Induction of metallothionein in proximal tubular cells by zinc and its potential as an endogenous antioxidant.
BACKGROUND
This study was undertaken to gain further insights into the expression of metallothionein (MT) in kidney, to define the necessary dosage of a metal (zinc) to achieve induction of MT and to evaluate the antioxidative potential of MT in comparison to other more common antioxidative therapeutics, like N-acetyl-L-cysteine (NAC), and endogenous molecules, like glutathione.


METHODS
MT was measured in renal specimens from cadaver kidneys from patients with chronic diseases (n = 76) and controls (n = 21) by immunohistochemistry. In addition, induction experiments were performed in cell cultures of proximal tubular cells (LCC-PK1) and MT measured on the RNA and protein level (immunohistochemistry, Western and dot blotting). Antioxidative potential of MT was compared to NAC and glutathione.


RESULTS
MT was restricted to tubular cells with no differences between controls and patients. Zn caused a dose-dependent increase of MT on the RNA as well as on the protein level (RNA (ratio MT/histone 3.3): control 0.34 +/- 0.12; Zn 17 microM 0.65 +/- 0.26; Zn 35 microM 1.25 +/- 0.43 (p < 0.05), Zn 52 microM 1.35 +/- 0.46 (p < 0.05), and protein: 5.8-fold increase from 47 +/- 13 mg/g total protein (n = 6) to 272 +/- 140 mg/g total protein (n = 6)). The antioxidative effect of MT was equal to NAC and glutathione.


CONCLUSIONS
Induction of renal MT by zinc is easily achievable and might be an interesting therapeutic and preventive tool against oxidative stress.
Alscher
Dominik M
DM
Division of General Internal Medicine and Nephrology, Department of Internal Medicine, Robert Bosch Krankenhaus, Stuttgart, Germany. dominik.alscher@bk.de
Braun
Nico
N
Biegger
Dagmar
D
Stuelten
Christina
C
Gawronski
Kerstin
K
Mürdter
Thomas E
TE
Kuhlmann
Ulrich
U
Fritz
Peter
P
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D016022:Case-Control Studies; D002460:Cell Line; D002908:Chronic Disease; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D008668:Metallothionein / Q000032:analysis / Q000235:genetics*; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis; D013552:Swine; D014018:Tissue Distribution; D015032:Zinc / Q000494:pharmacology*
D000975:Antioxidants; D012333:RNA, Messenger; D008668:Metallothionein; D015032:Zinc