Mass-spectrometric profiling of porphyrins in complex biological samples with fundamental, toxicological, and pharmacological applications

Evaluation of the potential use of protoporphyrins as biomarkers of anemic disease in human urine from inflammatory bowel disease patients

Protoporphyrins are organic compounds with cyclic structure that are synthesised by a wide variety of organisms. In humans, these compounds are detected in blood and urine, with significantly higher levels in blood. Their potential as biomarkers of anemia and other diseases is currently being investigated, as their levels change according to the biochemical processes associated with the disease. The most widely used biomarker of anemia is serum ferritin, but it is unreliable in patients with inflammatory bowel disease (IBD) because its levels can be altered by acute inflammation and/or infections. There is therefore a need to look for new markers to help diagnose anemia in IBD patients. This work develops and validates a method for the determination of three protoporphyrins in human urine: protoporphyrin IX (PPIX), protoporphyrin IX complex with Zn (ZnPPIX) and protoporphyrin IX complex with Fe (II) (FePPIX), the latter also known as heme. The aim is to evaluate their potential as biomarkers of anemic disease in patients diagnosed with IBD. The proposed analytical method is based on high performance liquid chromatography (HPLC) with dual detection based on photodiode array (PDA) and fluorescence (FD). Quantification of the analytes at very low concentrations is possible due to the efficient preconcentration provided by dispersive liquid-liquid microextraction (DLLME) and the sensitivity of the detection systems. The method was validated by evaluating linearity (25-1000 ng mL-1), matrix effect, sensitivity (limits of quantification were between 5 and 11 ng mL-1), selectivity, accuracy, carry-over, dilution integrity, stability and precision (< 12.1 %). Finally, statistical analyses applied to the sample quantification results showed these three markers, together with five clinical markers, were significantly different between anemic and non-anemic IBD patients.

Methods for Cultivation of Bacteroides thetaiotaomicron and Analysis of Heme Metabolism by Mass Spectrometry and Spectroscopic Approaches

Traditional studies of cellular metabolism have relied on the use of radioisotopes. These have clear disadvantages associated with safety and waste generation. Furthermore, detection of the labeled species by scintillation counting provides only a quantification of its presence or absence. The use of stable isotopes, by contrast, allows the application of powerful, orthogonal spectroscopic approaches such as nuclear magnetic resonance spectroscopy (NMR) and various mass spectrometric methods. Using stable isotope labeling to study heme metabolism requires integrating methods for (a) generating the heme in labeled forms, (b) cultivating and quantifying the organism of choice in chemically defined media, to which labeled compounds can be added, (c) recovering cellular components and/or spent growth media, and (d) analyzing these materials for the labeled species using spectroscopic and mass spectrometric methods. These methods are summarized here in the context of Bacteroides thetaiotaomicron, a generally nonpathogenic anaerobe and heme auxotroph.