Interleukin-1(beta) as a potential biomarker of methylmercury exposure in developing neural circuits of the frog, Xenopus laevis

The primary goal of this thesis was to identify new biomarkers of exposure for developing neural tissues in aquatic species. It was found that the cytokine, interleukin-1{dollar}beta{dollar} (IL-1{dollar}beta{dollar}) and its type 1 receptor are expressed in the very earliest functional neural circuits that regulate early locomotor behavior in the frog embryo. Even though IL-1{dollar}beta{dollar} is cleaved by ICE (interleukin-I{dollar}beta{dollar} converting enzyme), an enzyme that initiates apoptosis, IL-1{dollar}beta{dollar} expression is not associated with the expression of poly (ADP-ribose) polymerase (parp), a marker of apoptosis, indicating that IL-1{dollar}beta{dollar} expression is not a marker of programmed cell death in the developing frog embryo. Thus, IL-1{dollar}beta{dollar}, like other neurotrophins, may play a role in regulating cell growth or survival, or in regulating synapse formation and/or validation. Exposure of developing tadpoles to methylmercury chloride, a potent aquatic environmental contaminant, dramatically reduced IL-1{dollar}beta{dollar} levels within specific neural cell types. Thus, IL-1{dollar}beta{dollar} serves as a potential molecular biomarker of methylmercury exposure in the developing nervous system.