Suppression of inflammatory responses after onset of collagen-induced arthritis in mice by oral administration of the Citrus flavanone naringin.

Rheumatoid arthritis (RA) is closely related to the pathogenesis of tumor necrosis factor α in lesions. We investigated the suppressive effects of a Citrus flavanone naringin on inflammatory responses in mice with collagen-induced arthritis (CIA), a mouse model for RA. To investigate potential preventive and therapeutic effects of naringin, mice were given naringin orally three times a week from the second immunization with collagen (day 21) and from day 31, when symptoms of CIA had reached a plateau, respectively. In both cases, inflammation-related clinical scores for knee joints were significantly reduced by administration of naringin. Histological analyses demonstrated that representative phenomena, such as damage to interchondral joints, infiltration of inflammatory cells and pannus formation, were significantly depressed by treatment with naringin. In addition, increases in the expression of high-mobility group box-1 protein in the joints of mice with CIA were suppressed by naringin. These results suggest that oral administration of naringin might be effective for treating human patients with RA.

Limitation of polymyxin B on suppression of endotoxin shock induced by Salmonella infection in mice.

The protective effects of an antibiotic polymyxin B (PLB), having lipopolysaccharide (LPS)-binding activity, on infection-induced endotoxin shock in mice were investigated. Infection with 10(8) colony forming units of an attenuated Salmonella typhimurium aroA strain caused lethal endotoxin shock to ddY mice. Treatment with PLB 1 h post infection (p.i.) resulted in significant reduction of mortality and bacterial numbers in livers. In addition, treatment with PLB 1 h p.i. resulted in a transient increase at the early stage and gradual decline in plasma LPS levels. Although plasma levels of sCD14 and high mobility group box chromosomal protein-1 (HMGB-1) increased according with progression of infection, increases in plasma levels of sCD14 and HMGB-1 were downregulated by treatment with PLB 1 h p.i. However, the lethal shock was not blocked by treatment with anti-CD14 monoclonal antibody at 3 h and 6 h p.i. Interestingly, administration of PLB 6 h p.i. did not show any protective activities, indicating that a time window for effective PLB action is present.

A citrus flavonoid hesperidin suppresses infection-induced endotoxin shock in mice.

Administration of a citrus flavonoid hesperidin (HES) to mice before LPS challenge significantly reduced tumor necrosis factor (TNF)-alpha production in a dose-dependent manner. Treatment of HES 3 h before intraperitoneal (i.p.) infection with 10(8) CFU Salmonella typhimurium aroA resulted in rescue from lethal shock as similar to LPS-nonresponder mice. Not only bacterial numbers in livers and spleens but also plasma LPS levels significantly decreased by pretreatment with HES. In addition, HES markedly suppressed plasma levels of TNF-alpha and high mobility group box chromosomal protein 1 (HMGB-1), decreased the number of apoptotic cells in livers and normalized the activated states of blood coagulation factors such as prothrombin time and platelet numbers caused by infection. Pretreatment of LPS with HES suppressed the chromogenic Limulus reaction.

Suppression of infection-induced endotoxin shock in mice by a citrus flavanone naringin.

The protective effect of the Citrus flavanone naringin was demonstrated in an endotoxin shock model based on Salmonella infection. Intraperitoneal ( i. p.) infection with 10 (8) CFU Salmonella typhimurium aroA caused lethal shock in lipopolysaccharide (LPS) -responder but not LPS-non-responder mice. Administration of 1 mg naringin 3 h before infection resulted in protection from lethal shock, similar to LPS-non-responder mice. The protective effect of naringin was time- and dose-dependent. Treatment with naringin resulted not only in a significant decrease in bacterial numbers in spleens and livers, but also in a decrease in plasma LPS levels. In addition, naringin markedly suppressed TNF-alpha and normalized the activated states of blood coagulation factors such as prothrombin time, fibrinogen concentration and platelet numbers caused by infection. Interestingly, treatment with naringin suppressed high levels of soluble CD14 and high mobility group-1 molecule caused by infection.

Time- and dose-dependent effect of fosfomycin on suppression of infection-induced endotoxin shock in mice.

Therapeutic effects of fosfomycin (FOF) and imipenem (IPM) were investigated in a novel model for endotoxin shock that was caused by intraperitoneal (i.p.) infection with 10(8) colony forming units of attenuated Salmonella typhimurium. Acute lethal shock was observed in BALB/c and ddY but not in lipopolysaccharide (LPS)-nonresponder BALB/lps(d) mice. Effects of FOF, but not its enantiomer, and IPM were dose- and time-dependent, since therapeutic efficacy was demonstrated in mice injected i.p. or orally at doses of more than 20 mg/kg 15 min before or 1 h after infection. Treatment with FOF 1 h postinfection (p.i.) resulted in significant decreases in bacterial numbers in spleen and liver, suggesting that the antimicrobial activity of FOF seems to closely correlate to suppression of infection-induced lethal shock. Regarding coagulation systems, FOF inhibited increase in the prothrombin time but upregulated fibrinogen concentration. Plasma levels of LPS released from bacilli were significantly higher in FOF- than IPM-treated mice and infection controls, but both antibiotics showed similar efficacy in protection.

Does high mobility group 1 protein function as a late mediator for LPS- or TNF-induced shock in galactosamine-sensitized mice?

The role of high mobility group-1 protein (HMG-1) in LPS- and TNF-alpha-induced lethal shock in galactosamine (GalN)-sensitized mice was investigated. No detectable HMG-1 levels were observed by immunoblotting analysis in plasma from untreated or GalN-sensitized BALB/c mice 5 h after LPS injection, although significant levels of HMG-1 were detected in plasma 6 h after the challenge. All GalN-sensitized BALB/c but not BALB/lps(d) mice succumbed by 6 h after LPS injection. When GalN-sensitized mice were injected with TNF-alpha, the presence of HMG-1 was seen at 5.5 h in plasma of BALB/c mice and at 6 h in BALB/lps(d) mice, although almost all GalN-sensitized BALB/c mice died by 6 h after challenge. The time-dependent phenomenon correlated with elevated serum aspartate aminotransferase (AST) levels and the appearance of apoptotic cells in livers. Administration of pooled plasma, equivalent to approximately 200 microg recombinant murine HMG-1, taken from mice on the verge of near death, did not result in induction of lethal shock in GalN-sensitized mice. Taken together with the late appearance of HMG-1 in moribund mice, these data suggest that HMG-1 does not decisively contribute to lethality in the GalN sensitization model.