Effect of manganese on the development of glial cells cultured from prenatally alcohol exposed rats

Manganese protects against the effects of alcohol on hypothalamic puberty-related hormones

AIMS

Since manganese (Mn) is capable of stimulating the hypothalamic-pituitary unit and advancing female puberty, we assessed the possibility that this element might overcome some of the detrimental effects of prepubertal alcohol (ALC) exposure on the hypothalamic control of pituitary function.

MAIN METHODS

Rats received either saline or Mn (10mg/kg) daily by gastric gavage from day 12 to day 31. After weaning, all rats were provided Lab Chow diet ad libitum until day 27 when they began receiving either the Bio Serv control or ALC diet regime. On day 31, the medial basal hypothalamus (MBH) was collected to assess luteinizing hormone-releasing hormone (LHRH) and cyclooxygenase 2 (COX2) protein levels. Release of prostaglandin-E2 (PGE2), LHRH and serum luteinizing hormone (LH) were also assessed. Other animals were not terminated on day 31, but remained in study to assess timing of puberty.

KEY FINDINGS

Short-term ALC exposure caused elevated hypothalamic LHRH content, suggesting an inhibition in peptide release, resulting in a decrease in LH. Both actions of ALC were reversed by Mn supplementation. COX2 synthesis, as well as PGE2 and LHRH release were suppressed by ALC exposure, but Mn supplementation caused an increase in COX2 synthesis and subsequent PGE2 and LHRH release in the presence of ALC. Mn supplementation also ameliorated the action of ALC to delay puberty.

SIGNIFICANCE

These results suggest that low level Mn supplementation acts to protect the hypothalamus from some of the detrimental effects of ALC on puberty-related hormones.

Alteration of iron homeostasis following chronic exposure to manganese in rats

Recent studies suggest that manganese-induced neurodegenerative toxicity may be partly due to its action on aconitase, which participates in cellular iron regulation and mitochondrial energy production. This study was performed to investigate whether chronic manganese exposure in rats influenced the homeostasis of iron in blood and cerebrospinal fluid (CSF). Groups of 8-10 rats received intraperitoneal injections of MnCl2 at the dose of 6 mg Mn/kg/day or equal volume of saline for 30 days. Concentrations of manganese and iron in plasma and CSF were determined by atomic absorption spectrophotometry. Rats exposed to manganese showed a greatly elevated manganese concentration in both plasma and CSF. The magnitude of increase in CSF manganese (11-fold) was equivalent to that of plasma (10-fold). Chronic manganese exposure resulted in a 32% decrease in plasma iron (p<0.01) and no changes in plasma total iron binding capacity (TIBC). However, it increased CSF iron by 3-fold as compared to the controls (p<0.01). Northern blot analyses of whole brain homogenates revealed a 34% increase in the expression of glutamine synthetase (p<0.05) with unchanged metallothionein-I in manganese-intoxicated rats. When the cultured choroidal epithelial cells derived from rat choroid plexus were incubated with MnCl2 (100 microM) for four days, the expression of transferrin receptor mRNA appeared to exceed by 50% that of control (p<0.002). The results indicate that chronic manganese exposure alters iron homeostasis possibly by expediting unidirectional influx of iron from the systemic circulation to cerebral compartment. The action appears likely to be mediated by manganese-facilitated iron transport at brain barrier systems.

Paternal alcohol exposure: developmental and behavioral effects on the offspring of rats

The effect of paternal alcohol exposure on neurochemical and behavioral parameters was investigated using as a model system glial cells derived from newborn rat brain and cultured for 4 weeks. The total brain neurochemical parameters from rats born to mothers sired by an alcohol treated father were also investigated. Enzymatic markers of nerve cell development (enolase isoenzymes and glutamine synthetase) and the defense system (superoxide dismutase) against free radicals formed during alcohol degradation were measured in order to evaluate nerve cell damage. Behavioral locomotor tests (open-field, novelty-seeking, light/dark) were carried out to show long-lasting effects of paternal alcoholization on the offspring. Behavioral and developmental alterations were found until 1 year of age in the offspring and a significant growth retardation was observed in the males. Our results suggest that paternal alcohol exposure produces developmental and behavioral effects in the offspring. The consequence of either alcohol withdrawal during stage one spermatogenesis, or maternal diet supplementation with manganese during pregnancy were investigated. It was observed that some of the effects of paternal alcohol exposure on the offspring may be reversed by these treatments.

Development of glial cells cultured from prenatally alcohol treated rat brain: effect of supplementation of the maternal alcohol diet with a grape extract

The aim of this work was to investigate the effect of supplementation of a maternal alcohol diet with a grape extract on glial cell development. Glial cells were cultured during 4 weeks from cortical brain cells of the new born offspring in DMEM medium supplemented with fetal calf serum. Enzymatic markers of nerve cell development were measured (enolase isoenzymes and glutamine synthetase). Since alcohol consumption produces free radicals the antioxidant system superoxide dismutase was also investigated. Compared to the decrease found in only alcohol treated animals, all parameters except neuron-specific enolase were antagonized and even stimulated after grape extract supplementation. The effect was more important after only 1 month than 3 months of treatment. Also in the total brain an alcohol antagonizing effect and a glutamine synthetase activation were found. Our data demonstrate that addition of a grape extract to the maternal alcohol diet may partially or completely overcome the alcohol induced retardation of glial cell development.