Activation of hippocampal nitric oxide and calcium/calmodulin-dependent protein kinase II in response to Morris water maze learning in rats

Inflammatory Consequences of Maternal Diabetes on the Offspring Brain: a Hippocampal Organotypic Culture Study

Gestational diabetes is a disorder associated with abnormal chronic inflammation that poses a risk to the developing fetus. We investigated the effects of experimentally induced diabetes (streptozotocin model) in Wistar female rats on the inflammatory status of the hippocampi of their offspring. Additionally, the impact of antidiabetic drugs (metformin and glyburide) on inflammatory processes was evaluated. Organotypic hippocampal cultures (OHCs) were prepared from the brains of the 7-day-old rat offspring of control and diabetic mother rats. On the 7th day in vitro, the cultures were pretreated with metformin (3 μM) or glyburide (1 μM) and then stimulated for 24 h with lipopolysaccharide (LPS, 1 μg/ml). The OHCs obtained from the offspring of diabetic mothers were characterized by the increased mortality of cells and an enhanced susceptibility to damage caused by LPS. Although we showed that LPS stimulated the secretion of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) in the control and diabetic cultures, the levels of IL-1β and IL-6 in the OHC medium obtained from the offspring of diabetic mothers were more pronounced. In the diabetic cultures, enhanced levels of TLR-4 and the overactivation of the NLRP3 inflammasome were demonstrated. Metformin and glyburide pretreatment normalized the LPS-induced IL-1β secretion in the control and diabetic cultures. Furthermore, glyburide diminished both: LPS-induced IL-6 and TNF-α secretion in the control and diabetic cultures and increased NF-κB p65 subunit phosphorylation. Glyburide also diminished the levels of the NLRP3 subunit and caspase-1, but only in the diabetic cultures. The results showed that maternal diabetes affected inflammatory processes in the offspring brain and increased hippocampal sensitivity to the LPS-induced inflammatory response. The use of antidiabetic agents, especially glyburide, had a beneficial impact on the changes caused by maternal diabetes.

Genistein protects hippocampal neurons against injury by regulating calcium/calmodulin dependent protein kinase IV protein levels in Alzheimer's disease model rats

Genistein has a neuroprotective effect in Alzheimer's disease, but its mechanism of action needs further clarification. Accumulating evidence suggests that excessive phosphorylation of tau protein causes production of neurofibrillary tangles, which is one of the main pathological characteristics of Alzheimer's disease, and tau protein can be phosphorylated by calcium/calmodulin dependent protein kinase IV (CAMK4). After 7 days of pre-administration of genistein (90 mg/kg), an Alzheimer's disease rat model was established using an intraperitoneal injection of D-galactose combined with an intracerebral injection of amyloid-β peptide (25-35). The rat was then continuously administered genistein (90 mg/kg) for 42 days. The Morris water maze test, western blotting and hematoxylin-eosin staining results showed that genistein significantly decreased the escape latency and increased the number of times crossing the platform, reduced p-tau, CALM, CAMKK1 and p-CAMK4 protein levels in the hippocampus, and alleviated hippocampal neuron damage. These findings indicate that genistein may play a neuroprotective role in Alzheimer's disease through regulating CAMK4 to modulate tau hyperphosphorylation.

Expression of apoptosis-regulatory genes in the hippocampus of rat neonates born to mothers with diabetes

Diabetes during pregnancy impairs the development of the central nervous system (CNS) and causes cognitive and behavioral abnormalities in offspring. However, the exact mechanism by which the maternal diabetes affects the development of the brain remains to be elucidated. The aim of the present study was to investigate the effects of maternal diabetes in pregnancy on the expression of Bcl-2 and Bax genes and the numerical density of degenerating dark neurons (DNs) in the hippocampus of offspring at the first postnatal two weeks. Wistar female rats were maintained diabetic from a week before pregnancy through parturition and male offspring was sacrificed at P0, P7, and P14. Our findings demonstrated a significant down-regulation in the hippocampal expression of Bcl-2 in the diabetic group newborns (P < 0.05). In contrast, the mRNA expression of Bax was markedly up-regulated in the offspring born to diabetic dams at all of studied time-points (P < 0.05). Moreover, we found a striking increase in the numerical density of DNs in the various subfields of hippocampus of diabetic group pups (P < 0.05). The results of the present study revealed that maternal hyperglycemia during gestational period may result in disturbances in the expression of Bcl-2 and Bax genes as two important genes in neuronal apoptosis regulation and induces the production of DNs in the developing hippocampus of neonatal rats. These disturbances may be a reason for the cognitive, structural, and behavioral anomalies observed in offspring born to diabetic mothers. Furthermore, the control of maternal glycaemia by insulin administration in most cases normalized these negative impacts.

Maternal supplementation of nucleotides improves the behavioral development of prenatal ethanol-exposed mice

Maternal ethanol consumption during pregnancy can induce learning deficits in the offspring. The objective of this study was to assess whether supplementation of exogenous nucleotides during pregnancy and lactation would ameliorate prenatal ethanol-induced learning and memory deficits in the offspring of mice, and to explore the possible mechanisms. In the present study, pregnant C57BL/6J mice were exposed to ethanol (5 g/kg body weight) intragastrically from gestational day (GD) 6 to GD15. The dams in exogenous nucleotide intervention groups were fed with feed containing 0.01%, 0.04%, or 0.16% nucleotide powder, with control and ethanol groups receiving normal feed. The dams were allowed to deliver naturally and to breast feed their offspring. After weaning, behavioral tests were carried out in the offspring of each group. Serum oxidation indexes were analyzed, and the hippocampus of each offspring was collected and detected for acetyl cholinesterase (AChE) activity and the expression of p-CREB, CREB, and BDNF. The results showed that maternal supplementation with exogenous nucleotides during pregnancy could ameliorate prenatal ethanol-induced learning and memory deficits in the offspring of mice, through improving their antioxidant capacity, reversing hippocampus AChE levels, and allowing the expression of some proteins related to learning and memory. However, different sensitivities were found between the two sexes.

Influences of hyperthermia-induced seizures on learning, memory and phosphorylative state of CaMKIIα in rat hippocampus

Febrile seizure (FS) remains the most common childhood neurological emergency. Although many studies have been done, controversy exists as to whether these seizures are associated with a significant risk for cognitive impairment. The aim of our study is to check whether there is a spatial learning and memory deficit in the experimental FS rats using a heated-air FS paradigm and to determine the possible molecular mechanism of cognitive impairment. On days 10 to 12 postpartum, the male rat pups were subjected to one, three, or nine episodes of brief hyperthermia-induced seizures (HS). At adolescence and adulthood, the rats subjected to three, or nine episodes of HS had significant deficits in spatial learning and memory tested by Morris water maze. At adulthood, no apparent hippocampal neuronal loss was found in any HS group, but the seizure threshold to flurothyl was decreased significantly in the rats subjected to nine episodes of HS. In the rats subjected to three, or nine episodes of HS, the Western immunoblotting showed that there was a significant translocation of Ca(2+)-calmodulin stimulated protein kinase II (CaMKII) from the postsynaptic density to the cytosol. In the postsynaptic density the phosphorylation of CaMKIIα Thr(286) was reduced significantly, but the phosphorylation of CaMKIIα Thr(305) was increased significantly. Our study showed early-life brief but recurrent HS caused long-term cognitive impairment and CaMKIIα was involved in carrying forward the signal resulting from HS. The change of the phosphorylative level in Thr(286) and Thr(305) sites of CaMKIIα may underlie the molecular mechanism for the HS related cognitive impairment.