Transforming growth factor β1 up-regulates interferon regulatory factor 8 during dendritic cell development

Circulating extracellular vesicles in human cardiorenal syndrome promote renal injury in a kidney-on-chip system

BACKGROUNDCardiorenal syndrome (CRS) - renal injury during heart failure (HF) - is linked to high morbidity. Whether circulating extracellular vesicles (EVs) and their RNA cargo directly impact its pathogenesis remains unclear.METHODSWe investigated the role of circulating EVs from patients with CRS on renal epithelial/endothelial cells using a microfluidic kidney-on-chip (KOC) model. The small RNA cargo of circulating EVs was regressed against serum creatinine to prioritize subsets of functionally relevant EV-miRNAs and their mRNA targets investigated using in silico pathway analysis, human genetics, and interrogation of expression in the KOC model and in renal tissue. The functional effects of EV-RNAs on kidney epithelial cells were experimentally validated.RESULTSRenal epithelial and endothelial cells in the KOC model exhibited uptake of EVs from patients with HF. HF-CRS EVs led to higher expression of renal injury markers (IL18, LCN2, HAVCR1) relative to non-CRS EVs. A total of 15 EV-miRNAs were associated with creatinine, targeting 1,143 gene targets specifying pathways relevant to renal injury, including TGF-β and AMPK signaling. We observed directionally consistent changes in the expression of TGF-β pathway members (BMP6, FST, TIMP3) in the KOC model exposed to CRS EVs, which were validated in epithelial cells treated with corresponding inhibitors and mimics of miRNAs. A similar trend was observed in renal tissue with kidney injury. Mendelian randomization suggested a role for FST in renal function.CONCLUSIONPlasma EVs in patients with CRS elicit adverse transcriptional and phenotypic responses in a KOC model by regulating biologically relevant pathways, suggesting a role for EVs in CRS.TRIAL REGISTRATIONClinicalTrials.gov NCT03345446.FUNDINGAmerican Heart Association (AHA) (SFRN16SFRN31280008); National Heart, Lung, and Blood Institute (1R35HL150807-01); National Center for Advancing Translational Sciences (UH3 TR002878); and AHA (23CDA1045944).

TGF-β inhibitor Smad7 regulates dendritic cell-induced autoimmunity

TGF-β is an anti-inflammatory cytokine whose signaling is negatively controlled by Smad7. Previously, we established a role for Smad7 in the generation of autoreactive T cells; however, the function of Smad7 in dendritic cells (DCs) remains elusive. Here, we demonstrate that DC-specific Smad7 deficiency resulted in elevated expression of the transcription factors Batf3 and IRF8, leading to increased frequencies of CD8⁺CD103⁺ DCs in the spleen. Furthermore, Smad7-deficient DCs expressed higher levels of indoleamine 2,3-dioxygenase (IDO), an enzyme associated with tolerance induction. Mice devoid of Smad7 specifically in DCs are resistant to the development of experimental autoimmune encephalomyelitis (EAE) as a result of an increase of protective regulatory T cells (Tregs) and reduction of encephalitogenic effector T cells in the central nervous system. In agreement, inhibition of IDO activity or depletion of Tregs restored disease susceptibility. Intriguingly, when Smad7-deficient DCs also lacked the IFN-γ receptor, the mice regained susceptibility to EAE, demonstrating that IFN-γ signaling in DCs mediates their tolerogenic function. Our data indicate that Smad7 expression governs splenic DC subset differentiation and is critical for the promotion of their efficient function in immunity.

Cutting Edge: ACVRL1 Signaling Augments CD8α+ Dendritic Cell Development

Dendritic cells (DCs) are a collection of different subtypes, each of which is characterized by specific surface markers, gene-expression patterns, and distinct functions. Members of the IFN regulatory factor family play critical roles in DC development and functions. Recently, Irf8 was shown to activate TGF-β signaling, which led to exacerbated neuroinflammation in the experimental autoimmune encephalomyelitis mouse model. We analyzed the effect of Irf8 on TGF-β/bone morphogenetic protein pathway-specific genes in DCs and identified Acvrl1, a type I TGF-β superfamily receptor, as a gene strongly induced by Irf8 expression. Among various DC subtypes, Acvrl1 is differentially expressed in CD8α(+) DCs. ACVRL1 signaling augmented Irf8-directed classical CD8α(+) DC development. Irf8 expression is essential for plasmacytoid DC and CD8α(+) DC development, and this study demonstrates that ACVRL1 signaling plays a pivotal role whereby it suppresses plasmacytoid DC development while enhancing that of CD8α(+) DCs, thus contributing to DC diversity development.

BDCA3 expression is associated with high IFN-λ production by CD34(+)-derived dendritic cells generated in the presence of GM-CSF, IL-4, and/or TGF-β

High BDCA3 expression is associated with a specific human IFN-λ-producing dendritic cell (DC) subset. However, BDCA3 has also been detected on other DC subsets. Thus far, development and function of BDCA3 expression on DCs remains poorly understood. Human Langerhans cells (LCs) and interstitial DCs (intDCs) can be generated in vitro by differentiation of CD34(+) hematopoietic progenitors via distinct precursor DCs (preDCs), CD1a(+) preDCs, and CD14(+) preDCs, respectively. Here, we identified BDCA3 expression in this well-known GM-CSF/TNF-α-driven culture system and described the effect of IL-4 and/or TGF-β on induction of BDCA3 expression. In control or TGF-β cultures, BDCA3 was only detected on CD14(+) preDC-derived intDCs. IL-4 induced BDCA3 expression in both CD14(+)-derived and CD1a(+)-derived cultures. TGF-β and IL-4 together further increased CD14(+)-derived and CD1a(+)-derived BDCA3(+) DC frequencies, which partly expressed CLEC9A, but were not identical to the BDCA3(high) CLEC9A(+) DC subset in vivo. Importantly, BDCA3(+) cells, but not BDCA3(-) cells, in this system produced high IFN-λ levels upon polyinosinic:polycytidylic acid (polyI:C) stimulation. This culture system, in which BDCA3 expression is preferentially associated with the intDC lineage and IFN-λ-producing capacity, will greatly contribute to further research on the function and regulation of BDCA3 expression and IFN-λ production by DCs.

Temporal gene profiling of the 5XFAD transgenic mouse model highlights the importance of microglial activation in Alzheimer's disease

BACKGROUND

The 5XFAD early onset mouse model of Alzheimer's disease (AD) is gaining momentum. Behavioral, electrophysiological and anatomical studies have identified age-dependent alterations that can be reminiscent of human AD. However, transcriptional changes during disease progression have not yet been investigated. To this end, we carried out a transcriptomic analysis on RNAs from the neocortex and the hippocampus of 5XFAD female mice at the ages of one, four, six and nine months (M1, M4, M6, M9).

RESULTS

Our results show a clear shift in gene expression patterns between M1 and M4. At M1, 5XFAD animals exhibit region-specific variations in gene expression patterns whereas M4 to M9 mice share a larger proportion of differentially expressed genes (DEGs) that are common to both regions. Analysis of DEGs from M4 to M9 underlines the predominance of inflammatory and immune processes in this AD mouse model. The rise in inflammation, sustained by the overexpression of genes from the complement and integrin families, is accompanied by an increased expression of transcripts involved in the NADPH oxidase complex, phagocytic processes and IFN-γ related pathways.

CONCLUSIONS

Overall, our data suggest that, from M4 to M9, sustained microglial activation becomes the predominant feature and point out that both detrimental and neuroprotective mechanisms appear to be at play in this model. Furthermore, our study identifies a number of genes already known to be altered in human AD, thus confirming the use of the 5XFAD strain as a valid model for understanding AD pathogenesis and for screening potential therapeutic molecules.

Regulation of monocyte differentiation by specific signaling modules and associated transcription factor networks

Monocyte/macrophages are important players in orchestrating the immune response as well as connecting innate and adaptive immunity. Myelopoiesis and monopoiesis are characterized by the interplay between expansion of stem/progenitor cells and progression towards further developed (myelo)monocytic phenotypes. In response to a variety of differentiation-inducing stimuli, various prominent signaling pathways are activated. Subsequently, specific transcription factors are induced, regulating cell proliferation and maturation. This review article focuses on the integration of signaling modules and transcriptional networks involved in the determination of monocytic differentiation.

Two distinct types of Langerhans cells populate the skin during steady state and inflammation

Langerhans cells (LCs), the dendritic cells (DCs) in skin epidermis, possess an exceptional life cycle and developmental origin. Here we identified two types of LCs, short-term and long-term LCs, which transiently or stably reconstitute the LC compartment, respectively. Short-term LCs developed from Gr-1(hi) monocytes under inflammatory conditions and occurred independently of the transcription factor Id2. Long-term LCs arose from bone marrow in steady state and were critically dependent on Id2. Surface marker and gene expression analysis positioned short-term LCs close to Gr-1(hi) monocytes, which is indicative of their monocytic origin. We also show that LC reconstitution after UV light exposure occurs in two waves: an initial fast and transient wave of Gr-1(hi) monocyte-derived short-term LCs is followed by a second wave of steady-state precursor-derived long-term LCs. Our data demonstrate the presence of two types of LCs that develop through different pathways in inflammation and steady state.

Interferon consensus sequence binding protein-induced cell proliferation is mediated by TGF-β signaling and p38 MAPK activation

Interferon consensus sequence binding protein (ICSBP), also known as interferon regulatory factor (IRF)-8, is a member of the interferon (IFN)-γ regulatory transcription factors. Studies have suggested a connection between TGF-β signaling and IRFs. Thus, we investigated the effect of ICSBP on transforming growth factor (TGF)-β signaling in HL-60, an acute promyelocytic leukemia cell line. Stable expression of ICSBP in HL-60 cells resulted in strong induction of TGF-β receptor expression and activation of non-Smad as well as Smad pathways. ICSBP expression also augmented cell growth. ICSBP knockdown with small interfering RNA (siRNA) attenuated cell growth and decreased TGF-β receptor I (TGF-βRI) expression. In addition, reduction of TGF-βRI using siRNA or pharmacological inhibitor reduced growth of ICSBP-expressing cells. ICSBP expression also led to increased phosphorylation and activation of Akt and p38 MAPK. However, p38 MAPK, but not PI3K-Akt, inhibition abrogated ICSBP-mediated proliferation. Furthermore, siRNA knockdown of either ICSBP or TGF-βRI resulted in decreased p38 activation. Intriguingly, TGF-β-activated kinase 1 (TAK-1), which phosphorylates p38, was activated in ICSBP-expressing cells and its activity was reduced by TGF-βRI inhibition. Finally, siRNA knockdown of ICSBP or TGF-βRI reduced TAK-1 phosphorylation. This study identifies a novel role for ICSBP in regulating cell growth via TGF-β receptor upregulation and subsequent activation of the TGF-β receptor/TAK-1/p38 pathway.

Transcriptional profiling of the hematopoietic support of interleukin-stimulated human umbilical vein endothelial cells (HUVECs)

Endothelial cells can be successfully used to maintain or increase the number of hematopoietic stem cells in vitro. Previously we identified hematopoietic progenitor cell (HPC) expansion or survival benefit induced by IL-1β-, IL-3-, and IL-6-stimulated human umbilical vein endothelial cell (HUVEC) supernatants. In order to identify molecular mechanisms that support hematopoiesis, we examined the time-dependent expression profiles of IL-1β-, IL-3-, and IL-6-stimulated HUVECs via microarray. Here, we present 24 common upregulated elements and three common downregulated elements of IL-1β- and IL-3-stimulated HUVECs, with these factors exhibiting great potential for the observed HPC expansion. Furthermore, metabolic pathway analysis resulted in the identification of nonproteinogenic factors such as prostaglandin E(2) (PGE(2)) and nitric oxide (NO) and determined their HPC expansion potential via delta, methylcellulose, and cobblestone assays. We confirmed PGE(2) and spermine as hematopoietic expansion factors. Furthermore, we identified several factors such as SSAT, extracellular matrix components, microRNA21, and a microvesicle-mediated cross-talk between the endothelium and HPCs that may play a crucial role in determining stem cell fate. Our results suggest that microarray in combination with functional annotations is a convenient method to identify novel factors with great impact on HPC proliferation and differentiation.

TGF-beta1 accelerates dendritic cell differentiation from common dendritic cell progenitors and directs subset specification toward conventional dendritic cells

Dendritic cells (DCs) in lymphoid tissue comprise conventional DCs (cDCs) and plasmacytoid DCs (pDCs) that develop from common DC progenitors (CDPs). CDPs are Flt3(+)c-kit(int)M-CSFR(+) and reside in bone marrow. In this study, we describe a two-step culture system that recapitulates DC development from c-kit(hi)Flt3(-/lo) multipotent progenitors (MPPs) into CDPs and further into cDC and pDC subsets. MPPs and CDPs are amplified in vitro with Flt3 ligand, stem cell factor, hyper-IL-6, and insulin-like growth factor-1. The four-factor mixture readily induces self-renewal of MPPs and their progression into CDPs and has no self-renewal activity on CDPs. The amplified CDPs respond to all known DC poietins and generate all lymphoid tissue DCs in vivo and in vitro. Additionally, in vitro CDPs recapitulate the cell surface marker and gene expression profile of in vivo CDPs and possess a DC-primed transcription profile. TGF-β1 impacts on CDPs and directs their differentiation toward cDCs. Genome-wide gene expression profiling of TGF-β1-induced genes identified instructive transcription factors for cDC subset specification, such as IFN regulatory factor-4 and RelB. TGF-β1 also induced the transcription factor inhibitor of differentiation/DNA binding 2 that suppresses pDC development. Thus, TGF-β1 directs CDP differentiation into cDCs by inducing both cDC instructive factors and pDC inhibitory factors.

The IRF family transcription factors in immunity and oncogenesis

The interferon regulatory factor (IRF) family, consisting of nine members in mammals, was identified in the late 1980s in the context of research into the type I interferon system. Subsequent studies over the past two decades have revealed the versatile and critical functions performed by this transcription factor family. Indeed, many IRF members play central roles in the cellular differentiation of hematopoietic cells and in the regulation of gene expression in response to pathogen-derived danger signals. In particular, the advances made in understanding the immunobiology of Toll-like and other pattern-recognition receptors have recently generated new momentum for the study of IRFs. Moreover, the role of several IRF family members in the regulation of the cell cycle and apoptosis has important implications for understanding susceptibility to and progression of several cancers.

The influence of the NOD Nss1/Idd5 loci on sialadenitis and gene expression in salivary glands of congenic mice

The nonobese diabetic (NOD) Nss1 and Idd5 loci have been associated with sialadenitis development in mice. In this study the NOD Nss1 and Idd5 loci were backcrossed onto the healthy control strain B10.Q by using the speed congenic breeding strategy, resulting in three congenic strains: B10.Q.Nss1, B10.Q.Nss1/Idd5 heterozygous and B10.Q.Nss1/Idd5 homozygous. We investigated the effects of the Nss1 and Idd5 loci on sialadenitis and gene expression in NOD congenic mice. One submandibular salivary gland from each mouse was used for histological analysis of sialadenitis, whereas the contralateral salivary gland was used for gene expression profiling with the Applied Biosystems Mouse Genome Survey chip v.1.0. The results were validated using quantitative reverse transcriptase PCR. The NOD Nss1 and Idd5 loci had clear influence on the onset and progression of sialadenitis in congenic mice. Double congenic mice exhibited the most severe phenotype. We successfully identified several genes that are located in the NOD congenic regions to be differentially expressed between the congenic strains and the control strain. Several of these were found to be co-regulated, such as Stat1, complement component C1q genes and Tlr12. Also, a vast contingency of interferon-regulated genes (such as Ltb, Irf7 and Irf8) and cytokine and chemokine genes (such as Ccr7 and Ccl19) were differentially expressed between the congenic strains and the control strain. Over-representation of inflammatory signalling pathways was observed among the differentially expressed genes. We have found that the introgression of the NOD loci Nss1 and Idd5 on a healthy background caused sialadenitis in NOD congenic mouse strains, and we propose that genes within these loci are important factors in the pathogenesis. Furthermore, gene expression profiling has revealed several differentially expressed genes within and outside the NOD loci that are similar to genes found to be differentially expressed in patients with Sjögren's syndrome, and as such are interesting candidates for investigation to enhance our understanding of disease mechanisms and to develop future therapies.