Bacillus altitudinis AD13-4 Enhances Saline-Alkali Stress Tolerance of Alfalfa and Affects Composition of Rhizosphere Soil Microbial Community.

Saline and alkaline stresses limit plant growth and reduce crop yield. Soil salinization and alkalization seriously threaten the sustainable development of agriculture and the virtuous cycle of ecology. Biofertilizers made from plant growth-promoting rhizobacteria (PGPR) not only enhance plant growth and stress tolerance, but also are environmentally friendly and cost-effective. There have been many studies on the mechanisms underlying PGPRs enhancing plant salt resistance. However, there is limited knowledge about the interaction between PGPR and plants under alkaline-sodic stress. To clarify the mechanisms underlying PGPR's improvement of plants' tolerance to alkaline-sodic stress, we screened PGPR from the rhizosphere microorganisms of local plants growing in alkaline-sodic land and selected an efficient strain, Bacillus altitudinis AD13-4, as the research object. Our results indicate that the strain AD13-4 can produce various growth-promoting substances to regulate plant endogenous hormone levels, cell division and differentiation, photosynthesis, antioxidant capacity, etc. Transcriptome analysis revealed that the strain AD13-4 significantly affected metabolism and secondary metabolism, signal transduction, photosynthesis, redox processes, and plant-pathogen interactions. Under alkaline-sodic conditions, inoculation of the strain AD13-4 significantly improved plant biomass and the contents of metabolites (e.g., soluble proteins and sugars) as well as secondary metabolites (e.g., phenols, flavonoids, and terpenoids). The 16S rRNA gene sequencing results indicated that the strain AD13-4 significantly affected the abundance and composition of the rhizospheric microbiota and improved soil activities and physiochemical properties. Our study provides theoretical support for the optimization of saline-alkali-tolerant PGPR and valuable information for elucidating the mechanism of plant alkaline-sodic tolerance.

CD13 Inhibition Enhances Cytotoxic Effect of Chemotherapy Agents.

Multidrug resistance (MDR) of hepatocellular carcinoma is a serious problem. Although CD13 is a biomarker in human liver cancer stem cells, the relationship between CD13 and MDR remains uncertain. This study uses liver cancer cell model to understand the role of CD13 in enhancing the cytotoxic effect of chemotherapy agents. Cytotoxic agents can induce CD13 expression. CD13 inhibitor, bestatin, enhances the antitumor effect of cytotoxic agents. Meanwhile, CD13-targeting siRNA and neutralizing antibody can enhance the cytotoxic effect of 5-fluorouracil (5FU). CD13 overexpression increases cell survival upon cytotoxic agents treatment, while the knockdown of CD13 causes hypersensitivity of cells to cytotoxic agents treatment. Mechanistically, the inhibition of CD13 leads to the increase of cellular reactive oxygen species (ROS). BC-02 is a novel mutual prodrug (hybrid drug) of bestatin and 5FU. Notably, BC-02 can inhibit cellular activity in both parental and drug-resistant cells, accompanied with significantly increased ROS level. Moreover, the survival time of Kunming mice bearing H22 cells under BC-02 treatment is comparable to the capecitabine treatment at maximum dosage. These data implicate a therapeutic method to reverse MDR by targeting CD13, and indicate that BC-02 is a potent antitumor compound.

Synthesis and biological evaluation of novel benzofuroxan-based pyrrolidine hydroxamates as matrix metalloproteinase inhibitors with nitric oxide releasing activity.

On the basis of the strategy of "multifunctional drugs", a series of novel matrix metalloproteinase inhibitors (MMPIs) containing benzofuroxan scaffold as a nitric oxide donor were designed, synthesized and evaluated. All synthesized compounds, especially 16a, exhibited potent MMP-2,9 inhibitory activities, anti-proliferative activities and could produce high levels of NO in Hela cells. They were also evaluated for both of their anti-invasion and anti-angiogenesis effects. Furthermore, compared with LY52, 16a demonstrated competitive antitumor activity in vivo. These hybrid NO-MMPIs might offer suitable scaffolds to develop valuable MMP inhibitors for the further discovery of novel anti-cancer drugs.

Discovery of Novel Pazopanib-Based HDAC and VEGFR Dual Inhibitors Targeting Cancer Epigenetics and Angiogenesis Simultaneously.

Herein a novel series of pazopanib hybrids as polypharmacological antitumor agents were developed based on the crosstalk between histone deacetylases (HDACs) and vascular endothelial growth factor (VEGF) pathway. Among them, one ortho-aminoanilide 6d and one hydroxamic acid 13f exhibited considerable total HDACs and VEGFR-2 inhibitory activities. The HDAC inhibitory activities endowed 6d and 13f with potent antiproliferative activities, which was not observed in the approved VEGFR inhibitor pazopanib. Compounds 6d and 13f possessed comparable HDAC isoform selectivity profiles to the clinical class I HDAC inhibitor MS-275 and the approved pan-HDAC inhibitor SAHA, respectively. 6d and 13f also exhibited uncompromised multiple tyrosine kinases inhibitory activities relative to pazopanib. The intracellular dual inhibition to HDAC and VEGFR of 6d and 13f was validated by Western blot analysis. In both HUVECs tube formation assay and rat thoracic aorta rings assay, 6d and 13f showed comparable antiangiogenic potencies to pazopanib. What's more, 6d possessed desirable pharmacokinetic profiles with the oral bioavailability of 72% in SD rats and considerable in vivo antitumor efficacy in a human colorectal adenocarcinoma (HT-29) xenograft model.

Design, Synthesis, and Biological Evaluation of Pyrazoline-Based Hydroxamic Acid Derivatives as Aminopeptidase†N (APN) Inhibitors.

Aminopeptidase N (APN) has been recognized as a target for anticancer treatment due to its overexpression on diverse malignant tumor cells and association with cancer invasion, metastasis and angiogenesis. Herein we describe the synthesis, biological evaluation, and structure-activity relationship study of two new series of pyrazoline analogues as APN inhibitors. Among these compounds, 5-(2-(2-(hydroxyamino)-2-oxoethoxy)phenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-carboxamide (compound 13 e) showed the best APN inhibition with an IC50 value of 0.16±0.02 µm, which is more than one order of magnitude lower than that of bestatin (IC50 =9.4±0.5 µm). Moreover, compound 13 e was found to inhibit the proliferation of diverse carcinoma cells and to show potent anti-angiogenesis activity. At the same concentration, compound 13 e presents significantly higher anti-angiogenesis activity than bestatin in human umbilical vein endothelial cells (HUVECs) capillary tube formation assays. The putative binding mode of 13 e in the active site of APN is also discussed.

Synthesis and biological characterization of ubenimex-fluorouracil conjugates for anti-cancer therapy.

Previously a novel ubenimex-fluorouracil (5-FU) conjugate, BC-01 was identified and validated as a potent CD13 inhibitor with marked in vitro and in vivo antitumor potency. Herein, further structural modifications of the linker part of BC-01 was carried out to get more potent and stable ubenimex-fluorouracil conjugates. It was striking that most of these conjugates showed even more potent CD13 inhibitory activities than BC-01 and the approved CD13 inhibitor ubenimex. One representative compound 12a displayed significant in vitro anti-proliferation, pro-apoptosis, anti-metastasis, anti-angiogenesis and CD13+ cell elimination effects. In vitro stability and in vivo pharmacokinetic study revealed that compound 12a could release ubenimex and 5-FU slowly, which could act as a mutual prodrug of ubenimex and 5-FU. Compared with 5-FU or 5-FU plus ubenimex, 12a exhibited superior in vivo antitumor growth efficiency, even in our mice model of 5-FU-resistant liver cancer. Moreover, 12a exhibited more potent in vivo anti-metastasis and lifespan extension effects compared to the approved 5-FU prodrug capecitabine. Collectively, these results suggest that further optimization and evaluation of 12a as a promising anticancer candidate are warranted to develop effective therapeutic agents for human liver cancer.

Selective HDAC inhibitors with potent oral activity against leukemia and colorectal cancer: Design, structure-activity relationship and anti-tumor activity study.

Previously, we reported the discovery of a series of N-hydroxycinnamamide-based HDAC inhibitors, among which compound 11y exhibited high HDAC1/3 selectivity. In this current study, structural derivatization of 11y led to a new series of benzamide based HDAC inhibitors. Most of the compounds exhibited high HDACs inhibitory potency. Compound 11a (with 4-methoxybenzoyl as N-substituent in the cap and 4-(aminomethyl) benzoyl as the linker group) exhibited selectivity against HDAC1 to some extent, and showed potent antiproliferative activity against several tumor cell lines. In vivo studies revealed that compound 11a displayed potent oral antitumor activity in both hematological tumor cell U937 xenograft model and solid tumor cell HCT116 xenograft model with no obvious toxicity. Further modification of benzamide 3, 11a and 19 afforded new thienyl and phenyl compounds (50a, 50b, 63a, 63b and 63c) with dramatic HDAC1 and HDAC2 dual selectivity, and the fluorine containing compound 56, with moderate HDAC3 selectivity.

Discovery of a novel chimeric ubenimex-gemcitabine with potent oral antitumor activity.

Herein, a novel mutual prodrug BC-A1 was discovered by integrating ubenimex and gemcitabine into one molecule. Biological characterization revealed that compound BC-A1 could maintain both the anti-CD13 activity of ubenimex and the cytotoxic activity of gemcitabine in vitro. Further characterization also demonstrated that compound BC-A1 exhibited significant anti-invasion and anti-angiogenesis effects in vitro. The preliminary stability test of BC-A1 revealed that it could release gemcitabine in vitro. The in vivo anti-tumor results in liver cancer showed that at the same dosage, oral administration of BC-A1 was as potent as intraperitoneal administration of gemcitabine. This warranted the further research and development of the orally active prodrug BC-A1 because gemcitabine can not be orally administrated in clinic.

Discovery of BC-01, a novel mutual prodrug (hybrid drug) of ubenimex and fluorouracil as anticancer agent.

We designed and synthesized a novel mutual prodrug, named BC-01 (3), by integrating ubenimex and Fluorouracil (5-FU) into one molecule based on prior research results that showed that a combination of the aminopeptidase N (CD13) inhibitor, ubenimex, and the cytotoxic antitumor agent, 5-FU, exhibited improved in vitro and in vivo antitumor efficiency. 3 showed potent inhibitory activity against CD13 enzymatic activity. Compared with ubenimex, 3 exhibited more potent anti-angiogenesis effects, and compared with the approved 5-FU prodrug, capecitabine, 3 exhibited more potent tumor growth inhibitory and anti-metastasis effects. Additionally, compared with 5-FU or 5-FU plus ubenimex, 3 also exhibited a superior antitumor efficiency even in our 5-FU-resistant mice model. Other antitumor agents could be conjugated with ubenimex using this strategy to obtain novel mutual prodrugs with promising antitumor potency.

Design, synthesis and preliminary biological evaluation of 4-aminopyrazole derivatives as novel and potent JAKs inhibitors.

JAKs inhibitors were widely applied in the treatment of immunodeficiency diseases, inflammation and cancers. We designed and synthesized a novel series of 4-aminopyrazole derivatives, which showed inhibitory potency against various JAKs. The in vitro protein kinase inhibition experiment indicated that compounds 17k, 17l, 17m and 17n could inhibit JAKs effectively. Among them, compound 17m possessed the highest protein kinase inhibitory rates (%) at 10µM, which were 97, 96 and 100 to JAK1, JAK2 and JAK3, respectively. Further evaluation revealed that the IC50 values of 17m against JAK1, JAK2 and JAK3 were 0.67µM, 0.098µM and 0.039µM, respectively. Moreover, western blotting results showed compound 17m could inhibit the phosphorylation of JAK2 in Hela cells effectively. The data supports the further investigation of these compounds as novel JAKs inhibitors.

LJNK, an indoline-2,3-dione-based aminopeptidase N inhibitor with promising antitumor potency.

In our previous study, we found that LJNK showed potent aminopeptidase N (APN)-inhibitory activity. In the current study, we further evaluated the antitumor effects of LJNK both in vitro and in vivo. Enzyme experiments showed that LJNK showed better inhibitory activity than bestatin against APN both from human carcinoma cells' surface and from porcine kidney microsomes. In addition, LJNK could suppress rat aortic ring microvessel growth and HUVEC tubular structure formation, which showed its stronger antiangiogenesis effects than bestatin. [(3-[4,5-Dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide)] assay and clonogenic assay showed that LJNK suppressed cancer cell growth both in the short and the long term. Mice bearing H22 transplantation tumor proved its antitumor effects in vivo. Annexin V-fluorescein isothiocyanate/propidium iodide assay showed that LJNK could induce 28.1% PLC/PRF/5 cell apoptosis and the apoptotic pathway was probably identified by western blot. The above-mentioned results suggested that LJNK inhibited cell proliferation and angiogenesis, and induced apoptosis by decreasing APN activity.

Novel leucine ureido derivatives as aminopeptidase N inhibitors. Design, synthesis and activity evaluation.

Aminopeptidase N (APN/CD13) over-expressed on tumor cells and tumor microenvironment, plays critical roles in tumor invasion, metastasis and angiogenesis. Here we described the design, synthesis and preliminary activity studies of novel leucine ureido derivatives as aminopeptidase N (APN/CD13) inhibitors. The results showed that compound 7a had the most potent inhibitory activity against APN with the IC50 value of 20 nM, which could be used for further anticancer agent research.

Design, synthesis, and antitumor evaluation of histone deacetylase inhibitors with L-phenylglycine scaffold.

In our previous research, a novel series of histone deacetylase (HDAC) inhibitors with L-phenylglycine scaffold were designed and synthesized, among which amides D3 and D7 and ureido D18 were far superior to the positive control (suberoylanilide hydroxamic acid [SAHA]) in HDAC inhibition, but were only comparable to SAHA in antiproliferation on tumor cell lines. Herein, further structural derivation of lead compounds D3, D7, and D18 was carried out to improve their cellular activities. Most of our newly synthesized compounds exhibited more potent HDAC inhibitory activities than the positive control SAHA, and several derivatives were even better than their parent compounds. However, compared with SAHA and our lead compounds, only secondary amine series compounds exhibited improved antiproliferative activities, likely due to their appropriate topological polar surface area values and cell permeabilities. In a human histiocytic lymphoma (U937) xenograft model, the most potent secondary amine 9d exhibited similar in vivo antitumor activity to that of SAHA.

Enhanced anticancer activity of 5-FU in combination with Bestatin: Evidence in human tumor-derived cell lines and an H22 tumor-bearing mouse.

The clinical use of 5-fluorouracil (5-FU) is increasingly limited by low response rates, adverse reactions, and toxicity. A drug combination offers a new strategy for appropriate use of 5-FU. Bestatin, an aminopeptidase N (APN) inhibitor, has been used as an adjuvant chemotherapy drug because of its actions to suppress tumorigenesis and invasion. The current study evaluated the anticancer efficacy of 5-FU plus Bestatin at the cellular and animal level. The combination killed more colonic cancer, hepatic carcinoma, and ovarian cancer cells and fewer nonmalignant human embryonic kidney (HEK293) and Chinese hamster ovary (CHO) cells than 5-FU or Bestatin alone. Moreover, 41.58% of ES-2 and 20.86% of PLC/PRF/5 cell apoptosis was caused by the combination of the two, while 5-FU caused apoptosis of 20.86% of ES-2 cells and 8.85% of PLC/PRF/5 cells. The cell cycle was arrested in the S and G0/G1 phases when a combination of the two was used. In an experiment involving mice bearing tumors, a combination of the two had a rate of tumor inhibition of 61.98%, while 5-FU alone had a rate of tumor inhibition of just 49.17%. In addition, the combination of the two was safer than either drug alone and did not cause weight loss or death. In conclusion, combining 5-FU and Bestatin could enhance the anticancer activity of 5-FU and decrease its cytotoxicity. These results suggest that 5-FU plus Bestatin has greater efficacy as a tumor therapy.

Micromagnetic resonance relaxometry for rapid label-free malaria diagnosis.

We report a new technique for sensitive, quantitative and rapid detection of Plasmodium spp.-infected red blood cells (RBCs) by means of magnetic resonance relaxometry (MRR). During the intraerythrocytic cycle, malaria parasites metabolize large amounts of cellular hemoglobin and convert it into hemozoin crystallites. We exploit the relatively large paramagnetic susceptibility of these hemozoin particles, which induce substantial changes in the transverse relaxation rate of proton nuclear magnetic resonance of RBCs, to infer the 'parasite load' in blood. Using an inexpensive benchtop 0.5-Tesla MRR system, we show that with minimal sample preparatory steps and without any chemical or immunolabeling, a parasitemia level of fewer than ten parasites per microliter in a volume below 10 µl of whole blood is detected in a few minutes. We demonstrate this method both for cultured Plasmodium falciparum parasites and in vivo with Plasmodium berghei-infected mice.

Synthesis and testing of chromogenic phenoxazinone substrates for beta-alanyl aminopeptidase.

Novel 7-N-(beta-alanyl)aminophenoxazin-3-one salts 27a-d have been synthesized and tested as chromogenic substrates for beta-alanyl aminopeptidase, which is present in Pseudomonas aeruginosa, the most common respiratory pathogen in patients with cystic fibrosis. The biological results show that 7-N-(beta-alanyl)amino-1-pentylphenoxazin-3-one trifluoroacetate salt 27a is a chromogenic substrate for this bacterium, with a low degree of diffusion in nutrient media for growing bacterial cultures and a bright red colour, making it easily distinguishable from the agar background.

Synthesis and evaluation of novel chromogenic peptidase substrates based on 9-(4'-aminophenyl)-10-methylacridinium salts as diagnostic tools in clinical bacteriology.

The synthesis and initial evaluation of novel chromogenic substrates with potential in the detection and differentiation of cultured bacterial colonies are described. The substrates were readily hydrolysed by specific aminopeptidase activity to release the chromogen, 9-(4'-aminophenyl)-10-methylacridinium salt, which provided a clear visual indication of the presence of the corresponding bacteria.