Soy protects against cadmium induced fibrosis in lung. Role of hsps

Abstract

Cadmium (Cd) is a toxic metal and an important environmental contaminant.We studied its effects on fibrosis and heat shock proteins (HSP) expressionunder different diets. 4 lots of female Wistar rats were used: 2 lots receivedcasein (Cas) and 2 lots received soybean (Soy) as protein sources. Within eachgroup: 1 lot received regular water (control-Co) and the other 15ppm of Cd inthe drinking water for 60days. Lungs were hydrolysated for hydroxyproline(Hyp) quantification HCl at 107°C and taken up in acetate-citrate buffer.Samples were mixed with chloramine-T solution. After 20 min,aldehyde/perchloric acid solution was added. The color was read in aspectrophotometer at 550 nm. Standard solutions of L-Hyp were used forstandard curve elaboration. Lung tissues were fixed, dehydrated, cleared inxylene, and embedded in paraffin. Sections of 5?6µm thickness were stainedwith Masson?s trichrome solution for histology assessment.Immunohistochemistry was performed by using Hsp27 and Hsp70 antibodies.Hyp showed an increase in CasCd group vs CasCo (p<0.005); in SoCd, Hyplevels were higher than SoCo (p<0.01) but lesser compared with CasCd(p<0.05). Masson's Trichromic exposed that CasCo and SoCo groups havenormal alveolar septa, without deposits of connective tissue. In CasCd,advanced pulmonary fibrosis and blue collagen deposits were evidentthroughout the lung. In SoCd, collagen deposition was observed around theintrapulmonary tree and lung vessels. Hsp27 showed an increase of itsexpression in Cd intoxicated alveoli, being only significant in CasCd vs CasCo(p<0.05); however, the levels of this protein are higher in soy-fed groups whencompared to casein groups. Hsp70 exhibited higher levels in SoCd vs SoCo,without differences among casein-fed groups. We conclude that Cd inducefibrosis in lungs, and soy might have a protective effect. It has been proven thatHsp27 promotes fibrosis in animal models. The higher expression of Hsp70induced by soy could exert a protective effect against Cd-induced fibrosis.