Glutathione Redox Status in Neurodegenerative Diseases

Research Article

Austin J Clin Neurol 2019; 6(1): 1134.

Glutathione Redox Status in Neurodegenerative Diseases

Dellanoce C1, Fulgenzi A2 and Ferrero ME2*

¹CNR Institute of Clinical Physiology, Cardiothoracic and Vascular Department, Niguarda Ca’ Granda Hospital, Italy

²Department of Biomedical Sciences for Health, Università degli Studi di Milano, Italy

*Corresponding author: Maria Elena Ferrero, Department of Biomedical Sciences for Health, Università degli Studi di Milano, Italy

Received: March 28, 2019; Accepted: July 19, 2019; Published: July 26, 2019


Oxidative stress is involved in the pathogenesis of many diseases, particularly Neurodegenerative Diseases (ND). Glutathione (GSH) is the most abundant endogenous antioxidant, as well as being a critical regulator of oxidative stress. This study was carried out to analyze levels of GSH and other redox active compounds, known as aminothiols, in patients affected by ND or by Fibromyalgia (FM). We also evaluated the influence of GSH treatment during chelation therapy.

We studied 40 healthy subjects and 41 patients affected by ND or FM. All underwent chelation therapy with calcium disodium ethylenediaminetetraacetic acid (CaNa2EDTA or EDTA) to remove toxic metal burden. We evaluated aminothiol levels (cystine, cysteine and glycine, homocysteine, and GSH) in the plasma and red blood cells of healthy patients and ND (Multiple sclerosis and Amyotrophic lateral sclerosis, Parkinson’s disease, Alzheimer’s disease) or FM patients.

We found GSH levels to be significantly lower in ND and FM patients than in their healthy counterparts, both in plasma and in red blood cells. Treatment of ND and FM patients with 250mg GSH daily for one month significantly improved GSH levels in red blood cells. Homocysteine levels were unaffected by GSH treatment, suggesting impairment of the transsulfuration pathway of homocysteine metabolism in ND patients.

Lower GSH levels are present in ND and FM patients compared to healthy controls, with a reduction of the endogenous antioxidant defense system. Oral GSH supplements during chelation therapy counteracted the depletion of endogenous GSH in these patients.

Keywords: Glutathione; Aminothiols; Neurodegenerative diseases; fibromyalgia


ND: Neurodegenerative Diseases; GSH: Glutathione; FM: Fibromyalgia; EDTA: Ethylenediaminetetraacetic Acid; ROS: Reactive Oxygen Species; RNS: Reactive Nitrogen Species; MS: Multiple Sclerosis; ALS: Amyotrophic Lateral Sclerosis; PD: Parkinson’s Disease; AD: Alzheimer’s Disease


The delicate balance in cellular redox is created on the one hand by the production of oxidants, such as Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS), and on the other through activation of the antioxidant systems that eliminate them. Both ROS and RNS, when produced at physiological values, can activate the specific signaling pathways required for many cellular functions, including cell growth and immune responses [1]. However, increased ROS/RNS production or decreased antioxidant capacity can cause oxidative/nitrosative stress [2]. In particular, at the level of synapsis and neuronal cells, imbalance between oxidant production and antioxidant mechanisms can contribute to neurodegeneration. Oxidative and nitrative stress play a critical role in the pathogenetic mechanisms of Neurodegenerative Diseases (ND), such as Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), Parkinson’s Disease (PD), and Alzheimer’s Disease (AD). Glutathione (Gamma-L-Glutamyl-L-Cysteinyl-L-Glycine) (GSH) is a major component of the antioxidant system that defends cells against the toxic effects of ROS/RNS and provides a reducing environment within the cells. Neurons are the cells that are most vulnerable to ROS/RNS excess as they express antioxidants (scavengers and enzymes) at low levels; their survival relies on the antioxidant protection promoted by neighboring astrocytes [3]. Although GSH is widely distributed throughout human tissue, its concentration in neurons is lower than that found in astrocytes [4,5]. GSH is synthesized by the sequential action of the enzyme Glutamate-Cysteine Ligase (GCL) and GSH synthetase [6]. The heterodimer GCL, composed of two subunits, catalyzes the formation of gamma-glutamylcysteine, which represents the rate-limiting reaction in GSH synthesis. A chronic decrease in GSH content in GCLM knockout astrocytes can induce a response involving changes in protein expression and lysine acetylation [7]. There is much evidence to suggest that GSH depletion plays a role in the onset of ND. Indeed, transient GSH depletion in the substantia nigra compacta has been associated with neuroinflammation in rats [8]. Moreover, under conditions of chronic GSH decrease, moderate over-expression of wild-type Superoxide Dismutase (SOD1) in mice causes overt motor neuron degeneration, similar to that induced by ALS-linked mutant SOD1 over-expression [9]. In an in vitro model of nerve-cell death, GSH depletion by glutamate was potentiated using iron and copper, suggesting important implications for age-related ND [10].

Which arms can help regulate/improve GSH redox status? Some antioxidants have been proposed as GSH system modulators. Indeed, resveratrol, through the heme oxygenase pathway, is known to protect C6 astroglial cells against GSH depletion [11]. Curcumin treatment attenuates the inflammation, oxidative stress, and ultrastructural damage induced by spinal cord ischemia/reperfusion injury in rats, and in particular improves GSH peroxidase [12]. Many studies examine the modifications of GSH redox status in patients affected by ND. Improved oxidative DNA damage and DNA susceptibility to oxidation result from a diminished GSH/GSSG (oxidized glutathione) ratio in AD patients treated with or without memantine [13]. Furthermore, association between lower cortical GSH levels, brain amyloidosis, and reduced memory in healthy older adults examined with 1H-MR spectroscopy, suggests GSH measurement as a noninvasive biomarker for mild cognitive impairment and early AD [14,15]. During disease progression in ALS patients, a systemic pro-inflammatory state and an impaired endogenous antioxidant system (in particular GSH system) have been noted [16] and related to clinical status at diagnosis [17].

Treatment strategies in ND should aim to promote the reactivation and correct functioning of redox system balance. Treatment with N-acetylcysteine (to increase GSH) and selenium supplements (to protect against excessive exposure to copper and iron) has been proposed [18].

The rationale of the present study was to assess oxidative stress in the plasma and Red Blood Cells (RBC) of patients affected by ND or by Fibromyalgia (FM) undergoing chelation therapy by examining thiol levels (SH-) containing amino acids known as aminothiols, e.g. cystine, cysteine and glycine, homocysteine, and GSH. In particular, we verified whether ND and FM patients showed a lower GSH content compared to healthy controls and studied the effects of GSH treatment on the same patients.



Each patient elected to undergo chelation therapy to remove toxic metal burden. Out of 90 consecutive subjects who had undergone a medical checkup at an outpatient clinic, only the 81 that agreed to comply with the trial protocol were enrolled; they accepted to undergo chelation therapy once a week and take GSH daily. All patients received both chelation therapy and GSH treatment without randomization.

As reported in Table 1, we enrolled 41 patients (22 women and 19 men) affected by ND (3 ALS; 2 PD, 2 AD, 27 MS) or by FM (7). We also recruited as controls 40 (21 women and 19 men) patients not affected by any disease of note, but who had previously been exposed to environmental or occupational heavy metals. Age ranged from 18 to 84 years. Patients with early neurological diagnosis of ND or FM without mild cognitive impairment and controls spontaneously decided to undergo tests to verify their toxic metal burden and blood redox status. All subjects provided written informed consent. Declaration of Helsinki and all procedures involving human participants were approved by Milan University’s Ethical Advisory Committee (number 64/14). Further inclusion/exclusion criteria were also applied. Indeed, some patients had never previously been treated for ND or FM with conventional drugs due to the recent onset of the pathology. The ND patients involved were mostly affected by MS; ten of them had previously been treated with conventional drugs (e.g. immunosuppressant agents), but had spontaneously interrupted therapy for approximately 3 months before the beginning of the present study.