Intravenous infusion of ascorbic acid decreases serum histamine concentrations in patients with allergic and non-allergic diseases.

Histamine plays an important role in the development of symptoms in allergic, infectious, neoplastic and other diseases. Empirical findings have suggested beneficial effects of ascorbic acid supplementation in those diseases, and these effects are assumed to be related to a possible decrease in systemic histamine concentration. In the present study, we systematically investigated for the first time the effect of 7.5 g of intravenously administered ascorbic acid on serum histamine levels (as detected by ELISA) in 89 patients (19 with allergic and 70 with infectious diseases). When all patients were grouped together, there was a significant decline in histamine concentration from 0.83 to 0.57 ng/ml×m2 body surface area (BSA, p<0.0001). The decrease in serum histamine concentration in patients with allergic diseases (1.36 to 0.69 ng/ml×m2 BSA, p=0.0007) was greater than that in patients with infectious diseases (0.73 to 0.56 ng/ml×m2 BSA, p=0.01). Furthermore, the decline in histamine concentration after ascorbic acid administration was positively correlated with the basal, i.e. pre-therapeutic, histamine concentration. Intravenous infusion of ascorbic acid clearly reduced histamine concentrations in serum, and may represent a therapeutic option in patients presenting with symptoms and diseases associated with pathologically increased histamine concentration.

Activation of the transcription factor Nrf2 in macrophages, Caco-2 cells and intact human gut tissue by Maillard reaction products and coffee.

In addition to direct antioxidative effects, Maillard reaction products (MRPs) could increase the antioxidative capacity of cells through the induction of cytoprotective enzymes. Since many of those enzymes are regulated by the transcription factor Nrf2, the effect of MRPs on nuclear translocation of Nrf2 in macrophages and Caco-2 cells was investigated. Stimulation of both cell types by MRPs showed a concentration-dependent significant increase in nuclear translocation of Nrf2 up to fivefold after short-term (2 h) and up to 50-fold after long-term treatment (24 h). In intact human gut tissue, nuclear translocation of Nrf2 was significantly twofold increased after short-term incubation. To study the activation mechanisms, macrophages and Caco-2 cells were stimulated with MRPs in the presence of catalase, which significantly suppressed Nrf2 activation. Thus, activation was related to extracellular H2O2 continuously formed from MRPs. Short-term incubation with coffee, a MRP-rich beverage, led to a trend towards Nrf2 activation in macrophages, but not in Caco-2 cells or intact human gut tissue. Long-term incubation with coffee (1-4 mg/mL) significantly increased nuclear Nrf2 up to 17-fold. Since raw coffee was inactive under the tested conditions, the effect was related to roasting products. Coffee-induced Nrf2 translocation was, however, only slightly reversed by catalase. Therefore, the Nrf2 activity of coffee can only partially be explained by MRP-induced, H2O2-dependent mechanisms. Thus, it can be concluded that MRPs may increase the antioxidative capacity inside the cell by inducing Nrf2-regulated signalling pathways not only in different cell types, but also in intact gut tissue.

Nuclear translocation of NF-κB in intact human gut tissue upon stimulation with coffee and roasting products.

In the healthy gut, NF-κB is a critical factor of the intestinal immune system, whereas inflammatory bowel diseases are associated with chronic activation of NF-κB. Previous studies indicated that coffee induces nuclear translocation of NF-κB in macrophages, an effect attributed to roasting products. In the present work, coffee extract or roasting products induced nuclear translocation of NF-κB in macrophages, Caco-2 cells, and primary human intestinal microvascular endothelial cells (up to fivefold, p<0.001). Since the effect clearly depended on the cell type, ex vivo experiments were performed with intact human gut tissue from biopsies. The uniformity of the specimens and tissue viability during ex vivo incubation for up to 2 h were verified. Roasting products led to a concentration dependent significant increase of nuclear translocation of NF-κB in human gut tissue (up to 2.85 fold increase, p=0.0321), whereas coffee extract induced a trend towards higher nuclear NF-κB concentration. NF-κB activation in macrophages and Caco-2 cells by roasting products was significantly blocked by co-incubation with catalase (p=0.011 and p=0.024) indicating involvement of H(2)O(2)-signaling. Monitoring of extracellular H(2)O(2) indicated that roasting products in coffee constantly generate H(2)O(2) by spontaneous oxygen reduction, which is only partially detoxified by cellular antioxidative systems. Thus, it can be concluded that ex vivo stimulation of intact human gut tissue is a valuable model to study nutritional effects on complex tissue systems. Furthermore, the consumption of coffee and roasting products may be able to induce nuclear NF-κB translocation in the human gut.