In vitro cocaine toxicity: participation of the dopaminergic pathway and the transcription factor NF-kB.

Author(s)

Lucília Brochado Lepsch

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2008-04-18

Examining board members

Cristoforo Scavone; Luiz Roberto Giorgetti de Britto; Rosana Camarini; Luiz Carlos de Sá Rocha; Maria Aparecida Barbato Frazão Vital

• Advisor: Cristoforo Scavone

Abstract

Cocaine is a drug deeply used and its abuse is associated with physical, psychiatric and social problems. Abnormalities in newly born have been demonstrated due to the toxics effects of cocaine during fetal development. The mechanism by which cocaine causes neurological damages is very complex and involves interactions of the drug with several neurotransmitter systems, such as the increase of extracellular levels of dopamine and free radicals, and modulation of transcription factors. In this study we investigated the cocaine toxicity in striatum and mesencephalic primary cultures, and dopaminergic cells (PC 12). We observed that cocaine exposure causes death to these cells. In the mesencephalic primary culture, the cellular death was blunted by superoxide dismutase (SOD) pretreatment. Cocaine exposure also induced inhibition of neurite lengthening in these primary cultures. In PC 12 cells, cocaine activated the transcription factors NFkB and CREB (after 6 hours), which regulate genes involved in cellular death. GBR 12909, an inhibitor of dopamine reuptake; lidocaine, a local anesthetic; and dopamine did not activate NFkB as cocaine did, however, the attenuation of NFkB activity after the pretreatment of the cells with SCH 23390, a D1 receptor antagonist, suggests that the activation of NFkB by cocaine is, at least partially, due to activation of D1 receptors. NFkB seems to have a protective role in these cells, because its inhibition with PDTC and Sodium Salicilate increased cellular death caused by cocaine. The increase in BDNF RNAm, can also be related to the protective role of this transcription factor. The decrease in Bcl-2, the increase in caspase 3 activity, and the increase in caspase 3 cleavage suggest that apoptose participates in the development of cocaineinduced cell death. The understanding of the mechanisms by which cocaine induces cell death in the brain will contribute to the development of new therapies for drug abusers, which can help the interruption of the progress of degenerative processes. (AU)