IL-1 activates the Na+/H+ antiport in a murine T cell.
One of the early events following growth factor exposure is elevation of intracellular pH, a process mediated by the Na+/H+ antiport. We studied the effects of human rIL-1 alpha (HrIL-1 alpha) on intracellular pH (pHi) and calcium ([Ca2+]i) in a murine T cell line (MD10 cells), which proliferates in response to IL-1 alone. By using the intracellularly trapped fluorescent dyes (2(1),7(1)-bis-2-carboxyethyl)-5(and -6) carboxyfluorescein) and indo-1, we monitored immediate to early changes of pHi and [Ca2+]i in response to HrIL-1 alpha. Exposure to HrIL-1 alpha (120 pM) leads to an early, sustained intracellular alkalinization (delta pH = + 0.09 +/- 0.03) that plateaus within 20 min. Lower concentrations of the monokine (12 pM, 1.2 pM) have a positive but not statistically significant effect on pHi. These effects parallel the degree of MD10 IL-1R saturation predicted by the KD (49 pM) as assessed by 125I-HrIL-1 alpha binding by MD10 cells (Bmax = approximately 1300). Both the MD10 IL-1 receptor KD and the HrIL-1 alpha concentration required to induce early measurable alkaline pH shifts, however, exceed by three orders of magnitude the HrIL-1 alpha ED50 (50 fM) required for MD10 proliferation. The IL-1-induced rise in pHi is both sodium dependent and amiloride sensitive, indicative of activation of the Na+/H+ antiport. Additionally, PMA (100 nM) and IL-2 (2 nM) alkalinize MD10 cells, with the rise in pHi as a result of PMA exceeding the maximal IL-1 effect (delta pH = + 0.13 +/- 0.04). Furthermore, although PMA alkalinizes cells previously exposed to HrIL-1 alpha, the monokine does not alter the pHi of PMA-treated MD10 cells. Importantly, intracellular alkalinization induced by either HrIL-1 alpha or PMA is inhibited by staurosporine (1 mu iM). Finally, HrIL-1 alpha does not change MD10 [Ca2+]i, in either an acute or sustained fashion. These results indicate that IL-1 activates the Na+/H+ antiport in T cells by a mechanism that is unrelated to changes in [Ca2+]i but may involve protein kinase C activation.
Civitelli
R
R
Division of Bone and Mineral Metabolism, Jewish Hospital, St. Louis, MO 63110.
Teitelbaum
S L
SL
Hruska
K A
KA
Lacey
D L
DL
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007211:Indoles; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D011971:Receptors, Immunologic / Q000187:drug effects; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D005456:Fluorescent Dyes; D007211:Indoles; D007375:Interleukin-1; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C048960:indo-1; D013755:Tetradecanoylphorbol Acetate