Role of Th17 and Treg cells in septic arthritis and the impact of the Th17/Treg -derived cytokines in the pathogenesis of S. aureus induced septic arthritis in mice

Neutralization of TLR2 in combination with either TNF-α or IL-1β antibody reduces the severity of septic arthritis through STAT3/mTOR signalling in lymphocytes

Staphylococcus aureus induced Septic arthritis is considered a medical concern. S.aureus binds TLR2 to induce an array of inflammatory responses. Generation of pro-inflammatory cytokines induces T cell responses and control Th17/Treg cell balance. Regulation of T cell-mediated immunity in response to inflammation is significantly influenced by mTOR. Presence of elevated TNF-α, IL-1β decreases Treg cell activity through STAT3/mTOR, promoting proliferation of T cells towards Th17 cells. Therefore, we postulated, neutralizing TLR2 with either TNF-α or IL-1β in combination could be useful in modifying Th17/Treg cell ratio in order to treat septic arthritis by suppressing expression of mTOR/STAT3. To date, no studies have reported effects of neutralization of TLR2 along with either TNF-α or IL-1β on amelioration of arthritis correlating with mTOR/STAT3 expression. Contribution of T lymphocytes collected from blood, spleen, synovial tissues, their derived cytokines IFN-γ, IL-6, IL-17, TGF-β, IL-10 were noted. Expression of TLR2, TNFR1, TNFR2, NF-κB along with mTOR/STAT3 also recorded. Neutralization of TLR2 along with TNF-α and IL-1β were able to shift Th17 cells into immunosuppressive Treg cells. Furthermore,elevated expression of IL-10, TNFR2 and demoted expression of mTOR/ STAT3 along with NF-κB in lymphocytes confirms its role in resolution of arthritis. It was also effective in reducing oxidative stress via increasing expression of the antioxidant enzymes. As a result, it can be inferred that Treg-derived IL-10, which may mitigate inflammatory effects of septic arthritis by influencing the mTOR/STAT3 interaction in lymphocytes, may be selected as a different therapeutic strategy for reducing the impact of septic arthritis.

Endogenous blocking of TLR2 along with TNF-α and IL-1β ameliorates the severity of the S. aureus arthritis via modulating STAT3/SOCS3 expressions in tissue resident macrophages

In vivo studies identifying a role of TLR2 in septic arthritis models are lacking. TNF-α played as the most important proinflammatory cytokine, and connected directly to the pathogenesis of bacterial arthritis. IL-1β is another central mediator cytokine in arthritis. It is therefore reasonable to question the role of neutralization of endogenous TNF-α and IL-1β along with TLR2 and associated downstream signaling as crucial mediators in the S. aureus -induced inflammatory arthritis. In reaction to an injury or a pathogen encounter, innate immune cells serve as the initial line of defense. TLR2 mediated entry of S. aureus into macrophage cells initiates an array of inflammatory cascades. After macrophage cell gets activated at the site inflammation, they generate elevated number of cytokines which includes TNF-α, IL-1β. This cytokines signals through STAT1/STAT3 mediated pathways. Thus, aim of this study was to discover how This bone damage could be altered by altering the STAT/STAT3/SOCS3 ratio by blocking TLR2, a particular S. aureus binding site, in conjunction with the use of IL-1 and TNF- antibodies for neutralizing endogenous IL-1β and TNF-α. Additionally, the role of local macrophages in therapy of arthritis was investigated in synovial and Splenic tissue. To comprehend the inflammatory milieu within the system, ROS and other antioxidant enzymes, along with the expression of mTOR in macrophage cells, were also taken into consideration. The detrimental impact of bacterial burden on synovial joints was reduced by simultaneously inhibiting TLR2, TNF-α, and IL-1β. Lowered IFN-γ decreases its sensitivity to STAT1 and lowered IL-6 reduces STAT3 expressions. Whereas, elevated IL-10 enhances SOSC3 expression, which thereby able to limits STAT1/STAT3 inter-conversion. As a result, NF-κB activity was downregulated.

Simultaneous neutralization of TGF-β and IL-6 attenuates Staphylococcus aureus-induced arthritic inflammation through differential modulation of splenic and synovial macrophages

Septic arthritis is a joint disease caused by Staphylococcus aureus. Different macrophage populations contribute in various ways to control blood-borne infections and induce inflammatory responses. Macrophage tissue-resident niche is necessary for the suppression of chronic inflammation and may contribute to the pathogenesis of septic arthritis. Thus, to obtain a resolution of the disease and restoration of synovial homeostasis, it needs the activation of macrophages that further regulate the inflammatory consequences. The aim of this study was to find out the mechanism by which neutralization of transforming growth factor-beta (TGF-β) and/or interleukin (IL)-6 after induction of septic arthritis could alter the specific macrophage responses in spleen and synovial joints via different cytokines (osteoprotegerin (OPG), osteopontin (OPN), IL-10, IL-12 and CXCL8) cross-talking, and how the response could be modulated by reactive oxygen species vs antioxidant enzyme activities. Dual neutralization of TGF-β and IL-6 is notably effective in eliciting splenic and synovial tissue-resident macrophage responses. Synovial macrophage-derived IL-10 can elicit protection against septic arthritis via regulating receptor-activated nuclear factor Kappa-B ligand (RANKL)/OPG interaction. They also reduced oxidative stress by increasing the activity of antioxidant enzymes including SOD and catalase. Histopathological analysis revealed that dual neutralization of TGF-β and IL-6 prevented bone destruction and osteoclastic activity in septic arthritis by promoting the differential functional response of the splenic and synovial macrophages. Additionally, the macrophage-derived IL-10 can elicit protection against S. aureus-induced septic arthritis via regulating RANKL/OPG interaction. Further studies on STAT3 and STAT4 are needed for the understanding of such cross-talking in resident macrophages of arthritic mice.

Exploring the Role of Staphylococcus aureus in Inflammatory Diseases

Staphylococcus aureus is a very common Gram-positive bacterium, and S. aureus infections play an extremely important role in a variety of diseases. This paper describes the types of virulence factors involved, the inflammatory cells activated, the process of host cell death, and the associated diseases caused by S. aureus. S. aureus can secrete a variety of enterotoxins and other toxins to trigger inflammatory responses and activate inflammatory cells, such as keratinocytes, helper T cells, innate lymphoid cells, macrophages, dendritic cells, mast cells, neutrophils, eosinophils, and basophils. Activated inflammatory cells can express various cytokines and induce an inflammatory response. S. aureus can also induce host cell death through pyroptosis, apoptosis, necroptosis, autophagy, etc. This article discusses S. aureus and MRSA (methicillin-resistant S. aureus) in atopic dermatitis, psoriasis, pulmonary cystic fibrosis, allergic asthma, food poisoning, sarcoidosis, multiple sclerosis, and osteomyelitis. Summarizing the pathogenic mechanism of Staphylococcus aureus provides a basis for the targeted treatment of Staphylococcus aureus infection.

Transcriptome Architecture of Osteoblastic Cells Infected With Staphylococcus aureus Reveals Strong Inflammatory Responses and Signatures of Metabolic and Epigenetic Dysregulation

Staphylococcus aureus is an opportunistic pathogen that causes a range of devastating diseases including chronic osteomyelitis, which partially relies on the internalization and persistence of S. aureus in osteoblasts. The identification of the mechanisms of the osteoblast response to intracellular S. aureus is thus crucial to improve the knowledge of this infectious pathology. Since the signal from specifically infected bacteria-bearing cells is diluted and the results are confounded by bystander effects of uninfected cells, we developed a novel model of long-term infection. Using a flow cytometric approach we isolated only S. aureus-bearing cells from mixed populations that allows to identify signals specific to intracellular infection. Here we present an in-depth analysis of the effect of long-term S. aureus infection on the transcriptional program of human osteoblast-like cells. After RNA-seq and KEGG and Reactome pathway enrichment analysis, the remodeled transcriptomic profile of infected cells revealed exacerbated immune and inflammatory responses, as well as metabolic dysregulations that likely influence the intracellular life of bacteria. Numerous genes encoding epigenetic regulators were downregulated. The later included genes coding for components of chromatin-repressive complexes (e.g., NuRD, BAHD1 and PRC1) and epifactors involved in DNA methylation. Sets of genes encoding proteins of cell adhesion or neurotransmission were also deregulated. Our results suggest that intracellular S. aureus infection has a long-term impact on the genome and epigenome of host cells, which may exert patho-physiological dysfunctions additionally to the defense response during the infection process. Overall, these results not only improve our conceptual understanding of biological processes involved in the long-term S. aureus infections of osteoblast-like cells, but also provide an atlas of deregulated host genes and biological pathways and identify novel markers and potential candidates for prophylactic and therapeutic approaches.

Effect of prophylactic vitamin C administration on the efficiency of florfenicol or sulfadiazine-trimethoprim antimicrobial therapy in chickens with staphylococcal arthritis

Septic arthritis (SA) in chickens shows improper response to antibacterial therapy. This study evaluates the effect of prophylactic vitamin C administration on the efficiency of sulfadiazine-trimethoprim (SDT) or florfenicol (FF) in broilers with experimental SA. Broilers (210) were randomly allocated into 7 equal groups: (I) negative control (NC) (normal birds); (II) positive control (PC) arthritic birds by injection of Staphylococcus aureus in tibiotarsal joint at the age of 35 days; (III) vehicle control (injected with sterile medium); (IV) arthritic FF-treated (20 mg/kg/day); (V) arthritic vitamin C + FF-treated (as above + vitamin C at 15 g/100L of D.W. from day 25 of age); (VI) arthritic SDT-treated (35 mg/kg/day); (VII) arthritic vitamin C + SDT-treated. Antibacterial therapy started at day 39 of age and lasted for 5 days. Samplings were performed at the age of 44 and 54 days. A long lasting SA with severe fibrinoheterophilic synovitis and reduced body weights developed in PC broilers as compared to NC group (p < 0.05). Oxidative stress was present at sampling 1. Arthritis was not reflected in IL-6 levels of synovial fluid of PC group. None of the antibacterials resulted in completely successful treatment. Vitamin C did not appreciably improve lameness and arthritis scores, although it decreased lipid peroxidation and improved weights of FF treated-arthritic birds. For SDT-treated birds, vitamin C only ameliorated histopathological changes. In conclusion, except for improving body weight in FF-treated birds, prophylactic administration of vitamin C is not associated with improvements in clinical outcome of antimicrobial therapy of broilers with SA, although it ameliorates oxidative stress and some histopathological changes.

Bortezomib alleviates antibody-mediated rejection in kidney transplantation by facilitating Atg5 expression

Antibody‐mediated rejection (AMR) is one of the most dominant mechanisms responsible for the loss of kidney grafts. Previous researches have shown that donor‐specific antibodies (DSAs) are the major mediators of AMR. In order to prolong the survival time of grafts, it is vital to reduce the incidence of AMR and inhibit the generation of DSAs. We established an animal model of AMR by performing kidney transplantation in pre‐sensitized rats. Then, we investigated the effect of bortezomib (BTZ) on AMR. We found that BTZ could reduce the serum level of DSAs and alleviate post‐transplantation inflammation in peritubular capillaries (PTCs) and glomeruli, which was demonstrated by the reduction of C4d and IgG deposition in PTCs, and the reduced number of B cell and plasma cell in peripheral blood and the transplanted kidney (p < 0.05). Our results also suggested that BTZ increased the number of regulatory T cell (Treg) and significantly reduced the proportion of T helper (Th17) cell (p < 0.05). Besides, BTZ induced the significant upregulation of anti‐inflammatory cytokines but downregulated pro‐inflammatory cytokines (p < 0.05). After dealing with Atg5 siRNA‐lentivirus, the effect of BTZ alleviating AMR was reversed and Th17/Treg proportions were also significantly modulated. Collectively, these findings show that BTZ slows down the process of AMR and Atg5 may be the key mechanism. Furthermore, Atg5 silencing results may be demonstrated that Atg5 alleviated AMR by modulating the ratio of Th17/Treg.

Systemic and Local Cytokines Profile Determine Severity and Prognosis in Human Septic Arthritis: A Pilot Study

BACKGROUND

Septic arthritis (SA) is a medical emergency. The most common etiological agents are bacteria, which activate the local immune response coordinated by cytokines; however, little is known about the cytokine profile in human SA.

AIM

To determine the association of local and systemic cytokine profiles with the severity and prognosis of patients with SA.

METHODS

Patients with clinical and laboratory diagnosed SA were enrolled as well as a control group. Serum and synovial fluid (SF) samples were obtained for determining cytokines and glucose levels; SF samples were used for histological analysis. Osteochondral damage and general health status and quality of life (SF-36) were evaluated during recruitment day. WOMAC osteoarthritis index score and SF-36 questionnaire were used a year after recruitment day as a follow up.

RESULTS

A systemic and local proinflammatory cytokine profile was found in patients compared to the control group (p <0.05). IL-6 was 28 and 525 times higher than controls in sera and SF, respectively (p <0.0001). Systemic IL-6 correlated negatively with general mental health score (p = 0.0184) and was associated with a higher osteoarthritis index after one year follow-up in the patients (p = 0.0352). HMGB1 in SF was found higher in patients with SA (p <0.0001), and it was associated with osteochondral damage (p = 0.0042). TNF-α in SF correlated negatively with SF-36 questionnaire one year after patients' recruitment in role limitation score (p = 0.0318), body pain score (p = 0.0315), and general mental health score (p = 0.0197).

CONCLUSION

Serum and SF cytokine signatures are associated with disease severity and prognosis in patients with SA.

Neutralization of IL-17 and treatment with IL-2 protects septic arthritis by regulating free radical production and antioxidant enzymes in Th17 and Tregs: An immunomodulatory TLR2 versus TNFR response

Septic arthritis is a destructive joint disease caused by Staphylococcus aureus. Synovial inflammation involved Th17 proliferation and down regulation of Treg population, thus resolution of inflammation targeting IL-17 may be important to control arthritis. Endogenous inhibition of IL-17 to regulate arthritic inflammation correlating with Th17/Treg cells TLR2 and TNFRs are not done. The role of SOD, CAT and GRx in relation to ROS production during arthritis along with expression of TLR2, TNFR1/TNFR2 in Th17/Treg cells of mice treated with IL-17A Ab/ IL-2 were studied. Increased ROS, reduced antioxidant enzyme activity was found in Th17 cells of SA infected mice whereas Treg cells of IL-17A Ab/ IL-2 treated group showed opposite effects. Neutralization of IL-17 after arthritis cause decreased TNFR1 and increased TNFR2 expression in Treg cells. Thus, neutralization of IL-17 or IL-2 treatment regulates septic arthritis by enhancing anti-inflammatory properties of Treg via antioxidant balance and modulating TLR2/TNFR response.

MiR-206 regulates the Th17/Treg ratio during osteoarthritis

BACKGROUND

The present study aimed to determine the functional role of miR-206 in T helper 17 (Th17)/regulatory T (Treg) cell differentiation during the development of osteoarthritis (OA).

METHODS

Patients with OA and healthy controls were recruited for investigating the association between miR-206 and Th17/Treg ratio. Transfection experiments were conducted in CD4⁺ T cells to verify the mechanism of miR-206 on the balance of Treg/Th17. OA model was constructed to detect the clinical score, histopathological changes and Treg/Th17 ratio. OA model was induced in rats to verify the effect of miR-206 inhibition on Th17/Treg immunoregulation.

RESULTS

High expression of miR-206 was positively correlated with peripheral Th17/Treg imbalance in patients with OA. The interactions between miR-206 and the 3' untranslated regions (3'-UTR) of suppressor of cytokine signaling-3 (SOCS3) and fork head transcriptional factor 3 (Foxp3) were confirmed by luciferase reporter assays. MiR-206 disturbed the Th17/Treg balance by targeting SOCS3 and Foxp3. In vivo assay demonstrated that antagomiR directed against miR-206 restored Th17/Treg balance during the development of OA.

CONCLUSION

MiR-206 contributed to the progression of OA by modulating Th17/Treg imbalance, suggesting that miR-206 inhibition might be a promising therapeutic strategy for the treatment of OA.

C-reactive protein predicts complications in community-associated S. aureus bacteraemia: a cohort study

Background

Staphylococcus aureus (S. aureus) bacteraemia is increasingly acquired from community settings and is associated with a mortality rate of up to 40% following complications. Identifying risk factors for complicated S. aureus bacteraemia would aid clinicians in targeting patients that benefit from expedited investigations and escalated care.

Methods

In this prospective observational cohort study, we aimed to identify risk factors associated with a complicated infection in community-onset S. aureus bacteraemia. Potential risk factors were collected from electronic medical records and included: - patient demographics, symptomology, portal of entry, and laboratory results.

Results

We identified several potential risk factors using univariate analysis. In a multiple logistic regression model, age, haemodialysis, and entry point from a diabetic foot ulcer were all significantly protective against complications. Conversely, an unknown entry point of infection, an entry point from an indwelling medical device, and a C-reactive protein concentration of over 161 mg/L on the day of admission were all significantly associated with complications.

Conclusions

We conclude that several factors are associated with complications including already conducted laboratory investigations and portal of entry of infection. These factors could aid the triage of at-risk patients for complications of S. aureus bacteraemia.

T Cell Protein Tyrosine Phosphatase in Osteoimmunology

Osteoimmunology highlights the two-way communication between bone and immune cells. T cell protein tyrosine phosphatase (TCPTP), also known as protein-tyrosine phosphatase non-receptor 2 (PTPN2), is an intracellular protein tyrosine phosphatase (PTP) essential in regulating immune responses and bone metabolism via dephosphorylating target proteins. Tcptp knockout in systemic or specific immune cells can seriously damage the immune function, resulting in bone metabolism disorders. This review provided fresh insights into the potential role of TCPTP in osteoimmunology. Overall, the regulation of osteoimmunology by TCPTP is extremely complicated. TCPTP negatively regulates macrophages activation and inflammatory factors secretion to inhibit bone resorption. TCPTP regulates T lymphocytes differentiation and T lymphocytes-related cytokines signaling to maintain bone homeostasis. TCPTP is also expected to regulate bone metabolism by targeting B lymphocytes under certain time and conditions. This review offers a comprehensive update on the roles of TCPTP in osteoimmunology, which can be a promising target for the prevention and treatment of inflammatory bone loss.

Staphylococcus aureus Protein A Induces Human Regulatory T Cells Through Interaction With Antigen-Presenting Cells

Despite continuous exposure and development of specific immunity, Staphylococcus aureus (Sa) remains one of the leading causes of severe infections worldwide. Although innate immune defense mechanisms are well understood, the role of the T cell response has not been fully elucidated. Here, we demonstrate that Sa and one of its major virulence factors protein A (SpA) induce human regulatory T cells (Tregs), key players in immune tolerance. In human PBMC and MoDC/T cell cocultures CD4⁺CD25⁺CD127^dim Tregs were induced upon stimulation with Sa and to a lower extent with SpA alone. Treg induction was strongly, but not exclusively, dependent on SpA, and independent of antigen presentation or T cell epitope recognition. Lastly, soluble factors in the supernatant of SpA-stimulated MoDC were sufficient to trigger Treg formation, while supernatants of MoDC/T cell cocultures containing Sa-triggered Tregs displayed T cell suppressive activity. In summary, our findings identify a new immunosuppressory function of SpA, which leads to release of soluble, Treg-inducing factors and might be relevant to establish colonization.

Role of different Th17 and Treg downstream signalling pathways in the pathogenesis of Staphylococcus aureus infection induced septic arthritis in mice

Septic arthritis is a condition of bone disorder caused predominantly by Staphylococcus aureus. Following the bacterial entry activated immune cells specially macrophages and dendritic cells release pro-inflammatory mediators such as IL-6, TNF-α, IL-1β etc., which not only create an inflammatory microenvironment but also play crucial roles in the proliferation of different CD+ T cell subsets. Among them, Th17 and Tregs are of major concern in recent times because of their potential roles in regulating the ongoing inflammation in many diseases including experimental arthritis. But the downstream signalling mechanism of these cells in regulating the severity of inflammation in case of septic arthritis is not known yet. So, here we have established a murine model of S. aureus induced septic arthritis and kept the animal upto 15 days post-infection. To examine the signalling mechanism, Th17 and Treg cells were isolated from blood, spleen and synovial joints of control and infected mice and observed the expression of JNK, NFκB and RANKL in the lysate of isolated Th17 and Tregs. We have also estimated the levels of serum IL-21 and TGF-β. NFκB, JNK and RANKL expression was found to be higher at 3 and 15 days post-infection along with serum IL-21 levels. On the other hand, maximum TGF-β level was observed at 9 days post-infection along with increased Treg population. In conclusion it was hypothesized that bone resorption is related with downstream signalling pathways of Th17 cells, which stimulate osteoclast generation via NFκB/JNK-RANKL axis and helps in the persistence of the disease.

Impact of simultaneous neutralization of IL-17A and treatment with recombinant IL-2 on Th17-Treg cell population in S.aureus induced septic arthritis

The contribution of Th17 and Treg in the pathogenesis of septic arthritis is well known. The imbalance of Th17/Treg ratio, especially the skewed CD4⁺ T cell differentiation towards pathogenic Th17 lineage is a major reason that mediates bone damage through one of its prime cytokine member IL-17A. The neutralization of released IL-17A, as well as exogenous administration of IL-2 at a lower dose, was seen to be potent in dampening the inflammatory response in many cases. Interestingly the effect of IL-17A neutralization to limit IL-17 mediated inflammation and induction of Tregs by the administration of IL-2 has not been studied in experimental arthritis. So in this study, we have treated arthritic mice with IL-17A Ab and recombinant mouse IL-2 either alone or in combination at 3, 9 and 15 days post-infection. We have found a marked decrease in Th17 cell population and their related pro-inflammatory cytokine levels at 15DPI in arthritic mice after IL-17 neutralization. An increased Treg cell population was also observed in mice after application of rIL-2 with a significantly heightened TGF-β level in serum and synovial joints compared to the untreated one. However, in the case of combination therapy of IL-17A Ab and rIL-2 we have observed a beneficial effect in ameliorating the disease outcome as the arthritic index was decreased maximally at 15DPI with a significant reduction of arthritis compared to individual treatment. Overall the inflammatory microenvironment was counterbalanced most effectively in combination treatment by lowering the Th17/Treg ratio and their related cytokines that resulted in reducing the immunopathogenesis of the destructive arthritis.