@article {44532, title = {Multi-faceted role of melatonin in neuroprotection and amelioration of tau aggregates in alzheimer{\textquoteright}s disease}, journal = {Journal of Alzheimers Disease}, volume = {62}, year = {2018}, month = {MAY}, pages = {1481-1493}, abstract = {

Alzheimer{\textquoteright}s disease (AD) is one of the major age related neurodegenerative diseases whose pathology arises due to the presence of two distinct protein aggregates, viz., amyloid-beta plaques in extracellular matrix and tau neurofibrillary tangles in neurons. Multiple factors play a role in AD pathology, which includes familial mutations, oxidative stress, and post-translational modifications. Melatonin is an endocrine hormone, secreted during darkness, derived from tryptophan, and produced mainly by the pineal gland. It is an amphipathic molecule, which makes it suitable to cross not only blood-brain barrier, but also to enter several other subcellular compartments like mitochondria and endoplasmic reticulum. In this context, the neuroprotective effect of melatonin may be attributed to its role as an antioxidant. Melatonin{\textquoteright}s pleiotropic function as an antioxidant and neuroprotective agent has been widely studied. However, its direct effect on the aggregation of tau and amyloid-beta needs to be explored. Furthermore, an important aspect of its function is its ability to regulate the process of phosphorylation of tau by affecting the function of kinases and phosphatases. In this review, we are focusing on the pleiotropic function of melatonin on the aspect of its neuroprotective function in tau pathology, which includes antioxidant function, regulation of enzymes, including kinases and enzymes involved in free radical scavenging and mitochondrial protection.

}, keywords = {Alzheimer{\textquoteright}s disease, hyperphosphorylation, melatonin, mitochondria, Protein aggregation, tau protein}, issn = {1387-2877}, doi = {10.3233/JAD-170900}, author = {Balmik, Abhishek Ankur and Chinnathambi, Subashchandrabose} } @article {46945, title = {Melatonin interacts with repeat domain of Tau to mediate disaggregation of paired helical filaments}, journal = {Biochimica Et Biophysica Acta-General Subjects}, volume = {1864}, year = {2020}, month = {MAR}, pages = {129467}, type = {Article}, abstract = {

Tau is the major neuronal protein involved in the stabilization of microtubule assembly. In Alzheimer{\textquoteright}s disease, Tau self-assembles to form intracellular protein aggregates which are toxic to cells. Various methods have been tried and tested to restrain the aggregation of Tau. Most of the agents tested for this purpose have limitations in their effectiveness and availability to neuronal cells. We have tested melatonin, a neurohormone secreted by pineal gland and a well-known anti-oxidant, for its ability to interact with the repeat domain of Tau using ITC and NMR. In aggregation inhibition and disaggregation studies of repeat Tau, melatonin was found to modulate the aggregation propensity of repeat Tau at a concentration of 5000 mu M and was more effective in dissolving preformed aggregates rather than acting as an aggregation inhibitor. However, there were no major conformational changes in Tau in presence of melatonin as observed by CD spectroscopy. On the basis of our findings, we are proposing a mechanism by which melatonin can interact with the repeat domain of Tau and exhibit its disaggregation effect.

}, keywords = {Alzheimer{\textquoteright}s disease, Disaggregation, melatonin, Paired helical filaments, tau protein, Tauopathies}, issn = {0304-4165}, doi = {10.1016/j.bbagen.2019.129467}, author = {Balmik, Abhishek Ankur and Das, Rashmi and Dangi, Abha and Gorantla, Nalini Vijay and Marelli, Udaya Kiran and Chinnathambi, Subashchandrabose} } @article {46613, title = {Melatonin reduces GSK3 beta-mediated tau phosphorylation, enhances Nrf2 nuclear translocation and anti-inflammation}, journal = {ASN Neuro}, volume = {12}, year = {2020}, month = {DEC}, pages = {1759091420981204}, type = {Article}, abstract = {

Alzheimer{\textquoteright}s disease is a neuropathological condition with abnormal accumulation of extracellular Amyloid-beta plaques and intracellular neurofibrillary tangles of Microtubule-associated protein Tau (Tau) in the brain. In pathological conditions, Tau undergoes post-translational modifications such as hyperphosphorylation by the activity of cellular kinases, which eventually leads to protein aggregation in neurons. Melatonin is a neuro-hormone that is mainly secreted from the pineal gland and functions to modulate the cellular kinases. In our study, we have checked the neuroprotective function of Melatonin by MTT and LDH assay, where Melatonin inhibited the Tau aggregates-mediated cytotoxicity and membrane leakage in Neuro2A cells. The potency of Melatonin has also been studied for the quenching of intracellular reactive oxygen species level by DCFDA assay and caspase 3 activity. Melatonin was shown to reduce the GSK3 beta mRNA and subsequent protein level as well as the phospho-Tau level (pThr181 and pThr212-pSer214) in okadaic acid-induced Neuro2A cells, as observed by western blot and immunofluorescence assay. Further, Melatonin has increased the cellular Nrf2 level and its nuclear translocation as an oxidative stress response in Tauopathy. The Melatonin was found to induce pro- and anti-inflammatory cytokines levels in N9 microglia. The mRNA level of cellular kinases such as as-GSK3 beta, MAPK were also studied by qRT-PCR assay in Tau-exposed N9 and Neuro2A cells. The immunomodulatory effect of Melatonin was evident as it induced IL-10 and TGF-beta cytokine levels and activated MAP3K level in Tau-exposed microglia and neurons, respectively. Melatonin also downregulated the mRNA level of pro-inflammatory markers, IL-1 beta and Cyclooxygenase-2 in N9 microglia. Together, these findings suggest that Melatonin remediated the cytokine profile of Tau-exposed microglia, reduced Tau hyperphosphorylation by downregulating GSK3 beta level, and alleviated oxidative stress via Nrf2 nuclear translocation.

}, keywords = {Alzheimer\&\#8217, Anti-inflammatory, GSK3\&\#946, melatonin, microglia, neurodegeneration, Nrf2, s disease, Tau hyperphosphorylation}, issn = {1759-0914}, doi = {10.1177/1759091420981204}, author = {Das, Rashmi and Balmik, Abhishek Ankur and Chinnathambi, Subashchandrabose} } @article {47364, title = {Methylation as a key regulator of Tau aggregation and neuronal health in Alzheimer{\textquoteright}s disease}, journal = {Cell Communication and Signaling}, volume = {19}, year = {2021}, month = {MAY }, pages = {51}, type = {Review}, abstract = {

Neurodegenerative diseases like Alzheimer{\textquoteright}s, Parkinson{\textquoteright}s and Huntington{\textquoteright}s disease involves abnormal aggregation and accumulation of toxic proteins aggregates. Post-translational modifications (PTMs) of the causative proteins play an important role in the etiology of disease as they could either slow down or accelerate the disease progression. Alzheimer disease is associated with the aggregation and accumulation of two major protein aggregates-intracellular neurofibrillary tangles made up of microtubule-associated protein Tau and extracellular Amyloid-beta plaques. Post-translational modifications are important for the regulation of Tau{\textquoteleft}s function but an imbalance in PTMs may lead to abnormal Tau function and aggregation. Tau methylation is one of the important PTM of Tau in its physiological state. However, the methylation signature on Tau lysine changes once it acquires pathological aggregated form. Tau methylation can compete with other PTMs such as acetylation and ubiquitination. The state of PTM at these sites determines the fate of Tau protein in terms of its function and stability. The global methylation in neurons, microglia and astrocytes are involved in multiple cellular functions involving their role in epigenetic regulation of gene expression via DNA methylation. Here, we have discussed the effect of methylation on Tau function in a site-specific manner and their cross-talk with other lysine modifications. We have also elaborated the role of methylation in epigenetic aspects and neurodegenerative conditions associated with the imbalance in methylation metabolism affecting global methylation state of cells.

}, keywords = {Aggregation, Epigenetics, methylation, Methyltransferases, post-translational modifications, Tau}, doi = {10.1186/s12964-021-00732-z}, author = {Balmik, Abhishek Ankur and Chinnathambi, Subashchandrabose} }