Design, synthesis and biological evaluation of 1H-indazole derivatives as novel ASK1 inhibitors

Discovery of novel N-(5-chloro-2,4-dimethoxyphenyl)-N-heterocyclic ketone analogs as potent anti-inflammatory agents against ulcerative colitis

As the incidence of ulcerative colitis (UC) has increased globally, there is a great unmet clinical need for efficacious, tolerable, and economical, orally administered drugs for its treatment. To help meet this need, we investigated anti-inflammatory small-molecule drugs with a novel structure, high activity, and high selectivity for the treatment of UC. Here, we designed and synthesized a series of novel anti-inflammatory compounds based on the molecular hybridization strategy by merging fragments from anti-inflammatory drugs. Among them, compound 11a best-exhibited lipopolysaccharide (LPS)-induced inflammation in RAW264.7 cells in vitro. Anti-inflammatory mechanism studies showed that compound 11a inhibited the release of pro-inflammatory cytokines and alleviated the inflammatory process by blocking the activation of the ASK1/p38 MAPKs/NF-κB signaling pathway in LPS-stimulated RAW264.7 cells. Analysis of the in vivo biological activity showed that compound 11a significantly alleviated dextran sodium sulfate-induced ulcerative colitis in mice while demonstrating an excellent safety in acute toxicity tests. Our study provides a novel compound for the treatment of UC that is worthy of further investigation and structural optimization.

Inhibition of Endoplasmic Reticulum Stress Improves Chronic Ischemic Hippocampal Damage Associated with Suppression of IRE1α/TRAF2/ASK1/JNK-Dependent Apoptosis

Chronic cerebral ischemia is a complex form of stress, of which the most common hemodynamic characteristic is chronic cerebral hypoperfusion (CCH). Lasting endoplasmic reticulum (ER) stress can drive neurological disorders. Targeting ER stress shows potential neuroprotective effects against stroke. However, the role of ER stress in CCH pathological processes and the effects of targeting ER stress on brain ischemia are unclear. Here, a CCH rat model was established by bilateral common carotid artery occlusion. Rats were treated with 4-PBA, URB597, or both for 4 weeks. Neuronal morphological damage was detected using hematoxylin-eosin staining. The expression levels of the ER stress-ASK1 cascade-related proteins GRP78, IRE1α, TRAF2, CHOP, Caspase-12, ASK1, p-ASK1, JNK, and p-JNK were assessed by Western blot. The mRNA levels of TNF-α, IL-1β, and iNOS were assessed by RT-PCR. For oxygen-glucose deprivation experiments, mouse hippocampal HT22 neurons were used. Apoptosis of the hippocampus and HT22 cells was detected by TUNEL staining and Annexin V-FITC analysis, respectively. CCH evoked ER stress with increased expression of GRP78, IRE1α, TRAF2, CHOP, and Caspase-12. Co-immunoprecipitation experiments confirmed the interaction between TRAF2 and ASK1. ASK1/JNK signaling, inflammatory cytokines, and neuronal apoptosis were enhanced, accompanied by persistent ER stress; these were reversed by 4-PBA and URB597. Furthermore, the ASK1 inhibitor GS4997 and 4-PBA displayed synergistic anti-apoptotic effects in cells with oxygen-glucose deprivation. In summary, ER stress-induced apoptosis in CCH is associated with the IRE1α/TRAF2/ASK1/JNK signaling pathway. Targeting the ER stress-ASK1 cascade could be a novel therapeutic approach for ischemic cerebrovascular diseases.

Connecting GSK-3β Inhibitory Activity with IKK-β or ROCK-1 Inhibition to Target Tau Aggregation and Neuroinflammation in Alzheimer's Disease-Discovery, In Vitro and In Cellulo Activity of Thiazole-Based Inhibitors

GSK-3β, IKK-β, and ROCK-1 kinases are implicated in the pathomechanism of Alzheimer's disease due to their involvement in the misfolding and accumulation of amyloid β (Aβ) and tau proteins, as well as inflammatory processes. Among these kinases, GSK-3β plays the most crucial role. In this study, we present compound 62, a novel, remarkably potent, competitive GSK-3β inhibitor (IC50 = 8 nM, Ki = 2 nM) that also exhibits additional ROCK-1 inhibitory activity (IC50 = 2.3 µM) and demonstrates anti-inflammatory and neuroprotective properties. Compound 62 effectively suppresses the production of nitric oxide (NO) and pro-inflammatory cytokines in the lipopolysaccharide-induced model of inflammation in the microglial BV-2 cell line. Furthermore, it shows neuroprotective effects in an okadaic-acid-induced tau hyperphosphorylation cell model of neurodegeneration. The compound also demonstrates the potential for further development, characterized by its chemical and metabolic stability in mouse microsomes and fair solubility.

Exploring novel indazole derivatives as ASK1 inhibitors: Design, synthesis, biological evaluation and docking studies

Apoptosis signal regulated kinase 1 (ASK1, MAP3K5) is a member of the mitogen activated protein kinase (MAPK) signaling pathway, involved in cell survival, differentiation, stress response, and apoptosis. ASK1 kinase inhibition has become a promising strategy for the treatment of Non-alcoholic steatohepatitis (NASH) disease. A series of novel ASK1 inhibitors with indazole scaffolds were designed and synthesized, and their ASK1 kinase activities were evaluated. The System Structure Activity Relationship (SAR) study discovered a promising compound 33c, which has a strong inhibitory effect on ASK1. Noteworthy observations included a discernible reduction in lipid droplets within LO2 cells stained with Oil Red O, coupled with a decrease in LDL, CHO, and TG content within the NASH model cell group. Mechanistic inquiries revealed that compound 33c could inhibit the protein expression levels of the upregulated ASK1-p38/JNK signaling pathway in TNF-α treated HGC-27 cells and regulate apoptotic proteins. In summary, these findings suggest that compound 33c may be valuable for further research as a potential candidate compound against NASH.

Discovery of a quinoline-containing compound JT21-25 as a potent and selective inhibitor of apoptosis signal-regulating kinase 1 (ASK1)

ASK1 kinase inhibition has become a promising strategy for treating inflammatory diseases, such as non-alcoholic steatohepatitis and multiple sclerosis. Here, we reported the discovery of a promising compound 9h (JT21-25) containing quinoline structures as a potent small molecule inhibitor of ASK1. The compound JT21-25 was selective against MAP3K kinases TAK1 (>1960.8-fold), and much higher than the selectivity of GS-4997 for TAK1 (312.3-fold). In addition, different concentrations of JT21-25 did not show significant toxicity in normal LO2 liver cells, and the cell survival rate was greater than 80 %. The Oil Red O staining experiment showed that at the 4 μM and 8 μM concentrations of JT21-25, only slight cytoplasmic fat droplets were observed in LO2 cells, and there was no significant fusion between fat droplets. In the biochemical analysis experiment, JT21-25 significantly reduced the content of CHOL, LDL, TG, ALT, and AST. In summary, these findings suggested that compound JT21-25 might be valuable for further investigation as a potential candidate in the treatment of associated diseases.

Small-molecule inhibitors targeting apoptosis signal-regulated kinase 1

Apoptosis signal regulated kinase 1 (ASK1, also known as MAP3K5) is a member of the mitogen activated protein kinase kinase kinase (MAP3K) family. Since its first isolation from a human macrophage library in 1996, its research has been ongoing for over 25 years. A large number of reports have revealed that ASK1, as a key activator of the p38 mitogen-activated protein kinase and c-Jun N-terminal kinase (JNK) signaling cascade, responds to various stressors, and its inhibitors have important potential value in the treatment of diseases such as inflammation, cancer, and the nervous system and so on. This review summarizes the recent development in this field, including the structure and signaling pathways of ASK1, with a particular focus on the structure-activity relationships, and the hit-to-lead optimization strategies.