Serologic evaluation of human microcystin exposure

Abstract

Microcystins are among the most commonly detected toxins associated with cyanobacteria blooms worldwide. Two episodes of intravenous microcystin exposures occurred among kidney dialysis patients during 1996 and 2001. Analysis of serum samples collected during these episodes suggests that microcystins are detectable as free and bound forms in human serum. Our goal was to characterize the biochemical evidence for human exposure to microcystins, to identify uncertainties associated with interpretation of these observed results, and to identify research needs. We analyzed serum samples using enzyme-linked immunosorbent assay (ELISA) methods to detect free microcystins, and gas chromatography/mass spectrometry (GC/MS) to detect 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB). MMPB is derived from both free and protein-bound microcystins by chemical oxidation, and it appears to represent total microcystins present in serum. We found evidence of free microcystins in patient serum for more than 50 days after the last documented exposure. Serum concentrations of free microcystins were consistently lower than MMPB quantification of total microcystins: free microcystins as measured by ELISA were only 8-51% of total microcystin concentrations as detected by the GC/MS method. After intravenous exposure episodes, we found evidence of microcystins in human serum in free and protein-bound forms, though the nature of the protein-bound forms is uncertain. Free microcystins appear to be a small but variable subset of total microcystins present in human serum. Research is needed to elucidate the human toxicokinetics of microcystins, in part to determine how observed serum concentrations can be used to estimate previous microcystin exposure.

Rapid quantification of total microcystins in cyanobacterial samples by periodate-permanganate oxidation and reversed-phase liquid chromatography

“…These results suggest that lower amounts of permanganate are insufficient to generate MMPB from cyanobacterial samples; therefore, oxidization of cyanobacterial samples with a high dose of permanganate in the reaction solution should be considered. These findings differ from those of previous studies, which have usually been conducted using lower concentrations of permanganate [38][39][40][41][42][43][44][45][46][47].…”

“…The results revealed that the yields of MMPB under neutral or alkaline conditions were higher than those under acidic conditions, with the highest concentration being produced under weak alkaline conditions (pH ∼9). These results are consistent with those of previous studies in which the pH of the solution was adjusted to approximately 9 using potassium bicarbonate to produce MMPB in oxidation reactions [38][39][40][41][42][43][44][45][46][47]. Among the five pH values evaluated, the resulting MMPB concentrations were shown to have only minor differences after 1 h, indicating that MMPB was stable under different pH conditions.…”

“…This method is believed to be an accurate method for screening for total MCs because it can measure MMPB derived from the unusual C 20 amino acid, ␤-amino acid (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2, 6, 8-trimethyl-10-phenyldeca-4, 6-dienoic acid (Adda), which is a common constituent moiety of MCs [7]. Oxidizing toxins using the Lemieux oxidation method [33][34][35][36][37] have been widely used as a highly sensitive method for the detection of total MCs in a wide range of sample matrices, including cyanobacteria [38,39], animal tissues [40][41][42][43][44] and serum samples [45][46][47]. However, no studies have been conducted to evaluate the influence of reaction conditions on the formation of MMPB during the oxidation of MCs using permanganate-periodate.…”

Quantitative liquid chromatography–tandem mass spectrometry method for determination of microcystin-RR and its glutathione and cysteine conjugates in fish plasma and bile

“…most widely used as extraction solvent in biological fluid samples [2,[28][29][30]. In the plasma preparation, methanol was chosen for further development as it had better recoveries (93.7%, 91.1% and 85.8% for MC-RR, MC-RR-GSH and MC-RR-Cys, respectively), which were obviously higher than those of acetonitrile (78.6%, 75.0% and 78.2%) and EDTA-Na 2 (0.01 M)-5% acetic acid (35.6%, 32.9% and 32.8%).…”

“…Microcystins (MCs) are a family of cyanotoxins along with the occurrence of toxic cyanobacterial blooms in eutrophic fresh and brackish waters [1,2]. To date, more than 80 structural analogs of MCs have been identified, and microcystin-RR (MC-RR) is one of the dominant variants in cyanobacterial blooms in lakes of China [3,4].…”