Induction of oxidative stress, apoptosis and DNA damage by koumine in Tetrahymena thermophila.

Qiao Ye,Jixing Zou,Aiguo Zhou,Enfeng Song,Qiong Xiang,Chaonan Zhang,Yongyong Feng,Zhenlu Wang,Shaolin Xie,Mei Li

doi:10.1371/journal.pone.0212231

Abstract

Koumine is a component of the Chinese medicinal herb Gelsemium elegans and is toxic to vertebrates. We used the ciliate Tetrahymena thermophila as a model to evaluate the toxic effects of this indole alkaloid in eukaryotic microorganisms. Koumine inhibited T. thermophila growth and viability in a dose-dependent manner. Moreover, this drug produced oxidative stress in T. thermophila cells and expressions of antioxidant enzymes were significantly elevated at high koumine levels (p < 0.05). Koumine also caused significant levels of apoptosis (p < 0.05) and induced DNA damage in a dose-dependent manner. Mitophagic vacuoles were present in cells indicating induction of autophagy by this drug. Expression of ATG7, MTT2/4, CYP1 and HSP70 as well as the MAP kinase pathway gene MPK1 and MPK3 were significantly altered after exposed to koumine. This study represents a preliminary toxicological evaluation of koumine in the single celled eukaryote T. thermophila.

Highlights

Gelsemium elegans Benth is a genus in the family Loganiaceae that are widely distributed in China and Southeast Asia, and it is highly toxic to mammals [1] and its poisoning is usually through inadvertent ingestion [2]
We used growth of T. thermophila in the presence and absence of koumine to develop an initial indication of its toxic effects under ideal growth conditions
We determined that the EC50 at 24 h was 0.23±0.04 mg/mL indicating a low tolerance for the drug

Summary

Introduction

Gelsemium elegans Benth is a genus in the family Loganiaceae that are widely distributed in China and Southeast Asia, and it is highly toxic to mammals [1] and its poisoning is usually through inadvertent ingestion [2]. G. elegans Benth is used as a Chinese folk medicine for treatment of tumors [3], neuropathic pain, inflammation [4], rheumatic arthritis [5], and anxiety [6, 7]. G. elegans contains a variety of active constituents including alkaloids, the iridoid monoterpenes and triterpenes. Over a hundred alkaloids have been identified from G. elegans and predominant indole alkaloids include koumine, gelsemine, gelsemicine, etc [8, 9]. The indole alkaloid koumine is the most abundant of these alkaloids that are structurally similar but are diverse in pharmacological action and toxicity, and its biological effects are poorly described.

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Conclusion