Effects of pyrethroids on the cerebellum and related mechanisms: a narrative review

Abstract

Pyrethroids (PYRs) are a group of synthetic organic chemicals that mimic natural pyrethrins. Due to their low toxicity and persistence in mammals, they are widely used today. PYRs exhibit higher lipophilicity than other insecticides, which allows them to easily penetrate the blood-brain barrier and directly induce toxic effects on the central nervous system. Several studies have shown that the cerebellum appears to be one of the regions with the largest changes in biomarkers. The cerebellum, which is extremely responsive to PYRs, functions as a crucial region for storing motor learning memories. Exposure to low doses of various types of PYRs during rat development resulted in diverse long-term effects on motor activity and coordination functions. Reduced motor activity may result from developmental exposure to PYRs in rats, as indicated by delayed cerebellar morphogenesis and maturation. PYRs also caused adverse histopathological and biochemical changes in the cerebellum of mothers and their offspring. By some studies, PYRs may affect granule cells and Purkinje cells, causing damage to cerebellar structures. Destruction of cerebellar structures and morphological defects in Purkinje cells are known to be directly related to functional impairment of motor coordination. Although numerous data support that PYRs cause damage to cerebellar structures, function and development, the mechanisms are not completely understood and require further in-depth studies. This paper reviews the available evidence on the relationship between the use of PYRs and cerebellar damage and discusses the mechanisms of PYRs.

Keywords:

• Pyrethroids
• cerebellum
• development
• structure
• function
• mechanisms

Acknowledgments

The manuscript was prepared solely by the authors, whose contributions are declared herein. The authors thank Ximan MA, from the Office of International Affairs at China Medical University for the revision of the writing in English. Also, the authors thank the anonymous reviewers for their insight and valuable input which has improved the manuscript to its current form.

Author contributions

Fei Hao: Data curation, Investigation, Methodology, Writing an original draft, Writing review and editing. Ye Bu, Shasha Huang, Wanqi Li, Huiwen Feng: Writing review and editing. Yuan Wang: Data curation, Investigation, Writing review and editing.

Declaration of interest

The authors have no conflicts of interest to declare. The author’s affiliations are as shown on the cover page. The manuscript was written as part of the authors’ normal employment. The authors have not participated in, nor anticipate participation in, any legal, regulatory, or advocacy proceedings related to the contents of the paper. The authors had sole responsibility for the preparation of this manuscript. Opinions and conclusions expressed within are those of the authors and are not necessarily those of any sponsoring entity. This work was supported by the Natural Science Foundation of Liaoning Province, China (grant number 2020-MS-144).