Vitamin D3 improves spatial memory and modulates cytokine levels in aged rats.

Vitamin D3 deficiency is associated with an increased risk of dementia. An association between vitamin D3 deficiency and subjective cognitive complaints in geriatric patients has been previously reported. This study aimed to evaluate the effects of two doses of vitamin D3 on spatial memory (using the Radial Maze) and cytokine levels [tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and interleukin-10 (IL-10)] on 2-, 6-, 13-, 22-, and 31-month-old male Wistar rats. Animals were supplemented with vitamin D3 at doses of 42 IU/kg and 420 IU/kg for 21 days. A radial maze test was performed to evaluate spatial memory. After the behavioral test, the frontal cortex and hippocampus were dissected for enzyme immunoassay analyses to measure the cytokine levels (TNFα, IL-1ß, IL-6, and IL-10). Our results showed that vitamin D3 supplementation reversed spatial memory impairment at the supplemented doses (42 and 420 IU/kg) in 6-, 13-, and 22-month-old animals and at a dose of 420 IU/kg in 31-month-old animals. The lower dose (42 IU/kg) regulates both pro- and anti-inflammatory cytokines mainly in the frontal cortex. Our results suggest that vitamin D3 has a modulatory action on pro- and anti-inflammatory cytokines, since older animals showed increased cytokine levels compared to 2-month-old animals, and that vitamin D3 may exert an immunomodulatory effect on aging.

The Involvement of NLRP3 on the Effects of Minocycline in an AD-Like Pathology Induced by ß-Amyloid Oligomers Administered to Mice.

Alzheimer's disease (AD) is a neurodegenerative disease which is characterized by progressive memory loss, the accumulation of ß-amyloid peptide (Aß) (mainly Aß1-42), and more recently, by neuroinflammation, which has been highlighted as playing a central role in the development and progress of AD. This study utilized 100-day-old Balb/c mice for the induction of an AD-like dementia model. The animals were administered with Aß1-42 oligomers (400 pmol/site) or artificial cerebrospinal fluid (ACSF) into the left cerebral ventricle. Twenty-four hours after intracerebroventricular administration, the animals were treated with minocycline (50 mg/kg, via oral gavage) for 17 days. The animals' locomotion was evaluated using the open-field test. The spatial memory was tested using the Y-maze, and the aversive memory was evaluated using the inhibitory avoidance task. Treatment with minocycline was shown to improve both spatial and aversive memories in mice that were submitted to the dementia model. In addition, minocycline reduced the levels of Aß and microglial activation in the animals that received the administration of Aß1-42 oligomers. Moreover, the results suggest that the decrease in microglial activation occurred because of a reduction in the levels of toll-like receptors 2 (TLR2) content, and its adapter protein MyD88, as well as a reduction in the levels of the protein NLRP3, which is indispensable in the assembly of inflammasome. These observations were evaluated via immunohistochemistry and confirmed using the Western blot analysis. Treatment with minocycline had no effect in preventing apoptotic morphologic alterations of the neurons. Thus, the anti-inflammatory effect of minocycline involves TLR2 receptors and NLRP3, besides being beneficial by ameliorating memory impairments. Graphical Abstract.