Abstract
Gastric lesions result from an imbalance between aggressive and defensive factors. Indirect lines of evidence suggest that heat shock proteins (HSPs) induced by various aggressive factors provide a major protective mechanism. In this study, we compared gastric ulcerogenic response in wild-type mice and in those lacking heat shock factor 1 (HSF1), a transcription factor for hsp genes. The severity of gastric lesions induced by ethanol or hydrochloric acid was worsened in HSF1-null mice. Immunoblotting, real-time reverse transcription-polymerase chain reaction, immunohistochemical analysis, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assay revealed that the ethanol administration up-regulated gastric mucosal HSPs, in particular HSP70, in an HSF1-dependent manner, and more apoptotic cells were observed in the gastric mucosa of HSF1-null mice than in wild-type mice. In contrast, other parameters governing the gastric ulcerogenic response, including gastric acid secretion, gastric mucosal blood flow, and prostaglandin E2 levels, were not significantly affected by the absence of the hsf1 gene. Geranylgeranylacetone (GGA), a clinically used antiulcer drug with HSP-inducing activity, suppressed ethanol-induced gastric lesions in wild-type mice but not in heat shock factor 1 (HSF1)-null mice. The results suggest that the aggravation of irritant-induced gastric lesions in HSF1-null mice is due to their inability to up-regulate HSPs, leading to apoptosis. It is also suggested that the HSP-inducing activity of GGA contributes to the drug's antiulcer activity. This study provides direct genetic evidence that HSPs, after their HSF1-dependent up-regulation, confer gastric protection against the irritant-induced lesions.
Footnotes
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This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Health, Labor, and Welfare of Japan and by Japan Science and Technology Agency, the Daiwa Securities Health Foundation, the Mochida Memorial Foundation for Medical and Pharmaceutical Research, the Suzuken Memorial Foundation, and the Japan Research Foundation for Clinical Pharmacology.
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K.T. and S.T. contributed equally to this work.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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doi:10.1124/mol.106.033282.
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ABBREVIATIONS: NSAID, nonsteroidal anti-inflammatory drug; DAPI, 4′, 6-diamidino-2-phenylindole dihydrochloride; GGA, geranylgeranylacetone; GMBF, gastric mucosal blood flow; HE, hematoxylin and eosin; HSF, heat shock factor; HSP, heat shock protein; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; OCT, optimal cutting temperature; PG, prostaglandin; TNF, tumor necrosis factor; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling; HSF1, heat shock factor 1; ELISA, enzyme-linked immunosorbent assay; siRNA, short interfering RNA; AGS, human gastric carcinoma; iNOS, inducible nitric-oxide synthase; RT-PCR, reverse transcription-polymerase chain reaction.
- Received December 7, 2006.
- Accepted December 22, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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