Biomonitoring of heavy metals and their phytoremediation by duckweeds: Advances and prospects.

Heavy metals (HMs) contamination of water bodies severely threatens human and ecosystem health. There is growing interest in the use of duckweeds for HMs biomonitoring and phytoremediation due to their fast growth, low cultivation costs, and excellent HM uptake efficiency. In this review, we summarize the current state of knowledge on duckweeds and their suitability for HM biomonitoring and phytoremediation. Duckweeds have been used for phytotoxicity assays since the 1930s. Some toxicity tests based on duckweeds have been listed in international guidelines. Duckweeds have also been recognized for their ability to facilitate HM phytoremediation in aquatic environments. Large-scale screening of duckweed germplasm optimized for HM biomonitoring and phytoremediation is still essential. We further discuss the morphological, physiological, and molecular effects of HMs on duckweeds. However, the existing data are clearly insufficient, especially in regard to dissection of the transcriptome, metabolome, proteome responses and molecular mechanisms of duckweeds under HM stresses. We also evaluate the influence of environmental factors, exogenous substances, duckweed community composition, and HM interactions on their HM sensitivity and HM accumulation, which need to be considered in practical application scenarios. Finally, we identify challenges and propose approaches for improving the effectiveness of duckweeds for bioremediation from the aspects of selection of duckweed strain, cultivation optimization, engineered duckweeds. We foresee great promise for duckweeds as phytoremediation agents, providing environmentally safe and economically efficient means for HM removal. However, the primary limiting issue is that so few researchers have recognized the outstanding advantages of duckweeds. We hope that this review can pique the interest and attention of more researchers.

Metabolic flexibility during a trophic transition reveals the phenotypic plasticity of greater duckweed (Spirodela polyrhiza 7498).

The greater duckweed (Spirodela polyrhiza 7498) exhibits trophic diversity (photoautotrophic, heterotrophic, photoheterotrophic, and mixotrophic growth) depending on the availability of exogenous organic carbon sources and light. Here, we show that the ability to transition between various trophic growth conditions is an advantageous trait, providing great phenotypic plasticity and metabolic flexibility in S. polyrhiza 7498. By comparing S. polyrhiza 7498 growth characteristics, metabolic acclimation, and cellular ultrastructure across these trophic modes, we show that mixotrophy decreases photosynthetic performance and relieves the CO2 limitation of photosynthesis by enhancing the CO2 supply through the active respiration pathway. Proteomic and metabolomic analyses corroborated that S. polyrhiza 7498 increases its intracellular CO2 and decreases reactive oxygen species under mixotrophic and heterotrophic conditions, which substantially suppressed the wasteful photorespiration and oxidative-damage pathways. As a consequence, mixotrophy resulted in a higher biomass yield than the sum of photoautotrophy and heterotrophy. Our work provides a basis for using trophic transitions in S. polyrhiza 7498 for the enhanced accumulation of value-added products.

Identification and expression analysis of GARP superfamily genes in response to nitrogen and phosphorus stress in Spirodela polyrhiza.

BACKGROUND: GARP transcription factors perform critical roles in plant development and response to environmental stimulus, especially in the phosphorus (P) and nitrogen (N) sensing and uptake. Spirodela polyrhiza (giant duckweed) is widely used for phytoremediation and biomass production due to its rapid growth and efficient N and P removal capacities. However, there has not yet been a comprehensive analysis of the GRAP gene family in S. polyrhiza. RESULTS: We conducted a comprehensive study of GRAP superfamily genes in S. polyrhiza. First, we investigated 35 SpGARP genes which have been classified into three groups based on their gene structures, conserved motifs, and phylogenetic relationship. Then, we identified the duplication events, performed the synteny analysis, and calculated the Ka/Ks ratio in these SpGARP genes. The regulatory and co-expression networks of SpGARPs were further constructed using cis-acting element analysis and weighted correlation network analysis (WGCNA). Finally, the expression pattern of SpGARP genes were analyzed using RNA-seq data and qRT-PCR, and several NIGT1 transcription factors were found to be involved in both N and P starvation responses. CONCLUSIONS: The study provides insight into the evolution and function of GARP superfamily in S. polyrhiza, and lays the foundation for the further functional verification of SpGARP genes.

Cytotoxic Polyketides Isolated from the Deep-Sea-Derived Fungus Penicillium chrysogenum MCCC 3A00292.

The chemical examination of the solid cultures of the deep-sea-derived fungus Penicillium chrysogenum MCCC 3A00292 resulted in the isolation of three new versiol-type analogues, namely peniciversiols A-C (1-3), and two novel lactone derivatives, namely penicilactones A and B (6 and 7), along with 11 known polyketides. The planar structures of the new compounds were determined by the comprehensive analyses of the high-resolution electrospray ionization mass spectroscopy (HRESIMS) and nuclear magnetic resonance (NMR) data, while their absolute configurations were resolved on the basis of comparisons of the experimental electronic circular dichroism (ECD) spectra with the calculated ECD data. Compound 1 is the second example of versiols featuring a 2,3-dihydropyran-4-one ring. Additionally, compounds 6 and 7 are the first representatives of γ-lactone derivatives constructed by a 1,3-dihydroxy-5-methylbenzene unit esterifying with the α-methyl-γ-hydroxy-γ-acetic acid α,ß-unsaturated-γ-lactone moiety and α-hydroxy-γ-methyl-γ-acetic acid α,ß-unsaturated-γ-lactone unit, respectively. All of the isolated compounds were evaluated for their cytotoxic activities against five human cancer cell lines of BIU-87, ECA109, BEL-7402, PANC-1, and Hela-S3. Compound 1 exhibited a selective inhibitory effect against the BIU-87 cell line (IC50 = 10.21 µM), while compounds 4, 5, 8, and 12-16 showed inhibitory activities against the ECA109, BIU-87, and BEL-7402 cell lines with the IC50 values ranging from 7.70 to > 20 µM.

Attenuation of Remifentanil-Induced Hyperalgesia by Betulinic Acid Associates with Inhibiting Oxidative Stress and Inflammation in Spinal Dorsal Horn.

Remifentanil-induced hyperalgesia (RIH) is known to be associated with oxidative stress and inflammation. Betulinic acid (BA) was reported to reduce visceral pain owing to its anti-oxidative and anti-inflammatory potential. Here, we -explored whether BA can attenuate RIH through inhibiting oxidative stress and inflammation in spinal dorsal horn. Sprague-Dawley rats were randomly divided into 4 groups: Control, Incision, RIH, and RIH pre-treated with BA. After pretreated with BA (25 mg/kg, i.g.) for 7 days, rats were subcutaneously infused with remifentanil (40 µg/kg) for 30 min during right plantar incision surgery to induce RIH. The paw withdrawal mechanical threshold (PWMT), paw withdrawal thermal latency (PWTL), spinal oxidative stress and inflammatory mediators were determined. Intraoperative remifentanil infusion induced postoperative hyperalgesia, as evidenced by the significant decrease in PWMT and PWTL (p < 0.01), and the significant increase in oxidative stress and inflammation evidenced by up-regulations of malondialdehyde, 3-nitrotyrosine, interleukin-1ß and tumour necrosis factor-α (p < 0.01) in spinal dorsal horn and matrix metalloproteinase-9 (MMP-9) activity (p < 0.01) in dorsal root ganglion, as well as a decrease in manganese superoxide -dismutase activity (p < 0.01) compared with control and -incision groups. All these results mentioned above were markedly reversed by pre-treatment with BA (p < 0.01) compared with RIH group. These findings demonstrated that BA can effectively attenuate RIH, which associates with potentially inhibiting oxidative stress and subsequently down-regulating MMP-9-related pro-inflammatory cyokines in spinal dorsal horn.

Temperature is a cryptic factor shaping the geographical pattern of genetic variation in Ceratophyllum demersum across a subtropical freshwater lake.

Macrophyte habitats exhibit remarkable heterogeneity, encompassing the spatial variation of abiotic and biotic components such as changes in water conditions and weather as well as anthropogenic stressors. Environmental factors are thought to be important drivers shaping the genetic and epigenetic variation of aquatic plants. However, the links among genetic diversity, epigenetic variation, and environmental variables remain largely unclear, especially for clonal aquatic plants. Here, we performed population genetic and epigenetic analyses in conjunction with habitat discrimination to elucidate the environmental factors driving intraspecies genetic and epigenetic variation in hornwort (Ceratophyllum demersum) in a subtropical lake. Environmental factors were highly correlated with the genetic and epigenetic variation of C. demersum, with temperature being a key driver of the genetic variation. Lower temperature was detected to be correlated with greater genetic and epigenetic variation. Genetic and epigenetic variation were positively driven by water temperature, but were negatively affected by ambient air temperature. These findings indicate that the genetic and epigenetic variation of this clonal aquatic herb is not related to the geographic feature but is instead driven by environmental conditions, and demonstrate the effects of temperature on local genetic and epigenetic variation in aquatic systems.

[Dexmedetomidine preconditioning protects isolated rat hearts against ischemia/reperfusion injuries and its mechanism].

OBJECTIVE: To investigate the protective effect of dexmedetomidine (Dex) preconditioning against ischemia/reperfusion (I/R) injuries in isolated rat hearts and its relation to mitochondrial permeability transition pore (mPTP) and mitochondrial ATP-sensitive K(+) channel (mitoKATP). METHODS: The hearts of male SD rats were isolated to mount on the Langendorff apparatus and subjected to 30 min global ischemia followed by 120 min reperfusion. The isolated hearts were treated with Dex (10 nmol/L) before ischemia for 15 min. The left ventricular hemodynamic parameters,coronary flow (CF) and the lactate dehydrogenase (LDH) release in the coronary effluent at 5 min reperfusion were measured. The formazan content was assayed to determine the myocardial viability at the end of reperfusion. RESULTS: Compared with normal controls, I/R markedly decreased the left ventricular developed pressure and CF during the whole reperfusion period and the formazan content; while the left ventricular end diastolic pressure and LDH release were significantly increased. Dex preconditioning markedly improved the myocardial viability and cardiac function (P<0.01), which were reversed by the treatment with both atractyloside (20 µmol/L before ischemia), an opener of mPTP, and 5-hydroxydecanoate (100 µmol/L at the beginning of reperfusion), an inhibitor of mitoKATP, for 20 min. CONCLUSION: Dex has protective effect against I/R injuries in isolated rat hearts, which may be related to inhibiting the opening of mPTP at the beginning of reperfusion and activating mitoKATP before ischemia.

Water temperature and chlorophyll a density drive the genetic and epigenetic variation of Vallisneria natans across a subtropical freshwater lake.

Plant genetic diversity differs in habitat's oscillations, especially species distributed under heterogeneous environmental conditions. Freshwater ecosystems are vulnerable to biotic and abiotic impacts, which affect the genetic and epigenetic variations in aquatic plants. The extent of environmental heterogeneous attributes can be examined based on genetic and epigenetic variations. Such variations under environmental gradient can provide evidence for understanding the correlations between rapid environmental changes and species evolution. In this study, we performed amplified fragment polymorphism length and methylated-sensitive amplified polymorphism analysis to depict the genetic and epigenetic variations of Vallisneria natans in a subtropical lake. Results showed that this species maintained a relatively high genetic diversity (mean H E = 0.320, I = 0.474, PPL = 85.93%) and epigenetic variation (mean eH E = 0.282, eI = 0.428, ePPL = 83.91%). Water body temperature and chlorophyll a density were positively correlated to the genetic and epigenetic variations. The clonal generates of V. natans depicted a relative high methylation level and shew ancestral scenario between the genet and the second clonal generation. These findings revealed that species diversity is unevenly distributed under environmental heterogeneity, even at a fine geographic scale. Environmental characteristics in relation to temperature and chlorophyll a should be considered in the analysis of the genetic and epigenetic variations. Additionally, epigenetic variations between genets and ramets should be considered with caution when applied to analysis of other aquatic species.

Identification, Structural, and Expression Analyses of SPX Genes in Giant Duckweed (Spirodela polyrhiza) Reveals Its Role in Response to Low Phosphorus and Nitrogen Stresses.

SPX genes play important roles in the coordinated utilization of nitrogen (N) and phosphorus (P) in plants. However, a genome-wide analysis of the SPX family is still lacking. In this study, the gene structure and phylogenetic relationship of 160 SPX genes were systematically analyzed at the genome-wide level. Results revealed that SPX genes were highly conserved in plants. All SPX genes contained the conserved SPX domain containing motifs 2, 3, 4, and 8. The 160 SPX genes were divided into five clades and the SPX genes within the same clade shared a similar motif composition. P1BS cis-elements showed a high frequency in the promoter region of SPXs, indicating that SPX genes could interact with the P signal center regulatory gene Phosphate Starvation Response1 (PHR1) in response to low P stress. Other cis-elements were also involved in plant development and biotic/abiotic stress, suggesting the functional diversity of SPXs. Further studies were conducted on the interaction network of three SpSPXs, revealing that these genes could interact with important components of the P signaling network. The expression profiles showed that SpSPXs responded sensitively to N and P deficiency stresses, thus playing a key regulatory function in P and N metabolism. Furthermore, the expression of SpSPXs under P and N deficiency stresses could be affected by environmental factors such as ABA treatment, osmotic, and LT stresses. Our study suggested that SpSPXs could be good candidates for enhancing the uptake ability of Spirodela polyrhiza for P nutrients in wastewater. These findings could broaden the understanding of the evolution and biological function of the SPX family and offer a foundation to further investigate this family in plants.

Combined effects of temperature and nutrients on the toxicity of cadmium in duckweed (Lemna aequinoctialis).

Global anthropogenic changes are altering the temperature and nutrients of the ecosystem, which might also affect the extent of cadmium (Cd) toxicity in organisms. This study aimed to investigate the combined effects of temperature and nutrient availability (here, nitrogen [N] and phosphorus [P]) on Cd toxicity in duckweed (Lemna aequinoctialis). The growth parameters, nutrient uptake, and Cd tolerance of plantlets reached their highest values for duckweed grown in medium with 28 mg/L N and 2.4 mg/L P (N:P = 11.67) at 25 °C under 1 mg/L CdCl2 exposure. Raising the temperature (from 18 °C to 25 °C) and levels of N and P (from 0.01 N/P to 2 N/P) enhanced photosynthetic capacity and nutrient uptake, thus promoting plant growth and diluting the toxic effects of Cd. Although Cd uptake increased with increasing temperature, duckweed with relatively high biomass exhibited a lower accumulation of the toxic metal because their growth rate exceeded Cd uptake rate. Increasing N and P supply also enhanced the tolerance of duckweed to Cd by limiting Cd bioavailability. Our study therefore suggests the importance of combined effects from temperature and nutrients for Cd toxicity and provides novel insights for a comprehensive analysis of Cd toxicity associated with the environmental factors of a particular ecosystem.

[Effect of AT1 receptor on changes of tyrosine hydroxylase-immunoreactivity in rostral ventrolateral medulla induced by brain cholinergic stimuli in rats].

OBJECTIVE: To investigate the effect of AT1 receptor on the changes of tyrosine hydroxylase-immunoreactivity (TH-IR) in rostral ventrolateral medulla (RVLM) induced by brain cholinergic stimuli in rats. METHODS: Male SD rats were randomly divided into 4 groups: NS + CBC group, Los + CBC group, Los + NS group and NS + NS group. AT1 was blocked by pretreatment of 20 µg losartan in Los + CBC and Los + NS groups; intracerebroventricular injection of 0.5 µg carbachol was used for cholinergic stimuli in NS + CBC and Los + CBC groups; normal saline (NS) was used for control. The output amount of natrium in kidney, glomerular filtration rate (GFR) and renal plasma flow (PRF) were observed. The changes of TH-IR in the RVLM were observed by immunohistochemistry. RESULT: In NS + CBC group carbachol induced potent natriuresis, after pretreatment of losartan the natriuretic effect was partially inhibited in Los + CBC group. Both the number and optical density of TH-IR positive neurons in NS + CBC group were markedly increased than those in NS + NS group (P < 0.05); while those in Los + CBC group were significantly lower than those in NS+CBC group (P < 0.05). Intracerebroventricular injection of carbachol and losartan had no effect on GFR and RPF(P > 0.05). CONCLUSION: The results suggest that cholinergic stimuli can induce potent natriuresis and increase the activity of adrenergic neurons in the RVLM; the above effects can be down regulated by blockade of brain AT1 receptor.

Species-specific responses of submerged macrophytes to the presence of a small omnivorous bitterling Acheilognathus macropterus.

Recovery of submerged macrophytes has been considered a key factor in the restoration of shallow eutrophic lakes. However, in some subtropical restored lakes, small omnivorous fish dominate the fish assemblages and feed in part on submerged macrophytes. Knowledge of the effects of small omnivores on the growth of submerged macrophytes is scarce and their responses are potentially species-specific, i.e. the growth of some species may be hampered by fish grazing while growth of others may be promoted by the nutrients becoming available by fish excretion. We conducted mesocosm experiments to examine the effects of the small omnivorous bitterling Acheilognathus macropterus, a common species in restored subtropical lakes in China, on nutrient concentrations and the growth of four species of submerged macrophytes (Hydrilla verticillata, Vallisneria denseserrulata, Ceratophyllum demersum and Myriophyllum spicatum). We found that the bitterling significantly increased nutrient concentrations via excretion and thereby enhanced the net growth of the less grazed nuisance macrophyte M. spicatum. In contrast, the net growth of C. demersum was reduced by the bitterling, most likely due to grazing as indicated by gut content analyses. Dominance by bitterling may, therefore, pose a threat to the long-term success of lake restoration by provoking a shift in the submerged macrophyte community towards nuisance species through selective grazing. Nutrient excretion may potentially also stimulate the growth of phytoplankton and periphyton, hampering the growth of submerged macrophyte.

[Activation of mitochondrial aldehyde dehydrogenase 2 and inhibition of mitochondrial permeability transition pore involved in cardioprotection of ethanol postconditioning].

OBJECTIVE: To investigate whether activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) and inhibition of mitochondrial permeability transition pore (mitoPTP) were involved in the cardioprotection of ethanol postconditioning in isolated rat heart. METHODS: Hearts isolated from male Sprague-Dawley rats were perfused on a langendorff apparatus and subjected to 30 min of regional ischemia (occlusion of left anterior descending artery) followed by 120 min of reperfusion. The ventricular hemodynamic parameters and lactate dehydrogenase (LDH) release during reperfusion were measured. Infarct size was measured by TTC staining method and the expression of ALDH2 at mRNA level of left anterior myocardium was detected by RT-PCR. RESULT: In contrast to ischemia and reperfusion, ethanol postconditioning improved the recovery of left ventricular developed pressure, maximal rise/fall rate of left ventricular pressure during reperfusion, reduced LDH release and infarct size. The expression of ALDH2 mRNA level was increased. Administration of mitoPTP activator atractyloside attenuated the effect of ethanol postconditioning, LDH release and infarct size were increased, and the recovery of hemodynamic parameters was inhibited. The expression of ALDH2 mRNA was decreased. CONCLUSION: Ethanol postconditioning has cardioprotection effect, which may be associated with upregulating mitochondrial ALDH2 mRNA expression and inhibiting the opening of mitochondrial permeability transition pore.

[Hemodynamics and aortic tension induced by two septic shock models in rats].

OBJECTIVE: To compare the ventricular-dynamic parameters and thoracic aorta tension induced by two septic shock models in rats. METHODS: Septic shock models were induced by cecal ligation or puncture (CLP) and intraperitoneal injection of lipopolysaccharide (LPS) in rats. The carotid artery was cannulated and connected to a pressure transducer to determine mean arterial blood pressure (MABP). Ventricular dynamic parameters, including heart rate (HR), left ventricular developed pressure (LVDP) and maximal rise/fall velocity of ventricular pressure (± dP/dtmax) were determined. Isolated thoracic rings were mounted on an organ bath and the tension of the vessel was recorded. RESULT: The mortality was 65.2% in CLP shock rats, but no death in LPS shock rats. The MABP and HR of CLP rats were decreased more prominently than those of LPS rats (P < 0.01). Contraction induced by high K(+) (60 mmol/L) or 10⁻6 mol/L phenylephrine (PE) in endothelium-intact and endothelium-denuded aortic rings was all attenuated, but in LPS rats it was more prominent (P < 0.01). CONCLUSION: Two rat septic shock models can decrease ventricular-dynamic parameters and vasoconstriction responsiveness of aorta. The ventricular-dynamic parameters decrease more prominently in CLP model, while vasoconstriction responsiveness of aorta changes more in LPS model.

[Betulinic acid ameliorates impairment of endothelium-dependent relaxation induced by oxidative stress in rat aorta].

OBJECTIVE: To investigate the effect of betulinic acid (BA) on relaxation in isolated rat aortic rings and its antioxidant property on oxidative stress of blood vessels. METHODS: Aortic rings were isolated and BA was cumulatively added into organ bath. Isometric tension of endothelium intact or endothelium denuded thoracic aortic rings previously contracted by phenylephrine (PE) was recorded. Then aortic rings were randomly divided into normal control group, BA control group, H(2)O(2) group and BA+H(2)O(2) group, after being previously contracted by PE, isometric tension of endothelium-dependent relaxation induced by Ach was recorded. RESULT: Exposure of intact endothelium rings previously contracted by PE to BA at the concentrations of 10(-7) mol/L-10(-4) mol/L evoked a significant concentration dependent relaxation, which was inhibited by pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4)mol/L), but not by indometacin (10(-5)mol/L). The pD2 value of BA was 5.24 ± 0.04, and the EC(50)value was 2.45 x 10(-6)mol/L. Exposure of endothelium denuded rings previously contracted by PE to BA did not affect the relaxation in isolated aortic rings. ACh induced a dose-dependent relaxation that was weakened by pretreatment with H(2)O(2) (5 10(-4) mol/L) for 15 min. The EC(50) of BA markedly attenuated the inhibition of relaxation induced by H(2)O(2). CONCLUSION: BA can evoke a concentration-dependent relaxation in aortic rings previously contracted by PE, which may be mediated by NO. And the decrease of endothelium-dependent relaxation in rat aortic rings exposed to H(2)O(2) can be markedly attenuated by BA, which may be mediated by reducing oxidative stress and maintaining the activity of NO in aortic rings.

Cathepsin K Deficiency Impaired Ischemia-Induced Neovascularization in Aged Mice.

BACKGROUND: Aging is a major risk factor for cardiovascular disease. Cysteine protease cathepsin K (CatK) has been implicated in the process of angiogenesis, but the exact roles of individual CatK in vessel formation during aging are poorly understood. METHODS AND RESULTS: To study the putative role of CatK in ischemia-induced angiogenesis, we applied a hindlimb ischemia model to aged wild-type (CatK+/+) and CatK-deficient (CatK-/-) mice. A serial laser Doppler blood-flow analysis revealed that the recovery of the ischemic/normal blood-flow ratio in the aged CatK-/-mice was impaired throughout the follow-up period. On postoperative day 14, CatK deficiency had also impaired capillary formation. CatK deficiency reduced the levels of cleaved Notch1, phospho-Akt, and/or vascular endothelial growth factor (VEGF) proteins in the ischemic muscles and bone marrow-derived c-Kit+ cells. A flow cytometry analysis revealed that CatK deficiency reduced the numbers of endothelial progenitor cell (EPC)-like CD31+/c-Kit+ cells in the peripheral blood as well as the ischemic vasculature. In vitro experiments, CatK-/- impaired bone-derived c-Kit+ cellular functions (migration, invasion, proliferation, and tubulogenesis) in aged mice. Our findings demonstrated that aging impaired the ischemia-induced angiogenesis associated with the reductions of the production and mobilization of CD31+/c-Kit+ cells in mice. CONCLUSIONS: These findings established that the impairment of ischemia-induced neovascularization in aged CatK-/- mice is due, at least in part, to the reduction of EPC mobilization and the homing of the cells into vasculature that is associated with the impairment of Notch1 signaling activation at advanced ages.

A small omnivorous bitterling fish (Acheilognathus macropterus) facilitates dominance of cyanobacteria, rotifers and Limnodrilus in an outdoor mesocosm experiment.

Small omnivorous fish often dominate in subtropical shallow lakes, and they may affect the community structure of aquatic organisms on at least two trophic levels. However, in the study of aquatic food webs in subtropical lakes, most ecologists have focused on the effects of large-sized omnivorous species (e.g. common carp), studies of small-sized species being scarce. We conducted a mesocosm experiment with two treatments (fish presence and absence) to examine the effects of a small-sized omnivore, bitterling (Acheilognathus macropterus), on phytoplankton, zooplankton and benthic macroinvertebrates. Our results showed that bitterling presence significantly increased the chlorophyll a concentration and biomass of phytoplankton, which became dominated by cyanobacteria (mainly Aphanizomenon spp.) that accounted for >99% of both total phytoplankton abundance and biomass. Both the abundance and biomass of zooplankton were also higher in the fish-present treatment, but small rotifers became dominant, and the zooplankton:phytoplankton biomass ratio decreased, indicating less grazing on phytoplankton. Moreover, both the abundance and biomass of benthic macroinvertebrates (tubificids) were higher in the bitterling-present treatment than in the controls, which is opposite to the situation found when omni-benthivorous fish (e.g. crucian carp) dominate. Higher biomass of tubificids may, in turn, result in higher sediment nutrient release. Our study suggests that A. macropterus, and maybe also other bitterling species, can alter both pelagic and benthic assemblages via both top-down and bottom-up control effects and lead to more turbid water in eutrophic lakes. Thus, more attention should be paid to these small omnivorous species in the restoration and management of shallow subtropical lakes.

Chemical constituents from the deep sea-derived Streptomyces xiamenensis MCCC 1A01570 and their effects on RXRα transcriptional regulation.

From the deep sea-derived Streptomyces xiamenensis MCCC 1A01570, eight cyclic dipeptides (1-8) and five phenolics (9-13) were obtained. Cyclo-(I-Pro-D-Leu) (4) could moderately promote the gene transcriptional function of nuclear receptor RXRα, while 2, 3, and 13 showed weak reduction in RXRα gene transcriptional activities induced by 9-cis-retinoid acid (RA). These compounds might have beneficial effects against intractable diseases with relation to RXRα, such as cancer and metabolic diseases, due to their potential activities on regulating the transcriptional activation function of RXRα. In addition, 1-6, 8, 10, and 12 (20 µM) showed mild in vitro cytotoxicity against three cancer cell lines of ECA-109, Hela-S3 and PANC-1 with the inhibition rates arranging from 50% to 65%.

Luteolin Attenuates Cardiac Ischemia/Reperfusion Injury in Diabetic Rats by Modulating Nrf2 Antioxidative Function.

Luteolin has been reported to attenuate ischemia/reperfusion (I/R) injury in the diabetic heart through endothelial nitric oxide synthase- (eNOS-) related antioxidative response. Though the nuclear factor erythroid 2-related factor 2 (Nrf2) is regarded as a key endogenous factor to reduce diabetic oxidative stress, whether luteolin reduces cardiac I/R injury in the diabetic heart via enhancing Nrf2 function needs to be clarified. We hypothesized that pretreatment with luteolin could alleviate cardiac I/R injury in the diabetic heart by affecting the eNOS/Nrf2 signaling pathway. The diabetic rat was produced by a single injection of streptozotocin (65 mg/kg, i.p.) for 6 weeks, and then, luteolin (100 mg/kg/day, i.g.), eNOS inhibitor L-NAME, or Nrf2 inhibitor brusatol was administered for the succedent 2 weeks. After that, the isolated rat heart was exposed to 30 min of global ischemia and 120 min of reperfusion to establish I/R injury. Luteolin markedly ameliorated cardiac function and myocardial viability; upregulated expressions of heme oxygenase-1, superoxide dismutase, glutathione peroxidase, and catalase; and reduced myocardial lactate dehydrogenase release, malondialdehyde, and 8-hydroxydeoxyguanosine in the diabetic I/R heart. All these ameliorating effects of luteolin were significantly reversed by L-NAME or brusatol. Luteolin also markedly reduced S-nitrosylation of Kelch-like ECH-associated protein 1 (Keap1) and upregulated Nrf2 and its transcriptional activity. This effect of luteolin on Keap1/Nrf2 signaling was attenuated by L-NAME. These data reveal that luteolin protects the diabetic heart against I/R injury by enhancing eNOS-mediated S-nitrosylation of Keap1, with subsequent upregulation of Nrf2 and the Nrf2-related antioxidative signaling pathway.

Andrastone A From the Deep-Sea-Derived Fungus Penicillium allii-sativi Acts as an Inducer of Caspase and RXRα-Dependent Apoptosis.

Two new (1, 2) and one known (3) meroterpenoids were isolated from the deep-sea-derived fungus Penicillium allii-sativi. The relative structures of new compounds were determined on the basis of an extensive analysis of the NMR and MS data, and the absolute configurations were established by ECD calculations. Andrastone A (1) is a rare andrastin bearing an unusual cyclopentan-1,3-dione. It shows a selectively antiproliferative effect against HepG2 tumor cells with an IC50 value of 7.8 µM. Mechanism study showed that apoptosis via Caspase and RXRα pathways are responsible for the inhibitory effect.