Introdução: O fragmento amino-terminal do pró-peptídeo natriurético do tipo B (NT-proBNP) é um forte marcador de doença cardiovascular com evidências recentes de que a inflamação também pode influenciar seus valores. A diferenciação dessa variável de confusão é de particular interesse nas doenças reumáticas. Objetivos: Avaliar o comportamento dos valores de NT-proBNP em pacientes com espondilite anquilosante (EA) pré e pós uso de bloqueadores de TNF para determinar a possível associação entre os valores de NT-proBNP e os parâmetros inflamatórios. Métodos: Quarenta e cinco pacientes consecutivos com EA sem evidência prévia ou atual de doença cardiovascular ou disfunção miocárdica sistólica e que eram elegíveis para terapia anti-TNF foram incluídos prospectivamente. Todos os pacientes receberam bloqueadores de TNF e foram avaliados para concentrações circulantes de NT-proBNP, parâmetros clínicos e laboratoriais de atividade de doença, fatores de risco cardiovasculares tradicionais e ecodopplercardiografia convencional e tecidual no momento da inclusão e após seis meses de tratamento. Resultados: No momento da inclusão, todos os pacientes tinham EA ativa, os valores de NT-proBNP tinham uma mediana de 36 (20-72) pg/mL e 11% dos valores estavam altos mesmo na ausência de alteração miocárdica sistólica. A análise de regressão linear múltipla revelou que esse peptídeo estava independentemente correlacionado com o VHS (p < 0,001), com a idade dos pacientes (p = 0,01) e com a pressão de pulso (p = 0,01) no momento da inclusão. Após seis meses, todos os parâmetros relacionados a doença de base melhoraram e os valores de NT-proBNP se reduziram significativamente [24 (16-47) pg/mL, p = 0,037] quando comparados com os valores do momento da inclusão. As mudanças nos valores de NT-proBNP correlacionaram-se positivamente com as mudanças nos valores do VHS (r = 0,41, p = 0.006). Os fatores de risco cardiovasculares avaliados permaneceram estáveis durante o seguimento. Conclusão: As elevações nos valores de NT-proBNP devem ser interpretadas com cuidado nos pacientes com EA ativa e sem evidência de doença cardiovascular. A redução no curto prazo dos valores de NT-proBNP nesses pacientes recebendo terapia anti-TNF parece refletir uma melhora do estado inflamatório / Introduction: N-terminal pro-brain natriuretic peptide (NT-proBNP) is a strong marker of cardiovascular disease with recent evidence that inflammation may also influence its levels; discrimination of this confounding variable is of particular interest in rheumatic diseases. Objectives: to evaluate NT-proBNP in ankylosing spondylitis (AS) patients pre- and post-TNF blocker to determine the possible association between NT-proBNP levels and inflammatory parameters. Methods: Forty-five consecutive AS patients without previous/current cardiovascular disease or systolic myocardial dysfunction, who were eligible to anti-TNF therapy, were prospectively enrolled. All patients received TNF blockers and they were evaluated for circulating NT-proBNP levels, clinical and laboratory parameters of disease activity, traditional cardiovascular risk factors, and conventional and tissue Doppler imaging echocardiography at baseline (BL) and six months after (6M) treatment. Results: At BL, all patients had active AS, NT-proBNP levels had a median of 36 (20-72) pg/mL and 11% were high in spite of no systolic alteration. Multiple linear regression analysis revealed that this peptide, at BL, was independently correlated with ESR (p < 0.001), age (p = 0.01) and pulse pressure (p = 0.01). After 6M, all disease parameters improved and NT-proBNP levels were significantly reduced [24 (16-47) pg/mL, p = 0.037] compared to BL. Changes in NT-proBNP were positively correlated with ESR changes (r = 0.41, p = 0.006). Cardiovascular risk factors remained stable during follow-up. Conclusion: our data suggests that elevations of NT-proBNP should be interpreted with caution in active AS patients with no other evidence of cardiovascular disease. The short-term reduction of NT-proBNP levels in these patients receiving anti-TNF therapy appears to reflect an improvement in inflammatory status

Ankylosing spondylitis (AS) is a common inflammatory arthritis of the spine and other affected joints, which is highly heritable, being strongly influenced by the HLA-B27 status, as well as hundreds of mostly unknown genetic variants of smaller effect. The aim of my research was to confirm some of the previously observed genetic associations and to identify new associations, many of which are in biological pathways relevant to AS pathogenesis, most notably the IL-23/T_H17 axis (IL23R) and antigen presentation (ERAP1 and ERAP2). Studies presented in this thesis include replication and refinement of several potential associations initially identified by earlier GWAS (WTCCC-TASC, 2007 and TASC, 2010). I conducted an extended study of IL23R association with AS and undertook a meta-analysis, confirming the association between AS and IL23R (non-synonymous SNP rs11209026, p=1.5 x 10-9, OR=0.61). An extensive re-sequencing and fine mapping project, including a meta-analysis, to replicate and refine the association of TNFRSF1A with AS was also undertaken; a novel variant in intron 6 was identified and a weak association with a low frequency variant, rs4149584 (p=0.01, OR=1.58), was detected. Somewhat stronger associations were seen with rs4149577 (p=0.002, OR=0.91) and rs4149578 (p=0.015, OR=1.14) in the meta-analysis. Associations at several additional loci had been identified by a more recent GWAS (WTCCC2-TASC, 2011). I used in silico techniques, including imputation using a denser panel of variants from the 1000 Genomes Project, conditional analysis and rare/low frequency variant analysis, to refine these associations. Imputation analysis (1782 cases/5167 controls) revealed novel associations with ERAP2 (rs4869313, p=7.3 x 10-8, OR=0.79) and several additional candidate loci including IL6R, UBE2L3 and 2p16.3. Ten SNPs were then directly typed in an independent sample (1804 cases/1848 controls) to replicate selected associations and to determine the imputation accuracy. I established that imputation using the 1000 Genomes Project pilot data was largely reliable, specifically for common variants (genotype concordence~97%). However, more accurate imputation of low frequency variants may require larger reference populations, like the most recent 1000 Genomes reference panels. The results of my research provide a better understanding of the complex genetics of AS, and help identify future targets for genetic and functional studies.