Haruki Kurosawa

Prostaglandin E1 protects against ischemia-reperfusion injury of the liver by inhibition of neutrophil adherence to endothelial cells

BACKGROUND This study investigates the protective mechanism of prostaglandin E1 (PGE1) against hepatic ischemia-reperfusion injury in vivo. It has been demonstrated that activated leukocytes contribute to ischemia-reperfusion injury, and that administration of the monoclonal antibody (mAb) for adhesion molecules reduces the injury by inhibiting leukocyte-endothelial cell adhesion. We therefore attempted to find out whether PGE1 has an effect on the inhibition of neutrophil adherence to endothelial cells after reperfusion. METHODS We administered anti-intercellular adhesion molecule 1 (ICAM-1) mAb, antiserum against rat polymorphonuclear leukocytes, or PGE1 to a rat model of left lobar ischemia for 60 min followed by reperfusion. Leukocyte adherence was observed by intravital fluorescence microscopy. The effect of PGE1 on the expression of adhesion molecules was analyzed by immunohistochemistry and flow cytometry. RESULTS Ischemia-reperfusion caused endothelial dysfunction and hepatocellular injury with leukostasis in postsinusoidal venules. Anti-ICAM-1 mAb administration or leukopenia ameliorated both the hepatocellular injury and endothelial dysfunction. Although PGE1 administration did not affect the serum interleukin-8 level, it significantly decreased hepatic injury and leukostasis in the reperfused liver. Immunohistochemical findings showed that PGE1 decreased ICAM-1 expression on endothelial cells, but did not affect lymphocyte function-associated antigen 1, and membrane attack complex 1 on neutrophils in flow cytometric analysis. CONCLUSIONS We conclude that PGE1 protects the liver against ischemia-reperfusion injury by reducing leukocyte-endothelial cell adhesion via down-modulation of ICAM-1 expression on the endothelium.

Expression of Bcl-2 Family Reduces Apoptotic Hepatocytes after Excessive Hepatectomy

Excessive hepatectomy often causes fatal hepatic failure, but the mechanism is unknown. We used a novel protocol of partial 90 and 95% hepatectomy (PHx) to investigate this mechanism in 2 groups of rats. The 90% PHx rats survived, but the 95% PHx animals died of hepatic failure. In the latter, cytokine (interleukin-6, tumor necrosis factor-α) levels and the apoptotic hepatocyte count increased, and there were few mitotic cells. By contrast, in the 90% PHx rats, the mitotic cell count increased, and more anti-apoptotic Bcl-xL protein was expressed. These results demonstrate that expression of Bcl-xL protein as an anti-apoptotic factor or regeneration factor contributes to survival after 90% PHx. Using an adenovirus vector, the human bcl-2 gene (hbcl-2) was therefore transfected to DA rat livers where it was efficiently expressed, and then 95% PHx was performed. Liver damage was decreased and the apoptotic cell count decreased too, but the rats died. We concluded that transfection of the hbcl-2 gene partly prevents cytotoxicity (apoptosis), but cannot ensure survival. Thus, some other factor is required (e.g., a regeneration stimulator) to maintain life in these models.

A case of lymphoepithelioma-like carcinoma of the colon with ulcerative colitis

Follow-up colonoscopy of a 25-year-old Japanese man with ulcerative colitis (UC) who had undergone endoscopic mucosal resection twice for early colon cancers revealed the presence of a new 1.5-cm-diameter tumor in the sigmoid colon. It was diagnosed by preoperative biopsy as a poorly differentiated adenocarcinoma. Sigmoidectomy was performed, and the pathological findings revealed lymphoepithelioma-like carcinoma (LEC). In situ hybridization to detect Epstein-Barr virus (EBV)-encoded small RNAs showed positive signals in stromal lymphocytes, but weak signals in the tumor cells. The association between EBV and LEC was obscure in this case. Unlike typical UC-mediated colon cancers, the lesion was poorly differentiated, and negative for p53 signals immunohistochemically. These findings may hint at a novel mechanism of carcinogenesis in UC-mediated colorectal cancer.

The role of intracellular calcium in the production of Superoxide anion by Kupffer cells stimulated by lipopolysaccharide and the efficacy of prostaglandin E1

Abstract Kupffer cells stimulated by lipopolysaccharide (LPS) produce Superoxide anion and cause hepatocellular injury. Intracellular calcium has been noted to work as a second messenger in a variety of pathophysiological mechanisms. The aims of this study were to investigate the effect of LPS stimulation of Kupffer cells on intracellular calcium concentrations and the production of Superoxide anion, and determine the effect of prostaglandin E 1 (PGE 1 ) on intracellular calcium and the Superoxide anion production following stimulation with LPS. Kupffer cells were isolated from male Wistar rats. The intracellular calcium level and the production of Superoxide anion were measured using a fluorescence computed microscope (Mu-1000, Inter Dec) and a Luminescence Reader (BLR-103, Aloka). After LPS stimulation, the intracellular calcium level of Kupffer cells increased and pretreatment with PGE 1 reduced this increase. Pretreatment with PGE 1 and removal of extracellular calcium decreased the production of Superoxide anion from Kupffer cells stimulated by LPS. We conclude that an increase of intracellular calcium affects production of Superoxide anion from Kupffer cells stimulated by LPS. Pretreatment with PGE 1 reduces the production of Superoxide anion by preventing this rise in intracellular calcium.