Effect of erythropoietin on the expression of dynamin-related protein-1 in rat renal interstitial fibrosis

Delayed treatment with erythropoietin attenuates renal fibrosis in mouse model of unilateral ureteral obstruction

OBJECTIVES

Erythropoietin (EPO) exerts tissue-protective effects on various organs including the kidney. However, the effects of EPO on established renal fibrosis remain unclear. In this study, we aimed to examine the therapeutic potential of EPO against established renal fibrosis.

METHODS

Renal fibrosis was induced in mice by unilateral ureteral obstruction (UUO) and the mice were treated with recombinant human EPO (rhEPO) daily during 7 and 13 days after UUO. The degrees of renal fibrosis, myofibroblast accumulation, and macrophage infiltration; the mRNA expression levels of transforming growth factor (TGF)-β1 and α1(I) collagen; and the protein levels of Kelch-like ECH-associated protein 1 (Keap1) and nuclear NF-E2-related factor 2 (Nrf2) in the kidneys were assessed on day 14 after UUO.

RESULTS

Treatment with rhEPO significantly decreased fibrosis, myofibroblast accumulation, and α1(I) collagen mRNA expression, but it did not significantly affect TGF-β1 mRNA expression. Although treatment with rhEPO did not significantly affect the total number of interstitial macrophages, it significantly decreased the number of CD86-positive cells (M1 macrophages), while significantly increased the number of CD206-positive cells (M2 macrophages) in the interstitium. Treatment with rhEPO did not affect the Keap1/Nrf2 protein level or the peripheral blood hematocrit value.

CONCLUSIONS

These results indicate for the first time that EPO exerts antifibrotic effects against the evolution of established renal fibrosis, possibly by influencing the polarization of infiltrating macrophages.

Tetrahydrobiopterin (BH4) Supplementation Prevents the Cardiorenal Effects of Diabetes in Mice by Reducing Oxidative Stress, Inflammation and Fibrosis

Background: The effects of diabetes on the cardiovascular system as well as in the kidney are profound, which include hypertrophy and fibrosis. Diabetes also induces oxidative stress, at least in part due to the uncoupling of nitric oxide synthase (NOS); this is a shift in NO production toward superoxide production due to reduced levels of the NOS cofactor tetrahydrobiopterin (BH4). With this in mind, we tested the hypothesis that BH4 supplementation may prevent the development of diabetic cardiomyopathy and nephropathy. Methods: Diabetes was induced in Balb/c mice with streptozotocin. Then, diabetic mice were divided into two groups: one group provided with BH4 (sapropterin) in drinking water (daily doses of 15 mg/kg/day, during eight weeks) and the other that received only water. A third group of normoglycemic mice that received only water were used as the control. Results: Cardiac levels of BH4 were increased in mice treated with BH4 (p = 0.0019). Diabetes induced cardiac hypertrophy, which was prevented in the group that received BH4 (p < 0.05). In addition, hypertrophy was evaluated as cardiomyocyte cross-sectional area. This was reduced in diabetic mice that received BH4 (p = 0.0012). Diabetes induced cardiac interstitial fibrosis that was reduced in mice that received BH4 treatment (p < 0.05). We also evaluated in the kidney the impact of BH4 treatment on glomerular morphology. Diabetes induced glomerular hypertrophy compared with normoglycemic mice and was prevented by BH4 treatment. In addition, diabetic mice presented glomerular fibrosis, which was prevented in mice that received BH4. Conclusions: These results suggest that chronic treatment with BH4 in mice ameliorates the cardiorenal effects of diabetes,, probably by restoring the nitroso−redox balance. This offers a possible new alternative to explore a BH4-based treatment for the organ damage caused by diabetes.

AKT/foxo3a signal pathway mediates the protective mechanism of resveratrol on renal interstitial fibrosis and oxidative stress in rats with unilateral ureteral obstruction

OBJECTIVE

To explore whether protein kinase B (serine/threonrine kinase, AKT)/forkhead box protein O3a (foxo3a) pathway mediates the protective mechanism of resveratrol (RSV) on renal interstitial fibrosis (RIF) and oxidative stress.

METHODS

Sprague-Dawley (SD) rats were grouped into Sham group, unilateral ureteral obstruction (UUO) group and UUO + RSV group. HE staining was used to test the pathological damage of RIF intervened by RSV, biochemical analyzer was used to measure serum renal injury indexes (creatinine, Cr, blood urea nitrogen, Bun), and enzyme-linked immunosorbent assay (ELISA) was used to detect oxidative stress indexes (malondialdehyde, MDA; glutathione, GSH; superoxide dismutase, SOD). AKT/FoxO3a signaling pathway markers and renal interstitial indexes were measured by western blot analysis.

RESULTS

Compared with Sham group, HE staining in UUO group showed significant RIF pathological damage; Cr and Bun indexes were increased, and AKT/FoxO3a signal pathway was activated, as indicated by increased p-AKT/AKT and p-FoxO3a/FoxO3a; TGF-β1 and α-SMA protein levels in fibrosis indexes were increased, while E-cadherin decreased; MDA was increased, GSH and SOD were decreased in oxidative stress indexes, while those in UUO + RSV group were improved.

CONCLUSION

AKT/foxo3a signaling pathway mediates the protective mechanism of RSV on RIF and oxidative stress in UUO rats, and RSV can improve RIF and oxidative stress in UUO rats by inhibiting AKT/foxo3a signaling pathway.

PPAR γ/TLR4/TGF-β1 axis mediates the protection effect of erythropoietin on cyclosporin A-induced chronic nephropathy in rat

Objective: Nephrotoxicity is the main side effect of cyclosporine A and finding an effective combating method is urgent. The present study investigates the improving effect of erythropoietin (EPO) on cyclosporine A induce renal injury in rats and further explores its possible mechanism.Methods: Recombinant adenovirus for expression of EPO was constructed and injected into kidney with multipoint. Levels of blood urea nitrogen (BUN) and serum creatinine (SCr) were detected by kits. HE staining and Masson's trichrome staining were used to evaluate pathological changes. ELISA was performed to detect the levels of transforming growth factor (TGF)-β1, interleukin (IL)-1β, and IL-6 in serum. Levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in kidney were detected according to manufacturer's instruction. Western blotting was performed to observe the protein expression levels of peroxisome proliferator-activated receptor γ (PPAR γ), Toll-like receptor (TLR) 4, and TGF-β1.Results: Results showed that EPO overexpression in rat kidney could significantly improve renal injury and fibrosis, suppress the release of inflammatory factors and reduce oxidative stress induced by cyclosporine A. Western blotting results showed that EPO overexpression could up-regulate the expression of PPARγ and down-regulate the expression of TLR4 and TGF-β1. Interestingly, when PPARγ activity was inhibited by T0070907, an effective and specific PPARγ inhibitor, the therapeutic effect of EPO was significantly attenuated.Conclusion: Taken together, above results shown the protective effect of EPO on cyclosporine A-induced renal injury and confirmed that EPO's anti-inflammation and antioxidative stress involving the PPAR γ/TLR4/TGFβ1 axis.

Mitochondrial Dysfunction in Kidney Disease and Uremic Sarcopenia

Recently, there has been an increased focus on the influences of mitochondrial dysfunction on various pathologies. Mitochondria are major intracellular organelles with a variety of critical roles, such as adenosine triphosphate production, metabolic modulation, generation of reactive oxygen species, maintenance of intracellular calcium homeostasis, and the regulation of apoptosis. Moreover, mitochondria are attracting attention as a therapeutic target in several diseases. Additionally, a lot of existing agents have been found to have pharmacological effects on mitochondria. This review provides an overview of the mitochondrial change in the kidney and skeletal muscle, which is often complicated with sarcopenia and chronic kidney disease (CKD). Furthermore, the pharmacological effects of therapeutics for CKD on mitochondria are explored.

Mitochondrial dysfunction and endoplasmic reticulum stress in the promotion of fibrosis in obstructive nephropathy induced by unilateral ureteral obstruction

Obstructive nephropathy favors the progression to chronic kidney disease (CKD), a severe health problem worldwide. The unilateral ureteral obstruction (UUO) model is used to study the development of fibrosis. Impairment of renal mitochondria plays a crucial role in several types of CKD and has been strongly related to fibrosis onset. Nevertheless, in the UUO model, the impairment of mitochondria, their relationship with endoplasmic reticulum (ER) stress induction and the participation of both to induce the fibrotic process remain unclear. In this review, we summarize the current information about mitochondrial bioenergetics, redox dynamics, mitochondrial mass, and biogenesis alterations, as well as the relationship of these mitochondrial alterations with ER stress and their participation in fibrotic processes in UUO models. Early after obstruction, there is metabolic reprogramming related to mitochondrial fatty acid β-oxidation impairment, triggering lipid deposition, oxidative stress, (calcium) Ca²⁺ dysregulation, and a reduction in mitochondrial mass and biogenesis. Mitochondria and the ER establish a pathological feedback loop that promotes the impairment of both organelles by ER stress pathways and Ca²⁺ levels dysregulation. Preserving mitochondrial and ER function can prevent or at least delay the fibrotic process and loss of renal function. However, deeper understanding is still necessary for future clinically-useful therapies.

Advances in Understanding the Effects of Erythropoietin on Renal Fibrosis

Renal fibrosis is the common manifestation of the pathogenesis of end-stage renal disease that results from different types of renal insult, and is a hallmark of chronic kidney disease (CKD). The main pathologic characteristics of renal fibrosis are renal interstitial fibroblast hyperplasia and the aberrant and excessive deposition of extracellular matrix, pathologies that lead to the destruction of normal renal tubules and interstitial structures. However, the biological significance of fibrosis during the progression of CKD is not clear, and there are no approved clinical treatments for delaying or reversing renal fibrosis. Studies of the mechanism of renal fibrosis and of potential measures of prevention and treatment have focused on erythropoietin (EPO), a hormone best known as a regulator of red blood cell production. These recent studies have found that EPO may also provide efficient protection against renal fibrosis. Future therapeutic approaches using EPO offer new hope for patients with CKD. The aim of the present review is to briefly discuss the role of EPO in renal fibrosis, to identify its possible mechanisms in preventing renal fibrosis, and to provide novel ideas for the use of EPO in future treatments of renal fibrosis.