Current view of neutrophil dysfunction: an integrated clinical perspective

Cytoplasmic pH regulation in phorbol ester-activated human neutrophils

Activation of neutrophils by 12-O-tetradecanoylphorbol-13-acetate (TPA) is accompanied by an initial cytoplasmic acidification, followed by an alkalinizing phase due to Na+-H+ countertransport. The source of the acidification, which is fully expressed by activation with TPA in Na+-free or amiloride-containing media, was investigated. The acidification phase was detected also in degranulated and enucleated cytoplasts, ruling out a major contribution by the nucleus or secretory vesicles. Cytoplasmic acidification was found to be associated with an extracellular acidification, suggesting metabolic generation of H+. Two principal metabolic pathways are stimulated in activated neutrophils: the reduction of O2 by NADPH-oxidase and the hexose monophosphate shunt. A good correlation was found between the activity of these pathways and the changes in cytoplasmic pH. Inhibition of superoxide synthesis prevented the TPA-induced cytoplasmic acidification. Moreover, activation of the hexose monophosphate shunt with permeable NADPH-oxidizing agents (in the absence of TPA) also produced a cytoplasmic acidification. Cytoplasmic acidification was also elicited by exogenous diacylglycerol and by other beta-phorbol diesters, which are activators of the kinase, but not by unesterified phorbol or by alpha-phorbol diesters, which are biologically inactive. The results suggest that the cytoplasmic acidification induced by phorbol esters in neutrophils reflects accumulation of H+ liberated during the metabolic burst that follows activation.

Granulocyte dysfunction and myotonic dystrophy

A 52-year-old Caucasian male with typical features of myotonic dystrophy (MD) developed a lung abscess and was found to have a mild atypical cyclic neutropenia. Granulocyte function testing revealed a defect in phagocytosis, bactericidal activity and chemotaxis. The defects were less severe at the nadir of the granulocyte counts. Skin windows demonstrated that the granulocyte defects were not just an in vitro artifact. The patient was treated with lithium carbonate and improved. Mobilization into a skin window and clinical MD were unchanged. Studies of his 10 children and 2 siblings, including granulocyte function tests and complete neurological evaluations were obtained. The 4 children with abnormal parameters of granulocyte function all had definite evidence of MD. Two children had equivocal findings of MD and the others were normal. There was minimal evidence of granulocyte dysfunction in these children. Twelve of 19 unrelated patients with MD had evidence of impaired granulocyte function with the most consistent defect being chemotaxis in response to bacterial factor. Mild granulocyte dysfunction is frequently associated with MD, but severe dysfunction with many defects is uncommon but can occur, as in this family. There was a tendency for the more severely afflicted members of this family to have more pronounced granulocyte dysfunction. Longitudinal testing in this family may determine any relationship between the granulocyte dysfunction and the onset of MD, as well as any correlation with the progression of the disorder. MD patients who develop infection should have granulocyte function tests as part of their evaluation.

Characterization of the amiloride-sensitive Na+-H+ antiport of human neutrophils

In response to infection, neutrophils undergo a metabolic burst associated with a marked increase in acid generation. However, cytoplasmic pH (pHi) remains normal or even becomes slightly alkaline. Regulation of pHi is due, at least in part, to a Na+-H+ exchange mechanism. The basic properties of this antiport were investigated in human blood neutrophils using fluorescein derivatives as pHi indicators and by means of electronic cell sizing. Addition of external Na+ (Na+o) to acid-loaded cells resulted in intracellular alkalinization due to transmembrane H+ (equivalent) flux. The alkalinization was associated with Na+ uptake, and both processes were blocked by amiloride, suggesting Na+-H+ countertransport. The rate of amiloride-sensitive H+ efflux could be calculated from the rate of change of pHi, using a buffering power of 28 mmol X l-1 X pH unit-1, determined by titration with NH+4 or propionate-. The rate of Na+o-H+i exchange was a saturable function of Na+o (apparent Km = 73 mM). Forward (Na+o-H+i) exchange was inhibited by elevating external [H+] or internal [Na+] and competitively by amiloride (apparent Ki = 24 microM). The antiport was virtually inactive in unstimulated cells at pHi greater than or equal to 7.2 but was markedly stimulated by cytoplasmic acidification. This behavior is consistent with a role in pHi homeostasis. The possible mechanisms of stimulation of Na+-H+ countertransport in resting and activated neutrophils are discussed.

Comparison of blood and peritoneal neutrophil activity in rabbits with and without peritonitis

The neutrophil (polymorphonuclear cell, or PMN) function is an essential component of the host defense against infection. However, infection itself may alter PMN activity. To investigate both the effects of infection on PMN activity and PMN activity on survival, we evaluated control and infected blood and peritoneal PMN phagocytosis, chemotaxis, and superoxide anion production in rabbits with and without peritonitis. Control blood and peritoneal PMNs were obtained from noninfected rabbits which were subjected to intraperitoneal infusion of sterile hypertonic saline. Infected blood and peritoneal PMNs were obtained from rabbits which had undergone appendiceal devascularization and ligation 18 hr earlier. Phagocytosis was similar in all groups except for a threefold increase in normal peritoneal PMNs. Chemotaxis was inhibited by infection in the blood and peritoneal PMNs. Normal peritoneal PMNs also had decreased chemotaxis. Superoxide anion production was comparable in the infected and control blood; however, both control and infected peritoneal PMNs had elevated superoxide anion production. Of the infected rabbits, four died in 5 days or less. Of the six that lived, two developed intraabdominal abscesses. Blood and peritoneal PMN activity was similar in all rabbits despite their outcome. We conclude that (1) blood and peritoneal PMNs have different basal activities and responses to infection; (2) the milieu of the peritoneal cavity appears to alter the PMNs present; and (3) PMN activity did not predict morbidity or mortality.

The leukergy test in rheumatic diseases. New implications for an old test

In order to assess the value of the leukergy test in which leukocytes aggregate in citrated whole blood, we examined 65 patients with various rheumatic conditions. In addition, plasma samples from 40 patients were examined for neutrophil aggregation activity in vitro. Results of the leukergy test were found to be in very good correlation with disease activity (P = 0.0001), whereas no increased neutrophil aggregation activity was found in the 40 plasma samples examined. The value of the leukergy test in assessing patients with rheumatic disease and its theoretical etiopathogenic role in these diseases are discussed.

Pertussis toxin inhibition of chemotactic factor-induced calcium mobilization and function in human polymorphonuclear leukocytes

Chemotactic factors stimulate a rapid increase in the cytosolic concentration of intracellular calcium ions ([Ca2+]in) in human polymorphonuclear leukocytes (PMNL), which may be an event that is critical to the expression of chemotaxis and other PMNL functions. Treatment of PMNL with pertussis toxin catalyzes ADP-ribosylation of a protein similar or identical to the inhibiting regulatory protein of adenylate cyclase, Gi, and suppresses the increase in [Ca2+]in elicited by leukotriene B4(LTB4) and formyl-methionyl-leucyl-phenylalanine. Chemotactic migration and lysosomal enzyme release elicited by chemotactic factors were inhibited by pertussis toxin with a concentration-dependence similar to that for inhibition of the increase in [Ca2+]in, without an effect on lysosomal enzyme release induced by the ionophore A23187 and phorbol myristate acetate. Activated pertussis toxin catalyzed the [32P]ADP-ribosylation of a 41 kD protein in homogenates of PMNL. The extent of [32P]ADP-ribosylation of this protein was reduced 59% by pretreatment of intact PMNL with pertussis toxin. Pertussis toxin selectively decreased the number of high-affinity receptors for LTB4 on PMNL by 60% without altering the number or binding properties of the low-affinity subset of receptors. Pertussis toxin modification of a membrane protein of PMNL analogous to Gi thus simultaneously alters chemotactic receptors and attenuates the changes in cytosolic calcium concentration and PMNL function caused by chemotactic factors.

Effects of methotrexate, ampicillin and gentamicin alone and in combination on the in vitro locomotion on human polymorphonuclear cells (PMN)

The effect of ampicillin 25 mg/ml, gentamicin 5 mg/l and methotrexate 10 & 70 mg/l, alone and in combination, was tested for their influence on human polymorphonuclear cell-locomotion, using zymosan or a bacterial filtrate of E. coli, with or without 0.25 and 0.025 mg/l of ampicillin and gentamicin, respectively, as attractants. Methotrexate and gentamicin alone decreased the locomotion, using zymosan as attractant. No effect was observed using the pure bacterial filtrate. The filtrate containing antibiotics displayed a lower ability to induce locomotion when the leucocytes had been pre-treated with antibiotics alone or in combination with methotrexate but not with methotrexate alone. Aspects of these findings are discussed.

Amiloride-sensitive Na+/H+ exchange in human neutrophils: mechanism of activation by chemotactic factors

The cytoplasmic pH (pHi) of human blood neutrophils was measured using trapped carboxyfluorescein derivatives. Cells were acid-loaded using propionate or by pretreatment with NH4+. Acid-loaded cells were found to regain near-normal pHi by means of a Na+-dependent process. A concomitant Na+ uptake was recorded as a change in cell volume. Both events were amiloride-sensitive, indicating involvement of a Na+/H+ antiport. Activation of Na+/H+ exchange was also observed with chemotactic factors. Studies of the pHi-dependence of the H+ extrusion rate indicate that chemotactic factors increase the [H+i] sensitivity of the antiport.

Plaque and systemic disease: a reappraisal of the focal infection concept

The review presented here covers metastatic local and systemic disease secondary to the accumulation of plaque or the formation of other pathogenic microbial depots in the mouth. At least 3 pathways may link oral infection to secondary disease, to wit metastatic infection due to transient bacteremia, metastatic immunological injury, and metastatic toxic injury. The available evidence is presented and examples are provided. They concern among others such divergent diseases as acute bacterial myocarditis, infective endocarditis, brain abscess, uveitis and iridocyclitis, trigeminal and atypical facial neuralgia, unilateral facial paralysis, fever of "unknown' origin, and neutrophil dysfunction.

Newer aspects of regulation of human granulocyte function

The regulation of granulocyte function by cell-derived factors is emphasised in this review. The most important of these cell-derived factors belongs to a class of substances known as colony stimulating factors (CSF) so named because they stimulate the maturation of progenitor cells into clumps or "colonies" of mature cells. CSF mediated regulation of granulocytes is likely to be important for the two reasons (i) the site of CSF production can determine the site of granulocyte activation and (ii) the type of CSF produced can determine the type of granulocyte activated. Blood mononuclear cells were found to be a good source of granulocyte activating material suggesting that interaction between these two cell types is important in vivo. The potential clinical use of CSF-like substances is discussed.

Occlusion and infection in Broviac catheters during intensive cancer therapy

Before administration of intensive cytotoxic therapy, 90 central venous catheters were inserted into 80 patients with malignancies. Twenty-seven episodes of bacteremia and fungemia occurred during 96 treatment courses. The majority of these infections were due to gram-positive bacteria (45%) or fungi (22%), although gram-negative organisms accounted for 33%. Catheter occlusion occurred in patients receiving intravenous phenytoin, but blood products could be infused without difficulty. An increase in gram-positive bacteremias in patients with these catheters and drug-induced catheter occlusion must now be appreciated.

Oxidation of methionine residues in proteins of activated human neutrophils

A simple assay for the detection of 35S-labeled methionine sulfoxide residues in proteins is described. The assay, which is based on the ability of CNBr to react with methionine but not with methionine sulfoxide, requires the prelabeling of cellular proteins with [35S]methionine. The assay was used to study the extent of methionine oxidation in newly synthesized proteins of both activated and quiescent human neutrophils. In cells undergoing a phorbol 12-myristate 13-acetate-induced respiratory burst, about 66% of all methionine residues in newly synthesized proteins were oxidized to the sulfoxide derivative, as compared with 9% in cells not treated with the phorbol ester. In contrast, quantitation of methionine sulfoxide content in the total cellular protein by means of amino acid analysis showed that only 22% of all methionine residues were oxidized in activated cells as compared with 9% in quiescent cells. It is proposed that methionine residues in nascent polypeptide chains are more susceptible to oxidation than those in completed proteins.