Human immune and gut microbial parameters associated with inter-individual variations in COVID-19 mRNA vaccine-induced immunity.

COVID-19 mRNA vaccines induce protective adaptive immunity against SARS-CoV-2 in most individuals, but there is wide variation in levels of vaccine-induced antibody and T-cell responses. However, the mechanisms underlying this inter-individual variation remain unclear. Here, using a systems biology approach based on multi-omics analyses of human blood and stool samples, we identified several factors that are associated with COVID-19 vaccine-induced adaptive immune responses. BNT162b2-induced T cell response is positively associated with late monocyte responses and inversely associated with baseline mRNA expression of activation protein 1 (AP-1) transcription factors. Interestingly, the gut microbial fucose/rhamnose degradation pathway is positively correlated with mRNA expression of AP-1, as well as a gene encoding an enzyme producing prostaglandin E2 (PGE2), which promotes AP-1 expression, and inversely correlated with BNT162b2-induced T-cell responses. These results suggest that baseline AP-1 expression, which is affected by commensal microbial activity, is a negative correlate of BNT162b2-induced T-cell responses.

JunB Is Critical for Survival of T Helper Cells.

Clonal expansion and differentiation of various T helper subsets, such as Th1, Th2, and Th17 cells, depend on a complex of transcription factors, IRF4 and a BATF-containing AP-1 heterodimer. A major BATF heterodimeric partner, JunB, regulates Th17 differentiation, but the role of JunB in other T helper subsets is not well understood. Here we demonstrate that JunB is required for clonal expansion of Th1, Th2 and Th17 cells. In mice immunized with lipopolysaccharide (LPS), papain, or complete Freund's adjuvant (CFA), which induce predominantly Th1, Th2 and Th17 cells, respectively, accumulation of antigen-primed, Junb-deficient CD4+ T cells is significantly impaired. TCR-stimulated Junb-deficient CD4+ T cells are more sensitive to apoptosis, although they showed largely normal proliferation and cellular metabolism. JunB directly inhibits expression of genes involved in apoptosis, including Bcl2l11 (encoding Bim), by promoting IRF4 DNA binding at the gene locus. Taken together, JunB serves a critical function in clonal expansion of diverse T helper cells by inhibiting their apoptosis.

Altered pre-existing SARS-CoV-2-specific T cell responses in elderly individuals.

Pre-existing SARS-CoV-2-specific T cells, but not antibodies, have been detected in some unexposed individuals. This may account for some of the diversity in clinical outcomes ranging from asymptomatic infection to severe COVID-19. Although age is a risk factor for COVID-19, how age affects SARS-CoV-2-specific T cell responses remains unknown. We found that pre-existing T cell responses to specific SARS-CoV-2 proteins, Spike (S) and Nucleoprotein (N), were significantly lower in elderly donors (>70 years old) than in young donors. However, substantial pre-existing T cell responses to the viral membrane (M) protein were detected in both young and elderly donors. In contrast, young and elderly donors exhibited comparable T cell responses to S, N, and M proteins after infection with SARS-CoV-2. These data suggest that although SARS-CoV-2 infection can induce T cell responses specific to various viral antigens regardless of age, diversity of target antigen repertoire for long-lived memory T cells specific for SARS-CoV-2 may decline with age; however, memory T cell responses can be maintained by T cells reactive to specific viral proteins such as M. A better understanding of the role of pre-existing SARS-CoV-2-specific T cells that are less susceptible to age-related loss may contribute to development of more effective vaccines for elderly people.

JunB regulates homeostasis and suppressive functions of effector regulatory T cells.

Foxp3-expressing CD4+ regulatory T (Treg) cells need to differentiate into effector Treg (eTreg) cells to maintain immune homeostasis. T-cell receptor (TCR)-dependent induction of the transcription factor IRF4 is essential for eTreg differentiation, but how IRF4 activity is regulated in Treg cells is still unclear. Here we show that the AP-1 transcription factor, JunB, is expressed in eTreg cells and promotes an IRF4-dependent transcription program. Mice lacking JunB in Treg cells develop multi-organ autoimmunity, concomitant with aberrant activation of T helper cells. JunB promotes expression of Treg effector molecules, such as ICOS and CTLA4, in BATF-dependent and BATF-independent manners, and is also required for homeostasis and suppressive functions of eTreg. Mechanistically, JunB facilitates the accumulation of IRF4 at a subset of IRF4 target sites, including those located near Icos and Ctla4. Thus, JunB is a critical regulator of IRF4-dependent Treg effector programs, highlighting important functions for AP-1 in Treg-mediated immune homeostasis.

Tumor-Selective Cytotoxicity of Nitidine Results from Its Rapid Accumulation into Mitochondria.

We identified a nitidine- (NTD-) accumulating organelle and evaluated the net cytotoxicity of accumulated NTD. To evaluate tumor cell selectivity of the drug, we evaluated its selective cytotoxicity against 39 human cancer cell lines (JFCR39 panel), and the profile was compared with those of known anticancer drugs. Organelle specificity of NTD was visualized using organelle-targeted fluorescent proteins. Real-time analysis of cell growth, proliferation, and cytotoxicity was performed using the xCELLigence system. Selectivity of NTD in the JFCR39 panel was evaluated. Mitochondria-specific accumulation of NTD was observed. Real-time cytotoxicity analysis suggested that the mechanism of NTD-induced cell death is independent of the cell cycle. Short-term treatment indicated that this cytotoxicity only resulted from the accumulation of NTD into the mitochondria. The results from the JFCR39 panel indicated that NTD-mediated cytotoxicity resulted from unique mechanisms compared with those of other known anticancer drugs. These results suggested that the cytotoxicity of NTD is only induced by its accumulation in mitochondria. The drug triggered mitochondrial dysfunction in less than 2 h. Similarity analysis of the selectivity of NTD in 39 tumor cell lines strongly supported the unique tumor cell specificity of NTD. Thus, these features indicate that NTD may be a promising antitumor drug for new combination chemotherapies.

Monogalactosyldiacylglycerol: An abundant galactosyllipid of Cirsium brevicaule A. GRAY leaves inhibits the expression of gene encoding fatty acid synthase.

BACKGROUND: The leaves of Cirsium brevicaule A. GRAY (CL) significantly decreased hepatic lipid accumulation and the expression of fatty acid synthase gene (FASN) in mice. PURPOSE: We aimed to purify and identify the active compound(s) from CL and determine the inhibitory mechanism of expression of FASN. METHODS: We purified monogalactosyldiacylglycerol (MGDG) from extracts of CL (CL-MGDG) and showed that it was the active CL component through analyses of its effects on the expression of genes of human breast cancer cell line, SKBR-3. RESULTS: The content and fatty acid composition of CL-MGDG are distinctly different from those of other vegetable-derived MGDGs. Treatment of SKBR-3 cells with MGDG decreased the level of FASN mRNA as well as the levels of mRNA encoding other protein involved in lipogenesis. Further, MGDG treatments significantly inhibited luciferase activities of constructs containing liver X receptor response element in FASN promoter region without altering the levels of mRNA encoding transcription factors. MGDG and the FASN inhibitor C75 decreased the viabilities of SKBR-3 cells in a concentration-dependent manner. CL-MGDG more potently inhibited cell viability than a commercial MGDG preparation. CONCLUSIONS: CL represents a good source of glycoglycerolipids with potential as functional ingredients of food.

Mechanism of arctigenin-mediated specific cytotoxicity against human lung adenocarcinoma cell lines.

The lignan arctigenin (ARG) from the herb Arctium lappa L. possesses anti-cancer activity, however the mechanism of action of ARG has been found to vary among tissues and types of cancer cells. The current study aims to gain insight into the ARG mediated mechanism of action involved in inhibiting proliferation and inducing apoptosis in lung adenocarcinoma cells. This study also delineates the cancer cell specificity of ARG by comparison with its effects on various normal cell lines. ARG selectively arrested the proliferation of cancer cells at the G0/G1 phase through the down-regulation of NPAT protein expression. This down-regulation occurred via the suppression of either cyclin E/CDK2 or cyclin H/CDK7, while apoptosis was induced through the modulation of the Akt-1-related signaling pathway. Furthermore, a GSH synthase inhibitor specifically enhanced the cytotoxicity of ARG against cancer cells, suggesting that the intracellular GSH content was another factor influencing the susceptibility of cancer cells to ARG. These findings suggest that specific cytotoxicity of ARG against lung cancer cells was explained by its selective modulation of the expression of NPAT, which is involved in histone biosynthesis. The cytotoxicity of ARG appeared to be dependent on the intracellular GSH level.

Dietary phosphatidylinositol protects C57BL/6 mice from concanavalin A-induced liver injury by modulating immune cell functions.

SCOPE: Several recent studies have demonstrated that phospholipids (PLs) supplementation can modulate the function of cultured-immune cells. Furthermore, dietary PLs have been shown to ameliorate inflammatory processes and immune responses in arthritic and diabetic murine models, respectively. Thus, the aim of this study was to examine the immune-modulating activities of dietary soybean PLs in mice, with particular emphasis on the immune cell functions. METHODS AND RESULTS: Mice were fed semisynthetic diets for 6 weeks, which contained either 7% soybean oil or 5% soybean oil plus 2% of either PL: phosphatidylcholine (PC), phosphatidylinositol (PI), or phosphatidylserine (PS). Production of concanavalin A (Con A)-induced proinflammatory cytokines was significantly decreased in the splenocytes isolated from mice fed PI compared to other lipids. Supplementation of the diet with PI, but not with the other lipids, significantly suppressed the proinflammatory cytokine serum levels and the development of Con A-induced liver damages. CONCLUSION: These observations suggest that dietary PI influenced immune functions, resulting in the prevention of pathogenesis and development of the liver injury in mice.

Tumor specific cytotoxicity of arctigenin isolated from herbal plant Arctium lappa L.

The effectiveness of cancer chemotherapy is often limited by the toxicity to other tissues in the body. Therefore, the identification of non-toxic chemotherapeutics from herbal medicines remains to be an attractive goal to advance cancer treatments. This study evaluated the cytotoxicity profiles of 364 herbal plant extracts, using various cancer and normal cell lines. The screening found occurrence of A549 (human lung adenocarcinoma) specific cytotoxicity in nine species of herbal plants, especially in the extract of Arctium lappa L. Moreover, purification of the selective cytotoxicity in the extract of Arctium lappa L. resulted in the identification of arctigenin as tumor specific agent that showed cytotoxicity to lung cancer (A549), liver cancer (HepG2) and stomach cancer (KATO III) cells, while no cytotoxicity to several normal cell lines. Arctigenin specifically inhibited the proliferation of cancer cells, which might consequently lead to the induction of apoptosis. In conclusion, this study found that arctigenin was one of cancer specific phytochemicals, and in part responsible for the tumor selective cytotoxicity of the herbal medicine.