17 -Ethynyl-androst-5-ene-3 ,7 ,17 -triol (HE3286) Is Neuroprotective and Reduces Motor Impairment and Neuroinflammation in a Murine MPTP Model of Parkinson’s Disease
17α-Ethynyl-androst-5-ene-3β,7β,17β-triol (HE3286) is a synthetic androstenetriol in Phase II clinical development for the treatment of inflammatory diseases. HE3286 was evaluated for blood-brain barrier (BBB) permeability in mice, and efficacy in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) murine model of Parkinson’s disease (PD). We found that HE3286 freely penetrated the BBB. HE3286 treatment significantly improved motor function compared to vehicle in the rotarod test (mean 58.2？sec versus 90.9？sec, ), and reduced inflammatory mediator gene expression in the brain (inducible nitric oxide synthase, 20%, ; tumor necrosis factor α, 40%, , and interleukin-1β, 33%, ) measured by reverse-transcriptase polymerase chain reaction. Brain tissue histopathology and immunohistochemistry showed that HE3286 treatment increased the numbers of tyrosine hydroxylase-positive cells by 17% compared to vehicle ( ), and decreased the numbers of damaged neurons by 38% relative to vehicle ( ). L-3,4-dihydroxyphenylalanine (L-DOPA) efficacy was not enhanced by concurrent administration of HE3286. HE3286 administration prior to MPTP did not enhance efficacy. Our data suggest a potential role for HE3286 in PD treatment, and provides incentive for further investigation. 1. Introduction PD is a neurodegenerative disorder characterized by a progressive degeneration of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc) and decreased levels of dopamine in the putamen of the dorsolateral striatum. The loss of dopamine in the striatum manifests clinically as motor disabilities that include bradykinesia, resting tremor, and muscular rigidity. Diagnosis is based on motor symptoms, which become evident only after the loss of more than 50% of the SNpc DAergic neurons and 60–80% of striatal dopamine [1]. Prolonged treatment of PD with L-DOPA usually results in a dyskinesia that can be more disabling than the disease itself; therefore, there is a great need for alternative therapeutic modalities. The acute MPTP mouse model of nigrostriatal degeneration recapitulates the DAergic neuron loss seen in PD and currently represents the most commonly used toxin-induced mouse model of PD [2]. MPTP’s mechanism of toxicity is complex, and exerted through its toxic metabolite, methyl-4-phenylpyridinium (MPP+) ion, which is taken up selectively by DAergic neurons through the dopamine transporter. Inside the cell, MPP+ is a mitochondrial toxin, which induces neuronal death through several mechanisms that include oxidative stress [3], excitotoxicity [4], and
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