Alzheimer's disease (AD), a serious neurodegenerative disease, has been plaguing many patients and their families worldwide. Its main symptoms include behavioral disorders, cognitive decline, and memory loss, which have a great impact on patients' lives. In recent years, studies on the pathology of AD have found that the concentration of β-amyloid (Aβ) is strongly associated with the severity of dementia symptoms. the aggregation of Aβ is thought to trigger oxidative stress, which in turn impairs neuronal integrity and function, ultimately leading to apoptosis. Therefore, finding effective ways to reduce Aβ-induced oxidative stress and apoptosis has become a key direction in the treatment of AD.

Among numerous studies, plant-derived exosome-like nanovesicles (ELNs) have gradually become a research hotspot due to their unique biological activities and advantages. As a plant with a long history of medicinal and edible use, the ELNs (LRM-ELNs) of Lycium barbarum (LRM), a black-fruited wolfberry, have attracted even more attention. Previous studies have shown that LRM possesses remarkable properties such as anti-fatigue, antioxidant, anticancer, and memory enhancement, and it has been found that LRM can alleviate the key pathological features of AD by modulating the nervous system, immune responses, and signaling pathways. However, the specific modulatory effects of LRM-ELNs on Aβ-induced oxidative stress have not been fully understood.

Recently, a paper published in Foods entitled Response Surface Methodology Optimization of Exosome-like Nanovesicles Extraction from Lycium ruthenicum Murray and Their Inhibitory Effects on Aβ-Induced Apoptosis and Oxidative Stress in HT22 Cells optimized the extraction conditions of LRM-ELNs and explored their effects on Aβ-induced oxidative stress and apoptosis in HT22 cells, which opens up new possibilities for the treatment of AD. Thesis

The researchers first optimized the extraction conditions of LRM-ELNs by one-way experiments, and deeply explored the effects of molecular weight, concentration, relative centrifugal force and incubation time of PEG6000 on the yield and characteristics of LRM-ELNs. They found that when the molecular weight of PEG6000 was 6000, the yield of LRM-ELNs was higher and the particle size was smaller; when the concentration was around 10%, the indexes of yield and particle size were more desirable; when the relative centrifugal force was 8000×g, the yield and the particle size reached a better equilibrium; and when the incubation time was 20h, the yield was high but too long would cause the yield to decrease slightly.

Based on the results of the one-way experiments, the researchers further used RSM to optimize the parameters of LRM-ELN extraction, and conducted more in-depth experiments and analyses with PEG6000 concentration, relative centrifugal force and incubation time as variables. The optimal extraction conditions for LRM-ELNs were finally determined: PEG6000 concentration of 11.93%, centrifugal force of 9720 × g, and incubation time of 21.12 h, at which time the actual yield of LRM-ELNs could reach 4.24 g/kg.

In the subsequent experiments, the researchers carried out a comprehensive characterization of the extracted LRM-ELNs. Through transmission electron microscopy, it was found that the LRM-ELNs were spherical with an average particle size of 114.1 nm and a zeta potential of -6.36 mV.

Fig. 1. Characterization of LRM-ELN

In cellular experiments LRM-ELNs showed amazing effects. In experiments on HT22 cells (mouse hippocampal neuronal cells commonly used in AD studies), LRM-ELNs showed no significant toxicity to the cells and were able to significantly increase the viability of Aβ-treated HT22 cells and effectively inhibit Aβ-induced apoptosis, with this inhibitory effect showing a dose-dependent pattern. Further studies revealed that LRM-ELNs were able to regulate the mitochondrial apoptotic pathway, increase the mitochondrial membrane potential (MMP), decrease the Bax/Bcl-2 ratio, and reduce the expression of Cleaved Caspase-3, thus protecting the cells from Aβ-induced apoptosis.

Figure 2. LRM-ELNs reduced Aβ-induced cytotoxicity and apoptosis in HT22 cells

Meanwhile, LRM-ELNs were also able to attenuate Aβ-induced oxidative stress. It reduced intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels and increased the activity of antioxidant enzymes (e.g., superoxide dismutase, catalase, glutathione peroxidase). In addition, LRM-ELNs were able to activate the Nrf2/HO-1/NQO1 signaling pathway, increase the expression of Nrf2 in the nucleus, and up-regulate the expression of HO-1 and NQO1, which enhanced the antioxidant capacity of cells.

Figure 3. Effects of LRM-ELNs on Aβ-induced Nrf2/HO-1/NQO1 signaling pathway in HT22 cells

The researchers hypothesized that LRM-ELNs may be able to perform these roles because they are rich in biologically active components, such as lipids, proteins, DNA, and RNAs (including small RNAs and microRNAs), which may regulate cellular physiological processes by delivering miRNAs. However, this mechanism needs further in-depth study.

In summary, the present study provides new ideas and potential drug candidates for the treatment of AD by optimizing the extraction conditions of LRM-ELNs and deeply investigating their effects on Aβ-induced apoptosis and oxidative stress in HT22 cells.

In the future, as the research continues, LRM-ELNs are expected to become a new hope for the treatment of AD, and to bring good news to many AD patients around the world. However, before that, more studies are needed to verify their effectiveness and safety in vivo, as well as to further explore their mechanism of action. Let's look forward to new breakthroughs in this research field and contribute to the attack of Alzheimer's disease.

Reference：https://doi.org/10.3390/foods13203328