No abstract

Cell-free hemoglobin is increasingly playing a more central role in the pathogenesis of sepsis being proved to be a potent predictor of patient's outcome. It is crucial, hence, to further investigate the mechanisms of sepsis-induced hemolysis with the aim of deriving possible therapeutic principles. Herein, we collected the most important previously known triggers of hemolysis during sepsis, which are (1) transfusion reactions and complement activation, (2) disseminated intravascular coagulation, (3) capillary stopped-flow, (4) restriction of glucose to red blood cells, (5) changes in red blood cell membrane properties, (6) hemolytic pathogens, and (7) red blood cell apoptosis. Graphical Abstract ᅟ.

While hemolysis in patients with sepsis is associated with increased mortality its mechanisms are unknown and Toll-like receptor (TLR)-4 mediated effects, complement-mediated hemolysis, or direct cell membrane effects are all conceivable mechanisms. In this study, we tested the hypotheses that toxic lipopolysaccharide (LPS) as well as non-toxic RS-LPS evokes hemolysis (1) by direct membrane effects, and (2) independent of the complement system and TLR-4 activation. We found, that incubation with LPS resulted in a marked time and concentration dependent increase of free hemoglobin concentration and LDH activity in whole blood and washed red cells. Red cell integrity was diminished as shown by decreased osmotic resistance, formation of schistocytes and rolls, and a decrease in red cell membrane stiffness. Non-toxic RS-LPS inhibited the LPS-evoked increase in TNF-α concentration demonstrating its TLR-4 antagonism, but augmented LPS-induced increase in supernatant hemoglobin concentration and membrane disturbances. Removal of plasma components in washed red cell assays failed to attenuate hemolysis. In summary, this study demonstrates direct physicochemical interactions of LPS with red cell membranes resulting in hemolysis under in vitro conditions. It might thus be hypothesized, that not all effects of LPS are mediated by TLR and may explain LPS toxicity in cells missing TLR.

The diester 2a obtained from 1,1'-ferrocenedicarboxylic acid and the highly and indiscriminately cytotoxic fungal metabolite illudin M (1) displayed antiproliferative activity at submicromolar IC(50) (72 h) values against a panel of eight cancer cell lines. Compound 2a was about 40 times less toxic than 1 to nonmalignant human foreskin fibroblasts (HF). The analogous bis(illudinyl M) 1,1'-ruthenocenedicarboxylate (2b) exhibited submicromolar IC(50) (72 h) values only against MDA-MB-231 and MCF-7/Topo breast carcinoma and HL-60 leukemia cells. Cytotoxicity studies in the presence of inhibitors of c-Jun N-terminal kinase (JNK) or extracellular signal-regulated kinase (ERK) revealed that the high efficacy of 2a, but not that of 2b, against HCT-116 colon cancer cells depends on active JNK/ERK signaling. A new illudin M lactone 5 was of low anticancer activity, but its ruthenocene diester 6b also reached single-digit micromolar IC(50) (72 h) values in HCT-116, MCF-7, and HL-60 leukemia cells while not affecting HF. Compounds 2a and 6b were tolerated by mice symptom-free at single doses as high as 25 mg/kg body weight, which is evidence for them being chemically stable under physiological conditions. Compound 2a displayed a manageable in vivo toxicity profile when given repeatedly in high doses.