Stefan Pabst

Toll-like receptor (TLR) 4 polymorphisms are associated with a chronic course of sarcoidosis

The aetiology of sarcoidosis, an inflammatory granulomatous multi‐system disorder, is unclear. It is thought to be the product of an unknown exogenous antigenic stimulus and an endogenous genetic susceptibility. Toll‐like receptors (TLR) are signal molecules essential for the cellular response to bacterial cell wall components. Lipopolysaccharide (LPS), for example, binds to TLR 4. Two different polymorphisms for the TLR4 gene (Asp299Gly and Thr399Ile) have been described recently. This leads to a change in the extracellular matrix function of TLR4 and to impaired LPS signal transduction. We genotyped a total of 141 Caucasian patients with sarcoidosis and 141 healthy unrelated controls for the Asp299Gly and Thr399Ile polymorphisms in the TLR4 gene. The mutations were identified with polymerase chain reaction followed by restriction fragment length polymorphism (RFLP) analysis. Among sarcoidosis patients the prevalence for each Asp299Gly and Thr399Ile mutant allele was 15·6% (22/141). In the control group the prevalence was 5·67% (8/141) (P = 0·07). In the subgroup of patients with acute sarcoidosis there was no difference in the control group (P = 0·93), but there was a highly significant association between patients with a chronic course of sarcoidosis and TLR4 gene polymorphisms (P = 0·01).

BTNL2 gene variant and sarcoidosis.

Sarcoidosis is an inflammatory granulomatous disorder that primarily affects the lungs and lymph nodes. Other organs such as the brain, eyes, heart, and skin can also be affected. The disease is characterised by non-caseating granulomas and an exaggerated cellular immune response caused by increased inflammatory activity.1 The course of the disease is acute and mild in approximately 20% of all patients. In most patients a chronic stage develops which can lead to lung fibrosis. Although the exact pathogenesis of sarcoidosis remains unclear, familial clustering of the disease and the increased risk of relatives to develop sarcoidosis suggest that there might be a genetic predisposition to develop the disease.2 A significant association was recently reported in Germany between sarcoidosis and a frequent single nucleotide polymorphism (SNP) in the BTNL2 gene, …

Pulmonary Hypertension in Patients with Chronic Kidney Disease on Dialysis and without Dialysis: Results of the PEPPER-Study

Pulmonary hypertension (PH) is common in patients with dialysis-dependent chronic kidney disease and is an independent predictor of mortality. However, specific hemodynamics of the pulmonary circulation, changes induced by hemodialysis and characterization into pre- or postcapillary PH have not been evaluated in patients with chronic kidney disease. We assessed consecutive patients with end-stage chronic kidney disease in WHO FC≥II with dyspnea unexplained by other causes on hemodialysis (group 1, n = 31) or without dialysis (group 2, n = 31) using right heart catheterization (RHC). In group 1, RHC was performed before and after dialysis. In end-stage chronic kidney disease, prevalence of precapillary PH was 13% (4/31), and postcapillary PH was discovered in 65% (20/31). All four cases of precapillary PH were unmasked after dialysis. In group 2, two cases of precapillary PH were detected (6%), and postcapillary PH was diagnosed in 22 cases (71%). This is the first study examining a large cohort of patients with chronic kidney disease invasively by RHC for the prevalence of PH. The prevalence of precapillary PH was 13% in patients with end-stage kidney disease. That suggests careful screening for precapillary PH in this selected patient population. RHC should be performed after hemodialysis.

Identification of Immune-Relevant Factors Conferring Sarcoidosis Genetic Risk

RATIONALE Genetic variation plays a significant role in the etiology of sarcoidosis. However, only a small fraction of its heritability has been explained so far. OBJECTIVES To define further genetic risk loci for sarcoidosis, we used the Immunochip for a candidate gene association study of immune-associated loci. METHODS Altogether the study population comprised over 19,000 individuals. In a two-stage design, 1,726 German sarcoidosis cases and 5,482 control subjects were genotyped for 128,705 single-nucleotide polymorphisms using the Illumina Immunochip for the screening step. The remaining 3,955 cases, 7,514 control subjects, and 684 parents of affected offspring were used for validation and replication of 44 candidate and two established risk single-nucleotide polymorphisms. MEASUREMENTS AND MAIN RESULTS Four novel susceptibility loci were identified with genome-wide significance in the European case-control populations, located on chromosomes 12q24.12 (rs653178; ATXN2/SH2B3), 5q33.3 (rs4921492; IL12B), 4q24 (rs223498; MANBA/NFKB1), and 2q33.2 (rs6748088; FAM117B). We further defined three independent association signals in the HLA region with genome-wide significance, peaking in the BTNL2 promoter region (rs5007259), at HLA-B (rs4143332/HLA-B*0801) and at HLA-DPB1 (rs9277542), and found another novel independent signal near IL23R (rs12069782) on chromosome 1p31.3. CONCLUSIONS Functional predictions and protein network analyses suggest a prominent role of the drug-targetable IL23/Th17 signaling pathway in the genetic etiology of sarcoidosis. Our findings reveal a substantial genetic overlap of sarcoidosis with diverse immune-mediated inflammatory disorders, which could be of relevance for the clinical application of modern therapeutics.

A Novel Sarcoidosis Risk Locus for Europeans on Chromosome 11q13.1

RATIONALE Sarcoidosis is a complex inflammatory disease with a heterogeneous clinical picture. Among others, an acute and chronic clinical course can be distinguished, for which specific genetic risk factors are known. OBJECTIVES To identify additional risk loci for sarcoidosis and its acute and chronic subforms, we analyzed imputed data from a genome-wide association scan for these phenotypes. METHODS After quality control, the genome-wide association scan comprised nearly 1.3 million imputed single-nucleotide polymorphisms based on an Affymetrix 6.0 Gene Chip dataset of 564 German sarcoidosis cases, including 176 acute and 354 chronic cases and 1,575 control subjects. MEASUREMENTS AND MAIN RESULTS We identified chromosome 11q13.1 (rs479777) as a novel locus influencing susceptibility to sarcoidosis with genome-wide significance. The marker was significantly associated in three distinct German case-control populations and in an additional German family sample with odds ratios ranging from 0.67 to 0.77. This finding was further replicated in two independent European case-control populations from the Czech Republic (odds ratio, 0.75) and from Sweden (odds ratio, 0.79). In a meta-analysis of the included European case-control samples the marker yielded a P value of 2.68 × 10(-18). The locus was previously reported to be associated with Crohn disease, psoriasis, alopecia areata, and leprosy. For sarcoidosis, fine-mapping and expression analysis suggest KCNK4, PRDX5, PCLB3, and most promising CCDC88B as candidates for the underlying risk gene in the associated region. CONCLUSIONS This study provides striking evidence for association of chromosome 11q13.1 with sarcoidosis in Europeans, and thus identified a further genetic risk locus shared by sarcoidosis, Crohn disease and psoriasis.

VEGF gene haplotypes are associated with sarcoidosis.

BACKGROUND The cause of sarcoidosis is unclear. Evidence suggests that there is a genetic susceptibility toward the disease. In this study, we examined whether haplotypes of vascular endothelial growth factor (VEGF) and its receptors VEGFR-1 and VEGFR-2 are associated with the onset or the course of sarcoidosis. METHODS Three hundred white patients with sarcoidosis and 381 matched controls were included. Sixty-three haplotype-tagging single nucleotide polymorphisms (SNPs) in the VEGF and VEGFR-1 and VEGFR-2 genes were selected from the HapMap Project phase 2. Mass spectrometry-based SNP genotyping was performed. RESULTS Sarcoidosis, in general, was significantly associated with three SNPs in the VEGFR-1 gene: rs7337610 (P = .041), rs2296283 (P = .034), and rs12858139 (P = .027). In an acute course (defined as less than two episodes in a lifetime or a course lasting less than 2 years), an association of three SNPs in the VEGF gene was observed: rs833060 (P = .004), rs833068 (P = .008), and rs3025000 (P = .012). In the VEGFR-2 gene, one SNP was associated with an acute course of sarcoidosis (rs7667298, P = .023), whereas two SNPs were associated with a chronic course of sarcoidosis: rs7691507 (P = .029) and rs2125489 (P = .024). We then performed a haplotype analysis. After permutation-based correction, no significant haplotype association for the VEGF receptors was observed. However, we found two haplotypes associated with the onset of sarcoidosis in the VEGF gene. Even after correction for multiple testing, we obtained a P value of .0388. Moreover, patients with a chronic course of the disease showed a P value of .0103 for the same haplotype. CONCLUSIONS There is strong evidence that VEGF and its receptors are involved in the onset of sarcoidosis and influence its course.

Genome-wide association analysis reveals 12q13.3–q14.1 as new risk locus for sarcoidosis

Sarcoidosis is a systemic inflammatory disease of unknown aetiology, influenced by genetic and environmental factors. However, the loci so far identified for sarcoidosis explain only a part of its assumed heritability. To identify further susceptibility loci, we performed a genome-wide association analysis using the Affymetrix 6.0 Human GeneChip followed by validation and replication stages. After quality control, 637 cases, 1233 controls and 677 619 single-nucleotide polymorphisms (SNPs) were available for an initial screening. 99 SNPs were selected for validation in an independent study panel (1664 patients, 2932 controls). SNP rs1050045 was significantly associated with sarcoidosis (corrected p=0.0215) in the validation panel and yielded a p-value of 9.22×10−8 (OR 1.24) in the meta-analysis of the screening and validation stage. A meta-analysis of three populations from Germany, the Czech Republic and Sweden confirmed this finding (p=0.024; OR 1.14). Fine-mapping and mRNA expression studies pointed to osteosarcoma amplified 9 (OS9) as the most likely candidate for the underlying risk factor. The OS9 protein plays an important role in endoplasmic reticulum-associated protein degradation and acts during Toll-like receptor induced activation of myeloid cells. Expression analyses of OS9 mRNA provide evidence for a functional mechanism underlying the detected association signal.

Toll-like receptor-9 polymorphisms in sarcoidosis and chronic obstructive pulmonary disease.

The etiology of inflammatory diseases of the lung like sarcoidosis and chronic obstructive pulmonary disease (COPD) is multifactorial. The main trigger for developing a COPD is tobacco smoking while exogenous factors causing sarcoidosis are unclear. In both diseases there is an underlying genetic susceptibility determining both the onset and the course of the diseases. Toll-like receptor (TLR)-9 plays an important role in innate immunity by recognizing bacterial CpG-DNA motifs. It is unclear whether single nucleotide polymorphisms (SNPs) in TLR-9 are able to alter the course of sarcoidosis or COPD, or raise the susceptibility for developing one of the disorders. We examined two SNPs in the promoter region of the TLR-9 gene (T1486C and T1237C) in 175 COPD patients (59% with a stable course of the disease, 41% with an instable course with more than 3 exacerbations over the last 3 years) and 166 sarcoidosis patients (19% with an acute and 81% with a chronic course of the disease lasting >2 years) comparing each group to 233 healthy controls. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis was used for genotyping. The C-allele frequency of T1486C was significantly elevated in COPD patients (p = 0.008). For T1237C there were no significant associations comparing the COPD cohort with the controls. In the sarcoidosis cohort, we could observe a significantly higher prevalence of the C-allele for T1237C in the chronic sarcoidosis cohort in comparison to the control group (p = 0.026). For T1486 there no statistical association was observed. This is the first study showing an association between a SNP (T1486C) in the TLR-9 gene and the onset of COPD. Moreover, we could demonstrate that T1237C is able to alter the course of sarcoidosis as a disease-modifying gene. This study underlines that SNPs in TLR-9 might be involved in acquiring and maintaining lung diseases such as sarcoidosis and COPD.

First independent replication study confirms the strong genetic association of ANXA11 with sarcoidosis

Sarcoidosis is an inflammatory disease characterised by the presence of granulomas that can affect the skin, lungs, heart, brain and nervous system, eyes and various other tissues and organs.1 The disease can present in an acute or subacute form and is often self-limiting, but in many cases it is chronic with variable disease activity over many years.2 A genetic association between sarcoidosis and a truncating splice-site mutation in the gene BTNL2 (butyrophilin-like 2, a member of the immunoglobulin gene family) has been confirmed in different studies and populations.3–5 Very recently the first whole-genome association study (WGAS) reported a strong association …

Diagnostic Value of Echocardiography in the Diagnosis of Pulmonary Hypertension

Aims To determine the value of echocardiography including tissue Doppler imaging (TDI) and right ventricular (RV) speckle tracking analysis for the diagnosis of pulmonary hypertension (PH) and discrimination between pre- and postcapillary PH. Methods and Results 155 consecutive patients (mean age 70.5±13.0 years, 81 [52%] male gender, BMI 27.2±6.1 kg/m2) with PH undergoing right heart catheterization (RHC) and transthoracic echocardiography (TTE) with TDI between January 2008 and December 2009 were retrospectively evaluated including offline speckle tracking analysis of RV contractility. After RHC 23.2% of patients (36) were diagnosed with precapillary PH. Invasive results from RHC were significantly correlated to TTE measurements (E/é, postcapillary wedge pressure [PCWP], r = 0.61, P<0.001; mean, systolic pulmonary arterial pressure [mPAP, sPAP], r = 0.43, P<0.001). Single echocardiographic parameters were of good predictive value for final PH-diagnosis (sPAP, area under the curve [AUC] 0.63, P = 0.025; lateral apical RV longitudinal strain [RVaSl)], AUC 0.76, P = 0.001; E/é, AUC 0.84, P<0.001) which could be increased by combining most predictive parameters after receiver operating curves (ROC) cut off analysis (sPAP>69 mmHg, E/é<12, RVaSl ≥−8.4%). TTE had a sensitivity of 33.33% and a specificity of 100% to identify patients with precapillary PH, and a negative predictive value of 84.72% to rule out precapilary PH. Conclusion Echocardiography allows feasible and reliable estimation of PH and seems helpful to distinguish between pre-and postcapillary PH. Further prospective studies on patients with different manifestations of PH must validate the predictive value of echocardiography in this clinical setting.