Zn Supplement-Antagonized Cadmium-Induced Cytotoxicity in Macrophages In Vitro: Involvement of Cadmium Bioaccumulation and Metallothioneins Regulation

Abstract

Cadmium (Cd) is a toxic metal leading to multiple forms of organ damage. Zinc (Zn) was reported as a potential antagonist against Cd toxicity. The present study investigates the antagonistic effect of Zn (20 μM) on Cd (20 or 50 μM) cytotoxicity in macrophages in vitro. The results shows that Cd exposure caused dose-dependent morphologic and ultrastructural alterations in RAW 264.7 macrophages. Zn supplement significantly inhibited Cd cytotoxicity in RAW 264.7 or HD-11 macrophages by mitigating cell apoptosis, excessive ROS output, and mitochondrial membrane depolarization. Notably, Zn supplement for 12 h remarkably prevented intracellular Cd2+ accumulation in 20 μM (95.99 ± 9.93 vs 29.64 ± 5.08 ng/106 cells; P = 0.0008) or 50 μM Cd (179.78 ± 28.66 vs 141.62 ± 22.15 ng/106 cells; P = 0.003) exposed RAW 264.7 cells. Further investigation found that Cd promoted metallothioneins (MTs) and metal regulatory transcription factor 1 (MTF-1) expression in RAW 264.7 macrophages. Twenty μM Zn supplement dramatically enhanced MTs and MTF-1 levels in Cd-exposed RAW 264.7 macrophages. Intracellular Zn2+ chelation or MTF-1 gene silencing inhibited MTs synthesis in Cd-exposed RAW 264.7 macrophages, which was accompanied by the declined expression of MTF-1, indicating that regulation of Zn on MTs was partially achieved by MTF-1 mobilization. In conclusion, this study demonstrates the antagonism of Zn against Cd cytotoxicity in macrophages and reveals its antagonistic mechanism by preventing Cd2+ bioaccumulation and promoting MTs expression.

Metallothionein 1: A New Spotlight on Inflammatory Diseases

“…Notably, MT1 is widely expressed in almost every organ to maintain homeostasis. Therefore, it has been most extensively investigated in recent decades (4,7,10,(13)(14)(15)(16)(17)(18)(19)(20)(21).…”

Effects of Cadmium Exposure on the Immune System and Immunoregulation

“…Zn plays key roles in gene expression and cell division and growth via various pathways and is essential for the proper functioning of many enzymes (111). Zn supplementation can reduce Cd damage to cell morphology and improve the activity of immune cells, such as macrophages and NK cells (76,112). Jemai et al showed that Cd exposure significantly reduced superoxide dismutase (SOD), and catalase (CAT) activities, triggering oxidative stress reactions, in rats.…”

“…Macrophages Cd promotes macrophage TNF-a, IL-6, IL-1, NO, and catalase activity Glycine reduces Cd-induced alterations in the viability and activation of macrophages (84) Cd accumulated in macrophages and produces toxicity Metallothionein intervention can be combined with Cd to inhibit Cd-induced toxicity (85) Cd inhibits the phagocytotic activity of chicken peritoneal macrophages Antagonistic effect of N-acetyl-L-cysteine against Cd-induced Cytotoxicity (46) Cd caused dose-dependent morphologic and ultrastructural alterations in macrophages Zn against Cd cytotoxicity in macrophages (112) Neutrophiles Cd caused apoptosis by endoplasmic reticulum stress Se can be antagonists with cd, effectively protecting chicken neutrophils from changes caused by Cd. Cd has cytotoxicity and genotoxicity to human lymphocytes Catechin hydrate can inhibit the anti-genotoxicity and anti-cytotoxicity of Cd by inhibiting the expression of related apoptotic genes (130)…”

“…Zn plays key roles in gene expression and cell division and growth via various pathways and is essential for the proper functioning of many enzymes ( 111 ). Zn supplementation can reduce Cd damage to cell morphology and improve the activity of immune cells, such as macrophages and NK cells ( 76 , 112 ). Jemai et al.…”

Overview of the American Chemical Society Symposium on Metals and Trace Elements in Food Safety, Health, and Food Quality

“…Metals and trace elements have a large role in food and agricultural chemistry. The Journal of Agricultural and Food Chemistry and other related journals have recently published research articles on topics ranging from how agricultural practices can affect various target metals in foods and crops, − how processing affects heavy metals and trace elements in foods, − the effect of metals on food quality, , and the impact of trace metals and minerals on end points related to human health. − While scholarship within these topics has progressed in recent years, there still exists a need to enhance collaboration between researchers in these various areas to further the research field.…”