Neuroprotective effect of normal and modified mesenchymal stem cell‐derived exosomes by mitigating Alzheimer's‐related oxidative and inflammatory damage via Nrf2/HO‐1 in SH‐SY5Y cells

Abstract

Exosome therapy is emerging as a promising neuroprotective strategy for Alzheimer's disease (AD). We evaluated and compared whether normal exosomes (NE) and modified exosomes (ME) derived from AD rat brain extract‐treated rat bone marrow mesenchymal stem cells possess the potential to protect SH‐SY5Y cells against streptozotocin (STZ) induced toxicity. The effect of exosomes on oxidative stress, inflammation and neuronal survival was evaluated. Further, antioxidant mechanism of exosomes by nuclear factor erythroid 2‐related factor 2/heme oxygenase‐1 (Nrf2/HO‐1) signaling was explored. Cells were exposed to 5 mM STZ and treated with NE and ME at an equivalent concentration of 50 µg/mL. Exosomes were characterized by specific exosomal markers, CD63 and CD9. Cell viability was assessed using the MTT assay. Neuronal growth and survival were evaluated by measuring brain‐derived neurotrophic factor (BDNF) using ELISA and neuronal nuclei (NeuN) expression using immunocytochemistry. Intracellular reactive oxygen species (ROS) levels were determined using H ₂ DCFDA, while inflammatory mediators, including interleukin‐6 (IL‐6) and tumor necrosis factor‐α (TNF‐α) were quantified by ELISA. Expression levels of Nrf2 and HO‐1 were also determined. Exosome treatment improved cell viability, reduced ROS, and lowered IL‐6 and TNF‐α levels. Immunocytochemistry quantification showed increased nuclear Nrf2 and HO‐1 expression in exosome‐treated cells. Moreover, our data indicate that ME derived from AD rat brain extract‐treated rat bone marrow mesenchymal stem cells are more potent in protecting SH‐SY5Y cells from STZ‐induced oxidative stress and inflammation, possibly via Nrf2/HO‐1 signaling, as compared to NE. These in vitro results support further preclinical evaluation of exosome‐based strategies for AD.