Effects of genistein administration on cytokine induction in whole-body gamma irradiated mice Vijay K. Singh, a,b, ⁎, Marcy B. Grace b , Vaishali I. Parekh b , Mark H. Whitnall b , Michael R. Landauer b a Department of Radiation Biology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20889-5603, USA b Radiation Countermeasures Program, Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD 20889-5603, USA abstract article info Article history: Received 28 July 2009 Received in revised form 17 August 2009 Accepted 18 August 2009 Keywords: Cytokines Cytokine array Genistein G-CSF Luminex Radiation injury RT-PCR The development of an effective pharmacological countermeasure is needed to reduce the morbidity and mortality in military and civilian populations associated with possible exposure to ionizing radiation. We previously demonstrated that a single subcutaneous (sc) administration of genistein at a non-toxic dose provided protection against acute radiation injury and that the radioprotective effects were associated with multilineage, hematopoietic progenitor cell recovery. The purpose of this study was to determine whether hematopoietic recovery was preceded by cytokine induction. In mice treated with sc genistein 24 h before irradiation (7 Gy 60 Co), we quantified serum cytokine levels by multiplex Luminex and also investigated a larger number of cytokines using cytokine arrays. Genistein administration stimulated serum granulocyte- colony stimulating factor (G-CSF) 4 h and 24 h after sham irradiation or γ-irradiation. Interleukin-6 (IL-6) was significantly increased in genistein-treated animals 4 h after irradiation. Because G-CSF and IL-6 are important hematopoietic factors, these results support our hypothesis that the previously observed radioprotective efficacy by genistein may be a result of early recovery of hematopoietic cells due to enhanced production of G-CSF and IL-6. Published by Elsevier B.V. 1. Introduction Nuclear proliferation, terrorist activity, and the distribution of nuclear and radioactive materials through underground networks make incidents involving radiation injuries increasingly likely to the military, civilians and first responders. Scenarios involving radiolog- ical hazards include nuclear detonations, covert placement of radioactive substances, and dirty bombs [1]. Radiation hazards can vary from late life pathologies to acute mortality [2,3]. Radioprotective agents are compounds that are administered before exposure to ionizing radiation to reduce its damaging effects, including radiation- induced lethality [4,5]. Radioprotectants have applications for the military as well as in clinical oncology, space travel, radiation site clean-up, and radiological terrorism [6]. During the last six decades a number of compounds of diverse structures have been considered as countermeasures for radiation [5]. Despite promising observations with various agents to date, none have been approved by the U.S. Food and Drug Administration (FDA) as a radiation countermeasure for the acute radiation syndrome. The isoflavones are present predominantly in soybeans, and lignans, which are found in a variety of foods such as flaxseed, cereals, fruit and berries [7]. The major glycosides found in soybeans are daidzin, genistin, and glycitin. These glucose-conjugated compounds are relatively biologically inactive but upon consumption are hydrolyzed by enzymes and the gut microflora to form the active aglycone isoflavone compounds daidzein, genistein and glycitein. Genistein has a heterodiphenolic structure (4′,5,7-trihydroxyisoflavone) and has gained increased atten- tion due to its association with beneficial effects for individuals with breast cancer, prostate cancer, cardiovascular disease, high cholesterol levels, and osteoporosis [8]. Genistein has also been shown to inhibit growth of tumor cell lines from various malignancies including breast, cervical, endometrial, prostate, ovarian, head and neck squamous cell carcinoma, lung, melanoma, leukemia, and lymphoma [9–11]. It also inhibits chemical-carcinogen-induced reactive oxygen species, oxidative DNA damage and proto-oncogene expression, topoisomerase I and II, tyrosine protein kinases, protein histidine kinase and 5α-reductase and induces G2M cell cycle arrest in some cancer cells that leads to cell growth inhibition and has antibacterial properties [12–16]. Other studies have also shown the effectiveness of genistein as a radiosensitizer in tumor cells derived from prostate and esophageal cancers [17,18]. We previously demonstrated radioprotective efficacy by genistein against γ-irradiation without toxicity or any apparent side effects in mice receiving a single subcutaneous (sc) injection 24 h prior to irradiation [19,20]. Furthermore, we observed that sc administration of genistein prior to lethal irradiation supports multilineage, hematopoi- etic progenitor cell recovery [21]. Protection of the bone marrow was correlated with a genistein-induced transient pause in the cell cycle where hematopoietic stem cells remained in the Go quiescent phase International Immunopharmacology 9 (2009) 1401–1410 ⁎ Corresponding author. Armed Forces Radiobiology Research Institute, 8901 Wisconsin Avenue, Bethesda, MD 20889-5603, USA. Tel.: +1 301 295 2347; fax: +1 301 295 0292. E-mail address: singh@afrri.usuhs.mil (V.K. Singh). 1567-5769/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.intimp.2009.08.012 Contents lists available at ScienceDirect International Immunopharmacology journal homepage: www.elsevier.com/locate/intimp