Induction of pathogenic TH17 cells by inducible salt-sensing kinase SGK1

Th17 cells are highly proinflammatory cells that are critical for clearing extracellular pathogens and induction of multiple autoimmune diseases. IL-23 plays a critical role in stabilizing and endowing Th17 cells with pathogenic effector functions. IL-23 has been shown to reinforce the Th17 phenotype by increasing expression of IL-23 receptor (IL-23R). However, the molecular mechanism by which IL-23 sustains the Th17 response and induces pathogenic effector functions is unclear. Here we used unbiased transcriptional profiling of developing Th17 cells to construct a model of their signaling network and identify major nodes that regulate Th17 development. We identified serum glucocorticoid kinase-1 (SGK1) is critical for regulating IL-23R expression and for stabilizing the Th17 cell by deactivation of Foxo1, a direct repressor of IL-23R expression. SGK1 has been shown to govern Na+ transport and homeostasis. We show that a modest increase in salt (NaCl) concentration induces SGK1 expression, promotes IL-23R expression and enhances Th17 cell differentiation in vitro and in vivo, ultimately accelerating the development of autoimmunity. The loss of SGK1 resulted in abrogation of Na+-mediated Th17 differentiation in an IL-23-dependent manner. These data indicate that SGK1 is critical for the induction of pathogenic Th17 cells and provides a molecular insight by which an environmental factor such as a high salt diet could trigger Th17 development and promote tissue inflammation.

Th17 cells, pathogenic or not? TGF-β3 imposes the embargo

There has been a marked increase in the incidence of autoimmune diseases in the past half-century. Although the underlying genetic basis of this class of diseases has recently been elucidated, implicating predominantly immune-response genes, changes in environmental factors must ultimately be driving this increase. The newly identified population of interleukin (IL)-17-producing CD4(+) helper T cells (TH17 cells) has a pivotal role in autoimmune diseases. Pathogenic IL-23-dependent TH17 cells have been shown to be critical for the development of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, and genetic risk factors associated with multiple sclerosis are related to the IL-23-TH17 pathway. However, little is known about the environmental factors that directly influence TH17 cells. Here we show that increased salt (sodium chloride, NaCl) concentrations found locally under physiological conditions in vivo markedly boost the induction of murine and human TH17 cells. High-salt conditions activate the p38/MAPK pathway involving nuclear factor of activated T cells 5 (NFAT5; also called TONEBP) and serum/glucocorticoid-regulated kinase 1 (SGK1) during cytokine-induced TH17 polarization. Gene silencing or chemical inhibition of p38/MAPK, NFAT5 or SGK1 abrogates the high-salt-induced TH17 cell development. The TH17 cells generated under high-salt conditions display a highly pathogenic and stable phenotype characterized by the upregulation of the pro-inflammatory cytokines GM-CSF, TNF-α and IL-2. Moreover, mice fed with a high-salt diet develop a more severe form of EAE, in line with augmented central nervous system infiltrating and peripherally induced antigen-specific TH17 cells. Thus, increased dietary salt intake might represent an environmental risk factor for the development of autoimmune diseases through the induction of pathogenic TH17 cells.

The Atlantic killifish (Fundulus heteroclitus) is an environmental sentinel organism used extensively for studies on environmental toxicants and salt (NaCl) homeostasis. Previous research in our laboratory has shown that rapid acclimation of killifish to seawater is mediated by trafficking of CFTR chloride channels from intracellular vesicles to the plasma membrane in the opercular membrane within the first hour in seawater, which enhances chloride secretion into seawater, thereby contributing to salt homeostasis. Acute transition to seawater is also marked by an increase in both mRNA and protein levels of serum glucocorticoid kinase 1 (SGK1) within 15 minutes of transfer. Although the rise in SGK1 in gill and its functional analog, the opercular membrane, after seawater transfer precedes the increase in membrane CFTR, a direct role of SGK1 in elevating membrane CFTR has not been established in vivo. To test the hypothesis that SGK1 mediates the increase in plasma membrane CFTR we designed two functionally different vivo-morpholinos to knock down SGK1 in gill, and developed and validated a vivo-morpholino knock down technique for adult killifish. Injection (intraperitoneal, IP) of the splice blocking SGK1 vivo-morpholino reduced SGK1 mRNA in the gill after transition from fresh to seawater by 66%. The IP injection of the translational blocking and splice blocking vivo-morpholinos reduced gill SGK1 protein abundance in fish transferred from fresh to seawater by 64% and 53%, respectively. Moreover, knock down of SGK1 completely eliminated the seawater induced rise in plasma membrane CFTR, demonstrating that the increase in SGK1 protein is required for the trafficking of CFTR from intracellular vesicles in mitochondrion rich cells to the plasma membrane in the gill during acclimation to seawater. This is the first report of the use of vivo-morpholinos in adult killifish and demonstrates that vivo-morpholinos are a valuable genetic tool for this environmentally relevant model organism.

The adenylate cyclase toxin of Bacillus anthracis is a potent promoter of TH17 cell development

There has been a marked increase in the incidence of autoimmune diseases in the last half-century. While the underlying genetic basis of this class of diseases has recently been elucidated implicating predominantly immune response genes1, changes in environmental factors must ultimate be driving this increase. The recently identified population of interleukin (IL)-17 producing CD4+ helper T cells (Th17 cells) play a pivotal role in autoimmune diseases2. Pathogenic IL-23 dependent Th17 cells have been shown to be critical for the development of experimental autoimmune encephalomyelitis (EAE) an animal model for multiple sclerosis (MS) and genetic risk factors associated with MS are related to the IL23/Th17 pathway1, 2. However, little is known regarding the environmental factors that directly influence Th17 cells. Here we show that increased salt (sodium chloride; NaCl) concentrations found under physiological conditions in vivo dramatically boost the induction of murine and human Th17 cells. High salt conditions activates the p38/MAPK pathway involving the tonicity-responsive enhancer binding protein (TonEBP/NFAT5) and the serum- and glucocorticoid-inducible kinase 1 (SGK1) during cytokine-induced Th17 polarization. Gene silencing or chemical inhibition of p38/MAPK, NFAT5 or SGK1 abrogates the high salt induced Th17 cell development. The Th17 cells generated under high salt display a highly pathogenic and stable phenotype as compared to cells differentiated under normal conditions characterized by the up-regulation of the pro-inflammatory cytokines GM-CSF, TNFα and IL-2. Moreover, mice fed with a high salt diet develop a very severe form of EAE in line with increased central nervous system infiltrating and peripherally induced antigen specific Th17 cells. Thus, increased dietary salt intake might represent an environmental risk factor for the development of autoimmune diseases through the induction of pathogenic Th17 cells.

Interleukin (IL)-17 producing CD4+ helper T cells (Th17 cells) play a pivotal role in autoimmune diseases. Apart from their importance for the control of certain pathogens, IL-23 dependent Th17 cells have been shown to be critical for the development of experimental autoimmune encephalomyelitis (EAE). Moreover, genetic risk factors associated with multiple sclerosis (MS) are linked to the IL23/Th17 pathway. Besides genetic factors, the increased incidence of autoimmune diseases like MS in developed countries is also believed to be related to environmental risk factors. However, how environmental risk factors such as changes in diet, sun exposure or medications could directly influence the development of pathogenic Th17 cells is not well established. Here we show that increased salt (sodium chloride; NaCl) concentrations dramatically boost the induction of murine and human Th17 cells in vitro. Moreover, mice fed with a high salt diet develop a very severe form of EAE, dependent on the induction of highly pathogenic Th17 cells. The generation of Th17 cells under high salt conditions is well regulated on the molecular level and seems to be dependent on specific pathways. Thus, increased salt intake, which may represents one of the biggest contributors to changes in diet during the last half century and accounts for cardiovascular disease, might also represent an environmental risk factor for autoimmune diseases through the exacerbated induction of pathogenic Th17 cells.

Socs3 induction by PPARγ restrains cancer-promoting inflammation

AB0145 Sodium Chloride Aggravates Arthritis by TH17 Polarization

IL-17–producing T cells in lung immunity and inflammation

CD4+ T cells, especially Th17 cells, are instrumental in the development and progression of autoimmune diseases, such as multiple sclerosis (MS), psoriasis, and rheumatoid arthritis. While pathogenic Th17 cells drive inflammation in autoimmunity, the molecular programming underlying their pathogenicity remains insufficiently understood. Furthermore, very little is known regarding the role of the pattern recognition receptor TLR2 in Th17 pathogenicity. We have previously shown that activation of TLR2 with PAM3CSK4 during Th17 differentiation results in increased production of IL-17A and IL-17F and significantly increases the proliferation of Th17 cells in vitro. Herein, we show that TLR2 induces pathogenicity in Th17 cells, similar to what has been shown for IL-23. TLR2 signaling results in increased encephalitogenic migration of Th17 cells, in addition to increased cytokine production. To further investigate the effect of TLR2 activation on Th17 cells, we utilized RNA sequencing and found 390 genes that are upregulated and 355 genes that are downregulated following TLR2 signaling in Th17 cells. Several of these genes we have identified are important regulators that either increase or restrain the inflammatory potential of Th17 cells. We further address the role of TLR2 in Th17-mediated autoimmune disease using experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We show that encephalitogenic Th17 cells expanded with a TLR2 agonist induced EAE disease to the same extent as those expanded with IL-23. Altogether, this study establishes TLR2 signaling as crucial for induction of pathogenic Th17 cells in autoimmune disease.

T helper17 Cells Are Sufficient But Not Necessary to Induce Acute Graft-Versus-Host Disease

307 Establishment of D. farinae-loaded microneedle patches for allergen specific immunotherapy in allergic diseases

304 Tonicity signals drive and anti-inflammatory Th17 cell properties

306 Efficacy of Dermatophagoides farinae-specific subcutaneous immunotherapy for mouse atopic dermatitis model