| Summary: | 碩士 === 長庚大學 === 天然藥物研究所 === 93 === The effects of soluble guanylate cyclase (sGC) activators, YC-1 [3-(5’-hydroxymethyl-2’-furyl)-1-benzyl indazole] and BAY 41-2272 3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine, on N-formylmethionyl-leucyl-phanylalanine (fMLP)-, complement fragment 5a (C5a)-, and platelet-activating-factor (PAF)-induced homotypic human neutrophil aggregation were investigated in the study. Three distinct phases of aggregation were observation after neutrophil activation by fMLP, C5a, and PAF, and these responses were attenuated by Ca2+-chelators but not by superoxide dismutase. YC-1 and BAY412272 not only directly promoted sGC activity and cGMP formation but also dramatically potentiated sodium nitroprusside (SNP)-induce sGC activity and cGMP formation in human neutrophil. In spite of this, YC-1 but not BAY 41-2272 inhibited these responses. Further studies suggested that the function of cGMP on homotypic human neutrophil aggregation was excluded because the synergistic increase in the amount of cGMP was inconsistent with its cellular responses. Additionally, phosphodiesterase (PDE) 4 inhibitors but not PDE3 inhibitor significantly inhibited fMLP-, C5a-, and PAF-induced aggregation. Interestingly, the inhibition of PDE4 inhibitors and YC-1 was reversed by adenosine deaminase. Moreover, PGE1, but not BAY-412272 even at the combination with SNP, could significantly inhibit neutrophil aggregation in the presence of ADA. PDE4 inhibitors and YC-1, but not PDE3, inhibitor increased the cAMP concentration, and ADA abolished these increase effects. Analysis of cAMP PDE function using human neutrophil cytosolic fractions confirmed that PDE4 inhibitor and YC-1, but not PDE3 inhibitor and BAY 41-2272 significantly reduced its activity. Additionally, monoclonal antibody to CD11b and CD18, but not CD11a and CD11c, markedly inhibited fMLP-, C5a-, and PAF-induced homotypic aggregation, suggesting CD11b/CD18 participates in these responses. In summary, these results indicate that cAMP, but not cGMP, plays an important role in the modulation of homotypic human neutrophil aggregation. The inhibition of YC-1 in homotypic human neutrophil aggregation can probably be attributed to the blockade of PDE4 activity, which potentiates the negative feedback function of endogenous adenosine.
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