Omega-3 fatty acids (ω-3 FA, including eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]), are essential polyunsaturated fatty acids which are correlated with lower incidence of chronic diseases. DHA and EPA can be enzymatically converted to resolvins, protectins and maresins, which play important roles in resolution of inflammation. Additionally, ω-3 FA can also directly activate surface receptors, namely the long-chain free fatty acid receptors GPR40 and GPR120, two GPCRs with poorly investigated biology. Using real-time PCR analysis, GPR40 transcript in human neutrophils was detected; the protein expression was also confirmed by flow cytometry and image stream analysis. Expression of GPR40 protein was up-regulated after stimulation with platelet-activating factor (PAF, 10nM) or leukotriene B4 (LTB4, 10nM) for 10 minutes. I utilised the selective agonist GW9508 to investigate the biology of GPR40. Tested on human neutrophils, GW9508 elevated intracellular calcium when applied within the 0.1-10μM range. The up-regulation of GPR40 expression by pro-inflammatory stimuli suggested to us potential regulatory roles for this receptor during inflammation. I then showed that 1 and 10μM GW9508 increased neutrophil chemotaxis in response to the cytokine IL-8 (30ng/ml). In addition, GPR40 activation by GW9508 enhanced phagocytosis of E. coli by human neutrophils by approximately 50% when tested at 0.1 and 1μM. Moreover, GW9508-neutrophil stimulation augmented microvesicle release and delayed apoptosis after stimulation. Finally, I demonstrated that GPR40 is expressed in inflammatory cells isolated from murine arthritic joints, such as neutrophils, macrophages and inflammatory monocytes. KBN-serum induced arthritic mice developed a more severe disease when treated prophylactically with GW9508 (10mg/kg, i.p. treated from day 0, daily), characterized by a higher clinical score and increased oedema when compared to vehicle control mice. Therapeutic intervention with GW9508 at the peak of the disease (day 5) delayed the resolution of arthritis. In summary, the data suggest that activation of GPR40 by GW9508 enhances neutrophil activation, up regulating the pro-inflammatory properties of this cell type, and therefore, exacerbating experimental inflammatory arthritis.

Current therapies for chronic inflammatory diseases often abrogate the immune functions required to fight infections. Human cathelicidin host defence peptide (HDP) LL-37 selectively suppresses pathogen-induced inflammation, without compromising resistance to infections. These unique dual abilities of LL-37 make it a promising candidate as an alternative therapeutic for treating chronic inflammatory diseases. The objective of this study was to investigate the effects of LL-37 and its derivative peptide IG-19 in cytokine-mediated inflammation. I demonstrated that LL-37 and IG-19 selectively suppressed cytokine IL-32γ-induced pro-inflammatory cytokines, without compromising the production of anti-inflammatory cytokines, and chemokines in human PBMC and macrophages. However, significant quantitative differences between LL-37 and IG-19-mediated chemokine productions suggested that the mechanisms underlying the activity of these two peptides were different. I showed that both peptides suppressed IL-32γ-mediated phosphorylation of the Src-kinase FYN(Y420), known to enhance inflammation. Contrastingly, phosphorylation of the dual phosphatase MKP-1(S359), a negative regulator of inflammation, was enhanced in response to both peptides. Similarly, both peptides increased the activity of p44/42MAPK, which phosphorylates and stabilizes MKP-1. These results suggested that MKP-1 may be a critical mediator of the immunomodulatory activity of these peptides. Bioinformatic interrogation revealed that direct interacting protein partners of MKP-1 were overrepresented in MAPK and NF-κB signalling pathways. Both peptides enhanced the phosphorylation of p38MAPK. However, contrasting to LL-37, IG-19 did not mediate the phosphorylation of JNK MAPK and IKK-α signaling intermediates involved in inflammation. This was consistent with observations that chemokine production was significantly lower in response to IG-19 compared to LL-37. These results suggested that IG-19 may be a better immunomodulatory therapeutic candidate compared to LL-37. As cytokine-mediated inflammation plays critical roles in the disease pathogenesis of inflammatory arthritis, I examined the effects of exogenous administration of IG-19 in a murine model of collagen-induced arthritis. Administration of IG-19 decreased disease severity, suppressed pro-inflammatory cytokines and anti-collagen antibodies, and mitigated cartilage destruction in the CIA mice. These results provide a rationale to further develop IG-19 as a therapeutic agent for chronic inflammatory arthritis. The advantage of HDP based therapy is the potential to control inflammation without compromising the patient’s ability to resolve infections. / May 2017

Background: Presenteeism is an economic concept that is difficult to identify, measure, and value. Rheumatoid arthritis (RA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA) are three chronic auto-immune conditions that increase levels of presenteeism. Workplace interventions (WPIs) help individuals to manage their health condition at work. Existing methods used to quantify the impact of presenteeism are unable to adequately inform the employer of the productive benefits of WPIs. The overall aim of this thesis was to appraise current methods used to quantify presenteeism and to develop methods to value the impact of presenteeism suitable for use in economic evaluations (EE) of WPIs. Methods: Two systematic reviews were conducted: 1) to assess the extent to which self-report measure of presenteeism were underpinned by economic theory; and 2) to explore if, and how, productivity was quantified and included in EE of WPIs for musculoskeletal conditions (MSDs). Thematic analysis methods were used to analyse qualitative data collected from working individuals with RA, AS or PsA (n=22) that explored the extent to which measures of health status (EQ5D; SF6D) and capability (ICECAP-A) capture the impact on ability to work caused by RA, AS or PsA. Econometric methods were used to specify prediction models that included measures of health status, capability and presenteeism, using a sample of 542 working people with RA and AS. Results The first systematic review identified 24 self-report measures of presenteeism; all, except one measure were not underpinned by economic theory. The second systematic review identified 20 EE of WPIs for MSDs. Absenteeism was included in all studies (n=20); however, presenteeism was included in only four. The qualitative data confirmed measures of health status and capability had the ability to capture those aspects of RA, AS and PsA that impact an individual’s ability to work. The best performing prediction model used an OLS specification including SF6D, age and gender to predict presenteeism measured by the WPAI. Conclusion: The results suggest that HRQoL measures, specifically the SF6D, can be used to capture and predict levels of presenteeism caused by RA, AS and PsA.

Background Quantifying joint deformity in people with rheumatoid arthritis (RA) and psoriatic arthritis (PsA), using high resolution peripheral quantitative computed tomography (HR-pQCT), remains problematic because it is difficult to estimate where the healthy joint surface would have been. Methods The second metacarpophalangeal of RA, PsA and healthy subjects were imaged with HR-pQCT. Using the bone surfaces of the healthy cohort as a reference, the method predicted the healthy surface of each individual diseased bone surface. Quantifiable outcomes were measured based on differences between the predicted healthy surface and the actual diseased surface. Sensitivity studies were conducted to measure precision, and the algorithm was validated against artificially created deformities with known geometries. Results Subjects with PsA and RA had significantly greater occurrences of erosion based surface outcomes than the healthy cohort. Sensitivity analyses revealed precision errors of up to 0.26 mm. Validating the algorithm showed an average accuracy error of 0.12 mm (4%) for detecting erosions and 0.27 mm (20%) for detecting periosteal bone growths. Conclusions The new method allows for visualization and quantification of surface changes within the affected joint by identifying areas of erosion and periosteal bone formation. Surface based outcomes are a novel way to interpret and further quantify articular bone changes affected by PsA and RA.

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease that targets joints, resulting in in permanent disability. Synovial macrophages have been implicated in the pathogenesis of RA; however, their exact origins and functions remains unclear. In this study, we show evidence that synovial macrophages are mostly derived from embryonic origin during normal development. Macrophages are derived from either hematopoietic stem cells (HSC) or erythro-myeloid progenitors (EMP), and it is postulated that different subpopulations of synovial macrophages may have distinct functions contributing to either homeostasis or inflammation. To investigate the phenotypes of synovial macrophage populations and characterize their lineage-specific functions in arthritic joints, we utilized both cell lineage-tracing and K/BxN serum-transfer arthritis mouse models. Utilizing Flt3Cre;Rosa26LSL-YFP mice to label HSC-derived cells, we demonstrated that there is minimal HSC contribution to synovial macrophage populations during homeostasis. Use of RankCre;Rosa26LSL-YFP and Cx3cr1CreERT2;Rosa26LSL-tdTomato mice to label EMP-derived cells corroborated the finding that the EMP compartment maintains the largest contribution to synovial macrophage populations during normal development. Analysis of macrophages in Csf1rMericreMer;Rosa26-LSLtdTomato mice provided definitive prove that synovial macrophages derived from yolk-sac EMP precursors in adult mice. Use of serum transfer arthritis (STA) mice demonstrated that while most macrophages in the inflamed synovium were EMP-derived, there was a marked increase in HSC-derived cells compared to those present in homeostasis. Although this study has contributed to eluding that the heterogeneity of synovial macrophages in both homeostasis and inflammatory arthritis (IA) is complex and lineage-specific, further studies are needed to clearly define lineage-specific functions of macrophages in synovial tissues and in IA.