СHANGES OF IMMUNOREGULATORY INDEXES IN CHILDREN EXPOSED TO STRONTIUM

Evaluation of the immune system parameters can be used in order to assess capacity to adapt under conditions of increased external chemical load, including exposure to metals, which can exert either activating and inhibitory effects upon immune regulation parameters. The aim of this work was the analysis of immunoregulatory markers in a children’s population who consumed water with high strontium content (a sample from the Perm region). We carried out immunological evaluation of the children aged 7 to 12 years, living at a territory with a high strontium content in the drinking water. The comparison group included children from the conventionally clean region. We studied differential changes in cellular immunity (phagocytosis rates), humoral factors of immune defense (serum immunoglobulins), development of specific sensitization for strontium, as well as the processes of apoptosis triggering and regulation. A 3.68-fold increase in strontium levels was shown in fresh water within observation area, and the average  blood strontium content in the children of appropriate observation group was 1.55-fold higher than in children of the comparison group. At the same time, 1.2-fold increase in phagocytic activity determined as phagocytic number and phagocytic index was found, as compared to the control group. In 80% of the subjects, a reduction in serum IgG level was observed when compared to physiological norm, as well as a significant decrease in IgG and enhance in IgM production against the levels found in the comparison group. Wehave also shown an enhanced total sensitization in 55.0% of the observation group as shown by the total IgE test compared with normal age ranges, as well as excessive specific sensitization to strontium by 2.49 times, according to the IgG criterion. Disturbance in apoptosis triggering was associated with decreased number of CD95+ lymphocytes and TNFR1+ cells (2.8-fold compared to reference values), shifted balance in apoptogenic proteins, an average of 2.6-fold decrease in Bcl-2 expression, a 2.8-fold reduction of the p53 transcription factor expression relative to the reference interval. Thus, we have shown an ability of strontium excess in drinking water to influence the most important indices of immune regulation in pediatric population. These changes may serve as indices of populational health status under of external strontium exposure

EXPERIMENTAL MODELING OF APOPTOSIS UNDER CONDITIONS OF STABLE STRONTIUM EXPOSURE

Apoptosis is defined as a highly regulated form of programmed cell death with typical morphological and biochemical features. A variety of factors, including heavy metals, may influence the intensity of programmed cell death. The aim of the work was to simulate apoptosis in an in vitrosystem under the conditions of stable strontium exposure. The children’s population consuming drinking water with high strontium (Sr2+) content (n = 49) was observed. The level of lymphocyte apoptosis was determined with flow cytometry technique, by means of labeled annexin V-FITC conjugate (AnnV-FITC) and propidium iodide (PI) staining. AnnV-FITC+PI- cells were regarded as early apoptotic forms, whereas late apoptotic and/or necrotic cells were AnnV-FITC+PI+. The isolated leukocytes were incubated with Sr2+ at a concentration of 7.0 mg/l, the maximal permitted concentration (MPC) for water of aqueous objects, for 4 hours at 37 ºC. Expression of CD95 and p53 apoptosis markers was performed by flow cytometry using labeled monoclonal antibodies.In vitroexposure to strontium was associated with significantly decreased expression of apoptosisregulating factors, i.e., membrane marker CD95 and intracellular transcription protein p53, 1.56- and 1.68-fold, respectively. Meanwhile, we revealed a significantly (4.68-fold) decreased amounts of AnnV-FITC+PI--cells, as well as a statistically significant (1.35-fold) increase of the AnnV-FITC+PI+-cells. Moreover, the amounts of AnnV-FITC+ PI--lymphocytes in all samples were below the physiological ranges and control values. The number of samples with higher contents of AnnV-FITC+PI+-lymphocyte exceeding the established standards and control values, was 30.8%. Thus, it has been experimentally proven that strontium, at a concentration corresponding to MPC for water objects may significantly inhibit cell death along apoptotic pathways, with switching to necrotic cell death mechanisms, according to phosphatidylserine contents, as detected by annexin V binding test. The data have revealed an ability of strontium to have a significant effect upon the parameters of regulation and maintenance of cellular homeostasis, by influencing the apoptosis intensity, due to shifting a balance towards necrosis and reducing expression of apoptosis-regulating factors. The results of this study may be used in order to identify some marker indexes of immune disorders potentially induced by external influence of strontium upon human health under specific environmental factors