Alkaline phosphatases reduce toxicity of lipopolysaccharides in vivo and in vitro through dephosphorylation.
Intestinal alkaline phosphatase (AP), as a host defense factor, was first investigated in vivo using rats orally exposed to lipopolysaccharide (LPS). After the oral administration of LPS to rats, serum LPS content was increased within 2 hr and then decreased to 6 hr. In contrast, when L-phenylalanine (L-Phe), an inhibitor of intestinal-type AP isozymes, was simultaneously administered with LPS, serum LPS content significantly increased from 1 hr and the area under the concentration-time curve of serum LPS was augmented approximately 2-fold, suggesting that APs in the gastrointestinal tract reduced serum LPS content. In addition, LPS toxicity diminished by a treatment in vitro with intestinal APs, were recovered by the treatment in the co-presence of L-Phe. In the experiment using human aortic endothelial cells (HAECs), we observed that the cell viability decreased in a dose-dependent manner of LPS-exposure, and the LPS dose, exhibiting 50% viability of the cells, was 0.05 microg/ml. When the cells were exposed to LPS pretreated with 50 nIU/ml of intestinal AP at pH 10.0 and 8.0, the 50% viability was at 2.0 microg/ml of LPS. These results strongly suggest that the APs reduced the toxicity of LPS, as a host defense factor against LPS.
Koyama
Iwao
I
Department of Medical Technology, Junior College, Saitama Medical School, 38 Morohongo, Moroyama, Iruma-gun, Saitama 350-0495, Japan. koyamaw@saitama-med.ac.jp
Matsunaga
Toshiyuki
T
Harada
Tsuyoshi
T
Hokari
Shigeru
S
Komoda
Tsugikazu
T
D000284:Administration, Oral; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D015153:Blotting, Western; D004386:Duodenum / Q000187:drug effects / Q000201:enzymology; D058851:GPI-Linked Proteins; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism* / Q000633:toxicity*; D008297:Male; D009569:Nitric Oxide / Q000032:analysis; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar
D000951:Antigens, Neoplasm; D058851:GPI-Linked Proteins; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; C063088:ALPI protein, human; D000469:Alkaline Phosphatase