The effect of low levels of lead (Pb) in the blood on levels of sphingosine-1-phosphate (S1P) and expression of S1P receptor 1 in the brain of the rat in the perinatal period.

Sphingolipids are the main components of the lipid membrane. They also perform structural functions and participate in many signal transmission processes. One of the bioactive sphingolipids is sphingosine-1-phosphate (S1P), a ligand for five G protein-coupled receptors (S1PRs1-5), which can also act as an intracellular second messenger. S1P is responsible for the stimulation of progenitor cells in the brain, but it can also induce apoptosis of mature neurons. This study is aimed at assessing the effect of pre- and neonatal exposure to permissible Pb concentrations on S1P levels and S1PR1 (EDG1) expression in the prefrontal cortex, cerebellum, and hippocampus of rats. The concentrations of S1P were determined by RP-HPLC, S1PR1 expression was determined by RT PCR and Western Blot, and receptor immunolocalization was determined by immunohistochemistry method. Our results showed that even low blood Pb concentrations, i.e. within the acceptable limit of 10 µg/dL caused changes in the concentration of S1P in the cerebellum, prefrontal cortex, and hippocampus. Our data also showed a significant decrease in the level of S1PR1 in all studied part of brain, without significant changes in S1PR1 gene expression. Pre- and neonatal exposure to Pb also resulted in a decrease in the expression of S1PR1 in glial cells in all regions of the Cornu Ammonis (CA1-CA4) and Dentate Gyrus in the hippocampus, as well as in all layers of the cerebellum and prefrontal cortex, compared to the unexposed control group.

Novel evidence that crosstalk between the complement, coagulation and fibrinolysis proteolytic cascades is involved in mobilization of hematopoietic stem/progenitor cells (HSPCs).

The role of blood proteinases in the mobilization of hematopoietic stem/progenitor cells (HSPCs) is still not well understood. As previously reported, activation of the complement cascade (ComC) and cleavage of C5 by C5 convertase are enabling events in the release of C5a that plays a crucial role in the egress of HSPCs from bone marrow (BM) into peripheral blood (PB) and explains why C5-deficient mice are poor mobilizers. Here we provide evidence that during granulocyte colony-stimulating factor- and AMD3100-induced mobilization, not only the ComC but also two other evolutionarily ancient proteolytic enzyme cascades, the coagulation cascade (CoaC) and the fibrynolytic cascade (FibC), become activated. Activation of all three cascades was measured by generation of C5a, decrease in prothrombin time and activated partial thromboplastin time as well as an increase in the concentrations of plasmin/antiplasmin and thrombin/antithrombin. More importantly, the CoaC and FibC, by generating thrombin and plasmin, respectively, provide C5 convertase activity, explaining why mobilization of HSPCs in C3-deficient mice, which do not generate ComC-generated C5a convertase, is not impaired. Our observations shed more light on how the CoaC and FibC modulate stem cell mobilization and may lead to the development of more efficient mobilization strategies in poor mobilizers. Furthermore, as it is known that all these cascades are activated in all the situations in which HSPCs are mobilized from BM into PB (for example, infections, tissue/organ damage or strenuous exercise) and show a circadian rhythm of activation, they must be involved in both stress-induced and circadian changes in HSPC trafficking in PB.

Clinical analysis of systemic and adipose tissue levels of selected hormones/adipokines and stromal-derived factor-1.

Recent studies demonstrated that selected hormones/adipokines may be involved into the regulation of bone metabolism and bone marrow-derived hematopoietic stem/progenitor cells (HSPCs) mobilization in humans. Interestingly, in obese individuals significantly higher numbers of spontaneously circulating stem cells are also observed. Therefore in this study we comprehensively examined plasma and AT (subcutaneous and visceral/omental) levels of hormones/adipokines involved in HSPCs mobilization in lean, overweight and obese individuals as well as verified their potential associations with concentrations of HSPCs chemoattractant, stromal-derived factor-1 (SDF-1). Blood and AT samples (35 subcutaneous and 35 omental) were obtained from individuals undergoing elective surgery. Plasma and AT-derived interstitial fluid levels of resistin, visfatin, osteocalcin and SDF-1 were measured using ELISA. In our study obese patients had almost significantly (P<0.06) higher plasma visfatin and resistin levels as well as lower osteocalcin concentrations (P<0.04) than lean individuals. Osteocalcin and resistin concentrations were strongly associated with levels of SDF-1 and metalloproteinases (MMP 2 and 9). AT levels of all examined substances were significantly lower than the corresponding levels in the plasma (in all cases at least P<0.05), and depot-specific differences in the concentrations of these factors were found only in terms of osteocalcin and SDF-1. In addition, subcutaneous and visceral/omental concentrations of osteocalcin and visfatin, but not of resistin, were associated with values of such parameters as age, body mass or adiposity indexes (BMI and BAI, respectively) and/or waist-to-hip ratio (WHR). In summary, our study showed that in obese individuals the biochemical constellation of adipokines/hormones involved in the process of HSPCs mobilization resembles this observed during pharmacological HSPCs mobilization. Moreover, our study offers further indirect translational evidence for existence of a biochemical cross-talk between bone and AT metabolism (so called - bone-fat- axis) in humans.