title: 1,4-benzothiazine analogues and apoptosis: structure-activity relationship.
abstract: We have previously shown 1,4-benzothiazine (1,4-B) derivatives induce thymocyte apoptosis in vitro and thymus cell loss in vivo. Apoptosis is mediated through a complex of biochemical events including phosphatidylcholine specific-phospholipase C (PC-PLC) activation, acidic sphingomyelinase (aSMase) activation and ceramide generation, caspase-8 and caspase-3 activation. As preliminary analysis of the structure-activity relationship (SAR) suggested some structural features were responsible for apoptosis, we synthesised several derivatives and tested for apoptosis activity at equimolar concentrations. In particular, we synthesised analogues that differed in the nature of skeleton (1,4-benzothiazine, 1,4-benzoxazine and 1,2,3,4-tetrahydroquinoline) and in the nature of side chain (imidazole, benzimidazole or piperazine as azole substituent; presence, absence or transformation of alcoholic group). Results of apoptosis induction indicate that transforming the 1,4-benzothiazine skeleton into 1,2,3,4-tetrahydroquinoline does not result in significant change. Transformation into 1,4-benzoxazine decreased activity. Replacing imidazole at the side chain with different piperazines also decreased activity while replacing it with benzimidazole does not change apoptotic activity. Finally, removal of the alcoholic group by dehydration to olefin, or by transforming it into ether, increased activity. Moreover, in an attempt to analyse further the SAR characteristics that are responsible for 1,4-B-activated apoptosis we tested the effect on caspase-8,-9 and-3 activation. 1,4-B analogues activate caspases and the structural requirements correlate with those responsible for apoptosis induction.
authors.affiliation: Department of Drug Chemistry and Technology, University of Perugia, Via del Liceo 1, 06123 Perugia, Italy. fringuel@unipg.it
authors.forename: Renata
authors.initials: R
authors.lastname: Fringuelli
authors.forename: Fausto
authors.initials: F
authors.lastname: Schiaffella
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Utrilla Navarro
authors.forename: Lara
authors.initials: L
authors.lastname: Milanese
authors.forename: Cristina
authors.initials: C
authors.lastname: Santini
authors.forename: Michela
authors.initials: M
authors.lastname: Rapucci
authors.forename: Cristina
authors.initials: C
authors.lastname: Marchetti
authors.forename: Carlo
authors.initials: C
authors.lastname: Riccardi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D013329:Structure-Activity Relationship; D013843:Thiazines / Q000737:chemistry* / Q000494:pharmacology*; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000502:physiology
chemical_list: C446962:1,4-benzothiazine; D013843:Thiazines