Aurélien Mazeraud

Neuroanatomy and Physiology of Brain Dysfunction in Sepsis.

Sepsis-associated encephalopathy (SAE), a complication of sepsis, is often complicated by acute and long-term brain dysfunction. SAE is associated with electroencephalogram pattern changes and abnormal neuroimaging findings. The major processes involved are neuroinflammation, circulatory dysfunction, and excitotoxicity. Neuroinflammation and microcirculatory alterations are diffuse, whereas excitotoxicity might occur in more specific structures involved in the response to stress and the control of vital functions. A dysfunction of the brainstem, amygdala, and hippocampus might account for the increased mortality, psychological disorders, and cognitive impairment. This review summarizes clinical and paraclinical features of SAE and describes its mechanisms at cellular and structural levels.

The Sarcoglycan complex is expressed in the cerebrovascular system and is specifically regulated by astroglial Cx30 channels

Astrocytes, the most prominent glial cell type in the brain, send specialized processes called endfeet, around blood vessels and express a large molecular repertoire regulating the cerebrovascular system physiology. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction proteins Connexin 43 and 30 (Cx43 and Cx30) allowing in particular for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. In this study, we addressed the specific role of Cx30 at the gliovascular interface. Using an inactivation mouse model for Cx30 (Cx30Δ/Δ; Δ means deleted allele) we showed that absence of Cx30 does not affect blood-brain barrier (BBB) organization and permeability. However, it results in the cerebrovascular fraction, in a strong upregulation of Sgcg encoding γ-Sarcoglycan (γ-SG), a member of the Dystrophin-associated protein complex (DAPC) connecting cytoskeleton and the extracellular matrix. The same molecular event occurs in Cx30T5M/T5M mutated mice, where Cx30 channels are closed, demonstrating that Sgcg regulation relied on Cx30 channel functions. We further characterized the expression of other Sarcoglycan complex (SGC) molecules in the cerebrovascular system and showed the presence of α-, β-, δ-, γ-, ε- and ζ- SG, as well as Sarcospan. Their expression was however not modified in Cx30Δ/Δ. These results suggest that a full SGC might be present in the cerebrovascular system, and that expression of one of its member, γ-SG, depends on Cx30 channels. As described in skeletal muscles, the SGC may contribute to membrane stabilization and signal transduction in the cerebrovascular system, which may therefore be regulated by Cx30 channel-mediated functions.

Neuroanatomy of Sepsis-Associated Encephalopathy

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2017. Other selected articles can be found online at http://ccforum.com/series/annualupdate2017. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.Originally published in the Annual Update in Intensive Care and Emergency Medicine 2017. The number of authors differs in the two versions due to constraints regarding the number of authors in the Annual Update in Intensive Care and Emergency Medicine. In the Annual Update version of the review, the three senior authors appear in the acknowledgement section. In the Critical Care version, these three senior authors appear as full authors of the manuscript. All authors helped draft and revise the manuscript for critical intellectual content.

A Global View on the Availability of Methods and Information in the Neuropathological Diagnostics of CNS Tumors: Results of an International Survey Among Neuropathological Units.

In order to establish an accurate and reproducible diagnosis, neuropathologists have continuously refined their diagnostic criteria and applied methods. This process was reflected in the four different editions of the WHO classification of brain tumors (1). The current revision of the 4th edition of the WHO classification dates back to 2007 (2); its update is being currently performed and will be published in 2016. Over the years, essential ancillary techniques were developed and validated such as immunohistochemistry (IHC) for epitopes with diagnostic potential and Fluorescent in situ hybridization (FISH) for analysis of genomic changes. In the light of the upcoming revision to the WHO classification of brain tumors and the tremendous knowledge which has been accumulated on the genetics and biology of brain tumors, the crucial question is which markers and assays should be introduced as mandatory to lead to diagnosis of a brain tumor entity according to WHO classification in a balanced way, so that distinct brain tumor entities can be securely identified in (neuro)pathological departments in most countries. A controversial issue is the incorporation of more complex molecular techniques such as genome-wide studies on the protein, mRNA or DNA level because such methods have shown to allow a more accurate diagnosis of brain tumors, and often better correlation with outcome but have not been approved for clinical decision making. (2) During the discussion on these developments raised at the XVIII International Congress of Neuropathology in Rio de Janeiro 2014, it was realized that there are no robust data available on the current status on the techniques used by (neuro)pathologists for the diagnosis of brain tumors worldwide. Therefore, we performed an international survey within the framework of the International Society of Neuropathology (ISN) to provide these data.

Experimental and clinical evidences for glucose control in intensive care: is infused glucose the key point for study interpretation?

Stress-induced hyperglycemia has been considered an adaptive mechanism to stress up to the first intensive insulin therapy trial, which showed a 34% reduction in relative risk of in-hospital mortality when normalizing blood glucose levels. Further trials had conflicting results and, at present, stress-induced hyperglycemia management remains non-consensual. These findings could be explained by discrepancies in trials, notably regarding the approach to treat hyperglycemia: high versus restrictive caloric intake. Stress-induced hyperglycemia is a frequent complication during intensive care unit stay and is associated with a higher mortality. It results from an imbalance between insulin and counter-regulatory hormones, increased neoglucogenesis, and the cytokine-induced insulin-resistant state of tissues. In this review, we summarize detrimental effects of hyperglycemia on organs in the critically ill (peripheric and central nervous, liver, immune system, kidney, and cardiovascular system). Finally, we show clinical and experimental evidence of potential benefits from glucose and insulin administration, notably on metabolism, immunity, and the cardiovascular system.

MuscleJ: a high-content analysis method to study skeletal muscle with a new Fiji tool

BackgroundSkeletal muscle has the capacity to adapt to environmental changes and regenerate upon injury. To study these processes, most experimental methods use quantification of parameters obtained from images of immunostained skeletal muscle. Muscle cross-sectional area, fiber typing, localization of nuclei within the muscle fiber, the number of vessels, and fiber-associated stem cells are used to assess muscle physiology. Manual quantification of these parameters is time consuming and only poorly reproducible. While current state-of-the-art software tools are unable to analyze all these parameters simultaneously, we have developed MuscleJ, a new bioinformatics tool to do so.MethodsRunning on the popular open source Fiji software platform, MuscleJ simultaneously analyzes parameters from immunofluorescent staining, imaged by different acquisition systems in a completely automated manner.ResultsAfter segmentation of muscle fibers, up to three other channels can be analyzed simultaneously. Dialog boxes make MuscleJ easy-to-use for biologists. In addition, we have implemented color in situ cartographies of results, allowing the user to directly visualize results on reconstituted muscle sections.ConclusionWe report here that MuscleJ results were comparable to manual observations made by five experts. MuscleJ markedly enhances statistical analysis by allowing reliable comparison of skeletal muscle physiology-pathology results obtained from different laboratories using different acquisition systems. Providing fast robust multi-parameter analyses of skeletal muscle physiology-pathology, MuscleJ is available as a free tool for the skeletal muscle community.

Evaluation of Reperfusion Pulmonary Edema by Extravascular Lung Water Measurements After Pulmonary Endarterectomy.

Objectives: Reperfusion pulmonary edema is a specific complication of pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension. Extravascular lung water measurement may be valuable for diagnosing reperfusion pulmonary edema. The primary objective of this study was to describe and assess the clinical significance of extravascular lung water variations after pulmonary endarterectomy. Design: Prospective observational study. Setting: Nineteen-bed cardiothoracic ICU. Patients: Consecutive patients who were hemodynamically stable after pulmonary endarterectomy were divided into two groups based on whether their preoperative pulmonary vascular resistance indicated severe or nonsevere chronic thromboembolic pulmonary hypertension (> 900 or ⩽ 900 dynes·s/cm5, respectively). Interventions: Hemodynamic variables obtained by right heart catheterization and transpulmonary thermodilution measurements were recorded 1 hour, 1 day, and 2 days after pulmonary endarterectomy. Extravascular lung water was indexed to predicted body weight (EVLWPBW). Measurements and Main Results: We studied 31 patients. Overall, 26 patients (84%) experienced reperfusion pulmonary edema during the first 72 hours after pulmonary endarterectomy. EVLWPBW significantly increased between the first hour after pulmonary endarterectomy and day 2 (10.2 ± 2.6 vs 11.4 ± 3.6; p = 0.03). EVLWPBW measured at the first hour after pulmonary endarterectomy is closely associated with reperfusion pulmonary edema occurrence in the next 48 hours (area under the receiver-operating characteristics curve = 0.88 ± 0.07). EVLWPBW correlated with duration of mechanical ventilation (&rgr; = 0.59; p < 0.0001) and ICU stay (&rgr; = 0.52; p < 0.0001). Patients with severe chronic thromboembolic pulmonary hypertension (n = 15) had higher EVLWPBW values at day 2 compared with those without (n = 16) (13.2 ± 3.6 vs 9.7 ± 2.7 mL/kg; p = 0.004). Cardiac output was measured simultaneously by pulmonary artery catheter and aortic transpulmonary thermodilution on 92 occasions; agreement was good, with a bias of 0.50 ± 0.95 L/min (95% CI, –1.36–2.36). Conclusions: Accurate extravascular lung water measurements were obtained after pulmonary endarterectomy. Extravascular lung water may prove valuable for diagnosing reperfusion pulmonary edema after pulmonary endarterectomy and had prognostic value. Extravascular lung water values were significantly higher in patients with severe compared with nonsevere chronic thromboembolic pulmonary hypertension.

The Female mdx Mouse: An Unexpected Vascular Story

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease, caused by absence of functional dystrophin and inevitably leading to death. A variable proportion of women carriers (2.5 to 19%) can also manifest symptoms ranging from myalgia to cardiomyopathy, and pathophysiological mechanisms are still not completely understood. Our study focused on 12 month-old female mdx mice, displaying marked chronic muscle lesions, similar to the lesions observed in human DMD. Our aim was to focus on the alterations of the vascular network organisation, and functional repercussions using a combination of histology/morphometry techniques and totally non-invasive functional approach (multiparametric and functional nuclear magnetic resonance), clearly relevant for clinical diagnosis and research, combining arterial spin labeling imaging of perfusion, and 31P-spectroscopy of phosphocreatine kinetics. Collectively, our results demonstrate that the vasculature, both in its steady state organisation and dynamic behaviour after an ischemia-reperfusion stress, is altered in the 12 month-old female mdx mouse: increased density of vascular sections in histology, modification of the post-ischemic hyperemia profile, increase in mitochondrial oxidative rephosphorylation capacity, in striking opposition to what was observed in age-matched male mdx mice. We believe the apparent discordance between vascular and muscular features in the female mdx mouse make it an interesting tool to decipher further dystrophinopathy pathophysiological mechanisms.

Brain perfusion in sepsis or to resolve the macro part of the micro.

www.ccmjournal.org 485 Encephalopathy is a frequent and severe complication of sepsis impacting outcomes. It is associated with increased mortality, which varies from 20% in absence of altered mental status to 60% in case of coma (1). Epidemiological studies have shown that patients with sepsis are at higher risk of cognitive dysfunction, involving notably memory and executive functions (2). By definition, sepsis-associated encephalopathy (SAE) is not related to direct infection of the CNS but to mediators released during sepsis. SAE is characterized, clinically, by an alteration of consciousness (ranging from delirium to coma) that can be associated with seizures (convulsive or not) and exceptionally with focal neurological signs (1) and neurophysiologically by various electroencephalographic (EEG) changes, including excessive theta or predominant delta activity, triphasic waves, or burst suppression but also electrographic seizures and periodic epileptiform discharges (3). Therefore, its detection is based on a daily standardized neurological examination (4) combined possibly with an EEG monitoring (3). The pathophysiology of SAE is highly complex. Based on human and experimental studies, it is considered, schematically, to involve neuroinflammatory and ischemic processes. These two processes result in cellular dysfunction, including mitochondrial dysfunction, oxidative stress, and bioenergetics failure, which compromise, at the neuronal level, survival, and neurotransmission (5). The first process includes activation of the endothelial cells and dysfunction of the blood-brain barrier that allow the liberation or the passage into the brain parenchyma of inflammatory mediators that activates microglial cells, which in turn amplify these neuroinflammatory processes. It is believed that microglial activation is involved in neurodegenerative diseases (notably Alzheimer disease) and could therefore account to the translation of SAE toward cognitive impairment (1). This scenario links neuroinflammation with neurodegeneration. The latter process is related to macroand microcirculatory dysfunctions. At the macrocirculatory level, cerebral blood flow is tightly autoregulated to protect the brain from variation in cardiac output or systemic blood pressure; at the microcirculatory level, neurovascular coupling adapts the flow to energetic needs. A vascular process related to diffuse ischemic damage might be the second link between SAE and long-term cognitive decline (1). This scenario connects circulatory dysfunction with vascular dementia. Neuropathological and neuroradiological studies have documented the presence of ischemic damage in patients with sepsis (6, 7). We have recently shown that ischemic stroke occurs in 29% of patients with septic shock who underwent MRI for an acute brain dysfunction and was associated with both increased mortality (up to 60%) and disseminated intravascular coagulopathy (7). These results underline the deleterious impact of this ischemic process and the necessity to understand its mechanisms. In this issue of Critical Care Medicine, the experimental study by Taccone et al (8) provides interesting data on metabolic consequences of microcirculatory dysfunction within the first 24 hours of stercoral peritonitis in sheep, which were also intubated and resuscitated. By videomicroscopy and microdialysis, they showed that microcirculatory dysfunction occurs between the 6th and 12th hours from the onset of sepsis and is rapidly accompanied by a decrease in brain oxygen tension and an increase in lactate pyruvate ratio but also, after occurrence of hypotension, in glutamate. These are biochemical markers of cerebral metabolic suffering. Confirming their previous videomicroscopic changes in cortical perfused capillaries density (9), Taccone et al (8) have evidenced here the metabolic correlates of this early microcirculatory dysfunction. This is consistent with experimental studies showing impaired neurovascular coupling during sepsis (10). However, it would have been interesting to determine to what extend these metabolic changes were correlated with clinical, neurophysiological, and neuropathological changes. One may argue that late metabolic changes, especially glutamate increase, were also preagonic. However, the main limit of this descriptive experimental study—pointed out also by Taccone et al (8)—is that the contribution of macrocirculatory dysfunction to the metabolic suffering has not been investigated. It would have been useful Copyright