Accumulating evidence points to an important role for the gut microbiome in anti-tumor immunity. Here, we show that altered intestinal microbiota contributes to anti-tumor immunity, limiting tumor expansion. Mice lacking the ubiquitin ligase RNF5 exhibit attenuated activation of the unfolded protein response (UPR) components, which coincides with increased expression of inflammasome components, recruitment and activation of dendritic cells and reduced expression of antimicrobial peptides in intestinal epithelial cells. Reduced UPR expression is also seen in murine and human melanoma tumor specimens that responded to immune checkpoint therapy. Co-housing of Rnf5 −/− and WT mice abolishes the anti-tumor immunity and tumor inhibition phenotype, whereas transfer of 11 bacterial strains, including B. rodentium , enriched in Rnf5 −/− mice, establishes anti-tumor immunity and restricts melanoma growth in germ-free WT mice. Altered UPR signaling, exemplified in Rnf5 −/− mice, coincides with altered gut microbiota composition and anti-tumor immunity to control melanoma growth.

Highlights d Mucin and inulin, prebiotics, inhibit melanoma growth in syngeneic mouse models d Changes in gut microbiota taxa by these prebiotics induce anti-tumor immunity d Inulin attenuates melanoma resistance to MEKi in a mouse melanoma model d Inulin and mucin elicit distinct microbiota changes and an additive effect in select models

Objective Urolithin A (UroA) is a major metabolite of ellagic acid produced following microbial catabolism in the gut. Emerging evidence has suggested that UroA modulates energy metabolism in various cells. However, UroA’s physiological functions related to obesity and insulin resistance remain unclear. Methods Male mice were intraperitoneally administrated either UroA or dimethyl sulfoxide (vehicle) along with a high‐fat diet for 12 weeks. Insulin sensitivity was evaluated via glucose and insulin tolerance tests and acute insulin signaling. The effects of UroA on hepatic triglyceride accumulation, adipocyte size, mitochondrial DNA content, and proinflammatory gene expressions were determined. The impact of UroA on macrophage polarization and mitochondrial respiration were assessed in bone marrow–derived macrophages. Results Administration of UroA (1) improved systemic insulin sensitivity, (2) attenuated triglyceride accumulation and elevated mitochondrial biogenesis in the liver, (3) reduced adipocyte hypertrophy and macrophage infiltration into the adipose tissue, and (4) altered M1/M2 polarization in peritoneal macrophages. In addition, UroA favored macrophage M2 polarization and mitochondrial respiration in bone marrow‐derived macrophages. Conclusions UroA plays a direct role in improving systemic insulin sensitivity independent of its parental compounds. This work supports UroA’s role in the metabolic benefits of ellagic acid–rich foods and highlights the significance of its microbial transformation in the gut.

Although Act1 (adaptor for IL-17 receptors) is necessary for IL-17-mediated inflammatory responses, Act1- (but not Il17ra-, Il17rc-, or Il17rb-) deficient mice develop spontaneous SLE- and Sjögren’s-like diseases. Here, we show that Act1 functions as a negative regulator in T and B cells via direct inhibition of STAT3. Mass spectrometry analysis detected an Act1–STAT3 complex, deficiency of Act1 (but not Il17ra-, Il17rc-, or Il17rb) results in hyper IL-23- and IL-21-induced STAT3 activation in T and B cells, respectively. IL-23R deletion or blockade of IL-21 ameliorates SLE- and Sjögren’s-like diseases in Act1−/− mice. Act1 deficiency results in hyperactivated follicular Th17 cells with elevated IL-21 expression, which promotes T–B cell interaction for B cell expansion and antibody production. Moreover, anti-IL-21 ameliorates the SLE- and Sjögren’s-like diseases in Act1-deficient mice. Thus, IL-21 blocking antibody might be an effective therapy for treating SLE- and Sjögren’s-like syndrome in patients containing Act1 mutation.

Scope: We aimed to investigate the mechanisms by which red raspberry (RR) polyphenolic fractions regulate obesity and inflammation with an emphasis on the crosstalk between adipose tissue macrophages (ATM) and adipocyte progenitors. Methods and Results: C57BL/6 male mice were fed either a HF diet or a HF diet supplemented with a RR polyphenolic fraction from whole fruit, pulp, or seed. Supplementation with pulp significantly increased energy expenditure and reduced HF dietinduced obesity and insulin resistance. The pulp, and to a lesser extent, whole polyphenols decreased the recruitment of ATM, activation of the NLRP3 inflammasome and adipocyte hypertrophy, which was associated with epigenetic modulation of adipogenesis (e.g., H3K27Ac, H3K9Ac). Results from an IL-1 reporter assay in J774 macrophages recapitulated the inhibitory role of RR polyphenols on NLRP3 inflammasome activation. Using conditioned media from macrophages, we demonstrated that RR polyphenols reversed the IL-1-mediated epigenetic suppression of H3K27Ac in adipocyte progenitor cells. Conclusions: RR polyphenols from pulp and whole fruit serve as an inhibitor for NLRP3 inflammasome activation and an epigenetic modifier to regulate adipogenesis, which confers resistance against diet-induced obesity and metabolic dysfunction.