Rate Of Superoxide Release Research Articles

Suppressors of complex 1 and 3 sites Q electron leak (S1QEL, S3QEL) as tools for in vivo analysis of respiratory chain

We aimed to study contribution of flavin IF, or ubiquinone IQ and IIIQ sites of superoxide formation by the respiratory chain (RC) complexes 1 and 3 in vivo in cancer (HepG2) and non-cancer cells (insulinoma INS-1E) using novel site-specific S1QEL and S3QEL suppressors1. Rates of superoxide release into the mitochondrial matrix (Jm) were semiquantified by MitoSOX Red fluorescence using confocal microscopy (for feasibility see2). Reflecting the IQ superoxide formation, S1QEL nearly completely suppressed rotenone-induced superoxide formation in glycolytic HepG2 cells but was inactive when these cells were forced to oxidative phosphorylation by aglycemia. Similarly, S1QEL was inefficient in INS-1E independently of the glucose dose. In contrast, with the decreasing glucose in INS-1E cells, the S3QEL suppressor indicated a lower superoxide fraction ascribed to the IIIQ site and higher remaining complex 1 IF site contribution, which correlated with higher NADH/NAD+. The export of redox equivalents by three mitochondrial shuttles was responsible for the observed NAD+ increase at higher glucose.

Lercanidipine effect on polymorphonuclear leukocyte-related inflammation and insulin resistance in essential hypertension patients

Inflammation, insulin resistance and oxidative stress (OS), are among the mechanisms that have been implicated in pathogenesis of essential hypertension (EH). Peripheral polymorphonuclear leukocytes (PMNLs) are primed in EH patients, releasing uncontrolled superoxide anion contributing to OS in these patients. PMNL priming correlates with insulin resistance and with PMNL intracellular calcium ([Ca2+]i). Recent studies have attributed to the anti-hypertensive drug lercanidipine, a third generation calcium-channel blocker, and additional anti-ischemic and anti-oxidative characteristics. To evaluate the possible non-traditional effect of two months of lercanidipine treatment on insulin resistance and on PMNL-related inflammation in EH patients. Non-smoking EH patients with untreated mild to moderate high blood pressure (BP) were included. Low-graded inflammation was reflected by WBC and PMNL counts and by PMNL apoptosis. Systemic inflammation was measured by plasma fibrinogen, C-reactive protein (CRP) and albumin levels. Fasting serum insulin levels served as a marker of insulin resistance. Two months of lercanidipine treatment showed significant decrease in BP, WBC and PMNL counts, and also in PMNL apoptosis, CRP and serum insulin levels and significant increase in serum albumin levels. Rates of superoxide release from PMNLs, WBC and PMNL counts and insulin levels positively correlated with mean arterial blood pressure values. We imply that use of lercanidipine can be favored in EH patients due to its combined anti-PMNL priming and anti-inflammatory effects, in addition to its anti-hypertensive characteristics. Key words: Essential hypertension, lercanidipine, low-graded inflammation, primed polymorphonuclear leukocytes, oxidative stress.

Lercanidipine effect on polymorphonuclear leukocyte-related inflammation and insulin resistance in essential hypertension patients.

IntroductionInflammation, insulin resistance, and oxidative stress (OS) are among the mechanisms that have been implicated in the pathogenesis of essential hypertension (EH). Peripheral polymorphonuclear leukocytes (PMNLs) are primed in EH patients, releasing uncontrolled superoxide anions contributing to OS in these patients. PMNL priming correlates with insulin resistance and PMNL intracellular calcium ([Ca2+]i). Recent studies have attributed additional anti-ischemic and antioxidative characteristics to the antihypertensive drug, lercanidipine, a third-generation calcium-channel blocker. The purpose of this study was to evaluate the possible nontraditional effect of 2 months of lercanidipine treatment on insulin resistance and on PMNL-related inflammation in EH patients.MethodsNon-smoking EH patients with untreated mild-to-moderate high blood pressure (BP) were included. Low-grade inflammation was reflected by PMNL apoptosis and by white blood cell (WBC) and PMNL counts. Systemic inflammation was measured by plasma fibrinogen, C-reactive protein (CRP), and transferrin and albumin levels. Fasting serum insulin levels served as a marker of insulin resistance.ResultsTwo months of lercanidipine treatment showed a significant decrease in BP, WBC, and PMNL counts, PMNL apoptosis, CRP, and serum insulin levels, and a significant increase in serum albumin levels. Rates of superoxide release from PMNLs, WBC and PMNL counts, and insulin levels positively correlated with mean arterial BP values.ConclusionThe use of lercanidipine can be favorable in EH patients due to its combined anti-PMNL priming and anti-inflammatory effects, in addition to its antihypertensive characteristics.

Effects of statins on oxidative stress and primed polymorphonuclear leukocytes in hyperlipidemic patients

Inflammation and oxidative stress are among the factors that have been implicated in the pathogenesis of hyperlipidemia. In metabolic syndrome and hyperlipidemic patients, peripheral polymorphonuclear leukocytes (PMNL) are primed and they release uncontrolled superoxide that contributes to oxidative stress and inflammation. Recent studies have demonstrated that the anti-hyperlipidemic drug, Atrovastatin effects improvement in endothelial function, exhibits anti-oxidative characteristics and reduces lipid markers of oxidation. To evaluate possible nontraditional effects of treatment with Atrovastatin on PMNL priming, oxidative stress and inflammation in hyperlipidemia, 50 non-smoking hyperlipidemic patients were treated for 6 months with Atrovastatin and compared to age and gender-matched healthy controls. PMNL priming was assessed by the rate of superoxide release from separated, phorbol ester-stimulated PMNL and by PMNL-CD11b levels. Inflammation was reflected by blood inflammatory markers including albumin, transferrin, C-reactive protein (CRP) and fibrinogen levels, white blood cells (WBC), PMNL counts and PMNL apoptosis. Atrovastatin treatment showed a reduction in PMNL priming, PMNL apoptosis, fibrinogen and CRP levels concomitant with decreased lipid levels. Atrovastatin may be preferred for hyperlipidemic patients owing to its combined anti-PMNL priming and anti-inflammatory effects in addition to its anti-atherogenic effects.

Pro-oxidant mitochondrial matrix-targeted ubiquinone MitoQ 10 acts as anti-oxidant at retarded electron transport or proton pumping within Complex I

Oxidative stress of mitochondrial origin, i.e. elevated mitochondrial superoxide production, belongs to major factors determining aging and oxidative-stress-related diseases. Antioxidants, such as the mitochondria-targeted coenzyme Q, MitoQ 10, may prevent or cure these pathological conditions. To elucidate pro- and anti-oxidant action of MitoQ 10, we studied its effects on HepG2 cell respiration, mitochondrial network morphology, and rates of superoxide release (above that neutralized by superoxide dismutase) to the mitochondrial matrix ( J m). MitoSOX Red fluorescence confocal microscopy monitoring of J m rates showed pro-oxidant effects of 3.5-fold increased J m with MitoQ 10. MitoQ 10 induced fission of the mitochondrial network which was recovered after 24 h. In rotenone-inhibited HepG2 cells (i.e., already under oxidative stress) MitoQ 10 sharply decreased rotenone-induced J m, but not together with the Complex II inhibitor thenoyltrifluoroacetone. Respiration of HepG2 cells and isolated rat liver mitochondria with MitoQ 10 increased independently of rotenone. The increase was prevented by thenoyltrifluoroacetone. These results suggest that MitoQ 10 accepts electrons prior to the rotenone-bound Q-site, and the Complex II reverse mode oxidizes MitoQ 10H 2 to regenerate MitoQ 10. Consequently, MitoQ 10 has a pro-oxidant role in intact cells, whereas it serves as an antioxidant when Complex I-derived superoxide generation is already elevated due to electron flow retardation. Moreover, unlike mitochondrial uncoupling, MitoQ 10 exerted its antioxidant role when Complex I proton pumping was retarded by a hydrophobic amiloride, 5-(N-ethyl-N-isopropyl) amiloride. Consequently, MitoQ 10 may be useful in the treatment of diseases originating from impairment of respiratory chain Complex I due to oxidatively damaged mitochondrial DNA, when its targeted delivery to pathogenic tissues is ensured.

Intensification of oxidative stress and inflammation in type 2 diabetes despite antihyperglycemic treatment

IntroductionThe metabolic deregulation associated with diabetes mellitus (DM) causes secondary pathophysiologic changes in multiple organ systems. Endothelial injury is induced by oxidative stress (OS) and inflammation. We have previously shown that DM type 2 patients are exposed to increased OS and inflammation contributed in part by primed peripheral polymorphonuclear leukocytes (PMNLs).AimsTo characterize the effect of oral medication on PMNL priming, on PMNL-related and on systemic inflammation, in correlation to changed diabetes parameters in patient with newly diagnosed type 2 DM.MethodsPMNLs were separated from DM patient's prior and following treatment with either metformin (Glucophage), or Thiazolidinedione (rosiglitazone) and from healthy control subjects (HC). Rate of superoxide release from phorbol ester-stimulated PMNLs and CD11b on PMNLs assessed PMNL priming. White blood cells (WBC) and PMNL counts and apoptosis reflected PMNL-related inflammation. CRP, fibrinogen, transferrin and albumin blood levels reflected systemic inflammation.ResultsBoth metformin and rosiglitazone treatments reduced significantly the high levels of glucose and HbA1c, and slightly improved lipid profile during 2 months. PMNL priming parameters, higher compared to HC, increased after 2 months of metformin treatment. Rosiglitazone treatment decreased PMNL priming. ALP, higher in DM, significantly decreased following 2 months of both treatments. Systemic inflammation markers (fibrinogen, CRP), higher in DM, decreased following both treatments. Transferrin and albumin were similar to HC. PMNL-related inflammation markers were higher in DM; however, only PMNL apoptosis decreased after both treatments. Monocyte counts, higher in DM compared to HC, decreased following both treatments. Serum insulin levels, higher in DM compared to HC, decreased following both treatments. PMNL-related priming and inflammation parameters positively correlated with HbA1c.ConclusionThe present research adds new facet in evaluating anti-hyperglycemic treatment in type 2 DM patients. Despite sufficient glycemic control using both treatments, some PMNL-related parameters deteriorated. Thus, anti hyperglycemic treatment should be favored due to its combined anti-PMNL priming and anti-inflammatory effect, in addition to its anti-hyperglycemic characteristics, according to the correlation among these parameters. Such combined treatment may reduce morbidity and mortality common in DM patients.

Are primed polymorphonuclear leukocytes contributors to the high heparanase levels in hemodialysis patients?

Patients on chronic hemodialysis (HD) are at high risk for developing atherosclerosis and cardiovascular complications. Heparanase, an endoglycosidase that cleaves heparan sulfate (HS) side chains of proteoglycans, is involved in extracellular matrix degradation and, as such, may be involved in the atherosclerotic lesion progression. We hypothesize that heparanase is elevated in HD patients, partly due to its release from primed circulating polymorphonuclear leukocytes (PMNLs), undergoing degranulation. Priming of PMNLs was assessed by levels of CD11b and the rate of superoxide release. Heparanase mRNA expression in PMNLs was determined by RT-PCR. PMNL and plasma levels of heparanase were determined by immunoblotting, immunofluorescence, and flow cytometry analyses. The levels of soluble HS in plasma were measured by a competition ELISA. This study shows that PMNLs isolated from HD patients have higher mRNA and protein levels of heparanase compared with normal control (NC) subjects and that heparanase levels correlate positively with PMNL priming. Plasma levels of heparanase were higher in HD patients than in NC subjects and were further elevated after the dialysis session. In addition, heparanase expression inversely correlates with plasma HS levels. A pronounced expression of heparanase was found in human atherosclerotic lesions. The increased heparanase activity in the blood of HD patients results at least in part from the degranulation of primed PMNLs and may contribute to the acceleration of the atherosclerotic process. Our findings highlight primed PMNLs as a possible source for the increased heparanase in HD patients, posing heparanase as a new risk factor for cardiovascular complications and atherosclerosis.

Primed Peripheral Polymorphonuclear Leukocyte

This study characterizes the causal relationship between peripheral polymorphonuclear leukocyte (PMNL) priming, systemic oxidative stress (OS), and inflammation in patients with varying degrees of renal insufficiency (chronic kidney disease [CKD] not on renal replacement therapy [RRT]: continuous ambulatory peritoneal dialysis or hemodialysis [HD]) and healthy control subjects. Rate of superoxide release was measured after stimulation of PMNL with phorbol 12-myristate 13-acetate or zymosan. Priming was estimated by the rate of superoxide release after phorbol 12-myristate 13-acetate stimulation. Systemic OS was related to PMNL priming and intracellular myeloperoxidase activity. Inflammation was linked to peripheral white blood cells and PMNL counts, PMNL apoptosis, and PMNL ex vivo survival in autologous and heterologous sera. PMNL priming and counts were related to the severity of renal failure in CKD not on RRT. Compared with control subjects, PMNL from all CKD patients showed increased priming, highest in HD, with a significant decrease in their response to zymosan. PMNL myeloperoxidase activity and apoptosis were increased in all renal failure patients. Decreased ex vivo cell survival and elevated leukocyte counts were found in all patients, highest in HD. Both PMNL priming and counts correlated negatively with the GFR. A positive significant correlation was shown between PMNL counts and their priming in all groups, suggesting that the increased PMNL count in peripheral blood is an adaptive response to PMNL priming. Hence, PMNL priming is a key mediator of low-grade inflammation and OS associated with renal failure, occurring before the onset of RRT and further augmented in chronic HD.

Primed polymorphonuclear leukocytes, oxidative stress, and inflammation antecede hypertension in the Sabra rat.

Hypertension is accompanied by systemic oxidative stress, inflammation, and priming of peripheral polymorphonuclear leukocytes (PMNLs), yet the involvement of these factors in the pathophysiology of hypertension is incompletely understood. We investigated the relationship between oxidative stress, primed PMNLs, and inflammation and the development of hypertension in the Sabra rat model of salt-sensitive hypertension. Sabra hypertension-resistant rats (SBN/y) (salt-resistant) and Sabra hypertension-prone rats (SBH/y) (salt-sensitive) were studied under normal conditions or during salt loading. Systolic blood pressure (BP) was measured by the tail-cuff method. The extent of oxidative stress was evaluated by the rate of superoxide release from PMNLs, plasma-reduced glutathione (GSH) levels, malondialdehyde (MDA) levels (estimated by thiobarbituric acid-reacting substances), and plasma-carbonylated fibrinogen (Western blotting). Plasma fibrinogen levels and the peripheral PMNL count served as indices of inflammation. In SBH/y and SBN/y provided regular chow without salt loading, BP did not rise above baseline values, yet superoxide release, plasma MDA, carbonylated fibrinogen, and PMNL count were higher in SBH/y than in SBN/y, whereas GSH levels were lower in SBH/y. Four weeks of salt loading resulted in a gradual increase in systolic BP in SBH/y to 205+/-3 mm Hg, whereas BP remained in SBN/y at baseline normotensive levels. All the parameters reflecting oxidative stress and inflammation were further aggravated with the development of hypertension in salt-loaded SBH/y. We conclude that primed PMNLs, oxidative stress, and inflammation antecede the development of hypertension in this experimental model of hypertension.

Interaction between Erythropoietin and Peripheral Polymorphonuclear Leukocytes in Continuous Ambulatory Dialysis Patients

The effect of erythropoietin (EPO) on the oxidative stress (OS) and inflammation caused by polymorphonuclear leukocytes (PMNLs) in end-stage renal failure patients undergoing continuous ambulatory peritoneal dialysis (CAPD) was investigated in vivo and in vitro. The studies were performed on isolated PMNLs from peripheral blood of CAPD patients before and following 6 weeks of EPO treatment and from healthy controls. OS was expressed by the rate of superoxide release from phorbol 12-myristate 13-acetate (PMA) stimulated isolated PMNLs and the inflammatory state was evaluated by PMNL counts of the enrolled subjects. Following 6 weeks of EPO treatment in CAPD patients, both the rate of superoxide release from PMNLs and PMNL counts fell significantly when compared with the pretreatment values. In vitro incubation of PMNLs from CAPD patients with increasing amounts of EPO displayed a significant reduction in their rates of superoxide release. EPO, by direct interaction with PMNLs, attenuated their primed state, causing reduction in oxidative stress and inflammation.

Oxidative stress during hemodialysis: Effect of heparin

Patients on chronic hemodialysis (HD) are exposed to oxidative stress. An HD session is used in this study as an in vivo model for studying the influence of heparin on oxidative stress caused partially by activated peripheral blood polymorphonuclear leukocytes (PMNLs) during a HD session. Each patient underwent HD once with and once without heparin. Oxidative stress was determined by evaluating both the rate of superoxide release from phorbol 12-myristate 13-acetate (PMA)-stimulated PMNLs and plasma levels of oxidized glutathione (GSSG), both measured before and after the dialysis session. In vitro, heparin reduced the rate of superoxide release from separated PMA-stimulated PMNLs. In vivo, the rate of superoxide release from PMNLs was always increased after the dialysis session, regardless of the presence of heparin. However, in the presence of heparin, this increase was significantly smaller. The augmentation in the rate of superoxide release after the dialysis session without heparin was accompanied by a significant elevation of GSSG, reflecting a preceding oxidation of plasma glutathione. The increase in both parameters, the rate of superoxide release, and the plasma GSSG concentration after HD treatment suggest that heparin in vivo alleviates the oxidative stress induced by the dialysis process. Based on our results, heparin should be the anticoagulant of choice because of its suppressant action on HD-induced oxidative stress.

Involvement of peripheral polymorphonuclear leukocytes in oxidative stress and inflammation in type 2 diabetic patients.

To determine the extent to which peripheral polymorphonuclear leukocytes (PMNs) contributed to oxidative stress (OS) and inflammation in type 2 diabetic patients. PMNs and plasma were separated from blood withdrawn from 18 type 2 diabetic patients and 16 age- and sex-matched normal control subjects. The rate of superoxide release from phorbol 12-myristate 13-acetate (PMA)-stimulated PMNs and the plasma glutathione (GSH) levels served as measures of OS. Inflammation was assessed by PMN recruitment, expressed by peripheral blood PMN counts, and the in vitro survival of PMNs, which reflects cell necrosis. PMA-stimulated PMNs from diabetes released superoxide significantly faster, and plasma-reduced GSH was lower in diabetic patients than in normal control subjects. The rate of superoxide release from diabetic PMNs showed no correlation with the plasma glucose concentrations, whereas a positive linear correlation with HbA1c was found. The in vitro survival of diabetic PMNs was lower than normal control PMNs when each was incubated in its own serum. The in vitro survival of normal control PMNs was reduced when incubated with diabetic serum, whereas normal control sera promoted the survival of diabetic PMNs. Peripheral PMN counts were higher in diabetic patients than in normal control patients. Type 2 diabetes is accompanied by a priming of PMNs, resulting in OS and increased self-necrosis. Necrosis starts a chain of inflammatory reactions that result in cell recruitment and in the long run, with OS, may result in endothelial dysfunction. Understanding the contribution of PMNs to OS and inflammation in diabetes may illuminate new mechanisms through which endothelial dysfunction evolves and causes angiopathy and atherosclerosis.

Extracellular signal-related kinase 1/2 and p38 mitogen-activated protein kinase pathways serve opposite roles in neutrophil cytotoxicity.

Inflammatory stimuli rapidly activate mitogen-activated protein kinases (MAPKs) in neutrophils (PMNs). However, their role in cytotoxic function remains unknown. Elucidating the signals involved in release of cytotoxic agents from PMNs may provide new avenues for therapy in diseases of diminished or excessive PMN function. The p38 MAPK and extracellular signal-related kinase 1/2 (ERK1/2) modulate superoxide generation and elastase release in activated human PMNs. Isolated human PMNs were incubated with specific inhibitors of MAPK pathways, or vehicle control solution, before activation with the bacterial peptide f-Met-Leu-Phe. The rate of superoxide release from activated PMNs was measured by the superoxide dismutase-inhibitable reduction of cytochrome-c. Elastase release from PMNs was determined by cleavage of the substrate Ala-Ala-Pro-Val-pNA. Superoxide release from activated PMNs was inhibited by blockade of p38 MAPK activation but unaffected by blockade of ERK1/2. Conversely, elastase release was unaffected by p38 MAPK inhibition and increased by ERK1/2 inhibition. Activation of p38 MAPK promotes superoxide release from PMNs activated by f-Met-Leu-Phe. The ERK1/2 pathway may serve as a negative feedback mechanism for granule exocytosis.

Interaction between Erythropoietin and Peripheral Polymorphonuclear Leukocytes in Hemodialysis Patients

The effect of erythropoietin (EPO) on the oxidative stress and inflammation caused by polymorphonuclear leukocytes (PMNLs) in chronic hemodialysis (HD) patients was investigated in vivo and in vitro. The studies were performed on isolated PMNLs from peripheral blood of healthy controls and HD patients before and following 6 weeks of EPO treatment. The oxidative stress was expressed by the rate of superoxide release from phorbol 12-myristate 13-acetate stimulated PMNLs, and the inflammatory state was evaluated by in vitro PMNL survival, in addition to white blood cell and PMNL counts of the enrolled subjects. Following 6 weeks of EPO treatment, in HD patients, the rate of superoxide release from PMNLs as well as WBC and PMNL counts fell significantly when compared with the pretreatment values. PMNLs from HD patients and healthy controls incubated in vitro with increasing amounts of EPO displayed a significant reduction in their rates of superoxide release and a significant improvement in survival. We have concluded that EPO interacts with PMNLs, attenuating their primed state in HD patients, thus reducing oxidative stress and the extent of inflammation. To the best of our knowledge, this attenuation of the primed state of PMNLs by EPO is a new finding.

Participation of peripheral polymorphonuclear leukocytes in the oxidative stress and inflammation in patients with essential hypertension

Oxidative stress and inflammation have recently been linked to endothelial damage in essential hypertension (EH). Activated peripheral polymorphonuclear leukocytes (PMN) damage surrounding tissue by releasing reactive oxygen species (ROS) and proteolytic enzymes before self-necrosis. PMN necrosis further exacerbates inflammation and promotes chemotaxis and PMN recruitment. The number and properties of PMN from untreated EH patients is the focus of the present study. Oxidative stress was assessed by measuring the rate of superoxide anion release from separated, phorbol ester-stimulated PMN and the redox state of plasma glutathione. Inflammation was estimated indirectly by determining PMN number and their in vitro survival. PMN from EH patients (n = 37) released superoxide anion faster ( P < .0001) than those of normotensives (NC, n = 37), 17.7 ± 1.14 v 9.54 ± 0.51 nmol/10 min/10 6cells. The redox state of glutathione was twofold higher in EH plasma ( P < .02) indicating systemic oxidative stress. PMN survival in vitro correlates linearly with the rate of superoxide release (r 2 = 0.60, P < .02) and PMN count of EH patients, although in the normal range, were significantly higher ( P < .0001), indicating necrosis and recruitment. Hypertensive plasma significantly reduced NC PMN viability, whereas normal plasma significantly increased EH PMN viability. What our studies show is that EH is accompanied by a primed state PMN that does not correlate with the levels of blood pressure. PMN priming in EH patients reflects an in vivo exposure to a constant stimulus ending in oxidative stress, increased self-necrosis, and cell recruitment. Oxidative stress and inflammation will result in endothelial damage and atherosclerosis in the long run.

Dieldrin activates rat neutrophils in vitro

Suppression of phagocytic cell function has been proposed as a possible mechanism for the enhanced sensitivity to certain infectious agents exhibited by animals exposed to the organochloride insecticide, dieldrin. In the present study, we examined the effects of dieldrin on superoxide production by glycogen-eli citedperitoneal neutrophils (PMNs) from the rat. Dieldrin caused a concentration-dependent increase in superoxide production by PMNs incubated in vitro at 37°C. Superoxide release was increased significantly with 10 μ m dieldrin and reached a maximum of 17 nmol/10 min/2.0 × 10 6 PMNs at a dieldrin concentration of 35 μ m. Preincubation of PMNs for 5 min at room temperature with a barely suprathreshold concentration of either phorbol 12-myristate 13-acetate (PMA) or N-formyl- l-methionyl- l-leucyl- l-phenylalanine (FMLP) enhanced dieldrin-stimulated superoxide release by as much as ninefold or threefold, respectively. Maximum enhancement was obtained with 10 μ m dieldrin for both PMA and FMLP. Time course studies with PMA-pretreated cells revealed that the rate of superoxide release was dependent on the concentration of dieldrin. Extracellular calcium played an important role in dieldrin-stimulated superoxide release, since PMNs treated with dieldrin in the absence of extracellular calcium did not release superoxide. Also, pretreatment with calcium ionophore A23187 greatly enhanced superoxide release from dieldrin-stimulated PMNs. These results show that dieldrin has a stimulatory effect on superoxide release from rat PMNs in vitro and that this stimulation is dependent on extracellular calcium.

Factors which affect superoxide anion release from rat alveolar macrophages.

In order to investigate some of the characteristics of superoxide anion release from alveolar macrophages, the effects of substances known to influence superoxide release from polymorphonuclear leukocytes (PMN) were studied in rat alveolar macrophages. There is a relatively small, but constant, amount of superoxide released from alveolar macrophages at rest. The amount released increases 5- to 6-fold and becomes maximal in about 20-30 min following exposure to unopsonized zymosan particles. The rate of superoxide release is maximal only 2 min after exposure of the cells to particles, i.e., long before particle uptake is complete. In addition to particles, release of superoxide anion can be stimulated by phorbol-12-myristate-13-acetate (PMA). Lectins and chemotactic factors, which stimulate release in PMN, have little or no effect in alveolar macrophages. Superoxide release during exposure to zymosan appears to be dependent upon extracellular Ca++. Also, the release mechanism can be affected by the addition of cyclic AMP or various protein modifiers to the medium. Since many of these findings differ from those reported by others for PMN, the control of superoxide anion release from alveolar macrophages and PMN is probably different.