Conference Agenda

Introduction: Withania somnifera is utilized in Ayurvedic medicine, owing to its central and peripheral beneficial properties. Several studies have accrued indicating that the recreational amphetamine-related drug (±)-3,4-methylenedioxymethamphetamine (MDMA; Ecstasy) targets the nigrostriatal dopaminergic system in mice, inducing neurodegeneration and gliosis, causing acute hyperthermia and cognitive impairment.

Methods: This study aimed to investigate the effect of a standardized extract of W. somnifera (WSE) in contrasting MDMA-induced neurotoxicity, neuroinflammation, cognitive impairment and hyperthermia. Mice received a 3-day pretreatment with vehicle or WSE. Thereafter, vehicle- and WSE-pretreated mice were randomly divided into four groups: saline, WSE, MDMA alone, WSE plus MDMA. Body temperature was recorded throughout treatment, and, at the end of treatment, cognitive performance was assessed by a novel object recognition (NOR) task. Thereafter, immunohistochemistry was performed to evaluate, in the substantia nigra pars compacta (SNc) and striatum, the levels of tyrosine hydroxylase (TH), marker of dopaminergic degeneration, of glial fibrillary acidic protein (GFAP) and TMEM119, markers of astrogliosis and microgliosis, respectively.

Results: MDMA-treated mice showed a decrease in TH-positive neurons in both SNc and striatum, an increase in gliosis and body temperature, and a decrease in NOR performance, irrespective of vehicle or WSE pretreatment. Acute WSE plus MDMA counteracted the modifications in TH-positive cells in SNc, GFAP-positive cells in striatum, TMEM in both areas and NOR performance, as compared to MDMA alone, while no differences were observed as compared to saline.

Conclusions: Results indicate that WSE, acutely administered in combination with MDMA, but not as pretreatment, protects mice against the noxious central effects of MDMA.

Parkinson’s disease (PD) is the second most common neurodegenerative disorder characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN). However, the mechanisms that cause the vulnerability of these neurons are only partially elucidated. Accordingly, the currently available pharmacological treatments are not completely effective since they cannot restore DA neurons physiological condition. Recently, we have described that in both primary cultured of DA neurons and human DA neurons derived from induced pluripotent stem cells (iPSCs), the b2 subunit of the nicotinic acetylcholine receptor (nAChR) interacts with the DA D3 receptor (D3R) forming the D3R-nAChR heteromer, a molecular complex that physiologically represents a key molecular unit responsible for exerting neurotrophic and neuroprotective effects induced by both D2R/D3R agonists and nicotine. Interestingly, these effects were enhanced by 17-beta-estradiol, that act as a positive allosteric modulator for the D3R-nAChR heteromer by interacting with the C-terminal domain of the nAChR alfa4 subunit. Moreover, we also demonstrated that stimulation of the D3R-nAChR heteromer resulted in the activation of the PI3K-ERK1/2/Akt cascade, leading to the expression of the immediate early gene c-Fos and the activation of the p70 ribosomal S6 kinase, two molecular signals crucially required for DA neurons dendritic remodeling. On this line, we have shown that DA neurons derived from iPSCs of PD patients carrying the leucine-rich repeat kinase 2 (LRRK2) G2019S mutation lacked D3R-nAChR heteromer membrane expression, possibly leading to reduced activation of PI3K-ERK Akt survival pathway thus contributing to neurons vulnerability. Therefore, this heteromer may represent a novel target to sustain DA neurons health and protect them against neurotoxic injuries.

Light pollution has recently become a significant global environmental issue. Interestingly, several in vivo approaches and worldwide correlation studies of Parkinson disease onsets have shown to strongly correlate with the distribution of light pollution. In particular it has been shown that artificial light had profound detrimental effects on dopaminergic neurons. In fact, the prolonged exposure of rats and mice to fluorescent light resulted in increase of neuromelanin granules and damage of dopamine neurons in the substantia nigra. These findings suggest that light pollution may be a key environmental factor implicated in the preferential degeneration of dopamine neurons in PD. In addition, we have recently shown that electromagnetic wavelengths around 600nm, also emitted by florescent light lamps, reach deep into the mouse, rat, human brains. Our project aims at characterizing light-induced neurodegeneration by using the dopaminergic cell model MN9D. This cell line was exposed to four wavelengths: 485 nm, 535 nm, 610 nm and 710 nm in order to evaluate the wavelengths at which the fluorescent light was responsible for the detrimental effects observed on the dopaminergic neurons of rats and mice used in our previous studies. In particular we showed that light at 610 nm was the most harmful wavelength for the MN9D and stickily had no effect on control non-dopaminergic cells. Moreover, 610 nm exposure of differentiated MN9D caused a decrease in cell viability and a strong statistically significant increase in ROS production compared to controls, especially when cells were co-treated with an oxidative agent (H₂O₂). Our results strongly suggest that light potentiates oxidative stress specifically in dopaminergic cells through dopamine oxidation. Moreover, future experiments will be performed using human iPSC-cells from different patients having mutations associated with PD to investigate the relationship between environment such as the prolonged exposure to artificial light and genetic factors.

D- and L-serine play a crucial role in regulating various physiological processes in the mammalian brain, including synaptic plasticity, energy homeostasis, lipid metabolism, and cell survival, among others. Furthermore, recent research has demonstrated the potential therapeutic utility of these amino acids in the management of certain neuropathological disorders. Despite this progress, their precise involvement in the pathophysiology of Parkinson's disease (PD) remains uncertain. To better clarify the role of these amino acids, in the present study, we investigated how the degeneration of dopaminergic nigrostriatal neurons induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in non-human primates and MPTP-plus-probenecid (MPTPp) treatment in mice affects the striatal metabolism of serine enantiomers. In addition, the effects of oral D-serine supplementation (⁓100 mg/kg/day) were evaluated in MPTPp-treated mice. In non-human primates, administration of MPTP produced a severe denervation of nigrostriatal dopaminergic fibres (⁓75%), leading to a significant elevation in the levels of serine enantiomers in the rostral putamen, as well as reduced expression of the astrocytic serine transporter ASCT1, and of the glycolytic enzyme GAPDH. Conversely, the metabolism of serine enantiomers and the protein expression of ASCT1 and GAPDH remained unaffected in the brain of MPTPp-treated mice, which exhibited only a mild dopaminergic degeneration (⁓30%). Interestingly, D-serine supplementation did not produce any deleterious effects on the dopaminergic nigrostriatal system under both physiological and MPTP conditions. Our findings provide insights into a neuroadaptive mechanism linking the severity of dopaminergic nigrostriatal degeneration to striatal serine enantiomers upregulation and highlight the safety of D-serine supplementation in a rodent model of PD.