Therapeutic nuclear shuttling of YB-1 reduces renal damage and fibrosis.

Virtually all chronic kidney diseases progress towards tubulointerstitial fibrosis. In vitro, Y-box protein-1 (YB-1) acts as a central regulator of gene transcription and translation of several fibrosis-related genes. However, it remains to be determined whether its pro- or antifibrotic propensities prevail in disease. Therefore, we investigated the outcome of mice with half-maximal YB-1 expression in a model of renal fibrosis induced by unilateral ureteral obstruction. Yb1+/- animals displayed markedly reduced tubular injury, immune cell infiltration and renal fibrosis following ureteral obstruction. The increase in renal YB-1 was limited to a YB-1 variant nonphosphorylated at serine 102 but phosphorylated at tyrosine 99. During ureteral obstruction, YB-1 localized to the cytoplasm, directly stabilizing Col1a1 mRNA, thus promoting fibrosis. Conversely, the therapeutic forced nuclear compartmentalization of phosphorylated YB-1 by the small molecule HSc025 mediated repression of the Col1a1 promoter and attenuated fibrosis following ureteral obstruction. Blunting of these effects in Yb1+/- mice confirmed involvement of YB-1. HSc025 even reduced tubulointerstitial damage when applied at later time points during maximum renal damage. Thus, phosphorylation and subcellular localization of YB-1 determines its effect on renal fibrosis in vivo. Hence, induced nuclear YB-1 shuttling may be a novel antifibrotic treatment strategy in renal diseases with the potential of damage reversal.

Curcumin ameliorates nephrosclerosis via suppression of histone acetylation independent of hypertension.

BACKGROUND: Although histone acetylation, an epigenetic modification, has been reported to be related to the progression of various diseases, its involvement in nephrosclerosis is unclear. METHODS: Dahl salt-sensitive rats were used as a model of nephrosclerosis in this study. The rats were divided into three groups: (i) normal-salt diet group, (ii) high-salt diet group (HS), and (iii) HS administered daily with curcumin, a histone acetyltransferase inhibitor (HS+C). At 6 weeks after the treatment, the kidneys were dissected. Morphologic changes were assessed by Masson's trichrome staining. The number of macrophages, fibroblasts and the cells expressing acetylated histone H3 at Lys 9 (H3K9) were assessed by immunohistochemistry. RESULTS: Although both HS and HS+C rats revealed a marked increase in systolic blood pressure, serum creatinine was increased only in HS rats at 6 weeks. In the HS rats, nephrosclerosis was induced, accompanying a significant accumulation of macrophages and fibroblasts. The inflammation and fibrosis was markedly suppressed in the HS+C group. The level of histone acetylation at Lys 9 was enhanced in the HS rats, whereas curcumin administration suppressed the histone acetylation. Moreover, in the HS rats, interleukin-6 gene expression was associated with acetylated H3K9, as revealed by chromatin immunoprecipitation assay. CONCLUSIONS: Our results suggested that curcumin ameliorates nephrosclerosis via suppression of histone acetylation, independently of hypertension.

HMGB1 exacerbates renal tubulointerstitial fibrosis through facilitating M1 macrophage phenotype at the early stage of obstructive injury.

Previous studies have indicated that macrophage phenotype diversity is involved in the progression of renal fibrosis. However, the factors facilitating M1 or M2 phenotypes and the function of these polarized macrophages in kidney injury and fibrosis remain largely unknown. In the present study, we found that macrophages accumulated in the kidney interstitium exhibited mainly as the M1 phenotype at the early stage of unilateral ureter obstruction (UUO). High-mobility group box 1 (HMGB1) protein expressed and released from tubular epithelial cells and interstitial macrophages was essential for the M1 macrophage transition. HMGB1 significantly induced the expression of the M1 marker inducible nitric oxide synthase while decreasing the M2 marker IL-10 in macrophages. Moreover, a glycyrrhizic acid derivative, a blocker of HMGB1 release, reduced UUO-mediated kidney injury and ameliorated UUO-induced renal fibrosis. Interestingly and importantly, UUO caused a low pH value in the urine accumulated in the obstructed ureter, and the acidified urine induced HMGB1 release from tubular epithelial cells and macrophages in vitro. Our data demonstrate that HMGB1 is an essential contributor in facilitating M1 polarization at the early stage of UUO. Inhibition of HMGB1 release may alter macrophage phenotype and contribute to the protection of kidney tissue from injury and fibrosis.

Pharmacological inhibition of soluble epoxide hydrolase prevents renal interstitial fibrogenesis in obstructive nephropathy.

Treating chronic kidney disease (CKD) has been challenging because of its pathogenic complexity. Epoxyeicosatrienoic acids (EETs) are cytochrome P-450-dependent derivatives of arachidonic acid with antihypertensive, anti-inflammatory, and profibrinolytic functions. We recently reported that genetic ablation of soluble epoxide hydrolase (sEH), an enzyme that converts EETs to less active dihydroxyeicosatrienoic acids, prevents renal tubulointerstitial fibrosis and inflammation in experimental mouse models of CKD. Here, we tested the hypothesis that pharmacological inhibition of sEH after unilateral ureteral obstruction (UUO) would attenuate tubulointerstitial fibrosis and inflammation in mouse kidneys and may provide a novel approach to manage the progression of CKD. Inhibition of sEH enhanced levels of EET regioisomers and abolished tubulointerstitial fibrosis, as demonstrated by reduced collagen deposition and myofibroblast formation after UUO. The inflammatory response was also attenuated, as demonstrated by decreased influx of neutrophils and macrophages and decreased expression of inflammatory cytokines keratinocyte chemoattractant, macrophage inflammatory protein-2, monocyte chemotactic protein-1, TNF-α, and ICAM-1 in kidneys after UUO. UUO upregulated transforming growth factor-ß1/Smad3 signaling and induced NF-κB activation, oxidative stress, tubular injury, and apoptosis; in contrast, it downregulated antifibrotic factors, including peroxisome proliferator-activated receptor (PPAR) isoforms, especially PPAR-γ. sEH inhibition mitigated the aforementioned malevolent effects in UUO kidneys. These data demonstrate that pharmacological inhibition of sEH promotes anti-inflammatory and fibroprotective effects in UUO kidneys by preventing tubular injury, downregulation of NF-κB, transforming growth factor-ß1/Smad3, and inflammatory signaling pathways, and activation of PPAR isoforms. Our data suggest the potential use of sEH inhibitors in treating fibrogenesis in the UUO model of CKD.

GQ5 Hinders Renal Fibrosis in Obstructive Nephropathy by Selectively Inhibiting TGF-ß-Induced Smad3 Phosphorylation.

TGF-ß1, via Smad-dependent or Smad-independent signaling, has a central role in the pathogenesis of renal fibrosis. This pathway has been recognized as a potential target for antifibrotic therapy. Here, we identified GQ5, a small molecular phenolic compound isolated from the dried resin of Toxicodendron vernicifluum, as a potent and selective inhibitor of TGF-ß1-induced Smad3 phosphorylation. In TGF-ß1-stimulated renal tubular epithelial cells and interstitial fibroblast cells, GQ5 inhibited the interaction of Smad3 with TGF-ß type I receptor (TßRI) by blocking binding of Smad3 to SARA, suppressed subsequent phosphorylation of Smad3, reduced nuclear translocation of Smad2, Smad3, and Smad4, and downregulated the transcription of major fibrotic genes such as α-smooth muscle actin (α-SMA), collagen I, and fibronectin. Notably, intraperitoneal administration of GQ5 in rats immediately after unilateral ureteral obstruction (UUO) selectively inhibited Smad3 phosphorylation in UUO kidneys, suppressed renal expression of α-SMA, collagen I, and fibronectin, and resulted in impressive renal protection after obstructive injury. Late administration of GQ5 also effectively attenuated fibrotic lesions in obstructive nephropathy. In conclusion, our results suggest that GQ5 hinders renal fibrosis in rats by selective inhibition of TGF-ß1-induced Smad3 phosphorylation.

Renoprotective effect of vasopressin v2 receptor antagonist tolvaptan in Dahl rats with end-stage heart failure.

Tolvaptan is a highly selective and orally effective arginine vasopressin V2 receptor antagonist, and is potentially useful for the treatment of heart failure (HF) patients. However, the renoprotective effect of long-term tolvaptan therapy and its underlying mechanisms remain unknown. We evaluated the effects of chronic treatment with tolvaptan on renal dysfunction, podocyte injury, inflammation, oxidative stress, Rho-kinase, epithelial-mesenchymal transition (EMT), and the extracellular signal-regulated protein kinase (ERK1/2) pathway in the renal cortex of Dahl salt-sensitive hypertensive (DS) rats with end-stage severe HF. DS and Dahl salt-resistant rats were fed a high-salt diet at 6 weeks of age. DS rats were treated with vehicle and tolvaptan (0.05% concentration in diet) from the age of 11 to 18 weeks. Vehicle-treated DS rats developed proteinuria, renal dysfunction, glomerulosclerosis, and interstitial fibrosis, which were ameliorated by tolvaptan without changing blood pressure. Decreased expression of nephrin and podocin and increased desmin-positive area in failing rats were restored by tolvaptan. Upregulation of NAD(P)H oxidase p22(phox), p47(phox), and gp91(phox), EMT markers such as transforming growth factor-ß1, vimentin, and fibronectin expression, and Rho-kinase and ERK1/2 phosphorylation in DS rats were significantly suppressed by tolvaptan. Tolvaptan administration resulted in significant inhibition of tumor necrosis factor-α and monocyte chemoattractant protein-1 expression, and nuclear factor-κB phosphorylation. We concluded that long-term tolvaptan therapy may improve renal dysfunction, glomerulosclerosis, podocyte injury, and inflammation associated with oxidative stress, as well as EMT, ERK, and the Rho-kinase pathway in the failing heart of DS rats. Thus, tolvaptan may be a therapeutic strategy for end-stage severe HF.

An aqueous extract of Portulaca oleracea ameliorates diabetic nephropathy through suppression of renal fibrosis and inflammation in diabetic db/db mice.

Diabetic nephropathy is one of the most common microvascular complications of diabetes and the leading cause of end-stage renal disease. In the present study, we investigated the renoprotective effect of the aqueous extract of Portulaca oleracea (AP) on diabetic nephropathy accelerated by renal fibrosis and inflammation in type 2 diabetic db/db mice. The mice were treated with AP (300 mg/kg/day, p.o.) for ten weeks to examine the long-term effects on diabetic nephropathy and renal dysfunction. We found that AP treatment markedly lowered blood glucose to 412 ± 11.4 mg/dl and plasma creatinine level to 2.3 ± 0.8 mg/dl compared to db/db mice (p < 0.05, p < 0.01, respectively). This study also showed that treatment with AP significantly decreased water intake and urine volume in diabetic db/db mice (p < 0.05). In immunohistological study, the renal expression of transforming growth factor-ß1 (TGF-ß1), advanced glycation end products (AGE), and intercellular adhesion molecule (ICAM)-1 markedly increased in the renal cortex of untreated db/db mice (p < 0.01). In contrast, AP treatment significantly reduced these expressions to 50 ± 2.1%, 48 ± 2.8%, 61 ± 1.1%, respectively (p < 0.01). Furthermore, NF-κB p65 activation in renal tissues markedly increased in untreated db/db mice, which was significantly suppressed by AP treatment. Taken together, these findings suggest that AP attenuates diabetic nephropathy through inhibition of renal fibrosis and inflammation in db/db mice.

Induction of hemeoxygenase-1 reduces glomerular injury and apoptosis in diabetic spontaneously hypertensive rats.

Induction of hemeoxygenase-1 (HO-1) lowers blood pressure and reduces organ damage in hypertensive animal models; however, a potential protective role for HO-1 induction against diabetic-induced glomerular injury remains unclear. We hypothesize that HO-1 induction will protect against diabetes-induced glomerular injury by maintaining glomerular integrity and inhibiting renal apoptosis, inflammation, and oxidative stress. Diabetes was induced with streptozotocin in spontaneously hypertensive rats (SHR) as a model where the coexistence of hypertension and diabetes aggravates the progression of diabetic renal injury. Control and diabetic SHR were randomized to receive vehicle or the HO-1 inducer cobalt protoporphyrin (CoPP). Glomerular albumin permeability was significantly greater in diabetic SHR compared with control, consistent with an increase in apoptosis and decreased glomerular nephrin and α(3)ß(1)-integrin protein expression in diabetic SHR. CoPP significantly reduced albumin permeability and apoptosis and restored nephrin and α(3)ß(1)-integrin protein expression levels in diabetic SHR. Glomerular injury in diabetic SHR was also associated with increases in NF-κB-induced inflammation and oxidative stress relative to vehicle-treated SHR, and CoPP significantly blunted diabetes-induced increases in glomerular inflammation and oxidative stress in diabetic SHR. These effects were specific to exogenous stimulation of HO-1, since incubation with the HO inhibitor stannous mesoporphyrin alone did not alter glomerular inflammatory markers or oxidative stress yet was able to prevent CoPP-mediated decreases in these parameters. These data suggest that induction of HO-1 reduces diabetic induced-glomerular injury and apoptosis and these effects are associated with decreased NF-κB-induced inflammation and oxidative stress.

Astragalus mongholicus ameliorates renal fibrosis by modulating HGF and TGF-beta in rats with unilateral ureteral obstruction.

Astragalus mongholicus (AM) derived from the dry root of Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao is a widely used traditional Chinese medicine. The present study investigated the potential role of AM on renal fibrosis on a rat model of unilateral ureteral obstruction (UUO). We divided 48 Sprague-Dawley rats randomly into 4 groups: sham-operated group (Sham), untreated UUO group, AM-treated (10 g/(kg x d)) UUO group, and losartan-treated (20 mg/(kg x d)) UUO group as positive control. Haematoxylin & eosin (HE) and Masson staining were used to study the dynamic histological changes of the kidneys 7 and 14 d after operation. The expressions of fibronectin (FN), type I collagen (colI), hepatocyte growth factor (HGF), transforming growth factor-beta1 (TGF-beta1), and alpha-smooth muscle actin (alpha-SMA) were analyzed by real-time polymerase chain reaction (PCR), immunohistochemistry staining, and Western blot. Results show that, similar to losartan, AM alleviated the renal damage and decreased the deposition of FN and colI from UUO by reducing the expressions of TGF-beta1 and alpha-SMA (P<0.05), whereas HGF increased greatly with AM treatment (P<0.05). Our findings reveal that AM could retard the progression of renal fibrosis. The renoprotective effect of AM might be related to inhibition of myofibroblast activation, inducing of HGF and reducing of TGF-beta1 expression.

[Effect of astragalus-angelica mixture on osteopontin expression in rats with chronic nephrosclerosis].

OBJECTIVE: To observe the effect of Astragalus-Angelica Mixture (AAM) on osteopontin (OPN) expression in rats with chronic nephrosclerosis. METHODS: Chronic nephrosclerosis model rats induced by repeated intraperitoneal injection of puromycin were randomly divided into the model group, AAM group and Irbesartan (an antagonist of angiotensin) group. The experimental course lasted 12 weeks. Blood and urine samples were examined by biochemical method. Kidney tissue was taken for pathological stain and immunohistochemical method and was applied to examine OPN expression, mononuclear macrophage, laminin in extracellular matrix and decorin expressions. RESULTS: AAM showed the effects of decreasing urinary protein and improving renal function similar to that of Irbesartan. It also could alleviate the pathological damage of kidney tissue, especially in decreasing renal tubular mesenchymal damage index. The accumulation of decorin and laminin in the mesenchymal extracellular matrix significantly decreased. Renal tubular OPN expression and mesenchymal infiltration of mononuclear macrophage decreased significantly and in a positive correlated manner (r = 0.885, P < 0.01). CONCLUSION: AAM has similar renal protective action to that of Irbesartan, this action may be related to the inhibition of up-regulated OPN expression.

[Experimental study on effect of bushen qingli huoxue treatment on glomerular extracellular matrix of remnant kidney in rats].

OBJECTIVE: To study the effect of Bushen Qingli Huoxue (BQH) treatment on glomerular extracellular matrix (ECM) and in retarding glomerular sclerosis in rats and to explore the mechanism and key of regulation. METHODS: Animal model was established by 5/6 nephrectomy and the study was carried out by using immune histochemical and pathological methods. Treatment of BQH started 1 week after operation. RESULTS: After being treated with BQH, the serum creatinine (SCr), blood urea nitrogen (BUN) and urinary protein excretion reduced markedly. Pathological examination showed accumulation of ingredients of glomerular ECM such as type I, IV collagen and laminin decreased significantly, the number of glomerular cells and proliferation cell nuclear antigen positive cells also decreased obviously, and showed that the glomerular sclerosis was retarded. The effect of BQH was similar to that of Enapril, but superior to that of Enapril in reducing BUN and SCr. CONCLUSION: BQH has the effects of reducing ECM accumulation, improving renal function and retarding glomerular sclerosis.