title: New small-molecule inhibitors of dihydrofolate reductase inhibit Streptococcus mutans.
abstract: Streptococcus mutans is a major aetiological agent of dental caries. Formation of biofilms is a key virulence factor of S. mutans. Drugs that inhibit S. mutans biofilms may have therapeutic potential. Dihydrofolate reductase (DHFR) plays a critical role in regulating the metabolism of folate. DHFR inhibitors are thus potent drugs and have been explored as anticancer and antimicrobial agents. In this study, a library of analogues based on a DHFR inhibitor, trimetrexate (TMQ), an FDA-approved drug, was screened and three new analogues that selectively inhibited S. mutans were identified. The most potent inhibitor had a 50% inhibitory concentration (IC50) of 454.0±10.2nM for the biofilm and 8.7±1.9nM for DHFR of S. mutans. In contrast, the IC50 of this compound for human DHFR was ca. 1000nM, a >100-fold decrease in its potency, demonstrating the high selectivity of the analogue. An analogue that exhibited the least potency for the S. mutans biofilm also had the lowest activity towards inhibiting S. mutans DHFR, further indicating that inhibition of biofilms is related to reduced DHFR activity. These data, along with docking of the most potent analogue to the modelled DHFR structure, suggested that the TMQ analogues indeed selectively inhibited S. mutans through targeting DHFR. These potent and selective small molecules are thus promising lead compounds to develop new effective therapeutics to prevent and treat dental caries.
authors.affiliation: State Key Laboratory of Oral Diseases, Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan 610041, PR China; Department of Pediatric Dentistry, University of Alabama at Birmingham School of Dentistry, Birmingham, AL 35294, USA.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Thao
authors.initials: T
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: McMichael
authors.affiliation: Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Sadanandan E
authors.initials: SE
authors.lastname: Velu
authors.affiliation: State Key Laboratory of Oral Diseases, Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan 610041, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Oral Diseases, Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan 610041, PR China.
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Pediatric Dentistry, University of Alabama at Birmingham School of Dentistry, Birmingham, AL 35294, USA. Electronic address: hwu@uab.edu.
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects; D004353:Drug Evaluation, Preclinical / Q000379:methods; D005493:Folic Acid Antagonists / Q000737:chemistry / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D013295:Streptococcus mutans / Q000187:drug effects* / Q000502:physiology; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry; D016597:Trimetrexate / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D005493:Folic Acid Antagonists; D013762:Tetrahydrofolate Dehydrogenase; D016597:Trimetrexate
keywords: Biofilm; Dihydrofolate reductase; Streptococcus mutans; Trimetrexate analogues