Inhibition of iNOS by Benzimidazole Derivatives: Synthesis, Docking, and Biological Evaluations

Background: Inducible nitric Oxide Synthase (iNOS) plays a key role in the progression of inflammatory diseases by accelerating the production of NO, which makes it an intriguing target to treat inflammation in complex diseases. Therefore, the search is on to develop molecules as selective iNOS inhibitors. Objective: The present work was aimed to design, synthesize and evaluate benzimidazole-coumarin coupled molecules as anti-iNOS agents through in silico and pharmacological studies. Methods: A critical study of literature reports on iNOS inhibitors led to the selection of a (un)substituted coumarin nucleus, 2-aminobenzimidazole, and a 4-atom linker as important structural components for iNOS inhibition. Two series of compounds (7-16 and 17-26) were designed and synthesized by coupling these components. The compounds were subjected to docking using iNOS (1QW4) and nNOS (1QW6) as targets. All compounds were evaluated for NO and iNOS inhibitory activities in vitro. The selected compound was finally evaluated for anti-inflammatory activity in vivo using the carrageenan-induced rat paw edema model. Results : All compounds showed moderate to good inhibition of NO and iNOS in vitro. Compound 12 was the most potent inhibitor of NO and iNOS. Hence, it was evaluated in vivo for toxicity and anti-inflammatory activity. It was found to be safe in acute toxicity studies, and effective in reducing the rat paw edema significantly. Its anti-inflammatory behaviour was similar to that of aminoguanidine, which is a selective iNOS inhibitor. Conclusion: The newly synthesized benzimidazole-coumarin hybrids may serve as potential leads for the development of novel anti-iNOS agents.

Selective Inhibitors of the Inducible Nitric Oxide Synthase as Modulators of Cell Responses in LPS-Stimulated Human Monocytes

Inducible nitric oxide synthase (iNOS) is a crucial enzyme involved in monocyte cell response towards inflammation, and it is responsible for the production of sustained amounts of nitric oxide. This free radical molecule is involved in the defense against pathogens; nevertheless, its continuous and dysregulated production contributes to the development of several pathological conditions, including inflammatory and autoimmune diseases. In the present study, we investigated the effects of two new iNOS inhibitors, i.e., 4-(ethanimidoylamino)-N-(4-fluorophenyl)benzamide hydrobromide (FAB1020) and N-{3-[(ethanimidoylamino)methyl]benzyl}-l-prolinamidedihydrochloride (CM554), on human LPS-stimulated monocytes, using the 1400 W compound as a comparison. Our results show that CM544 and FAB1020 are selective and decrease cytotoxicity, IL-6 secretion and LPS-stimulated monocyte migration. Furthermore, the modulation of iNOS, nitrotyrosine and Nrf2 were analyzed at the protein level. Based on the collected preliminary results, the promising therapeutic value of the investigated compounds emerges, as they appear able to modulate the pro-inflammatory LPS-stimulated response in the low micromolar range in human monocytes.

Screening and Identification of Potential iNOS Inhibitors to Curtail Cervical Cancer Progression: An in-Silico Drug Repurposing Approach

Cervical cancer is the second most common cause of cancer deaths in women worldwide and remains the main reason of mortality amongst women of reproductive age in developing countries. Nitric oxide is involved in several physiological functions inclusive of inflammatory and immune responses. However, the function of NO in tumor biology is debatable. The inducibleNOS (iNOS/NOS2) isoform is the oneresponsible to maintain the levels of NO and it exhibits pleotropic effects in various cancer with concentration-dependent pro- and anti-tumor effects.NOS2 triggers angiogenesis and endothelial cell migration in tumors by regulating the levels of vascular endothelial growth factor (VEGF). In drug discovery, drug repurposing involves investigations of approved drug candidates to treat various other diseases. In this study, we used FDA-approved anti-cancer drugs and small molecules to target iNOS and identify a potential selective iNOS inhibitor. The structures of ligands were geometrically optimized, and energy minimized using Hyperchem software. Molecular docking was performed using Molegro virtual docker and ligands were selected based on MolDock score,Rerank score, and H-bonding energy. In the study showed 4 compounds, Degarelix, Goserelin, Triptorelin pamoate, and venetoclax demonstrated excellent binding affinity to NOS2 protein. These compounds exhibited the lowest MolDock score, Rerank score, with better H-bonding energy to NOS2. Based on the results theses ligands project to be promising potential NOS2 inhibitors to curtail cervical cancer progression

Bioactive α-Pyrone Derivatives from the Endophytic Fungus Diaporthe sp. CB10100 as Inducible Nitric Oxide Synthase Inhibitors

Inducible nitric oxide synthase (iNOS) produces NO from l-arginine and plays critical roles in inflammation and immune activation. Selective and potent iNOS inhibitors may be potentially used in many indications, such as rheumatoid arthritis, pain, and neurodegeration. In the current study, five new compounds, including a dibenzo-α- pyrone derivative ellagic acid B (5) and four α-pyrones diaporpyrone A–D (9–12), together with three known compounds (6–8), were isolated from the endophytic fungus Diaporthe sp. CB10100. The structures of these new natural products were unambiguously elucidated using NMR, HRESIMS or electronic circular dichroism calculations. Ellagic acid B (5) features a tetracyclic 6/6/6/6 ring system with a fused 2H-chromene, which is different from ellagic acid (4) with a fused 2H-chromen-2-one. Both 2-hydroxy-alternariol (6) and alternariol (7) reduced the expression of iNOS at protein levels in a dose-dependent manner, using a lipopolysaccharide (LPS)-induced RAW264.7 cell models. Also, they decreased the protein expression levels of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin-6 and monocyte chemotactic protein 1. Importantly, 6 and 7 significantly reduced the production of NO as low as 10 μM in LPS-induced RAW264.7 cells. Molecular docking of 6 and 7 to iNOS further suggests that both of them may interact with iNOS. Our study suggests that 6 and 7, as well as the alternariol scaffold may be further developed as potential iNOS inhibitors.

Nitric Oxide (NO) and NO Synthases (NOS)-Based Targeted Therapy for Colon Cancer

Colorectal cancer (CRC) is one of the most lethal malignancies worldwide and CRC therapy remains unsatisfactory. In recent decades, nitric oxide (NO)—a free-radical gas—plus its endogenous producer NO synthases (NOS), have attracted considerable attention. NO exerts dual effects (pro- and anti-tumor) in cancers. Endogenous levels of NO promote colon neoplasms, whereas exogenously sustained doses lead to cytotoxic functions. Importantly, NO has been implicated as an essential mediator in many signaling pathways in CRC, such as the Wnt/β-catenin and extracellular-signal-regulated kinase (ERK) pathways, which are closely associated with cancer initiation, metastasis, inflammation, and chemo-/radio-resistance. Therefore, NO/NOS have been proposed as promising targets in the regulation of CRC carcinogenesis. Clinically relevant NO-donating agents have been developed for CRC therapy to deliver a high level of NO to tumor sites. Notably, inducible NOS (iNOS) is ubiquitously over-expressed in inflammatory-associated colon cancer. The development of iNOS inhibitors contributes to targeted therapies for CRC with clinical benefits. In this review, we summarize the multifaceted mechanisms of NO-mediated networks in several hallmarks of CRC. We review the clinical manifestation and limitations of NO donors and NOS inhibitors in clinical trials. We also discuss the possible directions of NO/NOS therapies in the immediate future.

Acetamidine-Based iNOS Inhibitors as Molecular Tools to Counteract Inflammation in BV2 Microglial Cells

Neurodegenerative diseases are associated with increased levels of nitric oxide (NO) mainly produced by microglial cells through inducible nitric oxide synthase (iNOS) whose expression is induced by inflammatory stimuli. NO can both exert cytotoxic functions and induce a metabolic switch by inhibiting oxidative phosphorylation and upregulating glycolytic flux. Here, we investigated whether two newly synthesized acetamidine based iNOS inhibitors, namely CM292 and CM544, could inhibit lipopolysaccharide (LPS)-induced BV2 microglial cell activation, focusing on both inflammatory and metabolic profiles. We found that CM292 and CM544, without affecting iNOS protein expression, reduced NO production and reverted LPS-induced inflammatory and cytotoxic response. Furthermore, in the presence of the inflammatory stimulus, both the inhibitors increased the expression of glycolytic enzymes. In particular, CM292 significantly reduced nuclear accumulation of pyruvate kinase M2, increased mitochondrial membrane potential and oxygen consumption rate, and augmented the expression of pyruvate dehydrogenase, pointing to a metabolic switch toward oxidative phosphorylation. These data confirm the role played by NO in the connection between cell bioenergetics profile and inflammation, and suggest the potential usefulness of iNOS inhibitors in redirecting microglia from detrimental to pro-regenerative phenotype.