Inhibitors of RecA Activity Discovered by High-Throughput Screening: Cell-Permeable Small Molecules Attenuate the SOS Response in Escherichia coli

Abstract

The phenomenon of antibiotic resistance has created a need for the development of novel antibiotic classes with nonclassical cellular targets. Unfortunately, target-based drug discovery against proteins considered essential for in vitro bacterial viability has yielded few new therapeutic classes of antibiotics. Targeting the large proportion of genes considered nonessential that have yet to be explored by high-throughput screening, for example, RecA, can complement these efforts. Recent evidence suggests that RecA-controlled processes are responsible for tolerance to antibiotic chemotherapy and are involved in pathways that ultimately lead to full-fledged antibiotic resistance. Therefore inhibitors of RecA may serve as therapeutic adjuvants in combination chemotherapy of bacterial infectious diseases. Toward the goal of validating RecA as a novel target in the chemotherapy of bacterial infections, the authors have screened 35,780 small molecules against RecA. In total, 80 small molecules were identified as primary hits and could be clustered in 6 distinct chemotype clades. The most potent class of hits was further examined, and 1 member compound was found to inhibit RecA-mediated strand exchange and prevent ciprofloxacin-induced SOS expression in Escherichia coli. This compound represents the first small molecule demonstrating an ability to inhibit the bacterial SOS response in live bacterial cell cultures.

Ecology and Evolution as Targets: the Need for Novel Eco-Evo Drugs and Strategies To Fight Antibiotic Resistance

“…The search for site-specific recombination inhibitors (focused on transposon Tn3) started a quarter of century ago (49). Possible metal-chelate RecA inhibitors have been proposed as transition metal complexes (based on metal-dependent initia-tion of RecA aggregation), nucleotide analogs, structured peptides, and polysulfated naphthyl compounds (75,76,151). Unfortunately, these molecules are not cell permeable or have a pleiotropic effect on live bacteria.…”

“…Unfortunately, these molecules are not cell permeable or have a pleiotropic effect on live bacteria. Recently, a high-throughput target-based screening approach has permitted the identification of a new class of small, permeable compounds that can attenuate the SOS response in living bacteria (117,150,151), Conjugative plasmids have a natural RecA inhibitor, PsiB (108), and research in natural systems of controlling recombination will eventually be of interest. Finally, investigation on HIV-1 has yielded a large number of integrase inhibitors, which eventually could be tested for inhibition of resistance gene acquisition by genetic platforms (58; J. C. Galán, personal communication).…”

Overcoming Drug Resistance with Alginate Oligosaccharides Able To Potentiate the Action of Selected Antibiotics

“…Antibacterial strategies have included use of antimicrobial cationic peptides (AMPs) (7); cell membrane permeabilization (7); molecular chaperones (e.g., heat shock proteins) (4); inhibitors of RecA-mediated strand exchange (34); inhibitors of DNA synthesis (6); inhibitors of penicillinbinding protein production (18); and use of efflux pump inhibitors or inhibitors of beta-lactamase expression (27). Despite almost 20 years of intense research, none of these agents deemed useful in vitro have progressed to clinical use.…”

7-(1-Methyl-3-Pyrrolyl-)-4,6-Dinitrobenzofuroxan Reduces the Frequency of Antibiotic Resistance Mutations Induced by Ciprofloxacin in Bacteria

“…It was shown that the main generator of resistance mutations is the SOS-or error-prone repair system. [4] In order to compensate for the negative effects identified in the works of Cirz and Wigle et al, [3,5] it was proposed to synthesize new compounds, which would be able to switch off the launch of SOS-response and thus increase the sensitivity of the bacterial population to antibiotics. Currently, several laboratories are conducting screening for SOS-response inhibitors that would prevent the rapid development of bacterial resistance to antibiotics.…”