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Infection and Immunity, February 2000, p. 877-883, Vol. 68, No. 2
Microscopy Branch, National Institute of
Allergy and Infectious Diseases, National Institutes of Health,
Rocky Mountain Laboratories, Hamilton, Montana 59840
Received 15 September 1999/Accepted 27 October 1999
Mycobacterium ulcerans is the causative agent of Buruli
ulcer, a tropical ulcerative skin disease. One of the most intriguing aspects of this disease is the presence of extensive tissue damage in
the absence of an acute inflammatory response. We recently purified and
characterized a macrolide toxin, mycolactone, from M. ulcerans. Injection of this molecule into guinea pig skin
reproduced cell death and lack of acute inflammatory response similar
to that seen following the injection of viable bacteria. We also showed
that mycolactone causes a cytopathic effect on mouse fibroblast L929
cells that is characterized by cytoskeletal rearrangements and growth
arrest within 48 h. However, these results could not account for
the extensive cell death which occurs in Buruli ulcer. The results
presented here demonstrate that L929 and J774 mouse macrophage cells
die via apoptosis after 3 to 5 days of exposure to mycolactone.
Treatment of cells with a pan-caspase inhibitor can inhibit
mycolactone-induced apoptosis. We demonstrate that injection of
mycolactone into guinea pig skin results in cell death via
apoptosis and that the extent of apoptosis increases as the lesion
progresses. These results may help to explain why tissue damage
in Buruli ulcer is not accompanied by an acute inflammatory response.
0019-9567/00/$04.00+0
A Mycobacterium ulcerans Toxin,
Mycolactone, Causes Apoptosis in Guinea Pig Ulcers and Tissue
Culture Cells
*
Corresponding author. Mailing address: Microscopy
Branch, NIAID/NIH, Rocky Mountain Laboratories, 903 S 4th
St., Hamilton, MT 59840. Phone: (406) 363-9280. Fax: (406) 363-9371. E-mail: psmall{at}niaid.nih.gov.
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