Temporal onset of hypoxia and oxidative stress after pulmonary irradiation

PURPOSE

To investigate the temporal onset of hypoxia following irradiation, and to show how it relates to pulmonary vascular damage, macrophage accumulation, and the production of reactive oxygen species and cytokines. Our previous studies showed that tissue hypoxia in the lung after irradiation contributed to radiation-induced injury.

METHODS AND MATERIALS

Female Fisher 344 rats were irradiated to the right hemithorax with a single dose of 28 Gy. Serial studies were performed up to 20 weeks following irradiation. Radionuclide lung-perfusion studies were performed to detect changes in pulmonary vasculature. Immunohistochemical studies were conducted to study macrophages, tissue hypoxia (carbonic anhydrase-9 marker), oxidative stress (8-hydroxy-2'-deoxyguanosine), and the expression of profibrogenic (transforming growth factor-beta [TGF-beta]) and proangiogenic (vascular endothelial growth factor [VEGF]) cytokines.

RESULTS

Significant changes in lung perfusion along with tissue hypoxia were observed 3 days after irradiation. Significant oxidative stress was detected 1 week after radiation, whereas macrophages started to accumulate at 4 weeks. A significant increase in TGF-beta expression was seen within 1 day after radiation, and for VEGF at 2 weeks after radiation. Levels of hypoxia, oxidative stress, and both cytokines continued to rise with time after irradiation. The steepest increase correlated with vast macrophage accumulation.

CONCLUSIONS

Early changes in lung perfusion, among other factors initiate, the development of hypoxia and chronic oxidative stress after irradiation. Tissue hypoxia is associated with a significant increase in the activation of macrophages and their continuous production of reactive oxygen species, stimulating the production of fibrogenic and angiogenic cytokines, and maintaining the development of chronic radiation-induced lung injury.

Antitransforming growth factor-beta antibody 1D11 ameliorates normal tissue damage caused by high-dose radiation

PURPOSE

The aim of this study was to determine whether a neutralizing transforming growth factor-beta (TGFbeta) antibody can prevent radiation (RT) induced lung injury.

METHODS AND MATERIALS

Fractionated and sham right lung irradiation in Fischer 344 rats was delivered to assess the radioprotective effect of the antibodies. Animals were divided into the following groups: (1) control (sham RT, control antibody 13C4); (2) RT (800cGy x 5)+13C4); (3) RT + 0.1 mg/kg 1D11 anti-TGFbeta antibody; and (4) RT + 1 mg/kg 1D11 antibody. Antibodies were intraperitoneally administered immediately after the last fraction of RT. Animals were sacrificed at 6 and 26 weeks after irradiation. Lungs were assessed for histologic changes, activation of macrophages, expression/activation of TGFbeta and its signal transduction pathway.

RESULTS

At 6 weeks post-RT, there was a significant reduction in macrophage accumulation (p = 0.041), alveolar wall thickness (p = 0.0003), and TGF-beta activation (p = 0.032) in animals receiving 1.0 mg/kg 1D11 vs. in the control group. However, at 6 weeks, the low dose of 1D11 antibody (0.1 mg/kg) failed to produce any significant changes. At 6 months post-RT, radioprotection is apparent for the group receiving 1.0 mg/kg 1D11, with activated macrophages (p = 0.037), alveolar wall thickness (p = 0.0002), TGFbeta activation (p = 0.002) and its signal transduction proteins (p < 0.05) compared with the control group.

CONCLUSIONS

Administration of a single dose of 1.0 mg/kg of the anti-TGFbeta antibody 1D11 resulted in decreased morphologic changes, inflammatory response, and reduced expression and activation of TGFbeta 6 weeks and 6 months after 40 Gy to the right hemithorax. Targeting the TGFbeta pathway may be a useful strategy to prevent radiation-induced lung injury.

Small molecular inhibitor of transforming growth factor-beta protects against development of radiation-induced lung injury

PURPOSE

To determine whether an anti-transforming growth factor-beta (TGF-beta) type 1 receptor inhibitor (SM16) can prevent radiation-induced lung injury.

METHODS AND MATERIALS

One fraction of 28 Gy or sham radiotherapy (RT) was administered to the right hemithorax of Sprague-Dawley rats. SM16 was administered in the rat chow (0.07 g/kg or 0.15 g/kg) beginning 7 days before RT. The rats were divided into eight groups: group 1, control chow; group 2, SM16, 0.07 g/kg; group 3, SM16, 0.15 g/kg; group 4, RT plus control chow; group 5, RT plus SM16, 0.07 g/kg; group 6, RT plus SM16, 0.15 g/kg; group 7, RT plus 3 weeks of SM16 0.07 g/kg followed by control chow; and group 8, RT plus 3 weeks of SM16 0.15 g/kg followed by control chow. The breathing frequencies, presence of inflammation/fibrosis, activation of macrophages, and expression/activation of TGF-beta were assessed.

RESULTS

The breathing frequencies in the RT plus SM16 0.15 g/kg were significantly lower than the RT plus control chow from Weeks 10-22 (p <0.05). The breathing frequencies in the RT plus SM16 0.07 g/kg group were significantly lower only at Weeks 10, 14, and 20. At 26 weeks after RT, the RT plus SM16 0.15 g/kg group experienced a significant decrease in lung fibrosis (p = 0.016), inflammatory response (p = 0.006), and TGF-beta1 activity (p = 0.011). No significant reduction was found in these measures of lung injury in the group that received SM16 0.7 g/kg nor for the short-course (3 weeks) SM16 at either dose level.

CONCLUSION

SM16 at a dose of 0.15 g/kg reduced functional lung damage, morphologic changes, inflammatory response, and activation of TGF-beta at 26 weeks after RT. The data suggest a dose response and also suggest the superiority of long-term vs. short-term dosing.

Stab wounds to the back and flank in the hemodynamically stable patient: a decision algorithm based on contrast-enhanced computed tomography with colonic opacification

PURPOSE

The authors wanted to determine whether contrast-enhanced computed tomography (CE-CT) with colonic opacification is an accurate tool to triage hemodynamically stable victims of stab wounds to the flank and back.

PATIENTS AND METHODS

One hundred forty-five consecutive patients were categorized as low-risk ( penetration superficial to the deep fascia) or high-risk (penetration beyond the deep fascia) based on CE-CT findings.

RESULTS

There were no significant differences in admission vital signs, Glasgow Coma Scale, or complete blood counts between low- and high-risk groups. None of the 92 low-risk patients required surgery or had sequelae. Six of the 53 high-risk patients underwent surgery, 2 based on initial CE-CT, 4 due to evolving clinical signs. The CE-CT correctly predicted surgical findings in all cases.

CONCLUSIONS

Hemodynamically stable patients with stab wounds to the back and/or flank can be successfully triaged based on CE-CT findings. Low-risk patients may be discharged immediately. High-risk patients may have a discharge decision implemented at 24 hours.

Vitreous changes after neodymium-YAG laser irradiation of the posterior lens capsule or mid-vitreous

Exposure of four monkey and 26 rabbit eyes to neodymium-YAG laser irradiation to the posterior lens capsule or the mid-vitreous area clearly demonstrated significant vitreous changes (liquefaction) as measured by viscosity analyses and proton relaxation studies. We found marked molecular alterations in the vitreous of the exposed eye compared with the contralateral control (unirradiated) eye. These alterations, occurring immediately after laser treatment, were probably the result of acoustic transients accompanying the laser irradiation.