Biomedical subjects

M Spatz

Publications and source records attributed to M Spatz.

At least 55 records · Page 3Linked to original sources

PubMed1994

Effect of nitro-L-arginine on cerebral blood flow and monoamine metabolism during ischemia/reperfusion in the mongolian gerbil.

Inhibition of nitric oxide synthase with nitro-L-arginine (i.p., 40 mg/kg body weight) in contrast to L-arginine (300 mg/kg body weight) delayed the initial recovery of cerebral blood flow (CBF) and altered dopamine (DA) metabolism in brain ischemia/reperfusion of Mongolian gerbils. Similar changes but more severe were observed with pargyline (monoamine oxidase inhibitor). Data suggest nitric oxide involvement in postischemic CBF recovery and modulation of DA metabolism due to nitro-L-arginine-induced CBF reduction.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1994

L-arginine induces dopamine release from the striatum in vivo.

Recent reports indicate that induction of nitric oxide (NO) evokes dopamine (DA) release from the striatum in vitro. In this study, we used L-arginine (L-Arg) to demonstrate the in vivo stimulation of DA release from the striatum of Mongolian gerbils using microdialysis. The content of DA in the striatal extracellular fluid (ECF) increased 7-15-fold in the presence of L-Arg in the perfusate as compared with that of the controls (DA level in drug-free perfusate varied from 0.050 +/- 0.009 to 0.092 +/- 0.023 pmol 10 microliters-1). Simultaneous perfusion of L-Arg with nitro-L-arginine (NLA), an inhibitor of nitric oxide synthase, markedly reduced the L-Arg effect on DA release from the striatum. The NLA-perfused animals contained DA levels significantly lower than those observed in the control striatal dialysate. These findings indicate for the first time that DA release in vivo can be induced by L-Arg, the precursor of NO. The data strongly suggest that NO may modulate striatal DA release.

Amino Acid Oxidoreductases↗

PubMed1994

Agonist-stimulated release of von Willebrand factor and procoagulant factor VIII in rats with and without risk factors for stroke.

Lipopolysaccharide (LPS)-induced (i.v. or i.c.v., 1.8 mg/kg) release of von Willebrand factor (vWF) was examined in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. SHR rats released significantly (P < 0.05) more vWF than WKY rats in response to LPS. LPS also inhibited factor VIII procoagulant activity (FVIII:c) which may indicate an increase in thrombin activity. Cultured cerebrovascular endothelial cells (EC) derived from both SHR and WKY rats, as well as human umbilical vein EC (HUVEC) cultures constitutively released vWF. Treatment with agonists including LPS, thrombin and tumor necrosis factor-alpha (TNF alpha) did not affect the in vitro secretion of vWF by cerebrovascular EC cultures but significantly upregulated vWF release by HUVEC cultures. Preincubation of cerebrovascular EC cultures with interleukin-1 (IL-1) +/- TNF alpha or co-culturing in the presence of LPS-activated syngeneic monocytes had no effect on vWF secretion. The findings demonstrate that conditions of hypertension may affect endothelial cells and make them more responsive to agonist stimulation and thereby increase secretion of vWF, an important factor in hemostasis as well as thrombosis. The capacity of LPS to significantly affect the in vivo secretion of vWF in SHR and WKY rats but not cultured cerebrovascular EC indicates that observed elevations in plasma vWF were not derived from cerebrovascular EC. It is suggested that hypertension may function as a risk factor for thrombotic stroke by influencing factors involved in coagulation processes, such as vWF and factor VIII:c.

Animals↗

PubMed1994

Arachidonic acid release and permeability changes induced by endothelins in human cerebromicrovascular endothelium.

The vasoactive peptide endothelin-1 (ET-1) dose-dependently increased release of 51Cr from human cerebromicrovascular endothelial cells (HBEC), without affecting cell viability as assessed by lactate dehydrogenase release. ET-1 also induced transient accumulation of inositol triphosphate (IP3) and release of [3H] arachidonic acid (AA) from HBEC. The ET-1-induced 51Cr release, formation of IP3, and AA release from HBEC were competitively inhibited by selective ETA subtype receptor antagonist BQ-123. ET-1-stimulated 51Cr- and AA release from HBEC were potentiated by proteinkinase C (PKC) activator phorbol-myristate ester, and abolished by H7, an inhibitor of PKC. Dexamethasone, indomethacin, acetylsalicylic acid, imidazole, as well as the inhibitor of protein kinase A, H8, had no effect on 51Cr release. The results suggest that ETA-receptor mediated activation of PKC and increase in the HBEC 'permeability' for low molecular weight molecules in response to excessive release of endothelins from either HBEC or surrounding tissues during pathologic conditions may contribute to the formation of cerebral edema.

Arachidonic Acid↗

PubMed1994

The relationship between cerebral ischemic edema and monoamines: revisited.

The association of changes in the metabolic pathway of monoamines (dopamine and 5-hydroxytryptamine) with mitochondrial enzymatic systems which are involved in the production and removal of free radicals formed during dopamine metabolism and formation of edema was investigated in bilateral brain ischemia in gerbils. The results suggest that the involvement of DA-derived free radicals in brain edema is unlikely in early reflow, because disbalance between H2O2-producing reactions of DA-metabolism, and mitochondrial antioxidative capacity does not occur prior to 1 hour reflow after 15 min bilateral ischemia in gerbils. However, the findings of this study reinforce the participation of 5-HT in the formation of ischemic brain edema.

Animals↗

PubMed1994

'Therapeutic window's for multiple drug treatment of experimental cerebral ischemia in gerbils.

The effects of the following drugs: nimodipine (1 mg/kg b.w., i.p.), 2-amino-5-phosphonovaleric acid (4 mg/kg b.w., i.p.) and propentofylline (25 mg/kg b.w., i.p.), administered (alone or in combination) at the end of 15 min bilateral ischemia in gerbils were evaluated on mitochondrial superoxide dismutase (SOD), glutathione reductase (GR), glucose-6 phosphate dehydrogenase (G6PD), monoamine oxidase (MAO) activities, and thiobarbituric acid reactive material (TBARM), and brain water content at 1 hour of reperfusion. The combined treatment virtually abolished early postischemic brain edema (4.1% v.s. 0.6%) and efficiently counteracted ischemia-induced changes [decreased SOD (79% v.s. 98%), GR (52% v.s. 105%) and MAO (25% v.s. 79%), and increased TBARM (198% v.s. 108%)]. The same combination of drugs administered 15 min before ischemia had a similar effect (e.g., reduced brain swelling and lipid peroxidation) as when given at the end of ischemia, whereas a limited or absent impact was seen when the drugs were given 15 min or 1 hour after ischemia, respectively. The data suggest that (post)ischemic brain swelling and mitochondrial dysfunction can be reduced by drugs which synchronously prevent processes induced in the early stages of reperfusion.

2-Amino-5-phosphonovalerate↗

PubMed1994

Liposome-entrapped superoxide dismutase reduces ischemia/reperfusion 'oxidative stress' in gerbil brain.

Bilateral common carotid artery occlusion (15 min.) followed by two hours of recirculation reduced mitochondrial superoxide dismutase (SOD) and glutathione reductase (GR) activities, and increased susceptibility of mitochondrial membranes to in vitro lipid peroxidation in brain regions (i.e., cortex, striatum and hippocampus) of Mongolian gerbil. Intraperitoneal bolus injection (2 mg/kg b.w.) of liposome-entrapped CuZn superoxide dismutase (1-SOD) increased the endogenous SOD activity in normal brain tissue and, when given at the end of ischemia, counteracted both the ischemic reduction of endogenous SOD and the increased peroxidation of mitochondrial membranes. 1-SOD treatment was ineffective in reducing brain swelling, suggesting that superoxide radicals are not a main participant in the process of (post)ischemic brain edema formation.

Animals↗

PubMed1994

Interaction between histamine and adenosine in human cerebromicrovascular endothelial cells: modulation of second messengers.

This study demonstrates the presence of histamine H1 and H2 receptors and purinoreceptors A1 and A2 on endothelial cells derived from human brain microvessels (HBEC). Histamine induced formation of both inositol triphosphate (IP3) (EC50 = 10.2 +/- 0.9 microM) and cyclic adenosine monophosphate (cAMP) (EC50 = 5.2 +/- 0.9 microM) in HBEC in a concentration-dependent fashion. IP3 formation was inhibited by H1 receptor antagonists mepyramine maleate and chlorphenyramine, but not by H2 receptor antagonist cimetidine. Production of cAMP was efficiently inhibited by cimetidine. Selective A1 receptor agonists decreased, whereas A2 receptor agonists increased cAMP production in HBEC. When added together with histamine to HBEC cultures, both A1 and A2 receptor agonists diminished histamine-induced IP3 stimulation. This effect was reversed in the presence of specific A1 and A2 receptor antagonists, respectively. Marked augmentation of histamine-induced cAMP production by HBEC was observed in the presence of A2 agonist. This response was dependent on H1 receptors, since it was reduced in the presence of H1-receptor antagonist. It is suggested that interaction between histamine and adenosine modulating induction of second messengers in HBEC may influence endothelium-dependent responses of brain microvascular compartments.

Adenosine↗

PubMed1994

Dexamethasone down-regulates endothelin receptors in human cerebromicrovascular endothelial cells.

Human cerebromicrovascular endothelial cells (HBEC) in culture express high affinity ETA receptors coupled to phospholipase C activation. Pretreatment of HBEC with 1 microM dexamethasone for 24 h decreased the number of the ET-1 binding sites (Bmax) on HBEC (96 fmol/mg protein vs 57 fmol/mg protein) without changing the binding affinity (KD) (101 pM vs 92 pM) or displacing profile (ET-1 = ET-2 > ET-3 > S6c). Dexamethasone-pretreated HBEC also exhibited a 40% reduction in the maximal ET-1-stimulated inositol triphosphate (IP3) production, whereas half-maximal stimulatory concentration (EC50) was not affected. This effect of dexamethasone was concentration-dependent, and most pronounced after 24 h of pretreatment. The inhibitory effect of dexamethasone on the ET-1-induced IP3 production was abolished by glucocorticoid-receptor antagonist cortexolone. In contrast, vasopressin-mediated IP3 response in HBEC was not changed by dexamethasone. Cyclo-oxygenase inhibitors indomethacin and acetylsalicylic acid did not influence the ET-1-induced IP3 production by HBEC. The down-regulation of ETA receptors in HBEC by dexamethasone, may represent one of the mechanisms involving the described effects of glucocorticoids on cerebromicrovascular function (i.e. changes in blood brain barrier properties, secretion of vasoactive factors, vascular morphogenesis).

Capillaries↗

PubMed1994

Vasoactive peptides and prostaglandin D2 in human cerebromicrovascular endothelium.

Prostaglandin D2 (PGD2) is the major prostanoid formed among other prostanoids in cultured microvascular endothelium derived from human brain (HBEC). Angiotensin II, arginine vasopressin and endothelium-1 stimulated the production of PGD2 and PGF2 alpha in a concentration-dependent manner, and this effect was inhibited by their specific receptor antagonists or dexamethasone (inhibitor of phospholipase A2/cyclooxygenase II). Both the peptidergic-induced PGD2 and the exogenously added PGD2 were converted in HBEC to 9 alpha, 11 beta-PGF2, a potent vasoconstrictor. Exogenous PGD2 also dose-dependently enhanced the production of vasoconstrictive PGF2 alpha, thromboxane B2, vasodilatory prostaglandin PGE2, and cAMP in these cells. The PGD2 stimulated formation of the prostanoids was inhibited by acetylsalicylic acid or indomethacin (inhibitors of cyclooxygenase I) but not dexamethasone, demonstrating for the first time that PGD2 may contribute to the production of prostanoids in HBEC. These findings strongly suggest that PGD2 may play a pivotal role in the regulation of cerebromicrovascular function.

Capillaries↗

PubMed1994

Characterization of a murine central nervous system-derived cell line: infectability and presentation of viral antigen.

The cerebral endothelial cell line, 33-Mse, was characterized for its MHC antigen expression, infectability with viruses and capacity to present antigen to immune spleen cells. The cell line had interferon-gamma inducible MHC antigen expression. Infection by Theiler's murine encephalomyelitis influenced the expression of MHC molecules on the cell surface of this line. These cells could not stimulate T splenocyte proliferation or act as targets for Theiler's murine encephalomyelitis cytolytic immune spleen cells. These cells were able to present viral antigen to vaccinia virus immune spleen cells and act as targets for cytotoxic T cells from vaccinia virus immune mice.

Animals↗

PubMed1994

Quantitation of perivascular monocytes and macrophages around cerebral blood vessels of hypertensive and aged rats.

The numbers of monocytes and macrophages in the walls of cerebral blood vessels were counted on perfusion-fixed frozen brain sections (16 microns) of spontaneously hypertensive rats (SHR), stroke-prone SHR (SHR-SP), normotensive Wistar-Kyoto (WKY) rats, and young (16-week-old) and old (2-year-old) normotensive Sprague-Dawley rats (SD-16w and SD-2y, respectively) using monoclonal antibodies against rat macrophages (ED2). The staining was visualized with fluorescein-labeled second antibodies. The ED2-specific staining in brain sections was restricted to macrophages in a perivascular location. The number of perivascular cells per square millimeter of high-power field was significantly greater in SHR-SP (8.6 +/- 2.1; n = 4) and SHR (6.7 +/- 0.9; n = 6) than in normotensive WKY (4.0 +/- 0.5; n = 6; p < 0.01). The number of perivascular macrophages was also greater in SD-2y (7.5 +/- 2.7; n = 9) than in SD-16w (2.9 +/- 1.8; n = 8; p < 0.01). No ED2 staining was found in the resident microglia or in the endothelial cells, which were identified by double staining with rhodamine-labeled anti-factor VIII-related antigen antibodies. The results suggest that the stroke risk factors hypertension and advanced age are associated with increased subendothelial accumulation of monocytes and macrophages. This accumulation could increase the tendency for the endothelium to convert from an anticoagulant to a procoagulant surface in response to mediators released from these subendothelial cells.

Aging↗

PubMed1994

Endothelin-1 receptor binding and cellular signal transduction in cultured human brain endothelial cells.

The kinetic properties of endothelin-1 (ET-1) binding sites and the production of inositol phosphates (IPs; IP1, IP2, IP3), cyclic AMP, thromboxane B2, and prostaglandin F2 alpha induced by various endothelins (ET-1, ET-2, ET-3, and sarafotoxin S6b) were examined in endothelial cells derived from human brain microvessels (HBECs). The presence of both high- and low-affinity binding sites for ET-1 with KD1 = 122 pM and KD2 = 31 nM, and Bmax1 = 124 fmol/mg of protein and Bmax2 = 909 fmol/mg of protein, respectively, was demonstrated on intact HBECs. ET-1 dose-dependently stimulated IP accumulation with EC50 (IP3) = 0.79 nM, whereas ET-3 was ineffective. The order of potency for displacing ET-1 from high-affinity binding sites (ET-1 > ET-2 > sarafotoxin S6b > ET-3) correlated exponentially with the ability of respective ligands to induce IP3 formation. ET-1-induced IP3 formation by HBEC was inhibited by the ETA receptor antagonist, BQ123. The protein kinase C activator phorbol myristate ester dose-dependently inhibited the ET-1-stimulated production of IPs, whereas pertussis toxin was ineffective. Cyclic AMP production by HBECs was enhanced by both phorbol myristate ester and ET-1, and potentiated by combined treatment with ET-1 and phorbol myristate ester. Data indicate that protein kinase C plays a role in regulating the ET-1-induced activation of phospholipase C, whereas interaction of different messenger systems may regulate ET-1-induced accumulation of cyclic AMP. ET-1 also stimulated endothelial prostaglandin F2 alpha production, suggesting that activation of phospholipase A2 is most likely secondary to IP3-mediated intracellular calcium mobilization because both ET-1-induced IP3 and prostaglandin F2 alpha were inhibited by BQ123. These findings are the first demonstration of ET-1 (ETA-type) receptors linked to phospholipase C and phospholipase A2 activation in HBECs.

Brain↗

PubMed1994

Vasoconstrictive peptides induce endothelin-1 and prostanoids in human cerebromicrovascular endothelium.

Vasoconstrictive peptides and prostanoids have been implicated in the pathogenesis of hypertension and vasospasm. Recently, we have shown that human cerebromicrovascular endothelium [human brain endothelial cells (HBEC)] constitutively produces both endothelin-1 (ET-1) and prostanoids. The vasoactive peptides, arginine vasopressin (AVP) or angiotensin II (ANG II), stimulated secretion of both immunoreactive ET-1 and prostanoids from HBEC by a receptor-mediated induction of phospholipase C (PLC) and PLA2. The release of constitutive or AVP- or ANG II-induced ET-1 occurred at different rates during the 24-h incubation of HBEC in serum-free medium. The temporal profile of AVP-stimulated production of prostanoids differed from that of ANG II. AVP-induced release of prostaglandin D2 (PGD2) persisted for 24 h, whereas ANG II-stimulated PGD2 was only seen during the first 4 h of incubation. ANG II maximally stimulated PGI2 secretion during the 4- to 8-h interval, whereas AVP did not stimulate PGI2 secretion. Dexamethasone (Dxm), indomethacin (Indo), and nordihydroguaiaretic acid, the respective inhibitors of PLA2-cyclooxygenase II, cyclooxygenase, and lipoxygenase, increased both constitutive and AVP- or ANG II-stimulated secretion of ET-1. Dxm also decreased AVP- or ANG II-stimulated production of PGD2 and PGF2 alpha. These results indicate an interrelationship between HBEC production of ET-1 and prostanoids, which may play a role in regulating cerebral microcirculation.

Angiotensin II↗

PubMed1994

Monocyte adhesion to cerebromicrovascular endothelial cells derived from hypertensive and normotensive rats.

The stroke risk factor hypertension may function as a predisposing agent by increasing the vulnerability of blood vessels to thrombosis or hemorrhage. The research here demonstrates that cerebrovascular endothelial cells (EC) from spontaneously hypertensive (SHR) and Wistar-Kyoto normotensive (WKY) rats exhibit similar levels of adhesiveness for syngeneic peripheral blood monocytes (e.g., 22.53 +/- 1.32 and 24.35 +/- 1.16%, respectively). Monocyte adhesion to SHR EC was dramatically increased by treatment of EC with lipopolysaccharide, interferon-gamma, or interleukin-1 beta and tumor necrosis factor-alpha (e.g., 106, 68, and 171%, respectively). Identical treatment of WKY EC also increased adhesion albeit at significantly lower levels than observed on concomitantly tested SHR EC (e.g., 47.8, 12.7, and 60.7%, respectively). Allogeneic combinations of monocytes and EC again demonstrated significantly more upregulation of adhesion by treatment of SHR EC than WKY EC. Characterization of these adhesive interactions revealed the interplay of adhesion pathways, which include lymphocyte functional antigen-1/intercellular adhesion molecule-1 (ICAM-1), Mac-1/ICAM-1, and very late activation antigen-4/vascular adhesion molecule-1 as well as other undetermined mechanisms. In summary, these findings indicate hypertension may enhance responsiveness of endothelium to factors that promote monocyte adhesion.

Animals↗

PubMed1994

Adhesion molecules on normotensive and hypertensive rat brain endothelial cells.

The intercellular adhesion of circulating leukocytes to vascular endothelium is a prerequisite for leukocyte emigration from the blood to extravascular tissues. This process is facilitated by adhesion molecules on the surfaces of both the vascular endothelial cells and the leukocytes. The experiments presented here demonstrate for the first time that the leukocyte adhesion receptor, intercellular adhesion molecule-1, is constitutively expressed on cultured cerebromicrovascular endothelial cell lines derived from both spontaneously hypertensive (SHR) rats and normotensive Wistar-Kyoto (WKY) rats. Both cultures contained similar numbers of cells constitutively expressing this adhesion molecule (31.4% and 29.6%, respectively). Adhesion molecule expression was up-regulated by interleukin-1 beta, tumor necrosis factor-alpha, interferon-gamma and lipopolysaccharide in a dose- and time-dependent manner. Both cultures exhibited similar maximum levels of adhesion molecule up-regulation to optimal concentrations of all three cytokines. However, SHR endothelial cells were more sensitive to all three cytokines; significantly higher levels of intercellular adhesion molecule-1 expression were seen on SHR as opposed to WKY endothelial cells cultured with sub-optimal cytokine concentrations. It was also observed that lipopolysaccharide up-regulated intercellular adhesion molecule-1 expression on SHR endothelial cells to a greater extent than on WKY endothelial cells. The findings that intercellular adhesion molecule-1 can be up-regulated to a greater degree on SHR endothelial cells may have important implications for in vivo perivascular leukocyte accumulation under hypertensive conditions. These observations indicate a possible mechanism by which hypertension may predispose to the development of disorders such as atherosclerosis and stroke.

Animals↗

PubMed1993

Endothelin induction of adhesion molecule expression on human brain microvascular endothelial cells.

The adhesion of circulating leukocytes to vascular endothelium is a prerequisite for their emigration to extravascular tissues. The experiments presented here demonstrate that intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are constitutively expressed on cerebromicrovascular endothelial cell lines derived from human brain and that the expression of these molecules can be up-regulated by endothelins (ET-1, ET-2, and ET-3) in a dose- and time-dependent manner. The data also indicate that ET-1 treatment induced the expression of E-selectin on these cells. These findings implicate vasoactive peptides in the recruitment of blood cells at sites of inflammation.

Cell Adhesion Molecules↗

PubMed1993

Endothelins release 51Cr from cultured human cerebromicrovascular endothelium.

The effects of vasoactive peptides endothelins (ET-1, ET-2, ET-3, S6b, S6c) on release of 51Cr, production of inositol triphosphate (IP3), and release of arachidonic acid (AA) were examined in cultured microvascular endothelium derived from human brain (HBEC). ET-1 induced dose-dependent release of 51CR (EC50 = 7 +/- 2 nM), transient increase of IP3 (EC50 = 0.67 +/- 0.09 nM), and sustained release of AA (EC50= 59 +/- 7 nM) from HBEC. Under the same experimental conditions, viability of the cells was preserved (> 97%) as assessed by exclusion of vital dye trypan blue and release of lactate dehydrogenase (LDH). Dexamethasone (1 microM) inhibited ET-1-induced AA release, whereas it was ineffective on 51Cr release. Protein kinase C (PKC) inhibitor H7 (200 nM), calcium channel blocker verapamil (10 microM), or IP3 receptor antagonist ryonidine (5 microM) reduced ET-1 (100 nM)-induced release of 51Cr. These findings indicate that endothelins can induce an increase of HBEC permeability by a receptor-specific activation of PKC and intracellular calcium mobilization.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗