Renal failure induces telomere shortening in the rat heart.

BACKGROUND: Renal failure aggravates pathological cardiac remodelling induced by myocardial infarction (MI). Cardiac remodelling is associated with telomere shortening, a marker for biological ageing. We investigated whether mild and severe renal failure shorten cardiac telomeres and excessively shorten telomeres after MI. METHODS: Rats were subjected to sham, unilateral (UNX) or 5/6th nephrectomy (5/6NX) to induce none, mild or severe renal failure. MI was induced by left coronary artery ligation. Renal function parameters and blood pressure were measured. DNA was isolated from non-infarcted cardiac tissue. Telomere length was assessed by quantitative polymerase chain reaction (PCR). RESULTS: Proteinuria was unchanged in UNX and MI compared with control, but strongly increased in 5/6NX, UNX+MI and 5/6NX+MI. Serum creatinine levels were increased fourfold in 5/6NX and tenfold in 5/6NX+MI. 5/6NX and groups with both renal failure and MI showed an approximate 20% reduction of telomere length, similar to the MI group. No excess telomere shortening was observed in hearts from rats with renal ablation after MI. CONCLUSION: Severe renal failure, but not mild renal failure, leads to shortening of cardiac telomeres to a similar extent as found after MI. Renal failure did not induce excessive telomere shortening after MI. (Neth Heart J 2009;17:190-4.).

Blood pressure and the susceptibility to renal damage after unilateral nephrectomy and L-NAME-induced hypertension in rats.

BACKGROUND: Fawn-hooded hypertensive (FHH) rats carry several genes which determine the susceptibility to develop renal damage, while renal damage resistant August x Copenhagen Irish (ACI) rats do not. Kidneys from heterozygous (FHH x ACI) F(1) rats, appear to be largely, but not completely, protected after blood pressure elevation with N(omega)-nitro-L-arginine methyl ester (L-NAME). We examined the role of an increased haemodynamic burden on the development of renal damage combining unilateral nephrectomy (UNx)- and L-NAME-induced hypertension in F(1) and ACI rats. Additionally, we investigated whether a general toxic effect of L-NAME, independent from a blood pressure elevation, caused renal damage in F(1) rats in animals simultaneously treated with L-NAME and the ACE inhibitor lisinopril. METHODS: Surgery was performed and L-NAME treatment (50 or 150 mg/l) was started at the age of 15 weeks. Systolic blood pressure (SBP) and urinary albumin excretion (UaV) were measured at 6 and 12 weeks post-UNx, followed by autopsy to determine the incidence of focal glomerulosclerosis (FGS). Using lisinopril (LIS) and L-NAME, another group of rats was evaluated at 12, 18, and 24 weeks after start of treatment. RESULTS: At similar L-NAME intake, F, rats developed more severe hypertension and more UaV than ACI rats. The increase in UaV per mmHg increase in SBP was fivefold higher in F(1) compared with ACI rats. In F(1) rats, the increase in UaV per percentage incidence increase in FGS was three times higher. In LIS treated F(1) rats, no significant UaV or FGS was measured at low blood pressure levels, indicating that renal damage in hypertensive F(1) rats is not a direct effect of L-NAME, but the result of the high blood pressure or another action of the renin-angiotensin system. CONCLUSION: We conclude that heterozygosity for the genes influencing the development of renal damage in the FHH strain increases the susceptibility of the kidney to develop damage after UNx combined with systemic hypertension.

Genetic susceptibility of the donor kidney contributes to the development of renal damage after syngeneic transplantation.

Solitary kidneys, especially in rats, appear vulnerable to develop functional and structural damage. However, differences in susceptibility exist between strains. It is not clear whether this is intrinsic to the kidney or due to environmental factors. Therefore, the aim of the present study was to investigate possible differences in genetic susceptibility for renal damage. By transplanting different rat donor kidneys into a normotensive, histocompatible recipient, the kidneys were exposed to the same blood pressure profiles, metabolic and hormonal environment. Kidneys from young adult hypertensive fawn-hooded (FHH) rats, a strain showing early onset renal damage, normotensive, renal damage-resistant August x Copenhagen-Irish (ACI), and (ACI x FHH) F1 donors were transplanted into male F1 recipients. The native kidneys of the recipients were removed 1 week after transplantation. The results were mutually compared and to their unilaterally nephrectomized littermates. Systolic blood pressure (SBP) and albuminuria (UaV) were determined at the time of transplantation and at 8 and 16 weeks. The histomorphologic analysis included the incidence of focal glomerulosclerosis (FGS), and determination of chronic transplant dysfunction according to the BANFF criteria. A negative impact of the transplantation technique in this syngeneic situation could not be detected as F1 transplants did not differ functionally and morphologically from their UNx controls. Transplanting an ACI kidney did not result in significant changes of SBP, UaV, and incidence of FGS compared to F1 transplants and ACI-UNx. In contrast, FHH kidneys did show a progressive increase of UaV and glomerulosclerosis and a significantly higher BANFF score, whereas the SBP did not differ from F1 transplants. The moderate hypertension seen in FHH did not travel with the kidney. Compared to the FHH-UNx rats, transplantation of a FHH kidney did significantly attenuate the increase of UaV and FGS. The susceptibility of the donor kidney appears to be an important factor in the development of chronic renal damage. This may play a role in the long-term functional changes seen after clinical renal transplantation.

Altered renal hemodynamics and impaired myogenic responses in the fawn-hooded rat.

The present study examined whether an abnormality in the myogenic response of renal arterioles that impairs autoregulation of renal blood flow (RBF) and glomerular capillary pressure (PGC) contributes to the development of renal damage in fawn-hooded hypertensive (FHH) rats. Autoregulation of whole kidney, cortical, and medullary blood flow and PGC were compared in young (12 wk old) FHH and fawn-hooded low blood pressure (FHL) rats in volume-replete and volume-expanded conditions. Baseline RBF, cortical and medullary blood flow, and PGC were significantly greater in FHH than in FHL rats. Autoregulation of renal and cortical blood flow was significantly impaired in FHH rats compared with results obtained in FHL rats. Myogenically mediated autoregulation of PGC was significantly greater in FHL than in FHH rats. PGC rose from 46 +/- 1 to 71 +/- 2 mmHg in response to an increase in renal perfusion pressure from 100 to 150 mmHg in FHH rats, whereas it only increased from 39 +/- 2 to 53 +/- 1 mmHg in FHL rats. Isolated perfused renal interlobular arteries from FHL rats constricted by 10% in response to elevations in transmural pressure from 70 to 120 mmHg. In contrast, the diameter of vessels from FHH rats increased by 15%. These results indicate that the myogenic response of small renal arteries is altered in FHH rats, and this contributes to an impaired autoregulation of renal blood flow and elevations in PGC in this strain.

Impaired autoregulation of renal blood flow in the fawn-hooded rat.

The responses to changes in renal perfusion pressure (RPP) were compared in 12-wk-old fawn-hooded hypertensive (FHH), fawn-hooded low blood pressure (FHL), and August Copenhagen Irish (ACI) rats to determine whether autoregulation of renal blood flow (RBF) is altered in the FHH rat. Mean arterial pressure was significantly higher in conscious, chronically instrumented FHH rats than in FHL rats (121 +/- 4 vs. 109 +/- 6 mmHg). Baseline arterial pressures measured in ketamine-Inactin-anesthetized rats averaged 147 +/- 2 mmHg (n = 9) in FHH, 132 +/- 2 mmHg (n = 10) in FHL, and 123 +/- 4 mmHg (n = 9) in ACI rats. Baseline RBF was significantly higher in FHH than in FHL and ACI rats and averaged 9.6 +/- 0.7, 7.4 +/- 0.5, and 7.8 +/- 0.9 ml. min-1. g kidney wt-1, respectively. RBF was autoregulated in ACI and FHL but not in FHH rats. Autoregulatory indexes in the range of RPPs from 100 to 150 mmHg averaged 0.96 +/- 0.12 in FHH vs. 0.42 +/- 0.04 in FHL and 0.30 +/- 0.02 in ACI rats. Glomerular filtration rate was 20-30% higher in FHH than in FHL and ACI rats. Elevations in RPP from 100 to 150 mmHg increased urinary protein excretion in FHH rats from 27 +/- 2 to 87 +/- 3 microg/min, whereas it was not significantly altered in FHL or ACI rats. The percentage of glomeruli exhibiting histological evidence of injury was not significantly different in the three strains of rats. These results indicate that autoregulation of RBF is impaired in FHH rats before the development of glomerulosclerosis and suggest that an abnormality in the control of renal vascular resistance may contribute to the development of proteinuria and renal failure in this strain of rats.

Genetic differences define severity of renal damage after L-NAME-induced hypertension in rats.

Genetic factors are important in determining the susceptibility to renal damage. In a backcross of the hypertensive and proteinuric fawn-hooded Erasmus University Rotterdam (FHH/EUR) rat with the normotensive, nonproteinuric August Copenhagen Irish (ACI/EUR) rat, two genes (denoted Rf-1 and Rf-2) were genetically mapped for parameters of functional and structural renal damage. The aim of the present study was to investigate the susceptibility to functional and structural renal damage in heterozygous (FHH X ACI) F1 rats compared with the parental FHH and ACI strains at similar levels of systolic BP (SBP). BP elevation was induced by chronic treatment with NG-nitro-L-arginine methyl ester (L-NAME) in either a low dose (LD, 75 to 100 mg/L) or a high dose (HD, 175 to 250 mg/L) in the drinking fluid. Survival of FHH rats and, to a lesser extent, F1 rats, was adversely affected by L-NAME treatment. All ACI rats except for one ACI-HD animal survived. In all strains, L-NAME caused a dose-dependent increase in SBP. At similar levels of SBP, the increase in functional renal damage, as indicated by the level of albuminuria, was higher in F1 compared with ACI, but lower compared with FHH. The same differences were found for the level of structural renal damage, as indicated by the incidence of glomerulosclerosis. Both the SBP and the average BP burden (SBP-Av), defined as SBP averaged over the period of follow-up, directly correlated with the level of albuminuria and incidence of glomerulosclerosis in all strains. However, the increase in the degree of renal damage per mmHg increase in SBP or SBP-Av was significantly higher in the F1 rats compared with ACI, but lower compared with FHH rats. Values for these F1 rats were closer to the ACI rats than to values for the FHH rats and increased above an SBP level of 180 mmHg. The F1 rats, being heterozygous for Rf-1 and Rf-2, as well as for other potential genes responsible for renal disease, were largely, but not completely, protected from hypertension-induced renal damage. It is concluded that complete susceptibility to hypertension-associated renal damage in rats primarily depends on the presence of predisposing genes for renal failure even after a significant increase in BP.

Neurotrophic ACTH4-9 analogue therapy normalizes electroencephalographic alterations in chronic experimental allergic encephalomyelitis.

Chronic experimental allergic encephalomyelitis (CEAE) is an established experimental model for multiple sclerosis (MS). The demyelinating lesions in the white matter of the central nervous system observed in CEAE and in MS are accompanied by various neurophysiological alterations. Among the best defined electrophysiological abnormalities are the changes in event-related potentials, in particular evoked potentials involving the spinal cord, i.e. motor and sensory evoked potentials. Less familiar are the changes observed in the electroencephalogram of CEAE-affected animals, which are also encountered in the human equivalent, MS. In the present experiment we evaluated the therapeutic value of a neurotrophic peptide treatment [H-Met(O2)-Glu-His-Phe-D-Lys-Phe-OH, an ACTH4-9 analogue] and its effect on the delayed flash visual evoked potentials (VEP) and power spectra of the electroencephalogram, during a 17-week follow-up of CEAE. CEAE animals treated with the neurotrophic peptide were protected against the development of neurological symptoms during the course of the demyelinating syndrome. VEPs of animals suffering from CEAE showed a delay of the latencies of the late components which was significantly counteracted by peptide treatment. The peak-to-peak amplitude of the VEP afterdischarge recorded from CEAE animals was significantly increased during the course of CEAE and correlated closely with the progression of the myelinopathy. Furthermore, CEAE animals showed an increase of electroencephalogram (EEG) beta activity of up to 500% as compared with the age-matched control group. This increase in beta power mainly consisted of a prevailing 20-21 Hz peak, a frequency that normally is not dominant in control EEG recordings of the rat during passive wakefulness. All these electrophysiological phenomena were absent in ACTH4-9 analogue-treated animals. The present findings underscore the potential importance of a neurotrophic peptide treatment in the pharmacotherapy of central demyelinating syndromes, and possibly of MS.

Difference in susceptibility of developing renal damage in normotensive fawn-hooded (FHL) and August x Copenhagen Irish (ACI) rats after N(omega)-nitro-L-arginine methyl ester induced hypertension.

Previous studies using the fawn-hooded hypertensive (FHH) rat have indicated that genetic factors appear to be important in determining the susceptibility to develop renal damage. This was further investigated by comparing the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME) induced hypertension on functional and structural renal damage in two normotensive strains, the resistant August x Copenhagen Irish rat (ACI) and the normotensive fawn-hooded (FHL) rat, which also appears to carry a susceptibility locus for renal failure. Male rats were studied during chronic treatment with L-NAME in either a low dose (LD, 75 to 100 mg/L drinking fluid) or a high dose (HD, 175 to 250 mg/L). Survival of FHL rats was adversely affected by L-NAME treatment. All FHL-HD and 6 of 14 FHL-LD rats died before the end of the 11 weeks of follow-up, whereas all treated ACI rats except for one ACI-HD animal survived. In both strains, L-NAME caused a dose dependent increase in systolic blood pressure (SBP). However, at similar levels of SBP, the increase in albuminuria (UaV) was significantly higher in FHL compared with ACI, as was the incidence of glomerulosclerosis (GS). Both the SBP and the blood pressure burden (SBP-Av), defined as SBP averaged over the period of follow-up, directly correlated with UaV and GS in both strains. However, the increase in the degree of renal damage per millimeter of mercury increase in SBP or SBP-Av was significantly higher in the FHL than in the ACI rats. Our findings clearly show that FHL rats are more susceptible to developing renal damage after induction of hypertension by chronic L-NAME treatment. We conclude that there is an interaction between blood pressure and the genetic susceptibility to renal disease in the FHL rat.

Functional and neurophysiological evidence of the efficacy of trophic pharmacotherapy using an adrenocorticotrophic hormone4-9 analog in experimental allergic encephalomyelitis, an animal model of multiple sclerosis.

Chronic experimental allergic encephalomyelitis (CEAE) is a well-established animal model for the human syndrome, multiple sclerosis. CEAE has striking histological, electrophysiological and clinical analogies with multiple sclerosis and is a valuable animal model for the preclinical pharmacotherapeutical development of new putative therapeutic agents. In this paper, we describe a neurotrophic repair approach in Lewis rats suffering from CEAE. The neurotrophic peptide used is a degradation resistant adrenocorticotrophic hormone4-9 analog. The development of CEAE was examined using a combination of clinical, functional and electrophysiological parameters including somatosensory and motor evoked potentials. The latencies and amplitudes of the various evoked potentials can provide quantitative, objective data regarding the involvement of different nerve tracts in CEAE and the effectiveness of the neurotrophic peptide. Repeated subcutaneous injections of the neurotrophic peptide suppressed the development of CEAE-related clinical symptoms, markedly improved motor performance and reduced the reaction time upon thermal stimulation as compared to saline-treated CEAE animals during a 17 week follow-up study. Prolonged onset latencies of corticomotor evoked potentials and peak latencies of somatosensory evoked potentials due to the demyelination were normalized upon peptide treatment. In addition, peptide treatment substantially prevented total blocking of the corticomotor pathway in CEAE-animals and reduced the attenuation of sensory evoked potentials-related peak amplitudes as compared to saline-treated animals. The functional and electrophysiological improvements observed in CEAE-animals treated with the adrenocorticotrophic hormone4-9 analog, suggest that a neurotrophic repair approach could be of great value to promote the restoration of function in a disabling demyelinating disorder.