Ethanolic extract of Streblus asper leaves protects against glutamate-induced toxicity in HT22 hippocampal neuronal cells and extends lifespan of Caenorhabditis elegans

Abstract

BackgroundAlthough such local herb as Streblus asper (family Moraceae) has long been recognized for traditional folk medicines and important ingredient of traditional longevity formula, its anti-neurodegeneration or anti-aging activity is little known. This study aimed to investigate the neuroprotective effect of S. asper leaf extracts (SA-EE) against toxicity of glutamate-mediated oxidative stress, a crucial factor contributing to the neuronal loss in age-associated neurodegenerative diseases and the underlying mechanism as well as to evaluate its longevity effect.MethodsUsing mouse hippocampal HT22 as a model for glutamate oxidative toxicity, we carried out MTT and LDH assays including Annexin V-FITC/propidium iodide staining to determine the SA-EE effect against glutamate-induced cell death. Antioxidant activities of SA-EE were evaluated using the radical scavenging and DCFH-DA assays. To elucidate the underlying mechanisms, SA-EE treated cells were analyzed for the expressions of mRNA and proteins interested by immunofluorescent staining, western blot analysis and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) techniques. The longevity effect of SA-EE was examined on C. elegans by lifespan assay.ResultsWe demonstrate that a concentration-dependent reduction of glutamate-induced cytotoxicity was significant after SA-EE treatment as measured by MTT and LDH assays. Annexin V-FITC/propidium iodide and immunofluorescent staining showed that co-treatment of glutamate with SA-EE significantly reduced apoptotic-inducing factor (AIF)-dependent apoptotic cell death. DCFH-DA assay revealed that this extract was capable of dose dependently attenuating the ROS caused by glutamate. Western blot analysis and qRT-PCR showed that nuclear factor erythroid 2-related factor 2 (Nrf2) protein levels in the nucleus, as well as mRNA levels of antioxidant-related genes under Nrf2 regulation were significantly increased by SA-EE. Furthermore, this extract was capable of extending the lifespan of C. elegans.ConclusionsSA-EE possesses both longevity effects and neuroprotective activity against glutamate-induced cell death, supporting its therapeutic potential for the treatment of age-associated neurodegenerative diseases.

Acanthus ebracteatus leaf extract provides neuronal cell protection against oxidative stress injury induced by glutamate

“…Since the HT22 cells do not express the NMDA type of glutamate receptor, toxicity in this model occurs mainly through oxytosis. In this work, our experiments were performed using a high concentration of glutamate (5 mM), which caused a 50% reduction in cell viability relative to a previous report [ 33 ]. The present study also confirmed increased ROS generation and AIF nuclear translocation as the mechanism of cell death in this model.…”

“…The total flavonoid content was determined using the aluminum chloride colorimetric method modified for a microplate format as described previously [ 33 ]. In brief, 50 μL of the extract sample (1 mg/mL) was made up to 200 μL with 95% ethanol, and mixed well with 10 μL of 10% ( v /v) AlCl 3 solution and 10 μL of 1 M NaOAc solution.…”

“…The total phenolic content was determined using the Folin-Ciocalteu method adapted for analysis with a microplate reader, as previously described [ 33 ]. Briefly, 50 μL of the extract sample (1 mg/mL) was mixed thoroughly with 50 μL of 10-fold diluted Folin-Ciocalteu’s phenol reagent (Sigma-Aldrich).…”

Acid-base fractions separated from Streblus asper leaf ethanolic extract exhibited antibacterial, antioxidant, anti-acetylcholinesterase, and neuroprotective activities

“…After collection, the ethanolic extract of S. asper leaves was prepared as previously described [ 54 ]. In brief, the dry powered plant material (0.73 kg) was soaked in 100% ethanol (7.3 L) with a 1:10 sample-solvent ratio for 48 h at room temperature (RT) in the dark with continuous shaking.…”

“…Studies on the crude plant extract as well as the isolated compounds have demonstrated that S. asper exhibits various pharmacological properties including antioxidant, anticancer [ 47 ], antimicrobial [ 48 ], antimalarial [ 49 ], anti-filarial [ 50 ], anti-inflammation [ 51 ], and anti-hepatitis B activities [ 52 ]. Moreover, the neuroprotective properties of S. asper leaf extracts in both in vivo and in vitro models of neurodegenerative diseases were recently reported [ 53 , 54 ]. However, the active phytochemical ingredients responsible for neuroprotection have not been clearly identified.…”