A study of the effects of p,p'-DDE and other related chlorinated hydrocarbons on inhibition of platelet aggregation

Exposure to p,p'-DDE Alters Macrophage Reactivity and Increases Macrophage Numbers in Adipose Stromal Vascular Fraction

Exposure to p,p'-DDE (DDE), the main bioaccumulative metabolite of the organochlorine insecticide p,p'-DDT, is associated with a higher prevalence of obesity, dyslipidemia, insulin resistance, metabolic syndrome, and immunomodulation. The present study was carried out to determine whether DDE perturbs adipose tissue homeostasis through modulation of macrophage function. Treatment with DDE or a cyclooxygenase-2 inhibitor prior to lipopolysaccharide exposure significantly decreased production of prostaglandins (PG) from J774a.1 macrophages in vitro. Similarly, J774A.1 cell lysates incubated with DDE or a specific cyclooxygenase-2 inhibitor (NS-398) produced significantly less PGE2 and PGF2α. Macrophage polarization studies revealed a pattern of DDE effects that were not fully consistent with a purely pro- or purely anti- M1 or M2 effect. However, DDE suppressed expression of two M1 markers (induced by an M1 stimulus) and enhanced expression of an M2 marker (induced by an M2 stimulus). Further studies including assessment of macrophage function are needed to fully characterize the effects of DDE on macrophage polarization. Obesity is characterized by an increase in the number of resident adipose tissue macrophages. To assess monocyte/macrophage recruitment to the adipose tissue in vivo, male C57Bl/6H mice were treated with 2 mg/kg DDE or corn oil vehicle for 5 days by gavage. Epididymal fat pads were digested and macrophage populations were analyzed by flow cytometry. In DDE-treated animals, there was a significant increase (37%) in F4/80(+)CD11b(+) macrophages/g of epididymal adipose over vehicle (P < .05). Together, these results suggest a role for DDE in the enhancement of adipose tissue macrophage recruitment and/or proliferation, as well as modulation of immune cell function that may contribute to the etiology of metabolic diseases associated with organochlorine exposure.

Effects of p,p'-DDE on immature cells in culture at concentrations relevant to the Alaskan environment

Arctic Alaskan Natives who maintain a traditional lifestyle have a disease profile that is significantly different from the general US population. There is concern that food sources containing environmental pollutants may contribute to this profile. In a preliminary study, umbilical cord blood was examined for the presence of several environmental contaminants. All cord blood samples analyzed thus far contain p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) with an average concentration of 0.33 microg/l. This study was undertaken to ascertain if this concentration of p,p'-DDE had detectable effects on immature cells in culture. NIH 3T3 (embryonic mouse fibroblast) and WS1 (human fetal fibroblast) cultures were exposed to media containing either 1 or 10 times the average cord blood concentration of p,p'-DDE. Initial experiments indicated that exposure to p,p'-DDE resulted in a decrease in the cell number of both cell types. Subsequent analysis revealed that the decrease in cell number was due to cell death in NIH 3T3 cells and to cell-cycle arrest in WS1 cells. Furthermore, p,p'-DDE decreased the long-term survival of NIH 3T3 but not WS1 cells. This study has demonstrated that p,p'-DDE, at relevant environmental concentrations, has significant effects on two immature mammalian cell types in culture. In addition, these results highlight the necessity for further studies to address the specific effects of p,p'-DDE on developing fetal systems.

DDE-induced eggshell thinning in birds: effects of p,p'-DDE on the calcium and prostaglandin metabolism of the eggshell gland

1. The focus of this review is the effects and mechanism of action of p,p'-DDE on eggshell formation in birds. Inhibition of prostaglandin synthesis in the eggshell gland mucosa is a probable mechanism for p,p'-DDE-induced eggshell thinning. 2. The duck is sensitive to p,p'-DDE-induced eggshell thinning but the domestic fowl is not, and studies comparing the two species in regard to the calcium and prostaglandin metabolism of the eggshell gland have shown that eggshell thinning induced by p,p'-DDE in ducks is accompanied by reduced activity of prostaglandin synthetase, reduced levels of prostaglandin E2, and reduced uptake of 45Ca by the eggshell gland mucosa. The content of calcium, bicarbonate, chloride, sodium, and potassium are also reduced in the eggshell gland lumen in ducks exhibiting eggshell thinning. None of these effects are seen in the domestic fowl. 3. Inhibition of prostaglandin synthesis is a specific effect of p,p'-DDE. The detrimental effects of p,p'-DDE on the eggshell gland seem to be unique when comparing the compound with structurally related substances, i.e., similar treatment regimens with o,p'-DDE, p,p'-DDT, o,p'-DDT, and p,p'-DDD do not cause eggshell thinning in ducks. Neither do they inhibit prostaglandin synthesis in the eggshell gland mucosa. 4. Administration of other compounds that do inhibit prostaglandin synthesis, e.g., indomethacin, does cause the same effects as those seen with p,p'-DDE, i.e., eggshell thinning and the described effects on the calcium and prostaglandin metabolism of the eggshell gland.

Characterisation of the effects of cadmium on the release of calcium and on the activity of some enzymes from neonatal mouse calvaria in culture

Exposure to cadmium (Cd) causes skeletal impairments, such as osteoporosis and osteomalacia, in many mammalian species, including humans. There is, however, some controversy about the mechanism of action of these Cd-induced skeletal effects, although both a direct influence on bone cells and effects that are secondary to renal damage caused by the metal have been demonstrated. In the present study, we cultured calvarial bones from neonatal mice and exposed them to Cd to study the effects of the metal on calcium release and on the activity of some enzymes of importance for bone resorption and bone formation. Cd dose-dependently stimulated calcium release from the bones. Maximal release was noted at Cd concentrations of 0.4-0.8 microM, which was similar to the level of release in the presence of maximal stimulatory concentrations of parathyroid hormone (10 nM) and prostaglandin E2 (10 microM). Cykloheximide (1 microM) inhibited calcium release elicited by Cd, prostaglandin E2 and parathyroid hormone. Cd-induced calcium release was linearly increased from 24 to 72 hr of culture. Production of prostaglandin E2 by the bone specimens was dose-dependently stimulated by Cd and inhibited by 1 microM indomethacin. Cd-induced calcium release was inhibited by acetazolamide (100 microM), indomethacin (1 microM) and ibuprofen (10 microM). Prostaglandin E2-stimulated calcium release was not inhibited by indomethacin. Exposure to 32 microM Cd, present during a 48-hr incubation period, significantly decreased prostaglandin E2-stimulated calcium release from 38.9% to 29.8%. Calcium release induced by parathyroid hormone was more sensitive to inhibition by the metal (i.e., Cd concentrations of 0.2 and 32 microM decreased the release from 37.7% to 31% and 19%, respectively). Cd present in the culture medium during a 48-hr incubation dose-dependently inhibited the activity of alkaline phosphatase and tartrate-resistant acid phosphatase in the bones but did not influence the activity of carbonic anhydrase. We conclude that Cd has a direct stimulatory effect on bone resorption, and this effect is dependent on prostaglandin production and also on protein synthesis. On the other hand, Cd also has an inhibitory effect on bone resorption (i.e., resorption is inhibited by higher concentrations of the metal). Moreover, Cd may impair bone formation by impeding the activity of alkaline phosphatase.

Progesterone stimulates prostaglandin synthesis in eggshell gland mucosa of estrogen-primed chickens

1. Prostaglandins may be involved in calcium translocation in the avian shell gland, since indomethacin, administered at the beginning of shell formation, reduces eggshell thickness as well as 45Ca-uptake and prostaglandin synthesis by a homogenate of eggshell gland mucosa. 2. The stimulus for calcium transport in the shell gland during shell formation remains unknown. 3. The present study was undertaken to investigate the effects of progesterone on prostaglandin formation by the eggshell gland mucosa of the domestic fowl. 4. Progesterone significantly stimulated synthesis of PGF2 alpha, PGE2 and TXB2 by eggshell gland mucosa homogenate. 5. Progesterone treatment also induced the synthesis of the biotin-binding protein, avidin. 6. A microsomal fraction prepared from the eggshell gland mucosa had a high affinity for binding PGE2. 7. Progesterone treatment reduced the KD value of this binding without affecting the maximal number of binding sites. 8. Progesterone did not change the total calcium content of shell gland mucosa. 9. The role progesterone plays in prostaglandin formation and calcium transport in the eggshell gland mucosa is discussed.

Effects of p,p'-DDE and some other chlorinated hydrocarbons on the formation of prostaglandins by the avian eggshell gland mucosa

Some structurally related chlorinated hydrocarbons were investigated for their effects on the production of prostaglandins by the eggshell gland mucosa of ducks and domestic fowl. Formation of PGF2 alpha, PGE2 and TxB2 by homogenates of domestic fowl eggshell gland mucosa was significantly inhibited by in vitro addition of p,p'-DDE, Arochlor 1242 and, to a lesser extent, Arochlor 1260, but not by p,p'-DDT and o,p'-DDE. Comparatively, in duck eggshell gland mucosa homogenates, synthesis of the same prostaglandins was somewhat more sensitive to inhibition by 5 microM p,p'-DDE added in vitro. Eggshell gland mucosa synthesized significantly more PGF2 alpha, PGE2 and TxB2 than did the mucosa of the magnum and isthmus regions of the oviduct. Duck eggshell gland mucosa homogenates synthesized significantly more prostaglandins than similar homogenates from the domestic fowl, and, considering the former synthesis of PGF2 alpha was significantly higher when ducks were slaughtered at 08:00 than at 16:00 hours. In ducks, dietary administration of 40 ppm, p,p'-DDE for 45 days resulted in 21% eggshell thinning compared to the contemporary control values. This treatment also resulted in notable effects in homogenates of the eggshell gland mucosa, as compared to controls: Ca2+ uptake was reduced by 43%, synthesis of PGF2 alpha, PGE2 and TxB2 was reduced by 26%, 38% and 53%, respectively; the Ca content was increased to 145%. The role of p,p'-DDE in inhibiting prostaglandin formation in the eggshell gland is discussed as a mechanism of the eggshell thinning action of this chlorinated hydrocarbon.

Inhibition of eggshell formation in domestic fowl by indomethacin: Relation to calcium and prostaglandin metabolism in the eggshell gland mucosa

1. The involvement of prostaglandins in eggshell formation in the domestic fowl was investigated by considering the effects of the drug indomethacin on the calcium metabolism on the eggshell gland. Egglaying birds were given a single dose (100 mg) of indomethacin at the beginning of shell calcification. Fourteen hours later the birds were sacrificed and the effects of the drug were determined. There was a 21% reduction in the shell thickness of the egg present in the shell gland at the time of slaughter (P < 0.01). The calcium content of the eggshell gland mucosa was increased to 153% (P < 0.01) of the controls. In the treated birds, there was 43% more calcium (P < 0.05) present in the shell gland lumen (recovered by rinsing with Tris buffer) than in the gland lumen of control birds. Total calcium in blood plasma was decreased by 15% (P < 0.05). In homogenate and three subcellular fractions (MIII, FI and FIII) of eggshell gland mucosa, 45Ca uptake was significantly reduced (i.e. by 29%, 25%, 17% and 35%, respectively). A significant reduction (62-66%) was also observed in the synthesis of PGF2 alpha, PGE2 and TxB2 by eggshell gland mucosa homogenate. 2. The effects of indomethacin treatment on the calcium metabolism of the avian eggshell gland are discussed and compared with p,p-DDE-induced alterations in calcium metabolism and prostaglandin synthesis by the eggshell gland.