The multiple roles of dopamine receptor activation in the modulation of gastrointestinal motility and mucosal function

Managing gastrointestinal manifestations in systemic sclerosis, a mechanistic approach

INTRODUCTION

Systemic sclerosis (SSc) is a connective tissue disease with heterogeneous presentation. Gastrointestinal (GI) complications of SSc are characterized by esophageal reflux, abnormal motility, and microbiome dysbiosis, which impact patient quality of life and mortality. Preventative therapeutics are lacking, with management primarily aimed at symptomatic control.

AREAS COVERED

A broad literature review was conducted through electronic databases and references from key articles. We summarize the physiology of gastric acid production and GI motility to provide context for existing therapies, detail the current understanding of SSc-GI disease, and review GI medications studied in SSc. Finally, we explore new therapeutic options. We propose a management strategy that integrates data on drug efficacy with knowledge of disease pathophysiology, aiming to optimize future therapeutic targets.

EXPERT OPINION

SSc-GI complications remain a challenge for patients, clinicians, and investigators alike. Management presently focuses on treating symptoms and minimizing mucosal damage. Little evidence exists to suggest immunosuppressive therapy halts progression of GI involvement or reverses damage, leaving many unanswered questions about the optimal clinical approach. Further research focused on identifying patients at risk for GI progression, and the underlying mechanism(s) that drive disease will provide opportunities to prevent long-term damage, and significantly improve patient quality of life.

Systematic-Narrative Hybrid Literature Review: Crosstalk between Gastrointestinal Renin-Angiotensin and Dopaminergic Systems in the Regulation of Intestinal Permeability by Tight Junctions

In the first part of this article, the role of intestinal epithelial tight junctions (TJs), together with gastrointestinal dopaminergic and renin-angiotensin systems, are narratively reviewed to provide sufficient background. In the second part, the current experimental data on the interplay between gastrointestinal (GI) dopaminergic and renin-angiotensin systems in the regulation of intestinal epithelial permeability are reviewed in a systematic manner using the PRISMA methodology. Experimental data confirmed the copresence of DOPA decarboxylase (DDC) and angiotensin converting enzyme 2 (ACE2) in human and rodent enterocytes. The intestinal barrier structure and integrity can be altered by angiotensin (1-7) and dopamine (DA). Both renin-angiotensin and dopaminergic systems influence intestinal Na+/K+-ATPase activity, thus maintaining electrolyte and nutritional homeostasis. The colocalization of B0AT1 and ACE2 indicates the direct role of the renin-angiotensin system in amino acid absorption. Yet, more studies are needed to thoroughly define the structural and functional interaction between TJ-associated proteins and GI renin-angiotensin and dopaminergic systems.

Licorice flavonoid ameliorates ethanol-induced gastric ulcer in rats by suppressing apoptosis via PI3K/AKT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Licorice is the dry roots and rhizomes of Glycyrrhiza uralensis Fisch., Glycyrrhiza glabra L. and Glycyrrhiza inflata Bat., which was first recorded in Shengnong's herbal classic. Licorice flavonoid (LF) is the main compound isolated from licorice with an indispensable action in treating gastric ulcer (GU). However, the underlying mechanisms need to be further explored.

AIM OF THE STUDY

This study aimed to investigate and further elucidate the mechanisms of LF against ethanol-induced GU using an integrated approach.

MATERIALS AND METHODS

The anti-GU effects of LF were evaluated in an ethanol-induced gastric injury rat model. Then, the metabolomics approach was applied to explore the specific metabolites and metabolic pathways. Next, the network pharmacology combined with metabolomics strategy was employed to predict the targets and pathways of LF for GU. Finally, these predictions were validated by molecular docking, RT-qPCR, and western blotting.

RESULTS

LF had a positive impact on gastric injury and regulated the expression of GU-related factors. Upon serum metabolomics analysis, 25 metabolic biomarkers of LF in GU treatment were identified, which were primarily involved in amino acid metabolism, carbohydrate metabolism, and other related processes. Subsequently, a "components-targets-metabolites" network was constructed, revealing six key targets (HSP90AA1, AKT1, MAPK1, EGFR, ESR1, PIK3CA) that may be associated with GU treatment. More importantly, KEGG analysis highlighted the importance of the PI3K/AKT pathway including key targets, as a critical route through which LF exerted its anti-GU effects. Molecular docking analyses confirmed that the core components of LF exhibited a strong affinity for key targets. Furthermore, RT-qPCR and western blotting results indicated that LF could reverse the expression of these targets, activate the PI3K/AKT pathway, and ultimately reduce apoptosis.

CONCLUSION

LF exerted a gastroprotective effect against gastric ulcer induced by ethanol, and the therapeutic mechanism may involve improving metabolism and suppressing apoptosis through the PI3K-AKT pathway.

Probiotic Supplementation With Saccharomyces boulardii and Enterococcus faecium Improves Gastric Pain and Bloating in Airline Pilots With Chronic Non-atrophic Gastritis: An Open-Label Study

Background Commercial airline pilots (APs) are prone to upper gastrointestinal symptoms, such as epigastric pain and bloating. These issues are often linked to occupational risk factors like irregular diet, sleep disruption, and circadian rhythm disturbance. The use of probiotics to enhance intestinal health is well established, but their efficacy in treating upper gastrointestinal diseases is still debated. This is primarily due to the stomach's small resident microbiota and its low pH, which is inhospitable to most microbes. However, emerging research suggests that specific probiotic strains, such as Enterococcus faecium, can withstand acidic environments. Moreover, certain yeast species, including Saccharomyces boulardii, can survive at a low pH. Consequently, we conducted a preliminary, three-arm, randomized, open-label, dose-finding, four-week study to compare the effects of watchful waiting (WW) with the administration of an oral probiotic supplement containing S. boulardii and E. faecium in APs diagnosed with Helicobacter pylori-negative chronic non-atrophic gastritis (CNG). Methods The study included 39 APs with CNG who were randomized into three groups with a 1:1:1 ratio. The low-dose group (n = 13) received one capsule of the probiotic supplement twice daily, before meals, for four weeks. The high-dose group (n = 13) was administered two capsules of the supplement on the same schedule. The third group (n = 13) underwent WW and served as the control arm. Blinding was maintained for the examining physicians and laboratory staff, but not for the patients. All participants self-rated their experiences of gastric pain and bloating at the beginning and conclusion of the four-week treatment period. Additionally, serum levels of pepsinogen I (PGI) and pepsinogen II (PGII) were measured at these time points. Results Supplementation with probiotics significantly outperformed WW in reducing subjective gastric pain and bloating. This effect was consistent across both tested dosages, with no significant differences observed. However, only high-dose probiotics led to a statistically significant decrease in PGII levels and an increase in the PGI/PGII ratio after the four-week study period, a result not observed with low-dose probiotics. Conclusions Oral administration of S. boulardii and E. faecium demonstrated potential efficacy in reducing gastric pain and bloating symptoms in APs with CNG, as evidenced by statistically significant symptom improvement compared to the control group that did not receive the probiotic supplementation. Notably, high-dose probiotics resulted in a significant increase in the PGI/PGII ratio, indicating potential long-term cytoprotective effects on the gastric mucosa.