Manganese chloride enhances natural cell-mediated immune effector cell function: effects on macrophages

Impact of zinc, copper, manganese and chromium supplementation on growth performance and blood metabolic profile of Sahiwal (Bos indicus) male calves

This study aimed to see the effect of oral supplementation of specific trace minerals mixture on the growth, immunity, and reproductive development of indigenous growing bull calves. Eighteen Sahiwal bull calves, with an average age of 6 months were chosen and divided into three groups. Group 1 was fed with a basal diet, Group 2 was provided with an additional specific trace mineral supplement to achieve a diet containing 70 ppm of Zn, 17.50 ppm of Cu, 65 ppm of Mn, and 1.75 ppm of Cr. Group 3 received a 25% extra supplement to achieve a diet containing 87.50 ppm of Zn, 21.87 ppm of Cu, 81.25 ppm of Mn, and 2.18 ppm of Cr. The experiment was carried out for a total of 180 days. According to the findings, there was no significant impact of specific trace minerals supplementation on the animals' body weight, morphometric parameters, dry matter intake, average daily gain, nutritional value, digestibility and nitrogen retention. However, higher levels of Zn, Cu, and Mn led to increased (p < 0.05) total retention, while Cr retention remained the same. Serum mineral concentrations of Zn, Cu, and Mn increased significantly (p < 0.05) in G2 and G3 compared to the G1 group while Ca, P, and Cr had no significant change. Blood plasma glucose, albumin, globulin, and total protein showed no significant differences. Plasma alkaline phosphatase activity improved significantly (p < 0.05) in G2 and G3 but alanine transaminase, aspartate aminotransferase, hemoglobin, hematocrit, and IGF-1 remained unchanged. Superoxide dismutase activity, ferric-reducing antioxidant power, and total immunoglobulin concentration increased significantly (p < 0.05) in G2 and G3 groups, however, catalase activity and IgG count did not change among the groups. Mineral-supplemented groups (G2 and G3) showed a significant change (p < 0.05) in testosterone production during the 120th and the 180th day of the trial. Scrotal circumference and temperature gradient of the scrotal surface did not show any significant change. Supplementing growing bull calves with specific trace minerals above the basal level (70, 17.50, 65 and 1.75 ppm of Zn, Cu, Mn and Cr) has no direct beneficial effect on the growth parameters but can have positive effects on their antioxidant status, immunity and reproductive development as the related blood parameters were positively affected.

Microglia Signaling Pathway Reporters Unveiled Manganese Activation of the Interferon/STAT1 Pathway and Its Mitigation by Flavonoids

Neuroinflammatory responses to neurotoxic manganese (Mn) in CNS have been associated with the Mn-induced Parkinson-like syndromes. However, the framework of molecular mechanisms contributing to manganism is still unclear. Using an in vitro neuroinflammation model based on the insulated signaling pathway reporter transposon constructs stably transfected into a murine BV-2 microglia line, we tested effects of manganese (II) together with a set of 12 metal salts on the transcriptional activities of the NF-κB, activator protein-1 (AP-1), signal transducer and activator of transcription 1 (STAT1), STAT1/STAT2, STAT3, Nrf2, and metal-responsive transcription factor-1 (MTF-1) via luciferase assay, while concatenated destabilized green fluorescent protein expression provided for simultaneous evaluation of cellular viability. This experiment revealed specific and strong responses to manganese (II) in reporters of the type I and type II interferon-induced signaling pathways, while weaker activation of the NF-κB in the microglia was detected upon treatment of cells with Mn(II) and Ba(II). There was a similarity between Mn(II) and interferon-γ in the temporal STAT1 activation profile and in their antagonism to bacterial LPS. Sixty-four natural and synthetic flavonoids differentially affected both cytotoxicity and the pro-inflammatory activity of Mn (II) in the microglia. Whereas flavan-3-ols, flavanones, flavones, and flavonols were cytoprotective, isoflavones enhanced the cytotoxicity of Mn(II). Furthermore, about half of the tested flavonoids at 10-50 μM could attenuate both basal and 100-200 μM Mn(II)-induced activity at the gamma-interferon activated DNA sequence (GAS) in the cells, suggesting no critical roles for the metal chelation or antioxidant activity in the protective potential of flavonoids against manganese in microglia. In summary, results of the study identified Mn as a specific elicitor of the interferon-dependent pathways that can be mitigated by dietary polyphenols.

The adjuvanticity of manganese for microbial vaccines via activating the IRF5 signaling pathway

Manganese (Mn²⁺) has been reported to activate macrophages and NK cells, and to induce the production of type-I interferons (IFNs) by activating the cGAS-STING pathway. Few studies have been conducted on its adjuvanticity to microbial vaccines, and on the involvement of the interferon regulatory factor (IRF) 5 signaling pathway in the adjuvanticity. In this study, we demonstrated that Mn²⁺ could facilitate various microbial vaccines to induce enhanced antibody responses, and facilitate the influenza virus vaccine to induce protective immunity against the influenza virus challenge. When formulated in vaccines, Mn²⁺ could activate murine CD4⁺ T cells, CD8⁺ T cells, B cells and DCs, and induce the expression and phosphorylation of TANK-binding kinase 1 (TBK1) and IRF5 in the splenocytes of the immunized mice, resulting in the increased expression of type-I IFNs, TNF-α, B cell-activating factor of the TNF family (BAFF) and B lymphocyte-induced maturation protein-1 (Blimp-1). The induced TBK1 could recruit and bind the IRF5. Furthermore, the Mn²⁺ induced expression of IRF5 and Blimp-1 was prohibited by a IRF5 interfering oligonucleotide. The data suggest the Mn²⁺ could be used as a novel type of adjuvants for microbial vaccines, and the activation of IRF5 signaling pathway might involve in the adjuvanticity.

Impacts of Bovine Trace Mineral Supplementation on Maternal and Offspring Production and Health

Nutritional status can have major implications for animal health and production. Energy balance is easily determined using a body condition scoring system. This allows producers to readily adjust diets to meet an animal's needs. Far less obvious is an animal's trace mineral status, which is typically not assessed until an animal's performance falls below expectation or illness is detected. Trace mineral toxicities and deficiencies can manifest as reduced thriftiness and/or poor reproductive performance, resulting in economic consequences for producers. Maternal mineral status not only impacts dam heath, but also the health of subsequent offspring. Both the oocyte and embryo are susceptible to changes in maternal mineral status. This susceptibility is maintained throughout fetal development via placental control of nutrient transfer to the fetal system. Furthermore, maternal mineral status continues to impact offspring health via colostrum and milk quality. Herein we discuss the roles of trace minerals in bovine reproductive performance, maternal health, colostrum and milk quality, and offspring health.

The Impact of Dietary Transition Metals on Host-Bacterial Interactions

Transition metals are required cofactors for many proteins that are critical for life, and their concentration within cells is carefully maintained to avoid both deficiency and toxicity. To defend against bacterial pathogens, vertebrate immune proteins sequester metals, in particular zinc, iron, and manganese, as a strategy to limit bacterial acquisition of these necessary nutrients in a process termed "nutritional immunity." In response, bacteria have evolved elegant strategies to access metals and counteract this host defense. In mammals, metal abundance can drastically shift due to changes in dietary intake or absorption from the intestinal tract, disrupting the balance between host and pathogen in the fight for metals and altering susceptibility to disease. This review describes the current understanding of how dietary metals modulate host-microbe interactions and the subsequent impact on the outcome of disease.

Effect of High Dietary Manganese on the Immune Responses of Broilers Following Oral Salmonella typhimurium Inoculation

Manganese (Mn) is an essential nutrient for both host and pathogen. Recent studies have demonstrated the nutritional immunity of Mn against Salmonella infection in mammals. To investigate the effect of high dietary Mn on immune responses of broilers following Salmonella challenge, 144 1-day-old male broilers were fed a basal diet (containing 20.04 mg Mn/kg) plus an additional 40 (the control group) or 400 mg Mn/kg (the H-Mn group) for 7 days. The 72 broilers in each group were then orally inoculated with 5 × 10⁷ CFUs of Salmonella typhimurium (ATCC#14028) or phosphate-buffered saline. Peripheral blood, spleens, cecal tonsils, and bursa of Fabricius were collected from Salmonella-inoculated and Salmonella-noninoculated broilers (n = 6) at 2 days post inoculation (2 DPI) and 7 days post inoculation (7 DPI). Peripheral blood lymphocyte subpopulations were determined by flow cytometry. The messenger RNA (mRNA) abundance of genes was determined by quantitative real-time polymerase chain reaction. Salmonella counts were higher (P < 0.05) in the H-Mn group than that in the control group at 2 DPI in the cecal contents of Salmonella-inoculated broilers. High dietary Mn increased CD3⁺CD4⁺ and CD3⁺CD8⁺ percentages in the peripheral blood of Salmonella-inoculated broilers at 2 DPI. Salmonella inoculation increased interleukin (IL)-6 mRNA expression in spleens and bursa of Fabricius at 2 DPI and increased IL-1β and IL-6 mRNA expression in cecal tonsils at 7 DPI in the H-Mn group. These changes were not observed in the control group. High dietary Mn increased interferon-γ (IFN-γ) in spleens and decreased IFN-γ and IL-12 mRNA expression in cecal tonsils of Salmonella-inoculated broilers at 2 DPI. High dietary Mn decreased IL-17 mRNA expression in the bursa of Fabricius at 7 DPI, but increased this expression in cecal tonsils at 2 and 7 DPI in Salmonella-inoculated broilers. These results suggested that dietary Mn level affected T helper (Th) 1-cytokine reaction in spleens and cecal tonsils, and Th17-mediated immunity in cecal tonsils and the bursa of Fabricius of broilers when challenged with Salmonella.

Nitric-oxide generation induced by metals plays a role in their accumulation by Phallusia nigra hemocytes

Ascidians are good monitors for assessing water quality, since they filter large volumes of water; however, little is known about how xenobiotics, including metals, can affect ascidian hemocytes. Metals can be either toxic or beneficial to health, inducing many different responses. The response mechanism depends on the class of metals to which organisms are exposed: essential, nonessential, and borderline. To analyze the influence of metals from different classes on the protective mechanisms of an ascidian, we investigated the production of nitric oxide (NO) after exposure to various concentrations of Mg, Mn and Pb over different time periods. We also determined the amounts of each metal in the hemocytes. Our results indicated that especially Pb could stimulate NO production. Although Pb induced the highest NO production, cell viability was not severely altered in all Pb concentrations and time periods. Ascidians might serve as biomonitor for Pb, since their vanadocytes accumulate Pb.

Manganese deficiency or excess caused the depression of intestinal immunity, induction of inflammation and dysfunction of the intestinal physical barrier, as regulated by NF-κB, TOR and Nrf2 signalling, in grass carp (Ctenopharyngodon idella)

Intestinal mucosal immune components and mRNA levels of inflammatory cytokines, tight junction proteins, antioxidant enzymes and related signalling molecules in young grass carp (Ctenopharyngodon idellus) under dietary manganese (Mn) deficiency or excess were investigated. Fish were fed the diets containing graded levels of Mn [3.65-27.86 mg Mn kg(-1) diet] for 8 weeks. The results demonstrated that Mn deficiency significantly decreased the lysozyme and acid phosphatase (ACP) activities, up-regulated tumour necrosis factor α (TNF-α), interleukin 8 and the signalling factor nuclear factor-κB p65, and down-regulated interleukin 10 (IL-10), transforming growth factor β1, inhibitor of signalling factors κB-α and target of rapamycin mRNA levels in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI). However, Mn deficiency did not change the C3 content in the PI, whereas it decreased the C3 contents in the MI and DI. Additionally, Mn depletion also resulted in significantly low mRNA levels for tight junction proteins (claudin-b, claudin-c, claudin-15, occludin and zonula occludens-1), antioxidant enzymes (MnSOD, GPx and CAT) and NF-E2-related factor-2 in the intestines of fish. Excessive Mn exhibited toxic effects similar to Mn deficiency, where optimal Mn contents reversed those indicators. In conclusion, Mn deficiency or excess causes the depression of intestinal immunity, induction of inflammation and dysfunction of the intestinal physical barrier relating to NF-κB, TOR and Nrf2 signalling in grass carp. Furthermore, quadratic regression analysis at 95% maximum response of lysozyme and acid phosphatase activities in the distal intestine of young grass carp revealed the optimum dietary Mn levels to be 8.90 and 8.99 mg kg(-1) diet, respectively.

Genetic factors and manganese-induced neurotoxicity

Manganese (Mn), is a trace metal required for normal physiological processes in humans. Mn levels are tightly regulated, as high levels of Mn result in accumulation in the brain and cause a neurological disease known as manganism. Manganism shares many similarities with Parkinson’s disease (PD), both at the physiological level and the cellular level. Exposure to high Mn-containing environments increases the risk of developing manganism. Mn is absorbed primarily through the intestine and then released in the blood. Excessive Mn is secreted in the bile and excreted in feces. Mn enters and exits cells through a number of non-specific importers localized on the cell membrane. Mutations in one of the Mn exporters, SLC30A10 (solute carrier family 30, member 10), result in Mn induced toxicity with liver impairments and neurological dysfunction. Four PD genes have been identified in connection to regulation of Mn toxicity, shedding new light on potential links between manganism and PD.

Mechanisms of suppression of poly I:C-induced activation of NK cells by ethanol

We have previously reported that ethanol (EtOH) decreases polyinosinic-polycytidylic acid (poly I:C) and interleukin-2 (IL-2)-induced upregulation of natural killer (NK) cell lytic activity in mice. The present study was designed to determine if decreased production of or response to interferon-alpha (IFN-alpha) is involved and if this is associated with inhibited upregulation of perforin or granzyme B. Treatment of mice with poly I:C upregulated IFN-alpha and granzyme B, but not perforin, in the spleen. Administration of EtOH before poly I:C prevented the upregulation of IFN-alpha and granzyme B and decreased perforin levels. EtOH exposure in vivo rendered splenocytes less able to respond to IFN-alpha upon in vitro exposure to poly I:C. Exogenous IFN-alpha only partially prevented this decreased response. Thus, decreased production of and response to IFN-alpha as well as decreased levels of granzyme B and perforin are implicated in the diminished activation of NK cell lytic function in EtOH-treated mice.

Functional alterations of human blood monocytes after exposure to various nickel compounds in vitro: an effect on the production of hydrogen peroxide

It is generally known that nickel, a metal with distinct carcinogenic properties, can significantly alter the functioning of host defense mechanisms and impair various components of the immune system. In the present study the influence of 3 nickel salts on the production of hydrogen peroxide (H2O2) by human monocytes was examined in in vitro culture. Highly purified, resting and PMA-stimulated normal human monocytes were cultured with subtoxic concentrations of nickel subsulfide nickel sulfate, nickel acetate and manganese chloride. A portion of the cells was cultured with nickel-manganese salt mixture. Following culture cells were tested in an in vitro functional assay for H2O2 production. It has been shown that all nickel salts, used in micromole concentrations, suppressed H2O2 formation both in resting and PMA-stimulated monocytes, while it was not the case when manganese chloride was used for cell cultures. The strongest suppressive effect was manifested by nickel sulfate. The cells subjected to nickel-manganese mixture displayed H2O2 production similar to that of control ones. These results show that nickel salts in micromole concentrations exert a suppressive effect on oxygen-dependent antimicrobial system of human monocytes and manganese prevents this effect.

Manganese stimulates the oxidative burst of differentiated HL-60 cells

Incubation with manganese results in a twofold increase in the oxidative burst of differentiated HL-60 cells. This stimulation was characterized by examining the dose response, length of incubation time, and specificity of manganese. Manganese only stimulated the burst in cells induced to differentiated with retinoic acid and not in undifferentiated HL-60 cells. Incubation with manganese did not result in a greater number of differentiated cells. The maximum stimulation occurred at 0.2 mumol/L manganese. Stimulation of the oxidative burst required 96 h of incubation with manganese, since cells incubated with the same levels of manganese for the last 24 h of culture did not result in any stimulation. Magnesium, present in the incubation medium at physiological serum levels (820 mumol/L) also stimulated the oxidative burst, whereas iron (0.3 mumol/L), zinc (18 mumol/L), and copper (12 mumol/L) had no effect. To determine whether manganese and magnesium stimulated the burst differently, the initial rates of superoxide anion production was determined. The initial rate of the reaction proceeded rapidly in cells incubated with manganese, whereas there appeared to be a lag before magnesium-treated cells produced superoxide anion. Thus, manganese seems to stimulate the oxidative burst differently than magnesium.

The in vitro effects of mercury on peritoneal leukocytes (PMN and macrophages) from inbred brown Norway and Lewis rats

The present paper demonstrates that HgCl2 can affect rat peritoneal polymorphonuclear leukocyte (PMN) and macrophage (M phi) functions in vitro. In addition, we have noticed that these effects of mercury vary according to the rat strain: for example, HgCl2 stimulates H2O2 release from Lewis (LEW) but not Brown Norway (BN) PMN. Similarly, LEW M phi produce high levels of H2O2 when exposed to HgCl2 in vitro, whereas BN M phi do not. Finally, mercury inhibits erythrophagocytosis of both LEW and BN "resident" peritoneal M phi. Preliminary experiments using M phi from other rat strains have also shown that MAXX M phi are stimulated by HgCl2 to release H2O2 in vitro, whereas Yoshida M phi are inhibited. Differences in lymphocyte responses (e.g. delayed-type hypersensitivity reactions and mitogen stimulation) between rats of various strains are well known. To these examples one may now add variations in PMN and M phi responses to mercury and possibly other metals. Our results suggest that caution should be exercised in interpreting the outcome of immunotoxicity studies in experimental animals. In particular, outbred rats may not provide appropriate models, that might be better obtained by comparative investigations of rats from various inbred strains.

Host resistance to murine malaria in mice exposed to the adenosine deaminase inhibitor, 2'-deoxycoformycin

Resistance to infection with the nonlethal rodent malaria parasite Plasmodium yoelii 17XNL (Py 17XNL) is mediated by humoral, T-cell and accessory cell activity. The purpose this study was to profile host resistance to infection with this organism in mice exposed to 2'-deoxycoformycin (2dCF), a potent adenosine deaminase (ADA) inhibitor. Inhibition of ADA activity by 2dFC results in defective T-cell function and either suppression or augmentation of the humoral response, depending on whether 2dCF exposure precedes (suppression) or follows (augmentation) immunization. In this study, mice injected with 2dCF during the first five days of infection cleared the infection at the same time as controls, but had lower peak parasitemia than controls. Mice infected with the lethal variant of P. yoelii were more susceptible to infection when injected with 2dCF after infection, suggesting that 2dCF injection did not directly affect the parasite. Rather, suppression of parasitemia in 2dCF-treated mice may have been mediated by augmented humoral immunity, since 2dCF injection increases antibody responses when 2dCF injection follows antigen (in this case, parasite) injection. Conversely, in mice given 2dCF prior to infection, parasitemia peaked 2 days later and was eliminated more gradually than in control mice. Exposure to 2dCF did not deplete reticulocytes and thus temporarily limit parasitemia. Similarly, enrichment of NK cells or augmentation of macrophage phagocytic activity prior to infection were not sufficient to alter the pattern of infection. In contrast, the pattern of infection in mice treated with tilorone (a macrophage activator which also causes suppressed T-cell function) prior to infection was similar to that observed in 2dCF-exposed animals. These results indicate that 2dCF, given before or after infection, alters the host response to infection with Py17XNL. It appears that a combination of increased macrophage activity and altered T-cell activity contributed to the delay in peak parasitemia and clearance of infection in mice exposed to 2dCF before infection with Py17XNL.

Inhibitory effect of zinc on nickel subsulfide carcinogenesis in Fischer rats

The effects of zinc oxide (ZnO) and zinc acetate (ZnAcet) administered i.m. together with nickel subsulfide (Ni3S2), a potent muscle carcinogen, were observed over 66 weeks in male F344/NCr rats. The rats (20/group) received a single injection of 2.5 mg Ni3S2 (equal to 31 mumol Ni) alone or combined with different molar proportions of ZnO or ZnAcet (8-60 mumol Zn) into both thighs. One more group of rats given i.m. Ni3S2 received s.c. ZnO (60 mumol Zn) at the nape of the neck. Control rats were treated with i.m. ZnO (60 mumol Zn) or the injection vehicle, water. In rats given Ni3S2 alone the incidence of local tumors reached 100% in 40 weeks. In rats treated locally with Ni3S2 + ZnO or ZnAcet, the tumor incidence at week 40 was only 40-60%; it reached 85-100% in 66 weeks, with no significant differences among the treatments. Treatment with i.m. Ni3S2 + s.c. ZnO resulted in 100% muscle tumors at week 58. One local tumor was found in rats given ZnO alone and none in the water injected animals. Statistical analysis revealed highly significant differences in the tumor occurrence rates between rats treated with Ni3S2 alone and rats treated with Ni3S2 combined with ZnO or ZnAcet, whereas the final tumor incidences at week 66 were not different. The first tumors were found at weeks 24-31 regardless of the treatment. Hence, administration of zinc slows the carcinogenic process induced by nickel. This effect has a systemic character and is produced by both water-soluble and insoluble zinc compounds despite their different retention times in the muscle. The half-lives of ZnO and ZnAcet in the muscle were approx. 24 days and 2.5 days, respectively; that of Ni3S2 was 21 days. Zinc in either form exerted no apparent influence upon the retention of nickel at the injection site and did not significantly affect the early local cellular reactions to nickel.

Enhancement of natural killer cell activity and interferon production by manganese in young mice

The effect that MnCl2 has on murine splenic natural killer (NK) cell activity was investigated in infant (10 days old), pre-weanling (18 days old) and weanling (24 days old) C57BL/6J mice. A single intraperitoneal injection of 10, 20 or 40 micrograms MnCl2/g body weight caused a significant enhancement in NK activity, as determined by the in vitro 51Cr release assay. Comparable enhancement of NK activity was observed for age-matched mice injected intraperitoneally with polyinosinic polycytidylic acid (Poly I:C). Both MnCl2 and Poly I:C caused elevations in serum interferon levels. Time-course studies revealed that interferon levels returned to normal within 48 hours following injection with either MnCl2 or Poly I:C; however enhanced NK activity persisted for up to 48 hours in Poly I:C-injected mice and 72 hours in MnCl2-injected mice. The administration of rabbit anti-asialo GMl to MnCl2-injected mice completely abrogated the enhanced NK activity. In addition, the injection of rabbit anti-mouse interferon alpha, beta but not gamma completely abrogated the enhanced NK activity. In addition, the injection of rabbit anti-mouse interferon alpha, beta but not gamma completely abrogated the enhancement of NK activity by MnCl2 and to a lesser extent the enhancement of NK activity by Poly I:C. These results indicate that despite low levels of NK activity in pre-weanling mice, MnCl2 is capable of enhancing this activity by 8-9 fold. Furthermore, Mn-enhanced NK activity in these young mice appears to be mediated by the production of interferon alpha, beta.

Alteration of humoral and cellular immunity in manganese chloride-treated mice

Immunological effects of manganese chloride (MnCl2) were determined in male CD-1 mice injected (ip) daily with MnCl2 (0, 1, 3, or 10 mg/kg) for 4 wk. Liver and spleen weights increased in the 10-mg/kg MnCl2 treatment group. The weights of thymus, kidney, and adrenal glands were not affected by MnCl2 treatment. No significant differences in peripheral erythrocyte or leukocyte counts were observed; however, packed cell volumes decreased in the medium- and high-dose groups. Manganese treatment significantly increased the uptake of [3H]thymidine (3H-TdR) by cultured splenic cells. The lymphoproliferative responses to phytohemagglutinin (PHA) and concanavalin A (Con A) increased at all levels of MnCl2 exposure. No differences in the responses to lipopolysaccharide (LPS) were observed. Mixed lymphocyte responses increased significantly with exposure to 10 mg MnCl2/kg. Another immunological alteration induced by MnCl2 was a dose-dependent immunosuppressive effect on the development of antibody-forming cells. The production of anti-sheep red blood cell antibody (alpha-SRBC) nearly ceased following exposure to 10 mg MnCl2/kg. This effect was apparently reversible, as the number of plaque-forming cells in the 10-mg/kg treatment group increased after MnCl2 treatment had been halted for 2 wk. The alpha-SRBC titer also decreased significantly in the 10-mg/kg treatment group, corresponding to the reduction of antibody producing cells. MnCl2 treatment was immunomodulatory to the reduction of antibody producing cells. MnCl2 treatment was immunomodulatory in male CD-1 mice, as indicated by the increase in mitogen and mixed lymphocyte responses and decrease in antibody production.

Effects of manganese, calcium, magnesium, and zinc on nickel-induced suppression of murine natural killer cell activity

The effects that divalent metals have on nickel-induced suppression of natural killer (NK) cell activity were studied in mice. Male CBA/J mice were given a single intramuscular injection of metal salt on a body weight basis. The metal doses used were the following: nickel chloride, 4.5-36 micrograms/g; manganese chloride, 20-80 micrograms/g. Twenty-four hours after metal injection, splenic NK cell activity was assessed using a 51Cr-release assay. Ni significantly (p less than 0.01) suppressed NK activity, while Mn significantly (p less than 0.01) enhanced NK activity. No alteration in NK activity was observed in mice injected with Mg, Ca, or Zn. Since these divalent metals have been shown to have antagonistic effects on Ni-induced carcinogenicity and toxicity, they were used in combination with Ni to determine if such antagonisms exist for NK cell activity. The injection of Ni and Mn in combination at a single site resulted in the enhancement of NK activity, although this enhancement was at a level below that observed following the injection of Mn alone. Injection of Mg, Zn, or Ca in combination with Ni did not affect NK activity compared to saline controls. In contrast, the injection of Ni in one thigh followed immediately by Mn, Mg, Ca, or Zn into the other thigh resulted in significant suppression of NK activity for all metals compared with saline controls. An interesting finding was that the injection of Ni followed immediately by Mn into the opposite thigh resulted in even greater reductions in NK activity than Ni alone. Suppression of NK activity by Ni and Mn injected at separate sites was not seen when Mn injection preceded Ni injection by 1 h. These data indicate that both the divalent metal and the timing of its injection relative to Ni injection are critical for altering Ni-induced suppression of NK cell activity.

Modification of tissue distribution of trace elements by cyclosporin in rats

Cyclosporin-induced hypomagnesaemia, as observed in patients, could also be induced in rats by intramuscular administration of the drug (20 mg/kg/d) for 12 d. moreover, cyclosporin administration induced modifications in the concentrations of other elements in tissues, particularly an increase in Mg, Cu, and Zn in the thymus and an increase in Mo in the spleen and Sr in the liver.

In vitro augmentation of natural killer cell activity by manganese chloride

The in vitro cultivation of murine spleen cells with MnCl2 resulted in the enhancement of natural killer (NK) cell activity as measured in a 4-h 51Cr-release assay. Optimal enhancement of NK activity was observed at concentrations of 10-20 micrograms MnCl2/culture (72-144 microM Mn2+). Enhancement of NK activity by MnCl2 was not associated with any changes in the number or viability of cells following culture. The addition of antiasialo GM1 antibody and complement to spleen cell cultures completely abrogated the enhancement of NK activity by MnCl2. The enhancement of NK activity by MnCl2 in vitro was accompanied by interferon induction. The addition of rabbit antimouse interferon to spleen cells cultured with MnCl2 reduced NK activity. NK activity in cultures treated with MnCl2 was also reduced upon removal of plastic adherent cells. However, restoration of enhanced NK activity by addition of adherent cells to nonadherent cells in the presence of MnCl2 was not observed. Similar effects of NK activity were observed with polyinosinic-polycytidylic acid (Poly I X C), a known interferon inducer and NK enhancer. The results demonstrate that murine splenic NK activity is enhanced in vitro by MnCl2 and that this enhancement may be mediated by interferon induction. The results also suggest that in vitro enhancement of NK activity by MnCl2, as with Poly I X C, may require participation of an adherent cell population for NK augmentation.