Early cytotoxic effects of ochratoxin A in rat liver: a morphological, biochemical and molecular study.
We characterized the overall early effect of chronic ochratoxin A (OTA) treatment on rat liver, analyzing different aspects related to: (i) fibrosis, by measuring collagen content and turnover, and alpha-smooth muscle actin (alphaSMA); (ii) oxidative stress and stress response, by analyzing protein carbonylation, superoxide dismutase (SOD) and heat shock protein (HSP70) gene expression; (iii) the possible tumor promoter effect, evaluating cadherin and connexin (CX) mRNA levels. Light microscopy analysis showed no histological differences in OTA-treated and control (CT) rats. Collagen content, determined by computer analysis of Sirius red-stained liver sections, was similar in both groups. In liver homogenates COL-I, COL-III, TIMP-1 and TGF-beta1 mRNA levels and alphaSMA were unaffected by OTA. Matrix metalloproteinase (MMP)-1, MMP-2 and MMP-9 protein levels were also similar in the two groups. Protein carbonylation, a marker of severe oxidative stress, was not evident in the homogenates of OTA-treated livers; superoxide dismutase (SOD) mRNA tended to be lower and HSP70 was strongly down-regulated. OTA reduced E-cadherin and DSC-2 transcription, and down-regulated liver CX26, CX32 and CX43. In conclusion, these in vivo results show that OTA-induced liver injury involves a reduction in the ability to counterbalance oxidative stress, maybe leading to altered gap junction intercellular communication and loss of cell adhesion and polarity. This suggests that mild oxidative damage might be a key factor, in combination with other cytotoxic effects, in triggering the promotion of liver tumors after exposure to OTA.
Gagliano
Nicoletta
N
Department of Human Morphology-LITA Segrate, Via Fratelli Cervi 93, 20090 Segrate, Milan, Italy. nicoletta.gagliano@unimi.it
Donne
Isabella Dalle
ID
Torri
Carlo
C
Migliori
Massimiliano
M
Grizzi
Fabio
F
Milzani
Aldo
A
Filippi
Cristina
C
Annoni
Giorgio
G
Colombo
Piergiuseppe
P
Costa
Francesco
F
Ceva-Grimaldi
Giorgia
G
Bertelli
Alberto A E
AA
Giovannini
Luca
L
Gioia
Magda
M
D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002273:Carcinogens / Q000633:toxicity*; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D008297:Male; D009183:Mycotoxins / Q000633:toxicity*; D009793:Ochratoxins / Q000633:toxicity*; D009929:Organ Size / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D050050:Protein Carbonylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism
D015820:Cadherins; D002273:Carcinogens; D017630:Connexins; C000607042:GJB2 protein, human; D018840:HSP70 Heat-Shock Proteins; D009183:Mycotoxins; D009793:Ochratoxins; D012333:RNA, Messenger; D000072259:Connexin 26; C025589:ochratoxin A; D003094:Collagen; D013482:Superoxide Dismutase