Intermedin in Paraventricular Nucleus Attenuates Ang II-Induced Sympathoexcitation through the Inhibition of NADPH Oxidase-Dependent ROS Generation in Obese Rats with Hypertension

Mechanisms and treatment of obesity-related hypertension-Part 1: Mechanisms

The prevalence of obesity has tripled over the past five decades. Obesity, especially visceral obesity, is closely related to hypertension, increasing the risk of primary (essential) hypertension by 65%-75%. Hypertension is a major risk factor for cardiovascular disease, the leading cause of death worldwide, and its prevalence is rapidly increasing following the pandemic rise in obesity. Although the causal relationship between obesity and high blood pressure (BP) is well established, the detailed mechanisms for such association are still under research. For more than 30 years sympathetic nervous system (SNS) and kidney sodium reabsorption activation, secondary to insulin resistance and compensatory hyperinsulinemia, have been considered as primary mediators of elevated BP in obesity. However, experimental and clinical data show that severe insulin resistance and hyperinsulinemia can occur in the absence of elevated BP, challenging the causal relationship between insulin resistance and hyperinsulinemia as the key factor linking obesity to hypertension. The purpose of Part 1 of this review is to summarize the available data on recently emerging mechanisms believed to contribute to obesity-related hypertension through increased sodium reabsorption and volume expansion, such as: physical compression of the kidney by perirenal/intrarenal fat and overactivation of the systemic/renal SNS and the renin-angiotensin-aldosterone system. The role of hyperleptinemia, impaired chemoreceptor and baroreceptor reflexes, and increased perivascular fat is also discussed. Specifically targeting these mechanisms may pave the way for a new therapeutic intervention in the treatment of obesity-related hypertension in the context of 'precision medicine' principles, which will be discussed in Part 2.

Role of adrenomedullin2/ intermedin in pregnancy induced vascular and metabolic adaptation in mice

Introduction: Adrenomedullin2 (AM2) shares its receptor with Calcitonin gene related peptide and adrenomedullin with overlapping but distinct biological functions. Goal of this study was to assess the specific role of Adrenomedullin2 (AM2) in pregnancy induced vascular and metabolic adaptation using AM2 knockout mice (AM2 -/-). Method : The AM2 -/- mice were successfully generated using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Nuclease Cas nine system. Phenotype of pregnant AM2 -/- mice was assessed with respect to its fertility, blood pressure regulation, vascular health and metabolic adaptations and compared to the wild type littermates (AM2 +/+). Results : Current data shows that AM2 -/- females are fertile with no significant difference in number of pups/litter compared to the AM2 +/+. However, ablation of AM2 decreases the gestational length and the total number of pups born dead or that die after birth is greater in AM2 -/- mice compared to AM2 +/+ mice (p < 0.05). Further AM2 -/- mice exhibit elevated blood pressure and elevated vascular sensitivity for the contractile responses to angiotensin two and higher serum sFLT-1 trigylcerides levels compared to AM2 +/+(p < 0.05). In addition, AM2 -/- mice develop glucose intolerance with elevated serum levels of Insulin during pregnancy compared to the AM2 +/+mice. Discussion: Current data suggests a physiological role for AM2 in pregnancy induced vascular and metabolic adaptations in mice.

Oxidative stress triggers hyperdynamic circulation via central neural activation in portal hypertensive rats

BACKGROUND

Hyperdynamic circulation in portal hypertension (PHT) depends on central neural activation. However, the initiating mechanism that signals PHT to the central neural cardiovascular-regulatory centers remains unclear. We aimed to test the hypothesis that oxidative stress in the gut initiates the signal that activates central cardiovascular nuclei in portal hypertensive rats.

METHODS

Two groups of rats were used. One had portal hypertension produced by partial portal vein ligation, while controls underwent sham operation. Hemodynamics including portal pressure, cardiac output, mean arterial pressure (MAP) and peripheral vascular resistance were measured. Activation of central cardiovascular nuclei was determined by immunohistochemical Fos expression in the paraventricular nucleus (PVN) of the hypothalamus. Myeloperoxidase activity, an oxidative stress marker, was measured in the jejunum. Hydrogen peroxide, the antioxidant N-acetyl-cysteine (NAC) or saline controls were administered for 12-14 days by gavage or osmotic minipumps placed in the peritoneal cavity.

RESULTS

Compared with controls, PHT rats showed increased cardiac output (54.2 ± 9.5 vs 33.6 ± 2.4 ml/min/100 g BW, p < 0.01), decreased MAP (96.2 ± 6.4 mmHg vs 103.2 ± 7.8, p < 0.01) and systemic vascular resistance (1.84 ± 0.28 vs 3.14 ± 0.19 mmHg/min/ml/100 g BW, p < 0.01). PHT rats had increased jejunal myeloperoxidase and PVN Fos expression. NAC treatment eliminated the hyperdynamic circulation, decreased jejunal myeloperoxidase and PVN Fos expression in PHT rats, but had no effect on sham controls. H₂O₂ significantly increased PVN Fos expression and decreased MAP.

CONCLUSION

These results indicate that in PHT, mesenteric oxidative stress is the initial signal that activates chemoreceptors and triggers hyperdynamic circulation by central neural cardiovascular-regulatory centers.

Adrenomedullin in paraventricular nucleus attenuates adipose afferent reflex and sympathoexcitation via receptors mediated nitric oxide-gamma-aminobutyric acid A type receptor pathway in rats with obesity-related hypertension

BACKGROUND

Hypothalamic paraventricular nucleus (PVN) is an important central site for the control of the adipose afferent reflex (AAR) that increases sympathetic outflow and blood pressure in obesity-related hypertension (OH).

METHOD

In this study, we investigated the effects of nitric oxide (NO) and cardiovascular bioactive polypeptide adrenomedullin (ADM) in the PVN on AAR and sympathetic nerve activity (SNA) in OH rats induced by a high-fat diet.

RESULTS

The results showed that ADM, total neuronal NO synthase (nNOS) and phosphorylated-nNOS protein expression levels in the PVN of the OH rats were down-regulated compared to the control rats. The enhanced AAR in OH rats was attenuated by PVN acute application of NO donor sodium nitroprusside (SNP), but was strengthened by the nNOS inhibitor nNOS-I, guanylyl cyclase inhibitor (1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) and gamma-aminobutyric acid A type receptor (GABAA) antagonist Bicuculline. Moreover, PVN ADM microinjection not only decreased basal SNA but also attenuated the enhanced AAR in OH rats, which were effectively inhibited by ADM receptor antagonist ADM22-52, nNOS-I, ODQ or Bicuculline pretreatment. Bilateral PVN acute microinjection of ADM also caused greater increases in NO and cyclic guanosine monophosphate (cGMP) levels, and nNOS phosphorylation. Adeno-associated virus vectors encoding ADM (AAV-ADM) transfection in the PVN of OH rats not only decreased the elevated AAR, basal SNA and blood pressure (BP), but also increased the expression and activation of nNOS. Furthermore, AAV-ADM transfection improved vascular remodeling in OH rats.

CONCLUSION

Taken together, our data highlight the roles of ADM in improving sympathetic overactivation, enhanced AAR and hypertension, and its related mechanisms associated with receptors mediated NO-cGMP-GABAA pathway in OH condition.

Characterization of Antibodies against Receptor Activity-Modifying Protein 1 (RAMP1): A Cautionary Tale

Calcitonin gene-related peptide (CGRP) is a key component of migraine pathophysiology, yielding effective migraine therapeutics. CGRP receptors contain a core accessory protein subunit: receptor activity-modifying protein 1 (RAMP1). Understanding of RAMP1 expression is incomplete, partly due to the challenges in identifying specific and validated antibody tools. We profiled antibodies for immunodetection of RAMP1 using Western blotting, immunocytochemistry and immunohistochemistry, including using RAMP1 knockout mouse tissue. Most antibodies could detect RAMP1 in Western blotting and immunocytochemistry using transfected cells. Two antibodies (844, ab256575) could detect a RAMP1-like band in Western blots of rodent brain but not RAMP1 knockout mice. However, cross-reactivity with other proteins was evident for all antibodies. This cross-reactivity prevented clear conclusions about RAMP1 anatomical localization, as each antibody detected a distinct pattern of immunoreactivity in rodent brain. We cannot confidently attribute immunoreactivity produced by RAMP1 antibodies (including 844) to the presence of RAMP1 protein in immunohistochemical applications in brain tissue. RAMP1 expression in brain and other tissues therefore needs to be revisited using RAMP1 antibodies that have been comprehensively validated using multiple strategies to establish multiple lines of convincing evidence. As RAMP1 is important for other GPCR/ligand pairings, our results have broader significance beyond the CGRP field.

Resveratrol in the Hypothalamic Paraventricular Nucleus Attenuates Hypertension by Regulation of ROS and Neurotransmitters

BACKGROUND

The hypothalamic paraventricular nucleus (PVN) is an important nucleus in the brain that plays a key role in regulating sympathetic nerve activity (SNA) and blood pressure. Silent mating-type information regulation 2 homolog-1 (sirtuin1, SIRT1) not only protects cardiovascular function but also reduces inflammation and oxidative stress in the periphery. However, its role in the central regulation of hypertension remains unknown. It is hypothesized that SIRT1 activation by resveratrol may reduce SNA and lower blood pressure through the regulation of intracellular reactive oxygen species (ROS) and neurotransmitters in the PVN.

METHODS

The two-kidney one-clip (2K1C) method was used to induce renovascular hypertension in male Sprague-Dawley rats. Then, bilaterally injections of vehicle (artificial cerebrospinal fluid, aCSF, 0.4 μL) or resveratrol (a SIRT1 agonist, 160 μmol/L, 0.4 μL) into rat PVN were performed for four weeks.

RESULTS

PVN SIRT1 expression was lower in the hypertension group than the sham surgery (SHAM) group. Activated SIRT1 within the PVN lowered systolic blood pressure and plasma norepinephrine (NE) levels. It was found that PVN of 2K1C animals injected with resveratrol exhibited increased expression of SIRT1, copper-zinc superoxide dismutase (SOD1), and glutamic acid decarboxylase (GAD67), as well as decreased activity of nuclear factor-kappa B (NF-κB) p65 and NAD(P)H oxidase (NOX), particularly NOX4. Treatment with resveratrol also decreased expression of ROS and tyrosine hydroxylase (TH).

CONCLUSION

Resveratrol within the PVN attenuates hypertension via the SIRT1/NF-κB pathway to decrease ROS and restore the balance of excitatory and inhibitory neurotransmitters.

Intermedin Alleviates Vascular Calcification in CKD through Sirtuin 3-Mediated Inhibition of Mitochondrial Oxidative Stress

Vascular calcification (VC) is a common pathophysiological process of chronic kidney disease (CKD). Sirtuin 3 (Sirt3), a major NAD⁺-dependent protein deacetylase predominantly in mitochondria, is involved in the pathogenesis of VC. We previously reported that intermedin (IMD) could protect against VC. In this study, we investigated whether IMD attenuates VC by Sirt3-mediated inhibition of mitochondrial oxidative stress. A rat VC with CKD model was induced by the 5/6 nephrectomy plus vitamin D₃. Vascular smooth muscle cell (VSMC) calcification was induced by CaCl₂ and β-glycerophosphate. IMD_1-53 treatment attenuated VC in vitro and in vivo, rescued the depressed mitochondrial membrane potential (MMP) level and decreased mitochondrial ROS levels in calcified VSMCs. IMD_1-53 treatment recovered the reduced protein level of Sirt3 in calcified rat aortas and VSMCs. Inhibition of VSMC calcification by IMD_1-53 disappeared when the cells were Sirt3 absent or pretreated with the Sirt3 inhibitor 3-TYP. Furthermore, 3-TYP pretreatment blocked IMD_1-53-mediated restoration of the MMP level and inhibition of mitochondrial oxidative stress in calcified VSMCs. The attenuation of VSMC calcification by IMD_1-53 through upregulation of Sirt3 might be achieved through activation of the IMD receptor and post-receptor signaling pathway AMPK, as indicated by pretreatment with an IMD receptor antagonist or AMPK inhibitor blocking the inhibition of VSMC calcification and upregulation of Sirt3 by IMD_1-53. AMPK inhibitor treatment reversed the effects of IMD_1-53 on restoring the MMP level and inhibiting mitochondrial oxidative stress in calcified VSMCs. In conclusion, IMD attenuates VC by improving mitochondrial function and inhibiting mitochondrial oxidative stress through upregulating Sirt3.

Exercise Training Attenuates Hypertension via Suppressing ROS/MAPK/NF-κB/AT-1R Pathway in the Hypothalamic Paraventricular Nucleus

Background: Aerobic exercise training (ExT) is beneficial for hypertension, however, its central mechanisms in improving hypertension remain unclear. Since the importance of the up-regulation of angiotensin II type 1 receptor (AT-1R) in the paraventricular nucleus (PVN) of the hypothalamic in sympathoexcitation and hypertension has been shown, we testified the hypothesis that aerobic ExT decreases blood pressure in hypertensive rats by down-regulating the AT-1R through reactive oxygen species (ROS)/mitogen-activated protein kinase (MAPK)/nuclear factors κB (NF-κB) pathway within the PVN. Methods: Forty-eight male Sprague-Dawley (SD) rats were assigned to the following groups: sham operation (SHAM) + kept sedentary (Sed), SHAM + exercise training (ExT), two kidney-one clamp (2K1C) + Sed, and 2K1C + ExT groups. Results: The 2K1C + Sed hypertensive rats showed higher systolic blood pressure (SBP), upregulated ROS, phosphorylated (p-) p44/42 MAPK, p-p38 MAPK, NF-κB p65 activity, and AT-1R expression in the PVN, and increased circulating norepinephrine (NE) than those of SHAM rats. After eight weeks of aerobic ExT, the 2K1C + ExT hypertensive rats showed attenuated NE and SBP levels, suppressed NF-κB p65 activity, and reduced expression of ROS, p-p44/42 MAPK, p-p38 MAPK, and AT-1R in the PVN, relatively to the 2K1C + Sed group. Conclusions: These data are suggestive of beneficial effects of aerobic ExT in decreasing SBP in hypertensive rats, via down-regulating the ROS/MAPK/NF-κB pathway that targets AT-1R in the PVN, and eventually ameliorating 2K1C-induced hypertension.

Blockade of Microglial Activation in Hypothalamic Paraventricular Nucleus Improves High Salt-Induced Hypertension

BACKGROUND

It has been shown that activated microglia in brain releasing proinflammatory cytokines (PICs) contribute to the progression of cardiovascular diseases. In this study, we tested the hypothesis that microglial activation in hypothalamic paraventricular nucleus (PVN), induced by high-salt diet, increases the oxidative stress via releasing PICs and promotes sympathoexcitation and development of hypertension.

METHODS

High-salt diet was given to male Dahl salt-sensitive rats to induce hypertension. Those rats were bilaterally implanted with cannula for PVN infusion of minocycline, a selective microglial activation blocker, or artificial cerebrospinal fluid for 4 weeks.

RESULTS

High-salt diet elevated mean arterial pressure of Dahl salt-sensitive rats. Meanwhile, elevations of renal sympathetic nerve activity and central prostaglandin E2, as well as increase of plasma norepinephrine, were observed in those hypertensive rats. Tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 increased in the PVN of those rats, associated with a significant activation of microglia and prominent disruption of redox balance, which was demonstrated by higher superoxide and NAD(P)H oxidase 2 (NOX-2) and NAD(P)H oxidase 4 (NOX-4), and lower Cu/Zn superoxide dismutase in PVN. PVN infusion of minocycline attenuated all hypertension-related alterations described above.

CONCLUSION

This study indicates that high salt leads to microglial activation within PVN of hypertensive rats, and those activated PVN microglia release PICs and trigger the production of reactive oxygen species, which contributes to sympathoexcitation and development of hypertension. Blockade of PVN microglial activation inhibits inflammation and oxidative stress, therefore attenuating the development of hypertension induced by high-salt diet.

NADPH oxidase family proteins: signaling dynamics to disease management

Reactive oxygen species (ROS) are pervasive signaling molecules in biological systems. In humans, a lack of ROS causes chronic and extreme bacterial infections, while uncontrolled release of these factors causes pathologies due to excessive inflammation. Professional phagocytes such as neutrophils (PMNs), eosinophils, monocytes, and macrophages use superoxide-generating NADPH oxidase (NOX) as part of their arsenal of antimicrobial mechanisms to produce high levels of ROS. NOX is a multisubunit enzyme complex composed of five essential subunits, two of which are localized in the membrane, while three are localized in the cytosol. In resting phagocytes, the oxidase complex is unassembled and inactive; however, it becomes activated after cytosolic components translocate to the membrane and are assembled into a functional oxidase. The NOX isoforms play a variety of roles in cellular differentiation, development, proliferation, apoptosis, cytoskeletal control, migration, and contraction. Recent studies have identified NOX as a major contributor to disease pathologies, resulting in a shift in focus on inhibiting the formation of potentially harmful free radicals. Therefore, a better understanding of the molecular mechanisms and the transduction pathways involved in NOX-mediated signaling is essential for the development of new therapeutic agents that minimize the hyperproduction of ROS. The current review provides a thorough overview of the various NOX enzymes and their roles in disease pathophysiology, highlights pharmacological strategies, and discusses the importance of computational modeling for future NOX-related studies.

The Molecular Mechanism of Aerobic Exercise Improving Vascular Remodeling in Hypertension

The treatment and prevention of hypertension has been a worldwide medical challenge. The key pathological hallmark of hypertension is altered arterial vascular structure and function, i.e., increased peripheral vascular resistance due to vascular remodeling. The aim of this review is to elucidate the molecular mechanisms of vascular remodeling in hypertension and the protective mechanisms of aerobic exercise against vascular remodeling during the pathological process of hypertension. The main focus is on the mechanisms of oxidative stress and inflammation in the pathological condition of hypertension and vascular phenotypic transformation induced by the trilaminar structure of vascular endothelial cells, smooth muscle cells and extracellular matrix, and the peripheral adipose layer of the vasculature. To further explore the possible mechanisms by which aerobic exercise ameliorates vascular remodeling in the pathological process of hypertension through anti-proliferative, anti-inflammatory, antioxidant and thus inhibiting vascular phenotypic transformation. It provides a new perspective to reveal the intervention targets of vascular remodeling for the prevention and treatment of hypertension and its complications.

Chemokine-like Receptor 1 in Brain of Spontaneously Hypertensive Rats Mediates Systemic Hypertension

Adipocytokine chemerin is a biologically active molecule secreted from adipose tissue. Chemerin elicits a variety of functions via chemokine-like receptor 1 (CMKLR1). The cardiovascular center in brain that regulates blood pressure (BP) is involved in pathophysiology of systemic hypertension. Thus, we explored the roles of brain chemerin/CMKLR1 on regulation of BP in spontaneously hypertensive rats (SHR). For this aim, we examined effects of intracerebroventricular (i.c.v.) injection of CMKLR1 small interfering (si)RNA on both systemic BP as measured by tail cuff system and protein expression in paraventricular nucleus (PVN) of SHR as determined by Western blotting. We also examined both central and peripheral protein expression of chemerin by Western blotting. Systolic BP of SHR but not normotensive Wistar Kyoto rats (WKY) was decreased by CMKLR1 siRNA. The decrease of BP by CMKLR1 siRNA persisted for 3 days. Protein expression of CMKLR1 in PVN of SHR tended to be increased compared with WKY, which was suppressed by CMKLR1 siRNA. Protein expression of chemerin in brain, peripheral plasma, and adipose tissue was not different between WKY and SHR. In summary, we for the first time revealed that the increased protein expression of CMKLR1 in PVN is at least partly responsible for systemic hypertension in SHR.

The cardioprotective effect of the sodium-glucose cotransporter 2 inhibitor dapagliflozin in rats with isoproterenol-induced cardiomyopathy

Sodium-glucose cotransporter 2 inhibitor (SGLT2i) has been reported to improve glycemic control. This study was designed to investigate the effects of SGLT2i dapagliflozin (dapa) on cardiomyopathy induced by isoproterenol (ISO) and its potential mechanisms. Fifty male Sprague Dawley rats were randomly assigned to the control (n=10) and the ISO (2.5 mg/kg/day)-treated groups (n=40). After 2 weeks, the 28 surviving rats with obvious left ventricular dysfunction in the ISO group were randomized into three medication groups, including the angiotensin receptor neprilysin inhibitor (ARNI) sacubitril/valsartan group (S/V, n=9), the dapa group (n=9), and the ISO group (n=10) for 4 weeks. Next, electrical programmed stimulation was performed in all the groups to evaluate their susceptibility to ventricular arrhythmias (VAs). Compared to the ISO rats, the dapa administration not only effectively reduced the cumulative risk of death, the myocardial fibrosis, the plasma angiotensin II levels and its functional receptor AT1R protein expressions in the heart, and the proinflammatory cytokine levels in the cardiac tissue of the ISO-treated rats, but it also improved their cardiac function and inhibited oxidative stress. These effects were similar to S/V. However, dapa showed a greater efficacy than S/V in reducing the left ventricular end-diastolic volumes, lowing the heart rates and VAs, and decreasing the body weights and plasma glucose levels. The mechanisms by which dapa exerts protective effects on cardiomyopathy may be related to its indirect antioxidant capacity and direct hypoglycemic action.

Hydrogen sulfide exposure induces pyroptosis in the trachea of broilers via the regulatory effect of circRNA-17828/miR-6631-5p/DUSP6 crosstalk on ROS production

Hydrogen sulfide (H₂S) is an air pollutant to cause tracheal injury. Pyroptosis is responsible for tissue injury through reactive oxygen species (ROS) production. Competitive endogenous RNAs (ceRNAs) chelate microRNAs and reduce their inhibitory effect on other transcripts, thus affecting ROS levels and pyroptosis. However, it is not clear how H₂S regulates pyroptosis via the ceRNA axis. Therefore, we established a broilers model of H₂S exposure for 42 days to assess pyroptosis and obtain a ceRNA network by immunohistochemistry and RNA sequencing. We detected pyroptosis induced by H₂S and verified circRNA-IGLL1-17828/miR-6631-5p/DUSP6 axis by a double luciferase reporter assay. We also measured ROS levels and the expression of pyroptotic indicators such as (Caspase1) Casp-1, Interleukin 1β (IL-1β) and Interleukin 1β (IL-18). miR-6631-5p knockdown decreased pyroptotic indicators induced by H₂S. Overexpression of miR-6631-5p or DUSP6 knockdown stimulated ROS generation and upregulated pyroptotic indicators. N-acetyl-_L-cysteine (NAC) decreased pyroptotic indicators and ROS levels both induced by miR-6631-5p. Moreover, circRNA-IGLL1-17828, participated in intermolecular competition as a ceRNA of DUSP6. In conclusion, circRNA-IGLL1-17828/miR-6631-5p/DUSP6 crosstalk regulated H₂S-induced pyroptosis in broilers trachea via ROS generation. This is the first study to reveal regulation mechanism of circRNA-related CeRNAs on pyroptosis induced by H₂S, providing important reference for environmental toxicology.

Apigenin Improves Hypertension and Cardiac Hypertrophy Through Modulating NADPH Oxidase-Dependent ROS Generation and Cytokines in Hypothalamic Paraventricular Nucleus

Apigenin, identified as 4', 5, 7-trihydroxyflavone, is a natural flavonoid compound that has many interesting pharmacological activities and nutraceutical potential including anti-inflammatory and antioxidant functions. Chronic, low-grade inflammation and oxidative stress are involved in both the initiation and progression of hypertension and hypertension-induced cardiac hypertrophy. However, whether or not apigenin improves hypertension and cardiac hypertrophy through modulating NADPH oxidase-dependent reactive oxygen species (ROS) generation and inflammation in hypothalamic paraventricular nucleus (PVN) has not been reported. This study aimed to investigate the effects of apigenin on hypertension in spontaneously hypertensive rats (SHRs) and its possible central mechanism of action. SHRs and Wistar-Kyoto (WKY) rats were randomly assigned and treated with bilateral PVN infusion of apigenin or vehicle (artificial cerebrospinal fluid) via osmotic minipumps (20 μg/h) for 4 weeks. The results showed that after PVN infusion of apigenin, the mean arterial pressure (MAP), heart rate, plasma norepinephrine (NE), Beta 1 receptor in kidneys, level of phosphorylation of PKA in the ventricular tissue and cardiac hypertrophy, perivascular fibrosis, heart level of oxidative stress, PVN levels of oxidative stress, interleukin 1β (IL-1β), interleukin 6 (IL-6), iNOS, monocyte chemotactic protein 1 (MCP-1), tyrosine hydroxylase (TH), NOX2 and NOX4 were attenuated and PVN levels of interleukin 10 (IL-10), superoxide dismutase 1 (Cu/Zn-SOD) and the 67-kDa isoform of glutamate decarboxylase (GAD67) were increased. These results revealed that apigenin improves hypertension and cardiac hypertrophy in SHRs which are associated with the down-regulation of NADPH oxidase-dependent ROS generation and inflammation in the PVN.

Paraventricular Nucleus Infusion of Oligomeric Proantho Cyanidins Improves Renovascular Hypertension

Oxidative stress plays an important role in the pathogenesis of hypertension. Oligomeric proantho cyanidins (OPC) is the main polyphenol presents in grape seed and is known for its potent antioxidant and anti-inflammatory properties. In the present study, we hypothesize that OPC can attenuate oxidative stress in the paraventricular nucleus of hypothalamus (PVN), ameliorate neurotransmitter imbalance, decrease the blood pressure and sympathetic activity in renovascular hypertensive rats. After induction of renovascular hypertension by the two-kidney one-clip (2K-1C) method, male Sprague-Dawley rats received chronic bilateral PVN infusion of OPC (20 μg/h) or vehicle via osmotic minipump for 4 weeks. We found that hypertension induced by 2K-1C was associated with the production of reactive oxygen species (ROS) in the PVN. Infusion of OPC in the PVN significantly reduced the systolic blood pressure and norepinephrine in plasma of 2K-1C rats. In addition, PVN infusion of OPC decreased the level of ROS and the expression of stress-related nicotinamide adenine dinucleotide phosphate (NADPH) oxidases subunit NOX4, increased the levels of nuclear factor E2-related factor 2 (Nrf2) and antioxidant enzyme, balanced the content of cytokines, increased expression of glutamic acid decarboxylase and decreased the expression of tyrosine hydroxylase in the PVN of 2K-1C rats. Our findings provided strong evidence that PVN infusion of OPC inhibited the progression of renovascular hypertension through its potent anti-oxidative and anti-inflammatory function in the PVN.

Paraventricular Nucleus P2X7 Receptors Aggravate Acute Myocardial Infarction Injury via ROS-Induced Vasopressin-V1b Activation in Rats

The present study was designed to investigate the mechanisms by which P2X7 receptors (P2X7Rs) mediate the activation of vasopressinergic neurons thereby increasing sympathetic hyperactivity in the paraventricular nucleus (PVN) of the hypothalamus of rats with acute myocardial ischemia (AMI). The left anterior descending branch of the coronary artery was ligated to induce AMI in rats. The rats were pretreated with BBG (brilliant blue G, a P2X7R antagonist), nelivaptan (a vasopressin V1b receptor antagonist), or diphenyleneiodonium (DPI) [an nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor]. Hemodynamic parameters of the heart were monitored. Myocardial injury and cardiomyocyte apoptosis were assessed. In the PVN of AMI rats, P2X7R mediated microglial activation, while reactive oxygen species (ROS) and NADPH oxidase 2 (NOX2) were higher than in the sham group. Intraperitoneal injection of BBG effectively reduced ROS production and vasopressin expression in the PVN of AMI rats. Moreover, both BBG and DPI pretreatment effectively reduced sympathetic hyperactivity and ameliorated AMI injury, as represented by reduced inflammation and apoptosis of cardiomyocytes. Furthermore, microinjection of nelivaptan into the PVN improved cardiac function and reduced the norepinephrine (AE) levels in AMI rats. Collectively, the results suggest that, within the PVN of AMI rats, P2X7R upregulation mediates microglial activation and the overproduction of ROS, which in turn activates vasopressinergic neuron-V1b receptors and sympathetic hyperactivity, hence aggravating myocardial injury in the AMI setting.

Bortezomib activation of mTORC1 pathway mediated by NOX2-drived reactive oxygen species results in apoptosis in primary dorsal root ganglion neurons

Bortezomib (Bort), a chemotherapeutic agent, is widely used for the clinical treatment of cancers. However, Bort-induced peripheral neurotoxicity (BIPN) significantly restricts its clinical application, which is difficult to deal with since the underlying mechanisms of BIPN are unclear. Here, we showed that Bort activates mTORC1 pathway leading to dorsal root ganglion (DRG) neuronal apoptosis. Inhibition of mTORC1 with rapamycin or knockdown of raptor, regulatory-associated protein of mTORC1, with shRNA dramatically rescued the cells from Bort-caused apoptosis. In addition, we found that Bort-activated mTORC1 pathway was attributed to Bort elevation of reactive oxygen species (ROS). This is supported by the evidence that using ROS scavenger N-acetyl cysteine (NAC) significantly alleviated Bort-activated mTORC1 pathway. Furthermore, we revealed that upregulation of NOX2 contributed to Bort-elicited ROS overproduction, leading to mTORC1 pathway-dependent apoptosis in DRG neurons. Inhibition of NOX2 with apocynin remarkably diminished Bort-induced overgeneration of ROS, activation of mTORC1 pathway and apoptosis in the cells. Taken together, these results indicate that Bort activation of mTORC1 pathway mediated by NOX2-drived ROS leads to apoptotic death in DRG neurons. Our findings highlight that manipulation of intracellular ROS level or NOX2 or mTORC1 activity may be exploited for prevention of BIPN.

Adrenomedullin Attenuates Inflammation in White Adipose Tissue of Obese Rats Through Receptor-Mediated PKA Pathway

OBJECTIVE

Adrenomedullin (ADM) possesses therapeutic potential for inflammatory diseases. Consequently, the effects of ADM on inflammation in visceral white adipose tissue (vWAT) of obese rats or in adipocytes were explored in this study.

METHODS

Male rats were fed a high-fat diet for 12 weeks to induce obesity, and obese rats were implanted with osmotic minipumps providing constant infusion of ADM (300 ng/kg per hour) and continued to be fed a high-fat diet for 4 weeks.

RESULTS

When compared with the control group, endogenous protein expression of ADM and ADM receptors in vWAT and in lipopolysaccharide (LPS)-treated adipocytes was markedly increased. ADM significantly decreased the protein expression of the inflammatory mediators TNFα, IL-1β, cyclooxygenase-2, and inducible nitric oxide synthase in vWAT of obese rats and in adipocytes stimulated by LPS. It also inhibited the activation of the inflammatory signaling pathways MAPK and NF-κB induced by LPS in adipocytes. These effects of ADM in adipocytes were inhibited by the administration of ADM receptor antagonist and cAMP-dependent protein kinase (PKA) activation inhibitor.

CONCLUSIONS

ADM can inhibit inflammation in WAT in obesity, which may be mediated by the activation of ADM receptors and PKA.

Intermedin alleviates the inflammatory response and stabilizes the endothelial barrier in LPS-induced ARDS through the PI3K/Akt/eNOS signaling pathway

Inflammatory storms and endothelial barrier dysfunction are the central pathophysiological features of acute respiratory distress syndrome (ARDS). Intermedin (IMD), a member of the calcitonin gene-related peptide (CGRP) family, has been reported to alleviate inflammation and protect endothelial cell (EC) integrity. However, the effects of IMD on ARDS have not been clearly elucidated. In the present study, clinical ARDS data were used to explore the relationship between serum IMD levels and disease severity and prognosis, and we then established a model to predict the possibility of hospital survival. Mouse models of ARDS and LPS-challenged endothelial cells were used to analyze the protective effect and underlying mechanism of IMD. We found that in patients with ARDS, increased serum IMD levels were associated with reduced disease severity and increased rates of hospital survival. IMD alleviated the LPS-induced inflammatory response by decreasing proinflammatory cytokines, NF-κB p65 expression and NF-κB p65 nuclear translocation. In addition, IMD stabilized the endothelial barrier by repairing adherens junctions (AJs), cytoskeleton and capillary leakage. IMD exerted protective effects against ARDS on pulmonary endothelial cells, at least partly, through PI3K/Akt/eNOS signaling, while IMD's anti-inflammation effect was mediated through an eNOS-independent mechanism. Our study may provide new therapeutic insight for ARDS treatment.

Irisin lowers blood pressure by activating the Nrf2 signaling pathway in the hypothalamic paraventricular nucleus of spontaneously hypertensive rats

Exercise training is one of the major non-pharmacological treatments for hypertension. However, the central mechanism by which exercise training attenuates the hypertensive responses remains unclear. Irisin is a muscle-secreted cytokine derived from fibronectin type III domain containing 5 (FNDC5) that will be released into the circulation during exercise. We hypothesized that irisin may play a role in the blood pressure regulation by exercise. To examine the hypothesis, our study investigated the effect of irisin on hypertension and its central mechanism. The study was performed in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats. We found that intravenous injection of irisin effectively reduced blood pressure, plasma norepinephrine, paraventricular nucleus (PVN) levels of neuronal activation, oxidative stress and inflammation in SHRs. Moreover, irisin activated nuclear factor E2-related factor-2 (Nrf2) and restored the imbalance of neurotransmitters in the PVN. Our study also found PVN knockdown of Nrf2 abolished the protective effects of irisin on hypertension. These findings demonstrate irisin can improve hypertension via Nrf2-mediated antioxidant in the PVN.