The role of polyhalogenated aromatic hydrocarbons on thyroid hormone disruption and cognitive function: a review.

Thyroid hormones (TH) are essential to normal brain development, influencing behavior and cognitive function in both adult and children. It is suggested that conditions found in TH abnormalities such as hypothyroidism, hyperthyroidism and generalized resistance to thyroid hormone (GRTH) share symptomatic behavioral impulses found in cases of attention deficit hyperactivity disorder (ADHD) and other cognitive disorders. Disrupters of TH are various and prevalent in the environment. This paper reviews the mechanisms of TH disruption caused by the general class of polyhalogenated aromatic hydrocarbons (PHAH)'s acting as thyroid disrupters (TD). PHAHs influence the hypothalamus-pituitary-thyroid (HPT) axis, as mimicry agents affecting synthesis and secretion of TH. Exposure to PHAH induces liver microsomal enzymes UDP-glucuronosyltransferase (UGT) resulting in accelerated clearance of TH. PHAHs can compromise function of transport and receptor binding proteins such as transthyretin and aryl hydrocarbon receptors (Ahr). Glucose metabolism and catecholamine synthesis are disrupted in the brain by the presence of PHAH. Further, PHAH can alter brain growth and development by perturbing cytoskeletal formation, thereby affecting neuronal migration, elongation and branching. The complex relationships between PHAH and cognitive function are examined in regard to the disruption of T4 regulation in the hypothalamus-pituitary-thyroid axis, blood, brain, neurons, liver and pre and postnatal development.

Pentoxifylline does not attenuate acute lung injury in the absence of granulocytes.

Pentoxifylline (PTX), a methylxanthine, can suppress polymorphonuclear leukocyte (PMN) activation and attenuate sepsis-induced acute lung injury. We investigated whether PTX prevents non-PMN-dependent lung injury. First we studied four groups of granulocyte-depleted guinea pigs (control, PTX, Escherichia coli, and E. coli + PTX). Lung injury was assessed by wet-to-dry lung weight (W/D) ratio and lung tissue-to-plasma 125I-albumin ratio (albumin index, AI). The E. coli group showed a significant increase in the lung W/D ratio and AI compared with the control and PTX groups. However, PTX did not prevent the E. coli-induced increase in the lung W/D ratio and AI. Next we investigated the effects of PTX on endothelial cell monolayer permeability and adenosine 3',5'-cyclic monophosphate (cAMP) levels. Whereas E. coli lipopolysaccharide (LPS) alone increased the endothelial permeability, PMNs added to the endothelial monolayers and exposed to LPS enhanced the increase. PTX attenuated the permeability increase mediated by LPS-exposed PMNs. PTX did not prevent the LPS-induced increase in permeability when PMNs were not present, although PTX increased endothelial cell cAMP levels. These data demonstrate that 1) PTX does not prevent lung injury in granulocyte-depleted guinea pigs; 2) PTX does not prevent LPS-induced increases in endothelial cell permeability, despite increased cAMP levels; and 3) PTX attenuates PMN-dependent increases in endothelial cell permeability.

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.

Early post-treatment with pentoxifylline or dibutyryl cAMP attenuates Escherichia coli-induced acute lung injury in guinea pigs.

We examined effects of early post-treatment with the methylxanthine pentoxifylline (PTXF), or the cell-permeable adenosine 3', 5'-cyclic monophosphate (cAMP) analog dibutyryl cAMP (db-cAMP) on Escherichia-coli-induced acute lung injury in guinea pigs. Acute lung injury was assessed by measurements of lung water (lung wet/dry weight ratio; W/D ratio), the concentration ratio of 125I-albumin in bronchoalveolar lavage (BAL) fluid and lung tissue compared with plasma (albumin index; BAL-AI or tissue-AI), and total differential leukocyte count in BAL fluid. Mean arterial pressure (Pa) and peripheral WBC counts were monitored continuously over the 8-h experiment. Septicemia was induced by a bolus injection of 2 x 10(9)/kg live E. coli. Thirty minutes later the animals received a bolus injection followed by continuous infusion of PTXF (20 mg/kg + 20 mg/kg/h; n = 8) or db-cAMP (2 mg/kg + 2 mg/kg/h; n = 8) or saline (septic control; n = 8). Nonseptic control groups were also studied. The lung W/D ratio, BAL-AI, lung tissue-AI, and BAL leukocyte count increased significantly in the septic control group. The PTXF-septic and db-cAMP-septic groups showed no significant increase in lung W/D ratio, BAL-AI, and lung tissue-AI. However, there was no difference in BAL total and differential leukocyte count as compared with the septic control group. PTXF and db-cAMP had no effect on E. coli-induced changes in peripheral WBC count and Pa. Comparison in vitro experiments demonstrated that PTXF and db-cAMP inhibited the endotoxin-induced (E. coli) chemiluminescent response of isolated guinea-pig polymorphonuclear leukocytes (PMN).(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of tumor necrosis factor-induced endothelial cell cytotoxicity and neutrophil chemiluminescence.

Our laboratory has previously shown that the administration of tumor necrosis factor (TNF), a cytokine produced by activated mononuclear cells, to guinea pigs produces a syndrome similar to gram-negative sepsis or ARDS. Pentoxifylline (PTX), a methylxanthine, protects against TNF-induced and sepsis-induced acute lung injury in vivo. We now report on in vitro cellular studies of PMN-mediated cellular injury and its attenuation. We studied TNF-induced bovine pulmonary artery endothelial cell (EC) cytotoxicity both with and without PMN. A 51Cr release assay was used to measure EC damage. Further, we investigated PMN function in response to TNF by measuring chemiluminescence. Agents that attenuate EC damage and PMN activation were evaluated in the above assays. Results revealed that TNF causes EC injury (p less than 0.05) and PMN increase TNF-induced EC injury. Furthermore, PTX, aminophylline (AMPH), caffeine, and forskolin attenuate TNF-induced EC cytotoxicity only in the presence of PMN (p less than 0.05). Of interest, dibutyryl cAMP (DBcAMP) protects EC from TNF-induced injury both with and without PMN. Agents that may increase cAMP levels in PMN (PTX, DBcAMP, forskolin, isobutyl methylxanthine, and terbutaline) significantly attenuate TNF-induced PMN chemiluminescence (p less than 0.05). We conclude that TNF causes EC damage and PMN increase this damage. Furthermore, PTX, AMPH, caffeine, and forskolin can attenuate TNF-induced EC injury in the presence of PMN, whereas DBcAMP attenuates TNF-induced EC injury with and without PMN. In addition, agents that may increase intracellular cAMP levels in PMN can attenuate TNF-induced PMN chemiluminescence. Thus, these agents likely attenuate TNF-induced PMN-mediated EC injury through their inhibitory effects on PMN.

Sequential assessment of pulmonary epithelial diethylene triamine penta-acetate clearance and intrapulmonary transferrin accumulation during Escherichia coli peritonitis.

The individual roles of pulmonary capillary endothelial and alveolar epithelial permeability in the pathogenesis of the adult respiratory distress syndrome (ARDS) are unclear. We developed a method for the sequential assessment of pulmonary macromolecule accumulation and small solute clearance in vivo using a gamma camera. We measured the exponential clearance coefficient of 111In-labeled diethylene triamine penta-acetate (111In-DTPA) to assess airway clearance of small solutes. We also calculated the exponential equilibration coefficient of 111In-labeled transferrin (111In-TF) to assess intrapulmonary accumulation of transferrin. We determined these parameters in guinea pigs with Escherichia coli peritonitis and compared them with a saline-treated control group, oleic-acid-treated groups, and a group treated with low molecular weight dextran Ringer solution. The pulmonary DTPA clearance and the intrapulmonary transferrin accumulation were significantly increased in the peritonitis group (29.4 +/- 8.2 x 10(-3) min-1, p less than 0.02, and 15.1 +/- 3.1 x 10(-3) min-1, p less than 0.02) when compared with the control group (3.1 +/- 0.8 x 10(-3) min-1 and 4.5 +/- 0.5 x 10(-3) min-1). These changes developed within 5.5 h of the initial insult. Neither increased extravascular lung water nor elevated pulmonary artery and left atrial pressures were detected in the peritonitis group. The low molecular weight dextran Ringer group did not show a significant increase in the pulmonary DTPA clearance and the intrapulmonary transferrin accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of anti-C5a antibodies on human polymorphonuclear leukocyte function: chemotaxis, chemiluminescence, and lysosomal enzyme release.

Previous investigation has demonstrated that in vivo complement activation can produce acute lung injury. Complement component C5a has been implicated as a key factor in this damage. In addition, C5a is thought to play a central role in mediating polymorphonuclear leukocyte (PMN) function. Studies suggest that administering antibodies to C5a might play a role in attenuating lung injury in animal models of sepsis. To evaluate further the effects of anti-C5a antibodies, we compared the effects of anti-human C5a des-Arg monoclonal (MAb) and polyclonal (PAb) antibodies on PMN functions including chemotaxis, chemiluminescence, and lysosomal release. PMN chemotaxis was assayed in Boyden chambers using 0.5% zymosan-activated serum (ZAS) as a source of C5a and 0.5% normal human serum (NHS) as a control. PMN chemiluminescence was measured by scintillation counting using ZAS as a stimulant and NHS as control. In addition, the lysosomal marker enzyme beta-D-glucuronidase was spectrophotometrically determined to assess lysosomal release. The PMN chemotactic response to ZAS was completely abolished with MAb and PAb anti-C5a antibodies (p less than 0.01). Control antibodies had no effect on ZAS-stimulated chemotaxis. The anti-C5a MAb markedly inhibited PMN chemotaxis at concentrations ranging from 20 to 0.2 microgram/ml, and was approximately 30 times more potent than the PAb. ZAS-stimulated PMN chemiluminescence was markedly decreased in response to monoclonal antibodies to C5a. In contrast, the control antibody did not inhibit ZAS-stimulated PMN chemiluminescence. Anti-C5a antibodies also significantly attenuated the release of the lysosomal enzyme beta-D-glucuronidase from ZAS-stimulated PMN. Anti-C5a antibody treatment did not cause a significant lytic effect when incubated with PMN, as demonstrated by the absence of the cytoplasmic marker lactate dehydrogenase in the supernatant. These studies suggest that in states of complement activation, MAbs and PAbs may decrease PMN functions including chemotaxis, chemiluminescence, and lysosomal enzyme release.

Effects of tumor necrosis factor on PMN chemotaxis, chemiluminescence, and elastase activity.

Tumor necrosis factor (TNF) has been proposed as an important mediator of the inflammatory response in acute lung injury. To better understand polymorphonuclear leukocyte (PMN) activation during acute lung injury, we evaluated the effects of TNF on several in vitro PMN functions, including chemotaxis, chemiluminescence, and elastase activity. In the chemotaxis assay using a modified Boyden chamber, TNF alone or with N-formyl-methionyl-leucyl-phenylalanine (FMLP, 10(-8) mol/L) did not alter PMN migration. TNF suspended with 1% zymosan-activated serum (ZAS) increased PMN migration at low concentrations and decreased migration at high concentrations (control 99 +/- 4.8 microns, n = 9; TNF 0.1 ng/ml 135 +/- 9.4 microns, n = 5, p less than 0.01; TNF 1000 ng/ml 62 +/- 7.5 microns, n = 5, p less than 0.01). In the chemiluminescence assay, TNF (1000 ng/ml) induced a 3-fold increase in the PMN chemiluminescent response. However, TNF incubated with PMN did not cause an increase in supernatant elastase activity. These data reveal TNF induced the production of PMN reactive oxygen species as evidenced by an increased chemiluminescent response. Whereas TNF increased chemotaxis at low concentrations in the presence of 1% ZAS, high concentrations of TNF similar to levels detected in septic shock caused a decrease in chemotaxis that might contribute to retaining PMN in sites of inflammation. It is thus suggested that TNF may contribute to inflammation by stimulating the production of PMN-reactive oxygen species and modulating-PMN chemotaxis.

Prevention of interleukin 2-induced acute lung injury in guinea pigs by pentoxifylline.

We administered recombinant human interleukin 2 (IL-2) to guinea pigs to investigate whether IL-2 would cause acute lung injury. In addition, we examined the effects of pentoxifylline (PTXF) on IL-2-induced acute lung injury. Three groups of animals were studied over a period of 8 h. The saline control group was injected intravenously with 2 ml of pyrogen-free saline; the IL-2 group was injected intravenously with 4 X 10(6) U/kg recombinant IL-2; and the IL-2-PTXF group was injected with a 20-mg/kg bolus of PTXF followed by a continuous infusion (6 mg.kg-1.h-1) started 60 min before injection of 4 X 10(6) U/kg IL-2. Lung water (wet-to-dry lung weight ratio), the concentration ratios of 125I-albumin in bronchoalveolar lavage (BAL) fluid and lung tissue compared with plasma (125I-albumin BAL-to-plasma, 125I-albumin lung-to-plasma), and cell counts in BAL fluid were examined. An intravenous injection of IL-2 caused an increased lung water (P less than 0.01), an increased 125I-albumin lung-to-plasma ratio (P less than 0.05), and a significant increase in the absolute number of neutrophils, lymphocytes, and macrophages in BAL fluid compared with the saline control. In contrast, the PTXF-pretreated group did not demonstrate IL-2-induced acute lung injury (lung water, 125I-albumin lung-to-plasma) or increased accumulation of neutrophils, lymphocytes, and macrophages in the BAL. These data suggest a possible role for PTXF in attenuating the side effects of IL-2.

The effects of aminophylline and pentoxifylline on multiple organ damage after Escherichia coli sepsis.

We studied the effects of the methylxanthines, aminophylline (AMPH) and pentoxifylline (PTXF), on multiple organ damage following Escherichia coli sepsis in guinea pigs. To assess multiple organ damage, 125I-labeled albumin accumulation was measured in bronchoalveolar lavage (BAL) fluid, lung, kidneys, liver, heart, adrenal glands, and spleen and expressed as a ratio of BAL fluid or tissue to 125I-labeled albumin plasma (albumin index: Al). Wet-to-dry lung weight (W/D) ratios were also measured. The methylxanthines were administered by a bolus injection followed by a continuous infusion. The seven experimental groups included: saline-control, AMPH-control, PTXF-control, E. coli septic-control, E. coli septic-AMPH high dose, E coli septic-AMPH low dose, and E. coli septic-PTXF. The AI of the BAL fluid and all examined organs significantly increased in the septic-control group compared to those in the saline-, AMPH-, and PTXF-control groups, In all septic-methylxanthine groups, the AI of the BAL fluid and all organs, except for the spleen, were significantly lower than those of the septic-control group. Compared to the saline-, AMPH-, and PTXF-control groups, the septic-control group revealed a significant increase in lung W/D ratios, whereas the septic-AMPH high and low dose groups and the septic-PTXF group did not. Of importance, the septic-PTXF group did not cause a significant decrease in mean arterial pressure (MAP) as compared to the control groups, whereas the septic-AMPH groups did cause a significant decrease in MAP compared to the septic-control group. Therefore, the data from this experiment demonstrate that both AMPH and PTXF attenuate the multiple organ albumin leak seen in septic guinea pigs. However, PTXF exerted this protective effect with no discernible effect on the MAP whereas the MAP of AMPH-treated guinea pigs was significantly decreased.

Multiple organ damage caused by tumor necrosis factor and prevented by prior neutrophil depletion.

The effect of TNF on nonpulmonary multiple organ damage (MOD) was studied. Since polymorphonuclear leukocytes (PMN) are thought to play an important role in septic or TNF-induced MOD, we investigated both neutrophil sufficient (PMN+) and neutropenic (PMN-) guinea pigs. Sepsis was induced by Escherichia coli administration (2 x 10(9)/kg) or recombinant human TNF (1.4 x 10(6) U/kg) was infused into PMN+ and PMN- guinea pigs. During necropsy, the PMN+/TNF and PMN+/E coli animals exhibited marked damage in the adrenal glands, kidneys and liver as evidenced by hemorrhage, congestion, and PMN sequestration on histopathologic examination. There was also increased tissue albumin accumulation in the adrenal glands, kidneys, spleen, heart, and liver as demonstrated by 125I-labeled albumin determinations. In contrast, the PMN-/TNF group did not reveal histopathologic damage in any organ system and there was no abnormal organ accumulation of 125I-albumin. However, in PMN-/E coli animals, marked histopathologic damage in the adrenal glands and liver was evident. Furthermore, there were marked accumulations of 125I-albumin in the adrenals, heart, kidneys, liver, and spleen. Moreover, the PMN-/E coli guinea pigs had a much greater accumulation (p less than 0.01) of 125I-albumin in the kidneys than any other group including the PMN+/E coli group. Thus, nonpulmonary MOD in guinea pigs is caused by TNF administration and can be prevented by PMN depletion. However, while E coli administration also caused marked nonpulmonary MOD in neutrophil sufficient guinea pigs, equivalent or greater damage was produced in neutropenic animals. This suggests that while TNF-induced MOD may be primarily mediated by PMN, E coli-induced MOD seems to be mediated by more than PMN.

Attenuation of acute lung injury in septic guinea-pigs by a new xanthine derivative (HWA-138).

The protective effect of xanthines against E. coli-induced and cytokine-induced lung injury in guinea-pigs has been demonstrated recently. In the present study, the possible protective effects were examined of an analogue of pentoxifylline, HWA-138, a xanthine derivative, on lung injury in septic guinea-pigs. Three groups of animals were studied over a period of 8 hours: Group I animals--saline control injected intravenously with 3 ml 2% lysine/normal saline followed by a continuous lysine/saline infusion (1 ml/kg/hr); Group II--septic control injected intravenously with 2 x 10(9)/kg Escherichia coli followed by a continuous lysine/saline infusion (1 ml/kg/hr); and Group III--E. coli septicaemia plus HWA-138 continuous infusion (HWA-138 dissolved in lysine/saline) began with a bolus (10 mg/kg) followed by a HWA-138 continuous infusion (3 mg/kg/hr) started 60 minutes before injection of E. coli. Arterial blood pressure and white blood cell counts were monitored serially for 8 hours. Lung water (wet-to-dry ratio) and the concentration ratio of 125I-labelled albumin in bronchoalveolar lavage (BAL) fluid and lung tissue compared to plasma (125I-albumin BAL/plasma, 125I-albumin lung/plasma) were examined. Results demonstrated that an intravenous injection of E. coli caused an increased W/D ratio (p less than 0.01) and an increased 125I-albumin lung/plasma ratio (p less than 0.01). In contrast, the HWA-138-treated group did not demonstrate significantly increased W/D lung ratios (p less than 0.01) and 125I-albumin lung/plasma ratios (p less than 0.05). The data suggest a possible role for HWA-138 in attenuating sepsis-induced lung injury.

Thermal injury, intravascular hemolysis, and toxic oxygen products.

Acute thermal injury of rat skin produces an early, acute hemoglobinemia that is associated with the presence in blood of osmotically fragile red cells (RBC) that do not contain on their surfaces measurable amounts of complement components. The hemoglobinemia and the appearance in blood of osmotically fragile RBC appear to be the result of complement activation, which leads to oxygen radical production by neutrophils and damage of RBC. This has been demonstrated in vitro as well as in vivo by the ability of antioxidant interventions or neutrophil or complement depletion procedures to prevent the appearance of osmotically fragile RBC and the release of hemoglobin. These data may be relevant to the complications of hemoglobinemia and hemoglobinuria accompanying thermal injury in humans.

Systemic complement activation, lung injury, and products of lipid peroxidation.

Previously we have demonstrated that systemic activation of the complement system after intravenous injection of cobra venom factor (CVF) results in acute lung injury as reflected by increases in the vascular permeability of the lung as well as by morphologic evidence of damage to lung vascular endothelial cells. In using the vascular permeability of the lung as the reference, the current studies show a quantitative correlation between lung injury and the appearance in plasma of lipid peroxidation products (conjugated dienes) as well as increased concentrations of lactic dehydrogenase (LDH) and one of its isoenzymes (LDH-4). After injection of CVF, extracts of lungs also showed elevated levels of conjugated dienes, whereas no elevations were found in extracts of liver, kidney, and spleen. There was no evidence in CVF-injected rats of renal or hepatic injury as reflected by the lack of development of proteinuria and the failure to detect increased serum levels of liver-related enzymes. Other peroxidation products identified in plasma of CVF-injected rats involved hydroperoxides and fluorescent compounds with features of Schiff bases. Not surprisingly, malondialdehyde was not found to be a reliable plasma indicator of lipid peroxidation associated with oxygen radical-mediated lung vascular injury. In using a model of oxygen radical-independent lung injury induced by oleic acid, although large amounts of LDH and LDH-4 were found in the plasma, no increases in plasma levels of conjugated dienes were detected. In CVF-injected animals treated with interventions protective against lung injury (neutrophil depletion, catalase, hydroxyl radical scavengers, or iron chelators), there were striking reductions in the plasma levels of conjugated dienes, hydroperoxides, and fluorochromic products. Morphometric analysis of lung sections revealed that the protective interventions did not interfere with the accumulation of neutrophils in lung interstitial capillaries after systemic activation of complement. In vitro studies with phorbol-stimulated neutrophils failed to demonstrate appearance of conjugated dienes, suggesting that the dienes appearing in plasma of CVF-injected animals are not the result of autotoxic changes in neutrophils. The data presented in this paper suggest that acute lung injury mediated by oxygen radicals derived from phagocytic cells can be monitored by the appearance in plasma of products of lipid peroxidation.

Lipid peroxidation and acute lung injury after thermal trauma to skin. Evidence of a role for hydroxyl radical.

The authors have previously shown that thermal injury to the skin of rats results in the development of acute lung injury that is susceptible to systemic treatment of animals with catalase and dependent on the presence of neutrophils. The current studies have been expanded for exploration of the nature of the neutrophil-derived oxygen products responsible for the lung injury and have also focused on evidence of the appearance of products of lipid peroxidation (conjugated dienes). With respect to the former, treatment of rats with iron chelators (deferoxamine mesylate, 2,3-dihydroxybenzoic acid), with scavengers of hydroxyl radical (dimethyl sulfoxide, dimethyl thiourea, sodium benzoate), or with vitamin E affords a significant degree of protection from acute lung injury as assessed by changes in lung vascular permeability and by morphologic parameters. These data suggest that lung vascular injury after thermal trauma of the skin is related to the generation by neutrophils of the hydroxyl radical. Conjugated dienes have been demonstrated to appear sequentially both in the burned skin (at 1/4 hour) and in the lungs (at 2 hours), as well as in the plasma (with peaks at 1/2 and at 3 hours) after thermal injury. The appearance of the conjugated dienes in plasma at the two intervals of time is greatly diminished if animals are pretreated with the iron chelator deferoxamine, with catalase, or with scavengers of hydroxyl radical. Furthermore, the appearance of conjugated dienes in plasma at 30 minutes and 3 hours is significantly diminished if animals are depleted of neutrophils, complement-depleted, or the burned skin is excised immediately after thermal injury. These data indicate a linkage between thermal trauma of skin, secondary injury of lung, and appearance in plasma and tissues of products of lipid peroxidation.