| Objective To study the lipopolysaccharide(LPS)-induced liver injury in D-galactosamine(D-GalN) sensitized rats at a sub-lethal dose and to investigate the situation of hepatocellular apoptosis and the mechanism of liver injury therein.Methods Forty eight Wistar rats were randomly divided into three groups(6h,24h,48h 16 for each).The rats in each group were further divived into treatment (n=8) and control group(n=8).The rats in the treatment group were injected peritoneally with LPS(50μg/kg)and D-GalN(300mg/kg) in 1ml stroke-physiological saline solution,while the rats in control group were treated with normal saline of the same volume,and then were killed 6,24,48 hours.Blood samples were collected from the vena cava inferior to detect the contents of serum alamine aminotransferase(ALT),aspartate transaminase(AST) and total billirubin(TBIL).The morphological changes were observed by hematoxylin and eosin(HE) staining.The apoptosis of liver cells was detected by TUNEL assay or ultrastructral observations.The expressions of tunor necrosis factor-α(TNF-α), interleukin-1β(IL-1β), inducible nitric oxide synthase(iNOS),and p53 gene were detected by reversetranscription polymerase chain reaction(RT-PCR).Results Blood biochemical indicators,such as the ALT,AST,TBIL levels,were all significantly higher in the treatment groups than those of the corresponding control groups at 6 hours,which reached the peak at 24 hours,and sustained high levels at 48 hours. By naked eyes,sporadic,punctiform and lamellar hemorrhagic spots were observed on the surface of swelling and pale liver with tenacious texture in the rats of treatment group.Congestion,piecemeal necrosis and infiltration of inflammatory cells appeared at 6 hours,and cellular vacuolar degeneration,engorgement,focal necrosis and neutrophil infiltration were observed at 24 hours.At 48 hours,vacuolar degeneration appeared in a majority of liver cells,and structural disorder of liver lobule and spot necrosis were observed.Transmission electron microscopy showed that apoptotic cells were rare in the control groups,but were abundant in the liver tissues of the treatment groups.and appeared earlier period feature of apoptotic cells at 6 hours.The apoptotic cells,which showed later stage feature,were obviously increasing at 24 and 48 hours.The apoptotic indices of liver cells of 6h,24h,48h treatment groups were 7.3 %±1.5 % , 71.8 %±10.3 % , 68.2 %±11.9 % respectively,all significantly higher than those of the control groups(2.6%±1.1%).However,the apoptotic indices of the 24h and 48h treatment groups were not significantly different.The expression of TNF一αwas not significantly different at all time points.However,the expression of IL—lβwas significantly up-regulateed in treatment group and reached the peak at 6h.The expression levels of iNOS gene in the control group,6h treatment group,24h treatment group,48h treatment group were respectively 0,0.53±0.11,0.36±0.08 and 0.15±0.04 with a significantly difference among different groups,and with a peak at 6h.The p53 expression levels of the control group,6h treatment group,24h treatment group,48h treatment group were 0.031±0.006,0.022±0.008,0.49±0.11and 0.39±0.17 respectively,being low in both control group and 6h treatment group and significantly up-regulated in the 24h and 48h treatment group.Conclusion Acute liver failure can be induced by sub-lethal dose LPS in D-GalN-sensitized rats,which may be associated with the early high expression of iNOS gene;This animal model of acute liver failure,which induced by sub-lethal dose LPS in D-GalN-sensitized rats,may be ideal;Apoptosis is the important morphological feature in this process,which may be associated with the early high expression of p53 gene in later stage. |
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