Yakubu M A, Basso B, Kierszenbaum F
Department of Microbiology and Public Health, Michigan State University, East Lansing 48824.
J Parasitol. 1992 Jun;78(3):414-9.
DL-alpha-difluoromethylarginine (DFMA), a specific, irreversible inhibitor of arginine decarboxylase (ADC), decreases the capacity of Trypanosoma cruzi to invade and multiply within different types of mammalian host cells in vitro. In this work we found that inhibition of intracellular growth results from selective impairment of amastigote division without appreciable alteration of the capacity of the invading trypomastigotes to transform into the replicative amastigote form. Addition of agmatine, the product of arginine decarboxylation, reversed the inhibitory effect of DFMA. Inhibition of ornithine decarboxylase activity by DL-alpha-difluoromethylornithine present in the medium prior to and during infection did not affect trypomastigote transformation or amastigote replication and did not change the magnitude of the inhibitory effect of DFMA on parasite multiplication. Hence, neither polyamine synthesis via the ornithine decarboxylase pathway nor salvage of host cell polyamines by T. cruzi appeared to be a likely explanation for the normal rate of parasite transformation that was seen in the presence of DFMA. Two clones of T. cruzi, TMSU-1 and TMSU-2, were tested for their degrees of sensitivity to the inhibitory effects of DFMA. Both trypomastigote association with (i.e., binding to and penetration of) myoblasts, and intracellular amastigote multiplication by either clone were found to be significantly (P less than 0.05) but not completely inhibited by DFMA. Therefore, the partial inhibition of T. cruzi infectivity and replication caused by DFMA is unlikely to represent a composite of effects of the drug on DFMA-sensitive and insensitive clones.(ABSTRACT TRUNCATED AT 250 WORDS)
DL-α-二氟甲基精氨酸（DFMA）是精氨酸脱羧酶（ADC）的一种特异性、不可逆抑制剂，它能降低克氏锥虫在体外侵入不同类型哺乳动物宿主细胞并在其中增殖的能力。在本研究中，我们发现细胞内生长受到抑制是由于无鞭毛体分裂受到选择性损害，而侵入的锥鞭毛体转化为增殖性无鞭毛体形式的能力没有明显改变。添加精氨酸脱羧产物胍丁胺可逆转DFMA的抑制作用。在感染前及感染期间，培养基中存在的DL-α-二氟甲基鸟氨酸对鸟氨酸脱羧酶活性的抑制并不影响锥鞭毛体的转化或无鞭毛体的复制，也未改变DFMA对寄生虫增殖的抑制作用强度。因此，无论是通过鸟氨酸脱羧酶途径合成多胺，还是克氏锥虫对宿主细胞多胺的挽救，似乎都不太可能解释在存在DFMA的情况下寄生虫正常的转化速率。我们检测了克氏锥虫的两个克隆TMSU-1和TMSU-2对DFMA抑制作用的敏感程度。发现这两个克隆的锥鞭毛体与成肌细胞的结合（即与成肌细胞结合并穿透）以及细胞内无鞭毛体的增殖均受到DFMA的显著抑制（P<0.05），但未被完全抑制。因此，DFMA对克氏锥虫感染性和复制的部分抑制不太可能是该药物对DFMA敏感和不敏感克隆的综合作用结果。（摘要截短于250字）
