Pyridazinones and Structurally Related Derivatives with Anti-Inflammatory Activity

Anti-Inflammatory Activity of Pyrazolo[1,5-a]quinazolines

Chronic inflammation contributes to a number of diseases. Therefore, control of the inflammatory response is an important therapeutic goal. To identify novel anti-inflammatory compounds, we synthesized and screened a library of 80 pyrazolo[1,5-a]quinazoline compounds and related derivatives. Screening of these compounds for their ability to inhibit lipopolysaccharide (LPS)-induced nuclear factor κB (NF-κB) transcriptional activity in human THP-1Blue monocytic cells identified 13 compounds with anti-inflammatory activity (IC50 < 50 µM) in a cell-based test system, with two of the most potent being compounds 13i (5-[(4-sulfamoylbenzyl)oxy]pyrazolo[1,5-a]quinazoline-3-carboxamide) and 16 (5-[(4-(methylsulfinyl)benzyloxy]pyrazolo[1,5-a]quinazoline-3-carboxamide). Pharmacophore mapping of potential targets predicted that 13i and 16 may be ligands for three mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase 2 (ERK2), p38α, and c-Jun N-terminal kinase 3 (JNK3). Indeed, molecular modeling supported that these compounds could effectively bind to ERK2, p38α, and JNK3, with the highest complementarity to JNK3. The key residues of JNK3 important for this binding were identified. Moreover, compounds 13i and 16 exhibited micromolar binding affinities for JNK1, JNK2, and JNK3. Thus, our results demonstrate the potential for developing lead anti-inflammatory drugs based on the pyrazolo[1,5-a]quinazoline and related scaffolds that are targeted toward MAPKs.

Synthesis, Characterization and Cytotoxic Evaluation of New Pyrrolo[1,2-b]pyridazines Obtained via Mesoionic Oxazolo-Pyridazinones

New pyrrolo[1,2-b]pyridazines were synthesized by 3 + 2 cycloaddition reaction between mesoionic oxazolo-pyridazinones and methyl/ethyl propiolate. The mesoionic compounds were generated in situ by action of acetic anhydride on 3(2H)pyridazinone acids obtained from corresponding esters by alkaline hydrolysis followed by acidification. The structures of the compounds were confirmed by elemental analyses and IR, ¹H-NMR, ¹³C-NMR, and X-ray diffraction data. The regioselectivity of cycloaddition was evidenced by NMR spectroscopy and confirmed by X-ray analysis. The compounds were evaluated for their cytotoxicity on plant cells (Triticum aestivum L.) and crustacean animal cells (Artemia franciscana Kellogg and Daphnia magna Straus). The results indicated that the tested compounds exhibited low toxicity on the plant cell (IC₅₀ values higher than 200 µM), while on Artemia nauplii no lethality was observed. Daphnia magna assay showed that pyrrolo[1,2-b]pyridazines 5a and 5c could exhibit toxic effects, whereas, for the other compounds, toxicity was low to moderate. Also, the cytotoxic effects of the compounds were tested on three human adenocarcinoma-derived adherent cell lines (colon LoVo, ovary SK-OV-3, breast MCF-7). The in vitro compound-mediated cytotoxicity assays, performed by the MTS technique, demonstrated dose- and time-dependent cytotoxic activity for several compounds, the highest anti-tumor activity being observed for 5a, 2c, and 5f, especially against colon cancer cells.

G protein coupled pattern recognition receptors expressed in neutrophils : Recognition, activation/modulation, signaling and receptor regulated functions

Neutrophils, the most abundant white blood cell in human blood, express receptors that recognize damage/microbial associated pattern molecules of importance for cell recruitment to sites of inflammation. Many of these receptors belong to the family of G protein coupled receptors (GPCRs). These receptor-proteins span the plasma membrane in expressing cells seven times and the down-stream signaling rely in most cases on an activation of heterotrimeric G proteins. The GPCRs expressed in neutrophils recognize a number of structurally diverse ligands (activating agonists, allosteric modulators, and inhibiting antagonists) and share significant sequence homologies. Studies of receptor structure and function have during the last 40 years generated important information on GPCR biology in general; this knowledge aids in the overall understanding of general pharmacological principles, governing regulation of neutrophil function and inflammatory processes, including novel leukocyte receptor activities related to ligand recognition, biased/functional selective signaling, allosteric modulation, desensitization, and reactivation mechanisms as well as communication (receptor transactivation/cross-talk) between GPCRs. This review summarizes the recent discoveries and pharmacological hallmarks with focus on some of the neutrophil expressed pattern recognition GPCRs. In addition, unmet challenges, including recognition by the receptors of diverse ligands and how biased signaling mediate different biological effects are described/discussed.