Exploring the Multifaceted Neuroprotective Mechanisms of Bovine Lactoferrin in a Cell Culture Model of Parkinson’s Disease

Parkinson's disease (PD), the second most common neurodegenerative disease, is characterized by the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta along with the aggregation of α-synuclein in Lewy bodies. Among the pathological mechanisms involved is the alteration of iron homeostasis, which promotes oxidative stress and neuronal damage. Despite therapeutic advances, today, no treatment is available to modify the course of the disease. In this study, we investigated for the first time the neuroprotective potential of bovine lactoferrin (bLf) in both its Native (Nat-) and Holo forms, using rotenone-treated N1E-115 cells to mimic PD phenotype. The results showed that the Nat-bLf was more effective than Holo-bLf in counteracting rotenone-induced cytotoxicity and neurite retraction, preserving neuronal morphology and promoting neuritogenesis, as evidenced by increased β3-Tubulin and Growth-Associated Protein-43 markers (GAP-43). Both forms of bLf preserved Tyrosine Hydroxylase (TH) levels, crucial for dopamine synthesis, reduced the DNA damage marker γ-H2Ax and prevented rotenone-induced downregulation of Divalent Metal Transporter-1 (DMT-1) and Ferroportin (Fpn), key proteins involved in iron uptake and release, thereby limiting intracellular iron accumulation. Notably, only Nat-bLf reduced the levels of α-synuclein and markers of oxidative damage. Conversely, Holo-bLf exhibited pro-oxidant effects and increased α-synuclein accumulation even in absence of rotenone. Overall, these results highlight the differential neuroprotective effects of both Nat- and Holo-form, resulting from their distinct iron saturation level and their ability to modulate protein expression, with the native form emerging as a promising candidate for therapeutic strategies to counteract PD-associated neurodegeneration.