A new study in "Environmental Pollution" looked at the expression pattern of multiple genes after exposure to 4 different types of pesticides (these having 4 modes of action) that were administered at "field realistic" doses.  They found impacts on the immune function and implied effects on foraging ability of the bees.  "Implied effects" were suggested because they found altered vitellogenin expression patterns.





Exposure of honey bees (Apis mellifera) to different classes of insecticides exhibit distinct molecular effect patterns at concentrations that mimic environmental contamination

  *   Verena Christen<http://www.sciencedirect.com/science/article/pii/S0269749117305419#>a<http://www.sciencedirect.com/science/article/pii/S0269749117305419#aff1>,

  *   Karl Fent<http://www.sciencedirect.com/science/article/pii/S0269749117305419#>a<http://www.sciencedirect.com/science/article/pii/S0269749117305419#aff1>, b<http://www.sciencedirect.com/science/article/pii/S0269749117305419#aff2>, <http://www.sciencedirect.com/science/article/pii/S0269749117305419#cor1> , <mailto:[log in to unmask]> ,



  *   <mailto:[log in to unmask]>



  *   a University of Applied Sciences and Arts Northwestern Switzerland, School of Life Sciences, Gründenstrasse 40, CH-4132 Muttenz, Switzerland

  *   b Swiss Federal Institute of Technology Zürich (ETH Zürich), Department of Environmental System Sciences, Institute of Biogeochemistry and Pollution Dynamics, CH-8092 Zürich, Switzerland



Highlights



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4 insecticides with different modes of action were studied for transcriptional effects.



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Transcriptional effects pattern indicated adverse outcome pathways of insecticides.



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Effects pattern in bees were compound-specific and dynamic in time.



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Lowest observed effects were within or lower than environmental concentrations.



Abstract



Pesticides are implicated in the decline of honey bee populations. Many insecticides are neurotoxic and act by different modes of actions. Although a link between insecticide exposure and changed behaviour has been made, molecular effects underlying these effects are poorly understood. Here we elucidated molecular effects at environmental realistic concentrations of two organophosphates, chlorpyrifos and malathion, the pyrethroid cypermethrin, and the ryanodine receptor activator, chlorantraniliprole. We assessed transcriptional alterations of selected genes at three exposure times (24 h, 48 h, 72 h) in caged honey bees exposed to different concentrations of these compounds. Our targeted gene expression concept focused on several transcripts, including nicotinic acetylcholine receptor α 1 and α 2 (nAChRα1, nAChRα2) subunits, the multifunctional gene vitellogenin, immune system related genes of three immune system pathways, genes belonging to the detoxification system and ER stress genes. Our data indicate a dynamic pattern of expressional changes at different exposure times. All four insecticides induced strong alterations in the expression of immune system related genes suggesting negative implications for honey bee health, as well as cytochrome P450 enzyme transcripts suggesting an interference with metabolism. Exposure to neurotoxic chlorpyrifos, malathion and cypermethrin resulted in up-regulation of nAChRα1 and nAChRα2. Moreover, alterations in the expression of vitellogenin occurred, which suggests implications on foraging activity. Chlorantraniliprole induced ER stress which may be related to toxicity. The comparison of all transcriptional changes indicated that the expression pattern is rather compound-specific and related to its mode of action, but clusters of common transcriptional changes between different compounds occurred. As transcriptional alterations occurred at environmental concentrations our data provide a molecular basis for observed adverse effects of these insecticides to bees.



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I am interested in the possibility that reduced immune system function in the honeybee may impact their susceptibility to viruses.  Here in New York State, we have had severe winter losses in recent years that in many cases correlate with evidence of late summer viral infections.  Recently some work has shown that mite control is not enough to prevent hive collapse due to viral loads, thus treating bees for mites is not enough to ensure they don't succumb to viruses over the winter months.  This suggests to me that the bee immune system is not working well.  The honeybee immune system is different to human immunity in that it emphasizes different aspects of the defense system against pathogens.  For instance, honeybee behavior is more important to honeybee immunity against bacterial and viral pathogens than human behavior is important to human immunity against bacterial and viral pathogens.  Humans respond well to vaccines, but due to the mechanism for action of a vaccine, this approach is unlikely to be helpful in tackling honeybee health.



In a perfect world there would be fewer toxins and honeybees would naturally become healthier.  But in the world we have, bees' immune systems are depressed and we are losing them to viral diseases when multiple stressors are present including sustained periods of confinement due to subzero weather.   We need a way to help boost our bees' immune systems.





Christina



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