Effects of OPC-6535 on lipopolysaccharide-induced acute liver injury in the rat: involvement of superoxide and tumor necrosis factor-alpha from hepatic macrophages

Protective effect of extract from Paeonia lactiflora and Astragalus membranaceus against liver injury induced by bacillus Calmette-Guérin and lipopolysaccharide in mice

Paeonia lactiflora and Astragalus membranaceus are two popular traditional Chinese medicines, commonly used in Chinese herb prescription to treat liver disease. The extract from the roots of P. lactiflora and A. membranaceus demonstrated better hepatoprotective activity than the herbs used individually as shown in our previous studies. The present study was carried out to investigate the effects of P. lactiflora and A. membranaceus extract on immunological liver injury in mice induced by Bacillus Calmette-Guérin and lipopolysaccharide (BCG/LPS) and to explore a possible mechanism. After administration of P. lactiflora and A. membranaceus (60, 120 and 240 mg/kg, intragastrically) daily for 10 days, the extract significantly reduced the degree of liver damage in BCG/LPS-induced liver injury, as well as the elevation of serum transaminase activities and level of nitric oxide in live injury mice. The extract also restored the decrease in superoxide dismutase and glutathione peroxidase activities and inhibited the formation of lipid peroxidative products. Moreover, P. lactiflora and A. membranaceus (60, 120 and 240 mg/kg, intragastrically) repressed high levels of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) from peritoneal macrophages. In the primary cultured Kupffer cells, P. lactiflora and A. membranaceus also significantly decreased the production of TNF-alpha and IL-1 in cells stimulated with LPS (5 microg/ml). These results suggest that P. lactiflora and A. membranaceus have a protective effect on BCG/LPS-induced liver injury mice, which might be associated with the antioxidant properties, ability to reduce nitric oxide production and suppression of Kupffer cell activity and pro-inflammatory mediator and cytokines production.

Tetomilast suppressed production of proinflammatory cytokines from human monocytes and ameliorated chronic colitis in IL-10-deficient mice

BACKGROUND

Tetomilast (OPC-6535) was originally developed as a compound inhibiting superoxide production in neutrophils. Although its mechanism of action is not completely understood, phosphodiesterase type 4 inhibitory function has been postulated. The therapeutic effect of PDE4 inhibitors has been reported for chronic inflammatory disorders such as chronic obstructive pulmonary diseases. In this study we aimed to examine whether tetomilast could be a novel drug for inflammatory bowel diseases by further clarifying its antiinflammatory effects.

METHODS

Cytokines from human peripheral blood mononuclear cells were measured by enzyme-linked immunosorbent assay (ELISA) and Cytokine Beads Array. The transcripts were quantified by reverse-transcriptase polymerase chain reaction (RT-PCR). Phosphorylation of transcription factors was examined by phosflow. To examine its in vivo effect, a once-daily oral dose of tetomilast was tested in murine IL-10(-/-) chronic colitis.

RESULTS

Tetomilast suppressed TNF-alpha and IL-12 but not IL-10 production from lipopolysaccharide (LPS)-stimulated human monocytes. It suppressed TNF-alpha, IFN-gamma, and IL-10 from CD4 lymphocytes. Tetomilast suppressed cytokine production at the transcriptional level but did not alter phosphorylation of p65, ERK, p38, and STAT3. HT-89, a protein kinase A inhibitor, did not abolish the effect of tetomilast, suggesting that it was independent from the classical cAMP/PKA pathway. IL-10 was not essential to the inhibitory effect of tetomilast on TNF-alpha and IL-12. Tetomilast ameliorated IL-10(-/-) chronic colitis with reduced clinical symptoms, serum amyloid A, and histological scores with decreased TNF-alpha mRNA expression.

CONCLUSIONS

Tetomilast exerts its antiinflammatory effects on human monocytes and CD4 cells. Combined with in vivo data these findings support the feasibility of tetomilast as a novel drug for inflammatory bowel diseases.

CO liberated from CORM-2 modulates the inflammatory response in the liver of thermally injured mice

AIM

To explore the effects of CO-releasing molecules [tricarbonyldichlororuthenium (II) dimer, CORM-2]-liberated CO on attenuation of inflammatory responses in liver of an experimental animal model of thermal injury and to investigate the associated potential mechanisms.

METHODS

Thirty-six mice were assigned to three groups in three respective experiments. In each experiment, mice in sham group (n=4) received sham thermal injury, whereas mice in burn group (n=4) received a 15% of total body surface area (TBSA) full-thickness thermal injury, and mice in burn+CORM-2 group (n=4) received the same thermal injury with immediate administration of CORM-2 (8 mg/kg, iv). Hepatic tissue sections were stained with hematoxylin and eosin and examined under a light microscope. Levels of aminotransferases (ALT and AST) and nitric oxide (NO) were measured by biochemical methods. Tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL-1beta) activity, and the protein expression of iNOS and HO-1 in serum and tissue homogenates were assessed. In in vitro experiments, Kupffer cells were stimulated with LPS (10 microg/mL) for 4 h in the presence or absence of CORM-2 (10-100 micromol/L). Subsequently, the expression levels of TNF-alpha and NO production were assessed.

RESULTS

Pro-inflammatory mediators (TNF-alpha, IL-1beta, NO) in serum and liver homogenates of thermally injured mice were significantly reduced by CORM-2 administration. This was accompanied by a decrease in the expression of iNOS while an increase in the expression of HO-1 in the liver tissue. In parallel, the concentrations of TNF-alpha and NO in supernatants of LPS-stimulated Kupffer cells co-incubated with CORM-2 (10-100 micromol/L) were also markedly decreased. Histological examination demonstrated that CORM-2 could attenuate the leukocytes infiltration to the liver tissue.

CONCLUSION

CORM-released CO modulates liver inflammation and significantly protects liver injury in burn mice by inhibiting the expression of iNOS and NO production, down-regulating the expression of pro-inflammatory mediators (TNF-alpha, IL-1beta).

CO liberated from CORM-2 modulates the inflammatory response in the liver of thermally injured mice

AIM: To explore the effects of CO-releasing molecules [tricarbonyldichlororuthenium (II) dimer, CORM-2]-liberated CO on attenuation of inflammatory responses in liver of an experimental animal model of thermal injury and to investigate the associated potential mechanisms.

METHODS: Thirty-six mice were assigned to three groups in three respective experiments. In each experiment, mice in sham group (n = 4) received sham thermal injury, whereas mice in burn group (n = 4) received a 15% of total body surface area (TBSA) full-thickness thermal injury, and mice in burn + CORM-2 group (n = 4) received the same thermal injury with immediate administration of CORM-2 (8 mg/kg, iv). Hepatic tissue sections were stained with hematoxylin and eosin and examined under a light microscope. Levels of aminotransferases (ALT and AST) and nitric oxide (NO) were measured by biochemical methods. Tumor necrosis factor-α (TNF-α) and interleukin (IL-1β) activity, and the protein expression of iNOS and HO-1 in serum and tissue homogenates were assessed. In in vitro experiments, Kupffer cells were stimulated with LPS (10 &mgr;g/mL) for 4 h in the presence or absence of CORM-2 (10-100 &mgr;mol/L). Subsequently, the expression levels of TNF-α and NO production were assessed.

RESULTS: Pro-inflammatory mediators (TNF-α, IL-1β, NO) in serum and liver homogenates of thermally injured mice were significantly reduced by CORM-2 administration. This was accompanied by a decrease in the expression of iNOS while an increase in the expression of HO-1 in the liver tissue. In parallel, the concentrations of TNF-α and NO in supernatants of LPS-stimulated Kupffer cells co-incubated with CORM-2 (10-100 &mgr;mol/L) were also markedly decreased. Histological examination demonstrated that CORM-2 could attenuate the leukocytes infiltration to the liver tissue.

CONCLUSION: CORM-released CO modulates liver inflammation and significantly protects liver injury in burn mice by inhibiting the expression of iNOS and NO production, down-regulating the expression of pro-inflammatory mediators (TNF-α, IL-1β).

Direct hepatotoxic effect of KC chemokine in the liver without infiltration of neutrophils

KC is a mouse homolog of human chemokine gro-alpha (CXCL1), expression of which is increased in liver diseases. We show that activated, but not quiescent, hepatic stellate cells (HSCs) express KC. Hepatic stellate cells constitutively express the KC receptor, CXCR2. Addition of recombinant KC to HSCs undergoing activation in culture increases secretion and processing of Type I collagen. Overexpression of endogenous KC in the mouse liver could be achieved by an intraperitoneal injection of CCl(4), followed after 24 hrs by an injection of recombinant KC into circulation. This protocol resulted in about a 14-fold increase in concentration of KC protein in the liver. Overexpression of KC was associated with upregulation of the mRNA for CXCR2 and MIP-2 and with necrosis and increased synthesis of Type I collagen. This suggests that KC has a direct hepatotoxic effect, which led to a massive liver necrosis after 48 hrs. No accumulation of neutrophils was seen in the livers as judged by histology and reverse transcriptase-polymerase chain reaction analysis of myeloperoxidase mRNA. Autostimulation of KC and CXCR2 expression by recombinant KC protein in the mice with preexisting liver injury indicates a positive feedback regulation. Such regulation and direct hepatotoxicity of KC with increased collagen synthesis represent novel findings about the role of KC/ gro-alpha in liver pathology.

Nonspecific phosphodiesterase inhibition attenuates liver injury in acute endotoxemia

BACKGROUND

Endotoxemia is accompanied by pro-inflammatory cytokine production, generation of reactive oxygen species, and end-organ injury. Pentoxifylline (PTX), a methylxanthine derivative and phosphodiesterase inhibitor, is known for its anti-inflammatory properties, including down-regulation of interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha synthesis. Its effects on liver function and hepatic histology following acute endotoxemia have not been investigated fully. We hypothesized that PTX would preserve liver architecture and function after intravenous lipopolysaccharide (LPS) injection.

METHODS

Anesthetized Sprague-Dawley rats received an i.v. bolus injection of LPS (5 mg/kg), LPS + PTX (25 mg/kg), or saline (sham). Plasma concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), TNF-alpha, IL-6, and nitrite were measured at different time points after LPS injection. Liver injury was graded according to a scoring system in a blinded fashion from 0 (normal) to 4 (severe) for hepatocellular necrosis, hemorrhage, and parenchymal and sinusoidal inflammatory infiltrates. Neutrophil infiltration was measured by counting myeloperoxidase (MPO)-positive stained cells. Nuclear factor (NF)-kappaB p-65 was measured by counting positive stained nuclei of hepatocytes and Kupffer cells (KC). Inducible nitric oxide synthase (iNOS) was evaluated by positively stained KC. Data are presented as mean +/- SEM. Analysis of variance with p < 0.05 was considered statistically significant.

RESULTS

Animals treated with PTX showed a significant reduction in liver injury score and neutrophil infiltration. Treatment with PTX significantly decreased TNF-alpha, IL-6, and the concentrations of AST and ALT when compared to LPS alone. In addition, a significant decrease in NF-kappaB-positive staining in hepatocytes and KC, as well as in KC iNOS immunostaining was observed in PTX-treated animals compared to the LPS group.

CONCLUSIONS

Pentoxifylline downregulates the inflammatory response significantly and decreases liver injury in acute endotoxemia.