Autophagy induced by 2-deoxy-D-glucose suppresses intracellular multiplication of Legionella pneumophila in A/J mouse macrophages.

Legionella pneumophila Philadelphia-1 (Lp-1) can grow intracellularly in A/J mouse peritoneal macrophages (A/J Mphi). We previously reported that 2-deoxy-D-glucose (2dG), when added in macrophage culture medium, inhibited the intracellular multiplication of Lp-1 in A/J Mphi. We found that 1 mM of 2dG causes LC3-II-conversion that reflects an induction of autophagy and that 1 and 10 mM of 2dG induced apoptosis associated with caspase-4 activation. We therefore investigated whether 2dG-induced autophagy or apoptosis suppresses the replication ofLp-1 in 2dG-treated A/J Mphi. When the autophagy-related (Atg)gene Atg5 was knocked down by RNA interference, the Atg5-siRNA-transfected cells revealed an enhanced replication of Lp-1 in A/J Mphi compared with the non-targetting siRNA-transfected cells. However, caspase-4 inhibitor did not affect the 2dG-induced inhibition of intracellular multiplication of Lp-1 in A/J Mphi. These findings suggested that autophagy, not apoptosis, suppressed the intracellular growth of Lp-1 in A/J Mphi when 1 or 10 mM of 2dG were added to the culture media.