Investigating the role of NF-kappaB in the pathology of osteoarthritis

Globally the most prevalent muscoskeletal condition affecting humans, osteoarthritis is a complex, multifactorial disease characterised by deterioration of articular cartilage and varying degrees of synovial inflammation. The catabolic cytokine interleukin-1beta (IL-1beta), a potent inducer of the transcription factor NFkappaB, induces the production of cartilage destructive aggrecanases and matrix metalloproteinases (MMPs) and the inflammatory cytokine, interleukin-6 (IL-6), within the joint. The aim of the work described in this thesis was to investigate the role of NFkappaB within the osteoarthritic joint and its potential as a therapeutic target for disease intervention. NFkappaB activation was inhibited using adenoviral gene transfer or by two novel pharmacological inhibitors of IKK, R0100 and R0919. Inhibition of the NFkappaB signalling cascade in human synovial fibroblasts from osteoarthritic patients suppressed the IL-1beta induction of IL-6, MMP-1 and MMP-3 but did not affect the levels of tissue inhibitor of metalloproteinases-1 (TIMP-1). To further investigate the effects of these IKK inhibitors, cartilage degradation was investigated by culturing murine patellas with human synovial fibroblasts. Early stage cartilage deterioration, induced by IL-1beta, was prevented by NFkappaB inhibition. An animal model of OA, that reflected the early stage pathological changes, was set up as part of this study. The therapeutic efficacy of RO100 and R0919 was tested in vivo. It was observed that neither inhibitor prevented pathological changes associated with OA, for example cartilage degradation. The basis of the lack of efficacy demonstrated by RO100 and R0919 is unknown but may be due to poor bioavailability of the agents within the joint. In conclusion, the studies conducted during this thesis have shown, in various systems, that inhibiting NFkappaB can prevent changes such as cartilage degradation that occur in OA. Increasing the bioavailability of these or other inhibitors of NFkappaB may be key in the development of successful novel therapeutic modalities in the future

A distinct chemokine axis does not account for enrichment of Foxp3+ CD4+T cells in carcinogen-induced fibrosarcomas

The frequency of CD4+ Foxp3+ regulatory T (Treg) cells is often significantly increased in the blood of tumour-bearing mice and people with cancer. Moreover, Treg cell frequencies are often higher in tumours compared with blood and lymphoid organs. We wished to determine whether certain chemokines expressed within the tumour mass selectively recruit Treg cells, thereby contributing to their enrichment within the tumourinfiltrating lymphocyte pool. To achieve this goal, the chemokine profile of carcinogen-induced fibrosarcomas was determined, and the chemokine receptor expression profiles of both CD4+ Foxp3 � and CD4+ Foxp3+ T cells were compared. These analyses revealed that the tumours are characterized by expression of inflammatory chemokines (CCL2, CCL5, CCL7, CCL8, CCL12, CXCL9, CXCL10 and CX3CL1), reflected by an enrichment of activated Foxp3 � and Foxp3+ T cells expressing T helper type 1- associated chemokine receptors. Notably, we found that CXCR3+ T cells were significantly enriched in the tumours although curiously we found no evidence that CXCR3 was required for their recruitment. Instead, CXCR3 marks a population of activated Foxp3 � and Foxp3+ T cells, which use multiple and overlapping ligand receptor pairs to guide their migration to tumours. Collectively, these data indicate that enrichment of Foxp3+ cells in tumours characterized by expression of inflammatory chemokines, does not occur via a distinct chemokine axis, thus selective chemokine blockade is unlikely to represent a meaningful therapeutic strategy for preventing Treg cell accumulation in tumours

Enhanced antitumor immunity through sequential targeting of PI3Kδ and LAG3

Background Despite striking successes, immunotherapies aimed at increasing cancer-specific T cell responses are unsuccessful in most patients with cancer. Inactivating regulatory T cells (Treg) by inhibiting the PI3Kδ signaling enzyme has shown promise in preclinical models of tumor immunity and is currently being tested in early phase clinical trials in solid tumors. Methods Mice bearing 4T1 mammary tumors were orally administered a PI3Kδ inhibitor (PI-3065) daily and tumor growth, survival and T cell infiltrate were analyzed in the tumor microenvironment. A second treatment schedule comprised PI3Kδ inhibitor with anti-LAG3 antibodies administered sequentially 10 days later. Results As observed in human immunotherapy trials with other agents, immunomodulation by PI3Kδ-blockade led to 4T1 tumor regressor and non-regressor mice. Tumor infiltrating T cells in regressors were metabolically fitter than those in non-regressors, with significant enrichments of antigen-specific CD8+ T cells, T cell factor 1 (TCF1)+ T cells and CD69− T cells, compatible with induction of a sustained tumor-specific T cell response. Treg numbers were significantly reduced in both regressor and non-regressor tumors compared with untreated tumors. The remaining Treg in non-regressor tumors were however significantly enriched with cells expressing the coinhibitory receptor LAG3, compared with Treg in regressor and untreated tumors. This striking difference prompted us to sequentially block PI3Kδ and LAG3. This combination enabled successful therapy of all mice, demonstrating the functional importance of LAG3 in non-regression of tumors on PI3Kδ inhibition therapy. Follow-up studies, performed using additional cancer cell lines, namely MC38 and CT26, indicated that a partial initial response to PI3Kδ inhibition is an essential prerequisite to a sequential therapeutic benefit of anti-LAG3 antibodies. Conclusions These data indicate that LAG3 is a key bottleneck to successful PI3Kδ-targeted immunotherapy and provide a rationale for combining PI3Kδ/LAG3 blockade in future clinical studies

Interleukin-6 limits influenza-induced inflammation and protects against fatal lung pathology

Balancing the generation of immune responses capable of controlling virus replication with those causing immunopathology is critical for the survival of the host and resolution of influenza-induced inflammation. Based on the capacity of interleukin-6 (IL-6) to govern both optimal T-cell responses and inflammatory resolution, we hypothesised that IL-6 plays an important role in maintaining this balance. Comparison of innate and adaptive immune responses in influenza-infected wild-type control and IL-6-deficient mice revealed striking differences in virus clearance, lung immunopathology and generation of heterosubtypic immunity. Mice lacking IL-6 displayed a profound defect in their ability to mount an anti-viral T-cell response. Failure to adequately control virus was further associated with an enhanced infiltration of inflammatory monocytes into the lung and an elevated production of the pro-inflammatory cytokines, IFN-α and TNF-α. These events were associated with severe lung damage, characterised by profound vascular leakage and death. Our data highlight an essential role for IL-6 in orchestrating anti-viral immunity through an ability to limit inflammation, promote protective adaptive immune responses and prevent fatal immunopathology

Interferon gamma decreases interleukin 1 beta-mediated cartilage loss in rheumatoid arthritis [Abstract]

Introduction: The first few months after symptom onset represents a pathologically distinct phase in rheumatoid arthritis (RA). We used relevant experimental models to define the pathological role of interferon-γ (IFN-γ) during early inflammatory arthritis. Methods: We studied IFN-γ's capacity to modulate interleukin-1β (IL-1β) induced degenerative responses using RA fibroblast-like synoviocytes (FLS), a bovine articular cartilage explant (BACE)/RA-FLS co-culture model and an experimental inflammatory arthritis model (murine antigen-induced arthritis (AIA)). Results: IFN-γ modulated IL-1β driven matrix metalloproteinases (MMP) synthesis resulting in the down-regulation of MMP-1 and MMP-3 production in vitro. IFN-γ did not affect IL-1β induced tissue inhibitor of metalloproteinase-1 (TIMP-1) production by RA FLS but skewed the MMP/TIMP-1 balance sufficiently to attenuate glycosaminoglycan-depletion in our BACE model. IFN-γ reduced IL-1β expression in the arthritic joint and prevented cartilage degeneration on Day 3 of AIA. Conclusions: Early therapeutic intervention with IFN-γ may be critical to orchestrate tissue-protective responses during inflammatory arthritis

Type I interferon (IFNα) acts directly on human memory CD4+ T cells altering their response to antigen

Despite its use widely as a therapeutic agent, and proposed use as vaccine adjuvant, the effect of IFNα on T cell function is poorly understood. As a pleiotropic innate cytokine produced rapidly in response to pathogens, it is well placed to impinge on specific immune responses. The aim of this study was to examine the impact of IFNα on the function of human memory CD4+ T cells using the recall Ags purified protein derivative, tetanus toxoid, and hemagglutinin. IFNα administered either in vivo or added exogenously in vitro tended to enhance proliferative responses of purified protein derivative-specific T cells in marked contrast to the other cognate populations whose responses were often diminished. Purifying the memory CD4+CD45RO+ T cells confirmed IFNα acted directly on these cells and not via an intermediate. The T cells could be divided into two broad categories depending on how IFNα effected their responses to cognate Ag: 1) enhanced proliferation and a striking increase in IFNγ-production compared with smaller increases in IL-10 (increased ratio of IFNγ:IL-10), and 2) neutral or diminished proliferation coupled with a smaller increase in IFNγ relative to the increase in IL-10 (reduced IFNγ:IL-10 ratio). IFNα has a role in modifying memory T cell responses when they are exposed to cognate Ag and may be important in vaccination strategies designed to augment particular Th memory responses

Adenoviral gene transfer of the endogenous inhibitor IkappaBalpha into human osteoarthritis synovial fibroblasts demonstrates that several matrix metalloproteinases and aggrecanases are nuclear factor-kappaB-dependent

OBJECTIVE: To investigate the role of the transcription factor nuclear factor-kB (NF-kappaB) in promoting inflammatory and destructive responses in human osteoarthritis (OA) synovial fibroblasts, by assessing the effect of NF-kappaB blockade on the production of cytokines and destructive enzymes. METHODS: Infection with adenoviruses transferring the beta-galactosidase gene was used to ascertain that the OA fibroblasts could be infected (> 95%). Using an adenovirus transferring the inhibitory subunit IkappaBa, effective inhibition of NF-kappaB was achieved. The expression and production of several pro- and antiinflammatory cytokines and mediators, the major matrix metalloproteinases (MMP 1, 3, and 13), their main inhibitor tissue inhibitor of metalloproteinase-1 (TIMP-1), and the aggrecanases (ADAMTS4 and ADAMTS5) were measured by ELISA and/or reverse transcription-polymerase chain reaction, and their dependence on NF-kappaB evaluated. RESULTS: The production of interleukin 6 (IL-6), monocyte chemoattractant protein-1, and RANTES was potently inhibited by IkBa overexpression, irrespective of stimulus, but IL-8 was unaffected. The p55 soluble tumor necrosis factor (TNF) receptor was unaffected, but the p75 soluble TNF receptor was potently inhibited by IkBa overexpression. MMP-1, MMP-3, and MMP-13 were inhibited by IkappaBa overexpression, at both the mRNA and protein levels, whereas TIMP-1 was unaffected. The mRNA gene expression of ADAMTS4 was also inhibited by IkappaBa overexpression, particularly in IL-1-stimulated cells, but ADAMTS5 was unaffected. CONCLUSION: In OA synovial fibroblasts, inhibition of NF-kappaB has a beneficial effect on the balance between the expression of proinflammatory cytokines and antiinflammatory mediators. Inhibition of this transcription factor also results in the decreased expression of several destructive metalloproteinases and also the ADAMTS4 aggrecanase

Analysis of the T-cell receptor repertoires of tumor-infiltrating conventional and regulatory T cells reveals no evidence for conversion in carcinogen-induced tumors

A significant enrichment of CD4+Foxp3+ T cells (regulatory T cells, Treg) is frequently observed in murine and human carcinomas. As Tregs can limit effective antitumor immune responses, thereby promoting tumor progression, it is important that the mechanisms underpinning intratumoral accumulation of Tregs are identified. Because of evidence gathered mostly in vitro, the conversion of conventional T cells (Tconv) into Tregs has been proposed as one such mechanism. We assessed the contribution of conversion in vivo by analyzing the TCR (T-cell receptor) repertoires of Tconvs and Tregs in carcinogen-induced tumors in mice. Our results indicate that the TCR repertoires of Tregs and Tconvs within tumor-infiltrating lymphocytes (TIL) are largely distinct. Indeed, the cell population with the greatest degree of repertoire similarity with tumor-infiltrating Tregs was the Treg population from the tumor-draining lymph node. These findings demonstrate that conversion of Tconvs does not contribute significantly to the accumulation of tumor-infiltrating Tregs; rather, Tconvs and Tregs arise from different populations with unique TCR repertoires. Enrichment of Tregs within TILs most likely, therefore, reflects differences in the way that Tregs and Tconvs are influenced by the tumor microenvironment. Elucidating the nature of these influences may indicate how the balance between tumor-infiltrating Tregs and Tconvs can be manipulated for therapeutic purposes