Investigating the therapeutic potential of Rosmarinus Offficinalis and Bacillus Clausii in MPTP-induced mouse model of Parkinson’s Disease

Abstract

Parkinson's disease (PD) is a complex neurodegenerative disease affecting 1% of people age 60 and above worldwide. The disease is characterized by the ever-evolving loss of dopaminergic neurons in the substantia nigra pars compacta, alpha synuclein aggregation, oxidative stress, and neuroinflammation, all of which contributes to motor dysfunction, including postural instability, rigidity, bradykinesia, and tremors. Despite advancements in PD management, current treatments remain limited to symptomatic srelief and fail to target underlying disease mechanisms to halt progression. Therefore, the present study investigated the neuroprotective effects of Rosmarinus officinalis extract and Bacillus clausii, focusing on motor coordination, neuroinflammation, and oxidative stress in a 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced PD mouse model. MPTP (30 mg/kg, intraperitoneally) was used to develop PD mouse model. Mice were divided into eight groups (n=8), where the four groups were given MPTP intraperitoneally followed by treatment with R.officinalis (120 mg/kg, intraperitoneally) extract, Bacillus clausii (2x10⁹ CFU, oral) and a combination treatment of both. The other four groups received R. officinalis extract, Bacillus clausii and saline only. Behavioral tests were performed including open field test, pole test and cylinder test to asess bradykinesia, locomotor activity, motor disabilities and forelimb asymmetry, respectively. The open field test uncovered expanded exploratory activity in treatment groups, particularly in the combination treatment group (p<0.0001). Significant improvement (p<0.0001) in the movements in the combination treatment group was observed through pole test. Similarly, motor balance and forelimb symmetry was also restored in the treatment groups, with the combination treatment groups achieving the most significant results (p<0.001), assessed via the cylinder test. Histopathological examination using Hematoxylin & Eosin (H&E) staining showed marked preservation of neuronal density in the substantia nigra and hippocampus in the combination treatment group compared to the MPTP-treated group. Gene expression analysis revealed significant amelioration of antioxidants (SOD1, SOD2) and pro-inflammatory cytokines (IL-6, TNF-α) in the combination treatment group (p<0.0001) in comparision to MPTP-treated groups, supporting its antioxidative and anti-inflammatory effects. Molecular docking analyses of bioactive compounds of R. officinalis, including carnosic acid (CA) and ursolic acid (UA), demonstrated strong binding affinities to key PD-associated proteins, including SNCA, PRKN, APOE, SOD1, IL-6, SOD2, and TNF-α, indicating their potential role in modulating oxidative stress and inflammation pathways. The analysis of pharmacokinetic properties and drug likeness through (Absorption, Distribution, Metabolism, and Excretion) ADME and Lipinski filter analysis revealed the drug-relevant features of the compounds affirming their promising potential as therapeutic candidates for PD. The results demonstrate the neuroprotective potential of R.officinalis and B.clausii through their antioxidative, anti-inflammatory, and neuroprotective properties. These analysis gives foundation to additional investigation of their mechanistic roles and translational application as synergistic treatments to mitigate PD onset and progression.