The metabolism of histamine in rat hypothalamus and cortex after reserpine treatment

Novel insights on the probable mechanism associated with histamine oral model-inducing neuropathological and behavioral toxicity in rats

Histamine (HIS) is an important chemical mediator that causes vasodilation and contributes to anaphylactic reactions. Recently, HIS is an understudied neurotransmitter in the central nervous system, and its potential role in neuroinflammation and neurodegeneration is a critical area of research. So, the study's goal is to investigate the consequences of repeated oral intake of HIS on the rat's brain and explore the mechanistic way of its neurotoxicity. Thirty male rats were divided into three groups (n = 10). The following treatments were administered orally to all rats every day for 14 days. Group (1) was given distilled water, whereas groups (2 & 3) were given HIS at dosage levels 250 and 500 mg/kg body weight (BWT), respectively. Brain tissue samples were collected at 7- and 14-days from the beginning of the experiment. Our results revealed that continuous oral administration of HIS at both doses for 14 days significantly reduced the BWT and induced severe neurobehavioral changes, including depression, dullness, lethargy, tremors, abnormal walking, and loss of spatial learning and memory in rats. In all HIS receiving groups, HPLC data showed a considerable raise in the HIS contents of the brain. Additionally, the daily consumption of HIS causes oxidative stress that is dose- and time-dependent which is characterized by elevation of malondialdehyde levels along with reduction of catalase activity and reduced glutathione levels. The neuropathological lesions were commonly observed in the cerebrum, striatum, and cerebellum and confirmed by the immunohistochemistry staining that demonstrating moderate to strong caspase-3 and inducible nitric oxide synthase expressions in all HIS receiving groups, mainly those receiving 500 mg/kg HIS. NF-κB, TNF-α, and IL-1β gene levels were also upregulated at 7- and 14-days in all HIS groups, particularly in those getting 500 mg/kg. We concluded that ROS-induced apoptosis and inflammation was the essential mechanism involved in HIS-mediated neurobehavioral toxicity and histopathology.

Serum and Amniotic Fluid Metabolic Profile Changes in Response to Gestational Diabetes Mellitus and the Association with Maternal-Fetal Outcomes

This study was designed to identify serum and amniotic fluid (AF) metabolic profile changes in response to gestational diabetes mellitus (GDM) and explore the association with maternal-fetal outcomes. We established the GDM rat models by combining a high-fat diet (HFD) with an injection of low-dose streptozotocin (STZ), detected the fasting plasma glucose (FPG) of pregnant rats in the second and third trimester, and collected AF and fetal rats by cesarean section on gestational day 19 (GD19), as well as measuring the weight and crown-rump length (CRL) of fetal rats. We applied liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the untargeted metabolomics analyses of serum and AF samples and then explored their correlation with maternal-fetal outcomes via the co-occurrence network. The results showed that 91 and 68 metabolites were upregulated and 125 and 78 metabolites were downregulated in serum and AF samples exposed to GDM, respectively. In maternal serum, the obvious alterations emerged in lipids and lipid-like molecules, while there were great changes in carbohydrate and carbohydrate conjugates, followed by amino acids, peptides, and analogs in amniotic fluid. The altered pathways both in serum and AF samples were amino acid, lipid, nucleotide, and vitamin metabolism pathways. In response to GDM, changes in the steroid hormone metabolic pathway occurred in serum, and an altered carbohydrate metabolism pathway was found in AF samples. Among differential metabolites in two kinds of samples, there were 34 common biochemicals shared by serum and AF samples, and a mutual significant association existed. These shared differential metabolites were implicated in several metabolism pathways, including choline, tryptophan, histidine, and nicotinate and nicotinamide metabolism, and among them, N1-methyl-4-pyridone-3-carboxamide, 5'-methylthioadenosine, and kynurenic acid were significantly associated with both maternal FPG and fetal growth. In conclusion, serum and AF metabolic profiles were remarkably altered in response to GDM. N1-Methyl-4-pyridone-3-carboxamide, 5'-methylthioadenosine, and kynurenic acid have the potential to be taken as biomarkers for maternal-fetal health status of GDM. The common and inter-related differential metabolites both in the serum and AF implied the feasibility of predicting fetal health outcomes via detecting the metabolites in maternal serum exposed to GDM.

Integrating Pharmacology and Gut Microbiota Analysis to Explore the Mechanism of Citri Reticulatae Pericarpium Against Reserpine-Induced Spleen Deficiency in Rats

Citri Reticulatae Pericarpium (CRP), dried peels of Citrus reticulata Blanco and its cultivars, is an important traditional Chinese medicine for the treatment of spleen deficiency-related diseases. To date, the mechanism of CRP alleviating spleen deficiency has not been well investigated. This study aimed to explore corresponding mechanisms with integrating pharmacology and gut microbiota analysis. Firstly, the therapeutic effects of CRP against spleen deficiency were evaluated in reserpine-treated rats. CRP was found to effectively relieve the typical symptoms of spleen deficiency, including poor digestion and absorption capacity, and disorder in gastrointestinal hormones, immune cytokines and oxidative stress. Secondly, high throughput 16S rRNA gene sequencing revealed that CRP could not only up-regulate some short-chain fatty acids producing and anti-inflammatory bacteria but also down-regulate certain spleen deficiency aggravated related bacteria, eventually led to the rebalance of gut microbiota in spleen deficiency rats. In addition, a total of 49 compounds derived from CRP were identified in rat urine using ultra-high performance liquid chromatography-quadrupole- time of flight tandem mass spectrometry. Network pharmacology analysis showed that apigenin, luteolin, naringenin, hesperidin, hesperetin, homoeriodictyol, dihydroxy-tetramethoxyflavone, and monohydroxy-tetramethoxyflavone were the core bioactive components for CRP against spleen deficiency. Further Gene Ontology analysis and pathway enrichment suggested that therapeutic effects of CRP against spleen deficiency involved multiple pathways such as tumor necrosis factor signaling, hypoxia-inducible factor-1 signaling and Toll-like receptor signaling pathway. These results would help to understand the mechanism of CRP alleviating spleen deficiency and provide a reference for further studies.

Storage of neural histamine and histaminergic neurotransmission is VMAT2 dependent in the zebrafish

Monoaminergic neurotransmission is greatly dependent on the function of the vesicular monoamine transporter VMAT2, which is responsible for loading monoamines into secretory vesicles. The role of VMAT2 in histaminergic neurotransmission is poorly understood. We studied the structure and function of the histaminergic system in larval zebrafish following inhibition of VMAT2 function by reserpine. We found that reserpine treatment greatly reduced histamine immunoreactivity in neurons and an almost total disappearance of histamine-containing nerve fibers in the dorsal telencephalon and habenula, the most densely innervated targets of the hypothalamic histamine neurons. The reserpine treated larvae had an impaired histamine-dependent dark-induced flash response seen during the first second after onset of darkness, implying that function of the histaminergic network is VMAT2 dependent. Levels of histamine and other monoamines were decreased in reserpine treated animals. This study provides conclusive evidence of the relevance of VMAT2 in histaminergic neurotransmission, further implying that the storage and release mechanism of neural histamine is comparable to that of other monoamines. Our results also reveal potential new insights about the roles of monoaminergic neurotransmitters in the regulation of locomotion increase during adaptation to darkness.

Protective effect of polysaccharides fractions from Sijunzi decoction in reserpine-induced spleen deficiency rats

Polysaccharide fraction S-3 from SJZD could mitigate effect in the reserpine-induced rats which was investigated with a comprehensive screening strategy.