Artemisinin occurs naturally in the leaves of the sweet wormwood, a sweetly aromatic herb with small, yellow flower heads and the source of the Traditional Chinese Medicine ‘Qing Hao.’
The compound is a potent anti-malarial agent, and can kill highly drug-resistant strains.
In the new study, artemisinin stopped the ability of Mycobacterium tuberculosis(Mtb), the causative agent of tuberculosis, to become dormant. This stage of the disease often makes the use of antibiotics ineffective.
“When Mtb are dormant, they become highly tolerant to antibiotics. Blocking dormancy makes the bacteria more sensitive to these drugs and could shorten treatment times,” Dr. Abramovitch said.
Mtb needs oxygen to thrive in the body. The immune system starves this bacterium of oxygen to control the infection.
Dr. Abramovitch and co-authors found that artemisinin attacks a molecule called heme, which is found in the Mtb oxygen sensor.
By disrupting this sensor and essentially turning it off, artemisinin stopped the disease’s ability to sense how much oxygen it was getting.
“When the Mtb is starved of oxygen, it goes into a dormant state, which protects it from the stress of low-oxygen environments. If Mtb can’t sense low oxygen, then it can’t become dormant and will die,” Dr. Abramovitch said.
The researchers indicated that dormant Mtb can remain inactive for decades in the body. But if the immune system weakens at some point, it can wake back up and spread. Whether it wakes up or stays ‘asleep’ though, Mtb can take up to six months to treat and is one of the main reasons the disease is so difficult to control.
After screening 540,000 different compounds, the authors also found five other possible chemical inhibitors that target the Mtb oxygen sensor in various ways and could be effective in treatment as well.
The research could be key to shortening the course of therapy because it can clear out the dormant, hard-to-kill bacteria. This could lead to improving patient outcomes and slowing the evolution of drug-resistant Mtb.
