Enhancement of the water solubility and antioxidant capacities of mangiferin by transglucosylation using a cyclodextrin glycosyltransferase.

This study aimed to enhance the water solubility and antioxidant properties of mangiferin by transglucosylation using cyclodextrin glycosyltransferase (CGTase) from Thermoanaerobacter sp. The highest mangiferin to mangiferin glucoside conversion yield achieved was 88.9% using 60 mU/mL CGTase, 25 mM mangiferin, and 10% starch (w/v), with incubation at 60 °C for 10 h. The product of transglucosylation was purified and its chemical structure was determined to be glucosyl-α-(1→4)-mangiferin (MGF-g1) using matrix-assisted laser desorption ionization time-of-flight mass spectrometry and nuclear magnetic resonance spectroscopy. The water solubility of MGF-g1 was 5,093 times higher than that of mangiferin. MGF-g1 exhibited 1.6-fold higher 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, 1.24-fold higher oxygen radical antioxidant capacity, and 1.19-fold higher ferric reducing ability power, compared to mangiferin. Moreover, the cyclooxygenase-2 inhibitory activity (IC50) of mangiferin and MGF-g1 were 76.44 ± 11.7 µM and 59.74 ± 2.8 µM, respectively. Our results suggest that the novel MGF-g1 has potential applications as a functional material in the food and pharmaceutical industries.

Recycling and LFA-1-dependent trafficking of ICAM-1 to the immunological synapse.

Little is known about how adhesion molecules on APCs accumulate at immunological synapses. We show here that ICAM-1 on APCs is continuously internalized and rapidly recycled back to the interface after antigen-priming T-cell contact. The internalization rate is high in APCs, including Raji B cells and dendritic cells, but low in endothelial cells. Internalization is significantly reduced by inhibitors of Na(+)/H(+) exchangers (NHEs), suggesting that members of the NHE-family regulate this process. Once internalized, ICAM-1 is co-localized with MHC class II in the polarized recycling compartment. Surprisingly, not only ICAM-1, but also MHC class II, is targeted to the immunological synapse through LFA-1-dependent adhesion. Cytosolic ICAM-1 is highly mobile and forms a tubular structure. Inhibitors of microtubule or actin polymerization can reduce ICAM-1 mobility, and thereby block accumulation at immunological synapses. Membrane ICAM-1 also moves to the T-cell contact zone, presumably through an active, cytoskeleton-dependent mechanism. Collectively, these results demonstrate that ICAM-1 can be transported to the immunological synapse through the recycling compartment. Furthermore, the high-affinity state of LFA-1 on T cells is critical to induce targeted movements of both ICAM-1 and MHC class II to the immunological synapse on APCs.

ICAM-1/LFA-1 interaction contributes to the induction of endothelial cell-cell separation: implication for enhanced leukocyte diapedesis.

The basic route and mechanism for diapedesis has not yet to be fully defined. Here we present evidence that "cell-cell separation" between endothelial cells (ECs) may provide a route for leukocyte diapedesis. We unexpectedly found that extensive interaction between peripheral blood leukocytes and ECs that were activated by TNF-alpha induced the opening of EC contacts and, surprisingly, resulted in cell-cell separation. This event was specific to the intercellular adhesion molecules-1 (ICAM-1)/leukocyte function- associated antigen-1 interaction, as demonstrated by the following: (1) ICAM-1 expression correlated with increased EC contraction; and (2) the blocking of ICAM-1 selectively inhibited EC separation. Thus, we suggest that "cell-cell separation" could be a mechanism for diapedesis in situations that may require massive leukocyte infiltration.