Endothelial peroxynitrite causes disturbance of neuronal oscillations by targeting caspase-1 in the arcuate nucleus.

Severe anorexia limits the clinical application of cisplatin, and even leads to the discontinuation of treatment. However, the mechanisms underlying cisplatin-induced anorexia are unknown. Herein, we demonstrated that cisplatin could affect neuronal gamma oscillations and induce abnormal neuronal theta-gamma phase-amplitude coupling in the arcuate nucleus (Arc) of the hypothalamus, and these findings were associated with significantly decreased food intake and weight loss in mice. Chemogenetic activation of AgRP neurons in the Arc reversed the cisplatin-induced food intake reduction in mice. We further demonstrated that endothelial peroxynitrite (ONOO-) formation in the Arc induced nitrosative stress following cisplatin treatment via a previously uncharacterized pathway involving neuronal caspase-1 activation. Strikingly, treatment with the ONOO- scavenger uric acid (UA) reversed the reduced action potential (AP) frequency of AgRP neurons and increased the AP frequency of POMC neurons induced by SIN1, a donor of ONOO-, in the Arc, as determined by whole-cell patch-clamp electrophysiological recording. Consistent with these findings, UA treatment effectively alleviated cisplatin-induced dysfunction of neuronal oscillations and neuronal theta-gamma phase-amplitude coupling in the Arc of mice. Taken together, these results suggest, for the first time, that targeting the overproduction of endothelial ONOO- can regulate cisplatin-induced neurotoxicity through neuronal caspase-1, and thereby serve as a potential therapeutic approach to alleviate chemotherapy-induced anorexia and weight loss.

Endothelial Cdk5 deficit leads to the development of spontaneous epilepsy through CXCL1/CXCR2-mediated reactive astrogliosis.

Blood-brain barrier (BBB) dysfunction has been suggested to play an important role in epilepsy. However, the mechanism mediating the transition from cerebrovascular damage to epilepsy remains unknown. Here, we report that endothelial cyclin-dependent kinase 5 (CDK5) is a central regulator of neuronal excitability. Endothelial-specific Cdk5 knockout led to spontaneous seizures in mice. Knockout mice showed increased endothelial chemokine (C-X-C motif) ligand 1 (Cxcl1) expression, decreased astrocytic glutamate reuptake through the glutamate transporter 1 (GLT1), and increased glutamate synaptic function. Ceftriaxone restored astrocytic GLT1 function and inhibited seizures in endothelial Cdk5-deficient mice, and these effects were also reversed after silencing Cxcl1 in endothelial cells and its receptor chemokine (C-X-C motif) receptor 2 (Cxcr2) in astrocytes, respectively, in the CA1 by AAV transfection. These results reveal a previously unknown link between cerebrovascular factors and epileptogenesis and provide a rationale for targeting endothelial signaling as a potential treatment for epilepsy.

Functional coupling of Tmem74 and HCN1 channels regulates anxiety-like behavior in BLA neurons.

Anxiety disorders are the most prevalent psychiatric disorders, but their pathogenic mechanism remains poorly understood. Here, we report that transmembrane protein 74 (TMEM74), which contains two putative transmembrane domains and exhibits high levels of mRNA in the brain, is closely associated with the pathogenesis of anxiety disorders. TMEM74 was decreased in the serum of patients with anxiety and the basolateral amygdaloid nucleus (BLA) in chronic stress mice. Furthermore, genetic deletion of Tmem74 or selective knockdown of Tmem74 in BLA pyramidal neurons resulted in anxiety-like behaviors in mice. Whole-cell recordings in BLA pyramidal neurons revealed lower hyperpolarization-activated cation current (Ih) and greater input resistance and excitability in Tmem74-/- neurons than in wild-type neurons. Accordingly, surface expression of hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels was also lower in the BLA of Tmem74-/- mice. The Ih current blocker ZD7288 mimicked these effects in BLA pyramidal neurons in wild-type mice but not in Tmem74-/- mice. Consistent with the improvement in anxiety-like behaviors, Tmem74 overexpression restored HCN1 channel trafficking and pyramidal neuron excitability in the BLA of Tmem74-/- and chronic stress mice. Mechanistically, we demonstrate that interactions between Tmem74 and HCN1 are physiologically relevant and that transmembrane domain 1 (TM1) is essential for the cellular membrane localization of Tmem74 to enhance Ih. Together, our findings suggest that Tmem74 coupling with HCN1 acts as a critical component in the pathophysiology of anxiety and is a potential target for new treatments of anxiety disorders.

Cathepsin B inhibition ameliorates leukocyte-endothelial adhesion in the BTBR mouse model of autism.

AIMS: Autism spectrum disorder (ASD) is a wide range of neurodevelopmental disorders involving deficits in social interaction and communication. Unfortunately, autism remains a scientific and clinical challenge owing to the lack of understanding the cellular and molecular mechanisms underlying it. This study aimed to investigate the pathophysiological mechanism underlying leukocyte-endothelial adhesion in autism-related neurovascular inflammation. METHODS: Male BTBR T+tf/J mice were used as an autism model. The dynamic pattern of leukocyte-endothelial adhesion in mouse cerebral vessels was detected by two-photon laser scanning microscopy (TPLSM). Using FACS, RT-PCR, and Western blotting, we explored the expression of cell adhesion molecules, the mRNA expression of endothelial chemokine, the protein levels of cathepsin B, and inflammatory mediators. RESULTS: We found a significant increase in leukocyte-endothelial adhesion in BTBR mice, accompanied by elevated expression of the adhesion molecule neutrophils CD11b and endothelial ICAM-1. Our data further indicate that elevated neutrophil cathepsin B levels contribute to elevated endothelial chemokine CXCL7 levels in BTBR mice. The pharmacological inhibition of cathepsin B reverses the enhanced leukocyte-endothelial adhesion in the cerebral vessels of autistic mice. CONCLUSION: Our results revealed the prominent role of cathepsin B in modulating leukocyte-endothelial adhesion during autism-related neurovascular inflammation and identified a promising novel approach for autism treatment.

Endothelial GPR124 Exaggerates the Pathogenesis of Atherosclerosis by Activating Inflammation.

BACKGROUND/AIMS: Endothelial cell dysfunction is the principal pathological process underlying atherosclerotic cardiovascular disease. G protein-coupled receptor 124 (GPR124), an orphan receptor in the adhesion GPCR subfamily, promotes angiogenesis in the brain. In the present study, we explored the role of endothelial GPR124 in the development and progression of atherosclerosis in adult mice. METHODS: Using tetracycline-inducible transgenic systems, we generated mice expressing GPR124 specifically under control of the Tie-2 promoter. The animal model of atherosclerosis was constructed by intravenously injecting AAV-PCSK9DY into tetracycline-regulated mice and feeding the mice a high-fat diet for 16 consecutive weeks. Biochemical analysis and immunohistochemistry methods were used to address the role and mechanism of GPR124 in the pathological process of atherosclerosis. RESULTS: Higher TC (total cholesterol) and LDL-C (low density lipoprotein cholesterol) levels in serum and greater lipid deposition in the aortic sinus were found in atherosclerotic mice with GPR124 overexpression, coincident with the elevated proliferation of smooth muscle cells. We observed an elevation of ONOO- in the aortic sinus in this model by using immunofluorescence, and the experiments showed that the specific overexpression of GPR124 in the endothelium induced the up-regulation of CD68, NLRP3 and caspase-1 levels in the aortic sinus. CONCLUSION: The above results indicate that manipulating GPR124 in the endothelium may contribute to delayed pathological progression of atherosclerosis.

HIV Tat protein inhibits hERG K+ channels: a potential mechanism of HIV infection induced LQTs.

HIV-infected patients have a high prevalence of long QT syndrome (LQTs). hERG K(+) channel encoded by human ether-a-go-go related gene contributes to IKr K(+) currents responsible for the repolarization of cardiomyocytes. Inhibition of hERG K(+) channels leads to LQTs. HIV Tat protein, the virus transactivator protein, plays a pivotal role in AIDS. The aim of the present study is to examine the effects of HIV Tat protein on hERG K(+) channels stably expressed in HEK293 cells. The hERG K(+) currents were recorded by whole-cell patch-clamp technique and the hERG channel expression was measured by real-time PCR and Western blot techniques. HIV Tat protein at 200 ng/ml concentration showed no acute effect on hERG currents, but HIV Tat protein (200 ng/ml) incubation for 24 h significantly inhibited hERG currents. In HIV Tat incubated cells, the inactivation and the recovery time from inactivation of hERG channels were significantly changed. HIV Tat protein incubation (200 ng/ml) for 24h had no effect on the hERG mRNA expression, but dose-dependently inhibited hERG protein expression. The MTT assay showed that HIV Tat protein at 50 ng/ml and 200 ng/ml had no effect on the cell viability. HIV Tat protein increased reactive oxygen species (ROS) generation and the inhibition of hERG channel protein expression by HIV Tat protein was prevented by antioxidant tempol. HIV Tat protein in vivo treatment reduced IKr currents and prolonged action potential duration of guinea pig cardiomyocytes. We conclude that HIV Tat protein inhibits hERG K(+) currents through the inhibition of hERG protein expression, which might be the potential mechanism of HIV infection induced LQTs.

Heme oxygenase-1 transgenic overexpression did not prevent artery injury induced by electric stimulation and pressure overload in mice.

Heme oxygenase-1 (HO-1) shows multiple beneficial effects on cardiovascular diseases. However, the effect of HO-1 on the injury of artery has never been identified. In the present study, we established systemic HO-1 overexpression transgenic mice and investigated the effect of HO-1 on the injury of artery induced by electric stimulation and pressure-overload in transgenic mice. Artery injury was induced by electric stimulation and pressure overload. The contractive function, endothelium-dependent and -independent relaxation of arteries were measured through an isometric force transducer connected to a multichannel acquisition and analysis system. Western blot results showed that HO-1 protein level in transgenic mice arteries was significantly higher than that in wild type mice arteries, while no difference of HO-2 protein level in the arteries of transgenic and wild type mice. Arterial reendothelialization after electric injury was accelerated in transgenic mice. No significant difference in contractive function, endothelium-dependent and -independent relaxation of arteries was observed between wild type and transgenic mice at day 7 after electric injury and 4 weeks after pressure overload. We concluded that HO-1 overexpression accelerated the reendothelialization, but did not prevent the functional impairment of injured artery in mice.

Homocysteine inhibits potassium channels in human atrial myocytes.

1. A large body of evidence indicates that elevated homocysteine (Hcy) levels portend an increased risk for atrial fibrillation. However, little is known about the electrophysiological effects of Hcy on atrial myocytes. The present study was conducted to investigate the direct effects of Hcy on ion channels in human atria. 2. Whole-cell patch-clamp techniques were used to record potassium currents in human atrial cells. 3. In human atrial myocytes, transient outward potassium currents were significantly decreased by 24.8 +/- 5.9 and 38.4 +/- 10.4% in the presence of 50 and 500 micromol/L Hcy, respectively. The ultrarapid delayed rectifier potassium currents were decreased by approximately 30% when exposed to 500 micromol/L Hcy. The inward rectifier potassium currents were increased by approximately 40% in the presence of 500 micromol/L Hcy. 4. The results of the present study indicate that Hcy, an important risk factor for atrial fibrillation, could cause electrophysiological disturbances of potassium currents in human atrial myocytes.

Involvement of calcium-sensing receptor in ischemia/reperfusion-induced apoptosis in rat cardiomyocytes.

The calcium-sensing receptor (CaR) is a seven-transmembrane G-protein coupled receptor, which activates intracellular effectors, for example, it causes inositol phosphate (IP) accumulation to increase the release of intracellular calcium. Although intracellular calcium overload has been implicated in the cardiac ischemia/reperfusion (I/R)-induced apoptosis, the role of CaR in the induction of apoptosis has not been fully understood. This study tested the hypothesis that CaR is involved in I/R cardiomyocyte apoptosis by increasing [Ca2+]i. The isolated rat hearts were subjected to 40-min ischemia followed by 2 h of reperfusion, meanwhile GdCl3 was added to reperfusion solution. The expression of CaR increased at the exposure to GdCl3 during I/R. By laser confocal microscopy, it was observed that the intracellular calcium was significantly increased and exhibited a Deltapsim, as monitored by 5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolcarbocyanine iodide (JC-1) during reperfusion with GdCl3. Furthermore, the number of apoptotic cells was significantly increased as shown by TUNEL assay. Typical apoptotic cells were observed with transmission electron microscopy in I/R with GdCl3 but not in the control group. The expression of cytosolic cytochrome c and activated caspase-9 and caspase-3 was significantly increased whereas the expression of mitochondrial cytochrome c significantly decreased in I/R with GdCl3 in comparison to the control. In conclusion, these results suggest that CaR is involved in the induction of cardiomyocyte apoptosis during ischemia/reperfusion through activation of cytochrome c-caspase-3 signaling pathway.

[Comparison of the anti-arrhythmic effects of matrine and berbamine with amiodarone and RP58866].

AIM: To clarify mechanisms that the antiarrhythmic effects of matrine and berbamine are weaker than those of amiodarone and RP58866. METHODS: Experimental arrhythmic models were induced by aconitine, coronary artery ligation and electric stimulation in rats and rabbits. Whole-cell patch-clamp techniques were used to record IK1, IKr, IKs and Ito. RESULTS: Matrine and berbamine significantly increased the dose of aconitine for induction of ventricular premature and ventricular tachycardia in rats, decreased the number of arrhythmias induced by coronary artery ligation in rats and increased ventricular fibrillation threshold (VFT) induced by electric stimulation in rabbits, but the anti-arrhythmic potency of matrine and berbamine was lower than that of amiodarone and RP58866. The inhibitory actions of matrine and berbamine on IK1, IKr, IKs, Ito were lower than those of amiodarone and RP58866. The IC50 of matrine for IK1, IKr, IKs, Ito were (46 +/- 3), (32.9 +/- 1.2), (37 +/- 8) and (7.6 +/- 0.5) mol x L(-1), respectively. The IC50 of amiodarone for IK1, IKr, IKs, Ito were (21 +/- 5) , (3.7 +/- 0.7), (5.9 +/- 0.9) and (5.9 +/- 0.6) mol x L(-1), respectively. CONCLUSION: The inhibitory actions of matrine and berbamine on IK1, IKr, IKs, Ito were lower than those of amiodarone and RP58866, which might be the reason that the antiarrhythmic effects of matrine and berbamine were weaker than those of amiodarone and RP58866.

[The ion targets of arrhythmias induced by ouabain and aconitine in guinea pig and rat ventricular myocytes].

AIM: To observe the effects of ouabain and aconitine on APD and ion channels in isolated guinea pig and rat ventricular myocytes; to elucidate the action mechanisms of these two drugs and set up new arrhythmic models on cellular level. METHODS: In isolated ventricular myocytes of guinea pig and rat, the effects of ouabain and aconitine on APD, ICa-L, Ik, Ito and Ik1 were observed using the whole cell patch clamp technique. RESULTS: Ouabain (5 micromol x L(-1)) obviously prolonged the APD90, increased ICa-L, decreased Ik and Ik1 in guinea pig ventricular myocytes. Aconitine (1 micromol x L(-1)) lengthened the APD90, increased ICa-L, decreased Ito and increased Ik1 in rat ventricular myocytes. CONCLUSION: The targets on ouabain- and aconitine-induced arrhythmias included APD, ICa-L, Ik, Ito, and Ik1. APD, ICaL, Ik and Ito must be the powerful ones, both in arrhythmic and antiarrhythmic courses. The ouabain- and aconitine- induced arrhythmic models on cellular level were built to study the antiarrhythmic mechanisms of chemicals and evaluate new drugs. These two new-type models in vitro were stable, liable, repeatable and economic, which were superior to those typical models in vivo.