Evidence that inhibition of tubular cell apoptosis protects against renal damage and development of fibrosis following ureteric obstruction

The role and mechanism of action of miR-483-3p in mediating the effects of IGF-1 on human renal tubular epithelial cells induced by high glucose

This study aimed to elucidate the influence of miR-483-3p on human renal tubular epithelial cells (HK-2) under high glucose conditions and to understand its mechanism. Human proximal tubular epithelial cells (HK-2) were exposed to 50 mmol/L glucose for 48 h to establish a renal tubular epithelial cell injury model, denoted as the high glucose group (HG group). Cells were also cultured for 48 h in a medium containing 5.5 mmol/L glucose, serving as the low glucose group. Transfection was performed in various groups: HK-2 + low glucose (control group), high glucose (50 mM) (HG group), high glucose + miR-483-3p mimics (HG + mimics group), high glucose +miR-483-3p inhibitor (HG + inhibitor group), and corresponding negative controls. Real-time quantitative polymerase chain reaction (qPCR) assessed the mRNA expression of miR-483-3p, bax, bcl-2, and caspase-3. Western blot determined the corresponding protein levels. Proliferation was assessed using the CCK-8 assay, and cell apoptosis was analyzed using the fluorescence TUNEL method. Western blot and Masson's staining were conducted to observe alterations in cell fibrosis post miR-483-3p transfection. Furthermore, a dual-luciferase assay investigated the targeting relationship between miR-483-3p and IGF-1. The CCK8 assay demonstrated that the HG + mimics group inhibited HK-2 cell proliferation, while the fluorescent TUNEL method revealed induced cell apoptosis in this group. Conversely, the HG + inhibitor group promoted cell proliferation and suppressed cell apoptosis. The HG + mimics group upregulated mRNA and protein expression of pro-apoptotic markers (bax and caspase-3), while downregulating anti-apoptotic marker (bcl-2) expression. In contrast, the HG + inhibitor group showed opposite effects. Collagen I and FN protein levels were significantly elevated in the HG + mimics group compared to controls (P < 0.05). Conversely, in the HG + inhibitor group, the protein expression of Collagen I and FN was notably reduced compared to the HG group (P < 0.05). The dual luciferase reporter assay confirmed that miR-483-3p could inhibit the luciferase activity of IGF-1's 3'-UTR region (P < 0.05). miR-483-3p exerts targeted regulation on IGF-1, promoting apoptosis and fibrosis in renal tubular epithelial cells induced by high glucose conditions.

Empagliflozin and pirfenidone confer renoprotection through suppression of glycogen synthase kinase-3β and promotion of tubular regeneration in rats with induced metabolic syndrome

Metabolic syndrome (MetS) is largely coupled with chronic kidney disease (CKD). Glycogen synthase kinase-3β (GSK-3β) pathway drives tubular injury in animal models of acute kidney injury; but its contribution in CKD is still elusive. This study investigated the effect empagliflozin and/or pirfenidone against MetS-induced kidney dysfunction, and to clarify additional underpinning mechanisms particularly the GSK-3β signaling pathway. Adult male rats received 10%w/v fructose in drinking water for 20 weeks to develop MetS, then treated with either drug vehicle, empagliflozin (30 mg/kg/day) and/or pirfenidone (100 mg/kg/day) via oral gavage for subsequent 4 weeks, concurrently with the high dietary fructose. Age-matched rats receiving normal drinking water were used as controls. After 24 weeks, blood and kidneys were harvested for subsequent analyses. Rats with MetS showed signs of kidney dysfunction, structural changes and interstitial fibrosis. Activation of GSK-3β, decreased cyclinD1 expression and enhanced apoptotic signaling were found in kidneys of MetS rats. There was abundant alpha-smooth muscle actin (α-SMA) expression along with up-regulation of TGF-β1/Smad3 in kidneys of MetS rats. These derangements were almost alleviated by empagliflozin or pirfenidone, with evidence that the combined therapy was more effective than either individual drug. This study emphasizes a novel mechanism underpinning the beneficial effects of empagliflozin and pirfenidone on kidney dysfunction associated with MetS through targeting GSK-3β signaling which can mediate the regenerative capacity, anti-apoptotic effects and anti-fibrotic properties of such drugs. These findings recommend the possibility of using empagliflozin and pirfenidone as promising therapies for management of CKD in patients with MetS.

Long noncoding RNA: An emerging diagnostic and therapeutic target in kidney diseases

Long noncoding RNAs (lncRNAs) have critical roles in the development of many diseases including kidney disease. An increasing number of studies have shown that lncRNAs are involved in kidney development and that their dysregulation can result in distinct disease processes, including acute kidney injury, chronic kidney disease, and renal cell carcinoma. Understanding the roles of lncRNAs in kidney disease may provide new diagnostic and therapeutic opportunities in the clinic. This review provides an overview of lncRNA characteristics, and biological function and discusses specific studies that provide insight into the function and potential application of lncRNAs in kidney disease treatment.

Promising therapeutic mechanism for Chinese herbal medicine in ameliorating renal fibrosis in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most serious chronic microvascular abnormalities of diabetes mellitus and the major cause of uremia. Accumulating evidence has confirmed that fibrosis is a significant pathological feature that contributes to the development of chronic kidney disease in DN. However, the exact mechanism of renal fibrosis in DN is still unclear, which greatly hinders the treatment of DN. Chinese herbal medicine (CHM) has shown efficacy and safety in ameliorating inflammation and albuminuria in diabetic patients. In this review, we outline the underlying mechanisms of renal fibrosis in DN, including oxidative stress (OS) generation and OS-elicited ASK1-p38/JNK activation. Also, we briefly summarize the current status of CHM treating DN by improving renal fibrosis. The treatment of DN by inhibiting ASK1 activation to alleviate renal fibrosis in DN with CHM will promote the discovery of novel therapeutic targets for DN and provide a beneficial therapeutic method for DN.

Bupi Yishen formula may prevent kidney fibrosis by modulating fatty acid metabolism in renal tubules

BACKGROUND

Bupi Yishen formula (BYF), a traditional Chinese herbal mixture, has demonstrated better effectiveness than Losartan in preserving renal function and preventing composite severe adverse outcomes in patients with advanced chronic kidney disease (CKD) in a recent randomized controlled trial. Prior studies have shown that BYF exerts anti-inflammatory and anti-fibrotic effects in the kidneys of CKD models, but the underlying mechanisms have not been fully elucidated.

PURPOSE

The aim of this study was to investigate the protective effects of BYF administration on profibrotic phenotypic changes in the kidney and to elucidate its fundamental mechanisms of action.

METHODS

Adenine and 5/6 nephrectomy rat models were administered with two doses of BYF extract (15 or 30 g/kg/d) by intragastric administration, and Losartan treatment was used as a positive control group. The relationship between BYF renoprotection and restoration of fatty acid dysregulation was examined using the two fibrosis models and TGFb1-induced human tubular HK2 cells. Transcriptomic profiles of the fibrotic kidneys obtained from adenine-induced CKD rats were used to identify the key mechanisms that are affected by BYF intervention. Human relevance and clinical implications were established by re-analysis of the microarray databases of CKD patients and immunostaining on human biopsy specimens.

RESULTS

BYF effectively prevented kidney histological damage and ameliorated renal malfunction in the adenine rat model of CKD. BYF robustly attenuated the significant increase in profibrotic and proapoptotic markers in fibrotic kidneys of adenine-induced CKD rats. Transcriptomic analyses of the fibrotic kidneys of the adenine rats identified fatty acid metabolism as the key dysregulated pathway affected by BYF prevention. BYF significantly reversed defective fatty acid oxidation (FAO) and the intracellular lipids accumulation in the fibrotic kidneys induced by 5/6 nephrectomy. Furthermore, BYF prevented dysfunctional fatty acid metabolism, which were associated with the significant improvement of TGFb1-induced profibrotic changes in HK2 human proximal tubular cells. Furthermore, analyses of kidney microarray databases and biopsy specimens of CKD patients suggested that FAO defect is common in CKD in humans.

CONCLUSION

Our exploratory study found that BYF may exert protective effects on renal fibrosis by regulating the fatty acid metabolism of renal tubular cells, which may be a key mechanism for preventing kidney fibrosis in CKD.

Nr4a1 promotes renal interstitial fibrosis by regulating the p38 MAPK phosphorylation

BACKGROUND

Renal interstitial fibrosis (RIF) is a common pathway to end-stage renal disease regardless of the initial etiology. Currently, the molecular mechanisms for RIF remains not fully elucidated. Nuclear receptor subfamily 4 group A member 1(Nr4a1), a member of the NR4A subfamily of nuclear receptors, is a ligand-activated transcription factor. The role of Nr4a1 in RIF remains largely unknown.

METHODS

In this study, we determined the role and action mechanism of Nr4a1 in RIF. We used unilateral ureteral obstruction (UUO) mice and transforming growth factor (TGF)-β1-treated human renal proximal tubular epithelial cells (HK-2 cells) as in vivo and in vitro models of RIF. A specific Nr4a1 agonist Cytosporone B (Csn-B) was applied to activate Nr4a1 both in vivo and in vitro, and Nr4a1 small interfering RNA was applied in vitro. Renal pathological changes were evaluated by hematoxylin and eosin and Masson staining, and the expression of fibrotic proteins including fibronectin (Fn) and collagen-I (Col-I), and phosphorylated p38 MAPK was measure by immunohistochemical staining and western blot analysis.

RESULTS

The results showed that Nr4a1 was upregulated in UUO mouse kidneys, and was positively correlated with the degree of interstitial kidney injury and the levels of fibrotic proteins. Csn-B treatment aggravated UUO-induced renal interstitial fibrosis, and induced p38 MAPK phosphorylation. In vitro, TGF-β induced Nr4a1 expression, and Nr4a1 downregulation prevented TGF-β1-induced expression of Fn and Col-I and the activation of p38 MAPK. Csn-B induced fibrotic proteins expression and p38 MAPK phosphorylation, and moreover Csn-B induced fibrotic proteins expression was abrogated by treatment with p38 MAPK inhibitor SB203580. We provided further evidence that Csn-B treatment promoted cytoplasmic accumulation of Nr4a1.

CONCLUSION

The findings in the present study indicate that Nr4a1 promotes renal fibrosis potentially through activating p38 MAPK kinase.

p53 and Myofibroblast Apoptosis in Organ Fibrosis

Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.

SIK2 protects against renal tubular injury and the progression of diabetic kidney disease

Despite optimal medical therapy, many patients with diabetic kidney disease (DKD) progress to end-stage renal disease. The identification of new biomarkers and drug targets for DKD is required for the development of more effective therapies. The apoptosis of renal tubular epithelial cells is a key feature of the pathogenicity associated with DKD. SIK2, a salt-inducible kinase, regulates important biological processes, such as energy metabolism, cell cycle progression and cellular apoptosis. In our current study, a notable decrease in the expression of SIK2 was detected in the renal tubules of DKD patients and murine models. Functional experiments demonstrated that deficiency or inactivity of SIK2 aggravates tubular injury and interstitial fibrosis in diabetic mice. Based on transcriptome sequencing, molecular mechanism exploration revealed that SIK2 overexpression reduces endoplasmic reticulum (ER) stress-mediated tubular epithelial apoptosis by inhibiting the histone acetyltransferase activity of p300 to activate HSF1/Hsp70. Furthermore, the specific restoration of SIK2 in tubules blunts tubular and interstitial impairments in diabetic and vancomycin-induced kidney disease mice. Together, these findings indicate that SIK2 protects against renal tubular injury and the progression of kidney disease, and make a compelling case for targeting SIK2 for therapy in DKD.

Gene expression patterns in Atlantic salmon (Salmo salar) with severe nephrocalcinosis

Nephrocalcinosis is a common disorder in farmed Atlantic salmon, but the consequences for the fish physiology are not well understood. We performed a transcriptome study in kidneys of Atlantic salmon (Salmo salar) smolts without and with severe chronic nephrocalcinosis (NC). The study revealed that numerous genes are differentially expressed in fish with NC compared with healthy salmon. The most evident changes in gene expression patterns in the NC group were a massive downregulation of metabolism and energy production, upregulation of signalling pathways important for tissue repair and function maintenance and upregulation of inflammatory responses. Overall, the extensive tissue damage and the gene regulation responses that affect salmon with severe nephrocalcinosis are highly likely to have dramatic consequences on fish survival.

NFAT inhibitor 11R-VIVIT ameliorates mouse renal fibrosis after ischemia-reperfusion-induced acute kidney injury

Acute kidney injury (AKI) with maladaptive tubular repair leads to renal fibrosis and progresses to chronic kidney disease (CKD). At present, there is no curative drug to interrupt AKI-to-CKD progression. The nuclear factor of the activated T cell (NFAT) family was initially identified as a transcription factor expressed in most immune cells and involved in the transcription of cytokine genes and other genes critical for the immune response. NFAT2 is also expressed in renal tubular epithelial cells (RTECs) and podocytes and plays an important regulatory role in the kidney. In this study, we investigated the renoprotective effect of 11R-VIVIT, a peptide inhibitor of NFAT, on renal fibrosis in the AKI-to-CKD transition and the underlying mechanisms. We first examined human renal biopsy tissues and found that the expression of NFAT2 was significantly increased in RTECs in patients with severe renal fibrosis. We then established a mouse model of AKI-to-CKD transition using bilateral ischemia-reperfusion injury (Bi-IRI). The mice were treated with 11R-VIVIT (5 mg/kg, i.p.) on Days 1, 3, 10, 17 and 24 after Bi-IRI. We showed that the expression of NFAT2 was markedly increased in RTECs in the AKI-to-CKD transition. 11R-VIVIT administration significantly inhibited the nuclear translocation of NFAT2 in RTECs, decreased the levels of serum creatinine and blood urea nitrogen, and attenuated renal tubulointerstitial fibrosis but had no toxic side effects on the heart and liver. In addition, we showed that 11R-VIVIT administration alleviated RTEC apoptosis after Bi-IRI. Consistently, preapplication of 11R-VIVIT (100 nM) and transfection with NFAT2-targeted siRNA markedly suppressed TGFβ-induced HK-2 cell apoptosis in vitro. In conclusion, 11R-VIVIT administration inhibits IRI-induced NFAT2 activation and prevents AKI-to-CKD progression. Inhibiting NFAT2 may be a promising new therapeutic strategy for preventing renal fibrosis after IR-AKI.

Experimental Study on Danggui Shaoyao San Improving Renal Fibrosis by Promoting Autophagy

Renal fibrosis could lead to chronic kidney disease (CKD) developing into the end-stage with its pathological manifestation is the deposition of extracellular matrix (ECM). Danggui Shaoyao San (DSS) is one of the widely used herbal formulas in ancient China, which has been proven to have efficacy in the treatment of CKD. The experiment employed TGF-β1 to stimulate the NRK-52E cells to establish a renal fibrosis model. With rapamycin (RAPA) used as the positive control, we detected the expression of fibronectin (FN), caspase-3, and autophagy-related proteins in the NRK-52E cells treated with DSS by Western blot and immunofluorescence assay. In order to further verify autophagy-promoting effects of DSS, we adopted 3-MA to inhibit autophagy. The experiment has found that DSS can lower the protein levels of FN and caspase-3 in the NRK-52E cells induced by TGF-β1. After TGF-β1 stimulation, the expression of LC3 II/I and Beclin 1 has decreased, and the protein levels of mTOR and p62 have increased. Consistent with rapamycin, DSS has significantly reduced these effects of TGF-β1. It has also been found that DSS can increase the expression of LC3 II/I and Beclin 1 proteins and can reduce the level of mTOR in cells treated with 3-MA, suggesting that DSS can promote autophagy. In conclusion, DSS has been proved to reduce the apoptosis and fibrosis of NRK-52E cells induced by TGF-β1, which may be achieved by promoting autophagy.

Potential Therapeutic Strategies for Renal Fibrosis: Cordyceps and Related Products

At present, there is no effective drug for the treatment of renal fibrosis; in particular, a safe and effective treatment for renal fibrosis should be established. Cordyceps has several medical effects, including immunoregulatory, antitumor, anti-inflammatory, and antioxidant effects, and may prevent kidney, liver, and heart diseases. Cordyceps has also been reported to be effective in the treatment of renal fibrosis. In this paper, we review the potential mechanisms of Cordyceps against renal fibrosis, focusing on the effects of Cordyceps on inflammation, oxidative stress, apoptosis, regulation of autophagy, reduction of extracellular matrix deposition, and fibroblast activation. We also discuss relevant published clinical trials and meta-analyses. Available clinical studies support the possibility that Cordyceps and related products provide benefits to patients with chronic kidney diseases as adjuvants to conventional drugs. However, the existing clinical studies are limited by low quality and significant heterogeneity. The use of Cordyceps and related products may be a potential strategy for the treatment of renal fibrosis. Randomized controlled trial studies with good methodological quality, favorable experimental design, and large sample size are needed to evaluate the efficacy and safety of Cordyceps.

MicroRNA-34a: A Novel Therapeutic Target in Fibrosis

Fibrosis can occur in many organs, and severe cases leading to organ failure and death. No specific treatment for fibrosis so far. In recent years, microRNA-34a (miR-34a) has been found to play a role in fibrotic diseases. MiR-34a is involved in the apoptosis, autophagy and cellular senescence, also regulates TGF-β1/Smad signal pathway, and negatively regulates the expression of multiple target genes to affect the deposition of extracellular matrix and regulate the process of fibrosis. Some studies have explored the efficacy of miR-34a-targeted therapies for fibrotic diseases. Therefore, miR-34a has specific potential for the treatment of fibrosis. This article reviews the important roles of miR-34a in fibrosis and provides the possibility for miR-34a as a novel therapeutic target in fibrosis.

SS-31, a Mitochondria-Targeting Peptide, Ameliorates Kidney Disease

Mitochondria are essential for eukaryotic cell activity and function, and their dysfunction is associated with the development and progression of renal diseases. In recent years, there has been a rapid development in mitochondria-targeting pharmacological strategies as mitochondrial biogenesis, morphology, and function, as well as dynamic changes in mitochondria, have been studied in disease states. Mitochondria-targeting drugs include nicotinamide mononucleotide, which supplements the NAD+ pool; mitochondria-targeted protective compounds, such as MitoQ; the antioxidant coenzyme, Q10; and cyclosporin A, an inhibitor of the mitochondrial permeability transition pore. However, traditional drugs targeting mitochondria have limited clinical applications due to their inability to be effectively absorbed by mitochondria in vivo and their high toxicity. Recently, SS-31, a mitochondria-targeting antioxidant, has received significant research attention as it decreases mitochondrial reactive oxygen species production and prevents mitochondrial depolarization, mitochondrial permeability transition pore formation, and Ca²⁺-induced mitochondrial swelling, and has no effects on normal mitochondria. At present, few studies have evaluated the effects of SS-31 against renal diseases, and the mechanism underlying its action is unclear. In this review, we first discuss the pharmacokinetics of SS-31 and the possible mechanisms underlying its protective effects against renal diseases. Then, we analyze its renal disease-improving effects in various experimental models, including animal and cell models, and summarize the clinical evidence of its benefits in renal disease treatment. Finally, the potential mechanism underlying the action of SS-31 against renal diseases is explored to lay a foundation for future preclinical studies and for the evaluation of its clinical applications.

Cardiac Spinal Afferent Denervation Attenuates Renal Dysfunction in Rats With Cardiorenal Syndrome Type 2

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Epicardial application of RTX at the time of MI largely prevented renal dysfunction, attenuated renal congestion, and partially restored renal blood flow in rats with CHF.

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RNA sequencing analysis showed that renal injury, inflammation, hypoxia, and apoptosis genes were significantly up-regulated in the renal tissue of CHF rats, which was largely prevented by epicardial RTX at the time of MI.

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Cardiac afferent ablation by intra–stellate ganglia injection of RTX or unilateral renal denervation 4 weeks after MI had similar renal protective effects on renal tubular damage in CHF rats.

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These data provide evidence for cardiac spinal afferent modulation of renal function and a potential targeted therapy.

Cardiorenal syndrome type 2 (CRS2) is defined as a chronic cardiovascular disease, usually chronic heart failure (CHF), resulting in chronic kidney disease. We hypothesized that the cardiac spinal afferent reflex (CSAR) plays a critical role in the development of CRS2. Our data suggest that cardiac afferent ablation by resiniferatoxin not only improves cardiac function but also benefits the kidneys and increases long-term survival in the myocardial infarction model of CHF. We also found that renal denervation has a similar reno-protective effect in CHF rats. We believe this novel work contributes to the development of a unique neuromodulation therapy to treat CHF patients.

Suppression of LMCD1 ameliorates renal fibrosis by blocking the activation of ERK pathway

Tubulointerstitial fibrosis is a common pathway of chronic kidney disease (CKD) and is closely related to the progression of CKD. LMCD1, acting as an intermediary, has been reported to play a role in cardiac fibrosis. However, its role in renal fibrosis is yet to be deciphered. Based on the GEO database, we found the expression of LMCD1 is increased in kidney tissues of CKD patients and in human proximal tubular epithelial (HK-2) cells treated with transforming growth factor-β1 (TGF-β1), suggesting that LMCD1 may be involved in tubulointerstitial fibrosis. Herein, we investigated the role of LMCD1 in mice with unilateral ureteral obstruction (UUO) and in TGF-β1-stimulated HK-2 cells. In the UUO model, the expression of LMCD1 was upregulated. UUO-induced renal histopathological changes were mitigated by knockdown of LMCD1. LMCD1 silence alleviated renal interstitial fibrosis in UUO mice by decreasing the expression of TGF-β1, fibronectin, collagen I, and collagen III. LMCD1 deficiency suppressed cell apoptosis in kidney to prevent UUO-triggered renal injury. Furthermore, LMCD1 deficiency blocked the activation of ERK signaling in UUO mice. In vitro, LMCD1 was upregulated in HK-2 cells after TGF-β1 stimulation. LMCD1 silence abrogated TGF-β1-mediated upregulation of fibrotic genes. Treatment of HK-2 cells with ERK-specific inhibitor SCH772984 and agonist TPA validated LMCD1 exerted its function via activating ERK signaling. Together, our findings suggest that inhibition of LMCD1 protects against renal interstitial fibrosis by impeding ERK activation.

Qingda Granule Attenuates Angiotensin II-Induced Renal Apoptosis and Activation of the p53 Pathway

Background: Qingda granules (QDG) exhibit antihypertension and multiple-target-organ protection. However, the therapeutic potential of QDG on hypertensive renal injury remains unknown. Therefore, the main objective of the current study is to explore the effects and underlying mechanisms of QDG treatment on renal injury in angiotensin (Ang) II-infused mice. Methods and results: Mice were infused with Ang II (500 ng/kg/min) or saline for 4 weeks with subcutaneously implanted osmotic pumps. After infusion, mice in the Ang II + QDG group were intragastrically administrated with QDG daily (1.145 g/kg/day), whereas the control group and Ang II group were intragastrically administrated with the same amount of double-distilled water. Blood pressure of the mice monitored using the CODA™ noninvasive blood pressure system revealed that QDG treatment significantly attenuated elevated blood pressure. Moreover, hematoxylin-eosin staining indicated that QDG treatment ameliorated Ang II-induced renal morphological changes, including glomerular sclerosis and atrophy, epithelial cell atrophy, and tubular dilatation. RNA-sequencing (RNA-seq) identified 662 differentially expressed transcripts (DETs) in renal tissues of Ang II-infused mice, which were reversed after QDG treatment. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis based on DETs in both comparisons of Ang II vs. Control and Ang II + QDG vs. Ang II identified multiple enriched pathways, including apoptosis and p53 pathways. Consistently, terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining and Annexin V staining revealed that QDG treatment significantly attenuated Ang II-induced cell apoptosis in renal tissues and cultured renal tubular epithelial cell lines (NRK-52E). Furthermore, western blot analysis indicated that Ang II infusion significantly upregulated the protein expression of p53, BCL2-associated X (BAX), cle-caspase-9, and cle-caspase-3, while downregulating the protein expression of BCL-2 in renal tissues, which were attenuated after QDG treatment. Conclusion: Collectively, QDG treatment significantly attenuated hypertensive renal injury, partially by attenuating renal apoptosis and suppressing p53 pathways, which might be the underlying mechanisms.

Nesfatin-1 treatment preserves antioxidant status and attenuates renal fibrosis in rats with unilateral ureteral obstruction

BACKGROUND

Nesfatin-1 (NES-1), an anorexigenic peptide, was reported to have anti-inflammatory and anti-apoptotic actions in several inflammation models.

METHODS

To elucidate potential renoprotective effects of NES-1, unilateral ureteral obstruction (UUO) was induced in male Sprague Dawley rats by ligating left ureters. The rats were injected intraperitoneally with either saline (SL) or NES-1 (10 μg/kg/day) for 7 or 14 days (n = 8 in each group). On the 7th or 14th day, obstructed kidneys were removed for the isolation of leukocytes for flow-cytometric analysis and for the assessments of biochemical and histopathological changes.

RESULTS

Opposite to glutathione levels, renal myeloperoxidase activity in the SL-treated UUO group was significantly increased compared to sham-operated group, while NES-1 treatment abolished the elevation. The percentages of CD8+/CD4+ T-lymphocytes infiltrating the obstructed kidneys were increased in SL-treated groups but treatment with NES-1 did not prevent lymphocyte infiltration. Elevated TNF-a levels in SL-treated UUO group was decreased with NES-1. Although total degeneration scores were similarly increased in all UUO groups, tubular dilatation scores were significantly increased in UUO groups and lowered by NES-1 only in the 7-day treated group. Elevated interstitial fibrosis scores in the SL-treated groups were decreased in both 7- and 14-day NES-1 treated groups, while alpha smooth muscle actin (α-SMA) and apoptosis scores were depressed in both NES-1 treated groups.

CONCLUSION

The present data demonstrate that UUO-induced renal fibrosis is ameliorated by NES-1, which appears to involve the inhibition of neutrophil infiltration and thereby amelioration of oxidative stress and inflammation. These data suggest that NES-1 may have a regulatory role in protecting the kidneys against obstruction-induced renal injury.

Mesenchymal stem cells: A new therapeutic tool for chronic kidney disease

Chronic kidney disease (CKD) has a major impact on public health, which could progress to end-stage kidney disease (ESRD) and consume many medical resources. Currently, the treatment for CKD has many flaws, so more effective treatment tools are urgently required for CKD. Mesenchymal stem cells (MSCs) are primitive cells with self-renewal and proliferation capacity and differentiation potential. Extensive preclinical and clinical data has shown that cell-based therapies using MSCs can modulate immunity, inhibit inflammatory factors, and improve renal function in CKD, suggesting that MSCs have the potential to be a new, effective therapeutic tool for CKD. In this review, we will describe different kinds of MSCs and MSCs products for the treatment of CKD in experimental models and clinical trials, potential signaling pathways, therapeutic efficacy, and critical issues that need to be addressed before therapeutic application in humans.

Targeting Cpt1a-Bcl-2 interaction modulates apoptosis resistance and fibrotic remodeling

The mitochondrial calcium uniporter (MCU) regulates metabolic reprogramming in lung macrophages and the progression of pulmonary fibrosis. Fibrosis progression is associated with apoptosis resistance in lung macrophages; however, the mechanism(s) by which apoptosis resistance occurs is poorly understood. Here, we found a marked increase in mitochondrial B-cell lymphoma-2 (Bcl-2) in lung macrophages from subjects with idiopathic pulmonary fibrosis (IPF). Similar findings were seen in bleomycin-injured wild-type (WT) mice, whereas Bcl-2 was markedly decreased in mice expressing a dominant-negative mitochondrial calcium uniporter (DN-MCU). Carnitine palmitoyltransferase 1a (Cpt1a), the rate-limiting enzyme for fatty acid β-oxidation, directly interacted with Bcl-2 by binding to its BH3 domain, which anchored Bcl-2 in the mitochondria to attenuate apoptosis. This interaction was dependent on Cpt1a activity. Lung macrophages from IPF subjects had a direct correlation between CPT1A and Bcl-2, whereas the absence of binding induced apoptosis. The deletion of Bcl-2 in macrophages protected mice from developing pulmonary fibrosis. Moreover, mice had resolution when Bcl-2 was deleted or was inhibited with ABT-199 after fibrosis was established. These observations implicate an interplay between macrophage fatty acid β-oxidation, apoptosis resistance, and dysregulated fibrotic remodeling.

Genome-wide association studies identify the role of caspase-9 in kidney disease

Genome-wide association studies (GWAS) have identified hundreds of genetic risk regions for kidney dysfunction [estimated glomerular filtration rate (eGFR)]; however, the causal genes, cell types, and pathways are poorly understood. Integration of GWAS and human kidney expression of quantitative trait analysis using Bayesian colocations, transcriptome-wide association studies, and summary-based Mendelian randomization studies prioritized caspase-9 (CASP9) as a kidney disease risk gene. Human kidney single-cell epigenetic and immunostaining studies indicated kidney tubule cells as a disease-causing cell type. Mice with genetic deletion or pharmacological inhibition of CASP9 showed lower apoptosis while having improved mitophagy, resulting in dampened activation of cytosolic nucleotide sensing pathways (cGAS-STING), reduction of inflammation, and protection from acute kidney disease or renal fibrosis. In summary, here, we prioritized CASP9 as an eGFR GWAS target gene and demonstrated the causal role of CASP9 in kidney disease development via improving mitophagy and lowering inflammation and apoptosis.

Effects of andrographolide on renal tubulointersticial injury and fibrosis. Evidence of its mechanism of action

BACKGROUND

Diabetic nephropathy (DN) is associated with renal interstitial injury and fibrosis. Our previous study showed that andrographolide protected against the progression of DN and high glucose (HG)-induced mesangial dysfunction. However, the protective effects of andrographolide on renal tubular epithelial cells have not been fully elucidated.

PURPOSE

To determine the protective effects of andrographolide on renal tubular damage and explore the underlying mechanism.

STUDY DESIGN

Human tubular epithelial cells (HK-2 cells) were treated with andrographolide (5 and 10 μM) under HG conditions. Diabetic mice were treated with andrographolide (i.p. 2 and 4 mg/kg, twice per week).

METHODS

Western blotting, reverse transcription-polymerase chain reaction (RT-PCR), immunofluorescence and flow cytometry were used to analyze the effects of andrographolide on renal tubular injury and fibrotic mechanisms in HK-2 cells. The protective effects of andrographolide against renal tubulointerstitial injury and fibrosis were investigated in diabetic mice fed a high-fat diet (HFD). Renal interstitial tissue was collected at sacrifice for immunohistochemistry, immunofluorescence analysis, RT-PCR and Western blotting to analyze the effects of andrographolide on renal tubular injury and fibrosis.

RESULTS

In vitro assay results indicated that andrographolide (5 and 10 μM) effectively inhibited HG-induced apoptosis, epithelial-mesenchymal transition (EMT) and collagen deposition in HK-2 cells. Mechanistically, HG stimulated mitochondrial reactive oxygen species (mtROS)-mediated NOD-like receptor family and pyrin domain-containing protein 3 (NLRP3) inflammasome activation and EMT in tubular epithelial cells, and andrographolide (5 and 10 μM) inhibited these effects by ameliorating mitochondrial dysfunction. In vivo, treatment with andrographolide (2 and 4 mg/kg) inhibited renal tubular cell apoptosis, EMT and tubulointerstitial fibrosis, mitochondrial dysfunction and NLRP3 inflammasome activation in diabetic mice.

CONCLUSION

Andrographolide (5 and 10 μM) prevents HG-induced renal tubular cell damage, and andrographolide (2 and 4 mg/kg) protects against the progression of diabetic tubular injury and fibrosis in mice by suppressing mitochondrial dysfunction and NLRP3 inflammasome activation.

Non-Coding RNAs in Kidney Diseases: The Long and Short of Them

Recent progress in genomic research has highlighted the genome to be much more transcribed than expected. The formerly so-called junk DNA encodes a miscellaneous group of largely unknown RNA transcripts, which contain the long non-coding RNAs (lncRNAs) family. lncRNAs are instrumental in gene regulation. Moreover, understanding their biological roles in the physiopathology of many diseases, including renal, is a new challenge. lncRNAs regulate the effects of microRNAs (miRNA) on mRNA expression. Understanding the complex crosstalk between lncRNA–miRNA–mRNA is one of the main challenges of modern molecular biology. This review aims to summarize the role of lncRNA on kidney diseases, the molecular mechanisms involved, and their function as emerging prognostic biomarkers for both acute and chronic kidney diseases. Finally, we will also outline new therapeutic opportunities to diminish renal injury by targeting lncRNA with antisense oligonucleotides.

Combined protective effects of oligo-fucoidan, fucoxanthin, and L-carnitine on the kidneys of chronic kidney disease mice

Chronic kidney disease (CKD) is a common global progressive disease, but there are no ideal drugs for the treatment. Fucoidan and fucoxanthin, and L-carnitine are one of the very few natural products that have a therapeutic effect on CKD in animal experiments. However, the combined effects of these compounds on CKD are unknown. We established a mouse CKD model by right nephrectomy with transient ischemic injury to the left kidney. Oligo-fucoidan and fucoidan were extracted from Laminaria japonica. We fed CKD mice with the two compounds and L-carnitine to evaluate the combined effects on CKD. Oligo-fucoidan and fucoidan inhibited renal fibrosis and reduced serum creatine in CKD mice to a greater extent than any single compound. L-carnitine had no measurable effect on renal fibrosis but promoted the protective effect of the mixture of oligo-fucoidan and fucoidan on renal function in CKD mice. In the two-month safety test, the combined mixture further improved renal function and did not elevate serum aspartate aminotransferase and alanine aminotransferase levels in CKD mice. Furthermore, the weights of CKD mice treated with the combination increased to the normal level. We also found that all oligo-fucoidan, fucoxanthin, and L-carnitine inhibit H2O2-induced apoptosis and activated Akt in rat renal tubular cells. Our results confirm that oligo-fucoidan, fucoxanthin, and L-carnitine have a combined protective effect on the kidneys. The combined mixture may be beneficial for CKD patients.

Mechanism and restoration strategy of lysosomal abnormalities induced by urinary protein overload in proximal tubule epithelial cells

BACKGROUND

Persistent elevated concentrations of urinary protein can destroy proximal tubule epithelial cells (PTECs) by inducing lysosomal abnormalities, thereby aggravating PTEC damage and renal fibrosis. However, the specific mechanisms of these serial biochemical events and methods for treating or preventing PTEC damage upon proteinuria need further investigation.

RESULTS

In this study, electron microscopy and dual-labeled immunofluorescence analysis for identifying lysosome type revealed inadequate primary lysosome biogenesis and secondary lysosome accumulation in the PTECs of patients with minimal change nephrotic syndrome or membranous nephropathy who suffered from proteinuria. In vitro studies on HK-2 cells indicated that this abnormality was associated with decreased expression of transcription factor EB (TFEB). In contrast, TFEB overexpressing HK-2 cells under urinary protein overload exhibited significantly reduced accumulation of secondary lysosomes and increased proportion and quantity of primary lysosomes as indicated by dual-labeled immunofluorescence. Further, these cells could upregulate lysosomal degradation functions, as determined using Cathepsin L activity assays and flow cytometry for dye quenched-albumin.

CONCLUSIONS

These results indicate that abnormal TFEB expression is a key mechanism of lysosomal dyshomeostasis caused by protein overload in PTECs. TFEB is thus a potential therapeutic target for the treatment of urinary protein-related kidney disease.

A novel biomarker of chronic allograft dysfunction in renal transplant recipients (serum calreticulin and CD47)

Background

Chronic allograft dysfunction (CAD) is considered the leading cause of late allograft loss. The cluster of differentiation 47 (CD47) and calreticulin (CRT) are involved in many and diverse cellular processes. The present study was designed to study the role of the pro-phagocytic CRT and anti-phagocytic CD47 signals in patients with renal transplantation in relation to graft function.

Thirty renal transplantation recipients (RTR) for more than 6 months [15 with stable renal function and 15 with chronic allograft dysfunction (CAD)] and 15 healthy controls were enrolled in the study. Quantification of CRT, CD47, and high-sensitivity C-reactive protein (hsCRP) levels in serum was done using standardized enzyme-linked immunosorbent assay (ELISA) kits. Measurement of renal function and urinary alkaline phosphatase (U.ALP) was done. Renal interstitial fibrosis (IF) was graded in renal biopsies of CAD.

Results

Serum CRT and urinary ALP levels were statistically significant higher (P < 0.001) while serum CD47 level was statistically significant lower (P < 0.001) in patients with CAD than patients with stable graft function and controls. There was statistically insignificant difference between controls and patients with stable graft function. Serum CRT and serum CD47 levels were positively correlated with each other and with worsening renal and tubular function, serum hsCRP in RTR and with degree of renal IF in patients with CAD (P < 0.05).

Conclusions

The activation and dysregulation of CRT and CD47 could play a role in the development of CAD and could be a potential biomarker for renal allograft dysfunction.

Despite initial recovery of GFR, long-term renal functions deteriorate following short periods of unilateral ureteral obstruction

Following the release of short periods of unilateral ureteral obstruction (UUO), glomerular filtration rate (GFR) recovers by time. However, research in experimental animal models has demonstrated the presence of an ongoing element of renal interstitial fibrosis a few weeks following UUO reversal. Interstitial fibrosis can cause deterioration in GFR, and it is not known whether it leads to an ongoing slow deterioration in other renal functions despite the apparent initial recovery postreversal. To investigate this, rats underwent a 72-h reversible UUO. Renal functions of nonobstructed and previously obstructed kidneys were measured 1, 4, and 18 mo postreversal. GFR in nonobstructed and previously obstructed kidneys was similar up to 18 mo postreversal. However, there was ongoing tubulointerstitial fibrosis, and the degree of tubular atrophy and dilatation deteriorated by time. This was associated with an increase in urinary albumin leakage and alterations in renal injury markers, proinflammatory and profibrotic cytokines, and p53 from 4 mo onward despite the recovery in GFR. In conclusion, several aspects of renal functions continue to deteriorate following reversal of relatively short periods of UUO despite the initial recovery in GFR. This might stimulate further research in this area and might have clinical implications in terms of determining the best time for intervention following acute ureteral obstruction and long-term monitoring of these individuals.

Cordyceps cicadae Prevents Renal Tubular Epithelial Cell Apoptosis by Regulating the SIRT1/p53 Pathway in Hypertensive Renal Injury

Hypertensive renal injury is a primary etiology of end-stage renal disease, and satisfactory therapeutic strategies are urgently required. Cordyceps cicadae, a traditional Chinese herb, has potential renoprotective benefits and is widely used in the treatment of many kidney diseases. To investigate the mechanisms underlying the renoprotective effect of C. cicadae on hypertensive renal injury, we studied the effect of C. cicadae on tubular epithelial cells (TECs) in a spontaneously hypertensive rat (SHR) model and angiotensin II- (AngII-) cultured primary TECs. Our study showed that C. cicadae treatment could decrease 24-hour urine albumin, albumin-to-creatinine ratio (ACR), β2-MG level, and kidney injury molecule-1 (kim-1) level in SHR urine, alleviate interstitial fibrosis, and reduce α-smooth muscle actin (α-SMA) expression in SHR kidney. In primary TECs, medicated serum containing C. cicadae (CSM) might significantly reduce the AngII-induced production of kim-1 and neutrophil gelatinase-associated lipocalin (NGAL). Furthermore, C. cicadae treatment could decrease TEC apoptosis in SHRs as assessed by the terminal transferase-mediated biotin dUTP nick-end labeling (TUNEL) assay. CSM could inhibit caspase-3 activity and enhance cellular viability as measured by methyl thiazolyl tetrazolium in AngII-cultured TECs, suggesting that CSM might reduce the apoptosis level in TECs induced by AngII. We found that the SIRT1 expression level was markedly lowered, while the protein level of acetylated-p53 was elevated in the TECs of patients with hypertensive renal injury and SHRs. C. cicadae presented the effect of regulating the SIRT1/p53 pathway. Further SIRT1 inhibition with EX527 reversed the effect of C. cicadae on AngII-induced apoptosis. Taken together, our results indicate that C. cicadae offers a protective effect on TECs under hypertensive conditions, which may be related to its antiapoptotic effect through regulation of the SIRT1/p53 pathway.

Ameliorating effect of troxerutin in unilateral ureteral obstruction induced renal oxidative stress, inflammation, and apoptosis in male rats

Unilateral ureteral obstruction (UUO) induces renal injury and troxerutin attenuates the inflammatory parameters and decreases oxidative stress. Accordingly, this study explored the renoprotective effect of troxerutin in UUO-induced renal oxidative stress, inflammation, and apoptosis in male Wistar rats. Animals were randomly separated into five groups (n = 8): control, UUO, and three UUO groups treated with troxerutin (1, 10, and 100 mg/kg). UUO-induced and vehicle/troxerutin administration was continued for 3 days. Then serum creatinine, mean arterial pressure (MAP), renal perfusion pressure (RPP), renal vascular resistance (RVR), and renal blood flow (RBF) were measured. Superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase activities, total antioxidant capacity (TAC), and malondialdehyde (MDA) levels as some oxidative stress parameters were measured in the left kidney. The immunoblotting method was applied to evaluate the cleaved caspase-3 Bax, Bcl-2, and TNF-α proteins level. The hematoxylin and eosin method was used to assess the kidney tissue damage score (KTDS). In 3 days, UUO significantly increased serum creatinine level, KTDS, RVR, MDA, Bax, cleaved caspase-3, and TNF-α protein levels (p < 0.05); and decreased RBF, TAC, SOD, catalase, GPx activity levels and Bcl-2 protein expression level in the left kidney (p < 0.05). Troxerutin (100 mg/kg) significantly attenuates the indicators alteration induced by UUO. Our findings represented that the renoprotective effect of troxerutin may be related to its anti-oxidative stress, anti-inflammation, anti-apoptosis, and RBF improver properties.

The effect of oleuropein on unilateral ureteral obstruction induced-kidney injury in rats: the role of oxidative stress, inflammation and apoptosis

Unilateral ureteral obstruction (UUO) induces kidney injury. Oleuropein as a major compound of olive leaves modulates the inflammatory parameters and decreases oxidative stress. Accordingly, we evaluate the renoprotective effect of oleuropein against 3-day UUO rats. Forty rats were randomly divided into five groups (n = 8) including control, UUO and UUO + oleuropein groups (50, 100 and 200 mg/kg). UUO model was induced by left ureter ligation and continued for 3-day. Rats were treated synchronic daily for 3-day, then mean arterial pressure (MAP), renal perfusion pressure (RPP), renal blood flow (RBF), serum creatinine level, and also superoxide dismutase (SOD), glutathione peroxidase (GPx) activity levels and malondialdehyde (MDA) concentration (in the obstructed kidney) were measured. The western blotting method was applied to evaluate the Bax, Bcl-2, cleaved caspase-3 and TNF-α proteins expression level. The hematoxylin and eosin method was applied to evaluate the kidney tissue damage score (KTDS). UUO significantly increased RVR, KTDS, and MDA, cleaved caspase-3, Bax, serum creatinine and TNF-α protein levels (P < 0.05), and also significantly decreased RBF, SOD, and GPx and Bcl-2 protein expression levels (P < 0.001) in the obstructed kidney and oleuropein (200 mg/kg) significantly ameliorated the changes induced by UUO. Our findings showed that oleuropein has a renoprotective effect against 3-day UUO. The mechanisms underlying the observed effects may be related to its antioxidative stress, anti-apoptotic, and anti-inflammatory effects.

Fluorofenidone inhibits apoptosis of renal tubular epithelial cells in rats with renal interstitial fibrosis

This study aimed to investigate the mechanism of fluorofenidone (AKF-PD) in treating renal interstitial fibrosis in rats with unilateral urinary obstruction (UUO). Thirty-two male Sprague-Dawley rats were randomly divided into sham, UUO, UUO + enalapril, and UUO + AKF-PD groups. All rats, except sham, underwent left urethral obstruction surgery to establish the animal model. Rats were sacrificed 14 days after surgery, and serum was collected for renal function examination. Kidneys were collected to observe pathological changes. Immunohistochemistry was performed to assess collagen I (Col I) protein expression, and terminal deoxynucleotidyl transferase-mediated nick end-labeling staining to observe the apoptosis of renal tubular epithelial cells. The expression of Fas-associated death domain (FADD), apoptotic protease activating factor-1 (Apaf-1), and C/EBP homologous protein (CHOP) proteins was evaluated by immunohistochemistry and western blot analysis. AKF-PD showed no significant effect on renal function in UUO rats. The pathological changes were alleviated significantly after enalapril or AKF-PD treatment, but with no significant differences between the two groups. Col I protein was overexpressed in the UUO group, which was inhibited by both enalapril and AKF-PD. The number of apoptotic renal tubular epithelial cells was much higher in the UUO group, and AKF-PD significantly inhibited epithelial cells apoptosis. The expression of FADD, Apaf-1, and CHOP proteins was significantly upregulated in the UUO group and downregulated by enalapril and AKF-PD. In conclusion, AKF-PD improved renal interstitial fibrosis by inhibiting apoptosis of renal tubular epithelial cells in rats with UUO.

Suppression of TRPM2 reduces renal fibrosis and inflammation through blocking TGF-β1-regulated JNK activation

Chronic kidney disease (CKD) is a major cause of death. Renal fibrosis and inflammation are common pathways contributing to the development of this disease. However, the molecular mechanisms underlying CKD are not fully understood. TRPM2 (Transient receptor potential melastatin-2) was previously identified as a potential target in various diseases due to its multiple functions. In the study, mice with unilateral urethral obstruction (UUO) were used to explore the effects of TRPM2 on renal injury. First, TRPM2 expression was up-regulated in kidney of mice after UUO. Renal histological analysis using H&E and PAS staining showed that histological changes induced by UUO were markedly alleviated in TRPM2-deficient mice. In addition, TRPM2 knockout markedly improved renal dysfunction, as evidenced by the reduced serum creatine, blood urea nitrogen (BUN), kidney injury molecule 1 (KIM-1) expression and enhanced Nephrin levels. TRPM2 ablation significantly attenuated renal interstitial fibrosis in mice with UUO via decreasing transforming growth factor (TGF)-β1 expression, accompanied with the reduction of fibrotic genes, such as α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), fibronectin (FN) and Collagen 1 alpha 1 (Col1α1). Suppressing TRPM2 expression also suppressed inflammatory cell infiltration and release of pro-inflammatory factors in UUO-triggered renal fibrosis. Further, TRPM2 deficiency inhibited IκBα/nuclear factor (NF)-κB signaling in UUO-treated mice. Moreover, c-Jun N-terminal kinase (JNK) signaling was blocked by TRPM2 knockout in UUO mice. Surprisingly, the in vitro results indicated that blocking JNK activation resulted in the suppression of TGF-β1-induced fibrosis and inflammation. Together, these findings demonstrate that the inhibition of TRPM2 might protect against renal fibrosis and inflammation through impeding JNK activation regulated by TGF-β1.

FoxO1-mediated inhibition of STAT1 alleviates tubulointerstitial fibrosis and tubule apoptosis in diabetic kidney disease

Background

Tubulointerstitial fibrosis (TIF) plays an important role in the progression of diabetic kidney disease (DKD). Forkhead box O1 (FoxO1) is involved in the regulation of metabolism and cell apoptosis, but its function in renal TIF induced by DKD is less well understood.

Methods

Human kidney biopsies with DKD and normal controls were used to detect apoptosis and TIF induced by diabetes. A mouse model with kidney-specific overexpression of Pax2-3aFoxO1 was established to further investigate the functions of FoxO1 in vivo. The in vitro roles of FoxO1 were analyzed in HK-2 cells with 3aFoxO1-knockin (3aFoxO1-KI) or FoxO1-knockdown (FoxO1-KD) via CRISPR/Cas9. Western blot, immunohistochemistry, and chromatin immunoprecipitation were used to explore the underlying mechanisms.

Findings

In this study, DKD patients had increased renal TIF and apoptosis. In vivo study showed that kidney-specific overexpression of Pax2-3aFoxO1 significantly reduced the expression of p-STAT1 with resultant renal functional impairment, retarding renal TIF and apoptosis in diabetic mice. Meanwhile, We observed that FoxO1-KD in HK-2 cells aggravated the expression of p-STAT1, leading to activation of epithelial-to-mesenchymal transition (EMT) and intrinsic apoptotic pathway. Conversely, EMT and apoptosis were significantly attenuated in HK-2 cells with 3aFoxO1-KI under hyperglycemic conditions.

Interpretation

Taken together, these data suggest that the protection role of FoxO1 against renal TIF and apoptosis in DKD is likely in part to target STAT1 signaling, which may be a promising strategy for long-term treatment of DKD.

Fund

This work was supported by grants from the National Natural Science Foundation of China (grant numbers: 81570746 and 81770812).

Human umbilical cord-derived mesenchymal stem cells conditioned medium attenuate interstitial fibrosis and stimulate the repair of tubular epithelial cells in an irreversible model of unilateral ureteral obstruction

AIM

The growing number of patients suffering from chronic renal disease (CKD) is a challenge for the development of innovative therapies. Researchers have studied the therapeutic effects of cell therapy in acute kidney injury (AKI). However, the therapeutic effect of conditional medium (CM) in the CKD models have been rarely reported. Here, we examined the effects of umbilical cord derived-mesenchymal stem cells (hUC-MSCs) CM on renal fibrosis in a rat model of unilateral ureteral obstruction (UUO).

METHODS

Animals were randomly divided into three groups: sham-operated, UUO, UUO + CM. CM was administered via the left renal artery after total ligation of the left ureter. Rats were killed after 14 days of obstruction. Histological changes and oxidative stress parameters were assessed. Western blotting and immunohistochemistry analysis were used to measure epithelial-mesenchymal transition (EMT) markers, including epithelial cadherin (E-cadherin), α-smooth muscle actin (α-SMA), tumour necrosis factor-α (TNF-α), Collagen-I, and transforming growth factor β1 (TGF-β1). Proliferation and apoptosis of renal tubular epithelial cells (RTEs) were also measured.

RESULTS

HucMSC-CM significantly reduced the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), and increased the activity of glutathione (GSH) induced by UUO. Moreover, CM significantly reduced the expression of TGF-β1, α-SMA, TNF-α and Collagen-I in UUO kidney, promoted the proliferation of RTEs and inhibited its apoptosis. In addition, the increased expression of E-cadherin also reflects the effective improvement of renal interstitial fibrosis.

CONCLUSION

This study shows that CM protects UUO-induced kidney damage and therefore could be a potential tool to prevent CKD progression.

Cell Death in the Kidney

Apoptotic cell death is usually a response to the cell's microenvironment. In the kidney, apoptosis contributes to parenchymal cell loss in the course of acute and chronic renal injury, but does not trigger an inflammatory response. What distinguishes necrosis from apoptosis is the rupture of the plasma membrane, so necrotic cell death is accompanied by the release of unprocessed intracellular content, including cellular organelles, which are highly immunogenic proteins. The relative contribution of apoptosis and necrosis to injury varies, depending on the severity of the insult. Regulated cell death may result from immunologically silent apoptosis or from immunogenic necrosis. Recent advances have enhanced the most revolutionary concept of regulated necrosis. Several modalities of regulated necrosis have been described, such as necroptosis, ferroptosis, pyroptosis, and mitochondrial permeability transition-dependent regulated necrosis. We review the different modalities of apoptosis, necrosis, and regulated necrosis in kidney injury, focusing particularly on evidence implicating cell death in ectopic renal calcification. We also review the evidence for the role of cell death in kidney injury, which may pave the way for new therapeutic opportunities.

AXL targeting reduces fibrosis development in experimental unilateral ureteral obstruction

The AXL receptor tyrosine kinase (RTK) is involved in partial epithelial-to-mesenchymal transition (EMT) and inflammation - both main promoters of renal fibrosis development. The study aim was to investigate the role of AXL inhibition in kidney fibrosis due to unilateral ureteral obstruction (UUO). Eight weeks old male C57BL/6 mice underwent UUO and were treated with oral AXL inhibitor bemcentinib (n = 22), Angiotensin-converting enzyme inhibitor (ACEI, n = 10), ACEI and bemcentinib (n = 10) or vehicle alone (n = 22). Mice were sacrificed after 7 or 15 days and kidney tissues were analyzed by immunohistochemistry (IHC), western blot, ELISA, Sirius Red (SR) staining, and hydroxyproline (Hyp) quantification. RNA was extracted from frozen kidney tissues and sequenced on an Illumina HiSeq4000 platform. After 15 days the ligated bemcentinib-treated kidneys showed less fibrosis compared to the ligated vehicle-treated kidneys in SR analyses and Hyp quantification. Reduced IHC staining for Vimentin (VIM) and alpha smooth muscle actin (αSMA), as well as reduced mRNA abundance of key regulators of fibrosis such as transforming growth factor (Tgfβ), matrix metalloproteinase 2 (Mmp2), Smad2, Smad4, myofibroblast activation (Aldh1a2, Crlf1), and EMT (Snai1,2, Twist), in ligated bemcentinib-treated kidneys was compatible with reduced (partial) EMT induction. Furthermore, less F4/80 positive cells, less activity of pathways related to the immune system and lower abundance of MCP1, MCP3, MCP5, and TARC in ligated bemcentinib-treated kidneys was compatible with reduction in inflammatory infiltrates by bemcentinib treatment. The AXL RTK pathway represents a promising target for pharmacologic therapy of kidney fibrosis.

Renal sympathetic nerve activation via α2-adrenergic receptors in chronic kidney disease progression

Chronic kidney disease (CKD) is increasing worldwide without an effective therapeutic strategy. Sympathetic nerve activation is implicated in CKD progression, as well as cardiovascular dysfunction. Renal denervation is beneficial for controlling blood pressure (BP) and improving renal function through reduction of sympathetic nerve activity in patients with resistant hypertension and CKD. Sympathetic neurotransmitter norepinephrine (NE) via adrenergic receptor (AR) signaling has been implicated in tissue homeostasis and various disease progressions, including CKD. Increased plasma NE level is a predictor of survival and the incidence of cardiovascular events in patients with end-stage renal disease, as well as future renal injury in subjects with normal BP and renal function. Our recent data demonstrate that NE derived from renal nerves causes renal inflammation and fibrosis progression through alpha-2 adrenergic receptors (α₂-AR) in renal fibrosis models independent of BP. Sympathetic nerve activation-associated molecular mechanisms and signals seem to be critical for the development and progression of CKD, but the exact role of sympathetic nerve activation in CKD progression remains undefined. This review explores the current knowledge of NE-α₂-AR signaling in renal diseases and offers prospective views on developing therapeutic strategies targeting NE-AR signaling in CKD progression.

Microvesicles containing miR-34a induce apoptosis of proximal tubular epithelial cells and participate in renal interstitial fibrosis

Function and potential mechanism of microvesicles (MVs) containing microRNA34a in renal interstitial fibrosis were investigated. A rat model of renal interstitial fibrosis was established by unilateral ureteral ligation (UUO). Rat proximal tubular epithelial cell line (NRK-52E) was used to explore the effect of MVs containing microRNA-34a on tubular epithelial cells during fibrosis, which were secreted by tubulointerstitial fibroblasts. Regardless of the UUO renal interstitial fibrosis model, or the TGF-β1-treated renal tubular epithelial cells, microRNA-34a was increased in the MVs secreted by tubulointerstitial fibroblasts. miR-34a could be transmitted through the damaged tubule basement membrane to proximal tubular epithelial cells, where it induced apoptosis of renal tubular epithelial cells by inhibiting the expression of Bcl-2, further aggravating renal interstitial fibrosis. MicroRNA-34a secreted by damaged renal interstitial fibroblasts can promote renal tubular epithelial cell apoptosis and participate in renal interstitial fibrosis by inhibiting Bcl-2.

Protective Effect of Salidroside Against Diabetic Kidney Disease Through Inhibiting BIM-Mediated Apoptosis of Proximal Renal Tubular Cells in Rats

Background: Accumulating evidences indicate that the apoptosis of proximal tubular epithelial cells (PTECs) play a vital role in the progression of the diabetic kidney disease (DKD). This study aimed to explore the therapeutic potential of salidroside (SAL) in DKD and its underlying mechanism in anti-apoptosis of PTECs. Methods: Twenty-eight male Wistar rats were allocated into four groups: sham-operated, uninephrectomy (unx), diabetes with uninephrectomy (DKD) and DKD treated with SAL (DKD + SAL). SAL (70 mg/kg) was gavage administered for 8 weeks. 24-h albuminuria and serum creatinine (SCr), blood urea nitrogen (BUN), renal histological changes were examined. The silico analysis was used to identify the main therapeutic targets and pathways of SAL involved in DKD treatment. Apoptosis was determined by TUNEL and Annexin V-FITC/PI double staining in vivo and in vitro, respectively. The expression of BIM, BAX, and cleaved caspase-3 were evaluated by western blot and immunostaining. Results: Treatment with SAL significantly attenuated diabetic kidney injury via inhibiting 24-h albuminuria, SCr, BUN, glomerular mesangial dilatation and tubular injury in DKD rats. The silico analysis identified the intrinsic apoptotic pathway as an important pathway responsible for the nephroprotective properties of SAL. Our data validated that SAL effectively inhibited the apoptosis of PTECs induced by high-glucose (HG), both in vitro and in vivo. Silence of BIM by shRNA in HK-2 cells prevented HG-induced apoptosis. The up-regulated BIM and its downstream targets (BAX and cleaved caspase-3) were also inhibited by SAL. Conclusion: In summary, SAL significantly relieved DKD. And the possible mechanisms might be partially attributed to inhibiting apoptosis of proximal renal tubular cells. The apoptotic protein BIM could be an important target of SAL in this process.

Protein kinase C inhibitor chelerythrine attenuates partial unilateral ureteral obstruction induced kidney injury in neonatal rats

The present study aimed to evaluate the renoprotective effects of chelerythrine (CHE), a protein kinase C inhibitor, on neonatal rats after partial unilateral ureteral obstruction (UUO) surgery. New born Sprague Dawley rats were subjected to partial UUO 48 h after birth and received a daily intraperitoneal injection of 5 mg/kg CHE. At 21-day age, the rats were scarified and the kidneys were collected for analysis. Results showed that CHE treatment significantly increased kidney weight and restored renal function in the obstructed kidney. Histological examination demonstrated that CHE attenuated renal injury by reducing renal parenchymal loss and preventing glomerular and tubular degeneration. In addition, CHE inhibited partial UUO-induced upregulated kidney injury molecule-1 expression and apoptosis and renal fibrosis. Moreover, as a PKC inhibitor, CHE significantly inhibited PKCα and PKCβ membrane translocation. This action may be associated with its effects of anti-apoptosis and anti-fibrosis and contribute to the renoprotection. This short-term study suggests that CHE is beneficial for obstructive nephropathy in neonatal rats and provides foundation for further studies to reveal the long-term effects of CHE on obstructive nephropathy in children and infants.

Alleviative effect of fucoxanthin-containing extract from brown seaweed Laminaria japonica on renal tubular cell apoptosis through upregulating Na+/H+ exchanger NHE1 in chronic kidney disease mice

ETHNOPHARMACOLOGICAL RELEVANCE

Brown seaweed is a common food for Asians, and the bioactive ingredient fucoxanthin exerts anti-apoptotic activities in several cell types. Renal tubular cell apoptosis is one of the common cellular events leading to renal fibrosis and chronic kidney disease (CKD). However, the influence of fucoxanthin-containing brown seaweed extract on CKD is still unknown. We intended to evaluate the inhibitory effect of fucoxanthin-containing extract from brown seaweed on renal apoptosis under CKD condition and its molecular mechanism.

MATERIALS AND METHODS

The fucoxanthin-containing brown seaweed extract (LJE) was prepared from Laminaria japonica. We investigated how LJE influences on both doxorubicin-treated rat renal tubular cells (NRK-52E) and the renal symptoms of nephrectomy-induced CKD mice.

RESULTS

LJE inhibited doxorubicin-induced apoptosis and upregulated Na+/H+ exchanger isoform 1 (NHE1) expression in NRK-52E cells, which were blocked by the NHE1 inhibitor cariporide. LJE also upregulated peroxisome proliferator-activated receptor alpha (PPARα). PPARα siRNA transfection inhibited LJE-induced NHE1 expression and anti-apoptotic effect. In CKD mice, LJE increased NHE1 expression in renal tubules and reduced apoptotic renal tubular cells, but not in PPARα knockout mice. The inhibitory effect of LJE on apoptosis also reduced renal tubulointerstitial fibrosis and improved renal function in CKD mice.

CONCLUSION

We demonstrated that LJE inhibits renal apoptosis via NHE1 upregulation. The anti-apoptotic effect of LJE also improves renal function in CKD mice. Therefore, fucoxanthin-containing brown seaweed may have a therapeutic potential for CKD patients.

A cautionary note for researchers treating mice with the neurotransmitter norepinephrine

The sympathetic nervous system plays a crucial role in metabolic function and glucose homeostasis. Norepinephrine is the main neurotransmitter released from sympathetic neurons. The major goal of our studies was to examine the impact of norepinephrine on metabolism related gene expression in obesity in vivo. Interestingly, we discovered that norepinephrine had a detrimental effect in our studies. C57BL6/J mice fed a high fat diet were intraperitoneally injected with 0.2 or 2 mg/kg/day norepinephrine. These doses of norepinephrine have been used previously by other researchers. Survival of the mice was documented. Kidney and bladder tissues were excised and fixed for histological studies. A subset of norepinephrine treated mice experienced unexpected adverse events which included bladder distension and reduced kidney perfusion as suggested by kidney discolouration. This eventuated in the mice having to be sacrificed or the mice succumbed to the pathological condition. To our knowledge, such an effect of norepinephrine has not been previously reported in mice. Morphological examination of kidney and bladder indicated marked detrimental architectural changes, which we postulate is associated with norepinephrine induced vasoconstriction, urinary retention and renal impairment. Our studies highlight that administration of norepinephrine to mice may trigger adverse effects relating predominantly to the urogenital tract which can result in decline in a subpopulation of these mice. Researchers administering norepinephrine in mouse models should be aware and look out for these unexpected adverse events associated with the use of norepinephrine.

Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice

Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-β to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of β-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in β-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering β-catenin localization and downstream signaling.

Specific Inhibitor of Smad3 (SIS3) Attenuates Fibrosis, Apoptosis, and Inflammation in Unilateral Ureteral Obstruction Kidneys by Inhibition of Transforming Growth Factor β (TGF-β)/Smad3 Signaling

Background

Fibrosis is the common pathological feature in most kinds of chronic kidney disease (CKD). TGF-β/Smads signaling is the master pathway regulating kidney fibrosis pathogenesis, in which Smad3 acts as the integrator of various pro-fibrosis signals. In this study, we analyzed the role of SIS3, a specific inhibitor of Smad3, in mouse unilateral ureteral obstruction (UUO) kidneys.

Material/Methods

UUO mice were intraperitoneally injected with 0.2 mg/kg/day or 2 mg/kg/day of SIS3 or control saline for 7 days, followed by analysis of structure injury, fibrosis status, inflammation, apoptosis, and TGF-β/Smads signaling activity.

Results

Our results indicated that SIS3 treatment dosage-dependently relieved the gross structure injury and tubular necrosis in UUO kidneys. Masson staining, immunohistochemistry, and real-time PCR showed significantly decreased extracellular matrix deposition, fibronectin staining intensity, and RNA levels of collagen I and collagen III in SIS3-treated UUO kidneys. SIS3 treatment also suppressed the activation of myofibroblasts, as evidenced by decreased expression levels of α-SMA and vimentin in UUO kidneys. The TGF-β/Smads signaling activity analysis showed that SIS3 inhibited the phosphorylation of Smad3 but not Smad2 and decreased the protein level of TGF-β1, suggesting specific inhibition of the TGF-β/Smad3 pathway in UUO kidneys. Furthermore, SIS3 treatment also ameliorated the increased pro-inflammatory TNF-α and COX2 in UUO kidneys and circulating IL-1β in UUO mice, and inhibited caspase-3 activity and the number of apoptotic cells.

Conclusions

SIS3 ameliorated fibrosis, apoptosis, and inflammation through inhibition of TGF-β/Smad3 signaling in UUO mouse kidneys.

Cell death-based approaches in treatment of the urinary tract-associated diseases: a fight for survival in the killing fields

Urinary tract-associated diseases comprise a complex set of disorders with a variety of etiologic agents and therapeutic approaches and a huge global burden of disease, estimated at around 1 million deaths per year. These diseases include cancer (mainly prostate, renal, and bladder), urinary tract infections, and urolithiasis. Cell death plays a key role in the pathogenesis and therapy of these conditions. During urinary tract infections, invading bacteria may either promote or prevent host cell death by interfering with cell death pathways. This has been studied in detail for uropathogenic E. coli (UPEC). Inhibition of host cell death may allow intracellular persistence of live bacteria, while promoting host cell death causes tissue damage and releases the microbes. Both crystals and urinary tract obstruction lead to tubular cell death and kidney injury. Among the pathomechanisms, apoptosis, necroptosis, and autophagy represent key processes. With respect to malignant disorders, traditional therapeutic efforts have focused on directly promoting cancer cell death. This may exploit tumor-specific characteristics, such as targeting Vascular Endothelial Growth Factor (VEGF) signaling and mammalian Target of Rapamycin (mTOR) activity in renal cancer and inducing survival factor deprivation by targeting androgen signaling in prostate cancer. An area of intense research is the use of immune checkpoint inhibitors, aiming at unleashing the full potential of immune cells to kill cancer cells. In the future, this may be combined with additional approaches exploiting intrinsic sensitivities to specific modes of cell death such as necroptosis and ferroptosis. Here, we review the contribution of diverse cell death mechanisms to the pathogenesis of urinary tract-associated diseases as well as the potential for novel therapeutic approaches based on an improved molecular understanding of these mechanisms.

Role of Sirolimus in renal tubular apoptosis in response to unilateral ureteral obstruction

Renal tubule cell apoptosis plays a pivotal role in the progression of chronic renal diseases. The previous study indicates that Sirolimus is effective on unilateral ureteral obstruction (UUO)-induced renal fibrosis. However, the role of Sirolimus in renal tubular apoptosis induced by UUO has not yet been addressed. The aim of this study was to determine the role of Sirolimus in renal tubular apoptosis induced by UUO. Male Sprague-Dawley rats were divided into three groups, sham-operated rats, and after which unilateral ureteral obstruction (UUO) was performed: non-treated and sirolimus-treated (1mg/kg). After 4, 7 and 14 d, animals were sacrificed and blood, kidney tissue samples were collected for analyses. Histologic changes and interstitial collagen were determined microscopically following HE and Masson's trichrome staining. The expression of PCNA was investigated using immunohistochemistry and the expression of Bcl-2, Bax, caspase-9, and caspase-3 were investigated using Western blot in each group. Tubular apoptotic cell deaths were assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. Sirolimus administration resulted in a significant reduction in tubulointerstitial fibrosis scores. After UUO, there was an increase in tubular and interstitial apoptosis in untreated controls as compared to Sirolimus treatment rats (P<0.05). In addition, the expression of PCNA, Bcl-2, Bax, caspase-9, and caspase-3 in obstructed kidney was characterized by immunohistochemistry and Western blot analyses demonstrating that sirolimus treatment significantly reduced PCNA, Bax, caspase-9 and cleaved caspase-3 expression compared to those observed in controls (P<0.05), whereas, Bcl-2 in the obstructed kidney were decreased in untreated controls compared to Sirolimus treatment rats subjected to the same time course of obstruction (P<0.05). We demonstrated a marked renoprotective effect of sirolimus by inhibition of UUO-induced renal tubular apoptosis in vivo.

C/EBP homologous protein (CHOP) deficiency ameliorates renal fibrosis in unilateral ureteral obstructive kidney disease

Renal tubulointerstitial fibrosis is an important pathogenic feature in chronic kidney disease and end-stage renal disease, regardless of the initiating insults. A recent study has shown that CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) is involved in acute ischemia/reperfusion-related acute kidney injury through oxidative stress induction. However, the influence of CHOP on chronic kidney disease-correlated renal fibrosis remains unclear. Here, we investigated the role of CHOP in unilateral ureteral obstruction (UUO)-induced experimental chronic tubulointerstital fibrosis. The CHOP knockout and wild type mice with or without UUO were used. The results showed that the increased expressions of renal fibrosis markers collagen I, fibronectin, α-smooth muscle actin, and plasminogen activator inhibitor-1 in the kidneys of UUO-treated wild type mice were dramatically attenuated in the kidneys of UUO-treated CHOP knockout mice. CHOP deficiency could also ameliorate lipid peroxidation and endogenous antioxidant enzymes depletion, tubular apoptosis, and inflammatory cells infiltration in the UUO kidneys. These results suggest that CHOP deficiency not only attenuates apoptotic death and oxidative stress in experimental renal fibrosis, but also reduces local inflammation, leading to diminish UUO-induced renal fibrosis. Our findings support that CHOP may be an important signaling molecule in the progression of chronic kidney disease.