Enhanced endothelial cell senescence by lithium-induced matrix metalloproteinase-1 expression

A Single-Short Partial Reprogramming of the Endothelial Cells decreases Blood Pressure via attenuation of EndMT in Hypertensive Mice

Background

Small artery remodeling and endothelial dysfunction are hallmarks of hypertension. Growing evidence supports a likely causal association between cardiovascular diseases and the presence of endothelial-to-mesenchymal transition (EndMT), a cellular transdifferentiation process in which endothelial cells (ECs) partially lose their identity and acquire additional mesenchymal phenotypes. EC reprogramming represents an innovative strategy in regenerative medicine to prevent deleterious effects induced by cardiovascular diseases.

Methods

Using a partial reprogramming of ECs, via overexpression of Oct-3/4, Sox-2, and Klf-4 (OSK) transcription factors, we aimed to bring ECs back to a youthful phenotype in hypertensive mice. Primary ECs were infected with lentiviral vectors (LV) containing the specific EC marker cadherin 5 (Cdh5) and the fluorescent reporter enhanced green fluorescence protein (EGFP) with empty vector (LVCO) or with OSK (LV-OSK). Confocal microscopy and western blotting analysis were used to confirm the OSK overexpression. Cellular migration, senescence, and apoptosis were evaluated. Human aortic ECs (HAoECs) from male and female normotensive and hypertensive patients were analyzed after OSK or control treatments for their endothelial nitric oxide synthase (eNOS) levels, nitric oxide (NO), and genetic profile. Male and female normotensive (BPN/3J) and hypertensive (BPH/2J) mice were treated with an intravenous (i.v.) injection of LVCO or LV-OSK and evaluated 10 days post-infection. The blood pressure, cardiac function, vascular reactivity of small arteries, in vivo EGFP signal and EndMT inhibition were analyzed.

Results

OSK overexpression induced partial EC reprogramming in vitro , and these cells showed endothelial progenitor cell (EPC)-like features with lower migratory capability. OSK treatment of hypertensive BPH/2J mice normalized blood pressure and resistance arteries hypercontractility, via the attenuation of EndMT and elastin breaks. EGFP signal was detected in vivo in the prefrontal cortex of both BPN/3J and BPH/2J-treated mice, but OSK induced angiogenesis only in male BPN/3J mice. OSK-treated human ECs from hypertensive patients showed high eNOS activation and NO production, with low ROS formation. Single-cell RNA analysis showed that OSK alleviated EC senescence and EndMT, restoring their phenotypes in human ECs from hypertensive patients.

Conclusion

Overall, these data indicate that OSK treatment and EC reprogramming can decrease blood pressure and reverse hypertension-induced vascular damage.

Senescence induces fundamental changes in the secretome of mesenchymal stromal cells (MSCs): implications for the therapeutic use of MSCs and their derivates

Mesenchymal stromal cells (MSCs) are a heterogeneous population containing multipotent adult stem cells with a multi-lineage differentiation capacity, which differentiated into mesodermal derivatives. MSCs are employed for therapeutic purposes and several investigations have demonstrated that the positive effects of MSC transplants are due to the capacity of MSCs to modulate tissue homeostasis and repair via the activity of their secretome. Indeed, the MSC-derived secretomes are now an alternative strategy to cell transplantation due to their anti-inflammatory, anti-apoptotic, and regenerative effects. The cellular senescence is a dynamic process that leads to permanent cell cycle arrest, loss of healthy cells' physiological functions and acquiring new activities, which are mainly accrued through the release of many factors, indicated as senescence-associated secretory phenotype (SASP). The senescence occurring in stem cells, such as those present in MSCs, may have detrimental effects on health since it can undermine tissue homeostasis and repair. The analysis of MSC secretome is important either for the MSC transplants and for the therapeutic use of secretome. Indeed, the secretome of MSCs, which is the main mechanism of their therapeutic activity, loses its beneficial functions and acquire negative pro-inflammatory and pro-aging activities when MSCs become senescent. When MSCs or their derivatives are planned to be used for therapeutic purposes, great attention must be paid to these changes. In this review, we analyzed changes occurring in MSC secretome following the switch from healthy to senescence status.

Signaling pathways in vascular function and hypertension: molecular mechanisms and therapeutic interventions

Hypertension is a global public health issue and the leading cause of premature death in humans. Despite more than a century of research, hypertension remains difficult to cure due to its complex mechanisms involving multiple interactive factors and our limited understanding of it. Hypertension is a condition that is named after its clinical features. Vascular function is a factor that affects blood pressure directly, and it is a main strategy for clinically controlling BP to regulate constriction/relaxation function of blood vessels. Vascular elasticity, caliber, and reactivity are all characteristic indicators reflecting vascular function. Blood vessels are composed of three distinct layers, out of which the endothelial cells in intima and the smooth muscle cells in media are the main performers of vascular function. The alterations in signaling pathways in these cells are the key molecular mechanisms underlying vascular dysfunction and hypertension development. In this manuscript, we will comprehensively review the signaling pathways involved in vascular function regulation and hypertension progression, including calcium pathway, NO-NOsGC-cGMP pathway, various vascular remodeling pathways and some important upstream pathways such as renin-angiotensin-aldosterone system, oxidative stress-related signaling pathway, immunity/inflammation pathway, etc. Meanwhile, we will also summarize the treatment methods of hypertension that targets vascular function regulation and discuss the possibility of these signaling pathways being applied to clinical work.

Inflammaging: mechanisms and role in the cardiac and vasculature

Aging triggers a wide range of cellular and molecular aberrations in the body, giving rise to inflammation and associated diseases. In particular, aging is associated with persistent low-grade inflammation even in absence of inflammatory stimuli, a phenomenon commonly referred to as 'inflammaging'. Accumulating evidence has revealed that inflammaging in vascular and cardiac tissues is associated with the emergence of pathological states such as atherosclerosis and hypertension. In this review we survey molecular and pathological mechanisms of inflammaging in vascular and cardiac aging to identify potential targets, natural therapeutic compounds, and other strategies to suppress inflammaging in the heart and vasculature, as well as in associated diseases such as atherosclerosis and hypertension.

Aging, Cellular Senescence, and Alzheimer's Disease

Aging is the greatest risk factor for late-onset Alzheimer's disease (LOAD), which accounts for >95% of Alzheimer's disease (AD) cases. The mechanism underlying the aging-related susceptibility to LOAD is unknown. Cellular senescence, a state of permanent cell growth arrest, is believed to contribute importantly to aging and aging-related diseases, including AD. Senescent astrocytes, microglia, endothelial cells, and neurons have been detected in the brain of AD patients and AD animal models. Removing senescent cells genetically or pharmacologically ameliorates β-amyloid (Aβ) peptide and tau-protein-induced neuropathologies, and improves memory in AD model mice, suggesting a pivotal role of cellular senescence in AD pathophysiology. Nonetheless, although accumulated evidence supports the role of cellular senescence in aging and AD, the mechanisms that promote cell senescence and how senescent cells contribute to AD neuropathophysiology remain largely unknown. This review summarizes recent advances in this field. We believe that the removal of senescent cells represents a promising approach toward the effective treatment of aging-related diseases, such as AD.

The G2A Receptor Deficiency Aggravates Atherosclerosis in Rats by Regulating Macrophages and Lipid Metabolism

The orphan G protein-coupled receptor G2A has been linked to atherosclerosis development. However, available data from mouse models are controversial. Rat G2A receptor bears more similarities with its human homolog. We proposed that the atherosclerosis model established from Ldlr^–/– rat, which has been reported to share more similar phenotypes with the human disease, may help to further understand this lipid receptor. G2A deletion was found markedly aggravated in the lipid disorder in the rat model, which has not been reported in mouse studies. Examination of aortas revealed exacerbated atherosclerotic plaques in G2A deficient rats, together with increased oxidative stress and macrophage accumulation. In addition, consistently promoted migration and apoptosis were noticed in G2A deficient macrophages, even in macrophages from G2A single knockout rats. Further analysis found significantly declined phosphorylation of PI3 kinase (PI3K) and AKT, together with reduced downstream genes Bcl2 and Bcl-xl, suggesting possible involvement of PI3K/AKT pathway in G2A regulation to macrophage apoptosis. These data indicate that G2A modulates atherosclerosis by regulating lipid metabolism and macrophage migration and apoptosis. Our study provides a new understanding of the role of G2A in atherosclerosis, supporting it as a potential therapeutic target.

Lithium inhibits oxidative stress-induced neuronal senescence through miR-34a

Neuronal senescence, triggered by telomere shortening, oncogene activation, DNA damage, or oxidative stress, has been associated with neurodegenerative diseases' pathogenesis. Therefore, preventing neuronal senescence could be a novel treatment strategy for neurodegenerative diseases. Lithium (Li), the first-line treatment against bipolar disorder, has been shown to have neuroprotective effects in clinical, pre-clinical, and in vitro studies. Li can protect cells from senescence, and its effect on neuronal senescence was investigated in our study. Furthermore, we also investigated the effects of Li on the senescence-associated miR-34a/Sirt1/p53 pathway. In this study, hydrogen peroxide was used as an inducer for the "stress-induced premature senescence" model. In the senescence model, we have assessed Li's effects on senescence by analyzing β-galactosidase activity, Sudan Black B, and senescence-associated heterochromatin foci (SAHF) stainings, and on cell cycle arrest by BrdU staining. Furthermore, expression levels of senescence and cell cycle arrest-related proteins (p53, p21, p16INK4a, and SIRT1) by western blotting. Finally, the effects of Li on senescence-associated miR-34a levels were measured by quantitative PCR. We show via Sudan Black B staining, β-Gal activity assay, and by detecting SAHF, Li protects against senescence in neuronal cells. Then, Li's effect on signaling has also been determined on pathways involved in senescence and cell cycle arrest. Moreover, we have observed that Li has a modulatory effect on miR-34a expression. Therefore, we posit that Li suppresses senescence in neuronal cells and that this effect is mediated through miR-34a/Sirt1/p53 axis.

[Neurological complications attributable to lithium: An update]

Lithium intoxication may induce neurological complications, initially characterised by a conscience alteration and an encephalopathy clinical picture with a risk of death or sever long-term consequences. With an occurrence sometimes atypical and possibly without initial hyperlitemia, the diagnosis delay of these complications might be important. Moreover, no specific guidelines focused on these complications are available. The aim of this article is to propose an update on diagnosis and treatment of neurological complications attributable to lithium, as encephalopathy.

Derivation of Cell-Engineered Nanovesicles from Human Induced Pluripotent Stem Cells and Their Protective Effect on the Senescence of Dermal Fibroblasts

Stem cells secrete numerous paracrine factors, such as cytokines, growth factors, and extracellular vesicles. As a kind of extracellular vesicle (EV), exosomes produced in the endosomal compartment of eukaryotic cells have recently emerged as a biomedical material for regenerative medicine, because they contain many valuable contents that are derived from the host cells, and can stably deliver those contents to other recipient cells. Although we have previously demonstrated the beneficial effects of human induced potent stem cell-derived exosomes (iPSC-Exo) on the aging of skin fibroblasts, low production yield has remained an obstacle for clinical applications. In this study, we generated cell-engineered nanovesicles (CENVs) by serial extrusion of human iPSCs through membrane filters with diminishing pore sizes, and explored whether the iPSC-CENV ameliorates physiological alterations of human dermal fibroblasts (HDFs) that occur by natural senescence. The iPSC-CENV exhibited similar characteristics to the iPSC-Exo, while the production yield was drastically increased compared to that of iPSC-derived EVs, including exosomes. The proliferation and migration of both young and senescent HDFs were stimulated by the treatment with iPSC-CENVs. In addition, it was revealed that the iPSC-CNEV restored senescence-related alterations of gene expression. Treatment with iPSC-CENVs significantly reduced the activity of senescence-associated-β-galactosidase (SA-β-Gal) in senescent HDFs, as well as suppressing the elevated expression of p53 and p21, key factors involved in cell cycle arrest, apoptosis, and cellular senescence signaling pathways. Taken together, these results suggest that iPSC-CENV could provide an excellent alternative to iPSC-exo, and be exploited as a resource for the treatment of signs of skin aging.

Autophagy, Cellular Aging and Age-related Human Diseases

Macroautophagy/autophagy is a conserved degradation system that engulfs intracytoplasmic contents, including aggregated proteins and organelles, which is crucial for cellular homeostasis. During aging, cellular factors suggested as the cause of aging have been reported to be associated with progressively compromised autophagy. Dysfunctional autophagy may contribute to age-related diseases, such as neurodegenerative disease, cancer, and metabolic syndrome, in the elderly. Therefore, restoration of impaired autophagy to normal may help to prevent age-related disease and extend lifespan and longevity. Therefore, this review aims to provide an overview of the mechanisms of autophagy underlying cellular aging and the consequent disease. Understanding the mechanisms of autophagy may provide potential information to aid therapeutic interventions in age-related diseases.

Cooperative Action of Oxidized Low-Density Lipoproteins and Neutrophils on Endothelial Inflammatory Responses Through Neutrophil Extracellular Trap Formation

The function of oxidatively modified low-density lipoprotein (oxLDL) in the progression of cardiovascular diseases has been extensively investigated and well-characterized with regards to the activation of multiple cellular responses in macrophages and endothelial cells. Although accumulated evidence has revealed the presence of neutrophils in vascular lesions, the effect of oxLDL on neutrophil function has not been properly investigated. In the present decade, neutrophil extracellular traps (NETs) gained immense attention not only as a primary response against pathogenic bacteria but also due to their pathological roles in tissue damage in various diseases, such as atherosclerosis and thrombosis. In this study, we investigated if oxLDL affects NET formation and if it is a risk factor for inflammatory reactions in endothelial cells. HL-60-derived neutrophils were stimulated with phorbol 12-myristate 13-acetate (PMA) for 30 min to induce NET formation, followed by incubation with 20 μg/mL native or oxidized LDL for additional 2 h. Culture media of the stimulated cells containing released NETs components were collected to evaluate NET formation by fluorometric quantitation of released DNA and detection of myeloperoxidase (MPO) by western blot analysis. NET formation of HL-60-derived neutrophils induced by PMA was significantly enhanced by additional incubation with oxLDL but not with native LDL. Treatment of HL-60-derived neutrophils with oxLDL alone in the absence of PMA did not induce NET formation. Furthermore, the culture media of HL-60-derived neutrophils after NET formation were then transferred to human aortic endothelial cell (HAECs) culture. Treatment of HAECs with the culture media containing NETs formed by HL-60-derived neutrophils increased the expression of metalloproteinase-1 protein in HAECs when HL-60-derived neutrophils were incubated with native LDL, and the expression was accelerated in the case of oxLDL. In addition, the culture media from NETs formed by HL-60-derived neutrophils caused the elongation of HAECs, which was immensely enhanced by coincubation with native LDL or oxLDL. These data suggest that oxLDL may act synergistically with neutrophils to form NETs and promote vascular endothelial inflammation.

Matrix metalloproteinases in pro-atherosclerotic arterial remodeling

Matrix metalloproteinases (MMPs) is a family of Zn²⁺ endopeptidases that process various components of the extracellular matrix. These enzymes are also involved in activation and inhibition of signaling cascades through proteolytic cleavage of surface receptors. Moreover, MMPs play a key role in tissue remodeling and and repair. Dysregulation of MMPs is observed in patholofgical conditions, including atherosclerosis, which is associated with hyperactivation of MMPs, aberrant tissue remodeling and neovascularization of the growing atherosclerotic plaques. This makes MMPs interesting therapeutic targets that can be employed for developing novel therapies to treat atherosclerosis and its complications. Currently, a growing number of synthetic MMP inhibitors is available. In this review, we will discuss the role of these enzymes in atherosclerosis pathology and the ways of their pothential therapeutic use.

Down-regulation of senescence marker protein 30 by iron-specific chelator deferoxamine drives cell senescence

To our knowledge, this is the first study to report down-regulation of senescence marker protein 30 (SMP30) by iron-specific chelator deferoxamine (DFO) on FAO cell senescence, using a DNA microarray. Furthermore, DFO treatment increased senescence marker β-galactosidase activity, whereas this activity was attenuated by overexpression of SMP30. Our data suggested that down-regulation of SMP30 drives cell senescence in iron-chelated condition.

Investigation of the expressions of MMPs and TIMPs between isogeneic and allogeneic rat aortic transplantation

The present study investigated the effects of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) in transplantation-associated arteriosclerosis by observing their expression in transplanted aortas in rats. Allogenic and isogenic abdominal aortic transplantations were performed and grafts were removed from the recipients at the designated time points (day 7, 14, 28 and 56 post transplantation). Hematoxylin and eosin staining, immunohistochemistry, immunofluorescence and western blot analysis were used to evaluate the grafts. Significant proliferation of the intima was observed in the allogenic transplantation groups (P<0.05). The expressions of MMPs and TIMPs in the allografts were significantly increased compared with the isografts, and the suppression of MMP2 in allografts reduced injury after transplantation. The present study concluded that the imbalance of MMPs and TIMPs led to the disturbance of synthesis and the degradation of the extracellular matrix and it may represent a key cause of chronic rejection.

In Vitro Human Umbilical Vein Endothelial Cells Response to Ionic Dissolution Products from Lithium-Containing 45S5 Bioactive Glass

Since lithium (Li⁺) plays roles in angiogenesis, the localized and controlled release of Li⁺ ions from bioactive glasses (BGs) represents a promising alternative therapy for the regeneration and repair of tissues with a high degree of vascularization. Here, microparticles from a base 45S5 BG composition containing (wt %) 45% SiO₂, 24.5% Na₂O, 24.5% CaO, and 6% P₂O₅, in which Na₂O was partially substituted by 5% Li₂O (45S5.5Li), were obtained. The results demonstrate that human umbilical vein endothelial cells (HUVECs) have greater migratory and proliferative response and ability to form tubules in vitro after stimulation with the ionic dissolution products (IDPs) of the 45S5.5Li BG. The results also show the activation of the canonical Wnt/β-catenin pathway and the increase in expression of proangiogenic cytokines insulin like growth factor 1 (IGF1) and transforming growth factor beta (TGFβ). We conclude that the IDPs of 45S5.5Li BG would act as useful inorganic agents to improve tissue repair and regeneration, ultimately stimulating HUVECs behavior in the absence of exogenous growth factors.

Cellular Senescence and Vascular Disease: Novel Routes to Better Understanding and Therapy

Cellular senescence is a definable fate of cells within aging, diseased, and remodelling tissues. The traditional hallmark of cellular senescence is permanent cell cycle arrest but the senescent state is also accompanied by secretion of proteins that can reinforce the senescent phenotype and adversely affect the local tissue environment. Assessment for cellular markers of senescence has revealed the existence of senescent smooth muscle cells and senescent endothelial cells in vessels of patients with atherosclerosis and hypertension. This raises the possibility that cellular senescence might contribute to the initiation or progression of vascular disease. Potential disease-promoting pathways include blunted replicative reserve, reduced nitric oxide production, and increased cellular stiffness. Moreover, the secretory phenotype of senescent vascular cells might promote vascular degeneration through chronic inflammation and extracellular matrix degradation. Slowing of vascular cell aging and selective clearing of cells that have become senescent are emerging as exciting possibilities for controlling vascular disease.

Functional role of inorganic trace elements in angiogenesis part III: (Ti, Li, Ce, As, Hg, Va, Nb and Pb)

Many essential elements exist in nature with significant influence on human health. Angiogenesis is vital in developmental, repair, and regenerative processes, and its aberrant regulation contributes to pathogenesis of many diseases including cancer. Thus, it is of great importance to explore the role of these elements in such a vital process. This is third in a series of reviews that serve as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. Here we will review the roles of titanium, lithium, cerium, arsenic, mercury, vanadium, niobium, and lead in these processes. The roles of other inorganic elements in angiogenesis were discussed in part I (N, Fe, Se, P, Au, and Ca) and part II (Cr, Si, Zn, Cu, and S) of these series. The methods of exposure, structure, mechanisms, and potential activities of these elements are briefly discussed. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. These elements can promote and/or inhibit angiogenesis through different mechanisms. The anti-angiogenic effect of titanium dioxide nanoparticles comes from the inhibition of angiogenic processes, and not from its toxicity. Lithium affects vasculogenesis but not angiogenesis. Nanoceria treatment inhibited tumor growth by inhibiting angiogenesis. Vanadium treatment inhibited cell proliferation and induced cytotoxic effects through interactions with DNA. The negative impact of mercury on endothelial cell migration and tube formation activities was dose and time dependent. Lead induced IL-8 production, which is known to promote tumor angiogenesis. Thus, understanding the impact of these elements on angiogenesis will help in development of new modalities to modulate angiogenesis under various conditions.

Reversible posterior leukoencephalopathy syndrome after withdrawal of antipsychotic medication in the context of lithium intoxication

OBJECTIVE

To report a case of reversible posterior leukoencephalopathy syndrome (RPLS) after withdrawal of antipsychotic medication in a patient with acute lithium intoxication.

METHODS

Case report.

RESULTS

A patient with schizoaffective disorder was admitted with lithium intoxication, rhabdomyolysis and acute renal failure. After withdrawal of psychotropic medication, she developed a significant increase in blood pressure - though to moderately hypertensive levels - and prolonged disturbance of consciousness with profound agitation. MRI revealed RPLS. Resumption of antipsychotic treatment resulted in significant drop of blood pressure and improvement.

CONCLUSION

Acute withdrawal of antipsychotic medication may lead to rebound hypertension and development of RPLS, especially in the presence of lithium intoxication and renal dysfunction.

Cytokine-induced monocyte MMP-1 is negatively regulated by GSK-3 through a p38 MAPK-mediated decrease in ERK1/2 MAPK activation

Elucidation of the signal transduction events leading to the production of MMPs by monocytes/macrophages may provide insights into the mechanisms involved in the destruction of connective tissue associated with chronic inflammatory lesions. Here, we show that GSK-3 is a negative regulator of cytokine-induced MMP-1 production by monocytes. Inhibition of monocyte GSK-3 pharmacologically with SB216763 or GSK-3β siRNA caused a significant enhancement of MMP-1 by TNF-α- and GM-CSF-activated monocytes, indicating that induction of MMP-1 by TNF-α and GM-CSF involved phosphorylation/inactivation of GSK-3. TNF-α- and GM-CSF-induced phosphorylation of GSK-3 and subsequent MMP-1 production was blocked with the PKC inhibitor Gö6976 but not by the AKT1/2 inhibitor AKT VIII, showing that cytokine phosphorylation of GSK-3 occurs primarily through a PKC pathway. Inhibition of GSK-3 resulted in decreased phosphorylation of p38 MAPK with a corresponding increase in phosphorylation of ERK1/2 MAPK. Enhanced MMP-1 production by treatment with SB216763 was a result of increased ERK1/2 activation, as demonstrated by inhibition of MMP-1 by PD98059, a specific ERK1/2 inhibitor. Conversely, the p38 MAPK inhibitor SB203580 enhanced cytokine activation of ERK1/2 and the production of MMP-1 similar to that of SB216763. These findings demonstrate that the degree of cytokine-mediated phosphorylation/inhibition of GSK-3 determines the level of MMP-1 production through a mechanism involving decreased activation of p38 MAPK, a negative regulator of ERK1/2 required for cytokine-induced production of MMP-1 by monocytes.

Lithium toxicity and PRES: a novel association

We report two cases of posterior reversible encephalopathy syndrome (PRES) occurring in association with supra-therapeutic serum lithium levels. Although the neurologic manifestations of lithium toxicity are well known, this is, to our knowledge, the first report describing a link between lithium toxicity and PRES. We discuss the current understanding of the pathogenesis of PRES and suggest mechanisms by which lithium may play a role in its development.

Effects of the immunosuppressant rapamycin on the expression of human α2(I) collagen and matrix metalloproteinase 1 genes in scleroderma dermal fibroblasts

BACKGROUND

Rapamycin has been shown to exert an anti-fibrotic effect on skin fibrosis in a certain subset of patients with systemic sclerosis (SSc) and in bleomycin-treated animal models.

OBJECTIVES

To investigate the mechanism responsible for the anti-fibrotic effect of rapamycin especially by focusing on human α2(I) collagen (COL1A2) and matrix metalloproteinase 1 (MMP1) genes in normal and systemic sclerosis (SSc) dermal fibroblasts.

METHODS

The expression levels of type I procollagen and MMP1 proteins were analyzed by immunoblotting and the mRNA levels of COL1A2 and MMP1 genes were evaluated by quantitative real-time RT-PCR. The activities of COL1A2 and MMP1 promoters were determined by reporter analysis.

RESULTS

Rapamycin significantly decreased the levels of type I procollagen protein and COL1A2 mRNA, while significantly increasing the levels of MMP1 protein and mRNA in normal dermal fibroblasts. Similar effects of rapamycin were also observed in SSc dermal fibroblasts. Importantly, the inhibitory and stimulatory effects of rapamycin on the mRNA levels of COL1A2 and MMP1 genes, respectively, were significantly greater in SSc dermal fibroblasts than in normal dermal fibroblasts. In SSc dermal fibroblasts, rapamycin affected the expression of COL1A2 gene at the post-transcriptional level. In contrast, rapamycin altered the expression of MMP1 gene at the transcriptional level through the JNK/c-Jun signaling pathway in those cells.

CONCLUSION

Rapamycin has a potential to directly regulate the deposition of type I collagen in extracellular matrix through inhibiting type I collagen synthesis and promoting its degradation by MMP1, suggesting that this drug is useful for the treatment of SSc.

SIRT1 redresses the imbalance of tissue inhibitor of matrix metalloproteinase-1 and matrix metalloproteinase-9 in the development of mouse emphysema and human COPD

Sirtuin1 (SIRT1), a protein/histone deacetylase, protects against the development of pulmonary emphysema. However, the molecular mechanisms underlying this observation remain elusive. The imbalance of tissue inhibitor of matrix metalloproteinases (TIMPs)/matrix metalloproteinases (MMPs) plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD)/emphysema. We hypothesized that SIRT1 protects against emphysema by redressing the imbalance between MMPs and TIMPs. To test this hypothesis, SIRT1-deficient and overexpressing/transgenic mice were exposed to cigarette smoke (CS). The protein level and activity of MMP-9 were increased in lungs of SIRT1-deficient mice exposed to CS compared with wild-type (WT) littermates, and these effects were attenuated by SIRT1 overexpression. SIRT1 deficiency decreased the level of TIMP-1, which was augmented in SIRT1 transgenic mice compared with WT littermates by CS. However, the level of MMP-2, MMP-12, TIMP-2, TIMP-3, or TIMP-4 was not altered by SIRT1 in response to CS exposure. SIRT1 reduction was associated with imbalance of TIMP-1 and MMP-9 in lungs of smokers and COPD patients. Mass spectrometry and immunoprecipitation analyses revealed that TIMP-1 acetylation on specific lysine residues was increased, whereas its interaction with SIRT1 and MMP-9 was reduced in mouse lungs with emphysema, as well as in lungs of smokers and COPD patients. SIRT1 deficiency increased CS-induced TIMP-1 acetylation, and these effects were attenuated by SIRT1 overexpression. These results suggest that SIRT1 protects against COPD/emphysema, in part, via redressing the TIMP-1/MMP-9 imbalance involving TIMP-1 deacetylation. Thus redressing the TIMP-1/MMP-9 imbalance by pharmacological activation of SIRT1 is an attractive approach in the intervention of COPD.

Dkk-1 promotes angiogenic responses and cartilage matrix proteinase secretion in synovial fibroblasts from osteoarthritic joints

OBJECTIVE

Synovial hypervascularity is a prominent pathologic feature in osteoarthritic (OA) joints. Wnt inhibitor Dkk-1 contributes to joint remodeling. We undertook this study to investigate whether Dkk-1 regulates cartilage destruction activities in OA synovial fibroblasts.

METHODS

Synovial tissues were harvested from knees of patients with OA and from injured knees of non-OA patients who underwent arthroscopy. Expression of Dkk-1, angiogenic factors (stromal cell-derived factor 1 and colony-stimulating factor 1), and cartilage proteinases (ADAMTS-5 and matrix metalloproteinase 3 [MMP-3]) as well as vascularity in synovium and synovial fluid were quantified using enzyme-linked immunosorbent assay, reverse transcription-polymerase chain reaction, and histomorphometry. Synovial fibroblasts were treated with interleukin-1β (IL-1β), anti-Dkk-1 antibody, and RNA interference to characterize their angiogenic activity. Rats with OA knees were administered Dkk-1 antisense oligonucleotide to verify synovial angiogenesis and cartilage integrity.

RESULTS

OA synovium exhibited increased vascularity and expression of angiogenic factors and proteinases in association with up-regulated Dkk-1 levels. Neutralizing Dkk-1 reduced the inhibitory effects of OA synovial fluid on aggrecan expression in chondrocyte cultures. IL-1β induction of Dkk-1 increased expression of hypoxia-inducible factor 1α (HIF-1α), angiogenic factors, ADAMTS-5, and MMP-3 in synovial fibroblasts and promoted angiogenesis in vascular endothelial cells. Knockdown of HIF-1α decreased Dkk-1 enhancement of angiogenic factor expression. Stabilization of glycogen synthase kinase 3β phosphorylated at Ser(9) , β-catenin, T cell factor 4, and ERK signaling attenuated Dkk-1 up-regulation of angiogenic factor and proteinase expression in synovial fibroblasts. In vivo, Dkk-1 interference reduced the expression of angiogenic factors and proteinases and ameliorated synovial vascularity and cartilage deterioration in knees of rats with OA.

CONCLUSION

Dkk-1 promoted angiogenic and cartilage degradation activities in synovial fibroblasts, which accelerated synovial angiogenesis and cartilage destruction. Dkk-1 blockade has therapeutic potential for reducing OA-induced synovitis and joint deterioration.

A matrix metalloprotease-PAR1 system regulates vascular integrity, systemic inflammation and death in sepsis

Sepsis is a deadly disease characterized by the inability to regulate the inflammatory–coagulation response in which the endothelium plays a key role. The cause of this perturbation remains poorly understood and has hampered the development of effective therapeutics. Matrix metalloproteases (MMPs) are involved in the host response to pathogens, but can also cause uncontrolled tissue damage and contribute to mortality. We found that human sepsis patients had markedly elevated plasma proMMP-1 and active MMP-1 levels, which correlated with death at 7 and 28 days after diagnosis. Likewise, septic mice had increased plasma levels of the MMP-1 ortholog, MMP-1a. We identified mouse MMP-1a as an agonist of protease-activated receptor-1 (PAR1) on endothelial cells. MMP-1a was released from endothelial cells in septic mice. Blockade of MMP-1 activity suppressed endothelial barrier disruption, disseminated intravascular coagulation (DIC), lung vascular permeability as well as the cytokine storm and improved survival, which was lost in PAR1-deficient mice. Infusion of human MMP-1 increased lung vascular permeability in normal wild-type mice but not in PAR1-deficient mice. These findings implicate MMP-1 as an important activator of PAR1 in sepsis and suggest that therapeutics that target MMP1-PAR1 may prove beneficial in the treatment of sepsis.

Wnt signaling and aging-related heart disorders

Aging is associated with various heart diseases, and this may be attributable, in part, to the prolonged exposure of the heart to cardiovascular risk factors. However, aging is also associated with heart disorders such as diastolic dysfunction that are not necessarily linked to the risk factors for cardiovascular diseases. Recent studies have demonstrated a mechanistic link between Wnt signaling and premature aging or aging-related phenotypes. As a part of the review series on Wnt signaling and the cardiovascular system, we discuss here the possible involvement of Wnt signaling in aging-associated heart diseases or heart disorders.

Enhancement of intervertebral disc cell senescence by WNT/β-catenin signaling-induced matrix metalloproteinase expression

OBJECTIVE

To determine whether intervertebral disc (IVD) cells express β-catenin and to assess the role of the WNT/β-catenin signaling pathway in cellular senescence and aggrecan synthesis.

METHODS

The expression of β-catenin messenger RNA (mRNA) and protein in rat IVD cells was assessed by using several real-time reverse transcription-polymerase chain reaction, Western blot, immunohistochemical, and immunofluorescence analyses. The effect of WNT/β-catenin on nucleus pulposus (NP) cells was examined by transfection experiments, an MTT assay, senescence-associated β-galactosidase staining, a cell cycle analysis, and a transforming growth factor (TGFβ)/bone morphogenetic protein (BMP) pathway-focused microarray analysis.

RESULTS

We found that β-catenin mRNA and protein were expressed in discs in vivo and that rat NP cells exhibited increased β-catenin mRNA and protein upon stimulation with lithium chloride, a known activator of WNT signaling. LiCl treatment inhibited the proliferation of NP cells in a time- and dose-dependent manner. In addition, there was an increased level of cellular senescence in LiCl-treated cells. Long-term treatment with LiCl induced cell cycle arrest and promoted subsequent apoptosis in NP cells. Activation of WNT/β-catenin signaling also regulated the expression of aggrecan. We also demonstrated that WNT/β-catenin signaling induced the expression of matrix metalloproteinases (MMPs) and TGFβ in NP cells.

CONCLUSION

The activation of WNT/β-catenin signaling promotes cellular senescence and may modulate MMP and TGFβ signaling in NP cells. We hypothesize that the activation of WNT/β-catenin signaling may lead to an increased breakdown of the matrix, thereby promoting IVD degeneration.

The balance of TCF7L2 variants with differential activities in Wnt-signaling is regulated by lithium in a GSK3beta-independent manner

TCF7L2 transcription factor is a downstream effector of the canonical Wnt/beta-catenin signaling, which controls cell fate and homeostasis. However, the complexity of TCF7L2 expression with numerous mRNA isoforms coding for proteins with distinct N- and C-termini allows variability in TCF7L2 functions and regulations. Here, we show that although TCF7L2 mRNA isoforms distinguish fetal, immortalized and adult differentiated endothelial cells (EC), they cannot explain the lack of significant beta-catenin/TCF7 activities in ECs. Lithium, a Wnt-signaling activator, increases TCF7L2 mRNA levels and induces an RNA isoform switch favoring the expression of TCF7L2-short forms lacking the C-termini domains. Although the latter occurs in different cell types, its extent depends on the overall increase of TCF7L2 transcription, which correlates with cell responsiveness to Wnt/beta-catenin signaling. While GSK3beta down-regulation increases TCF7L2 expression, there is no concomitant change in TCF7L2 mRNA isoforms, which demonstrate the dual effects of lithium on TCF7L2 expression via a GSK3beta-dependent up-regulation and a GSK3beta-independent modulation of RNA splicing. TCF7L2E-long forms display a repressor activity on TCF7L2-promoter reporters and lithium induces a decrease of the endogenous TCF7L2 forms bound to native TCF7L2-promoter chromatin at two novel distal TCF7-binding sites. Altogether our data reveal a lithium-induced RNA switch favoring the expression of TCF7L2-short forms, which results in a transcriptional de-repression of lithium target genes negatively regulated by TCF7L2-long forms, like TCF7L2, and thus to an amplification of Wnt-signaling in responsive cells.

Lithium protects cartilage from cytokine-mediated degradation by reducing collagen-degrading MMP production via inhibition of the P38 mitogen-activated protein kinase pathway

OBJECTIVES

To determine the effects and mechanism of action of lithium chloride (LiCl) on cartilage destruction induced by the pro-inflammatory cytokines IL-1, IL-1 + oncostatin M and TNF-α.

METHODS

The release of collagen was assessed in bovine cartilage explant cultures, whereas collagenolytic activities (active and total) in conditioned culture supernatants were determined by bioassay. The expression and production of MMP from chondrocytes were analysed by real-time RT-PCR and ELISA. Signalling pathway analysis was performed using a phospho-antibody array and standard immunoblotting.

RESULTS

LiCl, but not selective glycogen synthase kinase 3 (GSK-3) inhibitor compounds SB-415286 and TDZD-8, significantly decreased pro-inflammatory cytokine-induced collagen release from bovine cartilage via the down-regulation of collagenolytic activity. Furthermore, MMP-1 and MMP-13 expression was reduced in both bovine and human chondrocytes. Pathway analysis revealed that LiCl selectively inhibited activation of the p38 mitogen-activated protein kinase pathway; effects that were recapitulated by specific p38 pathway inhibition.

CONCLUSIONS

This study demonstrates for the first time that LiCl can protect against cartilage damage induced by pro-inflammatory cytokines, and indicates that LiCl-mediated cartilage protection is not via a GSK-3-dependent mechanism, but potentially via inhibition of the p38 pathway. These data indicate that lithium administration may represent a potential therapy for arthritis.