Inhibition Of Cyclooxygenase-2 Protein Expression Research Articles

Synthesis and inhibitory effects of triarylpyrazoles on LPS-induced NO and PGE2 productions in RAW 264.7 macrophages

The inhibition of nitric oxide and prostaglandin E2 productions is a very interesting research topic in the field of anti-inflammatory drug development. In the current study, a new series of 1,3,4-triarylpyrazole derivatives was synthesized and evaluated for their capabilities to inhibit nitric oxide and prostaglandin E2 productions in lipopolysaccharide-induced RAW 264.7 macrophages. Among all the target analogs, the diarylurea hydroxyl compounds 1f and 1h possessing phenyl and 3-(trifluoromethyl)phenyl terminal moiety, respectively, showed the highest inhibitory effect on the production of prostaglandin E2. Both compounds exerted equal activity to the reference compound NS-398 at 3 µM concentration. This effect was due to inhibition cyclooxygenase-2 enzyme activity not inhibition of cyclooxygenase-2 protein expression. The IC50 value of compound 1f against lipopolysaccharide-induced prostaglandin E2 production in the macrophages was 1.12 μM. In addition, compound 1j with urea linker, hydroxyl group, and 3,5-bis(trifluoromethyl)phenyl terminal ring was the strongest nitric oxide inhibitor. Western blot study showed that it exerted that effect through inhibition of inducible nitric oxide synthase protein expression.

Differential expression of cyclooxygenase-2 in metastatic melanoma affects progression free survival

The possible correlation between cyclooxygenase-2 (COX-2) expression and disease progression in melanoma is still a matter of debate. Analysis of COX-2 expression in 45 lymph node melanoma metastases demonstrates a significant correlation between the percent of expression and progression free survival (PFS). A positive COX-2 expression ≥10% (COX-2high), as opposite to a positive expression ≤9% (COX-2low), translated into a striking significant reduction of PFS of about 3 years. The reduction in PFS correlated neither with BRAFV600E nor with NRASQ61 expression in the analyzed samples. This concept was reinforced by the finding that tumour development in COX-2−/− mice was almost blunted. Similarly, inhibition of COX-2 protein expression in human melanoma cell lines, by using siRNAs technology as well as selective inhibition of COX-2 activity by celecoxib, reduced cellular proliferation and invasiveness. In conclusion we show that COX-2high is a negative prognostic factor in metastatic melanoma. Our study also clarifies that the uncertainty about the role of COX-2 in metastatic malignant melanoma, found in the current relevant literature, is probably due to the fact that a threshold in COX-2 expression has to be reached in order to impact on cancer malignancy. Our findings suggest that COX-2 expression may become an useful diagnostic tool in defining melanoma malignancy as well as argue for a possible therapeutic use of NSAID as add on therapy in selected cases.

Protective effects of Isofraxidin against lipopolysaccharide-induced acute lung injury in mice.

Acute lung injury (ALI) is a life-threatening disease characterized by serious lung inflammation and increased capillary permeability, which presents a high mortality worldwide. Isofraxidin (IF), a Coumarin compound isolated from the natural medicinal plants such as Sarcandra glabra and Acanthopanax senticosus, has been reported to have definite anti-bacterial, anti-oxidant, and anti-inflammatory activities. However, the effects of IF against lipopolysaccharide-induced ALI have not been clarified. The aim of the present study is to explore the protective effects and potential mechanism of IF against LPS-induced ALI in mice. In this study, We found that pretreatment with IF significantly lowered LPS-induced mortality and lung wet-to-dry weight (W/D) ratio and reduced the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and prostaglandin E2 (PGE2) in serum and bronchoalveolar lavage fluid (BALF). We also found that total cells, neutrophils and macrophages in BALF, MPO activity in lung tissues were markedly decreased. Besides, IF obviously inhibited lung histopathological changes and cyclooxygenase-2 (COX-2) protein expression. These results suggest that IF has a protective effect against LPS-induced ALI, and the protective effect of IF seems to result from the inhibition of COX-2 protein expression in the lung, which regulates the production of PGE2.

Synthesis, characterization and preliminary analysis of in vivo biological activity of chitosan/celecoxib microcapsules

The use of chitosan as the wall of microcapsule designed for delivery of encapsulated celecoxib is reported. Microcapsules were characterised with respect to size and encapsulation efficiency of celecoxib. In vivo animals demonstrated that both free celecoxib administration and chitosan/celecoxib microcapsules administration lead to a significant inhibition of cyclooxygenase-2 protein expression in the hepatocytes when compared with vehicle control mice. Interestingly, microcapsule containing celecoxib showed a better inhibition of cyclooxygenase-2 protein expression when compared with a simple oral administration of free celecoxib. Gas-chromatography–mass-spectrometry analysis showed that in mice treated with free celecoxib or chitosan/celecoxib microcapsules, their plasma concentration of celecoxib was similar. Microcapsules-based biomaterials as oral drug delivery vehicles may help to improve the absorption efficiency of therapeutic drugs.

Calcium-sensing receptor-mediated TNF production in medullary thick ascending limb cells

Medullary thick ascending limb (mTAL) cells in primary culture express the Ca(2+)-sensing receptor (CaR), a G protein-coupled receptor that senses changes in extracellular Ca(2+) (Ca(o)(2+)) concentration, resulting in increases of intracellular Ca(2+) concentration and PKC activity. Exposure of mTAL cells to either Ca(o)(2+) or the CaR-selective agonist poly-L-arginine increased TNF-alpha synthesis. Moreover, the response to Ca(o)(2+) was enhanced in mTAL cells transfected with a CaR overexpression vector. Transfection of mTAL cells with a TNF promoter construct revealed an increase in reporter gene activity after exposure of the cells to Ca(o)(2+), suggesting that intracellular signaling pathways initiated by means of activation of a CaR contribute to TNF synthesis by a mechanism that involves transcription of the TNF gene. Neutralization of TNF activity with an anti-TNF antibody attenuated Ca(2+)-mediated increases in cyclooxygenase-2 (COX-2) protein expression and PGE(2) synthesis, suggesting that TNF exerts an autocrine effect in the mTAL, which contributes to COX-2-mediated PGE(2) production. Preincubation with the PKC inhibitor bisindolylmaleimide I inhibited Ca(2+)-mediated TNF production. Significant inhibition of COX-2 protein expression and PGE(2) synthesis also was observed when cells were challenged with Ca(o)(2+) in the presence of bisindolylmaleimide I. The data suggest that increases in TNF production subsequent to activation of the CaR may be the basis of an important renal mechanism that regulates salt and water excretion.

Down-regulation of cyclooxygenase-2 (COX-2) by interleukin-1 receptor antagonist in human monocytes.

Cyclooxygenase (COX) is the key rate-limiting enzyme in the synthesis of prostanoids from arachidonic acid. Two isoforms of COX have been described in mammalian cells, referred to as cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). COX-1 is a constitutively expressed enzyme; COX-2 is an inducible enzyme that appears to be expressed in inflamed tissue and following exposure to growth factors or cytokines, such as interleukin-1 (IL-1). The aim of the present study was to test if the antagonism on the binding of IL-1 to its cell-surface receptor by human recombinant IL-1 receptor antagonist (hrIL-1ra) may control the COX mRNA expression and prostaglandin E2 (PGE2) production by human monocyte cultures. Northern blot studies showed that hrIL-ra (500 ng/ml) had a strong inhibitory effect on inducible COX activity. The effect was evident after 6 hr incubation (2.7-fold decrease of mRNA COX-2 transcripts); and about a threefold decrease at 24hr incubation. A non-significant effect was observed with COX-1 transcripts. Induced PGE2 production by monocyte cultures treated with lipopolysaccharide (LPS) or interleukin-1 beta (IL-1 beta) was strongly inhibited in the presence of hrIL-1ra (500 ng/ml). In addition, a significant inhibition of COX-2 protein expression, as evaluated by Western blotting, was also observed. These data suggest that hrIL-1ra may be the key mediator in the down-regulation of the COX-2 inducible pathway.