Sepsis frequently induces intestinal barrier injury, which exacerbates systemic inflammation, and contributes to high mortality. Group 3 innate lymphoid cells (ILC3s) are key regulators of mucosal immunity, yet their role in sepsis-associated intestinal injury remains incompletely understood. We found circulating ILCPs were reduced in patients with sepsis. In an LPS-induced murine sepsis model, colonic ILC3 numbers declined whereas the residual population showed increased frequencies of IL-22- and GM-CSF-producing cells. RORγt-deficient mice exhibited impaired induction of colonic IL-22 and GM-CSF, increased intestinal permeability, and aggravated histopathological injury. Adoptive transfer of purified wild-type ILC3s restored colonic IL-22 and GM-CSF levels and partially improved barrier integrity. Mechanistically, septic ILC3s showed hypoxia-associated mitochondrial impairment and accumulation of mitochondrial ROS. increased mtROS contributed to enhanced NF-κB p65 phosphorylation and selectively supported IL-22 and GM-CSF production. Recombinant IL-22 or GM-CSF ameliorated intestinal injury. However, ROS scavenging or NF-κB inhibition increased ILC3 apoptosis, indicating that ROS-NF-κB axis also supports residual ILC3 survival. Together, these findings identify a mitochondria-associated ROS-NF-κB program that sustains protective cytokine production and survival in residual intestinal ILC3s during sepsis, although it is insufficient to prevent ongoing ILC3 loss and intestinal injury.

Group 2 innate lymphoid cells (ILC2s) play crucial roles in maintaining adipose tissue homeostasis. Recent studies indicate that ILC2s are dysregulated in obesity. However, the regulatory mechanisms governing adipose tissue ILC2 function remain inadequately explored. In this study, we demonstrated that mechanistic target of rapamycin complex 1 (mTORC1) activity is impaired in adipose tissue ILC2s from obese mice and humans. Deletion of Raptor, a critical adaptor protein in mTORC1, results in reduced numbers of ILC2s and diminished type 2 cytokine production in ILC2s, leading to increased adipose tissue inflammation and insulin resistance. Mechanistically, mTORC1 signaling upregulates PPARγ expression through HIF-1α, which promotes mitochondrial biogenesis and ST2 expression to sustain ILC2 metabolic and functional fitness. Together, our data identify mTORC1 as a crucial regulator that coordinates adipose tissue ILC2 metabolic and immunological homeostasis and prevents obesity-associated insulin resistance.

IntroductionGroup 3 Innate Lymphoid Cells (ILC3s) are important for maintaining intestinal homeostasis and host defense. Emerging studies have shown that metabolic regulation plays a crucial role in regulating ILC3 activation and function. However, the role of Liver Kinase B1 (LKB1), a key metabolic regulator, in regulating ILC3 function and intestinal immunity remains poorly understood.MethodsTo investigate the role of LKB1 in intestinal ILC3s, we generated LKB1 conditional knockout mice by crossing Rorccre and Stk11flox/flox mice. Cell number and cytokine production was examined using flow cytometry. Citrobacter rodentium infection model were used to determine the role of LKB1 in intestinal defense. RT-qPCR, flow cytometry and immunohistochemistry were used to assess the intestinal inflammatory responses.ResultsIn this study, we show that LKB1 is essential for ILC3 postnatal development, effector function, and intestinal immunity. LKB1-deficient mice exhibit a marked decrease in ILC3 number at 2 -3 weeks after birth. Ablation of LKB1 in ILC3s results in diminished IL-22 production and less protection against Citrobacter rodentium infection. Moreover, LKB1 deficiency leads to impaired cell metabolism, as indicated by reduced glycolysis and oxidative phosphorylation and less mitochondrial mass. Together, our data demonstrate that LKB1 promotes ILC3 postnatal development and effector function to maintain intestinal immune homeostasis.DiscussionOur findings reveal that LKB1 is a key regulator of intestinal ILC3 development, function, and metabolism, thereby linking metabolic control to intestinal immune homeostasis and offering potential therapeutic implications.

Group 2 innate lymphoid cells (ILC2) initiate pathologic type 2 inflammation in allergic asthma in response to diverse tissue-derived stimuli. However, the molecular mechanisms by which ILC2 cells integrate and respond to environmental signals are unclear. Here, we show in a mouse model that in allergic asthma, mechanistic target of rapamycin complex 1 (mTORC1) activation in lung ILC2 cells increases. Genetic ablation of Raptor, an obligatory component of mTORC1 complex, results in reduced IL-5 and IL-13 production in ILC2 cells and protects mice from allergic inflammation. Pharmacological inhibition of mTORC1 by rapamycin suppresses ILC2 activation and ameliorates allergic lung inflammation. Mechanistically, mTORC1 activation upregulates neuromedin U receptor 1 (NMUR1) expression through epigenetic reprogramming, which augments ILC2 activation in response to neuromedin U (NMU). However, our experiments suggest that NMUR1 is not an exclusive mediator of ILC2 activation downstream of mTORC1. In conclusion, our work reveals that in ILC2s, mTORC1 signaling coordinates neuro-immune crosstalk for optimal activation, and highlights mTORC1 as a potential therapeutic target for allergic asthma.

Group 2 innate lymphoid cells (ILC2s) play crucial roles in mediating allergic inflammation. Recent studies also indicate their involvement in regulating tumor immunity. The tumor suppressor liver kinase B1 (LKB1) inactivating mutations are associated with a variety of human cancers; however, the role of LKB1 in ILC2 function and ILC2-mediated tumor immunity remains unknown. Here, we show that ablation of LKB1 in ILC2s results in an exhausted-like phenotype, which promotes the development of lung melanoma metastasis. Mechanistically, LKB1 deficiency leads to a marked increase in the expression of programmed cell death protein-1 (PD-1) in ILC2s through the activation of the nuclear factor of activated T cell pathway. Blockade of PD-1 can restore the effector functions of LKB1-deficient ILC2s, leading to enhanced antitumor immune responses in vivo. Together, our results reveal that LKB1 acts to restrain the exhausted state of ILC2 to maintain immune homeostasis and antitumor immunity.

IntroductionGroup 3 innate lymphoid cells (ILC3s) are enriched in the intestinal mucosa and play important roles in host defense against infection and inflammatory diseases. Sirtuin 6 (SIRT6) is a nicotinamide adenine dinucleotide (NAD+)- dependent deacetylase and has been shown to control intestinal epithelial cell differentiation and survival. However, the role of SIRT6 in ILC3s remains unknown.MethodsTo investigate the role of SIRT6 in gut ILC3s, we generated SIRT6 conditional knockout mice by crossing Rorccre and Sirt6flox/flox mice. Cell number and cytokine production was examined using flow cytometry. Citrobacter rodentium infection and dextran sodium sulfate-induced colitis models were used to determine the role of SIRT6 in gut defense. RT-qPCR, flow cytometry and immunohistochemistry were used to assess the intestinal inflammatory responses.ResultsHere we show that SIRT6 inhibits IL-22 expression in intestinal ILC3s in a cell-intrinsic manner. Deletion of SIRT6 in ILC3s does not affect the cell numbers of total ILC3s and subsets, but results in increased IL-22 production. Furthermore, ablation of SIRT6 in ILC3s protects mice against Citrobacter rodentium infection and dextran sodium sulfate-induced colitis. Our results suggest that SIRT6 may play a role in ILC3 function by regulating gut immune responses against bacterial infection and inflammation.DiscussionOur finding provided insight into the relation of epigenetic regulators with IL-22 production and supplied a new perspective for a potential strategy against inflammatory bowel disease.

Adipose tissue group 2 innate lymphoid cells (ILC2s) help maintain metabolic homeostasis by sustaining type 2 immunity and promoting adipose beiging. Although impairment of the ILC2 compartment contributes to obesity-associated insulin resistance, the underlying mechanisms have not been elucidated. Here, we found that ILC2s in obese mice and humans exhibited impaired liver kinase B1 (LKB1) activation. Genetic ablation of LKB1 disrupted ILC2 mitochondrial metabolism and suppressed ILC2 responses, resulting in exacerbated insulin resistance. Mechanistically, LKB1 deficiency induced aberrant PD-1 expression through activation of NFAT, which in turn enhanced mitophagy by suppressing Bcl-xL expression. Blockade of PD-1 restored the normal functions of ILC2s and reversed obesity-induced insulin resistance in mice. Collectively, these data present the LKB1-PD-1 axis as a promising therapeutic target for the treatment of metabolic disease.

Group 3 innate lymphoid cells (ILC3s) play important roles in maintaining intestinal homeostasis by protecting the host from pathogen infections and tissue inflammation. The transcription factor PLZF (promyelocytic leukemia zinc finger), encoded by zinc finger BTB domain containing 16 (Zbtb16), is highly and transiently expressed in ILC precursors (ILCPs). However, the role of PLZF in regulating ILC3 development and function remains unknown. Here, we show that PLZF was specifically expressed in mature intestinal ILC3s compared with other ILC subsets. PLZF was dispensable for ILC3 development. However, PLZF deficiency in ILC3s resulted in increased innate interleukin-22 (IL-22) secretion and protection against gut infection and inflammation. Mechanistically, PLZF negatively regulated IL-22 expression by ILC3s in a cell-intrinsic manner by binding to the IL-22 promoter region for transcriptional repression. Together, our data suggest that PLZF restricts intestinal ILC3 function to regulate gut immune homeostasis.

Vγ9Vδ2 T cells play an important role in the development and progression of psoriasis vulgaris (PV), but how they promote skin inflammation and the molecular mechanisms underlying Vγ9Vδ2 T cell dysfunction are poorly understood. Here, we show that circulating Vγ9Vδ2 T cells are decreased and exhibit enhanced proliferation and increased production of IFN-γ and TNF-α in PV patients. Monocytes from PV patients express higher levels of the phosphoantigen sensor butyrophilin 3A1 (BTN3A1) than monocytes from healthy controls. Blockade of BTN3A1 suppresses Vγ9Vδ2 T cell activation and abolishes the difference in Vγ9Vδ2 T cell activation between PV patients and healthy controls. The CD14+ cells in PV skin lesions highly express BTN3A1 and juxtapose to Vδ2 T cells. In addition, IFN-γ induces the up-regulation of BTN3A1 on monocytes. Collectively, our results demonstrate a crucial role of BTN3A1 on monocytes in regulating Vγ9Vδ2 T cell activation and highlight BTN3A1 as a potential therapeutic target for psoriasis.

The involvement of cardiomyopathy during sepsis means higher mortality and prolonged length of hospital stay. Many efforts have been made to alleviate the apoptosis of cardiomyocytes in sepsis. The huge potential of IL-13 in tissue repair has attracted increasing attention. In the present study, we used LPS-treated mice or primary cardiomyocytes as a sepsis model to explore the anti-apoptotic ability of IL-13. It was found that an increased level of exogenous IL-13 was beneficial to the recovery of heart function in sepsis, and this anti-apoptotic effect of IL-13 was probably through enhancing the phosphorylation of STAT3 Ser727. In addition, we identified that the heart protective effect of IL-13 was associated with type 2 innate lymphocytes (ILC2). All these findings may provide a potential promising treatment for sepsis-induced cardiomyopathy.

Growing evidence suggests that obesity is associated with the susceptibility and disease severity of multiple sclerosis. The chronic inflammation induced by obesity is believed to contribute to this process. However, the immune mechanisms connecting obesity to the prevalence and pathogenesis of MS are poorly defined. In this study, we show that high fat diet (HFD)-induced obese mice developed an exacerbated EAE as indicated by higher clinical scores and more severe pathological changes in spinal cord than the control mice fed with normal diet (ND), following immunization with myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide. The exacerbation of EAE in HFD mice was associated with enhanced microglial activation and increased expansion of Th1 and Th17 cells. The HFD mice also showed aggravated disease in an adoptive T cell transfer EAE model. Mechanistically, HFD augmented the expression level of IL-6 and CCL-2 both in serum and brain, and blockade of IL-6 and CCL-2 signal ameliorated EAE with reduced T cells infiltration in CNS. Taken together, our results suggest that obesity promotes CNS inflammation in EAE through IL-6 and CCL-2 mediated the inflammatory cells infiltration.

肠道组织高表达表观遗传调控因子沉默信息调节因子(silent information regulator 6,SIRT6),在UC患者及动物模型的结肠组织中,SIRT6的表达水平显著下调.关于SIRT6在调控肠道免疫平衡中的作用尚不清楚.新近发现的Ⅲ型固有淋巴细胞(group 3 innate lymphoid cell,ILC3)主要分布于肠道,对维持肠道免疫稳态非常重要.为探讨ILC3中SIRT6在结肠炎发生发展中的作用,应用FCM检测小鼠肠道组织中固有淋巴细胞(innate lymphoid cell,ILC)亚群比例,FACS分选ILC,荧光定量PCR检测Sirt6表达.结果 发现,Sirt6在ILC3中有较高的表达丰度.运用Cre-loxp系统建立ILC3条件性敲除Sirt6小鼠模型,观察基础状态以及葡聚糖硫酸钠(dextran sulfate sodium salt,DSS)诱导性肠炎模型中小鼠的表型变化.结果 显示,Sirt6在ILC3中缺失并不影响基础状态下小鼠的生长发育和肠道结构,但能显著提高小鼠对DSS诱导性结肠炎的抵抗能力.以上结果提示SIRT6通过调控ILC3影响肠炎的发生发展过程.