Glutathione and mitochondria determine acute defense responses and adaptive processes in cadmium-induced oxidative stress and toxicity of the kidney.
Cadmium (Cd(2+)) induces oxidative stress that ultimately defines cell fate and pathology. Mitochondria are the main energy-producing organelles in mammalian cells, but they also have a central role in formation of reactive oxygen species, cell injury, and death signaling. As the kidney is the major target in Cd(2+) toxicity, the roles of oxidative signature and mitochondrial function and biogenesis in Cd(2+)-related stress outcomes were investigated in vitro in cultured rat kidney proximal tubule cells (PTCs) (WKPT-0293 Cl.2) for acute Cd(2+) toxicity (1-30 µM, 24 h) and in vivo in Fischer 344 rats for sub-chronic Cd(2+) toxicity (1 mg/kg CdCl2 subcutaneously, 13 days). Whereas 30 µM Cd(2+) caused ~50 % decrease in cell viability, apoptosis peaked at 10 µM Cd(2+) in PTCs. A steep, dose-dependent decline in reduced glutathione (GSH) content occurred after acute exposure and an increase of the oxidized glutathione (GSSG)/GSH ratio. Quantitative PCR analyses evidenced increased antioxidative enzymes (Sod1, Gclc, Gclm), proapoptotic Bax, metallothioneins 1A/2A, and decreased antiapoptotic proteins (Bcl-xL, Bcl-w). The positive regulator of mitochondrial biogenesis Pparγ and mitochondrial DNA was increased, and cellular ATP was unaffected with Cd(2+) (1-10 µM). In vivo, active caspase-3, and hence apoptosis, was detected by FLIVO injection in the kidney cortex of Cd(2+)-treated rats together with an increase in Bax mRNA. However, antiapoptotic genes (Bcl-2, Bcl-xL, Bcl-w) were also upregulated. Both GSSG and GSH increased with chronic Cd(2+) exposure with no change in GSSG/GSH ratio and augmented expression of antioxidative enzymes (Gpx4, Prdx2). Mitochondrial DNA, mitofusin 2, and Pparα were increased indicating enhanced mitochondrial biogenesis and fusion. Hence, these results demonstrate a clear involvement of higher mitochondria copy numbers or mass and mitochondrial function in acute defense against oxidative stress induced by Cd(2+) in renal PTCs as well as in adaptive processes associated with chronic renal Cd(2+) toxicity.
Environmental Biology, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium. ambilinair2006@gmail.com.
Ambily Ravindran
AR
Nair
Chair of Physiology, Pathophysiology and Toxicology, Centre for Biomedical Education and Research, Witten/Herdecke University, Witten, Germany. Wing-Kee.Lee@uni-wh.de.
Wing-Kee
WK
Lee
Environmental Biology, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium. karen.smeets@uhasselt.be.
Karen
K
Smeets
Environmental Biology, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium. quirine.swennen@uhasselt.be.
Quirine
Q
Swennen
Environmental Biology, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium. acastrosan@gmail.com.
Amparo
A
Sanchez
Chair of Physiology, Pathophysiology and Toxicology, Centre for Biomedical Education and Research, Witten/Herdecke University, Witten, Germany. frank.thevenod@uni-wh.de.
Frank
F
Thévenod
Environmental Biology, Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium. ann.cuypers@uhasselt.be.
Ann
A
Cuypers
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019256:Cadmium Chloride / Q000008:administration & dosage / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005260:Female; D005978:Glutathione / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000473:pathology; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D051381:Rats; D011916:Rats, Inbred F344; D011921:Rats, Inbred WKY; D017382:Reactive Oxygen Species / Q000378:metabolism
D017382:Reactive Oxygen Species; D053148:Caspase 3; D005978:Glutathione; D019256:Cadmium Chloride
Antioxidative enzymes; Apoptosis; Metallothionein; Mitochondrial DNA content; Oxidative stress