A protein which is composed N-terminally of one or several C-terminal parts of the amino acid sequence of the mature tumor necrosis factor and C-terminally of one or several N-terminal parts of the amino acid sequence of the mature tumor necrosis factor, which activates epithelial ion channels and improves the lung function and which can be used for the manufacture of medicaments for the treatment of diseases associated with the lung function, such as oedemas.