Reduced Fear Memory and Anxiety-like Behavior in Mice Lacking Formylpeptide Receptor 1

Abstract N-formylpeptide receptor 1 (FPR1) is a G protein-coupled receptor that mediates pro-inflammatory chemotactic responses by phagocytic leukocytes to N-formylpeptides produced by bacteria or mitochondria. Mice lacking Fpr1 (Fpr1 -/-mice) have increased susceptibility to challenge with certain bacteria. FPR1 is also a receptor for annexin-1, which mediates the anti-inflammatory effects of glucocorticoids as well as negative feedback by glucocorticoids of the hypothalamic-pituitary-adrenocortical axis. However, homeostatic functions of FPR1 in the neuroendocrine system have not previously been defined. Here we show that in systematic behavioral testing Fpr1 -/-mice exhibited increased exploratory activity, reduced anxiety-like behavior, and impaired fear memory, but normal spatial memory and learning capacity. Consistent with this, the homeostatic serum level of corticosterone in Fpr1 -/-mice was significantly lower compared with wild-type mice. The data implicate Fpr1 in modulation of anxiety-like behavior and fear memory by regulating glucocorticoid production

Reduced Fear Memory and Anxiety-like Behavior in Mice Lacking Formylpeptide Receptor 1

Abstract N-formylpeptide receptor 1 (FPR1) is a G protein-coupled receptor that mediates pro-inflammatory chemotactic responses by phagocytic leukocytes to N-formylpeptides produced by bacteria or mitochondria. Mice lacking Fpr1 (Fpr1 -/-mice) have increased susceptibility to challenge with certain bacteria. FPR1 is also a receptor for annexin-1, which mediates the anti-inflammatory effects of glucocorticoids as well as negative feedback by glucocorticoids of the hypothalamic-pituitary-adrenocortical axis. However, homeostatic functions of FPR1 in the neuroendocrine system have not previously been defined. Here we show that in systematic behavioral testing Fpr1 -/-mice exhibited increased exploratory activity, reduced anxiety-like behavior, and impaired fear memory, but normal spatial memory and learning capacity. Consistent with this, the homeostatic serum level of corticosterone in Fpr1 -/-mice was significantly lower compared with wild-type mice. The data implicate Fpr1 in modulation of anxiety-like behavior and fear memory by regulating glucocorticoid production

Tailor-made inflammation: how neutrophil serine proteases modulate the inflammatory response

Neutrophil granulocytes are important mediators of innate immunity, but also participate in the pathogenesis of (auto)inflammatory diseases. Neutrophils express a specific set of proteolytic enzymes, the neutrophil serine proteases (NSPs), which are stored in cytoplasmic granules and can be secreted into the extra- and pericellular space upon cellular activation. These NSPs, namely cathepsin G (CG), neutrophil elastase (NE), and proteinase 3 (PR3), have early been implicated in bacterial defense. However, NSPs also regulate the inflammatory response by specifically altering the function of cytokines and chemokines. For instance, PR3 and NE both inactivate the anti-inflammatory mediator progranulin, which may play a role in chronic inflammation. Here, we provide a concise update on NSPs as modulators of inflammation and discuss the biological and pathological significance of this novel function of NSPs. Mounting evidence support an important proinflammatory function for PR3, which may have been underestimated in the past

Targeting OGG1 arrests cancer cell proliferation by inducing replication stress

Altered oncogene expression in cancer cells causes loss of redox homeostasis resulting in oxidative DNA damage, e.g. 8-oxoguanine (8-oxoG), repaired by base excision repair (BER). PARP1 coordinates BER and relies on the upstream 8-oxoguanine-DNA glycosylase (OGG1) to recognise and excise 8-oxoG. Here we hypothesize that OGG1 may represent an attractive target to exploit reactive oxygen species (ROS) elevation in cancer. Although OGG1 depletion is well tolerated in non-transformed cells, we report here that OGG1 depletion obstructs A3 T-cell lymphoblastic acute leukemia growth in vitro and in vivo, validating OGG1 as a potential anti-cancer target. In line with this hypothesis, we show that OGG1 inhibitors (OGG1i) target a wide range of cancer cells, with a favourable therapeutic index compared to non-transformed cells. Mechanistically, OGG1i and shRNA depletion cause S-phase DNA damage, replication stress and proliferation arrest or cell death, representing a novel mechanistic approach to target cancer. This study adds OGG1 to the list of BER factors, e.g. PARP1, as potential targets for cancer treatment

Effects of neonatal handling and enriched environment on neurotrophins and cognitive function

Environmental stimulation plays a critical role in the development and maintenance of behaviours and neural processes. Two experimental models that have guided research on behavioural and neural plasticity are Postnatal handling and Environmental enrichment. The development, maintenance and function of the nervous system depend on neurotrophic factors. The neurotrophic factors constitute a group of target derived protein family with highly diverse functions for neurones survival, guidance, growth and phenotypic maturation. Three neurotrophic factors were examined in this thesis: Nerve growth factor (NGF) including NGF receptors, Brain-derived neurotrophic factor (BDNF) and Neurotrophin-3 (NT-3). The studies included in this thesis investigated the relationship of environment neurotrophins and behaviour. Postnatal handling of rats has been shown to alter the development of the stress response system at the cortical level. The underlying mechanism and the effects on cognitive function following postnatal handling are still unclear. In paper I, the behavioural effects of chronic mild stress on postnatal handled (H) and nonhandled (NH) rats were examined. In addition we also examined if exposure to mild stress would alter hippocampal nerve growth factor levels. In contrast to the reported deleterious effect of acute strong stress, exposure to mild stimulation for five months following postnatal handling resulted in improved spatial learning in H rats and increased production of hippocampal nerve growth factor in NH rats. Nonhandling lowered NGF levels and impaired spatial learning. To analyse further the influence of environmental effects on behaviour and NGF levels, we examined in paper II whether exposure to differential housing conditions would counteract the effects of early experience. After weaning, the H and NH animals were divided into 4 groups and were housed in either enriched (EC) or isolated (IC) environmental conditions. We found that housing in enrichment following nonhandling increased hippocampal NGF levels, and improved spatial learning. Our results therefore suggest that environmental enrichment has the potential to reduce the cognitive and neurochemical deficits in the nonhandled animals. In paper Ill, we examined the effects of long-term differential housing on NGF levels, its receptors and their relationship to cognitive function. Adults rats were housed in either enriched or isolated conditions for one year. At middle age, the EC animals had significantly higher levels of NGF in the hippocampus, entorhinal and visual cortices compared to the IC animals. Immunohistochemical analysis of the brain medial septal area also showed larger cell size and higher staining fibre density in both the low-affinity and the high-affinity NGF receptors. Middle aged EC rats performed better than IC rats in acquisition of spatial learning and had lower locomotion scores in the open field test. In order to determine if environmentally induced changes in NGF levels are associated with other neurotrophic factors and in different brain regions, we assessed in paper IV, NGF, BDNF and NT-3 levels in the cerebral cortex, hippocampal formation, basal forebrain, and hind brain of EC and IC middle aged rats. In general we found that NGF and levels were increased in all selected brain regions in the EC rats compared to age-matched IC rats. NT-3 levels were higher in the basal forebrain and cerebral cortex of EC animals. These findings provide possible biochemical basis of behavioural and morphological alterations that have been shown to occur with stimulus-rich environment. The results confirmed and extended our earlier observations that environmental stimulation results in increased production of trophic factors and structural reorganisation in specific brain regions known to be important for cognitive function. Paper V examined neurotrophins levels in separated hemispheres of H and NH animals. We found that postnatal handling increased NGF levels in the hippocampus. Furthermore hemispheric asymmetry in NT-3 levels was noted in the hippocampus, and also laterality of NGF levels in the dentate gyrus of the H rats. Our results also revealed higher NT-3 in the left basal forebrain and cerebellum of the H rats. Behavioural testing of H and NH rats caused changes in NGF and NT-3 levels in the basal forebrain, hippocampal and cerebellum. These findings implicate neurotrophins in environmentally induced changes in brain and cognitive function

Ex vivo culture of cells derived from circulating tumour cell xenograft to support small cell lung cancer research and experimental therapeutics

Background and Purpose: Small cell lung cancer (SCLC) is an aggressive disease with median survival of <2 years. Tumour biopsies for research are scarce, especially from extensive‐stage patients, with repeat sampling at disease progression rarely performed. We overcame this limitation for relevant preclinical models by developing SCLC circulating tumour cell derived explants (CDX), which mimic the donor tumour pathology and chemotherapy response. To facilitate compound screening and identification of clinically relevant biomarkers, we developed short‐term ex vivo cultures of CDX tumour cells. Experimental Approach: CDX tumours were disaggregated, and the human tumour cells derived were cultured for a maximum of 5 weeks. Phenotypic, transcriptomic and pharmacological characterization of these cells was performed. Key Results: CDX cultures maintained a neuroendocrine phenotype, and most changes in the expression of protein‐coding genes observed in cultures, for up to 4 weeks, were reversible when the cells were re‐implanted in vivo. Moreover, the CDX cultures exhibited a similar sensitivity to chemotherapy compared to the corresponding CDX tumour in vivo and were able to predict in vivo responses to therapeutic candidates. Conclusions and Implications: Short‐term cultures of CDX provide a tractable platform to screen new treatments, identify predictive and pharmacodynamic biomarkers and investigate mechanisms of resistance to better understand the progression of this recalcitrant tumour

A stromal progenitor and ILC2 niche promotes muscle eosinophilia and fibrosis-associated gene expression.

Despite the well-accepted view that chronic inflammation contributes to the pathogenesis of Duchenne muscular dystrophy (DMD), the function and regulation of eosinophils remain an unclear facet of type II innate immunity in dystrophic muscle. We report the observation that group 2 innate lymphoid cells (ILC2s) are present in skeletal muscle and are the principal regulators of muscle eosinophils during muscular dystrophy. Eosinophils were elevated in DMD patients and dystrophic mice along with interleukin (IL)-5, a major eosinophil survival factor that was predominantly expressed by muscle ILC2s. We also find that IL-33 was upregulated in dystrophic muscle and was predominantly produced by fibrogenic/adipogenic progenitors (FAPs). Exogenous IL-33 and IL-2 complex (IL-2c) expanded muscle ILC2s and eosinophils, decreased the cross-sectional area (CSA) of regenerating myofibers, and increased the expression of genes associated with muscle fibrosis. The deletion of ILC2s in dystrophic mice mitigated muscle eosinophilia and impaired the induction of IL-5 and fibrosis-associated genes. Our findings highlight a FAP/ILC2/eosinophil axis that promotes type II innate immunity, which influences the balance between regenerative and fibrotic responses during muscular dystrophy

A stromal progenitor and ILC2 niche promotes muscle eosinophilia and fibrosis-associated gene expression.

Despite the well-accepted view that chronic inflammation contributes to the pathogenesis of Duchenne muscular dystrophy (DMD), the function and regulation of eosinophils remain an unclear facet of type II innate immunity in dystrophic muscle. We report the observation that group 2 innate lymphoid cells (ILC2s) are present in skeletal muscle and are the principal regulators of muscle eosinophils during muscular dystrophy. Eosinophils were elevated in DMD patients and dystrophic mice along with interleukin (IL)-5, a major eosinophil survival factor that was predominantly expressed by muscle ILC2s. We also find that IL-33 was upregulated in dystrophic muscle and was predominantly produced by fibrogenic/adipogenic progenitors (FAPs). Exogenous IL-33 and IL-2 complex (IL-2c) expanded muscle ILC2s and eosinophils, decreased the cross-sectional area (CSA) of regenerating myofibers, and increased the expression of genes associated with muscle fibrosis. The deletion of ILC2s in dystrophic mice mitigated muscle eosinophilia and impaired the induction of IL-5 and fibrosis-associated genes. Our findings highlight a FAP/ILC2/eosinophil axis that promotes type II innate immunity, which influences the balance between regenerative and fibrotic responses during muscular dystrophy