Downregulating osteopontin reduces angiotensin II-induced inflammatory activation in vascular smooth muscle cells

Role of osteokines in atherosclerosis

Despite their diverse physiologies and roles, the heart, skeletal muscles, and smooth muscles all derive from a common embryonic source as bones. Moreover, bone tissue, skeletal and smooth muscles, and the heart share conserved signaling pathways. The maintenance of skeletal health is precisely regulated by osteocytes, osteoblasts, and osteoclasts through coordinated secretion of bone-derived factors known as osteokines. Increasing evidence suggests the involvement of osteokines in regulating atherosclerotic vascular disease. Therefore, this review aims to examine the evidence for the role of osteokines in atherosclerosis development and progression comprehensively. Specifically discussed are extensively studied osteokines in atherosclerosis such as osteocalcin, osteopontin, osteoprotegerin, and fibroblast growth factor 23. Additionally, we highlighted the effects of exercise on modulating these key regulators derived from bone tissue metabolism. We believe that gaining an enhanced understanding of how osteocalcin contributes to the process of atherosclerosis will enable us to develop targeted and comprehensive therapeutic strategies against diseases associated with its progression.

Smooth muscle NADPH oxidase 4 promotes angiotensin II-induced aortic aneurysm and atherosclerosis by regulating osteopontin

BACKGROUND AND AIMS

Angiotensin II (Ang II) is commonly used to induce aortic aneurysm and atherosclerosis in animal models. Ang II upregulates NADPH oxidase isoform Nox4 in aortic smooth muscle cells (SMCs) in mice. However, whether smooth muscle Nox4 is directly involved in Ang II-induced aortic aneurysm and atherosclerosis is unclear.

METHODS & RESULTS

To address this, we used smooth muscle-specific Nox4 dominant-negative (SDN) transgenic mice, in which Nox4 activity is constitutively inhibited. In non-transgenic (NTg) mice, Ang II increased the expression of proteins known to contribute to both aortic aneurysm and atherosclerosis, namely osteopontin (OPN), collagen type I&III (Col I&III), matrix metalloproteinase 2 (MMP2), and vascular cell adhesion molecule 1 (VCAM1), which were all significantly downregulated in SDN mice. The number and size of Ang II-induced aorta collateral aneurysms and atherosclerotic lesions in the renal artery and aortic root of SDN mice were significantly decreased compared to NTg mice, and directly correlated with a decrease in OPN expression. Replenishing OPN in SDN SMCs, increased the expression of Col I&III, MMP2, and VCAM1, and promoted SMC proliferation, migration, and inflammation.

CONCLUSIONS

Our data demonstrate that smooth muscle Nox4 directly promotes the development of Ang II-induced aortic aneurysm and atherosclerosis, at least in part, through regulating OPN expression.

Osteopontin: A Promising Therapeutic Target in Cardiac Fibrosis

Osteopontin (OPN) is recognized for its significant roles in both physiological and pathological processes. Initially, OPN was recognized as a cytokine with pro-inflammatory actions. More recently, OPN has emerged as a matricellular protein of the extracellular matrix (ECM). OPN is also known to be a substrate for proteolytic cleavage by several proteases that form an integral part of the ECM. In the adult heart under physiological conditions, basal levels of OPN are expressed. Increased expression of OPN has been correlated with the progression of cardiac remodeling and fibrosis to heart failure and the severity of the condition. The intricate process by which OPN mediates its effects include the coordination of intracellular signals necessary for the differentiation of fibroblasts into myofibroblasts, promoting angiogenesis, wound healing, and tissue regeneration. In this review, we discuss the role of OPN in contributing to the development of cardiac fibrosis and its suitability as a therapeutic target.

Osteopontin potentiates PM-induced IL-1α and IL-1β production via the ERK/JNK signaling pathway

Ambient particulate matter (PM) poses a great threat to global health and contributes to pulmonary inflammation. However, the potential mechanism of PM-induced inflammation of the lung remains unclear. Osteopontin (OPN) is a multifunctional protein that reportedly regulates inflammatory responses in different diseases. Here, we explored the expression of OPN with PM exposure in vivo and in vitro and attempted to elucidate the regulatory role of OPN in PM-induced airway inflammation. Our results showed that PM exposure increased the expression of OPN in the bronchial epithelium, serum, and bronchoalveolar lavage fluid (BALF) of mice. Moreover, PM induced OPN expression in human bronchial epithelial cells (HBECs) in a dose and time-dependent manner. In vitro, inflammatory cytokines such as IL-1α and IL-1β were increased in HBECs with PM exposure via the ERK and JNK signaling pathways. Recombinant human OPN could potentiate PM-induced expression of IL-1α and IL-1β, while OPN siRNA could alleviate PM-induced inflammatory responses in HBECs. Furthermore, we showed that OPN regulated PM-induced inflammatory cytokines via the ERK and JNK pathways in HBECs. This study shows for the first time the positive effect of OPN on PM-induced airway inflammation and contributes to a better understanding of its potential mechanism of action.

The Emerging Role of Bone Markers in Diagnosis and Risk Stratification of Patients With Coronary Artery Disease

Molecules that govern bone metabolism, such as osteoprotegerin (OPG) and osteopontin (OPN), have been isolated from other tissues, including blood vessels. Atherosclerosis and coronary artery disease (CAD) are leading causes of mortality worldwide. Despite novel biochemical and imaging techniques, early detection of CAD is still unsatisfactory. Experimental data indicate that bone turnover markers (BTMs) contribute to the development of atherosclerosis. This finding has sparked interest in their clinical use. This narrative review analyzed information from >50 human studies, which strongly suggest that OPG, OPN, and alkaline phosphatase (ALP) serum concentrations are altered in patients with CAD. Osteoprotegerin seems to be more useful for the detection of early disease, while OPN and ALP are recruited in vessels after the establishment of disease. Osteocalcin may be used as a flow cytometry marker for endothelial progenitor cells and can constitute a marker to monitor response to interventional treatments and risk of restenosis. However, most data derive from observational studies. Incorporation of BTMs in multifactorial computational algorithms could further determine their role in CAD diagnosis and prognosis together with other imaging techniques and biochemical markers.

Vascular smooth muscle cell in atherosclerosis

Vascular smooth muscle cells (VSMCs) exhibit phenotypic and functional plasticity in order to respond to vascular injury. In case of the vessel damage, VSMCs are able to switch from the quiescent 'contractile' phenotype to the 'proinflammatory' phenotype. This change is accompanied by decrease in expression of smooth muscle (SM)-specific markers responsible for SM contraction and production of proinflammatory mediators that modulate induction of proliferation and chemotaxis. Indeed, activated VSMCs could efficiently proliferate and migrate contributing to the vascular wall repair. However, in chronic inflammation that occurs in atherosclerosis, arterial VSMCs become aberrantly regulated and this leads to increased VSMC dedifferentiation and extracellular matrix formation in plaque areas. Proatherosclerotic switch in VSMC phenotype is a complex and multistep mechanism that may be induced by a variety of proinflammatory stimuli and hemodynamic alterations. Disturbances in hemodynamic forces could initiate the proinflammatory switch in VSMC phenotype even in pre-clinical stages of atherosclerosis. Proinflammatory signals play a crucial role in further dedifferentiation of VSMCs in affected vessels and propagation of pathological vascular remodelling.

Osteopontin is indispensible for AP1-mediated angiotensin II-related miR-21 transcription during cardiac fibrosis

Aims

Osteopontin (OPN) is a multifunctional cytokine critically involved in cardiac fibrosis. However, the underlying mechanisms are unresolved. Non-coding RNAs are powerful regulators of gene expression and thus might mediate this process.

Methods and results

OPN and miR-21 were significantly increased in cardiac biopsies of patients with myocardial fibrosis. Ang II infusion via osmotic minipumps led to specific miRNA regulations with miR-21 being strongly induced in wild-type (WT) but not OPN knockout (KO) mice. This was associated with enhanced cardiac collagen content, myofibroblast activation, ERK-MAP kinase as well as AKT signalling pathway activation and a reduced expression of Phosphatase and Tensin Homologue (PTEN) as well as SMAD7 in WT but not OPN KO mice. In contrast, cardiotropic AAV9-mediated overexpression of OPN in vivo further enhanced cardiac fibrosis. In vitro, Ang II induced expression of miR-21 in WT cardiac fibroblasts, while miR-21 levels were unchanged in OPN KO fibroblasts. As pri-miR-21 was also increased by Ang II, we studied potential involved upstream regulators; Electrophoretic Mobility Shift and Chromatin Immunoprecipitation analyses confirmed activation of the miR-21 upstream-transcription factor AP-1 by Ang II. Recombinant OPN directly activated miR-21, enhanced fibrosis, and activated the phosphoinositide 3-kinase pathway. Locked nucleic acid-mediated miR-21 silencing ameliorated cardiac fibrosis development in vivo.

Conclusion

In cardiac fibrosis related to Ang II, miR-21 is transcriptionally activated and targets PTEN/SMAD7 resulting in increased fibroblast survival. OPN KO animals are protected from miR-21 increase and fibrosis development due to impaired AP-1 activation and fibroblast activation.

Osteopontin (OPN) is a pleiotropic cytokine, which has been shown to be a pivotal factor in myofibroblast activation in cardiac fibrosis, thereby acting as a strong driver of heart failure development in humans. MicroRNAs (miRNAs) are under intense investigation as powerful regulators of various diseases. First phase I and II clinical trials using miRNA inhibitors have been initiated. We here show, that OPN is essential in the activation of AP-1 and subsequent transcription of miR-21 in cardiac fibrosis related to Ang II. OPN null mice are protected from miR-21 increase and fibrosis development due to impaired AP-1 activation and fibroblast activation. In the future, these findings may result in miRNA therapeutic approaches to treat patients with cardiac remodelling, in which levels of OPN and miR-21 are increased.

Downregulation of osteopontin enhances the sensitivity of glioma U251 cells to temozolomide and cisplatin by targeting the NF-κB/Bcl‑2 pathway

Glioma is resistant to the apoptotic effects of chemotherapy and the mechanism underlying its chemoresistance is not currently understood. In a previous study, we reported that osteopontin (OPN) was overexpressed in glioma tissues and had an important anti‑apoptotic effect. Furthermore, overexpression of OPN was observed following chemotherapy. To elucidate whether OPN plays a role in chemotherapy resistance and to investigate its downstream signaling pathway, this study used small interfering RNA (siRNA) to silence the expression of OPN in U251 human neuronal glioma astrocytoma cells. OPN downregulation in U251 cells enhanced the apoptotic effects induced by temozolomide (TMZ) and cisplatin (DDP). Furthermore, OPN siRNA suppressed the nuclear factor κ‑light‑chain‑enhancer of activated B cells (NF‑κB) activation and B cell lymphoma 2 (Bcl‑2) expression that was induced by chemotherapy. Taken together, these results demonstrated that the expression levels of OPN are involved in glioma chemoresistance. Knockdown of OPN through siRNA enhanced the effects of TMZ and DDP chemotherapy by targeting the NF‑κB/Bcl‑2 pathway.

Pioglitazone reduces angiotensin II-induced COX-2 expression through inhibition of ROS production and ET-1 transcription in vascular cells from spontaneously hypertensive rats

Glitazones have anti-inflammatory properties by interfering with the transcription of proinflammatory genes, such as cyclooxygenase (COX)-2, and with ROS production, which are increased in hypertension. This study analyzed whether pioglitazone modulates COX-2 expression in hypertension by interfering with ROS and endothelin (ET)-1. In vivo, pioglitazone (2.5 mg·kg(-1)·day(-1), 28 days) reduced the greater levels of COX-2, pre-pro-ET-1, and NADPH oxidase (NOX) expression and activity as well as O2 (·-) production found in aortas from spontaneously hypertensive rats (SHRs). ANG II increased COX-2 and pre-pro-ET-1 levels more in cultured vascular smooth muscle cells from hypertensive rats compared with normotensive rats. The ETA receptor antagonist BQ-123 reduced ANG II-induced COX-2 expression in SHR cells. ANG II also increased NOX-1 expression, NOX activity, and superoxide production in SHR cells; the selective NOX-1 inhibitor ML-171 and catalase reduced ANG II-induced COX-2 and ET-1 transcription. ANG II also increased c-Jun transcription and phospho-JNK1/2, phospho-c-Jun, and p65 NF-κB subunit nuclear protein expression. SP-600125 and lactacystin, JNK and NF-κB inhibitors, respectively, reduced ANG II-induced ET-1, COX-2, and NOX-1 levels and NOX activity. Pioglitazone reduced the effects of ANG II on NOX activity, NOX-1, pre-pro-ET-1, COX-2, and c-Jun mRNA levels, JNK activation, and nuclear phospho-c-Jun and p65 expression. In conclusion, ROS production and ET-1 are involved in ANG II-induced COX-2 expression in SHRs, explaining the greater COX-2 expression observed in this strain. Furthermore, pioglitazone inhibits ANG II-induced COX-2 expression likely by interfering with NF-κB and activator protein-1 proinflammatory pathways and downregulating ROS production and ET-1 transcription, thus contributing to the anti-inflammatory properties of glitazones.

Resistin derived from diabetic perivascular adipose tissue up-regulates vascular expression of osteopontin via the AP-1 signalling pathway

Perivascular adipose tissue (PVAT) is implicated in the development of vascular diseases; however, the roles of PVAT on OPN expression in diabetic vasculature remain to be determined. This study investigated the role of adipokines derived from diabetic PVAT in regulating the vascular expression of OPN and explored the mechanisms involved. Aortic sections of ob/ob and high-fat diet (HFD)-induced obese (DIO) mice showed an increased expression of OPN, which was paralleled by increased amounts of PVAT characterized by enlargement of adipocytes. In the earlier phase of HFD feeding, macrophage infiltration was mainly localized to the area of PVAT at which adipocytes were enlarged, suggesting a potential link of activated adipocytes to macrophage infiltration. PVAT sections of ob/ob and DIO mice revealed a significantly greater number of macrophages with increased expression of adipokines, including resistin and visfatin. The distribution of resistin in PVAT mostly co-localized with macrophages, while visfatin was expressed in macrophages and other cells. In in vitro studies, OPN expression in vascular smooth muscle cells (VSMCs) co-cultured with PVAT of DIO mice was significantly increased, which was attenuated by a resistin-neutralizing antibody. Likewise, resistin up-regulated expression of OPN mRNA and protein in cultured VSMCs and the pivotal role of AP-1 in resistin-induced OPN transcription was demonstrated. Resistin produced by PVAT plays a pivotal role in the up-regulated expression of OPN in the diabetic vasculature via a signalling pathway that involves activation of AP-1. © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Effects of interleukin-1 receptor antagonist on collagen and matrix metalloproteinases in stress-shielded achilles tendons of rats

Based on previous studies showing that interleukin-1 (IL-1) significantly increased after stress shielding, this article reports further research into the possible therapeutic applications of IL-1 receptor antagonist (IL-1Ra). Forty rats whose left Achilles tendons were denervated and completely stress shielded were divided into 5 groups: 2-week phosphate-buffered saline (PBS); 4-week PBS; 2-week IL-1Ra; 4-week IL-1Ra; and normal control. The Achilles tendons were tested morphologically, and the changes in collagen I and III, matrix metalloproteinases (MMP)-1 and -3, and tissue inhibitors of metalloproteinase (TIMP)-1 were determined. The collagen fibrils in the IL-1Ra groups were morphologically more similar to those in the control group than to those in the PBS groups. The collagen I levels increased in the 2-week groups. Significant differences existed between the PBS and IL-1Ra groups at 4 weeks. The MMP-1 level increased dramatically after stress shielding and increased less in the 2-week IL-1Ra group than in the 2-week PBS group. The degree of decrease of MMP-3 in the IL-1Ra groups was significantly less than that in the PBS groups. The collagen III and TIMP-1 levels continued to increase, and no difference was found between the PBS and IL-1Ra groups. Interleukin-1 receptor antagonist prevented morphological deterioration and collagen metabolism of the denervated Achilles tendons after stress shielding, likely by inhibiting the decline of MMP-3 and increasing MMP-1 levels at an early stage.

Mast cells contribute to altered vascular reactivity and ischemia-reperfusion injury following cerium oxide nanoparticle instillation

Cerium oxide (CeO₂) represents an important nanomaterial with wide ranging applications. However, little is known regarding how CeO₂ exposure may influence pulmonary or systemic inflammation. Furthermore, how mast cells would influence inflammatory responses to a nanoparticle exposure is unknown. We thus compared pulmonary and cardiovascular responses between C57BL/6 and B6.Cg-Kit(W-sh) mast cell deficient mice following CeO₂ nanoparticle instillation. C57BL/6 mice instilled with CeO₂ exhibited mild pulmonary inflammation. However, B6.Cg-Kit(W-sh) mice did not display a similar degree of inflammation following CeO₂ instillation. Moreover, C57BL/6 mice instilled with CeO₂ exhibited altered aortic vascular responses to adenosine and an increase in myocardial ischemia/reperfusion injury which was absent in B6.Cg-Kit(W-sh) mice. In vitro CeO₂ exposure resulted in increased production of PGD₂, TNF-α, IL-6 and osteopontin by cultured mast cells. These findings demonstrate that CeO₂ nanoparticles activate mast cells contributing to pulmonary inflammation, impairment of vascular relaxation and exacerbation of myocardial ischemia/reperfusion injury.

Complex regulation and function of the inflammatory smooth muscle cell phenotype in atherosclerosis

Vascular smooth muscle cell (SMC) phenotypic modulation plays a key role in atherosclerosis and is classically defined as a switch from a 'contractile' phenotype to a 'synthetic' phenotype, whereby genes that define the contractile SMC phenotype are suppressed and proliferation and/or migratory mechanisms are induced. There is also evidence that SMCs may take on a 'proinflammatory' phenotype, whereby SMCs secrete cytokines and express cell adhesion molecules, e.g. IL-8, IL-6, and VCAM-1, respectively, which may functionally regulate monocyte and macrophage adhesion and other processes during atherosclerosis. Factors that drive the inflammatory phenotype are not limited to cytokines but also include hemodynamic forces imposed on the blood vessel wall and intimate interaction of endothelial cells with SMCs, as well as changes in matrix composition in the vessel wall. However, it is critical to recognize that our understanding of the complex interaction of these multiple signal inputs has only recently begun to shed light on mechanisms that regulate the inflammatory SMC phenotype, primarily through models that attempt to recreate this environment ex vivo. The goal of this review is to summarize our current knowledge in this area and identify some of the key unresolved challenges and questions requiring further study.

Angiotensin II receptor blocker and statins lower elevated levels of osteopontin in essential hypertension--results from the EUTOPIA trial

BACKGROUND

Osteopontin is a pleiotropic cytokine that has been implicated as a key factor in the development of atherosclerosis, a major complication of hypertension. We have earlier shown that olmesartan reduces mediators of vascular inflammation in patients with hypertension and cardiovascular disease. We aimed at studying the effect of olmesartan and/or pravastatin on osteopontin plasma levels, and the association between vascular inflammation markers and osteopontin in hypertensive patients.

METHODS

We assessed a panel of vascular inflammation markers and osteopontin during 12 weeks of therapy with 20mg olmesartan (n=94) or placebo (n=96) in a prospective, double-blind, multi-center study in patients with essential hypertension (re-evaluation of the EUTOPIA trial blood samples). Pravastatin (20mg) was added to the double-blind therapy at week 6 in both arms. The association of demographic variables and inflammation markers with osteopontin has been analyzed as well.

RESULTS

Baseline osteopontin plasma concentrations in the study population were elevated compared to healthy controls (32.85+/-19.04ng/mL vs. 23.82+/-3.69ng/mL, p=0.027). Mono-therapy with olmesartan and co-therapy with pravastatin reduced levels of circulating osteopontin (p<0.001). The addition of pravastatin to the placebo treatment-arm resulted in a reduction of osteopontin levels as well (p<0.01). osteopontin plasma levels correlated with VCAM-1 (r=0.27; p=0.0002), ICAM-1 (r=0.18; p=0.015), IL-6 (r=0.35; p<0.0001) and hsCRP (r=0.22; p=0.0022).

CONCLUSION

We show, for the first time, that olmesartan significantly decreases osteopontin concentrations. Co-therapy with pravastatin also reduces osteopontin levels. Elevated osteopontin levels in hypertensive patients correlate with adhesion molecules and inflammation markers.