IL-33 regulates age-dependency of long-term immune dysfunction induced by sepsis

Sepsis survival in adults is commonly followed by immunosuppression and increased susceptibility to secondary infections. However, the long-term immune consequences of pediatric sepsis are unknown. Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages, and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. In contrast to adults, infant mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in post-septic adults but not infant mice. Impaired IL-33 production in post-septic infant mice was associated with increased DNA-methylation on lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in infant mice. Clinically, adults but not pediatric post-septic patients exhibited higher counts of Tregs and sera IL-33 levels. Hence, we describe a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression.

IFN-γ Attenuates Eosinophilic Inflammation but Is Not Essential for Protection against RSV-Enhanced Asthmatic Comorbidity in Adult Mice

The susceptibility to respiratory syncytial virus (RSV) infection in early life has been associated with a deficient T-helper cell type 1 (Th1) response. Conversely, healthy adults generally do not exhibit severe illness from RSV infection. In the current study, we investigated whether Th1 cytokine IFN-γ is essential for protection against RSV and RSV-associated comorbidities in adult mice. We found that, distinct from influenza virus, prior RSV infection does not induce significant IFN-γ production and susceptibility to secondary Streptococcus pneumoniae infection in adult wild-type (WT) mice. In ovalbumin (OVA)-induced asthmatic mice, RSV super-infection increases airway neutrophil recruitment and inflammatory lung damage but has no significant effect on OVA-induced eosinophilia. Compared with WT controls, RSV infection of asthmatic Ifng−/− mice results in increased airway eosinophil accumulation. However, a comparable increase in eosinophilia was detected in house dust mite (HDM)-induced asthmatic Ifng−/− mice in the absence of RSV infection. Furthermore, neither WT nor Ifng−/− mice exhibit apparent eosinophil infiltration during RSV infection alone. Together, these findings indicate that, despite its critical role in limiting eosinophilic inflammation during asthma, IFN-γ is not essential for protection against RSV-induced exacerbation of asthmatic inflammation in adult mice.

A whole-cell recording database of neuromodulatory action in the adult neocortex

Background: The recent release of two large intracellular electrophysiological databases now allows high-dimensional systematic analysis of mechanisms of information processing in the neocortex. Here, to complement these efforts, we introduce a freely and publicly available database that provides a comparative insight into the role of various neuromodulatory transmitters in controlling neural information processing. Findings: A database of in vitro whole-cell patch-clamp recordings from primary somatosensory and motor cortices (layers 2/3) of the adult mice (2-15 months old) from both sexes is introduced. A total of 464 current-clamp experiments from identified excitatory and inhibitory neurons are provided. Experiments include recordings with (i) Step-and-Hold protocol during which the current was transiently held at 10 steps, gradually increasing in amplitude, (ii) 'Frozen Noise' injections that model the amplitude and time-varying nature of synaptic inputs to a neuron in biological networks. All experiments follow a within neuron across drug design which includes a vehicle control and a modulation of one of the following targets in the same neuron: dopamine and its receptors D1R, D2R, serotonin 5HT1f receptor, norepinephrine Alpha1, and acetylcholine M1 receptors. Conclusions: This dataset is the first to provide a systematic and comparative insight into the role of the selected neuromodulators in controlling cellular excitability. The data will help to mechanistically address how bottom-up information processing can be modulated, providing a reference for studying neural coding characteristics and revealing the contribution of neuromodulation to information processing.

Microglia and infiltrating T-cells adopt long-term, age-specific, transcriptional changes after traumatic brain injury

Introduction: Traumatic brain injury (TBI) afflicts over 3 million Americans every year. Patients over 65 years of age suffer increased mortality as well as greater long-term neurocognitive and neuropsychiatric morbidity compared to younger adults. Microglia, the resident macrophages of the brain, are complicit in both. Our published and preliminary data have demonstrated a significant age-effect in which aged microglia are more prone to adopt a constitutively activated state associated with worse neurocognitive and neuropsychiatric outcomes. Therefore, we hypothesized that aged microglia would fail to return to a homeostatic state after TBI but instead adopt a long-term injury-associated state within the brain of aged mice as compared to young-adult mice after TBI. Methods: Young-adult (14-weeks) and aged (80-weeks) C57BL/6 mice underwent TBI via controlled cortical impact vs. sham injury. We utilized single-cell RNA sequencing to examine age-associated cellular responses after TBI. Four months post-TBI or sham injury, brains were harvested, and CD45+ cells (N=4,000 cells) were isolated via florescence-activated cell sorting. cDNA libraries were prepared via the 10x Genomics Chromium Single Cell 3' Reagent Kit, followed by sequencing on a HiSeq 4000 instrument. The raw data were processed using the Cell Ranger pipeline mapped to the mm10 mouse reference genome and Seurat following standard workflow. Seurat and GOrilla were used for downstream clustering, differential gene expression, and pathway analysis. All cell types were annotated using canonical markers and top expressed genes. ProjecTILs was additionally used to interpret T cell states. Results: Microglia from young-adult and aged mice have distinct transcriptional profiles pre-injury and markedly different transcriptional responses post-injury compared to young-adult mice. Pre-injury, aged mice demonstrated a disproportionate immune cell infiltration, including T cells, as compared to young-adult mice (aged versus young: 45.5% vs. 14.5%). Post-injury, the disparity was amplified with a proportional decrease in homeostatic microglia and greater increased infiltrating T cells compared to young-adult mice (Microglia: 27.5% vs. 71%; T cell: 45.5% vs. 4.5%). Of note, aged mice post-injury had a subpopulation of unique, age-specific, immune-inflammatory microglia resembling gene profiles of neurodegenerative disease-associated microglia (DAM) with enriched pathways involved in leukocyte recruitment and Alzheimer’s disease pathogenesis (FDR < 0.05). Contrastingly, post-injury, aged mice demonstrate a heterogenous T-cell infiltration with gene profiles corresponding to CD8 effector memory, CD8 native-like, CD4, and double-negative T cells (75.9%, 2.5%, 12.9%, and 8.6%, respectively) and enriched pathways including tau protein binding, macromolecule synthesis, and cytokine-mediated signaling pathways (FDR < 0.05). Conclusion: We hypothesized that aged microglia would fail to return to a homeostatic state after TBI and adopt a long-term, injury-associated state within the brain of aged mice as compared to young-adult mice after TBI. In particular, our data suggest an age-dependent reduction of homeostatic microglia post-injury yet an upregulation in a unique microglial subpopulation with a distinct immuno-inflammatory profile. Furthermore, aged subjects demonstrated a markedly disproportionate inflammatory infiltrate after TBI predominated by the presence of CD8+ T cells. In addition, post-injury, brain trauma reorganized the T cell milieu, especially CD8 effector memory T cells, via upregulating genes associated with macromolecule biosynthesis process and negative regulation of neuronal death, possibly linking TBI with its long-term sequelae and complications. Taken together, our data showed that age-specific gene signature changes in the T-cell infiltrates and the microglial subpopulation contributes to increased vulnerability of the aged brain to TBI. Age should be an a priori consideration in future TBI clinical trials.

Flexible cue anchoring strategies enable stable head direction coding in both sighted and blind animals

Vision plays a crucial role in instructing the brain's spatial navigation systems. However, little is known about how vision loss affects the neuronal encoding of spatial information. Here, recording from head direction (HD) cells in the anterior dorsal nucleus of the thalamus in mice, we find stable and robust HD tuning in blind animals. In contrast, placing sighted animals in darkness significantly impairs HD cell tuning. We find that blind mice use olfactory cues to maintain stable HD tuning and that prior visual experience leads to refined HD cell tuning in blind adult mice compared to congenitally blind animals. Finally, in the absence of both visual and olfactory cues, the HD attractor network remains intact but the preferred firing direction of HD cells continuously drifts over time. We thus demonstrate remarkable flexibility in how the brain uses diverse sensory information to generate a stable directional representation of space.

Prenatal stress programs behavioral pattern separation in adult mice

Stress is an unavoidable condition in human life. Stressful events experienced during development, including in utero, have been suggested as one major pathophysiological mechanism for developing vulnerability towards neuropsychiatric and neurodevelopmental disorders in adulthood. One cardinal feature of such disorders is impaired cognitive ability, which may in part rely on abnormal structure and function of the hippocampus. In the hippocampus, the dentate gyrus is a site of continuous neurogenesis, a process that has been recently implicated in spatial pattern separation, a cognitive phenomenon that serves to reduce the degree of overlap in the incoming information to facilitate its storage with minimal interference. We previously reported that adult neurogenesis is altered by prenatal stress allowing us to hypothesize that prenatal stress may possibly lead to impairment in pattern separation. To test this hypothesis, both control (C) and prenatally stressed (PS) adult mice were tested for metric and contextual discrimination abilities. We report for the first time that prenatal stress impairs pattern separation process, a deficit that may underlie their cognitive alterations and that may result in defective behaviors reminiscent of psychiatric illness such as post-traumatic stress disorder.

CCR2 promotes monocyte recruitment and intestinal inflammation in mice lacking the interleukin-10 receptor

Macrophages are a heterogeneous population of mononuclear phagocytes abundantly distributed throughout the intestinal compartments that adapt to microenvironmental specific cues. In adult mice, the majority of intestinal macrophages exhibit a mature phenotype and are derived from blood monocytes. In the steady-state, replenishment of these cells is reduced in the absence of the chemokine receptor CCR2. Within the intestine of mice with colitis, there is a marked increase in the accumulation of immature macrophages that demonstrate an inflammatory phenotype. Here, we asked whether CCR2 is necessary for the development of colitis in mice lacking the receptor for IL10. We compared the development of intestinal inflammation in mice lacking IL10RA or both IL10RA and CCR2. The absence of CCR2 interfered with the accumulation of immature macrophages in IL10R-deficient mice, including a novel population of rounded submucosal Iba1+ cells, and reduced the severity of colitis in these mice. In contrast, the absence of CCR2 did not reduce the augmented inflammatory gene expression observed in mature intestinal macrophages isolated from mice lacking IL10RA. These data suggest that both newly recruited CCR2-dependent immature macrophages and CCR2-independent residual mature macrophages contribute to the development of intestinal inflammation observed in IL10R-deficient mice.

Taurine Grafted Micro-Implants Improved Functions without Direct Dependency between Interleukin-6 and the Bile Acid Lithocholic Acid in Plasma

A recent study showed an association between diabetes development and the bile acid lithocholic acid (LCA), while another study demonstrated positive biological effects of the conjugated bile acid, taurocholic acid (TCA), on pancreatic cells. Thus, this study aimed to encapsulate TCA with primary islets (graft) and study the biological effects of the graft, post-transplantation, in diabetic mice, including effects on LCA concentrations. Sixteen mature adult mice were made diabetic and randomly divided into two equal groups, control and test (transplanted encapsulated islets without or with TCA). Graft pharmaceutical features pre-transplantation, and biological effects including on LCA concentrations post-transplantation, were measured. TCA-microcapsules had an oval shape and similar size compared with the control. The treatment group survived longer, showed improved glucose and interleukin-6 concentrations, and lower LCA concentrations in plasma, large intestine, faeces, liver and spleen, compared with control. Results suggest that TCA incorporation with islets encapsulated graft exerted beneficial effects, but there was no direct and significant dependency between concentrations of interleukin-6 and LCA.

Inhibition of aberrant Hif1α activation delays intervertebral disc degeneration in adult mice

The intervertebral disc (IVD) is the largest avascular tissue. Hypoxia-inducible factors (HIFs) play essential roles in regulating cellular adaptation in the IVD under physiological conditions. Disc degeneration disease (DDD) is one of the leading causes of disability, and current therapies are ineffective. This study sought to explore the role of HIFs in DDD pathogenesis in mice. The findings of this study showed that among HIF family members, Hif1α was significantly upregulated in cartilaginous endplate (EP) and annulus fibrosus (AF) tissues from human DDD patients and two mouse models of DDD compared with controls. Conditional deletion of the E3 ubiquitin ligase Vhl in EP and AF tissues of adult mice resulted in upregulated Hif1α expression and age-dependent IVD degeneration. Aberrant Hif1α activation enhanced glycolytic metabolism and suppressed mitochondrial function. On the other hand, genetic ablation of the Hif1α gene delayed DDD pathogenesis in Vhl-deficient mice. Administration of 2-methoxyestradiol (2ME2), a selective Hif1α inhibitor, attenuated experimental IVD degeneration in mice. The findings of this study show that aberrant Hif1α activation in EP and AF tissues induces pathological changes in DDD, implying that inhibition of aberrant Hif1α activity is a potential therapeutic strategy for DDD.