Protective effect of 4-Phenylbutyrate against proteolipid protein mutation-induced endoplasmic reticulum stress and oligodendroglial cell death

AMX0035 Mitigates Oligodendrocyte Apoptosis and Ameliorates Demyelination in MCAO Rats by Inhibiting Endoplasmic Reticulum Stress and Mitochondrial Dysfunction

Post-stroke cognitive impairment (PSCI) is a common complication of strokes and is associated with the demyelination of nerve fibers. AMX0035, a drug currently used to treat motor neuron diseases, may aid in preventing oligodendrocyte apoptosis and alleviating demyelination by targeting the pathways involved in ERS and mitochondrial dysfunction. All animals were randomly divided into four groups: the sham, sham+AMX0035, middle cerebral artery occlusion (MCAO), and MCAO+AMX0035 group. The Morris water maze was used to test cognitive function, and changes in myelin structure in the brain were investigated using transmission electron microscopy (TEM), Luxol fast blue (LFB) staining, and myelin basic protein (MBP) immunofluorescence staining. Western blot was performed to detect proteins associated with ER stress and mitochondrial dysfunction, and double-labeling immunofluorescence was utilized to localize oligodendrocytes and apoptosis-related proteins. Neurological function scores and TTC staining confirmed the successful establishment of the MCAO rat model. The Morris water maze experiment revealed impaired cognitive function in MCAO rats, which significantly improved following the AMX0035 intervention. TEM and LFB staining showed the disrupted myelin structure in the MCAO group, while AMX0035 effectively ameliorated this myelin damage. Immunofluorescence examination and Western blot revealed the decreased expression of MBP in MCAO rats, increasing with AMX0035 treatment. TUNEL staining demonstrated increased cell apoptosis in MCAO rats, which was reduced following AMX0035 therapy. Western blot detected significant increases in proteins associated with the ER stress pathway and proteins linked to mitochondrial dysfunction in the MCAO group, all of which were downregulated after AMX0035 intervention. Double-labeling immunofluorescence staining revealed a significant increase in the number of cytochrome c+ and caspase 12+ oligodendrocyte cells in MCAO rats, which decreased after AMX0035 administration. The activation of ER stress and mitochondrial dysfunction pathways following MCAO led to oligodendrocyte damage and apoptosis. AMX0035 can inhibit these pathways, reduce oligodendrocyte apoptosis, and alleviate demyelination, thereby improving PSCI.

Lipid Oxidation at the Crossroads: Oxidative Stress and Neurodegeneration Explored in Caenorhabditis elegans

Lipid metabolism plays a critical role in maintaining cellular integrity, especially within the nervous system, where lipids support neuronal structure, function, and synaptic plasticity. However, this essential metabolic pathway is highly susceptible to oxidative stress, which can lead to lipid peroxidation, a damaging process induced by reactive oxygen species. Lipid peroxidation generates by-products that disrupt many cellular functions, with a strong impact on proteostasis. In this review, we explore the role of lipid oxidation in protein folding and its associated pathological implications, with a particular focus on findings in neurodegeneration from Caenorhabditis elegans studies, an animal model that remains underutilized. Additionally, we highlight the effectiveness of different methodologies applied in this nematode to deepen our understanding of this intricate process. In the nervous system of any animal, including mammals and invertebrates, lipid oxidation can disturb the delicate balance of cellular homeostasis, leading to oxidative stress, the build-up of toxic by-products, and protein misfolding, key factors in neurodegenerative diseases. This disruption contributes to the pathogenesis of neurodegenerative disorders such as Alzheimer's, Parkinson's, or Huntington's disease. The findings from Caenorhabditis elegans studies offer valuable insights into these complex processes and highlight potential avenues for developing targeted therapies to mitigate neurodegenerative disease progression.

Pelizaeus-Merzbacher disease: on the cusp of myelin medicine

Pelizaeus-Merzbacher disease (PMD) is caused by mutations in the proteolipid protein 1 (PLP1) gene encoding proteolipid protein (PLP). As a major component of myelin, mutated PLP causes progressive neurodegeneration and eventually death due to severe white matter deficits. Medical care has long been limited to symptomatic treatments, but first-in-class PMD therapies with novel mechanisms now stand poised to enter clinical trials. Here, we review PMD disease mechanisms and outline rationale for therapeutic interventions, including PLP1 suppression, cell transplantation, iron chelation, and intracellular stress modulation. We discuss available preclinical data and their implications on clinical development. With several novel treatments on the horizon, PMD is on the precipice of a new era in the diagnosis and treatment of patients suffering from this debilitating disease.

Knockdown of Rab7B, But Not of Rab7A, Which Antagonistically Regulates Oligodendroglial Cell Morphological Differentiation, Recovers Tunicamycin-Induced Defective Differentiation in FBD-102b Cells

In the central nervous system (CNS), insulative myelin sheaths are generated from the differentiated plasma membranes of oligodendrocytes (oligodendroglial cells) and surround neuronal axons to achieve saltatory conduction. Despite the functional involvement of myelin sheaths in the CNS, the molecular mechanism by which oligodendroglial cells themselves undergo differentiation of plasma membranes remains unclear. It also remains to be explored whether their signaling mechanisms can be applied to treating diseases of the oligodendroglial cells. Here, we describe that Rab7B of Rab7 subfamily small GTPases negatively regulates oligodendroglial cell morphological differentiation using FBD-102b cells, which are model cells undergoing differentiation of oligodendroglial precursors. Knockdown of Rab7B or Rab7A by the respective specific siRNAs in cells positively or negatively regulated morphological differentiation, respectively. Consistently, these changes were supported by changes on differentiation- and myelination-related structural protein and protein kinase markers. We also found that knockdown of Rab7B has the ability to recover inhibition of morphological differentiation following tunicamycin-induced endoplasmic reticulum (ER) stress, which mimics one of the major molecular pathological causes of hereditary hypomyelinating disorders in oligodendroglial cells, such as Pelizaeus-Merzbacher disease (PMD). These results suggest that the respective molecules among very close Rab7 homologues exhibit differential roles in morphological differentiation and that knocking down Rab7B can recover defective differentiating phenotypes under ER stress, thereby adding Rab7B to the list of molecular therapeutic cues taking advantage of signaling mechanisms for oligodendroglial diseases like PMD.

Effects of MgSO4 Alone or Associated with 4-PBA on Behavior and White Matter Integrity in a Mouse Model of Cerebral Palsy: A Sex- and Time-Dependent Study

Cerebral palsy (CP) is defined as permanent disorders of movement and posture. Prematurity and hypoxia-ischemia (HI) are risk factors of CP, and boys display a greater vulnerability to develop CP. Magnesium sulfate (MgSO₄) is administered to mothers at risk of preterm delivery as a neuroprotective agent. However, its effectiveness is only partial at long term. To prolong MgSO₄ effects, it was combined with 4-phenylbutyrate (4-PBA). A mouse model of neonatal HI, generating lesions similar to those reported in preterms, was realized. At short term, at the behavioral and cellular levels, and in both sexes, the MgSO₄/4-PBA association did not alter the total prevention induced by MgSO₄ alone. At long term, the association extended the MgSO₄ preventive effects on HI-induced motor and cognitive deficits. This might be sustained by the promotion of oligodendrocyte precursor differentiation after HI at short term, which led to improvement of white matter integrity at long term. Interestingly, at long term, at a behavioral level, sex-dependent responses to HI were observed. This might partly be explained by early sex-dependent pathological processes that occur after HI. Indeed, at short term, apoptosis through mitochondrial pathways seemed to be activated in females but not in males, and only the MgSO₄/4-PBA association seemed to counter this apoptotic process.

Unfolded protein response in myelin disorders

Activation of the unfolded protein response in response to endoplasmic reticulum stress preserves cell viability and function under stressful conditions. Nevertheless, persistent, unresolvable activation of the unfolded protein response can trigger apoptosis to eliminate stressed cells. Recent studies show that the unfolded protein response plays an important role in the pathogenesis of various disorders of myelin, including multiples sclerosis, Charcot-Marie-Tooth disease, Pelizaeus-Merzbacher disease, vanishing white matter disease, spinal cord injury, tuberous sclerosis complex, and hypoxia-induced perinatal white matter injury. In this review we summarize the current literature on the unfolded protein response and the evidence for its role in the pathogenesis of myelin disorders.