In Vitro and In Silico Evaluation of New 1,3,4-Oxadiazole Derivatives of Pyrrolo[3,4-d]pyridazinone as Promising Cyclooxygenase Inhibitors.

Since long-term use of classic NSAIDs can cause severe side effects related mainly to the gastroduodenal tract, discovery of novel cyclooxygenase inhibitors with a safe gastric profile still remains a crucial challenge. Based on the most recent literature data and previous own studies, we decided to modify the structure of already reported 1,3,4-oxadiazole based derivatives of pyrrolo[3,4-d]pyridazinone in order to obtain effective COX inhibitors. Herein we present the synthesis, biological evaluation and molecular docking studies of 12 novel compounds with disubstituted arylpiperazine pharmacophore linked in a different way with 1,3,4-oxadiazole ring. None of the obtained molecules show cytotoxicity on NHDF and THP-1 cell lines and, therefore, all were qualified for further investigation. In vitro cyclooxygenase inhibition assay revealed almost equal activity of new derivatives towards both COX-1 and COX-2 isoenzymes. Moreover, all compounds inhibit COX-2 isoform better than Meloxicam which was used as reference. Anti-inflammatory activity was confirmed in biological assays according to which title molecules are able to reduce induced inflammation within cells. Molecular docking studies were performed to describe the binding mode of new structures to cyclooxygenase. Investigated derivatives take place in the active site of COX, very similar to Meloxicam. For some compounds, promising druglikeness was calculated using in silico predictions.

Effect of pyrrolo[3,4-d]pyridazinone derivatives in neuroinflammation induced by preincubation with lipopolysaccharide or coculturing with microglia-like cells.

Alzheimer's disease is one of the most serious disorders of the 21st century. There is still no effective therapy for this condition. The study investigated the potential regenerative effect of four pyrrolo[3,4-d]pyridazinone derivatives in cultures of SH-SY5Y neuron-like cells preincubated with lipopolysaccharide (LPS) or cocultured with microglia-like cells. In addition to the traditional investigation of the effect on viability, the level of free radicals and nitric oxide, the average length of neurites was also measured. Via in silico studies, the possibility of penetration of the blood-brain barrier (BBB) by the tested compounds was assessed. The administration of LPS to the culture of SH-SY5Y cells as well as coculturing with microglia-like cells had a significant negative effect on the results of all the assays performed. The treatment with the tested derivatives in most cases significantly reduced this negative effect. The obtained results suggest that the compound L2 may have a beneficial impact on neuronal damage caused by LPS or proinflammatory cytokines secreted by microglia-like cells. Importantly, tested compounds can pass through the BBB, which allows them to enter the brain.

Design, Synthesis and Comprehensive Investigations of Pyrrolo[3,4-d]pyridazinone-Based 1,3,4-Oxadiazole as New Class of Selective COX-2 Inhibitors.

The long-term use of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) in treatment of different chronic inflammatory disorders is strongly restricted by their serious gastrointestinal adverse effects. Therefore, there is still an urgent need to search for new, safe, and efficient anti-inflammatory agents. Previously, we have reported the Mannich base-type derivatives of pyrrolo[3,4-d]pyridazinone which strongly inhibit cyclooxygenase, have better affinity to COX-2 isoenzyme and exert promising anti-oxidant activity. These findings encouraged us to perform further optimization of that structure. Herein, we present the design, synthesis, molecular docking, spectroscopic, and biological studies of novel pyrrolo[3,4-d]pyridazinone derivatives bearing 4-aryl-1-(1-oxoethyl)piperazine pharmacophore 5a,b-6a,b. The new compounds were obtained via convenient, efficient, one-pot synthesis. According to in vitro evaluations, novel molecules exert no cytotoxicity and act as selective COX-2 inhibitors. These findings stay in good correlation with molecular modeling results, which additionally showed that investigated compounds take a position in the active site of COX-2 very similar to Meloxicam. Moreover, all derivatives reduce the increased level of reactive oxygen and nitrogen species and prevent DNA strand breaks caused by oxidative stress. Finally, performed spectroscopic and molecular docking studies demonstrated that new compound interactions with bovine serum albumin (BSA) are moderate, formation of complexes is in one-to-one ratio, and binding site II (subdomain IIIA) is favorable.