Morphologic and functional alterations induced by low doses of mercuric chloride in the kidney OK cell line: Ultrastructural evidence for an apoptotic mechanism of damage

TY - JOUR

T1 - Morphologic and functional alterations induced by low doses of mercuric chloride in the kidney OK cell line

T2 - Ultrastructural evidence for an apoptotic mechanism of damage

AU - Carranza-Rosales, Pilar

AU - Said-Fernández, Salvador

AU - Sepúlveda-Saavedra, Julio

AU - Cruz-Vega, Delia E.

AU - Gandolfi, A Jay

PY - 2005/6/1

Y1 - 2005/6/1

N2 - Mercury produces acute renal failure in experimental animal models, but the mechanism of tubular injury has not completely been clarified. There is an increased interest in the role of apoptosis in the pathogenesis of renal diseases that result primarily from injury to renal tubular epithelial cells. However, detailed studies of morpho-functional alterations induced by mercuric chloride in kidney cell lines are scarce. This work characterizes these alterations in OK cell cultures. Morphological alterations were profiled using light microscopy, transmission electron microscopy, and confocal microscopy, as well as mitochondrial functional assays in the cells exposed to low concentrations of HgCl2. At concentrations of 1 and 10 μM of HgCl2 there were no morphological or ultrastructural alterations, but the mitochondrial function (MTT assay) and intracellular ATP content was increased, especially at longer incubation times (6 and 9 h). At 15 μM HgCl2, both the mitochondrial activity and the endogenous ATP decreased significantly. At this concentration the OK cells rounded up, had increased number of cytoplasmic vacuoles, and detached from the cell monolayer. At 15 μM HgCl2 ultrastructural changes were characterized by dispersion of the ribosomes, dilatation of the cisterns of the rough endoplasmic reticulum, increase of number of cytoplasmic vacuoles, chromatin condensation, invaginations of the nuclear envelope, presence of cytoplasmic inclusion bodies, and alterations in the size and morphology of mitochondria. At 15 μM HgCl2 apoptotic signs included membrane blebbing, chromatin condensation, mitochondrial alterations, apoptotic bodies, and nuclear envelope rupture. Using confocal microscopy and the mitochondrial specific dye MitoTracker Red, it was possible to establish qualitative changes induced by mercury on the mitochondrial membrane potential after incubation of the cells for 6 and 9 h with 15 μM HgCl2. This effect was not observed at short times (1 and 3 h) with this same concentration, neither with 1 and 10 μM HgCl2 in all the studied times. Taken together, these findings indicate that low concentrations of HgCl2 induce apoptosis by inhibiting mitochondrial function, and the OK cell line may be considered a useful tool for the study of programmed cell death involving mercurial species and other heavy metals.

AB - Mercury produces acute renal failure in experimental animal models, but the mechanism of tubular injury has not completely been clarified. There is an increased interest in the role of apoptosis in the pathogenesis of renal diseases that result primarily from injury to renal tubular epithelial cells. However, detailed studies of morpho-functional alterations induced by mercuric chloride in kidney cell lines are scarce. This work characterizes these alterations in OK cell cultures. Morphological alterations were profiled using light microscopy, transmission electron microscopy, and confocal microscopy, as well as mitochondrial functional assays in the cells exposed to low concentrations of HgCl2. At concentrations of 1 and 10 μM of HgCl2 there were no morphological or ultrastructural alterations, but the mitochondrial function (MTT assay) and intracellular ATP content was increased, especially at longer incubation times (6 and 9 h). At 15 μM HgCl2, both the mitochondrial activity and the endogenous ATP decreased significantly. At this concentration the OK cells rounded up, had increased number of cytoplasmic vacuoles, and detached from the cell monolayer. At 15 μM HgCl2 ultrastructural changes were characterized by dispersion of the ribosomes, dilatation of the cisterns of the rough endoplasmic reticulum, increase of number of cytoplasmic vacuoles, chromatin condensation, invaginations of the nuclear envelope, presence of cytoplasmic inclusion bodies, and alterations in the size and morphology of mitochondria. At 15 μM HgCl2 apoptotic signs included membrane blebbing, chromatin condensation, mitochondrial alterations, apoptotic bodies, and nuclear envelope rupture. Using confocal microscopy and the mitochondrial specific dye MitoTracker Red, it was possible to establish qualitative changes induced by mercury on the mitochondrial membrane potential after incubation of the cells for 6 and 9 h with 15 μM HgCl2. This effect was not observed at short times (1 and 3 h) with this same concentration, neither with 1 and 10 μM HgCl2 in all the studied times. Taken together, these findings indicate that low concentrations of HgCl2 induce apoptosis by inhibiting mitochondrial function, and the OK cell line may be considered a useful tool for the study of programmed cell death involving mercurial species and other heavy metals.

KW - Apoptosis

KW - Mercuric chloride

KW - Nephrotoxicity

KW - OK cells

KW - Ultrastructure

UR - http://www.scopus.com/inward/record.url?scp=17144399886&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=17144399886&partnerID=8YFLogxK

U2 - 10.1016/j.tox.2005.01.006

DO - 10.1016/j.tox.2005.01.006

M3 - Article

C2 - 15840425

AN - SCOPUS:17144399886

VL - 210

SP - 111

EP - 121

JO - Toxicology

JF - Toxicology

SN - 0300-483X

IS - 2-3

ER -