# Oxymatrine-associated protection in an MPTP mouse model is accompanied by increased miR-141-3p and reduced HMGB1

## TL;DR

Oxymatrine protects against Parkinson's-like symptoms in mice by boosting miR-141-3p, which reduces harmful inflammation and neuron loss.

## Contribution

This study reveals that miR-141-3p targets HMGB1 to reduce neuroinflammation and that Oxymatrine enhances this protective effect.

## Key findings

- miR-141-3p binds to HMGB1 mRNA and reduces its expression in microglia and mouse models.
- Oxymatrine increases miR-141-3p levels, which in turn lowers HMGB1 and inflammation in the MPTP model.
- Inhibiting miR-141-3p reduces the protective effects of Oxymatrine on neurons and behavior.

## Abstract

Oxymatrine (OMT) alleviates damage to dopaminergic (DA) neurons and microglia-mediated neuroinflammation in an MPTP mouse model of parkinsonism by inhibiting the High-mobility group protein B1 (HMGB1) pathway. However, the precise mechanism by which OMT inhibits HMGB1 remains unclear. Although miR-141-3p is downregulated in the peripheral blood serum of Parkinson’s disease (PD) patients, its potential relationship with HMGB1 remains unclear.

TargetScan software and dual-luciferase reporter gene assays predicted that miR-141-3p binds to the 3’-UTR of HMGB1 mRNA. BV2 cells were transfected with miR-141-3p mimics and stimulated with MPP+in vitro experiments. C57BL/6 J mice received stereotaxic injections of miR-141-3p agomir or miR-141-3p antagomir into the bilateral substantia nigra pars compacta (SNpc). Subsequently, the mice were intraperitoneally injected with MPTP four times within a single day. After miR-141-3p antagomir injection, OMT was administered continuously by injection for 7 days. Behavioral tests were assessed using the rotarod and open field tests. Real-time PCR, western blot, ELISA, and immunofluorescence staining were performed on BV2 cells and SNpc tissues.

Our study showed an inverse correlation between HMGB1 and miR-141-3p expression in both BV2 microglia exposed to MPP+ and MPTP-treated mice. TargetScan analysis identified complementary binding sites between miR-141-3p and the 3’-UTR of HMGB1 mRNA, which was subsequently confirmed through dual-luciferase reporter assays. Through experiments in BV2 microglia exposed to MPP+ and in MPTP-treated mice, miR-141-3p downregulates HMGB1, reduces pro-inflammatory cytokine readouts, and in vivo is associated with improved rotarod and open-field performance and attenuated Tyrosine Hydroxylase (TH)-positive neuronal loss. OMT increases miR-141-3p in the MPTP model, alongside reduced HMGB1 and inflammatory readouts, and these effects are diminished by miR-141-3p inhibition.

miR-141-3p targets HMGB1 to inhibit microglial reaction and mitigate neuroinflammation both in vivo and vitro experiments, reduce TH-positive neuronal loss in the MPTP model. OMT increases miR-141-3p in the MPTP model, alongside reduced HMGB1 and inflammatory readouts, and these effects are diminished by miR-141-3p inhibition.