Microthrombus formation enhances tumor necrosis factor-alpha production in the development of ischemia/reperfusion-induced liver injury in rats

RETRACTED ARTICLE: Nafamostat mesilate inhibits the expression of HMGB1 in lipopolysaccharide-induced acute lung injury

PURPOSE

High mobility group box 1 (HMGB1) protein has recently been shown to be an important late mediator of acute lung injury and a promising therapeutic target. Nafamostat mesilate (NM) is a broad-range synthetic protease inhibitor with some anti-inflammatory action. The purpose of this study was to evaluate the effect of NM on HMGB1 in lipopolysaccharide (LPS)-induced lung injury in rats.

METHODS

Male Wistar rats were given either saline (LPS group) or NM (NM+LPS group) 30 min before the intravenous injection of a bolus of LPS (5 mg.kg(-1)). After the administration of LPS, injury to the lung and the expression of HMGB1, tumor necrosis factor-alpha (TNF-alpha), and plasminogen activator inhibitor-1 (PAI-1) were examined.

RESULTS

Histological examination revealed that interstitial edema, leukocytic infiltration, and HMGB1 protein expression were markedly reduced in the NM+LPS group compared to the LPS group. Furthermore, the LPS-induced increases in PAI-1 activity and in plasma TNF-alpha concentrations were also lower in the rats given both NM and LPS than in the rats given LPS alone.

CONCLUSIONS

The anticoagulatory activity of NM may have inhibited PAI-1, while its anti-inflammatory activity blockaded TNF-alpha, thereby indirectly inhibiting HMGB1 and reducing tissue damage in the lung. These findings indicate that NM can inhibit the lung injury induced by LPS in rats. NM is an excellent candidate for use in new therapeutic strategies to prevent or minimize lung injury.

Dalteparin, a low molecular weight heparin, attenuates inflammatory responses and reduces ischemia-reperfusion-induced liver injury in rats

OBJECTIVE

To examine whether dalteparin, a low molecular weight heparin, prevents hepatic damage by inhibiting leukocyte activation, we analyzed its effect on ischemia/reperfusion (I/R) injury of rat liver in which activated leukocytes play a critical role.

DESIGN

Prospective, randomized, controlled study.

SETTING

Research laboratory at a university medical center.

SUBJECTS

Male Wistar rats weighing 220-280 g.

INTERVENTIONS

Hepatic damage was evaluated by changes in serum transaminase concentrations after I/R. Coagulation abnormalities were evaluated by changes in serum concentrations of fragment E of fibrin and fibrinogen degradation products after I/R. Hepatic tissue blood flow was measured by laser-Doppler flow meter. Hepatic edema was evaluated by determination of the change in the wet/dry tissue weight ratio. Rats were intravenously injected with dalteparin or unfractionated heparin (300 units/kg) and subcutaneously injected with DX9056a, a selective inhibitor of activated factor X (3 mg/kg). To determine whether dalteparin inhibits leukocyte activation, we examined the effect of dalteparin on hepatic concentrations of interleukin-12, tumor necrosis factor-alpha, and hepatic myeloperoxidase activity after I/R in vivo. In addition, we examined increases in tumor necrosis factor-alpha production in rat monocytes and in intracellular calcium concentrations in neutrophils in vitro. We also examined the effect of dalteparin on endothelial production of prostacyclin using isolated rat hepatic sinusoidal cells in vitro.

MEASUREMENTS AND MAIN RESULTS

Intravenous administration of dalteparin inhibited increases in serum levels of both transaminases and serum concentrations of fragment E of fibrin and fibrinogen degradation products in animals subjected to hepatic I/R. Hepatic tissue blood flow after reperfusion was increased by dalteparin. Dalteparin inhibited hepatic edema, increases in hepatic tissue levels of interleukin-12 and tumor necrosis factor-alpha, and accumulation of neutrophils in animals subjected to hepatic I/R. Neither DX9065a nor unfractionated heparin showed any therapeutic effects, despite potent inhibition of increases in serum levels of fragment E of fibrin and fibrinogen degradation products. Neither monocytic tumor necrosis factor-alpha production nor neutrophil activation was inhibited by dalteparin in vitro. Dalteparin enhanced the hepatic I/R-induced increases in hepatic tissue levels of 6-keto-prostaglandin (PG) F1alpha, a stable metabolite of prostacyclin, which is capable of inhibiting monocytic tumor necrosis factor-alpha production. Pretreatment with indomethacin completely reversed both of the therapeutic effects of dalteparin, whereas pretreatment with NS-398, a selective inhibitor of cyclooxygenase-2, did not. Dalteparin did not directly increase the endothelial production of prostacyclin in vitro.

CONCLUSION

Dalteparin might reduce I/R-induced liver injury in rats by attenuating inflammatory responses. These therapeutic effects might be independent of its anticoagulant activity but dependent on its capacity to enhance endothelial production of prostacyclin via cyclooxygenase-1 activation. Furthermore, the mechanism or mechanisms by which dalteparin promotes the endothelial production of prostacyclin in vivo might involve unknown factors other than endothelial cells.

Urinary trypsin inhibitor reduces LPS-induced hypotension by suppressing tumor necrosis factor-alpha production through inhibition of Egr-1 expression

Although urinary trypsin inhibitor (UTI) has been shown to inhibit tumor necrosis factor (TNF)-alpha- production, the detailed mechanism(s) remains unclear. This study was undertaken to elucidate the molecular mechanism(s) underlying this inhibitory effect in monocytes in vitro and in rats given lipopolysaccharide (LPS). TNF-alpha production by monocytes stimulated with LPS (100 ng/ml) was inhibited by UTI at concentrations higher than 100 U/ml. Expression of early growth response factor-1 (Egr-1) and phosphorylation of extracellular signal-regulated protein kinases 1/2 in monocytes stimulated with LPS were inhibited by UTI. UTI (50,000 U/kg i.v.) inhibited LPS (5 mg/kg i.v.)-induced increases in lung tissue levels of Egr-1, TNF-alpha mRNA, and TNF-alpha in rats. UTI inhibited LPS-induced hypotension by inhibiting pulmonary induction of inducible nitric oxide synthase (iNOS). We previously demonstrated that anti-TNF-alpha antibody and aminoguanidine, a selective inhibitor of iNOS, reduced LPS-induced hypotension in this animal model. Furthermore, we also reported that reduction of LPS-induced coagulation abnormalities in rats did not affect inflammatory responses and hypotension in this animal model. Taken together, these observations strongly suggested that UTI inhibited LPS-induced production of TNF-alpha by inhibiting activation of the extracellular signal-regulated protein kinases 1/2-Egr-1 pathway in monocytes, which might at least partly contribute to reduction of hypotension through inhibition of iNOS induction in rats given LPS.

Regulation of inflammatory responses by activated protein C: the molecular mechanism(s) and therapeutic implications

Activated protein C (APC), a natural anticoagulant, is formed from protein C by the action of the thrombin-thrombomodulin (TM) complex on the endothelial cell surface. Endothelial protein C receptor augments the activation of protein C by the thrombin/TM system. APC inactivates the activated form of coagulation factors V and VIII in the presence of protein S. Administration of APC reduced the pulmonary vascular injury and hypotension as well as the coagulation abnormalities by inhibiting production of the tumor necrosis factor-alpha (TNF-alpha) in rats given endotoxin (ET). These therapeutic effects of APC could not be attributed to its anticoagulant effects. APC inhibited ET-induced TNF-alpha production in human monocytes by inhibiting activation of nuclear factor K-B and activator protein-1 in vitro. Administration of the human plasma-derived APC ameliorated coagulation abnormalities without any adverse effects in patients with disseminated intravascular coagulation (DIC). Recombinant APC was reported to reduce the mortality of patients with severe sepsis, and the therapeutic effect was more marked in such patients with overt DIC than those without it. These observations strongly suggest that APC plays important roles in the regulation of inflammation as well as coagulation. Both anti-inflammatory and anticoagulant properties of APC might contribute to the therapeutic usefulness in patients with severe sepsis.