Effect of three polychlorinated biphenyls on f-met-leu-phe-induced degranulation in rat neutrophils
Introduction
Polychlorinated biphenyls (PCBs) are organic compounds which are present as environmental contaminants in almost the entire food web (Evans et al., 1991). Their slow rates of metabolism and high liposolubilities allow them to bioaccumulate in an extension which may depend on the content of total lipid in the organism (Ali et al., 1997). A broad spectrum of biological effects has been associated with individual PCB congeners as well as mixtures, including induction of hepatic enzymes (McFarland and Clarke, 1989), cancer, alterations in reproduction, immunotoxicity (Safe, 1994), and neurobehavioral effects (Kimbrough, 1995).
In addition to effects on cells of the specific immune system, PCBs affect the function of polymorphonuclear neutrophils involved in inflammation. Activation of neutrophils initiates a cascade of intracellular events that leads to enzyme release, oxidative burst, chemotaxis and aggregation. These responses are essential for killing pathogens (Sha'afi and Molski, 1988). Exposure of isolated, rat neutrophils to Aroclor mixtures of PCBs causes them to generate superoxide anion and to undergo degranulation (Ganey et al., 1993). Moreover, pretreatment with PCBs alters the response of neutrophils to subsequent exposure to other stimuli. Phorbol ester-induced superoxide anion production is increased by exposure to PCBs, whereas degranulation stimulated by the peptide N-formyl-met-leu-phe (fmlp) is inhibited. It has been established that some PCBs activate neutrophils to undergo oxidative burst through stimulation of the production of inositol phosphates (Tithof et al., 1995) and arachidonic acid (Tithof et al., 1996), as well as through calcium-dependent mechanisms (Brown and Ganey, 1995). These activities are, in general, associated with ortho-substituted PCB congeners and not with coplanar, dioxin-like PCBs. Less is known about mechanisms involved in PCB-induced degranulation of neutrophils, and only limited structure–activity data are available. In this work we report the effect of in vitro exposure to three different PCB congeners on neutrophil degranulation in quiescent and fmlp-activated cells. The molecular properties that may be responsible for this action are discussed.
Section snippets
Chemicals
PCB congeners 8 (2,4′-dichlorobiphenyl), 126 (3,3′,4,4′,5-pentachlorobiphenyl) and 128 (2,2′,3,3′,4,4′-hexachlorobiphenyl) were purchased from ChemService, (West Chester, PA). Fmlp and cytochalasin B were obtained from Sigma (St. Louis, MO).
Isolation of rat, peritoneal neutrophils
Neutrophils were isolated from the peritoneum of male, Sprague–Dawley, retired breeder rats by glycogen elicitation as described previously (Hewett and Roth, 1988). Isolated neutrophils were resuspended in 1 ml Hanks' balanced salt solution (HBSS), pH 7.35,
Results
Fig. 2Fig. 3Fig. 4 show the effects of PCB congeners on degranulation and cytotoxicity of neutrophils, expressed as percentage of total MPO and LDH released, respectively. In the absence of stimulation with fmlp, PCB 8 caused neutrophil degranulation at 10 and 50 μM. Neither PCB 126 nor PCB 128 stimulated release of MPO (Fig. 2A). PCB 8 was cytotoxic to quiescent neutrophils at 10 and 50 μM, PCB 128 caused release of LDH at 50 μM, and PCB 126 was not cytotoxic at any concentration tested (Fig. 2
Discussion
Stimulation of degranulation in quiescent neutrophils and attenuation of fmlp-induced degranulation in the same cells have been observed for the PCB mixture Aroclor 1242 and for the congener PCB 47 (2,2′4,4′-tetrachlorobiphenyl) (Ganey et al., 1993). From the studies presented here it is clear that the patterns of activity for PCB congeners are structure dependent. For this study, three PCB congeners were chosen which differ in chlorine content (di, penta and hexa) and pattern of chlorine
Acknowledgements
This work was supported by NIH Grant ESO4911. The authors give thanks to SGI facility (NSF Grant CHE9321436) from the Chemistry Department of Michigan State University. Jesus Olivero is sponsored by the Scholarship Colciencias-Fulbright-Laspau, Santa Fé de Bogota, Colombia.
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Effects of polychlorinated biphenyls, hexachlorocyclohexanes, and mercury on human neutrophil apoptosis, actin cytoskelton, and oxidative state
2006, Environmental Toxicology and PharmacologyCitation Excerpt :Lindane stimulates neutrophil superoxide production that is associated with phosphoinositide remodeling, arachadonic acid release, cytosolic Ca2+ elevation, and degranulation, although lindane is not a chemoattractant (English et al., 1986; Kuhns et al., 1986; Kaplan et al., 1988; Omann and Sklar, 1989; Tithof et al., 2000; Olivero et al., 2002; Rebbapragada et al., 2005). Aroclor 1242 and other PCBs have been shown to stimulate neutrophil superoxide production, degranulation, phosphoinositide remodeling, calcium elevation, and phospholipase A2 activity (Ganey et al., 1993; Brown and Ganey, 1995; Tithof et al., 1995, 1996, 1997; Brown et al., 1998; Olivero-Verbel and Ganey, 1998; Olivero and Ganey, 2001). Effects of Aroclor 1242 on neutrophil degranulation are complex; whereas Aroclor 1242 is a modest stimulator of degranulation, it also inhibits N-formyl peptide-induced degranulation (Ganey et al., 1993).
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