Low dose of quercetin-loaded pectin/casein microparticles reduces the oxidative stress in arthritic rats.

AIMS: Quercetin has been investigated as an agent to treat rheumatoid arthritis. At high doses it improves inflammation and the antioxidant status of arthritic rats, but it also exerts mitochondriotoxic and pro-oxidant activities. Beneficial effects of quercetin have not been found at low doses because of its chemical instability and low bioavailability. In the hope of overcoming these problems this study investigated the effects of long-term administration of quercetin-loaded pectin/casein microparticles on the oxidative status of liver and brain of rats with adjuvant-induced arthritis. MAIN METHODS: Particle morphology was viewed with transmission electron microscopy and the encapsulation efficiency was measured indirectly by X-ray diffraction. Quercetin microcapsules (10 mg/Kg) were orally administered to rats during 60 days. Inflammation indicators and oxidative stress markers were measured in addition to the respiratory activity and ROS production in isolated mitochondria. KEY FINDINGS: Quercetin was efficiently encapsulated inside the polymeric matrix, forming a solid amorphous solution. The administration of quercetin microparticles to arthritic rats almost normalized protein carbonylation, lipid peroxidation, the levels of reactive oxygen species as well as the reduced glutathione content in both liver and brain. The paw edema in arthritic rats was not responsive, but the plasmatic activity of ALT and the mitochondrial respiration were not affected by quercetin, indicating absence of mitochondriotoxic or hepatotoxic actions. SIGNIFICANCE: Quercetin-loaded pectin/casein microcapsules orally administered at a low dose improve oxidative stress of arthritic rats without a strong anti-inflammatory activity. This supports the long-term use of quercetin as an antioxidant agent to treat rheumatoid arthritis.

Anti- and pro-oxidant effects of quercetin stabilized by microencapsulation on interstitial cells of Cajal, nitrergic neurons and M2-like macrophages in the jejunum of diabetic rats.

Given the well-known antioxidant and neuroprotective properties of quercetin, the aim of this work was to evaluate the effects of quercetin stabilized by microencapsulation at two doses (10 mg kg-1 and 100 mg kg-1) on the oxidative/antioxidant status, number and morphological features of ICC, nitrergic neurons and M2-like macrophages in jejunum of diabetic rats. The rats were randomly distributed into six groups: normoglycemic control (N), diabetic control (D) and either normoglycemic or diabetic groups treated with quercetin-loaded microcapsules at a dose of 10 mg kg-1 (NQ10 and DQ10, respectively) or 100 mg kg-1 (NQ100 and DQ100, respectively). After 60 days, the jejunum was collected. Whole mounts were immunostained for Ano1, nNOS and CD206, and oxidative stress levels and total antioxidant capacity of the jejunum were measured. Diabetes led to a loss of ICC and nitrergic neurons, but increased numbers of M2-like macrophages and elevated levels of oxidative stress were seen in diabetic animals. High-dose administration of quercetin (100 mg kg-1) further aggravated the diabetic condition (DQ100) but this treatment resulted in harmful effects on healthy rats (NQ100), pointing to a pro-oxidant activity. However, low-dose administration of quercetin (10 mg kg-1) gave rise to antioxidant and protective effects on ICC, nNOS, macrophages and oxidative/antioxidant status in DQ100, but NQ100 displayed infrequent negative outcomes in normoglycemic animals. Microencapsulation of the quercetin may become promising alternatives to reduce diabetes-induced oxidative stress but antioxidant therapies should be careful used under healthy status to avoid toxic effects.

Rheumatoid arthritis induces enteric neurodegeneration and jejunal inflammation, and quercetin promotes neuroprotective and anti-inflammatory actions.

AIMS: The aim of our study was to study the pathological mechanisms induced by the rheumatoid arthritis (RA) on the Enteric Nervous System (ENS). MAIN METHODS: We evaluated the effect of the chronic arthritis and its treatment with 50 mg/kg quercetin alone (AQ) and combined with 17.5 mg/kg ibuprofen (AIQ) for 60 days on neurons, glial cells and intestinal wall. Other groups were used: control (C), arthritic (A) and arthritic treated with 17.5 mg/kg ibuprofen (AI). After 60 days, the jejunum was removed and processed for immunohistochemical techniques. Immunostainings were performed for HuC/D and S100 (myenteric and submucosal plexuses), and GFAP (only myenteric plexus), while immunolabeling for CD45 and CD20 lymphocytes was performed using cryosections. Western blot was performed for GDNF, S100 and GFAP. KEY FINDINGS: A group yielded a remarkable density decrease of the neurons and glial cells with morphometric changes in the myenteric and submucosal plexuses, reduction of the GDNF expression and GFAP-related parameters (GFAP expression, occupancy area and GFAP-expressing glial cells) and intestinal inflammation and atrophy of the mucosa and intestinal wall. AQ group substantially reversed most of these effects, except for intestinal atrophy of the jejunum. The AI and AIQ groups displayed lower beneficial results than AQ for parameters related to the neurons and glial cells, although AIQ did not prevent the inflammation of the mucosa. SIGNIFICANCE: The severe chronic rheumatoid arthritis induced severe effects on ENS and mucosa, and quercetin treatment continues to be an important antioxidant supplement preventing the progression of the RA severity.