Sphingosine d18:1 promotes nonalcoholic steatohepatitis by inhibiting macrophage HIF-2α.

Non-alcoholic steatohepatitis (NASH) is a severe type of the non-alcoholic fatty liver disease (NAFLD). NASH is a growing global health concern due to its increasing morbidity, lack of well-defined biomarkers and lack of clinically effective treatments. Using metabolomic analysis, the most significantly changed active lipid sphingosine d18:1 [So(d18:1)] is selected from NASH patients. So(d18:1) inhibits macrophage HIF-2α as a direct inhibitor and promotes the inflammatory factors secretion. Male macrophage-specific HIF-2α knockout and overexpression mice verified the protective effect of HIF-2α on NASH progression. Importantly, the HIF-2α stabilizer FG-4592 alleviates liver inflammation and fibrosis in NASH, which indicated that macrophage HIF-2α is a potential drug target for NASH treatment. Overall, this study confirms that So(d18:1) promotes NASH and clarifies that So(d18:1) inhibits the transcriptional activity of HIF-2α in liver macrophages by suppressing the interaction of HIF-2α with ARNT, suggesting that macrophage HIF-2α may be a potential target for the treatment of NASH.

The microbial metabolite agmatine acts as an FXR agonist to promote polycystic ovary syndrome in female mice.

Polycystic ovary syndrome (PCOS), an endocrine disorder afflicting 6-20% of women of reproductive age globally, has been linked to alterations in the gut microbiome. We previously showed that in PCOS, elevation of Bacteroides vulgatus in the gut microbiome was associated with altered bile acid metabolism. Here we show that B. vulgatus also induces a PCOS-like phenotype in female mice via an alternate mechanism independent of bile acids. We find that B. vulgatus contributes to PCOS-like symptoms through its metabolite agmatine, which is derived from arginine by arginine decarboxylase. Mechanistically, agmatine activates the farnesoid X receptor (FXR) pathway to subsequently inhibit glucagon-like peptide-1 (GLP-1) secretion by L cells, which leads to insulin resistance and ovarian dysfunction. Critically, the GLP-1 receptor agonist liraglutide and the arginine decarboxylase inhibitor difluoromethylarginine ameliorate ovarian dysfunction in a PCOS-like mouse model. These findings reveal that agmatine-FXR-GLP-1 signalling contributes to ovarian dysfunction, presenting a potential therapeutic target for PCOS management.

Prophylactic Supplementation with Lactobacillus Reuteri or Its Metabolite GABA Protects Against Acute Ischemic Cardiac Injury.

The gut microbiome has emerged as a potential target for the treatment of cardiovascular disease. Ischemia/reperfusion (I/R) after myocardial infarction is a serious complication and whether certain gut bacteria can serve as a treatment option remains unclear. Lactobacillus reuteri (L. reuteri) is a well-studied probiotic that can colonize mammals including humans with known cholesterol-lowering properties and anti-inflammatory effects. Here, the prophylactic cardioprotective effects of L. reuteri or its metabolite γ-aminobutyric acid (GABA) against acute ischemic cardiac injury caused by I/R surgery are demonstrated. The prophylactic gavage of L. reuteri or GABA confers cardioprotection mainly by suppressing cardiac inflammation upon I/R. Mechanistically, GABA gavage results in a decreased number of proinflammatory macrophages in I/R hearts and GABA gavage no longer confers any cardioprotection in I/R hearts upon the clearance of macrophages. In vitro studies with LPS-stimulated bone marrow-derived macrophages (BMDM) further reveal that GABA inhibits the polarization of macrophages toward the proinflammatory M1 phenotype by inhibiting lysosomal leakage and NLRP3 inflammasome activation. Together, this study demonstrates that the prophylactic oral administration of L. reuteri or its metabolite GABA attenuates macrophage-mediated cardiac inflammation and therefore alleviates cardiac dysfunction after I/R, thus providing a new prophylactic strategy to mitigate acute ischemic cardiac injury.

Adipose triglyceride lipase suppresses noncanonical inflammasome by hydrolyzing LPS.

Intracellular recognition of lipopolysaccharide (LPS) by mouse caspase-11 or human caspase-4 is a vital event for the activation of the noncanonical inflammasome. Whether negative regulators are involved in intracellular LPS sensing is still elusive. Here we show that adipose triglyceride lipase (ATGL) is a negative regulator of the noncanonical inflammasome. Through screening for genes participating in the noncanonical inflammasome, ATGL is identified as a negative player for intracellular LPS signaling. ATGL binds LPS and catalyzes the removal of the acylated side chains that contain ester bonds. LPS with under-acylated side chains no longer activates the inflammatory caspases. Cells with ATGL deficiency exhibit enhanced immune responses when encountering intracellular LPS, including an elevated secretion of interleukin-1ß, decreased cell viability and increased cell cytotoxicity. Moreover, ATGL-deficient mice show exacerbated responses to endotoxin challenges. Our results uncover that ATGL degrades cytosolic LPS to suppress noncanonical inflammasome activation.

The orphan receptor Nur77 binds cytoplasmic LPS to activate the non-canonical NLRP3 inflammasome.

Intracellular sensing of lipopolysaccharide (LPS) by murine caspase-11 or human caspase-4 initiates a protease cascade, termed the non-canonical inflammasome, that results in gasdermin D (GSDMD) processing and subsequent NLRP3 inflammasome activation. In an effort aimed at identifying additional sensors for intracellular LPS by biochemical screening, we identified the nuclear orphan receptor Nur77 as an LPS-binding protein in macrophage lysates. Nr4a1-/- macrophages exhibited impaired activation of the NLRP3 inflammasome, but not caspase-11, in response to LPS. Biochemical mapping revealed that Nur77 bound LPS directly through a domain in its C terminus. Yeast two-hybrid assays identified NLRP3 as a binding partner for Nur77. The association between Nur77 and NLRP3 required the presence of LPS and dsDNA. The source of dsDNA was the mitochondria, requiring the formation of gasdermin-D pores. In vivo, Nur77 deficiency ameliorated host response to endotoxins. Thus, Nur77 functions as an intracellular LPS sensor, binding mitochondrial DNA and LPS to activate the non-canonical NLRP3 inflammasome.

Tissue-resident Lachnospiraceae family bacteria protect against colorectal carcinogenesis by promoting tumor immune surveillance.

The intestinal microbiota plays an important role in colorectal cancer (CRC) progression. However, the effect of tissue-resident commensal bacteria on CRC immune surveillance remains poorly understood. Here, we analyzed the intratissue bacteria from CRC patient colon tissues. We found that the commensal bacteria belonging to the Lachnospiraceae family, including Ruminococcus gnavus (Rg), Blautia producta (Bp), and Dorea formicigenerans (Df), were enriched in normal tissues, while Fusobacterium nucleatum (Fn) and Peptostreptococcus anaerobius (Pa) were abundant in tumor tissues. Tissue-resident Rg and Bp reduced colon tumor growth and promoted the activation of CD8+ T cells in immunocompetent mice. Mechanistically, intratissue Rg and Bp degraded lyso-glycerophospholipids that inhibited CD8+ T cell activity and maintained the immune surveillance function of CD8+ T cells. Lyso-glycerophospholipids alone promoted tumor growth that was abrogated with Rg and Bp injection. Collectively, intratissue Lachnospiraceae family bacteria facilitate the immune surveillance function of CD8+ T cells and control colorectal cancer progression.

The neuropeptide CGRP enters the macrophage cytosol to suppress the NLRP3 inflammasome during pulmonary infection.

The NLRP3 inflammasome plays an essential role in resistance to bacterial infection. The nervous system secretes multiple neuropeptides affecting the nervous system as well as immune cells. The precise impact of the neuropeptide CGRP on NLRP3 inflammasome activation is still unclear. Here, we show that CGRP negatively regulates the antibacterial process of host cells. CGRP prevents NLRP3 inflammasome activation and reduces mature IL-1ß secretion. Following NLRP3 inflammasome stimulation that triggers endosome leakage, CGRP internalized to endosomal compartments is released into the cell cytosol. Cytosolic CGRP binds directly to NLRP3 and dismantles the NLRP3-NEK7 complex, which is crucial for NLRP3 inflammasome activation. CGRP administration exacerbates bacterial infection, while the treatment with a CGRP antagonist has the opposite effect. Our study uncovers a unique role of CGRP in inhibiting inflammasome activation during infections, which might shed new light on antibacterial therapies in the future.

Maturation and specialization of group 2 innate lymphoid cells through the lung-gut axis.

Innate lymphoid cells (ILC) are abundant in mucosal tissues. They serve critical functions in anti-pathogen response and tissue homeostasis. However, the heterogenous composition of ILCs in mucosal sites and their various maturation trajectories are less well known. In this study, we characterize ILC types and functions from both the lung and the small intestine, and identify their tissue-specific markers. We find that ILC2s residing in the lung express CCR2, whereas intestinal ILC2s express CCR4. Through the use of CCR2 and CCR4 reporter mice, we show that ILC2s undergo translocation via the lung-gut axis upon IL-33 treatment. This trajectory of ILC2s is also observed at the postnatal stage. Allergen-induced activation of lung ILC2s affects the homeostasis of gut ILC2s. Together, our findings implicate that ILCs display tissue-specific features in both the lung and gut, and ILC2s mature along the lung-gut axis in particular homeostatic and inflammatory conditions.

Ginkgo Biloba Extract Reduces Cardiac and Brain Inflammation in Rats Fed a HFD and Exposed to Chronic Mental Stress through NF-κB Inhibition.

Background: Cardiac and brain inflammation can lead to a host of deleterious health effects. Our formal experimental research showed that Ginkgo Biloba Extract (GBE) contributed to the reduction of inflammation in mice with myocardial infarction along with depression. This study is aimed at expanding on these findings via analysis of the cardiac and brain inflammation, which was prevented by GBE in rats suffering with a high-fat diet (HFD) combined with unpredictable chronic mild stress (UCMS). Methods: Fifty male Wistar rats were randomly divided into 5 groups treated with normal diet, UCMS, HFD, HFD+UCMS, or HFD+UCMS+GBE respectively. Rats treated with HFD were fed a high-fat diet for 10 or 13 weeks. Rats treated with UCMS were exposed to 8 types of chronic physical and psychological stressors for 10 or 13 weeks. The HFD+UCMS+GBE group was given GBE via intragastric gavage for 8 consecutive weeks. Sucrose preference was established for the assessment of depressive behaviors. The heart function was evaluated by echocardiography. The rats were terminated at the end of the 10th or 13th week. The blood was used for detecting low-density lipoprotein cholesterol (LDL-c) and total cholesterol (TCHO) by the kit instructions; Helper T Lymphocytes (TH cells, CD3+CD4+) by flow cytometry; and Interleukin- (IL-) 1ß, IL-37, IL-38, NT-proBNP, hs-cTNI, and Ischemia-modified albumin (IMA) by enzyme-linked immunosorbent assay (ELISA). The cardiac tissues were used for detecting IL-1ß, nuclear factor kappa B (NF-κB), inhibitor molecule protein (IκB), and IL-1 receptor (IL-1R) by ELISA and P65, P-P65, IκB, and phosphorylated inhibitor molecule protein α (P-IκBα) for western blotting. Cortex tissues were used for detecting 8-iso-prostaglandinF2α (8-iso-PGF2α) by ELISA. Oil Red staining was carried out to evaluate the lipid deposits in the rats' aortic arteries. Sirius Red staining was performed to display collagen fibers in the arteries. Hematoxylin and Eosin (HE) staining was applied to reveal pathological changes to arteries and cardiac tissue. Immunohistochemical staining was employed to assess the distribution of inflammatory cytokine IL-1ß in arteries and cardiac tissues. Transmission Electron Microscopy (TEM) was performed to observe the ultrastructure of hippocampal cornu ammonis (CA)1 (CA1) neurons. Results: In the rats with HFD+UCMS+GBE, over 13 weeks, GBE exerted a protective role of both the heart and brain, by attenuating cardiac inflammation and brain oxidative stress. Levels of Helper T lymphocytes and serum anti-inflammatory cytokines involving IL-37 and IL-38 were all elevated, and the depressive behaviors of HFD+UCMS rats were attenuated by GBE. This protective role was accomplished via inhibition of the canonical NF-κB signaling pathway, through downregulation of the expressions of P-P65 and P-IκB-α in the heart, hippocampus, cortex, and hypothalamus. Conclusions: This study suggests that GBE poses a protective role from the various pathologies associated with high-fat diets, unpredictable chronic mild stress, and depression, possibly via improving peripheral immunity and reducing cardiac and brain inflammation.

Implication of a novel truncating mutation in titin as a cause of autosomal dominant left ventricular noncompaction.

BACKGROUND: Mutation in the titin gene (TTN) in left ventricular noncompaction (LVNC) has been reported with a highly heterogeneous prevalence, and the molecular mechanisms underlying the pathogenesis of TTN gene mutation are uncharacterized. In the present study, we identified a novel TTN mutation in a pedigree with LVNC and investigated the potential pathogenic mechanism by functional studies. METHODS: The whole-genome sequencing with linkage analysis was performed in a 3-generation family affected by autosomal dominant LVNC cardiomyopathy. The clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/Cas9) technology was used to establish novel truncating mutation in TTN in a rat cardiomyoblast H9C2 cell line in vitro, in which functional studies were carried out and characterized in comparison to its wild-type counterpart. RESULTS: A novel truncating mutation TTN p. R2021X was identified as the only plausible disease-causing variant that segregated with disease among the five surviving affected individuals, with an interrogation of the entire genome excluding other potential causes. Quantitative reverse transcription-polymerase chain reaction and cellular immunofluorescence supported a haploinsufficient disease mechanism in titin truncation mutation cardiomyocytes. Further functional studies suggested mitochondrial abnormities in the presence of mutation, including decreased oxygen consumption rate, reduced adenosine triphosphate production, impaired activity of electron translation chain, and abnormal mitochondrial structure on electron microscopy. Impaired autophagy under electron microscopy accompanied with activation of the Akt-mTORC1 signaling pathway was observed in TTN p. R2021X truncation mutation cardiomyocytes. CONCLUSIONS: The TTN p. R2021X mutation has a function in the cause of a highly penetrant familial LVNC. These findings expand the spectrum of titin's roles in cardiomyopathies and provide novel insight into the molecular basis of titin-truncating variants-associated LVNC.

Integrated Analysis of lncRNA and mRNA Expression Profiles Indicates Age-Related Changes in Meniscus.

Little has been known about the role of long non-coding RNA (lncRNA) involves in change of aged meniscus. Microarray analyses were performed to identify lncRNAs and mRNAs expression profiles of meniscus in young and aging adults and apple bioinformatics methods to analyse their potential roles. The differentially expressed (DE) lncRNAs and mRNAs were confirmed by qRT-PCR. A total of 1608 DE lncRNAs and 1809 DE mRNAs were identified. Functional and pathway enrichment analyses of all DE mRNAs showed that DE mRNAs were mainly involved in the TGF-beta, Wnt, Hippo, PI3K-Akt signaling pathway. The expressions of TNFRSF11B and BMP2 were significantly upregulated in aging group. LASSO logistic regression analysis of the DE lncRNAs revealed four lncRNAs (AC124312.5, HCG11, POC1B-AS1, and AP001011.1) that were associated with meniscus degradation. CNC analysis demonstrated that AP001011 inhibited the expression of TNFRSF11B and AC1243125 upregulated the expression of TNFRSF11B. CeRNA analysis suggested that POC1B-AS1 regulates the expression of BMP2 by sponging miR 130a-3p, miR136-5p, miR 18a-3p, and miR 608. Furthermore, subcellular localization and m6A modification sites prediction analysis of these four lncRNAs was performed. These data lay a foundation for extensive studies on the role of lncRNAs in change of aged meniscus.

SARS-CoV-2 nucleocapsid suppresses host pyroptosis by blocking Gasdermin D cleavage.

SARS-CoV-2 is an emerging coronavirus that causes dysfunctions in multiple human cells and tissues. Studies have looked at the entry of SARS-CoV-2 into host cells mediated by the viral spike protein and human receptor ACE2. However, less is known about the cellular immune responses triggered by SARS-CoV-2 viral proteins. Here, we show that the nucleocapsid of SARS-CoV-2 inhibits host pyroptosis by blocking Gasdermin D (GSDMD) cleavage. SARS-CoV-2-infected monocytes show enhanced cellular interleukin-1ß (IL-1ß) expression, but reduced IL-1ß secretion. While SARS-CoV-2 infection promotes activation of the NLRP3 inflammasome and caspase-1, GSDMD cleavage and pyroptosis are inhibited in infected human monocytes. SARS-CoV-2 nucleocapsid protein associates with GSDMD in cells and inhibits GSDMD cleavage in vitro and in vivo. The nucleocapsid binds the GSDMD linker region and hinders GSDMD processing by caspase-1. These insights into how SARS-CoV-2 antagonizes cellular inflammatory responses may open new avenues for treating COVID-19 in the future.

Dynamic regulation of innate lymphoid cells in the mucosal immune system.

The mucosal immune system is considered a local immune system, a term that implies regional restriction. Mucosal tissues are continually exposed to a wide range of antigens. The regulation of mucosal immune cells is tightly associated with the progression of mucosal diseases. Innate lymphoid cells (ILCs) are abundant in mucosal barriers and serve as first-line defenses against pathogens. The subtype changes and translocation of ILCs are accompanied by the pathologic processes of mucosal diseases. Here, we review the plasticity and circulation of ILCs in the mucosal immune system under physiological and pathological conditions. We also discuss the signaling pathways involved in dynamic ILC changes and the related targets in mucosal diseases.

Communication Pattern Changes Along With Declined IGF1 of Immune Cells in COVID-19 Patients During Disease Progression.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19) pandemic, represents a global crisis. Most patients developed mild/moderate symptoms, and the status of immune system varied in acute and regulatory stages. The crosstalk between immune cells and the dynamic changes of immune cell contact is rarely described. Here, we analyzed the features of immune response of paired peripheral blood mononuclear cell (PBMC) samples from the same patients during acute and regulatory stages. Consistent with previous reports, both myeloid and T cells turned less inflammatory and less activated at recovery phase. Additionally, the communication patterns of myeloid-T cell and T-B cell are obviously changed. The crosstalk analysis reveals that typical inflammatory cytokines and several chemokines are tightly correlated with the recovery of COVID-19. Intriguingly, the signal transduction of metabolic factor insulin-like growth factor 1 (IGF1) is altered at recovery phase. Furthermore, we confirmed that the serum levels of IGF1 and several inflammatory cytokines are apparently dampened after the negative conversion of SARS-CoV-2 RNA. Thus, these results reveal several potential detection and therapeutic targets that might be used for COVID-19 recovery.

Loss of Rsph9 causes neonatal hydrocephalus with abnormal development of motile cilia in mice.

Hydrocephalus is a brain disorder triggered by cerebrospinal fluid accumulation in brain cavities. Even though cerebrospinal fluid flow is known to be driven by the orchestrated beating of the bundled motile cilia of ependymal cells, little is known about the mechanism of ciliary motility. RSPH9 is increasingly becoming recognized as a vital component of radial spokes in ciliary "9 + 2" ultrastructure organization. Here, we show that deletion of the Rsph9 gene leads to the development of hydrocephalus in the early postnatal period. However, the neurodevelopment and astrocyte development are normal in embryonic Rsph9-/- mice. The tubular structure of the central aqueduct was comparable in Rsph9-/- mice. Using high-speed video microscopy, we visualized lower beating amplitude and irregular rotation beating pattern of cilia bundles in Rsph9-/- mice compared with that of wild-type mice. And the centriolar patch size was significantly increased in Rsph9-/- cells. TEM results showed that deletion of Rsph9 causes little impact in ciliary axonemal organization but the Rsph9-/- cilia frequently had abnormal ectopic ciliary membrane inclusions. In addition, hydrocephalus in Rsph9-/- mice results in the development of astrogliosis, microgliosis and cerebrovascular abnormalities. Eventually, the ependymal cells sloughed off of the lateral wall. Our results collectively suggested that RSPH9 is essential for ciliary structure and motility of mouse ependymal cilia, and its deletion causes the pathogenesis of hydrocephalus.

Correction: Transdifferentiation of tumor infiltrating innate lymphoid cells during progression of colorectal cancer.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Transdifferentiation of tumor infiltrating innate lymphoid cells during progression of colorectal cancer.

Innate lymphoid cells (ILCs) reside in mucosal surfaces to potentiate immune responses, sustain mucosal integrity and maintain tissue homeostasis. However, how tumor infiltrating ILCs modulate tumor development and progression is unclear. Here we profiled tumor infiltrating ILCs during colorectal cancer (CRC) progression by single-cell RNA sequencing. We identified six clusters of tumor infiltrating ILCs with unique features. ILC1s expressed inhibitory receptors and underwent inhibitory functional conversion at the late stage of CRC. ILC2s were classified into three subsets (called ILC2-A, -B, -C), of which ILC2-C subset could facilitate tumor progression. HS3ST1 and PD1 were highly expressed in ILC2s of late stage CRC tumors and deficiency of HS3ST1 or PD1 in ILC2s suppressed tumor growth. Moreover, ILC3s transdifferentiated into ILCregs during CRC progression and ILCregs promoted tumor growth. Of note, TGF-ß signaling initiated the conversion of ILC3s to ILCregs and blockade of TGF-ß signaling could disrupt the ILCreg transdifferentiation and inhibited tumor growth. Thus, intervention of ILC conversions might be a potential strategy for CRC immunotherapy.

Glutamylation of deubiquitinase BAP1 controls self-renewal of hematopoietic stem cells and hematopoiesis.

All hematopoietic lineages are derived from a limited pool of hematopoietic stem cells (HSCs). Although the mechanisms underlying HSC self-renewal have been extensively studied, little is known about the role of protein glutamylation and deglutamylation in hematopoiesis. Here, we show that carboxypeptidase CCP3 is most highly expressed in BM cells among CCP members. CCP3 deficiency impairs HSC self-renewal and hematopoiesis. Deubiquitinase BAP1 is a substrate for CCP3 in HSCs. BAP1 is glutamylated at Glu651 by TTLL5 and TTLL7, and BAP1-E651A mutation abrogates BAP1 glutamylation. BAP1 glutamylation accelerates its ubiquitination to trigger its degradation. CCP3 can remove glutamylation of BAP1 to promote its stability, which enhances Hoxa1 expression, leading to HSC self-renewal. Bap1E651A mice produce higher numbers of LT-HSCs and peripheral blood cells. Moreover, TTLL5 and TTLL7 deficiencies sustain BAP1 stability to promote HSC self-renewal and hematopoiesis. Therefore, glutamylation and deglutamylation of BAP1 modulate HSC self-renewal and hematopoiesis.

LC Domain-Mediated Coalescence Is Essential for Otu Enzymatic Activity to Extend Drosophila Lifespan.

In eukaryotic cells, RNA-binding proteins (RBPs) interact with RNAs to form ribonucleoprotein complexes (RNA granules) that have long been thought to regulate RNA fate or activity. Emerging evidence suggests that some RBPs not only bind RNA but also possess enzymatic activity related to ubiquitin regulation, raising important questions of whether these RBP-formed RNA granules regulate ubiquitin signaling and related biological functions. Here, we show that Drosophila Otu binds RNAs and coalesces to membrane-less biomolecular condensates via its intrinsically disordered low-complexity domain, and coalescence represents a functional state for Otu exerting deubiquitinase activity. Notably, coalescence-mediated enzymatic activity of Otu is positively regulated by its bound RNAs and co-partner Bam. Further genetic analysis reveals that the Otu/Bam deubiquitinase complex and dTraf6 constitute a feedback loop to maintain intestinal immune homeostasis during aging, thereby controlling longevity. Thus, regulated biomolecular condensates may represent a mechanism that controls dynamic enzymatic activities and related biological processes.

A Circular RNA Protects Dormant Hematopoietic Stem Cells from DNA Sensor cGAS-Mediated Exhaustion.

Disrupting the balance between self-renewal and differentiation of hematopoietic stem cells (HSCs) leads to bone marrow failure or hematologic malignancy. However, how HSCs sustain their quiescent state and avoid type I interferon (IFN)-mediated exhaustion remains elusive. Here we defined a circular RNA that we named cia-cGAS that was highly expressed in the nucleus of long-term (LT)-HSCs. Cia-cGAS deficiency in mice caused elevated expression of type I IFNs in bone marrow and led to decreased numbers of dormant LT-HSCs. Under homeostatic conditions, cia-cGAS bound DNA sensor cGAS in the nucleus to block its synthase activity, thereby protecting dormant LT-HSCs from cGAS-mediated exhaustion. Moreover, cia-cGAS harbored a stronger binding affinity to cGAS than self-DNA did and consequently suppressed cGAS-mediated production of type I IFNs in LT-HSCs. Our findings reveal a mechanism by which cia-cGAS inhibits nuclear cGAS by blocking its enzymatic activity and preventing cGAS from recognizing self-DNA to maintain host homeostasis.