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Synaptic dysfunction is linked to both major depressive disorder (MDD) and Alzheimer's disease (AD). Synapse protein concentrations in cerebrospinal fluid (CSF) may be useful biomarkers to monitor synaptic dysfunction and degeneration that lead to depressive symptoms and AD, respectively. CSF neurogranin (Ng), a post-synaptic protein, has emerged as a promising tool to measure synaptic dysfunction and/or loss in AD. The aim of this study was to test the specific hypothesis that CSF neurogranin (Ng) is able to differentiate AD from MDD and cognitively normal controls. CSF samples from 44 healthy control individuals (CTRL), 86 patients with mild cognitive impairment (MCI), 36 of whom had prodromal AD as defined by a positive CSF AD biomarker signature, 25 AD dementia and 6 patients with MDD were analysed using an in house enzyme-linked immunosorbent assay for Ng. CSF Ng levels were significantly higher in AD patients and in prodromal AD (MCI patients with an "AD-like" CSF tau and Aβ42 profile) compared with CTRL individuals (p < 0.0001 for both groups) and MDD patients (p < 0.001 and p < 0.01, respectively). Significantly higher CSF Ng concentration was also seen in prodromal AD patients as compared to MCI patients without biomarker evidence of underlying AD pathology (p < 0.0001). CSF Ng correlated positively with the classical axonal injury markers CSF T-tau and P-tau (p < 0.0001), whereas correlation to plaque pathology as reflected by CSF Aβ42 was less clear. Negative correlations of CSF Ng with cognitive evaluation scores (MMSE and CAMCOG) were observed. This study strengthens the clinical utility of CSF Ng as a CSF biomarker for AD. AD patients in both MCI and dementia stages of the disease had increased CSF Ng concentrations compared with cognitively normal control individuals, patients with non-AD MCI and patients with MDD. The lowest CSF Ng concentrations were seen in patients with MDD, a finding that warrants validation in further studies.

Aim of the present study was to investigate the neuroprotective effect of dental pulp cells (DPCs) in in vitro models of Alzheimer and Parkinson disease. Primary cultures of hippocampal and ventral mesencephalic neurons were treated for 24 h with amyloid beta (Abeta(1-42)) peptide 1-42 and 6-OHDA, respectively. DPCs isolated from adult rat incisors were previously cultured in tissue culture inserts and added to the neuron cultures 2 days prior to neurotoxin treatment. Cell viability was assessed by the MTT assay. The co-culture with DPCs significantly attenuated 6-OHDA and Abeta(1-42)-induced toxicity in primary cultures of mesencephalic and hippocampal neurons, and lead to an increase in neuronal viability in untreated cultures, suggesting a neurotrophic effect in both models. Furthermore, human dental pulp cells expressed a neuronal phenotype and produced the neurotrophic factors NGF, GDNF, BDNF, and BMP2 shown by microarray screening and antibody staining for the representative proteins. DPCs protected primary neurons in in vitro models of Alzheimer's and Parkinson's disease and can be viewed as possible candidates for studies on cell-based therapy.

Phospholipase A(2) (PLA(2)) is a key enzyme in cerebral phospholipid metabolism. Preliminary post-mortem studies have shown that PLA(2) activity is decreased in frontal and parietal areas of the AD brain, which is in accordance with recent (31)P-Magnetic Resonance Spectroscopy evidence of reduced phospholipid turnover in the pre-frontal cortex of moderately demented AD patients. Such abnormality may also be observed in peripheral cells, and reduced PLA(2) activity in platelet membranes of AD patients, and correlates with the severity of dementia. In rat hippocampal slices, PLA(2) has been implicated in mechanisms of synaptic plasticity. In adult rats, the stereotaxic injection of PLA(2) inhibitors in the CA1 area of hippocampus impaired, in a dose-dependent manner, the formation of short- and long-term memory. Additionally, such inhibition resulted in a reduction of the fluidity of hippocampal membranes. In primary cultures of cortical and hippocampal neurons, the inhibition of PLA(2) precluded neurite outgrowth, and the sustained inhibition of the enzyme in mature cultures lead to loss of viability. Taken together, these findings reinforce the involvement of PLA(2) enzymes in neurodevelopment and neurodegeneration processes, and further suggest that reduced PLA(2) activity, probably reducing membrane phospholipids breakdown, may contribute to the memory impairment in AD.

In neurons, phospholipase A2 (PLA2) plays a central role in the regulation of membrane phospholipid metabolism. We have addressed the pharmacological modulation of PLA2 in primary cultures of rat cortical neurons. Inhibition curves were obtained in 4 day-in-culture neurons treated for 30 minutes with either the dual PLA2 inhibitor methyl arachidonyl fluorophosphonate (MAFP), or the iPLA2 inhibitor bromoenol lactone (BEL). Full inhibition was achieved with 100 and 250 microM of MAFP, or 10 and 20 microM of BEL. Conversely, a dose-dependent activation of PLA2 was obtained with 10-20 microg/ml of melitin. PLA2 inhibition with MAFP or BEL was not acutely toxic for cultured neurons. However, sustained inhibition of the enzyme precluded the development of neurites, and resulted in long-term loss of neuronal viability. We present a model of pharmacological challenge of PLA2 in vitro, which can be further used to address the involvement of the enzyme in neurodevelopment and neurodegeneration models.

Phospholipase A(2) (PLA(2)) controls the metabolism of phospholipids in cell membranes. In the brain, PLA(2) influences the processing of the amyloid precursor protein (APP) and thus the production of the amyloid-beta peptides (Abeta), which are the major components of the senile plaques in Alzheimer's disease (AD). Reduced PLA(2) activity has been reported in brain and in platelets of AD patients. In the present study we investigated PLA(2) activity in platelets from 21 AD patients as compared to 17 healthy elderly controls and 11 individuals with mild cognitive impairment (MCI). Subjects were cognitively assessed by the Mini-Mental State Examination (MMSE) and the CAMDEX schedule. Platelet PLA(2) activity was determined by radio-enzymatic assay, which mainly detected a calcium-independent form of the enzyme present also in the brain (iPLA(2)). PLA(2) activity was significantly lower in AD than in controls (p < 0.001). Mean PLA(2) activity in MCI individuals was between the values of AD patients and controls, with a subgroup showing PLA as low as the lowest AD patients, but the differences from MCI were not significant from AD and control groups. Lower PLA(2) activity was significantly correlated with a worse cognitive performance both at the MMSE (p = 0.001) and the cognitive sub-scale of the CAMDEX inventory (p = 0.002). Our data replicate previous findings of reduced platelet PLA(2) activity in AD. Both reduced PLA(2) activity and the correlation with impaired cognition were also reported in brain tissue of AD patients, suggesting thus that the present determinations in platelets may be related to a reduction in the brain. In the brain the inhibition of PLA(2) inhibits the physiological secretion of the APP, a mechanism that increases Abeta formation. Further longitudinal studies should investigate whether those MCI individuals with the lowest PLA(2) values in platelets would be at a higher risk to develop AD during a longitudinal follow up.

We investigated, with the aid of a radio-enzymatic method, the developmental changes in the activity of 85 kDa calcium-dependent cytosolic phospholipase A(2) (cPLA(2)) in pre-term embryonic rat brain and in primary cultures of cortical neurons. PLA(2) activity was highest in the brains of 18 day embryos (E18) and gradually decreased toward birth (E18 through E21). No significant differences were found regarding cPLA(2) activity in different topographies, namely hippocampus, cortex, and total brain. In primary cultures of E18/E19 cortical neurons, cPLA(2) activity was higher than the respective embryonic tissue activity, straight from early development. In vitro cPLA(2) activity peaked on the 4th day in culture, and decreased after the six days of incubation, when the cultures became mature. This result reinforces previous evidence that cPLA(2) plays an important role in the early development of the nervous system, and further suggests that it may be implicated in neurodevelopmental processes and in in vitro neuronal survival. We believe that we have produced a useful model for the tissue culture study of PLA(2) metabolism and biochemistry, which can be further addressed to the investigation of the biology of neurodegenerative and neuropsychiatric disorders.

Muscarinic agonists alter the metabolism of amyloid precursor protein, leading to an increase in alpha-secretase cleavage and a decreased production of amyloidogenic peptides; suggesting that these compounds might modify the Alzheimer's disease process. A second therapeutic target in AD is the accumulation of stably phosphorylated tau into neurofibrillary tangles; an early event correlating with cognitive impairment. Glycogen synthase kinase-3 (GSK-3beta) phosphorylates tau and is inhibited via protein kinase C (PKC). As certain muscarinic receptors are linked to PKC, we examined the effect of a range of agonists on GSK-3beta phosphorylation of tau. In neurons a nonspecific muscarinic agonist, carbachol, reduced tau phosphorylation. In nonneuronal cells expressing the ml receptor a range of ml agonists reduced transiently-expressed tau phosphorylation and altered its microtubulebinding properties. These findings link the two pathological process of AD-APP metabolism and tau phosphorylation - and suggest that muscarinic and other cholinergic compounds might have disease-modifying properties.