Related Experiment Videos
Molecular mechanisms of c-Jun N-terminal kinase-mediated apoptosis induced by anticarcinogenic isothiocyanates
1Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.
Abstract:
Isothiocyanates have strong chemopreventive properties against many carcinogen-induced cancers in experimental animal models. Here, we report that phenylmethyl isocyacyanate (PMITC) and phenylethyl isothiocyanate (PEITC) induced sustained c-Jun N-terminal kinase (JNK) activation in a dose-dependent manner. The sustained JNK activation caused by isothiocyanates was associated with apoptosis induction in various cell types. An inhibitor of the caspase/interleukin-1 beta-converting enzyme blocked isothiocyanate-induced apoptosis without inhibiting the JNK activation, which suggests that JNK activation by isothiocyanates is an event that is independent or upstream of the activation of caspase/interleukin-1 beta-converting enzyme proteases. PEITC-induced apoptosis was suppressed by interfering with the JNK pathway with a dominant-negative mutant of JNK1 or MEKK1 (JNK1(APF) and MEKK1 (KR), respectively), implying that the JNK pathway is required for apoptotic signaling. Isothiocyanate-induced JNK activation was blocked by the antioxidants 2-mercaptoethanol and N-acetyl-L-cysteine, suggesting that the death signaling was triggered by oxidative stress. Overexpression of Bcl-2 suppressed PEITC-induced JNK activation. In addition, Bcl-2 and Bcl-xL suppressed PEITC-induced apoptosis, but failed to protect cells from death induced by overexpression of activated JNK1. These results suggest that Bcl-2 and Bcl-xL are upstream of JNK. Taken together, our results indicate (i) that JNK mediates PMITC- and PEITC-induced apoptosis and (ii) that PMITC and PEITC may have chemotherapeutic functions besides their chemopreventive functions.
Insights
Phenylmethyl isothiocyanate (PMITC) and phenylethyl isothiocyanate (PEITC) activate c-Jun N-terminal kinase (JNK), triggering apoptosis. This JNK activation, mediated by oxidative stress and upstream of Bcl-2, suggests potential chemotherapeutic applications for these compounds.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Isothiocyanates exhibit chemopreventive properties against carcinogen-induced cancers.
- Understanding the molecular mechanisms of isothiocyanate-induced cell death is crucial for therapeutic development.
Purpose of the Study:
- To investigate the role of c-Jun N-terminal kinase (JNK) activation in apoptosis induced by phenylmethyl isothiocyanate (PMITC) and phenylethyl isothiocyanate (PEITC).
- To elucidate the signaling pathway and upstream regulators involved in isothiocyanate-mediated apoptosis.
Main Methods:
- Dose-dependent induction of JNK activation by PMITC and PEITC.
- Assessment of apoptosis using caspase/interleukin-1 beta-converting enzyme inhibitors.
- Interference with the JNK pathway using dominant-negative mutants (JNK1(APF), MEKK1(KR)).
- Evaluation of antioxidant effects (2-mercaptoethanol, N-acetyl-L-cysteine) and Bcl-2/Bcl-xL modulation on JNK activation and apoptosis.
Main Results:
- PMITC and PEITC induced sustained JNK activation, leading to apoptosis in various cell types.
- JNK activation was upstream of caspase/interleukin-1 beta-converting enzyme activation.
- The JNK pathway was essential for isothiocyanate-induced apoptosis, which was triggered by oxidative stress.
- Bcl-2 and Bcl-xL were found to be upstream of JNK and suppressed PEITC-induced JNK activation and apoptosis.
Conclusions:
- JNK activation is a key mediator of PMITC- and PEITC-induced apoptosis.
- Isothiocyanates may possess chemotherapeutic potential beyond their known chemopreventive functions.
- The findings highlight a novel signaling axis involving oxidative stress, JNK, and Bcl-2 family proteins in isothiocyanate-induced cell death.