Xiangwen Xiao - Academia.edu (original) (raw)

Papers by Xiangwen Xiao

Research paper thumbnail of Ursolic acid induces apoptosis through mitochondrial intrinsic pathway and caspase-3 activation in M4Beu melanoma cells

International Journal of Cancer, 2005

Over the coming years, skin cancer could become a significant public health problem. Previous res... more Over the coming years, skin cancer could become a significant public health problem. Previous results indicate that ursolic acid (UA), a pentacyclic triterpene acid, has pleiotropic biologic activities such as antiinflammatory and antiproliferative activities on cancer cells. As UA represents a promising chemical entity for the protection of human skin, in agreement with tests done by the cosmetic industry, we investigated its effects on the M4Beu human melanoma cell line. In this report, we demonstrated for the first time that UA had a significant antiproliferative effect on M4Beu, associated with the induction of an apoptotic process, characterized by caspase-3 activation, the downstream central effector of apoptosis. We demonstrated that UA-induced apoptosis was dependent on the mitochondrial intrinsic pathway, as shown by transmembrane potential collapse (⌬⌿m) and by alteration of the Bax-Bcl-2 balance, with a concomitant increase in Bax expression and decrease in Bcl-2 expression. We also showed that UA-induced ⌬⌿m was associated with apoptosis-inducing factor leakage from mitochondria. Taken together, our results suggest that UA-induced apoptosis on M4Beu cells is accomplished via triggering of mitochondrial pathway. In conclusion, UA could be an encouraging compound in the treatment or prevention of skin cancer and may represent a new promising anticancer agent in the treatment of melanoma.

Research paper thumbnail of Adaptive responses to progressive drought stress in two Populus cathayana populations

Silva Fennica, 2008

The young, vegetatively propagated cuttings of Populus cathayana Rehder were exposed to a progres... more The young, vegetatively propagated cuttings of Populus cathayana Rehder were exposed to a progressive drought stress for 12 weeks in a greenhouse to characterize the physiological and biochemical basis of drought adaptation in woody plants. Two contrasting populations were employed in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that the adaptive responses of P. cathayana to drought were affected by drought intensity and poplar genotype (population). The progressive drought stress significantly inhibited plant growth, increased carotenoid contents and, at the same time, accumulated soluble sugars and free proline in the plants of both populations tested. On the other hand, the gradually increasing drought also induced antioxidative systems including the increase of the activities of superoxide dismutase (SOD) and guaiacol peroxidase (POD). Moreover, there were different responses to progressive drought stress between t...

Research paper thumbnail of Sex-specific responses of Populus cathayana to drought and elevated temperatures

Plant, Cell & Environment, 2008

Dioecious plant species represent an important component of terrestrial ecosystems. Yet, little i... more Dioecious plant species represent an important component of terrestrial ecosystems. Yet, little is known about sex-specific responses to drought and elevated temperatures. Populus cathayana Rehd, which is a dioecious, deciduous tree species, widely distributed in the northern, central and southwestern regions of China, was employed as a model species in our study. In closed-top chamber experiments, sex-specific morphological, physiological and biochemical responses of P. cathayana to drought and different elevated temperatures were investigated. Compared with the controls, drought significantly decreased the growth and the net photosynthesis rate (A), and increased the intrinsic water use efficiency (WUE(i)), carbon isotope composition (delta13C), and the malondialdehyde (MDA) and abscisic acid (ABA) contents in droughted plants. In contrast, elevated temperatures significantly promoted the growth and the A, but decreased the WUE(i), delta13C, MDA and ABA contents in well-watered individuals. When compared with males, elevated temperatures induced well-watered females to express a greater increase in the height growth (HG), basal diameter (BD), leaf area (LA), total number of leaves (TNL), dry matter accumulation (DMA) and specific leaf area (SLA), and a lower decrease in the A value, transpiration (E), stomatal conductance (g(s)), MDA and ABA contents, while elevated temperatures induced drought-stressed females to exhibit lower values of HG, BD, LA, TNL, DMA, A, E, g(s) and the intercellular CO2 concentration (C(i)), and higher levels of SLA, WUE(i), delta13C, MDA and ABA contents. Our results indicated that the female individuals of P. cathayana are more responsive and suffer from greater negative effects than do males when grown under environments with increased drought stress and elevated temperature.

Research paper thumbnail of Salt stress responses in Populus cathayana Rehder

Plant Science, 2009

An integrated physiological, biochemical and proteomic approach was used to systematically invest... more An integrated physiological, biochemical and proteomic approach was used to systematically investigate the salt stress responses of Populus cathayana Rehder. Cuttings of a one-year-old female clone were used. Saline treatments had the NaCl concentrations of 0, 50 and 100 mM added to full-strength Hoagland's solution. Salinity significantly decreased the relative water content (RWC) of leaves, the contents of chlorophyll a and chlorophyll b, CO 2 assimilation rate (A) and stomatal conductance (gs) in both salt stress treatments, which suggested that the chloroplast function was affected by salt stress. The observed increases of H 2 O 2 and malondialdehyde (MDA) contents, and electrolyte leakage suggested that salinity caused cellular damage, whereas the increases in compatible solutes and in the activities of antioxidant enzymes enhanced the salt tolerance. Total proteins of the leaves were extracted by a combination of TCA-acetone and phenol, and separated by two-dimensional gel electrophoresis at pH 4-7. More than 1000 protein spots were reproducibly detected on each gel, and 38 salt-responsive proteins were successfully identified by peptide mass fingerprint (PMF). Although the proteins identified in this investigation represent only a very small part of poplar leaf proteins, some of the novel salt-responsive proteins identified here may be involved in physiological and biochemical responses to salt stress in P. cathayana, while the other identified proteins play a role in numerous cellular functions, including signal transduction, mRNA processing and the regulation of the cell cycle. The analysis of physiological and proteomic alterations, and the identification of stress-related proteins contribute to knowledge of salt acclimation in poplar.

Research paper thumbnail of Physiological and proteomic responses of two contrastingPopulus cathayanapopulations to drought stress

Physiologia Plantarum, 2009

Research paper thumbnail of Responses to drought stress in two poplar species originating from different altitudes

Biologia plantarum, 2009

Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes ... more Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes in the eastern Himalaya, respectively, were examined during one growing season in a greenhouse to determine their responses to drought stress (soil moisture decreased from 100 to 55 or 25 % field capacity). Compared to control plants grown under 100 % field capacity, those poplars grown under 55 and 25 % field capacity possessed lower increases in height and stem diameter, and higher contents of soluble sugars, free proline, malondialdehyde (MDA) and hydrogen peroxide, and higher activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR). Compared with P. cathayana with greater leaf area, P. kangdingensis with greater root/shoot ratio exhibited lower MDA and H 2 O 2 contents, higher soluble sugar and free proline contents, and higher activities of CAT, SOD, POD, APX and GR. These results suggested that P. kangdingensis was more drought tolerant than P. cathayana.

Research paper thumbnail of Leaf morphological and physiological responses to drought and shade in two Populus cathayana populations

Biologia plantarum, 2009

Cuttings from two contrasting Populus cathayana Rehder populations originating from Hanyuan (wet ... more Cuttings from two contrasting Populus cathayana Rehder populations originating from Hanyuan (wet climate) and Ledu (dry climate) in western China were grown in a greenhouse to determine the effects of drought, shade and their interaction on the morphological and physiological traits of leaves. The dry climate population was more droughttolerant than the wet climate population, as indicated by smaller decreases in the leaf relative water content (RWC) and net photosynthetic rate (P N), as well as by greater increases in antioxidative enzyme activities and free proline content under drought. On the other hand, the negative effects of shade on leaf traits were more pronounced in the dry climate population, which suggested that the dry climate population was more light-demanding. In addition, moderate shade alleviated the drought stress of P. cathayana not only by improving the leaf RWC but also by maintaining the positive carbon balance. In contrast, severe shade aggravated drought stress as indicated by a pronounced decrease in leaf size, carbon and nitrogen contents, maximum P N , free proline content and antioxidative enzyme activities.

Research paper thumbnail of Ursolic acid induces apoptosis through mitochondrial intrinsic pathway and caspase-3 activation in M4Beu melanoma cells

International Journal of Cancer, 2005

Over the coming years, skin cancer could become a significant public health problem. Previous res... more Over the coming years, skin cancer could become a significant public health problem. Previous results indicate that ursolic acid (UA), a pentacyclic triterpene acid, has pleiotropic biologic activities such as antiinflammatory and antiproliferative activities on cancer cells. As UA represents a promising chemical entity for the protection of human skin, in agreement with tests done by the cosmetic industry, we investigated its effects on the M4Beu human melanoma cell line. In this report, we demonstrated for the first time that UA had a significant antiproliferative effect on M4Beu, associated with the induction of an apoptotic process, characterized by caspase-3 activation, the downstream central effector of apoptosis. We demonstrated that UA-induced apoptosis was dependent on the mitochondrial intrinsic pathway, as shown by transmembrane potential collapse (⌬⌿m) and by alteration of the Bax-Bcl-2 balance, with a concomitant increase in Bax expression and decrease in Bcl-2 expression. We also showed that UA-induced ⌬⌿m was associated with apoptosis-inducing factor leakage from mitochondria. Taken together, our results suggest that UA-induced apoptosis on M4Beu cells is accomplished via triggering of mitochondrial pathway. In conclusion, UA could be an encouraging compound in the treatment or prevention of skin cancer and may represent a new promising anticancer agent in the treatment of melanoma.

Research paper thumbnail of Adaptive responses to progressive drought stress in two Populus cathayana populations

Silva Fennica, 2008

The young, vegetatively propagated cuttings of Populus cathayana Rehder were exposed to a progres... more The young, vegetatively propagated cuttings of Populus cathayana Rehder were exposed to a progressive drought stress for 12 weeks in a greenhouse to characterize the physiological and biochemical basis of drought adaptation in woody plants. Two contrasting populations were employed in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that the adaptive responses of P. cathayana to drought were affected by drought intensity and poplar genotype (population). The progressive drought stress significantly inhibited plant growth, increased carotenoid contents and, at the same time, accumulated soluble sugars and free proline in the plants of both populations tested. On the other hand, the gradually increasing drought also induced antioxidative systems including the increase of the activities of superoxide dismutase (SOD) and guaiacol peroxidase (POD). Moreover, there were different responses to progressive drought stress between t...

Research paper thumbnail of Sex-specific responses of Populus cathayana to drought and elevated temperatures

Plant, Cell & Environment, 2008

Dioecious plant species represent an important component of terrestrial ecosystems. Yet, little i... more Dioecious plant species represent an important component of terrestrial ecosystems. Yet, little is known about sex-specific responses to drought and elevated temperatures. Populus cathayana Rehd, which is a dioecious, deciduous tree species, widely distributed in the northern, central and southwestern regions of China, was employed as a model species in our study. In closed-top chamber experiments, sex-specific morphological, physiological and biochemical responses of P. cathayana to drought and different elevated temperatures were investigated. Compared with the controls, drought significantly decreased the growth and the net photosynthesis rate (A), and increased the intrinsic water use efficiency (WUE(i)), carbon isotope composition (delta13C), and the malondialdehyde (MDA) and abscisic acid (ABA) contents in droughted plants. In contrast, elevated temperatures significantly promoted the growth and the A, but decreased the WUE(i), delta13C, MDA and ABA contents in well-watered individuals. When compared with males, elevated temperatures induced well-watered females to express a greater increase in the height growth (HG), basal diameter (BD), leaf area (LA), total number of leaves (TNL), dry matter accumulation (DMA) and specific leaf area (SLA), and a lower decrease in the A value, transpiration (E), stomatal conductance (g(s)), MDA and ABA contents, while elevated temperatures induced drought-stressed females to exhibit lower values of HG, BD, LA, TNL, DMA, A, E, g(s) and the intercellular CO2 concentration (C(i)), and higher levels of SLA, WUE(i), delta13C, MDA and ABA contents. Our results indicated that the female individuals of P. cathayana are more responsive and suffer from greater negative effects than do males when grown under environments with increased drought stress and elevated temperature.

Research paper thumbnail of Salt stress responses in Populus cathayana Rehder

Plant Science, 2009

An integrated physiological, biochemical and proteomic approach was used to systematically invest... more An integrated physiological, biochemical and proteomic approach was used to systematically investigate the salt stress responses of Populus cathayana Rehder. Cuttings of a one-year-old female clone were used. Saline treatments had the NaCl concentrations of 0, 50 and 100 mM added to full-strength Hoagland's solution. Salinity significantly decreased the relative water content (RWC) of leaves, the contents of chlorophyll a and chlorophyll b, CO 2 assimilation rate (A) and stomatal conductance (gs) in both salt stress treatments, which suggested that the chloroplast function was affected by salt stress. The observed increases of H 2 O 2 and malondialdehyde (MDA) contents, and electrolyte leakage suggested that salinity caused cellular damage, whereas the increases in compatible solutes and in the activities of antioxidant enzymes enhanced the salt tolerance. Total proteins of the leaves were extracted by a combination of TCA-acetone and phenol, and separated by two-dimensional gel electrophoresis at pH 4-7. More than 1000 protein spots were reproducibly detected on each gel, and 38 salt-responsive proteins were successfully identified by peptide mass fingerprint (PMF). Although the proteins identified in this investigation represent only a very small part of poplar leaf proteins, some of the novel salt-responsive proteins identified here may be involved in physiological and biochemical responses to salt stress in P. cathayana, while the other identified proteins play a role in numerous cellular functions, including signal transduction, mRNA processing and the regulation of the cell cycle. The analysis of physiological and proteomic alterations, and the identification of stress-related proteins contribute to knowledge of salt acclimation in poplar.

Research paper thumbnail of Physiological and proteomic responses of two contrastingPopulus cathayanapopulations to drought stress

Physiologia Plantarum, 2009

Research paper thumbnail of Responses to drought stress in two poplar species originating from different altitudes

Biologia plantarum, 2009

Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes ... more Cuttings of Populus kangdingensis and Populus cathayana, originating from high and low altitudes in the eastern Himalaya, respectively, were examined during one growing season in a greenhouse to determine their responses to drought stress (soil moisture decreased from 100 to 55 or 25 % field capacity). Compared to control plants grown under 100 % field capacity, those poplars grown under 55 and 25 % field capacity possessed lower increases in height and stem diameter, and higher contents of soluble sugars, free proline, malondialdehyde (MDA) and hydrogen peroxide, and higher activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR). Compared with P. cathayana with greater leaf area, P. kangdingensis with greater root/shoot ratio exhibited lower MDA and H 2 O 2 contents, higher soluble sugar and free proline contents, and higher activities of CAT, SOD, POD, APX and GR. These results suggested that P. kangdingensis was more drought tolerant than P. cathayana.

Research paper thumbnail of Leaf morphological and physiological responses to drought and shade in two Populus cathayana populations

Biologia plantarum, 2009

Cuttings from two contrasting Populus cathayana Rehder populations originating from Hanyuan (wet ... more Cuttings from two contrasting Populus cathayana Rehder populations originating from Hanyuan (wet climate) and Ledu (dry climate) in western China were grown in a greenhouse to determine the effects of drought, shade and their interaction on the morphological and physiological traits of leaves. The dry climate population was more droughttolerant than the wet climate population, as indicated by smaller decreases in the leaf relative water content (RWC) and net photosynthetic rate (P N), as well as by greater increases in antioxidative enzyme activities and free proline content under drought. On the other hand, the negative effects of shade on leaf traits were more pronounced in the dry climate population, which suggested that the dry climate population was more light-demanding. In addition, moderate shade alleviated the drought stress of P. cathayana not only by improving the leaf RWC but also by maintaining the positive carbon balance. In contrast, severe shade aggravated drought stress as indicated by a pronounced decrease in leaf size, carbon and nitrogen contents, maximum P N , free proline content and antioxidative enzyme activities.