The presence of serotonin in cigarette smoke – a possible mechanistic link to 5-HT-induced airway inflammation

We previously reported the involvement of serotonin (5-HT) metabolism in cigarette smoke-induced oxidative stress in rat lung in vivo. Here, we report cigarette smoke as a source of serotonin (5-HT) to the airways and aim at investigating the effects of 5-HT on oxidative stress and inflammation in human bronchial epithelial cells (BEAS-2B). A 5-HT analog was identified to be present in aqueous phase cigarette smoke using the LC-MS/MS approach, which was later confirmed by a 5-HT enzyme-linked immune assay (EIA). Furthermore, exposure to 5-HT caused a time-dependent elevation of intracellular ROS level, which was blocked in the presence of apocynin (a NOX inhibitor). In support, the immunoblot analysis indicated that there was an increase in the expression of NOX2 time-dependently. 5-HT-induced elevation of IL-8 at both mRNA and protein levels was observed, which was inhibited by TEMPOL (a free radical scavenger), and inhibitors for p38 MAPK (SB203580) and ERK (U0126), in line with the time-dependent phosphorylation of p38 MAPK and ERK. In conclusion, our findings suggest that 5-HT presented in bronchial epithelium of smokers may be involved in cigarette smoke-induced oxidative stress and inflammation via activation of p38 MAPK and ERK pathway after the formation of free radicals.     

Homodimeric PHD Domain-containing Rco1 Subunit Constitutes a Critical Interaction Hub within the Rpd3S Histone Deacetylase Complex

Recognition of histone post-translational modifications is pivotal for directing chromatin-modifying enzymes to specific genomic regions and regulating their activities. Emerging evidence suggests that other structural features of nucleosomes also contribute to precise targeting of downstream chromatin complexes, such as linker DNA, the histone globular domain, and nucleosome spacing. However, how chromatin complexes coordinate individual interactions to achieve high affinity and specificity remains unclear. The Rpd3S histone deacetylase utilizes the chromodomain-containing Eaf3 subunit and the PHD domain-containing Rco1 subunit to recognize nucleosomes that are methylated at lysine 36 of histone H3 (H3K36me). We showed previously that the binding of Eaf3 to H3K36me can be allosterically activated by Rco1. To investigate how this chromatin recognition module is regulated in the context of the Rpd3S complex, we first determined the subunit interaction network of Rpd3S. Interestingly, we found that Rpd3S contains two copies of the essential subunit Rco1, and both copies of Rco1 are required for full functionality of Rpd3S. Our functional dissection of Rco1 revealed that besides its known chromatin-recognition interfaces, other regions of Rco1 are also critical for Rpd3S to recognize its nucleosomal substrates and functionin vivo. This unexpected result uncovered an important and understudied aspect of chromatin recognition. It suggests that precisely reading modified chromatin may not only need the combined actions of reader domains but also require an internal signaling circuit that coordinates the individual actions in a productive way.     

Gibberellic acid is selectively downregulated in response to aphid-induced gall formation

The fluid-feeding aphid Schlechtendalia chinensis (Bell) induces horned galls on its primary host, the Chinese Sumac (Rhus chinensis Mill). Horned galls are harvested for their high content of tannins, and used in a range of medical and chemical applications. Gall development is a complex and highly controlled physiological process, where the growing insect population manipulates the plant developmental programs that allow the transformation of plant tissue into a gall. In this study, we examine whether Schlechtendalia alters the balance of plant hormones in the host tree as a means to achieve gall formation. For this, we measured concentrations for a series of endogenous hormones, including indole-3-acetic acid (IAA), cytokinin (CTK), gibberellic acid (GA), abscisic acid (ABA), jasmonic acid (JA), salicylic acid (SA), and ethylene (ETH). Specifically, we conducted a time course (namely, 30, 85, 100, 115, 125, 140, 155, and 170 days from gall initiation) analysis, where we measured both gall and leaf samples representing different developmental stages that spanned an entire growing season. To correlate these hormone data with developmental parameters during gall growth, we determined gall volume, tannin content, and aphid population size for the same time points. Interestingly, tannin production rose steeply in the early stages of gall development, while the aphid population size grew little. After this single peak (day 100), tannin concentrations declined moderately and aphid population size increased from then on. This switch in population growth was accompanied by notable changes in plant hormone titers. In general, all hormones but GA were elevated in all sample types isolated from the host tree (gall, leaves near and distant from gall) when compared with samples from an uninfected tree. Most of the elevated hormones showed similar changes over time; however, GA appeared to display the opposite behavior in all samples, suggesting that GA is a key target for controlling gall growth. When tannin concentrations spiked, GA levels peaked as well, while the remaining plant hormones exhibited a decline at that time. Principle component analysis revealed distinct functional groups in our hormone cohort. This yielded three groups comprising (1) CTK, ABA, ETH, and JA, (2) IAA and SA, (3) GA. The fact that GA comprised its own group and exhibited a unique profile during gall development prompted us to examine whether exogenous GA would alter the rate of gall growth. Indeed, we found that ectopic GA significantly accelerated gall growth, and more strongly than all other hormones, consistent with the notion that controlling GA levels within the gall is crucial for stimulating gall development. We propose a model, whereby the host plant downregulates GA concentrations in an attempt to throttle gall growth, while the gall-inducing aphid population counters these attempts.     

Relationship between root vigour,photosynthesis and biomass in soybean cultivars during 87 years of genetic improvement in the northern China

During the last century, the world soybean yield has been constantly enhancing at a remarkable rate. Factors limiting the soybean yield may be multiple. It is widely acknowledged that changes of root metabolism can influence aboveground characteristics, such as the seed yield and photosynthesis. In this study, we considered root bleeding sap mass (BSM) and root activity (RA) as indicators of the root growth vigour. We used 27 soybean cultivars, spanning from 1923 to 2009, to evaluate the contribution of root characteristic improvement to efficient photosynthesis and dry matter production. The BSM, RA, net photosynthetic rate (P_N), and organ biomass were measured at different growth stages, such as the fourth leaf node, flowering, podding, and seed-filling stage. Our results showed that the soybean cultivars increased their biomass and P_N thanks to genetic improvement. At the same time, BSM and RA also increased in dependence on a year of cultivar release. However, both P_N and biomass were positively correlated with root characteristics only at the podding stage. Our data revealed that the improved root characteristic may have contributed to the enhanced photosynthesis, biomass, and yield of soybean cultivars during last 87 years of genetic improvement. We suggest that BSM and RA could be used as important indexes for further practice in soybean production improvement.     

Novel <Emphasis Type="Italic">FBN1</Emphasis> mutations are responsible for cardiovascular manifestations of Marfan syndrome

The fibrillin-1 (FBN1) gene mutations result in Marfan syndrome (MFS) and have a variety of phenotypic variations. This disease is involved in the skeletal, ocular and cardiovascular system. Here we analyzed genotype-phenotype correlation in two Chinese families with MFS. Two patients with thoracic aortic aneurysms and dissections were diagnosed as MFS according to the revised Ghent criteria. Peripheral blood samples were collected and genomic DNAs were isolated from available cases, namely, patient-1 and his daughter and son, and patient-2 and his parents. According to the next-generation sequencing results, the mutations in FBN1 were confirmed by direct sequencing. A heterozygous frameshift mutation in exon 12 of FBN1 was found in the proband-1 and his daughter. They showed cardiovascular phenotype thoracic aortic aneurysms and dissections, a life-threatening vascular disease, and atrial septal defect respectively. One de novo missense mutation in exon 50 of FBN1 was identified only in the patient-2, showing aortic root aneurysm and aortic root dilatation. Intriguingly, two novel mutations mainly caused the cardiovascular complications in affected family members. No meaningful mutations were found in these two patients by screening all exons of 428 genes related with cardiovascular disease. The high incidence of cardiovascular manifestations might be associated with the two novel mutations in exon 12 and 50 of FBN1.     

Effects of Hindlimb Unweighting on MBP and GDNF Expression and Morphology in Rat Dorsal Root Ganglia Neurons

With the development of technology and space exploration, studies on long-duration space flights have shown that microgravity induces damage to multiple organs, including the dorsal root ganglia (DRG). However, very little is known about the effects of long-term microgravity on DRG neurons. This study investigated the effects of microgravity on lumbar 5 (L5) DRG neurons in rats using the hindlimb unweighting (HU) model. Male (M) and female (F) Sprague-Dawley rats were randomly divided into M- and F-control (CON) groups and M- and F-HU groups, respectively (n = 10). At the end of HU treatment for 4 weeks, morphological changes were detected. Myelin basic protein (MBP) and degenerated myelin basic protein (dgen-MBP) expressions were analyzed by immunofluorescence and western blot assays. Glial cell line-derived neurotrophic factor (GDNF) protein and mRNA expressions were also analyzed by immunohistochemistry, western blot, and RT-PCR analysis, respectively. Compared with the corresponding CON groups, the HU groups exhibited slightly loose junctions between DRG neurons, some separated ganglion cells and satellite cells, and lightly stained Nissl bodies that were of smaller size and had a scattered distribution. High levels of dgen-MBP and low MBP expressions were appeared and GDNF expressions were significantly decreased in both HU groups. Changes were more pronounced in the F-HU group than in the M-HU group. In conclusion, HU treatment induced damage of L5 DRG neurons, which was correlated with decreased total MBP protein expression, increased dgen-MBP expression, and reduced GDNF protein and mRNA expression. Importantly, these changes were more severe in F-HU rats compared with M-HU rats.