BMP6 attenuates oxidant injury in HK-2 cells via Smad-dependent HO-1 induction

Negative regulators of TGF-β1 signaling in renal fibrosis; pathological mechanisms and novel therapeutic opportunities

Elevated expression of the multifunctional cytokine transforming growth factor β1 (TGF-β1) is causatively linked to kidney fibrosis progression initiated by diabetic, hypertensive, obstructive, ischemic and toxin-induced injury. Therapeutically relevant approaches to directly target the TGF-β1 pathway (e.g., neutralizing antibodies against TGF-β1), however, remain elusive in humans. TGF-β1 signaling is subjected to extensive negative control at the level of TGF-β1 receptor, SMAD2/3 activation, complex assembly and promoter engagement due to its critical role in tissue homeostasis and numerous pathologies. Progressive kidney injury is accompanied by the deregulation (loss or gain of expression) of several negative regulators of the TGF-β1 signaling cascade by mechanisms involving protein and mRNA stability or epigenetic silencing, further amplifying TGF-β1/SMAD3 signaling and fibrosis. Expression of bone morphogenetic proteins 6 and 7 (BMP6/7), SMAD7, Sloan-Kettering Institute proto-oncogene (Ski) and Ski-related novel gene (SnoN), phosphate tensin homolog on chromosome 10 (PTEN), protein phosphatase magnesium/manganese dependent 1A (PPM1A) and Klotho are dramatically decreased in various nephropathies in animals and humans albeit with different kinetics while the expression of Smurf1/2 E3 ligases are increased. Such deregulations frequently initiate maladaptive renal repair including renal epithelial cell dedifferentiation and growth arrest, fibrotic factor (connective tissue growth factor (CTGF/CCN2), plasminogen activator inhibitor type-1 (PAI-1), TGF-β1) synthesis/secretion, fibroproliferative responses and inflammation. This review addresses how loss of these negative regulators of TGF-β1 pathway exacerbates renal lesion formation and discusses the therapeutic value in restoring the expression of these molecules in ameliorating fibrosis, thus, presenting novel approaches to suppress TGF-β1 hyperactivation during chronic kidney disease (CKD) progression.

Identifying chondroprotective diet-derived bioactives and investigating their synergism

Osteoarthritis (OA) is a multifactorial disease and nutrition is a modifiable factor that may contribute to disease onset or progression. A detailed understanding of mechanisms through which diet-derived bioactive molecules function and interact in OA is needed. We profiled 96 diet-derived, mainly plant-based bioactives using an in vitro model in chondrocytes, selecting four candidates for further study. We aimed to determine synergistic interactions between bioactives that affected the expression of key genes in OA. Selected bioactives, sulforaphane, apigenin, isoliquiritigenin and luteolin, inhibited one or more interleukin-1-induced metalloproteinases implicated in OA (MMP1, MMP13, ADAMTS4, ADAMTS5). Isoliquiritigenin and luteolin showed reactive oxygen species scavenging activity in chondrocytes whereas sulforaphane had no effect and apigenin showed only a weak trend. Sulforaphane inhibited the IL-1/NFκB and Wnt3a/TCF/Lef pathways and increased TGFβ/Smad2/3 and BMP6/Smad1/5/8 signalling. Apigenin showed potent inhibition of the IL-1/NFκB and TGFβ/Smad2/3 pathways, whereas luteolin showed only weak inhibition of the IL-1/NFκB pathway. All four bioactives inhibited cytokine-induced aggrecan loss from cartilage tissue explants. The combination of sulforaphane and isoliquiritigenin was synergistic for inhibiting MMP13 gene expression in chondrocytes. We conclude that dietary-derived bioactives may be important modulators of cartilage homeostasis and synergistic relationships between bioactives may have an anti-inflammatory and chondroprotective role.

BMP‑6 protects retinal pigment epithelial cells from oxidative stress‑induced injury by inhibiting the MAPK signaling pathways

Worldwide, neovascular age‑related macular degeneration (nAMD) is one of the most common causes of blindness in the elderly. In particular, degeneration of retinal pigment epithelial (RPE) cells represents the main pathological process in the development of nAMD, and oxidative stress serves a major role. The present study aimed to investigate the association between bone morphogenetic protein 6 (BMP‑6) and nAMD. BMP‑6 concentration was significantly reduced in patients with wet nAMD compared with in the control group. Furthermore, the present study investigated the protective effects of BMP‑6 on RPE cells following oxidative stress‑induced injury. Cell Counting Kit‑8 assay and terminal deoxynucleotidyl transferase dUTP nick‑end labeling staining demonstrated that BMP‑6 increased RPE cell viability, which was decreased following treatment with hydrogen peroxide (H2O2), and reduced H2O2‑induced apoptosis. In addition, western blotting revealed that BMP‑6 reversed the decrease in pro‑caspase‑3 levels and the dysregulation of the B‑cell lymphoma 2 (Bcl‑2)/Bcl‑2‑associated X protein (Bax) balance caused by H2O2. In addition, alterations in c‑Jun N‑terminal protein kinase (JNK) and p38 mitogen‑activated protein kinase (MAPK) expression were examined, and pretreatment with BMP‑6 was demonstrated to reduce H2O2‑induced activation of JNK and p38 MAPK. Conversely, the effects of BMP‑6 were attenuated by its inhibitor noggin. In conclusion, the present study demonstrated that BMP‑6 may protect RPE cells from oxidative stress injury to a certain extent, which may be associated with alterations in the MAPK signaling pathway. However, the specific mechanism of action underlying this effect requires further investigation. Overall, the present study laid a foundation for exploring novel nAMD treatment methods.

Activation of Nrf2 Attenuates Pulmonary Vascular Remodeling via Inhibiting Endothelial-to-Mesenchymal Transition: an Insight from a Plant Polyphenol

The endothelial-to-mesenchymal transition (EndMT) has been demonstrated to be involved in pulmonary vascular remodeling. It is partly attributed to oxidative and inflammatory stresses in endothelial cells. In current study, we conducted a series of experiments to clarify the effect of salvianolic acid A (SAA), a kind of polyphenol compound, in the process of EndMT in human pulmonary arterial endothelial cells and in vivo therapeutic efficacy on vascular remodeling in monocrotaline (MCT)-induced EndMT. EndMT was induced by TGFβ1 in human pulmonary arterial endothelial cells (HPAECs). SAA significantly attenuated EndMT, simultaneously inhibited cell migration and reactive oxygen species (ROS) formation. In MCT-induced pulmonary arterial hypertension (PAH) model, SAA improved vascular function, decreased TGFβ1 level and inhibited inflammation. Mechanistically, SAA stimulated Nrf2 translocation and subsequent heme oxygenase-1 (HO-1) up-regulation. The effect of SAA on EndMT in vitro was abolished by ZnPP, a HO-1 inhibitor. In conclusion, this study indicates a deleterious impact of oxidative stress on EndMT. Polyphenol antioxidant treatment may provide an adjunctive action to alleviate pulmonary vascular remodeling via inhibiting EndMT.

Nanoparticles combined with growth factors: recent progress and applications

Increasing attention has been focused on the applications of nanoparticles combined with growth factors (NPs/GFs) due to the substantial functions of GFs in regenerative medicine and disease treatments.

Altered cytokine gene expression in peripheral blood monocytes across the menstrual cycle in primary dysmenorrhea: a case-control study

Primary dysmenorrhea is one of the most common gynecological complaints in young women, but potential peripheral immunologic features underlying this condition remain undefined. In this paper, we compared 84 common cytokine gene expression profiles of peripheral blood mononuclear cells (PBMCs) from six primary dysmenorrheic young women and three unaffected controls on the seventh day before (secretory phase), and the first (menstrual phase) and the fifth (regenerative phase) days of menstruation, using a real-time PCR array assay combined with pattern recognition and gene function annotation methods. Comparisons between dysmenorrhea and normal control groups identified 11 (nine increased and two decreased), 14 (five increased and nine decreased), and 15 (seven increased and eight decreased) genes with ≥2-fold difference in expression (P<0.05) in the three phases of menstruation, respectively. In the menstrual phase, genes encoding pro-inflammatory cytokines (IL1B, TNF, IL6, and IL8) were up-regulated, and genes encoding TGF-β superfamily members (BMP4, BMP6, GDF5, GDF11, LEFTY2, NODAL, and MSTN) were down-regulated. Functional annotation revealed an excessive inflammatory response and insufficient TGF-β superfamily member signals with anti-inflammatory consequences, which may directly contribute to menstrual pain. In the secretory and regenerative phases, increased expression of pro-inflammatory cytokines and decreased expression of growth factors were also observed. These factors may be involved in the regulation of decidualization, endometrium breakdown and repair, and indirectly exacerbate primary dysmenorrhea. This first study of cytokine gene expression profiles in PBMCs from young primary dysmenorrheic women demonstrates a shift in the balance between expression patterns of pro-inflammatory cytokines and TGF-β superfamily members across the whole menstrual cycle, underlying the peripheral immunologic features of primary dysmenorrhea.

Loss of endogenous bone morphogenetic protein-6 aggravates renal fibrosis

Bone morphogenetic protein-6 (BMP-6) suppresses inflammatory genes in renal proximal tubular cells and regulates iron metabolism by inducing hepcidin. In diabetic patients, an increase of myofibroblast progenitor cells (MFPCs), also known as fibrocytes, was found to be associated with decreased BMP-6 expression. We hypothesized that loss of endogenous BMP-6 would aggravate renal injury and fibrosis. Wild type (WT) and BMP-6 null mice underwent unilateral ureteral obstruction. In WT mice, ureteral obstruction down-regulated BMP-6. Obstructed kidneys of BMP-6 null mice showed more casts (1.5-fold), epithelial necrosis (1.4-fold), and brush border loss (1.3-fold). This was associated with more inflammation (1.8-fold more CD45(+) cells) and more pronounced overexpression of profibrotic genes for αSMA (2.0-fold), collagen I (6.8-fold), fibronectin (4.3-fold), CTGF (1.8-fold), and PAI-1 (3.8-fold), despite similar BMP-7 expression. Also, 1.3-fold more MFPCs were obtained from BMP-6 null than from WT mononuclear cell cultures, but in vivo only very few MFPCs were observed in obstructed kidneys, irrespective of BMP-6 genotype. The obstructed kidneys of BMP-6 null mice showed 2.2-fold more iron deposition, in association with 3.3-fold higher expression of the oxidative stress marker HO-1. Thus, ureteral obstruction leads to down-regulation of BMP-6 expression, and BMP-6 deficiency aggravates tubulointerstitial damage and fibrosis independent of BMP-7. This process appears to involve loss of both direct anti-inflammatory and antifibrotic action and indirect suppressive effects on renal iron deposition, oxidative stress, and MFPCs.

BMP-6 inhibits MMP-9 expression by regulating heme oxygenase-1 in MCF-7 breast cancer cells

PURPOSE

BMP-6, which belongs to the TGF-β superfamily, is a multifunctional molecule with distinct abilities in embryogenesis and organogenesis. Our recent research has implied that BMP-6 may suppress breast cancer metastasis. In the present study, we extended to elucidate the molecular mechanism by which BMP-6 exerts its anti-tumorigenic effect.

METHODS

The Boyden chamber assay was used to examine the ability of BMP-6 and HO-1 in MCF-7 malignant progress. RT-PCR, western blot, luciferase assay, and quantitative CHIP were used to determine the potential mechanism and signaling pathways by which BMP-6 and HO-1 function as anti-metastatic factors in MCF-7 cells.

RESULTS

The Boyden chamber assay showed that BMP-6 inhibited the migration and invasion of MCF-7 cells, which effect was significantly deprived by knockdown of HO-1. We further demonstrated that BMP-6 treatment resulted in an activation of HO-1 transcription through the recruitment of Smad1/5 to the Smad-responsive element on its promoter. In addition, BMP-6-induced up-regulation of HO-1 exhibited an inhibitory effect on MMP-9 secretion in a paracrine action in MCF-7 cells. Overexpression of BMP-6 and HO-1 synergistically suppressed MMP-9 transcription, which effect was specifically mediated via the MAPK/p38/AP-1 signaling. However, blockade of HO-1 using ZnPPIX totally abolished BMP-6-regulated MMP-9 activation in MCF-7 cells.

CONCLUSIONS

These observations suggest a novel role of BMP-6/HO-1 cascade to relieve breast cancer metastasis by regulating the secretion of growth factors in tumor microenvironment.

Renal epithelial cell injury and its promoting role in formation of calcium oxalate monohydrate

The injurious effect of hydrogen peroxide (H(2)O(2)) on renal epithelial cells of the African green monkey (Vero cells) and the difference in the modulation of Vero cells on crystal growth of calcium oxalate (CaOxa) before and after injury were investigated. The degree of injury of Vero cells was proportional to the concentration and action time of H(2)O(2). After the cells had been injured, the released amount of malonaldehyde in the culture medium increased, the superoxide dismutase activity decreased, the expression quantity of osteopontin on the surface of Vero cells increased significantly, the zeta potential became more negative, and the amount of CaOxa crystals adhering to cells increased. The CaOxa crystals induced by the cells in the control group were round and blunt; however, those induced by the injured cells had irregular shapes with sharp edges and corners. As the crystallization time increased from 6 to 24 h, the size of the crystals induced by the injured cells increased accordingly, whereas that of crystals induced by the control cells did not increase significantly. The injured cells could promote the growth of CaOxa crystals and their adhesion to the cells; thus, the formation of CaOxa stones was promoted. The cells in the control group could also be injured after being incubated with supersaturated CaOxa solution for a long time, which promoted the crystallization of CaOxa. The results suggest that the retention of supersaturated CaOxa solution or CaOxa crystals in the urinary tract for a long time is a risk factor for the formation of kidney stones.

Targeting bone morphogenetic protein signaling on renal and vascular diseases

PURPOSE OF REVIEW

Normal development and adult physiology of the kidney and vasculature rely heavily on bone morphogenetic proteins (BMPs). Here we compile evidence that favors the notion that BMPs are also critically involved in the process of generation and maintenance of renal and vascular diseases.

RECENT FINDINGS

Molecular manipulation of BMP signaling in vivo and in vitro has been instrumental in showing the protective role of BMPs on renal fibrosis and diabetic nephropathy. Similarly, activation of those pathways produces phenotypic changes in vascular smooth muscle and endothelial cells, tightly linked to the pathogenesis of vascular calcification, hypertrophy and atherosclerosis.

SUMMARY

Gain-of-function and loss-of-function experiments targeting BMP pathway agonists and inhibitors lead to significant progress in the comprehension of renal and vascular normal and altered behavior. The demonstration that BMP signaling plays an important part in pathological conditions of the vasculature and the kidney opens up possibilities for the development of diagnostic and therapeutic tools.

BMP-6 and mesenchymal stem cell differentiation

Bone morphogenetic protein-6 (BMP-6) is produced by bone marrow-mesenchymal (BMSC) and hematopoietic stem cells, which can differentiate into bone, cartilage, adipose, muscle, hematopoietic, synovial and other tissues. Bmp6-/- null mice have low hepcidin serum levels and an iron overload, resembling hereditary hemochromatosis, which may cause a reduced number of pancreatic beta-cells, increased serum glucose and diabetes. BMP-6 circulates in the normal human plasma and is produced by BMSC prior to differentiation into osteoblasts. Moreover, it is also released by osteoclasts as a key bone coupling factor recruiting osteoblasts to the resorption site. Due to unique structural, receptor binding and signaling characteristics much smaller amounts of BMP-6 than BMP-7 are needed in vivo to induce regeneration of bone defects in animals.