Role of LKB1 in migration and invasion of Cr(VI)-transformed human bronchial epithelial Beas-2B cells.

Hexavalent chromium [Cr(VI)] is a common human carcinogen associated with lung cancer and other pulmonary diseases as exposure to excessive Cr(VI) induces malignant transformation in human lung epithelial cells. The mechanism underlying its carcinogenicity is unclear in terms of how it facilitates metastases. Cr(VI) compounds are reported to briefly promote cell migration in a concentration-dependent manner and oncogene liver kinase B1 (LKB1) was reduced in Cr(VI)-transformed cells. Overexpression of LKB1 in Beas-2B-Cr [Cr(VI) malignantly transformed Beas-2B cells] suppressed cell migration and invasion and inactivated FAK, Src, MMP-2, GSK3ß, ß-catenin, and HEF1, which contribute to cell migration and invasion. Silencing LKB1 with siRNA promoted migration and invasion, and activated these downstream proteins. Long-term exposure to Cr(VI) enhanced the migration and invasiveness of Beas-2B cells and reduced the expression of LKB1, while activating these proteins as mentioned above. Data suggest that LKB1 may regulate downstream proteins such as FAK, Src, MMP-2, GSK3ß, ß-catenin, and HEF1, and affect the migration and invasiveness of Beas-2B-Cr cells.

Apigenin inhibits cell proliferation, migration, and invasion by targeting Akt in the A549 human lung cancer cell line.

Apigenin (APG), a widely distributed flavonoid in vegetables and fruits, with low toxicity, and a nonmutagenic characteristic, has been reported to have many targets. Evidence indicates that APG can inhibit the proliferation, migration, invasion, and metastasis of some tumor cells, but the mechanism, specifically in lung cancer, is unclear. The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway regulates a diverse set of cellular functions relevant to the growth and progression of lung cancer, including proliferation, survival, migration, and invasion. Our results showed that APG exerted anti-proliferation, anti-migration, and anti-invasion effects in A549 human lung cancer cells by targeting the PI3K/Akt signaling pathway. 3-(4, 5-dimethylthiszol-2-yl)-2, 5-diphenytetrazolium bromide assay and colony formation assay showed that APG suppressed cell proliferation in a dose-dependent and time-dependent manner. Cell motility and invasiveness were assayed using a wound healing and Transwell assay, suggesting that APG inhibited the migration and invasion of A549 cells. Western blot analyses were carried out to examine the Akt signaling pathways. The results confirmed that APG decreased Akt expression and its activation. Then, cells were transfected with Akt-active and Akt-DN plasmids separately. The migration and invasion of A549 cells were significantly changed, constitutively activating Akt or knocking down Akt, indicating that APG can suppress the migration and invasion of lung cancer cells by modulating the PI3K/Akt signaling pathway. Furthermore, the results indicated that APG not only suppressed phosphorylation of Akt, thereby preventing its activation, but also inhibited its downstream gene expression of matrix metalloproteinases-9, glycogen synthase kinase-3ß, and HEF1. Together, APG is a new inhibitor of Akt in lung cancer and a potential natural compound for cancer chemoprevention.

2D-DIGE and MALDI TOF/TOF MS analysis reveal that small GTPase signaling pathways may play an important role in cadmium-induced colon cell malignant transformation.

Cadmium is a toxic heavy metal present in the environment and in industrial materials. Cadmium has demonstrated carcinogenic activity that induces cell transformation, but how this occurs is unclear. We used 2D-DIGE and MALDI TOF/TOF MS combined with bioinformatics and immunoblotting to investigate the molecular mechanism of cadmium transformation. We found that small GTPases were critical for transformation. Additionally, proteins involved in mitochondrial transcription, DNA repair, and translation also had altered expression patterns in cadmium treated cells. Collectively, our results suggest that activation of small GTPases contributes to cadmium-induced transformation of colon cells.

Acidification sensitivity and critical loads of acid deposition for surface waters in China.

Although decades of severe acid deposition have not resulted in serious surface water acidification in China, at present, the risk of some freshwaters becoming acidified cannot be neglected. To know more clearly about the possible impact acid deposition would have on Chinese surface waters, it is necessary to study the sensitivity of those surface waters to acidification and their critical loads of acid deposition on a national scale. Here we assess the acidification sensitivity of Chinese surface waters using an approach based on geology, soils, land use and hydrological conditions. Critical loads of S, N and acidity were also evaluated by a first-order acidity balance (FAB) model. Results show that most surface waters in China have very high critical loads of S and acidity and are not susceptible to acidification. Surface waters can be divided into three groups according to both sensitivity classes and critical loads. The few most sensitive surface waters are located in the northern part of Daxinganling region, with critical loads of S deposition and acidity lower than 2 keq ha(-1) year(-1). Surface waters in the northeastern region draining dark brown forest soils and in southern China belong to the second class of acidification sensitivity and their critical loads of S and acidity are generally between 2 and 15 keq ha(-1) year(-1), indicating they are not likely to be acidified under any flow conditions. Surface waters in other parts of China will not be acidified to any degree, with critical loads much higher than 15 keq ha(-1) year(-1). The magnitude and spatial distribution pattern of acidification sensitivity have significant similarity to the critical loads of S and acidity for Chinese surface waters. Although most surface waters are not likely to be acidified, attention should still be paid to the possible adverse impact acid deposition would have, especially in northeastern China, where the surface waters are the most sensitive, and the southern region, where acid pollution is among the most severe in China.

Bactericidal/permeability-increasing protein originates in both the testis and the epididymis and localizes in mouse spermatozoa.

Bactericidal/permeability-increasing protein (BPI) is an endogenous antibiotic protein with activity against gram-negative bacteria. In the present study, we examined the expression of BPI in postnatal mouse testes and epididymides as well as the subcellular localization within epididymal spermatozoa. Our results showed that, BPI mRNA was expressed in testis and epididymis independently. Throughout the epididymis, the BPI protein level gradually decreased in the epididymal epithelium in a spatial manner, specialized within the cytoplasm of clear cells in the cauda part. We detected BPI proteins in intact acrosome, implying its testicular origin; on the other hand, after the acrosome reaction, BPI proteins were observed dispersed across the entire sperm head, especially enriched at the equatorial segment. Our findings suggested a dual origin of the BPI that generated both in the testis and epididymis, and associated with mouse spermatozoa. BPI protein might be involved in the dynamics modification of the sperm plasma membrane and also the fertilization process.

[Calculating of critical loads of sulfur deposition for surface waters in southern China using a steady-state acidification model].

In order to study the response of Chinese surface waters to acid deposition, a steady-state model based on acidity balance was applied in this paper to calculate critical loads of sulphur deposition for surface waters in southern China. An empirical equation for Chinese surface waters was obtained to calculate the background sulfate concentration. The results showed that the critical loads of sulphur deposition for most surface waters in southern China were more than 2.0 keq.(hm2.a)-1, indicating that they were not sensitive to acidification. Surface waters with critical loads less than 2.0 keq.(hm2.a)-1 were those waters located on mountains. Except these mountain waters, the critical loads of sulphur deposition for other surface waters were not exceeded by the present sulphur deposition, indicating acidification will not occur in the near future for these waters. The spatial distribution of critical load exceedance was similar with that of the critical loads, showing the trend of increasing from the southeastern provinces, such as Fujian, Guangdong and Jiangxi, to the southwestern and the central region. The uncertainty analysis of the model results indicated that, the errors of the results caused by the uncertainty of parameters and the input data were minor and acceptable so long as the input data were among the appropriate ranges.

[Estimating critical loads of sulfur and nitrogen for Chinese soils by steady state method].

Supported by the geographical information system (GIS), critical loads of sulfur and nitrogen of Chinese soils were estimated through the steady state method. Results showed that the lowest critical loads of sulfur [< 0.3 g.(m2.a)-1] occurred on the Daxingan Mountain, Xiaoxingan Mountain and Changbai Mountain in northeast China, the valley of the Yaluzangbu River on the south of the Tibetan Plateau, and the catchments of the Nu River and the Lancang River in the southwest of Yunan province. However, the critical loads of southeast China, where acid deposition was very high, were intermediate and in the range of 0.8-3.2 g.(m2.a)-1. According to the critical loads of sulfur, China might be divide into two parts approximately by the 400 mm isohyet-the northwest part could generally tolerate more than 3.2 g.(m2.a)-1 sulfur deposition, but the southeast one could not. Dislike the distribution of the critical loads of sulfur, the critical loads of nitrogen were low in the west China and high in the east. The lowest critical loads of nitrogen [< 1.0 g.(m2.a)-1] occurred on the west of the Tibetan Plateau and on the Alashan Plateau, and the highest [> 4.0 g.(m2.a)-1] on the Dongbei Plain, the Huabei Plain, the Changjiangzhongxiayou Plain, and the Sichuan Basin, etc.

[Mapping critical loads of acid deposition for Chinese surface waters using a steady-state method].

In order to evaluate the response of Chinese surface waters to acid deposition, a steady-state method based on acidity balance was applied to map critical loads of acid deposition for surface waters in China. The results show that the critical loads of sulfur deposition for Chinese surface waters had distinct spatial distributions. Surface waters sited in the north of Daxinganling region have lowest critical loads of sulfur deposition, most of that were lower than 2 keq.(hm2.a)-1. Critical loads of sulfur deposition for those southern surface waters were within the range of 2-10 keq.(hm2.a)-1, while in the other parts of China, most surface waters had critical loads of sulfur deposition higher than 10 keq.(hm2.a)-1. The spatial and values pattern of critical loads of acidity for Chinese surface waters were very similar with that of the critical loads of sulfur deposition. Since critical loads of acidity for most Chinese surface waters were more than 2 keq.(hm2.a)-1, it can be concluded that they were not sensitive to acidification and that acidification will not occur in the near future for most these waters.

[Vegetation uptake of nitrogen and base cation in China and its role in soil acidification].

Vegetation uptake of nitrogen and base cation, as well as acid deposition, is an important source of soil acidity. Based on the net primary productivity and elemental composition, the uptake rate of nitrogen and base cation was estimated for each vegetation type in China. Result showed that the uptake rate of nitrogen was commonly low in southeast China and high in northwest China, and decreased gradually from southeast to northwest in northwest China. In addition, the uptake rate of base cation was very high (> 2.0 keq.(hm2.a)-1) for subtropical/tropical broadleaf evergreen forest, temperate limestone broadleaf deciduous forest, temperate deciduous shrub, and subtropical/tropical savanna in the northeast of Huabei Plain, the south of Yunan province, and the west of Hainan Island respectively, and low (< 0.5 keq.(hm2.a)-1) for subtropical evergreen coniferous forest in east China and deserts and steppes in arid region of west China. Although vegetation uptake caused no increase of soil acidity in almost all areas in China, the acidity input caused by vegetation uptake was quite high (> 0.5 keq.(hm2.a)-1) and even higher than the current acid deposition in some areas, where soil acidification might happen because the total acidity input exceeded the alkalinity produced by soil weathering.

[Calculating critical load of acid deposition with dynamic model].

Any natural ecosystem is a steady system which will ultimately approach a new steady state when it receives a fixed quantity of acid deposition. Dynamic models can be used to predict the changing potential of the chemical state of an ecosystem under different acid depositions. According to the theory of signal and system, this potential can be modeled by the first-order exponential attenuation function to get the value of chemical index when the ecosystem achieves steady state. A dose-response curve can be obtained according to the different quantity of acid deposition and the corresponding steady-state values of chemical index. Consequently, the critical load for an ecosystem can be evaluated from the dose-response curve, i.e., the quantity of acid deposition under which the steady-state value of the chemical index will achieve the critical chemical value. Taking MAGIC as an example, this method was applied to estimate critical loads of S deposition for a water body on Emei Mountain in Sichuan province and a lake on Nanshan Mountain in Chongqing city, the values being 1.54 and 6.51 keq.(hm2.a)-1, respectively. Through comparing the critical loads calculated using the method proposed in this paper with the target loads calculated with MAGIC and the critical loads estimated using SSWC method, it can be concluded that the method proposed in this paper are reasonable in estimating critical loads of acid deposition.

[Calculating critical loads of acid deposition with different percentiles in China].

While mapping critical loads of acid deposition in China, the 1 degree (latitude) x 1 degree (longitude) resolution was always adopted in critical load calculation. However, the results of mapping can not show the difference of sensitivity of ecosystems to acid deposition within a 1 degree x 1 degree grid. For the convenience of policy-makers to formulate acid deposition control strategies based on critical loads, and to improve the representation and practicability of 1 degree x 1 degree results, a series of critical load maps with different percentiles were compiled, which may be accordance with a given economic or technological level, and allows some degree of damage. Based on the cumulative distribution function, the critical load exceedance maps with different percentiles and the maximum allowable deposition of each province was also derived.

[Mapping sensitivity of surface waters to acidification in China].

Acidification of surface waters can be decided by some environmental factors, such as soil's buffering capacity, neutralization capacity of bedrock to acid deposition and types of land use, among which the most important factor is the soil's resistance to acidification. Therefore, information about soils, geology and land use can be used to predict the regional occurrence of acidification surface waters under different flows. In this paper, information and data about Chinese soils, geology and land use types were collected to determine and to map the sensitivity of surface waters to acidification. Results showed that in China, most surface waters were not sensitive to acidification. The few most sensitive surface waters were located in the north part of Northeastern China, accounting for 2.67% of all the country land. It was the combined results of strongly acidified ortho podzolic soil, acidified bedrock and coniferous forest. Surface waters which were not very sensitive to acidification were distributed both in the region of dark brown forest soil in Northeastern China and in the ferralsol and yellow-brown earth area in Southern China, occupying 15.2% of all the country land. The other surface waters which distributed on 82.11% of all the country land were not sensitive to acidification at all. Most in the Northern China because of the high resistance of soils to acidification and the others were in the Southern China where calcareous soils and agricultural lands were widely distributed. Since soils were quite resistant to acid, acidification of surface waters of large area will not likely occur in the southern region of China suffering from heavy acid deposition in the near future. Nevertheless, the acid deposition in Northern China should be controlled as soon as possible in case that acidified surface waters will be found there.