Jing-Jing Jiang

Hepatic Interleukin-7 Expression Regulates T Cell Responses

Systemic cytokine activity in response to Toll-like receptor (TLR) signaling induces the expression of various proteins in the liver after infections. Here we show that Interleukin-7 (IL-7), the production of which was thought to occur at a constant rate in vivo, was a hepatically expressed protein that directly controled T cell responses. Depletion of IL-7 expression in the liver abrogated several TLR-mediated T cell events, including enhanced CD4+ T cell and CD8+ T cell survival, augmented CD8+ T cell cytotoxic activity, and the development of experimental autoimmune encephalitis, a Th17 cell-mediated autoimmune disease. Thus, T cell responses are regulated by hepatocyte-derived IL-7, which is expressed in response to TLR signaling in vivo. We suggested that TLR-induced IL-7 expression in the liver, which is an acute-phase response, may be a good diagnostic and therapeutic target for efficient vaccine developments and for conditions characterized by TLR-mediated T cell dysregulation, including autoimmune diseases.

Inflammation Amplifier, a New Paradigm in Cancer Biology

Tumor-associated inflammation can induce various molecules expressed from the tumors themselves or surrounding cells to create a microenvironment that potentially promotes cancer development. Inflammation, particularly chronic inflammation, is often linked to cancer development, even though its evolutionary role should impair nonself objects including tumors. The inflammation amplifier, a hyperinducer of chemokines in nonimmune cells, is the principal machinery for inflammation and is activated by the simultaneous stimulation of NF-κB and STAT3. We have redefined inflammation as local activation of the inflammation amplifier, which causes an accumulation of various immune cells followed by dysregulation of local homeostasis. Genes related to the inflammation amplifier have been genetically associated with various human inflammatory diseases. Here, we describe how cancer-associated genes, including interleukin (IL)-6, Ptgs2, ErbB1, Gas1, Serpine1, cMyc, and Vegf-α, are strongly enriched in genes related to the amplifier. The inflammation amplifier is activated by the stimulation of cytokines, such as TNF-α, IL-17, and IL-6, resulting in the subsequent expression of various target genes for chemokines and tumor-related genes like BCL2L11, CPNE7, FAS, HIF1-α, IL-1RAP, and SOD2. Thus, we conclude that inflammation does indeed associate with the development of cancer. The identified genes associated with the inflammation amplifier may thus make potential therapeutic targets of cancers.

Disease-Association Analysis of an Inflammation-Related Feedback Loop

The IL-6-triggered positive feedback loop for NFκB signaling (or the IL-6 amplifier/Inflammation amplifier) was originally discovered as a synergistic-activation signal that follows IL-17/IL-6 stimulation in nonimmune cells. Subsequent results from animal models have shown that the amplifier is activated by stimulation of NFκB and STAT3 and induces chemokines and inflammation via an NFκB loop. However, its role in human diseases is unclear. Here, we combined two genome-wide mouse screens with SNP-based disease association studies, revealing 1,700 genes related to the IL-6 amplifier, 202 of which showed 492 indications of association with ailments beyond autoimmune diseases. We followed up on ErbB1 from our list. Blocking ErbB1 signaling suppressed the IL-6 amplifier, whereas the expression of epiregulin, an ErbB1 ligand, was higher in patients with inflammatory diseases. These results indicate that the IL-6 amplifier is indeed associated with human diseases and disorders and that the identified genes may make for potential therapeutic targets.

Temporal Expression of Growth Factors Triggered by Epiregulin Regulates Inflammation Development

In this study, we investigated the relationship between several growth factors and inflammation development. Serum concentrations of epiregulin, amphiregulin, betacellulin, TGF-α, fibroblast growth factor 2, placental growth factor (PLGF), and tenascin C were increased in rheumatoid arthritis patients. Furthermore, local blockades of these growth factors suppressed the development of cytokine-induced arthritis in mice by inhibiting chemokine and IL-6 expressions. We found that epiregulin expression was early and followed by the induction of other growth factors at different sites of the joints. The same growth factors then regulated the expression of epiregulin at later time points of the arthritis. These growth factors were increased in patients suffering from multiple sclerosis (MS) and also played a role in the development of an MS model, experimental autoimmune encephalomyelitis. The results suggest that the temporal expression of growth factors is involved in the inflammation development seen in several diseases, including rheumatoid arthritis and MS. Therefore, various growth factor pathways might be good therapeutic targets for various inflammatory diseases.

The Gateway Reflex, which is mediated by the inflammation amplifier, directs pathogenic immune cells into the CNS

The brain-blood barrier (BBB) tightly limits immune cell migration into the central nervous system (CNS), avoiding unwanted inflammation under the normal state. However, immune cells can traverse the BBB when inflammation occurs within the CNS, suggesting a certain signal that creates a gateway that bypasses the BBB might exist. We revealed the inflammation amplifier as a mechanism of this signal, and identified dorsal vessels of the fifth lumber (L5) spinal cord as the gateway. The inflammation amplifier is driven by a simultaneous activation of NF-κB and STATs in non-immune cells, causing the production of a large amount of inflammatory chemokines to open the gateway at L5 vessels. It was found that the activation of the amplifier can be modulated by neural activation and artificially operated by electric pulses followed by establishment of new gateways, Gateway Reflex, at least in mice. Furthermore, genes required for the inflammation amplifier have been identified and are highly associated with various inflammatory diseases and disorders in the CNS. Thus, physical and/or pharmacological manipulation of the inflammation amplifier holds therapeutic value to control neuro-inflammation.

Breakpoint Cluster Region–Mediated Inflammation Is Dependent on Casein Kinase II

The breakpoint cluster region (BCR) is known as a kinase and cause of leukemia upon fusing to Abl kinase. In this study, we demonstrate that BCR associated with the α subunit of casein kinase II (CK2α), rather than BCR itself, is required for inflammation development. We found that BCR knockdown inhibited NF-κB activation in vitro and in vivo. Computer simulation, however, suggested that the putative BCR kinase domain has an unstable structure with minimal enzymatic activity. Liquid chromatography–tandem mass spectrometry analysis showed that CK2α associated with BCR. We found the BCR functions are mediated by CK2α. Indeed, CK2α associated with adaptor molecules of TNF-αR and phosphorylated BCR at Y177 to establish a p65 binding site after TNF-α stimulation. Notably, p65 S529 phosphorylation by CK2α creates a p300 binding site and increased p65-mediated transcription followed by inflammation development in vivo. These results suggest that BCR-mediated inflammation is dependent on CK2α, and the BCR–CK2α complex could be a novel therapeutic target for various inflammatory diseases.

Rbm10 regulates inflammation development via alternative splicing of Dnmt3b

RNA-binding motif 10 (Rbm10) is an RNA-binding protein that regulates alternative splicing, but its role in inflammation is not well defined. Here, we show that Rbm10 controls appropriate splicing of DNA (cytosine-5)-methyltransferase 3b (Dnmt3b), a DNA methyltransferase, to regulate the activity of NF-κB-responsive promoters and consequently inflammation development. Rbm10 deficiency suppressed NF-κB-mediated responses in vivo and in vitro. Mechanistic analysis showed that Rbm10 deficiency decreased promoter recruitment of NF-κB, with increased DNA methylation of the promoter regions in NF-κB-responsive genes. Consistently, Rbm10 deficiency increased the expression level of Dnmt3b2, which has enzyme activity, while it decreased the splicing isoform Dnmt3b3, which does not. These two isoforms associated with NF-κB efficiently, and overexpression of enzymatically active Dnmt3b2 suppressed the expression of NF-κB targets, indicating that Rbm10-mediated Dnmt3b2 regulation is important for the induction of NF-κB-mediated transcription. Therefore, Rbm10-dependent Dnmt3b regulation is a possible therapeutic target for various inflammatory diseases.

Strong TCR-mediated signals suppress integrated stress responses induced by KDELR1 deficiency in naive T cells

KDEL receptor 1 (KDELR1) regulates integrated stress responses (ISR) to promote naive T-cell survival in vivo. In a mouse line having nonfunctional KDELR1, T-Red (naive T-cell reduced) mice, polyclonal naive T cells show excessive ISR and eventually undergo apoptosis. However, breeding T-Red mice with TCR-transgenic mice bearing relatively high TCR affinity rescued the T-Red phenotype, implying a link between ISR-induced apoptosis and TCR-mediated signaling. Here, we showed that strong TCR stimulation reduces ISR in naive T cells. In mice lacking functional KDELR1, surviving naive T cells expressed significantly higher levels of CD5, a surrogate marker of TCR self-reactivity. In addition, higher TCR affinity/avidity was confirmed using a tetramer dissociation assay on the surviving naive T cells, suggesting that among the naive T-cell repertoire, those that receive relatively stronger TCR-mediated signals via self-antigens survive enhanced ISR. Consistent with this observation, weak TCR stimulation with altered peptide ligands decreased the survival and proliferation of naive T cells, whereas stimulation with ligands having higher affinity had no such effect. These results suggest a novel role of TCR-mediated signals in the attenuation of ISR in vivo.

Role of Cytokine-Mediated Crosstalk between T Cells and Nonimmune Cells in the Pathophysiology of Multiple Sclerosis

Abstract Multiple sclerosis (MS) is a progressive demyelinating disease associated with chronic inflammation in the central nervous system (CNS). Genetic linkage is found in genes related to T cell function, and T cell infiltration is evident in MS lesions, suggesting a pathophysiological role for these cells. In the MS animal model experimental autoimmune encephalomyelitis (EAE), activated CD4+ and CD8+ T cells that recognize CNS antigens can induce MS-like symptoms. Various cytokines from these T cells trigger inflammation, critically contributing to the pathogenesis of the CNS disease. Evidence suggests an important role for cytokine-mediated crosstalk between T cells and nonimmune cells, including endothelial cells, glial cells, and fibroblasts in enhancing CNS inflammation. Counterbalancing T cell-induced inflammation, certain regulatory CD4+ and CD8+ T cell subsets can suppress CNS disease progression. Here, we discuss the pathophysiological role of T cells during MS and EAE, including neuro–immune interactions that allow T cells to invade the CNS.

Presenilin 1 Regulates NF-κB Activation via Association with Breakpoint Cluster Region and Casein Kinase II

We recently reported that NF-κB–mediated inflammation caused by breakpoint cluster region (BCR) is dependent on the α subunit of casein kinase II (CK2α) complex. In the current study, we demonstrate that presenilin 1 (Psen1), which is a catalytic component of the γ-secretase complex and the mutations of which are known to cause familial Alzheimer disease, acts as a scaffold of the BCR–CK2α–p65 complex to induce NF-κB activation. Indeed, Psen1 deficiency in mouse endothelial cells showed a significant reduction of NF-κB p65 recruitment to target gene promoters. Conversely, Psen1 overexpression enhanced reporter activation under NF-κB responsive elements and IL-6 promoter. Furthermore, the transcription of NF-κB target genes was not inhibited by a γ-secretase inhibitor, suggesting that Psen1 regulates NF-κB activation in a manner independent of γ-secretase activity. Mechanistically, Psen1 associated with the BCR–CK2α complex, which is required for phosphorylation of p65 at serine 529. Consistently, TNF-α–induced phosphorylation of p65 at serine 529 was significantly decreased in Psen1-deficient cells. The association of the BCR–CK2α–p65 complex was perturbed in the absence of Psen1. These results suggest that Psen1 functions as a scaffold of the BCR–CK2α–p65 complex and that this signaling cascade could be a novel therapeutic target for various chronic inflammation conditions, including those in Alzheimer disease.