T-Lymphocyte Survival under Conditions of Alkalosis and Autocrine Factor Deficiency

Alkalosis, a condition characterized by an elevated pH, is associated with various clinical disorders. Respiratory alkalosis results from hyperventilation, when partial pressure of CO2 is reduced in alveolar air and blood. Alkalosis of another type, metabolic alkalosis, develops due to an absolute or relative increase of the content of alkaline compounds in organism. Although it is well known that alkaline conditions are cytotoxic, the mechanisms of this effect. remain obscure, In multicellular organisms cell Survival is controlled by numerous cytokines. Among them are autocrine survival factors (AF) that, affect the same cells that secrete them and are implicated in cell survival. Previously we have found that AFs are involved in the control of cell survival and regulation of energy metabolism of T-lymphocytes (Lutsenko and Diachkova, 2003). We developed ail experimental model of artificial AF deficiency in cell culture. In this study we employ this model to study the effects of the AF deficit combined with alkalosis (pH 8.3) on cell survival, intracellular content of ATP, and mitochondrial transmembrane potential of T-lymphocytes. We used cytotoxic IL-2-dependent cell line CTLL-2 as a model of activated T-lymphocytes. In the absence of AF deficit, alkalosis had no influence on cells survival in CTLL-2 cell culture. The principal way of the defense of CTLL-2 cells against the alkalosis cytotoxicity wits intensification of anaerobic glycolysis and a consequent increase of lactate production. Alkalosis combined with the AF deficit in cell Culture produced it substantial decrease of cell survival, which dropped down to 53% after 6 firs of cultivation under these conditions and to about 10%, after 20 hrs. The ATP content in the cells dropped sharply under the conditions of AF deficit even at pH 7.3 and gradually restored up to initial level within 2-3 hrs; cell survival was at it high level. Alkalosis combined with AF deficit notably worsened the cell state; ATP content in such cells stayed at low level for the whole period of the alkaline stress. After 2-hr incubation under alkalosis and AF deficiency 23% of cells had depolarized mitochondria. Lactate production by CTLL-2 cells under alkalosis and AF deficit was significantly depressed. The results suggest that the intracellular ATP content reduction induced by alkalosis and AF deficit in CTLL-2 cells wits caused by the inhibition of anaerobic glycolysis and mitochondrial dysfunction. Cell death developed via the necrotic rather than apoptotic pathway.