Vascular smooth muscle function: The physiology and pathology of vasoconstriction

Impact of post-thrombectomy isolated subarachnoid hemorrhage on neurological outcomes in patients with anterior ischemic stroke - a retrospective single-center observational study

PURPOSE

We aimed to investigate the impact of post-thrombectomy isolated subarachnoid hemorrhage (i-SAH) and other types of intracranial hemorrhage (o-ICH) on patient's neurological outcomes.

METHODS

Stroke data from 2018 to 2022 in a tertiary care center were retrospectively analyzed. Patients with large vessel occlusion from ICA to M2 branch were included. Post-thrombectomy intracranial hemorrhages at 24 h were categorized with Heidelberg Bleeding Classification. Neurological impairment of patients was continuously assessed at admission, at 24 h, 48 h and 72 h, and at discharge. Predictors of i-SAH and o-ICH were assessed.

RESULTS

297 patients were included. i-SAH and o-ICH were found in 12.1% (36/297) and 11.4% (34/297) of patients. Overall, NIHSS of i-SAH patients at discharge were comparable to o-ICH patients (median 22 vs. 21, p = 0.889) and were significantly higher than in non-ICH patients (22 vs. 7, p < 0.001). i-SAH often resulted in abrupt deterioration of patient's neurological symptoms at 24 h after thrombectomy. Compared to non-ICH patients, the occurrence of i-SAH was frequently associated with worse neurological outcome at discharge (median NIHSS increase of 4 vs. decrease of 4, p < 0.001) and higher in-hospital mortality (41.7% vs. 23.8%, p = 0.022). Regardless of successful reperfusion (TICI 2b/3), the beneficial impact of thrombectomy appeared to be outweighed by the adverse effect of i-SAH. Incomplete reperfusion and shorter time from symptom onset to admission were associated with higher probability of i-SAH, whereas longer procedure time and lower baseline ASPECTS were predictive for o-ICH occurrence.

CONCLUSION

Post-thrombectomy isolated subarachnoid hemorrhage is a common complication with significant negative impact on neurological outcome.

Hesperetin Inhibits Sphingosylphosphorylcholine-Induced Vascular Smooth Muscle Contraction by Regulating the Fyn/Rho-Kinase Pathway

ABSTRACT

Cardiovascular diseases are the leading cause of mortality and disability worldwide. We have previously found that sphingosylphosphorylcholine (SPC) is the key molecule leading to vasospasm. We have also identified the SPC/Src family protein tyrosine kinase Fyn/Rho-kinase (ROK) pathway as a novel signaling pathway for Ca2+ sensitization of vascular smooth muscle (VSM) contraction. This study aimed to investigate whether hesperetin can inhibit the SPC-induced contraction with little effect on 40 mM K+-induced Ca2+-dependent contraction and to elucidate the underlying mechanisms. Hesperetin significantly inhibited the SPC-induced contraction of porcine coronary artery smooth muscle strips with little effect on 40 mM K+-induced contraction. Hesperetin blocked the SPC-induced translocation of Fyn and ROK from the cytosol to the membrane in human coronary artery smooth muscle cells (HCASMCs). SPC decreased the phosphorylation level of Fyn at Y531 in both VSMs and HCASMCs and increased the phosphorylation levels of Fyn at Y420, myosin phosphatase target subunit 1 at T853, and myosin light chain (MLC) at S19 in both VSMs and HCASMCs, which were significantly suppressed by hesperetin. Our results indicate that hesperetin inhibits the SPC-induced contraction at least in part by suppressing the Fyn/ROK pathway, suggesting that hesperetin can be a novel drug to prevent and treat vasospasm.

Interleukin-10 in the Vasculature: Pathophysiological Implications

Interleukin-10 (IL-10) is an important immunomodulatory cytokine, initially characterized as an anti-inflammatory agent released by immune cells during infectious and inflammatory processes. IL-10 exhibits biological functions that extend to the regulation of different intracellular signaling pathways directly associated with vascular function. This cytokine plays a vital role in vascular tone regulation through the change of important proteins involved in vasoconstriction and vasodilation. Numerous investigations covered here have shown that therapeutic strategies inducing IL-10 result in anti-inflammatory, anti-hypertrophic, antihyperplastic, anti-apoptotic and antihypertensive effects. This non-systematic review summarizes the modulating effects mediated by IL-10 in vascular tissue, particularly on vascular tone, and the intracellular pathway induced by this cytokine. We also highlight the advances in IL-10 manipulation as a therapeutic target in different cardiovascular pathophysiologies, including the physiological implications in animals and humans. Finally, the review illustrates current and potential future perspectives of the potential use of IL-10 in clinical trials, based on the clinical evidence.

Structure and function of resistance arteries from BB-creatine kinase and ubiquitous Mt-creatine kinase double knockout mice

Increasing evidence indicates that the enzyme creatine kinase (CK) is intimately involved in microvascular contractility. The mitochondrial isoenzyme catalyses phosphocreatine synthesis from ATP, while cytoplasmic CK, predominantly the BB isoenzyme in vascular tissue, is tightly bound near myosin ATPase, where it favours ATP production from phosphocreatine to metabolically support vascular contractility. However, the effect of CK gene inactivation on microvascular function is hitherto unknown. We studied functional and structural parameters of mesenteric resistance arteries isolated from 5 adult male mice lacking cytoplasmic BB-CK and ubiquitous mitochondrial CK (CK-/-) vs 6 sex/age-matched controls. Using a Mulvany Halpern myograph, we assessed the acute maximum contractile force with 125 mM K⁺ and 10^-5 M norepinephrine, and the effect of two inhibitors, dinitrofluorobenzene, which inhibits phosphotransfer enzymes (0.1 μM), and the specific adenylate kinase inhibitor P1, P5-di(adenosine 5') pentaphosphate (10^-6 to 10^-5 M). WT and CK-/- did not significantly differ in media thickness, vascular elasticity parameters, or acute maximum contractile force. CK-/- arteries displayed greater reduction in contractility after dinitrofluorobenzene 38%; vs 14% in WT; and after AK inhibition, 14% vs 5.5% in WT, and displayed abnormal mitochondria, with a partial loss of the inner membrane. Thus, CK-/- mice display a surprisingly mild phenotype in vascular dysfunction. However, the mitochondrial abnormalities and greater effect of inhibitors on contractility may reflect a compromised energy metabolism. In CK-/- mice, compensatory mechanisms salvage energy metabolism, as described for other CK knock-out models.

Pharmacological characterization of the cardiovascular effect of Nibethione: ex vivo, in vivo and in silico studies

OBJECTIVE

This work describes the vasorelaxant and antihypertensive effects and the mechanism of action on vascular smooth muscle cells of Nibethione, a synthetic thiazolidinedione derivative. Additionally, evidence of its cytotoxicity is assessed.

METHODS

Nibethione (NB) was synthesized, and its vasorelaxant effect and mechanism of action were assessed through ex vivo experiments. Molecular docking studies were used to predict the mode of interaction with L-type Ca²⁺ channel, and in vivo antihypertensive activity was assayed on spontaneously hypertensive rats (SHR). The cytotoxicity potential was evaluated in porcine aortic endothelial cells (PAECs) from primary explants.

KEY FINDINGS

Nibethione vasorelaxant effect was efficient on KCl (80 mm) and NE-contraction. This effect was deleteriously modified in the presence of potassium channel block drugs, while the maximal contraction induced with NE was significantly decreased by NB; the CaCl₂ -induced contraction was abolished entirely. In vivo experiments showed that NB decreased diastolic blood pressure in 20.3 % after its administration on SHR. The molecular docking showed that NB blocks L-type Ca²⁺ channel, and in vitro tests showed that NB did not produce cytotoxic activity on PAECs (IC₅₀ >1000 µm).

CONCLUSIONS

Nibethione showed in vivo antihypertensive and ex vivo vasorelaxant effects with implication of voltage-dependent L-type Ca²⁺ channel blocking, and this may contribute to the research of novel antihypertensive drugs.

Hypermetabolism and impaired endothelium-dependent vasodilation in mesenteric arteries of type 2 diabetes mellitus db/db mice

Besides being a metabolic disease, diabetes is considered a vascular disease as many of the complications relate to vascular pathologies. The aim of this study was to investigate how vascular tone and reactivity and vascular cell metabolism were affected in type 2 diabetes mellitus and whether β-hydroxybutyrate could have a positive effect as alternative energy substrate. Isolated mesenteric arteries of db/db and control mice were incubated in media containing [U-¹³C]glucose or [U-¹³C]β-hydroxybutyrate, and tissue extracts were analysed by mass spectrometry. Functional characterization was performed by wire myography to assess vasodilation and vasocontraction. Hypermetabolism of glucose and β-hydroxybutyrate was observed for mesenteric arteries of db/db mice; however, hypermetabolism was significant only with β-hydroxybutyrate as energy substrate. The functional characterization showed impaired endothelial-dependent vasodilation in mesenteric arteries of the db/db mice, whereas the contractility was unaffected. This study provides evidence that the endothelial cells are impaired, whereas the vascular smooth muscle cells are more robust and seemed less affected in the db/db mouse. Furthermore, the results indicate that hypermetabolism of energy substrates may be due to adaptive changes in the mesenteric arteries.

Creatine kinase, energy reserve, and hypertension: from bench to bedside

We hypothesized that human variation in the activity of the ATP regenerating enzyme creatine kinase (CK) activity affects hypertension and cardiovascular disease risk. CK is tightly bound close to ATP-utilizing enzymes including Ca2+-ATPase, myosin ATPase, and Na+/K+-ATPase, where it rapidly regenerates ATP from ADP, H+, and phosphocreatine. Thus, relatively high CK was thought to enhance ATP-demanding processes including resistance artery contractility and sodium retention, and reduce ADP-dependent functions. In a series of studies of our group and others, CK was linked to hypertension and bleeding risk. Plasma CK after rest, used as a surrogate measure for tissue CK, was associated with high blood pressure and failure of antihypertensive therapy in case-control and population studies. Importantly, high tissue CK preceded hypertension in animal models and in humans, and human vascular tissue CK gene expression was strongly associated with clinical blood pressure. In line with this, CK inhibition substantially reduced the contractility of human resistance arteries ex vivo. We also presented evidence that plasma CK reduced ADP-dependent platelet aggregation. In subsequent intervention studies, the oral competitive CK inhibitor beta-guanidinopropionic acid (GPA) reduced blood pressure in spontaneously hypertensive rats (SHRs), and a 1-week trial of sub-therapeutic dose GPA in healthy men was uneventful. Thus, based on theoretical concepts, evidence was gathered in laboratory, case-control, and population studies that high CK is associated with hypertension and with bleeding risk, potentially leading to a new mode of cardiovascular risk reduction with CK inhibition.

Add-on therapy with traditional Chinese medicine: An efficacious approach for lipid metabolism disorders

Add-on therapy with traditional Chinese medicine (TCM) has been extensively researched in the intractable diseases, such as asthma, cancer, and Alzheimer's disease. As an entirely new concept, add-on therapy of TCM has been also used to prevent and treat hyperlipidemia via lowering cholesterol level. However, the efficacy of add-on therapy with TCM for mediating lipid metabolism disorders remains controversial. In this review, we summarize and provide strong evidence that add-on therapy of TCM as a novel approach is efficacious and safe for hyperlipidemia associated diseases based on the mediation of lipid metabolism disorders.

Whole body vibration at different exposure frequencies: infrared thermography and physiological effects

The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3 ± 2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regions and both feet was determined using Von Frey monofilaments. Postural sway was measured using a force plate. Cutaneous temperature was obtained with an infrared camera. WBV influences the discharge of the skin touch-pressure receptors, decreasing sensitivity at all measured frequencies and foot regions (P ≤ 0.05). Regarding balance, no differences were found after 20 minutes of WBV at frequencies of 31 and 35 Hz. At 40 and 44 Hz, participants showed higher anterior-posterior center of pressure (COP) velocity and length. The cutaneous temperature of the lower limbs decreased during and 10 minutes after WBV. WBV decreases touch-pressure sensitivity at all measured frequencies 10 min after exposure. This may be related to the impaired balance at higher frequencies since these variables have a role in maintaining postural stability. Vasoconstriction might explain the decreased lower limb temperature.

Creatine kinase is associated with failure of hypertension treatment

BACKGROUND

Failure of hypertension treatment is a major clinical issue because of the high prevalence and the associated mortality risk. We have reported evidence that creatine kinase increases blood pressure through greater sodium retention and cardiovascular contractility, by rapidly providing ATP for these functions. Therefore, we hypothesized that high creatine kinase is associated with failure of antihypertensive treatment.

METHOD

We analyzed a cross-sectional, random multiethnic sample of the general population (N = 1444), aged 34-60 years. The primary outcome was the independent association between resting serum creatine kinase and treated uncontrolled hypertension in the population, using multinomial logistic regression analysis.

RESULTS

Hypertension prevalence was, respectively, 26.8; 30.8; and 41.2% for the lowest (<88  IU/l) through the highest population creatine kinase tertile (>145  IU/l; P < 0.001). Treatment failed in 72.9% of participants within the highest creatine kinase tertile vs. 46.7% within the lowest tertile (P = 0.004). In logistic regression analysis, creatine kinase was the main predictor of treatment failure (adjusted odds ratio 3.7; 95% confidence interval 1.2-10.9), independent of age, sex, BMI, fasting glucose, ethnicity, or education level.

CONCLUSION

Creatine kinase is associated with failure of antihypertensive therapy. Further investigations concerning this association might help improve treatment strategies for difficult-to-treat hypertension.

Role of bilirubin oxidation products in the pathophysiology of DIND following SAH

Despite intensive research efforts, by our own team and many others, the molecules responsible for acute neurological damage following subarachnoid hemorrhage (SAH) and contributing to delayed ischemic neurological deficit (DIND) have not yet been elucidated. While there are a number of candidate mechanisms, including nitric oxide (NO) scavenging, endothelin-1, protein kinase C (PKC) activation, and rho kinase activation, to name but a few, that have been investigated using animal models and human trials, we are, it seems, no closer to discovering the true nature of this complex and enigmatic pathology. Efforts in our laboratory have focused on the chemical milieu present in hemorrhagic cerebrospinal fluid (CSF) following SAH and the interaction of the environment with the molecules generated by SAH and subsequent events, including NO scavenging, immune response, and clot breakdown. We have identified and characterized a group of molecules formed by the oxidative degradation of bilirubin (a clot breakdown product) and known as BOXes (bilirubin oxidation products). We present a synopsis of the characterization of BOXes as found in human SAH patients' CSF and the multiple signaling pathways by which BOXes act. In summary, BOXes are likely to play an essential role in the etiology of acute brain injury following SAH, as well as DIND.

Bilirubin oxidation products seen post subarachnoid hemorrhage have greater effects on aged rat brain compared to young

INTRODUCTION

We have previously shown that novel oxidation products of Bilirubin, called Bilirubin oxidation products (BOXes), are found in humans and animal models post subarachnoid hemorrhage. We have also proposed that BOXes may play a role in the pathogenesis and clinical complications post SAH. In this study we report on the direct toxicity effects of BOXes on rat brain.

METHODS

Identical volumes of either vehicle (normal saline) or BOXes (30 μl of a 20 μM solution) were applied above the dura through a cranial window of young (approximately 7-13 weeks) and aged (approximately 12-18 months) adult male Sprague Dawley rats (Charles River, Wilmington, MA, USA). To determine the extent of BOX-mediated injury, histology and immunocytochemistry were performed at 1, 2, 4, and 7 days post-surgical application of BOXes. We assessed the area of stress gene induction of HSP25/27 and HSP32. Immunohistochemistry was performed using standard avidin-biotin techniques. A monoclonal antibody to HSP25/27 (StressGen, Victoria, British Columbia, Canada), a monoclonal antibody to HSP32/HO-1 (StressGen), and a polyclonal HSP 32/HO-1 antibody were used for the immunocytochemistry.

RESULTS

A single dose of BOXes produced substantial increases in HSP25 and HO-1 in the aged rats at all early time points (≤4 days). After 7 days all groups were not significantly different than saline control. Young rats were resistant to BOXes effects compared to saline control with trends towards increased stress gene expression caused by BOXes that did not reach statistical significance.

CONCLUSION

We conclude from these studies that BOXes have direct effects on stress gene expression of the cortex post single dose application and that this can be seen for several days with apparent resolution at about 7 days. If BOXes are produced at similar levels in patients, the latency and duration of some SAH complications are consistent with these results.

Ethnic differences in resistance artery contractility of normotensive pregnant women

Black women are at a greater risk to develop hypertension during pregnancy, with a 4.5 times higher rate of fatal preeclampsia than white women. Therefore, it is important to identify factors that may affect this risk. Our group previously proposed that high activity of the central regulatory enzyme of energy metabolism, creatine kinase (CK), may increase ATP-buffering capacity and lead to enhanced vascular contractility and reduced nitric oxide bioavailability. Therefore, we assessed microvascular contractility characteristics in isolated resistance arteries from self-defined black and white normotensive pregnant women using a Mulvany-Halpern myograph. Additionally, morphology was assessed with electron microscopy. Resistance-sized arteries obtained from omentum donated during cesarean sections (11 black women and 20 white women, mean age: 34 yr) studied in series showed similar morphology but significantly greater maximum contractions to norepinephrine (10(-5) M) in blacks [14.0 mN (1.8 SE)] compared with whites [8.9 mN (1.4 SE), P = 0.02]. Furthermore, we found greater residual contractility after the specific CK inhibitor dinitrofluorobenzene (10(-6) M) in black women [55% (6 SE)] compared with white women [28% (4 SE), P = 0.001] and attenuated vasodilation after bradykinin (10(-7) M) in black women [103% (6 SE)] compared with white women [84% (5 SE), P = 0.023], whereas responses to sodium nitroprusside (10(-4) M) and amlodipine (10(-6) M) were similar. We conclude that compared with white women, normotensive pregnant black women display greater resistance artery contractility and evidence of higher vascular CK activity with attenuated nitric oxide synthesis. These findings in normotensives may imply that the black population is at risk for a further incline in pregnancy-related hypertensive disorders.

Studying protein phosphorylation in low MW CSF fractions with capLC-ICPMS and nanoLC-CHIP-ITMS for identification of phosphoproteins

An initial study of protein phosphorylation in human cerebral spinal fluid (CSF) is described. CSF is an important body fluid for study of proteins and metabolites and may lead to the ultimate development of molecular markers to predict neurological diseases or their complications, such as in the case of hemorrhagic stroke. The use of capillary liquid chromatography coupled to inductively coupled plasma mass spectrometry (capLC-ICPMS) for screening using (31)P as the internal elemental tag atom at ultratrace levels, in combination with molecular mass spectrometry using Spectrum Mill and MASCOT database search engines for peptide identification, is a novel approach in its application to CSF relevant phosphopeptides and phosphorylated proteins. CapLC-ICPMS combined with nano liquid chromatography electrospray ionization, ion trap mass spectrometry (nanoLC-CHIP/ITMS), was utilized for initial experiments with CSF. Specific low-level screening for (31)P containing compounds is accomplished, and nanoLC-CHIP/ITMS provided the corresponding peptide information and subsequent protein identifications. The fractions containing (31)P from screening by the capLC-ICPMS were collected offline and analyzed separately with nanoLC-CHIP/ITMS. Synthetic phosphopeptides were used to test the method and to estimate lowest quantifiable limits for phosphorus. Tryptically digested beta-casein was then used to demonstrate the viability of the methodology for the complex CSF matrix from hemorrhagic stroke patients while also analyzing for native phosphopeptides in the CSF.

PKC and Rho in vascular smooth muscle: activation by BOXes and SAH CSF

Cerebral vasospasm (CV) remains a significant cause of delayed neurological deficit and ischemic damage after subarachnoid hemorrhage (SAH), despite intensive research effort. The current lack of an effective therapeutic approach is somewhat due to our lack of understanding regarding the mechanism by which this pathological constriction develops. Recent evidence implicates bilirubin oxidation products (BOXes) in the etiology of CV after SAH: BOXes are found in cerebrospinal fluid from SAH patients with symptomatic or angiographically visible vasospasm (CSFV) but not in CSF from SAH patients with no vasospasm (CSFC). We have previously published research suggesting that the etiology of CV comprises two components: a physiological stimulation to constrict and a pathological failure to relax. Both these components are elicited by CSFV, but not CSFC, and BOXes synthesized in the laboratory potentiate physiological constriction in arterial smooth muscle in vitro, and elicit contraction in pial arteries in vivo. In this paper, we will present our results concerning the action of BOXes on arterial smooth muscle constriction, compared with CSFV. We will also present evidence implicating temporal changes in PKC isoforms and Rho expression in both BOXes- and CSFV-elicited smooth muscle responses.

Brazilein-induced contraction of rat arterial smooth muscle involves activation of Ca2+ entry and ROK, ERK pathways

Brazilein (6a,7-dihydro-3,6a,10-trihydroxy-benz[b]indeno[1,2-d]pyran-9(6H)-one) is a compound isolated from Caesalpinia sappan. The vasoactivities of brazilein were evaluated in isolated rat thoracic aorta. The results showed that brazilein can dose-dependently induce contraction of rat thoracic aorta in the resting and phenylephrine pre-evoked state. The average response to 100 microM of brazilein was 30% of the 50 mM KCl contraction, 26% of the 10 muM phenylephrine and 116% of the 20 mM caffeine contraction in comparison. The effects of vasocontraction were proved not to be endothelial dependent and could not be inhibited by alpha-adrenergic receptor blocker phentolamine, beta-adrenergic receptor blocker propranolol, M-adrenaline receptor blocker atropine, angiotensin II receptor blocker losartan or the non-selective nitric oxide synthase (NOS) inhibitor NG-Nitro-L-Arginine Methyl Ester (L-NAME). However the influx of extracellular calcium seemed to be required for this action, because depletion of extracellular calcium and the addition of L-type calcium ion channel antagonist (nimodipine and diltiazem), calcium ion channel activator (BAY-K8644) and potassium ion channel opener (pinacidil) could significantly affect the contraction induced by brazilein. We also investigated the possible signal mechanisms underlying brazilein-induced contraction using selective inhibitors. The inhibitors of myosin light chain kinase (MLCK), Rho-kinase (ROK) and extracellular signal regulated kinase (ERK) can suppress the effect of brazilein respectively, whereas inhibitors of other signaling or receptor molecules such as protein kinase C (PKC) and inositol 1,4,5-triphosphate (IP3) receptor had no effect. All these results demonstrated that brazilein can induce contraction of rat aorta, that the Ca2+ influx, ROK and ERK signal pathways and MLCK activation must be involved in the contractile processes.

Leflunomide prevents vasospasm secondary to subarachnoid haemorrhage

BACKGROUND

Though cerebral vasospasm is one of the most serious complications of subarachnoid haemorrhage (SAH), its complex pathogenesis is poorly understood and available clinical treatment options are unsatisfactory. This study was designed to examine the efficacy of leflunomide, an immunomodulatory agent with inhibitory properties, on vascular smooth muscle cell proliferation and inflammation in a rabbit cerebral vasospasm model.

METHODS

Twenty-two adult New-Zealand rabbits were assigned to 4 groups: control, SAH, SAH plus vehicle, SAH plus leflunomide. Subarachnoid haemorrhage was induced by administration of 1 ml of fresh unheparinised autologous arterial blood into the cisterna magna. Oral leflunomide (2 mg/kg) or vehicle treatment was started 12 h after the induction of subarachnoid haemorrhage and administered once a day. Three days later, the animals were sacrificed and the basilar artery was examined histologically for the lumen area and the thickness of the vessel wall. Inflammatory reaction was also examined by counting white blood cells within the vessel wall by means of light microscopic examination using haematoxylin and eosin staining.

FINDINGS

Severe and moderate vasospasms were detected in the basilar artery of the SAH and SAH plus vehicle treated groups, respectively. Leflunomide effectively reduced the vasospasm of the basilar artery. Compared to the vehicle treated group, leflunomide significantly reduced the lumen area (p < 0.01) and hyperplasia of the vessel wall (p < 0.01). Although inflammatory response within the vessel wall was reduced in the leflunomide treated group, no statistical significance was found between groups (p = 0.07).

CONCLUSION

This study demonstrates for the first time that leflunomide treatment attenuates cerebral vasospasm in a rabbit SAH model while inflammatory reaction in the vessel wall is not affected. Although further studies are needed to reveal its molecular mechanisms in relieving vasospasm, leflunomide may provide a therapeutic potential for human cerebral vasospasm induced by SAH.

An in vitro model of aneurysmal subarachnoid hemorrhage: oxidation of unconjugated bilirubin by cytochrome oxidase

Aneurysmal subarachnoid hemorrhage is a stroke subtype with high rates of mortality and morbidity. Cerebral vasospasm can lead to ischemic injury or death and is a common complication of aneurysmal subarachnoid hemorrhage, usually occurring 3-9 days afterwards. The cause of vasospasm is not known. Recently, there has been strong evidence that vasoactive oxidation products of bilirubin may be involved. Currently, the factors that lead to bilirubin oxidation are poorly characterized. In this study, we have designed an in vitro model of hemorrhagic stroke in order to investigate conditions that promote the oxidation of bilirubin to form vasoactive compounds. Using our model, we created a basic hematoma system of blood, CSF, and hemeoxygenase-1. We manipulated this system in various ways, incubated it and determined the concentration of vasoactive bilirubin oxidation products that resulted. Conditions where cytochrome oxidase was stimulated caused an increase bilirubin oxidation products (292.6 +/- 39.9 micromol/L respectively, vs. 79.3 +/- 1.3 micromol/L for the basic reaction, p < 0.05), which was attenuated by cyanide. Our data suggest that bilirubin oxidation products may be produced by oxidation(s) requiring an oxygen-utilizing enzyme like cytochrome oxidase.

Increased vascular contractility in isolated vessels from cigarette smoking rats is mediated by basal endothelin release

The effect of chronic cigarette smoking on endothelin modulation of vascular contraction, and CYP enzyme levels was studied in 20 male Sprague-Dawley rats. The animals were divided equally into smoking and non-smoking groups. The smoking group was exposed to 6 research cigarettes per rat per day 5 days a week for 16 weeks. The control group was sham smoked. Functional contractile studies were performed in aortas and carotid arteries to determine the regulation of vascular tone by basal release of endothelin. Liver samples were analyzed for CYP1A1 and CYP1A2 gene expression by RT-PCR. Plasma samples were assessed for endothelin-1 (ET-1) level by enzyme immuno assay (EIA). Treatment of aortas and carotid arteries with bosentan, the dual endothelin receptor antagonist, caused a significant reduction in constrictor responses of smoking rats, indicating, increase greater regulation of tone by endothelin in smoker rats compared to controls. There was a greater expression of the cytochrome P450-liver enzymes (CYP1A1 and CYP1A2) in smoker rats. Body weight gain was also significantly decreased in smoker rats. We conclude that increased endothelin release in smoker rats significantly contributes to increased arterial tone and so contribute to the cardiovascular pathophysiology associated with cigarette smoking, such as increased vascular muscularization, increased contraction, decreased dilation and possibly vasospasm.

Bilirubin oxidation products (BOXes) and their role in cerebral vasospasm after subarachnoid hemorrhage

Many factors have been postulated to cause delayed subarachnoid hemorrhage (SAH)-induced vasospasm, including hemoglobin, nitric oxide, endothelin, and free radicals. We propose that free radicals (because of the high levels that are produced in the blood clots surrounding blood vessels after SAH) act on bilirubin, biliverdin, and possibly heme to produce BOXes (Bilirubin OXidized Products). Bilirubin oxidation products act on vascular smooth muscle cells to produce chronic vasoconstriction and vasospasm combined with a vasculopathy because of smooth muscle cell injury. This review summarizes recent evidence that BOXes play a role in SAH-induced vasospasm. The data supporting a role for BOXes includes (1) identification of molecules in cerebrospinal fluid (CSF) of patients with vasospasm after SAH that have structures consistent with BOXes; (2) BOXes are vasoactive in vitro and mimic the biochemical actions of CSF of patients with vasospasm; (3) BOXes are vasoactive in vivo, constricting rat cerebral vessels; and (4) there is a correlation between clinical occurrence of vasospasm and BOXes concentration in our preliminary study of patients with SAH. Since oxidation of bilirubin, biliverdin, and perhaps heme is proposed to produce BOXes that contribute to vasospasm, either blocking bilirubin formation, inactivating bilirubin or BOXes, or removing all of the blood clot before vasospasm are potential treatment targets.

Antihypertensive action of 2-hydroxyoleic acid in SHRs via modulation of the protein kinase A pathway and Rho kinase

Olive oil consumption leads to high monounsaturated fatty acid intake, especially oleic acid, and has been associated with a reduced risk of hypertension. However, the molecular mechanisms and contribution of its different components to lower blood pressure (BP) require further evaluation. Here, we examined whether a synthetic, non-beta-oxidation-metabolizable derivative of oleic acid, 2-hydroxyoleic acid (2-OHOA), can normalize BP in adult spontaneously hypertensive rats (SHRs) and whether its antihypertensive action involves cAMP-dependent protein kinase A (PKA) and Rho kinase, two major regulators of vascular smooth muscle contraction. Oral administration of 2-OHOA to SHRs induced sustained systolic BP decreases in a time-dependent (1-7 days) and dose-dependent (100-900 mg/kg every 12 h) manner. After 7 days of treatment with 2-OHOA (600 mg/kg), the systolic BP of SHRs was similar to that of normotensive Wistar Kyoto rats, returning to its initial hypertensive level after withdrawal of 2-OHOA. This treatment strongly increased the protein expression of the catalytic and regulatory RIalpha and RIIalpha PKA subunits as well as PKA activity in aortas from SHRs. Consistently, administration of the PKA inhibitor 8-bromo adenosine-3',5'-cyclic monophosphorothioate, Rp isomer, to 2-OHOA-treated SHRs induced a pronounced reversal (up to 59%) of the antihypertensive effect of 2-OHOA. Additionally, 2-OHOA completely reversed the pathological overexpression of aortic Rho kinase found in SHRs, suppressing the vasoconstrictory Rho kinase pathway.

Effects of common medications on cerebral vasospasm after subarachnoid haemorrhage

Cerebral vasospasm is a common and serious complication of aneurysmal subarachnoid haemorrhage (SAH). At present, no consistently effective preventative and therapeutic measures are available, perhaps because of incomplete understanding of the pathogenesis of vasospasm. Experimental studies provide evidence that the incidence and severity of vasospasm after SAH can be modulated by drugs that affect neurotransmitter levels, intracellular signalling mechanisms, vascular smooth muscle function, inflammation and cellular proliferation, and the concentration of 'spasmogenic' factors. Preliminary clinical studies indicate that some illicit drugs and common prescription medications can have similar effects in humans. Recognition of these pharmacological effects is important because medications that can worsen or alleviate vasospasm are frequently administered to SAH patients to treat coincident medical problems.