Browsing by Subject "Nutraceutical"

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Immunomodulatory effects of resveratrol on human intestinal mast cell signaling in vitro and mast cell associated enteritis and colitis in mice
(2023) Bilotta, Sabrina; Lorentz, Axel
By releasing their pre-stored or de novo synthesized mediators, mast cells (MC) are important immunoregulatory cells responsible for a variety of inflammatory reactions. Although known to be major effector cells in immunoglobuline (Ig) E dependent allergic reactions, MC have been widely shown to play a role in various inflammations of the gut. Diseases of the gastrointestinal tract (GIT) are widespread and multicausal. Those affected suffer from the sometimes severe symptoms and may experience restrictions on their daily life. Even if conventional medication is applied routinely, aim of the past and current research is to establish supportive and/or alternative medication that is based on natural substances. These may be on the basis of small natural components like resveratrol, a stilbene mostly found in grapes. Numerous positive properties are attributed to resveratrol. These are anti-inflammatory, anti-cancerogenic, anti-oxidative, as well as neuroprotective effects. The use of substances of natural origin as so-called nutraceuticals can help to increase the acceptance of medication by those affected, but also to reduce and overcome the side effects associated with conventional treatment. Effects of resveratrol were examined on the reactivity of MC isolated from patients’ tissue undergoing bowel resection. The results of this work show that resveratrol exhibited potent inhibitory effects on high affinity IgE receptor mediated activation of MC, strongly inhibiting not only MC degranulation, but also gene expression of the pro-inflammatory cytokines C-X-C motif chemokine ligand (CXCL) 8, C-C motif chemokine ligand (CCL) 2, CCL3, CCL4 and tumor necrosis factor (TNF-) α. Ultimately, the intracellular signaling cascade triggered during MC activation via IgE receptor leads to mediator release. Following IgE receptor mediated activation, phosphorylation of signaling molecules like extracellular signal-regulated kinase (ERK) 1/2 and signal transducer and activator of transcription (STAT) 3, occurs. ERK1/2 was found to be responsible for phosphorylation of mitochondrial STAT3, which contributes significantly to MC degranulation. Treatment with resveratrol was able to inhibit the phosphorylation of STAT3 by more than 50 % and that of ERK1/2 by almost 100 %. Furthermore, the experiments performed succeeded in isolating the mitochondrial fraction from relatively low human intestinal MC (hiMC) numbers. Also, in this fraction we could detect phosphorylation of STAT3 and ERK1/2 after MC activation, which was reduced after treatment with resveratrol. Having shown the strong inhibitory effects in vitro, we set out to examine immunomodulatory effects of resveratrol in vivo. Presence and activity of MC are closely related to intestinal inflammations in consequence of food allergy (FA) and inflammatory bowel disease (IBD). In mice, FA can be studied using the ovalbumin (OVA)-induced allergic enteritis model and colitis can be studied using the IL-10 knockout (-/-) mice, which develop a spontaneous form of chronic colitis. We could show that the oral application of resveratrol inhibited the increase of MC numbers in the colon and duodenum of affected animals in both experimental settings. Less pronounced but still visible effects of resveratrol administration were observed in the colon with regard to epithelial damage, cell infiltration and reduction of goblet cell numbers. In all cases, based on a scoring system, the damage decreased to the level of the corresponding controls receiving no additive and in which no allergic enteritis was induced or nor colitis developed. Overall, allergic enteritis resulted in a weaker symptomatology, and IL-10-/- animals showed a delayed appearance of the typical symptoms. The results of this thesis show a strong inhibitory effect of resveratrol on hiMC. This could be detected for mediator release as well as on gene expression levels and in the phosphorylation of the signaling molecules ERK1/2 and STAT3, which we could also identify in the mitochondria of hiMC. We observed positive influences on MC-associated parameters in the OVA enteritis and IL-10-/- colitis mouse models. With regard to its use as nutraceutical, resveratrol could therefore come more of a focus in the future.