Neuroprotective Effects of Intranasally Administered Octadecaneuropeptide Analog in a Mouse Model of MPTP-Induced Parkinson's Disease

Summary

Intranasal administration enables direct delivery of bioactive molecules to the brain, providing a non-invasive alternative to the intracerebroventricular method. This study demonstrates that intranasal administration of cyclo_(1-8)OP, an ODN analog, exerts strong neuroprotective effects against MPTP-induced oxidative damage and apoptosis in the striatum in a mouse model of Parkinson's disease, highlighting therapeutic potential.

Abstract

Parkinson's disease (PD) is a neurodegenerative disorder for which existing therapies are primarily palliative and lack curative efficacy. Octadecaneuropeptide (ODN) is a peptide exclusively produced by astrocytes that protects neurons against oxidative cell damage and apoptosis in in vitro and in vivo models of PD. However, ODN cannot cross the blood-brain barrier (BBB) and requires intracerebroventricular injection to reach the brain, presenting a significant challenge for therapeutic application. This study investigates the neuroprotective efficacy of cyclo_(1-8)OP, an ODN analog, delivered via the intranasal (IN) route to bypass the BBB in an in vivo model of PD. Male C57BL/6J mice were used for the experiments and divided into four groups: sham, MPTP- (20 mg/kg body weight, intraperitoneal), cyclo_(1-8)OP- (10 ng/10 µL, IN), and MPTP + cyclo_(1-8)OP-treated animals. On day 0 (D0), animals received three intraperitoneal injections of 100 µL MPTP solution at 2-h intervals (MPTP- and MPTP + cyclo_(1-8)OP-treated mice) or saline solution (sham and cyclo_(1-8)OP-treated mice). One hour after the final injection, 10 µL of IN instillation of cyclo_(1-8)OP (cyclo_(1-8)OP- and MPTP + cyclo_(1-8)OP-treated mice) or IN saline solution (sham and MPTP-treated mice) was administered. On D7, a cylinder test was performed to assess motor function. Subsequently, animals were sacrificed, and the striatum was removed and analyzed by RT-qPCR to assess caspase-3 gene expression. Tissue samples were also used to measure antioxidant enzyme activities, reactive oxygen species (ROS), malondialdehyde (MDA), and carbonylated protein abundance. A single IN dose of 10 ng cyclo_(1-8)OP, administered 1 h after the final MPTP dose, prevented neurotoxicity in the striatum 7 days post-treatment. Cyclo_(1-8)OP-mediated neuroprotection was associated with strong inhibition of caspase-3 expression induced by MPTP in the striatum. Additionally, cyclo_(1-8)OP restored the activities of antioxidant enzymes, preventing the accumulation of ROS, lipid peroxidation products, and protein carbonylation in the striatum.

Introduction

Parkinson's disease (PD) is a neurodegenerative disorder marked by the progressive loss of dopaminergic neurons in the substantia nigra, which innervates the striatum. This loss results in significant neurological symptoms, including severe motor deficits such as muscle rigidity, akinesia, and bradykinesia¹. The prevalence of neurodegenerative diseases like PD continues to rise, primarily due to an aging population, posing a substantial public health challenge². Current treatments for PD predominantly rely on dopaminergic analogs and intracerebral high-frequency stimulation^3,

Protocol

All experiments followed the American Veterinary Medical Association guidelines and were approved by the Medical Ethical Committee of the Pasteur Institute (approval number: FST/LNFP/Pro 160220). Ten-week-old C57BL/6J male mice were obtained from the Pasteur Institute of Tunis. Mice were housed in three per cage in a temperature-controlled room (21 °C ± 1 °C) with a 12-h light/dark cycle and provided free access to food and water for 1 week of acclimatization. Details of the reagents and equipment used are listed in the Table of Materials.

1. Treatment procedure

1. Divide anima....

Results

After MPTP administration, mice displayed characteristic Parkinsonian symptoms, including an elevated and rigid Straub tail, piloerection, immobility, and postural abnormalities such as spinal curvature, confirming the successful establishment of the MPTP model (Figure 3). Verification of IN delivery using methylene blue, with mice sacrificed 10 min post-injection, showed effective dye distribution within the targeted olfactory bulb and brain regions, supporting the precisio.......

Discussion

Previous studies demonstrated that ICV administration of ODN counteracted MPTP-induced degeneration of nigrostriatal dopaminergic neurons, oxidative damage, and neuroinflammation⁸. The current investigation assessed the efficacy of IN delivery of the ODN analog, cyclo_(1-8)OP, for preventing MPTP-induced motor impairments, oxidative damage, and neurotoxicity in an in vivo PD model using C57BL/6J mice.

The results demonstrated that MPTP-treated mice ex.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
2', 7'-Dichlorofluorescin DCFH2-DA	Sigma Aldrich	064M4008V
Bio-Rad spectrophotometer	Bio-Rad Laboratories, Philadelphia, PA, USA
Butanol
Camera
Catalase from bovine liver	SIGMA life science	SLBZ7596
cyclo(1-8)OP	INSERM U1239 NorDiC, Rouen
Cylinder test (graduated beaker )
DNPH
EDTA plus	Thermo Scientic	11836714
Ethanol 70%
Ethanol-ethylacetate solution
GraphPad software	La Jolla, CA, USA
Guanidine hydrochloride	GeneON	5CCAE310
H2O2	Pharmaghreb	AEQ10101-D
Insulin syringe 2ml
L-epinephrine	MP Biomedicals	151065
Methylene blue	Thermo Scientific Chemicals	10455081
Micropipette
Microplate reader Synergy LX-Agilent	Synergy LX-Agilent
MPTP	MedChemExpress	HY-15608
MPTP
Na2CO3/NaHCO3 buffer
NaCl 0.9
one-step Q-RT PCR kit	New England Biolabs
Pentobarbital	Sigma Aldrich
Synergy LX Nanodrop 2000 spectrophotometer	Biotek Agilent
Thiobarbituric acid (TBA, 0.67%)	LOBA CHEMIE PVT.LTD	626500025
Tips
Trichloroacetic acid (TCA, 20%)	Sisco Research laboratories SRL	6740608
Tri-Reagent	Sigma Aldrich	MFCD00213058
Tris-HCl	Thermo Scientic	J22638.K2
Triton X-100	Thermo Scientic	A16046.AE