Jose U. Scher

Expansion of intestinal Prevotella copri correlates with enhanced susceptibility to arthritis

Rheumatoid arthritis (RA) is a prevalent systemic autoimmune disease, caused by a combination of genetic and environmental factors. Animal models suggest a role for intestinal bacteria in supporting the systemic immune response required for joint inflammation. Here we performed 16S sequencing on 114 stool samples from rheumatoid arthritis patients and controls, and shotgun sequencing on a subset of 44 such samples. We identified the presence of Prevotella copri as strongly correlated with disease in new-onset untreated rheumatoid arthritis (NORA) patients. Increases in Prevotella abundance correlated with a reduction in Bacteroides and a loss of reportedly beneficial microbes in NORA subjects. We also identified unique Prevotella genes that correlated with disease. Further, colonization of mice revealed the ability of P. copri to dominate the intestinal microbiota and resulted in an increased sensitivity to chemically induced colitis. This work identifies a potential role for P. copri in the pathogenesis of RA. DOI: http://dx.doi.org/10.7554/eLife.01202.001

Periodontal Disease and the Oral Microbiota in New-Onset Rheumatoid Arthritis

OBJECTIVE To profile the abundance and diversity of subgingival oral microbiota in patients with never-treated, new-onset rheumatoid arthritis (RA). METHODS Periodontal disease (PD) status, clinical activity, and sociodemographic factors were determined in patients with new-onset RA, patients with chronic RA, and healthy subjects. Multiplexed-454 pyrosequencing was used to compare the composition of subgingival microbiota and establish correlations between the presence/abundance of bacteria and disease phenotypes. Anti-Porphyromonas gingivalis antibody testing was performed to assess prior exposure to the bacterial pathogen P gingivalis. RESULTS The more advanced forms of periodontitis were already present at disease onset in patients with new-onset RA. The subgingival microbiota observed in patients with new-onset RA was distinct from that found in healthy controls. In most cases, however, these microbial differences could be attributed to the severity of PD and were not inherent to RA. The presence and abundance of P gingivalis were also directly associated with the severity of PD and were not unique to RA. The presence of P gingivalis was not correlated with anti-citrullinated protein antibody (ACPA) titers. Overall exposure to P gingivalis was similar between patients with new-onset RA and controls, observed in 78% of patients and 83% of controls. The presence and abundance of Anaeroglobus geminatus correlated with the presence of ACPAs/rheumatoid factor. Prevotella and Leptotrichia species were the only characteristic taxa observed in patients with new-onset RA irrespective of PD status. CONCLUSION Patients with new-onset RA exhibited a high prevalence of PD at disease onset, despite their young age and paucity of smoking history. The subgingival microbiota profile in patients with new-onset RA was similar to that in patients with chronic RA and healthy subjects whose PD was of comparable severity. Although colonization with P gingivalis correlated with the severity of PD, overall exposure to P gingivalis was similar among the groups. The role of A geminatus and Prevotella/Leptotrichia species in this process merits further study.

The microbiome and rheumatoid arthritis

Humans are not (and have never been) alone. From the moment we are born, millions of micro-organisms populate our bodies and coexist with us rather peacefully for the rest of our lives. This microbiome represents the totality of micro-organisms (and their genomes) that we necessarily acquire from the environment. Micro-organisms living in or on us have evolved to extract the energy they require to survive, and in exchange they support the physiological, metabolic and immune capacities that have contributed to our evolutionary success. Although currently categorized as an autoimmune disorder and regarded as a complex genetic disease, the ultimate cause of rheumatoid arthritis (RA) remains elusive. It seems that interplay between predisposing genetic factors and environmental triggers is required for disease manifestation. New insights from DNA sequence-based analyses of gut microbial communities and a renewed interest in mucosal immunology suggest that the microbiome represents an important environmental factor that can influence autoimmune disease manifestation. This Review summarizes the historical clues that suggest a possible role for the microbiota in the pathogenesis of RA, and will focus on new technologies that might provide scientific evidence to support this hypothesis.

Decreased bacterial diversity characterizes the altered gut microbiota in patients with psoriatic arthritis, resembling dysbiosis in inflammatory bowel disease.

To characterize the diversity and taxonomic relative abundance of the gut microbiota in patients with never‐treated, recent‐onset psoriatic arthritis (PsA).

The Anti-Inflammatory Effects of Prostaglandins

Long regarded as proinflammatory molecules, prostaglandins (PGs) also have anti-inflammatory effects. Both prostaglandin D2 (PGD2) and its dehydration end product 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) seem to play important roles in regulating inflammation, via both receptor-dependent (DP1 and DP2 receptors) and receptor-independent mechanisms. Intracellular effects of PGD2 and 15d-PGJ2 that may suppress inflammation include inhibition of nuclear factor-κB (NF-κB) by multiple mechanisms (IκB kinase inhibition and blockade of NF-κB nuclear binding) and activation of peroxisome proliferator-activated receptor-γ (PPAR-γ). Prostaglandin F2α (PGF2α) may also have important anti-inflammatory effects, although current data are limited. In animal models, expression of both PGD and PGF synthases declines during acute inflammation, only to rise again during the resolution phase, suggesting their possible role in resolving inflammation. Prostaglandin E2 (PGE2), the classic model of a proinflammatory lipid mediator, also has anti-inflammatory effects that are both potent and context dependent. Thus, accumulating data suggest that PGs not only participate in initiation, but may also actively contribute to the resolution of inflammation. Indeed, classic inhibitors of PG synthesis such as nonselective and cyclooxygenase-2 (COX-2) selective inhibitors (nonsteroidal anti-inflammatory drugs) may actually prolong inflammation when administered during the resolution phase. These effects may regulate not only tissue inflammation but also vascular disease, possibly shedding light on the controversy surrounding nonsteroidal anti-inflammatory drug use and its relation to myocardial infarction. In this review, we summarize the current understanding of PGs as dichotomous molecules in the inflammatory process.

Microbiome and mucosal inflammation as extra-articular triggers for rheumatoid arthritis and autoimmunity.

Purpose of reviewDespite the progress toward understanding the molecular pathogenesis of rheumatoid arthritis (RA), its cause remains elusive. Genes are important but rather insufficient to explain the majority of RA cases. This review describes the novel data supporting the microbiome and its interactions with the human host as potential en(‘in’)vironmental factors in RA pathogenesis. Recent findingsAnimal models of inflammatory arthritis have shown that the presence of bacteria in mucosal surfaces is sufficient to alter local and systemic host immune responses and elicit joint inflammation. Human RA studies have focused on three mucosal sites: the gut, the gingiva, and the respiratory tree. The oral microbiome, and specifically Porphyromonas gingivalis, has long been implicated. Novel sequencing technologies have allowed investigations into the role of the gut microbiome in the development of autoimmune arthritis. Most recently, the pulmonary parenchyma has also been described as yet another possible mucosal site of initiation of autoimmunity in RA. SummaryEmerging data implicate the microbiome in RA pathogenesis. Mucosal sites exposed to a high load of bacterial antigens – such as the periodontium, lung, and gut – may represent the initial site of autoimmune generation. If validated, these findings could lead to the discovery of potential biomarkers and therapeutic approaches in the preclinical and clinical phases of RA.

Microbiome in Inflammatory Arthritis and Human Rheumatic Diseases.

Ever since its modern conception as a medical discipline, the study of microorganisms has paralleled the many technological advances in microbiology. In the 17th century, the inventor of the microscope, Antony van Leeuwenhoek, was also the first to describe—in the plaque of his own gums—the millions of microorganisms (or “animalcules”) that reside within us. It is that multitude of microbes populating most human body cavities and surfaces, including its genetic and enzymatic composition, that defines our microbiome (1). For centuries, the role of the microbiome as a potential determinant to health and disease has been rather ignored. This has been true in most fields of human research, but particularly so in autoimmune and rheumatic conditions. The reasons are multifactorial. Chief among those was the advent of Koch’s postulates in the late 1800s, which exerted a profound influence on how investigators thought about causality in medicine (2). Unknown at the time, however, were the facts that asymptomatic carriers are a common feature of many infectious diseases and that several microorganisms are fastidious in nature, with complex nutritional requirements for growth. The latter fundamentally prevented the study of bacteria within the context of a dynamic biologic community, the role of commensal taxa, the downstream molecular events, and the resulting immune interactions between microorganisms and their host. Consequently, only the prevalent microbiologic techniques in the past were used to characterize unique agents capable of triggering clinical rheumatic syndromes. Over time, the search led to correlative studies of specific bacteria and viruses in the etiopathogenesis of these disorders, most notably rheumatoid arthritis (RA), psoriasis, inflammatory bowel disease (IBD), and the related spondyloarthritides (SpA), including ankylosing spondylitis (AS) and reactive arthritis (ReA). The revolution of culture-independent, highthroughput microbial DNA sequencing, in parallel with the resurgence of interest in and further understanding of mucosal immunity, has exponentially advanced our knowledge of the interplay between our microbes and ourselves. That profound, bidirectional interaction and its consequences in physiology and disease have led to a whole new field of research. Despite the relative novelty of the human microbiome as a discipline, a substantial body of evidence has accumulated addressing its potential involvement in the pathogenesis of rheumatic disease (3). In this article, we will critically review the available data from animal and human studies, focusing on the role of the intestinal microbiome in RA, psoriatic arthritis (PsA), and SpA. The role of the microbiome in autoimmunity and in other rheumatic diseases has been reviewed elsewhere (4,5) and is beyond the scope of this article. We include a description of the prospects of microbiome manipulation for therapeutic purposes and conclude by delineating challenges and opportunities in the field. Supported by the NIH (National Institute of Arthritis and Musculoskeletal and Skin Diseases grants K23-AR-064318 to Dr. Scher and RC2-AR-058986 through the American Recovery and Reinvestment Act of 2009 to Drs. Littman and Abramson), the Judith and Stewart Colton Center for Autoimmunity, and the Riley Family Foundation. Jose U. Scher, MD, Steven B. Abramson, MD: New York University School of Medicine and New York University Hospital for Joint Diseases, New York, New York; Dan R. Littman, MD, PhD: Kimmel Center for Biology and Medicine of the Skirball Institute and New York University School of Medicine, New York, New York. Drs. Scher, Littman, and Abramson have a patent application pending on microbiota and byproducts for diagnostics and therapeutics in rheumatic disease. Address correspondence to Jose U. Scher, MD, Division of Rheumatology, New York University Hospital for Joint Diseases, 301 East 17th Street, Room 1608, New York, NY 10003. E-mail: Jose.Scher@nyumc.org. Submitted for publication March 10, 2015; accepted in revised form June 23, 2015.

Helicobacter pylori stimulates gastric epithelial cell MMP-1 secretion via CagA-dependent and -independent ERK activation.

Because the mechanisms of Helicobacter pylori-induced gastric injury are incompletely understood, we examined the hypothesis that H. pylori induces matrix metalloproteinase-1 (MMP-1) secretion, with potential to disrupt gastric stroma. We further tested the role of CagA, an H. pylori virulence factor, in MMP-1 secretion. Co-incubation of AGS cells with Tx30a, an H. pylori strain lacking the cagA virulence gene, stimulated MMP-1 secretion, confirming cagA-independent secretion. Co-incubation with strain 147C (cagA+) resulted in CagA translocation into AGS cells and increased MMP-1 secretion relative to Tx30a. Transfection of cells with the recombinant 147C cagA gene also induced MMP-1 secretion, indicating that CagA can independently stimulate MMP-1 secretion. Co-incubation with strain 147A, containing a cagA gene that lacks an EPIYA tyrosine phosphorylation motif, as well as transfection with 147A cagA, yielded an MMP-1 secretion intermediate between no treatment and 147C, indicating that CagA tyrosine phosphorylation regulates cellular signaling in this model system. H. pylori induced activation of the MAP kinase ERK, with CagA-independent (early) and dependent (later) components. MEK inhibitors UO126 and PD98059 inhibited both CagA-independent and -dependent MMP-1 secretion, whereas p38 inhibition enhanced MMP-1 secretion and ERK activation, suggesting p38 negative regulation of MMP-1 and ERK. These data indicate H. pylori effects on host epithelial MMP-1 expression via ERK, with p38 playing a potential regulatory role.

Selective oral ROCK2 inhibitor down-regulates IL-21 and IL-17 secretion in human T cells via STAT3-dependent mechanism

Significance Rho-associated kinase 2 (ROCK2) is implicated in the regulation of proinflammatory cytokines, such as IL-17 and IL-21, and the development of autoimmunity in mice. However, the role of ROCK2 signaling pathway in regulation of immune responses in humans is still an enigma. Here we show that targeted ROCK2 inhibition down-regulates proinflammatory responses via concurrent regulation of STAT3/STAT5 phosphorylation and shifting Th17/Treg balance in human T cells with a minimal effect on the rest of the immune response. This work provides previously unidentified insights into the molecular mechanism of ROCK2-mediated modulation of the immune response in man and has profound implications for development of a selective ROCK2 inhibitor as a new therapeutic target for autoimmunity treatment. Rho-associated kinase 2 (ROCK2) regulates the secretion of proinflammatory cytokines and the development of autoimmunity in mice. Data from a phase 1 clinical trial demonstrate that oral administration of KD025, a selective ROCK2 inhibitor, to healthy human subjects down-regulates the ability of T cells to secrete IL-21 and IL-17 by 90% and 60%, respectively, but not IFN-γ in response to T-cell receptor stimulation in vitro. Pharmacological inhibition with KD025 or siRNA-mediated inhibition of ROCK2, but not ROCK1, significantly diminished STAT3 phosphorylation and binding to IL-17 and IL-21 promoters and reduced IFN regulatory factor 4 and nuclear hormone RAR-related orphan receptor γt protein levels in T cells derived from healthy subjects or rheumatoid arthritis patients. Simultaneously, treatment with KD025 also promotes the suppressive function of regulatory T cells through up-regulation of STAT5 phosphorylation and positive regulation of forkhead box p3 expression. The administration of KD025 in vivo down-regulates the progression of collagen-induced arthritis in mice via targeting of the Th17-mediated pathway. Thus, ROCK2 signaling appears to be instrumental in regulating the balance between proinflammatory and regulatory T-cell subsets. Targeting of ROCK2 in man may therefore restore disrupted immune homeostasis and have a role in the treatment of autoimmunity.

Matrix metalloproteinase secretion by gastric epithelial cells is regulated by E prostaglandins and MAPKs.

Because matrix metalloproteinases (MMPs) play roles in inflammatory tissue injury, we asked whether MMP secretion by gastric epithelial cells may contribute to gastric injury in response to signals involved in Helicobacter pylori-induced inflammation and/or cyclooxygenase inhibition. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and epidermal growth factor (EGF) stimulated gastric cell MMP-1 secretion, indicating that MMP-1 secretion occurs in inflammatory as well as non-inflammatory situations. MMP-1 secretion required activation of the MAPK Erk and subsequent protein synthesis but was down-regulated by the alternate MAPK, p38. In contrast, secretion of MMP-13 was stimulated by TNF-α/IL-1β but not EGF and was Erk-independent and mediated by p38. MMP-13 secretion was more rapid (peak, 6 h) than MMP-1 (peak ≥30 h) and only partly depended on protein synthesis, suggesting initial release of a pre-existing MMP-13 pool. Therefore, MMP-1 and MMP-13 secretion are differentially regulated by MAPKs. MMP-1 secretion was regulated by E prostaglandins (PGEs) in an Erk-dependent manner. PGEs enhanced Erk activation and MMP-1 secretion in response to EGF but inhibited Erk and MMP-1 when TNF-α and IL-1β were the stimuli, indicating that the effects of PGEs on gastric cell responses are context-dependent. These data show that secretion of MMPs is differentially regulated by MAPKs and suggest mechanisms through which H. pylori infection and/or cyclooxygenase inhibition may induce epithelial cell signaling to contribute to gastric ulcerogenesis.