Subthreshold Concentrations of Melatonin and Galantamine Improves Pathological AD-Hallmarks in Hippocampal Organotypic Cultures

Abstract

Melatonin is a neurohormone whose levels are significantly reduced or absent in Alzheimer's disease (AD) patients. In these patients, acetylcholinesterase inhibitors (AChEI) are the major drug class used for their treatment; however, they present unwanted cholinergic side effects and have provided limited efficacy in clinic. Because combination therapy is being extensively used to treat different pathological diseases such as cancer or acquired immune deficiency syndrome, we posed this study to evaluate if melatonin in combination with an AChEI, galantamine, could provide beneficial properties in a novel in vitro model of AD. Thus, we subjected organotypic hippocampal cultures (OHCs) to subtoxic concentrations of β-amyloid (0.5 μM βA) plus okadaic acid (1 nM OA), for 4 days. This treatment increased by 95 % cell death, which was mainly apoptotic as shown by positive TUNEL staining. In addition, the combination of βA/OA increased Thioflavin S aggregates, hyperphosphorylation of Tau, oxidative stress (increased DCFDA fluorescence), and neuroinflammation (increased IL-1β and TNFα). Under these experimental conditions, melatonin (1-1000 nM) and galantamine (10-1000 nM), co-incubated with the toxic stimuli, caused a concentration-dependent neuroprotection; maximal neuroprotective effect was achieved at 1 μM of melatonin and galantamine. Most effective was the finding that combination of sub-effective concentrations of melatonin (1 nM) and galantamine (10 nM) provided a synergic anti-apoptotic effect and reduction of most of the AD-related pathological hallmarks observed in the βA/OA model. Therefore, we suggest that supplementation of melatonin in combination with lower doses of AChEIs could be an interesting strategy for AD patients.

Copper Toxicity Links to Pathogenesis of Alzheimer’s Disease and Therapeutics Approaches

“…Extracellular deposits of Aβ peptides in Alzheimer’s are the main pathological events in AD [ 31 , 32 , 33 , 34 ]. Senile plaques or amyloid plaques mainly consist of small amyloid beta-peptides (Aβ) (up to 42 or 43 amino acids long) [ 35 ].…”

Pharmacological doses of melatonin impede cognitive decline in tau‐related Alzheimer models, once tauopathy is initiated, by restoring the autophagic flux

“…23 This observation has proposed the measurement of melatonin levels as a potential biomarker of the disease. 24 However, preclinical and clinical studies that use melatonin in AD models [25][26][27][28] or patients 25,[29][30][31][32][33] indicate that the concentrations required for a beneficial effect are much higher than the physiological concentrations. 34 For example, the neuroprotective effects of melatonin against amyloid-dependent development of AD in different in vitro and in vivo models are achieved at doses ranging from 0.1 to 50 mg and total quantities from 1 to 440 mg/kg.…”

Serum Copper, Zinc, and Iron Levels in Patients with Alzheimer's Disease: A Meta-Analysis of Case-Control Studies

“…The deposition of β-amyloid peptide (Aβ) in the brain is one of the pathology hallmarks of AD (Citron, 2010 ; Buendia et al, 2016 ; Sepulcre et al, 2016 ; Kreutzer et al, 2017 ). Although high concentrations of endogenous copper (Cu) (Pal et al, 2015 ; Greenough et al, 2016 ; Xu et al, 2016 ), zinc (Zn) (Kulikova et al, 2015 ; Mezentsev et al, 2016 ), and iron (Fe) (Guo et al, 2015 ; Peters et al, 2015 ; Sands et al, 2016 ; James et al, 2017 ) have been found in these amyloidal plaques, the association of those metal ions with Aβ accumulation has not been well established.…”