Constriction Of Cerebral Arteries Research Articles

Abstract 154: Clustered Vascular Endotelial Growth Factor Nanoparticles Biomaterial for the Treatment of Moyamoya Disease

Introduction: Cerebrovascular ischemia poses a substantial neurological threat due to cerebral artery constriction. Innovative solutions, such as Vascular Endothelial Growth Factor (VEGF)-infused hydrogel biomaterials, have emerged. Hydrogels, mimicking the extracellular matrix, allow controlled VEGF delivery, prompting angiogenesis, tissue repair, and enhancing conditions like moyamoya disease. This non-invasive technique carries transformative potential. Hypothesis: Our hypothesis postulates that hyaluronic acid (HA) gels, with or without VEGF, can augment endothelial cell quantities and blood flow in fore-brain ischemic mice. Methods: We divided C57/B6 mice into four groups: control, vehicle (chronic ICA occlusion and stenosis), HA gel treatment, and Cluvena ( Cl uster VE GF Na noparticle) hydrogel treatment. Brain dissection, sectioning, and CD31 and DAPI staining were performed for cellular identification. Results: Following two weeks, CD31 staining unveiled diminished endothelial cell populations in ischemic animals, significantly differing from controls. HA gel effectively restored endothelial cell counts to control levels. DAPI analysis indicated ischemic animals displayed considerably fewer DAPI-stained cells, attesting to successful ischemia induction and ensuing damage. Biomaterial intervention revived cell counts, aligning with control conditions. Intriguingly, hydrogel-only treated animals closely mirrored Cluvena outcomes in CD31 counts. Conclusions: Therapeutic angiogenic biomaterials, whether incorporating VEGF or not, hold significant potential for ischemic conditions. Cluvena efficiently reinstated endothelial cell numbers, thus unveiling potential therapeutic avenues for moyamoya, an ischemic disease with related neurological disorders or symptoms. This minimally-invasive strategy bears the promise of revolutionizing the field of brain ischemic condition therapeutics.

Progesterone protects against ethanol-induced cerebral artery constriction

Progesterone protects against ethanol-induced cerebral artery constriction

Loss- and gain-of-function mutations in the Type 1 IP3 receptor (IP3R1) affect myogenic constriction of murine cerebral resistance arteries

Myogenic reactivity in resistance arteries/arterioles in response to changing intraluminal pressure is a key physiological mechanism for the regulation of blood pressure and flow. Although IP3-mediated intracellular Ca2+ release is known to contribute to the myogenic response, a lack of selective pharmacological agents to target the predominant IP3R1 Ca2+ release channel has prevented detailed investigation of this key mechanism. Mutations in the IP3R1 known to produce either loss-of-function (LOF) or gain-of-function (GOF) phenotypes lead to cerebellar ataxia in humans, yet the effect of these mutations on the cardiovascular system remains unclear. Here, we employed a novel genetic knock-in mouse model with a single point mutation in the S6 helix of IP3R1 that confers either a LOF (D2594A) or GOF (D2594K) phenotype. In endothelium-denuded posterior cerebral arteries of 3-4 month old WT mice, myogenic vasoconstriction was evident at ≥40 mmHg, maximal at ~120 mmHg, and began to decline at >120 mmHg (n=9). In contrast, myogenic constriction was initiated at higher pressures (≥50 mmHg) and was less robust in arteries of heterozygous IP3R1 LOF mice (n=11). In GOF arteries (n=10), myogenic tone developed at a lower pressure (~20 mmHg), was maximal at ~80 mmHg, and declined at >90 mmHg. Interestingly, pressure-induced Ca2+ elevations were similar in Fura-2 loaded arteries from WT, LOF and GOF mice. Using high sensitivity western blotting, we observed a similar pressure-dependent increase in phosphorylated myosin regulatory light chain (LC20) and myosin phosphatase targeting subunit (MYPT1) at 10, 40, 80 and 120 mmHg in arteries from WT, LOF and GOF mice (n=5 each). Although phospho-MYPT1-T855 content increased with intraluminal pressure in WT and LOF arteries, it did not change in vessels of GOF mice. Elevation of intraluminal pressure (i.e., from 10 to 60 or 120 mmHg) significantly decreased G-actin content in WT arteries, did not affect G-actin content in LOF vessels, and caused a biphasic effect in GOF arteries. Stabilizing the actin cytoskeleton with 0.1 mM jasplakinolide normalized myogenic reactivity in LOF arteries and left-shifted myogenic responsiveness in WT vessels; a minimal effect was observed in GOF arteries. Both jasplakinolide and the actin depolymerizing agent latrunculin B (2 mM) inhibited myogenic tone development at intraluminal pressures > 40-60 mmHg. Taken together, these data demonstrate that genetic modification of IP3R1-mediated Ca2+ mobilization affects the myogenic response of cerebral arteries to intraluminal pressure, possibly by affecting the dynamics of the actin cytoskeleton. Functionally, the observed vascular impairments may contribute to neurological dysfunction in patients with LOF and GOF IP3R1 mutations. Funding has been provided by the Canadian Institutes of Health Research: MOP-97988 (WCC), MOP-142467 (APB), PJT-173352 (SRWC) and PJT-155963 (APB, WCC, GRG and SRWC). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Reversible Cerebral Vasoconstriction Syndrome Treated by Continuous Intravenous Milrinone

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by severe headaches, with or without other acute neurological symptoms, and diffuse segmental constriction of cerebral arteries that resolves spontaneously within 3 months.[1] It can occur spontaneously, especially in middle-aged women[1]; at least half the cases occur after exposure to vasoactive drugs or post-partum. This syndrome is often associated with a favorable outcome in 95% of cases.[1] However, the prognosis of RCVS is especially determined by stroke occurrence. Its management is inspired by what is applied in aneurysmal subarachnoid hemorrhage (aSAH), whose main complication is vasospasm and delayed cerebral ischemia (DCI). Although the physiopathology of RCVS is unclear, it appears to be distinct from aSAH. Indeed, the vasoconstriction in RCVS may be dependent on the activity and sensitivity of vascular receptors, which can lead to a more systemic effect on all brain vessels, as opposed to being dependent on the vasospasm induced by local clot lysis, as has been suggested in aSAH.[2] As cerebral arteries are densely innervated, the release of norepinephrine or neuropeptide Y from the sympathetic nerve endings may cause vasoconstrictions.[3] Angiographically, SAH-induced vasospasm is more commonly long-segmental and mainly around the bleeding focus, compared with the multiple, short-segmental, and diffuse changes seen in RCVS.[4] However, by analogy, RCVS is treated by nimodipine, and in some rare cases, the use of milrinone might be considered.[3]

Aldosterone activates cerebrovascular smooth muscle BK channels in absence of β1 subunits, yet these potentiate steroid action and thus facilitate aldosterone-induced dilation of cerebral arteries.

Calcium/voltage-gated, big conductance K+ channels (BK α subunits or slo1 proteins) modulate smooth muscle (SM) tone and thus cerebral artery diameter. In cerebral arteries, the BK current phenotype is conditioned by regulatory β1 subunits which fine-tune channel activity to tissue-specific physiology. Several physiological steroids modify BK function and may modify cerebral artery function. Thus, cholesterol and pregnenolone inhibit SM BK and evoke middle cerebral artery (MCA) constriction through recognition by slo1 whereas estradiol and cholanes activate SM BK through recognition by β1. Aldosterone is a steroid with documented vasoactive properties, yet the involvement of BK in aldosterone's cerebrovascular action and the contribution of distinct channel subunits to this action remain unknown. Here, we first used nanoscale differential scanning fluorimetry to test whether aldosterone (0.3-100 μM) could directly bind BK α or β1 subunits. Changes in temperature of onset and inflection point (indicators of protein-steroid binding) were evident at 10 and 1 µM aldosterone for α and β1. Next, MCA SM cells were enzymatically isolated from mice, and cell-free recordings were conducted to determine changes in BK activity by aldosterone. Increased activity by aldosterone was concentration-dependent: EC50 = 3 μM; ECMAX = 10 μM, at which activity increased by 20%. Consistently with this small yet reproducible SM BK activation, 10 μM aldosterone dilated MCA by 2%, independently of circulating and endothelial factors. In SM cells and MCA segments from β1-/- mice, aldosterone activated BK with reduced potency and efficacy, and vasodilation by the steroid was evoked by very high concentrations (>>10 µM). Therefore, aldosterone is able to activate SM BK in absence of β1, yet this regulatory subunit potentiates aldosterone action and thus enables subµM-µM aldosterone to dilate MCA.

Interspecies and regional variability of alcohol action on large cerebral arteries: regulation by KCNMB1 proteins.

Alcohol intake leading to blood ethanol concentrations (BEC) ≥ legal intoxication modifies brain blood flow with increases in some regions and decreases in others. Brain regions receive blood from the Willis' circle branches: anterior, middle (MCA) and posterior cerebral (PCA), and basilar (BA) arteries. Rats and mice have been used to identify the targets mediating ethanol-induced effects on cerebral arteries, with conclusions being freely interchanged, albeit data were obtained in different species/arterial branches. We tested whether ethanol action on cerebral arteries differed between male rat and mouse and/or across different brain regions and identified the targets of alcohol action. In both species and all Willis' circle branches, ethanol evoked reversible and concentration-dependent constriction (EC50s ≈ 37-86 mM; below lethal BEC in alcohol-naïve humans). Although showing similar constriction to depolarization, both species displayed differential responses to ethanol: in mice, MCA constriction was highly sensitive to the presence/absence of the endothelium, whereas in rat PCA was significantly more sensitive to ethanol than its mouse counterpart. In the rat, but not the mouse, BA was more ethanol sensitive than other branches. Both interspecies and regional variability were ameliorated by endothelium. Selective large conductance (BK) channel block in de-endothelialized vessels demonstrated that these channels were the effectors of alcohol-induced cerebral artery constriction across regions and species. Variabilities in alcohol actions did not fully matched KCNMB1 expression across vessels. However, immunofluorescence data from KCNMB1-/- mouse arteries electroporated with KCNMB1-coding cDNA demonstrate that KCNMB1 proteins, which regulate smooth muscle (SM) BK channel function and vasodilation, regulate interspecies and regional variability of brain artery responses to alcohol.

Role of the endothelial reverse mode sodium-calcium exchanger in the dilation of the rat middle cerebral artery during hypoosmotic hyponatremia

A decrease in serum sodium ion concentration below 135 mmol L−1 is usually accompanied by a decrease in plasma osmolality (hypoosmotic hyponatremia) and leads to the disorder of intracranial homeostasis mainly due to cellular swelling. Recently, using an in vitro model of hypoosmotic hyponatremia, we have found that a decrease in sodium ion concentration in the perfusate to 121 mmol L−1 relaxes the isolated rat middle cerebral artery (MCA). The aim of the present study was to explore the mechanism responsible for this relaxation. Isolated, pressurized, and perfused MCAs placed in a vessel chamber were subjected to a decrease in sodium ion concentration to 121 mmol L−1. Changes in the diameter of the vessels were monitored with a video camera. The removal of the endothelium and inhibition of nitric oxide-dependent signaling or the reverse mode sodium-calcium exchanger (NCX) were used to study the mechanism of the dilation of the vessel during hyponatremia. The dilation of the MCA (19 ± 5%, p < 0.005) in a low-sodium buffer was absent after removal of the endothelium or administration of the inhibitor of the reverse mode of sodium-calcium exchange and was reversed to constriction after the inhibition of nitric oxide (NO)/cGMP signaling. The dilation of the middle cerebral artery of the rat in a 121 mmol L−1 Na+ buffer depends on NO signaling and reverse mode of sodium-calcium exchange. These results suggest that constriction of large cerebral arteries with impaired NO-dependent signaling may be observed in response to hypoosmotic hyponatremia.

Reversible cerebral artery constriction accompanied with stroke-like episode in MELAS: A case series

ObjectiveThe pathophysiology of stroke-like episode (SLE) in mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) was uncertain, though mitochondrial metabolic crisis of cortical neurons and mitochondrial proliferation in small vessels of brain have been considered. However, the involvement of major cerebral vessels was debated. We aimed to investigate whether major cerebral vessels participate in SLE. MethodsWe retrospectively collected the clinical and neuroimaging data of MELAS patients diagnosed in our center. Through follow-up, the cases harboring reversible cerebral artery constriction on brain magnetic resonance angiography (MRA) examination were included in this study. ResultsThere were 20 patients with intact brain MRA data at acute and non-acute phases. Only 3 cases with m.3243A > G mutation were enrolled. They suffered once or twice SLEs manifesting headache, blurred vision, seizures or mental and behavior disorder. New lesions were present in temporo-parietal and/or temporo-occipital regions. Segmental stenosis at middle cerebral artery and/or posterior cerebral artery, proximal portions in particular, was ipsilateral to the lesions at acute phase in all the 3 patients, which was resolved during the subacute or chronic stages. Moreover, the SLEs lesions were located within the stenotic arteries territory. In addition, dilation at distal portions of the stenotic arteries was observed at acute phase as well in 2 patients. ConclusionReversible constriction of cerebral arteries may contribute to SLE of MELAS. MELAS should be a differential diagnosis when stenosis of major cerebral vessels is present at acute phase of SLE.

Is there a role of proinflammatory cytokines on degenerin-mediated cerebrovascular function in preeclampsia?

Preeclampsia (PE) is associated with adverse cerebrovascular effects during and following parturition including stroke, small vessel disease, and vascular dementia. A potential contributing factor to the cerebrovascular dysfunction is the loss of cerebral blood flow (CBF) autoregulation. Autoregulation is the maintenance of CBF to meet local demands with changes in perfusion pressure. When perfusion pressure rises, vasoconstriction of cerebral arteries and arterioles maintains flow and prevents the transfer of higher systemic pressure to downstream microvasculature. In the face of concurrent hypertension, loss of autoregulatory control exposes small delicate microvessels to injury from elevated systemic blood pressure. While placental ischemia is considered the initiating event in the preeclamptic cascade, the factor(s) mediating cerebrovascular dysfunction are poorly understood. Elevated plasma proinflammatory cytokines, such as tumor necrosis factor α (TNF‐α) and interleukin‐17 (IL‐17), are potential mediators of autoregulatory loss. Impaired CBF responses to increases in systemic pressure are attributed to the impaired pressure‐induced (myogenic) constriction of small cerebral arteries and arterioles in PE. Myogenic vasoconstriction is initiated by pressure‐induced vascular smooth muscle cell (VSMC) stretch. Recent studies from our laboratory group indicate that proinflammatory cytokines impair the myogenic mechanism of CBF autoregulation via inhibition of vascular degenerin proteins, putative mediators of myogenic constriction in VSMCs. This brief review links studies showing the effect of proinflammatory cytokines on degenerin expression and CBF autoregulation to the pathological cerebral consequences of preeclampsia.

Statins stimulate voltage‐gated Ca2+ channels in arterial smooth muscle cells to induce rapid vasoconstriction in resistance‐size cerebral arteries

Statins are cholesterol‐lowering drugs with a range of beneficial vascular effects. Vascular effects are believed to result from long‐term statin therapy and reduction of cholesterol and mevalonate biosynthesis, and the inhibition of mevalonate‐dependent Rho/ROCK signaling. However, no studies have investigated the direct effects of acute statin application on fresh isolated resistance cerebral arteries using therapeutic concentrations of statins. Here, we examined acute vascular effects of rosuvastatin and simvastatin on Sprague Dawley rat cerebral arteries and underlying molecular mechanisms. We used pressurized arterial myography, simultaneous measurement of vessel Ca2+ fluorescence and diameter, pharmacological modulation, RNAi, Western blotting and biotinylation. Intravascular pressure in the mounted cerebral artery segments was gradually increased to 60 mmHg to stimulate the development of myogenic tone. At 60 mmHg, cerebral arteries developed ~36% myogenic tone, after which a cumulative dose response (0.01‐1000 nM) to rosuvastatin was performed and diameter changes recorded. Our data shows that, at 0.1, 1 and 10 nM concentrations, rosuvastatin induced a potent vasoconstriction – an observation never reported previously with any statin. Intriguingly, rosuvastatin, at 100 nM and 1000 nM concentrations (supratherapeutic), abolished myogenic tone and caused robust vasodilation. Rosuvastatin‐induced vasoconstriction reached a plateau at 1 nM concentration, which was used as reference for mechanistic studies. Within 2‐3 minutes of application, rosuvastatin and simvastatin constricted cerebral arteries by ~26 μm and ~24 μm, respectively. Endothelium denudation (intact ~23 μm vs denuded ~25 μm), or mevalonate supplementation did not alter statin‐induced vasoconstriction (control ~28 μm vs mevalonate ~29 μm), suggesting endothelium‐ and HMG‐CoA reductase‐independent mechanism. In contrast, removal of extracellular Ca2+with EGTA (~6 μm) or the application of nimodipine (~5 μm), a selective blocker of smooth muscle cell voltage‐gated Ca2+ channel, CaV1.2, or siRNA knockdown of CaV1.2 each abolished cerebral artery vasoconstriction and reduced [Ca2+]i, indicating that the Ca2+ entry through CaV1.2 plays a critical role here. Application of thapsigargin, a blocker of SR/ER membrane Ca2+‐ATPase pump, SERCA, but not ryanodine, a blocker of ryanodine receptor‐mediated Ca2+ release, fully reversed statin‐induced cerebral artery constriction and reduced [Ca2+]i. Arterial biotinylation data showed that short‐term statin exposure did not alter the surface expression, distribution and function of CaV1.2 channels.Altogether, our data demonstrate that statins at therapeutic concentrations directly stimulate smooth muscle cell CaV1.2 and Ca2+ influx to induce rapid vasoconstriction in resistance cerebral arteries.

A Central Role for TRPM4 in Ca2+-Signal Amplification and Vasoconstriction.

Transient receptor potential melastatin-4 (TRPM4) is activated by an increase in intracellular Ca2+ concentration and is expressed on smooth muscle cells (SMCs). It is implicated in the myogenic constriction of cerebral arteries. We hypothesized that TRPM4 has a general role in intracellular Ca2+ signal amplification in a wide range of blood vessels. TRPM4 function was tested with the TRPM4 antagonist 9-phenanthrol and the TRPM4 activator A23187 on the cardiovascular responses of the rat, in vivo and in isolated basilar, mesenteric, and skeletal muscle arteries. TRPM4 inhibition by 9-phenanthrol resulted in hypotension and a decreased heart rate in the rat. TRPM4 inhibition completely antagonized myogenic tone development and norepinephrine-evoked vasoconstriction, and depolarization (high extracellular KCl concentration) evoked vasoconstriction in a wide range of peripheral arteries. Vasorelaxation caused by TRPM4 inhibition was accompanied by a significant decrease in intracellular Ca2+ concentration, suggesting an inhibition of Ca2+ signal amplification. Immunohistochemistry confirmed TRPM4 expression in the smooth muscle cells of the peripheral arteries. Finally, TRPM4 activation by the Ca2+ ionophore A23187 was competitively inhibited by 9-phenanthrol. In summary, TRPM4 was identified as an essential Ca2+-amplifying channel in peripheral arteries, contributing to both myogenic tone and agonist responses. These results suggest an important role for TRPM4 in the circulation. The modulation of TRPM4 activity may be a therapeutic target for hypertension. Furthermore, the Ca2+ ionophore A23187 was identified as the first high-affinity (nanomolar) direct activator of TRPM4, acting on the 9-phenanthrol binding site.

Molecular Pathomechanisms of Impaired Flow-Induced Constriction of Cerebral Arteries Following Traumatic Brain Injury: A Potential Impact on Cerebral Autoregulation.

(1) Background: Traumatic brain injury (TBI) frequently occurs worldwide, resulting in high morbidity and mortality. Here, we hypothesized that TBI impairs an autoregulatory mechanism, namely the flow-induced constriction of isolated rat middle cerebral arteries (MCAs). (2) Methods: TBI was induced in anaesthetized rats by weight drop model, and then MCAs were isolated and transferred into a pressure-flow chamber. The internal diameter was measured by a video-microscopy. (3) Results: In MCAs from intact rats, increases in flow and pressure + flow elicited constrictions (−26 ± 1.9 µm and −52 ± 2.8 µm, p < 0.05), which were significantly reduced after TBI or in the presence of thromboxane-prostanoid (TP receptor) antagonist SQ 29,548. Flow-induced constrictions were significantly reduced by HET0016, inhibitor of cytochrome P450 4A (CYP450 4A). Arachidonic acid, (AA, 10−7 M), and CYP-450 4A metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) elicited constrictions of intact MCA (−26 ± 2.3% and −31 ± 3.6%), which were significantly reduced after TBI (to 11 ± 1.3% and −16 ±2.5%). The TP receptor agonist U46619 (10−7 M) elicited substantial constrictions of MCA from intact rats (−21 ± 3.3%), which were also significantly reduced, after TBI (to −16 ± 2.4%). (4) Conclusions: Flow-induced constrictor response of MCA is impaired by traumatic brain injury, likely due to the reduced ability of cytochrome P450 4A to convert arachidonic acid to constrictor prostaglandins and the mitigated sensitivity of thromboxane-prostanoid receptors.

Mechanism of direct regulation of cerebral artery contractility by statins

Statins are amongst the most widely prescribed drugs in the world with a range of vascular effects that have been primarily attributed to the inhibition of cholesterol and mevalonate biosynthesis, and the inhibition of mevalonate-dependent Rho/ROCK signaling upon long-term treatment. However, no studies have investigated the direct effects of acute statin application on fresh isolated resistance cerebral arteries using therapeutic concentrations of statins. We examined acute vascular effects of therapeutically relevant concentrations (0.01-10nM) of rosuvastatin and simvastatin on Sprague Dawley rat cerebral arteries and underlying molecular mechanisms. Cannulated arterial segments were maintained at 37°C in a perfusion chamber and intraluminal pressure slowly increased to 60 mmHg. For calcium imaging, the isolated arteries were preincubated in Fura-2AM (10μM) and 0.02% Kolliphor solution at room temperature for two hours before mounting in the perfusion chamber. At 60mmHg, cerebral arteries developed ~36% myogenic tone, after which increasing concentrations of statins were applied. Our data showed that the application of 1nM rosuvastatin and simvastatin constricted cerebral arteries by ~26 μm and ~24μm, respectively, within 2-3 minutes of drug application. Such statin-induced vasoconstriction remained unaltered upon endothelium denudation (intact ~23μm vs denuded ~25μm), suggesting an endothelium-independent mechanism. Co-application of mevalonate did not alter the vasoconstriction either (control ~28μm vs mevalonate ~29 μm), indicating that the effect is HMG-CoA reductase-independent. However, removal of extracellular Ca2+ with EGTA or the application of nimodipine, a selective blocker of smooth muscle cell voltage-gated Ca2+ channel, CaV1.2, each abolished cerebral artery vasoconstriction by statins, indicating that the Ca2+ entry through CaV1.2 plays a critical role here. Since Ca2+ entry into smooth muscle cells induces Ca2+ release from intracellular Ca2+ stores such as sarcoplasmic reticulum (SR) and endoplasmic reticulum (ER), we next examined the role of these Ca2+ release pathways. We found that co-application of ryanodine, a blocker of ryanodine receptor-mediated Ca2+ release, had no effects on statin-induced constriction. In contrast, statin-evoked vasoconstriction of cerebral arteries was significantly attenuated upon co-application of thapsigargin, a blocker of SR/ER membrane Ca2+-ATPase pump (SERCA), highlighting the involvement of thapsigargin-sensitive Ca2+ stores in regulating [Ca2+]i and vasoconstriction. Simultaneous measurement of arterial Ca2+ fluorescence and diameter further confirmed the involvement of CaV1.2 channel in mediating Ca2+ entry and subsequent Ca2+ release, leading to cerebral artery vasoconstriction. Altogether, our data suggests that smooth muscle cell CaV1.2 opening and Ca2+ influx is the primary mechanism underlying statin-induced constriction of cerebral arteries.

Tacrolimus Induced Severe Cerebral and Coronary Vasospasm after Heart Transplantation

IntroductionTacrolimus has several cardiovascular adverse events. We report case of tacrolimus-induced severe cerebral and coronary vasospasm after heart transplantation.Case ReportA 62-year-old female underwent orthotropic heart transplantation due to dialted cardiomyopathy. Her postoperative course was benign. At 2 months, she complained of severe pulsatile headache. CTA of the brain showed diffuse cerebral artery constriction with multifocal beaded features at nearly all distal cranial arteries and scant SAH in the right parietal area (Figure 1). We diagnosed reversible cerebral vasospasm syndrome (RCVS) induced by tacrolimus and planned to switch tacrolimus to sirolimus using the vasodilator. She inevitably maintained a low level of tacrolimus due to sirolimus induced diarrhea. Using nimodipine, her symptoms disappeared, and follow-up CTA of the brain showed relieved cerebral vasoconstriction and absorption of hemorrhage (Figure 1). At 5 months after surgery, she was admitted from acute rejection. After 2 weeks of treatment, she was stabilized with biopsy improvement. We maintained a triple regimen. She soon complained of chest pain. Telemetry revealed transient ST segment elevation (Figure 2). We assumed that this event was associated with elevated tacrolimus levels; thus, tacrolimus was reduced, and oral diltiazem was administered. Using a vasodilator, a coronary vasospasm provocation test was performed. During the test, severe coronary spasm was noted. Intracoronary and intravascular nitroglycerin was administered aggressively. The study was completed after confirming a normalized coronary artery(Figure 3). Twenty minutes later, she collapsed with squeezing chest pain. On-site CPR and ECMO insertion were performed. Two days later, she died of cardiogenic shock even with ECMO support.SummaryEarly detection of disease and withholding tacrolimus are important strategies. Tacrolimus has several cardiovascular adverse events. We report case of tacrolimus-induced severe cerebral and coronary vasospasm after heart transplantation. A 62-year-old female underwent orthotropic heart transplantation due to dialted cardiomyopathy. Her postoperative course was benign. At 2 months, she complained of severe pulsatile headache. CTA of the brain showed diffuse cerebral artery constriction with multifocal beaded features at nearly all distal cranial arteries and scant SAH in the right parietal area (Figure 1). We diagnosed reversible cerebral vasospasm syndrome (RCVS) induced by tacrolimus and planned to switch tacrolimus to sirolimus using the vasodilator. She inevitably maintained a low level of tacrolimus due to sirolimus induced diarrhea. Using nimodipine, her symptoms disappeared, and follow-up CTA of the brain showed relieved cerebral vasoconstriction and absorption of hemorrhage (Figure 1). At 5 months after surgery, she was admitted from acute rejection. After 2 weeks of treatment, she was stabilized with biopsy improvement. We maintained a triple regimen. She soon complained of chest pain. Telemetry revealed transient ST segment elevation (Figure 2). We assumed that this event was associated with elevated tacrolimus levels; thus, tacrolimus was reduced, and oral diltiazem was administered. Using a vasodilator, a coronary vasospasm provocation test was performed. During the test, severe coronary spasm was noted. Intracoronary and intravascular nitroglycerin was administered aggressively. The study was completed after confirming a normalized coronary artery(Figure 3). Twenty minutes later, she collapsed with squeezing chest pain. On-site CPR and ECMO insertion were performed. Two days later, she died of cardiogenic shock even with ECMO support. Early detection of disease and withholding tacrolimus are important strategies.

Reversible Cerebral Vasoconstriction Syndrome(RCVS)and Posterior Reversible Encephalopathy Syndrome(PRES)

Reversible cerebral vasoconstriction syndrome(RCVS)is a clinical and radiological syndrome that is characterized by recurrent severe thunderclap headaches with or without other neurological symptoms and diffuse segmental constriction of cerebral arteries that usually resolves spontaneously within three months. Posterior reversible encephalopathy syndrome(PRES)is also a clinical and radiological syndrome characterized by headache, seizures, altered consciousness, cortical blindness, other focal neurological signs, and a diagnostic imaging picture of brain vasogenic edema. Both syndromes can occur in similar clinical contexts such as hypertension, pre-eclampsia/eclampsia, drug neurotoxicity, uremia, and some autoimmune diseases, and are frequently associated. Although the syndromes are usually fully reversible with early diagnosis and prompt treatment, some cases can develop hemorrhagic or ischemic brain lesions, often resulting in permanent disability. We need to be aware of the typical and atypical imaging manifestations of the syndromes to make an accurate diagnosis.

The Effects of Ozone Oxidative Preconditioning on Subarachnoid Hemorrhage via Rat Cerebral Vasospasm Model

Objective: Cerebral vasospasm after subarachnoid hemorrhage (SAH) is a major cause of morbidity and mortality. Inflammation is the major molecular mechanism observed in vasospastic SAH. Ozone (O3) has been used as a therapeutic agent in the treatment of various conditions and diseases for years. The aim of this study was to evaluate the anti-inflammatory effect of ozone oxidative preconditioning (OOP) in a rat model of SAH in order to assess the therapeutic potential of O3 in SAH therapy. Materials and Methods: In the presented study, an experimental in vivo SAH rat model that provided constriction of large cerebral arteries was used. The inflammatory response of cerebral vasospasm after SAH and the effects of OOP were evaluated by comparing the mRNA levels of inflammatory molecules (tumor necrosis factor-α, interleukin-1β, and intercellular adhesion molecule-1) in the serum samples of rats. Results: The level of inflammatory molecules increased in vasospasm at 12 h, 24 h, and 48 h in the posttreatment groups. However, intraperitoneal OOP decreased the level of inflammatory molecules dramatically. Conclusions: Our study indicated that O3 treatment has potential in the management of inflammation created in a rat SAH model. These findings may inform further studies investigating possible uses of O3 in the treatment of vasospasm.

RCVS: An Unusual But Treatable Cause Of Headache

Introduction: Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by severe headaches, with or without other acute neurological symptoms, and diffuse segmental constriction of cerebral arteries that resolves spontaneously within 3 months. The mean age of onset is 42 years, and it affects more women than men. RCVS is possibly caused by a transient dysregulation of cerebral vascular tone, leading to multi-focal arterial constriction and dilation. Approximately 60% of the cases are secondary to a known likely cause. Case Report: We report the case of 20 year old female with severe headache, due to vasospasm of vessels with intraparenchymal haemorrhage and spasm that relieved spontaneously in 7 weeks documented with repeat MRI. Conclusion: RCVS is a secondary cause of headache. Patients who have thunderclap headache with normal brain CT and cerebrospinal fluid without xanthochromia should be investigated for reversible cerebral vasoconstriction syndrome.

Cholesterol antagonism of alcohol inhibition of smooth muscle BK channel requires cell integrity and involves a protein kinase C-dependent mechanism(s)

Alcohol constricts cerebral arteries via inhibition of voltage/calcium-gated, large conductance potassium (BK) channels in vascular myocytes. Using a rat model of high-cholesterol (high-CLR) diet and CLR enrichment of cerebral arteries in vitro, we recently showed that CLR protected against alcohol-induced constriction of cerebral arteries. The subcellular mechanism(s) underlying CLR protection against alcohol-induced constriction of the artery is unclear. Here we use a rat model of high-CLR diet and patch-clamp recording of BK channels in inside-out patches from cerebral artery myocytes to demonstrate that this diet antagonizes inhibition of BK currents by 50 mM ethanol. High-CLR-driven protection against alcohol inhibition of BK currents is reversed following CLR depletion in vitro. Similar to CLR accumulation in vivo, pre-incubation of arterial myocytes from normocholesterolemic rats in CLR-enriching media in vitro protects against alcohol-induced inhibition of BK current. However, application of CLR-enriching media to cell-free membrane patches does not protect against the alcohol effect. These different outcomes point to the involvement of cell signaling in CLR-alcohol interaction on BK channels. Incubation of myocytes with the PKC activators phorbol 12-myristate 13-acetate or 1,2-dioctanoyl-sn-glycerol, but not with the PKC inhibitor Gouml 6983, prior to patch excision precludes CLR enrichment from antagonizing alcohol action. Thus, PKC activation either disables the CLR target(s) or competes with elevated CLR. Favoring the latter possibility, 1,2-dioctanoyl-sn-glycerol protects against alcohol-induced inhibition of BK currents in patches from myocytes with naïve CLR. Our findings document that CLR antagonism of alcohol-induced BK channel inhibition requires cell integrity and is enabled by a PKC-dependent mechanism(s).

Celastrol Dilates and Counteracts Ethanol-Induced Constriction of Cerebral Arteries.

The increasing recognition of the role played by cerebral artery dysfunction in brain disorders has fueled the search for new cerebrovascular dilators. Celastrol, a natural triterpene undergoing clinical trials for treating obesity, exerts neuroprotection, which was linked to its antioxidant/anti-inflammatory activities. We previously showed that celastrol fit pharmacophore criteria for activating calcium- and voltage-gated potassium channels of large conductance (BK channels) made of subunits cloned from cerebrovascular smooth muscle (SM). These recombinant BK channels expressed in a heterologous system were activated by celastrol. Activation of native SM BK channels is well known to evoke cerebral artery dilation. Current data demonstrate that celastrol (1-100 µM) dilates de-endothelialized, ex vivo pressurized middle cerebral arteries (MCAs) from rats, with EC50 = 45 µM and maximal effective concentration (Emax)= 100 µM and with MCA diameter reaching a 10% increase over vehicle-containing, time-matched values (P < 0.05). A similar vasodilatory efficacy is achieved when celastrol is probed on MCA segments with intact endothelium. Selective BK blocking with 1 μM paxilline blunts celastrol vasodilation. Similar blunting is achieved with 0.8 mM 4-aminopirydine, which blocks voltage-gated K+ channels other than BK. Using an in vivo rat cranial window, we further demonstrate that intracarotid injections of 45 μM celastrol into pial arteries branching from MCA mimics celastrol ex vivo action. MCA constriction by ethanol concentrations reached in blood during moderate-heavy alcohol drinking (50 mM), which involves SM BK inhibition, is both prevented and reverted by celastrol. We conclude that celastrol could be an effective cerebrovascular dilator and antagonist of alcohol-induced cerebrovascular constriction, with its efficacy being uncompromised by conditions that disrupt endothelial and/or BK function. SIGNIFICANCE STATEMENT: Our study demonstrates for the first time that celastrol significantly dilates rat cerebral arteries both ex vivo and in vivo and both prevents and reverses ethanol-induced cerebral artery constriction. Celastrol actions are endothelium-independent but mediated through voltage-gated (KV) and calcium- and voltage-gated potassium channel of large conductance (BK) K+ channels. This makes celastrol an appealing new agent to evoke cerebrovascular dilation under conditions in which endothelial and/or BK channel function are impaired.

Pressure-induced constriction of the middle cerebral artery is abolished in TrpC6 knockout mice.

Pressure-induced constriction (PIC) is an inherent response of small arteries and arterioles in which increases in intraluminal pressure evoke vasoconstriction. It is a critical mechanism of blood flow autoregulation in the kidney and brain. Degenerin (Deg) and transient receptor potential (Trp) protein families have been implicated in transduction of PIC because of evolutionary links to mechanosensing in the nematode and fly. While TrpC6 has been suggested to contribute to PIC signaling, direct supporting evidence is contradictory. Therefore, the aim of this study was to determine the importance of TrpC6 in PIC signaling using a mouse model lacking TrpC6. To address this aim, we evaluated graded pressure (20-90 mmHg), depolarization (4-80 mM KCl)-, and adrenergic receptor (phenylephrine; PE 10-7-10-4 M)-mediated constriction of isolated middle cerebral artery (MCA) segments from 9-wk-old male wild-type (TrpC6+/+, n = 7) and homozygous null (TrpC6-/-, n = 9) TrpC6 mice (Jackson Laboratories). Isolated MCA segments were cannulated and pressurized with physiological salt solution using pressure myography (Living Systems). Vasoconstrictor responses to KCl and PE were identical in TrpC6-/- and TrpC6+/+ mice. In contrast, PIC responses were totally abolished in TrpC6-/- mice. At 90 mmHg, the calculated myogenic tone was -0.8 ± 0.5 vs. 10.7 ± 1.7%, P = 0.0002 in TrpC6-/- and TrpC6+/+ mice, respectively. Additionally, there were no changes in mechanical properties of circumferential wall strain and stress or morphological properties of wall thickness and wall-to-lumen ratio at 50 mmHg between TrpPC6-/- and TrpC6+/+ mice. Although these results demonstrate that TrpC6 is critical for the integrated PIC response, they do not identify whether TrpC6 acts as a mechanosensor or a downstream signaling component.NEW & NOTEWORTHY Pressure-induced, but not agonist-induced, vasoconstriction is abolished in the middle cerebral artery (MCA) of TrpC6 null mice. TrpC6 localization in dissociated cerebral vascular smooth muscle cells is primarily cytoplasmic and not associated with the surface membrane where a mechanoelectrical coupler might be expected. These findings suggest that TrpC6 is required for transduction of pressure-induced constriction in the MCA; however, its role as a mechanoelectrical coupler or downstream signal amplifier remains unresolved.