Jin-Min Guo

ALDH2 protects against stroke by clearing 4-HNE

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that metabolizes ethanol and toxic aldehydes such as 4-hydroxy-2-nonenal (4-HNE). Using an unbiased proteomic search, we identified ALDH2 deficiency in stroke-prone spontaneously hypertensive rats (SHR-SP) as compared with spontaneously hypertensive rats (SHR). We concluded the causative role of ALDH2 deficiency in neuronal injury as overexpression or activation of ALDH2 conferred neuroprotection by clearing 4-HNE in in vitro studies. Further, ALDH2-knockdown rats revealed the absence of neuroprotective effects of PKCε. Moderate ethanol administration that is known to exert protection against stroke was shown to enhance the detoxification of 4-HNE, and to protect against ischemic cerebral injury through the PKCε-ALDH2 pathway. In SHR-SP, serum 4-HNE level was persistently elevated and correlated inversely with the lifespan. The role of 4-HNE in stroke in humans was also suggested by persistent elevation of its plasma levels for at least 6 months after stroke. Lastly, we observed that 21 of 1 242 subjects followed for 8 years who developed stroke had higher initial plasma 4-HNE levels than those who did not develop stroke. These findings suggest that activation of the ALDH2 pathway may serve as a useful index in the identification of stroke-prone subjects, and the ALDH2 pathway may be a potential target of therapeutic intervention in stroke.

Genetics of stroke

AbstractStroke is the second most common cause of death and the most common cause of disability in developed countries. Stroke is a multi-factorial disease caused by a combination of environmental and genetic factors. Numerous epidemiologic studies have documented a significant genetic component in the occurrence of strokes. Genes encoding products involved in lipid metabolism, thrombosis, and inflammation are believed to be potential genetic factors for stroke. Although a large group of candidate genes have been studied, most of the epidemiological results are conflicting. Studies of stroke as a monogenic disease have made huge progress, and animal models serve as an indispensable tool to dissect the complex genetics of stroke. In the present review, we provide insight into the role of in vivo stroke models for the study of stroke genetics.

Involvement of Acetylcholine‐α7nAChR in the Protective Effects of Arterial Baroreflex against Ischemic Stroke

Decreased baroreflex sensitivity is associated with poor outcome in many cardiovascular diseases including stroke, but the molecular mechanism underlying this relationship is unclear. This work was designed to test the hypothesis that acetylcholine (ACh) and α7 nicotinic ACh receptor (α7nAChR) mediate the protection of arterial baroreflex against stroke.

Baroreflex deficiency hampers angiogenesis after myocardial infarction via acetylcholine-α7-nicotinic ACh receptor in rats

AIMS Angiogenesis is critical for re-establishing blood supply to ischaemic myocardium after myocardial infarction (MI). Human studies have associated arterial baroreflex (ABR) deficiency with higher rate of sudden death after MI. The present work was designed to examine whether ABR deficiency affects angiogenesis in MI rats. METHODS AND RESULTS Baroreflex sensitivity (BRS) was determined in conscious rats at 1 month after occlusion of the left anterior descending coronary artery. The survival time was significantly shorter in Sprague-Dawley rats with BRS <0.60 ms/mmHg vs. those with BRS ≥0.60 ms/mmHg. Sinoaortic denervation destroyed ABR, and decreased capillary density, regional blood flow and vascular endothelial growth factor (VEGF) concentration after MI. Ketanserin (0.6 mg/kg/day) enhanced BRS, and increased capillary density, regional blood flow, and VEGF. Sinoaortic denervation also reduced the expression of vesicular acetylcholine (ACh) transporter and α7-nicotinic ACh receptor (α7-nAChR). Angiogenesis after MI was significantly attenuated in α7-nAChR knockout mice. In contrast, increase in endogenous ACh with cholinesterase inhibitor pyridostigmine (30 mg/kg/day) increased angiogenesis after MI. In cultured cardiac microvascular endothelial cells, ACh stimulated the expression of VEGF, phosphorylation of VEGF receptor 2, and tube formation in a manner dependent upon α7-nAChR. CONCLUSION Our results demonstrated that ABR deficiency could attenuate angiogenesis in ischaemic myocardium. These findings provide further mechanistic basis for enhancing baroreflex function in the treatment of MI.

Involvement of arterial baroreflex in the protective effect of dietary restriction against stroke.

Dietary restriction (DR) protects against neuronal dysfunction and degeneration, and reduces the risk of ischemic stroke. This study examined the role of silent information regulator T1 (SIRT1) and arterial baroreflex in the beneficial effects of DR against stroke, using two distinct stroke models: stroke-prone spontaneously hypertensive rats (SP-SHRs) and Sprague-Dawley (SD) rats with middle cerebral artery occlusion (MCAO). Sirt1 knockout (KO) mice were used to examine the involvement of sirt1. Sinoaortic denervation was used to inactivate arterial baroreflex. Dietary restriction was defined as 40% reduction of dietary intake. Briefly, DR prolonged the life span of SP-SHRs and reduced the infarct size induced by MCAO. Dietary restriction also improved the function arterial baroreflex, decreased the release of proinflammatory cytokines, and reduced end-organ damage. The beneficial effect of DR on stroke was markedly attenuated by blunting arterial baroreflex. Lastly, the infarct area in sirt1 KO mice was significantly larger than in the wild-type mice. However, the beneficial effect of DR against ischemic injury was still apparent in sirt1 KO mice. Accordingly, arterial baroreflex, but not sirt1, is important in the protective effect of DR against stroke.

SIRT1‐dependent AMPK pathway in the protection of estrogen against ischemic brain injury

Stroke is a major cause of mortality and disability, especially for postmenopausal women. In view of the protective action of estrogen, hormone therapy remains the only effective way to limit this risk. The objective of this study was to investigate the efficiency and underlying mechanisms of estrogen neuroprotection.

New strategies for the prevention of stroke

1. Stroke is a major cause of disability and death worldwide. It is preferable to prevent stroke rather than to treat it and, for the prevention of stroke, all risk factors relating to stroke need to be understood. The present paper reviews potential new strategies for the prevention of stroke based on findings of new risk factors, as well as classical risk factors.

Heavy ethanol consumption aggravates the ischemic cerebral injury by inhibiting ALDH2

Background Heavy ethanol consumption is widely accepted as a risk for ischemic stroke. The molecular mechanisms of ethanol-induced brain injury have not been fully understood. Aim This study aims to find out the mechanism of the ischemic cerebral injury. Methods We used Sprague-Dawley rats with transient middle cerebral artery occlusion for acute experiment and stroke-prone spontaneously hypertensive rats for long-term experiment in vivo, and oxygen-glucose deprivation model in vitro to define a detrimental effect of different doses of ethanol on ischemic stroke injury. We also used mitochondrial aldehyde dehydrogenase 2 knockdown/overexpression or inhibitor/activator to investigate mechanism of the adverse effects of ethanol. Results High-dose ethanol (36% of calorie derived from ethanol) significantly increased the infarct size in rats (P < 0·01) and decreased the survival time of stroke-prone spontaneously hypertensive rats by about 20%. Six-week treatment with high-dose ethanol changed a distribution of isoelectric point of aldehyde dehydrogenase 2 and inhibited aldehyde dehydrogenase 2 activity in brain. High dose of ethanol increased the cerebral acetaldehyde level, and increased 4-hydroxy-2-nonenal and malondialdehyde in serum of rats with middle cerebral artery occlusion. The activator of aldehyde dehydrogenase 2, Alda-1 abolished neuronal cells death and ischemic injury induced by ethanol and the inhibitor reversed the injurious effects. An overexpression of aldehyde dehydrogenase 2 completely abolished the increased infarct size and neurological deficit score by ethanol. Conversely, knockdown of aldehyde dehydrogenase 2 increased the infarct size and exaggerated the cerebral injury induced by ethanol. Conclusions High concentrations of ethanol aggravate cerebral injury by inhibiting of aldehyde dehydrogenase 2 and inducing excess accumulation of aldehydes.

Activation of α7 Nicotinic Acetylcholine Receptor Decreases On-site Mortality in Crush Syndrome through Insulin Signaling-Na/K-ATPase Pathway

On-site mortality in crush syndrome remains high due to lack of effective drugs based on definite diagnosis. Anisodamine (Ani) is widely used in China for treatment of shock, and activation of α7 nicotinic acetylcholine receptor (α7nAChR) mediates such antishock effect. The present work was designed to test whether activation of α7nAChR with Ani decreased mortality in crush syndrome shortly after decompression. Sprague-Dawley rats and C57BL/6 mice with crush syndrome were injected with Ani (20 mg/kg and 28 mg/kg respectively, i.p.) 30 min before decompression. Survival time, serum potassium, insulin, and glucose levels were observed shortly after decompression. Involvement of α7nAChR was verified with methyllycaconitine (selective α7nAChR antagonist) and PNU282987 (selective α7nAChR agonist), or in α7nAChR knockout mice. Effect of Ani was also appraised in C2C12 myotubes. Ani reduced mortality and serum potassium and enhanced insulin sensitivity shortly after decompression in animals with crush syndrome, and PNU282987 exerted similar effects. Such effects were counteracted by methyllycaconitine or in α7nAChR knockout mice. Mortality and serum potassium in rats with hyperkalemia were also reduced by Ani. Phosphorylation of Na/K-ATPase was enhanced by Ani in C2C12 myotubes. Inhibition of tyrosine kinase on insulin receptor, phosphoinositide 3-kinase, mammalian target of rapamycin, signal transducer and activator of transcription 3, and Na/K-ATPase counteracted the effect of Ani on extracellular potassium. These findings demonstrated that activation of α7nAChR could decrease on-site mortality in crush syndrome, at least in part based on the decline of serum potassium through insulin signaling-Na/K-ATPase pathway.

Nicotinamide Postpones Stroke in Stroke‐Prone Spontaneously Hypertensive Rats

Stroke is the second most common cause of death and a major cause of disability worldwide [1]. Approximately, 80% of the cases are ischemic. Many stroke survivors require lifelong assistance. Prevention is considered the most effective strategy to curb stroke [2]. The improved control of risk factors could reduce the morbidity of stroke, such as reducing blood pressure and blood lipid. Besides these, finding some endogenous and safe medicines are also important. Nicotinamide (NAM) is a precursor of nicotinamide adenine dinucleotide (NAD+) and is used to generate ATP in the mitochondrial electron-transport chain. NAM could readily enter the brain [3]. Recently, NAM has been reported to offer neuroprotection on brain [4–6]. Whether it postpones stroke for lifelong treatment is unclear. In this study, we examined the preventive effect of NAM against ischemic stroke in stroke-prone spontaneously hypertensive rats (SHRSP), a commonly used animal model for spontaneous stroke. To test the potential effective dosage, six groups of SHRSP were received NAM (25–500 mg/kg/day) or vehicle for 4 weeks, and then were subjected to middle cerebral artery occlusion (MCAO). As shown in Figure 1(A), NAM (50, 100, and 200 mg/kg/day) significantly reduced infarction volume. Then, we administrated 80 SHRSP with NAM (50, 100, and 200 mg/kg/day) or vehicle via animal chow for their entire lifespan. Compared with the control group, long-term treatment with NAM did not affect the body weight (Figure 1B). Kaplan–Meier analysis of the survival is shown in Figure 1(C). Pretreatment with NAM (50, 100, and 200 mg/kg) significantly delayed the onset of stroke (log-rank testing, P < 0.01). These data demonstrated that NAM (50–200 mg/kg), when administrated to SHRSP before the ischemic event, could delay the onset of stroke and reduce infarction volume. Increased levels of reactive oxygen species (ROS) are a feature in ischemic stroke and exaggerate the ischemic damage [7,8]. In this study, ROS levels in infarct penumbra of cerebral cortex of male SHRSP (220–250 g) were assessed using rhodamine 123. Compared to sham operation, MCAO increased ROS level by 46% (Figure 2A). Such an increase was significantly attenuated by NAM (100 mg/kg, i.p.). Nicotinamide adenine dinucleotide phosphate oxidase (NOX), an important ROS-generating enzyme, is a major source of ROS [9]. As a multisubunit complex, gp91phox is the catalytic subunit of NOX and requires subunit p22phox. Superoxide dismutase (SOD), including Cu/Zn-SOD and Mn-SOD, is one of ROSscavenging enzymes. In our study, MCAO upregulated gp91phox and p22phox subunits, decreased SOD activity, and increased the MDA level in infarct penumbra of cerebral cortex of male SHRSP (220–250 g) (Figure 2B-D). These changes were reversed by NAM pretreatment (100 mg/kg, i.p.). The results suggested that NAM plays antioxidative action, possibly via reducing ROS formation and promoting ROS elimination. In addition, MCAO produced a significant decrease in mitochondrial membrane potential (Figure 2E). Consistent with a previous study [4], NAM pretreatment alleviated the MACO-induced loss of mitochondrial membrane potential in the infarct penumbra. Taken together, NAM could prevent/delay the occurrence of ischemic stroke in SHRSP, possibly via reducing ROS level and maintaining mitochondrial membrane potential.