Abstract-Vascular calcification is associated with cardiovascular morbidity and mortality. Hyperphosphatemia is an important contributor to vascular calcification. Our previous studies demonstrated that elevated phosphate induces calcification of smooth muscle cells (SMC) in vitro. Inhibition of phosphate transport by phosphonoformic acid blocked phosphate-induced calcification, implicating sodium-dependent phosphate cotransporters in this process. In the present study, we have investigated the role of the type III sodium-dependent phosphate cotransporter, Pit-1, in SMC calcification in vitro. Human SMC stably expressing Pit-1 small interfering double-stranded RNA (SMC-iRNA) were established using a retroviral system. SMC-iRNA had decreased Pit-1 mRNA and protein levels and sodium-dependent phosphate transport activity compared with the control transduced cells (SMC-CT) (2.9 versus 9.78 nmol/mg protein per 30 minutes, respectively). Furthermore, phosphate-induced SMC calcification was significantly inhibited in SMC-iRNA compared with SMC-CT at all time points examined. Overexpression of Pit-1 restored phosphate uptake and phosphate-induced calcification in Pit-1 deficient cells. Mechanistically, although Pit-1-mediated SMC calcification was not associated with apoptosis or cell-derived vesicles, inhibition of phosphate uptake in Pit-1 knockdown cells blocked the induction of the osteogenic markers Cbfa-1 and osteopontin. Our results indicate that phosphate uptake through Pit-1 is essential for SMC calcification and phenotypic modulation in response to elevated phosphate. (Circ Res. 2006;98:905-912.)Key Words: sodium-dependent phosphate cotransporter Ⅲ Pit-1 Ⅲ vascular calcification Ⅲ smooth muscle cell V ascular calcification refers to calcium phosphate deposition in blood vessels, myocardium, and cardiac valves under pathological conditions. Vascular calcification is associated with increased risk of cardiovascular morbidity and mortality. 1,2 It is highly prevalent in patients with atherosclerosis, diabetes, and renal failure. 3 Approximately 50% of all deaths in end-stage renal disease (ESRD) patients are attributed to cardiovascular diseases. 4 Intimal, as well as medial, calcification contributes to the increased mortality in these patients. 5 Recent evidence indicates that vascular calcification is an actively regulated process, and molecules that inhibit or promote vascular calcification are currently being identified. 6,7 Mineralization inhibiting molecules appear to play a major role in preventing ectopic calcification under physiological conditions. However, processes that promote calcification may predominate under pathological conditions and are less well defined.Although the mechanisms of vascular calcification are not fully understood, abnormalities in mineral metabolism are considered important risk factors. In particular, phosphate has emerged as an important regulator of vascular calcification as well as a risk factor for cardiovascular mortality in dialysis patients. In humans, normal levels...

Vascular calcification is associated with increased risk of cardiovascular events that are the most common cause of death in patients with end-stage renal disease. Clinical and experimental studies indicate that hyperphosphatemia is a risk factor for vascular calcification and cardiovascular mortality in these patients. Our previous studies demonstrated that phosphate transport through the type III sodium-dependent phosphate cotransporter, Pit-1, was necessary for phosphate-induced calcification and osteochondrogenic phenotypic change in cultured human smooth muscle cells (SMC). BMP-2 is a potent osteogenic protein required for osteoblast differentiation and bone formation that has been implicated in vascular calcification. In the present study, we have examined the effects of BMP-2 on human SMC calcification in vitro. We found that treatment of SMC with BMP-2 enhanced elevated phosphate-induced calcification, but did not induce calcification under normal phosphate conditions. mRNAs for BMP receptors, including ALK2, ALK3, ALK6, BMPR-II, ActR-IIA and ActR-IIB were all detected in human SMCs. Mechanistically, BMP-2 dose-dependently stimulated phosphate uptake in SMC (200 ng/ml BMP-2 vs vehicle: 13.94 vs 7.09 nmol/30 min/mg protein, respectively). Real-time PCR and Western blot revealed the upregulation of Pit-1 mRNA and protein levels, respectively, by BMP-2. More importantly, inhibition of phosphate uptake by a competitive inhibitor of sodiumdependent phosphate cotransport, phosphonoformic acid, abrogated BMP-2-induced calcification. These results indicate that phosphate transport via Pit-1 is crucial in BMP-2-regulated SMC calcification. In addition, BMP-2 induced Runx2 and inhibited SM22 expression, indicating that it promotes osteogenic phenotype transition in these cells. Thus, BMP-2 may promote vascular calcification via increased phosphate uptake and induction of osteogenic phenotype modulation in SMC.

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Many of the proinflammatory effects of gram-negative bacteria are elicited by the interaction of bacterial lipopolysaccharide (LPS) with Toll-like receptor 4 (TLR4) expressed on host cells. TLR4 signaling leads to activation of NF-κB and transcription of many genes involved in the inflammatory response. In this study, we examined the signaling pathways involved in NF-κB activation by TLR4 signaling in human microvascular endothelial cells. Akt is a major downstream target of phosphoinositide 3 kinase (PI3-kinase), and PI3-kinase activation is necessary and sufficient for Akt phosphorylation. Consequently, Akt kinase activation was used as a measure of PI3-kinase activity. In a stable transfection system, dominant-negative mutants of myeloid differentiation factor 88 (MyD88) and interleukin-1 (IL-1) receptor-associated kinase 1 (IRAK-1) (MyD88-TIR and IRAK-DD, respectively) blocked Akt kinase activity in response to LPS and IL-1β. A dominant-negative mutant (Mal-P/H) of MyD88 adapter-like protein (Mal), a protein with homology to MyD88, failed to inhibit LPS- or IL-1β-induced Akt activity. Moreover, a dominant-negative mutant of p85 (p85-DN) inhibited the NF-κB luciferase activity, IL-6 production, and IκBα degradation elicited by LPS and IL-1β but not that stimulated by tumor necrosis factor alpha. The dominant-negative mutant of Akt partially inhibited the NF-κB luciferase activity evoked by LPS and IL-1β. However, expression of a constitutively activated Akt failed to induce NF-κB luciferase activity. These findings indicate that TLR4- and IL-1R-induced PI3-kinase activity is mediated by the adapter proteins MyD88 and IRAK-1 but not Mal. Further, these studies suggest that PI3-kinase is an important mediator of LPS and IL-1β signaling leading to NF-κB activation in endothelial cells and that Akt is necessary but not sufficient for NF-κB activation by TLR4.

As more people live longer, age-related neurodegenerative diseases are an increasingly important societal health issue. Treatments targeting specific pathologies such as amyloid beta in Alzheimer’s disease (AD) have not led to effective treatments, and there is increasing evidence of a disconnect between traditional pathology and cognitive abilities with advancing age, indicative of individual variation in resilience to pathology. Here, we generated a comprehensive neuropathological, molecular, and transcriptomic characterization of hippocampus and two regions cortex in 107 aged donors (median = 90) from the Adult Changes in Thought (ACT) study as a freely-available resource (http://aging.brain-map.org/). We confirm established associations between AD pathology and dementia, albeit with increased, presumably aging-related variability, and identify sets of co-expressed genes correlated with pathological tau and inflammation markers. Finally, we demonstrate a relationship between dementia and RNA quality, and find common gene signatures, highlighting the importance of properly controlling for RNA quality when studying dementia.

Abstract-Vascular calcification is prevalent in aging as well as a number of pathological conditions, and it is nowrecognized as a strong predictor of cardiovascular events in the general population as well as diabetic and end-stage renal disease patients. Vascular calcification is a highly regulated process involving inductive and inhibitory mechanisms. In contrast, age and vascular disease-related vascular calcifications were previously considered benign. However, recent clinical studies have challenged this dogma. Calcification has been positively correlated with coronary atherosclerotic plaque burden, 11,12 increased risk of myocardial infarction, 13-15 and plaque instability. 2,16 Furthermore, in the Rotterdam Coronary Calcification Study, a large populationbased study, graded associations between coronary calcification score and stroke were identified. 17 Similarly, medial arterial calcification is strongly correlated with coronary artery disease and future cardiovascular events in type I diabetic subjects, 18,19 and is a strong prognostic marker of cardiovascular disease mortality in ESRD patients. 20 These findings may be explained by growing evidence that vascular medial calcification in large arteries leads to increased stiffness and therefore decreased compliance of these vessels. These mechanical changes are associated with increased arterial pulse wave velocity and pulse pressure, and lead to impaired arterial distensibility, increased afterload favoring left ventricular hypertrophy, and compromised coronary perfusion. 21 Thus, intimal and medial calcifications may contribute to the morbidity and mortality associated with cardiovascular disease.It is becoming increasingly clear that vascular calcification is an actively regulated process that may be initiated by a number of different, nonmutually exclusive mechanisms. These mechanisms have been extensively reviewed elsewhere 22 and include: (1) loss of mineral inhibiting factors; (2) induction of bone formation; (3) cell death; and (4) circulating nucleational complexes (ie, aggregates of calcium phosphate and proteins released from remodeling bone that may initiate ectopic mineralization). Abnormalities in mineral metabolism that enhance the calcium ϫ phosphate product (Ca ϫ P) may further exacerbate vascular calcification initiated by any of these mechanisms. This article focuses on recent evidence implicating elevated phosphate as a major inductive factor for vascular calcification and osteopontin as an inducible inhibitor of vascular calcification, and our current understanding of their mechanisms of action.

Vascular calcification is a major risk factor for cardiovascular morbidity and mortality. Smooth muscle cells (SMCs) may play an important role in vascular cartilaginous metaplasia and calcification via reprogramming to the osteochondrogenic state. To study whether SM lineage reprogramming and thus matrix calcification is reversible and what the necessary regulatory factors are to reverse this process, we used cells isolated from calcifying arterial medias of 4-week-old matrix Gla protein knockout mice (MGP−/− SMCs). We found that vascular cells with an osteochondrogenic phenotype regained SMC properties (positive for SM22α and SM α-actin) and down-regulated osteochondrogenic gene expression (Runx2/Cbfa1 and osteopontin) upon culture in medium that favors SMC differentiation. Over time, the MGP−/− SMCs no longer expressed osteochondrogenic proteins and became indistinguishable from wild-type SMCs. Moreover, phenotypic switch of the restored SMCs to the osteochondrogenic state was re-induced by the pro-calcific factor, inorganic phosphate. Finally, loss- and gain-of-function studies of myocardin, a SM-specific transcription co-activator, and Runx2/Cbfa1, an osteochondrogenic transcription factor, revealed that upregulation of Runx2/Cbfa1, but not loss of myocardin, played a critical role in phosphate-induced SMC lineage reprogramming and calcification. These results are the first to demonstrate reversibility of vascular SMCs to an osteochondrogenic state in response to local environmental cues, and that myocardin-enforced SMC lineage allocation was not sufficient to block vascular calcification. On the other hand, Runx2/Cbfa1 was found to be a decisive factor identified in the process.

Objective Elevated serum phosphate has emerged as a major risk factor for vascular calcification. The sodium-dependent phosphate cotransporter, PiT-1, was previously shown to be required for phosphate-induced osteogenic differentiation and calcification of cultured human VSMCs, but its importance in vascular calcification in vivo, as well as the potential role of its homologue, PiT-2, have not been determined. We investigated the in vivo requirement for PiT-1 in vascular calcification using a mouse model of chronic kidney disease, and the potential compensatory role of PiT-2 using in vitro knockdown and over-expression strategies. Approach and Results Mice with targeted deletion of PiT-1 in VSMCs were generated (PiT-1Δsm). PiT-1 mRNA levels were undetectable whereas PiT-2 mRNA levels were increased 2 fold in the vascular aortic media of PiT-1Δsm compared to PiT-1flox/flox control. When arterial medial calcification was induced in PiT-1Δsm and PiT-1flox/flox by chronic kidney disease followed by dietary phosphate loading, the degree of aortic calcification was not different between genotypes, suggesting compensation by PiT-2. Consistent with this possibility, VSMCs isolated from PiT-1Δsm mice had no PiT-1 mRNA expression, increased PiT-2 mRNA levels, and no difference in sodium-dependent phosphate uptake or phosphate-induced matrix calcification compared to PiT-1flox/flox VSMCs. Knockdown of PiT-2 decreased phosphate uptake and phosphate-induced calcification of PiT-1Δsm VSMCs. Furthermore, over-expression of PiT-2 restored these parameters in human PiT-1-deficient VSMCs. Conclusions PiT-2 can mediate phosphate uptake and calcification of VSMCs in the absence of PiT-1. Mechanistically, PiT-1 and PiT-2 appear to serve redundant roles in phosphate-induced calcification of vascular smooth muscle cells.