Molecular dynamics simulations reveal structural insights into inhibitor binding modes and functionality in human Group IIA phospholipase A2

Synthesis, molecular modelling, and biological evaluation of novel quinoxaline derivatives for treating type II diabetes

Quinoxalines are benzopyrazine derivatives with significant therapeutic impact in the pharmaceutical industry. They proved to be useful against inflammation, bacterial, fungal, viral infection, diabetes and other applications. Very recently, in January 2024, the FDA approved new quinoxaline containing drug, erdafitinib for treatment of certain carcinomas. Despite the diverse biological activities exhibited by quinoxaline derivatives and the role of secretory phospholipase A2 (sPLA2) in diabetes-related complications, the potential of sPLA2-targeting quinoxaline-based inhibitors to effectively address these complications remains unexplored. Therefore, we designed novel sPLA2- and α-glucosidase-targeting quinoxaline-based heterocyclic inhibitors to regulate elevated post-prandial blood glucose linked to patients with diabetes-related cardiovascular complications. Compounds 5a-d and 6a-d were synthesised by condensing quinoxaline hydrazides with various aryl sulphonyl chlorides. Biological screening revealed compound 6a as a potent sPLA2 inhibitor (IC50 = 0.0475 µM), whereas compound 6c most effectively inhibited α-glucosidase (IC50 = 0.0953 µM), outperforming the positive control acarbose. Moreover, compound 6a was the best inhibitor for both enzymes. Molecular docking revealed pharmacophoric features, highlighting the importance of a sulfonohydrazide moiety in the structural design of these compounds, leading to the development of potent sPLA2 and α-glucosidase inhibitors. Collectively, our findings helped identify promising candidates for developing novel therapeutic agents for treating diabetes mellitus.

Group IIA secreted phospholipase A2 inhibition by elemolic acid as a function of anti-inflammatory activity

Human group IIA secreted phospholipase A2 (GIIA) is a key enzyme in inflammatory reactions, worsening the condition of several chronic inflammatory diseases. The natural inhibitors of GIIA potentially block the production of inflammatory mediators. In the present study, elemolic acid, a triterpenoid from Boswellia serrata inhibited the GIIA enzyme in a concentration-dependent manner with IC50 value of 5.70 ± 0.02 µM. The mode of GIIA inhibition was studied by increasing the concentration of the substrate from 30 to 120 nM, and calcium from 2.5 to 15 mM, the level of inhibition was not changed. The inhibitor-enzyme interaction was examined by fluorimetry and Circular Dichroism (CD) studies; elemolic acid altered intrinsic fluorescence intensity and shifted far UV- CD spectra of GIIA enzyme, suggesting the direct interaction with GIIA. Elemolic acid neutralized the GIIA mediated indirect hemolytic activity from 94.5 to 9.8% and reduced GIIA induced mouse paw edema from 171.75 to 113.68%. Elemolic acid also reduced the hemorrhagic effect of GIIA along with Vipera russelii neurotoxic non-enzymatic peptide -VNTx-II (VR-HC-I). Thus, the elemolic acid has been proven as a potent inhibitor of GIIA enzyme and modulated the GIIA induced inflammatory response by in situ and in vivo methods.

Mann T, Bastard K, F. Scott K, Church WB. Structural and Functional Aspects of Targeting the Secreted Human Group IIA Phospholipase A2

Human group IIA secretory phospholipase A₂ (hGIIA) promotes the proliferation of cancer cells, making it a compelling therapeutic target, but it is also significant in other inflammatory conditions. Consequently, suitable inhibitors of hGIIA have always been sought. The activation of phospholipases A₂ and the catalysis of glycerophospholipid substrates generally leads to the release of fatty acids such as arachidonic acid (AA) and lysophospholipid, which are then converted to mediator compounds, including prostaglandins, leukotrienes, and the platelet-activating factor. However, this ability of hGIIA to provide AA is not a complete explanation of its biological role in inflammation, as it has now been shown that it also exerts proinflammatory effects by a catalysis-independent mechanism. This mechanism is likely to be highly dependent on key specific molecular interactions, and the full mechanistic descriptions of this remain elusive. The current candidates for the protein partners that may mediate this catalysis-independent mechanism are also introduced in this review. A key discovery has been that selective inhibition of the catalysis-independent activity of hGIIA is achieved with cyclised derivatives of a pentapeptide, FLSYK, derived from the primary sequence of hGIIA. The effects of hGIIA on cell function appear to vary depending on the pathology studied, and so its mechanism of action is complex and context-dependent. This review is comprehensive and covers the most recent developments in the understanding of the many facets of hGIIA function and inhibition and the insight they provide into their clinical application for disease treatment. A cyclic analogue of FLSYK, c2, the most potent analogue known, has now been taken into clinical trials targeting advanced prostate cancer.

Can Inhibitors of Snake Venom Phospholipases A₂ Lead to New Insights into Anti-Inflammatory Therapy in Humans? A Theoretical Study

Human phospholipase A₂ (hPLA₂) of the IIA group (HGIIA) catalyzes the hydrolysis of membrane phospholipids, producing arachidonic acid and originating potent inflammatory mediators. Therefore, molecules that can inhibit this enzyme are a source of potential anti-inflammatory drugs, with different action mechanisms of known anti-inflammatory agents. For the study and development of new anti-inflammatory drugs with this action mechanism, snake venom PLA₂ (svPLA₂) can be employed, since the svPLA₂ has high similarity with the human PLA₂ HGIIA. Despite the high similarity between these secretory PLA₂s, it is still not clear if these toxins can really be employed as an experimental model to predict the interactions that occur with the human PLA₂ HGIIA and its inhibitors. Thus, the present study aims to compare and evaluate, by means of theoretical calculations, docking and molecular dynamics simulations, as well as experimental studies, the interactions of human PLA₂ HGIIA and two svPLA₂s,Bothrops toxin II and Crotoxin B (BthTX-II and CB, respectively). Our theoretical findings corroborate experimental data and point out that the human PLA₂ HGIIA and svPLA₂ BthTX-II lead to similar interactions with the studied compounds. From our results, the svPLA₂ BthTX-II can be used as an experimental model for the development of anti-inflammatory drugs for therapy in humans.