Thymol Induces Conidial Apoptosis in Aspergillus flavus via Stimulating K+ Eruption
Liang-Bin Hu1, Fang-Fang Ban1, Hong-Bo Li1
1Department of Food Science , Henan Institute of Science and Technology , Xinxiang 453003 , China.
Abstract:
Aspergillus flavus is a notorious foodborne fungus, posing a significant risk to humans in the form of hepatocellular carcinoma or aspergillosis. Thymol, as a food preservative, could efficiently kill conidia of A. flavus. However, the underlying mechanisms by which thymol kills A. flavus are not completely understood. With specific fluorescent dyes, we detected several apoptotic hallmarks, including chromatin condensation, phosphatidylserine externalization, DNA damage, mitochondrial depolarization, and caspase 9 activation in conidia exposed to 200 μg/mL of thymol, indicating that thymol induced a caspase-dependent conidial apoptosis in A. flavus. Chemical-protein interactome (CPI) and autodock analyses showed that KCNAB, homologue to the β-subunit of the voltage-gated potassium channel (Kv) and aldo-keto reductase, was the potential target of thymol. Following studies demonstrated that thymol could activate the aldo-keto reductase activity of KCNAB in vitro and stimulate a transient K+ efflux in conidia, as determined using a Port-a-Patch. Blocking K+ eruption by 4-aminopyridine (a universal inhibitor of Kv) could significantly alleviate thymol-mediated conidial apoptosis, indicating that activation of Kv was responsible for the apoptosis. Taken together, our results revealed a K+ efflux-mediated apoptotic pathway in A. flavus, which greatly contributed to the development of an alternative strategy to control this pathogen.
Insights
Thymol induces apoptosis in Aspergillus flavus conidia by activating a potassium (K+) efflux pathway. This discovery offers a new strategy for controlling this foodborne fungus.
Area of Science:
- Mycology
- Food Safety
- Biochemistry
Background:
- Aspergillus flavus is a significant foodborne pathogen causing diseases like aspergillosis and hepatocellular carcinoma.
- Thymol shows potential as a food preservative by killing A. flavus conidia, but its mechanism of action requires elucidation.
Purpose of the Study:
- To investigate the molecular mechanisms underlying thymol-induced cell death in A. flavus conidia.
- To identify the specific molecular targets and pathways involved in thymol's antifungal activity.
Main Methods:
- Fluorescent dyes were used to detect hallmarks of apoptosis in thymol-treated conidia.
- Chemical-protein interactome (CPI) and autodock analyses identified KCNAB as a potential thymol target.
- Port-a-Patch electrophysiology was employed to measure potassium (K+) efflux.
Main Results:
- Thymol induced caspase-dependent apoptosis in A. flavus conidia, evidenced by chromatin condensation, phosphatidylserine externalization, DNA damage, and mitochondrial depolarization.
- KCNAB, a homologue of the voltage-gated potassium channel (Kv) β-subunit, was identified as a potential target of thymol.
- Thymol activated KCNAB's aldo-keto reductase activity and stimulated a transient K+ efflux.
- Inhibition of Kv channels with 4-aminopyridine significantly reduced thymol-mediated apoptosis.
Conclusions:
- Thymol triggers apoptosis in A. flavus conidia through a novel pathway involving the activation of Kv channels and subsequent K+ efflux.
- This study reveals a K+ efflux-mediated apoptotic mechanism, providing a basis for developing alternative strategies to control A. flavus contamination.
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