A novel imidazopyridine derivative, X22, prevents the retinal ischemia-reperfusion injury via inhibition of MAPKs

Imidazopyridine, a promising scaffold with potential medicinal applications and structural activity relationship (SAR): recent advances

Imidazopyridine scaffold has gained tremendous importance over the past few decades. Imidazopyridines have been expeditiously used for the rationale design and development of novel synthetic analogs for various therapeutic disorders. A wide variety of imidazopyridine derivatives have been developed as potential anti-cancer, anti-diabetic, anti-tubercular, anti-microbial, anti-viral, anti-inflammatory, central nervous system (CNS) agents besides other chemotherapeutic agents. Imidazopyridine heterocyclic system acts as a key pharmacophore motif for the identification and optimization of lead structures to increase medicinal chemistry toolbox. The present review highlights the medicinal significances of imidazopyridines for their rationale development as lead molecules with improved therapeutic efficacies. This review further emphasis on the structure-activity relationships (SARs) of the various designed imidazopyridines to establish a relationship between the key structural features versus the biological activities.Communicated by Ramaswamy H. Sarma.

CDK9 inhibition improves diabetic nephropathy by reducing inflammation in the kidneys

Diabetic nephropathy (DN) is a chronic inflammatory renal disease induced by hyperglycemia. Recent studies have implicated cyclin-dependent kinase 9 (CDK9) in inflammatory responses and renal fibrosis. In this study, we explored a potential role of CDK9 in DN by using cultured mouse mesangial cell line SV40 MES-13 and streptozotocin-induced type 1 mouse model of diabetes. We inhibited CDK9 in mice and in cultured cells by a highly selective CDK9 inhibitor, LDC000067 (LDC), and evaluated inflammatory and fibrogenic outcome by mRNA and protein analyses. Our studies show that treatment of diabetic mice with LDC significantly inhibits the levels of inflammatory cytokines and fibrogenic genes in kidney specimens. These reductions were associated with improved renal function. We also found that LDC treatment suppressed MAPK-AP1 activation. We then confirmed the involvement of CDK9 in cultured SV40 MES-13 cells and showed that deficiency in CDK9 prevents glucose-induced inflammatory and fibrogenic proteins. This protection was also afforded by suppression of MAPK-AP1. Taken together, our results how that hyperglycemia activates CDK9-MAPK-AP1 axis in kidneys to induce inflammation and fibrosis, leading to renal dysfunction. Our findings also suggest that CDK9 may serve as a potential therapeutic target for DN.

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an "On-Water" Platform

In a new and environmentally sustainable approach, a series of 2-arylimidazo[1,2-a]pyridine derivatives were synthesized in aqueous media in the presence of iodine as a catalyst. The reaction proceeded by condensation of various aryl methyl ketones with 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good overall yields. Although several of the reactions were efficiently performed "on water", the addition of a surfactant, namely, sodium dodecyl sulphate , was found effective in terms of substrate scope and yield enhancement. Both methods were successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The simple experimental setup, water as "green" media, and inexpensive catalyst are some of the merits of this protocol.

The imidazopyridine derivative X22 prevents diabetic kidney dysfunction through inactivating NF-κB signaling

Diabetic kidney disease (DKD) is considered a chronic inflammatory renal disease induced by hyperglycemia. Therefore, even meticulous control of blood glucose levels cannot prevent the progression of DKD efficiently. Management of the inflammatory response could be one of the most promising strategies for treatment. We previously validated an imidazopyridine derivative (X22) as an active compound in suppressing lipopolysaccharide-induced inflammation. However, its potential for protection against DKD has not been exanimated. In the present study, streptozotocin-induced type 1 diabetic mice were used to study the effect of X22 on DKD associated inflammation and fibrosis by Q-PCR and immunoblotting assays. The results showed that X22 significantly inhibited the production of inflammatory cytokines (IL-6, TNF-α) and fibrosis biomarkers. At the same time, kidney function was dramatically improved. To elucidate the mechanism of action of X22, we examined its effects on the NRK-52E cell line. Strikingly, X22 restored the protein level of IKB-α and blocked the nuclear translocation of P65. Collectively, the data indicate that X22 can attenuate diabetic kidney dysfunction and inflammatory injury and may represent a potential agent for the treatment of DKD. It could be a potential agent for use in the treatment of DKD.

Efficient and "Green" Synthetic Route to Imidazo[1,2-a]pyridine by Cu(II)-Ascorbate-Catalyzed A3-Coupling in Aqueous Micellar Media

An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-a]pyridine derivatives by domino A³-coupling reaction catalyzed by Cu(II)-ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO₄ with sodium ascorbate and aided a facile 5-exo-dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2-a]pyridines in good overall yields. A simple experimental setup, water as the "green" medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.

Myeloid differentiation protein 2 induced retinal ischemia reperfusion injury via upregulation of ROS through a TLR4-NOX4 pathway

Retinal ischemia reperfusion (I/R) injury is common in many ophthalmic diseases. Recent studies have shown that toll-like receptor 4 (TLR4) is involved in ischemic retinal injury. Activation of TLRs requires specific accessory proteins such as myeloid differentiation protein 2 (MD2), which facilitate in ligand responsiveness. Therefore, inhibiting MD2 may be a novel approach to modulate TLR4 signaling and deleterious downstream effects in ischemic retinal injury. We used human Müller MIO-M1 cells treated with tert-butyl hydroperoxide (TBHP) to establish an in vitro I/R model of oxidative injury and tested the therapeutic effect of inhibiting MD2. Furthermore, we inhibited MD2 in a mouse model of retinal I/R injury and confirmed the results using MD2 knockout mice. Our studies show that pharmacological inhibition of MD2 prevented TBHP-induced reactive oxygen species (ROS) generation, inflammation and subsequent apoptosis in Müller cells. We also show that retinal I/R injury in mice induced functional deficits, increased ROS levels, inflammation and apoptosis. These pathological changes were not observed in MD2 knockout mice and attenuated when MD2 was inhibited in wildtype mice. In addition, we discovered that the mechanism of these therapeutic effects involved regulation of NADPH oxidase 4 (NOX4)-MD2-TLR4 complex formation. This study provides evidence that MD2 plays a key role in the pathogenesis of retinal I/R damage by participating in TLR4-NOX4 complex formation and elaboration of oxidative and inflammatory damage. Hence, inhibition of MD2 may reduce TLR-dependent damage during retinal I/R injury.

Pharmacological Potential and Synthetic Approaches of Imidazo[4,5-b]pyridine and Imidazo[4,5-c]pyridine Derivatives

The structural resemblance between the fused imidazopyridine heterocyclic ring system and purines has prompted biological investigations to assess their potential therapeutic significance. They are known to play a crucial role in numerous disease conditions. The discovery of their first bioactivity as GABA_A receptor positive allosteric modulators divulged their medicinal potential. Proton pump inhibitors, aromatase inhibitors, and NSAIDs were also found in this chemical group. Imidazopyridines have the ability to influence many cellular pathways necessary for the proper functioning of cancerous cells, pathogens, components of the immune system, enzymes involved in carbohydrate metabolism, etc. The collective results of biochemical and biophysical properties foregrounded their medicinal significance in central nervous system, digestive system, cancer, inflammation, etc. In recent years, new preparative methods for the synthesis of imidazopyridines using various catalysts have been described. The present manuscript to the best of our knowledge is the complete compilation on the synthesis and medicinal aspects of imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines reported from the year 2000 to date, including structure–activity relationships.

A novel imidazopyridine derivative, X22, attenuates sepsis-induced lung and liver injury by inhibiting the inflammatory response in vitro and in vivo

Sepsis remains a leading cause of death worldwide. Despite years of extensive research, effective drugs to treat sepsis in the clinic are lacking. In this study, we found a novel imidazopyridine derivative, X22, which has powerful anti-inflammatory activity. X22 dose-dependently inhibited lipopolysaccharide (LPS)-induced proinflammatory cytokine production in mouse primary peritoneal macrophages and RAW 264.7 macrophages. X22 also downregulated the LPS-induced proinflammatory gene expression in vitro. In vivo, X22 exhibited a significant protection against LPS-induced death. Pretreatment or treatment with X22 attenuated the sepsis-induced lung and liver injury by inhibiting the inflammatory response. In addition, X22 showed protection against LPS-induced acute lung injury. We additionally found that pretreatment with X22 reduced the inflammatory pain in the acetic acid and formalin models and reduced the dimethylbenzene-induced ear swelling and acetic acid-increased vascular permeability. Together, these data confirmed that X22 has multiple anti-inflammatory effects and may be a potential therapeutic option in the treatment of inflammatory diseases.