The development of inhibitors that target the papain‐like protease (PLpro) has the potential to counteract the spread of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), the agent causing coronavirus disease 2019 (COVID‐19). Based on a consideration of its several downstream effects, interfering with PLpro would both revert immune suppression exerted by the virus and inhibit viral replication. By following a repurposing strategy, the current study evaluates the potential of antimalarial drugs as PLpro inhibitors, and thereby the possibility of their use for treatment of SARS‐CoV‐2 infection. Computational tools were employed for structural analysis, molecular docking, and molecular dynamics simulations to screen antimalarial drugs against PLpro, and in silico data were validated by in vitro experiments. Virtual screening highlighted amodiaquine and methylene blue as the best candidates, and these findings were complemented by the in vitro results that indicated amodiaquine as a μM PLpro deubiquitinase inhibitor. The results of this study demonstrate that the computational workflow adopted here can correctly identify active compounds. Thus, the highlighted antimalarial drugs represent a starting point for the development of new PLpro inhibitors through structural optimization.
The 1,2,3-triazole ring system can be easily obtained by copper-catalyzed click reaction of azides with alkynes. 1,2,3-Triazole exhibits a myriad of biological activities, including antimalarial, antibacterial, and antiviral activities. We herein reported the synthesis of quinoline-based [1,2,3]-triazole hybrid via Cu(I)-catalyzed click reaction of 4-azido-7-chloroquinoline with alkyne derivative of 2-bromobenzaldehyde. The compound was fully characterized by proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), heteronuclear single quantum coherence (HSQC), ultraviolet (UV), and high-resolution mass spectroscopies (HRMS). This compound was screened in vitro against two different normal cell lines. Preliminary studies attempted to evaluate its interaction with Delta RBD of spike protein of SARS-CoV-2 by bio-layer interferometry. Finally, the drug-likeness of the compound was also investigated by predicting its pharmacokinetic properties.
Epalrestat, an aldose reductase inhibitor (ARI), has been clinically adopted in treating diabetic neuropathy in China and Japan. Apart from the involvement in diabetic complications, AR has been implicated in inflammation. Here, we seek to investigate the feasibility of clinically approved ARI, epalrestat, for the treatment of rheumatoid arthritis (RA). The mRNA level of AR was markedly upregulated in the peripheral blood mononuclear cells (PBMCs) of RA patients when compared to those of healthy donors. Besides, the disease activity of RA patients is positively correlated with AR expression. Epalrestat significantly suppressed lipopolysaccharide (LPS) induced TNF-α, IL-1β, and IL-6 in the human RA fibroblast-like synoviocytes (RAFLSs). Unexpectedly, epalrestat treatment alone markedly exaggerated the disease severity in adjuvant induced arthritic (AIA) rats with elevated Th17 cell proportion and increased inflammatory markers, probably resulting from the increased levels of 4-hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA). Interestingly, the combined treatment of epalrestat with N -Acetylcysteine (NAC), an anti-oxidant, to AIA rats dramatically suppressed the production of 4-HNE, MDA and inflammatory cytokines, and significantly improved the arthritic condition. Taken together, the anti-arthritic effect of epalrestat was diminished or even overridden by the excessive accumulation of toxic 4-HNE or other reactive aldehydes in AIA rats due to AR inhibition. Co-treatment with NAC significantly reversed epalrestat-induced upregulation of 4-HNE level and potentiated the anti-arthritic effect of epalrestat, suggesting that the combined therapy of epalrestat with NAC may sever as a potential approach in treating RA. Importantly, it could be regarded as a safe intervention for RA patients who need epalrestat for the treatment of diabetic complications.
Ageing is an unavoidable process in humans and a major factor for the increasing risk of various diseases. In the United States, more than 50% of rheumatoid arthritis patients are middle-aged or elderly, but the risk factors and mechanisms by which ageing increases the incidence of rheumatoid arthritis are not known. It has been suggested that the accumulation of DNA fragments increases the risk of autoimmune diseases, such as systemic lupus erythematosus. DNA fragments are a common nucleic acid metabolite in ageing organisms as well as in the serum of humans and animals with rheumatoid arthritis; therefore, we hypothesize that DNA fragments are one of the factors contributing to the development of rheumatoid arthritis due to ageing. First, we analysed two in vitro DNA damage response models by using a gene silencing approach and determined that the DNA fragment clearance gene TREX1 can regulate inflammatory factor release in normal cells. Second, after TREX1 expression was knocked down locally or systemically in rats via the Cre-LoxP system and compared with that in AIA(adjuvant-induced arthritis) model rats treated with AAV-TREX1, it was determined that DNA fragments can result in manifestations of arthritis and abnormal activation of the immune system in rats. These results, including the low expression of the TREX1 gene in clinical patient and AIA model samples and the results of immunohistochemical, Western blot, and transcriptome analyses, revealed that the TREX1 gene can regulate cellular senescence-associated secretory phenotype (SASP)-related manifestations and showed that dysregulation of c-Jun and c-Fos, components of the TREX1 transcription factor AP-1, is associated with SASP induction. Finally, it was confirmed in vitro that different causes of decreased c-Fos expression can inhibit TREX1 expression. These DNA fragments are potent producers of inflammation-releasing mediators, and TREX1 is an effective degrader of DNA fragments; it is also a key gene that regulates cellular immunity and ageing. Therefore, effectively clearing excess DNA fragments from the body and ensuring the health of senescent cells may be a potential prevention strategy for RA.
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