Effect of pesticides on memory
Memory formation is fundamental for responding to the fluctuation of the environment and allowing behavioural adaptation. The neurotransmitter Acethylcholine (ACh) plays a major regulatory role in this area, as it is involved in both learning and memory retrieval. A growing body of evidence suggests that the ACh signalling pathway is disrupted after chronic exposure to next-generation pesticides. The difficulty in providing new information on the mechanism of action of these pesticides and their consequences on observed cognitive dysfunction lies, in part, in that the deregulation of ACh acts at different time points and on several organizational scales (behavioural, cellular and molecular). To understand how exposures to non-lethal doses of pesticides affect cognitive functions in the long term, our laboratory uses the honeybee as a model organism. Free-flying honeybees are thus subjected to memory behavioural paradigms within their natural environment in order to test their cognitive capacities with or without exposure to pesticides. We combine techniques able to detect localized brain changes at a single cell resolution as well as high throughput sequencing techniques - using Oxford Nanopore MinION sequencer - to describe transcriptomic and epigenetic dynamics during memory formation. This holistic approach aims to identify fundamental mechanisms of the ACh-dependent memory formation at different biological scales and then provide insight into neuropathologies related to chronic exposure to pesticides.
Cellular resilience is the ability for cells to recover from exposure to a toxic agent. After exposure to a non-lethal dose of a chemical, cellular metabolism will rapidly ensue functional responses that will reprogram cells back toward a homeostatic state. Whether temporary functional impairments caused by exposure will be fully restore or whether there will be persistent cell changes, is not yet clear. Recent evidences show that just like humans, honeybees are subject to widespread bioaccumulation of chemicals in their body that can impair brain cell functions and, in the long-term, manifest as chronic and delayed behavioural disorders. For instance, exposure to chemicals acaricides linked to beekeeping practices rarely result in immediate effects on honeybee behaviours and therefore on the functioning of the colony. Instead, colonies exhibit slow productivity impairment over time, indicating that residual effects of the chemical might have persisted and led to deleterious changes in honeybee brains. To determine to which extent reprogramming mechanisms allowing cellular resilience are restored, we are monitoring the recovery of honeybees after one-time exposure to chemical acaricides exhibiting different ranges of toxicities. After the removal of the chemical agent, we analyse the long-term relationship between the level of intoxication detected in honeybee brains (chemical profile by Mass Spectrometry) and their transcriptomic dynamics (RNA-seq). Our objective is to identify functions involved in cellular resilience after acaricide exposure as well as the cellular functions that might have been altered in the long term.
In Collaboration with Dr. Fani Hatjina Department of Beekeeping - Institute of Animal Production Science ELGO "DIMITRA"
Due to the complexity of environmental factors influencing organism's survival, scientists have traditionally used simplified approaches - in the laboratory - to study the effects of a specific factor on a particular species. When studying free-flying bees, it seems therefore virtually impossible to control the numerous environmental variables in which honeybees are subjected which might, to some extent, influence their cognitive skills and abilities to respond to environmental threats. Indeed, forager honeybees interact directly with numerous external factors (nectar and pollen of flowers, potential pathogens, chemicals, etc.) and, importantly, they bring back many of these external factors to their hive. Hence, all traces of their interactions are documented inside the produced honey. Thanks to this unique behaviour, we thereby benefit from a extraordinary natural biomarker of the surrounding biodiversity. Our laboratory applies and optimizes a metagenomic approach allowing the isolation of all environmental DNAs contained in honey and thus characterizes all species (plants, bacteria, viruses and fungi) interacting with the honeybees. Analysis of these sequencing data aims to impartially describe the complexity and dynamics of the micro-ecosystems surrounding honeybees and to better discern the factors influencing their health and survival.