Cholesterol-independent neuroprotective and neurotoxic activities of statins: perspectives for statin use in Alzheimer disease and other age-related neurodegenerative disorders

Statin use and the risk of Parkinson's disease in persons with diabetes: A nested case-control study

AIMS

Persons with diabetes may have an elevated risk of Parkinson's disease (PD). Statin use could also modify the progression of PD. The aim was to study whether there is an association between statin exposure and risk of PD in persons with diabetes.

METHODS

A nationwide, nested case-control study restricted to people with diabetes was performed as part of nationwide register-based Finnish study on PD (FINPARK). Study included 2017 PD cases and their 7934 matched controls without PD. Persons with PD were diagnosed between 1999 and 2015, and statin use (1995-2015) was determined from Prescription Register. In the main analysis, exposure at least 3 years before outcome was considered. Cumulative exposure was categorized into tertiles, and associations were analysed with conditional logistic regression (adjusted with comorbidities and number of antidiabetic drugs).

RESULTS

Prevalence of statin use was similar in PD cases and controls, with 54.2% of cases and 54.4% controls exposed before the lag time (adjusted odds ratio [aOR] = 1.03; 95% confidence interval [CI]: 0.92-1.15). Those in the highest cumulative statin exposure tertile had higher risk of PD than statin nonusers (aOR = 1.22; 95% CI: 1.04-1.43), or those in the lowest cumulative statin exposure tertile (aOR = 1.29; 95% CI: 1.07-1.57).

CONCLUSION

Our nationwide study that controlled for diabetes duration and used 3-year lag between exposure and outcome to account for reverse causality does not provide support for the hypothesis that statin use decreases the risk of PD.

The effects of cholesterol and statins on Parkinson's neuropathology: a narrative review

Parkinson disease (PD) is chronic and progressive neurodegenerative disease of the brain characterized by motor symptoms including tremors, rigidity, postural instability, and bradykinesia. PD neuropathology is due to the progressive degeneration of dopaminergic neurons in the substantia nigra and accumulation of Lewy bodies in the survival neurons. The brain contains a largest amount of cholesterol which is mainly synthesized from astrocytes and glial cells. Cholesterol is intricate in the pathogenesis of PD and may be beneficial or deleterious. Therefore, there are controversial points concerning the role of cholesterol in PD neuropathology. In addition, cholesterol-lowering agents' statins can affect brain cholesterol. Different studies highlighted that statins, via inhibition of brain HMG-CoA, can affect neuronal integrity through suppression of neuronal cholesterol, which regulates synaptic plasticity and neurotransmitter release. Furthermore, statins affect the development and progression of different neurodegenerative diseases in bidirectional ways that could be beneficial or detrimental. Therefore, the objective of the present review was to clarify the double-sward effects of cholesterol and statins on PD neuropathology.

Evaluation of the effect of pitavastatin on motor deficit and functional recovery in sciatic nerve injury: A CatWalk study

Objectives

This study aims to investigate the electrophysiological, scintigraphic, and histopathological effects of pitavastatin and its impact on functional status in rats with sciatic nerve injury.

Materials and methods

A total of 30 Wistar albino rats were divided into three equal groups including 10 rats in each group: sham group (no injury), control group (nerve injury induced), and pitavastatin group (nerve injury induced and 2 mg/kg of pitavastatin administered orally once a day for 21 days). Before and at the end of intervention, quantitative gait analysis with the CatWalk system and sciatic nerve conduction studies were performed. After the intervention, the gastrocnemius muscle was scintigraphically evaluated, and the sciatic nerve was histopathologically examined.

Results

There was no significant difference in the sciatic nerve conduction before the intervention and Day 21 among the groups (p>0.05). According to the quantitative gait analysis, there were significant differences in the control group in terms of the individual, static, dynamic, and coordination parameters (p<0.05). The histopathological examination revealed a significant difference in the total myelinated axon count and mean axon diameter among the groups (p<0.001).

Conclusion

Pitavastatin is effective in nerve regeneration and motor function recovery in rats with sciatic nerve injury.

DHCR24 reverses Alzheimer's disease-related pathology and cognitive impairment via increasing hippocampal cholesterol levels in 5xFAD mice

Accumulating evidences reveal that cellular cholesterol deficiency could trigger the onset of Alzheimer's disease (AD). As a key regulator, 24-dehydrocholesterol reductase (DHCR24) controls cellular cholesterol homeostasis, which was found to be downregulated in AD vulnerable regions and involved in AD-related pathological activities. However, DHCR24 as a potential therapeutic target for AD remains to be identified. In present study, we demonstrated the role of DHCR24 in AD by employing delivery of adeno-associated virus carrying DHCR24 gene into the hippocampus of 5xFAD mice. Here, we found that 5xFAD mice had lower levels of cholesterol and DHCR24 expression, and the cholesterol loss was alleviated by DHCR24 overexpression. Surprisingly, the cognitive impairment of 5xFAD mice was significantly reversed after DHCR24-based gene therapy. Moreover, we revealed that DHCR24 knock-in successfully prevented or reversed AD-related pathology in 5xFAD mice, including amyloid-β deposition, synaptic injuries, autophagy, reactive astrocytosis, microglial phagocytosis and apoptosis. In conclusion, our results firstly demonstrated that the potential value of DHCR24-mediated regulation of cellular cholesterol level as a promising treatment for AD.

Biliverdin reductase as a target in drug research and development: Facts and hypotheses

Biliverdin reductase-A (BVR) catalyzes the reduction of heme-derived biliverdin into bilirubin, this latter being a powerful endogenous free radical scavenger. Furthermore, BVR is also endowed with both serine/threonine/tyrosine kinase and scaffold activities, through which it interacts with the insulin receptor kinase, conventional and atypical protein kinase C isoforms, mitogen-activated protein kinases as well as the phosphatidylinositol-3 kinase/Akt system. By regulating this complex array of signal transduction pathways, BVR is involved in the pathogenesis of neurodegenerative, metabolic, cardiovascular and immune-inflammatory diseases as well as in cancer. In addition, both BVR and BVR-B, this latter being an alternate isozyme predominant during fetal development but sometimes detectable through adulthood, have been studied as peripheral biomarkers for an early detection of Alzheimer's disease, atherosclerosis and some types of cancer. However, despite these interesting lines of evidence, to date BVR has not been considered as an appealing drug target. Only limited evidence supports the neuroprotective effects of atorvastatin and ferulic acid through BVR regulation in the aged canine brain and human neuroblastoma cells, whereas interesting results have been reported regarding the use of BVR-based peptides in preclinical models of cardiac diseases and cancer.

High dose simvastatin and rosuvastatin impair cognitive abilities of healthy rats via decreasing hippocampal neurotrophins and irisin

BACKGROUND

Statins are cholesterol lowering drugs that decrease the risk of cardiovascular events, but they are related with a few unfavorable symptoms in skeletal muscle including myopathy, and mild to moderate fatigue. Additionally, there has been discrepancies about the impacts of statins on brain and cognition. This study aimed to examine the impacts of two different statins, lipophilic simvastatin and hydrophilic rosuvastatin on cognitive functions in normal healthy rats. Simultaneously, we investigated the alterations of neurotropins and irisin levels in hippocampus and myokine levels in skeletal muscle.

METHODS

The rats were dosed with 88 mg kg body weight^-1 day^-1 simvastatin (n = 8), 150 mg kg body weight^-1 day^-1 rosuvastatin (n = 8) or vehicle (n = 8) for 18 days via oral gavage. After that behavioral assessment was performed and hippocampus and skeletal muscle samples were taken for the analysis of neurotrophins and irisin levels.

RESULTS

Locomotion and learning and memory functions were lower, but anxiety levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05). Hippocampal neurotrophins and irisin levels were lower, but skeletal muscle brain-derived neurotrophic factor (BDNF) and irisin levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05).

CONCLUSION

These findings suggest that high dose simvastatin and rosuvastatin impair cognitive functions via decreasing BDNF, NGF and irisin levels in the hippocampus.

Conserved statin-mediated activation of the p38-MAPK pathway protects Caenorhabditis elegans from the cholesterol-independent effects of statins

OBJECTIVE

Statins are a group of medications that reduce cholesterol synthesis by inhibiting the activity of HMG-CoA reductase, a key enzyme in the mevalonate pathway. The clinical use of statins to lower excess cholesterol levels has revolutionized the cardiovascular field and increased the survival of millions, but some patients have adverse side effects. A growing body of data suggests that some of the beneficial and adverse effects of statins, including their anti-inflammatory, anti-tumorigenic, and myopathic activities, are cholesterol-independent. However, the underlying mechanisms for these effects of statins are not well defined.

METHODS

Because Caenorhabditis elegans (C. elegans) lacks the cholesterol synthesis branch of the mevalonate pathway, this organism is a powerful system to unveil the cholesterol-independent effects of statins. We used genetic and biochemical approaches in C. elegans and cultured macrophage-derived murine cells to study the cellular response to statins.

RESULTS

We found that statins activate a conserved p38-MAPK (p38) cascade and that the protein geranylgeranylation branch of the mevalonate pathway links the effect of statins to the activation of this p38 pathway. We propose that the blockade of geranylgeranylation impairs the function of specific small GTPases we identified as upstream regulators of the p38 pathway. Statin-mediated p38 activation in C. elegans results in the regulation of programs of innate immunity, stress, and metabolism. In agreement with this regulation, knockout of the p38 pathway results in the hypersensitivity of C. elegans to statins. Treating cultured mammalian cells with clinical doses of statins results in the activation of the same p38 pathway, which upregulates the COX-2 protein, a major regulator of innate immunity in mammals.

CONCLUSIONS

Statins activate an evolutionarily conserved p38 pathway to regulate metabolism and innate immunity. Our results highlight the cytoprotective role of p38 activation under statin treatment in vivo and propose that this activation underlies many of the critical cholesterol-independent effects of statins.

Oxidative Stress-Mediated Blood-Brain Barrier (BBB) Disruption in Neurological Diseases

The blood-brain barrier (BBB), as a crucial gate of brain-blood molecular exchange, is involved in the pathogenesis of multiple neurological diseases. Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the scavenger system. Since oxidative stress plays a significant role in the production and maintenance of the BBB, the cerebrovascular system is especially vulnerable to it. The pathways that initiate BBB dysfunction include, but are not limited to, mitochondrial dysfunction, excitotoxicity, iron metabolism, cytokines, pyroptosis, and necroptosis, all converging on the generation of ROS. Interestingly, ROS also provide common triggers that directly regulate BBB damage, parameters including tight junction (TJ) modifications, transporters, matrix metalloproteinase (MMP) activation, inflammatory responses, and autophagy. We will discuss the role of oxidative stress-mediated BBB disruption in neurological diseases, such as hemorrhagic stroke, ischemic stroke (IS), Alzheimer’s disease (AD), Parkinson’s disease (PD), traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and cerebral small vessel disease (CSVD). This review will also discuss the latest clinical evidence of potential biomarkers and antioxidant drugs towards oxidative stress in neurological diseases. A deeper understanding of how oxidative stress damages BBB may open up more therapeutic options for the treatment of neurological diseases.

Composite nanofibers incorporating alpha lipoic acid and atorvastatin provide neuroprotection after peripheral nerve injury in rats

Despite the new treatment strategies within the last 30 years, peripheral nerve injury (PNI) is still a worldwide clinical problem. The incidence rate of PNIs is 1 in 1000 individuals per year. In this study, we designed a composite nanoplatform for dual therapy in peripheral nerve injury and investigated the in-vivo efficacy in rat sciatic nerve crush injury model. Alpha-lipoic acid (ALA) was loaded into poly lactic-co-glycolic acid (PLGA) electrospun nanofibers which would release the drug in a faster manner and atorvastatin (ATR) loaded chitosan (CH) nanoparticles were embedded into PLGA nanofibers to provide sustained release. Sciatic nerve crush was generated via Yasargil aneurism clip with a holding force of 50 g/cm². Nanofiber formulations were administered to the injured nerve immediately after trauma. Functional recovery of operated rat hind limb was evaluated using the sciatic functional index (SFI), extensor postural thrust (EPT), withdrawal reflex latency (WRL) and Basso, Beattie, and Bresnahan (BBB) test up to one month in the post-operative period at different time intervals. In addition to functional recovery assessments, ultrastructural and biochemical analyses were carried out on regenerated nerve fibers. L-929 mouse fibroblast cell line and B35 neuroblastoma cell line were used to investigate the cytotoxicity of nanofibers before in-vivo experiments. The neuroprotection potential of these novel nanocomposite fiber formulations has been demonstrated after local implantation of composite nanofiber sheets incorporating ALA and ATR, which contributed to the recovery of the motor and sensory function and nerve regeneration in a rat sciatic nerve crush injury model.

Fruiting bodies of selected edible mushrooms as a potential source of lovastatin

Agaricus bisporus, Cantharellus cibarius, Imleria badia, and Lentinula edodes are among the most popular species of edible mushrooms in Poland. These edible mushrooms are an important source of biologically active substances exhibiting beneficial (e.g., antioxidant, antitumor, antimicrobial, anti-inflammatory) effects on the human body. The fruiting bodies of edible mushrooms are also a valuable source of lovastatin, which belongs to a group of compounds, called statins, commonly used as cholesterol-lowering drugs. Due to the presence of lovastatin, edible mushrooms can be useful in the prevention of hypercholesterolemia. Therefore, the aim of this study was to determine the content of lovastatin in the selected species of edible mushrooms and to evaluate its release into artificial digestive juices. This study was the first to determine the release of lovastatin into digestive juices after the extraction of materials obtained from edible mushrooms. The largest amount of lovastatin was found in the fruiting bodies of C. cibarius (67.89 mg/100 g d.w.), and the smallest in those of L. edodes (0.95 mg/100 g d.w.). The amount of lovastatin released from the extracts of the examined species into digestive juices was found to be relatively low. The highest content after incubation in artificial gastric juice was detected for the fruiting bodies of L. edodes (0.02 mg/100 g d.w.) and after incubation in the intestinal juice for the mycelium from the in vitro cultures of L. edodes (0.51 mg/100 g d.w.). Thus, the results of the present study showed that due to its ability to accumulate lovastatin from culture medium, L. edodes mycelium can be used to obtain a product with increased hypolipidemic activity.

Oxidative stress, dysfunctional glucose metabolism and Alzheimer disease

Alzheimer disease (AD) is a major cause of age-related dementia. We do not fully understand AD aetiology and pathogenesis, but oxidative damage is a key component. The brain mostly uses glucose for energy, but in AD and amnestic mild cognitive impairment glucose metabolism is dramatically decreased, probably owing, at least in part, to oxidative damage to enzymes involved in glycolysis, the tricarboxylic acid cycle and ATP biosynthesis. Consequently, ATP-requiring processes for cognitive function are impaired, and synaptic dysfunction and neuronal death result, with ensuing thinning of key brain areas. We summarize current research on the interplay and sequence of these processes and suggest potential pharmacological interventions to retard AD progression.

Statin therapy: does sex matter?

OBJECTIVE

Statins are a class of drugs that competitively bind to the active site of HMG-CoA reductase enzyme, thereby inhibiting the initial steps in cholesterol synthesis. Originally approved for use in lowering serum cholesterol, a risk factor for developing atherosclerosis and coronary heart disease, statins have subsequently been noted to have myriad extrahepatic effects, including potential effects on cognition, diabetes, breast cancer, bone, and muscle. This narrative review assesses the current state of the science regarding the risks and benefits of statin therapy in women to identify areas where additional research is needed.

METHODS

Basic and clinical studies were identified by searching PubMed with particular attention to inclusion of female animals, women, randomized controlled trials, and sex-specific analyses.

RESULTS

Statin therapy is generally recommended to reduce the risk of cardiovascular disease. None of the current clinical guidelines, however, offer sex-specific recommendations for women due to lack of understanding of sex differences and underlying mechanisms of disease processes. In addition, conclusions regarding efficacy of treatments do not consider lipid solubility for the drug, dosing, duration of treatment, interactions with estrogen, or comorbidities. Pleiotropic effects of statins are often derived from secondary analysis of studies with cardiovascular events as primary outcomes.

CONCLUSIONS

Many of the trials that have established the efficacy and safety of statins were conducted predominantly or entirely in men, with results extrapolated to women. Additional research is needed to guide clinical recommendations specific to women. : Video Summary:http://links.lww.com/MENO/A462.

Effect of pioglitazone and simvastatin in lipopolysaccharide-induced amyloidogenesis and cognitive impairment in mice: possible role of glutamatergic pathway and oxidative stress

Neuroinflammation and β-amyloid (Aβ) deposition in the brain are well known characteristics of neurodegeneration. Diabetes and hypercholesterolemia are the main risk factors leading to memory loss and cognitive impairment. Recently, it was found that statins and thiazolidinediones have promising anti-inflammatory and neuroprotective effects that could delay neurodegeneration and neuronal loss in diabetic and hypercholesterolemic patients. The aim of the present study was to investigate the protective effect of simvastatin, pioglitazone, and their combination in lipopolysaccharide (LPS)-induced neuroinflammation and amyloidogenesis. Mice were divided into five groups: group 1 received 0.9% saline, group 2 received LPS (0.8 mg/kg in saline), group 3 received LPS (0.8 mgl kg)+simvastatin (5 mg/kg in saline), group 4 received LPS (0.8 mg/kg)+pioglitazone (20 mg/kg in saline), group 5 receiving LPS (0.8 mg/kg)+simvastatin (5 mg/kg)+pioglitazone (20 mg/kg). Y-maze and novel object recognition were used to assess the spatial and nonspatial behavioral changes. Nitric oxide levels and glutamate levels were measured to elucidate the anti-glutamatergic and anti-inflammatory effects of the tested drugs. Immunohistochemistry was performed to detect the presence of Aβ1-42 in the mice brain. LPS impaired memory, and increased Aβ deposition, nitric oxide, and glutamate brain levels. Both drugs produced a significant improvement in all parameters. We conclude that simvastatin and pioglitazone may have a protective effect against cognitive impairment induced by LPS, through targeting the glutamatergic and inflammatory pathways, especially in patients having hypercholesterolemia and diabetes.

Association Between Statin Use and Risk of Dementia After a Concussion

Importance

Concussions are an acute injury that may lead to chronic disability, while statin use might improve neurologic recovery.

Objective

To test whether statin use is associated with an increased or decreased risk of subsequent dementia after a concussion.

Design, Setting, and Participants

Large extended population-based double cohort study in Ontario, Canada, from April 1, 1993, to April 1, 2013 (enrollment), and continued until March 31, 2016 (follow-up). Dates of analysis were April 28, 2014, through March 21, 2019. Participants were older adults diagnosed as having a concussion, excluding severe cases resulting in hospitalization, individuals with a prior diagnosis of dementia or delirium, and those who died within 90 days.

Exposure

Statin prescription within 90 days after a concussion.

Main Outcome and Measure

Long-term incidence of dementia.

Results

This study identified 28 815 patients diagnosed as having a concussion (median age, 76 years; 61.3% female), of whom 7058 (24.5%) received a statin, and 21 757 (75.5%) did not receive a statin. A total of 4727 patients subsequently developed dementia over a mean follow-up of 3.9 years, equal to an incidence of 1 case per 6 patients. Patients who received a statin had a 13% reduced risk of dementia compared with patients who did not receive a statin (relative risk, 0.87; 95% CI, 0.81-0.93; P < .001). The decreased risk of dementia associated with statin use applied to diverse patient groups, remained independent of other cardiovascular medication use, intensified over time, was distinct from the risk of subsequent depression, and was not observed in patients after an ankle sprain.

Conclusions and Relevance

In this study, older adults had a substantial long-term risk of dementia after a concussion, which was associated with a modest reduction among patients receiving a statin.

Rosuvastatin alleviates high-salt and cholesterol diet-induced cognitive impairment in rats via Nrf2-ARE pathway

OBJECTIVE

The objectives of our study were to investigate the possible effect of rosuvastatin in ameliorating high salt and cholesterol diet (HSCD)-induced cognitive impairment and to also investigate its possible action via the Nrf2-ARE pathway.

METHODS

In silico studies were performed to check the theoretical binding of rosuvastatin to the Nrf2 target. HSCD was used to induce cognitive impairment in rats and neurobehavioral studies were performed to evaluate the efficacy of rosuvastatin in enhancing cognition. Biochemical analyses were used to estimate changes in oxidative markers. Western blot and immunohistochemical analyses were done to check Nrf2 translocation. TUNEL and caspase 3 tests were performed to evaluate reversal of apoptosis by rosuvastatin.

RESULTS

Rosuvastatin showed good theoretical affinity to Nrf2, significantly reversed changes in oxidative biomarkers which were induced by HSCD, and also improved the performance of rats in the neurobehavioral test. A rise in nuclear translocation of Nrf2 was revealed through immunohistochemical analysis and western blot. TUNEL staining and caspase 3 activity showed attenuation of apoptosis.

DISCUSSION

We have investigated a novel mechanism of action for rosuvastatin (via the Nrf2-ARE pathway) and demonstrated that it has the potential to be used in the treatment of cognitive impairment.

Pitavastatin treatment induces neuroprotection through the BDNF-TrkB signalling pathway in cultured cerebral neurons after oxygen-glucose deprivation

OBJECTIVES

Along with their lipid-lowering effect, statins have been reported to have neuroprotective function in both in vivo and in vitro models of neurodegenerative diseases. We conducted this study in order to uncover the he neuroprotective effect of the lipophilic statin pitavastatin (PTV) and investigate the underlying molecular mechanisms using primary cultured cerebral neurons exposed to oxygen-glucose deprivation (OGD).

METHODS

The primary cultured cerebral neurons were randomly assigned into four groups: the control group, the pitavastatin treatment group, the OGD group and the OGD + pitavastatin treatment group. The pitavastatin's concentration were set as follows: 1μM, 15μM, 30μM. After 3 hours OGD treatment, we use MTT method to assessment cell viability, immunofluorescence to observe neuron morphology and western blot method analysis the BDNF, TrkB.

RESULTS

PTV at concentrations of 1 μM and 15 μM elevated the survival rate of cortical neurons exposed to OGD, whereas 30 μM PTV did not show such an effect. Moreover, PTV promoted neuronal dendrite growth at concentrations of 1 μM and 15 μM. Increased expression levels of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) were observed in both of the following two scenarios: when neurons were treated with PTV for 48 hours and when PTV was added after the OGD procedure.

CONCLUSION

Pitavastatin treatment induces neuroprotection in cultured cerebral neurons after oxygen-glucose deprivation this neuroprotection induced by PTV involves the BDNF-TrkB signalling pathway.

Mevastatin promotes neuronal survival against Aβ-induced neurotoxicity through AMPK activation

Statins or HMG-CoA reductase inhibitors have been shown to be effective at lowering cholesterol levels, and the application of these molecules has gradually emerged as an attractive therapeutic strategy for neurodegenerative diseases. Epidemiological studies suggest that statin use is associated with a decreased incidence of Alzheimer's disease (AD). Thus, statins may play a beneficial role in reducing amyloid β (Aβ) toxicity, the most relevant pathological feature and pathogenesis of AD. However, the precise mechanisms involved in statin-inhibited Aβ toxicity remain unclear. In the present study, we report that mevastatin significantly protects against Aβ-induced neurotoxicity in SK-N-MC neuronal cells by restoring impaired insulin signaling. This protection appears to be associated with the activation of AMP-activated protein kinase (AMPK), which has long been known to increase insulin sensitivity. Our results also indicate that high levels of cholesterol likely underlie Aβ-induced neurotoxicity and that activation of AMPK by mevastatin alleviates insulin resistance. Signaling through the insulin receptor substrate-1/Akt pathway appears to lead to cell survival. These findings demonstrate that mevastatin plays a potential therapeutic role in targeting Aβ-mediated neurotoxicity. The molecule presents a novel therapeutic strategy for further studies in AD prevention and therapeutics.

Statin use and cognitive function in middle-aged adults with type 1 diabetes

AIM

To test associations between statin use and cognitive impairment in adults with childhood-onset type 1 diabetes (T1D).

METHODS

In 2010-13, n = 108 middle-aged participants from ongoing observational Pittsburgh Epidemiology of Diabetes Complications Study underwent neurocognitive assessment (mean age and T1D duration of 49 and 41 years, respectively). All were diagnosed with childhood-onset (i.e., prior to age 18) T1D between 1950 and 1980 and were seen within one year of diagnosis at Children’s Hospital of Pittsburgh. Self-reported statin use (yes/no and if yes, name of statin) was collected biennially from parent study baseline (1986-1988) to time of neurocognitive testing. Logistic regression models tested associations between statin use groups and cognitive impairment (defined as having two or more cognitive test scores 1.5SD or worse than published norms) while linear regression models tested associations between statin use groups and cognitive domain z-scores (domains: Verbal IQ, memory, executive function, psychomotor speed, and visuo-construction). All models controlled for education and age. To address confounding by indication, models were repeated using a propensity score for statin use.

RESULTS

Of the 108 participants, 51 reported never using statins. Median duration of statin use among the 57 ever users was 6 years. These 57 ever statin users were split to create two groups (≤ or > median years of statin use): 1-6 years (n = 25), and 7-12 years (n = 32). Compared with never users, using statins 1-6 years tripled the odds of cognitive impairment (OR = 3.16; 95%CI: 0.93-10.72; P = 0.06) and using statins 7-12 years almost quintupled the odds of cognitive impairment (OR = 4.84; 95%CI: 1.63-14.44; P = 0.005). Compared with never users, using statins 1-6 or 7-12 years was related to worse performance in the memory domain (β = -0.52; P = 0.003, and -0.39; P = 0.014, respectively). Adjusting for coronary artery disease, low density lipoprotein cholesterol, and Apo E4 status did not substantially alter results, and none of these covariates were significantly related to cognitive outcomes (all P > 0.05). Propensity score analyses support that associations between poor cognitive outcomes and statin use were not due merely to confounding by indication.

CONCLUSION

Statin use was associated with cognitive impairment, particularly affecting memory, in these middle-aged adults with childhood-onset T1D, whom at this age, should not yet manifest age-related memory deficits.

Production of transgenic pig as an Alzheimer's disease model using a multi-cistronic vector system

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with memory loss and cognitive impairments. An AD transgenic (Tg) pig model would be useful for preclinical testing of therapeutic agents. We generated an AD Tg pig by somatic cell nuclear transfer (SCNT) using a multi-cistronic vector that harbored three AD-related genes with a total of six well-characterized mutations: hAPP (K670N/M671L, I716V, and V717I), hTau (P301L), and hPS1 (M146V and L286P). Four AD Tg cell lines were established from Jeju black pig ear fibroblasts (JB-PEFs); the resultant JB-PEFAD cells harbored transgene integration, expressed transgene mRNAs, and had normal karyotypes. Tg line #2-1, which expressed high levels of the transgenes, was used for SCNT; cleavage and blastocyst rates of embryos derived from this line were lower than those of Non-Tg. These embryos yielded three piglets (Jeju National University AD-Tg pigs, JNUPIGs) revealed by microsatellite testing to be genetically identical to JB-PEFAD. Transgenes were expressed in multiple tissues, and at especially high levels in brain, and Aβ-40/42, total Tau, and GFAP levels were high in brains of the Tg animals. Five or more copies of transgenes were inserted into chromosome X. This is the first report of an AD Tg pig derived from a multi-cistronic vector.

Overexpression of Toll-Like Receptors 2, 3, 4, and 8 Is Correlated to the Vascular Atherosclerotic Process in the Hyperlipidemic Rabbit Model: The Effect of Statin Treatment

BACKGROUND

Atherosclerosis is the major cause of cardiovascular disease; hypercholesterolemia is a major risk factor. We hypothesized that specific TLR members (TLR2, TLR3, TLR4, TLR8) may play a role in atherosclerosis progression and its accompanying inflammatory response. We determined the association of atherosclerotic lesions and TLR mRNA expression in different aortic sites. We also assessed the effects of fluvastatin (Flu) treatment on TLR expression and plaque characteristics.

METHODS

Male rabbits, fed with an atherogenic diet for a duration of 3 months, were screened for advanced atherosclerotic lesions in the aorta. Additional animals received normal diet or normal diet plus Flu for 1 additional month. TLR mRNA expression in various thoracic and abdominal aortic segments was assessed, together with atherosclerotic changes.

RESULTS

After high lipid diet, the atherosclerotic burden increased more in the abdominal than in the thoracic aorta; TLR2, 3, 4, and 8 also increased significantly. Flu decreased atherosclerotic plaque, calcium deposition, lipid cores, intraplaque hemorrhage, erythrocyte membranes, endothelial cells, and macrophage infiltration, while increasing smooth muscle cells in plaques of both aortic segments; it also lowered TLR2, 3, 4, and 8 expression in all aortic segments to a stronger degree than resumption of normal diet. There was a strong association between blood and tissue parameters during experimental period and finally a strong correlation found between these parameters with mRNA of TLR2, 3, 4, and 8 in various stages.

CONCLUSION

For the first time TLR2, 3, 4, and 8 mRNA expression is prospectively explored after hypercholesterolemic diet in the rabbit model. TLR2, 3, 4, and 8 mRNA expression is strongly upregulated and correlates with the progression of atherosclerosis in the aorta. Flu significantly inhibited this progress and reduced inflammation via TLR downregulation which was strongly associated with regression of plaque morphology and atherosclerosis promoting factors.

Studying neuroprotective effect of Atorvastatin as a small molecule drug on high glucose-induced neurotoxicity in undifferentiated PC12 cells: role of NADPH oxidase

Overproduction of reactive oxygen species (ROS) by NADPH oxidase (NOX) activation has been considered the essential mechanism induced by hyperglycemia in various tissues. However, there is no comprehensive study on the role of NOXs in high glucose (HG)-induced toxic effect in neural tissues. Recently, a therapeutic strategy in oxidative related pathologies has been introduced by blocking the undesirable actions of NOX enzymes by small molecules. The protective roles of Statins in ameliorating oxidative stress by NOX inhibition have been shown in some tissues except neural. We hypothesized then, that different NOXs may have role in HG-induced neural cell injury. Furthermore, we postulate that Atorvastatin as a small molecule may modulate this NOXs activity to protect neural cells. Undifferentiated PC12 cells were treated with HG (140 mM/24 h) in the presence and absence of Atorvastatin (1 μM/96 h). The cell viability was measured by MTT assay and the gene and protein expressions profile of NOX (1-4) were determined by RT-PCR and western blotting, respectively. Levels of ROS and malondialdehyde (MDA) were also evaluated. Gene and protein expression levels of NOX (1-4) and consequently ROS and MDA levels were elevated in HG-treated PC12 cells. Atorvastatin could significantly decrease HG-induced NOXs, ROS and MDA elevation and improve impaired cell viability. It can be concluded that HG could elevate NOXs activity, ROS and MDA levels in neural tissues and Atorvastatin as a small molecule NOX inhibitor drug may prevent and delay diabetic complications, particularly neuropathy.

Phytosterols and Dementia

As the aging of the world's population is becoming increasingly serious, dementia-related diseases have become a hot topic in public health research. In recent years, human epidemiological studies have focused on lipid metabolism disorders and dementia. The efficacy of phytosterol intake as a cholesterol-lowering agent has been demonstrated. Phytosterols directly serve as ligands of the nuclear receptors, peroxisome proliferator-activated receptors (PPARs), activating Sirtuin 1 (SIRT-1), which are involved in the regulation of lipid metabolism and the pathogenesis of dementia. Moreover, phytosterols mediate cell and membrane cholesterol efflux or beta amyloid (Aβ) metabolism, which have preventative and therapeutic effects on dementia. Additionally, incorporation of plant sterols in lipid rafts can effectively reduce dietary fat and alter the dietary composition of fiber, fat and cholesterol to regulate appetite and calories. Overall, the objectives of this review are to explore whether phytosterols are a potentially effective target for the prevention of dementia and to discuss a possible molecular mechanism by which phytosterols play a role in the pathogenesis of dementia via the PPARs-SIRT-1 pathway.

Protein Prenylation Constitutes an Endogenous Brake on Axonal Growth

Suboptimal axonal regeneration contributes to the consequences of nervous system trauma and neurodegenerative disease, but the intrinsic mechanisms that regulate axon growth remain unclear. We screened 50,400 small molecules for their ability to promote axon outgrowth on inhibitory substrata. The most potent hits were the statins, which stimulated growth of all mouse- and human-patient-derived neurons tested, both in vitro and in vivo, as did combined inhibition of the protein prenylation enzymes farnesyltransferase (PFT) and geranylgeranyl transferase I (PGGT-1). Compensatory sprouting of motor axons may delay clinical onset of amyotrophic lateral sclerosis (ALS). Accordingly, elevated levels of PGGT1B, which would be predicted to reduce sprouting, were found in motor neurons of early- versus late-onset ALS patients postmortem. The mevalonate-prenylation pathway therefore constitutes an endogenous brake on axonal growth, and its inhibition provides a potential therapeutic approach to accelerate neuronal regeneration in humans.

Modulating antibiotic activity towards respiratory bacterial pathogens by co-medications: a multi-target approach

Non-antibiotic drugs can modulate bacterial physiology and/or antibiotic activity, opening perspectives for innovative therapeutic strategies. Focusing on respiratory pathogens and considering in vitro, in vivo, and clinical data, here we examine the effect of these drugs on the expression of resistance mechanisms, biofilm formation, and intracellular survival, as well as their influence on the activity of antibiotics on bacteria. Beyond the description of the effects observed, we also comment on concentrations that are active and discuss the mechanisms of drug-drug or drug-target interactions. This discussion should be helpful in defining useful targets for adjuvant therapy and establishing the corresponding pharmacophores for further drug fine-tuning.

Statins and the brain: New perspective for old drugs

Statins are one of the most popular lipid-lowering drugs (LLDs). Upon oral administration, these drugs are well absorbed by the intestine and effectively used for the treatment of dyslipidemias. Recently, statins are becoming also well-known for their cholesterol-independent effects and their potential use in brain diseases and different types of cancers. While still controversial, recent research has suggested that statin's cholesterol-independent activities work possibly through alterations on isoprenoid levels. This reduction of isoprenoids in the central nervous system might result in effective biochemical and behavioral improvements on certain neurological disorders. This manuscript aims to highlight current research describing the use of statin therapy in the brain and discuss whether statins might affect neuronal dynamics and function independently of their cholesterol regulatory role.

An overview on therapeutics attenuating amyloid β level in Alzheimer's disease: targeting neurotransmission, inflammation, oxidative stress and enhanced cholesterol levels

Alzheimer's disease (AD) is the most common underlying cause of dementia, and novel drugs for its treatment are needed. Of the different theories explaining the development and progression of AD, "amyloid hypothesis" is the most supported by experimental data. This hypothesis states that the cleavage of amyloid precursor protein (APP) leads to the formation of amyloid beta (Aβ) peptides that congregate with formation and deposition of Aβ plaques in the frontal cortex and hippocampus. Risk factors including neurotransmitter modulation, chronic inflammation, metal-induced oxidative stress and elevated cholesterol levels are key contributors to the disease progress. Current therapeutic strategies abating AD progression are primarily based on anti-acetylcholinesterase (AChE) inhibitors as cognitive enhancers. The AChE inhibitor, donepezil, is proven to strengthen cognitive functions and appears effective in treating moderate to severe AD patients. N-Methyl-D-aspartate receptor antagonist, memantine, is also useful, and its combination with donepezil demonstrated a strong stabilizing effect in clinical studies on AD. Nonsteroidal anti-inflammatory drugs delayed the onset and progression of AD and attenuated cognitive dysfunction. Based upon epidemiological evidence and animal studies, antioxidants emerged as potential AD preventive agents; however, clinical trials revealed inconsistencies. Pharmacokinetic and pharmacodynamic profiling demonstrated pleiotropic functions of the hypolipidemic class of drugs, statins, potentially contributing towards the prevention of AD. In addition, targeting the APP processing pathways, stimulating neuroprotective signaling mechanisms, using the amyloid anti-aggregants and Aβ immunotherapy surfaced as well-tested strategies in reducing the AD-like pathology. Overall, this review covers mechanism of inducing the Aβ formation, key risk factors and major therapeutics prevalent in the AD treatment nowadays. It also delineates the need for novel screening approaches towards identifying drugs that may prevent or at least limit the progression of this devastating disease.

Simvastatin and atorvastatin facilitates amyloid β-protein degradation in extracellular spaces by increasing neprilysin secretion from astrocytes through activation of MAPK/Erk1/2 pathways

One of the major neuropathological hallmarks of Alzheimer's disease (AD) is the deposition of amyloid β-protein (Aβ) in the brain. Aβ accumulation seems to arise from an imbalance between Aβ production and clearance. Neprilysin (NEP) and insulin-degrading enzyme (IDE) are the important Aβ-degrading enzymes in the brain, and deficits in their expression may promote Aβ deposition in patients with sporadic late-onset AD. Statins, which are used clinically for reducing cholesterol levels, can exert beneficial effects on AD. Therefore, we examined whether various statins are associated with Aβ degradation by inducing NEP and IDE expression, and then evaluating the relation between activation of intracellular signaling transduction, inhibition of cholesterol production, and morphological changes to astrocytes. Treating cultured rat astrocytes with simvastatin and atorvastatin significantly decreased the expression of NEP but not IDE in a concentration- and time-dependent manner. The decrease in NEP expression was a result of activation of extracellular signal-regulated kinase (ERK) but not the reduction of cholesterol synthesis pathway. This NEP reduction was achieved by the release to the extracellular space of cultured astrocytes. Furthermore, the cultured medium prepared from simvastatin- and atorvastatin-treated astrocytes significantly induced the degradation of exogenous Aβ. These results suggest that simvastatin and atorvastatin induce the increase of Aβ degradation of NEP on the extracellular of astrocytes by inducing ERK-mediated pathway activity and that these reagents regulate the differential mechanisms between the secretion of NEP, the induction of cholesterol reduction, and the morphological changes in the cultured astrocytes.

Heat shock proteins and hormesis in the diagnosis and treatment of neurodegenerative diseases

Modulation of endogenous cellular defense mechanisms via the vitagene system represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. The possibility of high-throughoutput screening using proteomic techniques, particularly redox proteomics, provide more comprehensive overview of the interaction of proteins, as well as the interplay among processes involved in neuroprotection. Here by introducing the hormetic dose response concept, the mechanistic foundations and applications to the field of neuroprotection, we discuss the emerging role of heat shock protein as prominent member of vitagene network in neuroprotection and redox proteomics as a tool for investigating redox modulation of stress responsive vitagenes. Hormetic mechanisms are reviewed as possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the neurodegenerative disease process.

Statin Use, Incident Dementia and Alzheimer Disease in Elderly African Americans

OBJECTIVE

To investigate the association between statin use, incident dementia, and Alzheimer disease (AD) in a prospective elderly African American cohort.

DESIGN

Two stage design with a screening interview followed by a comprehensive in-home assessment conducted over an eight-year period. Diagnoses of incident AD and dementia were made by consensus. Statin use was collected at each evaluation. Measurements of low-density lipoprotein cholesterol (LDL), C-reactive protein (CRP) and APOE genotype were obtained from baseline blood samples. Logistic regression models were used to test the association of statin use on incident dementia and AD and its possible association with lipid and CRP levels.

SETTING

Indianapolis, Indiana.

PARTICIPANTS

From an original cohort of 2629 participants, a subsample of 974 African Americans aged >70 years with normal cognition, at least one follow up evaluation, complete statin information, and biomarker availability were included.

MAIN OUTCOME MEASURES

Incident dementia and incident AD.

RESULTS

After controlling for age at diagnosis, sex, education level, presence of the APOE ε4 allele and history of stroke for the incident dementia model, baseline use of statins was associated with a significantly decreased risk of incident dementia (OR=.44, P=.029) and incident AD (OR=.40, P=.029). The significant effect of statin use on reduced AD risk and trend for dementia risk was found only for those participants who reported consistent use over the observational period (incident AD: P=.034; incident dementia: P=.061). Additional models found no significant interaction between baseline statin use, baseline LDL, or CRP level and incident dementia/AD.

CONCLUSIONS

Consistent use of statin medications during eight years of follow-up resulted in significantly reduced risk for incident AD and a trend toward reduced risk for incident dementia.

Lovastatin Differentially Affects Neuronal Cholesterol and Amyloid-β Production in vivo and in vitro

BACKGROUND AND AIMS

Epidemiological and experimental studies indicate that high cholesterol may increase susceptibility to age-associated neurodegenerative disorders, such as Alzheimer's disease (AD). Thus, it has been suggested that statins, which are inhibitors of the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), may be a useful therapeutic tool to diminish the risk of AD. However, several studies that analyzed the therapeutic benefits of statins have yielded conflicting results. Herein, we investigated the role of lovastatin on neuronal cholesterol homeostasis and its effects on amyloid β protein production in vivo and in vitro.

METHODS AND RESULTS

Lovastatin effects were analyzed in vitro using differentiated human neuroblastoma cells and in vivo in a lovastatin-fed rat model. We demonstrated that lovastatin can differentially affect the expression of APP and Aβ production in vivo and in vitro. Lovastatin-induced HMGCR inhibition was detrimental to neuronal survival in vitro via a mechanism unrelated to the reduction of cholesterol. We found that in vivo, dietary cholesterol was associated with increased Aβ production in the cerebral cortex, and lovastatin was not able to reduce cholesterol levels. However, lovastatin induced a remarkable increase in the mature form of the sterol regulatory element-binding protein-2 (SREBP-2) as well as its target gene HMGCR, in both neuronal cells and in the brain.

CONCLUSIONS

Lovastatin modifies the mevalonate pathway without affecting cholesterol levels in vivo and is able to reduce Aβ levels only in vitro.

Targeting transporters: promoting blood-brain barrier repair in response to oxidative stress injury

The blood-brain barrier (BBB) is a physical and biochemical barrier that precisely regulates the ability of endogenous and exogenous substances to accumulate within brain tissue. It possesses structural and biochemical features (i.e., tight junction and adherens junction protein complexes, influx and efflux transporters) that work in concert to control solute permeation. Oxidative stress, a critical component of several diseases including cerebral hypoxia/ischemia and peripheral inflammatory pain, can cause considerable injury to the BBB and lead to significant CNS pathology. This suggests a critical need for novel therapeutic approaches that can protect the BBB in diseases with an oxidative stress component. Recent studies have identified molecular targets (i.e., putative membrane transporters, intracellular signaling systems) that can be exploited for optimization of endothelial drug delivery or for control of transport of endogenous substrates such as the antioxidant glutathione (GSH). In particular, targeting transporters offers a unique approach to protect BBB integrity by promoting repair of cell-cell interactions at the level of the brain microvascular endothelium. This review summarizes current knowledge in this area and emphasizes those targets that present considerable opportunity for providing BBB protection and/or promoting BBB repair in the setting of oxidative stress. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Neuronal marker recovery after Simvastatin treatment in dementia in the rat brain: in vivo magnetic resonance study

The aim of study was to search for new biomarkers with a magnetic resonance technique to identify the early stages of dementia, induced by D-galactose, and evaluate Simvastatin therapy. Localized proton magnetic resonance spectroscopy measurements showed a significant decrease in the concentration of N-acetylaspartate+N-acetylaspartylglutamate and myo-inositol in the D-galactose group compared to the control group, and, conversely, an increase of N-acetylaspartate+N-acetylaspartylglutamate in the D-galactose/Simvastatin group. Using a saturation transfer experiment, with phosphorus magnetic resonance spectroscopy, we observed a significant elevation of the forward rate constant of the creatine kinase reaction in the brains of the D-galactose group compared to controls, and subsequently, a significant reduction of this reaction in the D-galactose/Simvastatin group. Spatial learning and memory were evaluated using the modified Morris water maze test. The dynamics of the learning process represented by the learning index revealed a significant reduction in learning in the D-galactose group, but the deficits as a consequence of the D-galactose effects were recovered in the D-galactose/Simvastatin group, in which the learning dynamics resembled those of the control group. By determining the thiobarbituric acid reactive substances and total coenzyme Q9 in plasma, we have shown that long-term administration of D-galactose created conditions for oxidative stress, and that the administration of Simvastatin decreased oxidative stress in plasma. Volumetry analyses from the hippocampal area show a reduction in the segmented area in the D-galactose group, compared with the control group, and an enlarged area in the hippocampus in the d-galactose/Simvastatin group.

Modulatory role of simvastatin against aluminium chloride-induced behavioural and biochemical changes in rats

Objectives. Aluminium, a neurotoxic agent in humans, has been implicated in the pathogenesis of neurodegenerative disorders. In this study, we examined the behavioral and biochemical effects of aluminium in rats with special emphasis on memory centres, namely, hippocampus and frontal cortex. Further, the effect of simvastatin treatment on aluminium intoxication was evaluated. Methods. Rats were exposed to aluminium chloride (AlCl₃) for 60 days. Simvastatin (10 mg/kg/p.o.) and rivastigmine (1 mg/kg/p.o.) were administered daily prior to AlCl₃. Behavioral parameters were assessed using Morris water maze test and actophotometer followed by biochemical investigations, namely, acetylcholinesterase (AChE) activity, TNF-α level, antioxidant enzymes (GSH, catalase), lipid peroxidation, and nitrite level in hippocampus and frontal cortex. Triglycerides, total cholesterol, LDL, and HDL levels in serum were also determined. Key Findings. Simvastatin treatment improved cognitive function and locomotor activity in rats. Simvastatin reversed hyperlipidemia and significantly rectified the deleterious effect of AlCl₃ on AChE activity. Further, in hippocampus and frontal cortex, aluminium-induced elevation in nitrite and TNF-α and reduction in antioxidant enzymes were inhibited by simvastatin. Conclusion. To conclude, the present study suggests that simvastatin per se protects the neurons in hippocampus and frontal cortex from AlCl₃, an environmental toxin.

The 2013 SFRBM discovery award: selected discoveries from the butterfield laboratory of oxidative stress and its sequela in brain in cognitive disorders exemplified by Alzheimer disease and chemotherapy induced cognitive impairment

This retrospective review on discoveries of the roles of oxidative stress in brain of subjects with Alzheimer disease (AD) and animal models thereof as well as brain from animal models of chemotherapy-induced cognitive impairment (CICI) results from the author receiving the 2013 Discovery Award from the Society for Free Radical Biology and Medicine. The paper reviews our laboratory's discovery of protein oxidation and lipid peroxidation in AD brain regions rich in amyloid β-peptide (Aβ) but not in Aβ-poor cerebellum; redox proteomics as a means to identify oxidatively modified brain proteins in AD and its earlier forms that are consistent with the pathology, biochemistry, and clinical presentation of these disorders; how Aβ in in vivo, ex vivo, and in vitro studies can lead to oxidative modification of key proteins that also are oxidatively modified in AD brain; the role of the single methionine residue of Aβ(1-42) in these processes; and some of the potential mechanisms in the pathogenesis and progression of AD. CICI affects a significant fraction of the 14 million American cancer survivors, and due to diminished cognitive function, reduced quality of life of the persons with CICI (called "chemobrain" by patients) often results. A proposed mechanism for CICI employed the prototypical ROS-generating and non-blood brain barrier (BBB)-penetrating chemotherapeutic agent doxorubicin (Dox, also called adriamycin, ADR). Because of the quinone moiety within the structure of Dox, this agent undergoes redox cycling to produce superoxide free radical peripherally. This, in turn, leads to oxidative modification of the key plasma protein, apolipoprotein A1 (ApoA1). Oxidized ApoA1 leads to elevated peripheral TNFα, a proinflammatory cytokine that crosses the BBB to induce oxidative stress in brain parenchyma that affects negatively brain mitochondria. This subsequently leads to apoptotic cell death resulting in CICI. This review outlines aspects of CICI consistent with the clinical presentation, biochemistry, and pathology of this disorder. To the author's knowledge this is the only plausible and self-consistent mechanism to explain CICI. These two different disorders of the CNS affect millions of persons worldwide. Both AD and CICI share free radical-mediated oxidative stress in brain, but the source of oxidative stress is not the same. Continued research is necessary to better understand both AD and CICI. The discoveries about these disorders from the Butterfield Laboratory that led to the 2013 Discovery Award from the Society of Free Radical and Medicine provide a significant foundation from which this future research can be launched.

Possible modification of Alzheimer's disease by statins in midlife: interactions with genetic and non-genetic risk factors

The benefits of statins, commonly prescribed for hypercholesterolemia, in treating Alzheimer's disease (AD) have not yet been fully established. A recent randomized clinical trial did not show any therapeutic effects of two statins on cognitive function in AD. Interestingly, however, the results of the Rotterdam study, one of the largest prospective cohort studies, showed reduced risk of AD in statin users. Based on the current understanding of statin actions and AD pathogenesis, it is still worth exploring whether statins can prevent AD when administered decades before the onset of AD or from midlife. This review discusses the possible beneficial effects of statins, drawn from previous clinical observations, pathogenic mechanisms, which include β-amyloid (Aβ) and tau metabolism, genetic and non-genetic risk factors (apolipoprotein E, cholesterol, sex, hypertension, and diabetes), and other clinical features (vascular dysfunction and oxidative and inflammatory stress) of AD. These findings suggest that administration of statins in midlife might prevent AD in late life by modifying genetic and non-genetic risk factors for AD. It should be clarified whether statins inhibit Aβ accumulation, tau pathological features, and brain atrophy in humans. To answer this question, a randomized controlled study using amyloid positron emission tomography (PET), tau-PET, and magnetic resonance imaging would be useful. This clinical evaluation could help us to overcome this devastating disease.

Statins more than cholesterol lowering agents in Alzheimer disease: their pleiotropic functions as potential therapeutic targets

Alzheimer disease (AD) is a progressive neurodegenerative disorder characterized by severe cognitive impairment, inability to perform activities of daily living and mood changes. Statins, long known to be beneficial in conditions where dyslipidemia occurs by lowering serum cholesterol levels, also have been proposed for use in neurodegenerative conditions, including AD. However, it is not clear that the purported effectiveness of statins in neurodegenerative disorders is directly related to cholesterol-lowering effects of these agents; rather, the pleiotropic functions of statins likely play critical roles. The aim of this review is to provide an overview on the new discoveries about the effects of statin therapy on the oxidative and nitrosative stress levels as well as on the modulation of the heme oxygenase/biliverdin reductase (HO/BVR) system in the brain. We propose a novel mechanism of action for atorvastatin which, through the activation of HO/BVR-A system, may contribute to the neuroprotective effects thus suggesting a potential therapeutic role in AD and potentially accounting for the observation of decreased AD incidence with persons on statin.

Statins stimulate the production of a soluble form of the receptor for advanced glycation end products

The beneficial effects of statin therapy in the reduction of cardiovascular pathogenesis, atherosclerosis, and diabetic complications are well known. The receptor for advanced glycation end products (RAGE) plays an important role in the progression of these diseases. In contrast, soluble forms of RAGE act as decoys for RAGE ligands and may prevent the development of RAGE-mediated disorders. Soluble forms of RAGE are either produced by alternative splicing [endogenous secretory RAGE (esRAGE)] or by proteolytic shedding mediated by metalloproteinases [shed RAGE (sRAGE)]. Therefore we analyzed whether statins influence the production of soluble RAGE. Lovastatin treatment of either mouse alveolar epithelial cells endogenously expressing RAGE or HEK cells overexpressing RAGE caused induction of RAGE shedding, but did not influence secretion of esRAGE from HEK cells overexpressing esRAGE. Lovastatin-induced secretion of sRAGE was also evident after restoration of the isoprenylation pathway, demonstrating a correlation of sterol biosynthesis and activation of RAGE shedding. Lovastatin-stimulated induction of RAGE shedding was completely abolished by a metalloproteinase ADAM10 inhibitor. We also demonstrate that statins stimulate RAGE shedding at low physiologically relevant concentrations. Our results show that statins, due to their cholesterol-lowering effects, increase the soluble RAGE level by inducing RAGE shedding, and by doing this, might prevent the development of RAGE-mediated pathogenesis.

Biliverdin Reductase-A correlates with inducible nitric oxide synthasein in atorvastatin treated aged canine brain

Alzheimer's disease is a neurodegenerative disorder characterized by progressive cognitive impairment and neuropathology. Recent preclinical and epidemiological studies proposed statins as a possible therapeutic drug for Alzheimer's disease, but the exact mechanisms of action are still unknown. Biliverdin reductase-A is a pleiotropic enzyme involved in cellular stress responses. It not only transforms biliverdin-IX alpha into the antioxidant bilirubin-IX alpha but its serine/threonine/tyrosine kinase activity is able to modulate cell signaling networks. We previously reported the beneficial effects of atorvastatin treatment on biliverdin reductase-A and heme oxygenase-1 in the brains of a well characterized pre-clinical model of Alzheimer's disease, aged beagles, together with observed improvement in cognition. Here we extend our knowledge of the effects of atorvastatin on inducible nitric oxide synthase in parietal cortex, cerebellum and liver of the same animals. We demonstrated that atorvastatin treatment (80 mg/day for 14.5 months) to aged beagles selectively increased inducible nitric oxide synthase in the parietal cortex but not in the cerebellum. In contrast, inducible nitric oxide synthase protein levels were significantly decreased in the liver. Significant positive correlations were found between biliverdin reductase-A and inducible nitric oxide synthase as well as heme oxygenase-1 protein levels in the parietal cortex. The opposite was observed in the liver. Inducible nitric oxide synthase up-regulation in the parietal cortex was positively associated with improved biliverdin reductase-A functions, whereas the oxidative-induced impairment of biliverdin reductase-A in the liver negatively affected inducible nitric oxide synthase expression, thus suggesting a role for biliverdin reductase-A in atorvastatin-dependent inducible nitric oxide synthase changes. Interestingly, increased inducible nitric oxide synthase levels in the parietal cortex were not associated with higher oxidative/nitrosative stress levels. We hypothesize that biliverdin reductase-A-dependent inducible nitric oxide synthase regulation strongly contributes to the cognitive improvement observed following atorvastatin treatment.

Stress responses, vitagenes and hormesis as critical determinants in aging and longevity: Mitochondria as a "chi"

Understanding mechanisms of aging and determinants of life span will help to reduce age-related morbidity and facilitate healthy aging. Average lifespan has increased over the last centuries, as a consequence of medical and environmental factors, but maximal life span remains unchanged. Extension of maximal life span is currently possible in animal models with measures such as genetic manipulations and caloric restriction (CR). CR appears to prolong life by reducing reactive oxygen species (ROS)-mediated oxidative damage. But ROS formation, which is positively implicated in cellular stress response mechanisms, is a highly regulated process controlled by a complex network of intracellular signaling pathways. By sensing the intracellular nutrient and energy status, the functional state of mitochondria, and the concentration of ROS produced in mitochondria, the longevity network regulates life span across species by coordinating information flow along its convergent, divergent and multiply branched signaling pathways, including vitagenes which are genes involved in preserving cellular homeostasis during stressful conditions. Vitagenes encode for heat shock proteins (Hsp) Hsp32, Hsp70, the thioredoxin and the sirtuin protein systems. Dietary antioxidants, have recently been demonstrated to be neuroprotective through the activation of hormetic pathways, including vitagenes. The hormetic dose-response, challenges long-standing beliefs about the nature of the dose-response in a lowdose zone, having the potential to affect significantly the design of pre-clinical studies and clinical trials as well as strategies for optimal patient dosing in the treatment of numerous diseases. Given the broad cytoprotective properties of the heat shock response there is now strong interest in discovering and developing pharmacological agents capable of inducing stress responses. Here we focus on possible signaling mechanisms involved in the activation of vitagenes resulting in enhanced defense against energy and stress resistance homeostasis dysiruption with consequent impact on longevity processes.