2008 Landis Award lecture. Inflammation and the autodigestion hypothesis

COVID-19 vaccine adverse events: Evaluating the pathophysiology with an emphasis on sulfur metabolism and endotheliopathy

In this narrative review, we assess the pathophysiology of severe adverse events that presented after vaccination with DNA and mRNA vaccines against COVID-19. The focus is on the perspective of an undersulfated and degraded glycocalyx, considering its impact on immunomodulation, inflammatory responses, coagulation and oxidative stress. The paper explores various factors that lead to glutathione and inorganic sulfate depletion and their subsequent effect on glycocalyx sulfation and other metabolites, including hormones. Components of COVID-19 vaccines, such as DNA and mRNA material, spike protein antigen and lipid nanoparticles, are involved in possible cytotoxic effects. The common thread connecting these adverse events is endotheliopathy or glycocalyx degradation, caused by depleted glutathione and inorganic sulfate levels, shear stress from circulating nanoparticles, aggregation and formation of protein coronas; leading to imbalanced immune responses and chronic release of pro-inflammatory cytokines, ultimately resulting in oxidative stress and systemic inflammatory response syndrome. By understanding the underlying pathophysiology of severe adverse events, better treatment options can be explored.

Papain Suppresses Atopic Skin Inflammation through Anti-Inflammatory Activities Using In Vitro and In Vivo Models

Papain (PN) is a proteolytic enzyme derived from Carica Papaya L. While the pharmacological effects of PN have not been extensively studied compared to its enzymatic activity, PN also holds potential benefits beyond protein digestion. This study aimed to investigate the potential effects of PN against skin inflammation in house dust mite Dermatophagoides farinae body (Dfb)-exposed NC/Nga atopic dermatitis (AD) mice and human HaCaT keratinocytes and their underlying mechanisms. The effects of PN on the skin were assessed via histological examination, measurements of transepidermal water loss (TEWL), quantitative reverse transcription-polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assay. Our findings indicated that the oral intake of PN decreased the severity scores of lesions resembling AD, TEWL, and the levels of inflammatory cytokines and serum immunoglobulin E in Dfb-induced AD mice, along with a reduction in epidermal thickness and mast cell infiltration. Additionally, PN inhibited the activation of the mitogen-activated protein kinases (MAPKs) and the signal transducer and activator of transcription (STAT) pathways in Dfb-induced AD mice and HaCaT keratinocytes. Moreover, PN improved survival and reduced ROS production in H2O2-damaged HaCaT keratinocytes and enhanced the expression of antioxidant enzymes in Dfb-induced AD mice. Concludingly, the oral administration of PN suppressed inflammatory mediators and downregulated the MAPKs/STAT pathway, suggesting its potential role in AD pathogenesis.

Investigating the Relationship between Epigenetic Age and Cardiovascular Risk in a Population with Overweight/Obesity

Introduction: Cardiovascular diseases stand as the leading global cause of mortality. Major modifiable risk factors encompass overweight/obese conditions, high blood pressure, elevated LDL cholesterol, diabetes, smoking, secondhand smoke exposure, unhealthy diet, and physical inactivity. In the present study, we explored the relationship between cardiovascular risk factors and epigenetic age (DNAm age), an estimate reflecting an individual's actual physiological functionality and overall health. Additionally, we assessed the association between DNAm age acceleration and cardiovascular risk, as evaluated through the Framingham risk score (FRS). Methods: The study includes 190 subjects with overweight/obese conditions. We calculated their DNAm age using Zbieć-Piekarska et al.'s DNAm age estimator on five sets of CpGs analyzed in the peripheral leucocytes. Linear regression models were employed to test the associations. Results: Various parameters contributing to increased cardiovascular risk were associated with DNAm age acceleration, such as systolic blood pressure (β = 0.045; SE = 0.019; p = 0.019), heart rate (β = 0.096; SE = 0.032; p = 0.003), blood glucose (β = 0.025; SE = 0.012; p = 0.030), glycated hemoglobin (β = 0.105; SE = 0.042; p = 0.013), diabetes (β = 2.247; SE = 0.841; p = 0.008), and menopausal conditions (β = 2.942; SE = 1.207; p = 0.016), as well as neutrophil (β = 0.100; SE = 0.042; p = 0.018) and granulocyte (β = 0.095; SE = 0.044; p = 0.033) counts. Moreover, DNAm age acceleration raised the FRS (∆% 5.3%, 95% CI 0.8; 9.9, p = 0.019). Conclusion: For the first time, we report that cardiovascular risk factors accelerated DNAm age in a selected population of hypersusceptible individuals with overweight or obesity. Our results highlight the potential of DNAm age acceleration as a biomarker of cumulative effects in cardiovascular risk assessment.

Mechanoimmunology: Are inflammatory epigenetic states of macrophages tuned by biophysical factors?

Many inflammatory diseases that are responsible for a majority of deaths are still uncurable, in part as the underpinning pathomechanisms and how to combat them is still poorly understood. Tissue-resident macrophages play pivotal roles in the maintenance of tissue homeostasis, but if they gradually convert to proinflammatory phenotypes, or if blood-born proinflammatory macrophages persist long-term after activation, they contribute to chronic inflammation and fibrosis. While biochemical factors and how they regulate the inflammatory transcriptional response of macrophages have been at the forefront of research to identify targets for therapeutic interventions, evidence is increasing that physical factors also tune the macrophage phenotype. Recently, several mechanisms have emerged as to how physical factors impact the mechanobiology of macrophages, from the nuclear translocation of transcription factors to epigenetic modifications, perhaps even DNA methylation. Insight into the mechanobiology of macrophages and associated epigenetic modifications will deliver novel therapeutic options going forward, particularly in the context of increased inflammation with advancing age and age-related diseases. We review here how biophysical factors can co-regulate pro-inflammatory gene expression and epigenetic modifications and identify knowledge gaps that require urgent attention if this therapeutic potential is to be realized.

The gut brain in a dish: Murine primary enteric nervous system cell cultures

BACKGROUND

The enteric nervous system (ENS) is an extensive neural network embedded in the wall of the gastrointestinal tract that regulates digestive function and gastrointestinal homeostasis. The ENS consists of two main cell types; enteric neurons and enteric glial cells. In vitro techniques allow simplified investigation of ENS function, and different culture methods have been developed over the years helping to understand the role of ENS cells in health and disease.

PURPOSE

This review focuses on summarizing and comparing available culture protocols for the generation of primary ENS cells from adult mice, including dissection of intestinal segments, enzymatic digestions, surface coatings, and culture media. In addition, the potential of human ENS cultures is also discussed.

Enhanced intestinal permeability and intestinal co-morbidities in heat strain: A review and case for autodigestion

Enhanced intestinal permeability is a pervasive issue in modern medicine, with implications demonstrably associated with significant health consequences such as sepsis, multiorgan failure, and death. Key issues involve the trigger mechanisms that could compromise intestinal integrity and increase local permeability allowing the passage of larger, potentially dangerous molecules. Heat stress, whether exertional or environmental, may modulate intestinal permeability and begs interesting questions in the context of global climate change, increasing population vulnerabilities, and public health. Emerging evidence indicates that intestinal leakage of digestive enzymes and associated cell dysfunctions--a process referred to as autodigestion--may play a critical role in systemic physiological damage within the body. This increased permeability is exacerbated in the presence of elevated core temperatures. We employed Latent Dirichlet Allocation (LDA) topic modeling methods to analyze the relationship between heat stress and the nascent theory of autodigestion in a systematic, quantifiable, and unbiased manner. From a corpus of 11,233 scientific articles across four relevant scientific journals (Gut, Shock, Temperature, Gastroenterology), it was found that over 1,000 documents expressed a relationship between intestine, enhanced permeability, core temperature, and heat stress. The association has grown stronger in recent years, as heat stress and potential autodigestion are investigated in tandem, yet still by a limited number of specific research studies. Such findings justify the design of future studies to critically test novel interventions against digestive enzymes permeating the intestinal tract, especially the small intestine.

Enteral Tranexamic Acid Decreases Proteolytic Activity in the Heart in Acute Experimental Hemorrhagic Shock

The mechanisms for cardiac injury after hemorrhagic shock (HS) are unresolved. We hypothesize that remote organ damage can be caused by uncontrolled pancreatic proteolytic activity, as enteral protease inhibition improves outcomes in experimental HS. Uncontrolled proteolysis in the heart may disrupt cardiac metabolism and adrenergic control with subsequent deleterious outcomes. To test this hypothesis, the heart rate-pressure product (RPP) as an index of myocardial oxygen consumption and the levels of fatty acid transporter proteins CD36 and FATP6 as surrogates for metabolic activity in the heart were measured in rats subjected to experimental HS (n = 6/group) with and without the enteral protease inhibitor tranexamic acid (TXA). Plasma troponin I and heart fatty acid-binding protein (HFABP) concentrations were measured as indices of myocardial damage. Expression of the adrenergic receptors β₁, α_1D, and β₂ was also measured in the heart to determine the possible effects of shock with and without enteral TXA on the adrenergic control of heart function. Hemorrhagic shock was induced by reduction in mean arterial blood pressure to 35 mm Hg for 2 hours before reperfusion of shed blood. The RPP was maintained in shocked animals treated enterally with TXA but not in those subjected to HS alone; this group also demonstrated decreased HFABP and plasma troponin I levels. Serine protease (trypsin, chymotrypsin, and elastase) and matrix metalloproteinase (MMP)-2 and MMP-9 activity was elevated in cardiac tissue and plasma after HS and abrogated by enteral TXA. Levels of CD36, FATP6, β₁, α_1D, and β₂ were also increased after HS in cardiac tissue, and the increases were mitigated by TXA treatment. These results suggest that increased proteolytic activity may contribute to cardiac injury after HS. Enteral TXA prevents these changes, indicating a potential therapeutic option in the management of shock with resultant cardiac injury.

Targeting Complement Pathways in Polytrauma- and Sepsis-Induced Multiple-Organ Dysfunction

Exposure to traumatic or infectious insults results in a rapid activation of the complement cascade as major fluid defense system of innate immunity. The complement system acts as a master alarm system during the molecular danger response after trauma and significantly contributes to the clearance of DAMPs and PAMPs. However, depending on the origin and extent of the damaged macro- and micro -milieu, the complement system can also be either excessively activated or inhibited. In both cases, this can lead to a maladaptive immune response and subsequent multiple cellular and organ dysfunction. The arsenal of complement-specific drugs offers promising strategies for various critical conditions after trauma, hemorrhagic shock, sepsis, and multiple organ failure. The imbalanced immune response needs to be detected in a rational and real-time manner before the translational therapeutic potential of these drugs can be fully utilized. Overall, the temporal-spatial complement response after tissue trauma and during sepsis remains somewhat enigmatic and demands a clinical triad: reliable tissue damage assessment, complement activation monitoring, and potent complement targeting to highly specific rebalance the fluid phase innate immune response.

IGF-1 receptor cleavage in hypertension

Increased protease activity causes receptor dysfunction due to extracellular cleavage of different membrane receptors in hypertension. The vasodilatory effects of insulin-like growth factor-1 (IGF-1) are decreased in hypertension. Therefore, in the present study the association of an enhanced protease activity and IGF-1 receptor cleavage was investigated using the spontaneously hypertensive rats (SHRs) and their normotensive Wistar Kyoto (WKY) controls (n = 4). Matrix metalloproteinase (MMP) activities were determined using gelatin zymography on plasma and different tissue samples. WKY aorta rings were incubated in WKY or SHR plasma with or without MMP inhibitors, and immunohistochemistry was used to quantify the densities of the alpha and beta IGF-1 receptor (IGF-1R) subunits and to determine receptor cleavage. The pAkt and peNOS levels in the aorta were investigated using immunoblotting as a measure of IGF-IR function. Increased MMP-2 and MMP-9 activities were detected in plasma and peripheral tissues of SHRs. IGF-1R beta labeling was similar in both groups without plasma incubation, but the fraction of immunolabeled area for IGF-1R alpha was lower in the endothelial layer of the SHR aorta (p < 0.05). A 24-h incubation of WKY aorta with SHR plasma did not affect the IGF-1R beta labeling density, but reduced the IGF-1R alpha labeling density in the endothelium (p < 0.05). MMP inhibitors prevented this decrease (p < 0.01). Western blot analyses revealed that the pAkt and peNOS levels under IGF-1-stimulated and -unstimulated conditions were lower in SHRs (p < 0.05). A reduced IGF-1 cellular response in the aorta was associated with the decrease in the IGF-1R alpha subunit in the SHR hypertension model. Our results indicate that MMP-dependent receptor cleavage contributed to the reduced IGF-1 response in SHRs.

Early tranexamic acid administration ameliorates the endotheliopathy of trauma and shock in an in vitro model

BACKGROUND

Systemic vascular endothelial injury is a consequence of trauma (T)/hemorrhagic shock (HS) which results in disturbances of coagulation, inflammation, and endothelial barrier integrity. The effect of T/HS on the endothelium (endotheliopathy of trauma [EoT]) is of intense research interest and may lead to EoT-directed therapies. Administration of tranexamic acid (TXA) in trauma patients is associated with a survival benefit and fewer complications if given early after injury. Mechanisms for this protective effect include the antifibrinolytic and anti-inflammatory effects of TXA. We hypothesized that "early" administration of TXA would abrogate vascular endothelial cell activation and injury after T/HS. This was studied in vitro.

METHODS

Confluent human umbilical vein endothelial cells were exposed to hydrogen peroxide and/or epinephrine to stimulate post-T/HS oxidant exposure and/or sympathoadrenal activation. TXA was added 15 minutes, 60 minutes, or 120 minutes after H2O2 and/or epinephrine challenge. Endothelial cell injury was indexed by cell monolayer permeability, intracellular adhesion molecule expression, soluble thrombomodulin, syndecan release (marker for glycocalyx injury), tissue type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) and angiopoietin-2/angiopoietin-1 ratio (APO-2/APO-1).

RESULTS

Endothelial activation and injury as indexed by permeability, ICAM expression, soluble thrombomodulin were increased by H2O2 and/or epinephrine exposure. Biomarkers of endothelial coagulation profile (tPA/PAI-1) demonstrated a profibrinolytic profile (increased tPA and tPA/PAI-1 ratio) after challenge by H2O2 and/or epinephrine. Vascular "leakiness" as indexed by APO-2/APO-1 ratio was also evident. The most profound effects were noted with H2O2/epinephrine exposure. TXA administration within 60 minutes of H2O2/epinephrine challenge abolished the adverse effects noted on the endothelial-glycocalyx "double barrier." TXA administration after 60 minutes was not protective.

CONCLUSION

Antifibrinolytic and other protective effects of TXA administration on endothelial injury are time-dependent. This study supports the concept that the clinical efficacy of TXA administration requires "early administration."

Intraluminal tranexamic acid inhibits intestinal sheddases and mitigates gut and lung injury and inflammation in a rodent model of hemorrhagic shock

BACKGROUND

Intravenous tranexamic acid (TXA) is an effective adjunct after hemorrhagic shock (HS) because of its antifibrinolytic properties. TXA is also a serine protease inhibitor, and recent laboratory data demonstrated that intraluminal TXA into the small bowel inhibited digestive proteases and protected the gut. A Disintegrin And Metalloproteinase 17 (ADAM-17) and tumor necrosis factor α (TNF-α) are effective sheddases of intestinal syndecan-1, which when shed, exposes the underlying intestinal epithelium to digestive proteases and subsequent systemic insult. We therefore hypothesized that intraluminal TXA as a serine protease inhibitor would reduce intestinal sheddases and syndecan-1 shedding, mitigating gut and distant organ (lung) damage.

METHODS

Mice underwent 90 minutes of HS to a mean arterial pressure of 35 ± 5 mm Hg followed by the intraluminal administration of TXA or vehicle. After 3 hours, the small intestine, lung, and blood were collected for analysis.

RESULTS

Intraluminal TXA significantly reduced gut and lung histopathologic injury and inflammation compared with HS alone. Gut, lung, and systemic ADAM-17 and TNF-α were significantly increased by HS but lessened by TXA. In addition, gut and lung syndecan-1 immunostaining were preserved and systemic shedding lessened after TXA. TXA reduced ADAM-17 and TNF-α, but not syndecan-1, in TXA-sham animals compared with sham vehicles.

CONCLUSION

Results of the present study demonstrate a beneficial effect of intraluminal TXA in the gut and lung after experimental HS in part because of the inhibition of the syndecan-1 shedding by ADAM-17 and TNF-α. Further studies are needed to determine if orally administered TXA could provide similar intestinal protection and thus be of potential benefit to patients with survivable hemorrhage at risk for organ injury. This is particularly relevant in patients or soldiers who may not have access to timely medical care.

ShockOmics: multiscale approach to the identification of molecular biomarkers in acute heart failure induced by shock

BACKGROUND

The ShockOmics study (ClinicalTrials.gov identifier NCT02141607) is a multicenter prospective observational trial aimed at identifying new biomarkers of acute heart failure in circulatory shock, by means of a multiscale analysis of blood samples and hemodynamic data from subjects with circulatory shock.

METHODS AND DESIGN

Ninety septic shock and cardiogenic shock patients will be recruited in three intensive care units (ICU) (Hôpital Erasme, Université Libre de Bruxelles, Belgium; Hospital Universitari Mutua Terrassa, Spain; Hôpitaux Universitaires de Genève, Switzerland). Hemodynamic signals will be recorded every day for up to seven days from shock diagnosis (time T0). Clinical data and blood samples will be collected for analysis at: i) T1 < 16 h from T0; ii) T2 = 48 h after T0; iii) T3 = day 7 or before discharge or before discontinuation of therapy in case of fatal outcome; iv) T4 = day 100. The inclusion criteria are: shock, Sequential Organ Failure Assessment (SOFA) score > 5 and lactate levels ≥ 2 mmol/L. The exclusion criteria are: expected death within 24 h since ICU admission; > 4 units of red blood cells or >1 fresh frozen plasma transfused; active hematological malignancy; metastatic cancer; chronic immunodepression; pre-existing end stage renal disease requiring renal replacement therapy; recent cardiac surgery; Child-Pugh C cirrhosis; terminal illness. Enrollment will be preceded by the signature of the Informed Consent by the patient or his/her relatives and by the physician in charge. Three non-shock control groups will be included in the study: a) healthy blood donors (n = 5); b) septic patients (n = 10); c) acute myocardial infarction or patients with prolonged acute arrhythmia (n = 10). The hemodynamic data will be downloaded from the ICU monitors by means of dedicated software. The blood samples will be utilized for transcriptomics, proteomics and metabolomics ("-omics") analyses.

DISCUSSION

ShockOmics will provide new insights into the pathophysiological mechanisms underlying shock as well as new biomarkers for the timely diagnosis of cardiac dysfunction in shock and quantitative indices for assisting the therapeutic management of shock patients.

Mechanisms by which Stress Affects the Experimental and Clinical Inflammatory Bowel Disease (IBD): Role of Brain-Gut Axis

BACKGROUND

Stress of different origin is known to alter so called "braingut axis" and contributes to a broad array of gastrointestinal disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and other functional gastrointestinal diseases. The stressful situations and various stressors including psychosocial events, heat, hypo- and hyperthermia may worsen the course of IBD via unknown mechanism. The aims of this paper were to provide an overview of experimental and clinical evidences that stress activates the brain-gut axis which results in a mucosal mast cells activation and an increase in the production of proinflammatory cytokines and other endocrine and humoral mediators.

METHODS

Research and online content related to effects of stress on lower bowel disorders are reviewed and most important mechanisms are delineated.

RESULTS

Brain conveys the neural, endocrine and circulatory messages to the gut via brain-gut axis reflecting changes in corticotrophin releasing hormone, mast cells activity, neurotransmission at the autonomic nerves system and intestinal barrier function all affecting the pathogenesis of animal colitis and human IBD. Stress triggers the hypothalamus-pituitary axis and the activation of the autonomic nervous system, an increase in cortisol levels and proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-8, interleukin-1beta and interleukin-6.

CONCLUSION

The acute or chronic stress enhances the intestinal permeability weakening of the tight junctions and increasing bacterial translocation into the intestinal wall. An increased microbial load in the colonic tissue, excessive cytokine release and a partially blunted immune reactivity in response to stress result in its negative impact on IBD.

The Human Colon Is More Resistant to Ischemia-reperfusion-induced Tissue Damage Than the Small Intestine: An Observational Study

OBJECTIVE

Aim of this study was to draw comparisons between human colonic and jejunal ischemia-reperfusion sequelae in a human in vivo experimental model.

BACKGROUND

In patients, colonic ischemia-reperfusion generally has a milder course than small intestinal ischemia-reperfusion. It is unclear which pathophysiologic processes are responsible for this difference.

METHODS

In 10 patients undergoing colonic surgery and 10 patients undergoing pancreaticoduodenectomy, 6 cm colon or jejunum was isolated and exposed to 60 minutes ischemia followed by various reperfusion periods. Morphology (hematoxylin and eosin), apoptosis (M30), tight junctions (zonula occludens 1), and neutrophil influx (myeloperoxidase) were assessed using immunohistochemistry. Quantitative polymerase chain reaction and enzyme-linked immunosorbent assay were performed for interleukin-6 and tumor necrosis factor-α.

RESULTS

Hematoxylin and eosin staining revealed intact colonic epithelial lining, but extensive damage in jejunal villus tips after 60 minutes ischemia. After reperfusion, the colonic epithelial lining was not affected, whereas the jejunal epithelium was seriously damaged. Colonic apoptosis was limited to scattered cells in surface epithelium, whereas apoptosis was clearly observed in jejunal villi and crypts, (42 times more M30 positivity compared with colon, P < 0.01). Neutrophil influx and increased tumor necrosis factor-α mRNA expression were observed in jejunum after 30 and 120 minutes of reperfusion (P < 0.05). Interleukin-6 mRNA expression was increased in jejunum after 120 minutes of reperfusion (3.6-fold increase, P < 0.05), whereas interleukin-6 protein expression was increased in both colon (1.5-fold increase, P < 0.05) and small intestine (1.5-fold increase, P < 0.05) after 30 and 120 minutes of reperfusion.

CONCLUSIONS

Human colon is less susceptible to IR-induced tissue injury than small intestine.

Intraluminal nonbacterial intestinal components control gut and lung injury after trauma hemorrhagic shock

OBJECTIVE

To test whether the mucus layer, luminal digestive enzymes, and intestinal mast cells are critical components in the pathogenesis of trauma shock-induced gut and lung injury.

BACKGROUND

Gut origin sepsis studies have highlighted the importance of the systemic component (ischemia-reperfusion) of gut injury, whereas the intraluminal component is less well studied.

METHODS

In rats subjected to trauma hemorrhagic shock (T/HS) or sham shock, the role of pancreatic enzymes in gut injury was tested by diversion of pancreatic enzymes via pancreatic duct exteriorization whereas the role of the mucus layer was tested via the enteral administration of a mucus surrogate. In addition, the role of mast cells was assessed by measuring mast cell activation and the ability of pharmacologic inhibition of mast cells to abrogate gut and lung injury. Gut and mucus injury was characterized functionally, morphologically, and chemically.

RESULTS

Pancreatic duct exteriorization abrogated T/HS-induced gut barrier loss and limited chemical mucus changes. The mucus surrogate prevented T/HS-induced gut and lung injury. Finally, pancreatic enzyme-induced gut and lung injury seems to involve mast cell activation because T/HS activates mast cells and pharmacologic inhibition of intestinal mast cells prevented T/HS-induced gut and lung injury.

CONCLUSIONS

These results indicate that gut and gut-induced lung injury after T/HS involves a complex process consisting of intraluminal digestive enzymes, the unstirred mucus layer, and a systemic ischemic-reperfusion injury. This suggests the possibility of intraluminal therapeutic strategies.

Pancreatic digestive enzyme blockade in the intestine increases survival after experimental shock

Shock, sepsis, and multiorgan failure are associated with inflammation, morbidity, and high mortality. The underlying pathophysiological mechanism is unknown, but evidence suggests that pancreatic enzymes in the intestinal lumen autodigest the intestine and generate systemic inflammation. Blocking these enzymes in the intestine reduces inflammation and multiorgan dysfunction. We investigated whether enzymatic blockade also reduces mortality after shock. Three rat shock models were used here: hemorrhagic shock, peritonitis shock induced by placement of cecal material into the peritoneum, and endotoxin shock. One hour after initiation of hemorrhagic, peritonitis, or endotoxin shock, animals were administered one of three different pancreatic enzyme inhibitors--6-amidino-2-naphtyl p-guanidinobenzoate dimethanesulfate, tranexamic acid, or aprotinin--into the lumen of the small intestine. In all forms of shock, blockade of digestive proteases with protease inhibitor attenuated entry of digestive enzymes into the wall of the intestine and subsequent autodigestion and morphological damage to the intestine, lung, and heart. Animals treated with protease inhibitors also survived in larger numbers than untreated controls over a period of 12 weeks. Surviving animals recovered completely and returned to normal weight within 14 days after shock. The results suggest that the active and concentrated digestive enzymes in the lumen of the intestine play a central role in shock and multiorgan failure, which can be treated with protease inhibitors that are currently available for use in the clinic.

Regional susceptibility to stress-induced intestinal injury in the mouse

Injury to the intestinal mucosa is a life-threatening problem in a variety of clinical disorders, including hemorrhagic shock, trauma, burn, pancreatitis, and heat stroke. The susceptibility to injury of different regions of intestine in these disorders is not well understood. We compared histological injury across the small intestine in two in vivo mouse models of injury, hemorrhagic shock (30% loss of blood volume) and heat stroke (peak core temperature 42.4°C). In both injury models, areas near the duodenum showed significantly greater mucosal injury and reductions in villus height. To determine if these effects were dependent on circulating factors, experiments were performed on isolated intestinal segments to test for permeability to 4-kDa FITC-dextran. The segments were exposed to hyperthermia (42°C for 90 min), moderate simulated ischemia (Po2 ∼30 Torr, Pco2 ∼60 Torr, pH 7.1), severe ischemia (Po2 ∼20 Torr, Pco2 ∼80 Torr, pH 6.9), or severe hypoxia (Po2 ∼0 Torr, Pco2 ∼35 Torr) for 90 min, and each group was compared with sham controls. All treatments resulted in marked elevations in permeability within segments near the duodenum. In severe hypoxia or hyperthermia, permeability was also moderately elevated in the jejunum and ileum; in moderate or severe ischemia, permeability was unaffected in these regions. The results demonstrate increased susceptibility of proximal regions of the small intestine to acute stress-induced damage, irrespective of circulating factors. The predominant injury in the duodenum may impact the pattern of acute inflammatory responses arising from breach of the intestinal barrier, and such knowledge may be useful for designing therapeutic strategies.

Successful treatment with continuous enteral protease inhibitor in a patient with severe septic shock

OBJECTIVE

The mortality rate among patients with septic shock is high despite current therapy. We present a case of Fournier's gangrene and septic shock at 4 years post-heart transplantation that was reversed by "continuous enteral feeding" of the digestive enzyme inhibitor, gabexate mesilate. Recently, powerful pancreatic digestive proteases in the lumen of the intestine have been identified as initiators of the systemic inflammatory response. Intraluminal inhibitions of the proteases significantly attenuates intestinal damage, system inflammation, and multiorgan failure in experimental forms of shock but it has not been tested in man.

METHODS AND RESULTS

Gabexate mesilate, a synthetic digestive protease inhibitor, was continuously administered in two liters of crystalloid solution to a patient by enteral feeding during septic shock. The condition and markers for shock due to sepsis reversed in a few days.

CONCLUSION

This case suggested that "enteral" digestive protease inhibition may decrease and even reverse the sequelae of shock and sepsis.

Hyperthermia induces injury to the intestinal mucosa in the mouse: evidence for an oxidative stress mechanism

Loss of the intestinal barrier is critical to the clinical course of heat illness, but the underlying mechanisms are still poorly understood. We tested the hypothesis that conditions characteristic of mild heatstroke in mice are associated with injury to the epithelial lining of the intestinal tract and comprise a critical component of barrier dysfunction. Anesthetized mice were gavaged with 4 kDa FITC-dextran (FD-4) and exposed to increasing core temperatures, briefly reaching 42.4°C, followed by 30 min recovery. Arterial samples were collected to measure FD-4 concentration in plasma (in vivo gastrointestinal permeability). The small intestines were then removed to measure histological evidence of injury. Hyperthermia resulted in a ≈2.5-fold elevation in plasma FD-4 and was always associated with significant histological evidence of injury to the epithelial lining compared with matched controls, particularly in the duodenum. When isolated intestinal segments from control animals were exposed to ≥41.5°C, marked increases in permeability were observed within 60 min. These changes were associated with release of lactate dehydrogenase, evidence of protein oxidation via carbonyl formation and histological damage. Coincubation with N-acetylcysteine protected in vitro permeability during hyperthermia and reduced histological damage and protein oxidation. Chelation of intracellular Ca(2+) to block tight junction opening during 41.5°C exposure failed to reduce the permeability of in vitro segments. The results demonstrate that hyperthermia exposure in mouse intestine, at temperatures at or below those necessary to induce mild heatstroke, cause rapid and substantial injury to the intestinal lining that may be attributed, in part, to oxidative stress.

Proteolytic Activity Attenuates the Response of Endothelial Cells to Fluid Shear Stress

Recent evidence indicates that several experimental pathophysiological conditions are associated with elevated protease activity in plasma, which impacts endothelial function. We hypothesize that extracellular structures bound to the endothelial cell (EC) membrane may be degraded by proteolytic activity and cause the cells to respond abnormally to physiological shear stress (12 dyn/cm(2)). To test this hypothesis, cultured bovine aortic endothelial cells (BAECs) were exposed to low levels of a serine protease, trypsin. Extracellular mechanosensor densities of the glycocalyx and vascular endothelial growth factor receptor 2 (VEGFR-2) were determined. Metabolic dysfunction was tested by examining insulin receptor and glucose uptake levels. Protease treatment impaired the cells' ability to align in the direction of fluid flow after 12 hours of shear stress; however, cells realigned after an additional 12 hours of shear stress with protease inhibition. Proteases caused reduction in the densities of glycocalyx, VEGFR-2, and insulin receptor in static and shear conditions, except for static VEGFR-2 cells. Under static conditions, protease-treated endothelial cells had reduced glucose uptake compared to untreated controls. Under shear, however, glucose uptake for protease-treated BAECs was greater than untreated controls. In conclusion, protease activity in plasma alters the exofacial membrane components of ECs and may interfere with mechanotransduction.

Oral melatonin attenuates lung inflammation and airway hyperreactivity induced by inhalation of aerosolized pancreatic fluid in rats

Melatonin is a free radical scavenger with potent antioxidant properties and immunomodulatory effects. The purpose of this study was to determine the effects of orally administered melatonin in a pancreatic fluid (PF)-induced lung inflammation and airway hyperreactivity model. Aerosolized PF was introduced into airways to induce inflammation in rats. Animals were randomized into three experimental groups: sham treated; PF treated (200 μL/kg); and PF with melatonin (10 mg/kg) pretreatment. Airway reactivity to methacholine, airflow and airway resistance, bronchoalveolar lavage (BAL) cellular differential, the tumor necrosis factor α (TNFα) level, lavage nitric oxide, hydroxyl radical, and lactic dehydrogenase (LDH) were compared among groups. mRNA expressions of inducible nitric oxide synthase (iNOS) and TNFα in lung tissues were determined by real-time polymerase chain reaction. Protein expressions of iNOS and nitrotyrosine and lung tissue myeloperoxidase (MPO) activity were determined using an ELISA assay. Oral melatonin treatment indicated anti-inflammatory efficacy as evidenced by decreased methacholine sensitivity by 24% and airway obstruction by 28%, reduction in BAL eosinophil (P < 0.01) and neutrophil counts (P < 0.05), LDH (P < 0.05), and TNFα concentrations (P < 0.05) when compared to levels in sham-treated rats. Melatonin-treated animals also had reduced nitric oxide and hydroxyl radical concentrations (P < 0.05) in lavage fluid. Oral melatonin significantly reduced mRNA and protein expression of iNOS (P < 0.05 and P < 0.01, respectively), TNFα (P < 0.05), nitrotyrosine (P < 0.05), and MPO activity (P < 0.05) in lung tissues when compared with the sham-treated animals. These results suggest that oral treatment with melatonin had a beneficial effect on PF-induced obstructive ventilatory insufficiency by attenuating nitrosative and oxidative stress.