Discovery of a novel COX-2 inhibitor as an orally potent anti-pyretic and anti-inflammatory drug: design, synthesis, and structure-activity relationship

Cyclooxygenase (COX) has been considered as a significant pharmacological target because of its pivotal roles in the prostaglandin biosynthesis and following cascades that lead to various (patho)physiological effects. Non-steroidal anti-inflammatory drugs (NSAIDs) that suppress COX activities have been used clinically for the treatment of fever, inflammation, and pain; however, nonselective COX inhibitors exhibit serious side-effects such as gastrointestinal damage because of their inhibitory activities against COX-1. Thus, COX-1 is constitutive and expressed ubiquitously and serves a housekeeping role, while COX-2 is inducible or upregulated by inflammatory/injury stimuli such as interleukin-1β, tumor necrosis factor-α, and lipopolysaccharide in macrophage, monocyte, synovial, liver, and lung, and is associated with prostaglandin E₂ and prostacyclin production that evokes or sustains systemic/peripheral inflammatory symptoms. Also, hypersensitivity of aspirin is a significant concern clinically. Hence, design, synthesis, and structure–activity relationship of [2-{[(4-substituted)-pyridin-2-yl]carbonyl}-(6- or 5-substituted)-1H-indol-3-yl]acetic acid analogues were investigated to discover novel acid-type COX-2 inhibitor as an orally potent new-class anti-pyretic and anti-inflammatory drug. As significant findings, compounds 1–3 demonstrated potent COX-2 inhibitory activities with high selectivities for COX-2 over COX-1 in human cells or whole-blood in vitro, and demonstrated orally potent anti-pyretic activity against lipopolysaccharide-induced systemic-inflammatory fever model in F344 rats. Also compound 1 demonstrated orally potent anti-inflammatory activity against edema formation and a suppressive effect against PGE₂ production in carrageenan-induced peripheral-inflammation model on the paw of SD rats. These results suggest that compounds 1–3 are potential agents for the treatment of inflammatory disease and are useful for further pharmacological COX-2 inhibitor investigations.     

Inhibition of nucleotide excision repair and sensitisation of cells to DNA cross-linking anticancer drugs by F 11782, a novel fluorinated epipodophylloid

F 11782, or 2',3'-bis-pentafluorophenoxyacetyl-4',6'-ethylidene-beta-D-glucoside of 4'-phosphate-4'-dimethylepipodophyllotoxin 2-N-methyl glucamine salt, a novel dual catalytic inhibitor of topoisomerases I and II, was identified as a potent inhibitor of nucleotide excision repair (NER) by screening procedures using the in vitro 3D (DNA damage detection) assay. F 11782 was then shown predominantly to inhibit the incision rather than the repair synthesis step, using two new methodologies derived from this 3D assay, effectively ruling out any inhibition of polymerases delta/var epsilon. Moreover, data from two other in vitro assays showed an absence of any effect of F 11782 on: (i) the DNA damage binding of the XPA-RPA complex, and (ii) on SV40 large T-antigen helicase activity. Therefore, the inhibitory activity of F 11782 on NER may involve an inhibition of the ERCC1-XPF or XPG endonuclease activity. Moreover, inhibition of DNA repair by F 11782 was confirmed in human A549 cells by monitoring unscheduled DNA synthesis following mechlorethamine treatment. Such an inhibition provides an explanation for the highly synergistic cytotoxicity observed against cultured A549 lung tumour cells, when F 11782 was combined with cross-linking agents, such as cisplatin or mitomycin C. These results emphasise the unique mode of action of this novel molecule in inhibiting NER and provide a basis for its evaluation in clinical trials in combination with DNA cross-linking agents.     

Oxathiolene oxides: a novel family of compounds that induce ferritin,glutathione S-transferase,and other proteins of the phase II response

Compounds that induce the synthesis of cytoprotective phase II enzymes have shown promise as cancer chemopreventive agents. Although chemically diverse, phase II enzyme inducers are capable of participating in Michael reaction chemistry. We have synthesized a novel class of organosulfur compounds, termed oxathiolene oxides (OTEOs). Based on their chemical properties, we hypothesized that these compounds could function as phase II enzyme inducers. Northern blot analysis showed that oxathiolene oxides induce the phase II enzymes glutathione S-transferase (GST), NAD(P)H:quinone oxidoreductase 1 (NQO1), and ferritin H and L mRNA in a concentration-dependent fashion in a normal embryonic mouse liver cell line, BNLCL.2. OTEO-562 (3-cyclohexenyl-4-methyl-1,2-oxathiol-3-ene-2-oxide) was the strongest inducer. Western blot analysis demonstrated that GST-alpha and ferritin H protein levels were also induced in cells treated with OTEO-562, as was total GST and NQO1 enzyme activity. Further, induction of NQO1 activity by OTEO-562 was equivalent in aromatic hydrocarbon (Ah) receptor wild-type and Ah receptor mutant cell lines, suggesting that oxathiolene oxides activate phase II enzymes by an Ah receptor-independent mechanism. Consistent with this observation, OTEO-562 failed to induce cytochrome P450 1A1 mRNA. These results suggest that oxathiolene oxides may merit further investigation as candidate chemopreventive agents.     

Chemical screen identifies shikonin as a broad DNA damage response inhibitor that enhances chemotherapy through inhibiting ATM and ATR

DNA damage response (DDR) is a highly conserved genome surveillance mechanism that preserves cell viability in the presence of chemotherapeutic drugs. Hence, small molecules that inhibit DDR are expected to enhance the anti-cancer effect of chemotherapy. Through a recent chemical library screen, we identified shikonin as an inhibitor that strongly suppressed DDR activated by various chemotherapeutic drugs in cancer cell lines derived from different origins. Mechanistically, shikonin inhibited the activation of ataxia telangiectasia mutated (ATM), and to a lesser degree ATM and RAD3-related (ATR), two master upstream regulators of the DDR signal, through inducing degradation of ATM and ATR-interacting protein (ATRIP), an obligate associating protein of ATR, respectively. As a result of DDR inhibition, shikonin enhanced the anti-cancer effect of chemotherapeutic drugs in both cell cultures and in mouse models. While degradation of ATRIP is proteasome dependent, that of ATM depends on caspase- and lysosome-, but not proteasome. Overexpression of ATM significantly mitigated DDR inhibition and cell death induced by shikonin and chemotherapeutic drugs. These novel findings reveal shikonin as a pan DDR inhibitor and identify ATM as a primary factor in determining the chemo sensitizing effect of shikonin. Our data may facilitate the development of shikonin and its derivatives as potential chemotherapy sensitizers through inducing ATM degradation.