The effects of congenital brain serotonin deficiency on responses to chronic fluoxetine

The importance of reversing brain serotonin (5-HT) deficiency and promoting hippocampal neurogenesis in the mechanisms of action for antidepressants remain highly controversial. Here we examined the behavioral, neurochemical and neurogenic effects of chronic fluoxetine (FLX) in a mouse model of congenital 5-HT deficiency, the tryptophan hydroxylase 2 (R439H) knock-in (Tph2KI) mouse. Our results demonstrate that congenital 5-HT deficiency prevents a subset of the signature molecular, cellular and behavioral effects of FLX, despite the fact that FLX restores the 5-HT levels of Tph2KI mice to essentially the levels observed in wild-type mice at baseline. These results suggest that inducing supra-physiological levels of 5-HT, not merely reversing 5-HT deficiency, is required for many of the antidepressant-like effects of FLX. We also demonstrate that co-administration of the 5-HT precursor, 5-hydroxytryptophan (5-HTP), along with FLX rescues the novelty suppressed feeding (NSF) anxiolytic-like effect of FLX in Tph2KI mice, despite still failing to induce neurogenesis. Thus, our results indicate that brain 5-HT deficiency reduces the efficacy of FLX and that supplementation with 5-HTP can restore some antidepressant-like responses in the context of 5-HT deficiency. Our findings also suggest that feeding latency reductions in the NSF induced by chronic 5-HT elevation are not mediated by drug-induced increments in neurogenesis in 5-HT-deficient animals. Overall, these findings shed new light on the impact of 5-HT deficiency on responses to FLX and may have important implications for treatment selection in depression and anxiety disorders.     

Serum indoleamine 2,3 dioxygenase and tryptophan and kynurenine ratio using the UPLC-MS/MS method,in patients undergoing peritoneal dialysis,hemodialysis, and kidney transplantation

Background: The level and activity of indoleamine 2,3-dioxygenase (IDO) and the concentrations of L-tryptophan and its metabolite L-kynurenine were determined in association with various renal diseases. However, there have been no data regarding these parameters in patients on peritoneal dialysis compared to those undergoing hemodialysis or kidney transplantation.

Methods: This study investigated the level and activity of IDO and determined oxidative balance by calculating the total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI). We enrolled 60 kidney disease patients, including 20 on peritoneal dialysis (PD group), 19 on hemodialysis (HD group), and 21 with kidney transplantation (KT group), as well as 21 control group.

Results: IDO levels were increased in the PD, HD, and KT groups compared to the control group. The concentration of kynurenine was significantly increased in the PD group compared to the other groups (p?tryptophan ratio was increased in the PD group compared to the other groups (all p?p?Conclusion: The results showed that IDO levels were increased in peritoneal dialysis and hemodialysis patients and in renal transplant recipients, while oxidative stress was found to be related to IDO activity and was most increased in the patients on peritoneal dialysis.     

Thirteen week toxicity study of dietary l‐tryptophan in rats with a recovery period of 5 weeks

Although l ‐tryptophan is nutritionally important and widely used in medical applications, toxicity data for its oral administration are limited. The purpose of this study was to evaluate the potential toxicity of an experimental diet containing added l ‐tryptophan at doses of 0 (basal diet), 1.25%, 2.5% and 5.0% when administered to Sprague–Dawley rats for 13 weeks. There were no toxicological changes in clinical signs, ophthalmology, urinalysis, hematology, necropsy, organ weight and histopathology between control rats and those fed additional l ‐tryptophan. Body weight gain and food consumption significantly decreased throughout the administration period in males in the 2.5% group and in both sexes in the 5.0% group. At the end of the dosing period, decreases in water intake in males in the 5.0% group and in serum glucose in females in the 5.0% group were observed. The changes described above were considered toxicologically significant; however, they were not observed after a 5 week recovery period, suggesting reversibility. Consequently, the no‐observed‐adverse‐effect level of l ‐tryptophan in the present study was 1.25% for males and 2.5% for females (mean intake of l ‐tryptophan: 779 mg kg^–1 body weight day^–1 [males] and 1765 mg kg^–1 body weight day^–1 [females]). As the basal diet used in this study contained 0.27% of proteinaceous l ‐tryptophan, the no‐observed‐adverse‐effect level of overall l ‐tryptophan was 1.52% for males and 2.77% for females (mean intake of overall l ‐tryptophan: 948 mg kg^–1 body weight day^–1 (males) and 1956 mg kg^–1 body weight day^–1 (females)). We conclude that l ‐tryptophan has a low toxicity profile in terms of human use.     

槲皮素通过影响吲哚胺-2,3-双加氧酶活性抑制HeLa细胞增殖的研究

目的研究槲皮素抑制人宫颈癌HeLa细胞增殖的机制。方法采用CCK-8法检测细胞增殖;流式细胞术检测细胞周期的变化;运用紫外可见分光光度计测定OD₄₈₀值,反映色氨酸代谢及犬尿氨酸的生成情况;qPCR法检测IDO1的mRNA表达;表达、纯化IDO1蛋白并进行体外酶活性反应,用高效液相色谱法检测色氨酸和犬尿氨酸的含量变化。结果槲皮素抑制HeLa细胞的增殖,引起G0/G1细胞周期阻滞;槲皮素抑制色氨酸的代谢;槲皮素能够明显抑制IDO1的体外酶催化活性,但不影响IDO1的表达;外源性添加色氨酸的代谢产物犬尿氨酸可以逆转槲皮素引起的细胞增殖抑制。结论槲皮素可能通过抑制IDO1的酶催化活性,影响细胞色氨酸的代谢,这可能是槲皮素发挥其抗宫颈癌HeLa细胞增殖作用的机制之一。     

色氨酸分解代谢途径阻断对深海链霉菌ZH66次级代谢及生长的影响

【目的】以深海链霉菌Streptomyces somaliensis SCSIO ZH66为研究对象,通过阻断其色氨酸分解代谢途径,探究代谢产物与生长的变化。【方法】通过Blastp分析寻找S. somaliensis SCSIO ZH66基因组上编码色氨酸双加氧酶基因tdo(ORF0630和ORF6017),在前期阻断ORF0630的基础上采用PCR-targeting的策略阻断ORF6017,通过HPLC检测发酵产物的变化,并观察用不同培养基培养时突变株与野生株生长的差别。【结果】与野生株相比,突变株ZH66Δtdo不产生antimycins,但无其他次级代谢产物的变化。与此同时,ZH66Δtdo在MS平板上开始产生气生菌丝与孢子的时间均提前了12 h,在ISP-2液体培养基中生长对数期开始时间同样提前12 h。【结论】链霉菌S. somaliensis SCSIO ZH66中色氨酸分解代谢途径的阻断未促进其他可能以色氨酸为前体次级代谢产物的合成,而是促进了菌株的生长,为其他链霉菌中色氨酸分解代谢调控提供了借鉴。     

Interplay between the key proteins of serotonin system in SSRI antidepressants efficacy

Introduction: Selective serotonin reuptake inhibitors (SSRIs) are the most effective and most used antidepressant drugs. Acting by inhibiting serotonin (5-HT) transporter, SSRIs display a typical 3–4-week delay in their therapeutic effects, with nearly 40% of depressed patients remaining treatment-resistant. Recent evidence suggests complex interplay between 5-HT receptors and key proteins of 5-HT metabolism in molecular mechanisms of such delay and resistance to SSRIs.

Area covered: This paper concentrates on the interplay between 5-HT receptors in the delay of therapeutic effect of SSRIs, and the interaction between tryptophan hydroxylase 2 and 5-HT transporter in the SSRI resistance. Specifically, it discusses: (1) the data on the association between antidepressant drug efficacy and genetically defined characteristics of key proteins in the 5-HT signaling (TPH2, MAOA, SERT and 5-HT_1A receptor), (2) the effect of dimerization of 5-HT₇ and 5-HT_1A receptors on the internalization and functioning of 5-HT_1A presynaptic receptors, (3) the role of Tph2 deficiency in the resistance to SSRIs treatment. We shift the emphasis from individual proteins to their interactions in explaining antidepressant action of SSRI.

Expert opinion: These interactions should be considered when developing more effective antidepressant drugs as well as for predicting and improving the efficacy of antidepressant therapies.     

Tryptophan and Kynurenine Enhances the Stemness and Osteogenic Differentiation of Bone Marrow-Derived Mesenchymal Stromal Cells In Vitro and In Vivo

Aging tissues present a progressive decline in homeostasis and regenerative capacities, which has been associated with degenerative changes in tissue-specific stem cells and stem cell niches. We hypothesized that amino acids could regulate the stem cell phenotype and differentiation ability of human bone marrow-derived mesenchymal stromal cells (hBMSCs). Thus, we performed a screening of 22 standard amino acids and found that D-tryptophan (10 μM) increased the number of cells positive for the early stem cell marker SSEA-4, and the gene expression levels of OCT-4, NANOG, and SOX-2 in hBMSCs. Comparison between D- and L-tryptophan isomers showed that the latter presents a stronger effect in inducing the mRNA levels of Oct-4 and Nanog, and in increasing the osteogenic differentiation of hBMSCs. On the other hand, L-tryptophan suppressed adipogenesis. The migration and colony-forming ability of hBMSCs were also enhanced by L-tryptophan treatment. In vivo experiments delivering L-tryptophan (50 mg/kg/day) by intraperitoneal injections for three weeks confirmed that L-tryptophan significantly increased the percentage of cells positive for SSEA-4, mRNA levels of Nanog and Oct-4, and the migration and colony-forming ability of mouse BMSCs. L-kynurenine, a major metabolite of L-tryptophan, also induced similar effects of L-tryptophan in enhancing stemness and osteogenic differentiation of BMSCs in vitro and in vivo, possibly indicating the involvement of the kynurenine pathway as the downstream signaling of L-tryptophan. Finally, since BMSCs migrate to the wound healing site to promote bone healing, surgical defects of 1 mm in diameter were created in mouse femur to evaluate bone formation after two weeks of L-tryptophan or L-kynurenine injection. Both L-tryptophan and L-kynurenine accelerated bone healing compared to the PBS-injected control group. In summary, L-tryptophan enhanced the stemness and osteoblastic differentiation of BMSCs and may be used as an essential factor to maintain the stem cell properties and accelerate bone healing and/or prevent bone loss.     

Association of HTR2A-1438G/A Genetic Polymorphism With Smoking and Chronic Obstructive Pulmonary Disease

Introduction

Cigarette smoking is a major risk factor in the development of chronic obstructive pulmonary disease (COPD). Serotonin levels have been associated with COPD and smoking has been as a significant modulator. Elevated levels of serotonin are responsible for bronchoconstriction and pulmonary vasoconstriction and also nicotine dependence, thus serotonin response could be affected by genetic polymorphisms in transporters and receptors of serotonin.

Glycation of human high density lipoprotein by methylglyoxal: Effect on HDL-paraoxonase activity

Objective

Methylglyoxal (MG), a reactive carbonyl compound formed primarily from triose phosphates, appears to be involved in the molecular mechanisms of diabetes, end-stage renal disease and neurodegenerative diseases. Methylglyoxal exerts several biological activities. Among these it promotes advanced glycation end products (AGEs), which are crucial in pathogenesis of human disease. Previous studies have demonstrated that MG reacts with proteins and compositional modifications reflect loss of biological activity. The aim of the study was to investigate the effect of in vitro MG-induced glycation on human high density lipoprotein (HDL) and on the activity of the enzyme paraoxonase-1 (PON1).

Methods

HDL was incubated in the absence or in the presence of MG (0.2 mmol/L and 1.0 mmol/L) (MG-HDL) for different times (3, 6, 24 h) at 37 ° C. We evaluated apoprotein compositional changes, in both control and MG treated HDL, using intrinsic fluorescence of tryptophan and monitoring the decrease of free amino groups. Furthermore we evaluated fluorescent advanced glycation end products (Ex = 370 nm, Em = 440 nm) and the activity of HDL-paraoxonase.

Results

We demonstrated that human HDL is susceptible to glycation by MG (0.2 mmol/L and 1 mmol/L). The decrease of free amino groups and of intrinsic fluorescence of tryptophan demonstrates HDL apoprotein modifications in HDL incubated with MG. The compositional changes are associated with a significant increase in fluorescent advanced glycation end products and with a significant decrease of paraoxonase-1 enzyme activity associated with the HDL surface.

Conclusions

HDL-associated paraoxonase is responsible for the anti-inflammatory and anti-oxidative properties of HDL and detoxification against homocysteine-thiolactone. Therefore, modifications of apoprotein composition and the decrease of paraoxonase-1 activity in MG-treated HDL could affect the protective effect exerted by HDL against oxidative damage and could contribute to complications in patients affected by diseases associated with aging and oxidative stress.     

A comprehensive study on the relieving effect of Lilium brownii on the intestinal flora and metabolic disorder in p-chlorphenylalanine induced insomnia rats

ContextThe bulb of Lilium brownii F. E. Brown (Liliaceae) (LB) is a common Chinese medicine to relieve insomnia.ObjectiveTo investigate the molecular mechanism of LB relieving insomnia.Materials and methodsInsomnia model was induced by intraperitoneally injection p-chlorophenylalanine (PCPA) in Wistar rats. Rats were divided into three groups: Control, PCPA (400 mg/kg, i.p. 2 days), LB (598.64 mg/kg, oral 7 days). The levels of 5-hydroxytryptamine (5-HT), norepinephrine (NE), melatonin (MT), and the expression of GABA_A, 5-HT1A and MT receptors, as well as pathological changes in hypothalamus, were evaluated. 16S rDNA sequencing and UPLC-MS/MS were used to reveal the change of the intestinal flora and metabolic profile.ResultsThe adverse changes in the abundance and diversity of intestinal flora and faecal metabolic phenotype altered by PCPA in rats were reversed after LB treatment, accompanied by the up-regulated levels of 5-HT as 8.14 ng/mL, MT as 16.16 pg/mL, 5-HT1A R and GABA_A R, down-regulated level of NE as 0.47 ng/mL, and the improvement of pathological phenomena of cells in the hypothalamus. And the arachidonic acid metabolism and tryptophan metabolism pathway most significantly altered by PCPA were markedly regulated by LB. Besides, it was also found that LB reduced the levels of kynurenic acid related to psychiatric disorders and trimethylamine-N-oxide associated with cardiovascular disease.ConclusionThe mechanism of LB relieving insomnia involves regulating flora and metabolites to resemble the control group. As a medicinal and edible herb, LB could be considered for development as a health-care food to relieve increasing insomniacs in the future.