Faculty Bibliography

Rheumatoid arthritis (RA) is an inflammatory disease with a complex genetic component. An association between RA and the human leukocyte antigen (HLA) complex has long been observed in many different populations, and most studies have focused on a direct role for the HLA-DRB1 'shared epitope' in disease susceptibility. We have performed an extensive haplotype analysis, using 54 markers distributed across the entire HLA complex, in a set of 469 multicase families with RA. The results show that, in addition to associations with the DRB1 alleles, at least two additional genetic effects are present within the major histocompatibility complex. One of these lies within a 497-kb region in the central portion of the HLA complex, an interval that excludes DRB1. This genetic risk factor is present on a segment of a highly conserved ancestral A1-B8-DRB1*03 (8.1) haplotype. Additional risk genes may also be present in the HLA class I region in a subset of DRB1*0404 haplotypes. These data emphasize the importance of defining haplotypes when trying to understand the HLA associations with disease, and they clearly demonstrate that such associations with RA are complex and cannot be completely explained by the DRB1 locus

Human leukocyte antigen (HLA) class I and class II alleles are implicated as genetic risk factors for many autoimmune diseases. However, the role of the HLA loci in human systemic lupus erythematosus (SLE) remains unclear. Using a dense map of polymorphic microsatellites across the HLA region in a large collection of families with SLE, we identified three distinct haplotypes that encompassed the class II region and exhibited transmission distortion. DRB1 and DQB1 typing of founders showed that the three haplotypes contained DRB1*1501/ DQB1*0602, DRB1*0801/ DQB1*0402, and DRB1*0301/DQB1*0201 alleles, respectively. By visualizing ancestral recombinants, we narrowed the disease-associated haplotypes containing DRB1*1501 and DRB1*0801 to an approximately 500-kb region. We conclude that HLA class II haplotypes containing DRB1 and DQB1 alleles are strong risk factors for human SLE

Mouse interleukin-four induced gene-1 (mFig1) maps to a region of susceptibility for systemic lupus erythematosus (SLE) that includes the Sle3 locus. To begin examining this relationship in humans, we have isolated and characterized the human homolog of mFig1. Human Fig1 (hFig1) has the same eight exon genomic structure as mFig1. The predicted 63-kDa protein, like mFig1, contains a signal peptide, a large internal sequence that is most similar (43% identical over 484 amino acids) to L-amino acid oxidase (LAAO), and a carboxy terminal domain with no similarity to known genes. When compared to the LAAO crystal structure, hFig1 conserves key residues thought to be involved in catalysis and binding of the flavin adenine dinucleotide cofactor. Surprisingly, the carboxy terminal domains of hFig1 and mFig1 have little similarity (<11% identity), different lengths and amino acid composition. Like mFig1, hFig1 RNA is induced by interleukin-4 (IL-4) in B lymphocytes, and is primarily found in immune tissues. Finally, hFig1 maps to the predicted mFig1 syntenic region on human chromosome 19q13.3-19q13.4, a hot spot for susceptibility to several autoimmune diseases, including SLE

The macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine and regulates the anti-inflammator effects of glucocorticoids. An important role for MIF within the cytokine cascade is to act in concert with endogenous glucocorticoids to control the set-point and magnitude of the inflammatory response. Elevated expression of MIF in the circulation and in the synovial joint has been documented in rheumatoid arthritis. MIF also has been linked to the development of joint damage and disease pathology in experimental animal models. We describe herein a novel CATT-tetranucleotide repeat polymorphism at position -794 of the human Mif gene and show that it functionally affects the activity of the MIF promoter in gene reporter assays. We describe four genotypes which comprise 5, 6, 7, or 8-CATT repeat units and show that the 5-CATT allele has the lowest level of basal and stimulated MIF promoter activity in vitro. The presence of the low expressing, 5-CATT repeat allele correlated with low disease severity in a cohort of rheumatoid arthritis patients

The receptor for advanced glycation end products (RAGE) and its proinflammatory S100/calgranulin ligands are enriched in joints of subjects with rheumatoid arthritis (RA) and amplify the immune/inflammatory response. In a model of inflammatory arthritis, blockade of RAGE in mice immunized and challenged with bovine type II collagen suppressed clinical and histologic evidence of arthritis, in parallel with diminished levels of TNF-alpha, IL-6, and matrix metalloproteinases (MMP) 3, 9 and 13 in affected tissues. Allelic variation within key domains of RAGE may influence these proinflammatory mechanisms, thereby predisposing individuals to heightened inflammatory responses. A polymorphism of the RAGE gene within the ligand-binding domain of the receptor has been identified, consisting of a glycine to serine change at position 82. Cells bearing the RAGE 82S allele displayed enhanced binding and cytokine/MMP generation following ligation by a prototypic S100/calgranulin compared with cells expressing the RAGE 82G allele. In human subjects, a case-control study demonstrated an increased prevalence of the 82S allele in patients with RA compared with control subjects. These data suggest that RAGE 82S upregulates the inflammatory response upon engagement of S100/calgranulins, and, thereby, may contribute to enhanced proinflammatory mechanisms in immune/inflammatory diseases

Cerebral ischemia stimulates increased activity of polyamine oxidase, a ubiquitous enzyme that catabolizes polyamines to produce 3-aminopropanal. 3-Aminopropanal is a reactive aldehyde that mediates progressive neuronal necrosis and glial apoptosis. Here we report that increased levels of 3-aminopropanal-modified protein levels in humans after aneurysmal subarachnoid hemorrhage correlate with the degree of cerebral injury as measured by admission Hunt/Hess grade. In vitro screening of clinically approved drugs reveals that N-2-mercaptopropionyl glycine (N-2-MPG), an agent clinically approved for prevention of renal stones in patients with cysteinuria, significantly inhibits the cytotoxicity of 3-aminopropanal. N-2-MPG reacts with 3-aminopropanal to yield a nontoxic thioacetal adduct, as confirmed by electrospray ionization mass spectroscopy. Administration of N-2-MPG in clinically relevant doses to rats significantly reduces cerebral 3-aminopropanal-modified protein immunoreactivity and infarct volume in a standardized model of middle cerebral artery occlusion, even when the agent is administered after the onset of ischemia. These results implicate 3-aminopropanal as a therapeutic target for cerebral ischemia

Rheumatoid arthritis is a multifactorial disease, with genetic, environmental, and stochastic components to its susceptibility. The search for susceptibility genes is still in progress. Preliminary results suggest the involvement of multiple genes, each with relatively modest effect. Genes within the major histocompatibility complex appear to have the strongest influence on disease susceptibility