Figure 4.

Exposure of immature hippocampal neurons to unconjugated bilirubin (UCB) impairs neuronal arborization by reducing axonal ramification and dendritic output, while increasing microtubule stability by changing the expression and localization patterns of the microtubule (MT) associated protein 2 (MAP2) and Tau1. Embryonic hippocampal neurons were treated with vehicle (human serum albumin, HSA) alone (control) or with UCB 100 μM (UCB/HSA = 1) for 24 h at 1 day in vitro (DIV) and fixed at 3 DIV. Representative images of hippocampal neurons immunostained with MAP2 (green) to identify the cell body and dendrites, and Tau1 (red) to identify the axon, are shown in (A) for control and (B) for UCB. UCB induces MAP2 axonal entry, evidenced by the white arrowheads pointing to the portion of axon with MAP2 entry, and a decrease in the number of axonal and dendritic branches when compared with HSA alone. Graph bars representing total and MT-bound Tau1 are shown in (C) illustrating that UCB induces axonal expression of Tau1. Percentage of Rel-Tau1 and MT-Tau1 in the pie chart in (D) depicts that part of Tau1 will be increasingly bound to microtubules (MT-Tau) (C,D), although the major portion is released (Rel-Tau), as illustrated in (D). Data derived from Fernandes et al. (2009a, 2010).