Locally instilled tumor necrosis factor α antisense oligonucleotide contributes to inhibition of TH 2-driven pulmonary fibrosis via induced CD4+ CD25+ Foxp3+ regulatory T cells

Promising Biomarkers of Radiation-Induced Lung Injury: A Review

Radiation-induced lung injury (RILI) is one of the main dose-limiting side effects in patients with thoracic cancer during radiotherapy. No reliable predictors or accurate risk models are currently available in clinical practice. Severe radiation pneumonitis (RP) or pulmonary fibrosis (PF) will reduce the quality of life, even when the anti-tumor treatment is effective for patients. Thus, precise prediction and early diagnosis of lung toxicity are critical to overcome this longstanding problem. This review summarizes the primary mechanisms and preclinical animal models of RILI reported in recent decades, and analyzes the most promising biomarkers for the early detection of lung complications. In general, ideal integrated models considering individual genetic susceptibility, clinical background parameters, and biological variations are encouraged to be built up, and more prospective investigations are still required to disclose the molecular mechanisms of RILI as well as to discover valuable intervention strategies.

Immunological Aspect of Radiation-Induced Pneumonitis, Current Treatment Strategies, and Future Prospects

Delivery of high doses of radiation to thoracic region, particularly with non-small cell lung cancer patients, becomes difficult due to subsequent complications arising in the lungs of the patient. Radiation-induced pneumonitis is an early event evident in most radiation exposed patients observed within 2-4 months of treatment and leading to fibrosis later. Several cytokines and inflammatory molecules interplay in the vicinity of the tissue developing radiation injury leading to pneumonitis and fibrosis. While certain cytokines may be exploited as biomarkers, they also appear to be a potent target of intervention at transcriptional level. Initiation and progression of pneumonitis and fibrosis thus are dynamic processes arising after few months to year after irradiation of the lung tissue. Currently, available treatment strategies are challenged by the major dose limiting complications that curtails success of the treatment as well as well being of the patient's future life. Several approaches have been in practice while many other are still being explored to overcome such complications. The current review gives a brief account of the immunological aspects, existing management practices, and suggests possible futuristic approaches.

Oligonucleotide Therapy for Obstructive and Restrictive Respiratory Diseases

Inhaled oligonucleotide is an emerging therapeutic modality for various common respiratory diseases, including obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD) and restrictive airway diseases like idiopathic pulmonary fibrosis (IPF). The advantage of direct accessibility for oligonucleotide molecules to the lung target sites, bypassing systemic administration, makes this therapeutic approach promising with minimized potential systemic side effects. Asthma, COPD, and IPF are common chronic respiratory diseases, characterized by persistent airway inflammation and dysregulated tissue repair and remodeling, although each individual disease has its unique etiology. Corticosteroids have been widely prescribed for the treatment of asthma, COPD, and IPF. However, the effectiveness of corticosteroids as an anti-inflammatory drug is limited by steroid resistance in severe asthma, the majority of COPD cases, and pulmonary fibrosis. There is an urgent medical need to develop target-specific drugs for the treatment of these respiratory conditions. Oligonucleotide therapies, including antisense oligonucleotide (ASO), small interfering RNA (siRNA), and microRNA (miRNA) are now being evaluated both pre-clinically and clinically as potential therapeutics. The mechanisms of action of ASO and siRNA are highly target mRNA specific, ultimately leading to target protein knockdown. miRNA has both biomarker and therapeutic values, and its knockdown by a miRNA antagonist (antagomir) has a broader but potentially more non-specific biological outcome. This review will compile the current findings of oligonucleotide therapeutic targets, verified in various respiratory disease models and in clinical trials, and evaluate different chemical modification approaches to improve the stability and potency of oligonucleotides for the treatment of respiratory diseases.

Attenuation of Nitrogen Mustard-Induced Pulmonary Injury and Fibrosis by Anti-Tumor Necrosis Factor-α Antibody

Nitrogen mustard (NM) is a bifunctional alkylating agent that causes acute injury to the lung that progresses to fibrosis. This is accompanied by a prominent infiltration of macrophages into the lung and upregulation of proinflammatory/profibrotic cytokines including tumor necrosis factor (TNF)α. In these studies, we analyzed the ability of anti-TNFα antibody to mitigate NM-induced lung injury, inflammation, and fibrosis. Treatment of rats with anti-TNFα antibody (15 mg/kg, iv, every 9 days) beginning 30 min after intratracheal administration of NM (0.125 mg/kg) reduced progressive histopathologic alterations in the lung including perivascular and peribronchial edema, macrophage/monocyte infiltration, interstitial thickening, bronchiolization of alveolar walls, fibrin deposition, emphysema, and fibrosis. NM-induced damage to the alveolar-epithelial barrier, measured by bronchoalveolar lavage (BAL) protein and cell content, was also reduced by anti-TNFα antibody, along with expression of the oxidative stress marker, heme oxygenase-1. Whereas the accumulation of proinflammatory/cytotoxic M1 macrophages in the lung in response to NM was suppressed by anti-TNFα antibody, anti-inflammatory/profibrotic M2 macrophages were increased or unchanged. Treatment of rats with anti-TNFα antibody also reduced NM-induced increases in expression of the profibrotic mediator, transforming growth factor-β. This was associated with a reduction in NM-induced collagen deposition in the lung. These data suggest that inhibiting TNFα may represent an efficacious approach to mitigating lung injury induced by mustards.

Radiation-induced lung injury and inflammation in mice: role of inducible nitric oxide synthase and surfactant protein D

Reactive nitrogen species (RNS) generated after exposure to radiation have been implicated in lung injury. Surfactant protein D (SP-D) is a pulmonary collectin that suppresses inducible nitric oxide synthase (iNOS)-mediated RNS production. Herein, we analyzed the role of iNOS and SP-D in radiation-induced lung injury. Exposure of wild-type (WT) mice to γ-radiation (8 Gy) caused acute lung injury and inflammation, as measured by increases in bronchoalveolar lavage (BAL) protein and cell content at 24 h. Radiation also caused alterations in SP-D structure at 24 h and 4 weeks post exposure. These responses were blunted in iNOS(-/-) mice. Conversely, loss of iNOS had no effect on radiation-induced expression of phospho-H2A.X or tumor necrosis factor (TNF)-α. Additionally, at 24 h post radiation, cyclooxygenase expression and BAL lipocalin-2 levels were increased in iNOS(-/-) mice, and heme oxygenase (HO)-1(+) and Ym1(+) macrophages were evident. Loss of SP-D resulted in increased numbers of enlarged HO-1(+) macrophages in the lung following radiation, along with upregulation of TNF-α, CCL2, and CXCL2, whereas expression of phospho-H2A.X was diminished. To determine if RNS play a role in the altered sensitivity of SP-D(-/-) mice to radiation, iNOS(-/-)/SP-D(-/-) mice were used. Radiation-induced injury, oxidative stress, and tissue repair were generally similar in iNOS(-/-)/SP-D(-/-) and SP-D(-/-) mice. In contrast, TNF-α, CCL2, and CXCL2 expression was attenuated. These data indicate that although iNOS is involved in radiation-induced injury and altered SP-D structure, in the absence of SP-D, it functions to promote proinflammatory signaling. Thus, multiple inflammatory pathways contribute to the pathogenic response to radiation.