Combination of microbial and chemical synthesis for the sustainable production of ß-elemene, a promising plant-extracted anticancer compound.

Beta-elemene, a class of sesquiterpene derived from the Chinese medicinal herb Curcuma wenyujin, is widely used in clinical medicine due to its broad-spectrum antitumor activity. However, the unsustainable plant extraction prompted the search for environmentally friendly strategies for ß-elemene production. In this study, we designed a Yarrowia lipolytica cell factory that can continuously produce germacrene A, which is further converted into ß-elemene with 100% yield through a Cope rearrangement reaction by shifting the temperature to 250°C. First, the productivity of four plant-derived germacrene A synthases was evaluated. After that, the metabolic flux of the precursor to germacrene A was maximized by optimizing the endogenous mevalonate pathway, inhibiting the competing squalene pathway, and expressing germacrene A synthase gene in multiple copies. Finally, the most promising strain achieved the highest ß-elemene titer reported to date with 5.08 g/L. This sustainable and green method has the potential for industrial ß-elemene production.

Advances in Metabolic Engineering Paving the Way for the Efficient Biosynthesis of Terpenes in Yeasts.

Terpenes are a large class of secondary metabolites with diverse structures and functions that are commonly used as valuable raw materials in food, cosmetics, and medicine. With the development of metabolic engineering and emerging synthetic biology tools, these important terpene compounds can be sustainably produced using different microbial chassis. Currently, yeasts such as Saccharomyces cerevisiae and Yarrowia lipolytica have received extensive attention as potential hosts for the production of terpenes due to their clear genetic background and endogenous mevalonate pathway. In this review, we summarize the natural terpene biosynthesis pathways and various engineering strategies, including enzyme engineering, pathway engineering, and cellular engineering, to further improve the terpene productivity and strain stability in these two widely used yeasts. In addition, the future prospects of yeast-based terpene production are discussed in light of the current progress, challenges, and trends in this field. Finally, guidelines for future studies are also emphasized.

The Causal Role of Magnesium Deficiency in the Neuroinflammation, Pain Hypersensitivity and Memory/Emotional Deficits in Ovariectomized and Aged Female Mice.

PURPOSE: Postmenopausal women often suffer from chronic pain, memory decline and mood depression. The mechanisms underlying the neuronal disorders are not fully understood, and effective treatment is still lacking. METHODS: Oral administration of magnesium-L-threonate was tested to treat the neuronal disorders in ovariectomized and aged female mice. The pain hypersensitivity, memory function and depression-like behaviors were measured with a set of behavioral tests. Western blots, immunochemistry and in situ hybridization were used to assess molecular changes. RESULTS: Chronic oral administration of magnesium-L-threonate substantially prevented or reversed the chronic pain and memory/emotional deficits in both ovariectomized and aged female mice. We found that phospho-p65, an active form of nuclear factor-kappaB, tumor necrosis factor-alpha and interleukin-1 beta were significantly upregulated in the neurons of dorsal root ganglion, spinal dorsal horn and hippocampus in ovariectomized and aged mice. The microglia and astrocytes were activated in spinal dorsal horn and hippocampus. Calcitonin gene-related peptide, a marker for peptidergic C-fibers, was upregulated in dorsal horn, which is associated with potentiation of C-fiber-mediated synaptic transmission in the model mice. In parallel with neuroinflammation and synaptic potentiation, free Mg2+ levels in plasma, cerebrospinal fluid and in dorsal root ganglion neurons were significantly reduced. Oral magnesium-L-threonate normalized the neuroinflammation, synaptic potentiation and Mg2+ deficiency, but did not affect the estrogen decline in ovariectomized and aged mice. Furthermore, in cultured dorsal root ganglion neurons, estrogen at physiological concentration elevated intracellular Mg2+, and downregulated phospho-p65, tumor necrosis factor-alpha and interleukin-1 beta exclusively in the presence of extracellular Mg2+. CONCLUSION: Estrogen decline in menopause may cause neuroinflammation by reducing intracellular Mg2+ in neurons, leading to chronic pain, memory/emotional deficits. Supplement Mg2+ by oral magnesium-L-threonate may be a novel approach for treating menopause-related neuronal disorders.

Engineering Plant Sesquiterpene Synthesis into Yeasts: A Review.

Sesquiterpenes are natural compounds composed of three isoprene units. They represent the largest class of terpene compounds found in plants, and many have remarkable biological activities. Furthermore, sesquiterpenes have broad applications in the flavor, pharmaceutical and biofuel industries due to their complex structures. With the development of metabolic engineering and synthetic biology, the production of different sesquiterpenes has been realized in various chassis microbes. The microbial production of sesquiterpenes provides a promising alternative to plant extraction and chemical synthesis, enabling us to meet the increasing market demand. In this review, we summarized the heterologous production of different plant sesquiterpenes using the eukaryotic yeasts Saccharomyces cerevisiae and Yarrowia lipolytica, followed by a discussion of common metabolic engineering strategies used in this field.

Chronic Oral Administration of Magnesium-L-Threonate Prevents Oxaliplatin-Induced Memory and Emotional Deficits by Normalization of TNF-α/NF-κB Signaling in Rats.

Antineoplastic drugs such as oxaliplatin (OXA) often induce memory and emotional deficits. At present, the mechanisms underlying these side-effects are not fully understood, and no effective treatment is available. Here, we show that the short-term memory deficits and anxiety-like and depression-like behaviors induced by intraperitoneal injections of OXA (4 mg/kg per day for 5 consecutive days) were accompanied by synaptic dysfunction and downregulation of the NR2B subunit of N-methyl-D-aspartate receptors in the hippocampus, which is critically involved in memory and emotion. The OXA-induced behavioral and synaptic changes were prevented by chronic oral administration of magnesium-L-threonate (L-TAMS, 604 mg/kg per day, from 2 days before until the end of experiments). We found that OXA injections significantly reduced the free Mg2+ in serum and cerebrospinal fluid (from ~ 0.8 mmol/L to ~ 0.6 mmol/L). The Mg2+ deficiency (0.6 mmol/L) upregulated tumor necrosis factor (TNF-α) and phospho-p65 (p-p65), an active form of nuclear factor-kappaB (NF-κB), and downregulated the NR2B subunit in cultured hippocampal slices. Oral L-TAMS prevented the OXA-induced upregulation of TNF-α and p-p65, as well as microglial activation in the hippocampus and the medial prefrontal cortex. Finally, similar to oral L-TAMS, intracerebroventricular injection of PDTC, an NF-κB inhibitor, also prevented the OXA-induced memory/emotional deficits and the changes in TNF-α, p-p65, and microglia. Taken together, the activation of TNF-α/NF-κB signaling resulting from reduced brain Mg2+ is responsible for the memory/emotional deficits induced by OXA. Chronic oral L-TAMS may be a novel approach to treating chemotherapy-induced memory/emotional deficits.

Improving the homologous recombination efficiency of Yarrowia lipolytica by grafting heterologous component from Saccharomyces cerevisiae.

The oleaginous non-conventional yeast Yarrowia lipolytica has enormous potential as a microbial platform for the synthesis of various bioproducts. However, while the model yeast Saccharomyces cerevisiae has very high homologous recombination (HR) efficiency, non-homologous end-joining is dominant in Y. lipolytica, and foreign genes are randomly inserted into the genome. Consequently, the low HR efficiency greatly restricts the genetic engineering of this yeast. In this study, RAD52, the key component of the HR machinery in S. cerevisiae, was grafted into Y. lipolytica to improve HR efficiency. The gene ade2, whose deletion can result in a brown colony phenotype, was used as the reporter gene for evaluating the HR efficiency. The HR efficiency of Y. lipolytica strains before and after integrating the ScRad52 gene was compared using insets with homology arms of different length. The results showed that the strategy could achieve gene targeting efficiencies of up to 95% with a homology arm length of 1000 bp, which was 6.5 times of the wildtype strain and 1.6 times of the traditionally used ku70 disruption strategy. This study will facilitate the further genetic engineering of Y. lipolytica to make it a more efficient cell factory for the production of value-added compounds.

Bulleyaconitine A Inhibits Itch and Itch Sensitization Induced by Histamine and Chloroquine.

Itch (pruritus), specifically chronic itch associated with disease conditions, significantly impairs the patient's quality of life. At present, the mechanisms underlying this aversive experience are still unclear, and the effective treatment of itch is largely unmet. Here, we report that intragastrical administration of bulleyaconitine A (BLA), which has been used for treating chronic pain for 30 years in China, inhibited itch-like behaviors induced by intradermal injection of histamine and chloroquine in mice and rats, dose-dependently. We found that a single application of the pruritic agents at the skin region innervated by the sural nerve induced long-term potentiation (LTP) of C-fiber field potentials evoked by the stimulation of the same nerve in the spinal dorsal horn of rats. The spinal LTP was remarkably reversed by the spinal application of either BLA or gastrin-releasing peptide receptor (GRPR) antagonist (PD176252). The effect of PD176252 was completely occluded by BLA, while the effect of BLA was only partially occluded by PD176252. Repetitive injection (daily, for four days) of either histamine or chloroquine in the back of the neck enhanced scratching behaviors progressively, and the itch sensitization persisted for at least one week after the discontinuation of the injections. The behavioral change was accompanied with the potentiation of C-fiber synaptic transmission in the dorsal horn. Both the itch sensitization and synaptic potentiation were substantially attenuated by intragastrical BLA. Together, BLA was effective in inhibiting histamine-dependent and histamine-independent itches, and the mechanisms underlying these effects were involved but not limited to the inhibition of gastrin-releasing peptide (GRP)-GRPR signaling in the spinal dorsal horn.

Upregulation of N-type calcium channels in the soma of uninjured dorsal root ganglion neurons contributes to neuropathic pain by increasing neuronal excitability following peripheral nerve injury.

N-type voltage-gated calcium (Cav2.2) channels are expressed in the central terminals of dorsal root ganglion (DRG) neurons, and are critical for neurotransmitter release. Cav2.2 channels are also expressed in the soma of DRG neurons, where their function remains largely unknown. Here, we showed that Cav2.2 was upregulated in the soma of uninjured L4 DRG neurons, but downregulated in those of injured L5 DRG neurons following L5 spinal nerve ligation (L5-SNL). Local application of specific Cav2.2 blockers (ω-conotoxin GVIA, 1-100 µM or ZC88, 10-1000 µM) onto L4 and 6 DRGs on the operated side, but not the contralateral side, dose-dependently reversed mechanical allodynia induced by L5-SNL. Patch clamp recordings revealed that both ω-conotoxin GVIA (1 µM) and ZC88 (10 µM) depressed hyperexcitability in L4 but not in L5 DRG neurons of L5-SNL rats. Consistent with this, knockdown of Cav2.2 in L4 DRG neurons with AAV-Cav2.2 shRNA substantially prevented L5-SNL-induced mechanical allodynia and hyperexcitability of L4 DRG neurons. Furthermore, in L5-SNL rats, interleukin-1 beta (IL-1ß) and IL-10 were upregulated in L4 DRGs and L5 DRGs, respectively. Intrathecal injection of IL-1ß induced mechanical allodynia and Cav2.2 upregulation in bilateral L4-6 DRGs of naïve rats, whereas injection of IL-10 substantially prevented mechanical allodynia and Cav2.2 upregulation in L4 DRGs in L5-SNL rats. Finally, in cultured DRG neurons, Cav2.2 was dose-dependently upregulated by IL-1ß and downregulated by IL-10. These data indicate that the upregulation of Cav2.2 in uninjured DRG neurons via IL-1ß over-production contributes to neuropathic pain by increasing neuronal excitability following peripheral nerve injury.

Restoration of secreted frizzled-related protein 1 suppresses growth and increases cisplatin sensitivity in laryngeal carcinoma cells by downregulating NHE1.

It has been documented that secreted frizzled-related protein 1 (SFRP1) is epigenetically silenced in laryngeal carcinoma. However, the function of SFRP1 in laryngeal carcinoma remains elusive. In this study, we performed gain-of-function studies to determine the roles of SFRP1 in laryngeal carcinoma growth, tumorigenesis, and cisplatin resistance. Laryngeal carcinoma cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC) and examined for SFRP1 expression. The effects of overexpression of SFRP1 on cell proliferation, colony formation, apoptosis, tumorigenesis, and cisplatin sensitivity were assessed. It was found that 5-aza-dC exposure significantly induced the expression of SFRP1 in both Hep-2 and SNU899 laryngeal carcinoma cells. Ectopic expression of SFRP1 significantly decreased cell proliferation and colony formation in vitro and retarded xenograft tumor growth in vivo. SFRP1-overexpressing Hep-2 cells displayed a higher percentage of apoptosis and enhancement of caspase-3 cleavage, which was coupled with loss of Δψm and increased release of cytochrome c from the mitochondria to the cytosol. Moreover, SFRP1 overexpression sensitized laryngeal carcinoma cells to cisplatin and decreased intracellular pH values. Mechanistically, SFRP1 inhibited the expression of Na+/H+ exchanger 1 (NHE1) and overexpression of NHE1 reversed the suppressive activity of SFRP1 on laryngeal carcinoma cells. In conclusion, we demonstrate that SFRP1 induces mitochondrial apoptosis and increases cisplatin sensitivity in laryngeal carcinoma cells via downregulation of NHE1. Delivery of SFRP1 may offer therapeutic benefits in the treatment of laryngeal carcinoma.

Treatment for severe craniocerebral trauma combined with transtentorial hernia in children.

OBJECTIVE: To explore the treating method for severe craniocerebral trauma combined with transtentorial hernia in children. METHODS: We treated 58 children with severe craniocerebral trauma combined with transtentorial hernia through evacuating the hematomas, incising the tentorium but preserving the floating bone flap between January 1996 and January 2002. RESULTS: GCS was 3-5 in 17 cases and 6-8 in 41 cases. After treatment, 46 patients (79.30%) recovered well, 6 (10.30%) suffered from mild disability, 1 (1.72%) suffered from severe disability, 1 (1.72%) was in vegetative state, and 4 (6.90%) died. CONCLUSIONS: Evacuating hematomas and incising tentorium can effectively treat the child patients with severe craniocerebral trauma combined with transtentorial hernia, which can decrease the disability and mortality rates greatly, preserve the skull, exempt reoperation for cranioplasty and relieve the psychologic and physiologic burden of the child patients.