Splenocyte Apoptosis Research Articles

Immune responses in relation to the type and time of thermal injury: An experimental study

BackgroundThermal injuries are followed by a complex immune response, but the relationship between the severity of burn injury and the time exposure to the thermal injury on the extent of the immune response is still not known. ObjectiveThis study focuses on characterising the effect of temperature and time exposure on the post-burn immune response. MethodsWe used 120 C57BL/6 male mice divided equally in 5 burn groups and one sham operated group (groups A–E and sham). Ten mice per group were sacrificed at 24 and 48h after burn injury and whole blood was collected; specimens of liver, lung, spleen, kidney and bowel were excised. Apoptosis and TREM-1 expression on circulating blood cells were measured. Splenocytes were isolated and stimulated for cytokine production; the rate of apoptosis of splenocytes was also measured. ResultsProduction of IL-17 from splenocytes of mice group D was enhanced. Considerable effects were shown on the apoptosis of circulating lymphocytes and of spleen cells. The apoptotic rates varied between groups and also evolved after 24 and 48h. To examine the origin of this differential response, quantitative bacterial cultures of liver, lung and kidney were made but no differences were observed compared with sham-operated animals. LimitationsThis study was based on an experimental murine model. ConclusionThere is a unique response for each type of injury depending on the temperature of the thermal source and the exposure time.

Tumor cell lysate induces the immunosuppression and apoptosis of mouse immunocytes.

Although tumor cell lysate (TCL) is a type of immunocyte stimulator, its immunosuppressive function must not be ignored. The present study reported that TCL prepared from a Lewis lung cancer cell was able to induce the development of immunosuppressive macrophages (MΦ) and tolerogenic dendritic cells. In addition, TCL upregulated the expression of CD69 in mouse splenocytes, and cell apoptosis and the percentage of regulatory T cells in mouse splenocytes simultaneously increased. Furthermore, the present study found that the immunosuppressive factor, hyaluronan, and the apoptosis inducers, Fas ligand and transforming growth factor-β, are present in TCL. These components may be associated with the emergence of immunosuppressive cells or splenocyte apoptosis. Thus, the present study has enriched our understanding of the composition of TCL and its negative regulatory effect on immunocytes.

Mesenchymal stem cells decrease splenocytes apoptosis in a sepsis experimental model.

Mesenchymal stem cells (MSCs) are potent modulators of immune responses. Sepsis is the association of a systemic inflammatory response with an infection. The aim of this study was to test the ability of MSCs derived from adipose tissue, which have immunomodulatory effects, and to inhibit the septic process in an experimental model of mice. Three experimental groups (male C57BL/6 mice) were formed for the test: control group, untreated septic group and septic group treated with MSCs (1×10(6) cells/animal). In the control group, there were no deaths; in the untreated septic group, the mortality rate was 100% within 26h; in the septic group treated with MSCs, the mortality rate reached 40% within 26h. The group treated with MSCs was able to reduce the markers of tissue damage in the liver and pancreas. The treated group had a reduction of inflammatory markers. Furthermore, the MSCs-treated group was able to inhibit the increase of apoptosis in splenocytes observed in the untreated septic group. Our data showed that MSCs ameliorated the immune response with decrease of inflammatory cytokines and increase anti-inflammatory IL-10; moreover, inhibited splenocytes apoptosis and, consequently, inhibited tissue damage during sepsis.

Pretreatment of Transfused Donor Splenocytes and Allografts With Mitomycin C Attenuates Acute Rejection in Heart Transplantation in Mice

ObjectiveThe aim of this study was to investigate the effect of pretreatment of donor splenocytes and grafts with mitomycin C (MMC) on heart allograft survival, as well as to demonstrate the mechanism of function. MethodsDonor splenocytes from Balb/C mice were incubated with MMC (40 μg/mL) in vitro and then transfused into recipients (C57BL/6 mice). The heart allograft was perfused with MMC before harvest. Graft survival and histopathology were examined. Lymphocyte activation, regulatory T cells, and donor splenocyte apoptosis were examined with the use of flow cytometry. ResultsMMC incubation in vitro induced apoptosis of donor splenocytes (15.5 ± 2.3% vs 23.2 ± 4.2%; P < .01). Either intravenous injection of MMC-treated donor splenocytes or transplantation of allograft pretreated with MMC prolonged heart allograft mean survival time from 7 ± 0.8 days to 20.5 ± 1.9 days or 10 ± 0.9 days, respectively (both P < .01). A combination of MMC-pretreated donor splenocyte transfusion and allografts showed the best effect on prolongation of graft survival (28.5 ± 1.8 days). Activation of CD4+ T cells in spleen and peripheral lymph nodes of recipients was significantly inhibited by either MMC-splenocyte transfusion or the combination treatment. Meanwhile, the percentage of CD4+CD25+Foxp3+ regulatory T cells in the spleen was increased in the MMC-splenocyte transfusion group (15.5 ± 1.1% vs 18.2 ± 0.9%; P < .05). ConclusionsBoth injection of MMC-conditioned donor splenocytes and MMC-conditioned allograft have effects on prolongation of heart allograft survival in mice, and MMC-conditioned donor splenocytes might play an essential role. MMC pretreatment induced regulatory T cells likely through induction of donor splenocyte apoptosis, and thus it inhibited T-cell activation.

Program and AbstractsThirty-fourth Annual Meeting of the Surgical Infection SocietyBaltimore, MarylandMay 1–3, 2014

Program and AbstractsThirty-fourth Annual Meeting of the Surgical Infection SocietyBaltimore, MarylandMay 1–3, 2014

Protective effect of hydrogen‐rich saline against radiation‐induced immune dysfunction

Recent studies showed that hydrogen can be used as an effective radioprotective agent through scavenging free radicals. This study was undertaken to evaluate the radioprotective effects of hydrogen on immune system in mice. H2 was dissolved in physiological saline using an apparatus produced by our department. Spleen index and histological analysis were used to evaluate the splenic structural damage. Spleen superoxide dismutase, GSH, MDA were measured to appraise the antioxidant capacity and a DCF assay for the measurement of radical oxygen species. Cell apoptosis was evaluated by an Annexin V-FITC and propidium iodide staining method as well as the apoptotic proteins such as Bcl-2, Bax, caspase-3 and c-caspase-3. CD4+ and CD8+ T cells subtypes were detected by flow cytometry with FITC-labelled antimouse CD4 and PE antimouse CD8 staining. Real-time PCR was utilized to determine the CD4+ T cell subtypes and related cytokines. Our study demonstrated that pre-treatment with H2 could increase the spleen index and attenuate the radiation damage on splenic structure. Radical oxygen species level was also reduced by H2 treatment. H2 also inhibited radiation-induced apoptosis in splenocytes and down-regulated pro-apoptotic proteins in living mice. Radiation-induced imbalance of T cells was attenuated by H2. Finally, we found that H2 could regulate the polarization of CD4+ T cells and the level of related cytokines. This study suggests H2 as an effective radioprotective agent on immune system by scavenging reactive oxygen species.

The immunomodulatory and anti-apoptotic effect of dexamethasone in imminent preterm labor: An experimental study

The study was designed to investigate the effect of dexamethasone (DEX) on the latency period to delivery in a murine model of preterm labor. To this purpose, pregnant mice were randomly assigned in groups: the control group received water for injection (n=20), the preterm labor group was injected with lipopolysaccharide (LPS) (n=22), while the glucocorticoids group was administered DEX either 1h before (n=17) or after (n=7) lipopolysaccharide. In a first set of experiments animals were monitored to record perinatal outcomes. In another set of experiments, the remaining animals were sacrificed eight h after interventions. Fetuses were homogenized to measure tumor necrosis alpha in supernatants. Maternal splenocytes were isolated and stimulated for cytokine production. Serum of mice was incubated with donor cells from healthy pregnant and non-pregnant animals to induce apoptosis. LPS induced preterm labor but treatment or pretreatment with DEX delayed parturition exerting a favorable impact on survival of delivered fetuses. DEX inverted the increase of fetoplacental tumor necrosis alpha levels. Serum of LPS-stimulated mice induced apoptosis of splenocytes of either pregnant or non-pregnant healthy mice; this was reversed after incubation of splenocytes with serum coming from DEX pre-treated mice. The presented findings suggest that DEX administered either as pre-treatment or treatment prolonged gestation and promoted neonatal survival in a sterile murine model of preterm labor. These favorable outcomes were closely linked to alterations in both immune and apoptotic responses of animals.

Tim-3 signaling pathway as a novel negative mediator in lipopolysaccharide-induced endotoxic shock

Sepsis is a complex clinical condition caused by a dysregulated immune response to an infection. However, the mechanism by which our immune system controls this amplified inflammation is largely unknown. In this study, we investigated whether Tim-3 pathway could serve as a negative mediator in lipopolysaccharide (LPS)-induced endotoxic shock. Our results showed that Tim-3 was expressed on CD4+ T cells, CD8+ T cells, and NK cells, and was significantly increased in the peritoneal cavity of septic mice. Tim-3 acted as a marker of immune exhaustion and Tim-3-positive T cells and NK cells had a lower interferon (IFN)-γ production. Furthermore, blockade of Tim-3 pathway significantly accelerated mortality in septic mice, while activation of this pathway prolonged survival time. In vitro administration of Tim-3 blocking antibody restored the release of IFN-γ from splenocytes and decreased splenocyte apoptosis, and increased levels of IFN-γ and tumor necrosis factor (TNF)-α were also detected in septic mice at 24h post in vivo administration of the antibody. In contrast, activation of Tim-3 pathway prevented cell proliferation. Thus, Tim-3 signaling pathway acts as a novel negative mediator in LPS-induced endotoxic shock and could be a potential therapeutic target for the treatment of sepsis.

Protective effects of strawberry and mulberry fruit polysaccharides on inflammation and apoptosis in murine primary splenocytes

This study isolated polysaccharides from strawberry (SP) and mulberry (MP) fruit juice to compare their cytokine secretion regulatory and antiapoptotic activities using murine primary splenocytes. SP and MP in the absence or presence of lipopolysaccharide (LPS) were administered to splenocytes for 48 hours. The culture supernatant was used for cytokine secretion assay using the enzyme-linked immunosorbent assay method. The cell pellet was used for the determination of anti-/proapoptotic protein (B cell lymphoma 2/Bak) levels in the cells using the Western blotting method. The results showed that SP and MP treatment at appropriate concentrations significantly increased the proliferation of splenocytes (p < 0.05). SP and MP treatments in the absence of LPS, and SP treatments in the presence of LPS significantly decreased T helper type 1/T helper type 2 (p < 0.05), and SP in the presence of LPS slightly decreased tumor necrosis factor-α/interleukin-10 (pro-/anti-inflammatory) cytokine secretion ratios by splenocytes, suggesting that SP has strong and MP has mild anti-inflammation potential via modulating cytokine secretion profiles. However, MP treatment at an appropriate concentration in the absence of LPS exhibited an antiapoptotic activity via modulating pro- (Bak) and antiapoptotic (B cell lymphoma 2) protein expression ratios, suggesting that MP may protect primary immune cells from apoptotic cell death. Overall, our findings suggest that SP has better anti-inflammation potential, whereas MP has better cell proliferation and antiapoptotic potential in vitro.

Modulation of immune function by milk fat globule membrane isolates

The nutritional value and characterization of minor milk components on mammalian immune function are not fully understood. The aim of this research was to test the ability of a milk fat globule membrane (MFGM) isolate to modulate murine immune function in vitro, by studying its effects on splenocyte proliferation, apoptosis, and cytokine production. Proliferation of spleen cells was not affected by the MFGM isolate; however, in the presence of polyclonal activators, the MFGM isolate suppressed cell proliferation. Results obtained by flow cytometry did not support programmed cell death as the cause of the MFGM immune-modulating capacity. A mode of suppression on the splenocyte activation process was suggested from a marked decrease in the production of IFN-γ and tumor necrosis factor-α cytokines, typical indicators of immune cell activation. The effect of MFGM on IL-4 secretion was significantly less than that for the other 2 cytokines. The activity exerted by the MFGM over concanavalin A-stimulated cells differed from that observed in cells treated with lipopolysaccharide, suggesting a different mode of action depending on the activator used. These results indicate the potential of MFGM extracts as functional ingredients with bioactive modulating capacity.

Androstenediol Modulates Sepsis Induced Alterations of Survival and Immune Functions in a Murin Model of Sepsis

Recently the benefit of subcutaneously applied dehydroepiandrosterone (DHEA) during sepsis was demonstrated. It was therefore supposed that the impact of DHEA might be induced by its metabolite androstenediol produced via conversion in subcutaneous tissue. Thus we postulate a comparable impact of intravenously applied androstenediol like DHEA. Male NMRI mice were subjected to sham-operation (laparotomy) or sepsis (cecal ligation and puncture). Animals received saline, DHEA (20 mg/kg/day) subcutaneously, androstenediol (20 mg/kg/day) subcutaneously and androstenediol (10 mg/kg/day) intravenously. During 48 h of sepsis and treatment clinical parameters such as survival and body temperature were observed. Termination of animals was performed 48 hrs after induction of sepsis in order to monitor splenocyte apoptosis (Annexin V binding capacity), cytokine release (IL-10 and TNF-α, ELISA), and immunological capacity by DTH-Reaction (Delayed type of hypersensitivity). Subcutaneous and intravenous androstenediol administration improved the survival rate of septic mice 48 hrs after induction of CLP like subcutaneous administration of DHEA. (86% vs 53%). This effect was paralleled by a restoration of splenocyte proliferation and DTH reaction, a decreased cellular apoptosis rate of splenocytes, and an attenuation of cytokine release. Administration of androstenediol induces an increased survival rate and improved cellular immune functions in septic mice. This effect was detected independent of the way of administration and is comparable to those effects induced by subcutaneous DHEA administration. With respect to clinical use during critical illness, intravenous administration of androstenediol seems to be an alternative to subcutaneous DHEA administration.

Efficacy of crude extract of Emblica officinalis (amla) in arsenic-induced oxidative damage and apoptosis in splenocytes of mice.

Introduction:Arsenic, an environmental contaminant naturally occurred in groundwater and has been found to be associated with immune-related health problems in humans.Objective:In view of increasing risk of arsenic exposure due to occupational and non-occupational settings, the present study has been focused to investigate the protective efficacy of amla against arsenic-induced spleenomegaly in mice.Results:Arsenic exposures (3 mg/kg body weight p.o for 30 days) in mice caused an increase production of ROS (76%), lipid peroxidation (84%) and decrease in the levels of superoxide dismutase (53%) and catalase (54%) in spleen as compared to controls. Arsenic exposure to mice also caused a significant increase in caspases-3 activity (2.8 fold) and decreases cell viability (44%), mitochondrial membrane potential (47%) linked with apoptosis assessed by the cell cycle analysis (subG1-28.72%) and annexin V/PI binding in spleen as compared to controls. Simultaneous treatment of arsenic and amla (500 mg/kg body weight p.o for 30 days) in mice decreased the levels of lipid peroxidation (33%), ROS production (24%), activity of caspase-3 (1.4 fold), apoptosis (subG1 12.72%) and increased cell viability (63%), levels superoxide dismutase (80%), catalase (77%) and mitochondrial membrane potential (66%) as compared to mice treated with arsenic alone.Conclusions:Results of the present study indicate that the effect of arsenic is mainly due to the depletion of glutathione in liver associated with enhanced oxidative stress that has been found to be protected following simultaneous treatment of arsenic and amla.

Effect of selenite on T-cell mitogenesis: contribution of ROS production and apoptosis signal-regulating kinase 1.

Although supplementation with the selenocompound, sodium selenite has been shown to stimulate the concanavalin A-induced T-cell mitogenic response, the mechanisms responsible remain unclear. This study was conducted to evaluate the relationships between the induction of apoptosis, formation of tumor necrosis factor (TNF)-alpha and reactive oxygen species (ROS), activation of apoptosis signal-regulating kinase (ASK) 1 and the thioredoxin (Trx) system when mitogenesis was stimulated by selenite. TNF-alpha was dose-dependently released by mouse splenocytes treated with selenite, and apoptosis was induced when TNF-alpha was added at the indicated concentrations. However, supplementation with selenite at low concentrations inhibited the accumulation of ROS with the increased expression of Trx reductase 1 and induction of apoptosis in wild-type splenocytes, and also at high concentrations in Trx-1-transgenic mouse splenocytes. The suppression of apoptosis was accompanied by a decrease in the expression of phospho-ASK1. These results suggest that the stimulation of T-cell mitogenesis by selenite may be partly attributed to the inhibited accumulation of ROS due to a reduced Trx-1/TR1 system, the inactivation of ASK1, and the suppression of apoptosis.

The Lack of Cytotoxic Effect and Radioadaptive Response in Splenocytes of Mice Exposed to Low Level Internal β-Particle Irradiation through Tritiated Drinking Water in Vivo

Health effects of tritium, a β-emitter and a by-product of the nuclear industry, is a subject of significant controversy. This mouse in vivo study was undertaken to monitor biological effects of low level tritium exposure. Mice were exposed to tritiated drinking water (HTO) at 10 KBq/L, 1 MBq/L and 20 MBq/L concentrations for one month. The treatment did not result in a significant increase of apoptosis in splenocytes. To examine if this low level tritium exposure alters radiosensitivity, the extracted splenocytes were challenged in vitro with 2 Gy γ-radiation, and apoptotic responses at 1 and 24 h were measured. No alterations in the radiosensitivity were detected in cells from mice exposed to tritium compared to sham-treated mice. In contrast, low dose γ-irradiation at 20 or 100 mGy, resulted in a significant increase in resistance to apoptotic cell death after 2 Gy irradiation; an indication of the radioadaptive response. Overall, our data suggest that low concentrations of tritium given to mice as HTO in drinking water do not exert cytotoxic effect in splenocytes, nor do they change cellular sensitivity to additional high dose γ-radiation. The latter may be considered as the lack of a radioadaptive response, typically observed after low dose γ-irradiation.

The Association between Splenocyte Apoptosis and Alterations of Bax, Bcl-2 and Caspase-3 mRNA Expression, and Oxidative Stress Induced by Dietary Nickel Chloride in Broilers

Two hundred and forty avian broilers were equally divided into four groups, and raised with a corn-soybean basal diet or the same diet supplemented with 300, 600, 900 mg/kg NiCl2 for 42 days. Numbers or percentages of apoptotic splenocytes by flow cytometry (FCM) and TUNEL were higher (p < 0.05 or p < 0.01) in the 300, 600 and 900 mg/kg groups than those in the control group. Results measured by qRT-PCR and ELISA showed that mRNA expression and contents were significantly higher (p < 0.05 or p < 0.01) in Bax and Caspase-3, and were significantly lower (p < 0.05 or p < 0.01) in Bcl-2 of the 300, 600 and 900 mg/kg groups. Also, the SOD, CAT and GSH-Px activities, and the ability to inhibit hydroxyl radical, and GSH contents were significantly decreased (p < 0.05 or p < 0.01), and MDA contents were increased (p < 0.05 or p < 0.01) in all groups. In conclusion, dietary NiCl2 in excess of 300 mg/kg caused apoptosis, altered Bax, Bcl-2 and Caspase-3 mRNA expression levels and contents, and induced oxidative stress in the spleen. Also, splenocyte apoptosis was closely related to the alternations of Bax, Bcl-2 and Caspase-3 mRNA expression, and oxidative damage. The splenic immunity and blood filtration functions were impaired in broilers.

Immunomodulatory effects in the spleen‐injured mice following exposure to titanium dioxide nanoparticles

Immune injuries following the exposure of titanium dioxide nanoparticles (TiO₂ NPs) have been greatly concerned along with the TiO₂ NPs are widely used in pharmacology and daily life. However, very little is known about the immunomodulatory mechanisms in the spleen-injured mice due to TiO₂ NPs exposure. In this study, mice were continuously exposed to 2.5, 5, or 10 TiO₂ NPs mg kg(-1) body weight for 90 days with intragastric administration to investigate the immunomodulatory mechanisms in the spleen. The findings showed that TiO₂ NPs exposure resulted in significant increases in spleen and thymus indices, and titanium accumulation, in turn led to histopathological changes and splenocyte apoptosis. Furthermore, the exposure of TiO₂ NPs could significantly increase the levels of macrophage inflammatory protein (MIP)-1α, MIP-2, Eotaxin, monocyte chemotactic protein-1, interferon-γ, vascular cell adhesion molecule-1, interleukin-13, interferon-γ-inducible protein-10, migration inhibitory factor, CD69, major histocompatibility complex, protein tyrosine phosphatase, protein tyrosine kinase 1, basic fibroblast growth factor, Fasl, and GzmB expression, whereas markedly decrease the levels of NKG2D, NKp46, 2B4 expression involved in immune responses, lymphocyte healing and apoptosis. These findings would better understand toxicological effects induced by TiO₂ NPs exposure.

Baicalein Selectively Induces Apoptosis in Activated Lymphocytes and Ameliorates Concanavalin A-Induced Hepatitis in Mice

BackgroundInsufficient apoptosis in activated lymphocytes contributes to the development of autoimmune hepatitis (AIH). Baicalein (BE), a flavonoid originally isolated from the root of Scutellaria baicalensis Georgi, possesses anti-inflammatory properties. However, whether BE can selectively induce apoptosis in activated lymphocytes and exert therapeutic effect on AIH has not been studied.Methodology/Principal FindingsThe pro-apoptotic properties of BE were evaluated in vitro on different types of immune cells, and in vivo effects of BE were examined in a murine model of Concanavalin A (Con A)-induced hepatitis. In vitro treatment with BE resulted in a higher increase in the level of apoptosis in Con A-stimulated murine splenocytes, Con A-stimulated CD3+ splenocytes, lipopolysaccharide (LPS)-stimulated CD19+ splenocytes, and phorbol 12-myristate 13-acetate/ionomycin-stimulated Jurkat T cells, compared with that in unstimulated naïve ones. Murine bone marrow-derived dentritic cells, peritoneal macrophages, and RAW264.7 cells, either stimulated with LPS or unstimulated, were all insensitive to the BE-induced apoptosis. BE treatment also led to a loss of mitochondrial membrane potential, an increase of cytochrome c release from mitochondria to the cytosol, a decrease in the ratio of Bcl-2/Bax, and activation of caspase-9,-3 in Con A-stimulated CD3+ splenocytes and LPS-stimulated CD19+ splenocytes, while showing no impact on Fas/FasL expressions and caspase-8 activation. In vivo administration of BE alleviated Con A-induced liver injury, suppressed serum level of TNF-α and IFN-γ, and reduced liver infiltration of mononuclear cells (MNCs). Furthermore, BE treatment increased the incidences of apoptosis in liver-infiltrating MNCs and splenocytes, as well as in CD3+ and CD19+ splenocytes. When liver MNCs and splenocytes from BE-treated mice were cultured in vitro for 24 h, they exhibited marked increase in apoptosis compared to vehicle-treated control.Conclusions/SignificanceThe present study demonstrates the ability of BE to promote apoptosis in activated lymphocytes through mitochondrial pathway and its potential use in the treatment of AIH.

A critical role of Toll-like receptor 2 in chronic stress-induced immune suppression (P6309)

Abstract Stress can enhance or suppress immune functions depending on the duration and severity of stressful situation. Our previous studies observed that Toll-like receptor (TLR) participates in chronic restraint stress-induced immune dysfunction. However, the mechanism by which TLR2 contributes to immune suppression induced by chronic restraint stress remains elusive. Our investigation found that stimulation of TLR2 by peptidoglycan (PGN), a TLR2 ligand, significantly attenuates cell apoptosis in splenocytes induced by chronic restraint stress. Furthermore, we found that administration of PGN markedly blocks chronic restraint stress-induced alterations of anti-apoptotic and apoptotic genes, including Bcl/2 and glycogen synthase kinase-3β (GSK-3β). We also found that activation of TLR2 by PGN inhibits chronic stress-reduced level of c-Jun N-terminal kinase (JNK) phosphorylation. This effect of PGN is abolished in TLR2 deficient mice, suggesting PGN-induced protection of JNK phosphorylation through a TLR2 dependent manner. Moreover, our data have shown that chronic stress caused a dramatic decrease in cytokine IL-2 level but an increase in the cytokines IL-4 and IL-17 in CD4+ T cells. Interestingly, stimulation of TLR2 by PGN could block these alterations of cytokine levels induced by chronic stress. Collectively, our studies thus demonstrate that stimulation of TLR2 attenuates chronic stress-induced immune suppression by modulating apoptosis-related proteins and cytokines.

Stimulatory Toll-like receptor 2 suppresses restraint stress-induced immune suppression

Stress can enhance or suppress immune functions depending on a variety of factors. Our previous studies observed that Toll-like receptor 2 (TLR2) participates in chronic restraint stress-induced immune dysfunction. However, the mechanism by which TLR2 prevents immune suppression remains elusive. Our investigation found that stimulation of TLR2 by peptidoglycan (PGN) significantly attenuates splenocyte apoptosis and markedly blocks alterations of anti-apoptotic and apoptotic proteins. Activation of TLR2 inhibits chronic stress-reduced phosphorylation of c-Jun N-terminal kinase (JNK) and diminishes chronic stress-induced up-regulation of corticosterone production. Additionally, our data show that chronic stress causes a dramatic decrease of cytokine IL-2 level but an increase of IL-4 and IL-17 in CD4+ T cells. Interestingly, PGN could block these alterations of cytokine levels. Collectively, our studies demonstrate that stimulation of TLR2 attenuates chronic stress-induced immune suppression by modulating apoptosis-related proteins and immunoregulatory agents.

Pre-treatment with low-dose endotoxin prolongs survival from experimental lethal endotoxic shock: Benefit for lethal peritonitis by Escherichia coli

Although LPS tolerance is well-characterized, it remains unknown if it is achieved even with single doses of lipopolysaccharide (LPS) and if it offers protection against lethal bacterial infections. To this end, C57B6 mice were assigned to groups A (sham); B (saline i.p followed after 24h by i.p 30mg/kg LPS); and C (3mg/kg LPS i.p followed after 24h by i.p 30mg/kg LPS). Survival was monitored and animals were sacrificed early after lethal challenge for measurement of tumour necrosis factor-alpha (TNFα) in serum; isolation of splenocytes and cytokine stimulation; and flow-cytometry for apoptosis and TREM-1. Experiments were repeated with mice infected i.p by Escherichia coli after challenging with saline or LPS. Mortality of group B was 72.2% compared with 38.9% of group C (p: 0.020). Serum TNFα of group C was lower than group B. Expression of TREM-1 of group C on monocytes/neutrophils was greater than group B. Release of TNFα, of IFNγ and of IL-17 from splenocytes of group C was lower than group B and the opposite happened for IL-10 showing evidence of cellular reprogramming. In parallel, apoptosis of circulating lymphocytes and of splenocytes of group C was greater compared with group B. Pre-treatment of mice challenged by E. coli with low dose LPS led to 0% mortality compared with 90% of saline pre-treated mice; in these mice, splenocytes improved over-time their capacity for release of IFNγ. It is concluded that single low doses of LPS lead to early reprogramming of the innate immune response and prolong survival after lethal E. coli challenge.