NOS2 and schwannoma: The increase in NOS expression correlated with a decrease in the expression of the mitochondrial antioxidant enzyme manganese superoxide dismutase (MnSOD) (Fig. 1F), suggesting that the loss of merlin expression induces an increase in peroxynitrite formation by increasing nitric oxide production while decreasing superoxide clearance by MnSOD in NF2 schwannoma cells.