A Water-soluble Form of Dihydroquercetin Reduces LPS-induced Astrogliosis, Vascular Remodeling, and mRNA VEGF-A Levels in the Substantia Nigra of Aged Rats

Abstract

Background: The age-dependent sporadic form of PD is characterized by the degeneration of dopaminergic (DA) neurons in the Substantia Nigra (SN), gliosis, and vascular changes. Vascular changes may contribute to the onset of the disease and exacerbate the neurodegenerative process, as some vascular changes occur before the onset of neuronal loss. To demonstrate the anti-neuroinflammatory efficacy of a new compound, a water-soluble form of dihydroquercetin (DHQ-WF), we studied the structural changes of microcirculatory vasculature, astroglial GFAP, and vascular endothelial growth factor –A (VEGF-A) mRNA expression in the SN of young and old rats after unilateral nigral treatment by lipopolysaccharide (LPS) and oral administration of DHQ-WF. Materials and methods: The experiments were performed on 18 young (8 weeks - 10 weeks old; 250 g - 320 g) and 18 old (18 months - 19 months old; 390 g - 450 g) male Vistar rats. Young and adult rats from the experimental groups were stereotactically injected with 2 μL LPS solution (LPS from Escherichia coli; 0,01 μL/mL) into one side of the SN. Control young and old rats were similarly injected with 2 μL sterile saline. Half of the animals in both the control and experimental groups (6 animals in each group) received a 2 ml solution containing DHQ-WF at a concentration of 3 mg/ml orally every day. After 8 weeks, brains were harvested and serial cryostat sections were prepared for histochemical (FITC-labeled tomato lectin), immunohistochemical (anti-GFAP Antibody, Cy3 Conjugate) staining, and real-time PCR (mRNA VEGF-A). Results: Eight weeks after LPS injection into the SN, a significant excess of areas occupied by cell bodies and processes of astroglial cells, the density of microcirculatory vessels, and mRNA VEGF-A expression was observed in old animals compared to control old animals and young LPS-treated rats. Oral administration of DHQ-WF to LPS-treated rats resulted in a significant reduction of these parameters in old animals. Conclusion: Injection of LPS into rat SN induces neuroinflammation and vascular angiogenesis, maximally expressed in old animals. Administration of DHQ-WF for 8 weeks significantly reduces these LPS-induced changes. DHQ-WF may be an effective treatment for reducing the effects of neuroinflammation in the aging brain.