Cytotoxicity Produced by Silicate Nanoplatelets: Study of Cell Death Mechanisms.

Jie-Ting Huang,Ling-Chu Chang,San-Yuan Huang,Chung-Ssu Cheng,Shuen-Ei Chen,Jiang-Jen Lin

doi:10.3390/toxins12100623

Abstract

Nano-silicate platelets (NSP), an exfoliated product from natural clays, have been validated for biosafety and as an effective supplement to alleviate mycotoxicosis. Since NSP induced noticeable cell death, we therefore investigated further the mechanism of cytotoxicity caused by NSP. Exposure to NSP impaired membrane integrity and caused cell death in a dose-dependent manner. Reactive oxygen species (ROS) generation other than of NADH oxidase origin, and subcellular interactions by internalized NSP also contributed to NSP-induced cell death. NSP persistently provoked receptor-interacting protein 1 Ser/Thr (RIP1) kinase and caspase 6 and 3/7 activation without altering caspase 8 activity and induced evident chromatolysis of necrosis in the later stage. These events proceeded along with increased ER stress and mitochondrial permeability, to final Cyt-C (Cytochrome C) release and AIF (apoptosis inducing factor) translocation, a hallmark of cell necroptosis. Fluorescent probing further manifested NSP traffic, mostly adherence on the cell surfaces, or via internalization, being compartmentalized in the nuclei, cytosols, and mitochondria. Pharmacological approaches with specific inhibitors suggested that endocytosis and particularly RIP1 kinase provocation mediate NSP-induced cell death independent of caspase activation. In conclusion, the necroptotic process contributes to most of the cell death induced by NSP due to membrane interactions/impaired integrity, ROS generation, and subcellular interactions by internalized NSP.

Highlights

Sheet silicate minerals from phyllosilicates, including bentonite and montmorillonite clays, have been used as medical materials for diarrhea in humans, due to their antibacterial activity [1]
Exposure to nano-silicate platelets (NSP) induced cell death in a dose-dependent manner, in which early apoptosis accounted for most cell death (10.1 and 13.1% at 24 and 48 h by 200 μg/mL, respectively), and interestingly only late apoptosis increased during the time course (3.7 to 7.8%), whereas necrosis contributed to cell death less than 2% (p < 0.05, Figure 1, panel A)
Apoptosis, cell death proceeded to necrotic chromatinolysis with a more pronounced smearing pattern with a more pronounced smearing pattern of DNA size in electrophoresis after exposure to NSP for of DNA size in electrophoresis after exposure to NSP for 48 h (Figure 1, panel C)

Summary

Introduction

Sheet silicate minerals from phyllosilicates, including bentonite and montmorillonite clays, have been used as medical materials for diarrhea in humans, due to their antibacterial activity [1]. In livestock management, these aluminosilicate clays, as well as purified sodium calcium aluminosilicates (HSCAS), have been widely used as a supplement to alleviate mycotoxicosis in poultry and swine [2]. We demonstrated that exfoliated sheet-like aluminosilicate clays serve as an effective feed supplement to alleviate marker pathologies and improve growth performance in chickens intoxicated with fumonisin B1 (FB1) or AFB1 [6,7]. In pregnant mice intoxicated with FB1, oral administration of NSP at 2.5 mg/kg BW suppressed maternal plasma FB1 concentrations by 93%, ameliorated embryo neural tube defects and teratogenesis, and significantly improved fetus growth [8]

Methods

Results

Conclusion