| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The endothelial cell damage by Shiga toxin (Stx) -1 / -2, both of which are produced by enterohemorrhagic E. coli, has been believed to the crucial for the pathogenesis of hemolytic uremic syndrome. In in vitro systems, however, Stxs were hardly toxic against various human endothelial cells such as umbilical vein endothelial cells (HUVEC). To our surprise, the fresh primary cultures of HUVEC, appeared to be sensitive to merely pM order of Stxs, whereas they rendered resistant during passage of only 1-2 weeks. Moreover, apoptosis is apparently involved in the damage of the primary culture cells, but not of passaged ones, as shown by the annexin V stain, TUNEL or DNA fragmentation, despite that the well-established function of Stxs is the inhibition of protein synthesis. Concerning the intracellular event in apoptosis, the activation of caspase -3 was observed by immunoblotting, and correspondingly, the inhibitor of caspase-3 raised the viability of endothelial cells after Stx treatment. Common upstream cascades for apoptosis such as fas stimulation, mitochondria discharge and nitric oxide synthesis were examined and found not be engaged, indicating a novel unique path may be at work here. Although the mechanism underling the resistance of the passaged HUVEC is still unclear, the possible candidates of extracellular and intracellular factors may be IFN-αand bcl-xL, respectively, according to our data
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