Quercetin alleviates hypercholesterolemic diet induced inflammation during progression and regression of atherosclerosis in rabbits.

OBJECTIVE: Recent advances have established a fundamental role for inflammation in mediating all stages of atherosclerosis, from initiation through progression. Quercetin may be a powerful bioactive constituent of the human diet, as a free radical scavenging agent and through interactions with various endogenous proteins. The present study focused on the effect of quercetin on inflammation induced by a hypercholesterolemic diet (HCD) in rabbits. METHODS: The animals were subjected to two different experiments, atherosclerotic progression and regression. In the atherosclerotic progression study, quercetin (25 mg/kg of body weight) was administered with the HCD for 90 d. In the atherosclerotic regression study, the animals were fed with the HCD for 90 d and then supplemented with quercetin (25 mg/kg of body weight) for another 90 d. The inflammatory enzyme activities were examined and a histopathologic examination of the aorta was performed. RESULTS: In the atherosclerotic progression study, quercetin coadministered with the HCD significantly decreased the activities of inflammatory enzymes such as cyclooxygenase, lipoxygenases (LOX) such as 5-LOX and 12-LOX in monocytes, nitric oxide synthase activity in the plasma, myeloperoxidase activity in the aorta, and the level of C-reactive protein in serum. In the regression study, quercetin administration significantly decreased the increased activities of inflammatory mediators such as cyclooxygenase, 5-LOX, 12-LOX, myeloperoxidase, and nitric oxide synthase and the serum level of C-reactive protein in HCD-fed rabbits compared with regression control rabbits. This effect was confirmed by histopathologic examination of the aorta. CONCLUSION: This study demonstrates that quercetin modulates the deleterious inflammatory effects induced by an HCD in vivo in rabbits, suggesting its beneficial effect in decreasing inflammation in atherosclerotic progression and regression.

Molecular mechanisms of anti-inflammatory action of the flavonoid, tricin from Njavara rice (Oryza sativa L.) in human peripheral blood mononuclear cells: possible role in the inflammatory signaling.

Flavonoids are a group of natural substances that are located in sources of vegetal origin and are able to regulate acute and chronic inflammatory responses. The anti-oxidant and anti-inflammatory effects corroborate with the preferential use of Njavara, a rice variety in indigenous medicine and the phytochemical investigations revealed the occurrence of a flavonoid, tricin at significantly higher levels compared to staple varieties. This study describes the new aspects of inflammatory suppression by the Njavara rice by evaluating the role of active constituent, tricin in the regulation of production of various pro-inflammatory markers by human peripheral blood mononuclear cells stimulated with lipopolysaccharide. Treatment with tricin resulted in significant down-regulation of LPS-elicited production of TNF-α, IL-6, PGE(2) and NO. Tricin was found to be a potential blocker of the expression of isoforms of nitric oxide synthase, cyclooxygenase and matrix metalloproteinases. Modulation of the cascade of molecular events in lipopolysaccharide signaling also includes inhibition of transcription factor NF-κB evidenced by the detection of enhanced p65 subunit in the nuclear extracts on tricin supplementation. The present study summarizes the role of the flavonoid, tricin in the modulation of the expression of different inflammatory mediators and revealed that the inhibitory effects on cell signaling pathways are responsible for its anti-inflammatory activity.

Anti-inflammatory potential of an ethyl acetate fraction isolated from Justicia gendarussa roots through inhibition of iNOS and COX-2 expression via NF-κB pathway.

Justicia gendarussa Burm.f. (J. gendarussa) is a plant used as traditional medicine in different parts of India and China to treat inflammatory disorders like rheumatoid arthritis. But its mechanism of anti-inflammatory action is still unclear. Hence in this context, the objective of our study is to reveal the mechanism of anti-inflammatory activity of J. gendarussa which would form an additional proof to the traditional knowledge of this plant. The anti-inflammatory function and mechanism(s) of action was studied in an ethyl acetate fraction isolated from methanolic extract of J. gendarussa roots (EJG). Anti-inflammatory studies were conducted on rats using partitioned fractions isolated from methanolic extract of J. gendarussa roots. In carrageenan-induced rat paw edema, ethyl acetate fraction brought about 80% and 93% edema inhibition at 3rd and 5th hour at a dose of 50 mg/kg, when compared to other extracts and Voveran. We investigated whether EJG inhibits the release of cycloxygenase (COX), 5-lipoxygenase (5-LOX), interleukin-6 (IL-6) and nuclear factor kappa B (NF-κB) in LPS stimulated human peripheral blood mononuclear cells (hPBMCs). Results shows that EJG dose dependently inhibited LPS-activated COX, 5-LOX, IL-6, and NF-κB in hPBMCs. EJG also reduced LPS induced levels of iNOS and COX-2 mRNA expression in hPBMCs. This study provides an insight into the probable mechanism(s) underlying the anti-inflammatory activity of EJG and therefore, we report the first confirmation of the anti-inflammatory potential of this traditionally employed herbal medicine in vitro.

Quercetin regulates oxidized LDL induced inflammatory changes in human PBMCs by modulating the TLR-NF-κB signaling pathway.

Toll-like receptors (TLRs) have been shown to play a pivotal role in both innate and adaptive immune responses. TLR family is the essential recognition and signaling component of mammalian host defense. Both genetic and biochemical data support a common signaling pathway that finally leads to the activation of NF-κB and induction of the cytokines and co-stimulatory molecules required for the activation of the adaptive immune response. The present study was designed to examine the involvement of TLR2 and TLR4 in the oxidized LDL induced inflammation in human PBMCs and the effect of flavonoid quercetin on TLR-NF-κB signaling mechanism. LDL was isolated from human plasma and oxidation of LDL was done by incubating with 10 µM CuSO4 overnight at 37°C. The isolated human PBMCs in culture were used as the model system. 50 µg/ml ox-LDL treatment significantly up regulated TLR2 and TLR4 expression in isol human PBMCs after 24 h of culture and this was down regulated by quercetin at 25 µM concentration. ox-LDL caused a significant activation of NF-κB as evidenced by the detection of enhanced p65 subunit in nuclear extracts. Supplementation of quercetin significantly modulates the NF-κB p65 nuclear translocation. The cytokine IL-6 production was significantly increased in ox-LDL treated group and was decreased by quercetin treatment. Quercetin mediated reduction of TLR2 and TLR4 expression and the inhibition of nuclear translocation of NF-κB p65 in turn decreased the inflammatory enzymes like 5-LOX and COX and also decreased the mRNA expression of inducible enzymes like COX-2 and iNOS. Quercetin inhibited the ox-LDL induced TLR2 and TLR4 expression at mRNA level and modulated the TLR-NF-κB signaling pathway thereby inhibited the cytokine production and down regulated the activity of inflammatory enzymes thus have protective effect against the ox-LDL induced inflammation in PBMCs.

Modulatory effect of coffee on platelet function.

Blood platelets play a major role in cardiovascular disease (CVD) and thrombosis. Conflicting information exists regarding the effect of coffee consumption on the cardiovascular system. We have investigated whether the consumption of moderate amount of coffee affect platelet functions and primary hemostasis in vivo in normal and high fat diet fed rats. Coffee fed group showed significant (P < 0.05) decrease in mean platelet volume, platelet crit and platelet distribution width as compared to high fat diet (HFD) group. The concentration of malondialdehyde in platelets increased in atherosclerotic group indicates the increased thromboxane A2 (TXA2) production from membrane arachidonic acid and it was decreased in coffee treated group. Platelet aggregation studies with ADP, collagen, arachidonic acid and epinephrine showed significant (P < 0.05) decrease in aggregation in coffee fed group. Scanning electron microscopic studies revealed that platelet aggregation tendency increased in HFD group and was reduced in coffee fed group. These results indicate that coffee is active in inhibiting platelet aggregation, a critical step involved in thrombosis.