Franca Marino1, Simona Cattaneo1, Marco Cosentino1, Emanuela Rasini1, Laura Di Grazia1, A. Fietta2, Sergio Lecchini1, Gianmario Frigo1
1Department of Internal Medicine and Therapeutics, Section of Clinical Pharmacology, University of Insubria and University of Pavia, Varese, and
2Chair of Chemotherapy, University of Pavia, Italy
Tóm tắt
In isolated human neutrophils, diazepam (10 nmol/l to 10 µmol/l) concentration-dependently increased migration and phagocytosis. Diazepam-induced migration and phagocytosis were inhibited by the peripheral benzodiazepine receptor (PBR) antagonist PK11195 (10 µmol/l). The PBR agonist Ro5-4864 (10 nmol/l to 10 µmol/l) did not affect migration but slightly enhanced phagocytosis, while clonazepam, which binds to the central-type benzodiazepine receptors but has no affinity for PBRs, was ineffective on both parameters up to 10 µmol/l. Phagocytosis induced by diazepam or Ro5-4864 was inhibited by the Ca<sup>2+</sup> channel blocker <i>L</i>-verapamil (10 µmol/l), which however did not affect the action of diazepam on migration. Competition binding experiments performed by fluorescent staining of PBRs showed that diazepam directly interacts with PBRs on human neutrophils. Both diazepam and Ro5-4864 (10 nmol/l to 10 µmol/l) induced a rise of intracellular free Ca<sup>2+</sup> concentrations ([Ca<sup>2+</sup>]<sub>i</sub>), which was inhibited by PK11195 (10 µmol/l) and <i>L</i>-verapamil (10 µmol/l) and prevented by extracellular Ca<sup>2+</sup> chelation with EGTA (5 mmol/l). In conclusion, experimental evidence indicates that in human neutrophils diazepam stimulates both migration and phagocytosis through activation of PBRs. Diazepam-induced [Ca<sup>2+</sup>]<sub>i</sub> changes depend on a PBR-operated, <i>L</i>-verapamil-sensitive increase in the plasma membrane permeability and subsequent extracellular Ca<sup>2+</sup> entry, and contribute to diazepam-induced phagocytosis. On the contrary, the effect of diazepam on migration seems to occur through Ca<sup>2+</sup>-independent mechanisms.
