Upregulation of TRPC6 Mediated by PAX6 Hypomethylation Is Involved in the Mechanical Allodynia Induced by Chemotherapeutics in Dorsal Root Ganglion.

BACKGROUND: Although the action mechanism of antineoplastic agents is different, oxaliplatin, paclitaxel, or bortezomib as first-line antineoplastic drugs can induce painful neuropathy. In rodents, mechanical allodynia is a common phenotype of painful neuropathy for 3 chemotherapeutics. However, whether there is a common molecular involved in the different chemotherapeutics-induced painful peripheral neuropathy remains unclear. METHODS: Mechanical allodynia was tested by von Frey hairs following i.p. injection of vehicle, oxaliplatin, paclitaxel, or bortezomib in Sprague-Dawley rats. Reduced representation bisulfite sequencing and methylated DNA immunoprecipitation were used to detect the change of DNA methylation. Western blot, quantitative polymerase chain reaction, chromatin immunoprecipitation, and immunohistochemistry were employed to explore the molecular mechanisms. RESULTS: In 3 chemotherapeutic models, oxaliplatin, paclitaxel, or bortezomib accordantly upregulated the expression of transient receptor potential cation channel, subfamily C6 (TRPC6) mRNA and protein without affecting the DNA methylation level of TRPC6 gene in DRG. Inhibition of TRPC6 by using TRPC6 siRNA (i.t., 10 consecutive days) relieved mechanical allodynia significantly following application of chemotherapeutics. Furthermore, the downregulated recruitment of DNA methyltransferase 3 beta (DNMT3b) at paired box protein 6 (PAX6) gene led to the hypomethylation of PAX6 gene and increased PAX6 expression. Finally, the increased PAX6 via binding to the TPRC6 promoter contributes to the TRPC6 increase and mechanical allodynia following chemotherapeutics treatment. CONCLUSIONS: The TRPC6 upregulation through DNMT3b-mediated PAX6 gene hypomethylation participated in mechanical allodynia following application of different chemotherapeutic drugs.

TNF-α/STAT3 pathway epigenetically upregulates Nav1.6 expression in DRG and contributes to neuropathic pain induced by L5-VRT.

BACKGROUND: Studies showed that upregulation of Nav1.6 increased the neuronal excitability and participated in neuropathic pain in the dorsal root ganglion (DRG). However, the molecular mechanisms underlying Nav1.6 upregulation were not reported yet. METHODS: The paw withdrawal threshold was measured in the rodents following lumbar 5 ventral root transection (L5-VRT). Then qPCR, western blotting, immunoprecipitation, immunohistochemistry, and chromatin immunoprecipitation assays were performed to explore the molecular mechanisms in vivo and in vitro. RESULTS: We found that the levels of Nav1.6 and phosphorylated STAT3 were significantly increased in DRG neurons following L5-VRT, and TNF-α incubation also upregulated the Nav1.6 expression in cultured DRG neurons. Furthermore, immunoprecipitation and chromatin immunoprecipitation assays demonstrated that L5-VRT increased the binding of STAT3 to the Scn8a (encoding Nav1.6) promoter and the interaction between STAT3 and p300, which contributed to the enhanced transcription of Scn8a by increasing histone H4 acetylation in Scn8a promoter in DRG. Importantly, intraperitoneal injection of the TNF-α inhibitor thalidomide reduced the phosphorylation of STAT3 and decreased the recruitment of STAT3 and histone H4 hyperacetylation in the Scn8a promoter, thus subsequently attenuating Nav1.6 upregulation in DRG neurons and mechanical allodynia induced by L5-VRT. CONCLUSION: These results suggested a new mechanism for Nav1.6 upregulation involving TNF-α/STAT3 pathway activation and subsequent STAT3-mediated histone H4 hyperacetylation in the Scn8a promoter region in DRG, which contributed to L5-VRT-induced neuropathic pain.

Mitochondrial expression and activity of P-glycoprotein under oxidative stress in outer blood-retinal barrier.

AIM: To investigate the role of oxidative stress in regulating the functional expression of P-glycoprotein (P-gp) in mitochondria of D407 cells. METHODS: D407 cells were exposed to different ranges of concentrations of H2O2. The mitochondrial location of P-gp in the cells subjected to oxidative stress was detected by confocal analysis. Expression of P-gp in isolated mitochondria was assessed by Western blot. The pump activity of P-gp was evaluated by performing the efflux study on isolated mitochondria with Rhodamine 123 (Rho-123) alone and in the presence of P-gp inhibitor (Tariquidar) using flow cytometry analysis. The cells were pretreated with 10 mmol/L N-acetylcysteine (NAC) for 30min before exposing to H2O2, and analyzed the mitochondrial extracts by Western blot and flow cytometry. RESULTS: P-gp was co-localized in the mitochondria by confocal laser scanning microscopy, and it was also detected in the mitochondria of D407 cells using Western blot. Exposure to increasing concentrations of H2O2 led to gradually increased expression and location of P-gp in the mitochondria of cells. Rho-123 efflux assay showed higher uptake of Rho-123 on isolated mitochondria in the presence of Tariquidar both in normal and oxidative stress state. H2O2 up-regulated P-gp in D407 cells, which could be reversed by NAC treatment. CONCLUSION: H2O2 could up-regulate the functional expression of P-gp in mitochondria of D407 cells, while antioxidants might suppress oxidative-stress-induced over-expression of functional P-gp. It is indicative that limiting the mitochondrial P-gp transport in retinal pigment epithelium cells would be to improve the effect of mitochondria-targeted antioxidant therapy in age-related macular degeneration-like retinopathy.

[Effects of dexmedetomidine hydrochloride on ERK1/2 activation in a rat model of ventilator-induced lung injury].

OBJECTIVE: To investigate the effect of dexmedetomidine hydrochloride on inflammatory lung injury and phosphorylation of extracellular regulated protein (ERK1/2) in a rat model of ventilator-induced lung injury (VILI). METHODS: Thirty-six adult male SD rats were randomized into 3 groups (n=12) to receive a 4-h standard ventilation (group C, with tidal volume of 8 ml/kg and respiratory rate of 90/min), high-tidal volume ventilation (group H, with tidal volume of 20 ml/kg and respiratory rate of 50 /min), and high-tidal volume ventilation plus 0.5 µg·kg(-1)·h(-1) dexmedetomidine infusion (group D), with the maintenance of a positive end expiratory pressure (PEEP) of 0 cmH(2)O. After mechanical ventilation the rats were sacrificed to collect the lung lavage liquid and lung tissue to examine the pulmonary inflammatory changes and tumor necrosis factor-α (TNF-α) expression as well as the expressions of ERK1/2 and p-ERK1/2. RESULTS: Groups H and D showed obvious lung injury and significant elevations of the total protein, WBC, MPO, TNF-α, and ERK1/2 phosphorylation as compared with those of group C. The rats in group D showed milder lung pathologies with significantly lower levels of phosphorylation of ERK1/2 and TNF-α compared with those in group H. CONCLUSION: Dexmedetomidine can significantly attenuate VILI, decrease the production of the inflammatory molecules, and inhibit the activation of ERK1/2, demonstrating a protective effect against VILI.

[Effects of morphine and pethidine on the expression of P-glycoprotein in mouse brain microvascular endothelial cells].

OBJECTIVE: To observe the effects of morphine and pethidine on P-glycoprotein (P-gp) expression in mouse brain microvascular endothelial cells and investigate the role of nuclear factor-kappaB (NF-kappaB) signaling pathway in morphine-induced up-expression of P-gp. METHODS: The mouse brain microvascular endothelial cell line (b.END3) was subjected to pre-incubation with NF-kappaB inhibitor PDTC (5 micromol/L) for 1 h followed by stimulation with morphine (1 microg/ml) or pethidine (1 microg/ml) for 24 h. The bEnd.3 cells were then collected for Western blotting for P-gp expression. RESULTS: A 24-h morphine stimulation induced an up-expression of P-gp in bEnd.3 cells by almost 200%. Pethidine in similar conditions did not affect P-gp expression in the cells. PDTC, the specific inhibitor of NF-kappaB, inhibited morphine-induced up-expression of P-gp in the cells. CONCLUSION: Morphine can induce up-expression of endogenous P-gp in mouse brain microvascular endothelial cells. NF-kappaB signaling pathway is involved in the morphine-induced up-expression of P-gp.

[Protective effects of micro-encapsulated Bifidobacteria on gut barrier after hemorrhagic shock and resuscitation: experiment with rats].

OBJECTIVE: To investigate the effects of micro-encapsulated bifidobacteria on gut barrier and bacterial translocation after hemorrhagic shock and resuscitation. METHODS: Sprague-Dawley rats were divided into 6 groups: PBS+sham shock group fed with PBS for 7 days and then undergoing sham shock, bifidobacteria+sham shock group fed with bifidobacteria (10(9) cfu/d) for 7 days and then undergoing sham shock, micro-encapsulated bifidobacteria+sham shock group, fed with micro-encapsulated bifidobacteria (10(9) cfu/d) for 7 days and then undergoing sham shock, PBS+hemorrhagic shock group fed with PBS for 7 days and then undergoing hemorrhagic shock, bifidobacteria+shock group fed with bifidobacteria for 7 days and then undergoing hemorrhagic shock, and micro-encapsulated bifidobacteria+shock group, fed with micro-encapsulated bifidobacteria for 7 days and then undergoing hemorrhagic shock. Three hours after resuscitation laparotomy was performed, distal cecum was resected to undergo bacteriological analysis of the cecal content, mesenteric lymph nodes (MLNs), a liver lobe, and the middle part of spleen were resected to undergo bacterial culture for bacterial translocation, and the terminal ileum was resected to observe the villous damage. RESULTS: There was no significant difference in the amount of blood loss among the 3 hemorrhagic shock groups. The amounts of aerobes in cecum of the bifidobacteria+shock and micro-encapsulated bifidobacteria+shock groups, especially that of the latter group, were significantly lower than that of the PBS+shock group. The amounts of anaerobes and the amounts of bifidobacteria in cecum of the bifidobacteria+shock group and micro-encapsulated bifidobacteria+shock group, especially those of the latter group, were significantly higher than those of the PBS+shock group. No bacterial translocation to liver was observed in all groups. The magnitudes of total aerobes translocation in spleen of the bifidobacteria+shock and encapsulated bifidobacteria+shock groups were significantly lower than that of the PBS+shock group, however, there were not significant differences in the translocation in the MLN of total aerobes ad bifidobacteria among different groups. The percentage of ileal villous damage of the bifidobacteria+shock and encapsulated bifidobacteria+shock groups were significantly lower than that of the PBS+shock group. CONCLUSION: Bifidobacteria effectively protects the gut barrier, reduces bacterial translocation from the gut after hemorrhagic shock and resuscitation. And micro-encapsulated Bifidobacteria can enhance those effects further.

[Effects of epidural clonidine pretreatment in epidural patient-controlled analgesia using sufentanil combined with levobupivacaine].

OBJECTIVE: To investigate the clinical effects of epidural clonidine pretreatment in epidural patient-controlled analgesia (PCA) using sufentanil combined with levobupivacaine. METHODS: Sixty patients undergoing abdominal hysterectomy of ASA status I-II were randomly divided into 3 equal groups: C2 group was pretreated with epidural clonidine 2 microg/kg at the L2-3 interspace, 15 min later, epidural anesthesia was performed with 0.5% levobupivacaine, and then 0. 4 microg/ml combined with levobupivacaine 2 mg/ml was given for postoperative epidural patient-controlled analgesia. C4 group was pretreated with epidural clonidine 4 microg/kg, and C0 group was pretreated with normal saline. The analgesic effect, PCA drug dosage, adverse reaction, and visual analog scale (VAS) score were recorded. RESULTS: Anesthesia was clinically satisfactory in all patients. The rate of atropine use of the C4 group was 30%, significantly higher than those of the C2 group (15% ) and C0 group (5%, both P < 0.05). The rate of VAS < or = 3 at rest 24 h postoperatively of the C2 and C4 groups were 88% and 93% respectively, both significantly higher than that of the C0 group (75%, P < 0.01 and P < 0.01). The rate of VAS < or = 3 while coughing 24 h postoperatively of the C2 and C4 groups were 61% and 79% respectively, both significantly higher than that of the C0 group (48%). The dosages of PCA drug of the C2 and C4 groups were significantly lower than that of the C0 group by 11.8% and 22.8% respectively (both P < 0.05). The dosage of PCA drug 0-4 h after operation of the C2 was significantly higher than that of the C4 group. The sedative degree of the C4 group was higher than that of the C0 group. The rate of postoperative vomiting of the C0 group was 40%, significantly higher than that of the C4 group (10%, P < 0.05). CONCLUSION: Epidural clonidine 2-4 microg/kg pretreatment improves the clinical effects of epidural PCA using sufentanil combined with levobupivacaine.