Studies on the therapeutic modulation of inflammation in the synovial membrane of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation of the synovial membrane that can lead to joint deformity and physical disability. Despite recent progress in the therapeutic field of RA, the exact molecular mechanisms responsible for chronic joint inflammation are not yet completely understood. The overall aim of this thesis was to identify new molecular mechanisms responsible for inflammation in the rheumatoid joint and to understand how distinct anti rheumatic drugs act upon these mechanisms. I first focused on validating arthroscopy as a research tool for better understanding of the molecular mechanisms of action of anti rheumatic drugs, demonstrating that rheumatologic arthroscopy is a safe method, with very few complications and allowing retrieval of representative tissue in clinical longitudinal studies. We also propose an easy to perform way to quantitate macroscopic joint changes based on photos acquired during arthroscopies. Based on our validation study we then used this method to perform several mechanisms of action studies. We first investigated the effect of etanercept on synovial expression of lymphotoxin-α (LT-α) and tumor necrosis factor-α (ΤΝF-α). As predicted from previous in vitro studies etanercept was able to decrease synovial expression of both LT-α and TNF-α. The effect was however limited to good clinical responders. We propose LT-α modulation as an additional but not essential mechanism to explain the clinical efficacy observed with this drug in clinical practice. Defective apoptosis of lymphocytes is linked to pathogenesis of RA and glucocorticoids are good in vitro inducers of lymphocyte apoptosis. We therefore investigated the effect of intra articular glucocorticoids on synovial apoptosis demonstrating that in the complex milieu of rheumatoid joint glucocorticoids actually fail to induce lymphocyte apoptosis. We further demonstrate that monocytes are essential in rescuing synovial T cells from glucocorticoid-induced apoptosis through a soluble factor mediated mechanism, a feature that is specific for RA-derived synovial lymphocytes. LL-37 is an anti microbial peptide belonging to the cathelicidin family with important functions in innate immune response but recently also implicated as a modulator of acquired immune responses. We therefore investigated a potential role for LL-37 in RA pathogenesis, demonstrating that the peptide is present at low levels in healthy synovium, but up regulated in the context of inflammation. We also identified synovial neutrophils and to a lesser extent macrophages as the main cell types expressing LL-37. Distinct modulation patterns of LL-37 by some but not all anti rheumatic drugs and correlation with local levels of inflammation suggest a potential direct contribution of LL-37 to synovial pathology in RA. In conclusion, we demonstrated that arthroscopy is a safe and reliable research tool for studies on mechanisms of action of anti rheumatic drugs and pathogenic traits of the inflamed rheumatoid joint

The cathelicidins LL-37 and rCRAMP are associated with pathogenic events of arthritis in humans and rats

Background: In rheumatoid arthritis (RA), neutrophil granulocytes fuel inflammation and damage tissue in the joint by releasing cytotoxic agents, antimicrobial peptides, proteases and other inflammatory mediators. The human cathelicidin LL-37 has recently been implicated in the development of systemic lupus erythematosus and psoriasis. Objective: To elucidate if antimicrobial peptides (AMPs) contribute to the pathogenesis of arthritis. Methods: Expression of LL-37 was determined in synovial membranes from patients with arthritis and control subjects. Expression of the rat cathelicidin rCRAMP and defensins was characterised in joints, blood and secondary lymphoid organs during pristane-induced arthritis (PIA) in rats and in a transfer model of PIA induced by CD4 T cells. Serum samples of rats with arthritis were tested for IgG and IgM autoantibodies against rCRAMP by immunoblot and for interferon (IFNα) by ELISA. Results: Cathelicidins are strongly upregulated in RA synovial membranes and in joints from rats with arthritis as compared with healthy joints. Expression was most prominent in neutrophil granulocytes and macrophages/osteoclasts. Cathelicidin expression is also upregulated in the blood and spleen of pristane-injected rats, with strongest expression detected in activated CD62L− cells coexpressing granulocyte and monocyte markers. Pristane injection caused accumulation of low-density granulocytes in the blood. After pristane injection, the increased expression of rCRAMP coincided with higher levels of cell death, raised levels of interferon (IFN)α and development of autoantibodies. Conclusions: Our results show strong upregulation of cathelicidins and β-defensins coinciding with pathological events of arthritis. Higher expression and release of AMPs might contribute to development and/or maintenance of disease by systemic or local mechanisms

Validation of Patient Identification Algorithms for Atopic Dermatitis Using Healthcare Databases

Introduction: The use of real-world data offers a possibility to perform large-scale epidemiological studies in actual clinical settings. Despite their many advantages, administrative databases were not designed to be used in research, and the validation of diagnoses and treatments in administrative databases is needed. The primary objective of this study was to validate an existing algorithm based on dispensed prescriptions and diagnoses of skin conditions to identify pediatric patients with atopic dermatitis (AD), using a diagnosis of AD in primary care as a gold standard. Methods: Retrospective observational data were collected from nation-wide secondary care and pharmacy-dispensed medication databases and two regional primary care databases in Sweden. An existing algorithm and a Modified algorithm, using skin-specific diagnoses from secondary care and/or pharmacy-dispensed prescriptions to identify patients with AD, were assessed. To verify the presence of AD, diagnoses from primary care were used in the base case and complemented with diagnoses from secondary care in a sensitivity analysis. Results: The sensitivity (30.0%) and positive predictive value (PPV) (40.7%) of the existing algorithm were low in the pediatric patient population when using primary care data only but increased when secondary care visits were also included in the Modified algorithm (sensitivity, 62.1%; PPV, 66.3%). The specificity of the two algorithms was high in both the base case and sensitivity analysis (95.1% and 94.1%). In the adult population, sensitivity and PPV were 20.4% and 8.7%, respectively, and increased to 48.3% and 16.9% when secondary care visits were also included in the Modified algorithm. Conclusion: The Modified algorithm can be used to identify pediatric AD populations using primary and secondary administrative data with acceptable sensitivity and specificity, but further modifications are needed to accurately identify adult patients with AD

Comorbidity burden in adult atopic dermatitis : a population-based study

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease that has been shown to be associated with allergic comorbidities. However, studies examining comorbidities in patients with AD are incomplete, which may contribute to suboptimal care. Objectives: The objective was to compare the risk of developing different allergic and nonallergic comorbidities among adult patients with AD to that of a matched reference cohort in Sweden. Methods: This was a nationwide population-based cohort study using longitudinal data from primary and specialist care registers. AD patients were identified by confirmed diagnosis in primary or specialist care. A non-AD reference cohort was randomly drawn from the general population and matched 1:1 with the AD patients on age, gender, and geographical region. The risk of developing the following conditions was evaluated: asthma, food hypersensitivity, allergic rhinitis, neurological disorders, psychiatric disorders, infections, immunological & inflammatory disorders, type 1 diabetes (T1D), type 2 diabetes (T2D), endocrine & metabolic disorders, skeletal disorders, ocular disorders, cardiovascular diseases, and malignancies. Results: This study included 107,774 AD patients [mild-to-moderate (n = 92,413) and severe (n = 15,361)] and an equally-sized reference cohort. AD patients displayed a higher risk of developing comorbid conditions for all investigated categories, except for T1D, compared with the reference cohort. The highest risk compared with the reference cohort was observed for allergic comorbidities followed by immunological & inflammatory disorders (hazard ratio: 2.15) and infections (hazard ratio: 2.01). Patients with AD also had higher risk of developing multiple comorbidities (2 or more). The risk of comorbidity onset increased alongside AD severity and patients with active AD were associated with increased risk of comorbidity onset compared with patients in remission. Conclusions: AD patients are at an increased risk of developing many comorbidities that extend beyond allergic conditions. This study highlights the need for interdisciplinary follow-up of comorbidities in the management of AD patients to reduce overall patient burden

Societal economic burden and determinants of costs for atopic dermatitis

Background: Atopic dermatitis (AD) is a common inflammatory skin disease while the economic burden of AD by severity is not adequately understood. Objective: To estimate the societal economic burden and to identify cost determinants of AD. Methods: In this population-based, controlled cohort study in Sweden, patients with AD were identified through diagnosis codes in primary or secondary care or by dispensed medications using administrative healthcare registers. A reference cohort without AD was randomly selected from the general population. Healthcare costs (primary/secondary care visits and dispensed medication) and indirect costs (care for sick children and long-term sick leave for adults) were calculated annually. AD patients were stratified by age (paediatric [age < 12], adolescent [12 ≤ age < 18] or adult [age ≥ 18]), and severity (mild-to-moderate [M2M] or severe AD) and matched to the reference cohort. Results: Compared with controls, the annual mean per-patient direct healthcare costs in the first year following diagnosis were €941 and €1259 higher in paediatric patients with M2M and severe AD, respectively. In the first year following diagnosis, the mean indirect cost for care of sick children was €69 and €78 higher per patient in M2M and severe AD, respectively. In adolescents with M2M and severe AD, direct healthcare costs were €816 and €1260 higher, respectively. In adults, healthcare costs were €1583 and €2963 higher in patients with M2M and severe AD, respectively and indirect costs were €148 and €263 higher compared with controls. Management of comorbid medical conditions was an important driver of incremental healthcare costs. Total incremental societal economic burden for AD was €351 and €96 million higher in patients with M2M and severe AD, respectively, compared to controls. Conclusion: AD is associated with a significant societal economic burden primarily driven by the cost burden of M2M AD due to the high prevalence of this population. Regardless of severity level, management of non-AD comorbidities is a major driver of total costs

Comorbidities in childhood atopic dermatitis : a population-based study

Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease that is associated with allergic comorbidities. However, studies examining comorbidities in childhood AD are incomplete, which may contribute to suboptimal care. Objective: The objective was to compare the risk of developing different allergic and non-allergic comorbidities among children with AD to that of a matched non-AD reference cohort in Sweden. Methods: This was a nationwide population-based cohort study using longitudinal data from primary and specialist care registers. Patients with AD were identified by confirmed diagnosis in primary or specialist care. The non-AD reference cohort was randomly drawn from the general population and matched 1:1 with the AD patients. The risk of developing the following conditions was evaluated: hypersensitivity and allergic disorders, neurological disorders, psychiatric disorders, infections, immunological and inflammatory disorders, Type 1 diabetes (T1D), endocrine and metabolic disorders, skeletal disorders, ocular disorders and malignancies. Results: This study included 165,145 patients with AD (mild-to-moderate [n = 126,681] and severe [n = 38,464]) and an equally sized reference cohort. Patients with AD displayed a higher risk of developing comorbid conditions for all investigated categories, except for T1D and skeletal disorders, compared with the reference cohort. The highest risk compared with the reference cohort was observed for hypersensitivity and allergic disorders (hazard ratio [HR]: 3.87), followed by malignancies (HR: 2.53) and immunological and inflammatory disorders (HR: 2.36). Patients with AD also had higher risk of developing multiple comorbidities (≥2). The risk of comorbidity onset increased alongside AD severity and patients with active AD were associated with increased risk of comorbidity onset compared with patients in remission. Conclusions: The clinical burden of AD is substantial for children with AD and patients are at an increased risk of developing several comorbid conditions extending beyond the atopic march. Our results also showed a positive association between worsening severity of AD and an increased risk of comorbidity onset