Hyun Jung Hwang

Endoplasmic reticulum stress response is involved in nonsteroidal anti-inflammatory drug-induced apoptosis

AbstractApoptosis induced by nonsteroidal anti-inflammatory drugs (NSAIDs) is involved not only in the production of NSAID-induced gastric lesions but also in the antitumor activity of these drugs. The endoplasmic reticulum (ER) stress response is a cellular mechanism that aids in protecting the ER against ER stressors and is involved in ER stressor-induced apoptosis. Here, we examine the relationship between this response and NSAID-induced apoptosis in cultured guinea-pig gastric mucosal cells. Exposure of cells to indomethacin, a commonly used NSAID, induced GRP78 as well as CHOP, a transcription factor involved in apoptosis. Three factors that positively regulate CHOP expression (ATF6, ATF4 and XBP-1) were activated and/or induced by indomethacin. NSAIDs other than indomethacin (diclofenac, ibuprofen and celecoxib) also induced CHOP. Monitoring of the transcriptional activities of ATF6 and CHOP by luciferase assay revealed that both were stimulated in the presence of indomethacin. Furthermore, indomethacin-induced apoptosis was suppressed in cultured guinea-pig gastric mucosal cells by expression of the dominant-negative form of CHOP, or in peritoneal macrophages from CHOP-deficient mice. These results suggest that ER stress response-related proteins, particularly CHOP, are involved in NSAID-induced apoptosis.

C Terminal Half Fragment (50 kDa) of Heavy Chain Components of Clostridium botulinum Type C and D Neurotoxins Can Be Used as an Effective Vaccine

Recombinant whole heavy chains (H, 100 kDa) and their N‐terminal (Hn, 50 kDa) and C‐terminal (Hc, 50 kDa) half fragments of Clostridium botulinum type C and D neurotoxins were expressed as glutathione S‐transferase (GST) fusion proteins in Escherichia coli. GST eliminated‐preparations of H (10 μg), Hn (5 μg), Hc (5 μg), or a mixture of Hn (5 μg) and Hc (5 μg) of types C and D were mixed with an equal volume of adjuvant, and then were twice injected into mice subcutaneously. After immunization, the mice were challenged with up to 106 the minimum lethal doses (MLD)/0.5 ml of C or D toxin, the type of which was same as that of the immunogens. All of the mice immunized with antigens except for Hn survived against 105 to 106 MLD/0.5 ml of the toxins, but the mice immunized with Hn were killed by 100 MLD/0.5 ml. The mice immunized with a mixture of C‐Hc and D‐Hc, each 5 μg, also showed a high level of resistance against both C and D toxins. Antibody levels immunized with GST fused‐ or GST eliminated‐preparation were quite similar. These results indicate that recombinant GST‐fused Hc can be used as a safe and effective vaccine for type C and D botulism in animals. It also became clear that one time inoculation with a large amount of C‐Hc or D‐Hc, 100 μg, is useful for vaccine trials in mice.

Identification of the TPO1 gene in yeast, and its human orthologue TETRAN, which cause resistance to NSAIDs

Non‐steroidal anti‐inflammatory drugs (NSAIDs), such as indomethacin, have serious gastrointestinal side effects. Since their direct cytotoxicity was suggested to be involved in this side effect, we here tried to identify NSAID‐resistant genes. We screened for Saccharomyces cerevisiae genes whose overexpression causes indomethacin resistance and identified the TPO1 gene, which encodes a major facilitator superfamily transporter. Its overexpression or deletion made yeast cells resistant or sensitive, respectively, to some NSAIDs. A BLAST search identified the possible human orthologue of Tpo1p, tetracycline transporter‐like protein (TETRAN), whose overexpression in cultured human cells caused resistance to some NSAIDs, suggesting that TETRAN is an efflux pump for some NSAIDs.

Expression and function of TETRAN, a new type of membrane transporter

In contrast to transport across basolateral membranes, the mechanism governing transport of organic anions across the luminal membranes of proximal tubules has remained unclear. We recently found Tetracycline transporter-like protein (TETRAN), a human ortholog of yeast Tpo1p that can transport anionic Non-steroidal anti-inflammatory drugs (NSAIDs). In this study, we examine the expression and function of TETRAN. TETRAN mRNA is expressed in various human tissues, including kidney. When overexpressed in cultured cells, TETRAN was predominantly localized on cytoplasmic membranes. Immunohistochemical analysis of human and mouse kidney tissue showed that TETRAN was expressed at the luminal membranes of proximal tubules. Overexpression of TETRAN in cultured cells facilitated the uptake of organic anions such as indomethacin (a NSAID) and fluorescein. The results suggest that TETRAN is a novel human organic anion transporter, and that it serves as a transporter for some NSAIDs and various other organic anions at the final excretion step.