Remote Tissue Damage Research Articles

Is there a role for ischaemic pre-conditioning in orthopaedic and trauma surgery? A systematic review and meta-analysis of randomised controlled trials

Surgical procedures using a tourniquet submit tissues to ischaemia and reperfusion on restoring blood flow. Ischaemia-reperfusion may lead to local or remote tissue damage resulting in pain and complications. We aimed to evaluate the effectiveness of ischaemic preconditioning with a tourniquet in preventing pain, disability, adverse events, inflammation and facilitating recovery and discharge in patients receiving orthopaedic and trauma surgery. We conducted a systematic review of randomised controlled trials investigating ischaemic preconditioning in patients undergoing trauma and orthopaedic surgery. We searched The Cochrane Library, Medline and Embase until January 2021. Where possible continuous data were pooled and meta-analysis performed. Ten RCTs met inclusion criteria, eight of which underwent meta-analysis. Three studies reported lower acute post-operative pain or morphine consumption in patients randomised to IPC. We found weak evidence for shorter length of stay in the intervention group (MD-0.54 days; 95%CI-1.11, 0.03; p=0.0615). Malondialdehyde levels were lower in patients randomised to IPC at two hours following tourniquet deflation (MD -1.39 nmol/ml; 95%CI-2.23, -0.55; p=0.0012). We found no between group differences in Tumour Necrosis Factor-α, Lactate or Interleukin-6. The mechanism behind IPC may be related to reduced lipid peroxidation rather than reduced inflammation. There is evidence IPC reduces post-operative pain following knee surgery that merits further study.

Effect of Ischemia-Reperfusion injury and Preconditioning on Lung Parenchyma after Acute Limb Ischemia

Introduction. Acute limb ischemia, a sudden decrease of perfusion to the extremities, can compromise the survival of the limbs. Medical intervention and surgery are often needed to return perfusion. However, reperfusion injury can trigger oxidative stress and inflammatory response, leading to local and remote tissue damage, such as the lungs, which increases morbidity and mortality. This research aims to study the effects of hypothermia and remote ischemic preconditioning (RIPC) on the lung parenchyma after being exposed to reperfusion after acute limb ischemia in rabbits.

Allogenic mesenchymal stem cell intravenous infusion in reparation of mild intestinal ischemia/reperfusion injury in New Zealand rabbits

ABSTRACT: The present study aimed to evaluate the efficacy of mesenchymal stem cell (MSC) infusion, derived from adipose tissue, on reduction of local and remote tissue damage caused by the event of experimental intestinal I/R in New Zealand breed rabbits. For obtaining, characterization, and cultivation of MSC derived from adipose tissue (MSC-Adp), 3 juvenile animals (four months old) were used. The cells were considered to be viable for therapy after the fourth passage (in vitro phase). For the in vivo stage, 24 young adult animals (six months old) were used, weighing approximately 3.5 kg, in which were randomly divided into two groups, called: IR treated with MSC (I2H/R5H MSC 3D; I2H/R5H MSC 7D); IR treated with PBS (I2H/R5H PBS 3D; I2H/R5H PBS 7D). The animals were anesthetized and submitted to pre-retro-umbilical midline celiotomy. The extramural peri-intestinal marginal artery was located and clamped (predetermined and standardized region) with the aid of a vascular clip, promoting a 2 hour blood flow interruption. After this period, blood flow was reestablished, inhalatory anesthesia was suspended, and the animals awaken. After 5 hours of reperfusion, the treatments were performed by intravenous infusion according to the experimental groups. The animals were evaluated 72 hours and seven days after the treatment as for the macroscopic appearance (color and peristaltism) of the jejunal segment, and by histological evaluation of the ischemic segment for the presence or absence of destruction of the intestinal mucosa, edema, bleeding, dilation of lymph vessels, and presence of polymorphonuclear inflammatory cells, both in the mucosa and submucosa. The observed results revealed that the groups treated with MSC-Adp obtained smaller mucosal and submucosal lesions when compared to the groups treated with PBS. Also, MSC-Adp treated groups obtained controlled inflammatory response and higher mitotic rate, outcomes related to the therapeutic potential of MSC. Infusion of stem cells attenuated the lesions caused by intestinal I/R in both MSC groups when compared to the group treated with PBS.

Altered exosomal protein expression in the serum of NF-κB knockout mice following skeletal muscle ischemia-reperfusion injury.

BackgroundThe NF-κB signaling pathway plays a role in local and remote tissue damage following ischemia-reperfusion (I/R) injury to skeletal muscles. Evidence suggests that exosomes can act as intercellular communicators by transporting active proteins to remote cells and may play a role in regulating inflammatory processes. This study aimed to profile the exosomal protein expression in the serum of NF-κB knockout mice following skeletal muscle ischemia-reperfusion injury.ResultsTo investigate the potential changes in protein expression mediated by NF-κB in secreted exosomes in the serum following I/R injury, the levels of circulating exosomal proteomes in C57BL/6 and NF-κB−/− mice were compared using two dimensional differential in-gel electrophoresis (2-DE), liquid chromatography tandem mass spectrometry (LC-MS/MS), and proteomic analysis. In C57BL/6 mice, the levels of circulating exosomal proteins, including complement component C3 prepropeptide, PK-120 precursor, alpha-amylase one precursor, beta-enolase isoform 1, and adenylosuccinate synthetase isozyme 1, increased following I/R injury. However, in the NF-κB−/− mice, the expression of the following was upregulated in the exosomes: protease, serine 1; glyceraldehyde-3-phosphate dehydrogenase-like isoform 1; glyceraldehyde-3-phosphate dehydrogenase; and pregnancy zone protein. In contrast, the expression of apolipoprotein B, complement component C3 prepropeptide, and immunoglobulin kappa light chain variable region was downregulated in NF-κB−/− mice. Bioinformatic annotation using the Protein Analysis Through Evolutionary Relationships (PANTHER) database revealed that the expression of the exosomal proteins that participate in metabolic processes and in biological regulation was lower in NF-κB−/− mice than in C57BL/6 mice, whereas the expression of proteins that participate in the response to stimuli, in cellular processes, and in the immune system was higher.ConclusionsThe data presented in this study suggest that NF-κB might regulate exosomal protein expression at a remote site via circulation following I/R injury.

Neutrophils—A Key Component of Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a common occurrence following myocardial infarction, transplantation, stroke, and trauma that can lead to multiple organ failure, which remains the foremost cause of death in critically ill patients. Current therapeutic strategies for IRI are mainly palliative, and there is an urgent requirement for a therapeutic that could prevent or reverse tissue damage caused by IRI. Neutrophils are the primary responders following ischemia and reperfusion and represent important components in the protracted inflammatory response and severity associated with IRI. Experimental studies demonstrate neutrophil infiltration at the site of ischemia and show that inducing neutropenia can protect organs from IRI. In this review, we highlight the mechanisms involved in neutrophil recruitment, activation, and adherence and how this contributes to disease severity in IRI. Inhibiting neutrophil mobilization, tissue recruitment, and ultimately neutrophil-associated activation of local and systemic inflammatory responses may have therapeutic potential in the amelioration of local and remote tissue damage following IRI.

Complement depletion protects lupus-prone mice from ischemia-reperfusion-initiated organ injury

Ischemia-reperfusion (IR) injury causes a vigorous immune response that is amplified by complement activation, leading to local and remote tissue damage. Using MRL/lpr mice, which are known to experience accelerated tissue damage after mesenteric IR injury, we sought to evaluate whether complement inhibition mitigates organ damage. We found that complement depletion with cobra venom factor protected mice from local and remote lung tissue damage. Protection from injury was associated with less complement (C3) and membrane attack complex deposition, less neutrophil infiltration, and lower levels of local proinflammatory cytokine production. In addition, complement depletion was able to decrease the level of oxidative stress as measured by glutathione peroxidase 1 mRNA levels and superoxide dismutase activity. Furthermore, blockage of C5a receptor protected MRL/lpr mice from local tissue damage, but not from remote lung tissue damage. In conclusion, although treatments with cobra venom factor and C5a receptor antagonist were able to protect mice from local tissue damage, treatment with C5a receptor antagonist was not able to protect mice from remote lung tissue damage, implying that more factors contribute to the development of remote tissue damage after IR injury. These data also suggest that complement inhibition at earlier, rather than late, stages can have clinical benefit in conditions that are complicated with IR injury.

The Role of Platelet Factor 4 in Local and Remote Tissue Damage in a Mouse Model of Mesenteric Ischemia/Reperfusion Injury

The robust inflammatory response that occurs during ischemia reperfusion (IR) injury recruits factors from both the innate and adaptive immune systems. However the contribution of platelets and their products such as Platelet Factor 4 (PF4; CXCL4), during the pathogenesis of IR injury has not been thoroughly investigated. We show that a deficiency in PF4 protects mice from local and remote tissue damage after 30 minutes of mesenteric ischemia and 3 hours of reperfusion in PF4-/- mice compared to control B6 mice. This protection was independent from Ig or complement deposition in the tissues. However, neutrophil and monocyte infiltration were decreased in the lungs of PF4-/- mice compared with B6 control mice. Platelet-depleted B6 mice transfused with platelets from PF4-/- mice displayed reduced tissue damage compared with controls. In contrast, transfusion of B6 platelets into platelet depleted PF4-/- mice reconstituted damage in both intestine and lung tissues. We also show that PF4 may modulate the release of IgA. Interestingly, we show that PF4 expression on intestinal epithelial cells is increased after IR at both the mRNA and protein levels. In conclusion, these findings demonstrate that may PF4 represent an important mediator of local and remote tissue damage.

Platelet-associated CD40/CD154 mediates remote tissue damage after mesenteric ischemia/reperfusion injury (54.1)

Abstract Several innate and adaptive immune cell types participate in ischemia/reperfusion induced tissue injury. Amongst them, platelets have received little attention as contributors in the process of tissue damage after ischemia reperfusion (I/R) injury. It is currently unknown whether platelets participate through the immunologically important molecules including, CD40 and when activated, CD154 (CD40L), in the pathogenesis of I/R injury. We hypothesized that constitutive expression of CD40 and activation-induced expression of CD154 on platelets mediate local mesenteric and remote lung tissue damage after I/R injury. Wild type (WT; C57BL/6J), CD40 and CD154 deficient mice underwent mesenteric ischemia for 30 minutes followed by reperfusion for 3 hours. WT mice subjected to mesenteric I/R injury displayed both local intestinal and remote lung damage. In contrast, there was significantly less intestinal damage and no remote lung injury in CD40 and CD154 deficient mice when compared to WT mice. Platelet-depleted WT mice transfused with platelets from CD40 or CD154 deficient mice failed to reconstitute remote lung damage. In contrast, when CD40 or CD154 deficient mice were transfused with WT platelets lung tissue damage was re-established. Together, these findings suggest that multiple mechanisms are involved in local and remote tissue injury and also identify platelet-expressed CD40 and/or CD154 as mediators of remote tissue damage.

The role of Platelet Factor 4 in local and remote tissue damage in a mouse model of mesenteric ischemia/reperfusion injury (120.18)

Abstract The robust inflammatory response that takes place during ischemia reperfusion injury (IR/I) recruits factors from both the innate and adaptive immune system. However the contribution of platelets and their products such as Platelet Factor 4 (PF4; CXCL4), during the pathogenesis of IR/I has not been thoroughly investigated. We show that a deficiency in PF4 protects mice from local and remote tissue damage after 30 minutes of mesenteric ischemia and 3 hours of reperfusion in PF4-/- mice compared to control B6 mice. This protection was independent from Ig or complement deposition in the tissues. However, neutrophil and monocyte infiltration was decreased in the lungs of PF4-/- mice compared with B6 control mice. Platelet-depleted B6 mice transfused with platelets from PF4-/- mice displayed reduced tissue damage compared with controls. In contrast, transfusion of B6 platelets into platelet depleted PF4-/- mice reconstituted damage in both intestine and lung tissue. We also show that PF4 may modulate the release of IgA. Interestingly, we show that PF4 expression on intestinal epithelial cells is increased after ischemia/reperfusion at both the mRNA and protein levels. In conclusion, these findings demonstrate that PF4 represents an important mediator of local and remote tissue damage.

Inhibition of Syk activity by R788 in platelets prevents remote lung tissue damage after mesenteric ischemia-reperfusion injury

Tissue injury following ischemia-reperfusion (I/R) occurs as a consequence of actions of soluble factors and immune cells. Growing evidence supports a role for platelets in the manifestation of tissue damage following I/R. Spleen tyrosine kinase has been well documented to be important in lymphocyte activation and more recently in platelet activation. We performed experiments to evaluate whether inhibition of platelet activation through inhibition of spleen tyrosine kinase prevents tissue damage after mesenteric I/R injury. Platelets isolated from C57BL/6J mice fed with R788 for 10 days were transfused into C57BL/6J mice depleted of platelets 2 days before mesenteric I/R injury. Platelet-depleted mice transfused with platelets from R788-treated mice before mesenteric I/R displayed a significant reduction in the degree of remote lung damage, but with little change in the degree of local intestinal damage compared with control I/R mice. Transfusion of R788-treated platelets also decreased platelet sequestration, C3 deposition, and immunoglobulin deposition in lung, but not in the intestine, compared with control groups. These findings demonstrate that platelet activation is a requisite for sequestration in the pulmonary vasculature to mediate remote tissue injury after mesenteric I/R. The use of small-molecule inhibitors may be valuable to prevent tissue damage in remote organs following I/R injury.

Platelet-Associated CD40/CD154 Mediates Remote Tissue Damage after Mesenteric Ischemia/Reperfusion Injury

Several innate and adaptive immune cell types participate in ischemia/reperfusion induced tissue injury. Amongst them, platelets have received little attention as contributors in the process of tissue damage after ischemia reperfusion (I/R) injury. It is currently unknown whether platelets participate through the immunologically important molecules including, CD40 and when activated, CD154 (CD40L), in the pathogenesis of I/R injury. We hypothesized that constitutive expression of CD40 and activation-induced expression of CD154 on platelets mediate local mesenteric and remote lung tissue damage after I/R injury. Wild type (WT; C57BL/6J), CD40 and CD154 deficient mice underwent mesenteric ischemia for 30 minutes followed by reperfusion for 3 hours. WT mice subjected to mesenteric I/R injury displayed both local intestinal and remote lung damage. In contrast, there was significantly less intestinal damage and no remote lung injury in CD40 and CD154 deficient mice when compared to WT mice. Platelet-depleted WT mice transfused with platelets from CD40 or CD154 deficient mice failed to reconstitute remote lung damage. In contrast, when CD40 or CD154 deficient mice were transfused with WT platelets lung tissue damage was re-established. Together, these findings suggest that multiple mechanisms are involved in local and remote tissue injury and also identify platelet-expressed CD40 and/or CD154 as mediators of remote tissue damage.

Platelets orchestrate remote tissue damage after mesenteric ischemia-reperfusion

Ischemia-reperfusion (I/R) injury is a leading cause of morbidity and mortality. A functional role for platelets in tissue damage after mesenteric I/R is largely unknown. The hypothesis that mesenteric I/R local and remote injury are platelet dependent was tested. Using a murine mesenteric I/R model, we demonstrate that platelets orchestrate remote lung tissue damage that follows mesenteric I/R injury and also contribute, albeit to a lesser degree, to local villi damage. While lung damage is delayed compared with villi damage, it increased over time and was characterized by accumulation of platelets in the pulmonary vasculature early, followed by alveolar capillaries and extravasation into the pulmonary space. Both villi and lung tissues displayed complement deposition. We demonstrate that villi and lung damage are reduced in mice made platelet deficient before I/R injury and that platelet transfusion into previously platelet-depleted mice before I/R increased both villi and lung tissue damage. Increased C3 deposition accompanied platelet sequestration in the lung, which was mostly absent in platelet-depleted mice. In contrast, C3 deposition was only minimally reduced on villi of platelet-depleted mice. Our findings position platelets alongside complement as a significant early upstream component that orchestrates remote lung tissue damage after mesenteric I/R and strongly suggest that reperfusion injury mitigating modalities should consider the contribution of platelets.

Male Susceptibility to Hepatic Damage in Acute Uremia in Rats

To evaluate the role of gender in hepatic oxidative stress response and production of inflammatory cytokines in acute uremia after bilateral nephrectomy. Published studies indicate that the severity of tissue damage in kidney, brain, or heart injury may differ according to gender. We recently demonstrated that acute renal failure after kidney injury or bilateral nephrectomy activates oxidative stress and causes damage to the liver. Male and female rats were subjected to bilateral nephrectomy and euthanized four hours later. Serum and liver tissues were collected and analyzed. To ascertain the role of testosterone and estrogen in hepatic oxidative stress, castration was carried out 15 days before bilateral nephrectomy. In some groups, animals were administrated 17-β-estradiol or vehicle for 2 weeks before bilateral nephrectomy. Hepatic oxidative stress was significantly pronounced in male rats as determined by increase in malondialdehyde (MDA) levels and decrease in total glutathione (GSH) contents. An increase in proinflammatory cytokine concentration was seen in male rats, whereas the antiinflammatory cytokine level was more elevated in females. Castration reduced hepatic oxidative stress and proinflammatory cytokine concentration, whereas exogenous estradiol after castration did not have an additional effect on these parameters. There is a gender difference with regard to the severity of hepatic oxidative stress and inflammatory response in acute uremia after bilateral nephrectomy, with female rats displaying significant protection relative to male rats. We suggest that sex hormones could play an important role in the severity of remote tissue damage in acute kidney failure.

IMMUNE STATUS AND APOPTOSIS ACTIVATION DURING BRAIN DEATH

The present study evaluates the role of the inflammatory status and apoptosis activation in the development of organ dysfunction after brain death using plasma assays and macroarray analysis on skeletal muscle biopsies to look for evidence of remote tissue damage in two intensive care units in France and one in Belgium. As controls, we used patients undergoing hip surgery and healthy volunteers. Causes of brain death in the 85 consecutive patients included in the study were cardiac arrest (n = 29; 34%), stroke (n = 42; 49%, with 38 patients having hemorrhagic stroke), and head injury (n = 14; 17%). Of the 85 patients, 45 donated 117 organs. Plasma endotoxin and cytokine levels indicated a marked systemic inflammatory response in brain-dead patients, which was strongest in the cardiac arrest group. Leukocyte dysfunction, as assessed by cytokines production in response to various stimuli, was noted in a subgroup of patients with brain death after stroke. Interestingly, skeletal muscle biopsies showed no increase in mRNAs for genes related to inflammation, whereas mRNAs for both antiapoptotic and proapoptotic genes were increased, the balance being in favor of apoptosis induction. The increased activation of the proapoptotic caspase 9 was further confirmed by Western blot. In conclusion, the presence of inflammation and apoptosis induction may explain the rapid organ dysfunction seen after brain death. Both abnormalities may play a role in organ dysfunction associated with brain death. However, the level of systemic inflammation or the presence of circulating endotoxin was not associated with lower graft survival.

Historical overview of wound ballistics research

Ballistics involves the study of the scientific properties of projectiles, their behavior and their terminal effects on biological tissues and other materials. Wound ballistics deals with the analysis of injuries caused by projectiles and the behavior of projectiles within human or other biological tissues. The nineteenth century witnessed the development of both of these areas with Kocher's hydrodynamic theory and the understanding of the significance of bullet deformation in causing tissue injury. The degree of traumatic disruption of tissues and organs was also related to direct energy transfer from projectiles. While subsequent research has concentrated on elucidating further mechanisms of injury, the exact cause of remote tissue damage from high energy projectiles is still the subject of ongoing research. Much of the contemporary literature regarding wound ballistics concentrates on the forensic aspects and their application for legal purposes, in particular the investigation of shooting scenes. There have been many advances in this area, particularly in relation to the identification of various types of gunshot wounds and how their appearance can be used to establish if a shooting was accidental, deliberate (homicidal) or self inflicted (suicidal).

Anti-Phospholipid Antibodies Restore Mesenteric Ischemia/Reperfusion-Induced Injury in Complement Receptor 2/Complement Receptor 1-Deficient Mice

Complement receptor 2-deficient (Cr2(-/-)) mice are resistant to mesenteric ischemia/reperfusion (I/R) injury because they lack a component of the natural Ab repertoire. Neither the nature of the Abs that are involved in I/R injury nor the composition of the target Ag, to which recognition is lacking in Cr2(-/-) mice, is known. Because anti-phospholipid Abs have been shown to mediate fetal growth retardation and loss when injected into pregnant mice, we performed experiments to determine whether anti-phospholipid Abs can also reconstitute I/R injury and, therefore, represent members of the injury-inducing repertoire that is missing in Cr2(-/-) mice. We demonstrate that both murine and human monoclonal and polyclonal Abs against negatively charged phospholipids can reconstitute mesenteric I/R-induced intestinal and lung tissue damage in Cr2(-/-) mice. In addition, Abs against beta2 glycoprotein I restore local and remote tissue damage in the Cr2(-/-) mice. Unlike Cr2(-/-) mice, reconstitution of I/R tissue damage in the injury-resistant Rag-1(-/-) mouse required the infusion of both anti-beta2-glycoprotein I and anti-phospholipid Ab. We conclude that anti-phospholipid Abs can bind to tissues subjected to I/R insult and mediate tissue damage.

Richard Wood and intestinal transplantation

Richard Wood (1943–2003) developed an interest in small bowel transplantation on his appointment to the Chair of Surgery at the Medical College of St Bartholomew's Hospital, London, UK, in 1984 and he organized the first international symposium on the subject in October 1989. His research which initially focused on intestinal function evolved to assess the role of migration of leukocytes between graft and host tissues in the development of rejection and graft-versus-host disease (GvHD). His group explored avenues to prevent rejection and GvHD, but none of these initiatives were totally effective. They did show that ischemia, rejection, and GvHD in heteropic small bowel grafts were all associated with shifts in intestinal microflora toward potentially pathogenic organisms. When the research program relocated to the University of Sheffield in 1994, studies were undertaken to assess adhesion molecule and heat shock protein expression during intestinal allograft rejection. An interest in ischemia–reperfusion (I/R) injury also developed and in vivo microscopy was used to directly visualize the intestinal villus microcirculation after intestinal I/R injury. Hypothermia and the nitric oxide donor FK 409 were shown to prevent mortality, and to attenuate localized and remote tissue damage and leukocyte adherence in the villus microcirculation. In contrast, tacrolimus had no such effect. These studies were ongoing when ill health forced his retirement in 2002. He maintained a keen interest in, and enthusiasm for, the experimental program despite his progressive illness. This support continued to inspire all investigators around him.

Défaillance multiviscérale précoce associée à la pancréatite aiguë : stratégie thérapeutique chirurgicale ou conservatrice ?

The mortality of severe acute pancreatitis still ranges between 10% and 20%. Nowadays, infected pancreatic necrosis is the leading cause of death. Despite advances in intensive care therapy, however, early and worsening multi-system organ failure remains a source of substantial morbidity and still accounts for 20–50% of the deaths. News and hotspots.– The three interrelated pathophysiological mechanisms underlying glandular necrosis include the premature intra-acinar activation of pancreatic pro-enzymes, an early pancreatic microcirculatory impairment, and the excessive stimulation of immune effector cells. In recent years, the systemic inflammatory response syndrome and the relevant cascades of inflammatory mediators have been implicated as the key factor in the emergence of remote tissue damage. Early multi-system organ failure that supervenes in the first week is typically associated with a sterile necrotizing process. The correlation between pathomorphological and clinical severity and the similarity between their respective pathophysiological mechanisms are not straightforward, however. There are no pathophysiological, clinical or economical data to support the practice of debridement of sterile necrosis to prevent or to control early multi-system organ failure. This issue has never been addressed in a controlled study. Besides intensive care support, non-surgical therapeutic modalities including urgent endoscopic sphincterotomy for impacted stones, antibiotic prophylaxis for the prevention of pancreatic infection and early jejunal nutrition have been specifically developed hopefully to attenuate multiple organ failure, to obviate the need of surgical drainage and to improve survival. Fine needle aspiration of necrotic areas must be incorporated in any conservative therapeutic strategy in order not to jeopardize those with infected necrosis that remains an absolute indication for drainage. Perspectives.– There is ample experimental and pathophysiological evidence in favour of immunomodulatory therapy in severe acute pancreatitis. The administration of one or several antagonists of inflammatory mediators possibly combined with a protease inhibitor may at last provide the opportunity to interfere with the two major determinants of prognosis: the severity of multiple organ failure and the extent of necrotic areas that creates the culture medium for bacterial superinfection. These benefits remain to be substantiated in a controlled study, however.

FK409 inhibits both local and remote organ damage after intestinal ischaemia.

In addition to localized tissue injury, intestinal ischaemia-reperfusion (I/R) leads to remote organ damage, in particular to the lungs. Given that nitric oxide (NO) can attenuate I/R-induced tissue injury in many situations, this study evaluated the effects of the NO donor, FK409, on leukocyte adhesion in the microcirculation of the intestinal villus and also assessed pulmonary tissue damage after intestinal I/R injury. PVG rats were subjected to 30 min intestinal ischaemia and a sub-group of animals received the NO donor FK409 (10 mg/kg; i.v.) both 30 min prior to ischaemia and 30 min post-reperfusion. The intestinal mucosal surface was visualized via an incision made in an exteriorized ileal segment and leukocyte adhesion in the villous microcirculation was determined by in vivo microscopy. Total and differential leukocyte counts from peripheral blood were evaluated. Lungs were removed at the end for histological assessment. Six out of ten untreated I/R animals failed to survive the 2 h reperfusion period, whereas all ten FK409-treated animals survived. I/R induced a significant increase in villous leukocyte adhesion of untreated I/R animals (p<0.001) and this was significantly decreased by FK409 treatment (p<0.001). The total leukocyte count was significantly decreased in untreated I/R animals (p<0.001) and this primarily resulted from a reduction in circulating neutrophil numbers. This effect was not observed in FK409-treated animals. Collapsed alveoli, thickened interstitial walls, and a dense neutrophilic infiltrate were apparent in the lungs of untreated I/R animals, whereas lung histology was normal in FK409-treated animals. In conclusion, FK409 prevented mortality, significantly reduced villous leukocyte adhesion, maintained circulating leukocyte numbers, and prevented pulmonary tissue injury following intestinal I/R. FK409 may therefore be of value in reducing both local and remote tissue damage and improving outcome in situations where intestinal I/R injury is obligatory, such as small bowel transplantation.

Multiple organ dysfunction syndrome: Role of xanthine oxidase and nitric oxide

Abstract In general, the simple concepts first proposed over a decade ago for the role of xanthine oxidase (XO) in pathophysiolgy are no longer sufficient. This review summarizes evidence that has led to a resurgence in interest of XO physiology and pathology and in particular, data that implicates XO and nitric oxide (⋅NO) in the development of multiple organ dysfunction (MODS) following various pathologic states. The challenge for the next few years will be to define the precise mechanisms that XO plays in normal physiology and pathology. Although it has long been recognized that XO can produce oxidants, the significance of XO-generated oxidants extends beyond the concept of the intracellular generation of cytotoxic oxidants. It has been demonstrated that XO can be released into the circulation from cells and tissues with high intracellular XO specific activity following I/R, sepsis, burns, acute viral infection, and hemorrhagic shock. Once in the plasma the conversion to XO is rapid ( β , TNF- α , and TGF- β 1), in part, through activation of nuclear transcription regulatory factors. There also appears to be regulation of the vasoactive actions of ⋅NO by XO-generated oxidants to decrease rates of O 2 ⋅− generation, thus potentiating ⋅NO-mediated vasorelaxation. This regulation may be due to the reaction of ⋅NO with O 2 ⋅− to form ONOO − . Nitric oxide may also regulate O 2 ⋅− production post-transcriptionally by binding to the XO iron–sulfur moiety, sulfhydryl groups, or by reversible alteration of the flavin prosthetic site, thereby inhibiting activity. It is becoming apparent that tissue injury in MODS resulting from various pathologic states, including I/R, is the consequence not only excess production of reactive oxygen and nitrogen species (ROS and RNS) and their reaction with biologic target molecules, but also the effect of these oxidants in regulation of proinflammatory and anti-inflammatory mediators. The interplay of XO-generated oxidants and ⋅NO, has significant effects on cellular metabolism and organ function with their precise role in MODS requiring further elucidation. In summary, evidence was presented in this review that: (a) reactive species (ROS) are critical mediators of remote tissue injury; (b) ⋅NO and ⋅NO-derived oxidants contribute to the remote tissue damage; (c) XO, while a significant intracellular source of O 2 ⋅− ; is released into the circulation, binds, and concentrates on vessel walls to become a functionally critical source of oxidants even in tissues with low XO specific activity; and (d) that the balance between ⋅NO and O 2 ⋅− production determines whether the proinflammatory or anti-inflammatory properties are manifested.