Nobuchika Yamamoto

Essential role of the cryptic epitope SLAYGLR within osteopontin in a murine model of rheumatoid arthritis

It has been shown that osteopontin (OPN) plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). However, the molecular mechanism of OPN action is yet to be elucidated. Splenic monocytes obtained from arthritic mice exhibited a significant capacity for cell migration toward thrombin-cleaved OPN but not toward full-length OPN. Migratory monocytes expressed alpha9 and alpha4 integrins. Since cleavage of OPN by thrombin exposes the cryptic epitope recognized by alpha9 and alpha4 integrins, we investigated the role of the cryptic epitope SLAYGLR in a murine RA model by using a specific antibody (M5) reacting to SLAYGLR sequence. The M5 antibody could abrogate monocyte migration toward the thrombin-cleaved form of OPN. Importantly, M5 antibody could inhibit the proliferation of synovium, bone erosion, and inflammatory cell infiltration in arthritic joints. Thus, we demonstrated that a cryptic epitope, the SLAYGLR sequence of murine OPN, is critically involved in the pathogenesis of a murine model of RA.

Effect of FR167653, a cytokine suppressive agent, on endotoxin-induced disseminated intravascular coagulation

FR167653 (1-[7-(4-fluorophenyl)-1,2,3,4-tetrahydro-8-(4-pyridyl)pyrazolo[5-1-c] [1,2,4]triazin-2-yl]-2-phenylethanedione sulfate monohydrate) is a low molecular weight inflammatory cytokine inhibitor that inhibits the production of interleukin-1 alpha, interleukin-1 beta and tumor necrosis factor-alpha (TNF-alpha) in human monocytes stimulated with lipopolysaccharide, and in human lymphocytes stimulated with phytohemagglutinin-M. FR167653 inhibited these cytokines in a dose-dependent manner (IC50 values were 0.84, 0.088, 1.1 microM and 0.072, respectively). However, FR167653 did not inhibit even at 10 microM interleukin-6 production by human monocytes, and the production of interleukin-2 and interferon-gamma by human lymphocytes. We evaluated the effect of FR167653 on lipopolysaccharide-induced disseminated intravascular coagulation in rats. FR167653 (0.032-0.32 mg/kg/h for 4 h, intravenous infusion) markedly improved thrombocytopenia and plasma coagulation parameters in a dose-dependent manner, but not leukopenia in this mode. Plasma interleukin-1 and TNF-alpha levels were elevated by lipopolysaccharide administration and the treatment with FR167653 (0.31 mg/kg/h for 4 h) inhibited the increased plasma interleukin-1 (100.0%) and plasma TNF-alpha (89.2%) levels. These results suggest that interleukin-1 and TNF-alpha may play a pivotal role in the pathogenesis of DIC. FR167653 can act as a protective drug in lipopolysaccharide-induced DIC, and this protection is due to an inhibition of increased plasma interleukin-1 and TNF-alpha.

FR167653, a dual inhibitor of interleukin-1 and tumor necrosis factor-α, ameliorates endotoxin-induced shock

Increased production of interleukin-1 and tumor necrosis factor-alpha (TNF-alpha) have been implicated in the pathophysiology of a variety of diseases including circulatory shock. The present study evaluated the efficacy of FR167653 (1-[7-(4-fluorophenyl)-1,2,3,4-tetrahydro-8-pyridylpyrazolo[5,1-c] [1,2,4]triazin-2-yl]-2-phenylethanedione sulfate monohydrate), a dual inhibitor of interleukin-1 and TNF-alpha production, to protect rabbits from the shock and lethality induced by lipopolysaccharide. In this sepsis model, FR167653 at a dose of 0.32 mg/kg per h ameliorated the 7-day mortality from 93% in the placebo group to 47% in the FR167653-treated group and, at doses of 0.10-0.32 mg/kg per h, attenuated the hypotensive response to lipopolysaccharide challenge and returned mean arterial blood pressure to almost normal levels. The increases in plasma interleukin-1 and TNF-alpha levels evoked by lipopolysaccharide administration were also inhibited by treatment with FR167653, which was efficacious at doses of 0.1-0.32 mg/kg per h. In addition, FR167653 treatment attenuated the increases in plasma creatinine concentrations consistent with renal damage in a dose-dependent manner. These findings suggested that FR 167653 has a beneficial potential as a drug for septic shock or multiple organ dysfunction syndrome.

Prevention of the Cryptic Epitope SLAYGLR within Osteopontin Does Not Influence Susceptibility to Candida albicans Infection

ABSTRACT The effect of an antiosteopontin antibody (M5 Ab) reacting with the SLAYGLR sequence within osteopontin on the host susceptibility to infection was investigated in a murine model of disseminated candidiasis. The treatment with anti-tumor necrosis factor alpha antibody enhanced fungal infection, while the treatment with M5 Ab did not affect the infection.

Osteopontin is dispensable for protection against high load systemic fungal infection

Osteopontin (OPN) is a multi-functional cytokine which is involved in the pathogenesis of autoimmune disease. We previously reported that thrombin-cleaved form of OPN plays a pathogenic role in murine model of rheumatoid arthritis (RA) by using neutralizing antibody (M5) reacting against the cryptic epitope within OPN, exposed by thrombin cleavage of OPN. It has been shown that OPN-deficient mice are susceptible to various infections, demonstrating the protective role of OPN against various infectious diseases. However, it remains to be clarified whether and how OPN is involved in protection against systemic fungal infection. In a murine model of systemic fungal infection, OPN-deficient mice showed the increase in the susceptibility to low load, but not to high load fungal infection, indicating the protective of OPN against mild or severe forms of infections. However, mice treatment with M5 antibody did not alter the susceptibility to both high and low load fungal infection. These experiments suggest that in sharp contrast to the complete abrogation of OPN expression in OPN-deficient mice, the neutralization of OPN by antibody against thrombin-cleaved form of OPN does not interfere with the host defense against high and low load fungal infection. These findings suggest that the neutralizing antibody which is specific for the epitope of thrombin-cleaved OPN may become an attractive therapeutic means for the treatment of RA without interfering host defense system.

Constitutive Activation of Integrin α9 Augments Self-Directed Hyperplastic and Proinflammatory Properties of Fibroblast-like Synoviocytes of Rheumatoid Arthritis

Despite advances in the treatment of rheumatoid arthritis (RA), currently approved medications can have significant side effects due to their direct immunosuppressive activities. Additionally, current therapies do not address residual synovial inflammation. In this study, we evaluated the role of integrin α9 and its ligand, tenascin-C (Tn-C), on the proliferative and inflammatory response of fibroblast-like synoviocytes (FLSs) from RA patients grown in three-dimensional (3D)–micromass culture. FLSs from osteoarthritis patients, when grown in the 3D-culture system, formed self-directed lining-like structures, whereas FLSs from RA tissues (RA-FLSs) developed an abnormal structure of condensed cellular accumulation reflective of the pathogenic features of RA synovial tissues. Additionally, RA-FLSs grown in 3D culture showed autonomous production of proinflammatory mediators. Predominant expression of α9 and Tn-C was observed in the condensed lining, and knockdown of these molecules abrogated the abnormal lining-like structure formation and suppressed the spontaneous expression of matrix metalloproteinases, IL-6, TNFSF11/RANKL, and cadherin-11. Disruption of α9 also inhibited expression of Tn-C, suggesting existence of a positive feedback loop in which the engagement of α9 with Tn-C self-amplifies its own signaling and promotes progression of synovial hyperplasia. Depletion of α9 also suppressed the platelet-derived growth factor–induced hyperplastic response of RA-FLSs and blunted the TNF-α–induced expression of matrix metalloproteinases and IL-6. Finally, α9-blocking Ab also suppressed the formation of the condensed cellular lining by RA-FLSs in 3D cultures in a concentration-related manner. This study demonstrates the central role of α9 in pathogenic behaviors of RA-FLSs and highlights the potential of α9-blocking agents as a nonimmunosuppressive treatment for RA-associated synovitis.

Integrin, alpha9 subunit blockade suppresses collagen-induced arthritis with minimal systemic immunomodulation

Abstract Integrin, alpha9 subunit (hereinafter, alpha9) has been identified as a novel putative therapeutic target for rheumatoid arthritis (RA). Support for this target comes from the observations that alpha9 is overexpressed both in the joints of RA patients and in animal models of arthritis. In the experimental models, the increase in alpha9 expression precedes the onset of arthritic symptoms. The current study presents data on the pharmacological profile of an anti‐alpha9 antibody in a collagen‐induced arthritis (CIA) mouse model. Administration of an alpha9‐blocking antibody in CIA mice suppressed the development of arthritis and significantly decreased plasma level of activated fibroblast‐like synoviocyte (FLS)‐derived biomarkers without reducing the formation of anti‐type II collagen antibodies. While anti‐alpha9 antibody administration significantly suppress the accumulation of immune cells in arthritic joints it had no effect on immune cell number in the spleen. Furthermore, in non‐arthritic mice, alpha9 had no inhibitory effect in either a mixed lymphocyte reaction (MLR) or in a delayed type hypersensitivity (DTH) reaction. These results suggest that blocking alpha9 exerts its anti‐arthritic effect through suppression of FLS‐activation via a non‐immune mediated mechanism. Finally, therapeutic administration of anti‐alpha9 antibody alleviated established arthritis in CIA mice. Our data provide evidence that alpha9 blockade is a promising therapy for joint inflammation with minimal systemic immunomodulation.