THE DEVELOPMENT OF ACUTE RESPIRATORY DISTRESS SYNDROME AFTER GUT ISCHEMIA/REPERFUSION INJURY FOLLOWED BY FECAL PERITONITIS IN PIGS: A CLINICALLY RELEVANT MODEL

Complement as a vital nexus of the pathobiological connectome for acute respiratory distress syndrome: An emerging therapeutic target

The hallmark of acute respiratory distress syndrome (ARDS) pathobiology is unchecked inflammation-driven diffuse alveolar damage and alveolar-capillary barrier dysfunction. Currently, therapeutic interventions for ARDS remain largely limited to pulmonary-supportive strategies, and there is an unmet demand for pharmacologic therapies targeting the underlying pathology of ARDS in patients suffering from the illness. The complement cascade (ComC) plays an integral role in the regulation of both innate and adaptive immune responses. ComC activation can prime an overzealous cytokine storm and tissue/organ damage. The ARDS and acute lung injury (ALI) have an established relationship with early maladaptive ComC activation. In this review, we have collected evidence from the current studies linking ALI/ARDS with ComC dysregulation, focusing on elucidating the new emerging roles of the extracellular (canonical) and intracellular (non-canonical or complosome), ComC (complementome) in ALI/ARDS pathobiology, and highlighting complementome as a vital nexus of the pathobiological connectome for ALI/ARDS via its crosstalking with other systems of the immunome, DAMPome, PAMPome, coagulome, metabolome, and microbiome. We have also discussed the diagnostic/therapeutic potential and future direction of ALI/ARDS care with the ultimate goal of better defining mechanistic subtypes (endotypes and theratypes) through new methodologies in order to facilitate a more precise and effective complement-targeted therapy for treating these comorbidities. This information leads to support for a therapeutic anti-inflammatory strategy by targeting the ComC, where the arsenal of clinical-stage complement-specific drugs is available, especially for patients with ALI/ARDS due to COVID-19.

Gene Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome that leads to acute respiratory failure and accounts for over 70,000 deaths per year in the United States alone, even prior to the COVID-19 pandemic. While its molecular details have been teased apart and its pathophysiology largely established over the past 30 years, relatively few pharmacological advances in treatment have been made based on this knowledge. Indeed, mortality remains very close to what it was 30 years ago. As an alternative to traditional pharmacological approaches, gene therapy offers a highly controlled and targeted strategy to treat the disease at the molecular level. Although there is no single gene or combination of genes responsible for ARDS, there are a number of genes that can be targeted for upregulation or downregulation that could alleviate many of the symptoms and address the underlying mechanisms of this syndrome. This review will focus on the pathophysiology of ARDS and how gene therapy has been used for prevention and treatment. Strategies for gene delivery to the lung, such as barriers encountered during gene transfer, specific classes of genes that have been targeted, and the outcomes of these approaches on ARDS pathogenesis and resolution will be discussed.

Effect of Negative Pressure Therapy on the Inflammatory Response of the Intestinal Microenvironment in a Porcine Septic Model

In a swine model of ischemia/reperfusion injury coupled with sepsis, we have previously shown attenuation of secondary organ injury and decreased mortality with negative pressure therapy (NPT). We hypothesized that NPT modulates the intestinal microenvironment by mediating the innate immune system. Sepsis was induced in 12 anesthetized female pigs. Group 1 (n = 6) was decompressed at 12 hrs after injury (T₁₂) and treated with standard of care (SOC), and group 2 (n = 6) with NPT for up to T₄₈. Immunoparalysis was evident as lymphocytopenia at T₂₄ in both groups; however, survival was improved in the NPT group versus SOC (Odds ratio = 4.0). The SOC group showed significant reduction in lymphocyte numbers compared to NPT group by T₄₈ (p < 0.05). The capacity of peritoneal fluid to stimulate a robust reactive oxygen species response in vitro was greater for the NPT group, peaking at T₂₄ for both M1 (p = 0.0197) and M2 macrophages (p = 0.085). Plasma elicited little if any effect which was confirmed by microarray analysis. In this septic swine model NPT appeared to modulate the intestinal microenvironment, facilitating an early robust, yet transient, host defense mediated by M1 and M2 macrophages. NPT may help overcome immunoparalysis that occurs during inflammatory response to septic injury.

Oral complications in hematopoietic stem cell recipients: the role of inflammation

Hematopoietic stem cell transplantation (HSCT) is widely used as a potentially curative treatment for patients with various hematological malignancies, bone marrow failure syndromes, and congenital immune deficiencies. The prevalence of oral complications in both autologous and allogeneic HSCT recipients remains high, despite advances in transplant medicine and in supportive care. Frequently encountered oral complications include mucositis, infections, oral dryness, taste changes, and graft versus host disease in allogeneic HSCT. Oral complications are associated with substantial morbidity and in some cases with increased mortality and may significantly affect quality of life, even many years after HSCT. Inflammatory processes are key in the pathobiology of most oral complications in HSCT recipients. This review article will discuss frequently encountered oral complications associated with HSCT focusing on the inflammatory pathways and inflammatory mediators involved in their pathogenesis.

Evaluation of the inflammatory response in a two-hit acute lung injury model using [18F]FDG microPET

The aim of this study was to investigate whether a two-hit acute lung injury (ALI) model is better than a one-hit model in simulating ALI, and to evaluate the inflammatory response in the lungs in these two models using micro-positron emission tomography (microPET) with [¹⁸F]fluorodeoxyglucose (FDG). Sprague Dawley rats were divided into four groups; rats in the lipopolysaccharide (LPS; n=10) and LPS-HCl (n=10) groups were challenged by the intraperitoneal administration of 5 mg/kg LPS, while rats in the normal saline (NS; n=3) and HCl (n=10) groups received the same volume of normal saline solution. Sixteen hours following the administration, the rats in the HCl and LPS-HCl groups received an acid instillation (IT) of 0.5 ml/kg HCl (pH=1.2), while the rats in the remaining two groups received the same volume of normal saline solution. The mean arterial blood pressure (MAP) and blood gas concentrations were measured in all four groups. MicroPET was performed 4 h following HCl IT and the lungs were excised for histopathological examination. The rats in the LPS-HCl group exhibited a higher arterial PaO₂ and a lower arterial PaCO₂ compared with the rats in the remaining groups. The MAP decreased markedly in the LPS-HCl group, but remained stable in the LPS, HCl and NS groups. MicroPET results identified that the region of interest ratio in the LPS-HCl group (9.00±1.41) was significantly higher compared with those in the LPS (4.01±0.60) and HCl (3.33±0.55) groups (P<0.01). In addition, histological examination showed that the mean lung injury score in the LPS-HCl group (12.70±0.95) was significantly higher compared with those in the HCl (8.40±1.26) and LPS (7.00±0.82) groups (P<0.01). The present study demonstrates that LPS pretreatment significantly magnifies and prolongs the inflammatory response to subsequent acid IT in the lungs. Moreover, it is simpler to induce ALI using the two-hit model than with the one-hit model, and [¹⁸F]FDG microPET is a useful tool for evaluating the inflammatory reaction during ALI.

Acid aspiration provokes the pneumonia caused by multidrug-resistant Acinetobacter baumannii in BALB/c mice

OBJECTIVE

To determine whether acid aspiration provokes the development of multidrug-resistant Acinetobacter baumannii (MDRAB) pneumonia in its host.

METHODS

Groups of mice were inoculated intratracheally (IT) with 50 μl of 0.1N HCl and 1 × 10(8) colony-forming units (CFU) Ab396 (A+Ab group), or 50 μl of 0.1N HCl and 20 μl of 0.9% saline (A+S group), or 20 μl of 0.9% saline and 1 × 10(8) CFU of Ab396 (S+Ab group), or 50 μl of 0.9% saline and 20 μl of 0.9% saline (S+S group). Cytokines, bacterial loads in the bronchoalveolar lavage fluid (BALF), lung permeability, histopathology of the lungs, and survival rates were evaluated.

RESULTS

Only the A+Ab mice developed extensive Ab396 pneumonia and had significantly elevated bacterial loads, increased lung leakage, and lower levels of tumor necrosis factor alpha (TNF-α) compared with the other three groups (p<0.05, Mann-Whitney U-test). Moreover, a strong synergistic effect (p<0.05, two-way analysis of variance) was observed between the acid induction and Ab396 infection, resulting in lung injury and an unfavorable survival outcome.

CONCLUSIONS

Lung injury caused by acid aspiration provoked secondary MDRAB pneumonia; also synergistic effects between acid aspiration and Ab396 infection resulted in a detrimental outcome in the infected mice.

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.

Effects of continuous or intermittent lipopolysaccharide administration for 48 hours on the systemic inflammatory response in horses

OBJECTIVE

To determine whether the method of lipopolysaccharide (LPS) administration (intermittent vs continuous) affects the magnitude and duration of the systemic inflammatory response in horses and whether prolonged (48 hours) endotoxemia induces laminitis.

ANIMALS

12 healthy adult horses (10 mares and 2 geldings).

PROCEDURES

Horses were randomly assigned to receive LPS (total dose, 80 μg; n = 4) or saline (0.9% NaCl) solution (80 mL/h; 4) via constant rate infusion or 8 bolus IV injections of LPS (10 μg, q 6 h;4) during a 48-hour period. Physical examinations were performed every 4 hours, inflammatory cytokine gene expression was determined for blood samples obtained every 8 hours, and IV glucose tolerance tests were performed.

RESULTS

All LPS-treated horses had signs of depression and mild colic; those signs abated as the study progressed. Administration of LPS increased expression of interleukin-1β, interleukin-6, and interleukin-8, but results were not significantly different between LPS treatment groups. Cytokine expression was significantly higher on the first day versus the second day of LPS treatment. Interleukin-1β expression was positively correlated with rectal temperature and expression of other cytokines. Glucose and insulin dynamics for both LPS groups combined did not differ significantly from those of the saline solution group. Signs of laminitis were not detected in any of the horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses developed LPS tolerance within approximately 24 hours after administration was started, and the method of LPS administration did not affect the magnitude or duration of systemic inflammation. Laminitis was not induced in horses.

Effects of a "two-hit" model of organ damage on the systemic inflammatory response and development of laminitis in horses

The role of endotoxemia in the development of laminitis remains unclear. Although systemic inflammation is a risk factor for laminitis in hospitalized horses, experimental endotoxin administration fails to induce the disease. While not sufficient to cause laminitis by itself, endotoxemia might predispose laminar tissue to damage from other mediators during systemic inflammation. In "two-hit" models of organ damage, sequential exposure to inflammatory stimuli primes the immune system and causes exaggerated inflammatory responses during sepsis. Acute laminitis shares many characteristics with sepsis-associated organ failure, therefore an equine "two-hit" sepsis model was employed to test the hypothesis that laminitis develops with increased frequency and severity when repeated inflammatory events exacerbate systemic inflammation and organ damage. Twenty-four light breed mares (10) and geldings (14) with chronic disease conditions or behavioral abnormalities unrelated to laminitis that warranted euthanasia were obtained for the study. Horses were randomly assigned to receive an 8-h intravenous infusion of either lipopolysaccharide (5 ng/kg/h) or saline beginning at -24h, followed by oligofructose (OF; 5 g/kg) via nasogastric tube at 0 h. Euthanasia and tissue collection occurred at Obel grade 2 laminitis, or at 48 h if laminitis had not developed. Liver biopsies were performed at 24h in laminitis non-responders. Blood cytokine gene expression was measured throughout the study period. Lipopolysaccharide and OF administration independently increased mean rectal temperature (P<0.001), heart rate (P=0.003), respiratory rate (P<0.001), and blood interleukin (IL)-1β gene expression (P<0.0016), but responses to OF were not exaggerated in endotoxin-pretreated horses. The laminitis induction rate did not differ between treatment groups and was 63% overall. When horses were classified as laminitis responders and non-responders, area under the blood IL-1β expression curve (P=0.010) and liver and lung gene expression of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor-α (P<0.05) were higher in responders following OF administration. The results indicate that endotoxin pretreatment did not enhance responses to OF. However, systemic inflammation was more pronounced in laminitis responders compared to non-responders, and tissue-generated inflammatory mediators could pose a greater risk than those produced by circulating leukocytes.

Pretreatment with pentoxifylline attenuates lung injury induced by intestinal ischemia/reperfusion in rats

PURPOSE

To investigate the protective effect of pentoxifylline against the lung injury observed after intestinal ischemia (I) followed by a period of reperfusion (R).

METHODS

Twenty-eight male Wistar rats were equally divided into 4 experimental groups and operated under ketamine-xylazine anesthesia. (1) Sham: falsely-operated animals; (2) SS+IR: intestinal ischemia was accomplished by clipping the superior mesenteric artery during 60 minutes, with an administration of a standard volume of saline solution (SS) 5 min before the end of the ischemia period; the clip was then releases or a 120-min period of reperfusion; (3) I+PTX+R: ischemia as above, PTX was administered (25 mg/kg) and the gut reperfused as above; (4) PTX+I+PTX+R: Five minutes before arterial occlusion PTX was administered; the superior mesenteric artery was then clipped for 60 minutes. After 55-min ischemia, an additional dosis of PTX was administered; the clip was removed for reperfusion as above. At the 60th min of reperfusion a third dosis of PTX was administered.

RESULTS

PTX markedly attenuated lung injury as manifested by significant decreases (all P<0.001 as compared with the SS+IR group) of pulmonary wet/dry tissue weight ratio, total protein content, myeloperoxidase activity and tumor necrosis factor-alpha. Moreover, it was apparent that in the group PTX+I+PTX+R the improvements have been even more significant.

CONCLUSION

PTX exerted a protective effect on the lung from the injuries caused by intestinal ischemia/reperfusion.

Toward computational identification of multiscale "tipping points" in acute inflammation and multiple organ failure

Sepsis accounts annually for nearly 10% of total U.S. deaths, costing nearly $17 billion/year. Sepsis is a manifestation of disordered systemic inflammation. Properly regulated inflammation allows for timely recognition and effective reaction to injury or infection, but inadequate or overly robust inflammation can lead to Multiple Organ Dysfunction Syndrome (MODS). There is an incongruity between the systemic nature of disordered inflammation (as the target of inflammation-modulating therapies), and the regional manifestation of organ-specific failure (as the subject of organ support), that presents a therapeutic dilemma: systemic interventions can interfere with an individual organ system's appropriate response, yet organ-specific interventions may not help the overall system reorient itself. Based on a decade of systems and computational approaches to deciphering acute inflammation, along with translationally-motivated experimental studies in both small and large animals, we propose that MODS evolves due to the feed-forward cycle of inflammation → damage → inflammation. We hypothesize that inflammation proceeds at a given, "nested" level or scale until positive feedback exceeds a "tipping point." Below this tipping point, inflammation is contained and manageable; when this threshold is crossed, inflammation becomes disordered, and dysfunction propagates to a higher biological scale (e.g., progressing from cellular, to tissue/organ, to multiple organs, to the organism). Finally, we suggest that a combination of computational biology approaches involving data-driven and mechanistic mathematical modeling, in close association with studies in clinically relevant paradigms of sepsis/MODS, are necessary in order to define scale-specific "tipping points" and to suggest novel therapies for sepsis.

Peritoneal fluid: a potential mechanism of systemic neutrophil priming in experimental intra-abdominal sepsis

BACKGROUND

Recent studies suggest that peritoneal fluid (PF) may be an important mediator of inflammation. The aim of this study was to test the hypothesis that PF may drive systemic inflammation in intra-abdominal sepsis by representing a priming agent for neutrophils.

METHODS

PF was collected 12 hours after the initiation of intra-abdominal sepsis in swine. Naive human neutrophils were primed with PF before treatment with N-formyl-Met-Leu-Phe or phorbol 12-myristate 13-acetate to elucidate receptor-dependent and receptor-independent mechanisms of neutrophil activation. Flow cytometry was used to quantify neutrophil surface adhesion marker expression of integrins and selectins and superoxide anion production. Additionally, proinflammatory cytokines were quantified in PF.

RESULTS

PF primed neutrophils via receptor-dependent and receptor-independent mechanisms. There were significant increases in the proinflammatory cytokines interleukin-6 and tumor necrosis factor-α in PF correlating with the development of intra-abdominal sepsis.

CONCLUSIONS

PF represents a priming agent for naive polymorphonuclear cells in intra-abdominal sepsis. This may be secondary to increased levels of proinflammatory cytokines. Strategies to reduce the amount of PF may decrease the systemic inflammatory response by reducing a priming agent for neutrophils.

Periodontitis and arthritis interaction in mice involves a shared hyper-inflammatory genotype and functional immunological interferences

Periodontitis (PD) and rheumatoid arthritis (RA) have been found to be clinically associated and to share the chronic nature of the inflammatory reaction associated with bone resorption activity. However, the mechanisms underlying such association are unknown. Therefore, we examined the basis of Actinobacillus actinomycetemcomitans- and Porphyromonas gingivalis-induced PD and pristane-induced arthritis (PIA) interaction in mice. Higher severity PD in the genetically inflammation prone acute inflammatory reactivity maximum (AIRmax) mice strain was associated with higher levels of TNF-alpha, IL-1beta, IL-17, matrix metalloproteinase (MMP)-13, and RANKL, whereas PD/PIA co-induction resulted in even higher levels of IL-1beta, IFN-gamma, IL-17, RANKL, and MMP-13 levels. Conversely, PD/PIA co-induction in AIRmin strain did not alter the course of both pathologies. PIA/PD co-induction resulted in altered expression of T-cell subsets transcription factors expression, with T-bet and RORgamma levels being upregulated, whereas GATA-3 levels were unaltered. Interestingly, PIA induction resulted in alveolar bone loss, such response being highly dependent on the presence of commensal oral bacteria. No differences were found in PIA severity parameters by PD co-induction. Our results show that the interaction between experimental PD and arthritis in mice involves a shared hyper-inflammatory genotype and functional interferences in innate and adaptive immune responses.

Human adrenomedullin combined with human adrenomedullin binding protein-1 is protective in gut ischemia and reperfusion injury in the rat

Previous studies have demonstrated that co-administration of rat adrenomedullin (AM) and human AM binding protein-1 (AMBP-1) has various beneficial effects following adverse circulatory conditions. In order to reduce rat proteins to elicit possible immune responses in humans, we determined the effect of human AM combined with human AMBP-1 after intestinal ischemia and reperfusion (I/R). Intestinal ischemia was induced in the rat by occluding the superior mesenteric artery for 90 min. At 60 min after the beginning of reperfusion, human AM/AMBP-1 at 3 different dosages was administered intravenously over 30 min. At 240 min after the treatment, blood and tissue samples were harvested and measured for pro-inflammatory cytokines (i.e., TNF-alpha and IL-6), myeloperoxidase activities in the gut and lungs, and cleaved caspase-3 expression in the lungs, as well as serum levels of hepatic enzymes and lactate. In additional groups of animals, a 10-day survival study was conducted. Results showed that administration of human AM/AMBP-1 reduced pro-inflammatory cytokines, attenuated organ injury, and improved the survival rate in a seemingly dose-response fashion. Co-administration of the highest dose of human AM/AMBP-1 in this study had the optimal therapeutic effect in the rat model of intestinal I/R.

Ventilator-induced lung injury and mechanotransduction: why should we care?

Mechanotransduction holds the underlying mechanisms of ventilator-induced lung injury. Research on this subject, however, could be difficult for clinicians, especially when results are controversial. A recent study by Li and co-workers is used as an example, to explain how to critically read literatures related to basic science and how to understand the limitation of experimental studies.

The influence of early hemodynamic optimization on biomarker patterns of severe sepsis and septic shock

BACKGROUND

Despite abundant experimental studies of biomarker patterns in early severe sepsis and septic shock, human data are few. Further, the impact of the severity of global tissue hypoxia resulting from resuscitative strategies on these early biomarker patterns remains unknown.

METHODS

The temporal patterns of interleukin-1 receptor antagonist, intercellular adhesion molecule-1, tumor necrosis factor-alpha, caspase-3, and interleukin-8 were serially examined over the first 72 hrs of hospitalization after early hemodynamic optimization strategies of early goal-directed vs. standard therapy for severe sepsis and septic shock patients. The relationship of these biomarker patterns to each hemodynamic optimization strategy, severity of global tissue hypoxia (reflected by lactate and central venous oxygen saturation), organ dysfunction, and mortality were examined.

RESULTS

Abnormal biomarker levels were present upon hospital presentation and modulated to distinct patterns within 3 hrs based on the hemodynamic optimization strategy. The temporal expression of these patterns over 72 hrs was significantly associated with the severity of global tissue hypoxia, organ dysfunction, and mortality.

CONCLUSION

In early severe sepsis and septic shock, within the first 3 hrs of hospital presentation, distinct biomarker patterns emerge in response to hemodynamic optimization strategies. A significant association exists between temporal biomarker patterns in the first 72 hrs, severity of global tissue hypoxia, organ dysfunction, and mortality. These findings identify global tissue hypoxia as an important contributor to the early inflammatory response and support the role of hemodynamic optimization in supplementing other established therapies during this diagnostic and therapeutic "window of opportunity."

[Nutrition and immunonutrition in septic patients]

Nutrition in septic patients is more than just caloric support. Not all nutritional concepts in general intensive care may be applied to septic patients. A tight glycemic control successfully used in post-operative intensive care patients has to be modified for the septic patient. Enteral immunonutrition leading to reduced length of stay in post-operative patients may be associated with increased mortality in patients suffering from severe sepsis. Newly developed lipid emulsions for parenteral nutrition became available. Application of these emulsions may prove to be beneficial in septic patients. An intravenous supplementation with glutamine of long-term exclusively parenterally fed intensive care patients may reduce their mortality. A nutrition individually optimized and adapted to the severity of the disease is considered to be an adjunct therapeutic measure in the treatment concept in sepsis.

Intestinal anastomosis surgery with no septic shock primes for a dysregulatory response to a second stimulus

BACKGROUND

Major surgery is believed to contribute to immune dysregulation and high susceptibility to microbes. Recently, the inflammatory "two-hit" model has been accepted to elucidate development of multiple organ failure in surgical patients. Our purpose was to examine whether intestinal surgery, which causes a minor insult with no septic shock, may modify the immune response to exogenous LPS as a second stimulus.

MATERIALS AND METHODS

Using a rat intestinal transection and anastomosis surgery model, we sequentially examined blood cell counts, body temperatures, and plasma cytokines. Rats were administered with LPS intravenously or intratracheally various days after surgery. Phagocytic activity and TNFalpha production in bronchoalveolar lavage (BAL) cells, plasma cytokines, and survival rates were evaluated.

RESULTS

The surgery itself caused no severe shock or circulating cytokine elevation, whereas the number of granulocytes in the blood was significantly elevated after surgery. LPS-induced elevation of circulating IFNgamma attenuated 3 days after surgery. In contrast, IL-10 was enhanced 3-10 days after surgery. Hyporesponsiveness of BAL cells to LPS was observed 3 days after surgery but not the next day after surgery. However, rats intratracheally exposed to LPS 10-13 days after surgery exhibited higher mortality.

CONCLUSIONS

Although our surgical procedure was not supposed to be a severe insult, it sufficiently primed rats for an altered response to a second stimulus (endotoxin), which included enhanced mortality. This study provided an improved understanding of pathophysiological changes following surgery and described a useful model for developing preventive and therapeutic strategies for complications after surgery.

Chemically modified tetracycline prevents the development of septic shock and acute respiratory distress syndrome in a clinically applicable porcine model

Sepsis causes more than with 215,000 deaths per year in the United States alone. Death can be caused by multiple system organ failure, with the lung, in the form of the acute respiratory distress syndrome (ARDS), often being the first organ to fail. We developed a chronic porcine model of septic shock and ARDS and hypothesized that blocking the proteases neutrophil elastase (NE) and matrix metalloproteinases (MMP-2 and MMP-9) with the modified tetracycline, COL-3, would significantly improve morbidity in this model. Pigs were anesthetized and instrumented for hemodynamic monitoring and were then randomized to one of three groups: control (n = 3), laparotomy only; superior mesenteric artery occlusion (SMA) + fecal blood clot (FC; n = 7), with intraperitoneal placement of a FC; and SMA + FC + COL (n = 5), ingestion of COL-3 12 h before injury. Animals emerged from anesthesia and were monitored and treated with fluids and antibiotics in an animal intensive care unit continuously for 48 h. Serum and bronchoalveolar lavage fluid (BALF) were sampled and bacterial cultures, MMP-2, MMP-9, NE, and multiple cytokine concentrations were measured. Pigs were reanesthetized and placed on a ventilator when significant lung impairment occurred (PaO2/FiO2 < 250). At necropsy, lung water and histology were assessed. All animals in the SMA + FC group developed septic shock evidenced by a significant fall in arterial blood pressure that was not responsive to fluids. Lung injury typical of ARDS (i.e., a fall in lung compliance and PaO2/FiO2 ratio and a significant increase in lung water) developed in this group. Additionally, there was a significant increase in plasma IL-1 and IL-6 and in BALF IL-6, IL-8, IL-10, NE, and protein concentration in the SMA + FC group. COL-3 treatment prevented septic shock and ARDS and significantly decreased cytokine levels in plasma and BALF. COL-3 treatment also significantly reduced NE activity (P < 0.05) and reduced MMP-2 and MMP-9 activity in BALF by 64% and 34%, respectively, compared with the SMA + FC group. We conclude that prophylactic COL-3 prevented the development of ARDS and unexpectedly also prevented septic shock in a chronic insidious onset animal model of sepsis-induced ARDS. The mechanism of this protection is unclear, as COL-3 inhibited numerous inflammatory mediators. Nevertheless, COL-3 significantly reduced the morbidity in a clinically applicable animal model, demonstrating the possibility that COL-3 may be useful in reducing the morbidity associated with sepsis and ischemia/reperfusion injury in patients.