A quinol peroxidase inhibitor prevents secretion of a leukotoxin from Aggregatibacter actinomycetemcomitans.
OBJECTIVE
Quinol peroxidase (QPO) catalyzes peroxidase activity using quinol in the respiratory chain as a substrate. Quinol peroxidase is essential for the secretion of leukotoxin (LtxA), which destroys leukocytes and erythrocytes in humans and is one of the major virulence factors of Aggregatibacter actinomycetemcomitans, which is associated with localized aggressive periodontitis. In the present study, we aimed to find a highly potent QPO inhibitor to attenuate the virulence of A. actinomycetemcomitans.


METHODS
For screening of QPO inhibitors, QPO activity was measured kinetically by SpectraMax Plus with 96-well UV plates. Three hundred compounds in the Kitasato Institute for Life Sciences Chemical Library were screened. Secretion of LtxA in the culture supernatant was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cytotoxicity against human promyelocytic leukemia cell line (HL-60) cells from the culture supernatant was measured by Trypan Blue exclusion test.


RESULTS
The present study characterized ascofuranone as a highly potent inhibitor of QPO (K(i) = 9.557 +/- 0.865 nm). Ascofuranone inhibited secretion of LtxA by A. actinomycetemcomitans in a dose-dependent manner, making A. actinomycetemcomitans less pathogenic to HL-60 cells.


CONCLUSIONS
Quinol peroxidase inhibitors are promising candidates as alternative drugs for the treatment and prevention of the onset of localized aggressive periodontitis. Using ascofuranone as a seed compound, further study of QPO inhibitors could provide novel chemotherapeutic strategies for controlling localized aggressive periodontitis.
Takashima
E
E
Department of Microbiology, School of Life Dentistry at Tokyo, The Nippon Dental University, Chiyoda-ku, Tokyo, Japan. eizo.takashima@gmail.com
Yamada
H
H
Yajima
A
A
Shiomi
K
K
Omura
S
S
Kiyoshi
K
K
D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D003603:Cytotoxins / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D005098:Exotoxins / Q000037:antagonists & inhibitors*; D018922:HL-60 Cells; D006801:Humans; D006873:Hydroquinones / Q000037:antagonists & inhibitors*; D008826:Microbial Sensitivity Tests; D018384:Oxidative Stress / Q000187:drug effects; D010544:Peroxidases / Q000037:antagonists & inhibitors*; D012717:Sesquiterpenes / Q000008:administration & dosage / Q000494:pharmacology*; D054773:Streptococcus gordonii / Q000187:drug effects; D014774:Virulence / Q000187:drug effects; D037521:Virulence Factors / Q000037:antagonists & inhibitors
D001427:Bacterial Toxins; D003603:Cytotoxins; D004791:Enzyme Inhibitors; D005098:Exotoxins; D006873:Hydroquinones; D012717:Sesquiterpenes; D037521:Virulence Factors; C018579:leukotoxin; D010544:Peroxidases; C006640:ascofuranone