Statins and neuroprotection

Low-density lipoprotein cholesterol, statin therapy, and cerebral microbleeds: The CIRCLE study

BACKGROUND

Current evidence suggests a potential association between cerebral microbleeds (CMBs), low-density lipoprotein cholesterol (LDL-C) levels, and statin use, but the exact relationship remains unclear. This study aims to prospectively examine these relationships in a stroke-free population.

METHODS

From January 2010 to January 2020, we enrolled stroke-free individuals with at least one cerebral small vessel disease imaging marker from the CIRCLE study (ClinicalTrials.gov ID: NCT03542734). Participants underwent baseline and 1-year follow-up susceptibility-weighted imaging (SWI), and baseline LDL-C testing. New CMBs were categorized as strictly lobar and deep CMBs based on location.

RESULTS

A total of 209 individuals were included. Baseline serum LDL-C levels were divided into quartiles: Q1 (≤1.76 mmol/L), Q2 (1.77-2.36 mmol/L), Q3 (2.37-2.93 mmol/L), and Q4 (>2.93 mmol/L). The incidence of new deep CMBs was 30.0%, 11.1%, 10.9%, 8.2% in Q1, Q2, Q3, Q4, respectively. Multivariate logistic model revealed that only LDL-C in Q1 was associated with increased incidence of new deep CMBs (OR = 4.256; 95% CI: 1.156-15.666; p = 0.029). In a subset of 169 participants without prior statin use, the use of atorvastatin was associated with reduced occurrence of new deep CMBs (OR = 0.181; 95% CI: 0.035-0.928; p = 0.040), while it was not found with rosuvastatin (OR = 0.808; 95% CI: 0.174-3.741; p = 0.785).

CONCLUSIONS

While lower LDL-C levels were associated with higher CMB development, statin therapy did not increase the risk of new CMBs. Atorvastatin even demonstrated a protective effect.

Medications use among women with dementia: a cohort study

BACKGROUND

Older population with dementia use huge range of medications. In this study, we aimed to determine the prevalence of commonly used medications a year before and after first recorded dementia diagnosis among older Australian women.

METHODS

The study utilized Australian Longitudinal Study on Women's Health (ALSWH) data from 2090 women with known dementia, linked with administrative health datasets. The Pharmaceutical Benefits Scheme (PBS) data provided detailed information about prescribed medications. We applied latent class analysis (LCA) to the post-dementia data to identify patterns of medication use. Logistic regression model was used to explore the impact of potential predictors for medication utilization.

RESULTS

Antipsychotic use increased from 5% before dementia to 19% after dementia, while antidementia medication use increased from < 1 to 28%. There was a modest increase in benzodiazepines and antidepressants. Post-dementia, four distinct groups were identified using LCA (names based on probabilities of medications use) as: "High Psychotropic-Low Cardiovascular" (16% of the sample); "Moderate Psychotropic-High Cardiovascular" (12%); "Low Psychotropic-High Cardiovascular" (27%); and "Low Psychotropic-Low Cardiovascular" (45%). Living in Residential Aged Care (RAC) and frailty were associated with increased odds of being in the higher psychotropic use groups.

CONCLUSIONS

Substantial utilization of psychotropic medications by older people with dementia indicates a need for a careful review of the use of these medications. Appropriate alternative approaches to the management of dementia should be practiced with a special focus on RAC residents with frailty.

Statin Effects in Atrial Fibrillation-Related Stroke: A Systematic Review and Meta-Analysis

Background: Statins lower the risk of recurrent stroke and mortality and improve outcomes in patients with ischemic stroke. However, the effects of statins on atrial fibrillation (AF)-related stroke are not well-established. Our study aims to investigate the effects of statin therapy on the clinical outcomes in patients with AF-related stroke.

Methods: Electronic databases (MEDLINE, Embase, and Scopus) were searched for previous studies on the effects of pre- and post-stroke statins on the clinical outcomes in AF-related stroke patients. The primary outcome was all-cause mortality. Secondary outcomes included recurrent ischemic stroke, acute coronary events, major adverse cardiovascular events (MACE), and short-term functional outcomes. We extracted hazard ratios (HRs) or odds ratios (ORs) with 95% confidence interval (CI) from each study and pooled them through a meta-analysis.

Results: A total of eight studies (five on post-stroke statins and three on pre-stroke statins) with 12,216 patients were included in the analysis. Post-stroke statin therapy reduced the risk of all-cause mortality (HR, 0.63; 95% CI, 0.55–0.74). This beneficial effect was sustained regardless of statin intensity. However, no significant associations were observed between statin therapy and a reduction in the risk of recurrent ischemic stroke, acute coronary events, or MACE. Pre-stroke statin use was associated with a lower risk of poor short-term functional outcomes (OR, 0.63; 95% CI, 0.47–0.85).

Conclusions: Statin therapy for AF-related stroke may reduce all-cause mortality and improve functional outcomes. Randomized controlled studies are warranted to confirm the effects of statins on the outcomes of AF-related stroke.

Regulation of Small GTPase Prenylation in the Nervous System

Mevalonate pathway inhibitors have been extensively studied for their roles in cholesterol depletion and for inhibiting the prenylation and activation of various proteins. Inhibition of protein prenylation has potential therapeutic uses against neurological disorders, like neural cancers, neurodegeneration, and neurotramatic lesions. Protection against neurodegeneration and promotion of neuronal regeneration is regulated in large part by Ras superfamily small guanosine triphosphatases (GTPases), particularly the Ras, Rho, and Rab subfamilies. These proteins are prenylated to target them to cellular membranes. Prenylation can be specifically inhibited through altering the function of enzymes of the mevalonate pathway necessary for isoprenoid production and attachment to target proteins to elicit a variety of effects on neural cells. However, this approach does not address how prenylation affects a specific protein. This review focuses on the regulation of small GTPase prenylation, the different techniques to inhibit prenylation, and how this inhibition has affected neural cell processes.

Association of blood lipids, atherosclerosis and statin use with dementia and cognitive impairment after stroke: A systematic review and meta-analysis

BACKGROUND

Trial and observational evidence is conflicting in terms of the association of blood lipids, atherosclerosis and statin use with dementia and cognitive impairment in the general population. It is uncertain whether the associations occur in stroke patients, who are at known higher risk of cognitive decline. This systematic review was to synthesize the evidence for these associations among stroke patients.

METHODS

MEDLINE, EMBASE, the Cochrane Library and trial registries were searched. We included randomized controlled trials (RCTs) or observational cohort studies conducted among patients with stroke and reported on the association of blood lipids, atherosclerosis or statin use with dementia or cognitive impairment. Meta-analysis was conducted separately for crude and maximally adjusted odds ratios (ORs) and hazard ratios (HRs).

RESULTS

Of 18,026 records retrieved, 56 studies (one RCT and 55 cohort studies) comprising 38,423 stroke patients were included. For coronary heart disease, the pooled OR of dementia and cognitive impairment was 1.32 (95%CI 1.10-1.58, n = 15 studies, I² = 0%) and 1.23 (95%CI 0.99-1.54, n = 14, I² = 26.9%), respectively. Peripheral artery disease was associated with dementia (OR 3.59, 95%CI 1.47-8.76, n = 2, I² = 0%) and cognitive impairment (OR 2.70, 95%CI 1.09-6.69, n = 1). For carotid stenosis, the pooled OR of dementia and cognitive impairment was 2.67 (95%CI 0.83-8.62, n = 3, I² = 77.9%) and 3.34 (95%CI 0.79-14.1, n = 4, I² = 96.6%), respectively. For post-stroke statin use, the pooled OR of dementia and cognitive impairment was 0.89 (95%CI 0.65-1.21, n = 1) and 0.56 (95%CI 0.46-0.69, n = 3, I² = 0%), respectively. No association was observed for hypercholesterolemia. These results were mostly consistent with adjusted ORs or HRs, which were reported from limited evidence.

CONCLUSION

Atherosclerosis was associated with an increased risk of post-stroke dementia. Post-stroke statin use was associated with decreased risk of cognitive impairment. To confirm whether or not statins confer advantages in the post-stroke population in terms of preventing cognitive decline over and above their known effectiveness in reducing risk of further vascular events, further stroke trials including cognitive assessment and observational analyses adjusted for key confounders, focusing on key subgroups or statin use patterns are required.

Association of statin use with spontaneous intracerebral hemorrhage: A cohort study

OBJECTIVE

To examine the association between statin exposure in a dose-dependent manner and intracerebral hemorrhage (ICH) in a large nationwide study.

METHODS

The computerized database of the largest health care provider in Israel was used to identify diagnosed ICH among new users of statins, who started statin treatment between 2005 and 2010. We assessed a dose-response relationship between ICH and statins, using the average atorvastatin equivalent daily dose (AAEDD). Multivariable Cox proportional hazard regression models, adjusted for baseline disease risk score, were applied to estimate the hazard ratio of ICH.

RESULTS

Of the 345,531 included patients, 1,304 were diagnosed with ICH during a median follow-up of 9.5 years (interquartile range 7.6-11.0). Overall, 75.3% of patients had AAEDD <10 mg/d, 19.0% had AAEDD 0-19.9 mg/d, and 5.7% had AAEDD ≥20 mg/d. The corresponding proportions were 81.0%, 15.0%, 4.0% among ICH cases, and 75.3%, 19.0%, 5.7% among non-ICH cases. Compared to those with AAEDD <10 mg/d (reference), the adjusted hazard ratio (HR) for ICH was 0.68 (95% confidence interval [CI] 0.58-0.79) in those with AAEDD 10-19.9 mg/d, and 0.62 (0.47-0.81) in those with AAEDD ≥20 mg/d. Compared to the lowest baseline total cholesterol quartile, the adjusted HR for ICH was 0.71 (95% CI 0.62-0.82), 0.55 (0.47-0.64), and 0.57 (0.49-0.67) in those in the second, third, and highest quartiles, respectively. The results were similar and robust among highly persistent statin users and after controlling for the change in cholesterol level.

CONCLUSIONS

This study confirms that the risk of ICH decreases with increasing cholesterol levels, but suggests that statin use might be associated with decreased risk of ICH.

Therapeutic targets and delivery challenges for Alzheimer’s disease

Dementia, including Alzheimer’s disease, the 21^st Century epidemic, is one of the most significant social and health crises which has currently afflicted nearly 44 million patients worldwide and about new 7.7 million cases are reported every year. This portrays the unmet need towards better understanding of Alzheimer’s disease pathomechanisms and related research towards more effective treatment strategies. The review thus comprehensively addresses Alzheimer’s disease pathophysiology with an insight of underlying multicascade pathway and elaborates possible therapeutic targets- particularly anti-amyloid approaches, anti-tau approaches, acetylcholinesterase inhibitors, glutamatergic system modifiers, immunotherapy, anti-inflammatory targets, antioxidants, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors and insulin. In spite of extensive research leading to identification of newer targets and potent drugs, complete cure of Alzheimer’s disease appears to be an unreached holy grail. This can be attributed to their ineffective delivery across blood brain barrier and ultimately to the brain. With this understanding, researchers are now focusing on development of drug delivery systems to be delivered via suitable route that can circumvent blood brain barrier effectively with enhanced patient compliance. In this context, we have summarized current drug delivery strategies by oral, transdermal, intravenous, intranasal and other miscellaneous routes and have accentuated the future standpoint towards promising therapy ultimately leading to Alzheimer’s disease cure.

Analysis of hippocampal gene expression profile of Alzheimer's disease model rats using genome chip bioinformatics

In this study, an Alzheimer's disease model was established in rats through stereotactic injection of condensed amyloid beta 1–40 into the bilateral hippocampus, and the changes of gene expression profile in the hippocampus of rat models and sham-operated rats were compared by genome expression profiling analysis. Results showed that the expression of 50 genes was significantly up-regulated (fold change ≥ 2), while 21 genes were significantly down-regulated in the hippocampus of Alzheimer's disease model rats (fold change ≤ 0.5) compared with the sham-operation group. The differentially expressed genes are involved in many functions, such as brain nerve system development, neuronal differentiation and functional regulation, cellular growth, differentiation and apoptosis, synaptogenesis and plasticity, inflammatory and immune responses, ion channels/transporters, signal transduction, cell material/energy metabolism. Our findings indicate that several genes were abnormally expressed in the metabolic and signal transduction pathways in the hippocampus of amyloid beta 1–40-induced rat model of Alzheimer's disease, thereby affecting the hippocampal and brain functions.

Neuroprotection for traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Despite extensive preclinical research supporting the effectiveness of neuroprotective therapies for brain trauma, there have been no successful randomized controlled clinical trials to date. TBI results in delayed secondary tissue injury due to neurochemical, metabolic and cellular changes; modulating such effects has provided the basis for neuroprotective interventions. To establish more effective neuroprotective treatments for TBI it is essential to better understand the complex cellular and molecular events that contribute to secondary injury. Here we critically review relevant research related to causes and modulation of delayed tissue damage, with particular emphasis on cell death mechanisms and post-traumatic neuroinflammation. We discuss the concept of utilizing multipotential drugs that target multiple secondary injury pathways, rather than more specific "laser"-targeted strategies that have uniformly failed in clinical trials. Moreover, we assess data supporting use of neuroprotective drugs that are currently being evaluated in human clinical trials for TBI, as well as promising emerging experimental multipotential drug treatment strategies. Finally, we describe key challenges and provide suggestions to improve the likelihood of successful clinical translation.

Effect of Tiantai No.1 on gene expression profiles in hippocampus of Alzheimer's disease rats by bioinformatic analysis

OBJECTIVE

To study the effect of Tiantai No. 1 [symbol in text] on gene expression profile in hippocampus of Alzheimer's disease (AD) rat, molecular genetic target points of the effect of this drug were defined, its molecular genetic pharmacodynamic mechanism of anti-AD was further explored at molecular gene level, and a scientific basis was provided for its clinical availability and promotion.

METHODS

Thirty male Sprague-Dawley rats were divided into three groups with 10 rats per group: sham-operation group, model group and Tiantai No. 1 group. Sterile surgical procedure was applied, the model group with bilateral hippocampal injection of Aβ1-40 was established, and normal saline was used instead of Aβ1-40 in the sham-operation group. One week after the models was made, rats were administered by gastric lavage once every day for three consecutive weeks. The rats of the sham-operation group and the model group were daily fed with purified water by lavage; the rats of the Tiantai No.1 group treated group were administered with Tiantai No.1 by lavage. Total RNAs of hippocampus tissues were extracted with Trizol, the changes of hippocampus gene expression profiles in the above three groups were analyzed by using Affymetrix rat whole genome expression profile microarray.

RESULTS

Microarray analysis showed that, compared with the sham-operation group, the hippocampus of the model group had 50 up-regulated genes with significant difference (fold change >2), and 21 down-regulated genes with significant difference (fold change <0.5); compared with the hippocampus of the model group, the hippocampus of the Tiantai No. 1 group was found to have 5 up-regulated genes with significant difference (fold change >2) and 20 down-regulated genes with significant difference (fold change <0.5). The functions of differentially expressed genes of the groups were involved in nervous system's development, neuronic differentiation and function-regulation, cellular growth and differentiation and apoptosis, synaptic occurrence and plasticity, inflammation and immune response, ion channels/transporters, cellular signal transduction, cellular material/energy metabolism and so on.

CONCLUSION

Tiantai No. 1 can regulate hippocampal function, and further regulate the brain function of animals in multiple gene target points by a number of ways.

Neuroprotective effects of rosuvastatin against traumatic spinal cord injury in rats

Rosuvastatin, which is a potent statin, has never been studied in traumatic spinal cord injury. The aim of this study was to investigate whether rosuvastatin treatment could protect the spinal cord after experimental spinal cord injury. Rats were randomized into the following five groups of eight animals each: control, sham, trauma, rosuvastatin, and methylprednisolone. In the control group, no surgical intervention was performed. In the sham group, only laminectomy was performed. In all the other groups, the spinal cord trauma model was created by the occlusion of the spinal cord with an aneurysm clip. In the spinal cord tissue, caspase-3 activity, tumor necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, nitric oxide levels, and superoxide dismutase levels were analyzed. Histopathological and ultrastructural evaluations were also performed. Neurological evaluation was performed using the Basso, Beattie, and Bresnahan locomotor scale and the inclined-plane test.After traumatic spinal cord injury, increases in caspase-3 activity, tumor necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, and nitric oxide levels were detected. In contrast, the superoxide dismutase levels were decreased. After the administration of rosuvastatin, decreases were observed in the tissue caspase-3 activity, tumor necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, and nitric oxide levels. In contrast, tissue superoxide dismutase levels were increased. Furthermore, rosuvastatin treatment showed improved results concerning the histopathological scores, the ultrastructural score and the functional tests. Biochemical, histopathological, ultrastructural analysis and functional tests revealed that rosuvastatin exhibits meaningful neuroprotective effects against spinal cord injury.

Traumatic brain injury: oxidative stress and neuroprotection

SIGNIFICANCE

A vast amount of circumstantial evidence implicates high energy oxidants and oxidative stress as mediators of secondary damage associated with traumatic brain injury. The excessive production of reactive oxygen species due to excitotoxicity and exhaustion of the endogenous antioxidant system induces peroxidation of cellular and vascular structures, protein oxidation, cleavage of DNA, and inhibition of the mitochondrial electron transport chain.

RECENT ADVANCES

Different integrated responses exist in the brain to detect oxidative stress, which is controlled by several genes termed vitagens. Vitagens encode for cytoprotective heat shock proteins, and thioredoxin and sirtuins.

CRITICAL ISSUES AND FUTURE DIRECTIONS

This article discusses selected aspects of secondary brain injury after trauma and outlines key mechanisms associated with toxicity, oxidative stress, inflammation, and necrosis. Finally, this review discusses the role of different oxidants and presents potential clinically relevant molecular targets that could be harnessed to treat secondary injury associated with brain trauma.

Statin use prior to ischemic stroke onset is associated with decreased in-hospital mortality

Statins can reduce the risk of stroke in at-risk populations and improve survival after acute ischemic stroke (AIS) among patients with previous statin use. This study aimed to investigate the impact of statin use before AIS onset on in-hospital mortality and identify the factors related to in-hospital mortality among patients with and without previous statin use. A retrospective cohort study of all patients with AIS attending hospital from June 1, 2008 to December 31, 2008. Data were collected from medical records including demographic information, diagnostic information, risk factors, previous statin use, and vital discharge status. Chi-square, Fisher's exact tests, student's t-test, and Mann-Whitney U test, whatever appropriate, were used to test the significance between the variables, and multiple logistic regression was used to identify factors associated with in-hospital mortality. Altogether, 386 patients with AIS were studied, of which 113 (29.3%) had a documented previous statin use. A total of 62 (16.1%) patients with AIS died in hospital. In-hospital mortality was significantly lower among previous statin users (P = 0.013). The presence of atrial fibrillation (AF) increased in-hospital mortality among patients with or without previous statin use. The independent predictors for in-hospital mortality among AIS patients without previous statin use were the presence of diabetes mellitus (P = 0.047), AF (P = 0.045), and renal impairment (P < 0.001). The prophylactic administration of statins significantly reduces post-AIS in-hospital mortality. Furthermore, the identification of predictors of in-hospital mortality might reduce death rates and enhance the application of specific therapeutic and management strategies to patients at a high risk of dying.

Use of an adult rat retinal explant model for screening of potential retinal ganglion cell neuroprotective therapies

PURPOSE. To validate an established adult organotypic retinal explant culture system for use as an efficient medium-throughput screening tool to investigate novel retinal ganglion cell (RGC) neuroprotective therapies. METHODS. Optimal culture conditions for detecting RGC neuroprotection in rat retinal explants were identified. Retinal explants were treated with various recognized, or purported, neuroprotective agents and cultured for either 4 or 7 days ex vivo. The number of cells surviving in the RGC layer (RGCL) was quantified using histologic and immunohistochemical techniques, and statistical analyses were applied to detect neuroprotective effects. RESULTS. The ability to replicate previously reported in vivo RGC neuroprotection in retinal explants was verified by demonstrating that caspase inhibition, brain-derived neurotrophic factor treatment, and stem cell transplantation all reduced RGCL cell loss in this model. Further screening of potential neuroprotective pharmacologic agents demonstrated that betaxolol, losartan, tafluprost, and simvastatin all alleviated RGCL cell loss in retinal explants, supporting previous reports. However, treatment with brimonidine did not protect RGCL neurons from death in retinal explant cultures. Explants cultured for 4 days ex vivo proved most sensitive for detecting neuroprotection. CONCLUSIONS. The current adult rat retinal explant culture model offers advantages over other models for screening potential neuroprotective drugs, including maintenance of neurons in situ, control of environmental conditions, and dissociation from other factors such as intraocular pressure. Verification that neuroprotection by previously identified RGC-protective therapies could be replicated in adult retinal explant cultures suggests that this model could be used for efficient medium-throughput screening of novel neuroprotective therapies for retinal neurodegenerative disease.

Neuroprotection for traumatic brain injury: translational challenges and emerging therapeutic strategies

Traumatic brain injury (TBI) causes secondary biochemical changes that contribute to subsequent tissue damage and associated neuronal cell death. Neuroprotective treatments that limit secondary tissue loss and/or improve behavioral outcome have been well established in multiple animal models of TBI. However, translation of such neuroprotective strategies to human injury have been disappointing, with the failure of more than thirty controlled clinical trials. Both conceptual issues and methodological differences between preclinical and clinical injury have undoubtedly contributed to these translational difficulties. More recently, changes in experimental approach, as well as altered clinical trial methodologies, have raised cautious optimism regarding the outcomes of future clinical trials. Here we critically review developing experimental neuroprotective strategies that show promise, and we propose criteria for improving the probability of successful clinical translation.

Simvastatin inhibits the activation of p21ras and prevents the loss of dopaminergic neurons in a mouse model of Parkinson's disease

Parkinson's disease (PD) is second only to Alzheimer's disease as the most common devastating human neurodegenerative disorder. Despite intense investigation, no interdictive therapy is available for PD. We investigated whether simvastatin, a Food and Drug Administration-approved cholesterol-lowering drug, could protect against nigrostriatal degeneration after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication to model PD in mice. First, MPP(+) induced the activation of p21(ras) and nuclear factor-kappaB (NF-kappaB) in mouse microglial cells. Inhibition of MPP(+)-induced activation of NF-kappaB by Deltap21(ras), a dominant-negative mutant of p21(ras), supported the involvement of p21(ras) in MPP(+)-induced microglial activation of NF-kappaB. Interestingly, simvastatin attenuated activation of both p21(ras) and NF-kappaB in MPP(+)-stimulated microglial cells. Consistently, we found a very rapid activation of p21(ras) in vivo in the substantia nigra pars compacta of MPTP-intoxicated mice. However, after oral administration, simvastatin entered into the nigra, reduced nigral activation of p21(ras), attenuated nigral activation of NF-kappaB, inhibited nigral expression of proinflammatory molecules, and suppressed nigral activation of glial cells. These findings paralleled dopaminergic neuronal protection, normalized striatal neurotransmitters, and improved motor functions in MPTP-intoxicated mice. Similarly, pravastatin, another cholesterol-lowering drug, suppressed microglial inflammatory responses and protected dopaminergic neurons in MPTP-intoxicated mice, but at levels less than simvastatin. Furthermore, both the statins administered 2 d after initiation of the disease were still capable of inhibiting the demise of dopaminergic neurons and concomitant loss of neurotransmitters, suggesting that statins are capable of slowing down the progression of neuronal loss in the MPTP mouse model. Therefore, we conclude that statins may be of therapeutic benefit for PD patients.

Statin's excitoprotection is mediated by sAPP and the subsequent attenuation of calpain-induced truncation events, likely via rho-ROCK signaling

The widely used cholesterol-lowering drugs, statins, were reported to reduce the incidence of stroke and the progression of Alzheimer's disease. However, little is known on how statins exert these beneficial effects. In this study, we investigated the molecular mechanisms underlying the neuroprotective actions of statins in primary cultured cortical neurons. We found that chronic treatment of neurons with a low dosage of two CNS-permeable statins (lovastatin and simvastatin) selectively reduced NMDA-induced cell death but not the caspase-mediated apoptosis. The protective effects of stains were inhibited by mevalonate, a PI3K inhibitor, and tyrphostin AG538, suggesting roles for cholesterol and insulin/IGF-1 signaling in the neurotoxic response. We further demonstrate that statins block calcium-dependent calpain activation, resulting in complete suppression of protein truncation events on multiple calpain substrates that are involved in neuronal death including CDK5 coactivator p35 cleavage to p25, GSK3 and beta-catenin. This is followed by reduced and increased nuclear translocation of p25 and beta-catenin, respectively. Under excitotoxic conditions, the activities of CDK5 and beta-catenin are exclusively regulated by calpain-mediated cleavage while apoptosis modulates beta-catenin mainly through phosphorylation. Strikingly, our data demonstrate that the calpain-blocking effect of statins is largely mediated by stimulation of alpha-secretase cleavage of APP, resulting in increased secretion of its soluble form, sAPP. Finally, our data suggest that statin-regulated sAPP secretion occurs via activation of the PI3K pathway and inhibition of ROCK signaling. Altogether, our study provides novel insights into statin-mediated neuronal excitoprotection through both cholesterol-dependent and -independent mechanisms and links them to calpain-mediated neuronal death.

Multifunctional drugs for head injury

Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide in individuals under the age of 45 years, and, despite extensive efforts to develop neuroprotective therapies, there has been no successful outcome in any trial of neuroprotection to date. In addition to recognizing that many TBI clinical trials have not been optimally designed to detect potential efficacy, the failures can be attributed largely to the fact that most of the therapies investigated have been targeted toward an individual injury factor. The contemporary view of TBI is that of a very heterogenous type of injury, one that varies widely in etiology, clinical presentation, severity, and pathophysiology. The mechanisms involved in neuronal cell death after TBI involve an interaction of acute and delayed anatomic, molecular, biochemical, and physiological events that are both complex and multifaceted. Accordingly, neuropharmacotherapies need to be targeted at the multiple injury factors that contribute to the secondary injury cascade, and, in so doing, maximize the likelihood of a successful outcome. This review focuses on a number of such multifunctional compounds that have shown considerable success in experimental studies and that show maximum promise for success in clinical trials.

Effect of pretreatment with statins on ischemic stroke outcomes

BACKGROUND AND PURPOSE

Statins reduce the risk of stroke in at-risk populations and may improve outcomes in patients taking statins before an ischemic stroke (IS). Our objectives were to examine the effects of pretreatment with statins on poor outcome in IS patients.

METHODS

Over a 6-month period all acute IS admissions were prospectively identified in 15 hospitals participating in a statewide acute stroke registry. Poor stroke outcome was defined as modified Rankin score >/=4 at discharge (ie, moderate-severe disability or death). Multivariable logistic regression models and matched propensity score analyses were used to quantify the effect of statin pretreatment on poor outcome.

RESULTS

Of 1360 IS patients, 23% were using statins before their stroke event and 42% had a poor stroke outcome. After multivariable adjustment, pretreatment with statins was associated with lower odds of poor outcome (OR=0.74, 95% CI 0.52, 1.02). A significant interaction (P<0.01) was found between statin use and race. In whites, statins were associated with statistically significantly lower odds of poor outcome (OR=0.61, 95% CI 0.42, 0.86), but in blacks statins were associated with a nonstatistically significant increase in poor outcome (OR=1.82, 95% CI 0.98, 3.39). Matched propensity score analyses were consistent with the multivariable model results.

CONCLUSIONS

Pretreatment with statins was associated with better stroke outcomes in whites, but we found no evidence of a beneficial effect of statins in blacks. These findings indicate the need for further studies, including randomized trials, to examine differential effects of statins on ischemic stroke outcomes among whites and blacks.

Effects of pharmacologic inhibition of protein geranylgeranyltransferase type I on aqueous humor outflow through the trabecular meshwork

PURPOSE

To determine the effects of inhibition of protein geranylgeranyltransferase type I (GGTase-I), which isoprenylates so-called CaaX proteins, including the GTP-binding proteins such as Rho GTPases and the betagamma subunits of heterotrimeric G-proteins, on aqueous humor outflow and trabecular meshwork cytoskeletal integrity.

METHODS

A selective small molecular inhibitor of GGTase-I, GGTI-DU40, was tested in this study to investigate its effects on actin cytoskeletal integrity, cell adhesions, cell-cell junctions, myosin II phosphosphorylation, and membrane localization of GTP-binding proteins in trabecular meshwork (TM) cells, using immunofluorescence detection and immunoblotting analysis. The effects of GGTI-DU40 on aqueous humor outflow were determined using organ-cultured, perfused anterior segments of porcine eyes.

RESULTS

In the TM cell lysates, GGTI-DU40 was confirmed to inhibit GGTase-I activity in a dose-dependent manner. TM cells treated with GGTI-DU40 displayed dose-dependent changes in cell morphology and reversible decreases in actin stress fibers, focal adhesions, and adherens junctions. Myosin light chain phosphorylation was decreased significantly, and membrane localization of isoprenylated small GTPases and Gbetagamma was impaired in drug-treated TM cells. Aqueous outflow facility was increased significantly in eyes perfused with GGTI-DU40.

CONCLUSIONS

These data demonstrate that inhibition of geranylgeranyl isoprenylation of CaaX proteins in the aqueous outflow pathway increases aqueous humor outflow, possibly through altered cell adhesive interactions and actin cytoskeletal organization in cells of the outflow pathway. This study indicates that the GGTase-I enzyme is a promising molecular target for lowering increased ocular pressure in glaucoma patients.

Statins increase neurogenesis in the dentate gyrus, reduce delayed neuronal death in the hippocampal CA3 region, and improve spatial learning in rat after traumatic brain injury

Traumatic brain injury (TBI) remains a major public health problem globally. Presently, there is no way to restore cognitive deficits caused by TBI. In this study, we seek to evaluate the effect of statins (simvastatin and atorvastatin) on the spatial learning and neurogenesis in rats subjected to controlled cortical impact. Rats were treated with atorvastatin and simvastatin 1 day after TBI and daily for 14 days. Morris water maze tests were performed during weeks 2 and 5 after TBI. Bromodeoxyuridine (BrdU; 50 mg/kg) was intraperitoneally injected 1 day after TBI and daily for 14 days. Brain tissue was processed for immunohistochemical staining to identify newly generated cells and vessels. Our data show that (1) treatment of TBI with statins improves spatial learning on days 31-35 after onset of TBI; (2) in the non-neurogenic region of the hippocampal CA3 region, statin treatment reduces the neuronal loss after TBI, demonstrating the neuroprotective effect of statins; (3) in the neurogenic region of the dentate gyrus, treatment of TBI with statins enhances neurogenesis; (4) statin treatment augments TBI-induced angiogenesis; and (5) treatment with simvastatin at the same dose provides a therapeutic effect superior to treatment with atorvastatin. These results suggest that statins may be candidates for treatment of TBI.

Effect of HMG-CoA reductase inhibitors on beta-amyloid peptide levels: implications for Alzheimer's disease

To date, a number of hypotheses of the cause of Alzheimer's disease, the most common form of dementia, have been postulated. The beta-amyloid peptide (Abeta) is the major constituent of senile plaques, which together with atrophy and neurofibrillary tangles, is the main neuropathological finding in Alzheimer's disease. It is a widely accepted theory that aggregation of Abeta into plaques is an initial event in the pathogenesis of Alzheimer's disease, driving neurodegeneration. The cholesterol hypothesis, primarily based on in vitro and animal studies, states that increased levels of cholesterol promote the production of Abeta. Furthermore, treating animals with HMG-CoA reductase inhibitors ('statins'; cholesterol-lowering agents), or adding these agents to cell culture, results in decreased production of Abeta. This 'positive' effect of statin treatment has further been verified by some, but not all, longitudinal studies where a reduced prevalence of Alzheimer's disease is seen among patients taking statins. These findings have together been interpreted to indicate that statins act via a cholesterol-dependent mechanism, reducing the production of Abeta and, hence, the risk of developing Alzheimer's disease. This review focuses on the cholesterol hypothesis of Alzheimer's disease and investigations into its validity in the clinical setting, i.e. the outcome of clinical trials where the effect of statin treatment on Abeta production has been studied. To date, the cholesterol hypothesis has not been shown to be valid in clinical trials. We hypothesise that the vascular contributions in Alzheimer's disease may be one possible mechanism for statins to interfere with the disease process and reduce the prevalence of Alzheimer's disease. We also suggest that statins may act through the inflammatory pathway. Both of these mechanistic suggestions are good candidates, supported by the literature, for the underlying mechanistic link between statin treatment and a reduced prevalence for Alzheimer's disease.

Effect of statins on beta-amyloid metabolism in humans: potential importance for the development of senile plaques in Alzheimer's disease

According to the amyloid cascade hypothesis, both familial and sporadic Alzheimer's disease (AD) is caused by the toxic effect of over-production and/or aggregation of beta-amyloid (Abeta). Recent cell and animal studies have linked the production of Abeta to high levels of cholesterol and the use of statins, compounds inhibiting the de novo synthesis of cholesterol. Epidemiological studies have also supported such linkage by showing a reduced prevalence of AD for subjects taking statins. A limited number of clinical studies have been published trying to elucidate the effect of statin treatment on amyloid precursor protein (APP) processing and metabolism of brain cholesterol in AD in humans and this review focuses on the current state of these clinical studies. The results are contradictory, but the overall interpretation suggests that statin treatment probably does not have a direct impact through lowering of cholesterol on the APP processing and Abeta production in humans. To confirm this, further clinical studies needs to be performed with extended treatment periods and where several parameters (lipid profile, lipoproteins, sterols, biomarkers related to AD and APP metabolites) are analyzed, both in the cerebrospinal fluid and plasma. The pleiotropic effects of statins should be investigated further. One approach is presented in this review.

Convergence of atherosclerosis and Alzheimer's disease: inflammation, cholesterol, and misfolded proteins

Late-onset sporadic Alzheimer's disease is a heterogeneous disorder. In elderly patients, increasing evidence suggests a link between this neurodegenerative disease, and vascular risk factors and atherosclerosis. The nature of this link remains speculative. Some investigators have suggested that the disease arises as a secondary event related to atherosclerosis of extracranial or intracranial vessels. A toxic effect of vascular factors on the microvasculature of susceptible brain regions has also been argued. An alternative explanation is that atherosclerosis and Alzheimer's disease are independent but convergent disease processes. This hypothesis is lent support by observations of shared epidemiology, pathophysiological elements, and response to treatment in both disorders. It provides a potential framework for an improved understanding of the pathogenesis of Alzheimer's disease, especially in elderly patients with vascular risk factors, and offers some promise toward the search for preventive and therapeutic treatments.

Vascular dementia revisited: diagnosis, pathogenesis, treatment, and prevention

VaD is the second most common cause of dementia in the elderly after AD. VaD is defined as the loss of cognitive function resulting from ischemic, ischemic-hypoxic, or hemorrhagic brain lesions as a result of CVD and cardiovascular pathologic changes. Diagnosis requires (1) cognitive loss (often predominantly subcortical), (2) vascular brain lesions demonstrated by imaging, and (3) exclusion of other causes of dementia, such as AD. VaD is excluded by brain imaging showing no evidence of vascular lesions. VaD may be caused by multiple strokes (MID or poststroke dementia) but also by single strategic strokes, multiple lacunes, and hypoperfusive lesions such as border zone infarcts and ischemic periventricular leukoencephalopathy (Binswanger's disease). Primary and secondary prevention of stroke and cardiovascular disease decreases the burden of VaD. Genetic advice is needed in patients with familial forms, such as CADASIL. Treatment involves control of risk factors (i.e., hypertension, diabetes, smoking, hyperfibrinogenemia, hyperhomocystinemia, orthostatic hypotension, cardiac arrhythmias). Anticholinergic medications used for AD are also useful in VaD, and atypical antipsychotic agents and antidepressants (e.g., selective serotonin reuptake inhibitors) may be required in some patients.