Tannoid principles of Emblica officinalis attenuated aluminum chloride induced apoptosis by suppressing oxidative stress and tau pathology via Akt/GSK-3βsignaling pathway

Ethnopharmacological relevance: Fruits of Phyllanthus emblica Linn. or Emblica officinalis Gaertn. (Phyllanthaceae) are used in Ayurveda, Siddha, Unani, Arabic, Tibetan and various other folk medicinal systems to promote intelligence and memory. Recent study from our lab indicated the neuroprotective effect of tannoids principles of Emblica officinalis (EoT) against memory loss caused by aluminum chloride (AlCl₃) intoxication through attenuating acetylcholine esterase activity and the expression of amyloid β protein biosynthesis related markers. However the molecular mechanism of EoT has not yet been fully elucidated.

Aim of the study: The aim of the present study was to further investigate the neuroprotective mechanisms of EoT against AlCl₃-induced cognitive deficits, tau hyperphosphorylation, oxidative stress and apoptosis.

Materials and methods: Rats were treated with AlCl₃ for 60 days to induce biochemical and physiological abnormalities similar to AD patients. AD rats were treated with EoT (100mg/kg., bw. oral) for 60 days. For the examination of neuroprotective effect of EoT, behavior analysis, biochemical estimations and western blot were performed in the hippocampus and cortex of control, EoT treated and untreated AD rats.

Results: Intraperitoneal injections of AlCl₃ (100mg/kg., b.w.) for 60 days enhanced the learning and memory deficits, levels of TBARS and diminished the levels of reduced glutathione and activities of enzymatic antioxidants as compared to control group. Moreover toxicity of AlCl₃ is accompanied by the enhanced expressions of Bax, caspases-3,-9, cytosolic cytochrome c (cyto c), and pTau along with diminished expressions of Bcl-2, mitochondrial cyto c, pGSK-3β and pAkt. Coadministration of EoT nullified the cognitive deficits, biochemical abnormalities and apoptosis induced by AlCl₃ treatment. Moreover EoT prevents tau hyperphosphorylation by targeting the GSK-3β/Akt signaling pathway.

Conclusions: This study confirms that EoT would be used as a potential drug candidate for AD and other tau pathology-related neuronal degenerative diseases.