Using a stable isotope-labeled internal standard for liquid chromatography-tandem mass spectrometry quantitation of meloxicam in human plasma.

A sensitive and highly efficient LC-ESI-MS/MS method using a stable isotope-labeled internal standard (SIL IS) to detect meloxicam in human plasma was developed and validated. Sample preparation used only 50 µL human plasma with one-step methanol protein precipitation. A gradient mobile phase system was adopted for chromatographic separation on a Poroshell 120 SB-C18 column (2.1 × 50 mm, 2.7 µm). Positive ion pattern was chosen for quantification under multiple reaction monitoring. Ion pairs were [M + H]+ m/z 352.1 → 115.1 for meloxicam and [M + H]+ m/z 355.1 → 187.1 for meloxicam-d3 (SIL IS). Total run time was 4.0 min. Standard curve was linear over a concentration range from 8.00 to 1600 ng mL-1 . This method was fully validated to evaluate its performance, including specificity, carryover, sensitivity, linearity, accuracy, precision, recovery, matrix effects, stability, dilution reliability and incurred sample reanalysis, which provided a reliable basis for pharmacokinetic studies of meloxicam in 28 healthy Chinese volunteers. After a single-dose oral administration of 7.5 mg meloxicam, the main pharmacokinetic parameters were as follows: Cmax , 814.79 ± 201.37 ng mL-1 ; Tmax , 4.54 ± 1.42 h; AUC0-t , 24,572.04 ± 5766.93 ng·h mL-1 ; AUC0-∞ , 25,810.89 ± 6796.60 ng·h mL-1 and t1/2 , 21.11 ± 5.35 h.

Survivin mediates self-protection through ROS/cdc25c/CDK1 signaling pathway during tumor cell apoptosis induced by high fluence low-power laser irradiation.

Survivin, an important member of inhibitor-of-apoptosis (IAP) family, can be up-regulated by various pro-apoptotic stimuli, such as UV, photodynamic therapy (PDT) and cisplatin. High fluence low-power laser irradiation (HF-LPLI) is a newly discovered pro-apoptotic stimulator. The anti-apoptotic mechanism of survivin during HF-LPLI-induced apoptosis is still not investigated. Here, we report that HF-LPLI up-regulates survivin activity through reactive oxygen species (ROS)/cdc25c protein phosphatase (cdc25c)/cyclin-dependent kinase (CDK1) signaling pathway in human lung adenocarcinoma cells (ASTC-a-1). The up-regulation of survivin activity can reduce HF-LPLI-induced apoptosis, while down-regulation of the activity can promote the apoptosis. In addition, activated survivin delays mitochondrial depolarization, cytochrome c release, caspase-9 and Bax activation, all of which are typical pro-apoptotic events of cell apoptosis induced by HF-LPLI. On the basis of the present studies, we conclude that survivin can mediate self-protection during tumor cell apoptosis caused by HF-LPLI.