On the basis of the
On the basis of the published articles, it is known that chemokines are produced by leukocytes and tissue cells, constitutively or after induction. Chemokines are responsible for the recruitment of leukocytes to maintain proper functioning of the immune system . They exist in the central nervous system in both physiological and pathological conditions. In depression, they affect cell interactions, neuromodulation, and synaptic transmission. Depending on their functions in immune and inflammatory responses, chemokines are divided into two groups: proinflammatory and lymphoid (homeostatic, constitutive) chemokines , . The group of lymphoid chemokines includes, for example, stromal cell-derived factor-1 (SDF-1) also known as (C-X-C motif chemokine-12 – CXCL12). Lymphoid chemokines are secreted continuously in different spaces of lymphoid tissues and are involved in immune cell engraftment in places of their maturation, “guiding” dorsomorphin during hematopoiesis in the bone marrow and maturation in the thymus. They induce an immune response in the spleen, lymph nodes, and Peyer\'s patches. In contrast, pro-inflammatory chemokines, for example, the RANTES (Regulated on Activation, Normal T-cell Expressed and Secreted) chemokine – (chemokine CC motif ligand-5 – CCL-5), are released mainly during an immune response to interact with a pathogen. They are produced by tissues and leukocytes in response to inflammatory cytokines (IL-1, TNF-α, interferons) .
Research has shown that the chemokines belonging to both groups direct the cell motion necessary to initiate a T-cell immune response in inflammation. While the chemokine action mechanism is relatively well understood, types of chemokines involved in the immune response in depression have been studied rarely and remain unclear in many aspects .
Participants and methods for chemokines assessment
Results Based on the results for the control groups and the depression patients group, statistically significant differences have been found (p<0.0001), both for women and for men (Table 1). In comparisons of SDF-1 chemokine levels between women and men, and versus the corresponding control groups, a significant increase in the SDF-1 level was found depending on the degree of depression (mild, moderate, severe). These differences were statistically significant (Fig. 1, Fig. 2). A comparison of the CCL-5 chemokine levels in the depression patients group of women and men versus the control group also showed statistically significant differences for the different severities of depression. It is worth noting that the largest increase in the level of both chemokines was observed in the group of women with severe depression (Fig. 3, Fig. 4). In addition to the chemokine levels, the IL-6 level was also analyzed and the levels of relevant chemokine-specific receptors were determined. An increase in the levels of CXCR4 and CCR-5 receptors and an increase of IL-6 levels in both women and men versus the control group were observed in all types of depression. Furthermore, it was shown that the level of CCR-5 receptors exceeds the CCL-5 chemokine level, and that CXCR4 receptor level is below the SDF-1 chemokine level in both women and men. Moreover, the level of the CCR-5 receptors was higher in women with a moderate or severe depression episode as compared to its level in women with a mild depression episode and the control group, where these levels were similar. For IL-6, an increase in its level was observed in moderate depression episodes versus the control group. Moreover, in severe depression, the increase in the IL-6 level was the highest (Fig. 5). The statistical significance of differences between mean levels of various chemokines and their receptors in people with mild depression varies. The results obtained in the group of women and men show that the levels of SDF-1 and CCL-5 chemokines, as well as of CCR-5 and CXCR4 chemokine receptors, were higher in women than in men. These differences were statistically significant at the following significance levels: CCL-5 (p=0.003) and SDF-1 (p=0.03). The comparison of IL-6 levels between the sexes showed that the level of this interleukin is significantly higher in women than in men, regardless of the degree of depression.