C. Bentivoglio

Recombinant human prolactin induces protection against Salmonella typhimurium infection in the mouse: role of nitric oxide

In the present study, we demonstrated that repeated treatment with recombinant human prolactin (rhPRL) protected mice against Salmonella typhimurium infection. The protective activity was statistically significant, dose-dependent and present only when rhPRL treatments were performed before the infection. This activity was probably related to the observed increases in phagocytosis and intracellular killing of peritoneal macrophages induced by the hormonal treatment. The number of peripheral leukocytes was not modified, excluding a mobilization of cells from other compartments. A decrease in the mortality rate after challenge was also observed in mice treated with the monoclonal antibody anti-PRL receptor U5, confirming that the protective activity was associated with receptor activation. Our studies also suggest that nitric oxide (NO) production was involved in the protective effect of rhPRL since pre-treatment of the animals with L-NAME, an inhibitor of NO-synthase, was able to completely revert the protective activity, whereas D-NAME, the inactive D-isomer, was without effect.

Effects of benzodiazepines on immunodeficiency and resistance in mice.

Our results indicate that benzodiazepine (Bz) treatment time, greater than 2-3 months, induce a decrease of both specific and nonspecific responses. Mice treated for different times with diazepam or chlordemethyldiazepam showed decreased survival to experimental Salmonella typhimurium infections after three months of treatment. Adherence, expressed as the polymorphonuclear cells (PMN) capacity to attach to nylon wool, was impaired after 7 days of treatment. Longer treatments further increase this impairment. PMN from mice treated with Bz for 90 days also demonstrate on impaired chemotaxis and phagocytosis for Saccharomyces cerevisiae. Monocytes from mice treated for 7 days secreted more IL-1 alpha then controls; the antibody titer in mice given to prolonged treatment progressively diminished compared to controls. Con A or LPS stimulated lymphocytes showed an increase of H3-thymidine incorporation from mice treated for a short time and conversely a decreased incorporation when taken from mice that underwent longer treatments. Benzodiazepines were therefore found to affect PMN chemotaxis and phagocitosis, general immunity and survival of mice to infections.

Prolactin protection against lethal effects of Salmonella typhimurium

The immunoregulatory role of prolactin (PRL) has been well established. In order to clarify if the hormone is also able to stimulate a protective activity against pathogens-induced infections we have studied the modifications of the infective capacity of Salmonella typhimurium induced in mice by repeated treatments with ovine PRL. A significant dose-dependent reduction in the mortality rate was observed in comparison to controls. This activity is probably related to the observed increases in phagocytosis and intracellular killing of the peritoneal macrophages and chemotaxis of the peritoneal granulocytes induced by the hormonal treatment. On the contrary, the number of leukocytes in blood was not modified by PRL treatment excluding a mobilization of cells from other districts. Our findings confirm the existence of a linkage between the neuroendocrine and immune systems suggesting a possible role for PRL in the regulation of non-specific immune response.

In vivo inhibition of cell-mediated and humoral immune responses to cellular antigens by SV-IV, a major protein secreted from the rat seminal vesicle epithelium

Microgram amounts of protein SV-IV, a major secretory protein produced by adult rat seminal vesicle epithelium, markedly decrease the mouse humoral immune response to cellular xenogeneic or allogeneic antigens (sheep red blood cells (SRBC) or mouse epididymal spermatozoa). The significant reduction in the total number of splenocytes and their main cell subsets in SRBC-immunized mice, the dramatic decrease in the number of Ia+ splenic T cells and the marked inhibition of splenocyte ability to respond in vitro to polyclonal mitogen stimuli suggest that the macrophage accessory cells are the primary target of the SV-IV immunosuppressive activity in vivo. Moreover, the infection of SV-IV-treated mice with Salmonella typhimurium produced an increased mortality of the experimental animals associated with a marked decrease of the phagocytic and intracellular killing activities of their peritoneal macrophages.

Beneficial effects of myristic, stearic or oleic acid as part of liposomes on experimental infection and antitumor effect in a murine model

Liposomes consisting of dicetyl-phosphate, cholesterol, lecithin and stearic or myristic or oleic acid, exert a protective effect for mice against experimental infection by Salmonella typhimurium, and delay both the onset and mortality B16 melanoma in these animals. Liposomes labelled with 3H-myristic acid were used as probes in the spleen and liver. We found that the treatment schedule rather than route of administration of liposomes, is important. The results show that in order to induce protection, preventive treatment must start at least three days before. Longer treatments do not increase the degree of protection, and treatments started at the same time as, or following experimental infection or tumor transplantation, have no effect.

Correlation Between Modification of Membrane Phospholipids and Some Biological Activity of Lymphocytes, Neutrophils and Macrophages

Our study considered the possibility of modifying the functional response of human neutrophils, of mouse lymphocytes and macrophages treated with phospholipids having different polar groups, different isomerisms with saturated and unsaturated fatty acids from C12 to C20 carbon atoms. The results are as follows. a) Most of the phospholipids containing fatty acids from C12 to C20 cause inhibition of the blastogenic capacity of the polyclonal activators tested. b) The phospholipids tested cause a decrease in adherence of polymorphonuclear leukocytes with the exception of the phosphatidyl-choline containing saturated and unsaturated fatty acids. c) A decrease in polymorphonuclear leukocytes migrational capacity almost always occurs. d) The cells treated with L-phosphatidyl-ethanolamine having fatty acids from C14 to C17 show an increase in chemiluminescence; those treated with phosphatidyl-choline and L-phosphatidyl-glycerol show a decrease of the chemiluminescence; L-phosphatidic acid and L-phosphatidyl-ethanolamine having Microbial fatty acids (FAs) at C16 cause a decrease in the formation of phagolisosomes in the macrophages tested.

Effect of Protein SV-IV on Experimental Salmonella enterica Serovar Typhimurium Infection in Mice

ABSTRACT Seminal vesicle protein IV (SV-IV) is a secretory anti-inflammatory, procoagulant, and immunomodulatory protein produced in large amounts by the seminal vesicle epithelium of the rat under the strict transcriptional control of androgen. In particular, this protein was shown to possess the ability to markedly inhibit in vivo the humoral and cell-mediated immune responses of mice to nonbacterial cellular antigens (sheep erythrocytes and spermatozoa). We report data that demonstrate that in mice treated with SV-IV and infected with Salmonella enterica serovar Typhimurium, SV-IV is able to downregulate some important immunological and biochemical parameters that serovar Typhimurium normally upregulates in these animals. This event did not correlate with a lower bacterial burden but was associated with a markedly increased one (300%). Furthermore, the treatment of mice with SV-IV alone also produced a significant increase in the rate of mortality among serovar Typhimurium-infected animals. The mechanism underlying these phenomena was investigated, and the strong immunosuppression produced by SV-IV in serovar Typhimurium-infected mice was suggested to be the basis for the increased rate of mortality. The SV-IV-mediated immunosuppression was characterized by a decrease in the humoral and cell-mediated immune responses, altered lymphocyte-macrophage interaction, downregulation of cytokine and inducible nitric oxide synthase gene expression, inhibition of macrophage phagocytosis and intracellular killing activities, and absence of apoptosis in the splenocyte population of SV-IV- and serovar Typhimurium-treated mice. The immunosuppressive activity of SV-IV was specific and was not due to aspecific cytotoxic effects. SV-IV-specific receptors (Kd = 10−8 M) occurring on the macrophage and lymphocyte plasma membranes may be involved in the molecular mechanism underlying the SV-IV-mediated immunosuppression. Some results obtained by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay also revealed a functional impairment of mitochondria (a decrease in mitochondrial dehydrogenase activity), thus indicating the possible implication of these organelles in the immunosuppressive process.

Phagocytosis of bacterial aggregates by granulocytes

A study was conducted on the granulocytic phagocytosis of bacterial aggregates obtained under ideal environmental conditions. For the strains studied, aggregation was favored by low salt concentrations, low pH and temperatures between 30°C and 40°C. Our results show that the phagocytic capacity of granulocytes depends on the type and size of these aggregates. Those formed by a smaller number of cells are more easily phagocytized than the larger ones.

Further characterization of the impaired protective function in mice fed with lipid diet

Female mice were maintained on lipid diet for 20 days. The nonspecific and immunological defense capability was determined by in vitro and in vivo methods. It was found that mice held mostly on a lipid diet demonstrate an all-round lowered response. Following 20 days of lipid diet the splenocytes exhibit: (1) an inversed lipid-protein ratio; (2) an inability to respond to sheep erythrocytes; (3) a reduction in [3H] thymidine incorporation in splenocytes stimulated with lipopolysaccharide (LPS) or with concanavalin A; (4) a reduction in the number of cells bearing surface immunoglobulins in splenocytes stimulated with LPS; (5) an inhibition of phagocytosis and intracellular killing in macrophages; (6) a lowering in granulocyte chemotaxis and adherence capacity; (7) a higher mortality to LPS after loading with galactosamine; and (8) a lowered complement activity even following LPS activation.

MICROVISCOSITY OF MOUSE SPLENOCYTE CYTOPLASMIC MEMBRANE MODIFIED BY SOME ANTIBIOTICS

This study has assessed the changes in the polarization fluorescence of 1,6-diphenyl-1,3,5-hexatriene in the splenic membrane of mice treated with clindamycin, penicillin, cefoxitin, cefamandole, cephaloridine, tetracycline, and erythromycin. The data show that most of the antibiotics tested modified membrane activity, as was shown by the changes in membrane microviscosity parameters.