Abstract
1,4-Benzothiazine (1,4-B) derivatives exert numerous effects in vivo and in vitro, including neurotoxicity and antitumor cytotoxicity. To analyze the mechanisms responsible for 1,4-B-induced cytotoxicity, we performed experiments to evaluate the possible apoptotic effect. For that purpose, we used mouse thymocytes, a cell population well sensitive to induction of apoptosis that has been used to assay apoptosis in many experimental systems. Results indicate that a number of 1,4-B analogs are able to induce both thymocyte apoptosis in vitro and thymus cell loss in vivo. Moreover, analysis of the structure-activity relationship indicate that the sulfur (S) oxidation state, the presence of the carbonyl group, and the nature and position of the side chain modulate the apoptotic efficacy. Moreover, results of in vitro experiments show that the 1,4-B-induced apoptosis associates with different biochemical events including phosphatidylcholine-specific phospholipase C activation, acidic sphingomyelinase activation and ceramide generation, loss of mitochondrial membrane potential (ΔΨm) and cytochromec release, and caspase-8, -9, and -3 activation. These results indicate that 1,4-B analogs induce apoptosis through a complex of biochemical events.
Footnotes
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This work was supported by Consiglio Nazionale delle Ricerche target project on Biotechnology, Rome, Italy.
- Abbreviations:
- 1,4-B
- 1,4-benzothiazine
- SAR
- structure-activity relationship
- PC-PLC
- phosphatidylcholine specific-phospholipase C
- PI-PLC
- phosphatidylinositol-specific phospholipase C
- DAG
- diacylglycerol
- aSMase
- acidic sphingomyelinase
- ΔΨm
- mitochondrial membrane potential transition (or loss of mitochondrial membrane potential)
- JC-1
- 5,5′,6,6′-tetraethylbenzimidazolylcarbocyanine iodide
- DEX
- dexamethasone
- PBS
- phosphate-buffered saline
- PMSF
- phenylmethylsulfonyl fluoride
- SM
- sphingomyelin
- TLC
- thin layer chromatography
- PI
- propidium iodide
- PCD
- programmed cell death
- pNA
- p-nitroanilide
- TSO
- 4-methyl-3,4-dihydro-2H-1,4-benzothiazin-3-one
- Received August 29, 2001.
- Accepted November 12, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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