Metabolic characterization of Hyoscyamus niger root-specific putrescine N-methyltransferase.

N-methylputrescine is the precursor of nicotine and pharmaceutical tropane alkaloids such as hyoscyamine. Putrescine N-methyltransferase (PMT) catalyzes the N-methylation of putrescine to form N-methylputrescine. While the role of PMT in nicotine biosynthesis is clear, knowledge of PMT in the biosynthesis of tropane alkaloids (TAs) and the regulation of polyamines remains limited. We characterized a PMT gene from Hyoscyamus niger, designated HnPMT that was specifically expressed in roots, especially in the secondary roots and dramatically induced by methyl jasmonate (MeJA). The GUS gene was specifically expressed in Arabidopsis roots or in the vascular tissues, including pericycles and endodermis, of the H. niger hairy root cultures, when it was driven by the 5'-flanking promoter region of HnPMT. The recombinant HnPMT was purified for enzymatic assays. HnPMT converted putrescine to form N-methylputrescine, as confirmed by LC-MS. The kinetics analysis revealed that HnPMT had high affinity with putrescine but low catalytic activity, suggesting that it was a rate-limiting enzyme. When HnPMT was suppressed in the H. niger plants by using the VIGS approach, the contents of N-methylputrescine and hyoscyamine were markedly decreased, but the contents of putrescine, spermidine and a mixture of spermine and thermospermine were significantly increased; this suggested that HnPMT was involved in the biosynthesis of tropane alkaloids and played a competent role in regulating the biosynthesis of polyamines. Functional identification of HnPMT facilitated the understanding of TA biosynthesis and thus implied that the HnPMT-catalyzed step might be a target for metabolic engineering of the TA production in H. niger.

Ligustrazine suppresses neuron apoptosis via the Bax/Bcl-2 and caspase-3 pathway in PC12 cells and in rats with vascular dementia.

The aim of this study was to examine the comprehensive neuroprotective mechanism of ligustrazine, which is extracted from Ligusticum Chuanxiong Hort., against vascular dementia (VD) in rats and apoptosis in oxygen and glucose deprivation (OGD) PC12 cells. Rats were subjected to bilateral common carotid artery occlusion (BCCAO) surgery and administered ligustrazine intragastrically for 6 weeks. At the end of the experiments, the hippocampal biomarkers brain-derived neurotrophic factor (BDNF), monocyte chemotactic protein 1 (MCP-1), and homocysteine (Hcy) were examined. In experiments in vitro, OGD PC12 cells were treated with ligustrazine for 0.5, 1, 3, 6, 12, or 24 h. The cell-released biomarkers BDNF, MCP-1, and Hcy were examined. Microscopy, acridine orange-ethidium bromide (AO/EB) staining, and flow cytometry assays were performed to investigate apoptosis. Cleaved caspase-3, Bcl-2 associated X protein (Bax), and B cell lymphoma 2 (Bcl-2) expression was examined using Western blot assays. The results showed that biomarkers, including MCP-1 and Hcy, were significantly increased in both the in vivo and in vitro models, while the BDNF level was significantly decreased compared with the sham or vehicle models. Microscopy, AO/EB staining, and flow cytometry analysis showed that severe cell damage occurred in OGD PC12 cells, and apoptosis played a major role in this environment. Further Western blot studies showed that the apoptosis-related Bax/Bcl-2 protein ratio and cleaved caspase-3 were significantly increased in the experiment. However, ligustrazine profoundly suppressed the imbalance of these biomarkers, reduced cell damage, decreased the Bax/Bcl-2, and downregulated cleaved caspase-3. Pro- and anti-apoptotic biomarkers of multiple pathways including BDNF, MCP-1, and Hcy played a joint role in triggering the activation of the mitochondria-related Bax/Bcl-2 and caspase-3 apoptosis pathway in VD. Ligustrazine attenuated VD by comprehensively regulating BDNF, MCP-1, and Hcy and inactivating the Bax/Bcl-2 and caspase-3 apoptosis pathway. Our data provide novel insight into ligustrazine, which is a promising neuroprotective agent for VD disease treatment strategies. © IUBMB Life, 70(1):60-70, 2018.

Enhancing Tropane Alkaloid Production Based on the Functional Identification of Tropine-Forming Reductase in Scopolia lurida, a Tibetan Medicinal Plant.

Scopolia lurida, a native herbal plant species in Tibet, is one of the most effective producers of tropane alkaloids. However, the tropane alkaloid biosynthesis in this plant species of interest has yet to be studied at the molecular, biochemical, and biotechnological level. Here, we report on the isolation and characterization of a putative short chain dehydrogenase (SDR) gene. Sequence analysis showed that SlTRI belonged to the SDR family. Phylogenetic analysis revealed that SlTRI was clustered with the tropine-forming reductases. SlTRI and the other TA-biosynthesis genes, including putrescine N-methyltransferase (SlPMT) and hyoscyamine 6ß-hydroxylase (SlH6H), were preferably or exclusively expressed in the S. lurida roots. The tissue profile of SlTRI suggested that this gene might be involved in tropane alkaloid biosynthesis. By using GC-MS, SlTRI was shown to catalyze the tropinone reduction to yield tropine, the key intermediate of tropane alkaloids. With the purified recombinant SlTRI from Escherichiacoli, an enzymatic assay was carried out; its result indicated that SlTRI was a tropine-forming reductase. Finally, the role of SlTRI in promoting the tropane alkaloid biosynthesis was confirmed through metabolic engineering in S. lurida. Specifically, hairy root cultures of S. lurida were established to investigate the effects of SlTRI overexpression on tropane alkaloid accumulation. In the SlTRI-overexpressing root cultures, the hyoscyamine contents were 1.7- to 2.9-fold higher than those in control while their corresponding scopolamine contents were likewise elevated. In summary, this functional identification of SlTRI has provided for a better understanding of tropane alkaloid biosynthesis. It also provides a candidate gene for enhancing tropane alkaloid biosynthesis in S. lurida via metabolic engineering.

Rabbit conjunctivae edema and release of NO, TNF-α, and IL-1ß from macrophages induced by fractions and esculentosides isolated from Phytolacca americana.

CONTEXT: The roots of Phytolacca americana L. (Phytolaccaceae) may be toxic. Despite heated controversy over the toxic compounds of P. americana, especially esculentosides, relevant studies remain scarce. OBJECTIVE: The objective of this study is to screen the toxic fractions and compounds of P. americana, to determine the controlling indices, and to provide evidence for unraveling the mechanism. MATERIALS AND METHODS: Petroleum ether (PE), CH2Cl2, n-BuOH, and water fractions were isolated from 70% ethanol extract of P. americana. The n-BuOH fraction was dissolved in 50% ethanol and precipitated by adding ethyl ether. The resultant supernatants and precipitates were referred to as SUPs and SEDs fractions, respectively. SUPs fraction was separated by column chromatography into four main stimulating esculentosides that were identified by HR-ESI/MS and NMR as EsA, EsB, EsC, and EsF. The irritating effects of esculentosides on rabbit conjunctivae (500 µg/eye) was observed by pathological examination and those on macrophages (5, 25, 50 and 100 µg/mL) were evaluated by detecting changes of NO, TNF-α, and IL-1ß levels. RESULTS AND DISCUSSION: n-BuOH, SUP fractions, and EsC induced severe conjunctival edema. The four esculentosides induced dose-dependent releases of proinflammatory mediators NO, TNF-α, and IL-1ß from macrophages, and releasing amounts peaked after 2 h of treatment. EsC and EsF induced macrophages to release mediators most significantly. EsC (50 µg/mL) functioned more effectively than EsF did, and similarly n-BuOH and SUPs fractions functioned more effectively than the esculentoside mixture. Thus, the four esculentosides exerted proinflammatory effects synergistically. CONCLUSION: All extracted esculentosides, especially EsC, induced inflammatory stimulation. Phytolacca americana-induced irritation of the gastrointestinal tract may be associated with esculentosides such as EsC.

Pinellia ternata lectin exerts a pro-inflammatory effect on macrophages by inducing the release of pro-inflammatory cytokines, the activation of the nuclear factor-κB signaling pathway and the overproduction of reactive oxygen species.

Pinellia ternata (PT) is a widely used traditional Chinese medicine. The raw material has a throat-irritating toxicity that is associated with the PT lectin (PTL). PTL is a monocot lectin isolated from the tubers of PT, which exhibits mouse peritoneal acute inflammatory effects in vivo. The present study aimed to investigate the pro-inflammatory effect of PTL on macrophages. PTL (50 µg/ml)­stimulated macrophages enhanced the chemotactic activity of neutrophils. PTL (50, 100, 200 and 400 µg/ml) significantly elevated the production of cytokines [tumor necrosis factor­α (TNF-α) , interleukin (IL)­1ß and IL­6]. PTL (25, 50 and 100 µg/ml) induced intracellular reactive oxygen species (ROS) overproduction. PTL also caused transfer of p65 from the macrophage cytoplasm to the nucleus and activated the nuclear factor­κB (NF­κB) signaling pathway. Scanning electron microscope images revealed severe cell swelling and membrane integrity defection of macrophages following PTL (100 µg/ml) stimulation, which was also associated with inflammation. PTL had pro­inflammatory activity, involving induced neutrophil migration, cytokine release, ROS overproduction and the activation of the NF-κB signaling pathway, which was associated with the activation of macrophages.

[Antagonistic effect of gingerols against TNF-α release, ROS overproduction and RIP3 expression increase induced by lectin from Pinellia ternata].

To explore the antagonistic effect of gingerols against the inflammation induced by lectin from Pinellia ternata. In this study, ELISA method was used to determine the effect of different extracts from gingerols on the release of inflammatory factor TNF-α from macrophages induced by lectin from P. ternata. The fluorescence probe was used to determine the effect of gingerols on the changes in ROS of macrophages induced by lectin from P. ternata. The western-blot method was applied to study the effect of gingerols on the increase in expression of cell receptor interacting protein RIP3 in macrophages induced by lectin from P. ternata. The scanning electron microscope (SEM) was used to study the effect of gingerols on morphological changes in macrophages induced by lectin from P. ternata. According to the results, gingerols can significantly inhibit the release of inflammatory factor from macrophages induced by lectin from P. ternata, ROS overproduction and increase in RIP3 expression. SEM results showed that gingerols can inhibit the cytomorphosis and necrocytosis induced by lectin from P. ternata. Fresh ginger's detoxication may be related to gingerols' effects in inhibiing release of inflammatory factor, ROS overproduction and increase in RIP3 expression caused by macrophages induced by lectin from P. ternata, which are mainly inflammatory development.

[Comparative study on toxicity of extracts from Phytolaccae Radix before and after being processed with vinegar].

OBJECTIVE: To extract and separate toxic components from Phytolaccae Radix, and to comare the changes in toxicity of Phytolaccae Radix before and after being processed with vinegar. METHOD: The mucous membrane irritation response, mouse peritoneal inflammation model and in vitro macrophages release NO model were applied to compared the changes in inflammatory toxicity of toxic components from Phytolaccae Radix before and after being processed with vinegar. RESULT: Toxic components of Phytolacca Radix had significant inflammatory toxicity, which could cause conjunctival edema in rabbits, and increase of PGE2 and macrophages release NO content in peritoneal exudate in mice. After being processed with vinegar, they showed reduced irritation, which resulted in decrease of PGE2 and macrophages release NO content in peritoneal exudate in mice. CONCLUSION: After being processed with vinegar, the toxicity of toxic components from Phytolacca Radix decreased obviously.

A liquid chromatography-tandem mass spectrometry method for pharmacokinetics and tissue distribution of a camptothecin quaternary derivative in rats.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to identify and quantify the camptothecin quaternary derivative CPT8 for application in pharmacokinetics and tissue distribution studies. Rat plasma and tissue samples were extracted with methanol by using camptothecin as the internal standard (IS). Chromatographic separation of CPT8 and the IS was achieved using a Hypersil GOLD C18 column, with a flow rate of 1.0 mL/min followed by quantification with tandem mass spectrometry, operating with electrospray ionization in the positive ion mode and by applying multiple reaction monitoring. The MS/MS ion transitions were monitored at m/z 484.3-361.2 for CPT8 and m/z 349.0-305.2 for the IS (CPT). A calibration curve was constructed using CPT8 concentrations ranging from 2.5 ng/mL to 2500 ng/mL (r>0.993). The efficiency of CPT8 extraction from plasma and tissue samples ranged from 91.23% to 105.4%. Intra- and inter-day precision (relative standard deviation) values were 0.21% and 7.25%, respectively. No matrix effects were observed. The freeze-thaw stability, post-extraction stability, and stability following short- and long-term storage at low temperatures ranged from 84.12% to 108.2%. The preclinical data obtained using this method is expected to facilitate future clinical investigations of CPT8.

[Study on inflammatory effect of toxic raphides from Pinellia ternate and its correlation with macrophages].

OBJECTIVE: To study the toxic mechanism of toxic raphides from Pinellia ternata. METHOD: Mouse peritoneal macrophage in vitro culture model was adopted to study dose-dependent and time-dependent curves of toxic raphides, with TNF-alpha, IL-1beta and IL-6 in supernatant as indexes. Scanning electron microscopy was used to observe the changes in surface morphology of raphides-treated macrophages. Macrophages-neutrophils co-cultured the transport model to study the effect of toxic raphides' stimulation of macrophages on neutrophils migration. RESULT: Toxic raphides' stimulation of macrophages could cause the increase in the levels of TNF-alpha, IL-1beta and IL-6 released, and showed dose dependence and time dependence. Scanning electron microscopy showed that toxic raphides were swallowed by macrophages, with notable cell membrane creases, increase in the number of pseudopods and decrease in integrity of cell membranes, and could significantly induce migration of neutrophils. CONCLUSION: The inflammatory process induced by toxic raphides is mainly mediated by macrophages. The toxic mechanism of toxic raphides from P. ternata is that toxic raphides penetrate into tissues to activate resident macrophages, release phagocytic and inflammatory cytokines, and cause migration of neutrophils, which finally results in acute inflammatory response.

[Comparative study on pro-inflammatory toxicity of Pinellia pedatiecta before and after being processed with alum].

OBJECTIVE: To explore the pro-inflammatory toxicity of Pinellia pedatiecta, as well as the alum processing method on its pro-inflammatory effect. METHOD: Raphide and agglutinin (PPA) proteins were isolated from fresh P. pedatiecta. The overall animal and cellular level models were applied to investigate the pro-inflammatory effect of raphide and PPA in P. pedatiecta, as well as the impact of the alum processing method on the pro-inflammatory effect, with inflammatory mediators as the index. RESULT: Intraperitoneal injection with P. pedatiecta raphide suspension could significantly increase the content of inflammatory mediators PGE2 and NO. After the alum processing method was adopted, fresh P. pedatiecta and raphide-induced PGE2 and NO release significantly reduced. The stimulation of mice macrophages with P. pedatiecta agglutinin protein could cause the content of dose-dependent inflammatory mediators TNF-alpha and IL-6. After the alum processing method was adopted, PGE2 content in P. pedatiecta agglutinin protein-induced mice peritoneal exudate notably decreased. CONCLUSION: The irritation and toxicity of P. pedatiecta were inflammatory responses in organisms. Its raphide and agglutinin proteins were toxic components, both could cause significant the release of inflammatory medium. The alum processing method could help significantly reduce the pro-inflammatory toxicity of P. pedatiecta.

[Study on new toxicity-reducing methods of pinellia rhizoma prepared by ethanol (I)-new methods and technology].

OBJECTIVE: To explore new toxicity-reducing methods of Pinellia Rhizoma prepared by ethanol and the latest technical parameters. METHOD: Pinellia Rhizoma is prepared with ethanol. The orthogonal experimental design was adopted for investigating amount of ethanol, preparing time, ethanol concentration and preparing temperature. The optimal technology was determined by the comprehensive score of toxicological indicators of PGE2 content of rat celiac percolate, with the rabbit conjunctival irritation test as the intuitive validation on toxicology reduction. The pharmacodynamics validation was used to determine the reasonability of the preparation process. RESULT: The optimal technology was that Pinellia Rhizoma was prepared by 75% ethanol at the temperature of 60 degrees C by 4 days, and then dried. The effect of relieving cough, reducing sputum and anti-inflammatory of Pinellia Rhizoma is not reduced after prepared by ethanol. CONCLUSION: The optimal technology of Pinellia Rhizoma prepared by ethanol is simple and reasonable that it can be used as the new method to reduce toxicity and keep efficacy of Pinellia Rhizoma.