Zinc protects against cadmium-induced toxicity in neonatal murine engineered cardiac tissues via metallothionein-dependent and independent mechanisms

Abstract

Cadmium (Cd) is a nonessential heavy metal and a prevalent environmental toxin that has been shown to induce significant cardiomyocyte apoptosis in neonatal murine engineered cardiac tissues (ECTs). In contrast, zinc (Zn) is a potent metallothionein (MT) inducer, which plays an important role in protection against Cd toxicity. In this study, we investigated the protective effects of Zn against Cd toxicity in ECTs and explore the underlying mechanisms. ECTs were constructed from neonatal ventricular cells of wild-type (WT) mice and mice with global MT gene deletion (MT-KO). In WT-ECTs, Cd (5−20 μM) caused a dose-dependent toxicity that was detected within 8 h evidenced by suppressed beating, apoptosis, and LDH release; Zn (50−200 μM) dose-dependently induced MT expression in ECTs without causing ECT toxicity; co-treatment of ECT with Zn (50 µM) prevented Cd-induced toxicity. In MT-KO ECTs, Cd toxicity was enhanced; but unexpectedly, cotreatment with Zn provided partial protection against Cd toxicity. Furthermore, Cd, but not Zn, significantly activated Nrf2 and its downstream targets, including HO-1; inhibition of HO-1 by a specific HO-1 inhibitor, ZnPP (10 µM), significantly increased Cd-induced toxicity, but did not inhibit Zn protection against Cd injury, suggesting that Nrf2-mediated HO-1 activation was not required for Zn protective effect. Finally, the ability of Zn to reduce Cd uptake provided an additional MT-independent mechanism for reducing Cd toxicity. Thus, Zn exerts protective effects against Cd toxicity for murine ECTs that are partially MT-mediated. Further studies are required to translate these findings towards clinical trials.

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“…We used Pierce Lactate dehydrogenase (LDH) Cytotoxicity Assay Kit (Thermo Fisher Scientific) to determine the LDH release into the culture medium as previously described 12 . Briefly, 50 µL of each sample medium was transferred to a 96‐well flat‐bottom plate in duplicate wells, mixed with 50 µL of the reaction mixture, then incubated at room temperature for 30 minutes in the dark, followed by the addition of 50 µL of Stop Solution to each sample well.…”

Iron and Cadmium Entry Into Renal Mitochondria: Physiological and Toxicological Implications

“…In animals, chelators can reduce acute Cd-induced mortality, provided treatment started very soon after Cd ingestion. Zn may exert protective effects against acute Cd toxicity that are partially MT-mediated, as suggested from neonatal murine-engineered cardiac tissues ( Yu et al, 2020 ).…”

Zinc Chloride Can Mitigate the Alterations in Metallothionein and Some Apoptotic Proteins Induced by Cadmium Chloride in Mice Hepatocytes: A Histological and Immunohistochemical Study

“…The capacity of a biological system to detoxify these reactive intermediates determines how much oxidative stress is experienced by cells on an ongoing basis [ 28 ]. Early in the reaction to oxidative stress, NF-E2-related nuclear factor 2 (Nrf2) is quickly elevated, and as a protective strategy, it then translocates to the nucleus to boost the transcription of oxidative stress response genes [ 29 , 30 ].…”

“…Several studies suggested that Zn-induced metallothionein overexpression contributes to the Zn protective effect [ 29 , 31 ]. In the present investigation, we discovered that Zn might, in a dose-dependent manner, cause MT overexpression.…”