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Gut microbiota is regarded as the second human genome and forgotten organ, which is symbiotic with the human host and cannot live and exist alone. The gut microbiota performs multiple physiological functions and plays a pivotal role in host health and intestinal homeostasis. However, the gut microbiota can always be affected by various factors and among them, it is radiotherapy that results in gut microbiota 12dysbiosis and it is often embodied in a decrease in the abundance and diversity of gut microbiota, an increase in harmful bacteria and a decrease in beneficial bacteria, thereby affecting many disease states, especially intestine diseases. Furthermore, gut microbiota can produce a variety of metabolites, among which short-chain fatty acids (SCFAs) are one of the most abundant and important metabolites. More importantly, SCFAs can be identified as second messengers to promote signal transduction and affect the occurrence and development of diseases. Radiotherapy can lead to the alterations of SCFAs-producing bacteria and cause changes in SCFAs, which is associated with a variety of diseases such as radiation-induced intestinal injury. However, the specific mechanism of its occurrence is not yet clear. Therefore, this review intends to emphasize the alterations of gut microbiota after radiotherapy and highlight the alterations of SCFAs-producing bacteria and SCFAs to explore the mechanisms of radiation-induced intestinal injury from the perspective of gut microbiota and its metabolite SCFAs.

The tumor microenvironment is essential for the formation and development of tumors. Cytokines in the microenvironment may affect the growth, metastasis and prognosis of tumors, and play different roles in different stages of tumors, of which transforming growth factor β (TGF-β) and tumor necrosis factor α (TNF-α) are critical. The two have synergistic and antagonistic effect on tumor regulation. The inhibition of TGF-β can promote the formation rate of tumor, while TGF-β can promote the malignancy of tumor. TNF-α was initially determined to be a natural immune serum mediator that can induce tumor hemorrhagic necrosis, it has a wide range of biological activities and can be used clinically as a target to immune diseases as well as tumors. However, there are few reports on the interaction between the two in the tumor microenvironment. This paper combs the biological effect of the two in different aspects of different tumors. We summarized the changes and clinical medication rules of the two in different tissue cells, hoping to provide a new idea for the clinical application of the two cytokines.

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Composition analysis of coal tar remains a challenging task because of its complex components. In this paper, the compositions of low temperature coal tar (LTCT) and the wash oil fraction of high temperature coal tar (HTCT) were studied. A thermogravimetric analyzer (TG) combined with gas chromatography–mass spectrometry (GC/MS) with the same temperature program was put forward to analyze the quantitative determination of the GC/MS analyzable part of coal tar, and the composition and distribution of the GC/MS unanalyzable part (300LTCT and 300HTCT obtained from TG at the final temperature of 300 °C) was investigated by a pyrolysis gas chromatography–mass spectrometer (Py-GC/MS). Results reveal that light compositions can be extracted by petroleum ether (PE) more effectively than heavy compositions. PE soluble fractions of LTCT and HTCT cannot be totally gasified by GC/MS, and the remaining parts at above 300 °C are 6.51 wt % and 4.99 wt %, respectively. GC/MS combined with TG can accurately analyze the composition of ≤300 °C fractions in coal tar. Four dehydrogenation reactions were presented in the fast pyrolysis process of coal tar. An intermolecular association occurs in 300HTCT. 300LTCT is mainly composed of phenols, aliphatics, and aromatics. The composition analysis of 300LTCT and 300HTCT by Py-GC/MS indicates that there are some bridge bonds in the macromolecular structure of coal tar, and they have broken down to produce small molecular weight of phenolic compounds and aromatic hydrocarbons during pyrolysis.