A non-transformed mouse liver cell line (AML12) was used to show that blocking swelling-activated membrane Cl- current inhibits hepatocyte proliferation. Two morphologically distinguishable cell populations exhibited distinctly different responses to hypotonic stress. Hypotonic stress (from 280 to 221 mosmol kg(-1)) to rounded, dividing cells activated an ATP-dependent, outwardly rectifying, whole-cell Cl- current, which took 10 min to reach maximum conductance. A similar anionic current was present spontaneously in 20 % of the dividing cells. Hypotonic stress to flattened, non-dividing cells activated no additional current. The Eisenman halide permeability sequence of swelling-activated anionic current in the dividing cells was SCN(-) > I(-) > Br(-) > Cl(-) > gluconate. Addition of either 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), tamoxifen or mibefradil inhibited swelling-activated anionic current. Hyperosmolarity by added sucrose inhibited the spontaneous anionic current in dividing cells. Added Cl- channel blockers NPPB (IC50 = 40 microM), DIDS (IC50 = 31 microM), tamoxifen (IC50 = 1.3 microM) and mibefradil (IC50 = 7 microM) inhibited proliferative growth of AML12 as determined by cell counts over 4 days or by protein accumulation over 2 days. Only the inhibitory effects of NPPB and mibefradil reversed with the drug washout. Hyperosmolarity by added sucrose (50 and 100 mM) also inhibited cell proliferation. Of the hydrophobic inhibitors neither NPPB at 40 microM nor tamoxifen at 1.3 microM, added for 48 h, reduced cellular ATP; however, DIDS at 31 microM significantly reduced cellular ATP with an equivalent increase in cellular ADP. We conclude that those membrane Cl- currents that can be activated by hypotonic stress are involved in mechanisms controlling liver cell growth, and that NPPB, tamoxifen and mibefradil at their IC50 for growth do not suppress the metabolism of mouse hepatocytes.

No abstract

Opioids have been widely applied in clinics as one of the most potent pain relievers for centuries, but their abuse has deleterious physiological effects beyond addiction. We previously reported that opioids inhibit cell growth and trigger apoptosis in lymphocytes. However, the underlying mechanism by which microglia apoptosis in response to opioids is not yet known. In this study, we show that morphine induces microglia apoptosis and caspase-3 activation in an opioid-receptor dependent manner. Morphine decreased the levels of microglia phosphorylated Akt (p-Akt) and p-GSK-3β (glycogen synthase kinase 3 beta) in an opioid receptor dependent manner. More interestingly, GSK-3β inhibitor SB216763 significantly increases morphine-induced apoptosis in both BV-2 microglia and mouse primary microglial cells. Moreover, co-treatment of microglia with SB216763 and morphine led to a significant synergistic effect on the level of phospho-p38 mitogen-activated protein kinase (MAPK). In addition, inhibition of p38 MAPK by its specific inhibitor SB203580 significantly inhibited morphine-induced apoptosis and caspase-3 activation. Taken together, our data clearly demonstrates that morphine induced apoptosis in microglial cells, which is mediated via GSK-3β and p38 MAPK pathways.

No abstract

A case is presented of a fatal drug interaction caused by ingestion of clozapine (Clozaril™) and fluoxetine (Prozac™). Clozapine is a tricyclic dibenzodiazepine derivative used as an “atypical antipsychotic” in the treatment of severe paranoid schizophrenia. Fluoxetine is a selective serotonin reuptake inhibitor used for the treatment of major depression. Clinical studies have proven that concomitant administration of fluoxetine and clozapine produces increased plasma concentrations of clozapine and enhances clozapine's pharmacological effects due to suspected inhibition of clozapine metabolism by fluoxetine. Blood, gastric, and urine specimens were analyzed for fluoxetine by gas chromatography/mass spectrometry (GC/MS) and for clozapine by gas-liquid chromatography (GLC). Clozapine concentrations were: plasma, 4.9 µg/mL; gastric contents, 265 mg; and urine, 51.5 µg/mL. Fluoxetine concentrations were: blood, 0.7 µg/mL; gastric contents, 3.7 mg; and urine 1.6 µg/mL. Norfluoxetine concentrations were: blood, 0.6 µg/mL, and none detected in the gastric contents or urine. Analysis of the biological specimens for other drugs revealed the presence of ethanol (blood, 35 mg/dL; vitreous, 56 mg/dL; and urine 153 mg/dL) and caffeine (present in all specimens). The combination of these drugs produced lethal concentrations of clozapine and high therapeutic to toxic concentrations of fluoxetine. The deceased had pulmonary edema, visceral vascular congestion, paralytic ileus, gastroenteritis and eosinophilia. These conditions are associated with clozapine toxicity. The combined central nervous system, respiratory and cardiovascular depression of these drugs was sufficient to cause death. The death was determined to be a clozapine overdose due to a fatal drug interaction.