Possible function of the protein bound to nuclear complementary RNA

It was demonstrated that individual renal endothelial dilatory function of the healthy rat predicts susceptibility to subsequent renal damage induced by 5/6 nephrectomy. In addition, it is reported that myocardial infarction (MI) that was performed upon unilateral nephrectomy (UNx) induced highly variable renal damage. Therefore, whether the variability in renal damage after MI could be explained by the variation in individual renal endothelial function before the induction of injury was studied. Endothelium-dependent relaxation to acetylcholine was investigated in vitro in small arteries that were isolated from the extirpated kidney at UNx. MI was induced 1 wk after UNx by ligation of the left coronary artery. Proteinuria and systolic BP were evaluated weekly for 16 wk thereafter using metabolic cages and the tail-cuff method, respectively. Upon termination of the study, focal glomerulosclerosis was evaluated by histology as an additional marker of renal damage. After MI, nephrectomized male Wistar rats (n = 15) gradually developed variable proteinuria, ranging from 20 to 507 mg/24 h at week 16, with an average systolic BP of 131 +/- 7 mmHg. The individual renal endothelial function of the healthy rats predicted the extent of renal damage in terms of proteinuria (r = -0.62, P = 0.008) and focal glomerulosclerosis (r = -0.70, P = 0.003). The individual level of renal endothelial function in the healthy rat is able to predict the severity of renal damage that is induced by MI. Further exploration of the underlying mechanisms may lead to discovery of preventive renoprotective therapies

The Realm and Frontiers of Mycosis Fungoides

Objectives Chronic renal failure (CRF) is associated with altered systemic arterial tone and hypertension. Myogenic constriction and endothelium-derived hyperpolarizing factor (EDHF)-dependent relaxation represent major vasoregulatory mechanisms in small systemic arteries. Elevated myogenic response and impaired EDHF might participate in the development of essential hypertension; however, their role in CRF-related hypertension is unknown. We investigated whether myogenic response and EDHF are altered in subtotally nephrectornized (sNX) rats and whether these changes are modifiable by chronic treatment with angiotensin-converting enzyme (ACE) inhibitor. Methods In a pressure arteriograph, myogenic constriction and EDHF-mediated relaxation were evaluated in small mesenteric arteries isolated from male Wistar rats 15 weeks after either sham operation (n = 7) (SHAM), sNX (n = 12) or sNX followed by 9 weeks of treatment with lisinopril (sNX + LIS, 2.5 mg/kg, n = 13). Results Surprisingly, myogenic response was reduced in hypertensive CRF rats (maximal myogenic tone: 37 +/- 2 and 18 +/- 4%, P <0.01; peak myogenic index: -0.80 +/- 0.08 and -0.40 +/- 0.12%/mmHg, P <0.05 in SHAM and sNX respectively). At the same time EDHF-mediated relaxation was also impaired (maximal response: 92 +/- 2 and 77 +/- 5%, P <0.01; pD(2): 6.5 +/- 0.1 and 5.9 +/- 0.1, P <0.05). Both myogenic response and EDHF were inversely related to the severity of renal failure and restored by treatment with lisinopril to levels found in SHAM animals. Conclusion Major constrictive (myogenic) and dilatory (EDHF) mechanisms of small systemic arteries are impaired in hypertensive CRF rats. These alterations do not seem to participate in the development of hypertension, being rather directly related to the severity of renal impairment. Both systemic vascular changes might be restored by renoprotective treatment with ACE inhibitor

Author index for volume 286

Susceptibility to renal injury varies among individuals. Previously, we found that individual endothelial function of healthy renal arteries in vitro predicted severity of renal damage after 5/6 nephrectomy. Here we hypothesized that individual differences in endothelial function in vitro and renal perfusion in vivo predict the severity of renal damage in a model of adriamycin-induced nephropathy. In three separate studies, the following baseline parameters were measured in healthy male Wistar rats: (1) acetylcholine (ACh)-induced relaxation in small renal arteries in vitro (n = 16) and the contribution of prostaglandins, nitric oxide (NO) and endothelium-dependent hyperpolarizing factor (EDHF) to the relaxation; (2) glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in spontaneously voiding rats in vivo (n = 16) and (3) the acute effect of the NO-synthase inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME, n = 12) on renal blood flow (RBF) as compared to vehicle infusion (n = 9). Following these measurements, adriamycin (1.75 mg/kg i.v.) was injected and subsequent renal damage after 6 weeks was related to the baseline parameters. Total ACh-induced (r = 0.51, P <0.05) and EDHF-mediated relaxation (r = 0.68, P <0.05), as well as ERPF (r = 0.66, P <0.01), positively correlated with the severity of proteinuria 6 weeks after injection. In contrast, pronounced baseline NO-mediated dilation was associated with lower proteinuria (r = 0.71, P <0.01). Nevertheless, an acute L-NAME infusion, strongly reducing RBF by 22 +/- 8%, during adriamycin administration provided protection against the development of proteinuria. Individual animals with pronounced baseline endothelial dilatory ability measured in vitro and high ERPF in vivo are vulnerable to renal damage after the adriamycin injection. Acute inhibition of NO during adriamycin administration, resulting in a decrease of RBF, protects against renal injury, probably by limiting the delivery of the drug to the kidney. Therefore, interindividual variability in renal haemodynamics might be crucially involved in susceptibility to nephrotoxic renal damag

Circulating Endothelial Progenitor Cells in Kidney Transplant Patients

Background: Kidney transplantation (RTx) leads to amelioration of endothelial function in patients with advanced renal failure. Endothelial progenitor cells (EPCs) may play a key role in this repair process. The aim of this study was to determine the impact of RTx and immunosuppressive therapy on the number of circulating EPCs. Methods: We analyzed 52 RTx patients (58613 years; 33 males, mean 6 SD) and 16 age- and gender-matched subjects with normal kidney function (57617; 10 males). RTx patients received a calcineurin inhibitor (CNI)-based (65%) or a CNI-free therapy (35%) and steroids. EPC number was determined by double positive staining for CD133/VEGFR2 and CD34/VEGFR2 by flow cytometry. Stromal cell-derived factor 1 alpha (SDF-1) levels were assessed by ELISA. Experimentally, to dissociate the impact of RTx from the impact of immunosuppressants, we used the 5/6 nephrectomy model. The animals were treated with a CNI-based or a CNI-free therapy, and EPCs (Sca+cKit+) and CD26+ cells were determined by flow cytometry. Results: Compared to controls, circulating number of CD34+/VEGFR2+ and CD133+/VEGFR2+ EPCs increased in RTx patients. There were no correlations between EPC levels and statin, erythropoietin or use of renin angiotensin system blockers in our study. Indeed, multivariate analysis showed that SDF-1 – a cytokine responsible for EPC mobilization – is independently associated with the EPC number. 5/6 rats presented decreased EPC counts in comparison to control animals. Immunosuppressive therapy was able to restore normal EPC values in 5/6 rats. These effects on EPC number were associated with reduced number of CD26+ cells, which might be related to consequent accumulation of SDF-1. Conclusions: We conclude that kidney transplantation and its associated use of immunosuppressive drugs increases the number of circulating EPCs via the manipulation of the CD26/SDF-1 axis. Increased EPC count may be associated to endothelial repair and function in these patients.

Tissue functions mediated by β3-adrenoceptors—findings and challenges

As β3-adrenoceptor agonists metamorphose from experimental tools into therapeutic drugs, it is vital to obtain a comprehensive picture of the cell and tissue functions mediated by this receptor subtype in humans. Human tissues with proven functions and/or a high expression of β3-adrenoceptors include the urinary bladder, the gall bladder, and other parts of the gastrointestinal tract. While several other β3-adrenoceptor functions have been proposed based on results obtained in animals, their relevance to humans remains uncertain. For instance, β3-adrenoceptors perform an important role in thermogenesis and lipolysis in rodent brown and white adipose tissue, respectively, but their role in humans appears less significant. Moreover, the use of tools such as the agonist BRL 37344 and the antagonist SR59230A to demonstrate functional involvement of β3-adrenoceptors may lead in many cases to misleading conclusions as they can also interact with other β-adrenoceptor subtypes or even non-adrenoceptor targets. In conclusion, we propose that many responses attributed to β3-adrenoceptor stimulation may need re-evaluation in the light of the development of more selective tools. Moreover, findings in experimental animals need to be extended to humans in order to better understand the potential additional indications and side effects of the β3-adrenoceptor agonists that are beginning to enter clinical medicine

Vascular endothelial and myogenic function in renal disease: Focus on individual susceptibility to organ damage

Chronic kidney disease (CKD) is currently viewed as a generalized vasculopathic state associated with multiple alterations in various vascular beds. Moreover, the kidney can be regarded as an organ, where vascular changes are immediately and sensitively detected by protein (albumin) excretion, already in early stages of vascular disease. The vascular changes have been often considered a consequence of renal disease. However, the fact that several forms of vascular dysfunction occur early in the pathophysiology of CKD has brought the possibility that vascular changes may actually preceed and maybe even determine the progression of renal end-organ damage. This thesis provides data on the role of intrarenal and systemic vascular reactivity in early renal pathology in animal models of experimental and spontaneous renal disease. Chapter 2 introduces the concept, in which microalbuminuria, an early marker of CKD, is associated with both renal and systemic vascular dysfunction. Furthermore, we suggest that therapies targeted to improve early endothelial dysfunction may provide benefit in the primary prevention of CKD and related cardiovascular alterations. Endothelial function predicts the susceptibility to renal end-organ damage. Early vascular changes observed in the individuals with microalbuminuria suggest the role of vascular alterations in the development of CKD. Development of renal damage varies among individuals despite similar levels of blood pressure and it has been proposed that genetic factors might be responsible for increased susceptibility to CKD. Previously, it has been shown that variability in endothelial function among healthy rats of outbred Wistar rat strain predicts the susceptibility of the individual animals to renal injury after 5/6 nephrectomy (5/6Nx). In chapter 3 we demonstrated the predictive property of intrarenal endothelial function in yet another model of experimental renal damage induced by combined unilateral nephrectomy (UnX) and myocardial infarction (MI). We found that individuals with pronounced endothelium-dependent vasodilation of small renal arteries developed lower proteinuria and glomerulosclerosis after UnX+MI. This correlation suggests the presence of an intrarenal vascular factor determining the susceptibility to renal damage induced by cardiac injury. Together with observations from the 5/6 nephrectomy model, it is suggested that hemodynamic alterations mediated by endothelial reactivity may play a role in the development of experimental end-organ damage irrespective of how this damage is inflicted. The present findings implicate that modulation of endothelial function might provide protection against the development of end-organ damage in patients after MI. In chapter 4 we tested the concept of the predictive value of endothelial function in an experimental model with a different etiology of renal damage, i.e., nephropathy induced by the nephrotoxic drug adriamycin. In contrast to previous models, the rats with prominent endothelial relaxation seem to be more prone to the development of renal damage after injection of adriamycin. These contrasting findings suggest that predictive value of renal vascular function is critically dependent on the type of renal injury and etiology of progressive renal damage. However, we additionally found a positive significant correlation between the resulting proteinuria and the level of renal blood flow measured before the induction of injury. This might indicate that in this model, the endothelium-mediated hemodynamic status of the kidney determines the extent of renal damage through regulation of drug delivery to the kidney. Yet, in agreement with hemodynamic models of 5/6Nx and UnX+MI, individuals with pronounced nitric oxide (NO)-mediated vasodilation also seem to be protected against the toxic renal damage, regardless of the total endothelium-mediated vasodilation. Therefore, NO seems to play a protective role in various models of renal injury. Thus, assessment of NO-mediated relaxation may provide more consistent information on the susceptibility to renal end-organ damage than total endothelial response. This is in line with the protective role of NO against renal damage, described by several other authors. Consequently, drugs aiming at increasing renal NO bioavailability might prove effective in prevention of renal end-organ damage, induced either by nephron number reduction, nephrotoxic drug or myocardial infarction. Endothelial and myogenic dysfunction precede end-organ damage in spontaneous renal disease. Spontaneous animal models prone to the development of renal damage provide a valuable tool to define the genetic background for susceptibility to renal injury. In line with the hypothesis of the predictive value of endothelial function for the development of renal damage, in chapter 5 we describe endothelial dysfunction, preceding the development of proteinuria in the Fawn Hooded hypertensive (FHH) rats, a model of spontaneous hypertension-associated renal disease, when compared to FHL rats, a related strain resistant to hypertension and renal impairment. In this case, however, rather than NO, excessive production of cyclooxygenase-derived constrictive prostanoids was responsible for the impaired renal endothelial vasodilation prior to the development of renal injury. This suggests a specific mechanism of vascular alteration, possibly related to minor elevations of systemic blood pressure in this inbred strain. Furthermore, in the same arteries prior to the development of renal damage, we observed impaired myogenic reactivity, an additional vasoactive mechanism probably involved in the altered renal hemodynamics, hyperfiltration and renal injury, as previously described in other models of spontaneous renal disease. Interestingly, both endothelial and VSMC-mediated changes were specific for the renal vasculature and were not observed in systemic resistance or large conduit arteries, arguing against an a priori relationship between renal and systemic vascular dysfunction in CKD. Yet, another endothelial mediator, EDHF, seems to be impaired in the early course of renal disease in small systemic arteries. This suggests that renal injury might be associated with early renal as well as systemic vascular changes. Myogenic response and EDHF are impaired in systemic vasculature in experimental CKD. Whereas renal vascular changes may determine the severity of renal end-organ damage, impaired systemic reactivity might participate in CKD-related complications, such as hypertension. In chapter 5 we found impaired systemic vascular reactivity in a model of spontaneous renal disease prior to the development of end-organ damage. In chapter 6 we explored the systemic vascular reactivity in the experimental model of 5/6 nephrectomy. Two principal local vasomotor mechanisms in small systemic resistance arteries, VSMC-mediated myogenic constriction and endothelium-mediated EDHF-dependent relaxation were concomitantly altered in this setting, arguing against the hypothesis of their mutual inverse relationship. In this case, myogenic reactivity represents rather a beneficial mechanism counteracting elevated peripheral resistance, whereas loss of EDHF might actively participate in the development of CKD-related cardiovascular problems. Importantly, renoprotective therapeutic intervention in the renin-angiotensin system reversed both systemic vascular changes providing a useful therapeutic strategy to prevent CKD-related cardiovascular alterations. Conclusions and future perspectives. The association of endothelial dysfunction with cardiovascular disease has represented one of the major issues of cardiovascular medicine in recent 20 years. Currently, it becomes more and more clear that vascular changes may be involved in earlier stages of chronic disease development and may even determine the susceptibility to organ damage. Based on our results, measurements of endothelial function may provide a useful prognostic tool to identify individuals prone to end-organ impairment. A similar concept has been proposed for endothelial function in cardiac and systemic arteries in predicting cardiovascular outcomes, however, the majority of studies included high risk individual in contrast to our healthy experimental animals. In kidney, our experimental results will have to be confirmed by human studies. Furthermore, a specific test of nitric oxide-mediated vasodilation should be preferred to total endothelium-mediated vasodilation, as the other endothelial mediators may not properly reflect the sensitivity to renal injury. Although it cannot be concluded from our experiments whether the observed variability in endothelial function is genetically determined, several other authors suggest that the decrease expression of nitric oxide synthase (NOS) is associated with susceptibility to renal damage. Moreover, clinical studies showed an association between polymorphisms of endothelial NOS and CKD in various patient populations. Additionally, endothelial function might be a determinant of renoprotective therapeutic response as suggested in chapter 7. Dietary or pharmacologic strategies, such as plant-derived antioxidants or drugs interfering with the renin-angiotensin system, known to interfere with endothelial function, may prove beneficial in primary preventive strategies against CKD and related cardiovascular events. In addition to the endothelium, VSMC-mediated myogenic response may provide a novel therapeutic target for prevention of early hyperfiltration and subsequent renal pathology. Further characterization of the heterogeneous mechanisms underlying arterial reactivity in various vascular beds will help to further define the intricate relation between renal and systemic vasculature and the role of vascular tone regulation in the development of chronic end-organ damage.

Desirable properties of β(3)-adrenoceptor agonists: Implications for the selection of drug development candidates

β(3)-adrenoceptor agonists are currently in clinical development for the treatment of overactive bladder and considered for several other indications. This Perspective discusses desirable properties of such drugs mainly based on the example of overactive bladder, but at least partly they should also be applicable to other indications of β(3)-adrenoceptor agonists or other drug classes and therapeutic areas. These include degree of selectivity for the molecular target in terms of affinity, intrinsic efficacy and ligand-directed signaling. The ability to cause agonist-induced desensitization and the potential impact of gene polymorphisms also need to be considered. Depending on intended indication, specific pharmacokinetic considerations may also apply. These findings challenge the usefulness of high-throughput screening assays based upon a single molecular response in an artificial system and emphasize the need for early use of in vivo testing in species considered to be predictive for the human situatio

β-adrenoceptor agonist effects in experimental models of bladder dysfunction

β-adrenoceptor stimulation can enhance the storage function of the urinary bladder by acting on detrusor smooth muscle tone, mediator release from the urothelium and/or afferent nerve activity. In humans this may occur predominantly if not exclusively via the β₃-subtype. The effects of β-adrenoceptor agonists including several β₃-selective agonists have been studied in vitro and in vivo, in healthy animals of both genders and various age groups and in a wide range of animal (mostly rat) models of genetic or acquired bladder dysfunction. Such models included bladder irritation by intravesical instillation of acetic acid or prostaglandin E₂, bladder outlet obstruction, stroke, diabetes, spontaneously hypertensive rats, and NO synthase inhibition. Across all of these models β-adrenoceptor agonists had effects consistent with improved bladder storage function. β₃-adrenoceptor effects are resistant to agonist-induced desensitization in many cell types, but whether this also applies to the human bladder is unknown. The efficacy of β-adrenoceptor agonists appears to be largely unaffected by common polymorphisms of the β₃-adrenoceptor gene. Taken together these findings suggest that β₃-adrenoceptor agonists may become useful drugs for the treatment of bladder storage dysfunction, a view supported by recent phase III clinical studies for one such agent, mirabegro