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

Abstract

Severe hyperbilirubinemia causes neurological damage both in humans and rodents. The hyperbilirubinemic Gunn rat shows a marked cerebellar hypoplasia. More recently bilirubin ability to arrest the cell cycle progression in vascular smooth muscle, tumour cells, and, more importantly, cultured neurons has been demonstrated. However, the involvement of cell cycle perturbation in the development of cerebellar hypoplasia was never investigated before. We explored the effect of sustained spontaneous hyperbilirubinemia on cell cycle progression and apoptosis in whole cerebella dissected from 9 day old Gunn rat by Real Time PCR, Western blot and FACS analysis. The cerebellum of the hyperbilirubinemic Gunn rats exhibits an increased cell cycle arrest in the late G0/G1 phase (p < 0.001), characterized by a decrease in the protein expression of cyclin D1 (15%, p < 0.05), cyclin A/A1 (20 and 30%, p < 0.05 and 0.01, respectively) and cyclin dependent kinases2 (25%, p < 0.001). This was associated with a marked increase in the 18 kDa fragment of cyclin E (67%, p < 0.001) which amplifies the apoptotic pathway. In line with this was the increase of the cleaved form of Poly (ADP-ribose) polymerase (54%, p < 0.01) and active Caspase3 (two fold, p < 0.01). These data indicate that the characteristic cerebellar alteration in this developing brain structure of the hyperbilirubinemic Gunn rat may be partly due to cell cycle perturbation and apoptosis related to the high bilirubin concentration in cerebellar tissue mainly affecting granular cells. These two phenomena might be intimately connected.

Evaluation of region selective bilirubin-induced brain damage as a basis for a pharmacological treatment

“…This finding is in line with what has been reported in animal models. In both Gunn rats and UGT−/− mice, cerebellar damage took at least 7–9 days to become significant and was not detectable at early post-natal ages, despite the presence of hyperbilirubinemia early after birth34364041424344. Also in line with this hypothesis is the observation that 4 days of exposure to 140-nM Bf increased LDH release (>2.0-fold) in our Cll OBCs (data not shown).…”

“…Cerebellar hypoplasia due to bilirubin toxicity is a landmark finding of animal models of hyperbilirubinemia34364041424344 and is reported in pre-term babies4546. In our model, we found regions of the brain susceptible to an acute exposure (24 hrs) to UCB (Hip, IC) and others that are not.…”

CyclinD1 Down‐Regulation and Increased Apoptosis Are Common Features of Cohesinopathies

“…The importance of the equilibrium of apoptosis levels in patterning the CNS (Hayashi et al, 1996;He et al, 2004;Roue et al, 2008;Massa et al, 2009;Wei et al, 2009;Yochum et al, 2010;Gomez-Sintes et al, 2011;Tsai et al, 2012) in model systems are extensively described. Moreover, a mouse model of neurological damage and cerebellar hypoplasia, has suggested a direct correlation between decreased levels of CCND1, increased apoptosis and morphological abnormalities in the developing cerebellum (Robert et al, 2013).…”

The molecular basis of jaundice: An old symptom revisited

“…Moreover, highly elevated bilirubin activates microglia and induces the release of proinflammatory molecules and glutamate, causing calcium imbalance. Collectively, UCB affects neurotransmission cellular division and differentiation, migration and myelination [54][55][56][57]. UCB is a substrate for or inducer of several molecules, such as CYPs, 57-59 ABCB1/C1,60,61 and HMOX itself 62.…”