Tight blood pressure control decreases apoptosis during renal damage

Sex differences in apoptosis do not contribute to sex differences in blood pressure or renal T cells in spontaneously hypertensive rats

Apoptosis is a physiological and anti-inflammatory form of cell death that is indispensable for normal physiology and homeostasis. Several studies have reported aberrant activation of apoptosis in various tissues at the onset of hypertension. However, the functional significance of apoptosis during essential hypertension remains largely undefined. The current study was designed to test the hypothesis that apoptosis contributes to sex differences in blood pressure and the T cell profile in spontaneously hypertensive rats (SHR). Apoptosis was measured in kidney, aorta and spleen of 13-week-old adult hypertensive male and female SHR. Female SHR had greater renal and aortic apoptosis compared to age-matched males; apoptosis in the spleen was comparable between the sexes. Based on well-established sex differences in hypertension, we tested the hypothesis that greater apoptosis in female SHR contributes to the lower BP and pro-inflammatory profile compared to males. Male and female SHR were randomized to receive vehicle or ZVAD-FMK, a cell permeable pan-caspase inhibitor, in established hypertension from 13 to 15 weeks of age or at the onset of hypertension from 6 to 12 weeks or age. Treatment with ZVAD-FMK lowered renal apoptosis in both studies, yet neither BP nor renal T cells were altered in either male or female SHR. These results suggest that apoptosis does not contribute to the control or maintenance of BP in male or female SHR or sex differences in renal T cells.

Incidence and Predictors of Chronic Kidney Disease among Diabetes Mellitus Patients: A Retrospective Follow-Up Study at a Tertiary Health-Care Setting of Ethiopia

BACKGROUND

Chronic kidney disease (CKD) is one of the most common microvascular complications of diabetes mellitus (DM) and it is a major health burden worldwide. Despite the increasing trend of microvascular complications in developing countries, there is limited evidence on predictors of CKD among diabetic patients in Ethiopia. Therefore, this study was aimed to assess the incidence and predictors of CKD among DM patients.

METHODS

A retrospective follow-up study was conducted among type 1 and type 2 DM patients in Southwest Ethiopia. A total of 437 newly-diagnosed diabetes patients were selected using a simple random sampling technique. Data were extracted from patients' medical records. Cox proportional hazard model was fitted and a 95% confidence interval was used to select significant variables.

RESULTS

Overall, 15.56% of patients developed CKD, with an incidence rate of 2.29 per 1,000 person-month (PM) (95% CI=1.79-2.93). Female sex (AHR=0.51, 95% CI=0.27-0.94) was found to be a protective factor of CKD, while positive proteinuria (AHR=2.85, 95% CI=1.48-5.55), having hypertension (HTN) (AHR=2.31, 95% CI=1.03-5.56), and high-density lipoprotein cholesterol (HDL-C) <40 mg/dL (AHR=3.19, 95% CI=1.73-5.98) were significant predictors of CKD.

CONCLUSION

CKD among DM patients continues to be a significant public health problem in health-care settings of Ethiopia. The current study found being female was protective, while positive proteinuria, HTN, and HDL-C <40 mg/dL were risk factors for CKD. We recommend health professionals to give more attention to DM patients with the identified risk factors.

Hypertension and the Kidney: Reduced Kidney Mass Is Bad for Both Normotensive and Hypertensive Rats

BACKGROUND

Hypertension is a leading cause of chronic kidney disease worldwide. Early studies demonstrated the short-term effects of hypertension on kidney function and morphology in ablative nephropathy. The aim of this study was to investigate the long-term consequences of hypertension in 5/6 nephrectomy (5/6NE) model.

METHODS

Reduction of the kidney mass by 5/6NE was created in spontaneous hypertensive rats (SHR) and genetically similar normotensive Wistar Kyoto (WKY) rats. Blood pressure, serum creatinine (SCr), hematuria, and proteinuria were monitored weekly for 23 weeks. Kidney morphology was assessed at the end of the study. Sham-operated rats from both strains were used as controls.

RESULTS

Rats with 5/6NE had increased SCr, blood pressure, hematuria, and proteinuria in both SHR and WKY. Even though the SCr levels and blood pressure were greater in 5/6NE SHR as compared with 5/6NE WKY rats, absolute changes from sham-operated rats were not statistically significant between these 2 groups. 5/6NE SHR had earlier onset and higher proteinuria than 5/6NE WKY rats. Hematuria was similar in 5/6NE SHR and 5/6NE WKY rats. However, 5/6NE SHR had enlarged glomeruli, increased interstitial fibrosis, and prominent intimal thickening in the small arteries/arterioles as compared with 5/6NE WKY rats.

CONCLUSIONS

The long-term severity of kidney injury correlated with higher blood pressure. Reduction of the kidney mass increases SCr, hematuria, proteinuria, and blood pressure in both normotensive and hypertensive rats. Histological assessment provides better information about underlying chronic kidney injury than actual changes in SCr and urinalysis.

Induction of Tet3-dependent Epigenetic Remodeling by Low-dose Hydralazine Attenuates Progression of Chronic Kidney Disease

Progression of chronic kidney disease remains a principal problem in clinical nephrology and there is a pressing need for novel therapeutics and biomarkers. Aberrant promoter CpG island methylation and subsequent transcriptional silencing of specific genes have emerged as contributors to progression of chronic kidney disease. Here, we report that transcriptional silencing of the Ras-GTP suppressor RASAL1 contributes causally to progression of kidney fibrosis and we identified that circulating methylated RASAL1 promoter DNA fragments in peripheral blood correspond with levels of intrarenal levels of RASAL1 promoter methylation and degree of fibrosis in kidney biopsies, enabling non-invasive longitudinal analysis of intrarenal CpG island methylation.

Retrospective analysis of patients with hypertensive nephrosclerosis revealed that circulating methylated RASAL1 promoter DNA fragments in peripheral blood decrease with Dihydralazine treatment in patients with hypertensive nephrosclerosis, and provided evidence that low-dose Dihydralazine delays decline of excretory kidney function, whereas Dihydralazine at standard doses had no protective effect. We demonstrate that the protective effect of Dihydralazine is due to induction of endogenous Tet3/Tdg-mediated DNA-de-methylation activity reversing aberrant promoter CpG island methylation, while HIF1α induction at standard doses counterbalances its protective activity. We conclude that RASAL1 promoter methylation is a therapeutic target and a biomarker of renal fibrosis. Our study suggests that therapeutic use of low-dose Dihydralazine in patients with chronic kidney disease and fibrosis deserves further consideration.

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Aberrant RASAL1 promoter methylation contributes causally to progression of kidney fibrosis.

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Degree of intrarenal RASAL1 methylation is reflected by levels of circulating methylated RASAL1 promoter fragments.

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Low-dose Hydralazine induces endogenous Tet3-dependent de-methylation and inhibits progression of kidney fibrosis.

Loss of oxidative stress tolerance in hypertension is linked to reduced catalase activity and increased c-Jun NH2-terminal kinase activation

Hypertension is accompanied by increased levels of reactive oxygen species, which may contribute to progressive renal injury and dysfunction. Here we tested the hypothesis that sensitivity to exogenous hydrogen peroxide (H(2)O(2)) is enhanced in immortalized renal proximal tubular epithelial cells from spontaneously hypertensive rats (SHR) compared to normotensive control Wistar Kyoto rats (WKY). We found that SHR cells were more sensitive to H(2)O(2)-induced cell death than WKY cells. Lower survival in SHR cells correlated with increased DNA fragmentation, chromatin condensation, and caspase-3 activity, indicating apoptosis. H(2)O(2) degradation was slower in SHR than in WKY cells, suggesting that reduced antioxidant enzyme activity might be the basis for their increased sensitivity. In fact, catalase activity was downregulated in SHR cells, whereas glutathione peroxidase activity was similar in both cell types. We next examined whether MAPK signaling pathways contributed to H(2)O(2)-mediated apoptosis. Inhibition of c-Jun NH(2)-terminal kinase (JNK) with SP600125 partially rescued H(2)O(2)-induced apoptosis in WKY but not in SHR cells. In addition, p54 JNK2 isoform was robustly phosphorylated by H(2)O(2), this effect being more pronounced in SHR cells. Together, these results suggest that the survival disadvantage of SHR cells upon exposure to H(2)O(2) stems from impaired antioxidant mechanisms and activated JNK proapoptotic signaling pathways.

Regression of albuminuria and hypertension and arrest of severe renal injury by a losartan-hydrochlorothiazide association in a model of very advanced nephropathy

Treatments that effectively prevent chronic kidney disease (CKD) when initiated early often yield disappointing results when started at more advanced phases. We examined the long-term evolution of renal injury in the 5/6 nephrectomy model (Nx) and the effect of an association between an AT-1 receptor blocker, losartan (L), and hydrochlorothiazide (H), shown previously to be effective when started one month after Nx. Adult male Munich-Wistar rats underwent Nx, being divided into four groups: Nx+V, no treatment; Nx+L, receiving L monotherapy; Nx+LH, receiving the L+H association (LH), and Nx+AHHz, treated with the calcium channel blocker, amlodipine, the vascular relaxant, hydralazine, and H. This latter group served to assess the effect of lowering blood pressure (BP). Rats undergoing sham nephrectomy (S) were also studied. In a first protocol, treatments were initiated 60 days after Nx, when CKD is at a relatively early stage. In a second protocol, treatments were started 120 days after Nx, when glomerulosclerosis and interstitial fibrosis are already advanced. In both protocols, L treatment promoted only partial renoprotection, whereas LH brought BP, albuminuria, tubulointerstitial cell proliferation and plasma aldosterone below pretreatment levels, and completely detained progression of renal injury. Despite normalizing BP, the AHHz association failed to prevent renal damage, indicating that the renoprotective effect of LH was not due to a systemic hemodynamic action. These findings are inconsistent with the contention that thiazides are innocuous in advanced CKD. In Nx, LH promotes effective renoprotection even at advanced stages by mechanisms that may involve anti-inflammatory and intrarenal hemodynamic effects, but seem not to require BP normalization.

Amylin prevents TRAIL-mediated apoptotic effects of reserpine in the rat gastric mucosa

We have previously shown that amylin has a protective effect upon the damaged rat gastric mucosa via a cytokine-mediated mechanism. Here, the effects of amylin on the proapoptotic cytokine TNF-related-apoptosis-inducing-ligand (TRAIL) were tested in the rat gastric mucosa damaged by reserpine administration in vivo. Intraperitoneal administration of reserpine in adult male Sprague-Dawley rats resulted in increased TRAIL expression in the gastric mucosa. Immunohistochemistry showed that the TRAIL death-receptor 5 (DR5) was constitutively expressed by the mucosa cells. Western blot showed that pretreatment of reserpine-treated rats with amylin was associated with attenuated expression of TRAIL. In the same samples, we also investigated about TRAIL-related signaling and observed that activation of caspases-8 and -3 occurs in parallel to increased TRAIL expression in rats treated with reserpine. Similarly to the latter, activation of caspases was attenuated in rats pretreated with amylin. Treatment with reserpine was associated with increased expression of the proapoptotic protein Bax, whereas that of the antiapoptotic protein Bcl-2 was significantly decreased. Amylin prevented the effects of reserpine on these genes. Reserpine sets into motion mechanisms of apoptosis in the rat gastric mucosa, which appear mediated, at least in part, by TRAIL. In addition, TRAIL downstream signaling is activated along with subversion of gene expression related to apoptosis. Amylin was able to prevent detrimental effects of reserpine. Finally, amylin and related molecules may be envisioned as protective agent in gastric mucosa damage.

Anti-inflammatory actions of quinapril

OBJECTIVE

The role of angiotensin II (Ang-II) in inflammation and the mechanisms through which it exerts this role are explored. Signaling through angiotensin stimulation of inflammatory cells often amplifies inflammation. Formation of Ang-II from tissue angiotensin-converting enzyme (ACE) has been shown to be of greater importance in the development and progression of inflammatory diseases than plasma ACE.

CONCLUSION

Quinapril, which is a potent and selective inhibitor of both plasma and tissue ACE, has demonstrated anti-inflammatory properties in many disease states such as atherosclerosis, nephritis, scleroderma, diabetes and arthritis, and, thus, offers new therapeutic possibilities for disease treatment.

Losartan improves resistance artery lesions and prevents CTGF and TGF-beta production in mild hypertensive patients

Although structural and functional changes of resistance arteries have been proposed to participate in arterial hypertension (HTA) outcome, not all therapies may correct these alterations, even if they normalize the blood pressure (BP). The aim of this study was to investigate the mechanisms of the protection afforded by the angiotensin receptor antagonist losartan in resistance arteries from patients with essential HTA. In all, 22 untreated hypertensive patients were randomized to receive losartan or amlodipine for 1 year and the morphological characteristics of resistance vessels from subcutaneous biopsies were evaluated. Protein expression of connective tissue growth factor (CTGF), transforming growth factor beta (TGF-beta), and collagens III and IV was detected by immunohistochemistry. In comparison with normotensive subjects, resistance arteries from hypertensive patients showed a significant media:lumen (M/L) ratio increment and a higher protein expression of CTGF, TGF-beta, and collagens. After 1 year of treatment, both losartan and amlodipine similarly controlled BP. However, M/L only decreased in patients under losartan treatment, whereas in the amlodipine-treated group this ratio continued to increase significantly. The administration of losartan prevented significant increments in CTGF, TGF-beta, and collagens in resistance arteries. By contrast, amlodipine-treated patients showed a higher vascular CTGF, TGF-beta, and collagen IV staining than before treatment. Our results show that the administration of losartan, but not amlodipine, to hypertensive patients improves structural abnormalities and prevents the production of CTGF and TGF-beta in small arteries, despite similar BP lowering. These data may explain the molecular mechanisms of the better vascular protection afforded by drugs interfering with the renin-angiotensin system.

Long-term blood pressure control prevents oxidative renal injury

Arterial hypertension is a leading contributor to the progression of chronic renal disease. Short-term studies had addressed the role of oxidative stress in hypertensive nephropathy. We have now studied oxidative stress and caspase activation in a long-term model of hypertensive renal injury. Nontreated spontaneously hypertensive rats with uninephrectomy displayed severe arterial hypertension over a 36-week follow-up. Uncontrolled high blood pressure in the context of modest renal mass reduction resulted in significant histological renal injury. Blood pressure control by the angiotensin-converting enzyme (ACE) inhibitor, quinapril, or the AT1 receptor antagonist, losartan, decreased the degree of renal injury. Hypertensive renal injury was associated with evidence of activation of the apoptotic pathway (increased activation of caspase-3) and local renal (increased staining for 4-hydroxy-2-nonenal) and systemic [increased serum levels of 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha)] lipid oxidation when compared with normotensive control rats. In addition, severe hypertension decreased the renal antioxidant defenses, as exemplified by decreased expression of Cu/Zn superoxide dismutase. Treatment with quinapril or losartan decreased caspase-3 activation, 4-hydroxy-2-nonenal staining, and 8-iso-PGF2alpha levels and increased Cu/Zn superoxide dismutase expression. These results suggest that hypertension-associated oxidative stress and its consequences may be decreased by either ACE inhibition or AT1 receptor antagonist, emphasizing the role of angiotensin II in hypertensive renal damage.

Remission and regression of diabetic nephropathy

Diabetic kidney disease is considered to be an irreversible and inexorable progressive disease. Therefore, prevention of development of ESRD is extremely important. Animal studies have demonstrated that regression of existing renal morphologic lesions is feasible. In a sizable fraction of type 1 diabetic patients with overt nephropathy, remission (decrease in albuminuria to <300 mg/24 h) was obtained (31%), and regression of diabetic nephropathy (rate of decline in GFR < or = 1 mL/min/y), achieved (22%) by aggressive antihypertensive treatment. Furthermore, remission of nephrotic-range albuminuria (from >2500 mg/24 h to <600 mg/24 h) have been demonstrated to be achievable in one fifth of patients with nephrotic-range albuminuria. Remission of nephrotic-range albuminuria was associated with a reduction in decline in GFR and improved survival free of ESRD. However, to prevent development of ESRD in diabetic patients, an aggressive multifactorial approach, aiming at lowering blood pressure and albuminuria, and improving glycemic control, must be applied.

Persistent proteinuria up-regulates angiotensin II type 2 receptor and induces apoptosis in proximal tubular cells

Apoptosis is implicated in the progressive cell loss and fibrosis both at glomerular and tubulointerstitial level. In this study, we examined the potential mechanisms by which persistent proteinuria (protein-overload model) could induce apoptosis. After uninephrectomy (UNX), Wistar rats received daily injections of 0.5 g of bovine serum albumin (BSA)/100 g body weight or saline. Both at day 8 and day 28, rats receiving BSA had proteinuria and renal lesions characterized by tubular atrophy and/or dilation and mononuclear cell infiltration. In relation to control-UNX rats, renal cortex of nephritic rats showed an increment in AT2 mRNA (reverse transcriptase-polymerase chain reaction) and protein (Western blot) expression. In both groups, AT2 receptor immunostaining was mainly localized in proximal tubular cells. Rats with persistent proteinuria showed a significantly increased number of terminal dUTP nick-end labeling positive apoptotic cells compared with UNX-controls, both in glomeruli and tubulointerstitium. Double staining for apoptosis and AT2 receptor showed that most terminal dUTP nick-end labeling positive cells were found in tubules expressing AT2 receptor. Using an antibody that recognizes the active form caspase-3, we observed an increment in caspase-3 activation in rats receiving BSA with respect to those receiving saline. Rats with persistent proteinuria showed a diminution in the phosphorylation of Bcl-2 with respect to UNX-controls both at day 8 and day 28. By contrast, no changes were observed either in the Bax or in the Bcl-2 protein levels. The administration of BSA to UNX rats induced a diminution in the phosphorylation of ERK with respect to UNX-control at all times studied. The changes observed in ERK activities took place without alterations of ERK1/2 protein levels. In summary, our data suggest that persistent proteinuria causes apoptosis in tubular cells through the activation of AT2 receptor, which can, in turn, inhibit MAP kinase (ERK1/2) activation and Bcl-2 phosphorylation.