New Genetically Manipulated Mice Provide Insights Into the Development and Physiological Functions of Invariant Natural Killer T Cells

Protective effects of Ganoderma lucidum spores on estradiol benzoate-induced TEC apoptosis and compromised double-positive thymocyte development

Backgroud: Thymic atrophy marks the onset of immune aging, precipitating developmental anomalies in T cells. Numerous clinical and preclinical investigations have underscored the regulatory role of Ganoderma lucidum spores (GLS) in T cell development. However, the precise mechanisms underlying this regulation remain elusive. Methods: In this study, a mice model of estradiol benzoate (EB)-induced thymic atrophy was constructed, and the improvement effect of GLS on thymic atrophy was evaluated. Then, we employs multi-omics techniques to elucidate how GLS modulates T cell development amidst EB-induced thymic atrophy in mice. Results: GLS effectively mitigates EB-induced thymic damage by attenuating apoptotic thymic epithelial cells (TECs) and enhancing the output of CD4+ T cells into peripheral blood. During thymic T cell development, sporoderm-removed GLS (RGLS) promotes T cell receptor (TCR) α rearrangement by augmenting V-J fragment rearrangement frequency and efficiency. Notably, biased Vα14-Jα18 rearrangement fosters double-positive (DP) to invariant natural killer T (iNKT) cell differentiation, partially contingent on RGLS-mediated restriction of peptide-major histocompatibility complex I (pMHCⅠ)-CD8 interaction and augmented CD1d expression in DP thymocytes, thereby promoting DP to CD4+ iNKT cell development. Furthermore, RGLS amplifies interaction between a DP subpopulation, termed DPsel-7, and plasmacytoid dendritic cells (pDCs), likely facilitating the subsequent development of double-negative iNKT1 cells. Lastly, RGLS suppresses EB-induced upregulation of Abpob and Apoa4, curbing the clearance of CD4+Abpob+ and CD4+Apoa4+ T cells by mTECs, resulting in enhanced CD4+ T cell output. Discussion: These findings indicate that the RGLS effectively mitigates EB-induced TEC apoptosis and compromised double-positive thymocyte development. These insights into RGLS's immunoregulatory role pave the way for its potential as a T-cell regeneration inducer.

Natural Killer T cells and the invariant subset promote atherosclerosis: A meta-analysis

AIMS

Natural Killer T (NKT) cells are reported to be both pro- and anti-atherosclerotic. With this meta-analysis, we evaluated the NKT population and their subsets in regulating the atherosclerotic disease in mice.

MAIN METHODS

Eighteen pre-clinical (mice, n = 1276) and 6 clinical observational studies (humans, n = 116) met the eligibility criteria for inclusion. Random effects model was used and standard mean difference (SMD) was calculated for the cell counts and aortic lesion area.

KEY FINDINGS

Lesion area decreased in the absence of whole NKT cell population (-1.33[95%CI, -2.14, -0.52]), and in the absence of only iNKT subset (-0.66[95%CI, -1.69, 0.37]). However, lesion area increased after over-expression/activation of iNKTs (1.40[95%CI, 0.28, 2.52]). Atherogenic diet (AD) or high fat diet (HFD) increased the number of NKT cells (2.51[95%CI, 1.42, 3.61]), whereas the iNKT cell numbers and iNKT cell-specific gene expression decreased in mice (-2.04[95%CI, -3.34, -0.75]) and atherosclerotic patients (-1.81[95 % CI, -2.89, -0.74]).

SIGNIFICANCE

Here we show that, NKT and iNKT cells promote atherosclerosis. In general, NKT cell population increases with the progression of the plaque in mice and the numbers of iNKT cells reduce once the disease is established both in mice and humans.

Adipocyte CD1d Gene Transfer Induces T Cell Expansion and Adipocyte Inflammation in CD1d Knockout Mice

CD1d, a lipid Ag-presenting molecule for invariant NKT (iNKT) cells, is abundantly expressed on adipocytes and regulates adipose homeostasis through iNKT cells. CD1d gene expression was restored in visceral adipose tissue adipocytes of CD1d knockout (KO) mice to investigate the interactions between adipocytes and immune cells within adipose tissue. We developed an adipocyte-specific targeting recombinant adeno-associated viral vector, with minimal off-target transgene expression in the liver, to rescue CD1d gene expression in visceral adipose tissue adipocytes of CD1d KO mice, followed by assessment of immune cell alternations in adipose tissue and elucidation of the underlying mechanisms of alteration. We report that adeno-associated virus-mediated gene transfer of CD1d to adipocytes in CD1d KO mice fails to rescue iNKT cells but leads to massive and selective expansion of T cells within adipose tissue, particularly CD8+ T effector cells, that is associated with adipocyte NLRP3 inflammasome activation, dysregulation of adipocyte functional genes, and upregulation of apoptotic pathway proteins. An NLRP3 inhibitor has no effect on T cell phenotypes whereas depletion of CD8+ T cells significantly attenuates inflammasome activation and abolishes the dysregulation of adipocyte functional genes induced by adipocyte CD1d. In contrast, adipocyte overexpression of CD1d fails to induce T cell activation in wild-type mice or in invariant TCR α-chain Jα18 KO mice that have a normal lymphocyte repertoire except for iNKT cells. Our studies uncover an adipocyte CD1d → CD8+ T cell → adipocyte inflammasome cascade, in which CD8+ T cells function as a key mediator of adipocyte inflammation likely induced by an allogeneic response against the CD1d molecule.

Structure Elucidation of Calyxoside B, a Bipolar Sphingolipid from a Marine Sponge Cladocroce sp. through the Use of Beckmann Rearrangement

Marine sponges are an excellent source of biologically active secondary metabolites. We focus on deep-sea sponges for our discovery study. A marine sponge Cladocroce sp. exhibited cytotoxic activity in the bioactivity screening. From this sponge a previously unreported cytotoxic glycosphingolipid, calyxoside B, was isolated and the structure of this compound was elucidated by analyses of MS and NMR spectra and chemical derivatization. We converted the ketone in the middle of a long aliphatic chain into an oxime to which was applied Beckmann rearrangement to afford two positional isomers of amides. The products were subjected to acidic hydrolysis followed by LC-MS analysis, permitting us to assign unequivocally the position of the ketone. Calyxoside B shows cytotoxicity against HeLa cells with an IC50 value of 31 µM and also weakly stimulated the production of cytokines in mice.

T Cells in Adipose Tissue in Aging

Similar to obesity, aging is associated with visceral adiposity and insulin resistance. Inflammation in adipose tissue, mainly evidenced by increased accumulation and proinflammatory polarization of T cells and macrophages, has been well-documented in obesity and may contribute to the associated metabolic dysfunctions including insulin resistance. Studies show that increased inflammation, including inflammation in adipose tissue, also occurs in aging, so-called "inflamm-aging." Aging-associated inflammation in adipose tissue has some similarities but also differences compared to obesity-related inflammation. In particular, conventional T cells are elevated in adipose tissue in both obesity and aging and have been implicated in metabolic functions in obesity. However, the changes and also possibly functions of regulatory T cells (Treg) in adipose tissue are different in aging and obesity. In this review, we will summarize recent advances in research on the changes of these immune cells in adipose tissue with aging and obesity and discuss their possible contributions to metabolism and the potential of these immune cells as novel therapeutic targets for prevention and treatment of metabolic diseases associated with aging or obesity.

α-galactosylceramide generates lung regulatory T cells through the activated natural killer T cells in mice

Our previous study showed that intraperitoneal injection of α-galactosylceramide (α-GalCer) has the ability to activate lung iNKT cells, but α-GalCer-activated iNKT cells do not result in airway inflammation in wild-type (WT) mice. Many studies showed that iNKT cells had the capacity to induce Treg cells, which gave rise to peripheral tolerance. Therefore, we examined the influence of intraperitoneal administration of α-GalCer on the expansion and suppressive activity of lung Treg cells using iNKT cell-knockout mice and co-culture experiments in vitro. We also compared airway inflammation and airway hyperresponsiveness (AHR) after α-GalCer administration in specific anti-CD25 mAb-treated mice. Our data showed that intraperitoneal injection of α-GalCer could promote the expansion of lung Treg cells in WT mice, but not in iNKT cell-knockout mice. However, α-GalCer administration could not boost suppressive activity of Treg cells in WT mice and iNKT cell-knockout mice. Interestingly, functional inactivation of Treg cells could induce airway inflammation and AHR in WT mice treated with α-GalCer. Furthermore, α-GalCer administration could enhance iNKT cells to secrete IL-2, and neutralization of IL-2 reduced the expansion of Treg cells in vivo and in vitro. Thus, intraperitoneal administration of α-GalCer can induce the generation of lung Treg cells in mice through the release of IL-2 by the activated iNKT cells.