Na+/H+ exchange activation mediates the lipopolysaccharide-induced proliferation of human B lymphocytes and is impaired in malignant B-chronic lymphocytic leukemia lymphocytes.
In various mammalian cell types the stimulation of the plasma membrane amiloride-sensitive Na+/H+ exchange and the resulting increase of intracellular pH (pHi) play a key role in the initiation of cell proliferation. In the present work we have investigated whether Na+/H+ exchange is involved in normal human B cell proliferation and whether it is also operating in malignant B-chronic lymphocytic leukemia (B-CLL) lymphocytes. Our results show that: 1) normal human B cells contain an operating Na+/H+ exchanger, as inferred by their ability to recover pHi after acid-loading in a HCO3- -free medium and by evidences that LPS and phorbol ester PMA elicit a pHi rise inhibitable by either 5-(N-ethyl-N-isopropyl)amiloride (EIPA) or a Na+-free medium; 2) LPS-induced proliferation of normal human B cells is strongly inhibited when the amiloride analog EIPA (5 microM) is present in the culture medium (after 72 h the proportion of B cells incorporation bromodeoxyuridine falls from 13.9 +/- 3.9% to 2.8 +/- 1.1%); 3) EIPA does not affect BdR incorporation when B cells proliferation is induced by the co-mitogenic activity of IL-4 and low m.w. B cell growth factor (BCGF); 4) B-CLL cells, which proliferate in response to IL-4/BCGF but not to LPS, fail to increase pHi above their pHi resting levels when challenged with LPS or PMA and pHi recovery after acid-loading is highly impaired. These results lead to conclude that Na+/H+ exchange operation is necessary for LPS-(but not for IL-4/BCGF)-induced proliferation of human normal B lymphocytes and that Na+/H+ exchange activation is impaired in malignant B-CLL lymphocytes.
Gaidano
G
G
Dipartimento di Scienze Biomediche e Oncologia Umana, Università di Torino, Italy.
Ghigo
D
D
Schena
M
M
Bergui
L
L
Treves
S
S
Turrini
F
F
Cappio
F C
FC
Bosia
A
A
D000368:Aged; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D001402:B-Lymphocytes / Q000145:classification / Q000276:immunology / Q000378:metabolism*; D002352:Carrier Proteins / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015847:Interleukin-4; D007378:Interleukins; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000145:classification / Q000276:immunology / Q000378:metabolism*; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D007378:Interleukins; D008070:Lipopolysaccharides; D017923:Sodium-Hydrogen Exchangers; D015847:Interleukin-4; D000584:Amiloride; C039614:ethylisopropylamiloride