Search

Hydrogen sulfide ([H.sub.2]S) is one of three endogenous gases, along with carbon monoxide (CO) and nitric oxide (NO), that exert a variety of important vascular actions in vivo. Although it has been demonstrated that CO or NO can trigger the development of a preconditioned phenotype in postischemic tissues, it is unclear whether [H.sub.2]S may also induce protection in organs subsequently exposed to ischemia-reperfusion (I/R). In light of these observations, we postulated that preconditioning with the exogenous [H.sub.2]S donor sodium hydrosulfide (NaHS-PC) would inhibit leukocyte rolling (LR) and adhesion (LA) induced by I/R. We used intravital microscopic techniques to demonstrate that NaHS-PC 24 h, but not 1 h, before I/R causes postcapillary venules to shift to an anti-inflammatory phenotype in wild-type (WT) mice such that these vessels fail to support LR and LA during reperfusion. The protective effect of NaHS-PC on LR was largely abolished by coincident pharmacological inhibition of NO synthase (NOS) in WT animals and was absent in endothelial NOS-deficient ([eNOS.sup.-/-]) mice. A similar pattern of response was noted in WT mice treated concomitantly with NaHS plus p38 mitogen-activated protein kinase (MAPK) inhibitors (SB 203580 or SK-86002). Whereas the reduction in LA induced by antecedent NaHS was attenuated by pharmacological inhibition of NOS or p38 MAPK in WT mice, the antiadhesive effect of NaHS was still evident in [eNOS.sup.-/-] mice. Thus NaHS-PC prevents LR and LA by triggering the activation of an eNOS- and p38 MAPK-dependent mechanism. However, the role of eNOS in the antiadhesive effect of NaHS-PC was less prominent than its effect to reduce LR. ischemia; reperfusion; sodium hydrosulfide; endothelial nitric oxide synthase-deficient mice; leukocyte rolling; leukocyte adhesion

Vascular inflammation and enhanced production of angiotensin II (ANG II) are involved in the pathogenesis of hypertension and diabetes, disease states that predispose the afflicted individuals to ischemic disorders. In light of these observations, we postulated that ANG II may play a role in promoting leukocyte rolling (LR) and adhesion (LA) in postcapillary venules after exposure of the small intestine to ischemia-reperfusion (I/R). Using an intravital microscopic approach in C57BL/6J mice, we showed that ANG II type I (A[T.sub.1]) or type II (A[T.sub.2]) receptor antagonism (with valsartan or PD-123319, respectively), inhibition of angiotensin-converting enzyme (ACE) with captopril, or calcitonin generelated peptide (CGRP) receptor blockade (CGRP8-37) prevented postischemic LR but did not influence I/R-induced LA. However, both postischemic LR and LA were largely abolished by concomitant A[T.sub.1] and A[T.sub.2] receptor blockade or chymase inhibition (with Y-40079). Additionally, exogenously administered ANG II increased LR and LA, effects that were attenuated by pretreatment with a CGRP receptor antagonist or an NADPH oxidase inhibitor (apocynin). Our work suggests that ANG II, formed by the enzymatic activity of ACE and chymase, plays an important role in inducing postischemic LR and LA, effects that involve the engagement of both A[T.sub.1] and A[T.sub.2] receptors and may be mediated by CGRP and NADPH oxidase. ischemia; reperfusion; leukocyte rolling; leukocyte adhesion; angiotensin-converting enzyme; chymase; angiotensin A[T.sub.1] and A[T.sub.2] receptors; NADPH oxidase doi:10.1152/ajpheart.01210.2006.

Ingestion of low levels of ethanol 24 h before [ethanol preconditioning (EPC)] ischemia and reperfusion (I/R) prevents postischemic leukocyte rolling (LR) and adhesion (LA), effects that were abolished by adenosine [A.sub.2] receptor (ADO-[A.sub.2]R) antagonists or nitric oxide (NO) synthase (NOS) inhibitors. The aims of this study were to determine whether NO derived from endothelial NOS (eNOS) during the period of ethanol exposure triggered entrance into this preconditioned state and whether these events were initiated by an ADO-[A.sub.2]R-dependent mechanism. Ethanol or distilled water vehicle was administered to C57BL/6J [wild type (WT)] or eNOS-deficient (eNOS-/-) mice by garage. Twenty-four hours later, the superior mesenteric artery was occluded for 45 min. LR and LA were quantified by intravital microscopy after 30 and 60 min of reperfusion. I/R increased LR and LA in WT mice, effects that were abolished by EPC or NO donor preconditioning (NO-PC). NO-PC was not attenuated by coincident administration of an ADO-[A.sub.2]R antagonist. I/R increased LR and LA in eNOS-/- mice to levels comparable with those noted in WT animals. However, EPC only slightly attenuated postischemic LR and LA, whereas NO-PC remained effective as a preconditioning stimulus in eNOS-/- mice. Preconditioning with an ADO-[A.sub.2]R agonist (which we previously demonstrated prevents I/R-induced LR and LA in WT animals) failed to attenuate these postischemic adhesive responses in eNOS-/mice. Our results indicate that EPC is triggered by NO formed secondary to ADO-[A.sub.2]R-dependent eNOS activation during the period of ethanol exposure 24 h before I/R. ischemia; reperfusion; adenosine; nitric oxide; leukocyte rolling; endothelial nitric oxide synthase knockout mice

Preconditioning (PC) with nitric oxide (NO) donors or agents that increase endothelial NO synthase (eNOS) activity 24 h before ischemia-reperfusion (I/R) prevents postischemic leukocyte rolling (LR) and stationary leukocyte adhesion (LA). Since 5'-AMP-activated protein kinase (AMPK) phosphorylates eNOS at Ser1177, resulting in activation, we postulated that AMPK activation may trigger the development of a preconditioned anti-inflammatory phenotype similar to that induced by NO donors. Wild-type (WT) C57BL/6J and [eNOS.sup.-/-] mice were treated with the AMPK agonist 5-aminoimidazole-4-carboxamide 1-[beta]-D-furanoside (AICAR) 30 rain (early AICAR PC) or 24 h (late AICAR PC) before I/R; LR and LA were quantified in single postcapillary venules in the jejunum using intravital microscopy. I/R induced comparable marked increases in LR and LA in WT and [eNOS.sup.-/-] mice relative to sham-operated (no ischemia) animals. Late AICAR PC prevented postischemic LR and LA, whereas early AICAR PC prevented LA in WT mice. Late AICAR PC was ineffective in preventing I/R-induced LR but not LA in the [eNOS.sup.-/-] mice, and the same pattern was seen in WT animals treated with the NOS inhibitor [N.sup.[omega]-nitro-L-arginine. Early AICAR PC remained effective in preventing LA in [eNOS.sup.-/-] mice. Our results indicate that both early and late PC with an AMPK agonist produces an anti-inflammatory phenotype in postcapillary venules. Since the protection afforded by late AICAR PC on postischemic LR was prevented by NOS inhibition in WT mice and absent in eNOS-deficient mice, it appears that eNOS triggers this protective effect. In stark contrast, antecedent AMPK activation prevented I/R-induced LA by an eNOS-independent mechanism. ischemia; reperfusion; leukocyte rolling and adhesion; endothelial nitric oxide synthase-deficient mice

The aim of this study was to determine the role of calcitonin gene-related peptide (CGRP) in the postischemic anti-inflammatory effects of antecedent ethanol ingestion. Ethanol was administered to wild-type C57BL/6 mice on day 1 as a bolus by gavage at a dose that produces a peak plasma ethanol of 45 mg/dl 30 min after administration. Twenty-four hours later (day 2), the superior mesenteric artery was occluded for 45 min followed by 70 min of reperfusion (I/R). Intravital fluorescence microscopy was used to quantify the numbers of rolling (LR) and adherent (LA) leukocytes labeled with carboxyfluorescein diacetate succinimidyl ester in postcapillary venules of the small intestine. I/R increased LR and LA, effects that were prevented by antecedent ethanol. The postischemic anti-inflammatory effects of ethanol consumption were abolished by administration of a specific CGRP receptor antagonist [CGRP-(8-37)] or after sensory nerve neurotransmitter depletion using capsaicin administered 4 days before ethanol ingestion, which initially induces rapid release of CGRP from sensory nerves, thereby depleting stored neuropeptide. Administration of exogenous CGRP or induction of endogenous CGRP release by treatment with capsaicin 24 h before I/R mimicked the postischemic anti-inflammatory effects of antecedent ethanol ingestion. Preconditioning with capsaicin 24 h before I/R was prevented by coincident treatment with CGRP-(8-37), while exogenous CGRP induced an anti-inflammatory phenotype in mice depleted of CGRP by capsaicin administration 4 days earlier. Our results indicate that the effect of antecedent ethanol ingestion to prevent postischemic LR and LA is initiated by a CGRP-dependent mechanism. ischemia; reperfusion; leukocyte rolling; leukocyte adhesion; capsaicin

We previously demonstrated that preconditioning induced by ethanol consumption at low levels [ethanol preconditioning (EPC)] or with 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR-PC) 24 h before ischemia-reperfusion prevents postischemic leukocyte-endothelial cell adhesive interactions (LEI) by a mechanism that is initiated by nitric oxide formed by endothelial nitric oxide synthase. Recent work indicates that 1) ethanol increases the activity of AMP-activated protein kinase (AMPK) and 2) AMPK phosphorylates endothelial nitric oxide synthase at the same activation site seen following EPC (Ser1177). In light of these observations, we postulated that the heterotrimeric serine/threonine kinase, AMPK, may play a role in triggering the development of the anti-inflammatory phenotype induced by EPC. Ethanol was administered to C57BL/6J mice by gavage in the presence or absence of AMPK inhibition. Twenty-four hours later, the numbers of rolling and adherent leukocytes in postcapillary venules of the small intestine were recorded using an intravital microscopic approach. Following 45 min of ischemia, LEI were recorded after 30 and 60 min of reperfusion or at equivalent time points in control animals. Ischemia-reperfusion induced a marked increase in LEI relative to sham-operated control mice. The increase in LEI was prevented by EPC, an effect that was lost with AMPK inhibition during the period of ethanol exposure. Studies conducted in AMPK α1- and α2-knockout mice suggest that the anti-inflammatory effects of AICAR are not dependent on which isoform of the catalytic α-subunit is present because a deficiency of either isoform results in a loss of protection. In sharp contrast, EPC appears to be triggered by an AMPK α2-isoform-dependent mechanism. [ABSTRACT FROM AUTHOR]

Objective: We previously demonstrated that pharmacologic activation of AMP-activated protein kinase (AMPK) with 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) 24 hours prior to (AICAR preconditioning; AICAR-PC) ischemia/reperfusion (I/R) prevents postischemic leukocyte-endothelial cell adhesive interactions (LEI) by a mechanism initiated by endothelial nitric oxide synthase (eNOS)-dependent NO production during the period of AICAR-PC. The major aim of this study was to examine the role of ATP-sensitive potassium (KATP) channels and heme oxygenase as mediators of the antiadhesive effects of AICAR-PC during I/R 24 hours later. Methods: Intravital fluorescence microscopy was used to quantify LEI in the small intestine of AICAR-preconditioned C57BL/6J mice treated with KATP channel or heme oxygenase inhibitors during I/R 24 hours after AICAR-PC in separate experiments. Results: I/R induced marked increases in LEI relative to sham control mice, proadhesive responses that were prevented by AICAR-PC 24 hours prior to I/R. The effects of AICAR-PC to prevent postischemic LEI were abolished by KATP channel or heme oxygenase inhibition during I/R. Discussion/Conclusion: Our results indicate that the antiadhesive effects of AICAR-PC are mediated by KATP channel- and heme oxygenase-dependent mechanisms during I/R. [ABSTRACT FROM AUTHOR]

Ghrelin is a newly discovered gastric peptide, which has orexigenic effects. Ghrelin is the endogenous ligand for the growth hormone secretagogue receptor and stimulates growth hormone and gastrointestinal motility. We have previously shown that nitric oxide (NO) plays an important role as a mediator of feeding induced by a variety of neuropeptides. This raises the question of whether ghrelin’s effects are NO dependent. Here, we first determined that intracerebroventricular administration of 100 ng of ghrelin significantly increased food intake in satiated mice. We next examined the effects of Nω-nitro-l-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, on ghrelin-induced increase in food intake. A subthreshold dose (12.5 mg/kg; SC) of L-NAME significantly blocked the ghrelin-induced increase in food intake. Ghrelin administration increased the levels of nitric oxide synthase in the hypothalamus. This supports the hypothesis that nitric oxide is a central regulator of food consumption. [Copyright &y& Elsevier]

Vascular inflammation and enhanced production of angiotensin II (Ang II) are involved in the pathogenesis of hypertension and diabetes, disease states that predispose the afflicted individuals to ischemic disorders. Therefore, we postulated that Ang II may play a role promoting leukocyte rolling (LR) and adhesion (LA) in postcapillary venules after exposure of the small intestine to ischemia/reperfusion (I/R). Using an intravital microscopic approach in C57BL/6J mice, we show that Ang II AT1 or AT2 receptor antagonism (with valsartan or PD123,319, respectively), inhibition of ACE (captopril), or CGRP receptor blockade (CGRP8-37) prevents postischemic LR but does not influence I/R-induced LA. However, both postischemic LR and LA are greatly abolished by concomitant AT1 and AT2 receptor blockade or chymase inhibition (with Y-40079). Additionally, exogenously administered Ang II increases LR and LA, effects that are attenuated by pretreatment with a CGRP8-37 or apocynin, a NADPH oxidase inhibitor. Our work suggests that Ang II plays an important role in inducing LR and LA, through the engagement of both AT1 and AT2 receptors and may be mediated by CGRP and NADPH oxidase. [ABSTRACT FROM AUTHOR]

Amyloid beta protein (Aβ) is the primary constituent of plaque seen in Alzheimer''s disease. Aβ is proposed to play an etiological role in Alzheimer''s disease and to be a cause of the decrease in the level of acetylcholine in the hippocampus. The SAMP8 strain of mouse develops age-related increases in Aβ and deficits in learning and memory by 12 months of age. We examined in 12 month old SAMP8 mice the effects of giving antibody to Aβ by septal or intracerebroventricular (ICV) injection on acetylcholine levels in the hippocampus. Antibody to Aβ increased acetylcholine in the hippocampus over 100% after ICV injection and over 200% after septal injection. Injection of rabbit serum, antibody directed towards mouse IgG, or a blocking antibody directed towards human interleukin-1β were without effect. These results suggest that antagonism of Aβ increases acetylcholine concentrations in the hippocampus, an area important for learning and memory. [Copyright &y& Elsevier]