Cytoprotective mechanisms in rats lung parenchyma with zinc deprivation

Glycine max (soy) based diet improves antioxidant defenses and prevents cell death in cadmium intoxicated lungs

Cadmium (Cd) is a toxic metal and an important environmental contaminant. We analyzed its effects on oligoelements, oxidative stress, cell death, Hsp expression and the histoarchitecture of rat lung under different diets, using animal models of subchronic cadmium intoxication. We found that Cd lung content augmented in intoxicated groups: Zn, Mn and Se levels showed modifications among the different diets, while Cu showed no differences. Lipoperoxidation was higher in both intoxicated groups. Expression of Nrf-2 and SOD-2 increased only in SoCd. GPx levels showed a trend to increase in Cd groups. CAT activity was higher in intoxicated groups, and it was higher in Soy groups vs. Casein. LDH activity in BAL increased in CasCd and decreased in both soy-fed groups. BAX/Bcl-2 semiquantitative ratio showed similar results than LDH activity, confirmed by Caspase 3 immunofluorescence. The histological analysis revealed an infiltration process in CasCd lungs, with increased connective tissue, fused alveoli and capillary fragility. Histoarchitectural changes were less severe in soy groups. Hsp27 expression increased in both intoxicated groups, while Hsp70 only augmented in SoCd. This show that a soy-diet has a positive impact upon oxidative unbalance, cell death and morphological changes induced by Cd and it could be a good alternative strategy against Cd exposure.

Zinc supplementation prior to heat shock enhances HSP70 synthesis through HSF1 phosphorylation at serine 326 in human peripheral mononuclear cells

Zinc supplementation prior to heat shock increases HSP70 (Heat shock protein 70) expression, which has cytoprotective effects in tissue cells during inflammation. Effects of zinc deficiency in this regard are...

tert-Butylhydroquinone mobilizes intracellular-bound zinc to stabilize Nrf2 through inhibiting phosphatase activity

The nuclear factor erythroid 2-related factor 2 (Nrf2) is required to combat increases in oxidative stress. The chemical compound tert-butylhydroquinone (tBHQ) can downregulate Kelch-like ECH-associated protein 1 (Keap1), a repressor of Nrf2, thus maintaining the stability of Nrf2. tBHQ can also increase intracellular “free” zinc in human bronchial epithelial (16HBE) cells. We aim to investigate whether the intracellular free zinc change plays a role in Nrf2 activation. tBHQ exposure dose-dependently increases intracellular free zinc concentrations within 30 min in 16HBE cells by mobilizing intracellular zinc pools. Active Nrf2 and the antioxidant enzyme heme oxygenase-1 (HO-1) increase at 3 h after tBHQ treatment. Chelating intracellular free zinc with tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) during tBHQ exposure partially abrogates the tBHQ-induced activation of Nrf2 and HO-1 expression, while Keap1 is further decreased. These results indicate that tBHQ-induced stability of Nrf2 is associated with the intracellular free zinc level. Because the activated Nrf2 is phosphorylated, the serine/threonine protein phosphatase activity, which is known to be inhibited by zinc, is assayed. The results showed that tBHQ treatment can suppress cellular protein phosphatase-2A (PP2A) and protein phosphatase-2C (PP2C) activity, which can be abrogated by adding TPEN. This finding is verified in a cell-free protein extract experiment by supplying zinc or by chelating zinc with TPEN. These results provide a novel mechanistic insight into Nrf2 activation in antioxidant enzyme induction involving zinc signaling. The increase of intracellular free zinc may be one mechanism for Nrf2 activation. The inhibition of PP2A and PP2C activity may be involved in Nrf2 phosphorylation modulation.