Retrospective study of salazosulfapyridine in eight patients with rheumatoid arthritis on hemodialysis.

OBJECTIVE: We examined the pharmacokinetics (PK) of salazosulfapyridine (SASP) and its metabolite, sulfapyridine (SP), as well as the influence of hemodialysis (HD), and investigated the utility of consecutive administration of SASP in rheumatoid arthritis patients undergoing HD. METHODS: The PK of salazosulfapyridine and SP in serum samples from 8 patients was determined using high-performance liquid chromatography. RESULTS: When SASP 500 mg was administered, the area under curve for serum concentration of SASP was similar to that seen with normal subjects in the Phase I study. The maximum serum concentration of SP was significantly higher than that in normal subjects, but was far from the danger level. SASP was not dialyzed, whereas on average 62% of SP was dialyzed. Following 5 consecutive days of administration of SASP, serum levels of SASP and SP on day 5 were rather higher than those on day 1, although both remained within the safe range. SASP administration from four months to three years in seven subjects resulted in four American College of Rheumatology 20 improvement criteria (57.1%), with one developing a rash. CONCLUSIONS: If SASP is initiated at a low dosage (≤ 500 mg) and increased up to 1000 mg under careful monitoring, it is safe for HD patients.

HLA-B27 in transgenic rats forms disulfide-linked heavy chain oligomers and multimers that bind to the chaperone BiP.

To test the hypothesis that HLA-B27 predisposes to disease by forming disulfide-linked homodimers, we examined rats transgenic for HLA-B27, mutant Cys(67)Ser HLA-B27, or HLA-B7. In splenic Con A blasts from high transgene copy B27 lines that develop inflammatory disease, the anti-H chain mAb HC10 precipitated four bands of molecular mass 78-105 kDa and additional higher molecular mass material, seen by nonreducing SDS-PAGE. Upon reduction, all except one 78-kDa band resolved to 44 kDa, the size of the H chain monomer. The 78-kDa band was found to be BiP/Grp78, and the other high molecular mass material was identified as B27 H chain. Analysis of a disease-resistant low copy B27 line showed qualitatively similar high molecular mass bands that were less abundant relative to H chain monomer. Disease-prone rats with a Cys(67)Ser B27 mutant showed B27 H chain bands at 95 and 115 kDa and a BiP band at 78 kDa, whereas only scant high molecular mass bands were found in cells from control HLA-B7 rats. (125)I-surface labeled B27 oligomers were immunoprecipitated with HC10, but not with a mAb to folded B27-beta(2)-microglobulin-peptide complexes. Immunoprecipitation of BiP with anti-BiP Abs coprecipitated B27 H chain multimers. Folding and maturation of B27 were slow compared with B7. These data indicate that disulfide-linked intracellular H chain complexes are more prone to form and bind BiP in disease-prone wild-type B27 and B27-C67S rats than in disease-resistant HLA-B7 rats. The data support the hypothesis that accumulation of misfolded B27 participates in the pathogenesis of B27-associated disease.