Search

The aim of this study was to assess the utility applying an electron microscopy (EM) scoring system used in idiopathic membranous nephritis based on the location of subepithelial and/or intramembranous electron dense deposits in interpretation of renal biopsies from patients with lupus nephritis. We selected patients with electron dense deposits traditionally associated with membranous changes on EM from 84 patients treated with bolus cyclophosphamide, with five years follow-up. An EM scoring system designed for idiopathic membranous nephritis was applied (stages I or II, mild changes; stages III or IV, advanced changes). Twenty-seven out of 84 had membranous changes by light microscopy, of whom 22 had satisfactory tissue for EM membranous analysis. Eleven out of 22 had mild EM changes (EM stage I or II); 11 had advanced disease (EM stage III). Advanced EM stage was associated with a higher serum creatinine at entry when tests were adjusted for WHO class (2.62 + 0.6 versus 1.31 + 0.28 mg/dL, P, 0.022 by ANOVA), and EM stage was independent of NIH activity or chronicity indexes or disease duration. After five years, adverse outcomes (death or dialysis) were seen in one of the 11 patients with EM stages I-II versus five of the 11 EM stage III patients (P, 0.07). Advanced membranous type electron dense deposition in lupus as assessed by EM was associated with worse renal function in patients with comparable WHO classification and NIH activity and chronicity indexes. In this group of lupus patients initiating cyclophosphamide for severe nephritis, EM stage provided important additional information regarding the extent of renal injury.

Objective To define techniques used for complement measurements and examine the clinical relevance of alterations of complement determinations in disease. Data Sources Data have been assembled from the authors' research, original articles, and reviews, as well as chapters and complete books on complement. Study Selection Studies were chosen for inclusion by the opinions of the authors, relevant complement reviews, publications, and books. Results Complement has been shown to possess approximately 31 proteins, some of which are enzymes (C1r, C1s, C2, factor B, factor D), some cofactors, some inhibitors or inactivators, and others composed of membrane-integrated proteins. All of the complement proteins have been purified, and many of the respective genes have been identified. The complement cascade is a dual-edged sword, causing protection against bacterial and viral invasion by promoting phagocytosis and inflammation. Pathologically, complement can cause substantial damage to blood vessels (vasculitis), kidney basement membrane and attached endothelial and epithelial cells (nephritis), joint synovium (arthritis), and erythrocytes (hemolysis) if it is not adequately controlled. Conclusions Definitive evidence is available that complement-mediated tissue destruction occurs after immune complex injury in the kidney and lung and may be important in lupus erythematosus and adult respiratory distress syndrome. Future studies on complement receptor structure and function may provide clues to treat effectively lupus, hemolytic anemias, and nephritis. In addition, gene therapy and antibody therapy need further refinement to treat immunodeficiency diseases.

Improved standards for the evaluation of therapeutic interventions in systemic lupus erythematosus (SLE) are needed. The purpose of this study by a committee of the American College of Rheumatology was to define clinically meaningful improvement, no change, or worsening in 6 existing clinical measures of SLE disease activity. This represents an important step in a disease in which some organ symptoms get better and others get worse. It is intended to help investigators develop sample size estimates based on meaningful effect sizes and to gauge the clinical relevance of any observed change in disease activity.Medical records from 310 patients drawn from 3 sources were abstracted into a standard format. Each vignette included clinical and laboratory data obtained during 2-3 visits. Ratings on the following 6 instruments were obtained for the same patients during the visit or retrospectively: the British Isles Lupus Assessment Group (BILAG), the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), the revised Systemic Lupus Activity Measure (SLAM-R), the European Consensus Lupus Activity Measure (ECLAM), the Safety of Estrogens in Lupus Erythematosus: National Assessment (SELENA)-SLEDAI, and the Responder Index for Lupus Erythematosus (RIFLE). From this pool of vignettes, 5 common vignettes and 10 randomly selected vignettes were rated through a secure Web site by 88 international experts on SLE. The experts, who were blinded to the activity measure scores, were asked to rate each patient's clinical condition as worsened, improved, or unchanged relative to the previous visit. These ratings were transformed by statistical procedures into performance characteristic curves that related a change on a particular SLE activity measure to the physicians' agreement on whether that patient had worsened, improved, or remained the same clinically. These were discussed by the committee members, who were blinded to the actual instrument used. The committee then voted on what level of expert agreement would be used to determine clinically meaningful change.The physician ratings on the 5 common vignettes revealed considerable variation in their clinical appraisals. Overall, the 6 SLE activity measures showed excellent separation of clinical conditions as being worsened, improved, or the same. The committee voted to take 70% agreement by physicians as the point on the performance characteristic curves at which meaningful change in a score could be identified. For each instrument, we computed the units of change required to indicate improvement or worsening.To our knowledge, these are the first response criteria in any disease where a clinically relevant change has been determined a priori and mapped to standardized measures. This criterion should aid the clinical evaluation of new therapies, improve comparability between trials, and facilitate innovative trial designs.

The present studies demonstrate that infusion of a type B specific lectin derived from the mushroom Marasmius oreades (MOA) into mice binds selectively to the glomerular endothelial cells via surface carbohydrate moieties resulting in cell injury and death associated with platelet-fibrin thrombi. This selective MOA binding to the endothelial cells can be abrogated by a sugar specific for the carbohydrate sequence. Hemolytic-Uremic Syndrome (HUS) and the closely associated Thrombotic Thrombocytopenic Purpura (TTP) are diseases associated with widespread microvascular injury in various organs. Clinically, these diseases are associated with microangiopathic hemolytic anemia and thrombocytopenia. The kidney glomerulus is a primary target of this microvascular injury. There are many underlying etiologies including bacterial toxins. Experimentally, such toxins injure endothelial cells in vitro but in vivo studies have failed to reproduce the characteristic renal pathology. We suggest that MOA-induced glomerular microangiopathic injury could be used to study the pathophysiology of endothelial cell injury as related to glomerular microangiopathic injury.

Recent studies have demonstrated important pro-inflammatory roles for two matrix metalloproteinases (MMPs)-MMP-3 (stromelysin-1) and MMP-9 (gelatinase B)-in acute lung injury [Am. J. Respir. Cell Mol. Biol. 24 (2001) 1]. A role for MMP-3 in skin inflammation has also been demonstrated [Proc. Natl. Acad. Sci. U. S. A. 96 (1999) 6885]. While leukocytes (neutrophils and macrophages) are known to elaborate these tissue-destructive enzymes, parenchymal cells are also capable of synthesizing MMPs. In the present study, we examined the production of MMP-3 and MMP-9 by rodent lung fibroblasts, type II epithelial cells, and vascular endothelial cells. Dermal fibroblasts were also examined. Cells were examined under control conditions and in response to agonists that induce acute inflammatory tissue injury (IgG-containing immune complexes and lipopolysaccharide [LPS]). In the absence of stimulation, MMP-3 and MMP-9 were not detected or were present at low level. However, upon stimulation with either of the two pro-inflammatory agonists, production of both enzymes occurred in fibroblasts and epithelial cells (though not in endothelial cells). The observation that resident cells in the tissue parenchyma can elaborate MMPs in direct response to pro-inflammatory stimuli provides insight into possible mechanisms by which tissue damage occurs in acute inflammation.

OBJECTIVE: To devise new tools to assess activity and damage in patients with idiopathic myopathies (IIM). METHODS: An international multidisciplinary consensus effort to standardize the conduct and reporting of the myositis clinical trials has been established. Two tools, known as the myositis intention to treat index (MITAX) and the myositis disease activity assessment visual analogue scale (MYOACT), have been developed to capture activity in patients with IIM. In addition, the myositis damage index (MDI) has been devised to assess the extent and severity of damage developing in different organs and systems. These measures have been reviewed by the myositis experts participating in the International Myositis Assessment and Clinical Studies (IMACS) group and have been found to have good face validity and to be comprehensive. The instruments were assessed in two real patient exercises involving patients with adult dermatomyositis and inclusion body myositis. RESULTS: The reliability of MITAX, MYOACT and MDI, measured by the intraclass correlation coefficient among the physicians, and the inter-rater reliability, as assessed by variation in the physicians' rating of patients, was fair to good for most aspects of the tools. Reliability and inter-rater agreement improved at the second exercise after the participants had completed additional training. CONCLUSIONS: The MITAX, MYOACT and MDI tools, which are now undergoing validity testing, should enhance the consistency, comprehensiveness and reliability of disease activity and damage assessment in patients with myositis.

The properties of a proapoptotic 1,4-benzodiazepine, Bz-423, identified through combinatorial chemistry and phenotype screening are described. Bz-423 rapidly generated superoxide (O(2)(-)) in transformed Ramos B cells. This O(2)(-) response originated from mitochondria prior to mitochondrial transmembrane gradient collapse and opening of the permeability transition pore. Bz-423-induced O(2)(-) functioned as an upstream signal that initiated an apoptotic program characterized by cytochrome c release, mitochondrial depolarization, and caspase activation. Pretreatment of cells with agents that either block the formation of Bz-423-induced O(2)(-) or scavenge free radicals attenuated the death cascade, which demonstrated that cell killing by Bz-423 depends on O(2)(-). Parallels between Ramos cells and germinal center B cells prompted experiments to determine whether Bz-423 had therapeutic activity in vivo. This possibility was tested using the (NZB x NZW)F(1) murine model of lupus, in which the pathologically enhanced survival and expansion of germinal center B cells mediate disease. Administration of Bz-423 for 12 weeks specifically controlled germinal center hyperplasia and reduced the histological evidence of glomerulonephritis. Collectively, these studies define a new structure-function relationship for benzodiazepines and point to a new target and mechanism that could be of value for developing improved drugs to manage systemic lupus erythematosus and related disorders.

Study objective The overall physiologic effect of partial liquid ventilation (PLV) in the setting of unilateral lung injury remains unclear. Therefore, we evaluated the effect of PLV on gas exchange in unilateral lung injury. Design and methods Left unilateral lung injury was induced in 14 adult dogs by oleic acid instillation into a left pulmonary artery. The animals were divided into two groups: gas ventilation (GV) and PLV. During both GV and PLV, systemic blood gas levels were analyzed. Oxygen consumption ( V ˙ o2), carbon dioxide production ( V ˙ co2) and pulmonary blood flow (Q) of both the right lung (uninjured lung) and left lung (injured lung) were measured. Results During PLV, V ˙ o2 of the injured left lung ( V ˙ o2-injured), V ˙ co2 of the injured left lung ( V ˙ co2-injured), and Q of the injured left lung (Q-injured) were greater than those in GV ( V ˙ o2-injured, 41.6 mL/min vs 23.4 mL/min, p=0.006; V ˙ co2-injured, 34.4 mL/min vs 25.5 mL/min, p=0.026; and Q-injured, 0.47 L/min vs 0.22 L/min, p=0.002, respectively). However, overall Pao2 during PLV was less than that during GV, likely due to either a redistribution of Q toward the injured lung (PLV Q-injured, 0.47 L/min vs GV Q-injured, 0.22 L/min; p=0.002) or reduced gas exchange efficiency in the healthy lung. Conclusions We conclude that in our model, PLV increases V ˙ o2 and Vco2 in the injured lung. However, over all gas exchange efficiency is reduced.

DNA methylation modifies gene expression. Methylation patterns are established during ontogeny, but they change with aging, usually with a net decrease in methylation. The significance of this change in T cells is unknown, but it could contribute to autoimmunity, senescence, or both. We examined the effects of a null mutation in DNA methyltransferase 1 (Dnmt1), a gene maintaining DNA methylation patterns, on immune aging. Whereas aged control mice developed hypomethylated DNA, autoimmunity, and signs of immune senescence as predicted, the knockout mice surprisingly increased DNA methylation and developed signs of autoimmunity and senescence more slowly. To identify potential mechanisms, we compared transcripts of DNA methyltransferase and methylcytosine binding protein family members in control and knockout mice. MeCP2, a methylcytosine binding protein involved in gene suppression and chromatin inactivation, was the only transcript differentially expressed between old knockout mice and controls, and thus it is a candidate for a gene product mediating these effects.

Mice heterozygous (+/-) for either heregulin (HRG), ErbB2, or ErbB3 were created by gene targeting, resulting in the loss of one functional gene copy and an associated decrease in targeted protein. We examined the in vivo activity of recombinant HRG peptide, rHRG beta1 (amino acids 177 to 241), in the three heterozygous mouse lines and in wild-type (WT) mice, both pregnant and nonpregnant. Nonpregnant WT and HRG(+/-) mice of both sexes were sensitive to rHRG beta1 treatment as evidenced by a high mortality rate associated with abdominal enlargement and parietal cell loss. However, pregnant WT mice and ErbB2 and ErbB3 heterozygous mice treated with rHRG beta1 were less affected, with significantly lower mortality rates and a less severe abdominal phenotype. Histological analysis revealed extensive breast ductal hyperplasia in females of all genotypes after rHRG beta1 treatment. Hyperplasia of other epithelial tissues such as the pancreas and intestine and the growth of cardiac nerve bundles were also observed, independent of sex.

Prostate tissue was obtained from 22 radical prostatectomies (performed for clinical management of prostate carcinoma) immediately after surgery. A small piece of tissue was fixed immediately in formalin and used for routine histology while a second piece was frozen in OCT and used for immuno-histochemistry. Another small piece was used for isolation of epithelial and stromal cells. The remainder of the tissue was cut into 2 × 2 mm pieces and incubated in organ culture for 8 days. In organ culture, non-malignant, basal epithelial cells underwent a proliferative response. This was accompanied by de-differentiation of glandular structures and by migration of epithelial cells across the surface of the tissue. Erosion of the basement membrane could also be seen in places, but was not widespread. Invasion of epithelial cells into the adjacent stroma was not evident. Production of matrix metalloproteinases (MMPs) with gelatinolytic activity or collagenolytic activity was assessed in organ culture and compared to expression patterns in fresh tissue. MMP-1 (interstitial collagenase) and MMP-9 (92-kDa gelatinase B) were undetectable or low in fresh tissue specimens. Both enzymes were detected in organ culture and both increased over time. Even after 6 days, however, there was only a low level of gelatin-hydrolytic activity and no measurable collagen-hydrolytic activity. In past studies we used organ cultures of normal skin and malignant skin tumours (basal cell carcinomas) to help elucidate the role of collagenolytic and gelatinolytic MMPs in epithelial cell invasion (Varani et al, 2000). Compared to MMP levels observed in skin, levels of these enzymes in prostate are low. The low level of collagenolytic and gelatinolytic MMPs in fresh prostate tissue and in organ-cultured prostate tissue may help explain why there is little tissue destruction in many primary prostate tumours and why the majority of such tumours remain confined to the prostate for extended periods. © 2001 Cancer Research Campaign http://www.bjcancer.com

We examined the effects of decreasing respiratory rate (RR) at variable inspiratory times (It) and reducing inspiratory flow on the development of ventilator-induced lung injury.Forty sheep weighing 24.6+/-3.2 kg were ventilated for 6 hours with one of five strategies (FIO2 = 1.0, positive end-expiratory pressure = 5 cm H2O): (1) pressure-controlled ventilation (PCV), RR = 15 breaths/min, peak inspiratory pressure (PIP) = 25 cm H2O, n = 8; (2) PCV, RR = 15 breaths/min, PIP = 50 cm H2O, n = 8; (3) PCV, RR = 5 breaths/min, PIP = 50 cm H2O, It = 6 seconds, n = 8; (4) PCV, RR = 5 breaths/min, PIP = 50 cm H2O, It = 2 seconds, n = 8; and (5) limited inspiratory flow volume-controlled ventilation, RR = 5 breaths/min, pressure-limit = 50 cm H2O, flow = 15 L/min, n = 8.Decreasing RR at conventional flows did not reduce injury. However, limiting inspiratory flow rate (LIFR) maintained compliance and resulted in lower Qs/Qt (HiPIP = 38+/-18%, LIFR = 19+/-6%, p0.001), reduced histologic injury (HiPIP = 14+/-0.9, LIFR = 2.2+/-0.9, p0.05), decreased intra-alveolar neutrophils (HiPIP = 90+/-49, LIFR = 7.6+/-3.8,p = 0.001), and reduced wet-dry lung weight (HiPIP = 87.3+/-8.5%, LIFR = 40.8+/-17.4%,p0.001).High-pressure ventilation for 6 hours using conventional flow patterns produces severe lung injury, irrespective of RR or It. Reduction of inspiratory flow at similar PIP provides pulmonary protection.

Objective To determine the role of the chemokine, macrophage inflammatory protein (MIP)-2, in the pathogenesis of aspiration-induced lung injury in the rat. Design Prospective, randomized, controlled animal study. Setting University research laboratories. Subjects Adult, male Long-Evans rats. Interventions Anesthetized rats underwent induction of lung injury by well-described models of aspiration triggered by intra-tracheal delivery of acid alone, gastric particles alone, or the combination. After injury, induction of MIP-2 messenger RNA in whole lungs and immunoreactive MIP-2 in bronchoalveolar lavage (BAL) fluids was determined. The contribution of MIP-2 to BAL fluid chemotactic activity was defined by using an in vitro chemotaxis assay. The in vivo effect of blocking MIP-2 on pulmonary vascular leak, BAL fluid neutrophils, PaO2/FIO2 ratio, and alveolar-arterial oxygen tension gradient in acid-induced lung injury was determined. Measurements and main results Induction of MIP-2 messenger RNA and protein over time was observed in response to all three stimuli. A significant portion (25% to 41%) of the chemotactic activity in BAL fluids from injured rats was inhibited by anti-MIP-2 antibody. After acid injury, blocking of MIP-2 was associated with a 53% decrease in BAL fluid neutrophils and a 33% decrease in pulmonary vascular leak. Although acid injury both impaired oxygenation and increased venous admixture, in vivo blocking of MIP-2 was associated with improved oxygenation as well as decreased venous admixture. Conclusions MIP-2 was up-regulated during the development of aspiration-induced lung injury in rats. MIP-2 contributed to lung accumulation of neutrophils via a chemotactic mechanism. Although oxygenation and venous admixture are worsened by acid-induced lung injury in vivo, blocking of MIP-2 at the onset of injury improved these physiologic alterations. Because the aspiration event often is witnessed, chemokines may be valid therapeutic targets for inhibiting the subsequent inflammatory response.

Two nontoxic, antimicrobial nanoemulsions, BCTP and BCTP 401, have been developed. These emulsions are composed of detergents and oils in 80% water. BCTP diluted up to 1:1000 inactivated>90% of Bacillus anthracis spores in 4 h and was also sporicidal against three other Bacillus species. This sporicidal activity is due to disruption of the spore coat after initiation of germination without complete outgrowth. BCTP 401 diluted 1:1000 had greater activity than BCTP against Bacillus spores and had an onset of action of

Background Inhaled nitric oxide is often used in patients with adult respiratory distress syndrome. However, nitric oxide also may be significantly toxic, especially if administered concurrently with hyperoxia. The authors evaluated the isolated effect of nitric oxide and the combined effects of nitric oxide and hyperoxia on lung injury in rats after acid aspiration. Methods Animals were injured by instillation of 1.2 ml/kg hydrogen chloride in low-pH saline (the acid group) or acidified gastric particles (the casp group) into the lungs under halothane anesthesia via a tracheal catheter. Controls received no injury vehicle but rather underwent the surgical process. After recovery from anesthesia, the animals were exposed to 20% or 90% oxygen with or without 20, 40, or 80 ppm nitric oxide for 5 h. The permeability index, alveolar-arterial oxygen difference, the ratio of oxygen pressure to the inspired fraction of oxygen, and the ratio of wet to dry weight were assessed 5 h after injury as indices of lung injury. Data were assessed using analysis of variance. Results Each group included 6-10 rats. Exposure to nitric oxide (80 ppm) in air increased protein permeability in the lungs to a permeability index of 1.42+/-0.12 after acid aspiration. The combination of nitric oxide (80 ppm) and hyperoxia further increased protein leakage to a permeability index of 2.1+/-0.25. Exposure to lower concentrations of nitric oxide (e.g., 20 and 40 ppm) increased the permeability index of the lungs (1.44+/-0.21, 1.75+/-0.29, respectively) in the presence of hyperoxia, although it did not affect the permeability index of the lungs during exposure to air. Pretreatment of animals with deferoxamine and methylene blue partially inhibited the adverse effect of hyperoxia and nitric oxide, which suggested a complex underlying mechanism involving both reactive-species generation and pulmonary vasomotor changes. Conclusions These results show that inhaled nitric oxide at 80 ppm for a short duration (5 h) increases the severity of the inflammatory microvascular lung injury after acid aspiration. The pulmonary damage is exacerbated further in the presence of high oxygen concentrations. Although lower concentrations of nitric oxide did not increase the extent of lung injury, longer exposure times need to be assessed.

Evidence presented in the accompanying article (Gibbs, D. F., T. P. Shanley, R. L. Warner, H. S. Murphy, J. Varani, and K. J. Johnson. 1999. Role of matrix metalloproteinases in models of macrophage-dependent acute lung injury: evidence for alveolar macrophage as source of proteinases. Am. J. Respir. Cell Mol. Biol. 20:1145-1154) implicates alveolar macrophage matrix metalloproteinases (MMPs) in two models of acute lung inflammation in the rat. As a prerequisite to understanding which specific MMPs might be involved in the injury and how they might function, it was necessary to know the spectrum of enzymes present. To this end, alveolar macrophages were obtained from normal rat lungs by bronchoalveolar lavage, placed in culture with and without various agonists, and assessed by a variety of techniques for MMPs. The identification process involved characterization by gelatin, beta-casein, and kappa-elastin zymography, with confirmation of identity by Western blot/immunoprecipitation. Message levels of detected MMPs were assessed by Northern blot. Rat alveolar macrophages were found to produce a low constitutive level of MMP-2 (72-kD gelatinase A) that was only modestly upregulated following stimulation with phorbol myristate acetate, bacterial lipopolysaccharide, or immunoglobulin A-containing immune complexes. Although control cells were found to produce little or no MMP-9 (92-kD gelatinase B) or MMP-12 (metalloelastase), both enzymes were markedly upregulated upon stimulation. In the same stimulated macrophages there was little activity against type I collagen (associated with MMP-13 [collagenase-3] on the basis of Western blotting), no activity suggestive of stromelysin or matrilysin, and no measurable secretion of the serine proteinases, elastase and cathepsin G. These data demonstrate the ability of rat alveolar macrophages to elaborate certain MMPs under proinflammatory conditions, consistent with their possible involvement in the progression of acute inflammation.

Use of cyclosporine (CsA) in the management of children with steroid-resistant (SRNS) and steroid-dependent (SDNS) nephrotic syndrome has become increasingly popular in recent years. Although most children receive a renal biopsy prior to initiation of CsA, the relationship between initial renal histology and the subsequent clinical response to CsA is not known. We analyzed the correlation between pre-CsA segmental and global glomerular scarring and interstitial fibrosis and the subsequent response to CsA in 23 children (5.6+/-1.0 years, Mean+/-SEM) with SDNS (n=8) and SRNS (n=15) treated with CsA for 24.2+/-3.8 months and followed for 28.0+/-4.1 months. Complete remission was obtained in 78% of patients within 67.6+/-16 days, while 18% had a partial response and 4% no response. Quantitative histological analysis revealed a trend toward partial rather than complete response with increasing segmental glomerular (P=0.13), global glomerular (P=0.05), and interstitial (P=0.08) scarring, and among patients with minimal change nephrotic syndrome versus IgM nephropathy versus focal segmental glomerulosclerosis. Among complete responders, linear regression analyses revealed no correlation between time to response and pre-CsA glomerular or interstitial scarring. We conclude that increased glomerular or interstitial scarring on a pre-CsA renal biopsy tends to correlate with a partial, rather than complete, response to CsA in childhood nephrotic syndrome.

OBJECTIVE This study evaluates the ability of perflubron to inhibit pulmonary neutrophil accumulation during partial liquid ventilation (PLV) in the setting of acute lung injury. DESIGN Randomized, controlled, nonblinded study. SETTING Research laboratory at a university. SUBJECTS Male, Sprague-Dawley rats (n = 120, 506 +/- 42 g). INTERVENTIONS Animals were divided into eight groups (n = 15 in each group, of which n = 12 for myeloperoxidase content and n = 3 for histologic neutrophil counting): a) GV-CVF group, animals received gas ventilation (GV) with the induction of lung injury using cobra venom factor (CVF); b) PLV-CVF group, animals received partial liquid ventilation before the induction of lung injury; c) PEEP-CVF group, animals received positive end-expiratory pressure (PEEP) before the administration of cobra venom factor; d) CVF-PLV group, animals received partial liquid ventilation after cobra venom factor; e) CVF-PEEP group, animals received PEEP after cobra venom factor; f) PLV only group, animals received partial liquid ventilation only; g) GV only group, animals received gas ventilation only; and h) NVSBA group, nonventilated spontaneous breathing animals. MEASUREMENTS AND MAIN RESULTS After the experimental period, total lung myeloperoxidase content was significantly decreased in the PLV-CVF (0.29 +/- 0.08, p = .02) and PEEP-CVF (0.34 +/- 0.04, p = .01) groups when compared with the GV-CVF group (0.62 +/- 0.07). When compared with the GV-CVF group, a trend toward a reduction in myeloperoxidase was observed in the CVF-PLV (0.42 +/- 0.05, p = .07) and the CVF-PEEP (0.39 +/- 0.06, p = .07) groups. When compared with the cobra venom factor only group (GV-CVF 47 +/- 2 neutrophils/high-power field), reductions in neutrophil count were observed in all groups (neutrophils/high-power field): PLV-CVF (20 +/- 2, p = .009); PEEP-CVF (24 +/- 1, p = .01); CVF-PLV (30 +/- 2, p = .03); and CVF-PEEP (37 +/- 1, p = .04). CONCLUSION These data suggest that both partial liquid ventilation and PEEP result in a reduction in neutrophil accumulation in the setting of acute lung injury.

Hyperoxia increases pulmonary damage after acid aspiration. We hypothesize that free radicals play a role in acute lung injury. To examine this hypothesis, we injured rats by intratracheal instillation of acidic isotonic sodium chloride solution (NS) (pH 1.25); NS + gastric particles (particle pH 5.3); or acid + particles (pH 1.25). Animals were exposed to 98% oxygen or air for 5 h. Superoxide (HO2) generation was measured in either an aliquot of white blood cells (WBCs) recovered from bronchoalveolar lavage (BAL) or from blood. Lungs were analyzed for thiobarbituric acid-reactive substances (TBARS) and carbonylated proteins. The antioxidant capacity was measured using a 2-2'-azo-bis-amidinopropane hydrochloride neutralizing assay. Generation of HO2 by WBCs in peripheral blood was greater in animals exposed to 98% O2 (89.8 +/- 12.5 U. min-1.10(5) neutrophils) compared with air exposure (37.5 +/- 9.2 U.min-1.10(5) neutrophils) after combined injury (P0.05). Similarly, HO2 generation by WBCs retrieved from BAL was higher in oxygen-exposed rats (987.74 +/- 128 U.min-1.10(5) WBC) compared with air-exposed animals after an identical injury (348 +/- 9.2 U. min-1.10(5) WBC) (P0.05). TBARS and carbonylated protein levels in the lungs of oxygen-exposed animals (587.9 +/- 58.6 and 55.8 +/- 3.1 pmol/mg of protein, respectively) were higher than those in air-exposed rats after combined injury (342.8 +/- 15.1 and 28.6 +/- 4.6 pmol/mg of protein, respectively) and compared with air-exposed uninjured rats (340.6 +/- 9.8 and 18.3 +/- 2.8 pmol/mg of protein, respectively; P0.01). Antioxidant capacity decreased in acid and combined injury groups (2.41 +/- 0.13 min and 1.94 +/- 0.15 min, respectively) compared with the uninjured group after 5 h of exposure to 98% oxygen (4.85 +/- 0.19 min; P0.01). We demonstrated evidence of increased oxidant activity on lipids and proteins in injured lungs after oxygen exposure. The decrease in antioxidant capacity after low pH aspiration with exposure to hyperoxia may contribute to this increase.Oxygen administration results in a lung pathology known as oxygen toxicity. This effect is usually not significant if the duration of exposure is limited to24 h. In the presence of acute inflammatory lung injury, exposure to hyperoxia results in lung damage in a shorter time. We demonstrate that sufficiently decreased lung antioxidant reserve capacity may be accountable for this early toxicity.

To examine the effects of an increase in ambient oxygen (O2) concentrations on the extent of inflammatory pulmonary damage following acid aspiration.Prospective, controlled laboratory study.University-affiliated animal research facility.Male, Long Evans rats weighing 250 to 300 g.Rats were injured by instillation of 1.2 mL/kg normal saline solution/HCl, pH= 1.25 (acid), into the lungs via a tracheotomy. Animals were allowed to awaken and were exposed to 21%, 50%, or 98% O2 for 0 to 5 h (n/groupor = 10). In a separate set of experiments, injured rats exposed to 98% O2 were treated with different doses of deferoxamine, just prior to injury. Uninjured rats and rats injured with normal saline solution, pH = 5.3, were used as the control group.Injury was determined by assessing lung function (lung compliance and arterial blood gases) and alveolar-capillary wall integrity (wet/dry weight, lung albumin permeability index [PI], and intrapulmonary hemorrhage [HI]).Intrapulmonary instillation of acid increased PI, HI, and decreased static lung compliance compared to uninjured control animals. Increased ambient oxygen following acid aspiration decreased lung compliance, 1.06+/-0.03 mL/kg/cm H2O, in oxygen-exposed lungs when compared to the lungs exposed to air, 1.26+/-0.04, following a low pH aspirate (p0.05). An increase in protein leakage into the lung tissue was noted in oxygen-exposed animals, PI=1.33+/-0.10, vs air-exposed rats, 0.89+/-0.07 (p0.05). The hyperoxia-induced increase in lung injury was prevented by 30 mg/kg or higher deferoxamine treatment, 0.78+/-0.05 (p0.05). Exposure of animals to 98% O2 for 2 h was sufficient to produce the same increase in microvascular protein leakage as 5-h exposure to O2 following low pH aspirate.Hyperoxia increases acid aspiration-induced inflammatory microvascular lung injury. This appears to be mediated by production of reactive species of O2.

Objective. T cells treated with DNA methylation inhibitors overexpress lymphocyte function-associated antigen 1 (LFA-1), which results in autoreactivity, and the autoreactive cells cause a lupus-like disease in vivo, suggesting a mechanism by which some agents may cause drug-induced lupus. This study compared the effects of procainamide (Pca) and hydralazine (Hyd) with those of structural analogs, to determine if the degree of LFA-1 overexpression and T cell autoreactivity correlated with the ability of the agents to induce autoimmunity. Methods. Cloned murine T helper 2 cells were treated with Pca, N-acetylprocainamide, Hyd, Phthalazine, or hydroxyurea (HU). The treated cells were then compared for LFA-1 overexpression, autoreactivity, and the ability to induce autoimmunity in vivo. Results. Pca and Hyd were more potent than their analogs or HU in all 3 assays. Conclusion. The results support a relationship between LFA-1 overexpression, T cell autoreactivity, and autoimmunity, and suggest a mechanism by which Pca and Hyd, but not the analogs, may cause drug-induced lupus.

Considerable attention is directed to a surprising biologic phenomenon wherein tissues exposed to one insult acquire resistance to another. We identify a novel example of acquired resistance to acute renal failure and a mechanism that contributes to such resistance. Nephrotoxic serum, administered to rats 24 h before the induction of glycerol-induced acute renal failure, reduces functional and structural injury that occurs in this model. Since heme oxygenase, the rate-limiting enzyme in heme degradation, protects against heme protein-induced renal injury, we questioned whether induction of heme oxygenase underlies the protection afforded by nephrotoxic serum. Kidney heme oxygenase (HO-1) mRNA was induced 6 h after nephrotoxic serum and renal tubules were identified as the site of expression of heme oxygenase protein. Induction of heme oxygenase was accompanied by increased renal content of ferritin but not by induction of other antioxidant enzymes. Inhibition of heme oxygenase prevented the protection afforded by nephrotoxic serum. Nephrotoxic serum did not protect against ischemic acute renal failure, a model in which heme oxygenase is not induced. Thus, nephrotoxic serum protects against glycerol-induced acute renal failure by inducing heme oxygenase in tubules. This study provides the first demonstration of resistance to tubular injury acquired from glomerular inflammation, uncovers a mechanism for such resistance, and exposes the dialogue that occurs between glomeruli and tubules.

The complement activation product, C5a, may play a key role in the acute inflammatory response. Polyclonal antibody to rat C5a was used to define the requirements for C5a in neutrophil-dependent inflammatory lung injury after systemic activation of complement by cobra venom factor (CVF) or after intrapulmonary deposition of IgG immune complexes. In the CVF model, intravenous infusion (but not intratracheal instillation) of anti-C5a produced a dose-dependent reduction in lung permeability and in lung content of myeloperoxidase. In C6-deficient rats, CVF infusion caused the same level of lung injury (measured by leak of 125I-albumin) as found in C6-sufficient rats. In the IgG immune complex model of lung injury, anti-C5a administered intratracheally (but not intravenously) reduced in a dose-dependent manner both the increase in lung vascular permeability as well as the buildup of lung myeloperoxidase. Treatment with anti-C5a greatly suppressed upregulation of lung vascular intercellular adhesion molecule-1 (ICAM-1). This was correlated with a substantial drop in levels of TNFalpha in bronchoalveolar fluids. These data demonstrate the requirement for C5a in the two models of injury. In the IgG immune complex model, C5a is required for the full production of TNFalpha and the corresponding upregulation of lung vascular ICAM-1.

Cyclosporine (CsA) is effective in treating steroid-dependent (SDNS) and steroid-resistant (SRNS) nephrotic syndrome (NS) in children, but because of the potential for chronic nephrotoxicity, its long-term use is controversial. This study reports the results of long-term CsA treatment in 22 children with idiopathic NS. Indications for treatment included SDNS (N = 7) and SRNS (N = 15) children. Pre-CsA histology showed minimal change disease in three patients, immunoglobulin M nephropathy (IgM) in 14 patients, and focal segmental glomerulosclerosis (FSGS) in five patients. All patients had normal initial serum creatinine values. CsA was added to prednisone at 6.3 +/- 0.4 mg/kg per day (mean +/- SE) and adjusted to maintain whole blood trough HPLC levels of 70 to 120 ng/mL for a period of 6 to 53 months (mean, 22 months). Analysis by clinical course revealed that 13 of 15 patients with SRNS (87%) entered remission after a mean duration of CsA treatment of 58 days, whereas seven of seven patients with SDNS were able to be weaned off of daily prednisone therapy. Histologic analysis showed that all five patients with FSGS and 13 of 14 patients with IgM nephropathy either entered remission or were weaned off of daily steroids. Ten of the 22 patients (45%) with complete remission required CsA plus low-dose alternate-day prednisone to maintain remission. Hypertension was seen in eight of 22 patients (36%). No patient had a significant increase in serum creatinine concentration. Renal biopsies performed in 12 patients after 12 to 41 months (mean, 21 months) of CsA therapy showed no nephrotoxicity or disease progression in ten patients. Progression of the previous interstitial fibrosis and tubular atrophy was noted in two patients, suggesting a 17% incidence of CsA nephrotoxicity. This analysis of the long-term risks and benefits of CsA for childhood NS has identified two important findings: (1) combined CsA and alternate-day steroids can be highly effective in inducing complete remission in patients with SRNS and biopsy-proven IgM nephropathy, and (2) long-term use of CsA in moderate doses with closely monitored levels can result in a relatively low incidence of nephrotoxicity.

The pulmonary tree is exposed to neutrophil-derived serine proteinases and matrix metalloproteinases in inflammatory lung diseases, but the degree to which these enzymes participate in tissue injury remains undefined, as does the therapeutic utility of antiproteinase-based interventions. To address these issues, an in vivo rat model was examined in which the intrapulmonary deposition of immune complexes initiates a neutrophil-mediated acute alveolitis. In vitro studies demonstrated that rat neutrophils can release neutrophil elastase and cathepsin G as well as a neutrophil progelatinase, which was subsequently activated by either chlorinated oxidants or serine proteinases. Based on structural homologies that exist between rat and human neutrophil proteinases, rat neutrophil elastase and cathepsin G activities could be specifically regulated in vitro by recombinant human secretory leukoproteinase inhibitor, and rat neutrophil gelatinase activity proved sensitive to inhibition by recombinant human tissue inhibitor of metalloproteinases 2. When either of the recombinant antiproteinases were instilled intratracheally, in vivo lung damage as assessed by increased permeability or hemorrhage was significantly reduced. Furthermore, the coadministration of the serine and matrix metalloproteinase inhibitors almost completely prevented pulmonary damage while effecting only a modest decrease in neutrophil influx. These data support a critical role for neutrophil-derived proteinases in acute lung damage in vivo and identify recombinant human secretory leukoproteinase and recombinant human tissue inhibitor of metalloproteinases 2 as potentially efficacious interventions in inflammatory disease states.

Experimental aspiration pneumonitis studies in general have focused on the pathogenesis of the acidic component of the lung injury, although the injury produced by the particulate component of gastric contents largely has been ignored. The present study compares the inflammatory potential of small gastric particles to acidic lung injury and examines their interaction. Washed and filtered rat gastric food particles, 2-30 mu were resuspended in saline/HCl, pH = 5.3 or 1.25 at different particle densities and instilled intratracheally into anesthetized rats. Nonlethal lung injury was assessed at different times postaspiration by measuring changes in lung permeability and histology. Maximal survival after lung injury in this model occurred at a particle concentration of 40 mg/mL and at a volume of 1.5 mL/kg. Under these conditions, the alveolar capillary leak was less severe during the first 4 h after injury than that seen with a maximal nonlethal acidic injury (1.5 mL/kg, pH = 1.25). However, after 4 h postinjury the alveolar capillary leak increased to levels that were no different from the acidic injury. When the small gastric food particles were suspended in saline/HCl, pH = 1.25, the alveolar capillary leak was increased synergistically. Intratracheal instillation of inert, 10 mu (glass) particles, 40 mg/mL at 1.5 mL/kg, did not result in an increase in lung injury or interact additively or synergistically with acidic saline. Histologically, the small gastric particle injured lungs were associated with focal inflammatory changes as the acidic damage was diffuse.(ABSTRACT TRUNCATED AT 250 WORDS)

BACKGROUND The present studies were undertaken to determine the interactions between halothane and oxidative injury with respect to endothelial integrity, as measured by pulmonary capillary filtration coefficient (Kfc), and production of arachidonic acid-derived mediators, in perfused rabbit lungs challenged with the oxidant tert-butyl-hydroperoxide (t-bu-OOH). METHODS Isolated lungs were prepared from 27 New Zealand white rabbits (2-3 kg) and were perfused with Ca(2+)-free Krebs-Henseleit buffer solution. In group A (n = 9), lungs were ventilated with halothane 2.5% in carrier gas (5% CO2 in air); in group B (n = 9), with carrier gas alone; and in group C (n = 9), with carrier gas, but without injury. The lungs in the two injury groups (A and B) received four infusions of t-bu-OOH, 200 microM, over 1 min, directly into the pulmonary artery. The uninjured lungs received four infusions of vehicle (normal saline). Kfc was determined after each t-bu-OOH infusion. Concentrations of thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha were measured in samples of effluent perfusate obtained before and 30 s after the end of each infusion of t-bu-OOH. The wet/dry weight ratio of each pair of lungs was determined at the end of each experiment. RESULTS Kfc progressively increased after each infusion of oxidant in group A when compared with the other two groups. Lung wet/dry ratios were elevated in group A (14.3 +/- 0.7) and group B (13.2 +/- 0.2) compared with group C (12.1 +/- 1.1). TxB2 production in group A (2206 +/- 263 pg.min-1.g-1 dry lung tissue) was greater than in group B (1413 +/- 127) by the final infusion of t-bu-OOH. CONCLUSIONS Ex vivo perfused rabbit lungs ventilated with halothane exhibited, simultaneously, evidence of greater fluid conductance across the pulmonary capillary bed and production of thromboxane A2 when challenged with oxidant than did lungs ventilated with carrier gas. Both of these effects may be mediated by halothane-related enhancement of intracellular endothelial Ca2+ mobilization stimulated by intrapulmonary infusion of oxidant.

Human antigen-specific CD4+ T cells become autoreactive after treatment with various DNA methylation inhibitors, including 5-azacytidine, procainamide, and hydralazine. This suggests a mechanism that could contribute to the development of some forms of autoimmunity. In this report we have asked whether T cells treated with DNA methylation inhibitors can induce autoimmunity. Murine CD4+ T cells were treated with 5-azacytidine or procainamide and were shown to respond to syngeneic antigen-presenting cells, similar to CD4+ human T cell clones treated with these drugs. Functional characterization demonstrated that cells treated with either drug spontaneously lysed syngeneic macrophages and secreted IL-4, IL-6, and IFN-gamma. Adoptive transfer of 5-azacytidine- or procainamide-treated cells into unirradiated syngeneic recipients induced an immune complex glomerulonephritis and IgG anti-DNA and antihistone antibodies. These experiments demonstrate that T cells treated with either of two distinct DNA methyltransferase inhibitors are sufficient to induce a lupus-like disease. It is possible that the lysis of macrophages, together with the release of cytokines promoting B cell differentiation, contributes to the autoantibody production and immune complex deposition. These results suggest that environmental agents that inhibit DNA methylation could interact with T cells in vivo to produce a lupus-like illness, a mechanism that could have relevance to drug-induced and idiopathic lupus.

Ischemia-reperfusion injury occurs in many organs and is the underlying cause of many disease processes, including myocardial infarction, stroke, and acute renal failure, which in total are responsible for the majority of deaths seen in developed countries. Most of the injury seen with this process is associated with the reperfusion phase in which the blood flow to the ischemic tissues is reinstituted. This reperfusion phase is associated with the formation of reactive oxygen species (ROS) in the tissues, and the sources of these oxidants are both the neutrophil as well as parenchymal cells such as endothelium. In the kidney as well as other organs, antioxidant therapy is protective, suggesting an important role for these agents. However, there is emerging evidence that ROS are not solely responsible for the reperfusion injury. In many of the kidney models of ischemia-reperfusion, antioxidants are only partially effective in ameliorating the functional and morphologic alterations. Furthermore, in vitro, ROS do not appear to be primarily involved in the killing of renal tubular epithelial cells, which is the morphologic hallmark of acute renal failure. Thus, reperfusion injury, like other types of tissue injury, appears to be mediated by more than one class of inflammatory mediator.

The bone marrow produces large numbers of monocytes daily, but the mechanisms balancing production and elimination are unknown. In this report we demonstrate that macrophages (M phi) undergo apoptosis after activating autologous CD4+ cells. Since apoptosis is a genetically programmed response, these results argue that M phi death can be part of a normal immune response. This event may have relevance to monocyte/M phi homeostasis, as well as immune response regulation and host defenses to intracellular organisms.

The effect of halothane anesthesia on the influenza A specific immune response and the pathogenesis of infection was evaluated in mice. Three-wk-old CD-1 mice were anesthetized with either 2% halothane for 2 h or ketamine (100 mg/kg intraperitoneally) and subsequently inoculated intranasally with a sublethal dose of influenza type A/PR/8/34 virus. Bronchoalveolar lavage was performed on animals from each group at 4 h postinoculation and daily thereafter for 14 days. Total and differential white blood cell counts were measured in the lavage fluid and the lungs were examined histologically for evidence of injury. Infected mice anesthetized with halothane had lower daily cell counts in the lung than animals anesthetized with ketamine and a marked change in cell type distribution. On Days 4 and 11 postinoculation, there were significantly (P < 0.05) more white blood cells in the lavage fluid of animals anesthetized with ketamine than halothane (mean/mL, 738,000 +/- SEM, 128,000 vs 196,000 +/- 51,400, respectively, and 1,020,000 +/- 227,000 vs 117,000 +/- 34,600, respectively). Differential counts were significantly higher (P < 0.05) in the ketamine group compared to the halothane for neutrophils on Day 4 (452,000 +/- 77,900 vs 72,000 +/- 46,000, respectively) and on Day 11 for lymphocytes (340,000 +/- 59,000 vs 33,000 +/- 17,000, respectively) and macrophages (480,000 +/- 120,000 vs 130,000 +/- 61,000). Infected mice that were given ketamine were qualitatively "sicker" than the halothane-treated group as evidenced by the appearance of ruffled fur, tachypnea, and cachexia. Animals anesthetized with ketamine demonstrated a greater degree of pulmonary histopathology including diffuse infiltration of macrophages, neutrophils, hemorrhage, and fibrin deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

We recently reported a biphasic injury pattern of nonlethal acid aspiration pneumonitis in rats. The first phase consisted of the immediate effects of the direct tissue injury, and the second phase was associated with a neutrophilic inflammatory response. Using this model, the present report examines the possible role of neutrophils, oxidants, and proteases in the pathogenesis of the second phase of this lung injury. Acid aspiration injury was induced by instillation of saline/HCl, pH = 1.25, into the trachea of rats. Lung injury was assessed by measuring the degree of alveolar capillary permeability to 125I-labeled albumin (permeability index [PI]). Rats made neutropenic with polyclonal antineutrophil antibody had a lower PI (0.44 +/- 0.07, P less than 0.05) 6 h after acid aspiration than similarly injured animals with normal whole blood neutrophil counts (PI = 0.85 +/- 0.03). Even though neutrophils appeared necessary for the full development of the lung injury in this model, the administration of different intravenous and/or intratracheal concentrations of either deferoxamine or catalase offered no protection against injury. This suggests that neutrophil oxidants were minimally involved in the injury. Large increases in leukocyte-free serine protease activity (1,477 +/- 438 u/ml, P less than 0.05) were detected in the bronchoalveolar lavage fluid from the saline/HCl, pH = 1.25, injured rats at 6 h postinjury, as compared to saline/HCl, pH = 5.3, treated control animals (2.7 +/- 0.2 u/ml). This study supports the hypothesis that neutrophils are necessary for the full expression of acid-induced lung injury and that the generation of leukocyte-derived oxidants does not appear to be the primary mechanism involved in this injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent evidence indicates that under in vitro conditions, superoxide anion and hydrogen peroxide (H2O2) are unstable in the presence of manganese ion (Mn2+). The current studies snow that in the presence of Mn2+, H2O2-mediated injury of endothelial cells is greatly attenuated. A source of bicarbonate ion and amino acid is required for Mn2+ to exert its protective effects. Injury by phorbol ester-activated neutrophils is also attenuated under the same conditions. EDTA reverses the protective effects. Acute lung injury produced in vivo in rats by intratracheal instillation of glucose-glucose oxidase is almost completely blocked in rats treated with Mn2+ and glycine. Conversely, treatment of rats with EDTA, a chelator of Mn2+, markedly accentuates lung injury caused by glucose-glucose oxidase. These data are consistent with the findings of others that Mn2+ can facilitate direct oxidation of amino acids with concomitant H2O2 disproportionation. This could form the basis of a new therapeutic approach against oxygen radical-mediated tissue injury.

U937 cells have low levels of surface thrombospondin (TSP) under control conditions but express higher levels after treatment for 1 day with 100 nM phorbol myristate acetate (PMA). Increased surface expression is due, in part, to increased biosynthesis. Untreated U937 cells do not adhere to TSP-coated plastic culture dishes but adhere strongly to TSP after stimulation with PMA. Untreated U937 cells also adhere weakly to endothelial cell monolayers while PMA-treated U937 cells attach strongly to monolayers of rat pulmonary artery endothelial cells. Endothelial cell adhesion appears to be mediated, in part, by TSP since antibodies to TSP partially inhibit.

CD-1 mice infected with a sublethal dose of influenza A virus were anesthetized for 2 h with halothane. These mice were compared to a control group which was similarly infected using ketamine sedation. Mice anesthetized with halothane showed less physical signs of illness and demonstrated less lung histopathology than the control group of mice. Virus titers were reduced in the group of animals exposed to halothane 12 h after infection, but were the same as the infected controls at all other times measured (1–12 days after infection). Morphometric analysis of lung tissue demonstrated a delayed appearance of both neutrophils and monocytes in the halothane-exposed mice. These results suggest that the halogenated volatile anesthetic halothane decreases the pulmonary pathogenesis of influenza A virus by altering the recruitment of immunological effector cells during the course of the infection.

Using analogous models of acute dermal vasculities and alveolitis in rats, we have examined the role of oxygen-derived metabolities in the tissue damage associated with neutrophil influx into sites of immune complex deposition. In the lung, as previously reported, catalase and deferoxamine are highly protective, while superoxide dismutase (SOD) has a transient protective effect. The xanthine oxidase inhibitors, allopurinol, and lodoxamide, are also protective. In the skin, neither catalase (which has been covalently linked to the antibody) nor deferoxamine is protective, suggesting that H 2 O 2 and iron are not absolutely required for the development of dermal vasculitis. In the skin, SOD, as well as the inhibitors of xanthine oxidase, have protective effects. These data suggest that the neutrophil-mediated pahtwayws of immune complex injury in the dermal and pulmonary microvascular compartments are fundamentally different. As a measurement of neutrophil accumulation, measurements of myeloperoxidase in tissue extracts have been employed. In both the lung and skin, the protective effects of SOD and the xanthine oxidase inhibitors are paralleled by reductions in neutrophil influx into sites of injury. In contrast, catalase and deferoxamine have no effect on neutrophil accumulation. These data suggest that vascular beds in rat skin and lung are fundamentally different with respect to mechanisms of acute immune complex mediated injury. The data also provide evidence that O 2 − contributes significantly to the accumulation of neutrophils.

Adult respiratory distress syndrome (ARDS) is a multietiologic acute and progressive pulmonary dysfunction that may be precipitated by any of a number of pathogenic agents. Clinical and experimental studies suggest that activation of complement and blood neutrophils plays a significant role in the development of pulmonary vascular injury, which is an important pathophysiological feature of ARDS. Although the specific cellular and biochemical mechanisms resulting in the development of ARDS are unknown, it has been suggested that oxygen-derived free radicals generated from complement-activated granulocytes may be involved, directly or indirectly, in the destruction of lung vascular endothelium and alveolar tissue matrix. This hypothesis is supported by recent experimental studies showing that acute lung injury secondary to systemic complement activation can largely be prevented by interventions that scavenge for hydroxyl radicals or restrict availability of ionic iron.