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A response by R. Naik and colleagues to a letter to the editor about their article "Surgical training in gastrointestinal procedures within a Great Britain gynaecological oncology subspecialty programme" in the 2010 issue is presented.

In many diseases and acute inflammatory disorders, important components of pathological processes are linked to the neutrophils' ability to release a complex assortment of agents that can destroy normal cells and dissolve connective tissue. This review summarizes the mechanisms of tissue destruction by neutrophils and the role of kidney-specific factors that promote this effect. Nicotinamide adenine dinucleotide phosphate H (NADPH) oxidase is a membrane-associated enzyme that generates a family of reactive oxygen intermediates (ROI). There is increasing evidence that ROIs are implicated in glomerular pathophysiology: ROIs contribute to the development of proteinuria, alter glomerular filtration rate, and induce morphological changes in glomerular cells. Specific neutrophil granules contain microbicidal peptides, proteins, and proteolytic enzymes, which mediate the dissolution of extracellular matrix, harm cell structures or cell function, and induce acute and potentially irreparable damage. Although both ROI and neutrophil-derived proteases alone have the potential for tissue destruction, it is their synergism that circumvents the intrinsic barriers designed to protect the host. Even small amounts of ROI can generate hypochlorus acid (HOCl) in the presence of neutrophil-derived myeloperoxidase (MPO) and initiate the deactivation of antiproteases and activation of latent proteases, which lead to tissue damage if not properly controlled. In addition, neutrophil-derived phospholipase products such as leukotrienes and platelet-activating factor contribute to vascular changes in acute inflammation and amplify tissue damage. Increasing evidence suggests that mesangial cells and neutrophils release chemotactic substances (eg, interleukin 8), which further promote neutrophil migration to the kidney, activate neutrophils, and increase glomerular injury. Also, the expression of adhesion molecules (eg, intercellular adhesion molecule 1 on kidney-specific cells and beta-2-integrins on leukocytes) has been correlated with the degree of injury in various forms of glomerulonephritis or after ischemia and reperfusion. Together, these results suggest that neutrophils and adhesion molecules play an important role in mediating tissue injury with subsequent renal failure. Conversely, chronic renal failure reduces neutrophil function and thereby can increase susceptibility to infection and sepsis.

C-X-C chemokines play an important role in the migration and activation of neutrophils (PMNs) during an inflammatory event. We measured mRNA and protein expression of the murine C-X-C chemokines macrophage inflammatory protein-2 (MIP-2) and KC in the lungs, liver, blood, and peritoneal cavity of Swiss Webster mice after cecal ligation and puncture (CLP). Neutralizing antibodies to MIP-2 and KC were also used to determine the biological effects of these chemokines on neutrophil sequestration and organ injury in the CLP model. The data showed that early after CLP, MIP-2 mRNA and protein were expressed predominantly by the lung, whereas KC mRNA and protein were expressed by the liver. Inhibition of MIP-2 reduced both lung neutrophil sequestration and peritoneal neutrophil migration. Inhibition of KC had no effect on overall neutrophil sequestration in liver but reduced injury as measured by serum transaminases. An early survival benefit was found with anti-KC treatment, although overall survival was not different. Our study showed a differential expression by organs of C-X-C chemokines during sepsis and suggested that such chemokine effects are tissue-specific.

Neutrophil (PMN) migration into the peritoneal cavity in response to fecal peritonitis is an important mechanism of host defense against bacterial invasion. We show that the murine C-X-C (PMN-specific) chemokine, macrophage inflammatory protein-2 (MIP-2), on intraperitoneal injection in mice, causes PMN migration into the peritoneum. MIP-2 mRNA and protein were expressed by peritoneal leukocytes after cecal ligation and puncture (CLP) in mice and neutralization of MIP-2 reduced peritoneal PMN migration. A prerequisite for neutrophil-endothelial adhesion and subsequent migration from the circulation is selectin-mediated rolling. Pretreatment of mice with an anti-P-selectin antibody before intraperitoneal injection of MIP-2 significantly reduced peritoneal PMN migration. However, there are no reports that a C-X-C chemokine can up-regulate endothelial selectins. We postulated that MIP-2, when injected intraperitoneally, interacts with a cell that is known to release factors that up-regulate endothelial selectins. A likely candidate is the mast cell, which contains histamine and tumor necrosis factor alpha (TNF-alpha), and both of these factors induce selectins. Intraperitoneally injected MIP-2 caused an early significant increase in peritoneal TNF-alpha, whereas histamine levels were unaffected. In a subsequent experiment, mast cell-deficient mice and their normal controls were then injected intraperitoneally with MIP-2 or underwent CLP. Significantly fewer PMNs migrated into the peritoneal cavity in the mast cell-deficient mice after MIP-2 injection or CLP. Thus, our findings indicate that mast cells and MIP-2 are necessary for PMN migration into the peritoneum in response to intra-abdominal infection, and that MIP-2 appears to facilitate this through an increase in TNF-alpha release.

Previous studies have shown that the neutrophil-derived heparin-binding protein (HBP), also known as CAP37 or azurocidin, potentiates the LPS-induced release of proinflammatory cytokines (TNF-alpha, IL-1, and IL-6) from isolated human monocytes. To date, the mechanisms by which HBP enhances LPS-induced monocyte activation have not been elucidated, and it is not known whether HBP also increases the LPS-induced production of other bioactive substances. We studied human monocytes activated by recombinant human HBP and LPS and their interaction with the LPS receptor CD14. We hypothesized that the stimulatory effect of HBP on the LPS-induced release of proinflammatory mediators from monocytes was mediated by specific binding of HBP to monocytes, which resulted in an up-regulation of CD14. Our results demonstrated that HBP alone (10 microg/ml) stimulated the production of TNF-alpha from isolated monocytes. In addition, HBP had an additive effect on LPS-induced production of TNF-alpha and PGE2, suggesting a generalized monocyte activation. We used flow cytometry to demonstrate that HBP had a high affinity to monocytes but not to the LPS receptor CD14, and experiments performed at 4 degrees C indicated an energy-dependent step in this process. Confocal microscopy showed that monocytes internalize HBP within 30 min. These data suggest that mechanisms other than increased CD14 expression are responsible for the enhanced release of TNF-alpha or PGE2 in response to HBP and LPS.

The ability of bacterial organisms to produce an extracellular polysaccharide matrix known as slime has been associated with increased virulence and delayed infections in various prosthetic implants. Within a biofilm, this slime may protect the embedded bacteria from host defense mechanisms, especially phagocytosis by polymorphonuclear leukocytes. To determine whether planktonic Staphylococcus epidermidis is protected in a similar way, a novel flow cytometric assay was performed, measuring ingestion and adherence during phagocytosis and the production of superoxide during oxidative burst. Hydrophobicity was determined by hydrophobic interaction chromatography. Slime-producing S. epidermidis RP62A and its phenotypic variant, non-slime-producing RP62A-NA, were compared. The results showed increased phagocytosis of RP62A at 2, 5, 10, and 30 min; increased adherence of RP62A at 30 s and 30 min; and increased superoxide production of RP62A after 2 min. Decreased hydrophobicity of RP62A over RP62A-NA was correlated with a hydrophilic slime coat. The data argue that the host aggressively combats slime-producing S. epidermidis. This biological phenomenon is potentially important during bacteremia to prevent further adhesion, accumulation, and the genesis of a bacterial biofilm on implants or tissue surfaces.

Up-regulation of the leukocyte beta 2 integrin, CD18, is a key event in neutrophil-endothelial adhesion and neutrophil-mediated organ injury. Inhibition of CD18 with monoclonal antibodies reduces lung and liver neutrophil sequestration in animal models of Gram-negative bacteremia or endotoxemia. However, with a persistent septic challenge, interference with host leukocyte phagocytic defense could adversely affect outcome. To assess the effects of inhibiting CD18 on organ neutrophil responses, bacteremia, and organ injury after fecal peritonitis, mice underwent cecal ligation and puncture (CLP). At the time of CLP and 12 h later, mice received intravenous anti-CD18 antibody or control IgG. At 3, 6, and 18 h after CLP, lung and liver tissue neutrophil content were measured by myeloperoxidase (MPO) assay, peritoneal cells and blood leukocytes were differentially counted, blood was cultured, and serum aspartate aminotransferase was measured. There was a significant reduction in peritoneal neutrophil migration and an increase in blood neutrophils after anti-CD18 treatment compared with results from treatment with the control antibody. In the anti-CD18-treated group, liver MPO was increased fivefold at 6 and 18 h, while lung MPO was increased two-fold at 18 h when compared with the control antibody-treated group. The anti-CD18-treated group also had an increase in bacteria cultured from the blood at 6 and 18 h and an increase in serum aminotransferase at 18 h. Our data demonstrate that peritoneal neutrophil migration in response to an endogenous fecal challenge is CD18-dependent, and that this mechanism forms a vital part of host defense. Inhibition of CD18 increased neutrophil sequestration in the liver and lung and increased liver injury. This study demonstrates a paradoxical increase in organ neutrophil sequestration using a leukocyte anti-adhesion therapy during sepsis and suggests that anti-adhesion therapies targeted towards neutrophil may worsen outcome if given during an ongoing, localized infection.

The roles of endotoxin (LPS) and tumor necrosis factor-alpha (TNF-alpha) in the causation of organ injury during sepsis are unclear. To study LPS and TNF-alpha in the genesis of lung inflammation after cecal ligation and puncture (CLP), we used endotoxin-resistant (C3H/HeJ) and endotoxin-sensitive mice (C3H/HeOuJ). We examined lung neutrophil sequestration, interleukin 1 (IL-1)beta mRNA expression, IL-1 beta protein expression, and injury. We also determined the expression of two C-X-C chemokine mRNAs, macrophage inflammatory protein-2 (MIP-2) and KC, in the lung to determine whether in vivo, endotoxin, or TNF-alpha are significant modulators of MIP-2 and KC mRNA expression. After CLP, increased neutrophils sequestrated in the lungs of both strains of mice and coincided with an increase in expression of IL-1 beta, MIP-2 and KC mRNAs, and IL-1 beta protein. Lung and serum TNF-alpha were significantly increased in the C3H/HeOuJ strain but not in the C3H/HeJ strain. Histologic studies of the lung revealed similar injury in both strains. Our results suggest that bacterial factors other than endotoxin cause lung neutrophil sequestration and injury after CLP and, further, that TNF-alpha production is not a prerequisite. Our findings also suggest a potential role for local pulmonary chemokine production in the control of neutrophil sequestration after CLP.

Objective: The purpose of the study is to determine whether organ failure develops in patients despite control of peritoneal infection and whether the process is, in part, neutrophil (polymorphonuclear leukocyte [PMN]) mediated., Summary Background Data: Peritonitis generally responds to prompt surgical intervention and systemic antibiotics; however, some patients continue a septic course and progress to organ failure and death., Methods: One hundred five consecutive patients with peritonitis between 1988 and 1996 who required operation and a postoperative hospital stay greater than 10 days were studied. Mice were injected with a monoclonal anti-PMN antibody 24 hours before cecal ligation and puncture (CLP) to deplete PMNs., Results: Thirty-eight patients died, and all but 1 had identified organ failure. Seventy-seven patients had either pulmonary failure alone (25 patients) or as a component of multisystem organ failure (52 patients). All but one of these patients showed resolution of their intraperitoneal infection as evident by clinical course, abdominal computed tomographic scan, second-look laparotomy, or autopsy. Recurrent intra-abdominal infection developed in 15 patients, but only 1 had organ failure, and 2 died. At 18 hours after CLP, lung injury, PMN content, interleukin-1 mRNA expression, and liver injury were significantly reduced by anti-PMN treatment, whereas serum endotoxin levels actually increased., Conclusions: Disease acuity and organ failure, and not recurrent peritoneal infection, are the major causes of adverse outcome in patients with peritonitis. The authors' experimental data indicate that such organ injury is, in part, PMN mediated but not endotoxin mediated. Attraction of PMNs toward the site of primary infection, and thereby away from remote organs, is a logical future therapeutic approach in such patients who are critically ill with peritonitis.

Bacterial cell wall products such as lipopolysaccharide (LPS) and muramyl dipeptide (MDP) have the capacity to enhance immune responses to antigens. The expression of surface class II major histocompatibility antigens and the costimulatory receptors CD18 and CD54/ICAM-1 (intercellular adhesion molecule) was used to evaluate the comparative influence of these immunostimulators. On monocytes, both LPS and MDP increased the expression of human leukocyte antigen (HLA)-DR (maximal at 6 hr), CD18 (maximal at 1-3 hr), and ICAM-1 (maximal at 18-24 hr for LPS and 12 hr for MDP) without increasing the production of superoxide. MDP-induced ICAM-1 expression on monocytes returned to baseline values after 12 hr. On lymphocytes, only LPS increased ICAM-1 (after 18 hr) without affecting CD18, and a differential analysis demonstrated a generalized ICAM-1 upregulation in lymphocyte subsets after 18 hr: the most pronounced effect was measured in natural killer cells, followed by CD8(+) T cells, B cells, and CD4(+) T cells. MDP did not alter ICAM-1 or CD18 expression on lymphocytes. These similar but smaller effects of MDP may, in part, explain the lesser toxicity of MDP when compared to LPS.