Duodenal acidification induces gastric relaxation and alters epithelial barrier function by a mast cell independent mechanism.

Duodenal hyperpermeability and low-grade inflammation in functional dyspepsia is potentially related to duodenal acid exposure. We aimed to evaluate in healthy volunteers the involvement of mast cell activation on the duodenogastric reflex and epithelial integrity during duodenal acidification. This study consisted of 2 parts: (1) Duodenal infusion of acid or saline during thirty minutes in a randomized, double-blind cross-over manner with measurement of intragastric pressure (IGP) using high resolution manometry and collection of duodenal biopsies to measure epithelial barrier function and the expression of cell-to-cell adhesion proteins. Mast cells and eosinophils were counted and activation and degranulation status were assessed. (2) Oral treatment with placebo or mast cell stabilizer disodiumcromoglycate (DSCG) prior to duodenal perfusion with acid, followed by the procedures described above. Compared with saline, acidification resulted in lower IGP (P < 0.01), increased duodenal permeability (P < 0.01) and lower protein expression of claudin-3 (P < 0.001). Protein expression of tryptase (P < 0.001) was increased after acid perfusion. Nevertheless, an ultrastructural examination did not reveal degranulation of mast cells. DSCG did not modify the drop in IGP and barrier dysfunction induced by acid. Duodenal acidification activates an inhibitory duodenogastric motor reflex and, impairs epithelial integrity in healthy volunteers. However, these acid mediated effects occur independently from mast cell activation.

Mast cell-nerve interactions correlate with bloating and abdominal pain severity in patients with non-celiac gluten / wheat sensitivity.

BACKGROUND: Gastrointestinal (GI) and extra-GI symptoms/manifestations represent key clinical features of patients with non-celiac gluten/wheat sensitivity (NCG/WS). This study aimed to investigate neuro-immune (focusing on mast cells, MCs) interactions in the duodenal submucosa of patients with NCG/WS. METHODS: Submucosal whole mounts from duodenal biopsies of 34 patients with self-reported NCG/WS, 28 with celiac disease (CD), 13 with functional dyspepsia (FD), and 24 healthy controls (HC) were analyzed by immunohistochemistry. Quantitative data on neuronal and MCs density and the percentage of MCs in close vicinity to nerves were obtained, and correlations among neurons, MC density and MC-nerve distance (D), and symptoms were assessed in the three groups. KEY RESULTS: The number of submucosal neurons was not different among groups. In NCG/WS, MC density was not different from HC, while it was slightly increased vs. CD (P = .07) and significantly decreased vs. FD (P < .05). The percentage of MCs close to nerves (D < 15 µm) was similarly increased in all three pathological groups vs. HC (P < .001). In NCG/WS, MC infiltration correlated with bloating (P = .001) and abdominal pain severity (P = .03) and the percentage of MCs in proximity to neurons correlated with the number of GI symptoms (D < 5 µm; P = .05), bloating and abdominal pain severity (D < 15um; P = .01). CONCLUSIONS AND INFERENCES: Submucosal MC infiltration and the close (within 15 µm) MC-to-nerve proximity in the duodenum of NCG/WS patients are features providing a histopathological basis to better understand GI symptoms in this condition.

Relationship between bile salts, bacterial translocation, and duodenal mucosal integrity in functional dyspepsia.

BACKGROUND: Functional dyspepsia (FD) is a complex disorder, in which multiple mechanisms underlie symptom generation, including impaired duodenal barrier function. Moreover, an altered duodenal bile salt pool was recently discovered in patients with FD. We aimed to evaluate the relationship between bile salts, bacterial translocation, and duodenal mucosal permeability in FD. METHODS: Duodenal biopsies from patients with FD and healthy volunteers (HV) were mounted in Ussing chambers to measure mucosal resistance and bacterial passage in the absence and presence of fluorescein-conjugated Escherichia coli and glyco-ursodeoxycholic acid (GUDCA) exposure. In parallel, duodenal fluid aspirates were collected from patients and bile salts were analyzed. KEY RESULTS: The transepithelial electrical resistance of duodenal biopsies from patients was lower compared with HV (21.4 ± 1.3 Ω.cm2 vs. 24.4 ± 1.2 Ω.cm2 ; P = .02; N = 21). The ratio of glyco-cholic and glyco-chenodeoxycholic acid (GCDCA) to tauro- and GUDCA correlated positively with transepithelial electrical resistance in patients. Glyco-ursodeoxycholic acid slightly altered the mucosal resistance, resulting in similar values between patient and healthy biopsies (22.1 ± 1.0 Ω.cm2 vs. 23.0 ± 1.0 Ω.cm2 ; P = .5). Bacterial passage after 120 minutes was lower for patient than for healthy biopsies (0.0 [0.0-681.8] vs. 1684.0 [0.0-4773.0] E coli units; P = .02). Glyco-ursodeoxycholic acid increased bacterial passage in patient biopsies (102.1 [0.0-733.0] vs. 638.9 [280.6-2124.0] E coli units; P = .009). No correlation was found between mucosal resistance and bacterial passage. CONCLUSIONS & INFERENCES: Patients with FD displayed decreased duodenal mucosal resistance associated with bile salts, however, not associated with bacterial passage in vitro. In addition, the hydrophilic bile salt glyco-ursodeoxycholic acid abolished differences in mucosal resistance and bacterial passage between patient and control group.

Altered duodenal bile salt concentration and receptor expression in functional dyspepsia.

BACKGROUND: Functional dyspepsia is a common functional gastrointestinal disorder in which a variety of pathophysiological mechanisms such as increased intestinal permeability and low-grade inflammation are involved. The factor causing these alterations, however, has not been identified. OBJECTIVE: We aimed to evaluate the luminal bile salt content and receptor expression in patients with functional dyspepsia and healthy volunteers. METHODS: Gastroduodenoscopy was performed to obtain duodenal biopsies from 25 healthy volunteers and 25 patients with functional dyspepsia (Rome III) to measure duodenal bile salt receptor expression with Western blot. Duodenal fluid aspirates were collected at fixed time points during fasted and fed state conditions and bile salt composition analysis was performed by liquid chromatography-mass spectrometry/mass spectrometry. RESULTS: Patients (N = 17) displayed decreased fasted bile salt concentrations compared to healthy volunteers (N = 20) over time (1.8 ± 0.3 mM vs 3.6 ± 0.5 mM; p = 0.03). In addition, an increased expression of duodenal bile salt sensor vitamin D receptor was found in patients (3.7 ± 1.0-fold; p < 0.0005; N = 24 for both groups). CONCLUSION: Patients with functional dyspepsia are characterized by a decreased duodenal bile salt concentration in fasted state and an increased duodenal vitamin D receptor expression.

Erratum: Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

This corrects the article DOI: 10.1038/srep09921.

Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation.