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Polyamines are involved in the 1‐α,25‐dihydroxyvitamin D 3 ‐induced fusion of mouse alveolar macrophages
Author(s) -
Hayashi Takamune,
Shinki Toshimasa,
Tanaka Hirofumi,
Abe Etsuko,
Suda Tatsuo
Publication year - 1986
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650010211
Subject(s) - spermidine , spermine , trichloroacetic acid , putrescine , methylglyoxal , biochemistry , ornithine decarboxylase , microbiology and biotechnology , chemistry , biology , enzyme
We have reported that 1‐α,25‐dihydroxyvitamin D 3 [1‐α,25‐(OH) 2 D 3 ] directly induces fusion of mouse alveolar macrophages at a very high rate (circa 70–80%) by a mechanism involving protein synthesis (Proc. Natl. Acad. Sci. USA 80:5583, 1983; FEBS Letters 174:61, 1984). While examining further the mechanism of the 1‐α,25‐(OH) 2 D 3 ‐induced fusion of macrophages, we found that polyamines are involved in this mechanism. Mouse alveolar macrophages incubated with 12 n M 1‐α,25‐(OH) 2 D 3 began to fuse at 36 h and the fusion rate increased linearly up to 60 h. Addition of as much as 0.05–5 m M α‐difluoromethylornithine (α‐DFMO), a specific inhibitor of ornithine decarboxylase, did not inhibit fusion appreciably, but addition of 0.05–5 μM methylglyoxal bis(guanylhydrazone) (MGBG), an inhibitor of S‐adenosylmethionine decarboxylase, strikingly inhibited fusion. When macrophages were treated with both 12 n M 1‐α,25‐(OH) 2 D 3 and 5 μM MGBG for the first 12 h and incubated further for 60 h in fresh medium containing 1‐α,25‐(OH) 2 D 3 , fusion was significantly inhibited, suggesting that the 1‐α,25‐(OH) 2 D 3 ‐induced synthesis of polyamines precedes fusion. The inhibition by MGBG of the 1‐α,25‐(OH) 2 D 3 ‐induced fusion was restored completely by adding 1 μM spermidine or spermine or 100 μM putrescine. None of the polyamines alone induced fusion. MGBG suppressed the 1‐α,25‐(OH) 2 D 3 ‐induced incorporation of [ 3 H]‐leucine into the trichloroacetic acid‐insoluble fraction in macrophages, but its inhibitory effect was restored completely by adding 1 μM spermidine. When macrophages were incubated with [ 14 C]‐ornithine, the polyamine that accumulated most was [ 14 C]‐spermidine. 1‐α,25‐(OH) 2 D 3 further enhanced the accumulation of [ 14 C]‐spermidine. The accumulation of [ 14 C]‐putrescine and spermine was not appreciably altered by the 1‐α,25‐(OH) 2 D 3 treatment. Adding MGBG almost completely suppressed the accumulation of [ 14 C]‐spermidine and spermine, but it enhanced the accumulation of [ 14 C]‐putrescine considerably. These results indicate that spermidine or spermine is an important intracellular mediator of the 1‐α,25‐(OH) 2 D 3 action in inducing protein synthesis, which in turn somehow induces fusion of alveolar macrophages.