Selenium speciation in paired serum and cerebrospinal fluid samples

Area of Science:

• Biochemistry
• Neuroscience
• Analytical Chemistry

Background:

• Selenium (Se) is an essential trace element crucial for various physiological processes, including antioxidant defense and thyroid hormone metabolism.
• Understanding Se speciation and its transport across the blood-brain barrier (BBB) is vital for neurological health.
• Previous studies have focused on total Se levels, with limited information on individual Se species distribution in the central nervous system.

Purpose of the Study:

• To quantify and identify various selenium (Se) species in paired serum and cerebrospinal fluid (CSF) samples from neurologically healthy individuals.
• To investigate the passage of different Se species across neural barriers (NB).
• To compare the transport of Se species with albumin (Alb) as an indicator of NB integrity.

Main Methods:

• Paired serum and CSF samples from 24 healthy individuals were analyzed.
• Strong anion exchange (SAX) separation coupled with inductively coupled plasma-dynamic reaction cell-mass spectrometry (ICP-DRC-MS) was employed for Se speciation.
• Two-dimensional chromatography (SEC-SAX-ICP-DRC-MS and SAX-CE-ICP-DRC-MS) and standard addition methods were used for species identification.

Main Results:

• Several Se species were detected in both serum and CSF, including selenoprotein P (SePP), glutathione peroxidase (GPx), thioredoxinreductase (TrxR), Se IV, and Se-human serum albumin (Se-HSA).
• The passage of SePP across the NB was found to be independent of serum SePP levels.
• While Se-HSA passage showed a weak correlation with molecular size, antioxidant enzymes GPx and TrxR exhibited higher transport rates, suggesting facilitated diffusion or brain synthesis.

Conclusions:

• The transport of Se species across neural barriers is complex and not solely dependent on molecular size.
• Antioxidant Se-enzymes like GPx and TrxR may utilize specific transport mechanisms or be synthesized within the brain.
• Further research is needed to elucidate the precise mechanisms governing Se species transport and their implications for neurological health.