INVESTIGADORES
SERRA Esteban Carlos
artículos
Título:
Potential mechanism of fibronectin deposits in acute renal failure induced by mercuric chloride
Autor/es:
SABALL, ESTER; SALVARREY, MARCELA; ESTEBAN SERRA; PICO, GUILLERMO; ELIAS, MONICA
Revista:
MOLECULAR AND CELLULAR BIOCHEMISTRY
Editorial:
SPRINGER
Referencias:
Año: 2001 vol. 226 p. 67 - 75
ISSN:
0300-8177
Resumen:
Many glomerular diseases are associated with changes in the expression
and distribution in the components of extracellular matrix. A remarkable
feature in acute renal failure induced by mercuric chloride in rats was
large fibronectin
(Fn) deposits in kidneys 1 h post-HgCl2 injection (5 mg/kg body wt.,
s.c.). Our study examined some mechanisms as potential explanation of
the early Fn deposits in mercuric chloride induced acute renal failure.
Total tissue mRNA of livers and kidneys of control and treated rats were
used in Northern blot to determine whether accumulation of Fn in kidney
is associated with increases in the expression of this protein in the
kidney and/or in the liver. Analysis of Fn levels by Western blot were
also performed. Northern blot did not show significant difference
between control and treated rats, while the abundance of polymerized-Fn
in kidney tissue was increased 1 h and 5 h post HgCl2 injection. HgCl2
influence on Fn folding was studied in vitro to detect possible
conformational changes that could altered its normal pattern of matrix
assembly and/or binding to different ligands. In this context HgCl2
binding to Fn was measured following native tryptophan fluorescence of
Fn in the presence of HgCl2 (0.5-250 mM). Binding parameters for the
HgCl2-Fn complex formation were Kd = (1.6 +/- 0.2) 10(-4) M; n = 1 +/-
0.3, indicating a low apparent affinity and one type binding site.
Thermal denaturation of Fn showed, between 30-60 degrees C, a soft
reversible conformational change, while between 75-80 degrees C a highly
and irreversible transition is produced suggesting a modification of
the tertiary structure. HgCl2 abolished this transition. The kinetic of
thermal unfolding of Fn was also measured and the effects observed due
to HgCl2 presence reinforced the previous data. Finally, the effect of
HgCl2 on Fn binding to denatured collagen (gelatin) was also measured as
an index of the effect of this cation on biological properties of Fn.
Fn binds gelatin strongest in the presence of HgCl2. Our results suggest
that higher Fn deposits in kidney-treated rats seems not to be
associated to augmented mRNA-Fn neither in kidney nor in liver. On the
other hand, increased levels of polymerized Fn abundance was observed in
kidney tissue from mercury-treated rats. We also describe that HgCl2
promotes, in vitro, conformational changes on Fn structure, inducing its
denaturation and increasing its binding to gelatin, all events that
could be related to the Fn deposits in renal tissues of HgCl2 treated
rats, and could be expected in other situations that promoted
interstitial fibrosis, not associated to overexpression of
matrix-proteins.