Repeated administration of alpha-galactosylceramide ameliorates experimental lupus nephritis in mice

The iNKT cell ligand α-GalCer prevents murine septic shock by inducing IL10-producing iNKT and B cells

Introduction

α-galactosylceramide (α-GalCer), a prototypical agonist of invariant natural killer T (iNKT) cells, stimulates iNKT cells to produce various cytokines such as IFNγ and IL4. Moreover, repeated α-GalCer treatment can cause protective or pathogenic outcomes in various immune-mediated diseases. However, the precise role of α-GalCer-activated iNKT cells in sepsis development remains unclear. To address this issue, we employed a lipopolysaccharide (LPS)/D-galactosamine (D-GalN)-induced murine sepsis model and two alternative models.

Methods

Sepsis was induced in wild-type (WT) C57BL/6 (B6) mice by three methods (LPS/D-GalN, α-GalCer/D-GalN, and cecal slurry), and these mice were monitored for survival rates. WT B6 mice were intraperitoneally injected with α-GalCer or OCH (an IL4-biased α-GalCer analog) one week prior to the induction of sepsis. To investigate the effects of α-GalCer-mediated iNKT cell activation on sepsis development, immune responses were analyzed by flow cytometry using splenocytes and liver-infiltrating leukocytes. In addition, a STAT6 inhibitor (AS1517499) and an IL10 inhibitor (AS101) were employed to evaluate the involvement of IL4 or IL10 signaling. Furthermore, we performed B cell adoptive transfers to examine the contribution of α-GalCer-induced regulatory B (Breg) cell populations in sepsis protection.

Results

In vivo α-GalCer pretreatment polarized iNKT cells towards IL4- and IL10-producing phenotypes, significantly attenuating LPS/D-GalN-induced septic lethality in WT B6 mice. Furthermore, α-GalCer pretreatment reduced the infiltration of immune cells to the liver and attenuated pro-inflammatory cytokine production. Treatment with a STAT6 inhibitor was unable to modulate disease progression, indicating that IL4 signaling did not significantly affect iNKT cell-mediated protection against sepsis. This finding was confirmed by pretreatment with OCH, which did not alter sepsis outcomes. However, interestingly, prophylactic effects of α-GalCer on sepsis were significantly suppressed by treatment with an IL10 antagonist, suggesting induction of IL10-dependent anti-inflammatory responses. In addition to IL10-producing iNKT cells, IL10-producing B cell populations were significantly increased after α-GalCer pretreatment.

Conclusion

Overall, our results identify α-GalCer-mediated induction of IL10 by iNKT and B cells as a promising option for controlling the pathogenesis of postoperative sepsis.

Alpha-galactosylceramide pre-treatment attenuates clinical symptoms of LPS-induced acute neuroinflammation by converting pathogenic iNKT cells to anti-inflammatory iNKT10 cells in the brain

BACKGROUND

Invariant natural killer T (iNKT) cells play protective or pathogenic roles in a variety of immune and inflammatory diseases. However, whether iNKT cells contribute to the progression of acute neuroinflammation remains unclear. Thus, we addressed this question with a mouse model of lipopolysaccharide (LPS)-induced acute neuroinflammation.

METHODS

For induction of acute neuroinflammation, wild-type (WT) C57BL/6 (B6) mice were injected intraperitoneally (i.p.) with LPS for either three or five consecutive days, and then these mice were analyzed for brain-infiltrating leukocytes or mouse behaviors, respectively. To examine the role of iNKT cell activation in LPS-induced neuroinflammation, mice were injected i.p. with the iNKT cell agonist α-galactosylceramide (α-GalCer) seven days prior to LPS treatment. Immune cells infiltrated into the brain during LPS-induced neuroinflammation were determined by flow cytometry. In addition, LPS-induced clinical behavior symptoms such as depressive-like behavior and memory impairment in mice were evaluated by the open field and Y-maze tests, respectively.

RESULTS

We found that iNKT cell-deficient Jα18 mutant mice display delayed disease progression and decreased leukocyte infiltration into the brain compared with WT mice, indicating that iNKT cells contribute to the pathogenesis of LPS-induced neuroinflammation. Since it has been reported that pre-treatment with α-GalCer, an iNKT cell agonist, can convert iNKT cells towards anti-inflammatory phenotypes, we next explored whether pre-activation of iNKT cells with α-GalCer can regulate LPS-induced neuroinflammation. Strikingly, we found that α-GalCer pre-treatment significantly delays the onset of clinical symptoms, including depression-like behavior and memory impairment, while decreasing brain infiltration of pro-inflammatory natural killer cells and neutrophils, in this model of LPS-induced neuroinflammation. Such anti-inflammatory effects of α-GalCer pre-treatment closely correlated with iNKT cell polarization towards IL4- and IL10-producing phenotypes. Furthermore, α-GalCer pre-treatment restored the expression of suppressive markers on brain regulatory T cells during LPS-induced neuroinflammation.

CONCLUSION

Our findings provide strong evidence that α-GalCer-induced pre-activation of iNKT cells expands iNKT10 cells, mitigating depressive-like behaviors and brain infiltration of inflammatory immune cells induced by LPS-induced acute neuroinflammation. Thus, we suggest the prophylactic potential of iNKT cells and α-GalCer against acute neuroinflammation.

Metabolic signatures of immune cells in chronic kidney disease

Immune cells play a key role in maintaining renal dynamic balance and dealing with renal injury. The physiological and pathological functions of immune cells are intricately connected to their metabolic characteristics. However, immunometabolism in chronic kidney disease (CKD) is not fully understood. Pathophysiologically, disruption of kidney immune cells homeostasis causes inflammation and tissue damage via triggering metabolic reprogramming. The diverse metabolic characteristics of immune cells at different stages of CKD are strongly associated with their different pathological effect. In this work, we reviewed the metabolic characteristics of immune cells (macrophages, natural killer cells, T cells, natural killer T cells and B cells) and several non-immune cells, as well as potential treatments targeting immunometabolism in CKD. We attempt to elaborate on the metabolic signatures of immune cells and their intimate correlation with non-immune cells in CKD.

Roles and therapeutic potential of CD1d-Restricted NKT cells in inflammatory skin diseases

Natural killer T (NKT) cells are innate-like T lymphocytes that recognize glycolipid antigens rather than peptides. Due to their immunoregulatory properties, extensive work has been done to elucidate the immune functions of NKT cells in various immune contexts such as autoimmunity for more than two decades. In addition, as research on barrier immunity such as the mucosa-associated lymphoid tissue has flourished in recent years, the role of NKT cells to immunity in the skin has attracted substantial attention. Here, we review the contributions of NKT cells to regulating skin inflammation and discuss the factors that can modulate the functions of NKT cells in inflammatory skin diseases such as atopic dermatitis. This mini-review article will mainly focus on CD1d-dependent NKT cells and their therapeutic potential in skin-related immune diseases.

Tumor-Localized Administration of α-GalCer to Recruit Invariant Natural Killer T Cells and Enhance Their Antitumor Activity against Solid Tumors

Invariant natural killer T (iNKT) cells have the capacity to mount potent anti-tumor reactivity and have therefore become a focus in the development of cell-based immunotherapy. iNKT cells attack tumor cells using multiple mechanisms with a high efficacy; however, their clinical application has been limited because of their low numbers in cancer patients and difficulties in infiltrating solid tumors. In this study, we aimed to overcome these critical limitations by using α-GalCer, a synthetic glycolipid ligand specifically activating iNKT cells, to recruit iNKT to solid tumors. By adoptively transferring human iNKT cells into tumor-bearing humanized NSG mice and administering a single dose of tumor-localized α-GalCer, we demonstrated the rapid recruitment of human iNKT cells into solid tumors in as little as one day and a significantly enhanced tumor killing ability. Using firefly luciferase-labeled iNKT cells, we monitored the tissue biodistribution and pharmacokinetics/pharmacodynamics (PK/PD) of human iNKT cells in tumor-bearing NSG mice. Collectively, these preclinical studies demonstrate the promise of an αGC-driven iNKT cell-based immunotherapy to target solid tumors with higher efficacy and precision.

Infections, Reactions of Natural Killer T Cells and Natural Killer Cells, and Kidney Injury

Natural killer T (NKT) cells and NK cells are representative innate immune cells that perform antitumor and antimicrobial functions. The involvement of these cells in various renal diseases, including acute kidney injury (AKI), has recently become evident. Murine NKT cells are activated and cause AKI in response to various stimuli, such as their specific ligand, cytokines, and bacterial components. Both renal vascular endothelial cell injury (via the perforin-mediated pathway) and tubular epithelial cell injury (via the tumor necrosis factor-alpha/Fas ligand pathway) are independently involved in the pathogenesis of AKI. NK cells complement the functions of NKT cells, thereby contributing to the development of infection-associated AKI. Human CD56⁺ T cells, which are a functional counterpart of murine NKT cells, as well as a subpopulation of CD56⁺ NK cells, strongly damage intrinsic renal cells in vitro upon their activation, possibly through mechanisms similar to those in mice. These cells are also thought to be involved in the acute exacerbation of pre-existing glomerulonephritis triggered by infection in humans, and their roles in sepsis-associated AKI are currently under investigation. In this review, we will provide an overview of the recent advances in the understanding of the association among infections, NKT and NK cells, and kidney injury, which is much more profound than previously considered. The important role of liver macrophages in the activation of NKT cells will also be introduced.

Vaccine Based on Dendritic Cells Electroporated with an Exogenous Ovalbumin Protein and Pulsed with Invariant Natural Killer T Cell Ligands Effectively Induces Antigen-Specific Antitumor Immunity

Simple Summary

This study shows the potential of a novel dendritic cell vaccine therapy in antitumor immunity, in which bone marrow-derived dendritic cells are electroporated with an exogenous ovalbumin protein and simultaneously pulsed with α-galactosylceramide. This strategy enhances the induction of cytotoxic CD8⁺ T cells specific for tumor-associated antigens through the activation of invariant natural killer T cells, natural killer cells, and intrinsic dendritic cells. Moreover, this strategy sustains antigen-specific antitumor T cell responses over time.

Abstract

(1) Background: Cancer vaccines are administered to induce cytotoxic CD8⁺ T cells (CTLs) specific for tumor antigens. Invariant natural killer T (iNKT) cells, the specific T cells activated by α-galactosylceramide (α-GalCer), play important roles in this process as they are involved in both innate and adaptive immunity. We developed a new cancer vaccine strategy in which dendritic cells (DCs) were loaded with an exogenous ovalbumin (OVA) protein by electroporation (EP) and pulsed with α-GalCer. (2) Methods: We generated bone marrow-derived DCs from C57BL/6 mice, loaded full-length ovalbumin proteins to the DCs by EP, and pulsed them with α-GalCer (OVA-EP-galDCs). The OVA-EP-galDCs were intravenously administered to C57BL/6 mice as a vaccine. We then investigated subsequent immune responses, such as the induction of iNKT cells, NK cells, intrinsic DCs, and OVA-specific CD8⁺ T cells, including tissue-resident memory T (T_RM) cells. (3) Results: The OVA-EP-galDC vaccine efficiently rejected subcutaneous tumors in a manner primarily dependent on CD8⁺ T cells. In addition to the OVA-specific CD8⁺ T cells both in early and late phases, we observed the induction of antigen-specific T_RM cells in the skin. (4) Conclusions: The OVA-EP-galDC vaccine efficiently induced antigen-specific antitumor immunity, which was sustained over time, as shown by the T_RM cells.

Effects of a CCR2 antagonist on macrophages and Toll-like receptor 9 expression in a mouse model of diabetic nephropathy

The pathogenesis of diabetic nephropathy (DN) is related to macrophage (Mφ) recruitment to the kidneys, tumor necrosis factor-α (TNF-α) production, and oxidative stress. Toll-like receptor 9 (TLR9) activation is reportedly involved in systemic inflammation, and it exacerbates this condition in metabolic syndrome. Therefore, we hypothesized that TLR9 plays a role in the pathogenesis of DN. Two subsets of kidney Mφs in DN model (db/db) mice were analyzed using flow cytometry to evaluate their distribution and TLR9 expression and function. Mice were administered the CCR2 antagonist INCB3344 for 8 wk; changes in Mφ distribution and function and its therapeutic effects on DN pathology were examined. Bone marrow-derived CD11bhigh (BM-Mφ) and tissue-resident CD11blow Mφs (Res-Mφ) were identified in the mouse kidneys. As DN progressed, the BM-Mφ number, TLR9 expression, and TNF-α production increased significantly. In Res-Mφs, reactive oxygen species (ROS) production and phagocytic activity were enhanced. INCB3344 decreased albuminuria, serum creatinine level, BM-Mφ abundance, TLR9 expression, and TNF-α production by BM-Mφs and ROS production by Res-Mφs. Both increased activation of BM-Mφ via TLR9 and TNF-α production and increased ROS production by Res-Mφs were involved in DN progression. Thus, inactivating Mφs and their TLR9 expression by INCB3344 is a potential therapeutic strategy for DN.NEW & NOTEWORTHY We classified kidney macrophages (Mφs) into bone marrow-derived Mφs (BM-Mφs) expressing high CD11b and tissue-specific resident Mφ (Res-Mφs) expressing low CD11b. In diabetic nephropathy (DN) model mice, Toll-like receptor 9 (TLR9) expression and TNF-α production via TLR9 activation in BM-Mφs and ROS production in Res-Mφs were enhanced. Furthermore, CCR2 antagonist suppressed the kidney infiltration of BM-Mφs and their function and the ROS production by Res-Mφs, with concomitant TLR9 suppression. Our study presents a new therapeutic strategy for DN.

Unconventional T cells and kidney disease

Unconventional T cells are a diverse and underappreciated group of relatively rare lymphocytes that are distinct from conventional CD4⁺ and CD8⁺ T cells, and that mainly recognize antigens in the absence of classical restriction through the major histocompatibility complex (MHC). These non-MHC-restricted T cells include mucosal-associated invariant T (MAIT) cells, natural killer T (NKT) cells, γδ T cells and other, often poorly defined, subsets. Depending on the physiological context, unconventional T cells may assume either protective or pathogenic roles in a range of inflammatory and autoimmune responses in the kidney. Accordingly, experimental models and clinical studies have revealed that certain unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic biomarkers. The responsiveness of human Vγ9Vδ2 T cells and MAIT cells to many microbial pathogens, for example, has implications for early diagnosis, risk stratification and targeted treatment of peritoneal dialysis-related peritonitis. The expansion of non-Vγ9Vδ2 γδ T cells during cytomegalovirus infection and their contribution to viral clearance suggest that these cells can be harnessed for immune monitoring and adoptive immunotherapy in kidney transplant recipients. In addition, populations of NKT, MAIT or γδ T cells are involved in the immunopathology of IgA nephropathy and in models of glomerulonephritis, ischaemia-reperfusion injury and kidney transplantation.

Repeated α-GalCer Administration Induces a Type 2 Cytokine-Biased iNKT Cell Response and Exacerbates Atopic Skin Inflammation in Vα14Tg NC/Nga Mice

We have previously shown that Vα14 TCR Tg (Vα14^Tg) NC/Nga (NC) mice contain increased numbers of double-negative (DN) invariant natural killer T (iNKT) cells that protect against spontaneous development of atopic dermatitis (AD). iNKT cells can regulate immune responses by producing various cytokines such as IFNγ and IL4 rapidly upon stimulation with α-galactosylceramide (α-GalCer), a prototypical iNKT cell agonist. However, the precise role of α-GalCer-activated iNKT cells in AD development remains unclear. Therefore, we examined whether repeated activation of iNKT cells with α-GalCer can regulate the pathogenesis of AD in Vα14^Tg NC mice. We found that Vα14^Tg NC mice injected repeatedly with α-GalCer display exacerbated AD symptoms (e.g., a higher clinical score, IgE hyperproduction, and increased numbers of splenic mast cells and neutrophils) compared with vehicle-injected Vα14^Tg NC mice. Moreover, the severity of AD pathogenesis in α-GalCer-injected Vα14^Tg NC mice correlated with increased Th2 cells but reduced Th1 and Foxp3⁺ Treg cells. Furthermore, the resulting alterations in the Th1/Th2 and Treg/Th2 balance were strongly associated with a biased expansion of type 2 cytokine-deviated iNKT cells in α-GalCer-treated Vα14^Tg NC mice. Collectively, our results have demonstrated the adverse effect of repeated α-GalCer treatment on skin inflammation mediated by type 2 immunity.

The Current Landscape of NKT Cell Immunotherapy and the Hills Ahead

Simple Summary

Natural killer T (NKT) cells are a subset of lipid-reactive T cells that enhance anti-tumor immunity. While preclinical studies have shown NKT cell immunotherapy to be safe and effective, clinical studies lack predictable therapeutic efficacy and no approved treatments exist. In this review, we outline the current strategies, challenges, and outlook for NKT cell immunotherapy.

Abstract

NKT cells are a specialized subset of lipid-reactive T lymphocytes that play direct and indirect roles in immunosurveillance and anti-tumor immunity. Preclinical studies have shown that NKT cell activation via delivery of exogenous glycolipids elicits a significant anti-tumor immune response. Furthermore, infiltration of NKT cells is associated with a good prognosis in several cancers. In this review, we aim to summarize the role of NKT cells in cancer as well as the current strategies and status of NKT cell immunotherapy. This review also examines challenges and future directions for improving the therapy.

Donor Treg expansion by liposomal α-galactosylceramide modulates Tfh cells and prevents sclerodermatous chronic graft-versus-host disease

Background and Aim

Chronic graft‐versus‐host disease (cGVHD) is a major cause of nonrelapse morbidity and mortality following hematopoietic stem cell transplantation (HSCT). α‐Galactosylceramide (α‐GC) is a synthetic glycolipid that is recognized by the invariant T‐cell receptor of invariant natural killer T (iNKT) cells in a CD1d‐restricted manner. Stimulation of iNKT cells by α‐GC leads to the production of not only immune‐stimulatory cytokines but also immune‐regulatory cytokines followed by regulatory T‐cell (Treg) expansion in vivo.

Methods

We investigated the effect of iNKT stimulation by liposomal α‐GC just after transplant on the subsequent immune reconstitution and the development of sclerodermatous cGVHD.

Results

Our study showed that multiple administrations of liposomal α‐GC modulated both host‐ and donor‐derived iNKT cell homeostasis and induced an early expansion of donor Tregs. We also demonstrated that the immune modulation of the acute phase was followed by the decreased levels of CXCL13 in plasma and follicular helper T cells in lymph nodes, which inhibited germinal center formation, resulting in the efficient prevention of sclerodermatous cGVHD.

Conclusions

These data demonstrated an important coordination of T‐ and B‐cell immunity in the pathogenesis of cGVHD and may provide a novel clinical strategy for the induction of immune tolerance after allogeneic HSCT.

The protective function of invariant natural killer T cells in the relapse of experimental autoimmune uveoretinitis

Experimental autoimmune uveoretinitis (EAU) in mice provides a useful platform to study the pathogenesis and experimental therapeutics of human uveitis. One often used EAU model employs C57BL/6 (B6) mice sensitized with a peptide residue having 1 to 20 amino acids of human interphotoreceptor retinoid binding protein (hIRBP_1-20). The model using the B6 background has permitted a liberal use of genetically engineered strains and has provided insights for understanding uveoretinitis. However, this is usually acute/monophasic and does not represent human uveoretinitis that is characterized as a chronic/recurrent disease. Several chronic/recurrent EAU models have been developed; of these, we employed administration of staphylococcal enterotoxin B (SEB) for relapse in the present study, and found that recurrence was induced at day 24 after primary immunization, which is thought to be the convalescent phase. We reported the activation of invariant natural killer T (iNKT)-cells upon primary immunization of the EAU model mice with the ligand RCAI-56, which was found to mitigate the disease in our previous study. Here, we first attempted to ameliorate EAU in the relapse model using a preventive regimen by activating iNKT cells at the same time relapse induction (day 24) or in a regimen after 3 days of relapse induction (day 27). The preventive as well as post-inductive regimens were successful in reducing histopathological scores by inhibiting the Ag-specific Th17-biased response. Collectively, activation of iNKT cells may be useful to mitigate the relapse response of EAU induced with SEB.

Radiation-induced gastrointestinal syndrome is exacerbated in vitamin C-insufficient SMP30/GNL knockout mice

OBJECTIVES

Accidental exposure to high-dose radiation causes life-threatening acute radiation syndrome, features that include gastrointestinal syndrome (GIS) and hematopoietic syndrome (HS). Administration of vitamin C (VC), a free radical scavenger, has been reported to increase survival of mice in GIS and HS models. The effect of nutritional VC status on radiation injury remains unknown because, unlike humans, mice can synthesize VC. The aim of this study was to investigate the effect of VC insufficiency on acute radiation syndrome using senescence marker protein 30 (SMP30)/gluconolactonase knockout (SMP30-KO) mice.

METHODS

SMP30-KO mice, which cannot synthesize VC, were given water with or without sufficient VC supplementation, and were analyzed in GIS and HS models.

RESULTS

In the GIS model, in which bone marrow failure is rescued by bone marrow transplantation, VC-insufficient mice had a lower survival rate than VC-sufficient mice. The intestine of VC-insufficient GIS mice showed epithelial cell atrophy, inflammatory cell infiltration, and decreased crypt cell proliferation. We observed rapid VC oxidation after total body irradiation in the intestine of mice supplemented with VC-sufficient water. In the HS model, which was not combined with bone marrow transplantation, there was no difference in survival between VC-insufficient and -sufficient mice.

CONCLUSION

The results of this study demonstrated that nutritionally sufficient VC exerts a radioprotective effect against radiation-induced GIS.

Roles of Natural Killer T Cells and Natural Killer Cells in Kidney Injury

Mouse natural killer T (NKT) cells and natural killer (NK) cells are innate immune cells that are highly abundant in the liver. In addition to their already-known antitumor and antimicrobial functions, their pathophysiological roles in the kidney have recently become evident. Under normal circumstances, the proportion of activated NKT cells in the kidney increases with age. Administration of a synthetic sphingoglycolipid ligand (alpha-galactosylceramide) further activates NKT cells, resulting in injury to renal vascular endothelial cells via the perforin-mediated pathway and tubular epithelial cells via the TNF-α/Fas ligand pathway, causing acute kidney injury (AKI) with hematuria. Activation of NKT cells by common bacterial DNA (CpG-ODN) also causes AKI. In addition, NKT cells together with B cells play significant roles in experimental lupus nephritis in NZB/NZW F1 mice through their Th2 immune responses. Mouse NK cells are also assumed to be involved in various renal diseases, and there may be complementary roles shared between NKT and NK cells. Human CD56⁺ T cells, a functional counterpart of mouse NKT cells, also damage renal cells through a mechanism similar to that of mice. A subpopulation of human CD56⁺ NK cells also exert strong cytotoxicity against renal cells and contribute to the progression of renal fibrosis.