Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphodiesterase 4 (PDE4) inhibitors stimulate osteoclast formation by increasing the TRANCE/OPG mRNA ratio via cAMP-mediated pathways in a manner similar to parathyroid hormone (PTH) in osteoblasts. We investigated the role of cyclooxygenase-2 (COX-2) in osteoclast formation induced by the PDE4 inhibitor rolipram. Rolipram induced COX-2 expression in mRNA and protein levels, followed by increased prostaglandin E(2) production in osteoblasts. PKA, ERK, and p38 MAPK pathways regulate COX-2 mRNA expression induced by rolipram, in which PKA is a central regulator of the ERK and p38 MAPK pathways. A COX-2 inhibitor reversed the up-regulation of the TRANCE/OPG mRNA ratio induced by rolipram in osteoblasts, resulting in decreased osteoclast formation. These data suggest that COX-2 mediates rolipram induced osteoclast formation by regulating the TRANCE/OPG mRNA ratio in osteoblasts. Furthermore, the effects of the PDE4 inhibitor on osteoblasts were very similar to those of PTH, indicating that the PDE4 inhibitor largely shares the biological actions of PTH in osteoblasts.
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PMID:Phosphodiesterase 4 inhibitor regulates the TRANCE/OPG ratio via COX-2 expression in a manner similar to PTH in osteoblasts. 1722 89

Cardiovascular disease, such as atherosclerosis, has been associated with reduced bone mineral density and fracture risk. A major etiologic factor in atherogenesis is believed to be oxidized phospholipids. We previously found that these phospholipids inhibit spontaneous osteogenic differentiation of marrow stromal cells, suggesting that they may account for the clinical link between atherosclerosis and osteoporosis. Currently, anabolic agents that promote bone formation are increasingly used as a new treatment for osteoporosis. It is not known, however, whether atherogenic phospholipids alter the effects of bone anabolic agents, such as bone morphogenetic protein (BMP)-2 and parathyroid hormone (PTH). Therefore we investigated the effects of oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (ox-PAPC) on osteogenic signaling induced by BMP-2 and PTH in MC3T3-E1 cells. Results showed that ox-PAPC attenuated BMP-2 induction of osteogenic markers alkaline phosphatase and osteocalcin. Ox-PAPC also inhibited both spontaneous and BMP-induced expression of PTH receptor. Consistently, pretreatment of cells with ox-PAPC inhibited PTH-induced cAMP production and expression of immediate early genes Nurr1 and IL-6. Results from immunofluorescence and Western blot analyses showed that inhibitory effects of ox-PAPC on BMP-2 signaling were associated with inhibition of SMAD 1/5/8 but not p38-MAPK activation. These effects appear to be due to ox-PAPC activation of the ERK pathway, as the ERK inhibitor PD98059 reversed ox-PAPC inhibitory effects on BMP-2-induced alkaline phosphatase activity, osteocalcin expression, and SMAD activation. These results suggest that atherogenic lipids inhibit osteogenic signaling induced by BMP-2 and PTH, raising the possibility that hyperlipidemia and atherogenic phospholipids may interfere with anabolic therapy.
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PMID:Atherogenic phospholipids attenuate osteogenic signaling by BMP-2 and parathyroid hormone in osteoblasts. 1752 49

Calcitriol is a standard therapy for secondary hyperparathyroidism in chronic renal failure. We evaluated whether the effect of daily or intermittent calcitriol administration is more efficient in enhancing bone growth in renal failure with advanced secondary hyperparathyroidism in weanling 5/6 nephrectomized rats loaded with phosphorus to induce severe secondary hyperparathyroidism. The animals were treated daily or three times weekly with calcitriol for 4 weeks but the total weekly dose of calcitriol was the same. Although calcitriol increased the serum calcium, it did not lower parathyroid hormone (PTH) or improve tibia and body length. Animals with renal failure and advanced secondary hyperparathyroidism had decreased PTH/PTHrP, which was accompanied by an increase in the cyclin kinase inhibitor p57(Kip2). Calcitriol treatment upregulated the PTH/PTHrP receptor but also increased inhibitors of cell proliferation such as p21(Waf1/Cip1), IGFBP3, and FGFR3. Calcitriol also enhanced markers of chondrocyte differentiation, such as IGF1, Vitamin D receptor, FGF23, and bone morphogenetic protein-7. Receptor activator of nuclear factor-kappabeta ligand levels improved with calcitriol treatment but without changes in osteoprotegerin suggesting an enhancement of osteo/chondroclastogenesis and mineralization. Overall, both daily and intermittent calcitriol had similar effects on endochondral bone growth in phosphorus-loaded rats with renal failure.
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PMID:Bone growth during daily or intermittent calcitriol treatment during renal failure with advanced secondary hyperparathyroidism. 1771 61

In hypocalcaemia, elevated parathyroid hormone transitorily down-regulates the kidney vitamin D receptor, which returns to normal levels with the rise in serum extracellular calcium [Ca(2+)](e). In this study, we investigated the mechanism that underlies VDR increase in kidney in association with elevated [Ca(2+)](e). Examination of MAP kinase signals in a proximal tubule human kidney (HK-2G) epithelial cell line showed that treatment of [Ca(2+)](e) in the culture medium elevated phosphorylation of both ERK and p38 MAPKs. Blockade of p38 phosphorylation with SB203580 or SB202190 in turn abolished [Ca(2+)](e)-mediated VDR protein increase, while treatment with PD98059 and U0126, specifically blocked ERK phosphorylation, but had no effect on VDR stimulation by [Ca(2+)](e). Furthermore, SB203580 treatment potently repressed [Ca(2+)](e)-mediated activation of VDR promoter. We also demonstrate that si-RNA knock down of p38alpha completely diminished high [Ca(2+)](e)-mediated VDR induction. Direct CaSR involvement was demonstrated by using an si-RNA of CaSR that impeded [Ca(2+)](e)-mediated induction of VDR. In conclusion, a high extracellular [Ca(2+)](e) concentration in the physiological range is capable of directly increasing renal proximal VDR expression, and the induction mechanism requires activation of the CaSR and signal mediation by the p38alpha MAP kinase pathway.
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PMID:Extracellular calcium-sensing receptor activation induces vitamin D receptor levels in proximal kidney HK-2G cells by a mechanism that requires phosphorylation of p38alpha MAPK. 1797 68

An 80-year-old man presented with progressive fatigue. Blood tests showed that serum calcium was increased (2.93 mmol/l, normal range 2.20-2.55 mmol/l) and serum concentration of intact parathyroid hormone (iPTH) inappropriately high (198 pg/ml, normal range 15-85 pg/ml). Neck ultrasonography and Tc-MIBI scintigraphy revealed a right parathyroid adenoma and a multinodular goiter. Serum calcitonin was significantly increased (220 pg/ml, normal range<10 pg/ml). Concomitantly, a chest-abdominal computed tomography was performed and revealed a 22 mm right adrenal incidentaloma. The urinary catecholamines and metabolites were two-fold above the upper limit of normal. After right adrenalectomy which confirmed the diagnosis of pheochromocytoma, the patient underwent total thyroidectomy with dissection of the central lymph node compartment and right parathyroidectomy. On histopathologic examination, both thyroid lobes presented 13 foci of MTC without lymph node metastasis and the parathyroid gland presented a benign adenoma without hyperplasia. The patient underwent screening and genetic testing revealing a germ line C634 G RET mutation. The diagnosis of Men2a at the age of 80 years and the absence of lymph node metastasis of the multiple MTC in a carrier of C634G mutation were unusual and argued for the possible role of genetic modifier(s) in this MEN 2a patient.
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PMID:Multiple endocrine neoplasia type 2a and germ line C634G RET mutation diagnosed in an 80-year-old patient. 1920 92

As part of its catabolic action in bone, parathyroid hormone (PTH) inhibits extracellular matrix mineralization. We previously showed that PTH dose-dependently induces matrix gla protein (MGP) expression in osteoblasts and this induction is at least partially responsible for PTH-mediated inhibition of mineralization. Recently, we identified PKA and ERK/MAPK as the key signaling pathways involved in PTH regulation of MGP expression. The goal of this study was to further characterize the mechanism by which PTH stimulates expression of MGP. Deletion analysis of the murine Mgp gene promoter identified a PTH-responsive region between -173 bp and-49 bp. Using gel-mobility shift assays we found that Sp1/Sp3, and Runx2 bind to distinct sites within this region. Mutation of either the Sp or the Runx2 site reduced MGP induction by PTH, while mutation of both sites completely abolished PTH responsiveness. Overexpression of Runx2 or Sp1 activated the Mgp reporter, while Sp3 was a dose-dependent repressor of Sp1 and PTH-induced MGP expression. Collectively, these data show that PTH regulates MGP gene transcription in osteoblasts through altered activities of Sp and Runx2 transcription factors.
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PMID:Sp proteins and Runx2 mediate regulation of matrix gla protein (MGP) expression by parathyroid hormone. 1930 94

N-methyl-d-aspartate receptors (NMDAR) are tetrameric amino acid receptors which act as membrane calcium channels. The presence of the receptor has been detected in the principal organs responsible for calcium homeostasis (kidney and bone), pointing to a possible role in mineral metabolism. In the present work, the presence of the receptor was determined in normal parathyroid glands (PTG) by real-time PCR, immunoprecipitation, and immunohistrochemistry. Healthy animals showed a decrease in blood parathyroid hormone (PTH) levels 15 min after the treatment with NMDA. This effect was also observed in animals with high levels of PTH-induced EDTA injection, but not in uremic animals with secondary hyperparathyroidism (2HPT). Normal rat PTG incubated in media with low calcium concentration (0.8 mM CaCl2) showed a decrease in PTH release when NMDA was added to the media. This effect of NMDA was abolished when glands were coincubated with MK801 (a pharmacological blocker of the NMDA channel) or PD98059 (an inhibitor of the ERK-MAPK pathway). Glands obtained from animals with 2HPT showed no effect of NMDA in the in vitro release of PTH, together with a decrease in the expression of NMDAR1. In conclusion, NMDA receptor is present in PTG and is involved in the regulation of the PTH release. The mechanism by which NMDAR exerts its function is through the activation of the MAPK cascade. In uremic 2HPT animals the receptor expression is downregulated and the treatment with NMDA does not affect PTH secretion.
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PMID:N-methyl-D-aspartate receptors are expressed in rat parathyroid gland and regulate PTH secretion. 1935 80

Primary hyperparathyroidism (PHPT) is one of the most frequent endocrinological disorders. In PHPT, there is abnormal regulation of parathyroid hormone (PTH) by calcium, which translates into inappropriately high PTH secretion for the level of calcemia. Most patients with PHPT have increased serum PTH levels, with increases in serum calcium, especially ionic calcium. The incidence of PHPT rises with age, the mean age at diagnosis being 55 years. This disorder affects mainly women with a female-to-male ratio of approximately 3:1. Most (80-85%) of cases are produced by chief cell parathyroid adenomas. The factors involved in the genesis of PHPT are largely unknown. Gene mutations affecting oncogenes (cyclin D1, RET) or tumor suppressor genes (MEN1, HRPT2) are found in a minority of cases. These mutations are especially important in familial forms of PHPT, such as multiple endocrine neoplasia syndrome (MEN1, MEN2A). No mutations affecting the calcium-sensing receptor (CaSR) or vitamin D receptor (VDR) gene have been found. In parathyroid adenomas and hyperplasias, there may be abnormal Wnt signalling, with mutations of the coreceptor LRP5 gene and beta-catenin accumulation. Expression of the Klotho protein, which intervenes in serum calcium regulation, is reduced. Low levels of 25(OH) vitamin D frequently coexist, although whether vitamin D deficiency plays a pathogenic role in PHPT is unknown.
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PMID:[Concept, etiology and epidemiology of primary hyperparathyroidism]. 1962 54

The resorption, formation and maintenance of bone are coordinated by the action of several hormones, growth factors and transcription factors. Recent experiments based on genetically modified mouse models, gene microarrays and pharmacological intervention indicate that the epidermal growth factor receptor (EGFR) system plays important roles in skeletal biology and pathology. This network, including a family of seven growth factors - the EGFR ligands - and the related tyrosine kinase receptors EGFR (ERBB1), ERBB2, ERBB3 and ERBB4, regulates aspects such as proliferation and differentiation of osteoblasts, chondrocytes and osteoclasts, parathyroid hormone-mediated bone formation and cancer metastases in bone. Here, we summarize and discuss the role of the EGFR and its ligands in skeletal biology and pathology.
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PMID:The EGFR network in bone biology and pathology. 1981 18

Over the past few years there have been considerable advances in our understanding of the physiological regulation of mineral homeostasis. One of the most important breakthroughs is the identification of fibroblastic growth factor 23 (FGF23) and its role as a key regulator of phosphate and 1,25-dihydroxyvitamin D metabolism. FGF23 exerts its biological functions by binding to its cognate receptor in the presence of Klotho as a cofactor. FGF23 principally acts on the kidney to induce urinary phosphate excretion and suppresses 1,25-dihydroxyvitamin D synthesis, thereby indirectly modulating parathyroid hormone secretion. FGF23 also acts directly on the parathyroid to decrease parathyroid hormone synthesis and secretion. In patients with chronic kidney disease, FGF23 levels increase progressively to compensate for phosphate retention, but these elevated FGF23 levels fail to suppress the secretion of parathyroid hormone, particularly in the setting of uremia. Recent data suggest that this parathyroid resistance to FGF23 may be caused by decreased expression of Klotho-FGFR1 complex in hyperplastic parathyroid glands. This review summarizes recent insights into the role of FGF23 in mineral homeostasis and discusses the involvement of its direct and indirect interaction with the parathyroid gland, particularly focusing on the pathophysiology of secondary hyperparathyroidism in chronic kidney disease.
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PMID:FGF23-parathyroid interaction: implications in chronic kidney disease. 2001 May 46


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