Small Heat Shock Protein's Gene Expression Response to Iron Oxide Nanoparticles in the Brain

Abstract

Small heat shock proteins (SHSPs) are conserved proteins that participate in many cellular functions like preventing protein aggregation and stress response. However, their role in responding to nanoparticles (NPs) has not yet been explained. We used a chicken embryo model to investigate the effects of two different forms of iron oxide-NPs (IONPs) on the mRNA expression of HSPB1, HSPB5, HSPB8, and HSPB9 in cerebral tissue. Two hundred-ten fertilized eggs were randomly divided into seven groups (30 eggs/group; 10 eggs/replicate). Three groups received 100 ppm, 250 ppm, and 500 ppm of Fe₂O₃-NPs, respectively. Three other groups received 100 ppm, 250 ppm, and 500 ppm of Fe₃O₄-NPs, respectively, and one group remained untreated as a control. The NPs were given by in ovo method (0.3 ml/egg) only once on the first day of the embryonic period. Samples from cerebrums were collected on day 20 for gene expression analyses. HSPB1, HSPB5, HSPB8, and HSPB9 were all expressed in both normal and IONPs exposed cerebrums. SHSPs tested were differentially expressed in response to various concentrations of IONPs. The highest expression levels in response to Fe₂O₃-NPs and Fe₃O₄-NPs were observed for HSPB5 and HSPB9, respectively. The greatest gene expression changes due to the Fe₂O₃-NPs and Fe₃O₄-NPs exposure observed for HSPB1 and HSPB5, respectively. The results suggest a protective cellular mechanism against IONPs through SHSPs and recommend that expression profiling of SHSPs be included in the study of nanotoxicity.

Keywords: HSPB1; HSPB5; HSPB8; HSPB9; Heat shock proteins; Nanoparticle.