Human labour is associated with nuclear factor-kappaB activity which mediates cyclo-oxygenase-2 expression and is involved with the 'functional progesterone withdrawal'

Mechanisms underlying "functional" progesterone withdrawal at parturition

Progesterone is a major factor maintaining uterine quiescence throughout pregnancy. In most species, peripheral progesterone levels decline before initiation of labor, and treatments that inhibit progesterone synthesis or action cause termination of pregnancy and/or premature deliveries. These findings suggest that progesterone withdrawal is required for activation of myometrial contractions. However, in humans, circulating progesterone levels remain elevated until birth, which leads to the notion that a "functional" progesterone withdrawal occurs before parturition. The apparent loss of progesterone sensitivity at term could be a consequence of several different mechanisms including: (1) the catabolism of progesterone in the uterus into inactive compounds; (2) alterations in progesterone receptor (PR) isoform ratios; (3) changes in cofactor protein levels affecting PR transactivation; and (4) inflammation-induced trans-repression of PR by nuclear factor kappaB. All of these mechanisms are potentially capable of decreasing uterine progesterone responsiveness at term, thus enabling the expression of pathways that originally were blocked by progesterone in early pregnancy. However, the specific uterine genes whose transcription is directly controlled by PR, and thus affected by "functional" progesterone withdrawal, remain to be identified.

Progesterone receptor expression in human decidua and fetal membranes before and after contractions: possible mechanism for functional progesterone withdrawal

In humans, progesterone levels are sustained before the onset of labour. Therefore, the mechanism for parturition that has been proposed for humans is 'functional' progesterone withdrawal. Immunohistochemical staining for the progesterone receptor (PR) was positive in the decidua with a decline after contractions began. Western blot analysis revealed a number of PR isoforms expressed in the decidua, with the PR-B form being dominant. After contractions began, all PR isoforms decreased sharply. PR-B and PR-A decreased by 85.8% +/- 6.7 and 78.2% +/- 7.1, respectively (P < 0.001). Incubation of decidua with Prostaglandin F2alpha 1.0 microg/ml decreased the expression of all forms of PR isoforms. PR-B was reduced by 64% +/- 6.09 (P < 0.01); PR-A was reduced by 77% +/- 5.9 (P < 0.05), while PR-C was reduced by 80% +/- 7.24 (P < 0.05). Progesterone (80 microg/ml) increased the PR-B, PR-C the 45 and 36 kDa isoforms to 150% +/- 7.89, 210% +/- 12.4, 270% +/- 9.7 and 216% +/- 13.5, respectively (P < 0.05). In immunohistochemical studies, the PR was not identified in the amnion or in the chorion, regardless of the presence or absence of contractions. Western blot analysis demonstrated that PR-C (60 kDa) and the 36 kDa isoforms were dominant in the amnion. After contractions began, PR-A decreased significantly by 61.9% +/- 7.1 (P < 0.001).

Molecular and biochemical mechanisms of preterm labour

Parturition involves the synchronization of myometrial activity and structural changes of the cervix, leading to regular co-ordinated uterine contractions and cervical dilatation and effacement. The biochemical events involved in parturition resemble an inflammatory reaction, with growing evidence pointing to a crucial role for pro-inflammatory cytokines and prostaglandins in labour. There is accumulating evidence that there are common mediators involved in the regulation of 'labour-associated proteins', and that, in each case, an increase or decrease in gene expression mediates changes in their concentration. It is possible, therefore, that targeting these common mediators may represent newer strategies for the prevention of preterm labour. Our aim is to review the mechanical and biochemical mechanisms that may be involved in the processes of term and preterm labour. Specifically, we will consider the regulation of some of the 'labour-associated proteins', chemotactic cytokines, prostaglandins and enzymes of the prostaglandin biosynthetic pathway and the oxytocin receptor.

Effect of Proteasome Pathway on Initiation of Mouse Labor Induced by Antiprogesterone

PROBLEM

Various kinds of contraction-associated molecules are up-regulated at the initiation of labor. However, expression profiling has revealed that many molecules are also down-regulated. The effect of down-regulation of molecules by protein degradation on parturition is not known.

METHODS OF STUDY

We administered lactacystin, a specific proteasome inhibitor, to mouse preterm birth model induced by antiprogesterone RU486 on day 16.0 post-coitus. NF-kappaB activity, and the levels of transcripts for oxytocin receptor, prostaglandin F(2alpha) receptor (FP), cyclooxygenase-1, -2, and interleukin-1beta in the uterus were examined by electrophoretic mobility shift assay and semi-quantitative reverse transcriptase-polymerase chain reaction, respectively.

RESULTS

Administration of lactacystin significantly prolonged the time until the delivery of the first pup. FP mRNA level was solely elevated by RU486 treatment, and lactacystin significantly suppressed this up-regulation.

CONCLUSIONS

Proteolysis by proteasomes in the uterus regulates the initiation of labor, at least in part, via control of contraction-associated molecules such as FP.

Expression and deoxyribonucleic acid-binding activity of the nuclear factor kappaB family in the human myometrium during pregnancy and labor

In humans, the factors that govern the switch from myometrial quiescence to coordinated contractions at the initiation of labor are not well defined. The onset of parturition is itself associated with increases in a number of proinflammatory factors, many of which are regulated by the nuclear factor kappaB (NF-kappaB) family of transcription factors. The expression and DNA-binding activity of NF-kappaB in the myometrium during gestation and parturition were examined. Levels of c-Rel, p50, and p105 NF-kappaB species were dramatically reduced in pregnant myometrium compared with nonpregnant (NP) controls, whereas expression of the RelA subunit remained uniform. Importantly, during labor, expression of all subunits was observed to be significantly reduced in all myometrial samples studied relative to NP levels. Moreover, for RelA, c-Rel, and p50 subunits, there was a gradient of expression between laboring upper (corpus) and lower uterine segment myometrium. No RelB or p52 subunits could be detected. EMSAs identified changes in NF-kappaB subunit composition in the myometrium during pregnancy and labor, with p50 homodimers predominant in NP tissues being replaced with RelA:p50 heterodimers in pregnant and laboring samples. Significantly, RelA was observed to be phosphorylated at serine-536, implicating the involvement of the phosphatidylinositol-3-kinase/AKT pathway in NF-kappaB function in the myometrium.

Toll-like receptor-2 and -4 in the chorioamniotic membranes in spontaneous labor at term and in preterm parturition that are associated with chorioamnionitis

OBJECTIVE

The Toll-like receptor-2 and -4 recognize microbial products that are associated with gram-positive and gram-negative bacteria, respectively. This study examined Toll-like receptor-2 and -4 expression in fetal membranes in response to labor at term and histologic chorioamnionitis.

STUDY DESIGN

Immunohistochemistry and real-time quantitative reverse transcriptase-polymerase chain reaction were used to examine the chorioamnion from patients with (1) preterm labor and intact membranes, (2) preterm premature rupture of membranes who were delivered < or =34 weeks of gestation, and (3) women at term with or without labor. All groups were stratified on the basis of the presence of histologic chorioamnionitis.

RESULTS

Toll-like receptor-2 expression was significantly higher in patients with chorioamnionitis than in patients without this condition (all P < .05). The Toll-like receptor-2 and -4 messenger RNA amounts were significantly higher in membranes from women at term with spontaneous labor than women who were not in labor ( P = .001 and .002, respectively). Toll-like receptor-2 expression was polarized to the basal surface of amniotic epithelial cells in patients without chorioamnionitis, but this distribution was lost in the presence of inflammation.

CONCLUSION

Spontaneous labor at term and preterm delivery with histologic chorioamnionitis, regardless of the membrane status (intact or ruptured), are associated with an increased expression of Toll-like receptor-2 and -4 in the chorioamniotic membranes. These observations have implications for understanding the biologic nature of innate immunity.

Pregnancy-specific down-regulation of NF-kappa B expression in T cells in humans is essential for the maintenance of the cytokine profile required for pregnancy success

It is accepted that human pregnancy is associated with a shift away from Th1 type and a bias toward Th2-type immune responses. The molecular mechanisms that regulate this shift are as yet unknown. We assessed the expression and activity of NF-kappaB, a transcription factor that plays a central role in regulating immune responses. We isolated T cells from PBMCs from nonpregnant and pregnant females and demonstrated that the NF-kappaB/IkappaB signaling pathway is down-regulated in T cells in pregnancy. Using Western blotting, high levels of NF-kappaB (p65) were detected in all nuclear fractions of T cells from nonpregnant females. In contrast, low levels of p65 were detected in nuclear fractions from T cells from pregnant females. Levels of IkappaBalpha and -beta were also higher in cytoplasmic fractions from T cells from nonpregnant than from pregnant females. The reduction in p65 levels in pregnancy was reflected in the activity of NF-kappaB in EMSA; T cells from pregnant females contain less active NF-kappaB than from nonpregnant females. Stimulation of T cells from nonpregnant females with PMA/ionomycin resulted in IkappaBalpha degradation, p65 translocation, and subsequent production of the Th1 cytokines IFN-gamma and IL-2. In contrast, PMA stimulation had no effect on NF-kappaB activity in T cells from pregnant females, and this was reflected in reduced Th1 cytokine production. Using the inhibitor of NF-kappaB activity, SN50, we were able to show that NF-kappaB activity was essential for the production of Th1 cytokines, suggesting that specific down-regulation of NF-kappaB in T cells throughout gestation is paramount to pregnancy success through specific regulation of cytokine production.

Tumor necrosis factor-alpha suppresses the expression of steroid receptor coactivator-1 and -2: a possible mechanism contributing to changes in steroid hormone responsiveness

Inflammation is associated in some tissues with diminished responsiveness to steroid hormone action. We hypothesized that proinflammatory cytokines alter steroid hormone sensitivity, in part, by reducing levels of key nuclear receptor coactivators. Treatment of cultured human uterine smooth muscle cells (UtSMC) with TNF-alpha significantly reduced mRNA for the coactivators, SRC-1 (42%, P<0.01) and 2 (47%, P<0.03), and diminished the respective protein levels, but did not significantly alter the mRNAs encoding SRC-3, CBP and the corepressors, NCoR and SMRT; or progesterone receptor protein levels. To assess TNF-alpha effects on steroid hormone-mediated transcriptional activity, UtSMC were transfected with progesterone receptor B (PR-B) and a model PRE2-luciferase reporter construct. Transfected UtSMC were treated with progesterone alone or in the presence of TNF-alpha, and assayed for luciferase activity. TNF-alpha (10 ng/ml) diminished progesterone-stimulated PR-B-mediated transactivation by approximately 60% (P<0.02). The TNF-alpha-dependent decrease in PRE-luciferase activity was fully prevented by cotransfection with SRC-2, and partially prevented with exogenous SRC-1. In conclusion, TNF-alpha impairs progesterone-stimulated PR-B-mediated transactivation, and these effects appear to be due, in part, to reduced expression of SRC-1 and -2, which is a novel mechanism by which inflammation can functionally block steroid hormone action.

Prostaglandins and the myometrium and cervix

Prostaglandins have long been thought to play important roles in the mechanism of parturition. Here we review the involvement of prostaglandins in myometrial and cervical functions with emphasis on human labor and birth. In addition, the cellular sources of prostaglandins as well as their interactions with various other endocrine, paracrine and physical factors, such as oxytocin, corticotropin releasing hormone, nitric oxide, platelet activating factor, cytokines, endothelin and stretch are also addressed together with their potential role in the molecular reorganization of cervical structure associated with labor and delivery. Finally, the premier role of progesterone in pregnancy maintenance and parturition is juxtaposed with the proposed "fine-tuning", modulatory role of prostaglandins and the above listed factors in the regulation of parturition.

Transcriptional regulation of genes for enzymes of the prostaglandin biosynthetic pathway

Numerous studies over the years have demonstrated changes in prostaglandin (PG) levels in intrauterine tissues in association with labour, and PG administration has long been used to induce delivery. While it is now widely accepted that PGs play a major role in human parturition, the complex regulation of their levels is still being elucidated, with the focus on the transcriptional control of the enzymes responsible for the various steps in PG biosynthesis and catabolism.

Prostaglandin inhibitors in preterm labour

Prematurity accounts for the majority of neonatal morbidity and mortality in the developed world. The process of labour resembles inflammation, with prostaglandin and cytokine production both before and during labour. Anti-inflammatory drugs therefore have the potential to prevent preterm delivery. Indomethacin is the only tocolytic drug proven to delay delivery beyond 37 weeks and to reduce the incidence of low birth weight (<2500 g). There are, however, fetal side-effects such as ductal constriction and impaired renal function associated with its use. It is the type 2 isoform of cyclo-oxygenase (COX-2), which is important for the production of prostaglandins within intrauterine tissues and that up-regulation of COX-2 is associated with labour. Although indomethacin is currently the most common non-steroidal anti-inflammatory drug (NSAID) used in the treatment of preterm labour, it was hoped that COX-2-selective drugs, used as tocolytics, would target COX-2 activity and potentially spare COX-1-specific fetal side-effects. Experience with sulindac and nimesulide has been linked with both constriction of the ductus arteriosus and oligohydramnios. It is unclear whether this is due to COX-2-dependent side-effects, or due to accumulation of drug in the fetal circulation leading to levels that would cause COX-1 inhibition. Currently, the use of COX-2-selective drugs should therefore be confined to randomized controlled trials.

Immunohistochemical determination of thioredoxin and glutaredoxin distribution in the human cervix, and possible relation to cervical ripening

Thioredoxin (Trx) and glutaredoxin (Grx) are dithiol redox enzymes, catalyzing general thiol-disulfide oxidoreductions apart from being hydrogen donors for ribonucleotide reductase, an enzyme essential for DNA synthesis. In mammals, isoenzymes of Trx and Grx are found in the cytoplasm (Trx1 and Grx1) or in mitochondria (Trx2 and Grx2). Trx and Grx play a role in cellular defence against oxidative stress and in redox regulation of cellular function. The localization and levels of human Trx1 and human Grx1 have been determined in the human cervix by immunohistochemistry and image analysis. Cervical biopsies were obtained from five non-pregnant, five term pregnant and five postpartum women. The levels of both Trx1 and Grx1 were increased in the nuclei (after translocation from the cytoplasm) of stromal cells in cervices from the term pregnant group as compared to the non-pregnant group, but the levels in the postpartum group did not differ significantly from those of the other two groups. These results are in agreement with our previous data on the mRNA expression of these two redox enzymes. The increased levels of the redox enzymes in term pregnancy suggest that they can be regulating factors involved in the process of cervical ripening, e.g. transcription factors and enzymes. Secreted Trx may participate in removing inhibitors of collagen-degrading metalloproteinases.

Progesterone represses interleukin-8 and cyclo-oxygenase-2 in human lower segment fibroblast cells and amnion epithelial cells

Labor is preceded by cervical ripening through upregulation of interleukin (IL)-1beta, IL-8, and increased prostaglandin synthesis via inducible type 2 cyclooxygenase (COX-2). Progesterone maintains myometrial quiescence during pregnancy. In this study, we examined the effects of IL-1beta and progesterone on IL-8 and prostaglandin E2 (PGE2) synthesis and IL-8 and COX-2 mRNA and promoter activity in amnion cells and lower segment fibroblast (LSF) cells. In both cell types, progesterone had no effect on basal IL-8 or PGE2 synthesis. In LSF cells, IL-1beta significantly increased IL-8 and PGE2 synthesis and COX-2 and IL-8 mRNA expression, but progesterone significantly attenuated these effects. In prelabor amnion cells, IL-1beta also increased IL-8 and PGE2 synthesis and both COX-2 and IL-8 mRNA and promoter expression; however, progesterone significantly attenuated these effects on IL-8 and PGE2 synthesis and COX-2 expression. In postlabor amnion cells, IL-1beta increased IL-8 and PGE2 synthesis and COX-2 expression, but progesterone did not attenuate the effect of IL-1beta upon IL-8 synthesis. Progesterone repression of IL-8 and COX-2 in LSF cells suggests that IL-8 and COX-2 have similar regulatory mechanisms in LSF cells and that progesterone may play a role in maintenance of cervical competence. The lack of effect of progesterone on IL-8 in postlabor cells may be the result of downregulation of the progesterone receptor during labor.

The involvement of progesterone in the onset of human labour

Progesterone is essential for the maintenance of pregnancy, and acts to promote uterine quiescence. In many species progesterone levels fall prior to the onset of labour but no fall has been observed in humans. The concept of 'functional' progesterone withdrawal in association with labour has been proposed and a number of mechanisms have been suggested. Recent potential mechanisms of functional withdrawal include changes in progesterone receptor (PR) isoforms, regulation of PR responsive genes through nuclear factor kappaB (NF-kappaB) promoter sites and the non-genomic effects of progesterone or its metabolites.

Cytokines, prostaglandins and parturition--a review

The elaboration of cytokines, chemokines and immunomodulatory proteins in the placenta and gestational membranes has been extensively investigated in the context of both normal and abnormal pregnancy and delivery. Patterns of expression of cytokines in the foetal membranes and decidua suggest that inflammatory activation occurs modestly with term labour, but much more robustly in preterm delivery, particularly in the presence of intrauterine infection. Enhanced chemokine expression, particularly evident in deliveries with an infected amniotic cavity, is presumably responsible for recruiting infiltrating leukocytes into the membranes thereby amplifying the inflammatory process and hastening membrane rupture and delivery. Anti-inflammatory cytokines suppress inflammatory reactions in the placenta, but under some circumstances may act in a pro-inflammatory fashion in the membranes. Intracellular signalling by cytokines is modulated by proteins such as SOCS (Silencer Of Cytokine Signalling)-1, -2 and -3. Changes in the abundance of these proteins occur with term labour, implicating them as modulators of cytokine actions around the time of parturition. Prostaglandins, released by the membranes in response to stretch and the actions of pro-inflammatory cytokines, act not only upon the myometrium and cervix, but may also exert paracrine/autocrine effects on cell viability and matrix protein integrity. The localization and regulation of prostanoid isomerases, responsible for converting PGH(2) (derived from prostaglandin H synthase-1 and -2) to bioactive prostanoids, are being studied in these tissues, particularly in the context of cytokine interactions. Although the gestational tissues are known to be sources of PGD(2), PGJ(2) and its derivatives, the regulation of production of these prostaglandins has yet to be studied in any detail and their actions, which may include apoptosis and suppression of inflammation, remain poorly defined. A more complete understanding of these aspects of cytokine-prostaglandin interactions in pregnancy and parturition will, no doubt, unfold as current studies come to fruition.

Interleukin-1beta induces glycosaminoglycan synthesis via the prostaglandin E2 pathway in cultured human cervical fibroblasts

The aim of this study was to identify, in cultured human cervical fibroblasts, the mechanisms by which interleukin (IL)-1beta induces the synthesis of glycosaminoglycans (GAG) and to explore the putative role of prostaglandin E(2) (PGE(2)) in this process. Exposure of the cells for 24 h to IL-1beta induced a significant (P < 0.05) dose-dependent increase in GAG synthesis. IL-1beta (1 ng/ml) induced the expression of cyclooxygenase-2 (COX-2) protein 6 h after treatment, accompanied by a 7.5-fold increase in PGE(2) production. We confirmed that NS398, a selective COX-2 inhibitor, dose-dependently blocked PGE(2) augmentation following IL-1beta treatment. AH23848, the selective EP(4) receptor antagonist, completely abolished IL-1beta-induced GAG synthesis, whereas AH6809, an EP(2) receptor antagonist, had no effect on the stimulatory effects of IL-1beta. Furthermore, we demonstrated that 6 h exposure to IL-1beta induced a notable increase in EP(4) receptor mRNA expression and a decrease in EP(1) receptor mRNA but had no effect on the expression of EP(2) and EP(3) receptor transcripts. In conclusion, these findings indicate that IL-1beta not only induced GAG synthesis by increasing COX-2 protein expression and the subsequent PGE(2) production but also enhanced the responsiveness of cervical fibroblasts to PGE(2) by selectively up-regulating EP(4) receptor mRNA expression. These results suggest that PGE(2) may regulate human cervical ripening in an autocrine/paracrine manner via EP(4) receptors.

Nuclear factor kappa B activation and regulation of cyclooxygenase type-2 expression in human amnion mesenchymal cells by interleukin-1beta

Interleukin-1beta (IL-1beta) has been shown in numerous studies to increase prostaglandin (PG) output by up-regulating the expression of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in PG synthesis. In this study, we investigated the possible role of the nuclear factor kappa B (NFkappaB) in IL-1beta signaling, leading to the expression of COX-2 in human amnion cell culture. Fetal amnion was obtained following vaginal delivery and digested with collagenase, and the subepithelial (mesenchymal) cells were isolated. Cultures were characterized with antisera to keratin (epithelial cells) and vimentin (mesenchymal cells). Confluent cells were stimulated with human recombinant IL-1beta, and activation of NFkappaB was assessed by measuring changes in the inhibitory protein IkappaB (total IkappaB and phosphorylated IkappaB) using Western blot analysis as well as by nuclear binding of NFkappaB using an electrophoretic mobility shift assay. COX-2 protein levels were determined by Western blot analysis. After 5 min of stimulation with IL-1beta, phosphorylated IkappaB began to appear, 90% of which was degraded within 15 min. This was temporally associated with decreased total IkappaB and increased nuclear NFkappaB DNA-binding activity. In the IL-1beta-treated group, COX-2 protein began to increase after 6 h; this response was time-dependent, with a significant increase until 24 h after IL-1beta stimulation. When NFkappaB translocation was blocked by using SN50 (a cell-permeable inhibitory peptide of NFkappaB translocation), the synthesis of COX-2 protein was inhibited. These results suggest that NFkappaB is involved in the IL-1beta-induced COX-2 expression in the mesenchymal cells of human amnion.

The in vivo control of prostaglandin H synthase-2 messenger ribonucleic acid expression in the human amnion at parturition

Prostaglandin H synthase-2 (PGHS-2) activity and mRNA rise in the human amnion at late gestation, contributing to the increase in intrauterine PG production crucial for labor and delivery. In the present investigation we have determined the mechanism that controls amniotic PGHS-2 mRNA levels in vivo at term parturition. Amnion membranes were collected after elective cesarean section (n = 20), and after spontaneous labor (n = 20). PGHS-2 relative gene transcription rates were determined by transcriptional run-on, and PGHS-2 mRNA and heterogeneous nuclear RNA (hnRNA) relative abundance were measured by quantitative real-time RT-PCR. The PGHS-2 mRNA degradation rate was determined by incubating amnion in the presence of the transcription inhibitor 5,6-dichlorobenzimidazole riboside. The dynamics of PGHS-2 hnRNA and mRNA abundance were characterized in 0- to 24-h tissue incubations. The PGHS-2 relative gene transcription rate was a significant (P < 0.05) predictor of PGHS-2 hnRNA and mRNA abundance, and PGHS-2 hnRNA was also a predictor (P < 0.01) of PGHS-2 mRNA levels both before and after labor. Interestingly, even though PGHS-2 gene activity remained unchanged, PGHS-2 mRNA abundance increased with labor and displayed constitutive stability before and after labor. PGHS-2 mRNA levels spontaneously increased by 400% (P < 0.01) upon incubation for 24 h, whereas the transcription rate dropped by 95% during the first 2 h, then rebounded significantly between 6-24 h. Thus, PGHS-2 mRNA abundance is transcriptionally controlled in term amnion. Labor does not increase PGHS-2 gene activity or mRNA stability. The PGHS-2 gene is probably induced before labor by a factor(s) originating in the amnion membrane, and the resulting stable mRNA accumulates progressively in the tissue throughout labor and delivery.

Localization of nuclear factor-kappa B (NF kappa B) and inhibitory factor-kappa B (I kappa B) in human fetal membranes and decidua at term and preterm delivery

The human fetal membranes and decidua are thought to be involved in the onset of human parturition. These tissues produce and respond to various cytokines, which may be involved in preterm labour and possibly term labour. They also show increasing production of prostaglandins (PGs) with advancing gestation and labour. The expression of PGHS-2, a rate limiting enzyme in PG synthesis, is increased in the fetal membranes at labour. The gene for PGHS-2 and many of the cytokine genes (e.g. TNFalpha, IL-1, IL-6) are stimulated by the transcription factor NF kappa B. This factor is composed of two subunits, p50 and p65, which are localized in the cytoplasm bound to I kappa B. When activated I kappa B is metabolized, and p50, p65 translocate to the nucleus to activate various genes. The purpose of the present study was to examine the tissue and cellular distribution of p65 and I kappa B in the human fetal membranes and decidua throughout gestation. Term tissues were obtained prior to labour by elective caesarean section (n=10) or following vaginal delivery (n=10) and 10 preterm tissues were obtained following labour prior to 37 weeks gestation. None of the tissues had any evidence of infection. The immunoreactive NF kappa B and I kappa B were localized in the tissues. p65 protein was found in the nucleus and cytoplasm of cells in the amnion, chorion laeve and decidua. In the amnion and chorion laeve, no changes occurred in subcellular localization with advancing gestation or term labour. However, in the decidua, there was a marked increase in the nuclear localization of i.r. p 65 in tissues obtained at term when compared with tissues delivered preterm. In the case of I kappa B, it was localized to the cytoplasm of cells in all tissues and there was an increase i.r. I kappa B in decidua at term compared to preterm but no change occurred in the amnion or chorion. The increase in nuclear localization of p65 in the decidua that occurs with advancing gestation, highlights the potential importance of this factor in the regulation of parturition related genes in this tissue.

Integrin-linked kinase regulates inducible nitric oxide synthase and cyclooxygenase-2 expression in an NF-kappa B-dependent manner

Nitric oxide (NO) and prostaglandins are produced as a result of the stimulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2, respectively, in response to cytokines or lipopolysaccharide (LPS). We demonstrate that the activity of integrin-linked kinase (ILK) is stimulated by LPS activation in J774 macrophages. Inhibition of ILK activity by dominant-negative ILK or a highly selective small molecule ILK inhibitor, in epithelial cells or LPS-stimulated J774 cells and murine macrophages, resulted in inhibition of iNOS expression and NO synthesis. LPS stimulates the phosphorylation of IkappaB on Ser-32 and promotes its degradation. Inhibition of ILK suppressed this LPS-stimulated IkappaB phosphorylation and degradation. Similarly, ILK inhibition suppressed the LPS-stimulated iNOS promoter activity. Mutation of the NF-kappaB sites in the iNOS promoter abolished LPS- and ILK-mediated regulation of iNOS promoter activity. Overexpression of ILK-stimulated NF-kappaB activity and inhibition of ILK or protein kinase B (PKB/Akt) suppressed this activation. We conclude that ILK can regulate NO production in macrophages by regulating iNOS expression through a pathway involving PKB/Akt and NF-kappaB. Furthermore, we also demonstrate that ILK activity is required for LPS stimulated cyclooxygenase-2 expression in murine and human macrophages. These findings implicate ILK as a potential target for anti-inflammatory applications.