动物宿主——肠道微生物代谢轴研究进展

肠道中栖息着数量庞大且复杂多样的微生物菌群,在维持宿主肠道微环境稳态中发挥重要作用。微生物菌群可以利用宿主肠道的营养素,发酵产生代谢产物,与宿主机体形成宿主—微生物代谢轴(host-microbe metabolic axis)。该代谢轴既能影响营养素吸收和能量代谢,又可调控宿主各项生理过程。本文主要阐述宿主-肠道微生物代谢轴的概念、肠-肝轴、肠-脑轴、肠道微生物与宿主肠道代谢轴的互作以及对机体健康的影响。     

Nitric oxide (NO)-dependent and NO-independent signaling pathways act in ABA-inhibition of stomatal opening

We investigated the role of nitric oxide (NO) in ABA-inhibition of stomatal opening in Vicia faba L. in different size dishes. When a large dish (9 cm diameter) was used, ABA induced NO synthesis and the NO scavenger reduced ABA-inhibition of stomatal opening. When a small dish (6 cm diameter) was used, ABA induced stomatal closure and inhibited stomatal opening. The NO scavenger was able to reduce ABA-induced stomatal closure, but unable to reverse ABA-inhibition of stomatal opening. Furthermore, NO was not synthesized in response to ABA, indicating that NO is not required for ABA-inhibition of stomatal opening in the small dish. These results indicated that an NO-dependent and an NO-independent signaling pathway participate in ABA signaling pathway. An NO-dependent pathway is the major player in ABA-induced stomatal closure. However, in ABA-inhibition of stomatal opening, an NO-dependent and an NO-independent pathway act: different signaling molecules participate in ABA-signaling cascade under different environmental condition.Key words: ABA, environmental condition, nitric oxide, stomata, Vicia faba LNitric oxide (NO) is a key signaling molecule in plants.^1,2 It functions in disease resistance and programmed cell death,^3,4 root development,^5,6 and plant responses to various abiotic stresses.^1,2,7,8 In addition, NO is required for stomatal closure in response to ABA in several species including Arabidopsis, Vicia faba, pea, tomato, barley, and wheat.^9–11 ABA-inhibition of stomatal opening is a distinct process from ABA-induced stomatal closure.^12,13 In V. faba, these two processes employ a similar signaling pathway; NO is also a second messenger molecule for ABA-inhibition of stomatal opening in a large dish.¹⁴ In this study, we examined the role of NO in ABA-inhibition of stomatal opening using different dish sizes. In a small dish, NO is not involved in ABA-inhibition of stomatal opening: the NO-independent signaling pathway is the major player in it.     

Differential effects of maternal nutrient restriction through pregnancy on kidney development and later blood pressure control in the resulting offspring

The mechanisms whereby maternal nutritional manipulation through pregnancy result in altered blood pressure in the offspring may include changes in fetal and newborn and adult renal prostaglandin (PG) synthesis, metabolism, and receptor expression. Since the postnatal effects of nutrient restriction on the renal PG synthesis and receptor system during nephrogenesis in conjunction with nephron numbers and blood pressure have not been evaluated in the rat, the present study examined the effect of reducing maternal food intake by 50% of ad libitum through pregnancy on young male rats. Six control-fed mothers and eight nutrient-restricted pregnant rats with single litter mates were used at each sampling time point, most of which occurred during nephrogenesis. Offspring of nutrient-restricted dams were lighter from birth to 3 days. This was accompanied by reduced PGE2, with smaller kidneys up to 14 days. Nutrient restriction also decreased mRNA expression of the PG synthesis enzyme, had little effect on the PG receptors, and increased mRNA expression of the degradation enzyme during nephrogenesis and the glucocorticoid receptor in the adult kidney. These mRNA changes were normally accompanied by similar changes in protein. Nephron number was also reduced from 7 days up to adulthood when blood pressure (measured by telemetry) did not increase as much as in control offspring during the dark, active period. In conclusion, maternal nutrient restriction suppressed renal PG concentrations in the offspring, and this was associated with suppressed kidney growth and development and decreased blood pressure.     

p38 MAPK-dependent eNOS upregulation is critical for 17beta-estradiol-mediated cardioprotection following trauma-hemorrhage

Studies have shown that p38 MAPK and nitric oxide (NO), generated by endothelial NO synthase (eNOS), play key roles under physiological and pathophysiological conditions. Although administration of 17beta-estradiol (E2) protects cardiovascular injury from trauma-hemorrhage, the mechanism by which E2 produces those effects remains unknown. Our objective was to determine whether the E2-mediated activation of myocardial p38 MAPK and subsequent eNOS expression/phosphorylation would protect the heart following trauma-hemorrhage. To study this, male Sprague-Dawley rats underwent soft-tissue trauma (midline laparatomy) and hemorrhagic shock (mean blood pressure 35-40 mmHg for 90 min), followed by fluid resuscitation. Animals were pretreated with specific p38 MAPK inhibitor SB-203580 (SB; 2 mg/kg), and nonselective NO synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME; 30 mg/kg) 30 min before vehicle (cyclodextrin) or E2 (100 microg/kg) treatment, followed by resuscitation, and were killed 2 h thereafter. Cardiovascular performance and other parameters were measured. E2 administration following trauma-hemorrhage increased cardiac p38 MAPK activity, eNOS expression and phosphorylation at Ser(1177), and nitrate/nitrite levels in plasma and heart tissues; these were associated with normalized cardiac performance, which was reversed by SB administration. In addition, E2 also prevented trauma-hemorrhage-induced increase in cytokines (IL-6 and TNF-alpha), chemokines (macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant-1), and ICAM-1, which was reversed by l-NAME administration. Administration of E2 following trauma-hemorrhage attenuated cardiac tissue injury markers, myeloperoxidase activity, and nitrotyrosine level, which were reversed by treatment with SB and l-NAME. The salutary effects of E2 on cardiac functions and tissue protection following trauma-hemorrhage are mediated, in part, through activation of p38 MAPK and subsequent eNOS expression and phosphorylation.     

NADPH oxidases are involved in differentiation and pathogenicity in Botrytis cinerea

Nicotinamide adenine dinucleotide (NADPH) oxidases have been shown to be involved in various differentiation processes in fungi. We investigated the role of two NADPH oxidases in the necrotrophic phytopathogenic fungus, Botrytis cinerea. The genes bcnoxA and bcnoxB were cloned and characterized; their deduced amino acid sequences show high homology to fungal NADPH oxidases. Analyses of single and double knock-out mutants of both NADPH oxidase genes showed that both bcnoxA and bcnoxB are involved in formation of sclerotia. Both genes have a great impact on pathogenicity: whereas bcnoxB mutants showed a retarded formation of primary lesions, probably due to an impaired formation of penetration structures, bcnoxA mutants were able to penetrate host tissue in the same way as the wild type but were much slower in colonizing the host tissue. Double mutants showed an additive effect: they were aberrant in penetration and colonization of plant tissue and, therefore, almost nonpathogenic. To study the structure of the fungal Nox complex in more detail, bcnoxR (encoding a homolog of the mammalian p67(phox), a regulatory subunit of the Nox complex) was functionally characterized. The phenotype of DeltabcnoxR mutants is identical to that of DeltabcnoxAB double mutants, providing evidence that BcnoxR is involved in activation of both Bcnox enzymes.     

Activity of essential oils and individual components against acetyl- and butyrylcholinesterase

We have tested acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of nineteen essential oils obtained from cultivated plants, namely one from Anethum graveolens L. (organic fertilizer), two from Foeniculum vulgare Mill. collected at fully-mature and flowering stages (organic fertilizer), two from Melissa officinalis L. (cultivated using organic and chemical fertilizers), two from Mentha piperita L. and M. spicata L. (organic fertilizer), two from Lavandula officinalis Chaix ex Villars (cultivated using organic and chemical fertilizers), two from Ocimum basilicum L. (green and purple-leaf varieties cultivated using only organic fertilizer), four from Origanum onites L., O. vulgare L., O. munitiflorum Hausskn., and O. majorana L. (cultivated using organic fertilizer), two from Salvia sclarea L. (organic and chemical fertilizers), one from S. officinalis L. (organic fertilizer), and one from Satureja cuneifolia Ten. (organic fertilizer) by a spectrophotometric method of Ellman using ELISA microplate-reader at 1 mg/ml concentration. In addition, a number of single components widely encountered in most of the essential oils [gamma-terpinene, 4-allyl anisole, (-)-carvone, dihydrocarvone, (-)-phencone, cuminyl alcohol, cumol, 4-isopropyl benzaldehyde, trans-anethole, camphene, iso-borneol, (-)-borneol, L-bornyl acetate, 2-decanol, 2-heptanol, methyl-heptanol, farnesol, nerol, iso-pulegol, 1,8-cineole, citral, citronellal, citronellol, geraniol, linalool, alpha-pinene, beta-pinene, piperitone, iso-menthone, menthofurane, linalyl oxide, linalyl ester, geranyl ester, carvacrol, thymol, menthol, vanilline, and eugenol] was also screened for the same activity in the same manner. Almost all of the essential oils showed a very high inhibitory activity (over 80%) against both enzymes, whereas the single components were not as active as the essential oils.     

Syntheses of 4,6'-epoxymorphinan derivatives and their pharmacologies

A modification of the message site in the skeleton of naltrexone was carried out to improve the potency and selectivity of the compound for an opioid receptor subtype. In the course of conversion, we synthesized 7-membered ring ether derivatives, which had an inserted OCH(2) group between 4- and 6-positions of morphinan skeleton. One of the 7-membered ring ether derivatives possessed more potent antagonistic activity than naltrexone for the mu opioid receptor. Another compound possessing 17-methyl group derived from noroxycodone may be a mu opioid receptor partial agonist and showed analgesic activity. We are currently examining the subtype selectivity of these compounds.     

Synthesis of a novel 6,14-epoxymorphinan derivative and its pharmacology

A novel 6,14-epoxymorphinan benzamide derivative (NS22) was synthesized, which showed opioid kappa receptor agonistic activity in the [(35)S]GTPgammaS binding assay. The antinociceptive effect of NS22 was evaluated in the tail-flick and the hot-plate test. This compound showed a potent antinociceptive activity in mice by s.c. administration, which was attenuated with nor-BNI (selective opioid kappa receptor antagonist).     

Autographa californica multiple nucleopolyhedrovirus 38K is a novel nucleocapsid protein that interacts with VP1054, VP39, VP80, and itself

It has been shown that the Autographa californica multiple nucleopolyhedrovirus (AcMNPV) 38K (ac98) is required for nucleocapsid assembly. However, the exact role of 38K in nucleocapsid assembly remains unknown. In the present study, we investigated the relationship between 38K and the nucleocapsid. Western blotting using polyclonal antibodies raised against 38K revealed that 38K was expressed in the late phase of infection in AcMNPV-infected Spodoptera frugiperda cells and copurified with budded virus (BV) and occlusion-derived virus (ODV). Biochemical fractionation of BV and ODV into the nucleocapsid and envelope components followed by Western blotting showed that 38K was associated with the nucleocapsids. Immunoelectron microscopic analysis revealed that 38K was specifically localized to the nucleocapsids in infected cells and appeared to be distributed over the cylindrical capsid sheath of nucleocapsid. Yeast two-hybrid assays were performed to examine potential interactions between 38K and nine known nucleocapsid shell-associated proteins (PP78/83, PCNA, VP1054, FP25, VLF-1, VP39, BV/ODV-C42, VP80, and P24), three non-nucleocapsid shell-associated proteins (P6.9, PP31, and BV/ODV-E26), and itself. The results revealed that 38K interacted with the nucleocapsid proteins VP1054, VP39, VP80, and 38K itself. These interactions were confirmed by coimmunoprecipitation assays in vivo. These data demonstrate that 38K is a novel nucleocapsid protein and provide a rationale for why 38K is essential for nucleocapsid assembly.