ABSTRACT
RATIONALE: The immune response in sepsis is characterized by overt immune dysfunction. Studies indicate immunostimulation represents a viable therapy for patients. One study suggests a potentially protective role for interleukin 5 (IL-5) in sepsis; however, the loss of eosinophils in this disease presents a paradox. OBJECTIVES: To assess the protective and eosinophil-independent effects of IL-5 in sepsis. METHODS: We assessed the effects of IL-5 administration on survival, bacterial burden, and cytokine production after polymicrobial sepsis. In addition, we examined the effects on macrophage phagocytosis and survival using fluorescence microscopy and flow cytometry. MEASUREMENTS AND MAIN RESULTS: Loss of IL-5 increased mortality and tissue damage in the lung, IL-6 and IL-10 production, and bacterial burden during sepsis. Therapeutic administration of IL-5 improved mortality in sepsis. Interestingly, IL-5 administration resulted in neutrophil recruitment in vivo. IL-5 overexpression in the absence of eosinophils resulted in decreased mortality from sepsis and increased circulating neutrophils and monocytes, suggesting their importance in the protective effects of IL-5. Furthermore, novel data demonstrate IL-5 receptor expression on neutrophils and monocytes in sepsis. IL-5 augmented cytokine secretion, activation, phagocytosis, and survival of macrophages. Importantly, macrophage depletion before the onset of sepsis eliminated IL-5-mediated protection. The protective effects of IL-5 were confirmed in humans, where IL-5 levels were elevated in patients with sepsis. Moreover, neutrophils and monocytes from patients expressed the IL-5 receptor. CONCLUSIONS: Taken together, these data support a novel role for IL-5 on noneosinophilic myeloid populations, and suggest treatment with IL-5 may be a viable therapy for sepsis.
Subject(s)
Eosinophils/immunology , Interleukin-5/immunology , Interleukin-5/pharmacology , Sepsis/immunology , Animals , Cytokines/immunology , Cytokines/metabolism , Disease Models, Animal , Enzyme-Linked Immunosorbent Assay , Female , Flow Cytometry/methods , Humans , Immunity, Innate/immunology , Interleukin-10/immunology , Interleukin-10/metabolism , Interleukin-5/metabolism , Interleukin-6/immunology , Interleukin-6/metabolism , Lung/immunology , Lung/metabolism , Macrophages/immunology , Macrophages/metabolism , Mice , Mice, Inbred C57BL , Monocytes/immunology , Monocytes/metabolism , Neutrophil Infiltration/immunology , Phagocytosis/immunology , Sepsis/metabolism , Sepsis/prevention & control , Survival AnalysisABSTRACT
Previous studies have shown that telomerase facilitates DNA-damage repair and cell survival following stress. It is not clear how telomerase promotes DNA repair, or whether short-term telomerase inhibition, combined with genotoxic stress, can be exploited for cancer therapy. Here, we show that transient inhibition of telomerase activity by the specific inhibitor, GRN163L, increases the cytotoxicity of some, but not all, DNA-damaging agents. Such synergistic inhibition of growth requires the use of DNA-damaging agents that are toxic in the S/G(2) phase of the cell cycle. Notably, inhibition of Ataxia Telangiectasia Mutated (ATM) kinase, together with telomerase inhibition, synergistically increases the cytotoxicity induced by the G(2)-specific topoisomerase II inhibitor etoposide. By varying the timing of telomerase inhibition, relative to the timing of DNA damage, it is apparent that the prosurvival functions of telomerase occur at early stages of DNA damage recognition and repair. Our results suggest that the protective role of telomerase in cell cycle-restricted DNA damage repair could be exploited for combined anticancer chemotherapy.
