1. Introduction

In recent decades, a steady increase has been observed in the incidence of glomerulopathies in children with nephrotic syndrome (NS) [1–3]. At the same time, early prevention, pathogenetic approaches and adequate treatment of urinary system disorders caused by autoimmune processes remain insufficiently developed in the pediatric population. As a result, chronicity and mortality associated with these diseases remain high.

Chronic renal failure as a cause of disability in children is registered in 5 per 100,000 children, whereas the risk of developing end-stage chronic renal failure by the age of 20 years may reach 68.0% [4,5]. The formation and progression of chronic kidney diseases in children are often characterized by latent impairment of individual renal functions, with subsequent involvement of the tubules and interstitium [6–12].

This tendency requires increased attention to nephrotic syndrome in children with diseases influenced by environmental factors, including those living in the Aral Sea region. These problems are related to global challenges of modern medicine, including secondary immunodeficiency, allergic diseases and metabolic disorders. The ecological crisis zone of the Aral Sea directly includes Turkmenistan, Kazakhstan and Uzbekistan and indirectly affects Tajikistan and Kyrgyzstan [13,14]. Environmental problems in the Aral Sea region have a particularly negative impact on population health, especially on mothers and children [15–17].

The above considerations indicate that studying the clinical and immunological features of nephrotic syndrome in children living in the Aral Sea region, as well as improving immunocorrection approaches, remain urgent tasks of modern pediatrics and pediatric nephrology.

The aim of the study was to substantiate the effectiveness of immunocorrection in the early prevention of complications of nephrotic syndrome in children living in the Aral Sea region.

2. Materials and Methods

The study included 60 children aged 3–14 years with acute glomerulonephritis (AGN) and nephrotic syndrome. The patients were divided into two groups: group I included 30 patients with AGN and NS living in Tashkent, and group II included 30 patients with AGN and NS living in the Aral Sea region. The control group consisted of 30 practically healthy age-matched children.

The clinical diagnosis was established on the basis of medical history, clinical examination, laboratory tests and functional diagnostic methods. The serum levels of interleukin-2 (IL-2) and interleukin-4 (IL-4) [18], as well as complement components C3 and C4 [19], were assessed in all patients.

For the purpose of immunocorrection, azoximer bromide (Polyoxidonium; NPO PETROVAX PHARM, state registration No. B-250-95 No. 33801) was included in the complex therapy of patients in group II. The drug was administered parenterally at a dose of 0.15 mg/kg body weight per day for 5–10 days. No complications were observed after administration. Treatment effectiveness was evaluated using clinical and immunological parameters.

Venous blood collected in the morning after overnight fasting served as the study material. Quantitative data were processed using methods of variation statistics with assessment of the significance of numerical differences using Student's t-test.

3. Results and Discussion

Based on the results of the studies, it was revealed that of the observed patients, 35.0% were girls and 65.0% were boys. When assessing the clinical manifestations of NS in the examined children (groups I and II), a tendency was found to a statistically significantly higher frequency of the following symptoms in group II compared to group I: oliguria (91.0%-100.0%), edema (45.8%-85.6%), hematuria (88.8%-65.2%), arterial hypertension (79.8%-71.2%), azotemia (53.8%-64.2%), pale skin (65.8%-81.2%), fatigue (55.3%-79.1%), decreased appetite (78.1%-84.0%), positive percussion symptom (65.0%-71.5%), ascites (35.1%-58.4%), hepatomegaly (31.8%-58.0%), respectively (p<0.001-0.01).

The underlying disease was statistically significantly associated with several concomitant conditions (p < 0.01). The most frequent comorbidities were anemia (87.0% in group I and 100.0% in group II), chronic tonsillitis (77.0% - 86.0%), thyroid dysfunction (24.9% - 45.0%), recurrent bronchitis (9.6% - 14.0%), adenoids (4.6% - 18.1%), and polyvalent allergy (15.9% - 35.4%), respectively (Fig. 1).

Figure 1. Concomitant conditions in the examined children. Group I: children with AGN and NS living in Tashkent; group II: children with AGN and NS living in the Aral Sea region

Assessment of individual renal function parameters revealed a decrease in daily diuresis and relative urine density (p < 0.001), as well as an increase in daily erythrocyturia and leukocyturia (p < 0.001–0.01). A statistically significant increase was also observed in daily proteinuria and in serum urea and creatinine concentrations (p < 0.001–0.01). Intergroup comparison showed that impairment of renal functional activity was more pronounced in group II than in group I.

Cytokine status also differed between the groups (Fig. 2). IL-2 production was significantly increased in both patient groups compared with the control group (p < 0.001). In group II, IL-2 levels were significantly higher than in group I (p < 0.001). IL-4 production was also significantly higher in all patient groups than in the control group (p < 0.001). In children from group II, IL-4 levels were significantly higher than in group I (p < 0.001–0.01).

Figure 2. IL-2 and IL-4 production levels in the examined children

Complement components C3 and C4 were assessed in the examined children (Table 1).

Table 1. Levels of C3 and C4 complement components in the examined children, M ± m

Comparative evaluation of immunological parameters showed a significant decrease in C3 and C4 levels compared with the control group (p < 0.001–0.01). The decrease was more pronounced in group II; C3 and C4 levels were approximately 1.5-fold lower than in group I (p < 0.001–0.01).

Before discharge, patients in group II received Polyoxidonium as part of complex therapy, whereas group I received conventional therapy. After immunocorrection, dynamic assessment after 3–6 months showed improvement in immunological parameters in patients treated with Polyoxidonium, manifested by a significant decrease in IL-2 and IL-4 (p < 0.001) and an increase in C3 and C4 complement components (p < 0.001–0.01) compared with children who received conventional therapy.

During 6 months of follow-up, exacerbation of AGN with NS was observed in 3 of 30 patients (10.0%). A decrease in the frequency of intercurrent diseases, including tonsillitis, acute respiratory viral infections, bronchitis and allergy, was also noted. These conditions are clinically important because they may contribute to exacerbation of AGN with NS. Normalization of peripheral blood and urine parameters was observed, including hemoglobin level, leukocyte count, erythrocyte sedimentation rate, proteinuria, erythrocyturia, leukocyturia and daily diuresis, together with prolongation of the clinical remission period.

The findings indicate that children with AGN and NS living in the Aral Sea region had a more pronounced clinical and immunological burden than children living in Tashkent. The higher frequency of edema, ascites, hepatomegaly, pallor, fatigue, reduced appetite and concomitant disorders suggests a more complicated disease course in group II.

The observed increase in IL-2 and IL-4 supports the role of cytokine imbalance in the pathogenesis of nephrotic syndrome in children. IL-2 stimulates the synthesis of several cytokines, including IL-4. Important properties of IL-2 include protection of activated T cells from apoptosis and participation in the regulation of immunological tolerance. Through autocrine effects on Th1 cells and paracrine effects on the Th2-cell subpopulation, IL-2 influences the Th1/Th2 balance, stimulates the cytotoxic activity of CD8 lymphocytes and contributes to the formation of T-cell populations [20].

Based on the obtained results, the cytokine imbalance between Th1 and Th2 responses may determine the direction of immune response impairment. Dysregulated production of pro- and anti-inflammatory cytokines may have pathogenetic significance in uncontrolled inflammation and autoimmune pathology. IL-2 and IL-4 favor the formation of Th2 cells that produce IL-4, which may promote immediate-type hypersensitivity involving IgE [21].

The complement system also appears to be involved in the immunopathogenesis of AGN with NS. C3 is a key component of defense against infection and participates in both the classical pathway, which is activated by IgG and IgM, and the alternative pathway, which may be activated by toxins, endotoxins and IgA.

Activation of C3 contributes to histamine release from mast cells and platelets, leukocyte chemotaxis, antibody-antigen interactions, phagocytosis, increased vascular permeability and smooth muscle contraction.

C4 participates mainly in the classical pathway of complement activation. It supports phagocytosis, increases vascular wall permeability and participates in viral neutralization. Complement activation is finely regulated in the body; when this regulation is disturbed, glomerular lesions may be characterized by dense intramembranous deposits, which are diagnosed by electron microscopy [22,23].

The present results suggest that dysregulation of the alternative complement pathway plays an important role in both C3 glomerulopathy and immune complex-mediated glomerular diseases. Therefore, in children with AGN and NS, membranoproliferative glomerulonephritis may develop within the spectrum of C3 glomerulopathy, together with reduced serum C3 and C4 levels.

Thus, the results of the conducted immunological studies confirm that the body's immune system is closely linked to the function of IL-2, IL-4 and C3, C4 components of complement, which play an important role in the mechanism of immune defense, manifested in the form of antigen-structural homeostasis, carrying out specific processes of immunological reactivity.

The improvement observed after immunocorrection may be associated with the immunotropic effects of azoximer bromide. Polyoxidonium is described as a high-molecular-weight physiologically active compound with pronounced immunotropic activity. It interacts with the surface membranes of neutrophils, monocytes and lymphocytes. By its mechanism of action, Polyoxidonium is considered an immunomodulator with a complex and multifaceted influence on the immune system. It may restore impaired immune functions without affecting normal immune responses and acts primarily on innate immune cells, including neutrophils, monocytes/macrophages and natural killer cells [24].

The study has several limitations. The sample size was relatively small, the treatment comparison was not randomized, and follow-up lasted 6 months. Therefore, the findings should be interpreted as preliminary and require confirmation in larger controlled studies with longer follow-up and standardized assessment of renal outcomes.

4. Conclusions

1. In children living in the Aral Sea region, acute glomerulonephritis with nephrotic syndrome is characterized by frequent relapses and a more pronounced immunodeficiency state, manifested by hyperproduction of IL-2 and IL-4 and hypocomplementemia involving C3 and C4 complement components.

2. The high therapeutic effectiveness observed during treatment with Polyoxidonium and the absence of treatment-related complications allow it to be considered for use as part of complex therapy and prevention of secondary immunodeficiency in children with acute glomerulonephritis and nephrotic syndrome living in the Aral Sea region.