ИСТИНА

Previously, we reported that cell volume perturbations sharply affect respiratory burst in human neutrophils triggered by different stimuli including zymozan, formyl peptide, Ca 2+ionophore and activators of protein kinase C [1]. Under isosmotic conditions cell volume changes are caused by alterated content of monovalent ions and other intracellular osmolytes. Considering this, we hypothesized that inflammatory and immune responses are affected by intracellular [Na +]/[K +] ratio. To examine this hypothesis, we identified ubiquitous and tissue-specific [Na +] i/[K +] i-sensitive transcriptomes by comparative analysis of differentially expressed genes in vascular smooth muscle cells from rat aorta(RVSMC), the human adenocarcinoma cell line HeLa, and human umbilical vein endothelial cells (HUVEC). To augment [Na +] i and reduce [K +] i, cells were treated for 3 hrs with the Na +,K +-ATPase inhibitor ouabain or placed for the same time in the K +-free medium. Employing Affymetrix-based technology, we detected changes in expression levels of 684, 737 and 1839 transcripts in HeLa, HUVEC and RVSMC, respectively, that were highly correlated between two treatments ( p < 0.0001; R 2 > 0.62). Among these Na + i/K + i-sensitive genes, 80 transcripts were common for all three types of cells. To establish if changes in gene expression are dependent on increases in [Ca 2+] i, we performed identical experiments in Ca 2+-free media supplemented with extracellular and intracellular Ca 2+ chelators. Surprisingly, this procedure elevated rather than decreased the number of ubiquitous and cell-type specific Na + i/K + i-sensitive genes. Among the ubiquitous Na + i/K + i-sensitive genes whose expression was regulated independently of the presence of Ca 2+chelators by more than 3-fold, we discovered interleukin-6 (IL6), prostaglandin-endoperoxide synthase 2 (PTGS2) and several other genes playing a key role in inflammatory and immune system responses [2]. The role of elevation of [Na +]i/[K +]i ratio in the triggering of these responses is further confirmed by data showing that the plasma concentration of IL6 increases up to 100-fold during muscular exercise. This increase is followed by the expression of the IL1 receptor agonist ( Il1ra ) and the anti-inflammatory cytokine IL10. Importantly, contracting skeletal muscle rather than the immune cells is the only source of the IL6 in circulation in response to exercise [3]. Importantly, both in humans and experimental animals, intensive exercise increases [Na +] i in skeletal muscles by 3-4-fold and decreases [K +] i by 15-25% via activation of voltage-gated K + and Na + channels and partial inactivation of Na +,K +-ATPase.