Gaochun Zhu

Effect of emodin on neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

Neuropathic pain is the most difficult type of pain to cure. The P2X(2/3) receptors play a crucial role in facilitating the transmission of pain at neuropathic pain states. Emodin is a natural anthraquinone in rhubarb. The present research investigated the effects of emodin on the pain transmission in neuropathic pain states that was mediated by P2X(2/3) receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Emodin was dissolved in 0.5% sodium carboxymethyl cellulose (CMC) as vehicle. Sprague-Dawley male rats had been randomly divided into Sham+vehicle group, CCI+emodin group, and CCI+vehicle group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. P2X(2/3) expression in L4/L5 dorsal root ganglion (DRG) was detected by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mechanical withdrawal threshold and thermal withdrawal latency in CCI+vehicle group were lower than those in Sham+vehicle group and CCI+emodin group (p<0.05), while P2X(2) and P2X(3) receptor expression of L4/L5 DRG in CCI+vehicle group was higher than those in the other two groups (p<0.05). The co-local staining of P2X(2) and P2X(3) in the DRG of CCI group appeared to be more intense than that in the DRG of the other two groups with double-label fluorescence immunohistochemistry. The results showed that the application of emodin alleviated the hyperalgesia of CCI rats and significantly decreased the P2X(2/3) expression of L4/L5 DRG in CCI+emodin group compared with that in CCI+vehicle group (p<0.05). The data of ISH and RT-PCR in P2X(2) and P2X(3) mRNA expression suggest that the pharmacologic mechanism of emodin is involved in the nucleic acid level. The results showed that emodin can inhibit the transmission of neuropathic pain mediated by P2X(2/3) receptor of primary sensory neurons to alleviate chronic neuropathic pain.

P2X2/3 receptor activity of rat nodose ganglion neurons contributing to myocardial ischemic nociceptive signaling

Myocardial ischemia causes the production of a variety of chemical substances, which act on the cardiac afferent nerve to cause pain. Myocardial damage can affect cardiac vagal afferent activity. Survivors of myocardial infarction are often left with impaired activity of cardiac vagal sensory fibres. The nodose ganglia (NG) are lower ganglia of cardiac vagus nerve, which are chiefly visceral afferent in the sensation of heart. ATP as a possible damage signal may activate nociceptive sensory neurons. Activation of P2X(3), P2X(2/3) receptors by endogenous ATP contributes to the development of hyperalgesia. The present results have shown that the sensitivity of P2X(2/3) receptor in nodose ganglion neurons was increased after myocardial ischemic injury under electrophysiological observation. The inhibitive role of P2X(2/3) antagonist A-317491 on ATP-activated currents in myocardial ischemic rats was significantly increased, compared with that in control group at the same concentration of A-317491. The staining of P2X(2) and P2X(3) receptors in myocardial ischemic injury group appeared to be more intense than those in naive rats and myocardial ischemic rats treated with A-317491 with immunofluorescence double labeling methods. Therefore, the activity of P2X(2/3) receptors in NG neurons was involved in the transmission of myocardial ischemic nociceptive signal.

Long noncoding RNA MRAK009713 is a novel regulator of neuropathic pain in rats

Abstract Long noncoding RNAs have been implicated in neuropathy. Here, we identify and validate a long noncoding RNA, MRAK009713, as the primary regulator of neuropathic pain in chronic constriction injury (CCI) rats. MRAK009713 expression was markedly increased in CCI rats associated with enhanced pain behaviors, and small interfering RNA against MRAK009713 significantly reduced both mechanical and thermal hyperalgesia in the CCI rats. MRAK009713 is predicted to interact with the nociceptive P2X3 receptor by CatRAPID, a bioinformatics technology. Overexpression of MRAK009713 markedly increased expression of P2X3 in the dorsal root ganglia of the control rats, and MRAK009713 small interfering RNA significantly inhibited the P2X3 expression in the dorsal root ganglia of the CCI rats. MRAK009713 directly interacted with the P2X3 protein heterologously expressed in the human embryonic kidney (HEK) 293 cells and potentiated P2X3 receptor function. Thus, MRAK009713 is a novel positive regulator of neuropathic pain in rats through regulating the expression and function of the P2X3 receptor.

Co‐expression changes of lncRNAs and mRNAs in the cervical sympathetic ganglia in diabetic cardiac autonomic neuropathic rats

Cardiac autonomic neuropathy in Type 2 diabetes (T2D) is often a devastating complication. Long non‐coding RNAs (lncRNAs) have important effects on both normal development and disease pathogenesis. In this study, we explored the expression profiles of some lncRNAs involved in inflammation which may be co‐expressed with messenger RNA (mRNA) in superior cervical and stellate ganglia after type 2 diabetic injuries. Total RNA isolated from 10 pairs of superior cervical and stellate ganglia in diabetic and normal male rats was hybridized to lncRNA arrays for detections. Pathway analysis indicated that the most significant gene ontology (GO) processes that were upregulated in diabetes were associated with immune response, cell migration, defense response, taxis, and chemotaxis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway revealed that most of the target genes of the lncRNAs were located in cytokine–cytokine receptor interactions, the chemokine signaling pathway and cell adhesion molecules, which were involved in T2D. Gene co‐expression network construction showed that the co‐expression network in the experimental rats consisted of 268 regulation edges among 105 lncRNAs and 11 mRNAs. Our studies demonstrated the co‐expression profile of lncRNAs and mRNAs in diabetic cardiac autonomic ganglia, suggesting possible roles for multiple lncRNAs as potential targets for the development of therapeutic strategies or biomarkers for diabetic cardiac autonomic neuropathy.

Naringin Protects Against High Glucose-Induced Human Endothelial Cell Injury Via Antioxidation and CX3CL1 Downregulation

Background/Aims: The induction of endothelial injury by hyperglycemia in diabetes has been widely accepted. Naringin is a bio-flavonoid. Some studies showed that naringin alleviates diabetic complications, but the exact mechanisms by which naringin improves diabetic anomalies are not yet fully understood. The aim of this research was to study the protective effect of naringin on high glucose-induced injury of human umbilical vein endothelial cells (HUVECs). Methods: HUVECs were cultured with or without high glucose in the absence or presence of naringin for 5 days. The expression of CX3CL1 was determined by quantitative real-time RT-PCR (qPCR) and western blot. The cellular bioenergetic analysis oxygen consumption rate (OCR) was measured with a Seahorse Bioscience XF analyzer. Results: The production of reactive oxygen species (ROS), the expression of CX3CL1 and the level of AKT phosphorylation were increased in HUVECs cultured with high glucose compared with controls. However, naringin rescued these increases in ROS production, CX3CL1 expression and AKT phosphorylation. Nitric oxide (NO) production and OCR were lower in the high glucose group, and naringin restored the changes induced by high glucose. Molecular docking results suggested that Naringin might interact with the CX3CL1 protein. Conclusion: Naringin protects HUVECs from high-glucose-induced damage through its antioxidant properties by downregulating CX3CL1 and by improving mitochondrial function.

Effects of Baicalin on Diabetic Cardiac Autonomic Neuropathy Mediated by the P2Y12 Receptor in Rat Stellate Ganglia

Background/Aims: Chronic diabetic hyperglycemia can damage various of organ systems and cause serious complications. Although diabetic cardiac autonomic neuropathy (DCAN) is the primary cause of death in diabetic patients, its pathogenesis remains to be fully elucidated. Baicalin is a flavonoid extracted from Scutellaria baicalensis root and has antibacterial, diuretic, anti-inflammatory, anti- metamorphotic, and antispasmodic effects. Our study explored the effects of baicalin on enhancing sympathoexcitatory response induced by DCAN via the P2Y12 receptor. Methods: A type 2 diabetes mellitus rat model was induced by a combination of diet and streptozotocin. Serum epinephrine was measured by enzyme-linked immunosorbent assay. Blood pressure and heart rate were measured using the indirect tail-cuff method. Heart rate variability was analyzed using the frequency-domain of electrocardiogram recordings. The expression levels of P2Y12, interleukin-1beta (IL-1β), tumor necrosis factor alpha (TNF-α), and connexin 43 (Cx43) were determined by quantitative real-time reverse transcription-polymerase chain reaction and western blotting. The interaction between baicalin and P2Y12 determined using by molecular docking. Results: Baicalin alleviated elevated blood pressure and heart rate, improved heart rate variability, and decreased the elevated expression levels of P2Y12, IL-1β, TNF-α, and Cx43 in the stellate ganglia of diabetic rats. Baicalin also reduced the elevated concentration of serum epinephrine and the phosphorylation of p38 mitogen-activated protein kinase in diabetic rats. Conclusion: Baicalin decreases sympathetic activity by inhibiting the P2Y12 receptor in stellate ganglia satellite glial cells to maintain the balance between sympathetic and parasympathetic nerves and relieves DCAN in the rat.

The role of osthole on the human umbilical vein endothelial cells in chronic high glucose

Osthole is used as antiproliferation, vasorelaxation, antihepatitis, anti-inflammatory, antiaggregatory, and antiallergic effects in traditional medicine. Recently, osthole has been shown to ameliorate insulin resistance and decrease the fasting blood glucose (FBG) in high-sucrose and high-fat induced fatty liver rats. However the mechanism of its anti-diabetes is not very understood. In this work we observe the effect of osthole on the human umbilical vein endothelial cells (HUVEC) in chronic high glucose. Our data showed that osthole reduced the production of intracellular reactive oxygen species (ROS) and enhanced the the concentration of nitric oxide (NO) of cultured media in the dysfunctional vascular endothelium induced by chronic high glucose. Our current results indicated that osthole can reduce the dysfunctional vascular endothelium.

Chronic lead exposure enhances the sympathoexcitatory response associated with P2X4 receptor in rat stellate ganglia

Chronic lead exposure causes peripheral sympathetic nerve stimulation, including increased blood pressure and heart rate. Purinergic receptors are involved in the sympathoexcitatory response induced by myocardial ischemia injury. However, whether P2X4 receptor participates in sympathoexcitatory response induced by chronic lead exposure and the possible mechanisms are still unknown. The aim of this study was to explore the change of the sympathoexcitatory response induced by chronic lead exposure via the P2X4 receptor in the stellate ganglion (SG). Rats were given lead acetate through drinking water freely at doses of 0 g/L (control group), 0.5 g/L (low lead group), and 2 g/L (high lead group) for 1 year. Our results demonstrated that lead exposure caused autonomic nervous dysfunction, including blood pressure and heart rate increased and heart rate variability (HRV) decreased. Western blotting results indicated that after lead exposure, the protein expression levels in the SG of P2X4 receptor, IL‐1β and Cx43 were up‐regulated, the phosphorylation of p38 mitogen‐activated protein kinase (MAPK) was activated. Real‐time PCR results showed that the mRNA expression of P2X4 receptor in the SG was higher in lead exposure group than that in the control group. Double‐labeled immunofluorescence results showed that P2X4 receptor was co‐expressed with glutamine synthetase (GS), the marker of satellite glial cells (SGCs). These changes were positively correlated with the dose of lead exposure. The up‐regulated expression of P2X4 receptor in SGCs of the SG maybe enhance the sympathoexcitatory response induced by chronic lead exposure.