The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA2 and 15d-PGJ2) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.

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Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors

Radiation therapy is one of the most common treatment strategies for thorax malignancies One of the considerable limitations of this therapy is its toxicity to normal tissue The lung is the major dose-limiting organ for radiotherapy That is because ionizing radiation produces reactive oxygen species that induce lesions, and not only is tumor tissue damaged, but overwhelming inflammatory lung damage can occur in the alveolar epithelium and capillary endothelium This damage may result in radiation-induced pneumonitis and/or fibrosis While describing the lung response to irradiation generally, the main focus of this review is on cytokines and their roles and functions within the individual stages We discuss the relationship between radiation and cytokines and their direct and indirect effects on the formation and development of radiation injuries Although this topic has been intensively studied and discussed for years, we still do not completely understand the roles of cytokines Experimental data on cytokine involvement are fragmented across a large number of experimental studies; hence, the need for this review of the current knowledge Cytokines are considered not only as molecular factors involved in the signaling network in pathological processes, but also for their diagnostic potential A concentrated effort has been made to identify the significant immune system proteins showing positive correlation between serum levels and tissue damages Elucidating the correlations between the extent and nature of radiation-induced pulmonary injuries and the levels of one or more key cytokines that initiate and control those damages may improve the efficacy of radiotherapy in cancer treatment and ultimately the well-being of patients

Cytokines and radiation-induced pulmonary injuries.

Peroxisome proliferator-activated receptors (PPARs) belong to the family of ligand-activated nuclear receptors. The PPAR family consists of three subtypes encoded by three separate genes: PPARα (NR1C1), PPARβ/δ (NR1C2), and PPARγ (NR1C3). PPARs are critical regulators of metabolism and exhibit tissue and cell type-specific expression patterns and functions. Specific PPAR ligands have been proposed as potential therapies for a variety of diseases such as metabolic syndrome, cancer, neurogenerative disorders, diabetes, cardiovascular diseases, endometriosis, and retinopathies. In this review, we focus on the knowledge of PPAR function in angiogenesis, a complex process that plays important roles in numerous pathological conditions for which therapeutic use of PPAR modulation has been suggested.

PPARs and Angiogenesis-Implications in Pathology.

Structural analysis and cytotoxicity of host-guest inclusion complexes of cannabidiol with three native cyclodextrins

Radiation-induced lung injury (RILI) is the major complication of thoracic radiation therapy, and no effective treatment is available. This study explored the role of high-mobility group box 1 (HMGB1) in acute RILI and the therapeutic effect of glycyrrhizin, an inhibitor of HMGB1, on RILI. C57BL/6 mice received a 20 Gy dose of X-ray radiation to the whole thorax with or without administration of glycyrrhizin. Severe lung inflammation was present 12 weeks after irradiation, although only a mild change was noted at 2 weeks and could be alleviated by administration of glycyrrhizin. Glycyrrhizin decreased the plasma concentrations of HMGB1 and sRAGE as well as TNF-α, IL-1β and IL-6 levels in the bronchoalveolar lavage fluid (BALF). The expression of RAGE was decreased while that of TLR4 was significantly increased at 12 weeks, but not 2 weeks, after irradiation in mouse lung tissue. In vitro, the expression of TLR4 increased in RAW 264.7 cells after conditioning with the supernatant from the irradiated MLE-12 cells containing HMGB1 but showed no change when conditioned medium without HMGB1 was used. However, conditioned culture had no effect on RAGE expression in RAW 264.7 cells. Glycyrrhizin also inhibited the related downstream transcription factors of HMGB/TLR4, such as NF-κB, JNK and ERK1/2, in lung tissue and RAW 264.7 cells when TLR4 was activated. In conclusion, the HMGB1/TLR4 pathway mediates RILI and can be mitigated by glycyrrhizin.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jcmm.14703

Glycyrrhizin mitigates radiation-induced acute lung injury by inhibiting the HMGB1/TLR4 signalling pathway.

Ethyl pyruvate alleviates radiation-induced lung injury in mice.

Angiogenesis and inflammation are crucial processes through which the tumor microenvironment (TME) influences tumor progression. In this study, we showed that peroxisome proliferator-activated receptor γ (PPARγ) is not only expressed in CT26 and 4T1 tumor cell lines but also in cells of TME, including endothelial cells and tumor-associated macrophages (TAM). In addition, we showed that rosiglitazone may induce tumor vessel normalization and reduce TAM infiltration. Additionally, 4T1 and CT26 tumor-bearing mice treated with rosiglitazone in combination with radiotherapy showed a significant reduction in lesion size and lung metastasis. We reported that a single dose of 12 Gy irradiation strongly inhibits local tumor angiogenesis. Secretion of C-C motif chemokine ligand 2 (CCL2) in response to local irradiation facilitates the recruitment of migrating CD11b+ myeloid monocytes and TAM to irradiated sites that initiate vasculogenesis and enable tumor recurrence after radiotherapy. We found that rosiglitazone partially decreases CCL2 secretion by tumor cells and reduces the infiltration of CD11b+ myeloid monocytes and TAM to irradiated tumors, thereby delaying tumor regrowth after radiotherapy. Therefore, combination of the PPARγ agonist rosiglitazone with radiotherapy enhances the effectiveness of radiotherapy to improve local tumor control, decrease distant metastasis risks and delay tumor recurrence.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/cas.13650

Synergy between peroxisome proliferator-activated receptor γ agonist and radiotherapy in cancer.

e24012Background: Angiogenesis and inflammation are crucial processes, through which the tumor microenvironment (TME) influences tumor growth, invasion and metastasis PPARγ agonist rosiglitazone h

Guodong Huang

Papers

Ethyl pyruvate alleviates radiation-induced lung injury in mice.

Synergy between peroxisome proliferator-activated receptor γ agonist and radiotherapy in cancer.

PPARγ agonist to inhibit tumor progression by modulating tumor microenvironment.