The invention relates to a protein the N-terminal end of which is composed of one or more C-terminal parts of the amino acid sequence of the mature tumor necrosis factor, and the C-terminal end of which is composed of one or more N-terminal parts of the amino acid sequence of the mature tumor necrosis factor. The protein activates epithelial ion channels and improves the pulmonary function and can be used to produce drugs for the treatment of diseases that are associated with the pulmonary function, such as oedema.