Early life adversity drives sex-specific anhedonia and meningeal immune gene expression through mast cell activation

Quercetin and Kaempferol inhibit HMC-1 activation via SOCE/NFATc2 signaling and suppress hippocampal mast cell activation in lipopolysaccharide-induced depressive mice

OBJECTIVE AND DESIGN

Mast cells (MCs), as the fastest immune responders, play a critical role in the progression of neuroinflammation-related diseases, especially in depression. Quercetin (Que) and kaempferol (Kae), as two major diet-derived flavonoids, inhibit MC activation and exhibit significant antidepressant effect due to their anti-inflammatory capacity. The study aimed to explore the mechanisms of inhibitory effect of Que and Kae on MC activation, and whether Que and Kae suppress hippocampal mast cell activation in LPS-induced depressive mice.

SUBJECTS AND TREATMENT

In vitro assays, human mast cells (HMC-1) were pretreated with Que or Kae for 1 h, then stimulated by phorbol 12-myristate 13-acetate (PMA) and 2,5-di-t-butyl-1,4-benzohydroquinone (tBHQ) for 3 h or 12 h. In vivo assays, Que or Kae was administered by oral gavage once daily for 14 days and then lipopolysaccharide (LPS) intraperitoneally injection to induce depressive behaviors.

METHODS

The secretion and expression of TNF-α were determined by ELISA and Western blotting. The nuclear factor of activated T cells (NFAT) transcriptional activity was measured in HMC-1 stably expressing NFAT luciferase reporter gene. Nuclear translocation of NFATc2 was detected by nuclear protein extraction and also was fluorescently detected in HMC-1 stably expressing eGFP-NFATc2. We used Ca2+ imaging to evaluate changes of store-operated calcium entry (SOCE) in HMC-1 stably expressing fluorescent Ca2+ indicator jGCamP7s. Molecular docking was used to assess interaction between the Que or Kae and calcium release-activated calcium modulator (ORAI). The  hippocampal mast cell accumulation and activation  were detected by toluidine blue staining and immunohistochemistry with β-tryptase.

RESULTS

In vitro assays of HMC-1 activated by PtBHQ (PMA and tBHQ), Que and Kae significantly decreased expression and secretion of TNF-α. Moreover, NFAT transcriptional activity and nuclear translocation of NFATc2 were remarkably inhibited by Que and Kae. In addition, the Ca2+ influx mediated by SOCE was suppressed by Que, Kae and the YM58483 (ORAI inhibitor), respectively. Importantly, the combination of YM58483 with Que or Kae had no additive effect on the inhibition of SOCE. The molecular docking also showed that Que and Kae both exhibit high binding affinities with ORAI at the same binding site as YM58483. In vivo assays, Que and Kae significantly reversed LPS-induced depression-like behaviors in mice, and inhibited hippocampal mast cell activation  in LPS-induced depressive mice.

CONCLUSIONS

Our results indicated that suppression of SOCE/NFATc2 pathway-mediated by ORAI channels may be the mechanism of inhibitory effect of Que and Kae on MC activation, and also suggested Que and Kae may exert the antidepressant effect through suppressing hippocampal mast cell activation.

Exploring Immune Cell Diversity in the Lacrimal Glands of Healthy Mice: A Single-Cell RNA-Sequencing Atlas

The lacrimal gland is responsible for maintaining the health of the ocular surface through the production of tears. However, our understanding of the immune system within the lacrimal gland is currently limited. Therefore, in this study, we utilized single-cell RNA sequencing and bioinformatic analysis to identify and analyze immune cells and molecules present in the lacrimal glands of normal mice. A total of 34,891 cells were obtained from the lacrimal glands of mice and classified into 18 distinct cell clusters using Seurat clustering. Within these cell populations, 26 different immune cell subpopulations were identified, including T cells, innate lymphocytes, macrophages, mast cells, dendritic cells, and B cells. Network analysis revealed complex cell-cell interactions between these immune cells, with particularly significant interactions observed among T cells, macrophages, plasma cells, and dendritic cells. Interestingly, T cells were found to be the main source of ligands for the Thy1 signaling pathway, while M2 macrophages were identified as the primary target of this pathway. Moreover, some of these immune cells were validated using immunohistological techniques. Collectively, these findings highlight the abundance and interactions of immune cells and provide valuable insights into the complexity of the lacrimal gland immune system and its relevance to associated diseases.

Current views on meningeal lymphatics and immunity in aging and Alzheimer's disease

Alzheimer's disease (AD) is an aging-related form of dementia associated with the accumulation of pathological aggregates of amyloid beta and neurofibrillary tangles in the brain. These phenomena are accompanied by exacerbated inflammation and marked neuronal loss, which altogether contribute to accelerated cognitive decline. The multifactorial nature of AD, allied to our still limited knowledge of its etiology and pathophysiology, have lessened our capacity to develop effective treatments for AD patients. Over the last few decades, genome wide association studies and biomarker development, alongside mechanistic experiments involving animal models, have identified different immune components that play key roles in the modulation of brain pathology in AD, affecting its progression and severity. As we will relay in this review, much of the recent efforts have been directed to better understanding the role of brain innate immunity, and particularly of microglia. However, and despite the lack of diversity within brain resident immune cells, the brain border tissues, especially the meninges, harbour a considerable number of different types and subtypes of adaptive and innate immune cells. Alongside microglia, which have taken the centre stage as important players in AD research, there is new and exciting evidence pointing to adaptive immune cells, namely T and B cells found in the brain and its meninges, as important modulators of neuroinflammation and neuronal (dys)function in AD. Importantly, a genuine and functional lymphatic vascular network is present around the brain in the outermost meningeal layer, the dura. The meningeal lymphatics are directly connected to the peripheral lymphatic system in different mammalian species, including humans, and play a crucial role in preserving a "healthy" immune surveillance of the CNS, by shaping immune responses, not only locally at the meninges, but also at the level of the brain tissue. In this review, we will provide a comprehensive view on our current knowledge about the meningeal lymphatic vasculature, emphasizing its described roles in modulating CNS fluid and macromolecule drainage, meningeal and brain immunity, as well as glial and neuronal function in aging and in AD.

Mast cell ontogeny: From fetal development to life-long health and disease

Mast cells (MCs) are evolutionarily ancient innate immune cells with important roles in protective immunity against bacteria, parasites, and venomous animals. They can be found in most organs of the body, where they also contribute to normal tissue functioning, for example by engaging in crosstalk with nerves. Despite this, they are most widely known for their detrimental roles in allergy, anaphylaxis, and atopic disease. Just like macrophages, mast cells were conventionally thought to originate from the bone marrow. However, they are already present in fetal tissues before the onset of bone marrow hematopoiesis, questioning this dogma. In recent years, our view of myeloid cell ontogeny has been revised. We now know that the first mast cells originate from progenitors made in the extra-embryonic yolk sac, and later get supplemented with mast cells produced from subsequent waves of hematopoiesis. In most connective tissues, sizeable populations of fetal-derived mast cells persist into adulthood, where they self-maintain largely independently from the bone marrow. These developmental origins are highly reminiscent of macrophages, which are known to have critical functions in development. Mast cells too may thus support healthy development. Their fetal origins and longevity also make mast cells susceptible to genetic and environmental perturbations, which may render them pathological. Here, we review our current understanding of mast cell biology from a developmental perspective. We first summarize how mast cell populations are established from distinct hematopoietic progenitor waves, and how they are subsequently maintained throughout life. We then discuss what functions mast cells may normally have at early life stages, and how they may be co-opted to cause, worsen, or increase susceptibility to disease.

Early life maternal separation induces sex-specific antidepressant-like responses but has minimal effects on adult stress susceptibility in mice

Early life stress is known to increase the risk of depression and anxiety disorders, which are highly prevalent conditions that disproportionately affect women. However, the results of preclinical studies have been mixed, with some work suggesting that early life stress promotes anxiety-like behavior and/or increases susceptibility to subsequent stressors, and other research suggesting that early life stress reduces anxiety-like behavior and/or confers resilience to subsequent stress exposure. It is likely that factors such as sex and the timing and severity of early life and adult stress exposure dictate whether a particular early life experience promotes adaptive vs. maladaptive behavior later in life. Most work in this area has focused exclusively on males, but several sex differences in the effects of early life stress on subsequent stress susceptibility have been reported. The current study examined the impact of early life maternal separation on susceptibility to behavioral alterations induced by 3 days of variable stress in adulthood in male and female c57BL6 mice. Our results indicate that 3 days of adult stress is sufficient to increase anxiety-like behavior in several paradigms and to increase immobility in the forced swim test. In contrast, a history of maternal separation reduces anxiety-like behavior in several tests, particularly in males. These findings could contribute to our understanding of sex differences in mental illness by demonstrating that males are more likely than females to display adaptive responses to mild early life stressors.