Ischemia-induced glutamate release in rat frontoparietal cortex after chronic alcohol and withdrawal

Alcohol withdrawal is associated with poorer outcome in acute ischemic stroke

OBJECTIVE

To determine the association between alcohol abuse (AA) and alcohol withdrawal (AW) with acute ischemic stroke (AIS) outcomes.

METHODS

All adult AIS admissions in the United States from 2004 to 2014 were identified from the National Inpatient Sample (weighted n = 4,438,968). Multivariable-adjusted models were used to evaluate the association of AW with in-hospital medical complications, mortality, cost, and length of stay in patients with AIS.

RESULTS

Of the AA admissions, 10.6% of patients, representing 0.4% of all AIS, developed AW. The prevalence of AA and AW in AIS increased by 45.2% and 40.0%, respectively, over time (p for trend <0.001). Patients with AA were predominantly men (80.2%), white (65.9%), and in the 40- to 59-year (44.6%) and 60- to 79-year (45.6%) age groups. After multivariable adjustment, AIS admissions with AW had >50% increased odds of urinary tract infection, pneumonia, sepsis, gastrointestinal bleeding, deep venous thrombosis, and acute renal failure compared to those without AW. Patients with AW were also 32% more likely to die during their AIS hospitalization compared to those without AW (odds ratio 1.32, 95% confidence interval 1.11-1.58). AW was associated with ≈15-day increase in length of stay and ≈$5,000 increase in hospitalization cost (p < 0.001).

CONCLUSION

AW is associated with increased cost, longer hospitalizations, and higher odds of medical complications and in-hospital mortality after AIS. Proactive surveillance and management of AW may be important in improving outcomes in these patients.

Dose-Dependent Influences of Ethanol on Ischemic Stroke: Role of Inflammation

Chronic ethanol consumption dose-dependently affects both incidence and prognosis of ischemic stroke. Our goal was to determine whether the influence of chronic ethanol consumption on ischemic stroke is related to an altered inflammatory profile in the brain. Male C57BL/6J mice were divided into six groups and gavage fed with 0.175, 0.35, 0.7, 1.4, 2.8 g/kg/day ethanol or volume-matched water once a day for 8 weeks. Adhesion molecules, microglial activation, neutrophil infiltration, pro- and anti-inflammatory cytokines/chemokines, blood-brain barrier (BBB) permeability, and matrix metallopeptidases (MMPs) in the cerebral cortex before and following a 90-min unilateral middle cerebral artery occlusion (MCAO)/24-h reperfusion were evaluated. Brain ischemia/reperfusion (I/R) injury was significantly reduced in 0.7 g/kg/day ethanol group (peak blood ethanol concentration: 9 mM) and worsened in 2.8 g/kg/day ethanol group (peak blood ethanol concentration: 37 mM). Baseline E-selectin was downregulated in all ethanol groups, whereas baseline intercellular adhesion molecule-1 (ICAM-1) was only downregulated in 0.35 and 0.7 g/kg/day ethanol groups. Interestingly, baseline vascular cell adhesion molecule-1 (VCAM-1) was upregulated in 0.35, 0.7, and 1.4 g/kg/day ethanol groups. Post-ischemic upregulation of ICAM-1 and E-selectin were suppressed in all ethanol groups. Post-ischemic neutrophil infiltration and microglial activation were significantly less in the low-moderate (0.175–1.4 g/kg/day) ethanol groups but greater in the 2.8 g/kg/day ethanol group compared to the vehicle group. At basal conditions, ethanol increased one pro- and two anti-inflammatory cytokines/chemokines at the 0.7 g/kg/day dose, and 13 pro- and eight anti-inflammatory cytokines/chemokines at the 2.8 g/kg/day dose. After ischemia, 0.7 g/kg/day ethanol suppressed post-ischemic pro-inflammatory cytokines/chemokines and enhanced post-ischemic anti-inflammatory cytokines/chemokines. Moreover, 0.7 g/kg/day ethanol significantly reduced baseline MMP-9 activity and alleviated post-ischemic BBB breakdown. On the other hand, 2.8 g/kg/day ethanol worsened post-ischemic BBB breakdown. Our findings suggest that low-moderate ethanol consumption may prevent ischemic stroke and reduce brain I/R injury by suppressing inflammation, whereas heavy alcohol consumption may induce ischemic stroke and worsen brain I/R injury by aggravating inflammation.

Effects of Chronic Alcohol Exposure on the Modulation of Ischemia-Induced Glutamate Release via Cannabinoid Receptors in the Dorsal Hippocampus

BACKGROUND

Chronic alcohol consumption is a critical contributing factor to ischemic stroke, as it enhances ischemia-induced glutamate release, leading to more severe excitotoxicity and brain damage. But the neural mechanisms underlying this phenomenon are poorly understood.

METHODS

We evaluated the effects of chronic alcohol exposure on the modulation of ischemia-induced glutamate release via CB1 and CB2 cannabinoid receptors during middle cerebral artery occlusion, using in vivo microdialysis coupled with high-performance liquid chromatography, in alcohol-naïve rats or rats after 1 or 30 days of withdrawal from chronic ethanol intake (6% v/v for 14 days).

RESULTS

Intra-dorsal hippocampus (DH) infusions of ACEA or JWH133, selective CB1 or CB2 receptor agonists, respectively, decreased glutamate release in the DH in alcohol-naïve rats in a dose-dependent manner. Such an effect was reversed by co-infusions of SR141716A or AM630, selective CB1 or CB2 receptor antagonists, respectively. After 30 days, but not 1 day of withdrawal, ischemia induced an enhancement in glutamate release in the DH, as compared with non-alcohol-treated control group. Intra-DH infusions of JWH133, but not ACEA, inhibited ischemia-induced glutamate release in the DH after 30 days of withdrawal. Finally, 1 day of withdrawal did not alter the protein level of CB1 or CB2 receptors in the DH, as compared to non-alcohol-treated control rats. Whereas 30 days of withdrawal robustly decreased the protein level of CB1 receptors, but failed to alter the protein level of CB2 receptors, in the DH, as compared to non-alcohol-treated control rats.

CONCLUSIONS

Together, these findings suggest that loss of expression/function of CB1 receptors, but not CB2 receptors in the DH, is correlated with the enhancement of ischemia-induced glutamate release after prolonged alcohol withdrawal.

Impact of alcohol consumption on the outcome of ischemic stroke and thrombolysis: role of the hepatic clearance of tissue-type plasminogen activator

BACKGROUND AND PURPOSE

Tissue-type plasminogen activator (tPA) is the only acute treatment for ischemic stroke. Unfortunately, the benefit of tPA-driven thrombolysis is not systematic, and understanding the reasons for this is mandatory. The balance between beneficial and detrimental effects of tPA might explain the limited overall efficiency of thrombolysis. Here, we investigated whether this balance could be influenced by excessive alcohol intake.

METHODS

We used a murine model of thromboembolic stroke, coupled to an array of biochemical assays, near-infrared or magnetic resonance imaging scans, 2-photon microscopy, hydrodynamic transfections, and immunohistological techniques.

RESULTS

We found that 6 weeks of alcohol consumption (10% in drinking water) worsens ischemic lesions and cancels the beneficial effects of tPA-induced thrombolysis. We accumulate in vivo and in vitro evidence showing that this aggravation is correlated with a decrease in lipoprotein receptor-related protein 1-mediated hepatic clearance of tPA in alcohol-exposed mice.

CONCLUSIONS

An efficient liver-driven clearance of tPA might influence the safety of thrombolysis after stroke.

Alcohol-induced exacerbation of ischemic brain injury: role of NAD(P)H oxidase

BACKGROUND

 Chronic alcohol consumption increases ischemic stroke and exacerbates ischemic brain injury. We determined the role of NAD(P)H oxidase in exacerbated ischemic brain injury during chronic alcohol consumption.

METHODS

 Sprague Dawley rats were fed a liquid diet with or without alcohol (6.4% v/v) for 8 weeks. We measured the effect of apocynin on 2-hour middle cerebral artery occlusion (MCAO)/24-hour reperfusion-induced brain injury. In addition, superoxide production and expression of NAD(P)H oxidase subunit, gp91phox, in the peri-infarct area were assessed.

RESULTS

Chronic alcohol consumption produced a larger infarct volume, worse neurological score, and higher superoxide production. Acute (5 mg/kg, ip, 30 minutes before MCAO) and chronic treatment with apocynin (7.5 mg/kg/d in the diet, 4 weeks prior to MCAO) reduced infarct volume, improved neurological outcome, and attenuated superoxide production in alcohol-fed rats. Expression of gp91phox at basal conditions and following ischemia/reperfusion was greater in alcohol-fed rats compared to non-alcohol-fed rats. In addition, neurons are partially responsible for upregulated gp91phox during alcohol consumption.

CONCLUSIONS

Our findings suggest that NAD(P)H oxidase may play an important role in exacerbated ischemic brain injury during chronic alcohol consumption.

Neurotoxic consequences of chronic alcohol withdrawal: expression profiling reveals importance of gender over withdrawal severity

While women are more vulnerable than men to many of the medical consequences of alcohol abuse, the role of sex in the response to ethanol is controversial. Neuroadaptive responses that result in the hyperexcitability associated with withdrawal from chronic ethanol likely reflect gene expression changes. We have examined both genders for the effects of withdrawal on brain gene expression using mice with divergent withdrawal severity that have been selectively bred from a genetically heterogeneous population. A total of 295 genes were identified as ethanol regulated from each gender of each selected line by microarray analyses. Hierarchical cluster analysis of the arrays revealed that the transcriptional response correlated with sex rather than with the selected withdrawal phenotype. Consistent with this, gene ontology category over-representation analysis identified cell death and DNA/RNA binding as targeted classes of genes in females, while in males, protein degradation, and calcium ion binding pathways were more altered by alcohol. Examination of ethanol-regulated genes and these distinct signaling pathways suggested enhanced neurotoxicity in females. Histopathological analysis of brain damage following ethanol withdrawal confirmed elevated cell death in female but not male mice. The sexually dimorphic response was observed irrespective of withdrawal phenotype. Combined, these results indicate a fundamentally distinct neuroadaptive response in females compared to males during chronic ethanol withdrawal and are consistent with observations that female alcoholics may be more vulnerable than males to ethanol-induced brain damage associated with alcohol abuse.

Effect of chronic alcohol consumption on brain damage following transient focal ischemia

Chronic alcohol consumption impairs cerebral vasoreactivity, and thus, may result in an increase in ischemic brain damage. The goal of this study is to examine the influence of chronic alcohol consumption on transient focal ischemia-induced brain damage. Sprague-Dawley rats were divided into two groups, a control group and an alcohol group. Eight weeks after being fed a liquid diet with or without alcohol, responses of parietal pial arterioles to systemic hypoxia and hypercapnia were measured using a cranial window technique. In separate experiments, rats were subjected to right middle cerebral artery occlusion (MCAO) for 2 h under ketamine/xylazine or isoflurane anesthesia. Regional cerebral blood flow (rCBF) was monitored through a Laser-Doppler flow probe attached to the lateral aspect of the skull. Neurological evaluation and ischemic lesion were assessed 24 h after reperfusion. Dilation of pial arterioles in response to hypoxia and hypercapnia was significantly reduced in alcohol-fed rats. Alcohol-fed rats had significantly larger infarct volumes and worse neurological outcomes than non-alcohol-fed rats under ketamine/xylazine or isoflurane anesthesia. In addition, rCBF measurement indicated that alcohol-fed rats had less regulatory rebound increase in rCBF after the initial drop in rCBF at the onset of MCAO. Our findings suggest that chronic alcohol consumption exacerbates transient focal ischemia-induced brain damage. Increased ischemic brain damage during alcohol consumption may be related to an impaired cerebral vasoreactivity.

Cysteinyl leukotriene receptor 1 is involved in N-methyl-D-aspartate-mediated neuronal injury in mice

AIM

To determine whether cysteinyl leukotriene receptor 1 (CysLT1 receptor) is involved in N-methyl-D-aspartate (NMDA)-induced excitotoxic injury in the mouse brain.

METHODS

Brain injury was induced by NMDA microinjection (50-150 nmol in 0.5 microL) into the cerebral cortex. The changes in CysLT1 receptor expression 24 h after NMDA injection and the effects of a CysLT1 receptor antagonist, pranlukast (0.01 and 0.1 mg/kg), an NMDA receptor antagonist, ketamine (30 mg/kg), and an antioxidant, edaravone (9 mg/kg) were observed.

RESULTS

In the NMDA-injured brain, the CysLT1 receptor mRNA, and protein expression were upregulated, and the receptor was mainly localized in the neurons and not in the astrocytes. Pranlukast, ketamine and edaravone decreased NMDA-induced injury; pranlukast (0.1 mg/kg) and ketamine inhibited the upregulated expression of the CysLT1 receptor.

CONCLUSION

CysLT1 receptor expression in neurons is upregulated after NMDA injection, and NMDA-induced responses are inhibited by CysLT1 receptor antagonists, indicating that the increased CysLT1 receptor is involved in NMDA excitotoxicity.

Minocycline protects PC12 cells against NMDA-induced injury via inhibiting 5-lipoxygenase activation

Recently, we have reported that minocycline, a semi-synthetic tetracycline with neuroprotective effects, inhibits the in vitro ischemic-like injury and 5-lipoxygenase (5-LOX) activation in PC12 cells. In the present study, we further determined whether minocycline protects PC12 cells from excitotoxicity via inhibiting 5-LOX activation. We used N-methyl-d-aspartate (NMDA, 200 microM) to induce early (exposure for 6 h) and delayed (exposure for 6 h followed by 24 h recovery) injuries. We found that NMDA receptor antagonist ketamine, 5-LOX inhibitor caffeic acid and minocycline concentration dependently attenuated NMDA-induced early and delayed cell injuries (viability reduction and cell death). However, only ketamine (1 microM) inhibited NMDA-evoked elevation of intracellular calcium. In addition, immunohistochemical analysis showed that NMDA induced 5-LOX translocation to the nuclear membrane after 1- to 6-h exposure which was confirmed by Western blotting, indicating that 5-LOX was activated. Ketamine, caffeic acid and minocycline (each at 1 microM) inhibited 5-LOX translocation after early injury. After delayed injury, PC12 cells were shrunk, and 5-LOX was translocated to the nuclei and nuclear membrane; ketamine, caffeic acid and minocycline inhibited both cell shrinking and 5-LOX translocation. As a control, 12-LOX inhibitor baicalein showed a weak effect on cell viability and death, but no effect on 5-LOX translocation. Therefore, we conclude that the protective effect of minocycline on NMDA-induced injury is partly mediated by inhibiting 5-LOX activation.