Association between polycyclic aromatic hydrocarbon exposure and cognitive performance in older adults: a cross-sectional study from NHANES 2011-2014.

Background: polycyclic aromatic hydrocarbons (PAHs) are classified as neurotoxins, but the relationship between exposure to PAHs and cognition in adults is unclear, and their non-linear and mixed exposure association hasn't been explored. Objective: to evaluate the non-linear and joint association between co-exposure to PAHs and multiple cognitive tests in U.S. older people. Methods: restricted cubic spline (RCS) and Bayesian kernel machine regression (BKMR) were conducted to evaluate the non-linear and mixed exposure association, based on the cross-sectional data from NHANES 2011-2014: 772 participants over 60 years old, 4 cognitive test scores, including the Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution test (DSST), and 5 urinary PAH metabolites. Results: a V-shaped nonlinear relationship was found between 3-hydroxyfluorene (3-FLUO), 2-hydroxyfluorene (2-FLUO), and DRT. Negative trends between mixed PAH exposure and IRT, DRT, and DSST scores were observed. 2-FLUO contributed the most to the negative association of multiple PAHs with IRT and DRT scores and 2-hydroxynaphthalene (2-NAP) played the most important role in the decreasing relationship between mixed PAH exposure and DSST scores. Conclusion: our study suggested that PAH exposure in the U.S. elderly might be related to their poor performances in IRT, DRT and DSST. Further prospective studies are needed to validate the association.

Hippo kinases Mst1 and Mst2 maintain NK cell homeostasis by orchestrating metabolic state and transcriptional activity.

Natural killer (NK) cells play a crucial role in immune response against viral infections and tumors. However, further investigation is needed to better understand the key molecules responsible for determining the fate and function of NK cells. In this study, we made an important discovery regarding the involvement of the Hippo kinases Mst1 and Mst2 as novel regulators in maintaining mouse NK cell homeostasis. The presence of high Mst1 and Mst2 (Mst1/2) activity in NK cells is essential for their proper development, survival and function in a canonical Hippo signaling independent mode. Mechanistically, Mst1/2 induce cellular quiescence by regulating the processes of proliferation and mitochondrial metabolism, thereby ensuring the development and survival of NK cells. Furthermore, Mst1/2 effectively sense IL-15 signaling and facilitate the activation of pSTAT3-TCF1, which contributes to NK cell homeostasis. Overall, our investigation highlights the crucial role of Mst1/2 as key regulators in metabolic reprogramming and transcriptional regulation for mouse NK cell survival and function, emphasizing the significance of cellular quiescence during NK cell development and functional maturation.

Lkb1 orchestrates γδ T-cell metabolic and functional fitness to control IL-17-mediated autoimmune hepatitis.

γδ T cells play a crucial role in immune surveillance and serve as a bridge between innate and adaptive immunity. However, the metabolic requirements and regulation of γδ T-cell development and function remain poorly understood. In this study, we investigated the role of liver kinase B1 (Lkb1), a serine/threonine kinase that links cellular metabolism with cell growth and proliferation, in γδ T-cell biology. Our findings demonstrate that Lkb1 is not only involved in regulating γδ T lineage commitment but also plays a critical role in γδ T-cell effector function. Specifically, T-cell-specific deletion of Lkb1 resulted in impaired thymocyte development and distinct alterations in γδ T-cell subsets in both the thymus and peripheral lymphoid tissues. Notably, loss of Lkb1 inhibited the commitment of Vγ1 and Vγ4 γδ T cells, promoted the maturation of IL-17-producing Vγ6 γδ T cells, and led to the occurrence of fatal autoimmune hepatitis (AIH). Notably, clearance of γδ T cells or blockade of IL-17 significantly attenuated AIH. Mechanistically, Lkb1 deficiency disrupted metabolic homeostasis and AMPK activity, accompanied by increased mTORC1 activation, thereby causing overactivation of γδ T cells and enhanced apoptosis. Interestingly, activation of AMPK or suppression of mTORC1 signaling effectively inhibited IL-17 levels and attenuated AIH in Lkb1-deficient mice. Our findings highlight the pivotal role of Lkb1 in maintaining the homeostasis of γδ T cells and preventing IL-17-mediated autoimmune diseases, providing new insights into the metabolic programs governing the subset determination and functional differentiation of thymic γδ T cells.

Transcription factor TOX maintains the expression of Mst1 in controlling the early mouse NK cell development.

Rationale: TOX is a DNA-binding factor required for the development of multiple immune cells and the formation of lymph nodes. However, the temporal regulation mode of TOX on NK cell development and function needs to be further explored. Methods: To investigate the role of TOX in NK cells at distinct developmental phases, we deleted TOX at the hematopoietic stem cell stage (Vav-Cre), NK cell precursor (CD122-Cre) stage and late NK cell developmental stage (Ncr1-Cre), respectively. Flow cytometry was used to detect the development and functional changes of NK cell when deletion of TOX. RNA-seq was used to assess the differences in transcriptional expression profile of WT and TOX-deficient NK cells. Published Chip-seq data was exploited to search for the proteins directly interact with TOX in NK cells. Results: The deficiency of TOX at the hematopoietic stem cell stage severely retarded NK cell development. To a less extent, TOX also played an essential role in the physiological process of NKp cells differentiation into mature NK cells. Furthermore, the deletion of TOX at NKp stage severely impaired the immune surveillance function of NK cells, accompanied by down-regulation of IFN-γ and CD107a expression. However, TOX is dispensable for mature NK cell development and function. Mechanistically, by combining RNA-seq data with published TOX ChIP-seq data, we found that the inactivation of TOX at NKp stage directly repressed the expression of Mst1, an important intermediate kinase in Hippo signaling pathway. Mst1 deficient at NKp stage gained the similar phenotype with Toxfl/flCD122Cre mice. Conclusion: In our study, we conclude that TOX coordinates the early mouse NK cell development at NKp stage by maintaining the expression of Mst1. Moreover, we clarify the different dependence of the transcription factor TOX in NK cells biology.

mTORC1 signaling pathway integrates estrogen and growth factor to coordinate vaginal epithelial cells proliferation and differentiation.

The mouse vaginal epithelium cyclically exhibits cell proliferation and differentiation in response to estrogen. Estrogen acts as an activator of mTOR signaling but its role in vaginal epithelial homeostasis is unknown. We analyzed reproductive tract-specific Rptor or Rictor conditional knockout mice to reveal the role of mTOR signaling in estrogen-dependent vaginal epithelial cell proliferation and differentiation. Loss of Rptor but not Rictor in the vagina resulted in an aberrant proliferation of epithelial cells and failure of keratinized differentiation. As gene expression analysis indicated, several estrogen-mediated genes, including Pgr and Ereg (EGF-like growth factor) were not induced by estrogen in Rptor cKO mouse vagina. Moreover, supplementation of EREG could activate the proliferation and survival of vaginal epithelial cells through YAP1 in the absence of Rptor. Thus, mTORC1 signaling integrates estrogen and growth factor signaling to mediate vaginal epithelial cell proliferation and differentiation, providing new insights into vaginal atrophy treatment for post-menopausal women.

PD-1 mediates decidual γδ T cells cytotoxicity during recurrent pregnancy loss.

PROBLEM: Recurrent pregnancy loss (RPL) is one of the big challenges of normal pregnancy. Immune dysregulation has been proposed for the key underline mechanisms of RPL. However, the essential roles of T cells, especially γδ T cells, have not been defined. METHOD OF STUDY: Decidua were obtained from normal pregnancy women or recurrent pregnancy loss patients and the surface molecules of γδ T cells in decidua were evaluated via flow cytometric analysis. The expression of PD-1 in clinical samples was analyzed by immunohistochemistry assay. The intracellular cytokines of decidual PD-1+ and PD-1- γδ T cells were evaluated by flow cytometric analysis. The cytotoxicity of PD-1- γδ T cells were confirmed via an in vitro co-culture experiment. The specific inhibitors for Erk, p38 and JNK against the MAPK pathway were added to the co-culture media to evaluate the functions of the Erk, p38 and JNK. RESULTS: We demonstrated that PD-1 was significantly decreased on decidual tissue γδ T cells of patients with RPL, resulting in the enhanced cytotoxicity of γδ T cells against trophoblasts. We further elucidated an Erk-dependent TNF-α production mediates the γδ T cell cytotoxicity against the trophoblast cells. Finally, the reduced expression of PD-L1 in the villi tissues of patients with RPL might be the cause of the reduction of PD-1 on the tissue γδ T cells. CONCLUSION: Our study uncovers an important role of PD-1 expression on decidual γδ T cells in maintaining the normal pregnancy, and may provide a new strategy for immune therapy against RPL.

The kinase PDK1 regulates regulatory T cell survival via controlling redox homeostasis.

Rationale: Regulatory T cells (Treg cells) play an important role in maintaining peripheral tolerance by suppressing over-activation of effector T cells. The kinase PDK1 plays a pivotal role in conventional T cell development. However, whether PDK1 signaling affects the homeostasis and function of Treg cells remains elusive. Methods: In order to evaluate the role of PDK1 in Treg cells from a genetic perspective, mice carrying the floxed PDK1 allele were crossbred with Foxp3Cre mice to efficiently deleted PDK1 in Foxp3+ Treg cells. Flow cytometry was used to detect the immune cell homeostasis of WT and PDK1fl/flFoxp3Cre mice. RNA-seq was used to assess the differences in transcriptional expression profile of WT and PDK1-deficient Treg cells. The metabolic profiles of WT and PDK1-deficient Treg cells were tested using the Glycolysis Stress Test and Mito Stress Test Kits by the Seahorse XFe96 Analyser. Results: PDK1 was essential for the establishment and maintenance of Treg cell homeostasis and function. Disruption of PDK1 in Treg cells led to a spontaneous fatal systemic autoimmune disorder and multi-tissue inflammatory damage, accompanied by a reduction in the number and function of Treg cells. The deletion of PDK1 in Treg cells destroyed the iron ion balance through regulating MEK-ERK signaling and CD71 expression, resulting in excessive production of intracellular ROS, which did not depend on the down-regulation of mTORC1 signaling. Inhibition of excessive ROS, activated MEK-Erk signaling or overload Fe2+ could partially rescue the survival of PDK1-deficient Treg cells. Conclusion: Our results defined a key finding on the mechanism by which PDK1 regulates Treg cell survival via controlling redox homeostasis.