Oral administration of carvacrol/ß-cyclodextrin complex protects against 6-hydroxydopamine-induced dopaminergic denervation.

Carvacrol (CARV) presents valuable biological properties such as anti-inflammatory and antioxidant activities. However, pharmacological uses of CARV are largely limited due to disadvantages related to solubility, bioavailability, preparation and storage processes. The complexation of monoterpenes with ß-cyclodextrin (ß-CD) increases their stability, solubility and oral bioavailability. Here, the protective effect of oral treatment with CARV/ß-CD complex (25 µg/kg/day) against dopaminergic (DA) denervation induced by unilateral intranigral injection of 6-hydroxydopamine (6-OHDA - 10 µg per rat) was analyzed, in order to evaluate a putative application in the development of neuroprotective therapies for Parkinson's disease (PD). Pretreatment with CARV/ß-CD for 15 days prevented the loss of DA neurons induced by 6-OHDA in adult Wistar rats. This effect may occur through CARV anti-inflammatory and antioxidant properties, as the pretreatment with CARV/ß-CD inhibited the release of IL-1ß and TNF-α; besides, CARV prevented the increase of mitochondrial superoxide production induced by 6-OHDA in cultured SH-SY5Y cells. Importantly, hepatotoxicity or alterations in blood cell profile were not observed with oral administration of CARV/ß-CD. Therefore, this study showed a potential pharmacological application of CARV/ß-CD in PD using a non-invasive route of drug delivery, i.e., oral administration.

Systemic Inflammation Changes the Site of RAGE Expression from Endothelial Cells to Neurons in Different Brain Areas.

The receptor for advanced glycation endproducts (RAGE) is a transmembrane, immunoglobulin-like receptor that interacts with a broad repertoire of extracellular ligands. RAGE belongs to a family of cell adhesion molecules and is considered a key receptor in the inflammation axis and a potential contributor to the neurodegeneration. The present study aimed to investigate the content and cell localization of RAGE in the brain of Wistar rats subjected to systemic inflammation induced by a single dose of lipopolysaccharide (LPS, 5 mg/kg, i.p.). Fifteen days after LPS administration, the content of RAGE was analyzed in the prefrontal cortex (PFC), hippocampus (HIPP), cerebellum (CB), and substantia nigra (SN) were investigated. RAGE levels increased in all structures, except HIPP; however, immunohistochemistry analysis demonstrated that the cell site of RAGE expression changed from blood vessel-like structures to neuronal cells in all brain areas. Besides, the highest level of RAGE expression was found in SN. Immunofluorescence analysis in SN confirmed that RAGE expression was mainly co-localized in endothelial cells (RAGE/PECAM-1 co-staining) in untreated animals, while LPS-treated animals had RAGE expression predominantly in dopaminergic neurons (RAGE/TH co-staining). Decreased TH levels, as well as increased pro-inflammatory markers (TNF-α, IL-1ß, Iba-1, GFAP, and phosphorylated ERK1/2) in SN, occurred concomitantly to RAGE stimulation in the same site. These results suggest a role for RAGE in the establishment of a neuroinflammation-neurodegeneration axis that develops as a long-term response to systemic inflammation by LPS.