Ciprofloxacin increases survival after ionizing irradiation combined injury: γ-H2AX formation, cytokine/chemokine, and red blood cells

Abstract

Exposure to ionizing radiation alone (radiation injury, RI) or combined with traumatic tissue injury (radiation combined injury, CI) is a crucial life-threatening factor in nuclear and radiological accidents. It is well documented that RI and CI occur at the molecular, cellular, tissue, and system levels. However, their mechanisms remain largely unclear. It has been observed in dogs, pigs, rats, guinea pigs, and mice that radiation exposure combined with burns, wounds, or bacterial infection results in greater mortality than radiation exposure alone. In this laboratory, the authors found that B6D2F1/J female mice exposed to 9.75 Gy ⁶⁰Co-γ photon radiation followed by 15% total body surface area wounds experienced 50% higher mortality (over a 30-d observation period) compared to irradiation alone. CI enhanced DNA damages, amplified iNOS activation, induced massive release of pro-inflammatory cytokines, overexpressed MMPs and TLRs, and aggravated sepsis that led to cell death. In the present study, B6D2F1/J mice that received CI were treated with ciprofloxacin (CIP, 90 mg/kg p.o., q.d. within 2 h after CI through day 21). At day 1, CIP treatment reduced CI-induced γ-H2AX formation significantly. At day 10, CIP treatment not only reduced cytokine/chemokine concentrations significantly, including IL-6 and KC (i.e., IL-8 in humans), but also enhanced IL-3 production compared to vehicle-treated controls. CIP also elevated red blood cell counts, hemoglobin levels, and hematocrits. At day 30, CIP treatment increased 45% survival after CI (i.e., 2.3-fold increase over vehicle treatment). The results suggest that CIP may prove to be an effective therapeutic drug for CI.

Fig. 1. CIP increased survival after CI

Mice received 9.25 Gy ⁶⁰Co γ-photon radiation (RI) followed within 1 h by 15% TBSA skin wound (CI). Mice were given CIP (90 mg/kg p.o. q.d.) or vehicle for 21 days starting day 0 ≤2h after CI (N = 10 per group). Experiment was repeated to achieve statistical significance. *P < 0.05 vs. CI+CIP. W: wound; RI: radiation injury at 9.25 Gy; CI: 9.25 Gy + wound; Veh: vehicle; CIP: ciprofloxacin.

Fig. 2. CIP reduced γ-H2AX formation in lineage-negative bone marrow cells of CI-mice

On day 1 after wounding, RI, or CI, whole femoral bone marrow cells were collected (N=8 per group). *P<0.05 vs. CI+vehicle. RI: 8.5 Gy; CI: 8.5 Gy + wound; CIP: ciprofloxacin; VEH: vehicle. W: wound.

Fig. 3. CIP modulated cytokine/chemokine concentrations in serum of CI-mice

On day 10 after CI, whole blood was collected from surviving mice and the sera were separated. Sera were tested for their cytokine and chemokine concentrations (N = 3–5 per group); P<0.05 vs. Veh and CIP; **P<0.05 vs. CI. CI: 9.75 Gy + wound; CIP: ciprofloxacin; S: sham; V: vehicle.

Fig. 4. CIP ameliorated CI-induced depletion of RBC but not WBC and platelets

On day 10 after CI, whole blood was collected from surviving mice (N = 4–5 per group); *p < 0.05 vs. Veh and CIP; **P<0.05 vs. CI. CI: 9.75 Gy + wound; CIP: ciprofloxacin; S: sham; V: vehicle; RBC: red blood cell; RBG: hemoglobin; HCT: hematocrit; WBC: white blood cell; PLT: platelet