Alzheimer’s disease (AD) is the most common senile dementia in the world. Although important progress has been made in understanding the pathogenesis of AD, current therapeutic approaches provide only modest symptomatic relief. In this study, we evaluated the neuroprotective effect of quercetin (25 mg/kg) administration via i.p. injection every 48 hours for 3 months on aged (21–24 months old) triple transgenic AD model (3xTg-AD) mice. Our data show that quercetin decreases extracellular β-amyloidosis, tauopathy, astrogliosis and microgliosis in the hippocampus and the amygdala. These results were supported by a significant reduction in the paired helical filament (PHF), β-amyloid (βA) 1–40 and βA 1–42 levels and a decrease in BACE1-mediated cleavage of APP (into CTFβ). Additionally, quercetin induced improved performance on learning and spatial memory tasks and greater risk assessment behavior based on the elevated plus maze test. Together, these findings suggest that quercetin reverses histological hallmarks of AD and protects cognitive and emotional function in aged 3xTg-AD mice.

Upon loading with microbial Ag and adoptive transfer, dendritic cells (DC) are able to induce immunity to infections. This offers encouragement for the development of DC-based vaccination strategies. However, the mechanisms underlying the adjuvant effect of DC are not fully understood, and there is a need to identify Ag with which to arm DC. In the present study, we analyzed the role of DC-derived IL-12 in the induction of resistance to Leishmania major, and we evaluated the protective efficacy of DC loaded with individual Leishmania Ag. Using Ag-pulsed Langerhans cells (LC) from IL-12-deficient or wild-type mice for immunization of susceptible animals, we showed that the inability to release IL-12 completely abrogated the capacity of LC to mediate protection against leishmaniasis. This suggests that the availability of donor LC-derived IL-12 is a requirement for the development of protective immunity. In addition, we tested the protective effect of LC loaded with Leishmania homolog of receptor for activated C kinase, gp63, promastigote surface Ag, kinetoplastid membrane protein-11, or Leishmania homolog of eukaryotic ribosomal elongation and initiation factor 4a. The results show that mice vaccinated with LC that had been pulsed with selected molecularly defined parasite proteins are capable of controlling infection with L. major. Moreover, the protective potential of DC pulsed with a given Leishmania Ag correlated with the level of their IL-12 expression. Analysis of the cytokine profile of mice after DC-based vaccination revealed that protection was associated with a shift toward a Th1-type response. Together, these findings emphasize the critical role of IL-12 produced by the sensitizing DC and suggest that the development of a DC-based subunit vaccine is feasible.

We used the model of murine leishmaniasis to evaluate the signals enabling Ag-pulsed dendritic cells (DC) to prime a protective Th1 response in vivo. Bone marrow-derived DC (BMDC) that had been activated by TNF-α or CD40 ligation were not able to induce protection against leishmaniasis in susceptible BALB/c mice. In contrast, all mice vaccinated with a single dose of Leishmania major Ag-pulsed BMDC stimulated by prior in vitro exposure to CpG-containing oligodeoxynucleotides (ODN) were completely protected, had a dramatic reduction in parasite burden, and developed an Ag-specific Th1 response. Importantly, systemic administration of CpG ODN was not required. Protection mediated by ex vivo CpG ODN-activated and Ag-pulsed DC was solid, as documented by resistance to reinfection with a higher parasite dose, and long-lasting, as immunized mice were still protected against L. major challenge 16 wk after vaccination. A significantly increased level of protection could also be elicited in resistant C57BL/6 mice. Surprisingly, IL-12 expression by the immunizing BMDC was not required for induction of host resistance. In contrast, the availability of IL-12 derived from recipient cells was essential for the initial triggering of protective immunity by transferred BMDC. Together, these findings demonstrate that the type of stimulatory signal is critical for activating the potential of DC to induce a Th1 response in vivo that confers complete protection against an intracellular pathogen. Moreover, they show that the impact of activated DC on the initiation of a protective Th cell response in vivo may be independent of their ability to produce IL-12.

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Many studies have demonstrated that the flavonoid quercetin protects against cardiovascular disease (CVD) and related risk factors. Atherosclerosis, the underlying cause of CVD, is also attenuated by oral quercetin administration in animal models. Although macrophages are key players during fatty streak formation and plaque progression and aggravation, little is known about the effects of quercetin on atherogenic macrophages. Here, we report that primary bone marrow-derived macrophages internalized less oxidized low-density lipoprotein (ox-LDL) and accumulated less intracellular cholesterol in the presence of quercetin. This reduction of foam cell formation correlated with reduced surface expression of the oxLDL receptor CD36. Quercetin also targeted the lipopolysaccharidedependent, oxLDL-independent pathway of lipid droplet formation in macrophages. In oxLDL-stimulated macrophages, quercetin inhibited reactive oxygen species production and interleukin (IL)-6 secretion. In a system that evaluated cholesterol crystal-induced IL-1␤ secretion via nucleotide-binding domain and leucine-rich repeat containing protein 3 inflammasome activation, quercetin also exhibited an inhibitory effect. Dyslipidemic apolipoprotein E-deficient mice chronically treated with intraperitoneal quercetin injections had smaller atheromatous lesions, reduced lipid deposition, and less macrophage and T cell inflammatory infiltrate in the aortic roots than vehicle-treated animals. Serum levels of total cholesterol and the lipid peroxidation product malondialdehyde were also reduced in these mice. Our results demonstrate that quercetin interferes with both key proatherogenic activities of macrophages, namely foam cell formation and pro-oxidant/proinflammatory responses, and these effects may explain the atheroprotective properties of this common flavonoid.

Taken together our data suggest that live BCG>hk-BCG>CpG-ODN >PPD are effective in suppressing allergen-induced Th2 responses. The degree of suppression and the component of the Th2 response affected (airway inflammation vs. the production of allergen-specific IgE and IgG1) were dependent upon the adjuvant used and how it was applied. Our results contribute to the design of novel vaccines protecting humans from developing allergic disorders.

Pentacyclic triterpene Natural product Cytokine modulation Anti-inflammatory activity Dendritic cells Pentacyclic triterpenes are a large family of plant metabolites that exhibit a wide array of biological activities. The genus Cecropia,which encompasses many plant species, has been used as traditional medicine for the treatment of inflammatory diseases and is known to produce many active pentacyclic triterpenes. In this study we investigated the chemical composition of a pentacyclic triterpene fraction from the roots of Cecropia telenitida Cuatrec., Urticaceae. A novel compound, which we termed yarumic acid, and four known molecules (serjanic acid, spergulagenic acid A, 20-hydroxy-ursolic acid and goreishic acid I) were isolated and characterised. In a dendritic cell (DC)based assay, we demonstrated that non-toxic doses of these pentacyclic triterpenes inhibited the secretion of at least one of the proinflammatory cytokines tested (IL-1β, IL-12p40, IL-12p70, TNF-α). Spergulagenic acid A also inhibited nitric oxide production in lipopolysaccharide-stimulated dendritic cell. Serjanic acid and spergulagenic acid A, which were the most potent abundant compounds in the pentacyclic triterpene fraction, showed the most activity in the dendritic cell-based assay. These results show that all pentacyclic triterpenes might contribute to the anti-inflammatory activities of C. telenitida. Moreover, yarumic acid as well as the four known pentacyclic triterpenes, can be exploited as potential immunomodulatory/anti-inflammatory agents

The accumulation of oxidized ApoB-100-containing lipoproteins in the vascular intima and its subsequent recognition by macrophages results in foam cell formation and inflammation, key events during atherosclerosis development. Agents targeting this process are considered potentially atheroprotective. Since natural biflavonoids exert antioxidant and anti-inflammatory effects, we evaluated the atheroprotective effect of biflavonoids obtained from the tropical fruit tree Garcinia madruno. To this end, the pure biflavonoid aglycones morelloflavone (Mo) and volkensiflavone (Vo), as well as the morelloflavone’s glycoside fukugiside (Fu) were tested in vitro in primary macrophages, whereas a biflavonoid fraction with defined composition (85% Mo, 10% Vo, and 5% Amentoflavone) was tested in vitro and in vivo. All biflavonoid preparations were potent reactive oxygen species (ROS) scavengers in the oxygen radical absorbance capacity assay, and most importantly, protected low-density lipoprotein particle from both lipid and protein oxidation. In biflavonoid-treated macrophages, the surface expression of the oxidized LDL (oxLDL) receptor CD36 was significantly lower than in vehicle-treated macrophages. Uptake of fluorescently labeled oxLDL and cholesterol accumulation were also attenuated in biflavonoid-treated macrophages and followed a pattern that paralleled that of CD36 surface expression. Fu and Vo inhibited oxLDL-induced ROS production and interleukin (IL)-6 secretion, respectively, whereas all aglycones, but not the glucoside Fu, inhibited the secretion of one or more of the cytokines IL-1β, IL-12p70, and monocyte chemotactic protein-1 (MCP-1) in lipopolysaccharide (LPS)-stimulated macrophages. Interestingly, in macrophages primed with low-dose LPS and stimulated with cholesterol crystals, IL-1β secretion was significantly and comparably inhibited by all biflavonoid preparations. Intraperitoneal administration of the defined biflavonoid fraction into ApoE−/− mice was atheroprotective, as evidenced by the reduction of the atheromatous lesion size and the density of T cells and macrophages infiltrating the aortic root; moreover, this treatment also lowered the circulating levels of cholesterol and the lipid peroxidation product malondialdehyde. These results reveal the potent atheroprotective effects exerted by biflavonoids on key events of the oxLDL–macrophage interphase: (i) atheroligand formation, (ii) atheroreceptor expression, (iii) foam cell transformation, and (iv) prooxidant/proinflammatory macrophage response. Furthermore, our results also evidence the antioxidant, anti-inflammatory, hypolipemiant, and atheroprotective effects of Garcinia madruno’s biflavonoids in vivo.