In Vitro Human Dermal Absorption Studies on Pesticides in Complex Mixtures: Investigation of Guidance Criteria and Possible Impact Parameters.

Pesticides must not pose unacceptable risks to human health, so risk assessments are conducted before products are authorised. Dermal exposure is often the main route of intake, so estimating realistic and trustworthy dermal absorption values is crucial for risk assessment. Although there are agreed test guidelines for in vitro dermal absorption studies, not every product is tested due to cost reasons. The present dataset consists of 945 individual in vitro experiments on the dermal absorption of human skin with 179 active substances of pesticides in 353 different mixtures, including concentrates and dilutions. The dataset was evaluated to identify the possible impacts of experimental conditions and physico-chemical properties on dermal absorption. The dataset was also analysed to assess the appropriateness of the pro rata correction for untested dilutions, and the set concentration cut-off to decide on the dilution status for choosing a default value on dermal absorption. The study found that the implementation of specific guidelines improved the harmonisation of study conduct, with support for approaches such as pro rata correction and default values. Further analysis of the specific co-formulants may identify influencing factors that may be more important than the experimental variables.

N-Terminal Truncated Aß4-42 Is a Substrate for Neprilysin Degradation in vitro and in vivo.

In sporadic Alzheimer's disease (AD), an imbalance between production and clearance of amyloid-ß (Aß) peptides seems to account for enhanced Aß accumulation. The metalloprotease neprilysin (NEP) is an important Aß degrading enzyme as shown by a variety of in vitro and in vivo studies. While the degradation of full-length Aß peptides such as Aß1-40 and Aß1-42 is well established, it is less clear whether NEP is also capable of degrading N-terminally truncated Aß species such as the common variant Aß4-42. In the present report, we confirmed the degradation of Aß4-x species by neprilysin using in vitro digestion and subsequent analysis using gel-based assays and mass spectrometry. By crossing Tg4-42 mice expressing only Aß4-42 peptides with homozygous NEP-knock-out mice (NEP-/-), we were able to demonstrate that NEP deficiency increased hippocampal intraneuronal Aß levels and aggravated neuron loss in the Tg4-42 transgenic mouse model of AD.