Angiotensin II type 2 receptor agonist attenuates LPS-induced acute lung injury through modulating THP-1-derived macrophage reprogramming

Acute respiratory distress syndrome (ARDS) is a devastating respiratory disorder, characterized by overwhelming inflammation in the alveoli without effective pharmacological treatment. We aimed to investigate the effect and mechanism of angiotensin II type 2 receptor (AT2R) agonist, Compound 21 (C21), on the lipopolysaccharide (LPS)-induced acute lung injury (ALI) model. The protective effect of C21 was evaluated via enzyme-linked immunosorbent assay (ELISA), Western blot (WB), real-time PCR, and fluorescence microscopy in LPS-challenged THP1-derived macrophages. Besides, the in vivo efficacy of C21 was assessed using cell counting, ELISA, protein quantification, hematoxylin-eosin (H&E) staining, and WB in an LPS-induced ALI mouse model. The results showed that C21 significantly inhibited the secretion of pro-inflammatory cytokines (CCL-2, IL-6), overproduction of intracellular ROS, and activation of inflammatory pathways (NF-κB/NLRP3, p38/MAPK) in THP-1 cell-derived macrophages stimulated by LPS. In in vivo study, intraperitoneal injection of C21 could reduce airway leukocytes accumulation and chemokine/cytokine (keratinocyte chemoattractant (KC), IL-6) generation, as well as alleviate diffuse alveolar damage induced by LPS. Conclusively, the AT2R agonist C21 significantly inhibited LPS-stimulated excess inflammatory responses and oxidative stress in macrophages. Meanwhile, C21 could effectively alleviate acute inflammation and tissue damage in the lungs of ALI mice challenged by LPS. The results of this study bring new hope for the early treatment of ALI/ARDS.

Angiotensin Type 2 Receptor Pharmacological Agonist Relieves Neurocognitive Deficits via Reducing Neuroinflammation and Microglial Engulfment of Dendritic Spines

Mechanically ventilated patients suffering critical illness are at high risk of developing neurocognitive impairments. Angiotensin type 2 receptor (AGTR2) has been demonstrated to be anti-inflammatory and neuroprotective. The present study thus aimed to investigate whether AGTR2 can alleviate cerebral dysfunction in mice subjected to cochallenge with lipopolysaccharide (LPS) and mechanical ventilation (MV), and to reveal the underlying mechanism. We utilized a mice model that received a single injection of LPS (1 mg/kg, intraperitoneally) followed 2 h later by MV (10 ml/kg, lasting for 2 h). Pretreatment with the AGTR2 pharmacological agonist C21 (0.03, 0.3, and 3 mg/kg, intraperitoneally, once daily, lasting for 10 days). Locomotor activity and behavioral deficits were evaluated 24 h post-MV by open-field and fear-condition tests. Brain hippocampus and prefrontal cortex tissues were collected for immunofluorescence staining and western blotting to evaluate the resulting impacts on microglia, including morphological traits, functional markers, synaptic engulfment, superoxide production, and signaling molecules. Compared with vehicle-control, pre-administrated C21 reduced the branch endpoints and length of microglia processes in a dose-dependent manner in mice subjected to LPS/MV. The neuroprotective effect of AGTR2 was behaviorally confirmed by the improvement of memory decline in LPS/MV-treated mice following C21 pretreatment. In addition to morphological alterations, C21 reduced microglial functional markers and reduced microglial-dendrite contact and microglial engulfment of synaptic protein markers. In terms of the underlying molecular mechanism, AGTR2 stimulation by C21 leads to activation of protein phosphatase 2A, which subsequently mitigates microglial PKCδ and NF-κB activation, and inhibites NOX2-derived ROS production. The AGTR2 agonist C21 alleviates behavioral deficits in those mice subjected to LPS/MV, via mechanisms that involve reactive microglia and abnormal synaptic plasticity in NOX2-derived ROS and the PKCδ-NFκB pathway.

Adherence to guidelines in people with screen-detected type 2 diabetes, ADDITION, Denmark

OBJECTIVE

In people with screen-detected type 2 diabetes in primary care, (1) to assess adherence to guidelines, recommending consultation with the GP every three months and treatment initiation with an ACE inhibitor or an angiotensin-II receptor antagonist when systolic BP was > 120 mmHg and/or diastolic BP was > 80 mmHg, and (2) to identify predictors for adherence.

DESIGN

Prospective follow-up of a fixed cohort of patients.

SETTING

Fifty-four Danish general practices.

SUBJECTS AND MAIN OUTCOME MEASURES

A total of 361 people with screen-detected type 2 diabetes were followed up for 410 days to assess planned consultations with their GP and recording of BP. Some 226 people, with BP recorded above guideline threshold(s) and where treatment was not already initiated, were followed for up to 410 days to monitor prescription redemption.

RESULTS

At 3, 6, 9 and 12 months 80%, 77%, 74%, and 73% of the cohort attended a consultation. A total of 89% of the cohort attended two of the four planned consultations. The probability of redeemed prescriptions for an ACE inhibitor or an angiotensin-II receptor antagonist according to the guideline during the first year following diagnosis was 51%. High initial BP was associated with prescription redemption. No other analysed individual or organisational characteristics were found to be associated with treatment initiation.

CONCLUSION

The consultation attendance was reasonably high, and treatment initiation with an ACE inhibitor or an angiotensin-II receptor antagonist according to the guideline was found in half of the cases. High initial BP increased the probability of treatment initiation.

Clinical and experimental aspects of olmesartan medoxomil, a new angiotensin II receptor antagonist

Olmesartan medoxomil is a new orally active angiotensin II (Ang II) type 1 receptor antagonist. It is a prodrug and is rapidly de-esterified during absorption to form olmesartan, the active metabolite. Olmesartan is a potent, competitive and selective Ang II type 1 receptor antagonist. Olmesartan is not metabolized by the cytochrome P-450 and has a dual route of elimination, by kidneys and liver. In patients with essential hypertension olmesartan medoxomil administered once daily at doses of 10-80 mg dose-dependently reduced diastolic blood pressure (DBP). Troughto-peak ratios for both DBP and systolic blood pressure (SBP) were above 50%. At the recommended once-daily starting doses, olmesartan medoxomil (20 mg) was more effective than losartan (50 mg), valsartan (80 mg) or irbesartan (150 mg) in reducing cuff DBP in patients with essential hypertension. The results of cuff SBP and mean 24-h DBP and SBP were similar to those of cuff DBP measurement. In mild-to-moderate hypertensive patients the recommended starting dose of olmesartan medoxomil was as effective as that of amlodipine besylate (5 mg/day) in reducing both cuff and 24-h blood pressure. In lowering DBP olmesartan medoxomil, at 10-20 mg/day, was as effective as atenolol at 50-100 mg/day. In mild-to-moderate hypertensive patients, olmesartan medoxomil, at 5-20 mg once daily, was more effective than captopril at 12.5-50 mg twice daily. At 20-40 mg once daily olmesartan medoxomil was as effective as felodipine, at 5-10 mg once daily. Olmesartan medoxomil has minimal adverse effects with no clinically important drug interactions. Animal studies have shown that olmesartan medoxomil provides a wide range of organ protection. Olmesartan medoxomil ameliorated atherosclerosis in hyperlipidemic animals and ameliorated cardiac remodeling and improved survival in rats with myocardial infarction. Olmesartan medoxomil has renoprotective effects in a remnant kidney model and type 2 diabetes models. Future investigation should reveal whether these beneficial effects of olmesartan medoxomil are applicable to human diseases.

Angiotensin II type 2 receptor gene transfer elicits cardioprotective effects in an angiotensin II infusion rat model of hypertension

The role of the angiotensin II type 2 receptor (AT2R) in cardiovascular physiology remains elusive. We have developed an in vivo lentiviral vector-mediated gene transfer system to study the physiological functions of the AT2R. Our objectives in this study were to determine whether the AT2R influences cardiac hypertrophy and myocardial and perivascular fibrosis in a nongenetic rat model of hypertension. Lentiviral vector containing the AT2R or saline was injected intracardially in 5-day-old Sprague-Dawley rats. This resulted in a persistent overexpression of the AT2R in cardiac tissues. At 15 wk of age, animals were infused with either 200 ng·kg−1·min−1 of angiotensin II or saline by implantation of a 4-wk osmotic minipump. This resulted in an increase in blood pressure (BP) that reached maximal by 2 wk of treatment and was associated with a 123% increase in left ventricular wall thickness (LVWT) and a 129% increase in heart weight to body weight ratios (HW/BW). In addition, the increase in cardiac hypertrophy was associated with a 300% and 158% increase in myocardial and perivascular fibrosis, respectively. Cardiac transduction of the AT2R resulted in an 85% attenuation of LVWT, 91% attenuation of HW/BW, and a 43% decrease in myocardial fibrosis induced by angiotensin infusion. These improvements in cardiac pathology were observed in the absence of attenuation of high BP. Thus our observations indicate that long-term expression of the AT2R in the heart attenuates cardiac hypertrophy and fibrosis in a nongenetic rat model of hypertension.

Is the angiotensin ii type 2 receptor cerebroprotective?

Most of the deleterious effects of angiotensin II (Ang II) on blood pressure (BP), cardiovascular remodeling, and atherosclerosis are mediated by Ang II type 1 (AT1)-receptor activation. This explains why Ang-II-decreasing or blocking drugs have been successful in decreasing global cardiovascular morbimortality in patients with cardiac complications. However, in primary or secondary stroke prevention trials in patients with low cardiac risk, b-blockers and angiotensin-converting enzyme inhibitors (ACEIs), which decrease Ang II formation, seem to be less protective than thiazides and dihydropyridines, which increase Ang II. When compared with a beta-blocker, an Ang II-increasing AT1-receptor blocker better protects against stroke but not against cardiac events, whereas an ACEI gives the same protection against both cardiac and cerebral events. This dissociation between blood-pressure-independent cardiac and cerebral protection between b-blockers or ACEIs versus AT1-blockers in patients with low cardiac risk can be best explained if, besides the beneficial vascular effect of AT1-receptor blunting, there is evidence of a beneficial effect of non-AT1-receptor activation. In this review, we present experimental evidence for AT2- and AT4-receptor-mediated brain-anti-ischemic mechanisms and propose a direct comparison of AT1-blockers with ACEIs to prove the clinical effectiveness of non-AT1-mediated mechanisms in stroke prevention, particularly in patients with a higher risk for stroke than for cardiac complications.