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During the class of Trypanosma cruzi infection, the immunological system of the host is involved in distinguishable complex interactions with the hormone system, and the lactogenic hormone ( PRL ) is one among several other endocrines involved in immunoregulation. Although intensive surveies in seeking to understand the mechanisms which underlie Chagas disease, there are some pieces still losing in this complex mystifier. Since the scarceness of informations refering to the function of PRL engagement in Chagas disease and taking into history the being of a XT between neuroendocrine endocrines and the immune system, the intent of the current survey was to measure a possible up-regulation triggered by PRL on the cellular immune response of T. cruzi-infected rats and the propensity of PRL in change by reversaling the immunosuppression caused by the parasitic infection. The informations shown herein demonstrate that PRL strongly induced the proliferation of T lymphocytes coupled with an activation of macrophages and the production of enhanced concentrations of azotic oxide, taking to a decrease of blood trypomastigotes during the extremum of parasitaemia. Sing to phenotypic analysis of T cell populations during the acute stage of T. cruzi infection, an sweetening of both CD3+CD4+ and CD3+CD8+ subsets were observed in septic groups, being the highest Numberss of these T cells subsets found in the PRL treated and septic group. Since NO is a cardinal signaling molecule, involved in a figure of cellular interactions with some constituents of the immune system and those of the neuroendocrine system, PRL can be considered as an alternate endocrine able to up-regulate the host ‘s immune system accordingly take downing the pathological effects of T. cruzi infection.


The interaction between the hormone and the immune system is good established and it has been clearly demonstrated by several research workers that certain endocrines are capable of modulating cellular immune maps ( Santos et al. , 2008 ; Filipin et al. , 2008 ; Caetano et al. , 2009 ) . Additionally, these mechanisms of interaction may be good or damaging for the host opposition during a assortment of infections, including those caused by parasites ( Santello et al. , 2007, Escobedo et al. , 2005 ) .

Trypanosoma cruzi, the aetiologic agent of Chagas ‘ disease, is an intracellular protozoon that causes a serious immune instability during the acute stage, characterized by terrible thymocyte depletion and myocardial redness ( P & A ; eacute ; rez et al. , 2007 ) . The control of T. cruzi infection is achieved through the concerted interactions of a figure of cells including CD3+CD4+ and CD3+CD8+ T, B lymphocytes ( Tarleton, 1990 ) , NK cells, macrophages ( Sacks and Sher, 2002 ) , and the production of inflammatory cytokines, such as IFN-? and/or TNF-? which play a cardinal function in modulating parasite reproduction ( Umekita and Mota, 2000 ; Pascutti et al. , 2003 ) , by triping macrophages to synthesise NO, which, in the mouse, is considered the major effectual molecule for intracellular amastigotes killing ( Vespa et al. , 1994 ; Silva et al. , 2003 ) .

Several surveies have demonstrated the importance of CD4+ and CD8+ T cell compartments. Mice missing these T cell subsets display an enhanced susceptibleness to infection followed by increased parasitaemia and shortened survival clip in ( Tarleton et al. , 1994 ) .

The class of Chagas? disease can be deeply affected by the hormone host ‘s response ( Roggero et al. , 2006 ) . PRL is a peptide endocrine secreted by the anterior pituitary secretory organ and it is involved in the ordinance of the physiological procedures of growing and reproduction in a broad scope of craniate species ( Quintanar et al. , 2007 ) . Furthermore, groundss have demonstrated that this endocrine is besides produced at sites outside the pituitary secretory organ ( extrapituitary PRL ) , such as placenta, encephalon, uterus, cuticular fibroblasts, NK, T and B cells. ( Bole-Feysot et al. , 1998 ) .

The chief measure of PRL action is its adhering capacity to specific PRL receptors ( Bole-Feysot et al. , 1998 ; Yu-Lee, 2002 ) , that are found in cells and tissues of cardinal nervous system, pituitary secretory organ, adrenal cerebral mantle, Thymus, lien, lymphocytes T and B, macrophages, kidney, etc, moving among other maps as an immunoregulator ( Bole-Feysot et al. , 1998 ) .

Research dating from the 1930s had suggested a function of PRL in modulating the immune system ( Smith, 1930 ; Kooijman et al. , 1996 ) . Subsequently, several other documents demonstrated that PRL exhibited immunostimulatory belongingss ( Yu-Lee, 1997 ; Clevenger et al. , 1998 ) , up-regulates cytokine secernment and lymphocyte distinction, particularly in response to antigen and mitogens ( Biswas et al. , 2006 ) , besides its ability to change by reversal the glucocorticoid-induced immunosuppression ( Kelley and Dantzer, 1991 ) .

Based on the fact that T. cruzi infections cause terrible and durable suppression of the immune responses during the acute stage of infection, the rating of possible therapeutics in up-regulating the cellular immune reactivity of T.cruzi-infected rats having PRL was performed, utilizing as tools thymocytes proliferation, peritoneal macrophage counts, flow cytometry analysis of T cell subpopulations ( CD3+CD4+ and CD3+CD8+ ) and NO production.



Male Wistar rats 4 hebdomads old, weighing 90 to 100g were used in all experiments. Rats were obtained from the Facility House of the Universitary Campus of Ribeir & A ; atilde ; o Preto. Animals were randomized into one of the undermentioned groups: Control ( C ) ; Control PRL-treated ( CP ) ; Infected ( I ) ; Infected PRL-treated ( IP ) . A figure of 5 animate beings were used per group/per twenty-four hours of experiment. They were separated in figure of 5 in plastic coops and commercial gnawer diet and H2O were available ad libitum. Rat tablet was changed 3 times/week to avoid concentration of ammonium hydroxide from piss. The protocol of this survey was approved by the local Ethics Committee ( protocol figure ) . Experiments were done twice and samples of each parametric quantity were done in triplicate. Unfortunately, it was impossible to utilize more animate beings due to the orientations of the local Ethics Committee. In the sum it was used 120 animate beings ( the experiments were performed in extra ) , what seems to be a sensible figure of animate beings for an experiment enabling conditions to pull decisions.

Experimental Protocol

Parasites and Experimental Infection

Rats were intraperitoneally inoculated with 1 – 105 blood trypomastigotes of the Y strain of T. cruzi ( Silva and Nussenzweig, 1953 ) . The surveies were performed on 7, 14 and 21 yearss post-infection. Parasitemia was determined by Brener ‘s method ( Brener, 1969 ) . It is of import to stress that since Wistar rats are usually immune to most T.cruzi strains, we found it necessary to utilize comparatively high inoculants ( 1 – 105 blood trypomastigotes ) , which resulted in a more intense pathological response such as enhanced parasitaemia.

Prolactin intervention

Each animate being received subcutaneously, 40µg ( Ryn & A ; iacute ; kov & A ; aacute ; et al. , 1988 ; Zellweger et al. , 1996 ; Oberbeck et al. , 2003 ) of ovine PRL ( Sigma-Aldrich Chemicals ) diluted in 0.1ml of saline solution ( 0.9 % ) , one time a twenty-four hours at the same clip and during the class of the experiment ( 7, 14 and 21 yearss ) . Treatment agenda started at the same twenty-four hours of infection.


Animals were decapitated with anterior anaesthesia utilizing thribromoethanol ( 2.5 % ) , administrated intraperitoneally at a dosage of 0.1 ml/10g organic structure weight.

Peritoneal macrophage counts

Peritoneal cells were harvested by the injection of 10ml of cold RPMI 1640 medium into the peritoneal pit. The cells were centrifuged at 410g for 15 min, the pellet was resuspended in RPMI 1640 medium, diluted with Turkey solution ( 15ml glacial acetic acid ; 0.2ml gentian violet 2 % ; 500 milliliter distilled H2O ) and the macrophages were counted in a Neubauer chamber.

Preparation of peritoneal cell suspensions and measuring of nitrite production

NO production was measured harmonizing to Dost et Al. ( 2006 ) , as accumulated supernatant nitrite ( a stable breakdown merchandise of NO ) , determined by a spectrophotometric method utilizing the Griess reaction.

Macrophage cells, harvested from peritoneal pit, were adjusted to a concentration of 5 – 106 cells/ml and cultured in 96-well flat-bottomed home bases, with or without LPS ( 10 ?g/ml ) ( Escherichia coli, Sigma, USA ) , at 37 & A ; deg ; C for 48 H in 5 % CO2 atmosphere. Subsequently, the supernatants were collected, transferred to a new 96-well flat-bottom civilization home bases and incubated with Griess reagent, prepared by blending equal volumes of sulfanilamide 1 % in phosphorous acerb solution 5 % and naphthylethylene diamine dihydrochloride 0.1 % , at room temperature for 5 min. Samples of each animate being were done in triplicate, and the optical density determined at 540 nanometer. The concentration of nitrite was obtained by comparing with a standard curve of serially diluted Na nitrite ( Dinging et al. , 1988 ) and expressed in micromoles.

Thymocytes proliferation assay

Thymi were aseptically removed. To fix a single-cell suspension, the cells were teased out in serum-free RPMI-1640 medium. After centrifugation for 10 min at 300g at 4 & A ; deg ; C, pelleted cells were resuspended in RPMI-1640 incorporating 5 % FBS and added to 96-well flat-bottomed home bases ( 0.1 ml/well ) at a cell denseness of 5 – 106/ml. The cells were later stimulated with Concanavalin A ( mitogenic concentration: 4 ?g/ml ; Sigma ) and incubated at 37 & A ; deg ; C in humidified 5 % CO2 atmosphere for 72 h. The experiments were performed in triplicate with a concluding volume of 0.2 ml/well. Cellular proliferation was determined by MTT check. After incubation of the cells with the MTT reagent for about 4 H, acidified isopropyl alcohol was added to lyse the cells and solubilize the purple formazan salt crystals. Samples of each animate being were done in triplicate, and the optical density determined by a spectrophotometric method at a wavelength of 570 nanometer. An addition in cells proliferation consequences in an elevated sum of MTT formazan and accordingly increased optical density values are measured ( Gieni et al. , 1995 ) . Experiments were conducted in triplicate.

Flow cytometry

The splenetic tissue was automatically disrupted by bulge through a 70µm nylon cell strainer and homogenized in RPMI 1640 medium to bring forth a individual cell suspension. The staining stairss were performed in PBS incorporating 10 % heat inactivated normal rat serum, and the cells were washed with PBS incorporating 1 % FBS and 0.01 mol/l Na azide. Stained cells were stored for analysis in PBS incorporating 0.01 mol/l Na azide and 1 % paraformaldehyde, in certain tubings held in the dark. All stairss were performed at 4 & A ; deg ; C. Analysis of these cells was performed utilizing a Becton Dickinson FACScan flow cytometer with DIVA-BD package ( Becton Dickinson Immunocytometry Systems, San Jose, CA, USA ) . All conjugated monoclonal antibodies were obtained from BD Biosciences PharMingen ( CA, USA ) : anti-CD3+PE, anti-CD4+FITC and anti-CD8+PerCP.

Statistical analysis

The methods used for statistical analysis were chosen sing the little sample of animate beings. Differences among groups were determinate by One-way ANOVA with Bonferroni ‘s station trial ( Figure 2 and Figure 3 ) and by Kruskall-Wallis trial followed by Dunn ‘s multiple comparings trial ( Figure 4, Figure 5 and Table 1 ) . The difference between parasitaemia values ( Figure 1 ) was analyzed by the Mann-Whitney nonparametric trial.

The consequences were expressed as means/Standard Error of Mean and as Median and Range. A value of P & A ; lt ; 0.05 was considered statistically important. All statistical analysis were made utilizing Graph Pad Prism version 4.0 ( GraphPad Software, Inc. , San Diego, CA, USA ) .


Parasitemia ( Figure 1 )

The extremum of parasitaemia occurred on 7th twenty-four hours station infection and all groups showed a entire absence of trypomastigotes after the 21 yearss station infection.

On the extremum of parasitaemia, PRL-treated animate beings displayed decreased figure of parasites when compared to untreated opposite number ( p & A ; lt ; 0.05 ) .

Peritoneal macrophage counts ( Table 1 )

On 14th twenty-four hours station inoculant, the septic and PRL-treated group mediated a statistically important addition in the figure of peritoneal macrophages as compared to its septic opposite number ( I ) . However, on 7th and 21st yearss of the experiment, any important change in the figure of macrophages between non-treated or PRL-treated septic animate beings was observed.

Nitric Oxide ( Figure 2 )

Without LPS stimulation

For the LPS non-stimulated groups, important enhanced concentrations of nitrite were observed in septic and PRL-treated group when compared with all other groups, including the septic and non-supplemented opposite number, during the 7th and 21st yearss of experiments ( P & A ; lt ; 0.05 ) .

Refering the non-infected groups ( C and CP ) , no important changes in nitrite degrees were observed.

With LPS stimulation

On 7 and 14 yearss of experiments, nitrite concentration reached the highest values for septic and PRL-treated animate beings when compared to all other groups ( P & A ; lt ; 0.05 ) .

Thymocytes proliferation assay ( Figure 3 )

For Con-A non-stimulated septic groups ( I and IP ) , the highest thymocyte proliferation occurred in PRL-treated animate beings when compared to infected opposite number, during all yearss of experiments ( P & A ; lt ; 0.05 ) .

On 14 twenty-four hours station infection, Con A-stimulated cells from infected and PRL-treated animate beings displayed enhanced degrees of thymocyte proliferation when compared to its untreated and septic opposite number ( p & A ; lt ; 0.05 ) .

Refering the non-infected groups ( C and CP ) , no important thymic changes were observed between them.

Flow cytometry ( Figures 4 and 5 )

On 21 st twenty-four hours station infection an addition of both CD3+CD4+ and CD3+CD8+ subsets was noted in septic groups when compared to clean opposite numbers.

In add-on, on 14th twenty-four hours station infection, enhanced per centum of T CD3+CD4+ lymphocytes was found for PRL treated animate beings as compared to infected and non-treated animate beings ( P & A ; lt ; 0.05 ) .

For CD3+CD8+ splenocytes, the enlargement was besides more singular in septic animate beings subjected to PRL intervention, when compared with septic and non-treated opposite number, on 21st twenty-four hours station infection ( p & A ; lt ; 0.05 ) .


In the latest decennaries, renewed attending has been given to the of import actions of PRL outside of the generative system, particularly on the unsusceptibility ( Yu-Lee, 2002 ; Carre & A ; ntilde ; o et al. , 2005 ) .

Clinical, animate being, and in vitro surveies suggest that PRL exhibits immune stimulatory belongingss ( Yu-Lee, 1997 ) . This endocrine is able to excite T, B and NK cells, macrophages, neutrophils, CD34 haematopoietic cells, and antigen-presenting dendritic cells ( Matera et al. , 2001 ) . However, contentions are still described and discussed by several writers, such as Oberbeck and coworkers ( 2003 ) that observed a reduced endurance and a profound suppression of cellular immune maps in infected mice, after the disposal of lactogenic hormone, during systemic redness. Furthermore, surveies of Matera et Al. ( 1992 and 1997 ) indicated a double-faceted regulative function of PRL and concluded that the endocrine concentrations, the assortment of isotypes, the being of multiple receptor fractional monetary units, and the complexness of their intracellular signaling may explicate the specificity of PRL action on different mark cells.

Sing to T.cruzi infection, some documents demonstrate an immuno-stimulatory consequence of the pituitary endocrine PRL ( Pearson, 2007 ; Corr & A ; ecirc ; a-de-Santana et al. , 2009 ) . Several other documents describe a protection from a assortment of usually deadly infections, in mice which received PRL, including Salmonella typhimurium ( Di Carlo et al. , 1993 ) , and Toxoplasma gondii ( Benedetto et al. , 1995 ) . Furthermore, to complement the in vivo surveies Corr & A ; ecirc ; a-de-Santana and coworkers ( 2009 ) have shown that in rat cells the PRL production was down-regulated undermentioned T. cruzi infection. Our informations seem to be complementary to these observations, since PRL intervention induced an sweetening of the immune response, as indicated by the important decrease in parasitaemia degrees, on the extremum of parasitaemia ( 7 twenty-four hours post infection ) .

In our experiments, besides the important decrease of blood parasites cited above, it was besides observed enhanced figure of peritoneal macrophages every bit good as increased concentrations of NO compared to untreated groups. Several other documents indirectly confirm our consequences, showing that peritoneal macrophages activated by cytokines produce big measures of reactive N intermediates, such NO, which plays an of import function in the intracellular violent death of several pathogens, including T. cruzi ( Liew et al. , 1990 ; Adams et al. , 1990 ; Murray et al. , 1992 ; Vespa et al. , 1994 ) .

Bolander ( 2001 and 2002 ) , has besides reported that PRL leads to a transeunt lift in the production of NO in mammary epithelial cells and this NO could be responsible for the sweetening in DNA synthesis therefore modulating PRL effects and actions in the cell system. Additionally, surveies of Tripathi and Sodhi ( 2007 ) besides demonstrated that PRL intervention can bring on NO production in murine peritoneal macrophages and peripheral neutrophils.

Sing to the actions of PRL on lymphoproliferation, the informations presented in our paper describe enhanced degrees of Con A-stimulated thymocytes from infected and PRL-treated animate beings when compared to its septic and untreated opposite numbers. For Con-A non-stimulated and septic groups, the highest thymocyte proliferation occurred in PRL-treated animate beings when compared to infected 1s.

The PRL function in care of thymocytes unity is supported by the mitogenic mechanisms of this endocrine. Surveies suggest that PRL intervention can bring on look of the antiapoptotic protein ( Biswas et al. , 2006 ) , Bcl-2, which play an of import function in modulating the development, ripening, and activation of lymph cells. Some research workers describe an increasing consequence of PRL in bring oning enhanced antigen-specific peripheral T cells proliferation in vitro ( Clevenger et al. , 1991 ; Sabharwal et al. , 1992 ) . A figure of possible factors provide support for the look of PRL receptor on thymocytes ( De Mello-Coelho et al.,1998 ; Kooijman et al. , 2000 ) and thymic dendritic cells ( Carre & A ; ntilde ; o et al. , 2004 ) matching with the ordinance of cytokine secernment demonstrated in vitro ( Biswas and Chattopadhyay, 1992 ; Majumder et al. , 2002 ) .

Harmonizing to Abrahamsohn and Coffman ( 1995 ) and Braz & A ; atilde ; o et al. ( 2008 ) , T. cruzi infected cells loose increasingly their ability of lymphoproliferative responses to parasite antigens or mitogens, and this fact is a feature of the acute stage of Chagas disease ( Kierszenbaum and Sztein, 1994 ) . We besides observed that septic and untreated animate beings displayed a important decrease in the proliferative response when compared to its clean opposite numbers.

Phenotypic analysis to measure the composing and activation position of T lymphocytes during the acute stage of T. cruzi infection was performed, and an sweetening of both CD3+CD4+ and CD3+CD8+ subsets were observed in septic groups. However, it is notable to stress that the highest Numberss of these T cells subsets where found in the PRL treated and septic group. These consequences indirectly support some other surveies which describe that under nerve-racking conditions, like morbific challenges, PRL is of import to keep a steady-state homeostasis of the lymph cells sub-populations ( Dorshkind and Horseman, 2000 ) equilibrating the negative effects of immunosuppression mediated by glucocorticoids and other inflammatory go-betweens ( Dorshkind and Horseman, 2001 ) , such as those induced during the acute stage of T. cruzi infection

Our informations reveal an apparent function of PRL impacting at multiple degrees the ordinance of the constituents of the host ‘s immune response, through an incorporate cooperation of the immune and neuroendocrine systems. Future experiments in this field demand to be directed at bettering our apprehension of the cardinal mechanisms underlying the engagement of PRL and the immune response during infective diseases.

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