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Nitrotyrosine is an important marker for the formation of peroxynitrite and possibly other reactive nitrogen species derived from nitric oxide in vivo (1). Pathological conditions can substantially increase the production of nitric oxide, yet this molecule itself does not generally yield nitration of tyrosine residues in proteins when added to biological samples (1,2). However nitric oxide reacts at near diffusion-limited rates with superoxide (O2−) to form the strong oxidant peroxynitrite (ONOO−) (3). Nitration on the 3-position of tyrosine is a major product of peroxynitrite attack on proteins (4,5). Certainly, small amounts of nitrotyrosine can be produced in vivo by other mechanisms (6), but peroxynitrite is by far the most efficient mechanism for nitrating tyrosine under biologically relevant conditions with natural antioxidants and alternative targets present. [ABSTRACT FROM AUTHOR]

Sepsis and septic shock are major causes of acute renal failure (ARF). Although hemodynamic factors play a significant role in the pathogenesis of ARF during sepsis, it is now clear that nonhemodynamic factors are also extremely important. The predominant site of tissue injury in sepsis-induced ARF occurs within the proximal renal tubule. In vivo studies of the specific cellular mechanisms underlying renal injury are limited by the marked heterogeneity of the nephron. Establishing primary cultures of human proximal renal tubular epithelial cells (PTEC) provides a well-characterized in vitro model, phenotypically representative of PTEC in vivo. This in vitro system allows for investigation of the cellular mechanisms underlying proximal tubular injury during sepsis, in isolation without additional complicating cardiovascular and neuroendocrine factors. [ABSTRACT FROM AUTHOR]

The human airway is normally kept sterile despite continual exposure to airborne pathogens. This is achieved by host defense mechanisms that exist to prevent adherence, colonization, and invasion of the airway epithelium. The airway is, however, a potential route by which bacteria may enter the blood-stream if host defense mechanisms can be overcome. [ABSTRACT FROM AUTHOR]

This chapter describes the use of cultured adult primary ventricular cardiomyocytes as a model for cytokine-mediated septic shock. We describe the methods for preparation of adult cardiomyocytes from adult rat hearts for culture. We also describe techniques designed to assess the responses of single cells in culture to the proinflammatory cytokine, TNFα. We describe in detail the use of this cell-culture model to evaluate TNFα-induced voltage-dependent calcium fluxes as well as the expression of genes that mediate the TNFα response. Because cardiomyocyte cultures may be heterogeneous and may include a variety of other cell types (fibroblasts, endothelial cells, etc.), it is sometimes prudent to examine cells on a single-cell basis to ensure that the physiological or molecular process of interest is characteristic of the cardiomyocyte. The issue of heterogeneity is particularly problematic when attempting to examine the expression of low-abundant transcripts using reverse transcriptase-polymerase chain reaction (RT-PCR). In our laboratory, we have employed single-cell RT-PCR as a tool for examining the expression of genes coding for TNFα receptors in isolated myocardial cells. The procedures can be applied to acutely isolated cells as well as those cultured and subjected to chronic treatments. By using these techniques, it is possible to implicate molecular mechanisms/pathways in the physiological responsiveness of the adult ventricular cardiomyocyte to cytokines. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−) is both an oxidant and a nitrating agent (1-3). However, unlike other strong oxidants, peroxynitrite reacts selectively with biological targets. This selectivity is derived in part from the different second-order rate constants (vary from 103-106M−1 s−1) by which ONOO− reacts with biological targets. Competing for peroxynitrite-mediated oxidation of biological targets are two pathways. One is the protonation to form peroxynitrous acid and the second is the reaction with CO2. Peroxynitrous acid is also an oxidant but it readily isomerizes to nitrate. The reaction with CO2 results in the formation of the ONO(O)CO2− adduct that is a more potent nitrating agent but a weaker oxidant than peroxynitrite. Peroxynitrite can diffuse through biological membranes before it encounters and reacts with biological targets. This observation implies that diffusion can effectively compete with the isomerization to nitrate or the reaction with CO2. [ABSTRACT FROM AUTHOR]

To date three distinct isoforms of nitric oxide synthase (NOS) have been identified. Two isoforms are considered to be expressed constitutively—neu-ronal NOS (nNOS; type I NOS) and endothelial NOS (eNOS; type III NOS). The third isoform is not generally present in normal cells and tissues but is induced in response to infection, inflammation or trauma—inducible NOS (iNOS; type II NOS). In 1990 Bredt and Synder (1) succeeded in developing antibodies to rat brain NOS (nNOS) and used immuncytochemistry subsequently to furnish one of the first anatomical descriptions of the distribution and localization of nNOS. Today numerous antibodies to all three NOS isoforms isolated from various tissues and different animal species are available and the application of immunocytochemistry is commonplace in the investigation of NOS in healthy and diseased tissues including human (2-6) (Fig. 1 Fig. 2 Fig. 3). [ABSTRACT FROM AUTHOR]

The measurement of the concentration of nitric oxide (NO) is a challenging problem because of the short half-life of NO (t1/2=3-6 s) in biological systems (1). The instrumental techniques used currently for NO measurements are spec-troscopic and electrochemical methods (2). Electrochemical methods offer several features that are not available from analytical spectroscopic methods. Most important is the capability afforded by the use of ultramicroelectrodes for direct in situ measurements of NO in single cells near the source of NO synthesis. NO released from the cell can be detected within a few miliseconds after injection of nitric synthase agonist, and the NO concentration on the membrane surface may vary from submicromolar to micromolar levels (3). [ABSTRACT FROM AUTHOR]

In 1990, several studies reported that an enhanced formation of endogenous nitric oxide (NO) contributes to the hypotension caused by endotoxin and tumor-necrosis factor-α (TNFα) (1-3). In addition, it became apparent that this overproduction of NO also plays an important role in the pathophysiology of the vascular hyporesponsiveness to vasoconstrictor agents (also termed vasoplegia) (4,5). Since then, many studies have reported on the effects and side effects of NO synthase (NOS) inhibitors in animal models of shock. Prior to discussing the pharmacology of various classes of NOS inhibitors, this chapter will briefly introduce the physiological role(s) of NO as well as the various (beneficial as well as detrimental) roles of NO in animal models of septic shock. [ABSTRACT FROM AUTHOR]

Substantial interest has been generated by the potential roles of the cytokines in health and disease (1). This has prompted considerable investigation into how these mediators are regulated to answer such basic questions as which stimuli initiate transcription and what factors are responsible for inhibiting secretion. This has resulted in elegant studies that have begun to define the intracellular-signaling pathways responsible for the upregulation of cytokines (2,3). Many of these studies have been done with cultures of cell lines derived from cancers or primary cultures of isolated fibroblasts, endothelial cells, or isolated mononuclear cells. Whereas these studies have provided substantial insight, they may be limited in their scope because they do not include all cell-cell or cell-protein interactions that take place in vivo. Other studies have used endotoxin injection into normal human volunteers to study the upregulation of cytokines (4,5). These studies with the normal volunteers provide precise information about the kinetics of cytokine production, but they are difficult to perform and very expensive. The whole-blood model serves as a useful bridge between using normal volunteers and isolated peripheral blood mononuclear cells. For critically ill patients it would be impossible to perform endotoxin infusion studies, and it would even be difficult to conduct these types of studies in chronically ill patients. Whole blood may also be used to study the immune responses of such patients in an attempt to determine how their cytokine regulation differs from normal individuals. [ABSTRACT FROM AUTHOR]

Over the last decade, numerous basic biological as well as experimental and clinical studies have firmly established the significance of tumor necrosis factor (TNF) as a principal proximal mediator of sepsis (1-4). One of the major insights that has emerged during recent years has been that under physiological circumstances, TNF activity is tightly controlled and locally restricted. In this respect, the soluble TNF receptors (sTNF-Rs) have been recognized to exert an important regulatory control on the biological actions of TNF, not only in the normal host defense against infection, but also in systemic inflammatory disorders that are related to infectious as well as noninfectious etiologies. Moreover, elevated systemic levels of sTNF-R have been demonstrated to have accurate diagnostic as well as prognostic significance in clinical sepsis and other critical illnesses (5-13). Therefore, accurate determination of sTNF-R in plasma or serum has become an important tool to gain information about a variety of pathological conditions that are characterized by TNF-mediated immune activation, both in the experimental and in the clinical setting. [ABSTRACT FROM AUTHOR]

The realization that much of the toxicity of bacterial endotoxin resulted from production of a macrophage-derived intermediate (1) led to the isolation and cloning of tumor necrosis factor (TNF), also known as cachectin (2). Since then, much evidence has accumulated to demonstrate that TNF is of prime importance in the pathogenesis of endotoxin-related tissue injury, and occupies a key proximal position in the cascade of mediators that are produced as a result of bacterial infection. These conclusions have been based in part on the accurate measurement of TNF in blood and other body fluids of humans and animals as a result of infection. [ABSTRACT FROM AUTHOR]

This chapter describes a quantitative assay for the streptococcal superantigen, streptococcal pyrogenic exotoxin A (SPEA), which can be used in broth, tissue-culture media, and certain sera. The protocol can be adapted to allow measurement of any bacterial superantigen or protein toxin, using different oligonucleotides to amplify the coding sequences from bacterial DNA. Previously, measurement of bacterial toxins such as SPEA was limited by poor test sensitivity and test samples could only be analyzed if concentrated. Techniques included Ouchterlony immunodiffusion or enzyme-linked immuno-sorbent assay (ELISA), although the lower limit of detection was 100-fold greater than that achievable in this system. (1-3) Recent methods described have achieved improved sensitivities, some using sandwich ELISA techniques, others using competitive ELISA techniques. (4-8). [ABSTRACT FROM AUTHOR]

Group A streptococci secrete a variety of molecules, many of which are recognized as virulence factors important in the establishment of streptococcal infections. Among these extracellular products is streptococcal pyrogenic exotoxin A (SPE A, scarlet fever toxin A, erythrogenic toxin A) (1). Other SPEs include toxin serotypes B and C (1), streptococcal superantigen (SSA) (2), and SPE F (mitogenic factor) (3,4). Combinations of these toxins are believed to be important in streptococcal toxic shock syndrome. The latter two molecules will not be discussed in this chapter, but methods utilized to purify SPEs A-C also may be used to purify SSA and SPE F. [ABSTRACT FROM AUTHOR]

Lipopolysaccharide (LPS)-binding protein (LBP) is a critical component of innate immunity, implicated in the initiation of host defences against Gram-negative bacteria. LBP alerts the host to the presence of minute amounts of LPS (1). LPS released from Gram-negative bacteria is present as aggregates, because of the amphiphilic structure of the molecule. LPS aggregates are transformed to monomers by the action of LBP, which has been described as a lipid-transfer molecule catalyzing movement of phospholipids including LPS (2-6). When LPS/LBP monomers are transferred to lipoproteins, LPS is inactivated; when LPS/LBP complexes are transferred to cells harboring CD14 at their surface, cells are activated. Thus, the relative contribution of these two pathways will determine the response of the host to LPS. [ABSTRACT FROM AUTHOR]

Polymorphonuclear leukocytes (PMN) play a prominent role in host defense in mammals against invading bacteria (1,2). Among the essential attributes of these highly specialized cells are the elaboration of an array of cytotoxic peptides and polypeptides that can be targeted at bacterial prey. This includes the bactericidal/permeability-increasing protein (BPI), a cytotoxic protein that at nM concentrations acts selectively against many Gram-negative bacteria. The principal determinant of the target-cell selectivity and potency of BPI is its ability to bind avidly to lipopolysaccarides (LPS), abundant glycolipids found uniquely in the outer leaflet of the outer membrane of these bacteria (3,4). Binding of BPI to bacterial outer membrane LPS not only initiates antibacterial cytotoxicity but also blocks the potent pro-inflammatory activity of this bacterial product (5). Host responses to LPS fuel the delivery of host defenses (e.g., PMN) to sites of infection but can also lead to profound inflammatory injury if inadequately regulated (4,6). By contributing to the eradication of the bacteria that produce LPS and by blocking the activity of LPS already present, BPI can play a major role in elimination of invading Gram-negative bacteria and in downregulating further host responses to these bacteria. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides (LPS) constitute components of the outer membrane of Gram-negative bacteria. Chemically, they consist of a heteropolysaccharide and a covalently linked lipid, termed lipid A. The polysaccharide region is made up of the O-specific chain (built from repeating units of three to eight sugars) and the core part, divided into the inner core (the part linked to the lipid) and the outer core (the part linked to the O-specific chain). LPSs possessing an O-specific chain are called smooth LPS (S-LPS), those not having an O-chain are termed rough (R-LPS). The latter type of LPS may be observed in mutants that have lost the ability to synthesize the O-chain, or in wild-type bacteria without known genetic defect. LPS also represent the endotoxin of Gram-negative bacteria. In mammals, including humans, LPS exhibits a variety of biological effects that may be beneficial if administered in low amounts but harmful when present in higher concentrations as in the case of Gram-negative infection and Gram-negative septicemia. [ABSTRACT FROM AUTHOR]

Endotoxins have been recognized for decades as important structural components of the outer cell wall/cell membrane complex of Gram-negative microorganisms. These chemically heterogeneous macromolecular structures were recognized very early on to consist of lipid, polysaccharide, and protein, and to have the capacity to induce deleterious pathophysiological changes when administered either systemically or locally to a wide variety of experimental laboratory animals. The recognition of the very significant disease-causing potential of these interesting microbial constituents provided a sound conceptual basis for studies directed at the isolation, purification, and detailed chemical characterization of the active constituent(s). It is perhaps not particularly surprising, therefore, that there are now numerous methods and modifications of methods, that have been published in the scientific literature describing various approaches that have been employed for the extraction and purification of endotoxin from bacteria. It would be beyond the scope of this chapter to describe in detail all of these various methods. Therefore, we shall provide only a brief historical perspective of the evolution of different methodologies. We will then focus upon a more detailed discussion of those that will ultimately serve the investigative purposes of most researchers interested in isolating and purifying endotoxins. [ABSTRACT FROM AUTHOR]

Horseshoe crabs fight off infectious agents with a complex array of proteins present in amebocytes, the major cell type in their hemolymph. These amebocytes contain both large and small granules (1). When exposed to bacteria or other infectious agents the amebocytes release proteins into their surroundings by exocytosis. The small granules of Limulus amebocytes contain antibacterial proteins, including polyphemusins and the big defensins (2). The large granules contain the Limulus anti-lipopolysaccharide factor (LALF) and the clot-forming group of serine protease zymogens. Exocytosis is initiated by the reaction of amebocytes with lipopolysaccharide (LPS) from Gram-negative bacteria or other microbial components. LPS is also called endotoxin because it is found in the outer membrane of the gram-negative bacterial cell wall. A solid clot forms in response to the lipid A portion of LPS, thereby walling off the infection site or preventing the loss of blood when the animal is damaged physically (3). [ABSTRACT FROM AUTHOR]