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Updated: May 1, 2026
Activation of Apoptosis by Cytoplasmic Microinjection of Cytochrome c
Published on: June 29, 2011
γ-Rays-generated ROS induce apoptosis via mitochondrial and cell cycle alteration in smooth muscle cells
Sandra Claro1, Maria Etsuko Miyamoto Oshiro, Renato Arruda Mortara
1Department of Biophysics, Federal University of São Paulo , São Paulo , Brazil.
Purpose:
γ-rays (IR) cause an increase in intracellular calcium [Ca(2+)], alters contractility and triggers apoptosis via the activation of protein kinase C in intestinal guinea pig smooth muscle cells. The present study investigated the role of the mitochondria in these processes and characterized proteins involved in IR-induced apoptosis.
Materials And Methods:
Intestinal smooth muscle cells were exposed to 10-50 Gy from a (60)Co γ-source. Reactive oxygen species (ROS) levels were measured by colourimetry with a fluorescente probe. Protein expression was analyzed by immunoblotting and immunofluorescence.
Results:
Apoptosis was inhibited by glutathione, possible by inhibiting the generation or scavenging ROS. Apoptosis was mediated by the mitochondria releasing cytochrome c leading to caspase 3 activation. IR increased the expression of the cyclins A, B2 and E and led to unbalanced cellular growth in an absorption dose-dependent manner. However, radiation did not induce alterations in the mitochondrial ultrastructure or in transmembrane electric potential. In contrast, IR increased the nuclear expression of cytoplasmic proteins and cyclins A and E.
Conclusion:
Smooth muscle cells subjected to IR undergo mitochondrial-mediated apoptosis that involves oncoproteins activation and preserves mitochondrial structure. IR also cause alterations in the expression and localization of both pro- and anti-apoptotic proteins.
Insights
Ionizing radiation (IR) induces apoptosis in intestinal smooth muscle cells through mitochondrial pathways. This process involves cytochrome c release and caspase 3 activation, alongside changes in cell cycle proteins.
Area of Science:
- Cell Biology
- Radiation Biology
- Gastrointestinal Physiology
Background:
- Ionizing radiation (IR) is known to increase intracellular calcium, alter contractility, and induce apoptosis in intestinal smooth muscle cells via protein kinase C activation.
- Mitochondria play a crucial role in cellular responses to radiation, including the induction of programmed cell death.
Purpose of the Study:
- To investigate the role of mitochondria in IR-induced apoptosis in intestinal smooth muscle cells.
- To characterize proteins involved in IR-induced apoptosis.
Main Methods:
- Intestinal smooth muscle cells were exposed to varying doses of gamma radiation (10-50 Gy).
- Reactive oxygen species (ROS) levels were measured using a fluorescent probe.
- Protein expression and localization were analyzed via immunoblotting and immunofluorescence.
Main Results:
- Apoptosis was inhibited by glutathione, suggesting a role for ROS scavenging.
- Mitochondrial-mediated apoptosis was confirmed by cytochrome c release and subsequent caspase 3 activation.
- IR increased the expression of cyclins A, B2, and E, leading to unbalanced cellular growth in a dose-dependent manner.
- Mitochondrial ultrastructure and transmembrane potential remained unaltered, but nuclear expression of cyclins A and E increased.
Conclusions:
- Intestinal smooth muscle cells undergo mitochondrial-mediated apoptosis following IR exposure.
- This apoptosis involves oncoprotein activation while preserving mitochondrial structure.
- IR alters the expression and localization of both pro- and anti-apoptotic proteins.
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