Grape seed proanthocyanidin oligomers alleviate demyelination in cuprizone-fed mice

Abstract

BACKGROUND: Recent studies on the pathogenesis of multiple sclerosis suggest that intervening in glial cells may play a key role in reducing relapses and delaying disability progression. Grape seed proanthocyanidin oligomers significantly inhibit demyelination in cuprizone-treated mice. OBJECTIVE: To explore the mechanism by which grape seed proanthocyanidin oligomers protect myelin sheaths through regulating astrocytes. METHODS: (1) Animal experiment: Thirty mice were randomly divided into normal group, CPZ group, and CPZ+oligomeric proanthocyanidin group. The latter two groups were fed a diet containing 0.2% CPZ for 6 weeks to induce demyelination. From the 5th week, the normal and CPZ groups were given ddH2O by gavage, while the CPZ+oligomeric proanthocyanidin group received grape seed proanthocyanidin oligomers [50 mg/(kg·d)] once daily for 2 weeks. Behavioral changes were observed; LFB and oil red staining were used to assess myelin pathology; ELISA detected inflammatory factors in the brain; immunofluorescence staining detected related protein expression. (2) Cell experiment: In vitro, grape seed proanthocyanidin oligomers (30 μg/mL) were used to intervene in an astrocyte inflammation model induced by tumor necrosis factor α, interleukin 1α, and C1q. Conditioned medium was collected and used to culture oligodendrocytes. Cells were divided into normal, model, and model+oligomeric proanthocyanidin groups. L-lactate dehydrogenase and CCK-8 assays were used to detect oligodendrocyte damage and cell activity, and western blot was used to detect apoptosis-related protein expression. RESULTS AND CONCLUSION: (1) Grape seed proanthocyanidin oligomers significantly improved demyelination in CPZ mice, inhibited the expression of pro-inflammatory factors tumor necrosis factor α, interleukin 6, interleukin 1α, and interleukin 17 in the brain, promoted the secretion of anti-inflammatory factor transforming growth factor β, accompanied by astrocyte proliferation in the corpus callosum, significantly reduced the marker C3d of pro-inflammatory astrocytes, and inhibited the phosphorylation of JNK, a signaling molecule related to astrocyte polarization. (2) Compared with the model group, the conditioned medium after intervention with grape seed proanthocyanidin oligomers significantly reduced the apoptosis of oligodendrocytes induced by inflammatory astrocytes, promoted the expression of Bcl-2, and inhibited the expression of Bax and Caspase-3. (3) These results indicate that grape seed proanthocyanidin oligomers can inhibit demyelination in CPZ mice by inhibiting JNK phosphorylation in astrocytes, reducing the polarization of astrocytes to the pro-inflammatory A1 type, thereby inhibiting the apoptosis of oligodendrocytes induced by inflammatory astrocytes.

1. Introduction

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS), characterized by demyelination, neuroinflammation, neuronal loss, and gliosis (scar formation). Myelinated axons within the CNS are targets of MS attacks, leading to varying degrees of damage to myelin and axons [1-2]. The core pathological process of MS involves myelin-specific CD4+ T cells crossing the blood-brain barrier, migrating into the CNS, and recognizing and attacking myelin antigens, resulting in myelin destruction [3-4]. In addition, infiltrating CD4+ T cells can induce abnormal activation of astrocytes, triggering severe and persistent neuroinflammation that not only directly damages neural tissue but also disrupts CNS homeostasis, leading to widespread tissue damage and dysfunction [5].

MS predominantly affects young and middle-aged individuals aged 20-40 years [6-7]. Its etiology remains unclear, considered a complex interplay of genetic and environmental factors. Currently, there are no specific diagnostic biomarkers for MS, making early diagnosis difficult. Clinical treatments for MS mainly include immunomodulators, immunosuppressants, and neurotrophic agents, which have no direct effect on glial cells [8]. Most disease-modifying therapies focus on eliminating pathogenic T cells [9]. However, recent understanding of MS pathogenesis has shifted from a T-cell-centric view to recognizing the central role of glial cells. Increasing research focuses on targeting astrocytes, suggesting that intervening in glial cells may play a key role in reducing relapses and delaying disability progression.