Protective effect of insulin-like-growth-factor-1 against dopamine- induced neurotoxicity in human and rodent neuronal cultures: possible implications for Parkinson’s disease Daniel Offen a, * , Biana Shtaif a , Daphna Hadad a , Abraham Weizman b , Eldad Melamed a , Irit Gil-Ad b a Neurosciences Laboratory, Felsenstein Medical Research Center, Rabin Medical Center, Beilinson Campus, Tel Aviv University Sackler School of Medicine, Petah Tikva, 49100 Israel b Biological Psychiatry Laboratory, Felsenstein Medical Research Center, Rabin Medical Center, Beilinson Campus, Tel Aviv University Sackler School of Medicine, Petah Tikva, 49100 Israel Received 17 September 2001; accepted 27 September 2001 Abstract Parkinson’s disease (PD) is characterized by a progressive loss of 70–80% of dopaminergic (DA) neurons in the substantia nigra. High concentrations of DA were suggested to induce oxidative stress and selective neurodegeneration. We evaluated the effect of insulin-like-growth-factor-1 (IGF-1) on DA toxicity in neuronal cultures. IGF-1 (0.5 mg/ml) suppressed cell death induced by exposure to DA (0.3 mM) after 2 and 4 days, in a rat cerebellar culture. Similarly, IGF-1 (0.5 and 1.0 mg/ml) antagonized DA (0.125 and 0.250 mM) neurotoxicity in a human neuroblastoma cell line (SK-N- SH). Flowcytometric analysis of neuroblastoma cells treated with DA (0.5 mM) showed increased apoptosis, which was significantly reduced by IGF-1. The effect of IGF-1 was associated with increased Bcl-2 expression as indicated by flowcytometry and Western blot analysis. We suggest that IGF-1 possesses a neuroprotective effect against DA-induced toxicity, and may have a potential role in the treatment of PD. q 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Insulin-like growth factor; Dopamine; Apoptosis; Parkinson’s disease; Neurotoxicity; bcl-2 Parkinson’s disease (PD), one of the most common neurodegenerative disorders in the elderly, is characterized by a progressive and massive loss of midbrain dopaminergic (DA) neurons. The mechanism by which these neurons degenerate is still unknown. However, several environmen- tal and genetic factors, such as reactive oxygen species (ROS), mitochondrial dysfunction, excitotoxicity and inflammatory processes, have been suggested to contribute to this selective vulnerability. Postmortem studies performed in the substantia nigra (SN), have yielded evidence of massive lipid peroxidation, protein and DNA oxidation and degradation processes [10]. The precise trig- ger for the local oxidative stress in PD is not yet clear. It has been indicated however, that high concentrations of DA, neuromelanin and iron in a weak neuroprotective status, blunted the activity of neurotrophic growth factors (glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF)), thus contributing to the vulnerability of the nigral DA neurons [10]. The hypothesis that DA toxicity might be a major trigger for selective neurodegeneration of the DA neurons, is supported by substantial evidence both in-vivo and in-vitro [14,21]. One of the neurotrophic factors that might protect neurons in this harmful microenvironment is insulin-like-growth- factor-1 (IGF-1). The notion that IGF-1 has a role in PD is justified by the following: (a) SN is one of the regions in the human brain where a considerable density of IGF-1 receptors is evident [5]; (b) IGF-1 increases the survival of neurons in the brain stem including the SN [4]; (c) IGF-1 rescues embryonic DA neurons from programmed cell death [20]. The GH-IGF-1 axis activity is reduced with age. Low IGF-1 levels sometimes overlap a similar shortage in growth hormone (GH) and loss of GH and IGF-1 might be related to changes in body structure, metabolic activity and neurode- generation that appear with the aging process [7]. It is there- fore possible that loss of IGF-1 in adulthood influences the development of neurodegenerative diseases such as PD and Neuroscience Letters 316 (2001) 129–132 0304-3940/01/$ - see front matter q 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0304-3940(01)02344-8 www.elsevier.com/locate/neulet * Corresponding author. Tel.: 1972-3-9376130; fax: 1972-3- 9211478. E-mail address: doffen@post.tau.ac.il (D. Offen).