Hearing loss through apoptosis of the spiral ganglion neurons in apolipoprotein E knockout mice fed with a western diet
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Authors: Kim, Yoo Yeon; Chao, Janet Ren; Kim, Chulho; Kim, Boyoung; Phuong Thi-Thanh Nguyen; Jung, Harry; Chang, Jiwon; Lee, Jun Ho; Suh, Jun Gyo
Abstract
Age-related hearing loss (ARHL) is a neurodegenerative disease associated with an aged population. ARHL is influenced by biological factors such as aging, sex difference, and atherosclerosis. The mechanisms of ARHL caused by atherosclerosis have not been previously determined in apolipoprotein E knockout (ApoE KO) male mice. To investigate the onset and cause of the hearing loss, ApoE KO male mice were treated with a western diet (ApoE KO-WD) for 16 weeks. The lipid profile, atherosclerotic plaques throughout the aorta, and auditory brainstem response (ABR) thresholds were measured in the ApoE KO-WD male mice. The expression of 5100 calcium-binding protein B (S1006), a neuronal damage biomarker, was also observed. Reactive oxygen species (ROS) and apoptosis rates were detected in the cochlea of the ApoE KO male mice. Atherosclerotic plaques on the aorta and ABR thresholds were significantly increased in the ApoE KO-WD male mice at 24 weeks of age. ABR thresholds had a statistically significant positive correlation with the area of atherosclerotic plaques (r = 0.783, p = 0.013) in male mice at 24 weeks of age. SIOOB protein expression and the dihydroethidium (DHE) reaction to ROS in the cochlear spiral ganglion neurons (SGNs) were significantly increased in the ApoE KO and ApoE KO-WD male mice. Cells positive for active caspase-3 and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) in the SGNs were significantly increased in ApoE KO-WD male mice indicating an increased rate of cellular apoptosis. In conclusion, ROS in the SGNs were activated by increased S100B expression in ApoE KO-WD male mice, and this resulted in an increased apoptosis rate. Thus, hearing loss began at 16 weeks in ApoE KO-WD male mice. Our results suggest that the ApoE KO-WD male mice are a suitable animal model for studying ARHL associated with exacerbated atherosclerosis. (C) 2020 Elsevier Inc. All rights reserved.
The fundamental building blocks of cortical development are established in human exencephaly
PEDIATRIC RESEARCH
Authors: Falcone, Carmen; Vakilzadeh, Gelareh; Noctor, Stephen C.; Martinez-Cerdeno, Veronica
Abstract
Background The presence and status of progenitor/stem cells in excencephalic brain have not been previously examined. Methods Brain sections of excencephalic 17-week fetus were stained for specific stem and mature cell markers. Results The ventricles were open, the developing cerebral cortex was thin in the radial dimension, and the ventricular surface was undulated. There was a decreased ratio of subventricular/ventricular zone radial glia precursor cells (RGCs; PAX6(+) and HOPX+ cells), a decreased number of intermediate progenitor cells (IPCs; TBR2(+)), a decreased number of neurons (MAP2(+)), and an increased number of astrocytes (S100b(+)), compared to the control. MAP2(+) neurons, S100b(+) astrocytes, and OLIG2(+) oligodendrocytes were present within the subventricular zone. Conclusions This indicates that the underlying condition did not initially preclude radial glial cells from undergoing asymmetric divisions that produce IPCs but halted the developmental progression. RGC and IPC presence in the developing cerebral cortex demonstrates that the fundamental building blocks of cortical formation had been established and that a normal sequence of developmental steps had been initiated in this case of exencephaly. These data expand our understanding of exencephaly etiology and highlight the status of cortical progenitor cells that may be linked to the disorder.