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Biomedical subjects

Milita Crisby

Publications and source records attributed to Milita Crisby.

12 recordsLinked to original sources
PubMed2005

High cholesterol diet induces tau hyperphosphorylation in apolipoprotein E deficient mice.

We analysed the effects of high cholesterol (HC) intake and reduced apolipoprotein E (apoE) activity on tau phosphorylation and on the activities of the major tau kinases and phosphatases in brains from wild-type and apoE-knockout (apoEKO) mice. We show that HC diet potently induced intraneuronal accumulation of hyperphosphorylated tau in apoEKO mice, as well as upregulation of several tau kinases, without affecting tau phosphatases. Our results suggest an interaction between dietary and genetic factors in the development of tauopathies, which can be relevant in humans, where the apoE4 isoform could have a lack of function as compared to other isoforms.

Animals↗
PubMed2005

Effects of statins on microglia.

High serum cholesterol level has been shown as one of the risk factors for Alzheimer's disease (AD), and epidemiological studies indicate that treatment with cholesterol-lowering substances, statins, may provide protection against AD. An acute-phase reaction and inflammation, with increased levels of proinflammatory cytokines, are well known in the AD brain. Notably, there is evidence for antiinflammatory activities of statins, such as reduction in proinflammatory cytokines. Consequently, it is of interest to analyze the effects of statins on microglia, the main source of inflammatory factors in the brain, such as in AD. The aims of this study were to determine the effects of statins (atorvastatin and simvastatin) on microglial cells with regard to the secretion of the inflammatory cytokine interleukin-6 (IL-6) and cell viability after activation of the cells with bacterial lipopolysaccharides (LPS) or beta-amyloid1-40 (Abeta1-40) and in unstimulated cells. Cells of the human microglial cell line CHME-3 and primary cultures of rat neonatal cortical microglia were used. Incubation with LPS or Abeta1-40 induced secretion of IL-6, and Abeta1-40, but not LPS, reduced cell viability. Both atorvastatin and simvastatin reduced the basal secretion of IL-6 and the cell viability of the microglia, but only atorvastatin reduced LPS- and Abeta1-40-induced IL-6 secretion. Both statins potentiated the Abeta1-40-induced reduction in cell viability. The data indicate the importance of also considering the microglial responses to statins in evaluation of their effects in AD and other neurodegenerative disorders with an inflammatory component.

Amyloid beta-Peptides↗
PubMed2005

Small artery endothelial dysfunction in postmenopausal women: in vitro function, morphology, and modification by estrogen and selective estrogen receptor modulators.

OBJECTIVE: Our objective was to assess vascular endothelial function and morphology in resistance vasculature from healthy pre- and postmenopausal women in vitro and to determine potential mechanisms of vascular protection by estrogenic compounds. METHODS: Arteries (approximately 220 microm) were dissected from sc fat biopsies obtained from healthy premenopausal and postmenopausal women. Flow-mediated dilatation, agonist-induced endothelium-dependent and -independent relaxation, and myogenic responses to changes in intraluminal pressure were evaluated before and after incubation (3 h) with 17beta-estradiol, propyl pyrazole triol [a selective estrogen receptor-alpha (ERalpha) agonist], raloxifene (a second-generation selective ER modulator), and the phytoestrogen genistein, using pressure myography technique. In addition, endothelial morphology was assessed in arteries from pre- and postmenopausal women, and distribution of ERs within the artery wall from postmenopausal women was evaluated. RESULTS: Functional and morphological disturbances of endothelial function were observed in small arteries from postmenopausal women. Incubation with 17beta-estradiol improved postmenopausal resistance artery function, an effect mimicked by propyl pyrazole triol but not raloxifene or genistein. Immunohistochemical staining revealed similar expression of ERalpha and ERbeta in the smooth muscle of arteries from postmenopausal women; however, ERalpha was dominant in endothelium. CONCLUSIONS: The resistance arteries from postmenopausal women show functional and morphological abnormalities. ERalpha may contribute to vascular protection by estrogens in the peripheral resistance circulation in postmenopausal women. Selective ERalpha agonists warrant further investigation as therapeutic agents for prevention of cardiovascular disease in postmenopausal women.

Adult↗
PubMed2005

Modulation of the inflammatory process by statins.

Statins reduce cholesterol levels through competitive inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the key enzyme that regulates cholesterol synthesis. The cholesterol-lowering effect of statins is also due to an increase in the uptake of cholesterol by cells as a result of intracellular cholesterol depletion and enhanced expression of low-density lipoprotein (LDL) receptors. The use of statins as lipid-lowering agents has lead to remarkable changes in the treatment and prevention of ischemic heart disease. Results of large clinical trials of patients with ischemic heart disease have demonstrated that statins reduce inflammatory markers such as C-reactive protein, an independent risk factor in the disease. Statins exhibit properties that are beyond their lipid-lowering effects. These non-lipid-lowering properties involve the inhibition of the isoprenoid pathway through decreased synthesis of many nonsteroidal isoprenoid compounds. The focus on the immunomodulatory effect of statins is the result of the positive outcome of pravastatin treatment in cardiac transplantation patients, as well as angiographic regression studies showing insignificant changes in the degree of coronary stenosis despite a large reduction in cardiac events. Statin treatment reduces the risk of ischemic stroke despite the fact that LDL cholesterol is not directly associated with the risk of stroke. This observation lead to the investigation of the role of statins in inflammation and the immune system. Recent research data demonstrated that statins inhibit the induction of the major histocompatibility (MHC) class II expression by interferon-gamma (IFN-gamma), leading to repression of MHC II-mediated T-cell activation. Furthermore, statins inhibit the expression of specific cell surface receptors on monocytes, adhesion molecules and also integrin-dependent leucocyte adhesion. While statins may stimulate the secretion of caspase-1, IL-1beta and IL-18 in peripheral mononuclear cells in response to Mycobacterium tuberculosis, they exhibit additional effects on inflammation by decreasing IL-6 synthesis in human vascular smooth muscle cells (VSMC) in vitro. The focus of this monograph is to highlight the role of statins in the modulation of the immune system and inflammatory processes.

C-Reactive Protein↗
PubMed2004

HMG-CoA reductase inhibitors, statins, induce phosphorylation of Mdm2 and attenuate the p53 response to DNA damage.

3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors, statins, are widely used cholesterol-lowering drugs and have been shown to have anticancer effects in many models. We have investigated the effect of statins on Mdm2, a p53-specific ubiquitin ligase. It was found that pravastatin induced Mdm2 phosphorylation at Ser166 and at 2A10 antibody-specific epitopes in HepG2 cells, while mRNA levels were unchanged. Furthermore, pravastatin was found to induce phosphorylation of mTOR at Ser2448. Ser166 phosphorylation of Mdm2 was abrogated by an inhibitor of mTOR, rapamycin, but not by the PI3-kinase inhibitors LY294002 and wortmannin. Ser166 phosphorylation of Mdm2 has been associated to active Mdm2 and has been shown to increase its ubiquitin ligase activity and lead to increased p53 degradation. Our data show that statins attenuated the p53 response to DNA damage. Thus, in HepG2 cells pravastatin and simvastatin pretreatment attenuated the p53 response to DNA damage induced by 5-fluorouracil and benzo(a)pyrene. Similar attenuation was induced when p53 stabilization was induced by the inhibitor of nuclear export, leptomycin B. Furthermore, in the DNA-damaged cells, half-lives of Mdm2 and p53 were decreased by statins, indicating a more rapid formation of p53/Mdm2 complexes and facilitated p53 degradation. The induction of p53 responsive genes and apoptosis was attenuated. Mdm2 and p53 were also studied in vivo in rat liver employing immunohistochemistry, and it was found that constitutive Mdm2 expression was changed in livers of pravastatin-treated rats. We also show that the p53 response to a challenging dose of diethylnitrosamine was attenuated in hepatocytes in situ and in primary cultures of hepatocytes by pravastatin pretreatment. Taken together, these data indicate that statins induce an mTOR-dependent Ser166 phosphorylation of Mdm2, and this effect may attenuate the duration and intensity of the p53 response to DNA damage in hepatocytes.

Animals↗
PubMed2004

Rosuvastatin reduces caspase-3 activity and up-regulates alpha-secretase in human neuroblastoma SH-SY5Y cells exposed to A beta.

An increasing number of studies suggest that disturbances in cholesterol homeostasis may promote the formation and deposition of beta-amyloid (A beta) and the progression of Alzheimer's disease (AD). In this paper, we have analyzed the effect of the lipid-lowering compound rosuvastatin on apoptosis and caspase-3 activity in human neuroblastoma SH-SY5Y cells. Exposure of SH-SY5Y cells to A beta(1-42) alone resulted in a significantly increased caspase-3 activity approximately by 35% (135+/-15%, p<0.05), and decreased alpha-secretase activity by 34% (67.4+/-2.7%, p<0.001) compared to the controls (100+/-18.1%). Rosuvastatin alone decreased caspase-3 activity by 15% (85.3+/-1.5%, p<0.0005) compared to the controls and by 50% to cells exposed to A beta alone (p<0.00005). Cells exposed to rosuvastatin alone had a higher alpha-secretase activity compared to cells exposed to A beta (76.4+/-23.8%, n.s.) but a slightly lower activity compared to the controls (n.s.). Pre-treatment of SY-SY5Y cells with rosuvastatin prior to incubation with A beta(1-42) resulted in decreased caspase-3 activity by approximately 15% compared to the controls and by approximately 48% (86.8+/-16.9%, p<0.05) compared to cells treated with A beta(1-42) alone. Also, alpha-secretase activity was increased by approximately 50% compared to the controls and by 84% (151.3+/-10.1%, p<0.05), compared to cells treated with A beta(1-42) alone. Mevalonate abrogated the effect of rosuvastatin in vitro. To our knowledge, this is the first study demonstrating that the hydrophilic compound rosuvastatin decreases caspase-3 activity and increases alpha-secretase activity in human neuroblastoma SH-SY5Y cells exposed to A beta in vitro. These effects are essential for modulation of the amyloidogenic pathway and mediators of apoptosis in AD.

Amyloid Precursor Protein Secretases↗
PubMed2003

Pravastatin inhibits pro-inflammatory effects of Alzheimer's peptide Abeta(1-42) in glioma cell culture in vitro.

Statins are known to exert a number of biological effects apart from reducing cholesterol synthesis. The results of recent studies indicate that patients treated with pravastatin have a lower prevalence of diagnosed Alzheimer's disease (AD). These observations prompted us to examine the effects of pravastatin on Alzheimer's peptide (Abeta(1-42))-induced pro-inflammatory activation in the human glioma cell line in vitro. Cells alone or cells pre-treated with pravastatin (0.1mg x ml(-1)) for 24h were stimulated with 5 microM of freshly dissolved Abeta(1-42) for the next 24h. The pre-treatment of cells with pravastatin diminished the capacity of Abeta to induce metalloproteinases, cytokine IL-6 and free radical levels. Although both pravastatin and Abeta(1-42) separately increased PPARgamma activity, the combination of Abeta(1-42) and pravastatin resulted in no effect on PPARgamma expression. These data indicate that soluble forms of Abeta(1-42), which are a potent stimulus of pro-inflammatory activation of glioma cells in vitro, could be a good target for pravastatin.

Amyloid beta-Peptides↗
PubMed2003

Modulation of the inflammatory process by statins.

Statins reduce cholesterol levels through competitive inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the key enzyme that regulates cholesterol synthesis. The cholesterol-lowering effect of statins is also due to an increase in the uptake of cholesterol by cells as a result of intracellular cholesterol depletion and enhanced expression of low-density lipoprotein (LDL) receptors. The use of statins as lipid-lowering agents has lead to remarkable changes in the treatment and prevention of ischemic heart disease. Results of large clinical trials of patients with ischemic heart disease have demonstrated that statins reduce inflammatory markers such as C-reactive protein, an independent risk factor in the disease. Statins exhibit properties that are beyond their lipid-lowering effects. These non-lipid-lowering properties involve the inhibition of the isoprenoid pathway through decreased synthesis of many nonsteroidal isoprenoid compounds. The focus on the immunomodulatory effect of statins is the result of the positive outcome of pravastatin treatment in cardiac transplantation patients, as well as angiographic regression studies showing insignificant changes in the degree of coronary stenosis despite a large reduction in cardiac events. Statin treatment reduces the risk of ischemic stroke despite the fact that LDL cholesterol is not directly associated with the risk of stroke. This observation lead to the investigation of the role of statins in inflammation and the immune system. Recent research data demonstrated that statins inhibit the induction of the major histocompatibility (MHC) class II expression by interferon-gamma (IFN-gamma), leading to repression of MHC II-mediated T-cell activation. Furthermore, statins inhibit the expression of specific cell surface receptors on monocytes, adhesion molecules and also integrin-dependent leucocyte adhesion. While statins may stimulate the secretion of caspase-1, IL-1beta and IL-18 in peripheral mononuclear cells in response to Mycobacterium tuberculosis, they exhibit additional effects on inflammation by decreasing IL-6 synthesis in human vascular smooth muscle cells (VSMC) in vitro. The focus of this monograph is to highlight the role of statins in the modulation of the immune system and inflammatory processes.

Animals↗
PubMed2002

[Carotid endarterectomy in the elderly. Risk of ischemic stroke is reduced in patients older than 75 years].

Epidemiological studies indicate that the risk of first ever stroke is strongly related to age. Based on the NASCET and ECST results, carotid endarterectomy (CEA) is a well-established indication for the prevention of ischemic stroke in patients with 70-99% symptomatic internal carotid artery (ICA) stenosis and in selective cases with moderate stenosis (50-69%). A recent analysis of data from the NASCET group, clearly demonstrates that elderly patients (age > 75 years) with symptomatic ICA stenosis benefit more from CEA compared to younger patients. However, the NASCET collaborators point out that the greater benefits achieved in patients older than 75 years compared to other age groups in the trial depends on the fact that CEA was performed on the elderly having a higher risk of ipsilateral ischemic stroke if treated medically and the lowest surgical risk. In order to obtain the treatment benefit reported, operation performed by skilled surgeons and meticulous medical screening of the elderly patients is recommended to exclude life-threatening conditions.

Age Factors↗
PubMed2002

Modulation of inflammatory mediators and PPARgamma and NFkappaB expression by pravastatin in response to lipoproteins in human monocytes in vitro.

Statins are inhibitors of the rate-limiting step of cellular cholesterol synthesis. In vitro and in vivo studies suggest that statins have anti-inflammatory properties independent of their cholesterol-lowering effects. These observations prompted us to examine the effects of pravastatin (50 microM) and native or oxidized low density lipoprotein (nLDL or oxLDL) (50 microg ml(-1)) on primary human monocytes. We found that cells treated with pravastatin prior to nLDL and cells pre-treated with oxLDL prior to pravastatin showed increased activity of peroxisome proliferator-activated receptor gamma (PPAR gamma). Treatment of cells with drug either before incubation with oxLDL or afterwards suppressed nuclear factor kappa B (NF kappa B) expression and reduced uptake of(125)I-oxLDL by 1.7- and 1.5-fold, respectively. Pravastatin also increased PPAR gamma levels and abolished NF kappa B activity in non-stimulated monocytes. Statin added to monocytes prior to or after treatment with nLDL or oxLDL significantly inhibited generation of matrix metalloproteinases (MMPs), monocyte chemotactic protein-1 (MCP-1) and tumor necrosis factor alpha (TNF- alpha). These data corroborate previous findings of the pleiotropic role of statins and also suggest the involvement of transcription factors such as PPAR gamma and NF kappa B in the modulation of the inflammatory processes by statins.

Autoradiography↗
PubMedDate not supplied

Statins in the prevention and treatment of Alzheimer disease.

Vascular risk factors such as hypertension and hypercholesterolemia during midlife increase the risk for Alzheimer's disease (AD). Treatment of hypercholesterolemia and other vascular risk factors may have great implications in the prevention of AD. Recent findings illustrate that the sterol metabolism in the brain is an active process, well controlled and regulated by 24-hydroxylase, an enzyme that is uniquely expressed in the brain. The use of statins in ischemic heart disease (IHD) has proven to be a phenomenal advance in pharmacological disease prevention and treatment. A growing body of evidence, suggest that statins exhibit additional benefits that are independent of their cholesterol-lowering actions. Statin treatment has also considerable effect in prevention of ischemic stroke. In animal models of ischemic stroke, statins have proven to reduce infarct size through up-regulation of endothelial nitric oxide synthases. Data from recent observational studies have revealed a potential role for statins in prevention of AD. The following review comments the processes leading to dementia including the involvement of cholesterol regulation, cerebral circulation and inflammation in development of dementia. The mechanisms by which statins may be beneficial in controlling these processes is discussed.

Aged↗