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Query: UMLS:C0002871 (anemia)
 52,094 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A model is proposed for the role of the kidney in the control of erythropoietin production in which the initial trigger is an oxygen deficit created by anemia, hypobaria or ischemia. It is postulated that hypoxia creates a decrease in the oxygen level in a critical renal sensor cell, perhaps in the glomerular tuft, which eventually leads to the production of prostacyclin. It is possible that the endothelial cell in the glomerular tuft responds to this oxygen deficit to produce prostacyclin to trigger erythropoietin production. Recent studies on prostaglandin synthesis by human isolated glomeruli indicate that the most abundant prostanoid synthesized by the glomerular tuft cells was 6-keto PGF1 alpha, a metabolite of prostacyclin (PGI2). PGI2 has also been reported to be produced by isolated vascular endothelial cells. The mechanism by which hypoxia may initiate the synthesis and/or release of prostaglandins and prostacyclin in the renal cell has not been elucidated. Significant to erythropoietin production is the production by hypoxia of prostacyclin which eventually leads to the production of the metabolite 6-keto PGE1. We further propose that 6-keto PGE1 is the prostanoid which activates a specific cell membrane adenylate cyclase, causing the conversion of ATP to cyclic AMP. This is a very critical step in that there must be a sufficient amount of ATP remaining to generate cyclic AMP in order for erythropoietin biosynthesis to occur with the reduced level of ATP which may have caused a perturbation of the cell membrane. The elevated cyclic AMP leads to the activation of protein kinases which are essential in phosphorylating the lysosomal hydrolases released by hypoxia into the cytosol of the cell and may be the precursors of erythropoietin. Neutral proteases and lysosomal hydrolases, documented triggers of erythropoietin production, have been demonstrated to be elevated in the kidney after hypoxia. The mechanism of labilization and release of these enzymes from the renal lysosomes has been postulated to be related to increases in cyclic GMP levels in a renal cell. Hypoxia causes the release of renal lysosomal hydrolases which then undergo phosphorylation through activation by protein kinases following prostanoid stimulation of renal adenylate cyclase to generate cyclic AMP, resulting in increased biosynthesis of erythropoietin.
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PMID:Prostanoid activation of erythropoiesis. 654 29

A model has been presented for the role of the kidney in the physiologic and pathophysiologic control of erythropoiesis. It is postulated that an oxygen deficit created by anemia or hypobaric hypoxia results in the release of prostacyclin and its metabolite 6-keto PGE1, and the release of PGE2 with ischemic hypoxia. Prostacyclin, 6-keto-PGE1, or PGE2 activation of adenylate cyclase, an increase in cyclic AMP, activation of a protein kinase and the phosphorylation of hydrolases, which have been released from lysosomes by hypoxia, lead to increased biosynthesis of erythropoietin (Ep). The mechanism of labilization of lysosomes and the release of hydrolases from these cell organelles is postulated to be related to increases in cyclic GMP levels in a renal cell. An Ep-producing human renal carcinoma cell line grown in tissue culture has been demonstrated to produce significant amounts of PGE2. Meclofenamate, an inhibitor of prostaglandins synthesis, was found to inhibit in vitro production of PGE2, Ep, and dome formation in these renal carcinoma cells, giving support to our hypothesis that pathophysiologic production of Ep tumor cells depends upon prostaglandins production. An Ep-producing clone from this renal carcinoma cell line has been developed that contains low electron density (LED) cells after the cells reach confluency, which show a cytoplasm, with abundant and widely dilated endoplasmic reticulum, an oval nucleus, dispersed chromatin, and prominent nucleoli. These are the cells responsible for dome formation and Ep production. Non-EP-producing clones have also been produced from this renal carcinoma cell line, which did not produce domes even at high cell density and had a distinctly different cell type than the Ep-producing clone. Thus, it is postulated that prostacyclin (PGI2) and its metabolite 6-keto PGE1 play a significant role in hypoxic hypoxia stimulation of Ep production and PGE2 is involved in ischemic hypoxia and renal carcinoma cell production of Ep. A modulating effect of PGE2 and PGD2, the two primary bone marrow prostaglandins, has been proposed in Ep stimulation of the erythroid progenitor cell compartment (CFU-E and BFU-E).
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PMID:Effects of prostaglandins on erythropoiesis. 654 52

The common underlying heart diseases were ischemic heart disease (39%), valvular heart disease (27%), hypertensive heart disease (10%) in 104 patients (mean age 79 yrs) with congestive heart failure (CHF). Cardiomyopathy (5%) and congenital heart disease (2%) such as atrial septal defect were less common. In addition, many extracardiac diseases including anemia, hypothyroidism, renal failure and pulmonary disease contributed to the etiology of CHF in the elderly. Cardiac amyloidosis should be considered as an uncommon cause of refractory CHF. While the precipitating factor was not found in half of the 104 patients with CHF, the most common factors were respiratory infection, myocardial ischemia and arrhythmia. In addition, inappropriate drug usage including poor drug compliance, the use of beta-blockers and excessive intake of sodium and fluid precipitated or exacerbated heart failure. Renal failure was a most important complication and predisposed to refractory CHF. Aged patients with mild CHF (NYHA class II) showed an insufficient production of cyclic AMP and GMP in proportion to the increases of norepinephrine and atrial natriuretic peptide in comparison with health aged subjects after the submaximal treadmill exercise test. This finding may suggest that an inadequate compensation of neurohumoral factors is prone to cause CHF in the elderly. Appropriate management of acute CHF in the elderly begins with recognition of the underlying heart disease, complications and the severity of cardiac function. In addition to medical management including loop diuretics, vasodilator, beta-receptor agonist and phosphodiesterase inhibitor, cases associated with respiratory and renal failure require mechanical ventilation and continuous hemofiltration.
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PMID:[The etiology and management of congestive heart failure in the elderly]. 820 67

Chronic exposure of adult rats to dietary intake of cadmium (15 mg CdCl2/day/kg for 30 days) leads to development of anemia and thrombocytosis. Anemia is characterized by significant reticulocytosis (13.1 +/- 1.0%), anysocytosis, poikilocytosis, iron deficiency and marked alterations of antioxidant and metabolic status of red blood cells. Activities of SOD, catalase, GPx and GR were significantly increased in red blood cells of cadmium-treated rats. In treated animals cadmium induced an increase of red cell reduced and oxidized glutathione with no changes of GSSG/GSH ratio. However, significant reduction of lipid peroxidation was found. Plasma levels of tocopherol and ascorbate, as well as activity of glutathione-S-transferase, were all significantly increased in cadmium-treated rats. The energy metabolism of red blood cells was deeply altered in cadmium-treated rats. The levels of ATP, ADP, AMP and TAN were significantly increased while ATP/ADP ratio and adenylate energy charge (AEC) were significantly reduced. The level of 2,3-BPG was somewhat lower, but 2,3-BPG/Hb ratio was considerably higher, in red blood cells of cadmium-treated rats.
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PMID:Cadmium-induced changes of antioxidant and metabolic status in red blood cells of rats: in vivo effects. 837 Apr 23

Adenosine exerts various effects via membrane receptors in the kidney. It reduces the glomerular filtration rate by altering the resistance of the glomerular arterioles, and it inhibits the release of renin as well as neurotransmission. Adenosine receptors have been further found at different levels of the nephron as well as in glomerular cells. Little is known concerning the mechanisms that regulate the extracellular concentration of adenosine, namely, its production, transport, and catabolism. In the present review we first summarize the pathways of adenosine formation. Then we focus on the ecto-5'-nucleotidase, which seems to represent the major source of extracellular adenosine in the kidney; that enzyme is present in tubular luminal membranes, in fibroblasts, and in mesangial cells. In tubules the enzyme probably plays a role in the salvage of nucleotides present in the primary urine. The activity in fibroblasts is strategically located to convert any AMP released by tubules into adenosine in the close vicinity of glomerular arterioles, and it probably plays a predominant role in most of the regulatory mechanisms involving adenosine. Ecto-5'-nucleotidase activity in fibroblasts increases in anemia, maybe as a response to local hypoxia.
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PMID:Distribution and regulation of renal ecto-5'-nucleotidase: implications for physiological functions of adenosine. 845 51

Information on morphological and functional effects of anemia in kidney is scarce, although this organ plays a major role in erythropoietin production, which is strongly stimulated in anemia. We undertook a morphological study of kidneys of anemic rats. Anemia was induced by X-irradiation and subsequent injection of a hemolytic drug. The most striking effects of anemia on renal morphology were damages in the proximal tubule and a volume increase of the peritubular space. These effects were evident only in the cortical labyrinth. Morphometry showed that the enlargement of the peritubular space reflected an increase of the volumes of both capillaries and interstitium. The structural changes in the cortical interstitium were associated with increased activity of the ecto-5'-nucleotidase in the fibroblasts. We suggest that hypoxia accounts for most of the observed alterations. The hypoxic proximal tubule might release the nucleotide AMP, which would be hydrolyzed to adenosine by the ecto-5'-nucleotidase in the interstitium. Adenosine has been reported to trigger the synthesis of erythropoietin and the growth of blood capillaries.
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PMID:Effects of anemia on morphology of rat renal cortex. 847 74

Chicken anemia virus (CAV) is a small circular single-stranded DNA virus with a single promoter-enhancer region containing four consensus cyclic AMP response element sequences (AGCTCA), which are similar to the estrogen response element (ERE) consensus half-sites (A)GGTCA. These sequences are arranged as direct repeats, an arrangement that can be recognized by members of the nuclear receptor superfamily. Transient-transfection assays which use a short CAV promoter construct that ended at the transcription start site and drive expression of enhanced green fluorescent protein (EGFP) showed high basal activity in DF-1, LMH, LMH/2A, and primary theca and granulosa cells. The estrogen receptor-enhanced cell line, LMH/2A, had significantly greater expression than LMH cells, and this expression was significantly increased with estrogen treatment. A long promoter construct which included GGTCA-like sequences downstream of the first CAV protein translation start site was found to have significantly less EGFP expression in DF-1 cells than the short promoter, which was largely due to decreased RNA transcription. DNA-protein binding assays indicated that proteins recognizing a consensus ERE palindrome also bind GGTCA-like sequences in the CAV promoter. Estrogen receptor and other members of the nuclear receptor superfamily may provide a mechanism to regulate CAV activity in situations of low virus copy number.
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PMID:Positive and negative regulation of chicken anemia virus transcription. 1570 5

We have proposed an extension to the Q-learning algorithm that incorporates the existing clinical expertise into the trial-and-error process of acquiring an appropriate administration strategy of rHuEPO to patients with anemia due to ESRD. The specific modification lies in multiple updates of the Q-values for several dose/response combinations during a single learning event. This in turn decreases the risk of administering doses that are inadequate in certain situations and thus increases the speed of the learning process. We have evaluated the proposed method using a simulation test-bed involving an "artificial patient" and compared the outcomes to those obtained by a classical Q-learning and a numerical implementation of a clinically used administration protocol for anemia management. The outcomes of the simulated treatments demonstrate that the proposed method is a more effective tool than the traditional Q-learning. Furthermore, we have observed that it has a potential to provide even more stable anemia management than the AMP.
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PMID:Using clinical information in goal-oriented learning. 1744 6

Hepcidin is a peptide hormone that is secreted by the liver and controls body iron homeostasis. Hepcidin overproduction causes anemia of inflammation, whereas its deficiency leads to hemochromatosis. Inflammation and iron are known extracellular stimuli for hepcidin expression. We found that endoplasmic reticulum (ER) stress also induces hepcidin expression and causes hypoferremia and spleen iron sequestration in mice. CREBH (cyclic AMP response element-binding protein H), an ER stress-activated transcription factor, binds to and transactivates the hepcidin promoter. Hepcidin induction in response to exogenously administered toxins or accumulation of unfolded protein in the ER is defective in CREBH knockout mice, indicating a role for CREBH in ER stress-regulated hepcidin expression. The regulation of hepcidin by ER stress links the intracellular response involved in protein quality control to innate immunity and iron homeostasis.
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PMID:ER stress controls iron metabolism through induction of hepcidin. 2010 10

The circulating peptide hormone hepcidin maintains systemic iron homeostasis. Hepcidin production increases during inflammation and as a result of endoplasmic reticulum (ER) stress. Elevated hepcidin levels decrease dietary iron absorption and promote iron sequestration in reticuloendothelial macrophages. Furthermore, increased plasma hepcidin levels cause hypoferremia and the anemia associated with chronic diseases. The signal transduction pathways that regulate hepcidin during inflammation and ER stress include the IL-6-dependent STAT-3 pathway and the unfolded protein response-associated cyclic AMP response element-binding protein-H (CREBH) pathway, respectively. We show that carbon monoxide (CO) suppresses hepcidin expression elicited by IL-6- and ER-stress agents by inhibiting STAT-3 phosphorylation and CREBH maturation, respectively. The inhibitory effect of CO on IL-6-inducible hepcidin expression is dependent on the suppressor of cytokine signaling-3 (SOCS-3) protein. Induction of ER stress in mice resulted in increased hepatic and serum hepcidin. CO administration inhibited ER-stress-induced hepcidin expression in vivo. Furthermore, ER stress caused iron accumulation in splenic macrophages, which could be prevented by CO. Our findings suggest novel anti-inflammatory therapeutic applications for CO, as well as therapeutic targets for the amelioration of anemia in the hypoferremic condition associated with chronic inflammatory and metabolic diseases.
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PMID:Pretreatment with CO-releasing molecules suppresses hepcidin expression during inflammation and endoplasmic reticulum stress through inhibition of the STAT3 and CREBH pathways. 2226 59


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