The acute inflammatory reaction

Leukotriene inhibition in hamster periodontitis. A histochemical and morphometric study

The effects of leukotriene (LT) inhibition on gingival and adjacent bone compartments were assessed by using phenidone (100 mg/kg/d) and ketoconazole (50 mg/kg/d) given for 4 weeks to periodontitis-affected hamsters. In the gingiva the two agents significantly decreased PMNL recruitment and migration and increased the vascular lumen. At the bone level, they reduced significantly preosteoclast and osteoclast numbers but did not affect osteoclast activity. Phenidone had no action on periodontitis induced inhibition of bone formation; in contrast ketoconazole enhanced formation. As both phenidone and ketoconazole are unspecific LT inhibitors it cannot be ascertained that the effects observed were actually due to LT inhibition. However, phenidone and ketoconazole induced changes different from indomethacin used in previous studies to inhibit the cyclooxygenase pathway. These discrepancies suggest that LT inhibition occurred in the present study and that they participate in gingival inflammation and osteoclastic destruction during hamster periodontitis.

Inhibiting nonmuscle myosin II impedes inflammatory infiltration and ameliorates progressive renal disease

The motor protein nonmuscle myosin II (NMII) through its interaction with the actin cytoskeleton constitutes the machinery of cell crawling and has an important role in driving locomotion and infiltration of immune competent cells during inflammatory response and immune reaction. Blebbistatin is a highly selective inhibitor of NMII adenosine triphosphatase. This study examined the effect of NMII inhibition by blebbistatin on inflammation. In vitro, blebbistatin markedly induced actinomyosin complex disassembly in various cultured immunocytes, and functionally impaired their motile activity and invasive capacity as assessed by the Boyden chamber motility assay and the matrigel invasion assay. In vivo, in a rat model of acute inflammation induced by tumor necrosis factor, blebbistatin obliterated renal sequestration of circulating fluorescence-labeled macrophages in a dose-dependent fashion. Moreover, in rats with progressive obstructive nephropathy, blebbistatin treatment exhibited a remarkable renoprotective effect, as evidenced by normalized kidney weight, improved gross morphology, and diminished histologic injury in the tubulointerstitium. This beneficial effect was associated with significant amelioration of renal inflammation, consistent with a primary anti-inflammatory action by blebbistatin. In addition, in rats with established obstructive nephropathy, blebbistatin pretreated macrophages showed obliterated recruitment into the inflamed renal parenchyma, denoting that blebbistatin directly impedes inflammatory infiltration by immunocytes. Collectively, our findings suggest that inhibition of NMII has a potent and direct anti-inflammatory effect on the basis of impairment of the actinomyosin powered locomotive machinery, which is essential for migration and infiltration of immune competent cells.

Hepatocyte growth factor suppresses acute renal inflammation by inhibition of endothelial E-selectin

Vascular endothelial activation, marked by de novo expression of E-selectin, is an early and essential event in the process of leukocyte extravasation and inflammation. Evidence suggests that hepatocyte growth factor (HGF) ameliorates inflammation in animal models of renal disease, implying that HGF might inhibit specific components of the inflammatory response. This study examined the effect of HGF on endothelial E-selectin expression in acute inflammation induced by tumor necrosis factor (TNF)-α. In vitro, HGF suppressed TNF-α-induced cell surface expression of E-selectin in human umbilical vein endothelial cells (HUVEC) and inhibited E-selectin mediated monocytic adhesion to endothelial monolayers. HGF activated phosphatidylinositol 3-kinase (PI3K)–Akt that in turn inhibited its downstream transducer glycogen synthase kinase (GSK)3. Blockade of the PI3K–Akt pathway with specific inhibitors abrogated HGF induced inhibitory phosphorylation of GSK3 and suppression of E-selectin. In addition, selective inhibition of GSK3 activity by lithium suppressed TNF-α-induced E-selectin expression and monocytic adhesion, reminiscent of the action of HGF. Moreover, ectopic expression of an uninhibitable mutant GSK3β, in which the regulatory serine-9 is replaced by alanine, abolished HGF's suppressive effect on endothelial E-selectin. In vivo, administration of exogenous HGF reduced endothelial expression of E-selectin induced by bolus injection of TNF-α. This was associated with less sequestration of circulating fluorescence-labeled macrophages in the kidney. These findings suggest that HGF ameliorates acute renal inflammation in part by downregulating E-selectin mediated macrophage adhesion to the inflamed endothelium.

Early antioxidant therapy with Tempol during hemorrhagic shock increases survival in rats

BACKGROUND

Hemorrhagic shock (HS) is associated with the generation of reactive oxygen species, which may contribute to delayed multiple organ system failure and death. Previous studies have shown that the antioxidant Tempol improved physiologic variables, although not necessarily outcome, in septic shock and HS. We hypothesized that the combination of free Tempol with polynitroxylated albumin (PNA)-bound Tempol (which prolongs half-life and decreases toxicity) improves outcome after HS in rats.

METHODS

In study 1, HS was induced by blood withdrawal of 3 mL/100 g over 15 minutes. Mean arterial pressure was maintained at 40 mm Hg with either infusion of normal saline or withdrawal of blood from 20 to 90 minutes. Resuscitation (90-270 minutes) was with infusion of shed blood. Observation was to 72 hours. At HS 45 min, albumin (ALB) (n = 10) or PNA + Tempol (n = 10) was infused slowly (1 mL/100 g/h) until 120 minutes. Study 2 was the same as study 1 (n = 6 per group), but terminated at 150 minutes. Study 3 was the same as study 1, but started with ALB or PNA + Tempol (n = 7 per group) at 20 minutes. The primary outcome variable in studies 1 and 3 was survival, whereas the primary outcome variables in study 2 were antioxidant reserve (ability of the serum or tissue homogenate to scavenge peroxyl radicals produced by 2,2'-azobis [2-aminodipropane]-dihydrochloride) in serum and small intestine, and low-molecular-weight thiols in tissues (liver, small intestine, and kidney).

RESULTS

In study 1, 72-hour survival was 1 of 10 (ALB group) versus 2 of 10 (PNA + Tempol group). At 90 minutes, pH was lower in the ALB group versus the PNA + Tempol group (p = 0.02) and remained low. Arterial lactate increased to 8.9 +/- 3.2 (mean +/- SD) versus 6.5 +/- 1.8 mmol/L (p = 0.04) and base excess was -9.6 +/- 4.3 versus -5.2 +/- 3.2 mmol/L (p = 0.01) (ALB vs. PNA + Tempol groups, respectively). In study 2, antioxidant reserve in serum was lower in the ALB group versus the PNA + Tempol group (p = 0.002). There were no differences between groups in antioxidant reserve in the small intestine or low-molecular-weight thiols in liver, kidney, and small intestine. In study 3, 72-hour survival was zero of seven (ALB group) versus five of seven (PNA + Tempol group) (p = 0.02). Heart rate and systolic blood pressure during late HS were higher in the ALB group in studies 1 and 3 (p < 0.05).

CONCLUSION

When infused early in HS, PNA + Tempol can increase survival. When given late, it significantly improves acid-base and serum antioxidant status, without an effect on survival. Additional studies will be required to determine whether early resuscitation with PNA + Tempol attenuates reactive oxygen species-mediated injury as the mechanism for preventing the progression toward multiple organ failure and death after HS. The results suggest that antioxidant therapy with Tempol deserves further study as a potential adjunct in the initial resuscitation from HS.

Microcirculatory effects of experimental acute limb ischaemia-reperfusion

BACKGROUND

The object of this study was to develop an animal model in which changes in microvascular haemodynamics and leucocyte-vessel wall interactions due to acute limb ischaemia-reperfusion (I/R) can be measured in the skin. Furthermore, it was investigated whether these changes are related to local muscle injury.

METHODS

Male Lewis rats were subjected to unilateral limb ischaemia for 1 h (n = 8) or 2 h (n = 8) by cuff inflation, or to a sham protocol (n = 6). Intravital video microscopic measurements of leucocyte-vessel wall interactions, venular diameter, red blood cell velocity and reduced velocity (which is proportional to wall shear rate) were performed in skin venules before ischaemia and at 0.5, 1, 2, 3 and 4 h after the start of reperfusion. Oedema and leucocyte infiltration of ischaemic/reperfused skeletal muscle were quantified histologically.

RESULTS

In skin venules, both 1 and 2 h of ischaemia induced a significant increase in leucocyte rolling (six and five times baseline, respectively; P < 0.05) and adherence during reperfusion (eight and four times baseline; P < 0.05). No significant increase in muscular leucocyte infiltration was detected. After an initial hyperaemic response of 180 per cent of baseline values (P < 0.05), blood flow decreased to about 60 per cent after 4 h of reperfusion in skin venules of both experimental groups. I/R induced tibial muscle oedema, the severity of which depended on the ischaemic interval (wet to dry ratio: control, 4.0; 1 h, 4.5 (P not significant); 2 h, 5.8 (P < 0.05)).

CONCLUSION

A non-invasive animal model was developed that enables investigation of the consequences of acute limb I/R.

Endotoxin-induced lung inflammation is independent of the complement membrane attack complex

Several products of the activated complement system are known to modulate endothelial cell function in vitro. It has been shown that the membrane attack complex (MAC) (C5b-C9) can enhance tumor necrosis factor alpha (TNF-alpha)-induced expression of P- and E-selectin and intercellular adhesion molecule type 1 in cell cultures of human umbilical vein endothelial cells. In the present study the potential role of this synegism for lung injury during endotoxin-mediated septic shock in vivo was examined using a model of C6-deficient PVG (C-) (RT1(C)) rats and the congenic PVG (C+) (RT1(C)) strain. Following administration of a high (5 mg/kg) or low (0.5 mg/kg) dose of lipopolysaccharide (LPS) (Escherichia coli O55:B5), we determined the expression of cytokines, chemokines, and adhesion molecules as well as the recruitment of leukocytes in the lung. Challenge with intraperitoneal i.p. injections of LPS resulted in a strong induction of TNF-alpha, interleukin-1alpha/beta, cytokine-induced neutrophil chemoattractant, interferon-inducible protein 10, macrophage inflammatory proteins 1alpha and 2, macrophage chemotactic protein 1, and P-selectin. However, there were no significant differences between PVG (C-) and PVG (C+) rats. Immunoperoxidase staining showed a similar increase of lung infiltration by CD11b/c(+) leukocytes in both rat strains. We therefore conclude that the described synergism between TNF-alpha and the MAC of the complement system on the induction of endothelial adhesion molecules is dispensable for inflammatory processes during endotoxin-mediated septic shock in vivo.

Loxosceles spider venom induces the production of alpha and beta chemokines: implications for the pathogenesis of dermonecrotic arachnidism

Bites from the brown recluse spider and other Loxosceles arachnids result in dermonecrotic skin lesions. Neutrophils (PMN) are essential to the development of Loxosceles-induced skin lesions, but paradoxically, in vitro PMN activation is inhibited by direct exposure to Loxosceles venom. Neutrophil activation occurs in response to a myriad of soluble mediators that include members of both the alpha and beta chemokine families. Because arachnid envenomation results in the exposure of several different cell types to venom, we investigated venom-induced expression of alpha and beta chemokines in both endothelial cells (human umbilical vein; HUVEC) and epithelial cells (A549 pneumocytes). Chemokine-specific capture enzyme immunoassays (EIA) were used to measure Loxosceles deserta venom-induced alpha chemokines: interleukin-8 (IL-8), growth-related oncogene-alpha (GRO-alpha), and beta chemokines: monocyte chemoattractant protein-1(MCP-1), and regulated on activation, normal T cell expressed and secreted (RANTES) in cell-free conditioned media from HUVEC and A549 cell monolayers. Exposure of HUVECs (8 h) to Laxosceles venom resulted in the production of IL-8 (5.2+/-1.30 ng/ml), MCP-1 (1.44+/-0.11 ng/ml) and GRO-alpha (1.97+/-0.15 ng/ml) in a dose and time-dependent manner. Exposure of A549 cell monolayers to venom resulted in IL-8 (7.74+/-0.30 ng/ml), and MCP-1 (2.61+/-0.31 ng/ml), but neither GRO-alpha nor RANTES accumulated during an 8-hour incubation period. Chemokines accumulated in a venom dose and time-dependent manner. Neither cell type secreted RANTES in response to Loxosceles venom. These data indicate that Loxosceles spider venom is a potent inducer of alpha and beta chemokines in both endothelial and epithelial cell types. Based on the established roles of IL-8, MCP-1, and GRO-alpha, in inflammation, these observations have relevance to the pathophysiology of Loxosceles-induced dermonecrosis.

Reactive oxygen product formation after Fc gamma receptor-mediated neutrophil activation by monomeric mouse IgG2a: implications for the generation of first dose effects after OKT3 treatment

In the present study, we provide evidence that IgG2a monoclonal antibody (mAb) OKT3 is able to induce reactive oxygen intermediate (ROI) formation in polymorphonuclear leukocytes (PMN) when Fc gamma RIIIB as well as Fc gamma RII are bound concomitantly. Inhibition of binding to either Fc gamma R by specific mAb (3G8 or IV.3, respectively) resulted in complete abrogation of the OKT3-induced respiratory burst. The effect of OKT3 was independent from its specificity and thus also from its T cell-activating property, since nonbinding IgG2a isotype controls induced similar amounts of ROI. The IgG2b mAb BMA031 as well as the respective nonbinding isotype control were only minimally effective. With regard to the potential role of PMN activation in inflammation and tissue damage, our findings offer an extended explanation for the generation of initial adverse reactions to OKT3. Thus, one might speculate that the concerted action of cytokines liberated after its administration, what may lead to margination of leukocytes, and activation of PMN via Fc gamma R might produce first-dose reactions to OKT3 by directing radical-mediated damage against the endothelium.

Studies on the interaction of leucocytes and the myocardial vasculature

Granulocytes play an important role in increasing the infarct size after ischemia and reperfusion by the release of oxygen-derived free radicals (ODFR) and lysosomal enzymes. It has been shown that the number of granulocytes adhering to the vascular endothelium increases after occlusion of the coronary artery, and that the area of myocardial damage can be reduced by preventing granulocyte adherence with monoclonal antibodies directed against adhesion receptors. The underlying mechanism of granulocyte activation under these conditions is not yet known. We have investigated whether granulocytes can be activated directly by reduced oxygen tensions. Granulocytes were suspended in a hypoxic buffer and incubated on fibronectin and gelatin coated microtitre plates at 1-3% ambient oxygen to study their ability to adhere to these matrices. The results showed that the adherence of granulocytes to fibronectin was dependent on the duration of hypoxia. After 30 min of incubation under hypoxia granulocyte adherence increased 1.3 to 1.8 fold compared to the normoxic control. The adherence to fibronectin could be inhibited partially by anti-CD18 antibody, a monoclonal antibody to the common beta chain of a class of extracellular matrix receptors. This direct activation of granulocytes due to hypoxic conditions may have implications for the interaction of these cells with the vascular endothelium in vivo.

Effect of Haemophilus somnus on phagocytosis and hydrogen peroxide production by bovine polymorphonuclear leukocytes

The interactions between bovine polymorphonuclear leukocytes (PMNs) and the bacterium Haemophilus somnus are known to be complex. In this paper, we evaluated the effect of H. somnus on PMN function using a flow cytometric (FC) technique that simultaneously determined the extent of phagocytosis and hydrogen peroxide production by PMNs, as well as using conventional techniques, such as the nitroblue tetrazolium (NBT) and chemiluminescence assays, to analyse the PMN respiratory burst. Results from the FC and chemiluminescence assays demonstrated that in vitro exposure of PMNs to logarithmically growing H. somnus reduced the respiratory burst of PMNs obtained from healthy calves. However, this reduction was not detected by the NBT assay. A decrease in phagocytosis by PMNs could also be shown using the FC assay. In addition, PMNs from calves with acute Hemophilosis (i.e. exposed to H. somnus in vivo) showed reduced activity when compared to PMNs from healthy calves. These in vitro and in vivo observations indicate that the modulation of bovine PMN function by H. somnus may contribute significantly towards the pathogenesis of the disease.

Cell adhesion molecules: a unifying approach to topographic biology

Cell adhesion molecules are pivotal to the development and maintenance of tissue structure in metazoan organisms. In mammals, several families of proteins are involved in cell-cell and cell-matrix adhesion. The cadherins are homophilic, primary CAMs, involved in the establishment of boundaries between cell collectives early in embryogenesis. The Ig gene superfamily have diversified widely, with homophilic and heterophilic CAMs and antigen recognition molecules amongst the members. The Integrin family play an important role in binding to extracellular matrix, as well as counter-receptors on the surface of other cells. The Selectin family and HCAM are carbohydrate-binding proteins, and play a prominent role in the circulation of lymphocytes and neoplastic cells. CAMs are fundamental to development of tissue structure in metazoan organisms. Cellular differentiation dictates adherence to a specific microenvironment, through the pattern of surface CAM expression. Conversely, CAM binding can affect gene expression within the cell itself. Cell differentiation and cell adhesion are interdependent processes. In the adult, CAM are crucial to tissue maintenance. Cells frequently change their adhesive properties in response to physiological or pathological processes. The integrity of the vascular system is maintained by circulating platelets which are capable of rapid upregulation of cell adhesion and profound changes in metabolism, on contact with subendothelial matrix. Both endothelial cells and neutrophils undergo changes in CAM expression in response to inflammatory mediators, permitting rapid and appropriate recruitment of phagocytes to damaged tissue. Tissue repair is dependent on phenotypic changes in normally static cells, allowing increased motility and replication. The immune system requires constitutive cells to undergo multiple complex adhesion and detachment events over short periods of time, and is capable of discriminating normal self from aberrant-self or non-self, through antigen specific recognition and adhesion molecules. The pathophysiology of processes such as infection and neoplasia are profoundly affected by cellular CAM expression. CAMs and related molecules are fundamental to the development, maintenance and surveillance of tissue structure.

The activation of polymorphonuclear neutrophils and the complement system during immunotherapy with recombinant interleukin-2

The toxicity due to interleukin-2 (IL-2) strongly resembles the clinical picture seen during septic shock. In septic shock activation of polymorphonuclear neutrophils (PMN) and the complement system contribute significantly to the pathophysiology of the condition. We therefore investigated whether similar events contributed to the toxicity observed with IL-2. Four patients received seven cycles of escalating dose IL-2 (18.0 to 72.0 X 10(6) IU m-2 day-1) and 16 were treated with 20 cycles of fixed dose IL-2 (12.0 or 18.0 X 10(6) IU m-2 day-1). Toxicity, as judged by hypotension (P = less than 0.005) and capillary leakage (fall in serum albumin 18.2 vs 4.0 gm l-1; P = less than 0.0005 and weight gain 4.0 vs 1.2 kg; P = less than 0.025) were worse with the esc. dose protocol. PMN became activated following IL-2 with mean peak elastase/alpha 1-antitrypsin (E alpha 1 A) and lactoferrin values of 212 (SEM = 37) and 534 (SEM = 92) ng ml-1 respectively occurring 6 h after the IL-2. Peak values for the esc. dose IL-2 group being generally higher than 500 ng ml-1. Activation of the complement cascade was evidenced by a dose dependent elevation of peak C3a values (fixed dose 9.1 (SEM = 0.6); esc. dose 25.7 (SEM = 6.33); P = less than 0.005) on day 5 of IL-2. There was a significant correlation between C3a levels and the degree of hypotention during the first 24 h after IL-2 (r = 0.91) and parameters of capillary leakage such as weight gain and fall in serum albumin (r = 0.71). These data suggest that activation of PMN initiates endothelial cell damage which subsequently leads to activation of the complement cascade. This latter system then contributes to the haemodynamic changes and capillary leakage seen in IL-2 treated patients.

Hypochlorous acid-induced mobilization of zinc from metalloproteins

Hypochlorous acid (HOCl), a neutrophil oxidant, can contribute to tissue injury at sites of inflammation by its reactivity with protein sulfhydryls. The present study shows that physiological concentrations (50-200 microM) of HOCl can displace Zn2+ from metalloproteins, such as metallothionein and alcohol dehydrogenase, in which the metal is bound to sulfhydryls by means of thiolate (S-Zn) bonds. No mobilization of Zn2+ was observed from superoxide dismutase in which the metal is not bound to cysteine, suggesting that HOCl reacts selectively with thiolate bonds. Zn2+ mobilization, measured spectrophotometrically with the metallochromic indicator 4-(2-pyridylazo)resorcinol, was also observed from complexes of this metal with other thiol-containing compounds such as 2,3-dimercaptopropanol and metallothionein fragment 56-61. HOCl cleavage of the thiolate bonds was confirmed by the decrease in absorbance at 250 nm. This study shows for the first time that HOCl can mobilize protein-bound Zn2+ and suggests that neutrophil oxidant injury may be partially mediated by the mobilization of cellular Zn2+.

The cell in shock: the origin of multiple organ failure

The immediate organ damage seen after multiple trauma and in shock is a typical example of non-bacterial inflammation triggered by activation of various mediators of both the humoral and cellular systems. Anaphylatoxins and the low-flow syndrome during the shock phase account for increased PMN* margination, which in turn causes pulmonary leukostasis and may provoke massive mediator release by PMN (oxygen radicals, proteinases, eicosanoids, PAF etc). This probably leads to severe endothelial cell damage, especially in the lung. Adherence of PMN to the endothelium appears to create the micro-environment where high concentrations of proteolytic enzymes and reactive oxygen radicals exert a deleterious effect on the cell membrane. Endothelial cell membrane injury leads to increased vascular permeability and cell edema. The development of the 'organ in shock' may require a few hours and initially cause minor or no functional impairment at all. Only when shock is severe is there early organ failure, which in this stage may still be an expression of non-bacterial inflammation. Numerous studies have reported the existence of shock-induced cardiodepressant substances in association with various forms of circulatory shock. We have determined a net negative inotropic effect of the low-molecular-weight plasma fraction in severe hypovolemic-traumatic shock and have isolated a cardiodepressant factor (CDF), which by blockade of the calcium inward current has a negative inotropic a chronotropic effect. The intestine as a shock organ appears to range first among the organs involved. The translocation of bacteria from the intestinal tract, the 'intestine in shock' represents the trigger reaction that eventually leads from the 'organ in shock', early organ failure to late (septic) organ failure. Here the most prominent factor is endotoxin (LPS) as a basic mediator of gram-negative bacteria, which also triggers the activation of humoral and cellular systems. The posttraumatic hyperdynamic phase commonly starts on days 3-5 and is mainly caused by bacteremia and/or endotoxemia. Macrophages have a major impact on the late phase of organ failure. At present, the most prominent cellular mediator of the lethal effect of endotoxin is thought to be cachectin, which is identical with the tumor necrotising factor (TNF). TNF is secreted by monocytes/macrophages (MO/MA) in response to LPS. Via macrophage derived cytokines and by LPS there is activation of endothelial cells, with increased adhesiveness for PMN. Both due to this increased adhesiveness and the presence of LPS and cytokines, PMN undergo massive activation, which causes mediator release and tissue damage.(ABSTRACT TRUNCATED AT 400 WORDS)

Expression of adhesion molecules and histocompatibility antigens at the blood-brain barrier

The migration of inflammatory cells through the blood-brain barrier in health and disease involves complex interactions between hematogenous cells, endothelial cells, the basement membrane and the perivascular glia limitans. Recent evidence is presented, suggesting that part of these interactions involve antigen independent mechanisms, mediated by cellular adhesion molecules. The accessibility of endothelial adhesion molecules in the intact blood-brain barrier is lower compared to vessels in other organs. This may account for the low traffic of hematogenous cells through the normal blood-brain barrier. However, in inflammatory conditions the expression of endothelial adhesion molecules is upregulated, which may lead to recruitment of inflammatory cells into the lesions. Antigen specific activation of T-cells at the blood-brain barrier apparently takes place mainly at perivascular monocytes and microglia cells. In severe inflammatory lesions, however, astrocytes may be additionally involved in antigen presentation.