Vesicular acetylcholine transporter (VAChT) in the brain of spontaneously hypertensive rats (SHR): effect of treatment with an acetylcholinesterase inhibitor

The cholinergic marker vesicular acetylcholine transporter (VAChT) was investigated in different cerebral areas of spontaneously hypertensive rats (SHR) by immunochemistry (Western blot analysis) and by immunohistochemistry. SHR were used as an animal model of hypertensive brain damage. The sensitivity of manipulation of cholinergic system on VAChT was assessed in rats treated for four weeks with the acetylcholinesterase (AChE) inhibitor galantamine (3 mg/Kg/day). VAChT concentrations were increased in the brain of control SHR compared to age-matched normotensive Wistar-Kyoto rats. This increase probably represents an up-regulation of VAChT to oppose cholinergic deficits reported in SHR and is countered by galantamine administration. The possibility that cholinergic neurotransmission enhancement may represent a therapeutic strategy in cerebrovascular disease is discussed

ACTIVITY OF CHOLINE ALPHOSCERATE ON CEREBROVASCULAR MORPHOLOGY AND INFLAMMATORY MARKERS IN SPONTANEOUSLY HYPERTENSIVE RATS

The effect of cholinergic precursors on choline availability and acetylcholine synthesis/release is established. It is thought that this increase contributes to counter cognitive impairment occurring in adult-onset dementia disorders. Choline alphoscerate (alpha-gliceryl-phosphoryl-choline, GPC) is among cholinergic precursors so far available the most effective in enhancing acetylcholine biosynthesis and release in animal models. Chronic brain vascular injury is a severe risk factor of cerebral dysfunction. White matter lesions represent relevant and early consequences of cerebrovascular injury. Cerebral hypoperfusion can induce small vessel disease (SVD) and is linked to the development of white matter lesions. Brain hypoperfusion and white matter lesions correlate with the development of cognitive impairment in Alzheimer’s disease (AD) or vascular dementia (VaD). The present study has assessed if long term treatment with GPC has a cerebroprotective effect on brain injury of vascular origin in the rat. Analysis was made on spontaneously hypertensive rats (SHR used as an animal model of brain vascular injury. Male SHR aged 32 weeks and age-matched normotensive Wistar–Kyoto (WKY) rats were treated for 4 weeks with GPC (150 mg/kg/day) or vehicle. On pial and intracerebral arteries of different brain areas, vascular astrocytes, blood brain barrier (BBB) and endothelial markers were assessed by neuromorphological and immunohistochemical techniques associated with quantitative analysis. No significant changes in the size of perivascular astrocytes were found in SHR compared to WKY rats, whereas the expression of the BBB marker aquaporin-4 decreased in SHR. This phenomenon was countered by GPC treatment. Endothelial markers and vascular adhesion molecules (ICAM, VCAM, PECAM, and P-selectine) expression were not homogeneously affected by hypertension in both pial and intracerebral vessels. The observation that treatment with GPC reversed cerebral microanatomical changes occurring in SHR is consistent with data of clinical trials reporting an improvement of cognitive function in subjects suffering from cerebrovascular disorders. These preclinical results suggest a re-evaluation of GPC activity in cerebrovascular patients with cognitive dysfunction

Glial fibrillary acidic protein and vimentin expression is regulated by glucocorticoids and neurotrophic factors in primary rat astroglial cultures

The neurotrophic factors epidermal growth factor (EGF), basic fibroblast growth factor, (bFGF), insulin-like growth factor I (IGF-I) and insulin (INS) regulate neural and astroglial cell functions. Glucocorticoids may influence the metabolism of astroglial compartment and are key hormones in neurodegenerative events. This study was designed to assess the interactions between growth factors and dexamethasone (DEX) on cytoskeletal proteins (GFAP and vimentin) expression in 25 days in vitro (DIV) astrocyte cultures. An increase in GFAP and vimentin expression was observed after 12 h pretreatment with bFGF and subsequent treatment for 60 h with DEX. GFAP immunoreactivity was decreased after 24 h progression growth factors (EGF, IGF-I and INS) addition, when compared to control 36 h DEX and bFGF-pretreated cultures for the last 12 h. Vimentin immunoreactivity was decreased after 12 h bFGF pretreatment and subsequent 60 h DEX addition in astrocyte cultures compared to 12 h bFGF-pretreated ones. Pretreatment for 36 h with DEX plus bFGF in the last 12 h and subsequent treatment for 24 h with DMEM (Dulbecco's modified Eagle medium; DMEM) + BSA (bovine serum albumine) (harvesting), or with progression growth factors (EGF, IGF-I or INS) alone or two of them together, stimulated GFAP expression, compared to untreated controls. Immunochemical analysis of the mitogen-activated protein kinase ERK2 suggests an involvement of this enzyme in the control of GFAP expression. The above findings support the view of an interactive and complex dialogue between growth factors and glucocorticoids during astroglial cell proliferation and maturation in culture. This may have implications in therapeutic approach of neurologic disorders associated with astrogliosis, including cerebrovascular disease

BRAIN MORPHOLOGICAL ANALYSIS OF OBESE ZUCKER RAT: MODEL OF METABOLIC SYNDROME.

Metabolic syndrome (MetS) is a disorder characterized by the development of insulin resistance, with subsequent hyperinsulinemia, that increases the risk of cerebrovascular and cardiovascular diseases. Obesity is probably a risk factor for Alzheimer’s disease and vascular dementia and is associated with impaired cognitive function. The obese Zucker rat (OZR) represents a model of type 2 diabetes exhibiting a moderate degree of arterial hypertension and hyperlipidemia. To clarify the possible relationships between MetS and brain damage, the present study has investigated brain microanatomy of OZRs compared with their littermate controls lean Zucker rats (LZRs). Male OZRs and LZRs of 12 weeks of age were used. Their brain was processed for analysis of nerve cell number by neuronal specific nuclear protein (NeuN) immunohistochemistry and phosphorylated neurofilament (NFP) immunoreactive axons analysis. The possible occurrence of astrogliosis was investigated by processing brains for immunohistochemical analysis of glial fibrillary acidic protein (GFAP). In frontal cortex and hippocampus of OZRs reduced number of neurons was related to a decrease of Neu-N expression compared to LZRs. A significant increase in the size and number of GFAP immunoreactive astrocytes was also observed. These findings suggest that OZRs developed as an animal model of type 2 diabetes, may also represent a model for assessing the influence of MetS on brain. This could clarify the pathophysiology of neurological injury reported in obese individuals and/or affected by MetS