Roadway runoff exposure disrupts the blood-brain barrier in juvenile coho salmon

Coho salmon (Oncorhynchus kisutch) are highly sensitive to urban runoff exposure and are an important ecological indicator for emerging contaminants. Recurrent die-offs of adult prespawn coho salmon in urban streams are attributed to the newly discovered tire chemical 6PPD-quinone. Juvenile coho salmon lethally exposed to roadway runoff and 6PPD-quinone demonstrate a similar progression of behavioral symptoms. In previous studies, we demonstrated that juvenile coho exposed to roadway runoff show blood-brain barrier disruption concurrent with severe rises in hematocrit. This suggests that cause of death may be due to loss of neuronal function following increased permeability of cerebral vessels and plasma leakage. In more recent studies, we used high and low molecular weight fluorescent tracers to evaluate the timing and severity of blood-brain barrier disruption in juvenile coho exposed to roadway runoff. We provide additional quantitative and qualitative evidence that blood-brain barrier disruption is closely related to symptom development. Therefore, mechanisms leading to blood-brain barrier disruption in coho salmon are likely important to understand the toxic mode of action of 6PPD-quinone and the unique sensitivity of coho to this ubiquitous contaminant.