Systems Pharmacology and Multi-Compartment Pharmacokinetics of Apis mellifera Venom-Derived Peptides in Rotenone-Induced Parkinsonism: Unraveling the Interplay between Plasma Protein Binding, Brain Penetration Kinetics, and the Upregulation of Nrf2-Mediated Detoxifying Enzymes

Abstract

Background: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc), leading to debilitating motor and nonmotor symptoms. Current therapies are symptomatic and do not halt disease progression. Oxidative stress, neuroinflammation, and immune dysregulation play central roles in PD pathogenesis, presenting potential therapeutic targets. Apis mellifera (honey bee) venom (BV) has demonstrated anti-inflammatory, antioxidant, and immunomodulatory properties in various neurological disorder models, but its effects in the chronic, progressive rotenone-induced PD model remain incompletely characterized. Objective: To comprehensively evaluate the neuroprotective effects of Apis mellifera venom in a rotenoneinduced rat model of Parkinson's disease and elucidate the underlying mechanisms involving oxidative stress, neuroinflammation, and immunomodulation. Methods: Forty-eight adult male Wistar rats were randomly assigned to six groups (n=8): normal control, rotenone model (1.5 mg/kg, subcutaneous, every 48 hours for 15 days), low-dose BV (0.5 mg/kg), medium-dose BV (1.0 mg/kg), high-dose BV (2.0 mg/kg), and positive control (rasagiline 1 mg/kg). BV was administered intraperitoneally for 14 days post-induction. Motor function was assessed using open field, pole, and rotarod tests. Striatal dopamine and metabolite levels were quantified by HPLC. Oxidative stress markers (MDA, SOD, CAT, GPx, TAC) and pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) were measured by spectrophotometry and ELISA, respectively. Tyrosine hydroxylase (TH) immunohistochemistry assessed dopaminergic neuron survival. Nissl and H&E staining evaluated histopathological changes. Immunofluorescence for Iba-1 and GFAP assessed glial activation. Flow cytometry quantitated Treg (CD4⁺CD25⁺FoxP3⁺), Th1 (CD4⁺IFN-γ⁺), and Th17 (CD4⁺IL17⁺) populations in spleen. Results: Rotenone administration induced significant motor deficits (65% reduction in ambulation, p<0.001), striatal dopamine depletion (71% reduction, p<0.001), elevated oxidative stress (MDA increased 190%, p<0.001; SOD, CAT, GPx reduced by 55-57%, p<0.001), and robust neuroinflammation (IL-1β↑273%, IL-6↑238%, TNFα↑205%, all p<0.001) compared to normal controls. Medium-dose BV (1.0 mg/kg) significantly improved motor function (ambulation increased 112%, T-total reduced 57%, p<0.001), restored striatal dopamine to 69% of control values (5.74±0.71 vs. 2.52±0.48 ng/mg in model, p<0.001), and preserved TH⁺ neurons in SNpc (29.4±4.2 vs. 12.4±3.2, p<0.001). BV attenuated oxidative stress (MDA reduced 49%, p<0.001; SOD, CAT, GPx restored to 76-83% of control) and suppressed pro-inflammatory cytokines (IL-1β, IL-6, TNF-α reduced by ~50%, p<0.001). Immunofluorescence revealed BV reversed rotenone-induced microglial (amoeboid to ramified morphology) and astrocytic (GFAP intensity reduced 48%, p<0.001) activation. Flow cytometry demonstrated BV restored Tregs from 5.2% to 9.4% of CD4⁺ cells and suppressed Th1 (40% reduction) and Th17 (45% reduction) populations. Histopathological analysis confirmed BV preserved neuronal architecture across SNpc, striatum, cerebral cortex, and hippocampus. The neuroprotective effects of medium-dose BV were comparable to rasagiline (positive control). Conclusion: Apis mellifera venom exerts potent neuroprotective effects in rotenone-induced PD rats through multimodal mechanisms involving attenuation of oxidative stress, suppression of neuroinflammation, and immunomodulation via Treg/Th17 axis restoration. These findings support the potential of standardized bee venom preparations as a disease-modifying therapy for Parkinson's disease. Further translational studies are warranted to evaluate safety, efficacy, and optimal dosing in clinical settings.