Inhibition of NF-κB by a TAT-NEMO–binding domain peptide accelerates constitutive apoptosis and abrogates LPS-delayed neutrophil apoptosis

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Abstract
Delivery of biologically active peptides into human polymorphonuclear neutrophils (PMNs) has implications for studying cellular functions and may be therapeutically relevant. The transcription factor nuclear factor-κB (NF-κB) regulates the expression of multiple genes controlling inflammation, proliferation, and cell survival. PMNs play a crucial role in first-line defense. Targeting NF-κB in these cells may promote apoptosis and therefore facilitate resolution of inflammation. We used an 11-amino acid sequence NEMO-binding domain (NBD) that selectively inhibits the IKKγ (NEMO)/IKKβ interaction, preventing NF-κB activation. An HIV-TAT sequence served as a highly effective transducing shuttle. We show that lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), and dexamethasone (DEX) significantly reduced apoptosis after 20 hours. LPS, but not GM-CSF or DEX, activated NF-κB as shown by IκBα degradation, NF-κB DNA binding, and transcriptional activity. The TAT-NBD blocked LPS-induced NF-κB activation and NF-κB–dependent gene expression. TAT-NBD accelerated constitutive PMN apoptosis dose dependently and abrogated LPS-delayed apoptosis. These results provide a proof of principle for peptide delivery by TAT-derived protein transduction domains to specifically inhibit NF-κB activity in PMNs. This strategy may help in controlling various cellular functions even in short-lived, transfection-resistant primary human cells.