GJB2 and hearing loss disorder: The noise-induced hearing loss and decrease in the Cx26 protein level and Na+, K+-ATPase activity were abolished by a systemic treatment with a free radical-scavenging agent, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, or with a nitric oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester hydrochloride.