RNA Sensing by Gut Piezo1 Is Essential for Systemic Serotonin Synthesis.

Gastrointestinal enterochromaffin cells regulate bone and gut homeostasis via serotonin (5-hydroxytryptamine [5-HT]) production. A recent report suggested that gut microbes regulate 5-HT levels; however, the precise underlying molecular mechanisms are unexplored. Here, we reveal that the cation channel Piezo1 in the gut acts as a sensor of single-stranded RNA (ssRNA) governing 5-HT production. Intestinal epithelium-specific deletion of mouse Piezo1 profoundly disturbed gut peristalsis, impeded experimental colitis, and suppressed serum 5-HT levels. Because of systemic 5-HT deficiency, conditional knockout of Piezo1 increased bone formation. Notably, fecal ssRNA was identified as a natural Piezo1 ligand, and ssRNA-stimulated 5-HT synthesis from the gut was evoked in a MyD88/TRIF-independent manner. Colonic infusion of RNase A suppressed gut motility and increased bone mass. These findings suggest gut ssRNA as a master determinant of systemic 5-HT levels, indicating the ssRNA-Piezo1 axis as a potential prophylactic target for treatment of bone and gut disorders.

CGRP sensory neurons promote tissue healing via neutrophils and macrophages.

The immune system has a critical role in orchestrating tissue healing. As a result, regenerative strategies that control immune components have proved effective1,2. This is particularly relevant when immune dysregulation that results from conditions such as diabetes or advanced age impairs tissue healing following injury2,3. Nociceptive sensory neurons have a crucial role as immunoregulators and exert both protective and harmful effects depending on the context4-12. However, how neuro-immune interactions affect tissue repair and regeneration following acute injury is unclear. Here we show that ablation of the NaV1.8 nociceptor impairs skin wound repair and muscle regeneration after acute tissue injury. Nociceptor endings grow into injured skin and muscle tissues and signal to immune cells through the neuropeptide calcitonin gene-related peptide (CGRP) during the healing process. CGRP acts via receptor activity-modifying protein 1 (RAMP1) on neutrophils, monocytes and macrophages to inhibit recruitment, accelerate death, enhance efferocytosis and polarize macrophages towards a pro-repair phenotype. The effects of CGRP on neutrophils and macrophages are mediated via thrombospondin-1 release and its subsequent autocrine and/or paracrine effects. In mice without nociceptors and diabetic mice with peripheral neuropathies, delivery of an engineered version of CGRP accelerated wound healing and promoted muscle regeneration. Harnessing neuro-immune interactions has potential to treat non-healing tissues in which dysregulated neuro-immune interactions impair tissue healing.

Senso-immunology: the hidden relationship between sensory system and immune system.

The primary sensory neurons involved in pain perception express various types of receptor-type ion channels at their nerve endings. These molecules are responsible for triggering neuronal excitation, translating environmental stimuli into pain signals. Recent studies have shown that acute nociception, induced by neuronal excitation, not only serves as a sensor for signaling life-threatening situations but also modulates our pathophysiological conditions. This modulation occurs through the release of neuropeptides by primary sensory neurons excited by nociceptive stimuli, which directly or indirectly affect peripheral systems, including immune function. Senso-immunology, an emerging research field, integrates interdisciplinary studies of pain and immunology and has garnered increasing attention in recent years. This review provides an overview of the systemic pathophysiological functions regulated by receptor-type ion channels, such as transient receptor potential (TRP) channels in primary sensory neurons, from the perspective of senso-immunology.

Role of Kynurenine and Its Derivatives in the Neuroimmune System.

In recent years, there has been a growing realization of intricate interactions between the nervous and immune systems, characterized by shared humoral factors and receptors. This interplay forms the basis of the neuroimmune system, the understanding of which will provide insights into the pathogenesis of neurological diseases, in which the involvement of the immune system has been overlooked. Kynurenine and its derivatives derived from tryptophan have long been implicated in the pathogenesis of various neurological diseases. Recent studies have revealed their close association not only with neurological disorders but also with sepsis-related deaths. This review provides an overview of the biochemistry of kynurenine and its derivatives, followed by a discussion of their role via the modulation of the neuroimmune system in various diseases.

The transcription factor Jdp2 controls bone homeostasis and antibacterial immunity by regulating osteoclast and neutrophil differentiation.

Jdp2 is an AP-1 family transcription factor that regulates the epigenetic status of histones. Previous in vitro studies revealed that Jdp2 is involved in osteoclastogenesis. However, the roles of Jdp2 in vivo and its pleiotropic functions are largely unknown. Here we generated Jdp2(-/-) mice and discovered its crucial roles not only in bone metabolism but also in differentiation of neutrophils. Jdp2(-/-) mice exhibited osteopetrosis resulting from impaired osteoclastogenesis. Jdp2(-/-) neutrophils were morphologically normal but had impaired surface expression of Ly6G, bactericidal function, and apoptosis. We also found that ATF3 was an inhibitor of neutrophil differentiation and that Jdp2 directly suppresses its expression via inhibition of histone acetylation. Strikingly, Jdp2(-/-) mice were highly susceptible to Staphylococcus aureus and Candida albicans infection. Thus, Jdp2 plays pivotal roles in in vivo bone homeostasis and host defense by regulating osteoclast and neutrophil differentiation.

Associations between diet and mental health using the 12-item General Health Questionnaire: cross-sectional and prospective analyses from the Japan Multi-Institutional Collaborative Cohort Study.

BACKGROUND: Mental health has become a major public health issue worldwide. Biological and epidemiological studies suggest diet has a role in the prevention or cure of mental disorders. However, further research is required to elucidate the relationship between diet and mental health. This study aimed to investigate associations between dietary intake of nutrients (macronutrients, vitamins, calcium, and fatty acids) and food groups (fish, meat and chicken, dairy products, and vegetables) and mental health among middle-aged Japanese in cross-sectional and prospective studies. METHODS: In total, 9298 men and women that participated in two areas of the Japan Multi-Institutional Collaborative Cohort Study were eligible for analysis at the baseline (cross-sectional) survey. Of these, 4701 participants were followed for about 5 years and included in the follow-up (prospective) analysis. The 12-item General Health Questionnaire (GHQ) was used to assess participants' general mental health status over the past several weeks. The average intake of 46 foods over the past year was assessed by a validated food frequency questionnaire. We also evaluated lifestyle and medical factors using a self-administered questionnaire. A cross-sectional logistic regression analysis was performed to estimate odds ratios for a GHQ score ≥ 4 (poor mental health) according to dietary intake of foods/nutrients at baseline. The prospective study used baseline dietary and lifestyle factors and GHQ scores at follow-up. RESULTS: The cross-sectional logistic regression analysis showed vegetables, protein, calcium, vitamin D, carotene and n-3 highly-polyunsaturated fatty acids were inversely associated with a GHQ score ≥ 4. On the other hand, mono-unsaturated fatty acids showed a positive association with higher GHQ score. The prospective logistic regression analysis found dairy products, calcium, vitamin B2, and saturated fatty acids were inversely correlated with a GHQ score ≥ 4. Calcium was associated with GHQ scores in both the cross-sectional and follow-up studies. In the follow-up study, the multivariable-adjusted odds ratio for a GHQ score ≥ 4 was 0.71 (95% confidence interval, 0.55-0.92) for the highest versus lowest quartiles of calorie-adjusted dietary calcium intake. CONCLUSION: Consuming particular nutrients and foods, especially calcium and dairy products, may lead to better mental health in Japanese adults.

Antitumor effect of Batf2 through IL-12 p40 up-regulation in tumor-associated macrophages.

The development of effective treatments against cancers is urgently needed, and the accumulation of CD8+ T cells within tumors is especially important for cancer prognosis. Although their mechanisms are still largely unknown, growing evidence has indicated that innate immune cells have important effects on cancer progression through the production of various cytokines. Here, we found that basic leucine zipper transcription factor ATF-like 2 (Batf2) has an antitumor effect. An s.c. inoculated tumor model produced fewer IL-12 p40+ macrophages and activated CD8+ T cells within the tumors of Batf2-/- mice compared with WT mice. In vitro studies also revealed that the IL-12 p40 expression was significantly lower in Batf2-/- macrophages following their stimulation by toll-like receptor ligands, such as R848. Additionally, we found that BATF2 interacts with p50/p65 and promotes IL-12 p40 expression. In conclusion, Batf2 has an antitumor effect through the up-regulation of IL-12 p40 in tumor-associated macrophages, which eventually induces CD8+ T-cell activation and accumulation within the tumor.

Emerging Perspectives on Pain Management by Modulation of TRP Channels and ANO1.

Receptor-type ion channels are critical for detection of noxious stimuli in primary sensory neurons. Transient receptor potential (TRP) channels mediate pain sensations and promote a variety of neuronal signals that elicit secondary neural functions (such as calcitonin gene-related peptide [CGRP] secretion), which are important for physiological functions throughout the body. In this review, we focus on the involvement of TRP channels in sensing acute pain, inflammatory pain, headache, migraine, pain due to fungal infections, and osteo-inflammation. Furthermore, action potentials mediated via interactions between TRP channels and the chloride channel, anoctamin 1 (ANO1), can also generate strong pain sensations in primary sensory neurons. Thus, we also discuss mechanisms that enhance neuronal excitation and are dependent on ANO1, and consider modulation of pain sensation from the perspective of both cation and anion dynamics.

The association between self-rated health and high-sensitivity C-reactive protein level: a cross-sectional and 5-year longitudinal study.

BACKGROUND: Although self-rated health (SRH) independently predicts mortality, the biological background of this association remains unexplained. This study aimed to examine the association between SRH and serum high-sensitivity C-reactive protein (hsCRP) level. METHODS: Subjects were 899 participants aged 35-69 years (237 men and 662 women) in the Daiko Study, part of the Japan Multi-Institutional Collaborative Cohort Study. They were enrolled from 2008 to 2010. Of the subjects, 666 participated in a second survey 5 years later. Lifestyle factors and SRH were assessed using a self-administered questionnaire. Serum hsCRP level was measured using a latex-enhanced immunonephelometric assay. The association between SRH and serum hsCRP level was evaluated using a general linear model with covariates. We further longitudinally investigated whether higher serum hsCRP level at baseline predicts poor SRH after 5 years using an unconditional logistic regression model. RESULTS: A higher serum hsCRP level was significantly associated with poor SRH at baseline after adjusting for covariates (p for trend = 0.023). The age- and sex-adjusted odds ratio and 95% confidence interval (CI) for poor SRH after 5 years was 1.45 (95% CI: 0.76-2.78) for the highest tertile compared with the lowest tertile of serum hsCRP level at baseline with a significant linear trend (p for trend = 0.033), although the risk increase disappeared after adjustment for other covariates. CONCLUSIONS: The present study demonstrated that poor SRH is cross-sectionally associated with higher serum hsCRP level. However, the longitudinal data did not support the relationship between serum hsCRP level at baseline and future SRH. Further longitudinal studies that include data on mortality and multiple inflammatory markers are warranted to elucidate the possible role of low-grade inflammation in the association between SRH and mortality risk.

Bone-protective Functions of Netrin 1 Protein.

Netrin 1 was initially identified as an axon guidance factor, and recent studies indicate that it inhibits chemokine-directed monocyte migration. Despite its importance as a neuroimmune guidance cue, the role of netrin 1 in osteoclasts is largely unknown. Here we detected high netrin 1 levels in the synovial fluid of rheumatoid arthritis patients. Netrin 1 is potently expressed in osteoblasts and synovial fibroblasts, and IL-17 robustly enhances netrin 1 expression in these cells. The binding of netrin 1 to its receptor UNC5b on osteoclasts resulted in activation of SHP1, which inhibited VAV3 phosphorylation and RAC1 activation. This significantly impaired the actin polymerization and fusion, but not the differentiation of osteoclast. Strikingly, netrin 1 treatment prevented bone erosion in an autoimmune arthritis model and age-related bone destruction. Therefore, the netrin 1-UNC5b axis is a novel therapeutic target for bone-destructive diseases.

Netrins as prophylactic targets in skeletal diseases: A double-edged sword?

The netrin family of proteins are involved in axon guidance during central nervous system development. In vertebrates, two membrane bound forms and five secreted forms of netrin have been reported. In addition to their critical role in neural morphogenesis, a growing number of reports suggest that netrin family proteins also play a role in inflammatory conditions, angiogenesis, and tumorigenesis. In these processes, Unc5 and DCC family proteins serve as receptors of netrin proteins. Recently, it was reported that some netrin family proteins may be involved in the pathogenesis of skeletal diseases including osteoporosis and arthritis. For example, administration of secreted netrin family proteins such as netrin 1 and netrin 4 has prophylactic potential in pathogenic bone degradation in mice. However, netrin 1 blocking antibody also protects mice from inflammatory bone destruction. Therefore, netrin family proteins are involved in the regulation of bone homeostasis, but their bona fide roles in the skeletal system remain controversial. In this review, we discuss the osteo-innate-immune functions of the netrin family of proteins, and summarize their therapeutic potential.

5-Azacytidine-induced protein 2 (AZI2) regulates bone mass by fine-tuning osteoclast survival.

5-Azacytidine-induced protein 2 (AZI2) is a TNF receptor (TNFR)-associated factor family member-associated NF-κB activator-binding kinase 1-binding protein that regulates the production of IFNs. A previous in vitro study showed that AZI2 is involved in dendritic cell differentiation. However, the roles of AZI2 in immunity and its pleiotropic functions are unknown in vivo. Here we report that AZI2 knock-out mice exhibit normal dendritic cell differentiation in vivo. However, we found that adult AZI2 knock-out mice have severe osteoporosis due to increased osteoclast longevity. We revealed that the higher longevity of AZI2-deficient osteoclasts is due to an augmented activation of proto-oncogene tyrosine-protein kinase Src (c-Src), which is a critical player in osteoclast survival. We found that AZI2 inhibits c-Src activity by regulating the activation of heat shock protein 90 (Hsp90), a chaperone involved in c-Src dephosphorylation. Furthermore, we demonstrated that AZI2 indirectly inhibits c-Src by interacting with the Hsp90 co-chaperone Cdc37. Strikingly, administration of a c-Src inhibitor markedly prevented bone loss in AZI2 knock-out mice. Together, these findings indicate that AZI2 regulates bone mass by fine-tuning osteoclast survival.

DNA damage sensor MRE11 recognizes cytosolic double-stranded DNA and induces type I interferon by regulating STING trafficking.

Double-stranded DNA (dsDNA) derived from pathogen- or host-damaged cells triggers innate immune responses when exposed to cytoplasm. However, the machinery underlying the primary recognition of intracellular dsDNA is obscure. Here we show that the DNA damage sensor, meiotic recombination 11 homolog A (MRE11), serves as a cytosolic sensor for dsDNA. Cells with a mutation of MRE11 gene derived from a patient with ataxia-telangiectasia-like disorder, and cells in which Mre11 was knocked down, had defects in dsDNA-induced type I IFN production. MRE11 physically interacted with dsDNA in the cytoplasm and was required for activation of stimulator of IFN genes (STING) and IRF3. RAD50, a binding protein to MRE11, was also required for dsDNA responses, whereas NBS1, another binding protein to MRE11, was dispensable. Collectively, our results suggest that the MRE11-RAD50 complex plays important roles in recognition of dsDNA and initiation of STING-dependent signaling, in addition to its role in DNA-damage responses.

Emerging molecules in the interface between skeletal system and innate immunity.

Despite the improved treatment of bone destruction, significant unmet medical need remains. For example, there is a limited benefit of continued bisphosphonate therapy for osteoporotic patients, and only minor populations of rheumatoid arthritis patients obtain biologic-free remission. Therefore, the identification of a novel therapeutic target for bone destructive diseases remains an important issue in the field of skeletal biology. To date there has been little progress in identifying osteo-innate-immunological regulators that could be used for the prophylactic treatment of inflammatory bone destruction. Recently, we identified several new molecules that are critical osteo-innate-immunological regulators by using gene targeting technology. These findings may offer an invaluable opportunity to regulate bone-destructive diseases, such as osteoporosis and rheumatoid arthritis.

Critical role of AZI2 in GM-CSF-induced dendritic cell differentiation.

TNFR-associated factor family member-associated NF-κB activator (TANK)-binding kinase 1 (TBK1) is critical for the activation of IFN regulatory factor 3 and type I IFN production upon virus infection. A set of TBK1-binding proteins, 5-azacytidine-induced gene 2 (AZI2; also known as NAP1), TANK, and TBK1-binding protein 1 (TBKBP1), have also been implicated in the production of type I IFNs. Among them, TANK was found to be dispensable for the responses against virus infection. However, physiological roles of AZI2 and TBKBP1 have yet to be clarified. In this study, we found that none of these TBK1-binding proteins is critical for type I IFN production in mice. In contrast, AZI2, but not TBKBP1, is critical for the differentiation of conventional dendritic cells (cDCs) from bone marrow cells in response to GM-CSF. AZI2 controls GM-CSF-induced cell cycling of bone marrow cells via TBK1. GM-CSF-derived DCs from AZI2-deficient mice show severe defects in cytokine production and T cell activation both in vitro and in vivo. Reciprocally, overexpression of AZI2 results in efficient generation of cDCs, and the cells show enhanced T cell activation in response to Ag stimulation. Taken together, AZI2 expression is critical for the generation of cDCs by GM-CSF and can potentially be used to increase the efficiency of immunization by cDCs.

Neuroimmune modulation by tryptophan derivatives in neurological and inflammatory disorders.

The nervous and immune systems are highly developed, and each performs specialized physiological functions. However, they work together, and their dysfunction is associated with various diseases. Specialized molecules, such as neurotransmitters, cytokines, and more general metabolites, are essential for the appropriate regulation of both systems. Tryptophan, an essential amino acid, is converted into functional molecules such as serotonin and kynurenine, both of which play important roles in the nervous and immune systems. The role of kynurenine metabolites in neurodegenerative and psychiatric diseases has recently received particular attention. Recently, we found that hyperactivity of the kynurenine pathway is a critical risk factor for septic shock. In this review, we first outline neuroimmune interactions and tryptophan derivatives and then summarized the changes in tryptophan metabolism in neurological disorders. Finally, we discuss the potential of tryptophan derivatives as therapeutic targets for neuroimmune disorders.

TRAF family member-associated NF-κB activator (TANK) is a negative regulator of osteoclastogenesis and bone formation.

The differentiation of bone-resorbing osteoclasts is induced by RANKL signaling, and leads to the activation of NF-κB via TRAF6 activation. TRAF family member-associated NF-κB activator (TANK) acts as a negative regulator of Toll-like receptors (TLRs) and B-cell receptor (BCR) signaling by inhibiting TRAF6 activation. Tank(-/-) mice spontaneously develop autoimmune glomerular nephritis in an IL-6-dependent manner. Despite its importance in the TCRs and BCR-activated TRAF6 inhibition, the involvement of TANK in RANKL signaling is poorly understood. Here, we report that TANK is a negative regulator of osteoclast differentiation. The expression levels of TANK mRNA and protein were up-regulated during RANKL-induced osteoclastogenesis, and overexpression of TANK in vitro led to a decrease in osteoclast formation. The in vitro osteoclastogenesis of Tank(-/-) cells was significantly increased, accompanied by increased ubiquitination of TRAF6 and enhanced canonical NF-κB activation in response to RANKL stimulation. Tank(-/-) mice showed severe trabecular bone loss, but increased cortical bone mineral density, because of enhanced bone erosion and formation. TANK mRNA expression was induced during osteoblast differentiation and Tank(-/-) osteoblasts exhibited enhaced NF-κB activation, IL-11 expression, and bone nodule formation than wild-type control cells. Finally, wild-type mice transplanted with bone marrow cells from Tank(-/-) mice showed trabecular bone loss analogous to that in Tank(-/-) mice. These findings demonstrate that TANK is critical for osteoclastogenesis by regulating NF-κB, and is also important for proper bone remodeling.

Senso-immunology: The Emerging Connection between Pain and Immunity.

The sensory and immune systems have been studied independently for a long time, whereas the interaction between the two has received little attention. We have carried out research to understand the interaction between the sensory and immune systems and have found that inflammation and bone destruction caused by fungal infection are suppressed by nociceptors. Furthermore, we have elucidated the molecular mechanism whereby fungal receptors are expressed on nociceptors and skin epithelium, how they cooperate to generate fungal pain, and how colitis and bone metabolism are regulated by mechanosensors expressed on the gut epithelium. Recently, we found that nociceptors prevent septic death by inhibiting microglia via nociceptor-derived hormones. This review summarizes our current state of knowledge on pain biology and outlines the mechanisms whereby pain and immunity interact. Our findings indicate that the sensory and immune systems share a variety of molecules and interact with each other to regulate our pathological and homeostatic conditions. This prompted us to advocate the interdisciplinary science named "senso-immunology," and this emerging field is expected to generate new ideas in both physiology and immunology, leading to the development of novel drugs to treat pain and inflammation.

Senso-immunology: the past, present, and future.

Pain and mechanical stimulation are thought to be alarm systems that alert the brain to physical abnormalities. When we experience unpleasant feelings in infected or traumatized tissues, our awareness is directed to the afflicted region, prompting activities such as resting or licking the tissue. Despite extensive research into the molecular biology of nociceptors, it was unclear whether their role was limited to the generation and transmission of unpleasant feelings or whether they actively modulate the pathogenesis of infected or traumatized tissues. Recently, it has become clear how the sensory and immune systems interact with one another and share similar receptors and ligands to modify the pathogenesis of various diseases. In this paper, we summarize the mechanisms of crosstalk between the sensory and immune systems and the impact of this new interdisciplinary field, which should be dubbed 'senso-immunology,' on medical science.

[Physical Properties of Small Focal Spot Imaging with Deep Learning Reconstruction in Chest-abdominal Plain CT].

PURPOSE: The aim of this study was to compare the physical properties of small focal spot imaging with deep learning reconstruction (DLR) and small or large focal spot imaging with hybrid iterative reconstruction (IR) in chest-abdominal plain computed tomography. METHOD: In small focal spot imaging using DLR and hybrid IR, tube currents were set at 350 mA. For the large focal spot imaging using hybrid IR, the tube current was set at 360, 400, 450, and 500 mA. The spatial frequencies with 50% task transfer function (TTF) for delrin and acrylic were calculated to compare spatial resolution properties for lung and soft tissue in the chest. Additionally, the low-contrast object-specific contrast-to-noise ratio (CNRLO) was measured as noise property was measured for a 7-mm module with a CT value contrast of 10 HU in the abdomen. RESULT: Spatial frequencies with 50% TTF for delrin and acrylic were found to be greater in small focal spot imaging using DLR compared to those in small and large focal spot imaging using hybrid IR. Moreover, the CNRLO obtained from small focal spot imaging with DLR was also nearly equivalent to that of large focal spot imaging with hybrid IR at tube currents of 450 and 500 mA. CONCLUSION: In chest-abdominal plain computed tomography, small focal spot imaging with DLR has been demonstrated to exhibit greater spatial resolution properties compared to small and large focal spot imaging with hybrid IR, with equivalent or better noise performance.