Anti-HBV hairpin ribozyme-mediated cleavage of target RNA in vitro

AIM

To study the preparation and cleavage activity of HpRz directed against the transcript of HBV core gene in vitro.

METHODS

HpRz gene designed by computer targeting the transcript of HBV core gene was cloned into the vector p1.5 between 5'-cis-Rz and 3'-cis-Rz. 32p-labeled HpRz transcript proved whether the vector fit for the preparation of hairpin ribozyme in vitro. 32p-labeled pKC transcript containing HBV core region as target-RNA was transcribed using T7 RNA polymerase and purified by denaturing PAGE. Cold HpRz transcript was incubated with 32p-labeled target-RNAs under different conditions and radio autographed after denaturing polyacrylamide gel electrophoresis.

RESULTS

HpRz has the specific ability of cleavage of target RNA at 37 degrees and 12 mM MgCl2. Km=26.31 nmol/L, Kcat=0.18/min. These results revealed that the design of HpRz was correct.

CONCLUSION

HpRz prepared in this study possesses specific catalytic activity from the identification of cleavage activity. These results indicate that hairpin ribozyme may intracellularly inhibit the replication of HBV, therefore it may become a novel potent weapon for the treatment of hepatitis B.

Ribozymes against TGFbeta1 reverse character of activated hepatic stellate cells in vitro and inhibit liver fibrosis in rats

BACKGROUND/AIMS

Transforming growth factor beta (TGFbeta1) is considered the key mediator in the process of liver fibrosis. The purpose of this investigation was to evaluate the activity of ribozymes against TGFbeta1 in a cell-free system and activated hepatic stellate cells (HSCs), and antifibrotic effect in activated HSCs in vitro and in rats.

METHODS

Three ribozymes targeting against TGFbeta1 mRNA were designed, and then cloned into the U1 snRNA expression cassette. The chimeric ribozymes were selected for the analysis of their performances in activated HSCs through the detection of their cleavage activities in a cell-free system. After ribozyme-encoding plasmids had been transfected into HSC-T6 cells, the effects of ribozymes on activated HSCs were evaluated through the analysis of proliferation, activation and collagen deposition of HSC-T6. The adenoviral vector expressing the ribozymes was constructed, and then delivered into rat models of hepatic fibrosis induced by carbon tetrachloride.

RESULTS

TGFbeta1 expression was efficiently down-regulated in activated HSCs by U1 snRNA chimeric ribozymes which possessed perfect cleavage activity in a cell-free system. Further studies demonstrated that U1 snRNA chimeric ribozymes inhibited the synthesis of collagen I, reduced deposition of collagen I, suppressed BrdU incorporation, but had no effect on desmin and alpha-SMA expression in transfected HSC-T6 cells. Histological analysis demonstrated that the adenoviral vector expressing ribozyme (Rz803) could alleviate fibrotic pathology in rats treated with carbon tetrachloride.

CONCLUSIONS

The anti-TGFbeta1 ribozymes could reverse the character of activated HSCs in vitro and improve fibrotic pathology in vivo. It indicated that TGFbeta1 could be considered as a novel candidate for a therapeutic agent against hepatic fibrosis.

Difference between type 2 gastroesophageal varices and isolated fundic varices in clinical profiles and portosystemic collaterals

BACKGROUND

There is significant heterogeneity between gastroesophageal varices (GOV2) and isolated gastric varices (IGV1). The data on the difference between GOV2 and IGV1 are limited.

AIM

To determine the etiology, clinical profiles, endoscopic findings, imaging signs, portosystemic collaterals in patients with GOV2 and IGV1.

METHODS

Medical records of 252 patients with gastric fundal varices were retrospectively collected, and computed tomography images were analyzed.

RESULTS

Significant differences in routine blood examination, Child-Pugh classification and MELD scores were found between GOV2 and IGV1. The incidence of peptic ulcers in patients with IGV1 (26.55%) was higher than that of GOV2 (11.01%), while portal hypertensive gastropathy was more commonly found in patients with GOV2 (22.02%) than in those with IGV1 (3.54%). Typical radiological signs of cirrhotic liver were more commonly observed in patients with GOV2 than in those with IGV1. In patients with GOV2, the main afferent vessels were via the left gastric vein (LGV) (97.94%) and short gastric vein (SGV) (39.18%). In patients with IGV1, the main afferent vessels were via the LGV (75.61%), SGV (63.41%) and posterior gastric vein (PGV) (43.90%). In IGV1 patients with pancreatic diseases, spleno-gastromental-superior mesenteric shunt (48.15%) was a major collateral vessel. In patients with fundic varices, the sizes of gastric/esophageal varices were positively correlated with afferent vessels (LGVs and PGVs) and efferent vessels (gastrorenal shunts). The size of the esophageal varices was negatively correlated with gastrorenal shunts in GOV2 patients.

CONCLUSION

Significant heterogeneity in the etiology and vascular changes between GOV2 and IGV1 is useful in making therapeutic decisions.

Activity identification of ribozyme and U1 snRNA chimeric ribozyme against TGFbeta1 in cell-free system and in hepatic stellate cells

Transforming growth factorbeta1 (TGFbeta1) is known to be intimately involved in many cellular processes. To explore the mechanism of TGFbeta1 in these processes, the non-chimeric hammerhead ribozyme and U1 snRNA chimeric ribozyme against TGFbeta1 were designed to down-regulate TGFbeta1 expression. The activity of non-chimeric ribozyme and U1 snRNA chimeric ribozyme against TGFbeta1 in vitro and in activated hepatic stellate cells (HSCs) was detected. Cleavage reactions of both ribozymes in vitro demonstrated that non-chimeric ribozyme possessed better cleavage activity in vitro than U1 snRNA chimeric ribozyme. The further study showed U1 snRNA chimeric ribozyme inhibited TGFbeta1 expression more efficiently than non-chimeric ribozyme in transfected HSC cells. So it indicates that the U1 snRNA chimeric ribozyme provides an alternative approach for the research on the precise mechanism of TGFbeta1 in many cellular processes and a potential therapeutic candidate for TGFbeta1-related diseases.

[Hammerhead ribozyme-mediated cleavage of transforming growth factor beta1 RNA in a cell-free system and in hepatic stellate cells]

OBJECTIVE

To identify the activity of hammerhead ribozyme against transforming growth factor beta1 (TGFbeta1) in a cell-free system and in activated hepatic stellate cells (HSCs).

METHODS

The ribozyme against TGFb1 was designed with computer software. The transcripts of ribozyme, disabled ribozyme and target RNAs were prepared using the RiboMAX large scale RNA production system. The in vitro cleavage reactions were performed through incubation of 32P-labeled target RNAs with ribozyme or disabled ribozyme in different conditions. The eukaryotic expression vector encoding ribozyme and disabled ribozyme were constructed, and then transfected into HSC-T6 cells which exhibited characteristics of activated HSCs. The intracellular activity of the ribozyme was determined by detecting the ribozyme, disabled ribozyme and the TGFbeta1 expression.

RESULTS

The ribozyme cleaved target RNAs into anticipated products effectively. As expected, the disabled ribozyme possessed no cleavage activity in vitro. Further study demonstrated that the ribozyme expressed efficiently and inhibited TGFbeta1 expression in activated HSCs, while the disabled ribozyme displayed only a slight effect on TGFbeta1 expression.

CONCLUSION

The ribozyme with perfect cleavage activity in the cell-free system used inhibited TGFbeta1 expression effectively in activated HSCs. This ribozyme can provide a potential therapeutic approach for liver fibrosis.