Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated possible growth-promoting effects of angiotensin II (ANG II) in the pig tubular epithelial cell line LLC-PK1. 10(-6)-10(-10) M ANG II inhibited proliferation as measured by [3H]thymidine incorporation. However, the same concentration of peptide induced tubular hypertrophy as assessed by increases in de novo protein synthesis, total protein, and RNA content. These effects were mediated through AT1 receptors. Furthermore, LLC-PK1 cells exhibited specific binding sites for ANG II and expressed mature mRNA for the vascular smooth muscle AT1 receptor. ANG II incubation of cells significantly lowered intracellular cAMP, and the hypertrophogenic action of ANG II was abolished by co-incubation with the relative stable analogue dibutyryl-cAMP, suggesting the involvement of intracellular nucleotides in the signal-transduction processes leading to hypertrophy. Our results collectively suggest that ANG II is a hypertrophogenic growth factor for LLC-PK1 cells. Considering the importance of tubular hypertrophy in the progression of renal failure in many models, strategies to block the action of ANG II on tubular cells may offer an attractive alternative way to control deterioration of renal function besides modulation of haemodynamics.
Nephrol Dial Transplant 1993
PMID:Angiotensin II stimulates cellular hypertrophy of LLC-PK1 cells through the AT1 receptor. 768 Nov 54

The hydrolase aminopeptidase A is an important regulator of the renin-angiotensin system, since it inactivates its most vasoactive component angiotensin II (Ang II). A single i.v. injection of a monoclonal antibody against mouse aminopeptidase A (ASD-4) induces a membranous-like glomerulonephritis in mice, characterized by an acute albuminuria, that is not dependent on complement, the coagulation system, or inflammatory cells. We hypothesized that this albuminuria is the consequence of a reduction in aminopeptidase A enzyme activity, that might subsequently lead to an increase in Ang II levels. Aminopeptidase A enzyme activity was analysed in vitro by a fluorimetric enzyme assay and in vivo by enzyme histochemistry. The role of Ang II in the induction of albuminuria in this model was studied by measuring the renal aminopeptidase A mRNA expression in our model by a competitive PCR assay as an indirect measure of Ang II levels. In addition, the role of Ang II in this model was studied by preventing the formation of Ang II with the angiotensin-converting enzyme inhibitor enalapril or by blocking of the Ang II receptor with the AT1 receptor antagonist losartan. Only antibodies that were able to inhibit the aminopeptidase A enzyme activity in vitro and in vivo induced an acute albuminuria in mice. Renal aminopeptidase A mRNA expression was increased by injection of the anti-aminopeptidase A antibody. Both enalapril and losartan treatment reduced the acute albuminuria, measured 1 day after injection of a monoclonal antibody against aminopeptidase A, by 91% and 83%, respectively. It is concluded that the induction of acute albuminuria is correlated to the enzyme-inhibiting capacity of the anti-aminopeptidase A antibodies. This impaired enzymatic activity most likely leads to an increase in the levels of Ang II, the best known substrate of aminopeptidase A. The results of our additional experiments are in keeping with our hypothesis that Ang II mediates this acute albuminuria. Whether this occurs by an increase of blood pressure or by a growth factor-like effect remains to be defined by further studies in this model.
Nephrol Dial Transplant 1996 Nov
PMID:Inhibition of aminopeptidase A activity causes an acute albuminuria in mice: an angiotensin II-mediated effect? 894 74

At the present time we cannot assume that the proven benefits of ACEI on renal disease will be reproduced by using AT1-ra. With potentially differing modes of activity of these drugs, they cannot be seen as interchangeable and ACEI should remain the drug of choice in patients with progressive renal disease unless they are not tolerated. It is possible that AT1-ra may offer additional advantages in some patients or that synergy exists between the two agents, but this view will remain entirely speculative unless proper trials are conducted. Despite the results of the ELITE study [22], the uncertainty regarding the use AT1-ra in cardiovascular disease mirrors that of renal disease. This issue is obviously of relevance to the nephrologist in view of the spectrum of cardiac disease that accompanies chronic renal failure, such as left ventricular hypertrophy and cardiac failure, which provide multiple indications for manipulation of RAS. Despite their renoprotective effect, previous studies on ACEI [3,4] have not shown an overall reduction in mortality and this issue needs to be addressed in addition to renoprotection in studies comparing AT1-ra and ACEI.
Nephrol Dial Transplant 1999 Jan
PMID:Angiotensin converting enzyme inhibitors and angiotensin receptor (AT1) antagonists: either or both for primary renal disease? 1005 68

Multiple factors are involved in thrombus formation and require complex and highly therapeutic strategies. Platelet activation plays a critical role in the genesis of acute coronary syndromes involving not only platelets but also endothelial cells, leucocytes and erythrocytes. Angiotensin II (Ang II) is a vasoconstrictor that could participate in the thrombotic process. Platelets also express Ang II AT1 type receptors on their surface. Losartan is a non-peptidic inhibitor of AT1 receptors. It has been demonstrated that losartan reduced platelet aggregation induced by the thromboxane A2 (TXA2) analogue U46619. This effect was not observed with the losartan metabolite EXP 3174. The effect of losartan was assessed in binding studies in which losartan competitively inhibited the binding of [3H]U46619 to platelets in a dose-dependent manner. Irbesartan also inhibits the TXA2 receptor in platelets, an effect that was not obtained with the active form of candesartan, CV11974, and with valsartan. These results suggest that the structural requirements necessary to antagonize the TXA2/PGH2 platelet receptor may be different from those involved in AT1 receptor antagonism. The in vivo relevance of the in vitro findings has been confirmed by the fact that in vivo administration of losartan decreases P-selectin expression in platelets obtained from stroke-prone spontaneously hypertensive rats.
Nephrol Dial Transplant 2001
PMID:Angiotensin II AT(1) receptor antagonists and platelet activation. 1136 20

Accumulating evidence suggests that angiotensin II (ANG II) plays an important role in the complex affair of renal organogenesis. The renin-angiotensin system (RAS) is up-regulated during renal development and in the perinatal period. On the other hand, inhibition of the RAS, for example by angiotensin-converting enzyme (ACE) inhibitors, may produce specific renal abnormalities including abnormal renal vessels, failure to develop a renal pelvis and tubular atrophy associated with expansion of the interstitium. AT2 receptors are expressed abundantly during fetal development and are down-regulated markedly after birth, whereas the abundance of AT1 receptors increases as maturation proceeds. Mice with targeted deletions of genes for angiotensinogen or ACE revealed severe renal abnormalities. In contrast, AT1A, AT1B and AT2 receptor knockout animals exhibited milder abnormalities of the kidney. These findings suggest that AT1 and AT2 receptors are both involved in the development of the nephron, and that ANG II provides signals through both receptors. ANG II exerts in vitro growth-stimulatory effects on tubular cells. Moreover, ANG II induces synthesis of collagen type IV in tubular cells, a necessary prerequisite for successful basement membrane formation. These effects are mediated through AT1 receptors. Thus, it is feasible that blockade of the RAS during kidney organogenesis leads to a decrease in the growth factor ANG II that may be pivotal for tubular growth and differentiation. On the other hand, ANG II's growth-stimulatory effects through AT1 receptors may be counterbalanced by AT2 receptor-mediated apoptosis and growth inhibition. Therefore, alterations in AT2 receptor signalling may alter the delicate balance between growth stimulation and inhibition, leading to alterations in tubular formation.
Nephrol Dial Transplant 2002
PMID:Angiotensin II and tubular development. 1238 87

Angiotensin II (AngII) participates in the pathogenesis of renal diseases, through the regulation of two key processes inflammation and fibrosis. AT1 and AT2 are the main receptors of AngII. AT1 mediates most of the actions of AngII. This receptor regulates the expression of profibrotic factors, such as connective tissue growth factor (CTGF). The Smad signalling pathway and the Rho/Rho kinase system are two novel mechanisms involved in AngII-induced matrix regulation recently described. The role of AT2 receptors in renal pathophysiological processes is not fully elucidated. Experimental data suggest that AT2 receptors through activation of nuclear factor-kappaB participate in renal inflammatory cell recruitment. Studies in animal models of kidney injury have shown that the combined blockade of both AT1 and AT2 receptors, as well as the inhibition of the NF-kappaB pathway are necessary to stop the inflammatory process fully. On the whole, these data highlight the complex signalling systems activated by AngII and suggest novel potential targets to block fibrosis and inflammation in renal diseases.
Nephrol Dial Transplant 2006 Jan
PMID:Angiotensin II: a key factor in the inflammatory and fibrotic response in kidney diseases. 1628 Mar 70

Chronic rejection is a poorly understood entity albeit a frequent cause of graft failure. Despite the advent of new immunosuppressive agents, neither the slope of graft destruction nor the frequency is ameliorated. There are a number of hypothesis which try to explain the conundrum of chronic graft destruction: ongoing rejection, antibody-mediated rejection, poor choice of organs, hyperfiltration, calcineurin inhibitors (CNI) nephrotoxicity and non-compliance among them. None of these hypotheses can explain all features of the process, thus, it is likely that they act in combination. What seems to be clear is a beneficial effect of early angiotensin-converting enzyme (ACE)/AT1 blocker treatment. It is less clear, however, whether a reduction or a switch from CNIs to other immunosuppressants prolongs graft survival. This review highlights the pathophysiological aspects that are important for the development of chronic allograft damage in the context of possible treatment options.
Nephrol Dial Transplant 2013 Oct
PMID:Pathophysiology and treatment options of chronic renal allograft damage. 2362 70