Expression and regulation of AT1 receptor in rat lung microvascular endothelial cell

Angiotensin Receptor Blockers Are Not Just for Hypertension Anymore

Beyond blood pressure control, angiotensin receptor blockers reduce common injury mechanisms, decreasing excessive inflammation and protecting endothelial and mitochondrial function, insulin sensitivity, the coagulation cascade, immune responses, cerebrovascular flow, and cognition, properties useful to treat inflammatory, age-related, neurodegenerative, and metabolic disorders of many organs including brain and lung.

Candesartan could ameliorate the COVID-19 cytokine storm

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Activating Mas receptor protects human pulmonary microvascular endothelial cells against LPS-induced apoptosis via the NF-kB p65/P53 feedback pathways

The balance between Ang II/AT1R and Ang-(1-7)/Mas plays a pivotal role in the development of lipopolysaccharides (LPS)-induced acute respiratory distress syndrome. However, the mechanisms underlying the balancing process still remain unclear. Here we investigated the roles of nuclear factor (NF)-κB and p53 in regulating AT1R and Mas expression. The results demonstrated that Ang II pretreatment resulted in downregulation of Mas and upregulation of AT1R, phosphorylated p65, and apoptosis in LPS-treated Human pulmonary microvascular endothelial cells (HPMVECs), but had no effect on p53 expression. Lentiviral vector-mediated P65 knockdown, but not a P53 knockdown, reversed all these effects of Ang II. On the other hand, Ang-(1-7) pretreatment lead to an increased in Mas expression and a decrease in AT1R, p53, and phosphorylated p65 expressions with suppressed apoptosis in LPS-treated cells. P65 knockdown promoted the protein expression of both AT1R and Mas while inhibiting p53 expression. P53 knockdown, but not a p65 knockdown, reversed all these effects of Ang-(1-7). Interestingly, p65 overexpression upregulated p53 and AT1R but downregulated Mas. P53 knockdown activated p65. These results suggest that there is a two-way feedback regulation between AT1R and Mas receptor via the NF-kB p65/P53 pathway, which may play a key role in LPS-induced HPMVECs apoptosis.

Vitamin D alleviates lipopolysaccharide‑induced acute lung injury via regulation of the renin‑angiotensin system

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the clinical manifestations of severe lung damage and respiratory failure. ALI and ARDS result are associated with high mortality in patients. At present, no effective treatments for ALI and ARDS exist. It is established that vitamin D exhibits anti-inflammatory effects, however, the specific effect of vitamin D on ALI remains largely unknown. The aim of the present study was to investigate whether, and by which mechanism, vitamin D alleviates lipopolysaccharide (LPS)-induced ALI. The results demonstrated that a vitamin D agonist, calcitriol, exhibited a beneficial effect on LPS-induced ALI in rats; calcitriol pretreatment significantly improved LPS-induced lung permeability, as determined using Evans blue dye. Results from reverse transcription-quantitative polymerase chain reaction, western blotting and ELISA analysis demonstrated that calcitriol also modulated the expression of members of the renin-angiotensin system (RAS), including angiotensin (Ang) I-converting enzymes (ACE and ACE2), renin and Ang II, which indicates that calcitriol may exert protective effects on LPS-induced lung injury, at least partially, by regulating the balance between the expression of members of the RAS. The results of the present study may provide novel targets for the future treatment of ALI.

JAK2/STAT3 Pathway Was Associated with the Protective Effects of IL-22 On Aortic Dissection with Acute Lung Injury

Patients with aortic dissection (AD) may present acute lung injury (ALI) that may affect the prognosis. In this study, we aim to investigate the roles and mechanism of IL-22 in the pathogenesis of AD complicated with ALI. Six hundred and twenty-one AD patients were included, and the incidence of ALI and pulmonary CT findings were analyzed. Mouse ALI model was established through AngII, and then IL-22 injection and AG490 were given. The pathological changes, infiltration of inflammatory cells, and expression of STAT3 were determined. For the in vitro experiment, cultivated pulmonary microvascular endothelial cells (PMVECs) were treated by angiotensin II (AngII), followed by treating with IL-22 and/or AG490. The expression and migration of STAT3 was determined. Flow cytometry was carried out to evaluate the apoptosis. IL-22 contributed to the expression of STAT3 in lung tissues and attenuation of ALI. IL-22 obviously inhibited the apoptosis of PMVECs mediated by AngII and downregulated the expression and intranuclear transmission of STAT3. Such phenomenon was completely inhibited upon administration of AG490, an inhibitor of JAK2. Our data showed IL-22 contributed to the inhibition of PMVEC apoptosis mediated by AngII through activating the JAK2/STAT3 signaling pathway, which may attenuate the ALI induced by AngII.

Effect of lipopolysaccharide on angiotensin II type 1 receptor expression and function in human pulmonary microvascular endothelial cells

Lipopolysaccharides (LPSs) are an important initiation factor in acute respiratory distress syndrome. The aim of the present study was to investigate the effect of LPSs on the regulation of angiotensin II (Ang II) receptors in human pulmonary microvascular endothelial cells (HPMECs). HPMECs were treated with 0, 50, 100 or 200 ng/ml LPS and incubated for 4, 8, 12 or 16 h. The expression of Ang II type 1 receptor (AT1R) and Ang II type 2 receptor (AT2R) was determined using reverse transcription‑polymerase chain reaction and western blot analysis. The affinity to Ang II was measured using a radioligand binding assay. No AT2R expression was detected with or without LPS administration in HPMECs, and LPS treatment increased the expression level of AT1R. A time‑dependent increase of AT1R transcription was observed in the 50 ng/ml group, while in the 100 and 200 ng/ml groups, the AT1R mRNA levels reached peak values at 4 h and remained unchanged. The protein level of AT1R increased significantly in a dose‑dependent manner for each incubation time period. A time‑dependent increase in the protein level was observed in the 50 and 100 ng/ml groups. As for the 200 ng/ml group, the level of AT1R reached a peak value at 8 h. Maximal binding (Bmax) significantly increased following LPS treatment and Bmax of the 50 ng/ml group exhibited a time‑dependent increase. The Bmax of the 100 and 200 ng/ml groups reached peak values at 12 and 8 h, respectively, and decreased thereafter. The dissociation constant remained unchanged following LPS treatment. Thus, treatment with LPS increased AT1R expression and its Bmax to Ang II in HPMECs, however, did not alter the affinity of AT1R to Ang II.

Expression of IL-17A and IL-17F in lipopolysaccharide-induced acute lung injury and the counteraction of anisodamine or methylprednisolone

Th17 cytokines IL-17A and IL-17F as pro-inflammatory cytokines played an important role in triggering inflammatory responses. However, little was known about the expression of IL-17A and IL-17F in acute lung injury (ALI). Therefore, the present study investigated the expression of IL-17A and IL-17F in lipopolysaccharide (LPS)-induced ALI in rats and rat pulmonary microvascular endothelial cells (PMVEC) by enzyme-linked immunosorbant assay or reverse transcription-polymerase chains reaction. Anisodamine and methylprednisolone were also investigated as anti-inflammatory strategy in the process of LPS-induced ALI. Lung injury was evaluated by histological changes, right lung wet weight:body weight (LW/BW) ratios, and protein education and total leukocyte count of bronchoalveolar lavage fluid (BALF). Our findings showed that LPS exposure elevated the levels of leukocyte number, protein education in BALF and the ratios of LW/BW, increased the expression of IL-17A and IL-17F in the lung tissues homogenate, BALF and serum of ALI rats. Up-regulation of IL-17F expression was also observed after LPS challenge in rat PMVEC. Treatment with anisodamine or methylprednisolone significantly inhibited the increases of parameters of ALI induced by LPS, and markedly reduced the expression of IL-17A and IL-17F in rats and the IL-17F expression in PMVEC. These data suggested that IL-17A and IL-17F maybe play an important role in LPS-induced ALI via autocrine and paracrine mechanisms, and anisodamine is similar in extent to methylprednisolone that contributes to relieve LPS-induced ALI.

Role of p53-dependent placental apoptosis in the reproductive and developmental toxicities of caffeine in rodents

The aim of the present study was to evaluate the role of placental apoptosis in mediating the reproductive and developmental toxicity of caffeine in rodents. Female Kunming mice were treated with caffeine (60, 120 and 240 mg/kg per day) before and during pregnancy. The conception rate, maternal bodyweight gain, placental weight and indices of fetal developmental, including the rate of intrauterine growth retardation (IUGR; i.e. the actual number of fetuses exhibiting IUGR as a percentage of the total number of fetuses), were determined on gestational day (GD) 18. Female Wistar rats were treated with caffeine (20, 60 and 180 mg/kg per day) from GD11 to GD20. The IUGR rate, maternal plasma angiotensin (Ang) II and prolactin concentrations, placental pathology, expression of angiotensin AT(1) and AT(2) receptors and apoptosis-related proteins were measured on GD20. In mice, caffeine treatment dose-dependently reduced the total conception rate, delayed conception and decreased maternal bodyweight gain, placental weight, fetal bodyweight and fetal body and tail lengths, whereas the IUGR rate was increased. In rats, caffeine treatment dose-dependently decreased placental weight and fetal bodyweight and increased the IUGR rate. Abnormal placental structures and decreased maternal plasma prolactin concentrations were observed following 180 mg/kg per day caffeine treatment, which resulted in increases in renin-angiotensin system (RAS) activity, including maternal plasma AngII concentrations and placental AT(1B) and AT(2) receptor expression, and Bax and p53 expression, but decreases in placental Bcl-2 expression. On the basis of the results of the present study, it appears that caffeine ingestion has detrimental effects on the reproductive system and fetal development in rodents that are associated with chronic activation of the maternal and placental RAS, and induction of p53-dependent placental apoptosis.

Vasculoprotective effect of U50,488H in rats exposed to chronic hypoxia: role of Akt-stimulated NO production

Impairment of pulmonary endothelium function in the pulmonary artery is a direct result of chronic hypoxia. This study is to investigate the vasculoprotective effects of U50,488H (a selective κ-opioid receptor agonist) and its underlying mechanism in hypoxia-induced pulmonary artery endothelial functional injury. Chronic hypoxia was simulated by exposing the rats to 10% oxygen for 2 wk. After hypoxia, right ventricular pressure (RVP) and right ventricular hypertrophy index (RVHI) were measured. The pulmonary vascular dysfunction, effect of nitric oxide synthase inhibitor (l-NAME) on the relaxation of U50,488H, and level of nitric oxide (NO) were determined. In vitro, the signaling pathway involved in the anti-apoptotic effect of U50,488H was investigated. Cultured endothelial cells were subjected to simulated hypoxia, and cell apoptosis was determined by TUNEL staining. U50,488H (1.25 mg/kg) significantly reduced RVP and RVHI in hypoxia. U50,488H markedly improved both pulmonary endothelial function (maximal vasorelaxation in response to ACh: 74.9 ± 1.8%, n = 6, P <0.01 vs. hypoxia for 2 wk group) and increased total NO production (1.65 fold). U50,488H relaxed the pulmonary artery rings of the hypoxic rats. This effect was partly abolished by l-NAME. In cells, U50,488H both increased NO production and reduced hypoxia-induced apoptosis. Moreover, pretreatment with nor-binaltorphimine (nor-BNI, a selective κ-opioid receptor antagonist), PI3K inhibitor, Akt inhibitor or l-NAME almost abolished anti-apoptotic effect exerted by U50,488H. U50,488H resulted in increases in Akt and eNOS phosphorylation. These results demonstrate that pretreatment with U50,488H attenuates hypoxia-induced pulmonary vascular endothelial dysfunction in an Akt-dependent and NO-mediated fashion.

Effect of unilateral ureteral obstruction and anti-angiotensin II treatment on renal tubule and interstitial cell apoptosis in rats

AIM

To investigate the effects of angiotensin-converting enzyme inhibitor (cilazapril) and angiotensin II type I receptor antagonist (losartan) on tubular and interstitial cell apoptosis and caspase-3 activity in rats with obstructive nephropathy after unilateral ureteral obstruction.

METHODS

Rats with unilateral obstructive nephropathy and sham-operated rats were treated with cilazapril, losartan, or the vehicle (water). Tubular and interstitial cell apoptosis was detected morphologically on hematoxylin and eosin-stained renal specimens and by the terminal deoxynucleotidyl transferase-mediated nick end-labeling. Caspase-3 activity in whole-kidney tissue homogenates was measured colorimetrically.

RESULTS

After unilateral ureter ligation, there was a significant increase in the number of apoptotic tubular and interstitial cells in the obstructed kidney (P=0.049 and P=0.036, respectively, vs sham-operated rats, 10 days after ligation). In rats with unilateral obstructive nephropathy, neither cilazapril nor losartan had an effect on tubular cell apoptosis. However, cilazapril caused a significant increase in the number of renal apoptotic interstitial cells (P=0.019). Caspase-3 activity was not significantly different in rats with unilateral obstructive nephropathy than in sham-operated rats.

CONCLUSION

Rats with unilateral obstructive nephropathy had increased apoptosis of tubular and interstitial cells in comparison with sham-operated rats. Neither cilazapril nor losartan had an effect on tubular cell apoptosis, and cilazapril even increased interstitial cell apoptosis.

Interleukin-17F-induced pulmonary microvascular endothelial monolayer hyperpermeability via the protein kinase C pathway

BACKGROUND

Interleukin (IL)-17F is involved in lung inflammation, but the effect of IL-17F on endothelial permeability and its signaling pathway remain ill-defined. The current study sought to investigate the effect of IL-17F on endothelium and assess the role of protein kinase C (PKC) and src-suppressed C kinase substrate (SSeCKS) in this process.

METHODS

Rat pulmonary microvascular endothelial monolayers were constructed to determine changes of permeability as measured by means of FITC-dextran and Hank's solution flux across monolayers and transendothelial electrical resistance with or without IL-17F and PKC inhibitors. Additional monolayers were stained using FITC-phalloidin for filamentous actin (F-actin). The gene expression of SSeCKS was analyzed by the reverse transcription-polymerase chains. Alterations of SSeCKS protein were investigated by immunoblotting and immunoprecipitation.

RESULTS

IL-17F increased endothelial monolayer permeability in a dose- and time-dependent manner. F-actin staining revealed that permeability changes were accompanied by reorganization of cytoskeleton. In the presence of PKC inhibitors, the IL-17F-induced hyperpermeability and reorganization of F-actin were attenuated. The gene and protein expression of SSeCKS were conspicuously elevated after IL-17F challenge. The process of SSeCKS phosphorylation followed a time course that mirrored the time course of hyperpermeability induced by IL-17F. IL-17F-induced SSeCKS phosphorylation was abrogated after PKC inhibitors pretreatment. The translocation of SSeCKS from the cytosol to the membrane and a significant increase in the SSeCKS association with the cytoskeleton were found after IL-17F treatment.

CONCLUSIONS

IL-17F is an important mediator of increased endothelial permeability. PKC and SSeCKS are integral signaling components essential for IL-17F-induced hyperpermeability.

Synergism between AT1 receptor and hyperhomocysteinemia during vascular remodeling

BACKGROUND

Hyperhomocysteinemia (HHcy) is an independent risk factor of cardiovascular diseases. Extracellular signal-regulated kinase-1/2 (ERK-1/2) and the JAK/STAT pathway kinase, signal transducer and activator of transcription 3 (STAT3), are involved in matrix metalloproteinase-9 (MMP-9) induction and matrix remodeling. However, their role in homocysteine (Hcy)-mediated MMP-9 induction and matrix remodeling is unclear. Clinical and experimental evidence indicates that HHcy and activation of the renin-angiotensin system, mediated by angiotensin II type 1 (AT1) receptor, are involved in a variety of vascular pathologies. Despite this fact, the relationship between HHcy and activation of the renin-angiotensin system has not been comprehensively characterized. Therefore, we hypothesized that Hcy activates AT1 receptor that potentiates STAT3 via ERK-1/2 phosphorylation. STAT3 modulates target MMP-9 and collagen, resulting in vascular remodeling.

METHODS

Mouse aortic endothelial cells (MAEC) were treated with various doses of Hcy for different time periods. The levels of AT1 receptor, ERK-1/2, STAT3, MMP-9 and collagen type-1 were measured by immunoblot analyses. The activation of ERK-1/2 and STAT3 were determined by measuring ERK-1/2 phosphorylation and phosphoserine (727) STAT3.

RESULTS

Although Hcy dose-dependently induced AT1 receptor expression in the endothelial cells, a significant induction was observed at 100 microM at 48 h. We investigated Hcy-induced ERK-1/2 and STAT3 phosphorylation through AT1 receptor induction, and our results suggest that Hcy activated AT1 receptor which led to ERK-1/2 and STAT3 phosphorylation. In addition, findings of this study suggest that Hcy-mediated STAT3 activation regulated MMP-9 and collagen type-1. However, AT1 receptor blocker, valsartan, and the specific STAT3 inhibitor peptide attenuated MMP-9 and collagen type-1 induction.

CONCLUSIONS

These findings demonstrate for the first time the contribution of AT1 receptor in HHcy-induced atherosclerotic diseases; Hcy-induced activation of AT1 receptor involves MMP-9 and collagen type-1 modulation using ERK-1/2 and STAT3 signaling cascades.

Role of angiotensin II in endothelial dysfunction induced by lipopolysaccharide in mice

Endotoxin [or lipopolysaccharide (LPS)] increases levels of superoxide in blood vessels and impairs vasomotor function. Angiotensin II plays an important role in the generation of superoxide in several disease states, including hypertension and heart failure. The goal of this study was to determine whether the activation of the renin-angiotensin system contributes to oxidative stress and endothelial dysfunction after endotoxin. We examined the effects of enalapril (an angiotensin-converting enzyme inhibitor) or L-158809 (an angiotensin receptor blocker) on increases of superoxide and vasomotor dysfunction in mice treated with LPS. C57BL/6 mice were treated with either enalapril (60 mg.kg(-1).day(-1)) or L-158809 (30 mg.kg(-1).day(-1)) for 4 days. After the third day, LPS (10-20 mg/kg) or vehicle was injected intraperitoneally, and one day later, vasomotor function of the aorta was examined in vitro. After precontraction with PGF(2alpha), the maximal responses to sodium nitroprusside were similar in the aorta from normal and LPS-treated mice. In contrast, the relaxation to acetylcholine was impaired after LPS (54 +/- 5% at 10(-5), mean +/- SE) compared with vessels treated with vehicle (88 +/- 1%; P < 0.05). Enalapril improved (P < 0.05) relaxation in response to acetylcholine to 81 +/- 6% after LPS. L-158809 also improved relaxation in response to acetylcholine to 77 +/- 4% after LPS. Superoxide (measured with lucigenin and hydroethidine) was increased (P < 0.05) in aorta after LPS, and levels were reduced (P < 0.05) following enalapril and L-158809. Thus, after LPS, enalapril and L-158809 reduce superoxide levels and improve relaxation to acetylcholine in the aorta. The findings suggest that activation of the renin-angiotensin system contributes importantly to oxidative stress and endothelial dysfunction after endotoxin.