Pro-inflammatory cytokines increase reactive oxygen species through mitochondria and NADPH oxidase in cultured RPE cells

Reactive oxygen species (ROS) generated during inflammation are believed to play critical roles in various ocular diseases. However, the underlying mechanisms remain poorly understood. We investigated if pro-inflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin-1 beta (IL-1 beta), and interferon-gamma (IFN-gamma), induce ROS in human retinal pigment epithelial (RPE) cells. TNF-alpha, IL-1 beta and IFN-gamma increased both intracellular and extracellular ROS production in a time- and dose-dependent manner. Thenoyltrifluoroacetone (TTFA), an inhibitor of mitochondrial respiratory chain, blocked TNF-alpha- and IFN-gamma-, but not IL-1 beta-induced ROS, whereas other two mitochondrial respiratory chain inhibitors, rotenone and antimycin A, had no effect. NADPH oxidase inhibitor (diphenylene iodinium) abolished the ROS production induced by IL-1 beta or IFN-gamma, but not by TNF-alpha, whereas 6-aminonicotinamide (6AN), an inhibitor of the hexose monophosphate shunt (HMS), had no significant effects on the ROS induced by all three cytokines. ROS scavengers, pyrrolidinedithiocarbamate (PDTC) and N-acetyl-cysteine (NAC), reduced the levels of ROS induced by TNF-alpha, IL-1 beta and IFN-gamma (P<0.05). Collectively, these results demonstrate that TNF-alpha, IL-1 beta and IFN-gamma increase mitochondrial- and NADPH oxidase-generated ROS in human RPE cells.

Attenuation of half sulfur mustard gas-induced acute lung injury in rats

Airway instillation into rats of 2-chloroethyl ethyl sulfide (CEES), the half molecule of sulfur mustard compound, results in acute lung injury, as measured by the leak of plasma albumin into the lung. Morphologically, early changes in the lung include alveolar hemorrhage and fibrin deposition and the influx of neutrophils. Following lung contact with CEES, progressive accumulation of collagen occurred in the lung, followed by parenchymal collapse. The co-instillation with CEES of liposomes containing pegylated (PEG)-catalase (CAT), PEG-superoxide dismutase (SOD), or the combination, greatly attenuated the development of lung injury. Likewise, the co-instillation of liposomes containing the reducing agents, N-acetylcysteine (NAC), glutathione (GSH), or resveratrol (RES), significantly reduced acute lung injury. The combination of complement depletion and airway instillation of liposomes containing anti-oxidant compounds maximally attenuated CEES-induced lung injury by nearly 80%. Delayed airway instillation of anti-oxidant-containing liposomes (containing NAC or GSH, or the combination) significantly diminished lung injury even when instillation was delayed as long as 1 h after lung exposure to CEES. These data indicate that CEES-induced injury of rat lungs can be substantially diminished by the presence of reducing agents or anti-oxidant enzymes delivered via liposomes.

Protection from half-mustard-gas-induced acute lung injury in the rat

The chemical warfare agent analog, 2-chloroethyl ethyl sulfide, known as 'half-mustard gas' (HMG), is less toxic and less of an environmental hazard than the full molecule and has been shown to produce an acute lung injury in rats when instilled via intrapulmonary injection. This injury is characterized by massive, localized hemorrhage and edema into the alveolar compartment and can be quantitated by measuring extravasation of (125)I-bovine serum albumin into the extravascular compartment. Employing this rat model of HMG-induced lung injury, we observed significant attenuation of the pulmonary injury when experimental animals were complement or neutrophil depleted prior to HMG challenge. Significant protection also was provided by the use of antioxidants such as catalase, dimethyl sulfoxide, dimethyl thiourea, resveratrol and N-acetyl-L-cysteine (NAC). The last compound showed protection from lung injury as high as 70% and was still effective even when given up to 90 min after exposure of the lungs to HMG. These data suggest that acute lung injury caused by exposure to HMG may be related partially to complement mediated pathways and the generation by neutrophils of toxic oxygen species The data indicate that NAC is an effective antidote against HMG-induced acute lung injury in the rat.

Systemic and lung physiological changes in rats after intravascular activation of complement

Systemic complement activation has been noted in a variety of shock states, and there is growing evidence that, in addition to being proinflammatory effectors, products of complement activation contribute directly to generalized manifestations of shock, such as hypotension and acidosis. To study the effects of complement activation, we examined responses in rats to systemic activation of complement with cobra venom factor (CVF), including blood pressure, metabolic acidosis, changes in vascular permeability, and lung function. High doses of CVF produced circulatory collapse (mean arterial pressure = 110 ± 16 and 35 ± 9 mmHg in control and with CVF, respectively, P < 0.05), metabolic acidosis (HCO[Formula: see text] concentration = 27.8 ± 1.7 and 9.6 ± 3.4 meq/l in control and with CVF, respectively, P < 0.05), extravasation of albumin into the lung and gut, and modest arterial hypoxemia (Po 2 = 486 ± 51 and 201 ± 36 Torr in control and during 100% O2 breathing, respectively, P < 0.05). Prior depletion of complement protected against these abnormalities. Other interventions, including neutrophil depletion and cyclooxygenase inhibition, prevented lung injury but had much less effect on systemic hemodynamics or gut permeability, suggesting that complement activation products induce injury by neutrophil- and cyclooxygenase-dependent pathways in the lung but not in the gut. These studies underscore the significant systemic abnormalities developing after systemic activation of complement.

Detrimental effects of complement activation in hemorrhagic shock

The complement system has been implicated in early inflammatory events and a variety of shock states. In rats, we measured complement activation after hemorrhage and examined the hemodynamic and metabolic effects of complement depletion before injury and worsening of complement activation after hemorrhage and resuscitation [with a carboxypeptidase N inhibitor (CPNI), which blocks the clearance of C5a]. Rats were bled to a mean arterial pressure of 30 mmHg for 50 min and were then resuscitated for 2 h. Shock resulted in significant evidence of complement consumption, with serum hemolytic activity being reduced by 33% (P < 0.05). Complement depletion before injury did not affect hemorrhage volume (complement depleted = 28 +/- 1 ml/kg, complement intact = 29 +/- 1 ml/kg, P = 0.74) but improved postresuscitation mean arterial pressure by 37 mmHg (P < 0.05) and serum bicarbonate levels (complement depleted = 22 +/- 3 meq/ml, complement intact = 13 +/- 8 meq/ml, P < 0.05). Pretreatment with CPNI was lethal in 80% of treated animals vs. the untreated hemorrhaged group in which no deaths occurred (P < 0.05). In this model of hemorrhagic shock, complement activation appeared to contribute to progressive hypotension and metabolic acidosis seen after resuscitation. The lethality of CPNI during acute blood loss suggests that the anaphylatoxins are important in the pathophysiological events involved in hemorrhagic shock.

Protection by vitamin B2 against oxidant-mediated acute lung injury

The effect of vitamin B2 (riboflavin) on oxidant-mediated acute lung injury has been examined in three different rat models. Pulmonary injury was induced by intravenous injection of cobra venom factor (CVF), by the intrapulmonary deposition of IgG immune complexes, or by hind limb ischemia-reperfusion. In each of the three models, injury was characterized by increases in vascular permeability (leakage of 125I-labeled bovine serum albumin), alveolar hemorrhage (extravasation of 51Cr-labeled rat erythrocytes), and neutrophil accumulation (myeloperoxidase activity). Intraperitoneal administration of riboflavin at a dose of 6 micromoles/kg body weight reduced vascular leakage by 56% in the CVF model, by 31% in the immune complex model, and by 53% in the lung injury model following ischemia-reperfusion of the hind limbs. Similar treatment reduced hemorrhage by 76%, 51%, and 70% in the three models of lung injury. In the CVF model, riboflavin was also shown to decrease products of lipid peroxidation (conjugated dienes) in lungs (by 45%) and in plasma (by 74%). Neutrophil accumulation in the lungs was not influenced by riboflavin administration in any of the three models. The studies demonstrate that riboflavin can mount a significant protection against oxidant-mediated inflammatory organ injury.

Anti-L-selectin antibody treatment of hemorrhagic-traumatic shock in baboons

OBJECTIVES

The adhesion molecule L-selectin plays an important role in leukocyte-endothelium interactions, thereby contributing to inflammatory reactions. We tested the hypothesis that humanized anti-L-selectin antibodies reduce trauma-associated organ damage and mortality.

DESIGN

Prospective, randomized experimental study.

SETTING

Independent nonprofit research laboratory in a trauma hospital (Ludwig Boltzmann Institute) and a contract research institute (Biocon).

SUBJECTS

Twenty-eight male baboons (Papio ursinus), 18 to 29 kg.

INTERVENTIONS

Hemorrhagic-traumatic shock was created by complement activation with cobra venom factor, followed by withdrawal of blood to a mean arterial pressure of 35 to 45 mm Hg. Blood and lactated Ringer's solution were reinfused. Animals were randomized to receive either 2 mg/kg humanized anti-L-selectin antibody (HuDREG-55 [Ab]) or placebo (lactated Ringer's solution [LRS]).

MEASUREMENTS AND MAIN RESULTS

Treatment with humanized anti-L-selectin antibody decreased mortality (Ab 21% vs. LRS 71%; p = .011) and improved survival time (p = .016). A trend toward reduced organ damage, especially in the adrenal glands (score 1.2 +/- 0.2 placebo vs. 1.0 +/- 0.1 antibody; p = .059) was seen, and at 24 hrs was accompanied by significantly increased mean arterial pressure (Ab 99 +/- 6 mm Hg vs. LRS 79 +/- 8 mm Hg; p = .023), cardiac output (Ab 3.4 +/- 0.2 L/min vs. LRS 2.4 +/- 0.3 L/min; p = .007), core temperature (p = .048), and improved perfusion, with less negative base excess (Ab 2.9 +/- 1.1 vs. LRS 2.1 +/- 1.7; p = .019) and a trend toward less lactate (p = .065). These improvements were accompanied by significantly (p = .006) decreased fluid requirements in the treatment group (Ab 11.7 +/- 2.5 mL/kg/hr vs. LRS 23.0 +/- 2.3 mL/kg/hr). There were also fewer circulating leukocytes (p = .042) in the treatment group at 24 hrs.

CONCLUSION

Humanized anti-L-selectin antibody has beneficial effects on survival in a long-term in vivo model of hemorrhagic. traumatic shock.

Role of chemotactic factors in neutrophil activation after thermal injury in rats

Acute thermal trauma is well known to produce evidence of a "systemic inflammatory response" in vivo, as manifested by evidence of complement activation, appearance in plasma of a variety of inflammatory factors, and development of multi-organ injury. The current studies were focused on acute thermal injury of rat skin and factors responsible for accompanying activation of blood neutrophils. Acute thermal injury of rat skin resulted in a time-dependent loss of L-selectin and up-regulation of Mac-1 (CD11b/CD18) on blood neutrophils, with no changes in LFA-1 (CD11a/CD18). The loss of L-selectin was prevented by blockade of C5a but not by blockade of the alpha-chemokine, macrophage inflammatory protein-2 (MIP-2). C5a, the alpha chemokines, MIP-2 and keratinocyte-derived cytokine (KC), and platelet activating factor (PAF) contributed to up-regulation of blood neutrophil Mac-1. Blocking interventions against these mediators also blunted the degree of neutropenia developing after thermal trauma. These data suggest that activation of blood neutrophils after thermal trauma is related to the role of several chemotactic mediators. These studies may provide clues regarding factors responsible for development of the "systemic inflammatory response syndrome" after thermal injury in the experimental model employed.

Chemotactic mediator requirements in lung injury following skin burns in rats

Partial-thickness skin burns have been shown to induce neutrophil-dependent microvascular injury both locally (skin) and systemically (lung). In the present study, interventional measures to block inflammatory chemoattractants were employed to define the pathophysiologic role of these mediators in the development of secondary lung injury following thermal injury of skin. Rats were treated with blocking antibodies to either C5a or to the alpha-chemokines, keratinocyte-derived cytokine (KC), or macrophage inflammatory protein-2 (MIP-2). To study the role of platelet activating factor, a receptor antagonist (PAF-Ra) was utilized. The development of lung vascular injury following thermal injury to skin was significantly attenuated by treatment with anti-C5a (84%), anti-KC (67%), and anti-MIP-2 (77%), but treatment with PAF-Ra had no protective effects. Protective interventions were paralleled by significant reductions in the tissue buildup of myeloperoxidase. When bronchoalveolar lavage fluids from thermally injured rats were evaluated, elevations in TNF;ZA and IL-1 were found and were determined to be C5a-dependent (but unaffected by treatment with PAF-Ra). These studies indicate that lung tissue injury after thermal skin burns is dependent on chemotactic mediators. The data also suggest that lung expression of TNFalpha and IL-1 after thermal injury of skin is C5a-dependent.

Endothelial Targeting and Enhanced Antiinflammatory Effects of Complement Inhibitors Possessing Sialyl Lewisx Moieties

The complement inhibitor soluble complement receptor type 1 (sCR1) and a truncated form of sCR1, sCR1[desLHR-A], have been generated with expression of the selectin-reactive oligosaccharide moiety, sialyl Lewisx (sLex), as N-linked oligosaccharide adducts. These modified proteins, sCR1sLex and sCR1[desLHR-A]sLex, were assessed in the L-selectin- and P-selectin-dependent rat model of lung injury following systemic activation of complement by cobra venom factor and in the L-selectin-, P-selectin-, and E-selectin-dependent model of lung injury following intrapulmonary deposition of IgG immune complexes. In the cobra venom factor model, sCR1sLex and sCR1[desLHR-A]sLex caused substantially greater reductions in neutrophil accumulation and in albumin extravasation in lung when compared with the non-sLex-decorated forms. In this model, increased lung vascular binding of sCR1sLex and sCR1[desLHR-A]sLex occurred in a P-selectin-dependent manner, in contrast to the absence of any increased binding of sCR1 or sCR1[desLHR-A]. In the IgG immune complex model, sCR1[desLHR-A]sLex possessed greater protective effects relative to sCR1[desLHR-A], based on albumin extravasation and neutrophil accumulation. Enhanced protective effects correlated with greater lung vascular binding of sCR1[desLHR-A]sLex as compared with the non-sLex-decorated form. In TNF-α-activated HUVEC, substantial in vitro binding occurred with sCR1[desLHR-A]sLex (but not with sCR1[desLHR-A]). This endothelial cell binding was blocked by anti-E-selectin but not by anti-P-selectin. These data suggest that sLex-decorated complement inhibitors have enhanced antiinflammatory effects and appear to have enhanced ability to localize to the activated vascular endothelium.

Endothelial targeting and enhanced antiinflammatory effects of complement inhibitors possessing sialyl Lewisx moieties

The complement inhibitor soluble complement receptor type 1 (sCR1) and a truncated form of sCR1, sCR1[desLHR-A], have been generated with expression of the selectin-reactive oligosaccharide moiety, sialyl Lewisx (sLex), as N-linked oligosaccharide adducts. These modified proteins, sCR1sLex and sCR1[desLHR-A]sLex, were assessed in the L-selectin- and P-selectin-dependent rat model of lung injury following systemic activation of complement by cobra venom factor and in the L-selectin-, P-selectin-, and E-selectin-dependent model of lung injury following intrapulmonary deposition of IgG immune complexes. In the cobra venom factor model, sCR1sLex and sCR1[desLHR-A]sLex caused substantially greater reductions in neutrophil accumulation and in albumin extravasation in lung when compared with the non-sLex-decorated forms. In this model, increased lung vascular binding of sCR1sLex and sCR1[desLHR-A]sLex occurred in a P-selectin-dependent manner, in contrast to the absence of any increased binding of sCR1 or sCR1[desLHR-A]. In the IgG immune complex model, sCR1[desLHR-A]sLex possessed greater protective effects relative to sCR1[desLHR-A], based on albumin extravasation and neutrophil accumulation. Enhanced protective effects correlated with greater lung vascular binding of sCR1[desLHR-A]sLex as compared with the non-sLex-decorated form. In TNF-alpha-activated HUVEC, substantial in vitro binding occurred with sCR1[desLHR-A]sLex (but not with sCR1[desLHR-A]). This endothelial cell binding was blocked by anti-E-selectin but not by anti-P-selectin. These data suggest that sLex-decorated complement inhibitors have enhanced antiinflammatory effects and appear to have enhanced ability to localize to the activated vascular endothelium.

Mediators of microvascular injury in dermal burn wounds

In previous studies we have demonstrated that second-degree thermal injury of skin in rats leads to secondary effects, such as systemic complement activation, C5a-mediated activation of blood neutrophils, their adhesion-molecule-guided accumulation in lung capillaries and the development of acute pulmonary injury, largely caused by neutrophil-derived toxic oxygen metabolites. In the dermal burn wound, however, pathophysiologic events are less well understood. The injury is fully developed at four hours post-burn. To further elucidate the pathogenesis of the "late phase" dermal vascular damage, rats were depleted of neutrophils or complement by pretreatment with rabbit antibody against rat neutrophils or with cobra venom factor, respectively. In other experiments, rats were treated with blocking antibodies to IL-6, IL-1, and TNF alpha immediately following thermal burning or were pretreated with hydroxyl radical scavengers (dimethyl sulfoxide, dimethyl thiourea). Extravasation of 125I-labeled bovine serum albumin into the burned skin was studied, as well as, skin myeloperoxidase levels. The studies revealed that, like in secondary lung injury, neutrophils and toxic oxygen metabolites, are required for full development of microvascular injury. In contrast, however, development of dermal vascular damage in thermally injured rats was not affected by complement depletion. Our data suggest that the development of microvascular injury in the dermal burn wound is complement-independent, involves the pro-inflammatory cytokines IL-1, TNF alpha and IL-6, and may result from reactive oxygen metabolites generated by neutrophils accumulating in the burn wound.

Neutrophil accumulation is reduced during partial liquid ventilation

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.

Partial liquid ventilation decreases albumin leak in the setting of acute lung injury

PURPOSE

This study evaluated the ability of partial liquid ventilation (PLV, gas ventilation of the perfluorocarbon-filled lungs) to reduce the amount of lung albumin leak present in the setting of acute lung injury.

MATERIALS AND METHODS

An experimental controlled, randomized design was used. All studies were performed in the liquid ventilation laboratories at the University of Michigan Medical Center. Twenty-five Sprague-Dawley male rats 500+/-50 g were divided into five experimental groups: (1) CVF only (n=5), animals were cobra venom factor (CVF) lung injured; (2) PLV-CVF (n=5) animals received perflubron and PLV before CVF lung injury; (3) CVF-PLV (n=5) animals received PLV after CVF lung injury; (4) PLV only (n=5) animals underwent partial liquid ventilation without lung injury; and (5) Gas only (n=5) animals underwent gas ventilation without lung injury. In all groups iodinated bovine serum albumin (125I-BSA) was delivered by intravenous injection along with CVF or a saline placebo.

RESULTS

When the CVF animals were compared with all other groups, a decrease in albumin leak was observed for all groups when compared with the CVF only controls (P < .001 by ANOVA; CVF only=1.22+/-0.12 versus PLV-CVF=0.46+/-0.08, P < .001; CVF-PLV=0.70+/-0.25, P < .001; PLV only=0.22+/-0.01, P < .001; Gas only=0.17+/-0.02, P < .001).

CONCLUSIONS

These data suggest that intratracheal instillation of perfluorocarbon before or after induction of lung injury results in a reduction in pulmonary albumin leak.

The pattern of early lung parenchymal and air space injury following acute blood loss

Acute lung injury is a frequent clinical occurrence following blood loss and trauma. The nature of this injury remains poorly understood.

OBJECTIVE

To examine the relative parenchymal and intra-alveolar distribution of inflammation in a rat model of hemorrhage and resuscitation.

METHODS

Rats were anesthetized and subjected to hemorrhage followed by resuscitation with shed blood and saline. Myeloperoxidase activity of lung homogenates and cytology of bronchoalveolar lavage fluid were used to measure total lung and intra-alveolar neutrophil invasion. Extravasation of i.v.-administered [125I]-albumin was used to determine total lung and alveolar permeability. Permeability results were analyzed using their base-10 logarithmic transformations.

RESULTS

86 animals were studied. Whole-lung myeloperoxidase activity was increased (control = 0.34 +/- 0.16 units, injured = 0.84 +/- 0.43 units, p < 0.01), while there was no difference in intra-alveolar leukocyte counts (injured = 1.85 +/- 1.30 x 10(5)/mL, control = 2.44 +/- 1.75 x 10(5)/mL, p = 0.40), suggesting that the cellular component of the injury was more severe in the intravascular and interstitial spaces. There was a strong trend toward increased permeability in the interstitial compartment, and a significant increase in permeability in the intra-alveolar compartment (whole-lung permeability: control = -0.27 +/- 0.19 units, injured = 0.10 +/- 0.55 units, p = 0.06; alveolar permeability: control = -2.00 +/- 0.47 units, injured = -1.32 +/- 0.49 units, p < 0.01), suggesting that the loss of integrity to macromolecules was not limited to the interstitium.

CONCLUSION

Hemorrhage and resuscitation resulted in an acute lung injury characterized by extravasation of intravascular protein into both the interstitium and the intra-alveolar space. Neutrophil invasion of the lung was demonstrable only in the interstitial compartment.

Partial liquid ventilation protects lung during resuscitation from shock

Preliminary animal experience with partial liquid ventilation (PLV) suggests that this therapy may diminish neutrophil invasion and capillary leak during acute lung injury. We sought to confirm these findings in a model of shock-induced lung injury. Sixty anesthetized rats were studied. After hemorrhage to an arterial pressure of 25 mmHg for 45 min, animals were resuscitated with blood and saline and treated with gas ventilation alone or with 5 ml/kg of intratracheally administered perflubron. Myeloperoxidase activity was used to measure lung neutrophil content. A permeability index (the bronchoalveolar-to-blood ratio of 125I-labeled albumin activity) quantified alveolar leak. Injury caused an increase in myeloperoxidase that was reversed by PLV (injury = 0.837 +/- 0.452, PLV = 0.257 +/- 0.165; P < 0.01). Capillary permeability also increased with hemorrhage, with a strong trend toward improvement in the PLV group (permeability indexes: injury = 0.094 +/- 0.102, PLV = 0.045 +/- 0.045; 95% confidence interval for injury--PLV: -0.024, 0.1219). We conclude that PLV is associated with a decrease in pulmonary neutrophil accumulation and a trend toward decreased capillary leak after hemorrhagic shock.

Mechanisms of acantholysis in pemphigus foliaceus

Pemphigus foliaceus (PF) is a dermatosis characterized by subcorneal vesicles and pathogenic IgG autoantibodies against desmoglein 1. PF IgG passively transferred into neonatal mice induces a blistering disease that duplicates the key findings of PF. In this study we have used this animal model to investigate the role of complement and IgG valence in triggering blister formation. In the passive transfer experiments, we found that PF IgG, as well as the F(ab')2 and Fab fragments, was capable of inducing the typical subcorneal blistering disease in both complement-deficient and complement-sufficient mice. Moreover, the disease activity in these mice correlated well with the dose of IgG or its proteolytic fragments injected in the animals. We conclude that neither complement activation nor IgG-mediated cell surface antigen crosslinking is required for the induction of acantholysis in the experimental PF model.

A major role for neutrophils in experimental bullous pemphigoid

Bullous pemphigoid (BP) is an inflammatory subepidermal blistering disease associated with an IgG autoimmune response to the hemidesmosomal protein, BP180. Using a passive transfer mouse model, our group has shown previously that antibodies to the murine BP180 (mBP180) ectodomain are capable of triggering a blistering skin disease that closely mimics human BP. In this study, we investigated the role of neutrophils in the immunopathogenesis of this disease model. BALB/c mice depleted of circulating neutrophils by treatment with neutrophil-specific antibodies were no longer susceptible to the pathogenic effects of anti-mBP180 IgG. IgG and complement were deposited at the dermal-epidermal junction of these animals, but there was no evidence of inflammatory infiltration or blistering. C5-deficient mice, which are resistant to the pathogenic activity of anti-mBP180 IgG, could be made susceptible to this IgG-mediated blistering disease by intradermal administration of a neutrophil chemoattractant, IL-8 or C5a. Intraperitoneal injection of IL-8, which sequesters neutrophils in the peritoneal cavity, interferes with anti-mBP180-induced neutrophilic infiltration of the skin and prevented the development of BP disease in BALB/c mice. These findings provide the first direct evidence that neutrophils recruited to the skin via a C5-dependent pathway play an essential role in subepidermal blister formation in experimental BP, and suggest new directions for disease intervention.

Requirement for C5a in lung vascular injury following thermal trauma to rat skin

Previous studies in rats have shown that deep second degree dermal burns, involving 28-30% of total body surface area, result in systemic complement activation, appearance in plasma of chemotactic activity, sequestration of blood neutrophils in lung capillaries, and development of neutrophil-dependent dermal vascular and lung vascular injury. Although blockade of complement activation or depletion of complement before skin burns has resulted in significant attenuation of tissue injury both locally and distally (in lung), a role for C5a in these events is unclear. In the following studies, we demonstrate the presence of C5a and neutrophil chemotactic activity in serum and in lung homogenates after thermal injury. C5a has also been found in bronchoalveolar lavage fluids of thermally injured animals. Treatment of animals with a polyclonal neutralizing rabbit antibody to rat C5a was lung protective. The protective effects of the antibody (anti-C5a) were associated with diminished vascular permeability changes, as well as reduced tissue build-up of myeloperoxidase. Anti-C5a also prevented up-regulation of lung vascular ICAM-1 (intercellular adhesion molecule-1) in skin-burned rats. These observations indicate that C5a is essential for development of neutrophil accumulation and vascular permeability increases in distant (lung) organs after thermal trauma to skin. The protective effects of anti-C5a in lung, appear to be related to prevention of up-regulation of vascular ICAM-1. Accordingly, C5a may represent a target for clinical approaches in the treatment of organ injury following thermal trauma.

Neutrophil chemotactic activity and C5a following systemic activation of complement in rats

Using ELISA analysis, rat C5a was stimulated in serum from rats undergoing systemic activation of complement after intravenous infusion of purified cobra venom factor (CVF). Biological (neutrophil chemotactic) activity was also assessed. Serum levels of C5a were directly proportional to the amount of CVF infused. C5a and neutrophil chemotactic activity, peaked by 5 min, then plateaued. In vitro addition of anti-C5a to serum samples of CVF-infused rats totally abolished chemotactic activity, indicating that all biological activity could be ascribed to C5a. Blood neutrophils obtained from CVF-infused animals showed a significant upregulation of CD11b, the increase being reduced (38%) in animals pretreated with anti-C5a. These findings indicate that infusion of CVF into rats produces generation of C5a, all chemotactic activity in serum being related to C5a. The in vivo generation of C5a is, at least inpart, responsible for upregulation of CD11b on blood neutrophils.

C5a-dependent up-regulation in vivo of lung vascular P-selectin

Acute lung injury in rats following systemic activation of complement by i.v. infusion of cobra venom factor (CVF) is known to be P-selectin dependent. In the current studies, infusion of CVF caused the appearance in plasma of C5a (as revealed by ELISA analysis) together with neutrophil chemotactic activity, which was totally blocked by addition in vitro of anti-rat C5a. Using a detector 125I-labeled antibody to rat P-selectin, we have demonstrated quantitative up-regulation in vivo of lung vascular P-selectin in a time-dependent manner after infusion of CVF. This up-regulation was almost completely blocked by prior complement depletion or by the infusion of anti-rat C5a. Platelet depletion did not affect CVF-induced up-regulation of lung vascular P-selectin, indicating that platelets were not the source of P-selectin. These results demonstrate that complement and, specifically, C5a are necessary for up-regulation of lung vascular P-selectin after systemic activation of complement.

C5a-dependent up-regulation in vivo of lung vascular P-selectin

Acute lung injury in rats following systemic activation of complement by i.v. infusion of cobra venom factor (CVF) is known to be P-selectin dependent. In the current studies, infusion of CVF caused the appearance in plasma of C5a (as revealed by ELISA analysis) together with neutrophil chemotactic activity, which was totally blocked by addition in vitro of anti-rat C5a. Using a detector 125I-labeled antibody to rat P-selectin, we have demonstrated quantitative up-regulation in vivo of lung vascular P-selectin in a time-dependent manner after infusion of CVF. This up-regulation was almost completely blocked by prior complement depletion or by the infusion of anti-rat C5a. Platelet depletion did not affect CVF-induced up-regulation of lung vascular P-selectin, indicating that platelets were not the source of P-selectin. These results demonstrate that complement and, specifically, C5a are necessary for up-regulation of lung vascular P-selectin after systemic activation of complement.

Complement-induced retinal arteriolar occlusions in the cat

PURPOSE

To develop an animal model of complement-induced retinal vasculopathy and determine whether it resembles Purtscher's retinopathy.

METHODS

Intravenous cobra venom factor was used to achieve intravascular activation of the complement system in cats. After a single bolus of cobra venom factor (75 units/kg), retinal blood flow was monitored at regular intervals by fluorescein angioscopy and angiography.

RESULTS

Multiple small retinal arteriolar occlusions were present during the initial fluorescein transit of the immediate postinjection fluorescein study in 12 of 12 animals. Small, rapidly moving gaps in the fluorescein column were seen in two thirds of the animals observed continuously by fluorescein angioscopy. Angiographically, the obstructions were transient, and filling of the associated patches of capillary nonperfusion occurred within 3 minutes. Purtscher's-like ischemic retinal infarcts did not develop in any eye. Histopathologic analysis failed to demonstrate the nature of the transient vascular obstructive lesions, but indirect evidence suggested the possibility of granulocyte aggregates.

CONCLUSION

Intravascular activation of the complement system produces transient microembolic retinal arteriolar occlusions in the cat. Although this model may represent a mild form of Purtscher's retinopathy, factors in addition to complement activation appear necessary to induce ischemic retinal infarcts.

Requirement and role of C5a in acute lung inflammatory injury in rats

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.

The role of complement in experimental bullous pemphigoid

Bullous pemphigoid (BP) is a blistering skin disease associated with an IgG autoimmune response directed against the ectodomain of the hemidesmosomal protein, BP180. An animal model of BP has recently been developed by our laboratory based on the passive transfer of rabbit antimurine BP180 antibodies into neonatal BALB/c mice. The experimental animals develop a blistering disease that reproduces all of the key immunopathological features of BP. In the present study we have investigated the role of complement in the pathogenesis of subepidermal blistering in the mouse model of BP. We demonstrate the following. (a) Rabbit anti-murine-BP180 IgG was effective in inducing cutaneous blisters in a C5-sufficient mouse strain, but failed to induce disease in the syngeneic C5-deficient strain; (b) neonatal BALB/c mice, pretreated with cobra venom factor to deplete complement, became resistant to the pathogenic effects of the anti-BP180 IgG; (c) F(ab')2 fragments generated from the anti-BP180 IgG exhibited no pathogenic activity in the mouse model; and (d) histologic evaluation of the skin of mice described in points b and c above showed minimal or no neutrophilic cell infiltration in the upper dermis. Thus, anti-BP180 antibodies trigger subepidermal blistering in this BP model via complement activation. This experimental model of BP should greatly facilitate future studies on the pathophysiology of autoantibody-mediated diseases of the dermal-epidermal junction.

Phorbol-stimulated influx of extracellular calcium in rat pulmonary artery endothelial cells

Stimulation of rat pulmonary artery endothelial cells (RPAEC) with phorbol 12-myristate 13-acetate (PMA) resulted in an increase in intracellular calcium ([Ca2+]i). Unlike the response to bradykinin, C5a and tumor necrosis factor-alpha (TNF-alpha) previously reported (15), the PMA-induced increase in [Ca2+]i was predominantly dependent on extracellular calcium. The PMA response paralleled the BAY K 8644-induced, extracellular calcium-dependent increase in [Ca2+]i. Pretreatment of endothelial cells with the protein kinase C inhibitor staurosporine resulted in a concentration-dependent inhibition of the increase in [Ca2+]i in response to PMA. The ability of PMA analogues to induce significant increase in [Ca2+]i paralleled their ability to induce O2- generation in neutrophils. The PMA-induced influx of extracellular Ca2+ was inhibited by the L-channel selective antagonists diltiazem, nifedipine, nicardipine, and verapamil in a dose-dependent manner. Depolarizing conditions induced by high [K+]o enhanced the calcium response to PMA. The data presented are consistent with the hypothesis that PMA-induced increases in [Ca2+]i in endothelial cells are the result of Ca2+ influx through voltage-dependent L-type Ca2+ channels.

Acute skin injury releases neutrophil chemoattractants

BACKGROUND

Progressive or ongoing skin necrosis after traumatic injury is well known. Experimental evidence has associated these events with neutrophil activation and secondary oxidant injury. To determine the mechanism by which neutrophils migrate to a site of injury, cytokine release from injured skin was measured.

METHODS

Twenty-five skin biopsy specimens of acute partial thickness skin injuries were compared with uninjured skin of the same patient. Conditioned medium from explanted skin was assayed for tumor necrosis factor (TNF), interleukin-6 (IL-6), and IL-8.

RESULTS

Acute skin injury resulted in a significant release of IL-8 but not IL-6 or TNF. In eight patients gradient cytokine release was found; IL-8 levels for partial thickness burn were 26.4 ng/ml, for unburned skin adjacent to the burn were 2.1 ng/ml, and for distal normal skin were 0.2 ng/ml.

CONCLUSIONS

IL-8 is released from acutely injured skin; IL-6 and TNF are not. This selective release suggests a mechanism whereby neutrophils are recruited into injured tissue. These neutrophils might then induce further injury, increasing the extent of posttraumatic tissue loss.

Role of leukocyte adhesion molecules in lung and dermal vascular injury after thermal trauma of skin

Acute second degree thermal injury of rat skin involving 25 to 30% total body surface of anesthetized rats results at 4 hours in evidence of vascular injury both locally (in skin) and remotely (involving lung). The neutrophil dependency for both types of injury has now been established. Monoclonal antibodies to various adhesion molecules have been used to define the requirements for these molecules in the development of vascular injury. In dermal vascular injury, a requirement for Mac-1 (CD11b/CD18) but not for leukocyte function-associated antigen-1 (LFA-1, CD11a/CD18) has been established. In this model requirements have also been demonstrated for intercellular adhesion molecule-1 (ICAM-1) and E- and L-selectin but not for very late arising antigen-4 (VLA-4) or P-selectin. With respect to lung vascular injury, dual requirements for both leukocyte function-associated antigen-1 and Mac-1 were found as well as for ICAM-1 and E- and L-selectin but not for VLA-4 and P-selectin. In the lung, there was a close correlation between neutrophil content of the tissue (as assessed by myeloperoxidase) and the effects of protective interventions (directed against blocking of adhesion molecules). These data emphasize the roles of beta 2 integrins, selectins (L and E), and ICAM-1 in events that lead to neutrophil-mediated vascular injury of dermis and lung after thermal trauma to skin.

Role of selectins in local and remote tissue injury following ischemia and reperfusion

Ischemia (4-hour) followed by reperfusion (4-hour) of rat hind limbs results in local injury as well as remote (lung) injury. It has recently been shown that injury in this model is neutrophil- and cytokine-dependent and requires the beta 2 integrin adhesion molecules CD11a/CD18 and CD11b/CD18. The role of selectins in events leading to injury (as determined by leakage of albumin and by hemorrhage) was assessed either through the use of blocking antibodies to L-, E- or P-selectins or by the use of oligosaccharides that are reactive with selectins. Lung injury was found to be L- and E-selectin-dependent. When the ischemia and reperfusion times were reduced, lung injury was also found to be P-selectin dependent. In the case of hind limb injury involving the crural muscle mass, injury was L-selectin-dependent but independent of requirements for P- and E-selectin. Injury in both organs was blocked by the infusion of sialylated Lewis pentasaccharide, whereas sialyl-N-acetyllactosamine pentasaccharide failed to protect against injury. In general, when selectin-blocking approaches were protective, there were parallel reductions in tissue content of myeloperoxidase. These data underscore the role of selectins in ischemia-reperfusion injury and suggest that selectin requirements may vary with the vascular bed under study.

Role of beta 2 integrins and ICAM-1 in lung injury following ischemia-reperfusion of rat hind limbs

Ischemia/reperfusion involving the hind limbs of rats results in both local injury to skeletal muscle as well as injury to lungs, as measured by increased vascular permeability (125I-labeled bovine serum albumin leakage) and hemorrhage (extravasation of 51Cr-labeled rat erythrocytes). In the current study, we have focused on events in lungs occurring during reperfusion of hind limbs. Analysis of blood neutrophils obtained 4 hours after reperfusion has indicated up-regulation of CD11b and CD18 but not CD11a. Plasma from the same animals demonstrate the ability to induce similar effects in normal blood neutrophils, indicative of the presence of a neutrophil-activating agent in plasma. During reperfusion, lung injury, which develops progressively over a 4-hour period, has been shown to be neutrophil-dependent and requires CD11a/CD18 and CD11b/CD18 as well as intercellular adhesion molecule-1. These data suggest that ischemia and reperfusion injury of rat lower extremities causes systemic changes that result in neutrophil-dependent lung injury that is beta 2 integrin- (leukocyte function antigen-1, Mac-1) and intercellular adhesion molecule-1-dependent.

Requirements for tumor necrosis factor-alpha and interleukin-1 in limb ischemia/reperfusion injury and associated lung injury

Ischemia in rat hind limbs followed by reperfusion results in local as well as remote organ (lung) injury characterized by increased vascular permeability (125I-labeled bovine serum albumin leakage) and hemorrhage (51Cr-labeled rat erythrocytes extravasation) in skeletal muscle and lung, together with an associated increased tissue content of myeloperoxidase, reflecting neutrophil accumulation. Within 60 minutes of reperfusion following ischemia, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and IL-6 plasma levels increased significantly, reaching maximum levels after 2 hours of reperfusion. Polyclonal antibodies to TNF-alpha and IL-1 provided significant protection against vascular injury in both muscle and lung. These results were confirmed by the use of soluble TNF-alpha receptor and IL-1 receptor antagonist. In rat lungs following ischemia and reperfusion, there was immunohistochemical evidence of E-selectin expression in the lung vasculature; this expression was blocked by treatment of animals with anti-TNF-alpha. These data indicate that both local (hind limb) and remote (lung) organ injury after ischemia/reperfusion requires participation of TNF-alpha and IL-1. The cytokines may, in part, be involved in the up-regulation of endothelial adhesion molecules.

Identification of xanthine oxidase activity following reperfusion in human tissue

In this series of experiments, we surveyed xanthine oxidase activity after microvascular transfer in the venous effluent after reperfusion of human rectus abdominis muscle (n = 8) and jejunum (n = 4). Enzyme activity was correlated with duration of ischemia and biochemical markers of cellular injury. Xanthine oxidase (XO) activity was measured spectrofluorometrically using a pterin assay, whereas cellular injury was measured with commercial creatinine phosphokinase activity assay and lipid peroxidation products using a spectrophotometer. The data demonstrated that XO activity was statistically significantly increased in muscle flaps kept at room temperature during ischemia compared with muscle flaps that were cooled (p < 0.05). Creatinine phosphokinase activity was also increased after 15 minutes of reperfusion in muscle flaps that were not cooled (p < 0.05). Two of the jejunal free flaps had ischemia times of > 1 hour and had elevated XO activity after reperfusion despite cooling (p < 0.05). Two other jejunal flaps had ischemia times of < 1 hour, but in one case, the XO activity was increased before harvest. The other case had no increase in XO activity.

Correlation of the local and systemic cytokine response with clinical outcome following thermal injury

Eighty-eight patients with acute thermal injury were evaluated. Forty-eight hours after injury, TNF, IL-6, and IL-8 were significantly present in the systemic circulation, lung, normal skin, and thermally injured skin. The presence of TNF, IL-6, and IL-8 proteins in the lung, normal skin, and thermally injured skin were associated with TNF, IL-6, and IL-8 mRNA upregulation. Logistic regression analysis controlling for the Abbreviated Burn Severity Index demonstrated that the presence of IL-8 in the lung was associated with early pulmonary physiologic dysfunction (p = 0.006) and nosocomial pulmonary infection (p = 0.040). We conclude that acute thermal injury initiates an early systemic, lung, and skin response involving TNF, IL-6, and IL-8. The TNF, IL-6, and IL-8 protein present in the lung and skin in response to acute thermal injury are generated locally and do not originate from the systemic cytokine pool. The lung cytokine response to acute thermal injury may initiate local organ failure.

Requirements for neutrophil products and L-arginine in ischemia-reperfusion injury

Ischemia followed by reperfusion in rat limb results in evidence of vascular injury in the limb as well as in the lung as measured by leakage of [125I]albumin and extravasation of [51Cr] red blood cells. Vascular injury in lung and limb was proportional to the time of limb reperfusion and was associated with accumulation of myeloperoxidase, as well as evidence of complement consumption. In this model, the rank order of protective interventions was: neutrophil depletion > catalase + superoxide dismutase = allopurinol > dimethylthiourea = dimethylsulfoxide > deferoxamine = complement depletion. These data suggest that toxic oxygen products of neutrophils are related to the development of vascular injury. There was a reasonable correlation between protective effects of interventions and reduced tissue content of myeloperoxidase. Systemic treatment with the L-arginine antagonists, NG-monomethyl-L-arginine or nitro-L-arginine methyl ester, was also protective against vascular injury, suggesting that metabolic products of L-arginine participate in events leading to injury.

Evidence that NADPH-dependent methemoglobin reductase and administered riboflavin protect tissues from oxidative injury

NADPH-dependent methemoglobin reductase, first detected in erythrocytes sixty years ago, has subsequently been purified and characterized as a methylene blue reductase and a flavin reductase. The reductase plays no role in methemoglobin reduction under normal conditions, but its activity serves as the basis for the treatment of methemoglobinemia with methylene blue or flavin. On-going studies demonstrate that this cytosolic protein is also present in liver and that its primary structure distinguishes it from other known proteins. The bovine erythrocyte reductase tightly binds hemes, porphyrins, and fatty acids with resulting loss of activity. Pyrroloquinoline quinone serves as a high-affinity substrate of the reductase, suggesting that this naturally-occurring compound may be a physiological substrate. The ability of the reductase to catalyze the intracellular reduction of administered riboflavin to dihydroriboflavin suggested that this system might be exploited to protect tissues from oxidative damage. This hypothesis was supported by our finding that dihydroriboflavin reacts rapidly with Fe(IV)O and Fe(V)O oxidation states of hemeproteins, states that have been implicated in tissue damage associated with ischemia and reperfusion. Preliminary studies demonstrate that, as predicted, administration of low concentrations of riboflavin protects isolated rabbit heart from reoxygenation injury, rat lung from injury resulting from systemic activation of complement, and rat brain from damage caused by four hours of ischemia. Data from these animal studies suggest that flavin therapy holds promise in protecting tissue from the oxidative injuries of myocardial infarction, acute lung injury, stroke, and a number of other clinical conditions.

Adhesion molecules in experimental phacoanaphylactic endophthalmitis

Intraocular accumulation of inflammatory neutrophils is an important feature of experimental phacoanaphylactic endophthalmitis (EPE). Increasing evidence suggests that localization of neutrophils to the site of inflammation requires the participation of neutrophil and endothelial adhesion molecules. These studies were undertaken to determine if blocking of adhesion molecules on neutrophils (CD18) or endothelium (ELAM-1) could attenuate EPE in Lewis rats. Treatment of experimental animals with anti-CD18 or anti-ELAM-1 significantly suppressed intraocular neutrophil accumulation, retinal hemorrhage, and vasculitis, and attenuated retinal edema formation by 48% and 70%, respectively. These observations demonstrate that antibodies directed against adhesion molecules on the neutrophil (CD18) or the vascular endothelial cell (ELAM-1) exhibit potent anti-inflammatory effects, resulting in a striking amelioration of injury in EPE in rats.

Superoxide responses of endothelial cells to C5a and TNF-alpha: divergent signal transduction pathways

There is increasing evidence that endothelial cells respond to a variety of mediators. In the current studies rat pulmonary artery endothelial cells (RPAEC) responded to human recombinant C5a and tumor necrosis factor-alpha (TNF-alpha) with the generation of superoxide (O2-). RPAEC responsiveness was dependent on whether cells had been obtained from confluent or subconfluent cell monolayers. RPAEC responded to C5a and TNF-alpha in a dose-dependent manner, with increases in intracellular Ca2+ (Cai2+), formation of D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], and generation of O2-. Optimal O2- responses occurred in cells that had been pretreated with the inhibitor of superoxide dismutase (SOD), diethyldithiocarbamate, and O2- responses were allopurinol insensitive. Pertussis toxin pretreatment abolished the ability of C5a to cause increases in Ins(1,4,5)P3 and Cai2+ and formation of O2- but did not inhibit the changes in Cai2+ and formation of O2- after addition of TNF-alpha. The O2- response to C5a but not to TNF-alpha was abolished by pretreatment with the inhibitor of protein kinase C, staurosporine. These data indicate that signal transduction events in response to C5a and TNF-alpha were fundamentally different.

Roles of beta 2 integrins of rat neutrophils in complement- and oxygen radical-mediated acute inflammatory injury

The roles of beta 2 integrin molecules in neutrophil accumulation and tissue injury have been examined by the use of antibodies that are reactive with human CD11b and CD18 and cross-react with the homologous epitopes on rat neutrophils. Adherence to rat pulmonary artery endothelial cells by human neutrophils and endothelial cell killing by phorbol ester-activated human neutrophils required CD11b, CD11c, and CD18. Companion adherence studies between rat neutrophils and endothelial cells revealed a requirement for both CD11b and CD18. Neither anti-CD11b nor anti-CD18 depressed in vitro responses (O2- generation and chemotactic migration) of rat neutrophils. The accumulation of neutrophils in glycogen-induced peritoneal exudates was diminished substantially in rats treated with either anti-CD18 or anti-CD11b. In oxidant-mediated acute lung injury induced by rapid intravascular infusion of cobra venom factor, treatment of rats with either anti-CD18 or anti-CD11b significantly attenuated injury as assessed by increases in vascular permeability and hemorrhage. These protective effects correlated morphologically with diminished adhesion of neutrophils to interstitial intrapulmonary capillary endothelial cells. In studies of immune complex (BSA-anti-BSA)-induced alveolitis and dermal vasculitis, anti-CD18 had protective effects at all doses of anti-BSA employed. The protective effects of anti-CD18 correlated with diminished neutrophil accumulation in tissues at lower doses of anti-BSA. Although anti-CD11b was not effective under the same experimental conditions, intratracheal administration of this antibody conveyed protection against immune complex-induced lung injury, suggesting that both CD11b and CD18 are required for the full expression of injury. The current studies also demonstrated that when surface-bound IgG immune complexes were treated with fresh rat serum, the increment in O2- and TNF alpha generated by alveolar macrophages was suppressed by anti-CD18, but not by anti-CD11b, suggesting a heretofore unrecognized role for CD18 in the O2- and TNF-alpha responses of alveolar macrophages. Thus, neutrophil beta 2 integrins play a requisite role for the full expression of complement-dependent and oxygen radical-mediated injury of the lung and dermal vasculature.

Roles of beta 2 integrins of rat neutrophils in complement- and oxygen radical-mediated acute inflammatory injury

The roles of beta 2 integrin molecules in neutrophil accumulation and tissue injury have been examined by the use of antibodies that are reactive with human CD11b and CD18 and cross-react with the homologous epitopes on rat neutrophils. Adherence to rat pulmonary artery endothelial cells by human neutrophils and endothelial cell killing by phorbol ester-activated human neutrophils required CD11b, CD11c, and CD18. Companion adherence studies between rat neutrophils and endothelial cells revealed a requirement for both CD11b and CD18. Neither anti-CD11b nor anti-CD18 depressed in vitro responses (O2- generation and chemotactic migration) of rat neutrophils. The accumulation of neutrophils in glycogen-induced peritoneal exudates was diminished substantially in rats treated with either anti-CD18 or anti-CD11b. In oxidant-mediated acute lung injury induced by rapid intravascular infusion of cobra venom factor, treatment of rats with either anti-CD18 or anti-CD11b significantly attenuated injury as assessed by increases in vascular permeability and hemorrhage. These protective effects correlated morphologically with diminished adhesion of neutrophils to interstitial intrapulmonary capillary endothelial cells. In studies of immune complex (BSA-anti-BSA)-induced alveolitis and dermal vasculitis, anti-CD18 had protective effects at all doses of anti-BSA employed. The protective effects of anti-CD18 correlated with diminished neutrophil accumulation in tissues at lower doses of anti-BSA. Although anti-CD11b was not effective under the same experimental conditions, intratracheal administration of this antibody conveyed protection against immune complex-induced lung injury, suggesting that both CD11b and CD18 are required for the full expression of injury. The current studies also demonstrated that when surface-bound IgG immune complexes were treated with fresh rat serum, the increment in O2- and TNF alpha generated by alveolar macrophages was suppressed by anti-CD18, but not by anti-CD11b, suggesting a heretofore unrecognized role for CD18 in the O2- and TNF-alpha responses of alveolar macrophages. Thus, neutrophil beta 2 integrins play a requisite role for the full expression of complement-dependent and oxygen radical-mediated injury of the lung and dermal vasculature.

Xanthine oxidase: its role in the no-reflow phenomenon

This study was designed to probe the hypothesis that oxygen-derived free radicals are involved in initiation of the no-reflow phenomenon. We developed a reproducible model of no reflow in the rat hind limb. Laser Doppler studies confirmed that the hind limbs perfused well after 2 or 4 hours of ischemia, but perfusion ceased in the first 10 minutes after 6 hours of ischemia. Venous blood samples and biopsy specimens of skin and muscle were taken after 2 and 4 hours of ischemia to study tissue injury. Blood samples were evaluated for xanthine oxidase (XO), xanthine dehydrogenase, and creatine phosphokinase (CPK) activities. Conjugated dienes and iodine 125-labeled albumin extravasation were quantified in tissue samples. Groups of animals were treated with inhibitors of XO (allopurinol), antioxidant enzymes (superoxide dismutase plus catalase), and free radical scavengers (dimethyl sulfoxide and dimethyl thiourea) to assess the roles of free radicals in ischemia-reperfusion injury in the hind limbs. After 4 hours of ischemia followed by reperfusion, plasma XO activity rose threefold over preischemia levels (p less than 0.05). Xanthine dehydrogenase activity did not change; conjugated diene levels in muscle rose twofold; CPK levels rose sixfold, and 125I albumin extravasation rose twofold (p less than 0.05). Pretreatment with the XO inhibitor allopurinol reduced XO activity to negligible levels and significantly attenuated conjugated diene levels, CPK levels, and albumin extravasation. Albumin extravasation was also significantly attenuated by pretreating animals with superoxide dismutase together with catalase, dimethyl thiourea, and dimethyl sulfoxide. In all animals pretreated with allopurinol or superoxide dismutase and catalase, reperfusion persisted after 6 hours of ischemia. These data suggest that, in ischemia followed by reperfusion, tissue injury is related to oxygen products derived from XO activity.

Role of oxygen radicals in tourniquet-related ischemia-reperfusion injury of human patients

In the current study we evaluated effluent blood from extremities of human patients undergoing reconstructive surgical treatment which is routinely accompanied by upper extremity exsanguination and application of a tourniquet. Following tourniquet release (reperfusion), there were immediate increases in the plasma levels of xanthine oxidase activity, uric acid, and histamine. Xanthine dehydrogenase activity was not detectable. Plasma also contained products consistent with the formation of oxygen-derived free radicals, namely hemoglobin and fluorescent compounds. Our data indicate in humans that ischemia-reperfusion events are associated with the appearance of xanthine oxidase activity and its products in the plasma effluent.

Modulation of IgM antibody formation by lipid peroxidation products from burn plasma

Lipid peroxides (conjugated dienes) have been shown to increase in the plasma of thermally injured animals and in humans. The purpose of this study was to determine if conjugated diene-rich fractions extracted from the plasma of burned rats 3 hours after injury would alter humoral immune function in unburned animals. Plasma diene extracts from burned or normal rats were dissolved in ethanol and given intraperitoneally to Long-Evans rats. Fifteen minutes after diene injection, the rats were immunized with sheep erythrocytes. Five days later, serum and spleen cells obtained from these immunized rats were tested for IgM immunity against sheep erythrocytes. Both plaque-forming cells from spleen and hemagglutination titers in serum were significantly enhanced in the group treated with dienes obtained from the thermally injured rats. These data suggest that conjugated diene-bearing lipid fractions from burn plasma may modulate immune function and support the concept that humoral immunity is enhanced after thermal injury.

The use of immobilized protamine in removing heparin and preventing protamine-induced complications during extracorporeal blood circulation

Heparin, currently used in extracorporeal blood circulation procedures, may lead to hemorrhagic complications. Protamine, used for reversal of heparin-induced anticoagulation at the end of such procedures, can cause adverse hemodynamic responses. To prevent both types of complications, we have developed a reactor device containing immobilized protamine (i.e., a protamine bio-reactor) that can be placed at the distal end of the circuit, thus providing simultaneous extracorporeal heparin removal and protamine treatment. In preliminary in vivo studies involving dogs at a blood flow of 100 ml/min, the bio-reactor removed about 50% of the administered dose of heparin (i.e., 100 units/kg) in 10 min. While rapid injection of protamine in dogs anticoagulated with heparin produced a transient and significant (P less than 0.005) decreases in systemic arterial blood pressure (-39.5 +/- 9.2 mmHg), cardiac output (-1.59 +/- 0.23 L/min), and mixed venous oxygen saturation (-7.5 +/- 1.3%) and increases in pulmonary artery systolic (+12.7 +/- 4.4 mmHg) and diastolic pressures (+10.0 +/- 3.6 mmHg), the use of the protamine bio-reactor did not elicit any statistically significant change in any of the variables measured. Hemolysis was not significant, as reflected by a statistically insignificant change of the animals' red blood cell counts, hematocrits, and total hemoglobin values. In addition, hemolytic complement was found to be reduced only by 10% in animals with the protamine bio-reactor, whereas it was reduced rapidly by 20% in animals receiving intravenous protamine administration and progressively by 20% in control animals with a sham reactor that contained no protamine. Furthermore, the use of the protamine bio-reactor also significantly reduced the protamine-induced transient thrombocytopenic and granulocytopenic responses. The white blood cell counts and platelet counts decreased to 87.7 +/- 7.5 and 83.3 +/- 5.0% of baseline, respectively, in dogs with the protamine bio-reactor compared to 35.5 +/- 14.3 and 32.1 +/- 8.1% of baseline in dogs receiving intravenous protamine. The protamine bio-reactor may provide a unique means to simultaneously control both heparin- and protamine-induced complications.

Absence of complement-mediated events after protamine reversal of heparin anticoagulation

Protamine reversal of heparin anticoagulation is associated with adverse hemodynamic effects that may be attenuated with protamine pretreatment (PP). This study assesses the role of complement activation during these phenomena in adult cardiac surgery patients. Sixteen individuals undergoing cardiopulmonary bypass were given intravenous normal saline or protamine (2 mg/kg) as a randomized pretreatment prior to undergoing heparin anticoagulation (400 IU/kg), coronary artery revascularization, and subsequent reversal of the anticoagulated state with protamine (4 mg/kg). Blood pressure, pulmonary artery diastolic pressure (PAD), heart rate, and cardiac output (CO) were measured during and after pretreatment, prior to heparin reversal by protamine, and for 10 min after reversal. Total hemolytic complement (CH50), C3 conversion to C3b, C3a/C5a, platelet count, and white blood cell count (WBC) were also measured at the same time periods. No significant correlation existed between complement activation and hemodynamic events, as might have been evident by decreased CH50, increased C3 conversion to C3b, or elevations in C3a/C5a levels. PP significantly prevented the CO decrease occurring at 1 and 3 min following heparin reversal by protamine (-0.8 and -1.4 liters/min vs 0.1 and -0.2 liters/min, P less than 0.05 and P less than 0.01, respectively). Reversal hypotension was less with PP, although PAD fell equally in both groups. WBC decreases after heparin reversal were less after PP (-25% vs -7%, P = 0.06). These data support the conclusion that, contrary to earlier reports, adverse hemodynamic and hematologic responses accompanying protamine reversal of heparin anticoagulation do not appear to be correlated with activation of complement. In fact, those patients having the greatest C3a generation exhibited the least hemodynamic changes.

Mechanisms of oxidant-induced changes in erythrocytes

There is an increasing body of experimental studies demonstrating the toxic effects of oxygen-derived free radicals. Evidence supports an important role for free radicals in ischemic injuries, inflammation, and chemical-induced tissue injury. Free radicals are involved in normal biochemical processes like oxidative reduction and cellular metabolism; however, they also mediate disease processes. The participation of oxygen free radicals in lysis of red cells is important in some situations of intravascular hemolysis. This article will review neutrophil-derived oxygen free radicals, emphasizing: (1) their effects on the erythrocyte and (2) how these effects may be attenuated.

Enhancement of humoral immunity by heterologous lipid peroxidation products resulting from burn injury

Lipid peroxidation products (conjugated dienes) extracted from the plasma of scald-burned rats were injected intraperitoneally in mice before immunization of the mice with sheep erythrocytes. Five-day plaque-forming cell assays showed that mice receiving conjugated dienes isolated from the plasma of burned rats had enhanced specific immunoglobulin M antibody production compared to mice receiving dienes from normal rat plasma or sheep erythrocytes alone. These observations suggest that lipid peroxidation products in the plasma of burned animals may modulate the humoral immune response.