Development and optimization of cytokine ELISAs using commercial antibody pairs

A portable and low-cost centrifugal microfluidic platform for multiplexed colorimetric detection of protein biomarkers

Cytokines play a very important role in our immune system by acting as mediators to put up a coordinated defense against foreign elements in our body. Elevated levels of cytokines in the body can signal to an ongoing response of the immune system to some abnormality. Thus, the quantification of a panel of cytokines can provide valuable information regarding the diagnosis of specific diseases and state of overall health of an individual. Conventional Enzyme Linked Immunosorbent Assay (ELISA) is the gold-standard for quantification of cytokines, however the need for trained personnel and expensive equipment limits its application to centralized laboratories only. In this context, there is a lack of simple, low-cost and portable devices which can allow for quantification of panels of cytokines at point-of-care and/or resource limited settings. Here, we report the development of a versatile, low-cost and portable bead-based centrifugal microfluidic platform allowing for multiplexed detection of cytokines with minimal hands-on time and an integrated colorimetric signal readout without the need for any external equipment. As a model, multiplexed colorimetric quantification of three target cytokines i.e., Tumor necrosis factor alpha (TNF-α), Interferon gamma (IFN-γ) and Interleukin-2 (IL-2) was achieved in less than 30 min with limits of detection in ng/mL range. The developed platform was further evaluated using spiked-in plasma samples to test for matrix interference. The ease of use, low-cost and portability of the developed platform highlight its potential to serve as a sample-to-answer solution for detection of cytokine panels in resource limited settings.

Optimization of Capture ELISAs for Chicken Cytokines Using Commercially Available Antibodies

Cytokines like interferon (IFN)-γ, interleukin (IL)-2, IL-6, IL-10, and IL-12p40 are important biomarkers for characterizing the nature and strength of immune responses. It is important to be able to quantify the cytokines at the protein level in biological samples. Quantification of chicken cytokines is generally performed on the level of messenger RNA (mRNA) by quantitative polymerase chain reaction (qPCR) because very few capture ELISAs for the quantification of chicken cytokine proteins are commercially available. Here, we describe the optimization and validation of capture ELISAs for chicken IL-2, IL-6, IL-10, IL-12p40, and IFN-γ using commercially available antibodies and reagents. First, we determined the optimal concentrations of the antibodies. We then verified the ELISAs’ performance and established that the lower limit of detection (LLOD) for all cytokines was below 32 pg/mL. The ELISAs show the same binding characteristics for recombinant and native cytokines (parallelism was <15.2% CV). Values for inter-assay variation were consistently low and mostly <20% CV. Overall, the optimized capture ELISAs are sensitive (<32 pg/mL) and reliable tools to quantify chicken cytokines. These ELISAs can easily and inexpensively be utilized in any immunological lab and may therefore have wide applicability in immunological research for poultry.

Neurokinin-1 Receptor Deficiency Improves Survival in Murine Polymicrobial Sepsis Through Multiple Mechanisms in Aged Mice

OBJECTIVE

Substance P (SP) is a neuropeptide that contributes to a proinflammatory state by binding to the neurokinin 1 receptor (NK-1R). Limiting this interaction has been shown to attenuate the acute inflammation. Our hypothesis was that NK-1R activation would contribute to the morbidity and mortality of sepsis in a model using mice genetically deficient in the NK-1R.

METHODS

To investigate the role of the SP/NK-1R axis in a murine model of sepsis, cecal ligation and puncture (CLP) in NK-1R deficient and wild type (WT) aged mice was performed. Acute inflammation was assessed by measuring circulating cytokines and clinical parameters.

RESULTS

Deletion of the NK-1R results in improved survival following CLP (NK-1R knockout mice survival = 100% vs. WT = 14%). A reduction in the inflammatory cytokines interleukin (IL) 6, macrophage inflammatory peptide 2, and IL-1 receptor antagonist, improved hemodynamic parameters, and increased neutrophilia were present in the NK-1R-deficient mice after CLP compared with WT mice.

CONCLUSIONS

These data confirm the hypothesis that eliminating the SP/NK-1R interaction in a highly lethal murine model of sepsis leads to decreased morbidity and mortality through multiple mechanisms.

Semi-Mechanism-Based Pharmacodynamic Model for the Anti-Inflammatory Effect of Baicalein in LPS-Stimulated RAW264.7 Macrophages

Monitoring of the inhibition of TNF-α, IL-6, iNOS, and NO is used to effectively evaluate anti-inflammatory drugs. Baicalein was found to have good anti-inflammatory activities, but its detailed cellular pharmacodynamic events have not been expatiated by any other study. The inflammatory mediators, including TNF-α, IL-6, iNOS, and NO production in RAW264.7 macrophage induced by LPS, were measured. It was found that these data showed a sequential pattern on time and based on these points a cellular pharmacodynamic model was developed and tested. TNF-α and IL-6 were quantified by ELISA, NO was detected by Griess and iNOS expression was measured by Western blot. The pharmacodynamic model was developed using a NLME modeling program Monolix® 2016R1.¹The results showed that baicalein quickly suppressed release of TNF-α in a concentration-dependent manner, and consequently causing the diminution of IL-6 and iNOS/NO. The pharmacodynamic model simulation successfully described the experimental data, supporting the hypothesis that IL-6 and iNOS /NO release after LPS stimulation is mediated by TNF-α rather than LPS directly. The pharmacodynamic model allowed a well understanding of the cellular pharmacodynamic mechanism of baicalein in the treatment of inflammatory diseases.

Host immunity, nutrition and coinfection alter longitudinal infection patterns of schistosomes in a free ranging African buffalo population

Schistosomes are trematode parasites of global importance, causing infections in millions of people, livestock, and wildlife. Most studies on schistosomiasis, involve human subjects; as such, there is a paucity of longitudinal studies investigating parasite dynamics in the absence of intervention. As a consequence, despite decades of research on schistosomiasis, our understanding of its ecology in natural host populations is centered around how environmental exposure and acquired immunity influence acquisition of parasites, while very little is known about the influence of host physiology, coinfection and clearance in the absence of drug treatment. We used a 4-year study in free-ranging African buffalo to investigate natural schistosome dynamics. We asked (i) what are the spatial and temporal patterns of schistosome infections; (ii) how do parasite burdens vary over time within individual hosts; and (iii) what host factors (immunological, physiological, co-infection) and environmental factors (season, location) explain patterns of schistosome acquisition and loss in buffalo? Schistosome infections were common among buffalo. Microgeographic structure explained some variation in parasite burdens among hosts, indicating transmission hotspots. Overall, parasite burdens ratcheted up over time; however, gains in schistosome abundance in the dry season were partially offset by losses in the wet season, with some hosts demonstrating complete clearance of infection. Variation among buffalo in schistosome loss was associated with immunologic and nutritional factors, as well as co-infection by the gastrointestinal helminth Cooperia fuelleborni. Our results demonstrate that schistosome infections are surprisingly dynamic in a free-living mammalian host population, and point to a role for host factors in driving variation in parasite clearance, but not parasite acquisition which is driven by seasonal changes and spatial habitat utilization. Our study illustrates the power of longitudinal studies for discovering mechanisms underlying parasite dynamics in individual animals and populations.

Isolation of Rice Stripe Virus Preparation from Viruliferous Small Brown Planthoppers and Mechanic Inoculation on Rice

Tenuiviruses can infect the plants of the family Poaceae, and cause serious loss of crops, particularly rice and maize, in South-Eastern Asian countries. Tenuiviruses usually depend on insect vectors for their transmission and cannot be transmitted between plants through wounds or abrasions. Rice stripe virus (RSV), a typical member of tenuiviruses, is efficiently transmitted by the small brown planthopper Laodelphax striatellus in a persistent-propagative manner to cause rice stripe disease. Here we presented a convenient method, the midrib micro-injection, to mechanically inoculate insect-derived RSV into rice leaves for conducting pathogenicity assay on rice plants.

Crocetin Potentiates Neurite Growth in Hippocampal Neurons and Facilitates Functional Recovery in Rats with Spinal Cord Injury

Crocetin is an ingredient of traditional Chinese medicine and has therapeutic potential in various diseases due to its pharmacological properties, such as neuroprotection, anti-oxidative stress, and anti-inflammation. These properties might benefit the treatment of spinal cord injury. In the present study, we tested the effect of crocetin on neurite growth and sensorimotor dysfunction in a rat model of spinal cord injury. We evaluated the viability of cultured hippocampal neurons with tetrazolium dye and lactate dehydrogenase assays, visualized neurites and axons with antibody staining, and monitored motor and sensorimotor functions in rats with spinal cord injury using the Basso, Beattie, and Bresnahan assay and the contact plantar placement test, respectively, and measured cytokine expression using enzyme-linked immuno-absorbent assays. We found that crocetin (1) did not alter the viability of cultured hippocampal neurons; (2) accelerated neurite growth with preference for the longest process in individual hippocampal neurons; (3) reversed the inhibition of neurite growth by chondroitin sulfate proteoglycan and NogoA; (4) facilitated the recovery of motor and sensorimotor functions after spinal cord injury; and (5) did not inhibit pro-inflammatory responses, but restored the innervation of the descending 5-HT system in injured spinal cord. Crocetin promotes neurite growth and facilitates the recovery of motor and sensorimotor functions after spinal cord injury, likely through repairing neuronal connections.

Tetramethylpyrazine attenuates periorbital allodynia and neuroinflammation in a model of traumatic brain injury

Background

Traumatic brain injury (TBI) is a public health issue. As the major complaint in 51% of TBI patients, chronic pain is an important aspect in TBI treatment. Tetramethylpyrazine (TMP) is an important compound in Ligustrazine, an analgesic drug in traditional Chinese medicine, but its potential in relieving pain symptom in TBI has not been tested. We established a TBI mouse model with controlled cortical impact (CCI), and measured periorbital hypersensitivity with von Frey monofilaments. We examined activated microglia and astrocytes and the levels of substance P (SP) and inducible isoform of nitric oxide synthase (iNOS) with immunohistochemistry, measured mRNA and protein levels of proinflammatory cytokines with qPCR and enzyme-linked immunosorbent assay, respectively. Western blot was employed to detect molecules in NF-κB signaling pathway.

Results

TMP significantly attenuated periorbital hypersensitivity in TBI mice. Within 3 days after CCI, TMP attenuated activation of microglia and astrocytes, levels of SP, iNOS, and CGRP in trigeminal pathway, and levels of proinflammatory cytokines (including IL-6, TNF-α, IL-12). In isolated microglia, TMP attenuated the effects of lipopolysaccharide on the phosphorylation of cytoplasmic IKKα/β and IKB-α, and levels of nucleic p65.

Conclusion

TMP reversed periorbital hypersensitivity by limiting neuroinflammation at the primary stage of TBI, and could be a promising drug for pain treatment in TBI.

Antagonism of the Neurokinin-1 Receptor Improves Survival in a Mouse Model of Sepsis by Decreasing Inflammation and Increasing Early Cardiovascular Function

OBJECTIVES

Sepsis remains a serious clinical problem despite intensive research efforts and numerous attempts to improve outcome by modifying the inflammatory response. Substance P, the principal ligand for the neurokinin-1 receptor, is a potent proinflammatory mediator that exacerbates inflammatory responses and cardiovascular variables in sepsis.

DESIGN

The current study examined whether inhibition of the neurokinin-1 receptor with a specific antagonist (CJ-12,255) would improve survival in the cecal ligation and puncture model of sepsis in adult female outbred mice.

SETTING

University basic science research laboratory.

MEASUREMENTS AND MAIN RESULTS

Neurokinin-1 receptor treatment at the initiation of sepsis improved survival in cecal ligation and puncture sepsis (neurokinin-1 receptor antagonist survival = 79% vs vehicle = 54%). Delaying therapy for as little as 8 hours postcecal ligation and puncture failed to provide a survival benefit. Neurokinin-1 receptor antagonist treatment did not prevent the sepsis-induced decrease in circulating WBCs, augment the early (6 hr postcecal ligation and puncture) recruitment of inflammatory cells to the peritoneum, or improve phagocytic cell killing of pathogens. However, the neurokinin-1 receptor antagonist significantly reduced both circulating and peritoneal cytokine concentrations. In addition, the cardiovascular variable, pulse distension (a surrogate for stroke volume) was improved in the neurokinin-1 receptor antagonist group during the first 6 hours of sepsis, and there was a significant reduction in loss of fluid into the intestine.

CONCLUSION

These data show that early activation of the neurokinin-1 receptor by substance P decreases sepsis survival through multiple mechanisms including depressing stroke volume, increasing fluid loss into the intestine, and increasing inflammatory cytokine production.

Tramadol differentially regulates M1 and M2 macrophages from human umbilical cord blood

Tramadol is an analgesic drug and relieves pain through activating μ-opioid receptors and inhibiting serotonin and noradrenaline reuptake. Emerging evidence shows that it also stimulates immune cells, including NK cells, splenocytes, and lymphocytes, and elevates IL-2 production. However, it remains unknown whether and how tramadol directly affects macrophages. To answer these questions, we collected human umbilical cord blood, isolated macrophages, and examined their responses to tramadol. Although tramadol did not alter resting macrophages and the antigen-presenting function in lipopolysaccharide-activated macrophages, it regulated M1 and M2 macrophages, which are, respectively, transformed by IFN-γ and IL-4. Interestingly, tramadol inhibits production and secretion of cytokines in M1 macrophages, but facilitates the production of inflammation-responding molecules, synthesized in M2 macrophages. We also found that STAT6 cascade pathway in M2 macrophages was significantly enhanced by tramadol. Therefore, this study reveals that tramadol regulates inflammation by inhibiting M1 macrophages (killing process), but promoting the function of M2 macrophages (healing process).

Shorter Duration of Post-Operative Antibiotics for Cecal Ligation and Puncture Does Not Increase Inflammation or Mortality

Antimicrobial therapy for sepsis has beneficial effects, but prolonged use fosters emergence of resistant microorganisms, increases cost, and secondary infections. We tested whether 3 days versus 5 days of antibiotics in the murine model of cecal ligation and puncture (CLP) negatively influences outcomes. Following CLP mice were randomized to receive the antibiotic imipenem-cilastatin (25mg/kg) in dextrose 5% in Lactated Ringer’s solution every 12 hours for either three or five days. Serial monitoring over 28 days included body weight, temperature, pulse oximetry, and facial vein sampling for hematological analysis and glucose. A separate group of mice were euthanized on post-CLP day 5 to measure cytokines and peritoneal bacterial counts. The first study examined no antimicrobial therapy and demonstrated that antibiotics significantly improved survival compared to fluids only (p = 0.004). We next tested imipenem-cilastatin therapy for 3 days versus 5 days. Body weight, temperature, glucose, and pulse oximetry measurements remained generally consistent between both groups as did the hematological profile. Pro-inflammatory plasma cytokines were comparable between both groups for IL-6, IL-1β, MIP-2 and anti-inflammatory cytokines IL-10, and TNF SRI. At 5 days post-CLP, i.e. 2 days after the termination of antibiotics in the 3 day group, there were no differences in the number of peritoneal bacteria. Importantly, shortening the course of antibiotics by 40% (from 5 days to 3 days) did not decrease survival. Our results indicate that reducing the duration of broad-spectrum antibiotics in murine sepsis did not increase inflammation or mortality.

The diagnostic ability of procalcitonin and interleukin-6 to differentiate infectious from noninfectious systemic inflammatory response syndrome and to predict mortality

PURPOSE

The purpose of the study was to quantify the ability of procalcitonin (PCT) and interleukin-6 (IL-6) to differentiate noninfectious systemic inflammatory response syndrome (SIRS) and sepsis and to predict hospital mortality.

MATERIALS

We recruited consecutively adult patients with SIRS admitted to an intensive care unit. They were divided into sepsis and noninfectious SIRS based on clinical assessment with or without positive cultures. Concentrations of PCT and IL-6 were measured daily over the first 3 days.

RESULTS

A total of 239 patients were recruited, 164 (68.6%) had sepsis, and 68 (28.5%) died in hospital. The PCT levels were higher in sepsis compared with noninfectious SIRS throughout the 3-day period (P < .0001). On admission, PCT concentration was diagnostic of sepsis (area under the curve of 0.63 [0.55-0.71]), and IL-6 was predictive of mortality, (area under the curve of 0.70 [0.62-0.78]). Peak IL-6 concentration improved the risk assessment of Sequential Organ Failure Assessment (SOFA) score for prediction of mortality among those who went on to die by an average of 5% and who did not die by 2%

CONCLUSIONS

Procalcitonin measured on intensive care unit admission was diagnostic of sepsis, and IL-6 was predictive of mortality. Addition of IL-6 concentration to SOFA score improved risk assessment for prediction of mortality. Future studies should include clinical indices, for example, SOFA score, for prognostic evaluation of biomarkers.

Administration of DNA Encoding the Interleukin-27 Gene Augments Antitumour Responses through Non-adaptive Immunity

DNA-mediated immunization of a tumour antigen is a possible immunotherapy for cancer, and interleukin (IL)-27 has diverse functions in adaptive immunity. In this study, we examined whether IL-27 DNA administration enhanced antitumour effects in mice vaccinated with DNA encoding a putative tumour antigen, β-galactosidase (β-gal). An intramuscular injection of cardiotoxin before DNA administration facilitated the exogenous gene expression. In mice received β-gal and IL-27 DNA, growth of β-gal-positive P815 tumours was retarded and survival of the mice was prolonged. Development of β-gal-positive Colon 26 tumours was suppressed by vaccination of β-gal DNA and further inhibited by additional IL-27 DNA administration or IL-12 family cytokines. Nevertheless, a population of β-gal-specific CD8(+) T cells did not increase, and production of anti-β-gal antibody was not enhanced by IL-27 DNA administration. Spleen cells from mice bearing IL-27-expressing Colon 26 tumours showed greater YAC-1-targeted cytotoxicity although CD3(-)/DX5(+) natural killer (NK) cell numbers remained unchanged. Recombinant IL-27 enhanced YAC-1-targeted cytotoxicity of IL-2-primed splenic NK cells and augmented a phosphorylation of signal transducer and activator of transcription 3 and an expression of perforin. These data collectively indicate that IL-27 DNA administration activates NK cells and augments vaccination effects of DNA encoding a tumour antigen through non-adaptive immune responses.

Enemies and turncoats: bovine tuberculosis exposes pathogenic potential of Rift Valley fever virus in a common host, African buffalo (Syncerus caffer)

The ubiquity and importance of parasite co-infections in populations of free-living animals is beginning to be recognized, but few studies have demonstrated differential fitness effects of single infection versus co-infection in free-living populations. We investigated interactions between the emerging bacterial disease bovine tuberculosis (BTB) and the previously existing viral disease Rift Valley fever (RVF) in a competent reservoir host, African buffalo, combining data from a natural outbreak of RVF in captive buffalo at a buffalo breeding facility in 2008 with data collected from a neighbouring free-living herd of African buffalo in Kruger National Park. RVF infection was twice as likely in individual BTB+ buffalo as in BTB- buffalo, which, according to a mathematical model, may increase RVF outbreak size at the population level. In addition, co-infection was associated with a far higher rate of fetal abortion than other infection states. Immune interactions between BTB and RVF may underlie both of these interactions, since animals with BTB had decreased innate immunity and increased pro-inflammatory immune responses. This study is one of the first to demonstrate how the consequences of emerging infections extend beyond direct effects on host health, potentially altering the dynamics and fitness effects of infectious diseases that had previously existed in the ecosystem on free-ranging wildlife populations.

Acute-Phase Deaths from Murine Polymicrobial Sepsis Are Characterized by Innate Immune Suppression Rather Than Exhaustion

Sepsis, a leading cause of death in the United States, has poorly understood mechanisms of mortality. To address this, our model of cecal ligation and puncture (CLP) induced sepsis stratifies mice as predicted to Live (Live-P) or Die (Die-P) based on plasma IL-6. Six hours post-CLP, both Live-P and Die-P groups have equivalent peritoneal bacterial colony forming units and recruitment of phagocytes. By 24 h, however, Die-P mice have increased bacterial burden, despite increased neutrophil recruitment, suggesting Die-P phagocytes have impaired bacterial killing. Peritoneal cells were used to study multiple bactericidal processes: bacterial killing, reactive oxygen species (ROS) generation, and phagocytosis. Total phagocytosis and intraphagosomal processes were determined with triple-labeled Escherichia coli, covalently labeled with ROS- and pH-sensitive probes, and an ROS/pH-insensitive probe for normalization. Although similar proportions of Live-P and Die-P phagocytes responded to exogenous stimuli, Die-P phagocytes showed marked deficits in all parameters measured, thus suggesting immunosuppression rather than exhaustion. This contradicts the prevailing sepsis paradigm that acute-phase sepsis deaths (<5 d) result from excessive inflammation, whereas chronic-phase deaths (>5 d) are characterized by insufficient inflammation and immunosuppression. These data suggest that suppression of cellular innate immunity in sepsis occurs within the first 6 h.

Bayesian network analysis of multi-compartmentalized immune responses in a murine model of sepsis and direct lung injury

Background

Inflammatory disease processes involve complex and interrelated systems of mediators. Determining the causal relationships among these mediators becomes more complicated when two, concurrent inflammatory conditions occur. In those cases, the outcome may also be dependent upon the timing, severity and compartmentalization of the insults. Unfortunately, standard methods of experimentation and analysis of data sets may investigate a single scenario without uncovering many potential associations among mediators. However, Bayesian network analysis is able to model linear, nonlinear, combinatorial, and stochastic relationships among variables to explore complex inflammatory disease systems. In these studies, we modeled the development of acute lung injury from an indirect insult (sepsis induced by cecal ligation and puncture) complicated by a direct lung insult (aspiration). To replicate multiple clinical situations, the aspiration injury was delivered at different severities and at different time intervals relative to the septic insult. For each scenario, we measured numerous inflammatory cell types and cytokines in samples from the local compartments (peritoneal and bronchoalveolar lavage fluids) and the systemic compartment (plasma). We then analyzed these data by Bayesian networks and standard methods.

Results

Standard data analysis demonstrated that the lung injury was actually reduced when two insults were involved as compared to one lung injury alone. Bayesian network analysis determined that both the severity of lung insult and presence of sepsis influenced neutrophil recruitment and the amount of injury to the lung. However, the levels of chemoattractant cytokines responsible for neutrophil recruitment were more strongly linked to the timing and severity of the lung insult compared to the presence of sepsis. This suggests that something other than sepsis-driven exacerbation of chemokine levels was influencing the lung injury, contrary to previous theories.

Conclusions

To our knowledge, these studies are the first to use Bayesian networks together with experimental studies to examine the pathogenesis of sepsis-associated lung injury. Compared to standard statistical analysis and inference, these analyses elucidated more intricate relationships among the mediators, immune cells and insult-related variables (timing, compartmentalization and severity) that cause lung injury. Bayesian networks are an effective tool for evaluating complex models of inflammation.

Valproic acid attenuates the expression of pro-inflammatory cytokines lipopolysaccharide-treated canine peripheral blood mononuclear cells (in vitro) and in a canine endotoxemia model (in vivo)

Valproic acid (VPA), a known histone deacetylase inhibitor, has been used as an anticonvulsant in dogs. VPA also has anti-inflammatory properties, but there are no reports on the immunomodulatory effects of VPA in canine endotoxemia. In the present study, we demonstrate that the use of VPA significantly reduces the production of early-phase pro-inflammatory cytokines (TNF-α, IL-6) caused by lipopolysaccharide (LPS) stimulation both in vitro and in vivo. For the in vitro study, VPA was evaluated for 24h on LPS (100 ng/ml)-treated canine peripheral blood mononuclear cells (PBMCs) which isolated from 5 healthy Beagle dogs. VPA significantly decreased the mRNA expression of TNF-α and IL-6 in a dose-dependent manner (p<0.05 for IL-6; p<0.01 for TNF-α). Fourteen adult Beagles were studied for in vivo study; nine dogs received a low dose of LPS (10 μg/kg/h) via continuous IV infusion for 12h to induce endotoxemia whereas 5 dogs received normal saline as controls. Four out of 9 endotoxemic dogs were administered VPA (50mg/kg, IV) at 1h and 12h along with the LPS infusion. Three hours after the first administration of VPA, IL-6 mRNA expressions in PBMCs significantly decreased (p=0.033 vs. LPS group). VPA also significantly decreased the circulating TNF-α (p=0.044 vs. LPS group at 3h) and IL-6 protein at 3h (p=0.034 vs. LPS group) and 6h (p=0.026 vs. LPS group) post-treatment. Our study suggests that VPA attenuates the expression of pro-inflammatory cytokines in a canine endotoxemia model in vitro and in vivo. We speculate that valproic acid may be useful for reducing inflammatory cytokine levels in dogs with sepsis.

Location, location, location: cytokine concentrations are dependent on blood sampling site

OBJECTIVE

Considerable breakthroughs in the field of sepsis have been made using animal models. Sepsis exhibits a wide array of derangements that may be evaluated in the blood, including the release of proinflammatory and anti-inflammatory cytokines. The Shock journal adheres to the ARRIVE guidelines regarding reporting in vivo results to allow reproducibility of data findings. It is generally assumed that blood cytokine concentrations collected from typical sampling sites will be similar, but there are no data validating that this is true. The main purpose of the present study was to determine if the location of blood sampling results in cytokine concentration differences following inflammatory insults.

METHODS

Two different models of acute inflammation were studied. Adult, female ICR (Institute of Cancer Research) mice were injected with Escherichia coli lipopolysaccharide (n = 28) or subjected to cecal ligation and puncture (n = 16). They were killed at early time points following these inflammatory challenges for the collection of blood from the facial vein, retro-orbital sinus, and heart. Additional samples were collected in EDTA and heparin. Plasma cytokines from the same mouse were collected from each sampling site and evaluated by enzyme-linked immunosorbent assay. Clinical chemical parameters including plasma blood urea nitrogen and total protein were also analyzed.

RESULTS

Regardless of model, time of collection, or cytokine measured, cytokine values from heart blood were higher than facial vein values from the same mouse. Interleukin (IL-6) collected from the heart relative to the facial vein demonstrated elevated concentrations following injection of lipopolysaccharide. In a similar manner, higher concentrations of IL-6, macrophage inflammatory protein 2, IL-10, and IL-1 receptor antagonist were found in cardiac puncture samples compared with other sampling sites 24 h after sepsis induced by cecal ligation and puncture. Similar differences were not seen when comparing blood urea nitrogen and total protein values from the two different sites. Using plasma IL-6 collected from the heart would incorrectly stratify predicted-to-live mice into the predicted-to-die category. Therefore, a simple linear regression model was developed to correctly restratify mice to their predicted fate. These data demonstrate that proinflammatory and anti-inflammatory cytokine concentrations are dramatically elevated when drawn centrally from the heart compared with collection from peripheral locations such as the facial vein. It is critical for publications to document the sampling location when evaluating plasma cytokines and attempting to compare studies.

Fas ligand DNA enhances a vaccination effect by coadministered DNA encoding a tumor antigen through augmenting production of antibody against the tumor antigen

Interaction of Fas and Fas ligand (FasL) plays an important role in the regulation of immune responses by inducing apoptosis of activated cells; however, a possible role of FasL in DNA vaccination has not been well understood. We examined whether administration of DNA encoding FasL gene enhanced antitumor effects in mice that were vaccinated with DNA expressing a putative tumor antigen gene, β-galactosidase (β-gal). Growth of β-gal-positive Colon 26 tumors was retarded in the syngeneic mice immunized with β-gal and FasL DNA compared with those vaccinated with β-gal or FasL DNA. We did not detect increased numbers of β-gal-specific CD8(+) T cells in lymph node of mice that received combination of β-gal and FasL DNA, but amounts of anti-β-gal antibody increased with the combination but not with β-gal or FasL DNA injection alone. Subtype analysis of anti-β-gal antibody produced by the combination of β-gal and FasL DNA or β-gal DNA injection showed that IgG2a amounts were greater in mice injected with both DNA than those with β-gal DNA alone, but IgG2b amounts were lower in both DNA-injected than β-gal DNA-injected mice. These data suggest that FasL is involved in boosting humoral immunity against a gene product encoded by coinjected DNA and enhances the vaccination effects.

Substance P mediates reduced pneumonia rates after traumatic brain injury

OBJECTIVES

Traumatic brain injury results in significant morbidity and mortality and is associated with infectious complications, particularly pneumonia. However, whether traumatic brain injury directly impacts the host response to pneumonia is unknown. The objective of this study was to determine the nature of the relationship between traumatic brain injury and the prevalence of pneumonia in trauma patients and investigate the mechanism of this relationship using a murine model of traumatic brain injury with pneumonia.

DESIGN

Data from the National Trauma Data Bank and a murine model of traumatic brain injury with postinjury pneumonia.

SETTING

Academic medical centers in Cincinnati, OH, and Boston, MA.

PATIENTS/SUBJECTS

Trauma patients in the National Trauma Data Bank with a hospital length of stay greater than 2 days, age of at least 18 years at admission, and a blunt mechanism of injury. Subjects were female ICR mice 8-10 weeks old.

INTERVENTIONS

Administration of a substance P receptor antagonist in mice.

MEASUREMENTS AND MAIN RESULTS

Pneumonia rates were measured in trauma patients before and after risk adjustment using propensity scoring. In addition, survival and pulmonary inflammation were measured in mice undergoing traumatic brain injury with or without pneumonia. After risk adjustment, we found that traumatic brain injury patients had significantly lower rates of pneumonia compared to blunt trauma patients without traumatic brain injury. A murine model of traumatic brain injury reproduced these clinical findings with mice subjected to traumatic brain injury demonstrating increased bacterial clearance and survival after induction of pneumonia. To determine the mechanisms responsible for this improvement, the substance P receptor was blocked in mice after traumatic brain injury. This treatment abrogated the traumatic brain injury-associated increases in bacterial clearance and survival.

CONCLUSIONS

The data demonstrate that patients with traumatic brain injury have lower rates of pneumonia compared to non-head-injured trauma patients and suggest that the mechanism of this effect occurs through traumatic brain injury-induced release of substance P, which improves innate immunity to decrease pneumonia.

Early murine polymicrobial sepsis predominantly causes renal injury

Multiple organ failure in sepsis substantially increases mortality. This study examined if there was greater hepatic, pancreatic, splenic, or renal injury in mice that would die during sepsis induced by cecal ligation and puncture (CLP) compared with that of those that would survive. Mice were stratified into groups predicted to die (Die-P) or predicted to live (Live-P) in the first 5 days after CLP based on plasma interleukin 6 levels. Groups were sacrificed to harvest organs for histology. Separate animals were followed for survival with daily blood sampling to examine renal function. No significant histological evidence of organ injury was observed in either the Live-P or Die-P mice. Minimal hepatic injury occurred as plasma aspartate transaminase demonstrated less than a 2-fold increase over normal in both groups. In addition, pancreatic injury was minimal as there was also less than a 2-fold increase in plasma amylase levels. In contrast, blood urea nitrogen levels were nearly five times higher within 24 h in Die-P mice compared with those of mice predicted to live. Mice with blood urea nitrogen levels higher than 44 mg/dL had a 17.6 higher relative risk of dying (95% confidence interval, 4.5-69.4). Cystatin C, a more specific kidney function biomarker, was also elevated at 24 h after CLP. When the cystatin C levels were analyzed relative to the hours before death, rather than hours after CLP, they were also significantly increased in mice Dead by day 5 compared with those Alive after day 5. We conclude that limited liver, pancreas, and spleen injury develops during murine CLP-induced sepsis while significant kidney injury is present. The renal injury becomes worse closer to death.

Reduction of eotaxin production and eosinophil recruitment by pulmonary autologous macrophage transfer in a cockroach allergen-induced asthma model

We sought to investigate the effects of cockroach allergen (CRA) exposure on the lung macrophage population to determine how different macrophage phenotypes influence exacerbation of disease. CRA exposure caused significantly reduced expression of CD86 on lung macrophages. These effects were not systemic, as peritoneal macrophage CD86 expression was not altered. To investigate whether naïve macrophages could reduce asthma-like pulmonary inflammation, autologous peritoneal macrophages were instilled into the airways 24 h before the final CRA challenge. Pulmonary inflammation was assessed by measurement of airway hyperresponsiveness, mucin production, inflammatory cell recruitment, and cytokine production. Cell transfer did not have significant effects in control mice, nor did it affect pulmonary mucin production or airway hyperresponsiveness in control or CRA-exposed mice. However, there was significant reduction in the number of eosinophils recovered in the bronchoalveolar lavage (BAL) (5.8 × 10⁵ vs. 0.88 × 10⁵), and total cell recruitment to the airways of CRA-exposed mice was markedly reduced (1.1 × 10⁶ vs. 0.57 × 10⁶). The reduced eosinophil recruitment was reflected by substantially lower levels of eosinophil peroxidase in the lung and significantly lower concentrations of eotaxins in BAL (eotaxin 1: 3 pg/ml vs. undetectable; eotaxin 2: 2,383 vs. 131 pg/ml) and lung homogenate (eotaxin 1: 1,043 vs. 218 pg/ml; eotaxin 2: 10 vs. 1.5 ng/ml). We conclude that CRA decreases lung macrophage CD86 expression. Furthermore, supplementation of the lung cell population with peritoneal macrophages inhibits eosinophil recruitment, achieved through reduction of eotaxin production. These data demonstrate that transfer of naïve macrophages will reduce some aspects of asthma-like pulmonary inflammation in response to CRA.

Cecal ligation and puncture-induced murine sepsis does not cause lung injury

OBJECTIVE

The cause of death in murine models of sepsis remains unclear. The primary purpose of this study was to determine if significant lung injury develops in mice predicted to die after cecal ligation and puncture-induced sepsis compared with those predicted to live.

DESIGN

Prospective, laboratory controlled experiments.

SETTING

University research laboratory.

SUBJECTS

Adult, female, outbred Institute of Cancer Research mice.

INTERVENTIONS

Mice underwent cecal ligation and puncture to induce sepsis. Two groups of mice were euthanized at 24 and 48 hrs postcecal ligation and puncture and samples were collected. These mice were further stratified into groups predicted to die (Die-P) and predicted to live (Live-P) based on plasma interleukin-6 levels obtained 24 hrs postcecal ligation and puncture. Multiple measures of lung inflammation and lung injury were quantified in these two groups. Results from a group of mice receiving intratracheal normal saline without surgical intervention were also included as a negative control. As a positive control, bacterial pneumonia was induced with Pseudomonas aeruginosa to cause definitive lung injury. Separate mice were followed for survival until Day 28 postcecal ligation and puncture. These mice were used to verify the interleukin-6 cutoffs for survival prediction.

MEASUREMENTS AND MAIN RESULTS

After sepsis, both the Die-P and Live-P mice had significantly suppressed measures of respiratory physiology but maintained normal levels of arterial oxygen saturation. Bronchoalveolar lavage levels of pro- and anti-inflammatory cytokines were not elevated in the Die-P mice compared with the Live-P. In addition, there was no increase in the recruitment of neutrophils to the lung, pulmonary vascular permeability, or histological evidence of damage. In contrast, all of these pulmonary injury and inflammatory parameters were increased in mice with Pseudomonas pneumonia.

CONCLUSIONS

These data demonstrate that mice predicted to die during sepsis have no significant lung injury. In murine intra-abdominal sepsis, pulmonary injury cannot be considered the etiology of death in the acute phase.

Cytokine measurements and possible interference from heterophilic antibodies--problems and solutions experienced with rheumatoid factor

Cytokines are important in the understanding of the immune process in health and disease and are valuable indicators in diagnostics. Measurements of cytokines are based on immunometric methods, and it is important to understand possible pitfalls in these methods to produce reliable cytokine data. This paper focuses on obtaining optimal measurements when applying enzyme-linked immunosorbent assay (ELISA) or multiplex immunoassays (MIA). Cytokines are measured in serum or plasma, as well as in various other body fluids, all containing a series of antibodies and the possibility of interference from these. Some antibodies, such as heterophilic and human anti-animal antibodies, are able to interfere with all immunoassays, but the immunometric techniques are most prone to serious interference from this source. Another type, rheumatoid factor (RF) is a composite of different autoimmune antibodies which can be present in both blood and synovial fluid. RF is present in some arthritic diseases as well as in some other medical conditions. When present, especially RF IgM is known to interfere with the immunometric measurements. A possible and affordable solution to diminish this interference is PEG precipitation, but other efficient, but more expensive, methods, such as precipitation using Protein L or commercially available blocking agents, are also available. Interference of RF is at present not tested in all cytokine assays, but degree of interference from RF, human anti-animal and heterophilic antibodies, as well as from other possible disease-specific antibodies, must always be considered when developing and applying new assays for cytokine measurements.

A2B adenosine receptor expression by myeloid cells is proinflammatory in murine allergic-airway inflammation

Asthma is a chronic condition with high morbidity and healthcare costs, and cockroach allergens are an established cause of urban pediatric asthma. A better understanding of cell types involved in promoting lung inflammation could provide new targets for the treatment of chronic pulmonary disease. Because of its role in regulating myeloid cell-dependent inflammatory processes, we examined A(2B) R expression by myeloid cells in a cockroach allergen model of murine asthma-like pulmonary inflammation. Both systemic and myeloid tissue-specific A(2B) R deletion significantly decreased pulmonary inflammatory cell recruitment, airway mucin production, and proinflammatory cytokine secretion after final allergen challenge in sensitized mice. A(2B) R deficiency resulted in a dramatic reduction on Th2-type airways responses with decreased pulmonary eosinophilia without augmenting neutrophilia, and decreased lung IL-4, IL-5, and IL-13 production. Chemokine analysis demonstrated that eotaxin 1 and 2 secretion in response to repeated allergen challenge is myeloid cell A(2B) R dependent. In contrast, there were no differences in the levels of the CXC chemokines keratinocyte-derived chemokine and MIP-2 in the myeloid cell A(2B) R-deficient mice, strengthening A(2B) R involvement in the development of Th2-type airways inflammation. Proinflammatory TNF-α, IFN-γ, and IL-17 secretion were also reduced in systemic and myeloid tissue-specific A(2B) R deletion mouse lines. Our results demonstrate Th2-type predominance for A(2B) R expression by myeloid cells as a mechanism of development of asthma-like pulmonary inflammation.

Sepsis chronically in MARS: systemic cytokine responses are always mixed regardless of the outcome, magnitude, or phase of sepsis

The paradigm of systemic inflammatory response syndrome-to-compensatory anti-inflammatory response syndrome transition implies that hyperinflammation triggers acute sepsis mortality, whereas hypoinflammation (release of anti-inflammatory cytokines) in late sepsis induces chronic deaths. However, the exact humoral inflammatory mechanisms attributable to sepsis outcomes remain elusive. In the first part of this study, we characterized the systemic dynamics of the chronic inflammation in dying (DIE) and surviving (SUR) mice suffering from cecal ligation and puncture sepsis (days 6-28). In the second part, we combined the current chronic and previous acute/chronic sepsis data to compare the outcome-dependent inflammatory signatures between these two phases. A composite cytokine score (CCS) was calculated to compare global inflammatory responses. Mice were never sacrificed but were sampled daily (20 μl) for blood. In the first part of the study, parameters from chronic DIE mice were clustered into the 72, 48, and 24 h before death time points and compared with SUR of the same post-cecal ligation and puncture day. Cytokine increases were mixed and never preceded chronic deaths earlier than 48 h (3- to 180-fold increase). CCS demonstrated simultaneous and similar upregulation of proinflammatory and anti-inflammatory compartments at 24 h before chronic death (DIE 80- and 50-fold higher versus SUR). In the second part of the study, cytokine ratios across sepsis phases/outcomes indicated steady proinflammatory versus anti-inflammatory balance. CCS showed the inflammatory response in chronic DIE was 5-fold lower than acute DIE mice, but identical to acute SUR. The systemic mixed anti-inflammatory response syndrome-like pattern (concurrent release of proinflammatory and anti-inflammatory cytokines) occurs irrespective of the sepsis phase, response magnitude, and/or outcome. Although different in magnitude, neither acute nor chronic septic mortality is associated with a predominating proinflammatory and/or anti-inflammatory signature in the blood.

ELISA rescue protocol: recovery of sample concentrations from an assay with an unsuccessful standard curve

The Enzyme-linked Immunosorbant Assay (ELISA) is a method commonly used to measure proteins in various biological matrices, due to its ease of performance and relatively low cost. In order for quantitative data to be generated, a reference standard curve must be prepared for each assay; however, due to investigator error or standard protein degradation, otherwise representative experimental sample data are rendered useless. Herein, we describe a protocol by which sample concentrations can be recovered from assays in which the standard curve fails. The ΔOD values of the experimental samples are used to generate a new standard curve, which is applied back to the original plate. For validation of this method, experimental sample concentrations obtained using acceptable standard curves were potted against those calculated using this new method. Using linear regression analysis, we show a near 1:1 correlation between sample concentrations, with r(2) values between 0.98 and 0.99 and slopes between 0.97 and 1.10. This method demonstrates that assays resulting in unusable standard curves do not require re-assay of all samples. Instead, the experimental sample concentrations can be retrieved saving the investigator the time and resources required to rerun samples or repeat entire experiments.

Mannose-capped Lipoarabinomannan from Mycobacterium tuberculosis induces soluble tumor necrosis factor receptor production through tumor necrosis factor alpha-converting enzyme activation

Primary Mycobacterium tuberculosis infection results in granuloma formation in lung tissue. A granuloma encapsulates mycobacterium-containing cells, thereby preventing dissemination and further infection. Tumor necrosis factor alpha (TNF-α) is a host-protective cytokine during M. tuberculosis infection due to its role in promoting and sustaining granuloma formation. TNF activity is regulated through the production of soluble TNF receptors (sTNFRI and sTNFRII). Therefore, we examined the potential production of endogenous sTNFRs during M. tuberculosis infection. Using the murine model of aerosol M. tuberculosis infection, we determined that levels of sTNFR production were elevated in bronchoalveolar lavage fluid 1 month following infection. An investigation of M. tuberculosis cell wall components identified that the known virulence factor mannose-capped lipoarabinomannan (ManLAM) was sufficient to induce sTNFR production, with sTNFRII being produced preferentially compared with sTNFRI. ManLAM stimulated the release of sTNFRs without TNF production, which corresponded to an increase in TNF-α-converting enzyme (TACE) activity. To determine the relevance of these findings, serum samples from M. tuberculosis-infected patients were tested and found to have an increase in the sTNFRII/sTNFRI ratio. These data identify a mechanism by which M. tuberculosis infection can promote the neutralization of TNF and furthermore suggest the potential use of the sTNFRII/sTNFRI ratio as an indicator of tuberculosis disease.

Acute oral ethanol exposure triggers asthma in cockroach allergen-sensitized mice

Asthma may be triggered by multiple mediators, including allergen-IgE cross-linking and non-IgE mechanisms. Several clinical studies have shown acute ethanol consumption exacerbates asthma, yet no animal model exists to study this process. We developed a model of ethanol-triggered asthma in allergen-sensitized mice to evaluate the mechanisms of ethanol inducing asthma-like responses. Outbred mice were exposed to cockroach allergens on Days 0 and 14; and on Day 21, mice received ethanol by oral gavage. Tracer studies confirmed alcohol aspiration did not occur. Within 30 minutes, alcohol induced degranulation of over 74% of mast cells, and multiple parameters of asthma-like pulmonary inflammation were triggered. Ethanol-gavaged mice had a fivefold increased production of eotaxin-2 (534 pg/mL) and a sevenfold increase in bronchoalveolar eosinophils (70,080 cells). Ethanol induced a 10-fold increase in IL-13, from 84 pg/mL in sensitized mice to 845 pg/mL in ethanol-gavaged sensitized mice. In cockroach allergen-sensitized mice, ethanol triggered asthma-like changes in respiratory physiology and a significant fivefold increase in airway mucin production. Importantly, none of these asthmatic exacerbations were observed in normal mice gavaged with ethanol. Cromolyn sodium effectively stabilized mast cells, yet increased mucin production and bronchoalveolar eosinophil recruitment. Together, these data show a single oral alcohol exposure will trigger asthma-like pulmonary inflammation in allergen-sensitized mice, providing a novel asthma model.

Lipopolysaccharide binding protein inhibitory peptide alters hepatic inflammatory response post-hemorrhagic shock

Translocation of microorganisms and endotoxin (LPS) across the gastrointestinal mucosa may exacerbate the inflammatory response and potentiate hepatic injury associated with hemorrhagic shock. Lipopolysaccharide binding protein (LBP) augments LPS signaling through TLR4. In addition, evidence suggests that TLR4-mediated injury in liver ischemia/reperfusion occurs through the IRF-3/MyD88 independent pathway. We hypothesized that administration of LBP inhibiting peptide, LBPK95A, given at the time of resuscitation would reduce liver inflammation and injury in a murine model of hemorrhagic shock by limiting LPS-induced activation of the MyD88 independent pathway. Hemorrhagic shock was induced in male, C57BL/6 mice; a mean arterial blood pressure of 35 mmHg was maintained for 2.5 h. LBPK95A peptide or equal volume Lactated Ringer's solution was administered followed by fluid resuscitation. Mice were sacrificed at 2 and 6 h post-resuscitation. At 2 h, liver mRNA levels revealed a significant reduction in IFN-β, a cytokine produced via the MyD88 independent pathway, with LBPK95A treatment. However, mRNA levels of TNF-α, a cytokine associated with the MyD88 dependent pathway, were unaffected by treatment. The LBP inhibitory peptide did selectively reduce activation of TLR4 signaling via the IRF-3/MyD88 independent pathway. These results suggest that LBP promotes cytokine production through the MyD88 independent pathway during hemorrhagic shock.

Presence of preexisting antibodies mediates survival in sepsis

Sepsis is one of the leading causes of death in hospitals worldwide. Even with optimal therapy, severe sepsis results in 50% mortality, indicating variability in the response of individuals towards treatment. We hypothesize that the presence of preexisting antibodies present in the blood before the onset of sepsis induced by cecal ligation and puncture (CLP) in mice accounts for the differences in their survival. A plasma-enhanced killing (PEK) assay was performed to calculate the PEK capacity of plasma, that is, the ability of plasma to augment polymorphonuclear neutrophil killing of bacteria. Plasma-enhanced killing was calculated as PEK = [1 / log (N)] × 100, where N = number of surviving bacteria; a higher PEK indicated better bacterial killing. A range of PEK in plasma collected from mice before CLP was observed, documenting individual differences in bacterial killing capacity. Mortality was predicted based on plasma IL-6 levels at 24 h after CLP. Mice predicted to die (Die-P) had a lower PEK (<14) and higher peritoneal bacterial counts at 24 h after sepsis compared with those predicted to live (Live-P) with a PEK of greater than 16. Mice with PEK of less than 14 were 3.1 times more likely to die compared with the group with PEK of greater than 16. To understand the mechanism of defense conferred by the preexisting antibodies, binding of IgM or IgG to enteric bacteria was documented by flow cytometry. To determine the relative contribution of IgM or IgG, the immunoglobulins were specifically immunodepleted from the naive plasma samples and the PEK of the depleted plasma measured. Compared with naive plasma, depletion of IgM had no effect on the PEK. However, depletion of IgG increased PEK, suggesting that an inhibitory IgG binds to antigenic sites on bacteria preventing optimal opsonization of the bacteria. These data demonstrate that, before CLP, circulating inhibitory IgG antibodies exist that prevent bacterial killing by polymorphonuclear neutrophils in a CLP model of sepsis.

Prognostic value of the biomarkers procalcitonin, interleukin-6 and C-reactive protein in severe sepsis

AIM

To determine the prognostic value of the biomarkers procalcitonin, interlukin-6 and C-reactive protein in septic patients.

DESIGN

A cohort of 81 septic patients.

SETTING

Critical Care Unit. Dr. Peset Hospital. Valencia (Spain).

PATIENTS

Divided according to sepsis classification (sepsis, severe sepsis and septic shock), source and two different groups (medical and postsurgical). VARIABLES ANALYZED: Quantitative (procalcitonin, interleukin-6, C-reactive protein, lactate, age, Apache II and SOFA scores upon admission and after 3 and 7 days). Qualitative (ICU mortality, multiorgan failure development and sex).

STATISTICAL ANALYSIS

Mann-Whitney U-test for the comparison of quantitative variables, χ² test for qualitative variables. Multivariate analysis with mortality and multiorgan failure as dependent variables and the described quantitative parameters as independent variables. ROC curves of the variables found to be significant in the multivariate analysis.

RESULTS

Septic shock patients showed greater mortality and more frequent multiorgan failure. Comparison of survivors versus deceased patients showed significant differences in Apache II score, interleukin-6 and lactate (p<0.001) upon admission and after 3 and 7 days. Similar findings applied to the comparison of patients with and without multiorgan failure, and on the same days. Procalcitonin only showed differences on days 3 and 7 (p=0.001). In the multivariate analysis with mortality as dependent variable, interleukin-6 proved significant on day 3 (OR 2.6). With multiorgan failure as dependent variable, only the SOFA score showed significance (OR 2.3). The Apache II and interleukin-6 ROC curves corresponding to day 3 showed areas of 0.80 and 0.86, respectively.

CONCLUSIONS

1) Interleukin-6 is an inflammatory biomarker with mortality prognostic value. 2) None of the biomarkers proved predictive of multiorgan failure.

Kinetics of IL-6 and TNF-α changes in a canine model of sepsis induced by endotoxin

Sepsis is a major cause of death in veterinary medicine, although a better prognosis can result from an early diagnosis. To speed the diagnosis, the biomarkers TNF-α and IL-6 can provide valuable information regarding systemic inflammatory response. The purpose of this study was to investigate the changes in cytokine levels in an experimental model of sepsis using ELISA and real-time PCR. Ten adult Beagles were studied; seven received an IV bolus of high dose lipopolysaccharide solution (1mg/kg) to induce sepsis. The remaining three beagles were the control group. Blood samples were collected before and 1, 3, 6, 12, 24 and 48 h after administering LPS. Serum IL-6 level peaked at 3h (1.89 ± 0.10 ng/ml) and serum TNF-α peaked at 1h (1.11 ± 0.01 ng/ml). The expression of IL-6 mRNA in peripheral blood mononuclear cells (PBMC) increased 62-fold compared to the control group at 1h; TNF-α mRNA increased by 4.5-fold at 1h. The expressions of IL-6 and TNF-α mRNA in PBMCs changed more rapidly than serum IL-6 and TNF-α concentrations. In addition, TNF-α mRNA levels in PBMCs remained elevated longer than serum TNF-α. Our study establishes the basis for future work aimed at a better understanding of the systemic inflammatory response to infection and sepsis in canine patients.

Measuring Hsp72 (HSPA1A) by indirect sandwich ELISA

The enzyme-linked immunosorbent assay (ELISA) is an immunological technique which is used to determine the presence or quantity of an antigen within a sample. ELISAs rely on the use of at least one antibody (Ab) specific for the antigen being measured. This antibody is covalently linked to an enzyme which is detected through the use of an enzymatic substrate, which can be colorimetric, fluorogenic, or chemiluminescent. The ELISA for Hsp72 described here is a typical indirect sandwich ELISA, which can be used for measuring Hsp72 from cellular/tissue extracts, tissue culture supernatant, and serum. Typically, a 96-well ELISA plate is coated with a specific antibody which captures Hsp72 from the sample, and another antibody specific for a different Hsp72 epitope is used to detect Hsp72. An enzyme-labelled species-specific antibody conjugate is then applied which is consequently detected using a colorimetric enzyme substrate. The quantity of Hsp72 present in the samples is interpolated using a standard curve of known amounts of pure Hsp72.

Pulmonary endotoxin tolerance protects against cockroach allergen-induced asthma-like inflammation in a mouse model

BACKGROUND

Compounds which activate the innate immune system, such as lipopolysaccharide, are significant components of ambient air, and extremely difficult to remove from the environment. It is currently unclear how prior inhalation of endotoxin affects allergen sensitization. We examined whether lung-specific endotoxin tolerance induction prior to sensitization can modulate the response to allergen.

METHODS

Endotoxin tolerance was induced by repeated intratracheal exposure to endotoxin. All mice were then sensitized and challenged by direct intratracheal instillation of cockroach allergen.

RESULTS

After allergen sensitization and challenge, endotoxin tolerant mice had significantly decreased airways hyperresponsiveness to methacholine challenge, which was confirmed by invasive lung function tests. Decreased goblet cell hyperplasia and mucus production were also found by histological assessment. Tolerant mice were protected from airway eosinophilia through the mechanism of reduced CCL11 and CCL24. Interestingly, endotoxin tolerant mice had only a modest reduction in cockroach-specific IgE; however, total IgE was significantly reduced.

CONCLUSIONS

These data show that induction of endotoxin tolerance prior to sensitization protects against the hallmark features of asthma-like inflammation, and that transient modulation of innate immunity can have long-lasting effects on adaptive responses.

Detection and quantification of cytokines and other biomarkers

Accurate measurement of cytokine concentrations is a powerful and essential approach to the study of inflammation. The enzyme-linked immunosorbent assay (ELISA) is a simple, low-cost analytical tool that provides both the specificity and sensitivity required for the study of cytokines in vitro or in vivo. This communication describes a systematic approach to develop an indirect sandwich ELISA to detect and quantify cytokines, or other biomarkers, with accuracy and precision. Also detailed is the use of sequential ELISA assays to analyze multiple cytokines from samples with limited volumes. Finally, the concept of a multiplex ELISA is discussed with considerations given to cost and additional time required for development.

Herbal medicine treatment reduces inflammation in a murine model of cockroach allergen-induced asthma

BACKGROUND

Asthma is a significant disease among children, and its prevalence has increased notably during the last 2 decades. A traditional Korean medicine, So-Cheong-Ryong-Tang (SCRT), has been used for the treatment of asthma in Asia for centuries, but its mechanism for reducing bronchopulmonary inflammation in asthma has yet to be elucidated.

OBJECTIVE

To investigate whether the herbal extract SCRT inhibits inflammation in a mouse model of cockroach allergen-induced asthma.

METHODS

A house dust extract containing endotoxin and cockroach allergens was used for immunization and 2 additional pulmonary challenges in BALB/c mice. Mice were treated with SCRT or vehicle 1 hour before each pulmonary challenge. Respiratory parameters were evaluated by whole-body plethysmography and forced oscillation methods 24 hours after the last challenge. Bronchoalveolar lavage (BAL) fluid was collected, and histologic sections of lung were prepared either 4 or 24 hours after the last house dust extract challenge.

RESULTS

SCRT treatment significantly reduced the hyperreactivity of the airways as measured by whole-body plethysmography and direct measurement of airway resistance. Inflammation was significantly inhibited by SCRT treatment as demonstrated by reduced plasma IgE levels and improved pulmonary histologic characteristics. SCRT significantly reduced the number of neutrophils in the BAL fluid and also significantly reduced the BAL levels of CXC chemokines, providing a potential mechanism for the reduced inflammation. In a similar fashion, SCRT reduced eosinophil recruitment and BAL levels of eotaxin and RANTES.

CONCLUSION

These data indicate that SCRT treatment alleviates asthma-like pulmonary inflammation via suppression of specific chemokines.

Reducing LPS content in cockroach allergens increases pulmonary cytokine production without increasing inflammation: a randomized laboratory study

Background

Endotoxins are ubiquitously present in the environment and constitute a significant component of ambient air. These substances have been shown to modulate the allergic response, however a consensus has yet to be reached whether they attenuate or exacerbate asthmatic responses. The current investigation examined whether reducing the concentration of lipopolysaccharide (LPS) in a house dust extract (HDE) containing high concentrations of both cockroach allergens [1] and LPS would attenuate asthma-like pulmonary inflammation.

Methods

Mice were sensitized with CRA and challenged with the intact HDE, containing 182 ng of LPS, or an LPS-reduced HDE containing 3 ng LPS, but an equivalent amount of CRA. Multiple parameters of asthma-like pulmonary inflammation were measured.

Results

Compared to HDE challenged mice, the LPS-reduced HDE challenged mice had significantly reduced TNFα levels in the bronchoalveolar lavage fluid. Plasma levels of IgE and IgG1 were significantly reduced, however no change in CRA-specific IgE was detected. In HDE mice, plasma IgG2a levels were similar to naïve mice, while LPS-reduced HDE mice had significantly greater concentrations. Reduced levels of LPS in the HDE did not decrease eosinophil or neutrophil recruitment into the alveolar space. Equivalent inflammatory cell recruitment occurred despite having generally higher pulmonary concentrations of eotaxins and CXC chemokines in the LPS-reduced HDE group. LPS-reduced HDE challenge induced significantly higher concentrations of IFNγ, and IL-5 and IL-13 in the BAL fluid, but did not decrease airways hyperresponsiveness or airway resistance to methacholine challenge. Conclusion: These data show that reduction of LPS levels in the HDE does not significantly protect against the severity of asthma-like pulmonary inflammation.

Repetitive low-volume blood sampling method as a feasible monitoring tool in a mouse model of sepsis

Blood-based monitoring of immunoinflammatory and organ function fluctuations is essential in models of critical illness. This is challenging in diseased mice as repetitive blood collection may be harmful and/or affect end points. We studied the influence of daily sampling in acutely septic (days 1-5) mice upon survival and selected hematologic and organ function parameters. In addition, we tested the reliabilty of complete blood cell (CBC) count using resuspended blood cells. Female OF-1 and CD-1 mice underwent cecal ligation and puncture (CLP) and were subdivided into Daily and Day 5 groups. Blood was collected daily for 5 days in the Daily group and only on day 5 post-CLP in the Day 5 group. We tested 20 μL (both strains) and 35 μL (OF-1 mice) sampling volumes. The 35-μL volume simultaneously served to test the CBC reliabilty in resuspended versus unprocessed blood. Daily sampling did not affect the 14-day CLP mortality. Compared with the Day 5 group, daily 35-μL sampling in OF-1 mice decreased the red blood cell count and hemoglobin concentration by 22% and 23% (P < 0.05). In neither strain did daily 20-μL sampling affect the red blood cell count, whereas there was a 9% hemoglobin decrease (P < 0.05) in OF-1 mice. Although alanine aminotransferase, lactate dehydrogenase, and glucose levels were comparable, urea significantly increased by 24% in the Daily group (20-μL volume, OF-1 mice). Interleukin 6, platelets, and white blood cell counts remained unaffected. There was an excellent correlation between regular and resuspended CBC for all cell types (r ≥ 0.9; slope, ≥0.9), except lymphocytes (r > 0.5; slope, >0.5). This method provides a feasible and safe translation of clinically relevant daily immunomonitoring to the mouse sepsis model.

Oral tolerance inhibits pulmonary eosinophilia in a cockroach allergen induced model of asthma: a randomized laboratory study

Background

Antigen desensitization through oral tolerance is becoming an increasingly attractive treatment option for allergic diseases. However, the mechanism(s) by which tolerization is achieved remain poorly defined. In this study we endeavored to induce oral tolerance to cockroach allergen (CRA: a complex mixture of insect components) in order to ameliorate asthma-like, allergic pulmonary inflammation.

Methods

We compared the pulmonary inflammation of mice which had received four CRA feedings prior to intratracheal allergen sensitization and challenge to mice fed PBS on the same time course. Respiratory parameters were assessed by whole body unrestrained plethysmography and mechanical ventilation with forced oscillation. Bronchoalveolar lavage fluid (BAL) and lung homogenate (LH) were assessed for cytokines and chemokines by ELISA. BAL inflammatory cells were also collected and examined by light microscopy.

Results

CRA feeding prior to allergen sensitization and challenge led to a significant improvement in respiratory health. Airways hyperreactivity measured indirectly via enhanced pause (Penh) was meaningfully reduced in the CRA-fed mice compared to the PBS fed mice (2.3 ± 0.4 vs 3.9 ± 0.6; p = 0.03). Directly measured airways resistance confirmed this trend when comparing the CRA-fed to the PBS-fed animals (2.97 ± 0.98 vs 4.95 ± 1.41). This effect was not due to reduced traditional inflammatory cell chemotactic factors, Th2 or other cytokines and chemokines. The mechanism of improved respiratory health in the tolerized mice was due to significantly reduced eosinophil numbers in the bronchoalveolar lavage fluid (43300 ± 11445 vs 158786 ± 38908; p = 0.007) and eosinophil specific peroxidase activity in the lung homogenate (0.59 ± 0.13 vs 1.19 ± 0.19; p = 0.017). The decreased eosinophilia was likely the result of increased IL-10 in the lung homogenate of the tolerized mice (6320 ± 354 ng/mL vs 5190 ± 404 ng/mL, p = 0.02).

Conclusion

Our results show that oral tolerization to CRA can improve the respiratory health of experimental mice in a CRA-induced model of asthma-like pulmonary inflammation by reducing pulmonary eosinophilia.

Early enhanced local neutrophil recruitment in peritonitis-induced sepsis improves bacterial clearance and survival

Neutrophils are critical for the rapid eradication of bacterial pathogens, but they also contribute to the development of multiple organ failure in sepsis. We hypothesized that increasing early recruitment of neutrophils to the focus of infection will increase bacterial clearance and improve survival. Sepsis was induced in mice, using cecal ligation and puncture (CLP); blood samples were collected at 6 and 24 h; and survival was followed for 28 d. In separate experiments, peritoneal bacteria and inflammatory cells were measured. Septic mice predicted to die based on IL-6 levels (Die-P) had higher concentrations of CXCL1 and CXCL2 in the peritoneum and plasma compared with those predicted to live (Live-P). At 6 h, Live-P and Die-P had equivalent numbers of peritoneal neutrophils and bacteria. In Die-P mice the number of peritoneal bacteria increased between 6 and 24 h post-CLP, whereas in Live-P it decreased. The i.p. injection of CXCL1 and CXCL2 in naive mice resulted in local neutrophil recruitment. When given immediately after CLP, CXC chemokines increased peritoneal neutrophil recruitment at 6 h after CLP. This early increase in neutrophils induced by exogenous chemokines resulted in significantly fewer peritoneal bacteria by 24 h [CFU (log) = 6.04 versus 4.99 for vehicle versus chemokine treatment; p < 0.05]. Chemokine treatment significantly improved survival at both 5 d (40 versus 72%) and 28 d (27 versus 52%; p < 0.02 vehicle versus chemokines). These data demonstrate that early, local treatment with CXC chemokines enhances neutrophil recruitment and clearance of bacteria as well as improves survival in the CLP model of sepsis.

Chronic pulmonary LPS tolerance induces selective immunosuppression while maintaining the neutrophilic response

LPS challenge causes potent activation of innate immunity. Because LPS is ubiquitously present in ambient air, repeated inhalation may lead to activation of the pulmonary immune response. If this activation is unregulated, chronic LPS inhalation would lead to persistent inflammation and organ damage. We hypothesized that the lung uses the mechanism of LPS tolerance to maintain the balance between hypoinflammatory and hyperinflammatory states. We developed a model of chronic pulmonary LPS tolerance induced by pulmonary exposure to 1 microg LPS for 4 consecutive days. Mice were challenged with 10 microg of LPS 24 h later. TNF-alpha protein was significantly decreased in the bronchoalveolar lavage fluid of tolerant versus nontolerant mice, whereas IL-6 levels were significantly increased in the tolerant group. Tolerant mice were also protected from airway hyperresponsiveness. M2 and M3 muscarinic receptor mRNA was significantly decreased in the lungs of tolerant mice, suggesting a mechanism for the decreased airway hyperresponsiveness. CXCL2 was significantly reduced in tolerant mice, but CXCL1 was equivalent between groups. No difference was seen in neutrophil recruitment to the alveolar space. Interestingly, LPS tolerance does not confer cross-tolerance to the Toll-like receptor (TLR) 2 stimulus Pam3Cys. TNF-alpha and IL-6 concentrations were significantly increased in LPS-tolerant mice challenged with Pam3Cys; however, chemokine concentrations were unaffected. Our data show that repeated LPS inhalation results in differential regulation of cytokines but does not inhibit neutrophil recruitment. This unrestricted neutrophil recruitment may represent a mechanism by which individuals may be protected from pulmonary bacterial infection and pneumonia.

Delayed addition of glucocorticoids selectively suppresses cytokine production in stimulated human whole blood

Glucocorticoids (GC) are potent drugs proven to effectively treat inflammatory diseases, although patients typically begin therapy after the onset of symptoms. Clinical studies with cytokine inhibitors prove that these mediators drive inflammatory responses in diseases such as rheumatoid arthritis and Crohn's disease. Despite the clear sequence of cytokine-induced inflammation followed by effective GC treatment, most basic science investigations have examined the ability of GC to prevent an inflammatory response rather than halt its progression. The current studies used the Toll-like receptor 2 (TLR2) agonist palmitoyl(3)-cysteine-serine-lysine(4) (PAM) or the TLR4 agonist lipopolysaccharide (LPS) to stimulate human whole blood and determine whether postponing the addition of the GC dexamethasone (DEX) limits its ability to decrease cytokine production. Twenty-four hours after stimulation, tumor necrosis factor (TNF), interleukin-1beta (IL-1beta), IL-6, and IL-8 levels were measured, in addition to the cytokine inhibitors IL-1 soluble receptor II (SRII), IL-1 receptor antagonist, and TNF SRII. LPS rapidly induced all of the proinflammatory mediators over 24 h while failing to induce any of the cytokine inhibitors. PAM stimulation also induced IL-1beta, IL-6, and IL-8. Concomitant addition of DEX plus LPS or PAM significantly suppressed all cytokine levels. Delaying the addition of DEX until 6 h after LPS stimulation failed to decrease TNF or IL-6. In contrast, delayed DEX addition significantly suppressed PAM-induced IL-1beta, IL-6, or IL-8 and also suppressed LPS-induced IL-1beta and IL-8. Our results show that cytokines which typically increase in concentration between 6 and 24 h after stimulation were significantly suppressed by the addition of DEX 6 h after stimulation.

Functional contribution of CXCR2 to lung injury after aspiration of acid and gastric particulates

The effects of individual ELR+ CXC chemokines have been documented in experimental models of acid aspiration. However, aspiration lung injury would be influenced by the combined effects of these chemokines and other factors related to their function. Therefore, the role of the chemokine receptor CXCR2 was examined in lung injury induced by aspiration of acid and acid with gastric particulates. Anesthetized mice were given intratracheal injections of saline, acid solution, or acid containing gastric particles. Within 6 h, bronchoalveolar lavage fluid neutrophils and albumin increased relative to the severity of the insult. Immunohistochemistry and RT-PCR demonstrated striking increases in pulmonary expression of CXCR2 after aspiration. In CXCR2-deficient mice, neutrophil recruitment to airways was significantly reduced after aspiration of either acid or acid with particles. However, lung injury scores were unaffected in Ccr2-/- mice in the acid + particles group. Esterase-stained lung tissue demonstrated that focal aggregates of inflammatory cells contained neutrophils in the Ccr2-/- mice. These studies suggest CXCR2 and its ligands are dominant mediators of neutrophil recruitment to airways after aspiration. However, CXCR2-independent mechanisms recruit neutrophils into areas of cellular aggregation after aspiration of acidified gastric particulates.