Cytochemically detectable glucose-6-phosphate dehydrogenase is present in human fetal membrane chorion laeve trophoblasts

Characterization of NADPH-dependent oxidoreductase induced by auxin in rice

An NADPH-dependent oxidoreductase (NADPH-DO) with an isoelectric point of 5.2 and a molecular mass of 35 kDa was isolated from suspension-cultured rice cells. NADPH-DO was inducible by auxin and gibberellin. NADPH-DO mRNA was expressed in roots and leaf sheaths of rice seedlings, but not in leaf blades. The levels of NADPH-DO mRNA and protein in suspension-cultured cells were increased by auxin; they were further raised by the application of zinc. In contrast, NADPH-DO mRNA and protein accumulation in intact roots was stimulated by auxin, but in this case the stimulation was inhibited by zinc. Auxin-induced callus growth and root formation in intact rice plants were further enhanced by zinc. These results indicate that high levels of NADPH-DO are necessary for auxin- and zinc-induced callus formation, and imply that zinc plays a role in the regulation of NADPH-DO induction by auxin.

Hofbauer cell activation and its increased glucose-6-phosphate dehydrogenase activity in second trimester-spontaneous abortion: an ultrastructural dual staining enzyme-cytochemical study

PROBLEM

While activated/phagocytosing phagocytes infiltrating to the chorioamnion are considered to be one of the causal agents of preterm labor onset, whether placental villous macrophages (Hofbauer cells) are activated/phagocytosing in this condition is not known.

METHOD OF STUDY

We concomitantly localized two important phagocytosis-related enzymes, acid phosphatase (ACP) and glucose-6-phosphate dehydrogenase (G6PD), in Hofbauer cells in second trimester placental villi, and compared them with those from infection-related second trimester-spontaneous abortion (miscarriage) placentas.

RESULTS

There were two types of Hofbauer cells. The first cells exhibited ACP stainings confined to the lysosomes, suggesting that they are dormant/non-activated cells. Approximately two-thirds of these cells showed weak G6PD labeling on the cytosolic side of endoplasmic reticula, and G6PD labeling was hardly recognizable in the remaining one-third. The second cells, possessing large phagosomes, showed marked ACP labeling in the phagosomes, suggesting that they are activated/phagocytosing cells. All these cells exhibited G6PD labeling, and in 'bursting cells' (possibly hyperactivated cells) G6PD deposits were marked. The percentage of activated cells in miscarriage placentas was significantly higher (44.8 +/- 6.0%) than that in gestational age-matched controls (17.4 +/- 5.3%).

CONCLUSIONS

These observations indicated that (1) G6PD activity increased in activated/phagocytosing Hofbauer cells, and (2) the percentage of phagocytosing cells increased in infection-related miscarriage placentas. Hofbauer activation and G6PD may play an role in the pathogenesis/pathophysiology of preterm labor onset.

Enzyme-cytochemically detectable glucose-6-phosphate dehydrogenase in human villous macrophages (Hofbauer cells)

Though various tissue macrophages possess high glucose-6-phosphate dehydrogenase (G6PD) activity, which plays an important role in their phagocytosis/bactericidal function, the presence of this enzyme in human placental villous macrophages (Hofbauer cells) has not been determined. We examined the ultrastructural localization of glucose-6-phosphate dehydrogenase (G6PD) in Hofbauer cells in first and second trimester placental villi, using a newly developed enzyme-cytochemistry (copper-ferrocyanide) method. Electron-dense deposits indicative of G6PD activity were clearly visible in the cytoplasm and on the cytosolic side of the endoplasmic reticulum of Hofbauer cells. Positive and negative cytochemical controls ensured specific detection of enzyme activity. These observations indicated that Hofbauer cells abundantly possessed enzyme-cytochemically detectable G6PD activity. Hofbauer cell G6PD may play a role in placental defense, by supplying NADPH-dependent enzymes (i.e. nitric oxide synthase or NADPH oxidase) with NADPH. This enzyme may also fuel Hofbauer cells with ribose 5-phosphate during their cell proliferation and cell division.