Bidirectional effects of IFN-gamma on growth of Mycobacterium avium complex in murine peritoneal macrophages

Increased phagocytosis and growth inhibition of Encephalitozoon cuniculi by LPS-activated J774A.1 murine macrophages

Encephalitozoon cuniculi is an obligate macrophage parasite of vertebrates that commonly infects rodents, monkeys, dogs, birds, and humans. In the present study, we aimed to assess the phagocytosis and intracellular survival of E. cuniculi spores using untreated and lipopolysaccharide (LPS)-activated J774A.1 murine macrophages and assess the macrophage viability. The experimental groups comprised untreated spores, spores killed by heat treatment at 90 °C, and spores killed by treatment with 10% formalin. LPS-activated macrophages significantly increased the phagocytosis of spores and reduced their intracellular growth after 24 and 48 h (P < 0.01); however, after 72 h, we observed an increase in spore replication but no detectable microbicidal activity. These results indicate that LPS activation enhanced E. cuniculi phagocytosis between 24 and 48 h of treatment, but the effect was lost after 72 h, enabling parasitic growth. This study contributes to the understanding of the phagocytosis and survival of E. cuniculi in murine macrophages.

IFN-γTherapy of Tuberculosis and Related Infections

It is firmly established that interferon-gamma (IFN-gamma) plays a mandatory role in acquired protective immunity to pathogenic mycobacteria and other intracellular pathogens. Therefore, it seems conceivable that application of recombinant IFN-gamma could be exploited for the treatment of tuberculosis. However, the results of experimental studies and clinical trials, conducted mostly in patients with multidrug resistant (MDR) disease, have thus far been only moderately encouraging. Further studies are now needed to determine if a greater clinical benefit from IFN-gamma could be obtained for the prophylactic treatment of latent tuberculosis infection and for shortening of the protracted standard chemotherapy regimen. Thus, aerosolized IFN-gamma treatment could be particularly beneficial to AIDS patients at high risk of developing mycobacterial infections, that is, those with significantly declined CD4(+) T cell counts. This review describes the current state of research on IFN-gamma interventions in tuberculosis and related infections and highlights some of the future opportunities.

Induction of persistent in vivo resistance to Mycobacterium avium infection in BALB/c mice injected with interleukin-18-secreting fibroblasts

Interferon-gamma (IFN-gamma) is closely associated with the generation of cell-mediated immunity and resistance to intracellular parasites. Interleukin-18 (IL-18) is known to strongly induce IFN-gamma production by T cells and natural killer (NK) cells. To determine whether the paracrine secretion of IL-18 can efficiently stimulate the resistance to Mycobacterium avium complex (MAC) infection, 3T3 fibroblasts were stably transfected to secrete bioactive IL-18 and their effects on MAC infection were investigated in genetically susceptible BALB/c mice, compared with that of free recombinant IL-18. Immunization with IL-18-secreting fibroblasts (3T3/IL-18) during intranasal infection with MAC resulted in a significant decrease in bacterial load of lung during the entire 8-week observation period, while rIL-18 reduced the bacterial load at initial 1 week but not by 8 weeks postinfection. Immunization with the 3T3/IL-18 cells induced and maintained significantly higher levels of cytotoxic activity and nitric oxide production by lung cells than those of rIL-18 immunization. Furthermore, lung cells in mice injected with the 3T3/IL-18 cells showed persistent production of IFN-gamma throughout the 8-week period, suggesting that the 3T3/IL-18 cells induced the resistance to MAC infection via IFN-gamma production. This work suggests that IL-18-secreting fibroblasts may serve as a vehicle for paracrine secretion of IL-18 in immunotherapy of MAC infection.

Differential effects of synthetic indoloquinolizines on in vitro rat lymphocyte and macrophage functions

Indoloquinolizines are natural alkaloid indole products grouped as beta-carbolines. These compounds are commonly associated with neurological activities, but little is known about their role as immunomodulating agents. The present study was undertaken to evaluate the effects of synthetic indoloquinolizines on in vitro parameters of rat lymphocyte and macrophage functions. It was observed that proliferation of thymic lymphocytes was significantly (p<0.05) increased (20-30% increase) by dihydro-indoloquinolizinium chloride (2). dihydro-indoloquinolizinyl-ethanone (3). and dimeric dihydro-indoloquinolizinium dichloride (6). whereas dimeric indoloquinolizine (7). caused up to 40% increase in lymphoproliferation at concentrations ranging from 10(-11) to 10(-5) M, compared with untreated control. In contrast, indoloquinolizinium chloride (4) and indoloquinolizine (5). were toxic for lymphocytes at concentrations from 10(-9) to 10(-5) M, and compounds 6 and 7 were toxic at 10(-5) M. In addition, nitric oxide production by LPS-treated peritoneal macrophages was significantly (p<0.05) increased (up to 30% increase) by compounds 4 and 5 at concentrations of 10(-11) to 10(-5) M, and 10(-5) M, respectively; however, compounds 6 and 7 were toxic for macrophages at all concentrations tested. Furthermore, TNF-alpha production was also significantly increased (p<0.01) by compounds 4 and 5 (up to 30-fold increase) compared with untreated control. These novel synthetic indoloquinolizines could serve as immunotherapeutic agents by selectively increasing the pool of activated T lymphocytes or stimulating macrophage functions, with potential use in the treatment of infectious diseases including AIDS and cancer.

Differential responses of bovine macrophages to Mycobacterium avium subsp. paratuberculosis and Mycobacterium avium subsp. avium

Mycobacterium avium subsp. paratuberculosis and Mycobacterium avium subsp. avium are antigenically and genetically similar organisms; however, they differ in their virulence for cattle. M. avium subsp. paratuberculosis causes a chronic intestinal infection leading to a chronic wasting disease termed paratuberculosis or Johne's disease, whereas M. avium subsp. avium causes only a transient infection. We compared the response of bovine monocyte-derived macrophages to ingestion of M. avium subsp. paratuberculosis and M. avium subsp. avium organisms by determining organism survival, superoxide and nitric oxide production, and expression of the cytokines tumor necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma), interleukin-8 (IL-8), IL-10, IL-12, and granulocyte-monocyte colony-stimulating factor (GM-CSF). Unlike M. avium subsp. paratuberculosis, macrophages were able to kill approximately half of the M. avium subsp. avium organisms after 96 h of incubation. This difference in killing efficiency was not related to differences in nitric oxide or superoxide production. Compared to macrophages activated with IFN-gamma and lipopolysaccharide, macrophages incubated with M. avium subsp. paratuberculosis showed greater expression of IL-10 and GM-CSF (all time points) and IL-8 (72 h) and less expression of IL-12 (72 h), IFN-gamma (6 h), and TNF-alpha (6 h). When cytokine expression by macrophages incubated with M. avium subsp. paratuberculosis was compared to those of macrophages incubated with M. avium subsp. avium, M. avium subsp. paratuberculosis-infected cells showed greater expression of IL-10 (6 and 24 h) and less expression of TNF-alpha (6 h). Therefore, the combination of inherent resistance to intracellular degradation and suppression of macrophage activation through oversecretion of IL-10 may contribute to the virulence of M. avium subsp. paratuberculosis in cattle.

Immunoenhancing properties of Plantago major leaf extract

Plantago major (PM), also known as plantain, is a weed found in temperate zones worldwide. PM leaves have been associated with various biological properties ranging from antiinflammatory, antimicrobial and antitumour to wound healing. However, its mechanism of action associated with boosting of the immune function remains to be elucidated. We found that endotoxin-free methanol extracts from PM leaves, at doses of 50, 100, 250, and 500 microg/mL, were associated with 4.4 +/- 1, 6 +/- 1, 12 +/- 0.4, and 18 +/- 0.4-fold increases of nitric oxide (NO) production, and increased TNF-alpha production (621 +/- 31, 721 +/- 36, 727 +/- 36, and 1056 +/- 52 U/mL, respectively) by rat peritoneal macrophages, in the absence of IFN-gamma or LPS. NO and TNF-alpha production by untreated macrophages was negligible. In addition, PM extracts potentiated Con A-induced lymphoproliferation (3- to 12-fold increases) in a dose-dependent fashion, compared with the effect of Con A alone. The regulation of immune parameters induced by plant extracts may be clinically relevant in numerous diseases including chronic viral infections, tuberculosis, AIDS and cancer.

Differential effects of buprenorphine and morphine on immune and neuroendocrine functions following acute administration in the rat mesencephalon periaqueductal gray

The effects of the mu-opioid receptor agonists buprenorphine and morphine on immune and neuroendocrine functions through acute action in the rat mesencephalon periaqueductal gray (PAG) were evaluated. Buprenorphine is an analgesic recently approved for the treatment of drug dependency. In this study, it was shown that injection of an equianalgesic dose of buprenorphine (related to morphine) into the ventral-caudal PAG did not alter splenic NK cell, T cell, and macrophage functions, whereas morphine significantly (p<0.001) suppressed splenic NK cell cytotoxic activity (14-50% reduction), splenic and thymic T cell proliferation to concanavalin A (Con A, 43-76% reduction), antiTCR (T cell receptor) (85% reduction) and IL-2 (36-48% reduction), and macrophage functions including nitric oxide (36-41% reduction) and TNF-alpha production (26%), and phagocytosis of Candida albicans (39%). In addition, buprenorphine was associated with significant (p<0.0001) reductions in adrenocorticotropic hormone (ACTH) and corticosterone (CSO) plasma levels, without altering norepinephrine (NE) and serotonin splenic dialysate levels. In contrast, morphine significantly (p<0.0001) increased glucocorticoid and catecholamine levels in plasma and spleen dialysates, respectively. These results indicated that buprenorphine did not activate either the hypothalamic-pituitary-adrenal (HPA) axis with glucocorticoid release, or the sympathetic nerve (SNS) activity with bioamine production, and was not associated with immunosuppression. The lack of effects of buprenorphine on neuroendocrine systems may be related to its partial agonist properties, the absence of effects on immune system function, and may be associated with the reduction in craving observed in addictive disorders.

Suppression of splenic macrophage functions following acute morphine action in the rat mesencephalon periaqueductal gray

Morphine action in the periaqueductal gray (PAG) matter of the mesencephalon suppresses T cell proliferation and NK cell activity through actions at mu opioid receptors. We investigated the effect of acute microinjection of morphine in the rat PAG on macrophage function. We found that morphine injection in the PAG significantly (p <.01) suppressed nitric oxide production by untreated (82 +/- 23% suppression), IFN-gamma-primed (57 +/- 11% suppression), and LPS-activated (50 +/- 7% suppression) splenic macrophages and did not alter macrophage viability. In contrast, IFN-gamma- and LPS-activated macrophages from PAG-injected saline rats generated an increased output of nitric oxide, which was associated with significant (p <.01) reduction in cell viability. Morphine significantly (p <.01) inhibited TNF-alpha production by LPS-activated macrophages (28 +/- 8% inhibition compared with PAG-injected saline rats). In addition, morphine significantly (p <. 05) inhibited phagocytosis of Candida albicans by resident macrophages (40 +/- 20% inhibition compared with that of macrophages from PAG-injected saline rats). Responses of resident or activated macrophages from PAG-injected saline and untreated control groups did not differ significantly. The results of this ex vivo study suggest that suppressive effects of morphine on macrophage functions may contribute to increased susceptibility to infectious diseases and cancer associated with drug abuse.