Schisandrin A ameliorates airway inflammation in model of asthma by attenuating Th2 response.

Asthma is a persistent respiratory ailment that displays periodicity and is linked to the equilibrium of T cells. Several compounds obtained from Chinese herbal medicines display beneficial impacts on T cell regulation and the attenuation of inflammatory mediator synthesis. Schisandrin A, an active lignan derived from the Schisandra fruit, exhibits anti-inflammatory characteristics. In the present study, the network analysis conducted revealed that the nuclear factor-kappaB (NF-κB) signaling pathway is likely a prominent contributor to the anti-asthmatic effects of schisandrin A. In addition, it has been established that the inhibition of cyclooxygenase 2 (COX-2/PTGS2) is likely a significant factor in this process. The results of in vitro experiments have substantiated that schisandrin A can effectively lower the expression of COX-2 and inducible nitric oxide synthase (iNOS) in 16 HBE cells and RAW264.7 cells in a manner that is dependent on the dosage administered. It was able to effectively reduce the activation of the NF-κB signaling pathway while simultaneously improving the injury to the epithelial barrier function. Furthermore, an investigation utilizing immune infiltration as a metric revealed an inequity in Th1/Th2 cells and a surge in Th2 cytokines in asthma patients. In the OVA-induced asthma mice model, it was observed that schisandrin A treatment effectively suppressed inflammatory cell infiltration, reduced the Th2 cell ratio, inhibited mucus secretion, and prevented airway remodeling. To summarize, the administration of schisandrin A has been found to effectively alleviate the symptoms of asthma by impeding the production of inflammation, which includes reducing the Th2 cell ratio and improving the integrity of the epithelial barrier function. These findings offer valuable insights into the potential therapeutic applications of schisandrin A for the treatment of asthma.

The Impact of Cyanobacteria Blooms on the Aquatic Environment and Human Health.

Cyanobacteria blooms are a global aquatic environment problem. In recent years, due to global warming and water eutrophication, the surface cyanobacteria accumulate in a certain area to form cyanobacteria blooms driven by wind. Cyanobacteria blooms change the physical and chemical properties of water and cause pollution. Moreover, cyanobacteria release organic matter, N (nitrogen) and P (phosphorus) into the water during their apoptosis, accelerating the eutrophication of the water, threatening aquatic flora and fauna, and affecting the community structure and abundance of microorganisms in the water. Simultaneously, toxins and carcinogens released from cyanobacteria can be enriched through the food chain/web, endangering human health. This study summarized and analyzed the research of the influence of cyanobacteria blooms on the aquatic environment and human health, which is helpful to understand further the harm of cyanobacteria blooms and provide some reference for a related research of cyanobacteria blooms.

Exponential decay of between-month spatial dissimilarity congruence of phytoplankton communities in relation to phosphorus in a highland eutrophic lake.

Phytoplankton species composition has long been recognized to be structured by environmental filtering, but our knowledge of patterns of spatial dissimilarity congruence between the phytoplankton community and environmental divers is rather limited. Specifically, a study on whether there are specific temporal properties that could be more related to spatial dissimilarity remains to be seen. We examined the extent to how spatial dissimilarity changed with seasonal succession by measuring ß-diversity in phytoplankton communities in Lake Erhai (from January 2012 to December 2014 at 15 sampling sites) as a function of different period conditions (high-density period and low-density period). We found that congruences of spatial dissimilarity in algal communities over time were neither stable in time nor showed a seasonal pattern. The spatial dissimilarity congruence between the phytoplankton community and dissolved inorganic phosphorus (DIP) concentration followed exponential decay patterns, and this congruence was led by algal cell density. This result implies that species and functions of phytoplankton are specialized, and DIP concentration drastically increases in high-density periods than in low-density periods. This means that DIP enrichment is related to the loss of algal diversity and functions and the increase of algal biomass in eutrophic lakes.

Nutrient limitation and enzymolysis of phosphorus in Meiliang Bay, Lake Taihu, during algal blooms.

In this study, algal growth potential tests were performed in water samples collected from six sampling sites in Meiliang Bay, Lake Taihu. The potential release of soluble reactive phosphorus (SRP) by enzymatic hydrolysis of enzymatically hydrolyzable phosphorus (EHP) was simultaneously evaluated. Results show that all studied regions were in highly eutrophic states, with additional nitrogen (N) or phosphorus (P) inputs, inducing negligible further increase in algal growth. EHP in water could be rapidly transformed into SRP, further supporting the proliferation of algal blooms. The shortest EHP mineralization time was calculated as 69 minutes; therefore, limiting specific nutrient inputs alone in extremely eutrophic lakes can have a limited effect on suppressing the proliferation of algal blooms. Methods to establish a suitable environmental fate for excessive nitrogen and phosphorus nutrients may be more effective and provide more significant results. PRACTITIONER POINTS: N and P were no longer serving as the limiting factors in Meiliang Bay. Enzymatically hydrolysable phosphorus could be hydrolyzed into soluble reactive phosphorus in a very short period during algal blooms. Both enzymatically hydrolysable phosphorus and soluble reactive phosphorus are required to be curbed in practical eutrophication control.

The concentration thresholds establishment of nitrogen and phosphorus considering the effects of extracellular substrate-to-biomass ratio on cyanobacterial growth kinetics.

Harmful cyanobacterial blooms have caused serious threat to the sustainable development of freshwater ecosystems due to eutrophication, but there is no consensus on nutrients threshold for controlling cyanobacterial bloom. A Monod-based ratio-dependent model was originally developed to investigate the effects of the extracellular substrate-to-biomass (Chlorophyll a) ratio (Sex/X) on the growth kinetics of Cyanobacteria and to determine the concentration thresholds of nitrogen (N) and phosphorus (P) in the form of Sex/X. The results indicated that biomass growth was completely suppressed at Sex/X ≤ 0.21 µg µg-1 for P and Sex/X ≤ 2.82 µg µg-1 for N, which are far lower than the values of most of the eutrophic freshwater lakes. This indicates that in addition to curbing N and P nutrients of eutrophic water, to conduct some biologically mediated changes and to find a suitable environmental fate or a suitable position for excessive N and P nutrients is also of great significance in controlling HABs.

Exendin-4 decreases ghrelin levels through mTOR signaling.

Exendin-4 (EX-4), a long-acting glucagon-like peptide-1 receptor (GLP-1R) agonist, regulates feeding behavior through its ability to inhibit gastric emptying. Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate appetite. Here, we report that EX-4 suppresses ghrelin production through the mTORC1-dependent mechanism. Central administration of EX-4 reduces gastric, hypothalamic and plasma ghrelin in both C57BL/6J mice and diet induced obese mice. These changes were associated with a significant increase in mTORC1 activity. Both GLP-1 and EX-4 suppressed the expression and secretion of ghrelin in cultured mHypoE-42 cells, a hypothalamic cell line. These effects were associated with significant changes in mTOR signaling. Inhibition of mTORC1 activity by mTOR siRNA or rapamycin abolished the suppression of ghrelin production induced by GLP-1 and EX-4 in mHypoE-42 cells. Our results identify mTORC1 as a critical signaling pathway for the downregulation of ghrelin induced by activation of GLP-1R.

Thrombin mediates vagal apoptosis and dysfunction in inflammatory bowel disease.

BACKGROUND: In inflammatory bowel disease, autonomic dysfunction contributes to symptoms, morbidity, and health care resource utilization. Efferent vagal neurons, which provide the primary parasympathetic input to the gastrointestinal tract, are housed in the dorsal motor nucleus of the vagus (DMV) in the brainstem. This study seeks to characterize the effects of IBD on DMV neuronal survival and function. METHODS: TNBS (picrylsulfonic acid) was administered by enema to induce colitis in rats. Brain sections through the DMV were examined for neuronal apoptosis using TUNEL labeling, and for glial cell activation by immunofluorescence. Prothrombin production was evaluated via quantitative RT-PCR from DMV tissue, as well as by double immunofluorescence in DMV sections. To investigate the effects of thrombin in the DMV, thrombin or thrombin and an antagonist to its receptor were administered into the fourth ventricle via a stereotactically placed cannula. DMV sections were then examined for apoptosis by TUNEL assay. To evaluate the effect of thrombin on DMV neuronal function, we examined calcium signaling in primary DMV neuron cultures following exposure to thrombin and other neurotransmitters. RESULTS: TNBS colitis is associated with significantly increased rates of DMV neuronal apoptosis, affecting 12.7 % of DMV neurons in animals with colitis, compared to 3.4 % in controls. There was a corresponding increase in DMV neuron activated caspase-3 immunoreactivity (14.8 vs. 2.6 % of DMV neurons). TNBS-treated animals also demonstrated significantly increased DMV astrocyte and microglial immunoreactivity, indicating glial cell activation. DMV prothrombin production was significantly increased in TNBS colitis, with a close anatomic relationship between prothrombin and microglia. Direct DMV exposure to thrombin replicated the apoptosis and activation of caspase-3 seen in TNBS colitis; these effects were prevented by coadministration of the PAR-1 inhibitor FR171113. Cultured DMV neurons exhibited impaired calcium signaling in response to neurotransmitters following exposure to thrombin. Glutamate-induced calcium transients decreased by 59 %, and those triggered by GABA were reduced by 61 %. PAR-1 antagonism prevented these thrombin-induced changes in calcium signaling. CONCLUSIONS: IBD is associated with DMV microglial activation and production of prothrombin. Thrombin in the DMV causes vagal neuron apoptosis and decreased sensitivity to neurotransmitters.

TNFα causes thrombin-dependent vagal neuron apoptosis in inflammatory bowel disease.

BACKGROUND: The role of peripheral tumor necrosis factor alpha (TNFα) in inflammatory bowel disease (IBD) is well established, but its central nervous system (CNS) effects are not understood. Thrombin, another mediator of inflammation in IBD, has been implicated in CNS vagal neuron apoptosis in the dorsal motor nucleus of the vagus (DMV). This study evaluates DMV TNFα exposure, characterizes effects of TNFα on DMV neurons, and identifies a relationship between DMV TNFα and thrombin in IBD. METHODS: 2,4,6-Trinitrobenzene sulfonic acid was administered via enema to induce colonic inflammation in rats. TNFα in serum, cerebrospinal fluid (CSF), and DMV tissues were determined by ELISA and DMV TNFα expression by quantitative reverse transcription PCR (RT-PCR). TNFα was administered into the fourth intracerebral ventricle (4 V) adjacent to the DMV, with and without blockade of TNF receptor 1 (TNFR1) and the thrombin receptor proteinase-activated receptor 1 (PAR1). Immunofluorescence was used to evaluate microglial activation (Cd11b) and prothrombin presence in DMV sections. Apoptosis was examined using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) and activated caspase-3 immunofluorescence. RESULTS: IBD is associated with increased TNFα protein in serum, CSF, and DMV tissue; DMV TNFα transcription is also increased. TNFα (4 V) caused a 54 % increase in microglial activation, a 27 % increase in DMV prothrombin protein, and a 31 % increase in vagal neuron apoptosis by TUNEL. There was a 52 % increase in activated caspase-3 immunofluorescence in TNFα-treated animals (p < 0.05). All effects of 4 V TNFα were prevented by TNFR1 blockade. TNFα-induced apoptosis was prevented by PAR1 blockade. CONCLUSIONS: IBD is associated with DMV exposure to TNFα, causing excess DMV prothrombin and vagal apoptosis.

LGR4 and its ligands, R-spondin 1 and R-spondin 3, regulate food intake in the hypothalamus of male rats.

The hypothalamus plays a key role in the regulation of feeding behavior. Several hypothalamic nuclei, including the arcuate nucleus (ARC), paraventricular nucleus, and ventromedial nucleus of the hypothalamus (VMH), are involved in energy homeostasis. Analysis of microarray data derived from ARC revealed that leucine-rich repeat-containing G protein-coupled receptor 4 (LGR4) is highly expressed. LGR4, LGR5, and LGR6 form a subfamily of closely related receptors. Recently, R-spondin (Rspo) family proteins were identified as ligands of the LGR4 subfamily. In the present study, we investigated the distribution and function of LGR4-LGR6 and Rspos (1-4) in the brain of male rat. In situ hybridization showed that LGR4 is expressed in the ARC, VMH, and median eminence of the hypothalamus. LGR4 colocalizes with neuropeptide Y, proopiomelanocortin, and brain-derived neurotrophic factor neurons. LGR5 is not detectable with in situ hybridization; LGR6 is only expressed in the epithelial lining of the lower portion of the third ventricle and median eminence. Rspo1 is expressed in the VMH and down-regulated with fasting. Rspo3 is expressed in the paraventricular nucleus and also down-regulated with fasting. Rspos 1 and 3 colocalize with the neuronal marker HuD, indicating that they are expressed by neurons. Injection of Rspo1 or Rspo3 into the third brain ventricle inhibited food intake. Rspo1 decreased neuropeptide Y and increased proopiomelanocortin expression in the ARC. Rspo1 and Rspo3 mRNA is up-regulated by insulin. These data indicate that Rspo1 and Rspo3 and their receptor LGR4 form novel circuits in the brain to regulate energy homeostasis.

Ankyrin repeat and SOCS box containing protein 4 (Asb-4) colocalizes with insulin receptor substrate 4 (IRS4) in the hypothalamic neurons and mediates IRS4 degradation.

BACKGROUND: The arcuate nucleus of the hypothalamus regulates food intake. Ankyrin repeat and SOCS box containing protein 4 (Asb-4) is expressed in neuropeptide Y and proopiomelanocortin (POMC) neurons in the arcuate nucleus, target neurons in the regulation of food intake and metabolism by insulin and leptin. However, the target protein(s) of Asb-4 in these neurons remains unknown. Insulin receptor substrate 4 (IRS4) is an adaptor molecule involved in the signal transduction by both insulin and leptin. In the present study we examined the colocalization and interaction of Asb-4 with IRS4 and the involvement of Asb-4 in insulin signaling. RESULTS: In situ hybridization showed that the expression pattern of Asb-4 was consistent with that of IRS4 in the rat brain. Double in situ hybridization showed that IRS4 colocalized with Asb-4, and both Asb-4 and IRS4 mRNA were expressed in proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons within the arcuate nucleus of the hypothalamus. In HEK293 cells co-transfected with Myc-tagged Asb-4 and Flag-tagged IRS4, Asb-4 co-immunoprecipitated with IRS4; In these cells endogenous IRS4 also co-immunoprecipitated with transfected Myc-Asb-4; Furthermore, Asb-4 co-immunoprecipitated with IRS4 in rat hypothalamic extracts. In HEK293 cells over expression of Asb-4 decreased IRS4 protein levels and deletion of the SOCS box abolished this effect. Asb-4 increased the ubiquitination of IRS4; Deletion of SOCS box abolished this effect. Expression of Asb-4 decreased both basal and insulin-stimulated phosphorylation of AKT at Thr308. CONCLUSIONS: These data demonstrated that Asb-4 co-localizes and interacts with IRS4 in hypothalamic neurons. The interaction of Asb-4 with IRS4 in cell lines mediates the degradation of IRS4 and decreases insulin signaling.

Melanocortin-4 receptor activation inhibits c-Jun N-terminal kinase activity and promotes insulin signaling.

The melanocortin system is crucial to regulation of energy homeostasis. The melanocortin receptor type 4 (MC4R) modulates insulin signaling via effects on c-Jun N-terminal kinase (JNK). The melanocortin agonist NDP-MSH dose-dependently inhibited JNK activity in HEK293 cells stably expressing the human MC4R; effects were reversed by melanocortin receptor antagonist. NDP-MSH time- and dose-dependently inhibited IRS-1(ser307) phosphorylation, effects also reversed by a specific melanocortin receptor antagonist. NDP-MSH augmented insulin-stimulated AKT phosphorylation in vitro. The melanocortin agonist melanotan II increased insulin-stimulated AKT phosphorylation in the rat hypothalamus in vivo. NDP-MSH increased insulin-stimulated glucose uptake in hypothalamic GT1-1 cells. The current study shows that the melanocortinergic system interacts with insulin signaling via novel effects on JNK activity.

Melanocortin-4 receptor-mediated inhibition of apoptosis in immortalized hypothalamic neurons via mitogen-activated protein kinase.

The melanocortin-4 receptor (MC4R) is a seven transmembrane member of the melanocortin receptor family. The GT1-1 cell line exhibits endogenous expression of MC4R. In this study, GT1-1 cells were used to study MC4R signaling pathways and to examine the effects of melanocortin receptor agonist NDP-MSH on apoptosis. MC4R mRNA expression was demonstrated by RT-PCR. Functional melanocortin receptor expression was implied by specific binding of NDP-MSH and cAMP production. NDP-MSH-stimulated GnRH release in a dose-dependent manner. Serum deprivation-induced apoptosis in GT1-1 cells, and the NDP-MSH inhibited this effect. The melanocortin receptor antagonist SHU9119 blocked the antiapoptotic actions of NDP-MSH, and the MAP kinase inhibitor PD98059 significantly attenuated the antiapoptotic effect. NDP-MSH-stimulated ERK1/2 phosphorylation in a dose-dependent manner. ERK1/2 phosphorylation could be abolished by SHU9119. In GT1-1 cells, melanocortin receptor activation causes ERK1/2 phosphorylation. In these cells, MC4R activation is also associated with antiapoptotic effects.

Activation of the melanocortin-4 receptor mobilizes intracellular free calcium in immortalized hypothalamic neurons.

BACKGROUND: At least 4% of childhood obesity is due to mutations in the hypothalamic melanocortin-4 receptor. The melanocortin-4 receptor, a seven transmembrane G-protein-coupled receptor, is important in the regulation of feeding behavior and body weight. The specific pathways of intracellular signaling remain in investigative stages. To further understand its function, we hypothesized that the melanocortin-4 receptor activates the Galphaq/phospholipase C signaling pathway, resulting in alterations of cytoplasmic calcium in immortalized hypothalamic (GT1-1) neurons. MATERIALS AND METHODS: Changes in intracellular calcium were measured after loading GT1-1 cells with fura-2-AM. Cells were treated with NDP-alphaMSH, an alpha-melanocortin stimulating hormone analogue, and intracellular calcium changes were recorded. Cells treated with NDP-alpha-MSH were also treated with the melanocortin-4 receptor antagonist, SHU-9119. To assess the specific G-protein subunit involved, GT1-1 neurons were treated with the phospholipase C inhibitor U73122 and its inactive analogue, U73433. Experiments were also performed after inhibition of IP3 receptors with 2-aminoethoxydiphenylborate (2APB). Additional experiments were conducted in a calcium-depleted buffer environment. Data were analyzed by ANOVA with statistical significance of P < 0.05. RESULTS: Agonist treatment (0.01-1000 nm) of GT1-1 neurons resulted in dose-dependent increases in intracellular calcium. SHU-9119 (0.01-1000 nm) abolished the calcium response. Treatment with U73122 (10 microm) attenuated the calcium response, while U73433 (10 microm) had minimal effect. 2APB (200 microm) inhibited the calcium transient, and the use of calcium-free buffer did not affect the amplitude of the calcium spike. CONCLUSIONS: Our study demonstrates that, upon agonist binding, the melanocortin-4 receptor mediates increases in intracellular calcium through the Galphaq-protein/phospholipase C dependent signaling pathway. Understanding the physiological importance of calcium signaling by the melanocortin-4 receptor may be important for future development of therapeutic targets.