Inhibition of lipopolysaccharide activation of Kupffer cells by transition metals

Significance of malondialdehyde, superoxide dismutase and endotoxin levels in Budd-Chiari syndrome in patients and a rat model

Budd-Chiari syndrome (BCS) is a rare clinical syndrome caused by the obstruction of hepatic venous outflow. In theory, hepatic congestion and hypoxia induce pathological damage and changes in the liver. However, at present, laboratory evidence supporting this theory is lacking. The aim of the present study was to assess the expression and significance of the hypoxia-associated indicators malondialdehyde (MDA), superoxide dismutase (SOD) and endotoxin (ET) in the liver and serum of subjects with BCS. An animal model of BCS was established by partial ligation of the inferior vena cava (IVC) in rats. The levels of MDA, SOD and ET in the serum of BCS patients, as well as in the liver and serum of rats with BCS, were detected and analyzed. In human patients with BCS, the serum levels of MDA, ET and SOD were significantly different from those in healthy control subjects. In the animal model, similar trends were observed regarding the MDA, ET and SOD levels in liver homogenate and serum (P<0.05), the degree of which was more pronounced in the liver homogenate than in the serum. At 6 weeks after the surgery, these indicators reached peak/valley levels in the experimental group and were at least partially restored by week 12. A negative correlation between MDA and SOD, a positive correlation between MDA and ET, and a negative correlation between SOD and ET was identified. In conclusion, the levels of hypoxia-associated indicators significantly changed with BCS progression, suggesting that hypoxia is a major factor in the pathogenesis of BCS.

Effect of inhibitors of endocytosis and NF-kB signal pathway on folate-conjugated nanoparticle endocytosis by rat Kupffer cells

The regular accumulation of nanoparticles in the liver makes them hepatotoxic and decreases the circulation time, thus reducing their therapeutic effect. Resolving this problem will be significant in improving bioavailability and reducing side effects. In this study, we reduced the phagocytosis of epirubicin (EPI)-loaded folic acid-conjugated pullulan acetate (FPA/EPI) nanoparticles by Kupffer cells (KCs) through internalization and nuclear factor kappa B (NF-kB) signal pathway inhibitors, thus allowing development of FPA/EPI nanoparticles as a nanodrug delivery system (NDDS) based on our previous study. FPA/EPI nanoparticles were prepared by the dialysis method. Rat KCs were preincubated with the following individual or compound inhibitors: chlorpromazine (CPZ), nystatin (NY), colchicine (Col), amiloride (AMR), and pyrrolidine dithiocarbamate (PDTC). Dose- and time-dependent cellular uptake effects of inhibitors on FPA/EPI nanoparticles were determined through fluorometry. The cytokine levels of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-6 were tested in culture supernatants by bead-based multiplex flow cytometry. The uptake study demonstrated that inhibitors had an obvious inhibitory effect (P<0.05 or P<0.01), with NY, AMR and Col all showing time-dependent inhibitory effects. PDTC + NY had the strongest inhibitory effect, with an uptake rate of 14.62%. The levels of the three proinflammatory cytokines were changed significantly by the compound inhibitors. TNF-α was significantly inhibited (P<0.05 or P<0.01), but IL-1β and IL-6 showed smaller decreases. These results suggested that clathrin- and caveolae-mediated endocytosis were the main routes via which nanoparticles entered KCs and that the NF-kB signal pathway was very important too. In summary, multiple mechanisms, including clathrin- and caveolae-mediated endocytosis, contribute to cytokine production in macrophages following exposure to folic acid-conjugated pullulan acetate nanoparticles. Thus, the endocytosis inhibition strategy has great potential for improving therapy and reducing toxicity of an NDDS in the treatment of cancer.

The activation of EGFR promotes myocardial tumor necrosis factor-α production and cardiac failure in endotoxemia

To study the effect of EGFR activation on the generation of TNF-α and the occurrence of cardiac dysfuncetion during sepsis, PD168393 and erlotinib (both are EGFR inhibitors) were applied to decreased the production of TNF-α and phosphrylation of ERK1/2 and p38 induced by LPS in cardiomyocytes. These results were further proved by specifically knocked down the expression of EGFR in vitro. Both TAPI-1, a TNF-α converting enzyme (TACE) inhibitor, and TGF-α neutralizing antibody could inhibit the activation of EGFR and the generation of TNF-α mRNA after LPS treatment. The increase of TGF-α in response to LPS could also be suppressed by TAPI-1. On the other hand, exogenous TGF-α increased the expression of TNF-α mRNA and partially reversed the inhibitory effect of TAPI-1 on expression of TNF-α mRNA in response to LPS indicating that the transactivation of EGFR by LPS in cardiomyocytes needs the help of TACE and TGF-α. In endotoxemic mice, inhibition the activation of EGFR not only decreased TNF-α production in the myocardium but also improved left ventricular pump function and ameliorated cardiac dysfunction and ultimately improved survival rate. All these results provided a new insight of how EGFR regulation the production of TNF-α in cardiomyocytes and a potential new target for the treatment of cardiac dysfunction in sepsis.

Diazoxide attenuates ischemia/reperfusion injury via upregulation of heme oxygenase-1 after liver transplantation in rats

AIM: To evaluate the effects of diazoxide on ischemia/reperfusion (I/R)-injured hepatocytes and further elucidate its underlying mechanisms.

METHODS: Male Sprague-Dawley rats were randomized (8 for donor and recipient per group) into five groups: I/R group (4 h of liver cold ischemia followed by 6 h of reperfusion); heme oxygenase-1 (HO-1) small interfering RNA (siRNA) group (injection of siRNA via donor portal vein 48 h prior to harvest); diazoxide (DZ) group (injection of DZ via donor portal vein 10 min prior to harvest); HO-1 siRNA + DZ group; and siRNA control group. Blood and liver samples were collected at 6 h after reperfusion. The mRNA expressions and protein levels of HO-1 were determined by reverse transcription polymerase chain reaction and Western blotting, and tissue morphology was examined by light and transmission electron microscopy. Serum transaminases level and cytokines concentration were also measured.

RESULTS: We observed that a significant reduction of HO-1 mRNA and protein levels in HO-1 siRNA and HO-1 siRNA + DZ group when compared with I/R group, while the increases were prominent in the DZ group. Light and transmission electron microscopy indicated severe disruption of tissue with lobular distortion and mitochondrial cristae damage in the HO-1 siRNA and HO-1 siRNA + DZ groups compared with DZ group. Serum alanine aminotransferase, aspartate transaminase, tumor necrosis factor-α and interleukin-6 levels increased in the HO-1 siRNA and HO-1 siRNA + DZ groups, and decreased in the DZ group.

CONCLUSION: The protective effect of DZ may be induced by upregulation of HO-1. By inhibiting expression of HO-1, this protection pretreated with DZ was abolished.

Heme oxygenase-1 protects donor livers from ischemia/reperfusion injury: the role of Kupffer cells

AIM

To examine whether heme oxygenase (HO)-1 overexpression would exert direct or indirect effects on Kupffer cells activation, which lead to aggravation of reperfusion injury.

METHODS

Donors were pretreated with cobalt protoporphyrin (CoPP) or zinc protoporphyrin (ZnPP), HO-1 inducer and antagonist, respectively. Livers were stored at 4 degrees C for 24 h before transplantation. Kupffer cells were isolated and cultured for 6 h after liver reperfusion.

RESULTS

Postoperatively, serum transaminases were significantly lower and associated with less liver injury when donors were pretreated with CoPP, as compared with the ZnPP group. Production of the cytokines tumor necrosis factor-alpha and interleukin-6 generated by Kupffer cells decreased in the CoPP group. The CD14 expression levels (RT-PCR/Western blots) of Kupffer cells from CoPP-pretreated liver grafts reduced.

CONCLUSION

The study suggests that the potential utility of HO-1 overexpression in preventing ischemia/reperfusion injury results from inhibition of Kupffer cells activation.

Expression of IRAK-M in endotoxin-tolerant Kupffer cells and its significance

AIM: To observe the expression of IRAK-M in endotoxin-tolerant Kupffer cells and to explore its role in endotoxin tolerance of Kupffer cells.

METHODS: The model of endotoxin-tolerant Kupffer cells was established by lipopolysaccharide (LPS, 10 μg/L) pretreatment, and was compared with control cells. At different time points after LPS (100 μg/L) stimulation, the TNF-α level in culture medium was measured by ELISA. The mRNA expression of TNF-α and IRAK-M in Kupffer cells was detected by RT-PCR. TransAM NF-κB Kit was used to examine the activation of NF-κB. The expression of IRAK-M protein in Kupffer cells was detected by Western blot.

RESULTS: In both groups, LPS stimulation increased TNF-α level in culture medium, and enhanced TNF-α mRNA expression and NF-κB activation in Kupffer cells, but these parameters were significantly lower in tolerant group than in control group (P < 0.05). In control group, the expression of IRAK-M mRNA could not be detected until 24 h after LPS stimulation. However, this expression was slight in tolerant group before LPS stimulation and was rapidly up-regulated after stimulation, peaking at 6 h and was still stronger than the expression in control group at 24 h (P < 0.05). In addition, there was no IRAK-M protein expression in control group until 24 h after LPS stimulation, but this expression could be detected in tolerant group before LPS stimulation and was up-regulated in a time-dependent manner. There was significant difference between two groups (P < 0.01).

CONCLUSION: IRAK-M expression is significantly up-regulated in endotoxin-tolerant Kupffer cells and it may play an important role in endotoxin tolerance of Kupffer cells.