Xin He

Shanghai Jiao Tong University, Shanghai, Shanghai Shi, China

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Publications (5)6.34 Total impact

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    ABSTRACT: Synchrotron radiation (SR) X-ray has great potential for its applications in medical imaging and cancer treatment. In order to apply SR X-ray in clinical settings, it is necessary to elucidate the mechanisms underlying the damaging effects of SR X-ray on normal tissues, and to search for the strategies to reduce the detrimental effects of SR X-ray on normal tissues. However, so far there has been little information on these topics. In this study we used the testes of rats as a model to characterize SR X-ray-induced tissue damage, and to test our hypothesis that NAD(+) administration can prevent SR X-ray-induced injury of the testes. We first determined the effects of SR X-ray at the doses of 0, 0.5, 1.3, 4 and 40 Gy on the biochemical and structural properties of the testes one day after SR X-ray exposures. We found that 40 Gy of SR X-ray induced a massive increase in double-strand DNA damage, as assessed by both immunostaining and Western blot of phosphorylated H2AX levels, which was significantly decreased by intraperitoneally (i.p.) administered NAD(+) at doses of 125 and 625 mg/kg. Forty Gy of SR X-ray can also induce marked increases in abnormal cell nuclei as well as significant decreases in the cell layers of the seminiferous tubules one day after SR X-ray exposures, which were also ameliorated by the NAD(+) administration. In summary, our study has shown that SR X-ray can produce both molecular and structural alterations of the testes, which can be significantly attenuated by NAD(+) administration. These results have provided not only the first evidence that SR X-ray-induced tissue damage can be ameliorated by certain approaches, but also a valuable basis for elucidating the mechanisms underlying SR X-ray-induced tissue injury.
    International Journal of Physiology, Pathophysiology and Pharmacology 01/2012; 4(1):1-9.
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    ABSTRACT: Synchrotron radiation (SR) X-ray has characteristic properties such as coherence and high photon flux, which has excellent potential for its applications in medical imaging and cancer treatment. However, there is little information regarding the mechanisms underlying the damaging effects of SR X-ray on biological tissues. Oxidative stress plays an important role in the tissue damage induced by conventional X-ray, while the role of oxidative stress in the tissue injury induced by SR X-ray remains unknown. In this study we used the male gonads of rats as a model to study the roles of oxidative stress in SR X-ray-induced tissue damage. Exposures of the testes to SR X-ray at various radiation doses did not significantly increase the lipid peroxidation of the tissues, assessed at one day after the irradiation. No significant decreases in the levels of GSH or total antioxidation capacity were found in the SR X-ray-irradiated testes. However, the SR X-ray at 40 Gy induced a marked increase in phosphorylated H2AX - a marker of double-strand DNA damage, which was significantly decreased by the antioxidant N-acetyl cysteine (NAC). NAC also attenuated the SR X-ray-induced decreases in the cell layer number of seminiferous tubules. Collectively, our observations have provided the first characterization of SR X-ray-induced oxidative damage of biological tissues: SR X-ray at high doses can induce DNA damage and certain tissue damage during the acute phase of the irradiation, at least partially by generating oxidative stress. However, SR X-ray of various radiation doses did not increase lipid peroxidation.
    International Journal of Physiology, Pathophysiology and Pharmacology 01/2012; 4(2):108-14.
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    ABSTRACT: Numerous studies have indicated that four interacting factors, including oxidative stress, mitochondrial alterations, calcium dyshomeostasis and inflammation, play crucial pathological roles in multiple major neurological diseases, including stroke, Alzheimer's disease (AD) and Parkinson's disease (PD). Increasing evidence has also indicated that NAD(+) plays important roles in not only mitochondrial functions and energy metabolism, but also calcium homeostasis and inflammation. The key NAD(+)-consuming enzyme--poly(ADP-ribose) polymerase-1 (PARP-1) and sirtuins--have also been shown to play important roles in cell death and aging, which are two key factors in the pathology of multiple major age-dependent neurological diseases: PARP-1 plays critical roles in both inflammation and oxidative stress-induced cell death; and sirtuins also mediate the process of aging, cell death and inflammation. Thus, it is conceivable that increasing evidence has suggested that NAD(+) metabolism and NAD(+)-dependent enzymes are promising targets for treating a number of neurological illnesses. For examples, the key NAD(+)-dependent enzymes SIRT1 and SIRT2 have been indicated to strongly affect the pathological changes of PD and AD; PARP-1 inhibition can profoundly reduce the brain injury in the animal models of multiple neurological diseases; and administration of either NAD(+) or nicotinamide can also decrease ischemic brain damage. Future studies are necessary to further investigate the roles of NAD+ metabolism and NAD⁺-dependent enzymes in neurological diseases, which may expose novel targets for treating the debilitating illnesses.
    Current drug targets 12/2011; 13(2):222-9. · 3.93 Impact Factor
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    ABSTRACT: SIRT2 is a tubulin deacetylase, which can play either detrimental or beneficial roles in cell survival under different conditions. While it has been suggested that reduced SIRT2 expression in human gliomas may contribute to development of gliomas, there has been no study that directly determines the effects of decreased SIRT2 activity on the survival of glioma cells. In this study we applied both pharmacological and molecular approaches to determine the roles of SIRT2 in the survival of glioma cells. Our studies, by conducting such assays as flow cytometry-based Annexin V assay and caspase-3 immunostaining, have indicated that decreased SIRT2 activity leads to apoptosis of C6 glioma cells by caspase-3-dependent pathway. Our experiments have further shown that reduced SIRT2 activity produces necrosis of C6 glioma cells. Moreover, our study applying SIRT2 siRNA has also shown that decreased SIRT2 leads to both necrosis and apoptotic changes of C6 glioma cells. Collectively, our study has provided novel evidence indicating that SIRT2 activity plays a key role in maintaining the survival of glioma cells, and that reduced SIRT2 activity can induce both necrosis and caspase-3-dependent apoptosis of C6 glioma cells. These results have also suggested that inhibition of SIRT2 might become a novel therapeutic strategy for gliomas.
    Biochemical and Biophysical Research Communications 12/2011; 417(1):468-72. · 2.41 Impact Factor
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    ABSTRACT: Synchrotron radiation (SR) X-ray has great potential for its applications in both diagnosis and treatment of diseases, due to its characteristic properties including coherence, collimation, monochromaticity, and exceptional brightness. Great advances have been made regarding potential medical applications of SR X-ray in recent years, particularly with the development of the third generation of SR light sources. However, multiple studies have also suggested damaging effects of SR X-ray on biological samples ranging from protein crystals to cells and biological tissues. It has become increasingly important to conduct comprehensive studies on two closely related topics regarding SR X-ray in medical applications: The safety issues regarding the medical applications of SR X-ray and the fundamental mechanisms underlying the interactions between SR X-ray and biological tissues. In this article, we attempted to provide an overview of the literatures regarding these two increasingly significant topics. We also proposed our hypothesis that there are significant differences between the biological tissue-damaging mechanisms of SR X-ray and those of normal X-ray, due to the characteristic properties of SR X-ray such as high dose rate. Future studies are warranted to test this hypothesis, which may profoundly improve our understanding regarding the fundamental mechanisms underlying the interactions between light and matter. These studies would also constitute an essential basis for establishing the safety standard for the medical applications of SR X-ray.
    International Journal of Physiology, Pathophysiology and Pharmacology 01/2011; 3(4):243-8.