Immortalized Human Olfactory Ensheathing Glia-Bmi1/hTERT

LPS Mediates Mitochondrial Oxidative Stress and Energy Disorder of Olfactory Ensheathing Glia

Olfactory ensheathing glia (OEG) are key to neuronal survival and regeneration, but their viability decreases with aging and chronic inflammation. The regulation of cell viability and organ homeostasis in response to stress depends significantly on mitochondrial function. He's team investigated how lipopolysaccharide (LPS)-induced inflammation affects immortalized OEG apoptosis, focusing on mitochondrial dysfunction and the JNK-Bnip3-Bax signaling pathway as potential mechanisms.

Mitochondrial damage triggers oxidative stress while simultaneously causing ATP depletion. Therefore, they investigated the link between mitochondrial damage and LPS-induced OEG apoptosis by analyzing mitochondrial redox balance and energy metabolism. Flow cytometry analysis with a mitochondrial ROS probe demonstrated that 5 μg/ml LPS elevated mitochondrial ROS levels beyond control measurements. The results from figures 1 a and b demonstrate that there is an excessive accumulation of ROS during inflammation. The treatment with 5 μg/ml LPS resulted in significant reductions of antioxidant levels including SOD, GSH and GPX (Fig. 1c–e). For mitochondrial energy metabolism, we measured ATP production, primarily generated by mitochondria. In comparison to the control, 5 μg/ml LPS significantly lowered ATP levels (Fig. 1f), showing ATP depletion under inflammation stress. ATP synthesis depends on the mitochondrial respiratory complex, which was analyzed via western blotting. LPS treatment downregulated its expression compared to the control (Fig. 1g–j), confirmed by qPCR (Fig. 1k–m). LPS also caused cyt-c release from mitochondria to the cytoplasm (Fig. 2A–C) and increased apoptosis, as shown by flow cytometry (Fig. 2D–E). Overall, LPS-induced inflammation leads to mitochondrial oxidative stress and respiratory complex downregulation.

Fig. 1. LPS induces mitochondrial dysfunction as manifested by mitochondrial oxidative stress and mitochondrial respiratory complex downregulation in OEG (He M, Xiang Z, et al., 2019).

Fig. 2. The proapoptotic effect of LPS on OEG apoptosis (He M, Xiang Z, et al., 2019).

ZIKV Strains Replicate in Brain Endothelial and Neuroglial Cells

Zika virus (ZIKV) is associated with diseases like microcephaly and Guillain–Barré syndrome, with unclear neuroinvasion mechanisms. Mutso et al.examined the susceptibility of human and mouse neuroglial cells, including OECs and hCMEC/D3s, to various ZIKV strains.

They infected brain endothelial cells (hCMEC/D3) and immortalized neuroglial olfactory ensheathing cells (hOEC and mOEC) with three ZIKV strains (MR766, PRVABC59, and BeH819015) using an m.o.i. of 0.1. Vero cells served as a positive control. Vero cells exhibited maximum ZIKV replication (~10⁷ p.f.u. ml−1 at 3 days p.i., Fig. 3a), brain endothelial and neuroglial cell lines also showed replication: highest in hCMEC/D3 (~10⁶ p.f.u. ml−1 at 6 days p.i., Fig. 3b), followed by mOEC (~10⁵ p.f.u. ml−1 at 2 days p.i., Fig. 3c). Within hOEC cells, the MR776 strain uniquely exhibited meaningful replication reaching approximately 10⁴ p.f.u. ml−1 at 2 days p.i. (Fig. 3d). The MR766 strain exhibited faster replication rates compared to all other strains but mOEC. According to Figure 4a and 4b MR766 showed more significant cytopathic effects in Vero cells compared to other strains. Due to their intrinsic defense mechanisms neuroglial and endothelial cells showed resilience against both infection and toxic cell damage.

Fig. 3. ZIKV replication in non- neural and neuroglial cells (Mutso M, St John J A, et al., 2020).