Quercetin attenuates cisplatin-induced mitochondrial apoptosis via PI3K/Akt mediated inhibition of oxidative stress in pericytes and improves the blood labyrinth barrier permeability

Cisplatin (CDDP) is broadly employed to treat different cancers, whereas there are no drugs approved by the Food and Drug Administration (FDA) for preventing its side effects, including ototoxicity. Quercetin (QU) is a widely available natural flavonoid compound with anti-tumor and antioxidant properties. The research was designed to explore the protective effects of QU on CDDP-induced ototoxicity and its underlying mechanisms in male C57BL/6 J mice and primary cultured pericytes (PCs). Hearing changes, morphological changes of stria vascularis, blood labyrinth barrier (BLB) permeability and expression of apoptotic proteins were observed in vivo by using the auditory brainstem response (ABR) test, HE staining, Evans blue staining, immunohistochemistry, western blotting, etc. Oxidative stress levels, mitochondrial function and endothelial barrier changes were observed in vitro by using DCFH-DA probe detection, flow cytometry, JC-1 probe, immunofluorescence and the establishment in vitro BLB models, etc. QU pretreatment activates the PI3K/AKT signaling pathway, inhibits CDDP-induced oxidative stress, protects mitochondrial function, and reduces mitochondrial apoptosis in PCs. However, PI3K/AKT specific inhibitor (LY294002) partially reverses the protective effects of QU. In addition, in vitro BLB models were established by coculturing PCs and endothelial cells (ECs), which suggests that QU both reduces the CDDP-induced apoptosis in PCs and improves the endothelial barrier permeability. On the whole, the research findings suggest that QU can be used as a novel treatment to reduce CDDP-induced ototoxicity.

The effects of noise exposure on hippocampal cognition in C57BL/6 mice via transcriptomics

BACKGROUND

Noise is an important environmental stressor in the industrialized world and has received increasing attention in recent years. Although epidemiological research has extensively demonstrated the relationship between noise and cognitive impairment, the specific molecular mechanisms and targets remain to be fully explored and understood.

METHODS

To address this issue, 5-month-old C57BL/6 mice were divided into two groups, with one group exposed to white noise at 98 dB. The effects of noise on cognition in mice were investigated through molecular biology and behavioral experiments. Subsequently, transcriptomic sequencing of the hippocampus in both groups of mice was performed and enrichment analysis of differentially expressed genes (DEGs) was conducted using KEGG and GO databases. Furthermore, LASSO analysis was used to further narrow down the relevant DEGs, followed by enrichment analysis of these genes using KEGG and GO databases. The DEGs were further validated by rt-qPCR.

RESULTS

Following noise exposure, the hippocampus levels of inflammation-related factors increased, the phosphorylation of Tau protein increased, the postsynaptic density protein decreased, the number of Nissl bodies decreased, and cell shrinkage in the hippocampus increased. Moreover, the behavioral experiments manifest characteristics indicative of a decline in cognitive.A total of 472 DEGs were identified through transcriptomic analysis, and seven relevant genes were screened by the LASSO algorithm, which were further validated by PCR to confirm their consistency with the omics results.

CONCLUSION

In conclusion, noise exposure affects cognitive function in mice through multiple pathways, and the omics results provide new evidence for the cognitive impairment induced by noise exposure.

PGC-1α affects cochlear pericytes migration in noise-exposed mice

OBJECTIVE

The study aimed to observe the effects of noise exposure on the pericytes of the cochlear stria vascularis (SV) in mice and to investigate its molecular mechanism.

METHOD

Male C57BL/6J mice aged 6-8 weeks were used as the subjects. Auditory Brainstem Response (ABR) was used to assess hearing loss. Hematoxylin and Eosin (HE) staining was conducted to observe morphological alterations in the SV. Immunofluorescence combined with transmission electron microscopy (TEM) was used to scrutinize changes in pericytes following acoustic injury. Western blotting (WB) was used to assess the expression variations of the migration-related protein Osteopontin (OPN). Evans Blue assay was performed to evaluate the permeability of the blood labyrinth barrier (BLB). 4-Hydroxynonenal (4-HNE) staining, in conjunction with measurements of Superoxide Dismutase (SOD), Malondialdehyde (MDA), and Catalase (CAT) content, was used to ascertain whether oxidative stress injury occurred in the SV. WB, combined with immunofluorescence, was used to examine alterations in the expression of proliferator-activated receptor-gamma coactivator 1α (PGC-1α) in the SV and pericytes.

RESULTS

Noise exposure resulted in permanent hearing loss in C57BL/6J mice, accompanied by SV swelling, migration of pericytes from their vascular attachments, BLB leakage, elevated oxidative stress levels in the SV, and reduced expression of PGC-1α on both the SV and migrating pericytes.

CONCLUSION

Noise exposure may potentially increase oxidative stress levels in the SV, downregulate the expression levels of PGC-1α, promote pericytes migration, and subsequently lead to an elevation in BLB permeability.

Noise exposure increase apoptosis in the hippocampus of AD mice through the upregulation of CTSS

In recent years, it has become an acknowledged fact that noise exposure can lead to cognitive impairments, and researchers have shown increasing interest in this area. However, the detrimental impact of noise exposure on Alzheimer's disease (AD) animal models might be considerably greater than on ordinary model mice, yet the mechanisms by which noise exposure affects the hippocampus in these models have been scarcely investigated. This study we used 4D Label-free proteomics to identify distinctive differentially expressed proteins in the hippocampus of AD model mice following noise exposure. Among these proteins, the presence of Cathepsin S(CTSS) cannot be disregarded. Utilizing experimental techniques such as Western blot, immunofluorescence, and rt-qPCR, we confirmed the expression of CTSS in the hippocampus of APP/PS1 mice after noise exposure. Additionally, we examined downstream molecules including P53,BCL-2, BAX, and CASPASE3 using KEGG pathway analysis. The results indicated an elevation in CTSS expression, a reduction in the anti-apoptotic gene BCL-2, and an increase in the expression of BAX and cleaved CASPASE3. Based on these findings, we hypothesize that noise exposure potentially heightens apoptosis within the hippocampus through upregulating CTSS expression, subsequently posing a threat to AD model animals.

[Tanshinone ⅡA activates PI3K/AKT signaling pathway to inhibit the apoptosis of mice cochlear pericytes induced by high glucose]

Objective: To investigate whether tanshinone ⅡA can protect the apoptosis of mice cochlear pericytes induced by high glucose and its specific protective mechanism, so as to provide experimental evidence for the prevention and treatment of diabetic hearing loss. Methods: C57BL/6J male mice were used to prepare type 2 diabetes model, which were divided into normal (NG) group, diabetic (DM) group, diabetic+tanshinone ⅡA (HG+tanshinone ⅡA) group and tanshinone ⅡA group. Each group had 10 animals. Primary cochlear pericytes were divided into NG group, HG group (high glucose 35 mmol/L), HG+tanshinone ⅡA (1, 3, 5 μmol/L) group, HG+Tanshinone ⅡA+LY294002 (PI3K/AKT pathway inhibitor) group, LY294002 group, tanshinone ⅡA group and DMSO group. Auditory brainstem response (ABR) was used to measure hearing threshold. Evans blue was used to detect the permeability of blood labyrinth barrier in each group. TBA methods were used to detect oxidative stress levels in various organs of mice. Morphological changes of stria vascularis were observed by hematoxylin-eosin staining (HE). Evans blue was used to detect the vascular labyrinth barrier permeability in cochlea. The expression of apoptosis protein in stria vascularis pericytes was observed by immunofluorescence. Pericytes apoptosis rate was observed by flow cytometry. DCFH-DA was combined with flow cytometry to detect intracellular ROS content, and Western blot was used to detect the expression of apoptotic proteins (Cleaved-caspase3, Bax), anti-apoptotic proteins (BCL-2) and pathway proteins (PI3K, p-PI3K, AKT, p-AKT). SPSS software was used for statistical analysis. Independent sample t test was performed, and P<0.05 was considered statistically significant. Results: Animal experiments: Tanshinone ⅡA decreased the hearing threshold of DM group [(35.0±3.5) dB SPL vs. (55.3±8.1) dB SPL] (t=4.899, P<0.01), decreased the oxidative stress level in cochlea (t=4.384, P<0.05), improved the structure disorder, atrophy of cochlea vascular lines, vacuole increased phenomenon. Tanshinone ⅡA alleviated the increased permeability of the blood labyrinth barrier [Evans blue leakage (6.84±0.27) AU vs. (8.59±0.85) AU] in the cochlea of DM mice (t=2.770, P<0.05), reversed the apoptotic protein: Caspase3 (t=4.956, P<0.01) and Bax (t=4.388, P<0.05) in cochlear vascularis. Cell experiments: Tanshinone ⅡA decreased intracellular ROS content in a concentration-dependent way (t=3.569, P<0.05; t=4.772, P<0.01; t=7.494, P<0.01); Tanshinone ⅡA decreased apoptosis rate and apoptotic protein, and increased the expression of anti-apoptotic protein, p-PI3K/PI3K and p-AKT/AKT in concentration-dependent manner (all P values<0.05); LY294002 reversed the protective effect of tanshinone ⅡA on pericytes apoptosis (all P values<0.05). Conclusion: Tanshinone ⅡA can inhibit the apoptosis of cochlear pericytes induced by high glucose by reducing oxidative stress level and activating PI3K/AKT signaling pathway under high glucose environment, thus playing a protective role in diabetic hearing loss.

[Effects of probenecid on the migration and proliferation ability of platelet derived growth factor-BB induced pulmonary artery smooth muscle cells in rats]

OBJECTIVE

To investigate whether probenecid (PROB) could improve the proliferation and migration ability of rats' pulmonary artery smooth muscle cells induced by platelet-derived growth factor-BB (PDGF-BB).

METHODS

Primary pulmonary artery smooth muscle cells (PASMCs) of SD rats were cultured in vitro, and were randomly divided into control group (CON group), PDGF-BB group (10 ng/ml PDGF-BB treatment for 24 h) and PDGF-BB+PROB group (10 ng/ml PDGF-BB and 200 μmol/L PROB treatment for 24 h, PROB is a specific blocker of pannexin-1). CCK-8 method was used to select the suitable intervention concentrations of PROB and PDGF-BB, and to detect the proliferation of PASMCs in each group. The migration ability of PASMCs was detected by Transwell^TM assay and cell scratch test. Immunofluorescence cytochemistry and Western blot were used to detect the protein expressions and distribution of osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) in PASMCs.

RESULTS

Compared with CON group, the migration and proliferation ability of PASMCs in PDGF-BB group were enhanced (P＜0.05). After treated with PROB, the migration and proliferation ability of PASMCs in PDGF-BB+PROB group were decreased significantly (P＜0.05). Compared with CON group, the expression and protein levels of OPN and PCNA in PDGF-BB group were increased significantly (P＜0.05), while the expression and protein levels of OPN and PCNA in PDGF-BB+PROB were decreased significantly (P＜0.05).

CONCLUSION

Probenecid inhibits the migration and proliferation of PDGF-BB-induced PASMCs by blocking Pannexin-1.

Inhibition of KIR2.1 decreases pulmonary artery smooth muscle cell proliferation and migration

The investigation of effective therapeutic drugs for pulmonary hypertension (PH) is critical. KIR2.1 plays crucial roles in regulating cell proliferation and migration, and vascular remodeling. However, researchers have not yet clearly determined whether KIR2.1 participates in the proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) and its role in pulmonary vascular remodeling (PVR) also remains elusive. The present study aimed to examine whether KIR2.1 alters PASMC proliferation and migration, and participates in PVR, as well as to explore its mechanisms of action. For the in vivo experiment, a PH model was established by intraperitoneally injecting Sprague-Dawley rats monocrotaline (MCT). Hematoxylin and eosin staining revealed evidence of PVR in the rats with PH. Immunofluorescence staining and western blot analysis revealed increased levels of the KIR2.1, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) proteins in pulmonary blood vessels and lung tissues following exposure to MCT, and the TGF-β1/SMAD2/3 signaling pathway was activated. For the in vitro experiments, the KIR2.1 inhibitor, ML133, or the TGF-β1/SMAD2/3 signaling pathway blocker, SB431542, were used to pre-treat human PASMCs (HPASMCs) for 24 h, and the cells were then treated with platelet-derived growth factor (PDGF)-BB for 24 h. Scratch and Transwell assays revealed that PDGF-BB promoted cell proliferation and migration. Immunofluorescence staining and western blot analysis demonstrated that PDGF-BB upregulated OPN and PCNA expression, and activated the TGF-β1/SMAD2/3 signaling pathway. ML133 reversed the proliferation and migration induced by PDGF-BB, inhibited the expression of OPN and PCNA, inhibited the TGF-β1/SMAD2/3 signaling pathway, and reduced the proliferation and migration of HPASMCs. SB431542 pre-treatment also reduced cell proliferation and migration; however, it did not affect KIR2.1 expression. On the whole, the results of the present study demonstrate that KIR2.1 regulates the TGF-β1/SMAD2/3 signaling pathway and the expression of OPN and PCNA proteins, thereby regulating the proliferation and migration of PASMCs and participating in PVR.

[Role of Cav1.2 in cisplatin induced apoptosis of cochlear spiral ganglion neurons in C57BL/6J mice]

Objective: To investigate the role of Cav1.2 and its possible mechanism in the apoptosis of cochlear spiral ganglion neurons(SGNs) induced by cisplatin (CDDP) in C57BL/6J mice. Methods: Animal experiment: 8-week-old male C57BL/6J mice were randomly divided into the following two groups (10 mice/group) : normal saline group (Control group) and Cisplatin group (Cisplatin group). The Control group received daily intraperitoneal injections of normal saline, Cisplatin group was injected with cisplatin intraperitoneally at a dose of 3 mg/kg at the first 4 days of each cycle, and normal saline was injected daily at the last 10 days,repeat for 3 cycles. After administration, auditory threshold was detected by auditory brainstem response (ABR). Blood samples were collected from inner canthus of mice, and cochlea was cut off from neck. SOD and MDA kits were used to detect SOD activity and MDA content in serum and cochlea tissues. The expressions of apoptosis proteins in cochlear tissues were detected by Western blot. Morphological changes of spiral ganglion in mouse cochlea were observed by hematoxylin-eosin (HE) staining. TUNEL staining was used to observe the apoptosis of SGNs in cochlea of mice. The distribution and expression of Cav1.2 in SGNs of cochlea were observed by immunofluorescence. Cell experiment: Primary cultured SGNs were randomly divided into: control group (Control), solvent group (DMSO), Cav1.2 blocker group (N), cisplatin group, cisplatin and Cav1.2 blocker co-incubation group (Cisplatin+N). 5 μmol/L cisplatin was selected to treat SGNs based on the results of CCK8. Western blot was used to detect the protein expressions of Cav1.2.and apoptotic proteins. Hoechst33342 staining was used to observe the apoptosis of each group. Flow cytometry was used to detect the apoptosis rate of each group. Mitochondrial superoxide indicator (MitoSOX^TM-Red) was used to detect the ROS release of mitochondria. Results: Animal experiments: Compared to the Control group, the hearing threshold was increased in Cisplatin group (P<0.01), the content of MDA in serum and cochlea tissues, apoptosis protein Cleaved caspase-3, Bax protein level, TUNEL positive rate, Cav1.2 protein expression level were increased significantly (P<0.05, P<0.01); the activity of SOD in serum and cochlear tissue, anti-apoptotic protein bcl-2 protein level and SGCs density in cochlear tissue were decreased significantly (P<0.05, P<0.01). Cell tests: Compared with the Control group, the expression of Cav1.2, apoptosis rate, Cleaved caspase-3, Bax protein level, intracellular calcium ion concentration, and ROS release were increased significantly only in Cisplatin group (P<0.05, P<0.01). The levels of bcl-2 protein and mitochondrial membrane potential were decreased significantly (P<0.01). Cav1.2 blockers could partially reverse the above changes (P<0.05). Conclusion: Cisplatin may increase intracellular Ca²⁺ concentration through up-regulation of Cav1.2, and then damage mitochondria, causing oxidative stress injury of SGNs and inducing neuronal apoptosis.

Transcriptomic Profiling in Mice With CB1 receptor Deletion in Primary Sensory Neurons Suggests New Analgesic Targets for Neuropathic Pain

Type 1 and type 2 cannabinoid receptors (CB1 and CB2, respectively) mediate cannabinoid-induced analgesia. Loss of endogenous CB1 is associated with hyperalgesia. However, the downstream targets affected by ablation of CB1 in primary sensory neurons remain unknown. In the present study, we hypothesized that conditional knockout of CB1 in primary sensory neurons (CB1cKO) alters downstream gene expression in the dorsal root ganglion (DRG) and that targeting these pathways alleviates neuropathic pain. We found that CB1cKO in primary sensory neurons induced by tamoxifen in adult Advillin-Cre:CB1-floxed mice showed persistent hyperalgesia. Transcriptome/RNA sequencing analysis of the DRG indicated that differentially expressed genes were enriched in energy regulation and complement and coagulation cascades at the early phase of CB1cKO, whereas pain regulation and nerve conduction pathways were affected at the late phase of CB1cKO. Chronic constriction injury in mice induced neuropathic pain and changed transcriptome expression in the DRG of CB1cKO mice, and differentially expressed genes were mainly associated with inflammatory and immune-related pathways. Nerve injury caused a much larger increase in CB2 expression in the DRG in CB1cKO than in wildtype mice. Interfering with downstream target genes of CB1, such as antagonizing CB2, inhibited activation of astrocytes, reduced neuroinflammation, and alleviated neuropathic pain. Our results demonstrate that CB1 in primary sensory neurons functions as an endogenous analgesic mediator. CB2 expression is regulated by CB1 and may be targeted for the treatment of neuropathic pain.

17β-Estradiol promotes angiogenesis of stria vascular in cochlea of C57BL/6J mice

It is widely accepted that the stria vascularis (SV) in cochlea plays a critical role in the generation of endocochlear potential (EP) and the secretion of the endolymph. 17β-estradiol (E2) is the most potent and abundant endogenous estrogen during the premenopausal period, thus, considered as the reference estrogen. This study aimd to investigate the protective effect of E2 by promoting the expression of vascular endothelial growth factor (VEGF) and thus promoting the vascular regeneration of the SV in elderly mice. After being treated with E2 either in vivo or in vitro, the hearing threshold changes of C57BL/6J elder mice continuously reduced, endothelial cell morphology improved, the number of endothelial cells (ECs) tubular nodes increased significantly, the ability of tubular formation enhanced significantly and the expression of VEGF increased. In vitro, cell model in conjunction with in vivo ovariectomized model was established to demonstrate for the first time that E2 promotes angiogenesis by promoting the secretion of VEGF through the phosphatidylinositol 3-kinase (PI3K)/AKT pathway (PI3K/AKT). In conclusion, E2 demonstrated potent angiogenesis properties with significant protection against Age-Related Hearing Loss (ARHL), which provides a new idea for the improvement of ARHL.

[The effect of large-conductance calcium-activated potassium channels on the migration of pericytes in the mice of senile cochlear stria vascularis]

Objective: To investigate whether large conductance calcium-activated potassium channel (BK(Ca)) was involved in the migration of pericytes (PC) in the mice of senile cochlear stria vascularis capillaries PC. Methods: C57BL/6J mice were divided into 3-month (n=10) and 12-month groups (n=10). Auditory brainstem response (ABR) was used to test the hearing threshold of each group. The immunofluorescence was used to detect the expression changes of osteopontin (OPN) and β-BK(Ca) channels on cochlear stria vascularis PC. The morphological changes of perivascular cells in cochlea were observed by transmission electron microscope (TEM). Cell experiment: The PC, which were in the stria vascularis of the cochlea were primary cultured and identified. A cell senile model was made with D-gal. The appropriate intervention concentration of low galactose (D-gal) was determined by CCK8. β-galactosidase (SA-β-gal) staining was used to evaluate the cell decrept level. The change of BK(Ca) channels current on PC were recorded by whole cell patch clamp technique. The expression of BK(Ca) channels on PC was detected by immunofluorescence. The migration and invasion ability of two groups were detected by using Scratch test and Transwell. The levels of OPN and β-BK(Ca) channels were detected by Western blot. SPSS 22.0 software was used to analyze the data. Results: The ABR threshold in the 12-month group was higher than 3-month group (t=12.66, P<0.01). In the 12-month group, the expression of β-BK(Ca) channel was lower and the expression of OPN was increased (t=14.64, P<0.01; t=20.73, P<0.01). In TEM, cochlear stria vascularis PC were tightly connected to endothelial cells in 3-month group, while PC were loosely connected to endothelial cells or PC soma were separated from the capillary in 12-month group. Cell experiment: The positive rate of PC in the primary cultured cochlear stria vascularis is above 95%. Compared with the SA-β-gal stained cells in the control group, the positive rate of 15 mg/ml D-gal intervention PC was 85% (t=36.90, P<0.01). Whole cell patch clamp BK(Ca) channels current decreased in the D-gal group compared with the young group PC (t=12.18, P<0.05). The OPN expression in the senile group was higher than control group (t=16.30, P<0.01), while the β-BK(Ca) channels expression was decreased (t=11.98, P<0.01; t=15.72, P<0.05), and migration ability raised (t=7.91, P<0.01;t=7.59, P<0.01). After intervened of BK(Ca) channels specific blocker IBTX in the D-gal group, the expression of OPN and migration were increased (t=4.26, P<0.05; t=5.88, P<0.01; t=21.97, P<0.01). Conclusion: PC migration capacity were increased during the senile period, and the expression of β-BK(Ca) channel was decreased. The administration of IBTX, a specific blocker of BK(Ca) channel, at the cell level could increase the migration capacity, suggesting that BK(Ca) might be involved in the migration of PC in the stria vascularis of the aging cochlea.

[Effect of microvascular pericytes of cochlear stria vascularis on endothelial cell permeability in C57BL/6J mice]

Objective: To study the changes in the permeability of the blood labyrinth barrier of the aging cochlea in mice, and to establish a non-contact co-culture model of endothelial cells (EC) and pericytes (PC) to furtherly investigate the cochlear stria vascularis microvascular pericytes impact on the permeability of endothelial cells. Methods: C57BL/6J mice were divided into two groups, three months old as young group, 12 months old as senile group. Cell experiment was divided into four groups, EC group, EC+PC co-culture group, D-gal+EC group and D-gal+EC+PC co-culture group. Auditory brainstem response (auditory brain response, ABR) was used to detect the auditory function of the two groups of mice. Evans blue staining was applied to detect the permeability of the cochlear blood labyrinth barrier of the two groups of mice. Transmission electron microscopy was used to observe the ultrastructure of blood labyrinth barrier endothelial cells, pericytes and tight junctions in the two groups of mice. Immunohistochemistry was used to detect the expression levels of tight junction proteins in the stria vascularis of the cochlea of the two groups of mice. Transwell chamber was used to detect the permeability of endothelial cells. Western blot and immunofluorescence technology were used to detect the expression level of tight junction protein on endothelial cells. SPSS 20.0 software was used to analyze the data. Results: Compared with the young group, the ABR threshold of the aging group was significantly increased, the latency of wave I was prolonged (t=10.25, P<0.01;t=5.61, P<0.05), the permeability of the cochlear blood labyrinth barrier was increased and the expression of tight junction protein on the vascular stria was decreased (P<0.05). The cochlear ultrastructure showed that the cochlear vascular stria microvascular lumen was deformed, the basement membrane thickened and the tight junction gap between endothelium enlarged. The positive rate of ECs and PCs in primary culture was more than 95%. The cells induced by 15 g/L D-gal were determined to be senescent cells. Compared with EC group, the expression of tight junction protein in endothelial cells of D-gal+EC group decreased（t=7.42，P<0.01；t=13.19，P<0.05）and the permeability increased (t=11.17, P<0.01). In the co-culture group, the expression of tight junction protein between endothelial cells in EC+PC co-culture group and D-gal+EC+PC co-culture group increased and the permeability decreased. Conclusions: In aging mice, the permeability of cochlear blood labyrinth barrier will increase and the level of tight junction protein will decrease; in aging state, cochlear vascular stria microvascular pericytes may affect endothelial cell permeability by regulating the expression of tight junction protein.

The promoting role of Cx43 on the proliferation and migration of arterial smooth muscle cells for angiotensin II-dependent hypertension

BACKGROUND

Recent studies have shown that endothelin-1 and angiotensin II (AngII) can increase gap junctional intercellular communication (GJIC) by activating Mitogen-activated protein kinases (MAPKs) pathway. However, not only the precise interaction of AngII with Connexin43(Cx43) and the associated functions remain unclear, but also the regulatory role of Cx43 on the AngII-mediated promotion proliferation and migration of VSMCs is poorly understood.

MATERIAL AND METHODS

Our research applicated pressure myography measurements, immunofluorescence and Western blot analyses to investigate the changes in physiological indicators in spontaneously hypertensive rats (SHRs) and AngII-stimulated proliferation and migration of A7r5 SMCs(Rat vascular smooth muscle cells). The aim was to elucidate the role of CX43 in hypertension induced by AngII.

RESULTS

Chronic ramipril (angiotensin converting enzyme inhibitor) management for SHRs significantly attenuated blood pressure and blood vessel wall thickness, also reduced contraction rate in the cerebral artery. The cerebral artery contraction rates, mRNA and protein expression of Cx43, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) protein expression in the SHR + ramipril and SHR + ramipril + carbenoxolone (CBX, Cx43 specific blocker) groups were significantly lower than those in the SHR group. Cx43 protein expression and Ser368 phosphorylated Cx43 protein levels increased significantly in AngII-stimulated A7r5 cells. However, the levels of phosphorylated Cx43 decreased after pre-treatment with candesartan (AT1 receptor blocker), GF109203X (protein kinase C (PKC) blocker) and U0126 (mitogen-activated protein kinases/extracellular signal-regulated kinase1/2(MEK/ERK1/2)-specific blocker) in AngII-stimulated A7r5 cells. Cx43 was widely distributed in the cell membrane, nucleus, and cytoplasm of the SMCs. Furthermore, pre-treatment of the AngII- stimulated A7r5 cells with Gap26 (Cx43 blocker) significantly inhibited cell migration and decreased the expression levels of MEK1/2, ERK1/2, P-MEK1/2, and P-ERK1/2.

CONCLUSION

Our research confirms that Cx43 plays an important role in the regulation of proliferation and migration of VSMCs via MEK/ERK and PKC signal pathway in AngII-dependent hypertension.

Improving NKCC1 Function Increases the Excitability of DRG Neurons Exacerbating Pain Induced After TRPV1 Activation of Primary Sensory Neurons

Background Our aim was to investigate the effects of the protein expression and the function of sodium, potassium, and chloride co-transporter (NKCC1) in the dorsal root ganglion (DRG) after activation of transient receptor potential vanilloid 1 receptor (TRPV1) in capsaicin-induced acute inflammatory pain and the possible mechanism of action.

Methods Male Sprague–Dawley rats were randomly divided into control, capsaicin, and inhibitor groups. The expression and distribution of TRPV1 and NKCC1 in rat DRG were observed by immunofluorescence. Thermal radiation and acetone test were used to detect the pain threshold of heat and cold noxious stimulation in each group. The expressions of NKCC1 mRNA, NKCC1 protein, and p-NKCC1 in the DRG were detected by PCR and western blotting (WB). Patch clamp and chloride fluorescent probe were used to observe the changes of GABA activation current and intracellular chloride concentration. After intrathecal injection of protein kinase C (PKC) inhibitor (GF109203X) or MEK/extracellular signal-regulated kinase (ERK) inhibitor (U0126), the behavioral changes and the expression of NKCC1 and p-ERK protein in L_4–6 DRG were observed.

Result: TRPV1 and NKCC1 were co-expressed in the DRG. Compared with the control group, the immunofluorescence intensity of NKCC1 and p-NKCC1 in the capsaicin group was significantly higher, and the expression of NKCC1 in the nuclear membrane was significantly higher than that in the control group. The expression of NKCC1 mRNA and protein of NKCC1 and p-NKCC1 in the capsaicin group were higher than those in the control group. After capsaicin injection, GF109203X inhibited the protein expression of NKCC1 and p-ERK, while U0126 inhibited the protein expression of NKCC1. In the capsaicin group, paw withdrawal thermal latency (WTL) was decreased, while cold withdrawal latency (CWL) was prolonged. Bumetanide, GF109203X, or U0126 could reverse the effect. GABA activation current significantly increased in the DRG cells of the capsaicin group, which could be reversed by bumetanide. The concentration of chloride in the DRG cells of the capsaicin group increased, but decreased after bumetanide, GF109203X, and U0126 were administered.

Conclusion Activation of TRPV1 by exogenous agonists can increase the expression and function of NKCC1 protein in DRG, which is mediated by activation of PKC/p-ERK signaling pathway. These results suggest that DRG NKCC1 may participate in the inflammatory pain induced by TRPV1.

Galectin-3 participates in PASMC migration and proliferation by interacting with TGF-β1

Pulmonary vascular remodelling is one of the most important factors for pulmonary hypertension (PH). Galectin-3 (Gal-3) is a β-galactoside-binding lectin. In the latest literature, Gal-3 has been reported to be involved in pulmonary vascular remodelling, and its underlying mechanism is unclear. Our research aims to prove the effect of Gal-3 on the proliferation and migration of human pulmonary artery smooth muscle cells (HPASMC) induced by transforming growth factor β1 (TGF-β1) and to study its mechanism. In vivo experiment: In Sprague-Dawley (SD) rats, monocrotaline was injected intraperitoneally to establish a PH model, and the Gal-3 inhibitor (modified citrus pectin, MCP) 28 Ds was administered in the stomach. The results indicate that Gal-3 and TGF-β1 may be involved in the occurrence and development of PH, which may be related to the Smad2/3 signalling pathway. In vitro experiment: Human pulmonary artery smooth muscle cells were pretreated with the Gal-3 inhibitor (MCP) for 24 h, then TGF-β1 or Gal-3 was administered to the cells for 24 h. The results show that exogenous TGF-β1 and Gal-3 can activate the downstream Smad2/3 signalling pathway, and increase the proliferation and migration ability of HPASMC. However, the Gal-3 inhibitor (MCP) inhibited these effects. Further results display that TGF-β1 and Gal-3 could mutually regulate the protein and mRNA expression levels. In summary, the results of this study indicate that Gal-3 regulates the Smad2/3 signalling pathway through protein interaction with TGF-β1, in turn regulates the proliferation and migration of HPASMC, thereby regulating the occurrence and development of PH.

Upregulation of Nav1.7 by endogenous hydrogen sulfide contributes to maintenance of neuropathic pain

Na_v1.7 is closely associated with neuropathic pain. Hydrogen sulfide (H₂S) has recently been reported to be involved in numerous biological functions, and it has been shown that H₂S can enhance the sodium current density, and inhibiting the endogenous production of H₂S mediated by cystathionine β-synthetase (CBS) using O-(carboxymethyl) hydroxylamine hemihydrochloride (AOAA) can significantly reduce the expression of Na_v1.7 and thus the sodium current density in rat dorsal root ganglion (DRG) neurons. In the present study, it was shown that the fluorescence intensity of H₂S was increased in a spared nerve injury (SNI) model and AOAA inhibited this increase. Na_v1.7 is expressed in DRG neurons, and the expression of CBS and Na_v1.7 were increased in DRG neurons 7, 14 and 21 days post-operation. AOAA inhibited the increase in the expression of CBS, phosphorylated (p)-MEK1/2, p-ERK1/2 and Na_v1.7 induced by SNI, and U0126 (a MEK blocker) was able to inhibit the increase in p-MEK1/2, p-ERK1/2 and Na_v1.7 expression. However, PF-04856264 did not inhibit the increase in CBS, p-MEK1/2, p-ERK1/2 or Na_v1.7 expression induced by SNI surgery. The current density of Na_v1.7 was significantly increased in the SNI model and administration of AOAA and U0126 both significantly decreased the density. In addition, AOAA, U0126 and PF-04856264 inhibited the decrease in rheobase, and the increase in action potential induced by SNI in DRG neurons. There was no significant difference in thermal withdrawal latency among each group. However, the time the animals spent with their paw lifted increased significantly following SNI, and the time the animals spent with their paw lifted decreased significantly following the administration of AOAA, U0126 and PF-04856264. In conclusion, these data show that Na_v1.7 expression in DRG neurons is upregulated by CBS-derived endogenous H₂S in an SNI model, contributing to the maintenance of neuropathic pain.

Expression and effect of sodium-potassium-chloride cotransporter on dorsal root ganglion neurons in a rat model of chronic constriction injury

Sodium-potassium-chloride cotransporter 1 (NKCC1) and potassium-chloride cotransporter 2 (KCC2) are associated with the transmission of peripheral pain. We investigated whether the increase of NKCC1 and KCC2 is associated with peripheral pain transmission in dorsal root ganglion neurons. To this aim, rats with persistent hyperalgesia were randomly divided into four groups. Rats in the control group received no treatment, and the rat sciatic nerve was only exposed in the sham group. Rats in the chronic constriction injury group were established into chronic constriction injury models by ligating sciatic nerve and rats were given bumetanide, an inhibitor of NKCC1, based on chronic constriction injury modeling in the chronic constriction injury + bumetanide group. In the experiment measuring thermal withdrawal latency, bumetanide (15 mg/kg) was intravenously administered. In the patch clamp experiment, bumetanide (10 µg/µL) and acutely isolated dorsal root ganglion neurons (on day 14) were incubated for 1 hour, or bumetanide (5 µg/µL) was intrathecally injected. The Hargreaves test was conducted to detect changes in thermal hyperalgesia in rats. We found that the thermal withdrawal latency of rats was significantly decreased on days 7, 14, and 21 after model establishment. After intravenous injection of bumetanide, the reduction in thermal retraction latency caused by model establishment was significantly inhibited. Immunohistochemistry and western blot assay results revealed that the immune response and protein expression of NKCC1 in dorsal root ganglion neurons of the chronic constriction injury group increased significantly on days 7, 14, and 21 after model establishment. No immune response or protein expression of KCC2 was observed in dorsal root ganglion neurons before and after model establishment. The Cl^– (chloride ion) fluorescent probe technique was used to evaluate the change of Cl^– concentration in dorsal root ganglion neurons of chronic constriction injury model rats. We found that the relative optical density of N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (a Cl^– fluorescent probe whose fluorescence intensity decreases as Cl^– concentration increases) in the dorsal root ganglion neurons of the chronic constriction injury group was significantly decreased on days 7 and 14 after model establishment. The whole-cell patch clamp technique revealed that the resting potential and action potential frequency of dorsal root ganglion neurons increased, and the threshold and rheobase of action potentials decreased in the chronic constriction injury group on day 14 after model establishment. After bumetanide administration, the above indicators were significantly suppressed. These results confirm that CCI can induce abnormal overexpression of NKCC1, thereby increasing the Cl^– concentration in dorsal root ganglion neurons; this then enhances the excitability of dorsal root ganglion neurons and ultimately promotes hyperalgesia and allodynia. In addition, bumetanide can achieve analgesic effects. All experiments were approved by the Institutional Ethics Review Board at the First Affiliated Hospital, College of Medicine, Shihezi University, China on February 22, 2017 (approval No. A2017-169-01).

Carbenoxolone decreases monocrotaline‑induced pulmonary inflammation and pulmonary arteriolar remodeling in rats by decreasing the expression of connexins in T lymphocytes

The adaptive immune response mediated by T lymphocytes is a well-established factor in the pathogenesis of pulmonary inflammation. Changes in the expression of various connexins (Cxs) or disruption of connexin-mediated cellular communication in T lymphocytes contribute to inflammation or tissue remodeling. The aim of the present study was to investigate the potential therapeutic value of blocking Cxs in a monocrotaline (MCT)-induced pulmonary inflammation rat model. Carbenoxolone (CBX) was used to inhibit connexin-mediated cellular communication. An MCT rat model was established by intraperitoneal (i.p.) injection of a single dose of MCT (60 mg/kg), and CBX treatment (20 µg/kg/day, i.p.) was initiated on the day following MCT treatment for 28 days. Vehicle-treated male Sprague-Dawley rats were used as the negative control. The MCT rat model was evaluated by measuring the pulmonary artery flow acceleration time and right ventricular hypertrophy index (RVHI). Histopathological features of the lung tissues and pulmonary arteriolar remodeling were assessed. The proportions of T lymphocyte subtypes, Cx40/cx43 expression in the T cell subtypes and the cytokine levels in the plasma and the lung tissues were also analyzed. Pharmacological inhibition of Cxs using CBX attenuated MCT-induced right ventricular hypertrophy, pulmonary arteriolar remodeling, lung fibrosis and inflammatory cell infiltration by decreasing the RVHI, pulmonary arterial wall thickening, collagen deposition and pro-inflammatory cytokines production as well as CD3⁺ and CD4⁺ T cell accumulation in lung tissues of MCT-treated rats. Furthermore, flow cytometry analysis revealed that CBX may inhibit MCT-induced Cx40 and Cx43 expression in CD4⁺ and CD8⁺ T lymphocytes in lung tissues. The present study provides evidence that pharmacological inhibition of Cxs may attenuate MCT-induced pulmonary arteriolar remodeling and pulmonary inflammatory response, at least in part, by decreasing Cx expression. The results highlight the critical role of Cxs in T lymphocytes in the MCT-induced pulmonary inflammatory response and that targeting of Cxs may be a potential therapeutic method for treating pulmonary inflammatory diseases.

17β-Estradiol Attenuates Neuropathic Pain Caused by Spared Nerve Injury by Upregulating CIC-3 in the Dorsal Root Ganglion of Ovariectomized Rats

17β-estradiol plays a role in pain sensitivity, analgesic drug efficacy, and neuropathic pain prevalence, but the underlying mechanisms remain unclear. Here, we investigated whether voltage-gated chloride channel-3 (ClC-3) impacts the effects of 17β-estradiol (E2) on spared nerve injury (SNI)-induced neuropathic pain in ovariectomized (OVX) female Sprague Dawley rats that were divided into OVX, OVX + SNI, OVX + SNI + E2, OVX + SNI + E2 + DMSO (vehicle, dimethyl sulfoxide), or OVX + SNI + E2+Cltx (ClC-3-blocker chlorotoxin) groups. Changes in ClC-3 protein expression were monitored by western blot analysis. Behavioral testing used the paw withdrawal threshold to acetone irritation and paw withdrawal thermal latency (PWTL) to thermal stimulation. Immunofluorescence indicated the localization and protein expression levels of ClC-3. OVX + SNI + E2 rats were subcutaneously injected with 17β-estradiol once daily for 7 days; a sheathed tube was implanted, and chlorotoxin was injected for 4 days. Intrathecal Cltx to OVX and OVX + SNI rats was administered for 4 consecutive days (days 7–10 after SNI) to further determine the contribution of ClC-3 to neuropathic pain. Patch clamp technology in current clamp mode was used to measure the current threshold (rheobase) dorsal root ganglion (DRG) neurons and the minimal current that evoked action potentials (APs) as excitability parameters. The mean number of APs at double-strength rheobase verified neuronal excitability. There was no difference in behaviors and ClC-3 expression after OVX. Compared with OVX + SNI rats, OVX + SNI + E2 rats showed a lower paw withdrawal threshold to the acetone stimulus, but the PWTL was not significantly different, indicating increased sensitivity to cold but not to thermal pain. Co-immunofluorescent data revealed that ClC-3 was mainly distributed in A- and C-type nociceptive neurons, especially in medium/small-sized neurons. 17β-estradiol administration was associated with increased expression of ClC-3. 17β-estradiol-induced increase in ClC-3 expression was blocked by co-administration of Cltx. Cltx causes hyperalgesia and decreased expression of ClC-3 in OVX rats. Patch clamp results suggested that 17β-estradiol attenuated the excitability of neurons induced by SNI by up-regulating the expression of ClC-3 in the DRG of OVX rats. 17β-estradiol administration significantly improved cold allodynia thresholds in OVX rats with SNI. The mechanism for this decreased sensitivity may be related to the upregulation of ClC-3 expression in the DRG.

[Changes of BK(Ca) on vascular striaepericytes of D-galactose-induced aging model in guinea pigs]

Objective: The aging model of guinea pigs induced by D-galactose was set up to investigate the changes of BK(Ca) expression and function on cochlear pericytes and their relationship with age-related hearing loss. Methods: Thirty healthy 8-week-old guinea pigs were randomly divided into three groups, with 10 in each group: D-galactose aging model group, subcutaneous injection of D-galactose (500 mg/kg) daily for 6 weeks; saline control group, the same amount of saline was injected into the neck of the aging model group for 6 weeks; the blank control group, no treatment was performed. The threshold of auditory brainstem response (ABR) was detected. The content of BK(Ca) in the perivascular cells of the guinea pig cochlear cells was detected by immunofluorescence technique. The changes of peripheral current density and BK(Ca) current were detected by patch clamp technique. The data were analyzed by GraphPad Prism software. Results: Compared with the saline group and the control group, the ABR threshold and the amplitude of the wave I were significantly decreased in the aging model group, and the difference was statistically significant (P<0.01). Compared with the control group, the expression of BK(Ca) in the vascular pericytes of guinea pigs in the aging model group was significantly reduced (1.00±0.08 vs 0.27±0.03,the difference was statistically significant P<0.01), and the cell current density and BK(Ca) net current value were also significantly reduced with statistically significant (P<0.01). Conclusions: D-galactose can successfully induce guinea pig aging model, in which BK(Ca) expression decreases and net current value decreases in pericytes of cochlear striavascularis, and changes in BK(Ca) expression and function may be related to age-related hearing loss.

[G protein-coupled estrogen receptor alleviates cerebral ischemia-reperfusion injury through inhibiting endoplasmic reticulum stress]

The aim of this study was to investigate whether G protein-coupled estrogen receptor (GPER) could alleviate hippocampal neuron injury under cerebral ischemia-reperfusion injury (CIRI) by acting on endoplasmic reticulum stress (ERS). The CIRI animal model was established by middle cerebral artery occlusion (MCAO). Female ovariectomized (OVX) Sprague-Dawley (SD) female rats were randomly divided into 4 groups: control, ischemia-reperfusion injury (MCAO), vehicle (MCAO+DMSO), and GPER-specific agonist G1 (MCAO+G1) groups. The neurobehavioral score was assessed by the Longa score method, the morphological changes of the neurons were observed by the Nissl staining, the cerebral infarction was detected by the TTC staining, and the neural apoptosis in the hippocampal CA1 region was detected by TUNEL staining. The distribution and expression of GRP78 (78 kDa glucose-regulated protein 78) in the hippocampal CA1 region were observed by immunofluorescent staining. The protein expression levels of GRP78, Caspase-12, CHOP and Caspase-3 were detected by Western blot, and the mRNA expression levels of GRP78, Caspase-12, and CHOP were detected by the real-time PCR. The results showed that the neurobehavioral score, cerebral infarct volume, cellular apoptosis index, as well as GRP78, Caspase-12 and CHOP protein and mRNA expression levels in the MCAO group were significantly higher than those of control group. And G1 reversed the above-mentioned changes in the MCAO+G1 group. These results suggest that the activation of GPER can decrease the apoptosis of hippocampal neurons and relieve CIRI, and its mechanism may involve the inhibition of ERS.

Age‑associated variation in the expression and function of TMEM16A calcium‑activated chloride channels in the cochlear stria vascularis of guinea pigs

The present study was designed to investigate the expression and function of transmembrane protein 16 (TMEM16A), a calcium‑activated chloride channel (CaCC), in the stria vascularis (SV) of the cochlea of guinea pigs at different ages, and to understand the role of CaCCs in the pathogenesis of presbycusis (age‑related hearing loss), the most common type of sensorineural hearing loss that occurs with natural aging. Guinea pigs were divided into the following groups: 2 weeks (young group), 3 months (youth group), 1 year (adult group), D‑galactose intervention (D‑gal group; aging model induced by subcutaneous injection of D‑galactose) and T16Ainh‑A01 (intraperitoneal injection of 50 µg/kg/day TMEM16A inhibitor T16Ainh‑A01 for 2 weeks). Differences in the hearing of guinea pigs between the various age groups were analyzed using auditory brainstem response (ABR), and immunofluorescence staining was performed to detect TMEM16A expression in the SV and determine the distribution. Reverse transcription‑quantitative PCR and western blot analyses were conducted to detect the mRNA and protein levels of TMEM16A in SV in the different age groups. Morris water maze behavior analysis demonstrated that spatial learning ability and memory were damaged in the D‑gal group. Superoxide dismutase activity and malondialdehyde content assays indicated that there was oxidative stress damage in the D‑gal group. The ABR thresholds gradually increased with age, and the increase in the T16Ainh‑A01 group was pronounced. Immunofluorescence analysis in the cochlear SV of guinea pigs in different groups revealed that expression of TMEM16A increased with increasing age (2 weeks to 1 year); fluorescence intensity was reduced in the D‑gal model of aging. As the guinea pigs continued to mature, the protein and mRNA contents of TMEM16A in the cochlea SV increased gradually, but were decreased in the D‑gal group. The findings indicated that CaCCs in the cochlear SV of guinea pigs were associated with the development of hearing in guinea pigs, and that downregulation of TMEM16A may be associated with age‑associated hearing loss.

TGF-β2 Induces Gli1 in a Smad3-Dependent Manner Against Cerebral Ischemia/Reperfusion Injury After Isoflurane Post-conditioning in Rats

Isoflurane (ISO) post-conditioning attenuates cerebral ischemia/reperfusion (I/R) injury, but the underlying mechanism is incompletely elucidated. Transforming growth factor beta (TGF-β) and hedgehog (Hh) signaling pathways govern a wide range of mechanisms in the central nervous system. We aimed to investigate the effect of the TGF-β2/Smad3 and sonic hedgehog (Shh)/Glioblastoma (Gli) signaling pathway and their crosstalk in the hippocampus of rats with ISO post-conditioning after cerebral I/R injury. Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), 1.5 h occlusion and 24 h reperfusion (MCAO/R). To assess the effect of ISO after I/R injury, various approaches were used, including neurobehavioral tests, TTC staining, HE staining, Nissl staining, TUNEL staining, immunofluorescence (IF), qRT-PCR (quantitative real-time polymerase chain reaction) and Western blot. The ISO post-conditioning group (ISO group) received 1 h ISO post-conditioning when reperfusion was initiated, leading to lower infarct volumes and neurologic deficit scores, more surviving neurons, and less damaged and apoptotic neurons. IF staining, qRT-PCR and Western blot showed high expression levels of TGF-β2, Shh and Gli1 in the hippocampal CA1 of the ISO group. Phosphorylated Smad3 (p-Smad3), Patched (Ptch), and Smoothed (Smo) were also increased at protein level in the ISO group, whereas total Smad3 expression did not change in all groups. When TGF-β2 inhibitor, pirfenidone, or Smad3 inhibitor, SIS3 HCl, were administered, the expression levels of p-Smad3 and Gli1 were reduced, and surviving pyramidal neurons decreased. By contrast, the expression levels of TGF-β2 and p-Smad3 did not change significantly after pre-injection of Smo inhibitor cyclopamine, but reduced the expression levels of Shh, Ptch, and Gli1. Moreover, Gli showed the lowest expression levels with pirfenidone combined with cyclopamine. These findings indicate that the TGF-β and hedgehog signaling pathways mediate the neuroprotection of ISO post-conditioning after cerebral I/R injury, and crosstalk between two pathways at the Gli1 level.

[Effects of Ramipril on the expression of connexin 43 in cerebral arteries of spontaneously hypertensive rats]

The present study was designed to examine whether Ramipril (an inhibitor of angiotensin-converting enzyme) affected spontaneous hypertension-induced injury of cerebral artery by regulating connexin 43 (Cx43) expression. Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were randomly divided into WKY, WKY + Ramipril, SHR, and SHR + Ramipril groups (n = 8). The arterial pressure was monitored by the tail-cuff method, and vascular function in basilar arteries was examined by pressure myography. Hematoxylin-eosin (HE) staining was used to show vascular remodeling. The expression and distribution of Cx43 was determined by using immunofluorescence and immunohistochemistry analysis. The protein and mRNA levels of Cx43 were examined by Western blot and real-time PCR analysis, respectively. The results showed that chronic Ramipril treatment significantly attenuated blood pressure elevation (P < 0.01, n = 8) and blood vessel wall thickness in SHR (P < 0.01, n = 8). The cerebral artery contraction rate in the SHR group was higher than that in the WKY group (P < 0.05, n = 8). The cerebral artery contraction rate in the SHR + Ramipril group was lower than that in the SHR group (P < 0.05, n = 8). Pretreatment with 2-APB (Cx43 non-specific blocker) or Gap26 (Cx43 specific blocker) significantly decreased the vasoconstriction rate, while pretreatment with AAP10 (Cx43 non-specific agonist) significantly increased the vasoconstriction in the SHR + Ramipril group (P < 0.05, n = 8). In addition, the expression of Cx43 mRNA and protein in cerebral arteries of SHR group was higher than that of WKY group (P < 0.05, n = 8). The mRNA and protein expression of Cx43 in cerebral arteries of SHR + Ramipril group was significantly lower than that of SHR group (P < 0.05, n = 8). These results suggest that Ramipril can down-regulate the expression of Cx43 mRNA and protein in cerebral arterial cells of SHR, lower blood pressure, promote vasodilation, and improve arterial damage and vascular dysfunction caused by hypertension.

Inhibition of GABAergic Neurons and Excitation of Glutamatergic Neurons in the Ventrolateral Periaqueductal Gray Participate in Electroacupuncture Analgesia Mediated by Cannabinoid Receptor

Although electroacupuncture (EA) has become a worldwide practice, little is understood about its precise target in the central nervous system (CNS) and the cell type-specific analgesia mechanism. In the present study, we found that EA has significant antinociceptive effects both in inflammatory and neuropathic pain models. Chemogenetic inhibition of GABAergic neurons in the ventrolateral periaqueductal gray (vlPAG) replicated the effects of EA, whereas the combination of chemogenetic activation of GABAergic neurons and chemogenetic inhibition of glutamatergic neurons in the vlPAG was needed to reverse the effects of EA. Specifically knocking out CB1 receptors on GABAergic neurons in the vlPAG abolished the EA effect on pain hypersensitivity, while specifically knocking out CB1 receptors on glutamatergic neurons attenuated only a small portion of the EA effect. EA synchronously inhibits GABAergic neurons and activates glutamatergic neurons in the vlPAG through CB1 receptors to produce EA-induced analgesia. The CB1 receptors on GABAergic neurons localized in the vlPAG was the basis of the EA effect on pain hypersensitivity. This study provides new experimental evidence that EA can bidirectionally regulate GABAergic neurons and glutamatergic neurons via the CB1 receptors of the vlPAG to produce analgesia effects.

Isoflurane Post-conditioning Ameliorates Cerebral Ischemia/Reperfusion Injury by Enhancing Angiogenesis Through Activating the Shh/Gli Signaling Pathway in Rats

Background: Stroke is the second leading cause of death worldwide. Angiogenesis facilitates the formation of microvascular networks and promotes recovery after stroke. The Shh/Gli signaling pathway is implicated in angiogenesis and cerebral ischemia-reperfusion (I/R) injury. This study aimed at investigating the influence of isoflurane (ISO) post-conditioning on brain lesions and angiogenesis after I/R injury.

Methods: Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), 1.5 h occlusion and 24 h reperfusion (MCAO/R). The ISO post-conditioning group (ISO group) received 1 h ISO post-conditioning when reperfusion was initiated. Neurobehavioral tests, TTC staining, HE staining, Nissl staining, TUNEL staining, immunofluorescence (IF), immunohistochemistry (IH) and Western blot were performed to assess the effect of ISO after I/R injury.

Results: ISO post-conditioning resulted in lower infarct volumes and neurologic deficit scores, higher rate of neurons survival, and less damaged and apoptotic cells after cerebral I/R injury in rats. Meanwhile, ISO post-conditioning significantly increased the expression levels of vascular endothelial growth factor (VEGF) and CD34 in the ischemic penumbra, relative to that in the Sham and I/R groups. However, cyclopamine, the specific inhibitor of the Sonic hedgehog (Shh) signaling pathway, decreased the expression levels of VEGF and CD34, and counteracted the protective effects of ISO post-conditioning against I/R injury in rats.

Conclusions: ISO post-conditioning enhances angiogenesis in vivo partly via the Shh/Gli signaling pathway. Thus, Shh/Gli may represent new therapeutic targets for aiding recovery from stroke.

β‑estradiol alleviates hypertension‑ and concanavalin A‑mediated inflammatory responses via modulation of connexins in peripheral blood lymphocytes

Gap junctions (GJs) formed by connexins (Cxs) in T lymphocytes have been reported to have important roles in the T lymphocyte-driven inflammatory response and hypertension-mediated inflammation. Estrogen has a protective effect on cardiovascular diseases, including hypertension and it attenuates excessive inflammatory responses in certain autoimmune diseases. However, the mechanisms involved in regulating the pro-inflammatory response are complex and poorly understood. The current study investigated whether β-estradiol suppresses hypertension and pro-inflammatory stimuli-mediated inflammatory responses by regulating Cxs and Cx-mediated GJs in peripheral blood lymphocytes. Male, 16-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) rats were randomly divided into the following three groups: WKY rats, vehicle (saline)-treated SHRs, and β-estradiol (20 µg/kg/day)-treated SHRs. β-estradiol was administered subcutaneously for 5 weeks. Hematoxylin and eosin staining was performed to evaluate target organ injury. Flow cytometry and ELISA were used to measure the populations of T lymphocyte subtypes in the peripheral blood, and expression of Cx40/Cx43 in T cell subtypes, and pro-inflammation cytokines levels, respectively. ELISA, a dye transfer technique, immunofluorescence and immunoblotting were used to analyze the effect of β-estradiol on pro-inflammatory cytokine secretion, Cx-mediated GJs and the expression of Cxs in concanavalin A (Con A)-stimulated peripheral blood lymphocytes isolated from WKY rat. β-estradiol significantly decreased blood pressure and inhibited hypertension-induced target organ injury in SHRs. Additionally, β-estradiol treatment significantly improved the immune homeostasis of SHRs, as demonstrated by the decreased percentage of cluster of differentiation (CD)4⁺/CD8⁺ T-cell subset ratio, reduced serum levels of pro-inflammatory cytokines and increased the percentage of CD4⁺CD25⁺ T cells. β-estradiol also markedly reduced the expression of Cx40/Cx43 in T lymphocytes from SHRs. In vitro, β-estradiol significantly suppressed the production of pro-inflammatory cytokines, reduced communication via Cx-mediated gap junctions and decreased the expression of Cx40/Cx43 in Con A-stimulated lymphocytes. These results indicate that β-estradiol attenuates inflammation and end organ damage in hypertension, which may be partially mediated via downregulated expression of Cxs and reduced function of Cx-mediated GJ.

G protein-coupled estrogen receptor activation improves contractile and diastolic functions in rat renal interlobular artery to protect against renal ischemia reperfusion injury

OBJECTIVE

This work aimed to investigate whether G protein-coupled estrogen receptor (GPER) can improve the renal interlobular artery vascular function by increasing the NO content, thereby protecting against renal ischemia-reperfusion (IR) injury.

METHODS

This study classified ovariectomised (OVX) female Sprague-Dawley rats into OVX, OVX + IR, OVX + IR + G1 (the GPER agonist G1), OVX + IR + G1+G15 (GPER blocker) and OVX + IR + G1+L-NAME (eNOS blocker) groups. Enzyme-linked immunosorbent assay was performed to detect the estrogen levels in the body and eliminate interference from endogenous estrogens. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) and HE staining, renal function test and Paller scoring were performed to identify the successful model and detect the degree of renal and renal interlobular arteries injury. The in vitro microvascular pressure diameter measurement technique was used to detect the contraction and diastolic activities of the renal interlobular arteries in each group. Immunofluorescence technique was used to observe the localisation and expression levels of GPER and eNOS in renal interlobular arteries. The GPER and eNOS protein expression levels in each group were detected by Western blot. The NO content in the serum of each group was detected by the nitrate reductase method.

RESULT

After OVX, the estrogen level in the body decreased significantly (P < 0.01), and TUNEL staining showed a significant increase in the degree of renal tubular epithelial cell apoptosis in the IR group. Serum creatinine (SCr) and blood urea nitrogen (BUN) levels were significantly increased in the IR group (P < 0.01), and the Paller score showed significantly increased kidney damage. When performing drug treatment, the G1 intervention group significantly decreased serum BUN and SCr levels after IR injury (P < 0.01). The Paller score showed significantly decreased the degree of renal injury (P < 0.01). After IR, the renal interlobular artery contraction rate and systolic velocity of blood vessels were significantly decreased (P < 0.01). The G1 intervention group significantly restored contraction rate and systolic velocity of blood vessels (P < 0.01), and G15 and L-NAME partially reversed this effect (P < 0.01). Immunofluorescence technique showed that GPER was expressed in renal interlobular artery smooth muscle and endothelial cells. After IR injury, the GPER protein expression increased, and the eNOS protein expression decreased significantly (P < 0.01). Western blot showed that after IR injury, the GPER protein expression increased, and the eNOS protein expression decreased significantly. After G1 intervention, the GPER content did not change, and the eNOS content increased significantly (P < 0.01). After ischemia and reperfusion, the serum NO content decreased significantly, but it increased after G1 intervention. G15 and L-NAME reversed the effects of G1 to varying degrees (both at P < 0.01).

CONCLUSION

GPER may improve the renal interlobular artery vascular function by increasing the NO content, thereby protecting against renal IR injury.

Mechanism of persistent hyperalgesia in neuropathic pain caused by chronic constriction injury

Transmembrane member 16A (TMEM16A) is involved in many physiological functions, such as epithelial secretion, sensory conduction, nociception, control of neuronal excitability, and regulation of smooth muscle contraction, and may be important in peripheral pain transmission. To explore the role of TMEM16A in the persistent hyperalgesia that results from chronic constriction injury-induced neuropathic pain, a rat model of the condition was established by ligating the left sciatic nerve. A TMEM16A selective antagonist (10 μg T16Ainh-A01) was intrathecally injected at L5-6. For measurement of thermal hyperalgesia, the drug was administered once at 14 days and thermal withdrawal latency was recorded with an analgesia meter. For measurement of other indexes, the drug was administered at 12 days, once every 6 hours, totally five times. The measurements were performed at 14 days. Western blot assay was conducted to analyze TMEM16A expression in the L4-6 dorsal root ganglion. Immunofluorescence staining was used to detect the immunoreactivity of TMEM16A in the L4-6 dorsal root ganglion on the injured side. Patch clamp was used to detect electrophysiological changes in the neurons in the L4-6 dorsal root ganglion. Our results demonstrated that thermal withdrawal latency was shortened in the model rats compared with control rats. Additionally, TMEM16A expression and the number of TMEM16A positive cells in the L4-6 dorsal root ganglion were higher in the model rats, which induced excitation of the neurons in the L4-6 dorsal root ganglion. These findings were inhibited by T16Ainh-A01 and confirm that TMEM16A plays a key role in persistent chronic constriction injury-induced hyperalgesia. Thus, inhibiting TMEM16A might be a novel pharmacological intervention for neuropathic pain. All experimental protocols were approved by the Animal Ethics Committee at the First Affiliated Hospital of Shihezi University School of Medicine, China (approval No. A2017-170-01) on February 27, 2017.

GPER agonist G1 suppresses neuronal apoptosis mediated by endoplasmic reticulum stress after cerebral ischemia/reperfusion injury

Studies have confirmed a strong association between activation of the endoplasmic reticulum stress pathway and cerebral ischemia/reperfusion (I/R) injury. In this study, three key proteins in the endoplasmic reticulum stress pathway (glucose-regulated protein 78, caspase-12, and C/EBP homologous protein) were selected to examine the potential mechanism of endoplasmic reticulum stress in the neuroprotective effect of G protein-coupled estrogen receptor. Female Sprague-Dawley rats received ovariectomy (OVX), and then cerebral I/R rat models (OVX + I/R) were established by middle cerebral artery occlusion. Immediately after I/R, rat models were injected with 100 μg/kg E2 (OVX + I/R + E2), or 100 μg/kg G protein-coupled estrogen receptor agonist G1 (OVX + I/R + G1) in the lateral ventricle. Longa scoring was used to detect neurobehavioral changes in each group. Infarct volumes were measured by 2,3,5-triphenyltetrazolium chloride staining. Morphological changes in neurons were observed by Nissl staining. Terminal dexynucleotidyl transferase-mediated nick end-labeling staining revealed that compared with the OVX + I/R group, neurological function was remarkably improved, infarct volume was reduced, number of normal Nissl bodies was dramatically increased, and number of apoptotic neurons in the hippocampus was decreased after E2 and G1 intervention. To detect the expression and distribution of endoplasmic reticulum stress-related proteins in the endoplasmic reticulum, caspase-12 distribution and expression were detected by immunofluorescence, and mRNA and protein levels of glucose-regulated protein 78, caspase-12, and C/EBP homologous protein were determined by polymerase chain reaction and western blot assay. The results showed that compared with the OVX + I/R group, E2 and G1 treatment obviously decreased mRNA and protein expression levels of glucose-regulated protein 78, C/EBP homologous protein, and caspase-12. However, the G protein-coupled estrogen receptor antagonist G15 (OVX + I/R + E2 + G15) could eliminate the effect of E2 on cerebral I/R injury. These results confirm that E2 and G protein-coupled estrogen receptor can inhibit the expression of endoplasmic reticulum stress-related proteins and neuronal apoptosis in the hippocampus, thereby improving dysfunction caused by cerebral I/R injury. Every experimental protocol was approved by the Institutional Ethics Review Board at the First Affiliated Hospital of Shihezi University School of Medicine, China (approval No. SHZ A2017-171) on February 27, 2017.

Propofol-induced vasodilation of mesenteric arterioles via BKCa channel and gap junction

The present study aimed to investigate the role of propofol in mediating the vasomotor activity of the mesenteric arteriole (MA) of Sprague Dawley (SD) rats, and to elucidate the underlying mechanisms. The pressure myograph technique was used to examine the effect of different concentrations of propofol on the relaxation of blood vessels in the 2–3 mm MA segments freshly separated from the SD rats. The whole-cell patch-clamp technique was applied to observe the outward current of single vascular smooth muscle cells (VSMCs) obtained from the MAs of the SD rats. Furthermore, immunofluorescence was utilized to assess the expression of connexin (Cx) in the MAs of SD rats. The results indicated the following: i) Propofol relaxed the MA of SD rats in a concentration-dependent manner from 1×10⁻⁷ to 3×10⁻⁴ mol/l; ii) in the acutely dissociated VSMCs, propofol (1×10⁻⁷ to 3×10⁻⁴ mol/l) enhanced the outward current of VSMCs in a concentration-dependent manner; iii) the enhanced outward currents induced by propofol (1×10⁻⁵ mol/l) may be reversed by tetraethylammonium (TEA; 1 mmol/l), a calcium-activated K⁺ channel inhibitor; iv) the effect of propofol on the relaxation of the vasculature wAS reduced after perfusion with 1 mmol/l TEA; v) Cx40, Cx43 and Cx45 were expressed on the MA; 6) 18β-glycyrrhetintic acid and 2-aminoethoxydiphenyl borate, two types of gap junction blocker, inhibited the propofol-induced relaxation. The present study provides evidence that propofol relaxes the MA, which may be associated with its effect of enhancing the channel current of large-conductance calcium voltage-activated potassium channels, contributing to the K⁺ outflow and leading to VSMC hyperpolarization; the gap junction may facilitate the hyperpolarization, which may lead to vascular synchronized relaxation and thereby reduce the blood pressure.

Effects of the Calcium-Activated Chloride Channel Inhibitors T16Ainh-A01 and CaCCinh-A01 on Cardiac Fibroblast Function

BACKGROUND/AIMS

Calcium-activated chloride channels (CaCCs) regulate numerous physiological processes including cell proliferation, migration, and extracellular matrix secretion. T16Ainh-A01 and CaCCinh-A01 are selective inhibitors of CaCCs. But it is unknown whether these two compounds have functional effects on cardiac fibroblasts (CFs).

METHODS

Primary CFs were obtained by enzymatic dissociation of cardiomyocytes from neonatal rat hearts. Intracellular Ca2+ ([Ca2+]i) and Cl- ([Cl-]i) were measured using the fluorescent calcium indicators (Fluo-4 AM) and N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide respectively. The expression of anoctamin-1 (ANO1) and α-smooth muscle actin (α-SMA) was detected by quantitative RT-PCR, immunofluorescence, and western blotting. A hydroxyproline assay was used to examine collagen secretion. Cell proliferation, cell cycle distribution, and cell migration were assessed by Cell Counting Kit-8, flow cytometry, and Transwell assays, respectively.

RESULTS

ANO1 was preferentially expressed on the nuclear membrane and partially within intracellular compartments around the nucleus. T16Ainh-A01 and CaCCinh-A01 displayed different inhibitory effects on [Cl-]i in CFs. T16Ainh-A01 considerably decreased [Cl-]i in the nucleus, whereas CaCCinh-A01 reduced [Cl-]i in intracellular compartments around the nucleus, and both inhibitors exhibited a minimal effect on [Ca2+]i in CFs. ANO1 and α-SMA expression levels were significantly repressed by CaCCinh-A01. T16Ainh-A01 showed a marked inhibitory effect on the mRNA levels of ANO1 and α-SMA, but had a negligible effect on ANO1 at the protein level. T16Ainh-A01 and CaCCinh-A01 led to the significant repression of cell proliferation, cell migration, and collagen secretion in CFs.

CONCLUSION

Our findings indicate that T16Ainh-A01 and CaCCinh-A01 have the potential to inhibit the proliferation and collagen secretion of CFs and may serve as novel anti-fibrotic therapeutic drugs in the future.

A Meta-Analysis of Therapeutic Efficacy and Safety of Gabapentin in the Treatment of Postherpetic Neuralgia from Randomized Controlled Trials

OBJECTIVE

The study aims to systematically evaluate the clinical effect of gabapentin in the treatment of postherpetic neuralgia (PHN).

METHOD

Data were retrieved electronically from PubMed, Embase, CNKI, the China Biomedical Database, and the Library of Clinical Database, beginning from the time of inception to April 2017, in order to collect data on randomized controlled trials (RCTs) of gabapentin and placebo in PHN treatment.

RESULTS

A total of 11 RCTs (2376 people) were retrieved. The gabapentin group reported significantly reduced pain intensity [MD=-0.91, 95% CI -1.32 to -0.51, P<0.00001] compared with the placebo group. Those treated with gabapentin also experienced significantly improved sleep quality [SMD=-0.44, 95% CI -0.66 to -0.23, P<0.0001], but were more likely to experience incidence of adverse events, such as somnolence, dizziness, and peripheral edema. Results of the subgroup analysis showed that the source of heterogeneity may be related to the formulations of the drug.

CONCLUSION

Gabapentin can be used to effectively and safely treat PHN.

Hydrogen Sulfide Attenuates Hypertensive Inflammation via Regulating Connexin Expression in Spontaneously Hypertensive Rats

BACKGROUND Hydrogen sulfide (H2S) has anti-inflammatory and anti-hypertensive effects, and connexins (Cxs) are involved in regulation of immune homeostasis. In this study, we explored whether exogenous H2S prevents hypertensive inflammation by regulating Cxs expression of T lymphocytes in spontaneously hypertensive rats (SHR). MATERIAL AND METHODS We treated SHR with sodium hydrosulfide (NaHS) for 9 weeks. Vehicle-treated Wistar-Kyoto rats (WKYs) were used as a control. The arterial pressure was monitored by the tail-cuff method, and vascular function in basilar arteries was examined by pressure myography. Hematoxylin and eosin staining was used to show vascular remodeling and renal injury. The percentage of T cell subtypes in peripheral blood, surface expressions of Cx40/Cx43 on T cell subtypes, and serum cytokines level were determined by flow cytometry or ELISA. Expression of Cx40/Cx43 proteins in peripheral blood lymphocytes was analyzed by Western blot. RESULTS Chronic NaHS treatment significantly attenuated blood pressure elevation, and inhibited inflammation of target organs, vascular remodeling, and renal injury in SHR. Exogenous NaHS also improved vascular function by attenuating KCl-stimulated vasoconstrictor response in basilar arteries of SHR. In addition, chronic NaHS administration significantly suppressed inflammation of peripheral blood in SHR, as evidenced by the decreased serum levels of IL-2, IL-6, and CD4/CD8 ratio and the increased IL-10 level and percentage of regulatory T cells. NaHS treatment decreased hypertension-induced Cx40/Cx43 expressions in T lymphocytes from SHR. CONCLUSIONS Our data demonstrate that H2S reduces hypertensive inflammation, at least partly due to regulation of T cell subsets balance by Cx40/Cx43 expressions inhibition.

The association between the expression of PAR2 and TMEM16A and neuropathic pain

Chronic constriction injury (CCI) of the sciatic nerve may induce dorsal root ganglion (DRG) neuronal hyperexcitability and behaviorally expressed hyperalgesia. CCI is a model of neuropathic pain. To investigate the association between the expression of protease activated receptor 2 (PAR2), TMEM16A and neuropathic pain, the expression of PAR2 and TMEM16A proteins in the DRG neurons of rats following CCI of the sciatic nerve was investigated. Following the creation of the CCI model, the thermal withdrawal latency (TWL) was examined by a hot plate test. An immunofluorescence assay and western blot assay were performed to determine the expression of PAR2 and TMEM16A proteins in the ipsilateral L_4–6 DRG neurons. The concentration of inositol 1,4,5-triphosphate (IP₃) in the L_4–6 DRG was determined by ELISA. In the CCI-D7 (7 days after CCI) and CCI-D14 (14 days after CCI) treatment groups, the TWL of rats was significantly shorter than that in the sham operated group (P<0.01; n=12). The expression of PAR2 and TMEM16A proteins in the CCI-D7 and CCI-D14 groups were significantly upregulated compared with the sham operated group (P<0.05; n=12). Additionally, it was revealed that PAR2 and TMEM16A were co-expressed in DRG neurons. It was also observed that IP₃ significantly increased in the CCI-D7 and CCI-D14 groups compared with the sham operation group (P<0.05; n=6) as PAR2 and TMEM16A also increased. These findings suggest that the upregulation of PAR2 and TMEM16A in DRG neurons, the co-expression of the two proteins and increasing IP₃ are critical to the development of neuropathic pain.

Electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K+ channels

The present study was designed to investigate the electrophysiological properties of strial pericytes and the effect of aspirin on pericyte K⁺ channels. Pericytes were identified by determining their morphological characteristics and using pericyte-associated immunofluorescence techniques. The electrophysiological properties of strial pericytes were observed with a whole-cell patch-clamp technique. Alterations in the outward current of cochlear pericytes in the stria vascularis of guinea pigs were examined following the application of K⁺ channel retardants. The effects of aspirin on pericyte K⁺ channels were also evaluated with the whole-cell patch-clamp technique. The results demonstrated that pericytes were desmin positive, and their nuclei were large and surrounded by a small proportion of the cytoplasm. Cytoplasmic processes gradually declined in size as branches grew parallel to the capillary axis. Thus, capillaries were surrounded by tips. The electrophysiological properties of the cochlear pericytes in the stria vascularis of guinea pigs were also determined. The membrane capacitance of the pericytes was 5.9±0.3 pF, while the membrane resistance and resting potential were 2.2±0.3 GΩ and −30.9±1.2 mV, respectively. The current densities of the pericytes (pA/pF) were 3.2±0.7, 10.6±1.0, 15.7±0.9 and 21.3±1.2 at command voltages of 0, +20, +40, and +60 mV, respectively. The K⁺ channels were activated when the pericytes were within the range of −20 mV to +20 mV, particularly at 0 mV. The inhibition rates of the outward current of cochlear pericytes in the stria vascularis of the guinea pigs were determined by administering iberiotoxin (IBTX) and IBTX + 4-aminopyridine. Once the background leakage current was removed, the following inhibition rates were obtained with 3, 10, 30, 300 and 1,000 µmol/l aspirin: 20.8±4.8, 34.1±6.9, 48.2±6.7, 63.6±7.1 and 65.7±8.1%, respectively. The outward current of the cochlear pericytes in the stria vascularis was inhibited by aspirin with a half maximal inhibitory concentration of 24.5±4.5 µmol/l. The membranes of the pericytes in the stria vascularis are characterized by high-conductance calcium-activated K⁺ (BK_Ca) and voltage-dependent K⁺ (K_V) channels. The outward current of the cochlear pericytes in the stria vascularis of guinea pigs was inhibited by aspirin in a concentration-dependent manner. In addition, BK_Ca and K_V channels were inhibited by aspirin.

Connexin 43 in splenic lymphocytes is involved in the regulation of CD4+CD25+ T lymphocyte proliferation and cytokine production in hypertensive inflammation

Chronic inflammation promotes the development of hypertension and is associated with increased T cell infiltration and cytokine production in impaired organs. Gap junction protein connexin 43 (Cx43), is ubiquitously expressed in immune cells and plays an important role in T cell proliferation and activation, and cytokine production. However, the correlation between Cx43 in T cells and the hypertensive inflammatory response remains unknown. Thus, in this study, we wished to examine this correlation. First, our results revealed that hypertension caused significant thickening of the vascular wall, inflammatory cell infiltration into part of the renal interstitium and glomerular atrophy, and it increased the tubular damage scores in the kidneys of spontaneously hypertensive rats (SHRs). Moreover, the SHRs exhibited stenosis in the central artery wall of the spleen with increased serum levels of interleukin (IL)-2 and IL-6 compared with normotensive Wistar-Kyoto (WKY) rats. The spleens of the SHRs exhibited a significantly decreased percentage of CD4⁺CD25⁺ (Treg) T cells. However, the percentages of CD3⁺, CD4⁺ and CD8⁺ T cell and the levels of CD4⁺Cx43 and CD8⁺Cx43 did not differ significantly between the SHRs and WKY rats. In cultured lymphocytes from the SHRs and WKY rats, low percentages of Treg cells and reduced cytokine (IL-2 and IL-6) mRNA expression levels were observed in the lymphocytes obtained from the SHRs and WKY rats treated with the connexin blocker, Gap27, or concanavalin A (ConA) plus Gap27. The effects of ConA and Gap27 differed between the SHRs and WKY rats. On the whole, our findings demonstrate that the splenic Treg cell-mediated suppression in SHRs may be involved in hypertensive inflammatory responses. Cx43 in the gap junctional channel may regulate lymphocyte activation and inflammatory cytokine production.

Association between potassium channel SNPs and essential hypertension in Xinjiang Kazak Chinese patients

The aim of the present study was to examine whether single-nucleotide polymorphisms (SNPs) of β1 subunit of large-conductance Ca²⁺-activated K⁺ channel (KCNMB1) and inwardly rectifying K⁺ channel, subfamily J, member-11 (KCNJ11) are associated with essential hypertension (EH) in Xinjiang Kazak Chinese patients. A polymerase chain reaction-restriction fragment length polymorphism technique was applied to detect the distribution of selected alleles and genotype frequencies in a cohort of Xinjiang Kazak Chinese patients. Samples from 267 patients with EH and 259 normotensive (NT) controls were analyzed. An unconditional logistic regression analysis was used to estimate the odds ratio and 95% confidence interval of the risk factors that are associated with the development of EH. Genotype and allele frequency analyses revealed that the frequency of genotypes KCNJ11-rs2285676 and KCNMB1-rs11739136 was not significantly different between the EH and NT groups. Individuals carrying the GG genotype of KCNJ11-rs5219 had a 2.08 times higher risk of having EH than individuals carrying the GA+AA genotype of KCNJ11-rs5219. Furthermore, the G allele frequency of KCNJ11-rs5219 in the EH group was significantly higher than that of the NT group (P=0.048). Additionally, logistic regression analysis revealed that the body weight and GG genotype of KCNJ11-rs5219 were positively associated with EH in Xinjiang Kazak Chinese patients (P<0.01).

Up-regulation of gap junction in peripheral blood T lymphocytes contributes to the inflammatory response in essential hypertension

Inflammation has been shown to play an important role in the mechanisms involved in the pathogenesis of hypertension. Connexins (Cxs)-based gap junction channels (GJCs) or hemichannels (HCs) are involved in the maintenance of homeostasis in the immune system. However, the role of Cx43-based channels in T-lymphocytes in mediating the immune response in essential hypertension is not fully understand. The present study was designed to investigate the role of Cxs-based channels in T lymphocytes in the regulation of hypertension-mediated inflammation. The surface expressions of T lymphocyte subtypes, Cx40/Cx43, and inflammatory cytokines (IFN-γ (interferon-gamma) and TNF-ɑ (tumor necrosis factor alpha)) in T cells, as well as gap junction communication of peripheral blood lymphocytes from essential hypertensive patients (EHs) and normotensive healthy subjects (NTs) were detected by flow cytometry. Expression levels and phosphorylation of Cx43 protein in peripheral blood lymphocytes of EHs and NTs were analyzed by Western blot. The proliferation rate of peripheral blood mononuclear cells (PBMCs) after treatment with a Cxs inhibitor was examined by a CCK-8 assay. The levels of inflammatory cytokines were detected using ELISA. Within the CD3+ T cell subsets, we found a significant trend toward an increase in the percentage of CD4+ T cells and CD4+/CD8+ ratio as well as in serum levels of IFN-γ and TNF-ɑ in the peripheral blood of EHs compared with those in NTs. Moreover, the peripheral blood lymphocytes of EH patients exhibited enhanced GJCs formation, increased Cx43 protein level and Cx43 phosphorylation at Ser368, and a significant increase in Cx40/Cx43 surface expressions levels in CD4+ or CD8+ T lymphocytes. Cx43-based channel inhibition by a mimetic peptide greatly reduced the exchange of dye between lymphocytes, proliferation of stimulated lymphocytes and the pro-inflammatory cytokine levels of EHs and NTs. Our data suggest that Cx40/Cx43-based channels in lymphocytes may be involved in the regulation of T lymphocyte proliferation and the production of pro-inflammatory cytokines, which contribute to the hypertensive inflammatory response.

Effects of RMF on BKCa and Kv channels in basilar arterial smooth‑muscle cells of SHR

The current study observed the effects and investigated the mechanism of remifentanil (RMF) on the isolated cerebral basilar arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. A pressure myograph system was used to observe and compare the effects of different concentrations of RMF (10⁻¹⁰-10⁻⁵ mol/l) on the diameter changes of freshly isolated cerebral basilar arteries, which have been pre-shrunk by phenylephrine (PE), an endothelium-independent vasoconstrictor. Vascular smooth-muscle cells of the cerebral basilar artery (BASMCs) were freshly obtained via enzymolysis. BKCa (large-conductance calcium-activated potassium channels) current (I_BKCa) and Kv (voltage-gated potassium channels) current (I_Kv) were recorded using a whole-cell patch-clamp technique. The changes in I_BKCa and I_Kv produced by different concentrations of RMF (10⁻¹⁰ to 10⁻⁵ mol/l) on the two types of rats with the holding potential of −40 mV were observed and compared. The cerebral basilar arteries of the SHR and WKY rats were relaxed by RMF in a concentration-dependent manner (P<0.05; n=5). At the same concentration, the diastolic effect of RMF on SHR was weaker than that observed in WKY rats (P<0.05, n=5). When the rats were pre-perfused with 10⁻³ mol/l of the BKCa channel blocker tetraethylammonium (TEA), the diastolic amplitudes of RMF in SHR and WKY rats were decreased, and the fitting curves shifted down (P<0.05; n=7 and 6, respectively). However, no statistically significant difference was observed with 10⁻³ mol/l of the Kv channel blocker 4-aminopyridine (4-AP; n=6 and 9, respectively; P>0.05). Outward currents were increased by RMF in both BASMCs of SHR and WKY rats in a voltage- and dose-dependent manner (P<0.05; n=6). At the same concentration, the effect of RMF on the outward currents in BASMCs of WKY rats was stronger than that on SHR (P<0.05; n=6). The enhancing effect of RMF can be partially blocked by either 10⁻³ mol/l TEA (P<0.05; n=6) or 10⁻³ mol/l 4-AP (P<0.05 or 0.01; n=6 and 9, respectively) however can be totally blocked by the mixture of TEA and 4-AP (P<0.05, n=7). RMF served a diastolic role in the cerebral basilar arteries of rats in a dose-dependent manner, likely by activating the BKCa and Kv channels. However, SHR demonstrated a less pronounced diastolic reaction to RMF than that observed in WKY rats.

Effects of niflumic acid on γ-aminobutyric acid-induced currents in isolated dorsal root ganglion neurons of neuropathic pain rats

Niflumic acid (NFA) is a type of non-steroidal anti-inflammatory drug. Neuropathic pain is caused by a decrease in presynaptic inhibition mediated by γ-aminobutyric acid (GABA). In the present study, a whole-cell patch-clamp technique and intracellular recording were used to assess the effect of NFA on GABA-induced inward current in dorsal root ganglion (DRG) neurons of a chronic constriction injury (CCI) model. It was observed that 1–1,000 µmol/l GABA induced a concentration-dependent inward current in DRG neurons. Compared with pseudo-operated rats, the thermal withdrawal latency (TWL) of CCI rats significantly decreased (P<0.01); however, the TWLs of each NFA group (50 and 300 µmol/l) were significantly longer than that of the CCI group (P<0.01). In the CCI group, the response evoked by GABA (10⁻⁶-10⁻³ mol/l) was reduced in a concentration dependent manner compared with a normal control group (P<0.01), and the current amplitudes of CCI rats activated by the same concentrations of GABA (10⁻⁶-10⁻³ mol/l) were significantly decreased compared with the control group (P<0.05). The inward currents activated by 100 µmol/l GABA were suppressed by treatment with 1, 10 and 100 µmol/l NFA (5.32±3.51, 33.8±5.20, and 52.2±6.32%, respectively; P<0.05). The inverse potentials of GABA-induced currents were 9.87±1.32 and 9.64±1.24 mV with and without NFA, respectively (P<0.05). Pre-treatment with NFA exerted a strong inhibitory effect on the peak value of GABA-induced current, and the GABA-induced response was inhibited by the same concentrations of NFA (1, 10 and 100 µmol/l) in the control and CCI groups (P<0.05). The results suggest that NFA reduced the primary afferent depolarization (PAD) associated with neuropathic pain and mediated by the GABA_A receptor. NFA may regulate neuropathic pain by inhibiting dorsal root reflexes, which are triggered PAD.

Enhanced gap junctional channel activity between vascular smooth muscle cells in cerebral artery of spontaneously hypertensive rats

The aim of the present study is to investigate the effects of hypertension on the gap junctions between vascular smooth muscle cells (VSMCs) in the cerebral arteries (CAs) of spontaneously hypertensive rats (SHRs). The functions of gap junctions in the CAs of VSMCs in SHRs and control normotensive Wistar-Kyoto (WKY) rats were studied using whole-cell patch clamp recordings and pressure myography, and the expression levels of connexins were analyzed using reverse transcription-quantitative polymerase chain reaction and Western blot analyses. Whole-cell patch clamp measurements revealed that the membrane capacitance and conductance of in situ VSMCs in the CAs were significantly greater in SHRs than in WKY rats, suggesting that gap junction coupling is enhanced between VSMCs in the CAs of SHRs. Application of the endothelium-independent vasoconstrictors KCl or phenylephrine (PE) stimulated a greater vasoconstriction in the CAs of SHRs than in those of WKY rats. The EC₅₀ value of KCl was 24.9 mM (n = 14) and 36.9 mM (n=12) for SHRs and WKY rats, respectively. The EC₅₀ value of PE was 0.9 µM (n = 7) and 2.2 µM (n = 7) for SHRs and WKY rats, respectively. Gap junction inhibitors 18β-glycyrrhetinic acid (18β-GA), niflumic acid (NFA), and 2-aminoethoxydiphenyl borate (2-APB) attenuated KCl-induced vasoconstriction in SHRs and WKY rats. The mRNA and protein expression levels of the gap junction protein connexin 45 (Cx45) were significantly higher in the CAs of SHRs than in those of WKY rats. Phosphorylated Cx43 protein expression was significantly higher in the CAs of SHRs than in those of WKY rats, despite the total Cx43 mRNA and protein expression levels in the cerebral artery (CA) exhibiting no significant difference between SHRs and WKY rats. Increases in the expression of Cx45 and phosphorylation of Cx43 may promote gap junction communication among VSMCs in the CAs of SHRs, which may enhance the contractile response of the CA to vasoconstrictors.

Association of connexin gene polymorphism with essential hypertension in Kazak and Han Chinese in Xinjiang, China

Essential hypertension (EH) is affected by both genetic and environmental factors. The polymorphism of connexin (Cx) genes is found associated with the development of hypertension. However, the association of the polymorphism of Cxs with EH has not been investigated. This study aimed to investigate the association of the polymorphism of connexin (Cx) genes Cx37, Cx40, and Cx43 with EH in Kazak and Han Chinese in Xinjiang, China. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were used to analyze the polymorphism of Cx genes in Kazak and Han EH patients as well as their normotensive controls. The results showed that there were no significant differences in the frequencies of different three genotypes (A/A, A/G, and G/G) and A and G alleles of Cx40 rs35594137 and rs11552588 between EH patients and normotensive controls. However, in Kazak EH patients, the frequencies of three genotypes (A/A, A/G, and G/G) of Cx37 rs1630310 were 24.8%, 47.2% and 28.0%, respectively, which were significantly different from those in Han EH patients. In Han EH patients, the frequencies of the three genotypes (C/C, C/G and G/G) of Cx43 rs1925223 were 6.4%, 35.6% and 58.0%, respectively. Frequencies of the other four genotypes had no statistical differences among Kazak and Han EH patients and their normotensive controls. These results suggest polymorphisms of Cx37 rs1630310 and Cx43 rs1925223 genes may be associated with the pathogenesis of EH. Carrying Cx37 rs1630310-A or Cx43 rs1925223-G genotypes may protect against the development of EH.

Enhanced expression of Cx43 and gap junction communication in vascular smooth muscle cells of spontaneously hypertensive rats

Niflumic acid (NFA) is a novel gap junction (GJ) inhibitor. The aim of the present study was to investigate the effect of NFA on GJ communication and the expression of connexin (Cx) in vascular smooth muscle cells (VSMCs) of mesenteric arterioles of spontaneously hypertensive rats (SHR). Whole-cell patch clamp recording demonstrated that NFA at 1×10–4 M significantly inhibited the inward current and its effect was reversible. The time for charging and discharging of cell membrane capacitance (Cinput) reduced from 9.73 to 0.48 ms (P<0.05; n=6). Pressure myograph measurement showed that NFA at 3×10-4 M fully neutralized the contraction caused by phenylephrine. The relaxation responses of normotensive control Wistar Kyoto (WKY) rats were significantly higher, compared with those of the SHRs (P<0.05; n=6). Western blot and reverse transcription-quantitative polymerase chain reaction analyses showed that the mRNA and protein expression levels of Cx43 of the third-level branch of mesenteric arterioles of the SHRs and WKY rats were higher, compared with those of the first-level branch. The mRNA and protein expression levels of Cx43 of the primary and third-level branches of the mesenteric arterioles in the SHRs were higher, compared with those in the WKY rats (P<0.05; n=6). The mRNA levels of Cx43 in the mesenteric arterioles were significantly downregulated by NFA in a concentration-dependent manner (P<0.01; n=6). The protein levels of Cx43 in primary cultured VSMCs isolated from the mesenteric arterioles were also significantly downregulated by NFA in a concentration-dependent manner (P<0.01; n=6). These results showed that the vasorelaxatory effects of GJ inhibitors were reduced in the SHRs, which was associated with a higher protein expression level of Cx43 in the mesenteric arterioles of the SHRs. NFA also relaxed the mesenteric arterioles by reducing the expression of Cx43, which decreased blood pressure. Therefore, regulation of the expression of GJs may be a therapeutic target for the treatment of hypertension.

NSAIDs modulate GABA-activated currents via Ca2+-activated Cl- channels in rat dorsal root ganglion neurons

The ability of non-steroidal anti-inflammatory drugs (NSAIDs) to modulate γ-aminobutyrate (GABA)-activated currents via Ca²⁺-activated Cl⁻ channels in rat dorsal root ganglion neurons (DRG), was examined in the present study. During the preparation of DRG neurons harvested from Sprague-Dawley rats, the whole-cell recording technique was used to record the effect of NSAIDs on GABA-activated inward currents, and the expression levels of the TMEM16A and TMEM16B subunits were revealed. In the event that DRG neurons were pre-incubated for 20 sec with niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) prior to the administration of GABA, the GABA-induced inward currents were diminished markedly in the majority of neurons examined (96.3%). The inward currents induced by 100 µmol/l GABA were attenuated by (0±0.09%; neurons = 4), (5.32±3.51%; neurons = 6), (21.3±4.00%; neurons = 5), (33.8±5.20%; neurons = 17), (52.2±5.10%; neurons = 4) and (61.1±4.12%; neurons = 12) by 0.1, 1, 3, 10, 30 and 100 µmol/l NFA, respectively. The inward currents induced by 100 µmol/l GABA were attenuated by (13.8±6%; neurons = 6), (23.2±14.7%; neurons = 6) and (29.7±9.1%; neurons = 9) by 3, 10 and 30 µmol/l NPPB, respectively. NFA and NPPB dose-dependently inhibited GABA-activated currents with half maximal inhibitory concentration (IC₅₀) values of 6.7 and 11 µmol/l, respectively. The inhibitory effect of 100 µmol/l NFA on the GABA-evoked inward current were also strongly inhibited by nitrendipine (NTDP; an L-type calcium channel blocker), 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis (a highly selective calcium chelating reagent), caffeine (a widely available Ca²⁺ consuming drug) and calcium-free extracellular fluid, in a concentration-dependent manner. Immunofluorescent staining indicated that TMEM16A and TMEM16B expression was widely distributed in DRG neurons. The results suggest that NSAIDs may be able to regulate Ca²⁺-activated chloride channels to reduce GABA_A receptor-mediated inward currents in DRGs.

The enhancement of Cx45 expression and function in renal interlobar artery of spontaneously hypertensive rats at different age

BACKGROUND/AIMS

This study was designed to investigate the expression and function of gap junction protein connexin 45 (Cx45) in renal interlobar artery (RIA) of spontaneously hypertensive rats (SHR), and the association between hypertension and enhanced vasoconstrictive response in SHR.

METHODS

Western blot analysis and pressure myography were used to examine the differences in expression and function of Cx45 in vascular smooth muscle cells (VSMCs) of RIA between SHR and normotensive Wistar-Kyoto (WKY) rats.

RESULTS

Our results demonstrated that 1) whole-cell patch clamp measurements showed that the membrane capacitance and conductance of in-situ RIA VSMCs of SHR were significantly greater than those of WKY rats (p<0.05, n=6), suggesting that the coupling of gap junction between VSMCs of RIA was enhanced in SHR; 2) the KCl or phenylephrine (PE)-stimulated RIA constriction was more pronounced in SHR than that in WKY rats (p<0.05, n=10). After applying a gap junction inhibitor 18β-glycyrrhetintic acid (18β-GA), the inhibitory effect of 18β-GA on KCl or PE-induced vasoconstriction was greater in SHR (p<0.05, n=10); and 3) the expression of Cx45 in RIA of SHR was greater than that in WKY rats (p<0.05, n=3) at 4, 12 and 48 wks of age.

CONCLUSIONS

The hypertension-induced elevation of Cx45 may affect communication between VSMCs and coupling between VSMCs and endothelium, which results in an increased vasoconstrictive response in renal artery and might contribute to the development of hypertension.

[Isoliquiritigenin relaxes the cerebral basilar artery by enhancing BKCa current in spontaneously hypertensive rat: role of sGC/cGMP]

The purpose of the present study is to investigate the effect of isoliquiritigenin (ISL) on the cerebral basilar artery in spontaneously hypertensive rats (SHR). The change of SHR systolic pressure was measured by tail artery pressure measurement instrument before and after ISL intervention. After perfusion with 1 × 10(-5) mol/L phenylephrine (PE), 1 × 10(-5) mol/L PE + 1 × 10(-4) mol/L ISL and 1 × 10(-5) mol/L PE, the diameter of the cerebral basilar artery separated from SHR was measured by pressure myograph. The current of large-conductance calcium-activated potassium (BKCa) channel of SHR single vascular smooth muscle cell (VSMC) was recorded by whole-cell patch-clamp technique and the cGMP levels of basilar artery was evaluated by ELISA. The results showed that 1) after intervention with ISL for 14 days, the systolic pressure of SHR was decreased from (218.3 ± 1.6) mmHg to (119.2 ± 1.9) mmHg (P < 0.01), but there was no difference in systolic pressure between ISL-treated SHR and Wistar-Kyoto (WKY) rat; 2) 1 × 10(-4) mol/L ISL relaxed the SHR cerebral basilar artery (P < 0.01); 3) ISL significantly increased the outward current density of VSMC from SHR cerebral basilar artery (P < 0.01, n = 6), and the effect could be reversed by 1 × 10(-3) mol/L TEA (a BKCa channel inhibitor), but 3 × 10(-4) mol/L 4-AP (a Kv channel inhibitor) had no effect on the enhanced current density induced by ISL in VSMC; 4) 1 × 10(-5) mol/L Methylene blue (a sGC inhibitor) significantly inhibited the ISL-enhanced current density in VSMC (P < 0.05, n = 6); 5) ISL significantly increased the cGMP level of SHR basilar artery (P < 0.05, n = 6). The results suggest that the role of the ISL in relaxing the SHR cerebral basilar artery may be related to its effect in enhancing BKCa current by increasing the levels of cGMP in the VSMC.