Differences in arterial and mixed venous IL-6 levels: the lungs as a source of cytokine storm in sepsis

Mycobacterium tuberculosis effector PPE36 attenuates host cytokine storm damage via inhibiting macrophage M1 polarization

Tuberculosis caused by Mycobacterium tuberculosis remains a serious global public health threat. Macrophage polarization is crucial for the innate immunity against M. tuberculosis. However, how M. tuberculosis interferes with macrophage polarization is elusive. We demonstrated here that M. tuberculosis PPE36 (Rv2108) blocked macrophage M1 polarization, preventing the cytokine storm, and alleviating inflammatory damage to mouse immune organs. PPE36 inhibited the polarization of THP-1 cell differentiation to M1 macrophages, reduced mitochondrial dehydrogenase activity, inhibited the expression of CD16, and repressed the expression of pro-inflammatory cytokines IL-6 and TNF-α, as well as chemokines CXCL9, CXCL10, CCL3, and CCL5. Intriguingly, in the mouse infection model, PPE36 significantly alleviated the inflammatory damage of immune organs caused by a cytokine storm. Furthermore, we found that PPE36 inhibited the polarization of macrophages into mature M1 macrophages by suppressing the ERK signaling. The study provided novel insights into the function and mechanism of action of M. tuberculosis effector PPE36 both at the cellular and animal level.

Interleukin-6 in Critical Coronavirus Disease 2019, a Driver of Lung Inflammation of Systemic Origin?

To examine whether interleukin-6 in critical coronavirus disease 2019 is higher in arterial than in central venous blood, as a sign of predominantly local pulmonal rather than systemic interleukin-6 production.

The ACE2-deficient mouse: A model for a cytokine storm-driven inflammation

Angiotensin converting enzyme 2 (ACE2) plays an important role in inflammation, which is attributable at least, in part, to the conversion of the pro-inflammatory angiotensin (Ang) II peptide into angiotensin 1-7 (Ang 1-7), a peptide which opposes the actions of AngII. ACE2 and AngII are present in many tissues but information on the cornea is lacking. We observed that mice deficient in the Ace2 gene (Ace2-/- ), developed a cloudy cornea phenotype as they aged. Haze occupied the central cornea, accompanied by corneal edema and neovascularization. In severe cases with marked chronic inflammation, a cell-fate switch from a transparent corneal epithelium to a keratinized, stratified squamous, psoriasiform-like epidermis was observed. The stroma contained a large number of CD11c, CD68, and CD3 positive cells. Corneal epithelial debridement experiments in young ACE2-deficient mice showed normal appearing corneas, devoid of haze. We hypothesized, however, that these mice are "primed" for a corneal inflammatory response, which once initiated, would persist. In vitro studies reveal that interleukins (IL-1a, IL-1b), chemokines (CCL2, CXCL8), and TNF-α, are all significantly elevated, resulting in a cytokine storm-like phenotype. This phenotype could be partially rescued by treatment with the AngII type 1 receptor (AT1R) antagonist, losartan, suggesting that the observed effect was mediated by AngII acting on its main receptor. Since the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes human ACE2 as the receptor for entry with subsequent downregulation of ACE2, corneal inflammation in Ace2-/- mice may have a similar mechanism with that in COVID-19 patients. Thus the Ace2-/- cornea, because of easy accessibility, may provide an attractive model to explore the molecular mechanisms, immunological changes, and treatment modalities in patients with COVID-19.

Differences of plasma IL-1 and TNF-α in healthy Chinese Population

Pleiotropic proinflammatory cytokines, interleukin- 1 (IL-1) and tumor necrosis factor-α (TNF-α), involved in the regulations of various immune responses, inflammatory processes and hematopoiesis. In the present study, the expression levels of IL-1 and TNF-α were detected by enzyme-linked immunosorbent assay (ELISA). Following the cytokine blockade as a successful clinical therapy for autoimmune diseases such as rheumatoid arthritis, the patients are more susceptible to a variety of opportunistic infections. IL-1 and TNF-α may be useful predictive biomarkers of diseases and offer potential targets for therapeutic intervention of inflammatory diseases. However, our results showed that the plasma IL-1 level was significantly higher in women compared to men (69.5 ± 19.8 pg/ml in men and 80.1 ± 19.5 pg/ml in women, respectively); the plasma levels of TNF-α were higher in men than women (20.8 ± 4.9 pg/ml and 18.7 ± 7.1 pg/ml, respectively). The significant gender difference of plasma interleukin-1 (IL-1) and TNF-α levels present in healthy adults in Jiangsu Province, China (P=0.002 and P=0.015, respectively), and may be as a hint for sex differences of susceptibility to many diseases and elementary immune response.

Early detection of subclinical organ dysfunction by microdialysis of the rectus abdominis muscle in a porcine model of critical intra-abdominal hypertension

The aim of this study was to evaluate microdialysis of the rectus abdominis muscle (RAM) for early detection of subclinical organ dysfunction in a porcine model of critical intra-abdominal hypertension (IAH). Microdialysis catheters for analyses of lactate, pyruvate, and glycerol levels were placed in cervical muscles (control), gastric and jejunal wall, liver, kidney, and RAM of 30 anesthetized mechanically ventilated pigs. Catheters for venous lactate and interleukin 6 samples were placed in the jugular, portal, and femoral vein. Intra-abdominal pressure (IAP) was increased to 20 mmHg (IAH20 group, n = 10) and 30 mmHg (IAH30, n = 10) for 6 h by controlled CO2 insufflation, whereas sham animals (n = 10) exhibited a physiological IAP. In contrast to 20 mmHg, an IAH of 30 mmHg induced pathophysiological alterations consistent with an abdominal compartment syndrome. Microdialysis showed significant increase in the lactate/pyruvate ratio in the RAM of the IAH20 group after 6 h. In the IAH30 group, the strongest increase in lactate/pyruvate ratio was detected in the RAM and less pronounced in the liver and gastric wall. Glycerol increased in the RAM only. After 6 h, there was a significant increase in venous interleukin 6 of the IAH30 group compared with baseline. Venous lactate was increased compared with baseline and shams in the femoral vein of the IAH30 group only. Intra-abdominal pressure-induced ischemic metabolic changes are detected more rapidly and pronounced by microdialysis of the RAM when compared with intra-abdominal organs. Thus, the RAM represents an important and easily accessible site for the early detection of subclinical organ dysfunction during critical IAH.

Corticosteroid treatment ameliorates acute lung injury induced by 2009 swine origin influenza A (H1N1) virus in mice

BACKGROUND

The 2009 influenza pandemic affected people in almost all countries in the world, especially in younger age groups. During this time, the debate over whether to use corticosteroid treatment in severe influenza H1N1 infections patients resurfaced and was disputed by clinicians. There is an urgent need for a susceptible animal model of 2009 H1N1 infection that can be used to evaluate the pathogenesis and the therapeutic effect of corticosteroid treatment during infection.

METHODOLOGY/PRINCIPAL FINDINGS

We intranasally inoculated two groups of C57BL/6 and BALB/c mice (using 4- or 6-to 8-week-old mice) to compare the pathogenesis of several different H1N1 strains in mice of different ages. Based on the results, a very susceptible 4-week-old C57BL/6 mouse model of Beijing 501 strain of 2009 H1N1 virus infection was established, showing significantly elevated lung edema and cytokine levels compared to controls. Using our established animal model, the cytokine production profile and lung histology were assessed at different times post-infection, revealing increased lung lesions in a time-dependent manner. In additional,the mice were also treated with dexamethasone, which significantly improved survival rate and lung lesions in infected mice compared to those in control mice. Our data showed that corticosteroid treatment ameliorated acute lung injury induced by the 2009 A/H1N1 virus in mice and suggested that corticosteroids are valid drugs for treating 2009 A/H1N1 infection.

CONCLUSIONS/SIGNIFICANCE

Using the established, very susceptible 2009 Pandemic Influenza A (H1N1) mouse model, our studies indicate that corticosteroids are a potential therapeutic remedy that may address the increasing concerns over future 2009 A/H1N1 pandemics.

Beneficial and detrimental effects of plasmin(ogen) during infection and sepsis in mice

Plasmin has been proposed to be an important mediator during inflammation/infection. In this study, by using mice lacking genes for plasminogen, tissue-type plasminogen activator (tPA), and urokinase-type PA (uPA), we have investigated the functional roles of active plasmin in infection and sepsis. Two models were used: an infection model by intravenous injection of 1×10⁷ CFU of S. aureus, and a sepsis model by intravenous injection of 1.6×10⁸ CFU of S. aureus. We found that in the infection model, wild-type (WT) mice showed significantly higher survival rates than plasminogen-deficient (plg^-/-) mice. However, in the sepsis model, plg^-/- or tPA^-/-/uPA^-/- mice showed the highest survival rate whereas WT and tPA^+/-/uPA^+/- mice showed the lowest survival rate, and plg^+/-, tPA^-/-, and uPA^-/- mice had an intermediate survival rate. These results indicate that the levels of active plasmin are critical in determining the survival rate in the sepsis, partly through high levels of inflammatory cytokines and enhanced STAT3 activation. We conclude that plasmin is beneficial in infection but promotes the production of inflammatory cytokines in sepsis that may cause tissue destruction, diminished neutrophil function, and an impaired capacity to kill bacteria which eventually causes death of these mice.

Coagulation, fibrinolysis and cytokine responses to intramedullary nailing of the femur: an experimental study in pigs comparing traditional reaming and reaming with a one-step reamer-irrigator-aspirator system

INTRODUCTION

Operations in trauma patients represent a second insult and the extent of the surgical procedures influences the magnitude of the inflammatory response. Our hypothesis was that a reamer-irrigator-aspirator (RIA) system would cause a lesser inflammatory response than traditional reaming (TR).

MATERIALS AND METHODS

Coagulation, fibrinolysis and cytokine responses were studied in Norwegian landrace pigs during and after intramedullary nailing (IMN) with two different reaming systems using ELISA and chromogenic peptide substrate assays. The TR (n=8) and the RIA (n=7) reaming systems were compared to a control group (n=7). The animals were followed for 72 h. Arterial, mixed venous and femoral vein blood were withdrawn simultaneously peroperatively and until 2 h after the nail was inserted for demonstration of local, pulmonary and systemic activation of the cascade systems. At 6 h, 24 h, 48 h and 72 h postoperatively arterial blood samples were withdrawn.

RESULTS

Significantly procedure-related increased levels were found for thrombin-antithrombin (TAT) and tissue plasminogen activator (t-PA) in the TR group and TAT in the RIA group. The local and the pulmonary activation of coagulation and fibrinolysis were more pronounced in the TR than in the RIA group, the difference reached significance for plasminogen activator inhibitor-1 (PAI-1) (arterial blood). The cytokine response, mainly represented by IL-6 increase, was more pronounced in the TR than the RIA group, and was significant for IL-6 in femoral vein blood. The arterial levels of IL-6 exceeded the mixed venous levels indicating an additional pulmonary activation of IL-6. Two animals in the TR group, who died of pulmonary embolism (PE) prior to planned study end point, had a more pronounced response compared to the rest of the TR group.

CONCLUSION

A procedure-related coagulation and fibrinolytic response was demonstrated in both reaming groups, with more pronounced response in the TR than in the RIA group. Elevated levels of cytokines were demonstrated related to reaming and nailing, with significantly higher IL-6 levels in the TR than in the RIA group.

Particulate matter induces translocation of IL-6 from the lung to the systemic circulation

The biological mechanisms responsible for an association between elevated concentrations of ambient particulate matter (PM) and increased cardiovascular morbidity and mortality remain unclear. Our laboratory showed that exposure to PM induces systemic inflammation that contributes to vascular dysfunction. This study was designed to determine whether the lung is a major source of systemic inflammatory mediators, using IL-6 as a surrogate marker. We also sought to determine the impact on vascular dysfunction after exposure to PM of less than 10 μm in diameter (PM(10)). C57BL/6 mice were intratracheally exposed to a single instillation of PM(10) (10 or 200 μg) or saline. Four hours or 24 hours after exposure, venous and arterial blood samples were simultaneously collected from the right atrium and descending aorta. Concentrations of IL-6 were measured in bronchoalveolar lavage fluid (BALF) and serum samples. Vascular functional responses to acetylcholine (ACh) and phenylephrine were measured in the abdominal aorta. Concentrations of IL-6 in BALF samples were increased at 4 and 24 hours after exposure to PM(10). At baseline, concentrations of IL-6 in venous blood were higher than those in arterial blood. Exposure to PM(10) reversed this arteriovenous gradient, 4 hours after exposure. The relaxation responses of the abdominal aorta to ACh decreased 4 hours after exposure to 200 μg PM(10). In IL-6 knockout mice, the instillation of recombinant IL-6 increased IL-6 concentrations in the blood, and exposure to PM(10) did not cause vascular dysfunction. These results support our hypothesis that exposure to PM(10) increases pulmonary inflammatory mediators that translocate to the circulation, contributing to systemic inflammation, with downstream effects such as vascular dysfunction.

Endotoxin-induced translocation of interleukin-6 from lungs to the systemic circulation

It is widely postulated that systemic inflammation related to lung infections is largely caused by cytokine translocation from the lungs into the systemic circulation but there is a paucity of animal models to evaluate this hypothesis. In this proof-of-concept study, we developed a murine model to determine whether interleukin (IL)-6, a primary inflammatory cytokine, translocates following airway exposure to endotoxin. We collected central venous blood from the right atrium and arterial blood from the aorta simultaneously at 4 h and 24 h following intratracheal exposure to endotoxin (25 microg) and measured IL-6 in the serum and broncho-alveolar lavage (BAL) fluid (n = 33 mice). We repeated the experiment following 3 d of treatment with dexamethasone (n = 31 mice). Without stimulation, there was no significant arteriovenous gradient (3 pg/ml with interquartile range [IQR] of 3-5 pg/ml in arterial versus 18 pg/ml with IQR of 8-24 pg/ml in venous serum; P = 0.86). A significant arteriovenous difference was observed by 4 h post-exposure to endotoxin (2813 pg/ml with IQR of 1578-4316 pg/ml in arterial versus 1282 pg/ml with IQR of 778-2699 pg/ml in venous serum; P50.0001). The rise in the BAL IL-6 levels correlated with the increases in the arterial serum levels (P50.0001). Administration of intraperitoneal dexamethasone for 3 d attenuated the increased arteriovenous gradient. This murine model facilitates the estimation of cytokine translocation across the lungs and evaluation of compounds to modulate this gradient.

Adiponectin deficiency is associated with severe polymicrobial sepsis, high inflammatory cytokine levels, and high mortality

BACKGROUND

Adiponectin, a key substance in metabolic syndrome, is known to have anti-inflammatory properties. The relationship between adiponectin and sepsis in vivo is unclear. In this study, the possible involvement of adiponectin in polymicrobial sepsis was investigated using adiponectin-knockout (APN-KO) mice that underwent cecal ligation and puncture (CLP) and received the peroxisome proliferator-activated receptor gamma (PPAR-gamma) that increases the plasma adiponectin concentration.

METHODS

APN-KO and wild-type (WT) mice underwent either CLP or a sham operation. The plasma adiponectin, endotoxin, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) levels were determined before and at 2, 4, 6, 8, 12, 16, and 24 hours after the procedures, and the survival rates were compared. Mice were injected with rosiglitazone, a selective PPAR-gamma agonist, and compared survival rates after CLP with those without rosiglitazone.

RESULTS

After CLP, APN-KO mice had a significantly higher mortality than WT mice. The plasma endotoxin, TNF-alpha, and IL-6 levels in APN-KO mice were significantly higher than those in WT mice 24 hours after CLP. Within 4 hours after CLP, the plasma adiponectin level in WT mice decreased to half of the initial levels. Pre-CLP treatment with PPAR-gamma was shown to increase the plasma adiponectin level and to improve significantly mortality of WT mice during sepsis; mortality among APN-KO mice did not improve.

CONCLUSION

These results suggest that adiponectin deficiency may cause the high mortality and the high inflammatory cytokine levels in mice with polymicrobial sepsis.

TNF-alpha and IL-1beta increase pericyte/endothelial cell co-culture permeability

BACKGROUND

Pericytes (PC) have a unique synergistic relationship with microvascular endothelial cells (MVEC) in the regulation of capillary permeability. This study investigates the effect of TNF-alpha, IL-1beta, and IL-6 on the microvasculature by measuring changes in PC contractility, and also, albumin permeability across MVEC/PC co-cultures.

MATERIALS AND METHODS

Semi-permeable inserts were plated first with rat lung MVEC and then PCs (on the fourth day) at a ratio of 10:1 MVEC/PC. On day 5, 50 ng/ml of TNF-alpha, IL-1beta, and IL-6 were added with or without a secretory phospholipase A(2)-IIA (sPLA(2)-IIA) inhibitor for 24 h. After treatments, albumin clearances were quantified. For measuring contractility, PCs were cultured on collagen matrices and exposed for 24 h to TNF-alpha, IL-1beta, and IL-6 at 1 ng/ml, 10 ng/ml, and 50 ng/ml with/without inhibitors for sPLA(2)-IIA, phospholipase A(2) (PLA(2)), and cyclooxygenase-II (COX-II). After treatments, the surface area of the collagen disks was digitally quantified.

RESULTS

TNF-alpha and IL-1beta significantly increased albumin clearance in MVEC/PC co-cultures (P < 0.05) and induced dose-dependent relaxation of PCs (P < 0.05). PC relaxation was completely attenuated with the sPLA(2)-IIA and pLA(2) inhibitors; the COX-II inhibitor provided partial blockade. IL-6 had no effect on PC contractility or permeability.

CONCLUSION

TNF-alpha and IL-1beta directly increased microvascular permeability in co-cultures. They also induced relaxation of PCs through a sPLA(2)-IIA dependent mechanism. Interestingly, IL-6 had no effect, although its presence in high levels has been demonstrated in inflamed lungs. These findings may help elucidate the significance of PC in regulating the capillary response to various pro-inflammatory cytokines.

Increased IL-6 and TGF-beta1 concentrations in bronchoalveolar lavage fluid associated with thoracic radiotherapy

PURPOSE

To assess, in lung cancer patients, the effects of thoracic radiotherapy (RT) on the concentrations of transforming growth factor-beta(1) (TGF-beta(1)) and interleukin-6 (IL-6) in the bronchoalveolar lavage (BAL) fluid.

METHODS AND MATERIALS

Eleven patients with lung cancer requiring RT as part of their treatment were studied. BAL was performed bilaterally before, during, and 1, 3, and 6 months after RT. Before each BAL session, the patient's status was assessed clinically using pulmonary function tests and an adapted late effects on normal tissue-subjective, objective, management, analytic (LENT-SOMA) scale, including subjective and objective alterations. The National Cancer Institute Common Toxicity Criteria were used to grade pneumonitis. The TGF-beta(1) and IL-6 levels in the BAL fluid were determined using the Easia kit.

RESULTS

The TGF-beta(1) and IL-6 concentrations in the BAL fluid recovered from the irradiated areas were significantly increased by thoracic RT. The increase in TGF-beta(1) levels tended to be greater in the group of patients who developed severe pneumonitis. In the BAL fluid from the nonirradiated areas, the TGF-beta(1) and IL-6 concentrations remained unchanged.

CONCLUSION

The observed increase in TGF-beta(1) and IL-6 concentrations in the BAL fluid recovered from the irradiated lung areas demonstrated that these cytokines may contribute to the process leading to a radiation response in human lung tissue.

Effect of continuous hemofiltration on hemodynamics, lung inflammation and pulmonary edema in a canine model of acute lung injury

OBJECTIVE

This study examined whether continuous hemofiltration favorably affects cardiopulmonary variables, lung inflammation, and lung fluid balance in a canine model of oleic acid induced acute lung injury.

METHODS

Eleven pentobarbital-anesthetized dogs were randomly divided into a control (mechanical ventilation, MV) group (n=6) and a MV plus hemofiltration (HF) group (n=5). All animals received an intravenous injection of oleic acid (0.09 ml/kg) to induce acute lung injury. Continuous arterial-venous hemofiltration (blood flow 100 ml/min, ultrafiltration rate at 50-65 ml kg(-1) h(-1)) was started after establishment of oleic acid induced acute lung injury and continued for 4 h. Hemodynamics, lung mechanics, gas exchange, lung fluid balance, lung histology, and the level of plasma cytokines were assessed.

RESULTS

After 240 min of HF treatment there was a significant increase in cardiac output, reduction in pulmonary arterial pressure, and improvement in both oxygenation and lung mechanics. Also, in the HF group the lung wet-to-dry weight ratio was significantly reduced. Histologically, HF reduced edema and inflammatory cell infiltration in the lung. There was also a significantly greater decrease in plasma IL-6 and IL-8 levels in the HF group than in group receiving MV alone.

CONCLUSIONS

In a canine model of acute lung injury continuous HF improved cardiopulmonary function, reduced pulmonary edema, decreased lung permeability and inflammation, and decreased the plasma concentration of proinflammatory cytokines.

Systemic inflammatory response secondary to abdominal compartment syndrome: stage for multiple organ failure

BACKGROUND

The abdominal compartment syndrome (ACS) has been implicated in the pathogenesis of postinjury multiple organ failure. The ACS is defined as intra-abdominal hypertension causing adverse physiologic response. This study was designed to determine the effects of IAH on the production of interleukin-1b (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor (TNF-alpha), and the effects on remote organ injury.

METHODS

IAH was induced in Sprague-Dawley rats which were divided into 5 groups, 10 animals each. Intra-abdominal pressure (IAP) was increased to 20 mm Hg for 60 and 90 minutes in two different groups. In a third group following IAP of 20 mm Hg the abdomen was decompressed for 30 minutes before samples were collected. The other animals were used as controls. Hemodynamic response was monitored throughout the procedure. Cytokine levels were assessed in the plasma. Remote organ injury was assessed by histopathology and myeloperoxidase activity.

RESULTS

IAH caused a significant decrease in MAP. After abdominal decompression MAP returned to baseline levels. A significant decrease in arterial pH was also noted. Increase in the levels of TNF-alpha and IL-6 was noted 30 minutes after abdominal decompression. Plasma concentration of IL-1b was elevated after 60 minutes of IAH. Abdominal decompression, however, did not cause a significant increase in the levels of this cytokine. Lung neutrophil accumulation was significantly elevated only after abdominal decompression. Histopathological findings showed intense pulmonary inflammatory infiltration including atelectasis and alveolar edema.

CONCLUSIONS

IAH provokes the release of pro-inflammatory cytokines which may serve as a second insult for the induction of MOF.