Protein synthesis and immunoreactivities of contraction-related proteins in smooth muscle cells of canine basilar artery after experimental subarachnoid hemorrhage

SIRT-associated attenuation of cellular senescence in vascular wall

This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.

Oxidative Stress, Reductive Stress and Antioxidants in Vascular Pathogenesis and Aging

This review is focused on the mechanisms that regulate health, disease and aging redox status, the signal pathways that counteract oxidative and reductive stress, the role of food components and additives with antioxidant properties (curcumin, polyphenols, vitamins, carotenoids, flavonoids, etc.), and the role of the hormones irisin and melatonin in the redox homeostasis of animal and human cells. The correlations between the deviation from optimal redox conditions and inflammation, allergic, aging and autoimmune responses are discussed. Special attention is given to the vascular system, kidney, liver and brain oxidative stress processes. The role of hydrogen peroxide as an intracellular and paracrine signal molecule is also reviewed. The cyanotoxins β-N-methylamino-l-alanine (BMAA), cylindrospermopsin, microcystins and nodularins are introduced as potentially dangerous food and environment pro-oxidants.

Dual thick and thin filament linked regulation of stretch- and L-NAME-induced tone in young and senescent murine basilar artery

Stretch-induced vascular tone is an important element of autoregulatory adaptation of cerebral vasculature to maintain cerebral flow constant despite changes in perfusion pressure. Little is known as to the regulation of tone in senescent basilar arteries. We tested the hypothesis, that thin filament mechanisms in addition to smooth muscle myosin-II regulatory-light-chain-(MLC20)-phosphorylation and non-muscle-myosin-II, contribute to regulation of stretch-induced tone. In young BAs (y-BAs) mechanical stretch does not lead to spontaneous tone generation. Stretch-induced tone in y-BAs appeared only after inhibition of NO-release by L-NAME and was fully prevented by treatment with 3 μmol/L RhoA-kinase (ROK) inhibitor Y27632. L-NAME-induced tone was reduced in y-BAs from heterozygous mice carrying a point mutation of the targeting-subunit of the myosin phosphatase, MYPT1 at threonine696 (MYPT1-T696A/+). In y-BAs, MYPT1-T696A-mutation also blunted the ability of L-NAME to increase MLC20-phosphorylation. In contrast, senescent BAs (s-BAs; >24 months) developed stable spontaneous stretch-induced tone and pharmacological inhibition of NO-release by L-NAME led to an additive effect. In s-BAs the MYPT1-T696A mutation also blunted MLC20-phosphorylation, but did not prevent development of stretch-induced tone. In s-BAs from both lines, Y27632 completely abolished stretch- and L-NAME-induced tone. In s-BAs phosphorylation of non-muscle-myosin-S1943 and PAK1-T423, shown to be down-stream effectors of ROK was also reduced by Y27632 treatment. Stretch- and L-NAME tone were inhibited by inhibition of non-muscle myosin (NM-myosin) by blebbistatin. We also tested whether the substrate of PAK1 the thin-filament associated protein, caldesmon is involved in the regulation of stretch-induced tone in advanced age. BAs obtained from heterozygotes Cald1+/− mice generated stretch-induced tone already at an age of 20–21 months old BAs (o-BA). The magnitude of stretch-induced tone in Cald1+/− o-BAs was similar to that in s-BA. In addition, truncation of caldesmon myosin binding Exon2 (CaD-▵Ex2−/−) did not accelerate stretch-induced tone. Our study indicates that in senescent cerebral vessels, mechanisms distinct from MLC20 phosphorylation contribute to regulation of tone in the absence of a contractile agonist. While in y-and o-BA the canonical pathways, i.e., inhibition of MLCP by ROK and increase in pMLC20, predominate, tone regulation in senescence involves ROK regulated mechanisms, involving non-muscle-myosin and thin filament linked mechanisms involving caldesmon.

Treatment of cerebral vasospasm with biocompatible controlled-release systems for intracranial drug delivery

OBJECTIVE

The pharmacological treatment of cerebral vasospasm (CVS) now includes the experimental use of controlled-release biocompatible compounds that deliver a desired drug locally into the subarachnoid space. A controlled-release system consists of an active material that is incorporated into a carrier, usually in the form of a pellet or a gel. With such systems, the desired agent is delivered slowly and continuously, for long periods of time, directly to the desired site. This technology makes it possible to achieve high local concentrations of therapeutic agents while minimizing systemic toxicity and circumventing the need to cross the blood-brain barrier. This review describes controlled-release systems developed to date for local drug delivery in the treatment of CVS in both animal models and humans.

METHODS

A MEDLINE PubMed database search was performed for articles published from 1975 to 2007 with the following search topics: "controlled-release system/polymer," "controlled-release implants," "cerebral vasospasm," "subarachnoid hemorrhage," "subarachnoid space," and "intracranial drug delivery."

RESULTS

Over the past several decades, several controlled-release systems (lactic/ glycolic acid pellets, ethylene vinyl acetate copolymer, liposomes, silicone elastomers) have been developed to deliver various pharmacological agents (papaverine, nicardipine, ibuprofen, nitric oxide donor, calcitonin gene-related peptide, fasudil, recombinant tissue plasminogen activator) intracranially to treat subarachnoid hemorrhage in animal models (rats, rabbits, dogs, and primates). Animal studies have shown promising results, and the few human studies that have been published using controlled-release systems with papaverine or nicardipine report similarly encouraging outcomes.

CONCLUSION

Controlled-release systems have evolved over the past few years and have been shown experimentally to be an effective strategy for the local delivery of drugs to treat CVS.

Induction of housekeeping gene expression after subarachnoid hemorrhage in dogs

Changes in gene expression are commonly assessed relative to the expression of housekeeping genes, which are assumed to remain unchanged. We tested this assumption in cerebral arteries obtained from dogs 4 and 7 days after subarachnoid hemorrhage (SAH) had been created using the double hemorrhage model. Basilar arteries were removed and examined for expression of messenger ribonucleic acid (mRNA) levels using quantitative real-time polymerase chain reaction. Cross-sections of basilar arteries were stained immunohistochemically for proliferating cell nuclear antigen (PCNA) and 4',6-diamidino-2-phenylindole (DAPI). Positively stained cells were counted and numbers obtained were normalized to the cross-sectional area. The results were compared to normal dog basilar arteries contracted pharmacologically in vitro. SAH resulted in significant vasospasm (P<0.001 for each, paired t-tests). There were significant increases in mRNA for beta-actin (441%, P=0.01), glyceraldehyde-3-phosphate dehydrogenase (566%, P=0.007) and 18S ribosomal RNA (320%, P=0.025) 7 days after SAH. Total mRNA was increased 7 days after SAH relative to genomic DNA (157%, P=0.009). There were significant increases in the number of cells in the tunica media and adventitia of arteries after SAH and a significant decrease in the media after contraction in vitro. Cells in the tunica media and adventitia labeled with PCNA were significantly increased at both times after SAH. Transcripts for housekeeping genes are increased after SAH, making standardization to them potentially invalid. The increase is due to proliferation of cells in the adventitia and increased total mRNA in the media and adventitia.

Dexamethasone preventing contractile and cytoskeletal protein changes in the rabbit basilar artery after subarachnoid hemorrhage

OBJECT

The aim of this project was to study the perturbations of four smooth-muscle proteins and an extracellular protein, type I collagen, after subarachnoid hemorrhage (SAH) and to examine the possible preventive effects of dexamethasone.

METHODS

Using a one-hemorrhage rabbit model, the authors first examined the effects of SAH on the expression of alpha-actin, h-caldesmon, vimentin, smoothelin-B, and type I collagen; second, they studied whether post-SAH systemic administration of dexamethasone (three daily injections) corrected the induced alterations. Measurements were obtained at Day 7 post-SAH. The proteins were studied by performing immunohistochemical staining and using a laser-scanning confocal microscope. Compared with control (sham-injured) arteries, the density of the media of arteries subjected to SAH was reduced for alpha-actin (-11%, p = 0.01) and h-caldesmon (-15%, p = 0.06) but increased for vimentin (+15%, p = 0.04) and smoothelin-B (+53%, p = 0.04). Among animals in which SAH was induced, arteries in those treated with dexamethasone demonstrated higher values of density for alpha-actin (+13%, p = 0.05) and h-caldesmon (+20%, p = 0.01), lower values for vimentin (-55%, p = 0.05), and nonsignificantly different values for smoothelin-B. The density of type I collagen in the adventitia decreased significantly after SAH (-45%, p = 0.01), but dexamethasone treatment had no effect on this decrease.

CONCLUSIONS

The SAH-induced alterations in the density of three of four smooth-muscle proteins were prevented by dexamethasone treatment; two of these proteins--alpha-actin and h-caldesmon--are directly related to contraction. This drug may potentially be useful to prevent certain morphological and functional changes in cerebral arteries 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.

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.

Changes of beta-actin mRNA expression in canine vasospastic basilar artery after experimental subarachnoid hemorrhage

The aim of this study was to investigate whether vascular remodeling occurs during cerebral vasospasm after subarachnoid hemorrhage (SAH). Beta-actin mRNA expression and structural change of its 3' untranslated region (UTR) which are considered a non-specific marker for vascular remodeling, were examined by Northern analysis and polymerase chain reaction analysis in a canine basilar artery after experimental SAH. The changes in the area of tunica media in the basilar artery were also examined histopathologically. Increased beta-actin mRNA expression and its structural changes of 3' UTR in the vasospastic basilar artery were markedly seen 7 and 14 days after SAH accompanied by increased area of tunica media in the basilar artery. The results suggest that vascular remodeling occurs and takes part in the luminal narrowing during cerebral vasospasm.

Oxyhemoglobin produces necrosis in cultured smooth muscle cells

OBJECT

Myonecrosis in the tunica media, which is defined morphologically, is one of the most striking alterations in the cerebral arterial wall following subarachnoid hemorrhage (SAH). In this study, oxyhemoglobin (OxyHb) was added to cultured rat aortic smooth muscle cells to determine the pattern of cell death by morphological and biochemical techniques.

METHODS

Confluent rat aortic smooth muscle cells were treated with OxyHb in a concentration- and time-dependent manner. Cell density was assayed by counting the number of cells that attached to the culture dishes after exposed to OxyHb. To identify cell death pattern, DNA analysis, electron microscopy, and Western blotting using poly (ADP-ribose) polymerase (PARP) antibody were performed.

CONCLUSIONS

OxyHb decreased cell density in a concentration- and time-dependent manner. DNA analysis showed a smear pattern characteristic of cell necrosis. Transmission electron microscopy demonstrated disintegration of cell membrane and destruction of cell organelles. No apoptotic changes, such as condensation of chromatin or apoptotic bodies were observed. Western blotting using PARP antibody revealed that 116 kDa PARP was not cleaved to 85 kDa, an apoptosis-related fragment. These results demonstrated morphologically and biochemically that OxyHb induced necrosis, not apoptosis, in cultured smooth muscle cells.

Confocal microscopic evidence of decreased alpha-actin expression within rabbit cerebral artery smooth muscle cells after subarachnoid haemorrhage

Our objective was to determine whether subarachnoid haemorrhage modifies cerebral artery smooth muscle cell phenotype and the contractile protein alpha-actin measured 7 days after haemorrhage. We used a rabbit subarachnoid haemorrhage model and immunofluorescence labelling of alpha-smooth muscle actin, vimentin and desmin. The paired comparison between the haemorrhage and sham rabbits was performed using confocal laser-scanning microscopy. We found in the haemorrhage group significantly less intense alpha-actin immunostaining (p = 0.036) and more intense vimentin immunostaining (p = 0.043) but no significant change in the intensity of desmin staining. Our results indicate an absolute decrease after subarachnoid haemorrhage in the amount of functional alpha-actin and in the light of the literature may suggest a certain degree of dedifferentiation of smooth muscle cells in the cerebral artery wall.

Microvascular endothelial dysfunction and its mechanism in a rat model of subarachnoid hemorrhage

After subarachnoid hemorrhage (SAH), large cerebral arteries are prone to vasospasm. Using a rat model of SAH, we examined whether cortical microvessels demonstrate vasomotor changes that may make them prone to spasm and whether endothelial dysfunction may account for any observed changes. Two days after percutaneous catheterization into the cisterna magna, 0.3 mL of autologous blood was injected into the subarachnoid space. The brain tissue was harvested 20 min later, and microvessels were dissected from the parietal cortex. Vasomotor responses to the thromboxane analog U46619, the protein kinase C agonist phorbol acetate, endothelin-1, adenosine diphosphate, nitroprusside, and isoproterenol were examined in vitroin cerebral arterioles from the control, sham-operated, and SAH animals. Endothelial nitric oxide synthase (NOS3) messenger RNA and protein concentration was measured by northern and western blotting, respectively. Arterioles from the SAH animals demonstrated attenuated dilation to the endothelium-dependent dilator adenosine diphosphate and accentuated constriction to endothelin-1, while responses to the other agents tested were unchanged. NOS3 protein concentration was decreased, but NOS3 messenger RNA was increased after SAH. After SAH, cortical arterioles demonstrate endothelial dysfunction, which may be the basis for microvascular spasm. This is in part related to decreased NOS3, which occurs despite an increase in its transcription.

IMPLICATIONS

Acute microvascular endothelial dysfunction may occur after subarachnoid hemorrhage and contribute to microvascular spasm.

Oxyhemoglobin produces apoptosis and necrosis in cultured smooth muscle cells

Confluent rat aortic smooth muscle cells were treated with OxyHb in a concentration- and time-dependent manner. A high concentration of OxyHb (100 microM) within 24 h decreased cell density. DNA analysis showed a smear pattern characteristic of cell necrosis. Transmission electron microscopy demonstrated disintegration of the cell membrane and destruction of cell organelles. Western blotting using PARP antibody revealed that 116 kDa PARP was not cleaved to 85 kDa, an apoptosis-related fragment. On the contrary, a low concentration of OxyHb (10 microM) produced apoptotic cell death at 72 h that was supported by DNA analysis and TUNEL staining. These results demonstrated that a high level of OxyHb induced necrosis within 24 h and a low concentration of OxyHb produced apoptosis after 72 h in cultured smooth muscle cells. Morphological alterations induced by OxyHb might contribute to the vascular wall changes in the cerebral arteries following subarachnoid hemorrhage (SAH).

Doxorubicin, an RNA synthesis inhibitor, prevents vasoconstriction and inhibits aberrant expression of endothelin-1 in the cerebral vasospasm model of the rat

A vasoconstrictor peptide, endothelin-1 (ET-1), has been identified as one of the causative substances in cerebral vasospasm after subarachnoid hemorrhage. We investigated whether doxorubicin, an RNA synthesis inhibitor, effectively suppresses induction of ET-1 in the rat vasospasm model. Blood was injected around the right femoral artery and the left one was used as an internal control. Seven days later (day 7), diameters of the right femoral arteries narrowed to about 60% and this vasoconstriction was prevented by clinical dose (0.6 mg/kg) or one third of its dose of doxorubicin injected on day 1. Reverse transcriptase-polymerase chain reaction analysis demonstrated that expression of ET-1 mRNA in the vasospastic artery was not detected in doxorubicin-treated rats. It is concluded that doxorubicin effectively inhibits aberrant expression of ET-1 in the vasospasm-destined artery in the rat.

Molecular keys to the problems of cerebral vasospasm

The mechanisms responsible for subarachnoid hemorrhage (SAH)-induced vasospasm are under intense investigation but remain incompletely understood. A consequence of SAH-induced vasospasm, cerebral infarction, produces a nonrecoverable ischemic tissue core surrounded by a potentially amenable penumbra. However, successful treatment has been inconsistent. In this review, we summarize the basic molecular biology of cerebrovascular regulation, describe recent developments in molecular biology to elucidate the mechanisms of SAH-induced vasospasm, and discuss the potential contribution of cerebral microcirculation regulation to the control of ischemia. Our understanding of the pathogenesis of SAH-induced vasospasm remains a major scientific challenge; however, molecular biological techniques are beginning to uncover the intracellular mechanisms involved in vascular regulation and its failure. Recent findings of microvascular regulatory mechanisms and their failure after SAH suggest a role in the development and size of the ischemia. Progress is being made in identifying the various components in the blood that cause SAH-induced vasospasm. Thus, our evolving understanding of the underlying molecular mechanism may provide the basis for improved treatment after SAH-induced vasospasm, especially at the level of the microcirculation.

Activation of protein kinases in canine basilar artery in vasospasm

Subarachnoid hemorrhage (SAH) often leads to a long-term narrowing of cerebra! artery called vasospasm. To understand the molecular mechanisms in vasospasm, signal transduction of tyrosine kinase pathway and phosphorylation of myosin light chain (MLC) and calponin (CaP) in the basilar artery were studied. Vasospasm was produced in the canine basilar artery by a two-hemorrhage method, and vasocontraction was induced by a local application of KCI or serotonin to the basilar artery after a transclival exposure. Intracellular substrates of tyrosine kinase pathway, including Shc, Rafl, and extracellular-regulated kinases in the basilar artery, were activated after SAH, and the activation of Shc suggests stimulation of signal transductions from tyrosine kinase receptors, G-coupled receptors, or both. The activation of tyrosine kinase pathway in vasospasm also was supported by dose-dependent dilation of the spastic basilar artery on days 0 and 7 by topical application of genistein, a tyrosine kinase inhibitor, and associated marked inhibition of tyrosine phosphorylation of intracellular substrates, including Shc. In addition, the generation of protein kinase M, catalytic fragment of protein kinase C(alpha) (PKC alpha), in vasospasm on days 0 and 7 was inhibited in response to genistein, indicating an inactivation of mu-calpain. It is suggested, therefore, that the reversal of vasospasm by genistein is closely associated with the restoration of intracellular Ca2+ levels. However, the increased activities of Raf1 and extracellular-regulated kinases in vasospasm were declined on day 7 compared with those on day 0 or 2, suggesting that the activation of tyrosine kinase pathway is more closely associated with the early stage of vasospasm than with the late stage of vasospasm. The analysis by pyrophosphate polyacrylamide gel electrophoresis (PPi-PAGE) demonstrated three MLC bands in vasospasm on days 2 and 7, as well as in KCI- and serotonin-induced vasocontraction. Since PPi-PAGE resolves smooth muscle MLC into three bands in the MLC kinase (MLCK)-mediated phosphorylation and into a single band in the PKC-mediated phosphorylation based on the phosphorylation state, the current results suggest that MLC in vasospasm is phosphorylated by MLCK but not by PKC. In basilar artery, CaP was significantly down-regulated, and in addition, significantly phosphorylated on serine and threonine residues only in vasospasm on days 2 and 7. Although the significance of CaP phosphorylations in vivo still is controversial, CaP down-regulation and phosphorylation may attenuate the inhibition of Mg(2+)-ATPase activity by CaP and induce a potential enhancement of smooth muscle contractility in delayed vasospasm. Since CaP is phosphorylated in vivo by PKC, activated PKC in vasospasm may phosphorylate CaP. Thus, SAH stimulates tyrosine kinase pathway to increase intracellular Ca2+ and activate PKC, and the former activates MLCK to phosphorylate MLC, whereas the latter phosphorylates CaP but not MLC.

Myosin light chain phosphorylation and contractile proteins in a canine two-hemorrhage model of subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) impairs both contraction and relaxation response in cerebral arteries. We tested the hypothesis that cerebral vasospasm might be ATP-independent contraction, such as latch state, and protein synthesis might be substantially downregulated due to ATP consumption after long-lasting contraction.

METHODS

Chronic cerebral vasospasm was induced in the canine 2-hemorrhage model of SAH. The normal and spastic basilar arteries were stabilized in Krebs-Henseleit solution, and contraction was induced by 30 micromol/L prostaglandin F2alpha (PGF2alpha) in vitro and in vivo. Before and at 15 minutes and 1 hour after the treatment with PGF2alpha, the levels of phosphorylated 20-kDa myosin light chain (MLC20) were measured. The time course of expression of contraction proteins actin and MLC20, and contraction-inhibiting proteins h-caldesmon and calponin was determined by immunoblotting techniques.

RESULTS

A significant vasospasm occurred in the basilar artery during days 4 to 21, most prominently on days 7 and 14. There were no significant differences in the baseline levels of phosphorylated MLC20 between normal and spastic basilar arteries. The increase in MLC20 phosphorylation by PGF2alpha was significantly attenuated in the spastic basilar artery in vitro and in vivo (P<0.05). The immunoreactivity for actin, h-caldesmon, and calponin in the spastic basilar arteries was progressively decreased until day 14 and returned to the normal level on day 21. In contrast, protein levels of MLC20 did not significantly change during days 0 to 21.

CONCLUSIONS

Chronic cerebral vasospasm closely resembles the latch state, and temporary deficiencies of contractile proteins may result from increased destruction and inhibition of protein synthesis.

Impairment in biochemical level of arterial dilative capability of a cyclic nucleotides-dependent pathway by induced vasospasm in the canine basilar artery

The authors investigated the changes and the potential of cyclic nucleotide-dependent signal transduction, which induces smooth muscle relaxation, in the basilar artery with severe vasospasm in dogs with double experimental subarachnoid hemorrhage (SAH) to explore at which biochemical level the arterial dilative capability was impaired. The amount of cyclic adenosine and guanosine monophosphates (cAMP and cGMP) decreased significantly in the basilar artery after SAH. The activities of adenylate and guanylate cyclases also were decreased significantly in the smooth muscle cells of the basilar artery 4 days after SAH. In addition to the failure of the pathways to produce cyclic nucleotides, the activities of cAMP- and cGMP-dependent protein kinases, which are representative actual enzymes that amplify the signal for vascular dilation, also significantly decreased together with the almost total loss of activation by cyclic nucleotides in the same basilar artery after SAH. It was revealed that the system for smooth muscle relaxation was impaired severely in the cerebral arteries with severe vasospasm after SAH, on the biochemical basis of significantly less vasodilative capability and in several of the steps to produce the cyclic nucleotides of intracellular signal transduction.