Antiviral Agents ; pharmacology ; Dideoxyadenosine ; analogs & derivatives ; pharmacology ; Hepatitis B virus ; drug effects ; Virus Replication ; drug effects

OBJECTIVETo explore the effect and the molecular targets of anti-hepatitis B virus (HBV) by beta-L-D4A in vitro.

METHODS2.2.15 cells were cultured and treated with various concentrations of beta-L-D4A for 6 hours, then the effect of anti-HBV was examined by Southern blot and the replicating core particles from the cells were isolated. The endogenous polymerase reaction and activity gel experiment were performed to monitor the activities of the DNA polymerase and reverse transcriptase.

RESULTSThe replication of HBV DNA was inhibited in a dose-dependent manner. The endogenous polymerase reaction showed both the two enzymatic activities were irreversibly inactivated in a concentration -dependent manner, with IC50 at 0.51 micromol/L and 0.55 micromol/L, respectively. But the activities of DNA polymerase and reverse transcriptase were found to remain active by activity gel with exogenous templates.

CONCLUSIONSThe mechanism of inhibiting HBV replication by beta-L-D4A may be in that either the DNA replication priming is blocked or the elongation of DNA chain is terminated irreversibly.

Antiviral Agents ; pharmacology ; DNA, Viral ; biosynthesis ; Dideoxyadenosine ; analogs & derivatives ; chemistry ; pharmacology ; Dose-Response Relationship, Drug ; Hepatitis B virus ; drug effects ; enzymology ; physiology ; Humans ; Liver Neoplasms ; pathology ; Nucleic Acid Synthesis Inhibitors ; Tumor Cells, Cultured ; Virus Replication ; drug effects

According to our previous studies together with others, GnRH, a hypothalamic decapeptide, has been known to be a major regulator for LH release and its subunit biosynthesis in anterior pituitary gonadotropes. But the precise mechanisms by which GnRH exerts stimulatory effects on LH release and its subunit biosynthesis have not been clearly understood. In the present study we examined the effect of GnRH on protein kinase C (PKC) activity and intracellular cAMP content in cultured anterior pituitary cells of rat to clarify whether PKC or cAMP are involved in GnRH action. Moreover, we examined the effects of staurosporine (ST), a PKC inhibitor and 2',3'-dideoxyadenosine (2',3'-DDA), an adenylate cyclase inhibitor, on LH release and steady state LH beta subunit mRNA levels in cultured anterior pituitary cells of rat. PKC activity was rapidly increased within 30 min after GnRH treatment whereas intracellular cAMP level was elevated 18 h after GnRH treatment. ST significantly inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner, showing an half maximal response at 50 nM ST. 2',3'-DDA inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner in pituitary cells. From these results, it is suggested that GnRH stimulates LH beta subunit mRNA level as well as LH release in anterior pituitary cells and this GnRH action might be mediated by PKC activation and cAMP stimulation.
Adenylate Cyclase/*antagonists & inhibitors ; Alkaloids/*pharmacology ; Animal ; Cells, Cultured ; Cyclic AMP/metabolism ; Dideoxyadenosine/*pharmacology ; Female ; Gonadorelin/*pharmacology ; Luteinizing Hormone/*biosynthesis/*metabolism ; Pituitary Gland, Anterior/*drug effects/metabolism ; Protein Kinase C/*antagonists & inhibitors/metabolism ; Rats ; Rats, Sprague-Dawley ; Staurosporine ; Support, Non-U.S. Gov't

AIMNucleoside analogues have become the most promising candidates of anti-HBV drugs. In this study, beta-L-D4A was synthesized and explored its inhibitiory action against hepatitis B virus (HBV) in 2. 2. 15 cells derived from HepG2 cells transfected with HBV genome.

METHODSbeta-L-D4A was stereo-controlled synthesized from D-glutamic acid, and the structure was identified by IR, 1H NMR and MS. 2. 2. 15 Cells were placed at a density of 5 x 10(4) per well in 12-well tissue culture plates, and treated with various concentrations of beta-L-D4A for 6 days. At the end, medium was processed to obtain virions by a polyethlene glycol precipitation method. At the same time, intracellular DNA was also extracted and digested with Hind III. Both of the above DNA were subjected to Southern blot, hybridized with a 32P-labeled HBV probe and autoradiographed. The intensity of the autoradiographic bands was quantitated by densitometric scans of computer and EC50 was calculated. 2. 2. 15 cells were also seeded in 24-well tissue culture plates, and cytotoxicity with different concentrations was examined by MTT method. IC50 was calculated.

RESULTSThe synthesized compound structure conformed with beta-L-D4A; Autoradiographic bands showed similar for supernatant and intracellular HBV DNA. Episomal HBV DNA was inhibited in a dose-dependent manner. EC50 0.2 micromol x L(-1). The experiment of cytotoxicity gained IC50 200 micromol x L(-10.

CONCLUSIONbeta-L-D4A has been synthesized successfully. beta-L-D4A possessed potent inhibitory effect on replication of HBV in vitro with low cytotoxicity, TI value was 1 000. It is expected to be developed clinically into a new anti-HBV drug.

Antiviral Agents ; chemical synthesis ; chemistry ; pharmacology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; DNA Replication ; drug effects ; DNA, Viral ; drug effects ; Dideoxyadenosine ; analogs & derivatives ; chemical synthesis ; chemistry ; pharmacology ; Genome, Viral ; Hepatitis B virus ; drug effects ; genetics ; physiology ; Humans ; Liver Neoplasms ; pathology ; Transfection ; Virus Replication ; drug effects