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Published on: March 6, 2018
Sublethal Exposure to a Chlorpyrifos-Cypermethrin Mixture Disrupts Limb Development and Causes Severe Skeletal
Shashikant Sharma1, Juhi Vaishnav2, Pooja Raval1
1Department of Zoology, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India.
Insights
A combination insecticide containing chlorpyrifos (CP) and cypermethrin (CM) caused severe limb malformations in chick embryos by disrupting key developmental pathways. This highlights the need for stricter pesticide regulations to prevent birth defects.
Area of Science:
- Developmental Biology
- Toxicology
- Molecular Biology
Background:
- Pesticide exposure is a growing concern for developmental health.
- Sublethal doses of insecticides may cause adverse effects on embryonic development.
- Chick embryos are a valuable model for studying teratogenic effects.
Purpose of the Study:
- To investigate the teratogenic effects of a chlorpyrifos (CP) and cypermethrin (CM) combination insecticide on chick embryo limb development.
- To identify the molecular pathways disrupted by this insecticide exposure.
- To assess the binding interactions of CP and CM with key developmental proteins.
Main Methods:
- Chick embryos were exposed to a sublethal dose (0.1 ppm) of CP and CM combination insecticide.
- Limb development was assessed via morphological analysis, X-ray, and Alcian blue-Alizarin red staining.
- Gene and protein expression of key developmental pathways (SHH, FGF, WNT, HOX, Tbx4, Pitx1, CASPASE3) were analyzed.
- Molecular docking and biochemical assays (hydroxyproline content) were performed.
Main Results:
- Significant skeletal abnormalities, including limb shortening and digit malformations, were observed.
- Downregulation of SHH, FGF10, FGF8, and WNT7A impaired digit formation and limb elongation.
- Disruption of HOX gene expression affected limb segment identity.
- CP and CM showed strong binding affinities to SHH, FGF10, WNT7A, and HOX proteins.
- Impaired apoptosis and reduced collagen synthesis were noted.
Conclusions:
- The CP and CM combination insecticide causes severe teratogenic effects on chick embryo limb development.
- Disruption of the SHH-FGF-WNT signaling axis is a primary mechanism underlying these defects.
- Findings underscore the potential risks of pesticide exposure and advocate for stricter regulations to prevent congenital malformations.
Abstract:
This study examines the teratogenic effects of a sublethal dose (0.1 ppm) of a combination insecticide containing 50% chlorpyrifos (CP) and 5% cypermethrin (CM) on chick embryo limb development, revealing severe skeletal abnormalities and disruptions in key molecular pathways. Early-stage defects, including reduced somite numbers and abnormal somite patterning, were observed by day 2, with prominent limb deformities, such as limb shortening and twisted digits, emerging by days 10 and 21. X-ray analysis confirmed skeletal anomalies, while Alcian blue-Alizarin red staining revealed malformed cartilage and bone structures. Gene and protein expression analyses showed significant downregulation of Sonic hedgehog (SHH), Fibroblast Growth Factors (FGF10, FGF8), and WNT7A, leading to impaired digit formation and limb elongation. HOX genes (HOXA11, HOXD11) were initially upregulated but later downregulated, disrupting limb segment identity. Additionally, downregulation of Tbx4 and Pitx1 contributed to hindlimb malformations. Dysregulation of CASPASE3 impaired apoptosis, resulting in defective digit separation. Molecular docking studies indicated strong binding affinities of CP and CM to SHH, FGF10, WNT7A, and HOX proteins, suggesting interference with these signaling pathways. Notably, the disruption of the SHH-FGF-WNT axis, essential for limb patterning, was a key driver of these defects. Biochemical assays further revealed reduced hydroxyproline content, indicating impaired collagen synthesis. These findings highlight severe disruptions in SHH, FGF, WNT, HOX, Tbx4, and Pitx1 pathways, emphasizing the need for stricter pesticide regulations to prevent congenital limb malformations.
