Sex-dependent Lupus Blautia (Ruminococcus) gnavus strain induction of zonulin-mediated intestinal permeability and autoimmunity

Abstract

Imbalances in the gut microbiome are suspected contributors to the pathogenesis of Systemic Lupus Erythematosus, and our studies and others have documented that patients with active Lupus nephritis have expansions of the obligate anaerobe, Blautia (Ruminococcus) gnavus (RG). To investigate whether the RG strains in Lupus patients have in vivo pathogenic properties in a gnotobiotic system, we colonized C57BL/6 mice with individual RG strains from healthy adults or those from Lupus patients. These strains were similar in their capacity for murine intestinal colonization of antibiotic-preconditioned specific-pathogen-free, as well as of germ-free adults and of their neonatally colonized litters. Lupus-derived RG strains induced high levels of intestinal permeability that was significantly greater in female than male mice, whereas the RG species-type strain (ATCC29149/VPI C7-1) from a healthy donor had little or no effects. These Lupus RG strain-induced functional alterations were associated with RG translocation to mesenteric lymph nodes, and raised serum levels of zonulin, a regulator of tight junction formation between cells that form the gut barrier. Notably, the level of Lupus RG-induced intestinal permeability was significantly correlated with serum IgG anti RG cell-wall lipoglycan antibodies, and with anti-native DNA autoantibodies that are a biomarker for SLE. Strikingly, gut permeability was completely reversed by oral treatment with larazotide acetate, an octapeptide that is a specific molecular antagonist of zonulin. Taken together, these studies document a pathway by which RG strains from Lupus patients contribute to a leaky gut and features of autoimmunity implicated in the pathogenesis of flares of clinical Lupus disease.

Longitudinal gut microbiome analyses and blooms of pathogenic strains during lupus disease flares

“…Relevant, faecal transplants from mice with lupus-like glomerulonephritis into germ-free mice are reported to induce an inflammatory autoimmune condition,36 reiterating earlier findings reported for a murine gut pathobiont isolate 37. Notably, in vivo murine colonisation with the LG-expressing RG strains, S107-48 and S47-18, from LN patients, which express the LG previously shown to include potent TLR2 stimulatory activity,7 was also shown to induce severe impairment of the intestinal barrier 33. Neonatal colonisation with the S107-48 strain led to RG translocation into draining mesenteric lymph nodes, and induction of serum IgG anti-DNA antibodies at levels proportional to the induced functional impairment of the gut barrier 33.…”

Dietary tryptophan and genetic susceptibility expand gut microbiota that promote systemic autoimmune activation

“…The qPCR analysis also showed the dual effect of the microbiota origin and dietary tryptophan, with Rg abundance being higher in TCmbTrp lo than in B6mbTrp hi mice, and a similar trend between B6mbTrp hi and B6mbTrp lo mice. 16S rDNA sequence analysis cannot distinguish the LP-producing Rg pathobiont strain, Rg 2, from non-LP producing strain Rg1 47 . However, the growth of Rg2, but not Rg1, was enhanced by supplemental tryptophan in vitro ( Figure 4G-H ), suggesting that dietary tryptophan expand the Rg2 population present in the TC microbiota.…”

Intestinal permeability and inflammatory features of juvenile age correlate with the eventual systemic autoimmunity in lupus‐prone female SWR × NZB F1 (SNF1) mice

“…Recent reports, including ours, have shown that higher gut inflammation and permeability markers, calprotectin and zonulin (pre‐Hp2), are produced by SLE patients compared to healthy controls [51–53]. However, it is not known if these features are a consequence of the disease activities or occur prior to clinical stage disease.…”

“…Therefore, our observation that pre-Hp RNA levels and Hp protein levels can be detected in mice with higher gut permeability was intriguing. Of note, many reports have shown that a pre-HP2 inhibitory octapeptide (GGVLVQPG) called AT1001 could suppress gut permeability and suppress multiple clinical conditions in rodent models [52,[63][64][65][66]. However, it has been reported that neither human HP2 or mouse Hp harbours AT1001 sequence and it is an immunoglobulin sequence [67].…”