Cellular cholesterol loss by DHCR24 knockdown leads to Aß production by changing APP intracellular localization.

For the past 20 years, the majority of cell culture studies reported that increasing cholesterol level increases amyloid-ß (Aß) production. Conversely, other studies and genetic evidences support that cellular cholesterol loss leads to Aß generation. As a highly controversial issue in Alzheimer's disease pathogenesis, the apparent contradiction prompted us to again explore the role of cellular cholesterol in Aß production. Here, we adopted new neuronal and astrocytic cell models induced by 3ß-hydroxysterol-Δ24 reductase (DHCR24), which obviously differ from the widely used cell models with overexpressing amyloid precursor protein (APP) in the majority of previous studies. In neuronal and astrocytic cell model, we found that deficiency of cellular cholesterol by DHCR24 knockdown obviously increased intracellular and extracellular Aß generation. Importantly, in cell models with overexpressing APP, we found that APP overexpression could disrupt cellular cholesterol homeostasis and affect function of cells, coupled with the increase of APP ß-cleavage product, 99-residue transmembrane C-terminal domain. Therefore, we suppose the results derived from the APP knockin models will need to be re-evaluated. One rational explanation for the discrepancy between our outcomes and the previous studies could be attributed to the two different cell models. Mechanistically, we showed that cellular cholesterol loss obviously altered APP intracellular localization by affecting cholesterol-related trafficking protein of APP. Therefore, our outcomes strongly support cellular cholesterol loss by DHCR24 knockdown leads to Aß production.

Plasma-Free Blood as a Potential Alternative to Whole Blood for Transcriptomic Analysis.

RNA sequencing (RNAseq) technology has become increasingly important in precision medicine and clinical diagnostics, and emerged as a powerful tool for identifying protein-coding genes, performing differential gene analysis, and inferring immune cell composition. Human peripheral blood samples are widely used for RNAseq, providing valuable insights into individual biomolecular information. Blood samples can be classified as whole blood (WB), plasma, serum, and remaining sediment samples, including plasma-free blood (PFB) and serum-free blood (SFB) samples that are generally considered less useful byproducts during the processes of plasma and serum separation, respectively. However, the feasibility of using PFB and SFB samples for transcriptome analysis remains unclear. In this study, we aimed to assess the suitability of employing PFB or SFB samples as an alternative RNA source in transcriptomic analysis. We performed a comparative analysis of WB, PFB, and SFB samples for different applications. Our results revealed that PFB samples exhibit greater similarity to WB samples than SFB samples in terms of protein-coding gene expression patterns, detection of differentially expressed genes, and immunological characterizations, suggesting that PFB can serve as a viable alternative to WB for transcriptomic analysis. Our study contributes to the optimization of blood sample utilization and the advancement of precision medicine research. Supplementary Information: The online version contains supplementary material available at 10.1007/s43657-023-00121-1.

DHCR24 reverses Alzheimer's disease-related pathology and cognitive impairment via increasing hippocampal cholesterol levels in 5xFAD mice.

Accumulating evidences reveal that cellular cholesterol deficiency could trigger the onset of Alzheimer's disease (AD). As a key regulator, 24-dehydrocholesterol reductase (DHCR24) controls cellular cholesterol homeostasis, which was found to be downregulated in AD vulnerable regions and involved in AD-related pathological activities. However, DHCR24 as a potential therapeutic target for AD remains to be identified. In present study, we demonstrated the role of DHCR24 in AD by employing delivery of adeno-associated virus carrying DHCR24 gene into the hippocampus of 5xFAD mice. Here, we found that 5xFAD mice had lower levels of cholesterol and DHCR24 expression, and the cholesterol loss was alleviated by DHCR24 overexpression. Surprisingly, the cognitive impairment of 5xFAD mice was significantly reversed after DHCR24-based gene therapy. Moreover, we revealed that DHCR24 knock-in successfully prevented or reversed AD-related pathology in 5xFAD mice, including amyloid-ß deposition, synaptic injuries, autophagy, reactive astrocytosis, microglial phagocytosis and apoptosis. In conclusion, our results firstly demonstrated that the potential value of DHCR24-mediated regulation of cellular cholesterol level as a promising treatment for AD.

Clinical efficacy and safety of low-dose doxepin in Chinese patients with generalized anxiety disorder: A before-after study.

Clinical and animal studies have reported that low-dose doxepin may have positive effects on generalized anxiety disorder (GAD); however, its effectiveness and clinical safety are less well understood. This study is a before-after study and aims to investigate the effectiveness and side effects of low-dose doxepin by evaluating Hamilton Anxiety Scale (HAMA) scores, hormones, blood glucose, serum lipids, body weight, and body mass index (BMI) in patients with GAD. Forty-nine patients (20 males and 29 females) with GAD were randomly assigned to receive low-dose doxepin (6.25 mg-12.5 mg per day) for 12 weeks between February 2015 and March 2016. HAMA scores, fasting blood glucose (FBG) body weight, BMI, and some serum biochemical indexes, such as adrenocorticotropic hormone (ACTH), free triiodothyronine (FT3), total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDLC), and FBG, were assessed during pretreatment and post-treatment. Mean scores of HAMA decreased from 19.50 ±â€…1.22 to 8.50 ±â€…3.61 after low-dose doxepin treatment (P < .01). The serum levels of ACTH (4.33 ±â€…2.14 vs 6.12 ±â€…3.02 pmol/L), FT3 (4.78 ±â€…0.51 vs 5.15 ±â€…0.52 pg/mL), TC (4.55 ±â€…1.01 vs 5.93 ±â€…1.66 mmol/L), TG (1.69 ±â€…1.51 vs 3.39 ±â€…2.86 mmol/L), and LDLC (2.43 ±â€…0.88 vs 3.76 ±â€…1.25 mmol/L), and FBG (5.06 ±â€…0.43 vs 5.78 ±â€…0.81 mmol/L) were higher than that pretreatment with a significant difference (P < .01). Bodyweight (62.00 ±â€…7.45 vs 64.00 ±â€…6.44 kg, P = .23) and BMI (23.70 ±â€…2.35 vs 24.48 ±â€…2.11 kg/m2, P = .14) had no difference after treatment. These results suggest that low-dose doxepin has beneficial clinical efficacy and safety. Low-dose doxepin can ameliorate anxiety in GAD patients and has some effects on neuroendocrine systems and the metabolic activity of serum glucose and lipid.

DHCR24 Knockdown Induces Tau Hyperphosphorylation at Thr181, Ser199, Ser262, and Ser396 Sites via Activation of the Lipid Raft-Dependent Ras/MEK/ERK Signaling Pathway in C8D1A Astrocytes.

The synthetase 3ß-hydroxysterol-Δ24 reductase (DHCR24) is a key regulator involved in cholesterol synthesis and homeostasis. A growing body of evidence indicates that DHCR24 is downregulated in the brain of various models of Alzheimer's disease (AD), such as astrocytes isolated from AD mice. For the past decades, astrocytic tau pathology has been found in AD patients, while the origin of phosphorylated tau in astrocytes remains unknown. A previous study suggests that downregulation of DHCR24 is associated with neuronal tau hyperphosphorylation. Herein, the present study is to explore whether DHCR24 deficiency can also affect tau phosphorylation in astrocytes. Here, we showed that DHCR24 knockdown could induce tau hyperphosphorylation at Thr181, Ser199, Thr231, Ser262, and Ser396 sites in C8D1A astrocytes. Meanwhile, we found that DHCR24-silencing cells had reduced the level of free cholesterol in the plasma membrane and intracellular organelles, as well as cholesterol esters. Furthermore, reduced cellular cholesterol level caused a decreased level of the caveolae-associated protein, cavin1, which disrupted lipid rafts/caveolae and activated rafts/caveolae-dependent Ras/MEK/ERK signaling pathway. In contrast, overexpression of DHCR24 prevented the overactivation of Ras/MEK/ERK signaling by increasing cellular cholesterol content, therefore decreasing tau hyperphosphorylation in C8D1A astrocytes. Herein, we firstly found that DHCR24 knockdown can lead to tau hyperphosphorylation in the astrocyte itself by activating lipid raft-dependent Ras/MEK/ERK signaling, which might contribute to the pathogenesis of AD and other degenerative tauopathies.

The role of DHCR24 in the pathogenesis of AD: re-cognition of the relationship between cholesterol and AD pathogenesis.

Previous studies show that 3ß-hydroxysterol-Δ24 reductase (DHCR24) has a remarked decline in the brain of AD patients. In brain cholesterol synthetic metabolism, DHCR24 is known as the heavily key synthetase in cholesterol synthesis. Moreover, mutations of DHCR24 gene result in inhibition of the enzymatic activity of DHCR24, causing brain cholesterol deficiency and desmosterol accumulation. Furthermore, in vitro studies also demonstrated that DHCR24 knockdown lead to the inhibition of cholesterol synthesis, and the decrease of plasma membrane cholesterol and intracellular cholesterol level. Obviously, DHCR24 could play a crucial role in maintaining cholesterol homeostasis via the control of cholesterol synthesis. Over the past two decades, accumulating data suggests that DHCR24 activity is downregulated by major risk factors for AD, suggesting a potential link between DHCR24 downregulation and AD pathogenesis. Thus, the brain cholesterol loss seems to be induced by the major risk factors for AD, suggesting a possible causative link between brain cholesterol loss and AD. According to previous data and our study, we further found that the reduced cholesterol level in plasma membrane and intracellular compartments by the deficiency of DHCR24 activity obviously was involved in ß-amyloid generation, tau hyperphosphorylation, apoptosis. Importantly, increasing evidences reveal that the brain cholesterol loss and lipid raft disorganization are obviously linked to neuropathological impairments which are associated with AD pathogenesis. Therefore, based on previous data and research on DHCR24, we suppose that the brain cholesterol deficiency/loss might be involved in the pathogenesis of AD.