TLR4/MyD88/NF-κB signaling and PPAR-γ within the paraventricular nucleus are involved in the effects of telmisartan in hypertension

Activation AMPK in Hypothalamic Paraventricular Nucleus Improves Renovascular Hypertension Through ERK1/2-NF-κB Pathway

Hypertension is a globally prevalent disease, but the pathogenesis remains largely unclear. AMP-activated protein kinase (AMPK) is a nutrition-sensitive signal of cellular energy metabolism, which has a certain influence on the development of hypertension. Previously, we found a down-regulation of the phosphorylated (p-) form of AMPK, and the up-regulation of the angiotensin II type 1 receptor (AT1-R) and that of p-ERK1/2 in the hypothalamic paraventricular nucleus (PVN) of hypertensive rats. However, the exact mechanism underlying the relationship between AMPK and AT1-R in the PVN during hypertension remains unclear. Thus, we hypothesized that AMPK modulates AT1-R through the ERK1/2-NF-κB pathway in the PVN, thereby inhibiting sympathetic nerve activity and improving hypertension. To examine this hypothesis, we employed a renovascular hypertensive animal model developed via two-kidney, one-clip (2K1C) and sham-operated (SHAM). Artificial cerebrospinal fluid (aCSF), used as vehicle, or 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR, an AMPK activator, 60 μg/day) was microinjected bilaterally in the PVN of these rats for 4 weeks. In 2K1C rats, there an increase in systolic blood pressure (SBP) and circulating norepinephrine (NE). Also, the hypertensive rats had lowered expression of p-AMPK and p-AMPK/AMPK, elevated expression of p-ERK1/2, p-ERK1/2/ERK1/2 and AT1-R, increased NF-κB p65 activity in the PVN compared with the levels of these biomarkers in SHAM rats. Four weeks of bilateral PVN injection of AMPK activator AICAR, attenuated the NE level and SBP, increased the expression of p-AMPK and p-AMPK/AMPK, lessened the NF-κB p65 activity, decreased the expression of p-ERK1/2, p-ERK1/2/ERK1/2 and AT1-R in the PVN of 2K1C rats. Data from this study imply that the activation of AMPK within the PVN suppressed AT1-R expression through inhibiting the ERK1/2-NF-κB pathway, decreased the activity of the sympathetic nervous system, improved hypertension.

Modulation of TNF-α, interleukin-6, and interleukin-10 by nebivolol-valsartan and nebivolol-lisinopril polytherapy in SHR rats

Antihypertensive drug therapies have demonstrated their capacity to modulate the inflammatory processes associated with hypertension, leading to improvements in disease progression. Given the prevalent use of polytherapy in treating most hypertensive patients, comprehending the time-dependent effects of combination treatments on inflammation becomes imperative. In this study, spontaneously hypertensive rats (SHR) were divided into seven groups (n = 6): (i) SHR + vehicle, (ii) SHR + nebivolol, (iii) SHR + valsartan, (iv) SHR + lisinopril, (v) SHR + nebivolol-valsartan, (vi) SHR + nebivolol-lisinopril, and (vii) WKY + vehicle. Blood pressure was measured using the tail-cuff method. Temporal alterations in inflammatory cytokines TNF-α, IL-6, and IL-10 were assessed in serum through ELISA and mRNA expression in aortic tissue via qPCR after 1, 2, and 4 weeks of treatment with nebivolol, lisinopril, valsartan, and their respective combinations. Histological alterations in the aorta were assessed. The findings indicated that combined treatments reduced systolic and diastolic blood pressure in SHR. The nebivolol and lisinopril combination demonstrated a significant decrease in IL-6 serum and mRNA expression at both 1 week and 4 weeks into the treatment. Additionally, TNF-α mRNA expression also showed a reduction with this combination at the same time points. Particularly, nebivolol-valsartan significantly decreased TNF-α serum and mRNA expression after one and four weeks of treatment. Furthermore, an elevation in serum IL-10 levels was observed with both combination treatments starting from the second week onwards. This study provides compelling evidence that concurrent administration of nebivolol with lisinopril or valsartan exerts time-dependent effects, reducing proinflammatory cytokines TNF-α and IL-6 while modifying IL-10 levels in an experimental hypertensive model.

Toll-like receptors in cardiac hypertrophy

Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRRs) that can identify pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLRs play an important role in the innate immune response, leading to acute and chronic inflammation. Cardiac hypertrophy, an important cardiac remodeling phenotype during cardiovascular disease, contributes to the development of heart failure. In previous decades, many studies have reported that TLR-mediated inflammation was involved in the induction of myocardium hypertrophic remodeling, suggesting that targeting TLR signaling might be an effective strategy against pathological cardiac hypertrophy. Thus, it is necessary to study the mechanisms underlying TLR functions in cardiac hypertrophy. In this review, we summarized key findings of TLR signaling in cardiac hypertrophy.

Role of blood-borne factors in sympathoexcitation-mediated hypertension: Potential neurally mediated hypertension in preeclampsia

Hypertension remains a threat for society due to its unknown causes, preventing proper management, for the growing number of patients, for its state as a high-risk factor for stroke, cardiac and renal complication and as cause of disability. Data from clinical and animal researches have suggested the important role of many soluble factors in the pathophysiology of hypertension through their neuro-stimulating effects. Central targets of these factors are of molecular, cellular and structural nature. Preeclampsia (PE) is characterized by high level of soluble factors with strong pro-hypertensive activity and includes immune factors such as proinflammatory cytokines (PICs). The potential neural effect of those factors in PE is still poorly understood. Shedding light into the potential central effect of the soluble factors in PE may advance our current comprehension of the pathophysiology of hypertension in PE, which will contribute to better management of the disease. In this paper, we summarized existing data in respect of hypothesis of this review, that is, the existence of the neural component in the pathophysiology of the hypertension in PE. Future studies would address this hypothesis to broaden our understanding of the pathophysiology of hypertension in PE.

Faecalibacterium prausnitzii Attenuates CKD via Butyrate-Renal GPR43 Axis

BACKGROUND

Despite available clinical management strategies, chronic kidney disease (CKD) is associated with severe morbidity and mortality worldwide, which beckons new solutions. Host-microbial interactions with a depletion of Faecalibacterium prausnitzii in CKD are reported. However, the mechanisms about if and how F prausnitzii can be used as a probiotic to treat CKD remains unknown.

METHODS

We evaluated the microbial compositions in 2 independent CKD populations for any potential probiotic. Next, we investigated if supplementation of such probiotic in a mouse CKD model can restore gut-renal homeostasis as monitored by its effects on suppression on renal inflammation, improvement in gut permeability and renal function. Last, we investigated the molecular mechanisms underlying the probiotic-induced beneficial outcomes.

RESULTS

We observed significant depletion of Faecalibacterium in the patients with CKD in both Western (n=283) and Eastern populations (n=75). Supplementation of F prausnitzii to CKD mice reduced renal dysfunction, renal inflammation, and lowered the serum levels of various uremic toxins. These are coupled with improved gut microbial ecology and intestinal integrity. Moreover, we demonstrated that the beneficial effects in kidney induced by F prausnitzii-derived butyrate were through the GPR (G protein-coupled receptor)-43.

CONCLUSIONS

Using a mouse CKD model, we uncovered a novel beneficial role of F prausnitzii in the restoration of renal function in CKD, which is, at least in part, attributed to the butyrate-mediated GPR-43 signaling in the kidney. Our study provides the necessary foundation to harness the therapeutic potential of F prausnitzii for ameliorating CKD.

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.

Anti-inflammatory Mechanism of Action of Benzoylmesaconine in Lipopolysaccharide-Stimulated RAW264.7 Cells

Background

Benzoylmesaconine (BMA), the most abundant monoester alkaloid in Aconitum plants, has some biological activities and is a potential therapeutic agent for inflammation-related diseases. However, the potential anti-inflammatory mechanisms of BMA have not been clarified.

Purpose

This study aimed to investigate the underlying molecular mechanisms of the anti-inflammatory action of this compound using lipopolysaccharide (LPS)-activated RAW264.7 macrophages.

Methods

The release of pro-inflammatory cytokines and mediators were detected by nitric oxide (NO) assays, reactive oxygen species (ROS) assays, and enzyme-linked immunosorbent assays (ELISA) in LPS-activated RAW264.7 macrophage cells. Quantitative real-time PCR was used to measure the gene expression of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Cell viability was determined using a cell counting kit-8 (CCK-8) assay. The expression of iNOS, COX-2, mitogen-activated protein kinase (MAPK), and nuclear factor-κB (NF-κB)-related proteins were detected by western blot, and nuclear translocation of p65 was observed by immunofluorescence.

Results

BMA significantly decreased the production of IL-1β, IL-6, TNF-α, PGE₂, NO, and ROS and inhibited the protein and mRNA levels of COX-2 and iNOS in LPS-activated RAW264.7 macrophages. Moreover, LPS-induced phosphorylation of IκBα, JNK, p38, and ERK; degradation of IκBα; and nuclear translocation of p65 were significantly suppressed by BMA treatment.

Conclusion

These findings demonstrate that the anti-inflammatory effect of BMA was through the suppression of the NF-κB and MAPK signaling pathways and that it may be a therapeutic agent targeting specific signal transduction events required for inflammation-related diseases.

Effect of TLR4/MyD88/NF-kB axis in paraventricular nucleus on ventricular arrhythmias induced by sympathetic hyperexcitation in post-myocardial infarction rats

Sympathetic activation after myocardial infarction (MI) leads to ventricular arrhythmias (VAs), which can result in sudden cardiac death (SCD). The toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor-kappa B (NF-kB) axis within the hypothalamic paraventricular nucleus (PVN), a cardiac-neural sympathetic nerve centre, plays an important role in causing VAs. An MI rat model and a PVN-TLR4 knockdown model were constructed. The levels of protein were detected by Western blotting and immunofluorescence, and localizations were visualized by multiple immunofluorescence staining. Central and peripheral sympathetic activation was visualized by immunohistochemistry for c-fos protein, renal sympathetic nerve activity (RSNA) measurement, heart rate variability (HRV) analysis and norepinephrine (NE) level detection in serum and myocardial tissue measured by ELISA. The arrhythmia scores were measured by programmed electrical stimulation (PES), and cardiac function was detected by the pressure-volume loop (P-V loop). The levels of TLR4 and MyD88 and the nuclear translocation of NF-kB within the PVN were increased after MI, while sympathetic activation and arrhythmia scores were increased and cardiac function was decreased. However, inhibition of TLR4 significantly reversed these conditions. PVN-mediated sympathetic activation via the TLR4/MyD88/NF-kB axis ultimately leads to the development of VAs after MI.

Na+/K+-ATPase Alpha 2 Isoform Elicits Rac1-Dependent Oxidative Stress and TLR4-Induced Inflammation in the Hypothalamic Paraventricular Nucleus in High Salt-Induced Hypertension

Numerous studies have indicated that a high salt diet inhibits brain Na⁺/K⁺-ATPase (NKA) activity, and affects oxidative stress and inflammation in the paraventricular nucleus (PVN). Furthermore, Na⁺/K⁺-ATPase alpha 2-isoform (NKA α2) may be a target in the brain, taking part in the development of salt-dependent hypertension. Therefore, we hypothesized that NKA α2 regulates oxidative stress and inflammation in the PVN in the context of salt-induced hypertension. Part I: We assessed NKA subunits (NKA α1, NKA α2, and NKA α3), Na⁺/K⁺-ATPase activity, oxidative stress, and inflammation in a high salt group (8% NaCl) and normal salt group (0.3% NaCl). Part II: NKA α2 short hairpin RNA (shRNA) was bilaterally microinjected into the PVN of salt-induced hypertensive rats to knockdown NKA α2, and we explored whether NKA α2 regulates downstream signaling pathways related to protein kinase C γ (PKC γ)-dependent oxidative stress and toll-like receptor 4 (TLR4)-induced inflammation in the PVN to promote the development of hypertension. High salt diet increased NKA α1 and NKA α2 protein expression in the PVN but had no effect on NKA α3 compared to the normal salt diet. Na⁺/K⁺-ATPase activity and ADP/ATP ratio was lower, but NAD(P)H activity and NF-κB activity in the PVN were higher after a high salt diet. Bilateral PVN microinjection of NKA α2 shRNA not only improved Na⁺/K⁺-ATPase activity and ADP/ATP ratio but also suppressed PKC γ-dependent oxidative stress and TLR4-dependent inflammation in the PVN, thus decreasing sympathetic activity in rats with salt-induced hypertension. NKA α2 in the PVN elicits PKC γ/Rac1/NAD (P)H-dependent oxidative stress and TLR4/MyD88/NF-κB-induced inflammation in the PVN, thus increasing MAP and sympathetic activity during the development of salt-induced hypertension.

Antihypertensive effects of exercise involve reshaping of gut microbiota and improvement of gut-brain axis in spontaneously hypertensive rat

Exercise (Ex) has long been recognized to produce beneficial effects on hypertension (HTN). This coupled with evidence of gut dysbiosis and an impaired gut-brain axis led us to hypothesize that reshaping of gut microbiota and improvement in impaired gut-brain axis would, in part, be associated with beneficial influence of exercise. Male spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were randomized into sedentary, trained, and detrained groups. Trained rats underwent moderate-intensity exercise for 12 weeks, whereas, detrained groups underwent 8 weeks of moderate-intensity exercise followed by 4 weeks of detraining. Fecal microbiota, gut pathology, intestinal inflammation, and permeability, brain microglia and neuroinflammation were analyzed. We observed that exercise training resulted in a persistent decrease in systolic blood pressure in the SHR. This was associated with increase in microbial α diversity, altered β diversity, and enrichment of beneficial bacterial genera. Furthermore, decrease in the number of activated microglia, neuroinflammation in the hypothalamic paraventricular nucleus, improved gut pathology, inflammation, and permeability were also observed in the SHR following exercise. Interestingly, short-term detraining did not abolish these exercise-mediated improvements. Finally, fecal microbiota transplantation from exercised SHR into sedentary SHR resulted in attenuated SBP and an improved gut-brain axis. These observations support our concept that an impaired gut-brain axis is linked to HTN and exercise ameliorates this impairment to induce antihypertensive effects.

Protective mechanisms of telmisartan against hepatic ischemia/reperfusion injury in rats may involve PPARγ-induced TLR4/NF-κB suppression

Hepatic ischemia-reperfusion (I/R) is an important cause of liver damage in many clinical situations. Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) is an inflammatory pathway activated in hepatic I/R injury. Telmisartan, a selective angiotensin II type 1 receptor antagonist and peroxisome proliferator-activated receptor-gamma (PPARγ) partial agonist, can inhibit the expression of pro-inflammatory cytokines. The present work investigated the possible protective effect of telmisartan against hepatic I/R injury and explored its possible mechanisms in rats. Rats were divided into four equal groups: sham-operated control, telmisartan-treated sham-operated control, I/R untreated, and I/R telmisartan-treated groups. Hepatic injury was evaluated biochemically by serum activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and histopathological examination. Hepatic oxidative stress biomarkers, myeloperoxidase level, PPARγ and TLR4 mRNA expression, and NF-κB and active caspase 3 immunoexpression were determined. The study showed that telmisartan attenuated hepatic I/R, as evidenced by decreased serum ALT and AST activities and confirmed by improvement of the histopathological changes. The protective effect of telmisartan was associated with modulation of oxidative stress parameters, myeloperoxidase level, PPARγ and TLR4 mRNA expression, and NF-κB and caspase 3 immunoexpression. Taken together, the current study showed that telmisartan could protect the rat liver from I/R injury. This hepatoprotective effect was attributed to, at least in part, increase in PPARγ expression and suppression of TLR4/NF-κB pathway.

Bilateral Paraventricular Nucleus Upregulation of Extracellular Superoxide Dismutase Decreases Blood Pressure by Regulation of the NLRP3 and Neurotransmitters in Salt-Induced Hypertensive Rats

Aims: Long-term salt diet induces the oxidative stress in the paraventricular nucleus (PVN) and increases the blood pressure. Extracellular superoxide dismutase (Ec-SOD) is a unique antioxidant enzyme that exists in extracellular space and plays an essential role in scavenging excessive reactive oxygen species (ROS). However, the underlying mechanism of Ec-SOD in the PVN remains unclear. Methods: Sprague-Dawley rats (150-200 g) were fed either a high salt diet (8% NaCl, HS) or normal salt diet (0.9% NaCl, NS) for 6 weeks. Each group of rats was administered with bilateral PVN microinjection of AAV-Ec-SOD (Ec-SOD overexpression) or AAV-Ctrl for the next 6 weeks. Results: High salt intake not only increased mean arterial blood pressure (MAP) and the plasma noradrenaline (NE) but also elevated the NAD(P)H oxidase activity, the NAD(P)H oxidase components (NOX2 and NOX4) expression, and ROS production in the PVN. Meanwhile, the NOD-like receptor protein 3 (NLRP3)-dependent inflammatory proteins (ASC, pro-cas-1, IL-β, CXCR, CCL2) expression and the tyrosine hydroxylase (TH) expression in the PVN with high salt diet were higher, but the GSH level, Ec-SOD activity, GAD67 expression, and GABA level were lower than the NS group. Bilateral PVN microinjection of AAV-Ec-SOD decreased MAP and the plasma NE, reduced NAD(P)H oxidase activity, the NOX2 and NOX4 expression, and ROS production, attenuated NLRP3-dependent inflammatory expression and TH, but increased GSH level, Ec-SOD activity, GAD67 expression, and GABA level in the PVN compared with the high salt group. Conclusion: Excessive salt intake not only activates oxidative stress but also induces the NLRP3-depensent inflammation and breaks the balance between inhibitory and excitability neurotransmitters in the PVN. Ec-SOD, as an essential anti-oxidative enzyme, eliminates the ROS in the PVN and decreases the blood pressure, probably through inhibiting the NLRP3-dependent inflammation and improving the excitatory neurotransmitter release in the PVN in the salt-induced hypertension.

TLR4 and AT1R mediate blood-brain barrier disruption, neuroinflammation, and autonomic dysfunction in spontaneously hypertensive rats

Angiotensin II (AngII) is implicated in neuroinflammation, blood-brain barrier (BBB) disruption, and autonomic dysfunction in hypertension. We have previously shown that exogenous AngII stimulates Toll-like receptor 4 (TLR4) via AngII type 1 receptor (AT1R), inducing activation of hypothalamic microglia ex vivo, and that AngII-AT1R signaling is necessary for the loss of BBB integrity in spontaneously hypertensive rats (SHRs). Herein, we hypothesized that microglial TLR4 and AT1R signaling interactions represent a crucial mechanistic link between AngII-mediated neuroinflammation and BBB disruption, thereby contributing to sympathoexcitation in SHRs. Male SHRs were treated with TAK-242 (TLR4 inhibitor; 2 weeks), Losartan (AT1R inhibitor; 4 weeks), or vehicle, and age-matched to control Wistar Kyoto rats (WKYs). TLR4 and AT1R inhibitions normalized increased TLR4, interleukin-6, and tumor necrosis factor-α protein densities in SHR cardioregulatory nuclei (hypothalamic paraventricular nucleus [PVN], rostral ventrolateral medulla [RVLM], and nucleus tractus solitarius [NTS]), and abolished enhanced microglial activation. PVN, RVLM, and NTS BBB permeability analyses revealed complete restoration after TAK-242 treatment, whereas SHRs presented with elevated dye leakage. Mean arterial pressure was normalized in Losartan-treated SHRs, and attenuated with TLR4 inhibition. In conscious assessments, TLR4 blockade rescued SHR baroreflex sensitivity to vasoactive drugs, and reduced the SHR pressor response to ganglionic blockade to normal levels. These data suggest that TLR4 activation plays a substantial role in mediating a feed-forward pro-hypertensive cycle involving BBB disruption, neuroinflammation, and autonomic dysfunction, and that TLR4-specific therapeutic interventions may represent viable alternatives in the treatment of hypertension.

Astaxanthin Ameliorates Blood Pressure in Salt-Induced Prehypertensive Rats Through ROS/MAPK/NF-κB Pathways in the Hypothalamic Paraventricular Nucleus

Astaxanthin (AST) has a variety of biochemical effects, including anti-inflammatory, antioxidative, and antihypertensive functions. The aim of the present study was to determine whether AST ameliorates blood pressure in salt-induced prehypertensive rats by ROS/MAPK/NF-κB pathways in hypothalamic paraventricular nucleus.To explore the central effects of AST on the development of blood pressure, prehypertensive rats were induced by a high-salt diet (HS, 8% NaCl) and its control groups were treated with normal-salt diet (NS, 0.3% NaCl). The Dahl salt-sensitive (S) rats with HS diet for 6 weeks received AST or vehicle by gastric perfusion for 6 weeks. Compared to those with NS diet, rats with HS diet exhibited increased mean arterial pressure (MAP) and heart rate (HR). These increases were associated with higher plasma level of norepinephrine (NE), interleukin 1β (IL-1β), and interleukin 6 (IL-6); elevated PVN level of reactive oxygen species (ROS), NOX2, and NOX4, that of IL-1β, IL-6, monocyte chemotactic protein 1 (MCP-1), tyrosine hydroxylase (TH), phosphorylation extracellular-signal-regulated kinase (p-ERK1/2), phosphorylation Jun N-terminal kinases (p-JNK), nuclear factor-kappa B (NF-κB) activity; and lower levels of IL-10, superoxide dismutase (SOD), and catalase (CAT) in the PVN. In addition, our data demonstrated that chronic AST treatment ameliorated these changes in the HS but not NS diet rats. These data suggested that AST could alleviate prehypertensive response in HS-induced prehypertension through ROS/MAPK/NF-κB pathways in the PVN.

Curcumin ameliorates hypertension via gut-brain communication in spontaneously hypertensive rat

Gut dysbiosis and dysregulation of gut-brain communication have been identified in hypertensive patients and animal models. Previous studies have shown that probiotic or prebiotic treatments exert positive effects on the pathophysiology of hypertension. This study aimed to examine the hypothesis that the microbiota-gut-brain axis is involved in the antihypertensive effects of curcumin, a potential prebiotic obtained from Curcuma longa. Male 8- to 10-week-old spontaneously hypertensive rats (SHRs) and Wistar Kyoto (WKY) rats were divided into four groups: WKY rats and SHRs treated with vehicle and SHRs treated with curcumin in dosage of 100 or 300 mg/kg/day for 12 weeks. Our results show that the elevated blood pressure of SHRs was markedly decreased in both curcumin-treated groups. Curcumin treatment also altered the gut microbial composition and improved intestinal pathology and integrity. These factors were associated with reduced neuroinflammation and oxidative stress in the hypothalamus paraventricular nucleus (PVN). Moreover, curcumin treatment increased butyrate levels in the plasma, which may be the result of increased butyrate-producing gut microorganisms. In addition, curcumin treatment also activated G protein-coupled receptor 43 (GPR 43) in the PVN. These results indicate that curcumin reshapes the composition of the gut microbiota and ameliorates the dysregulation of the gut-brain communication to induce antihypertensive effects.

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.

An Insight on Multicentric Signaling of Angiotensin II in Cardiovascular system: A Recent Update

The multifaceted nature of the renin-angiotensin system (RAS) makes it versatile due to its involvement in pathogenesis of the cardiovascular disease. Angiotensin II (Ang II), a multifaceted member of RAS family is known to have various potential effects. The knowledge of this peptide has immensely ameliorated after meticulous research for decades. Several studies have evidenced angiotensin I receptor (AT1 R) to mediate the majority Ang II-regulated functions in the system. Functional crosstalk between AT1 R mediated signal transduction cascades and other signaling pathways has been recognized. The review will provide an up-to-date information and recent discoveries involved in Ang II receptor signal transduction and their functional significance in the cardiovascular system for potential translation in therapeutics. Moreover, the review also focuses on the role of stem cell-based therapies in the cardiovascular system.

Role of the Peroxisome Proliferator Activated Receptors in Hypertension

Nuclear receptors represent a large family of ligand-activated transcription factors which sense the physiological environment and make long-term adaptations by mediating changes in gene expression. In this review, we will first discuss the fundamental mechanisms by which nuclear receptors mediate their transcriptional responses. We will focus on the PPAR (peroxisome proliferator-activated receptor) family of adopted orphan receptors paying special attention to PPARγ, the isoform with the most compelling evidence as an important regulator of arterial blood pressure. We will review genetic data showing that rare mutations in PPARγ cause severe hypertension and clinical trial data which show that PPARγ activators have beneficial effects on blood pressure. We will detail the tissue- and cell-specific molecular mechanisms by which PPARs in the brain, kidney, vasculature, and immune system modulate blood pressure and related phenotypes, such as endothelial function. Finally, we will discuss the role of placental PPARs in preeclampsia, a life threatening form of hypertension during pregnancy. We will close with a viewpoint on future research directions and implications for developing novel therapies.

Toll-Like Receptors in the Pathogenesis of Essential Hypertension. A Forthcoming Immune-Driven Theory in Full Effect

Essential hypertension (EH) is a highly heterogenous disease with a complex etiology. Recent evidence highlights the significant contribution of subclinical inflammation, triggered and sustained by excessive innate immune system activation in the pathogenesis of the disease. Toll-like receptors (TLRs) have been implied as novel effectors in this inflammatory environment since they can significantly stimulate the production of pro-inflammatory cytokines, the migration and proliferation of smooth muscle cells and the generation of reactive oxygen species (ROS), facilitating a low-intensity inflammatory background that is evident from the very early stages of hypertension. Furthermore, the net result of their activation is oxidative stress, endothelial dysfunction, vascular remodeling, and finally, vascular target organ damage, which forms the pathogenetic basis of EH. Importantly, evidence of augmented TLR expression and activation in hypertension has been documented not only in immune but also in several non-immune cells located in the central nervous system, the kidneys, and the vasculature which form the pathogenetic core systems operating in hypertensive disease. In this review, we will try to highlight the contribution of innate immunity in the pathogenesis of hypertension by clarifying the deleterious role of TLR signaling in promoting inflammation and facilitating hypertensive vascular damage.

Chronic Infusion of Astaxanthin Into Hypothalamic Paraventricular Nucleus Modulates Cytokines and Attenuates the Renin-Angiotensin System in Spontaneously Hypertensive Rats

ABSTRACT

Oxidative stress, the renin-angiotensin system (RAS), and inflammation are some of the mechanisms involved in the pathogenesis of hypertension. The aim of this study is to examine the protective effect of the chronic administration of astaxanthin, which is extracted from the shell of crabs and shrimps, into hypothalamic paraventricular nucleus (PVN) in spontaneously hypertensive rats. Animals were randomly assigned to 2 groups and treated with bilateral PVN infusion of astaxanthin or vehicle (artificial cerebrospinal fluid) through osmotic minipumps (Alzet Osmotic Pumps, Model 2004, 0.25 μL/h) for 4 weeks. Spontaneously hypertensive rats had higher mean arterial pressure and plasma level of norepinephrine and proinflammatory cytokine; higher PVN levels of reactive oxygen species, NOX2, NOX4, IL-1β, IL-6, ACE, and AT1-R; and lower PVN levels of IL-10 and Cu/Zn SOD, Mn SOD, ACE2, and Mas receptors than Wistar-Kyoto rats. Our data showed that chronic administration of astaxanthin into PVN attenuated the overexpression of reactive oxygen species, NOX2, NOX4, inflammatory cytokines, and components of RAS within the PVN and suppressed hypertension. The present results revealed that astaxanthin played a role in the brain. Our findings demonstrated that astaxanthin had protective effect on hypertension by improving the balance between inflammatory cytokines and components of RAS.

Anemoside B4 Protects against Acute Lung Injury by Attenuating Inflammation through Blocking NLRP3 Inflammasome Activation and TLR4 Dimerization

Acute lung injury (ALI) is an acute inflammatory process in the lung parenchyma. Anemoside B4 (B4) was isolated from Pulsatilla, a plant-based drug against inflammation and commonly applied in traditional Chinese medicine. However, the anti-inflammatory effect and the mechanisms of B4 are not clear. In this study, we explored the potential mechanisms and anti-inflammatory activity of B4 both in vitro and in vivo. The results indicated that B4 suppressed the expression of iNOS, COX-2, NLRP3, caspase-1, and IL-1β. The ELISA assay results showed that B4 significantly restrained the release of inflammatory cytokines like TNF-α, IL-6, and IL-1β in macrophage cells. In addition, B4 rescued mitochondrial membrane potential (MMP) loss in (lipopolysaccharide) LPS plus ATP stimulated macrophage cells. Co-IP and molecular docking results illustrated that B4 disrupted the dimerization of TLR4. For in vivo results, B4 exhibited a protective effect on LPS and bleomycin- (BLM-) induced ALI in mice through suppressing the lesions of lung tissues, the release of inflammatory cytokines, and the levels of white blood cells, neutrophils, and lymphoid cells in the blood. Collectively, B4 has a protective effect on ALI via blocking TLR4 dimerization and NLRP3 inflammasome activation, suggesting that B4 is a potential agent for the treatment of ALI.

Key Player in Cardiac Hypertrophy, Emphasizing the Role of Toll-Like Receptor 4

Toll-like receptor 4 (TLR4), a key pattern recognition receptor, initiates the innate immune response and leads to chronic and acute inflammation. In the past decades, accumulating evidence has implicated TLR4-mediated inflammatory response in regulation of myocardium hypertrophic remodeling, indicating that regulation of the TLR4 signaling pathway may be an effective strategy for managing cardiac hypertrophy's pathophysiology. Given TLR4's significance, it is imperative to review the molecular mechanisms and roles underlying TLR4 signaling in cardiac hypertrophy. Here, we comprehensively review the current knowledge of TLR4-mediated inflammatory response and its interaction ligands and co-receptors, as well as activation of various intracellular signaling. We also describe the associated roles in promoting immune cell infiltration and inflammatory mediator secretion, that ultimately cause cardiac hypertrophy. Finally, we provide examples of some of the most promising drugs and new technologies that have the potential to attenuate TLR4-mediated inflammatory response and prevent or reverse the ominous cardiac hypertrophy outcomes.

Candesartan could ameliorate the COVID-19 cytokine storm

BACKGROUND

Angiotensin receptor blockers (ARBs) reducing inflammation and protecting lung and brain function, could be of therapeutic efficacy in COVID-19 patients.

METHODS

Using GSEA, we compared our previous transcriptome analysis of neurons injured by glutamate and treated with the ARB Candesartan (GSE67036) with transcriptional signatures from SARS-CoV-2 infected primary human bronchial epithelial cells (NHBE) and lung postmortem (GSE147507), PBMC and BALF samples (CRA002390) from COVID-19 patients.

RESULTS

Hundreds of genes upregulated in SARS-CoV-2/COVID-19 transcriptomes were similarly upregulated by glutamate and normalized by Candesartan. Gene Ontology analysis revealed expression profiles with greatest significance and enrichment, including proinflammatory cytokine and chemokine activity, the NF-kappa B complex, alterations in innate and adaptive immunity, with many genes participating in the COVID-19 cytokine storm.

CONCLUSIONS

There are similar injury mechanisms in SARS-CoV-2 infection and neuronal injury, equally reduced by ARB treatment. This supports the hypothesis of a therapeutic role for ARBs, ameliorating the COVID-19 cytokine storm.

TLR4/MyD88/NF-κB Signaling in the Rostral Ventrolateral Medulla Is Involved in the Depressor Effect of Candesartan in Stress-Induced Hypertensive Rats

This study aimed to investigate whether the proinflammatory and pressor effects of endogenous angiotensin II (AngII) are mediated by binding to the AngII type 1 receptor (AT₁R) and subsequently activating central Toll-like receptor 4 (TLR4) in the rostral ventrolateral medulla (RVLM) of stress-induced hypertensive rats (SIHR). The stress-induced hypertension (SIH) model was established by random electric foot shocks combined with noise stimulation. Mean arterial pressure, heart rate, plasma norepinephrine, and RVLM AngII and TLR4 increased in a time-dependent manner in SIHR. Pro-inflammatory cytokines (tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β)), myeloid differentiation factor 88 (MyD88), and nuclear factor (NF)-κB also increased, while anti-inflammatory cytokine IL-10 decreased in the RVLM of SIHR. These changes were attenuated by 14-day intracerebroventricular (ICV) infusion of VIPER (a TLR4 inhibitor) or candesartan (an AT₁R antagonist). Both TLR4 and AT₁R were expressed in the neurons and microglia in the RVLM of SIHR. Candesartan attenuated the expression of TLR4 in the RVLM of SIHR. This study demonstrated that endogenous AngII may activate AT₁R to upregulate TLR4/MyD88/NF-κB signaling and subsequently trigger an inflammatory response in the RVLM of SIHR, which in turn enhanced sympathetic activity and increased blood pressure.

Toll-like Receptor as a Molecular Link between Metabolic Syndrome and Inflammation: A Review

Metabolic Syndrome (MetS) involves a cluster of five conditions, i.e. obesity, hyperglycaemia, hypertension, hypertriglyceridemia and low High-Density Lipoprotein (HDL) cholesterol. All components of MetS share an underlying chronic inflammatory aetiology, manifested by increased levels of pro-inflammatory cytokines. The pathogenic role of inflammation in the development of MetS suggested that toll-like receptor (TLR) activation may trigger MetS. This review summarises the supporting evidence on the interactions between MetS and TLR activation, bridged by the elevation of TLR ligands during MetS. The regulatory circuits mediated by TLR activation, which modulates signal propagation, leading to the state of chronic inflammation, are also discussed. Taken together, TLR activation could be the molecular basis in the development of MetS-induced inflammation.

PPARγ: the dominant regulator among PPARs in dry eye lacrimal gland and diabetic lacrimal gland

AIM

To investigate the regulatory roles of the members of the peroxisome proliferator-activated receptor (PPAR) family in lacrimal gland dysfunction under conditions of desiccating stress or diabetes.

METHODS

Quantitative polymerase chain reaction (qPCR) was used to examine the expression of PPARs in the cornea, conjunctiva, meibomian gland, and lacrimal gland in adult rats. The rats were divided into 3 groups: a control group, dry eye group, and diabetic group. The phenol red threads test, tear film break-up time (BUT) test and fluorescein staining were carried out to evaluate the development of dry eye. Based on bioinformatics research, qPCR was used to examine the expression level of PPARγ, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), sirtuin 1 (Sirt1), myeloid differentiation factor 88 (MyD88) and transforming growth factor-β (TGF-β) in the lacrimal glands.

RESULTS

PPARα and PPARβ/δ were mainly expressed in the conjunctiva and the lacrimal gland, respectively. However, PPARγ was expressed in both the conjunctiva and lacrimal gland, at much higher levels than those measured for PPARα and PPARβ/δ. Dry eye rats and diabetic rats both showed decreased tear secretion, shortened BUT, and increased corneal staining. Significant changes in gene expression were observed compared with the control group. In the lacrimal glands of dry eye rats and diabetic rats, expression of PPARγ decreased (P<0.05), expression of Sirt1 also decreased (P<0.01), whereas expression of TNF-α, IL-1β, IL-6, MyD88, and TGF-β increased (P<0.05).

CONCLUSION

Among PPARs, PPARγ might play a dominant role in the regulation of metabolic- and inflammatory-signaling pathways on the ocular surfaces and in lacrimal glands. Down-regulation of PPARγ is highly relevant to lacrimal gland dysfunction under desiccating-stress and diabetic conditions. PPARγ, thus, is a potential therapeutic target in the treatment of environment- or diabetes-induced dry eye diseases.

Calcitriol ameliorated autonomic dysfunction and hypertension by down-regulating inflammation and oxidative stress in the paraventricular nucleus of SHR

The hypothalamic paraventricular nucleus (PVN) plays crucial roles in central cardiovascular regulation. Increasing evidence in humans and rodents shows that vitamin D intake is important for achieving optimal cardiovascular function. The purpose of this study was to investigate whether calcitriol, an active form of vitamin D, improves autonomic and cardiovascular function in hypertensive rats and whether PVN oxidative stress and inflammation are involved in these beneficial effects. Male spontaneously hypertensive rats (SHR) and normotensive control Wistar Kyoto (WKY) rats were treated with either calcitriol (40 ng/day) or vehicle (0.11 μL/h) through chronic PVN infusion for 4 weeks. Blood pressure and heart rate were recorded continuously by radiotelemetry. PVN tissue, heart and plasma were collected for molecular and histological analysis. Compared to WKY rats, SHR exhibited increased systolic blood pressure, sympathetic drive, and cardiac hypertrophy and remodeling. These were associated with higher mRNA and protein expression levels of high mobility box 1 (HMGB1), receptor for advanced glycation end products (RAGE), toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), proinflammatory cytokines, NADPH oxidase subunit in the PVN. In addition, increased norepinephrine in plasma, elevated reactive oxygen species levels and activation of microglia in the PVN were also observed in SHR. Chronic calcitriol treatment ameliorated these changes but not in WKY rats. Our results demonstrate that chronic infusion of calcitriol in the PVN ameliorates hypertensive responses, sympathoexcitation and retains cardiovascular function in SHR. Reduced inflammation and oxidative stress within the PVN are involved in these calcitriol-induced effects.

Systemic administration of pentoxifylline attenuates the development of hypertension in renovascular hypertensive rats

There is evidence to suggest that hypertension involves a chronic low-grade systemic inflammatory response; however, the underlying mechanisms are unclear. To further understand the role of inflammation in hypertension, we used a rat renovascular model of hypertension in which we administered the TNF-α synthesis inhibitor pentoxifylline (PTX, 30 mg/kg/day) in the drinking water for 60 days. In conscious rats, PTX administration significantly attenuated the development of hypertension (systolic blood pressure, PTX: 145 ± 8 vs. vehicle (Veh): 235 ± 11 mmHg, after 38 days of treatment, P < 0.05, N = 5/group). This attenuation in hypertension was coupled with a decrease in the low-frequency spectra of systolic blood pressure variability (PTX: 1.23 ± 0.2 vs Veh: 3.05 ± 0.8 arbitrary units, P < 0.05, N = 5/group). Furthermore, systemic PTX administration decreased c-Fos expression within the hypothalamic paraventricular nucleus (PTX: 17 ± 4 vs. Veh: 70 ± 13 cells, P < 0.01, N = 5, PVN) and increased the total number of microglial branches (PTX: 2129 ± 242 vs. Veh: 1415 ± 227 branches, P < 0.05, N = 4/group). Acute central injection of PTX (20 μg) under urethane anesthesia caused a small transient decrease in blood pressure but did not change renal sympathetic nerve activity. Surprisingly, we found no detectable basal levels of plasma TNF-α in either PTX- or vehicle-treated animals. These results suggest that inflammation plays a role in renovascular hypertension and that PTX might act both peripherally and centrally to prevent hypertension.

Exercise Training Attenuates Hypertension Through TLR4/MyD88/NF-κB Signaling in the Hypothalamic Paraventricular Nucleus

Exercise training (ExT) is beneficial for cardiovascular health, yet the central mechanism by which aerobic ExT attenuates the hypertensive responses remains unclear. Activation of pro-inflammatory cytokines (PICs) in the hypothalamic paraventricular nucleus (PVN) is important for the sympathoexcitation and hypertensive response. We thus hypothesized that aerobic ExT can decrease the blood pressure of hypertensive rats by reducing the levels of PICs through TLR4/MyD88/NF-κB signaling within the PVN. To examine this hypothesis, two-kidney-one-clip (2K1C) renovascular hypertensive rats were assigned to two groups: sedentary or exercise training and examined for 8 weeks. At the same time, bilateral PVN infusion of vehicle or TAK242, a TLR4 inhibitor, was performed on both groups. As a result, the systolic blood pressure (SBP), renal sympathetic nerve activity (RSNA) and plasma levels of norepinephrine (NE), epinephrine (EPI) were found significantly increased in 2K1C hypertensive rats. These rats also had higher levels of Fra-like activity, NF-κB p65 activity, TLR4, MyD88, IL-1β and TNF-α in the PVN than SHAM rats. Eight weeks of ExT attenuated the RSNA and SBP, repressed the NF-κB p65 activity, and reduced the increase of plasma levels of NE, EPI, and the expression of Fra-like, TLR4, MyD88, IL-1β and TNF-α in the PVN of 2K1C rats. These findings are highly similar to the results in 2K1C rats with bilateral PVN infusions of TLR4 inhibitor (TAK242). This suggests that 8 weeks of aerobic ExT may decrease blood pressure in hypertensive rats by reducing the PICs activation through TLR4/MyD88/NF-κB signaling within the PVN, and thus delays the progression of 2K1C renovascular hypertension.

Blockade of c-Src Within the Paraventricular Nucleus Attenuates Inflammatory Cytokines and Oxidative Stress in the Mechanism of the TLR4 Signal Pathway in Salt-Induced Hypertension

Toll-like receptor 4 (TLR4) and cellular Src (c-Src) are closely associated with inflammatory cytokines and oxidative stress in hypertension, so we designed this study to explore the exact role of c-Src in the mechanism of action of the TLR4 signaling pathway in salt-induced hypertension. Salt-sensitive rats were given a high salt diet for 10 weeks to induce hypertension. This resulted in higher levels of TLR4, activated c-Src, pro-inflammatory cytokines, oxidative stress, and arterial pressure. Infusion of a TLR4 blocker into the hypothalamic paraventricular nucleus (PVN) decreased the activated c-Src, while microinjection of a c-Src inhibitor attenuated the PVN levels of nuclear factor-kappa B, pro-inflammatory cytokines, and oxidative stress. Our findings suggest that a long-term high-salt diet increases TLR4 expression in the PVN and this promotes the activation of c-Src, which upregulates the expression of pro-inflammatory cytokines and results in the overproduction of reactive oxygen species. Therefore, inhibiting central c-Src activity may be a new target for treating hypertension.

Chemoattraction and Recruitment of Activated Immune Cells, Central Autonomic Control, and Blood Pressure Regulation

Inflammatory mediators play a critical role in the regulation of sympathetic outflow to cardiovascular organs in hypertension. Emerging evidence highlights the involvement of immune cells in the regulation of blood pressure. However, it is still unclear how these immune cells are activated and recruited to key autonomic brain regions to regulate sympathetic outflow to cardiovascular organs. Chemokines such as C-C motif chemokine ligand 2 (CCL2), and pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), are upregulated both peripherally and centrally in hypertension. More specifically, they are upregulated in key autonomic brain regions that control sympathetic activity and blood pressure such as the paraventricular nucleus of the hypothalamus and the rostral ventrolateral medulla. Furthermore, this upregulation of inflammatory mediators is associated with the infiltration of immune cells to these brain areas. Thus, expression of pro-inflammatory chemokines and cytokines is a potential mechanism promoting invasion of immune cells into key autonomic brain regions. In pathophysiological conditions, this can result in abnormal activation of brain circuits that control sympathetic nerve activity to cardiovascular organs and ultimately in increases in blood pressure. In this review, we discuss emerging evidence that helps explain how immune cells are chemoattracted to autonomic nuclei and contribute to changes in sympathetic outflow and blood pressure.

A Novel Biological Role of α-Mangostin via TAK1-NF-κB Pathway against Inflammatory

The oxysterone α-mangostin is isolated from mangosteen husks and is widely used in the treatment of abdominal pain, diarrhea, and dysentery. In this study, we established a lipopolysaccharide (LPS)-induced inflammatory model of rat intestinal epithelial cells (IEC-6 cells), at the same time we used differently concentration α-mangostin to detect its anti-inflammatory activity. We applied doses of α-mangostin (2.5, 5, and 10 μM) and detected apoptosis by flow cytometry, and the Griess reagent and the enzyme-linked immunosorbent assay (ELISA) method detected inflammatory factors such as nitric oxide (NO), prostaglandin (PG) E2, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. We also used quantitative real-time PCR (Q-PCR) to examine inflammatory factors and western blotting to examine the activation of transforming growth factor-activated kinase (TAK)-1-nuclear factor (NF)-κB signaling pathway-related proteins. Finally, we used laser confocal microscopy to detect the effect of the 10 μM α-mangostin on the nuclear import of NF-κB-p65. The results showed that α-mangostin treatment significantly reduced the apoptosis of LPS-stimulated IEC-6 cells, the production of inflammatory factors, the activation of TAK1-NF-κB signaling pathway-related proteins, and the entry of p65 into the nucleus. In conclusion, α-mangostin exerts its anti-inflammatory effects by inhibiting the activation of TAK1-NF-κB and it may be a potential choice for the treatment of inflammation diseases.

Neuroinflammation in hypertension: the renin-angiotensin system versus pro-resolution pathways

Overstimulation of the pro-inflammatory pathways within brain areas responsible for sympathetic outflow is well evidenced as a primary contributing factor to the establishment and maintenance of neurogenic hypertension. However, the precise mechanisms and stimuli responsible for promoting a pro-inflammatory state are not fully elucidated. Recent work has unveiled novel compounds derived from omega-3 polyunsaturated fatty acids (ω-3 PUFAs), termed specialized pro-resolving mediators (SPMs), which actively regulate the resolution of inflammation. Failure or dysregulation of the resolution process has been linked to a variety of chronic inflammatory and neurodegenerative diseases. Given the pathologic role of neuroinflammation in the hypertensive state, SPMs and their associated pathways may provide a link between hypertension and the long-standing association of dietary ω-3 PUFAs with cardioprotection. Herein, we review recent progress in understanding the RAS-driven pathophysiology of neurogenic hypertension, particularly in regards to the chronic low-grade neuroinflammatory response. In addition, we examine the potential for an impaired resolution of inflammation process in the context of hypertension.

Intermedin in Paraventricular Nucleus Attenuates Sympathoexcitation and Decreases TLR4-Mediated Sympathetic Activation via Adrenomedullin Receptors in Rats with Obesity-Related Hypertension

Intermedin/adrenomedullin-2 (IMD/AM2), a member of the calcitonin gene-related peptide/AM family, plays an important role in protecting the cardiovascular system. However, its role in the enhanced sympathoexcitation in obesity-related hypertension is unknown. In this study, we investigated the effects of IMD in the paraventricular nucleus (PVN) of the hypothalamus on sympathetic nerve activity (SNA), and lipopolysaccharide (LPS)-induced sympathetic activation in obesity-related hypertensive (OH) rats induced by a high-fat diet for 12 weeks. Acute experiments were performed under anesthesia. The dynamic alterations of sympathetic outflow were evaluated as changes in renal SNA and mean arterial pressure (MAP) in response to specific drugs. Male rats were fed a control diet (12% kcal as fat) or a high-fat diet (42% kcal as fat) for 12 weeks to induce OH. The results showed that IMD protein in the PVN was downregulated, but Toll-like receptor 4 (TLR4) and plasma norepinephrine (NE, indicating sympathetic hyperactivity) levels, and systolic blood pressure were increased in OH rats. LPS (0.5 µg/50 nL)-induced enhancement of renal SNA and MAP was greater in OH rats than in obese or control rats. Bilateral PVN microinjection of IMD (50 pmol) caused greater decreases in renal SNA and MAP in OH rats than in control rats, and inhibited LPS-induced sympathetic activation, and these were effectively prevented in OH rats by pretreatment with the AM receptor antagonist AM22-52. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor U0126 in the PVN partially reversed the LPS-induced enhancement of SNA. However, IMD in the PVN decreased the LPS-induced ERK activation, which was also effectively prevented by AM22-52. Chronic IMD administration resulted in significant reductions in the plasma NE level and blood pressure in OH rats. Moreover, IMD lowered the TLR4 protein expression and ERK activation in the PVN, and decreased the LPS-induced sympathetic overactivity. These results indicate that IMD in the PVN attenuates SNA and hypertension, and decreases the ERK activation implicated in the LPS-induced enhancement of SNA in OH rats, and this is mediated by AM receptors.

Silencing salusin β ameliorates heart failure in aged spontaneously hypertensive rats by ROS-relative MAPK/NF-κB pathways in the paraventricular nucleus

OBJECTIVE

Sustained hypertension is a major cause of heart failure in aging hypertensive patients. Salusin β, a novel bioactive peptide of 20 amino acids, has been reported to participate in various cardiovascular diseases, including hypertension. We therefore hypothesized that central knockdown of salusin β might be effective for hypertension-induced heart failure treatment.

METHODS AND RESULTS

Eighteen-month-old male aged spontaneously hypertensive rats (SHR) with heart failure and WKY rats were microinjected with either a specific adenoviral vector encoding salusin β shRNA (Ad-Sal-shRNA) or a scramble shRNA (Ad-Scr-shRNA) in the hypothalamic paraventricular nucleus (PVN) for 4 weeks. Radiotelemetry and echocardiography were used for measuring blood pressure and cardiac function, respectively. Blood samples and heart were harvested for evaluating plasma norepinephrine, tyrosine hydroxylase, and cardiac morphology, respectively. The mesenteric arteries were separated for measurement of vascular responses. The PVN was analyzed for salusin β, proinflammatory cytokines (PICs), mitogen-activated protein kinase (MAPK), NF-κB, and reactive oxygen species (ROS) levels. Compared with normotensive rats, aging SHR with heart failure had dramatically increased salusin β expression. Silencing salusin β with Ad-Sal-shRNA attenuated arterial pressure and improved autonomic function, cardiac and vascular dysfunction in aging SHR with heart failure, but not in aging WKY rats. Knockdown of salusin β significantly reduced paraventricular nucleus PICs levels, MAPK and NF-κB activity, and ROS levels in aging SHR with heart failure.

CONCLUSION

These data demonstrate that in aging SHR, the heart failure that was developed during the end stage of hypertension could be ameliorated by silencing salusin β.

Telmisartan Modulates the Oral Mucositis Induced by 5-Fluorouracil in Hamsters

Oral mucositis (OM) is a common adverse effect resulting from cancer therapy. The OM it has implications that may compromise oncologic treatment and decrease the patient's quality of life. The therapeutic options to prevent or treat the symptoms of OM are scarce; there is no effective therapy that improves the symptoms. Based on the need for further research for the treatment of OM, the present study objective was to evaluate the effect of telmisartan (TELM) on the OM induced by 5-fluorouracil (5-FU), using as animal model Golden Syrian hamsters. 5-FU followed by mechanical trauma on day 4 was used to induce OM in hamsters. Euthanasia occurred on the day 10. The experiments were constituted by the groups saline, mechanical trauma, 5-FU, and TELM in three doses (1, 5, or 10 mg/kg). Macroscopic, histopathological, and immunohistochemical analyses as well as immunofluorescence experiments were performed on the oral mucosa of the animals. The samples also were used for analysis enzyme-linked immunosorbent assays and quantitative real-time polymerase chain reactions (qPCR). TELM (5 or 10 mg/kg) was able to reduce the inflammatory ulceration and infiltration in the oral mucosa of the animals, decreasing the levels of the cytokines TNF-α and IL-1β. These treatments was minimize the immunostaining for cyclooxygenase-2, matrix metalloproteinase-9, transforming growth factor-β, and smad 2/3. The nuclear transcription factor kappa B (NFκB) p65 and inducible nitric oxide synthase were reduced in the oral mucosa. Finally, TELM (10 mg/kg) increased the PPARγ gene expression and reduced STAT1 and NFκB p65 gene expression relative to the 5-FU group. Therefore, TELM prevents the OM produced by 5-FU on animal model.

Targeting toll-like receptor 4 signalling pathways: can therapeutics pay the toll for hypertension?

The immune system plays a prominent role in the initiation and maintenance of hypertension. The innate immune system, via toll-like receptors (TLRs), identifies distinct signatures of invading microbes and damage-associated molecular patterns and triggers a chain of downstream signalling cascades, leading to secretion of pro-inflammatory cytokines and shaping the adaptive immune response. Over the past decade, a dysfunctional TLR-mediated response, particularly via TLR4, has been suggested to support a chronic inflammatory state in hypertension, inducing deleterious local and systemic effects in host cells and tissues and contributing to disease progression. While the underlying mechanisms triggering TLR4 need further research, evidence suggests that sustained elevations in BP disrupt homeostasis, releasing endogenous TLR4 ligands in hypertension. In this review, we discuss the emerging role of TLR4 in the pathogenesis of hypertension and whether targeting this receptor and its signalling pathways could offer a therapeutic strategy for management of this multifaceted disease. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Beneficial effects of rosiglitazone and losartan combination in diabetic rats

Diabetes with vascular complication needs strict interventions to retard possible serious complications. This research estimated the possible interaction of rosiglitazone (RGN) with losartan (Los) in diabetic rats. Male Sprague–Dawley rats were randomly divided into nondiabetic rats, diabetic rats, and diabetic rats that received RGN, Los, or a combination of RGN and Los. Measurement of serum glucose, vascular adhesion molecule-1, interleukin-6, tumor necrosis factor-α, aortic lipid peroxide (malondialdehyde), glutathione, superoxide dismutase, and total nitrate/nitrite levels was done. Also, the effects of RGN on the relaxation created by acetylcholine and sodium nitroprusside, contraction of isolated aortic rings provoked by phenylephrine and angiotensin II were determined. Results revealed that RGN or Los had a vasodilating effect to variable degrees indicated by enhanced effects on both acetylcholine-induced relaxation and the antagonistic effect on angiotensin II and phenylephrine-stimulated contraction of diabetic aortas with significant amelioration in serum glucose, vascular adhesion molecule-1, interleukin-6, and tumor necrosis factor-α levels and aortic oxidant/antioxidant balance. Treatment of diabetic rats with a combination of RGN and Los produced a more pronounced effect on the measured parameters compared to the diabetic, RGN-, and Los-treated groups. These findings point out the beneficial effects of RGN and Los combination in diabetic rats.

Effects of Ginkgo biloba leaf extract on local renin-angiotensin system through TLR4/NF-κB pathway in cardiac myocyte

The present study investigated the effects of Ginkgo biloba leaf extract (GBE50) on lipopolysaccharide (LPS) induced Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling pathway and its effects on angiotensinogen (ATG) and AT_1a receptor, so as to explore the mechanism of GBE50 in prevention and treatment of left ventricular remodeling. In vitro cultured neonatal rat ventricular myocytes (NRVMs) were divided into 4 groups including i) control group: DMEM medium; ii) LPS group: iii) LPS + GBE50 group; iv) LPS + caffeic acid phenethyl ester (CAPE, specific inhibitor of NF-κB) group. Nuclear translocation of NF-κB p65 was detected by immunocytochemical method after intervention for 24 h. Expression of TLR4, ATG, AT_1a receptors and β-myosin heavy chain (β-MHC) mRNA were detected by reverse transcription-polymerase chain reaction (RT-PCR). Protein content of cardiomyocytes was measured by Coomassie Brilliant Blue method. Under LPS stimulation, expression level of TLR4 mRNA in NRVMs was significantly increased (P<0.01), nuclear translocation of NF-κB p65 was increased, expression levels of ATG, AT_1a receptor and β-MHC mRNA and the protein content in cells were also increased significantly (P<0.01). GBE50 and CAPE significantly inhibited nuclear translocation of NF-κB p65. GBE50 and CAPE treatments also reduced the increased mRNA levels of TLR4, ATG, AT_1a receptor and β-MHC and protein content in cell caused by LPS stimulation. We concluded that, GBE50 can inhibit the activation of local renin-angiotensin system by inhibiting the activation of TLR4/NF-κB and TLR4/NF-κB, signaling pathway inhibition may be one of the mechanisms of the role of Ginkgo biloba leaf extract in preventing myocardial remodeling.

Vaccarin administration ameliorates hypertension and cardiovascular remodeling in renovascular hypertensive rats

Sympathetic overdrive, activation of renin angiotensin systems (RAS), and oxidative stress are vitally involved in the pathogenesis of hypertension and cardiovascular remodeling. We recently identified that vaccarin protected endothelial cell function from oxidative stress or high glucose. In this study, we aimed to investigate whether vaccarin attenuated hypertension and cardiovascular remodeling. Two-kidney one-clip (2K1C) model rats were used, and low dose of vaccarin (10 mg/kg), high dose of vaccarin (30 mg/kg), captopril (30 mg/kg) were intraperitoneally administrated. Herein, we showed that 2K1C rats exhibited higher systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), left ventricular mass/body weight ratio, myocardial hypertrophy or fibrosis, media thickness, and media thickness to lumen diameter, which were obviously alleviated by vaccarin and captopril. In addition, both vaccarin and captopril abrogated the increased plasma renin, angiotensin II (Ang II), norepinephrine (NE), and the basal sympathetic activity. The AT1R protein expressions, NADPH oxidase subunit NOX-2 protein levels and malondialdehyde (MDA) content were significantly increased, whereas superoxide dismutase (SOD) and catalase (CAT) activities were decreased in myocardium, aorta, and mesenteric artery of 2K1C rats, both vaccarin and captopril treatment counteracted these changes in renovascular hypertensive rats. Collectively, we concluded that vaccarin may be a novel complementary therapeutic medicine for the prevention and treatment of hypertension. The mechanisms for antihypertensive effects of vaccarin may be associated with inhibition of sympathetic activity, RAS, and oxidative stress.

Shikonin ameliorates isoproterenol (ISO)-induced myocardial damage through suppressing fibrosis, inflammation, apoptosis and ER stress

Shikonin, isolated from the roots of herbal plant Lithospermum erythrorhizon, is a naphthoquinone. It has been reported to exert beneficial anti-inflammatory effects and anti-oxidant properties in various diseases. Isoproterenol (ISO) has been widely used to establish cardiac injury in vivo and in vitro. However, shikonin function in ISO-induced cardiac injury remains uncertain. In our study, we attempted to investigate the efficiency and possible molecular mechanism of shikonin in cardiac injury treatment induced by ISO. In vivo, C57BL6 mice were subcutaneously injected with 5mg/kg ISO to induce heart failure. And mice were given a gavage of shikonin (2 or 4mg/kg/d, for four weeks). Cardiac function, fibrosis indices, inflammation response, apoptosis and endoplasmic reticulum (ER) stress were calculated. Pathological alterations, fibrosis-, inflammation-, apoptosis- and ER stress-related molecules were examined. In ISO-induced cardiac injury, shikonin significantly ameliorated heart function, decreased myocardial fibrosis, suppressed inflammation, attenuated apoptosis and ER stress through impeding collagen accumulation, Toll like receptor 4/nuclear transcription factor κB (TLR4/NF-κB), Caspase-3 and glucose-regulated protein 78 (GRP78) signaling pathways activity, relieving heart failure in vivo. Also, in vitro, shikonin attenuated ISO-induced cardiac muscle cells by reducing fibrosis, inflammation, apoptosis and ER stress. Our findings indicated that shikonin treatment attenuated ISO-induced heart injury, providing an effective therapeutic strategy for heart failure treatment for future.

Associations between PPARG polymorphisms and the risk of essential hypertension

Background

Peroxisome proliferator-activated receptor gamma (PPARG) plays an important role in the pathogenesis and maintenance of essential hypertension (EH). It has been suggested that polymorphisms of PPARG are associated with the risk of EH. However, findings to date remain controversial. To elucidate the associations between the PPARG Pro12Ala and C161T polymorphisms and EH risk, a meta-analysis was carried out.

Methods

A comprehensive literature search of PubMed, Embase, CNKI (Chinese National Knowledge Infrastructure), VIP and Wanfang databases was conducted. The pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated to estimate the size of the effect using the random-effects model. At the same time, the pooled standardized mean difference (SMD) with 95% CI was used for the meta-analysis of the PPARG Pro12Ala polymorphism and blood pressure.

Results

Finally, Fifteen papers (seventeen studies) including 4,151 cases and 4,997 controls to evaluate the association of the PPARGPro12Ala polymorphism and EH risk, were included in this study. Overall, the results suggested that Ala allele was associated with the decreased EH risk (for allelic model, OR = 0.757, 95%CI: 0.624–0.918, P = 0.005; for dominant model, OR = 0.771, 95%CI: 0.627–0.946, P = 0.013). The subgroup analysis stratified by ethnicity showed that the significant association between the PPARG Pro12Ala polymorphism and EH was only detected in the Asian subgroup. There was no difference in blood pressure values between Ala carriers and non-carriers. For the C161T polymorphism, only 5 studies comprising 1,118 cases and 1,357 controls met the inclusion criteria. The overall results showed that the PPARG C161T polymorphism was not associated with the risk of EH. But in the subgroup analysis, we found that the PPARG C161T polymorphism significantly associated with the risk of EH in the Asian subgroup (for allelic model, OR = 0.719, 95% CI: 0.537–0.963, P = 0.027; for dominant model, OR = 0.653, 95% CI: 0.439–0.972, P = 0.036).

Conclusion

Our meta-analysis suggested that the PPARG polymorphisms might be associated with the risk of EH.

Mechanisms of cardioprotection via modulation of the immune response

Both morbidity and mortality as a result of cardiovascular disease remain significant worldwide and account for approximately 31% of annual deaths in the US. Current research is focused on novel therapeutic strategies to protect the heart during and after ischemic events and from subsequent adverse myocardial remodeling. After cardiac insult, the immune system is activated and plays an essential role in the beginning, development, and resolution of the healing cascade. Uncontrolled inflammatory responses can cause chronic disease and exacerbate progression to heart failure and therefore, constitute a major area of focus of cardiac therapies. In the present overview, we share novel insights and promising therapeutic cardioprotective strategies that target the immune response.

The interplay between Angiotensin II, TLR4 and hypertension

Hypertension is a multifactorial disease. Although a number of different underlying mechanisms have been learned from the various experimental models of the disease, hypertension still poses challenges for treatment. Angiotensin II plays an unquestionable role in blood pressure regulation acting through central and peripheral mechanisms. During hypertension, dysregulation of the Renin-Angiotensin System is associated with increased expression of pro-inflammatory cytokines and reactive oxygen species causing kidney damage, endothelial dysfunction, and increase in sympathetic activity, among other damages, eventually leading to decline in organ function. Recent studies have shown that these effects involve both the innate and the adaptive immune response. The contribution of adaptive immune responses involving different lymphocyte populations in various models of hypertension has been extensively studied. However, the involvement of the innate immunity mediating inflammation in hypertension is still not well understood. The innate and adaptive immune systems intimately interact with one another and are essential to an effectively functioning of the immune response; hence, the importance of a better understanding of the underlying mechanisms mediating innate immune system during hypertension. In this review, we aim to discuss mechanisms linking Angiotensin II and the innate immune system, in the pathogenesis of hypertension. The newest research investigating Angiotensin II triggering toll like receptor 4 activation in the kidney, vasculature and central nervous system contributing to hypertension will be discussed. Understanding the role of the innate immune system in the development of hypertension may bring to light new insights necessary to improve hypertension management.