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High-throughput screening (HTS) involves testing of compound libraries against validated drug targets using quantitative bioassays to identify 'hit' molecules that modulate the activity of target, which forms the starting point of a drug discovery effort. Eicosanoids formed via cyclooxygenase (COX) and lipoxygenase (LOX) pathways are major players in various inflammatory disorders. As the conventional non-steroidal anti-inflammatory drugs (NSAIDs) that inhibit both the constitutive (COX-1) and the inducible (COX-2) isoforms have gastric and renal side effects and the recently developed COX-2 selective anti-inflammatory drugs (COXIBs) have cardiac side effects, efforts are being made to develop more potent and safer antiinflammatory drugs. Current assay methods for these enzymes, such as oxygraphic, radioisotopic, spectrophotometric etc. are not compatible for screening of large number of compounds as in drug discovery programs. In the present study, HTS-compatible assays for COX-1, COX-2 and 5-LOX were developed for screening of compound libraries with the view to identify potential anti-inflammatory drug candidates. A spectrophotometric assay involving co-oxidation of tetramethyl-p-phenylene diamine (TMPD) during the reduction of prostaglandin G2 (PGG2) to PGH2 was adopted and standardized for screening of compounds against COX-1 and COX-2. Similarly, the HTS-compatible FOX (ferrous oxidation-xylenol orange) based spectrophotometric assay involving the formation of Fe3+/xylenol orange complex showing absorption in the visible range was developed for screening of compounds against 5-LOX.

Chebulagic acid (CA), a natural anti-oxidant, showed potent anti-inflammatory effects in LPS-stimulated RAW 264.7, a mouse macrophage cell line. These effects were exerted via inhibition of NO and PGE2 production and down-regulation of iNOS, COX-2, 5-LOX, TNF-alpha and IL-6. CA inhibited NF-kappaB activation by LPS, and this was associated with the abrogation of IkappaB-alpha phosphorylation and subsequent decreases in nuclear p50 and p65 protein levels. Further, the phosphorylation of p38, ERK 1/2 and JNK in LPS-stimulated RAW 264.7 cells was suppressed by CA in a concentration-dependent manner. LPS-induced generation of reactive oxygen species (ROS) was also effectively inhibited by CA. These results suggest that CA exerts anti-inflammatory effects in LPS-stimulated RAW 264.7 macrophages by inhibition of NF-kappaB activation and MAP kinase phosphorylation.

Arachidonic acid (AA) metabolism in the non-pregnant sheep uterus was studied in vitro using conventional chromatographic and HPLC techniques. High expression of both lipoxygenase (LOX) as well as cyclooxygenase (COX) enzymes and their activities was found in the uterine tissues. On incubation of uterine enymes with AA, the LOX products formed were identified as 5-hydroperoxyeicosatetraenoic acid (5-HPETE), 12- and 15-hydroxyeicosatetraenoic acids (12- and 15-HETEs), based on their separation on TLC and HPLC. By employing differential salt precipitation techniques, the LOXs generating products 5-HPETE (5-LOX), 12-HETE and 15-HETE (12- and 15-dual LOX) were isolated. Based on their analysis on TLC, the COX products formed were identified as prostaglandins - PGF2alpha and prostacyclin derivative 6-keto PGF1alpha. The study forms the first report on the comprehensive analysis on the metabolism of AA in sheep uterus in vitro via the LOX and COX pathways.