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Cisplatin induces a persistent activation of JNK that is related to cell death
I Sánchez-Perez1, J R Murguía, R Perona
1Instituto de Investigaciones Biomédicas CSIC, Madrid, Spain.
Abstract:
Genotoxic stress triggers signalling pathways that either mediate cell killing or protection of affected cells. While induction of p53 is observed for most of the genotoxins, activation of MAPK/SAPK cascades is not a general response. The role of MAPK/SAPK activation on cell fate, seems to be dependent, in some systems, on the balanced response among both cascades. We have here examined the effect of cis and trans-DDP on the activation of ERK and JNK activities. While no significant induction of ERK was observed with the compounds, both of them are able to strongly activate JNK. Trans-DDP response is rapid and transient while the cis-DDP one is slow and persistent. In contrast with the observed nuclear translocation of JNK in response to U.V. light, none of the platinum compounds induces translocation, on the contrary, activation of JNK occurs in both the nuclear and cytoplasmic compartments. Inhibition of tyrosine phosphatases by orthovanadate pretreatment prolongs the time of JNK induction in response to both platinum compounds. The positive modulation of JNK activation correlates with an increase in toxicity that, for cis-DDP corresponds to a tenfold decrease in the IC50. A strong increase in MKP-1 levels was observed only in response to trans-DDP suggesting the involvement of this activity in the downregulation of JNK activity in response to this compound. Altogether the results suggest that the prolonged activation of JNK in response to cis-DDP contributes to cell death induction.
Insights
Genotoxic stress activates stress-activated protein kinase (SAPK) pathways, specifically c-Jun N-terminal kinase (JNK). Cisplatin (cis-DDP) causes prolonged JNK activation, leading to increased cell death, unlike transplatin (trans-DDP).
Area of Science:
- Molecular Biology
- Cellular Signaling
- Toxicology
Background:
- Genotoxic stress elicits cellular responses, including cell death or survival pathways.
- Mitogen-activated protein kinase (MAPK) and stress-activated protein kinase (SAPK) cascades are involved, but their activation is not universal for all genotoxins.
- The role of SAPK activation in cell fate is complex and may depend on the balance between different signaling cascades.
Purpose of the Study:
- To investigate the differential effects of cisplatin (cis-DDP) and transplatin (trans-DDP) on the activation of extracellular signal-regulated kinase (ERK) and JNK pathways.
- To elucidate the role of JNK activation kinetics and localization in response to these platinum compounds.
- To correlate JNK activation with cellular toxicity and identify mechanisms of JNK regulation.
Main Methods:
- Treatment of cells with cis-DDP and trans-DDP.
- Assay of ERK and JNK activities.
- Analysis of JNK subcellular localization (nuclear vs. cytoplasmic).
- Pretreatment with orthovanadate to inhibit tyrosine phosphatases.
- Measurement of Mitogen-activated protein kinase phosphatase-1 (MKP-1) levels.
- Determination of half-maximal inhibitory concentration (IC50) for toxicity.
Main Results:
- Both cis-DDP and trans-DDP strongly activated JNK, but not ERK.
- Trans-DDP induced a rapid and transient JNK activation, while cis-DDP caused a slow and persistent activation.
- JNK activation occurred in both nuclear and cytoplasmic compartments, without specific nuclear translocation for platinum compounds.
- Inhibition of tyrosine phosphatases prolonged JNK induction by both compounds.
- Prolonged JNK activation by cis-DDP correlated with a tenfold decrease in IC50, indicating increased toxicity.
- Increased MKP-1 levels were observed only with trans-DDP, suggesting its role in downregulating JNK activity.
Conclusions:
- The differential kinetics of JNK activation by cis-DDP and trans-DDP play a crucial role in determining their cytotoxic effects.
- Prolonged JNK activation induced by cis-DDP significantly contributes to its potent cell-killing activity.
- The findings highlight the importance of sustained SAPK signaling in genotoxin-induced apoptosis.