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c-Myc antisense limits rat liver regeneration and indicates role for c-Myc in regulating cytochrome P-450 3A activity
Abstract:
Expression of c-myc protein is associated with cell proliferation. The present study uses antisense oligomers to inhibit c-myc expression in the regenerating rat liver after 70% partial hepatectomy (PH). Antisense phosphorodiamidate morpholino oligomers (novel DNA analogs) were administered i.p. immediately after surgery to block expression of c-myc within the first 24 h after PH. A 20-mer PMO complimentary to the c-myc mRNA at the translation start site was an effective sequence (AVI-4126, 5'-ACGTTGAGGGGCATCGTCGC-3'). A single i.p. dose of 0.5 mg/kg AVI-4126 caused reduction of the regenerating liver c-myc protein in a sequence-specific and dose-dependent manner. Inhibition of c-myc expression resulted in reduction of proliferating cell nuclear antigen and arrested cells in the G(0)/G(1) phase of the cell cycle. The ratio of G(2):G(0) cell populations in the regenerating liver 24 h after PH dropped from 29.1 in saline vehicle-treated rats to 18.0 in rats treated with 2.5 mg/kg AVI-4126. The expression of cell cycle checkpoint protein p53 was inhibited with increasing doses of AVI-4126, but expression of p21(waf-1) was unaffected. The activity of cytochrome P-450 3A2 (CYP3A2) was evaluated by immunoblot analysis and erythromycin N-demethylation. AVI-4126 did not alter CYP3A activity in nonhepatectamized animals but showed a dose-dependent decrease in PH rats. We conclude that AVI-4126, antisense oligomer to c-myc, can reduce cell proliferation in the regenerating rat liver. Furthermore, inhibition of c-myc may indirectly influence the expression of CYP3A.
Insights
Antisense oligomers targeting c-myc protein effectively reduced cell proliferation in regenerating rat livers. This inhibition also affected cell cycle progression and cytochrome P-450 activity, demonstrating c-myc
Area of Science:
- Molecular Biology
- Hepatology
- Pharmacology
Background:
- c-myc protein expression is crucial for cell proliferation.
- Liver regeneration after partial hepatectomy (PH) involves rapid cell division.
- Antisense technology offers a method to specifically inhibit gene expression.
Purpose of the Study:
- To investigate the effect of inhibiting c-myc expression on liver regeneration.
- To evaluate the efficacy of a novel antisense phosphorodiamidate morpholino oligomer (PMO) against c-myc.
- To assess the impact of c-myc inhibition on cell cycle progression and liver function.
Main Methods:
- Administration of a c-myc-specific PMO (AVI-4126) in rats post-partial hepatectomy.
- Quantification of c-myc protein levels, proliferating cell nuclear antigen (PCNA), and cell cycle distribution.
- Analysis of cell cycle checkpoint proteins (p53, p21waf-1) and cytochrome P-450 3A2 (CYP3A2) activity.
Main Results:
- AVI-4126 significantly reduced c-myc protein expression in a dose-dependent manner.
- Inhibition of c-myc led to decreased PCNA and cell cycle arrest in the G(0)/G(1) phase.
- AVI-4126 treatment altered the G(2):G(0) cell population ratio and dose-dependently decreased CYP3A2 activity in regenerating livers.
Conclusions:
- Antisense inhibition of c-myc effectively reduces cell proliferation in regenerating rat liver.
- c-myc downregulation impacts cell cycle progression and may indirectly affect CYP3A expression.
- AVI-4126 demonstrates potential as a therapeutic agent for controlling liver cell proliferation.