Cigarette smoke exposure reduces hemorrhagic shock induced circulatory dysfunction in mice with attenuated glucocorticoid receptor function.

Introduction: We previously showed that attenuated glucocorticoid receptor (GR) function in mice (GRdim/dim) aggravates systemic hypotension and impairs organ function during endotoxic shock. Hemorrhagic shock (HS) causes impaired organ perfusion, which leads to tissue hypoxia and inflammation with risk of organ failure. Lung co-morbidities like chronic obstructive pulmonary disease (COPD) can aggravate tissue hypoxia via alveolar hypoxia. The most common cause for COPD is cigarette smoke (CS) exposure. Therefore, we hypothesized that affecting GR function in mice (GRdim/dim) and pre-traumatic CS exposure would further impair hemodynamic stability and organ function after HS. Methods: After 3 weeks of CS exposure, anesthetized and mechanically ventilated GRdim/dim and GR+/+ mice underwent pressure-controlled HS for 1h via blood withdrawal (mean arterial pressure (MAP) 35mmHg), followed by 4h of resuscitation with re-transfusion of shed blood, colloid fluid infusion and, if necessary, continuous intravenous norepinephrine. Acid-base status and organ function were assessed together with metabolic pathways. Blood and organs were collected at the end of the experiment for analysis of cytokines, corticosterone level, and mitochondrial respiratory capacity. Data is presented as median and interquartile range. Results: Nor CS exposure neither attenuated GR function affected survival. Non-CS GRdim/dim mice had a higher need of norepinephrine to keep target hemodynamics compared to GR+/+ mice. In contrast, after CS exposure norepinephrine need did not differ significantly between GRdim/dim and GR+/+ mice. Non-CS GRdim/dim mice presented with a lower pH and increased blood lactate levels compared to GR+/+ mice, but not CS exposed mice. Also, higher plasma concentrations of some pro-inflammatory cytokines were observed in non-CS GRdim/dim compared to GR+/+ mice, but not in the CS group. With regards to metabolic measurements, CS exposure led to an increased lipolysis in GRdim/dim compared to GR+/+ mice, but not in non-CS exposed animals. Conclusion: Whether less metabolic acidosis or increased lipolysis is the reason or the consequence for the trend towards lower catecholamine need in CS exposed GRdim/dim mice warrants further investigation.

Multiplex Fluorescent Bead-Based Immunoassay for the Detection of Cytokines, Chemokines, and Growth Factors.

The comprehensive analysis of serum cytokine levels can be challenging due to low sample volumes and time consuming when using single-target methods like enzyme-linked immunosorbent assay (ELISA). Bead-based detection systems allow the simultaneous detection of multiple analytes using minimal sample volumes. Here we describe the use of a multiplex cytokine, chemokine, and growth factor assay for mouse cytokines in a 96-well format. This assay is based on antibody-coupled fluorescent magnetic beads combined with biotinylated secondary detection antibody followed by fluorescent-tagged streptavidin in a sandwich-like composition. Final assay readout provides the concentrations of 23 different cytokines, chemokines, and growth factors in up to 76 samples.

Impaired Glucocorticoid Receptor Signaling Aggravates Lung Injury after Hemorrhagic Shock.

We previously showed that attenuated lung injury after hemorrhagic shock (HS) coincided with enhanced levels of the glucocorticoid (GC) receptor (GR) in lung tissue of swine. Here, we investigated the effects of impaired GR signaling on the lung during resuscitated HS using a dysfunctional GR mouse model (GRdim/dim). In a mouse intensive care unit, HS led to impaired lung mechanics and aggravated lung inflammation in GRdim/dim mice compared to wildtype mice (GR+/+). After HS, high levels of the pro-inflammatory and pro-apoptotic transcription factor STAT1/pSTAT1 were found in lung samples from GRdim/dim mice. Lungs of GRdim/dim mice revealed apoptosis, most likely as consequence of reduced expression of the lung-protective Angpt1 compared to GR+/+ after HS. RNA-sequencing revealed increased expression of pro-apoptotic and cytokine-signaling associated genes in lung tissue of GRdim/dim mice. Furthermore, high levels of pro-inflammatory cytokines and iNOS were found in lungs of GRdim/dim mice. Our results indicate impaired repression of STAT1/pSTAT1 due to dysfunctional GR signaling in GRdim/dim mice, which leads to increased inflammation and apoptosis in the lungs. These data highlight the crucial role of functional GR signaling to attenuate HS-induced lung damage.

Impact of downstream effects of glucocorticoid receptor dysfunction on organ function in critical illness-associated systemic inflammation.

Glucocorticoids (GCs) are stress hormones that regulate developmental and physiological processes and are among the most potent anti-inflammatory drugs to suppress chronic and acute inflammation. GCs act through the glucocorticoid receptor (GR), a ubiquitously expressed ligand-activated transcription factor, which translocates into the nucleus and can act via two different modes, as a GR monomer or as a GR dimer. These two modes of action are not clearly differentiated in practice and may lead to completely different therapeutic outcomes. Detailed aspects of GR mechanisms are often not taken into account when GCs are used in different clinical scenarios. Patients, with critical illness-related corticosteroid insufficiency, treated with natural or synthetic GCs are still missing a clearly defined therapeutic strategy. This review discusses the different modes of GR function and its importance on organ function in vivo.

Impaired Glucocorticoid Receptor Dimerization Aggravates LPS-Induced Circulatory and Pulmonary Dysfunction.

Background: Sepsis, that can be modeled by LPS injections, as an acute systemic inflammation syndrome is the most common cause for acute lung injury (ALI). ALI induces acute respiratory failure leading to hypoxemia, which is often associated with multiple organ failure (MOF). During systemic inflammation, the hypothalamus-pituitary-adrenal axis (HPA) is activated and anti-inflammatory acting glucocorticoids (GCs) are released to overcome the inflammation. GCs activate the GC receptor (GR), which mediates its effects via a GR monomer or GR dimer. The detailed molecular mechanism of the GR in different inflammatory models and target genes that might be crucial for resolving inflammation is not completely identified. We previously observed that mice with attenuated GR dimerization (GRdim/dim) had a higher mortality in a non-resuscitated lipopolysaccharide (LPS)- and cecal ligation and puncture (CLP)-induced inflammation model and are refractory to exogenous GCs to ameliorate ALI during inflammation. Therefore, we hypothesized that impaired murine GR dimerization (GRdim/dim) would further impair organ function in LPS-induced systemic inflammation under human like intensive care management and investigated genes that are crucial for lung function in this setup. Methods: Anesthetized GRdim/dim and wildtype (GR+/+) mice were challenged with LPS (10 mg·kg-1, intraperitoneal) and underwent intensive care management ("lung-protective" mechanical ventilation, crystalloids, and norepinephrine) for 6 h. Lung mechanics and gas exchange were assessed together with systemic hemodynamics, acid-base status, and mitochondrial oxygen consumption (JO2). Western blots, immunohistochemistry, and real time quantitative polymerase chain reaction were performed to analyze lung tissue and inflammatory mediators were analyzed in plasma and lung tissue. Results: When animals were challenged with LPS and subsequently resuscitated under intensive care treatment, GRdim/dim mice had a higher mortality compared to GR+/+ mice, induced by an increased need of norepinephrine to achieve hemodynamic targets. After challenge with LPS, GRdim/dim mice also displayed an aggravated ALI shown by a more pronounced impairment of gas exchange, lung mechanics and increased osteopontin (Opn) expression in lung tissue. Conclusion: Impairment of GR dimerization aggravates systemic hypotension and impairs lung function during LPS-induced endotoxic shock in mice. We demonstrate that the GR dimer is an important mediator of hemodynamic stability and lung function, possibly through regulation of Opn, during LPS-induced systemic inflammation.

Heterogeneity of Cell Surface Glutamate and GABA Receptor Expression in Shank and CNTN4 Autism Mouse Models.

Autism spectrum disorder (ASD) refers to a large set of neurodevelopmental disorders, which have in common both repetitive behavior and abnormalities in social interactions and communication. Interestingly, most forms of ASD have a strong genetic contribution. However, the molecular underpinnings of this disorder remain elusive. The SHANK3 gene (and to a lesser degree SHANK2) which encode for the postsynaptic density (PSD) proteins SHANK3/SHANK2 and the CONTACTIN 4 gene which encodes for the neuronal glycoprotein CONTACTIN4 (CNTN4) exhibit mutated variants which are associated with ASD. Like many of the other genes associated with ASD, both SHANKs and CNTN4 affect synapse formation and function and are therefore related to the proper development and signaling capability of excitatory and inhibitory neuronal networks in the adult mammal brain. In this study, we used mutant/knock-out mice of Shank2 (Shank2-/-), Shank3 (Shank3αß-/-), and Cntn4 (Cntn4-/-) as ASD-models to explore whether these mice share a molecular signature in glutamatergic and GABAergic synaptic transmission in ASD-related brain regions. Using a biotinylation assay and subsequent western blotting we focused our analysis on cell surface expression of several ionotropic glutamate and GABA receptor subunits: GluA1, GluA2, and GluN1 were analyzed for excitatory synaptic transmission, and the α1 subunit of the GABAA receptor was analyzed for inhibitory synaptic transmission. We found that both Shank2-/- and Shank3αß-/- mice exhibit reduced levels of several cell surface glutamate receptors in the analyzed brain regions-especially in the striatum and thalamus-when compared to wildtype controls. Interestingly, even though Cntn4-/- mice also show reduced levels of some cell surface glutamate receptors in the cortex and hippocampus, increased levels of cell surface glutamate receptors were found in the striatum. Moreover, Cntn4-/- mice do not only show brain region-specific alterations in cell surface glutamate receptors but also a downregulation of cell surface GABA receptors in several of the analyzed brain regions. The results of this study suggest that even though mutations in defined genes can be associated with ASD this does not necessarily result in a common molecular phenotype in surface expression of glutamatergic and GABAergic receptor subunits in defined brain regions.