Hydrogen sulfide-mediated regulation of contractility in the mouse ileum with electrical stimulation: roles of L-cysteine, cystathionine β-synthase, and K+ channels

Nitric oxide and ion channels mediate L-cysteine-induced inhibition of colonic smooth muscle contraction

Previous studies have suggested that L-cysteine regulates gut motility through hydrogen sulfide. However, the mechanisms involved in the L-cysteine-induced response have not been extensively studied. This study aimed to investigate the underlying mechanisms of action of L-cysteine on spontaneous contraction of rat colon. Longitudinal and circular muscle strips from rat middle colon were prepared to measure the spontaneous contractile activities of colon in an organ bath system. Whole-cell voltage-clamp techniques were applied to record the currents of L-type voltage-dependent Ca2+ channels (VDCCs) and voltage-gated K+ channels (Kv) in isolated smooth muscle cells (SMCs) from colon. L-cysteine inhibited the spontaneous contraction of longitudinal and circular muscle strips from the rat colon in a concentration-dependent manner. The inhibition induced by L-cysteine was significantly decreased by inhibitors of H2S synthesis (p < 0.05). Furthermore, the suppression induced by L-cysteine was partially attenuated by tetrodotoxin, L-NNA and glibenclamide (p < 0.05). Whole-cell voltage-clamp recordings showed that L-cysteine caused a remarkable reduction in the peak currents of VDCCs and significantly increased the membrane currents of Kv channels in isolated SMCs (p < 0.05). We concluded that L-cysteine inhibits the contractile activities of smooth muscle strips from the rat colon. The relaxation in response to L-cysteine may be in part mediated by a nitrergic pathway and by inhibiting the VDCCs in combination with a direct activation of the KV channels and KATP channels.

Brazil Nut (Bertholletia excelsa H.B.K) Retards Gastric Emptying and Modulates Enteric Glial Cells in a Dose-Dependent Manner

BACKGROUND

The role of food and nutrients in the regulation of enteric glial cell functions is unclear. Some foods influence enteric neurophysiology and can affect glial cell functions that include regulation of the intestinal barrier, gastric emptying, and colonic transit. Brazil nuts are the most abundant natural source of selenium, unsaturated fatty acids, fibers, and polyphenols.

OBJECTIVE

The study investigated the effects of a Brazil nut-enriched diet on enteric glial cells and gastrointestinal transit.

METHODS

Two-month-old male Wistar rats were randomized to a standard diet (control group, CG), standard diet containing 5% (wt/wt) Brazil nut (BN5), and standard diet containing 10% (wt/wt) Brazil nut (BN10) (n = 9 per group). After eight weeks, the animals underwent constipation and gastric emptying tests to assess motility. Evaluations of colonic immunofluorescence staining for glial fibrillary acidic protein (GFAP) and myenteric ganglia area were performed.

RESULTS

The BN5 group showed increased weight gain while the BN10 group did not (p < 0.0001). The BN10 group showed higher gastric residue amounts compared to the other groups (p = 0.0008). The colon exhibited an increase in GFAP immunoreactivity in the BN5 group compared to that in the other groups (p = 0.0016), and the BN10 group presented minor immunoreactivity compared to the CG (p = 0.04). The BN10 group presented a minor ganglia area compared to the CG (p = 0.0155).

CONCLUSION

The Brazil nut-enriched diet modified the gastric residual, colonic GFAP immunoreactivity, and myenteric ganglia area after eight weeks in healthy male Wistar rats.

The role of hydrogen sulfide in gastrointestinal tract functioning (review)

Despite a fairly large amount of literature data about the involvement of hydrogen sulfide in physiological and pathophysiological processes, its role in gastrointestinal tract functioning has not been studied sufficiently. This review systematizes and generalizes the mechanisms of H2S-associated regulation of gastrointestinal secretion and motility on the basis of literature sources processing and own research results. We analysed world professional literature and sources in Google Scholar, PubMed, MedLine, Embase, Cochrane, and data from more than 50 articles and books on the problem were processed in the article. This review gives a synopsis of the H2S function in the regulation of the secretory and motor-evacuation function, and in stimulating the reparative properties of the digestive tract, and indicates the main mechanisms.

Maternal disease and gasotransmitters

The three known gasotransmitters, nitric oxide, carbon monoxide, and hydrogen sulfide are involved in key processes throughout pregnancy. Gasotransmitters are known to impact on smooth muscle tone, regulation of immune responses, and oxidative state of cells and their component molecules. Failure of the systems that tightly regulate gasotransmitter production and downstream effects are thought to contribute to common maternal diseases such as preeclampsia and preterm birth. Normal pregnancy-related changes in uterine blood flow depend heavily on gasotransmitter signaling. In preeclampsia, endothelial dysfunction is a major contributor to aberrant gasotransmitter signaling, resulting in hypertension after 20 weeks gestation. Maintenance of pregnancy to term also requires gasotransmitter-mediated uterine quiescence. As the appropriate signals for parturition occur, regulation of gasotransmitter signaling must work in concert with those endocrine signals in order for appropriate labor and delivery timing. Like preeclampsia, preterm birth may have origins in abnormal gasotransmitter signaling. We review the evidence for the involvement of gasotransmitters in preeclampsia and preterm birth, as well as mechanistic and molecular signaling targets.

Antidiarrheal effect of sodium hydrosulfide in diabetic rats: In vitro and in vivo studies

BACKGROUND

The inhibitory effects of H₂ S on spontaneous contractions of smooth muscles of small, and large intestines well-established but its role in the pathophysiology of diarrhea has not been identified. Therefore, this study evaluated the role of exogenous H₂ S (NaHS) on diabetic-induced diarrhea and determined mRNA expression of cystathionine β-lyase (CSE) and cystathionine γ-synthase (CBS) in diabetic rats.

METHODS

In order to evaluate antidiarrheal effect of H₂ S, normal and diabetic rats received NaHS and L-Cysteine and the total number of fecal pellets (FP) determined. The effect of NaHS on intestinal transit ratio (ITR) was also evaluated in diabetic rats. The level of mRNA expressions of CBS and CSE determined in smooth muscles of jejunum, ileum, and colon in normal, and diabetic rats. The effect of NaHS on frequency and tension of spontaneous contractions of smooth muscle strips of colon, ileum, and jejunum were investigated.

KEY RESULTS

NaHS decreased ITR, total number of FP, frequency and tension of spontaneous contractions of colon, ileum, and jejunum muscle strips in diabetic rats. The level of mRNA expression of CSE and CBS in diabetic rats were lower than in normal rats. NaHS, and L-Cysteine decreased the number of FP in normal rats.

CONCLUSIONS & INFERENCES

These findings showed NaHS effectively controlled diarrhea in diabetic rats through decreasing the frequency, and tension of spontaneous contraction of smooth muscles of large, and small intestines. The increased frequency and tension of spontaneous contractions of smooth muscles in diabetic rats may be due to down-regulation of H₂ S biosynthesis enzymes.

Mechanism of sodium hydrosulfide modulation of L-type calcium channels in rat colonic smooth muscle cells

Hydrogen sulfide (H₂S) can exert different effects on the gastrointestinal tract by modulating ion channels. Previously, we found that H₂S donor sodium hydrosulfide (NaHS) regulates colonic motility through L-type calcium channels, but the molecular mechanism remains unknown. The present study was designed to investigate possible mechanisms underlying the modulation of L-type calcium channels by NaHS in rat colonic smooth muscle cells. L-type calcium currents in colonic smooth muscle cells were recorded using the whole-cell patch-clamp technique. Spontaneous contractions of mid-colonic smooth muscle strips were measured in an organ bath system and a biological signal acquisition system. NaHS evoked a significant rightward shift in the steady-state activation curve of L-type calcium channels, changed the shape of the current-voltage (I-V) curve, and decreased the peak current density at 0mV, although it significantly increased with higher stimulatory voltage. The sulfhydryl-modifying reagent DL-dithiothreitol (DTT) enhanced the effects of NaHS on L-type calcium channels, while diamide (DM) and reduced L-glutathione (GSH) alleviated the effects of NaHS. Additionally, NaHS inhibited the spontaneous high-amplitude contractions of both longitudinal and circular smooth muscle strips in a dose-dependent manner. The inhibitory effects were reversible. DTT and GSH enhanced the effects of NaHS, while DM attenuated the effects of NaHS. In conclusion, NaHS modulates L-type calcium channels in rat colonic smooth muscle cells and regulates the contractile activity of colonic smooth muscle, potentially by modifying the free sulfhydryl groups of L-type calcium channels.

Hydrogen sulphide as a signalling molecule regulating physiopathological processes in gastrointestinal motility

The biology of H₂ S is a still developing area of research and several biological functions have been recently attributed to this gaseous molecule in many physiological systems, including the cardiovascular, urogenital, respiratory, digestive and central nervous system (CNS). H₂ S exerts anti-inflammatory effects and can be considered an endogenous mediator with potential effects on gastrointestinal motility. During the last few years, we have investigated the role of H₂ S as a regulator of gastrointestinal motility using both animal and human tissues. The aim of the present work is to review published data regarding the potential role of H₂ S as a signalling molecule regulating physiopathological processes in gastrointestinal motor function. H₂ S is endogenously produced by defined enzymic pathways in different cell types of the intestinal wall including neurons and smooth muscle. Inhibition of H₂ S biosynthesis increases motility and H₂ S donors cause smooth muscle relaxation and inhibition of propulsive motor patterns. Impaired H₂ S production has been described in animal models with gastrointestinal motor dysfunction. The mechanism(s) of action underlying these effects may include several ion channels, although no specific receptor has been identified. At this time, even though there is much experimental evidence for H₂ S as a modulator of gastrointestinal motility, we still do not have conclusive experimental evidence to definitively propose H₂ S as an inhibitory neurotransmitter in the gastrointestinal tract, causing nerve-mediated relaxation.

Hydrogen Sulfide in Physiology and Diseases of the Digestive Tract

Hydrogen sulfide (H₂S) is a Janus-faced molecule. On one hand, several toxic functions have been attributed to H₂S and exposure to high levels of this gas is extremely hazardous to health. On the other hand, H₂S delivery based clinical therapies are being developed to combat inflammation, visceral pain, oxidative stress related tissue injury, thrombosis and cancer. Since its discovery, H₂S has been found to have pleiotropic effects on physiology and health. H₂S is a gasotransmitter that exerts its effect on different systems, such as gastrointestinal, neuronal, cardiovascular, respiratory, renal, and hepatic systems. In the gastrointestinal tract, in addition to H₂S production by mammalian cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), H₂S is also generated by the metabolic activity of resident gut microbes, mainly by colonic Sulfate-Reducing Bacteria (SRB) via a dissimilatory sulfate reduction (DSR) pathway. In the gut, H₂S regulates functions such as inflammation, ischemia/ reperfusion injury and motility. H₂S derived from gut microbes has been found to be associated with gastrointestinal disorders such as ulcerative colitis, Crohn’s disease and irritable bowel syndrome. This underscores the importance of gut microbes and their production of H₂S on host physiology and pathophysiology.

Targeting Ion Channels: An Important Therapeutic Implication in Gastrointestinal Dysmotility in Patients With Spinal Cord Injury

Gastrointestinal (GI) dysmotility is a severe, and common complication in patients with spinal cord injury (SCI). Current therapeutic methods using acetylcholine analogs or laxative agents have unwanted side effects, besides often fail to have desired effect. Various ion channels such as ATP-sensitive potassium (K_ATP) channel, calcium ions (Ca²⁺)-activated potassium ions (K⁺) channels, voltage-sensitive Ca²⁺ channels and chloride ion (Cl⁻) channels are abundantly expressed in GI tissues, and play an important role in regulating GI motility. The release of neurotransmitters from the enteric nerve terminal, innervating GI interstitial cells of Cajal (ICC), and smooth muscle cells (SMC), causes inactivation of K⁺ and Cl⁻ channels, increasing Ca²⁺ influx into cytoplasm, resulting in membrane depolarization and smooth muscle contraction. Thus, agents directly regulating ion channels activity either in ICC or in SMC may affect GI peristalsis and would be potential therapeutic target for the treatment of GI dysmotility with SCI.