BMP9/COX-2 axial mediates high phosphate-induced calcification in vascular smooth muscle cells via Wnt/β-catenin pathway

Cardioprotective function of sclerostin by reducing calcium deposition, proliferation, and apoptosis in human vascular smooth muscle cells

BACKGROUND

Sclerostin is an inhibitor of the Wnt/b-catenin pathway, which regulates bone formation, and can be expressed in vascular smooth muscle cells (VSMCs). Type 2 diabetes (T2D) is associated with an increased risk of cardiovascular disease (CVD) and increased serum and tissue expression of sclerostin. However, whether the role of sclerostin is detrimental or protective in the development of CVD is unknown. Therefore, our aims are to determine the level of sclerostin in T2D patients with/without CVD and in controls, both at serum and vascular tissue, and to analyze the role of sclerostin in VSMCs under calcified environments.

METHODS

Cross-sectional study including 121 controls and 139 T2D patients with/without CVD (48/91). Sclerostin levels in serum were determined by ELISA, and sclerostin expression was analyzed by RT-qPCR and immunohistochemistry in calcified and non-calcified artery of lower limb from T2D patients (n = 7) and controls (n = 3). In vitro experiments were performed in VSMCs (mock and sclerostin overexpression) under calcifying conditions analyzing the sclerostin function by determination of calcium and phosphate concentrations, and quantification of calcium deposits by Alizarin Red. Proliferation and apoptosis were analyzed by MTT assay and flow cytometry, respectively. The regulation of the expression of genes involved in bone metabolism was determined by RT-qPCR.

RESULTS

A significant increase in serum sclerostin levels in T2D patients with CVD compared to T2D patients without CVD and controls (p < 0.001) was observed. Moreover, higher circulating sclerostin levels were independently associated with CVD in T2D patients. Increased sclerostin expression was observed in calcified arteries of T2D patients compared to non-calcified arteries of controls (p = 0.003). In vitro experiments using VSMCs under calcified conditions, revealed that sclerostin overexpression reduced intracellular calcium (p = 0.001), calcium deposits (p < 0.001), cell proliferation (p < 0.001) and promoted cell survival (p = 0.015). Furthermore, sclerostin overexpression exhibited up-regulation of ALPL (p = 0.009), RUNX2 (p = 0.001) and COX2 (p = 0.003) and down-regulation of inflammatory genes, such as, IL1β (p = 0.005), IL6 (p = 0.001) and IL8 (p = 0.003).

CONCLUSIONS

Sclerostin could play a protective role in the development of atherosclerosis in T2D patients by reducing calcium deposits, decreasing proliferation and inflammation, and promoting cell survival in VSMCs under calcifying conditions. Therefore, considering the bone-vascular axis, treatment with anti-sclerostin for bone disease should be used with caution.

Insights into bone morphogenetic proteins in cardiovascular diseases

Bone morphogenetic proteins (BMPs) are secretory proteins belonging to the transforming growth factor-β (TGF-β) superfamily. These proteins play important roles in embryogenesis, bone morphogenesis, blood vessel remodeling and the development of various organs. In recent years, as research has progressed, BMPs have been found to be closely related to cardiovascular diseases, especially atherosclerosis, vascular calcification, cardiac remodeling, pulmonary arterial hypertension (PAH) and hereditary hemorrhagic telangiectasia (HHT). In this review, we summarized the potential roles and related mechanisms of the BMP family in the cardiovascular system and focused on atherosclerosis and PAH.

Pyruvate dehydrogenase kinase 4 promotes osteoblastic potential of BMP9 by boosting Wnt/β-catenin signaling in mesenchymal stem cells

Bone morphogenetic protein 9 (BMP9) is an effective osteogenic factor and a promising candidate for bone tissue engineering. The osteoblastic potential of BMP9 needs to be further increased to overcome its shortcomings. However, the details of how BMP9 triggers osteogenic differentiation in mesenchymal stem cells (MSCs) are unclear. In this study, we used real-time PCR, western blot, histochemical staining, mouse ectopic bone formation model, immunofluorescence, immunoprecipitation, and chromatin immunoprecipitation to investigate the role of pyruvate dehydrogenase kinase 4 (PDK4) in BMP9-induced osteogenic differentiation of C3H10T1/2 cells, as well as the underlying mechanism. We found that PDK4 was upregulated by BMP9 in C3H10T1/2 cells. BMP9-induced osteogenic markers and bone mass were increased by PDK4 overexpression, but decreased by PDK4 silencing. β-catenin protein level was increased by BMP9, which was enhanced by PDK overexpression and decreased by PDK4 silencing. BMP9-induced osteogenic markers were reduced by PDK4 silencing, which was almost reversed by β-catenin overexpression. PDK4 increased the BMP9-induced osteogenic markers, which was almost eliminated by β-catenin silencing. Sclerostin was mildly decreased by BMP9 or PDK4, and significantly decreased by combined BMP9 and PDK4. In contrast, sclerostin increased significantly when BMP9 was combined with PDK4 silencing. BMP9-induced p-SMAD1/5/9 was increased by PDK4 overexpression, but was reduced by PDK4 silencing. PDK4 interacts with p-SMAD1/5/9 and regulates the sclerostin promoter. These findings suggest that PDK4 can increase the osteogenic potential of BMP9 by enhancing Wnt/β-catenin signaling via the downregulation of sclerostin. PDK4 may be an effective target to strengthen BMP9-induced osteogenesis.

Klotho Ameliorates Vascular Calcification via Promoting Autophagy

Vascular calcification (VC) is regarded as a common feature of vascular aging. Klotho deficiency reportedly contributes to VC, which can be ameliorated by restoration of Klotho expression. However, the specific mechanisms involved remain unclear. Here, we investigated the role of autophagy in the process of Klotho-inhibiting VC. The clinical study results indicated that, based on Agatston score, serum Klotho level was negatively associated with aortic calcification. Then, Klotho-deficient mice exhibited aortic VC, which could be alleviated with the supplementation of Klotho protein. Moreover, autophagy increased in the aorta of Klotho-deficient mice and protected against VC. Finally, we found that Klotho ameliorated calcification by promoting autophagy both in the aorta of Klotho-deficient mice and in mouse vascular smooth muscle cells (MOVAS) under calcifying conditions. These findings indicate that Klotho deficiency induces increased autophagy to protect against VC and that Klotho expression further enhances autophagy to ameliorate calcification. This study is beneficial to exploring the underlying mechanisms of Klotho regulating VC, which has important guiding significance for future clinical studies in the treatment of VC.

Histone Lysine Methylation Modification and Its Role in Vascular Calcification

Histone methylation is an epigenetic change mediated by histone methyltransferase, and has been connected to the beginning and progression of several diseases. The most common ailments that affect the elderly are cardiovascular and cerebrovascular disorders. They are the leading causes of death, and their incidence is linked to vascular calcification (VC). The key mechanism of VC is the transformation of vascular smooth muscle cells (VSMCs) into osteoblast-like phenotypes, which is a highly adjustable process involving a variety of complex pathophysiological processes, such as metabolic abnormalities, apoptosis, oxidative stress and signalling pathways. Many researchers have investigated the mechanism of VC and related targets for the prevention and treatment of cardiovascular and cerebrovascular diseases. Their findings revealed that histone lysine methylation modification may play a key role in the various stages of VC. As a result, a thorough examination of the role and mechanism of lysine methylation modification in physiological and pathological states is critical, not only for identifying specific molecular markers of VC and new therapeutic targets, but also for directing the development of new related drugs. Finally, we provide this review to discover the association between histone methylation modification and VC, as well as diverse approaches with which to investigate the pathophysiology of VC and prospective treatment possibilities.

MiR-708-5p/Pit-1 axis mediates high phosphate-induced calcification in vascular smooth muscle cells via Wnt8b/β-catenin pathway

Recently, the underlying mechanism of vascular calcification (VC) has been partially elucidated. However, it is still high incidence, and no effective treatment has been found. This study aims at figuring out the underlying mechanisms of microRNA-708-5p (miR-708-5p)/sodium-phosphate transporter 1 (Pit-1) axis in high phosphate (HP)-induced VC of T/G HA-VSMCs. Alizarin Red S staining was used to evaluate calcium salt deposition, and the activity of alkaline phosphatase (ALP) was determined by measuring the absorbance at 405 nm. RT-qPCR and Western blot were performed to assess the levels of miR-708-5p and Pit-1, the levels of ALP, Pit-1, β-catenin, glycogen synthesis kinase 3 β (GSK3β), and p-GSK3β proteins, respectively. The interaction between miR-708-5p and Pit-1 was validated by luciferase reporter assay. Our findings illustrated that miR-708-5p was downregulated and Pit-1was upregulated in HP-induced VC. MiR-708-5p mimics inhibited HP-induced VC. Further experiments demonstrated that miR-708-5p targets Pit-1. In addition, miR-708-5p inactivates the Wnt8b/β-catenin pathway via targeting Pit-1 to reduce HP-induced VC. MiR-708-5p has a crucial effect on VC via targeting Pit-1 and inhibiting Wnt8b/β-catenin pathway, it may serve as a new target for VC treatment.

Impact of abdominal aortic calcification on clinical outcomes following initial hepatectomy for hepatocellular carcinoma: A retrospective cohort study

AIM

The clinical impact of abdominal aortic calcification (AAC) in patients who undergo hepatectomy for hepatocellular carcinoma (HCC) is unknown.

METHODS

To evaluate the impact of AAC on clinical outcomes, we analyzed 203 patients who underwent hepatectomy for HCC between 2010 and 2013.

RESULTS

Kaplan-Meier survival curve analysis showed significantly worse overall survival (OS) in the high AAC group than in the low AAC group. The recurrence-free survival (RFS) was also significantly worse in the high AAC group. In the multivariate analysis, high AAC (hazard ratio [HR], 2.51; 95% confidence interval [CI], 1.24-5.09; P = .01) was an independent risk factor for poor OS after hepatectomy for HCC. High AAC was also an independent risk factor for poor RFS (HR, 1.69; 95% CI, 1.04-2.76; P = .04).

CONCLUSIONS

Abdominal aortic calcification had a strong relationship with poor OS and RFS after hepatectomy for HCC. We suggest that AAC had a relationship with smoking and diabetes; therefore, AAC could reflect a surrogate for older age, worse health status, and inflammatory score.

The potential regulatory role of BMP9 in inflammatory responses

Inflammation is a protective response of the body to pathogens and injury. Hence, it is particularly important to explore the pathogenesis and key regulatory factors of inflammation. BMP9 is a unique member of the BMP family, which is widely known for its strong osteogenic potential and insensitivity to the inhibition of BMP3. Recently, several studies have reported an underlying pivotal link between BMP9 and inflammation. What is clear, though not well understood, is that BMP9 plays a role in inflammation in a carefully choreographed manner in different contexts. In this review, we have summarized current studies focusing on BMP9 and inflammation in various tissues and the latest advances in BMP9 expression, signal transduction, and crystal structure to better understand the relationship between BMP9 and inflammation. In addition, we also briefly summarized the inflammatory characteristics of some TGF-β superfamily members to provide better insights and ideas for the study of BMP9 and inflammation.

Regulatory Role of Sex Hormones in Cardiovascular Calcification

Sex differences in cardiovascular disease (CVD), including aortic stenosis, atherosclerosis and cardiovascular calcification, are well documented. High levels of testosterone, the primary male sex hormone, are associated with increased risk of cardiovascular calcification, whilst estrogen, the primary female sex hormone, is considered cardioprotective. Current understanding of sexual dimorphism in cardiovascular calcification is still very limited. This review assesses the evidence that the actions of sex hormones influence the development of cardiovascular calcification. We address the current question of whether sex hormones could play a role in the sexual dimorphism seen in cardiovascular calcification, by discussing potential mechanisms of actions of sex hormones and evidence in pre-clinical research. More advanced investigations and understanding of sex hormones in calcification could provide a better translational outcome for those suffering with cardiovascular calcification.

The Protective Effects of the Autophagic and Lysosomal Machinery in Vascular and Valvular Calcification: A Systematic Review

BACKGROUND

Autophagy is a highly conserved catabolic homeostatic process, crucial for cell survival. It has been shown that autophagy can modulate different cardiovascular pathologies, including vascular calcification (VCN).

OBJECTIVE

To assess how modulation of autophagy, either through induction or inhibition, affects vascular and valvular calcification and to determine the therapeutic applicability of inducing autophagy.

DATA SOURCES

A systematic review of English language articles using MEDLINE/PubMed, Web of Science (WoS) and the Cochrane library. The search terms included autophagy, autolysosome, mitophagy, endoplasmic reticulum (ER)-phagy, lysosomal, calcification and calcinosis. Study characteristics: Thirty-seven articles were selected based on pre-defined eligibility criteria. Thirty-three studies (89%) studied vascular smooth muscle cell (VSMC) calcification of which 27 (82%) studies investigated autophagy and six (18%) studies lysosomal function in VCN. Four studies (11%) studied aortic valve calcification (AVCN). Thirty-four studies were published in the time period 2015-2020 (92%).

CONCLUSION

There is compelling evidence that both autophagy and lysosomal function are critical regulators of VCN, which opens new perspectives for treatment strategies. However, there are still challenges to overcome, such as the development of more selective pharmacological agents and standardization of methods to measure autophagic flux.

Cyclooxygenase-2/sclerostin mediates TGF-β1-induced calcification in vascular smooth muscle cells and rats undergoing renal failure

In this study, we studied the effect and possible mechanism of TGF-β1 on vascular calcification. We found that the serum levels of TGF-β1 and cycloxygenase-2 (COX-2) were significantly increased in patients with chronic kidney disease. Phosphate up regulated TGF-β1 in vascular smooth muscle cells (VSMCs). TGF-β1 decreased the markers of VSMCs, but increased osteogenic markers and calcification in aortic segments. The phosphate-induced osteogenic markers were reduced by the TGFβR I inhibitor (LY364947), which also attenuated the potential of phosphate to reduce VSMC markers in VSMCs. Both phosphate and TGF-β1 increased the protein level of β-catenin, which was partially mitigated by LY364947. TGF-β1 decreased sclerostin, and exogenous sclerostin decreased the mineralization induced by TGF-β1. LY364947 reduced the phosphate and TGF-β1 induced COX-2. Meanwhile, the effects of TGF-β1 on osteogenic markers, β-catenin, and sclerostin, were partially reversed by the COX-2 inhibitor. Mechanistically, we found that p-Smad2/3 and p-CREB were both enriched at the promoter regions of sclerostin and β-catenin. TGF-β1 and COX-2 were significantly elevated in serum and aorta of rats undergoing renal failure. Therapeutic administration of meloxicam effectively ameliorated the renal lesion. Our results suggested that COX-2 may mediate the effect of TGF-β1 on vascular calcification through down-regulating sclerostin in VMSCs.

BMP9 attenuates occurrence of venous malformation by maintaining endothelial quiescence and strengthening vessel walls via SMAD1/5/ID1/α-SMA pathway

Venous malformation (VM) is a type of vascular morphogenic defect in humans with an incidence of 1%. Although gene mutation is considered as the most common cause of VM, the pathogenesis of those without gene mutation remains to be elucidated. Here, we aimed to explore the relation of bone morphogenetic protein 9 (BMP9) and development of VM. At first, we found serum and tissue BMP9 expression in VM patients was significantly lower than that in healthy subjects, detected via enzyme-linked immunosorbent assay. Next, with wound healing assay, transwell assay and tube formation assay, we discovered BMP9 could inhibit migration and enhance tube formation activity of human umbilical vein endothelial cells (HUVECs) via receptor activin receptor-like kinase 1 (ALK1). Besides, BMP9 improved the expression of structural proteins alpha-smooth muscle actin (α-SMA) and Desmin in human umbilical vein smooth muscle cells (HUVSMCs) via activation of the SMAD1/5-ID1 pathway, determined by RNA-based next-generation sequencing, qPCR, immunofluorescence and western blotting. Intriguingly, this effect could be blocked by receptor ALK1 inhibitor, SMAD1/5 inhibitor and siRNAs targeting ID1, verifying the BMP9/ALK1/SMAD1/5/ID1/α-SMA pathway. Meanwhile, knocking out BMP9 in C57BL/6 mice embryo led to α-SMA scarcity in walls of lung and mesenteric vessels, as well as walls of small trachea. BMP9-/- zebrafish also exhibited abnormal vascular maturity, indicating a critical role of BMP9 in vascular maturity and remodeling. Finally, a VM mice model revealed that BMP9 might have therapeutic effect in VM progression. Our study discovered that BMP9 might inhibit the occurrence of VM by strengthening the vessel wall and maintaining endothelium quiescence. These findings provide promising evidences of new therapeutic targets that might be used for the management of VM.

Three-dimensional silk fibroin scaffolds enhance the bone formation and angiogenic differentiation of human amniotic mesenchymal stem cells: a biocompatibility analysis

Silk fibroin (SF) is a fibrous protein with unique mechanical properties, adjustable biodegradation, and the potential to drive differentiation of mesenchymal stem cells (MSCs) along the osteogenic lineage, making SF a promising scaffold material for bone tissue engineering. In this study, hAMSCs were isolated by enzyme digestion and identified by multiple-lineage differentiation. SF scaffold was fabricated by freeze-drying, and the adhesion and proliferation abilities of hAMSCs on scaffolds were determined. Osteoblast differentiation and angiogenesis of hAMSCs on scaffolds were further evaluated, and histological staining of calvarial defects was performed to examine the cocultured scaffolds. We found that hAMSCs expressed the basic surface markers of MSCs. Collagen type I (COL-I) expression was observed on scaffolds cocultured with hAMSCs. The scaffolds potentiated the proliferation of hAMSCs and increased the expression of COL-I in hAMSCs. The scaffolds also enhanced the alkaline phosphatase activity and bone mineralization, and upregulated the expressions of osteogenic-related factors in vitro. The scaffolds also enhanced the angiogenic differentiation of hAMSCs. The cocultured scaffolds increased bone formation in treating critical calvarial defects in mice. This study first demonstrated that the application of 3D SF scaffolds co-cultured with hAMSCs greatly enhanced osteogenic differentiation and angiogenesis of hAMSCs in vitro and in vivo. Thus, 3D SF scaffolds cocultured with hAMSCs may be a better alternative for bone tissue engineering.

The Role of Sclerostin in Bone and Ectopic Calcification

Sclerostin, a 22-kDa glycoprotein that is mainly secreted by the osteocytes, is a soluble inhibitor of canonical Wnt signaling. Therefore, when present at increased concentrations, it leads to an increased bone resorption and decreased bone formation. Serum sclerostin levels are known to be increased in the elderly and in patients with chronic kidney disease. In these patient populations, there is a high incidence of ectopic cardiovascular calcification. These calcifications are strongly associated with cardiovascular morbidity and mortality. Although data are still controversial, it is likely that there is a link between ectopic calcification and serum sclerostin levels. The main question, however, remains whether sclerostin exerts either a protective or deleterious role in the ectopic calcification process.

Schnurri-3 regulates BMP9-induced osteogenic differentiation and angiogenesis of human amniotic mesenchymal stem cells through Runx2 and VEGF

Human amniotic mesenchymal stem cells (hAMSCs) are multiple potent progenitor cells (MPCs) that can differentiate into different lineages (osteogenic, chondrogenic, and adipogenic cells) and have a favorable capacity for angiogenesis. Schnurri-3 (Shn3) is a large zinc finger protein related to Drosophila Shn, which is a critical mediator of postnatal bone formation. Bone morphogenetic protein 9 (BMP9), one of the most potent osteogenic BMPs, can strongly upregulate various osteogenesis- and angiogenesis-related factors in MSCs. It remains unclear how Shn3 is involved in BMP9-induced osteogenic differentiation coupled with angiogenesis in hAMSCs. In this investigation, we conducted a comprehensive study to identify the effect of Shn3 on BMP9-induced osteogenic differentiation and angiogenesis in hAMSCs and analyze the responsible signaling pathway. The results from in vitro and in vivo experimentation show that Shn3 notably inhibits BMP9-induced early and late osteogenic differentiation of hAMSCs, expression of osteogenesis-related factors, and subcutaneous ectopic bone formation from hAMSCs in nude mice. Shn3 also inhibited BMP9-induced angiogenic differentiation, expression of angiogenesis-related factors, and subcutaneous vascular invasion in mice. Mechanistically, we found that Shn3 prominently inhibited the expression of BMP9 and activation of the BMP/Smad and BMP/MAPK signaling pathways. In addition, we further found activity on runt-related transcription factor 2 (Runx2), vascular endothelial growth factor (VEGF), and the target genes shared by BMP and Shn3 signaling pathways. Silencing Shn3 could dramatically enhance the expression of Runx2, which directly regulates the downstream target VEGF to couple osteogenic differentiation with angiogenesis. To summarize, our findings suggested that Shn3 significantly inhibited the BMP9-induced osteogenic differentiation and angiogenesis in hAMSCs. The effect of Shn3 was primarily seen through inhibition of the BMP/Smad signaling pathway and depressed expression of Runx2, which directly regulates VEGF, which couples BMP9-induced osteogenic differentiation with angiogenesis.

Vascular calcification is associated with Wnt-signaling pathway and blood pressure variability in chronic kidney disease rats

AIM

Vascular calcification (VC) is a common complication in chronic kidney disease (CKD) and has been shown to be associated with increased cardiovascular events and mortality. This study was to explore the role of Wnt-signaling pathway in CKD VC, and the association between VC and blood pressure variability (BPV) which is a risk factor of cardiovascular events.

METHODS

Adult male Sprague-Dawley rats were divided into adenine-induced CKD group (n = 5), 5/6 nephrectomy CKD group (n = 5), sham group (n = 5) and control group (n = 5). Low-calcium-high-phosphate diets were introduced to induce vascular calcification. Both daytime (hour-to-hour during the day) and mid-term (day-to-day for 9 days) blood pressure (BP) were collected and analyzed for BPV metrics. At sacrifice, kidney, heart and aorta samples were taken for histological analyses. Calcium deposition in aorta was identified with Alizarin Red stain and graded. Immunohistochemistry stain and western blot were performed for Wnt3a, Wnt5a, β-catenin, sclerostin, osteopontin, and α-SMA.

RESULTS

Compared with control rats, CKD rats suffered from markedly severer VC (Grade 2.6 ± 0.2 and 1.8 ± 0.8 vs 0.0 ± 0.0 and 0.2 ± 0.4, P = .0010). VC was positively correlated with vascular Wnt3a and β-catenin expression (P = .0032 and .0000), but not significantly associated with Wnta5a or sclerostin. Besides, CKD rats showed increased BPV (P < .001), which was also positively correlated with VC.

CONCLUSION

We confirmed that CKD rats had enhanced Wnt-signaling in vascular tissue and severer aorta calcification together with increased BPV. Wnt pathway may be a potential target in future VC and BPV management in CKD.

IGF-1 reverses the osteogenic inhibitory effect of dexamethasone on BMP9-induced osteogenic differentiation in mouse embryonic fibroblasts via PI3K/AKT/COX-2 pathway

Glucocorticoid-Induced Osteoporosis (GIOP) is a prevalent clinical complication caused by large dose administration of glucocorticoids, such as Dexamethasone (Dex) and Prednisone. GIOP may lead to fractures and even Osteonecrosis of the Femoral Head (ONFH). It has been reported that glucocorticoids inhibit osteogenesis via the suppression of osteogenic differentiation in Mesenchymal Stem Cells (MSCs), but the precise mechanism underlying this suppression awaits further investigation. Meanwhile, novel and efficacious therapies are recommended to cope with GIOP. In this study, we demonstrated that Dex had the inhibitory effect on Bone Morphogenetic Protein 9 (BMP9)-induced ALP activities and matrix mineralization in Mouse Embryonic Fibroblasts (MEFs). In addition, the study confirmed that Dex decreased the expression of osteogenic markers such as Runx2 and OPN. However, the inhibitory effect of Dex on these osteogenic markers can be reversed when combined with insulin-like growth factor 1 (IGF-1). Regarding the inhibitory mechanism, we found that the level of AKT and p-AKT can be decreased by Dex and that Ly294002, the PI3K inhibitor, can block the reversal effect of IGF-1. Moreover, the knockdown or inhibition of COX-2 produced similar results to those of Ly294002. Our findings indicated that IGF-1 may reverse the osteogenic inhibitory effect of Dex via PI3K/AKT pathway, which may be associated with the up-regulation of COX-2. This study may provide new clinical management strategy for GIOP cases.

Klotho/FGF23 axis mediates high phosphate-induced vascular calcification in vascular smooth muscle cells via Wnt7b/β-catenin pathway

Vascular calcification (VC) plays as a critical role on cardiovascular disease (CVD) and acts as a notable risk factor in cardiovascular system. Vascular smooth muscle cells (VSMCs) calcification can be triggered by high phosphate treatment; however, the explicit mechanism remains unclear. In the present study, we isolated VSMCs from primary rat artery, applied β-GP (β-glycerophosphate) for inducing VSMCs calcification in vitro to explore the mechanism of phosphate-induced calcification in VSMCs. Alizarin red staining was performed to assess the mineralization in VSMCs. Calcium deposition experiment was taken to evaluate the calcium content. ALP staining was determined to assess the ALP activity. The recombinant adenoviruses were constructed for the overexpression of Klotho and FGF23, respectively. qRT-PCR and western blot analysis were subjected to measure the expression of Klotho/FGF23 and correlated genes among Wnt7b/β-catenin pathway. We found that the calcium content was obviously increased and Alizarin red staining was positive in calcification group exposure with high phosphate in a time-dependent manner. The expression of Klotho and FGF23 was significantly decreased in the calcification group. However, overexpression of Klotho and FGF23 markedly reversed VSMCs calcification stimulating with high phosphate treatment. Moreover, Wnt7b/β-catenin inhibitor DKK1 could partly attenuate the effect of high phosphate on calcified VSMCs. These findings demonstrated that Klotho/FGF23 axis could modulate high phosphate-induced VSMCs calcification via Wnt7b/β-catenin signaling pathway. Our findings unravel that Klotho/FGF23- Wnt7b/β-catenin axis functions as a crucial role in the VSMCs calcification.

Protective effects of febuxostat against paraquat-induced lung toxicity in rats: Impact on RAGE/PI3K/Akt pathway and downstream inflammatory cascades

AIMS

The herbicide paraquat causes fatal lung toxicity by induction of xanthine oxidase, production of free radicals and inflammation. Febuxostat, a xanthine oxidase inhibitor and anti-gout has recently shown anti-inflammatory activity. Accordingly, this study was carried out to investigate whether febuxostat may attenuate paraquat-induced lung toxicity and to explore the possible underlying mechanisms.

MAIN METHODS

Rats were administered either vehicle, a single dose of paraquat (30 mg/kg, i.p.), febuxostat (15 mg/kg, oral), or both for 14 successive days. Serum LDH and sRAGE were estimated. Lung tissue xanthine oxidase activity, SOD, TAC, MDA, and RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression, MMP-9, IL-8, VEGF and COX-2 gene expression were estimated.

KEY FINDINGS

Results showed that paraquat induced lung injury characterized by enhanced oxidative stress and inflammation, upregulated RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression. Administration of febuxostat inhibited the deleterious effects of paraquat on lung through inhibition of xanthine oxidase activity and related oxidative stress, downregulation of RAGE/PI3K/Akt pathway, and suppression of β-catenin protein expression and its downstream inflammatory mediators.

SIGNIFICANCE

The present study showed that febuxostat may abrogate paraquat-induced lung toxicity and demonstrated a novel mechanism for its ameliorative effects.

CREB/Wnt10b mediates the effect of COX-2 on promoting BMP9-induced osteogenic differentiation via reducing adipogenic differentiation in mesenchymal stem cells

Bone morphogenetic protein 9 (BMP9) is one of the most potent osteogenic factors, which may be a potential candidate for bone tissue engineering. However, the osteogenic capacity of BMP9 still need to be further enhanced. In this study, we determined the effect of Wnt10b on BMP9-induced osteogenic differentiation in mesenchymal stem cell (MSCs) and the possible mechanism underlying this process. We introduced the polymerase chain reaction (PCR), Western blot analysis, histochemical stain, ectopic bone formation, and microcomputed tomography analysis to evaluate the effect of Wnt10b on BMP9-induced osteogenic differentiation. Meanwhile, PCR, Western blot analysis, chromatin immunoprecipitation, and immunoprecipitation were used to analyze the possible relationship between BMP9 and Wnt10b. We found that BMP9 upregulates Wnt10b in C3H10T1/2 cells. Wnt10b increases the osteogenic markers and bone formation induced by BMP9 in C3H10T1/2 cells, and silencing Wnt10b decreases these effects of BMP9. Meanwhile, Wnt10b enhances the level of phosphorylated Smad1/5/8 (p-Smad1/5/8) induced by BMP9, which can be reduced by silencing Wnt10b. On the contrary, Wnt10b inhibits adipogenic markers induced by BMP9, which can be decreased by silencing Wnt10b. Further analysis indicated that BMP9 upregulates cyclooxygenase-2 (COX-2) and phosphorylation of cAMP-responsive element binding (p-CREB) simultaneously. COX-2 potentiates the effect of BMP9 on increasing p-CREB and Wnt10b, while silencing COX-2 decreases these effects. p-CREB interacts with p-Smad1/5/8 to bind the promoter of Wnt10b in C3H10T1/2 cells. Our findings suggested that Wnt10b can promote BMP9-induced osteogenic differentiation in MSCs, which may be mediated through enhancing BMP/Smad signal and reducing adipogenic differentiation; BMP9 may upregulate Wnt10b via the COX-2/p-CREB-dependent manner.