The Role of Astragalus Polysaccharide in Alleviating Oxidative Stress and Mitochondrial Dysfunction in HIV-Associated Neurocognitive Disorders

Backgrounds:

HIV-associated neurocognitive disorder (HAND) is an important factor that seriously affects the quality of life of HIV-infected patients. More than 50% of HIV-1-infected patients will develop HAND. The HIV-1 envelope protein gp120 is implicated in many of the neuropathological features associated with HAND and is believed to play a crucial role in the development of these disorders. Evidence suggests that HAND is closely related to the signaling of high levels of reactive oxygen species (ROS), with its underlying mechanisms potentially being multifactorial, including autophagy and mitochondrial dysfunction. Astragalus polysaccharide (APS), a major bioactive compound derived from Astragalus membranaceus is one of the most important herbs used in the treatment of various diseases, including cancer, inflammatory diseases, and neurodegenerative disorders. APS has been extensively studied for its pharmacological activities, which encompass antioxidant, anti-inflammatory, neuroprotective, and anticancer effects. Consequently, this study aims to investigate the changes in ROS within a gp120 protein-induced cell model treated with APS and to elucidate the mechanism by which APS mitigates oxidative stress associated with HAND.

Methods:

HT22 cells were cultured in Dulbecco's Modified Eagle Medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 1% Penicillin-Streptomycin antibiotics in an incubator with 5% CO₂ in 37℃. Cultured HT22 cells were treated with 9 nM Gp120 protein for 24 hours, and then 100, 500 or 1000 μg/mL APS was applied for 24 hours, and different proteins level of expression were detected by Western blot. The ROS level was then analyzed on FACS Calibur-Tangerine flow cytometry in 502 nm. The alteration in mitochondrial membrane potential in HT22 cells was assessed through the utilization of the JC-1 Assay Kit in mPMs.

Results:

This study aims to determine whether treatment with APS can ameliorate the impairment of mitochondrial function induced by HIV-1 gp120 and reduce the production of ROS. We first analyzed APS-treated HAND cells using JC-1 to assess changes in mitochondrial membrane potential. In control HT22 cells, mitochondria exhibited punctate red fluorescence from JC-1, indicating a robust mitochondrial membrane potential. In contrast, prolonged gp120 treatment led to a significant decrease in red JC-1 fluorescence, predominantly diffuse green monomer fluorescence. This shift in JC-1 fluorescence from red to green signifies a loss of mitochondrial membrane potential in these cells. Interestingly, the administration of APS resulted in an increased amount of punctate red JC-1 fluorescence, accompanied by a decrease in both the quantity and intensity of green monomeric JC-1 fluorescence. We subsequently investigated the effect of APS on ROS production. The results indicated that, compared to the control group, HIV-1 gp120 elevated intracellular ROS levels; However, the addition of APS significantly mitigated this effect, with ROS levels decreasing substantially in response to increasing doses of APS.

Conclusions:

In conclusion, this study revealed that exposure to the HIV-1 envelope protein gp120 induced mitochondrial damage and cytotoxicity in HT22 cells. HIV-1 gp120 promoted the mitochondrial dysfunction. Moreover, we demonstrated that APS significantly reduces the level of cellular ROS induced by gp120 protein by improving mitochondrial dysfunction. These findings suggest that APS plays a crucial role in reducing HIV-1 gp120-induced ROS by enhancing the autophagic clearance of damaged mitochondria. (Acknowledgements: This study was supported by Natural Science Foundation of Guangdong, China (No. 2023A1515012231) to H. Cao and Grant from School of Public Health of Southern Medical University, China, Grant No. GW202431 to H. Cao; Corresponding author: Hong Cao, gzhcao@smu.edu.cn)

No relevant conflicts of interest to declare.