Prenatal exposure to bisphenol A interferes with the development of cerebellar granule neurons in mice and chicken.

In mice, prenatal exposure to low doses of bisphenol A has been shown to affect neurogenesis and neuronal migration in cortex, resulting in disturbance of both neuronal positioning and the network formation between thalamus and cortex in the offspring brain. In the present study we investigated whether prenatal exposure to bisphenol A disturbs the neurodevelopment of the cerebellum. Two different model systems were used; offspring from two strains of mice from mothers receiving bisphenol A in the drinking water before mating, during gestation and lactation, and chicken embryos exposed to bisphenol A (in the egg) on embryonic day 16 for 24h before preparation of cerebellar granule cell cultures. In the cerebellum, tight regulation of the level of transcription factor Pax6 is critical for correct development of granule neurons. During the development, the Pax6 level in granule neurons is high when these cells are located in the external granule layer and during their migration to the internal granule layer, and it is then reduced. We report that bisphenol A induced an increase in the thickness of the external granule layer and also an increase in the total cerebellar Pax6 level in 11 days old mice offspring. In cultured chicken cerebellar granule neurons from bisphenol A injected eggs the Pax6 level was increased day 6 in vitro. Together, these findings indicate that bisphenol A may affect the granule neurons in the developing cerebellum and thereby may disturb the correct development of the cerebellum.

Glucocorticoids dexamethasone and hydrocortisone inhibit proliferation and accelerate maturation of chicken cerebellar granule neurons.

Glucocorticoid (GC) treatment in premature infants may have detrimental effects on the immature brain. Here we show that GCs dexamethasone (Dex) and hydrocortisone (HC) reduce proliferation and induce differentiation of chicken embryo cerebellar neurons in vivo and in vitro. Granule neurons incorporating bromodeoxyuridine were reduced in the internal granular layer (IGL) after 24-h exposure to both substances on embryonic day 17, with Dex about 100-fold more potent than HC. The effects were blocked by GR antagonist RU 38486. Both GCs also increased the expression of neuronal differentiation markers microtubule-associated protein 2 (Map2) and neuronal nuclei protein (NeuN), measured by western blotting of whole cerebellar lysates and immunohistochemistry, respectively. Treatment of cerebellar granule neuron cultures with both GCs significantly reduced the percentage of proliferating-cell nuclear antigen (PCNA) positive neurons and increased NeuN positive neurons, with similar dose-response relationship as in vivo. The cytostatic agent cytosine arabinoside showed comparable effects both on proliferation and differentiation. In conclusion, the effects of Dex and HC on chicken cerebellar granule neuron proliferation are GR mediated and reflect their pharmacological potency. In addition, the effects on differentiation may be related to a cell cycle block per se, since cytosine arabinoside mimicked the effect of the GCs.

Newborn piglets exposed to hypoxia after nicotine or saline pretreatment: long-term effects on brain and heart.

OBJECTIVE: We wished to assess the effect of global hypoxia and the effect of nicotine pretreatment on the brain and heart of newborn pigs. Hypothesising that nicotine might give a better outcome because of its anti-apoptotic and anti-inflammatory effects. METHODS: Twenty-two anaesthetised piglets were randomised to pretreatment with saline or nicotine (130 microg/kg/h) before 45 min global hypoxia. They were observed for 27 h. The brain and heart were assessed with histopathological methods. Serum for Troponin t (TnT) analyses was collected at baseline and at the end of the experiment. RESULTS: There were no significant differences between the groups. At the end of hypoxia, BE was -14.8 +/- 4.9 mmol/l and MABP was 25 +/- 9 mmHg. Seven animals had autolysis of the cerebrum/cerebellum, their BE after hypoxia was -19 +/- 1.8 mmol/l and MABP 23 +/- 3 mmHg. The remaining 15 animals had a BE of -13 +/- 4.7mmol/l (p = 0.0004) and a MABP of 26 +/- 11 mmHg (ns). Eleven animals presented myocardial damage. A significant increase in TnT occurred in both groups. TnT increase and myocardial damage correlated (p = 0.001; r = 0.67). Animals with severe increase in TnT presented severe brain damage. CONCLUSIONS: Severe increase in serum TnT levels was linked to severe cerebral damage. Nicotine pretreatment had no impact on cerebral or cardiac histopathology.

Increased levels of PPARbeta/delta and cyclin D1 in flat dysplastic ACF and adenomas in Apc(Min/+) mice.

BACKGROUND: In Apc(Min/+) (Min; multiple intestinal neoplasia) mice two separate populations of aberrant crypt foci (ACF) develop in the colon after azoxymethane (AOM) exposure. ACF(Min), with a flat appearance, severe dysplasia and increased beta-catenin expression, are related to adenoma development, whereas classic ACF, with elevated structure, hyperplasia and normal beta-catenin level, are probably not. MATERIALS AND METHODS: The expressions of peroxisome proliferator-activated receptors (PPARs) beta/delta, cyclin D1 and beta-catenin in ACF, adenoma and normal tissue from AOM-treated Apc(Min/+) mice and a familial adenomatous polyposis (FAP) patient colon tumour were assessed by immunohistochemistry and immunoblotting. RESULTS: The flat ACF (ACF(Min)) displayed increased cytoplasmic levels of beta-catenin, and increased levels of cyclin D1 and PPARbeta/delta. In contrast, the expression in classic ACF resembled normal mucosa. Adenomas from Apc(Min/+) mice, as well as a FAP patient colon tumour, displayed increased nuclear and cytoplasmic levels of beta-catenin, and the same expression patterns of cyclin D1 and PPARbeta/delta as those found in flat ACF. CONCLUSION: In addition to activation of the Wnt signalling pathway in both flat ACF and in adenomas in Apc(Min/+) mice, the increased expression of PPARbeta/delta in these lesions could be a target for pro-inflammatory signals important for growth and reduced apoptosis.

Truncated mouse adenomatous polyposis coli reduces connexin32 content and increases matrilysin secretion from Paneth cells.

Heterozygous mutations in adenomatous polyposis coli (APC) is an early event in inheritable and sporadic colon cancer development. We recently found reduced connexin (Cx43) expression in intestinal cell lines with heterozygous Apc mutation. In this study we investigated Cx expression and the role of one mutated Apc allele in epithelia of multiple intestinal neoplasia (Min) mouse intestines by immunohistochemistry. Cx43 was not expressed in intestinal epithelia of Min and wild-type mice. Cx32 was specifically expressed in enterochromaffin cells in both mice types, and in Paneth cells of wild-type mice. In contrast, Min mice had nearly undetectable level of Cx32 in Paneth cells. Isolated small intestinal crypts from Min mice had markedly increased secretion of both lysozyme and matrilysin compared with wild-type mice. Absence of matrilysin in Min mice reduces adenoma development. Reduced Cx32 and increased matrilysin secretion from Paneth cells could be important to neoplastic development in the intestine.