The impairment of the immune system by fluoride is a public health concern worldwide, yet the underlying mechanism is unclear. Both riboflavin and IL-17A are closely related to immune function and regulate the testicular toxicity of fluoride. However, whether riboflavin or IL-17A is involved in fluoride-induced immunotoxicity is unknown. Here, we first established a male ICR mouse model by treating mice with sodium fluoride (NaF) (100 mg/L) via the drinking water for 91 days. The results showed that fluoride increased the expression of the proinflammatory factors IL-1β and IL-17A, which led to splenic inflammation and morphological injury. Moreover, the expression levels of the riboflavin transporters SLC52A2 and SLC52A3; the transformation-related enzymes RFK and FLAD1; and the key mitochondrial functional determinants SDH, COX, and ATP in the spleen were measured via real-time PCR, Western blotting, and ELISA. The results revealed that fluoride disrupted riboflavin transport, transformation, metabolism, and mitochondrial function. Furthermore, wild-type (WT) and IL-17A knockout (IL-17A-/-) C57BL/6 J male mice of the same age were treated with NaF (24 mg/kg·bw, equivalent to 100 mg/L) and/or riboflavin sodium phosphate (5 mg/kg·bw) via gavage for 91 days. Similar parameters were evaluated as above. The results confirmed that fluoride increased riboflavin metabolism through RFK but not through FLAD1. Fluoride also affected mitochondrial function and activated neutrophils (marked with Ly6g) and macrophages (marked with CD68) in the spleen. Interestingly, IL-17A partly mediated fluoride-induced riboflavin metabolism disorder and immunotoxicity in the spleen. This work not only reveals a novel toxic mechanism for fluoride but also provides new clues for exploring the physiological function of riboflavin and for diagnosing and treating the toxic effects of fluoride in the environment.

UNASSIGNED: Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated.
UNASSIGNED: We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM.
UNASSIGNED: VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells.
UNASSIGNED: These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

Thromboangiitis obliterans (TAO) is a rare, chronic, progressive, and segmental inflammatory disease characterized by a high rate of amputation, significantly compromising the quality of life of patients. Si-Miao-Yong-An decoction (SMYA), a traditional prescription, exhibits anti-inflammatory, anti-thrombotic, and various other pharmacological properties. Clinically, it was fully proved to be effective for TAO therapy, but the specific therapeutic effect of SMYA on TAO has been unknown. Thus, deep unveiling the mechanism of SMYA in TAO for identifying clinical therapeutic targets is extremely important. In this study, we observed elevated levels of IL-17A in the peripheral blood mononuclear cells (PBMCs) of TAO patients, whereas the expression of miR-548j-5p was significantly decreased. A negative correlation between the levels of miR-548j-5p and IL-17A was also demonstrated. In vitro experiments showed that overexpression of miR-548j-5p led to a decrease in IL-17A levels, whereas downregulation of miR-548j-5p showed the opposite effect. Using a dual luciferase assay, we confirmed that miR-548j-5p directly targets IL-17A. Furthermore, serum containing SMYA effectively decreased IL-17A levels by increasing the expression of miR-548j-5p. More importantly, the results of in vivo tests indicated that SMYA mitigated the development of TAO by inhibiting IL-17A through the upregulation of miR-548j-5p in vascular tissues. In conclusion, SMYA significantly enhances the expression of miR-548j-5p, thereby reducing the levels of the target gene IL-17A and alleviating TAO. Our research not only identifies novel targets and pathways for the clinical diagnosis and treatment of TAO but also advances the innovation in traditional Chinese medicine through the elucidation of the SMYA/miR-548j-5p/IL-17A regulatory axis in the pathogenesis of TAO.

BACKGROUND: Iguratimod (IGU) is widely used in clinical practice due to its stable anti-inflammatory effects. Our previous studies have confirmed that the proportion of Th17/Treg balance in patients taking IGU altered significantly. This study aims to explore the role of IGU in antibody-mediated rejection (ABMR) and its potential mechanisms.
METHODS: We conducted bioinformatics analysis of sequencing data from the GEO database to analyze the abundance of immune cell infiltration in transplanted kidney tissues. In vivo, IGU was intervened in a mice secondary skin transplantation model and a mice kidney transplantation ABMR model, and histological morphology of the grafts were examined by pathological staining, while relevant indicators were determined through qRT-PCR, immunohistochemistry, and enzyme-linked immunosorbent assay, observed T cell differentiation by flow cytometry, and preliminarily assessed the immunosuppressive effect of IGU. In vitro, we established Th17 and Treg cell induction and stimulation differentiation culture systems and added IGU for intervention to explore its effects on their differentiation.
RESULTS: Through bioinformatics analysis, we found that Th17 and Treg may play important roles in the occurrence and development of ABMR. In vivo, we found that IGU could effectively reduce the damage caused by ABMR to the grafts, alleviate the infiltration of inflammatory cells in the graft tissues, and reduce the deposition of C4d in the grafts. Moreover, it is also found that IGU regulated the differentiation of Th17 and Treg cells in the spleen and peripheral blood and reduced the expression of IL-17A in the grafts and serum. In addition, same changes were observed in the induction and differentiation culture system of Th17 and Treg cells in vitro after the addition of IGU.
CONCLUSIONS: IGU can inhibit the progression of ABMR by regulating the differentiation of Th17 and Treg cells, providing novel insights for optimizing clinical immunosuppressive treatment regimens.

OBJECTIVE: To investigate the possible roles of Interleukin 17A (IL-17A) and IL-17A neutralizing antibodies (IL-17Ab) in glaucoma and the potential mechanisms.
METHODS: The two glaucoma animal models, chronic ocular hypertension (COH) and N-methyl-D-aspartate (NMDA)-induced retinal ganglion cell (RGC) damage, were established and treated with intravitreal injection of IL-17A or IL-17Ab. Intraocular pressure (IOP) was measured by a rebound tonometer. The retina and RGC injury were evaluated by HE staining, TUNLE assay and Brn3a immunofluorescence staining. The frequency of IL-17A+CD4+T cells in peripheral blood was detected by flow cytometry. The expression of glial fibrillary acidic protein (GFAP) was detected by immunofluorescence staining, Western Blot and qPCR in retina. The RNA and protein expression of Act1/TRAF6/NF-κB were detected by Western Blot and qPCR in retina.
RESULTS: The expression of IL-17A increased in glaucoma models. After intravitreal injection of IL-17A, in the retina, the number of RGCs decreased, the apoptosis of RGCs increased, the Müller cell gliosis was more obvious. In addition, peripheral inflammation aggravated. Whereas the intravitreal injection of IL-17Ab alleviated the relevant manifestations and peripheral inflammation, reduced the gliosis of Müller cells. In the COH model, IOP increased after the injection of IL-17A, while the intravitreal injection of IL-17Ab led to a decrease in IOP. Furthermore, IL-17A promotes the apoptosis of RGCs by binding to IL-17A receptor, activating Act1/TRAF6/NF-κB pathways.
CONCLUSIONS: IL-17A plays a role in and aggravates RGC damage in glaucoma. IL-17Ab can neutralize the pro-inflammatory effect of IL-17A and have a protective function in glaucoma. These findings reveal the importance of IL-17A in the pathogenesis of glaucoma, which will shed light on a novel direction for the prevention and treatment of glaucoma, and also provide a reference for further research on other retinal diseases.

Inflammation is an important pathogenic driving force in the genesis and development of epilepsy. The latest researches demonstrated that IL-17A mediated blood-brain barrier (BBB) dysfunction through disruption of tight junction protein expression. To investigate whether IL-17A is involved in BBB disruption after acute seizure attack, the pilocarpine model was established with C57BL/6 J (wild type, WT) and IL-17R-deficient mice in vivo and with primary cultured rat brain microvascular endothelial cells in vitro. The mortality rate and brain water content were evaluated at 24 h after status epilepticus, and IL-17A concentration, endothelial tight junction, adherens junction proteins, and albumin leakage were assessed at 0 h, 4 h, 12 h, and 24 h after status epilepticus (SE). IL-17R-deficient mice showed lessen severity of epilepsy than WT mice, accompanied by less albumin leakage, reduced brain water content, decreased IL-17A, and upregulated expression of target proteins (ZO-1, Occludin and VE-cadherin). IL-17R knockout abrogated abnormal upregulation of Src kinase and phosphorylated Src kinase in the setting of SE, and Src kinase inhibitor PP1 abrogated IL-17A-induced SE related endothelial injury in vitro. In conclusion, IL-17A inhibition might be a promising therapeutic option to attenuate endothelial cell injury and further BBB disruption by reducing Src kinase activation.

Psoriasis is a common chronic inflammatory skin disease driven by the aberrant activation of dendritic cells (DCs) and T cells, ultimately leading to increased production of cytokines such as interleukin (IL)-23 and IL-17A. It is established that the cGAS-STING pathway is essential for psoriatic inflammation, however, the specific role of cGAS-STING signaling in DCs within this context remains unclear. In this study, we demonstrated the upregulation of cGAS-STING signaling in psoriatic lesions by analyzing samples from both clinical patients and imiquimod (IMQ)-treated mice. Using a conditional Sting-knockout transgenic mouse model, we elucidated the impact of cGAS-STING signaling in DCs on the activation of IL-17- and IFN-γ-producing T cells in psoriatic inflammation. Ablation of the Sting hampers DC activation leads to decreased numbers of IL-17-producing T cells and Th1 cells, and thus subsequently attenuates psoriatic inflammation in the IMQ-induced mouse model. Furthermore, we explored the therapeutic potential of the STING inhibitor C-176, which reduces psoriatic inflammation and enhances the anti-IL-17A therapeutic response. Our results underscore the critical role of cGAS-STING signaling in DCs in driving psoriatic inflammation and highlight a promising psoriasis treatment.

Acute liver failure (ALF) is a serious inflammatory disorder with high mortality rates, which poses a significant threat to human health. The IL-33/ST2 signal is a crucial regulator in inflammation responses associated with lipopolysaccharide (LPS)-induced macrophages. The IL-17A signaling pathway promotes the release of chemokines and inflammatory cytokines, recruiting neutrophils and T cells under LPS stimulation, thus facilitating inflammatory responses. Here, the potential therapeutic benefits of neutralizing the IL-17A signal and modulating the IL-33/ST2 signal in ALF were investigated. A novel dual-functional fusion protein, anti-IL-17A-sST2, was constructed, which displayed high purity and biological activities. The administration of anti-IL-17A-sST2 resulted in significant anti-inflammatory benefits in ALF mice, amelioration of hepatocyte necrosis and interstitial congestion, and reduction in TNF-α and IL-6. Furthermore, anti-IL-17A-sST2 injection downregulated the expression of TLR4 and NLRP3 as well as important molecules such as MyD88, caspase-1, and IL-1β. The results suggest that anti-IL-17A-sST2 reduced the secretion of inflammatory factors, attenuated the inflammatory response, and protected hepatic function by regulating the TLR4/MyD88 pathway and inhibiting the NLRP3 inflammasome, providing a new therapeutic approach for ALF.

OBJECTIVE: This study aims to investigate the effects of type 17 immune response on the proliferation of oral epithelial cells in periodontitis.
METHODS: A time-dependent ligature induced periodontitis mouse model was utilized to explore gingival hyperplasia and the infiltration of interleukin 17A (IL-17A) positive cells. Immunohistochemistry and flow cytometry were employed to determine the localization and expression of IL-17A in the ligature induced periodontitis model. A pre-existing single-cell RNA sequencing dataset, comparing individuals affected by periodontitis with healthy counterparts, was reanalyzed to evaluate IL-17A expression levels. We examined proliferation markers, including proliferating cell nuclear antigen (PCNA), signal transducer and activator of transcription (STAT3), Yes-associated protein (YAP), and c-JUN, in the gingival and tongue epithelium of the periodontitis model. An anti-IL-17A agent was administered daily to observe proliferative changes in the oral mucosa within the periodontitis model. Cell number quantification, immunofluorescence, and western blot analyses were performed to assess the proliferative responses of human normal oral keratinocytes to IL-17A treatment in vitro.
RESULTS: The ligature induced periodontitis model exhibited a marked infiltration of IL-17A-positive cells, alongside significant increase in thickness of the gingival and tongue epithelium. IL-17A triggers the proliferation of human normal oral keratinocytes, accompanied by upregulation of PCNA, STAT3, YAP, and c-JUN. The administration of an anti-IL-17A agent attenuated the proliferation in oral mucosa.
CONCLUSIONS: These findings indicate that type 17 immune response, in response to periodontitis, facilitates the proliferation of oral epithelial cells, thus highlighting its crucial role in maintaining the oral epithelial barrier.

The ocular surface is a mucosal barrier tissue colonized by commensal microbes, which tune local immunity by eliciting IL-17 from conjunctival γδ T cells to prevent pathogenic infection. The commensal Corynebacterium mastitidis (C. mast) elicits protective IL-17 responses from conjunctival Vγ4 T cells through a combination of γδ TCR ligation and IL-1 signaling. Here, we identify Vγ6 T cells as a major C. mast-responsive subset in the conjunctiva and uncover its unique activation requirements. We demonstrate that Vγ6 cells require not only extrinsic (via dendritic cells) but also intrinsic TLR2 stimulation for optimal IL-17A response. Mechanistically, intrinsic TLR2 signaling was associated with epigenetic changes and enhanced expression of genes responsible for metabolic shift to fatty acid oxidation to support Il17a transcription. We identify one key transcription factor, IκBζ, which is upregulated by TLR2 stimulation and is essential for this program. Our study highlights the importance of intrinsic TLR2 signaling in driving metabolic reprogramming and production of IL-17A in microbiome-specific mucosal γδ T cells.