[HBxAg enhanced p53 protein accumulation in hepatoma cells]

OBJECTIVE

In order to determine the interaction between HBxAg and p53 protein and its role in hepatocarcinogenesis.

METHODS

Cotransfection was performed using reporter gene, chloramphenical acetyltransferase (CAT), p53 and HBVx gene, and dexamethasone inducible HBx plasmid pMAMHBx was constructed for the experiment. Human hepatoma cell line Hep3B was used as the target cell. The activity of HBxAg and p53 was detected by CAT assay and immunohistochemical staining after transient transfection.

RESULTS

HBxAg could increase the accumulation of p53 protein in cells and enhance CAT expression. Immunohistochemical staining showed that p53 protein bound to HBxAg in the cytoplasm and formed a complex causing a partial block of the process of p53 during passing through the nuclear membrane from the cytoplasm.

CONCLUSION

Data strongly suggested that HBxAg is capable of binding p53 and forms a protein-protein complex which might reduce or inactivate p53's antiproliferative activity and plays an important role in the pathogenesis of HBV-associated hepatocellular carcinoma.

[Study on tissue culture of Poligonum multiflorum]

In the present thesis, suitable medium for callus inducement and relationship between culture time and callus growth of Poligonum multiflorum were studied by mono-factorial and orthogonal design test. The experiments showed that the best medium for callus inducement was MS + 2,4-D 1 mg/L + 6-BA 1 mg/L + IBA 0.5 mg/L, dark culture was better than light culture, callus grew fast when it was cultured 12 days, whole plant could be induced by callus, the induce rate was 95%.

Lipoprotein and apolipoprotein secretion by a newborn piglet intestinal cell line (IPEC-1)

The aim of these studies was to characterize the synthesis and secretion of lipoproteins and apolipoprotein B (apo B) and apo A-I by a newborn swine intestinal epithelial cell line (IPEC-1). Differentiated cells exhibited enterocytic features, including microvilli. [3H] oleic acid was taken up and incorporated into cellular lipids and secreted into the basolateral medium in lipoproteins. Total apo B and apo A-I secreted increased with oleic acid incubation. However, cellular apo B and apo A-I content did not change. Whereas undifferentiated cells synthesized and secreted only apo B-100, both apo B-100 and apo B-48 were produced by differentiated cells. The ratio of radiolabeled apo B-48 to apo B-100 in both basolateral medium and cell homogenate increased with oleic acid treatment after 24-h steady-state labeling. However, apo B mRNA editing was unchanged, indicating posttranslational regulation of this ratio. Pulse-chase radiolabeling demonstrated no major changes in cellular or basolateral medium apolipoprotein labeling kinetics with oleic acid or dexamethasone incubation. The dissociation of apo B and apo A-I mass secretion from the secretion of radiolabeled apo B and apo A-I in response to oleic acid absorption suggests the presence of an intracellular pool of apolipoprotein with a slow turnover that is mobilized for secretion in response to fatty acid uptake.

Effect of acute feeding of diets of varying fatty acid composition on intestinal apolipoprotein expression in the newborn swine

The purpose of this study was to determine the effects of dietary fatty acids of varying chain lengths and degrees of saturation on intestinal apolipoprotein (apo) B and A-I expression in the newborn piglet. Two-day-old female piglets received one of three isocaloric formulas containing 48% of total calories (120 kcal/kg/24 h) as medium-chain triglycerides (MCT) from MCT oil, intermediate-chain saturated triglycerides (ICST) from coconut oil, or long-chain polyunsaturated triglycerides (LCPUT) from safflower oil by continuous duodenal infusion for 24 h. After in situ radiolabeling, jejunal and ileal mucosal apo B-48 and A-I were immunoprecipitated, and synthesis was expressed as percentage of total protein synthesis. Mucosal apo B and A-I mass was measured by ELISA as nanograms of apoprotein/microgram of total protein. Fifty percent less apo B jejunal synthesis was present in the ICST group versus the MCT and LCPUT groups (0.67 +/- 0.07, 1.19 +/- 0.20, and 1.25 +/- 0.15, respectively, mean +/- SEM, p < 0.05). Jejunal apo B mass was lower in the MCT group versus the ICST and LCPUT groups (0.10 +/- 0.02, 0.21 +/- 0.03, and 0.16 +/- 0.03, respectively, p < 0.05). Ileal apo B synthesis was lowest in the ICST group. No differences were found in ileal apo B mass. Two-fold higher jejunal apo A-I synthesis was found in the LCPUT group versus the MCT and ICST groups (14.18 +/- 1.69, 7.56 +/- 2.63, and 6.36 +/- 0.58, respectively, p < 0.01). No differences were found for jejunal apo A-I mass. In the ileum, the only difference was a higher apo A-I mass in the LCPUT group (p < 0.05). We conclude that in the newborn piglet intestinal apo B and A-I expression is acutely and differentially regulated by dietary lipid varying in fatty acid chain length and saturation. The patterns of regulation are complex and vary among specific apolipoproteins and regions of the small intestine and include co- and posttranslational mechanisms.

Intestinal expression of apolipoprotein A-IV and C-III is coordinately regulated by dietary lipid in newborn swine

The purpose of this study was to determine the effects of dietary fatty acids on intestinal apolipoprotein (apo) A-IV and C-III expression in the newborn piglet. Two-day-old female piglets received one of three isocaloric formulas containing medium-chain triglycerides (TG) (MCT), intermediate-chain saturated TG (ICST), or long-chain polyunsaturated TG (LCPUT) by continuous duodenal infusion for 24 hrs. Control groups received a low-TG elemental formula infusion (LTG group) and a high-TG long-chain unsaturated lipid emulsion infusion (HTG group). Jejunal synthesis of both apo A-IV and C-III was increased by all infusions compared to the LTG group. Apo A-IV and C-III mRNA levels paralleled synthesis levels except for apo C-III with the MCT diet, where regulation appeared to occur at the translational level. Among all groups, apo A-IV synthesis and mRNA abundance were linearly correlated with that of apo C-III.

Sequence of the porcine apoA-I gene

The nucleotide sequence of the swine apoA-I gene (encoding apolipoprotein) has been determined. The structure of the gene is similar to that of the human gene, and the exons exhibit a high degree of homology with those of the human gene. The porcine apoA-I gene is located adjacent to the apoC-III gene, as in humans.

Modulation of murine hepatic lipase activity by exogenous and endogenous Kupffer-cell activation

Deficiency of hepatic lipase (HL) may play a role in the lipoprotein abnormalities in chronic inflammatory states which are characterized by reticuloendothelial-system activation and cytokine release. HL triacylglycerol hydrolase activity was measured in heparin perfusates of livers from autoimmune MRL/lpr mice, which spontaneously develop a condition closely resembling human lupus erythematosis and exhibit spontaneous Kupffer-cell activation after 8 weeks of age, as well as from normal mice treated with Corynebacterium parvum or polyinosinic-polycytidylic acid complex [poly(I.C)] to induce Kupffer-cell activation. HL activity in MRL/lpr mice older than 8 weeks was 29.5% (P = 0.002) of that in age-matched control MRL/++ mice. Treatment of normal mice with C. parvum or poly(I.C) resulted in HL activities 18.6% (P = 0.004) and 13.1% (P = 0.007) respectively of untreated controls. Northern-blot hybridization of liver poly(A)+ RNA showed no differences in HL mRNA abundance in MRL/++ mice compared with the MRL/lpr autoimmune strain after 8 weeks of age, or in normal control mice compared with those treated with C. parvum, indicating attenuation of HL activity at the translational or post-translational level. Deficiency of this enzyme may represent one of the mechanisms contributing to the dyslipoproteinaemia of autoimmune disease and chronic infection.