The role of nitric oxide in the effects of ovarian steroids on spontaneous myometrial contractility in rats

Uterine Dysfunction in Diabetic Mice: The Role of Hydrogen Sulfide

It is well-known that the physiological uterine peristalsis, related to several phases of reproductive functions, plays a pivotal role in fertility and female reproductive health. Here, we have addressed the role of hydrogen sulfide (H₂S) signaling in changes of uterine contractions driven by diabetes in non-obese diabetic (NOD) mice, a murine model of type-1 diabetes mellitus. The isolated uterus of NOD mice showed a significant reduction in spontaneous motility coupled to a generalized hypo-contractility to uterotonic agents. The levels of cyclic nucleotides, cAMP and cGMP, notoriously involved in the regulation of uterus homeostasis, were significantly elevated in NOD mouse uteri. This increase was well-correlated with the higher levels of H₂S, a non-specific endogenous inhibitor of phosphodiesterases. The exposure of isolated uterus to L-cysteine (L-Cys), but not to sodium hydrogen sulfide, the exogenous source of H₂S, showed a weak tocolytic effect in the uterus of NOD mice. Western blot analysis revealed a reorganization of the enzymatic expression with an upregulation of 3-mercaptopyruvate-sulfurtransferase (3-MST) coupled to a reduction in both cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) expression. In conclusion, the increased levels of cyclic nucleotides dysregulate the uterus peristalsis and contractility in diabetic mice through an increase in basal H₂S synthesis suggesting a role of 3-MST.

Essential oil from Lippia microphylla Cham. modulates nitric oxide pathway and calcium influx to exert a tocolytic effect in rat uterus

The essential oil of Lippia microphylla (LM-OE) presents several pharmacological activities. This work evaluates the tocolytic effect of LM-OE on rats. LM-OE inhibited phasic contractions and relaxed tonic contractions on rat uterus. Considering that nitric oxide (NO) pathway regulates uterine contraction, LM-OE potency was attenuated in the presence of NO synthase (NOS) inhibitor and this reduction was reversed in the presence of a NOS substrate. Similarly, the relaxant potency of LM-OE was reduced in the presence of soluble guanylyl cyclase (sGC) and protein kinase G (PKG) inhibitors. LM-OE also demonstrates a positive modulation of large and small conductance calcium-activated, voltage-gated and adenosine triphosphate-sensitive potassium channels and inhibited curves to CaCl₂ as well as relaxed the uterus pre-contracted by S-(-)-Bay K8644, suggesting voltage-gated calcium channels type-1 (Ca_V1) blockade. Thus, the tocolytic effect of LM-OE on rat involves positive modulation of NO/NOS/sGC/PKG/K⁺-channels pathway and Ca²⁺ influx blockade through Ca_V1.[Formula: see text].

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

Previous studies have shown that progesterone could inhibit muscle contraction in various sites of the gastrointestinal tract. The underlying mechanisms responsible for these inhibitory effects of progesterone are not fully known. The aim of the current study was to investigate the effect of progesterone on the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway and muscle contraction in the stomach. Single gastric smooth muscle cells from female Sprague-Dawley rats were used. The expression of progesterone receptor (PR) mRNA was analyzed by reverse transcription polymerase chain reaction. NO and cGMP levels were measured via specific ELISAs. Acetylcholine (ACh)-induced contraction of single gastric muscle cells preincubated with progesterone was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor, Nω-Nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and expressed as percent shortening from resting cell length. PR expression was detected in the stomach muscle cells. Progesterone inhibited ACh-induced gastric muscle cell contraction. Furthermore, progesterone increased NO and cGMP levels in single gastric muscle cells. Most notably, pre-incubation of muscle cells with either L-NNA or ODQ abolished the inhibitory action of progesterone on muscle contraction. These present observations suggest that progesterone promotes muscle cell relaxation in the stomach potentially via the NO/cGMP pathway.

The effect of dietary L-arginine intake on the level of antibody titer, the relative organ weight and colon motility in broilers

This study was carried out to determine the effect of L-arginine (L-Arg) levels in diet at the starter, grower and finisher phases on immune response, organ development, nitric oxide (NO) metabolism and colon motility in broilers. A total of 500 one-day-old Ross-308 broiler chickens of mixed sex were separated into one Arg-deficient group and four experimental groups. Each group was then divided into five subgroups of 20 birds each. Arginine deficient group for all phases was fed a basal diet which contained 10% less L-Arg than optimum Arg requirement recommended by the breeder. Experimental groups were fed a basal diet supplemented with L-Arg which was progressively 10% increased in groups. Thus, the diet contained 90, 100, 110, 120 and 130% of optimum Arg requirement for each phases in groups, respectively. The highest serum infectious bursal disease antibody titer (IBD) was observed in the experimental group which was fed the diet containing 110% L-Arg at grower phase (P < 0.05), whereas Newcastle disease antibody titer did not differ between groups. The relative weight of spleen increased in groups which were fed the diet containing 120 and 130% L-Arg at starter phase as compared to Arg-deficient group (P < 0.05). The group which was fed the diet containing 110% L-Arg showed highest relative weight of bursa Fabricii at grower (P < 0.05) and finisher (P < 0.01) phases. It was observed that serum nitric oxide (NO) concentration decreased in Arg-deficient group (P < 0.05). The amplitude of spontaneous colon contractility did not differ between groups at the end of all three phases. However, the frequency of spontaneous colon contractility in the Arg deficient group was higher at starter (P<0.05), grower (P < 0.01) and finisher (P < 0.05) phases. These results suggest that the supplementation of L-Arg at higher level than optimum Arg requirement in broiler diet has minimal effect on parameters investigated in the study. However, L-Arg-deficiency may negatively affect immune response and the motility of gastrointestinal system due to disruption of NO metabolism at three phases.

The effect of dietary supplementation of nitric oxide donor and inhibitor on nNOS expression in and motility of the small intestine of broilers

We investigated the effect of dietary supplementation of sodium nitroprusside (SNP), a nitric oxide (NO) donor, and N-nitro-L-arginine methyl ester (L-NAME), a NO inhibitor, on neuronal nitric oxide synthase (nNOS) expression in and motility of small intestinum in broilers. A total of 560, one-day-old Ross 308 hybrid mixed sex broiler chicks were divided randomly into one control and seven treatment groups for a 42 day feeding trial including starter phase (0-21 days) and grower phase (22-42 days). The control group was fed a basal diet and the experimental groups were the fed basal diet supplemented with 25, 50, 100 and 200 mg/kg SNP and 25, 50 or 100 mg/kg L-NAME. Ten chickens from each group were sacrificed to collect samples on days 21 and 42. The expression patterns of nNOS immunoreactivity in nerve fibers were determined by immunohistochemistry. In the contractility studies, longitudinal isolated strips of duodenum, jejunum and ileum were treated with 10(-5) M L-arginine and 10(-4) M SNP. Immunohistochemistry revealed that nNOS expression was not detectable in the duodenum or ileum of either the control or experimental groups. On the other hand, nNOS immunoreactivity in the jejunum control group showed a strong reaction on day 21, but the reaction was weak on day 42. nNOS expression clearly was suppressed on day 21 by the diet supplemented with L-NAME, while the diet supplemented with SNP stimulated nNOS expression on day 21. Contractility experiments revealed that spontaneous contractility of isolated strips of duodenum, jejunum and ileum showed no significant difference among groups. Spontaneous contractions of all strips were inhibited by L-arginine and SNP in all groups. The percentage inhibition rate of spontaneous contractions of jejunum application on days 21 and 42 after L-arginine decreased in the group supplemented with 100 mg/kg L-NAME. The percentage inhibition rate on day 21 after SNP application decreased in both groups that received 50 and 100 mg/kg L-NAME. We demonstrated the expression pattern of nNOS in nerve fibers in jejunum of broiler chickens. Contractility studies revealed that the NOS-NO pathway may play a role in smooth muscle contraction of small intestine of chickens. Feeding strategies that supplement NO donor and NO inhibitor can be of physiological importance to small intestine motility owing to alteration of nNOS expression in the jejunum.

Evidence of direct smooth muscle relaxant effects of the fibrate gemfibrozil

Fibrates are commonly employed to treat abnormal lipid metabolism via their unique ability to stimulate peroxisome proliferator-activated receptor alpha (PPARalpha). Interestingly, they also decrease systemic arterial pressure, despite recent evidence that PPAR alpha may contribute to expression of renin and related hypertension. Yet, mechanisms responsible for their potential antihypertensive activity remain unresolved. Rapid decreases in arterial pressure following bolus intravenous injections of bezafibrate strongly suggest they may relax arterial smooth muscle directly. But since bezafibrate is highly susceptible to photodegradation in aqueous media, it has never been critically tested for this possibility in vitro with isolated arterial smooth muscle preparations. Accordingly, we tested gemfibrozil which is resistant to photodegradation. We examined it over a therapeutically-relevant range (50-400 microM) for both acute and delayed relaxant effects on contractions of the isolated rat tail artery; contractions induced by either depolarizing its smooth muscle cell membranes with high potassium or stimulating its membrane-bound receptors with norepinephrine and arginine-vasopressin. We also examined these same gemfibrozil levels for effects on spontaneously-occurring phasic rhythmic contractile activity, typically not seen in arteries under in vitro conditions but commonly exhibited by smooth muscle of uterus, duodenum and bladder. We found that gemfibrozil significantly relaxed all induced forms of contraction in the rat tail artery, acutely at the higher test levels and after a delay of a few hours at the lower test levels. The highest test level of gemfibrozil (400 microM) also completely abolished spontaneously-occurring contractile activity of the isolated uterus and duodenum and markedly suppressed it in the bladder. This is the first evidence that a fibrate drug can directly relax smooth muscle contractions, either induced by various contractile agents or spontaneously-occurring. These findings are particularly relevant to both the recently renewed concern over the impact of fibrates on hypertension and a new understanding of their gastrointestinal side effects.

Estrogen and its role in gastrointestinal health and disease

INTRODUCTION

While the concept of a role of estrogen in gastrointestinal (in particular, colonic) malignancy has generated excitement in recent years, no review has examined the role of this potent and omnipresent steroid hormone in physiological states or its contribution to the development of benign pathological processes. Understanding these effects (and mechanisms therein) may provide a platform for a deeper understanding of more complex disease processes.

METHODS

A literature search was conducted using the PubMed database and the search terms were "estrogen," "estrogen AND gastrointestinal tract," "estrogen AND colon," "estrogen AND esophagus," "estrogen AND small intestine," "estrogen AND stomach," "estrogen AND gallbladder," and "estrogen AND motility." Bibliographies of extracted studies were further cross-referenced. In all, 136 full-text articles were selected for review. A logical organ-based approach was taken to enable extraction of data of clinical relevance and meaningful interpretation thereof. Insight is provided into the hypotheses, theories, controversies, and contradictions generated over the last five decades by extensive investigation of estrogen in human, animal, and cell models using techniques as diverse as autoradiographic studies of baboons to human population analysis.

CONCLUSIONS

Effects from esophagus through to the colon and rectum are summarized in this first concise collection of data pertaining to estrogenic actions in gastrointestinal health and disease. Mechanisms of these actions are discussed where possible. Undoubtedly, this hormone exerts many actions yet to be elucidated, and its potential therapeutic applications remain, as yet, largely unexplored.