Upregulation of Angiotensin (1-7)-Mediated Signaling Preserves Endothelial Function Through Reducing Oxidative Stress in Diabetes

The Salutary Effects of Diminazene, Lisinopril or Valsartan on Cisplatin - Induced Acute Kidney Injury in Rats: A Comparative Study

Nephrotoxicity as a cause of acute kidney injury (AKI) induced by cisplatin (CP), limits its usefulness as an anticancer agent. Diminazene, an angiotensin converting enzyme 2 activator, exhibited renoprotective properties on rat models of kidney diseases. This research aims to investigate the salutary effect of diminazene in comparison with lisinopril or valsartan in CP-induced AKI. The first and second groups of rats received oral vehicle (distilled water) for 9 days, and saline injection or intraperitoneal CP (6 mg/kg) on day 6, respectively. Third, fourth, and fifth groups received intraperitoneal injections of CP on day 6 and diminazene (15 mg/kg/day, orally), lisinopril (10 mg/kg/day, orally), or valsartan (30 mg/kg/day, orally), for 9 days, respectively. 24h after the last day of treatment, blood and kidneys were removed under anesthesia for biochemical and histopathological examination. Urine during the last 24 h before sacrificing the rats was also collected. CP significantly increased plasma urea, creatinine, neutrophil gelatinase-associated lipocalin, calcium, phosphorus, and uric acid. It also increased urinary albumin/creatinine ratio, N-Acetyl-beta-D-Glucosaminidase/creatinine ratio, and reduced creatinine clearance, as well the plasma concentrations of inflammatory cytokines [plasma tumor necrosis factor-alpha, and interleukin-1beta], and significantly reduced antioxidant indices [catalase, glutathione reductase , and superoxide dismutase]. Histopathologically, CP treatment caused necrosis of renal tubules, tubular casts, shrunken glomeruli, and increased renal fibrosis. Diminazine, lisinopril, and valsartan ameliorated CP-induced biochemical and histopathological changes to a similar extent. The salutary effect of the three drugs used is, at least partially, due to their anti-inflammatory and antioxidant effects. Keywords: Cisplatin, Diminazene, ACE2 activator, Lisinopril, Valsartan, Acute kidney injury.

Chicken Muscle-Derived ACE2-Upregulating Peptide VVHPKESF Reduces Blood Pressure Associated with the ACE2/Ang (1-7)/MasR Axis in Spontaneously Hypertensive Rats

SCOPE

This study aims to investigate the antihypertensive effect of four chicken muscle-derived angiotensin (Ang)-converting enzymes (ACE)-regulating peptides: Val-Arg-Pro (VRP, ACE inhibition), Leu-Lys-Tyr and Val-Arg-Tyr (LKY and VRY, ACE inhibition and ACE2 upregulation), and Val-Val-His-Pro-Lys-Glu-Ser-Phe (VVHPKESF [V-F], ACE2 upregulation) in spontaneously hypertensive rats.

METHODS AND RESULTS

Rats (12-14 weeks old) are grouped: 1) untreated, 2) VRP, 3) LKY, 4) VRY, and 5) V-F. Blood pressure (BP) is monitored using implantable telemetry technology. Over 18-day oral administration of 15 mg kg-1 body weight (BW) per day, only peptide V-F significantly (p < 0.05) reduces BP, decreases circulating Ang II, and increases ACE2 and Ang (1-7) levels, and enhances aortic expressions of ACE2 and Mas receptor (MasR). Peptide V-F also attenuates vascular inflammation (TNFα, MCP-1, IL-1α, IL-15, and cyclooxygenase 2 [COX2]) and vascular oxidative stress (nitrotyrosine). The gastrointestinal (GI)-degraded fragment of peptide V-F, Val-Val-His-Pro-Lys (VVHPK), is also an ACE2-upregulating peptide. Peptides VRP, LKY, and VRY do not reduce BP, possibly due to low bioavailability or other unknown reasons.

CONCLUSIONS

Peptide V-F is the first ACE2-upregulating peptide, purified and fractionated from food proteins based on in vitro ACE2 upregulation, that reduces BP associated with the activation of ACE2/Ang (1-7)/MasR axis; the N-terminal moiety VVHPK may be responsible for the antihypertensive effect of V-F.

The association of SPARC with hypertension and its function in endothelial-dependent relaxation

BACKGROUND AND AIMS

Secreted protein acidic and rich in cysteine (SPARC) is involved in the pathological processes of many metabolic diseases. However, studies on the relevance of SPARC to hypertension and its involvement in endothelial function are scarce. In this study, we aim to explore the relevance of SPARC to hypertension and investigate its role in endothelium-dependent relaxation (EDR).

METHODS

110 patients who met the criteria were recruited as participants. Serum SPARC concentrations were determined by Luminex assay. The correlation between SPARC levels and hypertension was analyzed. After treatment with SPARC ex vivo or in vivo, endothelial-dependent relaxation (EDR) was measured by wire myography. Western blotting was performed to detect the expression of proteins relevant to endothelial function.

RESULTS

Our results showed that serum SPARC levels were significantly higher in the hypertensive group and were positively associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP). Functional results demonstrated that SPARC dramatically impaired EDR and induced the excess production of reactive oxygen species (ROS) in endothelial cells. Further experimental results confirmed that SPARC reduced angiotensin-converting enzyme 2 (ACE2) expression and ACE2 overexpression or activation completely abolished the impairing effect of SPARC on endothelial function.

CONCLUSIONS

The present study reveals the correlation between elevated SPARC and hypertension and confirms its adverse effect on endothelial function, helping establish a comprehensive understanding of hypertension-related endothelial dysfunction in a new scope.

Nephroprotective effects of diminazene on doxorubicin-induced acute kidney injury in rats

This study aimed to investigate the potential protective effects of diminazene, an activator of angiotensin II converting enzyme (ACE2), on kidney function and structure in rats with acute kidney injury (AKI) induced by the anticancer drug doxorubicin (DOX). The impact of diminazene was compared to that of two other drugs: the ACE inhibitor lisinopril and the angiotensin II type 1 (AT1) receptor blocker valsartan. Rats were subjected to a single intraperitoneal injection of DOX (13.5 mg/kg) on the 5th day, either alone or in combination with diminazene (15 mg/kg/day), lisinopril (10 mg/kg/day), or valsartan (30 mg/kg/day) for 8 consecutive days. Various markers related to kidney function, oxidative stress, and inflammation were measured in plasma and urine. Additionally, kidney tissues were assessed histopathologically. DOX-induced nephrotoxicity was confirmed by elevated levels of plasma urea, creatinine, and neutrophil gelatinase-associated lipocalin (NGAL). DOX also led to increased urinary N-acetyl-β-D-glucosaminidase (NAG) activity and decreased creatinine clearance, albumin levels, and osmolality. Moreover, DOX caused a reduction in renal oxidative stress markers, including superoxide dismutase (SOD), glutathione reductase (GR), and catalase activities, while increasing malondialdehyde (MDA) levels. It also raised plasma inflammatory markers, tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β). Concurrently administering diminazene significantly mitigated these DOX-induced changes, including histopathological alterations like renal tubule necrosis, tubular casts, shrunken glomeruli, and increased renal fibrosis. Similar protective effects were observed with lisinopril and valsartan. These protective effects, at least in part, appear to result from the anti-inflammatory and antioxidant properties of these drugs. In summary, this study suggests that the administration of diminazene, lisinopril, or valsartan had comparable effects in ameliorating the biochemical and histopathological aspects of DOX-induced acute kidney injury in rats.

Neuraminidase inhibition improves endothelial function in diabetic mice

Neuraminidases cleave sialic acids from glycocalyx structures and plasma neuraminidase activity is elevated in type 2 diabetes (T2D). Therefore, we hypothesize circulating neuraminidase degrades the endothelial glycocalyx and diminishes flow-mediated dilation (FMD), whereas its inhibition restores shear mechanosensation and endothelial function in T2D settings. We found that compared with controls, subjects with T2D have higher plasma neuraminidase activity, reduced plasma nitrite concentrations, and diminished FMD. Ex vivo and in vivo neuraminidase exposure diminished FMD and reduced endothelial glycocalyx presence in mouse arteries. In cultured endothelial cells, neuraminidase reduced glycocalyx coverage. Inhalation of the neuraminidase inhibitor, zanamivir, reduced plasma neuraminidase activity, enhanced endothelial glycocalyx length, and improved FMD in diabetic mice. In humans, a single-arm trial (NCT04867707) of zanamivir inhalation did not reduce plasma neuraminidase activity, improved glycocalyx length, or enhanced FMD. Although zanamivir plasma concentrations in mice reached 225.8 ± 22.0 ng/mL, in humans were only 40.0 ± 7.2 ng/mL. These results highlight the potential of neuraminidase inhibition for ameliorating endothelial dysfunction in T2D and suggest the current Food and Drug Administration-approved inhaled dosage of zanamivir is insufficient to achieve desired outcomes in humans.NEW & NOTEWORTHY This work identifies neuraminidase as a key mediator of endothelial dysfunction in type 2 diabetes that may serve as a biomarker for impaired endothelial function and predictive of development and progression of cardiovascular pathologies associated with type 2 diabetes (T2D). Data show that intervention with the neuraminidase inhibitor zanamivir at effective plasma concentrations may represent a novel pharmacological strategy for restoring the glycocalyx and ameliorating endothelial dysfunction.

Induction of KLF2 by Exercise Activates eNOS to Improve Vasodilatation in Diabetic Mice

Diabetic endothelial dysfunction associated with diminished endothelial nitric oxide (NO) synthase (eNOS) activity accelerates the development of atherosclerosis and cardiomyopathy. However, the approaches to restore eNOS activity and endothelial function in diabetes remain limited. The current study shows that enhanced expression of Krüppel-like factor 2 (KLF2), a shear stress-inducible transcription factor, effectively improves endothelial function through increasing NO bioavailability. KLF2 expression is suppressed in diabetic mouse aortic endothelium. Running exercise and simvastatin treatment induce endothelial KLF2 expression in db/db mice. Adenovirus-mediated endothelium-specific KLF2 overexpression enhances both endothelium-dependent relaxation and flow-mediated dilatation, while it attenuates oxidative stress in diabetic mouse arteries. KLF2 overexpression increases the phosphorylation of eNOS at serine 1177 and eNOS dimerization. RNA-sequencing analysis reveals that KLF2 transcriptionally upregulates genes that are enriched in the cyclic guanosine monophosphate-protein kinase G-signaling pathway, cAMP-signaling pathway, and insulin-signaling pathway, all of which are the upstream regulators of eNOS activity. Activation of the phosphoinositide 3-kinase-Akt pathway and Hsp90 contributes to KLF2-induced increase of eNOS activity. The present results suggest that approaches inducing KLF2 activation, such as physical exercise, are effective to restore eNOS activity against diabetic endothelial dysfunction.

ARTICLE HIGHLIGHTS

Exercise and statins restore the endothelial expression of Krüppel-like factor 2 (KLF2), which is diminished in diabetic db/db mice. Endothelium-specific overexpression of KLF2 improves endothelium-dependent relaxation and flow-mediated dilation through increasing nitric oxide bioavailability. KLF2 promotes endothelial nitric oxide synthase (eNOS) coupling and phosphorylation in addition to its known role in eNOS transcription. KLF2 upregulates the expression of several panels of genes that regulate eNOS activity.

New Viral Diseases and New Possible Remedies by Means of the Pharmacology of the Renin-Angiotensin System

All strains of SARS-CoV-2, as well as previously described SARS-CoV and MERS-CoV, bind to ACE2, the cell membrane receptor of β-coronaviruses. Monocarboxypeptidase ACE2 activity stops upon viral entry into cells, leading to inadequate tissue production of angiotensin 1-7 (Ang1-7). Acute lung injury due to the human respiratory syncytial virus (hRSV) or avian influenza A H7N9 and H5N1 viruses is also characterized by significant downregulation of lung ACE2 and increased systemic levels of angiotensin II (Ang II). Restoration of Ang1-7 anti-inflammatory, antifibrotic, vasodilating, and natriuretic properties was attempted at least in some COVID-19 patients through i.v. infusion of recombinant human ACE2 or intranasal administration of the modified ACE2 protein, with inconsistent clinical results. Conversely, use of ACE inhibitors (ACEis), which increase ACE2 cell expression, seemed to improve the prognosis of hypertensive patients with COVID-19. To restore Ang1-7 tissue levels in all these viral diseases and avoid the untoward effects frequently seen with ACE2 systemic administration, a different strategy may be hypothesized. Experimentally, when metallopeptidase inhibitors block ACE2, neprilysin (NEP), highly expressed in higher and lower airways, starts cleaving angiotensin I (Ang I) into Ang1-7. We suggest a discerning use of ACEis in normohypertensive patients with β-coronavirus disease as well as in atypical pneumonia caused by avian influenza viruses or hRSV to block the main ACE-dependent effects: Ang II synthesis and Ang1-7 degradation into angiotensin 1-5. At the same time, i.v.-infused Ang I, which is not hypertensive provided ACE is inhibited, may become the primary substrate for local Ang1-7 synthesis via ubiquitous NEP; i.e., NEP could replace inadequate ACE2 function if Ang I was freely available. Moreover, inhibitors of chymase, a serine endopeptidase responsible for 80% of Ang II-forming activity in tissues and vessel walls, could protect patients with atypical pneumonia from Ang II-mediated microvascular damage without reducing arterial blood pressure.

Activation of angiotensin-converting enzyme 2 produces an antidepressant-like effect via MAS receptors in mice

Angiotensin (Ang)-converting-enzyme (ACE) 2 converts Ang II into Ang (1-7), which in turn acts on MAS receptors (ACE2/Ang (1-7)/MAS receptors pathway). This pathway has neuroprotective properties, making it a potential therapeutic target for psychiatric disorders such as depression. Thus, we examined the effects of diminazene aceturate (DIZE), an ACE2 activator, on depressive-like behavior using behavioral, pharmacological, and biochemical assays. To determine whether DIZE or Ang (1-7) produce antidepressant-like effects, we measured the duration of immobility of mice in the tail suspension test following their intracerebroventricular administration. Next, we measured the levels of ACE2 activation in the cerebral cortex, prefrontal cortex, hippocampus, and amygdala after DIZE injection, and examined which cell types, including neurons, microglia, and astrocytes, express ACE2 in the hippocampus using immunofluorescence. Administration of DIZE or Ang (1-7) significantly shortened the duration of immobility time in the tail suspension test, while this effect was inhibited by the co-administration of the MAS receptor antagonist A779. DIZE activated ACE2 in the hippocampus. ACE2 was localized to neurons, astrocytes, and microglia in the hippocampus. In conclusion, these results suggest that DIZE may act on ACE2-positive cells in the hippocampus where it increases the activity of ACE2, thereby enhancing signaling of the ACE2/Ang (1-7)/MAS receptor pathway and resulting in antidepressant-like effects.

Diminazene aceturate uses different pathways to induce relaxation in healthy and atherogenic blood vessels

Diminazene aceturate (DIZE), a putative angiotensin-converting enzyme 2 (ACE2) activator, elicits relaxation in various animal models. This study aimed to determine the relaxing mechanisms in internal iliac arteries utilised by DIZE in healthy and atherogenic rabbit models. Studies were conducted on internal iliac artery rings retrieved from male New Zealand White rabbits fed a 4-week healthy control (n = 24) or atherogenic diet (n = 20). To investigate pathways utilised by DIZE to promote arterial relaxation, a DIZE dose response [10^-9.0 M - 10^-5.0 M] was performed on pre-contracted rings incubated with pharmaceuticals that target: components of the renin-angiotensin system; endothelial- and vascular smooth muscle-dependent mechanisms; protein kinases; and potassium channels. ACE2 expression was quantified by immunohistochemistry analysis following a 2 hr or 4 hr DIZE incubation. DIZE significantly enhanced vessel relaxation in atherogenic rings at doses [10^-5.5 M] (p < 0.01) and [10^-5.0 M] (p < 0.0001), when compared to healthy controls. Comprehensive results from functional isometric studies determined that DIZE causes relaxation via different mechanisms depending on pathology. For the first time, we report that in healthy blood vessels DIZE exerts its direct relaxing effect through ACE2/AT₂R and NO/sGC pathways; however, in atherogenesis this switches to MasR, arachidonic acid pathway (i.e., COX1/2, EET and DHET), MCLP, Ca²⁺ activated voltage channels, AMPK and ERK1/2. Moreover, quantitative immunohistochemical analysis demonstrated that DIZE increases artery ACE2 expression in a time dependent manner. We provide a detailed investigation of DIZE's mechanisms and demonstrate for the first time that in healthy and atherogenic arteries DIZE provides beneficial effects through directly inducing relaxation, albeit via different pathways.

Counter-regulatory renin-angiotensin system in hypertension: Review and update in the era of COVID-19 pandemic

Cardiovascular disease is the major cause of mortality and disability, with hypertension being the most prevalent risk factor. Excessive activation of the renin-angiotensin system (RAS) under pathological conditions, leading to vascular remodeling and inflammation, is closely related to cardiovascular dysfunction. The counter-regulatory axis of the RAS consists of angiotensin-converting enzyme 2 (ACE2), angiotensin (1-7), angiotensin (1-9), alamandine, proto-oncogene Mas receptor, angiotensin II type-2 receptor and Mas-related G protein-coupled receptor member D. Each of these components has been shown to counteract the effects of the overactivated RAS. In this review, we summarize the latest insights into the complexity and interplay of the counter-regulatory RAS axis in hypertension, highlight the pathophysiological functions of ACE2, a multifunctional molecule linking hypertension and COVID-19, and discuss the function and therapeutic potential of targeting this counter-regulatory RAS axis to prevent and treat hypertension in the context of the current COVID-19 pandemic.

Transgenic rat with overproduction of ubiquitous angiotensin-(1-7) presents neuroprotection in a model of ischemia and reperfusion

Recent studies showed that angiotensin-(1-7) has cerebroprotective actions in stroke. In the present study, we aim to test whether tissue overexpression of Angiotensin-(1-7), mainly in the brain provides neuroprotection in a model of ischemia/reperfusion by bilateral common carotid arteries occlusion/reperfusion (BCCAo/R). Evaluation of neurological deficit scores and bilateral asymmetry test (BAT) were performed seven days after transient BCCAo/R in transgenic rats (TG-7371) overexpressing Angiotensin-(1-7) and Sprague-Dawley (SD) rats. To assess blood-brain barrier (BBB) permeability Evans blue dye (EB) was intravenously injected. Cytokine levels were quantified in the whole brain through Elisa assay and oxidative stress was measured 7 days after ischemia. The expression of AT₁ and Mas receptors and inducible nitric oxide synthase (iNOS) was evaluated by RT-PCR. Neurological deficits were observed in both SD-BCCAo/R and TG-BCCAo/R, contrasting to sham-operated groups. However, TG-BCCAo/R showed a significant lower neurological score and latency in BAT when compared with SD-BCCAo/R. BBB integrity in TG-BCCAo/R was improved, since these animals showed lower extravasation of EB than SD-BCCAo/R. Interestingly, TG-BCCAo/R presented lower levels of pro-inflammatory cytokines when compared to SD-BCCAo/R. Levels of IL-10 were higher in SD-BCCAo/R than in SD control and even higher in TG-BCCAo/R. TG-BCCAo/R animals presented decreased levels of TBARS and increase in SOD activity and GSH levels when compared to SD sham rats. RT-PCR results showed higher levels of AT₁ receptor and iNOS in SD-BCCAo/R compared to TG-BCCAo/R, but no difference was observed for Mas receptor. The present study shows that lifetime increase in cerebral expression of an Ang-(1-7)-producing fusion protein induces neuroprotection in experimental global cerebral ischemia and reperfusion, reassuring that, pharmacological strategies leading to increase in Ang-(1-7) can be an additional tool for stroke therapy.

H2O2 Mediates VEGF- and Flow-Induced Dilations of Coronary Arterioles in Early Type 1 Diabetes: Role of Vascular Arginase and PI3K-Linked eNOS Uncoupling

In diabetes, the enzyme arginase is upregulated, which may compete with endothelial nitric oxide (NO) synthase (eNOS) for their common substrate L-arginine and compromise NO-mediated vasodilation. However, this eNOS uncoupling can lead to superoxide production and possibly vasodilator hydrogen peroxide (H₂O₂) formation to compensate for NO deficiency. This hypothesis was tested in coronary arterioles isolated from pigs with 2-week diabetes after streptozocin injection. The NO-mediated vasodilation induced by flow and VEGF was abolished by NOS inhibitor L-NAME and phosphoinositide 3-kinase (PI3K) inhibitor wortmannin but was not affected by arginase inhibitor N^ω-hydroxy-nor-L-arginine (nor-NOHA) or H₂O₂ scavenger catalase in control pigs. With diabetes, this vasodilation was partially blunted, and the remaining vasodilation was abolished by catalase and wortmannin. Administration of L-arginine or nor-NOHA restored flow-induced vasodilation in an L-NAME sensitive manner. Diabetes did not alter vascular superoxide dismutase 1, catalase, and glutathione peroxidase mRNA levels. This study demonstrates that endothelium-dependent NO-mediated coronary arteriolar dilation is partially compromised in early type 1 diabetes by reducing eNOS substrate L-arginine via arginase activation. It appears that upregulated arginase contributes to endothelial NO deficiency in early diabetes, but production of H₂O₂ during PI3K-linked eNOS uncoupling likely compensates for and masks this disturbance.

Targeting endothelial dysfunction and inflammation

Vascular endothelium maintains vascular homeostasis through liberating a spectrum of vasoactive molecules, both protective and harmful regulators of vascular tone, structural remodeling, inflammation and atherogenesis. An intricate balance between endothelium-derived relaxing factors (nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor) and endothelium-derived contracting factors (superoxide anion, endothelin-1 and constrictive prostaglandins) tightly regulates vascular function. Disruption of such balance signifies endothelial dysfunction, a critical contributor in aging and chronic cardiometabolic disorders, such as obesity, diabetes, hypertension, dyslipidemia and atherosclerotic vascular diseases. Among many proposed cellular and molecular mechanisms causing endothelial dysfunction, oxidative stress and inflammation are often the pivotal players and they are naturally considered as useful targets for intervention in patients with cardiovascular and metabolic diseases. In this article, we provide a recent update on the therapeutic values of pharmacological agents, such as cyclooxygenase-2 inhibitors, renin-angiotensin-system inhibitors, bone morphogenic protein 4 inhibitors, peroxisome proliferator-activated receptor δ agonists, and glucagon-like peptide 1-elevating drugs, and the physiological factors, particularly hemodynamic forces, that improve endothelial function by targeting endothelial oxidative stress and inflammation.

Inhibition of endoplasmic reticulum stress combined with activation of angiotensin-converting enzyme 2: novel approach for the prevention of endothelial dysfunction in type 1 diabetic rats

Persistent hyperglycemia in type 1 diabetes triggers numerous signaling pathways, which may prove deleterious to the endothelium. As hyperglycemia damages the endothelial layer via multiple signaling pathways, including enhanced oxidative stress, downregulation of angiotensin-converting enzyme 2 signaling, and exacerbation of endoplasmic reticulum (ER) stress, it becomes difficult to prevent injury using monotherapy. Thus, the present study was conceived to evaluate the combined effect of ER stress inhibition along with angiotensin-converting enzyme 2 activation, two major contributors to hyperglycemia-induced endothelial dysfunction, in preventing endothelial dysfunction associated with type 1 diabetes. Streptozotocin-induced diabetic animals were treated with either diminazene aceturate (5 mg·kg-1 per day, p.o.) or tauroursodeoxycholic acid, sodium salt (200 mg·kg-1 per day i.p.), or both for 4 weeks. Endothelial dysfunction was evaluated using vasoreactivity assay, where acetylcholine-induced relaxation was assessed in phenylephrine pre-contracted rings. Combination therapy significantly improved vascular relaxation when compared with diabetic control as well as monotherapy. Restoration of nitrite levels along with prevention of collagen led to improved vasodilatation. Moreover, there was an overall reduction in aortic oxidative stress. We conclude that by simultaneously inhibiting ER stress and activating angiotensin-converting enzyme 2 deleterious effects of hyperglycemia on endothelium were significantly alleviated. This could serve as a novel strategy for the prevention of endothelial dysfunction.

Targeting inflammation and redox aberrations by perindopril attenuates methotrexate-induced intestinal injury in rats: Role of TLR4/NF-κB and c-Fos/c-Jun pro-inflammatory pathways and PPAR-γ/SIRT1 cytoprotective signals

AIMS

The use of methotrexate (MTX), a classical immunosuppressant and anti-cancer agent, is associated with multiple organ toxicities, including the intestinal injury. Components of the renin-angiotensin system are expressed in the intestinal epithelium and mucosal immune cells where they provoke pro-inflammatory and pro-oxidant action. The present study was conducted to investigate the potential ability of perindopril (PER), an angiotensin-converting enzyme inhibitor (ACEI), to attenuate MTX-induced intestinal injury with emphasis on the role of the pro-inflammatory TLR4/NF-κB and c-Fos/c-Jun pathways alongside PPAR-γ and SIRT1 cytoprotective signals.

MATERIALS AND METHODS

The intestinal injury was induced by a single-dose injection of 20 mg/kg of MTX i.p at the end of the 5th day. PER was administrated once daily in a dose of 1 mg/kg, i.p, for five days before MTX and five days later.

RESULTS

Herein, perindopril attenuated the intestinal injury as seen by lowering the histopathological aberrations and preserving the goblet cells in villi/crypts. These beneficial actions were associated with downregulating the expression of the pro-inflammatory angiotensin II, TNF-α, IL-1β, and IL-6 cytokines, alongside upregulating the anti-inflammatory angiotensin (1-7) and IL-10. At the molecular level, perindopril downregulated the TLR4/NF-κB and c-Fos/c-Jun pathways in inflamed intestine of rats. Moreover, it attenuated the pro-oxidant events by lowering intestinal MDA and boosting GSH, SOD, and GST antioxidants together with PPAR-γ and SIRT1 cytoprotective signals. The aforementioned findings were also highlighted using molecular docking and network pharmacology analysis.

CONCLUSIONS

Perindopril demonstrated notable mitigation of MTX-induced intestinal injury through suppression of TLR4/NF-κB and c-Fos/c-Jun pathways alongside the augmentation of PPAR-γ/SIRT1 cytoprotective signals.

Research Progress on Pulmonary Arterial Hypertension and the Role of the Angiotensin Converting Enzyme 2-Angiotensin-(1-7)-Mas Axis in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex aetiology and high mortality. Functional and structural changes in the small pulmonary arteries lead to elevated pulmonary arterial pressure, resulting in right heart failure. The pathobiology of PAH is not fully understood, and novel treatment targets in PAH are desperately needed. The renin-angiotensin system is critical for maintaining homeostasis of the cardiovascular system. The system consists of the angiotensin converting enzyme (ACE)-angiotensin (Ang) II-angiotensin type 1 receptor (AT₁R) axis and the ACE2-Ang-(1-7)-Mas receptor axis. The former, the ACE-Ang II-AT₁R axis, is involved in vasoconstrictive and hypertensive actions along with cardiac and vascular remodelling. The latter, the ACE2-Ang-(1-7)-Mas axis, generally mediates counterbalancing effects against those mediated by the ACE-Ang II-AT₁R axis. Based on established functions, the ACE2-Ang-(1-7)-Mas axis may represent a novel target for the treatment of PAH. This review focuses on recent advances in pulmonary circulation science and the role of the ACE2-Ang-(1-7)-Mas axis in PAH.

Angiotensin 1-7 prevents the excessive force loss resulting from 14- and 28-day denervation in mouse EDL and soleus muscle

Denervation leads to muscle atrophy, which is described as muscle mass and force loss, the latter exceeding expectation from mass loss. The objective of this study was to determine the efficiency of angiotensin (Ang) 1–7 at reducing muscle atrophy in mouse extensor digitorum longus (EDL) and soleus following 14- and 28-d denervation periods. Some denervated mice were treated with Ang 1–7 or diminazene aceturate (DIZE), an ACE2 activator, to increase Ang 1–7 levels. Ang 1–7/DIZE treatment had little effect on muscle mass loss and fiber cross-sectional area reduction. Ang 1–7 and DIZE fully prevented the loss of tetanic force normalized to cross-sectional area and accentuated the increase in twitch force in denervated muscle. However, they did not prevent the shift of the force–frequency relationship toward lower stimulation frequencies. The Ang 1–7/DIZE effects on twitch and tetanic force were completely blocked by A779, a MasR antagonist, and were not observed in MasR^−/− muscles. Ang 1–7 reduced the extent of membrane depolarization, fully prevented the loss of membrane excitability, and maintained the action potential overshoot in denervated muscles. Ang 1–7 had no effect on the changes in α-actin, myosin, or MuRF-1, atrogin-1 protein content or the content of total or phosphorylated Akt, S6, and 4EPB. This is the first study that provides evidence that Ang 1–7 maintains normal muscle function in terms of maximum force and membrane excitability during 14- and 28-d periods after denervation.

A comprehensive guide to the pharmacologic regulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 entry receptor

The recent emergence of coronavirus disease-2019 (COVID-19) as a global pandemic has prompted scientists to address an urgent need for defining mechanisms of disease pathology and treatment. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, employs angiotensin converting enzyme 2 (ACE2) as its primary target for cell surface attachment and likely entry into the host cell. Thus, understanding factors that may regulate the expression and function of ACE2 in the healthy and diseased body is critical for clinical intervention. Over 66% of all adults in the United States are currently using a prescription drug and while earlier findings have focused on possible upregulation of ACE2 expression through the use of renin angiotensin system (RAS) inhibitors, mounting evidence suggests that various other widely administered drugs used in the treatment of hypertension, heart failure, diabetes mellitus, hyperlipidemias, coagulation disorders, and pulmonary disease may also present a varied risk for COVID-19. Specifically, we summarize mechanisms on how heparin, statins, steroids and phytochemicals, besides their established therapeutic effects, may also interfere with SARS-CoV-2 viral entry into cells. We also describe evidence on the effect of several vitamins, phytochemicals, and naturally occurring compounds on ACE2 expression and activity in various tissues and disease models. This comprehensive review aims to provide a timely compendium on the potential impact of commonly prescribed drugs and pharmacologically active compounds on COVID-19 pathology and risk through regulation of ACE2 and RAS signaling.

Xanthenone, ACE2 activator, counteracted gentamicin-induced nephrotoxicity in rats: Impact on oxidative stress and ACE2/Ang-(1-7) signaling

Nephrotoxicity is a rapid deterioration of kidney function due to exposure to nephrotoxic drugs as gentamicin. Gentamicin increases the generation of reactive oxygen species (ROS) leading to inflammatory responses and nuclear factor-κB (NF-κB) activation. The renal renin-angiotensin system (RAS) is considered a crucial regulator for physiological homeostasis and disease progression through the classic ACE/Ang-II/AT1 axis and its antagonist, ACE2/Ang-(1-7)/Mas axis which exerts an important role in the kidney. The present study evaluates the protective effects of the angiotensin-converting enzyme 2 (ACE2) activator; xanthenone; against experimental nephrotoxicity induced by gentamicin. Rats were divided into 4 groups, normal control, xanthenone (2 mg/kg, s.c), gentamicin (100 mg/kg, i.p. for one week) and xanthenone + gentamicin groups. Blood urea nitrogen (BUN) and serum creatinine levels were measured. The kidney tissues were used for estimating glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), NF-κB, Angiotensin II (AngII), and Ang-(1-7). In addition, histopathological examination and Western blot analysis of ACE2 expression were done. Xanthenone significantly restored serum levels of BUN and creatinine. Xanthenone exerted significant antioxidant effect as revealed by increased GSH content and SOD activity together with reduced MDA content. It exerted anti-inflammatory effect by significant reduction in TNF-α, NF-κB and IL-6 expression compared to gentamicin group. Xanthenone increased Ang-(1-7) and ACE2 expression while significantly decreased Ang-II expression. Histopathologically, xanthenone markedly counteracted gentamicin-induced renal aberrations. Activation of ACE2/Ang-(1-7) by xanthenone produced significant antioxidant and anti-inflammatory effects that counteracted gentamicin-induced nephrotoxicity.

Brain angiotensin converting enzyme-2 in central cardiovascular regulation

The brain renin-angiotensin system (RAS) plays an important role in the regulation of autonomic and neuroendocrine functions, and maintains cardiovascular homeostasis. Ang-II is the major effector molecule of RAS and exerts most of its physiological functions, including blood pressure (BP) regulation, via activation of AT1 receptors. Dysregulation of brain RAS in the central nervous system results in increased Ang-II synthesis that leads to sympathetic outflow and hypertension. Brain angiotensin (Ang) converting enzyme-2 (ACE2) was discovered two decades ago as an RAS component, exhibiting a counter-regulatory role and opposing the adverse cardiovascular effects produced by Ang-II. Studies using synthetic compounds that can sustain the elevation of ACE2 activity or genetically overexpressed ACE2 in specific brain regions found various beneficial effects on cardiovascular function. More recently, ACE2 has been shown to play critical roles in neuro-inflammation, gut dysbiosis and the regulation of stress and anxiety-like behaviors. In the present review, we aim to highlight the anatomical locations and functional implication of brain ACE2 related to its BP regulation via modulation of the sympathetic nervous system and discuss the recent developments and future directions in the ACE2-mediated central cardiovascular regulation.

Ginsenoside Rc Ameliorates Endothelial Insulin Resistance via Upregulation of Angiotensin-Converting Enzyme 2

Type 2 diabetes mellitus (T2DM) is a major health concern which may cause cardiovascular complications. Insulin resistance (IR), regarded as a hallmark of T2DM, is characterized by endothelial dysfunction. Ginsenoside Rc is one of the main protopanaxadiol-type saponins with relatively less research on it. Despite researches confirming the potent anti-inflammatory and antioxidant activities of ginsenoside Rc, the potential benefits of ginsenoside Rc against vascular complications have not been explored. In the present study, we investigated the effects of ginsenoside Rc on endothelial IR and endothelial dysfunction with its underlying mechanisms using high glucose- (HG-) cultured human umbilical vein endothelial cells (HUVECs) in vitro and a type 2 diabetic model of db/db mice in vivo. The results showed that ginsenoside Rc corrected the imbalance of vasomotor factors, reduced the production of Ang (angiotensin) II, and activated angiotensin-converting enzyme 2 (ACE2)/Ang-(1–7)/Mas axis in HG-treated HUVECs. Besides, ginsenoside Rc improved the impaired insulin signaling pathway and repressed oxidative stress and inflammatory pathways which constitute key factors leading to IR. Interestingly, the effects of ginsenoside Rc on HG-induced HUVECs were abolished by the selective ACE2 inhibitor MLN-4760. Furthermore, ginsenoside Rc exhibited anti-inflammatory as well as antioxidant properties and ameliorated endothelial dysfunction via upregulation of ACE2 in db/db mice, which were confirmed by the application of MLN-4760. In conclusion, our findings reveal a novel action of ginsenoside Rc and demonstrate that ginsenoside Rc ameliorated endothelial IR and endothelial dysfunction, at least in part, via upregulation of ACE2 and holds promise for the treatment of diabetic vascular complications.

ACE2/Ang-(1-7)/Mas1 axis and the vascular system: vasoprotection to COVID-19-associated vascular disease

The two axes of the renin-angiotensin system include the classical ACE/Ang II/AT1 axis and the counter-regulatory ACE2/Ang-(1-7)/Mas1 axis. ACE2 is a multifunctional monocarboxypeptidase responsible for generating Ang-(1-7) from Ang II. ACE2 is important in the vascular system where it is found in arterial and venous endothelial cells and arterial smooth muscle cells in many vascular beds. Among the best characterized functions of ACE2 is its role in regulating vascular tone. ACE2 through its effector peptide Ang-(1-7) and receptor Mas1 induces vasodilation and attenuates Ang II-induced vasoconstriction. In endothelial cells activation of the ACE2/Ang-(1-7)/Mas1 axis increases production of the vasodilator's nitric oxide and prostacyclin's and in vascular smooth muscle cells it inhibits pro-contractile and pro-inflammatory signaling. Endothelial ACE2 is cleaved by proteases, shed into the circulation and measured as soluble ACE2. Plasma ACE2 activity is increased in cardiovascular disease and may have prognostic significance in disease severity. In addition to its enzymatic function, ACE2 is the receptor for severe acute respiratory syndrome (SARS)-coronavirus (CoV) and SARS-Cov-2, which cause SARS and coronavirus disease-19 (COVID-19) respectively. ACE-2 is thus a double-edged sword: it promotes cardiovascular health while also facilitating the devastations caused by coronaviruses. COVID-19 is associated with cardiovascular disease as a risk factor and as a complication. Mechanisms linking COVID-19 and cardiovascular disease are unclear, but vascular ACE2 may be important. This review focuses on the vascular biology and (patho)physiology of ACE2 in cardiovascular health and disease and briefly discusses the role of vascular ACE2 as a potential mediator of vascular injury in COVID-19.

ACE2 in the renin-angiotensin system

In 2020 we are celebrating the 20th anniversary of the angiotensin-converting enzyme 2 (ACE2) discovery. This event was a landmark that shaped the way that we see the renin-angiotensin system (RAS) today. ACE2 is an important molecular hub that connects the RAS classical arm, formed mainly by the octapeptide angiotensin II (Ang II) and its receptor AT1, with the RAS alternative or protective arm, formed mainly by the heptapeptides Ang-(1-7) and alamandine, and their receptors, Mas and MrgD, respectively. In this work we reviewed classical and modern literature to describe how ACE2 is a critical component of the protective arm, particularly in the context of the cardiac function, coagulation homeostasis and immune system. We also review recent literature to present a critical view of the role of ACE2 and RAS in the SARS-CoV-2 pandemic.

Targeting Neprilysin (NEP) pathways: A potential new hope to defeat COVID-19 ghost

COVID-19 is an ongoing viral pandemic disease that is caused by SARS-CoV2, inducing severe pneumonia in humans. However, several classes of repurposed drugs have been recommended, no specific vaccines or effective therapeutic interventions for COVID-19 are developed till now. Viral dependence on ACE-2, as entry receptors, drove the researchers into RAS impact on COVID-19 pathogenesis. Several evidences have pointed at Neprilysin (NEP) as one of pulmonary RAS components. Considering the protective effect of NEP against pulmonary inflammatory reactions and fibrosis, it is suggested to direct the future efforts towards its potential role in COVID-19 pathophysiology. Thus, the review aimed to shed light on the potential beneficial effects of NEP pathways as a novel target for COVID-19 therapy by summarizing its possible molecular mechanisms. Additional experimental and clinical studies explaining more the relationships between NEP and COVID-19 will greatly benefit in designing the future treatment approaches.

Vasculopathy and Coagulopathy Associated with SARS-CoV-2 Infection

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has resulted in > 500,000 deaths worldwide, including > 125,000 deaths in the U.S. since its emergence in late December 2019 and June 2020. Neither curative anti-viral drugs nor a protective vaccine is currently available for the treatment and prevention of COVID-19. Recently, new clinical syndromes associated with coagulopathy and vasculopathy have emerged as a cause of sudden death and other serious clinical manifestations in younger patients infected with SARS-CoV-2 infection. Angiotensin converting enzyme 2 (ACE2), the receptor for SARS-CoV-2 and other coronaviruses, is a transmembrane protein expressed by lung alveolar epithelial cells, enterocytes, and vascular endothelial cells, whose physiologic role is to induce the maturation of angiotensin I to generate angiotensin 1-7, a peptide hormone that controls vasoconstriction and blood pressure. In this review, we provide the general context of the molecular and cellular mechanisms of SARS-CoV-2 infection with a focus on endothelial cells, describe the vasculopathy and coagulopathy syndromes in patients with SARS-CoV-2, and outline current understanding of the underlying mechanistic aspects.

Endoplasmic reticulum stress and focused drug discovery in cardiovascular disease

Endoplasmic reticulum (ER) is an intracellular membranous organelle involved in the synthesis, folding, maturation and post-translation modification of secretory and transmembrane proteins. Therefore, ER is closely related to the maintenance of intracellular homeostasis and the good balance between health and diseases. Endoplasmic reticulum stress (ERS) occurs when unfolded/misfolded proteins accumulate after disturbance of ER environment. In response to ERS, cells trigger an adaptive response called the Unfolded protein response (UPR), which helps cells cope with the stress. In recent years, a large number of studies show that ERS can aggravate cardiovascular diseases. ERS-related proteins expression in cardiovascular diseases is on the rise. Therefore, down-regulation of ERS is critical for alleviating symptoms of cardiovascular diseases, which may be used in the near future to treat cardiovascular diseases. This article reviews the relationship between ERS and cardiovascular diseases and drugs that inhibit ERS. Furthermore, we detail the role of ERS inhibitors in the treatment of cardiovascular disease. Drugs that inhibit ERS are considered as promising strategies for the treatment of cardiovascular diseases.

The potential actions of angiotensin-converting enzyme II (ACE2) activator diminazene aceturate (DIZE) in various diseases

The renin angiotensin system (RAS) regulates fluid balance, blood pressure and maintains vascular tone. The potent vasoconstrictor angiotensin II (Ang II) produced by angiotensin-converting enzyme (ACE) comprises the classical RAS. The non-classical RAS involves the conversion of Ang II via ACE2 into the vasodilator Ang (1-7) to counterbalance the effects of Ang II. Furthermore, ACE2 converts AngA into another vasodilator named alamandine. The over activation of the classical RAS (increased vasoconstriction) and depletion of the non-classical RAS (decreased vasodilation) results in vascular dysfunction. Vascular dysfunction is the leading cause of atherosclerosis and cardiovascular disease (CVD). Additionally, local RAS is expressed in various tissues and regulates cellular functions. RAS dysregulation is involved in other several diseases such as inflammation, renal dysfunction and even cancer growth. An approach in restoring vascular dysfunction and other pathological diseases is to either increase the activity of ACE2 or reduce the effect of the classical RAS by counterbalancing Ang II effects. The antitrypanosomal agent, diminazene aceturate (DIZE), is one approach in activating ACE2. DIZE has been shown to exert beneficial effects in CVD experimental models of hypertension, myocardial infarction, type 1 diabetes and atherosclerosis. Thus, this review focuses on DIZE and its effect in several tissues such as blood vessels, cardiac, renal, immune and cancer cells.

Local angiotensin-(1-7) administration improves microvascular endothelial function in women who have had preeclampsia

Despite remission of clinical symptoms postpartum, women who have had preeclampsia demonstrate microvascular endothelial dysfunction, mediated in part by increased sensitivity to angiotensin II (ANG II). Angiotensin-(1-7) [Ang-(1-7)] is an endogenous inhibitor of the actions of ANG II and plausible druggable target in women who had preeclampsia. We therefore examined the therapeutic potential of Ang-(1-7) in the microvasculature of women with a history of preeclampsia (PrEC; n = 13) and parity-matched healthy control women (HC; n = 13) hypothesizing that administration of Ang-(1-7) would increase endothelium-dependent dilation and nitric oxide (NO)-dependent dilation and decrease ANG II-mediated constriction in PrEC. Using the cutaneous microcirculation, we assessed endothelium-dependent vasodilator function in response to graded infusion of acetylcholine (ACh; 10-7 to 102 mmol/L) in control sites and sites treated with 15 mmol/L NG-nitro-l-arginine methyl ester (l-NAME; NO-synthase inhibitor), 100 µmol/L Ang-(1-7), or 15 mmol/L l-NAME + 100 µmol/L Ang-(1-7). Vasoconstrictor function was measured in response to ANG II (10-20-10-4 mol/L) in control sites and sites treated with 100 µmol/L Ang-(1-7). PrEC had reduced endothelium-dependent dilation (P < 0.001) and NO-dependent dilation (P = 0.04 vs. HC). Ang-(1-7) coinfusion augmented endothelium-dependent dilation (P < 0.01) and NO-dependent dilation (P = 0.03) in PrEC but had no effect in HC. PrEC demonstrated augmented vasoconstrictor responses to ANG II (P < 0.01 vs. HC), which was attenuated by coinfusion of Ang-(1-7) (P < 0.001). Ang-(1-7) increased endothelium-dependent vasodilation via NO synthase-mediated pathways and attenuated ANG II-mediated constriction in women who have had preeclampsia, suggesting that Ang-(1-7) may be a viable therapeutic target for improved microvascular function in women who have had a preeclamptic pregnancy.

Potential of Renin-Angiotensin-Aldosterone System Modulations in Diabetic Kidney Disease: Old Players to New Hope!

Due to a tragic increase in the incidences of diabetes globally, diabetic kidney disease (DKD) has emerged as one of the leading causes of end-stage renal diseases (ESRD). Hyperglycaemia-mediated overactivation of the renin-angiotensin-aldosterone system (RAAS) is key to the development and progression of DKD. Consequently, RAAS inhibition by angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) is the first-line therapy for the clinical management of DKD. However, numerous clinical and preclinical evidences suggested that RAAS inhibition can only halt the progression of the DKD to a certain extent, and they are inadequate to cure DKD completely. Recent studies have improved understanding of the complexity of the RAAS. It consists of two counter-regulatory arms, the deleterious pressor arm (ACE/angiotensin II/AT1 receptor axis) and the beneficial depressor arm (ACE2/angiotensin-(1-7)/Mas receptor axis). These advances have paved the way for the development of new therapies targeting the RAAS for better treatment of DKD. In this review, we aimed to summarise the involvement of the depressor arm of the RAAS in DKD. Moreover, in modern drug discovery and development, an advance approach is the bispecific therapeutics, targeting two independent signalling pathways. Here, we discuss available reports of these bispecific drugs involving the RAAS as well as propose potential treatments based on neurohormonal balance as credible therapeutic strategies for DKD.

Onion bulb extract reduces colitis severity in mice via modulation of colonic inflammatory pathways and the apoptotic machinery

ETHNOPHARMACOLOGICAL RELEVANCE

The use of nutraceutical-based products has increased in recent years due to their demonstrated efficacy and their good safety profile. Onion is one of the most commonly used plants in the traditional medicine for the management of various conditions including inflammatory and gastrointestinal diseases. However, little is known regarding the molecular mechanism of the anti-inflammatory effects of onion particularly in inflammatory bowel disease (IBD).

AIM OF THE STUDY

To test the anti-inflammatory effects of onion bulb extract (OBE) in an IBD mouse model and the molecular mechanisms responsible for these effects such as modulation of the expression and/or the activity profile of various pro-inflammatory molecules.

MATERIALS AND METHODS

Colitis was induced in mice by dextran sulfate sodium (DSS) daily administration for 5 days. Animals were sacrificed, colons were removed and the severity of the inflammation was determined by the gross and histological assessments. The colonic level/activity of various cytokines and chemokines were measured using proteome profiling-based assay, western blotting, and immunofluorescence techniques.

RESULTS

DSS-induced colitis was significantly reduced by the daily OBE treatment and 5-aminosalicylic acid (5-ASA, positive control), particularly at 100-200 mg/kg doses, at both the gross and histological levels. OBE was also shown to reduce colonic expression and activity of several pro-inflammatory molecules and signaling pathways, such as mitogen activated protein kinase family, mammalian target of rapamycin, cyclooxygenase-2, and tissue inhibitors of metalloproteinases. In addition, OBE reduced the expression of interferon-γ, various C-C and C-X-C chemokines, and molecules involved in the apoptotic machinery such as cytochrome c, caspase-3 and -8, B-cell lymphoma-extra-large and -2.

CONCLUSIONS

OBE showed anti-inflammatory actions in IBD mouse model, which is attributed, in part, to the modulation of the expression and the activity of important pro-inflammatory molecules and signaling pathways involved in the inflammatory response. These data suggest that OBE may be a promising lead in the therapeutic management of IBD.

Effects of granulocyte colony‑stimulating factor on rabbit carotid and porcine heart models of chronic obliterative arterial disease

Previous studies suggest that granulocyte colony‑stimulating factor (G‑CSF) can promote bone marrow derived progenitor cells to mediate cardiovascular repair, potentially reversing mechanical dysfunction in chronic ischaemic heart disease and post myocardial infarction. Two models were used in the present study both using a surgical ameroid constrictor to induce arterial stenosis. The first model used the carotid artery of rabbits. They were divided into high fat diet (inducing atherosclerosis) or normal fat diet (control) groups. Each was subdivided into surgical exposure group without constrictor, ameroid constrictor receiving normal saline or receiving G‑CSF 15 µg/kg/day. Endothelial markers of endothelial nitric oxide synthase and endothelin 1 were increased by the use of ameroid constrictor in both atherosclerotic and non‑atherosclerotic mice, however were not further altered by G‑CSF. Scanning electron microscopy indicated that ameroid constrictor application altered endothelial morphology from an oval shape to a round shape and this was more prominent in the atherosclerotic compared with the non‑atherosclerotic group. G‑CSF injection increased the number of endothelial cells in all groups. The second model used the left coronary artery of pigs. They were equally divided into following groups, receiving normal saline (control), G‑CSF 2.5 µg/kg/day (low dose), 5 µg/kg/day (medium dose) and 10 µg/kg/day (high dose) for 5 days. G‑CSF at a low or high dose worsened intimal hyperplasia however at a medium dose improved it. In conclusion, G‑CSF had no effect in a rabbit carotid artery model of atherosclerosis. Its effects on the porcine heart were dose‑dependent; arterial disease worsened at a low or high dose, but improved at a medium dose.

Imbalance between Angiotensin II - Angiotensin (1-7) system is associated with vascular endothelial dysfunction and inflammation in type 2 diabetes with newly diagnosed hypertension

AIM

Diabetes is associated with Renin-angiotensin-aldosterone-system (RAAS) activation. Protective role of Angiotensin (1-7) has been recently identified. The study aims to identify associations between imbalance in RAAS components with vascular endothelial dysfunction and inflammation in diabetics with newly diagnosed hypertension.

METHODS

Brachial Flow-mediated-dilation (FMD), Carotid Intima-media-thickness (CIMT), pulse-wave-velocity (PWV), Serum E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), high-sensitivity C-Reactive Protein (hsCRP), Interleukin-10 (IL-10), Renin, AngiotensinII, Angiotensin-Converting-Enzyme 2 (ACE2) and Angiotensin1-7 were measured in 60 diabetic patients with newly diagnosed hypertension. Patients with AngiotensinII/Angiotensin1-7 ratio <1 were classified as Favourable-Axis (FA) group (n = 22) and those with ratio >1 were classified as Unfavourable-Axis (UA) group (n = 38).

RESULTS

hsCRP was higher [9.52 (4.64-16.19) vs 3.62 (1.77-13.09) (mg/l), p = 0.04], IL-10 was lower [2.26 (1.34-12.05) vs 10.98 (4.44-17.78) (pg/ml),p = 0.006], %FMD was lower [(5.51 ± 2.97) vs (7.66 ± 3.38) (%), p = 0.01] and CIMT was higher in UA compared to FA group [0.7 (0.55-0.79) vs 0.51 (0.49-0.65) (mm), p = 0.001]. Renin correlated positively with pressure, PWV, E-selectin and VCAM-1, opposing associations were obtained for Angiotensin1-7 and ACE2.

CONCLUSION

Imbalance between AngiotensinII - Angiotensin1-7 is associated with increased inflammation and vascular dysfunction in diabetics and can contribute to development of hypertension in these patients.

Fenofibrate improves vascular endothelial function in diabetic mice

Microvascular and macrovascular complications are major causes of disability and death in diabetic patients. High levels of blood glucose sabotage the integrity of blood vessels and induce endothelial dysfunction. Fenofibrate is an agonist of peroxisome proliferator-activated receptor α and can reduce the incidence of cardiovascular events in diabetic patients. This study tested the hypothesis that fenofibrate could ameliorate endothelium-dependent vasodilation in diabetic mice and relieve high glucose-induced endothelial dysfunction via activating endothelial nitric oxide synthase (eNOS) and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. A streptozotocin (STZ)-induced diabetic model was established by intraperitoneal injection of STZ (dissolved in sodium citrate buffer) at a dose of 60 mg/kg for 5 consecutive days. Mice were administered fenofibrate (100 mg/kg/d, i.g.) for 14 days. The endothelial function of extracted mouse aortae was examined by evaluating acetylcholine induced endothelium-dependent relaxation combined with phenylephrine-induced vasoconstriction and sodium nitroprusside-induced endothelium-independent relaxation. Superoxide onion (O₂^-) was determined using dihydroethidium staining of aortae. Functions of mouse aortic endothelial cells (MAECs) were assessed, and expression levels of eNOS and AMPK were determined by Western blotting. Fenofibrate ameliorated the impaired endothelium-dependent relaxation in diabetic mice and decreased the level of intracellular O₂- in diabetic mouse aortae. In-vitro, fenofibrate treatment improved the impaired function of MAECs, increased nitric oxide production, and decreased the O₂- level, as well as activated eNOS and AMPK phosphorylation in cultured MAECs by high glucose. Fenofibrate could ameliorate endothelium-dependent vasodilation in diabetic mice and relieve high glucose-induced endothelial dysfunction, which was possibly related to the activation of eNOS and AMPK phosphorylation.

AVE 0991 attenuates oxidative stress and neuronal apoptosis via Mas/PKA/CREB/UCP-2 pathway after subarachnoid hemorrhage in rats

Oxidative stress and neuronal apoptosis have been demonstrated to be key features in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Previous studies have indicated that Mas receptor activation initiates an anti-oxidative and anti-apoptotic role in the brain. However, whether Mas activation can attenuate oxidative stress and neuronal apoptosis after SAH remains unknown. To investigate the beneficial effect of Mas on oxidative stress injury and neuronal apoptosis induced by SAH, a total of 196 rats were subjected to an endovascular perforation model of SAH. AVE 0991 (AVE), a selective agonist of Mas, was administered intranasally 1 h after SAH induction. A779, a selective inhibitor of Mas, and small interfering ribonucleic acid (siRNA) for UCP-2 were administered by intracerebroventricular (i.c.v) injection at 1 h and 48 h before SAH induction respectively. Neurological tests, immunofluorescence, TUNEL, Fluoro-Jade C, DHE staining, and Western blot experiments were performed. We found that Mas activation with AVE significantly improved neurobehavioral scores and reduced oxidative stress and neuronal apoptosis in SAH+AVE group compared with SAH+vehicle group. Moreover, AVE treatment significantly promoted phosphorylation of CREB and the expression UCP-2, as well as upregulated expression of Bcl-2 and downregulation of Romo-1 and Bax. The protective effects of AVE were reversed by i.c.v injection of A779 and UCP-2 siRNA in SAH+AVE+A779 and SAH+AVE+UCP-2 siRNA groups, respectively. In conclusion, our data provides evidence that Mas activation with AVE reduces oxidative stress injury and neuronal apoptosis through Mas/PKA/p-CREB/UCP-2 pathway after SAH. Furthermore, our study indicates that Mas may be a novel therapeutic treatment target in early brain injury of SAH.

ACE2 activator diminazene aceturate reduces adiposity but preserves lean mass in young and old rats

The obesity epidemic is multi-generational and is particularly debilitating in the aging population, necessitating the use of pharmaceutical interventions. Recent evidence suggests that increasing the activity of the angiotensin converting enzyme-2 [ACE2]/angiotensin-(1-7)[Ang-(1-7)]/Mas receptor (MasR) axis in obese animal models leads to significant reductions in body weight. It was hypothesized that activation of ACE2 via diminazene aceturate (DIZE) will significantly reduce body weight of rats fed a high fat diet. Young and old (4 and 23 months, respectively) male Fisher 344 × Brown Norway rats were fed 60% high fat diet for one week, and subsequently given either 15 mg/kg/day DIZE s.c. or vehicle for three weeks. DIZE treatment resulted in a significant reduction of food intake and body weight in both young and old animals. However, that decrease was so dramatic in the older animals that they all nearly stopped eating. Interestingly, the TD-NMR assessments revealed that the weight-loss was primarily a result of decreased body fat percentage, with a relative preservation of lean mass. Tissue weights confirm the significant loss of white adipose tissue (WAT), with no change in muscle weights. Gene expression and serum ACE2 activity analyses implied that increased activation of the ACE2/Ang-(1-7)/MasR axis plays a role in reducing fat mass. Collectively, our results suggest that DIZE may be a useful tool in the study of obesity; however, caution is recommended when using this compound in older animals due to severe anorectic effects, although there is a mechanism by which muscle is preserved.

A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a deadly disease with no cure. Alternate conversion of angiotensin II (AngII) to angiotensin-(1-7) (Ang-(1-7)) by angiotensin-converting enzyme 2 (ACE2) resulting in Mas receptor (Mas1) activation improves rodent models of PAH. Effects of recombinant human (rh) ACE2 in human PAH are unknown. Our objective was to determine the effects of rhACE2 in PAH.We defined the molecular effects of Mas1 activation using porcine pulmonary arteries, measured AngII/Ang-(1-7) levels in human PAH and conducted a phase IIa, open-label pilot study of a single infusion of rhACE2 (GSK2586881, 0.2 or 0.4 mg·kg^-1 intravenously).Superoxide dismutase 2 (SOD2) and inflammatory gene expression were identified as markers of Mas1 activation. After confirming reduced plasma ACE2 activity in human PAH, five patients were enrolled in the trial. GSK2586881 was well tolerated with significant improvement in cardiac output and pulmonary vascular resistance. GSK2586881 infusion was associated with reduced plasma markers of inflammation within 2-4 h and increased SOD2 plasma protein at 2 weeks.PAH is characterised by reduced ACE2 activity. Augmentation of ACE2 in a pilot study was well tolerated, associated with improved pulmonary haemodynamics and reduced markers of oxidant and inflammatory mediators. Targeting this pathway may be beneficial in human PAH.

Isolated heart models for studying cardiac electrophysiology: a historical perspective and recent advances

Experimental models used in cardiovascular research range from cellular to whole heart preparations. Isolated whole hearts show higher levels of structural and functional integration than lower level models such as tissues or cellular fragments. Cardiovascular diseases are multi-factorial problems that are dependent on highly organized structures rather than on molecular or cellular components alone. This article first provides a general introduction on the animal models of cardiovascular diseases. It is followed by a detailed overview and a historical perspective of the different isolated heart systems with a particular focus on the Langendorff perfusion method for the study of cardiac arrhythmias. The choice of species, perfusion method, and perfusate composition are discussed in further detail with particular considerations of the theoretical and practical aspects of experimental settings.

Ang-(1-7) protects HUVECs from high glucose-induced injury and inflammation via inhibition of the JAK2/STAT3 pathway

Angiotensin (Ang)‑1‑7, which is catalyzed by angiotensin‑converting enzyme 2 (ACE2) from angiotensin‑II (Ang‑II), exerts multiple biological and pharmacological effects, including cardioprotective effects and endothelial protection. The Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway has been demonstrated to be involved in diabetes‑associated cardiovascular complications. The present study hypothesized that Ang‑(1‑7) protects against high glucose (HG)‑induced endothelial cell injury and inflammation by inhibiting the JAK2/STAT3 pathway in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with 40 mmol/l glucose (HG) for 24 h to establish a model of HG‑induced endothelial cell injury and inflammation. Protein expression levels of p‑JAK2, t‑JAK2, p‑STAT3, t‑STAT3, NOX‑4, eNOS and cleaved caspase‑3 were tested by western blotting. CCK‑8 assay was performed to assess cell viability of HUVECs. Apoptotic cell death was analyzed by Hoechst 33258 staining. Mitochondrial membrane potential (MMP) was obtained using JC‑1. Superoxide dismutase (SOD) activity was tested by SOD assay kit. Interleukin (IL)‑1β, IL‑10, IL‑12 and TNF‑α levels in culture media were tested by ELISA. The findings demonstrated that exposure of HUVECs to HG for 24 h induced injury and inflammation. This injury and inflammation were significantly ameliorated by pre‑treatment of cells with either Ang‑(1‑7) or AG490, an inhibitor of the JAK2/STAT3 pathway, prior to exposure of the cells to HG. Exposure of the cells to HG also increased the phosphorylation of JAK2/STAT3 (p‑JAK2 and p‑STAT3). Increased activation of the JAK2/STAT3 pathway was attenuated by pre‑treatment with Ang‑(1‑7). To the best of our knowledge, the findings from the present study provided the first evidence that Ang‑(1‑7) protects against HG‑induced injury and inflammation by inhibiting activation of the JAK2/STAT3 pathway in HUVECs.

Inhibition of miR-92a Suppresses Oxidative Stress and Improves Endothelial Function by Upregulating Heme Oxygenase-1 in db/db Mice

AIMS

Inhibition of microRNA-92a (miR-92a) is reported to suppress endothelial inflammation and delay atherogenesis. We hypothesize that miR-92a inhibition protects endothelial function through suppressing oxidative stress in diabetic db/db mice.

RESULTS

In this study, we found elevated expression of miR-92a in aortic endothelium from db/db mice and in renal arteries from diabetic subjects. Endothelial cells (ECs) exposed to advanced glycation end products (AGEs) and oxidized low-density lipoprotein express higher level of miR-92a. Overexpression of miR-92a impairs endothelium-dependent relaxations (EDRs) in C57BL/6 mouse aortas. Overexpression of miR-92a suppresses expression of heme oxygenase-1 (HO-1), a critical cytoprotective enzyme, whereas inhibition of miR-92a increases HO-1 expression in human umbilical vein ECs (HUVECs) and db/db mouse aortas. Importantly, miR-92a inhibition by Ad-anti-miR-92a improved EDRs and reduced reactive oxygen species (ROS) production in db/db mouse aortas. HO-1 inhibition by SnMP or HO-1 knockdown by shHO-1 reversed the suppressive effect of miR-92a inhibition on ROS production induced by AGE treatment in C57BL/6 mouse aortas. In addition, SnMP reversed miR-92a inhibition-induced improvement of EDRs in AGE-treated C57BL/6 mouse aortas and in db/db mouse aortas.

INNOVATION

Expression of miR-92a is increased in diabetic aortic endothelium and inhibition of miR-92a exerts vasoprotective effect in diabetic mice through HO-1 upregulation in ECs.

CONCLUSION

MiR-92a expression is elevated in diabetic ECs. MiR-92a overexpression impairs endothelial function and suppresses HO-1 expression in ECs. Inhibition of miR-92a attenuates oxidative stress and improves endothelial function through enhancing HO-1 expression and activity in db/db mouse aortas. Antioxid. Redox Signal. 28, 358-370.

Angiotensin converting enzyme 2 and diminazene: role in cardiovascular and blood pressure regulation

PURPOSE OF REVIEW

Angiotensin converting enzyme 2 (ACE2) is an important regulator of the renin-angiotensin system through actions to degrade angiotensin II. Loss of ACE2 can contribute to the development and progression of cardiovascular disease, and experimental studies have highlighted a beneficial role for novel therapeutic approaches that activate or replenish tissue ACE2. This review focuses on experimental studies that have used the off-target effects of the antitrypanosomal agent, diminazene aceturate (DIZE) to activate ACE2.

RECENT FINDINGS

In cardiovascular disease, activation of the classical renin-angiotensin system and depletion of ACE2 leads to pathophysiological changes. One approach to activate ACE2 involves the drug DIZE, which has been shown to have beneficial effects in experimental models of hypertension, pulmonary hypertension, myocardial infarction, stroke, atherosclerosis, type 1 diabetes, and eye disease. The precise mechanism of action of DIZE to activate ACE2 remains under scrutiny.

SUMMARY

Activation of ACE2 may represent an important therapeutic approach in cardiovascular disease. To date, most studies have focused on the off-target actions of DIZE, in experimental models of disease. More research is required to determine the exact mechanism of action of DIZE and evaluate its therapeutic potential in comparison with currently available clinical interventions. There are no clinical studies of DIZE, and its side-effects, and toxicity make such studies unlikely. Hence, new methods of selectively activating or replenishing ACE2 will be needed in the future if this approach is to be used in a clinical context.

Angiotensin-(1-7) Inhibits Thrombin-Induced Endothelial Phenotypic Changes and Reactive Oxygen Species Production via NADPH Oxidase 5 Downregulation

Background and Aims: The angiotensin-(1-7)/angiotensin-converting enzyme 2/Mas receptor axis counter-regulates the detrimental effects of angiotensin II. Beneficial effects of angiotensin-(1-7), including anti-inflammation, oxidative stress reduction, and anti-thrombosis, have been reported. Previous studies documented that ramipril decreased thrombin generation in human hypertension and that the anti-thrombotic effects of captopril and losartan were angiotensin-(1-7)-dependent, suggesting an interaction between thrombin and angiotensin-(1-7). However, it is not clear whether angiotensin-(1-7) can alleviate the endothelial phenotypic changes induced by thrombin. We have previously documented cytoskeleton remodeling, cell adhesion, and cell migration as dominant altered phenotypes in thrombin-stimulated human aortic endothelial cells (HAECs). In this study, we investigated whether angiotensin-(1-7) can modulate thrombin-induced phenotypic changes. Furthermore, we investigated whether NAPDH oxidase 5 (Nox5)-produced reactive oxygen species (ROS) play a significant role in angiotensin-(1-7)-mediated phenotypic changes.

Methods: HAECs were pretreated with 100 nM angiotensin-(1-7) for 1 h, followed by stimulation with 2 units/mL thrombin for different times. Immunofluorescent assay, monocyte adhesion assay, wound-healing assay, ROS assay, real-time PCR, Western blotting, and Nox5 siRNA transfection were conducted. HAECs were pretreated with the ROS scavenger N-acetylcysteine (NAC) to determine whether thrombin-induced phenotypic changes depended on ROS production.

Results: Angiotensin-(1-7) prevented thrombin-induced actin cytoskeleton derangements, monocyte adhesion, and migratory impairment. Nox5 siRNA transfection confirmed that thrombin-induced Nox5 expression stimulated ROS production and increased HO-1/NQO-1/ICAM-1/VCAM-1 gene expression, all of which were decreased by angiotensin-(1-7). Phenotypic changes induced by thrombin were prevented by NAC pretreatment.

Conclusion: Angiotensin-(1-7) prevents actin cytoskeleton derangement, monocyte adhesion, and migration impairment induced by thrombin via downregulation of ROS production. In addition, thrombin-induced Nox5 expression is involved in the production of ROS, and angiotensin-(1-7) decreases ROS through its inhibitory effect on Nox5 expression.

Angiotensin-converting enzyme 2-angiotensin (1-7)-Mas axis prevents pancreatic acinar cell inflammatory response via inhibition of the p38 mitogen-activated protein kinase/nuclear factor-κB pathway

The aim of the present study was to investigate the role of the angiotensin-converting enzyme (ACE)2-angiotensin‑(Ang)-(1-7)-Mas axis in the pathogenesis of pancreatitis and the association between this axis and the p38 mitogen-activated protein kinase (p38 MAPK)/nuclear factor (NF-κB) signaling pathway in pancreatic acinar cells. Mouse pancreatic acinar cancer (MPC-83) cells were stimulated with 10 nM caerulein (CAE) to create an in vitro model of acute pancreatitis, and collected for analysis at 2, 6, 12, 24 and 48 h post stimulation. In addition, cells were pretreated with different concentrations of Ang‑(1‑7), Ang‑(1‑7) antagonist A779, p38 MAPK inhibitor SB203580 or ACE2 inhibitor DX600 for 30 min, and then stimulated with CAE for 24 h. The ACE2, Mas receptor, p38 MAPK, phosphorylated (p)-p38 MAPK and NF-κB expression levels were evaluated using western blotting and immunofluorescence. p38 MAPK, NF-κB, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-8 and IL-10 mRNA expression levels were assessed using reverse transcription-quantitative polymerase chain reaction. The results of the immunofluorescence assay demonstrated that ACE2 and p38 MAPK were present mainly in the cytoplasm, while the Mas receptor was located mainly in the cell membrane. ACE2, p38 MAPK and p-p38 MAPK protein levels were significantly increased (P<0.05) following stimulation with CAE compared with those in the control group and peaked at 24 h. Mas receptor protein levels were significantly upregulated (P<0.05) between 6 and 24 h, peaking at 12 h. Ang‑(1‑7) and SB203580 downregulated p-p38 MAPK and NF-κB expression and the mRNA levels of inflammatory factors IL-6, TNF-α and IL-8, but upregulated the mRNA level of inflammatory factor IL-10 compared with those treated with CAE alone. These results were supported by the opposite outcomes observed for cells treated with A779 or DX600. Therefore, it was concluded that the ACE2-Ang‑(1‑7)-Mas axis significantly inhibits pancreatitis by inhibition of the p38 MAPK/NF-κB signaling pathway.

Anti-inflammatory action of angiotensin 1-7 in experimental colitis may be mediated through modulation of serum cytokines/chemokines and immune cell functions

We recently demonstrated Ang 1-7 reduced inflammation in the dextran sulfate sodium (DSS) colitis model. In this study we examined the effect of Ang 1-7 on modulation of plasma levels of selected cytokines and chemokines and immune cell effector functions (apoptosis, chemotaxis and superoxide release) in vitro. The degree of neutrophil recruitment to the colon was assessed by immunofluorescence and myeloperoxidase activity. Daily Ang 1-7 treatment at 0.01 mg/kg dose which previously ameliorated colitis severity, showed a significant reduction in circulating levels of several cytokines and chemokines, and neutrophil recruitment to the colonic tissue. It also significantly enhanced immune cell apoptosis, and reduced neutrophil chemotaxis and superoxide release in vitro. In contrast, daily administration of the Ang 1-7R antagonist A779 which previously worsened colitis severity showed significant up-regulation of specific mediators. Our results demonstrate a novel anti-inflammatory action of Ang 1-7 through modulation of plasma levels of cytokines/chemokines and immune cell activity.

Diminazene aceturate prevents nephropathy by increasing glomerular ACE2 and AT2 receptor expression in a rat model of type1 diabetes

BACKGROUND AND PURPOSE

One of the protective actions of angiotensin converting enzyme-2 (ACE2) is the inactivation of angiotensin II. Expression and activity of ACE2 was reduced in glomeruli of diabetic patients and in animal models of diabetes. Recently the potential role of recombinant ACE2 administration in preventing diabetic nephropathy (DN) has been shown. Here we have tested the effects of the ACE2 activator, diminazene aceturate (DIZE), in a model of DN.

EXPERIMENTAL APPROACH

Male Wistar rats were rendered diabetic using a single dose of streptozotocin (55 mg·kg^-1 , i.p.). After 4 weeks, diabetic animals were divided into experimental groups and treated with DIZE, at a low dose (5 mg·kg^-1 ·day^-1 ), a high dose (15 mg·kg^-1 ·day^-1 ) and the high dose with of the AT₂ receptor antagonist PD123319 (10 mg·kg^-1 ·day^-1 ). At the end of the treatment , kidneys from all the groups were collected and processed separately for glomerular isolation, protein isolation, mRNA extraction and for immunohistochemical studies.

KEY RESULTS

Treatment with DIZE restored ACE2 expression in glomeruli and increased expression of AT₂ receptors in whole kidney and isolated glomeruli of diabetic animals. DIZE administration reduced angiotensin II levels and increased angiotensin-(1-7) levels in diabetic kidney. However, PD123319 treatment reversed all these actions of DIZE.

CONCLUSIONS AND IMPLICATIONS

DIZE treatment reduced diabetes-induced renal damage as shown by reduction of fibrosis and apoptosis. These protective actions of DIZE were blocked by the AT₂ receptor antagonist. Taken together, these results suggest that DIZE protected against DN through the ACE2/angiotensin-(1-7)/ AT₂ receptor axis.

SIRT1 activation inhibits hyperglycemia-induced apoptosis by reducing oxidative stress and mitochondrial dysfunction in human endothelial cells

Sustained hyperglycemic stimulation of vascular cells is involved in the pathogenesis of diabetes mellitus‑induced cardiovascular complications. Silent information regulator T1 (SIRT1), a mammalian sirtuin, has been previously recognized to protect endothelial cells against hyperglycemia‑induced oxidative stress. In the present study, human umbilical vein endothelial cells (HUV‑EC‑C) were treated with D‑glucose, and the levels of oxidative stress, mitochondrial dysfunction, the rate of apoptosis and SIRT1 activity were measured. The effect of manipulated SIRT1 activity on hyperglycemia‑induced oxidative stress, mitochondrial dysfunction and apoptosis was then assessed using the SIRT1 activator, resveratrol (RSV), and the SIRT1 inhibitor, sirtinol. The present study confirmed that hyperglycemia promotes oxidative stress and mitochondrial dysfunction in HUV‑EC‑C cells. The accumulation of reactive oxygen species, the swelling of mitochondria, the ratio of adenosine 5'‑diphosphate to adenosine 5'‑triphosphate and localized mitochondrial superoxide levels were all increased following D‑glucose treatment, whereas the mitochondrial membrane potential was significantly reduced by >50 mg/ml D‑glucose treatment. In addition, hyperglycemia was confirmed to induce apoptosis in HUV‑EC‑C cells. Furthermore, the results confirmed the prevention and aggravation of hyperglycemia‑induced apoptosis by RSV treatment and sirtinol treatment, via the amelioration and enhancement of oxidative stress and mitochondrial dysfunction in HUV‑EC‑C cells, respectively. In conclusion, the present study revealed that hyperglycemia promotes oxidative stress, mitochondrial dysfunction and apoptosis in HUV‑EC‑C cells, and manipulation of SIRT1 activity regulated hyperglycemia‑induced mitochondrial dysfunction and apoptosis in HUV‑EC‑C cells. The data revealed the protective effect of SIRT1 against hyperglycemia‑induced apoptosis via the alleviation of mitochondrial dysfunction and oxidative stress.

Significance of angiotensin 1-7 coupling with MAS1 receptor and other GPCRs to the renin-angiotensin system: IUPHAR Review 22

Angiotensins are a group of hormonal peptides and include angiotensin II and angiotensin 1-7 produced by the renin angiotensin system. The biology, pharmacology and biochemistry of the receptors for angiotensins were extensively reviewed recently. In the review, the receptor nomenclature committee was not emphatic on designating MAS1 as the angiotensin 1-7 receptor on the basis of lack of classical G protein signalling and desensitization in response to angiotensin 1-7, as well as a lack of consensus on confirmatory ligand pharmacological analyses. A review of recent publications (2013-2016) on the rapidly progressing research on angiotensin 1-7 revealed that MAS1 and two additional receptors can function as 'angiotensin 1-7 receptors', and this deserves further consideration. In this review we have summarized the information on angiotensin 1-7 receptors and their crosstalk with classical angiotensin II receptors in the context of the functions of the renin angiotensin system. It was concluded that the receptors for angiotensin II and angiotensin 1-7 make up a sophisticated cross-regulated signalling network that modulates the endogenous protective and pathogenic facets of the renin angiotensin system.

Effect of two lipid-lowering strategies on high-density lipoprotein function and some HDL-related proteins: a randomized clinical trial

BACKGROUND

The influence of lipid-lowering therapy on high-density lipoprotein (HDL) is incompletely understood. We compared the effect of two lipid-lowering strategies on HDL functions and identified some HDL-related proteins.

METHODS

Thirty two patients were initially screened and HDLs of 21 patients were finally analyzed. Patients were randomized to receive atorvastatin 20 mg (n = 11) or atorvastatin 5 mg/ezetimibe 10 mg combination (n = 10) for 8 weeks. The cholesterol efflux capacity and other anti-inflammatory functions were assessed based on HDLs of the participants before and after treatment. Pre-specified HDL proteins of the same HDL samples were measured.

RESULTS

The post-treatment increase in cholesterol efflux capacities was similar between the groups (35.6% and 34.6% for mono-therapy and combination, respectively, p = 0.60). Changes in nitric oxide (NO) production, vascular cell adhesion molecule-1 (VCAM-1) expression, and reactive oxygen species (ROS) production were similar between the groups. The baseline cholesterol efflux capacity correlated positively with apolipoprotein (apo)A1 and C3, whereas apoA1 and apoC1 showed inverse associations with VCAM-1 expression. The changes in the cholesterol efflux capacity were positively correlated with multiple HDL proteins, especially apoA2.

CONCLUSIONS

Two regimens increased the cholesterol efflux capacity of HDL comparably. Multiple HDL proteins, not limited to apoA1, showed a correlation with HDL functions. These results indicate that conventional lipid therapy may have additional effects on HDL functions with changes in HDL proteins.

TRIAL REGISTRATION

ClinicalTrials.gov, number NCT02942602 .

PPARδ Is Required for Exercise to Attenuate Endoplasmic Reticulum Stress and Endothelial Dysfunction in Diabetic Mice

Physical activity has profound benefits on health, especially on cardiometabolic wellness. Experiments in rodents with trained exercise have shown that exercise improves vascular function and reduces vascular inflammation by modulating the balance between nitric oxide (NO) and oxidative stress. However, the upstream regulator of exercise-induced vascular benefits is unclear. We aimed to investigate the involvement of peroxisome proliferator-activated receptor δ (PPARδ) in exercise-induced vascular functional improvement. We show that PPARδ is a crucial mediator for exercise to exert a beneficial effect on the vascular endothelium in diabetic mice. In db/db mice and high-fat diet-induced obese mice, 4 weeks of treadmill exercise restored endothelium-dependent vasodilation of aortas and flow-mediated vasodilation in mesenteric resistance arteries, whereas genetic ablation of Ppard abolished such improvements. Exercise induces AMPK activation and subsequent PPARδ activation, which help to reduce endoplasmic reticulum (ER) and oxidative stress, thus increasing NO bioavailability in endothelial cells and vascular tissues. Chemical chaperones 4-phenylbutyric acid and tauroursodeoxycholic acid decrease ER stress and protect against endothelial dysfunction in diabetic mice. The results demonstrate that PPARδ-mediated inhibition of ER stress contributes to the vascular benefits of exercise and provides potentially effective targets for treating diabetic vasculopathy.

Mouse models of atherosclerosis: a historical perspective and recent advances

Atherosclerosis represents a significant cause of morbidity and mortality in both the developed and developing countries. Animal models of atherosclerosis have served as valuable tools for providing insights on its aetiology, pathophysiology and complications. They can be used for invasive interrogation of physiological function and provide a platform for testing the efficacy and safety of different pharmacological therapies. Compared to studies using human subjects, animal models have the advantages of being easier to manage, with controllable diet and environmental risk factors. Moreover, pathophysiological changes can be induced either genetically or pharmacologically to study the harmful effects of these interventions. There is no single ideal animal model, as different systems are suitable for different research objectives. A good understanding of the similarities and differences to humans enables effective extrapolation of data for translational application. In this article, we will examine the different mouse models for the study and elucidation of the pathophysiological mechanisms underlying atherosclerosis. We also review recent advances in the field, such as the role of oxidative stress in promoting endoplasmic reticulum stress, mitochondrial dysfunction and mitochondrial DNA damage, which can result in vascular inflammation and atherosclerosis. Finally, novel therapeutic approaches to reduce vascular damage caused by chronic inflammation using microRNA and nano-medicine technology, are discussed.

Treating the host response to emerging virus diseases: lessons learned from sepsis, pneumonia, influenza and Ebola

There is an ongoing threat of epidemic or pandemic diseases that could be caused by influenza, Ebola or other emerging viruses. It will be difficult and costly to develop new drugs that target each of these viruses. Statins and angiotensin receptor blockers (ARBs) have been effective in treating patients with sepsis, pneumonia and influenza, and a statin/ARB combination appeared to dramatically reduce mortality during the recent Ebola outbreak. These drugs target (among other things) the endothelial dysfunction found in all of these diseases. Most scientists work on new drugs that target viruses, and few accept the idea of treating the host response with generic drugs. A great deal of research will be needed to show conclusively that these drugs work, and this will require the support of public agencies and foundations. Investigators in developing countries should take an active role in this research. If the next Public Health Emergency of International Concern is caused by an emerging virus, a "top down" approach to developing specific new drug treatments is unlikely to be effective. However, a "bottom up" approach to treatment that targets the host response to these viruses by using widely available and inexpensive generic drugs could reduce mortality in any country with a basic health care system. In doing so, it would make an immeasurable contribution to global equity and global security.