Neutrophil function and metabolism in individuals with diabetes mellitus.

Neutrophils act as first-line-of-defense cells and the reduction of their functional activity contributes to the high susceptibility to and severity of infections in diabetes mellitus. Clinical investigations in diabetic patients and experimental studies in diabetic rats and mice clearly demonstrated consistent defects of neutrophil chemotactic, phagocytic and microbicidal activities. Other alterations that have been reported to occur during inflammation in diabetes mellitus include: decreased microvascular responses to inflammatory mediators such as histamine and bradykinin, reduced protein leakage and edema formation, reduced mast cell degranulation, impairment of neutrophil adhesion to the endothelium and migration to the site of inflammation, production of reactive oxygen species and reduced release of cytokines and prostaglandin by neutrophils, increased leukocyte apoptosis, and reduction in lymph node retention capacity. Since neutrophil function requires energy, metabolic changes (i.e., glycolytic and glutaminolytic pathways) may be involved in the reduction of neutrophil function observed in diabetic states. Metabolic routes by which hyperglycemia is linked to neutrophil dysfunction include the advanced protein glycosylation reaction, the polyol pathway, oxygen-free radical formation, the nitric oxide-cyclic guanosine-3'-5'monophosphate pathway, and the glycolytic and glutaminolytic pathways. Lowering of blood glucose levels by insulin treatment of diabetic patients or experimental animals has been reported to have significant correlation with improvement of neutrophil functional activity. Therefore, changes might be primarily linked to a continuing insulin deficiency or to secondary hyperglycemia occurring in the diabetic individual. Accordingly, effective control with insulin treatment is likely to be relevant during infection in diabetic patients.

Role of insulin on PGE2 generation during LPS-induced lung inflammation in rats.

Alterations in arachidonic acid (AA) metabolism have been reported to occur in diabetes mellitus. The present study was carried out to verify if these alterations are due to the relative lack of insulin or to high levels of blood glucose. Male Wistar rats were rendered diabetic by alloxan injection (42 mg/kg, i.v.), 10 or 30 days before the experiments. Some diabetic rats received a single dose (4 IU, s.c.) of NPH insulin 2 h before an intratracheal instillation of lipopolysaccharide (LPS, 750 microg) or saline. Six hours after LPS challenge, the following parameters were analysed: blood glucose levels, total and differential leukocyte counts in bronchoalveolar lavage (BAL) fluid; linoleic acid and AA content in blood neutrophils (HPLC), and levels of prostaglandin (PG)E(2) in BAL (ELISA). Relative to controls, a reduced number of neutrophils (18%) and decreased amounts of PGE(2) (40%) were observed in the BAL fluid of diabetic rats in response to LPS. A single dose of insulin was not able to reduce blood sugar levels to normal values, but instead resulted in the normalization of both leukocyte migration to the lungs and levels of PGE(2). Accordingly, these abnormalities might be primarily linked to a continuing insulin deficiency rather than to secondary hyperglycaemia occurring in the diabetic rat. In conclusion, data presented suggest that insulin might regulate neutrophil migration and generation of PGE(2) during the course of acute lung injury induced by LPS.

Inhibition of leukocyte chemotaxis by factor in alloxan-induced diabetic rat plasma.

The early local exudative cellular reaction in an inflammatory lesion was impaired in alloxan-induced diabetic rats due to reduced migration of neutrophils to the inflamed area. Neutrophils, however, were capable of moving from reserve compartments into blood in these animals. Furthermore, the functional integrity of their surface membranes, assessed by the capacity of the cells to adhere to nylon fiber, was not altered by alloxan diabetes. An intrinsic cellular defect also did not occur, because the cells were capable of responding to chemotactic stimuli in the Boyden chamber system, provided they were suspended in Eagle's medium or normal serum. Suspended in the corresponding diabetic serum, a blockade of the chemotactic response was observed. Increasing concentrations of diabetic serum, added to a suspension containing neutrophils collected from normal donors, progressively inhibited the response of the cells to a chemotactic stimulus. Hyperglycemia alone or hyperosmolality secondary to hyperglycemia, the presence of ketone bodies, or a direct effect of alloxan did not explain the results. In addition, the capacity to generate chemotactic factors remained intact in diabetic serum. Pretreatment of the diabetic animals with insulin resulted in a gradual recovery of the chemotactic response in vivo and in vitro. We conclude that alloxan-induced diabetic rat serum contains a substance that inhibits neutrophil chemotaxis and that insulin administration is essential for the clearance of this substance from plasma.

Secreted glucocorticoids regulate leukocyte-endothelial interactions in inflammation. A direct vital microscopic study.

Leukocytes come into intimate contact with the venular endothelium as they extravasate from blood to the interstitium during inflammation. In exteriorized tissues, the number of leukocytes rolling along the vessel wall was markedly increased in adrenalectomized and metyrapone-treated animals, relative to sham-operated and normal animals. During the development of an acute, local inflammatory response, rollers were numerically decreased and a stronger adhesion of the cells to the endothelium, with a concomitant migration into tissues, was observed. Adhesion and migration were much more marked in adrenalectomized and metyrapone-treated animals than in controls, suggesting that secreted glucocorticoids exert a suppressive effect on leukocyte-endothelial interactions. The increased number of rolling leukocytes in adrenalectomized and metyrapone-treated animals apparently resulted in more cells available to migrate into inflamed tissues. The effect appears to involve receptor occupancy and induction of gene expression because normal animals receiving the steroid antagonist RU 38 486, actinomycin D, or cycloheximide behaved as adrenalectomized or metyrapone-treated animals. Administration to adrenalectomized animals of a monoclonal antibody to the membrane glycoprotein complex CD18 did not affect the number of rolling cells, but dramatically reduced the number of adherent or migrated leukocytes. It is suggested that secreted glucocorticoids, in addition to an effect on rolling behavior of circulating leukocytes, might also modulate the activity of the glycoprotein complex CD18 on white blood cells. The ultimate consequence is a restrictive effect on cell emigration in inflammation.

Inhibition of neutrophil chemotaxis and chemokinesis associated with a plasma protein in aging rats: selective depression of cell responses mediated by complement-derived chemoattractants.

The influence of aging on neutrophil chemotaxis, chemokinesis, and superoxide production was investigated in rats. Animals of two age groups, 3 to 4 months and 20 to 21 months, were used. Equivalent neutrophil chemotactic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), leukotriene B4 (LTB4), and bacterial lipopolysaccharide (LPS)-activated plasma were observed in both groups of animals, with cells suspended in Hanks' balanced salt solution (HBSS). However, cross-incubation studies in which cells from young adult rats were exposed to plasma from aged donors, then resuspended in HBSS for testing, showed marked changes in the ability of the cells to respond to the chemoattractants. The response to LPS-activated plasma was reduced, whereas responses to fMLP and LTB4 remained unaltered. Previous incubation of the cells with homologous plasma from young donors produced no effect. The inhibitory activity developing with advancing age affected not only chemotaxis but also random movement stimulated by LPS-activated plasma. The inhibitory activity of chemotaxis and chemokinesis in plasma of aged animals was heat labile (56 degrees C), vanished in the presence of a proteolytic enzyme like trypsin, and was maintained after dialysis with 12,000-Mr retention dialysis tubing. The material did not influence superoxide production by stimulated neutrophils. It is suggested that inhibition of neutrophil locomotion with advancing age is associated with a plasma protein capable of interacting with neutrophil receptors for complement-derived chemoattractants. The inhibitory substance might influence neutrophil responses to infection and inflammation in the elderly.

Spontaneously hypertensive versus control rat aorta response to neutrophil-derived factors.

We designed experiments to study the interaction of activated rat peritoneal neutrophils with aortas from spontaneously hypertensive rats (SHR) compared with those from normotensive rats. In aortic rings precontracted with phenylephrine, neutrophils obtained from normotensive rats caused a cell number-dependent relaxation of normotensive rat aorta with or without endothelium, whereas relaxation (at lower concentrations) followed by contraction (at higher concentrations) was observed in SHR aorta with endothelium. In SHR aortic rings denuded of endothelium, neutrophils did not induce contraction. The relaxation might be due to a factor indistinguishable from nitric oxide. The contraction might be due to prostaglandin H2 because it was blocked by indomethacin, a cyclooxygenase inhibitor, and ridogrel, a thromboxane A2 synthetase inhibitor/thromboxane A2-prostaglandin H2 antagonist, but not by superoxide dismutase, a superoxide anion scavenger, or dazoxiben, a thromboxane A2 synthetase inhibitor. SHR neutrophils caused a cell number-dependent relaxation of normotensive rat aorta with or without endothelium, whereas relaxation followed by contraction was observed in SHR aorta with endothelium. In SHR aortic rings denuded of endothelium, neutrophils did not induce contraction. The relaxation might be due to a factor indistinguishable from nitric oxide. The contraction seems to be due to superoxide anion because it was inhibitable by indomethacin and superoxide dismutase but not by dazoxiben and ridogrel. Equivalent amounts of superoxide anion were produced by unstimulated and phorbol myristate acetate-stimulated neutrophils obtained from either SHR or normotensive rats. Therefore, increased production of this anion could not explain the contraction observed in hypertensive aortas.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoguanidine and the prevention of leukocyte dysfunction in diabetes mellitus: a direct vital microscopic study.

1. Defective leukocyte-endothelial interactions are observed in experimental diabetes mellitus. The present study investigated the effect of aminoguanidine, an inhibitor of advanced glycation end products formation, on leukocyte-endothelial interactions in alloxan-induced diabetic rats. 2. In rats anaesthetized with sodium pentobarbitone, the internal spermatic fascia was exteriorized and the microcirculation was observed by a closed-circuit TV coupled to a microscope. The number of leukocytes rolling along the venular endothelium and sticking to the vascular wall was determined after topical application of zymosan-activated plasma (1 mg ml(-1)), as well as the number of adherent and migrated cells after an irritative stimulus (carrageenan 100 microg). 3. The diabetic state decreased the number of rolling, sticking and migrated leukocytes. Pretreatment of diabetic animals with aminoguanidine (250 mg kg(-1) day(-1), for 18 days) normalized these values. To be effective, aminoguanidine had to be administered chronically, starting treatment before induction of the diabetic state. 4. The preventive effect was unrelated to the number of circulating leukocytes, or to the hyperglycaemia or to the hyperosmolality secondary to hyperglycaemia. 5. A non-dialyzed (>12,000-Mr) material in plasma from diabetic, but not normal animals, decreased the number of rolling, sticking and migrated leukocytes in recipient rats. This effect was completely abolished by chronic treatment of diabetic plasma donors with aminoguanidine. 6. The results suggest that a protein modified by glycosylation (>12 kDa) is associated with leukocyte dysfunction in diabetes mellitus and that the ability of aminoguanidine to prevent such dysfunction is related to an inhibitory effect on advanced glycation end products formation.

Inducible nitric oxide synthase in rat neutrophils: role of insulin.

Defective leukocyte-endothelial interactions are observed in experimental diabetes mellitus. Endogenous substances, including nitric oxide (NO), have anti-inflammatory effects within the vasculature by reducing leukocyte adherence to post-capillary venules. The purpose of this study was to examine the activity and expression of NO synthase in neutrophils from alloxan-induced diabetic rats. Glycogen-elicited peritoneal neutrophils were obtained from diabetic rats and matching controls 10, 30, and 180 days after alloxan (42 mg/kg, i.v.) or saline injection. NO synthase activity was determined by the [3H]L-citrulline assay method. Expression of the enzyme was investigated by western blot analysis. Relative to controls, neutrophils obtained from diabetic rats presented a 2-fold increase in the activity of inducible NO synthase (iNOS), accompanied by an increase in the expression of the enzyme depicted by western blot. Treatment of diabetic animals with NPH insulin (2 IU/day, for 3 days) reduced both the activity and expression of iNOS to normal levels. Results presented suggest that overexpression of the inducible isoform of NO synthase by neutrophils may be responsible, at least in part, for the defects in leukocyte-endothelial interactions in diabetes mellitus.

Denervation supersensitivity to noradrenaline in the guinea-pig vas deferens in vivo: absence of the postjunctional component.

The effects of denervation and cocaine on the responsiveness of the guinea-pig vas deferens to noradrenaline (NA) were studied. The magnitude of the denervation supersensitivity differed in vivo and in vitro. Cocaine-induced supersensitivity to NA was similar in vivo and in vitro. Only denervation increased the maximum response in experiments in vitro. It is suggested that in the guinea-pig vas deferens the postjunctional component of denervation supersensitivity to NA could result from the experimental conditions involving the isolation procedure.

Responsiveness of the guinea-pig vas deferens to phenylephrine and norepinephrine in vivo.

A method is described for the study of guinea-pig vas deferens in vivo response to phenylephrine and norepinephrine. Tissue sensitivity to both agonists did not differ in vivo but the maximum response to phenylephrine was smaller. Responsiveness to norepinephrine was depressed in vitro after in vivo experiments. No such effect was observed for phenylephrine. This method allowed the comparison of the responsiveness of the guinea-pig vas deferens to adrenoceptor agonists in vivo and in vitro.

Inhibition of eosinophil chemotaxis by chronic blockade of nitric oxide biosynthesis.

The effect of chronic N omega-nitro-L-arginine methyl ester (L-NAME) treatment on the in vivo eosinophil migration induced by bradykinin, platelet-activating factor (PAF), lipopolysaccharide and carrageenin has been investigated in the rat using the pleurisy model. The in vitro (microchemotaxis chamber) eosinophil migration induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP), PAF and zymosan-activated serum was also evaluated in the rat. The eosinophils were obtained from the peritoneal cavity of male Wistar rats and isolated on a discontinuous metrizamide gradient. Chronic inhibition of nitric oxide biosynthesis was achieved by adding L-NAME to the drinking water to give an intake of approximately 75 mumol/rat/day for 4 weeks. Rats treated chronically with L-NAME developed a significant level of hypertension (163 +/- 4.8 mmHg; P < 0.01) compared with animals which received either the same dose of the inactive enantiomer D-NAME (124 +/- 3.2 mmHg) or tap water alone (119 +/- 1.6 mmHg). The intrapleural injection of bradykinin (50 micrograms), PAF (1 microgram), lipopolysaccharide (0.25 microgram) and carrageenin (125 micrograms) into untreated rats in vivo induced a significant level of eosinophil migration by 24 h post-injection. This migration was markedly reduced in L-NAME-treated rats. Eosinophils obtained from untreated rats showed a significant level of migration in vitro in response to fMLP (5 X 10(-8) M), PAF (10(-8) M) and zymosan-activated serum (27 microliters). In contrast, the migration induced by these chemotactic agents was markedly reduced in cells isolated from animals treated chronically with L-NAME. L-Arginine (5.5 mM), but not D-arginine (5.5 mM), restored the ability of eosinophils from L-NAME-treated animals to migrate in response to fMLP. Our results indicate that nitric oxide plays a major role in the in vivo and ex vivo migration of eosinophils.

Nitric oxide modulates eosinophil infiltration in antigen-induced airway inflammation in rats.

The influence of nitric oxide (NO) on eosinophil infiltration into the airways was investigated in rats actively sensitized with ovalbumin. The animals were treated chronically with the NO synthase inhibitor, N omega-Nitro-L-arginine methyl ester (L-NAME; 75 mumol rat-1 day-1), for 4 weeks. Bronchoalveolar lavage was performed at 6, 24, 48 and 72 h after intratracheal injection of ovalbumin. Intratracheal challenge of the sensitized rats with ovalbumin caused a significant increase in total leucocyte infiltration in bronchoalveolar lavage fluid both 24 and 48 h post-ovalbumin injection. Neutrophils and eosinophils peaked, respectively, at 24 h (29%) and 48 h (30%) in bronchoalveolar lavage fluid whereas the mononuclear cell did not differ significantly from the counts in non-sensitized rats at any time. At both 6 and 24 h post-ovalbumin injection, the chronic treatment of the animals with L-NAME affected neither the total nor the differential leucocyte content. However, at 48 h post-ovalbumin challenge, the total cell count was reduced by approximately 48% in the L-NAME-treated animals and this was associated with a marked inhibition (81%) of the eosinophil influx. Histological examination of the lungs from these animals (48 h post-ovalbumin challenge) also showed a prominent reduction (69.5%; P < 0.05) of the eosinophil infiltration in the respiratory segments. Our results demonstrate that NO plays a pivotal role in the eosinophil infiltration in airways of actively sensitized rats.

Reduced inflammatory response in rats fed fat-rich diets: role of leukotrienes.

The effect of fat-rich diets on the acute inflammatory response was examined. Male Wistar rats aged 21 days were fed, for 6 weeks, with a control diet (4% fat content), or a control diet supplemented with coconut or soybean oils (15% fat content). Carrageenan-induced paw oedema and pleurisy were evaluated. Prostaglandin (PG) E2 and leukotriene (LT) C4/D4 concentrations were determined in the pleural exudate (ELISA). Pleural samples were tested for their effect on cutaneous vascular permeability of control rats and the effect of a LTD4 receptor antagonist (L660-711; 10 mg/kg; i.v.) examined. Relative to controls, rats fed both fat-rich diets presented a significant reduction in protein leakage and oedema formation without affecting the number of migrating leukocytes. Production of LTC4/D4 in pleural exudate was significantly increased from 1.8 +/- 0.2 ng/ml in controls to 2.8 +/- 0.2 and 3.0 +/- 0.3 ng/ml in animals fed coconut and soybean oil enriched diets, respectively, without changes in PGE2 production. The activity of these samples on cutaneous vascular permeability was 50% reduced, returning to control values after treatment of testing animals with a LTD4 receptor antagonist. Rats fed fat-rich diets presented a reduced inflammatory response due, at least in part, to the LTC4/D4 mediated vasoconstrictor effect.

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.

Effect of fatty acids on leukocyte function.

Fatty acids have various effects on immune and inflammatory responses, acting as intracellular and intercellular mediators. Polyunsaturated fatty acids (PUFAs) of the omega-3 family have overall suppressive effects, inhibiting lymphocyte proliferation, antibody and cytokine production, adhesion molecule expression, natural killer cell activity and triggering cell death. The omega-6 PUFAs have both inhibitory and stimulatory effects. The most studied of these is arachidonic acid that can be oxidized to eicosanoids, such as prostaglandins, leukotrienes and thromboxanes, all of which are potent mediators of inflammation. Nevertheless, it has been found that many of the effects of PUFA on immune and inflammatory responses are not dependent on eicosanoid generation. Fatty acids have also been found to modulate phagocytosis, reactive oxygen species production, cytokine production and leukocyte migration, also interfering with antigen presentation by macrophages. The importance of fatty acids in immune function has been corroborated by many clinical trials in which patients show improvement when submitted to fatty acid supplementation. Several mechanisms have been proposed to explain fatty acid modulation of immune response, such as changes in membrane fluidity and signal transduction pathways, regulation of gene transcription, protein acylation, and calcium release. In this review, evidence is presented to support the proposition that changes in cell metabolism also play an important role in the effect of fatty acids on leukocyte functioning, as fatty acids regulate glucose and glutamine metabolism and mitochondrial depolarization.

Inhibition of neutrophil chemotaxis by plasma of burned patients: effect of blood transfusion practice.

Incubation of normal human neutrophils with plasma from burned patients markedly reduced the ability of the cells to respond to a chemotactic stimulus in vitro. Previous transfusion of the patients with packed red blood cells did not alter the inhibited locomotion of neutrophils, whereas transfusion with normal plasma alone attenuated or even abolished the inhibitory activity. The finding provides direct evidence for the involvement of circulating suppressive factors in neutrophil chemotaxis, rendering burned patients more susceptible to infections. In addition, it stresses the relevance of plasma transfusion in clinical management and infection control following thermal injury.

Inhibition of autonomic storm by epidural anesthesia does not influence cardiac inflammatory response after brain death in rats.

BACKGROUND: After brain death (BD) donors usually experience cardiac dysfunction, which is responsible for a considerable number of unused organs. Causes of this cardiac dysfunction are not fully understood. Some authors argue that autonomic storm with severe hemodynamic instability leads to inflammatory activation and myocardial dysfunction. OBJECTIVES: To investigate the hypothesis that thoracic epidural anesthesia blocks autonomic storm and improves graft condition by reducing the inflammatory response. METHODS: Twenty-eight male Wistar rats (250-350 g) allocated to four groups received saline or bupivacaine via an epidural catheter at various times in relation to brain-death induction. Brain death was induced by a sudden increase in intracranial pressure by rapid inflation of a ballon catheter in the extradural space. Blood gases, electrolytes, and lactate analyses were performed at time zero, and 3 and 6 hours. Blood leukocytes were counted at 0 and 6 hours. After 6 hours of BD, we performed euthanasia to measure vascular adhesion molecule (VCAM)-1, intracellular adhesion molecule (ICAM)-1, interleukin (IL)-1ß, tumor necrosis factor (TNF)-α, Bcl-2 and caspase-3 on cardiac tissue. RESULTS: Thoracic epidural anesthesia was effective to block the autonomic storm with a significant difference in mean arterial pressure between the untreated (saline) and the bupivacaine group before BD (P < .05). However, no significant difference was observed for the expressions of VCAM-1, ICAM-1, TNF-α, IL-1ß, Bcl-2, and caspase-3 (P > .05). CONCLUSION: Autonomic storm did not seem to be responsible for the inflammatory changes associated with BD; thoracic epidural anesthesia did not modify the expression of inflammatory mediators although it effectively blocked the autonomic storm.

Effect of plant neutrophil elastase inhibitor on leucocyte migration, adhesion and cytokine release in inflammatory conditions.

BACKGROUND AND PURPOSE: The serine and cysteine peptidase inhibitor, BbCI, isolated from Bauhinia bauhinioides seeds, is similar to the classical plant Kunitz inhibitor, STI, but lacks disulphide bridges and methionine residues. BbCI blocks activity of the serine peptidases, elastase (K(iapp) 5.3 nM) and cathepsin G (K(iapp) 160.0 nM), and the cysteine peptidase cathepsin L (K(iapp) 0.2 nM). These three peptidases play important roles in the inflammatory process. EXPERIMENTAL APPROACH: We measured the effects of BbCI on paw oedema and on leucocyte accumulation in pleurisy, both induced by carrageenan. Leucocyte-endothelial cell interactions in scrotal microvasculature in Wistar rats were investigated using intravital microscopy. Cytokine levels in pleural exudate and serum were measured by elisa. KEY RESULTS: Pretreatment of the animals with BbCI (2.5 mg·kg(-1)), 30 min before carrageenan-induced inflammation, effectively reduced paw oedema and bradykinin release, neutrophil migration into the pleural cavity. The number of rolling, adhered and migrated leucocytes at the spermatic fascia microcirculation following carrageenan injection into the scrotum were reduced by BbCI pretreatment. Furthermore, levels of the rat chemokine cytokine-induced neutrophil chemo-attractant-1 were significantly reduced in both pleural exudates and serum from animals pretreated with BbCI. Levels of interleukin-1ß or tumour necrosis factor-α, however, did not change. CONCLUSIONS AND IMPLICATIONS: Taken together, our data suggest that the anti-inflammatory properties of BbCI may be useful in investigations of other pathological processes in which human neutrophil elastase, cathepsin G and cathepsin L play important roles.