ABSTRACT
Cisplatin is widely used for treating various solid tumors. However, this drug produces dose-limiting ototoxicity and nephrotoxicity, which significantly reduce the quality of life of cancer patients. While nephrotoxicity could be alleviated by diuresis, there is currently no approved treatment for hearing loss. Previous studies show that the ROS and inflammation are major contributors to cisplatin-induced hearing loss. In this study, we show that ROS trigger the inflammatory process in the cochlea by activating signal transducer and activator of transcription-1 (STAT1). Activation of STAT1 activation was dependent on ROS generation through NOX3 NADPH oxidase, knockdown of which by siRNA reduced STAT1 activation. Moreover, STAT1 siRNA protected against activation of p53, reduced apoptosis, reduced damage to OHCs and preserved hearing in rats. STAT1 siRNA attenuated the increase in inflammatory mediators, such as TNF-α, inhibition of which protected cells from cisplatin-mediated apoptosis. Finally, we showed that trans-tympanic administration of etanercept, a TNF-α antagonist, protected against OHC damage and cisplatin-induced hearing loss. These studies suggest that controlling inflammation by inhibition of STAT1-dependent pathways in the cochlea could serve as an effective approach to treat cisplatin ototoxicity and improve the overall quality of life for cancer patients.
Subject(s)
Antineoplastic Agents/toxicity , Cisplatin/toxicity , Inflammation/metabolism , RNA, Small Interfering/metabolism , STAT1 Transcription Factor/antagonists & inhibitors , Animals , Apoptosis , Cochlea/drug effects , Cochlea/metabolism , Etanercept , Hearing Loss/chemically induced , Immunoglobulin G/pharmacology , Immunologic Factors/pharmacology , Inflammation/pathology , Male , NADPH Oxidases/metabolism , Phosphorylation , RNA Interference , Rats , Rats, Wistar , Reactive Oxygen Species/metabolism , Receptors, Tumor Necrosis Factor , STAT1 Transcription Factor/genetics , STAT1 Transcription Factor/metabolism , Tumor Necrosis Factor-alpha/agonists , Tumor Necrosis Factor-alpha/metabolism , Tumor Suppressor Protein p53/metabolismSubject(s)
Breast Neoplasms/complications , Carcinoma, Ductal, Breast/complications , Tuberculosis, Lymph Node/complications , Tuberculosis, Osteoarticular/complications , Adult , Antineoplastic Agents , Axilla , Breast Neoplasms/pathology , Breast Neoplasms/therapy , Carcinoma, Ductal, Breast/pathology , Carcinoma, Ductal, Breast/therapy , Combined Modality Therapy , Female , Humans , Mastectomy , Tuberculosis, Lymph Node/pathology , Tuberculosis, Lymph Node/therapy , Tuberculosis, Osteoarticular/pathology , Tuberculosis, Osteoarticular/therapyABSTRACT
Human immunodeficiency virus (HIV)-1 Tat is a multifunctional protein involved in viral replication, inflammation and apoptosis. Tat activates phospholipase C-beta (PLC-beta), presumably via a pertussis toxin (PTX) sensitive G(i) protein, which is critical for neuronal apoptosis. In this study, we show that Tat-mediated intracellular Ca(2+) release in rat pheochromocytoma (PC-12) cells and rat primary cortical neuronal cultures was abrogated by pretreatment with either pertussis toxin and/or its B-oligomer subunit (PTX-B), devoid of ADP ribosyltransferase activity. PTX-B pretreatment also inhibited intracellular Ca(2+) release by bradykinin and 2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl) benzenesulfonamide (m-3M3FBS), a director activator of phospholipase C. Activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PdBu) mimicked the PTX-B-mediated inhibition of m-3M3FBS-stimulated intracellular Ca(2+) increase, while inhibition of PKC by bisindolylmaleimide I hydrochloride (BIM) reversed the inhibitory action of PTX-B. Functionally, PTX-B reduced Tat-induced Bax and caspase-3 proteins and reduced cell apoptosis. We conclude that PTX inhibition of Tat-mediated intracellular Ca(2+) release is independent of ADP ribosylation of the G(i) protein via the A protomer, but mediated by the B-oligomer. Furthermore, PTX-B suppresses HIV-1 Tat-mediated apoptosis by reducing its activation of PLC-beta through a PKC activation pathway.
