Angiotensin-(1-7) relieved renal injury induced by chronic intermittent hypoxia in rats by reducing inflammation, oxidative stress and fibrosis

Counter-regulatory RAS peptides: new therapy targets for inflammation and fibrotic diseases?

The renin-angiotensin system (RAS) is an important cascade of enzymes and peptides that regulates blood pressure, volume, and electrolytes. Within this complex system of reactions, its counter-regulatory axis has attracted attention, which has been associated with the pathophysiology of inflammatory and fibrotic diseases. This review article analyzes the impact of different components of the counter-regulatory axis of the RAS on different pathologies. Of these peptides, Angiotensin-(1-7), angiotensin-(1-9) and alamandine have been evaluated in a wide variety of in vitro and in vivo studies, where not only they counteract the actions of the classical axis, but also exhibit independent anti-inflammatory and fibrotic actions when binding to specific receptors, mainly in heart, kidney, and lung. Other functional peptides are also addressed, which despite no reports associated with inflammation and fibrosis to date were found, they could represent a potential target of study. Furthermore, the association of agonists of the counter-regulatory axis is analyzed, highlighting their contribution to the modulation of the inflammatory response counteracting the development of fibrotic events. This article shows an overview of the importance of the RAS in the resolution of inflammatory and fibrotic diseases, offering an understanding of the individual components as potential treatments.

Chronic intermittent hypoxia-induced cardiovascular and renal dysfunction: from adaptation to maladaptation

Chronic intermittent hypoxia (CIH) is the dominant pathological feature of human obstructive sleep apnoea (OSA), which is highly prevalent and associated with cardiovascular and renal diseases. CIH causes hypertension, centred on sympathetic nervous overactivity, which persists following removal of the CIH stimulus. Molecular mechanisms contributing to CIH-induced hypertension have been carefully delineated. However, there is a dearth of knowledge on the efficacy of interventions to ameliorate high blood pressure in established disease. CIH causes endothelial dysfunction, aberrant structural remodelling of vessels and accelerates atherosclerotic processes. Pro-inflammatory and pro-oxidant pathways converge on disrupted nitric oxide signalling driving vascular dysfunction. In addition, CIH has adverse effects on the myocardium, manifesting atrial fibrillation, and cardiac remodelling progressing to contractile dysfunction. Sympatho-vagal imbalance, oxidative stress, inflammation, dysregulated HIF-1α transcriptional responses and resultant pro-apoptotic ER stress, calcium dysregulation, and mitochondrial dysfunction conspire to drive myocardial injury and failure. CIH elaborates direct and indirect effects in the kidney that initially contribute to the development of hypertension and later to chronic kidney disease. CIH-induced morphological damage of the kidney is dependent on TLR4/NF-κB/NLRP3/caspase-1 inflammasome activation and associated pyroptosis. Emerging potential therapies related to the gut-kidney axis and blockade of aryl hydrocarbon receptors (AhR) are promising. Cardiorenal outcomes in response to intermittent hypoxia present along a continuum from adaptation to maladaptation and are dependent on the intensity and duration of exposure to intermittent hypoxia. This heterogeneity of OSA is relevant to therapeutic treatment options and we argue the need for better stratification of OSA phenotypes.

Effects of ACEI/ARB or CCB use on atrial fibrillation in hypertensive patients following permanent pacemaker implantation

Aims

Permanent pacemaker implantation (PPI) combined with hypertension leads to a higher risk of new-onset atrial fibrillation (NOAF) for patients. Hence, it is essential to study how to reduce this risk. Currently, the effects of the two common anti-hypertensive drugs, angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor blockers (ARB) and calcium channel blockers (CCB), on the risk of NOAF for such patients remain unknown. This study aimed to investigate this association.

Methods

This single-center retrospective study included hypertensive patients with PPI and without prior history of AF/atrial flutter, heart valve disease, hyperthyroidism, etc. Patients were classified into ACEI/ARB group and CCB group based on their exposure drug information. The primary outcome was NOAF events that occurred within 12 months after PPI. The secondary efficacy assessments were the changes from baseline to follow-up in blood pressure and transthoracic echocardiography (TTE) parameters. A multivariate logistic regression model was used to verify our aim.

Results

A total of 69 patients were finally included (51 on ACEI/ARB and 18 on CCB). Both univariate analysis [odds ratio (OR) 0.241, 95% confidence interval (CI) 0.078-0.745] and multivariate analysis (OR: 0.246, 95% CI: 0.077-0.792) demonstrated that ACEI/ARB were associated with a lower risk of NOAF compared to CCB. The mean reduction in left atrial diameter (LAD) from baseline was greater in ACEI/ARB group than in CCB group (P = 0.034). There was no statistical difference between groups in blood pressure and other TTE parameters after treatment.

Conclusion

For patients with PPI combined with hypertension, ACEI/ARB may be superior to CCB in selecting anti-hypertensive drugs, as ACEI/ARB further reduces the risk of NOAF. One reason for this may be that ACEI/ARB improves left atrial remodelling such as LAD better.

Comprehensive analysis of differentially expressed miRNAs in mice with kidney injury induced by chronic intermittent hypoxia

Background: miRNAs have been reported to participate in various diseases. Nevertheless, the expression patterns of miRNA in obstructive sleep apnea (OSA)-induced kidney injury remain poorly characterized. In the current study, miRNA sequencing (miRNA-seq) was conducted to investigate miRNA expression profiles in a chronic intermittent hypoxia (CIH)-induced renal injury mouse model.

Methods: The mouse model of chronic intermittent hypoxia was established. Differentially expressed miRNAs (DEmiRs) were detected using miRNA-seq technology. The sequencing data were subjected to Gene Ontology (GO) functional enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses using a bioinformatics approach. RT-qPCR was further used to evaluate the sequencing results. Finally, we created a network for clarifying the relationship between the miRNAs and target genes.

Results: In total, nine miRNAs were identified to be upregulated and nine to be downregulated in a mouse model of renal injury induced by chronic intermittent hypoxia. The Kyoto Encyclopedia of Genes and Genomes analyses revealed that the Wnt signaling pathway was involved in the development of chronic intermittent hypoxia-induced renal injury. Subsequently, eight DEmiRs, namely, mmu-miR-486b–3p, mmu-miR-215–5p, mmu-miR-212–3p, mmu-miR-344–3p, mmu-miR-181b-1-3p, mmu-miR-467a–3p, mmu-miR-467 d-3p, and mmu-miR-96–5p, showed a similar trend of expression when verified using RT-qPCR. Finally, five selected DEmiRs were used to construct a miRNA–mRNA network.

Conclusion: In conclusion, a total of 18 DEmiRs were identified in the mouse model of chronic intermittent hypoxia-induced renal injury. These findings advance our understanding of the molecular regulatory mechanisms underlying the pathophysiology of obstructive sleep apnea-associated chronic kidney disease.

Angiotensin 1-7 mitigates rhabdomyolysis induced renal injury in rats via modulation of TLR-4/NF-kB/iNOS and Nrf-2/heme‑oxygenase-1 signaling pathways

AIMS

Rhabdomyolysis (RM) is a critical condition with a high mortality rate, but effective management is still deficient. Till date, there are no studies that have addressed the effect of angiotensin 1-7 in this condition, hence, the rationale of this study was to evaluate the potential protective effect of Angiotensin 1-7 (Ang1-7), on rhabdomyolysis (RM) induced kidney injury in rats and detecting the underlying mechanistic insights.

MAIN METHODS

Forty adult male albino rats were divided into groups; the control group, RM group, RM+Ang1-7 group, and RM+Ang1-7+ A779 group. Sera and urine samples were collected for analysis of renal and muscle injury markers. Kidney tissues were taken for estimation of oxidative, inflammatory, and apoptotic markers as well as angiotensin-II (Ang II) and Ang1-7. Renal histology and expression of inducible nitric oxide synthase-1 (iNOS), real-time PCR for angiotensin-converting enzyme-2 (ACE-2), nuclear erythroid factor-2 (Nrf-2), Toll like receptor 4 (TLR-4) and NF-kB in kidney tissues were also measured.

KEY FINDINGS

Induction of RM caused renal oxidative stress injury, inflammation, apoptosis and marked deterioration in kidney functions as well as reduction of Ang1-7 and raised Angiotensin-II level in kidney tissues. Administration of Ang1-7 to the RM group reversed all the affected parameters which were blocked by A779 administration (Mas receptor blocker).

SIGNIFICANCE

We concluded that Ang1-7 could be a potential therapeutic agent that could mitigate RM-induced renal injury. The underlying mechanisms may involve Stimulation of the ACE-2/Ang1-7/MasR axis and modulation of TLR-4/NF-kB/iNOS and Nrf-2/heme‑oxygenase -1 pathways.

Intrarenal pelvic bradykinin-induced sympathoexcitatory reno-renal reflex is attenuated in rats exposed to chronic intermittent hypoxia

OBJECTIVE

In this study, we hypothesized that excitatory reno-renal reflex control of sympathetic outflow is enhanced in rats exposed to chronic intermittent hypoxia (CIH) with established hypertension.

METHODS

Under anaesthesia, renal sensory nerve endings in the renal pelvic wall were chemically activated using bradykinin (150, 400 and 700 μmol/l) and capsaicin (1.3 μmol/l), and cardiovascular parameters and renal sympathetic nerve activity (RSNA) were measured.

RESULTS

CIH-exposed rats were hypertensive with elevated basal heart rate and increased basal urine flow compared with sham. The intrarenal pelvic infusion of bradykinin was associated with contralateral increase in the RSNA and heart rate, without concomitant changes in blood pressure. This was associated with a drop in the glomerular filtration rate, which was significant during a 5 min period after termination of the infusion but without significant changes in urine flow and absolute sodium excretion. In response to intrarenal pelvic infusion of 700 μmol/l bradykinin, the increases in RSNA and heart rate were blunted in CIH-exposed rats compared with sham rats. Conversely, the intrarenal pelvic infusion of capsaicin evoked an equivalent sympathoexcitatory effect in CIH-exposed and sham rats. The blockade of bradykinin type 1 receptors (BK1R) suppressed the bradykinin-induced increase in RSNA by ∼33%, with a greater suppression obtained when bradykinin type 2 receptors (BK2R) and BK1R were contemporaneously blocked (∼66%).

CONCLUSION

Our findings reveal that the bradykinin-dependent excitatory reno-renal reflex does not contribute to CIH-induced sympathetic hyperactivity and hypertension. Rather, there is evidence that the excitatory reno-renal reflex is suppressed in CIH-exposed rats, which might relate to a downregulation of BK2R.

Alternative RAS in Various Hypoxic Conditions: From Myocardial Infarction to COVID-19

Alternative branches of the classical renin–angiotensin–aldosterone system (RAS) represent an important cascade in which angiotensin 2 (AngII) undergoes cleavage via the action of the angiotensin-converting enzyme 2 (ACE2) with subsequent production of Ang(1-7) and other related metabolites eliciting its effects via Mas receptor activation. Generally, this branch of the RAS system is described as its non-canonical alternative arm with counterbalancing actions to the classical RAS, conveying vasodilation, anti-inflammatory, anti-remodeling and anti-proliferative effects. The implication of this branch was proposed for many different diseases, ranging from acute cardiovascular conditions, through chronic respiratory diseases to cancer, nonetheless, hypoxia is one of the most prominent common factors discussed in conjugation with the changes in the activity of alternative RAS branches. The aim of this review is to bring complex insights into the mechanisms behind the various forms of hypoxic insults on the activity of alternative RAS branches based on the different duration of stimuli and causes (acute vs. intermittent vs. chronic), localization and tissue (heart vs. vessels vs. lungs) and clinical relevance of studied phenomenon (experimental vs. clinical condition). Moreover, we provide novel insights into the future strategies utilizing the alternative RAS as a diagnostic tool as well as a promising pharmacological target in serious hypoxia-associated cardiovascular and cardiopulmonary diseases.

Oral Treatment with Angiotensin-(1-7) Attenuates the Kidney Injury Induced by Gentamicin in Wistar Rats

BACKGROUND

Acute Kidney Injury (AKI), a common disease of the urinary system, can be induced by high doses of gentamicin (GM). The Renin-Angiotensin System exerts a key role in the progression of the AKI since elevated intrarenal levels of Ang II, and ACE activity is found in this condition. However, it is unknown whether oral administration of Ang-(1-7), a heptapeptide that evokes opposite effects of Ang II, may attenuate the renal injuries induced by gentamicin.

OBJECTIVES

To evaluate the effects of Ang (1-7) on GM-induced renal dysfunction in rats.

METHODS

AKI was induced by subcutaneous administration of GM (80 mg/Kg) for 5 days. Simultaneously, Ang-(1-7) included in hydroxypropyl β-cyclodextrin (HPβCD) was administered by gavage [46 μg/kg HPβCD + 30 μg/kg Ang- (1-7)]. At the end of the treatment period (sixth day), the rats were housed in metabolic cages for renal function evaluation. Thereafter, blood and kidney samples were collected.

RESULTS

The Ang-(1-7) attenuated the increase of the plasmatic creatinine and proteinuria caused by GM but did not change the glomerular filtration rate nor tubular necrosis. Ang-(1-7) attenuated the increased urinary flow and the fractional excretion of H2O and potassium observed in GM rats but intensified the elevated excretion of sodium in these animals. Morphological analysis showed that Ang-(1-7) also reduced the tubular vacuolization in kidneys from GM rats.

CONCLUSION

Ang-(1-7) promotes selective beneficial effects in renal injuries induced by GM.

Elevated reactivity of Apelin inhibited renal fibrosis induced by chronic intermittent hypoxia

BACKGROUND

Apelin and its receptor angiotensin receptor - like 1 (APJ) are closely related to renal fibrosis, but their specific roles in renal fibrosis are still controversial. In this article, we discussed the role of Apelin/APJ system in renal fibrosis and its mechanism.

METHODS

Chronic intermittent hypoxia (CIH) rat model was established to induce the environment of renal fibrosis and a competitive antagonist of the APJ receptor ML221 was administered to CIH rats. The rats were divided into Control, CIH and ML221 groups. HE staining was used to detect the inflammatory injury and fibrosis of renal tissue. The expressions of renal fibrosis-related indicators transforming growth factor-β (TGF-β), α-smooth muscle actin (α-SMA) and Human type I collagen (Col-Ⅰ) were detected by immunohistochemistry. The levels of oxidative stress indexes reactive oxygen species (ROS), Malondialdehyde (MDA), Superoxide Dismutase (SOD) and inflammation-related indexes Interleukin (IL) -6, tumor necrosis factor-α (TNF-α) and IL-1β were detected by ELISA. At the same time, the levels of Apelin-13 and AngiotensinII (AngⅡ) were also measured by ELISA. Finally, western blot was used to detect the expression of Apelin pathway and renal fibrosis-related proteins. In addition, at the cellular level, we divided the cells into Control, CIH, Apelin-13 and Apelin-13+ML-221 groups to further verify the specific mechanisms at the cellular level.

RESULTS

The expression of Apeline-13 and its related pathways was significantly increased after the induction of CIH in rats. However, the degree of renal fibrosis in ML221 group was further significantly increased after inhibiting the expression of Apelin. At the cellular level, CIH model cells treated with Apelin-13 significantly reduced cell proliferation, oxidative stress and inflammatory response, and decreased the expression of fibrosis-related proteins, which can be reversed by ML221 administration.

CONCLUSION

The increased reactivity of Apelin may be one of the protective mechanisms against renal fibrosis induced by CIH.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

Alamandine protects against renal ischaemia-reperfusion injury in rats via inhibiting oxidative stress

OBJECTIVE

This study was to determine whether alamandine (Ala) could reduce ischaemia and reperfusion (I/R) injury of kidney in rats.

METHODS

Renal I/R was induced by an occlusion of bilateral renal arteries for 70 min and a 24-h reperfusion in vivo, and rat kidney proximal tubular epithelial cells NRK52E were exposed to 24 h of hypoxia and followed by 3-h reoxygenation (H/R) in vitro.

RESULTS

The elevated serum creatinine (Cr), blood cystatin C (CysC) and blood urea nitrogen (BUN) levels in I/R rats were inhibited by Ala treatment. Tumour necrosis factor alpha (TNF)-α, IL-1β, IL-6, cleaved caspase-3, cleaved caspase-8 and Bax were increased, and Bcl2 was reduced in the kidney of I/R rats, which were reversed by Ala administration. Ala reversed the increase of TNF-α, IL-1β, IL-6, cleaved caspase-3, cleaved caspase-8 and Bax and the decrease of Bcl2 in the H/R NRK52E cells. Ala could also inhibit the increase of oxidative stress levels in the kidney of I/R rats. NADPH oxidase 1 (Nox1) overexpression reversed the improving effects of Ala on renal function, inflammation and apoptosis of I/R rats.

CONCLUSION

These results indicated that Ala could improve renal function, attenuate inflammation and apoptosis in the kidney of I/R rats via inhibiting oxidative stress.

Aryl Hydrocarbon Receptor and Cysteine Redox Dynamics Underlie (Mal)adaptive Mechanisms to Chronic Intermittent Hypoxia in Kidney Cortex

We hypothesized that an interplay between aryl hydrocarbon receptor (AhR) and cysteine-related thiolome at the kidney cortex underlies the mechanisms of (mal)adaptation to chronic intermittent hypoxia (CIH), promoting arterial hypertension (HTN). Using a rat model of CIH-HTN, we investigated the impact of short-term (1 and 7 days), mid-term (14 and 21 days, pre-HTN), and long-term intermittent hypoxia (IH) (up to 60 days, established HTN) on CYP1A1 protein level (a sensitive hallmark of AhR activation) and cysteine-related thiol pools. We found that acute and chronic IH had opposite effects on CYP1A1 and the thiolome. While short-term IH decreased CYP1A1 and increased protein-S-thiolation, long-term IH increased CYP1A1 and free oxidized cysteine. In addition, an in vitro administration of cystine, but not cysteine, to human endothelial cells increased Cyp1a1 expression, supporting cystine as a putative AhR activator. This study supports CYP1A1 as a biomarker of obstructive sleep apnea (OSA) severity and oxidized pools of cysteine as risk indicator of OSA-HTN. This work contributes to a better understanding of the mechanisms underlying the phenotype of OSA-HTN, mimicked by this model, which is in line with precision medicine challenges in OSA.

Ang(1-7) exerts Nrf2-mediated neuroprotection against amyloid beta-induced cognitive deficits in rodents

Alzheimer's disease (AD) is a neurodegenerative disorder with cognitive deficits in an individual. Ang(1-7) exhibits neuroprotection against amyloid beta (Aβ)-induced mitochondrial dysfunction and neurotoxicity in experimental conditions. Further, Ang(1-7) also exhibits nrf2-mediated antioxidant activity in experimental conditions. However, its therapeutic role on nrf2-mediated mitochondrial function is yet to be established in the Aβ-induced neurotoxicity. The experimental dementia was induced in the male rats by intracerebroventricular administration of Aβ_(1-42) on day-1 (D-1) of the experimental schedule of 14 days. Ang(1-7) was administered once daily from D-1 toD-14 to the Aβ-challenged rodents. Ang(1-7) attenuated Aβ-induced increase in escape latency and decrease in the time spent in the target quadrant during Morris water maze and percentage of spontaneous alteration behavior during Y-maze tests in the rats. Further, Ang(1-7) attenuated Aβ-induced cholinergic dysfunction in terms of decrease in the level of acetylcholine and activity of choline acetyltransferase, and increase in the activity of acetylcholinesterase, and increase in the level of Aβ in rat hippocampus, pre-frontal cortex and amygdala. Furthermore, Ang(1-7) reversed Aβ-induced decrease in the mitochondrial function, integrity and bioenergetics in all brain regions. Additionally, Ang(1-7) attenuated Aβ-induced increase in the extent of apoptosis and decrease in the level of heme oxygenase-1 in all selected brain regions. Trigonelline significantly abolished the therapeutic effectiveness of Ang(1-7) on Aβ-induced alterations in the behavioral, neurochemicals and molecular observations in the animals. Ang(1-7) may exhibit nrf2-mediated neuroprotection in these rodents. Hence, Ang(1-7) could be a potential therapeutic option in the pharmacotherapy of AD.

Protective effect of alamandine on doxorubicin‑induced nephrotoxicity in rats

BACKGROUND

This study aimed to evaluate the protective effects of alamandine, a new member of the angiotensin family, against doxorubicin (DOX)-induced nephrotoxicity in rats.

METHODS

Rats were intraperitoneally injected with DOX (3.750 mg/kg/week) to reach a total cumulative dose of 15 mg/kg by day 35. Alamandine (50 µg/kg/day) was administered to the rats via mini-osmotic pumps for 42 days. At the end of the experiment, rats were placed in the metabolic cages for 24 h so that their water intake and urine output could be measured. After scarification, the rats' serum and kidney tissues were collected, and biochemical, histopathological, and immunohistochemical studies were carried out.

RESULTS

DOX administration yielded increases in pro-inflammatory cytokines, including interleukin (IL)-1β and IL-6, pro-fibrotic proteins transforming growth factor-β (TGF-β), pro-inflammatory transcription factor nuclear kappa B (NF-κB), kidney malondialdehyde (MDA), creatinine clearance, blood urea nitrogen (BUN), and water intake. On the other hand, the DOX-treated group exhibited decreased renal superoxide dismutase (SOD), renal glutathione peroxidase (GPx) activity, and urinary output. Alamandine co-therapy decreased these effects, as confirmed by histopathology and immunohistochemical analysis.

CONCLUSIONS

The results suggest that alamandine can prevent nephrotoxicity induced by DOX‎ in rats.

Ang (1-7)/Mas receptor-axis activation promotes amyloid beta-induced altered mitochondrial bioenergetics in discrete brain regions of Alzheimer's disease-like rats

Renin Angiotensin System plays significant role in the memory acquisition and consolidation apart from its hemodynamic function in the pathophysiology of Alzheimer's disease (AD). It has been reported that Ang (1-7) ameliorates the cognitive impairment in experimental animals. However, the effect of Ang (1-7)/Mas receptor signaling is yet to be explored in Aβ42-induced memory impairment. Aβ42 was intracerebroventricularly injected into the male rats on day-1 (D-1) of the experimental schedule of 14 days. All the drugs were administered from D-1 to D-14 in the study design. Aβ42 significantly increased the escape latency during Morris water maze (MWM) test on D-10 to13 in the animals. Further, Aβ42 significantly decreased the time spent and percentage of total distance travelled in the target quadrant of the rats on D-14 in the MWM test. Aβ42 also significantly decreased the spontaneous alteration behavior on D-14 during Y-maze test. Moreover, there was a significant increase in the level of Aβ42, decrease in the cholinergic function (in terms of decreased acetylcholine and activity of cholinesterase, and increased activity of acetylcholinesterase), mitochondrial function, integrity and bioenergetics, and apoptosis in all the rat brain regions. Further, Aβ42 significantly decreased the level of expression of heme oxygenase-1 in all the rat brain regions. Ang (1-7) attenuated Aβ42-induced changes in the behavioral, biochemical and molecular observations in all the selected rat brain regions. However, A779, Mas receptor blocker, significantly abolished the beneficial effects of Ang (1-7) in Aβ42-induced cognitive deficit animals. These observations clearly indicate that the Ang (1-7)/Mas receptor activation could be a potential alternative option in the management of AD.

Effects of edpetiline from Fritillaria on inflammation and oxidative stress induced by LPS stimulation in RAW264.7 macrophages

The dry bulbs of Fritillaria cirrhosa species can help resolve phlegm, soothe cough, clear heat, and moisten the lung, and the main active components responsible for these effect are its alkaloids. However, it is unclear whether or how edpetiline in Fritillaria can inhibit the excessive inflammatory response and oxidative stress. In this research, we aimed to examine this aspect using lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages as an inflammatory model. The quantitative real-time polymerase chain reaction and western blot analysis results showed that edpetiline significantly inhibited the content and mRNA expression levels of proinflammatory cytokines (TNF-α and IL-6) in LPS-induced RAW264.7 cells, significantly increased the mRNA expression of IL-4 (anti-inflammatory cytokine), and markedly downregulated the inflammatory mediators inductible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA and protein expression levels. The oxidative stress induced by LPS was also inhibited by edpetiline, as the level of intracellular reactive oxygen species decreased notably. Edpetiline may exert anti-inflammatory and antioxidant effects through inhibiting the phosphorylation of IκB and the nuclear transcription of nuclear transcription factor-κB p65 and decreasing the phosphorylation of p38 and ERK in the mitogen-activated protein kinase signaling pathway, without activating the JNK/mitogen-activated protein kinase signaling pathway. These findings suggest that edpetiline may be a potential therapeutic agent for the prevention or treatment of inflammation- and oxidative stress-related pathophysiological processes and diseases.

Angiotensin-(1-7) treatment blocks lipopolysaccharide-induced organ damage, platelet dysfunction, and IL-6 and nitric oxide production in rats

Sepsis can lead to shock, multiple organ failure, and even death. Platelets play an active role in the pathogenesis of sepsis-induced multiple organ failure. Angiotensin (Ang)-(1–7), a biologically active peptide, counteracts various effects of Ang II and attenuates inflammatory responses, reactive oxygen species production, and apoptosis. We evaluated the effects of Ang-(1–7) on organ injury and platelet dysfunction in rats with endotoxaemia. We treated male Wistar rats with saline or lipopolysaccharide (LPS, 10 mg, intravenously) then Ang-(1–7) (1 mg/kg, intravenous infusion for 3 h beginning 30 min after LPS administration). We analysed several haemodynamic, biochemical, and inflammatory parameters, as well as platelet counts and aggregation. Ang-(1–7) improved hypotension and organ dysfunction, and attenuated plasma interleukin-6, chemokines and nitric oxide production in rats after LPS administration. The LPS-induced reduction in platelet aggregation, but not the decreased platelet count, was restored after Ang-(1–7) treatment. The protein expression of iNOS and IκB, but not phosphorylated ERK1/2 and p38, was diminished in Ang-(1–7)-treated LPS rats. The histological changes in liver and lung were significantly attenuated in Ang-(1–7)-treated LPS rats. Our results suggest that Ang-(1–7) ameliorates endotoxaemic-induced organ injury and platelet dysfunction, likely through the inhibition of the inflammatory response and nitric oxide production.

Chronic intermittent hypoxia impairs diuretic and natriuretic responses to volume expansion in rats with preserved low-pressure baroreflex control of the kidney

We examined the effects of exposure to chronic intermittent hypoxia (CIH) on baroreflex control of renal sympathetic nerve activity (RSNA) and renal excretory responses to volume expansion (VE) before and after intrarenal transient receptor potential vanilloid 1 (TRPV1) blockade by capsaizepine (CPZ). Male Wistar rats were exposed to 96 cycles of hypoxia per day for 14 days (CIH) or normoxia. Urine flow and absolute Na+ excretion during VE were less in CIH-exposed rats, but the progressive decrease in RSNA during VE was preserved. Assessment of the high-pressure baroreflex revealed an increase in the operating and response range of RSNA and decreased slope in CIH-exposed rats with substantial hypertension [+19 mmHg basal mean arterial pressure (MAP)] but not in a second cohort with modest hypertension (+12 mmHg). Intrarenal CPZ caused diuresis, natriuresis, and a reduction in MAP in sham-exposed (sham) and CIH-exposed rats. After intrarenal CPZ, diuretic and natriuretic responses to VE in CIH-exposed rats were equivalent to those of sham rats. TRPV1 expression in the renal pelvic wall was similar in both experimental groups. Exposure to CIH did not elicit glomerular hypertrophy, renal inflammation, or oxidative stress. We conclude that exposure to CIH 1) does not impair the low-pressure baroreflex control of RSNA; 2) has modest effects on the high-pressure baroreflex control of RSNA, most likely indirectly due to hypertension; 3) can elicit hypertension in the absence of kidney injury; and 4) impairs diuretic and natriuretic responses to fluid overload. Our results suggest that exposure to CIH causes renal dysfunction, which may be relevant to obstructive sleep apnea.

Angiotensin-(1-7) Rescues Chronic Intermittent Hypoxia-Aggravated Transforming Growth Factor-β-Mediated Airway Remodeling in Murine and Cellular Models of Asthma

Renin-angiotensin system (RAS) is involved in TGF-β-mediated epithelial-to-mesenchymal transition (EMT) and is responsible for airway remodeling in refractory asthma. Obstructive sleep apnea (OSA), which affects RAS activity, is a risk factor for refractory asthma. We aimed to investigate how chronic intermittent hypoxia (IH), the main pathophysiology of OSA, exacerbates asthma and whether Ang-(1-7) protects against chronic IH-induced airway remodeling in asthma. We exposed ovalbumin (OVA)-challenged asthma mice to chronic IH and observed that chronic IH aggravated airway inflammation and collagen deposit in OVA-challenged mice. Compared with the OVA group, the OVA + chronic IH group had a lower expression level of epithelial marker E-cadherin and higher expression levels of mesenchymal markers α-smooth muscle actin and collagen IV in airway epithelia, accompanied with activation of TGF-β/Smad pathway. These changes were reversed by the administration of Ang-(1-7). Consistently, Ang-(1-7) mitigated chronic IH-induced activation of TGF-β-mediated EMT in lipopolysaccharide-treated bronchial epithelial cells in a dose-dependent manner, which was blocked by Ang-(1-7)-specific Mas receptor antagonist A779. Taken together, Ang-(1-7) rescued chronic IH-aggravated TGF-β-mediated EMT to suppress airway remodeling, implying that RAS activity is involved in the mechanisms of OSA-related airway dysfunction in asthma. SIGNIFICANCE STATEMENT: OSA is a risk factor for refractory asthma. In this study, we aimed to explore the mechanisms of how OSA exacerbates refractory asthma. We found that chronic IH induces TGF-β-mediated EMT and aggravates airway collagen deposit. We also found that Ang-(1-7) erased the aggravation of TGF-β-mediated EMT and epithelial fibrosis upon chronic IH exposure. These findings provided new insights that the ACE2/Ang-(1-7)/Mas axis might be considered as a potential therapeutic target for patients with asthma and OSA.

Angiotensin (1-7) Inhibits Ang II-mediated ERK1/2 Activation by Stimulating MKP-1 Activation in Vascular Smooth Muscle Cells

The renin–angiotensin system (RAS) exerts profound physiological effects on blood pressure regulation and fluid homeostasis, mainly by modulating renal, cardiovascular, and central nervous systems. Angiotensin (Ang)-(1-7), an end-product of RAS, is recognized by its cardiovascular protective properties through stimulation of the Mas receptor, including vasodilation, anti-inflammatory, and antihypertensive actions, and consequently, counter-regulating the well-known Ang II-elicited actions. The overall hypothesis of this study is that Ang-(1-7) inhibits Ang II-induced ERK1/2 activation in vascular smooth muscle cells (VSMCs), via regulation of mitogen-activated protein phosphatase-1 (MKP-1) activity. Aortas from male Wistar rats were incubated with Ang-(1-7) or vehicle. Concentration-response curves to Ang II were performed in endothelium-denuded aortas, in the presence or absence of ERK1/2 (PD98059) inhibitor or Mas receptor (A-779) antagonist. Expression of proteins was assessed by western blot, and immunohistochemistry was conducted in VSMCs. Ang-(1-7) incubation decreased Ang II-induced contractile response in aortas, and this effect was not observed in the presence of PD98059 or A-779. Stimulation of VSMCs with Ang-(1-7) prevented Ang II-induced ERK1/2 phosphorylation, but not C-Raf-activation. Furthermore, Ang II decreased MKP-1 phosphorylation in VSMCs. Interestingly, simultaneous incubation of Ang-(1-7) with Ang II favored MKP-1 phosphorylation, negatively modulating ERK1/2 activation in VSMCs. The results suggest that Ang-(1-7) counter-regulates actions evoked by Ang II overproduction, as observed in cardiovascular diseases, mainly by modulating MKP-1 activity. This evidence suggests that the role of Ang-(1-7) in MKP-1-regulation represents a target for new therapeutic development.

Alteration and association between serum ACE2/ angiotensin(1-7)/Mas axis and oxidative stress in chronic kidney disease: A pilot study

Activation of the renin angiotensin system and renal oxidative stress (OS) are critical contributors in the progression of chronic kidney disease(CKD). Recent studies have confirmed that the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas(ACE2/Ang(1-7)/Mas) axis, the important components of renin angiotensin system, protected kidneys against damage by antagonizing angiotensin II and attenuating OS in rats with several nephropathy models, but its effect needs to be further evaluated in clinic. In this study, we aimed to detected serum ACE2/Ang (1-7)/Mas axis, OS conditions and described its clinical associations in patients with CKD at different stages.A total of 48 patients with CKD and 6 healthy controls (CT) were enrolled, and serum angiotensin converting enzyme (ACE), ACE2, Ang (1-7), 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined by ELISA. Serum extracellular glutathione peroxidase(eGSH-Px) activity and renal functions were determined by the biochemical method.Serum ACE and ACE2 levels in CKD stages 3 to 5 and serum Ang(1-7) levels in CKD stages 4 to 5 without Ang II receptor blockers treatment significantly increased compared to those in the CT group. However, ACE2 was decreased and Ang(1-7) level increased in early CKD stage with Ang II receptor blockers treatment. Higher serum 8-OHdG levels and lower eGSH-Px activity were noted in CKD stages 4 to 5. Serum 8-OHdG level was correlated with serum ACE2, Ang(1-7) expression. Estimated glomerular filtration rate (eGFR) was correlated with serum ACE, ACE2, Ang(1-7), 8-OHdG, Hcy levels and serum eGSH-Px activity. Multiple-regression analysis eGFR was predicted by ACE, Hcy, eGSH-Px, and also can be predicted by ACE2, Ang(1-7), Hcy in CT subgroup.The ACE2/Ang(1-7)/Mas axis is associated with OS, and both them were associated with eGFR in the progression of CKD. Activation of ACE2/Ang(1-7)/Mas axis may have renoprotective effect and can be a potential therapeutic target in patients with early CKD stages.

Sleep Apnea and the Kidney

Purpose of Review

There are some uncertainties about the interactions between obstructive sleep apnea (OSA) and chronic kidney disease (CKD). We critically reviewed recent studies on this topic with a focus on experimental and clinical evidence of bidirectional influences between OSA and CKD, as well as the effects of treatment of either disease.

Recent Findings

Experimental intermittent hypoxia endangers the kidneys, possibly through activation of inflammatory pathways and increased blood pressure. In humans, severe OSA can independently decrease kidney function. Treatment of OSA by CPAP tends to blunt kidney function decline over time, although its effect may vary. OSA may increase cardiovascular complications and mortality in patients with end-stage renal disease (ESRD), while it seems of little harm after renal transplantation. Excessive fluid removal may explain some of the improvements in OSA severity in ESRD and after transplantation.

Summary

Severe OSA and CKD do interact negatively, mainly through hypoxia and fluid retention. The moderate mutually interactive benefits that treatment of each disease exerts on the other one warrant further studies to improve patient management.

Losartan protects against intermittent hypoxia-induced peritubular capillary loss by modulating the renal renin-angiotensin system and angiogenesis factors

Obstructive sleep apnea is characterized by chronic intermittent hypoxia (CIH), which is a risk factor for renal peritubular capillary (PTC) loss, and angiotensin II receptor blockers can alleviate PTC loss. However, the mechanism by which losartan (an angiotensin II receptor blocker) reduces CIH-induced PTC loss and attenuates kidney damage is still unknown. Thus, in this study, we examined the protective effects of losartan against CIH-induced PTC loss and explored the underlying mechanisms in rat CIH model. The immunohistochemical staining of CD34 and morphological examination showed that CIH reduced PTC density and damaged tubular epithelial cells. Immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), real-time quantitative PCR, and western blot analysis results revealed that CIH increased the expression of hypoxia inducible factor-1α (HIF-1α), angiotensin II (Ang II), angiotensin II type 1 receptor (AT1R), pro-angiogenesis factor vascular endothelial growth factor (VEGF), and anti-angiogenesis factor thrombospondin-1 (TSP-1) in the renal cortex of rats. CIH may up-regulate VEGF expression and simultaneously increase TSP-1 production. By histopathological, immunohistochemistry, ELISA, RT-qPCR, and western blot analysis, we found that the expressions of renal renin-angiotensin system (RAS), HIF-1α, VEGF, and TSP-1 were decreased, and PTC loss and tubular epithelial cell injury were attenuated with losartan treatment. Losartan ameliorated CIH-induced PTC loss by modulating renal RAS to improve the crosstalk between endothelial cells and tubular epithelial cells and subsequently regulate the balance of angiogenesis factors. Our study provided novel insights into the mechanisms of CIH-induced kidney damage and indicated that losartan could be a potential therapeutic agent for renal protection by alleviating CIH-induced PTC loss.

Interaction of Sex Hormones and the Renin-Angiotensin System in Ovariectomized Rats Subjected to Ischemia-Reperfusion Induction

Backgrounds:

Ischemia-reperfusion (IR) injuries occur in a variety of clinical conditions, which lead to kidney damage. Most of the tissue damages after IR are due to the activation of the renin–angiotensin system (RAS). Hence, in this study, the interaction of sex hormones and RAS in ovariectomized (OV) rats subjected to IR induction has been studied.

Materials and Methods:

The animals were divided into different groups. Groups 1 (OV + E, OV rat + estradiol) and 2 (OV rat) each one consisted of three separate IR-induced subgroups treated with losartan, angiotensin 1–7 (Ang 1–7), and their combination, Group 3, as control and Group 4, as sham. Next, 72 h after IR, blood samples were collected, the right kidneys were homogenized, and left kidneys were fixed in 10% formalin.

Results:

Findings show that serum blood urea nitrogen, creatinine, and kidney tissue damage score levels increased significantly with induction of IR (P < 0.05). Mean serum levels of these factors in OV + E groups are higher than those of the OV. The presence or absence of estradiol did not affect the levels of antioxidants in the different groups receiving Los, Ang 1–7, and their combination. Los, Ang 1–7, and their combination reduced serum and kidney malondialdehyde levels in both OV and OV + E groups.

Conclusion:

Estrogen not only fails to improve renal functioning but it can also exacerbate it. While the treatments used in this study, in the absence of estradiol, it had a better effect on kidney damages and improved its functions.

The inhibition of miR‑101a‑3p alleviates H/R injury in H9C2 cells by regulating the JAK2/STAT3 pathway

Hypoxia/reoxygenation (H/R) is used as an in vivo model of ischemia/reperfusion injury, and myocardial ischemia can lead to heart disease. Therefore, it is necessary to prevent myocardial H/R injury to avoid the risk of heart disease. The aim of the present study was to investigate whether inhibiting microRNA (miR)-101a-3p attenuated H9C2 cell H/R injury, apoptosis mechanisms and key target proteins. Cell viability and apoptosis were determined by Cell Counting Kit-8 assays and flow cytometry using a cell apoptosis kit, respectively. The contents of creatine kinase (CK) and lactate dehydrogenase (LDH) were detected using colorimetric assays. Dual luciferase assays were carried out to determine if miR-101a-3p inhibited Janus kinase (JAK)2. Western blot analysis and reverse transcription-quantitative PCR were used to determine proteins levels and mRNAs expression. It was found that the inhibition of miR-101a-3p increased the growth of H9C2 cells and decreased H9C2 cell apoptosis during H/R injury. The inhibition of miR-101a-3p reduced the amounts of CK and LDH in H/R model H9C2 cells. The inhibition of miR-101a-3p lowered the levels of Bax, interleukin-6 and tumor necrosis factor-α, but raised the levels of phosphorylated (p)-STAT3 and p-JAK2 in H9C2 cells subjected to H/R injury treatment. miR-101a-3p mimic was found to inhibit H9C2 cell viability, raise p-JAK2 level and slightly increase p-STAT3 during H/R injury. AG490 induced H9C2 cell apoptosis, and decreased the levels of p-JAK2 and p-STAT3 during H/R injury. The data indicated that inhibiting miR-101a-3p reduced H/R damage in H9C2 cells and decreased apoptosis via Bax/Bcl-2 signaling during H/R injury. In addition, it was suggested that the inhibition of miR-101a-3p decreased H/R injury in H9C2 cell by regulating the JAK2/STAT3 signaling pathway.

Is Aberrant Reno-Renal Reflex Control of Blood Pressure a Contributor to Chronic Intermittent Hypoxia-Induced Hypertension?

Renal sensory nerves are important in the regulation of body fluid and electrolyte homeostasis, and blood pressure. Activation of renal mechanoreceptor afferents triggers a negative feedback reno-renal reflex that leads to the inhibition of sympathetic nervous outflow. Conversely, activation of renal chemoreceptor afferents elicits reflex sympathoexcitation. Dysregulation of reno-renal reflexes by suppression of the inhibitory reflex and/or activation of the excitatory reflex impairs blood pressure control, predisposing to hypertension. Obstructive sleep apnoea syndrome (OSAS) is causally related to hypertension. Renal denervation in patients with OSAS or in experimental models of chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoeas (pauses in breathing), results in a decrease in circulating norepinephrine levels and attenuation of hypertension. The mechanism of the beneficial effect of renal denervation on blood pressure control in models of CIH and OSAS is not fully understood, since renal denervation interrupts renal afferent signaling to the brain and sympathetic efferent signals to the kidneys. Herein, we consider the currently proposed mechanisms involved in the development of hypertension in CIH disease models with a focus on oxidative and inflammatory mediators in the kidneys and their potential influence on renal afferent control of blood pressure, with wider consideration of the evidence available from a variety of hypertension models. We draw focus to the potential contribution of aberrant renal afferent signaling in the development, maintenance and progression of high blood pressure, which may have relevance to CIH-induced hypertension.

Angiotensin-(1-7) and Alamandine Promote Anti-inflammatory Response in Macrophages In Vitro and In Vivo

The renin-angiotensin system (RAS) peptides play an important role in inflammation. Resolution of inflammation contributes to restore tissue homeostasis, and it is characterized by neutrophil apoptosis and their subsequent removal by macrophages, which are remarkable plastic cells involved in the pathophysiology of diverse inflammatory diseases. However, the effects of RAS peptides on different macrophage phenotypes are still emerging. Here, we evaluated the effects of angiotensin-(1-7) (Ang-(1-7)) and the most novel RAS peptide, alamandine, on resting (M0), proinflammatory M(LPS+IFN-γ), and anti-inflammatory M(IL-4) macrophage phenotypes in vitro, as well as on specific immune cell populations and macrophage subsets into the pleural cavity of LPS-induced pleurisy in mice. Our results showed that Ang-(1-7) and alamandine, through Mas and MrgD receptors, respectively, do not affect M0 macrophages but reduce the proinflammatory TNF-α, CCL2, and IL-1β transcript expression levels in LPS+IFN-γ-stimulated macrophages. Therapeutic administration of these peptides in LPS-induced inflammation in mice decreased the number of neutrophils and M1 (F4/80lowGr1+CD11bmed) macrophage frequency without affecting the other investigated macrophage subsets. Our data suggested that both Ang-(1-7) and alamandine, through their respective receptors Mas and MrgD, promote an anti-inflammatory reprogramming of M(LPS+IFN-γ)/M1 macrophages under inflammatory circumstances and potentiate the reprogramming induced by IL-4. In conclusion, our work sheds light on the emerging proresolving properties of Ang-(1-7) and alamandine, opening new avenues for the treatment of inflammatory diseases.

Renal cortical oxygen tension is decreased following exposure to long-term but not short-term intermittent hypoxia in the rat

Chronic kidney disease (CKD) occurs in more than 50% of patients with obstructive sleep apnea (OSA). However, the impact of intermittent hypoxia (IH) on renal function and oxygen homeostasis is unclear. Male Sprague-Dawley rats were exposed to IH (270 s at 21% O₂; 90 s hypoxia, 6.5% O₂ at nadir) for 4 h [acute IH (AIH)] or to chronic IH (CIH) for 8 h/day for 2 wk. Animals were anesthetized and surgically prepared for the measurement of mean arterial pressure (MAP), and left renal excretory function, renal blood flow (RBF), and renal oxygen tension (Po₂). AIH had no effect on MAP (123 ± 14 vs. 129 ± 14 mmHg, means ± SE, sham vs. IH). The CIH group was hypertensive (122 ± 9 vs. 144 ± 15 mmHg, P < 0.05). Glomerular filtration rate (GFR) (0.92 ± 0.27 vs. 1.33 ± 0.33 ml/min), RBF (3.8 ± 1.5 vs. 7.2 ± 2.4 ml/min), and transported sodium (TNa) (132 ± 39 vs. 201 ± 47 μmol/min) were increased in the AIH group (all P < 0.05). In the CIH group, GFR (1.25 ± 0.28 vs. 0.86 ± 0.28 ml/min, P < 0.05) and TNa (160 ± 39 vs. 120 ± 40 μmol/min, P < 0.05) were decreased, while RBF (4.13 ± 1.5 vs. 3.08 ± 1.5 ml/min) was not significantly different. Oxygen consumption (QO₂) was increased in the AIH group (6.76 ± 2.60 vs. 13.60 ± 7.77 μmol/min, P < 0.05), but it was not significantly altered in the CIH group (3.97 ± 2.63 vs. 6.82 ± 3.29 μmol/min). Cortical Po₂ was not significantly different in the AIH group (46 ± 4 vs. 46 ± 3 mmHg), but it was decreased in the CIH group (44 ± 5 mmHg vs. 38 ± 2 mmHg, P < 0.05). For AIH, renal oxygen homeostasis was preserved through a maintained balance between O₂ supply (RBF) and consumption (GFR). For CIH, mismatched TNa and QO₂ reflect inefficient O₂ utilization and, thereby, sustained decrease in cortical Po₂.

Evidence for a role of angiotensin converting enzyme 2 in proteinuria of idiopathic nephrotic syndrome

Introduction: Renin angiotensin system (RAS) plays a role in idiopathic nephrotic syndrome (INS). Most studies investigated only the classical RAS axis. Therefore, the aims of the present study were to evaluate urinary levels of RAS molecules related to classical and to counter-regulatory axes in pediatric patients with INS, to compare the measurements with levels in healthy controls and to search for associations with inflammatory molecules, proteinuria and disease treatment. Subjects and methods: This cross-sectional study included 31 patients with INS and 19 healthy controls, matched for age and sex. Patients and controls were submitted to urine collection for measurement of RAS molecules [Ang II, Ang-(1-7), ACE and ACE2] by enzyme immunoassay and cytokines by Cytometric Bead Array. Findings in INS patients were compared according to proteinuria: absent (<150 mg/dl, n = 15) and present (≥150 mg/dl, n = 16). Results: In comparison to controls, INS patients had increased Ang II, Ang-(1-7) and ACE, levels while ACE2 was reduced. INS patients with proteinuria had lower levels of ACE2 than those without proteinuria. ACE2 levels were negatively correlated with 24-h-proteinuria. Urinary concentrations of MCP-1/CCL2 were significantly higher in INS patients, positively correlated with Ang II and negatively with Ang-(1-7). ACE2 concentrations were negatively correlated with IP-10/CXCL-10 levels, which, in turn, were positively correlated with 24-h-proteinuria. Conclusion: INS patients exhibited changes in RAS molecules and in chemokines. Proteinuria was associated with low levels of ACE2 and high levels of inflammatory molecules.

Novel Medical Treatments for Hypertension and Related Comorbidities

Purpose of Review

The purpose of this review is to summarize the most recent data available on advances in development of novel medical treatments for hypertension and related comorbidities.

Recent Findings

Approximately half of all hypertensive patients have not achieved goal blood pressure with current available antihypertensive medications. Recent landmark studies and new hypertension guidelines have called for stricter blood pressure control, creating a need for better strategies for lowering blood pressure. This has led to a shift in focus, in recent years, to the development of combination pills as a means of achieving improved blood pressure control by increasing adherence to prescribed medications along with further research and development of promising novel drugs based on discovery of new molecular targets such as the counter-regulatory renin-angiotensin system.

Summary

Fixed-dose combination pills and novel treatments based on recently discovered pathogenic mechanisms of hypertension that have demonstrated promising results as treatments for hypertension and related comorbidities will be discussed in this review.

Elevated Oxidative Stress and Inflammation in Hypothalamic Paraventricular Nucleus Are Associated With Sympathetic Excitation and Hypertension in Rats Exposed to Chronic Intermittent Hypoxia

Obstructive sleep apnea (OSA), characterized by recurrent collapse of the upper airway during sleep leading to chronic intermittent hypoxia (CIH), is an independent risk factor for hypertension. Sympathetic excitation has been shown to play a major role in the pathogenesis of OSA-associated hypertension. Accumulating evidence indicates that oxidative stress and inflammation in the hypothalamic paraventricular nucleus (PVN), a critical cardiovascular and autonomic center, mediate sympathetic excitation in many cardiovascular diseases. Here we tested the hypothesis that CIH elevates oxidative stress and inflammation in the PVN, which might be associated with sympathetic excitation and increased blood pressure in a rat model of CIH that mimics the oxygen profile in patients with OSA. Sprague-Dawley rats were pretreated with intracerebroventricular (ICV) infusion of vehicle or superoxide scavenger tempol, and then exposed to control or CIH for 7 days. Compared with control+vehicle rats, CIH+vehicle rats exhibited increased blood pressure, and increased sympathetic drive as indicated by the blood pressure response to ganglionic blockade and plasma norepinephrine levels. Pretreatment with ICV tempol prevented CIH-induced increases in blood pressure and sympathetic drive. Molecular studies revealed that expression of NAD(P)H oxidase subunits, production of reactive oxygen species, expression of proinflammatory cytokines and neuronal excitation in the PVN were elevated in CIH+vehicle rats, compared with control+vehicle rats, but were normalized or reduced in CIH rat pretreated with ICV tempol. Notably, CIH+vehicle rats also had increased systemic oxidative stress and inflammation, which were not altered by ICV tempol. The results suggest that CIH induces elevated oxidative stress and inflammation in the PVN, which lead to PVN neuronal excitation and are associated with sympathetic excitation and increased blood pressure. Central oxidative stress and inflammation may be novel targets for the prevention and treatment of hypertension in patients with OSA.

Sinomenine Attenuates Chronic Intermittent Hypoxia-Induced Lung Injury by Inhibiting Inflammation and Oxidative Stress

Background

In the present study, we aimed to investigate the effects of sinomenine (SIN) on chronic intermittent hypoxia (CIH)- induced lung injury in rats, and to explore the underlying mechanisms.

Material/Methods

To perform the investigation, a CIH rat model was established. ELISA assay was applied to detect the level of inflammatory cytokines. Oxidative stress bio-markers (MDA, SOD, and CAT) were determined in lung tissues. In addition, the expression level of NADPH oxidase 2 (Nox2) was analyzed by Western blotting and qRT-PCR, respectively.

Results

The results showed that compared with other groups, more obvious pulmonary pathological changes were observed in the CIH group. The level of inflammatory cytokines in the CIH group was markedly higher than that in the control and Con-S groups. Compared with the control and Con-S groups, oxidative stress was notably increased in the CIH group. Expression of Nox2 was also increased in the CIH group. The effects caused by CIH in rats were attenuated by SIN treatment.

Conclusions

SIN can reverse chronic intermittent hypoxia-induced lung injury through inhibiting inflammation and oxidative stress.

Angiotensin-(1-7) and Alamandine on Experimental Models of Hypertension and Atherosclerosis

PURPOSE OF REVIEW

The purpose of this review was to summarize the current knowledge on the role of angiotensin-(1-7) [Ang-(1-7)] and alamandine in experimental hypertension and atherosclerosis.

RECENT FINDINGS

The renin-angiotensin system (RAS) is a very complex system, composed of a cascade of enzymes, peptides, and receptors, known to be involved in the pathogenesis of hypertension and atherosclerosis. Ang-(1-7), identified and characterized in 1987, and alamandine, discovered 16 years after, are the newest two main effector molecules from the RAS, protecting the vascular system against hypertension and atherosclerosis. While the beneficial effects of Ang-(1-7) have been widely studied in several experimental models of hypertension, much less studies were performed in experimental models of atherosclerosis. Alamandine has shown similar vascular effects to Ang-(1-7), namely, endothelial-dependent vasorelaxation mediated by nitric oxide and hypotensive effects in experimental hypertension. There are few studies on the effects of alamandine on atherosclerosis.