Cachectin/tumor necrosis factor: an endogenous mediator of shock and inflammation

Anti-inflammatory and urease inhibitory iridoid glycosides from Nyctanthes arbor-tristis Linn

ETHNOPHARMACOLOGICAL RELEVANCE

Nyctanthes arbor-tristis Linn. has been used by Ayruvedic physicians for the cure of different diseases including ulcers, gastric and inflammatory diseases.

AIM OF THE STUDY

To isolate and identify compounds from this source and investigate their therapeutic potential for the treatment of gastric ulcer and related disorders.

MATERIAL AND METHODS

The ethanol extract of fresh aerial parts of N. arbor-tristis was used in the present studies which was subjected to a bio-assay guided fractionation followed by chromatographic separations. The structures of pure compounds were elucidated using various spectroscopic techniques. The inhibition of urease enzyme was evaluated by weatherburn indophenol method. Molecular docking studies were determined by using Molecular Operating Environment (MOE) version 2020.0901 version. The intracellular ROS production from phagocytes was determined by chemiluminescence assay and NO generation was detected by Griess method. The proinflammatory cytokine TNF-α was quantified by ELISA. Cytotoxic activity was assessed by MTT assay.

RESULTS

One previously undescribed iridoid glycoside arborside F (1) and four known iridoid glycosides arborside A (2), arborside C (3), loganin (4) and 7-O-trans-cinnamoyl-6β-hydroxyloganin (5) were isolated and characterized in the present studies and their urease inhibitory activity was determined. Among these, 2 and 5 showed strong urease inhibition (IC50 = 12.1 ± 1.74 and 14.1 ± 0.59 μM respectively) (standard acetohydroxamic acid IC50 = 20.3 ± 0.42 μM), whereas rest of compounds showed moderate to low inhibition. Kinetic studies revealed that compounds 2 and 5 possess competitive type of inhibition. Molecular docking showed polar and non-polar interactions of compounds 2 and 5 with urease enzyme residues. Compounds 2 and 3 showed inhibition of ROS from whole blood (IC50 = 1.6 ± 0.3 and 2.5 ± 0.09 μg/mL respectively) and PMNs (IC50 = 1.5 ± 0.03 and 1.4 ± 0.0 μg/mL respectively). Compound 2 significantly inhibited nitric oxide and proinflammatory cytokine TNF-α (IC50 = 18.2 ± 3.0 and 73.8 ± 6.6 μg/mL respectively). Compounds 1, 4 and 5 were inactive on ROS. All isolated compounds were non-toxic on normal mouse fibroblasts (NIH-3T3) cells.

CONCLUSIONS

The ethno pharmacological repute of N. arbor-tristis in treating gastric and anti-inflammatory ailments is supported by present studies which resulted in isolation of a potent urease inhibitory and anti-inflammatory agent arborside A (2) a potential anti-ulcer and anti-inflammatory drug lead.

TNF-α evokes blood-brain barrier dysfunction through activation of Rho-kinase and neurokinin 1 receptor

Ischaemic stroke, accompanied by neuroinflammation, impairs blood-brain barrier (BBB) integrity through a complex mechanism involving activation of both RhoA/Rho kinase/myosin light chain-2 and neurokinin 1 receptor (NK1R). Using an in vitro model of human BBB composed of brain microvascular endothelial cells (BMEC), astrocytes and pericytes, this study examined the potential contributions of these elements to BBB damage induced by elevated availability of pro-inflammatory cytokine, TNF-α. Treatment of human BMECs with TNF-α significantly enhanced RhoA activity and the protein expressions of Rho kinase and phosphorylated Ser19MLC-2 while decreasing that of NK1R. Pharmacological inhibition of Rho kinase by Y-27632 and NK1R by CP96345 neutralised the disruptive effects of TNF-α on BBB integrity and function as ascertained by reversal of decreases in transendothelial electrical resistance and increases in paracellular flux of low molecular weight permeability marker, sodium fluorescein, respectively. Suppression of RhoA activation, mitigation of actin stress fibre formation and restoration of plasma membrane localisation of tight junction protein zonula occludens-1 appeared to contribute to the barrier-protective effects of both Y-27632 and CP96345. Attenuation of TNF-α-mediated increases in NK1R protein expression in BMEC by Y-27632 suggests that RhoA/Rho kinase pathway acts upstream to NK1R. In conclusion, specific inhibition of Rho kinase in cerebrovascular conditions, accompanied by excessive release of pro-inflammatory cytokine TNF-α, helps preserve endothelial cell morphology and inter-endothelial cell barrier formation and may serve as an important therapeutic target.

Effect of knife castration on leukocyte cytokine expression and indicators of stress, pain, and inflammation in Korean cattle bull calves

OBJECTIVE

This study investigated the effects of surgical castration on behavior, physiological and inflammatory indicators, and leukocyte cytokine mRNA levels in Korean cattle bull calves.

METHODS

Nineteen Korean cattle bull calves (average body weight, 254.5 kg; average age, 8.2 months) were divided into two treatment groups: control (n = 9) and castration (n = 10). Surgical castration was performed using Newberry knives and a Henderson castrating tool. Blood was obtained just before castration (0 h) and at 0.5 h, 6 h, 1 d, 3 d, 7 d, and 14 d after castration. Plasma cortisol (PC), saliva cortisol (SC), plasma substance P, and plasma haptoglobin concentrations, and the leucocyte mRNA levels of the interleukin-1-alpha (IL1A), interleukin-1-beta (IL1B), interleukin-1 receptor antagonist (IL1RN), and interleukin-6 (IL6) genes were analyzed.

RESULTS

Castration decreased (p<0.01) the average daily gain and gain/feed ratio. Castration reduced the time spent eating (p<0.001) and the eating frequency (p<0.01) and increased (p<0.001) the lying frequency. Castration temporarily increased (p<0.05) circulating PC and SC concentrations at 0.5 h after castration. Castration temporarily increased (p<0.05) plasma substance P concentrations at 1 d after castration. Castration increased (p<0.05) plasma haptoglobin concentrations at 1 and 3 d after castration. Castration increased (p< 0.05) leukocyte mRNA levels of the IL1A, IL1B, IL1RN, and IL6 genes at 6 h after castration.

CONCLUSION

Castration temporarily induced stress and expression of leucocyte inflammatory cytokine genes in Korean cattle bull calves.

Effects of fetal number on acute phase proteins, cortisol, and hematological parameters in ewes during the periparturient period

Many subclinical diseases associated with inflammation occur in sheep during the periparturient period. Clinical symptoms are usually detected at an advanced stage of the disease; therefore, there are considerable risks of permanent health disorders in fetuses or dams. Determination of acute phase proteins (APPs) as markers of inflammation may allow for an earlier diagnosis and effective treatment. Furthermore, multi-fetus pregnancies are often associated with hematological disturbances. The study objective was to compare plasma concentrations of serum amyloid A (SAA), haptoglobin (Hp), fibrinogen (Fb), and cortisol in ewes bearing one and two fetuses in the period from 2 weeks before to 2 weeks after parturition as well as to determine hematological parameters in peripheral blood. There was an important effect of fetal number on APP and cortisol concentrations in periparturient ewes. There was a greater concentration of SAA, Hp, Fb, and cortisol in ewes bearing two fetuses compared with those bearing one fetus. Profiles for APP and cortisol concentrations and hematological parameters were similar for ewes bearing one and two fetuses, and trends were within normal reference ranges for the periparturient period. Furthermore, there were no differences in values for hematological variables between ewes bearing one and two fetuses. with there being no ewes with anemia. In summary, separate determination of the previously undefined physiological ranges of APPs and cortisol for ewes bearing one and two fetuses may facilitate diagnosis of subclinical disorders and enable comparison of laboratory test results with different reference values for ewes bearing different numbers of fetuses.

Multiple action mechanism and in vivo antimicrobial efficacy of antimicrobial peptide Jelleine-I

With the extensive use of antibiotics in medicine, agriculture and food chemistry, the emergence of multi-drug resistant bacteria become more and more frequent and posed great threats to human health and life. So novel antimicrobial agents were urgently needed to defend the resistant bacteria. Jelleine-I was a small antimicrobial peptide (AMP) with eight amino acids in its sequence. It was believed to be an ideal template for developing antimicrobial agents. In the present study, the possible action mode against both gram-negative bacteria and gram-positive bacteria and in vivo antimicrobial activity was explored. Our results showed that Jelleine-I exhibits its antimicrobial activity mainly by disrupting the integrity of the cell membrane, which would not be affected by the conventional resistant mechanism. It also aims at some intracellular targets such as genomic DNA to inhibit the growth of microbes. In addition, the result of in vivo antimicrobial activity experiment showed that Jelleine-I performed a good therapeutic effect toward the mice with Escherichia coli infected peritonitis. Notably, Jelleine-I has negligible cytotoxicity toward the tested mammalian cells, indicating excellent cell selectivity between prokaryotic cells and eurkayotic cells. In summary, our results showed that Jelleine-I would be a potential candidate to be developed as a novel antimicrobial agent.

Ethanol Intoxication Alleviates the Inflammatory Response of Remote Organs to Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) may cause damage to distant organs. Acute ethanol intoxication (EI) induces complex local and systemic anti-inflammatory effects and influences the early outcomes of traumatized patients. Here, we evaluated its effects on the BI-induced expression of local inflammatory mediators in the trauma-remote organs the lungs and liver. Male mice were exposed to ethanol as a single oral dose (5g·kg^–1, 32%) before inducing a moderate blunt TBI. Sham groups underwent the same procedures without TBI. Ether 3 or 6h after the TBI, the lung and liver were collected. The gene expression of HMGB1, IL-6, MMP9, IL-1β, and TNF as well as the homogenate protein levels of receptor for advanced glycation end products (RAGE), IL-6, IL-1β, and IL-10 were analyzed. Liver samples were immunohistologically stained for HMGB1. EI decreased the gene expressions of the proinflammatory markers HMGB1, IL-6, and MMP9 in the liver upon TBI. In line with the reduced gene expression, the TBI-induced protein expression of IL-6 in liver tissue homogenates was significantly reduced by EI at 3h after TBI. While the histological HMGB1 expression was enhanced by TBI, the RAGE protein expression in the liver tissue homogenates was diminished after TBI. EI reduced the histological HMGB1 expression and enhanced the hepatic RAGE protein expression at 6h post TBI. With regard to the lungs, EI significantly reduced the gene expressions of HMGB1, IL-6, IL-1β, and TNF upon TBI, without significantly affecting the protein expression levels of inflammatory markers (RAGE, IL-6, IL-1β, and IL-10). At the early stage of TBI-induced inflammation, the gene expression of inflammatory mediators in both the lungs and liver is susceptible to ethanol-induced remote effects. Taken together, EI may alleviate the TBI-induced pro-inflammatory response in the trauma-distant organs, the lungs and liver, via the HMGB1-RAGE axis.

The Metabolic Basis of Immune Dysfunction Following Sepsis and Trauma

Critically ill, severely injured and high-risk surgical patients are vulnerable to secondary infections during hospitalization and after hospital discharge. Studies show that the mitochondrial function and oxidative metabolism of monocytes and macrophages are impaired during sepsis. Alternatively, treatment with microbe-derived ligands, such as monophosphoryl lipid A (MPLA), peptidoglycan, or β-glucan, that interact with toll-like receptors and other pattern recognition receptors on leukocytes induces a state of innate immune memory that confers broad-spectrum resistance to infection with common hospital-acquired pathogens. Priming of macrophages with MPLA, CPG oligodeoxynucleotides (CpG ODN), or β-glucan induces a macrophage metabolic phenotype characterized by mitochondrial biogenesis and increased oxidative metabolism in parallel with increased glycolysis, cell size and granularity, augmented phagocytosis, heightened respiratory burst functions, and more effective killing of microbes. The mitochondrion is a bioenergetic organelle that not only contributes to energy supply, biosynthesis, and cellular redox functions but serves as a platform for regulating innate immunological functions such as production of reactive oxygen species (ROS) and regulatory intermediates. This review will define current knowledge of leukocyte metabolic dysfunction during and after sepsis and trauma. We will further discuss therapeutic strategies that target leukocyte mitochondrial function and might have value in preventing or reversing sepsis- and trauma-induced immune dysfunction.

Hepatic alterations are accompanied by changes to bile acid transporter-expressing neurons in the hypothalamus after traumatic brain injury

Annually, there are over 2 million incidents of traumatic brain injury (TBI) and treatment options are non-existent. While many TBI studies have focused on the brain, peripheral contributions involving the digestive and immune systems are emerging as factors involved in the various symptomology associated with TBI. We hypothesized that TBI would alter hepatic function, including bile acid system machinery in the liver and brain. The results show activation of the hepatic acute phase response by 2 hours after TBI, hepatic inflammation by 6 hours after TBI and a decrease in hepatic transcription factors, Gli 1, Gli 2, Gli 3 at 2 and 24 hrs after TBI. Bile acid receptors and transporters were decreased as early as 2 hrs after TBI until at least 24 hrs after TBI. Quantification of bile acid transporter, ASBT-expressing neurons in the hypothalamus, revealed a significant decrease following TBI. These results are the first to show such changes following a TBI, and are compatible with previous studies of the bile acid system in stroke models. The data support the emerging idea of a systemic influence to neurological disorders and point to the need for future studies to better define specific mechanisms of action.

Harnessing the natural inhibitory domain to control TNFα Converting Enzyme (TACE) activity in vivo

Dysregulated activity of A Disintegrin And Metalloproteinase 17 (ADAM17)/TNFα Converting Enzyme (TACE) is associated with inflammatory disorders and cancer progression by releasing regulatory membrane-tethered proteins like TNFα, IL6R and EGFR ligands. Although specific inhibition of TACE is thought to be a viable strategy for inflammatory disorders and for malignancies treatment, the generation of effective inhibitors in vivo has been proven to be challenging. Here we report on the development of a protein inhibitor that leverages the endogenous modulator of TACE. We have generated a stable form of the auto-inhibitory TACE prodomain (TPD), which specifically inhibits in vitro and cell-surface TACE, but not the related ADAM10, and effectively modulated TNFα secretion in cells. TPD significantly attenuated TACE-mediated disease models of sepsis, rheumatoid arthritis (RA) and inflammatory bowel disease (IBD), and reduced TNFα in synovial fluids from RA patients. Our results demonstrate that intervening with endogenous ADAM sheddase modulatory mechanisms holds potential as a general strategy for the design of ADAM inhibitors.

The Physiological Role of Tumor Necrosis Factor in Human Immunity and Its Potential Implications in Spinal Manipulative Therapy: A Narrative Literature Review

OBJECTIVE

Although tumor necrosis factor (TNF) is a well-known inflammatory cytokine in the pathological development of various human diseases, its physiological roles are not widely understood nor appreciated. The molecular mechanisms underlying spinal manipulation therapy (SMT) remain elusive. The relationship between TNF and SMT is unclear. Thus, we performed this literature review to better understand TNF physiology and its potential relationship with SMT, and we propose a novel mechanism by which SMT may achieve clinical benefits by using certain beneficial features of TNF.

METHODS

We searched several databases for relevant articles published between 1975 and 2015 and then reexamined the studies from current immunophysiological perspectives.

RESULTS

The history and recent progresses in TNF physiology research were explored. Conflicting reports on the relationship between TNF and SMT were identified. Based on the newly discovered interaction between TNF and regulatory T cells, we proposed a putative biphasic TNF response to SMT, which may resolve the conflicts in the reported observations and interpretations.

CONCLUSION

The current literature about TNF informed our discussion of new physiological roles for TNF, which may help to better understand the physiological effects of SMT.

Sphingomyelin synthase 2 affects CD14‑associated induction of NF‑κB by lipopolysaccharides in acute lung injury in mice

Lipopolysaccharide (LPS) is the predominant component of the outer membrane of Gram-negative bacteria, which can cause severe inflammation in the body. The acute lung injury (ALI) induced by LPS can cause extensive damage to the lung tissue, the severe stage of which is termed acute respiratory distress syndrome, when multiple organ dysfunction syndrome may appear. There are no effective clinical treatment measures at present. The involvement of cluster of differentiation (CD)14 assists LPS in causing inflammatory reactions, and CD14 and sphingomyelin (SM), located in lipid rafts areas, are closely associated. SM synthase (SMS) is a key enzyme in the synthesis of SM, however, the effect of SMS on the inflammatory pathway involving nuclear factor (NF)‑κB induced by LPS remains to be elucidated. Under the premise of the establishment of an ALI mouse model induced by LPS, the present study established a control group, LPS group and pyrrolidine dithiocarbamate (PDTC; an NF‑κB pathway inhibitor) group. Hematoxylin‑eosin staining, reverse transcription‑quantitative polymerase chain reaction analysis, western blot analysis and thin layer chromatography were used to investigate the mechanism of SMS in ALI. Compared with the control group, the mRNA and protein levels of CD14 were significantly increased (P<0.001; n=5 and P<0.05, n=5), and the activity of SMS and expression of SMS2 were significantly upregulated (P<0.001; n=5 and P<0.05, n=5) in the model group. The increases of SMS2 and CD14 in the PDTC group were less marked, compared with those in the model group (P<0.05; n=5). These findings suggested that the degree of lung injury was reduced during the acute inflammatory reaction when NF‑κB was inhibited, and that the expression of SMS2 may affect the induction of the NF‑κB pathway by LPS through CD14.

Acute-phase responses in cattle infected with hydatid cysts and microbial agents

The aim of this study was to investigate the effect of hydatid cysts and microbial agents on the acute-phase response in cattle. Twenty-seven cattle with hydatid cysts and eight apparently healthy cattle comprised the study and control groups, respectively. Parasitological, microbiological, histopathological and immunohistochemical examinations of the liver and lungs were undertaken, and 49 of these organs were infected with cysts. In 14 of 31 (45.1%) livers and 10 of 18 (55.5%) lungs microbial growth was observed. The most frequent species occurring in the liver were Staphylococcus aureus, Escherichia coli, Corynebacterium spp. and Campylobacter spp., whereas in the lungs the most common species was Candida spp., followed by Streptococcus spp., Mannheimia haemolytica, Corynebacterium spp., Micrococcus spp. and S. aureus. The concentration of serum interleukin (IL-6) in infected cattle, 455.35 ± 39.68 pg/ml, was significantly higher than that of 83.02 ± 17.87 pg/ml in the control group (P0.05). The highest concentrations of IL-6 were detected in serum of the cattle where microbial growth had been detected, followed by cattle infected with bacteria + Trichostrongylus sp. (P< 0.001). Consequently, SAA showed an important increase in the group infected with hydatid cysts, whereas haptoglobin level decreased. It was noticed that IL-6, like SAA, had a significant role in hydatid cyst infection. Therefore IL-6 and SAA appear to be major markers in the detection of infection of cattle with hydatid cysts.

Lipopolysaccharide neutralization by a novel peptide derived from phosvitin

Lipopolysaccharide (LPS), also known as endotoxin, is the primary trigger of sepsis, which is associated with high mortality in patients. No therapeutic agents are currently efficacious enough to protect patients from sepsis characterized by LPS-mediated tissue damage and organ failure. Previously, a phosvitin-derived peptide, Pt5, which consists of the C-terminal 55 residues of zebrafish phosvitin, has been shown to function as an antibacterial agent. In this study, we have generated six mutants by site-directed mutagenesis based on the sequence of Pt5, and found that one of the six mutants, Pt5e, showed the strongest bactericidal activities against Escherichia coli and Staphylococcus aureus. We then demonstrated that Pt5e was able to bind to LPS and lipoteichoic acid (LTA). More importantly, we showed that Pt5e significantly inhibited LPS-induced tumor-necrosis factor (TNF)-α and interleukin (IL)-1β release from murine RAW264.7 cells and considerably reduced serum TNF-α and IL-1β levels in mice. Additionally, Pt5e protected the liver from damage by LPS, and remarkably promoted the survival rate of the endotoxemia mice. Furthermore, Pt5e displayed no cytotoxicity to murine RAW264.7 macrophages and no hemolytic activity toward human red blood cells. These data together indicate that Pt5e is an endotoxin-neutralizing agent with a therapeutic potential in clinical treatment of LPS-induced sepsis.

Soluble ST2 in the fetal inflammatory response syndrome: in vivo evidence of activation of the anti-inflammatory limb of the immune response

OBJECTIVE

Inflammation is a mechanism of host response to infection, which can be harmful when inappropriately modulated. Soluble ST2 (sST2) is a decoy receptor of interleukin (IL)-33, and this complex modulates the balance in the Th1/Th2 immune response. Moreover, sST2 inhibits the production of pro-inflammatory cytokines in cooperation with an anti-inflammatory cytokine, IL-10. The objectives of this study were to: (1) determine whether umbilical cord plasma sST2 concentration differs between preterm neonates with and without funisitis and between those with and without the fetal inflammatory response syndrome (FIRS); and (2) evaluate the relationship between sST2 and IL-10 among neonates with funisitis and/or FIRS.

METHODS

Umbilical cord plasma was collected from neonates delivered prematurely due to preterm labor or preterm prelabor rupture of membranes with (n = 36), and without funisitis (n = 30). FIRS (umbilical cord IL-6 concentration ≥ 17.5 pg/mL) was identified in 29 neonates. Plasma sST2 and IL-10 concentrations were determined by enzyme linked immune sorbent assay.

RESULTS

The median umbilical cord plasma sST2 concentration was 6.7-fold higher in neonates with FIRS than in those without FIRS (median 44.6 ng/mL, interquartile range (IQR) 13.8-80.3 ng/mL versus median 6.7 ng/mL, IQR 5.6-20.1 ng/mL; p < 0.0001). Similarly, the median umbilical cord plasma sST2 concentration was 2.7-fold higher in neonates with funisitis than in those without funisitis (median 19.1 ng/mL; IQR 7.1-75.0 ng/mL versus median 7.2 ng/mL; IQR 5.9-23.1 ng/mL; p = 0.008). There was a strong positive correlation between sST2 and IL-10 in neonates with funisitis and/or FIRS (Spearman's Rho = 0.7, p < 0.0001).

CONCLUSION

FIRS and funisitis are associated with an elevation of umbilical cord plasma concentrations of soluble ST2. This protein represents an important mediator of the immune response in neonates diagnosed with FIRS by promoting an anti-inflammatory effect in association with IL-10.

Dietary intake of magnesium may modulate depression

Depressive symptoms are frequent in students and may lead to countless problems. Several hypotheses associate magnesium with depression because of the presence of this mineral in several enzymes, hormones, and neurotransmitters, which may play a key role in the pathological pathways of depression. The aim of this study was to assess whether magnesium intake could modulate depressive symptoms. A cross-sectional study was conducted on a convenience sample of 402 Iranian postgraduate students studying in Malaysia to assess the relationship between magnesium intake and depressive symptoms. The mean age of the participants was 32.54 ± 6.22 years. The results of the study demonstrated an inverse relationship between magnesium intake and depressive symptoms, which persisted even after adjustments for sex, age, body mass index, monthly expenses, close friends, living on campus, smoking (current and former), education, physical activity, and marital status.

Neovascularization in retinopathy of prematurity: opposing actions of neuronal factors GPR91 and semaphorins 3A

Retinopathy of prematurity (ROP) is a major cause of severe visual deficits in children. This review focuses on the role of newly identified factors from retinal neurons, which through their opposing actions on vascular development contribute to ROP. These hypoxia-generated mediators include the Krebs cycle intermediate, succinate acting via GPR91, and the neuronal guidance molecule Semaphorin 3A.

CONCLUSION

Neuron-derived factors guide retinal vascularization and are major contributors to the pathogenesis of ROP.

Induction of heme oxygenase 1 prevents progression of liver fibrosis in Mdr2 knockout mice

Induction or overexpression of the heme-degrading enzyme, heme oxygenase 1 (HO-1), has been shown to protect mice from liver damage induced by acute inflammation. We have investigated the effects of HO-1 induction in a mouse model of chronic liver inflammation and fibrogenesis with progression to hepatocellular carcinoma (HCC) (Mdr2ko; FVB.129P2-Abcb4(tm1Bor)). HO-1 was induced in vivo by treatment with cobalt protoporphyrin IX, starting at week 5 or 12 of mice lifespan, and continued for 7 weeks. Our results showed that HO-1 induction reduced liver damage and chronic inflammation by regulating immune cell infiltration or proliferation as well as tumor necrosis factor receptor signaling. Fibrosis progression was significantly reduced by HO-1 induction in mice with mild, as well as established, portal and lobular fibrosis. HO-1 induction significantly suppressed hepatic stellate cell activation. During established fibrosis, HO-1 induction was able to revert portal inflammation and fibrosis below levels observed at the start of treatment. Moreover, hepatocellular proliferation and signs of dysplasia were decreased after HO-1 induction.

CONCLUSION

Induction of HO-1 interferes with chronic inflammation and fibrogenesis and, in consequence, might delay progression to HCC.

Activation of MDL-1 (CLEC5A) on immature myeloid cells triggers lethal shock in mice

Systemic inflammatory response syndrome (SIRS) is a potentially lethal condition, as it can progress to shock, multi-organ failure, and death. It can be triggered by infection, tissue damage, or hemorrhage. The role of tissue injury in the progression from SIRS to shock is incompletely understood. Here, we show that treatment of mice with concanavalin A (ConA) to induce liver injury triggered a G-CSF-dependent hepatic infiltration of CD11b+Gr-1+Ly6G+Ly6C+ immature myeloid cells that expressed the orphan receptor myeloid DAP12-associated lectin-1 (MDL-1; also known as CLEC5A). Activation of MDL-1 using dengue virus or an agonist MDL-1-specific antibody in the ConA-treated mice resulted in shock. The MDL-1+ cells were pathogenic, and in vivo depletion of MDL-1+ cells provided protection. Triggering MDL-1 on these cells induced production of NO and TNF-α, which were found to be elevated in the serum of treated mice and required for MDL-1-induced shock. Surprisingly, MDL-1-induced NO and TNF-α production required eNOS but not iNOS. Activation of DAP12, DAP10, Syk, PI3K, and Akt was critical for MDL-1-induced shock. In addition, Akt physically interacted with and activated eNOS. Therefore, triggering of MDL-1 on immature myeloid cells and production of NO and TNF-α may play a critical role in the pathogenesis of shock. Targeting the MDL-1/Syk/PI3K/Akt/eNOS pathway represents a potential new therapeutic strategy to prevent the progression of SIRS to shock.

Acute-phase proteins: As diagnostic tool

The varied reactions of the host to infection, inflammation, or trauma are collectively known as the acute-phase response and encompass a wide range of pathophysiological responses such as pyrexia, leukocytosis, hormone alterations, and muscle protein depletion combining to minimize tissue damage while enhancing the repair process. The mechanism for stimulation of hepatic production of acute-phase proteins is by proinflammatory cytokines. The functions of positive acute-phase proteins (APP) are regarded as important in optimization and trapping of microorganism and their products, in activating the complement system, in binding cellular remnants like nuclear fractions, in neutralizing enzymes, scavenging free hemoglobin and radicals, and in modulating the host's immune response. APP can be used as diagnostic tool in many diseases like bovine respiratory syncytial virus, prostate cancer, bronchopneumonia, multiple myeloma, mastitis, Streptococcus suis infection, starvation, or lymphatic neoplasia. Thus, acute-phase proteins may provide an alternative means of monitoring animal health.

Conservation of the ST6Gal I gene and its expression in the mammary gland

Milk sialoglycoconjugates can protect the gastrointestinal tract of the suckling neonate by competitively binding to invading pathogens and promoting growth of beneficial flora, and their potential role in postnatal brain development is of particular interest in human infant nutrition. Although the concentration and the distribution of sialoglycoconjugates have been extensively studied in the milk of various species, the investigation of sialyltransferase gene expression in the mammary gland, in the context of lactation, has been limited. The sialyltransferase enzyme ST6Gal I transfers sialic acid from CMP-sialic acid to type 2 (Galβ1,4GlcNAc) free disaccharides or the termini of N- or O-linked oligosaccharides using an α2,6-linkage. Expression of the ST6Gal I gene is primarily regulated at the level of transcription through the use of several cell and development-specific promoters, producing transcripts with divergent 5' untranslated regions (UTR). In the mouse mammary gland, the novel 5'UTR exon (L) appears to be associated with a drastic increase in ST6Gal I gene expression during lactation. We find that rats also possess an exon (L), suggesting conservation of this regulatory mechanism in rodents. In contrast, an exon (L)-containing transcript was not detected in the lactating bovine or human mammary gland. We also observed a trend of increasing ST6Gal I gene expression in the bovine mammary gland, culminating in involution. This is in contrast to species such as mice where the greatest change in ST6Gal I gene expression occurs between pregnancy and lactation, suggesting different roles in rodents vs. other mammals for α2,6-sialylated oligosaccharides present in milk.

Retinoblastoma protein-interacting zinc finger 1 (RIZ1) regulates the proliferation of monocytic leukemia cells via activation of p53

The role of retinoblastoma protein-interacting zinc finger 1 (RIZ1) on the cell growth of mouse and human monocytic leukemia cells was examined. RIZ1 expression was induced in response to tumor necrosis factor (TNF)-α. The expression was dependent on the nuclear factor-κB and AKT signaling. Further, RIZ1 expression led to the augmentation of p53 expression and the silencing of RIZ1 prevented it. On the other hand, a p53 inhibitor enhanced the TNF-α-induced RIZ1 expression. Silencing of RIZ1 augmented the proliferative activity of TNF-α-treated cells. Therefore, it is suggested that RIZ1 negatively regulated the cell proliferation of monocytic leukemia cells via activation of p53.

The fetal inflammatory response syndrome

The fetal inflammatory response syndrome (FIRS) is a condition characterized by systemic inflammation and an elevation of fetal plasma interleukin-6. This syndrome has been observed in fetuses with preterm labor with intact membranes, preterm prelabor rupture of the membranes, and also fetal viral infections such as cytomegalovirus. FIRS is a risk factor for short-term perinatal morbidity and mortality after adjustment for gestational age at delivery and also for the development of long-term sequelae such as bronchopulmonary dysplasia and brain injury. Multiorgan involvement in FIRS has been demonstrated in the hematopoietic system, thymus, adrenal glands, skin, kidneys, heart, lung, and brain. This article reviews the fetal systemic inflammatory response as a mechanism of disease. Potential interventions to control an exaggerated inflammatory response in utero are also described.

Oxidative stress expression status associated to Helicobacter pylori virulence in gastric diseases

OBJECTIVES

To analyze the status of expression of inflammation markers, antioxidant and oxidant enzymes in biopsies from patients diagnosed with gastritis, gastric ulcer (GU) and gastric cancer (GC) and the Helicobacter pylori virulence from these isolated biopsies in order to evaluate a possible association among these factors.

METHODS

H. pylori genotype from isolated biopsies was performed by PCR. The pattern of expression of inflammation (TNF-alpha, IL-1beta, IL-8, IL-10 and IL-12), oxidant (iNOS and Nox1) and antioxidant markers (MnSOD, GPX and CAT) of biopsies from gastritis, GU, GC and control groups was performed by RT-PCR.

RESULTS

Different from other gastric diseases studied here, gastritis is characterized by an oxidative stress with significant expression of TNF-alpha, IL-8, IL-12, iNOS and Nox and significant absence of MnSOD and GPX expression. Gastritis was the only condition where there was an association between TNF-alpha or IL-8 expression and H. pylori cagA+/vacAs1 genotype. In this case, TNF-alpha expression was about 3 times higher when compared to control subjects.

CONCLUSION

In this study, only gastritis was found to be associated with significant oxidative stress marker expression of TNF-alpha and IL-8 that was also related to H. pylori virulence, suggesting that they are the main oxidant stress markers responsible to trigger an increase in ROS level that contributes to decrease the expression of the MnSOD and GPX.

Human malarial disease: a consequence of inflammatory cytokine release

Malaria causes an acute systemic human disease that bears many similarities, both clinically and mechanistically, to those caused by bacteria, rickettsia, and viruses. Over the past few decades, a literature has emerged that argues for most of the pathology seen in all of these infectious diseases being explained by activation of the inflammatory system, with the balance between the pro and anti-inflammatory cytokines being tipped towards the onset of systemic inflammation. Although not often expressed in energy terms, there is, when reduced to biochemical essentials, wide agreement that infection with falciparum malaria is often fatal because mitochondria are unable to generate enough ATP to maintain normal cellular function. Most, however, would contend that this largely occurs because sequestered parasitized red cells prevent sufficient oxygen getting to where it is needed. This review considers the evidence that an equally or more important way ATP deficiency arises in malaria, as well as these other infectious diseases, is an inability of mitochondria, through the effects of inflammatory cytokines on their function, to utilise available oxygen. This activity of these cytokines, plus their capacity to control the pathways through which oxygen supply to mitochondria are restricted (particularly through directing sequestration and driving anaemia), combine to make falciparum malaria primarily an inflammatory cytokine-driven disease.

Association between non-Hodgkin lymphoma and haplotypes in the TNF region

The cytokines tumour necrosis factor-alpha (TNFalpha) and lymphotoxin-alpha (LTalpha) are known to play key roles in B-cell growth, differentiation and maturation. Genetic polymorphism within regulatory regions of these cytokine genes can alter expression levels and may be important in development of lymphoid malignancy. This study investigates a number of single nucleotide polymorphisms (SNPs) and microsatellite variants present within these genes in a large cohort of non-Hodgkin lymphoma (NHL) cases including 211 cases of follicular lymphoma (FL) and 281 cases of diffuse large B-cell lymphoma (DLBCL), and 478 unaffected controls. The study investigated whether particular alleles at these loci, or their combination across the TNF region in the form of haplotypes, may act as markers for predisposition and development of NHL. The study provided evidence for an influence of the TNF region in the susceptibility to NHL, whereby the loci -863, -857, TNFe and TNFd categorised five haplotype groups over which risk of both FL and DLBCL varied significantly. Prediction of disease risk was improved by the addition of loci to the haplotype, demonstrating the importance of considering the haplotype-specific context of the loci in genetic risk assessment.

Diversification and specialization of HIV protease function during in vitro evolution

Our goal is to understand how enzymes adapt to utilize novel substrates. We and others have shown that directed evolution tends to generate enzyme variants with broadened substrate specificity. Broad-specificity enzymes are generally deleterious to living cells, so this observed trend might be an artifact of the most commonly employed high throughput screens. Here, we demonstrate a more natural and effective screening strategy for directed evolution. The gene encoding model enzyme HIV protease was randomly mutated, and the resulting library was expressed in Escherichia coli cells to eliminate cytotoxic broad-specificity variants. The surviving variants were screened for clones with activity against a reporter enzyme. The wild-type human immunodeficiency virus type I protease (HIV PR) is cytotoxic and exhibits no detectable activity in reactions with beta-galactosidase (BGAL). In contrast, the selected variants were nontoxic and exhibited greater activity and specificity against BGAL than did the wild-type HIV PR in reactions with any substrate. A single round of whole gene random mutagenesis and conventional high-throughput screening does not usually effect complete inversions of substrate specificity. This suggests that a combination of positive and purifying selection engenders more rapid adaptation than positive selection alone.

The intriguing biology of the tumour necrosis factor/tumour necrosis factor receptor superfamily: players, rules and the games

The members of the tumour necrosis factor (TNF)/tumour necrosis factor receptor (TNFR) superfamily are critically involved in the maintenance of homeostasis of the immune system. The biological functions of this system encompass beneficial and protective effects in inflammation and host defence as well as a crucial role in organogenesis. At the same time, members of this superfamily are responsible for host damaging effects in sepsis, cachexia, and autoimmune diseases. This review summarizes recent progress in the immunobiology of the TNF/TNFR superfamily focusing on results obtained from animal studies using gene targeted mice. The different modes of signalling pathways affecting cell proliferation, survival, differentiation, apoptosis, and immune organ development as well as host defence are reviewed. Molecular and cellular mechanisms that demonstrate a therapeutic potential by targeting individual receptors or ligands for the treatment of chronic inflammatory or autoimmune diseases are discussed.

Effects of surgery on the acute phase response in clinically normal and diseased horses

The serum concentrations of serum amyloid A, haptoglobin and fibrinogen were measured in a group of horses before and at intervals after elective and non-elective surgery, and in a control group of normal horses. There was a significant, rapid and repeatable increase in the concentration of serum amyloid A in response to both elective and non-elective surgery. In the control horses its serum concentration was within the normal range, from 0 to 0.2 microg/ml. Twenty-four hours after elective surgery its mean peak concentration was 16.4 microg/ml, and after non-elective surgery it was 27.3 microg/ml. In contrast, the serum concentrations of haptoglobin and fibrinogen increased more slowly after surgery and had not decreased by 72 hours after surgery.

Peptidoglycan and lipoteichoic acid in gram-positive bacterial sepsis: receptors, signal transduction, biological effects, and synergism

In sepsis and multiple organ dysfunction syndrome (MODS) caused by gram-negative bacteria, lipopolysaccharide (LPS) initiates the early signaling events leading to the deleterious inflammatory response. However, it has become clear that LPS can not reproduce all of the clinical features of sepsis, which emphasize the roles of other contributing factors. Gram-positive bacteria, which lack LPS, are today responsible for a substantial part of the incidents of sepsis with MODS. The major wall components of gram-positive bacteria, peptidoglycan and lipoteichoic acid, are thought to contribute to the development of sepsis and MODS. In this review, the literature underlying our current understanding of how peptidoglycan and lipoteichoic acid activate inflammatory responses will be presented, with a focus on recent advances in this field.

Increased production of tumor necrosis factor-alpha by peritoneal fluid mononuclear cells induced by 60-kDa heat shock protein in women with minimal to mild endometriosis

PROBLEM

We sought to examine the role of Hsp60, a 60-kDa stress-responsive protein (hsp60) with potent immunostimulatory properties, in the pathophysiology of endometriosis. We investigated the response of peritoneal fluid mononuclear cells (PFMCs) to hsp60 to identify differences in PFMCs between women with and without endometriosis.

METHOD OF STUDY

PFMCs from women with or without endometriosis were incubated with hsp60 in vitro. The release of tumor necrosis factor (TNF)-alpha was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The rapid secretion of TNF-alpha was observed following the exposure of PFMCs to hsp60. PFMCs from women with minimal to mild endometriosis produced greater amounts of TNF-alpha in response to hsp60 stimulation than levels seen in cells from women without endometriosis.

CONCLUSION

Hsp60 may play a role in the activation of peritoneal immunity in patients with minimal to mild endometriosis.

Involution of the mouse mammary gland is associated with an immune cascade and an acute-phase response, involving LBP, CD14 and STAT3

Introduction

Involution of the mammary gland is a complex process of controlled apoptosis and tissue remodelling. The aim of the project was to identify genes that are specifically involved in this process.

Methods

We used Affymetrix oligonucleotide microarrays to perform a detailed transcript analysis on the mechanism of controlled involution after withdrawal of the pups at day seven of lactation. Some of the results were confirmed by semi-quantitative reverse transcriptase polymerase chain reaction, Western blotting or immunohistochemistry.

Results

We identified 145 genes that were specifically upregulated during the first 4 days of involution; of these, 49 encoded immunoglobulin genes. A further 12 genes, including those encoding the signal transducer and activator of transcription 3 (STAT3), the lipopolysaccharide receptor (CD14) and lipopolysaccharide-binding protein (LBP), were involved in the acute-phase response, demonstrating that the expression of acute-phase response genes can occur in the mammary gland itself and not only in the liver. Expression of LBP and CD14 was upregulated, at both the RNA and protein level, immediately after pup withdrawal; CD14 was strongly expressed in the luminal epithelial cells. Other genes identified suggested neutrophil activation early in involution, followed by macrophage activation late in the process. Immunohistochemistry and histological staining confirmed the infiltration of the involuting mammary tissue with neutrophils, plasma cells, macrophages and eosinophils.

Conclusion

Oligonucleotide microarrays are a useful tool for identifying genes that are involved in the complex developmental process of mammary gland involution. The genes identified are consistent with an immune cascade, with an early acute-phase response that occurs in the mammary gland itself and resembles a wound healing process.

New biological therapies in inflammatory bowel disease

Several biological therapies (monoclonal antibodies, designer molecules, recombinant cytokines) have been tested for clinical efficacy in inflammatory bowel disease, and some have been found to be effective. Anti-TNF-alpha (anti-tumour necrosis factor-alpha) antibody therapy is an important treatment modality in the treatment of active and fistulating Crohn's disease and should be considered in patients who fail standard medical therapies. Treatment with TNF-alpha-neutralizing antibodies is associated with immunosuppression that may lead to opportunistic infections and reactivation of tuberculosis, and patients should undergo Mantoux testing prior to treatment. Several other monoclonal antibodies, including anti-IL12 and anti-IFN-gamma, are currently in development for Crohn's disease. Other new approaches include ex vivo generation of regulatory T lymphocytes and antibodies that target and kill (subpopulations of) memory T lymphocytes.

Migration inhibitory factor in the cerebral and systemic endothelium in sepsis and malaria

OBJECTIVE

We have included migration inhibitory factor (MIF) in an ongoing immunohistochemical study comparing the site and intensity of the generation of inflammatory mediators in falciparum malaria, sepsis, and other causes of pediatric death in Africa. We wanted to determine whether it could account for our observation that inducible nitric oxide synthase is less strongly induced in the cerebral, compared with the systemic, vasculature.

DATA SOURCES

Comparisons of tissue samples taken from blood vessel walls from the brain and the axillary space in a series of sepsis and falciparum malaria autopsies of African children.

DATA SUMMARY

Intense staining for MIF has been detected in endothelial cells of axillary region vessels of all sepsis cases and most of the malaria cases examined. This parallels our findings with inducible nitric oxide synthase staining. African and Western control tissues from noninfectious causes of death stained lightly or not at all. In contrast, MIF could not be detected in vascular endothelial cells within the brain, where inducible nitric oxide synthase staining was much less intense. Detection of both MIF and inducible nitric oxide synthase in ependymal and glial cells in the same brains served as an internal positive staining control.

CONCLUSION

These outcomes add weight to the proposal that endothelial cells are a site of intense inflammatory mediator activity in sepsis and malaria. They also suggest that suppression of anti-inflammatory glucocorticoids by MIF may be lower in the brain than elsewhere in the body. The lack of MIF in cerebral vasculature endothelial cells may be linked to the absence of thrombomodulin in these cells. The systemic cellular distribution and intensity of MIF in human systemic inflammatory states has not been described.

Danger and OX40 receptor signaling synergize to enhance memory T cell survival by inhibiting peripheral deletion

This report defines a cell surface receptor (OX40) expressed on effector CD4 T cells, which when engaged in conjunction with a danger signal, rescues Ag-stimulated effector cells from activation-induced cell death in vivo. Specifically, three signals were necessary to promote optimal generation of long-lived CD4 T cell memory in vivo: Ag, a danger signal (LPS), and OX40 engagement. Mice treated with Ag or superantigen (SAg) alone produced very few SAg-specific T cells. OX40 ligation or LPS stimulation, enhanced SAg-driven clonal expansion and the survival of responding T cells. However, when SAg was administered with a danger signal at the time of OX40 ligation, a synergistic effect was observed which led to a 60-fold increase in the number of long-lived, Ag-specific CD4 memory T cells. These data lay the foundation for the provision of increased numbers of memory T cells which should enhance the efficacy of vaccine strategies for infectious diseases, or cancer, while also providing a potential target (OX40) to limit the number of auto-Ag-specific memory T cells in autoimmune disease.

Peptides and polypeptides as modulators of the immune response: thymopentin--an example with unknown mode of action

Peptides and polypeptides play a critical role in the immune system and are therefore predestined as a source for new approaches in immunotherapy. For example, antigenic peptides which can trigger a specific immunological response have been successfully used for vaccination. In contrast, cytokines have to be considered as rather non-specific immunomodulators. In addition, certain peptides with unknown mode of action have shown promising immunomodulating properties. An example is the pentapeptide thymopentin (TP5), which represents the active sequence of the originally described thymopoietin (TP). TP was recently identified as a fragment of the thymopoietins (TMPOs), a family of nuclear proteins. In vitro assays showed that TP5 affects the function of T cells and monocytes measured by enhanced cGMP level and the triggering of cellular signalling, respectively. In vivo studies demonstrated the capability of TP5 to improve an imbalanced immune system. TP5 exhibited important clinical features and further investigations on its mode of action are necessary to rationally create TP5 peptide analogs or peptidomimetics.

A synthetic lipopolysaccharide-binding peptide based on the neutrophil-derived protein CAP37 prevents endotoxin-induced responses in conscious rats

The lipid A component of lipopolysaccharide (LPS) derived from Escherichia coli has been implicated as a significant mediator in the development of circulatory and metabolic dysfunction and lethality associated with sepsis. A synthetic peptide corresponding to amino acid residues 20 through 44 of the neutrophil-derived 37-kDa cationic antimicrobial protein (CAP37 P(20-44)) possesses lipid A binding characteristics which may be useful in attenuating in vivo responses induced during circumstances of endotoxemia, including sepsis. The E. coli LPS to be used in the in vivo study was shown to be attenuated by CAP37 P(20-44) in a dose-dependent manner in the in vitro reaction with Limulus amoebocyte lysate. Intravenous infusion of CAP37 P(20-44) (1.5 or 3.0 mg/kg of body weight) with E. coli LPS (250 microg/kg over 30 min) into conscious, unrestrained rats prevented LPS-induced hyperdynamic and hypodynamic circulatory shock, hyperlactacidemia, and leukopenia in a dose-related fashion. CAP37 P(20-44) (0.2, 1.0, and 5.0 mg/kg) administered intravenously to conscious, actinomycin D-sensitized rats following a lethal dose of LPS neutralized LPS toxicity, resulting in dose-dependent 7-day survival rates of 30, 50, and 80%, respectively. CAP37 P(20-44) (5.0 mg/kg) significantly inhibited the endotoxin-induced increase in circulating tumor necrosis factor alpha in sensitized rats. These data demonstrate that CAP37 P(20-44) has the capacity to abolish in vivo biological responses to LPS that are relevant to human sepsis and to significantly neutralize the toxicity of circulating E. coli LPS.

The role of the Lps gene in experimental ulcerative colitis in mice

The effects of the Lps gene on the development of experimental ulcerative colitis were studied in two genetically different mouse strains: C57B1 and C3H. Acute colitis was induced by adding 3% dextran sulfate sodium (DSS) to the drinking water for a 7-day (C57B1 and C3H) or a 10-day (C57B1) experimental period. Although the DSS treatment initiated the same type of morphological changes in the colon in all groups of mice, an earlier onset and persistent intestinal bleeding occurred in the Lpsn mice (sensitive to lipopolysaccharide, LPS) in comparison with the Lpsd mice (hyporesponsive to LPS). Rectal bleeding appeared on day 7 in 90% of the Lpsn compared to 13% of the Lpsd mice (p < 0.0001). In C57B1 mice, followed for three additional days, 50% of the Lpsn mice died and the surviving animals showed as well as rectal bleeding a large number of Gram-negative bacteria in the liver and spleen. In contrast, the Lpsd mice of the C57B1 strain appeared unaffected by the treatment, although a transient rectal bleeding occurred in 90% on day 8. Also, significantly fewer Gram-negative bacteria were found in the liver and spleen. Even though significantly increased serum endotoxin levels were seen in all DSS-treated groups compared to controls on day 7, the serum levels of TNF alpha were significantly increased only in the Lpsn mice. In DSS-induced colitis the Lpsn genotype conferred on the mice an increased LPS susceptibility, resulting in an augmentation of the inflammatory response to Gram-negative bacteria and their endotoxins. The results suggest that LPS-induced host effector mechanisms significantly enhanced the intestinal bleeding, systemic inflammatory response, and mortality in mice with DSS-induced colitis. In addition, the host defense against the invading and systemically spread bacteria most probably involved additional genes.

Undetectable interleukin (IL)-10 and persistent IL-8 expression early in hyaline membrane disease: a possible developmental basis for the predisposition to chronic lung inflammation in preterm newborns

We are interested in determining whether premature birth alters expression of counterregulatory cytokines which modulate lung inflammation. Production of proinflammatory cytokines tumor necrosis factor alpha. IL-1 beta, and IL-8 is regulated in part by the antiinflammatory cytokine IL-10. For preterm newborns with hyaline membrane disease, deficiencies in the ability of lung macrophages to express antiinflammatory cytokines may predispose to chronic lung inflammation. We compared the expression of pro- and antiinflammatory cytokines at the mRNA and protein level in the lungs of preterm and term newborns with acute respiratory failure from hyaline membrane disease or meconium aspiration syndrome. Four sequential bronchoalveolar lavage (BAL) samples were obtained during the first 96 h of life from all patients. All patients rapidly developed an influx of neutrophils and macrophages. Over time, cell populations in both groups became relatively enriched with macrophages. The expression of proinflammatory cytokine mRNA and/or protein was present in all samples from both patient groups. In contrast, IL-10 mRNA was undetectable in most of the cell samples from preterm infants and present in the majority of cell samples from term infants. IL-10 concentrations were undetectable in lavage fluid from preterm infants with higher levels in a few of the BAL samples from term infants. These studies demonstrate that 1) IL-10 mRNA and protein expression by lung inflammatory cells is related to gestational age and 2) during the first 96 h of life neutrophil cell counts and IL-8 expression decrease in BAL from term infants, but remain unchanged in BAL samples from preterm infants.

Interleukin-10 is a central regulator of the response to LPS in murine models of endotoxic shock and the Shwartzman reaction but not endotoxin tolerance

Previous studies in vivo have shown that IL-10 infusion can prevent lethal endotoxic shock. Mice deficient in the production of IL-10 (IL10T) were used to investigate the regulatory role of IL-10 in the responses to LPS in three experimental systems. In a model of acute endotoxic shock, it was found that the lethal dose of LPS for IL10T mice was 20-fold lower than that for wild type (wt) mice suggesting that endogenous IL-10 determines the amount of LPS which can be tolerated without death. The high mortality rate of IL10T mice challenged with modest doses of LPS was correlated to the uncontrolled production of TNF as treatment with anti-TNF antibody (Ab) resulted in 70% survival. Additional studies suggested that IL-10 mediates protection by controlling the early effectors of endotoxic shock (e.g., TNF alpha) and that it is incapable of directly antagonizing the production and/or actions of late appearing effector molecules (e.g., nitric oxide). We also found that IL10T mice were extremely vulnerable to a generalized Shwartzman reaction where prior exposure to a small amount of LPS primes the host for a lethal response to a subsequent sublethal dose. The priming LPS dose for IL10T mice was 100-fold lower than that required to prime wt mice implying that IL-10 is important for suppressing sensitization. In agreement with this assumption, IL-10 infusion was found to block the sensitization step. Interestingly, IL-10 was not the main effector of endotoxin tolerance as IL10T mice could be tolerized to LPS. Furthermore, IL-10 infusion could not substitute for the desensitizing dose of LPS. These results show that IL-10 is a critical component of the host's natural defense against the development of pathologic responses to LPS although it is not responsible for LPS-induced tolerance.

Interleukin-1 and related pro-inflammatory cytokines in the treatment of bacterial infections in neutropenic and non-neutropenic animals

Bacterial infections in the immunocompromized host cause considerable mortality, and even the recently developed antimicrobial strategies often fail to cure these infections, especially in granulocytopenic patients. Cytokines and hematopoietic growth factors have been shown to stimulate host defense mechanisms in vitro and in vivo. We discuss the possible role of the pro-inflammatory cytokines interleukin-1, tumor necrosis factor-alpha, interleukin-6 and interleukin-8 as modulators of host resistance to bacterial infections. Interleukin-1 has been shown effective in various animal models of potentially lethal bacterial infection, even during severe granulocytopenia. The protective mechanism of interleukin-1 may be mediated via downregulation of cytokine receptors and cytokine production, and via induction of acute phase proteins. Moreover, in subacute and chronic infections interleukin-1 interferes with microbial outgrowth, via mechanisms that have only been partially elucidated.

Cytokines in the treatment of fungal infections

The incidence of invasive fungal infections in the immunocompromized host has increased during the past decade. Even the recently developed antifungal drugs are unable to cure these infections in patients with severely impaired host defense mechanisms. Cytokines have great potential to augment host resistance and as adjunctive therapy of invasive mycoses. We discuss the mechanisms of host defense against invasive candidiasis, aspergillosis, and cryptococcosis, and review the use of cytokines and growth factors in this setting. Interleukin-1 has been shown effective in an animal model of disseminated candidiasis, even during severe granulocytopenia. Interferon-gamma has been very effective as a modulator of resistance against a variety of fungal infections in vitro. The effect of interferon-gamma against disseminated candidiasis has been demonstrated in a mouse model. Activation of neutrophils is the main mechanism by which interferon-gamma enhances the elimination of Candida, and consequently the agent is not effective in severely granulocytopenic animals. Data on the role of colony-stimulating factors against fungal pathogens are accumulating, and trials with these agents for hematologic patients with invasive fungal infections are now being performed.

Identification of tumor necrosis factor as a transcriptional regulator of the phosphoenolpyruvate carboxykinase gene following endotoxin treatment of mice

The decreased synthesis of hepatic phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme of gluconeogenesis, that occurs during endotoxemia was shown previously in rats to occur at the transcriptional level. In the current study, the exogenous administration of human recombinant tumor necrosis factor (TNF), a proximal mediator of endotoxic shock, reduced the PEPCK transcription rate, mRNAPEPCK levels, and PEPCK enzyme activity in a time- and dose-dependent manner in CD-1 mice. Comparable amounts of circulating TNF were measured in mice 2 h after injection of human recombinant TNF (10(5) U) or a 50% lethal dose of Escherichia coli endotoxin (20 mg/kg). Direct action of TNF to decrease the PEPCK transcription rate was confirmed in vitro with H-4-II-E Reuber hepatoma cells, in which a dose-dependent inhibition of PEPCK transcription was observed with 1 to 100 U of TNF per ml. A role for TNF-elicited changes in PEPCK gene expression during endotoxemia was confirmed by the protective effect of rabbit polyclonal antibodies to recombinant murine TNF. C57BL/6 mice passively immunized with anti-TNF 4 h prior to endotoxin challenge exhibited normal PEPCK enzyme activity. Neutralization of circulating TNF with anti-TNF failed, however, to prevent the hypoglycemia commonly observed during endotoxemia, suggesting the participation of other mediators. Anti-TNF treatment reduced circulating interleukins 1 and 6 at 3 and 6 h after endotoxin treatment, respectively. These results suggest that during endotoxemia, the development of hypoglycemia is multifaceted and that several cytokines are most likely involved. The findings from the Reuber hepatoma cell model afford an opportunity in future work to map putative cytokine response elements in the PEPCK promoter responsible for perturbed hormonal regulation of the gene during endotoxemia.