Attenuation of both apoptotic and necrotic actions of cadmium by Bcl-2.
We examined the effects of cadmium on the bcl-2 family of proteins--bcl-2, bax, bad, and bcl-xS/L--in cadmium-induced cytotoxicity. Addition of 10 microM cadmium to cultured porcine kidney LLC-PK(1) cells caused apoptosis. Western blot analyses revealed that cadmium markedly increased endogenous bcl-2 protein (to 3-4 times the level in wild-type cells) earlier than metallothionein induction, but that the metal did not enhance the induction of bax, bad, or bcl-xS proteins. Cadmium also induced the transcript of bcl-2, with the amount of bcl-2 reaching a maximum at 1-2 hr of exposure; this increase occurred earlier than cadmium-induced increase in the protooncogene such as c-myc. A cadmium-induced increase in endogenous bcl-2 protein was also seen in rat primary thymocytes. Overexpression of the bcl-2 protein by gene transfection prevented cadmium-induced apoptosis. Following the detection of apoptosis, lactate dehydrogenase release in the culture medium (a marker of necrosis) was observed, and this release was also inhibited by overexpression of bcl-2. Electron microscopic observations also supported the fact that cadmium induced apoptotic chromatin condensation at an early stage of exposure, followed by necrotic features of the cells, both of which were also inhibited by overexpression of bcl-2 proteins. Thus, our data demonstrated that both apoptotic and necrotic actions of cadmium were attenuated by bcl-2.
Ishido
Masami
M
Pathophysiology Research Team, National Institute for Environmental Studies, Tsukuba, Japan. ishidou@nies.go.jp
Ohtsubo
Rieko
R
Adachi
Tatsumi
T
Kunimoto
Manabu
M
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002104:Cadmium / Q000009:adverse effects*; D018929:Cell Culture Techniques; D004785:Environmental Pollutants / Q000009:adverse effects*; D019254:Genes, bcl-2; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008854:Microscopy, Electron; D009336:Necrosis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000494:pharmacology; D013552:Swine
D004785:Environmental Pollutants; D019253:Proto-Oncogene Proteins c-bcl-2; D002104:Cadmium; D007770:L-Lactate Dehydrogenase