Induction of acute phase gene expression by brain irradiation

Using plasma transforming growth factor beta-1 during radiotherapy to select patients for dose escalation

PURPOSE

The ability to prescribe treatment based on relative risks for normal tissue injury has important implications for oncologists. In non-small-cell lung cancer, increasing the dose of radiation may improve local control and survival. Changes in plasma transforming growth factor beta (TGFbeta) levels during radiotherapy (RT) may identify patients at low risk for complications in whom higher doses of radiation could be safely delivered.

PATIENT AND METHODS

Patients with locally advanced or medically inoperable non-small-cell lung cancer received three-dimensional conformal RT to the primary tumor and radiographically involved nodes to a dose of 73.6 Gy (1.6 Gy twice daily). If the plasma TGFbeta level was normal after 73.6 Gy, additional twice daily RT was delivered to successively higher total doses. The maximum-tolerated dose was defined as the highest radiation dose at which < or = one grade 4 (life-threatening) late toxicity and < or = two grade 3 to 4 (severe life-threatening) late toxicities occurred.

RESULTS

Thirty-eight patients were enrolled. Median follow-up was 16 months. Twenty-four patients were not eligible for radiation dose escalation beyond 73.6 Gy because of persistently abnormal TGFbeta levels. Fourteen patients whose TGFbeta levels were normal after 73.6 Gy were escalated to 80 Gy (n = 8) and 86.4 Gy (n = 6). In the 86.4-Gy group, dose-limiting toxicity was reached because there were two (33%) grade 3 late toxicities.

CONCLUSION

It is feasible to use plasma TGFbeta levels to select patients for RT dose escalation for non-small-cell lung cancer. The maximum-tolerated dose using this approach is 86.4 Gy.

Targeting drug delivery to radiation-induced neoantigens in tumor microvasculature

Radiation can be used to guide drugs to specific sites such as neoplasms or aberrant blood vessels. When blood vessels are treated with ionizing radiation, they respond by expressing a number of cell adhesion molecules and receptors that participate in homeostasis. Examples of radiation-induced molecules in blood vessels include ICAM-1, E-selectin, P-selectin and the beta(3) integrin. We have observed that the endothelium and blood components respond to oxidative stress in a similar, if not identical manner in all tumor models. Although we have identified several other radiation-induced molecules within tumor blood vessels, the beta(3) target for drug delivery achieves the greatest site-specific peptide binding within irradiated tumor blood vessels. We have focused on peptides and antibodies that bind to integrin beta(3). beta(3)-binding proteins have been conjugated to fluorochromes and radionuclides to study the site specificity and microscopic distribution. We have found immunofluorescent and immunohistochemical staining of beta(3) within the lumen of blood vessels immediately following irradiation. To determine whether it is feasible to guide drug delivery to irradiated tumors, we studied ligands to alpha(2b)beta(3) (fibrinogen). Peptides within fibrinogen that bind to alpha(2b)beta(3) includes the dodecapeptide, HHLGGAKQAGDV and the RGD peptide. We utilized 131I conjugation to these ligands to study the biodistribution in tumor bearing mice. Our clinical trial consists of the RGD peptidomimetic, biapcitide, labeled with 99mTc. This study shows that it is feasible to guide drugs to human neoplasms by use of radiation-guided peptides. These studies have shown that peptides that bind to these integrins bind to tumors following exposure to ionizing radiation.

Characterization of the acute inflammatory response after irradiation in mice and its regulation by interleukin 4 (Il4)

The aim of this study was to determine the effects of total-body irradiation of mice on the acute release of a panel of several mediators of inflammation and to evaluate the efficacy of Il4 in regulating these radiation-induced modifications. We studied the effects of exposure of C57BL6/J mice to 8 Gy gamma rays on the early release of cytokines, chemokines, acute-phase proteins, prostaglandins and corticosterone in either plasma or tissues compared to those observed after intraperitoneal injection of lipopolysaccharide from 1 h to 3 days after stimulation. During the characterization of the acute inflammatory response induced by radiation or lipopolysaccharide, we observed differences both in the type of mediators produced and in the time course of release. We next determined the anti-inflammatory potential of Il4 in this model of total-body irradiation. We found that Il4 was able to down-regulate the radiation-induced production of mediators of inflammation such as Gro1 (also known as KC, N51) in plasma and lung, corticosterone in blood, Il1b in lung, and prostaglandin E(2) in colon, suggesting the anti-inflammatory potential of Il4 in regulating the radiation-induced response.

Ionizing radiation affects 26s proteasome function and associated molecular responses, even at low doses

BACKGROUND AND PURPOSE

Ionizing radiation is known to activate certain signal transduction pathways, the regulation of which could involve post-transcriptional as well as transcriptional mechanisms. One of the most important post-transcriptional pathways in eukaryotic cells is the ATP- and ubiquitin-dependent degradation of proteins by the 26s proteasome. This process controls initiation of many cellular stress responses, as well as inflammatory responses under control of the transcription factor NF-kappaB. The literature on the relationship between radiation and inflammation seems somewhat paradoxical. At high doses, radiation is generally pro-inflammatory. On the other hand, low dose radiation has a long history of use in the treatment of inflammatory disease. This suggests the involvement of multiple mechanisms that may operate differentially at different dose levels.

MATERIALS AND METHODS

In this paper, the ability of different doses of ionizing radiation to directly affect 26s proteasome activity was tested in ECV 304 cells. Proteasome activity, IkappaBalpha protein levels, and NF-kappaB activation were monitored.

RESULTS

Inhibition of chymotrypsin-like 20s and 26s proteasome activity was observed immediately after low- and high-dose irradiation either of cells or purified proteasomes. The inhibitory effect was independent of the availability of the known endogenous proteasome inhibitor heat shock protein 90 (hsp90). Levels of IkappaBalpha, a physiological 26s proteasome substrate, were increased only at low doses (0.25 Gy) and unaltered at higher doses whereas only the highest doses (8 and 20 Gy) activated NF-kappaB.

CONCLUSIONS

We conclude that the proteasome is a direct target of ionizing radiation and suggest that inhibition of proteasome function provides a molecular framework within which low dose anti-inflammatory effects of radiation, and radiation-induced molecular responses in general, should be considered.

Dose- and time-dependence of radiation-induced nitric oxide formation in mice as quantified with electron paramagnetic resonance

In vivo nitric oxide (NO) formation was quantified in mice after exposure to high-dose whole-body X-ray irradiation. NO produced and accumulated in the livers of irradiated mice was determined using NO trapping method with iron-dithiocarbamate complex combined with electron paramagnetic resonance (EPR) spectroscopy. When mice were irradiated with 50 Gy X-ray, NO formation peaked in approximately 3 h after the irradiation was terminated. Dose-dependence study indicated that NO formation measured 5 h after irradiation was leveled off at the dose higher than 50 Gy. Administration of NO synthase inhibitor, N(G)-monomethyl L-arginine (L-NMMA) shortly after irradiation completely abolished the NO signal, indicating that radiation-induced NO is produced through L-arginine-dependent NO synthase pathways. These results suggest that irradiation of X-ray initiates inflammation processes, resulting in delayed NO synthase expression and NO formation.

Behavioural consequences of an 8 Gy total body irradiation in mice: Regulation by interleukin-4

The effects of an 8 Gy γ total body irradiation (TBI) on exploration and locomotion activities as well as temperature were studied in C57BL6/J mice. Survival, body weight, and blood cell counts were also assessed in irradiated mice treated with placebo or interleukin (IL)-4. The efficacy of IL-4 treatment on improvement in exploration activity was evaluated. The study was carried out from 3 h to 30 days following exposure. Our results showed a biphasic response to irradiation concerning the exploration activity of mice. Irradiated mice had reduced activity as early as 3 h after exposure, with recovery of activity within 24 h. The exploration activity again decreased 4 days after irradiation and the recovery occurred slowly after day 17. IL-4 ameliorated the exploration status in mice in both phases. The locomotion activity was studied using a telemetry apparatus. A similar pattern to that of the exploration data was observed, with a minimal activity observed between days 13 and 17. A radiation-induced hypothermia was also noticed over the same time period.Key words: irradiation, behaviour, interleukin-4.

Assessment of alterations in gene expression in recurrent malignant glioma after radiotherapy using complementary deoxyribonucleic acid microarrays

OBJECTIVE

We used complementary deoxyribonucleic acid expression microarrays to assess the effects of radiotherapy on gene expression in glioblastoma multiforme. We hypothesized that postradiation recurrent tumors may demonstrate alterations in gene expression from the primary tumor specimen.

METHODS

Patients were diagnosed with glioblastoma multiforme at resection of the initial tumor, and they received 60 Gy of fractionated radiotherapy before recurrence. Ribonucleic acid samples from both the primary and the postradiation recurrent tumor in each patient were screened and compared using complementary deoxyribonucleic acid expression arrays and Northern blot analysis.

RESULTS

Messenger ribonucleic acid levels of growth factors participating in paracrine loops, such as vascular endothelial growth factor and platelet-derived growth factor receptor beta, were decreased in postradiation recurrent tumors as compared with primary tumors in three of four patients. However, messenger ribonucleic acid levels of growth factors involved in autocrine loops, such as epidermal growth factor receptor, platelet-derived growth factor alpha, platelet-derived growth factor A, and basic fibroblast growth factor, were decreased in two of four, two of four, three of four, and three of four patients' recurrent tumors, respectively. Microvessel counts demonstrated that blood vessel growth was decreased significantly in postradiation recurrent tumor specimens.

CONCLUSION

After radiotherapy of glioblastoma multiforme, levels of paracrine-acting growth factors are diminished in correspondence with the reduction in vascular density. In contrast, growth factors that participate in autocrine loops demonstrate elevated levels of gene expression. These results suggest that maintenance of autocrine loops may be important in tumor regrowth after radiotherapy.

Preservation of visual fields after peri-sellar gamma-knife radiosurgery

Radiosurgical treatment of pituitary and peri-sellar tumors has become an increasingly utilized modality as an alternative to conventional radiotherapy and surgery. Such radiosurgery results in a relatively high dose of radiation to the optic chiasm. The clinical data establishing safe single-fraction doses to the chiasm is immature, although taken together previous literature suggests a recommended maximal dose of 8 Gy. Optic neuropathy, when it occurs, tends to take place within 2 years of treatment. We evaluated the visual fields of 20 sequential patients that received significant doses to the optic chiasm by Gamma-knife radiosurgery. There were 17 cases of pituitary adenoma and 3 cases of meningioma, and two patients refused follow-up testing. Preoperative visual field and cranial nerve examinations were done prior to radiosurgery and in follow-up, with a median follow-up of 24 months. There were no cases of quantitative visual field deficit induced by treatment. No patients developed symptomatic visual deterioration. Radiat. Oncol. Invest. 90:343-350, 2000. 2000 Wiley-Liss, Inc.

Magnetic resonance imaging (MRI) controlled outcome of side effects caused by ionizing radiation, treated with 780 nm-diode laser -- preliminary results

BACKGROUND AND OBJECTIVE

Ionizing radiation therapy by way of various beams such as electron, photon and neutron is an established method in tumor treatment. The side effects caused by this treatment such as ulcer, painful mastitis and delay of wound healing are well known, too. Biomodulation by low level laser therapy (LLLT) has become popular as a therapeutic modality for the acceleration of wound healing and the treatment of inflammation. Evidence for this kind of application, however, is not fully understood yet. This study intends to demonstrate the response of biomodulative laser treatment on the side effects caused by ionizing radiation by means of magnetic resonance imaging (MRI).

STUDY DESIGN/PATIENTS AND METHODS

Six female patients suffering from painful mastitis after breast ionizing irradiation and one man suffering from radiogenic ulcer were treated with lambda=780 nm diode laser irradiation at a fluence rate of 5 J/cm2. LLLT was performed for a period of 4-6 weeks (mean sessions: 25 per patient, range 19-35). The tissue response was determined by means of MRI after laser treatment in comparison to MRI prior to the beginning of the LLLT.

RESULTS

All patients showed complete clinical remission. The time-dependent contrast enhancement curve obtained by the evaluation of MR images demonstrated a significant decrease of enhancement features typical for inflammation in the affected area.

CONCLUSION

Biomodulation by LLLT seems to be a promising treatment modality for side effects induced by ionizing radiation.

The physical parameters and molecular events associated with radiation-induced lung toxicity

Radiation therapy (RT) is frequently used to treat patients with tumors in and around the thorax. Clinical radiation pneumonitis is a common side effect, occurring in 5% to 20% of patients. Efforts to identify patients at risk for pneumonitis have focused on physical factors, such as dose and volume. Recently, the underlying molecular biological mechanisms behind RT-induced lung injury have come under study. Improved knowledge of the molecular events associated with RT-induced lung injury may translate into a better ability to individualized therapy. This review discusses our current understanding of the physical and molecular factors contributing to RT-induced pulmonary injury.

Melphalan and other anticancer modalities up-regulate B7-1 gene expression in tumor cells

In this study, we show that administration of low-dose melphalan (l -PAM, l -phenylalanine mustard) to mice bearing a large MOPC-315 plasmacytoma led to a rapid up-regulation of B7-1 (CD80), but not B7-2 (CD86), expression on the surface of MOPC-315 tumor cells. This l -PAM-induced preferential up-regulation of B7-1 surface expression was due, at least in part, to a direct effect of l -PAM on the tumor cells, as in vitro exposure of MOPC-315 tumor cells to l -PAM led to the preferential up-regulation of B7-1 surface expression. Moreover, in vitro exposure of MOPC-315 tumor cells to two other anticancer modalities, gamma-irradiation and mitomycin C, resulted in the preferential up-regulation of B7-1 surface expression. This effect was not restricted to MOPC-315 tumor cells, as preferential up-regulation of B7-1 surface expression was observed also following in vitro exposure of the P815 mastocytoma (that is negative for both B7-1 and B7-2 surface expression) to any of the three anticancer modalities. The up-regulation of B7-1 surface expression following in vitro exposure of tumor cells to l -PAM, gamma-irradiation, or mitomycin C required de novo protein and RNA synthesis, and was associated with the accumulation of mRNA for B7-1 within 4-8 h, indicating that the regulation of B7-1 expression is at the RNA transcriptional level. These results have important implications for an additional immune-potentiating mechanism of these anticancer modalities in clinical setting.

Induction of growth factors in rat cardiac tissue by X irradiation

To investigate the relationship between angiogenic growth factors and endothelial enzyme activity in capillaries after injury of rat cardiomyocytes caused by X irradiation, 7-week-old male Wistar rats were anesthetized with pentobarbitone and their hearts irradiated (X rays, 20 Gy) through a hole in the lead casing in which they were enclosed. The hearts were excised at 1 h, 1 week and 3 weeks after irradiation. Left ventricular cross sections were stained for capillary enzymes by double staining for two endothelial enzymes, alkaline phosphatase (AP) and dipeptidylpeptidase IV (DPP), immunohistochemically stained for basic fibroblast growth factor (Fgf, also known as bFgf) and vascular endothelial growth factor (Vegf), and stained for nick end-labeling of DNA by the TUNEL method. Staining for distribution of AP in the arteriolar portion was reduced at both 1 and 3 weeks after irradiation with 20 Gy, but staining for DPP in the venular portion was unchanged, suggesting a close relationship between growth factors and injury of the arteriolar capillary portion. Fgf and Vegf proteins were present within the cytoplasm of the cardiomyocytes, or around capillaries, 1 h, 1 week and 3 weeks after irradiation. Many TUNEL-stained cardiomyocyte nuclei were observed at 1 h, but they had decreased markedly at 1 week and had almost disappeared by 3 weeks after irradiation. Thus Fgf and Vegf were induced concomitantly with the decrease in the staining for endothelial AP by 20 Gy X irradiation, which also caused microeffects as indicated by TUNEL staining of many nuclei at 1 h postirradiation.

The radioresponse of the central nervous system: a dynamic process

Radiation continues to be a major treatment modality for tumors located within and close to the central nervous system (CNS). Consequently, alleviating or protecting against radiation-induced CNS injury would be of benefit in cancer treatment. However, the rational development of such interventional strategies will depend on a more complete understand-ing of the mechanisms responsible for the development of this form of normal tissue injury. Whereas the vasculature and the oligodendrocyte lineage have traditionally been considered the primary radiation targets in the CNS, in this review we suggest that other phenotypes as well as critical cellular interactions may also be involved in determining the radio-response of the CNS. Furthermore, based on the assumption that the CNS has a limited repertoire of responses to injury, the reaction of the CNS to other types of insults is used as a framework for modeling the pathogenesis of radiation-induced damage. Evidence is then provided suggesting that, in addition to acute cell death, radiation induces an intrinsic recovery/repair response in the form of specific cytokines and may

Enhanced levels of scrapie responsive gene mRNA in BSE-infected mouse brain

The expression of the mRNA of nine scrapie responsive genes was analyzed in the brains of FVB/N mice infected with bovine spongiform encephalopathy (BSE). The RNA transcripts of eight genes were overexpressed to a comparable extent in both BSE-infected and scrapie-infected mice, indicating a common series of pathogenic events in the two transmissible spongiform encephalopathies (TSEs). In contrast, the serine proteinase inhibitor spi 2, an analogue of the human alpha-1 antichymotrypsin gene, was overexpressed to a greater extent in the brains of scrapie-infected animals than in animals infected with BSE, reflecting either an agent specific or a mouse strain specific response. The levels of spi 2 mRNA were increased during the course of scrapie prior to the onset of clinical signs of the disease and the increase reached 11 to 45 fold relative to uninfected controls in terminally ill mice. Spi 2, in common with four of the other scrapie responsive genes studied, is known to be associated with pro-inflammatory processes. These observations underline the importance of cell reactivity in TSE. In addition, scrg2 mRNA the level of which is enhanced in TSE-infected mouse brain, was identified as a previously unrecognized long transcript of the murine aldolase C gene. However, the level of the principal aldolase C mRNA is unaffected in TSE. The increased representation of the longer transcript in the late stage of the disease may reflect changes in mRNA processing and/or stability in reactive astrocytes or in damaged Purkinje cells.

Effects of spinal cord X-irradiation on the recovery of paraplegic rats

Axonal regrowth is limited in the adult CNS, especially in the spinal cord, one of the major sites of traumatic lesions. Pathophysiological changes occurring after spinal cord injury include complex acute, subacute, and late processes. In this study, we assessed whether X-irradiation interferes with the acute/subacute phases, thereby improving the functional recovery of paraplegic animals. Two days after acute compression of adult rat spinal cords, various doses (0, 2, 5, 10, 20 Gy) of X-rays were administered as one single dose to the compression site. The animals were functionally evaluated over the course of 1 month after injury, using the Tarlov scale and the Rivlin and Tator scale. We also designed a "physiological" scale, including an assessment of urinary function and infection, appropriate for the evaluation of spinal-cord-lesioned animals. Behavioral analysis suggested that the high doses, 20 Gy and, to a lesser extent, 5 and 10 Gy, were toxic, as shown by morbidity rate and "physiological" score. The 2-Gy group showed better motor performances than the lesioned nonirradiated (LNI) animals and the 5- and 20-Gy groups. Motor performance in the 5-, 10-, and 20-Gy groups was poorer than that seen in the LNI group. Gliosis was reduced in the 2-Gy group compared to LNI animals, and there was high levels of gliosis in the highly (>/=5 Gy) irradiated animals. There was a 23% less lesion-induced syringomyelia in the 2-Gy group than in the other groups (LNI and 5-20 Gy). Thus, low doses of X-rays may interfere with the formation of syringomyelia and glial scar, thereby facilitating the recovery of paraplegic animals. These findings suggest that low-dose irradiation of the lesion site, in association with other therapies, is a potentially promising treatment for improving recovery after spinal cord injury.

Effects of carbon ions on primary cultures of mouse brain cells

Primary mixed cultures of astrocytes and microglia were obtained from neonatal mice, and were irradiated with high-LET carbon ions. Immunohistochemical staining showed astrocytes survived more prominently than microglia. Tagged with specific antibodies, astrocytes and microglia surviving after irradiation were counted by flow cytometry. Decreases in the number of microglia and astrocytes were detected at a dose as small as 2 Gy when Day 5 cultures were irradiated with 13 keV/micrometer carbon ions. When the cultures were irradiated on Day 10, the dose-dependent decrease of microglia was more prominent for 13 keV/micrometer carbon ions than 70 keV/micrometer carbon ions. Astrocytes showed a marginal decrease at Day 10 and Day 14. We concluded that microglia are more sensitive than astrocytes to carbon ions and X-rays, and that the radiosensitivity of microglia depends on both differentiation/proliferation status and radiation quality.

Pentoxifylline attenuates hypoxic-ischemic brain injury in immature rats

Inflammatory mediators are implicated in the pathogenesis of ischemic injury in immature brain. The phosphodiesterase inhibitor pentoxifylline inhibits production of tumor necrosis factor-alpha and platelet-activating factor. We hypothesized that pentoxifylline treatment would attenuate hypoxic-ischemic brain injury in immature rats. Seven-day-old rats (n = 79) underwent right carotid ligation, followed by hypoxia (FiO2 = 0.08). Rats received pentoxifylline immediately before and again after hypoxia (two doses, 25-150 mg/kg/dose, n = 34), or vehicle (n = 27). In separate experiments, rats received pentoxifylline treatment (40 mg/kg/dose, n = 8), or vehicle (n = 10) immediately and again 3 h after hypoxia-ischemia. Severity of injury was assessed 5 d later by visual evaluation of ipsilateral hemisphere infarction and by measurement of bilateral hemispheric cross-sectional areas. Pentoxifylline pretreatment reduced the incidence of liquefactive cerebral infarction, from 75% in controls to 10% with pentoxifylline, 40 mg/kg/dose (p<0.001, chi2 trend test). Quantification of hemispheric areas confirmed these findings. In contrast, posthypoxic-ischemic treatment with pentoxifylline resulted in only a modest reduction in cortical damage, without an overall reduction in incidence of infarction. Phosphodiesterase inhibition may be an effective strategy to use to decrease the severity of neonatal hypoxic-ischemic brain injury. Pretreatment regimens could be clinically relevant in settings in which an increased risk of cerebral ischemia can be anticipated, such as in infants undergoing surgery to correct congenital heart disease.

Inhibition of NF-kappaB, clonogenicity, and radiosensitivity of human cancer cells

BACKGROUND

Activation of the transcription factor NF-kappaB is part of the immediate early response of tissues to ionizing irradiation. This pathway has been shown to protect cells from tumor necrosis factor-alpha, chemotherapy, and radiation therapy-induced apoptosis (programmed cell death). However, because the role of NF-kappaB as a modifier of the intrinsic radiosensitivity of cancer cells is less clear, we have studied the impact of NF-kappaB on the intrinsic radiosensitivity of human cancer cells.

METHODS

We used PC3 prostate cancer cells and HD-MyZ Hodgkin's lymphoma cells transduced with an adenovirus vector that contains a gene encoding a form of IkappaB (an inhibitor of NF-kappaB) that cannot be phosphorylated. This form of IkappaB will remain bound to NF-kappaB; thus, NF-kappaB cannot be activated. We monitored NF-kappaB activity with a gel-shift assay and used a colony-forming assay to assess clonogenicity and radiosensitivity.

RESULTS

Constitutive DNA-binding activity of NF-kappaB was dramatically decreased in PC3 cells transduced with the IkappaB super-repressor gene. The clonogenicity of transduced PC3 cells declined to 19.6% of that observed for untreated control cells, a finding similar to one we have previously demonstrated for IkappaB-transduced HD-MyZ cells. However, inhibition of NF-kappaB activity in the surviving PC3 and HD-MyZ cells failed to alter their intrinsic radiosensitivity.

CONCLUSIONS

We conclude that activation of NF-kappaB does not determine the intrinsic radiosensitivity of cancer cells, at least for the cell lines tested in this study.

NF kappa B activity and target gene expression in the rat brain after one and two exposures to ionizing radiation

The central nervous system injury that can result after radiotherapy has been suggested to involve induced gene expression and cytokine production. We have previously shown that irradiation of primary cultures of rat astrocytes results in the activation of NF kappa B. To determine whether such an effect also occurs in vivo, NF kappa B activity was analyzed in the cerebral cortex of the rat brain after whole body irradiation. After a single dose of 15 Gy, NF kappa B activity was increased by 2 h postirradiation, returning to unirradiated levels by 8 hours. The increase was dose-dependent beginning at 2 Gy and continuing to at least 22.5 Gy. NF kappa B activity in the irradiated cortex was not accompanied by I kappa B alpha degradation. When 7.5 Gy was delivered 24 h before the 15 Gy, the increase in NF kappa B activity after 15 Gy was significantly reduced. These results suggest that an initial exposure to radiation induced a refractory period in the brain during which the susceptibility of NF kappa B to activation by subsequent irradiation was significantly reduced. This period of reduced sensitivity to radiation was also apparent for the induction of the NF kappa B-regulated cytokines IL-1 beta, IL-6, and TNF alpha.

Striking regression of subcutaneous fibrosis induced by high doses of gamma rays using a combination of pentoxifylline and alpha-tocopherol: an experimental study

PURPOSE

To establish a successful treatment of subcutaneous fibrosis developing after high doses of gamma rays, suitable for use in clinical practice.

METHODS AND MATERIALS

We used an animal model of acute localized gamma irradiation simulating accidental overexposure in humans. Three groups of 5 Large White pigs were irradiated using a collimated 192Ir source to deliver a single dose of 160 Gy onto the skin surface (100%) of the outer side of the thigh. A well-defined block of necrosis developed within a few weeks which had healed after 26 weeks to leave a block of subcutaneous fibrosis involving skin and skeletal muscle. One experimental group of 5 pigs was dosed orally for 26 weeks starting 26 weeks after irradiation with 1600 mg/120 kg body weight of pentoxifylline (PTX) included in the reconstituted food during its fabrication, and another group of 5 was dosed orally for the same period with a daily dose of 1600 mg/120 kg body weight of PTX combined with 2000 IU/120 kg body weight of alpha-tocopherol. Five irradiated control pigs were given normal food only. Animals were assessed for changes in the density of the palpated fibrotic block and in the dimensions of the projected cutaneous surface. Depth of scar tissue was determined by ultrasound. Physical and sonographic findings were confirmed by autopsy 26 weeks after treatment started. The density, length, width, and depth of the block of fibrotic scar tissue, and the areas and volume of its projected cutaneous surface, were compared before treatment, 6 and 13 weeks thereafter, and at 26 weeks.

RESULTS

The experimental animals exhibited no change in behavior and no abnormal clinical or anatomic signs. No modifications were observed in the block of fibrotic scar tissue of pigs dosed with PTX alone. However, significant softening and shrinking of this block were noted in the pigs dosed with PTX + alpha-tocopherol 13 weeks after treatment started and at autopsy, when mean regression was approximately 30% for length, approximately 50% for width and depth, and approximately 70% for area and volume. Histologic examination showed completely normal muscle and subcutaneous tissue surrounding the residual scar tissue. The 50% decrease in the linear dimensions of the scar tissue, were comparable to the results obtained in our previous clinical studies, and were highly significant compared to the clinical and autopsy results for the controls. Histologic examination of the residual scar tissue revealed tissue which was more homogenous and less cellular and inflammatory than in control and PTX-dosed pigs. The tissular and cellular immunolocalization of tumor necrosis factor alpha (TNFalpha) was similar in the residual fibrotic tissues of all three groups of pigs, whereas the immunostaining of transforming growth factor beta-1(TGFbeta-1) diminished much more in the residual fibrotic scar tissue of the PTX + alpha-tocopherol-dosed pigs than in the two other groups.

CONCLUSIONS

The present results showed a striking regression of the subcutaneous fibrotic scar tissue that develops as a consequence of high doses of gamma rays.

TNF alpha and IL-1beta mediate intercellular adhesion molecule-1 induction via microglia-astrocyte interaction in CNS radiation injury

Radiation injury to the central nervous system (CNS) results in glial activation accompanied by expression of pro-inflammatory cytokines and adhesion molecules. In this study we demonstrate intercellular adhesion molecule-1 (ICAM-1) induction in the irradiated mouse brain at the mRNA and protein levels. Immunocytochemical analysis revealed that ICAM-1 protein was primarily expressed in endothelial cells and microglia. In vitro, ionizing radiation significantly induces TNF alpha, IL-1beta and ICAM-1 mRNA in primary microglia cultures. Interestingly, although ionizing radiation activated primary astrocyte cultures, it did not induce ICAM-1 expression. However, exposure of astrocytes to conditioned medium collected from irradiated microglia resulted in ICAM-1 induction, which was abrogated when the conditioned medium was pre-incubated with neutralizing antibodies raised against murine TNF alpha and IL-1beta. These results indicate that pro-inflammatory cytokines may be necessary for ICAM-1 expression in astrocytes in CNS radiation injury.

Increased expression of prohormone convertase-2 in the irradiated rat brain

Changes in gene expression have been suggested to play a role in radiotherapy-induced central nervous system (CNS) injury. To begin to identify radiation-inducible genes in the CNS, we have applied the differential display of reverse transcription-polymerase chain reaction products to RNA extracted from the brain of adult rats. RNA was isolated from a rat brain 6 h after whole-body exposure to 10 Gy and compared with RNA from unirradiated brain. A cDNA band was consistently observed at about 600 bp in samples from the irradiated rat but not from unirradiated (control) rat. Amplification and sequencing of the cDNA revealed that it corresponded to the prohormone convertase-2 (PC2) gene, which is involved in the processing of inert prohormones and neuropeptides to their bioactive forms. Enhanced PC2 expression was detected after irradiation of neuronal cultures but not in cultures of astrocytes, suggesting that the cell type in the CNS responsible for the PC2 induction after in vivo irradiation is the neuron. These results indicate that radiation induces the expression of a neuronal enzyme that is critical to the activation of a number of prohormones and neuropeptides, which may influence the radioresponse of the CNS.

Correlation of increased mortality with the suppression of radiation-inducible microsomal epoxide hydrolase and glutathione S-transferase gene expression by dexamethasone: effects on vitamin C and E-induced radioprotection

Previous studies in this laboratory have shown that gamma-ray ionizing radiation in combination with oltipraz, a radioprotective agent, enhances hepatic microsomal epoxide hydrolase (mEH) and glutathione S-transferase (GST) expression. The present study was designed to investigate the effects of dexamethasone on the radiation-inducible expression of mEH and rGST genes and on the vitamin C and E-induced radioprotective effects in association with the expression of the genes. Treatment of rats with a single dose of dexamethasone (0.01-1 mg/kg, p.o.) caused a dose-dependent decrease in the constitutive mEH gene expression at 24 hr. The radiation-inducible mEH mRNA level (threefold increase after 3 Gy gamma-irradiation) was decreased by 21% and 88% by dexamethasone at the doses of 0.1 and 1 mg/kg, respectively. Although dexamethasone alone caused 2- to 5-fold increases in the hepatic rGSTA2 mRNA level, rats treated with dexamethasone prior to 3 Gy irradiation exhibited 80%-93% suppression in the radiation-inducible increases in the rGSTA2 mRNA level. The inducible rGSTA3 and rGSTA5 mRNA levels were also significantly decreased by dexamethasone, whereas the rGSTM1 mRNA level was reduced to a lesser extent. Vitamin C and/or E, however, failed to enhance the radiation-inducible increases in hepatic mEH and rGST mRNA levels. Whereas rats exposed to 3 Gy irradiation with or without vitamin C treatment (30 or 200 mg/kg/day, p.o., 2 days) exhibited approximately threefold increases in the mEH and rGSTA2/3/5 mRNA levels relative to untreated animals, dexamethasone treatment (1 mg/kg, p.o.) resulted in 64%-96% decreases in the mRNA levels at 24 hr. The inducible rGSTM1/2 mRNA levels in the vitamin C/E-treated rats were approximately 50% suppressed by dexamethasone. Although vitamin C and/or E treatment (200 mg/kg/day, p.o., 2 days) improved the 30-day survival rates of the 8 Gy gamma-irradiated mice from 39% up to 74%, the improved survival rate of gamma-irradiated animals was reduced to 30% by dexamethasone pretreatment (1 mg/kg/day, 2 days). The mean survival time of dexamethasone-treated animals was reduced to approximately 2 days from 14 days in the animals with total body irradiation alone. No significant hematologic changes were observed in mice at 10 days after dexamethasone plus gamma-irradiation, as compared with irradiation alone. These results demonstrate that: dexamethasone substantially suppresses radiation-inducible mEH, rGSTA and rGSTM expression in the liver; vitamins C/E exhibit radioprotective effects without enhancing radiation-inducible mEH and GST gene expression; and inhibition of radiation-inducible mEH and rGST gene expression in the vitamin C- and E-treated animals by dexamethasone was highly correlated with reduction in the survival rate and the mean survival time of gamma-irradiated animals.

Changes in histology and fibrogenic cytokines in irradiated colorectum of two murine strains

PURPOSE

A strain difference in the development of radiation-induced fibrosis of the colorectum was recently observed. C57B1/6 mice developed colorectal obstruction with significantly higher incidence compared to C3Hf/Kam mice after partial volume irradiation with 30 Gy. Previous reports have demonstrated differences in cytokine mRNA levels in fibrosis-prone and -resistant mice after lung irradiation. The aims of this study are to determine if there are strain differences in: 1) the histology of the lesion, 2) mRNA levels for transforming growth factor beta (TGFbeta) isoforms and tumor necrosis factor alpha (TNFalpha), and 3) immunohistochemical staining patterns using antibodies against the TGFbeta isoforms and latency-associated peptide (LAP).

METHODS AND MATERIALS

The colorectum of male C3Hf/Kam (C3H) and C57B1/6 (B6) mice were irradiated using a dose/length combination (30 Gy to 13.7 mm) that resulted in 10 or 100% incidence of obstruction by 6 months in each strain, respectively. Colorectal tissue was removed from 6 hours to 120 days after irradiation as well as from obstructed mice and prepared for histology, RNase protection assay, and immunofluorescence.

RESULTS

Distinct differences in the histological phenotype for the two strains were observed at times preceding obstruction. Samples from B6 mice showed increased hyperplastic crypts, colitis cystica profunda, and fibrosis within the lamina propria, compared to identically treated C3H mice. Fibrosis in the lamina propria of B6 mice appeared early, beginning at 75 days after irradiation, and was progressive, whereas fibrosis in C3H mice appeared simultaneous with obstruction and may have been a reaction to ulceration. No consistent strain difference in mRNA levels for TGFbeta1, 2, 3 or TNFalpha were observed, although mRNA levels of TGFbeta1 and TNFalpha were significantly elevated in both strains relative to nonirradiated controls. Immunofluorescent staining for TGFbeta1, 3 and LAP was observed in hyperplastic crypts and colitis cystica profunda adjacent to regions of fibrosis, histological changes that were present predominately in the B6 strain.

CONCLUSIONS

The response of the colorectum to irradiation involves changes in the expression of several different cytokines. However, the lack of a consistent strain difference in TGFbeta1, 2, 3 and TNFalpha mRNA levels, despite strain differences in both the incidence of colorectal obstruction and histological features preceding obstruction, suggests that mRNA changes in these fibrogenic cytokines are not the critical determinant of the strain difference and are not related to the process of radiation-induced colorectal fibrosis in these mouse strains. Strain-dependent differences were observed in the localization of active TGFbeta, but these differences were related to the histological changes specifically found in the irradiated colon of the B6 strain.

A hybrid neural network analysis of subtle brain volume differences in children surviving brain tumors

In the treatment of children with brain tumors, balancing the efficacy of treatment against commonly observed side effects is difficult because of a lack of quantitative measures of brain damage that can be correlated with the intensity of treatment. We quantitatively assessed volumes of brain parenchyma on magnetic resonance (MR) images using a hybrid combination of the Kohonen self-organizing map for segmentation and a multilayer backpropagation neural network for tissue classification. Initially, we analyzed the relationship between volumetric differences and radiologists' grading of atrophy in 80 subjects. This investigation revealed that brain parenchyma and white matter volumes significantly decreased as atrophy increased, whereas gray matter volumes had no relationship with atrophy. Next, we compared 37 medulloblastoma patients treated with surgery, irradiation, and chemotherapy to 19 patients treated with surgery and irradiation alone. This study demonstrated that, in these patients, chemotherapy had no significant effect on brain parenchyma, white matter, or gray matter volumes. We then investigated volumetric differences due to cranial irradiation in 15 medulloblastoma patients treated with surgery and radiation therapy, and compared these with a group of 15 age-matched patients with low-grade astrocytoma treated with surgery alone. With a minimum follow-up of one year after irradiation, all radiation-treated patients demonstrated significantly reduced white matter volumes, whereas gray matter volumes were relatively unchanged compared with those of age-matched patients treated with surgery alone. These results indicate that reductions in cerebral white matter: 1) are correlated significantly with atrophy; 2) are not related to chemotherapy; and 3) are correlated significantly with irradiation. This hybrid neural network analysis of subtle brain volume differences with magnetic resonance may constitute a direct measure of treatment-induced brain damage.

Pilot evaluation of cytokine levels in patients undergoing radiotherapy for brain tumor

This study was undertaken to evaluate plasma levels of interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) transforming growth factor-beta (TGF-beta), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF) in 3 pediatric and 14 adult patients receiving radiotherapy for brain tumor. Patients with glioblastoma, astrocytoma, chondrosarcoma, meningioma, schwannoma, and lung adenocarcinoma that had metastasized to the brain were included. Peripheral blood samples were collected before and after treatment with conventional photon and/or proton radiation; samples from healthy volunteers served as controls. Enzyme-linked immunosorbent assays were performed to quantitate the cytokines. Before irradiation, most patients had greater amounts of one or more of the cytokines compared with the mean obtained for control plasma. This was especially striking in patients with chondrosarcoma; the mean values for TGF-beta 1, TNF-alpha, bFGF, and EGF were 1458, 1289, 332, and 92% higher than in healthy subjects, respectively. After irradiation, bFGF and total TGF-beta 1 decreased in the majority of tested subjects. In contrast, IL-1 beta was detected only in pediatric patients (all with astrocytoma) and its levels after radiation were 33 to 67% higher than at pretreatment. EGF was found in four patients; post-treatment values were 125 to 608% higher in three of the individuals. These data show that cytokines are present at elevated concentrations in the blood circulation of patients with certain types of brain tumors and that changes in their levels can be detected after radiotherapy. Further investigations are warranted to determine whether these findings contribute to morbidity or therapeutic outcome.

Failure of a second X-ray dose to activate nuclear factor kappaB in normal rat astrocytes

Induced gene expression and subsequent cytokine production have been implicated in the normal tissue injury response to radiotherapy. However, studies of radiation-induced gene expression have used single radiation doses rather than the fractionated exposures typical of the clinical situation. To study the effects of multiple radiation doses on gene expression, we investigated nuclear factor kappaB (NFkappaB) DNA binding activity in primary astrocyte cultures after one and two exposures to x-rays. After a single dose of x-rays (3.8-15 gray (Gy)), NFkappaB binding activity in astrocytes increased in a dose-dependent manner, reaching a maximum by 2-4 h and returning to control levels by 8 h after irradiation. In split-dose experiments, when an interval of 24 h was used between two doses of 7.5 Gy, the second 7.5-Gy exposure failed to induce NFkappaB activation. The period of desensitization induced by the first radiation exposure was dose-dependent, persisting approximately 72 h after 7.5 Gy compared with 24 h after 1.5 Gy. No changes in IkappaBalpha protein levels were detected. However, the presence of a transcription inhibitor prevented the desensitizing effect of the initial irradiation. Irradiation also prevented NFkappaB activation in astrocytes by a subsequent exposure to H2O2, but it had no effect on the activation induced by tumor necrosis factor-alpha. These data indicate that an initial x-ray exposure can desensitize astrocytes to the NFkappaB-activating effects of a subsequent radiation exposure. Furthermore, they suggest that this desensitization depends on gene transcription and may have some specificity for NFkappaB activation mediated by reactive oxygen species.

Induction of c-fos and junB mRNA following in vivo brain irradiation

Although radiotherapy is a front line treatment for brain tumors, little is known about the in vivo molecular responses of brain to irradiation. In this study, expression of c-fos, c-jun and junB immediate-early genes were followed in mouse brain after irradiation. C-fos and junB, but not c-jun, mRNA was induced within 15 min in unanesthetized irradiated mice. Induction was transient and lasted < 4 h. The response was dose-dependent with increases in c-fos and junB mRNA levels after dose of > or = 2 and 7 Gy, respectively. Anesthesia of mice with pentobarbitol delayed the increases in mRNA expression and the response was attenuated. Pre-treatment of mice with dexamethasone, in a schedule which suppressed acute-phase gene expression after brain irradiation, did not significantly change c-fos and junB induction. Our results show that c-fos and junB responses occur in the brain in response to irradiation and that they can be modified by pentobarbital treatment but suggest that there is no direct correlation between the level of mRNA expression and later expression of cytokines or other acute-phase response genes.

Delayed molecular responses to brain irradiation

The chance of life-threatening complications occurring late after brain irradiation limits the efficacy of this form of cancer therapy. The molecular and cellular events that trigger radiation-induced brain damage are still unknown, but since they have the potential to serve as valuable targets for therapeutic intervention they are worth delineating. In this murine study, the effect of irradiation on the expression of molecules which are known to contribute to brain damage in other model systems was examined. Expression of genes encoding cytokines (TNF-alpha/beta, IL-1 alpha/beta, IL-2, IL-3, IL-4, IL-5, IL-6 and IFN-gamma), cytokine receptors (TNF-Rp55 and p75, IL-1R- p60 and p80, IFN-gamma R, and IL-6R), the cell adhesion molecule (ICAM-1), inducible nitric oxide synthetase (iNOS), anti-chymotrypsin (EB22/5.3), and the gliotic marker (GFAP) was evaluated over a 6-month period using a sensitive RNase protection assay (RPA). We had previously demonstrated that within 24 h of brain irradiation there is an acute transitory molecular response involving TNF-alpha, IL-1, ICAM-1, EB22/5.3 and GFAP. This study shows re-elevation of TNF-alpha, EB22/5.3 and GFAP mRNA levels at 2-3 months, but only TNF-alpha mRNA was overexpressed at 6 months. These time points are when neurological abnormalities are seen after higher doses. The data suggest that TNF-alpha may be involved in late brain responses to irradiation and could contribute to clinical symptoms.

Inflammatory reactions induced by pretransplant conditioning--an alternative target for modulation of acute GvHD and complications following allogeneic bone marrow transplantation?

Intensity of pretransplant conditioning has been closely correlated with regimen related toxicity in patients receiving allogeneic bone marrow transplantation (BMT). In this review, we summarize evidence for a direct link between inflammatory reactions induced by irradiation and cytotoxic treatment and occurrence of acute graft-versus-host disease (GvHD) as well as endothelial complications: In our studies, de novo release of TNFalpha during conditioning was associated with an increased risk of severe GvHD and mortality following BMT, whereas increased spontaneous production of IL-10, an endogenous TNF-antagonist, prior to conditioning protected from these complications. Immunogenetic differences in cytokine regulation and costimulation by endotoxin proved to be important cofactors determining the extent of inflammatory cytokine release in individual patients. Pathophysiological relevance of these findings seems to be confirmed by experimental as well as first clinical trials using TNF-antibodies and related antagonists during pretransplant conditioning. Preclinical experiments suggest additional, cytokine independent inflammatory reactions induced by irradiation such as expression of ICAM-1 and endothelial cell apoptosis. Although the exact impact of these findings on pathophysiology of BMT related complications needs further clarification by future studies, conditioning related inflammation as a first crucial step in induction of GvHD and complications has to be considered when designing new protocols for preparation of patients for allogeneic BMT.

Time course of radiation-induced apoptosis in the adult rat spinal cord

Radiation-induced apoptosis has been reported in thymic, lymphoid, haematopoietic cells and intestinal epithelium but is infrequently documented in other adult mammalian cell types. In this study, we examined the time course of radiation-induced apoptosis in the adult cervical rat spinal cord following a single dose of 8 or 22 Gy. Apoptosis was assessed by morphological criteria under light and electron microscopy, and immunohistochemically in-situ using Apoptag to detect 3' -OH ends of DNA fragments. Little evidence of apoptosis (0.3 +/- 0.1 apoptotic nuclei per spinal cord section) was observed in control un-irradiated spinal cord. A significant increase in the number of apoptotic cells per spinal cord section was seen at 4 h after 8 (13.6 +/- 1.3) or 22 Gy (22.0 +/- 2.7). The number of apoptotic nuclei reached a peak at 8 h (44.7 +/- 3.7 after 8 Gy, 49.5 +/- 4.3 after 22 Gy), and returned to the baseline level by 24 h (2.4 +/- 0.7 after 8 Gy, 3.3 +/- 0.7 after 22 Gy). A dose of 22 Gy induced significantly more apoptoses than 8 Gy at 4, 6, 10 and 12 h (P < or = 0.033), but not at 8 h. More apoptotic nuclei were observed in white matter (64-92%) than gray matter (8-36%). All the apoptotic cells were observed in glial cells, and there was no evidence of radiation-induced apoptosis in the vascular endothelial cells or neurons. The morphological features of the apoptotic cells under electron microscopy and the absence of GFAP staining suggested that they were oligodendrocytes. We conclude that radiation induces apoptosis in the adult rat spinal cord, and that the development of apoptosis follows a specific time course.