Reduction of bleomycin induced lung fibrosis by candesartan cilexetil, an angiotensin II type 1 receptor antagonist

Cell type-specific expression of angiotensin receptors in the human lung with implications for health, aging, and chronic disease

The renin-angiotensin system is a highly characterized integrative pathway in mammalian homeostasis whose clinical spectrum has been expanded to lung disorders such as chronic obstructive pulmonary disease (COPD)-emphysema, idiopathic pulmonary fibrosis (IPF), and COVID pathogenesis. Despite this widespread interest, specific localization of this receptor family in the mammalian lung is limited, partially due to the imprecision of available antibody reagents. In this study, we establish the expression pattern of the two predominant angiotensin receptors in the human lung, AGTR1 and AGTR2, using complementary and comprehensive bulk and single-cell RNA-sequence datasets that are publicly available. We show these two receptors have distinct localization patterns and developmental trajectories in the human lung, pericytes for AGTR1 and a subtype of alveolar epithelial type 2 cells for AGTR2. In the context of disease, we further pinpoint AGTR2 localization to the COPD-associated subpopulation of alveolar epithelial type 2 (AT2B) and AGTR1 localization to fibroblasts, where their expression is upregulated in individuals with COPD, but not in individuals with IPF. Finally, we examine the genetic variation of the angiotensin receptors, finding AGTR2 associated with lung phenotype (i.e., cystic fibrosis) via rs1403543. Together, our findings provide a critical foundation for delineating this pathway's role in lung homeostasis and constructing rational approaches for targeting specific lung disorders.

Postoperative Angiotensin Receptor Blocker Use is Associated With Decreased Rates of Manipulation Under Anesthesia, Arthroscopic Lysis of Adhesions, and Prosthesis-Related Complications in Patients Undergoing Total Knee Arthroplasty

BACKGROUND

The cellular mechanisms underlying excess scar tissue formation in arthrofibrosis following total knee arthroplasty (TKA) are well-described. Angiotensin receptor blockers (ARB), particularly losartan, is a commonly prescribed antihypertensive with demonstrated antifibrotic properties. This retrospective study aimed to assess the rates of 1- and 2-year postoperative complications in patients who filled prescriptions for ARBs during the 90 days after TKA.

METHODS

Patients undergoing primary TKA were selected from a large national insurance database, and the impact of ARB use after TKA on complications was assessed. Of the 1,299,106 patients who underwent TKA, 82,065 had filled at least a 90-day prescription of losartan, valsartan, or olmesartan immediately following their TKA. The rates of manipulation under anesthesia (MUA), arthroscopic lysis of adhesions (LOA), aseptic loosening, periprosthetic fracture, and revision at 1 and 2 years following TKA were analyzed using multivariable logistic regressions to control for various comorbidities.

RESULTS

ARB use was associated with decreased rates of MUA (odds ratio [OR] = 0.94, 95% confidence interval (CI), 0.90 to 0.99), arthroscopy/LOA (OR = 0.86, 95% CI, 0.77 to 0.95), aseptic loosening (OR = 0.71, 95% CI, 0.61 to 0.83), periprosthetic fracture (OR = 0.58, 95% CI, 0.46 to 0.71), and revision (OR = 0.79, 95% CI, 0.74 to 0.85) 2 years after TKA.

CONCLUSIONS

ARB use throughout the 90 days after TKA is associated with a decreased risk of MUA, arthroscopy/LOA, aseptic loosening, periprosthetic fracture, and revision, demonstrating the potential protective abilities of ARBs. Prospective studies evaluating the use of ARBs in patients at risk for postoperative stiffness would be beneficial to further elucidate this association.

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.

The mechanism of oxidative stress in keloid fibroblasts and the experimental study of early application of angiotensin-converting enzyme inhibitor

Objective To investigate the protective effects of an angiotensin-converting enzyme inhibitor after inducing oxidative stress on keloid fibroblasts. Methods Primary keloid fibroblasts were isolated and cultured by enzyme digestion combined with the tissue adhesion method in vitro, and the third to fifth generations of cells were selected for the experiment. For 24 hours, keloid fibroblasts were treated with different concentrations of hydrogen peroxide. Different concentrations of angiotensin-converting enzyme inhibitor were added to the keloid fibroblast culture medium, and then the cells were treated with hydrogen peroxide for 24 hours. Results With the increase of hydrogen peroxide concentration, the growth of keloid fibroblasts was inhibited and the levels of malondialdehyde, superoxide dismutase, and reactive oxygen species increased gradually, accompanied by an increase in the expression of nicotinamide adenine dinucleotide phosphate oxidase and collagen I mRNA. The expression of nicotinamide adenine dinucleotide phosphate oxidase-mRNA in keloid fibroblasts and the formation of reactive oxygen species in keloid fibroblasts were induced by different concentrations of angiotensin II, and the most significant effect was at 10-5 mmol/mL. The effects of diphenyleneiodonium chloride (NOX inhibitor), N-acetylcysteine (reactive oxygen species inhibitor) and nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) RNA treatment on angiotensin II-induced nicotinamide adenine dinucleotide phosphate oxidase and collagen I increased significantly. Hydrogen peroxide and angiotensin II alone or combined can induce NADPH oxidase and reactive oxygen species expression in keloid fibroblasts. When the angiotensin-converting enzyme inhibitor was added, the expression of NADPH oxidase and reactive oxygen species in keloid induced by hydrogen peroxide and angiotensin II could be inhibited. Conclusion Oxidative stress can lead to increased expression of reactive oxygen species, NADPH oxidase and collagen I in keloid fibroblasts, suggesting oxidative stress mediates the migration of human keloid fibroblasts and extracellular matrix synthesis.

The effect of losartan on range of motion and rates of manipulation in total knee arthroplasty: a retrospective matched cohort study

INTRODUCTION

Arthrofibrosis remains a common cause of patient dissatisfaction and reoperation after total knee arthroplasty (TKA). Losartan is an angiotensin receptor blocker (ARB) with inhibitory effects on transforming growth factor beta, previously implicated in tissue repair induced fibrosis, and has been studied to prevent stiffness following hip arthroscopy. This study aimed to evaluate pre- and postoperative range of motion (ROM) and the incidence of manipulation under anesthesia (MUA) following primary TKA in patients taking Losartan preoperatively for hypertension.

MATERIALS AND METHODS

A retrospective review of 170 patients from 2012 to 2020 who underwent a primary, elective TKA and were prescribed Losartan at least three months prior to surgery. All patients who were prescribed Losartan and had a preoperative and postoperative ROM in their chart were included and were matched to a control group of patients who underwent TKA and had no Losartan prescription. ROM, MUA, readmissions, reoperations, and revisions were assessed using chi-square and independent sample t tests.

RESULTS

Seventy-nine patients met the inclusion criteria. Preoperative ROM was similar between patients on Losartan and the control group (103.59° ± 16.14° vs. 104.59° ± 21.59°, respectively; p = 0.745). Postoperative ROM and ΔROM were greater for patients prescribed Losartan (114.29° ± 12.32° vs. 112.76° ± 11.65°; p = 0.429 and 10.57° ± 14.95° vs. 8.17° ± 21.68°; p = 0.422), though this difference did not reach statistical significance. There was no difference in readmission, rate of manipulation for stiffness, or all-cause revision rates.

CONCLUSION

In this study, we found that the use of Losartan did not significantly improve postoperative ROM, reduce MUA or decrease revision rates. Further prospective studies using Losartan are required to elucidate the potential effects on ROM and incidence of arthrofibrosis requiring MUA.

LEVEL III EVIDENCE

Retrospective cohort study.

[Surgical treatment of arthrofibrosis of the knee joint]

Die Arthrofibrose des Kniegelenks ist eine schwerwiegende Komplikation nach Trauma und Operation, da die Funktion des Gelenks häufig dauerhaft beeinträchtigt wird. Es werden nach wie vor frühzeitige Mobilisierungstechniken und die Anästhesie eingesetzt, ohne dass die zugrunde liegenden Prozesse ausreichend aufgeklärt wurden. Während die Frühphase der Arthrofibrose gut auf konservative Maßnahmen zur Schmerzreduktion und zur Wundheilungsregulation anspricht, ist in der Spätphase häufig straffes kollagenes Narbengewebe vorhanden, das die Beweglichkeit dauerhaft einschränkt. In dieser Phase ist eine Verbesserung der Beweglichkeit ohne chirurgische Maßnahmen in der Mehrzahl der Fälle aussichtslos. Bei einer chirurgischen Therapie sollte zwischen der lokalisierten (zumeist sekundären) Arthrofibrose (z. B. Kreuzbandoperation) und einer generalisierten Arthrofibrose (primär, in der Mehrzahl der Fälle nach einer Knietotalendoprothese [Knie-TEP]) unterschieden und die Behandlung entsprechend geplant werden. Begleitende pathologische Veränderungen (Transplantatposition, Instabilität der TEP, Implantatverschleiß, „Low-grade“-Infektion, patellofemorale Instabilität oder „maltracking“, Patella baja) müssen bei der Behandlung berücksichtigt werden. Eine multimodale Begleitbehandlung (Physiotherapie, Schmerztherapie, Psychosomatik) ist zur Sicherung des Behandlungserfolgs notwendig.

Capsulolabral Adhesions After Hip Arthroscopy for the Treatment of Femoroacetabular Impingement: Strategies During Rehabilitation and Return to Sport to Reduce the Risk of Revision

This article will review various strategies such as passive range of motion modalities, active range of motion movements, and pharmacological interventions for the prevention of adhesion formation after hip arthroscopy. Capsulolabral adhesions are a common cause of revision hip arthroscopy for which treatment methods are still evolving. Efforts to prevent and limit their formation postoperatively, including adjuncts such as losartan, as well as the use of consistent passive and active, multiplanar movements, both therapist and continuous passive motion machine assisted, should be considered.

Chemokine-Based Therapeutics for the Treatment of Inflammatory and Fibrotic Convergent Pathways in COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the SARS-CoV-2 betacoronavirus and has taken over 761,426 American lives as of the date of publication and will likely result in long-term, if not permanent, tissue damage for countless patients. COVID-19 presents with diverse and multisystemic pathologic processes, including a hyperinflammatory response, acute respiratory distress syndrome (ARDS), vascular injury, microangiopathy, tissue fibrosis, angiogenesis, and widespread thrombosis across multiple organs, including the lungs, heart, kidney, liver, and brain. C-X-C chemokines contribute to these pathologies by attracting inflammatory mediators, the disruption of endothelial cell integrity and function, and the initiation and propagation of the cytokine storm. Among these, CXCL10 is recognized as a critical contributor to the hyperinflammatory state and poor prognosis in COVID-19. CXCL10 is also known to regulate growth factor-induced fibrosis, and recent evidence suggests the CXCL10-CXCR3 signaling system may be vital in targeting convergent pro-inflammatory and pro-fibrotic pathways. This review will explore the mechanistic role of CXCL10 and related chemokines in fibrotic complications associated with COVID-19 and the potential of CXCL10-targeted therapeutics for early intervention and long-term treatment of COVID-19-induced fibrosis.

AGTR1 blocker attenuates activation of Tenon's capsule fibroblasts after glaucoma filtration surgery via the NF-κB signaling pathway

Activation of Tenon's capsule fibroblasts limits the success rate of glaucoma filtration surgery (GFS), the most efficacious therapy for patients with glaucoma. Angiotensin type 1 receptor (AGTR1) is involved in tissues remodeling and fibrogenesis. However, whether AGTR1 is involved in the progress of fibrogenesis after GFS is not fully elucidated. The aim of this study was to investigate the role of an AGTR1 in scar formation after GFS and the potential anti-fibrosis effect of AGTR1 blocker. AGTR1 expression level was increased in subconjunctival tissues in a rat model of GFS and transforming growth factor-beta 2 (TGF-β2)-induced human Tenon's capsule fibroblasts (HTFs). AGTR1 blocker treatment suppressed TGF-β2-induced HTF migration and α-smooth muscle actin (α-SMA) and fibronectin (FN) expression. AGTR1 blocker treatment also attenuated collagen deposition and α-SMA and FN expression in subconjunctival tissues of the rat model after GFS. Moreover, AGTR1 blocker decreased TGF-β2-induced P65 phosphorylation, P65 nuclear translocation, and nuclear factor kappa B (NF-κB) luciferase activity. Additionally, BAY 11-7082 (an NF-κB inhibitor) significantly suppressed HTF fibrosis. In conclusion, our results indicate that AGTR1 is involved in scar formation after GFS. The AGTR1 blocker attenuates subconjunctival fibrosis after GFS by inhibiting the NF-κB signaling pathway. These findings indicate that targeting AGTR1 is a potential approach to attenuate fibrosis after GFS.

The inhibitory mechanisms of losartan and vitamin D on amiodarone-induced lung inflammation in rats: Role of mitogen-activated protein kinases/activator protein-1

Amiodarone (AMD), an antiarrhythmic drug, is used cautiously due to its lung toxicity that is characterized by alveolar inflammation followed by fatal fibrosis. AMD induces lung inflammation via increasing the alveolar macrophages and disturbing the balance of T-helper-1 (Th1) and Th2 cells cytokines. In this study, the role of the mitogen-activated protein kinases (MAPKs)/activator protein-1 (AP-1) pathway in AMD-induced lung inflammation was evaluated. Also, the anti-inflammatory and antifibrotic effects of losartan and/or vitamin D were investigated following 7, 14, and 28 days of AMD administration. AMD resulted in lung injury, inflammatory infiltration, and increased pulmonary levels of inflammatory cytokines starting from Week 1 of exposure. A significant increase in serum levels of interleukin-4 along with a significant reduction of interferon-gamma, in addition to strong expression of CD68, were reported after 14 and 28 days of AMD administration reflecting Th1/Th2 cytokines imbalance and the accumulation of alveolar macrophages, respectively. The phosphorylation of MAPKs (ERK1/2, JNK, p38) and AP-1 was significantly enhanced starting from Week 1 of exposure. Marked expression of transforming growth factor beta-1 and massive deposition of collagen were detected after 28 days reflecting late fibrosis. All these abnormalities were significantly mitigated by vitamin D and its combination with losartan. Losartan alone has less prominent anti-inflammatory effects particularly after 28 days; however, it efficiently prevented late fibrosis. This study concludes that MAPKs/AP-1 pathway is involved in AMD-induced lung inflammation and that vitamin D and/or losartan could be used as a prophylactic agent to prevent AMD-induced lung toxicity.

Angiotensin Receptor Blockers Were Not Associated With Decreased Arthrofibrosis After Total Knee Arthroplasty

Stiffness after total knee arthroplasty (TKA) remains a challenging problem. Angiotensin receptor blockers (ARBs) have been associated with decreased muscle fibrosis. The aim of this study was to evaluate whether perioperative use of ARBs was associated with a reduction in arthrofibrosis and manipulation under anesthesia (MUA) in patients undergoing primary TKA at 90 days and 1 year postoperative. In this retrospective study, the authors used a national database to evaluate patients undergoing TKA for primary osteoarthritis from 2007 to 2017. They evaluated patients with filled prescriptions for ARBs within the study time frame and the specific type of ARB and its association with arthrofibrosis and MUA. After adjusting for age, sex, a comorbidity index, and obesity, any ARB or specific ARBs were not associated with a reduction in the rate of arthrofibrosis or MUA after TKA (P≥.05). Male sex, age 55 years or older, and obesity were associated with a reduction in the rate of arthrofibrosis and MUA after TKA (P≤.05). Studies should be performed to evaluate ARBs to see whether there is a more specific role in preventing joint stiffness in certain patient subpopulations following TKA. [Orthopedics. 2021;44(2):e274-e280.].

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.

Targeting angiotensinogen with RNA-based therapeutics

PURPOSE OF REVIEW

To summarize all available data on targeting angiotensinogen with RNA-based therapeutics as a new tool to combat cardiovascular diseases.

RECENT FINDINGS

Liver-targeted, stable antisense oligonucleotides and small interfering RNA targeting angiotensinogen are now available, and may allow treatment with at most a few injections per year, thereby improving adherence. Promising results have been obtained in hypertensive animal models, as well as in rodent models of atherosclerosis, polycystic kidney disease and pulmonary fibrosis. The next step will be to evaluate the optimal degree of suppression, synergy with existing renin-angiotensin-aldosterone system blockers, and to determine harmful effects of suppressing angiotensinogen in the context of common comorbidities, such as heart failure and chronic kidney disease.

SUMMARY

Targeting angiotensinogen with RNA-based therapeutics is a promising new tool to treat hypertension and diseases beyond. Their long-lasting effects are particularly exciting, and if translated to a clinical application of at most a few administrations per year, may help to eliminate nonadherence.

An immunohistochemical study of the effects of various antioxidants on rat lung during chemotherapy

We investigated using immunohistochemistry the possible protective effects of ascorbic acid, α-tocopherol and selenium during chemotherapy treatment with cyclophosphamide. Thirty female Wistar rats were divided into five groups of six: group 1, untreated control; group 2, 75 µg/kg cyclophosphamide; group 3, 75 µg/kg cyclophosphamide + 150 µg/kg/day α-tocopherol; group 4, 75 µg/kg cyclophosphamide + 200 µg/kg/day ascorbic acid and group 5, 75 µg/kg cyclophosphamide + 40 ppm/kg/day selenium. Proliferating cell nuclear antigen (PCNA) staining was used to detect cell proliferation and AT₁ was used to evaluate structural damage. Caspase-8, caspase-9 and caspase-3 signal molecules were used to investigate apoptosis. In group 2, epithelium, alveolar macrophages, infiltrated lymphocytes and connective tissue were immunostained moderately to strongly with PCNA. Bronchus, alveolar wall and infiltrated lymphocytes were immunostained moderately to strongly with AT₁ and diffuse strong caspase immunoreactions were observed throughout the lung tissue. AT₁ and caspase immunoreactions in groups 4 and 5 were similar to group 2. In group 3, PCNA immunoreactivity was strong in the bronchiolus epithelium, endothelial cell nuclei and in stacks of infiltrated lymphocyte cell nuclei. In group 3, AT₁ and caspase immunoreactions were identical to group 1. It appears that α-tocopherol inhibits lung tissue damage in rats during chemotherapy.

Local activation of the pulmonary extravascular angiotensin system induces epithelial apoptosis and lung fibrosis

Previous work suggests that a local extravascular angiotensin system plays an important role in the development of pulmonary fibrosis through stimulation of alveolar epithelial cell (AEC) apoptosis and collagen deposition. To demonstrate a causative role for the local tissue angiotensin (ANG) system in lung fibrosis, we hypothesize that overexpression of the angiotensinogen (AGT) gene or pharmacologic elevation of lung tissue ANG II levels might cause apoptosis of AECs and lung fibrosis. ANGII levels were elevated in rat or mouse lung tissue by intratracheal instillation of either purified ANGII or an adenovirus expressing AGT, or by ubiquitous overexpression of AGT in transgenic mice. Intratracheal instillation of purified ANGII caused significant collagen accumulation in lung tissue, both ex vivo and in vivo. Ubiquitous overexpression of AGT enhanced the profibrotic effect of bleomycin given at suboptimal doses. Intratracheal delivery of an adenoviral vector expressing mouse AGT (Ad-AGT) overexpressed AGT primarily in AECs and caused both apoptosis of AECs and pulmonary fibrosis. The lung collagen accumulation and AEC apoptosis caused by Ad-AGT was blocked by the caspase inhibitor ZVAD-fmk, by the ANG receptor AT1 antagonist Losartan or by the non-selective ANGII receptor antagonist Saralasin. Together, these data support the hypothesis that elevated pulmonary expression of AGT and its conversion to angiotensin II plays a causative role in the development of lung fibrosis through its induction of AEC apoptosis.

Potential Usefulness of Losartan as an Antifibrotic Agent and Adjunct to Platelet-Rich Plasma Therapy to Improve Muscle Healing and Cartilage Repair and Prevent Adhesion Formation

Postoperative tissue fibrosis represents a major complication in orthopedics. Transforming growth factor beta 1 is a key molecule in the development of postoperative fibrosis. High concentrations of transforming growth factor beta 1 have also been implicated in various diseases. Agents that counteract the actions of transforming growth factor beta 1 have been investigated as potential antifibrotic medications and as adjunct treatment to platelet-rich plasma injections (increased amounts of transforming growth factor beta 1) to improve their effectiveness and/or safety profile. Losartan blocks transforming growth factor beta 1 action and has attracted special interest in orthopedic research that focuses on how to reduce the risk of postoperative fibrosis. [Orthopedics. 2018; 41(5):e591-e597.].

Angiotensin Converting Enzyme Inhibitors and Angiotensin Receptor Blockers: A Promising Medication for Chronic Obstructive Pulmonary Disease?

Chronic obstructive pulmonary disease (COPD) is a complex disorder that primarily affects the lungs and is characterized not only by local pulmonary, but also by systemic inflammation which promotes the development of extrapulmonary and cardiovascular co-morbidities. Angiotensin converting enzyme (ACE) inhibitors and ARBs (angiotensin receptor blockers) are widely used drugs in the treatment of cardiovascular diseases, with growing evidence suggesting potential benefits in COPD patients. The purpose of this review is to describe the correlation of renin-angiotensin system (RAS) with COPD pathophysiology and to present the latest data regarding the potential role of RAS blockers in COPD.

Comparative effects of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers on the risk of pneumonia and severe exacerbations in patients with COPD

Objectives

This study aimed to compare the effects of angiotensin-converting-enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) on the risk of pneumonia and severe exacerbations in patients with COPD.

Patients and methods

All patients with COPD who used ACEis and ARBs for >90 days between 2000 and 2005 were recruited. Pairwise matching (1:1) of the ACEi and ARB groups resulted in two similar subgroups, with 6,226 patients in each. The primary outcomes were pneumonia and COPD exacerbations, and the secondary outcome was death.

Results

During the follow-up period, the incidence of pneumonia was 7.20 per 100 person-years in the ACEi group and 5.89 per 100 person-years in the ARB group. The ACEi group had a higher risk of pneumonia (adjusted hazard ratio [aHR], 1.22; 95% CI, 1.15–1.29) than the ARB group. The incidence of severe exacerbations was 0.65 per person-year for the patients receiving ACEis and 0.52 per person-year for those receiving ARBs. The patients receiving ACEis had a higher risk of severe exacerbations (aHR, 1.19; 95% CI, 1.16–1.21) than those receiving ARBs. Similar trends were noted in terms of severe exacerbations requiring hospitalization (aHR, 1.24; 95% CI, 1.21–1.28) or emergency department visits (aHR, 1.16; 95% CI, 1.13–1.18), pneumonia requiring mechanical ventilation (aHR, 1.35; 95% CI, 1.24–1.47), and mortality (aHR, 1.33; 95% CI, 1.26–1.42).

Conclusion

ARBs were associated with lower rates of pneumonia, severe pneumonia, and mortality than ACEis in patients with COPD.

Rapid Analysis and Guided Isolation of Astragalus Isoflavonoids by UHPLC-DAD-MSn and Their Cellular Antioxidant Defense on High-Glucose-Induced Mesangial Cell Dysfunction

Isoflavonoids, including isoflavones, isoflavans, and pterocarpans, the principal components in Astragalus membranaceus, have a great deal of versatile health-promoting benefits. In this work, as a continuation of our search for bioactive constituents from A. membranaceus, a fast high-performance liquid chromatography-diode array detection-multiple-stage mass spectrometry method was first used to analyze the isoflavonoid profile of A. membranaceus roots extract. Twelve diverse isoflavonoids in subclasses of isoflavones, isoflavans, and pterocarpans present in glycoside/aglycone pair forms were tentatively characterized; of those 12, eight major isoflavonoids were finally isolated and simultaneously quantified by the established fast UHPLC method. Furthermore, the results confirmed for the first time that Astragalus isoflavonoid aglycones could attenuate mesangial cell proliferation and extracellular matrix (ECM) accumulation triggered by high glucose levels, and the primary mechanism might be via protecting intracellular antioxidant enzymes activities and enhancing endogenous antioxidant function to lower levels of cellular oxidative damage induced by high glucose levels. Collectively, diverse Astragalus isoflavonoid antioxidants have the potential to ameliorate high-glucose-induced mesangial cell dysfunction through the regulation of cellular antioxidant defense.

Surfactant protein D is a useful biomarker for monitoring acute lung injury in rats

PURPOSE

The purpose of this study is to investigate the serial changes in the SP-D concentrations of serum and bronchoalveolar lavage fluid (BALF) in a bleomycin-induced lung injury rat model and compare them with the levels of conventional biochemical markers.

MATERIALS AND METHODS

Male Wister rats were anesthetized and intratracheally administered bleomycin (1.0 mg/kg). We evaluated the histological changes and SP-D expression of their lung tissues. We also measured the concentrations of SP-D, albumin, and lactate dehydrogenase (LDH) and the numbers of various types of cells in BALF, and the serum levels of SP-D and conventional markers, including LDH, high mobility group box 1, monocyte chemoattractant protein-1, and C-reactive protein.

RESULTS

The BALF SP-D level increased and peaked on day 3, and then gradually decreased. These variations were significantly correlated with the changes in the BALF albumin level and granulocyte cell count. The serum SP-D level increased from day 5, peaked on day 10, and then gradually decreased until day 28. The changes in the serum SP-D level accurately reflected the extent of the histological changes caused by the lung injury. On the other hand, the serum levels of conventional biomarkers were only elevated for a few days or did not change during the study period.

CONCLUSIONS

The SP-D level is the most useful marker of the severity of lung injuries. These results suggest that the measurement of SP-D levels is an additional tool for monitoring acute lung injuries in rats.

Treatment of pulmonary fibrosis with siRNA against a collagen-specific chaperone HSP47 in vitamin A-coupled liposomes

BACKGROUND

Pulmonary fibrosis is a life-threatening pathological state of progressive interstitial lung diseases, such as idiopathic pulmonary fibrosis. Myofibroblasts are known to play a critical role in the pathogenesis of pulmonary fibrosis. This study aimed to evaluate the inhibitory effect of a small interfering RNA (siRNA) on a collagen-specific chaperone heat shock protein 47 (HSP47). The siRNA was preferentially delivered to myofibroblasts in a bleomycin (BLM)-induced pulmonary fibrosis rat model using siRNA against HSP47, encapsulated in a vitamin A-coupled liposome (VA-lip-siRNA HSP47).

METHODS AND RESULTS

Male Sprague-Dawley rats were treated with an intratracheal injection of BLM or phosphate buffered saline followed by an intravenous injection of VA-lip-siRNA HSP47 three times per week under preventive administration schedules from day 1 to day 21 and therapeutic administration schedules from day 15 to day 35. The expression of HSP47 after the treatment was assessed by immunoblotting. The specific delivery of VA-lip-siRNA HSP47 conjugated with 6'-carboxyfluoresce into myofibroblasts was examined by immunofluorescence staining. The effect of VA-lip-siRNA HSP47 on fibrosis was analyzed by morphological and biochemical methods. Preferential delivery of VA-lip-siRNA HSP47 to myofibroblasts in fibrotic areas in BLM-treated rats was verified by immunofluorescence staining. Treatment of VA-lip-siRNA HSP47 clearly suppressed HSP47 expression and induced apoptosis of myofibroblasts in the lung of BLM-treated rats. Hydroxyproline levels and inflammatory cytokines in the lungs, and the number of inflammatory cells in the bronchial alveolar lavage of BLM-treated rats were significantly suppressed by the treatment. Morphological assessment showed that VA-lip-siRNA HSP47 also significantly improved the morphological pulmonary fibrosis of BLM-treated rats in both preventive and therapeutic schedules.

CONCLUSIONS

These results suggest that VA-lip-siRNA HSP47 improves pulmonary fibrosis in not only preventive, but also therapeutic schedules, and thus, this drug delivery system should provide a novel therapy for refractory pulmonary fibrosis.

Inhibition of airway remodeling and inflammation by isoforskolin in PDGF-induced rat ASMCs and OVA-induced rat asthma model

Isoforskolin (ISOF) has been reported to play an important role in many illnesses including respiratory, cardiovascular and ophthalmologic diseases. In our study, we aimed to investigate how ISOF regulates airway remodeling and inflammation in asthma. Based on SO₂-stimulated mouse cough model, we assessed the role of ISOF in cough and secretion of phlegm. Afterwards, platelet derived growth factor (PDGF)-induced primary rat airway smooth muscle cell (ASMC) model and ovalbumin (OVA)-induced rat asthma model were used to continue our following research. Our results showed that ISOF could prolong the cough latent period, reduce the cough times in two minutes, and increase the excretion of red phenol, which suggested the antitussive and expectorant effects of ISOF. Besides, ISOF pretreatment reversed the hypotonicity and cytoskeleton remodeling in PDGF-induced ASMCs, and reduced mucus hypersecretion and collagen overdeposition in OVA-induced rat asthma model, which indicated its inhibition on airway remodeling in vitro and in vivo. Moreover, ISOF reduced the invasion of inflammatory cells into bronchoalveolar lavage fluid (BALF) and lungs, which revealed its inhibitory role in airway inflammation. The down-regulation of transforming growth factor β1 (TGF-β1) and interleukin-1β (IL-1β) upon ISOF treatment might be responsible for its anti-remodeling and anti-inflammation roles. In conclusion, ISOF can reduce cough and sputum, as well as inhibit airway remodeling and inflammation by regulating the expression of TGF-β1 and IL-1β. These data indicate the potency of ISOF in treating asthma and also provide insights into the development of new anti-asthma agent.

Chronic vitamin D deficiency induces lung fibrosis through activation of the renin-angiotensin system

Pulmonary fibrosis, which influences lung function and exacerbates a patient’s condition, is the ultimate stage of many lung diseases. Vitamin D deficiency is associated with pulmonary fibrosis and impaired lung function, but the underlying mechanism has not yet been fully elucidated. Moreover, vitamin D deficiency may cause over-activation of the renin-angiotensin system (RAS), which aggravates extracellular matrix (ECM) deposition and lung fibrosis. This study aims to investigate the effect of chronic vitamin D deficiency on lung fibrosis in otherwise healthy mice and to explore the role of RAS in this process. Mice were depleted of vitamin D through diet control and were compared with healthy subjects. Chronic vitamin D deficiency destructs lung structures, impairs lung development and stimulates ECM deposition. RAS components are also found to increase. These effects seem to worsen with prolonged vitamin D deficiency. By giving RAS blockers, these changes can be largely rescued. However, a smooth muscle relaxant whose regulatory effect on blood pressure is independent of RAS does not show similar effects. This study demonstrated that chronic vitamin D deficiency may induce RAS activation, which subsequently stimulates the expression of profibrotic factors and activates the fibrotic cascade. This profibrotic effect of RAS is independent of elevated blood pressure.

Muscle Injuries and Repair: What's New on the Horizon!

Although we recognize the many advantages of improved musculoskeletal health, we also note that our ability to sustain this health and to maintain quality of life in an aging population is currently deficient. However, global efforts have produced numerous advances in tissue engineering and regenerative medicine that will collectively serve to fill this deficiency in the near future. The purpose of this review is to highlight our current knowledge, to outline our recent advances, and to discuss the evolving paradigms in skeletal muscle injury and repair.

Pharmacologic therapies for idiopathic pulmonary fibrosis, past and future

Idiopathic pulmonary fibrosis (IPF) is a severe, progressive fibrotic disease of the lung of unknown etiology that affects approximately 150,000 patients in the United States. It carries a median survival of two to three years, but clinical course can vary markedly from patient to patient. There has been no established treatment for IPF, but recent advances in coordinated clinical trials through groups such as IPFnet and academia-industry partnerships have allowed this relatively rare disease to be studied in much greater depth. Historically, the default therapy for IPF was a combination of prednisone, N-acetylcysteine, and azathioprine, but recent trials have shown that this regimen actually increases mortality. An enormous body of work in recent years, spanning the bench to the bedside, has radically altered our understanding of the molecular mechanisms underlying IPF. Newer modalities, particularly those involving monoclonal antibodies targeted at specific pathways known to contribute to the fibrotic process, have generated a great deal of excitement in the field, and recent clinical trials on therapies such as pirfenidone and nintedanib herald a new era in targeted IPF therapies.

The angiotensin-converting enzyme 2/angiotensin (1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rho kinase pathway

Reactive oxygen species (ROS) generated by NADPH oxidase-4 (NOX4) have been shown to initiate lung fibrosis. The migration of lung fibroblasts to the injured area is a crucial early step in lung fibrosis. The angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7) [Ang(1-7)]/Mas axis, which counteracts the ACE/angiotensin II (AngII)/angiotensin II type 1 receptor (AT1R) axis, has been shown to attenuate pulmonary fibrosis. Nevertheless, the exact molecular mechanism remains unclear.

AIMS

To investigate the different effects of the two axes of the renin-angiotensin system (RAS) on lung fibroblast migration and extracellular matrix accumulation by regulating the NOX4-derived ROS-mediated RhoA/Rho kinase (Rock) pathway.

RESULTS

In vitro, AngII significantly increased the NOX4 level and ROS production in lung fibroblasts, which stimulated cell migration and α-collagen I synthesis through the RhoA/Rock pathway. These effects were attenuated by N-acetylcysteine (NAC), diphenylene iodonium, and NOX4 RNA interference. Moreover, Ang(1-7) and lentivirus-mediated ACE2 (lentiACE2) suppressed AngII-induced migration and α-collagen I synthesis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway. However, Ang(1-7) alone exerted analogous effects on AngII. In vivo, constant infusion with Ang(1-7) or intratracheal instillation with lenti-ACE2 shifted the RAS balance toward the ACE2/Ang(1-7)/Mas axis, alleviated bleomycin-induced lung fibrosis, and inhibited the RhoA/Rock pathway by reducing NOX4-derived ROS.

INNOVATION

This study suggests that the ACE2/Ang(1-7)/Mas axis may be targeted by novel pharmacological antioxidant strategies to treat lung fibrosis induced by AngII-mediated ROS.

CONCLUSION

The ACE2/Ang(1-7)/Mas axis protects against lung fibroblast migration and lung fibrosis by inhibiting the NOX4-derived ROS-mediated RhoA/Rock pathway.

Beyond TGFβ--novel ways to target airway and parenchymal fibrosis

Within the lungs, fibrosis can affect both the parenchyma and the airways. Fibrosis is a hallmark pathological change in the parenchyma in patients with idiopathic pulmonary fibrosis (IPF), whilst in asthma or chronic obstructive pulmonary disease (COPD) fibrosis is a component of the remodelling of the airways. In the past decade, significant advances have been made in understanding the disease behaviour and pathogenesis of parenchymal and airway fibrosis and as a result a variety of novel therapeutic targets for slowing or preventing progression of these fibrotic changes have been identified. This review highlights a number of these targets and discusses the potential for treating parenchymal or airway fibrosis through these mediators/pathways in the future.

Epithelium-dependent profibrotic milieu in the pathogenesis of idiopathic pulmonary fibrosis: current status and future directions

BACKGROUND AND AIM

Idiopathic pulmonary fibrosis (IPF) is characterized by hyperplasia of type II alveolar epithelial cells, aggregation of activated (myo)fibroblasts and excessive deposition of extracellular matrix, which will ultimately lead to lung architecture destruction with no proven effective therapies. Despite a significant increase in our understanding on the etiology and pathogenesis of IPF, the real triggers that initiate epithelial cell injury and promote fibrosis evolution are still elusive. We wanted to discuss the evolution of hypothesis on IPF pathogenesis and to suggest some new directions which need to be further elucidated.

METHODS

We have done a literature search in PubMed database by using the term 'idiopathic pulmonary fibrosis' AND (pathogenesis OR inflammation OR wound healing OR apoptosis OR extracellular matrix OR animal model).

RESULTS

Inflammatory hypothesis had been the dominant idea for several decades which suggests that chronic inflammation drives the onset and advance of the fibrotic process. However, it is seriously challenged nowadays because lung tissues from IPF patients exhibit little inflammatory lesions. Also, anti-inflammation therapy failed to exert a beneficial effect to IPF patients. Furthermore, experimental lung fibrosis can be realized independent of inflammation. Today, modern paradigm suggests that IPF is mainly driven by the profibtic milieu formed by epithelial injury/ disability and dysregulated epithelial mesenchymal interaction.

CONCLUSIONS

Epithelium-dependent profibrotic milieu formation and mesenchymal activation is the current view on the pathogenesis of IPF. New evidence from more analogous animal models may emerge and shift our thinking to a new and more faithful concept in the future.

Metabolic spectroscopy of inflammation in a bleomycin-induced lung injury model using hyperpolarized 1-(13) C pyruvate

Metabolic activity in the lung is known to change in response to external insults, inflammation, and cancer. We report measurements of metabolism in the isolated, perfused rat lung of healthy controls and in diseased lungs undergoing acute inflammation using hyperpolarized 1-(13) C-labeled pyruvate. The overall apparent activity of lactate dehydrogenase is shown to increase significantly (on average by a factor of 3.3) at the 7 day acute stage and to revert substantially to baseline at 21 days, while other markers indicating monocarboxylate uptake and transamination rate are unchanged. Elevated lung lactate signal levels correlate well with phosphodiester levels as determined with (31) P spectroscopy and with the presence of neutrophils as determined by histology, consistent with a relationship between intracellular lactate pool labeling and the density and type of inflammatory cells present. We discuss several alternate hypotheses, and conclude that the most probable source of the observed signal increase is direct uptake and metabolism of pyruvate by inflammatory cells and primarily neutrophils. This signal is seen in high contrast to the low baseline activity of the lung.

Passion fruit peel extract attenuates bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis is a progressive fatal lung disease characterized by excessive collagen deposition, with no effective treatments. We investigated the efficacy of natural products with high anti-inflammatory activity, such as passion fruit peel extract (PFPE), in a mouse model of bleomycin-induced pulmonary fibrosis (PF). C57BL/6J mice were subjected to a single intratracheal instillation of bleomycin to induce PF. Daily PFPE treatment significantly reduced loss of body mass and mortality rate in mice compared with those treated with bleomycin. While bleomycin-induced PF resulted in elevated total numbers of inflammatory cells, macrophages, lymphocytes, and neutrophils in bronchoalveolar lavage fluid on both days 7 and 21, PFPE administration significantly attenuated these phenomena compared with bleomycin group. On day 7, the decreased superoxide dismutase and myeloperoxidase activities observed in the bleomycin group were significantly restored with PFPE treatment. On day 21, enhanced hydroxyproline deposition in the bleomycin group was also suppressed by PFPE administration. PFPE treatment significantly attenuated extensive inflammatory cell infiltration and accumulation of collagen in lung tissue sections of bleomycin-induced mice on days 7 and 21, respectively. Our results indicate that administration of PFPE decreased bleomycin-induced PF because of anti-inflammatory and antioxidant activities.

Effects of ionizing radiation on biological molecules--mechanisms of damage and emerging methods of detection

SIGNIFICANCE

The detrimental effects of ionizing radiation (IR) involve a highly orchestrated series of events that are amplified by endogenous signaling and culminating in oxidative damage to DNA, lipids, proteins, and many metabolites. Despite the global impact of IR, the molecular mechanisms underlying tissue damage reveal that many biomolecules are chemoselectively modified by IR.

RECENT ADVANCES

The development of high-throughput "omics" technologies for mapping DNA and protein modifications have revolutionized the study of IR effects on biological systems. Studies in cells, tissues, and biological fluids are used to identify molecular features or biomarkers of IR exposure and response and the molecular mechanisms that regulate their expression or synthesis.

CRITICAL ISSUES

In this review, chemical mechanisms are described for IR-induced modifications of biomolecules along with methods for their detection. Included with the detection methods are crucial experimental considerations and caveats for their use. Additional factors critical to the cellular response to radiation, including alterations in protein expression, metabolomics, and epigenetic factors, are also discussed.

FUTURE DIRECTIONS

Throughout the review, the synergy of combined "omics" technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies.

ACE2 - from the renin-angiotensin system to gut microbiota and malnutrition

The renin-angiotensin system (RAS) is a complex network that regulates blood pressure, electrolyte and fluid homeostasis, as well as the function of several organs. Angiotensin-converting enzyme 2 (ACE2) was identified as an enzyme that negatively regulates the RAS by converting Ang II, the main bioactive molecule of the RAS, to Ang 1-7. Thus, ACE2 counteracts the role of angiotensin-converting enzyme (ACE) which generates Ang II from Ang I. ACE and ACE2 have been implicated in several pathologies such as cardiovascular and renal disease or acute lung injury. In addition, ACE2 has functions independent of the RAS: ACE2 is the receptor for the SARS coronavirus and ACE2 is essential for expression of neutral amino acid transporters in the gut. In this context, ACE2 modulates innate immunity and influences the composition of the gut microbiota, which can explain diarrhea and intestinal inflammation observed in Hartnup disorder, Pellagra, or under conditions of severe malnutrition. Here we review and discuss the diverse functions of ACE2 and its relevance to human pathologies.

Preventive effect of irbesartan on bleomycin-induced lung injury in mice

BACKGROUND

Idiopathic pulmonary fibrosis is a specific form of chronic fibrosing interstitial pneumonia that is limited to the lung. Angiotensin receptor blockers (ARBs) and peroxisome proliferator-activated receptor (PPAR) γ ligands have anti-inflammatory and anti-fibrotic effects. We investigated the effects of irbesartan-an ARB with PPAR γ activity-on the development of bleomycin-induced pulmonary fibrosis in mice.

METHODS

Lung injury was induced in imprinting control region (ICR) mice by intratracheal instillation of 2mg/kg of bleomycin. The treatment group orally received 20mg/kg of irbesartan for 5 consecutive days before instillation. The mice were sacrificed and were evaluated 14 days after bleomycin instillation.

RESULTS

Irbesartan reduced the fluid content and hydroxyproline level in the lung and improved the pathological findings as indicated by the Ashcroft score. Total cell counts, the numbers of macrophages, neutrophils, and lymphocytes, and the levels of transforming growth factor (TGF) β1 and monocyte chemotactic protein (MCP) 1 in the bronchoalveolar lavage fluid (BALF) were decreased. Treatment with a PPARγ antagonist GW9662 reversed some of the effects of irbesartan.

CONCLUSIONS

The results of this study indicated that irbesartan attenuated the development of bleomycin-induced pulmonary fibrosis in mice by decreasing TGF-β1 and MCP-1 via blocking of ATI, by binding to CCR2b, and by PPARγ-mediated inhibition of inflammation.

Mast cells: a pivotal role in pulmonary fibrosis

Pulmonary fibrosis is characterized by an inflammatory response that includes macrophages, neutrophils, lymphocytes, and mast cells. The purpose of this study was to evaluate whether mast cells play a role in initiating pulmonary fibrosis. Pulmonary fibrosis was induced with bleomycin in mast-cell-deficient WBB6F1-W/W(v) (MCD) mice and their congenic controls (WBB6F1-(+)/(+)). Mast cell deficiency protected against bleomycin-induced pulmonary fibrosis, but protection was reversed with the re-introduction of mast cells to the lungs of MCD mice. Two mast cell mediators were identified as fibrogenic: histamine and renin, via angiotensin (ANG II). Both human and rat lung fibroblasts express the histamine H1 and ANG II AT1 receptor subtypes and when activated, they promote proliferation, transforming growth factor β1 secretion, and collagen synthesis. Mast cells appear to be critical to pulmonary fibrosis. Therapeutic blockade of mast cell degranulation and/or histamine and ANG II receptors should attenuate pulmonary fibrosis.

Endostatin, an angiogenesis inhibitor, ameliorates bleomycin-induced pulmonary fibrosis in rats

Background

Recent evidence has demonstrated the role of angiogenesis in the pathogenesis of pulmonary fibrosis. Endostatin, a proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis. The aim of our study was to assess whether endostatin has beneficial effects on bleomycin (BLM)-induced pulmonary fibrosis in rats.

Methods

The rats were randomly divided into five experimental groups: (A) saline only, (B) BLM only, (C) BLM plus early endostatin treatment, (D) BLM plus late endostatin treatment, and (F) BLM plus whole-course endostatin treatment. We investigated the microvascular density (MVD), inflammatory response and alveolar epithelial cell apoptosis in rat lungs in each group at different phases of disease development.

Results

Early endostatin administration attenuated fibrotic changes in BLM-induced pulmonary fibrosis in rats. Endostatin treatment decreased MVD by inhibiting the expression of VEGF/VEGFR-2 (Flk-1) and the activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). Endostatin treatment also decreased the number of inflammatory cells infiltrating the bronchoalveolar lavage fluid during the early inflammatory phase of BLM-induced pulmonary fibrosis. In addition, the levels of tumour necrosis factor-α (TNF-α) and transforming growth factor β1 (TGF-β1) were reduced by endostatin treatment. Furthermore, endostatin decreased alveolar type II cell apoptosis and had an epithelium-protective effect. These might be the mechanism underlying the preventive effect of endostatin on pulmonary fibrosis.

Conclusions

Our findings suggest that endostatin treatment inhibits the increased MVD, inflammation and alveolar epithelial cell apoptosis, consequently ameliorating BLM-induced pulmonary fibrosis in rats.

Expression of Angiotensin II and Aldosterone in Radiation-induced Lung Injury

OBJECTIVE

Radiation-induced lung injury (RILI) is the most common, dose-limiting complication in thoracic malignancy radiotherapy. Considering its negative impact on patients and restrictions to efficacy, the mechanism of RILI was studied.

METHODS

Wistar rats were locally irradiated with a single dose of 0, 16, and 20 Gy to the right half of the lung to establish a lung injury model. Two and six months after irradiation, the right half of the rat lung tissue was removed, and the concentrations of TGF-β1, angiotensin II, and aldosterone were determined via enzyme-linked immunosorbent assay.

RESULTS

Statistical differences were observed in the expression levels of angiotensin II and aldosterone between the non-irradiation and irradiation groups. Moreover, the expression level of the angiotensin II-aldosterone system increased with increasing doses, and the difference was still observed as time progressed.

CONCLUSIONS

Angiotensin II-aldosterone system has an important pathophysiological function in the progression of RILI.

Losartan Improves Adipose Tissue-Derived Stem Cell Niche by Inhibiting Transforming Growth Factor-β and Fibrosis in Skeletal Muscle Injury

Recently, adipose tissue-derived stem cells (ASCs) were emerged as an alternative, abundant, and easily accessible source of stem cell therapy. Previous studies revealed losartan (an angiotensin II type I receptor blocker) treatment promoted the healing of skeletal muscle by attenuation of the TGF-β signaling pathway, which inhibits muscle differentiation. Therefore, we hypothesized that a combined therapy using ASCs and losartan might dramatically improve the muscle remodeling after muscle injury. To determine the combined effect of losartan with ASC transplantation, we created a muscle laceration mouse model. EGFP-labeled ASCs were locally transplanted to the injured gastrocnemius muscle after muscle laceration. The dramatic muscle regeneration and the remarkably inhibited muscular fibrosis were observed by combined treatment. Transplanted ASCs fused with the injured or differentiating myofibers. Myotube formation was also enhanced by ASC+ satellite coculture and losartan treatment. Thus, the present study indicated that ASC transplantation effect for skeletal muscle injury can be dramatically improved by losartan treatment inducing better niche.

Biological approaches to improve skeletal muscle healing after injury and disease

Skeletal muscle injury and repair are complex processes, including well-coordinated steps of degeneration, inflammation, regeneration, and fibrosis. We have reviewed the recent literature including studies by our group that describe how to modulate the processes of skeletal muscle repair and regeneration. Antiinflammatory drugs that target cyclooxygenase-2 were found to hamper the skeletal muscle repair process. Muscle regeneration phase can be aided by growth factors, including insulin-like growth factor-1 and nerve growth factor, but these factors are typically short-lived, and thus more effective methods of delivery are needed. Skeletal muscle damage caused by traumatic injury or genetic diseases can benefit from cell therapy; however, the majority of transplanted muscle cells (myoblasts) are unable to survive the immune response and hypoxic conditions. Our group has isolated neonatal skeletal muscle derived stem cells (MDSCs) that appear to repair muscle tissue in a more effective manner than myoblasts, most likely due to their better resistance to oxidative stress. Enhancing antioxidant levels of MDSCs led to improved regenerative potential. It is becoming increasingly clear that stem cells tissue repair by direct differentiation and paracrine effects leading to neovascularization of injured site and chemoattraction of host cells. The factors invoked in paracrine action are still under investigation. Our group has found that angiotensin II receptor blocker (losartan) significantly reduces fibrotic tissue formation and improves repair of murine injured muscle. Based on these data, we have conducted a case study on two hamstring injury patients and found that losartan treatment was well tolerated and possibly improved recovery time. We believe this medication holds great promise to optimize muscle repair in humans.

Beneficial effects of candesartan, an angiotensin-blocking agent, on compensated alcoholic liver fibrosis - a randomized open-label controlled study

BACKGROUND

Recent studies have shown that the renin-angiotensin system is implicated in hepatic fibrogenesis in vitro and in vivo. However, no study was done in humans with alcoholic liver disease.

AIM

To investigate the antifibrotic effect of angiotensin II type 1 receptor (AT1-R) blocking agents (ARB) in patients with alcoholic liver disease.

METHODS

The primary outcome was improvement in patients' histological features. Eighty-five patients with compensated alcoholic liver fibrosis (≥ F2) which was confirmed by baseline liver biopsy were randomized (intention-to-treat (ITT)) to receive either ARB, candesartan (8 mg/day) with ursodeoxycholic acid (UDCA) (600 mg/day) (n = 42) or UDCA alone (n = 43) as control for 6 months and follow-up liver biopsies were conducted.

RESULTS

According to the Laennec fibrosis system, candesartan showed significantly higher rates of histological improvements (ITT, 33.3% vs. 11.6%, P = 0.020). In addition, the fibrosis score was significantly reduced from 3.4 ± 1.4 to 3.1 ± 1.5 (P = 0.005) in the candesartan group. Candesartan also reduced the area of fibrosis and α-smooth muscle actin positive from 11.3 ± 6.0 to 8.3 ± 4.7 and 28.7 ± 10.5 to 23.9 ± 10.3 (%), and the hydroxyproline levels (μg/g liver tissue) from 7.8 ± 2.4 to 6.3 ± 1.7 respectively (P < 0.05). In addition, the relative expression of transforming growth factor-β1(TGF-β1), collagen-1, AT1-R, tissue inhibitor of metalloproteinase 1 (TIMP-1), metalloproteinases2 (MMP2), Rac1 and p22phox by real-time RT-PCR decreased in the candesartan group (P < 0.05). Mean arterial blood pressure in the candesartan group decreased mildly but significantly (P < 0.001). No significant complications and side effects were observed during the present study.

CONCLUSIONS

Administration of ARB in compensated alcoholic liver disease induces improvement of fibrosis in histological and quantitative measurements.

Angiotensin signalling in pulmonary fibrosis

A large body of evidence demonstrates that angiotensin II and angiotensin receptors are required for the pathogenesis of experimental lung fibrosis. Angiotensin has a number of profibrotic effects on lung parenchymal cells that include the induction of growth factors for mesenchymal cells, extracellular matrix molecules, cytokines and increased motility of lung fibroblasts. Angiotensin is also proapoptotic for lung epithelial cells, and is synthesized by a local system (i.e., entirely within the lung tissue) after lung injury by a variety of agents of both xenobiotic and endogenous origins. Recent evidence shows that the counterregulatory molecule angiotensin 1-7, the product of the enzyme ACE-2, inhibits epithelial cell apoptosis and thus acts as an antifibrotic epithelial survival factor. This manuscript reviews the evidence supporting a role for angiotensin in lung fibrogenesis and discusses the signalling mechanisms underlying its action on lung parenchymal cells important in the pathogenesis of pulmonary fibrosis.

Activation of the renin-angiotensin system in hyperoxia-induced lung fibrosis in neonatal rats

BACKGROUND

Oxygen toxicity plays an important role in lung injury and may lead to bronchopulmonary dysplasia. We previously demonstrated that hyperoxia activated the renin-angiotensin system (RAS) in cultured human fetal lung fibroblasts.

OBJECTIVE

To examine whether the upregulation of RAS components is associated with hyperoxia-induced lung fibrosis in neonatal Sprague-Dawley rats.

METHODS

Experimental rat pups were exposed to 1 week of >95% O(2) and a further 2 weeks of 60% O(2). Control pups were exposed to room air over the same periods. Lung tissues were taken for biochemical and histochemical assays on postnatal days 7 and 21.

RESULTS

Hyperoxia significantly increased total collagen content and the expression of type I collagen and alpha smooth muscle actin when compared to control rats. RAS components including angiotensinogen, angiotensin-converting enzyme, angiotensin II, and angiotensin II type 1 receptor were significantly upregulated by hyperoxia. The results also demonstrated that only the extracellular signal-regulated kinase (ERK) signaling pathway was activated by hyperoxia exposure. p38 mitogen-activated protein kinase and c-Jun N-terminal kinase were not activated.

CONCLUSIONS

Local RAS activation is involved in the pathogenesis of hyperoxia-induced lung fibrosis in neonatal rats. ERK phosphorylation might mediate angiotensin II type 1 receptor activation.