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

Neurogenic Bowel Dysfunction in Patients with Spinal Cord Injury and Multiple Sclerosis-An Updated and Simplified Treatment Algorithm

Neurogenic bowel dysfunction (NBD) is a common condition in individuals with spinal cord injury (SCI) or multiple sclerosis (MS). It usually entails constipation, difficult evacuation of the rectum, and fecal incontinence (FI); often in combination. It is highly burdensome for affected patients and is correlated with poor quality of life. The current treatment algorithm, or treatment pyramid, does not completely correspond to actual clinical practice, and the known and classical pyramid contains both treatments still in their experimental stage as well as several treatments which are not available at all treatment centers. Thus, an updated treatment algorithm is called upon, and the authors of this paper therefore propose a simplified version of the treatment pyramid, aiming to guide clinicians in treating NBD.

Effect of Toll-like receptor-2, -4, -5, -7, and NOD2 stimulation on potassium channel conductance in intestinal epithelial cells

Disproportionate activation of pattern recognition receptors plays a role in inflammatory bowel disease (IBD) pathophysiology. Diarrhea is a hallmark symptom of IBD, resulting at least in part from an electrolyte imbalance that may be caused by changes in potassium channel activity. We evaluated the impact of Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain 2 (NOD2) stimulation on potassium conductance of the basolateral membrane in human intestinal epithelial cells (IECs) and the role of potassium channels through electrophysiological assays under short-circuit current in Ussing chambers. TLRs and NOD2 were stimulated using specific agonists, and potassium channels were selectively blocked using triarylmethane-34 (TRAM-34), adenylyl-imidodiphosphate (AMP-PNP), and BaCl₂. Potassium conductance of the basolateral membrane decreased upon activation of TLR2, TLR4, and TLR7 in T84 cells (means ± SE, -11.2 ± 4.5, -40.4 ± 7.2, and -19.4 ± 5.9, respectively) and in Caco-2 cells (-13.1 ± 5.7, -55.7 ± 7.4, and -29.1 ± 7.2, respectively). In contrast, activation of TLR5 and NOD2 increased basolateral potassium conductance, both in T84 cells (18.0 ± 4.1 and 18.4 ± 2.8, respectively) and in Caco-2 cells (21.2 ± 8.4 and 16.0 ± 3.6, respectively). TRAM-34 and AMP-PNP induced a decrease in basolateral potassium conductance upon TLR4 stimulation in both cell lines. Both K_Ca3.1- and K_ir6-channels appear to be important mediators of this effect in IECs and could be potential targets for therapeutic agent development.NEW & NOTEWORTHY This study highlights that PRRs stimulation directly influences K⁺-channel conductance in IECs. TLR-2, -4, -7 stimulation decreased K⁺ conductance, whereas TLR5 and NOD2 stimulation had the opposite effect, leading to an increase of it instead. This study reports for the first time that K_Ca3.1- and K_ir6-channels play a role in K⁺ transport pathways triggered by TLR4 stimulation. These findings suggest that K_Ca3.1- and K_ir6-channels modulation may be a potential target for new therapeutic agents in IBD.

Inhibitory Effects of Jakyakgamcho-Tang (Glycyrrhiza uralensis and Paeonia lactiflora) on the Pacemaker Potential of the Interstitial Cells of Cajal in the Murine Small Intestine

Jakyakgamcho-tang (JYGCT) has been used to treat various diseases. The interstitial cells of Cajal (ICC) regulate gastrointestinal (GI) motility as pacemaker cells. Here, we examined the effects of JYGCT on the pacemaker potential of the ICC in the small intestine. We observed that JYGCT inhibited the pacemaker potential in a dose-dependent manner. Glibenclamide did not affect the pacemaker potential and on these conditions, JYGCT also had no effect on the pacemaker potential. Pretreatment with capsazepine or SB452533 blocked the JYGCT-induced effects. In the presence of SQ-22536, JYGCT did not inhibit the pacemaker potential. Additionally, JYGCT inhibited spontaneous [Ca2+]i oscillations and JYGCT-induced ITR increase was associated with TMEM16A, motilin and substance P activation. Moreover, JYGCT was effective in alleviating the symptoms of irritable bowel syndrome. Our results suggest that JYGCT inhibited the pacemaker potential of the ICC via KATP, the TRPV1 or the cyclic AMP pathway, and intracellular Ca2+ regulation, indicating that JYGCT can affect ICC and thus have the function of regulating GI motility. Therefore, JYGCT may be used as a GI motility disorder regulator or disease prevention agent.

In Silico and Ex Vivo Studies on the Spasmolytic Activities of Fenchone Using Isolated Guinea Pig Trachea

Fenchone is a bicyclic monoterpene found in a variety of aromatic plants, including Foeniculum vulgare and Peumus boldus, and is used in the management of airways disorders. This study aimed to explore the bronchodilator effect of fenchone using guinea pig tracheal muscles as an ex vivo model and in silico studies. A concentration-mediated tracheal relaxant effect of fenchone was evaluated using isolated guinea pig trachea mounted in an organ bath provided with physiological conditions. Sustained contractions were achieved using low K⁺ (25 mM), high K⁺ (80 mM), and carbamylcholine (CCh; 1 µM), and fenchone inhibitory concentration–response curves (CRCs) were obtained against these contractions. Fenchone selectively inhibited with higher potency contractions evoked by low K⁺ compared to high K⁺ with resultant EC₅₀ values of 0.62 mg/mL (0.58–0.72; n = 5) and 6.44 mg/mL (5.86–7.32; n = 5), respectively. Verapamil (VRP) inhibited both low and high K⁺ contractions at similar concentrations. Pre-incubation of the tracheal tissues with K⁺ channel blockers such as glibenclamide (Gb), 4-aminopyridine (4-AP), and tetraethylammonium (TEA) significantly shifted the inhibitory CRCs of fenchone to the right towards higher doses. Fenchone also inhibited CCh-mediated contractions at comparable potency to its effect against high K⁺ [6.28 mg/mL (5.88–6.42, n = 4); CCh] and [6.44 mg/mL (5.86–7.32; n = 5); high K⁺]. A similar pattern was obtained with papaverine (PPV), a phosphodiesterase (PDE), and Ca²⁺ inhibitor which inhibited both CCh and high K⁺ at similar concentrations [10.46 µM (9.82–11.22, n = 4); CCh] and [10.28 µM (9.18–11.36; n = 5); high K⁺]. However, verapamil, a standard Ca²⁺ channel blocker, showed selectively higher potency against high K⁺ compared to CCh-mediated contractions with respective EC₅₀ values of 0.84 mg/mL (0.82–0.96; n = 5) 14.46 mg/mL (12.24–16.38, n = 4). The PDE-inhibitory action of fenchone was further confirmed when its pre-incubation at 3 and 5 mg/mL potentiated and shifted the isoprenaline inhibitory CRCs towards the left, similar to papaverine, whereas the Ca²⁺ inhibitory-like action of fenchone pretreated tracheal tissues were authenticated by the rightward shift of Ca²⁺ CRCs with suppression of maximum response, similar to verapamil, a standard Ca²⁺ channel blocker. Fenchone showed a spasmolytic effect in isolated trachea mediated predominantly by K⁺ channel activation followed by dual inhibition of PDE and Ca²⁺ channels. Further in silico molecular docking studies provided the insight for binding of fenchone with Ca²⁺ channel (−5.3 kcal/mol) and K⁺ channel (−5.7), which also endorsed the idea of dual inhibition.

Electroacupuncture at Zusanli (ST36) Repairs Interstitial Cells of Cajal and Upregulates c-Kit Expression in Rats with SCI-Induced Neurogenic Bowel Dysfunction

Background

Electroacupuncture (EA) could improve colonic transit activity in rats with neurogenic bowel dysfunction (NBD) caused by spinal cord injury (SCI). The function of interstitial cells of Cajal (ICCs) and c-Kit expression may play essential roles in this process. Material and Methods. Thirty-six Sprague Dawley rats were randomized to the sham group, the SCI group, or the SCI + EA group (bilateral Zusanli, 30 min/day, 14 days). Changes in the ultrastructural morphology of ICCs were observed. The c-Kit expression on different levels was analyzed by immunohistochemistry, Western blotting, and RT-qPCR, respectively.

Results

Abnormal morphology of ICCs and downregulation of the c-Kit expression occurred after SCI. While the number of ICCs was increased, the ultrastructural morphology was improved significantly in EA rats. They also showed better improvement in c-Kit expression at both protein and gene levels.

Conclusion

Abnormal ICCs in colon tissues and the downregulated expression of c-Kit could be observed after SCI. EA at Zusanli (ST36) could improve the colon function by repairing the morphology and increasing the number of ICCs and upregulating c-Kit expression.

Antifungal activity and antidiarrheal activity via antimotility mechanisms of (-)-fenchone in experimental models

BACKGROUND

(-)-Fenchone is a bicyclic monoterpene present in essential oils of plant species, such as Foeniculum vulgare and Peumus boldus, used to treatment of gastrointestinal diseases. Pharmacological studies report its anti-inflammatory, antioxidant, and antinociceptive activity.

AIM

To investigate antidiarrheal activity related to gastrointestinal motility, intestinal secretion and antimicrobial activity.

METHODS

A castor oil-induced diarrhea model was used to evaluate antidiarrheal activity. Intestinal transit and gastric emptying protocols were used to assess a possible antimotility effect. Muscarinic receptors, presynaptic α₂-adrenergic and tissue adrenergic receptors, K_ATP channels, nitric oxide were investigated to uncover antimotility mechanisms of action and castor oil-induced enteropooling to elucidate antisecretory mechanisms. The antimicrobial activity was evaluated in the minimum inhibitory concentration model, the fractional inhibitory concentration index using the (-)-fenchone association method with standard antifungal agents.

RESULTS

(-)-Fenchone (75, 150 and 300 mg/kg) showed antidiarrheal activity, with a significant decrease in the evacuation index. This activity is possibly related to a percentage of reduced intestinal transit (75, 150 and 300 mg/kg). The antimotility effect of (-)-fenchone decreased in the presence of pilocarpine, yohimbine, propranolol, L-NG-nitroarginine methyl ester or glibenclamide. In the enteropooling model, no reduction in intestinal fluid weight was observed. (-)- Fenchone did not show antibacterial activity; on the other hand, inhibits the growth of strains of fungi with a minimum fungicide concentration of 32 μg/mL. However, when it was associated with amphotericin B, no synergism was observed.

CONCLUSION

The antidiarrheal effect of (-)-fenchone in this study involves antimotility effect and not involve antisecretory mechanisms. (-)-Fenchone presents antifungal activity; however, it did not show antibacterial activity.

Lubeluzole: from anti-ischemic drug to preclinical antidiarrheal studies

BACKGROUND

Lubeluzole, a neuroprotective anti-ischemic drug, was tested for its ability to act as both antibiotic chemosensitizing and antipropulsive agent for the treatment of infectious diarrhea.

METHODS

In the present report, the effect of lubeluzole against antidiarrheal target was tested. The antimicrobial activity towards Gram-positive and Gram-negative bacteria was investigated together with its ability to affect ileum and colon contractility.

RESULTS

Concerning the antimicrobial activity, lubeluzole showed synergistic effects when used in combination with minocycline against four common Gram-positive and Gram-negative bacteria (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922), although relatively high doses of lubeluzole were required. In ex vivo experiments on sections of gut smooth muscles, lubeluzole reduced the intestinal contractility in a dose-dependent manner, with greater effects observed on colon than on ileum, and being more potent than reference compounds otilonium bromide and loperamide.

CONCLUSION

All above results identify lubeluzole as a possible starting compound for the development of a novel class of antibacterial adjuvants endowed with spasmolytic activity.

Assessment of Polygonum odoratum Lour. Leaf Extract on Rat's Ileum Contraction and the Mechanisms Involved

Vietnamese coriander (Polygonum odoratum Lour.) is a plant native to northern Thailand. The biological activities of P. odoratum Lour. extract (POE) include antibacterial, antiviral, and expectorant. However, the effect of POE on intestinal smooth muscle motility is unclear. The aim of this study was to evaluate the relaxant effects of POE on isolated rat ileum. Propranolol (1 μM), calcium chloride (1-20 mM), and Nω-nitro-l-arginine methylester (l-NAME, 100 μM) were used to investigate the mechanisms of action. The results showed that POE (0.01-5 mg/mL) reduced KCl-induced contraction. In addition, POE (1 mg/mL) reduced the contraction by propranolol and l-NAME and attenuated CaCl₂-induced contractions. Our results indicate that the relaxation effect of POE on ileum contractions seems to involve nitric oxide and β-adrenergic pathways, and blockade of calcium influx. These findings provide a pharmacological basis for the traditional use of POE to treat gastrointestinal disorders such as irritable bowel syndrome or diarrhea.

Relaxant effects of Azadirachta indica A. Juss var. siamensis Valeton flower extract on isolated rat ileum contractions and the mechanisms of action

Azadirachta indica A. Juss var. siamensis Valeton or commonly known as Siamese neem is one of the most well-known plant in traditional Ayurvedic medicine. The aim of the present study was to investigate the relaxant effects of A. indica on isolated rat ileum contractions and its potential underlying mechanisms involved. The isometric contractions of ileum segments were investigated in organ baths for spontaneous activity and response to aqueous extract of Siamese neem flower (SNF). The spasmolytic action of the extract was also assessed on contraction induced by acetylcholine and high potassium. Our findings indicate that cumulative concentrations of SNF aqueous extract induced relaxant effect on spontaneous rat ileum contractions. The extract has also suppressed the cumulative concentration response curve for acetylcholine and pottasium ions-induced contraction. The presence and absence of propranol (antagonist of β-adrenergic receptor) and l-Name (antagonist of nitric oxide synthase) in SNF aqeous extract co-treatment demonstrated no significant different in term of contraction activity when compared to SNF extract treatment alone. The treatment of SNF extract caused a significant inhibition in tissue contraction stimulated by accumulation of calcium ions. Our results showed the relaxant effect of SNF aqueous extract on the isolated rat ileum. In short, the SNF aqueous extract exhibited an inhibitory effect on the spontaneous ileum contactions particularly on the contraction stimulated by acetylcholine and high potassium. The observed effect might acted through the modulation of calcium channels. This findings provide a pharmacological basis for the traditional use of SNF for the treatment of gastrointestinal spasms.

Abdominal Manual Therapy Repairs Interstitial Cells of Cajal and Increases Colonic c-Kit Expression When Treating Bowel Dysfunction after Spinal Cord Injury

Background

This study aimed to evaluate the therapeutic effects of abdominal manual therapy (AMT) on bowel dysfunction after spinal cord injury (SCI), investigating interstitial cells of Cajal (ICCs) and related c-kit expression.

Methods

Model rats were divided as SCI and SCI with drug treatment (intragastric mosapride), low-intensity (SCI + LMT; 50 g, 50 times/min), and high-intensity AMT (SCI + HMT; 100 g, 150 times/min). After 14 days of treatment, weight, improved Basso-Beattie-Bresnahan (BBB) locomotor score, and intestinal movement were evaluated. Morphological structure of spinal cord and colon tissues were examined. Immunostaining, RT-PCR, and western blot were used to assess c-kit expression.

Results

In SCI rats, AMT could not restore BBB, but it significantly increased weight, shortened time to defecation, increased feces amounts, and improved fecal pellet traits and colon histology. AMT improved the number, distribution, and ultrastructure of colonic ICCs, increasing colonic c-kit mRNA and protein levels. Compared with the SCI + Drug and SCI + LMT groups, the SCI + HMT group showed better therapeutic effect in improving intestinal transmission function and promoting c-kit expression.

Conclusions

AMT is an effective therapy for recovery of intestinal transmission function. It could repair ICCs and increase c-kit expression in colon tissues after SCI, in a frequency-dependent and pressure-dependent manner.