Andreas Ragoschke

Endothelin-1 in Subarachnoid Hemorrhage An Acute-Phase Reactant Produced by Cerebrospinal Fluid Leukocytes

Background and Purpose The most potent vasoconstrictor known, endothelin-1, is currently considered to mediate cerebral vasospasm in subarachnoid hemorrhage (SAH), which can cause delayed cerebral ischemia. In our study, we performed clinical and in vitro experiments to investigate the origin and the mechanisms of the secretion of endothelin-1 in SAH. Methods Endothelin-1 and markers of inflammatory host response (interleukin [IL]-1&bgr;, IL-6, and tumor necrosis factor-&agr;) were comparatively quantified in the cerebrospinal fluid (CSF) of SAH patients and control subjects, and concentrations were related to clinical characteristics. Furthermore, mononuclear leukocytes isolated from the CSF of SAH patients and control subjects were analyzed regarding their mRNA expression of endothelin-1 and inflammatory cytokines. Finally, complementary in vitro experiments were performed to investigate whether coincubation of blood and CSF can trigger leukocytic mRNA expression and release of these factors. Results Activated mononuclear leukocytes in the CSF of SAH patients synthesize and release endothelin-1 in parallel with known acute-phase reactants (IL-1&bgr;, IL-6, and tumor necrosis factor-&agr;). Complementary in vitro experiments not only further confirmed this leukocytic origin of endothelin-1 but also showed that aging and subsequent hemolysis of blood is sufficient to induce such endothelin-1 production. Conclusions The demonstration that endothelin-1 is produced by activated CSF mononuclear leukocytes suggests that subarachnoid inflammation may represent a therapeutic target to prevent vasospasm and delayed cerebral ischemia after SAH.

Effects of statins on human cerebral cholesterol metabolism and secretion of Alzheimer amyloid peptide

Cerebral cholesterol metabolism has been linked with production of amyloid peptide (A&bgr;) crucial in AD. The association between use of cholesterol-lowering drugs (statins) and AD disease is currently being intensely discussed. In this case-control study on elderly nondemented subjects, the authors provide the first evidence that statins in clinically relevant dosages indeed affect cerebral cholesterol metabolism. However, these changes were not associated with altered intrathecal secretion of Alzheimer A&bgr;.

Temporal profile of release of interleukin-1β in neurotrauma

Timing and extent of trauma-induced release of interleukin-1beta (IL-1beta) in extracellular fluid of the CNS were analyzed. In brain tissue perfusates obtained by in vivo microdialysis a marked release of IL-1beta was unexpectedly detected within less than 60 min. At such an early stage of neurotrauma, mRNA expression of IL-1beta was detected whereas immunoreactivity for the IL-1beta protein was negative. Concentrations of extracellularly secreted IL-1beta protein gradually increased, peaked at day 2 and decreased thereafter. Drugs acting on mononuclear phagocytes significantly modulated IL-1beta secretion. This so far unrecognized acuity of IL-1beta release demonstrated here, may represent a precondition for the orchestrating role of this mediator in the cascade of inflammatory host response.

Increased release of interleukin-12p40 in MS Association with intracerebral inflammation

Objective: The p40 subunit of interleukin (IL)-12 was recently demonstrated in active lesions in MS. We tested whether the p40 subunit of IL-12 can also be detected in CSF and serum of patients with this disease and, if so, whether release is associated with inflammatory disease activity. Results: This study demonstrates an increased (up to 1,000-fold) compartmentalized release of the p40 subunit but not of the heterodimer p70 in MS. Release of IL-12p40 correlated with classic markers of CNS inflammation (CSF cell counts, immunoglobulin G index) and was significantly increased in patients with gadolinium-enhancing plaques on MRI. Moreover, release of IL-12p40 was associated with CSF levels of myelin basic protein as a measure of myelin degradation. Conclusion: These results suggest a role of IL-12p40 in the pathophysiology of MS.

“Mobile Stroke Unit” for Hyperacute Stroke Treatment

To the Editor: Ischemic stroke is a major cause of death and of permanent severe functional deficits in the developed countries. In most cases this disease is caused by obstruction of the cerebral blood vessels, ie, by emboli originating from the heart or large brain-supplying blood vessels. Experimental studies show that within minutes after vascular obstruction, cell death occurs in the core of the focal ischemic brain tissue. In the region around this core (penumbra), cells exhibit a compromised metabolism but might be rescued by adequate therapies.1 At present, the only acute treatment for acute stroke that has been shown to be effective and that has been approved in most Western countries is thrombolysis of the obstructing emboli by recombinant tissue plasminogen activator (rtPA).2 However, even in centers specialized for stroke <5% of the stroke patients are treated by thrombolysis. One explanation for this may be that most patients arrive at the hospital …

Protein S-100B: a serum marker for ischemic and infectious injury of cerebral tissue.

Abstract The S-100B protein is released by injured astrocytes. After passage through a disintegrated blood-brain barrier (BBB) the molecule can be detected in the peripheral circulation. We investigated the association between the extent of brain injury and S-100B concentration in serum in cerebral injury caused by cerebral ischemia and cerebral fungal infection. Study I: The S-100B serum concentration was serially determined in 24 patients with ischemic stroke at 4, 8, 10, 24, 72 hours after the onset of symptoms. We observed that patients with brain lesions larger than 5 cm3 exhibited significantly increased serum levels of S-100B at 10, 24 and 72 hours compared to those with lesion volumes below 5 cm3. Furthermore, an association between S-100B serum concentration and neurological outcome was observed. Study II: In a mouse model of systemic fungal infection with Candida albicans we observed that serum levels of S-100B increased at day 1 after intravenous infection. At this time we could histologically demonstrate brain tissue injury by invading hyphae which had crossed the BBB. Furthermore, reactive astrogliosis was demonstrated by immunohistochemistry. On day 7 we found a significant decrease of S-100B serum level compared to day 1 and 4. This was associated with a demarcation of the fungi with leukocytes in brain tissue at this late phase of infection. No further invasion through the BBB was seen on day 7. In conclusion, serum levels of S-100B reflect the time course of tissue injury in cerebral ischemia and cerebral infection to a similar extent. Thus, S-100B may be a useful marker to assess cerebral tissue injury.

Endothelial-derived adhesion molecules in bacterial meningitis: association to cytokine release and intrathecal leukocyte-recruitment

The release of circulating isoforms of selectin- (L-selectin, ELAM-1) and immunoglobulin-type- (ICAM-1) adhesion molecules, responsible for accumulation of leukocytes at sites of tissue injury was studied in CSF and serum of 21 patients with bacterial meningitis and in healthy subjects. Their concentrations were compared with the intrathecal leukocyte recruitment and release of inflammatory cytokines. In contrast to serum concentrations of the leukocyte-derived adhesion molecule, sL-selectin, serum concentrations of endothelial-derived adhesion molecules, sELAM-1 and sICAM-1, were significantly increased in meningitis. No intrathecal synthesis of these adhesion molecules was observed. Serum levels of sELAM-1 were associated with extent of CSF pleocytosis and with concentrations of proinflammatory cytokines IL-1beta and TNF alpha in CSF, but not in serum. Therefore, expression of endothelial adhesion molecules i.e. ELAM-1 may be responsible for the massive intrathecal recruitment of potentially harmful leukocytes in patients with bacterial meningitis. Intrathecally released proinflammatory cytokines may represent the inducing signals for their endothelial upregulation.

Homocysteine in cerebrovascular disease: an independent risk factor for subcortical vascular encephalopathy.

Abstract Hyperhomocysteinemia is a risk factor for obstructive large-vessel disease. Here, we studied plasma concentrations of homocysteine and vitamins in patients suffering from subcortical vascular encephalopathy (SVE), a cerebral small-vessel disease leading to dementia. These results were compared to the homocysteine and vitamin plasma concentrations from patients with cerebral large vessel disease and healthy control subjects. Plasma concentrations of homocysteine, vascular risk factors and vitamin status (B6, B12, folate) were determined in 82 patients with subcortical vascular encephalopathy, in 144 patients with cerebral large-vessel disease and in 102 control subjects. Patients with SVE, but not those with cerebral large-vessel disease, exhibited pathologically increased homocysteine concentrations in comparison with control subjects without cerebrovascular disease. Patients with SVE also showed lower vitamin B6 values in comparison to subjects without cerebrovascular disease. Logistic regression analysis showed that homocysteine is associated with the highest risk for SVE (odds ratio 5.7; CI 2.5–12.9) in comparison to other vascular risk factors such as hypertension, age and smoking. These observations indicate that hyperhomocysteinemia is a strong independent risk factor for SVE.

Subacute But Not Acute Generation of Nitric Oxide in Focal Cerebral Ischemia

Background and Purpose Excessive release of nitric oxide (NO) has been implicated in the pathophysiology of neurodegeneration in ischemic stroke. We compared intracerebral release of indicators of NO generation at the acute and subacute stages of transient focal cerebral ischemia. Methods In vivo microdialysis in the rat striatum was performed at the acute (first hours) and subacute (after 24 or 48 hours) stages of cerebral ischemia or sham operation to monitor intracerebral release of the stable NO metabolites nitrite and nitrate. Results Whereas only a nonsignificant trend toward increased release of these NO metabolites was evidenced in acute cerebral ischemia, a significant NO generation was observed subacutely, 48 hours after induction of cerebral ischemia. Aminoguanidine, a selective inhibitor of inducible NO synthase, suppressed this delayed release of nitrite and nitrate. Conclusions Whereas these observations do not support a major NO generation in acute cerebral ischemia, they indicate an inducible NO synthase–dependent NO generation predominantly at the subacute phase of ischemic neurodegeneration. Therefore, NO generation may play a pathophysiological role in delayed ischemic neurodegeneration.

Inflammatory Leukocyte Infiltration in Focal Cerebral Ischemia: Unrelated to Infarct Size

Objective: An inflammatory host response in the ischemically injured brain is well documented. However, its pathophysiological relevance is uncertain. We investigated whether inflammatory leukocyte response in the ischemic brain alters infarct size. Methods: The cellular inflammatory response to cerebral ischemia in Wistar-derived rats induced by the transient occlusion of the middle cerebral artery with a thread was pharmacologically upmodulated by lipopolysaccharide (LPS) or downmodulated by continuous infusion of carboxylated sialyl Lewisx (sLex). The effects of such experimental modulation of focal cerebral leukocyte recruitment on the extent of the resulting infarction were assessed. Results:Compared to control treatments, LPS strongly enhanced (540.5 ± 504.8 vs. 94.6 ± 60.6, p < 0.01) and sLex decreased (32.8 ± 29.1vs. 97.0 ± 49.7, p < 0.05) the numbers of neutrophils at the investigated sites in cerebral ischemia. Unexpectedly, despite such marked experimental modulation of leukocyte infiltration in the ischemic brain, the extent of the resulting cerebral infarction (percent of total hemisphere) remained unchanged under these different conditions (54.5 ± 10.8vs. 53.0 ± 19.1, n.s. and 50.3 ± 18.0 vs. 57.2 ± 10.0, n.s., respectively). Conclusions: The striking dissociation between the massively altered inflammatory leukocyte infiltration in the ischemic brain and the unchanged infarct outcome indicates that intracerebral inflammatory leukocyte recruitment is not a major pathogenic factor in the development of ischemic tissue damage.