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Proliferation and apoptosis of HeLa cells induced by in vitro stimulation with digitalis
Margarita Ramirez-Ortega1, Vilma Maldonado-Lagunas, Jorge Melendez-Zajgla
1Departamento de Farmacologia, Instituto Nacional de Cardiología Ignacio Chavez, Juan Badiano No. 1, Col. Seccion XVI, 14080 Mexico, Mexico. margarita0022@yahoo.com
Abstract:
In the HeLa tumor cell line, we studied the characteristics of the dual effect of digitalis compounds on cell growth (proliferation and death). In addition, we explored whether both effects occur by means of the same mechanism. HeLa cell cultures were exposed to increasing concentrations (0.01 nM-10 microM) of ouabain, strophantidin, digoxin, and digoxigenin at 24-96 h intervals. Cell growth in treated cultures was compared with cell growth under nontreated conditions. Additionally, we studied changes in nuclear morphology, as well as in genomic DNA degradation, cytochrome c release, and caspase-9 and -3 presence and processing induced by toxic concentrations of digitalis. Digitalis compounds increased HeLa cell number when exposed to concentrations <10 nM during a 48 h period. Ethacrynic acid (a nonsteroid inhibitor for Na+/K+-ATPase) did not induce cell growth at these concentrations. Digitalis concentrations >10 nM induced cell death in a concentration- and exposure period-dependent fashion. Changes in nuclear morphology, DNA fragmentation, mitochondrial cytochrome c release, and proteolytic processing of caspases-9 and -3, suggest apoptotic cell death. The IC50 for the inducing effect of apoptosis by ouabain at 96 h was 18 nM and corresponds with the IC50 for the Na+/K+-ATPase inhibition in HeLa cells. In conclusion, the dual effect of digitalis compounds on HeLa cells growth is concentration and time-dependent. The apoptosis-inducing effect correlates with inhibition of Na+/K+-ATPase. Proliferation does not appear to be mediated through this pathway. The apoptosis-induction pathway is possibly cytochrome c-dependent.
Insights
Digitalis compounds show a dual effect on HeLa cells: low concentrations promote growth, while higher concentrations induce apoptosis. This cell death pathway correlates with Na+/K+-ATPase inhibition.
Area of Science:
- Cell Biology
- Pharmacology
- Toxicology
Background:
- Digitalis compounds are known for their cardiac effects.
- Their impact on cancer cell lines, like HeLa, is less understood.
- A dual effect on cell growth (proliferation and death) has been suggested.
Purpose of the Study:
- To investigate the dual effect of digitalis compounds on HeLa tumor cell growth.
- To determine if proliferation and cell death share the same underlying mechanism.
- To explore the specific pathways involved in digitalis-induced apoptosis.
Main Methods:
- HeLa cell cultures were exposed to varying concentrations of digitalis compounds (ouabain, strophantidin, digoxin, digoxigenin) over 24-96 hours.
- Cell growth, nuclear morphology, DNA degradation, and cytochrome c release were analyzed.
- Caspase-9 and -3 presence and processing were assessed to identify apoptotic markers.
Main Results:
- Low digitalis concentrations (<10 nM) stimulated HeLa cell proliferation.
- Higher concentrations (>10 nM) induced cell death in a dose- and time-dependent manner.
- Apoptosis was characterized by nuclear changes, DNA fragmentation, cytochrome c release, and caspase activation, with IC50 for ouabain-induced apoptosis correlating with Na+/K+-ATPase inhibition.
Conclusions:
- Digitalis compounds exert a concentration- and time-dependent dual effect on HeLa cell growth.
- The apoptosis-inducing effect is linked to Na+/K+-ATPase inhibition and appears to be cytochrome c-dependent.
- Proliferation does not seem to be mediated by Na+/K+-ATPase inhibition.
