Pro- and Anti-Inflammatory Cytokines in the Context of NK Cell-Trophoblast Interactions

Palmitic Acid Upregulates CD96 Expression to Mediate Maternal-Foetal Interface Immune Tolerance by Inhibiting Cytotoxic Activity and Promoting Adhesion Function in Human Decidual Natural Killer Cells

Decidual natural killer cells (dNK cells) are an essential component of the immune cells present at the maternal-foetal interface during early pregnancy, and they play a vital role in various physiological processes. Abnormalities in the ratio or function of dNK cells have been linked to recurrent miscarriages. CD96 has been previously shown to regulate NK cell function in the tumour microenvironment; however, its role and mechanism at the maternal-foetal interface remains unclear. The present study aimed to investigate the immunomodulatory role of CD96 in dNK cells and its function at the maternal-foetal interface. Immunofluorescence staining and flow cytometry were used to detect the expression of cellular markers such as CD96. Furthermore, the secretory function, adhesion-function-related molecules, and cell proliferation markers of CD96+ and CD96- dNK cells were detected using flow cytometry. In addition, we performed cell culture experiments via the magnetic bead sorting of NK cells to detect changes in the expression of the aforementioned functional molecules in dNK cells after the CD96 blockade. Furthermore, we examined the functional characteristics of dNK cells after palmitic acid treatment at a concentration of 10 μM. We also examined the changes in dNK cell function when subjected to the combined effect of palmitic acid and CD96 antagonists. The results indicated that CD96, TIGIT, CD155, and CD112 were highly expressed at the maternal-foetal interface, with dNK cells predominantly expressing CD96, whereas TIGIT was mainly expressed on T cells, and CD155 and CD112 were mainly present in metaphase stromal and trophoblast cells. CD96+ dNK cells displayed low cytotoxic activity and a high adhesion phenotype, which mediated the immunosuppressive effect on dNK cells at the maternal-foetal interface. Palmitic acid upregulated CD96 expression on the surface of dNK cells in the coculture system, inhibiting dNK cell activity and increasing their adhesion molecule expression. CD96 antagonist treatment blocked the inhibitory effect of trophoblasts on dNK cells, resulting in enhanced cytokine secretion and reduced adhesion. The results of this study provide valuable insight into the immunomodulatory role of CD96 in dNK cells and its mechanism at the maternal-foetal interface, particularly in metaphase NK cells. This study sheds light on the mechanisms of immune regulation at the maternal-foetal interface and their implications for the study of recurrent miscarriages of unknown origin.

HMGB1: a double-edged sword and therapeutic target in the female reproductive system

HMGB1 that belongs to the High Mobility Group-box superfamily, is a nonhistone chromatin associated transcription factor. It is present in the nucleus of eukaryotes and can be actively secreted or passively released by kinds of cells. HMGB1 is important for maintaining DNA structure by binding to DNA and histones, protecting it from damage. It also regulates the interaction between histones and DNA, affecting chromatin packaging, and can influence gene expression by promoting nucleosome sliding. And as a DAMP, HMGB1 binding to RAGE and TLRs activates NF-κB, which triggers the expression of downstream genes like IL-18, IL-1β, and TNF-α. HMGB1 is known to be involved in numerous physiological and pathological processes. Recent studies have demonstrated the significance of HMGB1 as DAMPs in the female reproductive system. These findings have shed light on the potential role of HMGB1 in the pathogenesis of diseases in female reproductive system and the possibilities of HMGB1-targeted therapies for treating them. Such therapies can help reduce inflammation and metabolic dysfunction and alleviate the symptoms of reproductive system diseases. Overall, the identification of HMGB1 as a key player in disease of the female reproductive system represents a significant breakthrough in our understanding of these conditions and presents exciting opportunities for the development of novel therapies.

Natural Killer Cells and Immunotherapy

Natural killer (NK) cells are innate immune cells that demonstrate cytolytic activity against tumor cells, virus-infected cells and other physiologically stressed cells, such as senescent cells [...].

Overexpression of lipocalin 2 in PBX1-deficient decidual NK cells promotes inflammation at the maternal-fetal interface

PROBLEM

Impairment of PBX1 expression in decidual natural killer (dNK) cells is associated with the pathogenesis of unexplained recurrent spontaneous abortion, which results in fetal growth restriction (FGR) by affecting the secretion of downstream growth factors. However, whether other mechanisms limit embryo growth in decidua containing PBX1-deficient natural killer (NK) cells is unknown.

METHOD OF STUDY

Pbx1^f/f ; Ncr1^Cre mice were employed to explore the underlying mechanisms by which PBX1^- NK cells affect embryonic development. To simulate the clinical testing of pregnant women, Doppler ultrasound imaging was used to detect embryo implantation and development. Differentially expressed genes (DEGs) in PBX1^- NK cells that may affect normal pregnancy were screened using RNA-sequencing and real-time PCR. Immune cell changes caused by DEGs were detected by flow cytometry. Finally, the mechanism of FGR was explored by injecting the protein LCN2, corresponding to the selected DEG, into mice.

RESULTS

We verified the embryonic dysplasia in pregnant Pbx1^f/f ; Ncr1^Cre mice by Doppler ultrasound imaging and found that LCN2 was upregulated in dNK cells. We also observed higher infiltration of neutrophils and macrophages in the decidua of Pbx1^f/f ; Ncr1^Cre mice. Finally, we found an increase in the number and activation of neutrophils at the maternal-fetal interface after injecting LCN2 into pregnant mice and observed that these mice showed signs of FGR.

CONCLUSION

Excessive LCN2 secreted by PBX1^- dNK cells at the maternal-fetal interface recruit neutrophils and causes an inflammatory response, which is related to FGR.

dl-THP recovered the decreased NKp44 expression level on CD56dim CD16+ natural killer cells partially in choriocarcinoma microenvironment

Natural killer cell-based immunotherapy has become a leading-edge tool against cancer, but still faces a variety of challenges, such as phenotype shift and dysfunction of NK cells in tumor microenvironment. Thus, finding potent agents that could inhibit the phenotype shift and incapacity of NK cells in the tumor microenvironment is essential for improving antitumor effects. dl-tetrahydropalmatine (dl-THP), one of the active alkaloids of Chinese herb Corydalis Rhizoma, has been proven to possess antitumor activity. However, whether dl-THP acts on NK cells to enhance antitumor activity remains unknown. In this study, we found that the proportion of blood CD56^dimCD16⁺ NK cells was decreased while the proportion of CD56^brightCD16^- NK cells was increased when the cells were cultured in conditional medium (CM, medium from the human choriocarcinoma cell lines JEG-3). dl-THP could alter the varied proportion of CD56^dimCD16⁺ NK cells and CD56^brightCD16^- NK cells in CM respectively. Importantly, the expression level of NKp44 on CD56^dimCD16⁺ NK cells was dramatically reduced when the cells were cultured in CM, which could also be reversed by dl-THP. Furthermore, dl-THP increased the decreased NK-cell cytotoxicity when cells were cultured in CM. In summary, our study demonstrated that dl-THP could recover the decreased NKp44 expression level on CD56^dimCD16⁺ NK cells and restore the cytotoxicity of NK cells in tumor microenvironment.

Natural Killer Cell Derived Microvesicles Affect the Function of Trophoblast Cells

The interaction of natural killer (NK) and trophoblast cells underlies the formation of immune tolerance in the mother-fetus system and the maintenance of the physiological course of pregnancy. In addition, NK cells affect the function of trophoblast cells, interacting with them via the receptor apparatus and through the production of cytokines. Microvesicles (MVs) derived from NK cells are able to change the function of target cells. However, in the overall pattern of interactions between NK cells and trophoblasts, the possibility that both can transmit signals to each other via MVs has not been taken into account. Therefore, the aim of this study was to assess the effect of NK cell-derived MVs on the phenotype, proliferation, and migration of trophoblast cells and their expression of intracellular messengers. We carried out assays for the detection of content transferred from MV to trophoblasts. We found that NK cell-derived MVs did not affect the expression of CD54, CD105, CD126, CD130, CD181, CD119, and CD120a receptors in trophoblast cells or lead to the appearance of CD45 and CD56 receptors in the trophoblast membrane. Further, the MVs reduced the proliferation but increased the migration of trophoblasts with no changes to their viability. Incubation of trophoblast cells in the presence of MVs resulted in the activation of STAT3 via pSTAT3(Ser727) but not via pSTAT3(Tyr705). The treatment of trophoblasts with MVs did not result in the phosphorylation of STAT1 and ERK1/2. The obtained data indicate that NK cell-derived MVs influence the function of trophoblast cells, which is accompanied by the activation of STAT3 signaling.