Showing papers by "Costantino Iadecola published in 2021"

Revisiting the neurovascular unit.

Abstract: The brain is supplied by an elaborate vascular network that originates extracranially and reaches deep into the brain. The concept of the neurovascular unit provides a useful framework to investigate how neuronal signals regulate nearby microvessels to support the metabolic needs of the brain, but it does not consider the role of larger cerebral arteries and systemic vasoactive signals. Furthermore, the recently emerged molecular heterogeneity of cerebrovascular cells indicates that there is no prototypical neurovascular unit replicated at all levels of the vascular network. Here, we examine the cellular and molecular diversity of the cerebrovascular tree and the relative contribution of systemic and brain-intrinsic factors to neurovascular function. Evidence supports the concept of a 'neurovascular complex' composed of segmentally diverse functional modules that implement coordinated vascular responses to central and peripheral signals to maintain homeostasis of the brain. This concept has major implications for neurovascular regulation in health and disease and for brain imaging.

Endothelial S1P 1 Signaling Counteracts Infarct Expansion in Ischemic Stroke

Abstract: Rationale: Cerebrovascular function is critical for brain health, and endogenous vascular protective pathways may provide therapeutic targets for neurological disorders. S1P (Sphingosine 1-phosphat...

Association Between Intracerebral Hemorrhage and Subsequent Arterial Ischemic Events in Participants From 4 Population-Based Cohort Studies.

Abstract: Importance Intracerebral hemorrhage and arterial ischemic disease share risk factors, to our knowledge, but the association between the 2 conditions remains unknown. Objective To evaluate whether intracerebral hemorrhage was associated with an increased risk of incident ischemic stroke and myocardial infarction. Design, Setting, and Participants An analysis was conducted of pooled longitudinal participant-level data from 4 population-based cohort studies in the United States: the Atherosclerosis Risk in Communities (ARIC) study, the Cardiovascular Health Study (CHS), the Northern Manhattan Study (NOMAS), and the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. Patients were enrolled from 1987 to 2007, and the last available follow-up was December 31, 2018. Data were analyzed from September 1, 2019, to March 31, 2020. Exposure Intracerebral hemorrhage, as assessed by an adjudication committee based on predefined clinical and radiologic criteria. Main Outcomes and Measures The primary outcome was an arterial ischemic event, defined as a composite of ischemic stroke or myocardial infarction, centrally adjudicated within each study. Secondary outcomes were ischemic stroke and myocardial infarction. Participants with prevalent intracerebral hemorrhage, ischemic stroke, or myocardial infarction at their baseline study visit were excluded. Cox proportional hazards regression was used to examine the association between intracerebral hemorrhage and subsequent arterial ischemic events after adjustment for baseline age, sex, race/ethnicity, vascular comorbidities, and antithrombotic medications. Results Of 55 131 participants, 47 866 (27 639 women [57.7%]; mean [SD] age, 62.2 [10.2] years) were eligible for analysis. During a median follow-up of 12.7 years (interquartile range, 7.7-19.5 years), there were 318 intracerebral hemorrhages and 7648 arterial ischemic events. The incidence of an arterial ischemic event was 3.6 events per 100 person-years (95% CI, 2.7-5.0 events per 100 person-years) after intracerebral hemorrhage vs 1.1 events per 100 person-years (95% CI, 1.1-1.2 events per 100 person-years) among those without intracerebral hemorrhage. In adjusted models, intracerebral hemorrhage was associated with arterial ischemic events (hazard ratio [HR], 2.3; 95% CI, 1.7-3.1), ischemic stroke (HR, 3.1; 95% CI, 2.1-4.5), and myocardial infarction (HR, 1.9; 95% CI, 1.2-2.9). In sensitivity analyses, intracerebral hemorrhage was associated with arterial ischemic events when updating covariates in a time-varying manner (HR, 2.2; 95% CI, 1.6-3.0); when using incidence density matching (odds ratio, 2.3; 95% CI, 1.3-4.2); when including participants with prevalent intracerebral hemorrhage, ischemic stroke, or myocardial infarction (HR, 2.2; 95% CI, 1.6-2.9); and when using death as a competing risk (subdistribution HR, 1.6; 95% CI, 1.1-2.1). Conclusions and Relevance This study found that intracerebral hemorrhage was associated with an increased risk of ischemic stroke and myocardial infarction. These findings suggest that intracerebral hemorrhage may be a novel risk marker for arterial ischemic events.

Stroke affects intestinal immune cell trafficking to the central nervous system.

Abstract: Stroke is an acute neurological disease with a strong inflammatory component that can be regulated by the intestinal microbiota and intestinal immune cells. Although stroke has been shown to alter immune cell populations in the gut, the dynamics of cell trafficking have not been elucidated. To study the trafficking of gut-derived immune cells after stroke, we used mice expressing the photoconvertible protein Kikume Green-Red, which turns form green to red when exposed to violet light. Mice underwent laparotomy and the small intestine was exposed to violet laser light. Immune cells were isolated from the small intestine immediately after photoconversion and 2 days later. Percentage of immune cells (CD45+KikR+) that expressed the red variant of the protein (KikR) was higher immediately after photoconversion than 2 days later, indicating cell egress from the small intestine. To investigate whether intestinal immune cells traffic to the periphery and/or the central nervous system (CNS) after stroke, we analyzed KikR+ immune cells (2 days after photoconversion) in peripheral lymphoid organs, meninges and brain, 3 and 14 days after transient occlusion of the middle cerebral artery (tMCAo) or sham-surgery. Although migration was observed in naive and sham animals, stroke induced a higher mobilization of gut KikR+ immune cells, especially at 3 days after stroke, to all the organs analyzed. Notably, we detected a significant migration of CD45hi immune cells from the gut to the brain and meninges at 3 days after stroke. Comparison of cell trafficking between organs revealed a significant preference of intestinal CD11c+ cells to migrate from the small intestine to brain and meninges after stroke. We conclude that stroke increases immune cell trafficking from the small intestine to peripheral lymphoid organs and the CNS where they might contribute to post-stroke inflammation.

Mechanisms of Ischemic Stroke in Patients with Cancer: A Prospective Study

Abstract: Objective The objective of this study was to examine the pathophysiology of ischemic stroke with cancer. Methods We conducted a prospective cross-sectional study from 2016 to 2020 at 2 hospitals. We enrolled 3 groups of 50 adult participants each. The main group included patients with active solid tumor cancer and acute ischemic stroke. The control groups included patients with acute ischemic stroke only or active cancer only. The patients with stroke-only and patients with cancer-only were matched to the patients with cancer-plus-stroke by age, sex, and cancer type, if applicable. The outcomes were prespecified hematological biomarkers and transcranial Doppler microemboli detection. Hematological biomarkers included markers of coagulation (D-dimer and thrombin-antithrombin), platelet function (P-selectin), and endothelial integrity (thrombomodulin, soluble intercellular adhesion molecule-1 [sICAM-1], and soluble vascular cell adhesion molecule-1 [sVCAM-1]). Hematological biomarkers were compared between groups using the Kruskal-Wallis and Wilcoxon Rank-Sum tests. In multivariable linear regression models, we adjusted for race, number of stroke risk factors, smoking, stroke severity, and antithrombotic use. Transcranial Doppler microemboli presence was compared between groups using chi-square tests. Results Levels of all study biomarkers were different between groups. In univariate between-group comparisons, patients with cancer-plus-stroke had higher levels of D-dimer, sICAM-1, sVCAM-1, and thrombomodulin than both control groups; higher levels of thrombin-antithrombin than patients with cancer-only; and higher levels of P-selectin than patients with stroke-only. Findings were similar in multivariable analyses. Transcranial Doppler microemboli were detected in 32% of patients with cancer-plus-stroke, 16% of patients with stroke-only, and 6% of patients with cancer-only (p = 0.005). Interpretation Patients with cancer-related stroke have higher markers of coagulation, platelet, and endothelial dysfunction, and more circulating microemboli, than matched controls. ANN NEUROL 2021;90:159-169.

Role of microglial and endothelial CD36 in post-ischemic inflammasome activation and interleukin-1β-induced endothelial activation.

Abstract: Cerebral ischemia is associated with an acute inflammatory response that contributes to the resulting injury. The innate immunity receptor CD36, expressed in microglia and endothelium, and the pro-inflammatory cytokine interleukin-1β (IL-1β) are involved in the mechanisms of ischemic injury. Since CD36 has been implicated in activation of the inflammasome, the main source of IL-1β, we investigated whether CD36 mediates brain injury through the inflammasome and IL-1β. We found that active caspase-1, a key inflammasome component, is decreased in microglia of CD36-deficient mice subjected to transient middle cerebral artery occlusion, an effect associated with a reduction in brain IL-1β. Conditional deletion of CD36 either in microglia or endothelium reduced ischemic injury in mice, attesting to the pathogenic involvement of CD36 in both cell types. Application of an ischemic brain extract to primary brain endothelial cell cultures from wild type (WT) mice induced IL-1β-dependent endothelial activation, reflected by increases in the cytokine colony stimulating factor-3, a response markedly attenuated in CD36-deficient endothelia. Similarly, the increase in colony stimulating factor-3 induced by recombinant IL-1β was attenuated in CD36-deficient compared to WT endothelia. We conclude that microglial CD36 is a key determinant of post-ischemic IL-1β production by regulating caspase-1 activity, whereas endothelial CD36 is required for the full expression of the endothelial activation induced by IL-1β. The data identify microglial and endothelial CD36 as critical upstream components of the acute inflammatory response to cerebral ischemia and viable putative therapeutic targets.

Diffusion-Weighted Imaging Lesions After Intracerebral Hemorrhage and Risk of Stroke: A MISTIE III and ATACH-2 Analysis.

Abstract: Background and Purpose: Punctate ischemic lesions noted on diffusion-weighted imaging (DWI) are associated with poor functional outcomes after intracerebral hemorrhage (ICH). Whether these lesions ...

Elevated post-ischemic ubiquitination results from suppression of deubiquitinase activity and not proteasome inhibition

Abstract: Cerebral ischemia-reperfusion increases intraneuronal levels of ubiquitinated proteins, but the factors driving ubiquitination and whether it results from altered proteostasis remain unclear. To address these questions, we used in vivo and in vitro models of cerebral ischemia-reperfusion, in which hippocampal slices were transiently deprived of oxygen and glucose to simulate ischemia followed by reperfusion, or the middle cerebral artery was temporarily occluded in mice. We found that post-ischemic ubiquitination results from two key steps: restoration of ATP at reperfusion, which allows initiation of protein ubiquitination, and free radical production, which, in the presence of sufficient ATP, increases ubiquitination above pre-ischemic levels. Surprisingly, free radicals did not augment ubiquitination through inhibition of the proteasome as previously believed. Although reduced proteasomal activity was detected after ischemia, this was neither caused by free radicals nor sufficient in magnitude to induce appreciable accumulation of proteasomal target proteins or ubiquitin-proteasome reporters. Instead, we found that ischemia-derived free radicals inhibit deubiquitinases, a class of proteases that cleaves ubiquitin chains from proteins, which was sufficient to elevate ubiquitination after ischemia. Our data provide evidence that free radical-dependent deubiquitinase inactivation rather than proteasomal inhibition drives ubiquitination following ischemia-reperfusion, and as such call for a reevaluation of the mechanisms of post-ischemic ubiquitination, previously attributed to altered proteostasis. Since deubiquitinase inhibition is considered an endogenous neuroprotective mechanism to shield proteins from oxidative damage, modulation of deubiquitinase activity may be of therapeutic value to maintain protein integrity after an ischemic insult.