Unmetabolized folic acid in plasma is associated with reduced natural killer cell cytotoxicity among postmenopausal women

Folic acid (FA) supplements and food fortification are used to prevent neural tube defects and to lower plasma homocysteine. Through exposure to food fortification and vitamin supplement use, large populations in the United States and elsewhere have an unprecedented high FA intake. We evaluated dietary and supplemental intakes of folate and FA in relation to an index of immune function, natural killer cell (NK) cytotoxicity, among 105 healthy, postmenopausal women. Among women with a diet low in folate (<233 microg/d), those who used FA-containing supplements had significantly greater NK cytotoxicity (P = 0.01). However, those who consumed a folate-rich diet and in addition used FA supplements > 400 microg/d had reduced NK cytotoxicity compared with those consuming a low-folate diet and no supplements (P = 0.02). Prompted by this observation, we assessed the presence of unmetabolized FA in plasma as a biochemical marker of excess FA. Unmetabolized folic acid was detected in 78% of plasma samples from fasting participants. We found an inverse relation between the presence of unmetabolized FA in plasma and NK cytotoxicity. NK cytotoxicity was approximately 23% lower among women with detectable folic acid (P = 0.04). This inverse relation was stronger among women >or= 60 y old and more pronounced with increasing unmetabolized FA concentrations (P-trend = 0.002). Because of the increased intake of FA in many countries, our findings highlight the need for further studies on the effect of long-term high FA intake on immune function and health.     

子宫内膜异位症中骨桥蛋白对自然杀伤细胞杀伤功能的抑制作用

目的:观察骨桥蛋白(OPN)对自然杀伤(NK)细胞杀伤活性的影响,以探讨OPN在子宫内膜异位症中的作用。方法:用乳酸脱氢酶释放法测定不同浓度OPN及其抗体对NK细胞杀伤活性的影响;测定子宫内膜异位症患者腹水以及腹水中加入OPN抗体后对NK细胞杀伤活性的影响。结果:当OPN浓度为25、50、75、100、125、250、500ng/ml时,与对照组相比,NK细胞杀伤活性逐渐降低(P<0.05);但当OPN浓度为1 000ng/ml时,与浓度为500ng/ml时相比,NK细胞杀伤活性有所升高(P<0.05),但仍低于对照组(P<0.05)。当OPN与抗OPN的单克隆抗体共同孵育后,NK细胞的杀伤活性均有所升高(P<0.05)。子宫内膜异位症患者腹水可抑制NK细胞的杀伤活性(P<0.05);当在腹水中加入一定量的抗OPN单克隆抗体后,NK细胞的杀伤活性有所升高,但仍低于对照组(P<0.05)。结论:OPN可抑制NK细胞的杀伤活性,是子宫内膜异位症患者腹水中抑制NK细胞活性的因子之一。     

Chlorogenic acid protects against liver fibrosis in vivo and in vitro through inhibition of oxidative stress

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自然杀伤细胞活化性受体与妊娠

蜕膜自然杀伤(dNK)细胞是构成妊娠早期子宫蜕膜最主要的淋巴细胞,表型CD5 superbrightCD16-CD9+,功能明显区别于外周血NK细胞,通过分泌产生各种细胞因子和生长因子,在局部发挥着重要的免疫调节功能,以维持胎盘正常生成,进而保证母体和胎儿的健康.综述了利用人类标本观察到的子宫NK细胞所特有的功能,重点论述了NK细胞活化性受体与蜕膜基质细胞、滋养层细胞上的配体相互作用,介导dNK处于活化状态,而这种活化并不表现为细胞毒活性,而是通过分泌调节因子和各种生长因子,在维持健康妊娠中发挥积极作用.     

Choline and/or folic acid deficiency is associated with genomic damage and cell death in human lymphocytes in vitro

Choline and folate are interrelated methyl donors. Previous studies showed that folate prevents genomic damage in human lymphocytes in vitro; however, the association between choline and human genomic stability is uncertain. To explore the genotoxicity, cytotoxicity, and cytostatic effects and possible interactions of choline and/or folate deficiency on the human genome, lymphocytes from 6 volunteers were cultured in 18 combinations of choline (CC) and folic acid (FA) media for 9 days. The genotoxicity was evaluated by micronuclei, nucleoplasmic bridges, and nuclear buds in the binucleated cell; the cytotoxicity indices included apoptosis and necrosis, and the cytostatic effects were indicated by nuclear division index (NDI). Across all choline concentrations, the frequencies of all biomarkers except NDI were diminished when FA concentration was more than or equal to 120 nmol/L. The frequencies of micronuclei, buds, and necrosis were significantly higher at lower levels of CC (0-6 μmol/L) compared with higher concentrations of CC (12-21.5 μmol/L) while maintaining the same FA concentration. We concluded that both choline and folate significantly impact genomic stability and cell death, although effects of folate were 2.5- to 6.2-fold greater, depending on the biomarker and dose. A combination of 12 μmol/L CC and 120 nmol/L FA appears to be optimal for genomic integrity in vitro.     

叶酸对体外人胃腺癌细胞SGC-7901生长的作用

目的 以体外培养的人胃癌细胞株SGC—7901为材料，观察叶酸的抑癌防癌作用。方法 采用生长曲线法、MTT法观察叶酸对细胞的增殖和功能的影响；采用FCM进行细胞周期分析，观察叶酸对细胞凋亡的影响。结果 在叶酸浓度为375，750和1875nmol／L时对人胃癌细胞株的增殖和功能有抑制作用，浓度为375nmol／L时引起的凋亡率可达33．1％。结论 叶酸对人胚肌腱细胞无抑制作用，表明叶酸对正常人体细胞无不良影响而对癌细胞有抑制作用。     

Natural killer cell activation and modulation of chemokine receptor profile in vitro by an extract from the cyanophyta Aphanizomenon flos-aquae

The present research was designed to study the effects of an extract from the edible cyanophyta Aphanizomenon flos-aquae on human natural killer (NK) cells. We have previously shown, using a double-blind randomized placebo-controlled crossover design, that ingestion of 1.5 g of dried whole A. flos-aquae resulted in a transient reduction in peripheral blood NK cells in 21 healthy human volunteers, suggesting increased NK cell homing into tissue. We have now identified an extract from A. flos-aquae (AFAe) that directly activates NK cells in vitro and modulates the chemokine receptor profile. NK cell activation was evaluated by expression of CD25 and CD69 on CD3-CD56+ cells after 18 hours. Changes in CXCR3 and CXCR4 chemokine receptor expression after 5-60 minutes were evaluated by immunostaining and flow cytometry. AFAe induced the expression of CD69 on CD3-CD56+ NK cells, induced CD25 expression on 25% of these cells, and acted in synergy with interleukin 2. NK cells enriched by RosetteSep (StemCell Technologies Inc., Vancouver, BC, Canada) were not activated by AFAe, indicating that the NK activation was dependent on other cells such as monocytes. The low-molecular-weight fraction <5,000 of AFAe was responsible for the most robust NK cell activation, suggesting novel compounds different from previously reported macrophage-activating large polysaccharides.     

Effects of in vitro asbestos exposure on natural killer and antibody-dependent cellular cytotoxicity

Human peripheral blood lymphocytes (PBL) were exposed in vitro to asbestos fibers. Antibody-dependent cellular cytotoxicity (ADCC) activity and natural killer (NK) activity were examined by a chromium-51 release assay. There was a statistically significant enhancement of ADCC and NK activity by chrysotile and crocidolite fibers when cultured together with PBL for a period of 42 hr in medium containing a concentration of at least 2.5% fetal calf serum (P less than 0.05). Isolation of large granular lymphocytes to measure NK activity, however, showed the opposite effect when exposed to asbestos fibers (P less than 0.05). Our results indicate that asbestos fibers can directly affect lymphoid cytotoxic responses in vitro and may provide clues to immunopathogenic mechanisms for the occurrence of neoplasms in vivo.     

Frequent intentional weight loss is associated with lower natural killer cell cytotoxicity in postmenopausal women: possible long-term immune effects

OBJECTIVE: Weight-loss attempts are likely to become more frequent as the prevalence of obesity rises. Repeated cycles of loss and gain are a common consequence of failed weight-loss attempts. The question of whether this pattern has negative health effects is unresolved. The objective of this research was to investigate associations between weight-loss history and current measures of immune function. DESIGN: The study design was a cross-sectional study. SUBJECTS: One hundred fourteen healthy, overweight, sedentary, postmenopausal women were recruited for an exercise intervention study and were currently weight stable. METHODS: History of intentional weight loss was assessed by questionnaire. Flow cytometry was used to measure natural killer cell (NK) cytotoxicity at four effector-to-target (E:T) ratios and for enumerating and phenotyping lymphocytes. Multiple linear regression analysis was used to investigate associations between weight loss within the past 20 years and current immune function. RESULTS: Women who reported ever intentionally losing >or=10 pounds had lower measured NK cytotoxicity than those who did not (24.7%+/-12.1% vs 31.1%+/-14.7%, respectively, at E:T 25:1; P=.01). Increasing frequency of previous intentional weight loss was associated with lower NK cytotoxicity (P=.003, trend). As an independent predictor, longer duration of recent weight stability was associated with higher NK cytotoxicity (21.6%+/-11.9%, 24.4%+/-11.0%, and 31.9%+/-14.4% for 2 to 5 years of weight stability, respectively; P=.0002, trend). The frequency of weight loss episodes was also associated with differences in the number and proportion of NK cells. CONCLUSIONS: This study provides evidence that frequent intentional weight loss may have long-term effects on immune function.     

Cigarette smoking is associated with the reduction of lymphokine-activated killer cell and natural killer cell activities

Lymphokine-activated killer (LAK) cell and natural killer (NK) cell activities were determined in a group of healthy individuals with differing smoking habits. The study population consisted of 54 Japanese males, including 23 smokers, 8 ex-smokers and 23 non-smokers. Peripheral blood mononuclear cells (PBMC) were isolated and used as effector cells. LAK cells were generated by incubation of PBMC with interleukin-2 for 72 h. LAK cell activity against NK-resistant Raji cells and NK cell activity against NK-sensitive K562 cells were examined by 4-h51Cr-release assay. LAK cell activity in the smokers was significantly lower than that in the nonsmokers. The smokers showed significantly lower NK cell activity than the nonsmokers, whereas NK cell activity of the ex-smokers was comparable to that of the non-smokers. The proportion of NK cells (CD3-16+56-, CD3-16-56+, or CD3-16+56+ cells) in the smokers was significantly lower than that in the nonsmokers. The present study demonstrates for the first time that cigarette smokers have lower LAK cell activity than nonsmokers.     

Natural killer cell activity in alcoholic cirrhosis: influence of nutrition

Forty-five patients with alcoholic cirrhosis, 20 chronic alcoholics with normal liver function tests and 36 healthy subjects were investigated. A combined index of nine anthropometric and biochemical parameters (triceps skinfold, arm muscle circumference, mid-arm muscle area, body fat percentage, creatinine-height index, serum albumin, plasma transferrin, prealbumin and retinol-binding protein levels) was used to evaluate nutritional status, allowing a distinction to be made between those patients with adequate nutrition (group I: 40 per cent of cirrhotics and 55 per cent of alcoholics), those with slight malnutrition (group II: 37.7 per cent of cirrhotics and 45 per cent of alcoholics) and those with severe malnutrition (group III: 22.2 per cent of cirrhotics and none alcoholic). Natural Killer (NK) cell activity of peripheral blood lymphocytes was determined using a 51Cr releasing cytotoxicity assay against K562 target cells. This was significantly lower in the cirrhotics than in the controls and chronic alcoholics (P less than 0.001 and P less than 0.01 respectively), but there was no difference between the latter two groups. Natural Killer activity was significantly lower in samples obtained from cirrhotics with severe malnutrition than in those with adequate nutrition, suggesting that malnutrition may play a role in the onset of the immunological disorder. No relationship could be established between nutritional status, NK activity and the clinical activity of the disease using Orrego's index on the liver function tests.     

Natural killer cell activity in workers exposed to benzidine and beta-naphthylamine

To investigate the effects of benzidine (BZ) and beta-naphthylamine (BNA) on the immune system in man, the activity of natural killer (NK) cells as well as the relative number (percentage) of Leu 11a positive cells in peripheral blood lymphocytes were measured in 63 dyestuff workers exposed to BZ and BNA (aromatic amines, AA). The cytotoxic potential per NK cell (unit NK cell activity) was approximated by dividing the NK activity per fixed numbers of unseparated mononuclear cells by the percentage of Leu 11a positive lymphocytes that mediated NK activity. Thirty one of these workers had previously been treated for bladder cancer and then cured (ex-cancer AA workers) whereas the remaining 32 had not been diagnosed as having bladder cancer (non-cancer AA workers). There was no significant difference in the gross NK activity per unseparated peripheral mononuclear cells among ex-cancer AA workers, non-cancer AA workers, and the control group (p greater than 0.05). The relative number of Leu 11a positive cells, on the other hand, was significantly higher in AA workers than in the control group (p less than 0.01). The unit NK cell activity, as a result, was significantly more reduced in both ex-cancer and non-cancer AA workers than in the control group (p less than 0.05 and p less than 0.01, respectively). Between ex-cancer and non-cancer AA workers, no significant difference was observed in terms of unit NK cell activity. These results indicated that the function of NK cells per se was impaired in AA workers whereas the number of circulating NK cells was relatively increased.     

Postischemic supplementation of folic acid improves neuronal survival and regeneration in vitro

Supplementation of folic acid (FA) is beneficial to several neurological diseases because it promotes notch signaling and neurogenesis and reduces blood homocysteine levels. We hypothesized that postischemic supplementation of FA is beneficial for neuronal survival and regeneration. The objective of the present study was to determine the postischemic neuroprotective and neuroregenerative efficacy of FA supplementation and its effects on various cellular processes in vitro. This work benefited from the use of FA and glucose-free media to better assess the ischemic neuroprotection provided by FA supplementation. The postischemic supplementation of FA significantly improved cell viability, and the improvement was primarily by obstructing the oxygen-glucose deprivation (OGD)–activated apoptosis. Furthermore, postischemic treatment with FA significantly reduced the mitochondrial membrane depolarization and the formation of acidic organelles triggered by OGD. Moreover, FA's effect on neuroregeneration following OGD was evaluated by measuring the cell proliferation and neurite outgrowth length. Treatment with FA enhanced cell proliferation and neurite outgrowth significantly. Thus, these results revealed some of the mechanisms by which FA supplementation provided neuroprotection and neuroregeneration following ischemic injury and highlighted the need for further research into the potential of folic acid as a clinical drug for ischemic stroke.     

Pomegranate extract exhibits in vitro activity against Clostridium difficile

ObjectiveTo determine the possible utility of pomegranate extract in the management or prevention of Clostridium difficile infections or colonization.MethodThe activity of pomegranate was tested against 29 clinical C. difficile isolates using the Clinical and Laboratory Standards Institute-approved agar dilution technique. Total phenolics content of the pomegranate extract was determined by Folin-Ciocalteau colorimetric method and final concentrations of 6.25 to 400 μg/mL gallic acid equivalent were achieved in the agar.ResultsAll strains had MICs at 12.5 to 25 mg/mL gallic acid equivalent range. Our results suggest antimicrobial in vitro activity for pomegranate extract against toxigenic C. difficile.ConclusionPomegranate extract may be a useful contributor to the management and prevention of C. difficile disease or colonization.     

Iron deficiency alters DMBA-induced tumor burden and natural killer cell cytotoxicity in rats.

Natural killer (NK) cell activity is impaired in iron-deficient rats. Natural killer cells destroy tumor cells; therefore, iron-deficient rats may be less able to combat cancer growth. Natural killer cell cytotoxicity, both basal and interferon gamma (IFN gamma)-stimulated, was studied in moderately and severely iron-deficient rats challenged with the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Female weanling rats were fed ad libitum semipurified diets containing 8, 13 or 42 mg Fe/kg. A pair-fed group was fed the 42 mg Fe/kg diet at the level consumed by the 8 mg Fe/kg group. Following 6 wk of dietary treatment, DMBA-treated rats received a single intragastric dose of DMBA. Dietary treatment was continued. Rats were killed at 1, 4, 8, 14 and 20 wk post-DMBA treatment. Natural killer cell cytotoxicity (both basal and IFN gamma-stimulated) was analyzed. Feeding the 13 mg Fe/kg diet resulted in lower NK cell activity (P = 0.006) and greater tumor burden (P = 0.045) and tumor incidence. Interferon gamma treatment relieved the lower NK cell cytotoxicity observed in moderate iron deficiency. Feeding the 8 mg Fe/kg diet impaired NK cell activity (P = 0.006), but tumor burden and incidence were less than in moderate iron deficiency. In this model, iron deficiency, particularly moderate iron deficiency, contributed to cancer development and compromised NK cell cytotoxicity.