Is autophagy an elective strategy to protect neurons from dysregulated cholesterol metabolism?

Cholesterol metabolism: physiological versus pathological aspects in intracerebral hemorrhage

Cholesterol is an important component of plasma membranes and participates in many basic life functions, such as the maintenance of cell membrane stability, the synthesis of steroid hormones, and myelination. Cholesterol plays a key role in the establishment and maintenance of the central nervous system. The brain contains 20% of the whole body's cholesterol, 80% of which is located within myelin. A huge number of processes (e.g., the sterol regulatory element-binding protein pathway and liver X receptor pathway) participate in the regulation of cholesterol metabolism in the brain via mechanisms that include cholesterol biosynthesis, intracellular transport, and efflux. Certain brain injuries or diseases involving crosstalk among the processes above can affect normal cholesterol metabolism to induce detrimental consequences. Therefore, we hypothesized that cholesterol-related molecules and pathways can serve as therapeutic targets for central nervous system diseases. Intracerebral hemorrhage is the most severe hemorrhagic stroke subtype, with high mortality and morbidity. Historical cholesterol levels are associated with the risk of intracerebral hemorrhage. Moreover, secondary pathological changes after intracerebral hemorrhage are associated with cholesterol metabolism dysregulation, such as neuroinflammation, demyelination, and multiple types of programmed cell death. Intracellular cholesterol accumulation in the brain has been found after intracerebral hemorrhage. In this paper, we review normal cholesterol metabolism in the central nervous system, the mechanisms known to participate in the disturbance of cholesterol metabolism after intracerebral hemorrhage, and the links between cholesterol metabolism and cell death. We also review several possible and constructive therapeutic targets identified based on cholesterol metabolism to provide cholesterol-based perspectives and a reference for those interested in the treatment of intracerebral hemorrhage.

Neurological manifestations in mevalonate kinase deficiency: A systematic review

INTRODUCTION

Mevalonate kinase deficiency (MKD) is a monogenic auto-inflammatory disease. Its manifestations range from partial MKD to mevalonic aciduria (MVA). All patients display a periodic fever, and MVA patients additionally exhibit severe neurological involvement. The objective of this work was to describe neurological manifestations of MKD.

METHODS

A systematic literature review was performed from January 1990 to January 2022. Forty-five patients from 18 case reports and five cohort studies were included in the analysis.

RESULTS

In cohort studies, the most-reported manifestations were headaches (41%) and fatigue (31%). Serious involvements including ataxia and developmental delay were described less than 1% of patients but 22-31% of case reports. They consistently appeared in the first years of life. Retinal dystrophy was frequently reported (31%) in case reports. Other manifestations, including uveitis, aseptic meningitis, and stroke remained rare.

DISCUSSION

Severe neurological manifestations are rare in MKD but are responsible for major functional disabilities. They are present at onset and never appear at follow-up of patients with mild MKD. Conversely, headaches and fatigue are frequent symptoms that should be investigated. Visual examinations should be performed on the appearance of visual symptoms. The efficacy of anti-IL-1β therapy on neurological manifestations should be further investigated.

Biglycan protects human neuroblastoma cells from nitric oxide-induced death by inhibiting AMPK-mTOR mediated autophagy and intracellular ROS level

The ubiquitous proteoglycan, biglycan (BGN) acts as an important modulator, regulating key molecular pathways of metabolism and brain function. Autophagy is documented as a defining feature of neurodegeneration in Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). In the present study, we found that BGN protected neuronal cells from nitric oxide (NO)-induced cell apoptosis. However, it is still unclear that whether the neuroprotective effect of BGN relates to autophagy. Here, we discovered that an NO donor, sodium nitroprusside (SNP) induced autophagy in human SH-SY5Y neuroblastoma cells, including activating LC3B and inhibiting p62. Inhibiting autophagy by 3MA aggravated NO-induced cell death, otherwise promoting autophagy by Rapamycin rescued NO-triggered cell death. Notably, BGN downregulated by NO, significantly protected SH-SY5Y cells against NO-induced neurotoxicity by inhibiting the activation of autophagy-dependent AMPK signaling pathway. Moreover, BGN overexpression also diminished NO-induced the elevation of intracellular reactive oxygen species (ROS) level, but not NO content. These findings suggest that BGN protects neuroblastoma cells from NO-induced death by suppressing autophagy-dependent AMPK-mTOR signaling and intracellular ROS level.

Zebrafish C-reactive protein isoforms inhibit SVCV replication by blocking autophagy through interactions with cell membrane cholesterol

In the present work, the mechanisms involved in the recently reported antiviral activity of zebrafish C-reactive protein-like protein (CRP1-7) against the spring viraemia of carp rhabdovirus (SVCV) in fish are explored. The results neither indicate blocking of the attachment or the binding step of the viral replication cycle nor suggest the direct inhibition of G protein fusion activity or the stimulation of the host’s interferon system. However, an antiviral state in the host is induced. Further results showed that the antiviral protection conferred by CRP1-7 was mainly due to the inhibition of autophagic processes. Thus, given the high affinity of CRPs for cholesterol and the recently described influence of the cholesterol balance in lipid rafts on autophagy, both methyl-β-cyclodextrin (a cholesterol-complexing agent) and 25-hydroxycholesterol (a cholesterol molecule with antiviral properties) were used to further describe CRP activity. All the tested compounds exerted antiviral activity by affecting autophagy in a similar manner. Further assays indicate that CRP reduces autophagy activity by initially disturbing the cholesterol ratios in the host cellular membranes, which in turn negatively affects the intracellular regulation of reactive oxygen species (ROS) and increases lysosomal pH as a consequence. Ultimately, here we propose that such pH changes exert an inhibitory direct effect on SVCV replication by disrupting the pH-dependent membrane-fusogenic ability of the viral glycoprotein G, which allows the release of the virus from endosomes into cytoplasm during its entry phase.