The ω-3 Polyunsaturated Fatty Acid Docosahexaenoic Acid Enhances NK-Cell Antitumor Effector Functions.

ω-3 polyunsaturated fatty acids (PUFA) are known to directly repress tumor development and progression. In this study, we explored whether docosahexaenoic acid (DHA), a type of ω-3 PUFA, had an immunomodulatory role in inhibiting tumor growth in immunocompetent mice. The number of natural killer (NK) cells but not the number of T or B cells was decreased by DHA supplementation in various tissues under physiologic conditions. Although the frequency and number of NK cells were comparable, IFNγ production by NK cells in both the spleen and lung was increased in DHA-supplemented mice in the mouse B16F10 melanoma tumor model. Single-cell RNA sequencing revealed that DHA promoted effector function and oxidative phosphorylation in NK cells but had no obvious effects on other immune cells. Using Rag2-/- mice and NK-cell depletion by PK136 antibody injection, we demonstrated that the suppression of B16F10 melanoma tumor growth in the lung by DHA supplementation was dependent mainly on NK cells. In vitro experiments showed that DHA directly enhanced IFNγ production, CD107a expression, and mitochondrial oxidative phosphorylation (OXPHOS) activity and slightly increased proliferator-activated receptor gamma coactivator-1α (PGC-1α) protein expression in NK cells. The PGC-1α inhibitor SR-18292 in vitro and NK cell-specific knockout of PGC-1α in mice reversed the antitumor effects of DHA. In summary, our findings broaden the current knowledge on how DHA supplementation protects against cancer growth from the perspective of immunomodulation by upregulating PGC-1α signaling-mediated mitochondrial OXPHOS activity in NK cells.

Docosahexaenoic acid supplementation represses the early immune response against murine cytomegalovirus but enhances NK cell effector function.

BACKGROUND: Docosahexaenoic acid (DHA) supplementation is beneficial for several chronic diseases; however, its effect on immune regulation is still debated. Given the prevalence of cytomegalovirus (CMV) infection and because natural killer (NK) cells are a component of innate immunity critical for controlling CMV infection, the current study explored the effect of a DHA-enriched diet on susceptibility to murine (M) CMV infection and the NK cell effector response to MCMV infection. RESULTS: Male C57BL/6 mice fed a control or DHA-enriched diet for 3 weeks were infected with MCMV and sacrificed at the indicated time points postinfection. Compared with control mice, DHA-fed mice had higher liver and spleen viral loads at day 7 postinfection, but final MCMV clearance was not affected. The total numbers of NK cells and their terminal mature cell subset (KLRG1+ and Ly49H+ NK cells) were reduced compared with those in control mice at day 7 postinfection but not day 21. DHA feeding resulted in higher IFN-γ and granzyme B expression in splenic NK cells at day 7 postinfection. A mechanistic analysis showed that the splenic NK cells of DHA-fed mice had enhanced glucose uptake, increased CD71 and CD98 expression, and higher mitochondrial mass than control mice. In addition, DHA-fed mice showed reductions in the total numbers and activation levels of CD4+ and CD8+ T cells. CONCLUSIONS: These results suggest that DHA supplementation represses the early response to CMV infection but preserves NK cell effector functions by improving mitochondrial activity, which may play critical roles in subsequent MCMV clearance.

Screening for Active Compounds Targeting Human Natural Killer Cell Activation Identifying Daphnetin as an Enhancer for IFN-γ Production and Direct Cytotoxicity.

Natural killer (NK) cells are a potent weapon against tumor and viral infection. Finding active compounds with the capacity of enhancing NK cell effector functions will be effective to develop new anti-cancer drugs. In this study, we initially screened 287 commercially available active compounds by co-culturing with peripheral blood mononuclear cells (PBMCs). We found that five compounds, namely, Daphnetin, MK-8617, LW6, JIB-04, and IOX1, increased the IFN-γ+ NK cell ratio in the presence of IL-12. Further studies using purified human primary NK cells revealed that Daphnetin directly promoted NK cell IFN-γ production in the presence of IL-12 but not IL-15, while the other four compounds acted on NK cells indirectly. Daphnetin also improved the direct cytotoxicity of NK cells against tumor cells in the presence of IL-12. Through RNA-sequencing, we found that PI3K-Akt-mTOR signaling acted as a central pathway in Daphnetin-mediated NK cell activation in the presence of IL-12. This was further confirmed by the finding that both inhibitors of PI3K-Akt and its main downstream signaling mTOR, LY294002, and rapamycin, respectively, can reverse the increase of IFN-γ production and cytotoxicity in NK cells promoted by Daphnetin. Collectively, we identify a natural product, Daphnetin, with the capacity of promoting human NK cell activation via PI3K-Akt-mTOR signaling in the presence of IL-12. Our current study opens up a new potential application for Daphnetin as a complementary immunomodulator for cancer treatments.

Postnatal renin-angiotensin system inhibition prevents renal damage from prenatal inflammation in rats.

OBJECTIVE: To assess the protective role of benazepril, an angiotensin-converting enzyme inhibitor, in renal damage caused by prenatal inflammation. METHODS: Saline or lipopolysaccharide were administered intraperitoneally to pregnant Sprague- Dawley rats on gestation days 8, 10, and 12. After birth, offspring received either tap water or benazepril in water between 7 and 68 weeks. Blood pressure, blood urea nitrogen, creatinine, and 24-h urine volume were measured as indices of renal function. Hematoxylin, eosin, periodic acid-Schiff, and Sirius Red staining were used to evaluate renal damage. RESULTS: Postnatal benazepril treatment ameliorated hypertension and restored normal 24-h urine volume and blood urea nitrogen and serum creatinine levels. Benazepril treatment also reduced glycoprotein accumulation and fibrosis in the glomerulus and in tubular epithelial cells and inhibited nuclear factor-kappa B activation. CONCLUSION: Together with our previous findings that postnatal inhibition of nuclear factor-kappa B activation blocks intra-renal renin-angiotensin system activation, our current data demonstrate that intra-renal activation of the renin-angiotensin system interacts with nuclear factor-kappa B activation to cause renal damage in adulthood following prenatal inflammation.

Competing endogenous RNA screening based on long noncoding RNA-messenger RNA co-expression profile in Hepatitis B virus-associated hepatocarcinogenesis.

OBJECTIVE: To profile the liver cancer specific long noncoding RNAs (lncRNAs) and competing endogenous RNA (ceRNA) networks of Hepatitis B virus (HBV)-associated hepatocarcinogensis (HCG) and to examine the effect of compound K on the expression of identified ceRNA networks. METHODS: Based on lncRNA and messenger RNA (mRNA) microarray data of HBV-associated liver cancer, the current study profiles the cancer specific lncRNAs and ceRNA networks of HBV-associated HCG through comprehensive application of RegRNA 2, miRTarBase and Pearson correlation coefficient analysis. Compound K-treated liver cancer cells were harvested for analysis of transcriptional levels of both enoyl-CoA hydratase and 3-hydroxyacyl CoA dehydrogenase (EHHADH)-AS1 and ENTPD5. RESULTS: The results revealed that 11 Encyclopedia of DNA Elements annotated lncRNAs were differentially expressed in the process of HBV-associated HCG. Among these lncRNAs, 95 potential ceRNA networks with highly positively correlated expression profiles between the interacting lncRNAs and mRNAs (Pearson correlation coefficient > 0.7) were constructed. Of note, two HBV-associated ceRNA networks, EHHADH-AS1-hsa-miR-4459-ectonucleoside triphosphate diphosphohydrolase 5 and LINC01018-hsa-miRNA-574-5p-glucose-6-phosphatase catalytic subunit, with Pearson correlation coefficient > 0.9, may play a critical role in hepatocellular carcinoma development, which was supported by experimental evidence. Interestingly, compound K, an intestinal bacterial metabolite of ginseng protopanaxadiol saponin, which has been proven to promote apoptosis of human hepatocellular carcinoma cells, was found to impede the down-regulation of EHHADH-AS1 in several liver cancer cell lines including HepG3B, Huh-7 and plc/prf/5 cells. CONCLUSION: Comprehensive application of co-expression network analysis and prediction of RNA interaction may be a feasible strategy to unravel the potential ceRNA networks involved in the process of human diseases.

Curcumin down-regulates DNA methyltransferase 1 and plays an anti-leukemic role in acute myeloid leukemia.

Bioactive components from dietary supplements such as curcumin may represent attractive agents for cancer prevention or treatment. DNA methylation plays a critical role in acute myeloid leukemia (AML) development, and presents an excellent target for treatment of this disease. However, it remains largely unknown how curcumin, a component of the popular Indian spice turmeric, plays a role in DNA hypomethylation to reactivate silenced tumor suppressor genes and to present a potential treatment option for AML. Here we show that curcumin down-regulates DNMT1 expression in AML cell lines, both in vitro and in vivo, and in primary AML cells ex vivo. Mechanistically, curcumin reduced the expression of positive regulators of DNMT1, p65 and Sp1, which correlated with a reduction in binding of these transcription factors to the DNMT1 promoter in AML cell lines. This curcumin-mediated down-regulation of DNMT1 expression was concomitant with p15(INK4B) tumor suppressor gene reactivation, hypomethylation of the p15(INK4B) promoter, G1 cell cycle arrest, and induction of tumor cell apoptosis in vitro. In mice implanted with the human AML MV4-11 cell line, administration of curcumin resulted in remarkable suppression of AML tumor growth. Collectively, our data indicate that curcumin shows promise as a potential treatment for AML, and our findings provide a basis for future studies to test the clinical efficacy of curcumin - whether used as a single agent or as an adjuvant - for AML treatment.