Neuroprotective effects of lignan 7-hydroxymatairesinol (HMR/lignan) in a rodent model of Parkinson's disease

Objectives: Parkinson's disease (PD) is a neurodegenerative disease characterized by loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNc). The proinflammatory response can occur early in the disease, contributing to nigrostriatal degeneration. Identification of the new molecules, which are able to slow down the degenerative process associated with PD, represents one of the main interests. Recently, natural polyphenols, especially lignans, have raised attention for their anti-inflammatory, antioxidant, and estrogenic activity at a peripheral level. The aim of this study was to evaluate the central effects of chronic treatment with lignan 7-hydroxymatairesinol (HMR/lignan) on neurodegenerative, neuroinflammatory processes and motor deficits induced by a unilateral intrastriatal injection of 6-hydroxydopamine (6-OHDA) in rats to evaluate the potential neuroprotective properties of this compound. Methods: Sprague-Dawley male rats underwent lignan (10 mg/kg) or vehicle treatment (oral) for 4 wk starting from the day of 6-OHDA injection. The degree of nigrostriatal damage was evaluated by immunohistochemistry. Moreover, we performed a quantitative and qualitative assessment of neuroinflammatory process, including phenotypic polarization of microglia and astrocytes. The motor performance was assessed by behavioral tests. Results: We demonstrated that chronic treatment with HMR/lignan was able to slow down the progression of degeneration of striatal dopaminergic terminals in a rat model of PD, with a consequent improvement in motor performance. Nevertheless, the anti-inflammatory effect of HMR/lignan observed in SNc was not sufficient to protect dopaminergic cells bodies. Conclusion: These results suggest intriguing properties of HMR/lignan at neuroprotective and symptomatic levels in the context of PD.