In total, 50?l of bacteria suspension was added to each well of a 96-well ELISA plate and dried overnight in a 37?C incubator. and its?Supplementary Information Files and from the corresponding author upon reasonable request. Abstract Short-chain fatty acids (SCFAs) butyrate and propionate are metabolites from dietary fiber’s fermentation by gut microbiota that can affect differentiation or functions of T cells, macrophages and dendritic cells. We show here that at low doses?these SCFAs directly impact B cell intrinsic functions to moderately enhance class-switch DNA recombination (CSR), while decreasing at higher doses over Ropidoxuridine a broad physiological range, AID and Blimp1 expression, CSR, somatic hypermutation and plasma cell differentiation. In human and mouse B cells, butyrate and propionate decrease B cell and by upregulating select miRNAs that target and mRNA-3UTRs through inhibition of histone deacetylation (HDAC) of those miRNA host genes. By acting as HDAC inhibitors, not as energy substrates or through GPR-engagement signaling in these B cell-intrinsic processes, these SCFAs impair intestinal and systemic T-dependent and T-independent antibody responses. Their epigenetic impact on B cells extends to inhibition of autoantibody production and autoimmunity in mouse lupus models. locus15,25. SCFAs would mitigate autoimmunity by regulating T cells, DCs, innate lymphoid cells (ILCs), and macrophages2,3,15,19,20,24,26C29, increasing anti-inflammatory cytokines, such as TGF- and IL-10, and inhibiting production of proinflammatory cytokines, such as IL-6, IL-12, IL-17a, IFN-, and TNF-1,3,30C32. They can reduce recruitment of eosinophils and allergic cellular infiltration of airways, thereby dampening inflammation and IgE antibody responses20. Butyrate and/or propionate may indirectly affect B cells by modulating functions of Treg cells, particularly in autoimmune conditions. Treatment of lupus-prone MRL/mice with HDAC inhibitor (HDI) drugs, such as valproic acid (VPA), panobinostat (Farydak), vorinostat (SAHA, Zolinza), or romidepsin (Istodax), reduce autoreactive plasma cell numbers, nephritis, and dampened autoimmunity33,34. Other HDIs, such as suberoylanilide hydroxamic acid?(SAHA), Trichostatin-A (TSA), and bufexamac, exhert anti-inflammatory effects22. As we have shown, VPA, a strong HDAC inhibitor used for epileptic seizures35, acts directly on B Ropidoxuridine cells to downregulate and expression in a dose-dependent fashion7,8,33. HDAC inhibitory drugs are effective against B lymphocyte lineage malignancies, by inhibiting cell proliferation, survival, and Rabbit polyclonal to TRAP1 differentiation in an HDAC-class-dependent manner36,37. By boosting B-cell metabolism and plasma cell differentiation12, SCFAs would potentially support the antibody response, although this contrasts with a large body of evidence emphasizing a potent immunosuppressive activity of gut fiber-derived SCFAs1,4,9,10,20,22,25,34,38C40. Thus, whether and how SCFAs impact B-cell differentiation and/or functions remains to be elucidated. Here, we show that butyrate and propionate act directly on mouse and human B cells to inhibit AID and Blimp1 expression Ropidoxuridine through a B cell-intrinsic, dose-dependent epigenetic HDAC inhibitory activity (not as energy substrate or through GPCR signaling) that leads to upregulation of select miRNAs targeting and mice, and (NSG) mice grafted with purified B cells. The SCFAs B-cell modulatory potency extended to autoantibody responses in lupus-prone MRL/and NZB/W F1 mice. Thus, SCFAs derived from gut microbiota-processed dietary fibers modulate antibody and autoantibody responses by impacting directly B-cell-intrinsic epigenetic mechanisms through their HDAC inhibitory activity. Results Fiber-derived SCFAs reduce local and systemic antibody responses To address the impact of dietary fiber SCFAs around the antibody response, we fed (after weaning) ten C57BL/6 mice a fiber diet (regular chow, 18% fiber content) and ten mice a no-fiber diet (0% fiber). Two weeks later (at the age of 5 weeks), five mice in each group were started on water-containing SCFAs (20.0?mg/ml tributyrin, 140?mM sodium butyrate, and 150?mM sodium propionate, pH 7.4), and the other five mice on plain water (pH 7.4 and Na+ adjusted to match SCFAs water). All mice were then administered ovalbumin (OVA) together with cholera?toxin (CT) via intragastric gavage, once a week for 4 weeks. In mice fed fiber diet (regular chow) and plain water, the concentration of butyrate in feces, colon tissue, spleen, and mesenteric lymph nodes (MLNs) were 7.92, 0.46, 0.59, and 0.33?mol gC1, respectively, and those of propionate were 6.28, 0.67, 1.14, and 0.61?mol gC1, respectively (Supplementary Fig.?1a). In circulation, butyrate and propionate were 5C80?M. SCFAs water to mice on fiber diet increased butyrate and propionate in feces (12.1C23.4 and.