Role of extracellular matrix in experimental vasospasm. Inhibitory effect of antisense oligonucleotide on collagen induction

Molecular mechanisms of cerebral vasospasm following aneurysmal SAH

Cerebral vasospasm following aneurysmal vasospasm has been the subject of intensive research. However the underlying pathophysiological mechanisms remain obscure. This article should summarize the present state concerning smooth muscle contraction, endothelial dysfunction, inflammatory changes, gene expression, in the genesis of vasospasm following aneurysmal subarachnoid hemorrhage.

A novel inhibitor of inflammatory cytokine production (CNI-1493) reduces rodent post-hemorrhagic vasospasm

INTRODUCTION

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) is a devastating complication, yet despite multiple lines of investigation an effective treatment remains lacking. Cytokine-mediated inflammation has been implicated as a causative factor in the development of posthemorrhagic vasospasm. In previous experiments using the rat femoral artery model of vasospasm, we demonstrated that elevated levels of the proinflammatory cytokine interleukin (IL)-6 are present after hemorrhage and that a polyclonal antibody against IL-6 is capable of attenuating experimental vasospasm.

METHODS

In the present study, we tested the ability of a novel selective proinflammatory cytokine inhibitor (CNI-1493) to protect against the occurrence of experimental vasospasm in the same rat femoral artery model. CNI-1493 was administered by injection directly into the blood-filled femoral pouches of animals at the time of their initial surgery (hemorrhage). Control animals received an equal volume of vehicle alone. Animals were killed at 8 days posthemorrhage and degree of vasospasm was assessed by image analysis of artery cross-sectional area. In a separate series of experiments, enzyme-linked immunosorbent assay (ELISA) was used to assess levels of the proinflammatory cytokine IL-6 and the prototypical antiinflammatory cytokine transforming growth factor (TGF)-beta1 after treatment with CNI-1493.

RESULTS

Pretreatment with CNI-1493 provided dose-dependent attenuation of posthemorrhagic vasospasm, with the highest dose (200 microg in 8 microL dH2O) causing complete reversal of vasospasm (vessel cross-sectional area ratio 1.06 +/- 0.04 versus 0.87 +/- 0.06, p < 0.05, one-way analysis of variance). Assessment of cytokine levels by ELISA confirmed the selectivity of CNI-1493 by demonstrating significant reductions in IL-6 levels, but no suppression of TGF-beta1 levels.

CONCLUSIONS

These findings support the conclusion that inflammatory cytokines, in particular IL-6, play an important role in development of vasospasm in the rat femoral artery model. Furthermore, these results suggest that the inhibition of inflammatory cytokines may be an appropriate strategy for the treatment of vasospasm after SAH.

An overview of new pharmacological treatments for cerebrovascular dysfunction after experimental subarachnoid hemorrhage

Cerebral vasospasm and the resulting cerebral ischemia occurring after subarachnoid hemorrhage (SAH) are still responsible for the considerable morbidity and mortality in patients affected by cerebral aneurysms. Mechanisms contributing to the development of vasospasm, abnormal reactivity of cerebral arteries and cerebral ischemia after SAH have been intensively investigated in recent years. It has been suggested that the pathogenesis of vasospasm is related to a number of pathological processes, including endothelial damage, smooth muscle cell contraction resulting from spasmogenic substances generated during lyses of subarachnoid blood clots, changes in vascular responsiveness and inflammatory or immunological reactions of the vascular wall. A great deal of experimental and clinical research has been conducted in an effort to find ways to prevent these complications. However, to date, the main therapeutic interventions remain elusive and are limited to the manipulation of systemic blood pressure, alteration of blood volume or viscosity, and control of arterial dioxide tension. Even though no single pharmacological agent or treatment protocol has been identified which could prevent or reverse these deadly complications, a number of promising drugs have been investigated. Among these is the hormone erythropoietin (EPO), the main regulator of erythropoiesis. It has recently been found that EPO produces a neuroprotective action during experimental SAH when its recombinant form (rHuEPO) is systemically administered. This topic review collects the relevant literature on the main investigative therapies for cerebrovascular dysfunction after aneurysmal SAH. In addition, it points out rHuEPO, which may hold promise in future clinical trials to prevent the occurrence of vasospasm and cerebral ischemia after SAH.

Neutralizing Antibody against Interleukin-6 Attenuates Posthemorrhagic Vasospasm in the Rat Femoral Artery Model

OBJECTIVE

The degree to which inflammation contributes to the development of posthemorrhagic vasospasm is controversial. In the present study, we investigated the relationship between various inflammatory cytokines (tumor necrosis factor-alpha, interleukin [IL]-1alpha, IL-1beta, and IL-6) and the development of experimental vasospasm.

METHODS

Posthemorrhagic vasospasm was produced in the rat femoral artery model. A latex pouch was placed around each femoral artery, and one pouch was injected with autologous blood and the other with saline as an internal control. Animals were killed at various time points (1 h to 16 d) after surgery (blood exposure), and the degree of vasospasm was assessed by image analysis of artery cross sectional area. Levels of inflammatory cytokines were determined by enzyme-linked immunosorbent assay, and the ability of a polyclonal antibody against rat IL-6 to inhibit vasospasm was tested.

RESULTS

The rat femoral artery model produced a biphasic vasospasm response, with maximal chronic delayed vasospasm occurring at 8 days after hemorrhage. Enzyme-linked immunosorbent assay revealed a significant increase in IL-6 concentrations in blood-exposed arteries relative to saline-exposed arteries at multiple time points (6, 12, 24, and 48 h) after hemorrhage (P < 0.0001). A relative increase in IL-1alpha levels was noted at 24 hours (P < 0.01). IL-1beta levels were similarly elevated in both blood- and saline-exposed arteries, and tumor necrosis factor-alpha levels were not detectable. Administration of a neutralizing polyclonal antibody against rat IL-6 directly into the blood-exposed periarterial pouch at the time of initial surgery resulted in a dose-dependent reduction in the degree of vasospasm compared with vehicle-treated controls at 8 days after hemorrhage (P < 0.05).

CONCLUSIONS

These results indicate that cytokine-mediated inflammation is active in the setting of posthemorrhagic vasospasm produced by the rat femoral artery model. In particular, the profound increase in IL-6 levels after exposure to hemorrhage and the ability of a polyclonal antibody against IL-6 to reduce vasospasm suggest that IL-6 may play a prominent role in the development of vasospasm in this model.

Up-regulation of parathyroid hormone receptor in cerebral arteries after subarachnoid hemorrhage in monkeys

OBJECTIVE

Complementary deoxyribonucleic acid array analysis was used to determine whether vasospasm after subarachnoid hemorrhage (SAH) is associated with changes in gene expression.

METHODS

Right SAHs were created in three monkeys, and the right and left middle cerebral arteries were collected 3, 7, or 14 days after SAH. Vasospasm was assessed by angiography performed on Day 0 and at tissue harvest. A complementary deoxyribonucleic acid array containing 5184 genes was used to screen for changes in gene expression by comparing the right and left middle cerebral arteries.

RESULTS

There was significant expression (greater than fivefold expression of messenger ribonucleic acid compared with internal standard control) of 537 genes (10%) in the middle cerebral arteries. One hundred sixty-four genes (31%) did not change significantly, and 373 (69%) were differentially expressed at 3, 7, or 14 days after SAH. These 373 genes changed from 1.2- to 7-fold as compared with control arteries. The most common pattern was a progressive increase with increased time after SAH. The functions of differentially expressed genes included the regulation of gene expression, cell proliferation, inflammation, membrane proteins and receptors, kinases, and phosphatases. There was a marked increase in parathyroid hormone and parathyroid hormone receptor with time after SAH. Immunoblotting demonstrated a significant increase in parathyroid hormone receptor protein.

CONCLUSION

The up-regulation of these proteins involved in vascular relaxation suggests that they may play a role in vasospasm. The progressive increase in messenger ribonucleic acids involved in the functions noted suggests that the pathogenesis of cerebral vasospasm involves cell proliferation, inflammation, and possibly smooth muscle phenotype change.

Inhibition of experimental vasospasm by pretreatment with ultraviolet light irradiation in a rat femoral artery model

OBJECTIVE

Chronic cerebral vasospasm is resistant to conventional treatments despite recent advances in treatment modalities. We studied the preventive effect of ultraviolet (UV) irradiation on development of vasospasm and its mechanism in a rat femoral artery model.

METHODS

The rat femoral artery model for vasospasm was used in this investigation (n = 108). The femoral arteries were divided into four groups: empty and no irradiation (control), UV irradiation (UV group), blood placement (VS group), and blood placement after UV irradiation (VS + UV group). Luminal area was measured, and smooth muscle cell counts in the medial layer of the vessel wall were obtained. An immunohistochemical study was performed with cross sections of fixed femoral arteries at 12 hours and 1, 3, 5, 7, and 49 days after blood placement. The rings of femoral arteries on Day 7 were subjected to pharmacological study.

RESULTS

Pretreatment with UV irradiation (VS + UV group) resulted not only in significant inhibition of chronic vasospasm but also in a significant decrease in smooth muscle cells compared with the VS group on Days 5 and 7. The UV-treated arteries (UV and VS + UV groups) exhibited a significant number of Bax- and Bcl-2-positive cells on Days 5 and 7, but few CPP-32 positive cells were observed at the same time points. In the pharmacological study, contractile response to KCI or phenylephrine was reduced significantly in the UV-treated arteries.

CONCLUSION

These results imply that UV irradiation prevents chronic vasospasm and suggest that UV-induced cell death plays an important role in the preventive effect without causing complications during the chronic period.

Increased tropoelastin and procollagen expression in the lung of nitrofen-induced diaphragmatic hernia in rats

BACKGROUND/PURPOSE

Collagen and elastin, the predominant components of the lung connective tissue network, have been suggested to have an important influence on lung compliance and maximal expansion. Decrease in lung compliance and distensibility often is seen in human congenital diaphragmatic hernia (CDH) lung as well as in experimentally produced CDH lung. The aim of this study was to investigate mRNA levels of tropoelastin and alpha1 (I) procollagen, the precursors of elastin, and type I collagen, respectively, in CDH lung and to determine whether antenatal dexamethasone treatment has any effect on the production of these extracellular matrix proteins.

METHODS

CDH model was induced in pregnant rats after administration of 100 mg nitrofen on day 9.5 of gestation (term, 22 days). Dexamethasone (0.25 mg/kg) was given on day 18.5 and 19.5. Cesarean section was performed on day 21. The fetuses were divided into three groups: group I, normal controls; group II, nitrofen-induced CDH; and group III, nitrofen-induced CDH with antenatal dexamethasone treatment. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate relative amounts of tropoelastin and alpha1 (I) procollagen mRNA.

RESULTS

Levels of both tropoelastin and alpha1 (I) procollagen mRNA were significantly increased in group II compared with group I (P< .05). Neither tropoelastin nor alpha1 (I) procollagen mRNA levels were significantly different between group II and III.

CONCLUSIONS

The increased local synthesis of tropoelastin and type I procollagen in CDH lung may be responsible for the increased rigidity and decreased compliance observed in the CDH hypoplastic lung. Glucocorticoids have no effect on pulmonary tropoelastin and alpha1 (I) procollagen gene expression in CDH lungs.

Decoy administration of NF-kappaB into the subarachnoid space for cerebral angiopathy

Subarachnoid hemorrhage (SAH), encephalitis, meningitis, and autoimmune diseases sometimes lead to cerebral angiopathy, characterized specifically by narrowing of vessels, morphological changes in the structure of vessel walls, and a concomitant decrease in cerebral blood flow. Many patients also develop delayed ischemic neurological deficits. Thus, preventing vascular reactions is of paramount importance in treating SAH. Although cerebral vasospasm has some relationship with the inflammatory reaction of major cerebral vessels against the autologous blood, and many trials have attempted to prevent angiopathy after SAH, an effective treatment has not yet been established. The purpose of this article is to evaluate the preventive effect of nuclear factor KB (NF-kappaB) decoy oligo-DNA after SAH; since NF-kappaB is closely related to inflammation. In the rabbit angiopathy model after SAH, we evaluated the effectiveness of the decoy oligo-DNA using the angiographic (digital subtraction angiography) and histological (hematoxylin-eosin and Masson's trichrome staining) methods. Moreover, a gel-shift assay for NF-kappaB was also performed in order to evaluate the activity of NF-kappaB. We describe a new concept for treating cerebral angiopathy after SAH and for successfully inhibiting cerebral vasospasm and morphological changes in vessel walls in a rabbit model. In this treatment, we used synthetic double-strand oligo-DNA with a high affinity for transcription factor NF-kappaB, and cationic liposome complex administered through the cerebrospinal fluid.