piperidines and Radiation-Pneumonitis

The lung is one of the most sensitive organs to ionizing radiation, and damage to normal lung tissue remains a major dose limiting factor for patients receiving radiation to the thorax. Radiation induced lung injury (RILI) which is also named as "radiation pneumonpathy" is a continuous process and regarded as the result of an abnormal healing response. It has been shown that transforming growth factor β-1 (TGF-β1) plays an integral role in the radiation induced lung fibrosis formation by promoting the chemoattraction of fibroblasts and their conversion to myofibroblasts. Halofuginone is a, low molecular weight plant derived alkaloid, isolated from the Dichroa febrifuga plant that exhibits antifibrotic activity and inhibition of type I collagen synthesis. Halofuginone has been shown to protect against radiation induced soft tissue fibrosis by virtue of inhibiting various members of TFG-β signaling pathway. By the light of these findings, we hypothesize that Halofuginone may be able to ameliorate the radiation induced lung fibrosis.

Topics: Animals; Fibrosis; Humans; Lung Injury; Piperidines; Quinazolinones; Radiation Pneumonitis; Radiation-Protective Agents; Transforming Growth Factor beta

Patients receiving thoracic radiation often develop pulmonary injury and fibrosis. Currently, there are no effective measures to prevent or treat these conditions. We tested whether blockade of the chemokine, CC chemokine ligand (CCL) 3, and its receptors, CC chemokine receptor (CCR) 1 and CCR5, can prevent radiation-induced lung inflammation and fibrosis. C57BL/6J mice received thoracic radiation, and the interaction of CCL3 with CCR1 or CCR5 was blocked using genetic techniques, or by pharmacologic intervention. Lung inflammation was assessed by histochemical staining of lung tissue and by flow cytometry. Fibrosis was measured by hydroxyproline assays and collagen staining, and lung function was studied by invasive procedures. Irradiated mice lacking CCL3 or its receptor, CCR1, did not develop the lung inflammation, fibrosis, and decline in lung function seen in irradiated wild-type mice. Pharmacologic treatment of wild-type mice with a small molecule inhibitor of CCR1 also prevented lung inflammation and fibrosis. By contrast, mice lacking CCR5 were not protected from radiation-induced injury and fibrosis. The selective interaction of CCL3 with its receptor, CCR1, is critical for radiation-induced lung inflammation and fibrosis, and these conditions can be largely prevented by a small molecule inhibitor of CCR1.

Topics: Animals; Chemokine CCL3; Gamma Rays; Hydroxyproline; Lung; Mice; Mice, Knockout; Phenylurea Compounds; Piperidines; Radiation Injuries, Experimental; Radiation Pneumonitis; Receptors, CCR1; Receptors, CCR5

In this study, we assessed the effects of halofuginone and methylprednisolone on hypopharyngeal and esophageal stricture that can develop following radiation to the head and neck of rats. Rats were divided into four groups randomly and 18 Gy radiation was given to the head and neck regions of all rats except the control group. Group 1 (Control Group): No radiation or drugs were administered. Group 2 (Radiation Group): only radiation was applied without any drugs. Group 3 (Halofuginone Group): halofuginone 100 microg/kg per day was given intraperitoneally. Group 4 (Methylprednisolone Group): methylprednisolone 1 mg/kg per day was administered intramuscularly. In all groups, 90 days after application of radiation, sections of the proximal esophagus and hypopharynx were examined for fibrosis, fibroblast proliferation, vascularization, epithelial atypia, necrosis, polymorphonuclear leukocytes, mononuclear cells, and stenosis index by light microscope and the hydroxyproline levels were assessed biochemically. Fibrosis, epithelial atypia and hydroxyproline levels were found to be significantly higher in the radiation group compared to the control group (P < 0.05). We did not observe fibrosis in either the halofuginone or the control groups. Fibrosis was also significantly lower in the methylprednisolone group than the radiation group (P < 0.05). The differences of the stenosis index scores between the groups were not statistically significant (P < 0.05). Vascularization was similar in all groups. We think that especially halofuginone is a drug that can be used safely to prevent fibrosis due to radiotherapy, but further studies are needed.

Topics: Animals; Anti-Inflammatory Agents; Esophageal Stenosis; Esophagus; Female; Hydroxyproline; Hypopharynx; Injections, Intramuscular; Injections, Intraperitoneal; Methylprednisolone; Piperidines; Premedication; Protein Synthesis Inhibitors; Quinazolinones; Radiation Pneumonitis; Rats; Rats, Wistar

Radiation-induced fibrosis is an untoward effect of high dose therapeutic and inadvertent exposure to ionizing radiation. Transforming growth factor-beta (TGF-beta) has been proposed to be critical in tissue repair mechanisms resulting from radiation injury. Previously, we showed that interruption of TGF-beta signaling by deletion of Smad3 results in resistance to radiation-induced injury. In the current study, a small molecular weight molecule, halofuginone (100 nm), is demonstrated by reporter assays to inhibit the TGF-beta signaling pathway, by Northern blotting to elevate inhibitory Smad7 expression within 15 min, and by Western blotting to inhibit formation of phospho-Smad2 and phospho-Smad3 and to decrease cytosolic and membrane TGF-beta type II receptor (TbetaRII). Attenuation of TbetaRII levels was noted as early as 1 h and down-regulation persisted for 24 h. Halofuginone blocked TGF-beta-induced delocalization of tight junction ZO-1, a marker of epidermal mesenchymal transition, in NMuMg mammary epithelial cells and suggest halofuginone may have in vivo anti-fibrogenesis characteristics. After documenting the in vitro cellular effects, halofuginone (intraperitoneum injection of 1, 2.5, or 5 microg/mouse/day) efficacy was assessed using ionizing radiation-induced (single dose, 35 or 45 Gy) hind leg contraction in C3H/Hen mice. Halofuginone treatment alone exerted no toxicity but significantly lessened radiation-induced fibrosis. The effectiveness of radiation treatment (2 gray/day for 5 days) of squamous cell carcinoma (SCC) tumors grown in C3H/Hen was not affected by halofuginone. The results detail the molecular effects of halofuginone on the TGF-beta signal pathway and show that halofuginone may lessen radiation-induced fibrosis in humans.

Topics: Animals; Blotting, Northern; Blotting, Western; Carcinoma, Squamous Cell; Cell Line; Cell Line, Tumor; Cells, Cultured; COS Cells; DNA-Binding Proteins; Dose-Response Relationship, Drug; Down-Regulation; Fibrosis; Gene Deletion; Genes, Reporter; Humans; Immunoblotting; MAP Kinase Signaling System; Mice; Mice, Inbred C3H; Microscopy, Confocal; Microscopy, Fluorescence; Piperidines; Plasmids; Protein Synthesis Inhibitors; Quinazolines; Quinazolinones; Radiation Pneumonitis; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Smad3 Protein; Time Factors; Trans-Activators; Transforming Growth Factor beta; Transforming Growth Factor beta1