Anti-interleukin 6 receptor antibody inhibits murine AA-amyloidosis.

OBJECTIVE: AA-amyloidosis is a severe complication in chronic inflammatory diseases. AA-amyloidosis is caused by the deposition of insoluble fibrils containing AA amyloid protein derived from serum amyloid A (SAA), which is synthesized by inflammatory cytokine stimulation. We examined whether anti-interleukin 6 receptor (IL-6R) antibody prevented the development of AA-amyloidosis in mouse models. METHODS: A transient model was induced by the injection of amyloid enhancing factor (AEF) and adjuvant treatment in C57BL/6 mice. Monoclonal IgG1 antibody, MR16-1, was injected intraperitoneally just once before the injection of AEF and adjuvant. After 2 and 5 weeks, mice were sacrificed and histologically examined. In contrast, a chronic model was induced by AEF injection into IL-6 transgenic mice. One week later, in order to avoid neutralizing antibody production, MR16-1 (200 mg/kg) was injected intravenously. MR16-1 (5 mg/kg) was injected subcutaneously twice a week from the next week. Three and 6 weeks after AEF injection, mice were sacrificed and histologically examined. RESULTS: In the transient model, amyloid deposition was observed in the spleen, liver, and kidney as early as 2 weeks after treatment. MR16-1 completely prevented amyloid deposition. Although IL-6 production was not suppressed, SAA production was significantly suppressed. In the chronic model, substantial amyloid deposition was seen in multiple organs and tissues as well as the spleen, liver, and kidney. MR16-1 suppressed amyloid deposition in many organs, even when injected one week after AEF injection; it showed a tendency to decrease SAA and IL-6 levels were decreased. CONCLUSION: IL-6 is a key cytokine for the induction of AA-amyloidosis, and anti-IL-6R therapy appears promising for the treatment of AA-amyloidosis.

Polyglutamation of a novel antifolate, MX-68, is not necessary for its anti-arthritic effect.

N-[[4-[(2,4-diaminopteridin-6-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-7-yl]-carbonyl]-L-homoglutamic acid (MX-68), a derivative of methotrexate, was chemically designed to resist polyglutamation and to have a high affinity for dihydrofolate reductase, in an attempt to reduce the side effects of methotrexate. We confirmed that MX-68 did not undergo polyglutamation and investigated the pharmacological activities of MX-68 compared with methotrexate. (1) In vitro: MX-68 inhibited the activity of dihydrofolate reductase to the same degree as methotrexate-tetraglutamate. MX-68 treatment produced a similar anti-proliferative effect to that of methotrexate. However, the intracellular concentration of MX-68 was much lower than the sum of the levels of methotrexate and its polyglutamate, and the effects of MX-68 disappeared when it was removed from the culture medium. (2) In vivo: Oral administration of MX-68 suppressed the development of collagen-induced arthritis in mice and adjuvant-induced arthritis in rats, in a similar fashion to that of methotrexate. These results indicate that polyglutamation is not essential for the anti-arthritic effect of antifolates.

Anti-interleukin 6 (IL-6) receptor antibody suppresses Castleman's disease like symptoms emerged in IL-6 transgenic mice.

Transgenic mice carrying human IL-6 cDNA fused with a murine major histocompatibility class-I promoter (H-2L(d)) were serially administered with anti-interleukin-6 receptor (IL-6R) monoclonal antibody (mAb), MR16-1, from the age of 4 weeks to estimate its efficacy on a variety of disorders developed in these mice, most of which are similar to the disorders associated with Castleman's disease. In the control mice treated with isotype-matched mAb, a massive and multiple IgG1 plasmacytosis, mesangial proliferative glomerulonephritis, leukocytosis, thrombocytosis, anemia and abnormalities of blood chemical parameters have developed in accordance with the elevation of serum IL-6, and 50% of mice have died of renal failure by 18 weeks of age. In contrast, the treatment with MR16-1 prevented all these symptoms and prolonged the lifetime of the majority of the mice. Thus, the constitutive overexpression of IL-6 caused various disorders, and the treatment with anti-IL-6R mAb completely prevented from these symptoms. These results clearly confirm that IL-6 indeed plays an essential role in the pathogenesis of a variety of disorders. Furthermore, anti-IL-6R mAb could provide novel therapy for Castleman's disease and MR16-1 should be a useful tool to estimate therapeutic potential of IL-6 antagonists in a variety of murine models for human disease.