Immunomodulation by memantine in therapy of Alzheimer's disease is mediated through inhibition of K(v)1.3 channels and T cell responsiveness

Memantine is approved for the treatment of advanced Alzheimer's disease (AD) and reduces glutamate-mediated neuronal excitotoxicity by antagonism of N-methyl-D-aspartate receptors. In the pathophysiology of AD immune responses deviate and infectious side effects are observed during memantine therapy. However, the particular effects of memantine on human T lymphocytes are unresolved. Here, we provide evidence that memantine blocks K(v)1.3 potassium channels, inhibits CD3-antibody- and alloantigen-induced proliferation and suppresses chemokine-induced migration of peripheral blood T cells of healthy donors. Concurrent with the in vitro data, CD4(+) T cells from AD patients receiving therapeutic doses of memantine show a transient decline of K(v)1.3 channel activity and a long-lasting reduced proliferative response to alloantigens in mixed lymphocyte reactions. Furthermore, memantine treatment provokes a profound depletion of peripheral blood memory CD45RO(+) CD4(+) T cells. Thus, standard doses of memantine profoundly reduce T cell responses in treated patients through blockade of K(v)1.3 channels. This may normalize deviant immunopathology in AD and contribute to the beneficial effects of memantine, but may also account for the enhanced infection rate.