Neuroprotective effect of normal and modified mesenchymal stem cell-derived exosomes by mitigating...

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 H₂DCFDA, 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.