OBJECTIVE: Oral lichen planus (OLP) is a chronic inflammatory disease characterized by a dense T-cell infiltration and the degeneration of basal keratinocytes. The potential functions of mucosal associated invariant T (MAIT) cells in OLP have been analyzed in our previous study. Keratinocytes under proinflammatory conditions have been demonstrated to activate T cells. This study was aimed to investigate how keratinocytes stimulate MAIT cells in OLP, and to explore the role of activated MAIT cells on keratinocytes.
RESULTS: Increased MAIT cells and higher activation marker CD69 were detected in OLP lesions by flow cytometry. The enhanced expression of MHC class I-like molecule (MR1) required for MAIT cell activation in the epithelial layer of OLP lesions was determined by immunohistochemistry. Keratinocytes treated by 5-A-RU prodrug and lipopolysaccharide, respectively, exhibited higher expression of MR1 and secretion of IL-18. In direct coculture systems consisting of keratinocytes and peripheral blood mononuclear cells, both 5-A-RU prodrug-pretreated keratinocytes and lipopolysaccharide-pretreated keratinocytes activated MAIT cells to secrete granzyme B, contributing to elevated keratinocyte apoptosis.
CONCLUSIONS: Keratinocytes were capable to activate MAIT cells via MR1 and cytokines in OLP, and granzyme B produced by activated MAIT cells intensified keratinocyte apoptosis, engaging in the pathogenesis of OLP.

Human papillomavirus (HPV)-associated cancer continues to evade the immune system by promoting a suppressive tumor microenvironment. Therefore, immunotherapy appears to be a promising approach for targeting HPV-associated tumors. We hypothesized that valproic acid (VA) as an epigenetic agent combined with avelumab may enhance the antitumor immunity in HPV-associated solid tumors. We performed bulk RNA-sequencing (RNA-Seq) on total peripheral blood mononuclear cells (PBMCs) of seven nonresponders (NRs) and four responders (Rs). A total of 39 samples (e.g., pretreatment, post-VA, postavelumab, and endpoint) were analyzed. Also, we quantified plasma analytes and performed flow cytometry. We observed a differential pattern in immune response following treatment with VA and/or avelumab in NRs vs. Rs. A significant upregulation of transcripts associated with NETosis [the formation of neutrophil extracellular traps (NETs)] and neutrophil degranulation pathways was linked to the presence of a myeloid-derived suppressor cell signature in NRs. We noted the elevation of IL-8/IL-18 cytokines and a distinct transcriptome signature at the baseline and endpoint in NRs. By using the receiver operator characteristics, we identified a cutoff value for the plasma IL-8/IL-18 to discriminate NRs from Rs. We found differential therapeutic effects for VA and avelumab in NRs vs. Rs. Thus, our results imply that measuring the plasma IL-8/IL-18 and bulk RNA-Seq of PBMCs may serve as valuable biomarkers to predict immunotherapy outcomes.

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased pulmonary arterial pressure, inflammation, and neointimal remodeling of pulmonary arterioles. Serum levels of interleukin (IL)-1β and IL-18 are elevated in PAH patients and may enhance proinflammatory neointimal remodeling. NLRP3 inflammasome activation induces cleavage of the cytokines IL-1β and IL-18, required for their secretion. Pirfenidone (PFD), an antifibrotic and anti-inflammatory drug, has been suggested to inhibit NLRP3 inflammasome activation. We hypothesized that PFD delays the progression of PAH by suppressing NLRP3 inflammasome activation. We assessed the effects of PFD treatment in a rat model for neointimal PAH induced by monocrotaline and aortocaval shunt using echocardiographic, hemodynamic, and vascular remodeling parameters. We measured inflammasome activation by NLRP3 immunostaining, Western blots for caspase-1, IL-1β, and IL-18 cleavage, and macrophage IL-1β secretion. PFD treatment ameliorated pulmonary arterial pressure, pulmonary vascular resistance, and pulmonary vascular remodeling in PAH rats. In PAH rats, immunostaining of NLRP3 in pulmonary arterioles and caspase-1, IL-1β, and IL-18 cleavage in lung homogenates were increased compared to controls, reflecting NLRP3 inflammasome activation in vivo. PFD decreased IL-1β and IL-18 cleavage, as well as macrophage IL-1β secretion in vitro. Our studies show that PFD ameliorates pulmonary hemodynamics and vascular remodeling in experimental PAH. Although PFD did not affect all NLRP3 inflammasome parameters, it decreased IL-1β and IL-18 cleavage, the products of NLRP3 inflammasome activation that are key to its downstream effects. Our findings thus suggest a therapeutic benefit of PFD in PAH via suppression of NLRP3 inflammasome activation.

UNASSIGNED: In asthma, genome-wide association studies have shown that interleukin-18 (IL-18) receptor 1 gene (IL-18R1) and sputum IL-18 are increased during exacerbations. However, the role of the IL-18 axis in bronchial epithelial function is unclear. To investigate IL-18, IL-18 binding protein (BP) and IL-18R expression in bronchial biopsies and sputum samples from patients with asthma, and to determine its functional role using in vitro bronchial epithelial cells.
UNASSIGNED: The expression of IL-18, IL-18BP and IL-18Rα was examined in subjects with asthma and healthy controls in bronchial biopsies by immunohistochemistry and IL-18 and IL-18BP release in sputum. In epithelial cells, the mRNA and protein expression of IL-18, IL-18BP, IL-18Rα and IL-18Rβ was assessed by qPCR, flow cytometry, Western blotting and immunofluorescence respectively. IL-18 function in epithelial cells was examined by intracellular calcium, wound repair, synthetic activation and epithelial differentiation changes.
UNASSIGNED: In biopsies from subjects with asthma, the IL-18 expression was not different in the lamina propria compared with controls but was decreased in the epithelium. In contrast, the IL-18BP was decreased in the lamina propria in asthma and was absent in the bronchial epithelium. IL-18 was released in sputum with IL-18BP elevated in patients with asthma. The IL-18Rα expression was not different between health and disease. In vitro, IL-18-stimulated bronchial epithelial cells increased intracellular calcium, wound repair, metabolic activity, morphological changes and epithelial cellular differentiation.
UNASSIGNED: In asthma, the dynamic interaction between IL-18, its cognate receptor and natural inhibitor is complex, with differences between airway compartments. Upregulation of IL-18 can promote epithelial activation and cellular differentiation.

Interleukin 18 (IL-18) is a pleiotropic pro-inflammatory cytokine and is associated with arrested follicle development and anovulation which are the typical pathological changes of PCOS. Theca cells (TCs) have a key role in follicular growth and atresia. But whether IL-18 can directly affect ovarian TCs function is unknown. Therefore, the objective of this study was to determine the effect of IL-18 on proliferation and steroidogenesis of bovine TCs and to explore the biological effect of IL-18 on folliculogenesis. This work revealed that at 300-1000 pg/mL, IL-18 led to a time- and dose-dependently increase in cell proliferation (P < .05). IL-18 increased 17-hydroxyprogesterone (17OHP4) and androstenedione (A2) secretion with up-regulation of key steroidogenesis-related genes CYP11A1 and CYP17A1 (P < .05). Furthermore, our data demonstrated that the IL-18R protein is predominantly expressed in small-follicle (3-6 mm) TCs than large follicles (8-22 mm) by immunohistochemistry. We also found that the stimulation effects of IL-18 on TCs can be reversed with the addition of IL-18BP as early as at 4 hours of culture and reached the peak at 16 hours. We conclude that IL-18 appears to target TCs in bovine, and suggest an important role for this cytokine in ovarian function. Present findings further validate potential effects of IL-18 in the conditions associated with follicular dysplasia and excessive growth of ovarian TCs (such as PCOS). But additional research is needed to further understand the mechanism of action of IL-18 in theca cells as well as its precise role in folliculogenesis.

Interleukin-18 (IL-18) has been demonstrated to augment the antitumor capacity of chimeric antigen receptor-T cells (CAR-T) but the underlying mechanisms are largely unknown. Here we explored the effects and mechanisms of exogenous IL-18 on the antitumor response of CAR-T cells. IL-18 boosted the cytotoxicity of human epidermal growth factor receptor-2 (HER2)-specific CAR-T cells ex vivo and enhanced the antitumor efficacy of the CAR-T cells in immunodeficient mice, moreover, IL-18 improved the antitumor capacity of OVA-specific T cells in immunocompetent mice, indicating the universal enhancing function of IL-18 for adoptive cell therapy. To address the roles of IL-18 receptor (IL-18R) in the enhancing function, we evaluated the effects of IL-18R knockout (IL-18R-/-) condition in immunocompetent host and CAR-T cells on the IL-18-enhanced antitumor activities. Interestingly, IL-18 persisted to improve the antitumor ability of IL-18R intact CAR-T cells in IL-18R-/- mice. For IL-18R-/- CAR-T cells, however, IL-18 still holds the enhancing ability to boost the antitumor efficacy in IL-18R-/- mice, albeit the ex vivo tumor-killing ability was lower than that of IL-18R intact CAR-T cells, indicating that IL-18R-independent pathway is involved in the enhancement. Furthermore, tagged IL-18 binded to the membrane of IL-18R-/- splenic and lymph node cells and IL-18R intact and IL-18R-/- CAR-T cells showed distinct transcriptomic profiles when stimulated by IL-18. These data demonstrate that IL-18R-independent pathways contribute to functions of IL-18.

The NLRP3 inflammasome is formed by the sensor NLRP3, the adaptor ASC, and pro-caspase-1. Assembly and activation of the inflammasome trigger caspase-1-dependent cleavage of pro-IL-1β and pro-IL-18 into their secreted forms. Cigarette smoke is a risk factor for chronic inflammatory diseases and is associated with macrophage dysfunction. The impact of cigarette smoke on NLRP3-dependent responses in macrophages is largely unknown. Herein, we investigated the effects of cigarette smoke extract (CSE) on the NLRP3 inflammasome in human monocyte-derived macrophages (MDMs) and THP-1 cells stimulated with lipopolysaccharide (LPS) and LPS plus the NLRP3 inflammasome activator ATP. We found that CSE inhibited the release of IL-1β and IL-18 as well as the expression of NLRP3 acting mainly at the transcriptional level. Interestingly, we found that CSE increased the caspase-1 activity via an NLRP3-independent and TLR4-TRIF-caspase-8-dependent pathway. Activation of caspase-1 by CSE led to a reduction of the basal glycolytic flux and impaired glycolytic burst in response to LPS. Overall, our findings unveil novel pathways leading to immune-metabolic alterations in human macrophages exposed to cigarette smoke. These mechanisms may contribute to macrophage dysfunction and increased risk of infection in smokers.

UNASSIGNED: Systemic sclerosis (SSc) is an autoimmune disease characterised by fibrosis, vascular dysfunction and immune dysregulation. The pathogenesis of SSc remains poorly understood, although studies have indicated a role for the innate immune response.
UNASSIGNED: Here, we measured serum interleukin (IL)-1α, IL-1β and IL-18 levels in 105 SSc patients and 47 healthy controls (HC) and analysed them with respect to multiple clinical parameters.
UNASSIGNED: Serum IL-18 concentrations were significantly higher in SSc patients than in HC, while no significant differences in concentrations of IL-1α and IL-1β were observed between SSc and HC. In both SSc and HC serum, IL-1α and IL-1β were positively correlated, while in SSc, both cytokines negatively correlated with IL-18. Serum IL-18 was significantly negatively correlated with both carbon monoxide transfer coefficient (KCO) and diffusing capacity of the lungs for carbon monoxide (DLCO). Serum IL-1β was positively correlated with the modified Rodnan skin score (mRSS), particularly in patients with limited subtype. DLCO, KCO and tricuspid regurgitation (TR) velocity were significantly higher in patients with high serum IL-1β. Serum IL-1α was significantly lower in SSc patients with low KCO and positively correlated with KCO. SSc patients with high serum IL-1α concentrations were more likely to have digital ulcers.
UNASSIGNED: Our data suggest that these IL-1 family cytokines may have different roles in the pathogenesis of SSc fibrotic complications.

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck malignancies. Advanced stages of the disease are associated with poor survival, highlighting a need for new treatment modalities. We previously showed that the proinflammatory cytokine interleukin-18 (IL-18) has a tumor suppressive role in OSCC. Here, we investigated the effects of IL-18 on proliferation, migration, and invasion of OSCC cells ex vivo and in vitro, and in nude mouse xenografts. We report that expression of tankyrase 2 (TNKS2), β-catenin, and N-cadherin was higher in tumor cells than in normal mucosae, whereas the expression of IL-18 and E-cadherin was higher in normal than in tumor tissues. Elevated expression of IL-18 (P < 0.01) and E-cadherin (P = 0.034) was associated with tumor differentiation, whereas expression of TNKS2 (P < 0.01), β-catenin (P = 0.012), and N-cadherin (P < 0.01) was associated with tumor de-differentiation. Furthermore, compared with the vector control, IL-18 overexpression promoted tumor cell migration and invasion (P < 0.01), but inhibited growth of tumor cell xenografts (P < 0.05). At the protein level, expression levels of IL-18 (P < 0.01), TNKS2 (P = 0.045), β-catenin (P = 0.028), and N-cadherin (P = 0.068) were upregulated in tumor cells after IL-18 overexpression compared with those of the vector control mice, whereas expression levels of E-cadherin (P = 0.045) were decreased. In conclusion, our data suggest that IL-18 overexpression induces oral SCC cell invasion and metastasis by promoting the tumor cell epithelial-mesenchymal transition via the Wnt/β-catenin signaling pathway.

UNASSIGNED: Overactivated neutrophils are causes of acute lung injury, which is a major clinical problem with significant morbidity and mortality in sepsis. Serum interleukin (IL)-18 levels correspond to severity of systemic inflammation.
UNASSIGNED: To elucidate the roles of endogenous IL-18 in lung injury during endotoxin-induced systemic inflammation.
UNASSIGNED: Wild-type (WT) and IL-18 gene knockout (KO) mice were injected with lipopolysaccharide (40 mg/kg) intraperitoneally and killed. Lungs were collected at 0 and 12 h to assess mRNA for intercellular adhesion molecule (ICAM)-1, inducible nitric oxide synthase, myeloperoxidase, immunohistochemistry (cleaved caspase-3, 8-hydroxy-2-deoxyguanosine), and wet/dry ratio. Blood was collected at 0, 1, 12, 18, and 24 h to assess plasma cytokine levels.
UNASSIGNED: The survival rates at 24 h were approximately 43% and 76% in the WT and KO mice, respectively. Plasma IL-18 levels were induced time-dependently only in the WT mice. Plasma interferon-γ levels were significantly higher in the WT than in the KO mice at 12 h, but IL-6 and tumor necrosis factor-α levels did not differ between the WT and KO mice. At 12 h, the WT mice showed higher myeloperoxidase activity (P < 0.05), ICAM-1, and wet/dry ratios than KO mice. Cleaved caspase-3 positive neutrophils, which migrated in the lung interstitium, were lower in WT mice than in KO mice.
UNASSIGNED: Endogenous IL-18 induced neutrophil accumulation, accompanied by induction of ICAM-1 expression, inhibition of neutrophil apoptosis, and increased inducible nitric oxide synthase-induced oxidative tissue injury in the lung, leading to lung edema and poor outcome during endotoxemia.