title: Bafilomycin A1 inhibits chloroquine-induced death of cerebellar granule neurons.
abstract: Treatment of cells with the macrolide antibiotic bafilomycin A1, an inhibitor of vacuolar (V)-ATPase, or with the lysosomotropic agent chloroquine, has been shown to pharmacologically inhibit autophagy as evidenced by an accumulation of autophagosomes, which in turn causes Bax-dependent apoptosis. However, bafilomycin A1 has also been reported to inhibit chloroquine-induced apoptosis, suggesting a complex interrelationship between these two inhibitors of autophagy. To determine whether the cytoprotective effect of bafilomycin A1 on chloroquine-treated cells was dependent on inhibition of V-ATPase, we examined the single and combined effects of bafilomycin and chloroquine on cultured cerebellar granule neurons. When added separately, chloroquine or high concentrations of bafilomycin A1 (> or =10 nM) induced a dose-dependent inhibition of autophagy (as measured by an increase in LC3-II, a marker specific for autophagosomes), followed by caspase-3 activation and cell death. When added in combination, bafilomycin A1 potently inhibited chloroquine-induced caspase-3 activity and cell death at concentrations (< or =1 nM) that neither altered vacuolar acidification nor inhibited autophagy. The neuroprotective effects of bafilomycin A1 against chloroquine were substantially greater than those produced by Bax deficiency. Bafilomycin A1-induced neuroprotection seemed to be stimulus-specific, in that staurosporine-induced death was not attenuated by coaddition of bafilomycin A1. Together, these data suggest that in addition to promoting death via inhibition of V-ATPase and autophagy, bafilomycin A1 possesses novel, neuroprotective properties that inhibit Bax-dependent activation of the intrinsic apoptotic pathway resulting from the pharmacological inhibition of autophagy.
authors.affiliation: Department of Pathology, Division of Neuropathology, University of Alabama at Birmingham, SC961, 1530 3rd Ave South, Birmingham, AL 35294-0017, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Shacka
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Klocke
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shibata
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Uchiyama
authors.forename: Geeta
authors.initials: G
authors.lastname: Datta
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schmidt
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Roth
mesh_terms: D000818:Animals; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects*; D002738:Chloroquine / Q000494:pharmacology*; D003594:Cytoplasmic Granules / Q000187:drug effects*; D018942:Macrolides / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects*
chemical_list: D018942:Macrolides; D002738:Chloroquine; C040929:bafilomycin A1