Differential expression of inducible nitric oxide synthase messenger RNA along the longitudinal and crypt-villus axes of the intestine in endotoxemic rats

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

Role of nitric oxide in regulating epidermal permeability barrier function

Nitric oxide (NO), a free radical molecule synthesized by nitric oxide synthases (NOS), regulates multiple cellular functions in a variety of cell types. These NOS, including endothelial NOS (eNOS), inducible NOS (iNOS) and neural NOS (nNOS), are expressed in keratinocytes. Expression levels of both iNOS and nNOS decrease with ageing, and insufficient NO has been linked to the development of a number of disorders such as diabetes and hypertension, and to the severity of atherosclerosis. Conversely, excessive NO levels can induce cellular oxidative stress, but physiological levels of NO are required to maintain the normal functioning of cells, including keratinocytes. NO also regulates cutaneous functions, including epidermal permeability barrier homeostasis and wound healing, through its stimulation of keratinocyte proliferation, differentiation and lipid metabolism. Topical applications of a diverse group of agents which generate nitric oxide (called NO donors) such as S-nitroso-N-acetyl-D,L-penicillamine (SNAP) can delay permeability barrier recovery in barrier-disrupted skin, but iNOS is still required for epidermal permeability barrier homeostasis. This review summarizes the regulatory role that NO plays in epidermal permeability barrier functions and the underlying mechanisms involved.

Case report: Temporal alterations in vascular function during the first 2 weeks of pediatric septic shock

INTRODUCTION

During sepsis and septic shock, the host's immune systems generate an overwhelming and often, detrimental, inflammatory response. Part of this response results in significant alterations in blood flow and vasomotor tone regulated in part by endothelial and vascular smooth muscle cells. Here, we report on a series of 3 pediatric patients for whom vascular response was assessed by laser doppler perfusion coupled to iontophoresis over the first 2 weeks after hospitalization for septic shock to demonstrate similarities and dissimilarities in the vascular response.

CASE PRESENTATIONS

A 12-year-old male with a history of Burkitt's Lymphoma, a 21-year-old male with congenital porencephaly and epilepsy, and a 7-year-old male with no significant past medical history all were admitted to a tertiary care children's hospital with a diagnosis of septic shock requiring vasoactive infusions to maintain mean arterial blood pressure. Non-invasive laser doppler perfusion coupled with iontophoresis of either acetylcholine (endothelial-dependent response) or sodium nitroprusside (endothelial-independent response) was performed on hospital days 1, 3, 7, and 14. Variability and heterogeneity were demonstrated by the temporal assessments of the vascular response to sodium nitroprusside, but all three patients showed significant similarity in the temporal responsiveness to acetylcholine.

CONCLUSION

Assessment of baseline and temporal responsiveness to endothelial-dependent vascular reactivity may provide a predictable timeline to the resolution of pediatric septic shock.

Potential mechanistic pathways underlying intestinal and hepatic effects of kefir in high-fructose-fed rats

Excess intake of fructose may contribute to the high prevalence of metabolic disorder. In this study, we investigated the effects of kefir supplementation on the intestine-liver-adipose tissue axis in metabolic disorder induced by high-fructose diet in rats to describe mechanistic action and potential therapeutic value of kefir. Fructose was given to the rats as a 20% solution in drinking water for 15 weeks. Kefir was administrated by gastric gavage once a day during the final six weeks. Kefir supplementation improved metabolic parameters, including plasma triglyceride and insulin levels; hepatic weight, triglyceride content and fatty degeneration; omental fat mass in fructose-fed rats. Kefir supplementation decreased the ratio of Firmicutes/Bacteroidetes in feces, as well as necrotic degeneration, expression levels of nuclear factor-kappa B (NF-κB), and inducible nitric oxide synthase (iNOS), but increased expression of tight-junction proteins occludin and claudin-1, in the ileum of the fructose-fed rats. Kefir treatment also reduced the mRNA levels of key lipogenic genes sterol regulatory element-binding protein (SREBP-1c) and fatty acid synthase (FASN) together with a decline in expression of tumor necrosis factor-alpha (TNF-α), NF-κB, and glycosylated glycoprotein (CD68) in the liver. Moreover, kefir treatment improved insulin signaling at the level of insulin receptor substrate 1 (IRS-1) and phospho-endothelial nitric oxide synthase (peNOS) as well as fructose transporters (GLUT2 and GLUT5) in the liver, but not in the adipose tissue, of high-fructose-fed rats. Consequently, kefir supplementation suppresses hepatic lipogenesis and inflammatory status, but promotes insulin signaling, in association with a change of the fecal microbiota and attenuation of the intestinal permeability factors in high-fructose-fed rats. Thus, we propose that kefir has favorable effects on the hepatic and intestinal irregularities induced by fructose overconsumption.

Modeling age-dependent developmental changes in the expression of genes involved in citrulline synthesis using pig enteroids

BACKGROUND

Age-dependent changes in the intestinal gene expression of enzymes involved in the metabolism of citrulline and arginine are well characterized. Enteroids, a novel ex-vivo model that recreates the three-dimensional structure of the intestinal crypt-villus unit, have shown to replicate molecular and physiological profiles of the intestinal segment from where they originated ("location memory").

OBJECTIVE

The present study tested the hypothesis that enteroids recapitulate the developmental changes observed in vivo regarding citrulline production in pigs ("developmental memory").

METHODS

Preterm (10- and 5-d preterm) and term pigs at birth, together with 7- and 35-d-old pigs were studied. Gene expression was measured in jejunal samples and in enteroids derived from this segment. Whole body citrulline production was measured by isotope dilution and enteroid citrulline production by accumulation in the media.

RESULTS

With the exception of arginase I and inducible nitric oxide synthase, all the genes investigated expressed in jejunum were expressed by enteroids. In the jejunum, established markers of development (lactase and sucrase-isomaltase), as well as genes that code for enzymes involved in the production and utilization of citrulline and arginine, underwent the ontogenic changes described in the literature. However, enteroid expression of these genes, as well as citrulline production, failed to recapitulate the changes observed in vivo.

CONCLUSIONS

Under culture conditions used in our study, enteroids derived from jejunal crypts of pigs at different ages failed to replicate the gene expression observed in whole tissue and whole body citrulline production. Additional extracellular cues may be needed to reproduce the age-dependent phenotype.

Micro- and Macrocirculatory Changes During Sepsis and Septic Shock in a Rat Model

Microcirculation is the motor of sepsis. In the present study, we investigated whether microcirculatory alterations occur before changes of systemic hemodynamics in a rat model of cecum ligation and puncture (CLP)-induced sepsis. We further investigated renal microcirculatory changes during sepsis and compared those with buccal microcirculation. Twelve male Sprague-Dawley rats were randomized into a sham control group (n = 6) and a CLP group (n = 6). Perfused microvessel density (PVD) and microvascular flow index (MFI) were evaluated using sidestream dark field (SDF) video microscopy at baseline-60, 120, 180, 240, 300, and 360 min following CLP. A semiquantitative score was calculated for vessels of less than 20 μm, primarily representing the capillaries. Hemodynamic measurements such as cardiac output (CO), aortic pressure (AP), heart rate (HR), end-tidal CO2 (ETCO2), blood pH, and lactate were measured simultaneously. The serum cytokine interleukin 6 (IL-6) was measured at baseline-120, 240, and 360 min. In the CLP group, buccal PVD and MFI were reduced at 180 min (P < 0.05 vs. baseline); renal PVD and MFI were reduced at 180 min (P < 0.05 vs. baseline), but MAP and CO did not change until 300 min after CLP. In the rat model of peritonitis-induced sepsis, microcirculatory alterations of both peripheral mucosa and kidney occurred earlier than global hemodynamics. Monitoring the microcirculation may provide a means of early detection of circulatory failure during sepsis. The changes of renal microcirculation correlate with that of buccal during sepsis and septic shock.

Microcirculation dysfunction in endotoxic shock rabbits is associated with impaired S-nitrosohemoglobin-mediated nitric oxide release from red blood cells: a preliminary study

Background

Microcirculation dysfunction with blood flow heterogeneity is an important characteristic in sepsis shock. We hypothesized that impaired ability of red blood cells to release nitric oxide resulted in microcirculation dysfunction in sepsis shock.

Methods

4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid disodium salt hydrate (DIDS), an inhibitor of band3 protein, was used to inhibit S-nitrosohemoglobin-mediated nitric oxide release. Rabbits were randomly divided into four groups: control (n = 6), lipopolysaccharide (LPS) (n = 6), LPS + DIDS (n = 6), and control + DIDS group (n = 6). Macrocirculation (cardiac output and mean arterial pressure) and microcirculation (microvascular flow index and flow heterogeneity index) parameters were recorded. At 2-h time point, arterial and venous S-nitrosohemoglobin concentrations were measured.

Results

The arterial–venous difference for S-nitrosohemoglobin in the LPS group was lower than the control group (27.3 ± 5.0 nmmol/L vs. 40.9 ± 6.2 nmmol/L, P < 0.05) but was higher than the LPS + DIDS group, with a statistically significant difference (27.3 ± 5.0 nmmol/L vs. 16.0 ± 4.2 nmmol/L, P < 0.05). Microvascular flow index for the LPS group at 2 h was lower than the control group (1.13 ± 0.16 vs. 2.82 ± 0.08, P < 0.001) and higher than the LPS + DIDS group (1.13 ± 0.16 vs. 0.84 ± 0.14, P < 0.05). Flow heterogeneity index for the LPS group at 2 h was higher than the control group (1.03 ± 0.27 vs. 0.16 ± 0.06, P < 0.001) and lower than the LPS + DIDS group (1.03 ± 0.27 vs. 1.78 ± 0.46, P < 0.001).

Conclusions

In endotoxic shock rabbits, the ability of S-nitrosohemoglobin-mediated nitric oxide release from RBC was impaired, and there was an association between the ability and microcirculation dysfunction especially increased blood flow heterogeneity.

Electronic supplementary material

The online version of this article (10.1186/s40635-018-0215-0) contains supplementary material, which is available to authorized users.

Vasodilators in Septic Shock Resuscitation: A Clinical Perspective

Microcirculatory abnormalities have been shown to be frequent in patients with septic shock despite "normalization" of systemic hemodynamics. Several studies have explored the impact of vasodilator therapy (prostacyclin, inhaled nitric oxide, topic acetylcholine, and nitroglycerin) on microcirculation and tissue perfusion, with contradictory findings.In this narrative review, we briefly present the pathophysiological aspects of microcirculatory dysfunction, and depict the evidence supporting the use of vasodilators and other therapeutic interventions (fluid administration, blood transfusion, vasopressors, and dobutamine) aiming to improve the microcirculatory flow in septic shock patients.

Microcirculation and red cell transfusion in patients with sepsis

Early identification of sepsis followed by diagnostic blood cultures and prompt administration of appropriate intravenous antibiotics covering all likely pathogen remains the corner stone in the initial management of sepsis. Source control, obtained by harvesting microbiological cultures and removal or drainage of the infected foci, is mandatory. However, optimization of hemodynamically unstable patients including volume support supplemented with vasopressor, inotropic and transfusion of red blood cells (RBCs) in case of persistent hypoperfusion have the potential to reduce morbidity and mortality. Given the imbalance between the ability of the cardiovascular system to deliver enough oxygen to meet the oxygen demand, transfusion of RBCs should theoretically provide the ideal solution to the challenge. However, both changes in the septic patients' RBCs induced by endogenous factors as well as the storage lesion affecting transfused RBCs have negative effects on the microcirculation. RBC morphology, distribution of fatty acids on the membrane surface, RBC deformability needed for capillary circulation and the nitrogen oxide (NO) signaling systems are involved. Although these deteriorating effects develop during storage, transfusion of fresh RBCs has not proven to be beneficial, possibly due to limitations of the studies performed. Until better evidence exists, transfusion guidelines recommend a restrictive strategy of RBC transfusion i.e. transfuse when hemoglobin (Hb)<7g/dL in septic patients.

Review article: the role of the microcirculation in liver cirrhosis

BACKGROUND

Intrahepatic microvascular derangements and microcirculatory dysfunction are key in the development of liver cirrhosis and its associated complications. While much has been documented relating to cirrhosis and the dysfunction of the microcirculation in the liver parenchyma, far less is known about the state of the extrahepatic microcirculation and the role this may have in the pathogenesis of multiple organ failure in end stage liver cirrhosis.

AIM

To provide an update on the role of the microcirculation in the pathophysiology of cirrhosis and its associated complications and briefly discuss some of the imaging techniques which may be used to directly investigate the microcirculation.

METHODS

A Medline literature search was conducted using the following search terms: 'cirrhosis', 'microcirculation', 'circulation', 'systemic', 'inflammation', 'peripheral', 'hepatorenal' and 'hepatopulmonary'.

RESULTS

Significant heterogeneous microvascular alterations exist in patients with cirrhosis. Data suggest that the systemic inflammation, associated with advanced cirrhosis, induces microcirculatory dysregulation and contributes to haemodynamic derangement. The resultant vasoconstriction and hypoperfusion in the systemic extrahepatic microvasculature, is likely to be instrumental in the pathophysiology of organ failure in decompensated cirrhosis, however the mechanistic action of vasoactive agents used to correct the circulatory disturbance of advanced cirrhosis is poorly understood.

CONCLUSIONS

Further research into the role of the microcirculation in patients with liver cirrhosis, will improve physicians understanding of the pathophysiology of cirrhosis, and may provide a platform for real time evaluation of an individual's microcirculatory response to vasoactive mediators, thus guiding their therapy.

Marked regional endothelial dysfunction in mottled skin area in patients with severe infections

Background

Mottling around the knee, reflecting a reduced skin blood flow, is predictive of mortality in patients with septic shock. However, the causative pathophysiology of mottling remains unknown. We hypothesized that the cutaneous hypoperfusion observed in the mottled area is related to regional endothelial dysfunction.

Methods

This was a prospective, observational study in a medical ICU in a tertiary teaching hospital. Consecutive adult patients with sepsis admitted to ICU were included. After resuscitation, endothelium-dependent vasodilation in the skin circulation was measured before and after iontophoresis of acetylcholine (Ach) in the forearm and the knee area. We analyzed the patterns of induced vasodilatation according to the presence or absence of mottling and vital status at 14 days.

Results

We evaluated 37 septic patients, including 11 without and 26 with septic shock. Overall 14-day mortality was 22%. Ten patients had mottling around the knee (10/37, 27%). In the knee area, the increased skin blood flow following iontophoresis of Ach was lower in patients with mottled skin as compared to patients without mottled skin (area under curve (AUC) 3280 (2643–6440) vs. 7980 (4233–19,707), both P < 0.05). In the forearm area, the increased skin blood flow following iontophoresis of Ach was similar in patients with and without mottled skin. Among patients with septic shock, the increased skin blood flow following iontophoresis of Ach in the knee area was significantly lower in non-survivors as compared to survivors at 14 days (AUC 3256 (2600–4426) vs. 7704 (4539–15,011), P < 0.01). In patients with septic shock, the increased skin blood flow in the forearm area following iontophoresis of Ach was similar in survivors and non-survivors at 14 days.

Conclusion

Mottling is associated with regional endothelial dysfunction in patients with septic shock. Endothelial dysfunction in the knee skin area was more pronounced in non-survivors than in survivors.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1742-x) contains supplementary material, which is available to authorized users.

The nitric oxide synthase 2 pathway is targeted by both pro- and anti-inflammatory treatments in the immature human intestine

BACKGROUND AND AIM

NO synthase 2 (NOS2) was recently identified as one the most overexpressed genes in intestinal samples of premature infants with necrotizing enterocolitis (NEC). NOS2 is widely implicated in the processes of epithelial cell injury/apoptosis and host immune defense but its specific role in inflammation of the immature human intestinal mucosa remains unclear. Interestingly, factors that prevent NEC such as epidermal growth factor (EGF) attenuate the inflammatory response in the mid-gestation human small intestine using serum-free organ culture while drugs that are associated with NEC occurrence such as the non-steroidal anti-inflammatory drug, indomethacin (INDO), exert multiple detrimental effects on the immature human intestine. In this study we investigate the potential role of NOS2 in modulating the gut inflammatory response under protective and stressful conditions by determining the expression profile of NOS2 and its downstream pathways in the immature intestine.

METHODS

Gene expression profiles of cultured mid-gestation human intestinal explants were investigated in the absence or presence of a physiological concentration of EGF (50 ng/ml) or 1 μM INDO for 48 h using Illumina whole genome microarrays, Ingenuity Pathway Analysis software and quantitative PCR to investigate the expression of NOS2 and NOS2-pathway related genes.

RESULTS

In the immature intestine, NOS2 expression was found to be increased by EGF and repressed by INDO. Bioinformatic analysis identified differentially regulated pathways where NOS2 is known to play an important role including citrulline/arginine metabolism, epithelial cell junctions and oxidative stress. At the individual gene level, we identified many differentially expressed genes of the citrulline/arginine metabolism pathway such as ARG1, ARG2, GLS, OAT and OTC in response to EGF and INDO. Gene expression of tight junction components such as CLDN1, CLDN2, CLDN7 and OCN and of antioxidant markers such as DUOX2, GPX2, SOD2 were also found to be differentially modulated by EGF and INDO.

CONCLUSION

These results suggest that the protective effect of EGF and the deleterious influence of INDO on the immature intestine could be mediated via regulation of NOS2. Pathways downstream of NOS2 involved with these effects include metabolism linked to NO production, epithelial barrier permeability and antioxidant expression. These results suggest that NOS2 is a likely regulator of the inflammatory response in the immature human gut and may provide a mechanistic basis for the protective effect of EGF and the deleterious effects of INDO.

Update: Clinical Use of Plasma Lactate

Lactate is an essential, versatile metabolic fuel in cellular bioenergetics. In human emergency and critical care, lactate is used as a biomarker and therapeutic endpoint and evidence is growing in veterinary medicine supporting its clinical utility. Lactate production is a protective response providing ongoing cellular energy during tissue hypoperfusion or hypoxia and mitigating acidosis. Hence, hyperlactatemia is closely associated with disease severity but it is an epiphenomenon as the body attempts to protect itself. This article reviews lactate biochemistry, kinetics, pathophysiology, some practical aspects of measuring lactate, as well as its use in diagnosis, prognosis, and monitoring.

Hemodynamic coherence in sepsis

Microvascular alterations are a hallmark of sepsis and play a crucial role in its pathophysiology. Such alterations are the result of overwhelming inflammation, which negatively affects all the components of the microcirculation. As the severity of microvascular alterations is associated with organ dysfunction and mortality, several strategies have been tested for improving microcirculation. Nevertheless, they are mainly based on the conventional manipulation of systemic hemodynamics to increase the total flow to the organs and tissues. Other therapeutic interventions are still being investigated. In this review, we discuss the pathophysiology of septic microcirculatory dysfunction and its implications for possible treatments.

Microcirculatory alterations in shock states

Functional components of the microcirculation provide oxygen and nutrients and remove waste products from the tissue beds of the body's organs. Shock states overwhelmingly stress functional capacity of the microcirculation, resulting in microcirculatory failure. In septic shock, inflammatory mediators contribute to hemodynamic instability. In nonseptic shock states, the microcirculation is better able to compensate for alterations in vascular resistance, cardiac output, and blood pressure. Therefore, global hemodynamic and oxygen delivery parameters are appropriate for assessing, monitoring, and guiding therapy in hypovolemic and cardiogenic shock but, alone, are inadequate for septic shock.

Microcirculatory disorders during septic shock

PURPOSE OF REVIEW

Despite the progress made over the past 20 years in the treatment of septic shock, mortality remains high. Microcirculatory disorders raise considerable interest aiming to improve the understanding of the physiopathology of septic shock and its management.

RECENT FINDINGS

Numerous experimental and clinical studies have gradually focused on the analysis of microcirculatory blood flow and identified alterations in small vessels. These microcirculatory abnormalities appear early, are heterogeneous, and are directly linked to organ failure, as well as the patient's prognosis. These anomalies vary from one patient to the other, and their evolution during resuscitation cannot be predicted by the isolated analysis of global hemodynamic parameters such as blood pressure or heart rate.

SUMMARY

Microcirculatory disorders appear at a central place of the physiopathology and are highly associated with the patient prognosis; it therefore seems important to develop and integrate parameters reflecting tissue perfusion in the management of septic shock.

Randomized controlled trial of inhaled nitric oxide for the treatment of microcirculatory dysfunction in patients with sepsis*

OBJECTIVES

Sepsis treatment guidelines recommend macrocirculatory hemodynamic optimization; however, microcirculatory dysfunction is integral to sepsis pathogenesis. We aimed to test the hypothesis that following macrocirculatory optimization, inhaled nitric oxide would improve microcirculation in patients with sepsis and that improved microcirculation would improve lactate clearance and multiple organ dysfunction.

DESIGN

Randomized, sham-controlled clinical trial.

SETTING

Single urban academic medical center.

PATIENTS

Adult patients with severe sepsis and systolic blood pressure less than 90 mm Hg despite intravascular volume expansion and/or serum lactate greater than or equal to 4.0 mmol/L.

INTERVENTIONS

After achievement of macrocirculatory resuscitation goals, we randomized patients to 6 hours of inhaled nitric oxide (40 ppm) or sham inhaled nitric oxide administration. We administered study drug via a specialized delivery device that concealed treatment allocation so that investigators and clinical staff remained blinded.

MEASUREMENTS AND MAIN RESULTS

We performed sidestream dark-field videomicroscopy of the sublingual microcirculation prior to and 2 hours after study drug initiation. The primary outcome measure was the change in microcirculatory flow index. Secondary outcomes were lactate clearance and change in Sequential Organ Failure Assessment score. We enrolled 50 patients (28 of 50 [56%] requiring vasopressor agents; 15 of 50 [30%] died). Although inhaled nitric oxide significantly raised plasma nitrite levels, it did not improve microcirculatory flow, lactate clearance, or organ dysfunction. In contrast to previous studies conducted during the earliest phase of resuscitation, we found no association between changes in microcirculatory flow and lactate clearance or organ dysfunction.

CONCLUSIONS

Following macrocirculatory optimization, inhaled nitric oxide at 40 ppm did not augment microcirculatory perfusion in patients with sepsis. Further, we found no association between microcirculatory perfusion and multiple organ dysfunction after initial resuscitation.

Sublingual microcirculation in pulmonary arterial hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a pulmonary vasculopathy that leads to failure of the right ventricle and premature death.

OBJECTIVES

To determine whether the sublingual microcirculation is affected in patients with PAH compared with healthy age- and sex-matched control subjects.

METHODS

Using the CapiScope Handheld Video Capillaroscope we measured the sublingual microvasculature density, flow index, tortuosity, and curvature. Videos were acquired immediately after right heart catheterization, and determinations were made off-line by investigators blinded to the group assignment or hemodynamics.

MEASUREMENTS AND MAIN RESULTS

In this cross-sectional pilot study, we included 26 patients with PAH (age, mean ± SD, 56.7 ± 10 yr; 77% women) and 14 healthy control subjects (age, 53.1 ± 12 yr; 71% women). Sublingual microvasculature flow index was lower (2 ± 0.66 vs. 2.7 ± 0.37, P < 0.001) with higher heterogeneity index (0.63 ± 0.63 vs. 0.25 ± 0.25, P = 0.04) in patients with PAH than control subjects. Microvasculature density was similar between the groups, but tortuosity was more pronounced in patients than control subjects (tort 0: 45 ± 19 vs. 23.6 ± 12, P = 0.001 and tort 1: 0.2 ± 0.16 vs. 0.06 ± 0.04, P < 0.001).

CONCLUSIONS

Patients with PAH showed lower sublingual microvasculature flow index and higher tortuosity compared with healthy age- and sex-matched control subjects. Further investigations are needed to assess whether this methodology can provide information on disease prognosis and/or response to therapy in this condition.

Pharmacological preconditioning with vitamin C attenuates intestinal injury via the induction of heme oxygenase-1 after hemorrhagic shock in rats

Pre-induction of heme oxygenase (HO)-1, which is regarded as an effective method of “organ preconditioning”, exerts beneficial effects during hemorrhagic shock (HS). However, the available HO-1 inducers exhibit disadvantages such as toxicity or complex technical requirements. Therefore, a safe and convenient HO-1 inducer would be promising and could be exploited in the treatment of foreseeable hemorrhaging, such as prior to major surgery. Here we investigated the effect of vitamin C (VitC), a common antioxidant, on intestinal HO-1 expression and examined whether VitC pretreatment prevented HS related intestinal tissue injuries after HO-1 induction. First, we conducted an in vitro study and found that HO-1 expression in rat intestinal epithelial cells (IEC-6) was induced by non-toxic VitC in a time and concentration dependent manner, and the mechanism was related to the activation of extracellular signal-regulated kinase 1/2 (ERK1/2). Next, we conducted an in vivo study and found that VitC induced intestinal HO-1 protein expression (mainly observed in the intestinal epithelial cells) and HO-1 activity in normal SD rats, and that these HO-1 levels were further enhanced by VitC in a rat model of HS. The HS related intestinal injuries, including histological damage, pro-inflammatory cytokine levels (tumor necrosis factor and interleukin-6), neutrophil infiltration and apoptosis decreased after VitC pretreatment, and this alleviating of organ injuries was abrogated after the inhibition of HO-1 activity by zinc protoporphyrin-IX. It was of note that VitC did little histological damage to the intestine of the sham rats. These data suggested that VitC might be applied as a safe inducer of intestinal HO-1 and that VitC pretreatment attenuated HS related intestinal injuries via the induction of HO-1.

The renal microcirculation in sepsis

Despite identification of several cellular mechanisms being thought to underlie the development of septic acute kidney injury (AKI), the pathophysiology of the occurrence of AKI is still poorly understood. It is clear, however, that instead of a single mechanism being responsible for its aetiology, an orchestra of cellular mechanisms failing is associated with AKI. The integrative physiological compartment where these mechanisms come together and exert their integrative deleterious action is the renal microcirculation (MC). This is why it is opportune to review the response of the renal MC to sepsis and discuss the determinants of its (dys)function and how it contributes to the pathogenesis of renal failure. A main determinant of adequate organ function is the adequate supply and utilization of oxygen at the microcirculatory and cellular level to perform organ function. The highly complex architecture of the renal microvasculature, the need to meet a high energy demand and the fact that the kidney is borderline ischaemic makes the kidney a highly vulnerable organ to hypoxaemic injury. Under normal, steady-state conditions, oxygen (O2) supply to the renal tissues is well regulated; however, under septic conditions the delicate balance of oxygen supply versus demand is disturbed due to renal microvasculature dysfunction. This dysfunction is largely due to the interaction of renal oxygen handling, nitric oxide metabolism and radical formation. Renal tissue oxygenation is highly heterogeneous not only between the cortex and medulla but also within these renal compartments. Integrative evaluation of the different determinants of tissue oxygen in sepsis models has identified the deterioration of microcirculatory oxygenation as a key component in the development AKI. It is becoming clear that resuscitation of the failing kidney needs to integratively correct the homeostasis between oxygen, and reactive oxygen and nitrogen species. Several experimental therapeutic modalities have been found to be effective in restoring microcirculatory oxygenation in parallel to improving renal function following septic AKI. However, these have to be verified in clinical studies. The development of clinical physiological biomarkers of AKI specifically aimed at the MC should form a valuable contribution to monitoring such new therapeutic modalities.

Polydatin, a natural precursor of resveratrol, induces cell cycle arrest and differentiation of human colorectal Caco-2 cell

Background

Human colon adenocarcinoma cells are resistant to chemotherapeutic agents, such as anthracyclines, that induce death by increasing the reactive oxygen species. A number of studies have been focused on chemo-preventive use of resveratrol as antioxidant against cardiovascular diseases, aging and cancer. While resveratrol cytotoxic action was due to its pro-oxidant properties. In this study, we investigate whether the Resveratrol (trans-3,5,49-trihydroxystilbene) and its natural precursor Polydatin (resveratrol-3-O-b-mono- D-glucoside, the glycoside form of resveratrol) combination, might have a cooperative antitumor effect on either growing or differentiated human adenocarcinoma colon cancer cells.

Methods

The polydatin and resveratrol pharmacological interaction was evaluated in vitro on growing and differentiated Caco-2 cell lines by median drug effect analysis calculating a combination index with CalcuSyn software. We have selected a synergistic combination and we have evaluated its effect on the biological and molecular mechanisms of cell death.

Results

Simultaneous exposure to polydatin and resveratrol produced synergistic antiproliferative effects compared with single compound treatment. We demonstrated that polydatin alone or in combination with resveratrol at 3:1 molar ratio synergistically modulated oxidative stress, cell cycle, differentiation and apoptosis. Worthy of note treatment with polydatin induced a nuclear localization and decreased expression of heat shock protein 27, and vimentin redistributed within the cell.

Conclusions

From morphological, and biochemical outcome we obtained evidences that polydatin induced a transition from a proliferative morphology to cell-specific differentiated structures and caused human CaCo-2 cell death by induction of apoptosis. Our data suggest the potential use of polydatin in combination chemotherapy for human colon cancer.

Lipopolysaccharide-induced bacterial translocation is intestine site-specific and associates with intestinal mucosal inflammation

The present study aimed to determine whether any specific intestinal site or intestinal mucosal inflammation is highly correlated with bacterial translocation (BT). Enterostomy tubes were surgically placed in adult male Sprague-Dawley rats 5 days before induction of experimental model. After surgery, sterile water containing kanamycin (25 mg/L) was injected into each intestinal segment through the tubes for 3 days. Green fluorescent protein (GFP)-transfected Escherichia coli (n = 30 for lipopolysaccharide (LPS) group, and n = 30 for control group) or 0.9 % saline (n = 30 for blank group) were injected into each intestinal segment through the tubes for two consecutive days. Rats were then subjected to LPS-induced endotoxemia; lactulose and mannitol were injected into each intestinal segment through the tubes simultaneously. At 6 h after LPS injection, BT to distant organs and integrity of tight junctions (TJ) were examined by fluorescence and electron microscopy, respectively. The urinary excretion ratio of lactulose/mannitol (L/M) and intestinal mucosal cytokine levels were assessed. We found that the intestinal permeability, reflected by translocation rates of GFP-labeled E. coli, the levels of open TJ, the excretion ratio of L/M, and the inflammatory cytokine levels were higher in the LPS group than in the control and blank groups. The endotoxemia ileum showed the highest levels of both intestinal permeability and inflammatory cytokine, while the colon showed the lowest. The present study of endotoxemia rats suggests that LPS increases gut paracellular permeability and induces BT. The ileum is the site of greatest BT risk, while the colon is the lowest, and the difference in risk between these sites is correlated with intestinal mucosal inflammation.

Biphasic modulation of NOS expression, protein and nitrite products by hydroxocobalamin underlies its protective effect in endotoxemic shock: downstream regulation of COX-2, IL-1β, TNF-α, IL-6, and HMGB1 expression

Background. NOS/^•NO inhibitors are potential therapeutics for sepsis, yet they increase clinical mortality. However, there has been no in vivo investigation of the (in vitro) ^•NO scavenger, cobalamin's (Cbl) endogenous effects on NOS/^•NO/inflammatory mediators during the immune response to sepsis. Methods. We used quantitative polymerase chain reaction (qPCR), ELISA, Western blot, and NOS Griess assays, in a C57BL/6 mouse, acute endotoxaemia model. Results. During the immune response, pro-inflammatory phase, parenteral hydroxocobalamin (HOCbl) treatment partially inhibits hepatic, but not lung, iNOS mRNA and promotes lung eNOS mRNA, but attenuates the LPS hepatic rise in eNOS mRNA, whilst paradoxically promoting high iNOS/eNOS protein translation, but relatively moderate ^•NO production. HOCbl/NOS/^•NO regulation is reciprocally associated with lower 4 h expression of TNF-α, IL-1β, COX-2, and lower circulating TNF-α, but not IL-6. In resolution, 24 h after LPS, HOCbl completely abrogates a major late mediator of sepsis mortality, high mobility group box 1 (HMGB1) mRNA, inhibits iNOS mRNA, and attenuates LPS-induced hepatic inhibition of eNOS mRNA, whilst showing increased, but still moderate, NOS activity, relative to LPS only. experiments (LPS+D-Galactosamine) HOCbl afforded significant, dose-dependent protection in mice Conclusions. HOCbl produces a complex, time- and organ-dependent, selective regulation of NOS/^•NO during endotoxaemia, corollary regulation of downstream inflammatory mediators, and increased survival. This merits clinical evaluation.

From macrohemodynamic to the microcirculation

ICU patients need a prompt normalization of macrohemodynamic parameters. Unfortunately, this optimization sometimes does not protect patients from organ failure development. Prevention or treatment of organ failure needs another target to be pursued: the microcirculatory restoration. Microcirculation is the ensemble of vessels of maximum 100 μm in diameter. Nowadays the Sidestream Dark Field (SDF) imaging technique allows its bedside investigation and a recent round-table conference established the criteria for its evaluation. First, microcirculatory derangements have been studied in sepsis: they are mainly characterized by a reduction of vessel density, an alteration of flow, and a heterogeneous distribution of perfusion. Endothelial malfunction and glycocalyx rupture were proved to be the main reasons for the observed microthrombi, capillary leakage, leukocyte rolling, and rouleaux phenomenon, even if further studies are necessary for a better explanation. Therapeutic approaches targeting microcirculation are under investigation. Microcirculatory alterations have been recently demonstrated in other diseases such as hypovolemia and cardiac failure but this issue still needs to be explored. The aim of this paper is to gather the already known information, focus the reader's attention on the importance of microvascular physiopathology in critical illness, and prompt him to actively participate to achieve a more comprehensive understanding of the issue.

Kiwifruit extracts inhibit cytokine production by lipopolysaccharide-activated macrophages, and intestinal epithelial cells isolated from IL10 gene deficient mice

Inflammatory bowel disease (IBD) is a chronic, inflammatory disorder of the gastrointestinal tract involving an inappropriate immune response to commensal microorganisms in a genetically susceptible host. This study examined the effects of aqueous and ethyl acetate extracts of gold kiwifruit (Actinidia chinensis) or green kiwifruit (Actinidia deliciosa) using in vitro models of IBD. These models comprised primary macrophages and intestinal epithelial cells isolated from C57BL/5J and interleukin-10 gene deficient (Il10(-/-)) mice and RAW 264.7, a murine macrophage-like cell line. All four kiwifruit extracts reduced the activation of these models after lipopolysaccharide stimulation, decreasing nitric oxide and cytokine secretion by both Il10(-/-) and wild-type cells. The ethyl acetate extracts exhibited the highest anti-inflammatory activity, with almost complete suppression of lipopolysaccharide-stimulated macrophage activation. These results suggest that kiwifruit extracts have significant anti-inflammatory activity relevant to IBD. We suggest that the Il10(-/-) mouse is a suitable model for further study of these compounds.

Regionalization of pIgR expression in the mucosa of mouse small intestine

Few reports exist on the differences in cell populations or immunological functions between the proximal and distal segments of the small intestine (SI). In the current contribution we analyzed the expression of the polymeric immunoglobulin receptor (pIgR) and alpha chains as well as the density of IgA-producing cells from the proximal and distal intestinal segments from Balb/c mice. Furthermore, by using real-time RT-PCR we quantified the expression of cytokines (TNF-alpha, IFN-gamma, IL-4 and TGF-beta), Toll-like receptor-4 (TLR-4), and the glucocorticoid receptor (GR) involved in pIgR expression in intestinal epithelial cells (IEC). In this study, for the first time it has been demonstrated that the expression of the pIgR as well as alpha chain was greater in the proximal than the distal segment of the small intestine of normal mice. Moreover, we found striking differences in the expression of cytokines at the different intestinal compartments. Whereas the expression of TNF-alpha, IFN-gamma and TGF-beta was higher in lamina propria lymphocytes (LPL) of the distal than proximal segment, it was higher in IEC of the proximal than distal segment. In contrast, the expression of the gene for IL-4 was higher in the LPL of the proximal segment and the IEC of the distal segment. Although the overall expression of TNF-alpha, IL-4, IFN-gamma and TGF-beta was higher in the whole mucosa of the distal than proximal segment, we propose that cytokines produced by epithelial cells (TNF-alpha, IFN-gamma and TGF-beta) autocrinally up-regulate the expression of mRNA for the pIgR. Finally the expression of the GR was higher in the proximal segment, while the expression of the gene for TLR-4 was significantly higher in the IEC of the distal than proximal segment. The higher expression of pIgR found in the proximal segment is probably related to the effect on epithelial cells of the higher production of TNF-alpha, IFN-gamma and TGF-beta, as well as the higher expression of the glucocorticoid receptors. The increased expression of pIgR in the proximal segment appears primarily responsible for the increased secretory IgA levels in the small intestine of mice. These results confirm and extend previous findings supporting the compartmentalization of the intestinal immune system.

Extracellular activation of arginase-1 decreases enterocyte inducible nitric oxide synthase activity during systemic inflammation

Liver dysfunction secondary to severe inflammation is associated with the release of enzymes normally sequestered within hepatocytes. The purpose of these studies was to test the hypothesis that these enzymes are released, at least in part, to modulate potentially deleterious inflammatory processes in distant tissues like the gut. Human Caco-2(BBe) enterocyte-like cells were exposed to cytomix (IFN-gamma, TNF-alpha, and IL-1beta) in the absence or presence of human liver cytosol (LC). Nitric oxide (NO(*)) and inducible nitric oxide synthase (iNOS) protein production were measured by the Griess assay and Western analysis, respectively. Cytomix induced the expression of iNOS and release of NO(*). LC protein (400 microg/ml) added to the basal compartment but not apical compartment completely blocked the release of NO(*) but only slightly decreased the magnitude of iNOS protein induction. Ultrafiltration and ultracentrifugation studies demonstrated that microsome-associated arginase-1 activity was the iNOS-suppressing activity in LC. Liver arginase required activation by a <10-kDa factor that was present in supernatants of cytomix-stimulated cells. The selective iNOS inhibitor l-N(6)-(1-iminoethyl)-lysine.2HCl prevented production of this factor. The biotin switch assay detected increased S-nitrosylation of arginase-1 after incubation with supernatants from immunostimulated Caco-2 cells. Serum from endotoxemic mice contained significantly greater arginase activity compared with serum from control mice. Furthermore, the ratio of mucosal monomeric to dimeric iNOS increased in endotoxemic mice compared with controls. Thus reciprocal activation of arginase-1 and modulation of mucosal iNOS activity may be protective because it would be expected to decrease NO(*)-dependent intestinal barrier dysfunction on that basis.

iNOS expression in oral and gastrointestinal tract mucosa

It is known that the overproduction of nitric oxide (NO) by nitric oxide synthase (NOS) occurs during the progression of various inflammatory diseases in intestinal tract. NOS inhibitors or inducible nitric oxide synthase (iNOS) gene expression inhibitors should be considered as potential anti-inflammatory agents, as NO synthesized by iNOS is related to various pathophysiological processes including inflammation. In order to understand the relationship between iNOS and pathological reactions such as the inflammatory process and malign transformation clearly, the existence and amount of constitutive expression should be determined. It is crucial to comprehend the harmful and protective amounts of iNOS expressions in order to clarify the relationship between iNOS and pathological processes. Evidently, only after this inspection is it possible to utilize iNOS as a marker and treatment instrument during the diagnosis and treatment of malign transformation and the inflammatory process.

Resuscitating the microcirculation in sepsis: the central role of nitric oxide, emerging concepts for novel therapies, and challenges for clinical trials

Microcirculatory dysfunction is a critical element of the pathogenesis of severe sepsis and septic shock. In this Bench-to-Bedside review, we present: 1) the central role of the microcirculation in the pathophysiology of sepsis; 2) new translational research techniques of in vivo video microscopy for assessment of microcirculatory flow in human subjects; 3) clinical investigations that reported associations between microcirculatory dysfunction and outcome in septic patients; 4) the potential role of novel agents to "rescue" the microcirculation in sepsis; 5) current challenges facing this emerging field of clinical investigation; and 6) a framework for the design of future clinical trials aimed to determine the impact of novel agents on microcirculatory flow and organ failure in patients with sepsis. We specifically focus this review on the central role and vital importance of the nitric oxide (NO) molecule in maintaining microcirculatory homeostasis and patency, especially when the microcirculation sustains an insult (as with sepsis). We also present the scientific rationale for clinical trials of exogenous NO administration to treat microcirculatory dysfunction and augment microcirculatory blood flow in early sepsis therapy.

Mixed endothelin receptor antagonism with tezosentan improves intestinal microcirculation in endotoxemic shock

BACKGROUND

Microcirculatory dysfunction is a common feature of sepsis. The potent vasoconstrictor endothelin (ET) is released in sepsis and endotoxemia, potentially contributing to sepsis-induced microcirculatory failure. In this study we tested the hypothesis that mixed ET receptor antagonism with tezosentan would improve splanchnic microcirculatory blood flow in acute porcine endotoxemia.

MATERIALS AND METHODS

Sixteen anesthetized and mechanically ventilated pigs received an infusion of endotoxin for 300 min. After 120 min eight pigs received a bolus dose of tezosentan 1 mg/kg followed by an infusion of tezosentan of 1 mg/kg/h throughout the experiment. Eight pigs served as endotoxin controls. Laser Doppler flowmetry was used to measure microcirculatory blood flow in the liver and in the ileal and colon mucosa. PCO(2) in the ileal mucosa was measured by air tonometry and portal vein flow by an ultrasonic flow probe.

RESULTS

Endotoxin administration induced a state of shock with impaired splanchnic microcirculatory blood flow. Microcirculation in the mucosa of the colon and ileum and mucosal-arterial PCO(2) gap were improved by tezosentan. Portal vein flow was increased, but hepatic microcirculatory blood flow was not significantly improved. Tezosentan preserved cardiac index and decreased pulmonary capillary wedge pressure compared to controls, without causing any differences in the heart rate or mean arterial blood pressure response. Tezosentan also distinctly improved pH and arterial lactate values.

CONCLUSIONS

The findings of this study indicate that ET is involved in the microcirculatory dysfunction seen in the ileal and colon mucosa in early endotoxemia. Moreover, this detrimental effect was counteracted by i.v. administration of the mixed ET receptor antagonist tezosentan.

Tissue bioenergetics and microvascular perfusion are impaired in rat ileal mucosa in normotensive sepsis

OBJECTIVE

Sepsis is a systemic inflammatory response to a bacterial infection. Inflammation may result in injury to the small bowel and an increase in translocation of bacteria and toxins across the mucosal barrier, which may contribute to the progression of sepsis. Microcirculatory perfusion or cytopathic hypoxia may cause impairment of tissue bioenergetics and injury in sepsis. The objective of this study was to determine if sepsis is associated with microcirculatory hypoperfusion and impaired tissue bioenergetics in the ileal mucosa.

MATERIALS AND METHODS

Sprague-Dawley rats were randomized to cecal ligation and perforation (sepsis group, n = 12) or control group (n = 14) and received arterial and venous catheters and fluid resuscitation. Following 24 h, rats were anesthetized with isoflurane and the ileum was prepared for intravital microscopy. Images of NADH fluorescence, which is an index of tissue bioenergetics, central arterial diameter, red cell velocity, red cell flux, and average intercapillary area, were recorded in 6-9 villi in each rat.

RESULTS

Central arterial red cell flux (control 277 +/- 30 cell/s, sepsis 108 +/- 13 cells/s, p < .05), diameter (control 10.4 +/- 0.4 microm, sepsis 8.2 +/- 0.3 microm, p < .05) and red cell velocity (control 590 +/- 47 microm/s, sepsis 449 +/- 63 microm/s, p < .05) were decreased while average intercapillary area (control 815 +/- 171 microm(2), sepsis 1412 +/- 364 microm(2), p < .05) and NADH fluorescence (control 116 +/- 6 AIU, sepsis 154 +/- 9 AIU, p < .05) were increased at the villus tip in the sepsis group.

CONCLUSION

Sepsis is associated with bioenergetic impairment and capillary hypoperfusion at the villus tip and a decrease in red cell flux in the central arteriole.

The microcirculation is the motor of sepsis

Regional tissue distress caused by microcirculatory dysfunction and mitochondrial depression underlies the condition in sepsis and shock where, despite correction of systemic oxygen delivery variables, regional hypoxia and oxygen extraction deficit persist. We have termed this condition microcirculatory and mitochondrial distress syndrome (MMDS). Orthogonal polarization spectral imaging allowed the first clinical observation of the microcirculation in human internal organs, and has identified the pivotal role of microcirculatory abnormalities in defining the severity of sepsis, a condition not revealed by systemic hemodynamic or oxygen-derived variables. Recently, sublingual sidestream dark-field (SDF) imaging has been introduced, allowing observation of the microcirculation in even greater detail. Microcirculatory recruitment is needed to ensure adequate microcirculatory perfusion and the oxygenation of tissue cells that follows. In sepsis, where inflammation-induced autoregulatory dysfunction persists and oxygen need is not matched by supply, the microcirculation can be recruited by reducing pathological shunting, promoting microcirculatory perfusion, supporting pump function, and controlling hemorheology and coagulation. Resuscitation following MMDS must include focused recruitment of hypoxic-shunted microcirculatory units and/or resuscitation of the mitochondria. A combination of agents is required for successful rescue of the microcirculation. Single compounds such as activated protein C, which acts on multiple pathways, can be expected to be beneficial in rescuing the microcirculation in sepsis.

Inducible nitric oxide synthase inhibition improves intestinal microcirculatory oxygenation and CO2 balance during endotoxemia in pigs

OBJECTIVE

We examined whether selective inhibition of inducible nitric oxide synthase (iNOS) promotes intestinal microvascular oxygenation (microPO2) and CO2 off-load after endotoxic shock.

DESIGN AND SETTING

Prospective, controlled experimental study in a university animal research laboratory.

SUBJECTS

13 domestic pigs.

INTERVENTIONS

After baseline measurements shock was induced by 1 microg kg-1 h-1 endotoxin until mean arterial pressure fell below 60 mmHg. After 30 min in shock the animals were resuscitated with either fluid alone (control, n=6) or fluid and the iNOS inhibitor N-[3-(aminomethyl)benzyl]acetamidine hydrochloride (1400W, n=7). As final experimental intervention all animals received the nonselective NOS inhibitor L-NAME.

MEASUREMENTS AND RESULTS

Systemic and regional hemodynamic and oxygenation parameters were measured at baseline, during endotoxemia and shock, hourly for 3 h of 1400W therapy, and 30 min after the final L-NAME administration. microPO2 was assessed by the Pd-porphyrin phosphorescence technique, and the arterial to intestinal PCO2 gap was determined by air tonometry. Endotoxemia and shock resulted in a decrease in ileal mucosal and serosal microPO2 and a rise in PCO2 gap. The combination of 1400W and fluid resuscitation, but not fluid alone, normalized both the serosal microPO2 and the intestinal PCO2 gap. Administration of L-NAME decreased cardiac output and oxygen delivery and intestinal microPO2 and blood flow in both groups.

CONCLUSIONS

Partial blockade of NO production by 1400W increased serosal microvascular oxygenation and decreased the intestinal CO2 gap. This findings are consistent with the idea that 1400W corrects pathological flow distribution and regional dysoxia within the intestinal wall following endotoxic shock.

The lower intestinal tract-specific induction of heme oxygenase-1 by glutamine protects against endotoxemic intestinal injury

OBJECTIVE

The aim of the present study was to investigate whether glutamine pretreatment improves intestinal injury in rats with endotoxemia by its heme oxygenase-1 induction in the lower intestinal tract.

DESIGN

Randomized, blinded, controlled animal study.

SETTING

University-based animal research facility.

SUBJECTS

Sprague-Dawley male rats, weighing 220-250 g (n = 201).

INTERVENTIONS

Rats were treated with glutamine (0.75 g/kg) dissolved in lactated Ringer's solution via the tail vein. Endotoxemia was induced in rats by intraperitoneal injection of lipopolysaccharide (10 mg/kg or 20 mg/kg for survival study). Lipopolysaccharide-treated animals were pretreated with glutamine or lactated Ringer's solution 9 hrs before lipopolysaccharide treatment. Some of the glutamine-pretreated animals further received tin mesoporphyrin (1 micromol/kg), a specific inhibitor of heme oxygenase activity, 1 hr before lipopolysaccharide treatment.

MEASUREMENTS AND MAIN RESULTS

Glutamine treatment markedly induced heme oxygenase-1 messenger RNA and protein in the mucosal epithelial cells as well as in the lamina propria cells in the ileum and the colon, whereas its expression in the duodenum and the jejunum was not influenced by the treatment. Glutamine treatment before lipopolysaccharide administration significantly ameliorated lipopolysaccharide-induced mucosal injury, inflammation, and apoptotic cell death in the ileum and the colon, as judged by significant decreases in tumor necrosis factor-alpha gene expression, histologic damage scores, and expression of activated caspase-3 and by an increase in gene expression of Bcl-2. In addition, glutamine treatment markedly decreased lipopolysaccharide-induced mortality. In contrast, treatment with tin mesoporphyrin abolished the beneficial effect of glutamine pretreatment.

CONCLUSIONS

Glutamine pretreatment significantly ameliorated intestinal tissue injury of rats following lipopolysaccharide treatment. The same treatment also improved the survival of animals from endotoxemia. The protective effect of glutamine is mediated by its lower intestine-specific induction of heme oxygenase-1, since its inhibition by tin mesoporphyrin completely abolished the beneficial effect of glutamine.

Nitric Oxide Scavenging by the Cobalamin Precursor Cobinamide

Nitric oxide (NO) is an important signaling molecule, and a number of NO synthesis inhibitors and scavengers have been developed to allow study of NO functions and to reduce excess NO levels in disease states. We showed previously that cobinamide, a cobalamin (vitamin B12) precursor, binds NO with high affinity, and we now evaluated the potential of cobinamide as a NO scavenger in biologic systems. We found that cobinamide reversed NO-stimulated fluid secretion in Drosophila Malpighian tubules, both when applied in the form of a NO donor and when produced intracellularly by nitricoxide synthase. Moreover, feeding flies cobinamide markedly attenuated subsequent NO-induced increases in tubular fluid secretion. Cobinamide was taken up efficiently by cultured rodent cells and prevented NO-induced phosphorylation of the vasodilator-stimulated phosphoprotein VASP both when NO was provided to the cells and when NO was generated intracellularly. Cobinamide appeared to act via scavenging NO because it reduced nitrite and nitrate concentrations in both the fly and mammalian cell systems, and it did not interfere with cGMP-induced phosphorylation of VASP. In rodent and human cells, cobinamide exhibited toxicity at concentrations > or =50 microM with toxicity completely prevented by providing equimolar amounts of cobalamin. Combining cobalamin with cobinamide had no effect on the ability of cobinamide to scavenge NO. Cobinamide did not inhibit the in vitro activity of either of the two mammalian cobalamin-dependent enzymes, methionine synthase or methylmalonyl-coenzyme A mutase; however, it did inhibit the in vivo activities of the enzymes in the absence, but not presence, of cobalamin, suggesting that cobinamide toxicity was secondary to interference with cobalamin metabolism. As part of these studies, we developed a facile method for producing and purifying cobinamide. We conclude that cobinamide is an effective intra- and extracellular NO scavenger whose modest toxicity can be eliminated by cobalamin.

Opposite effect of oxidative stress on inducible nitric oxide synthase and haem oxygenase-1 expression in intestinal inflammation: anti-inflammatory effect of carbon monoxide

Inducible nitric oxide synthase (iNOS) is expressed in intestinal epithelial cells (IEC) of patients with active inflammatory bowel disease (IBD) and in IEC of endotoxaemic rats. The induction of iNOS in IEC is an element of the NF-kappaB-mediated survival pathway. Haem oxygenase-1 (HO-1) is an AP-1-regulated gene that is induced by oxidative stress. The enzyme produces carbon monoxide (CO), which may attenuate the inflammatory response. The aim of this study was to investigate the regulation and interaction of iNOS and HO-1 in response to inflammation and oxidative stress. Male Wistar rats were treated with the thiol-modifying agent diethylmaleate (DEM) to induce oxidative stress and rendered endotoxaemic by LPS injection. Human colonic biopsies and the human colon carcinoma cell line DLD-1 were treated with DEM and the lipid peroxidation end-product 4-hydroxynonenal to induce oxidative stress and exposed to cytokine mix (CM) to mimic inflammation. In some experiments, cells were incubated with 250-400 ppm CO prior to and during stimulation with CM. HO-1 and iNOS expression was evaluated by RT-PCR, western blotting, and immunohistology. NF-kappaB activation was evaluated by EMSA. LPS induced iNOS but not HO-1 in epithelial cells of the ileum and colon. Oxidative stress strongly induced HO-1 in epithelial and inflammatory cells. Combined oxidative stress and endotoxaemia decreased iNOS expression but strongly induced HO-1 expression. Similarly, CM induced iNOS but not HO-1 in colonic biopsies and DLD-1 cells. Oxidative stress prevented iNOS induction in an NF-kappaB-dependent manner but increased HO-1 expression in CM-exposed DLD-1 cells. CO inhibited iNOS mRNA induction in CM-stimulated DLD-1 cells. These data demonstrate opposite regulation of iNOS and HO-1 in intestinal epithelial cells in response to cytokine exposure and oxidative stress. These findings suggest that iNOS (NF-kappaB driven) and HO-1 (AP-1 driven) represent mutually exclusive survival mechanisms in intestinal epithelial cells.

Increased iNOS activity is essential for intestinal epithelial tight junction dysfunction in endotoxemic mice

We tested the hypothesis that increased production of nitric oxide (NO.) associated with lipopolysaccharide (LPS)-induced systemic inflammation leads to functionally significant alterations in the expression and/or targeting of key tight junction (TJ) proteins in ileal and colonic epithelium. Wild-type or inducible NO. synthase (iNOS) knockout male C57B1/6J mice were injected intraperitoneally with 2 mg/kg Escherichia coli O111:B4 LPS. iNOS was inhibited using intraperitoneal L-N(6)-(1-iminoethyl)lysine (L-NIL; 5 mg/kg). Immunoblotting of total protein and NP-40 insoluble proteins revealed decreased expression and decreased TJ localization, respectively, of the TJ proteins, zonula occludens (ZO)-1, ZO-2, ZO-3, and/or occludin in ileal mucosa and colonic mucosa (total protein only) after injection of C57B1/6J mice with LPS. Immunohistochemistry showed deranged distribution of ZO-1 and occludin in both tissues from endotoxemic mice. Endotoxemia was associated with evidence of gut epithelial barrier dysfunction evidenced by increased ileal mucosal permeability to fluorescein isothiocyanate-dextran (Mr=4 kDa) and increased bacterial translocation to mesenteric lymph nodes. Pharmacologic inhibition of iNOS activity using L-NIL or genetic ablation of the iNOS gene ameliorated LPS-induced changes in TJ protein expression and gut mucosal barrier function. These results support the view that at least one mechanism contributing to the pathogenesis of gastrointestinal epithelial dysfunction secondary to systemic inflammation is increased iNOS-dependent NO. production leading to altered expression and localization of key TJ proteins.

REGULATION OF ADOLESCENT RAT INTESTINAL EPITHELIAL INDUCIBLE NITRIC OXIDE SYNTHASE EXPRESSION IN ENDOTOXIN TOLERANCE: MODULATION OF SIGNAL TRANSDUCTION

Endotoxin/lipopolysaccharide (LPS) tolerance is a state of induced hyporesponsiveness to endotoxin or LPS characterized by alterations in the release of inflammatory mediators. As the gut is both a source of infection and target of injury, we tested the hypothesis that alterations in intestinal epithelial signal transduction would account for the acquisition of endotoxin tolerance as defined by decreased induction of a key mediator of gut injury, inducible nitric oxide synthase (iNOS). Rats (15 days of age) were injected with saline or LPS (1 microg/g i.p.). Tissue was harvested after 1, 4, or 6 h for assessment of signaling and iNOS expression. Other animals received a second dose of LPS 1 to 7 days after the initial dose. Selected animals received the p38 inhibitor, SB203580 (10 microg/g), which was co-administered with the first dose of LPS. Induction of iNOS mRNA and protein was significantly attenuated after repeated LPS administration. Epithelial cells from LPS-tolerant rats showed a minimal level of iNOS expression by immunohistochemistry. The down-regulation of intestinal iNOS was not gender dependent. p38 inhibition enhanced tolerance rather than blocking it. LPS-mediated activation of NF-kappaB was attenuated in a manner consistent with a primary role in the induction of tolerance. Endotoxin tolerance can be demonstrated in intestinal epithelial cells using an in vivo model. Modulation of NF-kappaB signaling may be key in the down-regulation of LPS effect seen in tolerance.

Protective role of heme oxygenase-1 in the intestinal tissue injury in an experimental model of sepsis

OBJECTIVE

The aim of this study was to examine the role of heme oxygenase-1 induction in the intestinal tissue injury in a rat model of sepsis.

DESIGN

Randomized, masked, controlled animal study.

SETTING

University-based animal research facility.

SUBJECTS

Sprague-Dawley male rats, weighing 220-250 g (n = 126).

INTERVENTIONS

Rats were injected with lipopolysaccharide (10 mg/kg) intraperitoneally. Another group of rats was injected with interleukin-6 (10 microg/kg) intravenously. In some rats, tin mesoporphyrin (1 micromol/kg) was administered intravenously 1 hr before lipopolysaccharide treatment.

MEASUREMENTS AND MAIN RESULTS

Following lipopolysaccharide treatment, expression of heme oxygenase-1 and nonspecific delta-aminolevulinate synthase (ALAS-N), the rate-limiting enzymes of heme catabolism and biosynthesis, respectively, was examined in various regions of the intestine. Lipopolysaccharide treatment markedly increased heme oxygenase-1 messenger RNA and protein concentrations in the mucosal epithelial cells in the duodenum and the jejunum, whereas its expression in the ileum and the colon was hardly detectable and was not influenced by the treatment. ALAS-N messenger RNA was also more markedly increased in the duodenum, the jejunum, and the ileum than in the colon following lipopolysaccharide treatment. Interleukin-6 administration also induced heme oxygenase-1 and ALAS-N gene expression in a pattern similar to that following lipopolysaccharide treatment. In contrast to the marked heme oxygenase-1 expression in the upper intestine, lipopolysaccharide-induced mucosal injury and inflammation in the upper intestine were far less than observed in the lower intestine as judged both by tumor necrosis factor-alpha gene expression and by histologic analysis. Of note, inhibition of heme oxygenase activity by tin mesoporphyrin produced a significant tissue injury in the upper intestine of the lipopolysaccharide-treated animals.

CONCLUSIONS

Intestinal heme oxygenase-1 and ALAS-N gene expression was regulated in a site-specific manner in a rat model of sepsis. Our findings also suggest that heme oxygenase-1 induction may play a fundamental role in protecting mucosal epithelial cells of the intestine from oxidative damages that occur in sepsis.