- Email: [email protected]
Plancetal release of endothelin-1 under hypoxic conditions in vitro
A.37
Abstracts
PLACENTAL RELEASE OF ENDOTI-IELINI-I UNDER HYPOXIC CONDITIONS IN VITRO. J.C.P. Kingdc)mI, L. Neth-Jesscc, A. Czekierdowski, and R.K. Miller, Obs, Univ. of Gla-~gow1, Glasgow, Scotland a~d Obs / Gyn, Univ. of Rochester, Rochester, NY USA. The severely growth-retarded fetus may exist in a chronically hypoxic and acidotic environment for several weeks prior to birth. In such cases tht:re is often an abnormal umbilical artery Doppler waveform suggestive of placental vasoconstriction. Since the local vasoconstrictor endothelin-1 (ET) is ~ynthcsized within the placenta, and its synthesis is stimulated under hypoxic conditions in vitro, we speculated that hypoxia/aeidosis may provoke release of ET from the dually perfused human placental lobule. Dual circuit perfusion with maternal to fetal oxygen transfer was established in normal term placentae (n=5) and an initial control period of 60 minutes followed (fetal vein if'V) perfusate stabilized at pH 7.4 and pO2 80-120 mmHg). Uterine tschemia was then repre~nted by closure of the maten~l circuit (in 3 cases) to allow fetal pH and FV pO2 tO fall in the closed fetal circuit through placental oxidative metabolism; after an ischcmic p.~riod of 60-120 minutes the maternal circuit was re-established and both circuits rcplaed with fresh pe.~fi~tcs. The other 2 perfusions continued as controls during this time. Perfusate [ETI was determined in FV and MV perfusatc-s at 15 minute intervals by an EIA method (Cayman, USI~) and results expressed in fmol/ml. FA perfusion pressure (at a constant rate of 3 ml/minutc) was measured. FV [ETI prior to the ischcmie, period averaged 3.8 fmol/ml. In the 3 cxperin'tents subiected to lschemia, the nadir of pH ,,v~s 7.08 + 0.04 due to a lactic acidosis, and pO2 fell to 32 • 2 mHg. FA perfusion pressure (30-40 mmHg) did not change significantly in any case. During this time the average FV lET] was 4.01 fmol/ml with no sigafificant trend in any individual case. FV [ETI remained ~table in the control perfusions, and no change was evident in FV [ETI in the 3 ischemic easc~, following rc-pcrfusion to normal pH artd pO2. MV I'ETI was similar to fetal values, and did not change following re-pcrfusion in the 3 isehemlc cases. Thc,,~ data do not support the theory that placental lsclaemia results in increased release of ET into either circula~on. Fetal lET] is elevated in some cases of severe IUGR with abnormal Doppler. Perhap:~ the degree of hypoxla in our experiments was not severe enough to trigger an incrase in placental ET mRNA (or release of preformed peptide). Alternatively, perhaps oth2r factors, such as membrane peroxtdation, serve to damage the fetal endothelium in c.ivo to increase local release and activity of this peptide in severe IUGR. (Supported by ;~n Ethicon Travel Award to JK and NIH grant ES02774,)
CHORIOAMNIONITIS:
A
ROLE
FOR
INTERLEUKIN-8?
H.J.
Kliman t,2, A y d i n M. Arici 2, M. E. Cunningham3, E. L. M e a d d o u g h t, Departments o f Pathology 1, O b / G y n 2 and Surgery 3, Yale University, N e w Haven, CT, U S A . The C o l l a b o r a t i v e Perinatal Study demonstrated that m o r e than a third o f all preterm births were associated with labor initiated by acute chorioamnionitis. The reason that c h o r i o a m n i o n i t i s appears to be so deleterious to the fetus is that the i n f l a m m a t o r y process i n d u c e s v i l l o u s edema. T h e factors that m e d i a t e acute i n f l a m m a t i o n and induce villous e d e m a in the placenta are not k n o w n at this time, although breakdown products o f growing bacteria---especiaUy the lipopolysaccharides (LPS) o f the bacterial cell walls ( e n d o t o x i n ) - - a p p e a r to play an important role in the initiation o f this process. L P S appears to mediate the i n f l a m m a t o r y r e s p o n s e by triggering the release of a cascade of cytokines from a variety of cell types. O n e of these cytokines, interleukin-8 (IL-8), appears to play an important role in initiating acute inflammation because of its known neutrophil chemoattractant properties. W e h a v e shown that LPS from E. coli (1 I.tg/ml) induced 0.5x106 purified human trophoblasts to secrete 6,975 + 810 pg/ml/24 h of IL-8, as m e a s u r e d by a specific E L I S A ( R & D , Minneapolis, MN). Unstimulated trophoblasts secreted 294 + 59 p g / m l / 2 4 h of IL-8. Addition o f 1 ktM progesterone and 1 ~tM d e x a m e t h a s o n e decreased IL-8 production to 3,015 + 650 and 1,360 + 440 p g / m l / 2 4 h, respectively. IL-8 m R N A levels in cultured trophoblasts grown in media, media + LPS, or media + LPS + dexamethasone paralleled the protein secretion results. These data suggest that 1) bacterial infections of the amniotic cavity may stimulate trophoblast production o f IL-8, w h i c h c h e m o a t t r a c t s n e u t r o p h i l s to and through the c h o r i o n i c plate; 2) p r o g e s t e r o n e m a y s e r v e as a natural IL-8 suppressor during p r e g n a n c y ; and 3) therapies e m p l o y i n g dexamethasone during pregnancy should take into account the IL-8 suppressive effects of this potent corticosteroid.
Abstracts
PLACENTAL RELEASE OF ENDOTI-IELINI-I UNDER HYPOXIC CONDITIONS IN VITRO. J.C.P. Kingdc)mI, L. Neth-Jesscc, A. Czekierdowski, and R.K. Miller, Obs, Univ. of Gla-~gow1, Glasgow, Scotland a~d Obs / Gyn, Univ. of Rochester, Rochester, NY USA. The severely growth-retarded fetus may exist in a chronically hypoxic and acidotic environment for several weeks prior to birth. In such cases tht:re is often an abnormal umbilical artery Doppler waveform suggestive of placental vasoconstriction. Since the local vasoconstrictor endothelin-1 (ET) is ~ynthcsized within the placenta, and its synthesis is stimulated under hypoxic conditions in vitro, we speculated that hypoxia/aeidosis may provoke release of ET from the dually perfused human placental lobule. Dual circuit perfusion with maternal to fetal oxygen transfer was established in normal term placentae (n=5) and an initial control period of 60 minutes followed (fetal vein if'V) perfusate stabilized at pH 7.4 and pO2 80-120 mmHg). Uterine tschemia was then repre~nted by closure of the maten~l circuit (in 3 cases) to allow fetal pH and FV pO2 tO fall in the closed fetal circuit through placental oxidative metabolism; after an ischcmic p.~riod of 60-120 minutes the maternal circuit was re-established and both circuits rcplaed with fresh pe.~fi~tcs. The other 2 perfusions continued as controls during this time. Perfusate [ETI was determined in FV and MV perfusatc-s at 15 minute intervals by an EIA method (Cayman, USI~) and results expressed in fmol/ml. FA perfusion pressure (at a constant rate of 3 ml/minutc) was measured. FV [ETI prior to the ischcmie, period averaged 3.8 fmol/ml. In the 3 cxperin'tents subiected to lschemia, the nadir of pH ,,v~s 7.08 + 0.04 due to a lactic acidosis, and pO2 fell to 32 • 2 mHg. FA perfusion pressure (30-40 mmHg) did not change significantly in any case. During this time the average FV lET] was 4.01 fmol/ml with no sigafificant trend in any individual case. FV [ETI remained ~table in the control perfusions, and no change was evident in FV [ETI in the 3 ischemic easc~, following rc-pcrfusion to normal pH artd pO2. MV I'ETI was similar to fetal values, and did not change following re-pcrfusion in the 3 isehemlc cases. Thc,,~ data do not support the theory that placental lsclaemia results in increased release of ET into either circula~on. Fetal lET] is elevated in some cases of severe IUGR with abnormal Doppler. Perhap:~ the degree of hypoxla in our experiments was not severe enough to trigger an incrase in placental ET mRNA (or release of preformed peptide). Alternatively, perhaps oth2r factors, such as membrane peroxtdation, serve to damage the fetal endothelium in c.ivo to increase local release and activity of this peptide in severe IUGR. (Supported by ;~n Ethicon Travel Award to JK and NIH grant ES02774,)
CHORIOAMNIONITIS:
A
ROLE
FOR
INTERLEUKIN-8?
H.J.
Kliman t,2, A y d i n M. Arici 2, M. E. Cunningham3, E. L. M e a d d o u g h t, Departments o f Pathology 1, O b / G y n 2 and Surgery 3, Yale University, N e w Haven, CT, U S A . The C o l l a b o r a t i v e Perinatal Study demonstrated that m o r e than a third o f all preterm births were associated with labor initiated by acute chorioamnionitis. The reason that c h o r i o a m n i o n i t i s appears to be so deleterious to the fetus is that the i n f l a m m a t o r y process i n d u c e s v i l l o u s edema. T h e factors that m e d i a t e acute i n f l a m m a t i o n and induce villous e d e m a in the placenta are not k n o w n at this time, although breakdown products o f growing bacteria---especiaUy the lipopolysaccharides (LPS) o f the bacterial cell walls ( e n d o t o x i n ) - - a p p e a r to play an important role in the initiation o f this process. L P S appears to mediate the i n f l a m m a t o r y r e s p o n s e by triggering the release of a cascade of cytokines from a variety of cell types. O n e of these cytokines, interleukin-8 (IL-8), appears to play an important role in initiating acute inflammation because of its known neutrophil chemoattractant properties. W e h a v e shown that LPS from E. coli (1 I.tg/ml) induced 0.5x106 purified human trophoblasts to secrete 6,975 + 810 pg/ml/24 h of IL-8, as m e a s u r e d by a specific E L I S A ( R & D , Minneapolis, MN). Unstimulated trophoblasts secreted 294 + 59 p g / m l / 2 4 h of IL-8. Addition o f 1 ktM progesterone and 1 ~tM d e x a m e t h a s o n e decreased IL-8 production to 3,015 + 650 and 1,360 + 440 p g / m l / 2 4 h, respectively. IL-8 m R N A levels in cultured trophoblasts grown in media, media + LPS, or media + LPS + dexamethasone paralleled the protein secretion results. These data suggest that 1) bacterial infections of the amniotic cavity may stimulate trophoblast production o f IL-8, w h i c h c h e m o a t t r a c t s n e u t r o p h i l s to and through the c h o r i o n i c plate; 2) p r o g e s t e r o n e m a y s e r v e as a natural IL-8 suppressor during p r e g n a n c y ; and 3) therapies e m p l o y i n g dexamethasone during pregnancy should take into account the IL-8 suppressive effects of this potent corticosteroid.