Screening Repurposed Antiviral Small Molecules as Antimycobacterial Compounds by a Lux-Based phoP Promoter-Reporter Platform

Abstract

The emergence of multidrug-resistant strains and hyper-virulent strains of Mycobacterium tuberculosis are big therapeutic challenges for tuberculosis (TB) control. Repurposing bioactive small-molecule compounds has recently become a new therapeutic approach against TB. This study aimed to identify novel anti-TB agents from a library of small-molecule compounds via a rapid screening system. A total of 320 small-molecule compounds were used to screen for their ability to suppress the expression of a key virulence gene, phop, of the M. tuberculosis complex using luminescence (lux)-based promoter-reporter platforms. The minimum inhibitory and bactericidal concentrations on drug-resistant M. tuberculosis and cytotoxicity to human macrophages were determined. RNA sequencing (RNA-seq) was conducted to determine the drug mechanisms of the selected compounds as novel antibiotics or anti-virulent agents against the M. tuberculosis complex. The results showed that six compounds displayed bactericidal activity against M. bovis BCG, of which Ebselen demonstrated the lowest cytotoxicity to macrophages and was considered as a potential antibiotic for TB. Another ten compounds did not inhibit the in vitro growth of the M. tuberculosis complex and six of them downregulated the expression of phoP/R significantly. Of these, ST-193 and ST-193 (hydrochloride) showed low cytotoxicity and were suggested to be potential anti-virulence agents for M. tuberculosis.

Repurposing High-Throughput Screening Identifies Unconventional Drugs with Antibacterial and Antibiofilm Activities against Pseudomonas aeruginosa under Experimental Conditions Relevant to Cystic Fibrosis

“…In this framework, the inconsistency between FIB/SEM analysis and those revealed by the PI uptake assay could be explained by the prolonged exposure time used for microscopic analysis and by other factors, among those the presence of damaged DNA. Indeed, as PI intercalates with intact DNA, the lack of staining bacteria could hint at the breakage of DNA after tratment with the hit, which may be caused by the formation of ROS ( 29 , 40 – 42 ). Therefore, we measured the ROS formation through H2DCFDA (2′,7′-dichlorodihydrofluorescein diacetate), a nonfluorescent dye converted into the fluorescent dye DCF in the presence of intracellular ROS.…”

“…Although not yet FDA approved, ebselen is safe in humans and is being evaluated in phase III trials for bipolar disorder, the treatment and prevention of hearing loss, Meniere’s disease, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ( 44 – 46 ). In vitro studies revealed antibacterial activity—targeting the thioredoxin reductase, thus leading to an intracellular elevation of ROS—for a wide range of infectious pathogens, including MDR Gram-positive bacteria, A. baumannii , and Mycobacterium tuberculosis complex ( 29 , 40 – 42 ). Our findings showed that ebselen exerts activity toward P. aeruginosa by damaging the membrane cell due to augmented membrane permeability rather than increased production of intracellular ROS.…”

Potential Repurposed Drug Candidates for Tuberculosis Treatment: Progress and Update of Drugs Identified in Over a Decade

“…The effect of Ebselen as an anti-TB agent and its synergistic effect with Isoniazid have been found effective against H 37 Rv and three clinically used drug-resistant strains (JAL2287, BND320, and MYC431) . In addition, a recent study showed that Ebselen imparts low cytotoxicity against macrophages, indicating that it might be used as an anti-TB …”

“…93 In addition, a recent study showed that Ebselen imparts low cytotoxicity against macrophages, indicating that it might be used as an anti-TB. 94 4.2.2. Anticancer Drugs.…”

Carbon dioxide regulates Mycobacterium tuberculosis PhoPR signaling and virulence

“…While the PhoPR regulon is regulated by acidic pH, it is possible that it is directly or indirectly regulated by pH or possibly other reported signals like magnesium or chloride [6,10]. Notably, the PhoPR regulon is inhibited by treatment with ethoxzolamide (ETZ) [11][12][13], a carbonic anhydrase (CA) inhibitor [14,15], providing a potential link between carbon dioxide (CO2), pH sensing, and PhoPR regulation.…”