A Common Carcinogen Benzo[a]pyrene Causes Neuronal Death in Mouse via Microglial Activation

BACKGROUND: Benzo[a]pyrene (B[a]P) belongs to a class of polycyclic aromatic hydrocarbons that serve as micropollutants in the environment. B[a]P has been reported as a probable carcinogen in humans. Exposure to B[a]P can take place by ingestion of contaminated (especially grilled, roasted or smoked) food or water, or inhalation of polluted air. There are reports available that also suggests neurotoxicity as a result of B[a]P exposure, but the exact mechanism of action is unknown. METHODOLOGY/PRINCIPAL FINDINGS: Using neuroblastoma cell line and primary cortical neuron culture, we demonstrated that B[a]P has no direct neurotoxic effect. We utilized both in vivo and in vitro systems to demonstrate that B[a]P causes microglial activation. Using microglial cell line and primary microglial culture, we showed for the first time that B[a]P administration results in elevation of reactive oxygen species within the microglia thereby causing depression of antioxidant protein levels; enhanced expression of inducible nitric oxide synthase, that results in increased production of NO from the cells. Synthesis and secretion of proinflammatory cytokines were also elevated within the microglia, possibly via the p38MAP kinase pathway. All these factors contributed to bystander death of neurons, in vitro. When administered to animals, B[a]P was found to cause microglial activation and astrogliosis in the brain with subsequent increase in proinflammatory cytokine levels. CONCLUSIONS/SIGNIFICANCE: Contrary to earlier published reports we found that B[a]P has no direct neurotoxic activity. However, it kills neurons in a bystander mechanism by activating the immune cells of the brain viz the microglia. For the first time, we have provided conclusive evidence regarding the mechanism by which the micropollutant B[a]P may actually cause damage to the central nervous system. In today's perspective, where rising pollution levels globally are a matter of grave concern, our study throws light on other health hazards that such pollutants may exert

Citizen science to monitor the distribution of the Egyptian mongoose in southern Spain: who provide the most reliable information?

The Egyptian mongoose (Herpestes ichneumon L.) is a medium-size carnivore widely distributed in Africa and in a small part of southern Europe, the Iberian Peninsula, where mongoose populations have recently expanded. The mongoose is relatively easily detectable because of its diurnal habits and because it is the only species of Herpestidae occurring in the Iberian Peninsula. Therefore, its distribution could be monitored through citizen science. In this sense, information provided by stakeholders that make frequent use of natural environments, including hunters, landowners, or wildlife rangers, would be potentially very valuable. Nevertheless, the accuracy of the information provided by these stakeholders as regards mongoose occurrence has never been tested. To do so, we compared mongoose occurrences gathered through field transects (i.e., 2-km walking surveys in which direct observations and indirect signs were recorded) carried out in 218 Andalusian municipalities during 2010–2015 with those obtained through questionnaires conducted in 2016 to hunters (n = 251), landowners (n = 116), and wildlife rangers (n = 133). We did not find any significant difference between mongoose distribution estimated by the reference method (i.e., field surveys) and by questionnaire to wildlife rangers. In contrast, mongoose occurrences reported by hunters and landowners were significantly correlated among them, but not with those collected in field transects (nor with those provided by the rangers). This suggests that a participatory network for monitoring mongoose distribution could rely on the information provided by wildlife rangers. Previous studies showed that hunters can provide useful information from less accessible areas like private estates where official data are not collected. In this sense, our results suggest that further effort is needed to incorporate hunters and landowners in a participatory network to monitor mongoose distribution, and this could include collaborative actions to promote their involvement in addition to increasing their skills in mongoose detection.This study is framed within the projects INIA-CON15-189, RTI2018-096348-RC21, and SBPLY/17/180501/000184