A defect in the oxidative metabolism of human polymorphonuclear leukocytes that remain in circulation early in hemodialysis

Human granulocytes harvested from uremic volunteers 15 min after the initiation of dialysis (at the nadir of neutropenia) were compared to predialysis controls. These intradialysis cells had a significant defect in peak luminol-enhanced chemiluminescence in response to opsonized zymosan, f-Met-Leu-Phe, and phorbol myristate acetate relative to predialysis control cells from the same patients. This defect could not be explained by a decrease in PMN myeloperoxidase concentration. H2O2 secretion by intradialysis cells (2 patients) was also depressed relative to predialysis controls. The ability to perform an independent function, orientation (polarization), was normal in both pre- and intradialysis cells relative to control. Whereas 125I-labeled formyl peptide binding studies demonstrated identical values for affinity and receptor number for predialysis and normal control cells, intradialysis cells displayed a 27% decrease in receptor number. This decrease in available receptor number. This decrease in available receptors may be related to the decreased chemiluminescence observed in response to f-Met-Leu-Phe. Furthermore, the results are consistent with the hypothesis that a defective PMN population remains in the circulation during the neutropenia of hemodialysis.</jats:p

A defect in the oxidative metabolism of human polymorphonuclear leukocytes that remain in circulation early in hemodialysis

Abstract Human granulocytes harvested from uremic volunteers 15 min after the initiation of dialysis (at the nadir of neutropenia) were compared to predialysis controls. These intradialysis cells had a significant defect in peak luminol-enhanced chemiluminescence in response to opsonized zymosan, f-Met-Leu-Phe, and phorbol myristate acetate relative to predialysis control cells from the same patients. This defect could not be explained by a decrease in PMN myeloperoxidase concentration. H2O2 secretion by intradialysis cells (2 patients) was also depressed relative to predialysis controls. The ability to perform an independent function, orientation (polarization), was normal in both pre- and intradialysis cells relative to control. Whereas 125I-labeled formyl peptide binding studies demonstrated identical values for affinity and receptor number for predialysis and normal control cells, intradialysis cells displayed a 27% decrease in receptor number. This decrease in available receptor number. This decrease in available receptors may be related to the decreased chemiluminescence observed in response to f-Met-Leu-Phe. Furthermore, the results are consistent with the hypothesis that a defective PMN population remains in the circulation during the neutropenia of hemodialysis.</jats:p

Intramolecular titanium-mediated aminocyclopropanation of terminal alkenes: Easy access to various substituted azabicyclo[n.1.0]alkanes

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PDE1B2 regulates cGMP and a subset of the phenotypic characteristics acquired upon macrophage differentiation from a monocyte

Monocyte-to-macrophage differentiation with the cytokine granulocyte–macrophage colony-stimulating factor induces expression of the cyclic nucleotide phosphodiesterase PDE1B2. However, what role PDE1B2 plays in macrophage biology has not been elucidated. We have addressed this question by inhibiting PDE1B2 induction by using RNA interference. Using a retrovirus-based system, we created HL-60 stable cell lines that express a short-hairpin RNA targeting PDE1B2. HL-60 cells treated with phorbol-12-myristate-13-acetate differentiate to a macrophage-like phenotype and up-regulate PDE1B2. However, expression of PDE1B2 short hairpin RNA effectively suppresses PDE1B2 mRNA, protein, and activity up-regulation. Using the HL-60 PDE1B2 knockdown cells and agonists for either adenylyl or guanylyl cyclase, it was found that PDE1B2 predominantly regulates cGMP and plays a lesser role in cAMP regulation in response to cyclase agonists. Furthermore, in intact HL-60 cells, PDE1B2 activity can be regulated by changes in Ca(+2) levels. Inhibiting PDE1B2 up-regulation does not prevent HL-60 cell differentiation, because several markers of macrophage differentiation are unaffected. However, suppression of PDE1B2 expression alters some aspects of the macrophage-like phenotype, because cell spreading, phagocytic ability, and CD11b expression are augmented. The cAMP analog 8-Bromo-cAMP reverses the changes caused by PDE1B2 knockdown. Also, PDE1B2 knockdown cells have lower basal levels of cAMP and alterations in the phosphorylation state of several probable PKA substrate proteins. Thus, the effects of PDE1B2 on differentiation may ultimately be mediated through decreased cAMP. In conclusion, PDE1B2 regulates a subset of phenotypic changes that occur upon phorbol-12-myristate-13-acetate-induced differentiation and likely also plays a role in differentiated macrophages by regulating agonist-stimulated cGMP levels