Inhibition of soluble guanylyl cyclase by small molecules targeting the catalytic domain

Identification of a Selective SCoR2 Inhibitor That Protects Against Acute Kidney Injury

Acute kidney injury (AKI) is associated with high morbidity and mortality, and no drugs are available clinically. Metabolic reprogramming resulting from the deletion of S-nitroso-coenzyme A reductase 2 (SCoR2; AKR1A1) protects mice against AKI, identifying SCoR2 as a potential drug target. Of the few known inhibitors of SCoR2, none are selective versus the related oxidoreductase AKR1B1, limiting therapeutic utility. To identify SCoR2 (AKR1A1) inhibitors with selectivity versus AKR1B1, analogs of the nonselective (dual 1A1/1B1) inhibitor imirestat were designed, synthesized, and evaluated. Among 57 compounds, JSD26 has 10-fold selectivity for SCoR2 versus AKR1B1 and inhibits SCoR2 potently through an uncompetitive mechanism. When dosed orally to mice, JSD26 inhibited SNO-CoA metabolic activity in multiple organs. Notably, intraperitoneal injection of JSD26 in mice protected against AKI through S-nitrosylation of pyruvate kinase M2 (PKM2), whereas imirestat was not protective. Thus, selective inhibition of SCoR2 has therapeutic potential to treat acute kidney injury.

Mathematical Model Predicts Effective Strategies to Inhibit VEGF-eNOS Signaling

The endothelial nitric oxide synthase (eNOS) signaling pathway in endothelial cells has multiple physiological significances. It produces nitric oxide (NO), an important vasodilator, and enables a long-term proliferative response, contributing to angiogenesis. This signaling pathway is mediated by vascular endothelial growth factor (VEGF), a pro-angiogenic species that is often targeted to inhibit tumor angiogenesis. However, inhibiting VEGF-mediated eNOS signaling can lead to complications such as hypertension. Therefore, it is important to understand the dynamics of eNOS signaling in the context of angiogenesis inhibitors. Thrombospondin-1 (TSP1) is an important angiogenic inhibitor that, through interaction with its receptor CD47, has been shown to redundantly inhibit eNOS signaling. However, the exact mechanisms of TSP1's inhibitory effects on this pathway remain unclear. To address this knowledge gap, we established a molecular-detailed mechanistic model to describe VEGF-mediated eNOS signaling, and we used the model to identify the potential intracellular targets of TSP1. In addition, we applied the predictive model to investigate the effects of several approaches to selectively target eNOS signaling in cells experiencing high VEGF levels present in the tumor microenvironment. This work generates insights for pharmacologic targets and therapeutic strategies to inhibit tumor angiogenesis signaling while avoiding potential side effects in normal vasoregulation.

Functional mechanism of tracheal relaxation, antiasthmatic, and toxicological studies of 6-hydroxyflavone

Previously, we described tracheal rat rings relaxation by several flavonoids, being 6-hydroxyflavone (6-HOF) the most active derivative of the series. Thus, its mechanism of action was determined in an ex vivo tracheal rat ring bioassay. The anti-asthmatic effect was assayed in in vivo OVAlbumin (OVA)-sensitized guinea pigs. Finally, the toxicological profile of 6-HOF was studied based on Organization of Economic Cooperation and Development guidelines with modifications. 6-HOF-induced relaxation appears to be related with receptor-operated calcium channel and voltage-operated calcium channel blockade as the main mechanism of action, and also through the production of relaxant second messengers NO and cGMP. Molecular docking supports that 6-HOF acts as calcium channel blocker and by activation of nitric oxide synthase. In addition, the in vivo anti-asthmatic experiments demonstrate the dose-dependent significant anti-allergic effect of 6-HOF induced by OVA, with best activity at 50 /kg. Finally, toxicological studies determined a LD50 > 2,000 mg/kg and, after 28 day of treatment with 6-HOF (50 mg/kg) by intragastric route, mice did not exhibit evidence of any significant toxicity. In conclusion, experiments showed that 6-HOF exerts significant relaxant activity through calcium channel blockade, and possibly, by NO/cGMP-system stimulation on rat trachea, which interferes with the contraction mechanism of smooth muscle cells in the airways. In addition, the flavonoid shows potential anti-asthmatic properties in an anti-allergic pathway. Furthermore, because the pharmacological and safety evidence, we propose this flavonoid as lead for the development of a novel therapeutic agent for the treatment of asthma and related respiratory diseases.

Molecular docking analysis of phytoconstituent from Momordica charantia with Guanylate Cyclase catalytic domain

Soluble guanylate cyclase (sGC) is a type of lyase enzyme with profoundly increasing importance in treatments of cardiovascular and neurodegenerative disorders. Modulation of sGC activity demonstrated beneficial effects against Parkinson's disease by reducing glutamate excitotoxicity. It is of interest to evaluate the pharmacological activity of Momordica charantia phytoconstituent (DGalacturonic acid) and ODQ with catalytic domain of sGC enzyme, using Autodock version 4.2 programs. Docking results revealed the binding ability of ODQ at the allosteric sites of sGC. D-galacturonic acid also shows binding interaction at the same allosteric sites in the catalytic domain of sGC like ODQ. Results show that both the ligands have efficient binding to THR 474 amino acid residue of beta 1 subunit of the enzyme. The drug likeliness score further implies the suitability of D-Galacturonic acid as a drug-like molecule. The binding property of ODQ and D-Galacturonic acid with the catalytic domain help to inhibit sGC activity having pharmacological effects. Moreover, ODQ interaction with heme site of sGC is already known while its interaction with the catalytic domain is shown in this report.

Structure/function of the soluble guanylyl cyclase catalytic domain

Soluble guanylyl cyclase (GC-1) is the primary receptor of nitric oxide (NO) in smooth muscle cells and maintains vascular function by inducing vasorelaxation in nearby blood vessels. GC-1 converts guanosine 5′-triphosphate (GTP) into cyclic guanosine 3′,5′-monophosphate (cGMP), which acts as a second messenger to improve blood flow. While much work has been done to characterize this pathway, we lack a mechanistic understanding of how NO binding to the heme domain leads to a large increase in activity at the C-terminal catalytic domain. Recent structural evidence and activity measurements from multiple groups have revealed a low-activity cyclase domain that requires additional GC-1 domains to promote a catalytically-competent conformation. How the catalytic domain structurally transitions into the active conformation requires further characterization. This review focuses on structure/function studies of the GC-1 catalytic domain and recent advances various groups have made in understanding how catalytic activity is regulated including small molecules interactions, Cys-S-NO modifications and potential interactions with the NO-sensor domain and other proteins.