Expression of interleukin-1 beta in lipopolysaccharide stimulated monocytes derived from patients with aneurysmal subarachnoid hemorrhage is correlated with cerebral vasospasm

Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH): Protocol for a prospective, triple-blinded, randomized controlled trial

Background

Inflammation has been implicated in driving the morbidity associated with subarachnoid hemorrhage (SAH). Despite understanding the important role of inflammation in morbidity following SAH, there is no current effective way to modulate this deleterious response. There is a critical need for a novel approach to immunomodulation that can be safely, rapidly, and effectively deployed in SAH patients. Vagus nerve stimulation (VNS) provides a non-pharmacologic approach to immunomodulation, with prior studies demonstrating VNS can reduce systemic inflammatory markers, and VNS has had early success treating inflammatory conditions such as arthritis, sepsis, and inflammatory bowel diseases. The aim of the Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH) trial is to translate the use of non-invasive transcutaneous auricular VNS (taVNS) to spontaneous SAH, with our central hypothesis being that implementing taVNS in the acute period following spontaneous SAH attenuates the expected inflammatory response to hemorrhage and curtails morbidity associated with inflammatory-mediated clinical endpoints.

Materials and methods

The overall objectives for the NAHSaH trial are to 1) Define the impact that taVNS has on SAH-induced inflammatory markers in the plasma and cerebrospinal fluid (CSF), 2) Determine whether taVNS following SAH reduces radiographic vasospasm, and 3) Determine whether taVNS following SAH reduces chronic hydrocephalus. Following presentation to a single enrollment site, enrolled SAH patients are randomly assigned twice daily treatment with either taVNS or sham stimulation for the duration of their intensive care unit stay. Blood and CSF are drawn before initiation of treatment sessions, and then every three days during a patient's hospital stay. Primary endpoints include change in the inflammatory cytokine TNF-α in plasma and cerebrospinal fluid between day 1 and day 13, rate of radiographic vasospasm, and rate of requirement for long-term CSF diversion via a ventricular shunt. Secondary outcomes include exploratory analyses of a panel of additional cytokines, number and type of hospitalized acquired infections, duration of external ventricular drain in days, interventions required for vasospasm, continuous physiology data before, during, and after treatment sessions, hospital length of stay, intensive care unit length of stay, and modified Rankin Scale score (mRS) at admission, discharge, and each at follow-up appointment for up to two years following SAH.

Discussion

Inflammation plays a central role in morbidity following SAH. This NAVSaH trial is innovative because it diverges from the pharmacologic status quo by harnessing a novel non-invasive neuromodulatory approach and its known anti-inflammatory effects to alter the pathophysiology of SAH. The investigation of a new, effective, and rapidly deployable intervention in SAH offers a new route to improve outcomes following SAH.

Trial registration

Clinical Trials Registered, NCT04557618. Registered on September 21, 2020, and the first patient was enrolled on January 4, 2021.

Intracranial Aneurysms and Lipid Metabolism Disorders: From Molecular Mechanisms to Clinical Implications

Many vascular diseases are linked to lipid metabolism disorders, which cause lipid accumulation and peroxidation in the vascular wall. These processes lead to degenerative changes in the vessel, such as phenotypic transformation of smooth muscle cells and dysfunction and apoptosis of endothelial cells. In intracranial aneurysms, the coexistence of lipid plaques is often observed, indicating localized lipid metabolism disorders. These disorders may impair the function of the vascular wall or result from it. We summarize the literature on the relationship between lipid metabolism disorders and intracranial aneurysms below.

The role of inflammation and potential use of sex steroids in intracranial aneurysms and subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (aSAH) continues to be a devastating neurological condition with a high risk of associated morbidity and mortality. Inflammation has been shown to increase the risk of complications associated with aSAH such as vasospasm and brain injury in animal models and humans. The goal of this review is to discuss the inflammatory mechanisms of aneurysm formation, rupture and vasospasm and explore the role of sex hormones in the inflammatory response to aSAH.

Methods

A literature review was performed using PubMed using the following search terms: "intracranial aneurysm," "cerebral aneurysm," "dihydroepiandrosterone sulfate" "estrogen," "hormone replacement therapy," "inflammation," "oral contraceptive," "progesterone," "sex steroids," "sex hormones" "subarachnoid hemorrhage," "testosterone." Only studies published in English language were included in the review.

Results

Studies have shown that administration of sex hormones such as progesterone and estrogen at early stages in the inflammatory cascade can lower the risk and magnitude of subsequent complications. The exact mechanism by which these hormones act on the brain, as well as their role in the inflammatory cascade is not fully understood. Moreover, conflicting results have been published on the effect of hormone replacement therapy in humans. This review will scrutinize the variations in these studies to provide a more detailed understanding of sex hormones as potential therapeutic agents for intracranial aneurysms and aSAH.

Conclusion

Inflammation may play a role in the pathogenesis of intracranial aneurysm formation and subarachnoid hemorrhage, and administration of sex hormones as anti-inflammatory agents has been associated with improved functional outcome in experimental models. Further studies are needed to determine the therapeutic role of these hormones in the intracranial aneurysms and aSAH.

Delayed ischemia after subarachnoid hemorrhage: result of vasospasm alone or a broader vasculopathy?

The term vasospasm is commonly used to describe constriction of cerebral blood vessels after subarachnoid hemorrhage which results in the restriction of blood flow and ischemia in affected portions of the brain. The pathophysiological changes that underlie vascular constriction after subarachnoid hemorrhage include changes within the vessel walls themselves, alteration of the levels of several vasoactive substances, and broader pathological conditions such as immune responses, inflammation, and oxidative damage. In this review, we summarize the current state of knowledge concerning the processes that occur in cerebral blood vessels after subarachnoid hemorrhage and how they may be involved in the development of vasospasm. We also propose that, rather than merely vasospasm, the multitude of vascular effects occurring after subarachnoid hemorrhage can be best described as a post-subarachnoid hemorrhage vasculopathy.

Neutrophil depletion after subarachnoid hemorrhage improves memory via NMDA receptors

Cognitive deficits after aneurysmal subarachnoid hemorrhage (SAH) are common and disabling. Patients who experience delayed deterioration associated with vasospasm are likely to have cognitive deficits, particularly problems with executive function, verbal and spatial memory. Here, we report neurophysiological and pathological mechanisms underlying behavioral deficits in a murine model of SAH. On tests of spatial memory, animals with SAH performed worse than sham animals in the first week and one month after SAH suggesting a prolonged injury. Between three and six days after experimental hemorrhage, mice demonstrated loss of late long-term potentiation (L-LTP) due to dysfunction of the NMDA receptor. Suppression of innate immune cell activation prevents delayed vasospasm after murine SAH. We therefore explored the role of neutrophil-mediated innate inflammation on memory deficits after SAH. Depletion of neutrophils three days after SAH mitigates tissue inflammation, reverses cerebral vasoconstriction in the middle cerebral artery, and rescues L-LTP dysfunction at day 6. Spatial memory deficits in both the short and long-term are improved and associated with a shift of NMDA receptor subunit composition toward a memory sparing phenotype. This work supports further investigating suppression of innate immunity after SAH as a target for preventative therapies in SAH.

Toll-like receptor 4 (TLR4) is correlated with delayed cerebral ischemia (DCI) and poor prognosis in aneurysmal subarachnoid hemorrhage

Toll-like receptor 4 (TLR4) is one of key players in regulation of inflammation. Animal experiments have suggested an important role of TLR4 in the pathophysiology of subarachnoid hemorrhage (SAH). In present study, TLR4 is investigated in clinical SAH patients to explore its clinical significance. 30 patients with aneurysmal subarachnoid hemorrhage (aSAH) and 20 healthy control patients (HC) were enrolled in this prospective study. Blood samples were collected on days 1, 3 and 7 after admission. TLR4 expression level on cell surface of peripheral blood mononuclear cells (PBMCs) was determined by flow cytometry and presented as mean fluorescence intensity (MFI). Patients were clinically assessed every day after admission to monitor the occurrence of delayed cerebral ischemia (DCI). Participants were followed up until completion of 3 months after SAH. Functional outcome was defined by modified Rankin score (mRs). Results show that SAH patients presented a significantly higher TLR4 levels on days 1 and 3 post SAH compared to HC; TLR4 levels in SAH patients on day 1 was highest compared with that on days 3 and 7 and in HC. TLR4 of SAH patients on day 7 declined to the level showing no significant difference with that of HC. In patients with Hunt-Hess grades I-III lower TLR4 levels were observed. Patients with DCI showed significantly higher TLR4 levels than those without DCI. High TLR4 levels were statistically significantly associated with poor functional outcome after 3 months. Logistic regression analysis showed that TLR4 level on day 1 was independent predictor for DCI and 3-month poor neurological outcome of aneurysmal SAH patients. In summary, admission TLR4 level on PBMCs (day 1) is an independent risk factor to predict the occurrence of DCI and 3-month poor neurological outcome in aneurysmal SAH patients.

Toll-like Receptor 4 (TLR4) is Associated with Cerebral Vasospasm and Delayed Cerebral Ischemia in Aneurysmal Subarachnoid Hemorrhage

In the present prospective study, the Toll-like receptor 4 (TLR4) levels on peripheral blood mononuclear cells (PBMCs) were investigated in 30 patients with aneurysmal subarachnoid hemorrhage (aSAH) and in 20 healthy controls (HCs). The relationship between TLR4 levels and the occurrence of cerebral vasospasm (CVS) was also analyzed. TLR4 expression level on cell surface of PBMCs on days 1, 3, and 7 after admission was determined by flow cytometry. Results showed that patients with aSAH presented a significantly higher TLR4 levels. For patients with Hunt-Hess grades IV–V, higher TLR4 levels were also observed; higher TLR4 levels have already been seen in patients developing CVS and/or delayed cerebral ischemia (DCI). Higher TLR4 levels were also associated with modified Fisher score, occurrence of dCVS, DCI, cerebral infarction (CT), and poor neurological functional recovery. Binary logistic regression analysis indicated that high TLR4 expression on blood monocytes was an independent predictive factor of the occurrence of dCVS, DCI, and poor neurological functional recovery. Taken together, TLR4 levels on PBMCs is significantly altered in the early stage of aSAH, especially in those patients experiencing CVS and DCI. Furthermore, higher TLR4 levels in the early stage of aSAH is also associated with the neurological function outcome. As far as we know, this is the first clinical study about TLR4's significance for patients with aSAH.

Vasospasm in cerebral inflammation

All forms of cerebral inflammation as found in bacterial meningitis, cerebral malaria, brain injury, and subarachnoid haemorrhage have been associated with vasospasm of cerebral arteries and arterioles. Vasospasm has been associated with permanent neurological deficits and death in subarachnoid haemorrhage and bacterial meningitis. Increased levels of interleukin-1 may be involved in vasospasm through calcium dependent and independent activation of the myosin light chain kinase and release of the vasoconstrictor endothelin-1. Another key factor in the pathogenesis of cerebral arterial vasospasm may be the reduced bioavailability of the vasodilator nitric oxide. Therapeutic trials in vasospasm related to inflammation in subarachnoid haemorrhage in humans showed a reduction of vasospasm through calcium antagonists, endothelin receptor antagonists, statins, and plasminogen activators. Combination of therapeutic modalities addressing calcium dependent and independent vasospasm, the underlying inflammation, and depletion of nitric oxide simultaneously merit further study in all conditions with cerebral inflammation in double blind randomised placebo controlled trials. Auxiliary treatment with these agents may be able to reduce ischemic brain injury associated with neurological deficits and increased mortality.

Inflammation, vasospasm, and brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) can lead to devastating neurological outcomes, and there are few pharmacologic treatments available for treating this condition. Both animal and human studies provide evidence of inflammation being a driving force behind the pathology of SAH, leading to both direct brain injury and vasospasm, which in turn leads to ischemic brain injury. Several inflammatory mediators that are elevated after SAH have been studied in detail. While there is promising data indicating that blocking these factors might benefit patients after SAH, there has been little success in clinical trials. One of the key factors that complicates clinical trials of SAH is the variability of the initial injury and subsequent inflammatory response. It is likely that both genetic and environmental factors contribute to the variability of patients' post-SAH inflammatory response and that this confounds trials of anti-inflammatory therapies. Additionally, systemic inflammation from other conditions that affect patients with SAH could contribute to brain injury and vasospasm after SAH. Continuing work on biomarkers of inflammation after SAH may lead to development of patient-specific anti-inflammatory therapies to improve outcome after SAH.

Phenotypic transformation of smooth muscle in vasospasm after aneurysmal subarachnoid hemorrhage

Differentiated smooth muscle cells (SMC) control vasoconstriction and vasodilation, but they can undergo transformation, proliferate, secret cytokines, and migrate into the subendotherial layer with adverse consequences. In this review, we discuss the phenotypic transformation of SMC in cerebral vasospasm after subarachnoid hemorrhage. Phenotypic transformation starts with an insult as caused by aneurysm rupture: Elevation of intracranial and blood pressure, secretion of norepinephrine, and mechanical force on an artery are factors that can cause aneurysm. The phenotypic transformation of SMC is accelerated by inflammation, thrombin, and growth factors. A wide variety of cytokines (e.g., interleukin (IL)-1β, IL-33, matrix metalloproteinases, nitric oxidase synthases, endothelins, thromboxane A2, mitogen-activated protein kinase, platelet-derived vascular growth factors, and vascular endothelial factor) all play roles in cerebral vasospasm (CVS). We summarize the correlations between various factors and the phenotypic transformation of SMC. A new target of this study is the transient receptor potential channel in CVS. Statin together with fasdil prevents phenotypic transformation of SMC in an animal model. Clazosentan prevents CVS and improves outcome in aneurysmal subarachnoid hemorrhage in a dose-dependent manner. Clinical trials of cilostazol for the prevention of phenotypic transformation of SMC have been reported, along with requisite experimental evidence. To conquer CVS in its complexity, we will ultimately need to elucidate its general, underlying mechanism.

Inflammation in subarachnoid hemorrhage and delayed deterioration associated with vasospasm: a review

Delayed deterioration associated with vasospasm (DDAV) after subarachnoid hemorrhage (SAH), (often called vasospasm) continues to be both a difficult entity to treat and a leading cause of morbidity in patients. Until recently, attention was focused on alleviating the vascular spasm. Recent evidence shows that vascular spasm may not account for all the morbidity of DDAV. There is renewed interest in looking for other potential targets for therapy. Inflammation has become a promising area of research for new treatments. This review explores the evidence that inflammation is a driver of DDAV by asking three questions: (1) If inflammation is important in the pathogenesis of the disease, what part or parts of the inflammatory response are involved? (2) When does inflammation occur in SAH? (3) In what compartment of the skull does the inflammation occur, the cerebrospinal fluid and meninges, the cerebral arteries, or the brain itself?

Monitoring of the inflammatory response after aneurysmal subarachnoid haemorrhage in the clinical setting: review of literature and report of preliminary clinical experience

BACKGROUND

Clinical and experimental studies showed a marked inflammatory response in aneurysmal subarachnoid haemorrhage (SAH), and it has been proposed to play a key role in the development of cerebral vasospasm (CVS). Inflammatory response and occurrence of CVS may represent a common pathogenic pathway allowing point of care diagnostics of CVS. Therefore, monitoring of the inflammatory response might be useful in the daily clinical setting of an ICU. The aim of the current report is to give a summary about factors contributing to the complex pathophysiology of inflammatory response in SAH and to discuss possible monitoring modalities.

METHODS

Review and analysis of the existing literature and definition of own study protocols.

RESULTS

In cerebrospinal fluid, interleukin (IL)-6 has been found to be significantly higher in patients with CVS during the peri-vasospasm period. While systemic inflammatory response syndrome, high C-reactive protein levels and leukocyte counts has been linked with the occurrence of CVS, less has been reported about cytokines levels in the jugular bulb of the internal jugular vein and in the peripheral blood. Preliminary evaluation of own data suggests, that IL-6 values in the peripheral blood and the arterio-jugular differences of IL-6 are increased with the inflammatory response after SAH.

CONCLUSION

Monitoring of the inflammatory response, in particular IL-6, might be a useful tool for the daily clinical management of patients with SAH and CVS.

Inflammation and cerebral vasospasm after subarachnoid hemorrhage

Morbidity and mortality of patients with aneurysmal subarachnoid hemorrhage (aSAH) is significantly related to the development of chronic cerebral vasospasm. Despite extensive clinical and experimental research, the pathophysiology of the events that result in delayed arterial spasm is not fully understood. A review of the published literature on cerebral vasospasm that included but was not limited to all PubMed citations from 1951 to the present was performed. The findings suggest that leukocyte-endothelial cell interactions play a significant role in the pathophysiology of cerebral vasospasm and explain the clinical variability and time course of the disease. Experimental therapeutic targeting of the inflammatory response when timed correctly can prevent vasospasm, and supplementation of endothelial relaxation by nitric oxide-related therapies and other approaches could result in reversal of the arterial narrowing and improved outcomes in patients with aSAH.

Role of inflammation (leukocyte-endothelial cell interactions) in vasospasm after subarachnoid hemorrhage

BACKGROUND

Delayed vasospasm is the leading cause of morbidity and mortality after aneurysmal subarachnoid hemorrhage (aSAH). This phenomenon was first described more than 50 years ago, but only recently has the role of inflammation in this condition become better understood.

METHODS

The literature was reviewed for studies on delayed vasospasm and inflammation.

RESULTS

There is increasing evidence that inflammation and, more specifically, leukocyte-endothelial cell interactions play a critical role in the pathogenesis of vasospasm after aSAH, as well as in other conditions including meningitis and traumatic brain injury. Although earlier clinical observations and indirect experimental evidence suggested an association between inflammation and chronic vasospasm, recently direct molecular evidence demonstrates the central role of leukocyte-endothelial cell interactions in the development of chronic vasospasm. This evidence shows in both clinical and experimental studies that cell adhesion molecules (CAMs) are up-regulated in the perivasospasm period. Moreover, the use of monoclonal antibodies against these CAMs, as well as drugs that decrease the expression of CAMs, decreases vasospasm in experimental studies. It also appears that certain individuals are genetically predisposed to a severe inflammatory response after aSAH based on their haptoglobin genotype, which in turn predisposes them to develop clinically symptomatic vasospasm.

CONCLUSION

Based on this evidence, leukocyte-endothelial cell interactions appear to be the root cause of chronic vasospasm. This hypothesis predicts many surprising features of vasospasm and explains apparently unrelated phenomena observed in aSAH patients. Therapies aimed at preventing inflammation may prevent and/or reverse arterial narrowing in patients with aSAH and result in improved outcomes.

Prediction of Cerebral Vasospasm in Patients Presenting with Aneurysmal Subarachnoid Hemorrhage: A Review

OBJECTIVE:

Cerebral vasospasm is a devastating medical complication of aneurysmal subarachnoid hemorrhage (SAH). It is associated with high morbidity and mortality rates, even after the aneurysm has been treated. A substantial amount of experimental and clinical research has been conducted in an effort to predict and prevent its occurrence. This research has contributed to significant advances in the understanding of the mechanisms leading to cerebral vasospasm. The ability to accurately and consistently predict the onset of cerebral vasospasm, however, has been challenging. This topic review describes the various methodologies and approaches that have been studied in an effort to predict the occurrence of cerebral vasospasm in patients presenting with SAH.

METHODS:

The English-language literature on the prediction of cerebral vasospasm after aneurysmal SAH was reviewed using the MEDLINE PubMed (1966–present) database.

RESULTS:

The risk factors, diagnostic imaging, bedside monitoring approaches, and pathological markers that have been evaluated to predict the occurrence of cerebral vasospasm after SAH are presented.

CONCLUSION:

To date, a large blood burden is the only consistently demonstrated risk factor for the prediction of cerebral vasospasm after SAH. Because vasospasm is such a multifactorial problem, attempts to predict its occurrence will probably require several different approaches and methodologies, as is done at present. Future improvements in the prevention of cerebral vasospasm from aneurysmal SAH will most likely require advances in our understanding of its pathophysiology and our ability to predict its onset.

Delayed Intracranial Delivery of a Nitric Oxide Donor from a Controlled-release Polymer Prevents Experimental Cerebral Vasospasm in Rabbits

OBJECTIVE

Decreased local availability of nitric oxide (NO) may mediate chronic vasospasm after aneurysmal subarachnoid hemorrhage (SAH). Previous reports have shown that early treatment with NO prevents vasospasm in animals. We evaluated the efficacy of controlled-release polymers that contain the NO donor diethylenetriamine (DETA-NO) for the delayed treatment of vasospasm in a rabbit model of SAH.

METHODS

DETA-NO 20% (wt/wt) was incorporated into ethylene-vinyl acetate (EVAc) polymers. Animals (n = 52) were randomized to two experimental groups. In the first group (n = 32), animals received SAH and implantation of either 20% DETA-NO/EVAc polymer at a dose of 0.5 mg/kg of DETA-NO (n = 16) or empty EVAc polymer (n = 16). Polymers were implanted 24 (n = 16) or 48 hours (n = 16) after SAH. In the second group (n = 20), animals received SAH and implantation of either 20% DETA-NO/EVAc polymer at a dose of 1.3 mg/kg (n = 10) or empty EVAc (n = 10). Polymers were implanted 24 (n = 10) or 48 hours (n = 10) after SAH. An additional group (n = 16) underwent either sham operation (n = 6) or SAH only (n = 10). Animals were killed 3 days after hemorrhage, and the basilar arteries were processed for morphometric measurements. Results were analyzed using Student's t test.

RESULTS

Treatment with 20% DETA-NO/EVAc polymers at a dose of 1.3 mg/kg significantly increased basilar artery lumen patency when administered at 24 (97 +/- 6% versus 73 +/- 10%; P = 0.0396) or 48 hours (94 +/- 6% versus 71 +/- 9%; P = 0.03) after SAH. Treatment with 20% DETA-NO/EVAc polymers at a dose of 0.5 mg/kg administered 48 hours after SAH significantly increased lumen patency (82 +/- 8% versus 68 +/- 12%; P = 0.03); a dose of 0.5 mg/kg, 24 hours after SAH, did not reach statistical significance (74 +/- 7% versus 65 +/- 9%; P = 0.16). The SAH-only group had a lumen patency of 67 +/- 12%.

CONCLUSION

Delayed treatment of SAH with controlled-release DETA-NO polymers prevented experimental posthemorrhagic vasospasm in the rabbit. This inhibition was dose-dependent. This further confirms the role of NO in the pathogenesis of vasospasm.

Cytotoxicity of cytokines in cerebral microvascular endothelial cell

OBJECTIVE

Several studies reported that the levels of proinflammatory cytokines such as TNF-alpha, IL-1beta, IL-6, and IL-8 are elevated in the cerebrospinal fluid (CSF) of patients after subarachnoid hemorrhage (SAH). Cytokines in CSF may contribute to the development of vasospasm and cerebral ischemia. In the present study, we investigated the possible cytotoxic effects of these cytokines on cultured cerebral microvascular endothelial cells.

METHOD

The effects of TNF-alpha, IL-1beta, IL-6, and IL-8 were tested using cell viability assay, DNA fragmentation analysis (DNA laddering), Western blot analysis (Anti-poly-(ADP-ribose) polymerase [PARP] antibody), and caspase-3 activity.

RESULTS

TNF-alpha and IL-1beta, but not IL-6 or IL-8, caused cell detachment in a dose-dependent manner (p<0.05). TNF-alpha (200 pg/ml) and IL-1beta (150 pg/ml) produced DNA ladders at 24-72 h. TNF-alpha but not IL-1beta cleaved the PARP from 116- to 85-kDa fragments and enhanced caspase-3 activity at 24-72 h after incubation with endothelial cells. Caspase-3 inhibitor at 10 micromol/l significantly prevented TNF-alpha-induced cell detachment (p<0.05).

DISCUSSION

TNF-alpha induces apoptosis in cultured cerebral endothelial cells through the cleavage of caspase-3. IL-1beta decreases the adherent cells, produces DNA ladders, but fails to cleave PARP or increase caspase-3 activity. IL-1beta may induce apoptosis in cerebral endothelial cells through different pathway from that of TNF-alpha.

Interleukin-1β and adverse effects on cerebral blood flow during long-term global hypoperfusion

Object. The effects of interleukin (IL)-1β on the cerebral vasculature are complex and incompletely understood. Many pathophysiological states in which inflammatory cascades have been implicated also have varying degrees of cerebral hypoperfusion. The purpose of this investigation was to examine the long-term effects of this proinflammatory cytokine and its antagonist on cerebral blood flow (CBF) following global cerebral hypoperfusion.

Methods. Sprague—Dawley rats were randomly assigned to 12 groups and given continuous intracerebroventricular (ICV) infusions of IL-1β, the IL-1 receptor antagonist (IL-1ra), or saline vehicle (control). Global cerebral hypoperfusion was produced by occlusion of both carotid arteries and one vertebral artery. Cerebral blood flow was measured at baseline and again after initiation of the infusions by performing a 133Xe clearance study.

Prolonged ICV administration of IL-1β resulted in a significant decrease in CBF compared with that in controls. Prolonged administration of the antagonist IL-1ra resulted in significant increases in CBF compared with that in both IL-1β—treated animals and controls.

Conclusions. This experiment demonstrates that long-term treatment with the proinflammatory cytokine IL-1β adversely affects CBF.

Serum von Willebrand factor, matrix metalloproteinase-9, and vascular endothelial growth factor levels predict the onset of cerebral vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Endothelial damage and intimal proliferation occur in vasospastic cerebral arteries after subarachnoid hemorrhage (SAH). In the peripheral vasculature, endothelial damage increases intimal matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) levels, causing neointimal proliferation. We hypothesized that serum von Willebrand factor (vWF) (a marker of endothelial cell death), MMP-9, and VEGF levels could serve as prognostic markers in predicting the occurrence of cerebral vasospasm.

METHODS

Venous serum vWF, MMP-9, and VEGF levels were prospectively measured daily, for 12 days or until the onset of vasospasm, for 45 consecutive patients admitted with SAH (n = 38) or admitted for elective aneurysm clipping (control subjects, n = 7). The development of transcranial Doppler flow velocities of more than 180 cm/s and/or new focal neurological deficits with angiographically confirmed vasospasm was considered the onset of vasospasm. To establish whether these markers were specific for vasospasm versus ischemia, blood samples were obtained from a concurrent group of 42 patients within 24 hours after stroke onset unrelated to SAH.

RESULTS

Fifty-seven percent of patients (22 of 38 patients) developed vasospasm, 4 to 11 days after SAH (median, 7 d). Mean peak serum vWF, MMP-9, and VEGF levels were increased in the SAH prevasospasm cohort, compared with the SAH nonvasospasm cohort (vWF, 5526 +/- 929 versus 4934 +/- 599 ng/ml, P = 0.01; MMP-9, 705 +/- 338 versus 438 +/- 154 ng/ml, P = 0.006; VEGF, 0.12 +/- 0.06 versus 0.06 +/- 0.06 ng/ml, P = 0.023). Mean peak vWF, MMP-9, and VEGF levels for the focal ischemia cohort (vWF, 4645 +/- 875 ng/ml, P = 0.01; MMP-9, 250 +/- 308 ng/ml, P = 0.001; VEGF, 0.03 +/- 0.04 ng/ml, P = 0.001) were markedly lower in comparison with the SAH prevasospasm cohort and were unchanged in comparison with the control cohort. vWF levels of more than 5500 ng/ml, VEGF levels of more than 0.12 ng/ml, and MMP levels of more than 700 ng/ml each independently increased the odds of subsequent vasospasm (18-, 20-, and 25-fold, respectively).

CONCLUSION

The development of cerebral vasospasm after SAH was preceded by increases in serum vWF, MMP-9, and VEGF levels. Increased serum vWF, MMP-9, and VEGF levels could accurately predict the onset of cerebral vasospasm after SAH. These factors were not elevated by SAH alone or in a separate cohort of patients with ischemic stroke, suggesting that these factors might play a role in the pathogenesis of human cerebral vasospasm.