Inflammatory response leading to organ dysfunction and failure continues to be the major problem after injury in many clinical conditions such as sepsis, severe burns, acute pancreatitis, haemorrhagic shock, and trauma. In general terms, systemic inflammatory response syndrome (SIRS) is an entirely normal response to injury. Systemic leukocyte activation, however, is a direct consequence of a SIRS and if excessive, can lead to distant organ damage and multiple organ dysfunction syndrome (MODS). When SIRS leads to MODS and organ failure, the mortality becomes high and can be more than 50%. Acute lung injury that clinically manifests as acute respiratory distress syndrome (ARDS) is a major component of MODS of various aetiologies. Inflammatory mediators play a key role in the pathogenesis of ARDS, which is the primary cause of death in these conditions. This review summarizes recent studies that demonstrate the critical role played by inflammatory mediators such as tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, platelet activating factor (PAF), IL-10, granulocyte macrophage-colony stimulating factor (GM-CSF), C5a, intercellular adhesion molecule (ICAM)-1, substance P, chemokines, VEGF, IGF-I, KGF, reactive oxygen species (ROS), and reactive nitrogen species (RNS) in the pathogenesis of ARDS. It is reasonable to speculate that elucidation of the key mediators in ARDS coupled with the discovery of specific inhibitors would make it possible to develop clinically effective anti-inflammatory therapy.

Hydrogen sulfide (H2S) is synthesized in the body from L-cysteine by several enzymes including cystathionine-gamma-lyase (CSE). To date, there is little information about the potential role of H2S in inflammation. We have now investigated the part played by H2S in endotoxin-induced inflammation in the mouse. E. coli lipopolysaccharide (LPS) administration produced a dose (10 and 20 mg/kg ip)- and time (6 and 24 h)-dependent increase in plasma H2S concentration. LPS (10 mg/kg ip, 6 h) increased plasma H2S concentration from 34.1 +/- 0.7 microM to 40.9 +/- 0.6 microM (n=6, P<0.05) while H2S formation from added L-cysteine was increased in both liver and kidney. CSE gene expression was also increased in both liver (94.2+/-2.7%, n=6, P<0.05) and kidney (77.5+/-3.2%, n=6, P<0.05). LPS injection also elevated lung (148.2+/-2.6%, n=6, P<0.05) and kidney (78.8+/-8.2%, n=6, P<0.05) myeloperoxidase (MPO, a marker of tissue neutrophil infiltration) activity alongside histological evidence of lung, liver, and kidney tissue inflammatory damage. Plasma nitrate/nitrite (NOx) concentration was additionally elevated in a time- and dose-dependent manner in LPS-injected animals. To examine directly the possible proinflammatory effect of H2S, mice were administered sodium hydrosulfide (H2S donor drug, 14 micromol/kg ip) that resulted in marked histological signs of lung inflammation, increased lung and liver MPO activity, and raised plasma TNF-alpha concentration (4.6+/-1.4 ng/ml, n=6). In contrast, DL-propargylglycine (CSE inhibitor, 50 mg/kg ip), exhibited marked anti-inflammatory activity as evidenced by reduced lung and liver MPO activity, and ameliorated lung and liver tissue damage. In separate experiments, we also detected significantly higher (150.5+/-43.7 microM c.f. 43.8+/-5.1 microM, n=5, P<0.05) plasma H2S levels in humans with septic shock. These findings suggest that H2S exhibits proinflammatory activity in endotoxic shock and suggest a new approach to the development of novel drugs for this condition.

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Background and Purpose: The aim of these experiments was to evaluate the significance of the chemical reaction between hydrogen sulphide (H 2 S) and nitric oxide (NO) for the control of vascular tone. Experimental Approach: The effect of sodium hydrosulphide (NaHS; H 2 S donor) and a range of NO donors, such as sodium nitroprusside (SNP), either alone or together, was determined using phenylephrine (PE)-precontracted rat aortic rings and on the blood pressure of anaesthetised rats. Key Results: Mixing NaHS with NO donors inhibited the vasorelaxant effect of NO both in vitro and in vivo. Low concentrations of NaHS or H 2 S gas in solution reversed the relaxant effect of acetylcholine (ACh, 400 nM) and histamine (100 mM) but not isoprenaline (400 nM). The effect of NaHS on the ACh response was antagonized by CuSO 4 (200 nM) but was unaffected by glibenclamide (10 mM). In contrast, high concentrations of NaHS (200-1600 mM) relaxed aortic rings directly, an effect reduced by glibenclamide but unaffected by CuSO 4 . Intravenous infusion of a low concentration of NaHS (10 mmol kg -1 min -1 ) into the anaesthetized rat significantly increased mean arterial blood pressure. L-NAME (25 mg kg -1 , i.v.) pretreatment reduced this effect. Conclusions and Implications: These results suggest that H 2 S and NO react together to form a molecule (possibly a nitrosothiol) which exhibits little or no vasorelaxant activity either in vitro or in vivo. We propose that a crucial, and hitherto unappreciated, role of H 2 S in the vascular system is the regulation of the availability of NO.

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Substance P, acting via the neurokinin 1 receptor (NK1R), plays an important role in mediating a variety of inf lammatory processes. However, its role in acute pancreatitis has not been previously described. We have found that, in normal mice, substance P levels in the pancreas and pancreatic acinar cell expression of NK1R are both increased during secretagogue-induced experimental pancreatitis. To evaluate the role of substance P, pancreatitis was induced in mice that genetically lack NK1R by administration of 12 hourly injections of a supramaximally stimulating dose of the secretagogue caerulein. During pancreatitis, the magnitude of hyperamylasemia, hyperlipasemia, neutrophil sequestration in the pancreas, and pancreatic acinar cell necrosis were significantly reduced in NK1R؊͞؊ mice when compared with wild-type NK1R؉͞؉ animals. Similarly, pancreatitisassociated lung injury, as characterized by intrapulmonary sequestration of neutrophils and increased pulmonary microvascular permeability, was reduced in NK1R؊͞؊ animals. These effects of NK1R deletion indicate that substance P, acting via NK1R, plays an important proinf lammatory role in regulating the severity of acute pancreatitis and pancreatitisassociated lung injury.The neuropeptide substance P has been shown to play an important role in asthma, inflammatory bowel disease, arthritis, and other inflammatory processes (1, 2). Subsequent to its release from nerve endings, substance P binds to neurokinin 1 receptors (NK1R) on effector cells, increases microvascular permeability, and promotes plasma extravasation from the intravascular to the extravascular space. Although pancreatic acinar cells are known to express NK1R and substance P has been detected within the pancreas (3-5), apparently no studies have been reported that have examined the possibility that this neuropeptide might play a role in the evolution of a pancreatic inflammatory disease such as acute pancreatitis. We have found that pancreatic levels of substance P and the expression of NK1R on pancreatic acinar cells are increased during experimental acute pancreatitis. We have also found that genetic deletion of NK1R reduces the severity of pancreatitis and pancreatitis-associated lung injury. These observations indicate that substance P, acting through NK1R, plays an important proinflammatory role in regulating the severity of acute pancreatitis and associated lung injury. MATERIALS AND METHODSAll experiments were performed according to protocols approved by the Institutional Animal Care and Use Committee of the Beth Israel Hospital. Breeding pairs of NK1R-deficient mice were generated as described (6), and the identity of their offspring as NK1R-deficient (Ϫ͞Ϫ) homozygotes was confirmed by Southern blotting (6). Animals were bred and housed in standard shoe box cages in a climate-controlled room with an ambient temperature of 23 Ϯ 2°C and a 12-h light͞12-h dark cycle. They were fed standard laboratory chow, given water ad libitum, randomly assigned to control or experimental groups, and...

A characteristic feature of all inflammatory disorders is the excessive recruitment of leukocytes to the site of inflammation. The loss of control in trafficking these cells contributes to inflammatory diseases. Leukocyte recruitment is a well-orchestrated process that includes several protein families including the large cytokine subfamily of chemotactic cytokines, the chemokines. Chemokines and their receptors are involved in the pathogenesis of several diseases. Acute lung injury that clinically manifests as acute respiratory distress syndrome (ARDS) is caused by an uncontrolled systemic inflammatory response resulting from clinical events including major surgery, trauma, multiple transfusions, severe burns, pancreatitis, and sepsis. Systemic inflammatory response syndrome involves activation of alveolar macrophages and sequestered neutrophils in the lung. The clinical hallmarks of ARDS are severe hypoxemia, diffuse bilateral pulmonary infiltrates, and normal intracardiac filling pressures. The magnitude and duration of the inflammatory process may ultimately determine the outcome in patients with ARDS. Recent evidence shows that activated leukocytes and chemokines play a key role in the pathogenesis of ARDS. The expanding number of antagonists of chemokine receptors for inflammatory disorders may hold promise for new medicines to combat ARDS.

Hydrogen sulfide (H2S) is a naturally occurring gas with potent vasodilator activity. Cystathionine-gamma-lyase (CSE) and cystathionine-beta-synthase (CBS) utilize L-cysteine as substrate to form H2S. Of these two enzymes, cystathionine-gamma-lyase (CSE) is believed to be the key enzyme that forms H2S in the cardiovascular system. Whilst H2S has been reported to relax precontracted rat arteries in vitro and to lower blood pressure in the rat, its effect in an inflammatory condition such as acute pancreatitis has not previously been reported. In this paper, we report the presence of H2S synthesizing enzyme activity and CSE (as determined by mRNA signal) in the pancreas. Also, prophylactic, as well as therapeutic, treatment with the CSE inhibitor, DL-propargylglycine (PAG), significantly reduced the severity of caerulein-induced pancreatitis and associated lung injury, as determined by 1) hyperamylasemia [plasma amylase (U/L) (control, 1204+/-59); prophylactic treatment: placebo, 10635+/-305; PAG, 7904+/-495; therapeutic treatment: placebo, 10427+/-470; PAG, 7811+/-428; P<0.05 PAG c.f. placebo; n=24 animals in each group]; 2) neutrophil sequestration in the pancreas [pancreatic myeloperoxidase oxidase (MPO) activity (fold increase over control) (prophylactic treatment: placebo, 5.78+/-0.63; PAG, 2.97+/-0.39; therapeutic treatment: placebo, 5.48+/-0.52; PAG, 3.03+/-0.47; P<0.05 PAG c.f. placebo; n=24 animals in each group)]; 3) pancreatic acinar cell injury/necrosis; 4) lung MPO activity (fold increase over control) [prophylactic treatment: placebo, 1.99+/-0.16; PAG, 1.34+/-0.14; therapeutic treatment: placebo, 2.03+/-0.12; PAG, 1.41+/-0.97; P<0.05 PAG c.f. placebo; n=24 animals in each group]; and 5) histological evidence of lung injury. These effects of CSE blockade suggest an important proinflammatory role of H2S in regulating the severity of pancreatitis and associated lung injury and raise the possibility that H2S may exert similar activity in other forms of inflammation.