Cross-Talk Between Neurons and Astrocytes in Response to Bilirubin: Early Beneficial Effects

Abstract

Hyperbilirubinemia remains one of the most frequent clinical diagnoses in the neonatal period. This condition may lead to the deposition of unconjugated bilirubin (UCB) in the central nervous system, causing nerve cell damage by molecular and cellular mechanisms that are still being clarified. To date, all the studies regarding bilirubin-induced neurological dysfunction were performed in monotypic nerve cell cultures. The use of co-cultures, where astrocyte-containing culture inserts are placed on the top of neuron cultures, provides the means to directly evaluate the cross-talk between these two different cell types. Therefore, this study was designed to evaluate whether protective or detrimental effects are produced by astrocytes over UCB-induced neurodegeneration. Our experimental model used an indirect co-culture system where neuron-to-astrocyte signaling was established concomitantly with the 24 h exposure to UCB. In this model astrocytes abrogated the well-known UCB-induced neurotoxic effects by preventing the loss of cell viability, dysfunction and death by apoptosis, as well as the impairment of neuritic outgrowth. To this protection it may have accounted the induced expression of the multidrug resistance-associated protein 1 and the 3.5-fold increase in the values of S100B, when communication between both cells was established independently of UCB presence. In addition, the presence of astrocytes in the neuronal environment preserved the UCB-induced increase in glutamate levels, but raised the basal concentrations of nitric oxide and TNF-α although no UCB effects were noticed. Our data suggest that bidirectional signalling during astrocyte-neuron recognition exerts pro-survival effects, stimulates neuritogenesis and sustains neuronal homeostasis, thus protecting cells from the immediate UCB injury. These findings may help explain why irreversible brain damage usually develops only after the first day of post-natal life.

Alterations in the Cell Cycle in the Cerebellum of Hyperbilirubinemic Gunn Rat: A Possible Link with Apoptosis?

“…However, this seems not to be our case, as FACS analysis on cerebella of hyperbilirubinemic pups confirmed a significant increase in the G0/G1 cell populations with concomitant decrease of cells in S phase. It is important to consider that the samples we analyzed (Western blot, real time PCR, FACS) represent the entire pool of cells that constitute the cerebellum, and include cells more (neurones) and less (glial cells) sensitive to bilirubin toxicity [70–73]. The presence of the less sensitive cells such as population A in Figure 5 B, might partially mask the effect of bilirubin toxicity to most sensible cells (population B, Figure 5 B), and minimize the difference between the two genotypes.…”

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

“…Additionally, in the early stages of PD, increased levels of BR were found [34]. Although BR in higher concentrations is a known neurotoxin [35,36], it has been found to exert distinct neuroprotective effects [37][38][39]. Protection is explained by the antioxidant capabilities of the BV/BR cycle, assumed to protect the membrane/water interface [40][41][42].…”

Strain-dependent brain defects in mouse models of primary ciliary dyskinesia with mutations in Pcdp1 and Spef2

“…White matter was visualized using anti-MBP (Millipore, NE1018) (Markakis et al, 2009; Steffenhagen et al, 2012) at a 1:1000 dilution. Cortical neurons were imaged using anti-MAP2 (Millipore, MAB3418) (Falcao et al, 2013; Srivastava et al, 2012) at a 1:500 dilution. Biotin-SP-conjugated AffiniPure Goat Anti-Rabbit IgG, Biotin-SP-conjugated AffiniPure Donkey Anti-Mouse IgG and Biotin-SP-conjugated AffiniPure Goat Anti-Rat IgG (Jackson ImmunoResearch) were diluted 1:1000 and used as secondary antibodies.…”