Renal effects of metallothionein induction by zinc in vitro and in vivo

Abstract

BackgroundMetallothionein (MTT) is an endogenous antioxidant that can be induced by both zinc (Zn) and ischemia. In kidneys, increased MTT expression exerts a putative protective role in diabetes and hypoxia. Our goal was to further investigate the behavior of MTT under the influence of Zn and hypoxia in vitro and in vivo.MethodsMTT expression was measured in vitro in cell cultures of proximal tubular cells (LCC-PK1) by immune-histochemistry and real-time PCR after incubation with increasing concentrations of Zn under hypoxic and non-hypoxic conditions. In addition, in vivo studies were carried out in 54 patients to study MTT induction through Zn. This is a sub-study of a prospective, randomized, double-blind trial on prevention of contrast-media-induced nephropathy using Placebo, Zn and N-Acetylcysteine. Blood samples were obtained before and after 2 days p.o. treatment with or without Zn (60 mg). ELISA-based MTT level measurements were done to evaluate the effects of Zn administration. For in vivo analysis, we considered the ratio of MTT to baseline MTT (MTT1/MTT0) and the ratio of eGFR (eGFR1/eGFR0), correspondingly.Results In vitro quantitative immuno-histochemical analysis (IHC) and real-time PCR showed that at increasing levels of Zn (5, 10, and 15 μg/ml) led to a progressive increase of MTTs: Median (IQR) expression of IHC also increased progressively from 0.10 (0.09–0.12), 0.15 (0.12–0.18), 0.25 (0.25–0.27), 0.59 (0.48–0.70) (p < 0.0001). Median (IQR) expression of PCR: 0.59 (0.51–1.72), 1.62 (1.38–4.70), 3.58 (3.06–10.42) and 10.81 (9.24–31.47) (p < 0.0001). In contrast, hypoxia did not change MTT-levels in vitro (p > 0.05). In vivo no significant differences (p = 0.96) occurred in MTT-levels after 2 days of Zn administration compared with no Zn intake. Nevertheless, there was a significant correlation between MTT (MTT1/MTT0) and eGFR (eGFR1/eGFR0) in case of Zn administration (rho = −0.49; 95%-CI: −0.78 to −0.03; p = 0.04).ConclusionsWe found that Zn did induce MTTs in vitro, whereas hypoxia had no significant impact. In contrast, no significant increase of MTTs was detected after in vivo administration of Zn. However, there was a significant negative correlation between MTT and eGFR in vivo in case of Zn administration, this could indicate a protective role of MTTs in a setting of reduced kidney function, which is possibly influenced by Zn.Trial registrationClinicalTrials.gov Identifier: NCT00399256. Retrospectively registered 11/13/2006.

Zinc mitigates renal ischemia‐reperfusion injury in rats by modulating oxidative stress, endoplasmic reticulum stress, and autophagy

“…After oral ZnCl 2 administration, a parallel elevation of Zn and MTs levels was observed in renal tissues, suggesting a close correlation between them. Indeed, MTs are crucially involved in maintaining Zn homeostasis, and Zn is well known as a potent inducer of MTs (Schanz et al, 2017). In the presence of zinc ions, MTs expression could be induced through binding metal regulatory transcription factor-1 (MTF-1) to the metal-responsive element of MTs gene initiating thus MT synthesis (Andrews, 2000).…”

Protective effect of zinc preconditioning against renal ischemia reperfusion injury is dose dependent

“…A connection between their antioxidant activity and protective effects against oxidative stress is well established [ 32 ]. Interestingly a recent study found that although zinc supplementation (oral 60 mg per day) did not increase serum metallothioneins in humans there was a significant positive correlation between metallothioneins and kidney function (as measured by glomerular filtration rate), which was influenced by zinc supplementation [ 33 ].…”

Copper–zinc imbalance induces kidney tubule damage and oxidative stress in a population exposed to chronic environmental cadmium

“…In particular, Ikeda et al (2007) found that β2-MG levels are more related to Cu levels than to Cd levels in women without environmental Cd exposure (Ikeda et al 2007). Schantz et al reported that an induction of MT by zinc acts as a potential endogenous antioxidant in renal proximal tubular cells, which has a protective effect against the reduction of kidney function (Schanz et al 2017). Therefore, this study suggests that the balance of essential metals, such as Cu and Zn, plays an important role in renal dysfunction, especially in groups with low levels of Cd exposure.…”