Two-Hit Exposure to Lipopolysaccharide and Acetaminophen Alters Larval Zebrafish (Danio rerio) Swim Behavior

Acetaminophen (APAP) has been implicated in the etiology of developmental disorders. While rodent models have demonstrated lasting neurobehavioral changes following prenatal and/or perinatal exposure to APAP, few studies have examined such effects in zebrafish (Danio rerio), and none have done so in the translationally relevant context of systemic inflammation. Zebrafish eggs were treated with Escherichia coli-derived lipopolysaccharide (LPS) and/or APAP in the first 24 h postfertilization (hpf). At 96 hpf, larval behavior was recorded during a light/dark transition test. Results showed embryonic APAP exposure elevated swim velocity, with APAP-treated larvae displaying more activity than those not treated with APAP. We also found significant interaction between LPS and APAP exposures, with "two-hit" LPS + APAP larvae exhibiting increased activity relative to LPS- and APAP-only groups during the dark phase. APAP-treated larvae also exhibited greater activity than controls during the light phase. In addition, LPS + APAP larvae displayed significantly fewer clockwise relative to counterclockwise rotations compared to LPS-only larvae. To explore a potential mechanism underlying observed behavioral differences, we analyzed glycogen synthase kinase-3 (GSK-3) Y216+Y279 ɑ/β phosphorylation and total levels in homogenized whole-brain tissue. Unexpectedly, the ratio of pGSK-3/total GSK-3 was not affected by any treatments. Nevertheless, this study demonstrates the utility of zebrafish as a model for studying the combinatorial effects of exposures such as inflammation and APAP early in life.