Background: Pomegranate (Punica granatum) can be used to prepare a bioactive extract exerting anti-inflammatory activities. Clinical studies demonstrated an improvement in clinical response in inflammatory bowel disease (IBD) patients when pomegranate extract (PG) was taken as a complement to standard medications. However, the molecular mechanisms underlying its beneficial effects are still scarcely investigated. This study investigates the effect of PG on bacterial biofilm formation and the promotion of mucosal wound healing. Methods: The acute colitis model was induced in C57BL/6N mice by 3% dextran sodium sulfate administration in drinking water for 5 days. During the recovery phase of colitis, mice received saline or PG (200 mg/kg body weight) by oral gavage for 11 days. Colitis was scored daily by evaluating body weight loss, bleeding, and stool consistency. In vivo intestinal permeability was evaluated by fluorescein isothiocyanate-conjugated dextran assay, bacterial translocation was assessed by fluorescence in situ hybridization on tissues, whereas epithelial and mucus integrity were monitored by immunostaining for JAM-A and MUC-2 markers. Bacterial biofilm formation was assessed using microfluidic devices for 24 or 48 h. Primary fibroblasts were isolated from healthy and inflamed areas of 8 IBD patients, and Caco-2 cells were stimulated with or without PG (5 μg/mL). Inflammatory mediators were measured at the mRNA and protein level by RT-PCR, WB, or Bio-plex multiplex immunoassay, respectively. Results: In vivo, PG boosted the recovery phase of colitis, promoting a complete restoration of the intestinal barrier with the regeneration of the mucus layer, as also demonstrated by the absence of bacterial spread into the mucosa and the enrichment of crypt-associated fibroblasts. Microfluidic experiments did not highlight a specific effect of PG on Enterobacterales biofilm formation, even though Citrobacter freundii biofilm was slightly impaired in the presence of PG. In vitro, inflamed fibroblasts responded to PG by downregulating the release of metalloproteinases, IL-6, and IL-8 and upregulating the levels of HGF. Caco-2 cells cultured in a medium supplemented with PG increased the expression of SOX-9 and CD44, whereas in the presence of HGF or plated with a fibroblast-conditioned medium, they displayed a decrease in SOX-9 and CD44 expression and an increase in AXIN2, a negative regulator of Wnt signaling. Conclusions: These data provide new insight into the manifold effects of PG on promoting mucosal homeostasis in IBD by affecting pathogen biofilm formation and favoring the regeneration of the intestinal barrier through the regulation of the crosstalk between epithelial and stromal cells.
Background Ulcerative Colitis (UC) is a chronic, idiopathic intestinal inflammatory disease whose diagnosis requires colonoscopy with biopsy. There is an unmet need for sensitive, and easy-to-detect biomarkers helping a rapid and non-invasive diagnosis, and suitable for following disease progression. Extracellular vesicles (EVs) have been proposed as promising carriers of biomarkers. Nevertheless, their plasma levels remain very low and thus difficult to detect. We explored Low-Intensity Pulsed Ultrasound (LIPUS) as a novel and safe approach to enhance the mucosal release of EVs in experimental models of UC. Methods LIPUS was applied at a frequency of 38 kHz and at an intensity of 150 mW/cm2 for 3 min, using devices dedicated to in vitro or in vivo studies. Primary intestinal fibroblasts, Human Intestinal microvasculature endothelial cells (HIMEC) and peripheral blood mononuclear cells (PBMC) were isolated from UC patients and healthy volunteers (n=6). Cell viability was tested in Caco-2 and all primary cells using MTT assay. Computer acoustic simulations, allowing a reliable control of the energy dose in the colon, were carried out using k-Wave software to translate in vivo the LIPUS. Acute and chronic colitis models were induced in C57BL/6N mice by administration of dextran sodium sulfate (DSS) respectively 2 and 2.5% ad libitum in their drinking water for seven days for the acute and three cycles of DDS for the chronic. Mice were monitored daily for body weight loss, bleeding and stool consistency. EVs were characterized in supernatants, plasma and mucosa at NanoSight and inflammatory mediators detected 1, 2 and 24 h after LIPUS by ELISA assay. Apoptosis and cell proliferation were evaluated by TUNEL and Ki67 stainings. Results After LIPUS, all cells appeared 100% viable and no pro-inflammatory changes were observed. In Caco-2 cells, fibroblasts and HIMEC, LIPUS significantly decreased the levels of IL-8. The maximum release of EVs, range in size from 100 to 120 nm, was recorded after 60 min in resident cells from both UC and healthy-derived cells. Conversely, PBMC displayed a progressive decrease. In both acute and chronic models, the physiological cellular turnover of the mucosa resulted unchanged after LIPUS. A significative increase of EVs was observed after 2 h of stimulation, and dropped down after 24 h. The levels of EVs were higher (p<0.01) in the chronic rather than acute phase of colitis. Conclusion LIPUS proved to be a safe and non pro-inflammatory approach to boost the release of EVs accumulated into the mucosa increasing their levels in the bloodstream. This feature is transient and more evident in the short term. Overall, the LIPUS could pave the way to a new era of a gut disruptive liquid biopsy.
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