Supplementary sulfide during inoculation for improved sulfur autotrophic denitrification performance and adaptation to low temperature.

Elemental sulfur (S0) autotrophic denitrification (SAD) has been considered an advanced denitrification technology due to its low operating cost and small secondary pollution in wastewater treatment plants. However, the wide application of this technology is still challenged by its low denitrification rate, long start-up time, and poor low-temperature adaptation. This study employed supplementary sulfide to facilitate the conversion of S0 into polysulfide, a critical step in SAD. Batch experiments indicated that more polysulfide could be generated when S0 served as an electron donor and partnered with additional Na2S, leading to greatly increased nitrate removal than the controls. Particularly when the sulfide concentration was relatively high at 160 mg/L, a denitrification rate up to 11.3 mg-N/(L·d) was achieved, 3.8-fold of control group working with solely S0. Sulfide was further applied during inoculation of a packed bed reactor (PBR) with S0 particles and significantly benefit the development of biofilm. Although the feeding of sulfide was stopped after inoculation, the reactor was fast started up in just 2 days and delivered an average denitrification rate of 346.9 mg-N/(L·d), 1.4-fold of the control. In addition, benefit from the thick and well-developed biofilm, the reactor was able to restore its nitrate removal performance, when challenged by a low temperature (15 °C), to a larger rate than the control. Compared to short-term employment of the sulfide which was found a temporary solution addressing declined SAD rate during operating the PBR, applying sulfide for inoculation facilitated the formation of biofilm, leading to sustained improvement of SAD performance and better adaptation to coldness.

Pyrrolidine Dithiocarbamate Enhances the Cytotoxic Effect of Arsenic Trioxide on Acute Promyelocytic Leukemia Cells.

BACKGROUND: More than 95% patients with acute promyelocytic leukemia (APL) carry the PML-RARα fusion oncoprotein. Arsenic trioxide (ATO) is an efficacious therapeutic agent for APL, and the mechanism involves the binding with PML and degradation of PML-RARα protein. Pyrrolidine dithiocarbamate (PDTC) demonstrates the function of facilitating the cytotoxic effect of ATO. PURPOSE: To investigate whether PDTC is potential to enhance the cytotoxic effect of ATO to APL cells by acting on PML-RARα oncoproteins. METHODS: Inhibitory effects of drugs on cell viability were examined by CCK-8 test, and apoptosis was evaluated by flow cytometry. Western blotting and immunofluorescence assays were used to explore the mechanism. RESULTS: PDTC improved the effect of ATO on inhibiting proliferation of NB4 cells in vitro. Further, PDTC-ATO promoted apoptosis and cell cycle arrest in NB4 cells. The expression of caspase- 3 and Bcl-2 was reduced in PDTC-ATO-treated NB4 cells, while cleaved caspase-3 and Bax was up-regulated. Furthermore, less PML-RARα expression were found in PDTC-ATO-treated NB4 cells than that in NB4 cells treated with ATO singly. Laser confocal microscopy showed that protein colocalization of PML and RARα was disrupted more significantly by PDTC-ATO treatment than that with ATO monotherapy. CONCLUSION: In conclusion, PDTC enhanced the cytotoxic effect of ATO on APL, and the mechanism was, at least in part, related to the promotion of ATO-induced degradation of PML-RARα fusion protein via forming a complex PDTC-ATO.

Improved sulfur autotrophic denitrification using supplementary bovine serum albumin.

Excess nitrate presented in natural water body and drinking water has been a challenge for maintaining safe ecosystem and human health. Sulfur autotrophic denitrification is proved a feasible technology to remove nitrate from water environment. However, comparatively low rate of sulfur autotrophic denitrification needs to be addressed before wide application of this technology, which is a result of the low solubility of elemental sulfur. Therefore, this study employed bovine serum albumin (BSA) as a supplementary material to modify the elemental sulfur for improved sulfur autotrophic denitrification rate. Artificial biofilm of Thiobacillus denitrificans was prepared and employed in experiments. By testing different amount of BSA applied in both elemental sulfur and the biofilm, including 1 %, 2 % and 4 % mass ratios, it was found that larger employment of BSA had significant effect in increasing the denitrification rate. Particularly when 4 % BSA was added into elemental sulfur, the highest denitrification rate reached 26.8 mg-N/(L·d), 3.7 times of the control group. Meanwhile, the largest reaction rate constant was achieved, 4.13 mg0.5/(L0.5·d), 2.78 times of the control group. This effect was attributed to promoted conversion of elemental sulfur to polysulfide that was easily utilized by sulfur-oxidizing bacteria. A long-term operation (14 days) of packed bed reactor filled with sulfur particles and 1 % BSA delivered a much faster start-up than the control and outperformed it with better denitrification performance all-through the experiment. This result evidenced again that BSA could make a highly effective supplement in sulfur autotrophic denitrification.

Microbial response to multiple-level addition of grass organic matter in lake sediments with different salinity.

Water surface expansion of saline lakes usually causes the inundation of surrounding grassland, leading to the increase of terrestrial grass organic matter (OM) input to the lakes and the decrease of lake salinity. However, the influence of terrestrial grass OM input increase and salinity decrease on organic carbon mineralization and microbial community composition remains unknown in saline lakes. Here, microbial mineralization of terrestrial grass (Achnatherum splendens) OM at different quantity levels in lake sediments with different salinity was investigated by performing microcosm experiments. The results showed that the CO2 production rates increased with the increase of grass OM supply in the studied sediments with different salinity, which may be driven by certain microbial groups (e.g. Bacteroidota, Firmicutes, and Ascomycota). The increase of grass OM supply reduced the richness of prokaryotic community, which will decrease the size and complexity of the studied microbial networks, but increase the interaction between prokaryotic and fungal taxa. Taken together, our results suggest that the increase of terrestrial grass OM input caused by lake expansion would enhance the mineralization of organic carbon and affect the community composition and interactions of related microorganisms in lake sediments with different salinity.

Nitrite- and N2O-reducing bacteria respond differently to ecological factors in saline lakes.

The distribution of nitrite- and N2O-reducing bacteria is key to potential N2O emission from lakes. However, such information in highland saline lakes remains unknown. Here, we investigated the abundance and community composition of nitrite- and N2O-reducing bacteria in the sediments of six saline lakes on the Qing-Tibetan Plateau. The studied lakes covered a wide range of salinity (1.0-340.0 g/L). Results showed that in the studied saline lake sediments, nitrite-reducing bacteria were significantly more abundant than N2O-reducing bacteria, and their abundances ranged 7.14 × 103-8.26 × 108 and 1.18 × 106-6.51 × 107 copies per gram sediment (dry weight), respectively. Nitrite-reducing bacteria were mainly affiliated with α-, ß- and γ-Proteobacteria, with ß- and α-Proteobacteria being dominant in low- and high-salinity lakes, respectively; N2O-reducing bacterial communities mainly consisted of Proteobacteria (α-, ß-, γ- and δ-subgroups), Bacteroidetes, Verrucomicrobia, Actinobacteria, Chloroflexi, Gemmatimonadetes and Balneolaeota, with Proteobacteria and Bacteroidetes/Verrucomicrobia dominating in low- and high-salinity lakes, respectively. The nitrite- and N2O-reducing bacterial communities showed distinct responses to ecological factors, and they were mainly regulated by mineralogical and physicochemical factors, respectively. In response to salinity change, the community composition of nitrite-reducing bacteria was more stable than that of N2O-reducing bacteria. These findings suggest that nitrite- and N2O-reducing bacteria may prefer niches with different salinity.

Formulation Comprising Arsenic Trioxide and Dimercaprol Enhances Radiosensitivity of Pancreatic Cancer Xenografts.

OBJECTIVE: To investigate the efficacy of a formula comprising arsenic trioxide and dimercaprol (BAL-ATO) as a radiosensitizing agent in model mice with pancreatic cancer xenografts. METHODS: Female BALB/c nude mice bearing SW1990 human pancreatic cancer xenografts were divided into four treatment arms, including control, radiotherapy (RT), BAL-ATO, and RT + BAL-ATO groups. Survival and tumor volume were analyzed. We also assessed apoptosis in tumor samples by live imaging and detected hypoxia by confocal laser microscope observation. We further investigated the mechanisms of BAL-ATO action in RT by detecting affected proteins by western blot and immunohistochemistry assays. RESULTS: Median survival was significantly longer in the RT + BAL-ATO group (64.5 days) compared with the control (49.5 days), RT (39 days), and BAL-ATO (48 days) groups (P < 0.001). RT + BAL-ATO inhibited the growth of tumors in mice by 73% compared with the control group, which was significantly higher than the rate of inhibition following RT alone (59%) (P < 0.01). Further analysis showed an improved microenvironment in terms of hypoxia in tumors treated with BAL-ATO alone or RT + BAL-ATO. Expression of signaling molecules associated with pancreatic cancer stem cells, including CD24, CD44, ALDH1A1, Gli-1, and Nestin, was detected in tumors treated with BAL-ATO alone or in combination with RT. CONCLUSION: These data suggest that BAL-ATO function as a radiosensitizer in mice with pancreatic cancer xenografts, via mechanisms involving hypoxia reduction and inhibition of signaling pathways associated with pancreatic cancer stem cells. BAL-ATO may thus be a promising radiosensitizing agent in patients with pancreatic cancer.

Additional polypyrrole as conductive medium in artificial electrochemically active biofilm (EAB) to increase the sensitivity of EAB based biosensor in water quality early-warning.

Researchers believe that adding conductive mediums in electrochemically active biofilms (EABs) would improve the sensitivity of EAB-based biosensor for real-time water quality early-warning through facilitating the extracellular electron transfer (EET), which has been hardly evidenced mostly because naturally formed EABs employed in previous biosensor studies were recognized distinct and incapable of delivering comparable electrical signals. By preparing artificial EABs where Shewanella oneidensis MR-1 was encapsulated in sodium alginate (SA), this study solved how polypyrrole (PPy) as conductive medium would affect the sensitivity of EAB-based biosensor, as well as mass transfer of toxicant during this process. Different mass ratios (0.125:1, 0.25:1 and 1:1) of PPy over SA were tested, and the sensitivity promoted by 20%, 15% and 6%, respectively. Results indicated that a small amount of PPy addition (PPy: SA = 0.125: 1 in mass ratio) was more effective to increase the biosensor's sensitivity compared to larger amount of PPy employed in EAB. This was when improved conductivity introduced by PPy would dominate in affecting the sensitivity over contrarily weakened mass transfer in the meantime.

Artificial electrochemically active biofilm for improved sensing performance and quickly devising of water quality early warning biosensors.

A major challenge for devising an electrochemically active biofilm (EAB)-based biosensor for real-time water quality early-warning is the formation of EAB that requires several days to weeks. Besides the onerous and time-consuming preparation process, the naturally formed EABs are intensively concerned as they can hardly deliver repeatable electrical signals even at identical experimental conditions. To address these concerns, this study employed sodium alginate as immobilization agent to encapsulate Shewanella oneidensis MR-1 and prepared EAB for devising a biosensor in a short period of less than 1 h. The artificial EAB were found capable of delivering highly consistent electrical signals with each other when fed with the same samples. Morphology and bioelectrochemical properties of the artificial EAB were investigated to provide interpretations for these findings. Different concentrations of bacteria and alginate in forming the EAB were investigated for their effects on the biosensor's sensitivity. Results suggested that lower concentration of bacteria would be beneficial until it increased to 0.06 (OD660). Concentration of sodium alginate affected the sensitivity as well and 1% was found an optimum amount to serve in the formation of EAB. A long-term operation of the biosensor with artificial EAB for 110 h was performed. Clear warning signals for incoming toxicants were observed over random signal fluctuations. All results suggested that the artificial EAB electrode would support a rapid devised and highly sensitivity biosensor.

Pyrrolidine Dithiocarbamate Facilitates Arsenic Trioxide Against Pancreatic Cancer via Perturbing Ubiquitin-Proteasome Pathway.

PURPOSE: To investigate whether pyrrolidine dithiocarbamate (PDTC) could facilitate arsenic trioxide (ATO) to induce apoptosis in pancreatic cancer cells via perturbing ubiquitin-proteasome pathway. METHODS: Mass spectrometry was performed to examine the interaction between PDTC and ATO, and the data showed they could form a complex termed PDTC-ATO. Inhibiting effects on cell viability were examined by CCK-8 test, and apoptosis was examined by flow cytometry. Four treatment arms (n = 6), including the control, PDTC, ATO, and PDTC-ATO, were evaluated using BALB/c nude mouse models bearing a xenograft tumor of SW1990 human pancreatic cancer line. Western blot, immunohistochemistry assays were to detect the mechanism. RESULTS: The results showed that PDTC-ATO had higher inhibiting effects on proliferation of pancreatic cancer cells than ATO in vitro. In bearing-tumor mice, PDTC-ATO inhibited tumor growth by 79%, being more potent than ATO (by 46%) or PDTC (by 35%) compared to the control. Results of Western blot and immunohistochemistry showed proteasome inhibition and apoptotic cell death, together with obvious suppression of associating E3 ubiquitin ligase activity, occurred more frequently in tumors treated with PDTC-ATO than those with ATO. CONCLUSION: PDTC demonstrated the function to facilitate ATO against pancreatic cancer due to forming a stable complex to perturb ubiquitin-proteasome pathway.

A binuclear complex constituted by diethyldithiocarbamate and copper(I) functions as a proteasome activity inhibitor in pancreatic cancer cultures and xenografts.

It is a therapeutic strategy for cancers including pancreatic to inhibit proteasome activity. Disulfiram (DSF) may bind copper (Cu) to form a DSF-Cu complex. DSF-Cu is capable of inducing apoptosis in cancer cells by inhibiting proteasome activity. DSF is rapidly converted to diethyldithiocarbamate (DDTC) within bodies. Copper(II) absorbed by bodies is reduced to copper(I) when it enters cells. We found that DDTC and copper(I) could form a binuclear complex which might be entitled DDTC-Cu(I), and it had been synthesized by us in the laboratory. This study is to investigate the anticancer potential of this complex on pancreatic cancer and the possible mechanism. Pancreatic cancer cell lines, SW1990, PANC-1 and BXPC-3 were used for in vitro assays. Female athymic nude mice grown SW1990 xenografts were used as animal models. Cell counting kit-8 (cck-8) assay and flow cytometry were used for analyzing apoptosis in cells. A 20S proteasome assay kit was used in proteasome activity analysis. Western blot (WB) and immunohistochemistry (IHC) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were used in tumor sample analysis. The results suggest that DDTC-Cu(I) inhibit pancreatic cancer cell proliferation and proteasome activity in vitro and in vivo. Accumulation of ubiquitinated proteins, and increased p27 as well as decreased NF-κB expression were detected in tumor tissues of DDTC-Cu(I)-treated group. Our data indicates that DDTC-Cu(I) is an effective proteasome activity inhibitor with the potential to be explored as a drug for pancreatic cancer.

Arsenic trioxide inhibits viability of pancreatic cancer stem cells in culture and in a xenograft model via binding to SHH-Gli.

OBJECTIVE: Overexpression of the sonic hedgehog (SHH) signaling pathway is an essential characteristic of pancreatic cancer stem cells (PCSCs) and arsenic trioxide (ATO) is described as a SHH inhibitor. This study evaluates whether ATO has the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins. METHODS: Cell counting kit-8 and flow cytometry were used for analyzing apoptosis in cells in vitro. The animal model was an athymic nude mouse model bearing subcutaneous xenografts of SW1990 pancreatic cancer cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay and immunohistochemistry were used for tumor tissue analysis. The interaction between Gli1 and ATO was examined by a confocal system and an ultraviolet absorption spectrum assay. RESULTS: ATO induced apoptosis in pancreatic cancer cells, especially CD24(+)CD44(+) cells in vitro. Combination treatment of ATO and low dose gemcitabine inhibited tumor growth by 60.9% (P = 0.004), and decreased the expression of CD24, CD44, and aldehyde dehydrogenase 1 family, member A1 significantly in vivo. ATO changed the structure of the recombinant Gli1 zinc finger peptides in a cell-free condition and the binding action of ATO to recombinant Gli1 was observed in cultured pancreatic cancer cells. CONCLUSION: ATO may have the potential to inhibit viability of PCSCs via binding to SHH-Gli proteins in vitro and in vivo.

Advances in Smoothened-targeting therapies for pancreatic cancer: implication for drug discovery from herbal medicines.

Smoothened (SMO) is a member of sonic hedgehog homology (SHH) signaling pathway. It plays a key role as a bridge between patched-1 (PTCH-1) and Gli. Aberrant SHH expression can be detected in various malignant tissues, and the expression in pancreatic cancer stem cells is higher apparently. SHH signals are closely associated with self-duplication of cancer stem cells, formation of tumor vessels as well as matrixes. SMO antagonists such as cyclopamine, GDC-0449 and so on show potential to inhibit activity of SHH signaling, and arrest the growth as well as metastases of tumors. Recently, a few of SMO antagonists have been studied in phase I clinical trials and some are in phase II, meanwhile, phase I or II trials of SMO antagonists to treat pancreatic cancer are performed currently. As the classical SMO antagonist, cyclopamine is extracted from a medicinal plant. Perhaps researchers may be able to determine more effective SMO-targeting drugs from herbal medicines in the future.