Evaluation of Alkaline-Labile Sulfane Sulfur in Biological Samples: The Influence of Hyperhomocysteinemia and Oxidative Stress

Polysulfides play an important role in regulating many physiological processes, making their study relevant in health and disease. This study aims to improve their evaluation method by determining alkaline-labile sulfane sulfur (ALSS) and to test it on various biological samples, as well as on models of hyperhomocysteinemia and oxidative/reductive stress. The ALSS assay is based on the photometric determination of H2S, which is generated from polysulfides under alkaline conditions. The limit of quantitative detection was 3.3 nmol, interday reproducibility was 5.7% (blood plasma), and the yields of H2S precipitation and product extraction were 97.8 and 89.7%, respectively. The specificity of the approach, determined with two different methods of sulfide destruction, was 80% on a model mixture of bovine albumin or blood plasma. A small but noticeable matrix effect was revealed. ALSS of control rats (n = 15) and human plasma (n = 10) was 133 (128; 135) and 177.6 (171.8; 183.6) μmol/g protein, respectively. Decreased ALSS levels were observed in rats with mild hyperhomocysteinemia (n = 14) and in patients with acute stroke (n = 20). Under 24h oxidative stress, ALSS decreased from 14.8 ± 1.3 to 10.4 ± 1.0 μmol/g protein (p = 0.0055) in the THP-1 culture, while 96h reductive stress caused it to increase from 10.9 ± 0.9 to 15.9 ± 2.0 μmol/g protein, p = 0.00034. The method presented in this paper allows for the assessment of ALSS in various biological matrices and has demonstrated sensitivity to oxidative stress in vitro and hyperhomocysteinemia in vivo. This makes it a promising indicator of sulfur metabolism disorders in pathological conditions.