Laminarin, a β-(1,3)-glucan from the seaweed Laminaria digitata, is a polysaccharide which provides anti-inflammatory and anti-oxidative properties. Its influence on both human dermal fibroblasts adult (HDFa) and normal human epidermal keratinocytes (NHEK) has not been established yet. Herein, laminarin effects were examined on skin cells’ mitochondrial and antioxidant activities. Cytokines, hyaluronic acid, and procollagen type I secretions and interaction mechanisms were explored after a maximum of 72 h treatment with laminarin. Our results demonstrated a decrease in mitochondrial activities with 72 h treatment with laminarin from 500 µg.mL⁻¹ for NHEK cells and from 100 µg.mL⁻¹ for HDFa cells without cytotoxicity. No variation of hyaluronic acid or type I procollagen was observed for all laminarin concentrations, while an antioxidant effect was found against reactive oxygen species (ROS) from 1 µg.mL⁻¹ for HDFa cells in both H₂O₂ and UVA radiation conditions, and from 10 µg.mL⁻¹ and 1 µg.mL⁻¹ for NHEK cells in both H₂O₂ and UVA radiation conditions, respectively. Laminarin treatment modulated both cells surface glycosylation and cytokine secretions of skin cells. Overall, our data suggest a positive effect of β-(1,3)-glucan on skin cells on oxidative stress and inflammation induced by environmental factors. Of note, these effects are through the modulation of glycan and receptors interactions at the skin cells surface.

Dendritic cells (DC) are key players in antitumor immune responses. Tumors exploit their plasticity to escape immune control; their aberrant surface carbohydrate patterns (e.g., glycans) shape immune responses through lectin binding, and manipulate the metabolism of immune cells, including DCs to alter their function and escape immune surveillance. DC metabolic reprogramming could induce immune subversion and tumor immune escape. Here we explore metabolic features of human DC subsets (cDC2s, cDC1s, pDCs) in melanoma, at single cell level, using the flow cytometry-based SCENITH (Single-Cell ENergetIc metabolism by profiling Translation inHibition) method. We demonstrate that circulating and tumor-infiltrating DC subsets from melanoma patients are characterized by altered metabolism, which is linked to their activation status and profile of immune checkpoint expression. This altered metabolism influences their function and affects patient clinical outcome. Notably, melanoma tumor cells directly remodel the metabolic profile of DC subsets, in a glycan-dependent manner. Strikingly, modulation of the mTOR/AMPK-dependent metabolic pathways and/or the MCT1 lactate transporter rescue cDC2s and cDC1s from skewing by tumor-derived glycans, Sialyl-Tn antigen and Fucose, and restore anti-tumor T-cell fitness. Our findings thus open the way for appropriate tuning of metabolic pathways to rescue DCs from tumor hijacking and restore potent antitumor responses.

The FimH type-1 fimbrial adhesin allows pathogenic Escherichia coli to adhere to glycoproteins in the epithelial linings of human bladder and intestinal tract, by using multiple fimbriae simultaneously. Pauci- and high-mannose type N-glycans are natural FimH receptors on those glycoproteins. Oligomannose-3 and oligomannose-5 bind with the highest affinity to FimH by using the same Manα1,3Man branch. Oligomannose-6 is generated from oligomannose-5 in the next step of the biogenesis of high-mannose N-glycans, by the transfer of a mannose in α1,2-linkage onto this branch. Using serial crystallography and by measuring the kinetics of binding, we demonstrate that shielding the high-affinity epitope drives the binding of multiple FimH molecules. First, we profiled FimH glycan binding on a microarray containing paucimannosidic N-glycans and in a FimH LEctPROFILE assay. To make the transition to oligomannose-6, we measured the kinetics of FimH binding using paucimannosidic N-glycans, glycoproteins and all four α-dimannosides conjugated to bovine serum albumin. Equimolar mixed interfaces of the dimannosides present in oligomannose-6 and molecular dynamics simulations suggest a positive cooperativity in the bivalent binding of Manα1,3Manα1 and Manα1,6Manα1 dimannosides. The binding of core α1,6-fucosylated oligomannose-3 in cocrystals of FimH is monovalent but interestingly the GlcNAc1—Fuc moiety retains highly flexibility. In cocrystals with oligomannose-6, two FimH bacterial adhesins bind the Manα1,3Manα1 and Manα1,6Manα1 endings of the second trimannose core (A-4′-B). This cooperative switch towards bivalent binding appears sustainable beyond a molar excess of oligomannose-6. Our findings provide important novel structural insights for the design of multivalent FimH antagonists that bind with positive cooperativity.