Evaluation of expanded 2-aminobenzothiazole library as inhibitors of a model histidine kinase and virulence suppressors in Pseudomonas aeruginosa.

Bacterial resistance to antibiotics is a rapidly increasing threat to human health. New strategies to combat resistant organisms are desperately needed. One potential avenue is targeting two-component systems, which are the main bacterial signal transduction pathways used to regulate development, metabolism, virulence, and antibiotic resistance. These systems consist of a homodimeric membrane-bound sensor histidine kinase, and a cognate effector, the response regulator. Histidine kinases play an essential role in the regulation of multiple virulence mechanisms including toxin production, immune evasion, and antibiotic resistance. Targeting virulence, as opposed to development of bactericidal compounds, could reduce evolutionary pressure for acquired resistance. Additionally, compounds targeting the highly conserved catalytic and adenosine triphosphate-binding (CA) domain have the potential to impair multiple two-component systems that regulate virulence in one or more pathogens. We conducted in vitro structure-activity relationship studies of 2-aminobenzothiazole-based inhibitors designed to target the CA domain. We found that these compounds, which inhibit the model histidine kinase, HK853 from Thermotoga maritima, have anti-virulence activities inPseudomonas aeruginosa, reducing motility phenotypes and toxin production associated with the pathogenic functions of this bacterium.

Investigation of an ALDH1A1-specific inhibitor for suppression of weight gain in a diet-induced mouse model of obesity.

BACKGROUND: Retinoic acid (RA) controls diverse physiological functions including weight regulation and energy metabolism. It has been reported that mice lacking ALDH1A1, one of the aldehyde dehydrogenases (ALDH) that synthesize RA, are healthy and resistant to weight gain, raising the possibility that inhibiting this enzyme might treat obesity. We previously demonstrated that treatment with a pan-ALDH1A enzyme inhibitor, WIN18446, suppressed weight gain in mice fed a high-fat diet (HFD), but caused increased hepatic lipidosis and reversible male infertility. METHODS: A series of piperazine compounds that inhibited ALDH1A1 were identified and their inhibitory activity was characterized in vitro using purified recombinant enzymes and cell-based assay systems. One potent compound, FSI-TN42 (N42) was examined for its oral bioavailability and pharmacodynamic effects. In addition, its effect on weight gain was investigated by daily oral administration to C57BL/6 male mice receiving a HFD, and compared with mice receiving WIN18446 or vehicle alone (n = 6/group, 200 mg compound/kg body weight) for 5 weeks. Body weights were measured weekly, and a glucose tolerance test was performed after 4 weeks of treatment. Tissues were collected to determine changes in adipose weight, hepatic lipidosis, retinoid metabolism, and expression of genes associated with RA and lipid metabolism. RESULTS: N42 irreversibly binds and inhibits ALDH1A1 in vitro with a low nM IC50 and 800-fold specificity for ALDH1A1 compared to ALDH1A2. Daily oral administration of N42 significantly suppressed weight gain (P < 0.05) and reduced visceral adiposity (p < 0.05) in mice fed a HFD without the hepatic lipidosis observed with WIN18446 treatment. CONCLUSIONS: We developed a potent and specific inhibitor of ALDH1A1 that suppressed weight gain in mice fed a HFD. These findings demonstrate that inhibition of ALDH1A1 is a feasible target for drug development to treat and/or prevent obesity.

Screening serine/threonine and tyrosine kinase inhibitors for histidine kinase inhibition.

Histidine kinases of bacterial two-component systems are promising antibacterial targets. Despite their varied, numerous roles, enzymes in the histidine kinase superfamily share a catalytic core that may be exploited to inhibit multiple histidine kinases simultaneously. Characterized by the Bergerat fold, the features of the histidine kinase ATP-binding domain are not found in serine/threonine and tyrosine kinases. However, because each kinase family binds the same ATP substrate, we sought to determine if published serine/threonine and tyrosine kinase inhibitors contained scaffolds that would also inhibit histidine kinases. Using select assays, 222 inhibitors from the Roche Published Kinase Set were screened for binding, deactivation, and aggregation of histidine kinases. Not only do the results of our screen support the distinctions between ATP-binding domains of different kinase families, but the lead molecule identified also presents inspiration for further histidine kinase inhibitor development.

Evaluation of Expanded 2-Aminobenzothiazole Library for Inhibition of Pseudomonas aeruginosa Virulence Phenotypes.

Bacterial resistance to antibiotics is a rapidly increasing threat to human health. New strategies to combat resistant organisms are desperately needed. One potential avenue is targeting two-component systems, which are the main bacterial signal transduction pathways used to regulate development, metabolism, virulence, and antibiotic resistance. These systems consist of a homodimeric membrane-bound sensor histidine kinase, and a cognate effector, the response regulator. The high sequence conservation in the catalytic and adenosine triphosphate-binding (CA) domain of histidine kinases and their essential role in bacterial signal transduction could enable broad-spectrum antibacterial activity. Through this signal transduction, histidine kinases regulate multiple virulence mechanisms including toxin production, immune evasion, and antibiotic resistance. Targeting virulence, as opposed to development of bactericidal compounds, could reduce evolutionary pressure for acquired resistance. Additionally, compounds targeting the CA domain have the potential to impair multiple two-component systems that regulate virulence in one or more pathogens. We conducted structure-activity relationship studies of 2-aminobenzothiazole-based inhibitors designed to target the CA domain of histidine kinases. We found these compounds have anti-virulence activities in Pseudomonas aeruginosa, reducing motility phenotypes and toxin production associated with the pathogenic functions of this bacterium.

Targeting a highly conserved domain in bacterial histidine kinases to generate inhibitors with broad spectrum activity.

With the rise in antimicrobial resistance and the dearth of effective strategies to combat this threat, the development of novel therapies is of utmost importance. Targeting of bacterial signaling through their the two-component systems (TCSs) may be a viable strategy. TCSs are comprised of a sensory histidine kinase (HK), of which a bacterium can have up to 160 distinct proteins, and a cognate response regulator (RR). The TCSs are generally non-essential for life, but control many virulence and antibiotic-resistance mechanisms. This, along with their absence in animals makes the TCSs an attractive target for antimicrobial therapy, whether as a stand-alone treatments or adjuvants for existing therapies. This review focuses on progress in the development of inhibitors that target the HK ATP-binding domain. Because this domain is highly conserved, it may be feasible to disrupt multiple TCSs within a single organism to increase effectiveness and reduce pressure for the evolution of resistance.