Protecting the brain with eNOS: run for your life

The interaction between dysfunction of vasculature and tauopathy in Alzheimer's disease and related dementias

Tauopathy is one of the pathological features of Alzheimer's disease and related dementias (ADRD). At present, there have been many studies on the formation, deposition, and intercellular transmission of tau in neurons and immune cells. The vasculature is an important component of the central nervous system. This review discusses the interaction between vasculature and tau in detail from three aspects. (1) The vascular risk factors (VRFs) discussed in this review include diabetes mellitus (DM), abnormal blood pressure (BP), and hypercholesterolemia. (2) In ADRD pathology, the hyperphosphorylation and deposition of tau interact with disrupted vasculature, such as different cells (endothelial cells, smooth muscular cells, and pericytes), the blood-brain barrier (BBB), and the cerebral lymphatic system. (3) The functions of vasculature are regulated by various signaling transductions. Endothelial nitric oxide synthase/nitric oxide, calcium signaling, Rho/Rho-associated coiled-coil containing Kinase, and receptors for advanced glycation end products are discussed in this review. Our findings indicate that the prevention and treatment of vascular health may be a potential target for ADRD combination therapy. HIGHLIGHTS: Persistent VRFs increase early disruption of vascular mechanisms and are strongly associated with tau pathology in ADRD. Cell dysfunction in the vasculature causes BBB leakage and drainage incapacity of the cerebral lymphatic system, which interacts with tau pathology. Signaling molecules in the vasculature regulate vasodilation and contraction, angiogenesis, and CBF. Abnormal signaling transduction is related to tau hyperphosphorylation and deposition.

A balanced formula of essential amino acids promotes brain mitochondrial biogenesis and protects neurons from ischemic insult

Mitochondrial dysfunction plays a key role in the aging process, and aging is a strong risk factor for neurodegenerative diseases or brain injury characterized by impairment of mitochondrial function. Among these, ischemic stroke is one of the leading causes of death and permanent disability worldwide. Pharmacological approaches for its prevention and therapy are limited. Although non-pharmacological interventions such as physical exercise, which promotes brain mitochondrial biogenesis, have been shown to exert preventive effects against ischemic stroke, regular feasibility is complex in older people, and nutraceutical strategies could be valuable alternatives. We show here that dietary supplementation with a balanced essential amino acid mixture (BCAAem) increased mitochondrial biogenesis and the endogenous antioxidant response in the hippocampus of middle-aged mice to an extent comparable to those elicited by treadmill exercise training, suggesting BCAAem as an effective exercise mimetic on brain mitochondrial health and disease prevention. In vitro BCAAem treatment directly exerted mitochondrial biogenic effects and induced antioxidant enzyme expression in primary mouse cortical neurons. Further, exposure to BCAAem protected cortical neurons from the ischemic damage induced by an in vitro model of cerebral ischemia (oxygen-glucose deprivation, OGD). BCAAem-mediated protection against OGD was abolished in the presence of rapamycin, Torin-1, or L-NAME, indicating the requirement of both mTOR and eNOS signaling pathways in the BCAAem effects. We propose BCAAem supplementation as an alternative to physical exercise to prevent brain mitochondrial derangements leading to neurodegeneration and as a nutraceutical intervention aiding recovery after cerebral ischemia in conjunction with conventional drugs.

Magnesium and the Brain: A Focus on Neuroinflammation and Neurodegeneration

Magnesium (Mg) is involved in the regulation of metabolism and in the maintenance of the homeostasis of all the tissues, including the brain, where it harmonizes nerve signal transmission and preserves the integrity of the blood-brain barrier. Mg deficiency contributes to systemic low-grade inflammation, the common denominator of most diseases. In particular, neuroinflammation is the hallmark of neurodegenerative disorders. Starting from a rapid overview on the role of magnesium in the brain, this narrative review provides evidences linking the derangement of magnesium balance with multiple sclerosis, Alzheimer's, and Parkinson's diseases.

Ensembles of endothelial and mural cells promote angiogenesis in prenatal human brain

Interactions between angiogenesis and neurogenesis regulate embryonic brain development. However, a comprehensive understanding of the stages of vascular cell maturation is lacking, especially in the prenatal human brain. Using fluorescence-activated cell sorting, single-cell transcriptomics, and histological and ultrastructural analyses, we show that an ensemble of endothelial and mural cell subtypes tile the brain vasculature during the second trimester. These vascular cells follow distinct developmental trajectories and utilize diverse signaling mechanisms, including collagen, laminin, and midkine, to facilitate cell-cell communication and maturation. Interestingly, our results reveal that tip cells, a subtype of endothelial cells, are highly enriched near the ventricular zone, the site of active neurogenesis. Consistent with these observations, prenatal vascular cells transplanted into cortical organoids exhibit restricted lineage potential that favors tip cells, promotes neurogenesis, and reduces cellular stress. Together, our results uncover important mechanisms into vascular maturation during this critical period of human brain development.

Phosphoinositide-3-Kinase/Akt-Endothelial Nitric Oxide Synthase Signaling Pathway Mediates the Neuroprotective Effect of Sevoflurane Postconditioning in a Rat Model of Hemorrhagic Shock and Resuscitation

BACKGROUND

Although extensive reports have demonstrated the neuroprotection of sevoflurane postconditioning in cases of focal and global cerebral ischemia/reperfusion, the underlying mechanisms are not completely elucidated. This study investigated whether this effect is related to endothelial nitric oxide synthase (eNOS) and mediated by the phosphoinositide-3-kinase pathway in a rat model of hemorrhagic shock and resuscitation.

METHODS

Adult male Sprague Dawley rats were subjected to hemorrhagic shock for 60 minutes and then resuscitation for 30 minutes in experimental groups. Sevoflurane postconditioning was performed at the beginning of resuscitation to completion. At 24 hours after resuscitation, the brain infarct volume was evaluated by 2,3,5-triphenyltetrazolium chloride staining. The neuronal morphological changes and apoptosis were determined by hematoxylin and eosin staining and immunohistochemistry analysis, respectively. The activity of phosphorylated Akt and eNOS was evaluated by Western blot analysis.

RESULTS

Brain injuries such as the cerebral infarct volume and pathological neuronal changes as well as cell apoptosis were observed in the hippocampus after hemorrhagic shock and resuscitation. Postconditioning with 2.4% sevoflurane significantly attenuated brain injuries. Wortmannin prevented the improvements of neuronal characteristics elicited by sevoflurane postconditioning as well as the hyperactivity of eNOS and phosphorylated Akt.

CONCLUSIONS

Sevoflurane postconditioning could attenuate brain injury induced by hemorrhagic shock and resuscitation, and this neuroprotective effect may be partly by upregulation of eNOS through the phosphoinositide-3-kinase/Akt signaling pathway.

Stimulatory effects of (-)-epicatechin and its enantiomer (+)-epicatechin on mouse frontal cortex neurogenesis markers and short-term memory: proof of concept

Consumption of (-)-epicatechin (Epi), a cacao flavanol improves cognition. The aim was to compare the effects of (-)-Epi or its stereoisomer (+)-Epi on mouse frontal cortex-dependent short-term working memory and modulators of neurogenesis. Three-month-old male mice (n = 7 per group) were provided by gavage either water (vehicle; Veh), (-)-Epi, at 1 mg kg-1 or (+)-Epi at 0.1 mg per kg of body weight for 15 days. After treatment, spontaneous alternation was evaluated by Y-maze. Brain frontal cortex was isolated for nitrate/nitrite measurements, Western blotting for nerve growth factor (NGF), microtubule associated protein 2 (MAP2), endothelial and neuronal nitric oxide synthase (eNOS and nNOS) and immunohistochemistry for neuronal specific protein (NeuN), doublecortin (DCX), capillary (CD31) and neurofilaments (NF200). Results demonstrate the stimulatory capacity of (-)-Epi and (+)-Epi on markers of neuronal proliferation as per increases in immunoreactive cells for NeuN (74 and 120% respectively), DCX (70 and 124%) as well as in NGF (34.4, 63.6%) and MAP2 (41.8, 63.8%). Capillary density yielded significant increases with (-)-Epi (∼80%) vs. (+)-Epi (∼160%). CD31 protein levels increased with (-)-Epi (∼70%) and (+)-Epi (∼140%). Effects correlated with nitrate/nitrite stimulation by (-)-Epi and (+)-Epi (110.2, 246.5%) and enhanced eNOS phosphorylation (Ser1177) with (-)-Epi and (+)-Epi (21.4, 41.2%) while nNOS phosphorylation only increased with (+)-Epi (18%). Neurofilament staining was increased in (-)-Epi by 135.6 and 84% with (+)-Epi. NF200 increased with (-)-Epi (116%) vs. (+)-Epi (84.5%). Frontal cortex-dependent short-term spatial working improved with (-)-Epi and (+)-Epi (15, 13%). In conclusion, results suggest that both enantiomers, but more effectively (+)-Epi, upregulate neurogenesis markers likely through stimulation of capillary formation and NO triggering, improvements in memory.

Sex differences in the blood-brain barrier and neurodegenerative diseases

The number of people diagnosed with neurodegenerative diseases is on the rise. Many of these diseases, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and motor neuron disease, demonstrate clear sexual dimorphisms. While sex as a biological variable must now be included in animal studies, sex is rarely included in in vitro models of human neurodegenerative disease. In this Review, we describe these sex-related differences in neurodegenerative diseases and the blood-brain barrier (BBB), whose dysfunction is linked to neurodegenerative disease development and progression. We explain potential mechanisms by which sex and sex hormones affect BBB integrity. Finally, we summarize current in vitro BBB bioengineered models and highlight their potential to study sex differences in BBB integrity and neurodegenerative disease.

Angiotensin II type 1 receptor autoantibody blockade improves cerebral blood flow autoregulation and hypertension in a preclinical model of preeclampsia

Introduction:Women with preeclampsia (PE) and reduced uterine perfusion pressure (RUPP) pre-clinical rat model of PE have elevated angiotensin II type 1 receptor agonistic autoantibodies (AT1-AA) and cerebrovascular dysfunction. Methods:Sprague Dawley rats had RUPP surgery with/without AT1-AA inhibitor ('n7AAc'144 μg/day) osmotic minipumps. Mean arterial pressure (MAP), CBF autoregulation, blood brain barrier (BBB) permeability, cerebral edema, oxidative stress, and eNOS were assessed. Results:'n7AAc' improved MAP, restored CBF autoregulation, prevented cerebral edema, elevated oxidative stress, and increased phosphorylated eNOS protein in RUPP rats. Conclusion:Inhibiting the AT1-AA in placental ischemic rats prevents hypertension, cerebrovascular dysfunction, and improves cerebral metabolic function.

Short-Term Acute Exercise Preconditioning Reduces Neurovascular Injury After Stroke Through Induced eNOS Activation

Physical exercise is known to reduce cardiovascular risk but its role in ischemic stroke is not clear. It was previously shown that an acute single bout of exercise reduced increased eNOS activation in the heart and reduced myocardial infarction. However, the impact of a single bout or short-term exercise on eNOS-induced neuroprotection after stroke was not previously studied. Accordingly, this study was designed to test the hypothesis that short-term acute exercise can provide "immediate neuroprotection" and improve stroke outcomes through induced eNOS activation. Male Wistar rats (300 g) were subjected to HIIT treadmill exercise for 4 days (25 min/day), break for 2 days, and then one acute bout for 30 min. Exercised animals were subjected to thromboembolic stroke 1 h, 6 h, 24 h, or 72 h after the last exercise session. At 24 h after stroke, control (sedentary) and exercised rats were tested for neurological outcomes, infarct size, and edema. The expression of active eNOS (p-S1177-eNOS) and active AMPK (p-T172-AMPK) was measured in the brain, cerebral vessels, and aorta. In an additional cohort, animals were treated with the eNOS inhibitor, L-NIO (I.P, 20 mg/kg), and stroked 1 h after exercise and compared with non-exercise animals. Acute exercise significantly reduced infarct size, edema, and improved functional outcomes, and significantly increased the expression of peNOS and pAMPK in the brain, cerebral vessels, and aorta. eNOS inhibition abolished the exercise-induced improvement in outcomes. Short-term acute preconditioning exercise reduced the neurovascular injury and improved functional outcomes after stroke through eNOS activation.

The modular architecture and neurochemical patterns in the cerebellar cortex

The review deals with topical issues of the neuronal arrangement underlying basic cerebellar functions. The cerebellum and its auxiliary structures contain several hundreds of modules (so called "microzones"). Each module receives the corticopetal input specific for the lobule it belongs to and forms the topographic projection. The precision of the major input-output signal flow in the cerebellar cortex is provided by a pronounced stratification of its synaptic zones of a various origin and regular topography of its afferent connections, interneurons, and efferent neurons. There is a nice match between the anatomical and functional coordinates of the modules, whose spatial boundaries are determined by the spread of afferent excitation and local interneuron connections. The dynamic characteristics of the modules are analyzed by the example of the formation of the nitrergic neuron ensembles and cerebellar projections of corticopetal fibers. The authors discuss the cerebellar blood flow and its relation to the activity of NO/GABAergic Lugaro cells and other interneurons in the cerebellar cortex. A generalized scheme of intra- and intermodular communication is proposed.

High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence

Exercise is a uniquely effective and pluripotent medicine against several noncommunicable diseases of westernised lifestyles, including protection against neurodegenerative disorders. High-intensity interval exercise training (HIT) is emerging as an effective alternative to current health-related exercise guidelines. Compared with traditional moderate-intensity continuous exercise training, HIT confers equivalent if not indeed superior metabolic, cardiac, and systemic vascular adaptation. Consequently, HIT is being promoted as a more time-efficient and practical approach to optimize health thereby reducing the burden of disease associated with physical inactivity. However, no studies to date have examined the impact of HIT on the cerebrovasculature and corresponding implications for cognitive function. This review critiques the implications of HIT for cerebrovascular function, with a focus on the mechanisms and translational impact for patient health and well-being. It also introduces similarly novel interventions currently under investigation as alternative means of accelerating exercise-induced cerebrovascular adaptation. We highlight a need for studies of the mechanisms and thereby also the optimal dose-response strategies to guide exercise prescription, and for studies to explore alternative approaches to optimize exercise outcomes in brain-related health and disease prevention. From a clinical perspective, interventions that selectively target the aging brain have the potential to prevent stroke and associated neurovascular diseases.

Progress on the protective effect of compounds from natural medicines on cerebral ischemia

The treatment of cerebral ischemic disease by natural medicines has a long history, and has accumulated a rich theoretical knowledge and treatment experience. The objective of this review is to critically evaluate the experimental research situation of the protective effect of the individual compounds from natural medicine on cerebral ischemia in the past ten years, emphasizing the major mechanisms underlying cerebral ischemic pathophysiology. Sixteen representative compounds from natural medicines which are often used to treat stroke are discussed. The results indicate that these components possess a protective effect on cerebral ischemia, and that these components have different mechanisms, including inhibiting excitotoxicity by ginkgolide B, antiapoptosis of breviscapine, influencing astrocytic activation and proliferation of tanshinone IIA, influencing free radicals by ginsenoside Rd, impairing blood-brain barrier disruption by baicalin, and the anti-inflammatory activity of tetramethylpyrazine. Moreover, some components have multiple neuroprotective mechanisms. Therefore, the combination of individual compounds from natural medicines, considering the mechanisms of cerebral ischemia, may be beneficial to patients with cerebral ischemia in the future. This approach will provide a direction for the further application and exploitation of new drug development in the treatment of cerebral ischemia.

Endothelium-dependent control of cerebrovascular functions through age: exercise for healthy cerebrovascular aging

Cognitive performances are tightly associated with the maximal aerobic exercise capacity, both of which decline with age. The benefits on mental health of regular exercise, which slows the age-dependent decline in maximal aerobic exercise capacity, have been established for centuries. In addition, the maintenance of an optimal cerebrovascular endothelial function through regular exercise, part of a healthy lifestyle, emerges as one of the key and primary elements of successful brain aging. Physical exercise requires the activation of specific brain areas that trigger a local increase in cerebral blood flow to match neuronal metabolic needs. In this review, we propose three ways by which exercise could maintain the cerebrovascular endothelial function, a premise to a healthy cerebrovascular function and an optimal regulation of cerebral blood flow. First, exercise increases blood flow locally and increases shear stress temporarily, a known stimulus for endothelial cell maintenance of Akt-dependent expression of endothelial nitric oxide synthase, nitric oxide generation, and the expression of antioxidant defenses. Second, the rise in circulating catecholamines during exercise not only facilitates adequate blood and nutrient delivery by stimulating heart function and mobilizing energy supplies but also enhances endothelial repair mechanisms and angiogenesis. Third, in the long term, regular exercise sustains a low resting heart rate that reduces the mechanical stress imposed to the endothelium of cerebral arteries by the cardiac cycle. Any chronic variation from a healthy environment will perturb metabolism and thus hasten endothelial damage, favoring hypoperfusion and neuronal stress.

Multimodal imaging in rats reveals impaired neurovascular coupling in sustained hypertension

BACKGROUND AND PURPOSE

Arterial hypertension is an important risk factor for cerebrovascular diseases, such as transient ischemic attacks or stroke, and represents a major global health issue. The effects of hypertension on cerebral blood flow, particularly at the microvascular level, remain unknown.

METHODS

Using the spontaneously hypertensive rat (SHR) model, we examined cortical hemodynamic responses on whisker stimulation applying a multimodal imaging approach (multiwavelength spectroscopy, laser speckle imaging, and 2-photon microscopy). We assessed the effects of hypertension in 10-, 20-, and 40-week-old male SHRs and age-matched male Wistar Kyoto rats (CTRL) on hemodynamic responses, histology, and biochemical parameters. In 40-week-old animals, losartan or verapamil was administered for 10 weeks to test the reversibility of hypertension-induced impairments.

RESULTS

Increased arterial blood pressure was associated with a progressive impairment in functional hyperemia in 20- and 40-week-old SHRs; baseline capillary red blood cell velocity was increased in 40-week-old SHRs compared with age-matched CTRLs. Antihypertensive treatment reduced baseline capillary cerebral blood flow almost to CTRL values, whereas functional hyperemic signals did not improve after 10 weeks of drug therapy. Structural analyses of the microvascular network revealed no differences between normo- and hypertensive animals, whereas expression analyses of cerebral lysates showed signs of increased oxidative stress and signs of impaired endothelial homeostasis upon early hypertension.

CONCLUSIONS

Impaired neurovascular coupling in the SHR evolves upon sustained hypertension. Antihypertensive monotherapy using verapamil or losartan is not sufficient to abolish this functional impairment. These deficits in neurovascular coupling in response to sustained hypertension might contribute to accelerate progression of neurodegenerative diseases in chronic hypertension.

Lumbrokinase attenuates side-stream-smoke-induced apoptosis and autophagy in young hamster hippocampus: correlated with eNOS induction and NFκB/iNOS/COX-2 signaling suppression

Recent studies have found that cigarette smoke is epidemiologically linked to an increased risk for impaired cognitive development in adolescents. This study evaluated the influence of side stream smoke (SSS) exposure on hippocampal apoptosis and of the lumbrokinase (LK) effects on SSS induced apoptosis in young hamster hippocampus. Twenty male hamsters at six weeks of age were randomly divided into control group, SSS group (exposed to tobacco cigarettes smoke at doses of 10 cigarettes for 30 min twice a day for 1 month), and SSS hamsters with LK treatment (1.2 mg/kg, ip) for twice a week for 1 month. TUNEL assay and Western blotting were performed. The TUNEL-positive apoptotic cells, as well as Fas-dependent activity and mitochondria-dependent apoptotic pathways, such as Fas, FADD, activated caspase-8, t-Bid, activated caspase-9, and activated caspase-3, were significantly increased in the SSS-exposed hippocampus compared to the control and highly attenuated in the LK treatment group. Additionally, SSS exposure significantly increased the autophagy marker proteins, Beclin-1, ATG7, and LC3-II levels, in the hippocampus compared to those in the control group and obviously attenuated after LK treatment. LK also reduced hippocampus injury by enhancing eNOS expression and remarkably inhibited the proinflammatory NFκB/iNOS/COX-2 signaling activity. We found that the detrimental effects of SSS on the hippocampus are truly mediated by cell apoptosis and autophagy. However, LK reduced the hippocampus apoptosis and autophagy related injuries induced by SSS in a widespread manner. We suggest that LK presents protective effects on hippocampus apoptosis and has therapeutic potential against abnormal hippocampal function.

The essential role of endothelial nitric oxide synthase activation in insulin-mediated neuroprotection against ischemic stroke in diabetes

BACKGROUND

Stroke patients with diabetes have a higher mortality rate, worse neurologic outcome, and more severe disability than those without diabetes. Results from clinical trials comparing the outcomes of stroke seen with intensive glycemic control in diabetic individuals are conflicting. Therefore, the present study was aimed to identify the key factor involved in the neuroprotective action of insulin beyond its hypoglycemic effects in streptozotocin-diabetic rats with ischemic stroke.

METHODS

Long-Evans male rats were divided into three groups (control, diabetes, and diabetes treated with insulin) and subjected to focal cerebral ischemia-reperfusion (FC I/R) injury.

RESULTS

Hyperglycemia aggravated FC I/R injuries with an increase in cerebral infarction and neurologic deficits, inhibition of glucose uptake and membrane-trafficking activity of glucose transporter 1, and reduction of Akt and endothelial nitric oxide synthase (eNOS) phosphorylation in the cerebrum. Insulin treatment alleviated hyperglycemia and the symptoms of diabetes in streptozotocin-diabetic rats. Insulin administration also significantly decreased cerebral infarction and neurologic deficits and increased phosphorylation of Akt and eNOS protein in the cerebrum of FC I/R-injured diabetic rats. However, the glucose uptake and membrane trafficking activity of glucose transporter 1 in the cerebrum were not restored by insulin treatment. Coadministration of the eNOS inhibitor, N-iminoethyl-L-ornithine, with insulin abrogated beneficial effects of insulin on cerebral infarct volume and neurologic deficits in FC I/R-injured diabetic rats without affecting the hypoglycemic action of insulin.

CONCLUSIONS

These results suggest that eNOS activation is required for the neuroprotection of insulin against ischemic stroke in patients with diabetes.

Correlation between hippocampal levels of neural, epithelial and inducible NOS and spatial learning skills in rats

In the present study, to better understand the role of different nitric oxide synthase (NOS) isoforms in hippocampus-dependent forms of learning, we examined the expression of neural, endothelial, and inducible NOS in the hippocampus of young-adult rats classified as "poor" and "good" learners on the basis of their performance in the partially baited 12-arm radial maze. Taking into consideration strain-dependent differences in learning skills and NOS expression, experiments were performed on two different lines of laboratory rats: the inbred Wistar (W) and the outcrossed Wistar/Spraque-Dawley (W/S) line. The hippocampal levels of NOS proteins were assessed by Western Blotting. In the present study, genetically more homogenous W rats showed a slower rate of learning compared to the genetically less homogenous outcrossed W/S rats. The deficient performance in the W rat group compared to outcrossed W/S rats, and in "poor" learners of both groups compared to "good" learners was due to a higher percentage of reference memory errors. The overall NOS levels were significantly higher in W group compared to outcrossed W/S rats. In both rat lines, the rate of learning positively correlated with hippocampal levels of nNOS and negatively correlated with iNOS levels. Hippocampal eNOS levels correlated negatively with animals' performance but only in the W rats. These results suggest that all 3 NOS isoforms are implemented but play different roles in neural signaling.

Pioglitazone delays proximal tubule dysfunction and improves cerebral vessel endothelial dysfunction in normoalbuminuric people with type 2 diabetes mellitus

AIM

The renal and cerebral protective effects of pioglitazone were assessed in normoalbuminuric patients with type 2 diabetes mellitus (DM).

METHODS

A total of 68 normoalbuminuric type 2 DM patients were enrolled in a one-year open-label randomized controlled trial: 34 patients (pioglitazone-metformin) vs. 34 patients (glimepiride-metformin). All patients were assessed concerning urinary albumin: creatinine ratio (UACR), urinary alpha1-microglobulin, urinary beta2-microglobulin, plasma asymmetric dymethyl-arginine (ADMA), GFR, hsC-reactive protein, fibrinogen, HbA1c; pulsatility index, resistance index in the internal carotid artery and middle cerebral artery, intima-media thickness in the common carotid artery; cerebrovascular reactivity was evaluated through the breath-holding test.

RESULTS

At 1 year there were differences between groups regarding ADMA, urinary beta2-microglobulin, urinary alpha1-microglobulin, parameters of inflammation, serum creatinine, GFR, UACR, the cerebral haemodynamic indices. Significant correlations were found between alpha 1-microglobulin-UACR (R(2)=0.143; P=0.001) and GFR (R(2)=0.081; P=0.01); beta2-microglobulin-UACR (R(2)=0.241; P=0.0001) and GFR (R(2)=0.064; P=0.036); ADMA-GFR (R(2)=0.338; P=0.0001), parameters of inflammation, HbA1c, duration of DM, cerebral indices. There were no correlations between ADMA-UACR, urinary alpha1-microglobulin and beta2-microglobulin.

CONCLUSION

Proximal tubule (PT) dysfunction precedes albuminuria and is dissociated from endothelial dysfunction in patients with type 2 DM. Pioglitazone delays PT dysfunction and improves cerebral vessels endothelial dysfunction in normoalbuminuric patients with type 2 DM.

Protecting against vascular disease in brain

Endothelial cells exert an enormous influence on blood vessels throughout the circulation, but their impact is particularly pronounced in the brain. New concepts have emerged recently regarding the role of this cell type and mechanisms that contribute to endothelial dysfunction and vascular disease. Activation of the renin-angiotensin system plays a prominent role in producing these abnormalities. Both oxidative stress and local inflammation are key mechanisms that underlie vascular disease of diverse etiology. Endogenous mechanisms of vascular protection are also present, including antioxidants, anti-inflammatory molecules, and peroxisome proliferator-activated receptor-γ. Despite their clear importance, studies of mechanisms that underlie cerebrovascular disease continue to lag behind studies of vascular biology in general. Identification of endogenous molecules and pathways that protect the vasculature may result in targeted approaches to prevent or slow the progression of vascular disease that causes stroke and contributes to the vascular component of dementia and Alzheimer's disease.

CDK5 phosphorylates eNOS at Ser-113 and regulates NO production

Phosphorylation of endothelial nitric oxide synthase (eNOS) is key mechanism in response to various forms of cellular stimulation. Through protein nitration by peroxynitrite, eNOS is believed to be responsible for the major abnormalities in several important neurodegenerative diseases including Alzheimer's (AD) and Parkinson's diseases (PD). Recent studies provide important in vivo evidence that hyperactivation of Cdk5 by p25 plays an essential role in the cell death of neurons in experimental models of AD and PD. This study focuses on the functional regulation of eNOS by Cdk5/p35 complex in a phosphorylation dependent manner. Our results showed that Cdk5 can phosphorylate eNOS both in vitro and in vivo. In vitro kinase assay together with the bioinformatic analysis and site direct mutagenesis revealed that Ser-113 is the major phosphorylation site for Cdk5. Most interestingly, the nitrite production was significantly reduced in eNOS and Cdk5/p35 co-transfected SH-SY5Y cells when compared with co-transfection of Cdk5/p35 and S113A. Together, our data suggest that Cdk5 can phosphorylate eNOS at the Ser-113 site and down-regulate eNOS-derived NO levels.

Cyclic GMP and nitric oxide synthase in aging and Alzheimer's disease

Cyclic guanosine monophosphate (cGMP) is an important secondary messenger synthesized by the guanylyl cyclases which are found in the soluble (sGC) and particular isoforms. In the central nervous system, the nitric oxide (NO)-sensitive sGC isoform is the major enzyme responsible for cGMP synthesis. Phosphodiesterases (PDEs) are enzymes for hydrolysis of cGMP in the brain, and they are mainly isoforms 2, 5, and 9. The NO/cGMP signaling pathway has been shown to play an important role in the process underlying learning and memory. Aging is associated with an increase in PDE expression and activity and a decrease in cGMP concentration. In addition, aging is also associated with an enhancement of neuronal NO synthase, a lowering of endothelial, and no alteration in inducible activity. The observed changes in NMDA receptor density along with the Ca(2+)/NO/cGMP pathway underscore the lower synaptic plasticity and cognitive performance during aging. This notion is in agreement with last data indicating that inhibitors of PDE2 and PDE9 improve learning and memory in older rats. In this review, we focus on recent studies supporting the role of Ca(2+)/NO/cGMP pathway in aging and Alzheimer's disease.

The role of oxidative stress and NADPH oxidase in cerebrovascular disease

The study of reactive oxygen species (ROS) and oxidative stress remains a very active area of biological research, particularly in relation to cellular signaling and the role of ROS in disease. In the cerebral circulation, oxidative stress occurs in diverse forms of disease and with aging. Within the vessel wall, ROS produce complex structural and functional changes that have broad implications for regulation of cerebral perfusion and permeability of the blood-brain barrier. These oxidative-stress-induced changes are thought to contribute to the progression of cerebrovascular disease. Here, we highlight recent findings in relation to oxidative stress in the cerebral vasculature, with an emphasis on the emerging role for NADPH oxidases as a source of ROS and the role of ROS in models of disease.

Pioglitazone exerts protective effects against stroke in stroke-prone spontaneously hypertensive rats, independently of blood pressure

BACKGROUND AND PURPOSE

Very recent subgroup analysis from the PROspective pioglitAzone Clinical Trial In macroVascular Events has shown that pioglitazone reduces the risk of recurrent stroke in type 2 diabetic patients. However, the underlying mechanism of stroke prevention by pioglitazone is unknown. Our aim was to examine the effect of pioglitazone on hypertension-based stroke in rats.

METHODS

Pioglitazone (1 mg x kg(-1) x d(-1)) was orally administered to stroke-prone spontaneously hypertensive rats (SHRSP) to examine the effect on incidental stroke, cerebrovascular injury, brain inflammation, oxidative stress, and vascular endothelial dysfunction induced by hypertension.

RESULTS

Treatment of SHRSP with pioglitazone for 4 weeks, without affecting blood pressure and blood glucose values, improved vascular endothelial dysfunction (P<0.05), suppressed remodeling of the middle cerebral artery (P<0.05) and brain microvessels (P<0.05), and inhibited brain macrophage infiltration (P<0.05) and the upregulation of brain monocyte chemoattractant protein-1 and tumor necrosis factor-alpha expression (P<0.01). Furthermore, pioglitazone treatment significantly delayed the onset of stroke signs and death in SHRSP (P<0.05). These beneficial effects of pioglitazone on cerebrovascular injury and stroke in SHRSP were associated with a reduction of brain and vascular superoxide via the inhibition of NADPH oxidase activity.

CONCLUSIONS

Our work provides the first evidence that pioglitazone significantly protects against hypertension-induced cerebrovascular injury and stroke by improving vascular endothelial dysfunction, inhibiting brain inflammation, and reducing oxidative stress. These beneficial effects of pioglitazone were independent of blood pressure or blood sugar values. Thus, pioglitazone appears to be a potential therapeutic agent for stroke in type 2 diabetes with hypertension.