Edaravone attenuates sustained pial arteriolar vasoconstriction independently of endothelial function after unclamping of the abdominal aorta in rabbits.

BACKGROUND: Cerebral blood flow (CBF) has direct effects on neuronal function and neurocognitive disorders. Oxidative stress from abdominal aortic surgery is important in the pathophysiology of CBF impairment. We investigated the effect of edaravone on the pial arteriolar diameter changes induced by abdominal aortic surgery and the involvement of the endothelium in the changes. METHODS: The closed cranial window technique was used in rabbits to measure changes in pial arteriolar diameter after the unclamping of abdominal aortic cross-clamping with an intravenous free radical scavenger, edaravone (control group [n = 6], edaravone 10 µg/kg/min [n = 6], 100 µg/kg/min [n = 6]). Pial vasodilatory responses to topical application of acetylcholine (ACh) into the cranial window were investigated before abdominal aortic cross-clamping and after unclamping with intravenous administration of edaravone (control group [n = 6], edaravone 100 µg/kg/min [n = 6]). RESULTS: Aortic unclamping-induced vasoconstriction was significantly attenuated by continuous infusion of edaravone at 100 µg/kg/min. Topical ACh after unclamping did not produce any changes in pial arteriolar responses in comparison to before aortic cross-clamping in the control or edaravone groups. The changes in the response to topical ACh after unclamping in the saline and edaravone groups did not differ significantly. CONCLUSIONS: Free radicals during abdominal aortic surgery might have contracted cerebral blood vessels independently of endothelial function in rabbits. Suppression of free radicals attenuated the sustained pial arteriolar vasoconstriction after aortic unclamping. Thus, the free radical scavenger might have some brain protective effect that maintains CBF independently of endothelial function.

Nicorandil protects pial arterioles from endothelial dysfunction induced by smoking in rats.

BACKGROUND: Our aims are to investigate the effect of nicorandil, which is used for angina prevention and treatment, on the endothelial dysfunction induced by acute smoking and to clarify the underlying mechanism. MATERIALS AND METHODS: A closed cranial window preparation was used to measure changes in pial vessel diameters in Sprague-Dawley rats. The responses of arterioles were examined to an endothelium-dependent vasodilator acetylcholine (ACh) before smoking. After intravenous nicorandil (200 µg/kg bolus infusion and then 60 µg/kg/min continuous infusion; n=6) or saline (control; n=6) pretreatment, the pial vasodilator response to topical 10 M ACh infusion was reexamined both before and 1 hour after 1-minute cigarette smoking. Thereafter, either glibenclamide or N-ω-nitro-L-arginine methyl ester (L-NAME) was infused 20 minutes before nicorandil infusion. In the glibenclamide (n=6) or L-NAME; n=6 pretreatment group, the pial vasodilator response to topical ACh was examined before and after smoking. Percentage changes in pial vessel diameters were used for the statistical analysis. RESULTS: Cerebral arterioles were dilated during topical ACh infusion. After smoking, 10 M ACh constricted cerebral arterioles (-7.7±1.8%). After smoking, in the nicorandil-pretreatment group, 10 M ACh dilated cerebral pial arterioles by 10.5±3.0%. When given before nicorandil infusion, glibenclamide, but not L-NAME, abolished the preventive effects of nicorandil against smoking-induced endothelial dysfunction in pial vessels. CONCLUSIONS: Acute cigarette smoking causes dysfunction of endothelium-dependent pial vasodilatation, and nicorandil prevents this effect of smoking. The mechanism underlying this protective effect may depend mainly on adenosine triphosphate-sensitive potassium-channel activation.

Role of salt-induced kinase 1 in androgen neuroprotection against cerebral ischemia.

Androgens within physiological ranges protect castrated male mice from cerebral ischemic injury. Yet, underlying mechanisms are unclear. Here, we report that, after middle cerebral artery occlusion (MCAO), salt-induced kinase 1 (SIK1) was induced by a potent androgen-dihydrotestosterone (DHT) at protective doses. To investigate whether SIK1 contributes to DHT neuroprotection after cerebral ischemia, we constructed lentivirus-expressing small interference RNA (siRNA) against SIK1. The SIK1 knockdown by siRNA exacerbated oxygen-glucose deprivation (OGD)-induced cell death in primary cortical neurons, suggesting that SIK1 is an endogenous neuroprotective gene against cerebral ischemia. Furthermore, lentivirus-mediated SIK1 knockdown increased both cortical and striatal infarct sizes in castrated mice treated with a protective dose of DHT. Earlier studies show that SIK1 inhibits histone deacetylase (HDAC) activities by acting as a class IIa HDAC kinase. We observed that SIK1 knockdown decreased histone H3 acetylation in primary neurons. The SIK1 siRNA also exacerbated OGD-induced neuronal death in the presence of trichostatin A (TSA), an HDAC inhibitor, and decreased histone H3 acetylation at 4 hours reoxygenation in TSA-treated neurons. Finally, we showed that DHT at protective doses prevented ischemia-induced histone deacetylation after MCAO. Our finding suggests that SIK1 contributes to neuroprotection by androgens within physiological ranges by inhibiting histone deacetylation.

Androgen receptor overexpression is neuroprotective in experimental stroke.

Male sex is a known risk factor in human stroke. However, the role of the cognate receptor for androgens-the androgen receptor (AR)-in stroke outcome remains unclear. Here, we found that AR mRNA is downregulated in the peri-infarct tissue of gonadally intact male mice subjected to middle cerebral artery occlusion (MCAO) and 6 h reperfusion. We then used genetically engineered mice overexpressing AR in brain (AR-Tg) to compare outcomes from MCAO in intact or castrated males and to evaluate the neuroprotective role of dihydrotestosterone (DHT) replacement in AR-Tg castrates. A further evaluation of AR overexpression in ischemic paradigms was performed using rat PC12 cells transfected with human AR and treated with oxidative and apoptotic stressors. We then studied the role of DHT in cultures overexpressing AR. Our results show (1) ischemia alters the expression of AR by decreasing AR mRNA levels, (2) AR overexpression is protective in vivo against MCAO in intact and castrated AR-Tg mice and in vitro against oxidative and apoptotic stressors in AR-PC12 cells, and (3) DHT does not enhance the protection triggered by AR overexpression in AR-Tg castrated mice nor in AR-PC12 cells.

Estradiol and G1 reduce infarct size and improve immunosuppression after experimental stroke.

Reduced risk and severity of stroke in adult females is thought to depend on normal endogenous levels of estrogen, a well-known neuroprotectant and immunomodulator. In male mice, experimental stroke induces immunosuppression of the peripheral immune system, characterized by a reduction in spleen size and cell numbers and decreased cytokine and chemokine expression. However, stroke-induced immunosuppression has not been evaluated in female mice. To test the hypothesis that estradiol (E2) deficiency exacerbates immunosuppression after focal stroke in females, we evaluated the effect of middle cerebral artery occlusion on infarct size and peripheral and CNS immune responses in ovariectomized mice with or without sustained, controlled levels of 17-beta-E2 administered by s.c. implant or the putative membrane estrogen receptor agonist, G1. Both E2- and G1-replacement decreased infarct volume and partially restored splenocyte numbers. Moreover, E2-replacement increased splenocyte proliferation in response to stimulation with anti-CD3/CD28 Abs and normalized aberrant mRNA expression for cytokines, chemokines, and chemokine receptors and percentage of CD4(+)CD25(+)FoxP3(+) T regulatory cells observed in E2-deficient animals. These beneficial changes in peripheral immunity after E2 replacement were accompanied by a profound reduction in expression of the chemokine, MIP-2, and a 40-fold increased expression of CCR7 in the lesioned brain hemisphere. These results demonstrate for the first time that E2 replacement in ovariectomized female mice improves stroke-induced peripheral immunosuppression.

Microwave discharge electrodeless lamps (MDEL). V. Microwave-assisted photolytic disinfection of Bacillus subtilis in simulated electroplating wash wastewaters.

This short article examines the microwave-assisted photolytic disinfection of aqueous solutions contaminated by Bacillus subtilis microorganisms using UV and vacuum-UV radiation emitted from a microwave discharge electrodeless lamp (MDEL), a device containing a Hg/Ar gas-fill that was proposed recently for use in Advanced Oxidation Processes (AOPs). Results of the disinfection are compared with those obtained from UV radiation emitted by a low-pressure electrode Hg lamp and by an excimer lamp. Also examined is the disinfection of B. subtilis aqueous media that contained Au3+ or Ni2+ ions, species often found in the treatment of electroplating wash wastewaters.

Dose-dependent effects of androgens on outcome after focal cerebral ischemia in adult male mice.

Males exhibit greater histologic and behavioral impairment after stroke than do age-matched females. However, the contribution of androgens to stroke outcome remains unclear. We compared outcomes from middle cerebral artery occlusion (MCAO) in castrated mice with those in testosterone- or dihydrotestosterone (DHT)-replaced castrated mice. Castrates treated with 1.5 mg testosterone or 0.5 mg DHT before MCAO showed smaller infarct volumes (hemisphere: 27 or 26%) at 24 h after 90 mins MCAO than did untreated castrates (37%), whereas 5 mg testosterone or 1.5 mg DHT exacerbated infarcts (53 or 51%). These outcomes were blocked by the androgen receptor antagonist, flutamide, suggesting that androgen receptors mediate these responses to ischemia. We further evaluated long-term outcomes with a milder 60-min MCAO in castrates treated with the protective 1.5 mg testosterone dose. Consistent with data obtained at 24 h reperfusion, the infarct volume was decreased at 9 days reperfusion. Neurobehavioral analysis showed that motor functional recovery was improved during the first 3 days of reperfusion, but not improved at 7 days. We conclude that testosterone exhibits dose-dependent and time-sensitive effects after ischemia and that testosterone is likely to be an important factor in sex-linked differences in cerebrovascular disease.

The effects of transient cerebral ischemia on vasopressin-induced vasoconstriction in rabbit cerebral vessels.

BACKGROUND: Vasopressin is a drug of choice for use during cardiopulmonary resuscitation because several experimental studies have shown that it is better than epinephrine at increasing systemic perfusion pressure and improving cerebral perfusion pressure without increasing myocardial oxygen consumption. We used a pial window preparation to determine the effects of vasopressin when applied topically to pial vessels and whether any effects were altered after cerebral ischemia in rabbits (n = 27). METHODS: We first examined the effects of topical application of arginine-vasopressin (AVP) (10(-11) M, 10(-9) M, 10(-7) M, and 10(-5) M, sequentially). We then examined the effects of topical application of AVP (10(-9) M and 10(-7) M, sequentially) before and after a 5-min intervention consisting of cerebral ischemia produced by inflation of a neck tourniquet plus systemic hypotension or systemic hypotension alone. RESULTS: Pial arteriolar diameters were (a) dilated by 10(-11) M AVP [7% +/- 11% (P = 0.014 versus baseline)], but constricted by 10(-9) M, 10(-7) M, and 10(-5) M AVP [7% +/- 14%, 20% +/- 14%, and 16% +/- 16% (each P < 0.05), respectively], and (b) constricted before hypotension (7% +/- 10% at 10(-9) M, 20% +/- 15% at 10(-7) M) or ischemia (7% +/- 11% at 10(-9) M, 21% +/- 15% at 10(-7) M). However, after the 5-min of ischemia, the decrease in diameter induced by 10(-7) M AVP was significantly reduced but not by hypotension alone [hypotension control group: 7% +/- 10% at 10(-9) M, 19% +/- 14% at 10(-7) M; ischemia group: 5% +/- 11% at 10(-9) M, 10% +/- 13% at 10(-7) M (P = 0.35 versus hypotension control)]. CONCLUSIONS: Topical application of AVP (except at the lowest concentration used here) induced concentration-dependent vasoconstriction of pial arterioles in anesthetized rabbits. The vasoconstrictor effect of 10(-7) M AVP was reduced after transient (5-min) cerebral ischemia.

The comparative effects of intravenous nicardipine and prostaglandin E1 on the cerebral pial arteriolar constriction seen after unclamping of an aortic cross-clamp in rabbits.

BACKGROUND: The potent vasodilators nicardipine and prostaglandin E1 (PGE1) are useful for the treatment of systemic hypertension or pulmonary hypertension during aortic surgery. METHODS: We measured cerebral pial arteriolar diameters, using a rabbit closed cranial window preparation: before (baseline) and 15 min after the start of an IV infusion (preclamp) (0.9% saline [control group], nicardipine [at 0.1, 1.0, or 10 microg x kg(-1) x min(-1)], or PGE1 [at 0.1 or 1.0 microg x kg(-1) x min(-1)]), just after aortic clamping, 20 min after clamping, and at 0-60 min after unclamping. RESULTS: In the control group, a significant decrease in diameter persisted for at least 60 min after unclamping (maximum [at 60 min], -16% for large [> or =75 microm], and -27% for small [<75 microm] arterioles versus baseline). Although the aortic unclamping-induced vasoconstriction was unaffected under the smallest dose of nicardipine, it was significantly attenuated under larger doses in both large and small arterioles (residual vasoconstriction, -10% and -6% for large and -18% and -10% for small arterioles; at 60 min). The pial arteriolar constriction observed at 5 min or more after unclamping in the control group was not altered by PGE1 in either large or small arterioles. CONCLUSIONS: The larger doses of nicardipine, but neither dose of PGE1, attenuated aortic unclamping-induced sustained cerebral pial arteriolar constriction.

Both milrinone and colforsin daropate attenuate the sustained pial arteriolar constriction seen after unclamping of an abdominal aortic cross-clamp in rabbits.

We previously reported that unclamping of an abdominal aortic cross-clamp causes initial dilation of pial arteries followed by sustained constriction. Both milrinone and colforsin daropate have a vasodilator action, and both have been used in such critical conditions as abdominal aortic aneurysmectomy. We measured cerebral pial arteriolar diameters using a rabbit closed cranial window preparation before (baseline) and 15 min after the start of an IV infusion of 0.9% saline (control group), milrinone, or colforsin daropate (0.05 and 0.5 microg . /kg(-1) . min(-1)) (pre-clamp), just after aortic clamping, 20 min after clamping, and at 0 to 60 min after unclamping. In the control group, a significant decrease in diameter persisted for at least 60 min after unclamping (maximum, -15% for large and -26% for small arterioles versus baseline). These values were significantly smaller after both doses of milrinone and the larger dose of colforsin daropate (-5% and -8%, 10% and 12%, and -2% and -5%, respectively vs baseline, at 60 min). In a second experiment, changes in regional cerebral blood flow and tissue oxygen tension reflected changes in vascular variables. Thus, sustained cerebral pial arteriolar constriction induced by aortic unclamping can be attenuated by IV milrinone or colforsin daropate.

The comparative effects of prostaglandin E1 and nicardipine on cerebral microcirculation in rabbits.

UNLABELLED: We compared the effects of the systemic hypotensive drugs prostaglandin E1 (PGE1) and nicardipine on the cerebral microcirculation and on the cerebrovascular reactivities to hypercapnia and hypoxia. In isoflurane-anesthetized rabbits (n = 48), we measured cerebral pial vessel diameters using a cranial-window preparation: (a) during IV PGE1- or nicardipine-induced mild or moderate hypotension (to 80% or 60% of initial mean arterial blood pressure), (b) after topical administration of these drugs, and (c) during hypercapnia or hypoxia induced during such mild or moderate hypotension. Pial arteriolar diameters were (a) unchanged when hypotension (mild or moderate) was induced by PGE1 but increased when it was induced by nicardipine and (b) increased dose-dependently by topical administration of nicardipine but not PGE1. Only small changes in cerebral venular diameter were observed in these experiments. The pial arteriolar dilator response to hypercapnia was potentiated during hypotension (mild or moderate) when it was induced by PGE1 but decreased when it was induced by nicardipine, whereas the response to hypoxia was maintained during PGE1-induced hypotension but decreased during nicardipine-induced hypotension. In conclusion, as a systemic hypotensive drug, PGE1 does not dilate cerebral arterioles and maintains cerebrovascular reactivities to hypercapnia and hypoxia, whereas nicardipine dilates such vessels and reduces these cerebrovascular reactivities. IMPLICATIONS: When given systemically to produce mild or moderate hypotension, prostaglandin E1 does not induce cerebral vasodilation and maintains cerebrovascular reactivity to hypercapnia and hypoxia, whereas nicardipine dilates cerebral vessels and reduces both reactivities.

Changes in cerebral microcirculation during and after abdominal aortic cross-clamping in rabbits: the role of thromboxane A2 receptor.

UNLABELLED: Little is known about any changes in cerebral hemodynamics, during and after abdominal aortic cross-clamping and unclamping, especially in the cerebral microcirculation. We studied the effects of abdominal aortic cross-clamping and unclamping on cerebral pial vessel diameter in the presence or absence of the thromboxane (Tx)A(2) receptor antagonist using a closed cranial window in 27 rabbits. Although infrarenal aortic cross-clamping did not affect pial vessel diameter, release of a 20-min aortic cross-clamp caused pial arterioles to dilate and then constrict. A significant constriction persisted for at least 60 min (maximum, -17% for large [> or =75 micro m] and -28% for small arterioles [<75 micro m] compared with baseline). Topical administration of a TxA(2) receptor antagonist, seratrodast, at 10(-7) M and 10(-6) M, significantly attenuated the constriction of large and small arterioles (at 60 min, -9% and -13% constriction for 10(-7) M, and -6% and -7% for 10(-6) M). Release of a 20-min aortic cross-clamp induced a sustained pial arteriolar constriction. Because this unclamping-induced vasoconstriction was attenuated by topical administration of seratrodast, it was likely partially mediated via the washout of TxA(2) produced in the ischemic region during the clamp and after cross-clamp release. IMPLICATIONS: Abdominal aortic unclamping after a 20-min clamp caused an initial dilation followed by a sustained constriction of pial arterioles. Seratrodast, a thromboxane A(2) receptor antagonist, attenuated the vasoconstriction suggesting that it is at least partly mediated by thromboxane A(2) washed out from the region rendered ischemic by clamping.