interleukin-8 and 24-hydroxycholesterol

Chronic inflammatory events appear to play a fundamental role in Alzheimer's disease (AD)-related neuropathological changes, and to result in neuronal dysfunction and death. The inflammatory responses observed in the AD brain include activation and proliferation of glial cells, together with up-regulation of inflammatory mediators and of free radicals. Along with glial cells, neurons themselves can also react and contribute to neuroinflammatory changes in the AD brain, by serving as sources of inflammatory mediators. Because excess cholesterol cannot be degraded in the brain, it must be excreted from that organ as cholesterol oxidation products (oxysterols), in order to prevent its accumulation. Among risk factors for this neurodegenerative disease, a mechanistic link between altered cholesterol metabolism and AD has been suggested; oxysterols appear to be the missing linkers between the two, because of their neurotoxic effects. This study shows that 24-hydroxycholesterol, 27-hydroxycholesterol, and 7β-hydroxycholesterol, the three oxysterols potentially implicated in AD pathogenesis, induce some pro-inflammatory mediator expression in human neuroblastoma SH-SY5Y cells, via Toll-like receptor-4/cyclooxygenase-2/membrane bound prostaglandin E synthase (TLR4/COX-2/mPGES-1); this clearly indicates that oxysterols may promote neuroinflammatory changes in AD. To confirm this evidence, cells were incubated with the anti-inflammatory flavonoid quercetin; remarkably, its anti-inflammatory effects in SH-SY5Y cells were enhanced when it was loaded into β-cyclodextrin-dodecylcarbonate nanoparticles, versus cells pretreated with free quercetin. The goal of loading quercetin into nanoparticles was to improve its permeation across the blood-brain barrier into the brain, and its bioavailability to reach target cells. The findings show that this drug delivery system might be a new therapeutic strategy for preventing or reducing AD progression.

Topics: Antioxidants; beta-Cyclodextrins; Cell Line, Tumor; Cell Survival; Chemokine CCL2; Gene Expression Regulation; Humans; Hydroxycholesterols; Inflammation; Inflammation Mediators; Integrin beta1; Interleukin-8; Matrix Metalloproteinase 9; Nanoparticles; Neurodegenerative Diseases; Quercetin

Aging is associated with an accumulation of cholesterol esters in the Bruch membrane. Cholesterol esters are prone to undergo oxidation and generate oxysterols that have cytotoxic and proinflammatory properties. We investigated the effects of three oxysterols on mitochondrial dysfunctions, inflammation, and oxidative stress in primary cultures of porcine retinal pigment epithelial (RPE) cells.. RPE cells were incubated with oxysterols (50 micro M of 24-hydroxycholesterol, 25-hydroxycholesterol, or 7-ketocholesterol) for 24 hr and 48 hr. Oxysterol content was determined in cells and in corresponding media by gas chromatography. Mitochondrial activity was measured by mitochondrial dehydrogenase activity. The intracellular formation of reactive oxygen species in RPE cells was detected by using the fluorescent probe DCFH-DA. IL-8 was assayed in the supernatants by ELISA, and the corresponding cellular transcripts were semiquantified by RT-PCR.. Analyses of the oxysterols content in the RPE cells and corresponding media suggested a high rate of cellular uptake, although some differences were observed between 7-ketocholesterol on the one hand and 24-hydroxycholesterol and 25-hydroxycholesterol on the other hand. All oxysterols induced slight mitochondrial dysfunctions but a significant 2- to 4-fold increase in reactive oxygen species (ROS) production compared with the control. They also enhanced IL-8 gene expression and IL-8 protein secretion in the following decreasing order: 25-hydroxycholesterol > 24-hydroxycholesterol > 7-ketocholesterol.. We conclude that in confluent primary porcine RPE cells, 24-hydroxycholesterol, 25-hydroxycholesterol, and 7-ketocholesterol are potent inducers of oxidation and inflammation.

Topics: Animals; Chromatography, Gas; Enzyme-Linked Immunosorbent Assay; Fluoresceins; Fluorescent Dyes; Hydroxycholesterols; Inflammation; Interleukin-8; Ketocholesterols; Mitochondria; Oxidative Stress; Pigment Epithelium of Eye; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Swine