Expression of Angiotensin II Receptor-1 in Human Articular Chondrocytes

Aging and "Age-Related" Diseases - What Is the Relation?

The study explores the intricate relationship between aging and the development of noncommunicable diseases [NCDs], focusing on whether these diseases are inevitable consequences of aging or primarily driven by lifestyle factors. By examining epidemiological data, particularly from hunter-gatherer societies, the study highlights that many NCDs prevalent in modern populations are rare in these societies, suggesting a significant influence of lifestyle choices. It delves into the mechanisms through which poor diet, smoking, and other lifestyle factors contribute to systemic physiological imbalances, characterized by oxidative stress, insulin resistance and hyperinsulinemia, and dysregulation of the sympathetic nervous system, the renin-angiotensin-aldosterone system, and the immune system. The interplay between this pattern and individual factors such as genetic susceptibility, biological variability, epigenetic changes and the microbiome is proposed to play a crucial role in the development of a range of age-related NCDs. Modified biomolecules such as oxysterols and advanced glycation end products also contribute to their development. Specific diseases such as benign prostatic hyperplasia, Parkinson's disease, glaucoma and osteoarthritis are analyzed to illustrate these mechanisms. The study concludes that while aging contributes to the risk of NCDs, lifestyle factors play a crucial role, offering potential avenues for prevention and intervention through healthier living practices. One possible approach could be to try to restore the physiological balance, e.g. through dietary measures [e.g. Mediterranean diet, Okinawan diet or Paleolithic diet] in conjunction with [a combination of] pharmacological interventions and other lifestyle changes.

Appraisal of anti-inflammatory and immunomodulatory potential of ramipril against Freund's adjuvant-provoked arthritic rat model

Because of evident role of renin-angiotensin system in the etiology of rheumatoid arthritis, the current study's objective was to assess the anti-arthritic efficacy of ramipril through CFA-instigated arthritic model. The drug has been shown to have anti-inflammatory potential. CFA-instigated arthritic model assessed the anti-arthritic efficacy of ramipril by estimating different parameters, including paw volume, arthritic index scoring, haematological and biochemical attributes, histological and radiographic analyses, and various cytokines level. Ramipril significantly (p < 0.001) reduced paw volume and the arthritic index especially at the dose of 4mg/kg. The biochemical and haematological changes were likewise restored to normal by ramipril administration with an increase in anti-inflammatory cytokines while reducing pro-inflammatory cytokines level. Ramipril's ability to prevent arthritis by preserving the normal architecture of arthritis-induced joints is further supported by radiographic and histological investigation. The study's findings demonstrated ramipril's considerable anti-arthritic activity. To identify the precise mechanism of action, however, thorough mechanistic studies are still needed.

Diminazene aceturate or losartan ameliorates the functional, radiological and histopathological alterations in knee osteoarthritis rodent model: repurposing of the ACE2/Ang1-7/MasR cascade

PURPOSE

Current therapies for osteoarthritis (OA) are limited to analgesics and anti-inflammatory drugs. Considering the importance of oxidative stress and inflammatory mediators in OA etiology, we tested the hypothesis that targeting the renin-angiotensin-aldosterone system (RAAS) can improve OA anomalies. Diminazene (DIZE), an activator of angiotensin-converting enzyme 2 and the angiotensin 2 type-1 receptor blocker losartan (LOS) were used for this purpose.

METHODS

OA was induced by a single intra-articular injection of monosodium iodoacetate. The effects of exposure to DIZE or LOS for 21 days on OA anomalies in rats' knees were investigated. Evaluation of motor function, nociception, and inflammatory response was done using rotarod, knee bend and knee swelling tests. Markers of knee joint inflammation, and cellular oxidation in addition to the RAAS biomarkers, were assessed in knee tissues, along with radiological and histopathological investigations.

RESULTS

Elevations in inflammatory and oxidative markers in knee tissues of OA rats were mostly improved by the two therapeutic drugs. Such effect was also reflected in the rotarod, knee bend and knee swelling tests. Treatment with DIZE has shown a more prominent effect than LOS in controlling OA-associated inflammation and cellular oxidation. Markers of RAAS have also shown better responsiveness to DIZE over LOS.

CONCLUSIONS

DIZE has shown a prominent increase in the angiotensin 1-7 amount, highlighting the involvement of the signaling pathway in the immunomodulatory effect. The radiological and histopathology examination came to confirm the outcome of biochemical markers, nominating diminazene aceturate as a possible therapeutic option for OA.

Dynamic interaction of obesity, age, MCP-1 Level, and ACE-1 gene with the severity of knee osteoarthritis: a cross-sectional study

The risk factors most strongly associated with knee osteoarthritis (OA) are old age and obesity. However, few studies have evaluated the interaction between aging and obesity in conjunction with inflammatory markers and knee OA severity as part of a complete assessment of knee OA management. Therefore, this study aims to evaluate the interaction between obesity, age, inflammation [including the I/D polymorphism of angiotensin converting enzyme-1 (ACE-1)], and the severity of knee OA.

METHODS

A total of 80 knee OA patients were included in this cross-sectional study. The severity of knee OA was determined based on the Kellgren-Lawrence system. All patients underwent physical and radiological examination; monocyte chemoattractant protein 1 (MCP-1) markers were measured. The parameters of the ACE-1 gene were examined with sequencing DNA.

RESULTS

There was a significant relationship between age and severity of knee OA (P=0.007), with subjects aged greater than or equal to 65 having a 3.56-fold higher risk of developing moderate to severe OA than subjects aged less than 65. There was a significant difference between body weight and knee OA severity (P=0.026), in which subjects weighing greater than or equal to 60 kg had 3.14 times the risk of experiencing severe knee OA. Multivariate regression analysis indicated that age was the strongest independent variable for knee OA severity compared with body weight. MCP-1 levels were significantly higher in mild knee OA than in moderate to severe knee OA. The DD genotype of the ACE-1 gene increases the risk of severe knee OA by four times in subjects aged greater than or equal to 65 compared to subjects aged less than 65. However, the DD genotype of the ACE-1 gene does not increase the risk of severe knee OA in subjects weighing greater than or equal to 60 kg.

CONCLUSION

While obesity and age were found to be associated with the severity of knee OA, age emerged as the independent risk factor for knee OA severity. Furthermore, MCP-1 levels were significantly higher in cases of mild knee OA compared to severe knee OA. It was observed that the DD genotype of the ACE-1 gene increases the risk of severe knee OA in individuals aged 65 years or older.

The effects of losartan or angiotensin II receptor antagonists on cartilage: a systematic review

OBJECTIVE

The aim of this study is to analyze the latest evidence on the effects of losartan or Ang II receptor antagonists on cartilage repair, with a focus on their clinical relevance.

DESIGN

The PubMed, Embase, and Cochrane Library databases were searched up to November 12th 2021 to evaluate the effects of losartan or Ang II receptor antagonists on cartilage repair in in vitro studies and in vivo animal studies. Study design, sample characteristics, treatment type, duration, and outcomes were analyzed. The risk of bias and the quality of the eligible studies were assessed using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk of bias assessment tool and Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES).

RESULTS

A total of 12 studies were included in this systematic review. Of the 12 eligible studies, two studies were in vitro human studies, three studies were in vitro animal studies, one study was an in vitro human and animal study, and six studies were in vivo animal studies. The risk bias and quality assessments were predominantly classified as moderate. Since meta-analysis was difficult due to differences in treatment type, dosage, route of administration, and method of outcome assessment among the eligible studies, qualitative evaluation was conducted for each study.

CONCLUSIONS

Both in vitro and in vivo studies provide evidence to demonstrate beneficial effects of Ang II receptor antagonists on osteoarthritis and cartilage defect models across animal species.

Angiotensin type 2 receptor antagonism as a new target to manage gout

BACKGROUND

There is a growing search for therapeutic targets in the treatment of gout. The present study aimed to evaluate the analgesic and anti-inflammatory potential of angiotensin type 2 receptor (AT₂R) antagonism in an acute gout attack mouse model.

METHODS

Male wild-type (WT) C57BL/6 mice either with the AT₂R antagonist, PD123319 (10 pmol/joint), or with vehicle injections, or AT₂R KO mice, received intra-articular (IA) injection of monosodium urate (MSU) crystals (100 µg/joint), that induce the acute gout attack, and were tested for mechanical allodynia, thermal hyperalgesia, spontaneous nociception and ankle edema development at several times after the injections. To test an involvement of AT₂R in joint pain, mice received an IA administration of angiotensin II (0.05-5 nmol/joint) with or without PD123319, and were also evaluated for pain and edema development. Ankle joint tissue samples from mice undergoing the above treatments were assessed for myeloperoxidase activity, IL-1β release, mRNA expression analyses and nitrite/nitrate levels, 4 h after injections.

RESULTS

AT₂R antagonism has robust antinociceptive effects on mechanical allodynia (44% reduction) and spontaneous nociception (56%), as well as anti-inflammatory effects preventing edema formation (45%), reducing myeloperoxidase activity (54%) and IL-1β levels (32%). Additionally, Agtr2^tm1a mutant mice have largely reduced painful signs of gout. Angiotensin II administration causes pain and inflammation, which was prevented by AT₂R antagonism, as observed in mechanical allodynia 4 h (100%), spontaneous nociception (46%), cold nociceptive response (54%), edema formation (83%), myeloperoxidase activity (48%), and IL-1β levels (89%). PD123319 treatment also reduces NO concentrations (74%) and AT₂R mRNA levels in comparison with MSU untreated mice.

CONCLUSION

Our findings show that AT₂R activation contributes to acute pain in experimental mouse models of gout. Therefore, the antagonism of AT₂R may be a potential therapeutic option to manage gout arthritis.

Alamandine, a new member of the renin-angiotensin system (RAS), attenuates collagen-induced arthritis in mice via inhibiting cytokine secretion in synovial fibroblasts

Alamandine is a novel component of the renin-angiotensin system (RAS) as well as an important biologically active peptide. It has predominantly been studied in cardiovascular context. However, its role in rheumatoid arthritis (RA) remains unknown. Here we illustrated its effects on inflammatory cytokines production by synovial fibroblasts from RA and pathological changes in collagen-induced arthritis (CIA) mice. Alamandine (0.1, 1 and 10 µg/ml) did not affect the survival of the synovial fibroblasts, but decreased the migration and proinflammatory cytokines expression in TNF-α (10 ng/ml) stimulated cells in vitro. Additionally, alamandine selectively decreased phosphorylated-JNK expression induced by TNF-a stimulation in RA FLS. DBA/1 J mice were induced arthritis by a primary injection with an emulsion of bovine type II collagen (CII) and complete Freund's adjuvant (day 0) and a booster injection of CII in incomplete Freund's adjuvant (day 21). Mice were then given alamandine intraperitoneally in saline (50 μg/kg/day) from days 21-42. Histology and multiplex immunobead assay showed that alamandine treatment inhibited the development of arthritis and reduced the joint damage. This effect was accompanied by the reduced inflammatory cytokines (IL-6, IL-23, IFN-γ) mRNA expression in local joints, the decreased TNF-α, IL-6, IL-17 and the increased IL-10 levels in the serum from alamandine administrated CIA mice. In conclusion, alamandine attenuates the development of arthritis by suppressing inflammatory cytokines expression in RA synovial fibroblasts via MAPK signaling pathway, suggesting a potential therapeutic role for RA.

Translating the Force - mechano-sensing GPCRs

Incorporating mechanical cues into cellular responses allows us to experience our direct environment. Specialized cells can perceive and discriminate between different physical properties such as level of vibration, temperature, or pressure. Mechanical forces are abundant signals that also shape general cellular responses such as cytoskeletal rearrangement, differentiation, or migration and contribute to tissue development and function. The molecular structures that perceive and transduce mechanical forces are specialized cytoskeletal proteins, cell junction molecules, and membrane proteins such as ion channels and metabotropic receptors. G protein-coupled receptors (GPCRs) have attracted attention as metabotropic force receptors as they are among the most important drug targets. This review summarizes the function of mechano-sensitive GPCRs, specifically, the angiotensin II type 1 receptor and adrenergic, apelin, histamine, parathyroid hormone 1, and orphan receptors, focusing particularly on the advanced knowledge gained from adhesion-type GPCRs. We distinguish between shear stress and cell swelling/stretch as the two major types of mechano-activation of these receptors and contemplate the potential contribution of the force-from-lipid and force-from-tether models that have previously been suggested for ion channels.

Identification of transcription factors and construction of a novel miRNA regulatory network in primary osteoarthritis by integrated analysis

Backgrounds

As osteoarthritis (OA) disease-modifying therapies are not available, novel therapeutic targets need to be discovered and prioritized. Here, we aim to identify miRNA signatures in patients to fully elucidate regulatory mechanism of OA pathogenesis and advance in basic understanding of the genetic etiology of OA.

Methods

Six participants (3 OA and 3 controls) were recruited and serum samples were assayed through RNA sequencing (RNA-seq). And, RNA-seq dataset was analysed to identify genes, pathways and regulatory networks dysregulated in OA. The overlapped differentially expressed microRNAs (DEMs) were further screened in combination with the microarray dataset GSE143514. The expression levels of candidate miRNAs were further validated by quantitative real-time PCR (qRT-PCR) based on the GEO dataset (GSE114007).

Results

Serum samples were sequenced interrogating 382 miRNAs. After screening of independent samples and GEO database, the two comparison datasets shared 19 overlapped candidate micRNAs. Of these, 9 up-regulated DEMs and 10 down-regulated DEMs were detected, respectively. There were 236 target genes for up-regulated DEMs and 400 target genes for those down-regulated DEMs. For up-regulated DEMs, the top 10 hub genes were KRAS, NRAS, CDC42, GDNF, SOS1, PIK3R3, GSK3B, IRS2, GNG12, and PRKCA; for down-regulated DEMs, the top 10 hub genes were NR3C1, PPARGC1A, SUMO1, MEF2C, FOXO3, PPP1CB, MAP2K1, RARA, RHOC, CDC23, and CREB3L2. Mir-584-5p-KRAS, mir-183-5p-NRAS, mir-4435-PIK3R3, and mir-4435-SOS1 were identified as four potential regulatory pathways by integrated analysis.

Conclusions

We have integrated differential expression data to reveal putative genes and detected four potential miRNA-target gene pathways through bioinformatics analysis that represent new mediators of abnormal gene expression and promising therapeutic targets in OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04894-2.

Efficacy of Chondroprotective Food Supplements Based on Collagen Hydrolysate and Compounds Isolated from Marine Organisms

Osteoarthritis belongs to the most common joint diseases in humans and animals and shows increased incidence in older patients. The bioactivities of collagen hydrolysates, sulfated glucosamine and a special fatty acid enriched dog-food were tested in a dog patient study of 52 dogs as potential therapeutic treatment options in early osteoarthritis. Biophysical, biochemical, cell biological and molecular modeling methods support that these well-defined substances may act as effective nutraceuticals. Importantly, the applied collagen hydrolysates as well as sulfated glucosamine residues from marine organisms were strongly supported by both an animal model and molecular modeling of intermolecular interactions. Molecular modeling of predicted interaction dynamics was evaluated for the receptor proteins MMP-3 and ADAMTS-5. These proteins play a prominent role in the maintenance of cartilage health as well as innate and adapted immunity. Nutraceutical data were generated in a veterinary clinical study focusing on mobility and agility. Specifically, key clinical parameter (MMP-3 and TIMP-1) were obtained from blood probes of German shepherd dogs with early osteoarthritis symptoms fed with collagen hydrolysates. Collagen hydrolysate, a chondroprotective food supplement was examined by high resolution NMR experiments. Molecular modeling simulations were used to further characterize the interaction potency of collagen fragments and glucosamines with protein receptor structures. Potential beneficial effects of collagen hydrolysates, sulfated glycans (i.e., sulfated glucosamine from crabs and mussels) and lipids, especially, eicosapentaenoic acid (extracted from fish oil) on biochemical and physiological processes are discussed here in the context of human and veterinary medicine.

Hypertension meets osteoarthritis - revisiting the vascular aetiology hypothesis

Osteoarthritis (OA) is a whole-joint disease characterized by subchondral bone perfusion abnormalities and neovascular invasion into the synovium and articular cartilage. In addition to local vascular disturbance, mounting evidence suggests a pivotal role for systemic vascular pathology in the aetiology of OA. This Review outlines the current understanding of the close relationship between high blood pressure (hypertension) and OA at the crossroads of epidemiology and molecular biology. As one of the most common comorbidities in patients with OA, hypertension can disrupt joint homeostasis both biophysically and biochemically. High blood pressure can increase intraosseous pressure and cause hypoxia, which in turn triggers subchondral bone and osteochondral junction remodelling. Furthermore, systemic activation of the renin-angiotensin and endothelin systems can affect the Wnt-β-catenin signalling pathway locally to govern joint disease. The intimate relationship between hypertension and OA indicates that endothelium-targeted strategies, including re-purposed FDA-approved antihypertensive drugs, could be useful in the treatment of OA.

Effect of Angiotensin II on Chondrocyte Degeneration and Protection via Differential Usage of Angiotensin II Receptors

The renin–angiotensin system (RAS) controls not only systemic functions, such as blood pressure, but also local tissue-specific events. Previous studies have shown that angiotensin II receptor type 1 (AT₁R) and type 2 (AT₂R), two RAS components, are expressed in chondrocytes. However, the angiotensin II (ANG II) effects exerted through these receptors on chondrocyte metabolism are not fully understood. In this study, we investigated the effects of ANG II and AT₁R blockade on chondrocyte proliferation and differentiation. Firstly, we observed that ANG II significantly suppressed cell proliferation and glycosaminoglycan content in rat chondrocytic RCS cells. Additionally, ANG II decreased CCN2, which is an anabolic factor for chondrocytes, via increased MMP9. In Agtr1a-deficient RCS cells generated by the CRISPR-Cas9 system, Ccn2 and Aggrecan (Acan) expression increased. Losartan, an AT₁R antagonist, blocked the ANG II-induced decrease in CCN2 production and Acan expression in RCS cells. These findings suggest that AT₁R blockade reduces ANG II-induced chondrocyte degeneration. Interestingly, AT₁R-positive cells, which were localized on the surface of the articular cartilage of 7-month-old mice expanded throughout the articular cartilage with aging. These findings suggest that ANG II regulates age-related cartilage degeneration through the ANG II–AT₁R axis.

The Beneficial Effect of an Intra-articular Injection of Losartan on Microfracture-Mediated Cartilage Repair Is Dose Dependent

BACKGROUND

A previous publication demonstrated that the oral intake of losartan promoted microfracture-mediated hyaline-like cartilage repair in osteochondral defects of a rabbit knee model. However, an intra-articular (IA) injection of losartan may have direct beneficial effects on cartilage repair and has not been studied.

PURPOSE

To determine the dosage and beneficial effects of an IA injection of losartan on microfracture-mediated cartilage repair and normal cartilage homeostasis.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rabbits were divided into 5 groups (n = 6 each): a microfracture group (MFX group) and 4 different losartan treatment groups that received varying doses of IA losartan (0.1, 1, 10, and 100 mg per knee). An osteochondral defect (5 mm) was created in the trochlear groove cartilage of 1 limb in each rabbit, and 5 microfracture perforations were made in the osteochondral defect. Both the injured and the contralateral knee joints were injected with IA losartan immediately after microfracture and at 2 and 4 weeks after surgery. Rabbits were sacrificed at 6 weeks after surgery for analysis including gross observation, micro-computed tomography, histology, and reverse transcription quantitative polymerase chain reaction.

RESULTS

Micro-computed tomography and gross observation demonstrated comparable subchondral bone healing and hyaline-like cartilage morphology in the 0.1-, 1-, and 10-mg losartan groups relative to the MFX group. Conversely, the 100-mg losartan group showed neither bony defect healing nor cartilage repair. Histology revealed higher O'Driscoll scores and hyaline-like cartilage regeneration in the 1-mg losartan group compared with the MFX group. In contrast, the 100-mg losartan group showed the lowest histology score and no cartilage repair. An IA injection of losartan at the doses of 0.1, 1, and 10 mg did not cause adverse effects on uninjured cartilage, while the 100-mg dose induced cartilage damage. Quantitative polymerase chain reaction results showed downregulation of the transforming growth factor β (TGF-β) signaling pathway after IA losartan injection.

CONCLUSION

An IA injection of losartan at the dose of 1 mg was most effective for the enhancement of microfracture-mediated cartilage repair without adversely affecting uninjured cartilage. Conversely, a high dose (100 mg) IA injection of losartan inhibited cartilage repair in the osteochondral defect and was chondrotoxic to normal articular cartilage.

CLINICAL RELEVANCE

An IA injection of losartan at an optimal dosage represents a novel microfracture enhancement therapy and warrants a clinical trial for future clinical applications.

The COVID-19 pandemic: an increased risk of rheumatoid arthritis

COVID-19 is a respiratory infection similar to viral pneumonia and is caused by SARS-CoV-2. Chloroquine and hydroxychloroquine make up the major part of the treatment regimen for the management of COVID-19 infections, which are also commonly used in treatment of patients with malaria as well as autoimmune diseases like rheumatoid arthritis (RA). In this review, we analyzed the scientific evidences pertaining to any possible association of SARS-CoV-2 infection with RA. We thus believe that people predisposed to RA carry a higher infection risk than the general population both due to the iatrogenic effects of the RA related drug therapy. Thus COVID-19 pandemic may bring a higher risk of health emergency in complex diseases such as RA.

Azilsartan prevented AGE-induced inflammatory response and degradation of aggrecan in human chondrocytes through inhibition of Sox4

Advanced glycation end products (AGEs)-induced inflammation and degradation of aggrecan in human chondrocytes play an important role in the progression and development of osteoarthritis (OA). Azilsartan, an angiotensin II receptor antagonist, has been licensed for the treatment of high blood pressure. However, the effects of Azilsartan in OA and AGEs-induced damages in chondrocytes have not been previously reported. The injured chondrocytes model was established by incubating with 5 μmol/L AGEs. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to evaluate the cell viability of treated SW1353 cells. The gene expression levels of interleukin-1α (IL-1α), tumor necrosis factor-β (TNF-β), IL-6, a disintegrin-like and metallopeptidase with thrombospondin type motif-4 (ADAMTS-4), ADAMTS-5, Aggrecan, and Sox-4 were evaluated using quantitative real-time polymerase chain reaction and their protein levels were determined using enzyme-linked immunosorbent assay or Western blot analysis. Mitogen-activated protein kinase p38 pathway was surveyed using phosp-p38 level and its specific inhibitor SB203580 was employed to block the p38 pathway. The overexpression of Sox4 plasmid was transfected into SW1353 cells to assess its regulation on ADAMTS-4 and ADAMTS-5. Azilsartan reduced AGEs-induced production of proinflammatory cytokines, such as IL-1α, TNF-β, and IL-6. Azilsartan prevented AGEs-induced expressions of ADAMTS-4 and ADAMTS-5 as well as the reduction of aggrecan. Mechanistically, AGEs treatment increased the expression of Sox4 in a dose-dependent manner. AGE treatment increased the level of phosphorylated p38. However, treatment with the p38 inhibitor SB203580 inhibited AGEs-induced expression of Sox4, suggesting that AGEs-induced expression of Sox4 is mediated by p38. Furthermore, Azilsartan suppressed AGEs-induced phosphorylation of p38 and expression of Sox4. Finally, the overexpression of Sox4 abolished the inhibitory effects of Azilsartan against the expressions of ADAMTS-4 and ADAMTS-5. Azilsartan treatment prevented AGEs-induced inflammatory response and degradation of aggrecan through inhibition of Sox4.

The role of the angiotensins in the pathogenesis of inflammatory joint disease

The significant humoral effect of the renin-angiotensin-aldosterone system on the regulation of the cardiovascular system and blood pressure has long been widely known. However, the identification and interpretation of new components of renin-angiotensin-aldosterone system in recent years can significantly expand the range of its potential effects on the body. The anti-inflammatory effect of drugs that block angiotensin II and its receptors, including in rheumatic diseases, can become practically significant for General therapists by their effect on reducing the concentration of inflammatory mediators and angiogenesis processes. The organoprotective and anti-inflammatory potentials of drugs that reduce the production of at demonstrated in vitro and in vivo experiments allow us to consider them as first-line angiotropic agents in patients with rheumatoid arthritis, especially in the presence of pathology of the cardiovascular system and kidneys.

Angiotensin II triggers knee joint lesions in experimental osteoarthritis

OBJECTIVES

This study aimed to evaluate the involvement of Angiotensin II (Ang II) in joint lesions associated with osteoarthritis (OA) in vitro and in vivo.

METHODS

Chondrocyte cultures were obtained from knee joints of neonatal rats and stimulated with Ang II/MIA/ACE inhibitors. In vivo, rats treated or not with the ACE inhibitor captopril, received daily injections of Ang II or sodium monoiodoacetate (MIA) in knee joints for evaluation of cartilage, bone, and synovial lesions.

RESULTS

Cultured chondrocytes expressed the mRNA for Ace, Agtr1, Agtr2, and Mas1. Stimulating cells with Ang II reduced chondrocyte viability and metabolism. Accordingly, in vivo Ang II injection into the knees of rats triggered hyperalgesia, joint edema, increased the number of leukocytes in the joint cavity, and induced cartilage lesions associated with OA alterations. In further experiments, Ang II synthesis was prevented with the ACE inhibitor Captopril in the context of MIA-induced OA. Ang II inhibition with captopril improved the OARSI score, induced chondroprotection, and reduced the leukocyte recruitment from synovium after MIA. Additionally, captopril prevented MIA-induced bone resorption, by decreasing the number of osteoclasts and increasing the expression of IL-10 in the bone. In vitro, inhibiting Ang II synthesis decreased MIA-induced chondrocyte death and increased Col2a1 transcription.

CONCLUSION

Ang II induces chondrocyte death and joint tissue damages associated with OA and its modulation can be a therapeutic strategy in osteoarthritis.

Synovial fluid peptidase activity as a biomarker for knee osteoarthritis clinical progression

AIMS

To analyze the potential role of synovial fluid peptidase activity as a measure of disease burden and predictive biomarker of progression in knee osteoarthritis (KOA).

METHODS

A cross-sectional study of 39 patients (women 71.8%, men 28.2%; mean age of 72.03 years (SD 1.15) with advanced KOA (Ahlbäck grade ≥ 3 and clinical indications for arthrocentesis) recruited through the (Orthopaedic Department at the Complejo Asistencial Universitario de León, Spain (CAULE)), measuring synovial fluid levels of puromycin-sensitive aminopeptidase (PSA), neutral aminopeptidase (NAP), aminopeptidase B (APB), prolyl endopeptidase (PEP), aspartate aminopeptidase (ASP), glutamyl aminopeptidase (GLU) and pyroglutamyl aminopeptidase (PGAP).

RESULTS

Synovial fluid peptidase activity varied significantly as a function of clinical signs, with differences in levels of PEP (p = 0.020), ASP (p < 0.001), and PGAP (p = 0. 003) associated with knee locking, PEP (p = 0.006), ASP (p = 0.001), GLU (p = 0.037), and PGAP (p = 0.000) with knee failure, and PEP (p = 0.006), ASP (p = 0.001), GLU (p = 0.037), and PGAP (p < 0.001) with knee effusion. Further, patients with the greatest functional impairment had significantly higher levels of APB (p = 0.005), PEP (p = 0.005), ASP (p = 0.006), GLU (p = 0.020), and PGAP (p < 0.001) activity, though not of NAP or PSA, indicating local alterations in the renin-angiotensin system. A binary logistic regression model showed that PSA was protective (p = 0.005; Exp (B) 0.949), whereas PEP (p = 0.005) and GLU were risk factors (p = 0.012).

CONCLUSION

These results suggest synovial fluid peptidase activity could play a role as a measure of disease burden and predictive biomarker of progression in KOA. Cite this article: Bone Joint Res 2020;9(11):789-797.

Atherosclerosis in Rheumatoid Arthritis: Promoters and Opponents

Substantial epidemiological data identified cardiovascular (CV) diseases as a main cause of mortality in patients with rheumatoid arthritis (RA). In light of this, RA patients may benefit from additional CV risk screening and more intensive prevention strategies. Nevertheless, current algorithms for CV risk stratification still remain tailored on general population and are burdened by a significant underestimation of CV risk in RA patients. Acute CV events in patients with RA are largely related to an accelerated atherosclerosis. As pathophysiological features of atherosclerosis overlap those occurring in the inflamed RA synovium, the understanding of those common pathways represents an urgent need and a leading challenge for CV prevention in patients with RA. Genetic background, metabolic status, gut microbiome, and systemic inflammation have been also suggested as additional key pro-atherosclerotic factors. The aim of this narrative review is to update the current knowledge about pathophysiology of atherogenesis in RA patients and potential anti-atherosclerotic effects of disease-modifying anti-rheumatic drugs.

[Expressions of Renin, angiotensin converting enzyme, angiotensin receptor 1, and angiotensin receptor 2 in synovial tissue of osteoarthritis at different stages]

OBJECTIVE

To study the expressions of Renin, angiotensin converting enzyme (ACE), angiotensin receptor 1 (AT1R), and AT2R in synovial tissue of osteoarthritis (OA) at different stages.

METHODS

The patients who were treated with upper knee amputation because of trauma or total knee arthroplasty for OA between January 2018 and December 2018 were enrolled. Among them, 32 patients who met the selection criteria were included in the study. According to the Kellgren-Lawrence (K-L) X-ray classification, they were allocated to normal synovial group (group A, n=9), moderate OA synovial group (group B, n=11, K-L level 3), and advanced OA synovial group (group C, n=12, K-L level 4). The relative expressions of Renin, ACE, AT1R, and AT2R mRNAs and proteins were detected by real-time fluorescence quantitative PCR (qRT-PCR) and Western blot.

RESULTS

The relative expressions of Renin, ACE, and AT1R mRNAs and proteins were significantly higher in group B and group C than in group A ( P<0.05). The relative expressions of ACE and AT1R mRNAs and proteins and Renin protein were significantly higher in group C than in group B ( P<0.05). However, the relative expressions of AT2R mRNA and protein were lower in group B and group C than in group A ( P<0.05), and in group C than in group B ( P<0.05).

CONCLUSION

The expressions of Renin, ACE, and AT1R in synovial tissue of osteoarthritis significantly increase as the K-L level increased, and the expression of AT2R decreases. Renin, ACE, AT1R, and AT2R have a certain degree of correlation with the development of OA.

Micro-fragmented Adipose Tissue Transplantation (MATT) for the treatment of acetabular delamination. A two years follow up comparison study with microfractures

Background: Delamination of acetabular articular cartilage is a common progressive abnormality in hips with femoroacetabular impingement. The aim of this study is to compare the effectiveness of two different procedures for the arthroscopic treatment of acetabular delamination: microfractures (MFx) and micro-fragmented autologous adipose tissue transplantation (MATT) technique. Methods: We carried out a controlled retrospective study of 35 patients affected by an acetabular cartilage delamination in femoroacetabular impingement (FAI). In all the selected cases the size of the defect ranged from 1 to 2 cm², with a mean size of 1.9 cm² in MFx group and 1.6 cm² in MATT group (p=0.1). Of these, 18 patients were treated with MFx while 17 patients were treated with MATT. The two groups were similar in terms of clinical, functional and radiological aspects. All the patients were assessed before and after the procedure, for pain and function, with the modified Harris Hip Score (mHHS). The mean preoperative mHHS was 50±5 for MFx group and 53±6 for MATT group (p = 0.245). All the patients were followed-up for two years. Results: The final mHHS was 76±12 in MFx group and 97.1±3 in MATT group (p<0.001). In both groups neither a conversion to total hip arthroplasty nor a revision hip arthroscopy was observed. Conclusions: The results of this study provide proof that MATT technique improves clinical outcomes with a mHH scoring significantly higher than MFx group. (www.actabiomedica.it)

Differential Expression of Renin-Angiotensin System-related Components in Patients with Rheumatoid Arthritis and Osteoarthritis

BACKGROUND

The purpose of this study was to demonstrate the role of renin-angiotensin system (RAS)-related components, vascular endothelial growth factor (VEGF) and atrial metalloproteinase-13 (MMP-13) in synovial tissue and synovial fluid from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

MATERIALS AND METHODS

Thirty-four patients with RA and 41 patients with OA were included in the study. Renin, angiotensin-converting enzyme (ACE), VEGF and MMP-13 protein levels in the synovial fluid were measured by enzyme-linked immunosorbent assay. Quantitative real-time polymerase chain reaction analysis, western blot analysis and immunohistochemistry were used to quantify renin, ACE, angiotensin type 1 and type 2 receptors, VEGF and MMP-13 in OA and RA. Additionally, the correlation was determined by Pearson's coefficient.

RESULTS

In synovial fluid, expression levels of renin, ACE, VEGF and MMP-13 in patients with RA were significantly higher than those in patients with OA. In synovial tissue, the RAS components VEGF and MMP-13 were also elevated in patients with RA. The results of immunohistochemistry in synovial tissue also showed that the RAS components VEGF and MMP-13 were significantly increased in patients with RA. Notably, the Pearson coefficient demonstrated that the levels of the RAS components were positively correlated with the expression of VEGF and MMP-13 in OA and RA.

CONCLUSIONS

The present results suggest that RAS-related components in RA and OA, including renin, ACE, angiotensin type 1 and type 2 receptors, are associated with increased expression of VEGF and play an important role in angiogenesis. Furthermore, there was a significant positive correlation between the expression of VEGF and MMP-13.

Renin-angiotensin system in osteoarthritis: A new potential therapy

Osteoarthritis (OA) is one of the most common chronic joint diseases. However, the mechanism remains unclear. The traditional renin-angiotensin system (RAS) is an important system for regulating homeostasis and controlling balance. In recent years, RAS-related components have played an important role in the occurrence of OA. The purpose of this review is to summarize the research results of RAS-related components that are associated with OA. This study systematically searched e-medical databases such as PubMed, Embase, Medline, and Web of Science. The search targets included English publications describing the effects of RAS-related components in OA, including the role of renin, angiotensin-converting enzyme (ACE), Angiotensin II (Ang II), and angiotensin receptor (ATR). Additionally, this study summarizes the potential pathways for RAS-related components to intervene in OA. This study found that RAS-related components including renin, ACE, Ang II, AT1R and AT2R are involved in inflammation and chondrocyte hypertrophy in OA. RAS is involved in signaling pathways including the NF-κB, JNK, VEGFR/Tie-2, and the Axna2/Axna2R axis ones, which may be potential targets for the treatment of OA. Although there are few studies on RAS in the field of OA, the pathogenic effect of RAS-related components is still an important topic in OA treatment, and great progress may be made in this aspect in future studies.

The skeletal renin-angiotensin system: A potential therapeutic target for the treatment of osteoarticular diseases

The classical renin-angiotensin system (RAS) is known to be a key regulator of blood pressure as well as fluid and electrolyte homeostasis. Additionally, it is now evident that components of the RAS are produced and act locally in many tissues, including liver, kidney, heart, lung, eye, bone, reproductive organ, adipose, and adrenal tissue, and these components are collectively known as tissue RAS. Recently, several studies have shown that local bone RAS is directly involved in bone metabolism, and activation of skeletal RAS plays an important role in bone diseases, such as osteoporosis, arthritis, and deterioration as well as in fracture healing. Based on the identification of RAS components in bone, we examined a new therapeutic approach to attenuate bone diseases through RAS inhibitors: renin inhibitor, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers. In this paper, we provide a systematic review of the skeletal RAS in the pathophysiology of bone diseases and the beneficial effect of RAS inhibitors on bone tissue.

Angiotensins and rheumatoid arthritis

At present, the role of the renin-angiotensin system (RAS) in regulating the cardiovascular system and maintaining water and electrolyte homeostasis has been well studied. However, over the past decades, new components of the RAS have been identified, suggesting a wider range of its potential effects on the body. It is of fundamentally importance for rheumatologists to affect inflammation, including rheumatoid inflammation, through blockade of angiotensin (AT) II formation via the effects of AT 1–7 and angiotensin-converting enzyme inhibitors, as well as through suppression of angiogenesis, primarily by reducing the production of endothelial growth factor. The organ-protective and antiinflammatory potential of drugs that reduce the production of AT, which has been proven in in vitro and in vivo experiments, allows us to consider them as first-line angiotropic agents in patients with rheumatoid arthritis, especially in the presence of concomitant hypertension and/or nephropathy.

The use of unlicensed bone marrow-derived platelet lysate-expanded mesenchymal stromal cells in colitis: a pre-clinical study

BACKGROUND

Mesenchymal stromal cells (MSCs) are a promising candidate for treatment of inflammatory disorders, but their efficacy in human inflammatory bowel diseases (IBDs) has been inconsistent. Comparing the results from various pre-clinical and clinical IBD studies is also challenging due to a large variation in study designs.

METHODS

In this comparative pre-clinical study, we compared two administration routes and investigated the safety and feasibility of both fresh and cryopreserved platelet-lysate-expanded human bone marrow-derived MSCs without additional licensing in a dextran sodium sulfate (DSS) colitis mouse model both in the acute and regenerative phases of colitis. Body weight, macroscopic score for inflammation and colonic interleukin (IL)-1β and tumor necrosis factor (TNF)α concentrations were determined in both phases of colitis. Additionally, histopathology was assessed and Il-1β and Agtr1a messenger RNA (mRNA) levels and angiotensin-converting enzyme (ACE) protein levels were measured in the colon in the regenerative phase of colitis.

RESULTS

Intravenously administered MSCs exhibited modest anti-inflammatory capacity in the acute phase of colitis by reducing IL-1β protein levels in the inflamed colon. There were no clear improvements in mice treated with fresh or cryopreserved unlicensed MSCs according to weight monitoring results, histopathology and macroscopic score results. Pro-inflammatory ACE protein expression and shedding were reduced by cryopreserved MSCs in the colon.

CONCLUSIONS

In conclusion, we observed a good safety profile for bone marrow-derived platelet lysate-expanded MSCs in a mouse pre-clinical colitis model, but the therapeutic effect of MSCs prepared without additional licensing (i.e. such as MSCs are administered in graft-versus-host disease) was modest in the chosen in vivo model system and limited to biochemical improvements in cytokines without a clear benefit in histopathology or body weight development.

Inflammation as a Regulator of the Renin-Angiotensin System and Blood Pressure

PURPOSE OF REVIEW

Mechanisms facilitating progression of hypertension via cross stimulation of the renin-angiotensin system (RAS) and inflammation have been proposed. Accordingly, we review and update evidence for regulation of RAS components by pro-inflammatory factors.

RECENT FINDINGS

Angiotensin II (Ang II), which is produced by RAS, induces vasoconstriction and consequent blood pressure elevation. In addition to this direct action, chronically elevated Ang II stimulates several pathophysiological mechanisms including generation of oxidative stress, stimulation of the nervous system, alterations in renal hemodynamics, and activation of the immune system. In particular, an activated immune system has been shown to contribute to the development of hypertension. Recent studies have demonstrated that immune cell-derived pro-inflammatory cytokines regulate RAS components, further accelerating systemic and local Ang II formation. Specifically, regulation of angiotensinogen (AGT) production by pro-inflammatory cytokines in the liver and kidney is proposed as a key mechanism underlying the progression of Ang II-dependent hypertension.

Cyclic compressive loading activates angiotensin II type 1 receptor in articular chondrocytes and stimulates hypertrophic differentiation through a G-protein-dependent pathway

Angiotensin II type 1 receptor (AT1R) appears to have a mechanosensing function in a number of cell types. The purpose of this study was to examine whether AT1R expressed in articular chondrocytes is involved in osteoarthritis (OA) progression in vivo and whether cyclic compressive loading activates the AT1R and stimulates hypertrophic differentiation of chondrocytes in vitro. The relationships between the modified Mankin score for cartilage degeneration and the expression of AT1R and type X collagen (Col X) were studied in mouse knees with OA induced using the destabilization-of-medial-meniscus model. Cyclic compressive loads were applied to cultured bovine articular chondrocytes in three-dimensional agarose scaffolds. Expression of Col X and runt-related transcription factor 2 (Runx2) was analyzed using RT-PCR and western blotting. We dissected the downstream pathway for intracellular signal transductions of AT1R including G-protein-dependent and G-protein-independent pathways. Positive significant correlations between the Mankin score and the rate of AT1R-immunopositive cells and between the rates of AT1R and Col X expression were noted. The expression of Col X and Runx2 was increased by compressive loading but suppressed by addition of olmesartan, an Ang II receptor blocker, to the agarose scaffolds. Compressive loading upregulated the phosphorylation of c-Jun N-terminal kinase (JNK), Src, and STAT1, but olmesartan significantly suppressed only JNK phosphorylation. We conclude that AT1R expressed by articular chondrocytes may be involved in OA progression in vivo. Mechanical stress can activate AT1R and stimulate hypertrophic differentiation of chondrocytes through the G-protein-dependent pathway. AT1R has a mechanosensing function in chondrocytes and may be a new therapeutic target in OA.

Aliskiren has chondroprotective efficacy in a rat model of osteoarthritis through suppression of the local renin-angiotensin system

The local renin-angiotensin system (RAS) has been reported to have an important role in the pathogenesis and progression of metabolic bone diseases, including osteoarthritis (OA). Aliskiren is the first in a new class of orally effective direct renin inhibitors and is approved for the treatment of hypertension in humans. However, its efficacy in patients with OA is unknown. A rat model of OA was induced to investigate the potential efficacy of aliskiren. Effects of aliskiren on the cartilage structure were detected by safranin O staining and its effects on the widths of the proliferation zone and hypertrophic zone (HZ) of chondrocytes were analyzed by Masson's staining. Tartate-resistant acid phosphatase staining was used to evaluate the effects of aliskiren on osteoclasts in the chondrocytes. Relative histological analyses were performed. Additionally, the expression levels of factors associated with osteoclast differentiation (receptor activator of nuclear factor κB ligand and osteoprotegerin), articular cartilage destruction [tumor necrosis factor-α (TNF-α) and matrix metalloproteinase 9] and osteoblast differentiation [runt related transcription factor 2 (Runx2)], along with RAS components (renin, renin-receptor, angiotensin type 1 receptor (AT1R), AT2R, angiotensin converting enzyme (ACE) and angiotensin II (Ang II)] were detected in samples from the proximal tibias. Aliskiren did not fully suppress the inflammatory reaction in OA model animals and had marginal regulatory effects on biochemical bone markers induced by OA. However, aliskiren attenuated cartilage destruction, abnormal cartilage cellularity and the expansion of the HZ of chondrocytes, and significantly attenuated the expression of interleukin-1, TNF-α, Runx2 and procollagen type I N-terminal propeptide. These chondroprotective properties were accompanied by reductions in the levels of RAS components (renin, Ang II, ACE and AT1R), indicating that aliskiren exerts multiple effects of on bone formation, osteoblast differentiation and articular cartilage protection via the RAS. OA activates the local bone RAS, inhibits bone formation and stimulates bone resorption. Aliskiren, a renin inhibitor, demonstrated chondroprotective efficacy in a rat model of OA through suppression of the local RAS.

Biological Therapies for Cartilage Lesions in the Hip: A New Horizon

Treatment of hip cartilage disease is challenging, and there is no clear algorithm to address this entity. Biomarkers are arising as promising diagnostic tools because they could play a role in the early assessment of the prearthritic joint and as a prognostic factor before and after treatment. The potential effect of biomarkers may be used to categorize individuals at risk of evolving to severe osteoarthritis, to develop new measures for clinical progression of the disease, and to develop new treatment options for the prevention of osteoarthritis progression. A trend toward a less invasive biological treatment will usher in a new treatment era. With the growth of surgical skills in hip arthroscopy, cartilage restoration techniques are evolving in a fast and exponential manner. Biological and surgical treatments have been proposed to treat these pathologies. Biological treatments include platelet-rich plasma, stem cells or bone marrow aspirate concentration, hyaluronic acid, losartan, and fish oil. Surgical treatments include microfracture alone or augmented, direct repair, autologous chondrocyte implantation, matrix-induced chondrocyte implantation, autologous matrix-induced chondrogenesis, mosaicplasty, osteochondral allograft transplantation, and stem cells implanted in matrix (stem cells in membranes/expanded stem cells). This article reviews new evidence available on treatment options for chondral lesions and early osteoarthritis of the hip. [Orthopedics. 2016; 39(4):e715-e723.].

Endothelial Dysfunction and Inflammation: Immunity in Rheumatoid Arthritis

Inflammation, as a feature of rheumatoid arthritis (RA), leads to the activation of endothelial cells (ECs). Activated ECs induce atherosclerosis through an increased expression of leukocyte adhesion molecules. Endothelial dysfunction (ED) is recognized as a failure of endothelial repair mechanisms. It is also an early preclinical marker of atherosclerosis and is commonly found in RA patients. RA is now established as an independent cardiovascular risk factor, while mechanistic determinants of ED in RA are still poorly understood. An expanding body of study has shown that EC at a site of RA is both active participant and regulator of inflammatory process. Over the last decade, a role for endothelial dysfunction in RA associated with cardiovascular disease (CVD) has been hypothesized. At the same time, several maintenance drugs targeting this phenomenon have been tested, which has promising results. Assessment of endothelial function may be a useful tool to identify and monitor RA patients.

Captopril, an angiotensin-converting enzyme inhibitor, possesses chondroprotective efficacy in a rat model of osteoarthritis through suppression local renin-angiotensin system

OBJECTIVE

A local tissue-specific renin-angiotensin system (local RAS) has emerged as a regulator of cartilage development and homeostasis. However, no report has described the chondroprotective efficacy of RAS inhibitor. Therefore, we studied the pharmacological function of captopril on hypertrophic differentiation of chondrocytes, cartilaginous degeneration and RAS components expression in a rat model of osteoarthritis (OA).

METHODS

OA was surgically induced in the right knee of male rats. Animal groups included age matched sham control (sham group), OA placebo (OA group), and OA treated with captopril (CAP group). Eight weeks after the induction of OA, the tibias were isolated and the sagittal sections were stained with Safranin O and Masson-Trichrome. The mRNA and protein expression of RAS components were measured by qRT-PCR and western blotting respectively.

RESULTS

The thickness of articular cartilage was reduced in the proximal tibia of the OA group, and decreased thickness of articular cartilage of the OA mice was effectively reversed by captopril treatment. Histological analyses revealed remarkable chondrocytes abnormality in OA rats, which were characterized by a marked expansion of hypertrophic zone and inhibition of proliferative zone of chondrocytes in the epiphyseal growth plate of tibia. However, captopril-treated could reverse chondrocytes abnormality in OA rats. Furthermore, the mRNA and protein expression of RAS components, renin, ACE, Ang II AT1R were upregulated in the proximal tibia of OA rats, however, the AT2R expression was suppressed. Intriguingly, captopril-treated could inhibit the activation of RAS in OA rats.

CONCLUSIONS

The present study demonstrated that captopril could attenuate OA-induced osteoarticular injury, at least partially, through suppression local RAS.

Losartan increases bone mass and accelerates chondrocyte hypertrophy in developing skeleton

Angiotensin receptor blockers (ARBs) are a group of anti-hypertensive drugs that are widely used to treat pediatric hypertension. Recent application of ARBs to treat diseases such as Marfan syndrome or Alport syndrome has shown positive outcomes in animal and human studies, suggesting a broader therapeutic potential for this class of drugs. Multiple studies have reported a benefit of ARBs on adult bone homeostasis; however, its effect on the growing skeleton in children is unknown. We investigated the effect of Losartan, an ARB, in regulating bone mass and cartilage during development in mice. Wild type mice were treated with Losartan from birth until 6 weeks of age, after which bones were collected for microCT and histomorphometric analyses. Losartan increased trabecular bone volume vs. tissue volume (a 98% increase) and cortical thickness (a 9% increase) in 6-weeks old wild type mice. The bone changes were attributed to decreased osteoclastogenesis as demonstrated by reduced osteoclast number per bone surface in vivo and suppressed osteoclast differentiation in vitro. At the molecular level, Angiotensin II-induced ERK1/2 phosphorylation in RAW cells was attenuated by Losartan. Similarly, RANKL-induced ERK1/2 phosphorylation was suppressed by Losartan, suggesting a convergence of RANKL and angiotensin signaling at the level of ERK1/2 regulation. To assess the effect of Losartan on cartilage development, we examined the cartilage phenotype of wild type mice treated with Losartan in utero from conception to 1 day of age. Growth plates of these mice showed an elongated hypertrophic chondrocyte zone and increased Col10a1 expression level, with minimal changes in chondrocyte proliferation. Altogether, inhibition of the angiotensin pathway by Losartan increases bone mass and accelerates chondrocyte hypertrophy in growth plate during skeletal development.

Angiotensin II in inflammation, immunity and rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that is characterized by increased cardiovascular morbidity and mortality, independent of the traditional risk factors for cardiovascular disease. Although classically known for its role in the regulation of circulatory homeostasis, angiotensin II (Ang II) is recognized to act as a powerful proinflammatory mediator. Some research has showed that Ang II plays important roles in autoimmune diseases, including RA, systemic lupus erythematosus and multiple sclerosis. Ang II blockers prove effective in reducing inflammation and autoimmunity in rheumatic diseases and their relative safety, together with their effects for reducing the cardiovascular disease risk, suggest that Ang II blockers may at least act as effective adjunctive therapy for disease control in patients with RA. The present review focuses systematically on the potential impact of Ang II and its receptors on inflammation and immunomodulation in patients with RA.

Protective effects of the angiotensin type 1 receptor antagonist losartan in infection-induced and arthritis-associated alveolar bone loss

BACKGROUND AND OBJECTIVE

The angiotensin type 1 (AT1) receptor has been implicated in the pathogenesis of inflammatory bone disorders. This study aimed to investigate the effect of an AT1 receptor antagonist in infection-induced and arthritis-associated alveolar bone loss in mice.

MATERIAL AND METHODS

Mice were subjected to Aggregatibacter actinomycetemcomitans oral infection or antigen-induced arthritis and treated daily with 10 mg/kg of the prototype AT1 antagonist, losartan. Treatment was conducted for 30 d in the infectious condition and for 17 d and 11 d in the preventive or therapeutic regimens in the arthritic model, respectively. The mice were then killed, and the maxillae, serum and knee joints were collected for histomorphometric and immunoenzymatic assays. In vitro osteoclast assays were performed using RAW 264.7 cells stimulated with A. actinomycetemcomitans lipopolysacharide (LPS).

RESULTS

Arthritis and A. actinomycetemcomitans infection triggered significant alveolar bone loss in mice and increased the levels of myeloperoxidase and of TRAP(+) osteoclasts in periodontal tissues. Losartan abolished such a phenotype, as well as the arthritis joint inflammation. Both arthritis and A. actinomycetemcomitans conditions were associated with the release of tumor necrosis factor alpha (TNF-α), interferon-gamma, interleukin-17 and chemokine (C-X-C motif) ligand 1 and an increased RANKL/osteoprotegerin ratio in periodontal tissues, but such expression decreased after losartan treatment, except for TNF-α. The therapeutic approach was as beneficial as the preventive one. In vitro, losartan prevented LPS-induced osteoclast differentiation and activity.

CONCLUSION

The blockade of AT1 receptor exerts anti-inflammatory and anti-osteoclastic effects, thus protecting periodontal tissues in distinct pathophysiological conditions of alveolar bone loss.

Continuous infusion of angiotensin II modulates hypertrophic differentiation and apoptosis of chondrocytes in cartilage formation in a fracture model mouse

Although components of the renin-angiotensin system (RAS) are reported to be expressed in cultured chondrocytes and cartilage, little is known about the precise function of Angiotensin II (Ang II) in chondrocytes. In this study, we employed a rib fracture model mouse to investigate the effect of Ang II on chondrocytes. Ang II type 1 receptor (AT1R) was expressed in chondrocytes in the growth plate of mouse tibia. Continuous infusion of Ang II to rib-fractured mice resulted in a significant increase in the volume of cartilage, suggesting Ang II-induced hypertrophic differentiation of chondrocytes. It was also confirmed by a significant increase in the mRNA expression of Sox9 and runt-related transcription factor 2 (Runx2), which are genes related to chondrocyte differentiation, and type X collagen, matrix metalloproteinase (MMP)-13 and Indian hedgehog (Ihh), which are hypertrophic chondrocyte-specific molecular markers. Chondrocyte hypertrophy with upregulation of these genes was attenuated by administration of olmesartan, an AT1R blocker, but not by hydralazine. Moreover, Ang II infusion significantly suppressed apoptosis of chondrocytes, accompanied by significant induction of mRNA expression of bcl-2 and bcl-xL. Olmesartan, but not hydralazine, significantly attenuated the reduction of apoptotic cells and the increase in anti-apoptotic genes induced by Ang II infusion. Overall, the present study demonstrated that Ang II promoted hypertrophic differentiation of chondrocytes and reduced apoptosis of hypertrophic chondrocytes independently of high blood pressure. The present data indicate the role of Ang II in cartilage, and might provide a new concept for treatment of cartilage diseases.

Mechanisms of the anti-inflammatory actions of the angiotensin type 1 receptor antagonist losartan in experimental models of arthritis

Angiotensin (Ang) II and its AT1 receptors have been implicated in the pathogenesis of rheumatoid arthritis. Activation of the counter-regulatory Ang-(1-7)-Mas receptor axis may contribute to some of the effects of AT₁ receptor blockers (ARBs). In this study, we have used losartan, an ARB, to investigate the role of and the mechanisms by which AT₁ receptors participated in two experimental models of arthritis: antigen-induced arthritis (AIA) in mice and adjuvant-induced arthritis (AdIA) in rats. Treatment with losartan decreased neutrophil recruitment, hypernociception and the production of TNF-α, IL-1β and chemokine (C-X-C motif) ligand 1 in mice subjected to AIA. Histopathological analysis showed significant reduction of tissue injury and inflammation and decreased proteoglycan loss. In addition to decreasing cytokine production, losartan directly reduced leukocyte rolling and adhesion. Anti-inflammatory effects of losartan were not associated to Mas receptor activation and/or Ang-(1-7) production. Anti-inflammatory effects were reproduced in rats subjected to AdIA. This study shows that ARBs have potent anti-inflammatory effects in animal models of arthritis. Mechanistically, reduction of leukocyte accumulation and of joint damage was associated with local inhibition of cytokine production and direct inhibition of leukocyte-endothelium interactions. The anti-inflammatory actions of losartan were accompanied by functional improvement of the joint, as seen by reduced joint hypernociception. These findings support the use of ARBs for the treatment of human arthritis and provide potential mechanisms for the anti-inflammatory actions of these compounds.