Clazosentan has been investigated globally for the prevention of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). The authors evaluated its effects on vasospasm-related morbidity ...and all-cause mortality following aSAH in Japanese patients.
Two similar double-blind, placebo-controlled phase 3 studies were conducted in 57 Japanese centers in patients with aSAH, after aneurysms were secured by endovascular coiling in one study and surgical clipping in the other. In each study, patients were randomly administered intravenous clazosentan (10 mg/hr) or placebo (1:1) starting within 48 hours of aSAH and for up to 15 days after aSAH. Stratified randomization based on World Federation of Neurosurgical Societies grade was performed using a centralized interactive web response system. Vasospasm-related morbidity and all-cause mortality within 6 weeks post-aSAH, including new cerebral infarcts and delayed ischemic neurological deficits as well as all-cause mortality, were the first primary endpoint in each study. The second primary endpoint was all-cause morbidity (new cerebral infarct or delayed ischemic neurological deficit from any causes) and all-cause mortality (all-cause morbidity/mortality) within 6 weeks post-aSAH. The incidence of individual components of the primary morbidity/mortality endpoints within 6 weeks and patient outcome at 12 weeks post-aSAH (including the modified Rankin Scale scores) were also evaluated. The above analyses were also performed in the population pooled from both studies.
In each study, 221 patients were randomized and 220 were included in the full analysis set of the primary analysis (109 in each clazosentan group, 111 in each placebo group). Clazosentan significantly reduced the incidence of vasospasm-related morbidity and all-cause mortality after aneurysm coiling (from 28.8% to 13.6%; relative risk reduction 53%; 95% CI 17%-73%) and after clipping (from 39.6% to 16.2%; relative risk reduction 59%; 95% CI 33%-75%). All-cause morbidity/mortality and poor outcome (dichotomized modified Rankin Scale scores) were significantly reduced by clazosentan after preplanned study pooling. Treatment-emergent adverse events were similar to those reported previously.
Clazosentan significantly reduced the combined incidence of vasospasm-related morbidity and all-cause mortality post-aSAH with no unexpected safety findings. Clinical trial registration nos.: JapicCTI-163368 and JapicCTI-163369 (https://www.clinicaltrials.jp).
Mitochondria are the powerhouse of the cell. Their primary physiological function is to generate adenosine triphosphate through oxidative phosphorylation via the electron transport chain. Reactive ...oxygen species generated from mitochondria have been implicated in acute brain injuries such as stroke and neurodegeneration. Recent studies have shown that mitochondrially-formed oxidants are mediators of molecular signaling, which is implicated in the mitochondria-dependent apoptotic pathway that involves pro- and antiapoptotic protein binding, the release of cytochrome c, and transcription-independent p53 signaling, leading to neuronal death. Oxidative stress and the redox state of ischemic neurons are also implicated in the signaling pathway that involves phosphatidylinositol 3-kinase/Akt and downstream signaling, which lead to neuronal survival. Genetically modified mice or rats that over-express or are deficient in superoxide dismutase have provided strong evidence in support of the role of mitochondrial dysfunction and oxidative stress as determinants of neuronal death/survival after stroke and neurodegeneration.
RNF213 gene mutations are the cause behind Moyamoya disease, a rare cerebrovascular occlusive disease. However, the function of RNF213 in the vascular system and the impact of its loss of function ...are not yet comprehended. To understand RNF23 function, we performed gene knockdown (KD) in vascular cells and performed various phenotypical analysis as well as extensive transcriptome and epitranscriptome profiling. Our data revealed that RNF213 KD led to disrupted angiogenesis in HUVEC, in part due to downregulation of DNA replication and proliferation pathways. Furthermore, HUVEC cells became sensitive to LPS induced inflammation after RNF213 KD, leading to retarded cell migration and enhanced macrophage transmigration. This was evident at the level of transcriptome as well. Interestingly, RNF213 led to extensive changes in mRNA splicing that were not previously reported. In vascular smooth muscle cells (vSMCs), RNF213 KD led to alteration in cytoskeletal organization, contractility, and vSMCs function related pathways. Finally, RNF213 KD disrupted endothelial-to-vSMCs communication in co-culture models. Overall, our results indicate that RNF213 KD sensitizes endothelial cells to inflammation, leading to altered angiogenesis. Our results shed the light on the important links between RNF213 mutations and inflammatory/immune inducers of MMD and on the unexplored role of epitranscriptome in MMD.
Despite the plethora of published studies on intracranial aneurysms (IAs) hemodynamic using computational fluid dynamics (CFD), limited progress has been made towards understanding the complex ...physics and biology underlying IA pathophysiology. Guided by 1733 published papers, we review and discuss the contemporary IA hemodynamics paradigm established through two decades of IA CFD simulations. We have traced the historical origins of simplified CFD models which impede the progress of comprehending IA pathology. We also delve into the debate concerning the Newtonian fluid assumption used to represent blood flow computationally. We evidently demonstrate that the Newtonian assumption, used in almost 90% of studies, might be insufficient to describe IA hemodynamics. In addition, some fundamental properties of the Navier–Stokes equation are revisited in supplementary material to highlight some widely spread misconceptions regarding wall shear stress (WSS) and its derivatives. Conclusively, our study draws a roadmap for next-generation IA CFD models to help researchers investigate the pathophysiology of IAs.
Following stress, transfer RNA (tRNA) is cleaved to generate tRNA halves (tiRNAs). These tiRNAs have been shown to repress protein translation. Angiogenin was considered the main enzyme that cleaves ...tRNA at its anticodon to generate 35–45 nucleotide long tiRNA halves, however, the recent reports indicate the presence of angiogenin‐independent cleavage. We previously observed tRNA cleavage pattern occurring away from the anticodon site. To explore this noncanonical cleavage, we analyze tRNA cleavage patterns in rat model of ischemia–reperfusion and in two rat cell lines. In vivo mitochondrial tRNAs were prone to this noncanonical cleavage pattern. In vitro, however, cytosolic and mitochondrial tRNAs could be cleaved noncanonically. Our results show an important regulatory role of mitochondrial stress in angiogenin‐mediated tRNA cleavage. Neither angiogenin nor RNH1 appear to regulate the noncanonical tRNA cleavage. Finally, we verified our previous findings of the role of Alkbh1 in regulating tRNA cleavage and its impact on noncanonical tRNA cleavage.
During oxidative stress, transfer RNA (tRNA) is cleaved at the anticodon via angiogenin to generate 35–45 nt long tiRNAs. This process regulates protein translation. Rashad et al. show a noncanonical form of tRNA cleavage, occurring away from the anticodon and is angiogenin in dependent. This noncanonical cleavage is in‐part regulated by tRNA methylation (via Alkbh1). Moreover, they show an important role of mitochondrial stress in regulating canonical and noncanonical tRNA cleavage.
Transfer RNA (tRNA) plays a role in stress response programs involved in various pathological conditions including neurological diseases. Under cell stress conditions, intracellular tRNA is cleaved ...by a specific ribonuclease, angiogenin, generating tRNA‐derived fragments or tRNA‐derived stress‐induced RNA (tiRNA). Generated tiRNA contributes to the cell stress response and has potential cell protective effects. However, tiRNA generation under stress conditions in neuronal cells has not been fully elucidated. To examine angiogenin‐mediated tiRNA generation in neuronal cells, we used the rat neuronal cell line, PC12, in combination with analysis of SYBR staining and immuno‐northern blotting using anti‐1‐methyladenosine antibody, which specifically and sensitively detects tiRNA. Oxidative stress induced by arsenite and hydrogen peroxide caused tRNA cleavage and tiRNA generation in PC12 cells. We also demonstrated that oxygen‐glucose deprivation, which is an in vitro model of ischemic–reperfusion injury, induced tRNA cleavage and tiRNA generation. In these stress conditions, the amount of generated tiRNA was associated with the degree of morphological cell damage. Time course analysis indicated that generation of tiRNA was prior to severe cell damage and cell death. Angiogenin over‐expression did not influence the amount of tiRNA in normal culture conditions; however, it significantly increased tiRNA generation induced by cell stress conditions. Our findings show that angiogenin‐mediated tiRNA generation can be induced in neuronal cells by different cell stressors, including ischemia–reperfusion. Additionally, detection of tiRNA could be used as a potential cell damage marker in neuronal cells.
Cover Image for this issue: doi: 10.1111/jnc.14191.
Cell stress conditions induce tRNA cleavage mediated by angiogenin, generating tRNA‐derived stress‐induced RNAs (tiRNAs), which have cell protective activities. We show that the angiogenin‐mediated tiRNAs generation can be induced in PC12 neuronal cells by different types of cell stresses including oxidative stress and ischemia–reperfusion. Additionally, detection of tiRNA could be used as a potential cell damage marker in neuronal cells.
Cover Image for this issue: doi: 10.1111/jnc.14191.
tiRNAs are small non-coding RNAs produced when tRNA is cleaved under stress. tRNA methylation modifications has emerged in recent years as important regulators for tRNA structural stability and ...sensitivity to cleavage and tiRNA generation during stress, however, the specificity and higher regulation of such a process is not fully understood. Alkbh1 is a m
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A demethylase that leads to destabilization of tRNA and enhanced tRNA cleavage. We examined the impact of Alkbh1 targeting via gene knockdown or overexpression on B35 rat neuroblastoma cell line fate following stresses and on tRNA cleavage. We show that Alkbh1 impact on cell fate and tRNA cleavage is a stress specific process that is impacted by the demethylating capacity of the cellular stress in question. We also show that not all tRNAs are cleaved equally following Alkbh1 manipulation and stress, and that Alkbh1 KD fails to rescue tRNAs from cleavage following demethylating stresses. These findings shed a light on the specificity and higher regulation of tRNA cleavage and should act as a guide for future work exploring the utility of Alkbh1 as a therapeutic target for cancers or ischaemic insult.
Contemporary paradigm of peripheral and intracranial vascular hemodynamics considers physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous ...diseases such as atherosclerosis, stenosis and aneurysm. Recently, turbulent flow patterns were detected in intracranial aneurysm at Reynolds number below 400 both in vitro and in silico. Blood flow is multiharmonic with considerable frequency spectra and its transition to turbulence cannot be characterized by the current transition theory of monoharmonic pulsatile flow. Thus, we decided to explore the origins of such long-standing assumption of physiologic blood flow laminarity. Here, we hypothesize that the inherited dynamics of blood flow in main arteries dictate the existence of turbulence in physiologic conditions. To illustrate our hypothesis, we have used methods and tools from chaos theory, hydrodynamic stability theory and fluid dynamics to explore the existence of turbulence in physiologic blood flow. Our investigation shows that blood flow, both as described by the Navier-Stokes equation and in vivo, exhibits three major characteristics of turbulence. Womersley's exact solution of the Navier-Stokes equation has been used with the flow waveforms from HaeMod database, to offer reproducible evidence for our findings, as well as evidence from Doppler ultrasound measurements from healthy volunteers who are some of the authors. We evidently show that physiologic blood flow is: (1) sensitive to initial conditions, (2) in global hydrodynamic instability and (3) undergoes kinetic energy cascade of non-Kolmogorov type. We propose a novel modification of the theory of vascular hemodynamics that calls for rethinking the hemodynamic-biologic links that govern physiologic and pathologic processes.
Moyamoya disease (MMD) is a rare cerebro-occlusive disease with unknown etiology that can cause both ischemic and hemorrhagic stroke. MMD is characterized by progressive stenosis of the terminal ...internal carotid artery (ICA) and development of basal brain collaterals. Early-stage MMD is known to cause hemodynamic insufficiency despite mild or moderate stenosis of the intracranial arteries, but the exact mechanism underlying this pathophysiological condition is undetermined. We used high-resolution Large Eddy Simulations to investigate multiple complex hemodynamic phenomena that led to cerebral ischemia in five patients with early-stage MMD. The effects of transitional flow, coherent flow structures and blood shear-thinning properties through regions of tortuous and stenosed arteries were explored and linked to symptomatology. It is evidently shown that in some cases complex vortex structures, such as Rankine-type vortices, redirects blood flow away from some arteries causing significant reduction in blood flow. Moreover, partial blood hammer (PBH) phenomenon was detected in some cases and led to significant hemodynamic insufficiency. PBH events were attributed to the interaction between shear-thinning properties, transitional flow structures and loss of upstream pressure-velocity phase lag. We clearly show that the hemodynamic complexities in early-stage MMD could induce ischemia and explain the non-responsiveness to antiplatelet therapy.
BACKGROUND AND PURPOSE—Multilineage-differentiating stress-enduring (muse) cells are endogenous nontumorigenic stem cells with pluripotency harvestable as pluripotent marker SSEA-3 cells from the ...bone marrow from cultured bone marrow-mesenchymal stem cells. After transplantation into neurological disease models, muse cells exert repair effects, but the exact mechanism remains inconclusive.
METHODS—We conducted mechanism-based experiments by transplanting serum/xeno-free cultured-human bone marrow-muse cells into the perilesion brain at 2 weeks after lacunar infarction in immunodeficient mice.
RESULTS—Approximately 28% of initially transplanted muse cells remained in the host brain at 8 weeks, spontaneously differentiated into cells expressing NeuN (≈62%), MAP2 (≈30%), and GST-pi (≈12%). Dextran tracing revealed connections between host neurons and muse cells at the lesioned motor cortex and the anterior horn. Muse cells extended neurites through the ipsilateral pyramidal tract, crossed to contralateral side, and reached to the pyramidal tract in the dorsal funiculus of spinal cord. Muse-transplanted stroke mice displayed significant recovery in cylinder tests, which was reverted by the human-selective diphtheria toxin. At 10 months post-transplantation, human-specific Alu sequence was detected only in the brain but not in other organs, with no evidence of tumor formation.
CONCLUSIONS—Transplantation at the delayed subacute phase showed muse cells differentiated into neural cells, facilitated neural reconstruction, improved functions, and displayed solid safety outcomes over prolonged graft maturation period, indicating their therapeutic potential for lacunar stroke.
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