XAS and XFM studies of selenium and copper speciation and distribution in the kidneys of selenite-supplemented rats

Abstract

Dietary selenium has been implicated in the prevention of cancer and other diseases, but its safety and efficacy is dependent on the supplemented form and its metabolites. In this study, X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM) have been used to investigate the speciation and distribution of Se and Cu in vivo. In kidneys isolated from rats fed a diet containing 5 ppm Se as selenite for 3 weeks, Se levels increased 5-fold. XFM revealed a strong correlation between the distribution of Se and the distribution of Cu in the kidney, a phenomenon that has previously been observed in cell culture (Weekley et al., JBIC, J. Biol. Inorg. Chem., 2014, DOI: 10.1007/s00775-014-1113-x). However, X-ray absorption spectra suggest that most of the Se in the kidney is found as Se-Se species, rather than Cu-bound, and that most of the Cu is bound to S and N, presumably to amino acid residues in proteins. Furthermore, SOD1 expression did not change in response to the high Se diet. We cannot rule out the possibility of some Cu-Se bonding in the tissues, but our results suggest mechanisms other than the formation of Cu-Se species and SOD1 upregulation are responsible for the highly correlated distributions of Se and Cu in the kidneys of rats fed high selenite diets.

Dynamic equilibrium of endogenous selenium nanoparticles in selenite-exposed cancer cells: a deep insight into the interaction between endogenous SeNPs and proteins

“…More recently, the combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM) has offered an alternative for determining the speciation and distribution of Se in vivo and has provided information about elemental Se distributions retained in intact samples, hinting at the possibility of metabolic generation of endogenous SeNPs in tumor tissue. 10,25,26 In addition, this result also implies the metabolism of artificial SeNPs in vivo. The study will fill the gap between the efficacy observed in laboratory studies and the mixed results of clinical trials, and thus has significant implications for public health.…”

“…10 The amount of in vivo Se species has been studied in both cell and animal models. 15,25,26 The percentage of elemental Se detected by EXAFS increased from 37% at 4 h to 55% at 48 h, before decreasing to 49% at 72 h in lung cancer H549 cells. 15 This result supports our finding that endogenous SeNP assembly is a dynamic flux process in cancer cells.…”

XAS studies of Se speciation in selenite-fed rats

“…In a recent publication, we investigated the possibility of the formation of a Cu–Se species in kidney tissues, but analysis of Cu K -edge EXAFS in addition to Se K -edge EXAFS indicated that the presence of a Cu–Se species was unlikely. 34 …”

2015 Atomic Spectrometry Update – a review of advances in X-ray fluorescence spectrometry and their applications

“…Weekley et al 347 continued their research on the speciation and distribution of Cu and Se in vivo, using XAS and XRF microscopy. Weekley et al 347 continued their research on the speciation and distribution of Cu and Se in vivo, using XAS and XRF microscopy.…”