The role of high-mobility group box 1 (hmgb1) protein in an mptp-induced parkinsonian zebrafish model

Abstract

Parkinson’s disease (PD) is the most common motor disorder of the brain, with its global prevalence increasing by 153% since 1990. It is a progressive neurodegenerative disorder characterized by dopaminergic neuronal loss in the substantia nigra, with mitochondrial dysfunction and neuroinflammation as key pathological contributors. High-mobility group box 1 (HMGB1), a nuclear protein that acts as a damage-associated molecular pattern (DAMP) upon extracellular release, is implicated in both processes; however, its role in PD pathogenesis and therapeutic targeting remains underexplored. This study aimed to (i) refine behavioural and intraperitoneal (i/p) injection protocols for adult zebrafish, (ii) validate an MPTP-induced zebrafish model of PD at behavioural and transcriptional levels, and (iii) elucidate the functional role of HMGB1 and the impact of its inhibition using glycyrrhizin. The research was conducted in three phases. Phase 1 systematically reviewed existing MPTP-zebrafish protocols and optimized key methodologies for reproducibility, particularly locomotor assessment and i/p injection procedure. Phase 2 validated the PD model: MPTP administration induced significant hypo-locomotion and altered expression of dopaminergic marker genes (th, slc6a3) and PD/mitophagy-associated genes (pink1, prkn), alongside dynamic regulation of hmgb1 gene. Phase 3 examined HMGB1 modulation: glycyrrhizin treatment attenuated locomotor deficits, reduced upregulation of inflammatory mediators (TLR4, NFκB, TNFα, IL-1β), and normalized mitochondrial stress markers, while mitigating blood-brain barrier disruption. Tissue morphological alterations in the posterior tuberculum and subpallium persisted, suggesting incomplete structural recovery. In silico analysis confirmed conserved glycyrrhizin binding to HMGB1 in zebrafish and humans, reinforcing translational relevance. Findings indicate that HMGB1 is a central mediator linking neuroinflammation and mitochondrial dysfunction in MPTP-induced parkinsonism. Its pharmacological inhibition alleviated functional and molecular impairments, highlighting HMGB1 as a promising biomarker and therapeutic target for PD. This work also contributes standardized zebrafish methodologies, enhancing model reproducibility for neurodegenerative research.

Keywords: Parkinson’s disease, HMGB1, adult zebrafish model, MPTP, neuroinflammation, mitochondrial dysfunction