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

Abstract

Alterations in autophagy are increasingly being recognized in the pathogenesis of proteinopathies like Alzheimer's disease (AD). This study was conducted to evaluate whether melatonin treatment could provide beneficial effects in an Alzheimer model related to tauopathy by improving the autophagic flux and, thereby, prevent cognitive decline. The injection of AAV‐hTauP301L viral vectors and treatment/injection with okadaic acid were used to achieve mouse and human ex vivo, and in vivo tau‐related models. Melatonin (10 μmol/L) impeded oxidative stress, tau hyperphosphorylation, and cell death by restoring autophagy flux in the ex vivo models. In the in vivo studies, intracerebroventricular injection of AAV‐hTauP301L increased oxidative stress, neuroinflammation, and tau hyperphosphorylation in the hippocampus 7 days after the injection, without inducing cognitive impairment; however, when animals were maintained for 28 days, cognitive decline was apparent. Interestingly, late melatonin treatment (10 mg/kg), starting once the alterations mentioned above were established (from day 7 to day 28), reduced oxidative stress, neuroinflammation, tau hyperphosphorylation, and caspase‐3 activation; these observations correlated with restoration of the autophagy flux and memory improvement. This study highlights the importance of autophagic dysregulation in tauopathy and how administration of pharmacological doses of melatonin, once tauopathy is initiated, can restore the autophagy flux, reduce proteinopathy, and prevent cognitive decline. We therefore propose exogenous melatonin supplementation or the development of melatonin derivatives to improve autophagy flux for the treatment of proteinopathies like AD.

Extracellular vesicles and melatonin benefit embryonic develop by regulating reactive oxygen species and 5‐methylcytosine

“…The Reactive Oxygen Species Assay Kit (Beyotime) was used to measure ROS levels. Embryos in each group (n = [15][16][17][18][19][20] were incubated in serum-free culture medium containing 10 mmol/L dichlorodihydrofluorescein diacetate (DCHF-DA) at 37°C for 20 minutes. The embryos were then washed three times in serum-free culture medium and imaged using a fluorescence microscope equipped with a digital camera (Nikon), followed by analysis using Image-Pro Plus (v6.0; Media Cybernetics).…”

“…Apoptosis assays were performed using the DeadEnd Fluorometric TUNEL System (Promega) as previously described. 28 Briefly, embryos (n = [15][16][17][18][19][20] were fixed in 4% paraformaldehyde for 2 hours at RT, permeabilized with 0.5% Triton X-100 for 5 minutes at RT, and incubated in FITCconjugated dUTP and terminal deoxynucleotidyl transferase at 37°C in the dark for 1 hour. The end-labeling reaction was terminated using 2X SSC in the dark at RT for 15 minutes.…”

“…8,9 It is involved in sleep and circadian rhythms, antioxidant activity, and immunity enhancement. 10 In addition, melatonin is regarded as a multifunctional oncostatic agent 11,12 and is potentially therapeutic for nonsmall cell lung cancer, 13 colorectal cancer, 14 Alzheimer's disease, 15 chronic kidney disease, 16 and acute ischemia-reperfusion liver injury. 17 Notably, some studies have showed that melatonin is involved in reproduction, fertility, and development.…”

Neuronal NOX4 knockdown alleviates pathological tau-related alterations in a humanized mouse model of tauopathy

“…Noteworthy, a large amount of immature autophagic vacuoles accumulate in dystrophic neurites in AD brains (45), suggesting that the accumulation of pathogenic proteins such as Ab and tau may be caused by a defective ALP performance (46,47). As NOX4 deficiency reduced the accumulation of pathological oligomeric hyperphosphorylated tau, we sought of interest to evaluate the performance of macroautophagy, a highly characterized proteolysis pathway involved in the clearance of tau (48,49), in the in vivo tauopathy model. Immunofluorescence analysis revealed that the macroautophagy markers p62 ( Figure 3, A and B) and microtubule-associated protein 1 light chain 3 (LC3) ( Figure 3, C and D) were accumulating in the ipsilateral CA1 hippocampal region of NOX4 +/+ AAV-hTau injected mice.…”

“…neuroinflammation, autophagy dysregulation, etc.) were already established (48). To selectively knockdown neuronal NOX4, we injected AAV serotype 9 particles, which exhibits neuronal tropism for transgene delivery (61), carrying a short hairpin RNA (shRNA) targeting NOX4 (AAV-shNOX4) or a control scramble shRNA (AAV-shSCR) in the right hemisphere´s hippocampus ( Figure 5B).…”