Effect of progesterone on nitric oxide/cyclic guanosine monophosphate signaling and contraction in gastric smooth muscle cells

Regulation of PDGFRα+ cells and ICC in progesterone-mediated slow colon transit in pregnant mice

Background

Progesterone can inhibit intestinal smooth muscle contraction; however, the specific mechanism remains unclear. Besides smooth muscle cells, smooth muscle has two important mesenchymal cells, namely interstitial cells of Cajal (ICC) and PDGFRα+ cells, which induce the contraction and relaxation of smooth muscles. We aimed to explore the regulation of PDGFRα+ cells and ICC in progesterone-mediated colon slow transit in pregnant mice.

Methods

Colon transit experiments were performed in vivo and in vitro to observe slow colon transit. The expression of PDGFRα and c-KIT was detected by Western blot, RT-PCR, and immunofluorescence. An isometric tension experiment was performed to investigate smooth muscle contractions.

Results

The colon transit time in pregnant mice was longer than that in non-pregnant mice. Progesterone significantly blocks colonic smooth muscle contractions. However, when the relaxation and contraction of PDGFRα+ cells and ICC are blocked, progesterone cannot inhibit smooth muscle contraction. When the function of only PDGFRα+ cells are blocked, progesterone has a more obvious inhibitory effect on smooth muscle in the non-pregnant group than that in the pregnant group. However, when ICC alone was blocked, progesterone inhibited smooth muscle contractions more clearly in pregnant mice. The protein and mRNA expression of PDGFRα was higher and c-KIT was lower in pregnant mice. PDGFRα+ cells and ICC from smooth muscle all co-localize progesterone receptors.

Conclusions

Under the regulation of progesterone, the relaxation function of PDGFRα+ cells is enhanced and the contraction function of ICC is weakened, leading to the slow colon transit of pregnant mice.

Prokinetic effects of Citrus reticulata and Citrus aurantium extract with/without Bupleurum chinense using multistress-induced delayed gastric emptying models

CONTEXT

Citrus aurantium L (Rutaceae) (Au) and Citrus reticulata Blanco (Rutaceae) (Ci) are commonly used as couplet prokinetics and Bupleurum chinense DC. (Umbelliferae) (Bup) is an herbal antidepressant in traditional Chinese medicine.

OBJECTIVE

This study evaluates the synergistic prokinetic effects of Bup with Au and Ci in mice suffering from multistress-induced delayed gastric emptying (DGE).

MATERIALS AND METHODS

Kunming mice were divided into four groups: control, DGE, AuCi and AuCiBup. Mice were gavaged with AuCi (14.25 g/kg) or AuCiBup (22.13 g/kg) extract for 12 days. Gastric reminder rate, intestinal driving ratio, sucrose preference and open field test were examined, and serotonin (5-HT), motilin (MTL), substance P (SP), 5-HT₄R and c-kit were assayed. Intracellular Ca²⁺ levels in primary cultured gastric smooth muscle cells (GSMCs) were determined.

RESULTS

Both AuCi and AuCiBup treatment significantly reduced gastric residual rate (39.5% and 67.7%, p < 0.01). Higher serum levels of 5-HT, MTL and SP were observed in treatment groups (AuCi: 0.060 mg/L, AuCiBup: 0.089 mg/L, DGE: 0.025 mg/L, p < 0.01). The expression of 5-HT₄R and c-kit in the antrum and duodenum was upregulated after treatment (AuCi and AuCiBup, 4.3-times, 2.8-times to DGE, p < 0.01). Medicated serums of AuCi and AuCiBup effectively increased the influx of Ca²⁺ into GSMCs in vitro (1.8-times, p < 0.01). In terms of 5-HT₄R expression, circulatory contents of 5-HT and SP and Ca²⁺ influx, AuCiBup demonstrated better prokinetic effects than AuCi.

CONCLUSIONS

These findings indicate the potential for developing combination therapy with antidepressants and prokinetics in gastrointestinal dysmotility management.

The Influence of Pregnancy on Female Prostate Morphophysiology in Gerbils (Meriones unguiculatus)

Morphophysiological changes of the female prostate during pregnancy are still little known. Considering that this gland is highly influenced by steroid hormones, the aim of this study was to evaluate the impact of the pregnancy on female prostate morphophysiology in gerbils. Pregnant females were timed, and the prostates were analyzed at pregnancy days 6 (P6), 12 (P12), 18 (P18), and 24 (P24). Virgin females were used as the control group (C). We observed a profound change in the hormonal profile during gestation, which was marked by a high oscillation of the progesterone (P4) hormone. P4 serum levels increased, peaking at the middle of gestation, and decreased to the end of the pregnancy. The morphology of the gland in pregnant females also changed, being marked by an increase of acini lumen, and a decrease in stroma. Indeed, the acinar changes during pregnancy were followed by a significant reduction of the epithelial height, besides a change of the smooth muscle cells' morphology that became more relaxed. The number of progesterone receptor (PR) and androgen receptor (AR)-positives cells decreased with the increase of progesterone serum levels, showing an inverse relationship. Finally, we observed a reduction of epithelial proliferation and a significant increase of gland PAS-positive secretion at the end of pregnancy. Altogether, these results showed, for the first time, that the female prostate morphophysioloy is profoundly influenced by the gestational period, suggesting that the fluctuation of the P4 serum levels is the main factor influencing the gland during this period.

Contractile function of the cervix plays a role in normal and pathological pregnancy and parturition

The cervix plays an integral part in ensuring the proper timing of pregnancy and parturition. It maintains the fetus within the uterus and protects it from pathogens present in the vaginal canal. The cervix undergoes extensive remodeling during pregnancy and parturition. This process is associated with collagen degradation, an increase in immune cell response and inflammation in the cervix. However, our understanding of the role of cervical smooth muscles and their contribution to cervical remodeling is still lacking. In this paper, we propose that the active contractile function of the cervix influences cervical remodeling during pregnancy and parturition. Contraction of the cervical smooth muscles helps the cervix to remain firm and closed during early pregnancy, while relaxation of the cervical smooth muscles help facilitate cervical dilatation during labor. This contractile function of the cervix can be influenced by endocrine signals, such as estrogen, progesterone, and oxytocin; local paracrine signals, such as inflammatory chemokines and cytokines, as well as extracellular vesicles, such as exosomes and ectosomes; and by pharmacological agents used for cervical ripening and the induction of labor. A deeper understanding of the role of smooth muscles in cervical remodeling can help us elucidate the cellular processes in the cervix during pregnancy and parturition. This can also help in finding critical signaling pathways and therapeutic targets in the cervix that may decrease the rates of premature cervical ripening and preterm birth.

Changes in Gastric Smooth Muscle Cell Contraction during Pregnancy: Effect of Estrogen

It is well known that pregnancy is associated with frequent gastrointestinal (GI) disorders and symptoms. Moreover, previous reports have shown that estrogen, which changes in levels during pregnancy, participates in the regulation of GI motility and is involved in the pathogenesis of various functional disorders in the stomach. The aim of the current study was to explore the changes in the expression of estrogen receptors (ERs) and examine the effect of estrogen on nitric oxide- (NO-) cyclic guanosine monophosphate (cGMP) pathway and thus relaxation in gastric smooth muscle cells (GSMC) during pregnancy. Single GSMC from early-pregnant and late-pregnant Sprague-Dawley rats were used. Protein and mRNA expression levels of ERs were measured via specifically designed enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), respectively. NO and cGMP levels were measured via specifically designed ELISA kits. Effect of estrogen on acetylcholine- (ACh-) induced contraction of single GSMC was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor, N-nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Estrogen increased both NO and cGMP levels and their levels were greater in early compared to late pregnancy. Expression of ERs was greater in early compared to late pregnancy. ACh induced greater contraction of GSMC in late pregnancy compared to early pregnancy. Estrogen inhibited ACh-induced contraction in both periods of pregnancy. Importantly, pretreatment of GSMC with either L-NNA or ODQ abolished estrogen inhibitory action on muscle contraction. In conclusion, GSMC contractile behavior undergoes drastic changes in response to estrogen during pregnancy and this might explain some of the pregnancy-associated gastric disorders.