Impact of aging on immune modulation by tumor

 Tumor development and aging can each alter immune competence. The present study aimed to determine the impact of Lewis lung carcinoma (LLC) presence on immune parameters of middle-aged (averaging 6.5 months) versus aged (averaging 21.3 months) mice. An age-associated decline in the CD4⁺ cell frequency was seen in freshly isolated spleen and lymph node cells, as well as in cultures stimulated with immobilized anti-CD3. This decline was not further exacerbated by tumor presence. What was prominently inhibited by tumor was the capacity of either splenic or lymph node CD4⁺ cells to become stimulated to express IFN-γ. Spleen and lymph node cultures from aged tumor-bearing mice had the lowest frequency of CD4⁺IFN-γ ⁺ cells and the least amount of secreted IFN-γ. CD8⁺ cells were not affected by aging, but tumor presence reduced the induction of CD8⁺IFN-γ ⁺ cells in lymph node cultures. We previously showed that LLC growth stimulates myelopoiesis, as seen by splenomegaly and the mobilization of immune inhibitory CD34⁺ progenitor cells. Tumor presence in middle-aged mice reduced spleen cell blastogenesis, which was mediated by CD34⁺ cells. Aged mice had reduced blastogenesis, and this was further reduced by presence of tumor. However, neither the age-associated immune dysfunction nor the tumor-induced immune suppression in aged mice was due to CD34⁺ progenitor cells. These studies show how tumor presence can further compromise the immune dysfunction that accompanies aging. In addition, they show that aging impacts on the mechanisms by which tumors inhibit T-cell capabilities, with myelopoiesis-associated CD34⁺ cells mediating the immune depression of middle-aged tumor-bearers and an independent mechanism being responsible for the immune depression in aged tumor-bearing mice. Received: 19 March 2001 / Accepted: 4 May 2001     

Effect of root canal sealers on mouse peritoneal macrophage functions

Three root canal filling materials, viz. calcium hydroxide-based cement (Apexit, resin-based cement (AH-plus) and glass-ionomer based material (Ketac Endo) were tested for their influence on several functions of peritoneal macrophages from Balb/c mice. Macrophage functions were evaluated by the adherence, phagocytic, candidacidal and Nitro blue tetrazolium-dye assays. Ketac-Endo enhanced all macrophage functions in the first 2 d (p < or = 0.05), when compared to the positive control, but this effect had changed after 7 and 14 d, causing inhibition of these functions. Other materials suppressed substrate adherence capacity and phagocytosis, while significantly stimulating macrophage microbicidal activity (p < or = 0.05) in a time-dependent manner.     

Effect of vitamin K3 on macrophage functions and intracellular calcium

1. The effect of vitamin(vit) K3 on guinea-pig macrophage functions was studied. 2. Vit K3 inhibited macrophage locomotion, phagocytosis and lysosomal enzyme release. 3. Vit K3 inhibited the rise in the intracellular free calcium level induced by stimuli at the concentration at which vit K3 suppressed functions. 4. These results suggest that vit K3 inhibits macrophage functions through the interference with the mobilization of intracellular calcium.     

Effect of streptococcal pyrogenic exotoxin on rabbit macrophage functions in vitro: mediation by splenic lymphocytes

Streptococcal pyrogenic exotoxin (SPE) showed no direct effect on rabbit macrophage functions in vitro. However, when splenic lymphocytes were added to macrophage cultures, SPE caused marked augmentation of glucose consumption and superoxide anion production, and concomitant inhibition of phagocytosis without loss of cell viability. The SPE effects were demonstrated to be mediated by a soluble factor(s) released from the splenic lymphocytes in response to SPE stimulus.     

ACTH and brain membrane phosphorylation: a model for modulation by neuropeptides

It has been hypothesized that changes in the phosphorylation of synaptic membrane constituents (proteins and lipids) may affect transmission in certain types of synapses. In this paper some of the recent evidence that neuropeptides like ACTH may bring about their behavioral activity by influencing brain protein and lipid phosphorylation is reviewed. An ACTH-sensitive, cAMP-independent protein kinase was isolated from rat brain synaptosomal plasma membranes. This enzyme was partially characterized and it was observed that its activity greatly depended on the presence of calcium ions. One of its substrate proteins B-50 (MW 48,000; IEP 4.5) may play a key role in the turnover of a special class of membrane phospholipids i.e. the (poly)phosphoinositides. Evidence was obtained to suggest that the degree of phosphorylation of the B-50 protein determines the conversion of diphosphoinositol to triphosphoinositol. A model which links the protein phosphorylation to lipid phosphorylation and which points to a functional role for peptides in the regulation of the permeability of brain membranes for calcium ions will be discussed. As the structure-activity relationship for the peptide effects on grooming behavior closely resembles that on phosphorylation, it is assumed that this neurochemical event may indeed be of relevance to the biological activity of the peptide. As the ion permeability may be altered by the peptide it can be suggested that this may lead to modulation of transynaptic information processing in the brain.     

Changes in the macrophage function with aging

Changes in the adherence, opsonization, phagocytosis, nitroblue tetrazolium reduction and antibody-dependent cell cytotoxicity of peritoneal macrophages were observed with aging in BALB/C mice. A decrease in all the parameters studied, except for the reduction capacity of nitroblue tetrazolium, which increased with aging, was found in the long-lived mice. The role of the macrophage in immune hyporesponsiveness with aging is discussed.     

In vivo modulation of atypical mycobacterial infection: adjuvant therapy increases resistance to Mycobacterium avium by enhancing macrophage effector functions

Susceptible BALB/c mice were infected iv with a strain of Mycobacterium avium and infused with different biological response modifiers (BRM) in a gel delivery system so as to modify the progression of the infection in a beneficial fashion. Infusion of IL-2 or IL-4 in hydrophobic gels led to no significant enhancement of resistance. Infusion of muramyl dipeptide in hypromellose led to a significant enhancement of resistance against the M. avium, as seen by a significant reduction of colony-forming units (CFU) in the spleens of infected mice. Similarly, infusion of interleukin-1 beta in hypromellose in infected mice led to a significant reduction in CFU counts in the organs of mice. The mechanism(s) responsible for this enhanced resistance was studied further. It was found that infected mice developed profound immunosuppression, as judged by mitogenic and antigenic stimulation. Mice infused with MDP/hypromellose developed a similar immuno-suppression, suggesting that this adjuvant immunotherapy did not act by stimulating a T-cell response or by abrogating a putative suppressive phenomenon. Macrophages from mice infused with MDP alone were no more bacteriostatic for a virulent M. avium than control cells. However, macrophages from infected mice infused with MDP/hypromellose were more bacteriostatic for M. avium than cells from mice infected with M. avium and infused with the hydrophobic gel only. Overall, these results suggest that adjuvant immunotherapy is beneficial in M. avium infections.     

Glucocorticoid modulation of lymphokine-induced macrophage proliferation

The ability of glucocorticoids to modify lymphokine-induced macrophage proliferation, an in vitro correlate of cellular immunity in the guinea pig, was investigated. Lymphocyte production of macrophage mitogenic factor (MMF) was decreased in the presence of physiological concentrations of glucocorticoids. Inhibition was concentration dependent (IC₅₀ of triamcinolone acetonide (TA): 2 × 10^?9M), glucocorticoid specific, and reversed by cortexolone. In contrast, pharmacological concentrations of glucocorticoids were necessary to inhibit macrophage proliferation induced by suboptimal dilutions of MMF. This inhibition was concentration dependent (IC₅₀ of TA: 4 × 10^?7M), glucocorticoid specific, and reversed by cortexolone. At supraoptimal dilutions of MMF, glucocorticoids caused a twofold potentiation of MMF-induced macrophage proliferation. Potentiation was concentration dependent (EC₅₀ of TA: 3 × 10^?8M), glucocorticoid specific, reversed by glucocorticoid antagonists, and occurred in the presence of indomethacin. Thus, glucocorticoids regulate both the initiation and effector phases of this in vitro model of delayed hypersensitivity. However, the results indicate that the major mechanism of glucocorticoid-mediated anti-inflammatory action occurs at the level of the MMF-producing lymphocyte rather than at the effector macrophage, as MMF-induced proliferation is likely controlled by opposing glucocorticoid-sensitive mechanisms.     

Effect of fumonisins on macrophage immune functions and gene expression of cytokines in broilers

Fumonisin (FB1), a mycotoxin, is produced by Fusarium moniliforme and F. proliferatum. A prevalence survey in Taiwan by our laboratory showed that there was a contamination rate of 40% in domestic animal feeds, and the average contaminated level was 4.5 mg/kg. Ninety-six birds were allotted into four treatments fed with diets containing 0 (control), 5, 10, or 15 mg/kg of FB1 for three weeks. The results showed that the growth performance was not influenced by the FB1 challenge, but relative bursa weight was significantly decreased. The activity of serum aspartate aminotransferase, and the serum levels of albumin and cholesterol were significantly elevated by the FB1 challenges. When broilers were stimulated with injection of lipopolysaccharides, mRNA abundance (determined by semi-quantitative RT-PCR) interleukin-1beta (IL-1beta), IL-2, interferon-alpha (IFN-alpha), IFN-gamma, and inducible nitric oxide synthase (iNOS) reached a plateau at 3 h, and declined at 6 h. A FB1 challenge for three weeks increased cytokine mRNA abundance in broilers. The results also showed that 15 mg FB1 per kg feed significantly inhibited the expression of IL-1beta, IL-2, IFN-alpha, IFN-gamma, but had no effect on iNOS. The macrophage functional profile was significantly changed under an exposure of 15 mg FB1 per kg for three weeks. Taken together, our results suggest that FB1 up to 15 mg/kg does not affect growth performance, but impairs some parameters of blood biochemistry and the immunocompetence in broilers.     

Bidirectional effect of met-enkephalin on macrophage effector functions

Summary Met-enkephalin (ME) exerts a bimodal effect on functional activities of rat peritoneal macrophages (PM); in a range of low concentration (10^-9-10^-7 M) antibody dependent cellular cytotoxicity (ADCC)was markedly stimulated with a simultaneous decrease of Fc receptor (FcR) mediated phagocytosis while the opposite was observed at 10^-6-10^-5 M concentrations.Studying the possible underlying mechanism(s) the followings were recorded: (1) ME in all applied concentrations induced an early Na⁺ influx which was followed by a Ca²⁺ efflux in the range of low concentrations. In the range of high concentrations Na⁺ influx was accompanied by a Ca²⁺ influx. (2) ME at 10^-8 M concentration induced a rise in cGMP level with a plateau in the 60–120th min of incubation. This effect was prevented by 10^-5 M of naloxone. At 10^-6 M concentration a transient rise of cAMP level was recorded which was not affected by naloxone. (3) Verapamil in 10^-6 M abolished both the Ca²⁺ influx and the rise in cAMP level induced by 10^-6-10^-5 M ME but not the rise in cGMP level induced by lower ME concentrations. (4) cAMP elevation by high ME concentrations was abolished by enkephalinase inhibitory puromycin. (5) PM-enkephalinase as assessed by the cleavage of fluorogenic substrate L-alanine beta naphthylamide (ABNA), was inhibited by 10^-6-10^-5 M of ME. This inhibition was abolished by verapamil, but not affected by naloxone. In the range of low concentrations ME appears to act on specific delta opioid receptors and its action is positively coupled to guanylate cyclase. In relatively higher concentrations ME-action is not mediated by specific delta opioid receptors and it appears to involve Ca²⁺ influx, adenylate cyclase activation as well as the processing of hormone by PM-enkephalinase.     

Inhibition of normal rat macrophage functions by soluble tumor products

Summary The phagocytic and chemotactic activities of normal rat peritoneal macrophages were inhibited by sera from tumor-bearing rats (TBR) and 3 M KCl extracts of tumor mass. However, sera from Corynebacterium parvum- or Listeria monocytogenes-treated TBR did not inhibit phagocytosis. On the other hand, sera from C. parvum-treated, but not from L. monocytogenes-treated TBR still inhibited the chemotactic response of the normal macrophages. Furthermore, 3 M KCl extracts of tumors from C. parvum-treated TBR did not inhibit phagocytosis and chemotactic response of the same cells. Similar results were obtained with extracts of tumor masses from L. monocytogenes-treated rats. It is suggested that treatment with bacterial immunomodulators can influence the release from neoplastic cells of soluble products influencing normal macrophage functions.     

Copper modulation of macrophage cyclooxygenase metabolite synthesis

The effect of copper on the release of cyclooxygenase metabolites from starch elicited, rat, peritoneal macrophages was investigated. Copper sulphate, in the range 10(-6)-10(-5) M, inhibited the formation of prostaglandin (PG) E2 and thromboxane (Tx) B2, the stable metabolite of TxA2, in a dose dependent manner but had no effect on the production of 6-keto-PGF1 alpha, the stable product of prostacyclin. At higher concentrations (5 x 10(-5) and 10(-4) M) the synthesis of all three metabolites of arachidonic acid (AA) was stimulated as was the release of radioactivity from macrophages prelabelled with 14C AA. Copper had no effect on the metabolism of exogenous AA however. At 10(-4) M copper also stimulated secretion of the lysosomal enzyme, beta-glucuronidase (GUR). Copper nitrate (10(-4) M), but not zinc sulphate, also stimulated eicosanoid formation and lysosomal enzyme release. Our results are consistent with the idea that copper stimulates eicosanoid formation via an effect on PL activity.     

Innate immunity in aging: impact on macrophage function

Innate and adaptive immune functions decline with age, leading to increased susceptibility to infectious diseases and cancer, and reduced responses to preventive vaccination in the elderly population. Macrophages function as 'pathogen sensors' and play an important role in the initiation of inflammatory responses, elimination of pathogens, manipulation of the adaptive immune response and reparation of damaged tissue. In this paper, we review the literature addressing the impact of aging on the macrophage population.     

In vitro modulation of macrophage tumoricidal activity

Summary NaIO₄ treatment of mouse adherent peritoneal cells or lymphocyte-free cloned macrophages enhances their cytotoxic and tumoricidal activity. 5×10^–3 M NaIO₄ treatment of nontumoricidal BCG-activated macrophages renders them completely tumoricidal, whereas the same treatment of stimulated (peptone-normal) macrophages renders them weakly tumoricidal. Addition of LPS in nanogram quantities too low to enhance tumor cell killing by untreated peptone-normal macrophages causes NaIO₄-treated peptone-normal macrophages to be maximally tumoricidal. The activating action of NaIO₄, MAF, or LPS can be potently, but inconsistently, blocked or reversed by the reducing agent NaBH₄ or the aldehyde-reacting agent dimedone. NaIO₄ treatment of lymphocyte-free macrophage colonies does not make them cytotoxic, but NaIO₄-treated colony macrophages are cytotoxic for tumor cells when cultured in 10 ng/ml LPS (an amount of LPS inadequate to render untreated colony macrophages cytotoxic). Supernatants of NaIO₄-treated adherent peritoneal cells contain MAF activity. Thus, the NaIO₄-induced enhancement of peritoneal cell tumoricidal activity may result from both direct NaIO₄ activating effects on macrophages and indirect NaIO₄ effects through NaIO₄-induced MAF production.     

Effect of hypoxia on macrophage infection by Leishmania amazonensis

In the present study, we compared the effect of 5% oxygen tension (hypoxia) with a normal tension of 21% oxygen (normoxia) on macrophage infection by the protozoan parasite Leishmania amazonensis. Macrophages from different sources (human cell line U937, murine cell line J774, and murine peritoneal macrophages) exposed to hypoxia showed a reduction of the percentage of infected cells and the number of intracellular parasites per cell. Observations on the kinetics of infection indicated that hypoxia did not depress L. amazonensis phagocytosis but induced macrophages to reduce intracellular parasitism. Furthermore, hypoxia did not act synergistically with gamma-interferon and bacterial lipopolysaccharides in macrophages to induce killing of parasites. Experiments also indicated no correlation between nitric oxide production and control of infection in macrophages under hypoxic condition. Thus, we have provided the first evidence that hypoxia, which occurs in various pathological conditions, can alter macrophage susceptibility to a parasitic infection.     

Role of prostaglandins on the regulation of macrophage proliferation and cytotoxic functions

The data presented show different effects of prostaglandins on proliferation and cytotoxic effector functions of murine bone-marrow derived mononuclear cells. Colony stimulating factor (CSF)-dependent proliferation of colony forming unit-cells (CFU c) was inhibited by PGE₁, PGE₂ and PGB₂. Lymphokine induced cytotoxicity and antibody mediated cytotoxicity (ADCC) of monocytes and macrophages were also affected by PG. We conclude that PGE₂ may regulate macrophage mediated tumorcell-lysis mainly at the induction phase.If there processes function in vivo, one would therefore expect high affinity binding sites for PGE₂ on macrophages. The existence of a receptor for PGE₂ one murine bone marrow derived macrophages is described.     

Role of prostaglandins on the regulation of macrophage proliferation and cytotoxic functions

The data presented show different effects of prostaglandins on proliferation and cytotoxic effector functions of murine bone-marrow derived mononuclear cells. Colony stimulating factor (CSF)-dependent proliferation of colony forming unit-cells (CFU c) was inhibited by PGE1, PGE2 and PGB2. Lymphokine induced cytotoxicity and antibody mediated cytotoxicity (ADCC) of monocytes and macrophages were also affected by PG. We conclude that PGE2 may regulate macrophage mediated tumorcell-lysis mainly at the induction phase. If these processes function in vivo, one would therefore expect high affinity binding sites for PGE2 on macrophages. The existence of a receptor for PGE2 one murine bone marrow derived macrophages is described.     

Effect of cyclophosphamide and 61.22 GHz millimeter waves on T-cell, B-cell, and macrophage functions

The present study was undertaken to investigate whether millimeter waves (MMWs) at 61.22 GHz can modulate the effect of cyclophosphamide (CPA), an anti-cancer drug, on the immune functions of mice. During the exposure each mouse's nose was placed in front of the center of the antenna aperture (1.5 x 1.5 cm) of MMW generator. The device produced 61.22 +/- 0.2 GHz wave radiation. Spatial peak Specific Absorption Rate (SAR) at the skin surface and spatial peak incident power density were measured as 885 +/- 100 W/kg and 31 +/- 5 mW/cm(2), respectively. Duration of the exposure was 30 min each day for 3 consecutive days. The maximum temperature elevation at the tip of the nose, measured at the end of 30 min, was 1 degrees C. CPA injection (100 mg/kg) was given intraperitoneally on the second day of exposure to MMWs. The animals were sacrificed 2, 5, and 7 days after CPA administration. MMW exposure caused upregulation in tumor necrosis factor-alpha (TNF-alpha) production in peritoneal macrophages suppressed by CPA administration. MMWs also caused a significant increase in interferon-gamma (IFN-gamma) production by splenocytes and enhanced proliferative activity of T-cells. Conversely, no changes were observed in interleukin-10 (IL-10) level and B-cell proliferation. These results suggest that MMWs accelerate the recovery process selectively through a T-cell-mediated immune response.