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Objective The potency of acute montelukast treatment, a leukotriene receptor antagonist, has been demonstrated as tocolytic on in vitro myometrial contractility. This study assessed the ability of a 48 h montelukast treatment to modify in vitro contractions under inflammatory conditions in a pregnant rat model. Study design Pregnant Sprague-Dawley rats were injected intraperitoneally (gestational days 20–22) with lipopolysaccharides (LPS) 200 μg/kg (4 treatments at 12 h intervals) alone or combined with montelukast 10 mg/kg/day or a saline solution for a 48 h period. Uterine rings ( n = 72) were obtained by median laparotomy at day 22. Spontaneous contractile activities were compared using pharmacological compounds (oxytocin, nifedipine) along with assessment of contractile parameters. Myometrial subcellular fractions were also analyzed by Western blot to quantify oxytocin, cysteinyl leukotriene receptors and inflammation markers. Results In in vitro experiments, the area under the curve, the amplitude and the duration of phasic contractions were significantly reduced following 48 h of LPS + montelukast treatment comparatively to the LPS group. Moreover, in this same group, oxytocin (10 −9 –10 −7 M) largely decreased uterine sensitivity ( p = 0.04). Following LPS and montelukast treatment, the tocolytic effectiveness of nifedipine (10 −9 –10 −7 M) was increased ( p Conclusion Our results strongly suggest that montelukast treatment could facilitate a relative uterine quiescence by decreasing its sensitivity to uterotonic agent or by increasing tocolytic efficiency under proinflammatory conditions.

Background Although physiologic transition from rhythmic contractions to uterine retraction postpartum remains a poorly understood process, it has been shown that the latter is essential in the prevention of hemorrhage and its negative consequences. Objective To investigate the transition from oscillatory contractions to tonic contracture in human myometrium after delivery, a mechanism purported to facilitate postpartum hemostasis. Protein kinase C (PKC) plays a key regulatory role in human uterine contractions because it can prevent dephosphorylation of regulatory proteins and sensitize the contractile machinery to low Ca 2+ . Thus, activation of PKC by phorbol 12,13-dibutyrate (PDBu) may act as a strong uterotonic agent. Study Design Uterine biopsies were obtained from consenting women undergoing elective caesarian delivery at term without labor (N = 19). Isometric tension measurements were performed on uterine strips (n = 114). The amplitudes and area under the curve of phasic contractions and tonic responses were measured and compared. A total of 1 μM PDBu was added to the isolated organ baths, and maximal tension of the uterine contracture was determined in the absence and presence of either 1 μM of staurosporine, 100 nM nifedipine, or 10 μM cyclopiazonic acid to assess the role of PKC and calcium sensitivity on uterine contractility. Results On the addition of PDBu on either basal or oxytocin-induced activity, consistent contractures were obtained concomitant with complete inhibition of phasic contractions. After a 30-minute incubation period, the mean amplitude of the PDBu-induced tone represented 65.3% of the amplitude of spontaneous contraction. Staurosporine, a protein kinase inhibitor, induced a 91.9% inhibition of PDBu contractures, a process not affected by nifedipine or cyclopiazonic acid, thus indicating that this mechanism is largely Ca 2+ independent. Conclusion Pharmacologic activation of PKC leads to a significant contracture of the myometrium. Together, these data suggest that the up-regulation of PKC plays a physiologic role in the modulation of uterine contracture after delivery. A switch from phasic to strong tonic contractions potentially may facilitate postpartum hemostasis.

Objective This study analyzed the ability of montelukast, a cysteinyl-leukotrienes receptor antagonist and anti-inflammatory agent, to produce a consistent tocolytic effect alone or in combination with nifedipine, a calcium (Ca 2+ ) channel blocker currently used in clinical practice. Study design Uterine biopsies were obtained from consenting women undergoing elective cesarean sections at term ( n =20). Myometrial microsomal fractions were analyzed by immunoblotting to quantify relative cysteinyl leukotrienes receptor 1 (CysLTR1) levels. Isometric tension measurements were performed in vitro on human myometrial strips ( n =120) in isolated organ baths in order to establish concentration–response curves to montelukast and to quantify changes in Ca 2+ sensitivity on β-escin permeabilized tissues. Results Immunodetection analysis revealed the presence of CysLTR1 receptor in uterine tissues, fetal membranes and placenta. A significant increase in area under the curve (AUC) was quantified following the addition of leukotriene D 4 (LTD 4 ) (0.01–0.3μM), an end-product of the lipoxygenase pathway. Conversely, addition of montelukast produced a significant tocolytic effect by decreasing the frequency and AUC (IC 50 =1μM). Moreover, addition of montelukast also resulted in a reduced Ca 2+ sensitivity as compared to control tissues (EC 50 values of 654 and 403nM; p =0.02 at pCa 6), while an additive effect was observed in combination with 0.1nM nifedipine ( p =0.004). Conclusion This original study demonstrates the potency of montelukast as a tocolytic agent in an in vitro human uterine model. Montelukast, in combination with nifedipine, could represent a therapeutic approach to reduce inflammation associated with prematurity while facilitating the inhibition of preterm labor.

Aim The aim of the present experimental study was to assess the tocolytic effect of eicosanoids on myometrium from non-pregnant and pregnant rats with or without an induced inflammatory condition. Methods Three hundred myometrial rings were obtained by median laparotomy from 50 Sprague–Dawley rats divided into three groups: (i) non-pregnant (n = 15); (ii) pregnant in absence (n = 20); or (iii) pregnant in presence (n = 15) of lipopolysaccharide treatment, timed at 22 days of pregnancy. Spontaneous contractile activities were compared by isometric tension measurements. The effects of epoxy- and hydroxyeicosanoids derived from arachidonic acid as well as specific enzyme inhibitors were assessed. Changes were expressed as percentage of basal activity by calculating the area under the curve as a function of drug concentration and compared to the effect of the vehicle. Results A decrease in contractile activity ranging 10–25% was observed upon addition of epoxy- and hydroxyeicosanoids. Increasing epoxyeicosanoid bioavailability by inhibiting their degradation induced a tocolytic effect in the non-pregnant group (20%) and in inflammation-induced condition (40%). There was a significant difference in reactivity between groups and pregnancy condition. Semiquantification of metabolic enzymes that produce (cytochrome P-450 epoxygenase) and degrade (soluble epoxide hydrolase) epoxyeicosanoids by western blot analysis revealed that these enzymes were mainly detected in the non-pregnant group. Conclusion Eicosanoids can modify myometrial reactivity and their presence and effects are amplified in non-pregnant and in inflammation-induced condition. Our data suggest that in contrast to prostaglandins, epoxyeicosatrienoic acids are likely involved in the quiescence phase of parturition because they reduce the rhythmic contractile activity of uterine tissues in pregnant rats.

Aim To study the effect of blocking the inflammatory cascade with interleukin-6 receptor antibody (anti-IL-6R) on feto-maternal outcomes in a rat model. Methods Pregnant Sprague–Dawley rats (n = 38) were injected intraperitoneally (day 22) (control, anti-IL-6R 30 μg/kg, lipopolysaccharide [LPS] 250 μg/kg or 500 μg/kg alone or combined with anti-IL-6R) followed by preterm caesarian performed 12 h later. Resuscitated pups (n = 179) were given to surrogate mothers. Primary outcomes were maternal and pup mortality. Results Fifty percent of pregnant rats died after LPS 500 μg/kg + anti-IL-6R injection but none in other groups. Neonatal mortality at 24 h was 63% and 86% in LPS 500 μg/kg and LPS 500 μg/kg + anti-IL-6R groups, respectively (P

The incidence of preterm birth is an increasing problem. Indomethacin, a non-specific cyclooxygenase inhibitor, has been largely used as tocolytic in the treatment of preterm labor. The aim of the present study was to assess a putative synergistic tocolytic effect between the inhibition of the production of prostanoids and stabilization of epoxides fatty acids, particularly arachidonate on spontaneous uterine contractile activity. The experimental work was performed on uterine biopsies from consenting women undergoing elective cesarean delivery at term. Isometric tension measurements were performed on fresh human myometrial strips. Contractile activities have been monitored upon individual and combined treatments of indomethacin, DDMS, an inhibitor of hydroxy-eicosanoids production and AUDA, an inhibitor of epoxy-eicosanoids degradation. Interestingly, a significant and consistent synergic effect was observed when indomethacin and AUDA were simultaneously added, raising the possibility of a combined clinical use of cyclooxygenase and sEH inhibitors in attempt to treat preterm labor.

The aim of this study was to assess the involvement of lipoxygenase (LOX) metabolic pathways in uterine tissues from pregnant women as well as the combined inhibition of LOX and cyclooxygenase (COX) on contractile activity.Uterine biopsies were performed from consenting women undergoing elective caesarean sections at term (n = 24). Western blot analysis and isometric tension measurements were performed in vitro on fresh human myometrial strips. Concentration-response curves to arachidonic acid (AA) 861 and baicalein (5- and 12-LOX inhibitors, respectively) were performed. The combined effects of baicalein and indomethacin were also assessed. Contractile activities were quantified by calculating both amplitude and the area under the curve over 20 minute periods.5- and 12-LOX were present in all tested tissues. Addition of AA861 or baicalein resulted in tocolytic effects (P.05). Finally, the combined inhibition of both COX and 12-LOX pathways resulted in additive tocolytic effects.5- and 12-LOX pathways modulate human myometrium contractility.

Significant time course modifications of uterine contractile activities were observed in Levothyroxine-treated pregnant women, including increased amplitude and duration of phasic contractions in vitro. This study aimed to investigate the involvement of Ca2+ and K+ conductance in controlling repetitive contractile activities in an in vitro model of human uterine strips. Thus, the ability of Ba2+ to modulate Ca2+ and K+ conductance was used to alter the pattern of control uterine contractile activities. Uterine biopsies were performed from consenting women undergoing elective caesarean sections at term (N=12). Isometric tension measurements were performed in vitro on fresh human myometrial strips in isolated organ baths. After a 2 h equilibration period, the effects of Iberiotoxin (IbTx), a selective BKca blocker, Ba2+ and Lemakalim, a potassium channel opener were assessed on spontaneous uterine contractile activities. Uterine contractions were quantified by calculating the amplitude, the duration, the frequency and the area under the curve over 20-min periods. Our data demonstrated a significant increase in both amplitude and duration of phasic contractions following addition of 2 mM Ba2+, partially mimicking the result obtained upon T4-treatment during pregnancy. Addition of 100 nM IbTx, slightly increased these parameters, similarly to acute T3 treatments (p

Objective The purpose of this study was to assess the effects of exogenous eicosanoids on spontaneous uterine contractile activity. Study Design Eight uterine biopsies were performed from women who were undergoing elective cesarean delivery. Tension measurements were performed in vitro on myometrial strips. Contractile activities were quantified by the calculation of the area under the curve. The effects of eicosanoids and specific enzyme inhibitors were assessed. Fractions from various uterine tissues were analyzed by Western blot. Results Data demonstrate the presence, in some tested tissues, of cytochrome P -450 epoxygenase and soluble epoxide hydrolase, which respectively produce and degrade epoxyeicosatrienoic acid regioisomers. Inhibition of soluble epoxide hydrolase with 12-(3-adamantan-1-yl-ureido)-dodecanoic acid or ω-hydroxylase with N -methylsulfonyl-12,12-dibromododec-11-enamide resulted in a tocolytic effect; N-methylsulfonyl-6-[2-propargyloxyphenyl] hexanamide, which is an epoxygenase inhibitor, had no effect. Exogenous epoxyeicosatrienoic acids displayed significant tocolytic effects on spontaneous contractile activities. Conclusion Epoxy- and hydroxyeicosanoids represent new bioactive, arachidonic acid by-products with in vitro tocolytic activities. These findings suggest that cytochrome P -450 isozymes may represent relevant pharmacologic targets under physiopathologic conditions.