Study of troponin, creatine kinase biomarkers, and histopathological lesions in experimental Nerium oleander toxicity in rats and mice

Screening tools to evaluate the neurotoxic potential of botanicals: building a strategy to assess safety

AREAS COVERED

This paper outlines the selection of NAMs, including in vitro assays using primary rat cortical neurons, zebrafish embryos, and Caenorhabditis elegans. These assays aim to assess neurotoxic endpoints such as neuronal activity and behavioral responses. Microelectrode array recordings of rat cortical neurons provide insights into the impact of botanical extracts on neuronal function, while the zebrafish embryos and C. elegans assays evaluate neurobehavioral responses. The paper also provides an account of the selection of botanical case studies based on expert judgment and existing neuroactivity/toxicity information. The proposed battery of assays will be tested with these case studies to evaluate their utility for neurotoxicity screening.

EXPERT OPINION

The complexity of botanicals necessitates the use of multiple NAMs for effective neurotoxicity screening. This paper discusses the evaluation of methodologies to develop a robust framework for evaluating botanical safety, including complex neuronal models and key neurodevelopmental process assays. It aims to establish a comprehensive screening framework.

Toxicity effects of Nerium oleander, basic and clinical evidence: A comprehensive review

Introduction:

Nerium oleander is a plant that is frequently grown in gardens and public areas. N. oleander is distributed originally in subtropical Asia but is now growing in many parts of the world, such as the United States, Australia, China, and Middle East countries. Pharmacological effects of plant including antinociceptive, anti-inflammatory, and anticancer activity were reported, but the potential toxic effects of all parts of the shrub either fresh or dried on animal and human body were documented.

Method:

The data of this review article were obtained from Medline/Pubmed, Scopusand Google Scholar databases in English until September 2019. To include all publications in this field, keywords such as N. oleander and toxicity were used.

Results:

The poisoning effects of plant or their active alkaloids induced infiltration of cells with hemorrhage and sever negative changes in the lung, induce lesions, and infiltration of inflammatory cells into the portal spaces with scattered necrosis of hepatocytes in the liver, cardiac toxicity of the plant in the heart were included, induced varying degrees of hemorrhage, myocardial degeneration, and necrosis. It also induced arrhythmia, sinus bradycardia, and prolonged P-R interval in electrocardiographic records.

Conclusions:

The toxic effects of N. oleander are mostly related to its inhibitory effects on the Na+-K+ ATPase pump in the cellular membrane. However, the exact molecular mechanism involved in the toxicity of N. oleander is not clear.

Circadian sensitivity to the cardiac glycoside oleandrin is associated with diurnal intestinal P-glycoprotein expression

The cardiac glycoside oleandrin is a main active constituent of the botanical anti-cancer drug candidate PBI-05204, an extract of Nerium oleander. Here, we aimed to determine the circadian sensitivity of mice to oleandrin, and to investigate the role of intestinal P-gp in generating rhythmic drug toxicity. Toxicity and pharmacokinetic experiments were performed with wild-type, Bmal1iKO (intestine-specific Bmal1 knockout) and Bmal1fl/fl (control littermates of Bmal1iKO) mice. The cardiac toxicity (reflected by plasma CK-MB, LDH and cTn-I levels) varied significantly with the times of drug dosing in wild-type mice (a lower toxicity at ZT10 and more severe at ZT2/22). Dosing at ZT2 generated a higher drug exposure than ZT10, supporting a lower toxicity at ZT10. Intracellular accumulation of oleandrin (2.5-10 μM) was reduced in MDCKⅡ-MDR1 than in parental cells. MDR1 overexpression decreased the cell sensitivity to oleandrin toxicity. The net flux ratio (MDCKⅡ-MDR1 versus parental cells) was 2.9 for oleandrin. These data indicated oleandrin as a P-gp substrate. Both mdr1a mRNA and P-gp protein oscillated with the times of the day in small intestine of Bmal1fl/fl mice. Intestinal ablation of Bmal1 down-regulated mdr1a mRNA and P-gp protein, and abrogated their rhythms. Likewise, Bmal1 silencing led to down-regulated mdr1a mRNA and to a loss of its rhythmicity in serum-shocked CT26 cells. Based on luciferase reporter assays, Bmal1 regulated rhythmic mdr1a transcription through the clock output genes Hlf and E4bp4. Intestinal ablation of Bmal1 exacerbated oleandrin toxicity and enhanced drug exposure. Moreover, time dependency of toxicity and drug exposure were lost in Bmal1iKO mice. In conclusion, diurnal intestinal P-gp is a critical factor influencing daily oleandrin exposure and toxicity. Our findings have implications in minimizing oleandrin (and possibly Nerium oleander) toxicity and improving drug efficacy via dosing time optimization.