Molecular and functional characteristics of β3-adrenoceptors in late pregnant mouse uterus: A comparison with β2-adrenoceptors

TXA2 mediates LPA1-stimulated uterine contraction in late pregnant mouse

Lysophosphatidic acid (LPA) is known to increase uterine contraction in the estrus cycle and early pregnancy, however, the effect of LPA in late pregnant uterus and its mechanisms are not clear. In the present study, we show the LPA receptor subtypes expressed and the mechanism of LPA-induced contractions in late pregnant mouse uterus. We determined the relative mRNA expression of LPA receptor genes by quantitative PCR and elicited log concentration-response curves to oleoyl-L-α-LPA by performing tension experiments in the presence and absence of nonselective and selective receptor antagonists and inhibitors of the TXA2 pathway. LPA1 was the most highly expressed receptor subtype in the late pregnant mouse uterus and LPA1/2/3 agonist (Oleoyl-L-α LPA) elicited increased contractions in this tissue that had lesser efficacy compared to oxytocin. LPA1/3 antagonist, Ki-16425, and a potent LPA1 antagonist (AM-095) significantly inhibited the LPA-induced contractions. Further, the nonselective COX inhibitor, indomethacin, and potent thromboxane A2 synthase inhibitor, furegrelate significantly impaired LPA-induced contractions. Moreover, selective thromboxane receptor (TP) antagonist, SQ-29548, and Rho kinase inhibitor, Y-27632 almost eliminated LPA-induced uterine contractions. LPA1 stimulation elicits contractions in the late pregnant mouse uterus using the contractile prostanoid, TXA2 and may be targeted to induce labor in uterine dysfunctions/ dystocia.

Role of Noradrenaline and Adrenoreceptors in Regulating Prostaglandin E2 Synthesis Cascade in Inflamed Endometrium of Pigs

In the inflamed uterus, the production and secretion of prostaglandins (PGs) and noradrenergic innervation pattern are changed. Receptor-based control of prostaglandin E2 (PGE2) production and secretion by noradrenaline during uterine inflammation is unknown. The aim of this study was to determine the role of α1-, α2- and β-adrenoreceptors (ARs) in noradrenaline-influenced PG-endoperoxidase synthase-2 (PTGS-2) and microsomal PTGE synthase-1 (mPTGES-1) protein levels in the inflamed pig endometrium, and in the secretion of PGE2 from this tissue. E. coli suspension (E. coli group) or saline (CON group) was injected into the uterine horns. Eight days later, severe acute endometritis developed in the E. coli group. Endometrial explants were incubated with noradrenaline and/or α1-, α2- and β-AR antagonists. In the CON group, noradrenaline did not significantly change PTGS-2 and mPTGES-1 protein expression and increased PGE2 secretion compared to the control values (untreated tissue). In the E. coli group, both enzyme expression and PGE2 release were stimulated by noradrenaline, and these values were higher versus the CON group. The antagonists of α1- and α2-AR isoforms and β-AR subtypes do not significantly alter the noradrenaline effect on PTGS-2 and mPTGES-1 protein levels in the CON group, compared to noradrenaline action alone. In this group, α1A-, α2B- and β2-AR antagonists partly eliminated noradrenaline-stimulated PGE2 release. Compared to the noradrenaline effect alone, α1A-, α1B-, α2A-, α2B-, β1-, β2- and β3-AR antagonists together with noradrenaline reduced PTGS-2 protein expression in the E. coli group. Such effects were also exerted in this group by α1A-, α1D-, α2A-, β2- and β3-AR antagonists with noradrenaline on mPTGES-1 protein levels. In the E. coli group, the antagonists of all isoforms of α1-ARs and subtypes of β-ARs as well as α2A-ARs together with noradrenaline decreased PGE2 secretion versus noradrenaline action alone. Summarizing, in the inflamed pig endometrium, α1(A, B)-, α2(A, B)- and β(1, 2, 3)-ARs mediate the noradrenaline stimulatory effect on PTGE-2 protein expression, while noradrenaline via α1(A, D)-, α2A- and β(2, 3)-ARs increases mPTGES-1 protein expression and α1(A, B, D)-, α2A- and β(1, 2, 3)-ARs are involved in PGE2 release. Data suggest that noradrenaline may indirectly affect the processes regulated by PGE2 by influencing its production. Pharmacological modulation of particular AR isoforms/subtypes can be used to change PGE2 synthesis/secretion to alleviate inflammation and improve uterine function.

Effect of blocking of alpha1-adrenoreceptor isoforms on the noradrenaline-induced changes in contractility of inflamed pig uterus

BACKGROUND

Disturbances in uterine contractility often lead to the origin, development and maintenance of endometritis and metritis, which are a very common and serious pathologies in domestic animals. Here we aimed to investigate the role of α1A-, α1B- and α1D-adrenoreceptors (ARs) in noradrenaline (NA)-induced contractility of inflammatory-changed porcine uterus.

METHODS

On Day 3 of the estrous cycle, either Escherichia coli (E. coli) suspension (E. coli group) or saline (SAL group) was injected into uterine horns, or only laparotomy was performed (CON group). Eight days later, infected gilts developed severe acute endometritis.

RESULTS

Compared to the period before NA application, NA reduced the contractile amplitude and frequency in myometrium (MYO) and endometrium (ENDO)/MYO strips from the CON, SAL and E. coli groups. In the last group, the amplitude in MYO and the frequency in ENDO/MYO were lowered versus other groups. After using α1A-ARs antagonist with NA, a greater decrease or occurrence of a drop in the amplitude and frequency in all groups (ENDO/MYO) were found compared to this neurotransmitter action alone. Such results were noted for NA action on the frequency after α1B-ARs blocking in the CON (both kinds of strips) and SAL (ENDO/MYO) groups. In response to α1D-ARs antagonist with NA, a greater decrease or occurrence of a drop in the amplitude was noted in the CON (both kinds of strips) and SAL and E. coli (MYO) groups. Use of these factors caused the similar changes in the frequency in CON and E. coli (MYO) and SAL (ENDO/MYO) groups. In response to NA, α1A,B,D-ARs antagonist led to a greater reduction or appearance of a drop in the amplitude in the CON and SAL (ENDO/MYO) and E. coli (both kinds of strips) as well as in the frequency in the CON and SAL (ENDO/MYO) and E. coli (MYO) groups.

CONCLUSIONS

In conclusion, activation of α1A- and α1D-ARs by NA promotes the contractile amplitude and frequency in the inflamed pig uterus; pharmacological modulation of these receptors can be utilized to enhance systolic activity of myometrium.

Role of beta-adrenergic receptor subtypes in pig uterus contractility with inflammation

Uterine inflammation is a very common and serious condition in domestic animals. To development and progression of this pathology often lead disturbances in myometrial contractility. Participation of β1-, β2- and β3-adrenergic receptors (ARs) in noradrenaline (NA)-influenced contractility of the pig inflamed uterus was studied. The gilts of SAL- and E.coli-treated groups were administered saline or E.coli suspension into the uterine horns, respectively. Laparotomy was only done in the CON group. Compared to the period before NA administration, this neurotransmitter reduced the tension, amplitude and frequency in uterine strips of the CON and SAL groups. In the E.coli group, NA decreased the amplitude and frequency, and these parameters were lower than in other groups. In the CON, SAL and E.coli groups, β1- and β3-ARs antagonists in more cases did not significantly change and partly eliminated NA inhibitory effect on amplitude and frequency, as compared to NA action alone. In turn, β2-ARs antagonist completely abolished NA relaxatory effect on these parameters in three groups. Summarizing, NA decreases the contractile amplitude and frequency of pig inflamed uterus via all β-ARs subtypes, however, β2-ARs have the greatest importance. Given this, pharmacological modulation of particular β-ARs subtypes can be used to increase inflamed uterus contractility.

Myometrial Calcium and Potassium Channels Play a Pivotal Role in Chromium-Induced Relaxation in Rat Uterus: an In Vitro Study

Hexavalent chromium, a well-known environmental toxicant, adversely affects female reproduction and results in abnormal implantation, fetal resorption, and reduction in litter size. Uterine myogenic activity is under control of number of receptors and ion channels, and it regulates fetal-implantation and feto-maternal communication. Despite several known adverse effects of chromium on female reproduction, direct action of chromium on myometrial activity is yet to be understood. In the present study, the effect of in vitro exposure of hexavalent chromium (Cr-VI) on the myogenic activity of isolated myometrial strips of rats was evaluated after mounting the tissue in thermostatically (37 ± 0.5 °C) controlled organ bath under a resting tension of 1 g. Chromium produced concentration-dependent (0.1 nM-0.1 mM) inhibitory effect on myometrial activity. Following pre-treatment of the myometrial strips with glibenclamide (a K_ATP channel blocker) and 4-aminopyridine (a K_v channel blocker), the concentration-response curve (CRC) of chromium was significantly (P < 0.05) shifted towards right with decrease in the maximum relaxant effect. Contractile effects of CaCl₂ and BAY K-8644 (a selective opener of L-type Ca²⁺ channel) were significantly (P < 0.05) attenuated in the presence of chromium. Chromium-induced myometrial relaxation was also significantly (P < 0.05) reduced in the presence of ICI 118,551 (a selective β₂-antagonist) and SR 59230A (a selective β₃-antagonist). These findings evidently suggest that chromium produced relaxant effect on rat myometrium by interfering with Ca²⁺ entry through voltage-dependent Ca²⁺ channels, and by interacting with beta-adrenoceptors (β₂ and β₃) and potassium channels (especially K_ATP and K_v channels). Graphical Abstract Proposed signaling pathway(s) of chromium (VI)-induced myometrial relaxations in rats. K_ATP: ATP-sensitive K⁺ channel; K_V: voltage-dependent K⁺ channel; VDCC: voltage-dependent Ca²⁺ channel; [Ca²⁺]_i: intracellular calcium concentration, stimulatory mechanism, inhibitory mechanism.

Leptin receptor stimulation in late pregnant mouse uterine tissue inhibits spontaneous contractions by increasing NO and cGMP

The adipokine, leptin exerts inhibitory effect on both spontaneous and oxytocin-induced contractions in myometrium. However, the mechanisms involved in leptin-induced effect are not clear. In the present study, we studied the altered characteristics of uterine contractions in the presence of leptin and the possible mechanisms of its effect in late pregnant (18.5 day) mouse uterus. We conducted functional, biochemical and molecular biology studies to demonstrate the mechanism of leptin-induced response. Leptin exerted an inhibitory response (E_max 40.5 ± 3.99%) on basal uterine contractions. The extent of inhibition was less than that obtained with known uterine relaxants, salbutamol (E_max103 ± 8.66%) and BRL-37344 (E_max 84.79 ± 8.12%). Leptin-induced uterine response was inhibited by leptin receptor antagonist SHLA and JAK-STAT pathway inhibitor, AG-490. The relaxant response was also subdued by NO-cGMP-PK-G pathway blockers L-NAME, 1400W, ODQ and KT-5823. Further, leptin enhanced the levels of NO and cGMP in uterine tissues. Also, SHLA, AG-490 and a combination of 1400 W and L-NAME prevented leptin-induced increase in NO. Similar effect was observed on cGMP levels in presence of leptin and SHLA. However, leptin did not influence CaCl₂-induced response in potassium-depolarized tissues. We also detected leptin receptor protein in late pregnant mouse uterus located in endometrial luminal epithelium and myometrial layers. Real-time PCR studies revealed significantly higher expression of short forms of the receptor (ObRa and ObRc) in comparison to the long form (ObRb). In conclusion, the results of the present study suggest that leptin inhibits mouse uterine contraction by stimulating short forms of the leptin receptors and activating NO pathway in a JAK-STAT-dependent manner.

Obesity alters the uterine environment before pregnancy

Obesity is a metabolic disorder that predisposes to numerous diseases and has become a major global public health concern. Cafeteria diet (CAF) is the animal model used for the study of obesity that more closely reflects Western diet habits. Previously, we described that CAF administration for 60 days induces obesity in female rats and their fetuses develop macrosomia. Given that, in our model, rats are not genetically modified and that obese mothers were fed standard chow during pregnancy, the aim of the current study was to test the hypothesis that obesity alters the intrauterine environment prior to pregnancy, and this may explain the exacerbated fetal weight gain. We found that uteri from obese rats during the estrous phase developed insulin resistance through mechanisms that involve the induction of uterine hypoxia and the down-regulation of the insulin receptor gene. Moreover, uterine cell proliferation was induced by obesity concomitantly with the reduction in the uterine contractile response to a β2 AR agonist, salbutamol, and this may be consequence of the down-regulation in the uterine β2 AR expression. We conclude that CAF-induced obesity alters the uterine environment in rats during the estrous phase and may cause the fetal macrosomia previously described by us in obese animals. The lower sensitivity of the uterus to a relaxation stimulus (salbutamol) is not a minor fact given that for implantation to occur the uterus must be relaxed for embryo nidation. Thus, the alteration in the uterine quiescence may impair implantation and, consequently, the foregoing pregnancy.

Phenylephrine, a common cold remedy active ingredient, suppresses uterine contractions through cAMP signalling

Regulation of uterine contractility is an important aspect of women’s health. Phenylephrine, a selective agonist of the α₁-adrenoceptor and a potent smooth muscle constrictor, is widely used in women even during pregnancy to relieve cold-related symptoms, to treat postpartum haemorrhoid, and during routine eye exams. We performed isometric tension recordings to investigate the effect of phenylephrine on mouse uterine contractility. Phenylephrine decreased spontaneous and oxytocin-induced contractions in non-pregnant mouse uterine rings and strips with an IC₅₀ of ~1 μM. Prazosin, an inhibitor of α₁-adrenoceptor, did not prevent phenylephrine-mediated relaxations. Conversely, ICI118551, an antagonist of β2-adrenoceptors, inhibited phenylephrine relaxation. In the presence of ICI118551, high concentrations (>30 μM) of phenylephrine caused mouse uterine contractions, suggesting that β-adrenoceptor-mediated inhibition interferes with the phenylephrine contractile potential. Phenylephrine-dependent relaxation was reduced in the uterus of pregnant mice. We used primary mouse and human uterine smooth muscle cells (M/HUSMC) to establish the underlying mechanisms. Phenylephrine stimulated large increases in intracellular cAMP in M/HUSMCs. These cAMP transients were decreased when HUSMCs were cultured in the presence of oestrogen and progesterone to mimic the pregnancy milieu. Thus, phenylephrine is a strong relaxant in the non-pregnant mouse uterus, but exhibits diminished effect in the pregnant uterus.

Casein kinase 2 inhibition impairs spontaneous and oxytocin-induced contractions in late pregnant mouse uterus

NEW FINDINGS

What is the central question of this study? Does the inhibition of the protein kinase casein kinase 2 (CK2) alter the uterine contractility? What is the main finding and its importance? Inhibition of CK2 impaired the spontaneous and oxytocin-induced contractility in late pregnant mouse uterus. This finding suggests that CK2 is a novel pathway mediating oxytocin-induced contractility in the uterus and thus opens up the possibility for this class of drugs to be developed as a new class of tocolytics.

ABSTRACT

The protein kinase casein kinase 2 (CK2) is a ubiquitously expressed serine or threonine kinase known to phosphorylate a number of substrates. The aim of this study was to assess the effect of CK2 inhibition on spontaneous and oxytocin-induced uterine contractions in 19 day pregnant mice. The CK2 inhibitor CX-4945 elicited a concentration-dependent relaxation in late pregnant mouse uterus. CX-4945 and another selective CK2 inhibitor, apigenin, also inhibited the oxytocin-induced contractile response in late pregnant uterine tissue. Apigenin also blunted the prostaglandin F_2α response, but CX-4945 did not. Casein kinase 2 was located in the lipid raft fractions of the cell membrane, and disruption of lipid rafts was found to reverse its effect. The results of the present study suggest that CK2, located in lipid rafts of the cell membrane, is an active regulator of spontaneous and oxytocin-induced uterine contractions in the late pregnant mouse.

ATP-sensitive and maxi potassium channels regulate BRL 37344-induced tocolysis in buffaloes-an in vitro study

Cellular coupling of beta₃-adrenoceptors (β₃-ADR) to potassium channels in myometrium is largely unknown. In vitro study was undertaken to unravel the presence of β₃-adrenergic receptors (ADR) and the role of K⁺-channels in mediating β₃-ADR-induced relaxation in isolated myometrial strips from cyclic non-pregnant water buffaloes. Isometric tension was recorded in isolated myometrial strips using data acquisition system based physiograph. Compared to SR 59230A, BRL 37344 was found to be more potent in inducing β₃-dependent myometrial relaxation which was significantly (p < 0.05) inhibited in the presence of β₃ antagonist, SAR 150640. The immunoreactive protein to β₃-ADR was also detected in membrane fraction of myometrial protein. Further, incubation with BRL 37344 (10 μM) significantly (p < 0.05) increased c-AMP accumulation (37.58 ± 9.52 pmol/mg protein; n = 4) in the myometrial strips compared to basal c-AMP level (16.85 ± 3.87 pmol/mg protein; n = 4). The concentration response curves (CRC) of BRL 37344 were significantly (p < 0.05) shifted towards right in the presence of K_ATP channels specific blocker, glibenclamide (10 μM) and maxi K⁺-channels (BK_Ca) specific blocker, iberiotoxin (100 nM), with decrease in both efficacy and potency as compared to control. However, 4-aminopyridine (4-AP), a specific blocker of the voltage gated K⁺-channels (Kv), failed to alter the CRC of BRL 37344. Existence of immunoreactive protein to Kir6.1, α-subunit of BK_Ca and Kv1.1 channels were also detected in the membrane fraction of myometrial protein. Based on the above findings, it can be concluded that BRL 37344 is a potent stimulator of β₃-adrenoceptors in buffalo myometrium and besides mediating their effect through rise in c-AMP, they are coupled to K_ATP and BK_Ca channels in inducing tocolytic effects.

Hypercholesterolemia impairs oxytocin-induced uterine contractility in late pregnant mouse

High cholesterol is known to negatively affect uterine contractility inex vivoconditions. The aim of the present study was to reveal the effect ofin vivohypercholesterolemia on spontaneous and oxytocin-induced uterine contractility in late pregnant mouse uterus. Female Swiss albino mice were fed with high cholesterol (HC) diet (0.5% sodium cholate, 1.25% cholesterol and 15% fat) for 6 weeks and then throughout the gestation period after mating. On day 19 of gestation, serum cholesterol level was increased more than 3-fold while triglycerides level was reduced in HC diet-fed animals as compared to control animals fed with a standard diet. In tension experiments, neither the mean integral tension of spontaneous contractility nor the response to CaCl2in high K+-depolarized tissues was altered, but the oxytocin-induced concentration-dependent contractile response in uterine strips was attenuated in hypercholesterolemic mice as compared to control. Similarly, hypercholesterolemia dampened concentration-dependent uterine contractions elicited by a GNAQ protein activator,Pasteurella multocidatoxin. However, it had no effect on endogenous oxytocin level either in plasma or in uterine tissue. It also did not affect the prostaglandin release in oxytocin-stimulated tissues. Western blot data showed a significant increase in caveolin-1 and GRK6 proteins but decline in oxytocin receptor, GNAQ and RHOA protein expressions in hypercholesterolemic mouse uterus. The results of the present study suggest that hypercholesterolemia may attenuate the uterotonic action of oxytocin in late pregnancy by causing downregulation of oxytocin receptors and suppressing the signaling efficacy through GNAQ and RHOA proteins.

β- and β-adrenergic receptors stimulation relaxes porcine myometrium in the peri-implantation period

These studies were to demonstrate whether the β-receptor is involved in regulating the contractility of the swine myometrium in the peri-implantation period and to compare a relaxing activity of selective β- and β-adrenergic agonists (salbutamol and BRL 37344, respectively). Myometrial strips were collected form the gilts ( = 8) on d 12 to 14 of pregnancy. Changes in the contractility of myometrial strips were assessed further to the administration of increasing concentrations of the agonists (10 to 10 ) with and without β-adrenergic receptor antagonists: butoxamine, propranolol, and bupranolol at 10 . Moreover, the -log EC (pD) of the agonists were compared. Following the incubation of myometrial strips with salbutamol and BRL 37344, a significant ( < 0.05 to 0.001) reduction in the contractility, seen as decreased tension, amplitude, and frequency of contractions, as compared to the pretreatment period was noted, although salbutamol induced these changes at a concentration of 10 to 10 , whereas BRL 37344 induced them at 10 to 10 . Salbutamol exerted a significantly ( < 0.001) more potent reduction of the tension (pD = 6.98 ± 0.93 [SD]) than BRL 37344 (pD = 3.41 ± 0.1.61). The impact of salbutamol was neutralized by all administered antagonists, while a relaxing effect of BRL 37344 was completely inhibited by bupranolol and partially by propranolol. The data indicate that the β-adenergic receptor is involved in the regulation of smooth muscle contractility in the swine uterus in the peri-implantation period and its activation triggers relaxation of the myometrium to a lesser degree than the activation of the β-adrenergic receptor.

Altered uterine contractility in response to β-adrenoceptor agonists in ovarian cancer

We aimed to prospectively examine β-adrenoceptor-mediated uterine contractility in women suffering from gynecological malignancies. Myometrial specimens were obtained from non-pregnant women undergoing hysterectomy for benign gynecological disorders, and ovarian, endometrial, synchronous ovarian–endometrial, and cervical cancer. Contractions of myometrial strips in an organ bath before and after cumulative dosages of β₂- and β₃-adrenoceptor agonists with preincubation of propranolol, SR 59230A, and butoxamine were studied. All agonists induced a dose-dependent attenuation for uterine contractility in endometrial or cervical cancer, similar to that observed in the reference group. Contradictory effects were observed for ovarian cancer alone or in combination with endometrial cancer. CL 316243 or ritodrine abolished the relaxation, whereas BRL 37344 increased the uterine contractility in ovarian cancer. Moreover, β-adrenoceptor antagonists caused varied effects for β₂- or β₃-adrenoceptor agonists. Our experiments demonstrate that ovarian cancer, alone or as synchronous ovarian–endometrial cancer, substantially alters uterine contractility in response to β-adrenoceptor agonists.