Abstract
Objective Study on the effects of protein tyrosine kinase, protein tyrosine phosphatase and protein kinase C (PKC)on apoptotic process, observe the changes of cytosolic calcium ([Ca2+]i) of human leukemia cells and cortex neurons after clinical relevant dosage of arsenic trioxide (As2O3) exposure in vitro.
Methods Marked [Ca2+]I of human leukemia cells and cortex neurons with Fluo-3/AM, assayed the changes of [Ca2+]I with laser confocal microscopy in real-time after managed with As2O3 in different concentrations respectively, detected the effects of protein tyrosine kinase, the protein tyrosine phosphatase and the activation of protein kinase C on these changes with confocal microscopy and Phosphorus radioisotope assay. Assayed the DNA ladders of leukemia cells and cortex neurons after exposed in As2O3.
Results As2O3 1μmol/L can increase the [Ca2+]I of NB4 cells remarkably but show no effects on neurons. Vanadate, a kind of protein tyrosine phosphatase inhibitor, can dose-dependently promote the increasing of [Ca2+]I caused by 2, 5, 10μmol/L As2O3.The mean value of total increased rate in 280 seconds after exposed in As2O3 in different concentrations were: 6.5±2.3%, 21.7±2.1 %,49.2±2.5% in NB4 cells, and 6.7±2.1%, 19.4±2.5 %, 52.3±2.7% in cortex neurons respectively. Genistein, a kind of protein tyrosine kinase inhibitor, can dose-dependently decrease the raising of [Ca2+]I caused by 2, 5, 10μmol/L As2O3.The mean value of total inhibited rate in 280 seconds after As2O3 management in different concentrations were 6.7±2.9%, 25.6±2.5 %, 52.2±3.5% in NB4 cells, and 7.8±3.1%, 18.1±2.8%, 51.3±3.3% in cortex neurons respectively. The activation of PKC began when exposed in As2O31μmol/L for 3 h, and keep raising continuously in NB4 cells., DNA ladders appeared after exposed in As2O31μmol/L for 24h. However, no appearances above were found in human cortex neurons. In 2μmol/L As2O3 exposedness, The activation of PKC and DNA ladders appeared in neurons.
Conclusions The phosphorylation and dephosphorylation of protein tyrosine kinase and protein tyrosine phosphatase participated in nonspecific apoptosis signal transduction pathway of As2O3, and accompanied with PKC activation. The [Ca2+] elevation was closely related to PKC increasing activation. The tolerances between leukemia cell and cortex neuron to As2O3 were differ in dosage.
Aspirin inhibits lipopolysaccharide-induced COX-2 expression and PGE2production in porcine alveolar macrophages by modulating protein kinase C and protein tyrosine phosphatase activity
