Mithramycin selectively attenuates DNA-damage-induced neuronal cell death.

Abstract

DNA damage triggers cell death mechanisms contributing to neuronal loss and cognitive decline in neurological disorders, including traumatic brain injury (TBI), and as a side effect of chemotherapy. Mithramycin, which competitively targets chromatin-binding sites of specificity protein 1 (Sp1), was used to examine previously unexplored neuronal cell death regulatory mechanisms via rat primary neurons in vitro and after TBI in mice (males). In primary neurons exposed to DNA-damage-inducing chemotherapy drugs in vitro we showed that DNA breaks sequentially initiate DNA-damage responses, including phosphorylation of ATM, H2AX and tumor protein 53 (p53), transcriptional activation of pro-apoptotic BH3-only proteins, and mitochondrial outer membrane permeabilization (MOMP), activating caspase-dependent and caspase-independent intrinsic apoptosis. Mithramycin was highly neuroprotective in DNA-damage-dependent neuronal cell death, inhibiting chemotherapeutic-induced cell death cascades downstream of ATM and p53 phosphorylation/activation but upstream of p53-induced expression of pro-apoptotic molecules. Mithramycin reduced neuronal upregulation of BH3-only proteins and mitochondrial dysfunction, attenuated caspase-3/7 activation and caspase substrates' cleavage, and limited c-Jun activation. Chromatin immunoprecipitation indicated that mithramycin attenuates Sp1 binding to pro-apoptotic gene promoters without altering p53 binding suggesting it acts by removing cofactors required for p53 transactivation. In contrast, the DNA-damage-independent neuronal death models displayed caspase initiation in the absence of p53/BH3 activation and were not protected even when mithramycin reduced caspase activation. Interestingly, experimental TBI triggers a multiplicity of neuronal death mechanisms. Although markers of DNA-damage/p53-dependent intrinsic apoptosis are detected acutely in the injured cortex and are attenuated by mithramycin, these processes may play a reduced role in early neuronal death after TBI, as caspase-dependent mechanisms are repressed in mature neurons while other, mithramycin-resistant mechanisms are active. Our data suggest that Sp1 is required for p53-mediated transactivation of neuronal pro-apoptotic molecules and that mithramycin may attenuate neuronal cell death in conditions predominantly involving DNA-damage-induced p53-dependent intrinsic apoptosis.

• Authors: Oleg Makarevich, Boris Sabirzhanov, Taryn G Aubrecht, Ethan P Glaser, Brian M Polster, Rebecca J Henry, Alan I Faden, Bogdan A Stoica
• Journal: Cell death & disease (Cell Death Dis) Vol. 11 Issue 7 Pg. 587 (07 27 2020) ISSN: 2041-4889 [Electronic] England
• PMID: 32719328 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Biomarkers
• Neuroprotective Agents
• Proto-Oncogene Proteins c-jun
• Tumor Suppressor Protein p53
• Etoposide
• Plicamycin

Topics

• Animals
• Apoptosis (drug effects)
• Biomarkers (metabolism)
• Brain Injuries, Traumatic (drug therapy, pathology)
• Cell Death (drug effects)
• DNA Damage
• Etoposide (pharmacology)
• Male
• Mice, Inbred C57BL
• Mitochondria (drug effects, metabolism)
• Models, Biological
• Neurons (drug effects, pathology)
• Neuroprotective Agents (pharmacology)
• Plicamycin (pharmacology, therapeutic use)
• Proto-Oncogene Proteins c-jun (metabolism)
• Rats, Sprague-Dawley
• Signal Transduction (drug effects)
• Transcription, Genetic (drug effects)
• Tumor Suppressor Protein p53 (metabolism)