Interleukin-10 (IL-10) inhibits Borrelia burgdorferi-induced IL-17 production and attenuates IL-17-mediated Lyme arthritis

IL-17 and IL-17-producing cells in protection versus pathology

IL-17 cytokine family members have diverse biological functions, promoting protective immunity against many pathogens but also driving inflammatory pathology during infection and autoimmunity. IL-17A and IL-17F are produced by CD4⁺ and CD8⁺ T cells, γδ T cells, and various innate immune cell populations in response to IL-1β and IL-23, and they mediate protective immunity against fungi and bacteria by promoting neutrophil recruitment, antimicrobial peptide production and enhanced barrier function. IL-17-driven inflammation is normally controlled by regulatory T cells and the anti-inflammatory cytokines IL-10, TGFβ and IL-35. However, if dysregulated, IL-17 responses can promote immunopathology in the context of infection or autoimmunity. Moreover, IL-17 has been implicated in the pathogenesis of many other disorders with an inflammatory basis, including cardiovascular and neurological diseases. Consequently, the IL-17 pathway is now a key drug target in many autoimmune and chronic inflammatory disorders; therapeutic monoclonal antibodies targeting IL-17A, both IL-17A and IL-17F, the IL-17 receptor, or IL-23 are highly effective in some of these diseases. However, new approaches are needed to specifically regulate IL-17-mediated immunopathology in chronic inflammation and autoimmunity without compromising protective immunity to infection.

Regulatory T Cells Contribute to Resistance against Lyme Arthritis

The symptoms of Lyme disease are caused by inflammation induced by species of the Borrelia burgdorferi sensu lato complex. The various presentations of Lyme disease in the population suggest that differences exist in the intensity and regulation of the host response to the spirochete. Previous work has described correlations between the presence of regulatory T cells and recovery from Lyme arthritis. However, the effects of Foxp3-expressing CD4⁺ T cells existing prior to, and during, B. burgdorferi infection have not been well characterized. Here, we used C57BL/6 "depletion of regulatory T cell" mice to assess the effects these cells have on the arthritis-resistant phenotype characteristic of this mouse strain. We showed that depletion of regulatory T cells prior to infection with B. burgdorferi resulted in sustained swelling, as well as histopathological changes, of the tibiotarsal joints that were not observed in infected control mice. Additionally, in vitro stimulation of splenocytes from these regulatory T cell-depleted mice resulted in increases in gamma interferon and interleukin-17 production and decreases in interleukin-10 production that were not evident among splenocytes of infected mice in which Treg cells were not depleted. Depletion of regulatory T cells at various times after infection also induced rapid joint swelling. Collectively, these findings provide evidence that regulatory T cells existing at the time of, and possibly after, B. burgdorferi infection may play an important role in limiting the development of arthritis.

IL-17 Inversely Correlated with IL-10 via the STAT3 Gene in Pneumocystis-Infected Mice

Background

Pneumocystis pneumonia (PCP) remains a common opportunistic infection in immunosuppressed individuals. Current studies showed that multiple immune cells and cytokines took part in the host defense against Pneumocystis (PC). However, the roles of IL-17 and IL-10 in the development of PCP have not been elucidated.

Methods

IL-10 and IL-17 levels in serum from PCP mice were detected via ELISA. The percentages of B10 cells, IL-10⁺ macrophages, and IL-10⁺ T cells in the lung from IL-17^–/– PCP mice and Th17 cells and IL-17⁺γδT cells in IL-10^–/– PCP mice were examined via flow cytometry. Also, antibody neutralization examination was also performed to elucidate the relationship of IL-17 and IL-10 in the PCP model.

Results

We noted the increase of IL-17 and IL-10 levels in serum from mice infected with Pneumocystis. Furthermore, deficiency of IL-17 or IL-10 could lead to the delayed clearance of Pneumocystis and more severed lung damage. Our data also demonstrated that IL-17 deficiency enhanced the serum IL-10 level and the percentages of B10 cells, IL-10⁺ macrophages, and IL-10⁺ T cells in the lung from PCP mice. Interestingly, we also noted an increase of the IL-17 level in serum and Th17 cell and IL-17⁺γδT cell percentages in the lung from IL-10^–/– PCP mice. Using antibody neutralization experiments, we found that the STAT3 gene might play a critical role in the interplay of IL-17 and IL-10 in PCP.

Conclusion

Taken together, our results demonstrated that IL-17 and IL-10 could play the protective roles in the progression of PCP and the inverse correlation of them might be mediated by STAT3.

Postoperative Lyme Arthritis in the Orthopaedic Patient

CONTEXT

Lyme disease is the most common tick-borne illness in North America and Europe, and Lyme arthritis is a frequent late-stage manifestation in the United States. However, Lyme arthritis has rarely been reported as a postoperative complication.

EVIDENCE ACQUISITION

The PubMed database was queried through June 2018, and restricted to the English language, in search of relevant articles.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 3.

RESULTS

A total of 5 cases of Lyme arthritis as a postoperative complication have been reported in the literature.

CONCLUSION

These cases highlight the importance for providers practicing in Lyme-endemic regions to keep such an infection in mind when evaluating postoperative joint pain and swelling. We propose herein an algorithm for the workup of potential postoperative Lyme arthritis.

STRENGTH OF RECOMMENDATION TAXONOMY (SORT)

C.

Anti-arthritic and anti-inflammatory effects of (-)-Epicatechin-3-O-β-d-allopyranoside, a constituent of Davallia formosana

BACKGROUND

(-)-Epicatechin-3-O-β-d-allopyranoside (ECAP) is isolated from the popular Chinese herbal medicine Davallia formosana, which has been used to treat bone diseases including bone fracture, arthritis, and osteoporosis.

PURPOSE

To investigate the antiarthritic and the anti-inflammatory effect of ECAP on a mouse model of collagen-induced arthritis (CIA) and in vitro.

METHODS

Male DBA/1 J mice were immunized by administering an intradermal injection of 100 µg of type II collagen in Freund's complete adjuvant. The control groups (vehicle) and ECAP were administered orally at doses of 1 ml/kg (H₂O), 50 and 100 mg/ml/kg once a day from Day 22 to Day 42 after primary immunization. Paw swelling, arthritis severity score, and histological changes were examined. Enzyme-linked immunosorbent assay was used to measure the levels of cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-10, IL-17, IL-4, and interferon-γ (IFN-γ), in splenocytes. Furthermore, the anti-inflammatory activities of ECAP were investigated in vitro by measuring nitric oxide (NO) levels in lipopolysaccharide (LPS)-activated RAW264.7 macrophages.

RESULTS

In the CIA model, the oral administration of ECAP ameliorated paw edema and reduced the arthritis severity score and disease incidence. Histopathological examination demonstrated that ECAP treatment effectively protected the bone and cartilage of knee joints from erosion, lesion formation, and deformation compared with the vehicle treatment. ECAP also reduced IL-1β and MMP-9 expression in inflamed joints. Compared with the vehicle-treated mice with CIA, the reduced severity of the disease in ECAP-treated mice was associated with decreased levels of TNF-α and IL-17 and increased levels of IL-10 and IL-4 in the supernatants of splenocyte cultures. Flow cytometry analysis demonstrated that ECAP increased the population of CD4⁺CD25⁺ regulatory T cells, thereby inhibiting the B cell population. Anticollagen IgG1 and IgG2a levels decreased in the serum of ECAP-treated mice. ECAP suppressed LPS-induced NO production in RAW264.7 macrophages.

CONCLUSION

The administration of ECAP effectively suppressed inflammation and inflammatory pain and adjuvant-induced arthritis, indicating its therapeutic potential in the treatment of rheumatoid arthritis.

Arthritis is inhibited in Borrelia-primed and infected interleukin-17A-deficient mice after administration of anti-gamma-interferon, anti-tumor necrosis factor alpha and anti-interleukin-6 antibodies

The role that cytokines play in the induction of Lyme arthritis is gradually being delineated. We showed previously that severe arthritis developed in a T-cell-driven murine model, even in mice lacking interleukin-17A (IL-17A) and administered anti-gamma-interferon (IFN-γ) antibody. Increased levels of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), two pro-inflammatory cytokines, were detected in cultures of popliteal lymph node cells obtained from these mice. We hypothesized that concomitantly administered anti-IL-6, anti-TNF-α and anti-IFN-γ antibodies would inhibit the development of arthritis in IL-17A-deficient mice. Our results showed that swelling of the hind paws and histopathological changes consistent with arthritis were significantly reduced in IL-17A-deficient mice that administered the three anti-cytokine antibodies. These results suggest that treatment with multiple anti-cytokine antibodies can abrogate the induction of Lyme arthritis in mice.

Role of human metapneumovirus and respiratory syncytial virus in asthma exacerbations: where are we now?

Since its discovery in 2001, human metapneumovirus (hMPV) has been identified as an important cause of respiratory tract infection in young children, second only to the closely related respiratory syncytial virus (RSV). Clinical evidence suggests that hMPV is associated with acute exacerbations of asthma in both children and adults, and may play a role in initiating asthma development in children. Animal models have demonstrated that airway hyperresponsiveness (AHR) and inflammation are triggered following hMPV infection, and hMPV is able to persist in vivo by inhibiting innate immune responses and causing aberrant adaptive responses. In this review, we discuss the prevalence of hMPV infection in pediatric and adult populations and its potential role in asthma exacerbation. We also review recent advances made in animal models to determine immune responses following hMPV infection, and compare to what is known about RSV.

Borrelia-primed and -infected mice deficient of interleukin-17 develop arthritis after neutralization of gamma-interferon

The immune mechanisms responsible for development of Lyme arthritis are partially understood with interleukin-17 (IL-17) and gamma-interferon (IFN-γ) playing a generally accepted role. Elevated levels of IL-17 and/or IFN-γ have been reported in samples from human Lyme arthritis patients and experimental mice. In addition, IL-17 and IFN-γ have been implicated in the onset of arthritis in Borrelia-primed and -infected C57BL/6 mice. Recently, we showed that IL-17-deficient mice developed swelling and histopathological changes consistent with arthritis in the presence of high levels of IFN-γ. We hypothesized that neutralization of IFN-γ in IL-17-deficient mice would inhibit Borrelia-induced arthritis. Our results, however, showed that swelling of the hind paws and histopathological changes of arthritis did not differ between Borrelia-primed and -infected IL-17-deficient and wild-type mice with or without neutralization of IFN-γ. We also found higher levels of tumor necrosis factor alpha (TNF-α) and IL-6 in the popliteal lymph node cells of Borrelia-primed and -infected IL-17-deficient mice after neutralization of IFN-γ. These results suggest that multiple cytokines interact in the development of Borrelia-induced arthritis.

CD4+ cell-derived interleukin-17 in a model of dysregulated, Borrelia-induced arthritis

Lyme borreliosis, which is caused in the United States by the spirochete Borrelia burgdorferi, may manifest as different arrays of signs, symptoms and severities between infected individuals. Recent studies have indicated that particularly severe forms of Lyme borreliosis in humans are associated with an increased Th17 response. Here, we hypothesized that a murine model combining the dysregulated immune response of an environment lacking interleukin-10 (IL-10) with a robust T-cell-driven inflammatory response would reflect arthritis associated with the production of IL-17 by CD4+ cells. We demonstrate that IL-10 regulates the production of IL-17 by Borrelia-primed CD4+ cells early after interaction with Lyme spirochetes in vitro and that infection of Borrelia-primed mice with B. burgdorferi leads to significant production of IL-17 that contributes to the development of severe arthritis. These results extend our previous findings by demonstrating that a dysregulated adaptive immune response to Lyme spirochetes can contribute to severe, Th17-associated arthritis. These findings may lead to therapeutic measures for individuals with particularly severe symptoms of Lyme borreliosis.

Arthritis is developed in Borrelia-primed and -infected mice deficient of interleukin-17

Interleukin-17 (IL-17) has been shown to participate in the development of Lyme arthritis in experimental mice. For example, neutralization of IL-17 with antibodies inhibits induction of arthritis in Borrelia-primed and -infected C57BL/6 wild-type mice. We hypothesized that mice lacking IL-17 would fail to develop Borrelia-induced arthritis. IL-17-deficient and wild-type C57BL/6 mice were primed with heat-inactivated Borrelia and then infected with viable spirochetes 3 weeks later. No swelling or major histopathological changes of the hind paws were detected in IL-17-deficient or wild-type mice that were primed with Borrelia or infected with viable spirochetes. By contrast, IL-17-deficient and wild-type mice that were primed and subsequently infected with heterologous Borrelia developed severe swelling and histopathological changes of the hind paws. In addition, Borrelia-primed and -infected IL-17-deficient mice exhibited elevated gamma-interferon (IFN-γ) levels in sera and increased frequencies of IFN-γ-expressing lymphocytes in popliteal lymph nodes compared to Borrelia-primed and -infected wild-type mice. These results demonstrate that IL-17 is not required for development of severe pathology in response to infection with Borrelia burgdorferi, but may contribute to disease through an interaction with IFN-γ.

Pristimerin, a naturally occurring triterpenoid, protects against autoimmune arthritis by modulating the cellular and soluble immune mediators of inflammation and tissue damage

Rheumatoid arthritis (RA) is a chronic autoimmune disorder affecting the synovial joints. The currently available drugs for RA are effective only in a proportion of patients and their prolonged use is associated with severe adverse effects. Thus, new anti-arthritic agents are being sought. We tested Pristimerin, a naturally occurring triterpenoid, for its therapeutic activity against rat adjuvant arthritis. Pristimerin effectively inhibited both arthritic inflammation and cartilage and bone damage in the joints. Pristimerin-treated rats exhibited a reduction in the pro-inflammatory cytokines (IL-6, IL-17, IL-18, and IL-23) and the IL-6/IL-17-associated transcription factors (pSTAT3 and ROR-γt), coupled with an increase in the immunomodulatory cytokine IL-10. Also increased was IFN-γ, which can inhibit IL-17 response. In addition, the Th17/Treg ratio was altered in favor of immune suppression and the RANKL/OPG ratio was skewed towards anti-osteoclastogenesis. This is the first report on testing Pristimerin in arthritis. We suggest further evaluation of Pristimerin in RA patients.

Activation of innate immune system in response to lipopolysaccharide in chicken Sertoli cells

Sertoli cells (SCs) play an important physiological role in the testis, as they support, nourish, and protect the germ cells. As protection of the developing spermatozoa is an emerging aspect of reproductive physiology, this study examined the expression pattern of innate immune-related genes, including avian β-defensins (AvBDs), Toll-like receptors (TLRs), and cytokines, and investigated the time course of an inflammatory response in rooster SCs triggered by exposure to the bacterial endotoxin lipopolysaccharide (LPS). SCs were isolated from 6-week-old chicken, culturedin vitro, and stimulated with 1 μg/ml LPS at different time courses (0, 6, 12, 24, and 48 h). Data on expression analysis revealed that all ten members of the chickenTLRfamily, nine members of theAvBDfamily, as well as eight cytokine genes were expressed in SCs. Quantitative real-time PCR analysis revealed that LPS treatment resulted in significant induction of the expression levels of sixTLRs, sixAvBDs, and four cytokine genes, while two cytokine genes were downregulated and two other genes were unchanged. The increasing interleukin 1β (IL1β) production was confirmed in the conditioned medium. Furthermore, the phagocytosis of SCs was increased after LPS treatment. In conclusion, these findings provide evidence that SCs express innate immune-related genes and respond directly to bacterial ligands. These genes represent an important component of the immune system, which could be integrated into semen, and present a distinctive constituent of the protective repertoire of the testis against ascending infections.