Transcriptome profile of Haemaphysalis longicornis (Acari: Ixodidae) exposed to Cymbopogon citratus essential oil and citronellal suggest a cytotoxic mode of action involving mitochondrial Ca2+ overload and depolarization

Abstract Background: The tick Haemaphysalis longicornis is well known as vector of several zoonotic pathogens responsible for various clinical conditions, increasingly threatens the veterinary and public health. It is mainly distributed in East Asia, New Zealand, Australia, and several Pacific islands, and has been expanded rapidly in United States since its first founding on a nonimported domestic sheep in New Jersey. Glutathione S-transferases (GSTs) are phase II detoxification enzymes, which function via combining with pesticidal molecules and catalyzing the conjugation of molecules by thiol of glutathione, so as to protect tissues from oxidative stress damage. In the tick H. longicornis, glutathione S-transferases (HlGST and HlGST2) have been previously identified. However, the relationship between the expression of glutathione S-transferases and the essential oil treatment in ticks remains unexplored. Hence, in the present study, the expression profiles of HlGST and HlGST2 mRNAs were evaluated in H. longicornis after exposure to Cymbopogon citratus essential oil. Results: At 24 h post-exposure of H. longicornis to different sublethal concentrations of C. citratus essential oil, ANOVA results revealed significant difference (F2,6 = 55.94, P = 0.0001) in the expression of HlGST. Tukey’s test showed that HlGST was significantly induced after treatment with 1% C. citratus essential oil (P = 0.0002); whereas no significant difference (P = 0.3551) was detected after treated by 2% C. citratus essential oil. No significant difference (F2,6 = 0.8990, P = 0.4555) in the expression of HlGST2 between the treatment and the control group of 50% ethanol. Nevertheless, the under-expression of HlGST2 in the treatment groups versus the untreated control group was not significant (F3,8 = 2.643, P = 0.1208). Conclusion: The results implied that GST mRNA is a potential molecular target for C. citratus essential oil in H. longicornis. Further understanding of the underlying mechanisms of the GST at the molecular level could contribute to develop effective control measures for ticks and tick-borne diseases.

Download Full-text

Expression profiles of glutathione S-transferases genes in semi-engorged Haemaphysalis longicornis (Acari: Ixodidae) exposed to Cymbopogon citratus essential oil

Systematic and Applied Acarology ◽

10.11158/saa.25.5.12 ◽

2020 ◽

Vol 25 (5) ◽

pp. 918-930

Author(s):

Desmond O. Agwunobi ◽

Tingwei Pei ◽

Jia Yang ◽

Xiaoshuang Wang ◽

Lihong Lv ◽

...

Keyword(s):

Essential Oil ◽

Expression Profiles ◽

Control Measures ◽

Detoxification Enzymes ◽

Effective Control ◽

Control Group ◽

Haemaphysalis Longicornis ◽

Cymbopogon Citratus ◽

Significant Difference ◽

Glutathione S Transferases

Glutathione S-transferases (GSTs) are phase II detoxification enzymes, which function via combining with pesticidal molecules and catalyzing the conjugation of molecules by thiol of glutathione, so as to protect tissues from oxidative stress damage. In the tick Haemaphysalis longicornis, glutathione S-transferases (HlGST and HlGST2) have been previously identified. However, the relationship between the transcription of glutathione S-transferases and the essential oil treatment in ticks remains unexplored. Hence, in the present study, the transcription profiles of HlGST and HlGST2 mRNAs were evaluated in H. longicornis after exposure to Cymbopogon citratus essential oil. At 24 h post-exposure of H. longicornis to different sublethal concentrations of C. citratus essential oil, there was significant difference (P = 0.0001) in the transcription of HlGST. Tukey’s test showed that HlGST was significantly induced after treatment with 1% C. citratus essential oil (P = 0.0002); whereas no significant difference (P = 0.3551) was detected after treated by 2% C. citratus essential oil. No significant difference (P = 0.4555) in the transcription of HlGST2 between the treatment and the control group of 50% ethanol. Nevertheless, the down-regulation of HlGST2 in the treatment groups versus the untreated control group was not significant (P = 0.1208). The above results imply that the essential oil can modulate the expression of GST mRNA, therefore, further understanding of the underlying mechanisms of the GST at the molecular level could contribute to the development of effective control measures for ticks and tick-borne diseases.

Download Full-text

Cymbopogon citratus essential oil-induced ultrastructural & morphological changes in the midgut, cuticle & Haller’s organ of the tick Haemaphysalis longicornis (Acari: Ixodidae)

Systematic and Applied Acarology ◽

10.11158/saa.25.11.10 ◽

2020 ◽

Vol 25 (11) ◽

pp. 2047-2062

Author(s):

Desmond O. Agwunobi ◽

Yuhong Hu ◽

Zhijun Yu ◽

Jingze Liu

Keyword(s):

Essential Oil ◽

Morphological Changes ◽

Immersion Test ◽

Tick Control ◽

Haemaphysalis Longicornis ◽

Cymbopogon Citratus ◽

Promising Alternative ◽

Cytoplasmic Vacuolization ◽

Haller's Organ ◽

Lemongrass Essential Oil

Haemaphysalis longicornis Neumann is a widely distributed species known for its capacity to transmit pathogens of medical, public health, and veterinary importance. Due to the environmental contamination caused by synthetic acaricides, plant essential oils have emerged as a promising alternative to manage tick infestation. This study evaluated the ultrastructural and morphological changes induced by Cymbopogon citratus Stapf (lemongrass) essential oil on adult H. longicornis tick. The concentrations of lemongrass essential oil used for the treatment via the adult immersion test were from 10 to 40 mg/mL. The most significant alterations 24 h post-exposure include the proliferation of lysosomes, reduction in the number of the rough endoplasmic reticulum, disorganization of the microvilli, the disappearance of lipid droplets and hematin granules, and cytoplasmic vacuolization (midgut); a thinner endocuticle and epicuticle, the deletion of the subdivision’s demarcation of the procuticle, disfiguration of the lamellar arrangements of the exocuticle, and cytoplasmic vacuolization of the epithelial cells (integument); cracks on the sensilla sockets, the detachment of one or two sensilla in the anterior pit, and partial disfiguration of part of the slit’s edge (Haller’s organ). These results reflect the acaricidal properties of the essential oil and could be an alternative means of tick control.

Download Full-text