Interestingly, similar to Aβ protein, the fragments exhibit a high aggregation propensity and form fibril structures. It has been noted that ER stress is involved in the pathogenesis of AD. In this study, we examined the effect of BSP fragments on aggregation and cytotoxicity of Aβ_1-40 protein, which is generated as a major species of Aβ protein, but has a lower aggregative property than Aβ_1-42 protein. We demonstrated that BSP fragments promote aggregation of Aβ_1-40 protein. Aggregates of Aβ_1-40 protein mediated by BSP fragments also exhibited potent neurotoxicity. Our findings suggest the possibility that BSP fragments affect accumulation of Aβ proteins and are involved in the pathogenesis of AD.

Wolfram syndrome 1 gene regulates pathways maintaining beta-cell health and survival

Wolfram Syndrome 1 (WFS1) protein is an endoplasmic reticulum (ER) factor whose deficiency results in juvenile-onset diabetes secondary to cellular dysfunction and apoptosis. The mechanisms guiding β-cell outcomes secondary to WFS1 function, however, remain unclear. Here, we show that WFS1 preserves normal β-cell physiology by promoting insulin biosynthesis and negatively regulating ER stress. Depletion of Wfs1 in vivo and in vitro causes functional defects in glucose-stimulated insulin secretion and insulin content, triggering Chop-mediated apoptotic pathways. Genetic proof of concept studies coupled with RNA-seq reveal that increasing WFS1 confers a functional and a survival advantage to β-cells under ER stress by increasing insulin gene expression and downregulating the Chop-Trib3 axis, thereby activating Akt pathways. Remarkably, WFS1 and INS levels are reduced in type-2 diabetic (T2DM) islets, suggesting that WFS1 may contribute to T2DM β-cell pathology. Taken together, this work reveals essential pathways regulated by WFS1 to control β-cell survival and function primarily through preservation of ER homeostasis.

Calnexin promotes the folding of mutant iduronate 2-sulfatase related to mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is one of the most common mucopolysaccharidoses, which is caused by mutation of the gene encoding iduronate 2-sulfatase (IDS). The loss of function of IDS leads to the accumulation of heparan sulfate and dermatan sulfate of glycosaminoglycans throughout the body, resulting in skeletal deformities, mental retardation, rigid joints, and thick skin. Recently, enzyme replacement therapy has become a common strategy for treating this condition. However, its effectiveness on the central nervous system (CNS) is limited because intravenously administered recombinant IDS (rIDS) cannot pass through the blood brain barrier. Therefore, several methods for delivering rIDS to the CNS, using anti-human transferrin receptor antibody and adeno-associated virus 9, have been explored. To investigate additional approaches for treatment, more cognition about the intracellular dynamics of mutant IDS is essential. We have already found that mutant IDS accumulated in the endoplasmic reticulum (ER) and was degraded by ER-associated degradation (ERAD). Although the dynamics of degradation of mutant IDS was revealed, the molecular mechanism related to the folding of mutant IDS in the ER remained unclear. In this research, we confirmed that mutant IDS retained in the ER would be folded by binding with calnexin (CNX). Thus, knockdown of CNX reduced the translocation of mutant IDS from ER to lysosome and its enzyme activity, indicating that the correct folding of this protein via interaction with CNX ensures its functional activity. These findings reveal the possibility that modifying the interaction of mutant IDS and CNX could contribute to alternative therapeutic strategies for MPS II.

Renal medullary tonicity regulates RNF183 expression in the collecting ducts via NFAT5

Nuclear factor of activated T-cells 5 (NFAT5) directly binds to the promoter of the RING finger protein 183 (RNF183) gene and induces its transcription under hypertonic conditions in mouse inner-medullary collecting duct (mIMCD-3) cells. However, there is no specific anti-RNF183 antibody for immunostaining; therefore, it is unclear whether NFAT5 regulates RNF183 expression in vivo and where RNF183 is localized in the kidney. This study investigated NFAT5-regulated in vivo RNF183 expression and localization using CRISPR/Cas9-mediated RNF183-green fluorescent protein (RNF183-GFP) knock-in mice. GFP with linker sequences was introduced upstream of an RNF183 open reading frame in exon 3 by homologous recombination through a donor plasmid. Immunofluorescence staining using GFP antibody revealed that GFP signals gradually increase from the outer medulla down to the inner medulla and colocalize with aquaporin-2. Furosemide treatment dramatically decreased RNF183 expression in the renal medulla, consistent with the decrease in NFAT5 protein and target gene mRNA expression. Furosemide treatment of mIMCD-3 cells did not affect mRNA expression and RNF183 promoter activities. These results indicated that RNF183 is predominantly expressed in the renal medullary collecting ducts, and that decreased renal medullary tonicity by furosemide treatment decreases RNF183 expression by NFAT5 downregulation.

NFAT5 up-regulates expression of the kidney-specific ubiquitin ligase gene Rnf183 under hypertonic conditions in inner-medullary collecting duct cells

We previously reported that among the 37 RING finger protein (RNF) family members, RNF183 mRNA is specifically expressed in the kidney under normal conditions. However, the mechanism supporting its kidney-specific expression pattern remains unclear. In this study, we elucidated the mechanism of the transcriptional activation of murine Rnf183 in inner-medullary collecting duct cells. Experiments with anti-RNF183 antibody revealed that RNF183 is predominantly expressed in the renal medulla. Among the 37 RNF family members, Rnf183 mRNA expression was specifically increased in hypertonic conditions, a hallmark of the renal medulla. RNF183 up-regulation was consistent with the activation of nuclear factor of activated T cells 5 (NFAT5), a transcription factor essential for adaptation to hypertonic conditions. Accordingly, siRNA-mediated knockdown of NFAT5 down-regulated RNF183 expression. Furthermore, the -3,466 to -3,136-bp region upstream of the mouse Rnf183 promoter containing the NFAT5-binding motif is conserved among mammals. A luciferase-based reporter vector containing the NFAT5-binding site was activated in response to hypertonic stress, but was inhibited by a mutation at the NFAT5-binding site. ChIP assays revealed that the binding of NFAT5 to this DNA site is enhanced by hypertonic stress. Of note, siRNA-mediated RNF183 knockdown increased hypertonicity-induced caspase-3 activation and decreased viability of mIMCD-3 cells. These results indicate that (i) RNF183 is predominantly expressed in the normal renal medulla, (ii) NFAT5 stimulates transcriptional activation of Rnf183 by binding to its cognate binding motif in the Rnf183 promoter, and (iii) RNF183 protects renal medullary cells from hypertonicity-induced apoptosis.

Sec16A, a key protein in COPII vesicle formation, regulates the stability and localization of the novel ubiquitin ligase RNF183

We identified 37 ubiquitin ligases containing RING-finger and transmembrane domains. Of these, we found that RNF183 is abundantly expressed in the kidney. RNF183 predominantly localizes to the endoplasmic reticulum (ER), Golgi, and lysosome. We identified Sec16A, which is involved in coat protein complex II vesicle formation, as an RNF183-interacting protein. RNF183 colocalized with Sec16A and interacted through the central conserved domain (CCD) of Sec16A. Although Sec16A is not a substrate for RNF183, RNF183 was more rapidly degraded by the ER-associated degradation (ERAD) in the absence of Sec16A. Sec16A also stabilized the interacting ubiquitin ligase RNF152, which localizes to the lysosome and has structural similarity with RNF183. These results suggest that Sec16A appears to regulate the protein stability and localization of lysosomal ubiquitin ligases.

Neuronal activity-dependent local activation of dendritic unfolded protein response promotes expression of brain-derived neurotrophic factor in cell soma

Unfolded protein response (UPR) has roles not only in resolving the accumulation of unfolded proteins owing to endoplasmic reticulum (ER) stress, but also in regulation of cellular physiological functions. ER stress transducers providing the branches of UPR signaling are known to localize in distal dendritic ER of neurons. These reports suggest that local activation of UPR branches may produce integrated outputs for distant communication, and allow regulation of local events in highly polarized neurons. Here, we demonstrated that synaptic activity‐ and brain‐derived neurotrophic factor (BDNF)‐dependent local activation of UPR signaling could be associated with dendritic functions through retrograde signal propagation by using murine neuroblastoma cell line, Neuro‐2A and primary cultured hippocampal neurons derived from postnatal day 0 litter C57BL/6 mice. ER stress transducer, inositol‐requiring kinase 1 (IRE1), was activated at postsynapses in response to excitatory synaptic activation. Activated dendritic IRE1 accelerated accumulation of the downstream transcription factor, x‐box‐binding protein 1 (XBP1), in the nucleus. Interestingly, excitatory synaptic activation‐dependent up‐regulation of XBP1 directly facilitated transcriptional activation of BDNF. BDNF in turn drove its own expression via IRE1‐XBP1 pathway in a protein kinase A‐dependent manner. Exogenous treatment with BDNF promoted extension and branching of dendrites through the protein kinase A‐IRE1‐XBP1 cascade. Taken together, our findings indicate novel mechanisms for communication between soma and distal sites of polarized neurons that are coordinated by local activation of IRE1‐XBP1 signaling. Synaptic activity‐ and BDNF‐dependent distinct activation of dendritic IRE1‐XBP1 cascade drives BDNF expression in cell soma and may be involved in dendritic extension.

Cover Image for this issue: doi. 10.1111/jnc.14159.

Neuronal activity-dependent local activation of dendritic unfolded protein response promotes expression of brain-derived neurotrophic factor in cell soma

Unfolded protein response (UPR) has roles not only in resolving the accumulation of unfolded proteins owing to endoplasmic reticulum (ER) stress, but also in regulation of cellular physiological functions. ER stress transducers providing the branches of UPR signaling are known to localize in distal dendritic ER of neurons. These reports suggest that local activation of UPR branches may produce integrated outputs for distant communication, and allow regulation of local events in highly polarized neurons. Here, we demonstrated that synaptic activity- and brain-derived neurotrophic factor (BDNF)-dependent local activation of UPR signaling could be associated with dendritic functions through retrograde signal propagation by using murine neuroblastoma cell line, Neuro-2A and primary cultured hippocampal neurons derived from postnatal day 0 litter C57BL/6 mice. ER stress transducer, inositol-requiring kinase 1 (IRE1), was activated at postsynapses in response to excitatory synaptic activation. Activated dendritic IRE1 accelerated accumulation of the downstream transcription factor, x-box-binding protein 1 (XBP1), in the nucleus. Interestingly, excitatory synaptic activation-dependent up-regulation of XBP1 directly facilitated transcriptional activation of BDNF. BDNF in turn drove its own expression via IRE1-XBP1 pathway in a protein kinase A-dependent manner. Exogenous treatment with BDNF promoted extension and branching of dendrites through the protein kinase A-IRE1-XBP1 cascade. Taken together, our findings indicate novel mechanisms for communication between soma and distal sites of polarized neurons that are coordinated by local activation of IRE1-XBP1 signaling. Synaptic activity- and BDNF-dependent distinct activation of dendritic IRE1-XBP1 cascade drives BDNF expression in cell soma and may be involved in dendritic extension. Cover Image for this issue: doi. 10.1111/jnc.14159.

Multivesicular body formation enhancement and exosome release during endoplasmic reticulum stress

The endoplasmic reticulum (ER) plays a pivotal role in maintaining cellular homeostasis. However, numerous environmental and genetic factors give rise to ER stress by inducing an accumulation of unfolded proteins. Under ER stress conditions, cells initiate the unfolded protein response (UPR). Here, we demonstrate a novel aspect of the UPR by electron microscopy and immunostaining analyses, whereby multivesicular body (MVB) formation was enhanced after ER stress. This MVB formation was influenced by inhibition of ER stress transducers inositol required enzyme 1 (IRE1) and PKR-like ER kinase (PERK). Furthermore, exosome release was also increased during ER stress. However, in IRE1 or PERK deficient cells, exosome release was not upregulated, indicating that IRE1- and PERK-mediated pathways are involved in ER stress-dependent exosome release.

Genome-wide identification and gene expression profiling of ubiquitin ligases for endoplasmic reticulum protein degradation

Endoplasmic reticulum (ER)-associated degradation (ERAD) is a mechanism by which unfolded proteins that accumulate in the ER are transported to the cytosol for ubiquitin–proteasome-mediated degradation. Ubiquitin ligases (E3s) are a group of enzymes responsible for substrate selectivity and ubiquitin chain formation. The purpose of this study was to identify novel E3s involved in ERAD. Thirty-seven candidate genes were selected by searches for proteins with RING-finger motifs and transmembrane regions, which are the major features of ERAD E3s. We performed gene expression profiling for the identified E3s in human and mouse tissues. Several genes were specifically or selectively expressed in both tissues; the expression of four genes (RNFT1, RNF185, CGRRF1 and RNF19B) was significantly upregulated by ER stress. To determine the involvement of the ER stress-responsive genes in ERAD, we investigated their ER localisation, in vitro autoubiquitination activity and ER stress resistance. All were partially localised to the ER, whereas CGRRF1 did not possess E3 activity. RNFT1 and RNF185, but not CGRRF1 and RNF19B, exhibited significant resistance to ER stressor in an E3 activity-dependent manner. Thus, these genes are possible candidates for ERAD E3s.

IRE1α-XBP1 is a novel branch in the transcriptional regulation of Ucp1 in brown adipocytes

The unfolded protein response (UPR) not only resolves endoplasmic reticulum (ER) stress, but also regulates cellular physiological functions. In this study, we first linked the UPR to the physiological roles of brown adipose tissue (BAT). BAT is one of the tissues that control energy homeostasis in the body. Brown adipocytes are able to dissipate energy in the form of heat owing to their mitochondrial protein, uncoupling protein 1 (UCP1). We found that one of the UPR branches, the IRE1α-XBP1 pathway, was activated during the transcriptional induction of Ucp1. Inhibiting the IRE1α-XBP1 pathway reduced the induction of Ucp1 expression. However, the activation of the IRE1α-XBP1 pathway by ER stress never upregulated Ucp1. On the other hand, the activation of protein kinase A (PKA) induced Ucp1 transcription through the activation of IRE1α-XBP1. The inhibition of PKA abrogated the activation of IRE1α-XBP1 pathway, while the inhibition of a p38 mitogen activated protein kinase (p38 MAPK), which is one of the downstream molecules of PKA, never suppressed the activation of IRE1α-XBP1 pathway. These data indicate that PKA-dependent IRE1α-XBP1 activation is crucial for the transcriptional induction of Ucp1 in brown adipocytes, and they demonstrate a novel, ER stress -independent role of the UPR during thermogenesis.

OASIS modulates hypoxia pathway activity to regulate bone angiogenesis

OASIS/CREB3L1, an endoplasmic reticulum (ER)-resident transcription factor, plays important roles in osteoblast differentiation. In this study, we identified new crosstalk between OASIS and the hypoxia signaling pathway, which regulates vascularization during bone development. RT-PCR and real-time PCR analyses revealed significant decreases in the expression levels of hypoxia-inducible factor-1α (HIF-1α) target genes such as vascular endothelial growth factor A (VEGFA) in OASIS-deficient (Oasis^−/−) mouse embryonic fibroblasts. In coimmunoprecipitation experiments, the N-terminal fragment of OASIS (OASIS-N; activated form of OASIS) bound to HIF-1α through the bZIP domain. Luciferase assays showed that OASIS-N promoted the transcription activities of a reporter gene via a hypoxia-response element (HRE). Furthermore, the expression levels of an angiogenic factor Vegfa was decreased in Oasis^−/− osteoblasts. Immunostaining and metatarsal angiogenesis assay showed retarded vascularization in bone tissue of Oasis^−/− mice. These results suggest that OASIS affects the expression of HIF-1α target genes through the protein interaction with HIF-1α, and that OASIS-HIF-1α complexes may play essential roles in angiogenesis during bone development.

Luman is involved in osteoclastogenesis through the regulation of DC-STAMP expression, stability and localization

Luman (also known as CREB3) is a type-II transmembrane transcription factor belonging to the OASIS family that localizes to the endoplasmic reticulum (ER) membrane under normal conditions. In response to ER stress, OASIS-family members are subjected to regulated intramembrane proteolysis (RIP), following which the cleaved N-terminal fragments translocate to the nucleus. In this study, we show that treatment of bone marrow macrophages (BMMs) with cytokines – macrophage colony-stimulating factor (M-CSF) and RANKL (also known as TNFSF11) – causes a time-dependent increase in Luman expression, and that Luman undergoes RIP and becomes activated during osteoclast differentiation. Small hairpin (sh)RNA-mediated knockdown of Luman in BMMs prevented the formation of multinucleated osteoclasts, concomitant with the suppression of DC-STAMP, a protein that is essential for cell–cell fusion in osteoclastogenesis. The N-terminus of Luman facilitates promoter activity of DC-STAMP, resulting in upregulation of DC-STAMP expression. Furthermore, Luman interacts with DC-STAMP, and controls its stability and localization. These results suggest that Luman regulates the multinucleation of osteoclasts by promoting cell fusion of mononuclear osteoclasts through DC-STAMP induction and intracellular distribution during osteoclastogenesis.

Highlighted Article: Luman, an ER-resident transcription factor, regulates the multinucleation of osteoclasts by promoting cell fusion of mononuclear osteoclasts through DC-STAMP induction and transportation during osteoclastogenesis.

Promotion of Cancer Cell Proliferation by Cleaved and Secreted Luminal Domains of ER Stress Transducer BBF2H7

BBF2H7 is an endoplasmic reticulum (ER)-resident transmembrane basic leucine zipper (bZIP) transcription factor that is cleaved at the transmembrane domain by regulated intramembrane proteolysis in response to ER stress. The cleaved cytoplasmic N-terminus containing transcription activation and bZIP domains translocates into the nucleus to promote the expression of target genes. In chondrocytes, the cleaved luminal C-terminus is extracellularly secreted and facilitates proliferation of neighboring cells through activation of Hedgehog signaling. In the present study, we found that Bbf2h7 expression levels significantly increased by 1.070-2.567-fold in several tumor types including glioblastoma compared with those in respective normal tissues, using the ONCOMINE Cancer Profiling Database. In some Hedgehog ligand-dependent cancer cell lines including glioblastoma U251MG cells, the BBF2H7 C-terminus was secreted from cells into the culture media and promoted cancer cell proliferation through activation of Hedgehog signaling. Knockdown of Bbf2h7 expression suppressed the proliferation of U251MG cells by downregulating Hedgehog signaling. The impaired cell proliferation and Hedgehog signaling were recovered by addition of BBF2H7 C-terminus to the culture medium of Bbf2h7-knockdown U251MG cells. These data suggest that the secreted luminal BBF2H7 C-terminus is involved in Hedgehog ligand-dependent cancer cell proliferation through activation of Hedgehog signaling. Thus, the BBF2H7 C-terminus may be a novel target for the development of anticancer drugs.

Master regulator for chondrogenesis, Sox9, regulates transcriptional activation of the endoplasmic reticulum stress transducer BBF2H7/CREB3L2 in chondrocytes

The endoplasmic reticulum (ER) stress transducer, box B-binding factor 2 human homolog on chromosome 7 (BBF2H7), is a basic leucine zipper (bZIP) transmembrane transcription factor. This molecule is activated in response to ER stress during chondrogenesis. The activated BBF2H7 accelerates cartilage matrix protein secretion through the up-regulation of Sec23a, which is responsible for protein transport from the ER to the Golgi apparatus and is a target of BBF2H7. In the present study, we elucidated the mechanisms of the transcriptional activation of Bbf2h7 in chondrocytes. The transcription of Bbf2h7 is regulated by Sex determining region Y-related high-mobility group box 9 (Sox9), a critical factor for chondrocyte differentiation that facilitates the expression of one of the major cartilage matrix proteins Type II collagen (Col2), through binding to the Sox DNA-binding motif in the Bbf2h7 promoter. BBF2H7 is activated as a transcription factor in response to physiological ER stress caused by abundant synthesis of cartilage matrix proteins, and consequently regulates the secretion of cartilage matrix proteins. Taken together, our findings demonstrate novel regulatory mechanisms of Sox9 for controlling the secretion of cartilage matrix proteins through the activation of BBF2H7-Sec23a signaling during chondrogenesis.

Increased susceptibility to dextran sulfate sodium-induced colitis in the endoplasmic reticulum stress transducer OASIS deficient mice

OASIS is a basic leucine zipper (bZIP) transmembrane transcription factor that is activated in response to endoplasmic reticulum (ER) stress. Previously, we showed that OASIS regulates final maturation of goblet cells in the large intestine. In the present study, to elucidate the roles of OASIS under pathophysiological conditions, we examined the stress response and inflammatory responses in Oasis deficient (Oasis−/−) mice exposed to dextran sulfate sodium (DSS) to induce colitis. A significant loss of body weight and an increase of mortality were observed in Oasis−/− mice with DSS-induced colitis compared with those in WT mice. The mucosa of the large intestine in Oasis−/− mice exhibited severe damage involving inflammatory cell infiltration. The expression levels of ER stress and apoptosis markers in intestinal epithelial cells were upregulated in Oasis−/− mice. These abnormalities were improved by treatment with tauroursodeoxycholic acid, a chemical chaperone that facilitates protein folding. Taken together, our findings demonstrate that OASIS plays important roles in protection of the large intestinal mucosa in DSS-induced colitis through attenuation of ER stress and inflammation.

The endoplasmic reticulum stress transducer BBF2H7 suppresses apoptosis by activating the ATF5-MCL1 pathway in growth plate cartilage

BBF2H7 (box B-binding factor 2 human homolog on chromosome 7) is a basic leucine zipper transmembrane transcription factor that belongs to the cyclic AMP-responsive element-binding protein (CREB)/activating transcription factor (ATF) family. This novel endoplasmic reticulum (ER) stress transducer is localized in the ER and is cleaved in its transmembrane region in response to ER stress. BBF2H7 has been shown to be expressed in proliferating chondrocytes in cartilage during the development of long bones. The target of BBF2H7 is Sec23a, one of the coat protein complex II components. Bbf2h7-deficient (Bbf2h7(-/-)) mice exhibit severe chondrodysplasia, with expansion of the rough ER in proliferating chondrocytes caused by impaired secretion of extracellular matrix (ECM) proteins. We observed a decrease in the number of proliferating chondrocytes in the cartilage of Bbf2h7(-/-) mice. TUNEL staining of the cartilage showed that apoptosis was promoted in Bbf2h7(-/-) chondrocytes. Atf5 (activating transcription factor 5), another member of the CREB/ATF family and an antiapoptotic factor, was also found to be a target of BBF2H7 in chondrocytes. ATF5 activated the transcription of Mcl1 (myeloid cell leukemia sequence 1), which belongs to the antiapoptotic B-cell leukemia/lymphoma 2 family, to suppress apoptosis. Finally, we found that the BBF2H7-ATF5-MCL1 pathway specifically suppressed ER stress-induced apoptosis in chondrocytes. Taken together, our findings indicate that BBF2H7 is activated in response to ER stress caused by synthesis of abundant ECM proteins and plays crucial roles as a bifunctional regulator to accelerate ECM protein secretion and suppress ER stress-induced apoptosis by activating the ATF5-MCL1 pathway during chondrogenesis.

The endoplasmic reticulum stress transducer OASIS is involved in the terminal differentiation of goblet cells in the large intestine

OASIS is a basic leucine zipper transmembrane transcription factor localized in the endoplasmic reticulum (ER) that is cleaved in its transmembrane region in response to ER stress. This novel ER stress transducer has been demonstrated to express in osteoblasts and astrocytes and promote terminal maturation of these cells. Additionally, OASIS is highly expressed in goblet cells of the large intestine. In this study, we investigated the roles of OASIS in goblet cell differentiation in the large intestine. To analyze the functions of OASIS in goblet cells, we examined morphological changes and the expression of goblet cell differentiation markers in the large intestine of Oasis(-/-) mice. By disrupting the Oasis gene, the number of goblet cells and production of mucus were decreased in the large intestine. Oasis(-/-) goblet cells showed abnormal morphology of mucous vesicles and rough ER. The expression levels of mature goblet cell markers were lower, and conversely those of early goblet cell markers were higher in Oasis(-/-) mice, indicating that differentiation from early to mature goblet cells is impaired in Oasis(-/-) mice. To determine the association of OASIS with other factors involved in goblet cell differentiation, in vitro experiments using a cell culture model were performed. We found that OASIS was activated in response to mild ER stress that is induced in differentiating goblet cells. Knockdown of the Oasis transcript perturbed goblet cell terminal differentiation. Together, our data indicate that OASIS plays crucial roles in promoting the differentiation of early goblet cells to mature goblet cells in the large intestine.

The signalling from endoplasmic reticulum-resident bZIP transcription factors involved in diverse cellular physiology

Eukaryotic cells can adapt to endoplasmic reticulum (ER) dysfunction by producing diverse signals from the ER to the cytosol or nucleus. These signalling pathways are collectively known as the unfolded protein response (UPR). The canonical branches of the UPR are mediated by three ER membrane-bound proteins: PERK, IRE1 and ATF6. These ER stress transducers basically play important roles in cell survival after ER stress. Recently, novel types of ER stress transducers that share a region of high sequence similarity with ATF6 have been identified. They have a transmembrane domain, which allows them to associate with the ER, and possess a transcription-activation domain and a bZIP domain. These membrane-bound bZIP transcription factors include Luman, OASIS, BBF2H7, CREBH and CREB4. Despite their structural similarities with ATF6, differences in activating stimuli, tissue distribution and response element binding indicate specialized functions of each member on regulating the UPR in specific organs and tissues. Here, we summarize our current understanding of the biochemical characteristics and physiological functions of the ER-resident bZIP transcription factors.

Physiological unfolded protein response regulated by OASIS family members, transmembrane bZIP transcription factors

The endoplasmic reticulum (ER) plays role in the maintenance of numerous aspects of cellular and organismal homeostasis by folding, modifying, and exporting nascent secretory and transmembrane proteins. Failure of the ER's adaptive capacity results in accumulation of unfolded or malfolded proteins in the ER lumen (ER stress). To avoid cellular damage, mammalian cells activate the specific signals from the ER to the cytosol or nucleus to enhance the capacity for protein folding, attenuate the synthesis of proteins, and degrade unfolded proteins. These signaling pathways are collectively known as the unfolded protein response (UPR). The canonical branches of the UPR are mediated by three ER membrane-bound proteins, PERK, IRE1, and ATF6. These ER stress transducers basically play important roles in cell survival after ER stress. Recently, novel types of ER stress transducers, OASIS family members that share a region of high sequence similarity with ATF6 have been identified. They have a transmembrane domain, which allows them to associate with the ER, and possess a transcription-activation domain and a bZIP domain. OASIS family proteins include OASIS, BBF2H7, CREBH, AIbZIP, and Luman. Despite the structural similarities among OASIS family proteins and ATF6, differences in activating stimuli, tissue distribution, and response element binding indicate specialized functions of each member on regulating the UPR in the specific organs and tissues. Here, we summarize our current understanding of biochemical characteristics and in vivo functions of OASIS family proteins, particularly focusing on OASIS and BBF2H7. A growing body of new works suggests that the UPR branches regulated by OASIS family members play essential roles in cell differentiation and maturation or maintenance of basal cellular homeostasis in mammals.

Promotive effects of hyperthermia on the cytostatic activity to Ehrlich ascites tumor cells by diverse delta-alkyllactones

AIM

To evaluate promotive effects of hyperthermia on antitumor activity of new delta-alkyllactones (DALs) of low molecular weight (184-254 Da), chemically synthesized, which are different from natural macrocyclic lactones of high molecular weight (348-439 Da), such as camptothecin and sultriecin.

METHODS

A suspension of Ehrlich ascites tumor (EAT) cells was mixed with a DAL in a glass tube, heated at 37 or 42 degrees C for 30 min in a water bath, and cultured at 37 degrees C for 20 or 72 h. Cell viability was measured by the mitochondrial dehydrogenase- based WST-1 assay. DALs incorporated into EAT cells was extracted and measured by gas-liquid chromatography.

RESULTS

The reduction of cell viability by DALs was markedly enhanced upon the treatment at 42 degrees C compared to that at 37 degrees C. At 37 degrees C, delta-hexadecalactone (DH16:0) and delta-tetradecalactone (DTe14:0) displayed cytostatic activity (at 100 microM survival level: 20.7%, 66.1%; at 50 microM--41.2%, 82.4%, respectively). Their activity was more marked at 42 degrees C (at 100 microM 10.6%, 27.6%; at 50 microM 30.6, 37.5%, ibid). The other DALs, delta-undecalactone (DU11:0), delta-dodecalactone (DD12:0), and delta-tridecanolactone (DTr13:0) were almost ineffective. Evaluation of survival rate in the cells treated for 30 min by DALs with the next culturing of EAT cells for 72 h resulted in the enhanced carcinostatic activity of DH16:0 and DTe14:0 even at concentrations as low as 25 microM at either 37 degrees C (18.5%, 78.5%, ibid) or 42 degrees C (5.0%, 42.0%, ibid), but the others exhibited slight activity or none. DH16:0 was effective at either 37 degrees C (36.0%) or 42 degrees C (23.0%) even at a lower dose of 10 microM. At the same time only the most cytostatic DH16:0 was incorporated into EAT cells and the rate of incorporation was more at 42 degrees C than at 37 degrees C.

CONCLUSION

Delta-hexadecanolactone (DH16:0) exhibited the most cytostatic effect that was significantly enhanced by hyperthermia. It allows to consider it as a potent antitumor agent, especially in combination with hyperthermia.

Promotive effects of hyperthermia on the inhibition of DNA synthesis in ehrlich ascites tumor cells by eicosapentaenoic and docosahexaenoic acids

AIM

To evaluate inhibitory effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on DNA synthesis in combination with hyperthermia in vitro.

METHODS

A suspension of Ehrlich ascites tumor cells (EAT) was mixed with DHA or EPA in a glass tube, heated at 37 degrees C, 40 degrees C, or 42 degrees C for 1 h in a water bath, and cultured at 37 degrees C for 19 or 96 h. DNA synthesis was assayed by monitoring of the incorporation of [3H]-thymidine into the acid-insoluble fraction. DHA or EPA incorporated into EAT cells was extracted and measured by thin-layer chromatography and gas-liquid chromatography.

RESULTS

The inhibition of DNA synthesis by EPA or DHA increased markedly upon the treatment at 42 degrees C and 40 degrees C compared to that at 37 degrees C. At 37 degrees C, inhibitory action of EPA was more potent than that of DHA at low concentrations (at 50 microM -- DNA synthesis level: EPA, 63.1%; DHA, 87.9%), whereas inhibitory action of DHA was higher at 150 muM (16.7%, 4.4%, ibid.). The effect of DHA compared to EPA was more marked at 40 degrees C (29.0%, 19.2% at 100 microM) or 42 degrees C (19.7%, 10.6% at 100 microM). Evaluation of DNA synthesis rate in the cells treated for 1 h by EPA or DHA with the next culturing of EAT cells for 19 h resulted in the enhanced inhibitory activity of EPA even at concentrations as low as 50 microM at either 37 degrees C (0.5%, 11.3%) or 42 degrees C (0.6%, 4.5%), which in these conditions was higher than that of DHA. At the same time the rate of incorporation of EPA in EAT cells at 37 degrees C or 42 degrees C was lower than that of DHA.

CONCLUSION

Administration of DHA or EPA in vitro significantly inhibit DNA synthesis, and such effect is enhanced by combination of PUFAs with hyperthermia.

Absence of endothelial cells, central necrosis, and fibrosis are associated with aggressive inflammatory breast cancer

We recently established a new human inflammatory breast cancer (IBC) xenograft (WIBC-9) originating from a patient with IBC. The graft was transplantable in BALB/c nude and severe combined immunodeficient (SCID) mice. WIBC-9 was frequently accompanied by lung metastasis and exhibited erythema of the overlying skin, reflecting its human counterpart. Histological study of the original tumor and WIBC-9 revealed invasive ductal carcinoma with a hypervascular structure of solid nests and marked lymphatic permeation in the overlying dermis. In the central part of the solid nests, absence of endothelial cells, central necrosis, and fibrosis were observed. In vitro, WIBC-9 formed tube-like structures and loops, reflecting its in vivo feature and its human counterpart. WIBC-9 exhibited aneuploidy, ErbB-2 gene amplification, and an absence of estrogen receptor and progesterone receptor, which is consistent with IBC. Comparative studies of WIBC-9, three established non-IBC xenografts, and a human breast cancer cell line (SK-BR3) by reverse transcription-PCR, ELISA, and immunohistochemistry indicated that certain human genes (interleukin 8, vascular epidermal growth factor, basic fibroblast growth factor, angiopoietin 13, Flt-1, Tie-2, and Tie-1) and certain murine genes (integrin alpha(v)beta3, flt-1, tie-2, vascular epidermal growth factor, and CD31) were overexpressed in exposure to tumor cells. The molecular basis and these unique histological features may be associated with aggressive IBC on angiogenic and nonangiogenic pathways.

'Silent' cerebral infarction is associated with hypercoagulability, endothelial cell damage, and high Lp(a) levels in elderly Japanese

"Silent" lacunar stroke, often found in the elderly, has been proposed as a predisposing condition for clinically overt stroke. However, the risk factors related to this condition have not been studied thoroughly. We conducted brain magnetic resonance imaging and measured the levels of fibrinogen, molecular markers of coagulation activation [prothrombin fragment 1 + 2 (F1 + 2)] and endothelial cell damage [von Willebrand factor (vWF) and thrombomodulin], and lipid profiles including lipoprotein (a) [Lp(a)] in 178 asymptomatic, high-risk, Japanese subjects aged 44 to 93 years. We also studied 32 symptomatic patients with lacunar stroke (symptomatic lacunar group). The prevalence of silent lacunar stroke increased with age up to 85 years but decreased with age in those 85 years old and older. Of the 160 elderly subjects ( > or = 60 years) 84 (53%) had > or = 1 lacunar infarcts (silent lacunar group) and the remaining 76 were considered as the nonlacunar group. Fibrinogen and F1 + 2 levels in the silent lacunar group were significantly higher than those in the nonlacunar group (P < .01). Mean Lp(a) levels and the prevalence of subjects with an Lp(a) level > 30 mg/dL were significantly higher in the symptomatic lacunar group than the nonlacunar group (P < .05), whereas these levels in the silent lacunar group were intermediate to those of the other two groups. When we further classified the silent lacunar group into three subgroups based on the number of lacunes (few lacunes, 1 or 2; moderate number of lacunes, 3 or 4; and numerous lacunes, > or = 5), levels of Lp(a), F1 + 2, vWF, and thrombomodulin were significantly higher and Lp(a) levels > 30 mg/dL more common in the numerous-lacune than in the few-lacune subgroup. We conclude that silent lacunar stroke is often found in asymptomatic, high-risk, elderly Japanese patients and that silent multiple lacunar stroke is associated with hypercoagulability, endothelial cell damage, and high Lp(a) levels.

An inappropriate erythropoietic response to iron deficiency anaemia in the elderly

This study was carried out to clarify the features of iron deficiency anaemia in the elderly. Subjects were chosen from residents undergoing an annual health check in a home for the aged and the features of anaemia in the elderly were compared with those in middle-aged adults under 60 years old. The red cell count, red cell size and haemoglobin content in an elderly group with iron-deficiency anaemia did not differ from those in middle-aged adults. No significant differences of the serum ferritin and iron levels were noted between the two groups. Total iron binding capacity was higher in the middle-aged adults than in the elderly, while the reticulocyte count was significantly lower in the elderly group. Immature reticulocytes showing a considerable amount of residual RNA by flow cytometry with fluorescent staining were also lower in the elderly group than in the middle-aged adults. Serum erythropoietin levels in both groups were significantly higher than in non-anaemic age-matched controls and no difference in erythropoietin levels was noted between them. The ratio of the reticulocyte count to the log-transformed erythropoietin level was low in the elderly group with iron-deficiency anaemia compared with the middle-aged adults with iron deficiency anaemia. The same result was seen when the immature reticulocyte count was related to the log-transformed erythropoietin level. These findings suggest that the red cell production response to erythropoietin in the elderly with iron-deficiency anaemia might be inappropriate compared with both non-anaemic and anaemic middle-aged adults.

High lipoprotein (a) levels in chronic hemodialysis patients are closely related to the acute phase reaction

To study the mechanism underlying the high lipoprotein (a) [Lp(a)] level in uremic patients on chronic hemodialysis, we investigated the levels of Lp(a), acute phase reactants (C-reactive protein and sialic acid), and interleukin-6 (IL-6) in 54 dialysis patients. The mean [95% CI] Lp(a) level was increased in the hemodialysis patients compared with the 30 controls (30 [25-36] vs. 18 [14-23] mg/dl, p < 0.005). Among dialysis patients, 46% had an Lp(a) level > 30 mg/dl, which was significantly higher than the percentage in the control group (17%). The levels of C-reactive protein, sialic acid, and IL-6 were also increased in dialysis subjects compared with controls (200 [134-299] vs. 37 [24-58] micrograms/dl, p < 0.0001; 63 [59-66] vs. 54 [52-56] mg/dl, p < 0.002; and 9.2 [7.8-11] vs. 5.5 [5.0-6.1] pg/ml, p < 0.0005, respectively). The Lp(a) level was positively correlated with that of C-reactive protein (r = 0.415, p < 0.002), sialic acid (r = 0.426, p < 0.002), and IL-6 (r = 0.298, p < 0.05) in the hemodialysis patients, but not in the controls or non-dialysis uremic patients. The Lp(a) level in the dialysis patients was also positively correlated with activation markers of coagulation (thrombin-antithrombin III complex and plasmin-alpha 2-plasmin inhibitor complex, p < 0.005). These results indicate that the Lp(a) level is closely related to the acute phase reaction and hypercoagulability in chronic hemodialysis patients.

The strong positive correlation between factor VII clotting activity using bovine thromboplastin and the activated factor VII level

We compared factor VII clotting activity (FVIIc) assays using different thromboplastins to determine which is the most sensitive for activated FVII (FVIIa) or for FVII antigen (FVIIag). FVIIc levels were measured using thromboplastins derived from bovine brain (FVIIc Bov), human placenta (FVIIc Hum), and rabbit brain (FVIIc Rab). FVIIa levels were measured by fluorogenic assays using human soluble tissue factor (rsTF) or bovine rsTF. We also measured FVII activity by an amidolytic assay (FVIIc:am Hum) using human thromboplastin and a chromogenic substrate for thrombin. FVIIag levels were determined by ELISA. In the FVIIa assay, the reaction time obtained from using bovine rsTF was shorter than that with human rsTF, suggesting that the interaction of plasma FVIIa with bovine rsTF was stronger than with human rsTF. The plasma FVIIa levels measured using human rsTF and bovine rsTF were almost the same (r = 0.947, p < 0.0001). Among the three FVIIc assays, FVIIc Bov had the strongest positive correlation with the plasma FVIIa level (r = 0.886, p < 0.0001), but had no correlation with FVIIag. An increase of 1 ng/ml in the plasma FVIIa level yielded a 27.9% increase of FVIIc Bov. Plasma FVIIc Hum and FVIIc:am Hum showed moderate correlations with both FVIIa (r = 0.520, p < 0.02 and r = 0.569, p < 0.01, respectively) and FVIIag (r = 0.438, p < 0.05 and r = 0.468, p < 0.05, respectively). FVIIc Rab had the lowest correlation with FVIIa (r = 0.367, p < 0.1), but had a moderate correlation with FVIIag (r = 0.436, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced erythropoietin secretion in senile anemia

To investigate the etiology of the age-related decrease in hemoglobin (Hb) concentration, we measured serum erythropoietin (EPO), serum iron, total iron binding capacity, and serum ferritin levels in 247 elderly subjects aged 60-99 years. EPO levels were determined by radioimmunoassay. An age-related increase in the serum EPO concentration (r = 0.220; P < 0.01) and a significant inverse relationship between EPO and Hb concentrations were found in normal elderly subjects without anemia (r = -0.302; P < 0.001), but not in 111 younger controls. Serum EPO levels were slightly higher in elderly subjects with pre-anemic iron deficiency than in the normal elderly subjects (P < 0.05). These results suggest that the EPO secretion is accelerated in the elderly even though the Hb remains above 12.0 g/dl, probably as a compensatory mechanism for peripheral tissue hypoxia. An inverse relationship between the EPO and Hb concentrations was found in the elderly subjects with iron deficiency anemia, but not in those with unexplained senile anemia. The changes of EPO levels were also assessed in 20 elderly subjects who had developed anemia when reviewed after 12 months. Serum EPO levels increased in relation to the decrease in Hb concentration in those with iron deficiency anemia, but not in those with unexplained senile anemia. Reduced EPO secretion thus seems to play a role in the progression of unexplained senile anemia, and recombinant human EPO may possibly be effective for treating this type of anemia by mobilizing excess iron.

Long-term follow-up of membranoproliferative glomerulonephritis type II and pregnancy: a case report

A 24-year-old female was diagnosed as having membranoproliferative glomerulonephritis type II (or dense deposit disease), 11 years prior to becoming pregnant. The patient's first renal biopsy was performed 5 years after the onset of her renal symptoms. This biopsy was compared to a second renal biopsy taken just before the patient became pregnant. The second renal biopsy only showed a slight progression in the disease process. During the course of pregnancy, neither renal insufficiency nor hypertension were clinically evident. However, both an increase in proteinuria and a transient hypoalbuminemia were observed. The pregnancy, labor and delivery, and postpartum course for both the mother and child were without complications. Cases of membranoproliferative glomerulonephritis type I and pregnancy have been reported. However, to our knowledge, there are few reports documenting the outcome of pregnancy when a patient has membranoproliferative glomerulonephritis type II. We suggest that it is possible for a patient with membranoproliferative glomerulonephritis type II to have an uneventful pregnancy if she has neither hypertension nor renal insufficiency.

Glomerulonephritis with focal and segmental distribution of glomerular basement membrane antigen(s)

In this report, the authors describe a case of a 2-year, 11-month-old girl with glomerulonephritis and no family history of renal diseases and deafness. Immunofluorescent studies in the renal biopsy specimens with the use of anti-sera against human glomerular basement membrane (GBM) and P3 antigen (prepared from bovine GBM and inducible of Steblay's type nephritis in rats) demonstrated focal and segmental distribution of the GBM antigen(s). Electron microscopic examination revealed splitting and thinning of the GBM. Indirect immunofluorescence showed that there was no binding of Goodpasture's anti-GBM antibodies to the glomeruli. These findings are similar to those in patients with hereditary nephritis. The immunofluorescent examination of the fixation of the various anti-sera, including anti-types IV and V collagens, laminin, fibronectin, and actomyosin sera on the GBM, revealed normal reactivity. The abnormalities observed in this case may be a part of the spectrum of primary GBM defects.

Chlorambucil central nervous toxicity: a significant side effect of chlorambucil therapy in childhood nephrotic syndrome

Chlorambucil (CHL) was used in combination with prednisolone in the treatment of nine children with frequently relapsing nephrotic syndrome. Serial electroencephalograms were obtained to evaluate CHL central nervous toxicity, before, during and after treatment with this agent. EEG abnormalities were observed in two of the nine children during chlorambucil therapy. EEG changes were diffuse spike and wave complexes and disappeared after discontinuation of therapy. There were no other neurological abnormalities and more particularly, no seizures or myocloni were observed. According to the literature, chlorambucil central nervous toxicity is found almost exclusively in childhood nephrotic syndrome. Strict neurological supervision of patients treated with chlorambucil is recommended.