Increased bradykinin Bl receptor expression in diabetic placental tissue correlates with both hyperhistaminaemia and increased histidine decarboxylase (HDC) activity

摘要

Increased histamine content and bradykinin levels were reported in placental tissue obtained after diabetic pregnancies. Both compounds are well known mediators of the inflammatory reactions. Bradykinin induces mast cell degranulation, leading to increase in the local histamine concentration. Bradykinin Bl receptor shows strong involvement in the inflammatory response, whereas the B2 receptor mediates most of the effects induced by kinins. The aim of this study was to examine comparatively correlations between placental HDC activity, histamine concentration, and placental bradykinin receptors Bl and B2 expression in diabetes class C versus normal pregnancy. Sixteen diabetic placentae were compared with 16 normal placentae (Group I and II, respectively). Tissular activity of HDC was assayed in placental samples obtained in a standardized manner, using a modified method, described previously by Endo. Histamine concentrations in placental cuts were estimated fluorimetrically, whereas expression of Bl and B2 was examined in immunostained paraffin sections by quantitative morphometry in the areas matched in mean vascular density. Mean HDC activity in group I was significantly (p < 0.05) increased compared to controls (3.97 ±0.25 vs 2.88 +0.15 nmol/h/g ±SEM). Histamine concentration in Group I was significantly increased compared to Group II (387 ±25.3 vs 239 ±14.3 ng/g of wet weight ±SEM). Mean expression of the Bl was augmented in diabetes and reached 289.8% of the value for Group II (p<0.05). The differences in mean expression of B2 receptors were non significant. Increased HDC activity may explain particular phenomena observed in diabetic placental tissue. HDC-dependent histamine elevation may change locally vascular properties by influence on bradykinin receptors expression. Proinflammatory reactions mediated via Bl should be expected rather, than changed vasomotor reactivity related to B2. Angiogenic properties of histamine and kinins should also be considered.