Metabolic changes of lymphocytes in a rat model of autoimmunity

Abstract

Autoimmune diseases are highly prevalent in humans, being characterized by early onset and high risks of disability, thus determining the relevance of the present work and its aim, i.e., studying metabolic characteristics of lymphocytes upon the adjuvant-induced autoimmune disorder in rats. Modeling of the autoimmune process was performed in Wistar rats by subcutaneous administration of a Freund’s complete adjuvant, i.e., water-oil emulsion with heat-killed M. tuberculosis. Hematology testing (complete blood counts), biochemical markers (hydroperoxides, malondialdehyde (MDA), catalase), and cytobiochemical changes in lymphocytes (lactate dehydrogenase, succinate dehydrogenase; LDH, SDH) were followed in dynamics. X-ray examination was performed at the end of the experiment. At the initial stage of autoimmune arthritis (2 weeks), leukocytosis was registered (26.12±2.30 × 109/L, i.e., 65% over the controls, p < 0.01), thrombocytosis (675±30 × 109/L, compared with 536±27 × 109/L in controls, p < 0.01), and oxidative stress were also observed (hydroperoxides increased by 7%, and MDA, by 32%, p < 0.001); energy levels of the lymphocytes increased due to activation of LDH by 6.5%, and SDH, by 49% against the controls. At chronic stage of the disorder (7 weeks), the systemic inflammation was milder (total WBC counts of 19.6±1.40 × 109/L, compared with 13.68±0.86 × 109 /L in controls, p < 0.01, associated with shift to the right in differential conuts), along with persisting oxidative stress (MDA exceeds the control levels by 37%; decrease in catalase activity), and lower LDH activity in lymphocytes (by 43%, p < 0.01) associated by their decrease in size (the correlation quotient between the lymphocyte radius and LDH activity is rxy= 0.87). Profound molecular changes were observed in the cell energy supply: the respiratory quotient for control animals (LDH/SDH ratio) varied within 4.6-5.0. Meanwhile, in autoimmune animals, metabolic contribution of glycolysis showed a significant decrease (the quotient of 3.2 by the 2ndweek, and 2.4 by the 7thweek). On the radiograph by 7thweek, the experimental animals show uneven joint space narrowing, cyst-like formations and subchondral sclerosis of the bone heads. Autoimmune rheumatoid arthritis in rats is characterized by metabolic disorders of lymphocytes manifesting as general energy deficiency, and imbalance between glycolysis and oxidative phosphorylation pathways. These findings allow of deeper insight into pathogenesis and suggesting further search for molecular targeted therapy and prevention of the disease.