M L Casey

Tissue distribution and ontogeny of steroid 5 alpha-reductase isozyme expression.

The synthesis of dihydrotestosterone is catalyzed by steroid 5 alpha-reductase isozymes, designated types 1 and 2. Mutation of type 2 results in male pseudohermaphroditism, in which the external genitalia are phenotypically female at birth. Two striking and unexplained features of this disorder are that external genitalia of affected males undergo virilization during puberty and that these individuals have less temporal hair regression. The tissue-specific and developmental expression patterns of the 5 alpha-reductase isozymes were investigated by immunoblotting. The type 1 isozyme is not detectable in the fetus, is transiently expressed in newborn skin and scalp, and permanently expressed in skin from the time of puberty. There was no qualitative difference in 5 alpha-reductase type 1 expression between adult balding vs. nonbalding scalp. The type 2 isozyme is transiently expressed in skin and scalp of newborns. Type 2 is the predominant isozyme detectable in fetal genital skin, male accessory sex glands, and in the prostate, including benign prostatic hyperplasia and prostate adenocarcinoma tissues. Both isozymes are expressed in the liver, but only after birth. These results are consistent with 5 alpha-reductase type 1 being responsible for virilization in type 2-deficient subjects during puberty, and suggest that the type 2 isozyme may be an initiating factor in development of male pattern baldness.

Cachectin/tumor necrosis factor-alpha formation in human decidua. Potential role of cytokines in infection-induced preterm labor.

This study was conducted as part of an investigation to evaluate the hypothesis that bacterial toxins (LPS or lipoteichoic acid), acting on macrophage-like uterine decidua to cause increased formation of cytokines, may be involved in the pathogenesis of infection-associated preterm labor. We found that cachectin/tumor necrosis factor-alpha (TNF-alpha) was synthesized and secreted into the culture medium by human decidual cells and explants in response to treatment with LPS. LPS treatment also caused an increase in PGF2 alpha production by decidual cells and explants. In amnion cells in monolayer culture, TNF-alpha stimulated PGE2 formation, and TNF-alpha was cytostatic (inhibited [3H]thymidine incorporation into DNA) but not cytolytic in amnion cells. TNF-alpha was not detectable (less than 0.34 ng/ml) in the amniotic fluid of normal pregnancies at midtrimester or at term before or after the onset of labor (n = 44); but TNF-alpha was present at concentrations between 2.8 and 22.3 ng/ml in amniotic fluids of 4 of 20 pregnancies with intact membranes complicated by preterm labor (less than 34 wk gestational age). LPS was present in 10 of the 20 amniotic fluids of preterm labor pregnancies, including all four in which TNF-alpha was present. Bacteria were identified in only one of the four LPS-positive, TNF-alpha-positive fluids. Cytokine formation in macrophage-like decidua may serve a fundamental role in the pathogenesis of preterm labor, including increased prostaglandin formation and premature rupture of the membranes.

Contractile elements and myosin light chain phosphorylation in myometrial tissue from nonpregnant and pregnant women.

Smooth muscle contraction is initiated primarily by an increase in intracellular Ca2+, Ca(2+)-dependent activation of myosin light chain kinase, and phosphorylation of myosin light chain. In this investigation, we identified pregnancy-associated alterations in myosin light chain phosphorylation, force of contraction, and content of contractile proteins in human myometrium. Steady-state levels of myosin light chain phosphorylation and contractile stress were correlated positively in both tissues, but the myometrial strips from pregnant women developed more stress at any given level of myosin light chain phosphorylation. During spontaneous contractions and during conditions that favor maximal generation of stress, the rate and extent of myosin light chain phosphorylation were attenuated in myometrial strips from pregnant women. The content of myosin and actin per milligram of protein and per tissue cross-sectional area was similar between myometrium of nonpregnant and pregnant women. Although cell size was significantly increased in tissues obtained from pregnant women, the amounts of contractile proteins per cellular cross-sectional area were similar. In addition, myosin light chain kinase and phosphatase activities were similar in the two tissues. The content of caldesmon was significantly increased in myometrium of pregnant women, whereas that of calponin (a smooth muscle-specific protein associated with the thin filaments) was not different. We conclude that adaptations of human myometrium during pregnancy include (a) cellular mechanisms that preclude the development of high levels of myosin light chain phosphorylation during contraction and (b) an increase in the stress generating capacity for any given level of myosin light chain phosphorylation.

Cytokines and infection-induced preterm labour

Our present understanding of the physiologic role of prostaglandins during pregnancy and, in particular, the precise function of these agents in the initiation of human parturition, is limited. This uncertain posture persists in spite of evidence (reviewed in detail recently by Challis and Olson 1988) in favour of a fundamental role for prostaglandins in a host of physiological processes in reproductive biology, including the onset and progression of labour. All investigators agree that prostaglandin E2 (PGE2) and prostaglandin F2, (PGF2,) can act, pharmacologically, as uterotonins (to cause myometrial contraction) when administered to pregnant women at any stage of gestation; moreover, the ingestion of inhibitors of prostaglandin synthesis by pregnant women is associated with a delay in the onset of labour-whether spontaneous or induced. There is much evidence in support of the conclusion that there is an increase in the rate of production of prostaglandins during labour: namely, during labour, there are increases in the levels of PGE2, PGF2, and 13,14-dihydro-15-keto-PGF2, (PGFM) in amniotic fluid and increases in PGFM in maternal blood. Also, prostaglandins will effect cervical dilatation. However, it has not been proven that prostaglandins serve as the physiological uterotonins of parturition or that prostaglandins are obligatorily involved in parturition at all stages of pregnancy, i.e. term and preterm labour. The evidence that there is an increase in the levels of prostaglandins in the maternal or fetal compartment prior to the onset of labour is limited. The possibility that the increase in prostaglandins is a consequence of labour (and not an initiating event) has not been excluded. Importantly, based on the findings of studies conducted recently, the possibility exists that labour (and delivery) may occur in some preterm pregnancies in the absence of an increase in prostaglandin production of the same magnitude that occurs during normal labour at term (Cox et al. 1989). Thus, we suggest that it is timely to consider the role of prostaglandins in the parturitional process with a new view, i.e, one that may enable an expansion of our understanding of the biochemical events involved in the initiation of parturition at term and preterm. Nowadays, the statement that human pregnancy is characterized by profound alterations in a host of biochemical and physiologic processes that encompass most all organ systems may rightly be considered timeworn. Yet, recent analyses of this well-recognized premise have led to the concepts that among these pregnancy-altered processes are those that facilitate recognition of pregnancy and, thereby, adaptation to pregnancy and maintenance of pregnancy. Perhaps the most remarkable compliance of normal human pregnancy is the maintenance of uterine quiescence for 38 weeks. For more than 99% of gestation, normal pregnancy is characterized by remarkable uterine repose and equanimity -a state that is essential to the maintenance of pregnancy. This quiescent state is uncommon for this smooth

Transforming growth factor-β inhibits prostaglandin production in amnion and A431 cells☆

We studied the effect of transforming growth factor-beta (TGF-beta) on prostaglandin E2 (PGE2) production and mitogenesis in human amnion cells and compared the response in amnion cells with that in A431 cells. Both amnion cells and A431 cells respond to epidermal growth factor (EGF) with increased production of PGE2 whereas EGF promotes mitogenesis in amnion cells but not in A431 cells. In amnion cells, TGF-beta was not mitogenic, and did not alter the mitogenic response of cells to EGF. Treatment of amnion cells with TGF-beta did, however, cause a decrease in PGE2 production relative to untreated cells, although EGF stimulated PGE2 production was not attenuated. In A431 cells, TGF-beta acted to decrease PGE2 production relative to untreated cells and to attenuate the stimulation of PGE2 production effected by EGF. The inhibitory action of TGF-beta on PG production in amnion and A431 cells is contrary to the stimulation of PG production in mouse calvaria reported by others and is suggestive that the effect of TGF-beta on prostaglandin production, like its effect on growth, varies between different cell types. Inhibition of PG production by treatment of amnion or A431 cells with mefenamic acid did not alter thymidine incorporation into DNA in response to EGF; similarly, the addition of PGE2 or PGF2 alpha to culture media of amnion or A431 cells had no effect on mitogenesis (in the absence or presence of EGF). Based on these findings, we conclude that PG production and EGF action on proliferation (stimulation in amnion cells; inhibition in A431 cells) are dissociated.

Origin of urinary nonconjugated 19-nor-deoxycorticosterone and metabolism of infused radiolabeled 19-nor-deoxycorticosterone in men and women.

It is known that 19-nor-deoxycorticosterone (19-nor-DOC) is a potent mineralocorticosteroid that is present in urine of rats and humans in a free, i.e., nonconjugated, form. In some forms of hypertension in rats, the levels of free 19-nor-DOC in urine are increased compared with those in urine of normotensive animals. Yet, despite the potential importance of this mineralocorticosteroid in the pathogenesis of certain forms of hypertension, little is known of its site of origin or metabolism. In the present investigation, we evaluated the metabolism of intravenously infused [3H]19-nor-DOC and the possibility that 19-nor-DOC was formed from plasma DOC. We found that the metabolism of [3H]19-nor-DOC infused intravenously in men and women was similar to that of DOC with important exceptions. The majority of the radiolabeled urinary metabolites of intravenously infused [3H]19-nor-DOC were excreted in urine as glucuronosides. Little radioactivity, infused as [3H]19-nor-DOC, was recovered in urine as nonconjugated or sulfoconjugated steroids. There was no free radiolabeled 19-nor-DOC in urine after the simultaneous infusion of [3H]19-nor-DOC and [14C]DOC. A major metabolite of [3H]19-nor-DOC in urine was 19-nor-DOC-21-glucuronoside, whereas little or no intravenously infused radiolabeled DOC was excreted as radiolabeled DOC-glucuronoside. We also found that intravenously infused [14C]DOC was not converted to urinary [14C]19-nor-DOC (glucuronoside) and that other tritium-labeled metabolites of infused [3H]19-nor-DOC contained no carbon-14. The production rate of 19-nor-DOC, computed from the specific activity of urinary 19-nor-DOC (glucuronoside), in one normal man was 16 micrograms/d and in the two women of this study, it was 10 micrograms/d. These findings are supportive of the proposition that free urinary 19-nor-DOC is not formed from plasma DOC; it may be formed in kidney from a precursor other than DOC or it may be formed nonenzymatically in kidney or urine from a precursor such as 19-oic-DOC.